JPH0154361B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a methacrylic resin that imparts impact resistance without impairing the inherent properties of the methacrylic resin. Methacrylic resin has excellent optical properties such as transparency, not only among plastic materials, but even compared to inorganic glass, and has excellent surface gloss, weather resistance, and coloration. sex,
It also has excellent moldability, and by taking advantage of these properties, it can be used in lighting, signboards, window materials, optical lenses, tail lenses, meter covers, dust covers, displays, tableware, optical applications, building materials, and electrical equipment parts. , vehicle parts, decoration field,
It is used in many fields such as miscellaneous goods. However, methacrylic resins have a problem of insufficient impact resistance, and the reality is that there is a strong demand for improvement in each application field. Various proposals have been made for a long time as methods for improving the impact resistance of methacrylic resins. The most common and effective method is to disperse a rubber-like elastic body discontinuously in the form of particles at room temperature in a continuous resin phase containing methyl methacrylate as the main component. As the rubbery elastic body, unsaturated rubbery polymers mainly composed of butadiene, butyl acrylate,
Acrylic acid ester polymers containing 2-ethylhexyl acrylate as a main component, or saturated rubber-like elastic bodies such as ethylene/vinyl acetate copolymers are used. Although the introduction of an unsaturated rubber-like elastic material is excellent in terms of impact resistance, there is a problem of poor weather resistance due to the unsaturated bonds in the polymer main chain.On the other hand, the introduction of a saturated rubber-like elastic material Although it has excellent weather resistance, the elastic modulus and elastic recovery of the rubber component itself are low, and it also has poor graft polymerization with hard resin components, resulting in poor impact resistance, transparency, surface gloss, etc. There are also problems with the surface appearance, such as poor quality and flow marks. In general, when synthesizing a two-component impact-resistant resin composition in which these rubber-like elastic bodies are uniformly dispersed as particulate discontinuous phases in a continuous phase of hard resin such as methacrylic resin, important factors are These include the particle size of the rubber-like elastic material, the degree of crosslinking, the graft polymerizability of the hard resin phase to the rubber phase, and the molecular weight of the hard resin phase.In fact, the superiority and balance of resin properties depend on these factors. be greatly affected. Among these, the degree of crosslinking and graft polymerization of the rubber phase are important.
In other words, the selection of crosslinking or grafting monomers is an important factor. In addition, in recent years, impact-resistant resin compositions or impact-resistant methacrylic resin compositions in which a rubber phase is made of an acrylic ester-based elastic material with excellent weather resistance, the effect of developing impact resistance of the rubber phase, the transparency of molded products, A method of incorporating a hard resin into rubber particles has been proposed for the purpose of improving stress whitening resistance, pearl-like luster caused by deformation of rubber particles during the molding process, and weather resistance (Japanese Patent Publication No. 52-30996). , Japanese Patent Publication No. 1973
-55233), although its effects are certainly recognized, when viewed as a methacrylic resin, it still has problems in terms of transparency and surface gloss. In view of the above facts, the present inventors conducted intensive studies on methacrylic resins that added impact resistance without impairing the original excellent properties of methacrylic resins such as transparency, surface gloss, surface appearance, and weather resistance. When polymerizing the crosslinked acrylic ester copolymer that contains a hard crosslinked resin mainly composed of methyl methacrylate inside the particles and constitutes the outer layer, a crosslinkable monomer with a special structure is used as a copolymerization component. The present invention was accomplished by discovering that a methacrylic resin with excellent impact resistance and excellent appearance of molded products can be obtained by using the same. That is, the gist of the present invention is that 5 to 50 parts by weight of a hard crosslinked resin (A) containing 80% by weight or more of methyl methacrylate units is contained inside the particles, and the alkyl group has 1 to 8 carbon atoms. 69.9 to 89.9% by weight of at least one acrylic acid alkyl ester and styrene alone or a mixture of styrene and its derivatives10
~30% by weight and the following formula or 0.1 to 10% by weight of at least one substance shown in
In the presence of 100 parts by weight of a multi-structure acrylic elastomer with a particle size of 0.2 to 0.45 μm, which constitutes the outer layer, 95 to 50 parts by weight of a crosslinked acrylic ester copolymer (B) of a monomer mixture consisting of , methyl methacrylate
80 to 100% by weight, at least one acrylic acid alkyl ester having an alkyl group of 1 to 8 carbon atoms, 0 to 100% by weight;
It is characterized by polymerizing 10 to 1000 parts by weight of a monomer or monomer mixture (C) consisting of 20% by weight and 0 to 10% by weight of other vinyl monomers copolymerizable therewith. This is a method for producing impact-resistant methacrylic resin. The most important feature of the present invention is that when the crosslinked acrylic ester copolymer (B) is provided on the outer layer of the hard crosslinked resin core by polymerization, the formula (1) and
The special substance shown in formula (2) is used as a crosslinking agent. The hard crosslinked resin phase (A) and non-crosslinked hard resin phase used in the present invention contain auxiliary agents and crosslinkable monomer components that are individually required at each polymerization step in order to impart good transparency. It is desirable that the monomer compositions excepted are the same or very similar. In addition, the refractive index of the crosslinked acrylic ester copolymer (B) is
It is preferable to make it very similar to the hard resin segment described above. Furthermore, in the methacrylic resin of the present invention, it is necessary to consider the diameter of the rubber particles to be dispersed in order to balance transparency, surface appearance, and impact resistance performance. In the methacrylic resin of the present invention, in order to obtain a product excellent in both transparency and impact resistance, at the time when the polymerization of the crosslinked acrylic ester copolymer (B) is substantially completed, the range of 0.2 to 0.45 μm is preferable.
If the particle size is less than 0.2 μm, the resulting resin will have good transparency but poor impact resistance, while if it exceeds 0.45 μm, the resulting resin will have excellent impact resistance but will be transparent. Poor quality and surface appearance. The multi-structure acrylic elastic body [] in the present invention has a hard crosslinked resin (A) containing 80% by weight or more of methyl methacrylate units inside the particles,
The outer layer is a cross-linked acrylic ester copolymer (B)
It consists of a structure with The hard crosslinked resin (A) in the present invention is methyl methacrylate alone or 80 to 100% by weight of methyl methacrylate and 0% of other copolymerizable vinyl or vinylidene monomers.
Monomer or monomer mixture consisting of ~20% by weight
100 parts by weight, 0.1 to 10 parts by weight, more preferably
It is a copolymer obtained by polymerization with the addition of 0.5 to 5 parts by weight of a crosslinkable monomer, and is preferably 5 to 50 parts by weight, more preferably 10 parts by weight out of 100 parts by weight of the multilayer acrylic elastomer. It is necessary to contain up to 40 parts by weight. If the amount is less than 5 parts by weight, the effect of developing impact resistance will be small and transparency will also decrease. 50 on the contrary
