JP2918168B2 - Method for producing composite particles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing composite particles in which the surface of a polymer particle is coated with a coating material particle having a smaller diameter than the polymer particle.

[Background of the Invention]

Recently, composite particles in which the surface of large-diameter particles are coated with small-diameter particles are used as a new material that combines the physical properties of large-diameter particles with those of small-diameter particles.
It is attracting attention in the electronics industry, biology, medical field, and the like.

[Conventional technology]

Conventionally, as such composite particles, silica, alumina and the like are used as large-diameter particles, and the ceramic particles such as silica and alumina are dispersed in, for example, a synthetic resin emulsion and hetero-aggregated to obtain the surface of the ceramic particles. Is provided with small particles of the synthetic resin (for example, Polymer Processing, Vol. 38, No. 7, No. 10-
16: 1989).

The inorganic-organic composite particles are attracting attention as a new material having both the hardness of ceramics and the flexibility of synthetic resin.

[Problems to be solved by the invention]

However, the hardness of the large-diameter ceramic particles cannot be selected over a wide range in the inorganic-organic composite particles. If the large-diameter particles of the composite particles are true spheres and the diameter is uniform, for example, when used as a pigment for paints and cosmetics, paints and cosmetics exhibiting good spreadability are obtained, In addition, excellent surface activity due to the large surface area due to the spherical shape is obtained, and the usefulness and application of the composite particles will be further expanded, but the above ceramic particles have a large particle size and a spherical shape can be obtained. Hateful.

[Means for solving the problem]

As a means for solving the above-mentioned conventional problems, the present invention provides a comonomer of a monomer A having a functional group and another monomer B copolymerizable with the monomer A, The spherical polymer particles obtained by dissolving the comonomer and polymerizing in a solvent in which the copolymer based on the comonomer does not dissolve are separated, and the spherical polymer particles are separated into the spherical polymer particles. An object of the present invention is to provide a method for producing composite particles in which a coating material particle having a smaller particle size than the coalesced particles is dispersed in an aqueous dispersion and then the aqueous dispersion is aggregated.

 The present invention will be described in detail below.

(Production of spherical polymer particles)

[Monomer A] The monomer A having a functional group used in the present invention is a monomer having a functional group such as a carboxyl group, a hydroxyl group, a methylol group, an amino group, an acid amide group, and a glycidyl group.
Examples of those having a carboxyl group include acrylic acid, methacrylic acid, and itaconic acid, and those having a hydroxyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, and allyl alcohol. Those having a methylol group include N-methylolacrylamide and N-methylol methacrylamide; those having an amino group include dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate; those having an acid amide group include acrylamide and methacrylamide. Examples of those having a glycidyl group include glycidyl acrylate, glycidyl methacrylate, and glycidyl allyl ether. The above examples do not limit the invention. Further, in the present invention, a monomer having a hydrolyzable silyl group as a functional group as the monomer A, for example, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane and the like can also be used. . The above examples also do not limit the present invention.

[Monomer B]

The other monomer B copolymerizable with the above monomer A is methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl Acrylate, tetrahydrofurfuryl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, iso-butyl vinyl ether , N-butyl vinyl ether, styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, vinyl acetate, chloride Cycloalkenyl, vinylidene chloride, vinyl fluoride, vinylidene fluoride, ethylene, propylene, isoprene, chloroprene, butadiene and the like. The above examples do not limit the invention.

(Comonomer)

One or two or more of the monomers A and the monomers B
Or a mixture of two or more of them to form a comonomer. In the comonomer, the monomer A is desirably 0.2 to 7
%, And the difference in the solubility parameter of the comonomer is desirably 1 or more.

〔solvent〕

With the solvent used in the present invention, the comonomer is dissolved,
The copolymer based on the comonomer does not dissolve, and methanol, ethanol, isopropanol, n-
Examples thereof include lower alcohols such as butanol, mixed solvents of the lower alcohols and water, and nonpolar solvents such as n-hexane and n-heptane. The above examples do not limit the invention.

