JPH0366323B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD This invention relates to porous polymeric materials and, more particularly, to a process for making cross-linked polymer block materials with very low density and high absorbency. In US Pat. No. 4,039,489, a process for producing relatively low density oil-absorbing polymeric materials in the form of polystyrene and polyurethane foams using various blowing agents is proposed. UK patent no.
No. 1291649 discloses the production of relatively low density, oil-absorbing polymeric materials by impregnating a prepolymer with a volatile material, then rapidly reducing the pressure and allowing the volatile material to expand the polymeric material to form a foam. A method for manufacturing foam was proposed. In U.S. Pat. No. 3,988,508, Lissant disclosed the production of polymeric materials by polymerization of an oil-in-water emulsion system with a high discrete phase ratio of monomer to water, preferably between 85 and 95%. , disclose monomer to water ratios in the range of 20:80 to 95:5, without crosslinking agents. Research on highly discontinuous phase emulsions has been conducted for a long time, but the basic theory behind their manufacturing method and structure was first published in 1974 by Marcel Dekker Inc., New York. Edited by Surfactant Science Series
Science Series) Volume 6, Emulsion and Emulsion Technology (Emulsion
and Emulsion Technology)” Part 1
As KJ Ritusanto explains: In this paper, Ritssanto describes the geometric packing of droplets in highly discontinuous phase emulsions and points out that for such compositions the emulsifier must be chosen particularly carefully and that the discontinuous phase is 94 In the region of ~97% by volume, it is suggested that a critical change occurs in highly discontinuous phase emulsions (HIPEs). Esso Research and Engineering Company
Engineering Co.'s Beerbower, Nixon, Philippoff, and Wallace on research on high discontinuous phase emulsions as safe fuels containing at least 97% by weight hydrocarbon-based fuels. [American Chemicals Society's Petrochemical Preprints]
Chemical Pre-prints) 14 , 79-59 (1969)]. US Patent No. 3,255,127 discloses polymeric materials made by polymerization in reverse phase emulsions. In that patent, a relatively small proportion of water is emulsified in a mixture of emulsifier, catalyst and monomer, and the resulting emulsion is mixed into a much larger proportion of water. This large proportion of water typically contains a stabilizer, such as polyvinyl alcohol, to keep the inverse emulsion droplets in a relatively stable form. Polymerization is carried out at 55° C. for a period of time on the order of 24 hours, yielding particulate polymer or polymer blocks that can be easily crushed into particulate polymer. In U.S. Pat. No. 1,576,228, the production of thermoplastic microporous cellular structures was disclosed by AKZO, which structures have an average diameter of 0.5 to 100 μm.
The microcells are connected to pores with a smaller diameter. These structures are prepared by dissolving a suitable thermoplastic polymer in a solvent at elevated temperatures, then cooling the solution to solidify the polymer, and then removing the liquid from the thermoplastic polymer structure. manufactured by It is clear that the application of this method is limited to polymers that are easily soluble in suitable solvents. In British Patent No. 1513939, Ceskoslovenska Akademie Ved also disclosed porous polymers which are formed as porous beads and whose fusion creates a plastic material. It is clear that this molding is not homogeneous or uniform in its porosity. These porous beads are
Porous beads of polymer are precipitated by dissolving the polymer to be used in a solvent, then dispersing this solution in a compatible carrier liquid, and adding this mixture to a coagulating liquid such as water. Manufactured. If cross-linked polymers are desired, this method also has limitations, since such polymers can only be produced by random bonding of preformed linear polymer chains. GB 2000150 discloses the manufacture and use of cross-linked polymeric porous beads. These beads can be used to extract components from liquid mixtures, have a pore volume of 2.42 ml/g, and are hard enough to be packed into absorption columns. GB 1458203 suggests a method for producing shaped cellular articles by curing an emulsion containing up to 90 parts by weight of water and 10 parts by weight of a polymerizable mixture. In UK Patent No. 1428125, ICI notes that it is desirable to maximize the water content of water-extended polymers, but it is difficult to obtain oil-water droplet emulsions with a water content of more than 88% water by weight. It suggests something. Due to its very low density and high ability to absorb and retain liquids, and due to the cross-linked nature of the polymer, it is much more liquid-carrying than previously known porous, thermoplastic compositions. good,
