Thermosetting prepreg and method for producing the same

Abstract

To provide a thermoset prepreg having good mechanical properties, particularly good handling properties.SOLUTION: The present invention relates to a thermoset prepreg including: a fiber sheet; a first thermoset resin composition soaking in a central region in a thickness direction of the fiber sheet in a cross section perpendicular to a surface direction of the fiber sheet; and a second thermoset resin composition soaking in an outside region in the thickness direction of the fiber sheet in the cross section perpendicular to the surface direction of the fiber sheet. The first and second thermoset resin compositions individually include a thermoset resin and a curing agent. An equivalence ratio of the curing agent in the first thermoset resin composition is larger than an equivalence ratio of the curing agent in the second thermoset resin composition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to thermosetting prepregs and methods for producing the same. In particular, this disclosure relates to thermosetting prepregs and methods for producing the same that can be used in the production of carbon fiber reinforced plastics (CFRP) used in applications such as aircraft. [Background technology]

[0002] Carbon fiber reinforced composite materials (also known as CFRP), which consist of carbon fibers as reinforcing fibers and a matrix resin, possess characteristics such as lightness, high strength, and high modulus of elasticity, and are widely applied in aircraft, sports and leisure, and general industry.

[0003] These composite materials are often manufactured using prepregs, in which carbon fibers and a matrix resin are pre-integrated. For example, composite materials can be manufactured by laminating multiple prepregs.

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

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

[0006] One type of prepreg is a thermosetting prepreg. A thermosetting prepreg has a structure in which a thermosetting resin, such as epoxy resin, is impregnated into a reinforcing fiber sheet, such as a carbon fiber sheet. For example, a composite material can be manufactured 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 composed of a reinforcing fiber and a resin composition (I) impregnated in the reinforcing fiber layer, and a surface layer composed 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

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

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

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

Means for Solving the Problems

[0011] The above problems can be solved by the following aspects according to the present invention: <Aspect 1> A thermosetting prepreg, a fiber sheet, in a cross section perpendicular to the plane direction of the fiber sheet, a first thermosetting resin composition impregnated in a central region in the thickness direction of the fiber sheet, and In a cross-section perpendicular to the plane direction of the fiber sheet, a second thermosetting resin composition is impregnated in the outer region in the thickness direction of the fiber sheet. It has and The first and second thermosetting resin compositions each comprise 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. Thermosetting prepreg. <Aspect 2> The thermosetting prepreg according to embodiment 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 region is 10 to 90%. <Aspect 3> The thermosetting prepreg according to embodiment 1 or 2, wherein the first and second thermosetting resin compositions each further comprise a thermoplastic resin and a conductive material. <Aspect 4> A thermosetting prepreg according to any one of embodiments 1 to 3, wherein the second thermosetting resin composition is impregnated into the outer region of the fiber sheet and also disposed on the surface of the fiber sheet. <Aspect 5> The thermosetting prepreg according to embodiment 4, wherein the second thermosetting resin composition disposed on the surface of the fiber sheet has resin particles. <Aspect 6> The thermosetting prepreg according to embodiment 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 embodiments 1 to 6. <Aspect 8> The viscosity of the first thermosetting resin composition at 50°C is 500 to 10000 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 embodiments 1 to 7. <Pattern 9> When the aforementioned thermosetting prepreg is subjected to a heat curing treatment at 180°C for 120 minutes, In a cross-section perpendicular to the plane direction of the fiber sheet, there exists a region where the crosslinking 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 embodiments 1 to 8. <Aspect 10> The thermosetting prepreg according to any one of embodiments 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 described in any one of embodiments 1 to 10 are laminated. <Aspect 12> A method for producing a thermosetting prepreg, including the following: (a) To provide a thermosetting prepreg precursor sheet, wherein the precursor sheet comprises a fiber sheet and first and second thermosetting resin compositions impregnated in the fiber sheet and each comprising a thermosetting resin and a curing agent, respectively, 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 of the 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. 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> A method for producing a thermosetting prepreg precursor sheet, To provide a fiber sheet, To provide a first thermosetting resin composition comprising a thermosetting resin and a curing agent, To provide a second thermosetting resin composition comprising a thermosetting resin and a curing agent, The first thermosetting resin composition is placed on one main surface of the fiber sheet. The second thermosetting resin composition is placed on the other main surface of the fiber sheet, and The first thermosetting resin composition and the second thermosetting resin composition are impregnated into the fiber sheet, at least partially. 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. <Aspect 14> The basis weight (g / m²) of the sheet-like first thermosetting resin composition 2 ) The basis weight (g / m²) of the sheet-like second thermosetting resin composition of M1 2 The method according to embodiment 13, wherein the ratio (M1 / M2) to M2 is 0.25 to 4.0. <Aspect 15> The method according to embodiment 13 or 14, wherein the second thermosetting resin composition further comprises resin particles. [Effects of the Invention]

[0012] The inventions described herein provide a thermosetting prepreg having excellent mechanical properties and a method for manufacturing the same. In particular, the inventions described herein provide a thermosetting prepreg having excellent mechanical properties and good handling properties, and a method for manufacturing the same. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 shows a schematic cross-sectional view of a thermosetting prepreg according to one embodiment of the present disclosure. [Figure 2] Figure 2 shows a conceptual diagram of one embodiment of the method for manufacturing a thermosetting prepreg according to this disclosure. [Figure 3] Figure 3 shows a conceptual diagram of one embodiment of the method for producing a thermosetting prepreg precursor sheet according to this disclosure. [Modes for carrying out the invention]

[0014] The thermosetting prepreg relating to this disclosure is Fiber sheets, and In a cross-section perpendicular to the plane direction of the fiber sheet, a first thermosetting resin composition is impregnated into the central region in the thickness direction of the fiber sheet, and In a cross-section perpendicular to the plane direction of the fiber sheet, a second thermosetting resin composition is impregnated into the outer region in the thickness direction of the fiber sheet. It has and The first and second thermosetting resin compositions each comprise 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 intended to aid in understanding the present invention and are not to scale, nor do they limit the present invention.