(Dispersion stabilizer)

As the dispersion stabilizer, a polymer soluble in the solvent, for example, polyvinylpyrrolidone, polyacrylic acid, polyacrylamide, polyvinyl alcohol, polyvinyl alkyl ether, or the like is used.If desired, a surfactant may be further added to the polymer. You may use together. As the surfactant, any of anionic, nonionic and cationic surfactants are used. For example, as the anionic surfactant, higher alcohol sulfate (Na salt or amine salt), alkyl allyl sulfonate (Na salt) ), Alkyl naphthalene sulfonate, alkyl phosphate, dialkyl sulfosuccinate, rosin soap, nonionic polyoxyethylene alkyl ether,
Polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, polyoxyethylene alkylamine, polyoxyethylene alkyl amide, sorbitan alkyl ester, polyoxyethylene sorbitan alkyl ester, trimethylaminoethyl alkyl amide halogenide as a cationic one,
There are alkylpyridinium sulfate, alkyltrimethylammonium halogenide and the like. The above examples also do not limit the invention.

The polymer is usually dissolved in the solvent in an amount of 0.5 to 10% by weight, and the surfactant is usually dissolved in the solvent in an amount of about 0.1 to 3% by weight. The polymer and the surfactant may be used in combination of two or more.

〔polymerization〕

As the polymerization initiator used for the polymerization of the comonomer, oil-soluble initiators such as lauroyl peroxide, benzoyl peroxide, cumene hydroperoxide, azobisisobutyronitrile and the like are used. The oil-soluble initiator is usually added in an amount of about 0.1 to 8% by weight based on the above comonomer. The above comonomer is usually 10 to 65% by weight based on the above solvent.
Degree mixed. The mixture of the above comonomer and the above solvent is then polymerized using the above oil-soluble initiator, usually by heating and stirring at about 50 to 80 ° C. in a reactor equipped with a stirrer, a condenser, a thermometer and the like. At this time, it is desirable to replace most of the air in the reactor with an inert gas such as nitrogen gas or argon gas in order to smooth the polymerization.

As the comonomer is polymerized, the comonomer becomes a polymer and precipitates as a true spherical powder in the solvent. After completion of the polymerization, the obtained spherical polymer particles are separated from the solvent by filtration, centrifugation, etc., and dried at room temperature or heated.

Thus, the spherical polymer particles of the present invention are obtained.The diameter of the spherical polymer particles is affected by the type of the comonomer and the solvent, but is in the range of about 0.5 to 10 μm and is uniform. It becomes something.

(Coating material particle aqueous dispersion)

As the coating material particle aqueous dispersion used in the present invention,
Natural or natural rubber, styrene-butadiene rubber, styrene-butadiene block copolymer, styrene-isoprene block copolymer, acrylonitrile-butadiene rubber, isoprene rubber, chloroprene rubber, butyl rubber, polyisobutylene rubber, polybutene rubber, graft rubber, etc. Latex of synthetic rubber, polyethylene, polypropylene, acrylate resin, methacrylate resin, vinyl acetate resin, vinyl propionate resin, vinyl acetate-ethylene copolymer resin, vinyl acetate-maleic acid copolymer resin , Styrene resin, vinyl chloride resin, vinyl chloride-ethylene copolymer resin, vinyl chloride-vinyl acetate copolymer resin, vinylidene chloride resin, polyvinyl ether resin, alkyd resin, urethane resin, Synthetic resin emulsion such as epoxy resins, other wax emulsions, paraffin emulsion, terpene resin emulsion, rosin emulsion, a petroleum resin emulsion, etc., the aqueous dispersion may be a mixture of two or more.

It is usually desirable that the diameter of the coating material particles be 1/10 or less of the diameter of the polymer particles.

Particularly useful among the aqueous dispersions of coating material particles are wax emulsions. By using the wax emulsion, the surface of a hard polymer particle such as a polystyrene-based polymer particle can be coated with a wax particle, and such a composite particle is useful for, for example, an electronic copy toner.

(Production of composite particles)

In the present invention, the polymer particles are dispersed in the coating material particle aqueous dispersion, and then the aqueous dispersion is agglomerated, whereby the coating material particles are adhered to the surface of the polymer particles and coated.

