Thermosetting prepreg and its manufacturing method

Abstract

The purpose of the present invention is to provide a thermosetting prepreg having good mechanical properties, and particularly having good handleability. The present invention relates to a thermosetting prepreg including: a fiber sheet; a first thermosetting resin composition that is impregnated in a central region in the thickness direction of the fiber sheet in a cross section perpendicular to the surface direction of the fiber sheet; and a second thermosetting resin composition that is impregnated in an outer region in the thickness direction of the fiber sheet in the cross section perpendicular to the surface direction of the fiber sheet, wherein the first and second thermosetting resin compositions each contain a thermosetting resin and a curing agent, and the equivalence ratio of the curing agent in the first thermosetting resin composition is greater than the equivalence ratio of the curing agent in the second thermosetting resin composition.

Description

[Technical Field]

[0001] The present disclosure relates to a thermosetting prepreg and a method for producing the same, and in particular to a thermosetting prepreg that can be used to produce carbon fiber reinforced plastics (CFRP) used in applications such as aircraft, and a method for producing the same. [Background technology]

[0002] Carbon fiber reinforced composite materials (also known as composites or CFRP), which consist of carbon fiber as the reinforcing fiber and a matrix resin, are characterized by their light weight, high strength, and high elastic modulus, and are widely used in aerospace, sports and leisure, general industry, and other fields.

[0003] In many cases, composite materials are manufactured using prepregs, which are pre-assembled carbon fibers and matrix resins. For example, composite materials can be manufactured by laminating multiple prepregs.

[0004] Developments are underway to improve the performance of composite materials made from prepregs. For example, composite materials generally made by laminating prepregs have resin layers made of matrix resin between laminated carbon fiber layers. However, the matrix resins typically used in composite materials have low electrical conductivity, which can result in relatively low electrical conductivity in the thickness direction of the composite material.

[0005] Patent Documents 1 and 2 describe blending metal particles or carbon particles into the matrix resin of a composite material.

[0006] Prepregs include thermosetting prepregs. Thermosetting prepregs have a structure in which a reinforcing fiber sheet, such as a carbon fiber sheet, is impregnated with a thermosetting resin, such as an epoxy resin. For example, a composite material can be produced by laminating multiple thermosetting prepregs (e.g., 24 layers) and then performing a thermosetting treatment.

[0007] Patent Document 3 describes a prepreg comprising a primary prepreg made of reinforcing fibers and a resin composition (I) impregnated into the reinforcing fiber layer, and a surface layer made of a resin composition (II) formed on one or both sides of the primary prepreg. According to Patent Document 3, the resin composition (I) contains an epoxy resin and a thermoplastic resin, and the resin composition (II) contains an epoxy resin and conductive particles. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 6-344519 [Patent Document 2] Japanese Patent Application Publication No. 8-34864 [Patent Document 3] International Publication No. 2014 / 050896 Summary of the Invention [Problem to be solved by the invention]

[0009] With conventional thermosetting prepregs, it has not been easy to achieve excellent mechanical properties, and in particular, it has not been easy to achieve good handling properties in addition to excellent mechanical properties with conventional thermosetting prepregs.

[0010] An object of the present disclosure is to provide a thermosetting prepreg having excellent mechanical properties and, in particular, good handling properties, and a method for producing the same. [Means for solving the problem]

[0011] The above problems can be solved by the following aspects of the present invention: <Aspect 1> A thermosetting prepreg, Fiber sheets, a first thermosetting resin composition impregnated in a central region in a thickness direction of the fiber sheet in a cross section perpendicular to the surface direction of the fiber sheet; and a second thermosetting resin composition impregnated into an outer region in a thickness direction of the fiber sheet in a cross section perpendicular to the surface direction of the fiber sheet; and the first and second thermosetting resin compositions each contain a thermosetting resin and a curing agent; an equivalent ratio of the curing agent in the first thermosetting resin composition is greater than an equivalent ratio of the curing agent in the second thermosetting resin composition; Thermosetting prepreg. <Aspect 2> A thermosetting prepreg according to aspect 1, wherein in a cross section perpendicular to the plane direction of the fiber sheet, the ratio of the thickness of the central region to the total thickness of the central region and the outer regions is 10 to 90%. <Aspect 3> 3. The thermosetting prepreg of claim 1 or 2, wherein the first and second thermosetting resin compositions each further comprise a thermoplastic resin and a conductive material. <Aspect 4> Aspect 4. The thermosetting prepreg of any one of Aspects 1 to 3, wherein the second thermosetting resin composition impregnates an outer region of the fiber sheet and is disposed on a surface of the fiber sheet. <Aspect 5> 5. The thermosetting prepreg of claim 4, wherein the second thermosetting resin composition disposed on the surface of the fiber sheet comprises resin particles. <Aspect 6> Aspect 6. The thermosetting prepreg of aspect 4 or 5, wherein the second thermosetting resin composition disposed on the surface of the fiber sheet comprises an additional conductive material. <Aspect 7> The viscosity of the first thermosetting resin composition at 50°C is higher than the viscosity of the second thermosetting resin composition at 50°C. A thermosetting prepreg according to any one of aspects 1 to 6. <Aspect 8> the viscosity of the first thermosetting resin composition at 50°C is 500 to 10,000 Pa s; The viscosity of the second thermosetting resin composition at 50°C is 100 to 1000 Pa s. A thermosetting prepreg according to any one of aspects 1 to 7. <Aspect 9> When the thermosetting prepreg was heat-cured at 180°C for 120 minutes, In a cross section perpendicular to the plane direction of the fiber sheet, there is a region in which the crosslink density of the thermosetting resin decreases from the center in the thickness direction of the fiber sheet toward the surface. A thermosetting prepreg according to any one of aspects 1 to 8. <Aspect 10> Aspect 10. The thermosetting prepreg according to any one of aspects 1 to 9, wherein the thermosetting resin is an epoxy resin. <Aspect 11> A thermosetting prepreg laminate having a structure in which two or more thermosetting prepregs according to any one of aspects 1 to 10 are laminated together. <Aspect 12> 1. A method for producing a thermoset prepreg, comprising: (a) providing a thermosetting prepreg precursor sheet, the precursor sheet having a fiber sheet, and first and second thermosetting resin compositions impregnated into the fiber sheet, each containing a thermosetting resin and a curing agent, wherein, in a cross section perpendicular to the plane direction of the fiber sheet, the first thermosetting resin composition impregnates a first outer region in the thickness direction of the fiber sheet, and the second thermosetting resin composition impregnates a second outer region in the thickness direction of the fiber sheet opposite to the first outer region; (b) overlapping the two thermosetting prepreg precursor sheets so that a first outer region of the fiber sheet of one thermosetting prepreg precursor sheet faces a first outer region of the fiber sheet of the other thermosetting prepreg precursor sheet; Here, in the thermosetting prepreg precursor sheet, the equivalent ratio of the curing agent in the first thermosetting resin composition is greater than the equivalent ratio of the curing agent in the second thermosetting resin composition. <Aspect 13> 1. A method for producing a thermosetting prepreg precursor sheet, comprising: Providing a fiber sheet; providing a first thermosetting resin composition comprising a thermosetting resin and a curing agent; providing a second thermosetting resin composition comprising a thermosetting resin and a curing agent; disposing the first thermosetting resin composition on one main surface of the fiber sheet; disposing the second thermosetting resin composition on the other main surface of the fiber sheet; and impregnating the fiber sheet at least partially with the first thermosetting resin composition and the second thermosetting resin composition; Includes an equivalent ratio of the curing agent in the first thermosetting resin composition is greater than an equivalent ratio of the curing agent in the second thermosetting resin composition; method. <Aspect 14> The basis weight (g / m) of the sheet-shaped first thermosetting resin composition 2 ) M1 of the basis weight (g / m 2 14. The method according to embodiment 13, wherein the ratio of M1 to M2 (M1 / M2) is 0.25 to 4.0. <Aspect 15> 15. The method of any one of claims 13 to 14, wherein the second thermosetting resin composition further comprises resin particles. [Effects of the Invention]

[0012] According to the invention of the present disclosure, it is possible to provide a thermosetting prepreg having excellent mechanical properties and a method for producing the same. In particular, according to the invention of the present disclosure, it is possible to provide a thermosetting prepreg having excellent mechanical properties and good handleability, and a method for producing the same. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 shows a cross-sectional schematic diagram of a thermosetting prepreg according to one embodiment of the present disclosure. [Figure 2] FIG. 2 shows a conceptual diagram of one embodiment of a method for producing a thermosetting prepreg according to the present disclosure. [Figure 3] FIG. 3 shows a conceptual diagram of one embodiment of a method for producing a thermosetting prepreg precursor sheet according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] The thermosetting prepreg according to the present disclosure is Fiber sheets, and a first thermosetting resin composition impregnated in a central region in the thickness direction of the fiber sheet in a cross section perpendicular to the surface direction of the fiber sheet; and a second thermosetting resin composition impregnated into an outer region in the thickness direction of the fiber sheet in a cross section perpendicular to the surface direction of the fiber sheet; and the first and second thermosetting resin compositions each contain a thermosetting resin and a curing agent; The equivalent ratio of the curing agent in the first thermosetting resin composition is greater than the equivalent ratio of the curing agent in the second thermosetting resin composition.

[0015] The thermosetting prepreg according to the present invention will be specifically described below with reference to the drawings. The drawings are schematic diagrams for aiding in understanding the present invention, and are not to scale and are not intended to limit the present invention.

[0016] Fig. 1 is a schematic cross-sectional view of one embodiment of a thermosetting prepreg according to the present disclosure, showing a cross section of the thermosetting prepreg cut perpendicular to the plane direction of the fiber sheet. T in Fig. 1 indicates the thickness direction of the thermosetting prepreg.

[0017] The thermosetting prepreg 100 shown in FIG. 1 has a fiber sheet 110. The fiber sheet 110 is, in particular, a carbon fiber sheet. A central region (B) in the thickness direction of the fiber sheet 110 is impregnated with a first thermosetting resin composition 112. The first thermosetting resin composition 112 contains a thermosetting resin and a curing agent, and optionally further contains a thermoplastic resin and a conductive material.

[0018] The thermosetting prepreg 100 also has a second thermosetting resin composition 122 impregnated into an outer region (A) in the thickness direction of the fiber sheet 110. The second thermosetting resin composition 122 contains a thermosetting resin and a curing agent, and optionally further contains a thermoplastic resin and a conductive material.

[0019] In the thermosetting prepreg 100 shown in Fig. 1, a second thermosetting resin composition 122 is further disposed on the surface of the fiber sheet 110. In Fig. 1, the second thermosetting resin composition 122 disposed on the surface forms a resin layer 120. The resin layer 120 in Fig. 1 contains resin particles 150.

[0020] 1, the equivalence ratio of the curing agent in the first thermosetting resin composition is greater than the equivalence ratio of the curing agent in the second thermosetting resin composition. Therefore, in the thermosetting prepreg 100, the equivalence ratio of the curing agent in the central region (B) of the thermosetting prepreg is greater than the equivalence ratio of the curing agent in the outer region (A).

[0021] The "equivalent ratio" of the curing agent in the thermosetting resin composition can be calculated by the following formula 1: Curing agent equivalent ratio = (total number of moles of active hydrogen in the curing agent) / (total number of moles of polymerizable groups in the thermosetting resin) (Equation 1)

[0022] In particular, when the thermosetting resin is an epoxy resin, the equivalent ratio of the curing agent can be calculated by the following formula 1': Curing agent equivalent ratio = (total number of moles of active hydrogen in the curing agent) / (total number of moles of epoxy groups in the epoxy resin) (Equation 1')

[0023] Although there is no intention to be limited by theory, it is believed that when the thermosetting prepreg according to the present disclosure as described above is subjected to a thermosetting treatment, a relatively high crosslink density of the thermosetting resin can be obtained inside the fiber sheet, thereby improving the elasticity of the matrix resin and, as a result, improving the mechanical properties.

