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
2000-05-23
2002-06-18
Wilson, D. R. (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...
C525S194000, C525S197000, C525S198000, C525S100000, C525S103000, C525S104000, C525S105000, C525S106000, C525S133000, C524S424000, C524S425000, C524S444000, C524S506000, C524S508000, C524S515000, C524S518000, C524S519000, C524S521000, C524S525000
Reexamination Certificate
active
06407174
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to thermoplastic elastomer vulcanizates (TPV) having superior physical properties and excellent processability comprising a blend (alloy) of a thermoplastic component and a fully vulcanized rubber component. The present invention further relates to a method for preparing said thermoplastic vulcanizate under dynamic vulcanization conditions.
2. Background/Prior Art
Polymer blends which have a combination of both thermoplastic and elastic properties (thermoplastic elastomers, TPE) are generally obtained by blending a thermoplastic polyolefin with an elastomeric composition (rubber) in a way such that the elastomer in intimately and uniformly dispersed as a discrete particulate phase within a continuous phase of the thermoplastic. Early work with vulcanized compositions is found in U.S. Pat. No. 3,037,954 which discloses static vulcanization as well as the technique of dynamic vulcanization wherein a vulcanizable elastomer is dispersed into a resinous thermoplastic polymer and the elastomer is cured while continuously mixing and shearing the polymer blend. The resulting composition (vulcanizate or dynamically vulcanized alloy, DVA) is a microgel dispersion of cured elastomer, such as butyl rubber, chlorinated butyl rubber, polybutadiene or polyisobutene in an uncured matrix of thermoplastic polymer such as polypropylene. Since then the technology has advanced significantly.
U.S. Pat. No. 3,037,954 discloses compositions comprising polypropylene and a rubber such as, inter alia, butyl rubber, chlorinated butyl rubber, polybutadiene, polychloroprene and polyisobutene. Compositions of about 50 to 95 parts polypropylene and about 5 to 50 parts of rubber are disclosed.
U.S. Pat. No. 3,758,643 and U.S. Pat. No. 3,806,558 disclose polymer blends comprising an olefin thermoplastic resin and an olefin copolymer rubber wherein the rubber is dynamically cured to a partial cure state. The compositions can be reprocessed, however, the potential applications of such blends are limited by their high compression set and/or low softening temperature resulting from only a partial cure of the rubber. Furthermore, the partial peroxide cure utilized in such blends is difficult to control from the standpoint of completeness of reaction, resulting in batch to batch variations in product properties.
U.S. Pat. No. 4,639,487 is directed to heat shrinkable DVAs including an ethylene copolymer resin blended with a butyl or halogenated butyl rubber. The butyl rubber should be at least partially dynamically vulcanized to a cured state in the presence of the copolymer.
U.S. Pat. No. 4,212,787 is directed to the production of partially cured DVA compositions which include 40-100 wt. % of a peroxide curable copolymer (such as EPDM); 0-60 wt. % of a peroxide decomposing copolymer (such as PE and PP); and 5-100 wt. % of a peroxide non-curable rubber, either polyisobutylene or butyl rubber.
U.S. Pat. No. 4,202,801 relates to the partial dynamic curing of a blend of a monoolefin copolymer rubber, such as saturated EPM or EPDM; a polyolefin resin such as PP or PE, with a conjugated diene rubber such as polybutadiene or polychloroprene. Crystalline polyolefin resin may be used. More than one monoolefin copolymer rubber, conjugated diene rubber and polyolefin resin may be used in combination. The DVAs of this invention are said to provide low compression set and high tensile strength at elevated temperatures.
U.S. Pat. No. 4,480,074 discloses DVA compositions said to exhibit improved surface characteristics and fabricability wherein the compositions are prepared by blending an unvulcanized, but vulcanizable, monoolefin rubber with a blend containing cured polyolefin rubber with crystalline polyolefin and subsequently vulcanizing such that the final blend comprises about 15-45 parts by weight of crystalline polyolefin and 85-55 parts by weight of vulcanized rubber. EPDM is taught as both the vulcanized polyolefin rubber and the unvulcanized but vulcanizable rubber in the disclosed blends.