If the amount exceeds 1 part by weight, the surface gloss tends to decrease and the impact resistance also tends to decrease. Examples of vinyl or vinylidene monomers copolymerizable with methyl methacrylate used in the polymerization of the hard crosslinked resin (A) include styrene, acrylonitrile, and acrylic acid alkyl esters in which the alkyl group has 1 to 8 carbon atoms. . Further, the crosslinkable monomer used in the polymerization of the hard crosslinked resin (A) does not need to be particularly limited as long as it copolymerizes with methyl methacrylate, and commonly used,
Bifunctional monomers such as ethylene glycol dimethacrylate, ethylene glycol diacrylate, 1,3-butylene dimethacrylate, and tetraethylene glycol diacrylate, or trimethylolpropane triacrylate, triallyl cyanurate, triallyl isocyanunate, etc. No. 3
Functional monomers or tetrafunctional monomers such as pentaerythritol tetraacrylate can be used alone or in combination. The crosslinked acrylic ester copolymer (B) preferably contains at least one of n-butyl acrylate and 2-ethylhexyl acrylate among the acrylic alkyl ester group in which the alkyl group has 1 to 8 carbon atoms, 69.9 to 89.9% by weight. % and styrene alone or a mixture of styrene and its derivatives 10-30% by weight and the following formula or 0.1 to 10% by weight of at least one substance shown in
It is a copolymer of a monomer mixture consisting of a range of 95 to 50
Polymerize parts by weight. The composition ratio of the acrylic acid ester monomer and styrene or a mixture of styrene and its derivatives is one of the important factors for imparting transparency, and transparency decreases outside the above composition range. The substances represented by formulas (1) and (2) are one of the most important components of the present invention, and the objects of the present invention are thereby achieved.
Although the details of its effects are not clear,
It is inferred that this is because the degree of crosslinking of the crosslinked acrylic ester copolymer (B) and the graft polymerizability with methyl methacrylate are controlled in a well-balanced manner. The appropriate amount to add is 0.1 to 10% by weight, although the appropriate value differs depending on whether it is used alone or in combination.
A range of is appropriate. In addition to the substances represented by formulas (1) and (2), a known polyfunctional monomer can also be used in a range of 0 to 9% by weight. Further, this polyfunctional monomer does not need to be particularly limited and is one commonly used. Specific compounds include ethylene glycol di(meth)acrylate, 1,3
Butylene di(meth)acrylate, tetraethylene glycol di(meth)acrylate, divinylbenzene, etc. can be used. Next, the monomer or monomer mixture (C) is polymerized in the presence of the multi-structure acrylic elastomer [ ], and the component composition constituting this is 80 to 100% by weight of methyl methacrylate, carbon of the alkyl group, Numbers 1-8
0 to 20% by weight of at least one acrylic acid alkyl ester and 0 to 10% by weight of another vinyl monomer copolymerizable therewith. If the content of methyl methacrylate in the monomer or monomer mixture (C) is less than 80% by weight, properties such as transparency and heat resistance will be poor, and the acrylic acid alkyl ester copolymerized with it will be inferior. Examples include methyl acrylate, ethyl acrylate, butyl acrylate, and the like. Other vinyl monomers that can be used as copolymerization components include styrene, acrylonitrile, and methacrylic acid. If the amount of acrylic ester exceeds 20% by weight in the monomer or monomer mixture (C), it will be unfavorable in terms of heat resistance and transparency of the resulting resin, and other vinyl monomers that can be copolymerized may If the amount exceeds 10% by weight, it is unfavorable in terms of transparency, heat resistance, water resistance, etc. The monomer or monomer mixture (C) must be polymerized in an amount of 10 to 1000 parts by weight per 100 parts by weight of the multilayer acrylic elastomer. If it is less than 10 parts by weight, it is not preferable because impact resistance may be poor or surface gloss may be reduced. while 1000
If it exceeds parts by weight, productivity will decrease, which is undesirable. A degree of polymerization regulator such as mercaptan may be used in the monomer or monomer mixture (C) to adjust the molecular weight as necessary. Examples of the polymerization degree regulator that can be used include alkyl mercaptans, thioglycolic acid and its esters, β-mercaptopropionic acid and its esters, and aromatic mercaptans such as thiophenol and thiocresol. Since it is preferable to manufacture the methacrylic resin of the present invention by emulsion polymerization, an example in which emulsion polymerization is used will be described. After adding deionized water and an emulsifier if necessary to the reaction vessel, the monomer mixture constituting the hard crosslinked resin (A) is polymerized, and then the monomer mixture constituting the crosslinked acrylic ester copolymer (B) is polymerized. The monomer mixture is polymerized, and then the monomer or monomer mixture (C) is polymerized. Polymerization temperature is 30-120℃, more preferably 50-100℃
It is ℃. The polymerization time varies depending on the type and amount of the polymerization initiator and emulsifier, the polymerization temperature, etc., but is usually 0.5 to 7 hours for each polymerization step (A), (B), and (C). The ratio of polymer to water is monomer/water = 1/20 to 1/1
is preferred. A polymerization initiator and an emulsifier can be added to either or both of the aqueous monomer phases. The monomers in the polymerization steps (A), (B), and (C) can be charged all at once or in portions, but the split-charging method is more preferable from the viewpoint of heat generation during polymerization. The emulsifier is not particularly limited as long as it is a commonly used emulsifier, and examples of emulsifiers that can be used include long-chain alkyl carboxylates, sulfosuccinic acid alkyl ester salts, alkylbenzene sulfonates, and the like. There is no need to particularly limit the type of polymerization initiator, and commonly used water-soluble inorganic initiators such as persulfates and perborates can be used alone or in combination with sulfites, thiosulfates, etc. as redox initiators. It can also be used. Further, redox initiation systems such as organic hydroperoxide-ferrous salts, organic hydroperoxide-sodium sulfoxylate, benzoyl peroxide, azobisisobutyronitrile, and the like can also be used. The polymer latex obtained by the emulsion polymerization method is coagulated and dried by a known method. By molding the methacrylic resin thus obtained using an extrusion molding machine, an injection molding machine, etc., a molded product with excellent transparency, surface gloss, and high impact resistance can be obtained. The present invention will be explained in more detail below based on Examples. In the examples, parts represent polymerized parts, and % represents weight %. Examples 1 to 2, Comparative Examples 1 to 5 (1) Production of hard crosslinked resin (A) First, the following raw materials (A) were charged in various proportions into a stainless steel reaction vessel with an internal volume of 50 mm, and nitrogen was added under stirring. After blowing into the mixture to make it substantially free from the influence of oxygen, the temperature was raised to 70°C, the following raw materials (b) were added, and polymerization was carried out for 2 hours to obtain a latex of hard crosslinked resin. (a) Raw material deionized water 500 parts Sarcosinate LN ^*1) (S-LN) 0.10 parts Boric acid 1.0 parts Sodium carbonate 0.1 parts Methyl methacrylate (MMA) Ethyl acrylate (EA) 1,3-butylene dimethacrylate 97% 1% 2% 15 parts (b) Raw material deionized water 10 parts Potassium persulfate (KPS) 0.3 parts *1 N-acyl sarcosinate (product of Nikko Chemicals Co., Ltd.) The polymerization rate of MMA in this latex is 98.5%. The particle size was 0.16 μm. (2) Production of multi-layered acrylic elastomer [] by polymerization of cross-linked acrylic ester copolymer (B) An amount of hard material equivalent to 15 parts of the solid content after substantially completing the polymerization in (1) above In the above container containing the crosslinked resin latex, add the following sodium formaldehyde sulfoxylate (hereinafter referred to as Rongarit).
and an aqueous solution of sarcosinate LN at 80°C.
After raising the temperature to
0.32 part was added continuously over 150 minutes. After the addition was completed, polymerization was continued for an additional 3 hours to obtain a latex of a multi-layered acrylic elastomer containing the hard crosslinked resin (A) inside the particles. Sarcosinate LN 0.2 parts Rongarit 0.32 parts Deionized water 10 parts