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

[0017] The thermosetting prepreg 100 shown in Figure 1 has a fiber sheet 110. The fiber sheet 110 is particularly a carbon fiber sheet. The 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 has a thermosetting resin and a curing agent, and optionally further contains a thermoplastic resin and a conductive material.

[0018] Furthermore, the thermosetting prepreg 100 has a second thermosetting resin composition 122 impregnated into the outer region (A) in the thickness direction of the fiber sheet 110. The second thermosetting resin composition 122 has 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 Figure 1, a second thermosetting resin composition 122 is further disposed on the surface of the fiber sheet 110. In Figure 1, the second thermosetting resin composition 122 disposed on the surface forms a resin layer 120. The resin layer 120 in Figure 1 has resin particles 150.

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

[0021] The equivalent ratio of the curing agent in a thermosetting resin composition can be calculated using the following formula 1: Equivalent ratio of curing agent = (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 using the following formula 1': Equivalent ratio of curing agent = (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 limit the scope to theory, when the thermosetting prepreg relating to this disclosure as described above is subjected to thermosetting treatment, a relatively high crosslinking density of the thermosetting resin can be obtained within the fiber sheet, which is thought to improve the elasticity of the matrix resin and, as a result, improve the mechanical properties.

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

[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 including a conductive material, the conductivity of the thermosetting prepreg can be further improved. Furthermore, by including a thermoplastic resin, the handling properties of the thermosetting prepreg can be further improved. In particular, the handling properties of the thermosetting prepreg refer to the handling properties when automatically laminating multiple thermosetting prepregs (automatic lamination properties).

[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, particularly good tackiness can be obtained, and it is considered that particularly good handling properties (especially automatic lamination properties) of the thermosetting prepreg can be achieved.

[0027] In particular, the viscosity of the first thermosetting resin composition at 50°C is 500 to 10000 Pa·s, and the viscosity of the second thermosetting resin composition at 50°C is 100 to 1000 Pa·s.

[0028] The method for manufacturing the thermosetting prepreg according to this disclosure is not particularly limited, but it can be manufactured by the method for manufacturing the thermosetting prepreg according to this disclosure described below.

[0029] The method for producing a thermosetting prepreg according to this disclosure includes the following steps (a) and (b): (a) To provide 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 and containing a thermosetting resin and a curing agent, respectively, 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 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. 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, within a prepreg, for example, the fiber sheet portion and the resin layer portion require different functions, and therefore, the necessary physical properties for each also differ. Conventional methods have made it difficult to achieve such part-specific optimized physical properties.

[0031] In contrast, the method for producing a thermosetting prepreg according to this disclosure uses a precursor sheet containing multiple resin compositions having different compositions. That is, according to the manufacturing method according to this disclosure, a thermosetting prepreg is produced using a precursor sheet impregnated with multiple resin compositions having different compositions, making it possible to realize a thermosetting prepreg with site-specifically optimized physical properties.

[0032] Furthermore, in conventional methods for manufacturing thermosetting prepregs, when impregnating a fiber sheet with a resin composition, the degree of impregnation of the resin composition into the central part of the fiber sheet may decrease due to the impregnation properties of the resin composition. In particular, if the degree of impregnation of the curing agent in the central region of the fiber sheet is low, the mechanical properties of the fiber sheet may decrease.

[0033] In contrast, the above-mentioned method according to the present disclosure involves manufacturing a thermosetting prepreg by overlapping two thermosetting prepreg precursor sheets, and in doing so, overlapping the outer regions of the two outer regions in the thickness direction of the precursor sheet that have a resin composition with a relatively large equivalent ratio of curing agent. This method makes it possible to increase the amount of curing agent distributed in the center of the resulting thermosetting prepreg.

[0034] Figure 2 conceptually illustrates a manufacturing method according to one embodiment of the present disclosure. The thermosetting prepreg precursor sheet 200 in Figure 2 has 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 Figure 2, the second thermosetting resin composition 222 is arranged on the main surface of the fiber sheet 210 to form a resin layer 220. The resin layer 220 has resin particles 250. In the thermosetting prepreg precursor sheet 200 of Figure 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] In the method described in Figure 2, two thermosetting prepreg precursor sheets 200a and 200b are further superimposed 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 region are in contact with each other, either directly or through the resin composition. Preferably, after the two thermosetting prepreg precursor sheets 200a and 200b are superimposed, a process to integrate them, such as heating and pressurizing, can be performed.

[0036] According to the manufacturing method described herein, 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 region in the thickness direction.

[0037] The method for producing a thermosetting prepreg precursor sheet is not particularly limited, but it can be produced by the method for producing a thermosetting prepreg precursor sheet according to this disclosure, which includes the following steps: To provide a fiber sheet, To provide a first thermosetting resin composition comprising a thermosetting resin and a curing agent, To provide a second thermosetting resin composition comprising a thermosetting resin and a curing agent, The first thermosetting resin composition is placed on one main surface of the fiber sheet. The second thermosetting resin composition is placed on the other main surface of the fiber sheet, and The first thermosetting resin composition and the second thermosetting resin composition are impregnated into the fiber sheet, at least partially. 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] Figure 3 is a conceptual diagram showing one embodiment of the method for producing a thermosetting prepreg precursor sheet according to this disclosure.

