Carbon fiber bundle process for producing the same and thermoplastic resin composition and molded article thereof

Abstract

A carbon fiber bundle is provided which can develop satisfactory interfacial adhesion to polyolefin-based resins, especially polypropylene resins. The carbon fiber bundle comprises a plurality of single fibers that was sized with a sizing agent comprising: a polymer having a main chain formed of carbon-carbon bonds, containing an acid group in at least part of side chains or at least a part of main chain ends, and representing an acid value of 23 to 120 mgKOH/g as measured in accordance with ASTM D1386; or a polymer having a main chain formed of carbon-carbon bonds and containing at least either of an epoxy group and an ester group in at least a part of side chains or at least a part of main chain ends.

1 . A carbon fiber bundle comprising a plurality of single fibers, and sized with a sizing agent comprising: 
 a polymer having a main chain formed of carbon-carbon bonds, containing an acid group in at least a part of side chains or at least a part of main chain ends, and representing an acid value of 23 to 120 mgKOH/g as measured in accordance with ASTM D1386; or    a polymer having a main chain formed of carbon-carbon bonds, and containing at least either of an epoxy group and an ester group in at least a part of side chains or at least a part of main chain ends.    
   
   
       2 . The carbon fiber bundle according to  claim 1 , wherein the sizing was conducted after pre-sized with a pre-sizing agent consisting of an epoxy resin.  
   
   
       3 . The carbon fiber bundle according to  claim 2 , wherein the sizing agent comprises at least 35 wt % of an acid modified polypropylene resin (compound a1) having a weight average molecular weight of 45,000 or less and an acid value of 23 to 120 mgKOH/g as measured in accordance with ASTM D1386.  
   
   
       4 . The carbon fiber bundle according to  claim 3 , wherein the sizing agent comprises at least 5 wt % of an olefin-based thermoplastic elastomer resin (compound b).  
   
   
       5 . The carbon fiber bundle according to  claim 4 , wherein the compound b has a Vicat softening point of 120° C. or less as measured in accordance with ASTM D1525-70.  
   
   
       6 . The carbon fiber bundle according to  claim 1 , wherein the compound a1 has a weight average molecular weight of 20,000 or less, and an acid value of 40 to 75 mgKOH/g as measured in accordance with ASTM D1386.  
   
   
       7 . The carbon fiber bundle according to  claim 2 , wherein the sizing agent comprises at least 40 wt % of a copolymer (compound c) obtained by copolymerizing ethylene or propylene and an epoxy-containing monomer.  
   
   
       8 . The carbon fiber bundle according to  claim 1 , wherein the single fibers comprise a plurality of wrinkles on their surface, wherein a vertical difference between a highest portion and a lowest portion in a region defined by 2 μm of circumferential length×1 μm of fiber axial direction length of the single fibers is 40 nm or more.  
   
   
       9 . The carbon fiber bundle according to  claim 1 , wherein the sizing agent comprises no more than 5 wt % of a silane coupling agent having in the molecule any one of an epoxy group, a vinyl group, an amino group, a methacrylic group, an acrylic group and a straight chain alkyl group in its molecule.  
   
   
       10 . The carbon fiber bundle according to  claim 1 , cut to a prescribed length, wherein an amount of the sizing agent deposited to the total is 1 to 5 wt %.  
   
   
       11 . The carbon fiber bundle according to  claim 10 , having a mass per unit length of 0.4 to 15 g/m, and a width/thickness of 3 to 10.  
   
   
       12 . A method for producing a carbon fiber bundle comprising a plurality of single fibers, comprising the steps of: 
 pre-sizing the carbon fiber bundle with a pre-sizing agent consisting of an epoxy resin;    sizing the pre-sized carbon fiber bundle, so that an amount of a sizing agent to the total is 1 to 5 wt %, by using an aqueous sizing agent solution dissolving or dispersing in water the sizing agent comprising:    a polymer having a main chain formed of carbon-carbon bonds, containing an acid group in at least a part of side chains or at least a part of main chain ends, and representing an acid value of 23 to 120 mgKOH/g as measured in accordance with ASTM D1386; or    a polymer having a main chain formed of carbon-carbon bonds, containing at least either of an epoxy group and an ester group in at least a part of side chains or at least a part of main chain ends;    cutting the carbon fiber bundle to a prescribed length; and    drying the carbon fiber bundle cut to the prescribed length.    
   
   
       13 . A thermoplastic resin composition comprising a thermoplastic resin and the carbon fiber bundle according to  claim 2 , wherein the carbon fiber bundle content is 3 to 60 wt %.  
   
