JP2013049873A - Methacrylic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a methacrylic resin composition excellent in flowability, heat resistance, mechanical strength and transparency.SOLUTION: This methacrylic resin composition includes a copolymer (1) having a methyl methacrylate unit (a) and an alkyl (meth)acrylate unit (b) other than methyl methacrylate and having 50,000-250,000 weight-average molecular weight; and a copolymer (2) having a methyl methacrylate unit (a) and an alkyl (meth)acrylate unit (b) other than methyl methacrylate and having 6,000-40,000 weight-average molecular weight; includes neither dispersion stabilizer nor emulsifier; where the mass fraction of the unit (b) included in the copolymer (1) is less than the mass fraction of the unit (b) included in the copolymer (2).

Description

  The present invention relates to a methacrylic resin composition excellent in fluidity, heat resistance, mechanical strength and transparency.

  Methacrylic resin compositions are used in various fields because of their excellent transparency and weather resistance. Recently, a methacrylic resin composition molded into an arbitrary shape has been widely used as an optical component such as a light guide plate, various video lenses, and optical lenses.

  In recent years, optical components have become larger, and there are increasing opportunities for them to be produced by injection molding or extrusion molding. Furthermore, in order to increase the productivity, it is preferable that the molding cycle in the molding of optical components is short, and in order to shorten the cooling time until the heat-melted resin is solidified, further flow of the resin so that it can be molded at a low temperature. There is a tendency to improve performance.

  In addition, methacrylic resin compositions are also used in vehicle lamp lenses and the like because of their excellent transparency and weather resistance. In that case, improvement in chemical resistance by various chemicals is desired. Yes. In a methacrylic resin composition, it is common to improve chemical resistance by increasing the molecular weight, but in this case, there is a problem that fluidity is lowered and moldability is deteriorated.

  Various studies have been made on methods for improving the fluidity of methacrylic resin compositions. For example, Patent Documents 1 and 2 describe a method of mixing acrylic copolymers having different molecular weights.

JP 58-101140 A JP 2006-193647 A

  However, the methods described in any of the patent documents are insufficient in transparency because they are mixed with a suspension polymerized copolymer using a dispersion stabilizer.

  An object of the present invention is to provide a methacrylic resin composition excellent in fluidity, heat resistance, mechanical strength and transparency.

The gist of the present invention is as follows:
A copolymer (1) comprising a unit (a) of methyl methacrylate and a unit (b) of an alkyl (meth) acrylate other than methyl methacrylate, and having a weight average molecular weight of 50,000 to 250,000,
A copolymer (2) comprising a unit (a) of methyl methacrylate and a unit (b) of an alkyl (meth) acrylate other than methyl methacrylate, and having a weight average molecular weight of 6,000 to 40,000. Contains neither stabilizers nor emulsifiers,
The present invention relates to a methacrylic resin composition in which the mass fraction of the unit (b) contained in the copolymer (1) is smaller than the mass fraction of the unit (b) contained in the copolymer (2).

  According to the present invention, it is possible to provide a methacrylic resin composition excellent in fluidity, heat resistance, mechanical strength, and transparency.

  Hereinafter, the present invention will be described more specifically.

  The present invention relates to a methacrylic resin composition containing two types of copolymers having a methyl methacrylate unit (a) and an alkyl (meth) acrylate unit (b) other than methyl methacrylate. This copolymer can be obtained by copolymerizing methyl methacrylate and an alkyl (meth) acrylate other than methyl methacrylate. “(Meth) acrylate” means methacrylate or acrylate.

  The alkyl group in the alkyl acrylate copolymerizable with methyl methacrylate is preferably selected from alkyl groups having 1 to 18 carbon atoms, such as methyl, ethyl, n-propyl, n-butyl, 2-ethylhexyl, and dodecyl. , Stearyl and the like. The alkyl group in the alkyl methacrylate copolymerizable with methyl methacrylate is preferably selected from alkyl groups having 2 to 18 carbon atoms, such as ethyl, n-propyl, n-butyl, 2-ethylhexyl, dodecyl, stearyl. Etc.

  As the copolymer, a copolymer of methyl methacrylate and an alkyl acrylate selected from methyl acrylate, ethyl acrylate, and n-butyl acrylate is preferable.

  The copolymer may further have another monomer unit (c). Examples of other monomers forming the unit (c) include styrene, α-methylstyrene, acrylonitrile, methacrylonitrile and the like. The mass fraction of the other monomer units (c) is preferably 0 to 30% by mass.

