CHOPPED FIBER BUNDLE, MOLDING MATERIAL, AND FIBER REINFORCED PLASTIC, AND PROCESS FOR PRODUCING THEM

• US 20100178495A1
• Filed: 04/23/2008
• Published: 07/15/2010
• Est. Priority Date: 06/04/2007
• Status: Active Grant

• Current Assignee: Toray Industries Incorporated
• Original Assignee: Toray Industries Incorporated
• Inventors: Wadahara, Eisuke, Sato, Narumichi, Taketa, Ichiro
• Granted Patent: US 8,329,280 B2
• Time in Patent Office: Days
• US Class Current: 428/339
• CPC Class Codes: B29C 70/14 oriented
• CPC Class Codes: B29C 70/22 oriented in at least two directions forming a two dimensional structure woven fabrics per se D03D; knitted fabrics per se D04D; braid per se D04C
• CPC Class Codes: B29C 70/305 Spray-up of reinforcing fibres with or without matrix to form a non-coherent mat in or on a mould B29C41/365, B29C70/32, B29C70/34, B29C70/502, B29C70/508 take precedence; coating a former by spraying plastics B29C41/08
• CPC Class Codes: C03B 37/16 Cutting or severing light guides G02B6/25
• CPC Class Codes: C03C 25/24 Coatings containing organic materials
• CPC Class Codes: C08J 2375/04 Polyurethanes
• CPC Class Codes: C08J 5/042 with carbon fibres
• CPC Class Codes: Y02P 40/57 Improving the yield, e-g- reduction of reject rates
• CPC Class Codes: Y10T 156/1084 of continuous or running length bonded web
• CPC Class Codes: Y10T 428/24 Structurally defined web or sheet [e.g., overall dimension, etc.]
• CPC Class Codes: Y10T 428/24058 including grain, strips, or filamentary elements in respective layers or components in angular relation
• CPC Class Codes: Y10T 428/24132 including grain, strips, or filamentary elements in different layers or components parallel
• CPC Class Codes: Y10T 428/269 including synthetic resin or polymer layer or component
• CPC Class Codes: Y10T 428/298 Physical dimension
• CPC Class Codes: Y10T 83/04 Processes

Abstract

A chopped fiber bundle includes a large number of unidirectionally arranged reinforced fibers. The length of each of the reinforced fibers is in the range of 5 to 100 mm. The chopped fiber bundle has a transition segment in which the number of the reinforced fibers increases toward the central part of the chopped fiber bundle in the aligned direction of the reinforced fibers with both ends in the aligned of the reinforced fibers in the chopped fiber bundle being a starting point. The level of a change in total sectional area of the large number of reinforced fibers is not more than 0.05 mm² per mm in the aligned direction of the reinforced fibers over the whole area in the longitudinal direction of the chopped fiber bundle.

Claims

1. A chopped fiber bundle comprising:

(a) a large number of unidirectionally arranged reinforcing fibers and a bundling agent which bundles said large number of reinforcing fibers, wherein

(b) the fiber length of said reinforcing fiber is 5 to 100 mm,

(c) said chopped fiber bundle has a first transition section in which the number of said reinforcing fibers in a cross-section of the fiber bundle perpendicular to the arranging direction of said reinforcing fibers increases from a first tip which is one in an arranging direction of said reinforcing fibers toward a second tip which is another tip and also has a second transition section in which said number of the reinforcing fibers in the cross-section of the fiber bundle increases from said second tip toward said first tip, and

(d) said chopped fiber bundle having a constant section located between said first transition section and said second transition section in the arranging direction of said reinforcing fibers in which said number of reinforcing fibers in the cross-section of the fiber bundle is constant, wherein one end face of said constant section coincides with a first terminal end face of said first transition section which is at an opposite end of said first tip while another end face of said constant section coincides with a second terminal end face of said second transition section which is at an opposite end of said second tip, or wherein said first terminal end face directly coincides with said second terminal end face, and wherein

(e) between said first tip and said second tip, change in the total cross-sectional area of the reinforcing fibers in said cross-section of the fiber bundle, measured along the arranging direction of said reinforcing fiber, is 0.05 mm² or less per 1 mm.

