JP5442360B2 - Method for producing silicone rubber fine particles coated with organic polymer fine particles - Google Patents

Description

  The present invention relates to silicone rubber fine particles coated with organic polymer fine particles and a method for producing the same.

  Silicone rubber fine particles are used in various applications such as an internal stress relaxation agent for a thermosetting resin, a surface lubricant for an organic resin film, a light diffusing agent, a progress of cosmetics, and a feel improver. As a method for producing such silicone rubber fine particles, a method of preparing an aqueous emulsion of a curable liquid silicone composition and curing the composition to prepare an aqueous dispersion of silicone rubber fine particles (for example, Patent Documents 1 to 3). See).

  However, in the above method, when water is removed from the aqueous dispersion of the silicone rubber fine particles, the silicone rubber fine particles are easily aggregated, and thus the obtained silicone rubber fine particles become an aggregate of primary particles. there were. For example, the silicone rubber fine particles obtained by these methods are inferior in fluidity and dispersibility and can be crushed to some extent by an atomizer or a jet mill, but are completely elastic primary particles because they are soft elastic rubber particles. It cannot be crushed. In order to solve this problem, silicone rubber coated with inorganic fine particles as a silicone rubber fine particle having no dispersibility and fluidity and having good dispersibility and fluidity (for example, see Patent Document 4), polyorganosilsesquioxane Resins coated with a resin (see, for example, Patent Document 5) have been proposed, but those coated with inorganic fine particles have the disadvantage of poor compatibility with various resins. In the case of coating with an oxan resin, there is a problem that disposal of the separated liquid becomes difficult because alcohol is generated in the system because organosilane is hydrolyzed and condensed during the coating.

JP-A 63-77942 JP-A 64-70558 JP-A 63-309565 JP-A-4-348143 Japanese Patent Laid-Open No. 7-196815

  An object of the present invention is to provide silicone rubber fine particles excellent in fluidity and dispersibility coated with organic polymer fine particles, and a method for producing the fine particles with high productivity without by-products such as alcohol.

  The silicone rubber fine particles of the present invention are obtained by coating silicone rubber fine particles having a volume average particle diameter of 0.1 to 200 μm with organic polymer fine particles, and there is no aggregation or fusion between primary particles, and fluidity and dispersion. It is rich in nature. These fine particles can be easily obtained with high productivity by adding organic polymer fine particle powder or organic polymer fine particle emulsion to an aqueous dispersion of silicone rubber fine particles having an average particle size of 0.1 to 200 μm and removing water. it can. Details will be described below.

  The silicone rubber fine particles used in the present invention have a volume average particle size of 0.1 to 200 μm, preferably 0.5 to 100 μm, more preferably 1 to 50 μm.

Silicone rubber fine particles are produced by condensation reaction of methoxysilyl group (≡SiOCH ₃ ) and hydroxysilyl group (≡SiOH), radical of mercaptosilyl group (≡SiSH) and vinylsilyl group (≡SiCH = CH ₂ ). Examples thereof include reaction, addition reaction of vinylsilyl group (≡SiCH═CH ₂ ) and ≡SiH group, etc., but it is preferable to produce by addition reaction from the viewpoint of reactivity and reaction process, and (a) It is preferable that the vinyl group-containing polydimethylsiloxane and (b) polymethylhydrogensiloxane are subjected to an addition reaction in the presence of (c) a platinum-based catalyst and cured.

  The component (a) is a main component of the silicone rubber fine particles, and is a component that is cured by addition reaction with the component (b) by the catalytic action of the component (c). This component (a) has at least two vinyl groups bonded to silicon atoms in one molecule. This vinyl group may be present in any part of the molecule (a), but is preferably present at the end of the molecule. The viscosity of this component at 25 ° C. can be advantageously used with a molecular weight of 100 to 5000 centipoise, and the higher the viscosity, the softer the rubber particles can be obtained. Rubber particles that can be handled as elastic fine particles are obtained. When it exceeds 5000 centipoise, it becomes a soft gel-like material, and it becomes difficult to maintain the shape as particles.

