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
1998-10-05
2001-02-06
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C524S505000, C525S09200D
Reexamination Certificate
active
06184292
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to hydrogenated block copolymer containing gel compositions being superior in high-temperature (100° C.) compression set, mechanical strength and moldability, having utility at temperatures up to 150° C. and being useful as a molding material for various molded products.
BACKGROUND OF THE INVENTION
It is extremely desirable to develop thermoplastic elastomers of a rubber-like soft material, requiring no vulcanization, and having moldability like thermoplastic resins, for applications in the fields of automobile parts, household electric appliance parts, electric wire-protecting materials, medical appliance parts, miscellaneous goods, footwear, and the like. Various elastomer compositions containing the hydrogenated product of vinyl-substituted aromatic hydrocarbon/conjugated diene block copolymers (hereinafter referred to as hydrogenated block copolymer) have been used in thermoplastic elastomeric applications.
U.S. Pat. No. 5,710,206, to Francis et al, discloses gels containing block copolymers, polyphenylene ether and at least 500 parts of an extender oil per 100 parts by weight of the block copolymer. Such mixtures are too soft having low tensile strength and lower than desirable compression set.
WO 81/020020 discloses high-impact polyphenylene compositions comprising a polyphenylene ether resin, the hydrogenated block copolymer and an oil. The compositions obtained here provided thermoplastic resins having a good processability, but could not substantially provide thermoplastic elastomers superior in processability as well as compression set at 100° C.
Japanese Pat. 89-49423 B teaches a composition of polyphenylene ether (PPO), hydrogenated styrene/butadiene/styrene block copolymer (SEBS) and a non-aromatic oil; wherein the parts by weight per hundred parts by weight of rubber hydrocarbon (hereinafter “PHR”) of SEBS is 100 PHR; the weight proportion of SEBSIPPO ranges from about 90/1~30/70; the PHR of non-aromatic oil is from about 10~300; and, the composition has a compression set of less than 65% at 100° C. Japanese Pat. 94-70162 B teaches a composition of PPO, SEBS and a non-aromatic oil; wherein the PHR of SEBS is about 100; the weight proportion of SEBS/PPO ranges from about 90/10~30/70; the weight proportion of non-aromatic oil to the sum of SEBS and PPO is greater than 0.43; and, the composition has a compression set of less than 65% at 100° C.
It has long been recognized that two or more polymers may be blended together to form a wide variety of random or structured morphologies to obtain products that potentially offer desirable combinations of characteristics. However, in many cases, it may be difficult or even impossible in practice to achieve many potential combinations through simple blending because of some inherent and fundamental problem. Frequently, the two polymers are thermodynamically immiscible, which precludes generating a truly homogeneous product. This immiscibility may not be a problem per se since often it is desirable to have a two-phase structure. However, the situation at the interface between these two phases very often does lead to problems. The typical case is one of high interfacial tension and poor adhesion between the two phases. This interfacial tension contributes, along with high viscosities, to the inherent difficulty of imparting the desired degree of dispersion to random mixtures and to their subsequent lack of stability, giving rise to gross separation or stratification during later processing or use. Poor adhesion leads, in part, to the very weak and brittle mechanical behavior often observed in dispersed blends and may render some highly structured morphologies impossible.
The hydrogenated block copolymer-based thermoplastic elastomers produced according to the prior arts have a high-temperature (100° C.) compression set of 65% or more, do not reach the required level of high-temperature compression set for vulcanized rubber applications. Consequently, hydrogenated block copolymer-based thermoplastic elastomer compositions that are molded repeatedly without losing their excellent high-temperature (100° C.) compression set, often require the use of a fourth ingredient such as a polyolefin or polystyrene, or in other instances a curative such as a peroxide as shown in the prior art such as in U.S. Pat. No. 4,772,657, to Akiyama et al.
The use of low molecular weight oils, as required in the prior art to obtain soft gels, often results in an undesirable property, called bleeding; whereupon oil exudes to the surface of a molded part formed from such gels, resulting in potential contamination of the immediate area and increasing the hardness of the part. Furthermore, oils are readily extractable from a molded part containing oil when that part is bought into contact with cleaning fluids or aqueous solutions containing solvents or surfactants, thereby limiting the areas of use of such parts.
The present invention was made to solve the above problems that could not readily be solved with the conventional molding materials for elastomers. Particularly, it was found that thermoplastic elastomer compositions which can be processed easily and used repeatedly, and yet which are superior in high-temperature (100° C.) compression set, can be obtained by a simple blending technique.
OBJECTS OF THE INVENTION
Accordingly, it is an object of the instant invention to provide a soft gel that has utility at temperatures up to about 150° C.
More specifically, it is an object of this invention to provide a composition of hydrogenated styrene/butadiene/styrene block copolymer (SEBS), polyphenylene ether (PPO) and ethylene-propylene rubber (EPR) blended in proportions sufficient to provide a soft gel product having utility at temperature up to about 150° C.
Still more specifically, it is an object of this invention to provide a composition consisting essentially of SEBS, PPO and ethylene-propylene rubber (EPR) blended in proportions sufficient to provide product having utility as a super soft gel at temperature up to about 150° C.
Another object of the invention is to provide a relatively low molecular weight component composition of blended polymers that exhibit improved properties including: low Shore A hardness of less than about 30; high damping properties and a service temperature of up to about 150 ° C.; and are useful in the production of various other rubber compounds.
SUMMARY OF THE INVENTION
The present invention is most broadly directed to compositions useful in the manufacture of articles comprised of soft gels and having a service temperature of up to, and including, about 150° C.
More specifically, the primary object of the present invention under such circumstances is to provide a composition of hydrogenated block copolymer such as hydrogenated styrene/butadiene/styrene block copolymer (SEBS), polyphenylene ether (PPO) and ethylene-propylene rubber (EPR) blended in proportions specifically selected with respective weight proportions sufficient to provide a soft gel having: a service temperature of up to, and including, about 150° C. and a Shore A hardness of about 30 or less. The compositions of the invention have damping properties useful in producing molded products having heat resistance and a high elasticity and damping properties, such as industrial materials, electric and electronic materials, industrial construction materials, car parts, sporting goods, shoes, domestic electrical appliances, various mechanical parts, and the like.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a hydrogenated block copolymer composition having a compression set (100° C.) of 65% or less which comprises:
(a) 100 parts by weight of a hydrogenated block copolymer obtained by hydrogenating a block copolymer comprising at least two polymer blocks A composed mainly of a vinyl-substituted aromatic hydrocarbon and at least one polymer block B composed mainly of a conjugated diene, (b) 10 to 150 parts by weight of a homopolymeric and/or copolymeric polyphenylene ether resin comprising
Hall James E.
Mashita Naruhiko
Takeichi Hideo
Wang Xiaorong
Bridgestone Corporation
Burleson David G.
Cain Edward J.
McCollister Scott A.
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