Spun yarn and intermediate for fiber-reinforced resin, and molded article of fiber-reinforced resin using the same

Abstract

Disclosed is a spun yarn for a fiber-reinforced plastic, which is composed of blended yarns ( 3 a, 3 b ) of a natural plant fiber and a synthetic fiber. The synthetic fiber is a thermoplastic synthetic fiber capable of serving as a matrix resin in a FRP. Also disclosed is an intermediate for a fiber-reinforced plastic that is a woven fabric, a knitted fabric, a multiaxial warp knitted fabric or a braided fabric, formed of the aforementioned spun yarn for a fiber-reinforced plastic. Also disclosed is a fiber-reinforced plastic molded article that is obtained by heating and press-molding the intermediate for a fiber-reinforced plastic at a mold temperature equal to or higher than the melting point of the synthetic fiber, or by aligning the spun yarn for a fiber-reinforced plastic in at least one direction, heating and press-molding the same at a mold temperature equal to or higher than the melting point of the synthetic fiber. Thus, the spun yarn for a fiber-reinforced plastic that exhibits superior integrity between the natural plant fiber and the synthetic fiber and that also a good moldability can be obtained at a low cost. And furthermore, the intermediate and the fiber-reinforced plastic molded article using the same can be provided.

1 . A spun yarn for a fiber-reinforced plastic (FRP) comprising a natural plant fiber and a thermoplastic synthetic fiber,
 wherein the natural plant fiber and the synthetic fiber make a blended yarn,   the synthetic fiber is a thermoplastic synthetic fiber that is melted and penetrates into the natural plant fiber so as to integrate with the natural plant fiber in the FRP and to serve as a matrix resin in the FRP, and   the natural plant fiber is a fiber to serve as a reinforcing fiber in the FRP.   
     
     
         2 . The spun yarn for a fiber-reinforced plastic according to  claim 1 , wherein the natural plant fiber is at least one fiber selected from the group consisting of cotton, hemp, kapok and bamboo. 
     
     
         3 . The spun yarn for a fiber-reinforced plastic according to  claim 1 , wherein the resin that forms the thermoplastic synthetic fiber has a melting point not lower than 90° C. and not higher than 200° C. 
     
     
         4 . The spun yarn for a fiber-reinforced plastic according to  claim 1 , wherein the thermoplastic synthetic fiber is a fiber of: polypropylene (PP), polyethylene (PE), and a copolymer thereof; copolyester, copolyamide, polyvinyl chloride, copolyacetal, polylactic acid or polysuccinate butyl. 
     
     
         5 . The spun yarn for a fiber-reinforced plastic according to  claim 1 , wherein the natural plant fiber and the synthetic fiber are blended at a weight ratio in a range of 80:20 to 30:70. 
     
     
         6 . An intermediate for a fiber-reinforced plastic prepared by processing a spun yarn for a fiber-reinforced plastic so as to make a woven fabric, a knitted fabric, a multiaxial warp knitted fabric, or a braided fabric, the spun yarn being prepared as a blended yarn comprising a natural plant fiber and a thermoplastic synthetic fiber, and the synthetic fiber being a thermoplastic fiber that is melted and penetrates into the natural plant fiber so as to integrate with the natural plant fiber in the FRP thereby serving as a matrix resin in the FRP. 
     
     
         7 . A fiber-reinforced plastic molded article prepared by heating and press-molding an intermediate for a fiber-reinforced plastic at a mold temperature equal to or higher than the melting point of the synthetic fiber, the intermediate being prepared by processing a spun yarn for a fiber-reinforced plastic so as to make a woven fabric, a knitted fabric, a multiaxial warp knitted fabric, or a braided fabric, the spun yarn being prepared as a blended yarn comprising a natural plant fiber and a thermoplastic synthetic fiber, and the synthetic fiber being a thermoplastic synthetic fiber that is melted and penetrates into the natural plant fiber so as to integrate with the natural plant fiber in the FRP thereby serving as a matrix resin in the FRP. 
     
     
         8 . A fiber-reinforced plastic molded article prepared by aligning a spun yarn for a fiber-reinforced plastic in at least one direction and heating and press-molding at a mold temperature equal to or higher than the melting point of the synthetic fiber, the spun yarn being a blended yarn comprising a natural plant fiber and a thermoplastic synthetic fiber, and the synthetic fiber being a thermoplastic synthetic fiber that is melted and penetrates into the natural plant fiber so as to integrate with the natural plant fiber in the FRP thereby serving as a matrix resin in the FRP. 
     
     
         9 . The spun yarn for a fiber-reinforced plastic according to  claim 1 , wherein the blended yarn is subjected to an actual twist described below at a twist factor K of 2 to 7 in cotton count:
     K=t/√{square root over (S)}     
       where t denotes a twist amount per unit length of 25.4 mm, and S denotes cotton count. 
     
     
         10 . The spun yarn for a fiber-reinforced plastic according to  claim 1 , wherein the spun yarn has fineness in a range of 4 to 100 in cotton count (50 to 1,500 dtex). 
     
     
         11 . The intermediate for a fiber-reinforced plastic according to  claim 6 , wherein the natural plant fiber is at least one fiber selected from the group consisting of cotton, hemp, kapok and bamboo. 
     
     
         12 . The intermediate for a fiber-reinforced plastic according to  claim 6 , wherein the resin that forms the thermoplastic synthetic fiber has a melting point not lower than 90° C. and not higher than 200° C. 
     
     
         13 . The intermediate for a fiber-reinforced plastic according to  claim 6 , wherein the thermoplastic synthetic fiber is a fiber of: polypropylene (PP), polyethylene (PE), and a copolymer thereof; copolyester, copolyamide, polyvinyl chloride, copolyacetal, polylactic acid or polysuccinate butyl. 
     
     
         14 . The intermediate for a fiber-reinforced plastic according to  claim 6 , wherein the natural plant fiber and the synthetic fiber are blended at a weight ratio in a range of 80:20 to 30:70. 
     
     
         15 . The intermediate for a fiber-reinforced plastic according to  claim 6 , wherein the blended yarn is subjected to an actual twist described below at a twist factor K of 2 to 7 in cotton count:
     K=t/√{square root over (S)}     
       where t denotes a twist amount per unit length of 25.4 mm, and S denotes cotton count. 
     
     
         16 . The intermediate for a fiber-reinforced plastic according to  claim 6 , wherein the spun yarn has fineness in a range of 4 to 100 in cotton count (50 to 1,500 dtex). 
     
     
         17 . The fiber-reinforced plastic molded article according to  claim 8 , wherein the natural plant fiber is at least one fiber selected from the group consisting of cotton, hemp, kapok and bamboo. 
     
     
         18 . The fiber-reinforced plastic molded article according to  claim 8 , wherein the resin that forms the thermoplastic synthetic fiber has a melting point not lower than 90° C. and not higher than 200° C. 
     
     
         19 . The fiber-reinforced plastic molded article according to  claim 8 , wherein the thermoplastic synthetic fiber is a fiber of: polypropylene (PP), polyethylene (PE), and a copolymer thereof; copolyester, copolyamide, polyvinyl chloride, copolyacetal, polylactic acid or polysuccinate butyl. 
     
     
         20 . The fiber-reinforced plastic molded article according to  claim 8 , wherein the natural plant fiber and the synthetic fiber are blended at a weight ratio in a range of 80:20 to 30:70.