JP5075441B2 - Method for producing resin particles - Google Patents

Description

  The present invention relates to a method for producing resin particles. More specifically, the present invention relates to a method for producing resin particles using a seed polymerization method. The resin particles obtained by the production method of the present invention exhibit excellent water dispersibility, and are electronic spacers such as LCD spacers, silver salt film surface modifiers, magnetic tape film modifiers, thermal paper running stabilizers, and the like. Industrial fields, chemical fields such as paints, inks and adhesives such as rheology control agents and matting agents, medical fields such as antigen-antibody reaction test particles, cosmetics fields such as slip agents and extender pigments, polyesters such as unsaturated polyester It can be used in general industrial fields such as resin shrinkage-reducing agents, paper, dental materials, anti-blocking agents, light diffusing agents, matting agents, and resin modifiers.

In recent years, in the industrial field, an aqueous solvent having a low environmental load is often used. Therefore, hydrophilicity is required for the resin particles mixed with the solvent. Conventionally known resin particles that have been made hydrophilic are resin particles whose particle surfaces are coated with a hydrophilic polymer. The resin particles are manufactured using emulsion polymerization.
In emulsion polymerization, a polymerizable monomer is added to resin particles (core particles) that are nuclei dispersed in an aqueous phase, and a polymerization reaction proceeds to produce resin particles larger than the core particles. Therefore, sequential addition of a polymerizable monomer in emulsion polymerization has the advantage that the polymerization stability is increased and the reaction heat is easily removed. In such emulsion polymerization, if a hydrophilic polymerizable monomer is added to the polymerization system at a later stage of the polymerization, resin particles having a hydrophilic surface can be easily generated. In addition, a reactive functional group is introduced into the core particle using this polymerization method.

However, in emulsion polymerization, it is difficult to industrially produce resin particles having a particle diameter of 1 μm or more which are useful for light diffusing agents, antiblocking agents and the like.
As a method for producing resin particles other than emulsion polymerization, there is suspension polymerization. In this suspension polymerization, resin particles having a relatively large particle diameter of 1 to 100 μm can be produced. However, the obtained resin particles have a wide distribution, and it is extremely difficult to produce monodisperse resin particles.
Therefore, when obtaining monodispersed resin particles, it is necessary to classify the resin particles obtained by suspension polymerization. Therefore, there is a problem that the number of steps increases and the manufacturing becomes complicated.

  Furthermore, as a kind of suspension polymerization, there is seed polymerization in which resin particles (seed particles) serving as nuclei absorb a polymerizable monomer and then polymerize the absorbed polymerizable monomer to obtain resin particles. . In this seed polymerization, normally, a polymerizable monomer is absorbed into seed particles and heated in a polymerization vessel to polymerize the polymerizable monomer to obtain resin particles. Therefore, when a hydrophilic polymerizable monomer is used to obtain hydrophilic resin particles, the polymerizable monomer may move to the aqueous phase and not participate in the polymerization reaction. Therefore, it is difficult to produce hydrophilic resin particles.

The following methods are known as methods for obtaining hydrophilic resin particles.
In JP-A-7-228608 (Patent Document 1), a polymerizable monomer containing 10 to 90% by weight of a hydrophilic polymerizable monomer after polymerizing a polymerizable monomer to a conversion rate of 90% or more is disclosed. A method for producing resin particles comprising adding a monomer to a polymerization system and polymerizing it is described.

  Japanese Patent Laid-Open No. 7-149993 (Patent Document 2) describes the following method. That is, at least one non-crosslinkable polymerizable monomer selected from alkyl methacrylate having 1 to 4 carbon atoms in the alkyl group, alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, and an aromatic vinyl monomer. 100 parts by weight and 0.5 to 50 parts by weight of a crosslinkable polymerizable monomer are polymerized to obtain crosslinkable resin particles. Next, 0.01 to 25 parts by weight of a polymerizable poly (alkylene oxide) glycol monomer having one or more double bonds in the molecular structure with respect to 100 parts by weight of the crosslinkable resin particles, or polymerizable 0.01 to 10 parts by weight of sulfonate is added to the polymerization system. Thereafter, it is described that an antistatic resin particle can be obtained by polymerizing a glycol-based monomer and coating the surface of the crosslinkable resin particle.

