JPS6321684B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a new thermoplastic resin having excellent impact resistance. Impact-resistant resins such as ABS resin and high-impact polystyrene contain styrene and rubber components.
It is obtained by graft polymerizing acrylonitrile, methyl methacrylate, and other monomers, but the composition and structure of the graft copolymer, the rubber content, the polymerization method, etc. have a large influence on the physical properties of the final composition. In particular, when graft polymerizing rubber components using emulsion polymerization, it is a widely known fact that the particle size of the base rubber component controls the impact resistance and processability of the final composition. The larger the size, the better the impact resistance and processability of the resulting resin. Therefore, attempts have been made to make the rubber particle size as large as possible, and various proposals have been made so far. The present applicant has also previously discovered that diene rubber can be enlarged with a copolymer latex consisting of an unsaturated acid monomer and an alkyl acrylate, and in the presence of the obtained enlarged rubber latex, a group of styrene, acrylonitrile and methyl methacrylate can be enlarged. We have proposed a resin composition with good impact resistance obtained by polymerizing at least one selected monomer, but as a result of further studies, we have arrived at the present invention. The present invention comprises 100 to 50% by weight of an alkyl acrylate having an alkyl group having 2 to 10 carbon atoms, 0 to 50% by weight of a monofunctional monomer copolymerizable with this, and a polyfunctional monomer copolymerizable with these. For 100 parts by weight (as solid content) of acrylic rubber (A) latex obtained by polymerizing monomers consisting of 0 to 5% by weight, a compound selected from the group of acrylic acid, methacrylic acid, itaconic acid and crotonic acid at least one monomer 3 to 30
Obtained by polymerizing a monomer consisting of 97-35% by weight of at least one alkyl acrylate whose alkyl group has 1 to 12 carbon atoms and 0-48% by weight of other copolymerizable monomers. Enlarged rubber latex with a particle size of at least 0.2 μ obtained by adding 0.1 to 5 parts by weight (as solid content) of acid group-containing copolymer (B) latex and 0.05 to 4 parts by weight of an inorganic electrolyte if necessary CH ₂ =C copolymerizable with 30-100% by weight of at least one monomer selected from the group of styrene, acrylonitrile and methyl methacrylate in the presence of 70 parts by weight (as solids);
This is a method for producing a thermoplastic resin having excellent impact resistance and surface properties, which is characterized by polymerizing 93 to 30 parts by weight of a monomer mixture comprising 0 to 30 parts by weight of a monomer having << groups. The rubber component (A) includes an alkyl acrylate homopolymer or a copolymer consisting of 50% or more of alkyl acrylate and 50% or less of a vinyl monomer that can be copolymerized therewith, in addition to a crosslinking agent. These can also be easily obtained by commonly known emulsion polymerization. There are no particular restrictions on catalysts, emulsifiers, etc., and the particle size is 0.04 to 0.2μ.
belongs to. A copolymer (B) containing acid group-containing monomers such as acrylic acid, methacrylic acid, itaconic acid and crotonic acid is then used to thicken the rubber latex. It is essential that this copolymer (B) contains an acid group-containing monomer and an acrylate, and at least one type of alkyl acrylate whose alkyl group has 1 to 12 carbon atoms is selected as the acrylate. It will be done. Even if a monomer such as methacrylate, styrene, or acrylonitrile is used instead of acrylate, no effect is observed. However, it is possible to replace up to half of the acrylate with other monomers. The acid group-containing monomer is used in a range of 3 to 30% by weight, and if it is less than 3%, the enlargement ability is small;
%, on the contrary, the enlargement ability is too strong and excessive particles exceeding 1μ are produced, which is not preferable. In addition, the optimal content of the acid group-containing monomer varies depending on the degree of hydrophilicity of the acrylate used. If the acrylate has a high hydrophilicity, the enlargement effect will be reduced in the region where the amount of the acid group-containing monomer is small. On the other hand, if the amount of acid group-containing monomer increases, the latex will be destroyed, which is undesirable.On the other hand, if the hydrophilicity of acrylate is low, the area with a low amount of acid group-containing monomer will have a thickening effect. The effect will not be obtained unless the amount of the acid group-containing monomer exceeds a certain level. For example, in the case of highly hydrophilic acrylates such as methyl acrylate and ethyl acrylate, it is optimal when the amount of acid group-containing monomer is 5 to 10%, whereas hydrophobic Butyl acrylate and 2, which are alkyl acrylates,
- In the case of ethylhexyl acrylate, it is optimal when the amount of acid group-containing monomer is 13 to 20%. However, when a highly hydrophilic acrylate is used, even if the amount of acid group-containing monomer is 5 to 10%, the system tends to become unstable, which leads to the formation of cullets (coarse particles). On the other hand, when hydrophobic acrylates such as those described above are used, the system does not become unstable and uniform enlarged particles can often be obtained. In addition to the above, examples of acid group-containing monomers or similar monomers include cinnamic acid, maleic anhydride,
There are butenetricarboxylic acids and the like, but their use is not practical due to their low enlargement ability. The acid group-containing copolymer (B) is added in the form of a latex to the base rubber (A) latex. At this time, when an inorganic electrolyte, preferably an inorganic salt, especially a neutral inorganic salt, is added, the particle size of the base rubber increases. It enlarges extremely efficiently and stably. The amount of the acid group-containing copolymer (B) latex added is 0.1 to 5 parts by weight, particularly preferably 0.5 to 3 parts by weight, per 100 parts by weight of the base rubber (A). When an inorganic electrolyte is added, the amount added is 0.05 to 4 parts by weight, particularly preferably 0.1 to 1 part by weight, per 100 parts by weight of the base rubber (A).