[0039] In the method shown in Figure 3, a fiber sheet 310 having a first main surface 314 and a second main surface 316 is provided. A sheet 320 formed from a first thermosetting resin composition 322 is placed on the first main surface 314, and a sheet 330 formed from a second thermosetting resin composition 332 is placed on the second main surface 316. Here, 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. Note that the sheet 330 in Figure 3 contains resin particles 350.

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

[0041] This method allows for simultaneous impregnation of the fiber sheet with both the first and second thermosetting resin compositions. Compared to the case where the fiber sheet is impregnated with the first thermosetting resin composition first, and then with the second thermosetting resin composition, the impregnation of the fiber sheet with the second thermosetting resin composition can be further improved.

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

[0043] Thermosetting prepregs The thermosetting prepreg according to this disclosure comprises a fiber sheet, a first thermosetting resin composition, and a second thermosetting resin composition.

[0044] In relation to this disclosure, the fiber basis weight of the thermosetting prepreg is, for example, 50 to 1000 g / m². 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 this disclosure is, in particular, a reinforced fiber sheet composed of reinforcing fibers. The reinforced fiber sheet 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 slug fibers. Among these reinforcing fibers, carbon fibers, glass fibers, and aramid fibers are preferred, with carbon fibers being more preferred as they offer good specific strength and specific modulus, and provide a lightweight yet high-strength composite material. Among carbon fibers, polyacrylonitrile (PAN) carbon fibers, which have excellent tensile strength, are particularly preferred.

[0047] When carbon fiber is used as a reinforcing fiber, its tensile modulus is preferably 170 GPa to 600 GPa, and particularly preferably 220 GPa to 450 GPa. Furthermore, the tensile strength is preferably 3920 MPa or higher. While there is no particular upper limit to the tensile strength, it may be, for example, 10000 MPa or less. By using such carbon fiber, the mechanical properties of the composite material can be improved. The tensile strength and tensile modulus of carbon fiber can be measured according to the standard JIS R 7608, respectively.

[0048] Examples of fiber sheets include sheet-like materials made by aligning many fibers (especially reinforcing fibers) in one direction, two-way woven fabrics such as plain weave or twill weave, multi-axial woven fabrics, nonwoven fabrics, mats, knits, braids, and paper made by papermaking using fibers (especially reinforcing fibers).

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

[0050] The fiber sheet content in the thermosetting prepreg is preferably 40 to 80% by mass, more preferably 45 to 75% by mass, and even more preferably 50 to 70% by mass, relative to the total amount 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 region in the thickness direction.

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

[0053] (viscosity) Preferably, the viscosity of the first thermosetting resin composition at 50°C (V1 (unit: Pa·s)) is higher than the viscosity of the second thermosetting resin composition at 50°C (V2 (unit: Pa·s)), 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 10000 Pa·s, or 550 to 5000 Pa·s, more preferably 600 to 3000 Pa·s, or 600 to 2000 Pa·s, even more preferably 650 to 1500 Pa·s or 650 to 1000 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 obtained, and particularly good handling properties of the thermosetting prepreg can be obtained.

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

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

[0058] The first thermosetting resin composition and the second thermosetting resin composition each comprise at least a thermosetting resin and a curing agent. These resin compositions may further include 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, forming a three-dimensional molecular structure (e.g., a network structure). Thermosetting resins may include thermosetting monomers and / or oligomers, and / or prepolymers. Examples of thermosetting resins include epoxy resins and urethane resins, particularly epoxy resins. Thermosetting resins may be used individually or in combination of two or more types.

[0060] Epoxy resins crosslink and 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 aromatic groups in their molecules, and especially bifunctional or trifunctional or more functional epoxy resins having either a glycidylamine structure or a glycidyl ether structure. Alicyclic epoxy resins can also be mentioned.

[0061] Examples of epoxy resins having a glycidylamine 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 resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, and cresol novolac type epoxy resin.

[0063] These epoxy resins may, if necessary, have non-reactive substituents such as aromatic ring structures. 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 (such as chlorine and bromine).

[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 individually or in combination of two or more. Furthermore, as the epoxy resin, a so-called B-stage epoxy resin, which has been pre-reacted with a curing agent, can also be used. If both the first thermosetting resin composition and the second thermosetting resin composition contain epoxy resin as the thermosetting resin, they may be the same or different from each other.

[0066] Thermosetting resins can impart good mechanical properties and tackiness to thermosetting prepregs.

[0067] (Hardening agent) The curing agent is particularly a curing agent for thermosetting resins, such as an epoxy resin or a urethane resin. Examples of epoxy resin curing agents include dicyandiamide, various isomers of aromatic amine curing agents, and aminobenzoic acid esters. The curing agent may be one type or two or more types may be used in combination. Furthermore, the first thermosetting resin composition and the second thermosetting resin composition may have the same curing agent, or they may have different curing agents.

[0068] Dicyandiamide is preferred because it provides excellent storage stability for prepregs. Aromatic diamine compounds such as 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, and 4,4'-diaminodiphenylmethane, and their derivatives having non-reactive substituents, are particularly preferred from the viewpoint of providing a highly heat-resistant cured product. Examples of 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.).

[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 diaminodiphenylsulfone, but it is possible to obtain a composite material with particularly excellent tensile elongation.

[0070] Thermosetting resins and curing agents may have the effect of improving the mechanical properties (particularly elastic modulus 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 handling properties of the thermosetting prepreg and physical properties (especially 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 handling properties of the thermosetting prepreg and physical properties (especially 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 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 amount of 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 per 100 parts by mass of thermosetting resin.

