JPH0952919A - Production of styene-based cross-linked polymer particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject particle having a sharp particle diameter distribution, useful as power for cosmetics, etc., by homogenizing a monomer mixture, a polymerization initiator and an aqueous dispersion. SOLUTION: (A) A monomer mixture comprising (i) a styrene-based monomer (e.g. styrene) and (ii) 1-50% of a polyfunctional (math) acrylic ester-based monomer having 17-18.5 (MPz)<0.5> solubility parameter (δ) at 25 deg.C (e.g. neopentyl glycol diacrylate, etc.), (B) an oil-soluble polymerization initiator (e. g. lauroyl peroxide, etc.) and (C) an aqueous dispersion containing an anionic emulsifying agent (e.g. sodium cetylsulfate, etc.) are homogenized and the component A is polymerized to give the objective particle.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing styrene-based crosslinked polymer particles.

[0002]

2. Description of the Related Art Styrene-based crosslinked polymer particles are used as makeup cosmetics, matting agents for paints, and light diffusing agents that are dispersed in transparent resin plates to impart light diffusing properties. A method for producing the crosslinked polymer particles by suspension polymerization or fine suspension polymerization of a styrene-based monomer is widely known.
For example, in JP-A-59-66406, an average particle size of about 3 is obtained by homogenizing an aqueous dispersion containing a styrene-based monomer, a monomer-soluble catalyst, and an anionic emulsifier, and then polymerizing the same. Disclosed is a method for producing fine spherical polymer particles having a particle size of ˜30 μm.

[0003]

When the crosslinked polymer particles are used as a light diffusing agent, in order to enhance not only the light diffusing property but also the light transmitting property, the styrene weight may be increased depending on the refractive index of the transparent resin plate. In some cases, it may be preferable that the refractive index of the united body is not the same and that the refractive index thereof is slightly lower. Therefore, in order to obtain the crosslinked polymer particles having a low refractive index, copolymerization with a monomer that gives a polymer having a lower refractive index than a styrene polymer may be performed. On the other hand, in order to obtain polymer particles having a uniform particle size by fine suspension polymerization, the monomers are previously dispersed uniformly in the aqueous dispersion system as oil droplets, and the particles are uniformly dispersed without agglomeration during the progress of polymerization. Must be maintained. The method disclosed in JP-A-59-66406 is not sufficient to satisfy both the selectivity of the refractive index and the uniformity of the particle diameter of the polymer particles obtained. Therefore, there is provided a method for producing styrene-based polymer particles having a uniform particle diameter and capable of setting the refractive index to an arbitrarily low value.

[0004]

Means for Solving the Problems That is, the present invention provides a polyfunctional (meth) acrylic acid having a styrene-based monomer content of 50 to 99% by weight and a solubility parameter δ at 25 ° C. of 17 to 18.5 (MPa) ^0.5. A styrene-based composition in which a monomer mixture comprising 1 to 50% by weight of an ester-based monomer, an aqueous dispersion containing an oil-soluble polymerization initiator and an anionic emulsifier is homogenized, and then the monomer-mixed substance is polymerized. It is a method for producing crosslinked polymer particles.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The styrene-based monomer used in the present invention is styrene and a derivative of styrene, and examples of the styrene derivative include halogenated styrene such as chlorostyrene and bromostyrene, vinyltoluene, and α-methyl. Alkyl-substituted styrenes such as styrene are mentioned. Two or more kinds of the above styrene-based monomers may be used in combination. The amount of the styrene-based monomer is 50 to 99 in all monomers.
% By weight.

Solubility parameter (δ) in the present invention
Of 17 to 18.5 (MPa) ^0.5
Acrylic ester monomers include neopentyl glycol diacrylate (δ = 18.04), neopentyl glycol dimethacrylate (δ = 17.65), 1.6
-Hexanediol dimethacrylate (δ = 18.22),
1.3-Butylene glycol dimethacrylate (δ = 1
8.14) and other diol di (meth) acrylates: trimethylolpropane trimethacrylate (δ = 18.37) and other trifunctional (meth) acrylates.
You may use together 2 or more types of these monomers. The amount of the polyfunctional (meth) acrylic acid ester-based monomer is 1 to 50% by weight based on all monomers. The larger this amount, the lower the refractive index of the polymer particles obtained.

