JP5966969B2 - Manufacturing method of prepreg - Google Patents

Description

  The present invention relates to a prepreg used in sports applications, aerospace applications, and general industrial applications, and particularly uses a cloth in which carbon fibers are arranged in two directions, which can provide a fiber-reinforced composite material having good appearance quality. The present invention relates to a prepreg and a manufacturing method thereof. Moreover, it is related with the fiber reinforced composite material obtained from this cross prepreg.

  As raw materials for high-performance composite materials, prepregs composed of reinforced fibers such as carbon fiber, glass fiber, and aramid fiber and matrix resins such as epoxy resin, unsaturated polyester resin, phenol resin, and polyimide resin are generally used. Has been.

  Examples of the prepreg molding method include an autoclave method, a vacuum bag molding method, a press molding method, and an internal pressure molding method. For example, the autoclave method is a method that is generally used when producing a fiber-reinforced composite material (hereinafter sometimes referred to as FRP, and the carbon fiber-reinforced composite material may be referred to as CFRP). However, after the prepreg is laminated on the mold and the whole is covered with a heat-resistant film or the like, the prepreg is placed in an autoclave and the outside is pressurized and heated while being evacuated to be cured. The autoclave method uses a large-scale apparatus and pressurizes and heats, so it costs a molding cost. However, the quality of the obtained FRP molded product is good, and the mechanical properties including tensile strength are high. . Further, in the vacuum bag forming method, the laminated prepreg is covered with a bag material, and is heated and cured while evacuating the inside. Since pressure is not applied from the outside, there is a problem that voids are likely to be generated in the FRP, but there is an advantage that molding costs are not required as compared with the autoclave method.

  A prepreg is formed by using these methods. The prepreg has adhesiveness (tack) on the surface due to its structure, and air is easily caught between the layers and the mold surface when the prepreg is laminated. Internal voids are generated due to the bubbles and air dissolved in the resin during molding. Furthermore, bi-directional cross prepregs using reinforced fiber fabrics have unevenness due to the texture of the reinforced fiber fabrics, and the outermost layer is difficult to adhere to the mold. Compared with prepreg, pinholes are likely to occur on the surface of the molded product. Cloth prepregs are not only widely used for large-sized molded products, but also have high needs as design materials that use a beautiful texture on the molding surface, and improvement in moldability is desired.

  In general, it is known that the occurrence of pinholes on the surface of a molded product as described above largely depends on the molding method and molding conditions. Conventionally, by optimizing the molding method and molding conditions, Efforts have been made to reduce the hall. However, even when a good molded product can be obtained by optimizing the molding conditions, the range of the optimum conditions is very narrow, so it depends on skilled engineers and is difficult to produce stably. is there.

  As a technique for suppressing pinholes, Patent Document 1 discloses a method using a film of reinforcing fibers and a thermosetting resin as an alternative to a prepreg. In this method, the reinforcing fiber and the resin film are laminated at the time of molding and then heated, so that the resin of the resin film is impregnated into the reinforcing fiber and molded at the same time, so the air inside and between the prepreg layers is discharged out of the mold. Easily reduces voids and pinholes generated on the surface of the molded body.

  Patent Document 2 proposes a method for producing CFRP by vacuum bag molding using an unimpregnated prepreg containing foam beads. An unimpregnated prepreg is a prepreg in which a thermosetting resin film is bonded to one side of a base material made of reinforcing fibers, and a part of the thermosetting resin is impregnated into a part of the base material, or a thermosetting resin film Is a prepreg in which a base material is bonded to both sides of the base material, and a part of the thermosetting resin is impregnated into a part of the base material. The expanded beads contained in the unimpregnated prepreg of Patent Document 2 are expanded and expanded by heating at the time of forming the unimpregnated prepreg, and the generation of voids and pinholes in the molded product can be suppressed. Therefore, generation of voids and pinholes is reduced as compared with a molded product using a conventional unimpregnated prepreg.

  By using these methods, the generation of voids can be reduced to some extent without performing autoclave molding in which pressure is applied from the outside.However, when the shape of the molded product is complicated, unevenness is caused when impregnating the resin. Therefore, it is difficult to completely suppress voids and pinholes. In any of the methods, it takes time to impregnate the fiber reinforcement with the resin, and there is a problem that the molding time is longer than that of the conventional prepreg.

