JPS646210B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing fine polymer particles, and more particularly to a method for producing fine particles of a methyl methacrylate polymer or a methyl methacrylate and alkyl acrylate copolymer. Acrylic resins containing methyl methacrylate as a main component are produced by bulk polymerization or suspension polymerization, and have a wide range of uses due to their excellent weather resistance and outstanding transparency. In recent years, with the advancement of processing technology for acrylic resin, polymer particles have been used not only for general purposes such as conventional molded products, extruded plates, and pipes, but also for filters, bubble-generating porous materials, etc. There are also some applications where it is needed. Furthermore, such polymer particles can be used, for example, to prepare syrup for template polymerization by dissolving them in monomers such as methyl methacrylate, to prepare surface coating agents by dissolving them in organic solvents, or to improve the viscosity index. It is expected to be used as a lubricating oil additive for the purpose of In these applications, the particle size distribution of polymer fine particles and the presence of impurities have a large effect on the quality of the product and the processing process.In the case of filters, the smaller the bead diameter, the smaller the voids between the beads. In addition, during casting and surface coating, the dissolution rate of beads in a solvent is greatly affected by the bead particle size, and when the bead particle size is halved, the dissolution rate decreases. The work time is reduced by ten times more. For these reasons, fine polymer particles have come to be desired for various uses. Conventionally known methods for producing fine polymer particles include:
There is a method in which a molten polymer is sprayed into a gas or liquid as fine particles and then solidified, but this requires an extra processing step and is extremely costly. In the normal suspension polymerization method, the average particle size is
Polymers obtained by emulsion polymerization usually have a particle size of 1μ or less, but in many cases these fine particles are aggregated and are not single particles. It is difficult to obtain them as particles. Furthermore, the emulsion polymerization method requires post-treatment steps, aging steps, etc. The present inventors conducted extensive research with the aim of obtaining fine acrylic polymer particles, and found that by using a small amount of polyvinyl alcohol, a small amount of anionic surfactant, and an appropriate amount of electrolyte, it was possible to obtain It was discovered that fine polymer particles with an average particle size that cannot be obtained by general suspension polymerization methods can be obtained in high yield without the need for such post-treatment steps,
This led to the present invention. Furthermore, according to the method of the present invention,
There is no need for post-treatment steps required in ordinary emulsion polymerization methods, and almost no aggregation of the obtained polymer particles is observed. That is, in the present invention, when a monomer mixture consisting of 100 to 80% by weight of methyl methacrylate and 0 to 20% by weight of alkyl acrylate having an alkyl group having 1 to 8 carbon atoms is polymerized in an aqueous medium, 100% by weight of methyl methacrylate is mainly used.
An aqueous medium consisting of 0.01 to 0.3 parts by weight of polyvinyl alcohol with a degree of polymerization of 1000 to 3000 and a degree of saponification of 80% or more, 0.001 to 0.1 parts by weight of an anionic surfactant, and 0.1 to 2.0 parts by weight of a water-soluble electrolyte. This is a method for producing polymer fine particles characterized by using the present invention. Examples of monomers that can be used in the method of the present invention include methyl methacrylate and a monomer mixture of methyl methacrylate and an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms that can be copolymerized therewith. . Among such alkyl acrylates having an alkyl group having 1 to 8 carbon atoms, methyl acrylate, ethyl acrylate, and n-butyl acrylate are particularly preferred, and a mixture of these may also be used. The monomer composition can be selected widely depending on the purpose, but if hard polymer particles are intended, 100 to 80% by weight of methyl methacrylate and 0 to 20% by weight of alkyl acrylate are preferred. In the method of the present invention, it is also possible to use conventionally known chain transfer agents, and examples of such chain transfer agents include mercaptans such as n-dodecylmercaptan, n-octylmercaptan, and n-butylmercaptan. Furthermore, it is also possible to use crosslinkable monomers in the method of the present invention, and examples of such crosslinkable monomers include divinylbenzene, acrylic acrylate, polyethylene glycol diacrylates, and polyethylene glycol dimethacrylate. Such crosslinking monomers can be used preferably in an amount of about 3% by weight. The aqueous medium used in the method of the invention primarily contains polyvinyl alcohol, an anionic surfactant and a water-soluble electrolyte. If only polyvinyl alcohol and an anionic surfactant are used, there will be a large amount of agglomerated particles mixed into the generated polymer particles.If only polyvinyl alcohol and an electrolyte are used and the anionic surfactant is excluded, the polymer particles will The particle size becomes large, and the desired fine polymer particles cannot be obtained. The polyvinyl alcohol referred to in the present invention preferably has a degree of polymerization of 1000 to 3000 and a degree of saponification of 80% or more. When the degree of polymerization is higher than 3000, the particle size of the resulting fine polymer particles becomes large, making it impossible to obtain the desired fine polymer particles. When the degree of polymerization is less than 1000, polymerization stability decreases, the particle shape of the