Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-07-14
2002-05-07
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S425000, C524S434000, C524S449000, C524S494000
Reexamination Certificate
active
06384123
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is related to a thermoplastic elastomer film composition for use in forming films for use in automotive interiors, wallcoverings, upholstery, advertising films, and tenting materials.
Thermoplastic elastomer compositions are known for their rubbery characteristics and frequently are used to modify polyolefin compositions, such as polyethylene and polypropylene. Often these thermoplastic elastomers are copolymers of ethylene and olefins, such as butene or octene, which are produced with metallocene or Kaminsky catalysts. One example of a polyolefin/thermoplastic elastomer blends are U.S. Pat. No. 5,998,524 to Srinivasan et al (and related U.S. Pat. Nos. 5,763,534; 5,773,515; 5,703,629; and 5,985,971), which disclose a composition having a majority of polyolefin, modified by the elastomeric component. Another example is U.S. Pat. No. 5,834,381 to Roe et al, which discloses a rubber (i.e., an elastomer) modified polypropylene which is 10 mils in thickness and is laminated to a scrim for use as auto security shades or covers. U.S. Pat. No. 5,576,374 to Betso et al discloses a polyolefin combined with a thermoplastic elastomer for use in filled composites and to make molded parts. U.S. Pat. No. 5,750,600 to Nozokido et al discloses an oil-extended olefin thermoplastic elastomer composition for use in skins of interior automotive trim. The Nozokido composition has a majority of elastomer (i.e., 50 to 70%) and 30 to 50% of a combination of polypropylene resins having different crystal melting points and is used to make sheets having a thickness of 0.25 to 0.45 mm. As noted in Nozokido, when the elastomer content is higher than 70% by weight, problems in manufacturing are encountered and vacuum forming suffers.
SUMMARY OF THE INVENTION
The present invention has resulted from the discovery that a composition which comprises a major amount of a thermoplastic elastomer or a blend of thermoplastic elastomers having an average melt index of less than 6, a minor amount (i.e., less than 30% by weight) of polyolefin, a minor amount of polymeric elastomer (i.e., less than 30% by weight), and a filler material results in a thermoplastic elastomer film composition which is useful for automotive interiors, wallcoverings, upholstery, advertising films or banners, and tenting. The composition is processable by calendering to make films having a thickness of less than 10 mils. The film can then be handled to be combined with other films or to be bonded to other support materials such as scrim fabrics.
DETAILED DESCRIPTION OF THE INVENTION
The thermoplastic elastomer composition for use in automotive interiors, wallcoverings, upholstery, advertising banners, and tenting comprises a major amount of a thermoplastic elastomer or a blend of thermoplastic elastomers having an average melt index of less than 6, a minor amount of a polyolefin and a polymeric elastomer (i.e., less than 30% by weight), and a filler material.
The thermoplastic elastomer (or “TPE”) can be any copolymer of ethylene and a C
3
to C
8
olefin produced with a metallocene or Kaminsky catalyst (or “single site”) catalysts and having a molecular weight distribution (Mw/Mn) of less than or equal to 3 is contemplated for use as this component. Examples are copolymers of ethylene and butene, copolymers of ethylene and hexene and copolymers of ethylene and octene. It is preferred that the TPE is a mixture of TPE's, where the TPE's have different melt indexes with one being higher than the other, but with the weighted average melt index being less than 6, less than 3 and less than 2 being also preferred. Examples of TPEs are the Exact® polymers from Exxon Mobil Chemical. The TPE will be present in a majority amount of from 50% by weight to about 95% by weight based upon the weight of all of the polymers. Preferably, the TPE is more than 60% by weight, with more than 80% by weight being further preferred.
The polyolefin resin can be a polyethylene or a polypropylene, but is preferably a general purpose homopolymer polypropylene. The polypropylene resin for use in the preparation of the olefin thermoplastic elastomer composition according to the present invention is a crystalline propylene resin having a crystal melting point of 140° C. to 165° C., preferably, 150° C. to 156° C. and an ethylene unit content of 1 to 2% by weight, preferably, 1.2 to 1.6% by weight. The characteristics of the polyolefin are not critical, but the amount of polyolefin will preferably be less than 30% by weight of the total polymeric composition, usually be about 1% to 30% by weight with up to 20% by weight and up to 10% by weight being further preferred.
The “polymeric elastomer” is a rubbery elastomer which will provide improved tear and elongation at break in the TPE composition and is preferred to be one of, but not limited to, a styrene-ethylene-butylene or “SEB” rubber with a Shore “A” hardness of 60 to 80, and a solution (25% weight in toluene viscosity of 6,000 to 9,000 CPS), a non-vulcanized chlorinated polyethylene with a chlorine content of between 30 and 42%, and a mooney viscosity (MS 1+4 121C) of between 42 and 94; and an (ethylene/vinyl acetate) copolymer or (ethylene/carbon monoxide) copolymer with a melt flow index of between 8 and 100 and a crystalline melt temperature of between 59 and 70° C. Examples of polymeric elastomers are Kraton® G-1650 thermoplastic rubber, which is a styrene-ethylene-butylene block copolymer, Elvaloy® HP511 resin from duPont, which is an ethylene vinyl acetate copolymer, and Tyrin 3615 from duPont Dow Elastomers, which is a chlorinated polyethylene. The polymeric elastomer will be present in a minor amount, about 1% to 30% by weight based upon the total weight of the polymers, preferably up to 20% by weight, with up to 10% by weight being further preferred.
The TPE composition of the present invention is achieved using processing equipment, which is typical for such materials. For example, in the preferred process, the ingredients will be weighed, pre-blended, mixed in a Banbury mixer, then passed through two 2-roll mills, a strainer extruder, and finally, calendered on an inverted “L” calender. There is no criticality in the equipment as long as it effectively mixes the composition and produces a thin film having an appropriate surface finish. It is preferred that the olefin thermoplastic elastomer composition for use in the present invention be prepared by blending together the components without the formation of crosslinking, from the viewpoint of formability at the final calendering and workability at lamination and/or vacuum forming.
For example, the thermoplastic elastomer composition can be prepared by preparing specified amounts of the ethylene/alpha-olefin copolymer elastomer and the polypropylene resin, charging them into an agitation mixer such as Henschel mixer (trade name), a supermixer or a tumbler mixer and effecting agitation blending generally for 1 to 10 min. In particular, while the use of the tumbler mixer takes about 10 min, the supermixer advantageously enables preparing the desired composition by agitation blending within about 3 min. According to necessity, the olefin thermoplastic elastomer composition can be melt kneaded by the use of a screw extruder or the like generally at 170° C. to 250° C., preferably, 210° C. to 230° C. and thereafter pellet
When a composition comprising a polypropylene resin having an ethylene unit content of much greater than 2% by weight is sheeted and subjected to postforming, for example, by embossing and vacuum forming, the problems are encountered such that the composition sticks to the embossing rolls at the time of postforming embossing and that the emboss disappears at the time of subsequent vacuum forming. On the other hand, when a composition comprising a polypropylene resin having an ethylene unit content of far lower than 0.5% by weight is sheeted, the problem encountered is that breakage of the postformed article often occurs at the time of vacuum forming. The polypropylene resin may be a res
McDowell Brouse
Moxon II George W.
RJF International Corporation
Sanders Kriellion A.
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