JPH05155907A - Production of methacrylic resin particle - Google Patents

Abstract

PURPOSE:To obtain methacrylic resin particles having particle diameters of 5-100mum through suspension polymerization. CONSTITUTION:A monomer consisting mainly of methyl methacrylate is suspension-polymerized in an aqueous medium using, as suspension stabilizers, 0.001-2wt.% alkali metal salt of (meth)acrylic acid homopolymer having a mol.wt. of 1,000,000-20,000,000 and 0.01-5wt.% polyoxyethylene polyoxypropylene ether having a mol.wt. of 1,000-30,000, thereby obtaining the desired particles.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing methacrylic resin particles by suspension polymerization.

[0002]

2. Description of the Related Art A methacrylic resin is widely used in various fields as a material for various molded products by taking advantage of its characteristics such as transparency, gloss, surface hardness, weather resistance and mechanical properties. Also,
Spherical resin particles having a small particle size are used in high value-added fields such as toners, paints, light diffusing agents, and cosmetics.

The particles of methacrylic resin are usually produced by suspension polymerization. However, in general suspension polymerization, it is difficult to obtain particles having a particle size of 100 μm or less, and various suspension polymerization methods have been proposed in order to obtain polymer particles having a desired particle size and a narrow particle size distribution. There is.

For example, in JP-B-58-27283, as a suspension stabilizer, polyethylene oxide having an average molecular weight of 100,000 or more is added in a specific ratio to obtain styrene and methyl methacrylate copolymer particles having extremely uniform particle diameters. Has been shown.

Japanese Patent Laid-Open No. 1-146910 discloses a suspension stabilizer having a polymerization degree of 1500 or more and a saponification degree of 75 to 85.
A method for obtaining spherical polymer particles of methacrylic acid ester by using mol% of polyvinyl alcohol is shown.

JP-A-1-266104 discloses that, as a suspension stabilizer, sodium polyacrylate, sodium polymethacrylate, or sodium methacrylate-alkyl methacrylate copolymer is used, and methacrylic acid is used. A method for producing a fine particle polymer by subjecting an ester, an acrylate ester, and an aromatic vinyl compound to high-speed shearing for preliminary dispersion and then suspension polymerization is disclosed.

Japanese Patent Laid-Open No. 1-172412 discloses a suspension stabilizer containing a sulfonic acid group, a carboxyl group, or
By using a polymer compound having an alkali metal salt thereof, an electrolyte having a monovalent cation, and an electrolyte having a divalent or trivalent cation, an acrylic vinyl monomer and an aromatic vinyl monomer are rapidly stirred. Polymer particles that are finely dispersed, charged in a reaction vessel, polymerized under stirring, and then secondary-assembled by adding an electrolyte having a monovalent, divalent, or trivalent cation to the polymerization reaction product Is shown.

[0008]

For some time, methacrylic resin particles having a particle size of several .mu.m to 100 .mu.m have been desired for use as toners, paints, cosmetics, light diffusing agents for resins, surface modifiers and the like. .. However, among the conventionally proposed methods for obtaining methacrylic resin particles by suspension polymerization, Japanese Patent Publication No.
The method described in JP-A-27283 has a particle size of 500 μm to 100 μm.
It is suitable for producing polymer particles having a relatively large particle size of about 0 μm, and it is difficult to obtain polymer particles of 100 μm or less.

According to the method disclosed in JP-A 1-146910, polyvinyl alcohol used as a suspension stabilizer is adsorbed on polymer particles and it is difficult to remove it sufficiently. In addition, the remaining polyvinyl alcohol causes coloring in a post process such as molding.

In the method disclosed in JP-A-1-266104, a step of predispersing a mixture in which a polymer is dissolved in a monomer is added, and the addition of such a step makes the operation complicated. ..

In the method disclosed in Japanese Patent Application Laid-Open No. 1-172412, the suspension stabilizer system is complicated, and the step of preliminarily dispersing the monomer by high-speed stirring is added, and the operation is complicated.

Therefore, a range of several μm to 100 μm, which is an intermediate range between the particle sizes obtained by the general suspension polymerization method and the emulsion polymerization method.
There is provided a method for obtaining the methacrylic resin particles by the suspension polymerization method without a complicated operation.

[0013]

Means for Solving the Problems The present invention provides a suspension stability method for producing methacrylic resin particles by suspension-polymerizing a monomer containing methyl methacrylate as a main component in an aqueous medium. As an agent, an alkali metal salt of poly (meth) acrylic acid having a molecular weight of 1 to 20 million and an aqueous medium concentration of 0.001 to 20% by weight and a molecular weight of 1000 to
A method for producing methacrylic resin particles, which comprises using 30,000 polyoxyethylene polyoxypropylene ether in an aqueous medium concentration of 0.01 to 5.0% by weight.