  Further, in Japanese Patent No. 3390991 (Cited Document 3), when producing resin particles by polymerizing a polymerizable monomer in the presence of seed particles dispersed in water, an aqueous dispersion of the polymerizable monomer. And a method of adding an aqueous solution of a water-soluble polymer compound continuously or intermittently to a polymerization system.

However, when a hydrophilic polymerizable monomer is added at a later stage of polymerization or after polymerization, resin particles of only the hydrophilic polymerizable monomer may be formed. Furthermore, since the hydrophilic polymerizable monomer moves to the aqueous phase and does not participate in the polymerization, it is difficult to produce resin particles having strong hydrophilicity.
In addition, in the method described in Japanese Patent No. 3339091, the water-soluble polymer compound is added simultaneously with the polymerizable monomer, so that the absorption of the polymerizable monomer into the seed particles becomes poor. Therefore, there exists a subject that the uniformity of a resin particle is inferior.
JP 7-228608 A JP-A-7-149993 Japanese Patent No. 3339091

As a result of extensive research, the inventors of the present invention have found that resin particles having monodispersity and strong hydrophilicity can be obtained by using a water-soluble polymer having a thiol group at the terminal in seed polymerization. The present invention has been reached.
Thus, according to the present invention, a step of adding seed particles to an emulsion composed of a polymerizable monomer and an aqueous medium to cause the seed particles to absorb the polymerizable monomer, and the absorbed polymerization. wherein the polymerization sexual monomer, said water-soluble polymer having a thiol group at the terminal while the polymerizable monomer is absorbed into the seed particles are added to the emulsion,
The end in a water-soluble polymer having a thiol group, polyvinyl alcohol, polycarboxylic acid, the production method of the resin particles being selected celluloses and thiol induction of polyvinylpyrrolidone or we are provided.

  According to the production method of the present invention, resin particles having excellent monodispersibility, strong hydrophilicity, and excellent dispersibility in an aqueous medium can be easily obtained.

In the production method of the present invention, at least a polymerizable monomer, an aqueous medium, seed particles, and a water-soluble polymer having a thiol group at a terminal are used.
Examples of the polymerizable monomer include styrene such as styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene, and chloromethylstyrene; derivatives thereof; vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; Unsaturated nitriles such as acrylonitrile; (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate (Meth) acrylic acid or its ester derivatives such as: monofunctional monomers such as conjugated dienes such as butadiene and isoprene, divinylbenzene, trimethylolpropane diacrylate, trimethylolpropane trimethacrylate, tetramethylolpropanetetra (Meth) acrylate, D Polyfunctional monomers such as glycol dimethacrylate. These polymerizable monomers may be used alone or in combination of two or more.

Examples of the aqueous medium include water and a mixed medium of water and a water-soluble solvent (for example, lower alcohol).
Seed particles include particles made of polymers such as styrene, styrene / butadiene, (meth) acrylic ester, vinyl acetate, and copolymers of styrene and (meth) acrylic monomers. Is mentioned. The seed particles are preferably non-crosslinked particles having an average particle diameter of 0.1 to 10 μm and a Cv value (expressed by (standard deviation of particle diameter / average particle diameter) × 100) of 15% or less. The seed particles are not particularly limited and can be produced by a known method. For example, it can be produced using a soap-free emulsion polymerization or dispersion polymerization method. In addition, (meth) acryl means methacryl or acryl.

Examples of the water-soluble polymer having a thiol group at the terminal include thiol derivatives such as polyvinyl alcohol, polycarboxylic acid, celluloses (hydroxyethylcellulose, carboxymethylcellulose, etc.), and polyvinylpyrrolidone. Among these water-soluble polymers, polyvinyl alcohol and thiol derivatives of polyvinyl pyrrolidone are preferable, and polyvinyl alcohol having a saponification degree of 80 to 98% and a polymerization degree of 50 to 3000 is particularly preferable. Examples of polyvinyl alcohol having a thiol group at the terminal include Poval M series commercially available from Kuraray. Among the Poval M series, M115 and M205 are preferable.
An inorganic water-soluble polymer such as sodium tripolyphosphate can also be used in combination with a water-soluble polymer having a thiol group at the terminal.

