JPS61215603A - Production of polymer particle - Google Patents

Abstract

PURPOSE:To facilitate the formation of monodisperse polymer particles of a relatively large particle diameter, by consecutively mixing an aqueous dispersion of seed particles with two polymerizable monomers of different water solubilities and polymerizing these monomers in the resulting mixture. CONSTITUTION:An aqueous dispersion of seed particles comprising polystyrene, polyvinyl acetate or the like is mixed with an aqueous dispersion of a first monomer having a water solubility of 0.001-0.1wt% (e.g., styrene) in a state of particles having a particle diameter smaller than that of the seed particles to allow the seed particles to adsorb the monomer. the obtained dispersion is further mixed with a second polymerizable monomer having a water solubility >=0.1wt% (e.g., vinyl acetate) and polymerized in the presence of a suspension stabilizer (e.g., polyvinyl alcohol) comprising a suspension protecting agent and/or a surfactant at a concentration not exceeding critical micelle concentration to obtain monodisperse polymer particles of a relatively large particle diameter in the range of about 1-100mum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing relatively large monodisperse polymer particles having a particle size in the range of about 1 to 100 μm.

[Conventional technology]

Although monodisperse polymer particles with a particle size in the range of about 1 to 10011 m are in demand in the field of polymerization, it is generally extremely difficult to produce them.Polymer particles by emulsion polymerization Monodisperse polymer particles can be obtained relatively easily in the production of
Only particles with a small particle size of less than 1.0 m can be obtained, and even under special conditions, 3 μm is said to be the limit. On the other hand, in the production of polymer particles by suspension polymerization, the particle size is 1 to 100 μm.
However, it is extremely difficult to produce monodisperse polymer particles with a wide particle size distribution. Therefore, when trying to obtain monodisperse polymer particles, it is necessary to classify the particles obtained by suspension polymerization, which increases the number of steps, making production difficult and resulting in low yields. There is a problem.

As a method for producing monodisperse polymer particles with a relatively large diameter, Japanese Patent Application Laid-Open No. 54-97582 or Japanese Patent Application Laid-open No. 54
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. A process is disclosed for absorbing and polymerizing unsaturated monomers that are somewhat soluble in water.

However, in this method, the use of commonly used oil-soluble initiators or water-soluble initiators causes problems such as the generation of coagulum or new particles, and it is difficult to reliably collect monodisperse polymer particles with large diameters. It is difficult to obtain a good rate.

Furthermore, in JP-A-54-126288, in the first step, an organic compound having a solubility in water smaller than 10-''g/l H*O, which functions as a swelling aid, is absorbed into sheet particles, and then in the second step, an organic compound is absorbed into sheet particles. After absorbing the somewhat water-soluble monomer in the second step to form swollen particles of the monomer, a water-soluble polymerization initiator such as potassium persulfate or azoisobutyronitrile ( A method of polymerizing while maintaining the particle shape using an oil-soluble polymerization initiator such as AIBN) has been disclosed. However, in this method, when an oil-soluble polymerization initiator is used as the polymerization initiator, sheet particles Even dispersed particles of monomers that are not absorbed by the polymer are polymerized as they are, resulting in the formation of a large amount of coagulum and a low yield.Additionally, water-soluble polymerization initiators such as persulfates are used as polymerization initiators. When using an emulsifier, even if the emulsifier concentration is below the critical micelle concentration,
The propagating radicals in the aqueous phase act as emulsifiers, and so-called soap-free emulsion polymerization proceeds in part or in whole.
There is a drawback that the swollen particle morphology is not maintained.

Furthermore, this method has the problem that the resulting polymer particles are not perfectly spherical but distorted due to the action of the 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, a method of enlarging the sheet particles without using a swelling aid has been proposed in References J and P.
olym, Sci. , Polym.

L ett, Ed, 21.937-943
(1983) (J.

H, Jans son, M, C, We 11 ons
.

Proposed in G., W. Poehlein)
Ru. According to this method, a monomer and an oil-soluble polymerization initiator are mixed, this mixture is finely dispersed to create a monomer emulsion, and this is made into a dispersion (latex) of sheet particles.
It is possible to achieve enlargement of sheet particles with a high swelling ratio of 14=1.

However, in this method, if the monomer used is highly water-soluble, even if the emulsion of the monomer and the dispersion of sheet particles are mixed, the absorption of the monomer to the sheet particles is insufficient. It has become clear that there is a problem in that the ratio is extremely low, and new giant particles are generated regardless of the sheet particles, making it impossible to obtain polymer particles of uniform particle size.

