JPS61215602A - Production of polymer particle - Google Patents

Abstract

PURPOSE:To obtain monodisperse polymer particles of a relatively large particle diameter, by mixing an aqueous dispersion of seed particles with an aqueous dispersion of fine particles of a polymerizable unsaturated monomer and an aqueous dispersion of fine particles of an oil-soluble polymerization initiator to allow the seed particles to adsorb the fine particles and polymerizing the monomer in the resulting dispersion. CONSTITUTION:An aqueous dispersion of seed particles comprising polystyrene, polyvinyl acetate or the like is mixed with an aqueous dispersion containing a polymerizable unsaturated monomer (e.g., styrene or butyl acrylate) in a state of particles having a particle diameter smaller than that of the seed particles and an aqueous dispersion of an oil-soluble polymerization initiator (e.g., azobisisobutyronitrile or acetyl peroxide) in a state of particles having a particle diameter smaller than that of the seed particles. After the seed particles are allowed to absorb or adsorb the polymerizable unsaturated monomer and the oil-soluble polymerization initiator, the monomer in the resulting dispersion is polymerized to obtain the purpose polymer particles of a particle diameter in the range of about 1-100mum.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides particles having a particle size in the range of about 1 to 100 μm.
The present invention relates to a method for producing relatively large diameter monodisperse polymer particles.

[Conventional technology]

Although monodisperse polymer particles having a particle size in the range of about 1 to 100 μm are in demand in many fields, it is generally extremely difficult to produce them. In the production of polymer particles by emulsion polymerization, monodisperse polymer particles can be obtained relatively easily, but they are usually 1 μm in size.
Only the following small particle sizes can be obtained, and 3 μm is said to be the limit even under special conditions. On the other hand, in the production of polymer particles by suspension polymerization, relatively large polymer particles with a particle size of 1 to 100 μm can be obtained, but monodisperse polymer particles with a wide particle size distribution can be produced. It is extremely difficult to do so. Therefore, when trying to obtain all monodispersed polymer particles, it is necessary to classify all the particles obtained by suspension polymerization, which increases the number of steps, making production difficult and resulting in low yield. As a method for producing monodisperse polymer particles with a relatively large diameter, there is a method disclosed in JP-A No. 54-97582 or JP-A No. 54-Sho.
A technique disclosed in Japanese Patent No.-126288 is known.

In JP-A No. 54-97582, a polymer having a molecular weight much lower than that of ordinary polymer latex is synthesized by adding a chain transfer agent during emulsion polymerization, and this is made into sheet particles. UH is a method of polymerizing by completely absorbing unsaturated monomers that are somewhat soluble in water. However, in this method, if a commonly used oil-soluble initiator or water-soluble initiator is used, problems such as generation of coagulum or new particles occur, and it is difficult to ensure that all large-sized, monodisperse polymer particles are collected. In addition, in JP-A-54-126288, in the first step, an organic compound with a solubility in water that functions as a swelling aid and whose solubility in water is 10 g/) is smaller than H2O and is absorbed into the entire sheet particle. After that, in the second step, a somewhat water-soluble monomer is absorbed in an amount of about 100 times the volume of the sheet particles to form swollen particles of the monomer, and then persulfuric acid is added as a polymerization initiator. A method is disclosed in which a water-soluble polymerization initiator such as potassium or an oil-soluble polymerization initiator such as azoisobutyronitrile (AIBN) is polymerized while maintaining the entire particle shape. However, in this method, when an oil-soluble polymerization initiator is used as a polymerization initiator, even the dispersed phase of the monomer that is not absorbed into the sheet particles is polymerized, resulting in a large amount of coagulum. The drawback is that the yield is low. In addition, when all water-soluble and polymerization initiators such as persulfates are used as polymerization initiators,
Even if the emulsifier concentration is below the critical micelle concentration, the propagating radicals in the aqueous phase act as the emulsifier, resulting in so-called Soap I.
J - There is a drawback that emulsion polymerization proceeds partially or entirely and the swollen particle morphology is not maintained. Furthermore, in this method, there is a problem that the resulting polymer particles are not perfectly spherical but distorted due to the action of a low water-soluble organic compound as a swelling aid that is absorbed into the sheet particles in the first step of the process. .

As a method to solve these problems, there is a method of enlarging sheet particles without using any swelling aid, as described in Document J.
Polym, Sci, Polym, Let
t, Kd,, 2t.

