Carbon fiber nonwoven fabric prepreg, its manufacturing method and carbon fiber reinforced resin molded body using the same

Abstract

To provide a carbon fiber nonwoven fabric prepreg that can be used in the same way as a prepreg containing continuous carbon fibers and has good handling properties, a method for manufacturing the same, and a fiber-reinforced resin molded body using the same.SOLUTION: There are provided a carbon fiber nonwoven fabric sheet containing discontinuous carbon fibers and a carbon fiber nonwoven fabric prepreg containing resin. The carbon fiber nonwoven fabric sheet is formed by laminating two or more rectangular fiber webs in which fibers are oriented, and the resin is integrated with the carbon fiber nonwoven fabric sheet. The prepreg is made by opening fibers, including discontinuous carbon fibers, in a carding machine, orienting the fibers in substantially one direction to make a fiber web, laminating the fiber web to make a laminated web, cutting both ends to make a carbon fiber nonwoven fabric sheet 15, and impregnating it with the resin or sandwiching it between resin sheets 18a and 18b.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a nonwoven fabric prepreg containing discontinuous carbon fibers, a method for producing the same, and a fiber-reinforced resin molding using the same. [Background technology]

[0002] Carbon fiber reinforced plastics (CFRP), which are made from carbon fibers and a matrix resin, are lightweight, have high specific strength and specific modulus, excellent mechanical properties, and high weather and chemical resistance. Therefore, they are used or are being considered for a variety of applications, including aircraft, automobiles, tanks, concrete reinforcement, and sports applications. When manufacturing CFRP, scrap materials are generated by cutting carbon fiber sheets, and their effective use becomes an issue. Furthermore, when disposing of CFRP molded bodies, the effective use (recycling) of carbon fibers becomes an issue.

[0003] Methods for extracting carbon fibers from waste CFRP include the burning method and the dissolution method, and Patent Document 1 proposes the dissolution method. This is a method in which the resin is dissolved, and high-quality recycled carbon fibers can be obtained. However, the carbon fibers after the dissolution process become discontinuous and are in a flocculent tangled state, making it difficult to recycle them into CFRP as is. Patent Documents 2 to 4 propose opening the recycled carbon fibers into CFRP using a dry method (carding). The present applicants also propose opening the fibers using a carding machine in Patent Document 5. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-297641 [Patent Document 2] Re-table No. 2012-086682 [Patent Document 3] Special Publication No. 2013-519546 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-025175 [Patent Document 5] Japanese Patent Application Laid-Open No. 2016-151081 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the conventional techniques of Patent Documents 2 to 4 have a problem in producing a long carbon fiber nonwoven fabric sheet in which the fibers are oriented in a predetermined direction to obtain a molded product that can be used in the same way as a continuous carbon fiber sheet, and the technique of Patent Document 5 has a problem in that although the fiber is highly oriented, it is difficult to handle.

[0006] In order to solve the above-mentioned conventional problems, the present invention provides a carbon fiber nonwoven fabric prepreg that can be used in the same manner as a prepreg containing continuous carbon fiber and has good handleability, a method for producing the same, and a fiber-reinforced resin molding using the same. [Means for solving the problem]

[0007] The carbon fiber nonwoven fabric prepreg of the present invention is a carbon fiber nonwoven fabric prepreg comprising a carbon fiber nonwoven fabric sheet containing discontinuous carbon fibers and a resin, wherein the carbon fiber nonwoven fabric sheet is formed by laminating two or more rectangular fiber webs in which fibers are oriented, The rectangular fiber webs are stacked with their ends offset to form a continuous web, The carbon fiber nonwoven fabric sheet is integrated with resin. attitude The rectangle here does not necessarily have to have corner angles of 90 degrees, and includes trapezoids and parallelograms.

[0008] A first method of producing a carbon fiber nonwoven fabric prepreg of the present invention comprises: opening fibers containing discontinuous carbon fibers in a carding machine, orienting the fibers substantially in one direction to form a fiber web; winding the fiber web around a roller to laminate the fiber web; slicing open the laminated fiber web to form a roller-wound parallel web; cutting both ends to form a carbon fiber nonwoven fabric sheet; and impregnating the carbon fiber nonwoven fabric sheet with a resin. The laminated fiber web is rectangular and is a parallel web.

