HK1123059A - Expandable resins - Google Patents

Description

Foamable resin

1. Field of the invention

The present invention relates to expandable thermoplastic resin beads, and more particularly to expandable resins having good toughness and cushioning properties, good retention of blowing agent, and the resulting expanded articles made from such resins.

2. Background of the invention

In general, polystyrene beads having a high expansion ratio are easily obtained. The resulting foamed articles produced from such beads have high hardness and good shape retention, but have disadvantages in that they are brittle and have poor chemical resistance, oil resistance and thermal stability. On the other hand, the foamed product of the polypropylene resin has better elasticity, chemical resistance, oil resistance and thermal stability than the polystyrene foam. Blowing agents impregnated within polypropylene resin beads tend to dissipate rapidly, so it is necessary to pre-foam them rapidly after preparation to obtain expanded beads, or to store these expandable resin beads under pressure in a container. Thus, such impregnated polypropylene resin beads have disadvantages during storage and transportation, and it is generally difficult to obtain polypropylene expandable beads having a high expansion ratio.

When polypropylene and polystyrene are simply mixed in an attempt to obtain a resin having the desired characteristics of both polymers, it is impossible to obtain a homogeneous mixture. Foamed products prepared from such mixtures undergo phase separation and do not have an attractive appearance. In many cases, the amount of polyolefin mixed is small because when the vinyl aromatic polymer and the polyolefin are simply physically mixed, the two resins are not uniformly mixed and phase separation occurs. As a result, the permeation of the foaming agent and the foaming ratio are not uniform, and it is impossible to obtain a uniform foamed article. Furthermore, due to the low polyolefin content, the toughness and elasticity of the resulting foamed product cannot be improved.

It is known to polymerize vinylaromatic monomers, such as styrene, in polyethylene particles. U.S. patent No.3959189 discloses a method for producing polyethylene resin particles, which comprises suspending polyethylene resin particles in an aqueous medium. Adding 30-100 wt% of styrene monomer and initiator to the suspension based on the weight of the particles for monomer polymerization, and polymerizing the monomer inside the polyethylene resin particles. Preferably, after polymerizing the styrene monomer and the crosslinked polyethylene resin, the particles can be made expandable by impregnating the particles with a blowing agent. The blowing agents are generally volatile blowing agents, i.e. aliphatic hydrocarbons, such as n-propane, n-butane, isobutane, n-pentane, isopentane, n-hexane and neopentane; or alicyclic hydrocarbons such as cyclobutane and cyclopentane; and halogenated hydrocarbons such as methyl chloride, ethyl chloride, methylene chloride, trichloromonofluoromethane, dichloromonofluoromethane, dichlorodifluoromethane, monochlorodifluoromethane, dichlorotetrafluoroethane and the like, in an amount of 5 to 20% by weight based on the weight of the polyethylene-polystyrene resin particles.

U.S. patent No.4782098 discloses expandable copolymer beads comprising a polyphenylene ether resin and a polymerized vinyl aromatic monomer to be polymerized in the presence of a polymerization catalyst to form copolymerized thermoplastic resin beads. The volatile blowing agent is introduced under pressure into the thermoplastic resin beads.

U.S. patent nos.4303756 and 4303757 disclose a method for producing expandable thermoplastic resin beads in which a vinyl aromatic monomer is polymerized on a polypropylene main chain; and introducing a blowing agent into the thermoplastic resin beads. The blowing agent is the same as taught in U.S. patent No. 4782098.

U.S. patent No.4429059 discloses a method for producing expandable polyolefin particles, which comprises adding a mixture of 3 to 15 parts by weight of a blowing agent and 0.5 to 5 parts by weight of a foaming aid to 100 parts by weight of polyolefin particles. Column 2, lines 63-66, teach that the foaming aid causes the interior of the particles to assume a plastic state to facilitate foaming of the particles. Representative foaming aids for use as plasticizers are benzene, toluene, xylene, trichloroethylene, perchloroethylene, cyclohexane, carbon tetrachloride and the like.

Similarly, copolymers of polyolefins and vinyl aromatic monomer polymers that can be foamed to form foamed articles are disclosed in U.S. patent nos.4303756, 4303757, 4622347, 4647593, 4692471, 4677134 and 4666946 and U.S. application publication 2004/0152795.

While copolymers of polyolefins and vinyl aromatic monomer polymers can be foamed to form materials characterized by good toughness and cushioning properties, the cost of such materials limits their commercial application.

Rubber reinforced polymers of monovinylaromatic compounds such as styrene, alpha methyl styrene and ring substituted styrene are also known to be desirable for various applications. More particularly, rubber-reinforced polymers of styrene comprising discrete particles of rubber, such as polybutadiene, therein (wherein the discrete particles of rubber are dispersed throughout the styrene polymer matrix) can be used in a variety of applications, including refrigerator liners, packaging applications, furniture, household appliances, and toys, among others. The conventional term for such rubber reinforced polymers is "high impact polystyrene" or "HIPS". The physical characteristics and mechanical properties of HIPS depend on many factors, including particle size and the amount of crosslinking within the rubber particles.

U.S. patent No.4777210 discloses a continuous flow process for producing high impact polystyrene and providing a reliable and reproducible process for various particle sizes. According to this process, a preinversion reactor is used to convert a solution of styrene, polystyrene, rubber (e.g., polybutadiene), and peroxide catalyst into a high impact polystyrene material.

U.S. patent No.4144204 discloses monovinylaromatic compounds modified with rubber wherein the amount of rubber dissolved in the monomer prior to polymerization is selected so that the content of soft components (gel phase) in the impact polymer is at least 28 wt% based on the weight of the impact polymer.

GB2153370 discloses HIPS materials prepared using a high molecular weight rubber material of at least 300,000 of said molecular mass, a viscosity greater than or equal to 140 cps; wherein the resulting HIPS contains 7 to 10% by weight of rubber and is polymerized in the presence of alpha methyl styrene dimer or a compound selected from n-dodecyl mercaptan, t-dodecyl mercaptan, diphenyl-1, 3-butadiene, or various other compounds or mixtures thereof. Furthermore, the process is carried out in the presence of cyclohexane and ethylbenzene in an amount equal to at least 7% by weight of the total composition. In addition, there is a need for additives that include monoglycerides of stearic acid from polyethylene waxes.

U.S. patent No.5084513 discloses a method of preparing a stable interpenetrating polymer blend network comprising preparing a gel of a poly (alkylene) polymer by dissolving the poly (alkylene) polymer in a mixture of one or more organic solvents and one or more vinyl aromatic monomers, followed by polymerizing the mixture.

Typically, HIPS-based materials are less expensive than copolymers of polyolefins and vinyl aromatic monomer polymers and have good impact resistance, but may be brittle and/or lack toughness, and are generally not foamable to provide articles having desirable physical properties obtained with copolymers of polyolefins and vinyl aromatic monomer polymers.

Thus, there is a need in the art for materials comprising an elastomeric or rubber type material and a monovinyl aromatic monomer polymer that are foamable, and that form articles having toughness and cushioning properties close to those obtainable using copolymers of polyolefins and vinylaromatic monomer polymers.

Disclosure of Invention

The present invention provides unexpanded resin beads having an average particle size of from 0.001mm to 10mm and containing a continuous phase and a particulate dispersed phase. The continuous phase includes one or more elastomeric polymers. The dispersed phase comprises one or more homopolymers and/or copolymers containing repeat units derived from polymerizing one or more aryl polymerizable monomers.

The present invention provides a method for producing the resin beads described above, the method comprising:

I) a dispersion of organic droplets forming an organic liquid phase within an aqueous phase that may be stationary or flowing, wherein the organic phase contains an organic solution comprising one or more elastomeric polymers dissolved in a monomer solution comprising one or more aryl polymerizable monomers, the organic droplets having an average diameter of about 0.001mm to about 10mm, and

II) polymerizing the monomer in the organic droplets under low shear flow regime.

The invention further provides a molded article comprising any of the above-described resin beads.

Drawings

Fig. 1A is a Transmission Electron Microscope (TEM) image of a resin bead according to the present invention.

Fig. 1B and 1C are Atomic Force Microscopy (AFM) images of resin beads according to the present invention.

Fig. 2 and 3 are Scanning Electron Microscope (SEM) images of expanded beads prepared according to the present invention.

Fig. 4A and 4B are AFM images of resin beads according to the present invention.

Fig. 5A, 5B, and 5C are AFM images of unfoamed resin beads according to the present invention.

FIG. 6 shows blowing agent retention for impregnated beads prepared according to the present invention.

FIG. 7 shows AFM images of unexpanded resin beads prepared according to the invention resulting from polymerization at different stirrer speeds.

FIG. 8 shows a TEM image of HIPS resin beads prepared according to the prior art.

Detailed Description

Other than in the operating examples, or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, and the like used in the specification and claims are to be understood as modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention, at the very least, and are not intended to limit the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

Further, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges therebetween, including the recited minimum value of 1 and the recited maximum value of 10; that is, the minimum value is equal to or greater than 1 and the maximum value is equal to or less than 10. Because the disclosed numerical ranges are continuous, they include every value between the minimum and maximum values. Unless specifically stated otherwise, the various numerical ranges specifically set forth in this application are approximations.

The terms "(meth) acrylic acid", "(meth) acrylate" and "(meth) acrylonitrile" as used herein are meant to include both acrylic and methacrylic acid derivatives, such as the corresponding alkyl esters (often referred to as acrylates) and (meth) acrylates, as well as acrylonitrile and (meth) acrylonitrile, which are encompassed by the terms "(meth) acrylate" and "(meth) acrylonitrile", respectively.

The term "polymer" as used herein includes, but is not limited to, homopolymers, copolymers, graft copolymers, and blends and combinations thereof.

Unless otherwise indicated, all molecular weight values were determined using Gel Permeation Chromatography (GPC) using appropriate polystyrene standards. Unless otherwise indicated, the molecular weight values referred to herein are weight average molecular weights (Mw).

The term "elastomeric polymer" as used herein refers to a natural or synthetic polymer, rubber or rubbery material, which has the ability to undergo deformation under the influence of a force and to recover its original shape once the force is removed.

The term "morphology" as used herein refers to microstructural features such as the size, shape, arrangement of chains and features of the regions occupied by the elastomeric polymer in the continuous phase and the homopolymer and/or copolymer in the dispersed phase and their spatial arrangement relative to each other.

As used herein, the term "crosslinked network morphology" refers to the morphology of microstructured beads wherein domains of elastomeric polymer within a continuous phase are arranged within a three-dimensional network of horizontal, vertical, circumferential, tangential lines, and/or within triangular fibrils of a network structure wherein a majority of the fibrils within the network are crosslinked and/or woven together with each other, wherein at least some of the fibrils are crosslinked by or at discrete particulate regions within a dispersed phase, the regions being present as discrete particles dispersed throughout the network structure.

The term "network" as used herein refers to any connected series of filaments that make up a network within a resin bead.

The phrase "morphology comprising filaments having a large aspect ratio, optionally at least partially crosslinked and/or connected by locally formed branches and/or interconnected network structures" as used herein refers to the morphology of microstructured beads wherein the elastomeric polymer within the continuous phase is present in the form of individual filamentous domains having a large aspect ratio, as a non-limiting example greater than 100, wherein optionally some, but not most, of the domains are crosslinked to each other, and the dispersed phase is present as discrete particulate domains dispersed and entangled throughout the filamentous domains of the continuous phase. This morphology differs from the crosslinked network morphology in that there are significantly fewer crosslinks and framework structures between the fibrillar regions of the continuous phase.

The terms "beads", "resin beads", "unexpanded resin beads" and "unexpanded particles" as used herein refer to resin beads having any of the above-described morphologies, which are substantially the same size and shape, and which are formed from the organic droplets only after polymerization of the monomers within the droplets is complete.

The terms "expanded resin beads" and "expanded particles" as used herein refer to resin beads and/or particles that are impregnated with a blowing agent, wherein at least some of the blowing agent is subsequently removed (by way of non-limiting example, heating and foaming, followed by evaporation and diffusion from the beads) in a manner such as to increase the volume, and thus reduce the bulk density, of the resin beads and/or particles.

In its broadest sense, the term "low shear flow pattern" refers to a process by which dispersed organic droplets maintain motion and flow within an aqueous continuous phase such that the shear stresses experienced by the droplets during their motion do not significantly deform or change the shape of the droplets. In particular embodiments, the term "low shear flow pattern" refers to the maintenance of motion and flow of dispersed organic droplets within an aqueous continuous phase such that the shear stress experienced by the droplets during droplet motion is sufficiently low that no phase inversion occurs within the organic phase. The expression "no phase inversion occurs within the organic phase" means that the resulting resin beads have a continuous phase comprising one or more elastomeric polymers and a dispersed phase comprising one or more homopolymers and/or copolymers comprising repeating units derived from the polymerization of one or more aryl polymerizable monomers and optionally one or more non-aryl monomers.

The term "crosslinked polymer" as used herein refers to two or more polymer chains (at the molecular level) that are linked to each other. A low degree of crosslinking (by way of non-limiting example, less than 5%) in the polymer composition is referred to herein as a branched polymer. A high degree of crosslinking (by way of non-limiting example, greater than 25%) within the polymer composition is referred to herein as a network structure.

The present invention relates to unexpanded resin beads which contain a continuous phase and a particulate dispersed phase.

The unexpanded resin beads can have any suitable shape, non-limiting examples of which are circular, oval, elliptical, and/or cylindrical cross-sectional shapes. In one embodiment of the invention, the shape of the beads is substantially bead-shaped (circular or oval in cross-section).

In one embodiment of the invention, the unexpanded resin beads have an aspect ratio of less than 10, in some cases less than 7, and in other cases less than 5.

