JPH0616707A - Three-dimensional polymer fine particle, its production, low-shrinkage agent and unsaturated polyester resin composition - Google Patents

Abstract

PURPOSE:To obtain a three-dimensional polymer fine particle suitable as a low- shrinkage agent for a curable unsaturated polyester resin by producing a dispersion emulsion from a vinyl group-containing monomer, a cross-linking agent, a polymeriza tion initiator, an aqueous medium and a suspending agent and polymerizing the resul tant dispersed emulsion. CONSTITUTION:The three-dimensional polymer fine particle is obtained by feeding a mixture containing (A) 100 pts.wt. styrenic and/or acrylic monomer having one vinyl group, (B) 0.02-5 pts.wt. cross-linking agent composed of a monomer having two or more vinyl groups in one molecule (e.g. ethylene glycol dimethacrylate), (C) 0.05-10 pts.wt. polymerization initiator (preferably a peroxide-based polymerization initiator), (D) 80-400 pts.wt. aqueous medium and (E) 0.1-20 pts.wt. suspending agent (preferably tricalcium phosphate, hydroxyapatite, etc.) to a cylindrical vessel having a shearing stirrer (preferably a pipeline homomixer) and stirring the resultant mixture so as to provide 1-100mum average particle diameter of oil droplets at a high shearing rate while keeping the interior of the vessel in a pressurized state under >=0.2kg/cm<2>G pressure and polymerizing the obtained dispersed emulsion. This three-dimensional polymer fine particle has 2-40 swelling degree.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to three-dimensional polymer fine particles useful as a low-shrinking agent for curable unsaturated polyester resin, a process for producing the same, a low-shrinking agent and an unsaturated polyester resin composition.

[0002]

2. Description of the Related Art Curable unsaturated polyester resin compositions are used in various molded products such as molded products such as SMC, BMC and RIM. This curable unsaturated polyester resin composition is obtained by adding a polymerizable monomer such as styrene to an unsaturated polyester resin, and if necessary, a polymerization initiator, a low shrinkage agent, a reinforcing agent, a release agent, and a filling agent. It contains additives such as agents, thickeners and colorants, and is itself used as a molding material.

The low-shrinking agent added to the curable unsaturated polyester resin is for the purpose of preventing shrinkage during molding or preventing the reinforcing agent from floating on the surface of the molded product. For example, acrylic and styrene resins. Polymerizable monomer solution, resin powder such as thermoplastic nylon and polyethylene, polyvinyl chloride resin powder, three-dimensional acrylic resin and styrene resin powder.

However, conventional low-shrinkage agents have various problems. For example, when a polymerizable monomer solution of an acrylic resin, a styrene resin, or a vinyl acetate resin is used, or when these resin powders are used, the low shrinkage effect is sufficiently obtained, but the dispersibility and stability thereof are improved. Poorly, the composition becomes non-uniform. Further, when mixed, the low-shrinking agent is dissolved in the polymerizable monomer to increase the viscosity, which causes a problem that workability is deteriorated.

When a thermoplastic resin powder such as nylon, polyethylene, or polyvinyl chloride is used as the low-shrinking agent, the composition is excellent in uniform coloring but has low compatibility with the polymerizable monomer. Therefore, there is a problem that the low shrinkage effect is not sufficient. Furthermore, when three-dimensional acrylic and styrene resin powders are used (Japanese Patent Publication No. 51-1276).
If the crosslink density is less than 0.5%, the resin powder rapidly absorbs the polymerizable monomer and swells, thickens, or aggregates, and a uniform compound cannot be obtained. 5%
In the above case, a uniform compound can be obtained, but there is a problem that a sufficient low shrinkage effect cannot be obtained.

As a means for solving these problems, Japanese Patent Laid-Open No. 148558/1987 discloses a low-shrinking agent having a substance which is not readily soluble in a polymerizable monomer on the surface and a polymerizable monomer. By using a three-dimensional acrylic-based, styrene-based, vinyl acetate-based resin powder having a swelling degree of 2 to 40 with respect to the body, it has a sufficiently low shrinkage property with respect to the curable unsaturated polyester resin. It is disclosed that it is effective as a material exhibiting uniform colorability, dispersibility, and gloss of a molded article. However, the effect cannot be said to be sufficient. In particular, according to the disclosed method for producing a low-shrinking agent, a product having a sharp particle size distribution cannot be obtained, so that the molded product has insufficient properties such as uniform dispersibility, uniform colorability, and gloss.

