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
2001-01-26
2002-08-13
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...
C525S199000, C525S216000, C525S217000, C525S219000, C525S232000, C525S240000, C525S241000, C525S254000, C525S263000
Reexamination Certificate
active
06433090
ABSTRACT:
TECHNICAL FIELD
This invention is directed toward thermoplastic elastomers and processes for making the same, as well as foams made from these thermoplastic elastomers. Specifically, the thermoplastic elastomers include a rubber that is at least partially cured, a long-chain branched thermoplastic resin, and optionally a linear thermoplastic resin.
BACKGROUND OF THE INVENTION
Thermoplastic elastomers are known. They have many of the properties of thermoset elastomers, yet they are processable as thermoplastics. One type of thermoplastic elastomer is a thermoplastic vulcanizate, which may be characterized by finely-divided rubber particles dispersed within a plastic. These rubber particles are crosslinked to promote elasticity. Thermoplastic vulcanizates are conventionally produced by dynamic vulcanization, which is a process whereby a rubber is cured or vulcanized within a blend with at least one non-vulcanizing polymer while the polymers are undergoing mixing or masticating at some elevated temperature, preferably above the melt temperature of the non-vulcanizing polymer.
Thermoplastic vulcanizates are useful for forming molded articles such as boots, seals, and like for use in the automotive, industrial, and consumer markets. These uses require that the articles demonstrate low set under both stress and strain. This is especially true in cold environmental conditions. Therefore, there is a continued need to lower the compression and tension set of thermoplastic vulcanizates without deleteriously impacting the mechanical properties of the thermoplastic vulcanizate.
Thermoplastic vulcanizates can also be foamed to form cellular articles such as weather seals. Typically, a foaming agent is added to the thermoplastic vulcanizate and the composition is extruded at or above the melt temperature of the thermoplastic phase. These cellular articles, however, have not always been competitive because they suffer from a relatively high compression set and high compression load deflection. As a result, their use, such as in weather seals, has been limited.
SUMMARY OF INVENTION
In general the present invention provides a thermoplastic vulcanizate prepared by a process comprising the steps of dynamically vulcanizing a vulcanizable rubber within a mixture that includes from about 15 to about 90 percent by weight of the rubber and from about 10 to about 85 percent by weight of a long-chain branched thermoplastic resin, where the long-chain branched thermoplastic resin is (i) an &agr;-olefin polymer, (ii) a copolymer of an &agr;-olefin and an &agr;-&ohgr;-olefin diene, or (iii) a mixture thereof, where the long-chain branched thermoplastic resin is characterized by a weight average molecular weight from about 100,000 to about 600,000, a number average molecular weight from about 40,000 to about 200,000, a z-average molecular weight from about 400,000 to about 2,000,000, a <g′>
vis
from about 0.2 to about 0.95, and a melt flow rate from about 0.3 to about 30 dg/min.
The present invention also includes a thermoplastic vulcanizate prepared by a process comprising the steps of dynamically vulcanizing a vulcanizable rubber within a mixture that includes the rubber and a long-chain branched thermoplastic resin, where the long-chain branched thermoplastic resin is (i) an &agr;-olefin polymer, (ii) a copolymer of an &agr;-olefin and an &agr;-&ohgr;-olefin diene, or (iii) a mixture thereof, where the long-chain branched thermoplastic resin is characterized by a <g′>
vis
from about 0.2 to about 0.95, and a melt flow rate from about 0.3 to about 30 dg/min.
The present invention further includes a thermoplastic vulcanizate comprising a vulcanized rubber that has been vulcanized in the substantial absence of a peroxide curative, and a long-chain branched thermoplastic resin.
The present invention still further includes a thermoplastic vulcanizate comprising a vulcanized rubber, and from about 27 to about 40 percent by weight of a long-chain branched thermoplastic resin based upon the total weight of the vulcanized rubber and the long-chain branched thermoplastic resin.