  The component (b) is a crosslinking agent for the component (a), and a hydrogen atom bonded to a silicon atom in this component undergoes an addition reaction with the vinyl group in the component (a) by the catalytic action of the component (c). Harden. Therefore, the component (b) having at least two hydrogen atoms bonded to silicon atoms in one molecule is used. Further, it is desirable that this component (b) has good compatibility with the component (a). For this purpose, the viscosity at 25 ° C. is preferably 1 to 1000 centipoise, and 1 to 100 centipoise. Is more preferable. The amount of component (b) added is good when the amount of hydrogen atoms bonded to silicon atoms in this component is less than 0.5 per one vinyl group in component (a). If the amount is more than 10 hydrogen atoms, it is not preferable because the physical properties of the rubber after curing are lowered. The amount of hydrogen atoms is 0.5 to 10, preferably 1.0 to 3.0.

  Component (c) is a catalyst for addition reaction of a vinyl group bonded to a silicon atom and a hydrogen atom bonded to a silicon atom. For example, chloroplatinic acid, platinum-olefin complex, platinum-alcohol complex, platinum Examples include phosphorus complexes and platinum coordination compounds. If the amount of this component used is less than 5 ppm as platinum relative to component (a), curing will be slow and susceptible to catalyst poisons, but if it exceeds 50 ppm, it will not be possible to expect an improvement in curing rate, etc. Since it is not preferable in terms of properties, a range of 5 to 50 ppm is preferable. The platinum catalyst is preferably added dropwise after stirring the dispersion after the silicone component is dispersed in water.

  The silicone rubber spherical fine particles in the present invention are obtained by preparing dispersed droplets of a silicone composition and then curing in the droplets. For this, after mixing a predetermined amount of the above-mentioned vinyl group-containing polydimethylsiloxane as component (a) and polymethylhydrogensiloxane as component (b), after adding water and a surfactant, a homomixer, etc. Is used to disperse and form droplets. At this time, the content of the silicone rubber fine particle component in the aqueous dispersion is not particularly limited as long as the aqueous dispersion does not lose fluidity, specifically, 0.1 to 90% by weight, Preferably it is 0.1 to 50 weight%.

  As the surfactant to be used, nonionic surfactants such as polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene sorbitan fatty acid ester and glycerin fatty acid ester which have little adverse effect on the curing reaction may be used. Preferably, those having an HLB of 10 to 14 are preferably used. The addition amount of this surfactant is usually 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the total amount of component (a) and component (b). It is determined in consideration of time stability.

The organic polymer fine particles used in the production method of the present invention are components that impart fluidity and dispersibility to the silicone rubber fine particles. Specifically, polymethyl methacrylate, polystyrene, methyl methacrylate-styrene copolymer Examples thereof include fine particles made of polyamide, polyurethane and the like. These can be mixed with the silicone rubber fine particles as an aqueous dispersion, or can be mixed as a powder. The organic polymer fine particles have a volume average particle size that is large enough to coat the silicone rubber fine particles, and is usually in the range of 0.01 to 10 μm, preferably in the range of 0.05 to 2 μm. Is used. In addition, organic polymer fine particles having a volume average particle size of usually 1/5 to 1/100, particularly 1/10 to 1/50 of the volume average particle size of the silicone rubber fine particles to be coated are preferably used.
The organic polymer fine particles may be uniformly coated on the entire surface of the silicone rubber fine particles or may partially cover the surface. In the production method of the present invention, the amount of the organic polymer fine particles There is no particular limitation as long as the aqueous dispersion of the mixture of rubber fine particles and organic polymer fine particles does not lose fluidity, and specifically, 0.5 to 100 weights with respect to 100 parts by weight of the silicone rubber fine particle component. Part, preferably 1 to 50 parts by weight.