The monomer containing methyl methacrylate as a main component in the present invention is methyl methacrylate alone or a mixture of other vinyl monomers copolymerizable with methyl methacrylate. Other vinyl monomers copolymerizable with methyl methacrylate include ethyl methacrylate, propyl methacrylate, butyl methacrylate,
Methacrylic acid esters such as cyclohexyl methacrylate, lauryl methacrylate, benzyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, acrylic acid Acrylic esters such as benzyl, aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, monochlorostyrene, dichlorostyrene, methacrylic acid, acrylic acid, maleic acid, fumaric acid, cinnamic acid, acrylonitrile methacrylic acid. Examples include ronitrile, vinyl acetate, acrylamide, and maleimides. Further, as a polyfunctional monomer, ethylene glycol dimethacrylate,
1,4-butanediol dimethacrylate, 1,6-
Hexanediol dimethacrylate, allyl methacrylate, allyl cinnamate, divinylbenzene and other bifunctional monomers, trimethylolpropane triacrylate, trimellitate triallyl, diallyl maleate and other trifunctional monomers, and Examples thereof include tetrafunctional monomers such as pentaerythritol tetraacrylate. These vinyl monomers can be used alone or in combination of two or more.

The alkali metal salt of poly (meth) acrylic acid as the suspension stabilizer used in the present invention is an alkali metal salt of polymethacrylic acid and / or polyacrylic acid, for example, "New Experimental Chemistry Course 19, Polymer I, Showa 53
Published on Mar. 20, 2010, by the method described in page 264 of Maruzen Co., Ltd., and the number average molecular weight is 1,000,000 to
Use about 20 million. Examples of the alkali metal include K, Na and Li. The amount of the suspension stabilizer comprising an alkali metal salt of poly (meth) acrylic acid used is selected from the range of 0.001 to 2.0% by weight, preferably 0.01 to 0.5% by weight in the aqueous medium. It 0.0
Below 01 polymerized parts, the polymerization system becomes unstable. If it exceeds 2.0 parts by weight, a fine granular polymer is produced, the particle size distribution is broadened, and more of the particles remain on the particle surface, which is not preferable.

Polyoxyethylene polyoxypropylene ether is represented by the general formula HO (C ₂ H ₄ O) _a- (C ₃ H ₆ O) _b- (C ₂ H ₄ O) _c H and has a molecular weight of 1000. To 30,000, preferably 5000 to 20000, so-called nonionic surfactants. And (a + b) / (a + b + c) is 0.05
-0.95 It is 0.5-0.9 preferably. If this molecular weight is too small, the protective power when adsorbed on the droplets becomes weak. If the ratio of polyoxyethylene chains in the molecule is too small, the suspension stability becomes poor. This polyoxyethylene polyoxypropylene ether is commercially available from Asahi Denka Co., Ltd. as Pluronic and from Sanyo Chemical Co., Ltd. as Newpol PE.

The amount of the suspension stabilizer comprising polyoxyethylene polyoxypropylene ether used is selected from the range of 0.01 to 5.0% by weight, preferably 0.1 to 2.0% by weight in the aqueous dispersion. However, it is preferable that the polymerization system is stable and the amount thereof is small as long as a desired particle size is obtained. 0.0
Below 1 polymerization part, the particle size does not fall below 100 μm,
If it exceeds 5.0 parts by weight, a fine granular polymer is produced, the particle size distribution is widened, the particle surface is contaminated, and more suspension stabilizers are attached to the polymer particles.

As a method for adding the suspension stabilizer, both the poly (meth) acrylic acid alkali metal salt and the polyoxyethylene polyoxypropylene ether are added in a predetermined amount before the polymerization is started to form an aqueous medium. Good. Further, if necessary, a part of the suspension stabilizer may be appropriately divided and added during the polymerization.

A suspension aid can also be used in combination with the suspension stabilizer. Here, the suspension aid is an anionic surfactant such as sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate: sodium carbonate, disodium hydrogenphosphate, dihydrogenphosphate. Inorganic salts such as sodium and sodium sulfate. Of these, inorganic salts that serve as PH buffers are preferred. The amount of these used is 0.01 to 2.0% by weight with respect to the monomer.
The range is. The suspension aid may be added at the initial stage of polymerization or simultaneously with the addition of the polymerization stabilizer.

The ratio of aqueous medium to monomer or monomer mixture is in the range 1: 1 to 10: 1, preferably 1: 1 to 4: 1. When the amount of the aqueous medium is too small, the dispersion of the monomer tends to be non-uniform and the polymerization system becomes unstable. When the amount is large, it is disadvantageous in terms of production efficiency.