937--943 (1983) (J, H, Ja
nsson, M., C. Wellons.

G., W. Poehlein). According to this method, a monomer and an oil-soluble polymerization initiator are mixed, this mixture is finely dispersed to make a monomer emulsion, and this is then used as a dispersion (latex) of sheet particles.
It is possible to achieve enlargement of sheet particles with a swelling ratio as high as 14:1.

However, in this method, the above-mentioned JP-A-54-1
Compared to the method using a swelling aid in Publication No. 2688,
Even if sheet particles under the same conditions are used, there is a major problem in that the uniformity of the particle size of the resulting polymer particles is poor.

Such non-uniformity in particle size in polymer particles is thought to be caused by the following phenomenon.

That is, since the monomer mixture is dispersed in an aqueous dispersion medium after an oil-soluble polymerization initiator is mixed with the monomers, the monomers are partially absorbed by the heat generated by the high shear energy applied to the system during the dispersion process. part polymerizes, forming a small amount of polymer in the droplets of the monomer mixture. Then, the surrounding monomer mixture is absorbed by this polymer and the droplets 4 of this monomer mixture (droplets of the monomer mixture remaining in the dispersion medium without being absorbed by the sheet particles are stabilized). As a result, a large number of unnecessary polymer particles are produced by the polymerization process, and the range of the particle size distribution of the resulting polymer particles increases, resulting in polydispersity.

In the above, the generation of unnecessary polymer ligands during the dispersion process can be prevented by cooling the system and removing heat generated by shearing, but it is necessary to sufficiently remove such heat throughout the system. This is actually extremely difficult, and it is difficult to completely eliminate the above problems even with advanced cooling equipment.

In addition, this method for producing polymer particles has a problem in that the storage stability is extremely low because the monomer and the polymerization initiator are used in a mixed state.

[Problem that the invention seeks to solve]

The present invention solves the following problems of the prior art: 0) It is impossible to obtain all polymer particles with a wide and uniform particle size distribution, and (2) It is difficult to obtain perfectly spherical polymer particles. It is an object of the present invention to provide a method for producing polymer particles that can reliably produce truly spherical polymer particles with high monodispersity through a simple process.

[Means for solving problems]

The above problems are related to the aqueous dispersion of sheet particles and the following two problems.
(a) an aqueous dispersion in which a polymerizable unsaturated monomer is dispersed with a particle size smaller than the sheet particles; and (b) particles in which an oil-soluble polymerization initiator is smaller than the sheet particles. A polymer characterized in that the polymerizable unsaturated monomer and the oil-soluble polymerization initiator are completely absorbed or adsorbed onto the sheet particles, and then polymerization is carried out. The problem is solved by a method of manufacturing particles.

That is, in the present invention, the polymerizable unsaturated monomer and the oil-soluble polymerization initiator are first dispersed in water in such a state that the particle size of each dispersed particle (oil droplet) is smaller than the particle size of the sheet particle. each aqueous dispersion is prepared, and then these aqueous dispersions and the aqueous dispersion of sheet particles are mixed to bring the polymerizable unsaturated monomer and oil-soluble polymerization initiator into contact with and absorbed by the sheet particles, The feature is that the polymerization is then carried out.

The present invention will be explained in detail below.

The polymerizable unsaturated monomer that can be used in the present invention preferably has a solubility in water of 0.001 to 0.2% by weight. If the solubility of the monomer in water is too low, it will take a significant amount of time for the monomer to be absorbed into the sheet particles because the finely dispersed polymerizable unsaturated monomer has good stability. do not have. On the other hand, if the solubility of the monomer in water is too high, the oil droplets of the finely dispersed monomer will be unstable and their lifetime will be significantly shortened. Preparation of aqueous dispersions becomes difficult.

Examples of polymerizable unsaturated monomers having a solubility in water in the range of 00001 to 0°2 weight Jt% and which can be suitably used in the present invention include styrene, α-methylstyrene, P-methylstyrene, and divinylbenzene. Aromatic vinyl monomers such as butyl acrylate-1-*-1 + methacrylate 2-f/L/hexyl acrylate-1, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, trimethylolpropane tri All examples include ethylenically unsaturated carboxylic acid alkyl esters such as methacrylate, conjugated diolefins such as butadiene, and isoprene. These monomers can be used alone or in combination of two or more.

