JP3534862B2 - Method for producing highly monodispersed fine particles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing highly monodispersed fine particles having a uniform particle size by a seed polymerization method. [0002] Polymer fine particles used for spacers for liquid crystal panels, packing materials for chromatography, diagnostic reagents and the like are required to have a uniform particle size. Conventionally, as a method of obtaining such fine particles having a uniform particle size, there is a method of classifying fine particles obtained by suspension polymerization mainly using a dry or wet classifier. However, in such a method, the yield was remarkably low, and the uniformity of the particle size was not sufficient. Further, in emulsion polymerization, it is difficult to synthesize micron-order fine particles, and in dispersion polymerization, micron-order monodisperse fine particles can be obtained, but it is difficult to obtain crosslinked fine particles. As a method for producing monodisperse crosslinked fine particles on the order of microns, for example, Japanese Patent Publication No. 57-24369
Japanese Patent Application Laid-Open No. 5-64964 discloses an improved swelling seed polymerization method using a nonionic compound. However,
All of these methods produce uncrosslinked or crosslinked fine particles by diffusing the monomer into the seed particles using an auxiliary that promotes the transfer of the monomer, and then polymerizing the monomer. In particular, when producing crosslinkable fine particles, there is a problem that the auxiliary agent bleeds out during the polymerization to generate porous fine particles. For example, Japanese Patent Publication No. 63-32,500 and Japanese Patent Publication No. 4-71921 disclose a method in which a monomer or an organic compound having a volume 20 to 500 times that of a low molecular weight seed latex is absorbed and polymerized. A method for doing so is disclosed. However, the obtained fine particles have poor particle size accuracy, and when the molecular structure of the seed latex and the substance to be absorbed are different, phase separation occurs, and voids and cracks are generated inside as the polymerization proceeds, and the generated fine particles However, there is a problem that the mechanical strength of the steel is remarkably reduced. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to produce highly monodispersed fine particles having a uniform particle size and excellent mechanical strength by a simple polymerization reaction. It is to provide a method. The method for producing highly monodispersed fine particles of the present invention comprises the steps of:
When the ethylenically unsaturated monomer is adsorbed and polymerized in the presence of an oil-soluble polymerization initiator, a monomer having two or more ethylenically unsaturated groups in the molecule as the ethylenically unsaturated monomer The method is characterized in that an ethylenically unsaturated monomer containing 15% by weight or more of the polymer is finely dispersed in water together with an oil-soluble polymerization initiator, and is then absorbed by seed particles and polymerized. As the seed particles, a polymer containing 50% by weight or more of styrene and its derivatives is used. In the seed particles, the ratio of styrene and its derivative decreases as the ratio decreases, causing phase separation with a monomer having two or more ethylenically unsaturated groups in a molecule to be added later, and the mechanical strength of the resulting crosslinked fine particles. Is significantly reduced. Examples of the styrene derivative include p-methylstyrene, p-chlorostyrene, p-chloromethylstyrene, p-methoxystyrene and the like. These may be used alone or in combination of two or more. Good. As the components other than the styrene and its derivatives, (meth) acrylic acid, (meth) acrylate, butadiene and the like are used. When the weight-average molecular weight of the seed particles is small, monodisperse spherical fine particles are not formed. And the mechanical strength of the resulting crosslinked fine particles is significantly reduced.
000. The seed particles have an average particle size of 0.1.
Non-crosslinked particles having a diameter of 10 to 10 μm and a Cv value (expressed as (particle diameter standard deviation / average particle diameter) × 100) of 10 or less are preferred. These seed particles are produced using, for example, soap-free polymerization or dispersion polymerization, but are not limited to these methods, and a known technique can be applied. The above ethylenically unsaturated monomers include styrene, α-methylstyrene, p-methylstyrene and p-methylstyrene.
Styrene derivatives such as chlorostyrene and chloromethylstyrene; vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; unsaturated nitriles such as acrylonitrile; methyl (meth) acrylate, ethyl (meth) acrylate, ( (Meth) acrylate derivatives such as butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and stearyl (meth) acrylate; monofunctional monomers such as conjugated dienes such as butadiene and isoprene; These may be used alone or in combination of two or more. The ethylenically unsaturated monomers having two or more ethylenically unsaturated groups in the molecule include divinylbenzene, ethylene oxide di (meth) acrylate, tetraethylene oxide di (meth) acrylate,
Polyfunctional monomers such as 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, trimethylolpropane tri (meth) acrylate, tetramethylol methane triacrylate, and tetramethylol propane tetra (meth) acrylate; These may be used alone or in combination of two or more. When the proportion of the ethylenically unsaturated monomer having two or more ethylenically unsaturated groups in the molecule among the above ethylenically unsaturated monomers decreases, the mechanical strength of the fine particles decreases. Therefore, 15% by weight or more is preferable,
It is more preferably at least 30% by weight. The amount of the ethylenically unsaturated monomer added is:
When the amount of the cross-linking component to be reduced is insufficient, the mechanical strength of the generated fine particles becomes insufficient, and when the amount is not large, the accuracy of the generated fine particles is deteriorated.