The present invention also includes a foam profile prepared by a process comprising the steps of foaming a thermoplastic vulcanizate, where the thermoplastic vulcanizate is prepared by a process comprising the step of dynamically vulcanizing a rubber within a mixture that includes from about 15 to about 90 percent by weight of the rubber and from about 10 to about 85 percent by weight of a thermoplastic component, where the thermoplastic component includes from about 5 to about 75 percent by weight of a long-chain branched thermoplastic resin and from about 95 to about 25 percent by weight linear thermoplastic resin, where the long-chain branched thermoplastic resin is (i) an &agr;-olefin polymer, (ii) a copolymer of an &agr;-olefin and an &agr;-&ohgr;-olefin diene, or (iii) a mixture thereof, where the long-chain branched thermoplastic resin is characterized by a weight average molecular weight from about 100,000 to about 600,000, a number average molecular weight from about 40,000 to about 200,000, and a z-average molecular weight from about 400,000 to about 2,000,000, a <g′>
vis
from about 0.2 to about 0.95, and a melt flow rate from about 0.3 to about 30 dg/min.
The use of long-chain branched thermoplastic resins within thermoplastic vulcanizates has surprisingly improved the tension set and compression set of the thermoplastic vulcanizates. Additionally, the use of long-chain branched thermoplastic resins provides soft thermoplastic vulcanizates having improved foaming characteristics.
PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION
The thermoplastic vulcanizates of this invention include at least one cured rubber, at least one long-chain branched thermoplastic resin, and optionally one or more linear thermoplastic resins. These thermoplastic vulcanizates can be foamed to form cellular articles by employing a foaming agent.
Any rubber or mixture thereof that is capable of being crosslinked or cured can be used as the rubber component. Reference to a rubber may include mixtures of more than one rubber. Useful rubbers typically contain some degree of unsaturation in their polymeric main chain. Some non-limiting examples of these rubbers include elastomeric copolymers, butyl rubber, natural rubber, styrene-butadiene copolymer rubber, butadiene rubber, acrylonitrile rubber, halogenated rubber such as brominated and chlorinated isobutylene-isoprene copolymer rubber, butadiene-styrene-vinyl pyridine rubber, urethane rubber, polyisoprene rubber, epichlolorohydrin terpolymer rubber, and polychloroprene. The preferred rubbers are elastomeric copolymers and butyl rubber.
The term elastomeric copolymer refers to rubbery copolymers polymerized from ethylene, at least one &agr;-olefin monomer, and optionally at least one diene monomer. The &agr;-olefins may include, but are not limited to, propylene, 1-butene, 1-hexene, 4-methyl-1 pentene, 1-octene, 1-decene, or combinations thereof. The preferred &agr;-olefins are propylene, 1-hexene, 1-octene or combinations thereof. The diene monomers may include, but are not limited to, 5-ethylidene-2-norbornene; 1,4-hexadiene; 5-methylene-2-norbornene; 1,6-octadiene; 5-methyl-1,4-hexadiene; 3,7-dimethyl-1,6-octadiene; 1,3-cyclopentadiene; 1,4-cyclohexadiene; dicyclopentadiene; 5-vinyl-2-norbornene and the like, or a combination thereof. The preferred diene monomers are 5-ethylidene-2-norbornene and 5-vinyl-2-norbornene. In the event that the copolymer is prepared from ethylene, &agr;-olefin, and diene monomers, the copolymer may be referred to as a terpolymer or even a tetrapolymer in the event that multiple &agr;-olefins or dienes are used.
Elastomeric copolymers are commercially available under the tradenames Vistalon™ (Exxon Mobil Chemical Co.; Houston, Tex.), Keltan™ (DSM Copolymers; Baton Rouge, Louisiana), Nordel™ IP (DuPont Dow Elastomers; Wilmington, Delaware), ElastoFlo™ (Union Carbide; Danbury, Conn.), and Buna™ (Bayer Corp.; Germany).
In one embodiment, th
Ellul Maria D.
Sahnoune Abdelhadi
Advanced Elastomer Systems L.P.
Nutter Nathan M.
Reginelli Arthur M.
Skinner William A.
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