  The methacrylic resin composition of the present invention has a weight average molecular weight of 50,000 to 250,000 [copolymer (1)] and a weight average molecular weight of 6,000 to 40,000 among the above copolymers. It contains two types: [Copolymer (2)]. In such a methacrylic resin composition, the heat resistance and mechanical strength can be maintained by the copolymer (1) having a large molecular weight, and the fluidity can be secured by the copolymer (2) having a small molecular weight. When the weight average molecular weight of the copolymer (1) is less than 50,000, the heat resistance and mechanical strength of the resulting methacrylic resin composition are lowered. When the weight average molecular weight of the copolymer (1) is larger than 250,000, the fluidity of the resulting methacrylic resin composition is lowered. When the weight average molecular weight of the copolymer (2) is smaller than 66,000, the heat resistance of the resulting methacrylic resin composition is extremely lowered. When the weight average molecular weight of the copolymer (2) is larger than 40,000, the advantage of mixing the copolymer (2) becomes small. The weight average molecular weight of the copolymer (1) is preferably 50,000 to 250,000, and more preferably 60,000 to 200,000. The weight average molecular weight of the copolymer (2) is preferably from 6,000 to 40,000, and more preferably from 7,000 to 30,000.

  In the methacrylic resin composition of the present invention, the mass fraction of the unit (b) contained in the copolymer (1) is smaller than the mass fraction of the unit (b) contained in the copolymer (2). The reason why this is preferable is as follows.

  When alkyl methacrylate (meth) acrylate other than methyl methacrylate is copolymerized with methyl methacrylate, the fluidity of the copolymer is improved, but the heat resistance (softening temperature) is lowered. On the other hand, when the copolymer (2) is mixed with the copolymer (1), the fluidity of the resulting methacrylic resin composition is improved, but the mechanical strength is lowered. That is, when the copolymer (2) is mixed with the copolymer (1) to improve fluidity, the mass fraction of the unit (b) contained in the copolymer (2) and the copolymer (2) When the present inventors diligently investigated about the relationship with the compounding quantity of this, the following results were obtained. First, when the mass fraction of the unit (b) contained in the copolymer (2) is reduced and the amount of the copolymer (2) is increased, the heat resistance of the resulting methacrylic resin composition is reduced. Is small, but the mechanical strength is greatly reduced. On the other hand, when the mass fraction of the unit (b) contained in the copolymer (2) is increased and the blending amount of the copolymer (2) is decreased, the heat resistance of the resulting methacrylic resin composition is slightly Although it decreased, it was possible to suppress a decrease in mechanical strength.

  Therefore, it is preferable to increase the mass fraction of the unit (b) contained in the copolymer (2) and reduce the blending amount of the copolymer (2).

  0.1-20 mass% is preferable and, as for the mass fraction of the unit (b) in a copolymer (1), 0.1-15 mass% is more preferable. The mass ratio of the unit (a) to the unit (b) in the copolymer (1) is preferably 99.9 / 0.1 to 80/20, and 99.9 / 0.1 to 85/15. More preferred.

  0.2-30 mass% is preferable and, as for the mass fraction of the unit (b) in a copolymer (2), 0.2-20 mass% is more preferable. The mass ratio of the unit (a) to the unit (b) in the copolymer (2) is preferably 99.8 / 0.2 to 70/30, and 99.8 / 0.2 to 80/20. More preferred.

  The mass ratio of the copolymer (1) and the copolymer (2) blended in the methacrylic resin composition of the present invention is preferably 95/5 to 60/40, more preferably 90/10 to 65/35. .

  In addition to the copolymer (1) and the copolymer (2), the methacrylic resin composition of the present invention includes a plasticizer, an ultraviolet absorber, a light diffusing agent, a matting agent, a light stabilizer, an antioxidant, and a lubricant. Further, it may contain a release agent, an antistatic agent, a colorant and the like.

  The methacrylic resin composition of the present invention contains neither a dispersion stabilizer nor an emulsifier, thereby improving transparency. Generally, bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, and the like are known as polymer production methods. In the suspension polymerization method, a dispersion stabilizer is used, and in the emulsion polymerization method, an emulsifier is used. Use. The dispersion stabilizer is an additive used to stabilize suspended particles in which a monomer is dispersed in water in suspension polymerization, and is a water-soluble polymer such as polyvinyl alcohol, methyl cellulose, hydroxy cellulose; alkylbenzene sulfonate. And surfactants such as nonionic surfactants such as polyoxyethylene alkyl ethers; inorganic salts such as magnesium oxide and calcium phosphate. The emulsifier is an additive used to disperse the emulsion in water in emulsion polymerization, an anionic surfactant such as sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium lauryl sulfate, sorbitan polyethylene glycol monolaurate, Nonionic surfactants such as monopalmitic acid ester, monooleic acid ester, stearic acid ester, polyethylene glycol stearyl acid ester, polyethylene glycol stearyl ether and the like can be mentioned. Although these dispersion stabilizers or emulsifiers used in the suspension polymerization method and the emulsion polymerization method are removed by washing after the polymerization, it is difficult to completely remove them.