[0024] In particular, in the thermosetting prepreg 100, in a cross section perpendicular to the plane direction of the fiber sheet, the ratio of the thickness of the central region to the total thickness of the central region and the outer regions is 10 to 90%.

[0025] In one embodiment of the present disclosure, at least one of the first thermosetting resin composition 112 and the second thermosetting resin composition 122 further contains a thermoplastic resin and / or a conductive material (particularly conductive particles). By containing a conductive material, the conductivity of the thermosetting prepreg can be further improved. Furthermore, by containing a thermoplastic resin, the handleability of the thermosetting prepreg can be further improved. Note that the handleability of the thermosetting prepreg particularly refers to the handleability (automatic lamination) when multiple thermosetting prepregs are automatically laminated.

[0026] In another embodiment of the present disclosure, the viscosity of the first thermosetting resin composition at 50° C. is higher than the viscosity of the second thermosetting resin composition at 50° C. In this case, it is believed that particularly good tackiness can be obtained, and therefore particularly good handleability (particularly automatic lamination) of the thermosetting prepreg can be realized.

[0027] In particular, the viscosity of the first thermosetting resin composition at 50°C is 500 to 10,000 Pa·s, and the viscosity of the second thermosetting resin composition at 50°C is 100 to 1,000 Pa·s.

[0028] The method for producing the thermosetting prepreg according to the present disclosure is not particularly limited, but in particular, the prepreg can be produced by the following method for producing the thermosetting prepreg according to the present disclosure.

[0029] The method for producing a thermosetting prepreg according to the present disclosure comprises the following steps (a) and (b): (a) Providing a thermosetting prepreg precursor sheet, wherein the precursor sheet comprises a fiber sheet, and first and second thermosetting resin compositions impregnated into the fiber sheet, each containing a thermosetting resin and a curing agent, wherein, in a cross section perpendicular to the plane direction of the fiber sheet, the first thermosetting resin composition impregnates a first outer region in the thickness direction of the fiber sheet, and the second thermosetting resin composition impregnates a second outer region in the thickness direction of the fiber sheet opposite to the first outer region; and, (b) overlapping two thermosetting prepreg precursor sheets so that a first outer region of a fiber sheet of one thermosetting prepreg precursor sheet faces a first outer region of a fiber sheet of the other thermosetting prepreg precursor sheet; Here, in the thermosetting prepreg precursor sheet, the equivalent ratio of the curing agent in the first thermosetting resin composition is greater than the equivalent ratio of the curing agent in the second thermosetting resin composition.

[0030] Generally, the fiber sheet portion and the resin layer portion of a prepreg have different required functions, and therefore different physical properties are required for each portion. With conventional methods, it has not been easy to achieve such site-specific optimized physical properties.

[0031] In contrast, the method for producing a thermosetting prepreg according to the present disclosure uses a precursor sheet containing a plurality of resin compositions having different compositions. That is, according to the production method according to the present disclosure, a thermosetting prepreg is produced using a precursor sheet impregnated with a plurality of resin compositions having different compositions, thereby realizing a thermosetting prepreg having site-specific optimized physical properties.

[0032] Furthermore, in conventional methods for producing thermosetting prepregs, when a fiber sheet is impregnated with a resin composition, the degree of impregnation of the resin composition into the center of the fiber sheet may be reduced due to the impregnation properties of the resin composition. In particular, if the degree of impregnation of the curing agent in the center region of the fiber sheet is low, the mechanical properties of the fiber sheet may be reduced.

[0033] In contrast, the method according to the present disclosure involves stacking two thermosetting prepreg precursor sheets to produce a thermosetting prepreg, and stacking the outer regions of the precursor sheets in the thickness direction that have a resin composition with a relatively high curing agent equivalence ratio together, thereby increasing the distribution of the curing agent in the center of the resulting thermosetting prepreg.

[0034] FIG. 2 conceptually illustrates a manufacturing method according to one embodiment of the present disclosure. The thermosetting prepreg precursor sheet 200 in FIG. 2 includes a fiber sheet 210. A first outer region (B′) in the thickness direction of the fiber sheet 210 is impregnated with a first thermosetting resin composition 212. A second outer region (A′) in the thickness direction of the fiber sheet 210 is impregnated with a second thermosetting resin composition 222. In the embodiment of FIG. 2, the second thermosetting resin composition 222 is disposed on a main surface of the fiber sheet 210 to form a resin layer 220. The resin layer 220 includes resin particles 250. In the thermosetting prepreg precursor sheet 200 in FIG. 2, the equivalent ratio of the curing agent in the first thermosetting resin composition 212 is greater than the equivalent ratio of the curing agent in the second thermosetting resin composition 222.

[0035] 2 further includes overlapping two thermosetting prepreg precursor sheets 200a, 200b so that the first outer region of the fiber sheet of one thermosetting prepreg precursor sheet 200a faces the first outer region of the fiber sheet of the other thermosetting prepreg precursor sheet 200b. Particularly preferably, the surfaces adjacent to the first outer regions are in contact with each other directly or via a resin composition. Preferably, after overlapping the two thermosetting prepreg precursor sheets 200a, 200b, they can be subjected to a treatment, such as a heat and pressure treatment, to integrate them.

[0036] According to the manufacturing method of the present disclosure, a thermosetting prepreg 100 can be obtained in which, in a cross section perpendicular to the surface direction of the sheet, the amount of curing agent in the central region in the thickness direction is greater than the amount of curing agent in the outer regions in the thickness direction.

[0037] The method for producing the thermosetting prepreg precursor sheet is not particularly limited, but in particular, the thermosetting prepreg precursor sheet can be produced by a method for producing a thermosetting prepreg precursor sheet according to the present disclosure, which includes the following steps: Providing a fiber sheet; providing a first thermosetting resin composition comprising a thermosetting resin and a curing agent; providing a second thermosetting resin composition comprising a thermosetting resin and a curing agent; disposing a first thermosetting resin composition on one main surface of a fiber sheet; disposing a second thermosetting resin composition on the other main surface of the fiber sheet; and at least partially impregnating a fiber sheet with a first thermosetting resin composition and a second thermosetting resin composition; Here, the equivalent ratio of the curing agent in the first thermosetting resin composition is greater than the equivalent ratio of the curing agent in the second thermosetting resin composition.

[0038] FIG. 3 is a conceptual diagram showing one embodiment of a method for producing a thermosetting prepreg precursor sheet according to the present disclosure.

[0039] 3, a fiber sheet 310 having a first major surface 314 and a second major surface 316 is provided, a sheet 320 formed from a first thermosetting resin composition 322 is disposed on the first major surface 314, and a sheet 330 formed from a second thermosetting resin composition 332 is disposed on the second major surface 316. The equivalent ratio of the curing agent contained in the first thermosetting resin composition 322 is greater than the equivalent ratio of the curing agent contained in the second thermosetting resin composition 332. The sheet 330 in FIG. 3 contains resin particles 350.

[0040] Then, by applying heat and / or pressure to the intermediate laminate 340 thus formed, for example using a heated roller, the resin compositions 322 and 332 are each at least partially impregnated into the fiber sheet 310, thereby obtaining the thermosetting prepreg precursor sheet 200.

[0041] According to this method, the fiber sheet can be simultaneously impregnated with the first thermosetting resin composition and the second thermosetting resin composition, which can further improve the impregnation of the fiber sheet with the second thermosetting resin composition compared to a case in which the fiber sheet is impregnated with the first thermosetting resin composition and then with the second thermosetting resin composition.

[0042] The embodiments and components of the present invention will be described in more detail below.

[0043] <Thermosetting prepreg> The thermosetting prepreg according to the present disclosure comprises a fiber sheet, a first thermosetting resin composition, and a second thermosetting resin composition.

[0044] In the present disclosure, the fiber basis weight of the thermosetting prepreg is, for example, 50 to 1000 g / m 2 , 100~800g / m 2 , especially 200-600g / m 2The thickness of the thermosetting prepreg may be, for example, 0.02 mm to 3.6 mm, 0.04 mm to 2.9 mm, or 0.08 mm to 2.2 mm.

[0045] <Fiber sheet> The fiber sheet contained in the thermosetting prepreg according to the present disclosure is particularly a reinforcing fiber sheet made of reinforcing fibers, and is preferably a carbon fiber sheet.

[0046] Examples of reinforcing fibers include carbon fibers, glass fibers, aramid fibers, silicon carbide fibers, polyester fibers, ceramic fibers, alumina fibers, boron fibers, metal fibers, mineral fibers, rock fibers, and slag fibers. Among these reinforcing fibers, carbon fibers, glass fibers, and aramid fibers are preferred, and carbon fibers, which have good specific strength and specific modulus and can produce lightweight, high-strength composite materials, are more preferred. Among carbon fibers, polyacrylonitrile (PAN)-based carbon fibers, which have excellent tensile strength, are particularly preferred.

[0047] When carbon fibers are used as reinforcing fibers, the tensile modulus is preferably 170 GPa to 600 GPa, and particularly preferably 220 GPa to 450 GPa. The tensile strength is preferably 3920 MPa or more. There is no particular upper limit to the tensile strength, but it may be, for example, 10000 MPa or less. By using such carbon fibers, the mechanical properties of the composite material can be improved. The tensile strength and tensile modulus of carbon fibers can be measured according to JIS R 7608.

[0048] Examples of fiber sheets include sheet-like materials in which a large number of fibers (especially reinforcing fibers) are aligned in one direction, bidirectional fabrics such as plain weave or twill weave, multiaxial fabrics, nonwoven fabrics, mats, knits, braids, and paper made from fibers (especially reinforcing fibers).

[0049] The thickness of the fiber sheet may be 0.02 to 3.6 mm, 0.04 to 2.9 mm, or 0.08 to 2.2 mm. The basis weight of the fiber sheet is 50 to 1000 g / m2 and 100 to 800 g / m 2 is preferable, and 200 to 600 g / m 2 The distance between fibers in the fiber sheet is preferably less than 10 μm.

[0050] The content of the fiber sheet in the thermosetting prepreg is preferably 40 to 80 mass %, particularly 45 to 75 mass %, and further particularly 50 to 70 mass %, based on the total mass of the thermosetting prepreg.

[0051] <Resin composition> The fiber sheet is impregnated with a first thermosetting resin composition in its central region in the thickness direction, and with a second thermosetting resin composition in its outer regions in the thickness direction.

[0052] (center area and outer area) In one embodiment of the present disclosure, in a cross section perpendicular to the plane direction of the fibrous sheet, the ratio of the thickness of the central region to the total thickness of the central region and the outer regions is 10 to 90%. Generally, a fibrous sheet has two main surfaces, and the outer regions of the fibrous sheet are particularly regions extending along each of the two main surfaces of the fibrous sheet.

[0053] (viscosity) Preferably, the viscosity (V1 (unit: Pa s)) of the first thermosetting resin composition at 50°C is higher than the viscosity (V2 (unit: Pa s)) of the second thermosetting resin composition at 50°C, and in particular, the difference between these viscosities (V1-V2) is 10 or more, 25 or more, 50 or more, 75 or more, 100 or more, 150 or more, 200 or more, 250 or more, 300 or more, 400 or more, or 500 or more. The upper limit of the viscosity difference (V1-V2) may be, for example, 3000 or less, 2600 or less, 2000 or less, 1500 or less, 1000 or less, or 750 or less.

[0054] The viscosity of the first thermosetting resin composition at 50°C is preferably 500 to 10,000 Pa·s or 550 to 5,000 Pa·s, more preferably 600 to 3,000 Pa·s or 600 to 2,000 Pa·s, even more preferably 650 to 1,500 Pa·s or 650 to 1,000 Pa·s, and most preferably 700 to 900 Pa·s. When the viscosity of the first thermosetting resin composition at 50°C is within this range, particularly good impregnation of the resin composition into the fiber sheet may be obtained.