Hereinafter, a method for producing resin particles will be described.
First, seed particles are added to an emulsion composed of a polymerizable monomer and an aqueous medium. The emulsion can be prepared by a known method. For example, an emulsion can be obtained by adding a polymerizable monomer to an aqueous medium and dispersing it with a fine emulsifier such as a homogenizer, an ultrasonic treatment machine, or a nanomizer. The polymerizable monomer may contain a polymerization initiator as necessary. The polymerization initiator may be preliminarily mixed with the polymerizable monomer and then dispersed in an aqueous medium, or a mixture of both separately dispersed in an aqueous medium. The droplet diameter of the polymerizable monomer in the obtained emulsion is preferably smaller than the seed particle because the polymerizable monomer is efficiently absorbed by the seed particle.

The seed particles may be added directly to the emulsion, or may be added in a form in which the seed particles are dispersed in an aqueous dispersion medium (hereinafter referred to as seed particle dispersion).
After the seed particles are added to the emulsion, the polymerizable monomer is absorbed into the seed particles. This absorption can usually be performed by stirring the emulsion after addition of seed particles at room temperature (about 20 ° C.) for 1 to 12 hours. Moreover, you may accelerate | stimulate absorption by heating an emulsion to about 30-50 degreeC.

  The seed particles swell due to absorption of the polymerizable monomer. The degree of swelling of the seed particles can be adjusted by changing the mixing ratio of the polymerizable monomer and the seed particles. Usually, the mixing ratio is preferably in the range of 5 to 200 parts by weight of the polymerizable monomer with respect to 1 part by weight of the seed particles, and more preferably 10 to 100 parts by weight. When the mixing ratio of the polymerizable monomer is reduced, the increase in particle diameter due to polymerization is small, and when it is large, it is not completely absorbed by the seed particles, and may be suspended and polymerized uniquely in an aqueous medium to generate abnormal particles. The degree of swelling here means the volume ratio of the seed particles after swelling to the seed particles before swelling. The end of absorption can be determined by confirming the enlargement of the particle diameter by observation with an optical microscope.

  Examples of the polymerization initiator to be added as needed include benzoyl peroxide, lauroyl peroxide, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, and t-butyl peroxide. Organic peroxides such as oxy-2-ethylhexanoate and di-t-butyl peroxide; azobisisobutyronitrile, azobiscyclohexacarbonitrile, 2,2′-azobis (2,4-dimethylvalero) And azo compounds such as nitrile). The polymerization initiator is preferably used in the range of 0.1 to 1.0 part by weight with respect to 100 parts by weight of the polymerizable monomer.

  Furthermore, in the present invention, a water-soluble polymer having a thiol group at the terminal is added to the emulsion while the polymerizable monomer is absorbed by the seed particles. By adding a water-soluble polymer having a thiol group at the terminal at such timing, the water-soluble polymer having a terminal thiol group is localized near the surface of the seed particle that has absorbed the polymerizable monomer. The inventor believes that it can.

  The addition time of the water-soluble polymer having a thiol group at the terminal is preferably between 20 and 80, preferably 100 to 25 when the completion time of absorption of the polymerizable monomer into the seed particles is 100. It is more preferable that The definition of the above addition time means, for example, that when the polymerizable monomer is absorbed into the seed particles over 10 hours, the addition time of the water-soluble polymer having a thiol group at the terminal is 2 to 8 hours. .

  The addition amount of the water-soluble polymer having a thiol group at the terminal is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the polymerizable monomer. Further, the water-soluble polymer having a thiol group at the terminal may be added as it is, but it is preferable to add it after dissolving in water. At this time, it is preferable to dissolve the water at 40 to 80 ° C. because the water-soluble polymer having a thiol group at the terminal is easily dissolved. It is preferable to dissolve 0.1 to 10 parts by weight of the water-soluble polymer with respect to 100 parts by weight of water. At this time, a surfactant such as sodium lauryl sulfate may be added to water as necessary.