[0007]

SUMMARY OF THE INVENTION The present invention is particularly directed to sharpening the particle size distribution of the resin fine particles used as the low-shrinking agent so as to obtain those characteristics, that is, uniform dispersibility, uniform colorability and gloss of the molded product. The present invention aims to improve properties such as transparency and transparency, and further provides a method for producing polymer fine particles in high yield.

[0008]

That is, according to the present invention, 100 parts by weight of a monomer having one styrene and / or acrylic vinyl group, 0.02 to 5 parts by weight of a crosslinking agent, and a polymerization initiator of 0.1. A mixture containing 05 to 10 parts by weight, 80 to 400 parts by weight of an aqueous medium, and 0.1 to 20 parts by weight of a suspending agent was supplied into a cylindrical container equipped with a shear stirring mechanism, and the inside of the container was adjusted to 0.2.
While maintaining a pressurized state of kg / cm ² G or more, high-speed shear stirring is performed so that the average particle diameter of the oil droplet particles is 1 to 100 μm to produce a dispersion emulsion, and this is polymerized. Method for producing three-dimensional polymer fine particles, three-dimensional polymer fine particles obtained by the production method, a low-shrinking agent comprising the same, and an unsaturated polyester resin composition containing an unsaturated polyester resin and the low-shrinking agent Regarding things.

Examples of the monomer having one styrene type and / or acrylic type vinyl group used in the present invention include the following. As the styrene-based monomer, besides styrene, α-methylstyrene, vinyltoluene, pt-
There are styrene derivatives such as butyl styrene.

As the acrylic monomer, acrylic acid,
Derivatives of acrylic acid, such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate,
Pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, undecyl acrylate, dodecyl acrylate, glycidyl acrylate, methoxyethyl acrylate, propoxyethyl acrylate, butoxyethyl acrylate , Methoxydiethylene glycol acrylate,
Ethoxydiethylene glycol acrylate, methoxyethylene glycol acrylate, butoxytriethylene glycol acrylate, methoxydipropylene glycol acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, phenoxytetraethylene glycol acrylate, benzyl acrylate, acrylic Cyclohexyl acid, tetrahydrofurfuryl acrylate, dicyclopentenyl acrylate, dicyclopentenyl oxyethyl acrylate, N-vinyl-2-pyrrolidone acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, acrylic acid 2-hydroxy-3-phenyloxypropyl, glycidyl acrylate, acrylonitrile, acrylamide, N Methylol acrylamide, diacetone acrylamide, or methacrylic acid, derivatives of methacrylic acid, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, Nonyl methacrylate, decyl methacrylate, undecyl methacrylate, dodecyl methacrylate, glycidyl methacrylate, methoxyethyl methacrylate, propoxyethyl methacrylate, butoxyethyl methacrylate, methoxydiethylene glycol methacrylate, ethoxydiethylene glycol methacrylate, methoxyethylene glycol methacrylate , Butoxytriethylene glycol methacrylate, methoxydipromethacrylate Ren glycol, phenoxyethyl methacrylate, phenoxydiethylene glycol methacrylate, phenoxytetraethylene glycol methacrylate, benzyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, dicyclopentenyl methacrylate, dicyclopentenyl oxyethyl methacrylate , N-vinyl-2-pyrrolidone methacrylate, methacrylonitrile, methacrylamide, N-methylol methacrylamide, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, 2-hydroxy-3-methacrylic acid methacrylate. Enyloxypropyl,
A vinyl-based monomer having one vinyl group in one molecule, such as vinylpyridine, may be mentioned. These can be used alone or in combination of two or more. In the present invention,
The amount of this monomer used is 100 parts by weight in order to make it the basic amount of other additives.

