JPH0735404B2 - Suspension polymerization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a suspension polymerization method particularly suitable for obtaining polymer particles having a particle size of 50 μm or less, and more specifically to organic pigments, particularly cosmetics having an ultraviolet absorbing ability. The present invention relates to a suspension polymerization method capable of stably and efficiently producing polymer particles that can be suitably used in applications such as a pigment for toner and a toner resin for electrostatic image development.

<Conventional Technology and Problems> In the conventional suspension polymerization method, a water-soluble polymer or a poorly water-soluble inorganic salt is used as a suspension stabilizer, and further, a surfactant is used as a suspension stabilizer auxiliary when necessary. Although it is used, it has been considered unavoidable that an emulsified fine particle is by-produced in the aqueous phase. The emulsified fine particles can be removed to some extent by washing with water, but most of them are adhered to the surface of the suspension polymer particles fairly strongly, which causes clogging during washing with water.

As means for solving such a drawback, for example, Japanese Patent Laid-Open No.
-17737 and JP-A-57-41649, a method of adding a water-soluble metal salt, which is generally known as a polymerization inhibitor, to an aqueous phase for the purpose of preventing emulsion polymerization in the aqueous phase is described in JP-A-60-8302 discloses a method of adding vanadium pentoxide and / or cupric chloride to an aqueous phase, and JP-A-61-2.
Japanese Patent No. 55353 discloses a method of adding a water-soluble mercaptan compound and the like. However, even if such a water-soluble substance is used, it is difficult to sufficiently suppress the generation of emulsified fine particles by emulsion polymerization, and since the additives in the aqueous phase are included in the wastewater, it is difficult to prevent industrial pollution. Is also not preferable.

<Means and Actions for Solving Problems> The inventors of the present invention have made extensive studies in view of the above circumstances, and as a result, emulsified when a compound having a phenolic hydroxyl group during suspension polymerization is interposed in the reaction system. It was found that the polymerization can be suppressed and prevented, and the suspension polymer particles can be obtained stably and efficiently, and the present invention has been completed.

That is, the present invention provides a compound (A) having a phenolic hydroxyl group, that is, a compound (A-1) represented by the following general formula (I) when suspension-polymerizing a polymerizable monomer in an aqueous medium, The present invention provides a suspension polymerization method characterized in that one or more compounds (A-2) represented by the following general formula (II) are interposed in a reaction system.

The compound (A) having a phenolic hydroxyl group used in the present invention is used for the purpose of suppressing the emulsion polymerization reaction which concurrently occurs during suspension polymerization to produce by-product emulsion fine particles, and the addition method is dispersion. Either method of adding it to the medium or dissolving it in the polymerizable monomer may be used. The amount added is usually 0.001 to 10% by weight, preferably 0.05 to 5% by weight, based on the polymerizable monomer, in order to exert a remarkable effect.
Therefore, even if it is used in excess of 10% by weight, it is only economically disadvantageous.

As the compound (A) having a phenolic hydroxyl group, one or more compounds (A-1) represented by the following general formula (I) and compound (A-2) represented by the following general formula (II) are used. The resulting polymer particles are preferable because they have an ultraviolet absorbing ability as a secondary function and can be used in a wider range of applications.

(In the formula, R represents a hydroxyl group, an alkyl group having 1 to 15 carbon atoms, an alkoxy group, an alkenyl group, an alkenoyloxy group or an alkenoyloxyethoxy group, and l is 0 or 1
Is an integer of 5 and m is 0 or an integer of 1 to 4, respectively. ) (In the formula, R is the same as the definition in the general formula (I),
n represents 0 or an integer of 1 to 4. The reason why the compound (A) having a phenolic hydroxyl group is effective for preventing the suppression of emulsion polymerization reaction that occurs concurrently during suspension polymerization is not clear, but it is considered as follows. That is, the place where the emulsion polymerization which occurs concurrently in the suspension polymerization system is considered to be in the vicinity of the surface of the suspension droplet of the polymerizable monomer, but the compound (A) having a phenolic hydroxyl group used in the present invention is Since it can form a hydrogen bond, it is likely to be distributed on the surface of the polymerizable monomer oil droplets, and can be present on the particle surface where the emulsion polymerization reaction occurs, and it is considered that it exerts a sufficient effect for preventing emulsion polymerization inhibition. . However, the present invention is not limited to this reason.

The polymerizable monomer that can be used in the present invention is not particularly limited as long as it is a polymerizable monomer, and examples thereof include styrenes such as styrene and methylstyrene; methyl acrylate, ethyl acrylate, butyl acrylate and the like. Acrylic acid derivatives; methyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, and other methacrylic acid derivatives; vinyl acetate, vinyl propionate, and other vinyl esters; acrylonitrile, methacrylonitrile, vinyl methyl ether, vinyl methyl ketone, Examples thereof include vinyl compounds such as N-vinylcarbazole and vinyl chloride. Further, a crosslinkable vinyl compound such as divinylbenzene, ethylene glycol diacrylate and trimethylolpropane trimethacrylate may be used in the range of 0.005 to 20% by weight based on the vinyl compound.