  In producing the methacrylic resin composition of the present invention, the copolymer (1) and the copolymer (2) are usually mixed using a kneader such as an extruder, but the copolymer (1) The copolymer (2) is preferably polymerized by a bulk polymerization method or a solution polymerization method which does not use a dispersion stabilizer or an emulsifier.

  Since the methacrylic resin composition of the present invention is excellent in transparency and fluidity, it is suitable for use as a vehicle member, a sanitary member, a household appliance member, an optical member, and miscellaneous goods.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, these do not limit this invention. In addition, the physical property evaluation of the polymer of an Example was performed with the following method.

(Weight average molecular weight)
It measured by the gel permeation chromatography method (GPC). The measurement of the gel permeation chromatography method was performed using a liquid chromatography HLC-8020 type (trade name) manufactured by Tosoh Corporation after dissolving the methacrylic resin composition in tetrahydrofuran (THF). Separation column is TSK-Gel GMHXL (trade name) in series, solvent is THF, flow rate is 1.0 ml / min, detector is differential refractometer, measurement temperature is 40 ° C, injection volume is 0.1 ml, standard Polymethyl methacrylate was used as the polymer.

[Mass fraction (composition ratio)]
The composition ratio is a gas component HP-6890 (trade name) manufactured by Agilent Technologies using a pyrolysis device (product name: Double Shot Pyrolyzer PY-2020D type) decomposed at a decomposition temperature of 500 ° C. It measured by the FID gas chromatograph method using and calculated from the obtained peak area. The measurement conditions were as follows.
Separation column: HP-5 (0.32 mm diameter, 30 m length, 0.25 μm film thickness)
Column measurement temperature program: 40 ° C./5 minutes → (10 ° C./min)→150° C./5 minutes Carrier gas He (1.2 ml / min, linear velocity 40 cm / sec)
〔Liquidity〕
The fluidity was compared by the shear viscosity of pellet-shaped methacrylic resin compositions dried at 80 ° C. for 24 hours. The shear viscosity was measured using a capillograph (trade name) manufactured by Toyo Seiki Co., Ltd. under the conditions of L / D = 10/1 mm for the capillary, 230 ° C. for the temperature, and 600 sec ^{−1 for} the shear rate.

〔Heat-resistant〕
As an index of heat resistance, the deflection temperature under load in accordance with JIS standard K7191-2 and test condition A method was measured.

(Bending strength)
Conforms to JIS standard K6911. The thickness of the test piece was 4 mm.

[Total light transmittance]
Conforms to JIS standard K7361-1. The thickness of the test piece was 3 mm.

[Cloudiness value]
Conforms to JIS standard K7136. The thickness of the test piece was 3 mm.

[Example 1]
(Production of copolymer (1) -a)
After introducing nitrogen into a monomer mixture composed of 94 parts by weight of methyl methacrylate and 6 parts by weight of methyl acrylate, 0.3 part by weight of n-octyl mercaptan and 1,1-bis as a polymerization initiator are added to the monomer mixture. (T-Butylperoxy) -3,5,5-trimethylcyclohexane 0.009 part by mass was mixed to obtain a raw material monomer. This raw material monomer was continuously supplied to a fully mixed reactor controlled at 140 ° C., which is a polymerization temperature, with stirring and mixing, and polymerization was carried out while continuously extracting the polymer composition with a gear pump. The residence amount of the polymer composition in the reaction zone was 60 kg, and the average residence time was 2.0 hours.

  The obtained polymer composition was devolatilized with an extruder to obtain pellets of copolymer (1) -a. The polymerization rate of the copolymer (1) -a determined from the raw material monomer supply amount and the mass flow rate of the copolymer (1) -a was 50%, and the weight average molecular weight of the copolymer (1) -a was 75,000. It was. The composition ratio of copolymer (1) -a measured from the ratio of peak areas by pyrolysis gas chromatography was methyl methacrylate / methyl acrylate = 95/5 (mass ratio).