The average particle size of the unexpanded resin beads can be at least 0.001. In some cases, at least 0.01, in other cases at least 0.05, and in some cases, at least 0.1 mm. Further, the unexpanded bead particle size can be up to 10, in some cases up to 9, in other cases up to 8, in some cases up to 7, in other cases up to 6, and in some cases up to 4 mm. The size of the unexpanded resin beads is determined based on the processing conditions and the desired properties of the expanded article produced using the unexpanded beads.

The average bead size can be determined by conventional mechanical separation methods, screening methods well known in the art, wherein a sample of beads is passed through a set of sieves having standard and reduced openings, so as to determine a sample mass fraction having a size corresponding to the openings of each sieve.

In an alternative method, a sample of beads may be captured by removing a sample of the beads from a given population of beads and analyzing the captured image using software known in the art that is capable of sizing the diameter of each bead within the image. Using a set of diameters obtained by any of the above methods, the mean diameter, standard deviation and sample size distribution of the sample can be calculated. The average size of the unexpanded resin beads can be any value or can range between any of the values recited above.

The resin beads of the present invention comprise a continuous phase comprising one or more elastomeric polymers. Any suitable elastomeric polymer may be used in the present invention. Suitable elastomeric polymers are those that facilitate the desired properties described below.

In embodiments of the present invention, suitable elastomeric polymers include homopolymers of butadiene or isoprene, and random, block, AB diblock or ABA triblock copolymers of conjugated dienes and aryl monomers and/or (meth) acrylonitrile, as well as random, alternating or block copolymers of ethylene and vinyl acetate, and combinations thereof.

The term "conjugated diolefin" as used herein refers to straight, branched or cyclic hydrocarbons containing from 4 to 32 carbon atoms and optionally a heteroatom selected from O, S or N, which contain two double bonds separated by a single bond within the structure, wherein the two double bonds are not part of an aromatic group.

In a particular embodiment of the invention, the elastomeric polymer comprises one or more block copolymers selected from: diblock and triblock copolymers of styrene-butadiene, styrene-butadiene-styrene, styrene-isoprene-styrene, partially hydrogenated styrene-isoprene-styrene, ethylene-vinyl acetate, and combinations thereof.

In another particular embodiment of the invention, suitable elastomeric polymers include copolymers of one or more conjugated dienes such as, but not limited to, butadiene, isoprene (i.e., 2-methyl-1, 3-butadiene), 3-butadiene, 2, 3-dimethyl-1, 3-butadiene, and 1, 3-pentadiene, one or more suitable unsaturated nitriles such as acrylonitrile or methacrylonitrile, and optionally one or more polar monomers such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid, alkyl esters of unsaturated carboxylic acids such as methyl acrylate and butyl acrylate; alkoxyalkyl esters of unsaturated carboxylic acids, such as methoxyethyl acrylate, ethoxyethyl acrylate, methoxyethyl acrylate, acrylamide, methacrylamide; n-substituted acrylamides, such as N-methylolacrylamide, N' -dimethylolacrylamide and N-ethoxymethylolacrylamide; n-substituted methacrylamides, such as N-methylolmethacrylamide, N' -dimethylolmethacrylamide, N-ethoxymethylmethacrylamide and vinyl chloride. These copolymers may also include repeat units from the polymerization of one or more aromatic vinyl monomers such as, but not limited to, styrene, ortho-, meta-, para-methylstyrene, dimethylstyrene, and ethylstyrene. These types of copolymers are known to those skilled in the art as "acrylonitrile-butadiene rubber" or "acrylonitrile-butadiene-styrene rubber" or collectively as "nitrile rubber".

In some embodiments of the present invention, the nitrile rubber may be partially hydrogenated in the presence of hydrogen, preferably with a suitable hydrogenation catalyst. Suitable hydrogenation catalysts are well known in the art and include, but are not limited to, rhodium and ruthenium catalysts. "partial hydrogenation" means selective hydrogenation in which carbon-carbon double bonds in the nitrile rubber are preferentially hydrogenated over carbon-nitrogen triple bonds in the nitrile groups, which remain predominantly inert. The phrase "remains predominantly inert" means that less than 10%, in some cases less than 5%, and in other cases less than 2% of the nitrile groups originally present in the nitrile rubber are hydrogenated. The hydrogenation of nitrile rubber can be controlled to produce polymers having varying degrees of hydrogenation. The degree of hydrogenation of the carbon-carbon double bond can be determined using IR or NMR spectroscopy, methods well known to those skilled in the art.

In an embodiment of the present invention, the use of "nitrile rubber" in the continuous phase within the resin beads of the present invention results in extended retention of the blowing agent, a non-limiting example of which is pentane, at room temperature and pressure.

In an embodiment of the invention, the elastomeric polymer has a weight average molecular weight of at least 6,000, in some cases at least 10,000, in other cases at least 15,000, in some cases at least 20,000, and in other cases at least 25,000. Further, the elastomeric polymer may have a weight average molecular weight of up to 500,000, in some cases up to 450,000, in other cases up to 400,000, in some cases up to 350,000, in other cases up to 300,000, and in particular cases up to 250,000. The weight average molecular weight of the elastomeric polymer used is determined based on the physical properties desired within the bead. The weight average molecular weight of the elastomeric polymer may be any value or range between any of the values recited above.

In embodiments of the invention, the elastomeric polymer may be crosslinked within the unexpanded resin beads. The elastomeric polymer may be crosslinked either during or after (but not before) homopolymerization or copolymerization of one or more aryl and/or non-aryl polymerizable monomers described below. In this embodiment, the elastomeric polymer is crosslinked, to the extent necessary to provide the desired physical properties. In one embodiment, the elastomeric polymer contains a low degree of crosslinking.

The resin beads of the present invention comprise a dispersed phase comprising one or more homopolymers and/or copolymers containing repeat units from polymerizing one or more aryl polymerizable monomers.

The term "aryl polymerizable monomer" or "aryl monomer" as used herein refers to a molecule containing a non-aromatic unsaturated hydrocarbon group comprising 2 to 12 carbon atoms and a group obtained by removing a hydrogen atom from an aromatic compound containing 6 to 24 carbon atoms.

In embodiments of the invention, the aryl monomer comprises one or more of styrene, p-methylstyrene, α -methylstyrene, t-butylstyrene, dimethylstyrene, and nuclear brominated or chlorinated derivatives and combinations thereof.

In another embodiment of the invention, the dispersed phase contains a copolymer of an aryl monomer and optionally one or more non-aryl monomers. Any suitable non-aryl monomer may be used in the present invention. Suitable non-aromatic comonomers include, but are not limited to, C of maleic anhydride, maleic acid, maleimide, fumaric acid, maleic acid₁-C₁₂Straight, branched or cyclic alkyl esters, C of fumaric acid₁-C₁₂Linear, branched or cyclic alkyl esters, itaconic acid, C of itaconic acid₁-C₁₂Linear, branched or cyclic alkyl esters, itaconic anhydride, ethylene, propylene, 1-butene, isobutene, 2-butene, diisobutylene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, 3-hexene, vinyl acetate, C of (meth) acrylic acid₁-C₁₂Linear, branched or cyclic alkyl esters, acrylonitrile, methacrylonitrile, di-or higher functional monomers, non-limiting examples of which are divinylbenzene and conjugated dienes, and combinations thereof.

In one embodiment of the invention, homopolymers and/or copolymers of aryl monomers within the unexpanded resin bead can be crosslinked. In this embodiment, the homopolymer and/or copolymer is crosslinked to the extent necessary to provide the desired physical properties. In one embodiment, the homopolymer and/or copolymer comprises a low level of crosslinking.

In one embodiment of the invention, the weight average molecular weight of the homopolymer and/or copolymer within the dispersed phase is at least 10,000, in some cases at least 15,000, in other cases at least 20,000, in some cases at least 25,000, in other cases at least 30,000, and in some cases at least 35,000, and may be at most 1,000,000, in some cases at most 750,000, in other cases at most 600,000, in some cases at most 500,000, and in other cases at most 250,000. The weight average molecular weight of the homopolymer and/or copolymer in the dispersed phase depends on the polymerization conditions used and the physical properties desired in the resulting beads. The molecular weight of the homopolymer and/or copolymer in the dispersed phase may be any value or may range between any of the values recited above.

Generally, "aryl monomers" or "non-aryl monomers" (also referred to herein simply as "monomers") are converted to homopolymers and/or copolymers to a significantly higher degree within the dispersed phase. As such, the amount of unreacted monomer within the resin beads can be less than 5, in some cases less than 4, and in other cases less than 2.5 weight percent based on the weight of the resin beads.

In one embodiment of the invention, at least some of the monomer is grafted to at least some of the elastomeric polymer within the continuous phase.

In another embodiment of the invention, a portion of the homopolymer and/or copolymer of the aryl monomer is present in the continuous phase. In this embodiment, the amount of homopolymer and/or copolymer present in the continuous phase is at least 0.01, in some cases at least 0.1, and in other cases at least 1, and may be up to 50, in some cases up to 40, in other cases up to 30, in some cases up to 20, in other cases up to 10, and in some situations up to 5 weight percent of the total amount of homopolymer and/or copolymer of the aryl monomer present in the resin beads. The amount of homopolymer and/or copolymer of aryl monomer present in the continuous phase depends on the type of processing used to prepare the resin beads. The amount of homopolymer and/or copolymer of aryl monomer in the continuous phase of the resin beads can be any value or can range between any of the values recited above.

In one embodiment of the invention, the resin beads may include a skin layer on substantially all of their outer surface. The skin layer may have a thickness of at least 0.1 microns, in some cases at least 0.25 microns, and in other cases at least 0.5 microns, in some cases at least 1 micron, in other cases at least 1.5 microns, and in some cases at least 2 microns. Additionally, the skin layer may be up to 7 microns thick, in some cases up to 6 microns thick, and in other cases up to 5 microns thick. The skin thickness is defined by the skin volume cited below. The thickness of the surface layer of the resin beads may be any value or may be a range between any of the values cited above.

The resin bead skin layer only occupies a portion of the resin bead volume. As such, the skin layer may comprise at least 1 volume percent, in some cases at least 2.5 volume percent, and in other cases at least 5 volume percent of the resin bead. Further, the skin layer may comprise up to 25 volume percent, in some cases up to 20 volume percent, in other cases up to 15 volume percent, and in some cases up to 10 volume percent of the resin bead. The volume of the resin beads constituting the surface layer of the resin beads may be any value or may be a range between any of the values cited above.

In one embodiment of the invention, the surface layer of the resin beads comprises the homopolymer and/or copolymer of the dispersed phase described above.

In one embodiment of the invention, the resin beads of the present invention do not melt or decompose when exposed to temperatures of 225 ℃, in some cases 200 ℃, and in other cases 175 ℃ for 10 minutes.

The unexpanded resin beads of the present invention can be prepared by the following steps:

A) forming a dispersion of organic droplets containing one or more elastomeric polymers dissolved in a monomer solution comprising one or more aryl polymerizable monomers, in an aqueous phase that may be stationary or flowing, and

B) within the low shear flow pattern, the monomers are polymerized in the dispersed organic droplets to form unfoamed polymer beads.

In one embodiment of the invention, a dispersion of organic droplets is formed by pressure atomizing the organic phase below the free surface of the aqueous phase, which may be stationary or flowing.

In another embodiment of the invention, a dispersion of organic droplets of an organic liquid phase is formed within an aqueous phase, which may be stationary or flowing, by applying mechanical agitation.

The term "aqueous phase" as used herein does not mean or require that the continuous phase in the dispersion contains water. As used herein, "aqueous phase" refers to the non-organic phase in the dispersion, which may include water and/or other polar and/or protic solvents, non-limiting examples of which are alcohols, glycols, and glycerol.

The density of the organic phase (i.e., organic droplets) may be ± 20% of the density of the aqueous phase.

In addition, the organic phase (i.e., organic droplets) may contain an organic solution comprising one or more of the above-described elastomeric polymers dissolved in a monomer solution containing one or more aryl polymerizable monomers as described above.

The dispersed droplets in the organic phase can comprise at least 0.01 volume percent, in some cases 0.1 volume percent, in other cases at least 1 volume percent, and in some cases at least 5 volume percent of the total volume of the organic and aqueous liquids. In addition, the dispersed droplets of organic phase may be present at a level of up to 60 volume percent, in some cases 55 volume percent, in other cases 50 volume percent, in some cases at least 45 volume percent, and in other cases at least 40 volume percent of the total volume of the organic and aqueous liquids. The dispersed droplets of organic phase may be present in the dispersion at any level or may be in a range between any of the values recited above.

The aqueous liquid or phase may comprise at least 40 volume percent, in some cases 45 volume percent, in other cases at least 50 volume percent, in some cases at least 55 volume percent, and in other cases at least 60 volume percent of the total volume of the organic and aqueous liquids. Additionally, the aqueous liquid or phase may be present at a level of up to 99.99 volume percent, in some cases 99.9 volume percent, in other cases 99 volume percent, and in some cases at least 95 volume percent of the total volume of the organic and aqueous liquids. The aqueous liquid or phase may be present in the dispersion at any level or may be in a range between any of the values recited above.

The organic phase may be contained in a tank or pipe or loop reactor from which it is fed into the dispersion tank or reactor.