JP-A-85,530/87 discloses a DVA composition including a crystalline polypropylene as a matrix and two elastomers: a bromobutyl rubber and an olefin copolymer rubber such as EPM or EPOM rubber.
The thermoplastic elastomer vulcanizates known in the art, however, show limitations with respect to the balance of physical properties (tensile strength, elongation at break) and processability, i.e., allowing to obtain shaped articles after injection-molding, extrusion and blow-molding which show no defect, such as on the surface, at the edges, etc.
It is an object of the present invention to provide a thermoplastic elastomer vulcanizate which has an improved balance of physical properties and superior processability. Additionally, it is desirable to provide thermoplastic elastomer vulcanizates allowing formulations with a high mineral filler content while maintaining a good balance of physical properties and an excellent processability.
DESCRIPTION OF THE INVENTION
It has surprisingly been found according to the present invention that thermoplastic vulcanizates obtained from a terpolymer comprising propylene, ethylene and an &agr;-olefin containing at least 4 carbon atoms as the thermoplastic component and a vulcanizable rubber as the elastomer component has both, superior physical properties and superior processability compared to thermoplastic elastomer vulcanizates based on homopolypropylene and reactor copolymer polypropylene (blend of polypropylene/ethylene-propylene copolymer rubber made in the polymerization reactor) as the thermoplastic component.
In detail the present invention relates to a thermoplastic elastomer vulcanizatce comprising
(a) 10 to 75% by weight of at least one thermoplastic terpolymer of ethylene propylene and an (&agr;-olefin containing at least 4 carbon atoms,
(b) 90 to 25% by weight of at least one fully cured rubber component, based on the total weight of components (a)+(b), and optionally
(c) 0 to 70% by weight of additive(s), based on the total weight of components (a)+(b)+(c).
Preferably the thermoplastic elastomer vulcanizate (dynamically vulcanized rubber/plastic alloy (“DVA”)) comprises 15 to 70% by weight of the thermoplastic terpolymer (a), 85 to 30% by weight of the fully cured rubber component (b), based on the total weight of components (a)+(b), and up to 65% by weight of the additive(s) (c), based on the total weight of components (a)+(b)+(c). The range defined above for the amount of the rubber (b) is based on the pure rubber component, excluding any extending oil which may be contained in the rubber.
In the specification and the claims the term “thermoplastic terpolymer” may be used interchangeably for “thermoplastic polyolefin” or just “polyolefin”. The term “rubber” may be used interchangeably for “elastomer”. The term “vulcanizate” in terms of the present invention means a blend or alloy which is obtainable from a thermoplastic olefinic polymer and a curable elastomer by melt-blending them in the presence of a curative to dynamically vulcanize the elastomer. The resulting DVA is a polyolefin matrix having micron or submicron size cured elastomer particles dispersed therein.
Thermoplastic Terpolymer
The terpolymer may have a random distribution in structure or a multi-sequence (multi-block) structure.
The thermoplastic terpolymer (a) consists of 0.5 to 19.5% by weight, more preferably from 2.0 to 15.0% by weight of ethylene monomer, 80.0 to 99.0% by weight, preferably from 96.0 to 80.0% by weight of propylene monomer and 19.5 to 0.5% by weight, preferably from 2.0 to 15.0% by weight of the &agr;-olefin monomer containing at least 4 carbon atoms, based on the weight of the thermoplastic terpolymer (a).
The &agr;-olefin monomer used in the preparation of the terpolymer (a) is a monoolefin and preferably contains 4 to 12 carbon atoms, more preferably from 4 to 8 carbon atoms. As the &agr;-olefin 1-butene, 1-pentene, 1-hexene and 1-octene are preferred. Most preferably 1-butene, 1-hexene an
Advanced Elastomer Systems L.P.
Skinner WiIliam A.
Wilson D. R.
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