   
       14 . The thermoplastic resin composition according to  claim 13 , wherein the thermoplastic resin is a polyolefin-based resin.  
   
   
       15 . A molded article obtained by molding the thermoplastic resin composition according to  claim 14 .  
   
   
       16 . The carbon fiber bundle according to  claim 1 , wherein the single fibers comprise a plurality of wrinkles on their surface, wherein a vertical difference between a highest portion and a lowest portion in a region defined by 2 μm of circumferential length×1 μm of fiber axial direction length of the single fibers is 40 nm or more.  
   
   
       17 . The carbon fiber bundle according to  claim 16 , wherein the sizing agent comprises: 
 at least 35 wt % of an acid modified polypropylene resin (compound a2) having a number average molecular weight of 45,000 or less and an acid value of 23 to 120 mgKOH/g as measured in accordance with ASTM D1386; and    at least 5 wt % of an olefin-based thermoplastic elastomer resin (compound b).    
   
   
       18 . The carbon fiber bundle according to  claim 17 , wherein the compound b has a Vicat softening point of 120° C. or less as measured in accordance with ASTM D1525-70.  
   
   
       19 . The carbon fiber bundle according to  claim 16 , wherein the sizing agent comprises at least 40 wt % of a copolymer component consisting of one or both of: 
 a copolymer (compound c) obtained by copolymerizing ethylene or propylene and an epoxy-containing monomer; and    a copolymer (compound d) obtained by copolymerizing ethylene or propylene, an epoxy-containing monomer and an acrylic ester.    
   
   
       20 . The carbon fiber bundle according to  claim 19 , wherein the sizing agent further comprises a copolymer (compound e) obtained by copolymerizing ethylene or propylene, an acrylic ester and a monomer containing an acid anhydride group.  
   
   
       21 . The carbon fiber bundle according to  claim 16 , wherein cross-section of the single fiber have a ratio of major axis to minor axis of 1.03 to 1.20, and a Si content of 500 ppm or less as measured by ICP emission spectrometry.  
   
   
       22 . The carbon fiber bundle according to  claim 19 , wherein the sizing agent comprises no more than 5 wt % of a silane coupling agent having in the molecule any one of an epoxy group, a vinyl group, an amino group, a methacrylic group, an acrylic group and a straight chain alkyl group.  
   
   
       23 . The carbon fiber bundle according to  claim 19 , cut to a prescribed length, wherein an amount of the sizing agent deposited to the total is 1 to 5 wt %.  
   
   
       24 . The carbon fiber bundle according to  claim 23 , having a mass per unit length of 0.4 to 15 g/m, and a width/thickness of 3 to 10.  
   
   
       25 . A method for producing a carbon fiber bundle comprising a plurality of single fibers, wherein the single fibers comprise a plurality of wrinkles on their surface, wherein a vertical difference between a highest portion and a lowest portion in a region defined by 2 μm of circumferential length×1 μm of fiber axial direction length of the single fibers is 40 nm or more, comprising the steps of: 
 sizing the carbon fiber bundle, so that an amount of a sizing agent to the total is 1 to 5 wt %, by using an aqueous sizing agent solution dissolving or dispersing in water the sizing agent comprising:    a polymer having a main chain formed of carbon-carbon bonds, containing an acid group in at least a part of side chains or at least a part of main chain ends, and representing an acid value of 23 to 120 mgKOH/g as measured in accordance with ASTM D1386; or    a polymer having a main chain formed of carbon-carbon bonds, containing at least either of an epoxy group and an ester group in at least a part of side chains or at least a part of main chain ends;    cutting the carbon fiber bundle to a prescribed length with regulating the moisture content of the carbon fiber bundle to 20 to 60 wt %; and    drying the carbon fiber bundle cut to a prescribed length.    
   
   
       26 . A thermoplastic resin composition comprising a thermoplastic resin and the carbon fiber bundle according to  claim 2 , wherein the carbon fiber bundle content is 3 to 60 wt %.  
   
   
       27 . The thermoplastic resin composition according to  claim 26 , wherein the thermoplastic resin is at least one selected from the group consisting of polyolefin-based resin, polycarbonate resin, ABS resin, AS resin, polyoxymethylene resin, nylon resin, polyphenylene sulfide resin, polyether sulfine resin, polyether imide resin, polyester resin and alloy-based resins thereof.  
   
   
       28 . A molded article obtained by molding the thermoplastic resin composition according to  claim 27.