The average diameter of the dispersed organic droplets within the dispersions of the present invention can be at least 0.001, in some cases at least 0.01, in other cases at least 0.1, and in some cases at least 1 mm. Furthermore, the average diameter of the dispersed organic droplets within the dispersions of the invention may be up to 10, in some cases up to 7.5, and in other cases up to 5 mm. The size of the dispersed organic droplets depends on the equipment used, the particular formulation used to prepare the dispersion, and the type of agitation used. The desired final bead size is used to identify the desired size of the dispersed organic droplets. The size distribution of the droplets can be assessed using one of the methods described above to estimate the size distribution of the polymerized beads, i.e., taking a sample from the population, taking a picture of the droplets, and analyzing the image in the picture using software known in the art that measures the size of the droplet diameter within the image. Using the diameters of the resulting set, the mean diameter of the sample, the standard deviation and sample size distribution can be calculated. In the particular case where dispersed droplets are obtained by the atomization method described herein, the size distribution of the droplets can also be estimated by recording the dispersion process with a video recorder and capturing images of the dispersed droplets recorded separately at different times during the atomization process. The size of the image can then be analyzed using software known in the art that can determine the diameter of the droplets displayed on the image. The diameters of the resulting droplet sets are used to calculate statistical parameters such as mean droplet diameter, standard deviation, and droplet size distribution. The size of the organic droplets dispersed in the dispersion of the invention may be any value or may range between any of the values recited above.

In the present invention, dispersed organic droplets are polymerized in a low shear flow pattern. In other words, only a minimal amount of agitation energy is imparted to the dispersion in order to minimize the shear stress experienced by the droplets during their movement. In this way, mixing within the droplet and any distortion or change in droplet shape will be minimal. This process is characterized in that in the process of the invention the dispersed droplets of the organic phase are allowed to act as a mini-bulk reactor, resulting in resin beads having the desired morphology, wherein the continuous phase contains the elastomeric polymer and the dispersed phase contains the homopolymer and/or copolymer of one or more aryl polymerizable monomers.

In contrast, known in the art (see, e.g., Freegard G.F., J.of applied Polymer Science, vol 15, No.7, 1971, pp 1657-1663, production of Rubber modified polystyrene, importance of II shearing in Phase inversion), Keskula H., Plastics and Rubber. materials and polymers. Vol.4, 1979, pp 66-71, factor affecting Rubber Phase morphology in polystyrene, Keskula H., Plastics and Rubber. materials and polymers (factor affecting Rubber Phase morphology in polystyrene), Keskula H., polystyrene and Rubber. materials and polymers, polystyrene, polybutadiene, polystyrene, j.of Applied Polymer Science, vol.92, No.3, 5.5.2004, p.1397-: effect of Initiator Type and copolymerization considerations on particle Morphology (bulk polymerization of styrene in the presence of polybutadiene: Effect of Initiator Type and Prepolymerization Conditions on particle Morphology); molau G.E., Keskula H., J.Polymer Science, vol.4, 1966, p.1595-1607, heterogenous copolymer system.IV.Mechanism of rubber particle formation in rubber modified vinyl polymers; riess G., Gaill P., Preparation of rubber-modified polystyrene: nonfluence of thermal conditions on phase inversion and morphology, polymerization engineering: influence of reaction engineering on polymer properties (preparation of rubber-modified polystyrene: influence of reaction conditions on phase inversion and morphology, polymer reaction engineering: influence of reaction engineering on polymer properties), edited by Reichert and Geisekler, Munich, 1983; eastmond G.C., Phillips D.G., Colloid and polymer Science, vol 262, No.8, 1984, p. 627-634, On the Form and Formation of Rubber Particles in impact polystyrene and synthetic materials (shape and Formation of Rubber Particles within impact polystyrene and Their Relationship to Natural and synthetic materials)) during polymerization of a styrene/elastomer organic phase, high levels of shear and turbulence are produced using intensive mixing, which promotes phase inversion and provides a resin morphology that is opposite to the inventive morphology described above. Thus, polymerization under high shear and turbulence can provide a morphology in which the elastomeric polymer forms discrete inclusions (occlusions) within a continuous phase that includes homopolymers and/or copolymers of one or more aryl polymerizable monomers. For example, standard High Impact Polystyrene (HIPS) resin beads contain discrete particles of elastomeric polymer dispersed throughout a continuous styrenic polymer matrix. The preparation of HIPS involves vigorous agitation during prepolymerization of the dissolved elastomer component containing styrene, followed by a process to disperse and further polymerize the styrene monomer. The morphology of the resulting HIPS resin is quite the opposite of that provided by the present invention.

Additionally, while bulk polymerization processes (e.g., in situ polymerization processes without mixing or agitation) exist that can provide bulk materials containing a continuous phase comprising an elastomeric polymer and a dispersed phase comprising homopolymers and/or copolymers of aryl-containing polymerizable monomers, the prior art processes do not provide for the preparation of resin beads having such morphology.

The inventors have surprisingly found that when dispersed organic droplets are polymerised in a low shear flow regime as described above, resin beads are formed having a morphology as described above. That is, the resin beads of the present invention have a morphology in which the continuous phase contains an elastomeric polymer and the dispersed phase contains homopolymers and/or copolymers of one or more aryl polymerizable monomers. The exact morphological properties can be influenced by the type of agitation and the energy input provided by the method used to provide the low shear flow pattern.

Generally, a crosslinked network morphology exists under very low shear and/or energy input conditions during polymerization. Under conditions of low shear flow patterns which provide greater shear and/or energy input, a filament (thread) morphology having a large aspect ratio is present within the resin bead, wherein the filaments are optionally at least partially crosslinked and/or connected by means of locally formed branches and/or interconnected networks.

In the present invention, the organic liquid phase can have a shear viscosity of at least 0.1 centipoise, in some cases at least 10 centipoise, in other cases at least 50 centipoise, and in some cases at least 100 centipoise (cp), and can be up to 10,000 centipoise, in some cases up to 8,000 centipoise, in other cases up to 6,000 centipoise, in some cases up to 4,500 centipoise, and in other cases up to 2,500 centipoise, measured at ambient temperature and pressure. The viscosity of the organic liquid phase may be any of the values recited above or ranges between numerical resins.

The organic phase contains an organic solution comprising an elastomeric polymer dissolved in a monomer solution comprising one or more aryl polymerizable monomers. As such, the elastomeric polymer is present in the organic solution at a level of at least 1 wt%, in some cases at least 5 wt%, and in other cases at least 10 wt% of the organic solution. In addition, the elastomeric polymer may be present in up to 50 wt%, in some cases up to 40 wt%, and in other cases up to 30 wt% of the organic solution. The exact amount of elastomeric polymer used depends on the desired properties of the resulting resin beads and/or the expanded resin beads prepared therefrom. The amount of elastomeric polymer in the organic solution may be any amount or may be in a range between any of the amounts recited above.

In addition, the monomer solution can be present in the organic solution at a level of at least 50 wt%, in some cases at least 60 wt%, and in other cases at least 70 wt% of the organic solution. In addition, the elastomeric polymer may be present at up to 99 wt%, in some cases up to 95 wt%, and in other cases up to 90 wt% of the organic solution. The exact amount and composition of the monomer solution used depends on the desired properties of the resulting resin beads and/or expanded resin beads prepared therefrom. The amount of monomer solution in the organic solution may be any amount or may be in a range between any of the amounts recited above.

When a homopolymer is desired in the dispersed phase of the resin beads of the present invention, the monomer solution contains only one type of aryl monomer. When a copolymer is desired in the dispersed phase of the resin beads, the aryl monomer can be included in the monomer solution in an amount of at least 25 weight percent, in some cases at least 35 weight percent, and in other cases at least 40 weight percent of the monomer solution. In addition, the monomer solution can include up to 99 wt.%, in some cases up to 95 wt.%, in other cases up to 90 wt.%, in some situations up to 80 wt.%, and in other situations up to 75 wt.% of the aryl monomer. The exact amount and type of aryl monomer used in the monomer solution depends on the desired properties of the resulting resin beads and/or expanded resin beads prepared therefrom. The amount of aryl monomer in the monomer solution may be any amount or may be in a range between any of the amounts recited above.

Further, when a copolymer is desired in the dispersed phase of the resin beads, non-aromatic monomers can be included in the monomer solution in an amount of at least 1 weight percent, in some cases at least 5 weight percent, in other cases at least 10 weight percent, in some cases at least 20 weight percent, and in other cases at least 25 weight percent of the monomer solution. In addition, up to 75 wt%, in some cases up to 65 wt%, and in other cases up to 55 wt% of the monomer solution can be included. The exact amount and type of non-aromatic monomer used in the monomer solution depends on the desired properties of the resulting resin beads and/or expanded resin beads prepared therefrom. The amount of non-aryl monomer in the monomer solution may be any amount or may be in a range between any of the amounts recited above.

The aqueous phase (suspension medium) may be selected to enhance the production of uniform droplets of the organic liquid phase. The viscosity of the aqueous phase may be at least 1 centipoise, in some cases at least 2 centipoise, and in other cases at least 5 centipoise, and can be up to 400 centipoise, in some cases up to 250 centipoise, and in other cases up to 100 centipoise. The viscosity of the aqueous phase may be any amount or may be in a range between any of the amounts recited above.

In addition, the aqueous phase may have a density sufficiently different from the density of the organic liquid phase. In one embodiment of the invention, the density of the aqueous phase is greater than or equal to the density of the droplets in the dispersed organic liquid, wherein the density of the aqueous phase is from about 1.02 to about 1.2 times the density of the droplets in the dispersed organic liquid. If the dispersed organic liquid is further polymerized, the density of the dispersed droplets or particles can be altered and typically increased. Alternatively, if the droplets of the dispersed organic liquid are descending through the suspension medium, the density of the aqueous phase may be from about 0.98 to about 0.80 times the density of the droplets in the dispersed organic liquid.

The aqueous phase is suitably inert and immiscible with the organic liquid phase. As used herein, the term "immiscible" means that less than about 1 weight percent of the organic liquid phase is miscible (or soluble) in the suspension (i.e., the aqueous phase is not solvated by more than about 1 weight percent of the organic liquid phase). In embodiments of the invention, less than about 0.1 wt% of the organic liquid phase is miscible in the aqueous phase.

The aqueous phase contains water and may be a mixture of water and one or more water-miscible organic liquids, such as lower alkyl alcohols, e.g., methanol or butanol. An organic liquid immiscible with the organic liquid phase and which may or may not be immiscible with the aqueous phase, and a salt may be added to alter (increase) the density of the aqueous phase.

In one embodiment of the invention, the aqueous phase contains one or more surfactants or suspending aids. However, it is also possible to add suspension aids to the organic liquid phase. Suitable suspension aids are those materials which are capable of forming a monomer phase within the desired size of the bead-like droplets and which prevent coalescence or secondary dispersion (breakup) of the droplets so formed.

Suspension stabilizers are well known in the art and include organic stabilizers such as poly (vinyl alcohol), typically at least 70%, in many cases up to 95%, and in some cases no more than 98% hydrolyzed and having a weight average molecular weight of about 30,000-300,000, typically 75,000-300,000; carboxymethyl cellulose, typically having a weight average molecular weight of at most 500,000; gelatin; agar; polyvinylpyrrolidone; polyacrylamide; a cationic polymer; non-limiting examples include dimethyldiallylammonium chloride, (meth) acrylamidopropyltrimethylammonium chloride, homopolymers and copolymers of (meth) acryloyloxyethyltrimethylammonium chloride, poly (meth) acryloyloxyethyltrimethylammonium methylsulfate, and combinations thereof; inorganic stabilizers such as alumina, bentonite, magnesium silicate; surfactants such as sodium dodecylbenzene sulfonate; or a phosphate salt, such as tricalcium phosphate, disodium hydrogen phosphate, optionally in combination with any of the stabilizing compounds mentioned previously. In some cases, the effect of the stabilizer may be enhanced by the use of an extender. The availability of any particular stabilizer or combination of stabilizers and/or extenders can be readily determined by one skilled in the art. The amount of stabilizer used may vary from 0 to 10 wt%, in some cases from 0.01 wt% to 10 wt%, in other cases from 0.1 wt% to 8 wt%, and in particular cases from 0.1 to 5 wt%, based on the weight of the aqueous phase, and depending on the viscosity of the organic liquid phase (e.g., higher viscosity liquids require more stabilizer). If suspension aids or stabilizers are added to the organic liquid phase, amounts sufficient to provide the same amount of stabilizer may be added.

The suspension stabilizer may form a surface between the droplets of the aqueous and organic liquid phases having an interfacial tension of no less than 3 dynes/cm, in some cases no less than 8 dynes/cm, and in other cases greater than or equal to 12 dynes/cm when measured at ambient pressure and temperature according to ASTM D-971.

According to this embodiment of the invention, one or more members selected from the group consisting of initiators, antistatic agents or additives, flame retardants, pigments (colorants) or dyes, fillers, stabilizers (UV and/or heat and light stabilizers), coating agents, plasticizers, chain transfer agents, crosslinking agents, nucleating agents and insecticides and or rodenticides may be added to either the organic liquid phase, the aqueous phase or both in an amount of 0 to 10 wt%, in some cases 0.1 to 10 wt%, in other cases 0.05 to 8 wt%, and in particular cases 0.1 to 5 wt% of the organic liquid phase.

Suitable initiators include, but are not limited to, organic peroxy compounds, such as peroxides, peroxycarbonates, and peresters. A typical example of such peroxy compounds is C_6-20Acyl peroxides, e.g. decanoyl peroxide, benzoyl peroxide, octanoyl peroxide, stearyl peroxide, peresters, e.g. tert-butyl perbenzoate, tert-butyl peracetate, tert-butyl perisobutyrate, tert-butyl peroxy-2-ethylhexyl carbonate, carboperoxoic acid, (1, 1-dimethylpropyl) (2-ethylhexyl ester), hydroperoxides and dihydrocarbyl peroxides, e.g. containing C_3-10Those of the hydrocarbyl moieties include diisopropylbenzene hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, and combinations thereof.

Other initiators than peroxy compounds are also possible, for example nitrites, such as 2, 2' -azobisisobutyronitrile. The amount of initiator used is suitably from 0.01 to 1% by weight, based on the amount of organic liquid phase.