[0055] The viscosity of the second thermosetting resin composition at 50°C is preferably 100 to 1250 Pa·s, 100 to 1000 Pa·s, or 200 to 1000 Pa·s, more preferably 400 to 800 Pa·s, and even more preferably 500 to 750 Pa·s. When the viscosity of the second thermosetting resin composition at 50°C is within this range, particularly good impregnation of the resin composition into the fiber sheet can be achieved, and particularly good handleability of the thermosetting prepreg can be achieved.

[0056] The viscosity can be obtained from a temperature-viscosity curve measured using a rheometer.

[0057] The viscosity of the thermosetting resin composition can be adjusted by selecting the amount and / or type of the thermosetting resin and / or curing agent contained in the thermosetting resin composition, and can also be adjusted by selecting the amount and / or type of the thermoplastic resin, resin particles, and / or conductive material optionally contained therein.

[0058] The first thermosetting resin composition and the second thermosetting resin composition each contain at least a thermosetting resin and a curing agent, and may further contain a thermoplastic resin and / or a conductive material.

[0059] (thermosetting resin) Thermosetting resins can be crosslinked by heating in the presence of a curing agent to form a three-dimensional molecular structure (e.g., a network structure). Thermosetting resins can contain thermosetting monomers and / or oligomers and / or prepolymers. Examples of thermosetting resins include epoxy resins and urethane resins, particularly epoxy resins. Thermosetting resins can be used alone or in combination of two or more.

[0060] Epoxy resins crosslink to form a network structure through a curing reaction with a curing agent. Examples of epoxy resins include conventionally known epoxy resins, particularly epoxy resins having an aromatic group in the molecule, particularly bifunctional, trifunctional or higher functional epoxy resins having either a glycidyl amine structure or a glycidyl ether structure. Alicyclic epoxy resins may also be used.

[0061] Examples of epoxy resins having a glycidyl amine structure include various isomers of N,N,N',N'-tetraglycidyldiaminodiphenylmethane, N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-m-aminophenol, N,N,O-triglycidyl-3-methyl-4-aminophenol, and triglycidylaminocresol.

[0062] Examples of epoxy resins having a glycidyl ether structure include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, and cresol novolac type epoxy resins.

[0063] These epoxy resins may, if necessary, have a non-reactive substituent on the aromatic ring structure, etc. Examples of such non-reactive substituents include alkyl groups such as methyl, ethyl, and isopropyl groups, aromatic groups such as phenyl groups, alkoxyl groups, aralkyl groups, and halogen groups (chlorine, bromine, etc.).

[0064] Examples of trifunctional epoxy resins include N,N,O-triglycidyl-p-aminophenol and N,N,O-triglycidyl-m-aminophenol.

[0065] These epoxy resins can be used alone or in combination of two or more. It is also possible to use, as the epoxy resin, a so-called B-stage epoxy resin that has been preliminarily reacted with a curing agent or the like. When both the first thermosetting resin composition and the second thermosetting resin composition contain an epoxy resin as the thermosetting resin, they may be the same or different.

[0066] The thermosetting resin can impart good mechanical properties and tackiness to the thermosetting prepreg.

[0067] (hardening agent) The curing agent is particularly a curing agent for thermosetting resins, for example, a curing agent for epoxy resins or urethane resins. Examples of curing agents for epoxy resins include dicyandiamide, various isomers of aromatic amine-based curing agents, and aminobenzoic acid esters. One type of curing agent may be used, or two or more types may be used in combination. Furthermore, the first thermosetting resin composition and the second thermosetting resin composition may contain the same curing agent, or may contain different curing agents.

[0068] Dicyandiamide is preferred because it provides excellent storage stability to the prepreg. Aromatic diamine compounds such as 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, and 4,4'-diaminodiphenylmethane, as well as their derivatives having non-reactive substituents, are particularly preferred because they provide cured products with high heat resistance. Examples of non-reactive substituents include alkyl groups such as methyl, ethyl, and isopropyl groups, aromatic groups such as phenyl, alkoxyl groups, aralkyl groups, and halogen groups (chlorine, bromine, etc.).

[0069] Examples of aminobenzoic acid esters include trimethylene glycol di-p-aminobenzoate and neopentyl glycol di-p-aminobenzoate. When these are used as curing agents, the heat resistance of the composite material may be inferior to that of diaminodiphenyl sulfone, but composite materials with particularly excellent tensile elongation may be obtained.

[0070] The thermosetting resin and curing agent can have the effect of improving the mechanical properties (particularly the modulus of elasticity and strength) and / or heat resistance of the matrix resin of the thermosetting prepreg.

[0071] (equivalent ratio) The equivalent ratio of the curing agent in the first thermosetting resin composition is preferably 0.70 to 1.00, more preferably 0.75 to 0.90. When the equivalent ratio of the curing agent is within this range, particularly good handleability of the thermosetting prepreg and good physical properties (particularly mechanical properties) of the composite material formed from the thermosetting prepreg can be obtained.

[0072] The equivalent ratio of the curing agent in the second thermosetting resin composition is preferably 0.50 to 0.90, more preferably 0.60 to 0.80. When the equivalent ratio of the curing agent is within this range, particularly good handleability of the thermosetting prepreg and particularly good physical properties (particularly mechanical properties) of the composite material formed from the thermosetting prepreg can be obtained.

[0073] The difference (E1-E2) between the equivalent ratio of the curing agent in the first thermosetting resin composition (E1) and the equivalent ratio of the curing agent in the second thermosetting resin composition (E2) may be 0.01 or more, 0.05 or more, or 0.10 or more, and / or may be 1.0 or less, 0.50 or less, 0.40 or less, 0.30 or less, 0.20 or less, 0.18 or less, or 0.16 or less.

[0074] The content of the curing agent in the thermosetting resin composition may be 5 to 70 parts by mass, 10 to 60 parts by mass, 20 to 50 parts by mass, or 30 to 45 parts by mass relative to 100 parts by mass of the thermosetting resin.

[0075] (Crosslink density) In particular, when the thermosetting prepreg according to the present disclosure is subjected to a heat curing treatment at 180°C for 120 minutes, a region in the cross section perpendicular to the surface direction of the fiber sheet exists in which the crosslink density of the thermosetting resin decreases from the center in the thickness direction of the fiber sheet toward the surface.

[0076] The cross-link density (ρ crosslink ) (unit: mol / m 3 ) can be calculated from the rubber state equation shown in equation (2) after measuring the glass transition temperature (Tg) of a cured product of the resin composition by DMA (dynamic viscoelasticity measurement). ρ crosslink =E' / 3φRT Formula (2)

[0077] In equation (2), E' is the storage modulus (unit: Pa) at Tg + 50°C, φ is the front modulus (here, φ = 1 (unit: dimensionless)), R is the machine constant (8.31 J / K·mol), and T is the temperature (unit: K) at Tg + 50°C.

[0078] DMA measurements are performed using a dynamic viscoelasticity measuring device, such as Rheogel-4000 (manufactured by UBM Co., Ltd.), under conditions of double-support bending mode, strain amplitude of 5 μm, heating rate of 5°C / min, in air, and frequency of 1 Hz, and the onset of the obtained storage modulus is taken as Tg.

[0079] (thermoplastic resin) The thermoplastic resin is preferably a thermoplastic resin soluble in thermosetting resins. The thermoplastic resin is particularly an epoxy resin-soluble thermoplastic resin. The resin composition may contain, in addition to a soluble thermoplastic resin (particularly an epoxy resin-soluble thermoplastic resin), an insoluble thermoplastic resin composition that is insoluble in thermosetting resins (particularly an epoxy resin-insoluble thermoplastic resin composition). One type of thermoplastic resin may be used alone, or two or more types may be used in combination.

[0080] The thermoplastic resin can improve the impregnation of the thermosetting resin composition into the fiber sheet, and can also improve the tackiness of the thermosetting prepreg. The thermoplastic resin can also improve the mechanical properties (especially toughness) of the matrix resin of the thermosetting prepreg.

[0081] The amount of the thermoplastic resin in the resin composition is not particularly limited, and can be set depending on the desired viscosity of the thermosetting resin composition, etc. For example, the amount of the thermoplastic resin in each of the first and second thermosetting resin compositions may be 1 to 60 parts by mass, particularly 2 to 50 parts by mass, 5 to 40 parts by mass, 10 to 30 parts by mass, or 15 to 25 parts by mass, per 100 parts by mass of the thermosetting resin (particularly the epoxy resin).

[0082] In one embodiment of the present disclosure, the first thermosetting resin composition may contain 1 to 50 parts by mass, 2 to 40 parts by mass, 5 to 30 parts by mass, or 10 to 25 parts by mass of a soluble thermoplastic resin (particularly an epoxy resin-soluble thermoplastic resin) relative to 100 parts by mass of the thermosetting resin (particularly an epoxy resin); and / or The second thermosetting resin composition may contain, per 100 parts by mass of the thermosetting resin (particularly the epoxy resin), 1 to 50 parts by mass, 2 to 40 parts by mass, 5 to 30 parts by mass, or 10 to 25 parts by mass of a soluble thermoplastic resin (particularly an epoxy resin-soluble thermoplastic resin), and 1 to 50 parts by mass, 2 to 40 parts by mass, 5 to 30 parts by mass, 8 to 25 parts by mass, or 10 to 20 parts by mass of an insoluble thermoplastic resin composition (particularly an epoxy resin-insoluble thermoplastic resin composition).

[0083] (Epoxy resin soluble thermoplastic resin) The epoxy resin-soluble thermoplastic resin is a thermoplastic resin that can be partially or completely dissolved in the epoxy resin by heating or the like. The epoxy resin-soluble thermoplastic resin is preferably a resin that dissolves in the epoxy resin at 190°C in an amount of 80% by mass or more. Examples of the epoxy resin-soluble thermoplastic resin include polyethersulfone, polysulfone, polyetherimide, and polycarbonate. These may be used alone or in combination of two or more. The insoluble thermoplastic resin composition (epoxy resin-insoluble thermoplastic resin composition) will be described later.

[0084] The form of the epoxy resin-soluble thermoplastic resin is not particularly limited. In particular, in a resin composition used when producing a thermosetting prepreg, the epoxy resin-soluble thermoplastic resin is preferably in a particulate form, and the average particle diameter is preferably 1 to 50 μm, particularly preferably 3 to 30 μm. The average particle diameter of the particulate thermoplastic resin can be measured using a laser diffraction / scattering particle size distribution analyzer.

[0085] When both the first thermosetting resin composition and the second thermosetting resin composition contain a thermoplastic resin, they may be the same as or different from each other.

[0086] (Conductive material) The conductive material present in the fiber sheet, particularly in the resin layer, can improve the electrical conductivity of the thermosetting prepreg.

[0087] The conductive material is not particularly limited as long as it is a particle that acts as a good electrical conductor, but it is preferable that it can be dispersed in the resin composition and can improve the conductivity of the thermosetting prepreg.

[0088] The conductive material is particularly conductive particles. The conductive particles preferably have a volume resistivity of 10 to 10 -9 Ωcm, and more preferably 1 to 10 -9 Ωcm, and particularly preferably 10 -1 ~10 -9Ωcm particles.

[0089] The conductive particles include conductive polymer particles, carbon particles, metal particles, coated conductive particles, and carbon fiber particles, which may be used alone or in combination.

[0090] Conductive polymer particles include polyacetylene particles, polyaniline particles, polypyrrole particles, polythiophene particles, polyisothianaphthene particles, and polyethylenedioxythiophene particles.

