JP3149487B2 - Method for producing methacrylic resin particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Methacrylic resins are widely used in various fields as materials for various molded articles, utilizing 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.

[0003] 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 to obtain polymer particles having a desired particle size and a narrow particle size distribution. I have.

For example, in Japanese Patent Publication No. 58-27283, polyethylene oxide having an average molecular weight of 100,000 or more is added as a suspension stabilizer at a specific ratio to obtain styrene and methyl methacrylate copolymer particles having extremely uniform particle sizes. It has been shown.

JP-A-1-46910 discloses a suspension stabilizer having a degree of polymerization of 1500 or more and a degree of caking of 75 to 85.
A method for obtaining spherical polymer fine particles of methacrylate using mol% of polyvinyl alcohol is disclosed.

JP-A-1-266104 discloses that sodium polyacrylate, sodium polymethacrylate, or a sodium methacrylate-alkyl methacrylate copolymer is used as a suspension stabilizer, and methacrylic acid is used. A method is disclosed in which an ester, an acrylate ester, and an aromatic vinyl compound are pre-dispersed by high-speed shearing and then subjected to suspension polymerization to produce a particulate polymer.

[0007] Japanese Patent Application Laid-Open No. 1-172412 discloses that a suspension stabilizer contains a sulfonic acid group, a carboxyl group, or
Using high-molecular compounds having an alkali metal salt and an electrolyte having a monovalent cation, and an electrolyte having a divalent or trivalent cation, acrylic and aromatic vinyl monomers are stirred at high speed. After microdispersed, charged in a reaction vessel and polymerized under stirring, an electrolyte having a monovalent, divalent, or trivalent cation is further added to the polymerization reaction product to secondarily collect polymer particles. Is shown.

[0008]

For some time, methacrylic resin particles having a size of several μm to 100 μm have been demanded for use in toners, paints, cosmetics, resin light diffusing agents and surface modifiers. . However, among the conventionally proposed methods of obtaining methacrylic resin particles by suspension polymerization, Japanese Patent Publication No.
The method described in JP-A-27283 discloses that the particle size is 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.

In 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 sufficiently remove it. Further, the remaining polyvinyl alcohol causes coloring in a post-process such as molding.

In the method of JP-A-1-266104, a step of pre-dispersing a mixture in which a polymer is dissolved in a monomer is added, and the operation becomes complicated by adding such a step. .

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

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

[0013]

SUMMARY OF THE INVENTION The present invention provides a method for producing methacrylic resin particles by suspension polymerization of a monomer containing methyl methacrylate as a main component in an aqueous medium. As an agent, a poly (meth) acrylic acid alkali metal salt having a molecular weight of 1,000,000 to 20,000,000 is added to an aqueous medium at a concentration of 0.001 to 20% by weight and a molecular weight of 1,000 to 1,000.
A method for producing methacrylic resin particles, wherein 30,000 polyoxyethylene polyoxypropylene ethers are used 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,
Methacrylates 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 Ronitrile, vinyl acetate, acrylamide, maleimides, and the like are included. Further, as a polyfunctional monomer, ethylene glycol dimethacrylate,
1,4-butanediol dimethacrylate, 1,6-
Difunctional monomers such as hexanediol dimethacrylate, allyl methacrylate, allyl cinnamate, divinylbenzene, etc .; trifunctional monomers such as trimethylolpropane triacrylate, triallyl trimellitate, diallyl maleate; and Examples 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) acrylate as the suspension stabilizer used in the present invention is an alkali metal salt of polymethacrylic acid and / or polyacrylic acid. Polymer I, Showa 53
Synthesized using a method described on page 264 issued by Maruzen Co., Ltd. on May 20, 2011, and has a number average molecular weight of 1,000,000 or more.
Use about 20 million. Examples of the alkali metal include K, Na, and Li. The amount of the suspension stabilizer comprising the alkali metal salt of poly (meth) acrylic acid 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. You. 0.0
Below 01 polymerization part, the polymerization system becomes unstable. If the amount exceeds 2.0 parts by weight, a fine granular polymer is formed, the particle size distribution is widened, and the amount remaining on the particle surface increases, which is not preferable.