The reason why such a phenomenon occurs is considered to be due to the following reasons. Monomers with relatively high water solubility, such as methyl methacrylate and acrylonitrile, have a high diffusion rate in water, so even if they are dispersed in the form of fine particles in an aqueous dispersion medium, they will gradually enlarge due to diffusion, resulting in the formation of fine particles. Unable to maintain status. The monomer dispersed particles, which are larger than the sheet particles, remain in the dispersion medium without being absorbed by the sheet particles, and become new giant polymerized particles through polymerization.

[Problem that the invention seeks to solve]

The present invention solves the following problems of the prior art: (a) inability to obtain polymer particles with a wide and uniform particle size distribution; and (b) difficulty in obtaining truly spherical polymer particles. It is an object of the present invention to provide a method for producing polymer particles that can reliably produce true spherical cane polymer particles with high monodispersity through a simple process.

[Means for solving problems]

The above problem can be solved by mixing an aqueous dispersion of a first polymerizable monomer with an aqueous dispersion of sheet particles, causing the sheet particles to absorb or adsorb the first polymerizable monomer, and then 2
The first polymerizable monomer has a solubility in water of 0°001.
~0.1% by weight, and is dispersed in an aqueous dispersion with a particle size smaller than that of the sheet particles, and the second polymerizable monomer has a solubility in water of 0.01% by weight or more. The problem is solved by a method for producing polymer particles characterized by the following.

That is, in the present invention, an aqueous dispersion is prepared by first dispersing the first polymerizable monomer with low water solubility in water in such a state that the particle size of the dispersed particles is smaller than the particle size of the sheet particles. This aqueous dispersion is characterized in that a highly water-soluble second polymerizable monomer is added to the mixed system, and then polymerization is carried out.

The present invention will be explained in detail below.

The first polymerizable monomer that can be used in the present invention has a solubility in water of 0.001 to 0.1% by weight, preferably 0.002 to 0.1% 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, which is undesirable because the finely dispersed polymerizable monomer has good stability. On the other hand, if the solubility of the monomer in water is excessive, the oil droplets of the finely dispersed monomer will be unstable and their lifetime will be significantly shortened, resulting in a state in which the monomer is dispersed smaller than the sheet particles. It becomes difficult to prepare an aqueous dispersion of

Examples of the first polymerizable monomer having a solubility in water in the range of 0.001 to 0.1% by weight and which can be suitably used in the present invention include styrene, α-methylstyrene, p-methylstyrene, Aromatic vinyl monomers such as divinylbenzene, ethylenically unsaturated carboxylic acids such as butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, trimethylolpropane trimethacrylate, etc. Examples include conjugated diolefins such as alkyl esters, butadiene, and isoprene. These monomers can be used alone or in combination of two or more.

The second polymerizable monomer that can be used in the present invention has a solubility in water of 0.1% by weight or more, and examples of such monomers include vinylpyridine, vinylidene chloride, vinyl acetate, acrylonitrile, methyl acrylate, Methyl methacrylate, ethyl acrylate, ethyl methacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, N-methylol acrylamide, N-methylol methacrylamide, 2-hydroxyethyl acrylate, 2- Examples include hydroxyethyl methacrylate, diallyl phthalate, allyl acrylate, allyl methacrylate, acrylic acid, methacrylic acid, itaconic acid, and fumaric acid.

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 monomers is a monomer with a high polymerization conversion rate, such as divinylbenzene, acrylonitrile, or It is preferable to use vinyl chloride or the like.

In addition, when there are multiple types of first polymerizable monomers, an aqueous dispersion may be prepared by mixing the multiple monomers and then finely dispersing the same. An aqueous dispersion may be prepared by finely dispersing each monomer individually. When using an aqueous dispersion in which each monomer is finely dispersed individually, the monomers are added in order of decreasing solubility in water. It is preferable to mix the aqueous dispersion of the monomer with the aqueous dispersion of the sheet particles and allow the monomer to be absorbed or adsorbed onto the sheet particles.

The sheet particles that can be used in the present invention are preferably those that absorb polymerizable monomers and swell, such as styrene polymers, styrene copolymers such as styrene-butadiene copolymers, acrylic ester polymers, Examples include polymers such as vinyl acetate polymers. These sheet particles are used in the form of a dispersion such as an aqueous latex, emulsion, or suspension. 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 polymer particles finally obtained uniform, and the particle size of the sheet particles may vary depending on the use of the obtained polymer particles, etc. Selected appropriately.

The particle size range of polymer particles of uniform particle size obtained by soap-free polymerization or the like is usually 0.1 to 0.9 μm, and these particles can be preferably used. Furthermore, polymer particles having a larger particle size can also be produced by using the polymer particles obtained by the present invention as sheet particles.

is preferably oil-soluble and has a water solubility in the range of 0.001 to 0.1% by weight. If the solubility of the 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 due to the good stability of the finely dispersed polymerization initiator, which is undesirable.
If the solubility of the polymerization initiator in water is excessive, the oil droplets of the finely dispersed polymerization initiator will be unstable and their life will be significantly shortened. Preparation of dispersion becomes difficult.