Carbon black and carbon nanotubes may be mentioned as particles having the same color as carbon fiber. However, a technique for mixing carbon black into a thermosetting resin has been known for some time. For example, Patent Document 3 discloses thermosetting. There has been proposed a fiber reinforced composite material in which carbon black is contained in a functional resin to improve the light shielding property. However, in order to improve the light-shielding property, carbon black is contained in the resin in an amount of 5 to 40% by mass, and further, the amount of resin on the surface of the molded body is not controlled, so the design of the cross prepreg is not taken into consideration. . In addition, no consideration is given to the mechanical properties of the resulting molded body. Further, Patent Document 4 proposes a fiber reinforced composite material in which carbon black is contained in a thermosetting resin to improve the light shielding property, but a carbon fiber woven fabric having a basis weight of 20 g / m ² is small. Since carbon black is contained in the resin in an amount of 10 to 40% by mass and control of the amount of resin on the surface of the molded body is not taken into consideration, it is unsuitable for applications that make use of the design of the cross prepreg.

Further, Patent Document 5 has a carbon fiber basis weight of 7 to 150 g / m ² , and improves the light shielding property by using a prepreg containing 0.5 to 15% by mass of carbon black with respect to the thermosetting resin. Although a method is disclosed, the carbon fiber basis weight is limited to a unidirectional prepreg of 150 g / m ² or less, and it cannot be applied to an application utilizing the design of a cross prepreg.

  Furthermore, Patent Document 6 discloses a method for improving the light-shielding property by blending 0.1 to 2% by mass of carbon black having a particle size of 1 to 30 nm with respect to the thermosetting resin. However, like Patent Document 5, the design properties of the cross prepreg and the void improvement method are not considered.

JP 2007-099966 A JP 2004-059872 A Japanese Patent No. 2526833 JP 2004-4231 A Japanese Examined Patent Publication No. 6-68594 JP 2011-195723 A

  An object of the present invention is that when a prepreg containing an epoxy resin composition containing carbon black is molded using autoclave molding or vacuum back molding, the resulting fiber-reinforced composite material does not have a decrease in strength and is generated. To make the pinholes inconspicuous.

  In order to make the pinhole appearing on the surface of the molded product inconspicuous as an improvement in designability, the present inventors have focused on dispersing particles of the same color as the carbon fiber in the thermosetting resin in advance, and have reached the present invention. That is, this invention for achieving the said subject consists of the following structures.

In the method for producing a prepreg of the present invention, a carbon fiber bi-directional cloth having a basis weight of 170 to 800 g / m ² is used , and a carbon black having an average particle size of 0.01 to 1.0 μm is an epoxy resin component in the resin composition. Is impregnated at an impregnation temperature of 70 to 90 ° C. and a linear pressure by a press roll of 5 to 200 kg / m, with an epoxy resin composition containing 0.05 to 1.0 part by mass. When the mass content of the matrix resin in the prepreg is 30 to 50% by mass, the thickness of the resin layer on the surface of the cross prepreg is 0.1 to 0.7 mm.

  In the present invention, carbon black is contained in the epoxy resin composition which is a matrix resin, and the thickness of the resin layer on the surface of the prepreg is specified, so that even if the matrix resin flows during molding, pinholes are made inconspicuous. Can do. Moreover, the molded object excellent in the design property which can confirm the woven structure of the surface of CFRP obtained can be obtained, and the mechanical characteristics of the molded object are also excellent.

  The reinforcing fiber used in the present invention is a carbon fiber. As the carbon fiber used in the present invention, pitch-based and polyacrylonitrile-based carbon fibers are used, and it is preferable to use polyacrylonitrile-based carbon fibers having high tensile strength.

  The bi-directional cloth used in the present invention may be a woven fabric having any woven structure such as plain weave, satin weave, twill weave, etc., but it is particularly preferable to use twill weave excellent in design and formability.