The solubility parameter (δ) referred to in the present invention is the square root of the cohesive energy density of molecules, and is an index of the attractive force between molecules. This numerical value is obtained from the calculation method by Small. The calculation method is R &
D Report No. 8 “Polymer Blend” (CMC Co., Ltd., issued on September 28, 1979) on pages 97-99 or POLYMER HANDBOOK third edition (Polymer Handbook 3rd edition) VII / 524-VII / 525 It can be determined from the group mol traction force constant (F), the specific gravity of the monomer, and the molecular weight as described in [Equation 1]. The unit of δ is (MPa) ^0.5 .

[0008]

Where ρ is the specific gravity of the substance, Fi is the molar traction force constant of a specific group forming one molecule of the substance, and M is
Is the molecular weight of the substance.

An example of calculating the solubility parameter is shown below. For example, in the case of 1.6-hexanediol dimethacrylate,
From the above-mentioned "Polymer Blend" magazine, the F value is CH ₂ = 1
90, CH ₃ − is 214, ═C <is 19, —COO— is 310, and —CH ₂ — is 133, so 190 × 2 +
It becomes 214 × 2 + 19 × 2 + 310 × 2 + 133 × 6, which is 2264. Since the specific gravity of 1.6-hexanediol dimethacrylate at 25 ° C is 0.997 and the molecular weight is 254, δ is 8.89 (cal / cal) from [Equation 1].
cm ³ ) ^0.5 , which is 18.2 (MP
a) It becomes ^0.5 .

This solubility parameter is 17-18.5.
If a monomer deviating from (MPa) ^0.5 is used, aggregation of particles tends to occur during the polymerization, and the particle size distribution tends to be broad.

As the polymerization initiator in the present invention, benzoyl peroxide, lauroyl peroxide, t
There are organic peroxides such as butyl peroxybenzoate and azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. These can be used alone or in combination.

These polymerization initiators are used in an amount of 0.2 to 5 parts by weight based on 100 parts by weight of all monomers.

Examples of the anionic emulsifier in the present invention include aliphatic salts such as sodium oleate and potassium castor oil soap, higher alcohol ester salts such as sodium lauryl sulfate and sodium cetyl sulfate, and alkylaryl sulfones such as sodium dodecylbenzenesulfonate. Acid salts, sodium alkylnaphthalene sulfonate, sodium salts of β-naphthalene sulfonic acid formalin condensate, derivatives of naphthalene sulfonates, dialkyl sulfosuccinates, dialkyl phosphates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl Examples thereof include ether sulfate triethanolamines and polyethylene alkylphenol ether sulfates. Among these, higher alcohol sulfates are preferably used because the polymerization is more stable.

The amount of the anionic emulsifier is generally 0.1 to 5 parts by weight based on 100 parts by weight of all the monomers. If the amount of the emulsifier is too small, the particles may aggregate during the polymerization, while if it is too large, the generation of fine particles of less than 1 μm increases.

In addition to the anionic emulsifier, a nonionic emulsifier as a dispersion aid, such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, sorbitan alkyl ester, or lauryl alcohol. It is also possible to add higher alcohols such as myristyl alcohol and cetyl alcohol, as well as polyvinyl alcohol, methyl cellulose and gelatin.

The aqueous dispersion of the present invention comprises water as the above-mentioned monomer, polymerization initiator and emulsifier. If necessary, the monomer may contain an ultraviolet absorber, a dye or the like. And the ratio of water to total monomers W / O = 1-10.

The aqueous dispersion is homogenized. The homogenization treatment is a known method in which fine homogenization of vinyl monomers is carried out in advance. That is, a suspension containing fine monomer droplets is prepared using a device such as a two-stage high pressure pump, a colloid mill, a homomixer.