[0091] Examples of carbon particles include carbon black, carbon nanotubes (CNTs), carbon nanostructures (CNSs), carbon nanofibers, expanded graphite, flake graphite, graphite powder, graphite particles, graphene sheets, and carbon milled fibers. Examples of carbon milled fibers include milled fibers of PAN-based carbon fibers, pitch-based carbon fibers, and phenol-based carbon fibers. Among these, pitch-based carbon fiber milled fibers are preferred. The carbon fiber content of the carbon milled fibers is preferably 94% by mass or more.

[0092] Although the metal particles are not particularly limited, when carbon fibers are used as reinforcing fibers, from the viewpoint of preventing corrosion due to the potential difference with the carbon fibers, particles of platinum, gold, silver, copper, tin, nickel, titanium, cobalt, zinc, iron, chromium, and aluminum, particles of alloys containing these metals as the main component, tin oxide, indium oxide, and indium tin oxide (ITO) are preferred. Among these, particles of platinum, gold, silver, copper, tin, nickel, and titanium, and particles of alloys containing these metals as the main component are more preferred because they exhibit high conductivity and stability, and particles of silver, copper, and nickel are particularly preferred.

[0093] Examples of preferred conductive particles include carbon nanotubes, carbon nanostructures, carbon black, carbon milled fibers, and silver nanoparticles.

[0094] The conductive material preferably has a size that allows it to diffuse into the fiber sheet as it is impregnated with the resin composition. The conductive material is preferably in the form of particles (i.e., conductive particles) and has an average particle size of, for example, 1 to 1000 nm or 1 to 500 nm, preferably 2 to 200 nm, 3 to 100 nm, 4 to 50 nm, or 5 to 25 nm.

[0095] It is believed that conductive particles with a relatively small particle size (e.g., a particle size of 1 μm or less) can further improve the conductivity of the composite material molded from the prepreg, as the conductive particles are dispersed in both the fiber sheet and the resin layer.

[0096] The average particle size of the conductive material is the 50% particle size (D 50 ) value.

[0097] The content of the conductive material (particularly conductive particles) may be 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass, and more preferably 0.10 to 1 part by mass, per 100 parts by mass of the thermosetting resin (particularly epoxy resin) contained in the resin composition. When the content is 0.01 part by mass or more, the effect of improving the conductivity of the prepreg and composite material can be particularly good. When the content is 10 parts by mass or less, the viscosity of the resin composition can be prevented from increasing significantly, and good handleability of the prepreg can be ensured.

[0098] When both the first thermosetting resin composition and the second thermosetting resin composition contain a conductive material, they may be the same as or different from each other.

[0099] (additional conductive material) In addition to the conductive materials described above, the thermosetting prepreg may contain an additional conductive material. This additional conductive material is intended to be present in the second thermosetting resin composition (particularly the resin layer described below) present on the surface of the fiber sheet. In other words, in one embodiment according to the present disclosure, the second thermosetting resin composition disposed on the surface of the fiber sheet contains the additional conductive material.

[0100] Additional conductive materials include carbon fiber, pitch carbon fiber, milled fiber (particularly carbon milled fiber), and silver aggregates, which may be used alone or in combination.

[0101] The additional conductive material preferably has an average length of 1 μm or more, or 1.5 μm or more, more preferably 2 μm or more, and particularly preferably 4 μm or more. The upper limit of the average length of the additional conductive material is not particularly limited, but may be, for example, 10 mm or less, 1 mm or less, 300 μm or less, 200 μm or less, or 100 μm or less. When the additional conductive material has such a length, it becomes difficult for the additional conductive material to penetrate into the fiber sheet, and as a result, it tends to remain on the surface of the fiber sheet (particularly in the resin layer). The additional conductive material present on the surface of the fiber sheet (particularly in the resin layer) can further improve the overall conductivity of the thermosetting prepreg.

[0102] The average length of the additional conductive material can be calculated by measuring the lengths of 30 or more additional conductive materials in an image obtained using an electron microscope or an optical microscope and averaging the measured values. If the additional conductive material is granular, the average diameter or average particle size can be used as the average length.

[0103] When both the first thermosetting resin composition and the second thermosetting resin composition contain an additional conductive material, they may be the same as each other or different from each other.

[0104] (resin layer) In one embodiment of the thermosetting prepreg according to the present disclosure, the second thermosetting resin composition is impregnated into the outer region of the fiber sheet and is also disposed on the surface of the fiber sheet, particularly forming a resin layer (surface resin layer) on the surface of the fiber sheet.

[0105] The resin layer is preferably laminated on the main surface of the fiber sheet, and particularly preferably laminated directly on the main surface of the fiber sheet.

[0106] The thickness of the resin layer is preferably 5 to 50 μm, particularly 10 to 40 μm. When the thickness is 5 μm or more, a thermosetting prepreg having particularly good tackiness may be obtained. When the thickness is 50 μm or less, a thermosetting prepreg having particularly good handleability may be obtained, and particularly good moldability may be ensured when producing a composite material.

[0107] (resin particles) The second thermoplastic resin composition (particularly the resin layer) disposed on the surface of the fiber sheet may contain resin particles. The resin particles are preferably dispersed in the resin layer. These resin particles may be present in the resin layer between the fiber sheets in a laminate produced by laminating thermosetting prepregs, and are therefore also referred to as "interlayer particles."

[0108] The resin particles contained in the resin layer have the effect of improving the interlaminar toughness of a composite material (particularly a carbon fiber reinforced composite material) formed from a thermosetting prepreg.

[0109] The resin particles contained in the resin layer may be made of a thermoplastic resin, preferably a thermoplastic resin that is poorly soluble in thermosetting resins, and particularly an epoxy resin-insoluble thermoplastic resin.

[0110] (epoxy resin insoluble thermoplastic resin) The epoxy resin-insoluble thermoplastic resin is a thermoplastic resin that is substantially insoluble in epoxy resin at or below the temperature at which the composite material is molded. In particular, it is a thermoplastic resin whose particle size does not change when resin particles are added to and stirred in epoxy resin at the temperature at which the composite material is formed. Generally, the temperature at which the composite material is molded is 100 to 190°C.

[0111] Examples of epoxy resin-insoluble thermoplastic resins include polyamide, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyester, polyamideimide, polyimide, polyether ketone, polyether ether ketone, polyethylene naphthalate, polyether nitrile, and polybenzimidazole. Among these, polyamide, polyamideimide, and polyimide are preferred due to their high toughness and heat resistance. These may be used alone or in combination of two or more. Copolymers of these may also be used.

[0112] In particular, amorphous polyimides, polyamides such as Nylon 6 (registered trademark) (a polyamide obtained by ring-opening polycondensation of caprolactam), Nylon 12 (registered trademark) (a polyamide obtained by ring-opening polycondensation of lauryllactam), and amorphous Nylon (registered trademark) can be used. The use of these polyamides may result in particularly good heat resistance of the composite material.

[0113] The average particle size of the resin particles contained in the resin layer is preferably 5 to 50 μm, particularly 10 to 40 μm.

[0114] The average particle size of the resin particles can be measured by a laser diffraction / scattering particle size distribution measuring device.

[0115] (Other ingredients) The thermosetting resin composition may contain other components as long as they do not impair the objects and effects of the present invention. Examples of other components include amine compounds such as tertiary amines and imidazoles, phosphorus compounds such as phosphines and phosphonium compounds, curing accelerators such as N,N-dimethylurea derivatives, reactive diluents, fillers, antioxidants, flame retardants, pigments, and various other additives. The amount of these other components is preferably 5% by mass or less, or 1% by mass or less, of the thermosetting resin composition.

[0116] <Polymer film> The thermosetting prepreg according to the present disclosure may have a release paper or polymer film, such as a polyethylene film, on one or both sides thereof. This release paper or polymer film can serve to protect the thermosetting prepreg. When producing a laminate (particularly a fiber-reinforced composite material) from the thermosetting prepreg, this release paper or polymer film can be removed.

[0117] <Laminate> A laminate can be formed by laminating the thermosetting prepregs according to the present disclosure and optionally subjecting them to a thermosetting treatment. This laminate is particularly a fiber-reinforced composite material, more particularly a carbon fiber-reinforced composite material. This laminate (thermosetting prepreg laminate) has a structure in which two or more thermosetting prepregs according to the present invention are laminated. The number of layers of thermosetting prepregs forming this laminate may be, for example, 2 to 200, 5 to 100, or 10 to 50.

[0118] This laminate may be in the form of a sheet, and may have a thickness of, for example, 1 mm to 100 mm, 2 mm to 50 mm, 3 mm to 25 mm, or 4 mm to 10 mm.

[0119] Such laminates can be produced by methods known in the art, including, for example, manual layup, automated tape layup (ATL), automated fiber placement, vacuum bagging, autoclave cure, non-autoclave cure, fluid-assisted processing, pressure-assisted processes, matched mold processes, simple press cure, presclave cure, and methods using a continuous hand press.

[0120] Specifically, for example, a laminate (particularly a fiber-reinforced composite material) can be formed by laminating multiple thermosetting prepregs according to the present invention, pressurizing them to 0.2 to 1.0 MPa in an autoclave, and heating them at 150 to 204°C for 1 to 8 hours.

[0121] The laminate (particularly the fiber-reinforced composite material) according to the present invention preferably has a thickness direction electrical conductivity of 3.5 kΩ cm or less, preferably 0.3 kΩ cm or less, and particularly preferably 0.2 kΩ cm or less, as measured by the method described in the Examples. There is no particular lower limit to the thickness direction electrical conductivity, but it may be, for example, 0.1 Ω cm or more or 1.0 Ω cm or more.

[0122] <Method for manufacturing thermosetting prepreg> The method for producing the thermosetting prepreg according to the present disclosure is not particularly limited. The thermosetting prepreg according to the present disclosure can be produced, for example, by producing thermosetting prepreg precursor sheets and stacking the thermosetting prepreg precursor sheets according to the following production method.

[0123] <Method of manufacturing a thermosetting prepreg by stacking precursor sheets> One embodiment of a method for producing a thermosetting prepreg according to the present disclosure comprises the following steps (a) and (b): (a) providing a thermosetting prepreg precursor sheet (precursor providing step), wherein the precursor sheet has a fiber sheet, and first and second thermosetting resin compositions impregnated into the fiber sheet, each containing a thermosetting resin and a curing agent, and in a cross section perpendicular to the plane direction of the fiber sheet, the first thermosetting resin composition impregnates a first outer region in the thickness direction of the fiber sheet, and the second thermosetting resin composition impregnates a second outer region opposite to the first outer region in the thickness direction of the fiber sheet; and, (b) overlapping two thermosetting prepreg precursor sheets so that the first outer region of the fiber sheet of one thermosetting prepreg precursor sheet faces the first outer region of the fiber sheet of the other thermosetting prepreg precursor sheet to form a thermosetting prepreg (overlapping step); Here, in the thermosetting prepreg precursor sheet, the equivalent ratio of the curing agent in the first thermosetting resin composition is greater than the equivalent ratio of the curing agent in the second thermosetting resin composition.

[0124] (Precursor provision process) In the precursor providing step, one or more (particularly two) thermosetting prepreg precursor sheets are provided. For the fiber sheet, first thermosetting resin composition, and second thermosetting resin composition contained in the thermosetting prepreg precursor sheet, the above description regarding the thermosetting prepreg can be referenced.

[0125] (Layering process) In the overlapping step, two thermosetting prepreg precursor sheets are overlapped so that the first outer region of the fiber sheet of one thermosetting prepreg precursor sheet faces the first outer region of the fiber sheet of the other thermosetting prepreg precursor sheet.

[0126] That is, in the laminate obtained by overlapping two thermosetting prepreg precursor sheets, the first outer regions of the two thermosetting prepreg precursor sheets face each other, while the second outer regions of the two thermosetting prepreg precursor sheets face away from each other.