In the suspension polymerization of the present invention, a polymerization initiator is used. This polymerization initiator may be a well-known one for polymerization of vinyl monomers. For example, 2,2'azobis (2,4dimethylvaleronitrile), azobisisobutyronitrile,
Azo compounds such as dimethyl 2,2′azobisisobutyrate; peroxyesters such as tertiary butyl peroxypivalate, tertiary butyl peroxy 2-ethylhexanoate, cumylperoxy 2-ethylhexanoate; Examples thereof include organic peroxides of diacyl peroxides such as 8,5,5 trimethylhexanoyl peroxide and dilauroyl peroxide, and one kind or two or more kinds thereof are used. The amount of these polymerization initiators used is 0.02 to 2% by weight based on the monomer or monomer mixture.

In the production method of the present invention, a well-known chain transfer agent may be used to control the molecular weight of the polymer. Examples of the chain transfer agent include alkyl mercaptan, alkyl sulfide, alkyl disulfide, thioglycolic acid ester, and α-methylstyrene dimer.

Further, additives such as a colorant, an ultraviolet absorber, a color stabilizer, a plasticizer, a lubricant and various fillers suitable for the purpose may be mixed and used.

The temperature condition for the polymerization may be about 60 to 120 ° C. and a temperature suitable for the polymerization initiator used.

The stirring conditions may be the same as those used in producing a methacrylic resin by ordinary suspension polymerization. As the apparatus, a polymerization vessel equipped with a well-known stirring blade, such as a turbine blade, a Fowler blade, a propeller blade, and a blue margin blade is used, and a baffle is generally attached to the vessel. ..

After completion of the suspension polymerization, washing by a known method,
Dehydrated and dried to obtain a granular polymer.

[0027]

According to the production method of the present invention, methacrylic resin particles having a particle size range of several μm to 100 μm, which are difficult to produce by ordinary suspension polymerization, can be easily obtained by using a specific suspension stabilizer. You can The obtained methacrylic resin particles are suitably used in applications such as general molding materials, light diffusing agents, dye matting agents, cosmetic base materials, and toners that take advantage of the characteristics of small particle size particles.

[0028]

The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the invention. The polymer particle size in the examples is a light diffraction / scattering particle size measuring device (Malvern Co., Ltd., Mastersizer).
It was measured at. Here, D ₅₀ is a cumulative particle size of 50% by weight, D ₉₀ is a cumulative particle size of 90% by weight, and D ₁₀ is a cumulative particle size of 10.
The particle size was evaluated by setting the particle size as% by weight.

Example 1 In a glass container having an internal volume of 2 L, 1200 g of ion-exchanged water,
As a suspension stabilizer, 0.25 g of sodium polymethacrylate (a molecular weight of about 7 million obtained by polymerizing methacrylic acid manufactured by Wako Pure Chemical Industries, Ltd. by the above-mentioned method) and a molecular weight of 8350,
After charging 2.5 g of polyoxyethylene polyoxypropylene ether (Pluronic F68 manufactured by Asahi Denka Co., Ltd.) having an ethylene oxide ratio of 80% by weight in the molecule, 1.2 g of disodium hydrogen phosphate and 1.2 g of sodium dihydrogen phosphate. , Methyl methacrylate 380 g, methyl acrylate 17 g, ethylene glycol dimethacrylate 2
g, lauroyl peroxide 0.8 g, and n-dodecyl mercaptan 1.5 g were charged. Then, polymerization was carried out at 75 ° C. for 2 hours and further at 100 ° C. for 1 hour while stirring at 800 rpm. At this time, 0.5 g of Pluronic F68 was continuously added during the polymerization rate of 12 to 100%. After polymerization, washing,
After dehydration and drying, D ₅₀ 30 μm, D ₉₀ 60 μm, D ₁₀
13 μm spherical polymer particles were obtained.

Example 2 As a monomer mixture, 300 g of methyl methacrylate, 100 g of styrene, and ethylene glycol dimethacrylate 2
g, and lauroyl peroxide (1.5 g) were carried out in the same manner as in Example 1, except that D ₅₀ 30 μm and D ₉₀ 5
Spherical polymer particles of 8 μm and D ₁₀ 14 μm were obtained.

Example 3 The procedure of Example 1 was repeated, except that the amount of Pluronic F68 added at the time of charging the aqueous phase was 5 g and continuous addition was not performed. The obtained beads had D ₅₀ = 25 μm, D ₉₀ = 56 μm, and D ₁₀ = 10 μm.