  As a method for producing the organic polymer fine particles used in the present invention, known techniques such as an emulsion polymerization method, a dispersion polymerization method, a fine suspension polymerization method and a suspension polymerization method can be used. When producing these organic polymer fine particles, divinylbenzene, ethylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, hexane are used to provide required performance such as heat resistance and solvent resistance depending on the application. Crosslinkable monomers such as diol di (meth) acrylate, diethylene glycol di (meth) acrylate, allyl (meth) acrylate, allyl malate, diallyl fumarate, diallyl itaconate and triallyl isocyanurate can be copolymerized. Furthermore, in order to improve compatibility with the silicone rubber fine particles, β-methacryloyloxyethyldimethoxymethylsilane, γ-methacryloyloxypropylmethoxydimethylsilane, γ-methacryloyloxypropyldimethoxymethylsilane, γ-methacryloyloxypropyltrimethoxysilane, So-called silane coupling agents such as γ-methacryloyloxypropylethoxydiethylsilane, γ-methacryloyloxypropyldiethoxymethylsilane, and δ-methacryloyloxybutyldiethoxymethylsilane can also be copolymerized. In addition, when taking out as a powder, there are a method of adding a metal salt such as calcium chloride, magnesium chloride and magnesium sulfate to an organic polymer fine particle aqueous dispersion, and a method of solidifying and separating by freezing and thawing the aqueous dispersion. can give. A spray drying method can also be used.

  As a method of attaching the organic polymer fine particles to the surface of the silicone rubber fine particles, there is a method of mechanically mixing the silicone rubber fine particle powder and the organic polymer fine particle powder by a Henschel mixer or the like. Since it is difficult to uniformly coat with organic polymer fine particles and it takes a long time, productivity is inferior. In order to obtain a uniform powder mixture composed of silicone rubber fine particles and organic polymer fine particles with good productivity, a method of removing water from an aqueous dispersion of a mixture composed of silicone rubber fine particles and organic polymer fine particles is preferable. Specific examples include a method of drying an aqueous dispersion of a powder mixture composed of silicone rubber fine particles and organic polymer fine particles in an oven, a method of drying the aqueous dispersion with a spray dryer, and the like.

  According to the present invention, it is possible to easily coat organic polymer fine particles on the surface of silicone rubber fine particles without complicated reaction and generation of by-products, and the obtained coated fine particles have excellent fluidity and dispersibility. have. In addition, since the type and amount of organic polymer fine particles to be coated on the silicone rubber fine particles can be easily adjusted, it is possible to produce silicone rubber fine particles having excellent compatibility with the resin to be dispersed. The silicone rubber fine particles obtained in this manner are very well dispersed and mixed in an organic resin, and are excellent as organic resin modifying powder, coating powder or cosmetic powder.

  The present invention will be specifically described with reference to synthesis examples, examples and comparative examples. In the examples, the viscosity value is a value measured at 25 ° C., and the average particle size of the silicone rubber fine particles is a volume average value measured by Multisizer III manufactured by Beckman-Coulter. The average particle size of the organic polymer fine particle emulsion is an average particle size value measured by ELS-8000 of Otsuka Electronics.

[Synthesis Example 1]
Production example 1 of silicone rubber fine particles
In a separable flask, 98 parts by weight of divinylpolydimethylsiloxane at both ends (molecular weight 10000, viscosity 230 mm ² / s, Si-bonded vinyl group content 0.5 wt%), 2 parts of polymethylhydrogensiloxane (molecular weight 2000, viscosity 25 mm ² / s, Si-bonded hydrogen content 1.5 wt%) was added and stirred and mixed for 10 minutes. Next, with a homomixer, 3.5 parts of polyoxyethylene lauryl ether (HLB 13.8) and 50 parts of ion-exchanged water were added dropwise with rotary stirring at 8000 rpm, and after 20 minutes of emulsification, ion exchange was performed. 200 parts of water was dropped and dissolved under low stirring. To this emulsion, 0.45 wt% (platinum content) platinum complex catalyst toluene solution 1.8 mL of polyoxyethylene lauryl ether was added dropwise, stirred at room temperature (25 ° C.), and then heated to 70 ° C. Then, a curing reaction was performed for 3 hours. The volume average particle diameter of the obtained fine particle dispersion was measured and found to be 6.5 μm.

