Thermoplastic elastomeric compositions

Details Thermoplastic elastomeric compositions Thermoplastic elastomeric compositions

1997-12-16

2001-07-31

Wu, David W. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S197000, C526S127000, C526S119000, C526S160000, C526S348100, C502S113000, C502S117000, C521S143000

Reexamination Certificate

active

06268438

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to at least partially cross-linked olefin thermoplastic elastomers containing at least one polymer derived from a metallocene production process.
BACKGROUND OF THE INVENTION
Olefin thermoplastic elastomers have been widely used, particularly as substitutes for vulcanized rubbers, and more particularly in the field of molded products. These cross-linked olefin thermoplastic elastomers possess exceptional properties, including tensile strength, elongation at break, elastomeric properties, and heat resistance.
Historically, many of the elastomers of the type identified above, have been constructed of polymers made from a Ziegler-Natta catalyzed reaction. However, as described in U.S. Pat. No. 5,198,401, herein incorporated by reference, and International Application No. W097/11115, also herein incorporated by reference, the polymerization of olefins, diolefins and acetylenically unsaturated monomers to homopolymers and copolymers in the presence of an ionic metallocene catalyst is now producing unique materials. For example, the polypropylene polymers obtained via the metallocene catalysis process are generally at least substantially isotactic and often fully isotactic. As an additional example of a unique compound obtained via metallocene catalysis, low ethylene content EPR's are being produced. Specifically, the reactions are performed in the presence of a metallocene catalyst of the general formula
Cp
m
MR
n
X
q
wherein Cp is a cyclopentadienyl ring or a derivative thereof; M is a Group IV, V or VI transition metal; R is a hydrocarbyl group or hydrocarboxyl group having from 1 to 20 carbon atoms; X is a halogen and, m equals 1 to 3; n equals 0 to 3; Q equals 0 to 3, and the sum of m+n+q is equal to the oxidation strength of the transition metal. Further examples of metallocenes catalysts and processes are provided for in U.S. Pat. Nos. 4,530,914; 4,871,705; 4,937,299; 5,124,418; 5,017,714; 5,120,867; 5,278,119; 5,304,614; 5,324,800; 5,347,025; 5,350,723; 5,391,790; and 5,391,789, each of which is herein incorporated by reference.
SUMMARY OF THE INVENTION
It is a primary advantage to this invention to provide new and improved dynamically vulcanized thermoplastic elastomers (TPEs) demonstrating superior characteristics and/or lower production costs.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
In accordance with the purpose of the invention, as embodied and broadly described herein, the compositions of this invention comprise a cross-linked or at least partially cross-linked thermoplastic elastomeric composition formed of from 10 to 90 percent of a first polymeric material comprised of ethylene, &agr;-olefin and optionally a nononjugated diene, and 90 to 10 percent of a second olefin polymeric material, wherein at least one of the first or second polymeric materials is at least partially the product of a metallocene polymerization reaction. In this regard, the first or second polymeric material can be comprised of a blend of two or more polymers provided at least one is a metallocene polymer.
In one form of the invention, the first polymeric material is an elastomer of ethylene-propylene-diene-polymethylene, i.e., an EPDM. As used herein, EPDM is intended to reflect a terpolymer of ethylene, propylene and a non-conjugated diene. In an alternative form of the invention, the copolymer is an elastomer of ethylene and propylene, referred to sometimes as EPR and sometimes as EP(D)M—wherein the diene is optional.
In a particularly preferred form of the invention, the EP(D)M rubber has an ethylene content of less than 40 percent. More preferably, the EP(D)M rubber will have an ethylene content of less than 20 percent by weight. However, it is believed that metallocene EP(D)M may have certain advantages even with a C
2
above 40 percent.
Polyolefins suitable for use in the thermoplastic phase of the invention include thermoplastic crystalline polyolefin, homopolymers and copolymers. They are desirably prepared from monolefin monomers having three to six carbon atoms such as propylene, 1-butene, isobutylene, 1-pentene and the like, with polypropylene being preferred.
In a further preferred form of the invention, the second olefin polymeric material is polypropylene. In a particularly preferred form, the polypropylene is a metallocene derived polypropylene. In an additional embodiment, a third-or more-polymeric material is added to the composition.


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Polymer Technology Dictionary, T. Whelan, !-st edition Chapman & Hall, p. 125, 1994.

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