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

[0076] The crosslink density (ρ crosslink ) (unit: mol / m 3 ) of the thermosetting resin in a cross-section perpendicular to the plane direction of the fiber sheet can be calculated by the rubber state equation shown in Equation (2) after measuring the glass transition temperature (Tg) of the cured product of the resin composition by DMA (dynamic viscoelasticity measurement). ρ crosslink = E’ / 3φRT Equation (2)

[0077] In Equation (2), E’ represents the storage modulus (unit: Pa) at Tg + 50° C., φ represents the front coefficient (here, φ = 1 (unit: dimensionless)), R represents the universal gas constant (8.31 J / K·mol), and T represents the temperature (unit: K) at Tg + 50° C.

[0078] The DMA measurement is performed using a dynamic viscoelasticity measurement device, for example, Rheogel-4000 (manufactured by UBM Co., Ltd.), under the conditions of a two-point bending mode, a strain amplitude of 5 μm, a heating rate of 5° C. / min, in air, and a 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 the thermosetting resin. In particular, the thermoplastic resin is an epoxy resin-soluble thermoplastic resin. Note that the resin composition may also contain an insoluble thermoplastic resin composition (particularly an epoxy resin-insoluble thermoplastic resin composition) that is insoluble in the thermosetting resin in addition to the soluble thermoplastic resin (particularly an epoxy resin-soluble thermoplastic resin). The thermoplastic resin may be used alone or in combination of two or more.

[0080] Thermoplastic resins can improve the impregnation of thermosetting resin compositions into fiber sheets. Furthermore, thermoplastic resins can improve the tackiness of thermosetting prepregs. Additionally, thermoplastic resins can improve the mechanical properties (particularly toughness) of the matrix resin of thermosetting prepregs.

[0081] The amount of thermoplastic resin in the resin composition is not particularly limited, but can be set according to the desired viscosity of the thermosetting resin composition. For example, the amount of thermoplastic resin in the first and second thermosetting resin compositions may be 1 to 60 parts by mass, and more 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 thermosetting resin (especially epoxy resin).

[0082] In one embodiment relating to this 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 epoxy resin-soluble thermoplastic resin) per 100 parts by mass of a thermosetting resin (particularly epoxy resin). and / or, The second thermosetting resin composition may contain, per 100 parts by mass of a thermosetting resin (particularly an 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) An epoxy resin-soluble thermoplastic resin is a thermoplastic resin that can be partially or completely dissolved in epoxy resin by heating or other means. Preferably, the epoxy resin-soluble thermoplastic resin is a resin that dissolves in epoxy resin at 190°C in an amount of 80% by mass or more. Examples of epoxy resin-soluble thermoplastic resins include polyethersulfone, polysulfone, polyetherimide, and polycarbonate. These may be used individually or in combination of two or more. Insoluble thermoplastic resin compositions (epoxy resin-insoluble thermoplastic resin compositions) will be described later.

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

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

[0086] (Conductive material) The presence of conductive materials within the fiber sheet, and particularly within the resin layer, can improve the conductivity of the thermosetting prepreg.

[0087] The conductive material can be any particles that behave as good electrically conductive particles, and is not particularly limited, but it is preferable that it can be dispersed in the resin composition and improve the conductivity of the thermosetting prepreg.

[0088] The conductive material is, in particular, conductive particles. The conductive particles preferably have a volume resistivity of 10 to 10 -9 It is Ωcm, and more preferably 1 to 10 -9 It is Ωcm, and particularly preferably 10 -1 ~10 -9It is a particle with an area of ​​Ωcm.

[0089] Examples of conductive particles include conductive polymer particles, carbon particles, metal particles, coated conductive particles, and carbon fiber particles. These can be used individually or in combination.

[0090] Examples of conductive polymer particles include polyacetylene particles, polyaniline particles, polypyrrole particles, polythiophene particles, polyisothianaphthene particles, and polyethylene dioxythiophene particles.

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

[0092] While the metal particles are not particularly limited, when carbon fibers are used as reinforcing fibers, from the viewpoint of preventing corrosion due to potential differences with the carbon fibers, particles of platinum, gold, silver, copper, tin, nickel, titanium, cobalt, zinc, iron, chromium, and aluminum, particles of alloys mainly composed of these metals, 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 mainly composed of these metals are more preferred due to their high conductivity and stability, with silver, copper, and nickel particles being 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 is preferably of a size that allows it to diffuse into the fiber sheet as it is impregnated with the resin composition. The conductive material is preferably particulate (i.e., conductive particles) and has an average particle diameter 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] Conductive particles with a relatively small particle size (for example, a particle size of 1 μm or less) are thought to further improve the conductivity of composite materials molded from prepregs, as the conductive particles are dispersed in both the fiber sheet and the resin layer.

[0096] The average particle size of conductive materials is the 50% particle size (D) of the particle size distribution measured using a laser diffraction / scattering particle size distribution analyzer. 50 This refers to the value of ).

[0097] The content of conductive material (especially 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 thermosetting resin (especially epoxy resin) contained in the resin composition. When the content is 0.01 parts 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 becoming excessively high, and good handling of the prepreg can be ensured.

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

[0099] (Additional conductive material) The thermosetting prepreg may have additional conductive materials in addition to the conductive materials described above. These additional conductive materials are intended to be present, in particular, in a second thermosetting resin composition (particularly a resin layer described below) present on the surface of the fiber sheet. In other words, in one embodiment of the present disclosure, the second thermosetting resin composition disposed on the surface of the fiber sheet contains additional conductive materials.

[0100] Additional conductive materials include carbon fibers, pitch carbon fibers, milled fibers (especially carbon milled fibers), and silver aggregates. These can be used individually 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 is less likely to penetrate into the fiber sheet, resulting in it being more likely 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 images acquired using an electron microscope or optical microscope, and averaging the measured values. If the additional conductive material is granular, its average diameter or average particle size can be used as the average length.

