JP3514650B2 - Method for producing polymer fine particles having a layered structure - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing polymer fine particles having a layered structure, and particularly to a production method suitable for producing polymer fine particles having a volume average particle diameter of 2 to 20 μm.

[0002]

2. Description of the Related Art In recent years, polymer fine particles having a particle size of micron size have been used for various purposes. For example, it is used as an additive for resin modification, for light diffusion and for delustering paints, as a slipperiness imparting agent in the field of cosmetics, or as a toner for electrophotography. Depending on the application, such polymer fine particles may require the morphology of the polymer particles themselves. For example, rubber-like polymer fine particles having a layered structure having a hard outer edge portion are used as an additive for resin modification, and impart impact resistance to a thermoplastic resin.

[0003]

As a method for producing polymer fine particles having such a layered structure, for example, a rubber-like substance obtained by emulsification as proposed in JP-A-7-70255. A method is known in which a hard outer edge portion of methyl methacrylate is formed on polymer particles (core portion) by seed emulsion polymerization. However, the polymer fine particles obtained by emulsion polymerization have a particle diameter of 1 μm or less, and it is difficult to obtain micron-sized (2 to 20 μm) polymer fine particles.

Further, as a method for producing polymer fine particles having an average particle diameter of 1 μm or more and having a layered structure, rubber-like alkyl acrylate copolymer fine particles are produced by emulsion polymerization, followed by a swelling step and a multi-step swelling step. A method for producing polymer fine particles having a desired particle size by repeating a seed emulsion polymerization step using a water-soluble polymerization initiator has been proposed (JP-A-7-238200). However, it is difficult to remove the emulsifier from the polymer fine particles produced by such multi-stage seed emulsion polymerization, and the resin may be colored or turbid due to the residual emulsifier depending on the use of the polymer fine particles. There was a problem such as.

Further, in the method for producing polymer fine particles having a layered structure by multistage suspension polymerization as proposed in Japanese Patent Publication No. 2-52936, the monomer forming the outer edge portion is independent. The polymer may not be compatible with the core. As a result, there is a problem that a single polymer fine particle is not formed, or even if a single polymer fine particle is formed, the inside of the particle is intermittent.

Further, Japanese Patent Application Laid-Open No. 6-279509 proposes a method for producing polymer fine particles in which the refractive index continuously changes from the central part of the particle toward the outer edge part, and a polymerization initiator is newly added. Without this, a method of continuously adding a monomer to carry out polymerization is disclosed. However, in this method, the added monomer exists as large oil droplets,
50 μm because monomers are not smoothly absorbed by the core
It is not suitable as a method for producing particles having a layered structure having a smaller particle size. Further, in this method, when the polymer fine particles to be the core have a constant polymerization conversion rate, a monomer is added to carry out further polymerization, but it is difficult to control the polymerization conversion rate, and a polymer having the same morphology There is a problem that it is difficult to obtain fine particles.

Further, in JP-A-10-120714, a surfactant or a water-soluble polymer is used as a dispersion stabilizer, and a poorly water-soluble organic substance (halogenated hydrocarbon) is added to a monomer for dispersion. Thus, there has been proposed a method of improving the stability of oil droplets, producing core particles of 2 to 20 μm, and forming an outer edge portion by adding an aqueous dispersion containing a monomer. However, in this method, for example, a halogenated hydrocarbon that is a poorly water-soluble organic substance is used,
Since this halogenated hydrocarbon remains inside the particles, there is a concern that gas will be generated when the particles are molded at a high temperature. Further, when polyvinyl alcohol is used as a dispersion stabilizer, it is difficult to completely remove polyvinyl alcohol from the obtained particles, and there is a problem that it is colored yellowish brown under a high temperature atmosphere.

Further, in JP-A-4-337303, monodisperse polymer particles produced by dispersion polymerization are dispersed in an aqueous dispersion medium, and monomers are continuously added so that absorption and polymerization are continuously carried out. To produce monodisperse particles having different crosslink densities inside and outside the particles. However, in this method, although monodisperse fine particles having a layered structure are produced, since the particles dispersed and polymerized in a non-aqueous organic solvent are used as core particles, the process becomes complicated,
There was a problem that productivity fell.

