JPH0977833A - Production of high-monodisperse crosslinked fine particulate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high-monodisperse crosslinked fine particulates having porosity and uniform granular diameter without core shell or pore by a specific and simple method comprising absorbing an ethylenic unsaturated monomer and an oil-soluble initiator into a seed particulate and polymerizing. SOLUTION: (B) An emulsion of an ethylenic unsaturated monomer containing >=45wt.% divinylbenzene and (C) an emulsion of an oil-soluble initiator (e.g.; benzoyl peroxide) are added to (A) water in which a polymer seed particulate composed of >=90wt.% styrene and its derivative and having 1,000-10,000 weight- average molecular weight is dispersed, to make 1 pt.wt. of the particulate A absorb 20-500 pts.wt. of the monomer B and the initiator C, and the monomer B is polymerized preferably at 50-90 deg.C. Preferably, a non-crosslinking particulate having 0.1-10μm and <=10 Cv -value ((standard deviation/average particulate diameter)×100) is used as the particulate A. Preferably, the monomer B and the initiator C are finely dispersed in water and absorbed in the particulate A.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has a particle size of 1 to 10 μm.
The present invention relates to a method for producing highly monodisperse crosslinked fine particles in the range of m.

[0002]

2. Description of the Related Art Polymer particles used for spacers for liquid crystal panels, packing materials for chromatography, diagnostic reagents and the like are required to have uniform particle diameter and mechanical strength. Conventionally, such fine particles have been obtained mainly by classifying fine particles obtained by suspension polymerization using a dry type and wet type classifying device. However, in such a method, the yield is extremely low,
Moreover, the particle size accuracy was also insufficient. Further, it is difficult to synthesize micron-order fine particles by emulsion polymerization and micron-order monodisperse fine particles are obtained by dispersion polymerization, but it is difficult to synthesize crosslinked fine particles.

As a method for producing the monodisperse crosslinked fine particles of the above-mentioned micron order, for example, Japanese Patent Publication No.
No. 24369 and Japanese Patent Publication No. 5-64964. However, in any of these methods, uncrosslinked or crosslinked fine particles are produced by diffusing the monomer into the seed particles using an auxiliary agent that promotes the migration of the monomer, and then polymerizing it. However, there is a drawback that the auxiliary agent bleeds out during the polymerization to produce porous fine particles, particularly in the production of crosslinkable fine particles.

Further, for example, Japanese Patent Publication No. 63-32500 discloses a method of using a low molecular weight seed particle having a weight average molecular weight of less than 10,000 to absorb a monomer or organic compound in a volume of 1 to 500 times. However, in this method, when the molecular structure of the seed particle and the substance to be absorbed are different, phase separation occurs, resulting in a core-shell structure and sliding at the interface between the core and the shell, or a structure with cavities. As a result, there is a problem that the mechanical strength of the generated particles is significantly reduced. Further, this method relates to a method for synthesizing uncrosslinked fine particles, and does not describe a method for crosslinkable fine particles.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has a simple polymerization reaction, which has porosity, is free of core shells and cavities, and has uniform particle size and uniform high monodisperse crosslinking. It is an object to provide a method for producing fine particles.

[0006]

The method for producing highly monodisperse crosslinked fine particles according to the present invention comprises the step of dispersing ethylenically unsaturated monomers in water in which polymer seed particles containing styrene and a derivative thereof in an amount of 90% by weight or more are dispersed. And an emulsion of an oil-soluble initiator are added, the polymer seed particles are allowed to absorb the ethylenically unsaturated monomer and the oil-soluble initiator, and then the ethylenically unsaturated monomer is polymerized. It is what

The seed particles used in the production method of the present invention include styrene derivative components such as styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene, p-chloromethylstyrene and p-methoxystyrene in an amount of 90% by weight. Examples of the polymer include the above, and these may be used alone or in combination of two or more kinds.