[0009] A second method for producing a carbon fiber nonwoven fabric prepreg of the present invention includes: opening fibers containing discontinuous carbon fibers in a carding machine, orienting the fibers in substantially one direction to form a fiber web, and cutting the web in the width direction to form a rectangular shape; Each of the rectangular fiber webs is stacked with its end portions offset to form a continuous web; The carbon fiber nonwoven fabric sheet is characterized by being impregnated with a resin.

[0010] The fiber reinforced resin molding of the present invention is A fiber-reinforced resin molding is produced using the carbon fiber nonwoven fabric prepreg. [Effects of the Invention]

[0011] The carbon fiber nonwoven fabric prepreg of the present invention is a carbon fiber nonwoven fabric prepreg comprising a carbon fiber nonwoven fabric sheet containing discontinuous carbon fibers and a resin, wherein the carbon fiber nonwoven fabric sheet is formed by laminating two or more rectangular fiber webs in which fibers are oriented, and the carbon fiber nonwoven fabric sheet is integrated with a resin, thereby allowing it to be used in the same manner as a continuous carbon fiber prepreg and providing good handleability. The manufacturing method of the present invention can produce the carbon fiber nonwoven fabric sheet by a dry method, allowing for efficient and rational production of the carbon fiber nonwoven fabric prepreg of the present invention. Furthermore, by containing the carbon fiber nonwoven fabric sheet and a matrix resin, the fiber-reinforced resin molding of the present invention can be a fiber-reinforced resin molding having high tensile strength in the fiber orientation direction. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view of a carding machine according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic explanatory view of the same example, in which rectangular fiber webs obtained by a carding machine are stacked with their edges shifted to form a long web. [Figure 3] FIG. 3 is a schematic perspective view of a carbon fiber nonwoven fabric sheet according to one embodiment of the present invention. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a manufacturing process of a carbon fiber nonwoven fabric prepreg according to one embodiment of the present invention. [Figure 5] Figure 5 is a photograph of the surface of the carbon fiber web. [Figure 6]Figure 6 is an enlarged photograph of the surface of the carbon fiber web. [Figure 7] FIG. 7 is a surface photograph showing a portion where the ends of the carbon fiber webs are stacked with the edges shifted. [Figure 8] FIG. 8 is a schematic perspective view of a long cross web according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The carbon fiber nonwoven fabric prepreg of the present invention is a carbon fiber nonwoven fabric prepreg made of a carbon fiber nonwoven fabric sheet containing discontinuous carbon fibers and a resin. The carbon fiber nonwoven fabric sheet is a laminated web in which two or more rectangular fiber webs, each having fibers oriented in a predetermined direction, are laminated, and a resin is integrated with the carbon fiber nonwoven fabric sheet. The carbon fiber nonwoven fabric sheet of the present invention is a carbon fiber nonwoven fabric sheet containing discontinuous carbon fibers as one component. This allows for the production of a fiber-reinforced resin molded article that has high strength in the fiber orientation direction and is of high quality. The predetermined direction in the above description refers to the length direction of the fiber web.

[0014] The carbon fiber nonwoven fabric sheet is preferably at least one carbon fiber nonwoven fabric sheet selected from a parallel web and a cross web. These carbon fiber nonwoven fabric sheets have fibers oriented in a predetermined direction, and when formed into a fiber-reinforced resin molded product, a high-quality fiber-reinforced resin molded product with high strength in the fiber orientation direction can be obtained. Specifically, in a parallel web carbon fiber nonwoven fabric sheet, the constituent fibers are oriented substantially in one direction. In a cross web carbon fiber nonwoven fabric sheet, the constituent fibers are oriented along the stacking direction of the rectangular fiber webs by changing the stacking direction of the rectangular fiber webs.