Parts by weight are sufficient, and by adding such a small amount, the base rubber can be enlarged efficiently in a short period of time, and the stability of the resulting large particle size rubber latex can be greatly improved. As the inorganic electrolyte, commonly known inorganic salts such as KCl, NaCl, Na ₂ SO ₄ etc. can be used. Further, this inorganic electrolyte can be added in advance during polymerization of the base rubber latex, and has the same effect as when added during enlargement. When carrying out the enlargement treatment of the present invention, it is preferable to maintain the pH of the base rubber (A) latex at 7 or higher. When the PH value is on the acidic side, even if the acid group-containing copolymer (B) latex is added, the enlargement efficiency is low, and the composition targeted by the present invention cannot be advantageously produced. For example, polybutyl acrylate rubber latex polymerized with sodium octylsulfosuccinate as an emulsifier and potassium persulfate as a catalyst has a pH of 2 to 3, but even if an acid group-containing polymer latex is added to this latex, it will not thicken at all. No change will occur. However, if a small amount of alkali such as potassium hydroxide is added to raise the pH to 7 or higher, a rubber with a large particle size can be easily obtained. The pH of the base rubber (A) latex may be adjusted to 7 or higher during the polymerization of the base rubber, or may be adjusted separately before the enlargement treatment. In the presence of 7 to 70 parts by weight of the rubber latex that has been enlarged in this way, the desired impact-resistant resin can be obtained by polymerizing monomers mainly consisting of styrene, acrylonitrile, and methyl methacrylate. . If the rubber content is less than 7% by weight, the impact resistance is low and there is no practical value, and if it exceeds 70% by weight, fluidity and processability deteriorate, which is not preferable. The preferred rubber content is 10-25% by weight. Monomers to be grafted to rubber latex include styrene alone, methyl methacrylate alone, and
Styrene-acrylonitrile monomer mixture, styrene-acrylic ester monomer mixture, methyl methacrylate-acrylonitrile monomer mixture, methyl methacrylate-acrylic ester monomer mixture, acrylonitrile-acrylic ester monomer mixture, etc. Furthermore, a monomer mixture of three or more of these monomers may also be used. In this emulsion graft polymerization, commonly known emulsifiers and catalysts are used, and there are no particular restrictions on the type and amount added. It is also possible to obtain a resin composition with good impact resistance by further blending a rubber-free resin with the above-obtained graft polymer. In this case, the rubber content in the base graft polymer may not be in the range of 7 to 70% by weight, but the final content after blending may be in the range of 7 to 70% by weight. preferable. Examples of rubber-free resins used at this time include polystyrene, polymethyl methacrylate, AS resin, polyvinyl chloride, and polycarbonate. When graft polymerizing the enlarged rubber, the graft monomers may be added all at once, or may be added in portions or continuously, or each monomer may be graft polymerized individually in stages. Also good. Known antioxidants, lubricants, colorants, fillers, etc. can be added to the obtained graft polymer or graft-blend polymer. In the following examples, parts and % mean parts by weight and % by weight, respectively. The surface appearance of the molded product is as follows. ◎: Very good ○: Good ×: Bad example 1 Production of acrylic rubber (A-1) latex Ion exchange water 200 parts Potassium oleate 5.0 parts Methyl methacrylate 4 parts Styrene 12 parts Acrylonitrile 12 parts n-butyl acrylate 72 parts Triallylisocyanurate 0.5 parts Potassium persulfate 0.6 parts A mixture consisting of the above composition was polymerized at 70°C for 4 hours. The polymerization rate was 96%, the average particle size of the obtained elastic latex was 0.09μ, and the pH was 9.1. Synthesis of acid group-containing copolymer (B-1) latex for enlargement n-butyl acrylate 85 parts Methacrylic acid 15 parts Sodium dioctylsulfosuccinate 0.5 parts Cumene hydroperoxide 0.4 parts Sodium formaldehyde sulfoxylate 0.3 parts Ion exchange water 200 Using a mixture having the above composition, polymerization was carried out at 70°C for 4 hours. The conversion rate of the obtained latex was 98%, and the pH was
It was 2.4. 100 parts (solid content) of latex (A-1) was placed in a container and, while stirring, 2.0 parts (solid content) of latex (B-1) was added thereto at room temperature. After stirring this latex for 30 minutes and then leaving it for 5 days, samples were taken and the average particle size was measured.
