JPH0559124B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rubber-modified thermoplastic resin composition that is excellent in weather resistance, impact resistance, and appearance of molded articles. Graft copolymers obtained by graft copolymerizing styrene, acrylonitrile, etc. to ethylene/propylene/nonconjugated diene copolymer rubber (hereinafter referred to as EPDM), or graft copolymers obtained by blending them with copolymers of styrene and acrylonitrile, etc. The rubber-reinforced resin composition has excellent weather resistance and impact resistance.
It is expected to be used as a molding material in a wide range of fields, and many methods have been proposed for its production. However, although the resin compositions according to the prior art certainly have excellent weather resistance and impact resistance, they have the drawback that when molded products are closely observed, they exhibit a pearl-like appearance.
Particularly, during injection molding, the weld portion where resin flows meet in the mold cavity exhibits a poor appearance phenomenon in which linear pearl-like color separation is severe. For this reason, despite its excellent weather resistance, its use in exterior parts of automobiles and electrical products is severely restricted.
This improvement was strongly requested. An object of the present invention is to provide a rubber-modified thermoplastic resin composition that does not reduce impact resistance or mechanical strength and has a molded article with a good appearance without pearl-like linear color separation. According to the present invention, a (co)polymer of monomers mainly composed of an ethylene/α-olefin/nonconjugated diene copolymer rubber component and an aromatic vinyl compound or an aromatic vinyl compound and a vinyl cyanide compound is prepared. In the rubber-modified impact-resistant resin composition contained as a matrix resin component, the rubber-modified thermoplastic resin composition is characterized in that the swelling degree of the methyl ethyl ketone insoluble portion in the composition with n-hexane is 0.4-1.5. provided. The EPDM used in the present invention preferably has an ethylene to propylene weight ratio of 90:10 to 20:80, more preferably 80:20 to 30:70, and is further copolymerized with a small amount of a non-conjugated diene compound. It is something. Examples of the non-conjugated diene compound used here include alkenylnorbornenes such as 5-ethylidene-2-norbornene, cyclic dienes such as dicyclopendadiene, and aliphatic dienes such as 1,4-hexadiene. The non-conjugated diene in EPDM is used within the range of 5 to 40 in terms of iodine value. Also, Mooney viscosity of EPDM used in the present invention (ML ₁₊₄ 100℃)
There is no particular limit, but usually 20 to 100℃, preferably
25 to 85 are used. The method for producing the rubber-modified thermoplastic resin composition is not particularly limited, and known emulsion polymerization, solution polymerization, suspension polymerization, etc. can be employed. For example, a graft polymerization method in which a monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound is graft-polymerized as a matrix resin component in the presence of EPDM, or the graft copolymer obtained in this way can be further A so-called graft blend method may be used in which a polymer or copolymer of at least one monomer selected from the above monomers is blended. Examples of aromatic vinyl compounds include styrene, α-methylstyrene, P-methylstyrene, vinyltoluene, monocrossstyrene, etc., and vinyl cyanide compounds include acrylonitrile, methacrylonitrile, etc., each of which may be used alone or in combination of two or more. It can be used as Furthermore, (meth)acrylic acid esters such as methyl methacrylate that can be copolymerized with these can be used in combination, but styrene and acrylonitrile are particularly preferred, with a polymerization ratio of 80:20.
