JPH06306109A - Production of methacrylic resin - Google Patents

Abstract

PURPOSE:To provide a process for producing a methacrylic resin high in melt flowability under a high shear and excellent in mechanical properties such as flexural strength, tensile strength and solvent resistance. CONSTITUTION:In polymerizing a monofunctional monomer comprising methyl methacrylate as the main component under the coexistence of a copolymerizable polyfunctional monomer and a chain transfer gaent while using a raidcal polymn. initiator, the amt. of the chain transfer agent is 2.5X10<-4>mol to 5X10<-3>mol per mol of the monofunctional monomer, the amt. of the polyfunctional monomer is such as to provide 1X10<-5>mol to {amt. (mol) of the chain transfer agent -2.5X10<-4>} mol of the functional groups thereof, and the intrinsic viscosity [eta] of the resulting polymer is 0.25 to 1.5gl/g.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a methacrylic resin. Among them, it is a method for producing a methacrylic resin suitable for being melt-fluidized and molded. [0002] In general, as to the method for producing an acrylic resin for molding, as described in “Plastic Material Course [12]“ Acrylic Resin ”, 2nd edition, page 31, published by Nikkan Kogyo Shimbun, Inc. In addition, in order to increase the fluidity of the resin, a method of polymerizing a small amount of an acrylic ester as a copolymerization component and using a polymerization initiator or a polymerization regulator is disclosed. Chubu Management Development Center Publishing Department, Showa 60
Issued July 1, 2012, "Synthesis and design of acrylic resin and development of new applications", page 21, 2.4, "Manufacturing method of methacrylic resin molding material", methacrylic resin molding material, injection, extrusion, blow, etc. Since it is molded with, it is necessary to have good fluidity and thermal stability in the temperature range of 200 to 300 ° C. For this reason, in order to improve fluidity and thermal stability,
It has been shown to use acrylates as comonomers, to use mercaptans as chain transfer agents for controlling the degree of polymerization and for improving thermal stability. Further, Japanese Patent Publication No. 58-455 and Japanese Patent Publication No. 58-154.
No. 90, Japanese Patent Publication No. 62-34046, etc., a solvent-resistant acrylic resin having a wider molecular weight distribution by adding a chain transfer agent during the polymerization of a monomer mainly composed of methyl methacrylate. Is disclosed. In JP-A-48-95491, a chain transfer agent and a polyfunctional monomer are added to methyl methacrylate to polymerize to prepare an infusible crosslinked polymer, which is pulverized into a powder form. A method for producing an acrylic resin having high heat resistance by further polymerizing methyl methacrylate in the presence thereof is disclosed. As a means for improving the melt moldability of a methacrylic resin, there is a method of lowering the melt viscosity of the resin to increase its melt fluidity. As one of the methods, using a resin having a composition with a large number of comonomer units such as an acrylate ester lowers the glass transition temperature of the obtained resin as the amount of the comonomer increases, so that the heat deformation resistance is lowered and the limit is naturally limited. is there. Also, the method of lowering the molecular weight is also limited because the lower the molecular weight, the lower the mechanical strength and the poorer the solvent resistance. Further, the resin having a wide molecular weight distribution must contain a component having a lower molecular weight in order to improve the melt fluidity, and therefore physical properties such as mechanical strength are unavoidably deteriorated. The resin obtained by adding a gelled crosslinked methylmethacrylate polymer to a monomer and polymerizing it, which is disclosed in JP-A-48-95491, has a high melt resistance since it contains a crosslinked polymer. High and low melt flowability. Therefore, it is not suitable for injection molding or extrusion molding in which the material is melted and molded. Therefore, the present invention has a high melt fluidity without deteriorating the mechanical properties and the like, which are the original characteristics of methacrylic resin, and particularly the melt fluidity under high shear which influences the moldability such as extrusion molding and injection molding. And a method for producing a methacrylic resin molding material having high solvent resistance. In the present invention, a monofunctional monomer having methyl methacrylate as a main component is copolymerized with a radical polymerization initiator to obtain a polyfunctional monomer and chain transfer. When polymerized in the coexistence of an agent, the amount of the chain transfer agent is 2.5 × 10 ⁻⁴ mol to 5 × 10 1 mol of the monofunctional monomer.