2. The chopped fiber bundle according to claim 1, wherein the maximum value of a total cross-sectional area of said reinforcing fibers is 0.1 mm² or more.

3. The chopped fiber bundle according to claim 1, wherein the maximum value of a total cross-sectional area of said reinforcing fibers is less than 0.1 mm² and, between said first tip and said second tip, a change in the number of said reinforcing fibers in the cross-section of the fiber bundle, measured along the arranging direction of said reinforcing fibers, is 30% or less of said maximum number of reinforcing fibers per 1 mm.

4. The chopped fiber bundle according to claim 1, wherein all of said reinforcing fibers have the same length.

5. The chopped fiber bundle according to claim 1, wherein said reinforcing fibers are carbon fibers, the number of said carbon fibers is 1,000 to 700,000, and between said first tip and said second tip, a change in the number of said reinforcing fibers in the cross-section of the fiber bundle, measured along the arranging direction of said reinforcing fibers, is 1,400 or less per 1 mm.

6. The chopped fiber bundle according to claim 1, wherein a value of ratio Wb/Tb is 20 to 400, where Wb represents width of said fiber bundle measured perpendicular to the arranging direction of said reinforcing fibers in a plan view which has a state that said width becomes largest, while Tb represents the maximum thickness of said chopped fiber bundle measured perpendicular to the plan view.

7. The chopped fiber bundle according to claim 1, wherein, in a plan view which has a state that the width of said fiber bundle becomes largest, a side extending from said tip to an end forms a straight segment in the arranging direction of said reinforcing fibers in transition sections while another side forms a straight segment inclined by an angle of 2 to 30°

from the arranging direction of said reinforcing fibers.

8. The chopped fiber bundle according to claim 1, wherein said bundling agent is a sizing agent used to produce the reinforcing fiber bundle and an amount of the sizing agent accounts for 0.1 to 10 mass % of the chopped fiber bundle.

9. The chopped fiber bundle according to claim 1, wherein said bundling agent is a matrix resin used to produce a resin molded material containing reinforcing fibers and an amount of the matrix resin accounts for 20 to 75 mass % of the chopped fiber bundle.

10. A molding material comprises an aggregate of chopped fiber bundles comprising one or more layers of a large number of the chopped fiber bundles according to claim 1, wherein said large number of chopped fiber bundles are integrated into one body by the bundling agent of said chopped fiber bundles and/or by entanglement of said reinforcing fibers in adjacent said chopped fiber bundles.

11. The molding material according to claim 10, wherein said bundling agent is a matrix resin used to produce a resin molded material containing reinforcing fibers, an amount of the matrix resin accounts for 20 to 75 mass % of said chopped fiber bundle and said aggregate of chopped fiber bundles is in a sheet form.

12. The molding material according to claim 11, wherein said reinforcing fibers in each chopped fiber bundle in said sheet of aggregate of the chopped fiber bundles are arranged in the same direction.

13. The molding material according to claim 12, wherein said aggregate of the chopped fiber bundles comprises a laminate including a lamination of a plurality of said sheets of aggregate of the chopped fiber bundles, and in the laminate, arranging directions of the reinforcing fibers in a layer of said sheet of aggregate of the chopped fiber bundles and another layer are different each other.

14. The molding material according to claim 10, wherein arranging directions of said reinforcing fibers in each chopped fiber bundle in said aggregate of the chopped fiber bundles are random.

15. The molding material according to claim 10, wherein said aggregate of the chopped fiber bundles has a three-dimensional shape so that it has at least one bending portion in its cross-section.

16. A molding material comprising a pellet for injection molding comprising a mixture of a large number of chopped fiber bundles as set forth in claim 1 and a thermoplastic resin.

17. A fiber reinforced plastic comprises an aggregate of a large number of chopped fiber bundles as set forth in claim 1 and a matrix resin combined with said aggregate of chopped fiber bundles.