[0127] In this case, the two thermosetting prepreg precursor sheets may be two separate thermosetting prepreg precursor sheets, or may be two parts of one thermosetting prepreg precursor sheet. That is, for example, the above overlapping may be performed by folding one precursor sheet.

[0128] Preferably, when two precursor sheets are superposed on each other in the superposing step, the fiber directions of the fiber sheets of the precursor sheets are aligned. In particular, when the fiber sheets are composed of fibers aligned in one direction, it is preferable to align the fiber directions of the fiber sheets of the two precursor sheets in substantially the same direction. By doing so, it may be possible to reduce or substantially eliminate the resin composition remaining between the two superposed precursor sheets.

[0129] Preferably, during the above-mentioned overlapping, the amount of resin composition present between the two first outer regions of the two thermosetting prepreg precursor sheets is reduced. More preferably, substantially no resin composition is present between the surface of one thermosetting prepreg precursor sheet adjacent to the first outer region and the surface of the other thermosetting prepreg precursor sheet adjacent to the first outer region, so that the fiber sheets of the two thermosetting prepreg precursor sheets come into contact with each other.

[0130] (heat and pressure treatment) In a preferred embodiment of the present disclosure, two thermosetting prepreg precursor sheets are stacked together and then subjected to a treatment (e.g., heating and pressure treatment) to integrate them, thereby obtaining a thermosetting prepreg. For this heating and pressure treatment, a heated roller can be used, for example. Regarding the conditions for this heating and pressure treatment, a heating temperature of 40 to 140°C is preferred, and a pressure condition of 0.1 to 200 N / cm, particularly 5 to 100 N / cm, is preferred.

[0131] According to the method of the present disclosure for producing a thermosetting prepreg by overlapping two thermosetting prepreg precursor sheets, the outer region of the two thermosetting prepreg precursor sheets with a relatively high curing agent equivalence ratio is located in the central region of the thermosetting prepreg obtained as a result of the overlapping. Therefore, according to this method of the present disclosure, the thermosetting prepreg of the present disclosure can be obtained relatively simply and efficiently.

[0132] The method for producing a thermosetting prepreg according to the present disclosure may include a step of placing a release paper or polymer film on both or one of the surfaces (one or two main surfaces) of the thermosetting prepreg. That is, in one embodiment of the present disclosure, the thermosetting prepreg obtained by overlapping two thermosetting prepreg precursor sheets may be provided in a state in which both or one of the surfaces is covered with a release paper or polymer film. In particular, the release paper or polymer film may be placed so as to cover the entire both or one of the surfaces (one or two main surfaces) of the thermosetting prepreg. Examples of polymer films include polyethylene film.

[0133] <Method for producing a thermosetting prepreg precursor sheet> The thermosetting prepreg precursor sheet that can be used in the above method can be produced by the following method: Providing a fiber sheet (sheet providing process) providing a first thermosetting resin composition containing a thermosetting resin and a curing agent (first resin composition providing step); providing a second thermosetting resin composition containing a thermosetting resin and a curing agent (second resin composition providing step); disposing a first thermosetting resin composition on one main surface of the fiber sheet (first resin composition disposing step); disposing a second thermosetting resin composition on the other main surface of the fiber sheet (second resin composition disposing step); and impregnating a fiber sheet at least partially with the first thermosetting resin composition and the second thermosetting resin composition to form a thermosetting prepreg precursor sheet (impregnation step); Includes The equivalent ratio of the curing agent in the first thermosetting resin composition is greater than the equivalent ratio of the curing agent in the second thermosetting resin composition; method.

[0134] (Sheet provision process) In the sheet providing step, a fiber sheet is provided. For the fiber sheet, the above description of the thermosetting prepreg can be referred to. The thickness of this fiber sheet may be 0.01 to 1.8 mm, 0.02 to 1.5 mm, or 0.04 to 1.1 mm. The basis weight of this fiber sheet is 25 to 500 g / m 2 and 50 to 400 g / m 2 is preferable, and 100 to 300 g / m 2 is more preferred.

[0135] (First resin composition providing step, second resin composition providing step) In the first resin composition providing step and the second resin composition providing step, a first thermosetting resin composition and a second thermosetting resin composition are provided, respectively. These resin compositions contain a thermosetting resin and a curing agent, and may optionally further contain a thermoplastic resin and a conductive material. For details of the resin compositions and their components, please refer to the above description of the thermosetting prepreg.

[0136] The thermosetting resin composition can be produced by kneading the respective components. The kneading temperature is adjusted appropriately taking into consideration the viscosity, thermal properties, curing temperature, etc. of the resins to be blended, but is preferably below the curing initiation temperature, 50 to 120°C. Kneading may be carried out in one stage or multiple stages. The order in which the components of the resin composition are mixed is not particularly limited.

[0137] As the kneading machine for kneading, known kneading machines can be used, such as a roll mill, a planetary mixer, a kneader, an extruder, a Banbury mixer, etc.

[0138] The thermosetting resin composition provided in the providing step may be in the form of, for example, a sheet.

[0139] The method for producing a sheet-like thermosetting resin composition (hereinafter also referred to as a "resin composition sheet" or "resin sheet") is not particularly limited, and the composition can be produced by a known method. For example, the composition can be produced by applying (casting, etc.) the composition onto a support such as release paper or a release sheet using a die coater, an applicator, a reverse roll coater, a comma coater, a knife coater, or the like.

[0140] Specifically, for example, the prepared thermosetting resin composition is applied to release paper using a film coater, dried, and formed into a sheet, which is then peeled off from the release paper, thereby producing a sheet of the thermosetting resin composition.

[0141] When the thermosetting resin composition contains an epoxy resin, the processing temperature during sheet production is usually preferably 70 to 160°C, more preferably 75 to 140°C.

[0142] The thickness of the resin sheet is preferably 2 to 500 μm, more preferably 5 to 100 μm. The basis weight of the resin sheet is 10 to 200 g / m 2 and may be 20 to 100 g / m 2 is preferable, and 30 to 75 g / m2 is more preferred.

[0143] Preferably, the viscosity (V1 (unit: Pa s)) of the first thermosetting resin composition at 50°C is higher than the viscosity (V2 (unit: Pa s)) of the second thermosetting resin composition at 50°C, and in particular, the difference between these viscosities (V1-V2) is 10 or more, 25 or more, 50 or more, 75 or more, 100 or more, 150 or more, 200 or more, 250 or more, 300 or more, 400 or more, or 500 or more. The upper limit of the viscosity difference (V1-V2) may be, for example, 3000 or less, 2600 or less, 2000 or less, 1500 or less, 1000 or less, or 750 or less.

[0144] The viscosity of the first thermosetting resin composition at 50°C is preferably 500 to 10,000 Pa·s, or 550 to 5,000 Pa·s, more preferably 600 to 3,000 Pa·s or 600 to 2,000 Pa·s, even more preferably 650 to 1,500 Pa·s or 650 to 1,000 Pa·s, and most preferably 700 to 900 Pa·s.

[0145] The viscosity of the second thermosetting resin composition at 50° C. is preferably 100 to 1250 Pa·s, 100 to 1000 Pa·s, or 200 to 1000 Pa·s, more preferably 400 to 800 Pa·s, and even more preferably 500 to 750 Pa·s.

[0146] (First resin composition placement step, second resin composition placement step) In the first resin composition disposing step and the second resin composition disposing step, the first thermosetting resin composition and the second thermosetting resin composition are disposed on the first and second main surfaces of the fiber sheet, respectively. In this step, for example, the first and second thermosetting resin compositions in sheet form (e.g., in the form of resin films) can be laminated, particularly directly, on the main surfaces of the fiber sheet.

[0147] When the first thermosetting resin composition and the second thermosetting resin composition are in a sheet form, the basis weight M1 (g / m 2) of the sheet-shaped second thermosetting resin composition basis weight M2 (g / m 2 The ratio (M1 / M2) to the total mass (M1 / M2) may be 0.25 to 4.0, preferably 0.3 to 3.0, or even 0.5 to 2.0.

[0148] In one embodiment of the present invention, the basis weight (g / m ) of the sheet-shaped first thermosetting resin composition is 2 ) M1 is the basis weight (g / m ) of the sheet-shaped second thermosetting resin composition 2 ) is greater than M2. In this case, a prepreg exhibiting particularly good prepreg tackiness and composite compression properties may be obtained. In this embodiment, the ratio (M1 / M2) may be, for example, 1.2 to 3.0, 1.4 to 2.8, or 1.6 to 2.6.

[0149] In another embodiment of the present invention, the basis weight (g / m ) of the sheet-shaped first thermosetting resin composition is 2 ) M1 is the basis weight (g / m ) of the sheet-shaped second thermosetting resin composition 2 ) is smaller than M2. In this case, a prepreg exhibiting particularly good composite compressive strength after impact may be obtained. In addition, in this case, particularly excellent electrical conductivity (particularly electrical conductivity in the thickness direction) may be obtained. In this embodiment, the ratio (M1 / M2) may be, for example, 0.2 to 0.9, 0.3 to 0.8, or 0.4 to 0.7.

[0150] (Impregnation process) In the impregnation step, the fiber sheet is at least partially impregnated with the first thermosetting resin composition and the second thermosetting resin composition.

[0151] The method for impregnating the thermosetting resin composition into the fiber sheet is not particularly limited, but a preferred method is to impregnate the fiber sheet with a resin composition whose viscosity has been reduced by heating (dry method).

[0152] In this impregnation step, for example, heat and pressure are optionally applied to the intermediate laminate obtained through the first resin composition disposing step and the second resin composition disposing step, i.e., the intermediate laminate consisting of a sheet of the first thermosetting resin composition, a fiber sheet, and a sheet of the second thermosetting resin composition, to impregnate the resin compositions. To apply heat and pressure, for example, hot pressing may be performed using heated rollers, and impregnation can be performed, for example, by passing the intermediate laminate between two rollers while heating it.

[0153] The heating temperature for the impregnation treatment can be appropriately determined taking into consideration the viscosity, curing temperature, etc. of the thermosetting resin composition. When the thermosetting resin composition contains an epoxy resin, the heating temperature is preferably 70 to 160°C, and more preferably 90 to 140°C.

[0154] The impregnation treatment time is preferably 10 to 300 seconds.

[0155] The pressure conditions for the impregnation treatment can be appropriately determined taking into consideration the viscosity of the thermosetting resin composition, the curing temperature, etc. The pressure conditions for the impregnation treatment are preferably a linear pressure of 1 to 245 N / cm (0.1 to 25 kg / cm), more preferably 9.8 to 147 N / cm (1 to 15 kg / cm) or 9.8 to 50 N / cm (1 to 5 kg / cm).

[0156] The impregnation treatment may be carried out once or multiple times.

[0157] In the impregnation step, the first thermosetting resin composition and the second thermosetting resin composition may be completely impregnated into the fiber sheet, or a portion of the first thermosetting resin composition and / or the second thermosetting resin composition may remain on the surface of the fiber sheet. The resin composition remaining on the surface of the fiber sheet can form a resin layer.

[0158] In one embodiment of the present disclosure, substantially all of the first thermosetting resin composition is impregnated into the fiber sheet, while a portion of the second thermosetting resin composition remains on the surface without being impregnated into the fiber sheet, forming a resin layer there. To achieve this, the basis weight of the fiber sheet, the heating and pressing conditions, and / or the viscosity of the resin composition can be appropriately adjusted. Furthermore, the formation of the resin layer can be promoted by adding intercalation particles to the thermosetting resin composition.

[0159] <Method for producing a thermosetting prepreg by successively impregnating a first and a second resin composition> The above-described thermosetting prepreg according to the present disclosure can also be produced by sequentially impregnating a fiber sheet with the first and second thermosetting resins (hereinafter, this method is referred to as the "sequential impregnation method").