^-3 mol, the amount of the polyfunctional monomer is 1 × 10.
^-5 mol to {amount of the chain transfer agent (mol) -2.5 × 10 ^-4 }
And the intrinsic viscosity [η] is 0.25 to
The present invention provides a method for producing a methacrylic resin, which comprises producing a polymer of 1.5 dl / g. The monofunctional monomer having methyl methacrylate as a main component used in the present invention is methyl methacrylate alone or 50% by weight or more, preferably 70% by weight.
It is a mixture of the above-mentioned monofunctional unsaturated monomers copolymerizable with methyl methacrylate. When the amount of methyl methacrylate is less than 50% by weight, the transparency and mechanical strength, which are the characteristics of so-called polymethylmethacrylate, are difficult to develop. As the copolymerizable monofunctional unsaturated monomer, for example, methacrylic acid esters such as ethyl methacrylate, propyl methacrylate, butyl methacrylate and benzyl methacrylate: methyl acrylate, ethyl acrylate, acryl Acrylic acid esters such as propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate:
Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid, acid anhydrides such as maleic anhydride and itaconic anhydride: 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, monoglycerol acrylate, Hydroxyl group-containing monomers such as 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, and monoglycerol methacrylate: Nitrogen-containing monomers such as acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, diacetone acrylamide, and dimethylaminoethyl methacrylate. There are monomers: epoxy group-containing monomers such as allyl glycidyl ether, glycidyl acrylate, and glycidyl methacrylate: styrene-based monomers such as styrene and α-methylstyrene. The radical polymerization initiator may be a well-known one for polymerization of vinyl monomers. For example, azo compounds such as 2,2 ′ azobis (2,4 dimethylvaleronitrile), azobisisobutyronitrile, dimethyl 2,2′azobisisobutyrate; tertiary butyl peroxypivalate, tertiary butyl peroxy. 2-Ethylhexanoate, cumylperoxy Peroxyesters such as 2-ethylhexanoate; Organic peroxides of diacyl peroxides such as di8,5,5 trimethylhexanoyl peroxide and diuraloyl peroxide Among these, one kind or two or more kinds are used. The amount of these polymerization initiators used is 0.001-1 with respect to 100 parts by weight of the monomer or the monomer mixture.
It is about part by weight, preferably 0.01 to 0.7 part by weight. This amount may be a well-known suitable amount depending on the polymerization method. That is, in the suspension polymerization method, about 0.05 to 0.5 parts by weight,
In the bulk polymerization method, it is about 0.001 to 0.1 part by weight. The copolymerizable polyfunctional monomers include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, nonaethylene. Ethylene glycol such as glycol di (meth) acrylate and tetradecaethylene glycol (meth) acrylate or its oligomers whose both hydroxyl groups have been esterified with acrylic acid or methacrylic acid; propylene glycol or its oligomer whose both hydroxyl groups have acrylic acid Or those esterified with methacrylic acid; other such as neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, butanediol di (meth) acrylate, etc. A hydroxyl group of a polyhydric alcohol esterified with acrylic acid or methacrylic acid; a bisphenol A or an alkylene oxide adduct of bisphenol A or a halogen-substituted product thereof whose both hydroxyl groups are esterified with acrylic acid or methacrylic acid; trimethylol Propylene, pentaerythritol, and other polyhydric alcohols esterified with acrylic acid or methacrylic acid; and those obtained by ring-opening addition of epoxy groups of glycidyl acrylate or glycidyl methacrylate to the terminal hydroxyl groups of these dihydric alcohols or polyhydric alcohols. Succinic acid, adipic acid, terephthalic acid, phthalic acid, dibasic acids such as halogen-substituted products thereof or alkylene oxide adducts thereof with glycidyl acrylate or glycidylmethac Those with an epoxy group of rates by ring-opening addition; aryl (meth) acrylate, divinylbenzene, and the like. Preferred are ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate. The amount of the polyfunctional monomer is the monofunctional monomer 1
The amount is 1 × 10 ⁻⁵ mol to {mol of chain transfer agent (mol) −2.5 × 10 ⁻⁴ } mol per mol. That is, depending on the amount of the chain transfer agent described later, even if the amount of the chain transfer agent (mol) -2.5 × 10 ⁻⁴ } mol is less than 1 × 10 ⁻⁵ mol, 1 × 10 ^{− 5} moles are needed. When the number of functional groups is less than 1 × 10 ⁻⁵ mol, the resulting resin has low fluidity at a high shear rate and also has insufficient solvent resistance. In addition, {the amount of the chain transfer agent (mol) -2.5
