Carbon fiber bundle, method for producing the same, and molded article made thereof

1. A carbon fiber bundle comprising carbon fibers and a copolymerized polyolefin attached to a surface of the carbon fibers, the copolymerized polyolefin containing an aromatic vinyl compound and an acid, an acid anhydride, or a combination thereof as copolymerization components,

the copolymerized polyolefin being obtainable by a graft copolymerization of (i) a member selected from the group consisting of propylene-aromatic vinyl compound copolymers, propylene-α-olefin-aromatic vinyl compound copolymers, and a combination thereof, with (ii) a member selected from the group consisting of unsaturated dicarboxylic acids, acid anhydrides thereof, and a combination thereof,

a copolymerization ratio between the olefin and the aromatic vinyl compound in the copolymerized polyolefin being such that a molar ratio of the aromatic vinyl compound is 0.1 to 5 per 100 of the olefin,

an amount of the copolymerized polyolefin attached being 0.01 to 10 parts by mass per 100 parts by mass of the carbon fiber bundle.

2. The carbon fiber bundle according to claim 1 , wherein the aromatic vinyl compound is represented by the following general formula (1):

ArCH═CH 2   (1)

wherein Ar is a C 6-15 aromatic group.

3. The carbon fiber bundle according to claim 1 , wherein a copolymerization ratio between the olefin and the acid, acid anhydride, or combination thereof in the copolymerized polyolefin is such that a molar ratio of the acid, acid anhydride, or combination thereof is 0.01 to 5 per 100 of the olefin.

4. The carbon fiber bundle according to claim 1 , wherein the copolymerized polyolefin containing an aromatic vinyl compound and acid, acid anhydride, or combination thereof as copolymerization components has a weight average molecular weight of 35,000 to 100,000.

5. A random mat comprising the carbon fiber bundle of claim 1 , wherein the carbon fiber bundles are randomly oriented in a plane of the random mat.

6. The random mat according to claim 5 , wherein the carbon fibers have a carbon fiber length of 2 to 60 mm, and the random mat is a weight of 25 to 3,000 g/m 2 .

7. The random mat according to claim 5 , wherein the random mat comprises the carbon fiber bundle and a thermoplastic resin.

8. The random mat according to claim 7 , wherein the thermoplastic resin is a polypropylene resin.

9. The random mat according to claim 7 , wherein an amount of the thermoplastic resin present in the random mat is 50 to 1,000 parts by weight per 100 parts by weight of the carbon fibers.

10. The random mat according to claim 7 , wherein the thermoplastic resin is present in fibrous, powdery, or granular form.

11. A method for producing a random mat, comprising the following steps:

(1) a step in which a carbon fiber bundle is cut;

(2) a step in which the cut carbon fiber bundle is introduced into a tube, and air is blown to the carbon fiber bundle to open the carbon fiber bundle; and

(3) a step in which carbon fiber bundles opened in the step (2) are spread and simultaneously sucked, whereby the carbon fibers are dispersed, applied, and fixed,

wherein the carbon fiber bundle comprises carbon fibers and a copolymerized polyolefin attached to a surface of the carbon fibers, the copolymerized polyolefin containing an aromatic vinyl compound and an acid, an acid anhydride, or a combination thereof as copolymerization components,

the copolymerized polyolefin being obtainable by a graft copolymerization of (i) a member selected from the group consisting of propylene-aromatic vinyl compound copolymers, propylene-α-olefin-aromatic vinyl compound copolymers, and a combination thereof, with (ii) a member selected from the group consisting of unsaturated dicarboxylic acids, acid anhydrides thereof, and a combination thereof,

a copolymerization ratio between the olefin and the aromatic vinyl compound in the copolymerized polyolefin being such that a molar ratio of the aromatic vinyl compound is 0.1 to 5 per 100 of the olefin,

an amount of the copolymerized polyolefin attached being 0.01 to 10 parts by mass per 100 parts by mass of the carbon fiber bundle, and

wherein the carbon fiber bundles are randomly oriented in a plane of the random mat.

12. A carbon fiber composite material comprises the carbon fiber bundle of claim 1 and a thermoplastic resin.

13. The carbon fiber composite material according to claim 12 , wherein the carbon fibers are randomly oriented a plane of the random mat.

14. The carbon fiber composite material according to claim 12 , wherein the carbon fiber bundle is aligning in the thermoplastic resin.

15. The carbon fiber composite material according to claim 12 , wherein the carbon fiber composite material comprising a carbon fiber random mat and an uniaxially oriented carbon fiber composite material.

16. The carbon fiber composite material according to claim 12 , having a three-dimensional shape and obtainable by press-molding a plate-shaped article.

17. The carbon fiber composite material according to claim 15 , comprising the carbon fiber random mat as a skin layer and the uniaxially oriented carbon fiber composite material as a core material.

18. The carbon fiber composite material according to claim 15 , comprising the carbon fiber random mat as a core material and the uniaxially oriented carbon fiber composite material as a skin layer.

19. An automotive floor pan comprises the carbon fiber bundle of claim 1 and a thermoplastic resin.

20. The automotive floor pan according to claim 19 , comprising a carbon fiber random mat as a substrate and an uniaxially oriented carbon fiber composite material of as a part of the automotive floor pan.