In this case, the theoretical coverage ratio of the polymer particles and the coating material particles is usually calculated based on the formula of FK, Hansen, and the like, and the number of small particles Nm of radius b when covering one large particle of radius a is calculated. Then, Nm = zπ (a + b) ² / 3b ² , and therefore the number ratio to be mixed is 1: Nm / 3 to 1: 1.5N
m, desirably 1: Nm / 2 to 1: 1.2Nm, depending on the surface potential of the particles, but if the coated particles are too small, the system will be unstable and large particles will aggregate, and if too large, aggregation will occur. Only small particles that do not belong are collected. In order to coagulate the aqueous dispersion, a heterocoagulation method is usually used. The hetero-aggregation method refers to a phenomenon in which when two types of spherical particles having different sizes and charges are mixed, one of the two types of spherical particles is adsorbed on the other surface by electrostatic bonding. Therefore, when the aqueous dispersion having a different charge from the polymer particles is combined, the coating material particles are adsorbed on the surface of the polymer particles. At this time, since the surface potential of the particles changes depending on the pH of the system, it is desirable to adjust the system to a pH at which the difference between the surface potentials of the polymer particles and the coating material particles becomes largest.

Thus, the composite particles of the present invention are obtained. The composite particles are separated from the system by filtration, centrifugation, etc., and further washed with water and dried if desired.

[Action]

In producing the true spherical polymer particles of the present invention, the functional group of the monomer A contained in the comonomer is oriented on the surface of the polymer particles during the polymerization, It is considered that polymer particles having a functional group on a stable surface are stably dispersed in a solvent and that the particles hardly associate with each other.

Therefore, in the present invention, polymer particles having high sphericity and high particle size uniformity can be obtained. Further, by selecting the type of the monomer A having a functional group and the amount added in the comonomer, the polarity of the functional group and the concentration of the functional group oriented on the surface of the polymer particle are adjusted, and the polymer particle is adjusted. Can be controlled. When the dispersion stabilizer is washed and removed from the polymer particles separated after the polymerization, the surface potential of the polymer particles can also be controlled by adjusting the remaining amount of the dispersion stabilizer. As described above, in the present invention, since the surface potential of the polymer particles can be controlled, various aqueous dispersions of the coating material particles can be used, and a monomer of a comonomer can be selected. By doing so, the hardness of the polymer particles can be arbitrarily adjusted.

[Effects of the Invention] Therefore, in the present invention, it is possible to obtain composite particles in which polymer particles having various compositions and hardnesses are coated with various coating material particles, and the composite particles have a sphericity. Further, since the particle size uniformity is high, the application range of the composite particles is widened.

Hereinafter, examples for more specifically describing the present invention will be described.

〔Example〕

Example 1 [Production of polymer particles A] A solution prepared by dissolving 4 parts by weight of polyvinylpyrrolidone K-30 in 160 parts by weight of ethanol was charged into a reactor equipped with a stirrer, a condenser, a thermometer, and a gas inlet tube. Further, 60 parts by weight of styrene, 2 parts by weight of methacrylic acid, and 0.6 parts by weight of benzoyl peroxide are dissolved and filled, and the atmosphere is replaced with nitrogen through a gas inlet tube. And polymerize for 24 hours. After the polymerization reaction, the polymer particles obtained by cooling to room temperature are collected by filtration,
Wash with methanol and dry with air at 60 ° C for 2 hours. When 100 particles of the polymer particles A thus obtained were arbitrarily selected and the particle diameter was measured by a scanning electron micrograph, it was found to be a true sphere having a particle diameter uniformly distributed of 7.1 ± 0.5 μm. found.

Example 2 [Production of polymer particles B] A solution prepared by dissolving 4 parts by weight of polyacrylic acid in 160 parts by weight of isopropanol was charged into the same reactor as in Example 1, and 20 parts by weight of styrene and β-hydroxyethyl were further added. Azobisisobutyronitrile (0.5 part by weight) was dissolved in a comonomer obtained by mixing 2 parts by weight of methacrylate, and polymerization was carried out in the same manner as in Example 1. When the particle size of the polymer particles B thus obtained was measured, it was found to be a true sphere having a uniformly distributed particle size of 5.2 ± 0.3 μm.

Example 3 [Production of polymer particles C] In a reactor similar to that in Example 1, 3 parts by weight of polyvinyl methyl ether and 160 parts by weight of methanol in which 1 part by weight of polyoxyethylene alkyl ether were dissolved were charged. A copolymer containing 0.5 part by weight of isobutyronitrile dissolved in 20 parts by weight of styrene, 10 parts by weight of acrylonitrile, and 2 parts by weight of dimethylaminoethyl methacrylate was further charged and polymerized in the same manner as in Example 1. Polymer particles
It was a true sphere having a uniformly distributed particle size of C3.3 ± 0.2 μm.