The cloth prepreg of the present invention requires a fiber basis weight of 170 to 800 g / m ² . Furthermore, it is more preferable that it is 190-700 g / m < ² >. By setting the fiber basis weight to 800 g / m ² or less, a cross prepreg excellent in formability can be obtained. In addition, by setting the fiber basis weight to 170 g / m ² or more, it is possible to suppress the bending of the reinforcing fiber fabric and the bending due to the movement of the fibers in the longitudinal direction of the reinforcing fiber fabric. In addition, the reinforcing fiber woven fabric having a fabric basis weight of 170 g / m ² or more can reduce the number of laminated layers at the time of molding, and thus can contribute to the effect of reducing the molding cost and the efficiency of work in the molding process.

  The mass content of the matrix resin in the prepreg of the present invention needs to be 30 to 50% by mass. Furthermore, it is preferable that it is 40-45 mass%. When the mass content of the resin is 30% by mass or more, the resin layer can be left on the surface of the prepreg, and the resin can be easily present on the surface when molded. Moreover, since the protrusion amount of the resin in the prepreg manufacturing process can be suppressed by setting the mass content of the resin to 50% by mass or less, a cross prepreg having a stable basis weight and excellent mechanical properties can be obtained. Moreover, since the amount of resin on the surface can be controlled, a molded article having excellent design properties can be obtained.

  The matrix resin used in the cross prepreg of the present invention is an epoxy resin composition comprising an epoxy resin component, a curing agent component, and others. Specific examples of the resin component include glycidyl ether obtained from polyol, active hydrogen. Glycidylamine obtained from an amine having a plurality of glycidyl esters, glycidyl ester obtained from a polycarboxylic acid, polyepoxide obtained by oxidizing a compound having a plurality of double bonds in the molecule, and the like. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol type epoxy resin such as tetrabromobisphenol A type epoxy resin, phenol novolac type epoxy resin, novolac type epoxy such as cresol novolac type epoxy resin Resins, glycidylamine type epoxy resins such as tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, tetraglycidylxylenediamine, and the like, or combinations thereof are preferably used.

  As the curing agent component, any compound having an active group capable of reacting with an epoxy group can be used. For example, amine-based curing agents such as ethylenediamine, diethylenetriamine, triethylenetetramine, hexamethylenediamine, aliphatic amines such as m-xylylenediamine, metaphenylenediamine, diaminodiphenylmethane, diaminodiethyldiphenylmethane, diaminodiethyldiphenylsulfone, etc. Tertiary amines such as aromatic amines, benzyldimethylamine, tetramethylguanidine, 2,4,6-tris (dimethylaminomethyl) phenol, basic active hydrogen compounds such as dicyandiamide, adipic acid dihydrazide, etc. Organic acid dihydrazide, 2-methylimidazole, 2-ethyl-4-methylimidazole, and other imidazoles. In the present invention, it is preferable to use a basic active hydrogen compound which is an amine-based curing agent as a curing agent because it is cured at a relatively low temperature and has good storage stability. Of these, use of dicyandiamide is preferred.

  In the present invention, in order to improve the curability of the epoxy resin composition, these curing agents can be used in combination with an appropriate curing accelerator. Specifically, an example in which a urea derivative or an imidazole derivative is combined as a curing accelerator with an amine curing agent such as dicyandiamide, which is a curing agent. In the present invention, it is preferable to use together a urea-based curing accelerator composed of a urea derivative as a curing accelerator. Among these, urea-based curing accelerators include 3-phenyl-1,1 dimethylurea, 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU), 1,1′-4 (methyl-m-phenylene). Bis (3,3′dimethylurea) and the like are preferably used, and among them, a compound having two urea groups in the molecule, such as 1,1′-4 (methyl-m-phenylene), because of its high curability. Bis (3,3′dimethylurea) is preferably used.

  Generally, as the curability increases, the room temperature stability of the epoxy resin composition decreases. In the present invention, in order to achieve both handleability at room temperature and curability at the time of molding, 3 to 8 parts by mass of the curing agent with respect to 100 parts by mass of the resin component, and 0.5 to 5 parts by mass of the curing accelerator. It is preferable to add in the range. In addition, the epoxy resin composition of the present invention can be used in combination with a thermoplastic resin because it can be expected to have an effect of improving the adhesive properties of those having high viscosity characteristics and prepreg, and having high polarity. It is also preferable to do.