When using a polymerizable unsaturated monomer with a solubility in water of more than 0.02% by weight, it is preferable to perform fine dispersion so that the total particle size of the monomer is 1 μm or less. The solubility in water is O60 for all ribbons.
It suffices if the lipophilic substance is less than or equal to 01, n-hex →
Tan, -\butane, octane, 1-chlordodecane, dioctyl adipate pond, stearyl vinyl ether 1
．． Examples include polymerizable unsaturated monomers such as stearyl and methacrylate.

Polymerizable unsaturated monomers having a solubility in water of more than 0.2 weight % include vinyl acetate, acrylonitrile,
Methyl acrylate, methyl methacrylate, ethyl acrylate, vinylidene chloride, ethyl methacrylate,
Ethylene glycol, diacrylate, ethylene glyco-dimethacrylate, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, N-notyrol acrylamide, N-methyloltutacrylamide, 2-hydroxyethyl acrylate
2=-Hydroxyethyl methacrylate-1, diallyl phthalate, allyl methacrylate, allyl methacrylate l/
= l・, acrylic acid, methacrylic acid, itaconic acid,
Examples include fumaric acid.0 When using a monopolymerizable unsaturated monomer whose solubility in water is less than 09001% by weight, it is finely dispersed in water and then absorbed or adsorbed onto sheet particles. It is preferable to add a water-soluble organic solvent to destabilize the finely dispersed droplets to promote absorption or adsorption onto the sheet particles. Water-soluble organic solvents that can be used for this purpose include acetone, methanol, ethanol,
Examples include dimethylformamide and tetravitrofuran.

Examples of the polymerizable unsaturated monomer having a solubility in water of less than 0.001% include stearyl vinyl ether and stearyl methacrylate.

In the present invention, from the viewpoint of preventing the generation of new particles in the aqueous phase during polymerization, at least a part of the polymerizable unsaturated monomers is a monomer with a high polymerization conversion rate, such as divinylbenzene, It is preferable to use Ac+79 nitrile or vinyl chloride. If there are multiple types of polymerizable unsaturated monomers, mix the multiple monomers and then finely disperse the mixture to prepare an aqueous dispersion. Alternatively, each monomer may be individually finely dispersed to prepare an aqueous dispersion.

When using an aqueous dispersion in which each monomer is finely dispersed individually, the aqueous dispersion of the monomer and the aqueous dispersion of the sheet particles are mixed in descending order of solubility of the monomer in water. Preferably, the monomer is absorbed or adsorbed onto the sheet particles.

The sheet particles that can be used in the present invention are preferably those that swell by completely absorbing the polymerizable unsaturated monomer, such as styrene polymers, styrene copolymers such as styrene-butadiene copolymers, and acrylic esters. Polymers such as vinyl acetate polymers and vinyl acetate polymers can be exemplified. These sheet particles are used in the form of a dispersion such as an aqueous latex or emulsion. Also usable are polymers with non-swellable compositions, highly crosslinked polymers, and even aqueous dispersions of inorganic substances whose surfaces have been treated to make them lipophilic.

The particle size of the sheet particles is preferably uniform in order to make the particle size of the finally obtained polymer particles uniform. The particle size of the sheet particles is appropriately selected depending on the intended use of the resulting polymer particles, but is usually 1 μm or less, preferably in the range of 062 to 0.9 μm. In addition, the polymer particles obtained in the present invention are used as sheet particles in the next step, and larger particles '5r: #! You can also build one.

The oil-soluble polymerization initiator that can be used in the present invention preferably has a water solubility in the range of 0.001 to 0.2% by weight. If the solubility of the oil-soluble polymerization initiator in water is too low, it will take a significant amount of time for the polymerization initiator to be absorbed into the sheet particles because the finely dispersed oil-soluble polymerization initiator has good stability. do not have. On the other hand, if the solubility of the oil-soluble polymerization initiator in water is excessive, the oil droplets of the finely dispersed polymerization initiator will be unstable and their lifespan will be significantly shortened. It becomes difficult to prepare an aqueous dispersion in such a state.

An oil-soluble polymerization initiator that has a solubility in water in the range of 0.001 to 0.2% by weight and can be suitably used in the present invention is %315951'! J Methylhexanoyl peroxide, t-butylperoxy
Examples include stealth-blocking oxides such as 2-ethylhexanoate and di-t-butyl peroxide, and azo compounds such as azobisisobutyronitrile and azobiscyclohexanecarbonitrile.

