JPH0632809A - Three-dimensional polymer fine particle, its production, shrink-controlling agent and unsaturated polyester resin composition - Google Patents

Abstract

PURPOSE:To produce fine particles having extremely sharp particle size distribution and giving a product having high colorability and gloss by continuously polymerizing an aqueous suspension of a monomer containing styrene-type and/or acrylate-type vinyl group in a reactor having a shearing agitation mechanism at the lower part. CONSTITUTION:A mixture of 100 pts.wt. of a monomer having one styrene-type and/or acrylate-type vinyl group, 0.02-5 pts.wt. of a crosslinking agent, 0.05-10 pts.wt. of a polymerization initiator, 80-400 pts.wt. of an aqueous medium and 0.1-20 pts.wt. of a suspension agent is continuously introduced into a cylindrical vessel having a shearing agitation mechanism and connected to the lower part of a reactor. The mixture is subjected to high-speed shearing and agitation while keeping the inside of the vessel to a pressurized state of >=0.2kg/cm<2>G to get oil droplets having an average particle diameter of 1-100mum and continuously produce a dispersed emulsion liquid. The liquid is continuously returned to the reactor to perform continuous polymerization. The suspension agent is hydroxyapatite, tricalcium phosphate, etc.

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 thereof, 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, it is difficult to say that the effect is sufficient, and in particular, according to the disclosed method for producing a low-shrinking agent, it is not possible to obtain a sharp particle size distribution. The characteristics such as sex were insufficient.

[0007]

The present invention, in particular, makes the particle size distribution of the resin fine particles used as the low-shrinking agent very sharp so that those characteristics, that is, the uniform dispersibility and the uniform colorability of the molded product can be obtained. The present invention aims to improve properties such as gloss and transparency, and further provides a method for producing the 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 charged into a reaction kettle, which was equipped with a shear stirring mechanism connected to the lower part of the reaction kettle. It is continuously fed into a cylindrical container, and high-speed shear stirring is performed so that the average particle size of the oil droplet particles becomes 1 to 100 μm while maintaining a pressurized state of 0.2 kg / cm ² G or more inside the container. A method for producing three-dimensional polymer fine particles, characterized by carrying out continuously to produce a dispersion emulsion and continuously polymerizing it while returning it to the reaction vessel, which is obtained by the production method. Three-dimensional polymer fine particles, low-shrinking agent made of the same, and unsaturated polyester The present invention relates to an unsaturated polyester resin composition containing a telluric resin and the low-shrinking agent.

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, henzyl acrylate, cyclohexyl acrylate, Tetrahydrofurfuryl acrylate, dicyclopentenyl acrylate, dicyclopentenyl oxyethyl acrylate, N-vinyl-2-pyrrolidone acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, 2-hydroxy acrylate -3-Phenyloxypropyl, glycidyl acrylate, acrylonitrile, acrylamide, N Methylol acrylamide, diacetone acrylamide, or derivatives of methacrylic acid or methacrylic acid, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, methacrylic acid. Nonyl acid, 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, methoxydipropymethacrylate Glycol, phenoxyethyl methacrylate, phenoxydiethylene glycol methacrylate, phenoxytetraethylene glycol methacrylate, benzyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, dicyclopentenyl methacrylate, dicyclopentenyloxyethyl methacrylate, methacrylic acid N-vinyl-2-pyrrolidone, methacrylonitrile, methacrylamide, N-methylolmethacrylamide, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, 2-hydroxy-3-phenyloxypropyl methacrylate,
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 the preferable monomer 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 radical initiators are preferred, for example benzoyl peroxide, 2-ethylhexyl perbenzoate, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, cumene hydroperoxide. , Methyl ethyl ketone peroxide,
4,4,6-Trimethylcyclohexanone di-tert-butylperoxyketal, cyclohexanone peroxide, methylcyclohexanone peroxide, acetylacetone peroxide, cyclohexanone di-tert-
Examples thereof include peroxide radical polymerization initiators such as butyl peroxyketal, acetone di-tert-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 hydroxyapatite, tricalcium phosphate, 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. Of these, particularly preferred suspending agents are hydroxyapatite and tricalcium phosphate, which are excellent in terms of 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.

A mixture containing the above materials is first charged to a reaction kettle. A cylindrical container equipped with a shear stirring mechanism is connected to the lower part of the reaction vessel, and a liquid is discharged from the discharge port of the cylindrical vessel so as to return to the reaction vessel in an annular shape.
The mixture charged in the reaction kettle is continuously supplied to the cylindrical container. As the cylindrical 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 homo mixer
In general, it is a device that uniformly disperses other substances that are immiscible with this in a liquid to prepare a stable suspension, and forcibly pumps the liquid mixture to be processed through a narrow gap precisely manufactured by a rigid body, Next, the pressure is released, and liquid friction due to violent turbulence at that time, sharp decrease in pressure, shearing, impacting, etc. to atomize and uniformly disperse.