  The thermoplastic resin is selected from a carbon-carbon bond, amide bond, imide bond, ester bond, ether bond, carbonate bond, urethane bond, urea bond, thioether bond, sulfone bond, imidazole bond, and carbonyl bond in the main chain. A thermoplastic resin having such a bond is preferably used. Among these thermoplastic resins, there are thermoplastic resins such as polyacrylate, polyamide, polyaramid, polyester, polycarbonate, polyphenylene sulfide, polybenzimidazole, polyvinyl formal, polymethyl methacrylate, polyimide, polyetherimide, polysulfone, and polyethersulfone. More preferably used. Polyethersulfone and polyvinyl formal are particularly preferably used because they are effective in improving the adhesion to carbon fibers and improving the interlaminar shear strength and compressive strength.

  The amount of the thermoplastic resin is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the resin component. By blending the number of parts, the prepreg can be easily handled during molding, and the mechanical properties of the obtained molded body can be enhanced. Examples of the particles to be blended in the thermosetting resin of the present invention include carbon black, carbon nanotube, and fullerene as particles having the same color as the reinforcing fiber, but carbon black not only fills the uneven portion of the cross prepreg, It is indispensable to use carbon black because it can suppress a decrease in physical properties of the resin used, is inexpensive and has good handleability.

The average particle diameter of the carbon black, which is a particle of the same color as the carbon fiber that is the reinforcing fiber, blended in the epoxy resin composition of the present invention is the particle diameter at an integrated value of 50% in the particle size distribution determined by the laser diffraction method. diameter, it is required is 0.01 to 1.0 [mu] m, it is good preferable is 0.02～0.7Myuemu. By making the average particle size 0.01 μm or more, pinholes can be made inconspicuous, and by making the average particle size 1.0 μm or less, the smoothness of the prepreg surface can be maintained and the deterioration of mechanical properties can be suppressed. .

  Furthermore, the content of carbon black, which is a particle to be blended in the epoxy resin composition of the present invention, is 0.05 to 1.0 part by mass with respect to 100 parts by mass of the epoxy resin component in the epoxy resin composition. is necessary. The pinhole of CFRP obtained by setting it as 0.05 mass part or more can be made not conspicuous, and the design nature of the CFRP surface can be maintained by setting it as 1.0 mass part or less. The design property in the present invention means that pinholes are not conspicuous, and even if carbon black is contained, the texture of the carbon fiber bi-directional cloth can be clearly distinguished. Further, no deterioration of the mechanical properties of CFRP is observed.

  A resin film produced by kneading the epoxy resin composition and particles and using a known method is suitable as a film for a cross prepreg of the present invention.

  The cloth prepreg of the present invention can be obtained by impregnating a fiber reinforcement with a resin film made of an epoxy resin composition containing particles. The resin film is preferably impregnated from both sides of the fiber reinforcing material in order to improve handleability, but it is sufficient to impregnate at least one side. The fiber reinforcing material of the present invention may have a resin-impregnated layer impregnated with the epoxy resin composition and an unimpregnated layer not impregnated with the resin.

  The CFRP of the present invention can be obtained by curing the cross prepreg. A method for molding and curing the cross prepreg is not particularly limited, and a conventionally known autoclave method, vacuum back molding method, or the like can be used.

  In the cross prepreg of the present invention, the thickness of the resin layer on the prepreg surface needs to be 0.1 to 0.7 mm in order to make pinholes generated on the CFRP surface inconspicuous. 6 mm is preferable.

  The thickness of the resin layer on the surface of the prepreg defined in the present invention is determined by sampling the prepreg at five points in the width direction and measuring the cross section of the prepreg with a laser microscope. The five points in the width direction are sampled with a width of 6 cm with the center of the prepreg and 10 cm and 25 cm away from both ends. Further, the thickness of the resin layer is defined as an average value of a total of 10 points obtained by measuring the minimum resin layer thickness on the warp of the carbon fiber fabric at 2 points within the range of 6 cm.

By setting the thickness of the resin layer on the prepreg surface to 0.1 mm or more, even if the resin flows during molding, the pinhole can be made inconspicuous. Moreover, the void inside CFRP obtained can be suppressed by setting it as 0.7 mm or less. The method for controlling the thickness of the resin layer on the surface of the prepreg is as follows. In the cross prepreg in which the range of the mass content of the resin is defined, for example, the impregnation temperature is 70 to 90 ° C. in order to prevent the resin from being impregnated into the prepreg. It is possible to adjust the linear pressure to 5 to 200 kg / m, preferably within the range of 10 to 100 kg / m , to the above range.