-20 parts by weight. The above oil-soluble polymerization initiator includes, for example,
Benzoyl peroxide, lauroyl peroxide, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide,
3,5,5-trimethylhexanoyl peroxide,
Organic peroxides such as t-butylperoxy-2-ethylhexanoate and di-t-butyl peroxide; azobisisobutyronitrile, azobiscyclohexacarbonitrile, 2,2′-azobis (2, Azo compounds such as 4-dimethylvaleronitrile). In the production method of the present invention, the above-mentioned ethylenically unsaturated monomer is finely dispersed in water together with an oil-soluble polymerization initiator to form a finely dispersed emulsion, and then dispersed in the finely dispersed emulsion and an aqueous dispersion medium. The seed particles (seed particle dispersion) are mixed, and the ethylenically unsaturated monomer and the oil-soluble polymerization initiator are adsorbed on the seed particles to perform polymerization. In the above-mentioned polymerization step, it is preferable that the ethylenically unsaturated monomer is finely dispersed in water together with an oil-soluble polymerization initiator and then adsorbed on seed particles. To finely disperse the ethylenically unsaturated monomer and the oil-soluble polymerization initiator, they may be finely dispersed by a homogenizer or the like, or may be finely dispersed by ultrasonic treatment, a nanomizer or a mount Gaulin type fine emulsifier. . In order to obtain a finely dispersed emulsion of both components, both components may be mixed and finely dispersed in advance, or each component may be separately finely dispersed and then both components may be mixed. The particle size of the finely dispersed emulsion is preferably smaller than the particle size of the seed particles. By selecting such a particle size, the rate at which the ethylenically unsaturated monomer and the oil-soluble polymerization initiator dissolve in water and diffuse into the seed particles can be increased. When the diffusion speed is reduced, the particle size distribution accuracy of the generated fine particles is deteriorated. In order to adsorb the finely dispersed emulsion on the seed particles, the seed particle dispersion and the finely dispersed emulsion are mixed and stirred at room temperature for 1 to 12 hours. By doing so, adsorption can be promoted. The degree of swelling of the seed particles due to the adsorption of the finely dispersed emulsion can be arbitrarily selected by adjusting the mixing ratio of the seed particle dispersion and the finely dispersed emulsion. A swelling degree of 2 to 15 times is preferred. The degree of swelling here is defined by the volume ratio of the fine particles after swelling to the seed particles before swelling. The end of the adsorption is determined by confirming the enlargement of the particle size by observation with an optical microscope. In the polymerization step, the seed particles are polymerized with the finely dispersed emulsion adsorbed on the seed particles. The polymerization temperature can be appropriately selected depending on the type of the ethylenically unsaturated monomer or the oil-soluble polymerization initiator to be used, but is usually preferably 25 to 100 ° C, more preferably 50 to 90 ° C. . Further, it is preferable to start the polymerization after the ethylenically unsaturated monomer and the oil-soluble polymerization initiator are completely adsorbed on the seed particles. In the above polymerization step, a surfactant or a polymer dispersion stabilizer may be added in order to improve the dispersion stability of the polymer fine particles. Examples of such a surfactant include anionic surfactants such as sodium lauryl sulfate and sodium laurylbenzenesulfonate; and polymer dispersion stabilizers such as polyvinylpyrrolidone, gelatin, starch, hydroxyethylcellulose, polyvinyl ether, and polyvinyl alcohol. These may be used alone or in combination of two or more. The above-mentioned surfactant or polymer dispersion stabilizer may be added after the ethylenically unsaturated monomer and the polymerization initiator are absorbed in the seed particles, or the above-mentioned ethylenically unsaturated monomer may be added. And when the polymerization initiator is finely dispersed. By addition at the time of fine dispersion, both the stability at the time of fine dispersion and the dispersion at the time of polymerization can be obtained. The particle size of the highly monodispersed fine particles obtained by the above polymerization method can be freely designed depending on the particle size of the seed particles used and the mixing ratio of the ethylenically unsaturated monomer and the seed particles. The above polymerization method has a particle size of 1 to 1
It is suitable for the production of highly monodispersed crosslinked fine particles having 0 μm and a Cv value of 5 or less. After polymerization, the fine particles can be centrifuged to remove the aqueous phase, washed with water and a solvent, and then dried and isolated. Next, embodiments of the present invention will be described. Production of Seed Particles (1) Seed Particles (A) 1.2 parts by weight of polyvinylpyrrolidone (weight average molecular weight 30,000), 0.57 parts by weight of an anionic surfactant (“Aerosol OT” manufactured by Wako Pure Chemical Industries, Ltd.) and azo A solution prepared by dissolving 1.43 parts by weight of bisisobutyronitrile in 83.8 parts by weight of ethanol was mixed with styrene 1 under a nitrogen stream while stirring.