The 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 1,000. 3,000 to 20,000, preferably 5000 to 20,000 so-called nonionic surfactants. And (a + b) / (a + b + c) is 0.05
-0.95, preferably 0.5-0.9. If the molecular weight is too small, the protective power when adsorbed on the droplets will be weak. If the ratio of the polyoxyethylene chains in the molecule is too small, the suspension stability will be 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 composed of polyoxyethylene polyoxypropylene ether 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 is small as long as a desired particle size can be obtained. 0.0
When the amount is less than 1 polymerization part, the particle size does not become 100 μm or less,
If the amount exceeds 5.0 parts by weight, a fine particulate polymer is formed, the particle size distribution is widened, the particle surface is contaminated, and the amount of the suspension stabilizer attached to the polymer particles increases.

As a method of adding the suspension stabilizer, both an alkali metal salt of poly (meth) acrylate and polyoxyethylene polyoxypropylene ether are added in a predetermined amount before the initiation of polymerization to form an aqueous medium. Is also good. In addition, if necessary, a part of the suspension stabilizer may be appropriately divided and added during the polymerization.

A suspension aid can 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 hydrogen phosphate, dihydrogen phosphate. And inorganic salts such as sodium and sodium sulfate. Among them, an inorganic salt serving as a PH buffering agent is preferable. These are used in an amount of 0.01 to 2.0% by weight based on the weight of the monomer.
Range. The suspension aid may be added at the beginning of the polymerization or simultaneously with the addition of the polymerization stabilizer.

The ratio of aqueous medium to monomer or monomer mixture ranges from 1: 1 to 10: 1, preferably from 1: 1 to 4: 1. If the amount of the aqueous medium is too small, the dispersion of the monomer tends to be uneven and the polymerization system becomes unstable. If the amount is too 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 any of those known for polymerizing vinyl monomers. For example, 2,2 'azobis (2,4 dimethylvaleronitrile), azobisisobutyronitrile,
Azo compounds such as dimethyl 2,2 ′ azobisisobutyrate; peroxy esters such as tertiary butyl peroxypivalate, tertiary butyl peroxy 2-ethylhexanoate, cumylperoxy 2-ethylhexanoate; Organic peroxides of diacyl peroxides such as 8,5,5 trimethylhexanoyl peroxide and dilauroyl peroxide can be exemplified, and one or more of these are used. These polymerization initiators are used in an amount of 0.02 to 2% by weight based on the monomer or the monomer mixture.

In the production method of the present invention, a known chain transfer agent may be used in order to adjust 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 coloring agents, ultraviolet absorbers, color stabilizers, plasticizers, lubricants and various fillers suitable for the intended use may be mixed and used.

The polymerization is carried out at a temperature of about 60 to 120 ° C., which is suitable for the polymerization initiator used.

The stirring conditions may be the conditions for producing a methacrylic resin by ordinary suspension polymerization. As the apparatus, a polymerization vessel equipped with a stirrer having a well-known stirring blade such as a turbine blade, a Faudler blade, a propeller blade, a blue margin blade, etc. is used, and the vessel is generally equipped with a baffle. .

After completion of the suspension polymerization, washing is performed by a well-known method,
Dehydration and drying give 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. Can be. The obtained methacrylic resin particles are suitably used for applications utilizing the characteristics of small particle size particles such as general molding materials, light diffusing agents, dye matting agents, cosmetic base materials, and toners.

[0028]

Next, the present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. In addition, the polymer particle diameter in an Example is a light-diffraction scattering particle diameter measuring device (Malvern Co., Ltd., Mastersizer).
Was measured. Here, D ₅₀ is the particle diameter at a cumulative 50% weight, D ₉₀ is the particle diameter at a cumulative 90% weight, and D ₁₀ is the cumulative 10% weight.
%, And the particle size distribution was evaluated.