[0015] The rectangular fiber webs are preferably stacked with their ends offset to form a continuous web. Since the rectangular fiber webs have the same width, stacking them with their ends offset by a predetermined length results in a continuous web with the same number of layers. The continuous web can have any number of layers and any length. Both ends of the continuous web are cut to form carbon fiber nonwoven fabric sheets, and the carbon fiber nonwoven fabric sheets are impregnated with resin to obtain a carbon fiber nonwoven fabric prepreg. This carbon fiber nonwoven fabric prepreg can be used in the same way as a continuous carbon fiber prepreg. That is, it can be molded using a vacuum bag method, a pressure bag method, an autoclave method, a hot press method, a sheet winding method, a pultrusion molding method, or the like, and the carbon fiber nonwoven fabric prepreg of the present invention can be used in the same way. As an example, when a carbon fiber nonwoven fabric sheet is obtained by cutting both ends of a long parallel web made by stacking rectangular fiber webs with the ends shifted by a specified length so that the fiber orientation is the same, and an epoxy resin is used as the matrix resin in the carbon fiber reinforced resin obtained from the carbon fiber nonwoven fabric prepreg, the tensile strength in the carbon fiber orientation direction is 340 MPa or more, which is comparable to that of aluminum alloy A2024 (super duralumin).

[0016] The carbon fiber nonwoven fabric sheet preferably contains 50 to 100% by mass of discontinuous carbon fibers and 0 to 50% by mass of reinforcing fibers other than carbon fibers, more preferably 70 to 100% by mass of discontinuous carbon fibers and 0 to 30% by mass of reinforcing fibers other than carbon fibers, and even more preferably 90 to 100% by mass of discontinuous carbon fibers and 0 to 10% by mass of reinforcing fibers other than carbon fibers. High-strength, high-elasticity organic fibers with a strength of 18 cN / decitex or greater and a modulus of elasticity of 380 cN / decitex or greater are preferred. Specific examples include aramid fibers (including para- and meta-types), polyarylate fibers, poly(p-phenylenebenzobisoxal) (PBO) fibers, poly(p-phenylenebenzobisthiazole) (PBZT) fibers, high-molecular-weight polyethylene fibers, polyetheretherketone fibers, and polyvinyl alcohol fibers.

[0017] The following description will be given taking as an example a carbon fiber nonwoven sheet containing discontinuous carbon fibers. The fiber web is formed by carbon fibers spread on a carding machine's fiber spreading device, which are oriented in a substantially unidirectional direction. The fiber spreading device is preferably a cylinder or belt conveyor. A large number of metal needles are provided on the cylinder or belt conveyor, and the carbon fibers are spread and oriented in a substantially unidirectional manner between the numerous metal needles, and then peeled off. This results in a fiber web oriented in a unidirectional direction. The fiber web is cut widthwise or diagonally to form a rectangular fiber web. Various widths, diameters, and lengths of the cylinder or belt conveyor can be selected, and one appropriate for the production volume is selected and used.

[0018] The mass per unit area of ​​the carbon fiber nonwoven sheet is 1 to 1000 g / m 2 and more preferably 5 to 500 g / m 2 and more preferably 10 to 300 g / m 2 The mass per unit area of ​​the fiber web is 0.1 to 100 g / m 2 is preferable, and more preferably 0.5 to 50 g / m 2 and more preferably 1 to 30 g / m 2 The above range is convenient for molding.

[0019] The number of layers of the rectangular fiber web is preferably 2 to 100, more preferably 5 to 50, and even more preferably 10 to 40. With this number of layers, the mass per unit area can be increased, and a carbon fiber reinforced resin molding with high strength can be produced.

[0020] The edges of the rectangular fiber webs are preferably stacked with a shift of 1 to 1,000 mm per sheet, more preferably 5 to 500 mm, and even more preferably 10 to 300 mm. This amount of shifting allows a uniform, long web to be obtained. Here, "long" is theoretically infinite, but in practice it is about 1 to 25 m.

