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
2000-09-29
2003-01-21
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S068000, C525S133000, C524S504000, C524S505000, C524S508000
Reexamination Certificate
active
06509412
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the use of a compatibilizer to produce hydrogenated block copolymer containing gel compositions 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
Thermoplastic elastomers of a rubberlike soft material, requiring no vulcanization, and having moldability like thermoplastic resins are highly desirable, especially for automobile parts, household electric appliance parts, electric wire-protecting materials, coatings, 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.
Gels containing block copolymers, polyphenylene ether (PPO), and at least 500 parts by weight of an extender oil per 100 parts by weight (pbw) of block copolymer are known but generally are too soft, have insufficient tensile strength, and have a compression set that is less than desirable.
Also known are high-impact polyphenylene compositions that include a PPO resin, a hydrogenated block copolymer, and an oil. These can provide thermoplastic resins having good processability, but have not been shown to provide thermoplastic elastomers having superior compression set at 100° C.
Combinations of PPO, hydrogenated styrene/butadiene/styrene block copolymer (SEBS), and a non-aromatic oil also are known. One such combination includes 100 pbw SEBS per hundred parts by weight of rubber (hereinafter phr) and from about 10 to 30 phr non-aromatic oil, has a weight ratio of SEBS/PPO of from about 90:1 to about 30:70, and has a compression set at 100° C. of less than 65%.
Previously available hydrogenated block copolymer-based thermoplastic elastomers exhibiting a high-temperature (100° C.) compression set of at least 65% do not reach the required level of high-temperature compression set for vulcanized rubber applications. Consequently, to obtain hydrogenated block copolymer-based thermoplastic elastomer compositions that can be molded repeatedly without losing their excellent high-temperature (100° C.) compression set often requires the use of a fourth ingredient such as a polyolefin or polystyrene. In some instances, a curative such as a peroxide, also has been added.
The use of low molecular weight oils to obtain soft gels, often results in oil exuding 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 contacted with cleaning fluids or aqueous solutions containing solvents or surfactants, thereby limiting the areas where such parts can be used. Attempts to form non-oil polymeric compositions of SEPS/PPO matrices by bulk mixing have suffered from poor compatibilization. Therefore, an extra step of dissolving the components in solvent prior to mixing is often required. This step increases both the cost and time required to form the desired polymer compositions.
Accordingly, a strong need remains for thermoplastic elastomer compositions that can be processed easily and used repeatedly but which are superior in high-temperature (100° C.) compression set and can be obtained in a simple manner, preferably using bulk mixing equipment.
SUMMARY OF THE INVENTION
The present invention provides a composition of hydrogenated block copolymer, such as hydrogenated SEBS; PPO; amorphous polyolefin; and compatibilizer blended in bulk proportions specifically selected with respective weight proportions sufficient to provide a soft gel having a service temperature of up to about 150° C. and a Shore A hardness of no more than about 30. In an exemplary embodiment, a composition having a compression set at 100° C. for 22 hours of less than 65% that includes 100 pbw of a hydrogenated polymer, 10 to 150 pbw of a homo- and/or co-polymeric PPO resin, 10 to 500 pbw of a substantially amorphous polyolefin or hydrogenated polydiene, and 5 to 75 pbw of a diblock polymer including a first block that includes units derived from a vinyl-substituted aromatic hydrocarbon and a second block that includes units derived from a conjugated diene is provided. The diblock polymer acts to compatibilize the other components. The hydrogenated polymer includes at least two polymer blocks derived from a vinyl-substituted aromatic hydrocarbon and at least one polymer block derived from a conjugated diene. The PPO resin includes a binding unit of the general formula:
wherein R
1
, R
2
, R
3
, and R
4
independently are a hydrogen atom, a halogen atom, and/or a hydrocarbon group. The compositions have damping properties useful in producing molded products having heat resistance and high elasticity.
One advantage of the present polymer composition is that compression set values of less than about 65% may be consistently achieved when the non oil (low oil) blend is mixed in bulk mixing equipment. This eliminates the step of dissolving the components in a common solvent.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The present invention provides a hydrogenated block copolymer composition having a compression set at 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 a binding unit represented by the general formula:
wherein R
1
, R
2
, R
3
, and R
4
, which may be the same or different, represent substituents selected from one or more of hydrogen, halogen, hydrocarbon groups and substituted hydrocarbon groups,
c) 10 to 500 parts by weight of a substantially amorphous polyolefin such as EPR or a hydrogenated polydiene, and
d) 5 to 75 parts by weight of a compatibilizer in the form of a vinyl-substituted aromatic hydrocarbon/conjugated diene diblock polymer.
The hydrogenated block copolymer is 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. This hydrogenated block copolymer has the polymer structure of hydrogenated products of vinyl-substituted aromatic hydrocarbon/conjugated diene block copolymers represented by formulae such as: (AB)
n
A, (BAB)
n
A, (BAB)
n
AB, (AB)
m
X, etc., wherein n is an integer of 1 or more, m is an integer of 2 or more and X represents a coupling or polyfunctional initiator residue having two or more functional groups.
This hydrogenated block copolymer contains 5 to 60 wt. %, preferably 10 to 50 wt. % of a vinyl-substituted aromatic hydrocarbon. Referring now to its block structure, the polymer block A composed mainly of vinyl-substituted aromatic hydrocarbon has the structure of the homopolymer block of a vinyl-substituted aromatic hydrocarbon containing more than 50 wt. %, preferably not less than 70 wt. % of vinyl-substituted aromatic hydrocarbon with a hydrogenated conjugated diene. The polymer block B composed mainly of a hydrogenated conjugated diene has the structure of the homopolymer block of a hydrogenated conjugated diene or the copolymer block of a hydrogenated conjugated diene containing more than 50 wt. %, preferably not less than 70 wt. % of hydrogenated conjugated diene with a vinyl-substituted aromatic hydrocarbon. Both polymer blocks may take any of random, tapered and partial block arrangements and combinations thereof; and when the numbers of both of the polymer blocks A and B are 2 or more, the structu
Bridgestone Corporation
McCollister Scott
Palmer Meredith
Short Patricia A.
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