[0103] If both the first thermosetting resin composition and the second thermosetting resin composition contain additional conductive materials, they may be identical to each other or different from each other.

[0104] (Resin layer) In one embodiment of the thermosetting prepreg according to this disclosure, the second thermosetting resin composition is impregnated into the outer region of the fiber sheet and also disposed on the surface of the fiber sheet. In particular, the second thermosetting resin composition forms 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 more preferably directly laminated on the main surface of the fiber sheet.

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

[0107] (Resin particles) A second thermoplastic resin composition (particularly a resin layer) disposed on the surface of a fiber sheet may contain resin particles. The resin particles are preferably dispersed in the resin layer. These resin particles can be present in the resin layer between fiber sheets in a laminate made 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 composite materials (particularly carbon fiber reinforced composite materials) formed from thermosetting prepregs.

[0109] The resin particles contained in the resin layer may be composed of a thermoplastic resin. Preferably, the resin particles are poorly soluble in thermosetting resins, and in particular, they are composed of an epoxy resin-insoluble thermoplastic resin.

[0110] (Epoxy resin-insoluble thermoplastic resin) Epoxy resin-insoluble thermoplastic resins refer to thermoplastic resins that do not substantially dissolve in epoxy resin at or below the temperature at which composite materials are molded. In particular, they refer to thermoplastic resins in which the particle size does not change when resin particles are added to epoxy resin and stirred at the temperature at which composite materials are formed. Generally, the temperature at which composite materials are molded is 100 to 190°C.

[0111] Examples of epoxy resin-insoluble thermoplastic resins include polyamides, polyacetals, polyphenylene oxides, polyphenylene sulfides, polyesters, polyamide-imides, polyimides, polyether ketones, polyether ether ketones, polyethylene naphthalates, polyether nitriles, and polybenzimidazoles. Among these, polyamides, polyamide-imides, and polyimides are preferred due to their high toughness and heat resistance. These may be used individually or in combination of two or more. Copolymers of these resins can also be used.

[0112] In particular, amorphous polyimides, nylon 6® (a polyamide obtained by the ring-opening polycondensation reaction of caprolactam), nylon 12® (a polyamide obtained by the ring-opening polycondensation reaction of lauryl lactam), and amorphous nylon® can be used. By using these polyamides, particularly good heat resistance can be obtained in composite materials.

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

[0114] The average particle size of resin particles can be measured using a laser diffraction / scattering particle size distribution analyzer.

[0115] (Other ingredients) The thermosetting resin composition may contain other components as long as they do not impair the purpose 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 phosphoniums, curing accelerators such as N,N-dimethylurea derivatives, reactive diluents, fillers, antioxidants, flame retardants, pigments, and various other additives. These other components are preferably present in an amount of 5% by mass or less, or 1% by mass or less, relative to the thermosetting resin composition.

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

[0117] <Laminate> A laminate can be formed by laminating the thermosetting prepregs according to this disclosure and optionally performing a thermosetting treatment. This laminate is particularly a fiber-reinforced composite material, and 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 manufactured by conventionally known methods, such as manual layup, automated tape layup (ATL), automated fiber placement, vacuum bagging, autoclave curing, non-autoclave curing, fluid-assisted processing, pressure-assisted processes, match-molding processes, simple press curing, pressclave curing, and continuous hand presses.

[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 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. The lower limit of the thickness-direction conductivity is not particularly limited, but may be, for example, 0.1 Ω·cm or more or 1.0 Ω·cm or more.

[0122] ≪Method for manufacturing thermosetting prepregs≫ The method for producing the thermosetting prepreg according to this disclosure is not particularly limited. The thermosetting prepreg according to this disclosure can be produced, for example, by producing thermosetting prepreg precursor sheets according to the manufacturing method described below, and stacking the thermosetting prepreg precursor sheets.

[0123] <Method for producing thermosetting prepregs by stacking precursor sheets> One embodiment of the method for producing a thermosetting prepreg according to this disclosure includes the following steps (a) and (b): (a) To provide a thermosetting prepreg precursor sheet (precursor provision step), wherein the precursor sheet comprises a fiber sheet and first and second thermosetting resin compositions impregnated into the fiber sheet and containing a thermosetting resin and a curing agent, respectively, wherein in a cross section perpendicular to the plane direction of the fiber sheet, the first thermosetting resin composition is impregnated into a first outer region in the thickness direction of the fiber sheet, and the second thermosetting resin composition is impregnated into 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 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, thereby forming 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 provisioning step, one or more (particularly two) thermosetting prepreg precursor sheets are provided. The fiber sheets, the first thermosetting resin composition, and the second thermosetting resin composition contained in the thermosetting prepreg precursor sheet can be described in the above-mentioned description of the thermosetting prepreg.

[0125] (Overlay process) In the overlapping process, 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] In other words, in a 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 prepregs are oriented away from each other.

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

[0128] Preferably, when the two precursor sheets are stacked on top of each other in the stacking process, it is preferable to align the fiber directions of the fiber sheets in the precursor sheets. 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 in the two precursor sheets substantially in the same direction. By doing so, it may be possible to reduce or substantially eliminate the resin composition remaining between the two stacked precursor sheets.

[0129] Preferably, during the superposition described above, the amount of resin composition present between the two first outer regions of the two thermosetting prepreg precursor sheets is reduced. More preferably, there is substantially no resin composition 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, thereby allowing the fiber sheets of the two thermosetting prepreg precursor sheets to come into contact with each other.