When the oil-soluble polymerization initiator is in a solid state such as a powder, it is preferably used after dissolving it in an inert organic solvent such as toluene or cyclohexane.

When using an oil-soluble polymerization initiator with a solubility in water of more than 0.2% by weight, it is difficult to finely disperse the polymerization initiator, so 0.2% by weight of the dispersion aid is added to 100 parts by weight of the polymerization initiator. It is necessary to add 1 part by weight or more. Such a dispersion aid has a solubility in water of 0.000
An inert oil-soluble substance of 0.01% by weight or less is acceptable.
-Hexane, heptane, octane, dioctyl 1-chlordodecane adipate, etc. can all be used.

Examples of oil-soluble initiators having a solubility in water of more than 0.02% by weight include t-butyl peroxyacetate, t-butyl peroxyisobutyrate, 1-butyl peroxypivalate, t-butyl hydroperoxide, and acetyl peroxide. , imbutyryl peroxide, etc. can all be mentioned.

Next, the process of the manufacturing method of the present invention will be specifically explained.

In the present invention, in order to efficiently and reliably absorb or adsorb the polymerizable unsaturated monomer and oil-soluble polymerization initiator onto the sheet particles, suppress the generation of unnecessary new particles, and increase monodispersity, It is important to make these polymerizable unsaturated monomers and oil-soluble polymerization initiators into aqueous dispersions before adding them to the reaction system, and to make the particle size of these dispersed oil droplets smaller than the particle size of the sheet particles. It is.

When the monomer is absorbed into the sheet particles, the particle size of the sheet particles usually increases due to swelling. is within the scope of the method of the present invention as long as the particle size is smaller than the particle size of the sheet particles after expansion by swelling. However, in that case, it takes a long time for the monomer or polymerization initiator to be absorbed into the sheet particles.

In order to finely disperse the oil droplets of the polymerizable unsaturated monomer and the oil-soluble polymerization initiator, it is necessary to apply a high shearing force to the dispersion, for example, by shearing under high pressure. A method using a Manton Galarin homogenizer or a method using ultrasonic waves can be employed. In these methods, it is necessary to perform a cooling operation to avoid heat generation due to shearing.

Furthermore, in preparing the dispersion, a surfactant is used to improve dispersibility. Common surfactants can be used as such surfactants, and examples include anionic emulsifiers such as sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium dialkylsulfosuccinate, and formalin condensates of naphthalenesulfonic acid. Furthermore, it is also possible to use a nonionic surfactant such as polyoxyethylene nonylphenol ether, polyethylene glycol monostearate, or sorbitan monostearate.

The order in which the aqueous dispersions of the polymerizable unsaturated monomer and the oil-soluble polymerization initiator are added to the aqueous dispersion of sheet particles is not particularly limited; the monomer is then added to the aqueous dispersion, or vice versa. They may be added sequentially in this order, or both may be added at the same time. Further, the addition of each aqueous dispersion may be continuous or intermittent. For example, specifically, first, the entire aqueous dispersion of the oil-soluble polymerization initiator is added to the aqueous dispersion of sheet particles, The entire system is slowly stirred, usually for at least 1 hour, until the oil droplets of the polymerization initiator are completely absorbed into the sheet particles, and then an aqueous dispersion of a polymerizable unsaturated monomer is added, and the monomer is dissolved in oil. Stir gently until the drops are completely absorbed into the sheet particles, usually for an hour or more.

In such an absorption operation, it is also possible to add a water-soluble organic solvent or a water-soluble base to speed up the absorption of the finely dispersed oil droplets into the sheet particles. However, care must be taken at this time since the sheet particles may become unstable and aggregate, resulting in a wide particle size distribution of the resulting polymer particles.

After the finely dispersed oil droplets disappear through the above absorption operation and absorption into the sheet particles is completed, the temperature of the system is raised to carry out polymerization. The polymerization temperature is usually 40 to 90°C, preferably 50 to 80°C.

During polymerization, it is necessary to use a dispersion stabilizer to increase the stability of the dispersed particles. Such dispersion stabilizers may be those commonly used, such as anionic or nonionic surfactants, or organic or inorganic suspension protectants. As a preferable dispersion stabilizer, polyvinyl alcohol with a degree of saponification of 75 to 55, 1 synthetic leather 500 to a, and o o o can be used.