generated polymer particles becomes irregular, and irregularly shaped polymer particles are mixed. Furthermore, if the degree of saponification is less than 80%, the solubility of polyvinyl alcohol in water decreases, which not only reduces its effectiveness as a polymerization stabilizer, but also causes polyvinyl alcohol to remain in the formed polymer fine particles, causing discoloration. becomes. The amount of polyvinyl alcohol used is 0.01 to 0.3 parts by weight, preferably 0.05 to 0.15 parts by weight, per 100 parts by weight of water. If the amount of polyvinyl alcohol added exceeds 0.3 parts by weight, it becomes difficult to wash away the polyvinyl alcohol from the formed polymer particles, and the remaining polyvinyl alcohol deteriorates the quality of the product. Furthermore, if the amount is less than 0.01 part by weight, the action as a polymerization stabilizer will be reduced, and the resulting polymer fine particles will aggregate to form block-like materials. Anionic surfactants include sodium and potassium salts of dodecylbenzenesulfonic acid;
Sodium and potassium salts of 2-butyloctylbenzenesulfonic acid, sodium and potassium salts of isopropylnaphthalenesulfonic acid,
Sodium and potassium salts of β-naphthalene sulfonic acid, sodium and potassium salts of dioctyl sulfosuccinic acid, sodium and potassium salts of dioctyl sulfosuccinic acid, sodium and potassium salts of lauryl sulfate, sodium and potassium salts of stearic acid , sodium and potassium salts of oleic acid, etc., but particularly preferred are sodium and potassium salts of dodecylbenzenesulfonic acid, sodium and potassium salts of β-naphthalenesulfonic acid, and sodium and potassium salts of lauryl sulfate. be done. The amount used is per 100 parts by weight of water.
The amount is 0.001 to 0.1 part by weight, preferably 0.01 to 0.05 part by weight. If the amount used is more than 0.1 part by weight, the amount of agglomerated polymer particles will increase, and the shape of the polymer particles will deteriorate; if the amount is less than 0.001%, the particle size of the polymer particles will become large and non-uniform. The desired fine polymer particles cannot be obtained. Water-soluble electrolytes include sodium chloride,
Potassium chloride, calcium chloride, lithium chloride,
Sodium sulfate, calcium sulfate, sodium nitrate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, potassium bromide, etc. can be used, but sodium chloride, potassium chloride, and calcium chloride are particularly preferred in appropriate amounts, based on 100 parts by weight of water. te 0.1～
2.0 parts by weight, preferably 0.3 to 1.0 parts by weight. If the amount used is more than 2.0 parts by weight, the solubility of polyvinyl alcohol in water will decrease, and the resulting polymer may solidify into a block shape.
When the amount is less than 0.1 part by weight, the particle size distribution of the polymer fine particles produced is wide, and aggregates of fine powder particles are mixed in. In the method of the present invention, the weight ratio of water to monomer can vary within the range of 1.0 to 5.0, but a ratio of 2.0 to 3.0 is preferred in order to obtain fine polymer particles with high uniformity. The method of the present invention can be carried out by stirring and polymerizing the monomer and the aqueous medium at a temperature of 70 to 120°C for 2 to 10 hours, preferably 3 to 6 hours, in the same manner as known suspension polymerization. The polymerization atmosphere may be either the air or a nitrogen atmosphere, but a nitrogen atmosphere is more preferable from the viewpoint of improving the polymerization rate. Further, the pressure of the polymerization system may be atmospheric pressure, or may be pressurized if necessary. As a polymerization initiator, known oil-soluble free radical polymerization initiators, such as organic peroxides such as benzoyl peroxide and lauroyl peroxide; azo initiators such as azobisisobutyronitrile; or benzoyl peroxide and Redox initiators such as dimethylaniline can be used. Thus, according to the method of the invention, a diameter of 10 to
resulting in a mixture of particles with a mean particle size of 150 μ and an average particle size of 40
It is possible to produce fine polymer particles having any particle size within the range of ~100μ and having high particle size uniformity. In addition, due to the decrease in polymerization stability in conventional suspension polymerization, it is difficult to perform polymerization without a chain transfer agent, that is, to obtain a polymer with a high degree of polymerization, or to polymerize by adding a crosslinking agent, that is, to obtain a three-dimensional polymer. However, in the method of the present invention, even without a chain transfer agent or in the presence of a small amount of a crosslinking agent,
It is possible to produce fine polymer particles of any particle size without any change in the fine polymer particle size or polymerization stability. The present invention will be specifically explained below using Examples.
Note that all parts in the examples are parts by weight. Example 1 300 parts of pure water and various parts of polyvinyl alcohol (molecular weight 2000, degree of saponification 85%), sodium dodecylbenzenesulfonate, and sodium chloride were charged into a stainless steel pressure-resistant reaction tank with an internal volume of 50, and stirred. Dissolve, then 100 parts of methyl methacrylate, 0.5 parts of lauroyl peroxide
After adding a mixture of 0.2 parts and 0.2 parts of n-dodecyl mercaptan, keeping the stirring speed at 100 rpm and replacing the air in the reaction tank with nitrogen, the reaction tank jacket was heated with hot water to cool the system. Polymerization was carried out for 2 hours while maintaining the temperature at 80°C. Subsequently, post-polymerization was carried out at 90°C for 1.5 hours, followed by washing with water and drying to obtain particles of various particle sizes. The results are shown in Table 1. Particle size distribution and average particle size are based on micrographs.