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

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

[0132] A method for manufacturing a thermosetting prepreg according to this disclosure may include a step of placing release paper or a polymer film on both sides or one side (one or two main surfaces) of the thermosetting prepreg. That is, in one embodiment of this disclosure, the thermosetting prepreg obtained by stacking two thermosetting prepreg precursor sheets may be provided in a state in which both sides or one side are covered with release paper or a polymer film. The release paper or polymer film may be placed such that both sides or one side (one or two main surfaces) of the thermosetting prepreg are entirely covered. Examples of polymer films include polyethylene films.

[0133] <Method for producing thermosetting prepreg precursor sheets> The thermosetting prepreg precursor sheet that can be used in the above method can be manufactured by the following method: Providing a fiber sheet (sheet provisioning process) To provide a first thermosetting resin composition comprising a thermosetting resin and a curing agent (step of providing the first resin composition), To provide a second thermosetting resin composition comprising a thermosetting resin and a curing agent (step of providing the second resin composition), The first thermosetting resin composition is placed on one main surface of the fiber sheet (first resin composition placement step). The process involves placing a second thermosetting resin composition on the other main surface of the fiber sheet (second resin composition placement step), and The first thermosetting resin composition and the second thermosetting resin composition are impregnated, at least partially, into a fiber sheet 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 supply process, a fiber sheet is provided. For details regarding the fiber sheet, please refer to the description of the thermosetting prepreg above. The thickness of this fiber sheet may be 0.01-1.8 mm, 0.02-1.5 mm, or 0.04-1.1 mm. The basis weight of this fiber sheet may be 25-500 g / m². 2 It is fine to have a density of 50-400g / m². 2 Preferably, 100-300 g / m 2 This is preferable.

[0135] (First resin composition providing step, second resin composition providing step) The first resin composition providing step and the second resin composition providing step provide a first thermosetting resin composition and a second thermosetting resin composition, 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, refer to the above description of thermosetting prepregs.

[0136] Thermosetting resin compositions can be manufactured by kneading their constituent components. The kneading temperature is adjusted as appropriate, taking into account the viscosity, thermal properties, and curing temperature of the resins being blended, but it is preferably below the curing start temperature and between 50 and 120°C. Kneading may be carried out in one stage or in multiple stages. The mixing order of the constituent components of the resin composition is not particularly limited.

[0137] For mixing, known mixing machinery and equipment can be used, such as roll mills, planetary mixers, kneaders, extruders, and Banbury mixers.

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

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

[0140] Specifically, for example, a sheet of thermosetting resin composition can be produced by applying and drying the prepared thermosetting resin composition onto release paper using a film coater, forming it into a sheet, and then peeling it off the release paper.

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

[0142] The thickness of the resin sheet is preferably 2 to 500 μm, and more preferably 5 to 100 μm. The basis weight of the resin sheet is 10 to 200 g / m². 2 It is acceptable for it to be 20-100g / m² 2 Preferably, 30-75 g / m2 This is preferable.

[0143] Preferably, the viscosity of the first thermosetting resin composition at 50°C (V1 (unit: Pa·s)) is higher than the viscosity of the second thermosetting resin composition at 50°C (V2 (unit: Pa·s)), 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 10000 Pa·s, or 550 to 5000 Pa·s, more preferably 600 to 3000 Pa·s, or 600 to 2000 Pa·s, even more preferably 650 to 1500 Pa·s or 650 to 1000 Pa·s, and most preferably 700 to 900 Pa·s.

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

[0146] (First resin composition placement step, second resin composition placement step) In the first resin composition placement step and the second resin composition placement step, the first thermosetting resin composition and the second thermosetting resin composition are placed on the first main surface and the second main surface 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 a resin film) can be laminated on the main surface of the fiber sheet, and in particular, they can be laminated directly.

[0147] When the first thermosetting resin composition and the second thermosetting resin composition are in sheet form, the basis weight M1 (g / m²) of the sheet-like first thermosetting resin composition is... 2The basis weight M2 (g / m²) of the sheet-like second thermosetting resin composition. 2 The ratio (M1 / M2) to ) may be 0.25 to 4.0, preferably 0.3 to 3.0 or even more preferably 0.5 to 2.0.

[0148] In one embodiment of the present invention, the basis weight (g / m²) of the sheet-like first thermosetting resin composition is 2 )M1 is the basis weight (g / m²) of the second thermosetting resin composition in sheet form. 2 ) is greater than M2. In this case, a prepreg exhibiting particularly good prepreg tack and composite compression characteristics 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 / m²) of the sheet-like first thermosetting resin composition is specified. 2 )M1 is the basis weight (g / m²) of the second thermosetting resin composition in sheet form. 2 ) is smaller than M2. In this case, a prepreg exhibiting particularly good composite impact compressive strength may be obtained. Also, in this case, particularly excellent conductivity (especially 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 process, the first thermosetting resin composition and the second thermosetting resin composition are impregnated into the fiber sheet, at least partially.

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

[0152] In this impregnation process, for example, the intermediate laminate obtained through the first resin composition placement process and the second resin composition placement process described above, 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, is impregnated with the resin composition by applying heat and pressure as desired. For the application of heat and pressure, a heat press may be performed using, for example, a heat roller, and impregnation can be performed, for example, by heating the intermediate laminate and passing it between two rollers.

[0153] The heating temperature for the impregnation treatment can be appropriately determined considering the viscosity, curing temperature, etc., of the thermosetting resin composition. If the thermosetting resin composition contains 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 pressurizing conditions for the impregnation treatment can be appropriately determined considering the viscosity of the thermosetting resin composition, the curing temperature, etc. Preferably, the pressurizing conditions for the impregnation treatment are 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 performed once or multiple times.