When the content of styrene and its derivative component in the seed particles is 90% by weight or less, the seed particles are phase-separated from the crosslinking component to be added later, and the mechanical strength of the resulting crosslinked fine particles is remarkably lowered. Further, (meth) acrylic acid, (meth) acrylic acid ester, butadiene, etc. may be added to the seed particles as other components.

The weight average molecular weight of the seed particles is 1,0.
00 to 10,000 is preferred. When it is 10,000 or more, the mechanical strength is lowered due to phase separation with the crosslinking component added later, and when it is 1,000 or less, the particle size is not uniform and the sphericity is also lowered.

The seed particles have an average particle size of 0.1 to 1
0 μm and Cv value (standard deviation / average particle size ×
Non-crosslinked particles having a 100) of 10 or less are preferred.

These seed particles are produced by emulsion polymerization, soap-free polymerization or dispersion polymerization, but the method is not limited to these methods and known techniques can be used.

Examples of the ethylenically unsaturated monomer used in the production method of the present invention include styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene,
Styrene derivatives such as chloromethylstyrene; vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; unsaturated nitriles such as acrylonitrile; methyl acrylate, methyl methacrylate, ethyl acrylate,
(Meth) acrylic acid ester derivatives such as ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, stearyl acrylate, stearyl methacrylate; conjugated dienes such as butadiene and isoprene These may be used alone or in combination of two or more.

Examples of the monomer having two or more ethylenically unsaturated groups used in the production method of the present invention include divinylbenzene, ethylene oxide diacrylate, ethylene oxide dimethacrylate, tetraethylene oxide diacrylate and tetraethylene oxide dimethacrylate. 1,6-hexanediol diacrylate,
Examples include neopentyl glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane triacrylate, tetramethylolpropane tetraacrylate, tetramethylolpropane tetramethacrylate, etc. The above may be used in combination.

The ethylenically unsaturated monomer used in the production method of the present invention preferably contains at least 45% by weight of divinylbenzene, and more preferably 5%.
0% by weight or more. If it is less than 45% by weight, the strength of the crosslinked fine particles will be insufficient.

The amount of the ethylenically unsaturated monomer added is
It is limited to 20 to 500 parts by weight with respect to 1 part by weight of seed particles. If the amount is less than 20 parts by weight, the strength of the fine particles produced is small and the strength of the fine particles is insufficient.

In the production method of the present invention, the ethylenically unsaturated monomer is finely dispersed in water together with the oil-soluble initiator and then absorbed by the seed particles. For fine dispersion of the ethylenically unsaturated monomer and the oil-soluble initiator, for example, disperse with a homogenizer or the like, or form a fine dispersion emulsion by ultrasonic treatment, a nanomizer or a mount Gaulin type fine emulsifier. It is obtained by These monomers and oil-soluble initiators may be mixed in advance and finely dispersed, or those separately finely dispersed in advance may be mixed.

The particle size of the finely dispersed emulsion is
It is preferably smaller than the seed particles. These are finely dispersed in order to accelerate the speed at which the monomer and the oil-soluble initiator are dissolved in water and diffused into the seed particles. If this diffusion is slow, the particle size distribution accuracy of the generated fine particles is reduced.

Examples of the oil-soluble initiator used in the production method of the present invention include benzoyl peroxide, lauroyl peroxide, benzoyl orthochloroperoxide, benzoyl orthomethoxyperoxide, and 3,5,5-trimethylhexanoylperoxide. Organic peroxides such as oxides, t-butylperoxy-2-ethylhexanoate and di-t-butylperoxide, azobisisobutyronitrile, azobiscyclohexacarbonitrile, azobis (2,4-dimethylberero) Azo compounds such as nitrile).

In the production method of the present invention, the finely dispersed emulsion is mixed with a dispersion aqueous solution of seed particles, and the mixture of the monomer and the oil-soluble initiator is absorbed in the seed particles, and then polymerization is carried out. This absorption process is usually achieved by mixing the seed particle-dispersed aqueous solution and the finely dispersed emulsion and stirring at room temperature for 1 to 12 hours, but the absorption is further accelerated by heating to about 30 to 50 ° C. be able to.