It has now been discovered that homogeneous, porous, cross-linked polymer blocks can be produced. Furthermore, these cross-linked polymers
It has much better dimensional stability than polymers which have significant elasticity because they are not cross-linked. According to the invention, a porous, homogeneous, cross-linked polymeric block material with a dry density of 0.1 g/cc or less, having a pore volume of 9 c.c./g or more and a pore volume of at least 7 c.c./g. Hydrophobic liquid (as oleic acid)
There is provided a polymeric block material formed as a cross-linked porous structure having an absorbent capacity for water. The porous materials provided by the present invention include a series of pores that communicate with pinhole openings, thereby giving the material an unparalleled absorbent capacity. A porous polymeric block material is provided which may contain liquid or air or other gaseous substances incorporated therein. Therefore, according to the present invention, the dry density is 0.1 g/cc.
The following is preferably 0.02 to 0.08 g/cc, and 9
A porous polymeric block material is provided which consists of continuous pores with a pore volume of greater than or equal to 15 c.c./g, preferably greater than or equal to 15 c.c./g, and which may contain an aqueous or non-aqueous liquid within the pores. . The polymer/liquid composite of the present invention comprises at least
90, preferably at least 95% by weight liquid (as water). Due to the structure of the polymer, the liquid is retained within the pore system of the polymer, with little or no tendency for the liquid to leak out under the influence of gravity.
However, the liquid can be easily squeezed out by pressing the cross-linked polymer block with manual pressure. Once the liquid has been squeezed out of the block, it is impossible for a non-resilient polymer block to regain its original shape or pore structure. Transferring or displacing built-in liquid from the polymer can be accomplished in a variety of ways. For many liquids that adequately wet the polymer, transfer can be accomplished by diffusion of the liquid. For example, in the case of a liquid such as an aqueous liquid in which the polymer has a not very high affinity for liquid, the liquid may be transferred with the aid of reduced pressure. It is clear that this absorption capacity is related both to the hydrophobicity of the absorbent and to its viscosity. Similarly, if the absorbent were to act as a solvent for the cross-linked polymeric material, the absorption capacity would be reduced due to the loss of structure of the polymeric material. Microscopic examination of a sample of the porous polymer reveals that the polymer consists essentially of a series of substantially spherical, thin-walled cavities with holes in the walls that communicate with adjacent cavities. It was observed that When a polymer sample is examined under an electron microscope, it is found that there are 6
One or more holes can often be found. It was determined that the absorption capacity, expressed as maximum oil absorption, is related to the size of the cavity, expressed as the diameter of the voids, and the number and size of holes in the cavity wall, expressed as pinholes. . It is generally desired that the average pinhole diameter be no less than 0.5μ and that the average void diameter be at least 20% larger than the above numbers. The mechanism by which holes form in thin-walled cavities is not completely understood. However, experimental results suggested that the content of the surfactant and its compatibility with the crosslinked polymer is related, and thus also to the degree of crosslinking in the polymer. The highly discontinuous phase emulsion before polymerization contains 3
The main elements of the species are considered to be composed of monomers, surfactants in the continuous phase, and water in the discontinuous phase. The homogeneous solution of surfactant, monomer, and crosslinking agent, and the continuous phase composed of the surfactant in this case, are compatible with the monomer mixture. At this stage, it is considered that no communicating holes exist in the continuous phase. Chain propagation occurs during the polymerization process, and since the surfactant is not polymerizable and has no reactive sites within its structure, it cannot intervene in the polymerization reaction. As a result, the surfactant becomes incompatible with the growing polymer structure and, since it is also insoluble