[Table] In all of the above cases, the polymerization yields of BA and ST were 97% and 99.5% or more, respectively, and the particle size of the obtained latex was 0.26 to 0.28 μm. (3) Production of methacrylic resin by polymerization of monomer mixture (C) Inside the above container containing latex equivalent to 100 parts solids of the multi-layered acrylic elastomer [] obtained in the above polymerization (2). In, Sarcosinate LN0.25
After adding and stirring 10 parts of deionized water, the following monomer mixture (C) was added continuously over 2.5 hours. Thereafter, polymerization was continued for an additional hour to obtain a methacrylic resin in the form of a latex. In all cases, the polymerization yield of MMA in monomer mixture (C) is
It was over 99.5%. Monomer mixture (C) MMA EA Normal octyl mercaptan (n-C ₈ SH) 9.87% 6% 0.3% 300 parts TBH 0.9 parts This latex is coagulated, washed and dried by the method described below to form methacrylic resin powder. I got it. 1400 parts of 1.0% sulfuric acid water was placed in a stainless steel container, and the temperature was raised to 80°C while stirring to produce the latex produced earlier.
700 parts were added continuously over 20 minutes, and then the internal temperature was raised to 95°C and held for 5 minutes. After cooling to room temperature, the polymer was separated and washed with deionized water to obtain a white creamy polymer, which was
It was dried at ℃ for 24 hours to obtain a white powdery polymer. Next, this powder was processed using a screw type extruder (manufactured by Japan Steel Works, Ltd., P-40-26AB-V type, with an outer diameter of 40 mmφ).
L/D=26), cylinder temperature 200-260
℃, melt-kneaded at a die temperature of 250℃ to form pellets, content of multi-layered acrylic elastic body [ ] 25%
An impact-resistant methacrylic resin was obtained. This was injection molded under the following conditions, and the evaluation results shown in Table 2 were obtained from the test pieces obtained. Injection molding machine: V-17-65 screw type automatic injection molding machine manufactured by Japan Steel Works Co., Ltd. Injection molding conditions: Cylinder temperature 250℃, injection pressure 700
Kg/cm ² Test piece size: 110mm x 110mm x 2mm (thickness) 70mm x 12.5mm x 6.2mm (thickness)