[0157] In the impregnation process, 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 thereon. To this end, the basis weight of the fiber sheet, the heating and pressurizing 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 interlayer particles to the thermosetting resin composition.

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

[0160] Specifically, this method is: Providing a fiber sheet (sheet provisioning process) To provide a first thermosetting resin composition comprising a thermosetting resin and a curing agent (step of providing the first resin composition), To provide a second thermosetting resin composition comprising a thermosetting resin and a curing agent (step of providing the second resin composition), The first thermosetting resin composition is placed on the main surface of the fiber sheet (first resin composition placement step). Impregnating the fiber sheet at least partially with the first thermosetting resin composition (first resin composition impregnation step), The process involves placing a second thermosetting resin composition on the main surface of the fiber sheet impregnated with the first thermosetting resin composition (second resin composition placement step), and The second thermosetting resin composition is impregnated at least partially into the fiber sheet 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 supply process) In the sheet supply process, a fiber sheet is provided. For details regarding the fiber sheet, please refer to the description of the thermosetting prepreg above. The thickness of this fiber sheet may be 0.01-4.0 mm, 0.05-2.0 mm, or 0.1-1.0 mm. The basis weight of this fiber sheet may be 70-600 g / m². 2 It is fine to have 100-500g / m² 2 Preferably, 200-450 g / m 2 This is preferable.

[0162] (Sequential impregnation method: first resin composition provisioning step, second resin composition provisioning step) The first resin composition providing step and the second resin composition providing step provide a first thermosetting resin composition and a second thermosetting resin composition, 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 details of the resin compositions and their components, refer to the above description of thermosetting prepregs.

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

[0164] (Sequential impregnation method: First resin composition placement step) In the first resin composition placement step, the first thermosetting resin composition is placed on the first main surface and / or second main surface (preferably on the first and second main surfaces) of the fiber sheet. In this step, for example, two sheet-like (e.g., in the form of resin films) 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 first thermosetting resin composition is impregnated into the fiber sheet, at least partially. In this step, for example, heat and pressure are applied to the fiber sheet (first intermediate laminate) on which the sheet of the first thermosetting resin composition is arranged on both main surfaces to impregnate it with the resin composition. For the application of heat and pressure, a heat press may be performed using, for example, a heat roller, and impregnation can be performed, for example, by heating the first intermediate laminate and passing it between two rollers.

[0166] (Sequential impregnation method: Second resin composition placement step) In the second resin composition placement step, the second thermosetting resin composition is placed on the first main surface and / or second main surface (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 sheet-like (e.g., in the form of a resin film) second thermosetting resin compositions 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 second thermosetting resin composition is impregnated into the fiber sheet, at least partially. In this step, heat and pressure are applied to the fiber sheet (second intermediate laminate), which is impregnated with the first thermosetting resin composition and has sheets of the second thermosetting resin composition on both sides, to impregnate it with the resin composition. For example, heat pressing using a hot roller may be performed to apply heat and pressure, and impregnation can be performed, for example, by passing the sheet between two rollers while heating it.

[0168] According to the above method, a resin composition having a relatively low equivalent ratio of curing agent is impregnated into the outer region of a fiber sheet impregnated with a resin composition having a relatively high equivalent ratio of curing agent. As a result, the thermosetting prepreg according to this disclosure, having a relatively large equivalent ratio of curing agent in the central region, can be manufactured.

[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 impregnation of the additional resin composition into the fiber sheet is hindered by the resin composition already impregnated in the fiber sheet.

[0170] In contrast, to sufficiently impregnate a 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 may exist in the fiber sheet into which the second thermosetting resin composition can be impregnated, making it relatively easy to impregnate the fiber sheet with the second thermosetting resin composition.

[0171] For this purpose, for example, 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 relative to the fiber sheet, 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.

[0172] Furthermore, for example, the total basis weight (g / cm²) of the sheets of the first thermosetting resin composition placed on the fiber sheet in the first resin composition placement step. 2 ) is the basis weight (g / cm²) of the fiber sheet. 2 ) 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 70-140°C and the pressurizing conditions to 9.8-245 N / cm. It is believed that performing the impregnation treatment under these conditions reduces the viscosity of the thermosetting resin composition and promotes the impregnation of the second thermosetting resin composition. [Examples]

[0174] 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> For viscosity measurement, a rheometer (product name: ARES-G2) manufactured by TA Instruments Inc. was used, with a 25 mm diameter parallel plate and a resin composition thickness of 0.5 mm between the parallel plates. Viscosity measurements were performed up to 180°C at an angular velocity of 10 radians / second and a heating rate of 2°C / min. The resin viscosity was then determined from the temperature-viscosity curve.

[0176] <Impregnation level> The impregnation level of the prepreg, i.e., the degree to which the resin composition is impregnated into the fiber sheet, can be determined by measuring the water per unit (WPU) based on a water absorption test. Specifically, the following steps are followed: Cut a 1-ply prepreg to 100mm x 100mm. After removing the backing paper, measure the mass (W1) of one ply of prepreg for each sample. Next, firmly fix this prepreg in the WPU apparatus so that the 0° fiber direction is perpendicular to the water surface. When positioning the fixed prepreg vertically in the apparatus, immerse 5mm of the prepreg in room temperature water in a laboratory environment of 23°C and 50% relative humidity. After 5 minutes of immersion, remove the sample from the water, remove any excess water from the outside, measure the mass (W2) of the sample again, and obtain the percentage of water absorption from the initial state (WPU) using the following formula (3). WPU=(W1−W2) / W1 Formula (3) The percentage of water absorption (WPU) was calculated by averaging the weights measured for three samples. The samples were then evaluated according to the following criteria. ◎: WPU usage is less than 3% ○: WPU usage is between 3% and 5% △: WPU usage is between 5% and 10% ×: WPU usage is 10% or higher