in water, the surfactant molecules separate. Due to the nature of surfactants, aggregated molecules of surfactants remain part of the polymer phase, which causes weak spots and, in turn, the formation of pinholes within the cross-linked polymer film. Ru. The homogeneous structure of the porous polymer block provided by the present invention is in contrast to the structure obtained by compression coalescence of polymer beads. When porous polymer beads are compressed and bonded together to form a block, many of the cavities and continuous pores on the surface of the beads will be sealed, forming non-homogeneous zones within the polymer block. , and the applied compressive force will further increase the density of the porous polymer within these non-homogeneous zones. In the block provided by the present invention, the interior of the block is homogeneous. Thus, by removing the skin of the block formed in contact with the emulsion container, the block will be homogeneous and uniform in pore and cavity distribution. Another factor that influences the structure of porous crosslinked polymers is the structure of the starting highly discontinuous phase emulsion. This is easiest to understand if it is defined using the concept of viscosity. The following tables and tables show the effect of stirrer speed on two typical emulsions, the viscosity of emulsions made with different stirrer speeds, and the crosslinking obtained from emulsions with different stirrer speeds. Figure 2 shows data on the structure of porous polymers. The basic emulsions used in the experiments shown in the table are:
It consisted of 10 ml of styrene, 1 ml of divinylbenzene, 2 g of Span 80, and 200 ml of water containing 0.2% sodium persulfate. The emulsions used in the experiments in the table were the same as those described above except that 300 ml of water were used, and in both cases the preparation was generally as described in Example 1 below. The emulsion was prepared at a stirrer speed of 200 rpm, and after all ingredients had been mixed, the emulsion sample was stirred at the speed shown in the table for 30 minutes before cross-linking, and the sample of porous cross-linked polymer was prepared. I got it. Viscosity measurements were made using a Bruckfield viscometer, rotating the "C" spindle at 10 rpm and 20 rpm as indicated in the table.

【table】

TABLE From the table above, it is clearly seen that the viscosity of the emulsion is related to the size of the pores or cavities of the crosslinked polymer and the size of the continuous passages between the pores or cavities. It is clear that by appropriate selection of the speed of the stirrer and thus the viscosity of the emulsion, the cavity and size of the crosslinked polymer can be precisely controlled. A variety of monomers can be used to make porous polymers according to the invention. A preferred polymer is slightly cross-linked polystyrene with a low proportion of divinylbenzene. moreover,
Polymeric block materials have been prepared using various cross-linked acrylate polymers of, for example, allyl methacrylate. Generally, the ratio of sphere or cavity size to continuous pore or pinhole size is on the order of 7:1. It is desirable to include the polymerization catalyst in the aqueous phase and allow polymerization to occur after it has migrated into the oil phase. Alternatively, the polymerization catalyst may be added directly into the oil phase. Suitable water-soluble catalysts include potassium persulfate, as well as various redox systems such as ammonium persulfate with sodium pyrosulfite. Monomer soluble catalysts include azodibisisobutyronitrile (AIBN),
Included are benzoyl peroxide and di-2-ethylhexyl peroxydicarbonate. It will be appreciated that the temperature at which the polymerization is carried out can vary quite widely over about 30 DEG to 90 DEG C., depending on the particular catalyst used. The surfactant used in the production of highly discontinuous phase emulsions to be polymerized is a very important element.
The long-term stability of highly discontinuous phase emulsions does not need to be given much importance; it is sufficient that the stability is maintained during polymerization. Using the well-known term HLB for surfactants, it is desirable to use a surfactant having an HLB value of 2 or more and 6 or less, preferably about 4. Many surfactants can be used in the production of porous crosslinked polymers as long as they meet the HLB requirements. The main suitable surfactants are: nonionic HLB sorbitan monooleate (span 80) 4.3 Glycerol monooleate 3.8 Glycerol monoricinolate 4.0 PEG 200 dioleate 4.6 Some fatty acid esters of polyglycerols [Bronborough, England] Admul wall sold by Food Industries Ltd.