Next, resin particles are obtained by polymerizing the polymerizable monomer absorbed in the seed particles.
The polymerization temperature can be appropriately selected according to the kind of the polymerizable monomer and the polymerization initiator. The polymerization temperature is preferably 25 to 100 ° C, more preferably 50 to 90 ° C. The polymerization reaction is preferably carried out by raising the temperature after the polymerizable monomer, and optionally the polymerization initiator, are completely absorbed by the seed particles. After completion of the polymerization, the resin particles are centrifuged as necessary to remove the aqueous medium, washed with water and a solvent, and then dried and isolated.
In the polymerization step, a surfactant or a polymer dispersion stabilizer may be added in order to improve the dispersion stability of the resin particles.

  Examples of the surfactant include anionic surfactants such as sodium lauryl sulfate and sodium lauryl benzene sulfonate, and polymer dispersion stabilizers such as polyvinyl pyrrolidone, gelatin, starch, hydroxyethyl cellulose, polyvinyl ether, and polyvinyl alcohol. These may be used alone or in combination of two or more. The addition amount of the surfactant is preferably 0.01 to 1 part by weight with respect to 100 parts by weight of the polymerizable monomer.

  Examples of the polymer dispersion stabilizer include polyvinyl alcohol, polycarboxylic acid, celluloses (such as hydroxyethyl cellulose and carboxymethyl cellulose), and polyvinyl pyrrolidone. An inorganic water-soluble polymer compound such as sodium tripolyphosphate can also be used in combination. Of these, polyvinyl alcohol and polyvinyl pyrrolidone are preferable. The addition amount of the polymer dispersion stabilizer is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the polymerizable monomer.

The surfactant may be added after absorbing the polymerizable monomer, optionally the polymerization initiator, in the seed particles, or may be added when the polymerizable monomer is dispersed in the aqueous medium. By adding at the time of dispersion, both dispersion stabilization of the polymerizable monomer droplets at the time of dispersion and dispersion stabilization of the resin particles at the time of polymerization can be obtained.
The particle diameter of the resin particles obtained by the present invention can be freely designed according to the particle diameter of the seed particles and the mixing ratio of the polymerizable monomer and the seed particles. The method of the present invention is suitable for producing monodispersed resin particles having a particle diameter of 1 to 50 μm and a Cv value of 15% or less.

  The resin particles obtained by the production method of the present invention exhibit excellent water dispersibility, and are electronic spacers such as LCD spacers, silver salt film surface modifiers, magnetic tape film modifiers, thermal paper running stabilizers, and the like. Industrial fields, chemical fields such as paints, inks and adhesives such as rheology control agents and matting agents, medical fields such as antigen-antibody reaction test particles, cosmetics fields such as slip agents and extender pigments, polyesters such as unsaturated polyester It can be used in general industrial fields such as resin shrinkage-reducing agents, paper, dental materials, anti-blocking agents, light diffusing agents, matting agents, and resin modifiers.

Hereinafter, although the manufacturing method of the polymeric particle of this invention is demonstrated more concretely based on an Example, this invention is not limited to these Examples. In the following examples, “parts” and “%” represent parts by weight and% by weight, respectively. The measurement method of the average particle diameter and the hydrophilicity evaluation method in the following examples are described below.
(Average particle size)
The measurement is carried out by performing calibration using a 50 μm aperture according to Reference MANUAL FOR THE COULTER MULTISIZER (1987) published by Coulter Electronics Limited.
Specifically, 0.1 g of resin particles are predispersed in 10 ml of a 0.1% nonionic surfactant solution using a touch mixer and ultrasonic waves, and this is provided with ISOTON II (manufactured by Beckman Coulter, Inc .: measurement) In a beaker filled with an electrolytic solution), dripping with a dropper while gently stirring, adjust the reading of the densitometer on the main body screen to about 10%. Next, an aperture size of 50 μm, a current of 800, a gain of 4, and a polarity of + are input to the Multisizer II body, and measurement is performed manually. During the measurement, the beaker is gently stirred to the extent that bubbles do not enter, and the measurement is terminated when 100,000 resin particles are measured. The average diameter of the volume load (arithmetic average diameter in volume% mode: volume median diameter) is calculated as the average particle diameter (x) of the resin particles.
The coefficient of variation (Cv value) is a value calculated from the standard deviation (σ) and the average particle diameter (x) by the following formula.
Cv value (%) = (σ / x) × 100