The present invention is directed to a method for solving the above problems of the prior art and efficiently producing fine polymer particles having a micron-sized (2 to 20 μm) multilayer structure.

[0010]

As a result of earnest research, the present inventor has found that the degree of crosslinking of the core particles, the method of adding the monomer mixture for forming the outer edge portion, the addition conditions (adding speed), and the method for forming the outer edge portion. It was found that polymer fine particles having a layered structure of 2 to 20 μm can be efficiently produced by performing the polymerization by selecting conditions such as the type of polymerization initiator and the type of dispersant at the time of polymerization, and complete the present invention. Came to.

According to the present invention, 95 to 99.9% by weight of hydrophobic monovinyl monomer and 0.1 to 5 of crosslinkable vinyl monomer.
A monomer mixture (A) containing 1 wt% and an oil-soluble polymerization initiator is suspension-polymerized to form polymer fine particles (core portion),
Then, a unit amount containing a hydrophobic monovinyl monomer, a crosslinkable vinyl monomer, and an oil-soluble polymerization initiator having a 10-hour half-life temperature of 60 to 80 ° C. and a solubility in water of 0.3 g / 100 ml or less. Body mixture (B) [wherein the monomer mixture (A) and the monomer mixture (B) are different in at least a hydrophobic monovinyl monomer or different in a crosslinkable vinyl monomer, or The mixing ratio of the hydrophobic monovinyl monomer and the crosslinkable vinyl monomer is different], based on 1 g of the polymer fine particles (core portion).
A method for producing polymer fine particles having a layered structure, which comprises adding 0.05 to 1 g per hour to carry out suspension polymerization of the polymer fine particles (core portion) and the monomer mixture (B). Provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION According to the method of the present invention, first, 95 to 99.9% by weight of a hydrophobic monovinyl monomer, 0.1 to 5% by weight of a crosslinkable vinyl monomer and an oil-soluble polymerization initiator. Polymer fine particles (core portion) are produced by suspension-polymerizing a monomer mixture (A) containing

Examples of the hydrophobic monovinyl monomer include styrene derivatives such as styrene, p-methylstyrene and o-chlorostyrene; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate and n-butyl methacrylate; acrylic acid. Examples thereof include acrylic acid esters such as methyl, ethyl acrylate, and n-butyl acrylate.
These hydrophobic monovinyl monomers may be used alone or in combination of two or more kinds.

Examples of the crosslinkable vinyl monomer include monomers having two or more radically polymerizable functional groups in one molecule such as ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, divinylbenzene and allyl methacrylate. To be These crosslinkable vinyl monomers may be used alone or in combination of two or more kinds.

The ratio of the hydrophobic monovinyl monomer to the crosslinkable vinyl monomer used is 95 to 9 for the hydrophobic monovinyl monomer.
9.9% by weight, and the crosslinkable vinyl monomer is 0.1 to 5
%, But from the viewpoint of controlling the obtained morphology, the hydrophobic monovinyl monomer is 97 to 99.5% by weight, and the crosslinkable vinyl monomer is 0.5 to 3% by weight. preferable.

% Of crosslinkable vinyl monomer
If it is lower, when the polymer fine particles finally obtained are melt-mixed with a thermoplastic resin at a high temperature, there is a problem that the particles are deformed or fused, and when they are used by being added to a paint or the like. Is not preferable because it has poor solvent resistance. On the other hand, if the proportion of the crosslinkable vinyl monomer exceeds 5% by weight, the amount of the monomer mixture (B) for forming the outer edge portion tends to polymerize in no small amount, which is not preferable.

Well-known oil-soluble polymerization initiators used for radical polymerization, for example, azo compounds such as 2,2'-azobis (2,4-dimethylvaleronitrile) and azobisisobutyronitrile; Examples thereof include organic peroxides such as dilauroyl peroxide, dibenzoyl peroxide and t-butylperoxy-2-ethylhexanoate. These oil-soluble polymerization initiators may be used alone or in combination of two or more kinds. The amount of the oil-soluble polymerization initiator used is not particularly limited, but is usually 0.01 to 3% by weight based on the monomer.