The aqueous or organic liquid phase may also contain antistatic additives or agents; a flame retardant; pigments (colorants) or dyes; filler material, plasticizers, such as white oil. The aqueous or organic liquid phase may also contain a coating compound, which typically includes a polysiloxane; metal or glycerol carboxylates, suitable carboxylates including glycerol monostearate, glycerol distearate, glycerol tristearate, zinc stearate, calcium stearate and magnesium stearate; and mixtures thereof. Examples of such compositions are disclosed in GB1409285 and us patent No. 4781983. The coating composition can be applied to the particles by dry coating, or by slurry or solution in a readily evaporable liquid in various types of batch and continuous mixing devices. This coating helps prevent the resulting foamed cell particles from forming aggregates during the pre-foaming stage, thus helping to improve the quality of any resulting molded foamed article.

The aqueous or organic liquid phase or both may contain various additives, such as chain transfer agents, suitable examples include C_2-15Alkyl mercaptans such as n-dodecyl mercaptan, t-butyl mercaptan and n-butyl mercaptan, and other reagents such as pentaphenyl ethane, and dimers of alpha-methylstyrene. The organic or aqueous phase may contain crosslinking agents, such as butadiene and divinylbenzene, and nucleating agents, such as polyolefin waxes. A non-limiting example of a polyolefin wax is polyethylene wax, which has a weight average molecular weight of 500-5,000. The wax may be used in an amount of 0.05 to 1.0 wt% based on the amount (weight) of the organic liquid phase. The aqueous or organic liquid phase may also contain 0.1 to 0.5 wt% talc, organic bromide-containing compounds, and polar agents, which may include alkyl sulfosuccinates, sorbitol-C as described in WO98/01489₈-C₂₀Carboxylic acid esters and C₈-C₂₀Alkyl xylene sulfonate. Nucleating agents can be incorporated in either the aqueous or organic liquid phase or both, and are particularly useful because if the invention is used to form a foamable polymer, it isThey tend to improve cell formation.

Suitable insecticides are disclosed in U.S. patent nos. 6153307 and 6080796. These include boron compounds (borates and boric acid). Some useful insecticides can be selected from the group consisting of 1- [ (6-chloro-3-pyridyl) methyl]-4, 5-dihydro-N-nitro-1H-imidazol-2-amine and 3- (2, 2-dichloroethylene) -2, 2-dimethylcyclopropanecarboxylic acid cyano (3-phenoxyphenyl) methyl ester (cypermethrin), active ingredients within Demon TC such as sold by Zeneca; 3- (2, 2-dichloroethylene) -2, 2-dimethylcyclopropanecarboxylic acid (3-phenoxyphenyl) methyl ester (Heldis), active ingredients within, for example, Dragnet FT and Torpedo sold by Zeneca; and 1- [ (6-chloro-3-pyridyl) methyl group]4, 5-dihydro-N-nitro-1H-imidazol-2-amine (imidacloprid), PREMISE sold, for example, by BayerThe active ingredients in (a).

In one embodiment, the organic liquid phase contains from 0 to about 40, in some cases from 3 to 20, and in other cases from 8 to 15 weight percent water to produce polymer particles having from 4 to 16 percent water, as taught in U.S. patent No. 6176439. In another embodiment, the organic liquid phase may contain from 1 to 20 weight percent, and in some cases, from 3 to 15 weight percent water, as taught in column 3, lines 19 to 26 of U.S. Pat. No.6160027, discussed above.

One of the methods used for dispersing the organic phase according to the invention is to use a pressure atomizer, especially when single-size droplets are desired. Pressure atomizers are typically circular pores and have a diameter of 0.01 to 2mm, in some cases 0.1 to 1mm, in other cases 0.1 to 0.8mm, in some cases 0.1 to 0.5mm, and in other cases 0.1 to 0.4mm, and a length of less than about 5 mm. Generally, the length to diameter (L/D) ratio of the atomizer ranges from about 0.2 to about 10, and in some cases from 0.2 to 5.

In one embodiment of the invention, the organic liquid phase may be injected into the aqueous phase and dispersed into droplets using an atomizer or header plate (e.g., a plate having a plurality of apertures therein of the size described above) containing an atomizer. The number of atomizers that can be accommodated in the header plate depends on the size of the plate and the size and space of the atomizers. The header plate may contain a plurality of atomizers, provided that their operation does not interfere with one another. Care should be taken to minimize interaction between the atomized streams, particularly in the vicinity of the atomizer outlet. It is desirable to space the individual atomizers far enough apart to minimize interaction between adjacent streams from adjacent atomizers. Excessive interaction between adjacent streams can cause deformation of the atomized droplets due to their direct collision, or can cause premature dispersion of the streams, resulting in a broad size distribution of the atomized droplets. When adjacent streams of the organic liquid phase are separated by a distance of at least 5 times, and in some cases 10 times, the average diameter of the atomized droplets, the interaction between adjacent streams in the organic liquid phase is not significant.

The atomizers may be evenly spaced in a square or other pattern across the entire surface of the header plate.

In order to reduce the viscosity of the organic liquid phase and improve the quality of the atomization, in one embodiment of the invention the organic liquid phase to be atomized is heated at one or more locations selected from the group consisting of a reservoir for the organic liquid phase, a transfer line from the reservoir to the inlet of the atomizer, and the atomizer.

The organic liquid phase contained within the storage tank and/or transfer line can be heated from ambient temperature (20 ℃) to below the decomposition point of the liquid components (e.g., the decomposition point of the polymer within the liquid to be atomized). In one embodiment of the invention, the temperature may be the set temperature of the process if, for example, the atomized liquid polymerizes at a temperature of at most about 135 ℃. The temperature range may be at least about 30 ℃, in some cases no less than 45 ℃, and in other cases no less than 50 ℃. Generally, a temperature of the organic liquid of about 50 ℃ to 95 ℃ at the atomizer inlet is useful and sufficient for the desired dispersion.

The atomizer may also be heated to a similar temperature. For example, the outlet portion of the atomizer containing the apertured plate may be heated with a circulating liquid, such as water or another heated transfer liquid, or may preferably be heated by other means, such as an electric heater.

The organic liquid phase may be added to the aqueous phase at a rate of from 0.05 to 15, in some cases from 0.1 to 12, and in other cases from 0.5 to 10ml/s per atomizer. The liquid flows through the atomizer below the free surface of the aqueous phase and forms a liquid stream within the aqueous phase and this stream is dispersed as droplets within the aqueous phase downstream from the atomizer outlet. The average size of the atomized droplets is determined by the geometry of the atomizer, the exit velocity of the organic liquid from the atomizer, and the properties of both the aqueous and organic liquid phases. A higher viscosity suspension medium and/or an atomized organic phase may be used in preparing larger droplets of the atomized organic liquid phase.

In one embodiment of the invention, the average size of the droplets may be about 0.1 to 10mm, in some cases 0.1 to 5mm, and in other cases 0.3 to 3 mm. For relatively uniform atomized droplets, the standard deviation of the size distribution is typically less than about 10%, and in many cases less than 8%, of the mean droplet diameter of the atomized liquid. By way of non-limiting example, for a droplet size of about 0.3-5mm, the standard deviation of the average droplet size can be about 0.03-0.35mm (e.g., no greater than 8% of the average droplet diameter). Typically, the average droplet diameter is significantly larger than the diameter of the atomizer.

The organic liquid phase is forced under pressure through an atomizer. Typically, the pressure is no greater than 100bar, and can be 3 to 100bar, in some cases 3 to 80, and in other cases 5 to 60 bar. The pressure energy of the atomized liquid in the atomizer is converted into the kinetic energy of the stream. This kinetic energy further causes the stream to disintegrate as it interacts with the orifice outlet of the atomizer and with the surrounding water phase. This interaction creates a disturbance (disturbance) that either breaks the stream into droplets at the atomizer outlet or the disturbance expands downstream within the stream and breaks the stream into droplets at a distance further away from the atomizer outlet. In one embodiment of the invention, the pressure of the flowing organic liquid phase to be atomized is subjected to continuous or intermittent pulsations of less than 20%, in some cases from 1 to 10%, and in other cases from 3 to 10% of the static pressure of the atomizing liquid upstream of the atomizer inlet. The frequency of the pulsation depends, inter alia, on the viscosity of the organic liquid phase and may range from 1 to 500, in some cases less than 200Hz, and in other cases less than 150 Hz. The imposed pressure pulsation enhances and simplifies the initial disturbance of the stream by interaction with the atomizer in such a way as to affect the droplet size distribution and generally make it more uniform. By adjusting the frequency and amplitude of the imposed pressure pulsations, a binary size or prescribed (atomized) distribution of atomized droplets can be produced. In the case of atomization of relatively viscous non-newtonian liquids, pressure pulsations are imposed as the primary mechanism/source of stream breakup (droplet formation). See, by way of non-limiting example, U.S. patent No.6747107, the relevant portions of which are incorporated herein by reference.

In one embodiment of the invention, the atomization may occur directly within the reactor, below the free surface of the aqueous phase, or may occur within a reservoir for subsequent transfer into the reactor. The atomized droplets should be maintained under conditions of shear and turbulence that will minimize droplet interaction and provide low momentum movement of the droplets in order to reduce the likelihood of droplet agglomeration or secondary breakup. Generally, such conditions should require a flow pattern within the aqueous phase with low, preferably relatively uniform shear, and low levels of controlled turbulence. Advantageously, the aqueous phase may undergo laminar motion which may be substantially uniform through the volume of the aqueous phase, as opposed to regions of local laminar motion which may generate low velocity vortices.

Such conditions are particularly important when the atomized droplets are subsequently polymerized, and the initial size distribution should either be maintained during the process or modified (decreased) in a controlled manner, resulting in the desired final size distribution of the bead product.

During polymerization, the dispersed droplets or solid particles desirably remain immersed below the free surface of the aqueous phase and substantially uniformly distributed within the aqueous phase in a manner that minimizes droplet-to-droplet interactions (e.g., particle or droplet collisions) and provides other requirements, such as adequate heat transfer.

By way of non-limiting example, the very low shear conditions described above are provided using the polymerization process disclosed in U.S. Pat. No.6610798, the relevant portions of which are incorporated herein by reference. As such, the low shear flow pattern is a controlled, low turbulence flow pattern created without mechanical agitation by continuously or periodically injecting one or more gas streams inert to and immiscible with the contents of the reactor into selected portions of the reactor at a gauge pressure of up to 15 bar.

One way to maintain this condition is to create a low shear flow pattern in the aqueous phase contained in the vessel with a controlled low turbulence level without mechanical agitation, which involves continuously or periodically injecting a stream of a fluid immiscible with and inert to the contents of the vessel and having a density lower than that of the contents of the reactor into a selected portion of the vessel, and recovering this fluid above the free surface of the aqueous phase, and in many cases reinjecting it back into the vessel. In one embodiment of the invention, the injected fluid is an inert gas that is insoluble in the aqueous or organic phase.

If it is desired to maximize the initial droplet size distribution during processing, the dispersed droplets can be uniformly distributed within the volume of the aqueous phase, exposed to low shear and maintained in laminar flow motion within the aqueous phase.

Optionally, the initial droplet size distribution may be modified so as to become more uniform and/or slightly lower in average diameter. In this embodiment, a percentage of the largest droplets within the colony (e.g., up to 15% of the largest droplets) may be broken down in a controlled manner by exposure to a low turbulence, low shear flow pattern within the aqueous phase.

In a further embodiment, the overall droplet size distribution can be reduced by causing a secondary break-up of a majority (e.g., at least 85%) of the droplets within the aqueous phase.

In one embodiment of the invention, the desired flow pattern may be created within the vessel by injecting one or more fluid streams having a density significantly lower than that of the dispersed liquid droplets in the aqueous and organic liquid phases, inert to and immiscible with the contents of the reactor, into selected locations, which in many cases comprise the bottom of the reactor or vessel volume. Depending on the density to volume ratio of the dispersed droplets in the aqueous and organic liquid phases, the fluid can be injected continuously or periodically at a controlled injection frequency (to avoid the dispersed droplets in the organic liquid phase sinking to the bottom of the reactor or rising onto the free surface of the aqueous phase).

In one embodiment of the invention, the fluid of sufficiently low density suitable for injection is a gas. The gas may be selected from inert gases that are insoluble in the aqueous phase, in many cases air and nitrogen. The gas can be injected into the aqueous phase at a gauge pressure of up to 15bar (a non-limiting example being a gauge pressure of 0.001-15 bar). The gauge pressure referred to herein is the difference between the absolute static gas pressure upstream of the gas injection port and the combined (sum) of the static pressure of the aqueous phase in the vessel and the absolute ambient static pressure above the free surface of the aqueous phase.

If the gas is selected as the fluid to be injected into the reactor, two injection modes are possible, see, for example, U.S. patent No.6727328, the relevant portions of which are incorporated herein by reference.

The first injection mode is to inject gas through the injection port at low pressure (in many cases less than 3bar gauge) so that the injected gas forms a stream of bubbles in the aqueous phase downstream of the injection port, wherein the average bubble size is significantly greater (in many cases at least 2 times, in other cases at least 5 times) than the average diameter of the dispersed liquid droplets in the organic liquid phase. Due to the balance of buoyancy, gravity and drag forces, the stream of bubbles rises to the free surface of the water phase where the gas can be recovered and, in many cases, recycled back into the vessel. As the stream of bubbles flows toward the free surface, it interacts with the aqueous phase and its momentum creates a flow pattern within the reactor, thereby forcing the aqueous phase to change into an annular low shear, low turbulence motion, creating a recirculation zone within the reactor. The velocity gradient and geometry of the resulting region can be controlled by the geometry (number, diameter and location) of the gas injection ports and by the gas flow rate. The droplets of dispersed particles or organic liquid phase in the circulation zone flow and are subjected to sufficiently low shear velocities and turbulence so that they remain immersed without excessive interaction, their momentum is sufficiently low, and as a result, even when they collide, the probability of aggregation or fragmentation due to such low impact collisions remains very low. This particle movement can be maintained for particles lighter than the aqueous phase and for particles heavier than the aqueous phase, provided that the difference in density between the dispersed droplets in the organic liquid phase and the aqueous phase is typically in the range of ± 20% (i.e. the ratio of the density of the dispersed droplets in the organic liquid phase to the density of the aqueous phase can be in the range of 0.8: 1 to 1.2: 1).