(Hydrophilicity evaluation method)
The hydrophilicity is evaluated by the following method.
90 parts of ion-exchanged water, 10 parts of ethanol and a stirring bar having a length of 30 mm are placed in a 200 ml beaker and stirred by a magnetic stirrer (MGP-301 type, scale setting 6 manufactured by Shibata Kagaku Kagaku Kogyo) to such an extent that the liquid level flows. Thereafter, 1 part of resin particles is added and the time until sedimentation and dispersion below the liquid surface is measured. Those that are completely settled and dispersed in the liquid within 180 seconds (3 minutes) are highly hydrophilic, and those that have resin particles observed on the liquid surface after 180 seconds (3 minutes) are evaluated as poorly hydrophilic. .

(Example of seed particle production)
A 5-liter autoclave equipped with a thermometer and a nitrogen inlet tube was charged with 1 part normal octyl mercaptan dissolved in 100 parts ethyl methacrylate as a polymerizable monomer and 600 parts ion-exchanged water. . While stirring the resulting mixture, the temperature was raised to 70 ° C. in a nitrogen stream, 0.5 parts of potassium persulfate was added as a polymerization initiator, and a soap-free polymerization reaction was performed at 70 ° C. for 12 hours. By this polymerization reaction, a dispersion of monodispersed polymethyl methacrylate particles (seed particles A) having an average particle size of 0.5 μm and a Cv value of 10% was obtained.

  Next, 700 parts of ion-exchanged water and 30 parts of the seed particle A dispersion were added to the same autoclave as above to obtain a dispersion. The dispersion was heated to 70 ° C. while stirring. Next, a solution obtained by dissolving 0.4 part of potassium persulfate in 15 parts of ion exchange water was added to the dispersion. Further, 80 parts of methyl methacrylate and 0.8 part of normal octyl mercaptan were mixed and added from a nitrogen inlet tube over 60 minutes. While maintaining the obtained mixed liquid at 70 ° C., a polymerization reaction was performed for 12 hours. By this polymerization reaction, a dispersion liquid containing 10 parts of monodispersed polymethyl methacrylate particles (seed particles B) having an average particle diameter of 1.2 μm and a Cv value of 11% was obtained.

Example 1
60 parts of styrene as a polymerizable monomer, 10 parts of methyl methacrylate, 30 parts of ethylene glycol dimethacrylate, 0.6 parts of dimethyl-2,2-azobisisobutylnitrile and 0.6 parts of benzoyl peroxide as polymerization initiators It melt | dissolved and the monomer mixture was obtained. The obtained monomer mixture was mixed with 100 parts of ion-exchanged water containing 0.5 part of sodium succinate as a surfactant. An emulsion was obtained by stirring for 10 minutes at 8000 rpm with a K homomixer Mark 2.5 (manufactured by Tokushu Kika Kogyo Co., Ltd .; currently manufactured by Primemics). To this emulsion, 15 parts of a dispersion containing 10 parts of seed particles B having an average particle diameter of 1.2 μm was added with stirring.

  Further, after stirring for 1 hour, an aqueous solution in which 0.5 part of polyvinyl alcohol having a thiol group at the terminal (Poval M-115 manufactured by Kuraray Co., Ltd.) was added to 10 parts of ion exchange water. At this time, although the dispersion liquid was confirmed with the optical microscope, the particle size distribution was broad in the range of 1 to 10 μm. Stirring was continued for 3 hours, and the dispersion was observed with an optical microscope. As a result, it was found that the polymerizable monomer in the emulsion was absorbed by the seed particles. In this case, assuming that the time (4 hours) when the polymerizable monomer is completely absorbed into the seed particles is 100, the polyvinyl alcohol having a thiol group at the terminal is dispersed after the time corresponding to 25 (1 hour) has elapsed. To be added.

  Thereafter, 200 parts of an aqueous solution of 20 parts of polyvinyl alcohol (PVA-217EE manufactured by Kuraray Co., Ltd.) as a dispersion stabilizer was placed in an autoclave and polymerized at 70 ° C. for 4 hours while stirring. When the particle size distribution of the obtained resin particles was measured with a Coulter counter manufactured by Coulter, the average particle size was 4.5 μm, the Cv value was 9.0%, and it was confirmed that the particle sizes were very well aligned. It was. The obtained resin particle dispersion was dehydrated, washed, dried, and sieved to isolate the resin particles.