When carrying out suspension polymerization of the monomer mixture (A), it is preferable to use a dispersant. As a dispersant,
Examples thereof include water-soluble polymer compounds such as polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, sodium polyacrylate; poorly water-soluble inorganic salts such as tricalcium phosphate, magnesium hydroxide, magnesium pyrophosphate, barium sulfate, etc. A sparingly water-soluble inorganic salt is preferred because it can be easily removed from the surface of the particles obtained later and the particle size distribution of the polymer particles produced can be narrowed. The amount of the dispersant used is not particularly limited, but it is usually 0.1 to 20 g per 100 g of the polymer particles finally obtained.

When a poorly water-soluble inorganic salt is used as the dispersant, it is preferable to use an anionic surfactant together.
Examples of the anionic surfactant include those used in suspension polymerization, such as sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene lauryl ether sulfate, and sodium dioctylsulfosuccinate. The amount of the anionic surfactant used is not particularly limited, but is usually preferably 0.005 to 0.3% by weight with respect to water as the reaction solvent.

In carrying out suspension polymerization of the monomer mixture (A), a conventional dispersing device such as a homomixer, an ultrasonic homomixer, a high-pressure homomixer, etc. is used as described in JP-A-10-152506. It is preferred to use and disperse the oil droplets for polymerization.

By dispersing the monomer mixture (A) in oil droplets of uniform size and carrying out suspension polymerization, polymer fine particles having a relatively uniform particle size distribution can be obtained. When polymer fine particles having a layered structure obtained by using such polymer fine particles as a core are used for a light diffusing plate or the like, it is possible to suppress light scattering due to extremely fine particles or glare due to coarse particles. .

According to the method of the present invention, the polymer fine particles (core portion) obtained as described above have a hydrophobic monovinyl monomer, a crosslinkable vinyl monomer and a 10-hour half-life temperature of 60 to 80. Solubility in water is 0.3g / 1
A layered structure composed of a core portion and an outer edge portion is formed by suspension-polymerizing a monomer mixture (B) containing an oil-soluble polymerization initiator in an amount of 00 ml or less with polymer fine particles (core portion). To produce polymer fine particles.

Examples of the hydrophobic monovinyl monomer and the crosslinkable vinyl monomer in the monomer mixture (B) are the same as those contained in the above-mentioned monomer mixture (A). It

However, the monomer mixture (A) and the monomer mixture (B) are different in at least a hydrophobic monovinyl monomer, different in a crosslinkable vinyl monomer, or hydrophobic. It is assumed that the mixing ratios of the monovinyl monomer and the crosslinkable vinyl monomer are different. The hydrophobic monovinyl monomer and the crosslinkable vinyl monomer are different from each other here because the kinds of the monomers are different from each other, or both monomers are composed of two or more components. It means that the blending ratios are different.

The proportion of the hydrophobic monovinyl monomer and the crosslinkable vinyl monomer used in the monomer mixture (B) is 80 to 99.9% by weight of the hydrophobic monovinyl monomer. The content of the monomer is preferably 0.1 to 20% by weight, the content of the hydrophobic monovinyl monomer is 85 to 99% by weight, and the content of the crosslinkable vinyl monomer is preferably 1 to 15% by weight. .

Examples of the oil-soluble polymerization initiator in the monomer mixture (B) include azobisisobutyronitrile, dilauroyl peroxide, dibenzoyl peroxide and t.
-Butylperoxy-2-ethylhexanoate and the like can be preferably used.

If the 10-hour half-life temperature of the oil-soluble polymerization initiator is lower than 60 ° C. or higher than 80 ° C., it becomes difficult to control the polymerization reaction, which is not preferable. The solubility of the oil-soluble polymerization initiator in water is 0.3 g / 100 ml.
If it is higher, the polymerization is initiated by the polymerization initiator dissolved in the aqueous medium, and the monomer mixture (B) added afterwards is not a small amount but polymerized alone to form extremely fine particles, and further the system. It is not preferable because the polymer stability is lowered and the polymer fine particles aggregate.

The ratio of the core portion and the monomer mixture (B) used in the polymerization reaction for forming the outer edge portion is usually 6 by weight.
0:40 to 98: 2, preferably 60:40 to 9
5: 5, more preferably 70:30 to 90: 1.
It is 0.

