JPH10218935A - Production of fine polymer particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing fine polymer particles having a mean particle diameter of 1-10μm by safely and easily separating them from an organic solvent slurry obtained by dispersion polymerization. SOLUTION: The production process comprises radical-polymerizing a vinyl monomer in an organic solvent which dissolves the monomer, swells but hardly dissolves the formed polymer and is azeotropically distillable with water in the presence of a dispersion stabilizer having good dispersion stability in the organic solvent but having poor dispersion stability in water. The organic solvent is removed from the fine polymer particle slurry by introducing steam thereinto, and the obtained aqueous slurry of the fine polymer particles is subjected to solid/liquid separation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing polymer fine particles. More specifically, the present invention relates to a method for producing polymer fine particles by separating polymer fine particles safely and easily from an organic solvent slurry of polymer fine particles obtained by dispersion polymerization. The polymer fine particles are used by being added to various resins as a modifier.

[0002]

2. Description of the Related Art Conventionally, a dispersion polymerization method has been known as a method for obtaining polymer fine particles having an average particle diameter of 1 to 10 μm and having a relatively uniform particle diameter.

[0003] For example, the British polymer
Journal (Brit.Polym.J.) 14,131-136 (1982)
In dispersion polymerization of styrene or methyl methacrylate in an alcohol solvent such as ethanol, synthetic polymer stabilizers such as polyethyleneimine, polyvinylpyrrolidone, polyvinylmethylether, polyacrylic acid, vinyl alcohol / vinyl acetate copolymer, and tricaprylyl are used. There is disclosed a method for obtaining monodispersed particles having an average particle size of 1 to 6 μm using a quaternary amine such as ammonium chloride as a dispersion stabilizer.

Further, Canadian Journal Chem. (Can. J. Chem.) 63, 209 (1985) discloses that in a dispersion polymerization of styrene in an alcoholic solvent, a cellulose derivative is used as a dispersion stabilizer and the average particle size is 1 to 10. 12μ
A method for obtaining m monodisperse particles is shown.

On the other hand, polymer fine particles are isolated from a slurry obtained by dispersion polymerization by a solid-liquid separation method such as simple filtration or centrifugation, which is generally used because the fine particles are well dispersed. Impossible. As a method for isolating polymer fine particles, for example, Brit.Polym.J.14,131 (1
982) discloses a method of precipitating polymer fine particles by high-speed centrifugation of a slurry after polymerization, removing a supernatant, and then vacuum drying. Further, JP-A-61-1960
No. 2 discloses a filtration method using a microfilter, and JP-A No. 61-228458 discloses a method using freeze drying or spray drying.

[0006]

However, the method using high-speed centrifugal sedimentation and vacuum drying has an average particle size of 1 to 10 μm.
Since it is as small as m, a very large centrifugal force and time are required, and the polymer fine particles finally obtained by vacuum drying solidify in a block shape, which is difficult to handle. Also,
The filtration method using a microfilter also requires a special filter because the particles are small, and has problems such as filter strength and clogging, and is not industrial. On the other hand, the freeze-drying and spray-drying methods are easy to handle in the form of powder as the final product and are industrial, but require special equipment such as refrigeration equipment. It is necessary to work with care and not always enough. Further, in these methods, polymer fine particles containing an organic solvent are dried, and therefore, it is necessary to pay particular attention to safety at that time.

In view of the above circumstances, the present invention has made intensive studies on a method for safely and easily separating polymer fine particles from an organic solvent slurry of polymer fine particles obtained by dispersion polymerization. After removing most of the organic solvent by blowing steam into the organic solvent slurry of the polymer fine particles, the water slurry of the obtained polymer fine particles is subjected to solid-liquid separation, so that it is safe and easy by a simple filtration or centrifugal separation method. The present inventors have found that polymer fine particles can be separated, and have reached the present invention.

