Crystalline polyamide resin composition

#The present invention relates to a crystalline polyamide resin composition containing crystalline polyamide resin having high relative viscosity, modified polyolefin resin and carbon fiber. To be more specific, the present invention relates to a crystalline polyamide resin composition in which specific gravity is light, strength, rigidity and moldability are excellent and sliding durability is good. It is particularly suitable for mechanism parts requiring sliding characteristics such as door checker and gear for automobiles.

#Although sliding characteristics of polyamide resin are excellent due to its crystallinity, many investigations have been conducted from old time already in order to achieve more excellent sliding characteristics. Solid lubricants such as molybdenum disulfide, graphite and fluorine resin and liquid lubricants such as various kinds of lubricating oil and silicone oil have been investigated as main improving agents for sliding characteristics (for example, Non-Patent Document 1).

#As to a solid lubricant among those improving agents for sliding characteristics, it is necessary to compound large amount of a solid lubricant when sliding characteristics are to be further improved in a resin inherently having excellent sliding characteristics such as polyamide resin. As a result, tenacity of a polyamide resin acting as abase is significantly lowered and evaluation standards of molded parts for automobiles such as heat cycle cannot be cleared. Moreover, it is not preferred from economical viewpoint because large amount of expensive solid lubricant is compounded. On the other hand, liquid lubricant can impart highly effective sliding characteristics to the resin such as engineering plastic in a relatively small amount. However, in many cases, compatibility with the resin acting as a base is bad and there are many cases wherein surface of a molded product is polluted with such a liquid lubricant. Therefore, in a product wherein sliding characteristics are improved using such a liquid lubricant, its use is limited.

#The present invention will now be more specifically illustrated as follows.

#With regard to the crystalline polyamide resin (A) wherein relative viscosity measured in 96% sulfuric acid is 3.0 or more and the crystalline polyamide resin (B) wherein melting point is lower than melting point of the crystalline polyamide resin (A) by 20° C. or more and relative viscosity measured in 96% sulfuric acid is 3.6 or less of the present invention, there is no particular limitation therefor so far as they are crystalline polymers having an amide bond (—NHCO—) in the main chain. Examples thereof are crystalline polyamide resin such as polyamide 6 (NY6), polyamide 66 (NY66), polyamide 46 (NY46), polyamide 11 (NY11), polyamide 12 (NY12), polyamide 610 (NY610), polyamide 612 (NY612), poly-m-xylylene adipamide (MXD6), a polymer of hexamethylenediamine-terephthalic acid (6T), a polymer of hexamethylenediamine-terephthalic acid with adipic acid (66T), a copolymer of hexamethylenediamine-terephthalic acid with ε-caprolactam (6T/6), a polymer of trimethylhexamethylene-diamine-terephthalic acid (TMD-T), a copolymer of m-xylylenediamine with adipic acid and isophthalic acid (MXD-6/I), a copolymer of trihexamethylenediamine with terephthalic acid and ε-caprolactam (TMD-T/6) and a copolymer of diaminodicyclohexylenemethane (CA) with isophthalic acid and lauryllactam although they are non-limitative.

#As to the crystalline polyamide resin (A) according to the present invention, the particularly preferred one is polyamide 66. Relative viscosity of the crystalline polyamide resin (A) of the present invention is particularly important. Generally, in case the relative viscosity of the polyamide resin is measured, there are three measuring methods depending on kinds of solvents used for dissolving the polyamide resin which are m-cresol, 96% sulfuric acid (96% by mass sulfuric acid) and 90% formic acid. The relative viscosity of the crystalline polyamide resin (A) in the present invention is measured using 96% sulfuric acid solution (concentration of polyamide resin: 1 g/dl; temperature: 25° C.). The resulting relative viscosity of the crystalline polyamide resin (A) in the present invention is 3.0 or more, preferably 3.1 to 5.0, and more preferably 3.1 to 4.7.