During polymerization, depending on the monomer composition, particles may be generated and grow in the aqueous phase independently of the sheet particles. To suppress this, ferric chloride, sodium sulfite,
Water-soluble polymerization inhibitors such as hydroquinone can also be added.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited thereto. In the following description, "part" and "ch" represent parts by weight and weight %, respectively.

Example 1 2 parts of t-butyl peroxy 2-ethylhexanoate "Perbutyl 0" (manufactured by NOF Corporation), 5 parts of sodium lauryl sulfate O, and 20 parts of water were stirred and emulsified using ultrasonic waves to produce perbutyl. O was finely dispersed so that the particle size of the oil droplets was 0.5 μm or less. This dispersion? , particle size O, SOμ
m monodispersed polystyrene latex (solid content concentration 5%)
40 parts of Perbutyl O was added to the mixture, and the mixture was slowly stirred on a thread for 12-JR at a temperature of 30° C., so that the oil droplets of Perbutyl O were absorbed into the polystyrene particles that were sheet particles.

Next, a monomer mixture of 90 parts of styrene and 4210 parts of divinylbenzene, 2.85 parts of sodium lauryl sulfate, and 342 parts of water were ultrasonically stirred and emulsified. Particle size is 0.5μ
The resulting dispersion was added to the dispersion of sheet particles. and 1 at a temperature of 30℃
The system was slowly stirred for 2 hours to absorb the monomer into the sheet particles.
(manufactured by Nippon Gosei Kagaku Co., Ltd.) was added, and the temperature was raised to 80°C to start polymerization.
It was almost completed in no time. There was almost no generation of coagulum, and no new particles were generated in the aqueous phase. When the obtained polymer particles were observed using a scanning electron microscope,
It was confirmed that the particles were almost perfectly spherical and had an extremely uniform particle size with an average particle size of 2.8 μm and a deviation value of 5% per particle size. FIG. 1 is an electron micrograph showing this polymer particle.

Comparative Example 1 90 parts of styrene, 4210 parts of divinylben, 3 parts of sodium lauryl sulfate
1 part and 400 parts of water were emulsified by ultrasonication and finely dispersed so that the particle size of oil droplets was 0.5 μm or less. This dispersion was added to 2 parts (in terms of solid content) of monodispersed polystyrene latex (solid content concentration 5%) with a particle size of O-S Oμm, and stirred slowly at a temperature of 30°C for 24 hours to form monodispersed polystyrene latex into sheet particles. The polymer and polymerization initiator were completely absorbed into the oil droplets, but the oil droplets did not disappear, and even after further stirring for 48 hours, the oil droplets did not disappear. Then a 10% aqueous solution of polyvinyl alcohol
0 part was added, the temperature of the system was raised to 'tso c, and the reaction was carried out for 4 hours, at which point the polymerization was almost completed. When the obtained polymer particles were observed with a scanning electron microscope, the particles had a uniform particle size of about 2.7 μm and 0.
．． It was a mixture of particles with a non-uniform particle size of 5-2 μm. FIG. 2 is a microscopic photograph showing all of the polymer particles.

Example 2 3.5.5-trimethylhexanoyl peroxide r
20 parts of Perloyl 355J (manufactured by Nippon Oil & Fats Corporation), 5 parts of sodium lauryl sulfate Q, and 100 parts of water were emulsified using ultrasonic waves and finely dispersed so that the particle size of oil droplets was 0.6 μm or less. This dispersion was added to 50 parts of an aqueous polystyrene dispersion # (solid content concentration 2%) with a particle size of 0.9 μm, and the sheet particles of polystyrene were mixed with Perloyl 355T-2 while slowly stirring at 30°C for 24 hours.
I let it absorb. Mix 300 parts of styrene, 3.75 parts of sodium lauryl sulfate, and 500 parts of water in a singaraline homogenizer? The dispersion was finely dispersed so that the particle size of the oil droplets was 0.8 μm or less, and this dispersion was added to the dispersion of the sheet particles, and the mixture was slowly stirred at 30°C for 10 hours to disperse the oil droplets into the sheet particles. further absorbed styrene.

Next, 300 parts of butyl acrylate, 3.75 parts of sodium lauryl sulfate, and 500 parts of water were finely dispersed using a Manton Galarin homogenizer so that the particle size of oil droplets was 0.8 μm or less, and this dispersion and a sheet were mixed. More was added into the dispersion of particles and slowly stirred at 30° C. for 5 hours to absorb the butyl acrylate into the sheet particles.