[0021] In the present invention, "orientation substantially in one direction" means that 50% by mass or more of the fibers are oriented at an angle within ±10 degrees. Therefore, it is preferable that 50% by mass or more of the fibers constituting the rectangular fiber web are oriented at an angle within ±10 degrees, more preferably 60% by mass or more are oriented at an angle within ±10 degrees, and even more preferably 70% by mass or more are oriented at an angle within ±10 degrees. Within the above ranges, a high-quality fiber-reinforced resin molding with high orientation and strength can be obtained.

[0022] The rectangular fiber web has an average density of 0.01 to 0.40 g / cm when a load of 500 Pa is applied. 3 The average density is preferably 0.02 to 0.20 g / cm. 3 and more preferably 0.03 to 0.15 g / cm 3 The above range is convenient for molding.

[0023] The fiber length of the fibers constituting the rectangular fiber web can be any length, but the fiber length distribution is preferably 1 to 300 mm, more preferably 5 to 200 mm, and even more preferably 10 to 150 mm. If the fiber length is within the above range, there is no problem in terms of quality and it is convenient for molding.

[0024] The size of the rectangular fiber web is preferably 30 to 5000 mm in the machine direction (MD) of the carbon fiber nonwoven fabric sheet and 20 to 3000 mm in the direction perpendicular to the MD (CD).Within these ranges, there is no problem in terms of quality and it is convenient for molding.

[0025] The carbon fiber component contained in the carbon fiber nonwoven fabric sheet is preferably recycled carbon fiber, but any carbon fiber can be used, such as cut new carbon fiber or scraps generated by cutting carbon fiber sheets during CFRP production. The carbon fiber raw material may be any type, such as polyacrylonitrile (PAN) or pitch. Furthermore, the carbon fiber nonwoven fabric sheet of the present invention can be laminated with a carbon fiber sheet (e.g., continuous fiber sheet, carbon fiber fabric, etc.) prepared by a different method to form a prepreg.

[0026] The carbon fiber nonwoven fabric prepreg can also be laminated with a carbon fiber sheet (for example, a continuous fiber sheet) prepared by a different method or a prepreg prepared by a different method to form a molded product.

[0027] The resin is preferably at least one resin selected from thermosetting resins and thermoplastic resins, and is impregnated into the carbon fiber nonwoven fabric sheet or integrated in a melt-solidified state. Thermosetting resins include epoxy resins, unsaturated polyester resins, vinyl ester resins, phenolic resins, polyimide resins, and bismaleimide resins. These resins are used in combination with a curing agent. Thermoplastic resins include polyolefin resins such as polyethylene and polypropylene, polyamide resins such as nylon 6 and nylon 66, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate resins, ABS resins, polyacetal resins, and polyphenylene sulfide resins.

[0028] The ratio of the fibers to the resin is preferably 5 to 70 volume % of fibers and 95 to 30 volume % of resin, more preferably 10 to 65 volume % of fibers and 90 to 35 volume % of resin, and even more preferably 15 to 60 volume % of fibers and 85 to 40 volume % of resin. Within these ranges, the resin can be used as at least a part of the matrix resin of the fiber-reinforced resin molding.

[0029] In order to improve degassing properties during molding, it is preferable that the carbon fiber nonwoven fabric sheet is partially impregnated with the resin.

[0030] Next, the first method of producing the carbon fiber nonwoven fabric prepreg of the present invention will be described. (1) Fiber web forming process Fibers containing discontinuous carbon fibers are opened in a carding machine, and the fibers are oriented substantially in one direction to form a fiber web. A sizing agent may be added as needed. If reinforcing fibers other than carbon fibers are added, they are added and mixed in this process. (2) Parallel web forming process The fiber web is wound around a roller to be laminated, and the laminated fiber web is cut open to form a roller-wound parallel web. (3) Nonwoven fabric forming process Both ends of the roller-wound parallel web are cut to form a carbon fiber nonwoven fabric sheet. (4) Resin integration process The carbon fiber nonwoven fabric sheet is sandwiched between resin sheets and hot-pressed. This results in a carbon fiber nonwoven fabric prepreg in which the carbon fiber nonwoven fabric sheet is integrated with the resin in an impregnated or melt-solidified state. When sandwiching the carbon fiber nonwoven fabric sheet between the resin sheets, a sizing agent may be applied or multiple carbon fiber nonwoven fabric sheets may be stacked.