[0008]

That is, the present invention provides a method for dispersing and polymerizing a vinyl monomer in the presence of an organic solvent and a dispersion stabilizer, and separating the polymer particles from an organic solvent slurry of the obtained polymer particles. In a method for producing polymer fine particles, a method for producing polymer fine particles, wherein steam is blown into an organic solvent slurry to remove most of the organic solvent, and then a water slurry of the obtained polymer fine particles is subjected to solid-liquid separation. It is. Hereinafter, the present invention will be described in detail.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The vinyl monomer used in the present invention includes aromatic vinyl monomers such as styrene, α-methylstyrene, ethylstyrene, chlorostyrene and vinylpyringin; methyl (meth) acrylate; (Meth) acrylates such as butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate; ) Vinyl cyanide monomers such as acrylonitrile; amide vinyl monomers such as (meth) acrylamide; carboxylic acids and carboxylic anhydrides such as (meth) acrylic acid, maleic acid and itaconic acid. These vinyl monomers are 1
Species or two or more can be used.

[0010] A polyfunctional monomer may be added to the vinyl monomer. Examples of the polyfunctional monomer include divinylbenzene, trivinylbenzene, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, Examples include allyl (meth) acrylate, allyl cinnamate, trimethylolpropane tri (meth) acrylate, triallyl trimellitate, diallyl maleate, and pentaerythritol tetra (meth) acrylate. These polyfunctional monomers may be used alone or in combination of two or more.

As the organic solvent in the present invention, those which dissolve the vinyl monomer and swell the polymer formed from the vinyl monomer but hardly dissolve, and azeotrope with water are used. . For example, lower alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol and t-butanol; ether alcohols such as methyl cellosolve, cellosolve and butyl cellosolve; ketones such as acetone and methyl ethyl ketone; Examples include hydrocarbons such as hexane, octane, petroleum ether, benzene, toluene, and xylene. These solvents may be used alone or as a mixture of two or more kinds as long as they are compatible with each other. Further, water may be mixed as long as the vinyl monomer used is dissolved.

The dispersion stabilizer used in the present invention is one which disperses the polymer fine particles well in the above-mentioned organic solvent but does not disperse well in water. By using such a dispersion stabilizer, a secondary aggregate of polymer fine particles is formed by removing the organic solvent, so that solid-liquid separation can be easily performed. When a dispersion stabilizer that does not disperse the polymer fine particles well in the organic solvent is used, aggregation during polymerization of the vinyl monomer, and deformation of the particles are caused, and the desired spherical polymer fine particles cannot be obtained. Absent. In addition, when a dispersion stabilizer having good dispersion stability in water is used, secondary aggregated particles are hardly generated even when the organic solvent is removed, and polymer fine particles are sufficiently recovered during solid-liquid separation. Not preferred.

A dispersion stabilizer which disperses polymer fine particles well in an organic solvent but does not disperse well in water does not have a cloud point in an organic solvent or has a cloud point higher than the temperature at the time of polymerization, and Has a cloud point of 100 ° C. or lower, for example, a polymer dispersion stabilizer.

Examples of such a polymer dispersion stabilizer include cellulose derivatives such as hydroxypropylcellulose, hydroxyethylcellulose, carboxymethylcellulose and methoxycellulose when the organic solvent is an alcohol having 1 to 4 carbon atoms. Can be

Even when a dispersion stabilizer having a cloud point of 100 ° C. or more in water is used, when the organic solvent is removed by blowing steam into the polymer fine particle slurry, the cloud point of the dispersion stabilizer in water is reduced. Of 100.degree. C. or less can be added. As such an example, polyethylene oxide has a cloud point of 100 degrees or more in water, but the cloud point can be reduced to 100 ° C. or less by adding a salt or alkali such as sodium carbonate to water. . The polyacrylic acid can lower the cloud point by making it acidic.

In the dispersion polymerization of a vinyl monomer, a vinyl monomer, an organic solvent, and a dispersion stabilizer are uniformly dissolved, and then radically polymerized by a known method. When the dispersion stabilizer has a cloud point in an organic solvent, it undergoes radical polymerization at a temperature lower than the cloud point.