The crosslinking agent used in the present invention may be any monomer having two or more vinyl groups in one molecule, but one having two vinyl groups in one molecule is preferable. . Examples of preferable monomers include divinylbenzene, a reaction product of glycol and methacrylic acid or acrylic acid, such as ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, and 1 ，
Examples include, but are not limited to, 5-pentanediol methacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, and tripropylene glycol dimethacrylate. Not something. The addition amount thereof is 0.02 to 5 parts by weight with respect to 100 parts by weight of the monomer having one vinyl group. When the addition amount is less than 0.02 part by weight, the degree of swelling of the obtained polymer fine particles with respect to the polymerizable monomer is 40.
And the effect of low shrinkage is reduced. Meanwhile, 5
If the amount is more than parts by weight, the degree of swelling of the resulting polymer fine particles with respect to the polymerizable monomer will be less than 2, and the low shrinkage effect will be lost. Since the amount of the cross-linking agent added and the cross-linking density differ depending on the type, the swelling degree of the obtained polymer fine particles with respect to the polymerizable monomer is 2 to 40, particularly 5 as a guide.
It is preferable to adjust the addition amount of the cross-linking agent so as to be ˜20.

The polymerization initiator used in the present invention includes
Peroxide-based radical initiators are preferred, for example benzoyl peroxide, 2-ethylhexyl perbenzoate, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, lauroyl peroxide, ditert-butyl peroxide, cumene hydroperoxide, Methyl ethyl ketone peroxide,
4,4,6-Trimethylcyclohexanone ditert-
Butyl peroxyketal, cyclohexanone peroxide, methyl cyclohexanone peroxide, acetylacetone peroxide, cyclohexanone di-tert
-Butyl peroxyketal, acetone di-tert-
Examples thereof include peroxide-based radical polymerization initiators such as butyl peroxyketal and diisopropyl hydroperoxide. The radical polymerization initiator is used in an amount of 0.05 to 10 parts by weight based on 100 parts by weight of the monomer having one vinyl group. If the amount used is less than 0.05 parts by weight, the polymerization time will be long and the particle size distribution of the polymer particles will be broad. On the other hand, when the amount used exceeds 10 parts by weight, not only the polymerization initiator is wasted but also the crosslinking density is difficult to increase.

At the time of polymerization, a chain transfer agent can be added appropriately. Examples of the chain transfer agent include alkyl mercaptans such as t-dodecyl mercaptan, lower alkyl xanthogens such as diisopropyl xanthogen, carbon tetrachloride, carbon tetrabromide and the like. When these are used, a monomer having one vinyl group is used. It is preferable to add 0.1 part by weight or less to 100 parts by weight. It is preferable to adjust the addition amount of these in consideration of the degree of swelling.

The amount of the aqueous medium used in the present invention is basically 80 to 4 with respect to 100 parts by weight of a monomer having one vinyl group in order to emulsify and disperse oil droplets to a desired size.
It is 00 parts by weight. If the amount is less than 80 parts by weight, the viscosity of the emulsified dispersion liquid increases and it is difficult to adjust desired oil droplets, and if it exceeds 400 parts by weight, there is a problem that productivity is deteriorated.

The suspending agent used in the present invention is preferably a substance which is not readily soluble in the polymerizable monomer, and examples thereof include tricalcium phosphate, hydroxyapatite, titanium oxide and calcium hydroxide. , Calcium carbonate and silica are preferable, and others, red iron oxide, carbon black, glass, metal powder, starch powder, cellulose powder, polyacrylonitrile, metal salt of polyacrylic acid,
A metal salt of polymethacrylic acid, polyacrylamide and the like can also be used. Among these, particularly preferable suspending agents are tricalcium phosphate and hydroxyapatite, which are excellent in stability of oil droplets and sharp particle size distribution of fine particle powder.

The amount of the suspending agent used is specifically determined according to the average particle diameter of the desired three-dimensional polymer fine particles, and is based on 100 parts by weight of the monomer having one vinyl group. On the other hand, it is 0.1 to 20 parts by weight. If the amount is less than 0.1 part by weight, the desired polymer fine particles cannot be obtained, whereas if the amount exceeds 20 parts by weight, the suspending agent is wasted.