[0031] The second method for producing a carbon fiber nonwoven fabric prepreg of the present invention is as follows. (1) Fiber web forming process Fibers containing discontinuous carbon fibers are opened in a carding machine, and the carbon fibers are oriented substantially in one direction to form a fiber web. A sizing agent may be added as needed. If reinforcing fibers other than carbon fibers are added, they are added and mixed in this process. (2) First cutting process The fiber web is obtained in a long shape, and is cut in the width direction or diagonally to form a rectangle. The method for cutting in the width direction or diagonally is not particularly limited, but for example, it may be cut with a cutter that moves at the same speed. Alternatively, there is a method in which the long fiber web is cut while being left stationary. In this way, a rectangular fiber web is formed. (3)Lamination process The rectangular fiber webs are stacked with their ends offset to form a continuous web. (4) Second cutting process The carbon fiber nonwoven fabric sheet of the present invention is obtained by cutting both ends of the continuous web. The both ends here refer to the unevenly laminated portions at the leading and trailing ends. The continuous web may be cut to a predetermined length as needed. (5) Resin integration process The carbon fiber nonwoven fabric sheet is sandwiched between resin sheets and hot-pressed. This results in a carbon fiber nonwoven fabric prepreg in which the carbon fiber nonwoven fabric sheet is integrated with the resin in an impregnated or melt-solidified state. When sandwiching the carbon fiber nonwoven fabric sheet between the resin sheets, a sizing agent may be applied or multiple carbon fiber nonwoven fabric sheets may be stacked.

[0032] The fiber-reinforced resin molded product of the present invention is a fiber-reinforced resin molded product containing a carbon fiber nonwoven fabric sheet and a matrix resin, and the matrix resin of the molded product contains at least a portion of the resin contained in the prepreg. When molding the fiber-reinforced resin molded product, a new resin can be added. Molding methods that use the carbon fiber nonwoven fabric prepreg of the present invention include a vacuum bag method, a pressure bag method, an autoclave method, a hot press method, a sheet winding method, and a pultrusion molding method.

[0033] The following description will be made with reference to the drawings. In the following drawings, the same reference numerals indicate the same parts. FIG. 1 is a schematic cross-sectional view of a carding machine 1 according to one embodiment of the present invention. In this carding machine 1, discontinuous carbon fibers 2 are fed from feed rollers 3a and 3b, pass through a take-in roller 4, are opened by the cooperation of a cylinder 5, workers 6a and 7a, and strippers 6b and 7b, pass through a doffer 8, are stripped by a vibrating comb 9, and are taken out as a fiber web. 11 is a base. The fiber web is formed by opening discontinuous carbon fibers, oriented in one direction, and is long. This fiber web is taken out from a discharge belt 12. At this time, it is cut in the width direction by a cutter 13, which moves, for example, at the same speed as the fiber web, and is taken out as a rectangular fiber web 10.

[0034] 2 is a schematic explanatory diagram of the same, in which rectangular fiber webs 10 obtained by a carding machine are stacked with their ends offset to form long webs 14, 24. These long webs 14, 24 are cut to a predetermined length to form carbon fiber nonwoven fabric sheets 15. The carbon fiber nonwoven fabric sheets 15 have a stable mass per unit area, and even when multiple sheets are produced, each carbon fiber nonwoven fabric sheet 15 has a substantially uniform mass. Both ends may be cut and the sheet may be fed again into the carding machine to form a carbon fiber nonwoven fabric sheet 15. The arrow indicates the direction of travel.

[0035] FIG. 3 is a schematic perspective view of a long parallel web 14 according to one embodiment of the present invention. The carbon fibers 16 that make up the long parallel web 14 are aligned in one direction. Rectangular fiber webs 10a-10i are stacked in the same direction with their ends offset. The left side (left side of the arrow cut line 17) including rectangular fiber web 10f is a carbon fiber nonwoven fabric sheet with a uniform number of layers. In this example, there are six layers. The arrow MD indicates the length direction (MD) of the carbon fiber nonwoven fabric sheet.