This is when used in the range of ~60:40. The rubber component content in the rubber-modified thermoplastic resin can be arbitrarily selected depending on the purpose, but in order not to impair the impact resistance of the resin composition, it is 5 to 45% by weight, preferably 10 to 40% by weight. is within the range of In order to exhibit the effects of the present invention, it is important that the degree of swelling of the gel in the rubber-modified thermoplastic resin composition is in the range of 0.4 to 1.5, particularly preferably 0.6 to 1.3. Gels with a swelling degree of 0.4 to 1.2 have excellent paintability, solvent resistance, and surface appearance in addition to the effects of the present invention, and are therefore suitable for coating applications and applications requiring solvent resistance. In particular, it is preferably 0.5 to 0.9. In addition to the effects of the present invention, gels with a swelling degree of 1.0 to 1.5 have excellent extrusion moldability, and the extruded sheet has excellent vacuum moldability, making them suitable for extrusion molding or vacuum forming applications. . A particularly preferred range is 1.1 to 1.5. When the degree of swelling exceeds 1.5, the effect of improving appearance is significantly reduced, and when the degree of swelling is less than 0.4,
Impact strength is significantly reduced. The degree of swelling of the gel in the resin composition as used in the present invention refers to the degree of swelling of the methyl ethyl ketone insoluble portion of the composition due to n-hexane, and is determined as follows. That is, the product obtained by dissolving about 1 g of the resin composition in 100 ml of methyl ethyl ketone and then separating the insoluble matter by centrifugation is called a wet gel. This wet gel is dried at 80°C for 3 hours and is called a gel (dry gel). This gel was weighed and designated as Ag. Next, prepare an airtight glass container, partition the bottom with a punching board, put n-hexane in the bottom, place a weighing bottle (without lid) filled with the above dry gel on the punching board, and add n-hexane. The gel was left in a steam atmosphere at 23° C. for 48 hours, and the gel swollen with n-hexane (wet gel) was weighed and designated as Bg. The degree of swelling is determined by the following formula. Swelling degree = B-A/A The range of swelling degree of the gel of the resin composition defined in the present invention is determined by the polymerization temperature and type of polymerization initiator used in each production method when producing the resin composition by a known method. This can be achieved by determining operating conditions such as quantity and quantity. Further, the intrinsic viscosity [η] of the methyl ethyl ketone soluble portion in the resin composition of the present invention is 0.35 to 0.55 dl/g.
(30°C in methyl ethyl ketone) is preferred. 0.35
If it is less than 0.55, the impact resistance will be poor, and if it exceeds 0.55, the molded appearance will be poor. Further, the content of tetrahydrofuran insoluble matter (gel) in the resin composition is preferably 2 to 10% by weight.
If it is less than 2% by weight, the molded appearance will be poor, and if it exceeds 10% by weight, the extrusion moldability will be poor. The above tetrahydrofuran insoluble matter was obtained by accurately weighing about 1 g of the resin composition, dissolving it in 100 ml of tetrahydrofuran, separating the insoluble matter by centrifugation, drying the resulting wet gel at 80°C for 3 hours, and weighing it. It is determined by calculating the content (%) in the resin composition. The rubber-modified resin of the present invention can be produced by various methods in which vinyl monomers are radically polymerized in the presence of rubber, such as emulsion polymerization, bulk polymerization, suspension polymerization, and solution polymerization. Due to problems in controlling the solubility polymerization reaction of rubber into vinyl monomers and in handling, the solution polymerization method has a good balance of physical properties and is suitable for the present invention. In the solution polymerization method, vinyl monomers and rubber dissolved in an inert solvent are used as starting materials for radical polymerization using an initiator, forming a particulate dispersion of rubber during polymerization, which essentially prevents polymerization. This is a method for producing a graft polymer by separating and removing the solvent and the like after completion of the reaction. The gel swelling degree in the resin composition can be adjusted by the polymerization temperature, the type and amount of the polymerization catalyst, and the type and amount of the non-conjugated diene component in EPDM. As a catalyst, benzoyl peroxide, di-t-butyl peroxide, dicumyl peroxide, t
- Peroxides such as butyl peroxybezoate are preferred. The present invention will be explained in more detail with reference to Examples below. Example 1 EPDM-1 20 parts by weight Styrene 56 Acrylonitrile 24 Toluene 100 (here, EPDM-1 contains 40% by weight of propylene,
Nonconjugated diene = ethylidene norbornene, iodine number = 29, Mooney viscosity = 74. ),
Stir at 50℃ until the rubber is completely dissolved, then tert-
After adding 0.1 parts by weight of dodecyl mercaptan, 0.3 parts by weight of benzoyl peroxide, and 0.4 parts by weight of di-tert-butyl peroxide, the mixture was heated at 80°C for 8 hours.