Wol) 1403] Castor oil 5-10EO 3-6 cationic Distearyl Dimethyl ammonium chloride 5-6 Dioleyl Dimethyl ammonium chloride
5-6 anionic bis-tridecyl sulfosuccinic acid (Na salt)
5-6 Experiments have shown that the amount of surfactant in the system is a critical factor, and if there is not enough surfactant, the cavities cannot have the desired absorption capacity. I also realized that. This can be clearly seen by looking at Figure 1. FIG. 1 shows a 96.5
Figure 2 shows the effect of surfactant concentration on oil absorption capacity in discontinuous phase emulsions in %.
From this experiment, it can be seen that the optimum concentration of surfactant is of the order of 20% relative to the weight of the monomer, but advantageous results are obtained within the range of 5-30%, preferably 15-25%. be able to. The polymers of the present invention are prepared by first forming a highly discontinuous phase emulsion of the water-in-oil type in which the oil phase is made up of a monomer or a mixture of monomers with a small amount of crosslinking agent. The polymerization initiator or catalyst may be dissolved in either the water phase or the oil (monomer) phase. Highly discontinuous phase emulsion systems are prepared using oil (monomer) preferably containing an emulsifier (surfactant) under moderate shear and agitation.
It is produced by gradually adding an aqueous discontinuous phase to the phase. The polymerization vessel is advantageously capped to minimize depletion of volatile monomers, and the emulsion is polymerized in the vessel by heating. Water contained in cavities or voids within the polymer structure can be exchanged with other liquids;
Alternatively, the polymer can be easily removed by subjecting it to reduced pressure or by leaving it in a dry atmosphere at about 30° to 60°C. The liquid can then be reintroduced into the dry polymer, preferably after removing the air under reduced pressure. Also according to the invention, the discontinuous phase comprises at least 90% water of the emulsion, the remaining polymerizable monomer, and 5 to 30% by weight of the monomers a surfactant and 0.005 to 10% by weight of the monomers a polymerization catalyst. A method is provided for producing a homogeneous, porous, crosslinked polymeric block material by polymerizing monomers in the form of a highly discontinuous phase emulsion comprising: The container may be of any convenient shape that allows the blocks to be manufactured into the shape desired for the end use and that does not cause agglomeration of the beads under pressure. The homogeneous porous cross-linked polymeric block material of the present invention, upon washing and drying, becomes an absorbent block that is particularly useful for absorbing hydrophobic substances such as oils. This block substance should be a liquid (as water) of at least 10 times its own weight, preferably 15
times its own weight, and in its most preferred form, from as little as 35 times its own weight to the highest possible limit of its own weight.
It can hold up to 65 times more water. The method according to the invention can be modified by using an aqueous liquid containing useful solutes instead of using water as the discontinuous phase. It goes without saying that such in-situ polymerization methods can only be used with aqueous liquids that do not destabilize highly discontinuous phase emulsions. For example, it is not suitable for liquids containing high HLB surfactants, which can destabilize emulsions. One class of liquids suitable for in-situ polymerization consists of solutions of oxygen bleaches, especially hydrogen peroxide-based bleaches. The method for producing the porous polymer block material of the present invention will be explained below by way of example. In the examples, "Span,""Antarox,""Polyhipe," and "Admal" are trade names. Example 1 10 ml of styrene, 0.5 ml of commercial divinylbenzene containing 0.25 ml of ethylene vinylbenzene, 2 g of emulsifier (sorbitan monooleate, Span 80)
were mixed together in a plastic beaker at 15°C. After setting up the stirrer, a protective film was placed over the beaker to reduce evaporation of the monomer. Adjust the stirrer speed to 300 rpm and add distilled water.