Example 4 [Production of polymer particles D] In a reactor similar to that in Example 1, 160 parts by weight of methanol in which 1 part by weight of sodium alkylbenzenesulfonate was dissolved was charged, and 0.5 part by weight of benzoyl peroxide was dissolved. Styrene 20 parts by weight, methyl methacrylate 10 parts by weight, γ-methacryloxypropyltrimethoxysilane 3
The polymer particles D obtained by further filling the comonomer with parts by weight and polymerizing in the same manner as in Example 1 were spherical having a uniformly distributed particle size of 3.0 ± 0.2 μm.

Example 5 [Production of Cationic Wax Emulsion] Into the same reactor as in Example 1, 22 parts by weight of pure water, 0.5 parts by weight of lauryldimethylbenzylammonium chloride and 2.5 parts by weight of carnauba wax were added, and heated to 90 ° C. The dispersion was finely dispersed by a homogenizer so that the maximum diameter became 0.3 μm or less, to prepare a cationic wax emulsion. The particle size of the cationic wax emulsion was 78 nm.

Example 6 [Production of anionic wax emulsion] A mixture of 19 parts by weight of pure water, 1 part by weight of sodium laurylbenzenesulfonate, and 5 parts by weight of 145 ° F paraffin wax was finely dispersed at 80 ° C in the same manner as in Example 5 to form an anion. A wax emulsion was made. The particle size of the anionic wax emulsion was 101 nm.

Example 7 [Production of polymer particles A] 20 parts by weight of the polymer particles A obtained in Example 1 were dispersed in 180 parts by weight of water using an ultrasonic homogenizer, and then gently stirred (cation prepared in Example 5). 6 parts by weight of the wax emulsion was added dropwise over 30 minutes.
After dropping the cationic wax emulsion, the temperature was maintained at 50 ° C., and after cooling, the resulting composite particles were collected by filtration, washed repeatedly with water and methanol, and dried at 60 ° C. for 2 hours to obtain composite particles A. I got The composite particles A were confirmed to be composited by a scanning electron microscope and a differential scanning calorimeter.

Example 8 [Production of polymer particles B] In the same manner as in Example 7, 20 parts by weight of the polymer particles B obtained in Example 2 were dispersed in 180 parts by weight of water, and then the cationic wax emulsion prepared in Example 5 was prepared. 15 parts by weight were added dropwise over 30 minutes. After the addition of the cationic wax emulsion, composite particles B were obtained in the same manner as in Example 7, and composite formation was confirmed.

Example 9 [Production of polymer particles C] In the same manner as in Example 7, 20 parts by weight of the polymer particles C obtained in Example 3 were dispersed in 180 parts by weight of water, and then the anionic wax emulsion prepared in Example 6 was dispersed. 20 parts by weight were added dropwise over 30 minutes. After the dropping of the anionic wax emulsion, composite particles C were obtained in the same manner as in Example 7, and composite formation was confirmed.

Example 10 [Production of polymer particles D] In the same manner as in Example 7, 20 parts by weight of the polymer particles D obtained in Example 4 were dispersed in 180 parts by weight of water in the same manner as in Example 7; Anionic wax emulsion made with
20 parts by weight were added dropwise over 30 minutes. After the dropping of the anionic wax emulsion, composite particles D were obtained in the same manner as in Example 7, and composite formation was confirmed.

(56) References JP-A-63-93346 (JP, A) JP-A-62-213839 (JP, A) JP-A-56-5802 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) C08J 3/12-3/16 B01J 13/02 C08F 2/04-2/10

Claims (2)

(57) [Claims] 1. A comonomer of a monomer A having a functional group and another monomer B copolymerizable with the monomer A, wherein the comonomer is dissolved and the comonomer is dissolved. The copolymer based on the monomer is separated into spherical polymer particles obtained by polymerization in a solvent that does not dissolve, and the spherical polymer particles are coated with a particle size smaller than the spherical polymer particles. A method for producing composite particles, comprising dispersing in an aqueous dispersion of material particles and then aggregating the aqueous dispersion. 2. The method according to claim 1, wherein the aqueous dispersion of the coating material particles is a wax emulsion.