When it exceeds × 10 ^-4 } mol, the melt fluidity of the obtained resin is low and the moldability is low. The chain transfer agent of the present invention may be a known one used in the polymerization of methyl methacrylate. Among these, there are monofunctional chain transfer agents having one chain transfer functional group and polyfunctional chain transfer agents having two or more chain transfer functional groups. Examples of monofunctional chain transfer agents include alkyl mercaptans, thioglycolic acid esters, 3-mercaptopropionic acid esters, thiophenols, alkyl sulfides, alkyl disulfides and α-methylstyrene dimer. Preferred are alkyl mercaptans and 3-mercaptopropionic acid esters. Examples of polyfunctional chain agents include ethylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol,
Examples thereof include those obtained by esterifying hydroxyl groups of polyhydric alcohols such as tripentaerythritol and sorbitol with thioglycolic acid or 3-mercaptopropionic acid. The amount of the chain transfer agent is
It is from 2.5 × 10 ⁻⁴ mol to 5 × 10 ⁻³ mol. 2.5 x
If it is less than 10 ⁻⁴ mol, [η] of the obtained methacrylic resin becomes excessive and the melt fluidity becomes low. Also, 5
If it exceeds 10 ⁻³ mol and is too large, [η] becomes too small and the resulting methacrylic resin has low mechanical strength. The methacrylic resin of the present invention has an intrinsic viscosity [η] of 0.25 to 1.5 dl / g. [Η] is 0.
If it is less than 25 dl / g, the mechanical strength and solvent resistance of the resin cannot be sufficient. On the other hand, if it exceeds 1.5 dl / g, the melt fluidity becomes too low and the moldability is lowered. [Η] of the methacrylic resin is generally controlled mainly by the concentration of the polyfunctional monomer, the concentration of the chain transfer agent and the concentration of the radical initiator which are mainly used. The concentration of the radical initiator may be a concentration suitable for the polymerization method as described above. Therefore, in the present invention, the concentration is adjusted so that the above [η] can be obtained by appropriately changing the concentration within the concentration range of the polyfunctional monomer and the concentration range of the chain transfer agent. This can be easily set by a few trials. As the polymerization method of the present invention, a well-known method for industrially producing an acrylic resin is used. In other words, suspension polymerization method,
Bulk polymerization method and emulsion polymerization method. For example, in the suspension polymerization method, the above-mentioned monomer containing methyl methacrylate as a main component, a polymerization initiator, a chain transfer agent, and a copolymerizable compound are contained in an aqueous medium in which a well-known suspension stabilizer is present. A polyfunctional monomer, and if necessary, a release agent,
In this method, a stabilizer, a colorant, a plasticizer, etc. are suspended and polymerized. The ratio of the aqueous medium and the monomer or monomer mixture,
It is in the range of 1: 1 to 10: 1, preferably 1: 1 to 4: 1. The temperature condition for the polymerization is about 60 to 120 ° C., which is an appropriate temperature for the polymerization initiator used. Well-known suspension stabilizers include polyacrylic acid and its alkali salt, polymethacrylic acid and its alkali salt, sodium methacrylic acid-methacrylic acid alkyl ester copolymer and the like, and these are used alone or in combination. be able to. After the suspension polymerization is completed, the polymer is washed, dehydrated and dried by a known method to obtain a granular polymer. The methacrylic resin of the granular polymer thus obtained is in the form suitable for the application by being extruded, injection-molded, compression-molded or the like while being granulated or pelletized by an extruder, while being heated. It can be a molded article. By the method of the present invention, it is possible to obtain a methacrylic resin having excellent mechanical properties, particularly bending strength, tensile strength, solvent resistance and the like, and excellent melt flowability at high shear. it can. By injection-molding or extrusion-molding this resin, it has excellent moldability when processed into a large-sized molded product or a molded product having a thick end portion. The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. The evaluations in the examples were carried out using the following methods.・ MFR: 230 ° C. based on JIS K7210
It was measured under a load of 3.80 kg for 10 minutes (g / 10 minutes).・ Spiral flow length: Injection molding machine (Toshiba Machine Co., Ltd. I
S130FII-3AV) at a cylinder temperature of 280 ° C., an injection pressure of 820 kgf / cm ² , and an injection speed of 155 cm ³ / sec.
