Block copolymer

Abstract

The present invention relates to a block copolymer (A) including a (meth)acrylic polymer block (a) and an acrylic polymer block (b). The (meth)acrylic polymer block (a) is preferably copolymerized with a monomer having a functional group having high cohesive force, such as a carboxyl group, so that the 5%-weight-loss temperature is 300° C. or more or the tensile strength is 3 MPa or more, and the hardness measured by a type A durometer according to JIS K6253 is 50 or less, and a compression set measured after 22 hours at 70° C. is 45% or less. The block copolymer (A) exhibits excellent thermal decomposition resistance and low compression set at high temperatures. The block copolymer (A) can be used as a soft material for automobile, and has low hardness, high adhesion, high oil resistance, high weather resistance, high heat resistance, high recycling property, high tensile properties, and high wax remover resistance.

Description

TECHNICAL FIELD [0001] The present invention relates to a block copolymer having excellent thermal decomposition resistance and oil resistance, exhibiting good compression set even at high temperatures, and being usable as a rubber, a thermoplastic resin, an impact modifier for thermoplastic resins, a compounding agent for a compound material having elasticity between those of resins and rubber, a paint, a binding agent, or an adhesive. More specifically, the present invention relates to a block copolymer containing a methacrylic polymer and an acrylic polymer and having excellent balance between physical properties, particularly thermal decomposition resistance and oil resistance, and good compression set at high temperatures. [0002] The present invention further relates to a soft material for automobile containing a thermoplastic elastomer composition having low hardness, excellent adhesion, excellent heat resistance, excellent oil resistance, and excellent tensile properties (mec...

AI Technical Summary

Benefits of technology

[0019] It is an object of the present invention to provide a thermoplastic elastomer (block copolymer) excellent in thermal decomposition resistance and heat resistance allowing the elastomer to exhibit good rubber elasticity even at high temperatures.

Problems solved by technology

However, conventional styrene or olefin thermoplastic elastomer is insufficient in rubber elasticity, particularly compression set at high temperatures, as compared with crosslinked rubber.

However, the hard segments of these (meth)acrylic block copolymers have glass transition temperatures of 150° C. or less, and thus have difficulty in exhibiting rubber characteristics at high temperatures which are required in the automobile field.

Also, acrylic block polymers having hard segments of acrylic acid exhibit a breaking strength of less than 3 MPa (NITTO DENKO Technical Report (Nitto-Giho), Vol. 38, No. 2, November, 2000), and thus have the problem of failing to exhibit sufficient strength for use as elastomeric materials.

However, the thermoplastic resins usable with the block copolymers are limited to low-polarity resins such as polystyrene resins, polyolefin resins, and polyphenylene ether resins.

However, when the thermal decomposition temperature of the thermoplastic elastomer is lower than the injection molding temperature, the thermoplastic elastomer may cause thermal deterioration.

For example, the above-described high-polarity resin such as a polyvinyl chloride resin, a polymethyl methacrylate resin, a polycarbonate resin, a polyester resin, or a polyamide resin has both a high molding temperature and high heat resistance, and thus such a resin cannot be used for molding a mixture with the thermoplastic elastomer because the thermoplastic elastomer is thermally decomposed.

However, these materials have the problem of resources saving and environmental protection, i.e., the problem of recycling.

Thus, it is impossible or difficult to recycle these materials.

Although conventional olefin thermoplastic elastomer and styrene thermoplastic elastomer are excellent in recycling property and mechanical properties, these elastomers have the problem of low adhesion to resins and metals and low oil resistance.

Although the olefin thermoplastic elastomer is known to have proper flexibility and processability, the olefin thermoplastic elastomer does not exhibit sufficient weather resistance and oil resistance and cannot be directly used as an alternative.

Thus, the use of the olefin thermoplastic elastomer as a material for exterior members has the problem of causing poor surface appearance during the removal of the wax.

Although the thermoplastic polyester elastomers are excellent in mechanical properties, heat resistance and oil resistance, the polyester elastomers have the problem of low flexibility due to high hardness, thereby significantly degrading mountability.

However, these thermoplastic copolyester compositions does not have flexibility and oil resistance sufficient for boots and hoses, and further investigation is required.

Therefore, molding is difficult, and the problem of flexibility remains unsolved, thereby causing the need for further improvement.

As described above, the thermoplastic polyester elastomer has excellent mechanical strength, but it has disadvantages of high hardness and poor oil resistance.

Also, the acrylic rubber-compounded thermoplastic elastomer has improved oil resistance, but it still has disadvantages of poor formability and poor flexibility.

Therefore, the application to automobile hollow-molded products is limited, and a material for automobile hollow-molded products having excellent oil resistance and excellent flexibility is required.