The entire solution of 0.7 g of potassium persulfate in 350 ml was added dropwise to the beaker. A thick, creamy, white stable emulsion was thus obtained. The emulsion was placed in a sealed plastic container and allowed to polymerize at 50°C for 3 days. The resulting water-filled polymer was cut into small blocks and dried in a dry atmosphere at 25°-30°C. The dried polymer has a semiflexible structure and continuous voids. When this polymer was placed in oleic acid, it absorbed more than 30 times its own weight in 10 minutes, and when the polymer was placed in a mixture of oleic acid and water, only oleic acid was effective. Absorbed. This polymer is
It had a dry density of 0.037 g/cc and a pore volume of 27 c.c./g. Example 2 10 ml of styrene, 0.25 ml of divinylbenzene and 2 ml of Span 80 were mixed in a plastic beaker at 25°C. Example 1 Add 300 ml of a solution of 0.25% potassium persulfate in distilled water to the monomer phase and hold at 60°C for 8 hours.
The polymerization was carried out in the same manner as described in . When this polymer was placed in heavy grade liquid paraffin with a density of 0.870-0.890 at 20°C and a viscosity of 178 centipoise at 25°C, approximately 20 times its own weight of paraffin was absorbed. This polymer is 0.044
It had a dry density of g/cc and a pore volume of 22 c.c./g. Example 3 Styrene 8.5ml, monooctyl itaconate 1.0
ml, divinylbenzene 0.5ml, di-2-ethylhexyl peroxycarbonate (initiator) 0.2ml,
and nonylphenol/1.5EO-antalox
2 ml of C0210 were mixed together at 15°C. Following the method described in Example 1, 200 ml of distilled water was added to the monomer phase before polymerization at 50° C. for 24 hours. When this polymer was placed in oleic acid, it absorbed about 15 times its own weight in oleic acid. This polymer is
It had a dry density of 0.061 g/cc and a pore volume of 16 c.c./g. Example 4 5 ml of styrene, 5 ml of butyl methacrylate, 0.25 ml of allyl methacrylate (crosslinking agent) and 2 ml of Span 80 in a plastic beaker at 20°C.
mixed together at. Potassium persulfate 0.2%
300 ml of the solution were added to the monomer phase and the polymerization was carried out according to the method of Example 1. When the dry polymer was placed inside a perfume, it absorbed about 50 times its own weight in perfume and then released it very slowly. The dry polymer had a flexible structure. Example 5 10ml of styrene, 1ml of divinylbenzene (50% ethylvinylbenzene) and 2g of Span 80 were mixed together. 450 ml of a solution of 0.2% potassium persulfate in distilled water were added to the monomer phase and the resulting emulsion was polymerized in the same manner as described in Example 1. The dried polymer absorbed about 40 times its own weight in oleic acid. After removal of soluble impurities with methanol using a Soxhlet extraction apparatus, the polymer absorbed approximately 43 times its own weight in oleic acid. The dry density of the polymer after drying is 0.025cc/g, and the emulsion is
It contained 97.8% dispersed aqueous phase. Examples 6-27 Using the general procedure described in Example 1, experiments were conducted using the raw materials shown below and in the table. The data for Examples 6-27 are as shown in the table. Explanation of the raw materials listed in the table used in Examples 6 to 27 Raw materials used in the continuous phase A Styrene B Butylstyrene C Butyl methacrylate D Ethyl methacrylate E Approximately 50% divinylbenzene + 50% ethyl vinylbenzene F Allyl methacrylate G N- Octadecyl Succinic Acid H Span 80 (Sorbitan Monooleate) J Ethomeen 18/12 [Bis-(2
-Hydroxyethyl)octadecylamine] K Arodobs [DOb 102
Acid + Arromox DMHTD Alkylbenzenesulfonic acid + dimethyl cured tallow, amine oxide] L Admar Wall 1403 (partial fatty acid ester of polyglycerol) N Raw material used for benzoyl peroxide discontinuous phase O Water P Glycerol Q Sodium persulfate R Potassium persulfate S 2,2-azobis-(2-amidinopropane)
hydrochloride

【table】

【table】

[Table] *Dry density after washing with methanol/water.