[Table] Examples 3 to 4, Comparative Examples 6 to 9 Among the series of production methods of Example 1, only the monomer composition of the portion shown in Table 3 was changed to obtain a methacrylic resin, and the same as that of Example 1 was obtained. The same evaluation was performed, and the results shown in Table 4 were obtained.

【table】

【table】

[Table] As is clear from the above results, the substances of general formulas (1) and (2) used in the present invention in the polymerization of the crosslinked acrylic acid ester copolymer (B) are free of additives. (Comparative Example 6), even if it is added, it is outside the range of use of the present invention (Comparative Examples 7 and 8), and even if the amount added is within the range of use of the present invention, the hard crosslinked resin (A) is contained inside. It can be seen that the object of the present invention cannot be achieved when the core of the present invention is not possessed (Comparative Example 9).

Claims (1)

[Scope of Claims] 1. An acrylic acid alkyl ester containing 5 to 50 parts by weight of a hard crosslinked resin (A) containing 80% by weight or more of methyl methacrylate units inside the particles, and in which the alkyl group has 1 to 8 carbon atoms. 69.9 to 89.9% by weight of at least one of the above, 10 to 30% by weight of styrene alone or a mixture of styrene and its derivatives, and the following formula: or 0.1 to 10% by weight of at least one substance shown in
In the presence of 100 parts by weight of a multi-structure acrylic elastomer with a particle size of 0.2 to 0.45 μm, which constitutes the outer layer, 95 to 50 parts by weight of a crosslinked acrylic ester copolymer (B) of a monomer mixture consisting of , methyl methacrylate
80 to 100% by weight, at least one acrylic acid alkyl ester having an alkyl group of 1 to 8 carbon atoms, 0 to 100% by weight;
It is characterized by polymerizing 10 to 1000 parts by weight of a monomer or monomer mixture (C) consisting of 20% by weight and 0 to 10% by weight of other vinyl monomers copolymerizable therewith. A method for producing methacrylic resin with excellent impact resistance.