Example 1 A glass container having an inner volume of 2 L was charged with 1200 g of ion-exchanged water.
0.25 g of polysodium methacrylate (molecular weight of about 7,000,000 obtained by polymerizing methacrylic acid manufactured by Wako Pure Chemical Industries, Ltd. by the method described above) and a molecular weight of 8350 as a suspension stabilizer;
After charging 2.5 g of polyoxyethylene polyoxypropylene ether (Pluronic F68 manufactured by Asahi Denka) 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 380 g of methyl methacrylate, 17 g of methyl acrylate, ethylene glycol dimethacrylate 2
g, lauroyl peroxide 0.8 g, and n-dodecyl mercaptan 1.5 g. Then, while stirring at 800 rpm, polymerization was carried out at 75 ° C. for 2 hours and further at 100 ° C. for 1 hour. At this time, 0.5 g of Pluronic F68 was continuously added while the polymerization rate was 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, ethylene glycol dimethacrylate 2
g, lauroyl peroxide 1.5 g, and the same procedure as in Example 1 was carried out. D ₅₀ 30 μm, D ₉₀ 5
Spherical polymer particles of 8 μm and 14 μm of D ₁₀ were obtained.

Example 3 Example 3 was carried out in the same manner as in Example 1, 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, the amount of Pluronic F68 was 1.2 g, and the polymerization rate was 12 to 100%.
The procedure was performed in the same manner as in Example 1 except that 0.4 g of sodium polymethacrylate was continuously added. The resulting beads were D ₅₀ = 50 μm, D ₉₀ = 100 μm, D ₁₀ = 15
μm.

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

Example 6 1900 g of ion-exchanged water was placed in a glass container having an internal volume of 5 L.
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, and ethylene glycol 1 dimethacrylate
A monomer mixture consisting of 0 g, 5 g of lauroyl peroxide and 7 g of n-dodecyl mercaptan was charged. Then, while stirring at 1300 rpm, polymerization was performed at 75 ° C. for 2 hours and further at 100 ° C. for 1 hour. After polymerization, washing, dehydration and drying were performed, and D ₅₀ = 26 μm and D ₉₀ = 52 μm
m, D ₁₀ = 11 μm spherical polymer particles were obtained.

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

Example 8 In a glass container having an inner volume of 2 L, 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. After charging
240 g of methyl methacrylate, 10 methyl acrylate
g, 1.5 g of ethylene glycol dimethacrylate, 0.8 g of lauroyl peroxide, and 1 g of n-dodecyl mercaptan. And 4
While stirring at 40 rpm, at 75 ° C. for 2 hours, further 1 hour
Polymerization was carried out at 00 ° C. for 1 hour. After polymerization, washing, dehydration, and drying were performed, and D ₅₀ = 20 μm, D ₉₀ = 40 μm,
₁₀ = 8 µm spherical polymer particles were obtained.

Comparative Example 1 The procedure of Example 8 was repeated, except that 5 g of sodium polymethacrylate was used as a suspension stabilizer and no Pluronic F68 was charged. As a result, the polymerization system became unstable during the polymerization, and polymer particles could not be obtained.

Comparative Example 2 In Example 6, Pluronic F6 was used as a suspension stabilizer.
8 was performed in the same manner as in Example 6, except that 25 g was used and sodium polymethacrylate was not charged. The result was interrupted because the suspension was destroyed during the polymerization and separated into two phases.

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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08F 2/18-2/20

Claims (1)

(57) [Claims] 1. A method for producing methacrylic resin particles by subjecting a monomer containing methyl methacrylate as a main component to suspension polymerization in an aqueous medium, and having a molecular weight of 1,000,000 to 2,000 as a suspension stabilizer. Of poly (meth) acrylic acid in an aqueous medium at a concentration of 0.001-2.0.
A method for producing methacrylic resin particles, comprising using a polyoxyethylene polyoxypropylene ether having a molecular weight of 1,000 to 30,000 by weight and an aqueous medium concentration of 0.01 to 5.0% by weight.