Furthermore, 400 parts of acrylonitrile, 7.5 parts of sodium lauryl sulfate, 1000 parts of water, and 40 g of n-hexane were emulsified and finely dispersed using a Manton Galarin homogenizer to reduce the particle size of oil droplets to 0.5 μm or less. was added and slowly stirred at 30° C. for 42 hours to absorb the acrylonitrile into the sheet particles. The size of the uniformly sized swollen sheet particles thus obtained was about 9 μm. Add 1000 parts of 10% water fBWitt of polyvinyl alcohol to this dispersion.
The polymerization was carried out by raising the temperature to 70°C and was almost completed in 6 hours. When the obtained polymer particles were observed under an optical microscope, it was confirmed that the polymer particles were almost perfectly spherical particles with an average particle size of 8.6 μm and a standard deviation of 7 inches.

Example 3 30 parts of t-butyl peroxy 2-ethylhexanoate "Perbutyl 0" (manufactured by NOF Corporation), 2 parts of sodium lauryl sulfate and 150 parts of water. It was finely dispersed so that the particle size was 0.5 μm or less. This dispersion was immediately mixed with a particle size of 0683μ.
m monodisperse polystyrene latex (solid content concentration 2%)
The perbutyl O oil droplets were absorbed into the sheet particles by stirring slowly at 20° C. for 24 hours.

Next, 700 parts of styrene, 8 parts of sodium lauryl sulfate, and 1000 parts of water were finely dispersed using a Manton Galarin homogenizer so that the particle size of oil droplets was 0.5 μm or less. This dispersion was added to the above dispersion of sheet particles in two portions and stirred for 12 hours each time to absorb the styrene oil droplets into the sheet particles.

Next, 800 parts of acrylonitrile and 2 parts of 1-chlordodecane
A mixture of 0 parts of lauryl sulfate, 10 parts of sodium, and 2,000 parts of water was finely dispersed using an all-manganese homogenizer, and while confirming that the oil droplets were finely dispersed to a particle size of 0.7 μm or less, The mixture was divided into four equal parts and added to the dispersion of sheet particles, and the absorption operation was performed four times, each time taking 12 hours.◇This absorption was observed.

This dispersion was added with polyvinyl alcohol “GOHSENOL GH”.
10% aqueous solution of 20J (manufactured by Nippon Gosei Kagaku ■) 1500
Add 5 parts of a 10% aqueous solution of Beyama and ferric chloride, and
The reaction was carried out at 0°C for 10 hours. The obtained polymer particles were perfectly spherical particles having a uniform particle size with an average particle size of 9.2 μm and a standard deviation of 3 inches per particle size.

Example 4 20 parts of magnetite "EPT5ooJ (manufactured by Toda Kogyo Co., Ltd.) was dispersed in 60 parts of an aqueous ferric chloride solution of o, o o s mol/! to give a positive charge to the surface of the magnetite particles. Next, After adding 40 parts of a 10% sodium oleate aqueous solution to this dispersion to completely adsorb oleic acid, the pH was adjusted to 6 to 7 with dilute hydrochloric acid and excess oleic acid was removed to obtain a lipophilic treated magnetite. magnetite 20
This was used as sheet particles, which were dispersed in 200 g of an aqueous solution of polyvinyl alcohol Go-Sevenol GH20J to obtain a dispersion of sheet particles having a particle size of 0.3 to 0.5 μm.

To this dispersion, a dispersion obtained by emulsifying and dispersing 80 parts of styrene, 200 parts of water, and 1.5 parts of sodium lauryl sulfate using a Manton Galarin homogenizer until the styrene droplets become 0.1 part m or less is added, After stirring for 18 hours to adsorb styrene on the magnetite surface, 1 part of azobisisobutyronitrile, 10 parts of toluene, 50 parts of water, and 0.3 parts of sodium lauryl sulfate were added to this dispersion. Emulsified and dispersed liquid droplets with a particle size of 0.1 μm or less were added, and the oil droplets were adsorbed onto the surface of the magnetite.

This was polymerized for 10 hours at t-70 DEG C. to obtain magnetite-containing polymer particles having a particle size range of 2 to 72 ml and a magnetic material content of 23 ml.

