JP3334434B2 - Method for producing inorganic-containing polymer particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to polymer particles containing inorganic particles. In particular, the present invention relates to a method for producing polymer particles containing inorganic particles and having a particle diameter of 0.1 to 10 μm and having a relatively narrow particle diameter distribution by radical polymerization, which was difficult to produce by the conventional technique.

[0002]

2. Description of the Related Art Methods for producing polymer particles by radical polymerization are roughly classified into suspension polymerization and emulsion polymerization. Suspension polymerization is a polymerization method in which an oil-based monomer in which an oil-soluble initiator has been dissolved in advance is dispersed in water containing a suspension protective agent or an emulsifier and polymerized. The obtained polymer particles generally have a large particle size of several μm to several hundred μm and have a wide particle size distribution.
In addition, as long as it does not affect the polymerization reaction, if inorganic particles are mixed with the monomer, inorganic-containing polymer particles can be produced relatively easily. That is, in the suspension polymerization, the production of the inorganic-containing polymer particles is easy, but the particles have a particle diameter of several μm or more and have a wide particle diameter distribution. JP 56
164,503 discloses that a part or all of the monomer mixed with inorganic particles is mechanically dispersed in water with high shearing force and subjected to suspension polymerization to reduce the particle diameter to 1 μm or less. Was broad. In Japanese Patent Publication No. 59-500691, an attempt was made to prepare a monomer swelling polymerization on seeds and to deposit inorganic particles on the obtained particles in order to produce inorganic-containing polymer particles having a narrow particle size distribution by suspension polymerization. But this is still 1μ
m or less, it was difficult to produce inorganic-containing polymer particles. On the other hand, emulsion polymerization is a polymerization method in which an oily monomer is emulsified in water with an emulsifier and polymerized with a water-soluble initiator. At the beginning of the polymerization, the monomer dissolved in the emulsifier micelle in water or in a trace amount in water is polymerized by radicals in water from a water-soluble initiator. This initial polymerization component precipitates without being dissolved in water, and becomes innumerably small particles formed in the system and has a huge interface area, so that it becomes colloidally unstable,
Aggregate with each other until the interfacial area can be stably present in the system. This stage is usually completed very early, within a few percent in polymerization conversion. Thereafter, the number of the remaining particles does not change, and the monomer molecules and radicals enter the particles by molecular diffusion via water, and the polymerization is continued. Here, the monomer gradually elutes from the monomer droplets in the system into water, the particles being polymerized gradually become thicker, and the polymerization is completed. In this emulsion polymerization, the particle diameter is usually 0.05 to 0.5 μm.
m, and the particle size distribution is relatively narrow. However, it was difficult to make the polymer particles of the emulsion polymerization contain inorganic particles due to the mechanism in which the monomer diffuses water and transfers to the particles in most stages of the polymerization. Even when the emulsion polymerization was carried out by mixing the inorganic particles with the monomer, only the monomer was transferred to the particles and polymerized, and the inorganic particles were left in the water. Japanese Patent Application Laid-Open No. 57-125203 discloses that emulsion polymerization is carried out in the presence of inorganic particles dispersed in water, whereby inorganic particles are embraced at the initial nucleation stage to produce inorganic-containing polymer particles by emulsion polymerization. Is disclosed. However, this method has limitations such as that the amount of inorganic particles that can be contained is small and that the inorganic particles are well dispersed in water. In addition, JP-A-59-111
929 and JP-A-63-65085 attempt to attach or bond inorganic particles to the surface of previously synthesized polymer particles of 1 μm or less in size. However, in these, inorganic particles exist on the particle surface, and there is a problem that the particle performance is deteriorated due to the inorganic material. Further, it is conceivable to further coat the particles with a polymer, but it has been technically quite difficult. As described above, it is technically difficult to produce polymer particles having a particle size distribution of 10 μm or less and having a relatively narrow particle size and containing inorganic particles in the conventional technology.

[0003]

SUMMARY OF THE INVENTION Based on the above situation,
The present invention provides a method for producing inorganic-containing polymer particles in which the particle size distribution is relatively narrow at 10 μm or less and inorganic particles are present inside.

