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
2003-03-03
2004-07-06
Woodward, Ana (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...
C524S505000, C524S514000
Reexamination Certificate
active
06759474
ABSTRACT:
FIELD OF INVENTION
This invention relates to a polymer blend. More particularly, the invention concerns a fiber reinforced polymer alloy comprising a homopolymer or a copolymer of polypropylene and a polyamide.
BACKGROUND OF THE INVENTION
Thermoplastic polyamides such as nylon 6,6 have been widely used in the formation of mechanical parts and electrical parts for which excellent mechanical characteristics, high heat resistance and good durability are required. Although thermoplastic polyamides have good heat resistance and high mechanical strength, they also exhibit relatively poor impact resistance, poor notch sensitivity, and poor moisture resistance.
The impact resistance of thermoplastic polyamides can sometimes be improved by blending them with one or more other polymers to form a blended polymer composition or polymer alloy. Throughout the specification and claims, the terms “blend” and “alloy” are used interchangeably with respect to the polymer composition. In general, the physical blending of polymers does not provide a complete solution to the poor impact properties of polyamides. Generally speaking, polymers that improve the impact resistance of thermoplastic polyamides are generally immiscible with the polyamides, which results in a poor adhesion between the polymers of the blend. As a result, interfaces between blend component domains are areas of weakness in molded parts, which can result in mechanical failure.
As noted above, thermoplastic polyamides tend to absorb water, which can result in the degradation of their desirable properties. The blending of polyolefins with polyamides has been suggested as a method for decreasing the water absorption for such a blend since the water-absorbing portion of the polyamide would be replaced by a polyolefin which is generally hydrophobic. However, initial attempts to blend polyamides and polyolefins were generally unsuccessful because polyamides are incompatible with polyolefins.
It is difficult to obtain a good dispersion of a combination of a polar polymer such as a thermoplastic polyamide with a non-polar polymer such as a polyolefin. U.S. Pat. No. 4,795,782 to Lutz et al. describes a polymer blend that purports to exhibit improved impact resistance, comprising a polyamide, a functionalized polyolefin, and a functionalized elastomer. The functionalized polyolefins are obtained by reacting a polyolefin with an unsaturated mono- or polycarboxylic acid or derivative thereof. Suitable unsaturated mono- or polycarboxylic acids include maleic acid, maleic anhydride, fumaric acid, etc. The functionalized elastomers described in U.S. Pat. No. 4,795,782 are generally functionalized selectively hydrogenated block copolymers of conjugated dienes and vinyl aromatic compounds. The block copolymers are functionalized by grafting the copolymers with a mono- or polycarboxylic acid compound such as maleic acid, maleic anhydride, fumaric acid, etc. Other monomers which are utilized for introducing the functionality include vinyl monomers such as acrylamide, acrylonitrile, monovinyl aromatic compounds (i.e., styrene), vinyl esters, vinyl ethers, etc.
The addition of a graft or a block copolymer of similar chemical structure to the blend components can improve the quality of the dispersion. These copolymer additives, generally referred to as compatibilizers, are often added as a third component to the blend. A compatibilizing agent is a material which, on a molecular scale, has particular regions that are compatible with each of the incompatible constituent polymers. Such compatibilizing agents typically surround one polymeric phase providing a chemical and/or physical bridge to the other polymeric phase. Insomuch as portions of the compatibilizing agent are compatible with each of the constituent polymers, the bonding between the two incompatible polymeric phases is effectively enhanced through this intermediate compatibilizing phase. Such a system of incompatible polymers coupled by a compatibilizing agent results in a material which advantageously combines the more desirable properties of the constituent polymers. Maleic anhydride grafted polypropylene has been suggested as a compatibilizer for polypropylene
ylon blends. The compatibilization of polyethylene/polyamide blends with maleic anhydride grafted polypropylene has been reported.
It is well-known to employ glass fibers into composite articles to strengthen and reinforce the articles. In addition to increased dimensional stability in the presence of moisture, glass fiber facings provide improved physical and mechanical properties. Glass fibers are most generally placed into a plastic or polymer matrix where the high tensile strength glass fibers cause the deformable or elastic matrix to become more rigid. To form glass-reinforced composites, fiber-reinforced resin pellets made of short fibers and thermoplastic resin powder or granules are processed in an extruder. A variety of articles are made of the fiber-reinforced resin pellets by injection molding.
Despite the recent advancements in polymer alloy technology, there remains substantial room for improvement in the polymer alloy field. While articles formed from these alloys initially exhibit good strength, many of these alloys exhibit poor knit-line strength and poor drop-impact results after a period of several months. There remains a need for a glass-filled polymer alloy with improved physical and mechanical properties.
SUMMARY OF INVENTION
The present invention provides a polymer alloy composition formed by melt mixing a composition comprising from about 40% to about 75% by weight of at least one polyamide, from about 10% to about 50% by weight polypropylene, from about 0.01% to about 1.0% by weight of at least one block copolymer comprising a vinyl aromatic monomer and a conjugated diene, and further comprising an unsaturated dicarboxylic reagent, from about 0.1% to about 5.0% by weight of at least one block copolymer or a terpolymer, wherein the terpolymer may have an unsaturated dicarboxylic reagent grafted thereto, from about 0.01% to about 7.5% of a compatibilizing agent comprising an alpha-olefin and an unsaturated dicarboxylic reagent, and from about 5% to about 50% by weight of a filler.
The alloy of the present invention exhibits improved knitline strength and improved drop impact results compared to prior art fiberglass-reinforced nylon blends. The fiberglass-reinforced nylon/polypropylene alloy of the present invention minimizes negative effects due to water absorption commonly experienced when processing glass-filled nylons. The alloy of the present invention has lower water absorption in addition to dimensional stability in high moisture conditions, as well as high heat resistance, improved physical and mechanical properties, and a wide range of processing for various applications.
The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the present invention may be employed.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Unless the context indicates otherwise, throughout the specification and claims, the amount of the polymers present is determined inclusive of fillers, glass or other nonpolymer additives in the polymer compositions. Therefore, the amount of each polymer is determined by dividing the weight of the polymer by the combined weight of all of the components present in the composition.
The fiberglass-reinforced nylonipolypropylene alloy of the present invention exhibits improved knitline strength and improved drop impact results compared to prior art fiberglass-reinforced nylon blends. The fiberglass-reinforced nylon/polypropylene alloy of the present invention minimizes negative effects due to water absorption commonly experienced when processing glass-filled nylons, and exhibits other advantages including dimensional stability in high
Chundury Deenadayalu
Evans Daniel L.
Julian Donald E.
Keener Brian D.
Lee Morris M.S.
Ferro Corporation
Rankin, Hill Porter & Clark LLP
Woodward Ana
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