[0036] 4 is a schematic cross-sectional view showing the manufacturing process of a carbon fiber nonwoven fabric prepreg 21 according to one embodiment of the present invention. Resin sheets 18a, 18b are laminated to both sides of a carbon fiber nonwoven fabric sheet 15, with release sheets 19a, 19b laminated to the outside, and the resin is heat-pressed with heating and pressure rollers 20a, 20b to reduce the viscosity of the resin and integrate it with the carbon fibers that make up the carbon fiber nonwoven fabric sheet 15. The resulting carbon fiber nonwoven fabric prepreg 21 is easy to handle and is wound into a roll 22.

[0037] Fig. 5 is a photograph of the surface of a fiber web according to one embodiment of the present invention, Fig. 6 is an enlarged photograph of the surface of the same fiber web, and Fig. 7 is a photograph of the surface showing a portion where rectangular fiber webs have been stacked with their edges offset. 23a and 23b are the stacked portions. The number of layers is one on the right side, two in the middle, and three on the left side.

[0038] FIG. 8 is a schematic perspective view of a long cross web 24 according to another embodiment of the present invention. Rectangular fiber webs 10a-10i are alternately stacked with their ends offset so that the fiber directions of each web are 0° and 90°. For example, the fiber direction of rectangular fiber web 10a is 0°, and the fiber direction of rectangular fiber web 10b is 90°. This increases the strength in the length and width directions. Orienting the fibers vertically, horizontally, or diagonally increases the strength in each direction. 3, the left side (left side of the arrow cut line 17) including the fiber web 10f is a carbon fiber nonwoven fabric sheet with a uniform number of layers. In this example, there are six layers. The arrow MD indicates the length direction (MD) of the carbon fiber nonwoven fabric sheet. [Example]

[0039] The present invention will be explained in more detail below using examples, but it should be noted that the present invention is not limited to the following examples. <Tensile test of test piece> Referring to ASTM D3039 (2017), the tensile strength of the carbon fiber reinforced resin molding was measured using an Instron universal testing machine model 5982 with a load cell of 100 kN and a tensile speed of 1.0 mm / sec.

[0040] Example 1 Carbon fiber (manufactured by Toray Industries, Inc., product name "T800S", fiber length 80 mm) recycled from fiber tow waste by a dissolution method was fed into a wire carding machine to obtain a fiber web 30 cm wide. The fiber web had a basis weight of 2.2 g / m. 2 The fiber web was wound around a roller and laminated, and the laminated fiber web was cut open to have an average basis weight of 42 g / m 2A roller-wound parallel web carbon fiber nonwoven fabric sheet was obtained. When the carbon fibers constituting this carbon fiber nonwoven fabric sheet were observed under a microscope, it was found that 50% by mass or more were oriented at an angle within ±10 degrees. The obtained carbon fiber nonwoven fabric sheet was trimmed to approximately 250 mm in the length direction and 150 mm in the width direction, and a sizing agent was applied (average 7 wt%) and dried to prepare a substrate. Five of these substrates were stacked and coated with a sheet of epoxy resin (cured at 180°C, basis weight 579.6 g / m2). 2 The sheet was sandwiched between two sheets of plastic and pressed in a hot press at 100°C and 0.3 MPa for 10 minutes to obtain a carbon fiber nonwoven fabric prepreg that integrated the resin sheet and substrate. Two layers of the prepreg were laminated, bagged, and placed in an autoclave. While applying pressure at 0.5 MPa, the sheet was heated at 120°C for 15 minutes and then at 180°C for 2 hours to form a base plate for a carbon fiber reinforced resin molding. The base plate had a thickness of 1.8 mm and a density of 1.32 g / cm. 3 The fiber volume content was 19%. Test pieces measuring 230 mm in length and 25 mm in width were cut out from this base plate. The physical properties are summarized in Table 1.