In one embodiment of the invention, the diameter of the injection port is significantly (i.e. at least 2 times) larger than the average diameter of the dispersed droplets in the organic liquid phase. The location of the gas injection port is selected based on the concentration of dispersed droplets in the organic liquid phase and the density of the dispersed droplets/particles. Typically, the injection port is located in the reactor below the layer of dispersed droplets in the organic liquid phase contained in the aqueous phase. Thus, in order to impregnate dispersed droplets/particles in an organic liquid phase having a density lower than the density of the aqueous phase and prevent floating movement thereof, the injection port may be located below the layer of floating particles/droplets and may be located within the reactor wall or bottom.

To increase the weight of the particles/droplets above the water phase and to prevent them from settling on the bottom of the vessel, some injection ports may be located in the bottom of the reactor. In this case, it may be desirable to modify the reactor bottom geometry, for example to an inverted cone or a part cone (frustoconical) type. In one embodiment of the invention, the bottom of the reactor is an inverted cone, with one injection port located at the top of the cone and a plurality of other ports located at the tangent to the cross-section of the cone at a level corresponding to the height of the cone.

Both types of port arrangements (i.e. in the reactor wall and at the bottom of the reactor) can be used in combination if the density of the dispersed droplets/particles of the organic liquid phase changes during the process, for example when the monomer polymerizes in the dispersed droplets of the organic liquid phase. Typical port arrangement positions are those in which the main port is located at the bottom of the reactor, and optionally the lower portion of the reactor wall (e.g., the bottom half, preferably the bottom quarter) includes some auxiliary ports.

The gas injection velocity determines the degree of turbulence of the flow pattern generated within the reactor. The gas injection rate depends on a number of factors including the volume to density ratio of the dispersed droplets in the organic liquid phase and the aqueous phase; the viscosity of the aqueous phase; the geometry of the container; and the size of the droplets/particles in the dispersed organic liquid phase. One skilled in the art can determine the appropriate gas injection rate by repeated experimentation.

Generally, to prevent the initial size distribution of dispersed droplets/particles in the organic liquid phase, the degree of turbulence of the flowing aqueous phase within the reactor is at its maximum low enough so that the movement of the reactor contents is laminar.

If desired, the starting particle or droplet size distribution in the organic liquid phase can also be modified to some extent during processing by suitably adjusting the gas flow rate. While it is not possible to increase the average droplet/particle size by controlled agglomeration of droplets/particles, in some cases only the largest droplet/particle breakup may be caused by increasing the gas injection velocity, decreasing its size or improving towards a more uniform distribution to cause only the largest droplet/particle breakup in the population (e.g., 15% of the largest particles). The degree of turbulence is increased by controlling within the flow pattern created by the bubbles, rather than causing breakup by particle or droplet interactions (e.g., collisions).

In a further embodiment of the invention, the average droplet/particle size of the dispersed organic liquid phase may be significantly reduced by causing the droplets in the majority (e.g., at least 85%) of the dispersed organic liquid phase to break up. In this embodiment, the droplet breakup is caused by applying a higher gas injection velocity, creating a flow pattern with a higher degree of shear and turbulence within the aqueous phase.

If left standing without the inventive processing described herein, a second gas injection mode may be employed in a process in which dispersed droplets/particles of the organic liquid phase to be distributed and suspended have a density lower than that of the aqueous phase and flow in the direction of the free surface and are agglomerated there within a layer. In this mode, gas is injected at high pressure, typically greater than and equal to 5bar (gauge) to produce a large number of very small bubbles distributed in the volume of the aqueous phase. The diameter of the injection port is at least one order of magnitude, and in many cases several orders of magnitude, smaller than the average diameter of the dispersed droplets/particles in the organic liquid phase. The concentration of the gas bubbles should be high enough so that the effective density of the aqueous phase drops to a value below the density of the dispersed organic liquid phase and as a result dispersed droplets/particles in the organic liquid phase start to sink. In this mode, periodic gas injection is particularly useful for generating an "oscillating" motion of the particles or droplets, since during injection the particles or droplets sink and then when the gas supply is cut off and the bubbles flow out through the free surface of the aqueous phase, leaving the aqueous phase, the particles rise from the bottom of the vessel or reactor and float again towards the free surface. The next gas injection should take place before the droplets/particles in the dispersed organic liquid phase reach the free surface of the aqueous phase. The mechanism responsible for the small bubble size is mainly the turbulence of the gas stream. Typically at high velocities, the bubbles rise towards the free surface, their residence time in the aqueous phase being brief, but the flow pattern created in the aqueous phase can be at a much higher degree of turbulence than in the first injection mode. Therefore, care should be taken, if necessary, not to break up floating particles or droplets. In this injection mode, the higher viscosity of the aqueous phase (typically greater than or equal to 10cps) is advantageous because it slows down the gas bubbles, thereby increasing their residence time in the aqueous phase and reducing the overall degree of turbulence in the vessel.

In another embodiment of the invention, the monomers within the dispersed droplets described above may be polymerized while being subjected to low shear conditions applied or generated by using mechanical agitation. Any suitable mechanical stirrer may be used in the present invention, provided that its energy input is low enough to minimize any droplet-to-droplet interaction and provide sufficiently low momentum even when the droplets do collide, the likelihood of aggregation or fragmentation resulting from such low impact collisions remaining very low.

In particular embodiments of the invention, mechanical agitation may be provided by a turbine (impeller) or, in some cases, by more than one turbine, one or more magnetically driven agitators, and/or other mechanically driven agitators. Further, for this embodiment, and not meant to be limiting, two particular low shear situations may be encountered.

In the first case, a turbine or mechanically driven agitator interacts with the aqueous phase in a continuous manner. The turbine or agitator provides momentum which will create a flow pattern within the reactor that forces the aqueous phase to change into an annular low shear, low turbulence motion, thereby creating a circulation zone within the reactor. The velocity gradient and the geometry of the resulting zone can be controlled by the position, direction of rotation and/or geometry of the turbine or agitator. The particular location and geometry of the turbine and/or agitator is selected based on the concentration of dispersed droplets and the density of the dispersed droplets/particles in the organic liquid phase. The flow pattern generated may be radial or axial and may include single or multiple circulation loops within the reactor volume. The circulation flow type keeps the dispersed droplets in continuous motion. The flow pattern also prevents the droplets from collecting on the free surface of the reactor when the droplet density is lower than the density of the aqueous phase, and/or prevents the droplets/particles from settling at the bottom of the reactor when the droplet/particle density is higher than the continuous aqueous phase density. The dispersed particles or droplets of the organic liquid phase flow in the circulation zone and are subjected to sufficiently low shear velocities and turbulence so that they remain immersed without excessive interaction, their momentum being sufficiently low, so that even when they collide, the probability of aggregation or fragmentation resulting from such low impact collisions remains very low. This particle movement can be maintained for particles lighter than the aqueous phase and for particles heavier than the aqueous phase, provided that the difference in density between the dispersed droplets in the organic liquid phase and the aqueous phase is generally within the range of ± 20% (i.e. the ratio of the density of the dispersed organic liquid phase to the density of the aqueous phase can be in the range of 0.8: 1 to 1.2: 1).

In most cases, the rotational speed and geometry of the turbine and/or stirrer determine the degree of turbulence within the flow pattern generated within the reactor. The rotation speed depends on many factors including the volume and density ratio of the dispersed droplets and the aqueous phase in the organic liquid phase; the geometry of the container; and droplet/particle size in the dispersed organic liquid phase. Suitable rotational speeds can be determined by trial and error, and it will be apparent to those skilled in the art that suitable types of turbine and/or agitator can be selected for use.

Generally, to provide good size distribution of dispersed droplets/particles in the organic liquid phase and to ensure the formation of resin beads with a continuous phase containing elastomeric polymer (i.e., no phase inversion occurs within the polymerized organic droplets), the degree of turbulence of the flow pattern within the reactor is uniform and low enough so that the motion of the reactor contents is laminar or transitional (between laminar and turbulent). To maintain adequate mixing within the reactor, and to keep the organic droplets immersed without agglomeration in a low shear and low turbulence flow pattern, agitation should be generated by one or, in some cases, multiple low speed rotating turbines. The ratio of the turbine diameter to the can diameter, or the ratio of the turbine diameter to the sum of the can diameter and the baffle width, is between 0.6 and 0.95. In some cases, the ratio of the turbine diameter to the can diameter, or the ratio of the turbine diameter to the sum of the can diameter and the baffle width, is between 0.75 and 0.95. The turbine should rotate at a relatively low speed in order to perform similar reactions in geometry with the same capacity and the same organic phase loadingThe linear velocity v (v ═ pi DN, where D is the turbine diameter and N is the revolutions per second of the turbine) at the tip of the turbine, as it occurs in-line, should not exceed the tip speed of the turbine typical for conventional styrene monomer polymerization processes. In many cases, the turbine tip speed of the present invention is 20-60% lower than that used in conventional styrene polymerization processes, so that agitation occurs under transitional flow conditions (where Re < 5000) or under laminar flow conditions (where Re < 50). Reynolds number Re of the turbine is defined as Re ═ ND²Where N is the number of revolutions per second of the turbine, D is the turbine diameter and v is the kinematic viscosity of the liquid processed in the tank. This configuration within the reactor produces low and uniform shear flow conditions. Without wishing to be bound by theory, these conditions result in improved droplet size distribution and a more stable suspension process, with a reduced likelihood of aggregation of the organic droplets.

If desired, the starting particle or droplet size distribution of the organic liquid phase can also be modified to some extent during the process by suitably adjusting the rotation speed. While it is not possible to increase the average droplet/particle size by controlled agglomeration of droplets/particles, in some cases it may be possible to reduce their size or improve towards a more uniform distribution by increasing the rotational speed of the turbine and/or agitator to cause only the largest droplets/particles in the population to break up (e.g. 15% of the largest particles). Controlled increases in the degree of turbulence within the flow pattern, caused by the turbine and/or agitator, rather than by particle or droplet interaction (e.g., collision), cause breakup.

In a further embodiment of the invention, the average droplet/particle size of the dispersed organic liquid phase can be greatly reduced by causing a majority (e.g., at least 85%) of the droplets in the dispersed organic liquid phase to break up. In this embodiment, the droplets are broken up by applying a higher turbine and/or agitation rotational speed, creating a flow pattern with a higher degree of shear and turbulence within the aqueous phase.

In another possible mechanical stirring variant of the invention, the mechanical stirring is applied in a discontinuous periodic manner during the polymerization process, in which mode the periodic rotation of the turbine and/or of the stirrer can be used in particular to generate an "oscillating" movement of the particles or droplets and can be applied to particles having a density lighter or heavier than that of the continuous aqueous phase. The movement of the turbine or agitator forces the droplets and/or particles to move within the volume of the aqueous phase, causing the lighter particles to be pulled down the free surface or lifting the heavier particles from the bottom of the vessel or reactor, respectively. The next rotation and driving of the turbine and/or agitator takes place before the droplets/particles in the dispersed organic liquid phase start to lose their momentum, based on either floating towards the free surface or descending towards the vessel or the bottom of the reactor, respectively. The flow pattern generated within the aqueous phase may be at a higher degree of turbulence than the first continuous (non-periodic) mixing mode. The flowing particles or droplets should therefore be broken up carefully if necessary.

In another embodiment of the invention, the organic liquid phase is added to the aqueous phase and dispersed into droplets by applying mechanical agitation, wherein said mechanical agitation is applied continuously during the polymerization of the monomers within the dispersed droplets. The principles surrounding this embodiment of the invention are well known to those skilled in the art of suspension polymerization processes using stirred tank reactors. However, a key difference from conventional processes is that the process of the present invention is carried out at relatively low turbine and/or agitator rotational speeds in order to disperse the organic liquid phase by shear forces during the early stages of the process. The low rotational speed of the turbine and/or agitator and the resulting low shear applied to the dispersion does not promote the occurrence of phase inversion within the droplets (as opposed to the known HIPS suspension polymerization process).

To create such a stirring pattern, a structure comprising one, and in some cases, a plurality of turbines rotating at a low speed is used. Typically the ratio of turbine diameter to can diameter, or the ratio of turbine diameter to the sum of can diameter and baffle width, is between 0.6 and 0.95, or in some cases between 0.75 and 0.95. The turbine should rotate at a relatively low speed so that the linear velocity v (v pi DN, where D is the turbine diameter and N is the turbine diameter) of the turbine tip when conducted in a geometrically similar reactor of the same capacity and the same organic phase loadingIs the number of revolutions per second of the turbine) should not exceed the typical turbine tip speed for conventional styrene monomer polymerization. In some embodiments of the invention, the turbine tip speed of the present invention is 20-60% lower than that used in conventional styrene polymerization processes, so that agitation occurs under transitional flow conditions (where Re < 5000) or under laminar flow conditions (where Re < 50). Reynolds number Re of the turbine is defined as Re ═ ND²Where N is the number of revolutions per second of the turbine, D is the turbine diameter and v is the kinematic viscosity of the liquid processed in the tank. This configuration within the reactor produces low and uniform shear flow conditions that result in improved droplet size distribution and a more stable suspension process in which the likelihood of organic droplet agglomeration is reduced.