The droplet size of the monomer in this aqueous dispersion directly becomes the particle size of the polymer particles. The monomer droplet size can be easily adjusted by controlling the amount of the anionic emulsifier used and the shearing force for homogenization. The smaller the amount of the anionic emulsifier used and the smaller the shearing force for homogenization, the larger the size of the liquid droplets, and thus the particles having the desired particle diameter can be obtained by several trials. In the present invention, the droplet size is about 2 to 20 μm in average particle diameter.

Since the homogenization treatment contains a polymerization initiator in the dispersion, it is desirable that the homogenization treatment be carried out at a temperature not higher than the decomposition temperature of the polymerization initiator, preferably near room temperature. In the homogenization treatment, it is desirable to homogenize the whole amount of the monomer used, but it is also possible to homogenize a part of the monomer and then add the rest continuously or intermittently in the polymerization process.

The homogenized dispersion is polymerized in an ordinary stirring tank. Since the polymerization temperature is suitably 50 to 90 ° C., a polymerization initiator which is easy to polymerize in the temperature range may be appropriately selected from among those listed above and used.

After the completion of the polymerization, the polymer particle dispersion is spray-dried as it is, or the polymer is isolated by centrifugation or filtration. Upon filtration, an electrolyte or an acid is added to the polymer particle dispersion liquid for salting out, followed by filtration to separate the polymer.

[0022]

By the production method of the present invention, it is possible to obtain styrene-based crosslinked polymer particles having a sharp particle size distribution. The fine particles can be suitably used as a powder for cosmetics, as an anti-blocking agent, a light diffusing agent, a matting agent by being contained in various resins, and further as a matting agent for paints and toners.

[0023]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The evaluation method is as follows.・ Average particle size; optical diffraction scattering particle size measuring instrument (Nikkiso Co., Ltd.)
Manufactured by Microtrac Particle Size Analyzer Model 9220 FRA), and the value of D ₅₀ was taken as the average particle diameter.

Example 1 In a glass container having an internal volume of 2 L, 250 parts by weight of ion-exchanged water and 0.25 part by weight of sodium cetyl sulfate were prepared. 92 parts by weight of styrene and 1.6-hexanediol which had been prepared in advance. 8 parts by weight of dimethacrylate and 1.5 parts by weight of lauroyl peroxide were charged, and the solution was 8000 with a homomixer (TK HOMOMIXER, Tokushu Kika Kogyo Co., Ltd.).
Polymerization was carried out by stirring at rpm for 30 minutes to homogenize, followed by heating to an elevated temperature and holding at 70 ° C. for 3 hours while gently stirring. After the polymerization is completed, it is spray-dried and the refractive index is 1.5.
8, crosslinked polymer particles having an average particle diameter of 5 μm were obtained.

Example 2 Example 1 was repeated except that neopentyl glycol dimethacrylate was used in place of 1.6-hexanediol dimethacrylate in Example 1 and the homomixer rotation speed was 4000 rpm. Crosslinked polymer particles having a refractive index of 1.58 and an average particle diameter of 8 μm were obtained.

Example 3 The amount of styrene in Example 1 was 98.5% by weight and 1.
Example 1 was repeated except that the amount of 6-hexanediol dimethacrylate was 1.5% by weight. Refractive index 1.
59, cross-linked polymer particles having an average particle diameter of 4.5 μm were obtained.

Comparative Example 1 The procedure of Example 1 was repeated except that ethylene glycol dimethacrylate (δ = 18.86 (MPa) ^0.5 ) was used instead of 1.6-hexanediol dimethacrylate in Example 3. The obtained polymer had a large number of aggregated solids having a diameter of about 1 cm.

Claims (1)

[Claims] 1. Styrene-based monomer 50 to 99% by weight, 25
The solubility parameter (δ) at 17 ° C is 17 to 18.5.
An aqueous dispersion containing a monomer mixture consisting of 1 to 50% by weight of a polyfunctional (meth) acrylic acid ester monomer having (MPa) ^0.5 , an oil-soluble polymerization initiator and an anionic emulsifier is homogenized. Then, a method for producing styrene-based crosslinked polymer particles, in which the monomer mixture is polymerized.