Further, the cross prepreg of the present invention may be laminated in a number of times when a molded product is produced, but it is preferable to arrange at least one layer on the outermost layer. By arranging one layer on the outermost layer, the number of pinholes on the surface of the fiber reinforced composite material becomes 1 or less per 1 m ² , and the woven structure of the surface layer of the fiber reinforced composite material becomes visible.

The surface pinhole in the fiber-reinforced composite material of the present invention is defined by the number of visible voids formed on a panel surface of a molded product of 0.3 m × 0.3 m. At this time, the temperature rising rate during molding may be adjusted to a range of 1.5 to 2.5 ° C./min.

  When the prepreg of the present invention is used, the resin flows excessively at the time of molding the fiber reinforced composite material, and pinholes are generated on the surface, air between layers is not completely removed, and voids are preferably generated. . The CFRP obtained by such a method makes it difficult to notice pinholes that were unavoidable with conventional cross prepregs, and at the same time can ensure design.

  Hereinafter, the present invention will be described in detail by way of examples.

Example 1
At a heating medium set temperature of 100 ° C., 30 parts by mass of bisphenol A type epoxy resin jER828 (manufactured by Mitsubishi Chemical), 35 parts by mass of jER1001 (manufactured by Mitsubishi Chemical), 35 parts by mass of jER154 (manufactured by Mitsubishi Chemical), heat 3 parts by mass of Vinylec K (manufactured by JNC Corporation) as a plastic resin, 3.5 parts by mass of DICY-7T (manufactured by Mitsubishi Chemical Corporation) as a curing agent, and 3 of Omicure 24 (manufactured by PTI Japan Co., Ltd.) as a curing accelerator The resin composition blended in parts by mass was designated as Resin Composition I, and carbon black E-V9333 (manufactured by Resino Color Industry Co., Ltd.) having the parts by mass shown in Table 1 was added thereto to prepare a carbon black-blended epoxy resin composition. The carbon black used had an average particle size of 0.02 μm, and the content was adjusted to be 0.2 parts by mass of the epoxy resin composition. Using the epoxy resin composition, a reverse roll coater method was used to coat the resin on one side of the release paper so that the resin basis weight was 217 g / m ² .

The resin film obtained as described above is a 2/2 twill weave cloth with a basis weight of 650 g / m ² using T700SC-12K-60E carbon fiber (strength: 4.9 GPa, elastic modulus: 230 GPa) manufactured by Toray Industries, Inc. In addition, the resin was impregnated by applying pressure from both sides with a press roll heated to 70 ° C. to produce a cross prepreg. When the resin film was impregnated from both sides, the impregnation speed, temperature and impregnation pressure were adjusted so that the average thickness of the resin layer on the surface was 0.5 mm.

The cross prepreg is cut into a square of 0.3 m × 0.3 m, and four pieces are laminated so as to be in the same direction, in an autoclave at a temperature of 130 ° C. and a pressure of 3.0 kg / cm ² , Cured for 60 minutes. When the surface of the obtained CFRP was visually confirmed and the number of pinholes was counted, it was confirmed that there were no pinholes on the surface.

  In the evaluation of the weaving pattern, 5 judges judge and 4 or more people can confirm the weaving pattern of the fabric clearly and visually. The case where it was recognized was evaluated as x, and the case where there were 0 people who were recognized as good was evaluated as x. The obtained CFRP was judged to be good by the judgment of all the members, and it was confirmed that the evaluation was good. When the mechanical properties were evaluated using the CFRP, it was confirmed that the CFRP had the same compressive strength and interlaminar shear strength as the laminate using the resin not containing the carbon black of the reference example.

(Example 2)
Using the carbon fiber bi-directional cloth and resin composition used in Example 1, a carbon prepreg was prepared by adjusting the blended carbon black to 0.05 parts by mass with respect to 100 parts by mass of the epoxy resin component. At that time, the production conditions were adjusted so that the thickness of the resin layer on the prepreg surface was 0.6 mm.

  The obtained cross prepreg was laminated by the same method as in Example 1 to obtain a molded body. When the surface of the obtained CFRP was visually confirmed and the number of pinholes was counted, it was confirmed that there were no pinholes on the surface. In addition, it was confirmed that the evaluation of the woven pattern was ○ evaluation. When the mechanical properties were evaluated using the CFRP, it was confirmed to be equivalent to the reference example.