Examples of the polymerization initiator used in the present invention include peroxides such as benzoyl peroxide and lauroyl peroxide; 2,2′-azobisisobutyronitrile and 2,2′-azobis- (2,4-dimethyl). And azo compounds such as valeronitrile). These are used in an amount of 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the polymerizable monomer.

In the present invention, a water-soluble polymer compound and / or a poorly water-soluble inorganic salt is used as the suspension stabilizer. Examples of the water-soluble polymer compound used include gelatin, starch, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl alcohol, and the like, and the poorly water-soluble inorganic salt includes, for example, barium sulfate, calcium sulfate, barium carbonate, and carbonic acid. Examples thereof include calcium, magnesium carbonate and calcium phosphate. These are used in an amount of 0.1 to 5% by weight based on the aqueous medium.

<Effects of the Invention> As described in detail above, according to the suspension polymerization method of the present invention, since the compound (A) having a phenolic hydroxyl group is used, the formation of emulsion fine particles by-produced during suspension polymerization is sufficient. Can be prevented and suppressed, the production process can be facilitated to improve the work efficiency, the yield of polymer particles can be increased, and further, the compound having a specific structure as a compound (A) having a phenolic hydroxyl group can be obtained. It was found that when a compound is used, a secondary function called ultraviolet absorption ability can be imparted. Therefore, the suspension polymerization method of the present invention is suitable for producing polymer particles that can be used for organic pigments, particularly cosmetic pigments, toner resins for electrostatic image development, and the like.

<Example> The present invention will be specifically described below with reference to Examples, but the present invention is not limited thereto.

Example 1 49 parts by weight of methyl methacrylate, 1 part by weight of trimethylolpropane trimethacrylate, 1 part by weight of 2,4-dihydroxybenzophenone, 0.5 part by weight of 2,2'-azobis (2,4-dimethylvaleronitrile), benzoyl peroxide. The homogeneous solution prepared by mixing 0.5 parts by weight was added to 450 parts by weight of a 0.33% polyvinyl alcohol aqueous solution, and the mixture was stirred with a homomixer at 5100 rpm for 5 minutes. This dispersion was placed in a separable flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a reflux condenser, and heated under a nitrogen stream at 60 ° C for 2 hours and then at 80 ° C for 3 hours to polymerize.

When the reaction system was cooled and allowed to stand after completion of the polymerization, the reaction system was separated into two layers of polymer particles and transparent water, and almost no emulsion polymer was observed. This is passed through a nutsche to take out polymer particles, washed with water and repeated repeatedly, and dried to have an average particle size of 6.
48 parts by weight of 0 μ polymer particles were obtained.

Example 2 49 parts by weight of methyl methacrylate, 1 part by weight of trimethylolpropane trimethacrylate, 1 part by weight of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole (trade name Tinuvin P; manufactured by Ciba Geigy), 2, 0.5 parts by weight of 2'-azobis- (2,4-dimethylvaleronitrile),
Add 0.33 of a homogeneous solution of 0.5 part by weight of benzoyl peroxide.
% Polyvinyl alcohol aqueous solution, and the mixture was stirred at 5100 rpm for 5 minutes with a homomixer. This dispersion was placed in a separable flask equipped with a stirrer, a thermometer, a nitrogen introduction tube, and a reflux condenser, and heated under a nitrogen stream at 60 ° C for 2 hours and then at 80 ° C for 3 hours to polymerize. When the reaction system was cooled and allowed to stand after completion of the polymerization, the reaction system was separated into two layers of polymer particles and transparent water, and almost no emulsion polymer was observed. Pass it through a nutsche to take out polymer particles, wash with water,
Polymer particles with an average particle size of 7.0μ
Parts by weight were obtained.

Example 3 49 parts by weight of methyl methacrylate, 1 part by weight of trimethylolpropane trimethacrylate, 2-hydroxy-4-
Methacryloyloxybenzophenone 1 part by weight, 2,2'-
A homogeneous solution was prepared by mixing 0.5 parts by weight of azobis- (2,4-dimethylvaleronitrile) and 0.5 parts by weight of benzoyl peroxide.
In addition to 450 parts by weight of 0.33% polyvinyl alcohol aqueous solution,
The mixture was stirred with a homomixer at 5100 rpm for 5 minutes. This dispersion was placed in a separable flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a reflux condenser, and was placed in a nitrogen stream at 60 ° C. for 2 hours,
Then, it was heated at 80 ° C. for 3 hours for polymerization. When the reaction system was cooled and allowed to stand after completion of the polymerization, the reaction system was separated into two layers of polymer particles and transparent water, and almost no emulsion polymer was observed. Pass it through a nutsche, remove the polymer particles, and wash with water.
The polymer was repeatedly dried to obtain 49 parts by weight of polymer particles having an average particle size of 8.2μ.