4 parts by weight were charged, the temperature was raised to 70 ° C., and a polymerization reaction was carried out for 24 hours to obtain a seed particle (A) dispersion. The resulting seed particles (A) had an average particle size of 1.63 μm and a Cv value of 2.
2. The weight average molecular weight (Mw) was 5,000 and the number average molecular weight (Mn) was 2,400. (2) Seed Particles (B) In the synthesis of the seed particles (A), the amount of azoisobutyronitrile was changed to 0.45 parts by weight in the same manner as the seed particles (A). Polymerization was performed to obtain seed particles (B). The obtained seed particles (B) have an average particle size of 1.6 μm.
m, Cv value 2.31, Mw = 18,000, Mn = 7,
500. (3) Seed Particles (C) In the synthesis of the seed particles (A), except that the amount of azoisobutyronitrile used was changed to 2.9 parts by weight, the same procedure as for the seed particles (A) was carried out. Polymerization was performed to obtain seed particles (C). The resulting seed particles (C) have an average particle size of 1.88 μm.
m, Cv value 2.4, Mw = 2,100, Mn = 800. (4) Seed particles (D) In the synthesis of the seed particles (A), instead of styrene,
Polymerization was carried out in the same manner as for the seed particles (A), except that 7 parts by weight of styrene, 6 parts by weight of p-methylstyrene and 1 part by weight of acrylic acid were used to obtain seed particles (D). The resulting seed particles (D) had an average particle size of 1.65 μm and Cv
The value was 2.4, Mw = 5,200, Mn = 2,100. (5) Seed particles (E) In the synthesis of the seed particles (A), except that the amount of azoisobutyronitrile used was changed to 0.28 parts by weight, the same procedure as for the seed particles (A) was carried out. Polymerization was performed to obtain seed particles (E). The resulting seed particles (E) had an average particle size of 1.61 μm.
m, Cv value 2.28, Mw = 28,000, Mn = 1
3,500. (6) Seed Particles (F) In the synthesis of the seed particles (A), the amount of azoisobutyronitrile was changed to 11.2 parts by weight in the same manner as the seed particles (A). Polymerization was performed to obtain seed particles (F). The resulting seed particles (F) had flat particles, the average particle size of which was not measurable, a Cv value of polydisperse, and Mw = 8.
00, Mn = 350. (7) Seed Particles (G) Polymerization and seed particles (G) were prepared in the same manner as the seed particles (A) except that methyl methacrylate was used in place of styrene in the synthesis of the seed particles (A). Got. The resulting seed particles (G) have an average particle size of 1.66 μm,
The v value was 2.25, Mw = 5,200, Mn = 2,100. (Example 1) To 5 parts by weight of the seed particles (A), 200 parts by weight of ion-exchanged water and 0.13 parts by weight of sodium lauryl sulfate were added and uniformly dispersed to obtain a seed particle dispersion. Separately, 0.6 part by weight of benzoyl peroxide was added to 40 parts by weight of an ethylenically unsaturated monomer mixture composed of 50% by weight of styrene and 50% by weight of divinylbenzene, and coarsely dispersed with a homogenizer. It was finely dispersed and emulsified to a particle size of 0.2 μm. The obtained emulsion was added to the seed particle dispersion, and the mixture was added at 25 ° C. and 200 rpm.
After stirring at m for 3 hours, the monomer mixture was completely absorbed by the seed particles. Next, polyvinyl alcohol (“GH-17” manufactured by Nippon Synthetic Chemical Co., Ltd., saponification degree 88) was added to the dispersion.
Mol%) of 100% by weight of a 3% by weight aqueous solution.
Polymerization was carried out at 70 ° C. for 12 hours under nitrogen while stirring at 00 rpm to obtain a dispersion of polymer fine particles. Polymer particles were taken out of the obtained dispersion by centrifugation, washed three times with ion-exchanged water and ethanol, and then dried to obtain highly monodispersed crosslinked fine particles (yield 98%, average particle size 3.1).
9 μm and a Cv value of 2.14) were obtained. These highly monodispersed crosslinked fine particles were subjected to an optical microscope ("BX-4" manufactured by Olympus Optical Co., Ltd.).