(Example 2)
Resin particles were obtained in the same manner as in Example 1 except that the amount of polyvinyl alcohol having a thiol group at the terminal was 4 parts. The obtained resin particles had an average particle diameter of 4.5 μm and a Cv value of 9.1%, and it was confirmed that the particle diameters were very well aligned.

(Example 3)
30 parts of styrene as a polymerizable monomer, 60 parts of methyl methacrylate, 10 parts of ethylene glycol dimethacrylate, 0.6 parts of dimethyl-2,2-azobisisobutylnitrile and 0.6 parts of benzoyl peroxide as polymerization initiators It melt | dissolved and the monomer mixture was obtained. The obtained monomer mixture was mixed with 100 parts of ion-exchanged water containing 0.5 part of sodium succinate as a surfactant. An emulsion was obtained by stirring for 10 minutes at 8000 rpm with K homomixer Mark 2.5 (manufactured by Tokushu Kika Kogyo Co., Ltd.). To this emulsion, 25 parts of a dispersion containing 10 parts of seed particles B having an average particle diameter of 1.2 μm was added with stirring.

  Further, after stirring for 30 minutes, an aqueous solution in which 1.0 part of polyvinyl alcohol having a thiol group at the terminal (Poval M-205 manufactured by Kuraray Co., Ltd.) was added to 10 parts of ion exchange water. At this time, although the dispersion liquid was confirmed with the optical microscope, the particle size distribution was broad in the range of 1 to 10 μm. Stirring was continued for 3 hours, and the dispersion was observed with an optical microscope. As a result, it was found that the monomer in the emulsion was absorbed by the seed particles.

  Thereafter, 200 parts of an aqueous solution of 20 parts of polyvinyl alcohol (PVA-217EE manufactured by Kuraray Co., Ltd.) as a dispersion stabilizer was placed in an autoclave and polymerized at 70 ° C. for 4 hours while stirring. The obtained resin particles had an average particle size of 3.8 μm and a Cv value of 8.8%, and it was confirmed that the particle sizes were very well aligned. The obtained resin particle dispersion was dehydrated, washed, dried, and sieved to isolate the resin particles.

Example 4
Resin particles were obtained in the same manner as in Example 1 except that the addition of polyvinyl alcohol having a thiol group at the end was after stirring for 3 hours. The obtained resin particles had an average particle diameter of 4.5 μm and a Cv value of 9.3%, and it was confirmed that the particle diameters were very well aligned.

(Comparative Example 1)
Resin particles were obtained in the same manner as in Example 1 except that polyvinyl alcohol having a thiol group at the terminal was not added. The obtained resin particles had an average particle diameter of 4.5 μm and a Cv value of 9.3%.

(Comparative Example 2)
60 parts of styrene as a polymerizable monomer, 10 parts of methyl methacrylate, 30 parts of ethylene glycol dimethacrylate, 0.6 parts of dimethyl-2,2-azobisisobutylnitrile and 0.6 parts of benzoyl peroxide as polymerization initiators It melt | dissolved and the monomer mixture was obtained. Ion exchange water 100 containing 0.5 parts of polyvinyl alcohol (M-115, manufactured by Kuraray Co., Ltd.) having 0.5 parts of sodium succinate as a surfactant and a terminal thiol group as a surfactant. The mixture is mixed with T.W. An emulsion was obtained by treatment at 8000 rpm for 10 minutes with K homomixer Mark 2.5 (manufactured by Tokushu Kika Kogyo Co., Ltd.). To this emulsion, 20 parts of a dispersion containing 10 parts of seed particles B having an average particle diameter of 1.2 μm was added with stirring, and stirring was continued for 3 hours.

When the emulsion was observed with an optical microscope, it was found that the polymerizable monomer in the emulsion was completely absorbed by the seed particles and had a uniform particle size.
Thereafter, 200 parts of an aqueous solution of 10 parts of polyvinyl alcohol (PVA-217EE manufactured by Kuraray Co., Ltd.) as a dispersion stabilizer was placed in an autoclave and polymerized at 70 ° C. for 2 hours with stirring. The obtained resin particles had an average particle diameter of 4.2 μm and a Cv value of 10.2%. The obtained resin particle dispersion was dehydrated, washed, dried, and sieved to isolate the resin particles.