The oil-soluble polymerization initiator, which has a solubility in water in the range of 0.01 to 0.1% by weight and can be suitably used in the present invention, includes 3,5.5-)limethylhexinoyl peroxide, t Examples include organic peroxides such as -butyl peroxy 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.

In addition, as a method for adding an oil-soluble polymerization initiator to the reaction system, there is a method in which the polymerization initiator is dissolved in advance in the first polymerizable monomer, or a method in which the oil-soluble polymerization initiator is added to the first polymerizable monomer. It is possible to use a method such as preparing an aqueous dispersion by finely dispersing it in water separately from the polymerization initiator, mixing this dispersion with an aqueous dispersion of sheet particles, and absorbing or adsorbing the polymerization initiator into the sheet particles. . However, in the former method, there is a risk that the monomers will polymerize due to the heat generated by the stimulant action required for dispersion during the preparation of the dispersion, and in this case, the latter method is used.

Next, a preferred 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 first polymerizable monomer onto the sheet particles, suppress the generation of unnecessary new particles, and increase monodispersity, the first polymerizable monomer is It is important to form the monomer into an aqueous dispersion before adding it to the reaction system, and to make the dispersed oil droplets smaller in diameter than the sheet particles.

In order to finely disperse the oil droplets of the polymerizable monomer in this way,
It is necessary to apply a high shearing force to the dispersion, and for this purpose, for example, a method using a Manton Galarin homogenizer that performs shearing under high pressure or a method using an ultrasonic homogenizer can be employed. In these methods, it is necessary to perform a cooling operation to avoid heat generation due to shearing.

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

The aqueous dispersion of the first polymerizable monomer thus obtained is added and mixed with the aqueous dispersion of the sheet particles until the oil droplets of this monomer are completely absorbed into the sheet particles. The mixture is stirred slowly for usually one hour or more. Further, the polymerization initiator is absorbed into the sheet particles together with the first polymerizable monomer by the method described above. Note that the method of adding the aqueous dispersion of the first polymerizable monomer is not particularly limited;
Either a divided method or a continuous method may be used.

Through the above process, an aqueous dispersion of enlarged sheet particles is prepared by absorbing or adsorbing the first polymerizable monomer and the oil-soluble polymerization initiator.

Next, a second polymerizable monomer is added to this aqueous dispersion, and the second polymerizable monomer is brought into contact with and absorbed by the enlarged sheet particles.

After the above absorption operation is completed, the temperature of the system is raised to carry out polymerization. The polymerization temperature varies depending on the polymerization initiator, but 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. However, when using a surfactant,
It is necessary to keep the concentration below the critical micelle concentration. As a preferable dispersion stabilizer, polyvinyl alcohol having a degree of saponification of 75 to 95% and a degree of polymerization of 500 to 3.000 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, water-soluble substances such as ferric chloride, sodium nitrite, and hydroquinone are Polymerization inhibitors 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, "parts" and "%" represent parts by weight and % by weight, respectively.

Example 1 t-Butylperoxy 2-ethylhexanoate (30
(Solubility in water at °C: 0.15% by weight) 2 parts of Perbutyl OJ (manufactured by NOF Corporation), 0.15 parts of sodium lauryl sulfate, and 20 parts of water were emulsified by ultrasonication, and Perbutyl 0 was made into particles of 0.5 μm or less. 50 parts of monodispersed polystyrene latex (solid content concentration 2%) with a particle size of 0.80 μm was added to this, and
Slow stirring was performed for a period of time to absorb the Vertiple O into the sheet particles.

Next, 50 parts of styrene, 0.3 parts of sodium lauryl sulfate, and 100 parts of water were emulsified using ultrasonic waves, and then heated to 30°C.
The mixture was stirred slowly for 12 hours to absorb the styrene into the sheet particles.

Next, 50 parts of acrylonitrile was added without finely dispersing it,
The mixture was further stirred for 1 hour. After that, polyvinyl alcohol “GOHSENOL G H20J (manufactured by 8 bottles of synthetic chemicals)”
200 parts of a 5% aqueous solution of was added and the temperature was raised to 80°C to initiate polymerization, which was almost completed in 6 hours. There was almost no generation of coagulum, and no new particles were generated in the aqueous phase.

When the obtained polymer particles were observed with a scanning electron 1gi microscope, the particles were almost perfectly spherical, with an average particle size of 3.5 μm,
It was confirmed that the particles had extremely uniform particle sizes with a standard deviation value of 4%.