The radical polymerization is usually carried out by reacting 7
It ends when 0% by weight or more is polymerized.

Next, steam is introduced into an organic solvent slurry of polymer fine particles obtained by the dispersion polymerization to vaporize the organic solvent, and the organic solvent is removed by 90% or more, preferably 95% or more, more preferably 99% or more. Depending on the organic solvent and dispersion stabilizer used, the removal of the organic solvent by 90% or more facilitates the separation of the polymer fine particles. However, the larger the residual amount of the organic solvent, the more the amount of the organic solvent in the wastewater during solid-liquid separation. Increases the amount of organic solvent, resulting in a considerable wastewater treatment load,
Also, a large amount of organic solvent remains in the separated polymer fine particles,
The risk of foul odors, fires, explosions, etc. increases, making handling difficult in terms of safety and health.

Steam is blown into an organic solvent slurry of polymer fine particles to evaporate the organic solvent, and the organic solvent removed from the slurry is usually condensed and recovered by a well-known cooler. The recovered organic solvent can be purified and reused for polymerization, or used for other purposes.

A method of solid-liquid separation for separating polymer fine particles from an aqueous slurry of polymer fine particles from which an organic solvent has been removed includes:
A well-known method may be used, and it is easily performed by a filtration method such as natural filtration, centrifugal filtration, or pressure filtration, or a centrifugal sedimentation method using a decanter or a cyclone.

The wet product of polymer particles obtained by solid-liquid separation is used as it is or after drying. From the viewpoint of safety such as dust explosion, it is preferable to use without drying or to leave 5% by weight or more of moisture when drying.

[0022]

According to the method of the present invention, polymer fine particles obtained by dispersion polymerization can be safely and easily separated from a slurry of polymer fine particles obtained by dispersion polymerization in an organic solvent.

[0023]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

The measured values in the examples and comparative examples were measured by the following methods. (1) Weight average particle size: Leeds
It was measured with a light diffraction scattering particle size analyzer (Microtrack FRA) manufactured by And Northrup Company. (2) Solvent recovery rate:
The solvent concentration in the condensate recovered from the condenser was measured by gas chromatography analysis, and was calculated from the amount of the condensate.

Example 1 A glass container equipped with a stirrer and a reflux condenser was charged with 100 parts by weight of ethanol and 0.6 part by weight of hydroxypropylcellulose having an average molecular weight of about 120,000. After dissolution, 20 parts by weight of styrene were further added. 0.4 parts by weight of 55% divinylbenzene and 0.4 parts by weight of benzoyl peroxide were added and dissolved. After uniformly dissolving, the temperature was raised to 78 ° C., and polymerization was carried out for 15 hours while refluxing ethanol to obtain an organic solvent slurry A of polymer fine particles. When a part of the organic solvent slurry A was sampled and the particle size was measured, monodispersed particles having an average particle size of 1.8 μm were obtained. Subsequently, 0.5 kg / cm ² steam was blown into the slurry A, and the evaporating ethanol / water mixture was collected by a condenser.
When the temperature of the polymerization liquid reached 99 ° C., the blowing of steam was terminated, and a water slurry B was obtained. When a part of the obtained water slurry B was sampled and observed with an optical microscope, particles were aggregated. The measured average particle diameter of the aggregated particles was about 240 μm. Ethanol recovery rate is 9
7%. Water slurry B was mixed with qualitative filter paper No. When the mixture was subjected to suction filtration using No. 1, filtration was easy, and polymer fine particles having a water content of 45% were obtained. The filtrate was transparent and no polymer fine particles were detected.

The 0.5% ethanol solution of hydroxypropylcellulose used in Example 1 was heated at 120 ° C.
However, the 0.5% by weight aqueous solution turned cloudy at 60 ° C.

Comparative Example 1 An organic solvent slurry A obtained in the same manner as in Example 1 Suction-filtered at 1. The polymer fine particles passed through the filter paper and almost went to the filtrate side.

