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Described are fuel parts comprising a crystalline polyamide resin having a terminal amino group concentration>a terminal carboxyl group concentration and excellent in fuel resistance at their weld portion, which fuel parts are suited for use as various parts to be attached to fuel tanks of automo

Described are fuel parts comprising a crystalline polyamide resin having a terminal amino group concentration>a terminal carboxyl group concentration and excellent in fuel resistance at their weld portion, which fuel parts are suited for use as various parts to be attached to fuel tanks of automobiles and the like, and a process for producing the fuel parts.

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What is claimed is: 1. A fuel part comprising a crystalline polyamide resin having a terminal amino group concentration greater than a terminal carboxyl group concentration, wherein the fuel part is attached by a welding portion to at least one selected from the group consisting of a fuel tank, a f

What is claimed is: 1. A fuel part comprising a crystalline polyamide resin having a terminal amino group concentration greater than a terminal carboxyl group concentration, wherein the fuel part is attached by a welding portion to at least one selected from the group consisting of a fuel tank, a fuel hose, and a fuel canister, and has excellent fuel resistance at the welding portion. 2. The fuel part according to claim 1, wherein a terminal amino group concentration is at least 50 milliequivalent per kg of the resin. 3. The fuel part according to claim 1, wherein the crystalline polyamide resin is an aliphatic polyamide resin comprising an aliphatic diamine and an aliphatic dicarboxylic acid, a lactam, or an aminocarboxylic acid. 4. The fuel part according to claim 1, wherein the crystalline polyamide resin is a crystalline semi-aromatic polyamide resin comprising at least one aromatic monomer component. 5. The fuel part according to claim 1, wherein the polyamide resin contains 3 to 27 wt. % of a plate-crystal inorganic filler. 6. The fuel part according to claim 5, wherein the part has a multilayer structure comprising an inner layer (A) comprising high-density polyethylene modified with an unsaturated carboxylic acid or a derivative thereof; and an outer layer (B) comprising the crystalline polyamide resin. 7. The fuel part according to claim 5, wherein the part has a multilayer structure comprising an inner layer (A) and an outer layer (C) comprising high-density polyethylene modified with an unsaturated carboxylic acid or a derivative thereof; and an intermediate layer (B) comprising the crystalline polyamide resin. 8. The fuel part according to claim 6, wherein the modified high-density polyethylene has a density of 0.935 to 0.955 g/cm3. 9. The fuel part according to claim 6, wherein the plate-crystal inorganic filler is fine talc powder or fine mica powder. 10. The fuel part according to claim 6, wherein the fuel part is a valve cover and is attached to a fuel tank, further comprising a pipe portion for bonding a tube for fluid to the tank and an end portion for welding the pipe portion to the tank. 11. The fuel part according to claim 10, wherein the end portion comprises a flange. 12. A fuel part comprising a first portion comprising a crystalline polyamide resin having a terminal amino group concentration greater than a terminal carboxyl group concentration and a second portion comprising a polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof; wherein the fuel part is attached to at least one selected from the group consisting of a fuel tank, a fuel hose, and a fuel canister and has excellent fuel resistance at a weld portion between the first and the second portions. 13. A fuel part comprising a polyamide resin composition comprising (A) 100 parts by weight of a crystalline polyamide resin having a terminal amino group concentration greater than a terminal carboxyl group concentration, and (B) 0.05 to 10 parts by weight of layered silicates uniformly dispersed in the polyamide resin, wherein the fuel part is attached to at least one selected from the group consisting of a fuel tank, a fuel hose, and a fuel canister and has excellent fuel resistance at a weld portion thereof. 14. The fuel part according to claim 12, wherein the part is a resin valve cover welded to an outer layer of a resin fuel tank to seal a valve-mounting slot formed in the tank, the valve cover has a cylindrical shape having one end closed with a pipe hole for delivering a fuel; and wherein an inside portion of the cylinder to be brought into contact with the fuel comprises the crystalline polyamide resin and an outer portion of the cylinder not brought into contact with the fuel comprises the polyolefin resin. 15. The fuel part according to claim 14, further comprising a pipe tube having a hollow hole communicated to the pipe hole, wherein the pipe tube comprises the crystalline polyamide resin and a cyclic concave in a vicinity of a root of the pipe for engagement with the polyolefin resin. 16. The fuel part according to claim 14, further comprising a first plurality of convexities or holes on a member comprising the polyamide resin and a second plurality of holes or convexities to be fitted in the first plurality of convexities or holes on a member comprising the polyolefin resin. 17. The fuel part according to claim 14, further comprising a first plurality of convexities or holes on a member comprising the polyamide resin and a second plurality of holes or convexities to be fitted in the first plurality of convexities or holes on a member comprising the polyolefin resin. 18. The fuel part according to claim 12, wherein the part is a resin valve cover welded to an outer layer of a resin fuel tank to seal a valve-mounting slot formed in the tank, the valve cover has a cylindrical shape having one end closed with a pipe hole for delivering a fuel; and wherein an inside portion of the cylinder to be brought into contact with the fuel comprises the polyolefin resin and an outer portion of the cylinder not brought into contact with the fuel comprises the crystalline polyamide resin. 19. The fuel part according to claim 18, further comprising a pipe tube having a hollow hole communicated to the pipe hole, wherein the pipe tube comprises the polyolefin resin and a cyclic concavity in a vicinity of a root of the pipe for engagement with the crystalline polyamide resin. 20. The fuel part according to claim 13, further comprising a polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof welded to the polyamide resin composition.