Example 28 Polyhype loaded with silica particles 10ml styrene, 1ml divinylbenzene (50% ethylvinylbenzene), 1g Span 80 and
1.5 g of silica (Aerosil R972 from Degussa) was mixed in. 0.5%
200 ml of sodium persulfate solution were added to the above mixture and polymerized as in Example 1 to obtain a porous material known as Polyhype. After drying, the resulting polymer absorbed about 10 times its own weight in oleic acid. Example 29 Preparation of a porous polymer containing a streak-free cleaning composition A liquid cleaning composition was prepared as follows: C ₁₂ ~ condensed with 7 moles of ethylene oxide by weight %
C ₁₅ Primary linear alcohol 10 Partial ester of styrene-maleic anhydride copolymer, neutralized to sodium salt (average molecular weight
10000, theoretical acid value 190) 2 Make 100% with deionized water and fragrance. This composition was then expanded 100 times with deionized water. Polymers were prepared as described in Example 2 and 25°
It was dried under a dry atmosphere at ~30 °C. Using a Soxhlet extractor, the dried polymer was washed several times with ethanol and then dried again under a dry atmosphere at 25°-30°C. The diluted liquid composition described above was then filled into the polymer under reduced pressure. The liquid absorption amount was 96% by weight. The resulting polymeric material, including the liquid cleaning composition, was a solid block that felt only slightly wet to the touch. The liquid could be released by simply pressing or squeezing. Example 30 Hydrogen peroxide-containing product Styrene 10 ml DVB 1 ml Span 80 28 g Water (25% hydrogen peroxide, 0.2% potassium persulfate)
A cross-linked polymer containing 300 ml H ₂ O ₂ was used as a stain remover for textiles. Example 31 Large scale production (26Kg) Styrene 800ml DVB 80ml Span 80 160g are mixed together at 20°C in a hydrophobic container with moderate agitation (using a PTFE coated spiral paddle stirrer) ), the monomer phase contains 25
of water (+0.2% sodium persulfate) was added (12/hour). The obtained emulsion was polymerized at 60°C overnight,
A homogeneous crosslinked polymer block of the invention was obtained.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between surfactant concentration and oil absorption in the products of the present invention.

Claims (1)

[Scope of Claims] 1. A porous, homogeneous structure comprising a number of substantially spherical cavities separated from each other by thin walls, the walls having pores connecting the cavities. a crosslinked vinyl polymer block material formed in a container by vinyl polymerization from a water-in-oil emulsion containing at least 90% by weight water, and
It has a dry density of 0.1 g/cc or less, and further has a dry density of 9
cc/g or more and an absorption capacity for hydrophobic liquids (as oleic acid) of at least 7 c.c./g. 2. A porous homogeneous crosslinked polymeric block material according to claim 1 having a dry density of 0.02 to 0.08 g/cc. 3 water or an aqueous solution as a discontinuous phase, at least 90% by weight of the emulsion, a polymerizable vinyl monomer as a continuous phase, and 5 to 5% by weight of the monomers.
30% of 2 to 6 selected from anionic, nonionic and cationic types and mixtures thereof.
forming a highly discontinuous phase emulsion of water-in-oil containing a surfactant having an HLB value and a polymerization catalyst of 0.005 to 10% by weight of the monomers in a vessel and polymerizing the continuous phase of the emulsion; characterized by a structure consisting of a number of substantially spherical cavities separated from each other by thin walls, the walls having holes connecting the cavities, and a and a pore volume of at least 9 c.c./g and a dry density of at least 7 c.c./g.
A method for producing a porous homogeneous crosslinked vinyl polymer block material having an absorption capacity for hydrophobic liquids (as oleic acid) of cc/g.