Example 4 In Example 1, the amount of sodium polymethacrylate initially charged was 0.4 g and the amount of Pluronic F68 was 1.2 g, and the polymerization rate was between 12 and 100%.
The same procedure as in Example 1 was repeated except that 0.4 g of sodium polymethacrylate was continuously added. The obtained beads had D ₅₀ = 50 μm, D ₉₀ = 100 μm, and D ₁₀ = 15.
was μm.

Example 5 In Example 1, the amount of sodium polymethacrylate initially charged was 0.36 g and the amount of Pluronic F68 was 1.2 g, and when the polymerization rate was 60%, 0.12 g was added.
The same procedure as in Example 1 was performed except that g of sodium polymethacrylate was added. The beads obtained are D ₅₀
= 50 μm, D ₉₀ = 126 μm, D ₁₀ = 11 μm.

Example 6 In a glass container having an internal volume of 5 L, 1900 g of ion-exchanged water,
7 g of sodium polymethacrylate as a suspension stabilizer,
After charging 20 g of Pluronic F68, 2 g of disodium hydrogen phosphate and 2 g of sodium dihydrogen phosphate, 1500 g of methyl methacrylate, 65.0 g of methyl acrylate, ethylene glycol 1 of dimethacrylate
A monomer mixture consisting of 0 g, 5 g lauroyl peroxide and 7 g n-dodecyl mercaptan was charged. Then, polymerization was carried out at 75 ° C. for 2 hours and further at 100 ° C. for 1 hour while stirring at 1300 rpm. After the polymerization, washing, dehydration and drying are carried out, and D ₅₀ = 26 μm, D ₉₀ = 52 μm.
m, D ₁₀ = 11 μm spherical polymer particles were obtained.

Example 7 In a glass container having an internal volume of 5 L, 2150 g of ion-exchanged water,
Sodium polymethacrylate 7.5 as suspension stabilizer
g, Pluronic F68 15 g, and sodium dihydrogen phosphate 7 g, and then methyl methacrylate 1700
g, 100 g of methyl acrylate, 3 g of n-dodecyl mercaptan, and 5.5 g of lauroyl peroxide were charged. Then, polymerization was carried out at 84 ° C. for 1.5 hours and at 100 ° C. for 1 hour while stirring at 1300 rpm. After polymerization, washing, dehydration and drying are performed to obtain D ₅₀
= 70 μm, D ₉₀ = 130 μm, D ₁₀ = 35 μm, spherical polymer particles were obtained.

Example 8 950 g of ion-exchanged water, 1 g of sodium polymethacrylate as a suspension stabilizer, and 10 g of Pluronic F68, 1 g of disodium hydrogen phosphate and 1 g of sodium dihydrogen phosphate were placed in a glass container having an internal volume of 2 L. After charging
240 g of methyl methacrylate, methyl acrylate 10
g, 1.5 g of ethylene glycol dimethacrylate, 0.8 g of lauroyl peroxide, and 1 g of n-dodecyl mercaptan were charged. And 4
Stir at 40 rpm for 2 hours at 75 ° C, then 1
Polymerization was carried out at 00 ° C. for 1 hour. After the polymerization, washing, dehydration and drying are carried out, D ₅₀ = 20 μm, D ₉₀ = 40 μm, D
Spherical polymer particles of ₁₀ = 8 μm were obtained.

Comparative Example 1 The procedure of Example 8 was repeated, except that 5 g of sodium polymethacrylate was used as the suspension stabilizer and Pluronic F68 was not charged. As a result, during the polymerization, the polymerization system became unstable and polymer particles could not be obtained.

Comparative Example 2 Pluronic F6 was used as a suspension stabilizer in Example 6.
Example 8 was carried out in the same manner as in Example 6 except that 8 g was set to 25 g and sodium polymethacrylate was not charged. The result was interrupted because the suspension system was destroyed during the polymerization and the two phases were separated.

Comparative Example 3 In Example 6, 0.1% of Pluronic F68 was added to the aqueous phase.
It carried out by the same method as Example 6 except having charged g.
After the polymerization, washing, dehydration and drying are performed, and D ₅₀ = 350 μm,
Granular polymer particles having D ₉₀ = 680 μm and D ₁₀ = 130 μm were obtained.

Claims (1)

[Claims] 1. When a methacrylic resin particle is produced by suspension-polymerizing a monomer containing methyl methacrylate as a main component in an aqueous medium, a suspension stabilizer has a molecular weight of 1,000,000 to 2,000. Tens of thousands of alkali metal salts of poly (meth) acrylic acid are added to the aqueous medium at a concentration of 0.001 to 2.0.
%, And polyoxyethylene polyoxypropylene ether having a molecular weight of 1,000 to 30,000 is used in an aqueous medium concentration of 0.01 to 5.0% by weight, and a method for producing methacrylic resin particles.