The swelling degree of the seed particles can be arbitrarily selected by adjusting the mixing ratio of the mixed emulsion of the ethylenically unsaturated monomer / oil-soluble initiator and the seed particle-dispersed aqueous solution. A swelling degree of 20 to 200 times is preferably used in the present invention. Here, the degree of swelling is defined as the volume ratio of the fine particles after swelling to the seed particles before swelling. The end of absorption can be confirmed by observing with an optical microscope.

The ethylenically unsaturated monomer / oil-soluble initiator thus absorbed by the seed particles is polymerized in the next step. The polymerization temperature can be appropriately selected depending on the types of the initiator and the monomer, but is usually in the range of 25 to 100 ° C, more preferably 50 to 90 ° C. In the present invention, it is preferred that the mixed emulsion of the ethylenically unsaturated monomer / oil-soluble initiator is completely absorbed by the seed particles, and then the temperature is raised to carry out the polymerization.

In the polymerization step, various surfactants or polymer dispersion stabilizers may be used in order to improve the dispersion stability of the polymer particles. Examples of the dispersion stabilizer include anionic surfactants such as sodium lauryl sulfate and sodium laurylbenzenesulfonate; polymeric dispersion stabilizers such as polyvinylpyrrolidone, gelatin, starch, hydroxyethyl cellulose, polyvinyl ether and polyvinyl alcohol. May be used alone or in combination of two or more.

The above dispersion stabilizer may be added after the seed particles have absorbed the mixed emulsion of ethylenically unsaturated monomer / oil-soluble initiator, or may be added at the time of fine dispersion emulsification and at the time of fine dispersion. It may have both the function of stabilizing and the function of stabilizing dispersion during polymerization.

By carrying out the polymerization in this way, highly monodisperse crosslinked polymer fine particles can be obtained. The particle size of the highly monodisperse crosslinked fine particles can be freely designed depending on the particle size of the seed particles to be used and the ratio of ethylenically unsaturated monomer / seed particles. It is useful for obtaining monodisperse crosslinked fine particles.

In the production method of the present invention, the fine particles after polymerization can be obtained by centrifuging to remove the aqueous phase, washing with water and a solvent, and then drying and isolating.

Mechanical properties of the synthesized highly monodisperse crosslinked fine particles
In order to evaluate the characteristics, K value shown below and recovery after compression
The rate was measured. (1) K value measurement method: According to the method described in Japanese Patent Publication No. 6-503180.
It measured based on it. Micro compression tester (PCT-200 type)
Shimadzu Corporation)
Fine particles are compressed by the smooth end surface of the cylinder (compression speed 0.27 g
/ Sec, test load up to 10g) and calculate the K value from the following formula.
I asked. K = (3/2) ・ FS^-3/2・ R^-1/2 [F, S, and R are loads in 10% compression deformation of fine particles.
Value (kg), compressive displacement (mm), particle radius
The K value thus obtained is 25 at 20 ° C.
0 to 700 kg / mm ²Is preferred.

(2) Recovery rate after compression deformation Measurement method: The recovery rate was measured according to the method described in JP-A-6-503180. Using the same micro compression tester as in (1), the load is compressed to 1 g at a speed of 0.27 gf / sec, and conversely the load is reduced to 0.1 g. The recovery rate is defined by the ratio (L ₂ / L ₁ ) of the displacement L ₁ to the reversal point and the displacement L ₂ from the reversal point to the point where the origin load value is taken, expressed in%. The recovery rate is preferably in the range of 30 to 80% at 20 ° C.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. [Production of seed particles (A)] Polyvinylpyrrolidone (weight average molecular weight 30,000) 1.2 parts (parts represent parts by weight; the same applies hereinafter), aerosol OT (anionic surfactant manufactured by Wako Pure Chemical Industries, Ltd.) 0.57 Part, azobisisobutyronitrile 5.7
While stirring a solution prepared by dissolving 2 parts of ethanol in 62.8 parts and water of 21 parts, 14 parts of styrene was charged under a nitrogen stream and the temperature was raised to 70 ° C. to carry out a polymerization reaction for 24 hours to obtain seed particles (A). Got

[Production of seed particles (B) and (C)] Except that the addition amount of azobisisobutyronitrile was changed, synthesis was performed in the same manner as the seed particles (A), and seed particles (B) and (C) was obtained.