0 ") at a magnification of 1,000 times, the structure was uniform. Example 2 Instead of the seed particles (A),
Except for using the seed particles (B), highly single crosslinked fine particles (98% yield, average particle size 3.16 μm, Cv value 2.25) were obtained in the same manner as in Example 1. Observation of these highly monodispersed crosslinked fine particles with an optical microscope revealed a uniform structure. Example 3 Instead of the seed particles (A),
Except for using the seed particles (C), highly monodispersed crosslinked fine particles (98% yield, average particle size 3.3 μm, Cv value 2.32) were obtained in the same manner as in Example 1. Observation of these highly monodispersed crosslinked fine particles with an optical microscope revealed a uniform structure. Example 4 Instead of the seed particles (A),
Except for using the seed particles (D), highly monodispersed crosslinked fine particles (98% yield, average particle size 3.28 μm, Cv value 2.3) were obtained in the same manner as in Example 1. Observation of these highly monodispersed crosslinked fine particles with an optical microscope revealed a uniform structure. Example 5 The procedure of Example 1 was repeated except that the amount of the ethylenically unsaturated monomer mixture comprising 50% by weight of styrene and 50% by weight of divinylbenzene was changed to 10 parts by weight. Single-part crosslinked fine particles (99% yield, average particle size 2.33 μm, Cv value 2.2) were obtained. Observation of these highly monodispersed crosslinked fine particles with an optical microscope revealed a uniform structure. Example 6 The procedure of Example 1 was repeated except that the amount of the ethylenically unsaturated monomer mixture consisting of 50% by weight of styrene and 50% by weight of divinylbenzene was changed to 80 parts by weight. Monodispersed crosslinked fine particles (yield 97%, average particle size 4.1 μm, Cv value 2.09) were obtained. Observation of these highly monodispersed crosslinked fine particles with an optical microscope revealed a uniform structure. (Comparative Example 1) Instead of the seed particles (A),
Except for using the seed particles (E), highly monodispersed crosslinked fine particles (98% yield, average particle size 3.22 μm, Cv value 2.31) were obtained in the same manner as in Example 1. Observation of these highly monodispersed crosslinked fine particles with an optical microscope revealed many voids. (Comparative Example 2) Instead of the seed particles (A),
Except for using the seed particles (F), it was attempted to obtain highly monodispersed crosslinked fine particles in the same manner as in Example 1, but gelation was caused and no highly monodispersed crosslinked fine particles were obtained. (Comparative Example 3) Instead of the seed particles (A),
Except for using the seed particles (G), highly monodisperse crosslinked fine particles (98% yield, average particle size 3.23 μm, Cv value 2.45) were obtained in the same manner as in Example 1. Observation of these highly monodispersed crosslinked fine particles with an optical microscope revealed many voids. Comparative Example 4 Example 1 was repeated except that the amount of the ethylenically unsaturated monomer mixture consisting of 50% by weight of styrene and 50% by weight of divinylbenzene was changed to 4 parts by weight.
In the same manner as described above, highly monodispersed crosslinked fine particles (99% yield, average particle size 1.98 μm, Cv value 2.2) were obtained. Observation of these highly monodispersed crosslinked fine particles with an optical microscope revealed many voids. Comparative Example 5 The same procedure as in Example 1 was repeated except that the amount of the ethylenically unsaturated monomer mixture comprising 50% by weight of styrene and 50% by weight of divinylbenzene was changed to 200 parts by weight. Monodisperse crosslinked fine particles (97% yield,
The average particle size was 5.21 μm and the Cv value was polydispersed). The structure of the method for producing highly monodispersed crosslinked fine particles of the present invention is as described above, and has a uniform particle size by a simple polymerization reaction, and has a high mechanical strength. Dispersed fine particles can be obtained in high yield.

Claims (1)

(57) [Claim 1] Manufactured by a dispersion polymerization method containing 50% by weight or more of styrene having a weight average molecular weight of 1,000 to 20,000 and a derivative thereof dispersed in an aqueous dispersion medium. When the ethylenically unsaturated monomer is adsorbed on the seed particles to be polymerized and polymerized in the presence of an oil-soluble polymerization initiator, an ethylenically unsaturated group is contained in the molecule as the ethylenically unsaturated monomer. After using an ethylenically unsaturated monomer containing 15% by weight or more of a monomer having two or more monomers, 100 parts by weight of the ethylenically unsaturated monomer is finely dispersed in water together with an oil-soluble polymerization initiator. A method of producing highly monodispersed fine particles, wherein the particles are absorbed by 5 to 100 parts by weight of the seed particles and polymerized.