[0041] Example 2 From the same raw materials as in Example 1, a weight of 2.2 g / m 2 The fiber web was cut in the width direction to a length of 50 cm to obtain a rectangular fiber web. 32 rectangular fiber webs were stacked with the cut edges shifted by 3.1 cm each to obtain a fiber web with an average basis weight of 35 g / m. 2 The same operation as in Example 1 was carried out, and 10 of the obtained substrates were stacked, and a sheet-shaped epoxy resin (cured at 180°C, basis weight about 970 g / m) was added. 2 The sheet was sandwiched between two sheets of plastic and pressed in a vacuum hot press at 100°C and 0.3 MPa for 10 minutes to obtain a prepreg in which the resin sheet and substrate were integrated. One layer of prepreg was bagged and placed in an autoclave, and heated at 120°C for 15 minutes and then at 180°C for 2 hours while applying pressure at 0.5 MPa to form a base plate of a carbon fiber reinforced resin molding. The base plate had a thickness of 1.2 m and a density of 1.28 g / cm. 3 The fiber volume content was 19%. Test pieces measuring 230 mm in length and 25 mm in width were cut out from this base plate. The physical properties are summarized in Table 1.

[0042] (Comparative Example 1) This comparative example is an example in which carbon fibers and binder fibers were formed into a sheet by a wet papermaking method, and a carbon fiber reinforced resin molding was produced. Carbon fibers (manufactured by Toho Tenax Co., Ltd., product name "IMS60", fiber length 6 mm) recycled from carbon fiber tow by a dissolution method and binder fibers (polyethylene terephthalate (PET) fiber, fiber length 6 mm) were mixed in a mass ratio of 7:3 and stirred in water to produce a fiber slurry. The obtained slurry was made into a paper using a hand-made paper cylinder to obtain a wet paper. This wet paper was dried using a heater and produced into a sheet with a mass per unit area of ​​30 g / m. 2 The carbon fibers constituting the wet-laid carbon fiber nonwoven fabric sheet obtained were not oriented in one direction. Eight sheets of this wet-laid carbon fiber nonwoven fabric were stacked, giving a weight of 240 g / m 2 A carbon fiber reinforced resin molded body substrate was formed. This carbon fiber reinforced resin molded body substrate was impregnated with epoxy resin (manufactured by Nagase ChemteX Corporation, product name "XNR / 6809") by the VaRTM method, and a carbon fiber reinforced resin molded body mother plate was molded from this mother plate. The mother plate was then molded according to ASTM D3039 (2017) with a length of 240 mm, width of 25 mm, thickness of 1.1 mm, and density of 1.2 g / cm. 3 The physical properties of the test pieces are summarized in Table 1.

[0043] [Table 1]

[0044] As is clear from Table 1, the carbon fiber nonwoven fabric prepreg of the present invention had high tensile strength in the fiber orientation direction, and molded articles similar to those obtained with continuous carbon fiber unidirectional prepreg were obtained. The tensile strength of molded articles using this carbon fiber nonwoven fabric prepreg was comparable to that of aluminum alloy A2024 (super duralumin). [Industrial Applicability]

[0045] The carbon fibers of the present invention are preferably recycled carbon fibers for efficient resource utilization, but any materials can be used, such as cut new carbon fibers or scraps generated by cutting carbon fiber sheets during CFRP production. In particular, it is expected that large amounts of waste CFRP will be generated as waste materials from aircraft and automobiles in the future. Since the carbon fibers extracted from waste CFRP are in an entangled state, the present invention, which can improve the openability and orientation of such entangled carbon fibers, has a wide range of applications. Furthermore, it is useful for applications in automobiles, sporting goods, nursing care products, conductive electrical and electronic components, electromagnetic wave shielding materials, and the like. [Explanation of symbols]