[0004]

Means for Solving the Problems The present inventors diligently study various polymerization methods and emulsify and polymerize a monomer phase in which inorganic particles are present under specific conditions using a specific porous membrane. The inventors have found that it is possible to synthesize inorganic-containing polymer particles having a narrow particle size distribution, and have reached the present invention. That is, the present invention relates to an aqueous dispersion of monomer droplets in which inorganic particles are dispersed through a porous membrane that has been obtained by dispersing inorganic particles having a particle diameter of 0.1 μm or less in a hydrophobic vinyl monomer into a hydrophilic membrane. And then polymerizing the inorganic-containing polymer particles. Specific examples of the hydrophobic vinyl monomer in the present invention, styrene, vinyl toluene, α-methylstyrene, aromatic vinyl compounds such as divinylbenzene,
Methyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, isobutyl (meth) acrylate, cyclohexyl (meth) acrylate, ( Meta)
2-ethylhexyl acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, benzyl (meth) acrylate, mono or di (meth) acrylate of (poly) ethylene glycol, mono or di of (poly) propylene glycol (Meth) acrylate, 1,
Unsaturated carboxylic esters such as mono- or di- (meth) acrylate of 4-butanediol, mono-, di- or tri- (meth) acrylate of trimethylolpropane, diallyl phthalate, diallyl acrylamide, triallyl (iso) cyanurate And allyl compounds such as triallyl trimellitate; and (poly) oxyalkylene glycol di (meth) acrylates such as (poly) ethylene glycol di (meth) acrylate and (poly) propylene glycol di (meth) acrylate. Also, conjugated diene compounds such as butadiene, isoprene, and chloroprene. In addition, acrylic acid,
Functional group-containing monomers such as methacrylic acid, itaconic acid, fumaric acid, glycidyl methacrylate, vinyl pyridine, diethylaminoethyl acrylate, N-methyl methacrylamide, and acrylonitrile are exemplified. Among these, monomers having high water solubility such as acrylic acid, methacrylic acid, and itaconic acid can be used within a range where the water solubility of the monomer as a whole becomes high and an oil-in-water type monomer emulsion cannot be formed. Specifically, the amount of the water-soluble monomer is 10% by weight or less of all the monomers.

[0005] The inorganic particles used in the present invention must be insoluble in the hydrophobic vinyl monomer and have no fatal effect on radical polymerization. Many inorganic particles have some degree of inhibitory or accelerating effect on radical polymerization, but those which can be dealt with by adjusting the amount of the polymerization initiator can be used as the inorganic particles of the present invention. Specific examples of the inorganic particles that can be used in the present invention include metal particles such as copper particles, gold particles, and brass particles, or metal oxide particles such as iron oxide, ferrite, zinc oxide, titanium oxide, magnesium oxide, and fly ash. Or calcium carbonate, carbonates such as magnesium carbonate, calcium phosphates, phosphates such as lead phosphate, silica, and clays and glasses such as silicates, metal salts such as silver chloride,
Aluminum hydrates such as aluminum hydroxide. Of these, metal oxide fine particles including ferrite, which is a magnetic substance, are particularly preferable. Particularly, the magnetic fluid is preferable as a dispersion of magnetic particles which are superparamagnetic fine particles in the monomer and are easily dispersed in the monomer.

It is necessary that the inorganic particles of the present invention have a small particle size, are lipophilic and are well dispersed in a monomer. The particle diameter of the inorganic particles must be 0.1 μm or less, preferably 0.05 μm or less, and more preferably 0.03 μm or less. For this reason, it is necessary to use the inorganic particles adjusted to a small particle size, and to treat the surface of the inorganic material when the inorganic particles are poorly compatible with the monomer. For the surface treatment of the inorganic particles, a known method such as a dispersant treatment for adsorbing a pigment dispersant on the inorganic material surface, a coupling agent treatment with a silane coupling agent, a titanate coupling agent, or a polymer coating treatment by capsule polymerization or the like is applied. be able to.
In addition, an oil paint and a semi-finished product thereof in which a magnetic fluid or a coloring material pigment in which a magnetic substance is dispersed in oil in advance are suitable as the inorganic particles of the present invention. To disperse the inorganic particles in the hydrophobic vinyl monomer in the present invention may be a normal stirrer, but when the dispersibility of the inorganic particles is poor,
Alternatively, when it is necessary to make the inorganic content between particles in the obtained inorganic-containing polymer particles uniform, a high-shearing disperser such as a homomixer, a homogenizer, a paint mill, or a bead mill may be used.