[Synthesis Example 2]
Production example 2 of silicone rubber fine particles
In a separable flask, both ends divinylpolydimethylsiloxane (molecular weight 19000, viscosity 600 mm ² / s, Si-bonded vinyl group content 0.35 wt%) 98 parts, polymethylhydrogen siloxane (molecular weight 2000, viscosity 25 mm ² / s, Si 2 parts of hydrogen content (bonded hydrogen content 1.5 wt%) was charged, stirred and mixed. Then, a solution of 3.5 parts of polyoxyethylene lauryl ether (HLB 13.8) and 50 parts of ion-exchanged water was added dropwise with a homomixer while stirring at 6000 rpm, and after 20 minutes of emulsification, ion exchange was performed. 200 parts of water was dropped and dissolved under low stirring. To this emulsion, 0.45% (platinum content) platinum catalyst toluene solution 1.8 mL of polyoxyethylene lauryl ether emulsion was dropped, and after stirring at room temperature, the temperature was raised to 70 ° C. and the curing reaction was carried out for 3 hours. went. The volume average particle size of the obtained fine particle dispersion was measured and found to be 9.9 μm.

[Synthesis Example 3]
Production Example of Polymethyl Methacrylate Fine Particle Emulsion A separable flask was charged with 580 parts of ion-exchanged water and 3.5 parts of sodium lauryl sulfate, and the temperature was raised to 70 ° C. while stirring at 180 rpm, and the atmosphere was replaced with nitrogen. To this, 0.9 part of sodium persulfate was added, and 400 parts of methyl methacrylate monomer was added dropwise over 5 hours to react. Thereafter, aging was performed for 3 hours at the same temperature. The solid content and average particle diameter of the emulsion at the end of the polymerization were measured and found to be 40.5% and 290 nm.

[Synthesis Example 4]
Production Example of Polystyrene Fine Particle Emulsion A separable flask was charged with 550 parts of ion-exchanged water and 6 parts of sodium dodecylbenzenesulfonate, and the temperature was raised to 80 ° C. while stirring at 200 rpm, and the atmosphere was replaced with nitrogen. To this, 0.8 part of potassium persulfate was added, and 400 parts of styrene monomer was added dropwise over 4 hours to react. Thereafter, aging was performed for 3 hours at the same temperature. The solid content and average particle size of the emulsion at the end of the polymerization were measured and found to be 41.2% and 380 nm.

[Synthesis Example 5]
Production Example of Polymethyl Methyl Methacrylate-γ-Methacryloyloxypropyltrimethoxysilane Copolymer Fine Particle Emulsion The same operation as in Application Example 1 except that 4 parts of γ-methacryloyloxypropyltrimethoxysilane was added to 400 parts of methyl methacrylate monomer Then, a copolymer emulsion of methyl methacrylate and γ-methacryloyloxypropyltrimethoxysilane was obtained. The solid content and average particle diameter of the obtained emulsion were measured and found to be 40.9% and 270 nm.

[Synthesis Example 6]
Polystyrene-γ-methacryloyloxypropyltrimethoxysilane copolymer fine particle emulsion production example Polystyrene-γ was prepared in the same manner as in Application Example 2 except that 4 parts of γ-methacryloyloxypropyltrimethoxysilane was added to 400 parts of styrene monomer. -A copolymer emulsion of methacryloyloxypropyltrimethoxysilane was obtained. The solid content and average particle diameter of the obtained emulsion were measured and found to be 41.7% and 350 nm.

  To 100 parts of the silicone rubber fine particle dispersion prepared in Synthesis Example 1, 7.2 parts of the polymethyl methacrylate fine particle emulsion prepared in Synthesis Example 3 was added and mixed uniformly, and then the inlet temperature was 140 ° C and the outlet temperature was 70 ° C. Drying was performed with a spray dryer set to 1. As shown in the scanning electron micrograph of FIG. 1, the obtained powder mixture was confirmed to have the surface of the silicone rubber fine particles coated with polymethyl methacrylate fine particles. The granules remained as primary particles and were extremely fluid.

  After adding 7.4 parts of the polystyrene-γ-methacryloyloxypropyltrimethoxysilane copolymer fine particle emulsion prepared in Synthesis Example 6 to 100 parts of the silicone rubber fine particle dispersion prepared in Synthesis Example 1 and mixing them uniformly, Drying was performed with a spray dryer set at an inlet temperature of 140 ° C and an outlet temperature of 70 ° C. The obtained powder mixture was rich in fluidity because the silicone rubber fine particles were coated with polystyrene-γ-methacryloyloxypropyltrimethoxysilane copolymer fine particles.