18. The fiber reinforced plastic according to claim 17, wherein at least 20 of said chopped fiber bundles are accumulated in the thickness direction in the cross-section in the thickness direction of said fiber reinforced plastic.

19. A chopped fiber bundle production method comprising:

(a) a continuous reinforcing fiber bundle supplying step which supplies a continuous reinforcing fiber bundle comprising a large number of unidirectionally arranged continuous reinforcing fibers and a bundling agent to bundle the reinforcing fibers, and

(b) a continuous reinforcing fiber bundle cutting step in which chopped fiber bundles are formed by cutting the continuous reinforcing fiber bundle supplied from the continuous reinforcing fiber bundle supplying step, at constant intervals in the longitudinal direction of the continuous reinforcing fiber bundle, wherein

(c) the continuous reinforcing fiber bundle is cut in the continuous reinforcing fiber bundle cutting step, in such a manner that each chopped fiber bundle formed in the continuous reinforcing fiber bundle cutting step meets the chopped fiber bundle as set forth in claim 1.

20. The chopped fiber bundle production method according to claim 19, wherein the continuous reinforcing fiber bundle supplying step includes a continuous reinforcing fiber bundle opening step in which the continuous reinforcing fiber bundle is opened in such a manner that the large number of reinforcing fibers are arranged flatly in the cross-section of the continuous reinforcing fiber bundle.

21. The chopped fiber bundle production method according to claim 19, wherein said bundling agent is a sizing agent used to produce said continuous reinforcing fiber bundle and an amount of the sizing agent accounts for 0.1 to 10 mass % of said continuous reinforcing fiber bundle.

22. The chopped fiber bundle production method according to claim 19, wherein said bundling agent is a matrix resin used to produce a resin molded material containing reinforcing fibers, and an amount of the matrix resin accounts for 20 to 75 mass % of said continuous reinforcing fiber bundle.

23. A chopped fiber bundle production method comprising:

(a) a continuous reinforcing fiber sheet supplying step that supplies a continuous reinforcing fiber sheet in which a plurality of continuous reinforcing fiber bundles comprising a large number of unidirectionally arranged continuous reinforcing fibers are arranged in parallel,

(b) a prepreg sheet forming step that forms a prepreg sheet in which said continuous reinforcing fiber sheet supplied by the continuous reinforcing fiber sheet supplying step is placed on a resin sheet formed from a matrix resin used to produce a resin molded material containing reinforcing fibers, followed by combining said reinforcing fiber and said matrix resin, and

(c) a prepreg sheet cutting step in which the prepreg sheet formed in the prepreg sheet forming step is cut at constant intervals in an arranging direction of the reinforcing fibers, or cut at constant intervals both in the arranging direction of the reinforcing fiber and in a direction perpendicular to the arranging direction of the reinforcing fibers, to form a chopped fiber bundle, wherein

(d) the prepreg sheet is cut in the prepreg sheet cutting step, in such a manner that each chopped fiber bundle formed in the prepreg sheet cutting step meets the chopped fiber bundle as set forth in claim 1.

24. The chopped fiber bundle production method according to claim 23, wherein, on the resin sheet on which the continuous reinforcing fiber sheet is placed in the prepreg sheet forming step, another resin sheet formed from a matrix resin used to produce a resin molded material containing reinforcing fibers is placed, and the reinforcing fibers and the matrix resin are combined to form a prepreg in which an amount of the matrix resin is controlled in such a manner that an amount of the matrix resin in the chopped fiber bundle to be obtained accounts for 20 to 75 mass %.

25. A molding material production method comprising:

(a) a chopped fiber bundle scattering step in which a large number of chopped fiber bundles as set forth in claim 1 are scattered on a molding base in such a manner that the large number of chopped fiber bundles are accumulated in one or more layers, and

(b) a chopped fiber bundle aggregate forming step to form a molding material comprising an aggregate of chopped fiber bundles, by bonding together the large number of chopped fiber bundles scattered on the molding base to form an aggregate.