In the production 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. The preferred pressure is 0.3-5 kg / cm ² G. 0.
If it is less than 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, 5 kg / cm ² G
If it exceeds, the target fine particles can be sufficiently obtained, but the mixer needs to have a pressure resistant structure and 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 continuously returned to the reaction vessel. Then, the reaction vessel is heated to a temperature of 70 to 95 ° C. according to a usual suspension polymerization to continuously carry out the polymerization reaction. In this polymerization, it is preferable to obtain three-dimensional polymer fine particles having an average particle diameter of 1 to 100 μm from the characteristics as a low shrinkage agent. By carrying out such a so-called loop polymerization, a very sharp particle size distribution of 3
Three-dimensional polymer particles are obtained.

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 component and the alcohol component are appropriately selected according to a conventional method.

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
It is used for various molded products by the MC and RIM methods.

[0023]

【Example】

Example 1 5 equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a reflux condenser
A 0 liter reaction kettle was prepared, and a quantitative pump and a pipeline homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd., pipeline homomixer, SL) were provided under the 50 liter reaction kettle.
Type), and the outlet of the pipeline homomixer was connected to the 50 liter reaction kettle. 18 kg of methyl methacrylate (100
Part), divinylbenzene 0.09 kg (0.5 part), benzoyl peroxide 0.09 kg (0.5 part), water 9 kg (50 parts)
Part), hydroxyapatite (Super Tight 10, manufactured by Nippon Kagaku Kogyo Co., Ltd.) 18 kg (solid content 10 parts, water content 90)
Part) and sodium dodecylbenzenesulfonate 1%
90 g of the aqueous solution was charged and stirred. The discharge rate of the metering pump was set to about 10 kg / min, and the mixed solution was continuously fed 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 mixture was continuously returned to the 50-liter reaction kettle while using it as a dispersion emulsion. The emulsion was sampled, and the average particle diameter of the oil droplet particles was measured with a Coulter counter to find that it was 10 μm. In this state, the temperature of the 50 liter reaction kettle was raised to 80 ° C. and the reaction was carried out at 80 ° C. for 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. The average particle size was 13 when the particle size distribution of the fine particles was measured.
μm, and the sharpening degree was 0.45, which was found to be 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, the low-shrinking effect was sufficient and the uneven coloring gloss was also good. Further, B containing the fine particles added
The MC molded product 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 changed to 0.18 kg. However, unless otherwise specified for the mixing ratio, parts by weight are shown.

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.

[Equation 1] (3) Method for measuring swelling degree 0.5 g of a sample is precisely weighed in a 20 ml measuring cylinder made of colorless glass, having an inner diameter of 14 mm, a height of 135 mm, graduation of 0.2 ml, and tapping several times. After that, gently put the styrene monomer on the wall and put it on the scale of 20 ml. Let stand for 16 to 24 hours at room temperature, read the height of swollen gel in ml,

[Equation 2] The swelling degree is calculated by.

Production of polyester resin composition and SM
Manufacture of C molded product and BMC molded product (1) Manufacture of unsaturated polyester resin composition In a container equipped with a stirrer, an unsaturated polyester resin having the composition shown in Table 5 (Polyset PS-9195, maleic acid,
A mixture of terephthalic acid and unsaturated polyester resin made from propylene glycol and styrene monomer, manufactured by Hitachi Chemical Co., Ltd., pigment (Tokyo Ink Co., Ltd., ivory), curing agent (Perbutyl Z, NOF Corporation) ))
Are mixed and dissolved uniformly. 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. Unsaturated polyester resin composition (A) in which magnesium oxide particles are sufficiently dispersed until they disappear.
And (B) were obtained. (2) Manufacture of SMC molded product An unsaturated polyester resin composition (A) was set in an SMC machine so that the glass fiber content was 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. Take 700g of this and measure 220 x 220 (mm)
Put in the mold of molding, molding temperature 140 ℃, molding pressure 100kg
A BMC molded product having a thickness of 6 mm was manufactured under the conditions of f / cm ² and 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 is 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 SMC molded product was visually evaluated. -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 part is blocked to set 0% transmittance. After this correction, the BMC 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]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain three-dimensional polymer fine particles having a very sharp particle size distribution and a high yield, and to obtain unsaturated compounds using the three-dimensional polymer fine particles as a low-shrinking agent. The polyester resin composition can ensure uniformity in coloring and gloss of the SMC molded product, and
Exhibits sufficient low shrinkage. Furthermore, when used as a BMC molded product, it has excellent transparency.

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 of 0.05 to 10 parts by weight, an aqueous medium of 80 to 400 parts by weight, and a suspending agent of 0.1 to 20 parts by weight are charged into a reaction kettle, which is added to the reaction kettle. It is continuously supplied into a cylindrical container equipped with a shear stirring mechanism connected to the lower part, and the average particle size of the oil droplet particles is maintained while maintaining a pressurized state of 0.2 kg / cm ² G or more in the container. 1-100 μm
High-speed shearing and stirring to produce a dispersion emulsion continuously, while continuously returning it to the reaction kettle,
A method for producing three-dimensional polymer fine particles, which comprises continuously polymerizing. 2. The suspending agent is selected from hydroxyapatite, tricalcium phosphate, 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.