The monomer mixtures (A) and (B)
It is preferable that the glass transition temperature of the polymer obtained by polymerizing each of these is 90 ° C. or higher. When the glass transition temperature is lower than 90 ° C., the polymer particles may be aggregated or deformed when the finally obtained layered polymer particles are melt-mixed with the thermoplastic resin at a high temperature.

The polymerization reaction between the core and the monomer mixture (B) is carried out in an amount of 0.05 to 1 g per hour with respect to 1 g of the core in which the monomer mixture (B) is dispersed in an aqueous medium. Each, preferably 0.1 to 0.5 g, continuously or intermittently, and suspension polymerization is performed.

1 g of the monomer mixture (B) was added to 1 g of the core.
Addition at a rate exceeding 1 g per hour is not preferable because the monomer mixture (B) is not insignificantly polymerized alone. On the contrary, it is not preferable to add it in a ratio of less than 0.05 g in terms of productivity.

When the monomer mixture (B) is added, the added monomer is promptly absorbed by the polymer particles in the core,
In forming the designed morphology, an anionic surfactant is added to the aqueous dispersion medium to form a monomer mixture (B).
It is preferable to carry out suspension polymerization by using as a droplet having an average particle size smaller than that of the core.

Examples of the anionic surfactant include sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene lauryl ether sulfate, sodium dioctyl sulfosuccinate and the like. The amount of these used is not particularly limited, but is usually 0.005 to 0.3% by weight with respect to water used as a reaction solvent.

The particle diameter of the polymer fine particles having a layered structure obtained by the method of the present invention is the same as the particle diameter of the polymer fine particles (core portion) and the polymer fine particles (core portion) and the monomer mixture (B). It may vary depending on the usage ratio, but is usually 2 to 20.
It has a volume average particle diameter of μm.

When the polymer fine particles obtained by the method of the present invention are used by being melt-mixed with a thermoplastic resin, they are often molded at a temperature higher than 200 ° C., and therefore the air of the polymer fine particles themselves is used. Decomposition temperature is 25
It preferably has a heat resistance of 0 ° C. or higher. To this end, for example, a mercaptan having 8 or more carbon atoms or an antioxidant having at least one hydroxyl group in one molecule is added to at least one of the above-mentioned monomer mixtures (A) and (B). Is preferred.

Examples of such mercaptans having 8 or more carbon atoms include n-octyl mercaptan, n-nonyl mercaptan, n-dodecyl mercaptan and the like. Examples of the antioxidant having at least one hydroxyl group in one molecule include 2,6-di-t-butyl-4-methylphenol and n-octadecyl-3-.
(3,5-di-t-butyl-4-hydroxyphenyl)
Examples include propionate. Among these antioxidants, n-octadecyl-3-, which has a vapor pressure at 20 ° C. of about 10 ⁻⁷ pa or less and is excellent in transpiration resistance.
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate is particularly preferred. The addition amount of these antioxidants is not particularly limited, but is usually 0.01 to 1 with respect to the finally obtained polymer fine particles having a layered structure.
%, Preferably 0.05 to 0.5% by weight, more preferably 0.1 to 0.3% by weight.

The polymer fine particles obtained by the present invention are
It has a layered structure and can be used as a resin modifier, an additive for cosmetics or paints, or a toner for electrophotography.

[0038]

EXAMPLES The present invention will be described in more detail by way of examples, but the present invention is not limited thereto.
In addition, the particle diameter of the polymer fine particles in the examples was measured by Coulter Multisizer (II) manufactured by Coulter Co., Ltd. and expressed as a volume average. The glass transition temperature of the polymer obtained by polymerizing each of the monomer mixtures (A) and (B) alone was measured using a DSC200 type manufactured by Seiko. The thermal decomposition temperature of the obtained polymer fine particles is the temperature at the time of weight loss of 3% as measured by the weight loss measurement using a thermal analyzer DT-40 manufactured by Shimadzu Corporation.

