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
1999-11-19
2001-11-06
Lipman, Bernard (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...
C525S195000, C525S226000, C525S230000
Reexamination Certificate
active
06313223
ABSTRACT:
BACKGROUND OF THE INVENTION
Hydrogenated nitrile rubbers offer the advantage of being resistant to oxidative degradation at high temperatures and also offer outstanding oil resistance. By virtue of these properties hydrogenated nitrile rubbers have excellent characteristics for utilization in applications where high temperatures and organic solvents, such as oils, are encountered. For instance, hydrogenated nitrile rubbers are frequently utilized in automotive applications where it is critical to have good heat resistance and good oil resistance. Accordingly, hydrogenated nitrile rubbers are frequently employed in belts, seals, gaskets, and hoses for internal combustion engines.
Hydrogenated nitrile rubber is made by hydrogenating the double bonds of conventional nitrile rubber. U.S. Pat. No. 4,452,950 discloses a process for hydrogenating the double bonds in a nitrile rubber while it is in latex form. The process of U.S. Pat. No. 4,452,950 is carried out in the presence of hydrazine, an oxidizing agent, and a metal ion initiator. Unfortunately, it is expensive to hydrogenate the double bonds of a nitrile rubber regardless of the specific hydrogenation procedure used. Hydrogenated nitrile rubber currently sells at a price of about $12-14 per pound. High cost has greatly limited the commercial utilization of hydrogenated nitrile rubber even though it has excellent physical and chemical properties for a wide variety of applications.
Sunigum® rubber is currently being sold by The Goodyear Tire & Rubber Company at a small fraction of the price of hydrogenated nitrile rubber. Sunigum® rubber is comprised of repeat units which are derived from (a) butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to about 40 percent 2-ethylhexyl acrylate, (b) methyl methacrylate, ethyl methacrylate, methyl acrylate or ethyl acrylate, (c) acrylonitrile, (d) styrene, and (e) a crosslinking agent. Rubbery polymers of this type can be made by utilizing a free radical emulsion polymerization technique, such as the technique described in U.S. Pat. Nos. 5,380,785, 5,616,651, 5,674,933 or 5,767,173.
SUMMARY OF THE INVENTION
The present invention relates to a blend of hydrogenated nitrile rubber with Sunigum® rubber that has physical and chemical properties that are similar to those of hydrogenated nitrile rubber by itself The polymeric blend of this invention offers the advantage of being much less expensive than pure hydrogenated nitrile rubber. Thus, significant cost savings can be realized by utilizing the polymeric composition of this invention in applications where heat resistance and oil resistance are required.
This invention more specifically discloses a polymeric composition having excellent heat and oil resistance which is comprised of (1) from about 2 to about 50 parts by weight of a rubbery polymer which is comprised of repeat units which are comprised of (a) butyl acrylate, (b) at least one member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate and ethyl acrylate, (c) acrylonitrile, (d) styrene, and (e) a crosslinking agent; and (2) from about 50 to about 98 parts by weight of a hydrogenated nitrile rubber.
In applications where high tensile strength is required it is highly advantageous for the polymeric composition of this invention to be cured with a peroxide cure system. By utilizing such peroxide cure systems, tensile strengths after heat aging that approach those of unblended hydrogenated nitrile rubbers can be attained. The present invention accordingly further discloses a curable polymeric composition which is comprised of (1) from about 2 to about 50 parts by weight of a rubbery polymer which is comprised of repeat units which are comprised of (a) butyl acrylate, (b) at least one member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate and ethyl acrylate, (c) acrylonitrile, (d) styrene, and (e) a crosslinking agent; (2) from about 50 to about 98 parts by weight of a hydrogenated nitrile rubber; and (3) a peroxide cure system.
DETAILED DESCRIPTION OF THE INVENTION
Conventional hydrogenated nitrile rubber can be used in making the polymeric compositions of this invention. The second component used in the blends of this invention is a rubbery polymer synthesized utilizing a free radical emulsion polymerization technique, such as the technique described in U.S. Pat. Nos. 5,380,785, 5,616,651, 5,674,933 or 5,767,173. The teachings of U.S. Pat. Nos. 5,380,785, 5,616,651, 5,674,933 and 5,767,173 are incorporated herein by reference in their entirety. Rubbery polymers of this type are sold by The Goodyear Tire & Rubber Company as Sunigum® rubber. These rubbery polymers are comprised of repeat units which are derived from (a) butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to about 40 percent 2-ethylhexyl acrylate, (b) methyl methacrylate, ethyl methacrylate, methyl acrylate or ethyl acrylate, (c) acrylonitrile, (d) styrene, and (e) a crosslinking agent. The crosslinking agent is typically a multi-functional acrylate, a multi-functional methacrylate or divinylbenzene. Some specific examples of crosslinking agents which can be used include ethylene glycol methacrylate, divinylbenzene and 1,4-butanediol dimethacrylate.
Technically, the rubbery polymers used in the blends of this invention contain repeat units (chain linkages) which are derived from (a) butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to about 40 percent 2-ethylhexyl acrylate, (b) methyl methacrylate, ethyl methacrylate, methyl acrylate or ethyl acrylate, (c) acrylonitrile, (d) styrene, and (e) a crosslinking agent. These repeat units differ from the monomers that they were derived from in that they contain one less carbon-to-carbon double bond than is present in the respective monomer. In other words, a carbon-to-carbon double bond is consumed during the polymerization of the monomer into a repeat unit in the rubbery polymer. Thus, in saying that the rubbery polymer contains various monomers, in actuality means that it contains repeat units that are derived from those monomers.
The rubbery polymers used in the blends of this invention will normally contain (a) from about 40 weight percent to about 80 weight percent butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to 40 weight percent 2-ethylhexyl acrylate, (b) from about 5 weight percent to about 35 weight percent methyl methacrylate, ethyl methacrylate, methyl acrylate or ethyl acrylate, (c) from about 4 weight percent to about 30 weight percent acrylonitrile, (d) from about 3 weight percent to about 25 weight percent styrene, and (e) from about 0.25 weight percent to about 8 weight percent of a crosslinking agent.
Such rubbery polymers will preferably contain (a) from about 50 weight percent to about 80 weight percent butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to about 40 percent 2-ethylhexyl acrylate, (b) from about 3 weight percent to about 25 weight percent of at least one member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate and ethyl acrylate, (c) from about 6 weight percent to about 30 weight percent acrylonitrile, (d) from about 5 weight percent to about 18 weight percent styrene, and (e) from about 0.5 weight percent to about 4 weight percent of a crosslinking agent.
The rubbery polymers used in the polymeric compositions of this invention will more preferably be comprised of repeat units which are derived (a) from about 55 weight percent to about 75 weight percent butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to about 40 percent 2-ethylhexyl acrylate, (b) from about 5 weight percent to about 20 weight percent of at least one member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate and ethy
Lipman Bernard
Rockhill Alvin T.
The Goodyear Tire & Rubber Company
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