As a result, the morphology of the polymerized droplets causes the rubber to retain a form in which it remains within the continuous phase, and the polymerized monomer forms small complexes distributed within the network formed in the continuous phase. This morphology is maintained throughout the polymerization of the monomer and within the resulting resin beads.

In a further embodiment of the present invention, the atomization process described above may be used in conjunction with the mechanical agitation scheme described above to provide the resin beads of the present invention.

Typically, the polymerization of monomer within dispersed droplets in the organic liquid phase is no less than 90%, in many cases no less than 95%, and in other cases no less than 99.5% or greater conversion. The aqueous phase may be heated during the process as described above to a temperature of at most 135 c, in many cases no greater than 130 c.

The resulting particles can be used in a number of applications, such as foamable resins, ion exchange resins, or applications requiring uniform or tailored particle size distributions.

However, in a further embodiment of the invention, the polymerization of the monomers in the dispersed organic liquid phase takes place in the presence of a blowing agent. The blowing agent can be incorporated in the aqueous phase or in the organic liquid phase to be dispersed. If the blowing agent is in the aqueous phase, it may be present in an amount of from 2.5 to 7% by weight, based on the weight of the dispersed organic liquid phase. If it is introduced into the organic liquid phase to be dispersed, it can be used in a corresponding amount.

In another embodiment, the polymerization may be completed and the resulting resin beads obtained, followed by impregnation with a blowing agent. The resin beads or particles may be resuspended in a liquid medium, such as water, and the medium may be based on a polymeric dispersed organic liquid phase (e.g., polymer beads) and additionally contain 2.5 to 7 weight percent of a blowing agent.

The expandable resin beads may be impregnated with a suitable blowing agent using any conventional method. Any gaseous substance or material that generates a gas when heated can be used as the blowing agent. Conventional blowing agents include aliphatic hydrocarbons having from 4 to 6 carbon atoms in the molecule, such as butanes, pentanes, hexanes, and halogenated hydrocarbons, such as CFCs and HCFCs, which boil at temperatures below the softening point of the selected polymer. Mixtures of these aliphatic hydrocarbon blowing agents may also be used.

As non-limiting examples, the resin beads may be impregnated with liquid n-pentane or isopentane, or any mixture of liquid n-pentane and isopentane. The amount of foaming agent absorbed within the resin beads may vary from 3% to 25%, in some cases about 6% to 15% of the initial mass of the non-impregnated beads.

Alternatively, water may be mixed with these aliphatic hydrocarbon blowing agents, or water may be used as the sole blowing agent, as taught in U.S. patent nos.6127439, 6160027 and 6242540, where water retention agents are used. The weight percentage of water used as blowing agent may range from 1 to 20%. The contents of U.S. patent nos.6127439, 6160027 and 6242540 are incorporated herein by reference.

The resin beads of the present invention may be impregnated with any of the blowing agents described above and may be stored for optional future foaming. During storage, the blowing agent gradually evolves from the resin, the rate of which is an important consideration for further resin bead processing. If the rate of blowing agent loss is too high (i.e., days or weeks), the impregnated resin beads must be frozen to prevent premature blowing agent loss.

In a particular embodiment of the invention, resin beads having improved blowing agent retention time are provided by the following steps:

a-1) forming a dispersion of organic droplets by atomizing an organic liquid phase under pressure below the free surface of an aqueous phase which may be stationary or may flow; or

A-2) forming a dispersion of organic droplets in an organic liquid phase in an aqueous phase, which may be stationary or flowing, by applying mechanical agitation;

wherein the organic liquid phase comprises an "acrylonitrile-butadiene rubber" or an "acrylonitrile-butadiene-styrene rubber" and one or more polymerizable aryl monomers, and

B) within the low shear flow pattern, the monomers are polymerized in the dispersed organic droplets to form unfoamed polymer beads.

The resin beads formed above have a continuous phase comprising acrylonitrile-butadiene or acrylonitrile-butadiene-styrene rubber, and a dispersed phase comprising homopolymers or copolymers of one or more polymerizable aromatic monomers, and moreover have the ability to retain blowing agent for months without any additional bead treatment, such as freezing. This is in contrast to beads having a continuous phase comprising butadiene rubber (i.e., rubber without acrylonitrile or methacrylonitrile) and a dispersed phase comprising a homopolymer or copolymer of one or more polymerizable aromatic monomers, which typically retain blowing agent for no more than a few weeks.

Optionally expanding the resin beads to a bulk density of at least 0.51b/ft³In some cases at least 1.251b/ft³And in other cases at least 1.51b/ft³In some cases at least 1.751b/ft³In some cases at least 21b/ft³Otherwise at least 31b/ft³And in special cases at least 3.251b/ft³Or 3.51b/ft³. In addition, the density of the bulk can be as high as 501b/ft³In some casesCondition 401b/ft³In some cases as high as 301b/ft³And in other cases up to 201b/ft³In some cases up to 121b/ft³In some cases up to 101b/ft³And in other cases up to 51b/ft³. The bulk density of the expanded resin beads may be any value or range between any of the values recited above.

The foaming step is conventionally carried out by heating the impregnated resin beads by any conventional heating medium, such as steam, hot air, hot water or radiant heat. One generally accepted method of achieving pre-expansion of impregnated resin beads is taught in U.S. patent No. 3023175.

The resin beads may include conventional ingredients and additives such as flame retardants, pigments, dyes, colorants, plasticizers, mold release agents, stabilizers, ultraviolet light absorbers, mold inhibitors, antioxidants, rodenticides, insect repellents, and the like. Typical pigments include, but are not limited to, inorganic pigments such as carbon black, graphite, expandable graphite, zinc oxide, titanium dioxide, and iron oxide, and inorganic pigments such as quinacridone reds and violets and copper phthalocyanine blues and greens.

The expanded resin beads may have an average particle size of at least 0.3, in some cases at least 0.5, in some cases at least 0.75, in other cases at least 0.9, and in some cases at least 1mm, and may be up to 15, in some cases up to 10, in other cases up to 6, in some cases up to 4, in other cases up to 3, and in some cases up to 2.5 mm. The average particle size of the expanded resin beads may be any value and may be a range between any of the values recited above. The average particle size of the expanded resin beads can be determined by sieving according to the mesh size using a laser diffraction technique or by using a mechanical separation method well known in the art.

The expanded beads may have any density in the range of 0.6 to 4.0 pcf.

As noted above, unexpanded resin beads having a continuous phase comprising acrylonitrile-butadiene or acrylonitrile-butadiene-styrene rubber and a dispersed phase comprising homopolymers or copolymers of one or more polymerizable aromatic monomers, when impregnated with a blowing agent, exhibit very good blowing agent retention compared to other materials. As an example, such resin beads may retain up to 75%, in some cases up to 50%, by weight of the starting blowing agent (i.e., obtained immediately after impregnation) after 1000 hours of storage at room temperature and pressure, in some cases after 1500 hours. In addition, such beads can be expanded to their original volume after storage at room temperature and pressure for greater than 1500 hours. As an example, beads impregnated with 12 wt% blowing agent and left to stand on an open tray at ambient conditions still expanded to their original size after more than 5 months (i.e., the same size as beads expanded immediately after impregnation); the beads impregnated with 6-8 wt% blowing agent still expanded to their original size after 3 months. The expression "immediately after impregnation" means that not more than 24 hours have elapsed since the impregnation of the beads with the blowing agent.

In one embodiment of the present invention, and in order to provide expanded resin beads with desired physical properties, the expanded polymer particles are not expanded to their maximum expansion factor; because such extreme expansion results in particles having undesirably thin cell walls and insufficient toughness and strength. As such, the resin beads are expandable to at least 5%, in some cases at least 10%, and in other cases at least 15% of their maximum expansion factor. However, in order not to cause the cell wall thickness to be too thin, the resin beads are expanded to up to 80%, in some cases up to 75%, in other cases up to 70%, in some cases up to 65%, in other cases up to 60%, in some cases up to 55%, and in other cases up to 50% of their maximum expansion factor. The resin beads may be expanded to any of the degrees described above, or the expansion may be in a range between any of the values recited above.

The expandable resin beads obtained according to the present invention can be formed into an expanded molded article of a desired structure by pre-expanding the resin beads, and expanding and molding them in a mold cavity. The resulting foamed, shaped article has excellent thermal stability, chemical resistance (e.g., oil resistance), toughness, and flexural strength due to the elastomeric continuous phase.

Without wishing to be bound by theory, it is believed that the continuous elastomer morphology will improve the performance of the expanded beads because the continuous rubber network will stretch during bead expansion, thereby increasing the strength and elasticity of the polystyrene matrix. The expanded resin beads of the present invention are in contrast to conventional expanded High Impact Polystyrene (HIPS) in which the rubber component is distributed as discrete particles within the polystyrene matrix. In conventional foamed HIPS, the elastomer particles are not forced to stretch and only marginally participate in the bead foaming process.

In particular, the foamed article can be used as a packaging material, a base layer of a roofing material or a container, because it does not shrink or soften due to exposure to heat when it is placed at a high temperature, and thus it is widely used for a heat or sound insulating material or a cushioning material,

The invention is further described by reference to the following examples. The following examples merely illustrate the invention and are not intended to be limiting. All percentages are by weight unless otherwise indicated.

Examples

Example 1

This example illustrates a method of preparing resin beads according to the present invention. By dissolving 10 wt% of the mediator cis-DIENE in 90 wt% of styrene monomer55AC10 polybutadiene rubber (available from Firestone Polymers, Akron Ohio) was used to prepare the organic liquid phase. By dissolving 2 wt% polydiallyldimethylammonium chloride (PDAC, available from Sigma-Aldrich Corp., St. Louis, Mo.) and 3 wt% polyvinyl alcohol (available from Nippon Gohsei (UK) Limited, Kingston upon Hull, UK, GOSHENOL^TMGH-23), an aqueous phase is prepared.

The polymerization was carried out in the apparatus described in example 1 of U.S. Pat. No. 6610798. About 5 liters of aqueous phase was added to the reactor. Benzoyl peroxide (0.5 parts per 100 parts of styrene) was added to the organic liquid phase, which was subsequently fed by means of a conveying device to the reactor, where it was heated to 80 ℃. Downstream of the heating line, the organic phase was subjected to pressure pulses at an applied frequency of 45 Hz. A pulsed flow of the organic phase was fed at a flow rate of about 1.3ml/s into an atomizer located at the bottom of the reactor. About 1.5 liters of organic phase was dispersed as single size droplets within the aqueous phase. Nitrogen was bubbled through the reactor, creating a low shear flow pattern of interfering and suspended droplets. The contents of the reactor were heated to 90 ℃ and maintained at that temperature for 6 hours, after which time the resulting resin beads were recovered.

The Mw of the polymer within the resin beads was about 80,000, the unreacted styrene monomer content was 1.5 wt% based on the weight of the beads, and there was no melting or decomposition after exposure to a temperature of 250 ℃ for 10 minutes. The amount of cross-linking within the beads was determined to be about 65% to 83%, as measured by the two methods described below.

The first method is based on measuring the dissolved concentration of the soluble fraction in tetrachloroethylene at 60 ℃ and filtering through a 450nm syringe to calculate the percentage of cross-linked/insoluble fraction in the sample. The concentration was determined using fourier transform infrared spectroscopy (FTIR).

The second process is a modified xylene extraction process, wherein the xylene extraction process is carried out according to modified astm d 2765-01: "Standard Test Methods for Determination of GelContent and Swell Ratio of Crosslinked Ethylene Plastics (Standard Test Methods for determining gel content and swelling Ratio in Crosslinked Ethylene Plastics)", Test method A, the percentage of Crosslinked/insoluble fraction in a sample was estimated. The modifications used were: 1g of sample (instead of 0.3 g); xylene reflux for 6 hours (instead of 12 hours); and the sample was not crushed or sieved.

Fig. 1A is a Transmission Electron Microscopy (TEM) image showing the crosslinked network morphology of the resin beads. The lighter areas are discrete granular areas of polystyrene and the darker areas are the three-dimensional network structure of the rubber.

FIGS. 1B and 1C are Atomic Force Microscopy (AFM) images showing the cross-linked network morphology of the resin beads. The lighter areas are discrete granular areas of polystyrene and the darker areas are the three-dimensional network structure of the rubber. Fig. 1C particularly shows an outer skin of about 3 microns of the resin bead.

Example 2

The bead samples of example 1 were impregnated with blowing agents (n-pentane, isopentane and a mixture of n-pentane and isopentane at 50/50 w/w) such that the blowing agent was about 16 wt% of the impregnated resin beads. The impregnated beads were then expanded from 1 to 28 minutes using steam at 95 ℃. The beads form expanded particles that are spherical in shape, which do not deform or decrease in volume when exposed to longer periods of steam. The beads are relatively insensitive to the time of the steam treatment. After 1 minute of steaming, the beads were expanded to about 5 times the diameter of the unexpanded beads. For comparison, steam treatment for 7 minutes resulted in only slightly larger diameters within the expanded beads (up to about 10% larger diameter). After a long steaming time (i.e. 7 minutes), the beads still had a smooth surface and a good cell structure. The beads did not shrink or "burn" when exposed to steam for extended periods of time as other materials. FIGS. 2 and 3 show 20X and 100X Scanning Electron Microscope (SEM) images, respectively, of beads expanded for 8 minutes using 50/50v/v mixtures of isopentane and n-pentane as blowing agents.