(Production of copolymer (2) -a)
After introducing nitrogen into a monomer mixture composed of 78 parts by weight of methyl methacrylate and 22 parts by weight of methyl acrylate, 0.6 parts by weight of n-octyl mercaptan and 1,1-bis as a polymerization initiator are added to the monomer mixture. Copolymer in the same manner as Copolymer (1) -a, except that raw material monomer mixed with 0.015 part by mass of (t-butylperoxy) -3,5,5-trimethylcyclohexane was used. (2) -a pellets were obtained. The copolymer (2) -a had a polymerization rate of 48%, a weight average molecular weight of 19000, and a composition ratio of methyl methacrylate / methyl acrylate = 80/20 (mass ratio).

(Production of methacrylic resin composition)
90 parts by mass of copolymer (1) -a pellets and 10 parts by mass of copolymer (2) -a pellets were mixed in a Henschel mixer, and then a twin screw extruder (manufactured by Ikegai Co., Ltd., trade name: PCM-30) was kneaded and extruded at 250 ° C. to obtain a methacrylic resin composition. Measured using the obtained methacrylic resin composition, the shear viscosity was 105 Pa · s, the deflection temperature under load was 93 ° C., the bending breaking strength was 82 MPa, the total light transmittance was 92.0%, and the haze was 0. 2%.

[Comparative Example 1]
(Production of copolymer (2) -b)
After introducing nitrogen into a monomer mixture consisting of 98.5 parts by mass of methyl methacrylate and 1.5 parts by mass of methyl acrylate, 0.6 parts by mass of n-octyl mercaptan and 1 as a polymerization initiator are added to the monomer mixture. , 1-bis (t-butylperoxy) -3,5,5-trimethylcyclohexane Copolymer (1) -a of Example 1 except that a raw material monomer mixed with 0.015 part by mass was used. In the same manner, a pellet of copolymer (2) -b was obtained. The copolymer (2) -b had a polymerization rate of 50%, a weight average molecular weight of 19000, and a composition ratio of methyl methacrylate / methyl acrylate = 99/1 (mass ratio).

(Production of methacrylic resin composition)
A methacrylic resin composition was obtained in the same manner as in Example 1 except that 80 parts by mass of copolymer (1) -a pellets and 20 parts by mass of copolymer (2) -b pellets were used. . Measured using the obtained methacrylic resin composition, the shear viscosity was 104 Pa · s, the deflection temperature under load was 94 ° C., the bending breaking strength was 60 MPa, the total light transmittance was 92.0%, and the haze value was 0.2. %Met.

  Although the methacrylic resin composition of Comparative Example 1 has the same shear viscosity, load deflection temperature, total light transmittance and haze as the methacrylic resin composition of Example 1, it has a bending rupture strength. Declined.

[Example 2]
(Production of copolymer (1) -b)
After introducing nitrogen into a monomer mixture consisting of 95 parts by weight of methyl methacrylate and 5 parts by weight of methyl acrylate, 0.32 parts by weight of n-octyl mercaptan and 1,1-bis as a polymerization initiator are added to the monomer mixture. (T-Butylperoxy) -3,5,5-trimethylcyclohexane In the same manner as the copolymer (1) -a in Example 1 except that a raw material monomer mixed with 0.009 part by mass was used. Copolymer (1) -b pellets were obtained. The copolymer (1) -b had a polymerization rate of 49%, a weight average molecular weight of 69000, and a composition ratio of methyl methacrylate / methyl acrylate = 96/4 (mass ratio).

(Production of copolymer (2) -c)
After introducing nitrogen into a monomer mixture consisting of 91 parts by mass of methyl methacrylate and 9 parts by mass of methyl acrylate, 0.58 parts by mass of n-octyl mercaptan and 1,1-bis as a polymerization initiator are added to the monomer mixture. (T-Butylperoxy) -3,5,5-trimethylcyclohexane In the same manner as the copolymer (1) -a in Example 1 except that a raw material monomer mixed with 0.015 parts by mass was used. A pellet of copolymer (2) -c was obtained. The copolymer (2) -c had a polymerization rate of 51%, a weight average molecular weight of 20000, and a composition ratio of methyl methacrylate / methyl acrylate = 92/8.