In the present invention, in order to emulsify a hydrophobic vinyl monomer in which inorganic particles are dispersed in water, the hydrophobic vinyl monomer is discharged into water through a hydrophilic porous membrane. The porous pores in the present invention need to have an average pore diameter of 0.01 to 5 μm, have a uniform pore diameter, and penetrate both sides of the membrane.
Glass is preferable as the material of the film, and a specific example is SiO ₂ —Al ₂ O ₃ fired using volcanic ash shirasu as a main raw material.
Porous glass (referred to as SPG) obtained by subjecting —B ₂ O ₃ —CaO-based glass to microphase separation by heat treatment and dissolving and removing a boric acid-rich phase with an acid is preferred. In addition, even if the ordinary ceramic porous membrane has the same pore diameter, the pore diameter distribution is much larger than that of the glass porous membrane, so that the inorganic particles in the monomer are clogged in the pores and cannot be put to practical use. The surface of the porous membrane used in the present invention needs to be hydrophilic. If the surface has lipophilic or oily substance adhered, monomer droplets extruded through the membrane adhere to the membrane surface on the outlet side and spread, resulting in a coarse monomer droplet having a very wide particle size distribution. Inorganic-containing polymer particles with a small particle size cannot be formed. By making the surface of the porous membrane hydrophilic, when the hydrophobic vinyl monomer is ejected through the pores, it does not adhere to the membrane surface on the exit side, but is formed into droplets of a certain size determined by the surface tension and pore diameter. It will come off regularly. As a result, monomer droplets having a uniform diameter and containing inorganic particles are obtained. The surface of the porous glass can be made hydrophilic by immersing it in an acid such as sulfuric acid or hydrochloric acid.

In the present invention, a surfactant or a water-soluble polymer must be present as a stabilizer for monomer droplets in the aqueous phase in which a hydrophobic vinyl monomer containing inorganic particles is extruded through a porous membrane. Without the stabilizer, the monomer droplets ejected through the membrane fuse with each other to form a broad particle size distribution. As a preferable stabilizer, when the monomer droplet is about 1 μm or more, a water-soluble polymer-based stabilizer such as polyvinyl alcohol, hydroxypropylcellulose, and polyvinylpyrrolidone is preferable, and a small amount of an anionic surfactant or It is also preferable to add a nonionic emulsifier. When the monomer droplet size is less than about 1 μm, an anionic surfactant and a combination of an anionic surfactant and a nonionic surfactant are preferred. In particular, a preferable stabilizer in terms of the stability of monomer droplets having a small particle diameter is a long-chain aliphatic sulfate having 10 to 18 carbon atoms as an emulsifier,
It is a combination using 2 to 18 aliphatic higher alcohols as a coemulsifier. Specifically, a combination of sodium lauryl sulfate as an emulsifier and 1-hexadecanol as a co-emulsifier is strongly adsorbed on the surface of a droplet and has a large stabilizing effect, and is particularly preferable as a stabilizer in the present invention.

In the present invention, an oil-soluble radical initiator is mainly used to polymerize an aqueous dispersion of monomer droplets containing inorganic particles emulsified. Examples of the initiator that can be used as the oil-soluble radical initiator include azo initiators such as azobisisobutyronitrile, benzoyl peroxide, 2,
Examples include aromatic peroxides such as 4-dichlorobenzoyl peroxide, and aliphatic peroxides such as isobutyl peroxide, diisopropylperoxydicarbonate, and di (2-ethylhexylperoxy) dicarbonate. These can be used by dissolving them in the monomer phase before emulsification. In addition, the particle diameter of the droplet is 0.7
If it is less than about μm, polymerization can be performed with a water-soluble initiator such as potassium persulfate or hydrogen peroxide. In order to inhibit polymerization other than monomer droplets in the polymerization of the present invention, a water-soluble radical polymerization inhibitor such as hydroquinone and iron chloride can be added. This suppresses the generation of new particles in the aqueous phase and broadening the particle size distribution.
The particle diameter of the inorganic-containing polymer particles obtained by the method of the present invention is 0.2 to 10 μm in volume average particle diameter (D). The particle size distribution is expressed as a volume fraction of all particles in the range of 0.6D to 1.4D, and the value is 70% or more. The measurement of the particle diameter can be obtained by measuring and calculating 200 or more particles with an electron microscope photograph. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0010]