[0160] Specifically, this method: Providing a fiber sheet (sheet providing process) providing a first thermosetting resin composition containing a thermosetting resin and a curing agent (first resin composition providing step); providing a second thermosetting resin composition containing a thermosetting resin and a curing agent (second resin composition providing step); disposing a first thermosetting resin composition on a main surface of the fiber sheet (first resin composition disposing step); impregnating the fiber sheet at least partially with a first thermosetting resin composition (first resin composition impregnation step); disposing a second thermosetting resin composition on a main surface of the fiber sheet impregnated with the first thermosetting resin composition (a second resin composition disposing step); and At least partially impregnating the fiber sheet with a second thermosetting resin composition to form a thermosetting prepreg (second resin composition impregnation step); Includes The equivalent ratio of the curing agent in the first thermosetting resin composition is greater than the equivalent ratio of the curing agent in the second thermosetting resin composition.

[0161] (Sequential impregnation method: sheet provision process) In the sheet providing step, a fiber sheet is provided. For the fiber sheet, the above description of the thermosetting prepreg can be referred to. The thickness of this fiber sheet may be 0.01 to 4.0 mm, 0.05 to 2.0 mm, or 0.1 to 1.0 mm. The basis weight of this fiber sheet is 70 to 600 g / m 2 and 100 to 500 g / m 2 is preferable, and 200 to 450 g / m 2 is more preferred.

[0162] (Sequential impregnation method: first resin composition providing step, second resin composition providing step) In the first resin composition providing step and the second resin composition providing step, a first thermosetting resin composition and a second thermosetting resin composition are provided, respectively. These resin compositions contain a thermosetting resin and a curing agent, and may optionally further contain a thermoplastic resin and a conductive material. These thermosetting resin compositions may be in the form of, for example, a sheet. For the resin compositions and their components, please refer to the above description of the thermosetting prepreg.

[0163] A sheet-shaped thermosetting resin composition (resin composition sheet or resin sheet) can be produced in the same manner as described above. For example, a sheet of the thermosetting resin composition can be produced by applying the prepared curable resin composition to a release paper using a film coater, drying the composition, forming it into a sheet, and peeling it off from the release paper.

[0164] (Sequential impregnation method: first resin composition placement step) In the first resin composition disposing step, a first thermosetting resin composition is disposed on the first and / or second main surfaces (preferably on the first and second main surfaces) of the fiber sheet. In this step, for example, two sheet-like (e.g., resin film-shaped) first thermosetting resin compositions can be laminated on the two main surfaces of the fiber sheet, respectively.

[0165] (Sequential impregnation method: first resin composition impregnation step) In the first resin composition impregnation step, the fiber sheet is at least partially impregnated with the first thermosetting resin composition. In this step, for example, heat and pressure are applied to a fiber sheet (first intermediate laminate) having sheets of the first thermosetting resin composition arranged on both main surfaces to impregnate the resin composition. To apply heat and pressure, for example, a heat press may be performed using heated rollers, and impregnation can be performed, for example, by passing the first intermediate laminate between two rollers while heating it.

[0166] (Sequential impregnation method: second resin composition placement step) In the second resin composition disposing step, the second thermosetting resin composition is disposed on the first and / or second main surfaces (preferably on the first and second main surfaces) of the fiber sheet impregnated with the first thermosetting resin composition. In this step, for example, two sheets of the second thermosetting resin composition (e.g., in the form of resin films) can be laminated on the two main surfaces of the fiber sheet, respectively.

[0167] (Sequential impregnation method: second resin composition impregnation step) In the second resin composition impregnation step, the fiber sheet is at least partially impregnated with the second thermosetting resin composition. In this step, for example, heat and pressure are applied to a fiber sheet (second intermediate laminate) that has been impregnated with the first thermosetting resin composition and has sheets of the second thermosetting resin composition on both sides thereof, thereby impregnating the resin composition. To apply heat and pressure, for example, a hot press using heated rollers or the like may be performed. For example, impregnation can be performed by passing the sheet between two rollers while heating.

[0168] According to the above method, the outer region of the fiber sheet impregnated with a resin composition having a relatively high curing agent equivalence ratio is impregnated with a resin composition having a relatively low curing agent equivalence ratio, so that the above-mentioned thermosetting prepreg according to the present disclosure can be produced, in which the central region has a relatively high curing agent equivalence ratio.

[0169] Generally, when an additional resin composition sheet is placed on top of a fiber sheet that has already been impregnated with a resin composition and then heated and pressurized, it is believed that the resin composition already impregnated in the fiber sheet will prevent the additional resin composition from being impregnated into the fiber sheet.

[0170] On the other hand, in order to sufficiently impregnate the fiber sheet impregnated with the first thermosetting resin composition with the second thermosetting resin composition, for example, the amount of the first thermosetting resin composition impregnated in the fiber sheet can be reduced. In this case, gaps that can be impregnated with the second thermosetting resin composition can be present in the fiber sheet, making it relatively easy to impregnate the second thermosetting resin composition.

[0171] For this purpose, for example, the amount of the first thermosetting resin composition impregnated into the fiber sheet may be 10% by mass or more, 12% by mass or more, or 14% by mass or more, and / or 30% by mass or less, less than 30% by mass, 28% by mass or less, 26% by mass or less, 24% by mass or less, or 22% by mass or less, relative to the fiber sheet.

[0172] In addition, for example, the total basis weight (g / cm 3 ) of the sheet of the first thermosetting resin composition placed on the fiber sheet in the first resin composition placing step is 2 ) is the basis weight of the fiber sheet (g / cm 2 ), and / or may be 10% or more, 12% or more, 14% or more, or 16% or more, and / or 30% or less, less than 30%, 28% or less, 26% or less, or 24% or less.

[0173] Furthermore, in order to impregnate the fiber sheet impregnated with the first thermosetting resin composition with the second thermosetting resin composition, the heating temperature in the second resin composition impregnation step can be set to 70 to 140°C and the pressure condition can be set to 9.8 to 245 N / cm. By carrying out the impregnation treatment under these conditions, the viscosity of the thermosetting resin composition is reduced, which is thought to promote the impregnation of the second thermosetting resin composition. [Example]

[0174] EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The components and test methods used in these examples and comparative examples are described below.

[0175] <Viscosity> The viscosity was measured using a TA Instruments rheometer (product name: ARES-G2) with parallel plates of 25 mm diameter, with the thickness of the resin composition between the parallel plates set to 0.5 mm, at an angular velocity of 10 radians / second and a heating rate of 2°C / min up to 180°C, and the resin viscosity was measured from the temperature-viscosity curve.

[0176] <Impregnation level> The impregnation level of the prepreg, i.e., the degree to which the resin composition has impregnated the fiber sheet, can be determined by measuring the water absorption rate (WPU) based on a water absorption test. Specifically, the following steps are followed: One ply of prepreg is cut to a 100 mm x 100 mm size. After removing the backing paper, the mass of one ply of prepreg (W1) is measured for each sample. The prepreg is then firmly clamped in a WPU apparatus with the 0° fiber direction perpendicular to the water surface. With the clamped prepreg positioned vertically in the apparatus, 5 mm of the prepreg is immersed in room temperature water in a laboratory environment of 23°C and 50% relative humidity. After 5 minutes of immersion, the sample is removed from the water, excess water on the outside is removed, and the mass of the sample (W2) is measured again to calculate the percent water absorption from the initial state (WPU) using the following equation (3): WPU=(W1−W2) / W1 Formula (3) The percent water absorption (WPU) was calculated by averaging the weights measured for the three samples, and then evaluated according to the following criteria: ◎: WPU is less than 3% 〇: WPU is 3% or more and less than 5% △: WPU is 5% or more and less than 10% ×: WPU is 10% or more

[0177] <Tackiness> The tackiness of the prepreg was evaluated using a tack testing device (manufactured by Rhesca Co., Ltd., product name: TAC-II). Specifically, the prepreg was set on a test stage maintained at 27°C, and an initial load of 100 gf was applied using a Φ5 stainless steel cylindrical tack probe also maintained at 27°C. The maximum load (F0 and F 14 ) was sought. The prepreg immediately after production (F0) and the prepreg stored at a temperature of 26.7°C and a humidity of 65% for 14 days (F 14 ) were subjected to a tack probe test. The tack retention rate was calculated using the following formula (4), and the calculation results were expressed according to the following criteria: Tack retention rate = 100·(F0-F 14 ) / F0 formula (4) ◎: The load immediately after manufacturing is 500gf or more, and the tack retention rate after 14 days of storage is 80% or more. Good: The load immediately after manufacturing is 500gf or more, and the tack retention rate after 14 days of storage is 50% or more but less than 80%. △: The load immediately after manufacturing was 500 gf or more, and the tack retention rate after storage for 14 days was 25% or more and less than 50%. ×: The load immediately after manufacturing was 500 gf or more, and the tack retention rate after storage for 14 days was less than 25%.

[0178] <Compression characteristics> Compression properties were determined as follows: The prepreg is cut into 360mm square pieces and laminated to a laminate structure of [+45 / 0 / -45 / 90]. nS A laminate of the above formula was obtained. It was molded using a conventional vacuum autoclave molding method at 180°C under a pressure of 0.59 MPa for 2 hours. The molded product was cut into test pieces measuring 38.10 mm wide x 304.8 mm long, and a 6.35 mm diameter hole was drilled in the center of each piece to obtain a test piece for open hole compression strength (OHC) testing. The compressive strength (OHC) of this test piece was measured according to SACMA SRM 3R-94. The crosshead speed of the test piece compression tester was 1 mm / min, and five test pieces were measured.

[0179] <Compression strength after impact> Compression strength after impact was performed as follows: The prepreg is cut into 360mm square pieces and laminated to a laminate structure of [+45 / 0 / -45 / 90]. nS A laminate of the above formula was obtained. Using a conventional vacuum autoclave molding method, molding was performed under a pressure of 0.59 MPa and a temperature of 180°C for 2 hours. The resulting molded product was cut into a 100 mm wide x 150 mm long specimen for compression after impact (CAI) testing. This specimen was subjected to a 30 J impact to damage it, and then the compression after impact (CAI) was measured according to SACMA SRM 2R-94. The crosshead speed of the specimen compression tester was 1 mm / min, and five specimens were measured.

[0180] <Conductivity in the thickness direction> Conductivity in the thickness direction (volume resistivity) was measured by measuring the volume resistivity in the Z direction (thickness direction) of the composite (composite material) produced as described below using a digital ohmmeter (AX-111A, manufactured by Adex Yell Co., Ltd.). Volume resistivity is the specific resistance of a given material. The Z-direction volume resistivity ρ of the material was calculated using the following formula: ρ=RA / L R: Electrical resistance of a uniform specimen from the material (Ω) L: thickness of test piece (m) A: Cross-sectional area of ​​the test piece (m 2 )

[0181] The composite fabrication and through-thickness conductivity measurements were carried out as follows: Cut prepreg, stack and laminate structure [+45 / 0 / -45 / 90] 2SA laminate of the above formula was obtained. It was molded using a vacuum autoclave molding method under a pressure of 0.59 MPa and a temperature of 180°C for 2 hours. The resulting molded product was cut into a 40 mm wide x 40 mm long piece. The top and bottom surfaces of the molded product were polished with sandpaper until the carbon fibers were exposed, and finally, the surface was finished with #2000 sandpaper. The unpolished side was then covered with fluorine tape, and the polished top and bottom surfaces were copper-plated using an electrolytic plating method using copper sulfate as the electrolyte and copper as the electrode plate. The resulting test piece was sandwiched between 50 mm wide x 50 mm long gold-plated electrodes, and a load of 0.06 MPa was applied to the test piece. The resistance in the Z direction was measured using a digital ohmmeter, and the conductivity through the thickness was calculated using the above formula.