The temperature was further raised to 130°C, and polymerization was carried out for 3 hours, for a total of 8 hours. After removing the solvent and drying using a conventional method, 0.2 parts by weight of 2,2'-methylenebis-(4-ethyl-6-tert-butylphenol) was added, passed through a 40 mm extruder (220°C), pelletized, and then 50Z injection molded. Machine (230℃)
A test piece was molded and its physical properties were measured. The results are shown in Table 1. The solvent resistance was determined by dripping 0.3 to 0.4 ml of regular gasoline onto the surface of the molded product, leaving it at room temperature for 4 hours, then wiping the surface and checking for abnormalities (blistering, discoloration, softening, etc.). Examples 2 and 3; Comparative Examples 1 to 3 Table 1: Catalyst type, amount used, polymerization temperature, and time
The same operations as in Example 1 were performed except for the changes shown in Table 2. Example 4 The same operation as in Example 1 was performed except that EPDM-1 was changed to EPDM-2. Here, EPDM-2 has a propylene content of 30% by weight,
Non-conjugated diene = dicyclopentadiene, iodine number = 12, Mooney viscosity = ML ₁₊₄ (100°C) = 44. Examples 5 and 6 Methyl methacrylate or α in the monomer mixture
- The same operation as in Example 1 was carried out except that methylstyrene was used in combination. Example 7 40 parts by weight of EPDM-1 40 parts by weight of styrene 42 parts by weight of acrylonitrile 18 parts by weight of toluene 200 parts by weight of toluene were charged into a 10 stainless steel reactor equipped with a paddle type stirring blade, and the mixture was stirred at 50°C until the rubber was completely dissolved. - After adding 0.1 parts by weight of dodecyl mercaptan, 0.4 parts by weight of benzoyl peroxide, and 0.5 parts by weight of di-tert-butyl peroxide, the polymerization reaction was carried out at 80°C for 10 hours, and then heated to 130°C for 4 hours in total for 14 hours. carried out. After removing the solvent and drying in a conventional manner, 0.4 parts by weight of 2,2'-methylenebis-(4-ethyl-6-tert-butylphenol) is added and pelletized through a 40 mm extruder (220 DEG C.). The obtained graft copolymer and acrylonitrile-styrene copolymer resin (Lightac 120PC, manufactured by Mitsui Toatsu Co., Ltd.) were blended at a weight ratio of 50:50 to form a 40mm
After pelletizing again through an extruder (220℃),
A test piece was molded using a 50Z injection molding machine (230°C), and its physical properties were measured. The results are shown in Table-1. Example 8 After substantially completing the polymerization reaction by changing the catalyst amount and polymerization time of Example 1, 0.3 parts by weight of di-tert-butyl peroxide was added, the temperature was raised to 140°C, and the mixture was heated for another 2 hours. Stirring was continued. Other than that, the same operation as in Example 1 was performed. As is clear from the results of Examples 1 to 8 in Table 1, by controlling the swelling degree of the gel of the resin composition within the range of the present invention, the appearance of the molded product is greatly improved, and the physical properties are also improved. It turns out that it is well balanced. On the other hand, as shown in Comparative Examples 1 to 3, if the swelling degree of the gel of the resin composition is outside the range of the present invention, no effect of improving the appearance of the formed product is observed or the impact strength is significantly reduced.

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Claims (1)

[Claims] 1. A (co)polymer of monomers whose main components are an ethylene/α-olefin/nonconjugated diene copolymer rubber component and an aromatic vinyl compound or an aromatic vinyl compound and a vinyl cyanide compound as a matrix resin component. 1. A rubber-modified thermoplastic resin composition comprising a rubber-modified impact-resistant resin composition, characterized in that the degree of swelling of methyl ethyl ketone insoluble components in the composition with n-hexane is 0.4-1.5.