[Production of Seed Particles (D)] Synthesis was conducted in the same manner as the seed particles (A) except that 7 parts of styrene, 6 parts of α-methylstyrene and 1 part of acrylic acid were used instead of styrene. , Seed particles (D) were obtained.

[Production of Seed Particles (E) and (F)] The seed particles (E) and (F) were synthesized in the same manner as the seed particles (A) except that the addition amount of azobisisobutyronitrile was changed. (F) was obtained. Incidentally, the seed particles (F) had a flat particle size, and the Cv value was polydisperse.

[Production of seed particles (G)] Seed particles (G) were obtained in the same manner as the seed particles (A) except that methyl methacrylate was used instead of styrene.

Seed particles (A) to (G) obtained above
About the weight average molecular weight (Mw) and the number average molecular weight (M
n), the particle size and the Cv value were measured, and the results are shown in Table 1.

[0034]

[Table 1]

Example 1 To 5 parts of the seed particles (A), 200 parts of ion-exchanged water and 0.13 part of sodium lauryl sulfate were added and uniformly dispersed. 75 parts of divinylbenzene, 75 parts of styrene and 2.5 parts of benzoyl peroxide were mixed and roughly dispersed by a homogenizer, and then finely dispersed and emulsified to an average particle size of 0.2 μm by ultrasonic treatment. The obtained emulsion is added to the dispersion liquid of the seed particles (A), and 25
After stirring for 3 hours at a rotation speed of 200 rpm and a rotation speed of 200 rpm, the monomer was completely absorbed by the seed particles (A). Polyvinyl alcohol (“GH-1 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.”
7 "; 100 parts of a 3 wt% aqueous solution having a saponification degree of 88 mol%) was added, and then polymerization was carried out at 70 ° C. for 12 hours under nitrogen while stirring at a rotation speed of 200 rpm to prepare a dispersion liquid of highly monodisperse crosslinked fine particles. did. Polymer particles were taken out from the obtained dispersion liquid by centrifugation, washed three times with ion-exchanged water and ethanol, and then dried to obtain highly monodisperse crosslinked fine particles. The above highly monodisperse crosslinked fine particles are magnified at 1,000 with an optical microscope ("BX-40" manufactured by Olympus Optical Co., Ltd.).
When it was observed at double magnification, it had a uniform structure.

(Example 2) Instead of the seed particles (A),
Highly monodisperse crosslinked fine particles were obtained by performing the same synthesis as in Example 1 except that the seed particles (B) were used. When the obtained highly monodisperse crosslinked fine particles were observed with an optical microscope in the same manner as in Example 1, it had a uniform structure.

(Example 3) Instead of the seed particles (A),
Highly monodisperse crosslinked fine particles were obtained by performing the same synthesis as in Example 1 except that the seed particles (C) were used. When the obtained highly monodisperse crosslinked fine particles were observed with an optical microscope in the same manner as in Example 1, it had a uniform structure.

(Example 4) Instead of the seed particles (A),
Highly monodisperse crosslinked fine particles were obtained by performing the same synthesis as in Example 1 except that the seed particles (D) were used. When the obtained highly monodisperse crosslinked fine particles were observed with an optical microscope in the same manner as in Example 1, it had a uniform structure.

Example 5 Highly monodisperse crosslinked fine particles were obtained by performing the same synthesis as in Example 1 except that the addition amounts of styrene and divinylbenzene were each 55 parts.
When the obtained highly monodisperse crosslinked fine particles were observed with an optical microscope in the same manner as in Example 1, it had a uniform structure.