Comparative Example 1 Perbutyl 02 parts, styrene 50 parts, acrylonitrile 50 parts, sodium lauryl sulfate 0.65 parts, water 120 parts
was emulsified by ultrasonic waves, but even if the emulsification operation was performed for a long time, droplets with a particle size of 1 to 20 μm were formed, and droplets with a particle size of 0.5 μm were obtained.
It was not possible to finely disperse the particles to the following particle sizes. 50 parts of monodispersed polystyrene latex (solid content concentration 2%) with a particle size of 0.80 μm was added to this, and after stirring slowly at 30°C for 24 hours to perform a sufficient absorption operation, 200 parts of 5z aqueous solution was added, and the temperature was raised to 80°C for polymerization.

When the obtained polymer particles were observed with a scanning electron microscope, they were found to be a polymer of particles having a uniform particle size of approximately 1.4 μm and particles having a nonuniform particle size of 1 to 20 μm. Ta.

Example 2.3 Sodium lauryl sulfate was used instead of polyvinyl alcohol in Example 1, and 0.1 part in Example 2.
In Example 3, polymer particles were produced in the same manner as in Example 1, except that 0.2 parts were used. In this case, the dispersion stability during polymerization is not good, so
The system must be stirred slowly and intermittently during polymerization.

In Example 2, polymer particles having a uniform particle size with an average particle size of 3.2 μm and a standard deviation value of particle size of 10% were obtained. Also,
The amount of coagulum produced as a result of polymerization was 4.5% by weight.

In Example 3, polymer particles having a uniform particle size with an average particle size of 3.1 μm and a standard deviation value of particle size of 8% were obtained. Further, the amount of coagulated material generated as a result of polymerization was 2.8%.

Examples 4 to 11 Polymer particles were obtained in the same manner as in Example 1, except that nine types of polyvinyl alcohol having the characteristics shown in Table 1 were used instead of polyvinyl alcohol (PVA) in Example 1. The average particle size and standard deviation of the polymer particles in each example, as well as the amount of coagulated material generated by polymerization, are also shown in Table 1. The data of Example 1 are also shown in Table 1. do.

Table 1 Example 12 2 parts of azobisisobutyronitrile, 90 parts of styrene, 10 parts of divinylbenzene, 1.5 parts of sodium lauryl sulfate
and 200 parts of water were mixed into monomer droplets with a particle size of 0.4 μm using a Manton Galarin homogenizer (model 15M).
Finely dispersed as follows. At this time, the temperature of the system is 25
The operation was performed while cooling to prevent the temperature from rising above ℃.

This dispersion was added to 50 parts of monodispersed polystyrene latex (solid content concentration 2%) with a particle size of 0.7 μm and slowly stirred at 25° C. for 48 hours to absorb the monomer into the polystyrene particles.

To this, 20 parts of 4-vinylpyridine was added, and 100 parts of a 10% aqueous solution of polyvinyl alcohol Gohsenol GH20J was added, and the temperature was raised to 70°C to start polymerization. The polymerization was almost completed in 5 hours. When the obtained polymer particles were observed with an optical microscope, it was confirmed that the polymer particles were almost perfectly spherical particles with an average particle size of 866 μm and a standard deviation of particle size of 5%.

In addition, the obtained polymer particles have a wood-philic particle surface,
The dispersibility in water was good.

〔Effect of the invention〕

According to the present invention, first, a first polymerizable monomer with low water solubility is finely dispersed and absorbed into sheet particles, and then a second polymerizable monomer with high water solubility is finely dispersed. By adding these polymerizable monomers to the sheet particles and performing polymerization, it becomes possible to easily and reliably absorb or adsorb both of these polymerizable monomers into the sheet particles, thereby preventing the generation of unnecessary new particles and reducing the amount of monomers. Polymer particles with good dispersibility can be easily and reliably produced.

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 excellent monodispersity, with no giant particles or microparticles, and since no swelling aid is used during production, the polymer particles do not become distorted and have a true spherical shape. It has the characteristic of being.

The polymer particles obtained by the production method of the present invention can be used as standard samples for microscopic examination.

Materials for model systems such as fluid flow, centrifugation, diffusivity measurement and dust studies, 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 pigments for cosmetics. , column packing materials for ion chromatography, etc., and are extremely useful in a variety of fields.

Claims (1)

[Scope of Claims] 1) Mixing an aqueous dispersion of a first polymerizable monomer with an aqueous dispersion of sheet particles to cause the sheet particles to absorb or adsorb the first polymerizable monomer; The first polymerizable monomer has a solubility in water of 0.001 to 0.1% by weight, and the first polymerizable monomer is an aqueous dispersion. A method for producing polymer particles, characterized in that the second polymerizable monomer has a solubility in water of 0.1% by weight or more. . 2) The method for producing polymer particles according to claim 1, wherein the polymerization is carried out in the presence of a dispersion stabilizer consisting of a suspension protectant and/or a surfactant having a concentration below the critical micelle concentration.