[0182] 〔component〕 The components in the examples and comparative examples are as follows. (epoxy resin) Epoxy resin [A] A-1: Tetraglycidyl-4,4'-diaminodiphenylmethane (hereinafter abbreviated as "TGDDM") (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: YH-404) A-2: Bisphenol A diglycidyl ether (hereinafter abbreviated as "DGBPA") (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: YD-8125) A-3: GAN (manufactured by Nippon Kayaku Co., Ltd.) A-4: GOT (manufactured by Nippon Kayaku Co., Ltd.) A-5: Triglycidyl-m-aminophenol (hereinafter abbreviated as "m-TGAP") (Araldite, manufactured by Huntsman, product name: MY0600)

[0183] (Curing agent (amine-based curing agent)) B-1: 4,4-diaminodiphenylsulfone (hereinafter abbreviated as "44DDS") (manufactured by Wakayama Seika Kogyo Co., Ltd., product name: Seikacure-S) B-2: 3,3'-diaminodiphenyl sulfone (hereinafter abbreviated as "33DDS") (manufactured by Konishi Chemical Industry Co., Ltd., product name: 33DAS) B-3: 3,3'-diaminodiphenyl sulfone pulverized product (33DDS adjusted to an average particle size of 5 μm using a pulverizer, hereinafter abbreviated as "33DDS pulverized product")

[0184] (Epoxy resin soluble thermoplastic resin) C-1: Polyethersulfone (hereinafter abbreviated as "PES") (manufactured by Sumitomo Chemical Co., Ltd., product name: Sumikaexcel PES-5003MP, average particle size 50 μm)

[0185] (Epoxy resin insoluble thermoplastic resin (interlayer particles)) D-1: Polyamide resin (hereinafter abbreviated as "PA1010") (manufactured by Daicel-Evonik, product name: MSP-A7723, average particle size 18 μm) D-2: Polyamide 12 (hereinafter abbreviated as "PA12") (manufactured by Daicel-Evonik, product name: MSP-A7673, average particle size 20 μm)

[0186] (Conductive material) E-1: Carbon nanotubes (hereinafter abbreviated as "CNT") (manufactured by Nanocyl, product name: NC7000, average particle diameter 9.5 nm) E-2: Carbon nanostructure (hereinafter abbreviated as "CNS") (manufactured by Cabot Corporation, product name: Athlos SR1200 CNS, average particle size 10 to 20 nm) E-3: Milled fiber (Mitsubishi Plastics, Inc., product name: DIALEAD K223HM, pitch-based carbon fiber milled fiber with an aspect ratio of 18, average fiber length 200 μm (catalog value))

[0187] (carbon fiber) "Tenax (registered trademark)" IMS65 E23 830tex: (carbon fiber strand, tensile strength 5800 MPa, tensile modulus 290 GPa, manufactured by Teijin Limited) "Tenax (registered trademark)" ITS55 E23 1600tex: (carbon fiber strand, tensile strength 5200MPa, tensile modulus 280GPa, manufactured by Teijin Limited)

[0188] Examples 1 to 4 and Comparative Examples 1 to 3 Thermosetting prepregs according to Examples 1 to 4 and Comparative Examples 1 to 3 were produced and their physical properties were evaluated.

[0189] Example 1 (Preparation of Resin Composition 1) In a kneading machine, epoxy resins TGDDM (70 parts by mass), DGBPA (25 parts by mass), and GAN (5 parts by mass) were added to PES (18 parts by mass), which is an epoxy resin-soluble thermoplastic resin, and the mixture was stirred using a planetary mixer at 120°C for 60 minutes to completely dissolve the PES in the epoxy resin.The resin temperature was then cooled to below 80°C to prepare an epoxy resin composition.Then, using a roll mill, the curing agent (40 parts by mass in total) shown in Table 1 below was added to the above resin and kneaded to prepare Resin Composition 1.

[0190] (Preparation of a sheet of resin composition 1) The prepared resin composition 1 was applied onto a release paper using a film coater to give a coating of 48 g / m 2 A sheet (resin film) of the resin composition 1 was prepared.

[0191] (Preparation of Resin Composition 2) In a kneading machine, epoxy resins TGDDM (70 parts by mass), DGBPA (25 parts by mass), and GAN (5 parts by mass) were added to the epoxy resin-soluble thermoplastic resin PES (15 parts by mass) and heat-treated PA1010 particles (13 parts by mass). The mixture was stirred at 120°C for 60 minutes using a planetary mixer to completely dissolve the PES in the epoxy resin, and then cooled to below 80°C to prepare an epoxy resin composition. Subsequently, a roll mill was used to add and knead the curing agent (34 parts by mass in total) shown in Table 1 below to the resin, preparing Resin Composition 2.

[0192] (Preparation of a sheet of resin composition 2) The prepared resin composition 2 was applied onto a release paper using a film coater to give a coating of 48 g / m 2 A sheet (resin film) of resin composition 2 was prepared.

[0193] (Preparation of thermosetting prepreg precursor sheet) Next, a carbon fiber sheet was prepared in which carbon fiber bundles (manufactured by Teijin Limited, product name: IMS65) were aligned in one direction as reinforcing fibers, and a sheet of the prepared resin composition 1 and a sheet of the prepared resin composition 2 were placed on each side of the carbon fiber sheet. Thereafter, the carbon fiber sheet was impregnated with resin composition 1 and resin composition 2 by heating and pressing at 110°C and 15 N / cm using a heated roller, and the carbon fiber sheet was impregnated with resin composition 1 and resin composition 2, until the basis weight of the carbon fiber became 190 g / m. 2 Thus, a unidirectional prepreg precursor sheet (thermosetting prepreg precursor sheet according to Example 1) having a matrix resin mass fraction of 35.0% was produced.

[0194] Two thermosetting prepreg precursor sheets prepared as described above were prepared and stacked together so that the sides of their main surfaces impregnated with resin composition 1 faced each other. The two precursor sheets were heated and pressed using a heated roller at 50°C and 15 N / cm to integrate the two precursor sheets, resulting in a carbon fiber weight of 380 g / m 2 A unidirectional prepreg sheet (thermosetting prepreg according to Example 1) with a matrix resin mass fraction of 35.0% was produced. The evaluation results of the properties of the prepreg according to Example 1 are shown in Table 1 below.

[0195] A composite material was produced using the thermosetting prepreg according to Example 1. Specifically, 24 sheets of the thermosetting prepreg according to Example 1 were stacked in a lamination configuration of [45° / 0° / -45° / 90°]3s, and the stacked sheets were subjected to a thermosetting treatment to produce the composite material. The evaluation results of the properties of the resulting composite material are shown in Table 1 below.

[0196] Example 2A A thermosetting prepreg according to Example 2A was produced in the same manner as in Example 1 above, except that the basis weight of the resin film was changed as shown in Table 1 below. A composite material was produced using the obtained thermosetting prepreg according to Example 2A in the same manner as in Example 1 above. The evaluation results of the properties of the obtained prepreg and composite material are shown in Table 1 below.

[0197] Example 2B A thermosetting prepreg according to Example 2B was produced in the same manner as in Example 2A above, except that the amount of interlayer particles and the basis weights of Resin Compositions 1 and 2 were changed as shown in Table 1 below. A composite material was produced using the obtained thermosetting prepreg according to Example 2B in the same manner as in Example 1 above. The evaluation results of the properties of the obtained prepreg and composite material are shown in Table 1 below.

[0198] Example 3 A thermosetting prepreg according to Example 3 was produced in the same manner as in Example 1, except that the composition of the resin composition was changed to the types and amounts added shown in Table 1 below. A composite material was produced using the obtained thermosetting prepreg in the same manner as in Example 1. The evaluation results of the properties of the obtained prepreg and composite material are shown in Table 1 below.

[0199] Example 4 (Preparation of Resin Composition 1') In a kneading machine, epoxy resins TGDDM (45 parts by mass), DGBPA (50 parts by mass), and GAN (5 parts by mass) were added to PES (20 parts by mass), which is an epoxy resin-soluble thermoplastic resin, and the mixture was stirred using a planetary mixer at 120°C for 60 minutes to completely dissolve the PES in the epoxy resin.The resin temperature was then cooled to 80°C or below to prepare an epoxy resin composition.Then, using a roll mill, the curing agent shown in Table 1 below (36 parts by mass in total) was added to the above resin and kneaded to prepare Resin Composition 1'.

[0200] (Preparation of a sheet of resin composition 1') The prepared resin composition 1' was applied onto a release paper using a film coater to give a coating of 68 g / m 2 A sheet of the resin composition 1' was prepared.

[0201] (Preparation of Resin Composition 2') In a kneading machine, epoxy resins TGDDM (45 parts by mass), DGBPA (50 parts by mass), and GOT (5 parts by mass) were added to the epoxy resin-soluble thermoplastic resin PES (20 parts by mass) and heat-treated PA1010 particles (35 parts by mass). The mixture was stirred at 120°C for 60 minutes using a planetary mixer to completely dissolve the PES in the epoxy resin, and then cooled to below 80°C to prepare an epoxy resin composition. Subsequently, a roll mill was used to add and knead the curing agent (32 parts by mass in total) shown in Table 1 below to the resin, preparing Resin Composition 2'.

[0202] (Preparation of a sheet of resin composition 2') The prepared resin composition 2' was applied onto a release paper using a film coater to give a coating of 68 g / m 2 A sheet of the resin composition 2' was prepared.

[0203] (Preparation of thermosetting prepreg precursor sheet) Next, a carbon fiber sheet was prepared in which carbon fiber bundles (manufactured by Teijin Limited, product name: IMS65) were aligned in one direction as reinforcing fibers, and a sheet of the prepared resin composition 1' and a sheet of the prepared resin composition 2' were placed on each side of the carbon fiber sheet. Thereafter, the carbon fiber sheet was impregnated with resin composition 1' and resin composition 2' by heating and pressing at 110°C and 15 N / cm using a heated roller, and the carbon fiber sheet was impregnated with resin composition 1' and resin composition 2', until the basis weight of the carbon fiber became 260 g / m 2 Thus, a unidirectional prepreg precursor sheet (thermosetting prepreg precursor sheet according to Example 4) having a matrix resin mass fraction of 35.0% was produced.

[0204] Two thermosetting prepreg precursor sheets prepared as described above were prepared and stacked together so that the sides of their main surfaces impregnated with resin composition 1' faced each other. The two precursor sheets were heated and pressed using a heated roller at 80°C and 50 N / cm to integrate the two precursor sheets, resulting in a carbon fiber basis weight of 520 g / m 2 Thus, a unidirectional prepreg sheet (thermosetting prepreg according to Example 4) having a matrix resin mass fraction of 35.0% was produced.

[0205] A composite material was produced using the thermosetting prepreg according to Example 4. Specifically, the composite material was produced by laminating 16 sheets of the thermosetting prepreg according to Example 4 in a lamination configuration of [45° / 0° / -45° / 90°]2s and subjecting them to a thermosetting treatment. The evaluation results of the properties of the obtained composite material are shown in Table 1 below.

[0206] <Comparative Example 1> A thermosetting prepreg according to Comparative Example 1 was prepared in the same manner as in Example 1, except that the content of the curing agent was changed as shown in Table 1 below. Using the prepared thermosetting prepreg, a composite material was produced in the same manner as in Example 1 above. The properties of the obtained prepreg and composite material are shown in Table 1 below.

[0207] <Comparative Example 2> Resin composition 1 was prepared in the same manner as in Example 1.

[0208] The prepared resin composition 1 was applied to release paper using a film coater, dried, and formed into a sheet. The sheet was peeled off from the release paper and had a basis weight of 96 g / m. 2 Two sheets of the resin composition 1 were prepared.

