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
1994-06-03
2001-10-23
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...
C525S066000
Reexamination Certificate
active
06306951
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to polyphthalamide compositions of improved toughness. More particularly, the invention relates to toughened compositions comprising a high melting, crystalline polyamide component comprising recurring terephthalamide units and a modifier component comprising a functionalized block copolymer comprising polymerized styrene blocks and rubber blocks comprising ethylene/propylene, ethylene/butylene or ethylene/pentylene polymer blocks.
BACKGROUND OF THE INVENTION
As is known, polyamides generally exhibit a balance of thermal, strength and stiffness properties which make them suitable for many applications. However, impact strengths typically are low as measured by mechanical tests such as the Notched Izod Impact Test or the high speed instrumented Dart Impact Test. In some cases, elongation measured in tensile testing is also relatively low. Improvements in impact strength and elongation are needed for better performance of articles fabricated from polyamides for use in high impact applications and especially those in which the articles may be subject to cracks or have imperfections. Polyamides of improved impact strength over a broad range of temperatures would be particularly desirable.
Crystalline polyamides comprising at least about 50 mole percent aliphatic terephthalamide units exhibit particularly good thermal properties making them useful in relatively high temperature applications such as under-the-hood automotive parts. Other desirable properties of such compositions include their high strength and stiffness. However, impact strengths are relatively low. Further, such polyamides have relatively high melting points, e.g., about 290° C. or higher, and degradation temperatures of some of the materials do not greatly exceed their melting points; accordingly, requirements for melt processing the compositions are more rigorous and complex than those for lower melting polyamides such as nylon 66 which melts at about 260-265° C.
Various additives have been proposed for improving impact strength of polyamides. Generally, these additives are rubbery compositions that can be blended or incorporated into the polyamides to provide improvements in impact strength. Of course, it also is important that such improvements be achieved without substantial adverse effects on desirable properties of the polyamide. It also is important that the additives retain their effectiveness after processing of polyamide compositions containing the same and during use of articles prepared therefrom.
U.S. Pat. No. 4,427,828 issued Jan. 24, 1984, and U.S. Pat. No. 4,508,874, issued Apr. 2, 1985, both to Hergenrother et al., disclose impact resistant polyamide compositions containing about 50-90 wt. % polyamide having a number average molecular weight of at least 10,000 and about 10-50 wt. % of a pendant succinic anhydride group-containing reaction product of maleic anhydride with a hydrogenated polymer of a conjugated diene or hydrogenated random or block copolymer of a conjugated diene and a vinyl aromatic hydrocarbon. The disclosed hydrogenated polymer or copolymer has about 0.5-20% of its original unsaturation content before hydrogenation and at least 5 wt. % of the polyamide and the maleic anhydride-hydrogenated polymer or copolymer reaction product is present in the form of a graft polymer containing at least 20% polyamide. Polyamides mentioned in the patent include those prepared from various aminocarboxylic acids or lactams thereof or from dicarboxylic acids and diamines, including polycaprolactam, poly(hexamethylene adipamide), poly(hexamethylene isophthalamide), “poly(methoxylylene adipamide)” and hexamethylene adipamide/caprolactam, hexamethylene adipamide/hexamethylene isophthalamide, hexamethylene adipamide/hexamethylene terephthalamide, hexamethylene adipamide/hexamethylene azeleamide copolyamides and hexamethylene adipamide/hexamethylene azeleamide/caprolactam terpolyamides. Examples of various maleic anhydride-hydrogenated diene polymer and diene-vinyl aromatic copolymer adducts also are given. Included are those in which the diene is butadiene and the vinyl aromatic is styrene.
U.S. Pat. No. 4,783,503 issued Nov. 8, 1988, to Gergen et al. discloses impact resistant blends of a polyamide and a thermally stable, modified, selectively hydrogenated, block copolymer of a conjugated diene and a vinyl aromatic compound. The polyamides are semi-crystalline or amorphous resins having molecular weights of at least 5000. Polyamides named in the patent include poly(hexamethylene adipamide), poly(hexamethylene dodecaneamide), polycaprolactam, and adipic acid/isophthalic acid/hexamethylene diamine copolyamides. The disclosed, modified, selectively hydrogenated, block copolymer component has residual unsaturation in the polydiene block of about 0.5-20% of its original unsaturation content and is grafted in the vinylarene block with an electrophilic group. Examples of various dienes, vinyl aromatics and electrophiles are disclosed and the examples of the patent illustrate an acid-functionalized styrene-ethylene/butylene-styrene block copolymer containing 29 wt. % styrene and blends thereof with a commercial nylon 66 prepared at temperatures up to 285° C. The modified, hydrogenated block copolymers are said to exhibit greater thermal stability than materials prepared by the ENE process such as in Hergenrother et al.
Published European Patent Application 86201336.4 (Publication No. 0 211 467) of Gelles et al., published Feb. 25, 1987, discloses impact resistant polymeric compositions containing a polyamide or polyester and a thermally stable, acid-functionalized, selectively hydrogenated block copolymer of a vinyl aromatic compound and a conjugated diene in which unsaturation in the polydiene block is less than 10% of its original unsaturation and substantially all of the acid groups or derivatives thereof are grafted to a secondary or tertiary carbon of the polydiene group. Various polyamides, including poly(hexamethylene adipamide), poly(hexamethylene isophthalamide), poly(hexamethylene dodecaneamide), polycaprolactam and adipic acid/isophthalic acid/hexamethylene diamine and polyhexamethylene ter-co-isophthalamide copolyamides, are mentioned. Various diene and vinyl aromatic monomers are disclosed for preparation of block copolymers, 1,3-butadiene and styrene, respectively, being identified as preferred. The polydiene block is selectively hydrogenated and the hydrogenated result is grafted with an acid group or derivative to provide functionality. Preferred monomers for the grafting reaction are said to be maleic anhydride, maleic acid, fumeric acid and their derivatives and sulfonic acids. The examples illustrate maleic anhydride-functionalized styrene-ethylene/butylene-styrene block copolymer blends with nylon 66 prepared at temperatures up to 285° C. and having improved Izod impact strength relative to the neat nylon 66. Like the modified, hydrogenated block copolymers used according to Gergen et al., those of Gelles et al. are said to exhibit improved thermal stability relative to modified polymers prepared by the ENE process such as those according to Hergenrother et al.
A published advertisement for Kraton® FG 1901X by Shell Chemical Company, appearing in
Plastics Compounding
March/April, 1989, discloses a block copolymer having styrene and ethylene/butylene polymer blocks functionalized with maleic anhydride and utility thereof as an impact modifier for engineering thermoplastics, as a tie layer and as a compatibilizer for dissimilar scrap thermoplastics. Improvement in Izod impact strength resulting from incorporation of the material into nylon 66 also is reported in the advertisement as is the material's ability to withstand processing temperatures of engineering thermoplastics.
British Patent Specification 998,439 to E.I. dupont de Nemours and Company discloses blends of polyamides with olefin copolymers containing acid groups. The blends are described as having improved toughness as measured by the Izod Impact Test. The polyamides used accor
Corbin George Albert
Garrett David William
Montag Ruth Ann
BP Corporation North America Inc.
Nemo Thomas E.
Woodward Ana
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