Example 1 [First Step] In an autoclave having a capacity of 5 L equipped with a stirrer, 3000 g of water, 80 g of tricalcium phosphate, 1.2 g of sodium dodecyl sulfate, 544 g of styrene, 16 g of divinylbenzene and 5 g of azobisisobutyronitrile. Then, this monomer mixture was dispersed using a TK-Homomixer manufactured by Tokushu Kika Co., Ltd. to form droplets of about 15 μm. Then, the temperature was raised to 70 ° C. under a nitrogen stream to start suspension polymerization. The polymerization was completed 8 hours after the suspension polymerization was started. The polymerization conversion rate was 97%, and the volume average particle diameter of the obtained polymer fine particles (core portion) was 14.3 μm.

[Second Step] Separately from this, 216 g of methyl methacrylate, 24 g of divinylbenzene, 1.2 g of n-dodecyl mercaptan and 3 g of benzoyl peroxide (solubility in water at 20 ° C .: 0.01 g / 10
0 g, 10-hour half-life temperature of 72 ° C.) was added to 300 g of water in which 1.2 g of sodium dodecyl sulfate was dissolved, and this monomer mixture was dispersed using an ultrasonic homogenizer to make the particle diameter of oil droplets 2 μm. And

[Third step] The dispersion obtained in the second step is continuously added to the aqueous dispersion medium in which the polymer fine particles (core portion) obtained in the first step are dispersed at 70 ° C for 86 minutes. Dropped.
Furthermore, after polymerizing for 5 hours, the temperature was raised to 90 ° C. and the reaction was continued for 3 hours. Then, after cooling, hydrochloric acid is added to completely dissolve the tricalcium phosphate, followed by washing with water and dehydration.
Dry in an oven at 0 ° C overnight to obtain a volume average particle size of 1
Polymer fine particles having a layered structure of 5.4 μm were obtained.

Comparative Example 1 Polymerization was carried out under the same conditions as in Example 1 except that the amounts of styrene and divinylbenzene used in the first step were 515 g and 45 g, respectively. Thus, the finally obtained polymer fine particles contained a large amount of particles obtained by polymerizing the monomers of the second step alone.

Comparative Example 2 Polymerization was carried out under the same conditions as in Example 1 except that the monomer mixture was continuously added dropwise over 22 minutes in the second step. Thus, the finally obtained polymer fine particles contained a large amount of particles obtained by polymerizing the monomers of the second step alone.

Comparative Example 3 In the second step, instead of benzoyl peroxide,
2,2-Azobis- (2-methylbutyronitrile) (2
Polymerization was carried out under the same conditions as in Example 1 except that the solubility in water at 0 ° C. was 0.4 g / 100 g, and the 10-hour half-life temperature was 67 ° C. 3 g. As a result, the polymer fine particles finally obtained contained a large number of extremely fine particles.

Comparative Example 4 Polymerization was carried out under the same conditions as in Example 1 except that 2 g of potassium persulfate (water-soluble polymerization initiator) was used in place of benzoyl peroxide as the oil-soluble polymerization initiator in the second step. I went. As a result, the finally obtained polymer fine particles contained a large number of extremely fine particles, and further, the stability during polymerization was poor and a large amount of aggregates were contained.

Example 2 Polymerization was carried out under the same conditions as in Example 1 except that the amounts of styrene and divinylbenzene used in the first step were 554 g and 6 g, respectively. As a result, polymer fine particles having a layered structure having a volume average particle diameter of 14.8 μm were obtained.

Example 3 [First Step] In an autoclave having a capacity of 5 L equipped with a stirrer, 3000 g of water, 80 g of tribasic calcium phosphate, 1.2 g of sodium dodecyl sulfate, 340 g of styrene, 296 g of methyl methacrylate, 4 g of divinylbenzene, azobisiso 3.2 g of butyronitrile and 3.2 g of n-dodecyl mercaptan were added, and this monomer mixture was dispersed using a TK-Homomixer manufactured by Tokushu Kika Co., Ltd.
The droplet size was about m. Then, the temperature was raised to 70 ° C. under a nitrogen stream to start polymerization. The polymerization was completed in 8 hours after the polymerization was started. The polymerization conversion rate was 97%, and the volume average particle diameter of the obtained polymer fine particles was 8.3 μm.