Example 3

This example illustrates the preparation of resin beads of the present invention using a low shear flow pattern created by mechanical agitation. An aqueous phase containing 2 wt% PDAC and 0.5 wt% polyvinyl alcohol was prepared in water. By dissolving 10 wt% DIENE in 90 wt% styrene monomer55AC10 PolyButadiene rubber, preparing an organic liquid phase. About 1 liter of aqueous phase was added to a reactor with a stirrer. About 0.18 liters of organic liquid phase was mixed with benzoyl peroxide (0.5 parts per 100 parts styrene) and the combination added to the aqueous phase and agitation applied at 150rpm to form a dispersion of discrete organic droplets. The dispersion was heated to 90 ℃. This temperature was maintained for 4 hours, then increased to 95 ℃ and maintained for 2 hours. The resin beads are then recovered from the reactor.

Fig. 4A and 4B are AFM images showing the morphology of the crosslinked network of resin beads. The lighter areas are discrete granular areas of polystyrene and the darker areas are the three-dimensional network structure of the rubber. Fig. 4B particularly shows an outer skin of about 3 microns of the resin bead.

Example 4

This example illustrates the preparation of resin beads with extended (improved) blowing agent retention according to the invention using a low shear flow pattern generated by mechanical agitation. An aqueous phase containing 2 wt% PDAC and 0.08 wt% polyvinyl alcohol was prepared in water. The organic liquid phase was prepared by dissolving A)7 wt%, B)10 wt% and C)15 wt% acrylonitrile-butadiene rubber 3965F (from Lanxess) in A)93 wt% B)90 wt% and C)85 wt% styrene monomer, respectively. About 700g of the aqueous phase was added to a reactor with a stirrer. About 500g of the organic liquid phase were mixed with benzoyl peroxide (0.5 part per 100 parts of styrene) and Luperox (TAEC), tert-amylperoxy 2-ethylhexyl carbonate, in an amount of 0.2 part per 100 parts of styrene, as an auxiliary peroxide. And the combination was added to the aqueous phase and stirring was applied at 185rpm to form a dispersion of discrete organic droplets. The dispersion was heated to 90 ℃ and maintained at this temperature for 4 hours, then increased to 93 ℃ and maintained at this temperature for an additional 2 hours. Next, in order to carry out further polymerization and in order to reduce the residual styrene content in the beads to several hundred ppm (< 1000ppm), a "finishing step" is carried out: the contents of the entire reactor (dispersed organic and aqueous phases) were heated to 120 ℃ (this is the temperature when the ancillary peroxide TAEC becomes active) and held for 4 hours. The reactor was cooled and the resin beads were then recovered.

Fig. 5A, 5B and 5C are AFM images showing the crosslinked network morphology of resin beads modified with 7%, 10% and 15% nitrile rubber, respectively. The lighter areas are discrete granular areas of polystyrene and the darker areas are the three-dimensional network structure of the rubber. It shows that as the concentration of dissolved rubber becomes higher, the size of the polystyrene domains decreases.

The beads containing 10% nitrile rubber were further impregnated by immersion in a liquid blowing agent at ambient conditions. Some of the beads were impregnated in n-pentane and some of the beads were impregnated in a mixture containing 50: 50 wt% of n-pentane and isopentane. After impregnation, the beads were analyzed for blowing agent absorption to determine the wt% of starting blowing agent within the beads. The beads were then allowed to stand on the tray at atmospheric pressure and temperature. The level of blowing agent remaining within the beads was monitored over the course of several months. FIG. 6 shows the results indicating the retention of blowing agent in nitrile rubber modified beads impregnated with n-pentane and with a mixture of n-pentane and isopentane at 50/50. The data of fig. 6 shows that the beads retained blowing agent very well, losing only about 50% of the blowing agent within the first 1500-. In addition, there was no visible difference in the volume of the resin beads after > 1500 hours of expansion relative to beads that were expanded (steam at 96 ℃) shortly after impregnation (i.e., after 24 hours). In each case, the resin beads can be expanded to their original size, increasing their diameter by a factor of 4 to more than 5 (depending on the type of blowing agent used) relative to the unexpanded beads. These expansions correspond to an increase in the volume of the unexpanded beads of about 64 to 125 times.

For comparison, data indicating pentane retention for several other types of expandable polystyrene beads, such as PS/PE resins, polystyrene modified with butadiene rubber, and conventional HIPS, are also provided in FIG. 6.

Example 5

This example shows the effect of the flow pattern (specifically-shear velocity and degree of turbulence) maintained during the polymerization process on the morphology of polystyrene beads containing 10% by weight of nitrile rubber. The three polymerization processes were carried out in a tank equipped with a mechanical stirrer, using the same formulation and the same set of operating conditions. However, each time the polymerization was carried out at a different stirrer speed. Fig. 7 shows the morphology of the resulting beads. The beads polymerized in the first two processes, carried out at 135rpm and 280rpm respectively, have a similar morphology: this morphology includes a continuous network of rubber (darker areas) and regular small discrete polystyrene clathrates (lighter areas). However, the beads polymerized in the third batch using the highest stirring speed of 600rpm and thus at the highest turbulence and shear levels had a non-uniform morphology throughout the batch and exhibited two different types of morphology: some beads with morphology #1 have a continuous rubber network, but the inclusion of polystyrene is very large and irregular; other beads had morphology #2, where there was no different polystyrene clathrate, and it was often difficult to distinguish between rubber and polystyrene. This example shows that turbulence and shear stress levels during polymerization can affect the morphology of the beads and can result in different types of morphology in individual beads from the same batch.

Example 6 (prior art)

This example shows the morphology of conventional HIPS resin beads using the existing high shear flow pattern created by mechanical agitation. FIG. 8 is a graph showing STYROSUN being prepared using a high shear dispersion polymerization process as known in the prior art(NOVA Chemicals Inc., Pittsburgh, Pa.) typical HIPS morphology of the resin beads. The light areas are the continuous phase of polystyrene and the darker areas, generally bead-shaped areas, are the rubber particles.

The data indicate the unique morphology of the resin beads of the present invention compared to known HIPS resin beads.

The present invention has been described with reference to specific details of particular embodiments thereof. It is not intended that such details be regarded as limitations upon the scope of the invention except in-so-far as and to the extent that they are included in the accompanying claims.

Claims (103)

1. An unexpanded resin bead having an average particle size of 0.001mm to 10mm and containing a continuous phase and a particulate dispersed phase, wherein

The continuous phase comprises one or more elastomeric polymers; and

the dispersed phase comprises one or more homopolymers and/or copolymers containing repeat units derived from polymerizing one or more aryl polymerizable monomers.

2. The resin bead according to claim 1, wherein the particulate dispersed phase comprises particles having an aspect ratio of 1 to 10.

3. The resin bead according to claim 1, wherein the particulate dispersed phase comprises particles having a circular, oval or elliptical cross-sectional shape.

4. The resin bead according to claim 1, wherein the continuous phase has a cross-linked network morphology.

5. The resin bead according to claim 1, wherein the continuous phase has the morphology of fibrils (threads) with a large length to diameter ratio, said fibrils being optionally at least partially crosslinked and/or connected by means of locally formed branches and/or an interconnected network.

6. The resin beads according to claim 1, wherein the elastomeric polymer is selected from homopolymers of butadiene or isoprene, and random, block, AB diblock or ABA triblock copolymers of conjugated dienes with aryl monomers and/or (meth) acrylonitrile, and random, alternating or block copolymers of ethylene with vinyl acetate.

7. The resin bead according to claim 1, wherein the elastomeric polymer comprises one or more block copolymers selected from the group consisting of diblock and triblock copolymers of styrene-butadiene, styrene-butadiene-styrene, styrene-isoprene-styrene, ethylene-vinyl acetate, partially hydrogenated styrene-isoprene-styrene, and combinations thereof.

8. The resin bead according to claim 1, wherein the elastomeric polymer is a copolymer containing repeating units derived from the polymerization of one or more conjugated dienes and at least one unsaturated nitrile selected from the group consisting of acrylonitrile and methacrylonitrile.

9. The resin bead according to claim 8, wherein the elastomeric polymer is a copolymer further comprising repeating units derived from polymerizing one or more aryl monomers selected from the group consisting of styrene, p-methylstyrene, α -methylstyrene, t-butylstyrene and dimethylstyrene.

10. The resin bead according to claim 8, wherein the elastomeric polymer is partially hydrogenated.

11. The resin bead according to claim 9, wherein the elastomeric polymer is partially hydrogenated.

12. The resin bead according to claim 1, wherein the elastomeric polymer has a weight average molecular weight of from about 6,000 to about 500,000.

13. The resin bead according to claim 1, wherein the elastomeric polymer is crosslinked.

14. The resin bead according to claim 13, wherein from about 5% to about 95% of the elastomeric polymer is crosslinked.

15. The resin bead according to claim 1, wherein the aryl monomer is selected from the group consisting of styrene, p-methylstyrene, α -methylstyrene, t-butylstyrene, dimethylstyrene, nuclear brominated or chlorinated derivatives thereof, and combinations thereof.

16. The resin bead according to claim 1, wherein the copolymer in the dispersed phase comprises a copolymer obtained by polymerizing one or more aryl polymerizable monomers with one or more C selected from the group consisting of maleic anhydride, maleic acid, maleimide, fumaric acid, and maleic acid₁-C₁₂Straight, branched or cyclic alkyl esters, C of fumaric acid₁-C₁₂C of linear, branched or cyclic alkyl esters, itaconic acid₁-C₁₂Linear, branched or cyclic alkyl esters, itaconic anhydride, ethylene, propylene, 1-butene, isobutylene, 2-butene, diisobutylene, 1-pentene, 2-pentaneAlkenes, 1-hexene, 2-hexene, 3-hexene, vinyl acetate, C of (meth) acrylic acid₁-C₁₂Linear, branched or cyclic alkyl esters, acrylonitrile, methacrylonitrile and combinations thereof.

17. The resin bead according to claim 1, wherein the homopolymer and/or copolymer comprising repeat units derived from polymerizing one or more aryl polymerizable monomers has a weight average molecular weight of about 10,000 to about 1,000,000.

18. The resin beads of claim 1, containing less than 5 weight percent unreacted monomer of the resin bead content.

19. The resin bead according to claim 1, wherein at least some of the monomers in the dispersed phase are grafted to at least some of the elastomeric polymers in the continuous phase.

20. The resin bead according to claim 1, further comprising a blowing agent.

21. The resin beads of claim 20, wherein the blowing agent is selected from nitrogen, sulfur hexafluoride (SF)₆) Argon, carbon dioxide, 1, 1, 1, 2-tetrafluoroethane (HFC-134a), 1, 1, 2, 2-tetrafluoroethane (HFC-134), 1, 1, 1, 3, 3-pentafluoropropane, difluoromethane (HFC-32), 1, 1-difluoroethane (HFC-152a), pentafluoroethane (HFC-125), fluoroethane (HFC-161) and 1, 1, 1-trifluoroethane (HFC-143a), methane, ethane, propane, N-butane, isobutane, N-pentane, isopentane, cyclopentane, neopentane, hexane, azodicarbonamide, azobisisobutyronitrile, benzenesulfonylhydrazide, 4-oxybenzenesulfonylsemicarbazide, p-toluenesulfonylaminourea, barium azodicarboxylate, N '-dimethyl-N, N' -dinitrosoterephthalamide, azodicarbonamide, methyl-N-dimethylmethane, N-152 a-bis (HFC-152a), pentafluoroethane (HFC-, Trihydrazinotriazine, mixtures of citric acid and sodium bicarbonate, and combinations thereof.

22. The resin bead according to claim 20, which is expanded to about 1.01 to about 500 times the starting volume of the unexpanded resin bead to form an expanded resin bead.

23. The resin bead according to claim 22, wherein the expanded resin bead has a density of from about 10 to about 50 g/l.

24. The resin beads of claim 1, having an aspect ratio of less than 10.

25. The resin bead according to claim 1, further comprising a skin layer substantially covering the outer surface of the resin bead.

26. The resin bead according to claim 25, wherein the skin layer has a thickness of 0.1 to 7 microns.

27. The resin bead according to claim 25, wherein the skin layer comprises a homopolymer and/or copolymer of the dispersed phase.

28. A method of preparing unexpanded resin beads, the method comprising:

a dispersion of organic droplets forming an organic liquid phase in an aqueous phase which may be stationary or flowing,

wherein the organic phase comprises an organic solution comprising one or more elastomeric polymers dissolved in a monomer solution comprising one or more aryl polymerizable monomers, and

the dispersed organic droplets have an average diameter of from about 0.001mm to about 10mm, and

monomers are polymerized within the dispersed organic droplets under low shear flow conditions to form unfoamed polymer beads.

29. A process for preparing unexpanded resin beads according to claim 28, wherein the dispersion of organic droplets is formed by pressure atomization of an organic liquid phase below the free surface of an aqueous phase that may be stationary or flowing.

30. A process for the preparation of unexpanded resin beads according to claim 28, wherein a dispersion of organic droplets of an organic liquid phase is formed within the aqueous phase, which may be static or flowing, by applying mechanical agitation.

31. The process of claim 29, wherein the organic phase is contained within a storage tank or a pipeline or a loop reactor.

32. The process of claim 29, wherein the organic liquid phase is pressure atomized at a pressure of at least 5 bar.

33. The process of claim 29, wherein the density of the organic phase is ± 20% of the density of the aqueous phase.

34. The method of claim 29, wherein the dispersed organic droplets comprise 0.01 to 60 volume percent of the total volume of the organic and aqueous liquids.

35. The process of claim 29, which comprises passing the organic phase to be atomized through at least one atomizer having an opening diameter of from 0.01mm to 2mm and an L/D ratio of from 0.2 to 10 at a flow rate of from 0.05 to 15 ml/s/atomizer and a gauge pressure of from 3 to 100 bar.