The results are shown in Table-1. Synthesis of Graft Polymer (G-1) The enlarged latex obtained by stirring for 30 minutes was immediately subjected to graft polymerization at 80° C. for 4 hours according to the following composition to synthesize a graft polymer. Thickened rubber (solid content) 60 parts Methyl methacrylate 8 parts Acrylonitrile 8 parts Styrene 24 parts n-octyl mercaptan 0.04 parts Potassium persulfate 0.2 parts Potassium oleate 1.0 parts Evaluation of various physical properties 50 parts of the graft polymer obtained in () above and
The content of acrylic rubber in the total resin composition was determined by blending 50 parts of suspended particles separately produced using a monomer mixture of MMA/AN/St = 20/20/60 (%).
It was set at 30%. Furthermore, 1 part of barium stearate and 0.1 part of Tinuvin P (ultraviolet absorber manufactured by Geigy) were added to this resin composition and formed into a pellet using an extruder. Using this beret, various test pieces were prepared by injection molding and various physical properties were evaluated. These results are shown in Table 1. The notched isot strength values in Table 1 are based on ASTM-D-256, the melt index (MI) is based on the number of grams of polymer flowing out in 10 minutes at 200°C and a load of 5 kg, and the surface gloss is 1/8 inch. Form a flat plate with a thickness of
-D523-62T, the specular gloss was determined at an incident angle of 60 degrees. These evaluation methods are the same in subsequent examples and comparative examples. Comparative Example 1 Acrylic rubber (A-2) having a particle size comparable to that of the enlarged rubber was synthesized by the following method. Synthesis of (A-2) Put 200 parts of ion-exchanged water into a reaction vessel, raise the internal temperature to 80°C, then add 1.5 parts of potassium oleate and 0.6 parts of potassium persulfate, same as (A-1). of the monomer mixture (excluding potassium oleate and potassium persulfate) was continuously injected over a period of 2 hours and 30 minutes. The average particle size of the acrylic rubber latex thus obtained was 0.30μ. Using this rubber, a graft polymer was prepared in the same manner as in G-1, and the same amount of suspended particles as blended in Example 1 was blended and the same evaluation was performed.

[Table] Regarding the surface condition of the molded product, when injection molding was performed with the resin composition of the comparative example, a rainbow-colored striped pattern appeared near the gate of the molded product, but in the present invention, such a pattern was not observed. There was no iridescence at all and it was beautiful. Example 2 Different amounts of latex (B-1) were added to 100 parts (solid content) of latex (A-1) in Example 1, and the same evaluation as in Example 1 was conducted. Comparative Example 2 For comparison, the same evaluation was performed on the case where the latex (A-1) was graft-polymerized without enlarging it.

[Table] Example 3 In (A-1) of Example 1, acrylic rubber (A
-2) Made latex. Ion exchange water 200 parts n-butyl acrylate 76 parts acrylonitrile 9 parts styrene 15 parts triallyl cyanurate 1 part dioctyl sodium sulfosuccinate 1.0 parts potassium persulfate 0.9 parts Polymerization rate 97%, average particle size 0.08μ, PH 2.4 It was hot. (A-2) 100 parts of rubber latex was mixed with caustic soda to change the pH of the latex, and after adding 2.0 parts of (B-1) latex to thicken it, the graft polymer was prepared in the same manner as in Example 1. We created and attempted to evaluate the physical properties.

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Claims (1)

[Claims] 1 100 to 50% by weight of an alkyl acrylate whose alkyl group has 2 to 10 carbon atoms, 0 to 50% by weight of a monofunctional monomer copolymerizable with this, and a polyfunctional monomer copolymerizable with these. Acrylic rubber (A) latex obtained by polymerizing monomers consisting of 0 to 5% by weight
Acrylic acid, per 100 parts by weight (as solid content)
3 to 30% by weight of at least one monomer selected from the group of methacrylic acid, itaconic acid, and crotonic acid, 97 to 35% by weight of at least one alkyl acrylate whose alkyl group has 1 to 12 carbon atoms, and Acid group-containing copolymer (B) latex obtained by polymerizing monomers consisting of 0 to 48% by weight of other copolymerizable monomers 0.1 to 5 parts by weight (as solid content) and an inorganic electrolyte if necessary at least one selected from the group of styrene, acrylonitrile and methyl methacrylate in the presence of 7 to 70 parts by weight (as solids) of a thickened rubber latex having a particle size of at least 0.2μ, obtained by adding 0.05 to 4 parts by weight. A kind of monomer 30~
An impact-resistant material characterized by polymerizing 93 to 30 parts by weight of a monomer mixture consisting of 100% by weight and 0 to 30% by weight of a monomer having a CH ₂ =C< group copolymerizable therewith. A superior method for producing thermoplastic resins.