And, an elliptical spiral flow mold having a thickness of 2 mm and a width of 10 mm was used at 40 ° C. and was injected into the cylinder of the injection molding machine under the condition that the cushion amount remained, and the reaching distance of the resin in the mold was measured.・ Solvent resistance: Injection molding machine (M140 manufactured by Meiki Seisakusho Co., Ltd.)
-SJ) and a plate die with a film gate for 150
A flat plate of × 150 × 3 mm was formed. A 150 × 25 × 3 mm plate was cut out from the flat plate in a direction parallel to the flow of injection. The cut plate was annealed at 80 ° C. under reduced pressure for 6 hours.
Cellophane tape was attached to the short side surface of this plate to prepare a sample piece. The cantilever method is applied, one end of the sample piece is fixed, a point 6 cm away from it is used as a fulcrum, a load is applied to the other end of the sample piece, and isopropyl alcohol is applied to the surface of the sample piece on the fulcrum, The load at which craze occurs 100 seconds after application is represented by stress. (Kgf / cm ² ). Bending strength: Measured according to ASTM-D790.
(Kgf / cm ²⁾ · tensile strength: measured in accordance with ATEM-D638. (Kgf / cm ² ) ・ Intrinsic viscosity: Chloroform solution based on JIS Z8803, 2
It was measured and determined at 5 ° C. Abbreviations of various monomers and chain transfer agents used in the examples are as follows. -MA: methyl acrylate-OctSH: n-octyl mercaptan-DDSH: n-dodecyl mercaptan-PEMP: pentaerythritol tetrakis (3-mercaptopropionate) -DPEMP: dipentaerythritol hexakis (3
-Mercaptopropionate) -TPEMP: tripentaerythritol octakis (3-mercaptopropionate) -EGDMA: ethylene glycol dimethacrylate-TGDMA: tetraethylene glycol dimethacrylate-NPGDMA: neopentyl glycol dimethacrylate-TMPTM: trimethylol Propane trimethacrylate / HDA: 1,6-hexanediol diacrylate / PETA: pentaerythritol tetraacrylate Example 1 In a 200 liter autoclave made of SUS, 96 parts by weight of methyl methacrylate, 4 parts by weight of methyl acrylate, ethylene glycol. 0.03 part by weight of dimethacrylate, 0.3 part by weight of lauroyl peroxide, 0.22 part by weight of n-ocrylmercaptan, io 200 parts by weight of exchanged water,
1 part by weight of sodium polymethacrylate was added and mixed, heated and heated to start polymerization at 80 ° C., and after 90 minutes, further polymerized at 100 ° C. for 60 minutes. After polymerization, washing,
Dehydration and drying were performed to obtain a beaded polymer. The polymer obtained was evaluated. The evaluation results are shown in Table 2. Examples 2 to 12, Comparative Examples 1 to 6, except that the type and addition amount of the chain transfer agent and the polyfunctional monomer in the monomer mixture of Example 1 were changed as shown in [Table 1]. Was performed in the same manner as in Example 1. The obtained polymer was similarly evaluated. The results are shown in Table 2. [Table 1] [Table 2]

Claims (1)

Claim: What is claimed is: 1. A monofunctional monomer containing methyl methacrylate as a main component is used in the coexistence of a copolymerizable polyfunctional monomer and a chain transfer agent using a radical polymerization initiator. When polymerizing,
The amount of the chain transfer agent is 2.5 per mol of the monofunctional monomer.
× 10 ^-4 mol to 5 × 10 ^-3 mol, the amount of the polyfunctional monomer is 1 × 10 ^-5 mol to {the amount of the chain transfer agent (mol) -2.5 × 10 ^-4. } A method for producing a methacrylic resin, which comprises producing a polymer having an intrinsic viscosity [η] of 0.25 to 1.5 dl / g. 2. The method according to claim 1, wherein the chain transfer agent is a monofunctional mercaptan. 3. The method according to claim 1, wherein the chain transfer agent is a polyfunctional mercaptan.