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
1998-06-22
2001-08-07
Acquah, Samuel A. (Department: 1711)
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...
C524S522000, C524S296000, C524S318000, C524S275000, C524S378000, C525S233000
Reexamination Certificate
active
06271301
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to thermoplastic elastomers that include polyvinyl chloride and a nitrile rubber additive.
Thermoplastic elastomers are useful in a variety of applications such as, for example, automotive products, grips, seals, gaskets, constant velocity joint boots and wire insulation, cable insulation and jacketing.
Thermoplastic elastomers have been formed from block copolymers or blends of thermoplastics and elastomers. Examples of block copolymer thermoplastic elastomers include styrenic block copolymers, polyolefin block copolymers, thermoplastic polyurethane block copolymers, polyamide block copolymers and polyester block copolymers. Thermoplastic elastomers formed from blends of thermoplastics and elastomers include thermoplastic polyolefin physical blends and thermoplastic vulcanizates.
SUMMARY OF THE INVENTION
The invention relates to thermoplastic elastomers that include polyvinyl chloride and a nitrile rubber additive. The nitrile rubber additive can be crosslinked. The thermoplastic elastomers can also include other materials such as a copolyester and/or a plasticizer.
The thermoplastic elastomers can be soft, elastomeric and/or oil resistant. The thermoplastic elastomers can have relatively low brittle points. The thermoplastic elastomers can have good smoke suppressant, flame retardant and/or char forming properties.
In one aspect, the invention features a thermoplastic elastomer that includes a polyvinyl chloride and a nitrile rubber. The thermoplastic elastomer has a compression set of from about 20 to about 50 and a shore A hardness of no greater than about 60. The thermoplastic elastomer retains its integrity when immersed in ASTM #1 oil for a period of about three days at a temperature of about 125° C. or when immersed in ASTM #3 oil for a period of about three days at a temperature of about 125° C.
In another aspect, the invention features a thermoplastic elastomer that includes a polyvinyl chloride and a nitrile rubber additive. The polyvinyl chloride has a weight average molecular weight of at least about 100,000.
In a further aspect, the invention features a thermoplastic elastomer that includes a polyvinyl chloride, a crosslinked nitrile rubber additive and at least about 105 parts of a plasticizer per 100 parts of the polyvinyl chloride.
In yet a further aspect, the invention features a method of making a molded article. The method includes combining a polyvinyl chloride and a nitrile rubber additive to form a thermoplastic elastomer composition. The method further includes injection molding the thermoplastic elastomer composition to form the molded article.
In still a further aspect, the invention features a method of making a thermoplastic elastomer composition. The method includes combining a polyvinyl chloride with a crosslinked nitrile rubber additive.
In another aspect, the invention features a thermoplastic elastomer composition that includes a polyvinyl chloride and a nitrile rubber additive. The thermoplastic elastomer has a brittle point of no greater than about −50° C.
In yet another aspect, the invention features a thermoplastic elastomer composition that includes a polyvinyl chloride, a nitrile rubber and one or more compounds selected from smoke suppressants, flame retardants and char formers.
The thermoplastic elastomers can be used in applications in which it is desirable to use a material that can be soft and provide low compression set even when the compositions are subjected to high temperatures and/or oils for extended periods of time. Such applications include wire and cable insulation and jacketing, garden hoses, medical devices, automotive parts, and construction materials.
The thermoplastic elastomers can be used in applications in which it is advantageous to use a material that has a relatively low brittle point, such as in a constant velocity joint boot.
The thermoplastic elastomers can be used in applications in which it can be important to use a material that exhibits good smoke suppression, good flame retardancy and/or good char forming properties. These applications include wire and cable insulation and jacketing.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The thermoplastic elastomers include at least one polyvinyl chloride and at least one a nitrile rubber additive. The thermoplastic elastomers can further include additional compounds such as a copolyester and/or a plasticizer.
The thermoplastic elastomers can have a relatively low compression set. When a low compression set is desirable, the thermoplastic elastomers preferably have a compression set of from about 20 to about 50, more preferably from about 25 to about 45, and most preferably from about 30 to about 40 as measured according to the ASTM D-395 test at 70° C.
The thermoplastic elastomers can be comparatively soft. When good softness is advantageous, the thermoplastic elastomers preferably have a shore A hardness of no greater than about 60, more preferably from about 30 to about 60, and most preferably from about 40 to about 50 as measured according to ASTM D-746 at 70° C. after a 15 second dwell.
In some instances, the thermoplastic elastomers may be exposed to oils for extended periods of time, so it can be advantageous for the thermoplastic elastomers to have good oil resistant properties. In these instances, it is preferable that, when immersed in ASTM #1 oil for a period of about three days at a temperature of about 125° C. or when immersed in ASTM #3 oil for a period of about three days at a temperature of about 125° C., the chemical and physical properties of the thermoplastic elastomers do not undergo any substantial changes so that the thermoplastic elastomer retains its integrity. In some embodiments, when the thermoplastic elastomer is immersed in ASTM #1 oil for a period of about three days at a temperature of about 125° C. and when the thermoplastic elastomer is immersed in ASTM #3 oil for a period of about three days at a temperature of about 125° C., the chemical and physical properties of the thermoplastic elastomer do not undergo any substantial changes so that the thermoplastic elastomer retains its integrity.
The thermoplastic elastomers can have relatively low brittle points. When a low brittle point is desirable, the thermoplastic elastomers preferably have a brittle point of no greater than about −50° C., more preferably no greater than about −55° C., and most preferably no greater than about −60° C. as measured according to ASTM D-746.
As used herein, “polyvinyl chloride” refers to omopolymers of vinyl chloride, as well as polymerization roducts of vinyl chloride and one or more co-monomers. Examples of polyvinyl chlorides include copolymers of vinyl chloride and ethylene and copolymers of vinyl chloride and propylene. The polyvinyl chloride resin can also be the polymerization product of vinyl chloride and an ester monomer having the formula H
2
C═C(R
1
)C(═O)OR
2
, where R
1
and R
2
are, independently, C
1-12
alkyl. An example of such a resin is a copolymer of a vinyl chloride monomer and a methyl methacrylate monomer. These resins may be used alone or in combination. Polyvinyl chlorides may or may not include an internal plasticizer (i.e., a comonomer that is copolymerized with vinyl chloride monomer).
The polyvinyl chloride can have a relatively high weight average molecular weight. Preferably, the polyvinyl chloride has a weight average molecular weight of at least about 100,000, more preferably at least about 110,000, and most preferably from about 110,000 to about 200,000.
The polyvinyl chlorides preferably have a degree of polymerization of at least about 1500, more preferably at least about 1650, and most preferably from about 1650 to about 4350.
In certain embodiments, the thermoplastic elastomers can include more than one polyvinyl chloride. These polyvinyl chlorides can have different molecular weights and/or different molecular structures. For example, the thermoplastic elastomers can include two different polyvinyl chlorides with
Andries John C.
Saunders Keith G.
Weng Dexi
Acquah Samuel A.
Fish & Richardson P.C.
Rajguru U. K
Teknor Apex Company
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