26. The molding material production method according to claim 25, wherein, in the chopped fiber bundle scattering step, the molding base has a flat surface, and the chopped fiber bundles are scattered on the flat surface in such a manner that the reinforcing fibers of the large number of chopped fiber bundles on the flat surface are arranged in the same direction and also that a chopped fiber bundle sheet comprising the large number of chopped fiber bundles is formed on the flat surface, while in the chopped fiber bundle aggregate forming step, a molding material comprising the chopped fiber bundle sheet produced from the large number of chopped fiber bundles is formed.

27. The molding material production method according to claim 26, wherein, after formation of the chopped fiber bundle sheet, the chopped fiber bundles are scattered on the formed chopped fiber bundle sheet in such a manner that the reinforcing fibers in the large number of chopped fiber bundles on the formed chopped fiber bundle sheet are arranged in the same direction, but arranged in a different direction from the reinforcing fibers in the chopped fiber bundles in the formed chopped fiber bundle sheet, and another chopped fiber bundle sheet comprising the large number of chopped fiber bundles is formed on the chopped bundle sheet formed first, to produce a molding material comprising a laminate of chopped fiber bundle sheets.

28. The molding material production method according to claim 25, wherein the chopped fiber bundles are scattered on the molding base in such a manner that the reinforcing fibers of the large number of chopped fiber bundles on the molding base are arranged in random directions.

29. The molding material production method according to claim 25, wherein the molding base is a resin sheet formed from a matrix resin used to produce a resin molded material containing reinforcing fibers.

30. The molding material production method according to claim 25, wherein the chopped fiber bundle scattering step comprises:

(a) a first layer forming step in which a molding base has a three dimensionally shaped surface, and the chopped fiber bundles are scattered on a three dimensionally shaped surface in such a manner that the reinforcing fibers of the large number of chopped fiber bundles on the three dimensionally shaped surface are arranged in the same direction to form a first chopped fiber bundle layer comprising a large number of chopped fiber bundles, and

(b) a second layer forming step in which the chopped fiber bundles are scattered on the first chopped fiber bundle layer in such a manner that the reinforcing fibers of the large number of chopped fiber bundles on the first chopped fiber bundle layer formed in the first layer forming step are arranged in the same direction, and also that the reinforcing fibers are arranged in a different direction from the reinforcing fibers in the chopped fiber bundles in the first chopped fiber bundle layer to form a second chopped fiber bundle layer comprising a large number of chopped fiber bundles.

31. A molding material production method comprising:

(a) a chopped fiber bundle scattering step in which a large number of chopped fiber bundles as set forth in claim 1 are scattered on a molding base comprising a first resin sheet formed from a matrix resin to be used to produce a resin molded material containing reinforcing fibers,

(b) a resin sheet laminating step in which a second resin sheet comprising the matrix resin is laminated on the large number of chopped fiber bundles of the first resin sheet having the large number of chopped fiber bundles obtained in the chopped fiber bundle scattering step, and,

(c) an aggregate of chopped fiber bundles forming step in which a laminate comprising the large number of chopped fiber bundles obtained in the resin sheet laminating step and the first and second resin sheets are pressurized and/or heated, to combine the large number of chopped fiber bundles and said first and second resin sheets, to form an aggregate of chopped fiber bundles.

32. A molding material production method comprising a kneading step in which a large number of chopped fiber bundles as set forth in claim 1 and a thermoplastic resin are kneaded together to prepare a kneaded mixture of the chopped fiber bundles and the thermoplastic resin, and a molding step in which the kneaded mixture prepared by the kneading step is continuously extruded into a rod or sheet, to form a continuous molded product having a rod or sheet shape and a pelletizing step in which the continuous molded product obtained in the molding step is cut at intervals in the longitudinal direction, to form pellets for injection molding.

33. A fiber reinforced plastic production method in which one or more molding material as set forth in claim 11 having an area smaller than a projected area of a cavity of a mold and a thickness larger than that of the cavity are placed in the cavity, and then the mold is clamped followed by pressurizing the molding material or pressurizing and heating to extend the molding material to allow the molding material to fill the cavity, and after finishing molding of the fiber reinforced plastic in the cavity, removing the molded fiber reinforced plastic out of the cavity.