(Production of methacrylic resin composition)
A methacrylic resin composition was obtained in the same manner as in Example 1, except that 75 parts by mass of copolymer (1) -b pellets and 25 parts by mass of copolymer (2) -c pellets were used. . Measured using the obtained methacrylic resin composition, the shear viscosity was 164 Pa · s, the deflection temperature under load was 92 ° C., the bending breaking strength was 86 MPa, the total light transmittance was 92.0%, and the haze value was 0.2. %Met.

[Comparative Example 2]
(Production of copolymer (2) -d)
After introducing nitrogen into a monomer mixture consisting of 98 parts by weight of methyl methacrylate and 2 parts by weight of methyl acrylate, 0.58 parts by weight of n-octyl mercaptan and 1,1-bis as a polymerization initiator are added to the monomer mixture. (T-Butylperoxy) -3,5,5-trimethylcyclohexane In the same manner as the copolymer (1) -a in Example 1 except that a raw material monomer mixed with 0.015 parts by mass was used. Copolymer (2) -d pellets were obtained. The copolymer (2) -d had a polymerization rate of 50%, a weight average molecular weight of 20000, and a composition ratio of methyl methacrylate / methyl acrylate = 98.5 / 1.5 (mass ratio).

(Production of methacrylic resin composition)
A methacrylic resin composition was obtained in the same manner as in Example 1 except that 70 parts by mass of copolymer (1) -b pellets and 30 parts by mass of copolymer (2) -d pellets were used. . Measured using the obtained methacrylic resin composition, the shear viscosity was 163 Pa · s, the deflection temperature under load was 93 ° C., the bending breaking strength was 70 MPa, the total light transmittance was 92.0%, and the haze value was 0.2. %Met.

  Although the methacrylic resin composition of Comparative Example 2 has the same shear viscosity, load deflection temperature, total light transmittance, and haze as the methacrylic resin composition of Example 2, it has a bending fracture strength. Declined.

[Comparative Example 3]
(Production of copolymer (1) -c)
A solution prepared by dissolving 96 parts by weight of methyl methacrylate, 4 parts by weight of methyl acrylate, 0.35 parts by weight of n-octyl mercaptan and 0.1 part by weight of 2,2′-azobis (isobutyronitrile) as a polymerization initiator, 150 parts by mass of ionic water and 0.15 parts by mass of poly (methyl methacrylate) and 0.15 parts by mass of sodium sulfate as a dispersion stabilizer were charged, and suspension polymerization was performed at a polymerization temperature of 80 ° C. Then, after hold | maintaining at 95 degreeC for 30 minute (s), it cooled, wash | cleaned, and dried and obtained copolymer (1) -c. The weight average molecular weight of copolymer (1) -c was 69000, and the composition ratio was methyl methacrylate / methyl acrylate = 96/4 (mass ratio).

(Production of copolymer (2) -e)
A solution in which 92 parts by mass of methyl methacrylate, 8 parts by mass of methyl acrylate, 0.65 parts by mass of n-octyl mercaptan, and 0.2 parts by mass of 2,2′-azobis (isobutyronitrile) were used as a polymerization initiator was used. Except for the above, copolymer (2) -e was obtained by suspension polymerization in the same manner as for copolymer (1) -c. The weight average molecular weight of copolymer (2) -e was 19000, and the composition ratio was methyl methacrylate / methyl acrylate = 92/8 (mass ratio).

(Production of methacrylic resin composition)
A methacrylic resin composition was obtained in the same manner as in Example 1, except that 75 parts by mass of copolymer (1) -c pellets and 25 parts by mass of copolymer (2) -e pellets were used. . Measured using the obtained methacrylic resin composition, the shear viscosity was 165 Pa · s, the deflection temperature under load was 92 ° C., the bending breaking strength was 85 MPa, the total light transmittance was 91.9%, and the haze value was 0.3. %Met.

  Although the methacrylic resin composition of Comparative Example 3 has the same shear viscosity, load deflection temperature and bending breaking strength as the methacrylic resin composition of Example 2, the total light transmittance and haze value are It decreased and white turbidity was recognized visually.

Claims (1)

A copolymer (1) comprising a methyl methacrylate unit (a) and an alkyl (meth) acrylate unit (b) other than methyl methacrylate, and having a weight average molecular weight of 50,000 to 250,000,
A dispersion stabilizer comprising a methyl methacrylate unit (a) and a copolymer (2) comprising an alkyl (meth) acrylate unit (b) other than methyl methacrylate and having a weight average molecular weight of 6,000 to 40,000. And no emulsifier,
A methacrylic resin composition in which the mass fraction of the unit (b) contained in the copolymer (1) is smaller than the mass fraction of the unit (b) contained in the copolymer (2).