  After adding 7.3 parts of the polystyrene fine particle emulsion prepared in Synthesis Example 4 to 100 parts of the silicone rubber fine particle dispersion prepared in Synthesis Example 2 and mixing them uniformly, the inlet temperature was set to 140 ° C. and the outlet temperature was set to 70 ° C. Drying was performed with a spray dryer. The obtained powder mixture was a silicone rubber fine particle coated with polystyrene fine particles, and was rich in fluidity.

  To 100 parts of the silicone rubber fine particle dispersion prepared in Synthesis Example 2, 7.3 parts of the polymethyl methacrylate-γ-methacryloyloxypropyltrimethoxysilane copolymer fine particle emulsion prepared in Synthesis Example 5 was added and mixed uniformly. Then, drying was performed with a spray dryer set to an inlet temperature of 140 ° C and an outlet temperature of 70 ° C. The obtained powder mixture had high fluidity because the silicone rubber fine particles were coated with polymethyl methacrylate-γ-methacryloyloxypropyltrimethoxysilane copolymer fine particles.

  After adding 14.8 parts of the polystyrene-γ-methacryloyloxypropyltrimethoxysilane copolymer fine particle emulsion prepared in Synthesis Example 6 to 100 parts of the silicone rubber fine particle dispersion prepared in Synthesis Example 1 and mixing them uniformly, Drying was performed with a spray dryer set at an inlet temperature of 140 ° C and an outlet temperature of 70 ° C. The obtained powder mixture was rich in fluidity because the silicone rubber fine particles were coated with polystyrene-γ-methacryloyloxypropyltrimethoxysilane copolymer fine particles.

[Comparative Example 1]
The silicone rubber fine particle dispersion prepared in Synthesis Example 1 was dried with a spray dryer set at an inlet temperature of 140 ° C. and an outlet temperature of 70 ° C. The obtained powder was partially agglomerated with silicone rubber fine particles and had poor fluidity.

[Comparative Example 2]
The silicone rubber fine particle dispersion prepared in Synthesis Example 2 was dried with a spray dryer set at an inlet temperature of 140 ° C. and an outlet temperature of 70 ° C. The obtained powder was partially agglomerated with silicone rubber fine particles and had poor fluidity.

[Test Example 1]
In order to evaluate the fluidity and dispersibility of the obtained powder, a low tap type vibration sieve machine A type (manufactured by Advantech Toyo Co., Ltd.) was applied with a vibration frequency of 290 rpm and a vibration frequency of 156 strokes / min for 180 seconds. The sieving properties of 200 g (75 μm) and 100 mesh (150 μm) of 10 g of sample were measured. The results are shown in Table 1.

As is clear from Table 1, the powders of Examples 1 to 5 existed as primary particles and did not form secondary particles, so they were extremely fluid. On the other hand, in the powders of Comparative Examples 1 and 2, the primary particles aggregated to form secondary particles having a large particle size, and the fluidity was significantly reduced.

  By the production method of the present invention, silicone rubber fine particles coated with organic polymer fine particles can be produced with high productivity, and the obtained silicone rubber fine particles coated with organic polymer fine particles are aggregated and fused between primary particles. Since it has the characteristics that it is not worn and has excellent fluidity and dispersibility, it is suitable for various applications such as modifiers for lightening resin stress, light diffusing agents, extensibility of cosmetics, and touch modifiers. can do.

Scanning electron micrograph of a powder mixture comprising the silicone rubber fine particles and polymethyl methacrylate fine particles produced in Example 1

Claims (1)

100 parts by weight of silicone rubber fine particles (A) having a volume average particle size of 0.1 to 200 μm and polymethyl methacrylate, polystyrene, methyl methacrylate and γ-methacryloyloxypropyltrimethyl having a volume average particle size of 0.01 to 10 μm Organic that removes water with spray dryer from aqueous dispersion of mixture of 0.5 to 100 parts by weight of organic polymer (B) selected from copolymer of methoxysilane and copolymer of styrene and γ-methacryloyloxypropyltrimethoxysilane A method for producing silicone rubber fine particles coated with polymer fine particles.