Some of the above-mentioned suspending agents exhibit the function of the suspending agent alone, and those that do not exhibit the function of the suspending agent. As the suspension aid, generally known surfactants, cationic, anionic,
Nonionic surfactants are used, of which anionic surfactants are particularly preferred. Examples of the anionic surfactant include sodium alkylbenzene sulfonate,
Examples include sodium α-olefin sulfonate, sodium alkyl sulfonate, and metal salts thereof. The anionic surfactant is 1 × 10 ^{−4 to} 0.
It is preferably added at 1% by weight. If it is less than 1 × 10 ⁻⁴ % by weight, the function as a suspension aid is difficult to appear, and if it exceeds 0.1% by weight, it itself functions as a suspending agent or an emulsifying agent, and good suspension polymerization cannot be performed. There is a tendency.

The mixture containing the above materials is then fed into a cylindrical vessel equipped with a shear stirring mechanism. As the container used in the present invention, a cylindrical container provided with a high-speed shearing stirring mechanism, generally called a pipeline homomixer or a line mixer, is preferably used. Pipeline homomixer is a device that regulates a stable suspension by uniformly dispersing other substances that are not miscible with the liquid in the liquid. It is forcibly fed, then the pressure is released, and liquid friction due to violent turbulence at that time, sharp decrease in pressure, shearing, impact, etc. to atomize and uniformly disperse.

In the method of the present invention, the cylindrical container needs to be pressurized to a relatively low pressure of 0.2 kg / cm ² G or more. Preferred pressure is 0.3-5 kg / cm ² G
Is. If it is less than 0.2 kg / cm ² G, a foaming phenomenon occurs in the mixer, and finally the target fine particles cannot be obtained. On the other hand, if it exceeds 5 kg / cm ² G, the target fine particles can be sufficiently obtained, but the mixer needs to have a pressure resistant structure, which tends to be expensive. The high-speed shear stirring mechanism of the mixer is not limited, and any mechanism can be adopted as long as the average particle size of the fine particles can be 1 to 100 μm.

The dispersion emulsion in which the average particle size of the oil droplet particles obtained by high-speed shear stirring is 1 to 100 μm is reacted at a temperature of 70 to 95 ° C. according to the usual suspension polymerization. It is preferable to obtain three-dimensional polymer fine particles having an average particle diameter of 1 to 100 μm because they exhibit good properties as a low-shrinking agent.

The resulting three-dimensional polymer fine particles are contained in the unsaturated polyester resin composition of the present invention as a low-shrinking agent. As the unsaturated polyester resin, a known one produced by a known method can be used. Examples of the acid component used as the raw material of the unsaturated polyester resin include unsaturated dibasic acids such as maleic acid, fumaric acid, itaconic acid and mesaconic acid or their anhydrides, as well as isophthalic acid, terephthalic acid, phthalic anhydride and succinic acid. Further, polybasic acids such as adipic acid and sebacic acid can also be used. As the alcohol component, ethylene glycol, diethylene glycol, propylene glycol, dipyropyrene glycol,
A diol such as butanediol and neopentyl glycol and a triol such as trimethylolpropane are used. The reaction conditions of the acid and alcohol are appropriately selected according to a conventional method.

Further, as a component of the unsaturated polyester resin composition, styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene and divinylbenzene, lower alkyl esters of acrylic acid or methacrylic acid, diallyl phthalate and diallyl isophthalate. A polymerizable monomer such as can be used in an amount usually used. Other,
If necessary, a filler such as calcium carbonate or alumina,
Various additives such as thickeners such as magnesium oxide, magnesium hydroxide and calcium oxide, curing catalysts such as various organic peroxides, colorants such as various dyes and pigments can be used. The resulting polyester resin composition is SMC, B
Used in various molded products by the MC and RIM methods.