[Second Step] Methyl Methacrylate 144
g, 16 g of divinylbenzene, 0.8 g of n-dodecyl mercaptan and 2.4 g of benzoyl peroxide,
200 g of water in which 1.2 g of sodium dodecyl sulfate was dissolved
It was put in, and this monomer mixture was dispersed using a TK-homo mixer.

[Third step] The dispersion obtained in the second step is added to the aqueous medium in which the polymer particles obtained in the first step are dispersed.
It dripped continuously over 0 minutes. After polymerizing for another 5 hours, the temperature was raised to 90 ° C. and the reaction was continued for 3 hours. afterwards,
After cooling and adding hydrochloric acid to completely dissolve the tricalcium phosphate, it was washed with water, dehydrated and dried overnight in an oven at 60 ° C. to obtain polymer fine particles having a layered structure with a volume average particle diameter of 9.1 μm. Obtained.

Example 4 [First step] In an autoclave having a volume of 5 L equipped with a stirrer, 3000 g of water and 80 parts of metathesis magnesium pyrophosphate were added.
g, sodium dodecyl sulfate 1.2 g, styrene 605
g, methyl methacrylate 100 g, divinylbenzene 15 g, azobisisobutyronitrile 5 g, n-octadecyl-3- (3,5-di-t-butyl-4-hydroxylphenyl) propionate (manufactured by Sumitomo Chemical Co., Ltd., product A monomer mixture containing 0.7 g of the name Sumilizer BP-76) was added, and the monomer mixture was dispersed using a TK-Homomixer manufactured by Tokushu Kika Co., Ltd. to form droplets of about 7 μm. Then, the temperature was raised to 70 ° C. under a nitrogen stream to start polymerization. The polymerization was completed in 8 hours after the polymerization was started. The polymerization conversion rate was 97%, and the volume average particle diameter of the obtained polymer particles was 6.8 μm.

[Second Step] Methyl Methacrylate 72
g, 8 g of divinylbenzene, 0.4 g of n-dodecyl mercaptan and 1.2 g of t-butylperoxy-2-ethylhexanoate (solubility in water at 20 ° C.
12g / 100ml, 10 hours half-life temperature 72.5 ° C)
10 g of water in which 1.0 g of sodium dodecyl sulfate was dissolved
0 g, the mixture of the monomers was dispersed using an ultrasonic homogenizer, and the particle size of oil droplets was 2 μm.

[Third step] The dispersion liquid obtained in the second step was continuously added dropwise to the aqueous medium in which the polymer fine particles obtained in the first step are dispersed, over 8 minutes. After polymerizing for another 5 hours, the temperature was raised to 90 ° C. and the reaction was continued for 3 hours. afterwards,
After cooling, hydrochloric acid was added to completely dissolve the metathesis magnesium pyrophosphate, followed by washing with water, dehydration, and drying overnight in an oven at 60 ° C., and polymer fine particles having a layered structure with a volume average particle diameter of 7.9 μm. Got

Example 5 100 g of n-butyl acrylate was used instead of methyl methacrylate, and n-dodecyl mercaptan 0 was used instead of n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate. Using 0.7 g,
Polymerization was performed under the same conditions as in Example 4 except that the dropping of the monomer mixture in the second step was 33 minutes. As a result, polymer fine particles having a layered structure having a volume average particle diameter of 7.5 μm were obtained. The results of Examples and Comparative Examples are shown below in Tables 1 and 2.

[0054]

[Table 1]

[0055]

[Table 2]

According to Tables 1 and 2, the amount of the monomer mixture (A) used in the first step, the kind of the polymerization initiator in the second step, and the addition rate of the monomer mixture (B) in the third step. By selecting, the volume average particle size is 2 to 2
It can be seen that polymer particles having a layered structure of 0 μm can be produced.

Reference Example The characteristics of the polymer particles obtained in each example during high temperature melt processing were evaluated under the following conditions.