【Example】

Example 1 40 g of an oil-based dispersion of a ferrite magnetic substance (ferricolloid manufactured by Taiho Kogyo KK, particle size 0.02 μm), 94 g of styrene, 1 g of divinylbenzene, 5 g of glycidyl methacrylate and 3 g of azobisisobutyronitrile were mixed, While cooling, the mixture was thoroughly mixed and dispersed in a paint mill for 10 minutes to obtain a hydrophobic vinyl monomer in which inorganic particles were dispersed. As a porous film, SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ —C
AO-based glass is microphase-separated by heat treatment, and a boric acid-rich phase is dissolved and removed with an acid to form a porous tube (Ise Chemical Co., Ltd.)
(SPG, pore size: 0.3 μm) was immersed in 2N sulfuric acid at 70 ° C. for 2 hours, washed sufficiently with water, and subjected to a hydrophilization treatment. Subsequently, a solution obtained by adding 2 liters of water to 10 g of sodium lauryl sulfate and 25.3 g of 1-hexadecanol was subjected to ultrasonic irradiation for 10 minutes, immersed in an aqueous solution in which the gel structure was destroyed, and decompressed while applying ultrasonic waves. Air was removed to remove air bubbles inside the porous glass. Next, the above aqueous solution was flowed at a flow rate of 200 ml / min inside the porous glass tube, and a hydrophobic vinyl monomer in which inorganic particles were dispersed was flown outside at a pressure of 1.3 kg / cm ² . The aqueous phase flowing out from the inside of the porous glass contained microdroplets in which the hydrophobic vinyl monomer phase was emulsified, and became cloudy. The aqueous phase was circulated, and the aqueous phase was circulated and the hydrophobic vinyl monomer phase was pressurized until the hydrophobic vinyl monomer phase disappeared. During the operation, the porous glass was not clogged with the hydrophobic vinyl monomer phase. One liter of the aqueous dispersion of the hydrophobic vinyl monomer droplets in which the obtained inorganic particles were dispersed was replaced with nitrogen to obtain 7
When the polymerization reaction was carried out by slowly stirring at 0 ° C. for 8 hours, magnetic material-containing polymer particles were obtained with a polymerization yield of 96%.
The magnetic material-containing polymer particles were able to be settled by suction with a magnet. When the magnetic material-containing polymer particles were taken with an electron microscope photograph, the magnetic material was present inside the particles in all the particles, and particles having no magnetic material or particles containing only the magnetic material were not found. When the particle diameter of 200 magnetic substance-containing polymer particles was randomly measured on the photograph, the volume average particle diameter (D) was 1.12 μm, which was 0.6D to 1.4D, and was in the range of 0.67 to 1.57 μm. The volume fraction of particles entering was 91%. The particles were dried and measured by thermogravimetry to find that the inorganic content was 13.3% by weight.

Example 2 and Comparative Example 1 0.05 μm (Example 2) and 0.15 μm as inorganic particles
μm (Comparative Example 1) each of 15 g of magnetite particles treated with a silane coupling agent was used, 40 g of styrene was used as a hydrophobic vinyl monomer, and a polyester pigment dispersant (BYK-161 manufactured by BYK-Chemie KK)
A dispersion of monomer droplets was produced in the same manner as in Example 1, except that a dispersion obtained by using the above was used as a hydrophobic vinyl monomer in which inorganic particles were dispersed. In Example 2, the emulsification operation could be performed without any particular problem, and magnetic polymer particles were obtained by polymerizing the emulsion. The particles of Example 2 had a volume average particle diameter (D) of 0.95 μm, and the particles in the range of 0.6D to 1.4D had a volume fraction of 82%. On the other hand, Comparative Example 1
In the case of membrane emulsification, some monomer phase passed through the membrane immediately after the start of the operation and was emulsified, but the membrane was clogged immediately and the operation could not be performed. Here, the glass was replaced with porous glass having a large pore diameter of 1 μm, but clogging could not be eliminated. Comparative Example 2 The same operation as in Example 1 was performed except that a ceramic porous pipe (NGK INSULATORS, pore diameter 0.3 μm, no hydrophilic treatment) was used as the porous membrane. The inorganic particles are clogged in the porous pipe and the pressure of the monomer phase is increased to 5 kg / cm ^2.
No monomer phase was able to pass at all.

[0012]

According to the production method of the present invention, inorganic-containing polymer particles having a relatively narrow particle size distribution of 0.1 to 10 μm, which were conventionally difficult to synthesize, can be easily produced with good reproducibility.
The inorganic-containing polymer particles produced by the present invention include various functional binder particles, polymer particles for special coatings, polymer particles for wet development, carrier particles for immunodiagnosis, carrier particles for cell separation, carrier particles for medical drugs, and genes. It can be applied to nucleic acid-binding polymer particles for engineering or medical diagnosis, polymer particles for information recording, polymer particles for information display, sustained-release polymer particles, catalyst carrier particles, etc., and is practically useful.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-166707 (JP, A) JP-A-6-49104 (JP, A) JP-A-6-192305 (JP, A) JP-A-6-192305 1854 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 2/00-2/60

Claims (1)

(57) [Claims] 1. An aqueous dispersion of monomer droplets in which inorganic particles are dispersed by discharging a monomer in which inorganic particles having a particle diameter of 0.1 μm or less are dispersed in a hydrophobic vinyl monomer into water through a hydrophilic membrane. And then polymerizing the mixture.