36. The process of claim 35, wherein the pore size of the atomizer is from 0.1 to 0.8mm, the flow rate through the atomizer is from 0.1 to 10ml/s, and the static pressure of the organic mixture is from 3 to 80 bar.

37. The process of claim 29, wherein the low shear flow pattern for polymerizing monomer within dispersed organic droplets is a controlled low turbulence flow pattern generated without mechanical agitation by continuous or periodic injection of one or more gas streams inert to and immiscible with the reactor contents into selected reactor sections at a gauge pressure of up to 15 bar.

38. The process of claim 37, wherein the gas is injected into the aqueous phase at a gauge pressure of less than 3bar and forms one or more streams of gas bubbles having a diameter substantially greater than the average size of the atomized organic droplets.

39. The process of claim 37, wherein the gas is injected into the reactor through an injection port located at the bottom of the reactor and optionally in the reactor wall at a gauge pressure of at most 15 bar.

40. The method of claim 37, wherein the gas is selected from the group consisting of air and nitrogen.

41. The method of claim 37, wherein the unexpanded resin bead includes a continuous phase and a dispersed phase, and the continuous phase includes the elastomeric polymer in a cross-linked network form.

42. The method of claim 41, wherein the dispersed phase within the unexpanded beads comprises particles having an aspect ratio of 1 to 10, said particles comprising a polymer formed by polymerizing monomer within the atomized organic droplets.

43. The method of claim 29, wherein the unexpanded resin bead includes a continuous phase and a dispersed phase, and the continuous phase includes an elastomeric polymer, and the dispersed phase includes a homopolymer and/or copolymer comprising repeat units resulting from polymerizing one or more aryl polymerizable monomers.

44. The method of claim 29, wherein the low shear flow pattern for polymerizing monomer within the dispersed organic droplets is provided by mechanical agitation.

45. The method of claim 44, wherein the unexpanded resin bead comprises a continuous phase and a dispersed phase, and the continuous phase comprises the elastomeric polymer in a morphology comprising filaments having a large aspect ratio, said filaments optionally being at least partially crosslinked and/or connected by means of locally formed branches and/or an interconnected network.

46. The process of claim 44, wherein the dispersed phase comprises particles having an aspect ratio of 1 to 10, said particles comprising a polymer formed by polymerizing monomers within the atomized organic droplets.

47. The process of claim 29, wherein the continuous aqueous phase in the reactor is a liquid having a viscosity of up to 250cp at 25 ℃.

48. The process of claim 29, wherein the continuous aqueous phase further comprises from 0.1 to 10 wt% of one or more suspension stabilizers, based on the weight of the continuous aqueous phase.

49. The method of claim 48, wherein the suspension stabilizer is selected from the group consisting of carboxymethylcellulose; gelatin; agar; polyvinyl pyrrolidine; polyacrylamide; poly (vinyl alcohol); (ii) a homopolymer or copolymer of dimethyldiallylammonium chloride, (meth) acrylamidopropyltrimethylammonium chloride, (meth) acryloyloxyethyltrimethylammonium chloride; poly (meth) acryloxyethyltrimethylammoniummethylsulfate, and combinations thereof; alumina, bentonite, magnesium silicate; surfactants, and combinations thereof.

50. The method of claim 29, wherein the organic phase comprises one or more components selected from the group consisting of polymerization initiators, antistatic agents, flame retardants, pigments, dyes, fillers, UV stabilizers, heat and light stabilizers, coating agents, plasticizers, chain transfer agents, crosslinking agents, nucleating agents, biocides, and rodenticides.

51. The process of claim 29 wherein the flow of organic liquid to be atomized is regulated with pressure pulsations applied on the flowing organic liquid upstream of the atomizer outlet at a step amplitude (amplitude) of less than 20% of the static pressure of the flowing liquid and a frequency of up to 200 Hz.

52. The method of claim 29, wherein the organic phase comprises from about 5 to about 50 weight percent of one or more elastomeric polymers, and from about 95 to about 50 weight percent of a monomer solution comprising one or more aryl polymerizable monomers, based on the weight of the organic phase, wherein the elastomeric polymers are soluble in the monomer solution.

53. The method of claim 29, wherein the monomer solution comprises a monomer selected from the group consisting of C_8-16One or more of vinylaromatic monomers, said C_8-16The vinylaromatic monomer being unsubstituted or selected from C_1-4Up to 2 substituents of the linear and branched alkyl groups of (a).

54. The method of claim 53, wherein the monomer solution further comprises C selected from the group consisting of maleic anhydride, maleic acid, maleimide, fumaric acid, maleic acid₁-C₁₂Straight, branched or cyclic alkyl esters, C of fumaric acid₁-C₁₂C of linear, branched or cyclic alkyl esters, itaconic acid₁-C₁₂Linear, branched or cyclic alkyl esters, itaconic anhydride, ethylene, propylene, 1-butene, isobutylene, 2-butene, diisobutylene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, 3-hexene, vinyl acetate, C of (meth) acrylic acid₁-C₁₂One or more monomers of a linear, branched, or cyclic alkyl ester, acrylonitrile, methacrylonitrile, and combinations thereof.

55. The process of claim 29, wherein the organic phase has a viscosity of from 1cP to 10,000 cP.

56. The method of claim 29, wherein the atomized organic droplets have a droplet size of 0.3 to 8mm and a standard deviation from the mean droplet diameter of 0.03 to 0.35 mm.

57. Unexpanded resin beads, prepared according to the process of claim 29, having an average particle size of 0.001mm to 10 mm.

58. The resin bead according to claim 57, further comprising a blowing agent and expanded to about 1.01 to about 500 times the original volume of the unexpanded resin bead to form an expanded resin bead.

59. The resin beads of claim 57, further comprising a blowing agent retained at a level of up to 50% of the weight percent of the starting blowing agent (obtained immediately after impregnation) when the resin beads are stored at atmospheric temperature and pressure for greater than 1500 hours, wherein the elastomeric polymer is a copolymer containing repeat units derived from polymerizing one or more conjugated dienes, one or more unsaturated nitriles selected from the group consisting of acrylonitrile and methacrylonitrile, and optionally one or more aryl monomers selected from the group consisting of styrene, p-methylstyrene, alpha-methylstyrene, tert-butylstyrene, and dimethylstyrene.

60. The resin bead according to claim 59, wherein the elastomeric polymer forms a continuous phase.

61. The resin bead according to claim 59, wherein the resin bead is expanded to from about 1.01 to greater than about 500 times the original volume of the unexpanded resin bead to form an expanded resin bead.

62. A molded article comprising the resin bead of claim 58.

63. A molded article comprising the resin bead of claim 61.

64. The resin bead according to claim 57, further comprising a skin layer substantially covering the outer surface of the resin bead.

65. The resin bead according to claim 64, wherein the skin layer has a thickness of 0.1 to 40 microns.

66. The resin bead according to claim 65, wherein the skin layer comprises a homopolymer and/or copolymer of the dispersed phase.

67. The resin bead according to claim 59, further comprising a skin layer substantially covering the outer surface of the resin bead.

68. The resin bead according to claim 67, wherein the skin layer has a thickness of 0.1 to 40 microns.

69. The resin bead according to claim 68, wherein the skin layer comprises a homopolymer and/or copolymer of the dispersed phase.

70. The resin beads of claim 59, wherein the resin beads stored for greater than 1500 hours can expand to a volume similar to resin beads that expand immediately after impregnation.

71. The resin bead according to claim 70, wherein the resin bead is expanded to about 1.01 to greater than about 500 times the original volume of the unexpanded resin bead to form an expanded resin bead.

72. A molded article comprising the resin bead of claim 71.

73. The process of claim 30, wherein the density of the organic phase is ± 20% of the density of the aqueous phase.

74. The method of claim 30, wherein the dispersed organic droplets comprise 0.01 to 60 volume percent of the total volume of the organic and aqueous liquids.

75. The method of claim 30, wherein the unexpanded resin beads comprise a continuous phase and a dispersed phase, and the continuous phase comprises the elastomeric polymer in a cross-linked network.

76. The method of claim 75, wherein the dispersed phase within the unexpanded beads comprises particles having an aspect ratio of 1 to 10, said particles comprising a polymer formed by polymerizing monomer within the atomized organic droplets.

77. The method of claim 30, wherein the unexpanded resin bead includes a continuous phase and a dispersed phase, and the continuous phase includes an elastomeric polymer, and the dispersed phase includes a homopolymer and/or copolymer comprising repeat units resulting from polymerizing one or more aryl polymerizable monomers.

78. The method of claim 30, wherein the low shear flow pattern for polymerizing monomer within the dispersed organic droplets is provided by mechanical agitation.

79. The method of claim 78, wherein the unexpanded resin bead comprises a continuous phase and a dispersed phase, and the continuous phase comprises the elastomeric polymer in a morphology comprising filaments having a large aspect ratio, said filaments optionally being at least partially crosslinked and/or connected by means of locally formed branches and/or an interconnected network.

80. The process of claim 30, wherein the continuous aqueous phase in the reactor is a liquid having a viscosity of up to 250cp as measured at 25 ℃.

81. The process of claim 30, wherein the continuous aqueous phase further comprises 0.1 to 10 wt% of one or more suspension stabilizers, based on the weight of the continuous aqueous phase.

82. The method of claim 81 wherein the suspension stabilizer is selected from the group consisting of carboxymethylcellulose; gelatin; agar; polyvinyl pyrrolidine; polyacrylamide; poly (vinyl alcohol); (ii) a homopolymer or copolymer of dimethyldiallylammonium chloride, (meth) acrylamidopropyltrimethylammonium chloride, (meth) acryloyloxyethyltrimethylammonium chloride; poly (meth) acryloxyethyltrimethylammoniummethylsulfate, and combinations thereof; alumina, bentonite, magnesium silicate; surfactants, and combinations thereof.

83. The method of claim 30, wherein the organic phase comprises one or more components selected from the group consisting of polymerization initiators, antistatic agents, flame retardants, pigments, dyes, fillers, UV stabilizers, heat and light stabilizers, coating agents, plasticizers, chain transfer agents, crosslinking agents, nucleating agents, biocides, and rodenticides.

84. The method of claim 30, wherein the organic phase comprises from about 5 to about 50 weight percent of the one or more elastomeric polymers, based on the weight of the organic phase, and from about 95 to about 50 weight percent of a monomer solution comprising the one or more aryl polymerizable monomers, wherein the elastomeric polymers are soluble in the monomer solution.

85. The method of claim 30, wherein the monomer solution comprises a monomer selected from the group consisting of C_8-16One or more of vinylaromatic monomers, said C_8-16The vinylaromatic monomer being unsubstituted or selected from C_1-4Up to 2 substituents of the linear and branched alkyl groups of (a).

86. The method of claim 85, wherein the monomer solution further comprises C selected from the group consisting of maleic anhydride, maleic acid, maleimide, fumaric acid, maleic acid₁-C₁₂Straight, branched or cyclic alkyl esters, C of fumaric acid₁-C₁₂Linear, branched or cyclic alkyl esters, itaconic acid,c of itaconic acid₁-C₁₂Linear, branched or cyclic alkyl esters, itaconic anhydride, ethylene, propylene, 1-butene, isobutylene, 2-butene, diisobutylene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, 3-hexene, vinyl acetate, C of (meth) acrylic acid₁-C₁₂One or more monomers of a linear, branched, or cyclic alkyl ester, acrylonitrile, methacrylonitrile, and combinations thereof.

87. The process of claim 30, wherein the organic phase has a viscosity of from 1cP to 10,000 cP.

88. An unexpanded resin bead prepared by the process of claim 30, having an average particle size of 0.001mm to 10 mm.

89. The resin bead according to claim 88, further comprising a blowing agent and expanded to about 1.01 to about 500 times the original volume of the unexpanded resin bead to form an expanded resin bead.

90. The resin bead according to claim 88 further comprising a blowing agent retained at a level of up to 50% of the weight percent of the starting blowing agent (obtained immediately after impregnation) when the resin bead is stored at atmospheric temperature and pressure for greater than 1500 hours, wherein the elastomeric polymer is a copolymer comprising repeat units derived from the polymerization of one or more conjugated dienes, one or more unsaturated nitriles selected from the group consisting of acrylonitrile and methacrylonitrile, and optionally one or more aryl monomers selected from the group consisting of styrene, p-methylstyrene, α -methylstyrene, t-butylstyrene, and dimethylstyrene.

91. The resin bead according to claim 90, wherein the elastomeric polymer forms a continuous phase.

92. The resin bead according to claim 90, wherein the resin bead is expanded to from about 1.01 to greater than about 500 times the original volume of the unexpanded resin bead to form an expanded resin bead.

93. A molded article comprising the resin bead of claim 89.

94. A molded article comprising the resin bead of claim 92.

95. The resin bead according to claim 88, further comprising a skin layer substantially covering an outer surface of the resin bead.

96. The resin bead according to claim 95, wherein the skin layer has a thickness of 0.1 to 40 microns.

97. The resin bead according to claim 96, wherein the skin layer comprises a homopolymer and/or copolymer of the dispersed phase.

98. The resin bead according to claim 90, further comprising a skin layer substantially covering an outer surface of the resin bead.

99. The resin bead according to claim 98, wherein the skin layer has a thickness of 0.1 to 40 microns.

100. The resin bead according to claim 99, wherein the skin layer comprises a homopolymer and/or copolymer of the dispersed phase.

101. The resin bead according to claim 90, wherein the resin bead stored for greater than 1500 hours can expand to a volume similar to the resin bead expanded immediately after impregnation.

102. The resin bead according to claim 101, wherein the resin bead is expanded to about 1.01 to greater than about 500 times the original volume of the unexpanded resin bead to form an expanded resin bead.

103. A molded article comprising the resin bead of claim 102.