Reference Example 1 Polymer fine particles 10 having a layered structure produced in Example 1
90 parts by weight of polymethylmethacrylate resin (Sumitpex MG-5, manufactured by Sumitomo Chemical Co., Ltd.) was added, and the mixture was stirred and mixed with a Henschel mixer. Then, the polymethylmethacrylate resin was melted and extruded at 280 ° C. by a twin-screw extruder to produce pellets. Using an injection molding machine, the pellets were molded at a temperature of 200 ° C. and a mold temperature of 5
Injection molding was performed under the condition of 0 ° C. to obtain a resin molded plate having a thickness of 1 mm.

Reference Example 2 A resin molded plate was obtained under the same conditions as in Reference Example 1 except that polymer fine particles prepared according to the method described in Example 4 of JP-A-7-238200 were used.

Reference Example 3 A resin molded plate was obtained under the same conditions as in Reference Example 1 except that polymer fine particles prepared according to the method described in Example 5 of JP-A-10-120714 were used. Each molded plate obtained in Reference Examples 1, 2 and 3 was visually evaluated for color and appearance. The evaluation results are shown in Table 3. The polymer fine particles having a layered structure obtained by the production method of the present invention were free from coloring at the time of high temperature melting and poor appearance of the molded product, as compared with polymer fine particles obtained by the conventional technique.

[0061]

[Table 3]

[0062]

According to the present invention, polymer fine particles (core portion)
The polymerization is carried out by selecting the conditions such as the degree of crosslinking, the addition method of the monomer mixture (B) for forming the outer edge portion, the addition conditions (addition speed), the type of the polymerization initiator, the type of the dispersant at the time of the polymerization. As a result, polymer particles having a layered structure having a volume average particle diameter of 2 to 20 μm can be efficiently produced, and the morphology as designed can be molded.

Therefore, the production method of the present invention is for producing polymer particles used for resin modification, paint matting additive, electrophotographic toner material, or slippery agent in the cosmetics field. Suitable for In particular, when the polymer fine particles obtained by the production method of the present invention are dispersed in a transparent base resin and used as a light diffusing agent, the outer edge portion can be adjusted to a composition having a refractive index close to that of the base resin. The light reflection at the interface between the polymer particles and the base resin can be reduced, and the light utilization efficiency can be improved.

Claims (6)

(57) [Claims] 1. A hydrophobic monovinyl monomer 95-99.9.
By weight, a monomer mixture (A) containing 0.1 to 5% by weight of a crosslinkable vinyl monomer and an oil-soluble polymerization initiator is subjected to suspension polymerization to form polymer fine particles (core portion), and then, The hydrophobic monovinyl monomer, the crosslinkable vinyl monomer, and the 10-hour half-life temperature of 60 to 80 ° C and the solubility in water of 0.
A monomer mixture (B) containing an oil-soluble polymerization initiator of 3 g / 100 ml or less [however, the monomer mixture (A) and the monomer mixture (B) are different in at least a hydrophobic monovinyl monomer). The crosslinkable vinyl monomer is different, or the mixing ratio of the hydrophobic monovinyl monomer and the crosslinkable vinyl monomer is different], 1 g of polymer fine particles (core portion) As opposed to 0.05 per hour
A method for producing polymer fine particles having a layered structure, characterized in that the polymer fine particles (core portion) and the monomer mixture (B) are subjected to suspension polymerization by adding 1 to 1 g each. 2. The production method according to claim 1, wherein the hydrophobic monovinyl monomer of the monomer mixture (A) is different from the hydrophobic monovinyl monomer of the monomer mixture (B). 3. The production method according to claim 1, wherein the crosslinkable vinyl monomer of the monomer mixture (A) is different from the crosslinkable vinyl monomer of the monomer mixture (B). 4. The mixing ratio of the hydrophobic monovinyl monomer and the crosslinkable vinyl monomer of the monomer mixture (A) is such that the hydrophobic monovinyl monomer and the crosslinkable vinyl monomer of the monomer mixture (B) are mixed. The manufacturing method according to any one of claims 1 to 3, wherein the mixing ratio is different from that of the monomer. 5. The suspension polymerization of the monomer mixture (A) is carried out in the presence of a poorly water-soluble inorganic salt as a dispersant and an anionic surfactant. Production method. 6. The production method according to claim 1, wherein the monomer mixture (B) is added in the form of droplets having an average particle diameter smaller than that of the polymer fine particles (core portion).