(Example 3)
Using the carbon fiber bidirectional cloth and resin composition used in Example 1 , a carbon prepreg containing 1.0 part by mass of carbon black to be blended with respect to 100 parts by mass of the epoxy resin component was produced. At that time, the manufacturing conditions were adjusted so that the thickness of the resin layer on the prepreg surface was 0.5 mm.

  The obtained cross prepreg was laminated in the same manner as in Example 1 to obtain a molded body. When the surface of the obtained CFRP was visually confirmed and the number of pinholes was counted, it was confirmed that there were no pinholes on the surface. In addition, it was confirmed that the evaluation of the woven pattern was ○ evaluation. When the mechanical properties were evaluated using the CFRP, it was confirmed to be equivalent to the reference example.

(Comparative Example 1)
Using the carbon fiber bidirectional cloth and resin composition used in Example 1, a cross prepreg containing 10 parts by mass of carbon black to be blended with respect to 100 parts by mass of the resin component was produced. At that time, the production conditions were adjusted so that the thickness of the resin layer on the prepreg surface was 0.6 mm.

  The obtained cross prepreg was laminated in the same manner as in Example 1 to obtain a molded body. When the surface of the obtained CFRP was visually confirmed and the number of pinholes was counted, it was confirmed that there were no pinholes on the surface. However, it was confirmed that the evaluation of the woven pattern was x evaluation. When the mechanical properties were evaluated using the CFRP, it was confirmed that the compressive strength and the interlaminar shear strength were reduced as compared with the reference example.

(Comparative Example 2)
Using the carbon fiber bidirectional cloth and resin composition used in Example 1, a cross prepreg containing 0.01 part by mass of carbon black to be blended with respect to 100 parts by mass of the epoxy resin component was produced. At that time, the production conditions were adjusted so that the thickness of the resin layer on the prepreg surface was 0.5 mm.

  The obtained cross prepreg was laminated in the same manner as in Example 1 to obtain a molded body. When the surface of the obtained CFRP was visually confirmed and the number of pinholes was counted, it was confirmed that there were 17 pinholes on the surface. It was confirmed that the evaluation of the woven pattern was ○ evaluation. When the mechanical properties were evaluated using the CFRP, it was confirmed that the compression strength and interlayer shear strength were the same as those of the reference example.

Example 4
Using the resin composition used in Example 1, a carbon black-containing epoxy resin composition having a carbon black particle content of 0.2 parts by mass was prepared. Using this epoxy resin composition, the resin was applied to one side of the release paper by the reverse roll coater method so that the mass content of the matrix resin in the cross prepreg was 30% by mass. A cross prepreg was produced from the resin film obtained as described above by the method used in Example 1. Manufacturing conditions were set so that the thickness of the resin layer on the surface of the obtained cross prepreg was 0.2 mm.

  The obtained cross prepreg was laminated in the same manner as in Example 1 to obtain a molded body. When the surface of the obtained CFRP was visually confirmed and the number of pinholes was counted, it was confirmed that there were no pinholes on the surface. In addition, it was confirmed that the evaluation of the woven pattern was ○ evaluation. When the mechanical properties were evaluated using the CFRP, it was confirmed that the compression strength and interlayer shear strength were the same as those of the reference example.

(Example 5)
Using the resin composition used in Example 1, a carbon black-containing epoxy resin composition having a carbon black particle content of 0.2 parts by mass was prepared. Using this resin, the resin was applied to one side of the release paper by the reverse roll coater method so that the mass content of the matrix resin in the cross prepreg was 45% by mass. A cross prepreg was produced by the method used in Example 1 using the resin film obtained as described above. At that time, the production conditions were set so that the thickness of the resin layer on the surface of the obtained cross prepreg was 0.4 mm. The obtained cross prepreg was laminated in the same manner as in Example 1 to obtain a molded body.

  When the surface of the obtained CFRP was visually confirmed and the number of pinholes was counted, it was confirmed that there were no pinholes on the surface. In addition, it was confirmed that the evaluation of the woven pattern was ○ evaluation. When the mechanical properties were evaluated using the CFRP, it was confirmed that the compression strength and interlayer shear strength were the same as those of the reference example.

