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
2000-11-02
2002-08-20
Henderson, Christopher (Department: 1713)
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...
C524S089000, C524S371000, C524S405000, C524S515000, C524S525000
Reexamination Certificate
active
06437035
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is related to a flame retardant thermoplastic elastomer film composition for use in forming films for use in automotive interiors, wallcoverings, upholstery, advertising films, and tenting materials, which employs a maleated polypropylene to improve the physical properties such as melt processing, tear strength, and tensile properties while allowing the incorporation of more flame retardant into the composition.
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, is flame retardant, 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.
Maleated polypropylenes are substituted polyolefins which have been used to copolymerize with thermoplastic elastomers or as compatabilizers for thermoplastic elastomers. For example, U.S. Pat. Nos. 5,912,296, 5,910,530, and 5,905,116, to Wang, et al., disclose a process for preparing an oil extended graft copolymer compositions that are composed of a maleated polypropylene grafted to a functionalized thermoplastic elastomer. However, no prior art has taught maleated polypropylene as compatibilizing the flame retardants and fillers, enhancing the physical properties and allowing higher levels of flame retardant and filler while being processed. U.S. Pat. No. 5,910,540, to Takahashi, discloses a thermoplastic elastomer composition that exhibits favorable heat fusion properties, and a maleated polyolefin, such as a maleated polypropylene, is added to the composition as a compatibilizer. However, Takahashi is distinguishable from the present invention because Takahashi teaches the maleated polyolefin as a compatibilizer for different polymers, mainly a modified polystyrene. It also does not teach the maleated polyproplene as enhancing the physical properties and allowing more flame retardant to be incorporated. Although U.S. Pat. No. 5,843,577, to Ouhadi et al. discloses a thermoplastic elastomer having improved surface properties due to the addition of, among other things, certain types of maleated polypropylenes, it also is distinguishable in that the maleated polypropylene is compatibilizing different materials and does not enhance physical properties that allow the incorporation of additional flame retardant.
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 polymeric elastomer, a maleated polypropylene, a flame retardant, and a filler material results in a thermoplastic elastomer film composition that has improved physical properties, processing, and flame retardancy while being 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 a polymeric elastomer (i.e., less than 30% by weight), a maleated polypropylene, a flame retardant, 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 “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(D 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 agitat
Brouse McDowell
Henderson Christopher
Moxon II George W.
RJF International Corporation
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