Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-08-15
2003-04-29
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S232000, C525S240000, C525S241000
Reexamination Certificate
active
06555624
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a thermoplastic crosslinked rubber composition. More particularly, the present invention relates to a thermoplastic crosslinked rubber composition with superior appearance, feeling, heat and light stabilities, scratch resistance, oil resistance and mechanical strength.
(2) Description of the Related Art
A thermoplastic elastomer composition obtained by, so to speak, dynamic crosslinking, that is crosslinking during melt mixing of a radically crosslinkable elastomer and a radically non-crosslinkable resin such as polypropylene (PP) in an extruder in the presence of a radical initiator, is well known technology and widely used in applications such as automotive parts.
As one of such rubbery compositions, a composition prepared by applying the dynamic crosslinking technology to an olefinic elastomer is known (JP-A-8-120127 and JP-A-9-137001). However, it has not necessarily been satisfied in the market due to its inferior scratch resistance.
One the other hand, as examples of dynamic crosslinking technology using a rubber other than olefinic elastomers, the followings are known: A dynamically crosslinked elastomer composition comprising an olefinic elastomer together with a hydrogenated diene rubber, compounded further with a crystalline &agr;-olefinic polymer, an ethylenic polymer and a softening agent (JP-A-9-302156), and a thermoplastic elastomer composition obtained by melt mixing of a polyolefinic resin and a random or a block copolymer of a conjugated diene type monomer and an aromatic vinyl monomer in the presence of a crosslinking agent (JP-A-3-2240). None of these compositions has enough mechanical strength, scratch resistance, appearance and heat and light stabilities. Thus there remains a need of a thermoplastic rubber composition acceptable for the practical use.
SUMMARY OF THE INVENTION
Based on these problems, an object of the present invention is to provide a thermoplastic crosslinked rubber composition, which does not have the above described problems, that is, superior in appearance, feeling, heat and light stabilities, scratch resistance, oil resistance and mechanical strength.
A thermoplastic crosslinked rubber composition of the present invention is mainly composed of partially or completely crosslinked rubber and a thermoplastic resin as a flow component. The inventors conducted thorough study to improve the thermoplastic rubber composition, and suprisingly found out the followings. In the case of a thermoplastic resin as a flow component being an olefinic resin as a rubber component, use of a a hydrogenated rubber of a homopolymer rubber of conjugated diene type monomer or a random copolymer of a conjugated diene type monomer unit and an aromatic vinyl monomer unit as a rubber component, having a specified crystallinity, dramatically improves appearance, feeling, heat and light stabilities, scratch resistance, oil resistance and mechanical strength.
The present invention thus provides a thermoplastic crosslinked rubber composition comprising (A) from 1 to 99 parts by weight of a hydrogenated rubber obtained by hydrogenating not less than 50% of total double bonds of at least one homopolymer rubber of a conjugated diene type monomer or a random copolymer rubber consisting of a conjugated diene type monomer unit and an aromatic vinyl monomer unit and (B) from 1 to 99 parts by weight of an olefinic thermoplastic resin, total amount of (A) and (B) being 100 parts by weight, said (A) being partially or completely crosslinked, wherein said (A) is crystalline rubber, having a crystallization temperature in a range of from −50 to 70° C. and a heat quantity of crystallization at peak in a range of from 3 to 100 J/g in differential scanning calorimetry (DSC method).
The present invention preferably provides a thermoplastic crosslinked rubber composition obtained by crosslinking (A) from 1 to 99 parts by weight of a hydrogenated rubber obtained by hydrogenating not less than 50% of total double bonds of at least one homopolymer rubber of a conjugated diene type monomer or a random copolymer rubber consisting of a conjugated diene type monomer unit and an aromatic vinyl monomer unit and (B) from 1 to 99 parts by weight of an olefinic thermoplastic resin, total amount of (A) and (B) being 100 parts by weight, wherein said (A) is crystalline rubber, having a crystallization temperature in a range of from −50 to 70° C. and a heat quantity of crystallization at peak in a range of from 3 to 100 J/g in differential scanning calorimetry (DSC method).
Further, in the case of a thermoplastic resin as a flow component being a non-olefinic thermoplastic resin, preferably styrene-based resin (an olefinic thermoplastic resin may present together), a hydrogenated rubber of a homopolymer rubber of a conjugated diene type monomer or a random copolymer of a conjugated diene type monomer unit and an aromatic vinyl monomer unit as a rubber component, having a specified crystallinity, even if it is a non-crystalline rubber, shows superior appearance, feeling, heat and light stabilities, scratch resistance, oil resistance and mechanical strength. In the case of a thermoplastic resin as a flow component being a non-olefinic thermoplastic resin (an olefinic thermoplastic resin may present together), even non-hydrogenated rubber as a rubber component also shows superior appearance, feeling, scratch resistance, oil resistance and mechanical strength, although inferior in heat and light stabilities. It was found out that, in the case using this non-hydrogenated rubber, a rubber composition can be used in applications where heat and light stabilities are not required, due to satisfying practical characteristics, although it lacks heat and light stabilities. It was also found out that, in the case of a thermoplastic resin as a flow component being a non-olefinic thermoplastic resin (an olefinic thermoplastic resin may present together), even a block copolymer of a conjugated diene type monomer unit and an aromatic vinyl monomer unit as a rubber component shows superior appearance, feeling, heat and light stabilities, scratch resistance, oil resistance and mechanical strength.
The present invention thus provides a thermoplastic crosslinked rubber composition comprising (A) from 1 to 99 parts by weight of at least one homopolymer rubber of a conjugated diene type monomer or a random or block copolymer rubber consisting of a conjugated diene type monomer unit and an aromatic vinyl monomer unit or a hydrogenated rubber thereof (preferably not has than 50% of the total double bonds thereof being hydrogenated) and (B) from 1 to 99 parts by weight of a non-olefinic thermoplastic resin (preferably a styrene-based resin) or a mixture of an olefinic thermoplastic resin and a non-olefinic thermoplastic resin (preferably styrene-based resin), total amount of (A) and (B) being 100 parts by weight, said (A) being partially or completely crosslinked wherein said (A) is a non-crystalline rubber or a crystalline rubber (preferably a crystalline rubber having a crystallization temperature in a range of from −50 to 70° C. and a heat quantity of cyrstallization at peak in a range of from 3 to 100 J/g in differential scanning calorimetry (DSC method)).
The present invention preferably provides a thermoplastic crosslinked rubber composition obtained by crosslinking (A) from 1 to 99 parts by weight of at least one homopolymer rubber of a conjugated diene type monomer or a random or block copolymer rubber consisting of a conjugated diene type monomer unit and an aromatic vinyl monomer unit or a hydrogenated rubber thereof (preferably not has than 50% of the total double-bonds thereof being hydrogenated) and (B) from 1 to 99 parts by weight of a non-olefinic thermoplastic resin (preferably a styrene-based resin) or a mixture of an olefinic thermoplastic resin and a non-olefinic thermoplastic resin (preferably styrene-based resin), total amount of (A) and (B) being 100 parts by weight, wherein said (A) is a non-crysta
Nishihara Hajime
Ohtani Ikuji
Sasaki Sigeru
Suda Yoshikazu
Asahi Kasei Kabushiki Kaisha
Birch & Stewart Kolasch & Birch, LLP
Nutter Nathan M.
Tran Thao
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