[0209] Next, two sheets of the resin composition 1 prepared above were placed on both sides of a carbon fiber sheet in which carbon fiber bundles (manufactured by Teijin Limited, product name: IMS65) were aligned in one direction as reinforcing fibers. Thereafter, the carbon fiber sheet was impregnated with the resin composition 1 by heating and pressing under conditions of 110°C and 15 N / cm using a heated roller, and the carbon fiber weight per unit area was 380 g / m. 2 A unidirectional prepreg sheet according to Comparative Example 2 (thermosetting prepreg according to Comparative Example 2) having a matrix resin mass fraction of 35.0% was produced using the above method. The evaluation results of the properties of the prepreg according to Comparative Example 2 are shown in Table 1 below.

[0210] A composite material was produced using the thermosetting prepreg produced in Comparative Example 2, and its properties were evaluated in the same manner as in Example 1. The properties of the obtained composite material are shown in Table 1 below.

[0211] <Comparative Example 3> A thermosetting prepreg according to Comparative Example 3 was prepared in the same manner as in Comparative Example 2, except that a sheet of Resin Composition 2 was used instead of the sheet of Resin Composition 1. Using the prepared thermosetting prepreg, a composite material was produced in the same manner as in Example 1. The properties of the obtained prepreg and composite material are shown in Table 1 below.

[0212] [Table 1]

[0213] As shown in Table 1, the thermosetting prepregs of Examples 1 to 4 exhibited favorable handling properties (impregnation level and tackiness) due to the resin having a low equivalent ratio of curing agent, as well as favorable mechanical properties (compression properties and compression after impact properties) due to the resin having a high equivalent ratio of curing agent, compared to the thermosetting prepregs of Comparative Examples 2 and 3, which were produced using only one resin composition.

[0214] Furthermore, the thermosetting prepreg of Comparative Example 1 exhibited mechanical properties that were inferior to those of Examples 1 to 4. In the prepreg of Comparative Example 1, the equivalent ratio of the curing agent in the first resin composition impregnated in the central region was smaller than the equivalent ratio of the curing agent in the second resin composition impregnated in the outer region. While not intending to be limited by theory, it is believed that the mechanical properties of Comparative Example 1 were insufficient because a sufficient crosslink density of the thermosetting resin in the central region could not be ensured.

[0215] <<Example 5>> A thermosetting prepreg according to Example 5 was produced and its physical properties were evaluated. In Example 5, the prepreg was produced using only one fiber sheet as follows.

[0216] Resin composition 1 was prepared in the same manner as in Example 1.

[0217] The prepared resin composition 1 was applied to release paper using a film coater, dried, and formed into a sheet. The sheet was peeled off from the release paper and had a basis weight of 48 g / m. 2 Two sheets of the resin composition 1 were prepared.

[0218] Resin composition 2 was prepared in the same manner as in Example 1.

[0219] The prepared resin composition 2 was applied to release paper using a film coater, dried, and formed into a sheet, which was then peeled off from the release paper to give a sheet having a basis weight of 48 g / m 2 Two sheets of resin composition 2 were prepared.

[0220] Next, two sheets of the resin composition 1 prepared above were placed on both sides of a carbon fiber sheet in which carbon fiber bundles (manufactured by Teijin Limited, product name: IMS65) were aligned in one direction as reinforcing fibers. Thereafter, the carbon fiber sheet was impregnated with the resin composition 1 by heating and pressing under conditions of 110°C and 15 N / cm using a heated roller, and the carbon fiber weight per unit area was 380 g / m. 2 A unidirectional prepreg sheet with a matrix resin mass fraction of 20.5% was produced.

[0221] Next, two sheets of the prepared resin composition 2 were placed on both sides of the carbon fiber sheet impregnated with resin composition 1. Then, by heating and pressing using a heated roller at 80°C and 15 N / cm, the carbon fiber sheet was impregnated with resin composition 2, and the weight of the carbon fiber was 380 g / m 2 A unidirectional prepreg sheet according to Example 5 (thermosetting prepreg according to Example 5) having a matrix resin mass fraction of 35.0% was produced using the above method. The evaluation results of the properties of the prepreg according to Example 5 are shown in Table 2 below.

[0222] A composite material was produced using the thermosetting prepreg of Example 5 and its properties were evaluated in the same manner as in Example 1. The properties of the obtained composite material are shown in Table 2 below.

[0223] [Table 2]

[0224] As seen in Table 2, the prepreg of Example 5, which was impregnated with resin composition 1 having a relatively high curing agent equivalent ratio and then further impregnated with resin composition 2 having a relatively low curing agent equivalent ratio, exhibited better prepreg and composite properties than Comparative Examples 2 and 3, which used only a single resin composition. While not intending to be limited by theory, these effects of Example 5 are believed to be brought about by the use of two resin compositions with different curing agent contents, etc. In particular, the prepreg of Example 5 exhibited relatively high crosslink density of the thermosetting resin in the central region, resulting in good mechanical properties. Furthermore, because the amount of resin composition 1 impregnated into the fiber sheet in Example 5 was relatively reduced, resin composition 2 was impregnated relatively well into the fiber sheet already impregnated with resin composition 1.

[0225] Examples 6A and 6B and Examples 7 to 11 In Examples 6A and 6B and Examples 7 to 11, the effect of adding a conductive material was evaluated.

[0226] Example 6A A thermosetting prepreg according to Example 6A was produced in the same manner as in Example 1 above, except that a resin composition was prepared using the ingredients and amounts shown in Table 3 below and that the type of carbon fiber used as the reinforcing fiber was changed (manufactured by Teijin Limited, product name: ITS55 E23 24K). A composite material was produced in the same manner as in Example 1 above, using the obtained thermosetting prepreg according to Example 6A. The evaluation results of the properties of the obtained prepreg and composite material are shown in Table 3 below.

[0227] Example 6B The basis weight M1 (g / m 2 ) and the basis weight M2 (g / m 2 A thermosetting prepreg according to Example 6B was produced in the same manner as in Example 6A, except that the ratio (M1 / M2) of the two components was changed to 0.57, and evaluations were carried out in the same manner as in Example 6A. The results are shown in Table 3 below.

[0228] <Examples 7 to 11> Thermosetting prepregs according to Examples 7 to 11 were produced in the same manner as in Example 6A above, except that resin compositions were prepared using the components and amounts shown in Table 3 below, and that a conductive material shown in Table 3 below (an additional conductive material was added in Example 8) was added. The conductive material was added to the resin after adding the amount of curing agent shown in Table 3 below using a roll mill. The evaluation results of the properties of the obtained thermosetting prepregs according to Examples 7 to 11, and composite materials (composites) produced from these prepregs in the same manner as in Example 1 above, are shown in Table 3 below.

[0229] <Comparative Examples 4 and 5> Thermosetting prepregs according to Comparative Examples 4 to 5 were produced in the same manner as in Example 7 above, except that resin compositions were prepared using the components and amounts shown in Table 3 below. The evaluation results of the properties of the obtained thermosetting prepregs according to Comparative Examples 4 to 5, and composite materials (composites) produced from these prepregs in the same manner as in Example 1 above, are shown in Table 3 below.

[0230] [Table 3]

[0231] As shown in Table 3, the thermosetting prepregs of Examples 6A, 6B, and 7 to 11 exhibited sufficient conductivity through the thickness. In particular, Examples 7 to 11, which contained a conductive material, exhibited particularly good conductivity through the thickness compared to Example 6A, which did not contain a conductive material. Furthermore, the thermosetting prepreg of Example 8, which further contained a relatively large additional conductive material in addition to the conductive material, exhibited even better conductivity through the thickness compared to a prepreg without the additional conductive material.

[0232] Furthermore, Examples 7 to 11 exhibited electrical conductivity equivalent to or superior to that of Comparative Examples 4 and 5, and also exhibited superior composite properties. In Comparative Example 4, the curing agent equivalent ratios of the first and second resin compositions were the same, and there was no difference between the curing agent equivalent ratios in the outer and central regions of the prepreg. In Comparative Example 5, the curing agent equivalent ratio of the first resin composition was smaller than that of the second resin composition, resulting in a resin composition with a relatively high curing agent equivalent ratio being present in the outer region of the prepreg. In contrast, in Examples 7 to 11, the resin composition with a relatively high curing agent equivalent ratio (first resin composition) was present in the central region of the prepreg. While not intending to be limited by theory, it is believed that the composites of Examples 7 to 11 exhibited superior composite properties compared to the composites of Comparative Examples 4 and 5 as a result of a relatively high crosslink density in the central region of the prepreg that constitutes the composite.

[0233] Furthermore, as can be seen in Table 3, Example 6B, in which the ratio of the basis weights of the resin films (M1 / M2) when producing the prepreg was 0.57, exhibited superior thickness direction conductivity compared to Example 6A, in which this ratio was 1.00. [Explanation of symbols]

[0234] 100 Thermosetting prepreg 110, 210, 310 fiber sheet 120, 220 resin layer 112, 212, 322 First thermosetting resin composition 122, 222, 332 Second thermosetting resin composition 150, 250, 350 resin particles 200, 200a, 200b Thermosetting prepreg precursor sheet 314 1st main surface 316 2nd main surface 320 Sheet of first thermosetting resin composition 330 Sheet of second thermosetting resin composition 340 Intermediate laminate A outer area B central area A´ second outer region of the fibrous sheet B´ First outer region of the fibrous sheet T thickness direction

Claims

1. A thermosetting prepreg, Fiber sheets, a first thermosetting resin composition impregnated into a central region in a thickness direction of the fiber sheet in a cross section perpendicular to the surface direction of the fiber sheet; and a second thermosetting resin composition impregnated into an outer region in a thickness direction of the fiber sheet in a cross section perpendicular to the surface direction of the fiber sheet; and the first and second thermosetting resin compositions each contain a thermosetting resin and a curing agent; a thermosetting prepreg, wherein an equivalent ratio of the curing agent in the first thermosetting resin composition is greater than an equivalent ratio of the curing agent in the second thermosetting resin composition.

2. 2. The thermosetting prepreg according to claim 1, wherein in a cross section perpendicular to the plane direction of the fiber sheet, the ratio of the thickness of the central region to the total thickness of the central region and the outer regions is 10 to 90%.

3. The thermosetting prepreg according to claim 1 or 2, wherein the first and second thermosetting resin compositions each further comprise a thermoplastic resin and a conductive material.

4. 3. The thermosetting prepreg according to claim 1 or 2, wherein the second thermosetting resin composition impregnates an outer region of the fiber sheet and is disposed on a surface of the fiber sheet.

5. The thermosetting prepreg according to claim 4 , wherein the second thermosetting resin composition disposed on the surface of the fiber sheet contains resin particles.

6. The thermosetting prepreg of claim 4 , wherein the second thermosetting resin composition disposed on the surface of the fibrous sheet includes an additional conductive material.

7. The viscosity of the first thermosetting resin composition at 50°C is higher than the viscosity of the second thermosetting resin composition at 50°C. The thermosetting prepreg according to claim 1 or 2.

8. The viscosity of the first thermosetting resin composition at 50°C is 500 to 10,000 Pa s, The viscosity of the second thermosetting resin composition at 50°C is 100 to 1000 Pa s. The thermosetting prepreg according to claim 1 or 2.

9. When the thermosetting prepreg was heat-cured at 180°C for 120 minutes, In a cross section perpendicular to the plane direction of the fiber sheet, there is a region in which the crosslink density of the thermosetting resin decreases from the center in the thickness direction of the fiber sheet toward the surface. The thermosetting prepreg according to claim 1 or 2.

10. 3. The thermosetting prepreg according to claim 1, wherein the thermosetting resin is an epoxy resin.

11. A thermosetting prepreg laminate having a structure in which two or more thermosetting prepregs according to claim 1 or 2 are laminated together.

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