(Comparative Example 3)
60 parts of styrene as a polymerizable monomer, 10 parts of methyl methacrylate, 30 parts of ethylene glycol dimethacrylate, 0.6 parts of dimethyl-2,2-azobisisobutylnitrile and 0.6 parts of benzoyl peroxide as polymerization initiators It melt | dissolved and the monomer mixture was obtained. The obtained monomer mixture was mixed with 100 parts of ion-exchanged water containing 0.5 part of sodium succinate as a surfactant. An emulsion was obtained by stirring for 10 minutes at 8000 rpm with K homomixer Mark 2.5 (manufactured by Tokushu Kika Kogyo Co., Ltd.). To this emulsion, 20 parts of a dispersion containing 10 parts of seed particles B having an average particle diameter of 1.2 μm was added with stirring, and stirring was continued for 3 hours.

When the emulsion was observed with an optical microscope, it was found that the polymerizable monomer in the emulsion was completely absorbed by the seed particles and had a uniform particle size.
Thereafter, 200 parts of an aqueous solution of 10 parts of polyvinyl alcohol having a thiol group at the terminal (M-115 manufactured by Kuraray Co., Ltd.) was placed in an autoclave and polymerized at 70 ° C. for 2 hours with stirring. Aggregation occurred during the polymerization, A stable aqueous dispersion was not obtained.

(Comparative Example 4)
Resin particles were obtained in the same manner as in Example 1 except that a dispersion of seed particles B having an average particle size of 1.2 μm was not used. The obtained resin particles had an average particle size of 4.6 μm, a Cv value of 30.3%, and a broad particle size distribution of 1 to 10 μm.
(Comparative Example 5)
Resin particles were obtained in the same manner as in Example 1 except that polyvinyl alcohol having a thiol group at the terminal was replaced with polyvinyl alcohol having no thiol group (PVA-224E manufactured by Kuraray Co., Ltd.). The obtained resin particles had an average particle size of 4.4 μm and a Cv value of 9.8%.
Table 1 shows the dispersion time, average particle diameter, Cv value, addition timing and addition amount of the water-soluble polymer having a thiol group at the terminal in Examples and Comparative Examples.

It can be seen from Examples 1 to 4 and Comparative Example 1 that resin particles excellent in dispersibility in an aqueous medium can be obtained by using a water-soluble polymer having a thiol group at the terminal.
From Examples 1 to 4 and Comparative Examples 2 to 3, by adding a water-soluble polymer having a thiol group at the terminal to the polymerization system at a specific time, it is excellent in monodispersibility and dispersible in an aqueous medium. It can be seen that excellent resin particles can be obtained.
It can be seen from Examples 1 to 4 and Comparative Example 4 that resin particles having excellent monodispersibility and excellent dispersibility in an aqueous medium can be obtained by employing the seed polymerization method.
From Examples 1 to 4 and Comparative Example 5, it can be seen that resin particles having excellent dispersibility in an aqueous medium can be obtained when the water-soluble polymer has a thiol group at the terminal.

Claims (3)

Adding seed particles to an emulsion composed of a polymerizable monomer and an aqueous medium to cause the seed particles to absorb the polymerizable monomer, and polymerizing the absorbed polymerizable monomer; includes the step, the water-soluble polymer polymerizable monomer having a terminal thiol group while being absorbed in the seed particles are added to the emulsion,
The end in a water-soluble polymer having a thiol group, polyvinyl alcohol, polycarboxylic acid, the production method of the resin particles, characterized in that the celluloses and thiol-induced body or we choose polyvinylpyrrolidone.   The resin particles according to claim 1, wherein the water-soluble polymer is added to the emulsion between 20 and 80, assuming that the completion time of absorption of the polymerizable monomer into the seed particles is 100. Method.   The method for producing resin particles according to claim 1 or 2, wherein the water-soluble polymer is added in an amount of 0.1 to 5 parts by weight with respect to 100 parts by weight of the polymerizable monomer.