[0046] 1 card machine 2. Discontinuous carbon fiber 3a, 3b Feed rollers 4 Tekain Roller 5 cylinders 6a,7a Worker 6b,7b Stripper 8 Dohwa 9 Vibration Comb 10,10a-10i Rectangular fiber web 11 Foundation 12 Discharge belt 13 Cutter 14 Long parallel web 15 Carbon fiber nonwoven sheet 16 Carbon fibers that make up the fiber web 17 Cutting line 18a, 18b Resin sheet 19a, 19b Release sheet 20a, 20b Heating and pressure rollers 21 Prepreg 22 Hoisting body 23a, 23b Laminated part 24 Long cross web

Claims

1. A carbon fiber nonwoven fabric sheet containing discontinuous carbon fibers and a carbon fiber nonwoven fabric prepreg containing a resin, The carbon fiber nonwoven fabric sheet is formed by laminating two or more rectangular fiber webs in which fibers are oriented, The rectangular fiber webs are stacked with their ends offset to form a continuous web, A carbon fiber nonwoven fabric prepreg characterized in that a resin is integrated with the carbon fiber nonwoven fabric sheet.

2. 2. The carbon fiber nonwoven fabric prepreg according to claim 1, wherein the carbon fiber nonwoven fabric sheet is a laminate of at least one fiber web selected from a parallel web and a cross web.

3. 2. The carbon fiber nonwoven fabric prepreg according to claim 1, wherein the carbon fiber nonwoven fabric sheet has a discontinuous carbon fiber content of 50 to 100 mass% and a reinforcing fiber other than carbon fiber content of 0 to 50 mass% when the carbon fiber nonwoven fabric sheet is used as a parameter.

4. 2. The carbon fiber nonwoven fabric prepreg according to claim 1, wherein the resin is at least one resin selected from a thermosetting resin and a thermoplastic resin, and is integrated into the carbon fiber nonwoven fabric sheet in an impregnated or melt-solidified state.

5. 2. The carbon fiber nonwoven fabric prepreg according to claim 1, wherein the ratio of the fibers to the resin constituting the carbon fiber nonwoven fabric sheet is 5 to 70 volume % of the fibers and 30 to 95 volume % of the resin.

6. The carbon fiber nonwoven fabric sheet has a mass per unit area of ​​1 to 1000 g / m 2 The carbon fiber nonwoven fabric prepreg according to claim 1,

7. The carbon fiber nonwoven fabric prepreg according to claim 1, wherein the number of laminations of the rectangular fiber webs is 2 to 100.

8. The carbon fiber nonwoven fabric prepreg according to claim 1, wherein the ends of the rectangular fiber webs are stacked with a shift of 1 to 1000 mm per sheet.

9. 2. The carbon fiber nonwoven fabric prepreg according to claim 1, wherein the carbon fibers constituting the rectangular fiber web have a fiber length distribution of 1 to 300 mm.

10. The carbon fiber nonwoven fabric prepreg according to claim 1 , wherein the carbon fibers constituting the carbon fiber nonwoven fabric sheet include recycled carbon fibers.

11. A method for producing a carbon fiber nonwoven fabric prepreg according to any one of claims 1 to 10, The fibers containing discontinuous carbon fibers are opened using a carding machine to orient the fibers in substantially one direction to form a fiber web; The fiber web is wound around a roller to be laminated, the laminated fiber web is cut open to form a roller-wound parallel web, and both ends are cut to form a carbon fiber nonwoven fabric sheet; A method for producing a carbon fiber nonwoven fabric prepreg, comprising impregnating the carbon fiber nonwoven fabric sheet with a resin.

12. A method for producing a carbon fiber nonwoven fabric prepreg according to any one of claims 1 to 10, The fibers containing discontinuous carbon fibers are opened using a carding machine, and the fibers are oriented in substantially one direction to form a fiber web, which is then cut in the width direction to form a rectangular shape; Each of the rectangular fiber webs is stacked with its end portions offset to form a continuous web; A method for producing a carbon fiber nonwoven fabric prepreg, comprising impregnating the carbon fiber nonwoven fabric sheet with a resin.

13. A fiber-reinforced resin molding manufactured using the carbon fiber nonwoven fabric prepreg described in any one of claims 1 to 10.

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