[Table] 5 each of polymer fine particles of Examples 1-1 to 1-9 above
When g was dissolved in 95 g of chloroform, everything was completely dissolved and the solution had good transparency. Example 2 350 parts of pure water, polyvinyl alcohol (molecular weight
3000, degree of saponification 95%), 0.35 parts, sodium dodecylbenzenesulfonate 0.08 parts, calcium chloride
Charge 1.7 parts into a reaction tank and dissolve with stirring, then add 60 parts of methyl methacrylate, 10 parts of methyl acrylate,
A mixed solution of 0.35 parts of lauroyl peroxide and 0.2 parts of n-dodecyl mercaptan was added. Thereafter, the polymerization was completed in the same manner as in Example 1. The fine particles obtained had a particle size distribution of 20-125μ, with an average particle size of 83μ. No emulsion polymers or irregularly shaped polymers were contained. Example 3 250 parts of pure water, polyvinyl alcohol (molecular weight
1250, saponification degree 90%), 0.15 parts of sodium lauryl sulfate, and 0.7 parts of sodium chloride were charged into a reaction tank, stirred and dissolved, and then methyl methacrylate
A mixed solution of 100 parts of methyl acrylate, 25 parts of lauroyl peroxide, and 0.75 parts of lauroyl peroxide was added. Thereafter, the polymerization was completed in the same manner as in Example 1. The obtained particles had a distribution of 20-130μ, with an average particle size of 89μ,
Even without the addition of a chain transfer agent, there was no effect on particle size or polymerization stability, and no aggregates or irregularly shaped polymers were contained. Example 4 250 parts of pure water, polyvinyl alcohol (molecular weight
2500, degree of saponification 80%) 0.15 parts, sodium β-naphthalene sulfonate 0.025 parts, sodium chloride 3.0
of the mixture was charged into a reaction tank and dissolved with stirring, and then a mixed solution of 113 parts of methyl methacrylate, 12 parts of ethyl acrylate, 0.6 parts of lauroyl peroxide, and 1.25 parts of allyl acrylate was added. Polymerization was then carried out in the same manner as in Example 1. The fine particles obtained were 15
The average particle size was 65μ with a distribution of ~105μ. Despite the addition of a crosslinking agent, there was no change in bead particle size or polymerization stability, and no aggregates or irregularly shaped polymers were contained. When 5 g of the obtained beads were dissolved in 95 g of chloroform, they completely gelled and did not dissolve. A special use of this cross-linked polymer fine particles is to use ordinary acrylic beads80.
% by weight and 20% by weight of the resulting cross-linked polymer beads
When a prototype extruded board was made by mixing the two, the light was diffusely reflected and a distinctive decorative lighting louver was obtained. Example 5 300 parts of pure water, polyvinyl alcohol (molecular weight
2000, degree of saponification 95%) 0.06 part, sodium dodecylbenzenesulfonate 0.006 part, sodium sulfate
0.5 part was charged into a reaction tank and dissolved with stirring, followed by 95 parts of methyl methacrylate and 5 parts of n-butyl acrylate.
After adding a mixture of 0.7 parts of benzoyl peroxide, and 0.2 parts of n-dodecyl mercaptan, and keeping the stirring speed at 120 rpm and replacing the air in the reaction tank with nitrogen, the reaction tank jacket was flushed with warm water. The system was heated at 75°C and polymerized for 3 hours. This was then post-polymerized at 95°C for 1.5 hours. The obtained fine polymer particles were washed with water and dried, and the particle size distribution was measured using a microscopic photograph, and found to have a distribution of 15 to 95μ, with an average particle size of 56μ. No emulsion polymers or irregular polymers were contained. Example 6 240 parts of pure water, polyvinyl alcohol (molecular weight
2500, degree of saponification 90%) 0.24 part, sodium β-naphthalene sulfonate 0.15 part, calcium chloride 0.48
144 parts of methyl methacrylate, 8 parts of methyl acrylate, 8 parts of n-butyl acrylate, 0.8 parts of lauroyl peroxide, and 0.25 parts of n-dodecyl mercaptan were added. . Thereafter, the polymerization was completed in the same manner as in Example 5. The obtained polymer beads are 10~
It had a distribution of 140μ and an average particle size of 93μ. No emulsion polymers or irregular polymers were contained.

Claims (1)

[Claims] 1 When polymerizing a monomer mixture consisting of 100 to 80% by weight of methyl methacrylate and 0 to 20% by weight of alkyl acrylate having an alkyl group having 1 to 8 carbon atoms in an aqueous medium, mainly 100 parts by weight of water, polymerization Polyvinyl alcohol with a degree of 1000 to 3000, saponification degree of 80% or more, 0.01 to 0.3 parts by weight, anionic surfactant
0.001~0.1 parts by weight and 0.1~ water soluble electrolyte
A method for producing fine polymer particles, characterized by using an aqueous medium consisting of 2.0 parts by weight.