Example 4 49 parts by weight of methyl methacrylate, 1 part by weight of trimethylolpropane trimethacrylate, 2-hydroxy-4-
Methacryloyloxybenzophenone 0.5 parts by weight, 2,2'-
A homogeneous solution was prepared by mixing 0.5 parts by weight of azobis- (2,4-dimethylvaleronitrile) and 0.5 parts by weight of benzoyl peroxide.
In addition to 450 parts by weight of 0.33% polyvinyl alcohol aqueous solution,
The mixture was stirred with a homomixer at 5100 rpm for 5 minutes. This dispersion was placed in a separable flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a reflux condenser, and was placed in a nitrogen stream at 60 ° C. for 2 hours,
Then, it was heated at 80 ° C. for 3 hours for polymerization. When the reaction system was cooled and allowed to stand after completion of the polymerization, the reaction system was separated into two layers of polymer particles and transparent water, and almost no emulsion polymer was observed. Pass it through a nutsche, remove the polymer particles, and wash with water.
The polymer was repeatedly dried to obtain 48 parts by weight of polymer particles having an average particle size of 7.4μ.

Example 5 49 parts by weight of methyl methacrylate, 1 part by weight of trimethylolpropane trimethacrylate, 1 part by weight of 2,2'-dihydroxy-4,4'-dimethacryloyloxybenzophenone, 2,2'-azobis- (2,4 0.5 parts by weight of dimethylvaleronitrile) and 0.5 parts by weight of benzoyl peroxide were added to 450 parts by weight of a 0.33% polyvinyl alcohol aqueous solution, and the mixture was stirred with a homomixer at 5100 rpm for 5 minutes. This dispersion was placed in a separable flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a reflux condenser, and was placed under a nitrogen stream at 60
Polymerization was carried out by heating at 0 ° C for 2 hours and then at 80 ° C for 3 hours. When the reaction system was cooled and allowed to stand after completion of the polymerization, the reaction system was separated into two layers of polymer particles and transparent water, and almost no emulsion polymer was observed. The polymer particles were passed through a Nutsche, and the polymer particles were taken out and washed with water and dried repeatedly to obtain 48 parts by weight of polymer particles having an average particle diameter of 8.0 μ.

Example 6 40 parts by weight of methyl methacrylate, 5 parts by weight of styrene, 5 parts by weight of butyl acrylate, 1 part by weight of 2-hydroxy-4-methacryloyloxybenzophenone, 2,2'-azobis- (2,4-dimethylvaleronitrile) 0.33% of a homogeneous solution prepared by mixing 0.5 part by weight and 0.5 part by weight of benzoyl peroxide
The mixture was added to 450 parts by weight of an aqueous polyvinyl alcohol solution, and stirred with a homomixer at 5100 rpm for 5 minutes. This dispersion was placed in a separable flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a reflux condenser, and was placed in a nitrogen stream at 60 ° C. for 2 hours, then
Polymerization was carried out by heating at 80 ° C for 3 hours. When the reaction system was cooled and allowed to stand after completion of the polymerization, the reaction system was separated into two layers of polymer particles and transparent water, and almost no emulsion polymer was observed. The polymer particles were passed through a Nutsche, and the polymer particles were taken out and repeatedly washed with water and dried to obtain 47 parts by weight of polymer particles having an average particle size of 8.4 μ.

Comparative Example 1 49 parts by weight of methyl methacrylate, 1 part by weight of trimethylolpropane trimethacrylate, 2,2'-azobis-
A uniform solution prepared by mixing 0.5 part by weight of (2,4-dimethylvaleronitrile) and 0.5 part by weight of benzoyl peroxide was added to 450 parts by weight of a 0.33% polyvinyl alcohol aqueous solution, and the mixture was stirred with a homomixer at 5100 rpm for 5 minutes. Stirrer this dispersion,
The mixture was placed in a separable flask equipped with a thermometer, a nitrogen introduction tube, and a reflux condenser, and heated at 60 ° C. for 2 hours and then at 80 ° C. for 3 hours under a nitrogen stream to carry out polymerization. After the polymerization was completed, the emulsion polymer was not separated into two layers even after cooling and standing, and a large amount of emulsion polymer was observed. Since it was not possible to pass due to clogging, the polymer particles and emulsion polymer were separated using a centrifuge, and then washed with water and repeatedly dried to obtain 14 parts by weight of polymer particles having an average particle size of 7.5μ. Obtained.

<Ultraviolet Absorption Ability of Polymer Particles> The polymer particles obtained in Examples 1 to 6 were molded into tablets, the ultraviolet reflection spectrum was measured using an integrating sphere, and then back calculated to obtain the ultraviolet absorption ability on the surface of the polymer particles. I checked. The results are shown in Table 1.

Claims (1)

[Claims] 1. When suspension-polymerizing a polymerizable monomer in an aqueous medium, the compound (A-1) represented by the following general formula (I) and the following general formula as the compound (A) having a phenolic hydroxyl group. A suspension polymerization method characterized by interposing one or more compounds (A-2) represented by (II) in a reaction system. (Wherein R represents a hydroxyl group, an alkyl group having 1 to 15 carbon atoms, an alkoxy group, an alkenyl group, an alkenoyloxy group or an alkenoyloxyethoxy group, and l represents 0 or 1 to
An integer of 5 and m represent 0 or an integer of 1 to 4, respectively. ) (In the formula, R has the same definition as in the general formula (I), and n
Represents 0 or an integer of 1 to 4. )