(Comparative Example 3)
Using the resin composition used in Example 1, a carbon black-containing epoxy resin composition having a carbon black particle content of 0.2 parts by mass was prepared. Using this resin, the resin was applied to one side of the release paper by a reverse roll coater method so that the mass content of the matrix resin in the cross prepreg was 20% by mass. A cross prepreg was produced from the resin film obtained as described above in the same manner as in Example 1. At that time, the production conditions were set so that the thickness of the resin layer on the surface of the obtained cross prepreg was 0.1 mm.
The obtained cross prepreg was laminated in the same manner as in Example 1 to obtain a molded body.

  When the surface of the obtained CFRP was visually confirmed and the number of pinholes was counted, it was confirmed that there were 20 pinholes on the surface. In addition, it was confirmed that the evaluation of the woven pattern was ○ evaluation. When the mechanical properties were evaluated using the CFRP, it was confirmed that the physical properties were lower than those of the reference examples.

(Comparative Example 4)
Using the resin composition used in Example 1, a carbon black-containing epoxy resin composition having a carbon black particle content of 0.2 parts by mass was prepared. Using this resin, the resin was applied to one side of the release paper by the reverse roll coater method so that the mass content of the matrix resin in the cross prepreg was 60% by mass.

A cross prepreg was produced from the resin film obtained as described above in the same manner as in Example 1. At that time, the manufacturing conditions were set so that the thickness of the resin layer on the surface of the obtained cross prepreg was 1.2 mm.
The obtained cross prepreg was laminated in the same manner as in Example 1 to obtain a molded body.

  When the surface of the obtained CFRP was visually confirmed and the number of pinholes was counted, it was confirmed that there were no pinholes on the surface. However, it was confirmed that the evaluation of the woven pattern was Δ evaluation. When the CFRP was used and the mechanical properties were evaluated, it was confirmed that the compressive strength and the interlaminar shear strength were reduced as compared with the reference example due to the high resin content.

(Example 6)
Using T300B-3K-40B manufactured by Toray Industries with a strength of 3.5 GPa and an elastic modulus of 230 GPa as a carbon fiber, a carbon fiber bi-directional cloth having a basis weight of 198 g / m ² was prepared. Got. At that time, the production conditions were set so that the thickness of the resin layer on the surface of the obtained cross prepreg was 0.4 mm.

  The obtained cross prepreg was laminated as in Example 1 to obtain a molded body. When the surface of the obtained CFRP was visually confirmed and the number of pinholes was counted, it was confirmed that there were no pinholes on the surface. In addition, it was confirmed that the evaluation of the woven pattern was ○ evaluation. When the mechanical properties were evaluated using the CFRP, it was confirmed that the compression strength and interlayer shear strength were the same as those of the reference example.

(Example 7)
A prepreg produced in the same manner as in Example 1 was obtained using a carbon fiber bi-directional cloth basis weight of 400 g / m ² . At that time, the production conditions were set so that the thickness of the resin layer on the surface of the obtained cross prepreg was 0.5 mm. The obtained cross prepreg was laminated in the same manner as in Example 1 to obtain a molded body.

  When the surface of the obtained CFRP was visually confirmed and the number of pinholes was counted, it was confirmed that there were no pinholes on the surface. In addition, it was confirmed that the evaluation of the woven pattern was ○ evaluation. When the mechanical properties were evaluated using the CFRP, it was confirmed that the compression strength and interlayer shear strength were the same as those of the reference example.

Claims (1)

A method for producing a cross prepreg comprising a carbon fiber bi-directional cloth and a matrix resin containing carbon black having an average particle diameter of 0.01 to 1.0 μm , and having a basis weight of 170 to 800 g / m ² The bi-directional cloth is an epoxy resin composition containing 0.05 to 1.0 part by mass of carbon black with respect to 100 parts by mass of the epoxy resin component , the impregnation temperature is 70 to 90 ° C., and the linear pressure by the press roll is When the mass content of the matrix resin in the prepreg is set to 30 to 50% by impregnation as 5 to 200 kg / m, the thickness of the resin layer on the surface of the prepreg is set to 0.1 to 0.7 mm. A method for producing a prepreg, which is characterized.