Example 6 High monodisperse crosslinked fine particles were obtained by the same synthesis as in Example 1, except that the addition amounts of styrene and divinylbenzene were each 400 parts. When the obtained highly monodisperse crosslinked fine particles were observed with an optical microscope in the same manner as in Example 1, it had a uniform structure.

Comparative Example 1 Highly monodisperse crosslinked fine particles were obtained by the same synthesis as in Example 1 except that the addition amount of divinylbenzene was 60 parts and the addition amount of styrene was 90 parts. When the obtained highly monodisperse crosslinked fine particles were observed with an optical microscope in the same manner as in Example 1, they had a core-shell structure.

(Comparative Example 2) Instead of the seed particles (A),
Highly monodisperse crosslinked fine particles were obtained by performing the same synthesis as in Example 1 except that the seed particles (E) were used. When the obtained highly monodisperse crosslinked fine particles were observed with an optical microscope in the same manner as in Example 1, they had a core-shell structure.

(Comparative Example 3) Instead of the seed particles (A),
Highly monodisperse crosslinked fine particles were obtained by performing the same synthesis as in Example 1 except that the seed particles (F) were used. When the obtained highly monodisperse crosslinked fine particles were observed with an optical microscope in the same manner as in Example 1, it had a uniform structure.

(Comparative Example 4) Instead of the seed particles (A),
Highly monodisperse crosslinked fine particles were obtained by performing the same synthesis as in Example 1 except that the seed particles (G) were used. When the obtained highly monodisperse crosslinked fine particles were observed with an optical microscope in the same manner as in Example 1, they had a core-shell structure.

(Comparative Example 5) Except that the addition amounts of divinylbenzene and styrene were each 2 parts,
The same synthesis as in Example 1 was performed to obtain highly monodisperse crosslinked fine particles. When the obtained highly monodisperse crosslinked fine particles were observed with an optical microscope in the same manner as in Example 1, they had a core-shell structure.

Comparative Example 6 High monodisperse crosslinked fine particles were obtained by the same synthesis as in Example 1 except that the addition amounts of divinylbenzene and styrene were each 1500 parts. When the obtained highly monodisperse crosslinked fine particles were observed with an optical microscope in the same manner as in Example 1, they had a core-shell structure.

With respect to the highly monodisperse crosslinked fine particles obtained in the above Examples and Comparative Examples, the yield, average particle size, Cv value, K value and recovery rate after compression deformation were measured, and the results are shown in Table 2. Indicated. The K value and the recovery rate were measured using the micro compression tester.

[0048]

[Table 2]

In Comparative Examples 1 and 4, there was no recovery after compression and the recovery rate could not be measured. In Comparative Example 3,
The highly monodisperse crosslinked fine particles are gelated, and the average particle diameter, Cv value,
The K value and recovery rate could not be measured. Furthermore, in Comparative Example 4, the Cv value was polydisperse, and the K value and the recovery rate could not be measured.

[0050]

The method for producing highly monodisperse crosslinked fine particles of the present invention has the above-mentioned constitution, and the monomer mixture containing the polyfunctional monomer easily contains styrene and its derivative as a main component even at room temperature. Since the particles are absorbed by the seed particles, highly monodisperse crosslinked fine particles having porosity and having no core-shell structure or voids are provided by a simple polymerization reaction.

Claims (1)

[Claims] 1. An emulsion of an ethylenically unsaturated monomer and an emulsion of an oil-soluble initiator is added to water in which polymer seed particles containing 90% by weight or more of styrene and a derivative thereof are dispersed, and the polymer seed is added. A method for producing highly monodisperse crosslinked fine particles, which comprises polymerizing an ethylenically unsaturated monomer after absorbing an ethylenically unsaturated monomer and an oil-soluble initiator into the particles, wherein the weight average of the polymer seed particles is The molecular weight is 1,000 to 10,000, the ethylenically unsaturated monomer contains at least 45 wt% of divinylbenzene, and the ethylenically unsaturated monomer is 1 wt% of polymer seed particles. A method for producing highly monodisperse crosslinked fine particles, which comprises absorbing 20 to 500 parts by weight per part.