[0023]

【Example】

Example 1 A 50 liter tank equipped with a stirrer was prepared and
A metering pump and a pipeline homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd., Pipeline homomixer, SL type) are connected to the lower part of the 0-liter tank, and the outlet of the pipeline homomixer, a stirrer, and a thermometer are further connected. Connect another 50 liter reaction kettle equipped with a nitrogen inlet tube and reflux condenser. 18 kg (100 parts) of methyl methacrylate and 0.09 kg of divinylbenzene in a 50 liter tank
(0.5 parts), benzoyl peroxide 0.09 kg (0.5
Part), 9 kg of water (about 140 parts together with water contained in hydroxyapatite), 18 kg of hydroxyapatite (Supertite 10, manufactured by Nippon Kagaku Kogyo Co., Ltd.) (10 parts in solid content) and 1 sodium dodecylbenzenesulfonate. % Aqueous solution was charged and stirred. The discharge rate of the metering pump was set to about 1 kg / min, and the mixed solution was sent to the pipeline homomixer. The internal pressure of the homomixer was set to 1.0 kg / cm ² G and the rotation speed was set to 9000 rpm, and the mixed solution was made into a dispersion emulsion, which was then charged in a 50-liter reaction kettle. The emulsion was sampled, and the average particle diameter of the oil droplet particles was measured with a Coulter counter, and it was 10 μm. After finishing the dispersion emulsification process,
Increase the temperature of the 50 liter reaction kettle to 80 ° C and
The reaction was completed in 8 hours. After cooling, it was dehydrated with a centrifugal dehydrator and dried with a dryer at 80 ° C. to obtain three-dimensional polymethylmethacrylate fine particles. The yield of the fine particles was 97%, which was a high yield. Further, the particle size distribution of the fine particles was measured, and it was found that the average particle diameter was 15 μm and the sharpening degree was 0.5, which was considerably sharp.
The swelling degree of the fine particles was measured and found to be 10.
When the fine particles were used as a low-shrinking agent for SMC by the method described below, the low-shrinking effect was sufficient and the uneven coloring gloss was also good. Further, by the method shown below, BM
When used as a C low-shrinking agent, it was particularly excellent in transparency. Tables 3 and 4 show the results of each Example and Comparative Example performed by the same method except that the conditions shown in Tables 1 and 2 were changed. In the case of using styrene shown in Table 2, the amount of benzoyl peroxide was 0.
Changed to 18 kg. However, parts are parts by weight unless otherwise specified.

Evaluation Method of Polymer Fine Particles (1) Measuring Method of Particle Size Distribution of Polymer Fine Particles and Oil Droplet Fine Particles A Coulter counter was used as a measuring instrument. As the coulter counter, ZM type manufactured by Nikkaki Co., Ltd. was used. As the electrolytic solution, Isoton II manufactured by Nikkaki Co., Ltd. was used. The method of measuring the particle size distribution was measured according to the manual. (2) How to obtain the sharpening degree (Cv value) in the particle size distribution It was obtained by the following method based on the data of the particle size distribution measured with a Coulter counter. Sharpness Cv = (D ₈₅ −D ₁₅ ) / D ₅₀ where D ₁₅ : volume cumulative%, particle diameter at 15% (μ
m) D ₅₀ : Particle diameter at 50% at 50% cumulative volume (μm) D ₈₅ : Particle size at 85% at cumulative cumulative volume (μm) (3) Swelling degree measuring method: Inner diameter 14 mm, height 135 mm , Graduation 0.2 m
l, a sample 0.
5 g is accurately weighed and tapped several times. After that, gently move the styrene monomer through the wall surface and add up to the scale of 20 ml. After standing at room temperature for 16 to 24 hours, the height of the swollen gel is read in ml, and the degree of swelling is calculated by the degree of swelling = (reading value (ml) x 0.5) / sample amount (g).