Comparative Example 2 Perbutyl 02 parts, 5 sodium lauryl sulfate 0.15
1 part and 20 parts of water were emulsified using a homomixer and finely dispersed so that the particle size of perbutyl O oil droplets was in the range of 0.8 to 5 μm. Further, 90 parts of styrene, 10 parts of divinylbenzene, 2.85 parts of sodium lauryl sulfate, and 342 parts of water were emulsified using a homomixer and finely dispersed so that the particle size of oil droplets was in the range of 0.8 to 5 μm.

The above dispersion was added to 2 parts (solid content equivalent) of monodispersed polystyrene latex (solid content concentration 5%) with a particle size of 0,804 m, and the mixture was slowly stirred at a temperature of 30°C for 72 hours to absorb the polyvinyl latex. 100 parts of a 10% aqueous alcohol solution was added, the temperature of the system was raised to 80°C, and the reaction was carried out for 4 hours.

When the obtained polymer particles were observed with an optical microscope, it was found that the particles were dispersed over a wide range of particle diameters of 1 to 50 μm.

(Effects of the Invention) According to the present invention, an aqueous dispersion is prepared by separately finely dispersing an oil-soluble polymerization initiator and a polymerizable unsaturated monomer, and these dispersions and a dispersion of sheet particles are combined. By mixing and stirring to absorb the polymerization initiator and monomer into the sheet particles, polymerization due to heat generated during the microdispersion operation is avoided, and as a result, most of the monomers are reliably absorbed into the sheet particles. This prevents the generation of unnecessary new particles, and therefore it is possible to reliably produce polymer particles with good monodispersity.

In addition, by using an inorganic substance that has been subjected to a lipophilic treatment as the sheet particles, it is possible to obtain composite particles in which the surfaces of the sheet particles are uniformly coated with a polymer.

The polymer particles produced in this way have no microparticles and are excellent in monodispersity, and since no swelling aid is used in the production, the polymer particles do not become distorted and have a true spherical shape. It has the following characteristics.

Applications of the polymer particles obtained by the production method of the present invention include standard samples for microscopic examination, separation, and the like.

Model optical materials for fluid flow, centrifugation, diffusivity measurement and dust research, carriers for biomedical diagnostics, immobilized enzyme carriers, powder inks, toners for electrostatic development, paints, powder lubricants,
Microcapsules, spacer materials for protecting microcapsules in pressure-sensitive copying paper, spacers for liquid crystal cells, plastic pigments for coated paper, plastic pigments for adhesives, binders for ceramics, base polymer particles for impact-resistant resins, plastic ivy pigments for cosmetics. It is extremely useful in a variety of fields, such as membranes and column packing materials for ion chromatography.

[Brief explanation of the drawing]

FIGS. 1 and 2 are scanning electron micrographs showing the structures of polymer particles according to Examples and Comparative Examples.

Claims (1)

[Scope of Claims] 1) an aqueous dispersion of sheet particles and the following two types of aqueous dispersions, (a) a polymerizable unsaturated monomer in which the polymerizable unsaturated monomer is separated in a state in which it has a particle size smaller than that of the sheet particles; and (b) an aqueous dispersion in which an oil-soluble polymerization initiator is dispersed with a particle size smaller than that of the sheet particles;
A method for producing polymer particles, characterized in that polymerization is carried out after a polymerizable unsaturated monomer and an oil-soluble polymerization initiator are absorbed or adsorbed onto sheet particles. 2) The polymerizable unsaturated monomer is 0.001 to 0.0% relative to water.
A method for producing polymer particles according to claim 1 having a solubility of 2% by weight. 3) The oil-soluble polymerization initiator is 0.001 to 0.2 relative to water.
A method for producing polymer particles according to claim 1 or 2, which has a solubility of % by weight. 4) The polymerizable unsaturated monomer has a solubility in water greater than 0.2% by weight, and the solubility in water is 0.001% by weight or less based on 100 parts by weight of the polymerizable unsaturated monomer. 2. The method for producing polymer particles according to claim 1, wherein 0.1 parts by weight or more of a highly lipophilic substance is added. 5) High lipophilicity in which the oil-soluble polymerization initiator has a solubility in water greater than 0.2% by weight, and the solubility in water is 0.001% by weight or less based on 100 parts by weight of the oil-soluble polymerization initiator. 5. The method for producing polymer particles according to claim 1 or 4, wherein the substance is added in an amount of 0.1 part by weight or more.