Comparative Example 2 The organic solvent slurry A obtained in the same manner as in Example 1 was subjected to suction filtration with a 0.5 μm membrane filter. Although filtration could be performed in the very early stage, clogging occurred immediately and the filtration became impossible. The recovered polymer fine particles were lumpy clay-like and difficult to handle.

Comparative Example 3 The organic solvent slurry A obtained in the same manner as in Example 1 was separated into solid and liquid by centrifugal sedimentation. The wet product of the obtained polymer fine particles was a slimy clay like in Comparative Example 2, and was difficult to handle.

Comparative Example 4 The organic solvent slurry A obtained in the same manner as in Example 1 was
It dried with a 0 degreeC vacuum dryer. The dried product of the obtained polymer fine particles became a strong lump, and dusting was dangerous when it was crushed.

Comparative Example 5 The procedure of Example 1 was repeated, except that 0.6 parts by weight of hydroxypropyl cellulose having an average molecular weight of about 120,000 was replaced by 0.6 parts by weight of polyethylene oxide having an average molecular weight of about 20,000. Average particle size 1.8 μm in the same manner as 1.
To obtain a slurry of polymer fine particles in an organic solvent. When the water slurry after steam injection was observed with an optical microscope, it was 2
No secondary aggregated particles were generated, and the measurement result of the particle size was 1.8 μm, which was the same as before the steam was blown. The ethanol recovery was 98%. This water slurry is qualitative filter paper N
o. When suction filtration was performed using No. 1, polymer fine particles almost escaped to the filtrate side. Polymer fine particles could not be recovered.

The 0.5% by weight ethanol solution and the 0.5% by weight aqueous solution of polyethylene oxide used in Comparative Example 5 did not become cloudy when heated to 120 ° C.

Example 2 Polymerization was carried out in the same manner as in Comparative Example 5 to obtain an organic solvent slurry of polymer fine particles having an average particle size of 1.8 μm. 2 parts by weight of sodium carbonate was added before blowing in steam, and steam was blown in the same manner as in Example 1. When the temperature of the polymerization solution reached 99 ° C., the blowing of steam was stopped to obtain a water slurry. In the obtained water slurry, the polymer fine particles are aggregated,
The average particle size was about 180 μm. The ethanol recovery was 98%. The obtained water slurry was qualitative filter paper No.
By suction filtration using No. 1, polymer particles could be easily filtered and had a water content of 48%.

When 2% by weight of sodium carbonate was added to the 0.5% by weight aqueous solution of polyethylene oxide used in Example 2, the solution became cloudy at 70 ° C.

Claims (5)

[Claims] 1. A method for producing polymer fine particles by dispersion-polymerizing a vinyl monomer in the presence of an organic solvent and a dispersion stabilizer, separating polymer fine particles from an organic solvent slurry of the obtained polymer fine particles, A method for producing polymer fine particles, wherein steam is blown into an organic solvent slurry to remove most of the organic solvent, and then a water slurry of the obtained polymer fine particles is subjected to solid-liquid separation. 2. A solvent in which an organic solvent dissolves a vinyl monomer and a polymer formed from the vinyl monomer swells but hardly dissolves, and azeotropes with water. 2. The production method according to claim 1, wherein the dispersion stabilizer is a dispersion stabilizer which disperses the polymer fine particles well in an organic solvent but does not disperse it well in water. 3. A high molecular weight dispersion stabilizer having no cloud point in an organic solvent or having a cloud point higher than the polymerization temperature and having a cloud point of 100 ° C. or lower in water. The method according to claim 1 or 2, wherein: 4. The organic solvent is an alcohol having 1 to 4 carbon atoms,
3. The method according to claim 1, wherein the dispersion stabilizer is a cellulose derivative. 5. The method according to claim 1, wherein, when removing the organic solvent, a coagulant is added to the dispersion stabilizer so that the cloud point of the dispersion stabilizer in water is 100 ° C. or less.