Production of polyester resin composition and SM
Manufacture of C molded product and BMC molded product (1) Manufacture of unsaturated polyester resin composition An unsaturated polyester resin (polyset PS-9195, maleic acid, terephthalic acid, and propylene glycol is used as a raw material in a container equipped with a stirrer. A mixture of unsaturated polyester resin and styrene monomer, manufactured by Hitachi Chemical Co., Ltd.
6.3 kg, a pigment (Ivory, manufactured by Tokyo Ink Co., Ltd.), and a curing agent (Perbutyl Z, manufactured by NOF CORPORATION) were compounded in the composition shown in Table 5 and uniformly dissolved. Thereafter, zinc stearate, aluminum hydroxide and polymer fine particles of the examples and comparative examples of the present invention are added and uniformly dispersed, and then magnesium oxide is added. The magnesium oxide was sufficiently dispersed until the grains were removed to obtain unsaturated polyester resin compositions (A) and (B). (2) Manufacture of SMC molded product An unsaturated polyester resin composition (A) was put into an SMC machine and set to have a glass fiber content of 25% by weight to prepare an SMC sheet. In order to prevent the scattering of styrene, it was packed with a polyester film and the SMC was aged at 40 ° C. for 2 days. Next, size 250 x 500 x
800 g of SMC aged in a 3 (mm) mold was taken, and an SMC molded product was manufactured under the conditions of a molding temperature of 140 ° C., a molding pressure of 130 kgf / cm ² , and a molding time of 3 minutes. (3) Production of BMC molded product The unsaturated polyester resin composition (B) was blended so that the content of the 1.5 mm glass fiber was 3% by weight, and kneaded well with a kneader for 10 minutes to prepare a compound. . Next, in order to prevent the scattering of styrene, it was packed with a polyester film, and the compound was aged at 40 ° C. for 20 hours. 700g of this is taken and the size is 220 × 220 (m
m) into the mold, molding temperature 140 ° C, molding pressure 10
A BMC molded product having a thickness of 6 mm was manufactured under the conditions of 0 kgf / cm ² and a molding time of 9 minutes. (4) Evaluation of Molded Product-Low Shrinkage The length of the side of the obtained SMC molded product corresponding to a mold length of 500 mm was measured and evaluated according to the following criteria. Good: Shrinkage rate of 0.02% or less. A little: Shrinkage exceeds 0.02% and 0.05% or less. None: Shrinkage rate exceeds 0.05%. -Coloring and uneven gloss The obtained molded product was visually judged. -Transparency Using visible light from a turbidimeter manufactured by Nippon Denshoku Industries Co., Ltd., the sample-free state is set to 100% transmittance, and the sample portion is shielded to 0% transmittance. After this correction, BM
The C molded product is put in the sample part, and the transmittance of the molded product is measured.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

[Table 5]

[0031]

According to the present invention, three-dimensional polymer fine particles having a sharp particle size distribution and a high yield can be obtained, and an unsaturated polyester resin using the three-dimensional polymer fine particles as a low-shrinking agent. The composition can ensure uniformity in coloring and gloss of the SMC molded product, and exhibits sufficient low shrinkability.

Claims (8)

[Claims] 1. 100 parts by weight of a monomer having one styrene-based and / or acrylic vinyl group, and a crosslinking agent of 0.02
To 5 parts by weight, a polymerization initiator 0.05 to 10 parts by weight, an aqueous medium 80 to 400 parts by weight, and a suspension agent 0.1 to 20 parts by weight in a cylindrical container equipped with a shear stirring mechanism. The average particle diameter of the oil droplets is 1 to 100 μm while the pressure inside the container is maintained at a pressure of 0.2 kg / cm ² G or more.
The method for producing three-dimensional polymer fine particles is characterized in that high-speed shear stirring is carried out to produce a dispersion emulsion, and the dispersion emulsion is polymerized. 2. The suspending agent is selected from tricalcium phosphate, hydroxyapatite, titanium oxide, calcium hydroxide, calcium carbonate and silica.
A method for producing the three-dimensional polymer fine particles described. 3. The method for producing three-dimensional polymer fine particles according to claim 1 or 2, wherein the cylindrical container equipped with the shear stirring mechanism is a pipeline homomixer. 4. Three-dimensional polymer fine particles obtained by the production method according to claim 1, 2 or 3. 5. The three-dimensional polymer fine particles according to claim 4, wherein the degree of swelling is 2 to 40. 6. The three-dimensional polymer fine particles according to claim 4, which have an average particle diameter of 1 to 100 μm. 7. A low-shrinkage agent comprising the three-dimensional polymer fine particles according to claim 4, 5 or 6. 8. An unsaturated polyester resin composition containing an unsaturated polyester resin and the low-shrinking agent according to claim 7.