[0177] <Tuckiness> The tackiness of the prepreg was evaluated using a tacking test apparatus (manufactured by Resca Co., Ltd., product name: TAC-II). Specifically, the prepreg was set on a test stage maintained at 27°C, and an initial load of 100gf was applied using a Φ5 stainless steel cylindrical tack probe maintained at 27°C. The maximum load (F0 and F) when the probe was pulled out at a test speed of 10mm / sec was measured. 14 ) was sought. Prepreg immediately after manufacturing (F0) and prepreg stored at 26.7°C and 65% humidity for 14 days (F 14 A tack probe test was performed on each of the following. 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. ○: 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 is 500gf or more, and the tack retention rate after 14 days of storage is 25% or more but less than 50%. ×: The load immediately after manufacturing is 500gf or more, and the tack retention rate after 14 days of storage is less than 25%.

[0178] <Compression characteristics> The compression characteristics were determined as follows: The prepreg is cut into 360mm squares, laminated, and constructed as a laminate [+45 / 0 / -45 / 90]. nS A laminate was obtained. Using a standard vacuum autoclave molding method, it was molded at a pressure of 0.59 MPa and a temperature of 180°C for 2 hours. The obtained molded material was cut to dimensions of 38.10 mm in width and 304.8 mm in length to prepare test specimens, and then a 6.35 mm diameter hole was drilled in the center of each specimen to obtain a specimen for perforated compressive strength (OHC) testing. Using this specimen, the compressive strength (OHC) was measured according to SACMA SRM 3R-94. The crosshead speed of the specimen compression tester was set to 1 mm / min, and measurements were taken on five specimens.

[0179] <Post-impact compressive strength> The post-impact compressive strength was determined as follows: The prepreg is cut into 360mm squares, laminated, and constructed as a laminate [+45 / 0 / -45 / 90]. nS A laminate was obtained. It was molded using a standard vacuum autoclave molding method at a pressure of 0.59 MPa and a temperature of 180°C for 2 hours. The obtained molded material was cut to dimensions of 100 mm wide x 150 mm long to obtain test specimens for post-impact compressive strength (CAI) testing. Using these test specimens, the CAI was measured after damaging them by applying a 30 J impact according to SACMA SRM 2R-94. The crosshead speed of the specimen compression tester was set to 1 mm / min, and measurements were taken on five test specimens.

[0180] <Conductivity in the thickness direction> The conductivity (volume resistivity) in the thickness direction was determined by measuring the volume resistivity in the Z direction (thickness direction) of a composite material manufactured as described below, using a digital ohmmeter (AX-111A, manufactured by Addex-Yell Co., Ltd.). Volume resistivity is the intrinsic resistivity of a given material. The volume resistivity ρ in the Z direction of the material was calculated using the following formula. ρ = RA / L R: Electrical resistance (Ω) of a uniform test specimen from the material. L: Thickness of the test specimen (m) A: Cross-sectional area of ​​the test specimen (m²) 2 )

[0181] The composite was manufactured and its conductivity in the thickness direction was measured as follows: Prepreg is cut and laminated, resulting in a laminated structure [+45 / 0 / -45 / 90] 2SA laminate was obtained. Using the vacuum autoclave molding method, it was molded under a pressure of 0.59 MPa and a temperature of 180°C for 2 hours. The obtained molded material was cut to dimensions of 40 mm wide x 40 mm long, and the top and bottom surfaces of the molded material were polished with sandpaper until the carbon fibers were exposed. Finally, the surface was finished with 2000 grit sandpaper. After that, the unpolished sides were covered with fluorine tape, and the polished top and bottom surfaces were copper plated using an electrolytic plating method with copper sulfate as the electrolyte and copper as the electrode plate. The resulting test piece was sandwiched between gold-plated electrodes measuring 50 mm wide x 50 mm long, and a load of 0.06 MPa was applied to the test piece. The resistance value in the Z direction was measured using a digital ohmmeter, and the conductivity in the thickness direction was determined from the above formula.

[0182] 〔component〕 The components of 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, Huntsman, product name: MY0600)

[0183] (Hardening agent (amine-based hardening agent)) B-1: 4,4-diaminodiphenylsulfone (hereinafter abbreviated as "44DDS") (manufactured by Wakayama Seika Kogyo Co., Ltd., product name: Seika Cure-S) B-2: 3,3'-Diaminodiphenylsulfone (hereinafter abbreviated as "33DDS") (manufactured by Konishi Chemical Industry Co., Ltd., product name: 33DAS) B-3: 3,3'-Diaminodiphenylsulfone 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: Sumika Excel 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 size 9.5 nm) E-2: Carbon nanostructures (hereinafter abbreviated as "CNS") (Manufactured by Cabot, product name: Athlos SR1200 CNS, average particle size 10-20 nm) E-3: Milled Fiber (Manufactured by 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®" 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 5200 MPa, tensile modulus 280 GPa, manufactured by Teijin Limited)

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

[0189] <Example 1> (Preparation of resin composition 1) In a mixing device, TGDDM (70 parts by mass), DGBPA (25 parts by mass), and GAN (5 parts by mass), all epoxy resins, were mixed with PES (18 parts by mass), an epoxy resin-soluble thermoplastic resin. The mixture was stirred at 120°C for 60 minutes using a planetary mixer to completely dissolve the PES in the epoxy resin. After that, the resin temperature was cooled to 80°C or below to prepare the epoxy resin composition. Subsequently, using a roll mill, the curing agents shown in Table 1 below (total 40 parts by mass) were added to the resin and mixed to prepare resin composition 1.

[0190] (Preparation of a sheet of resin composition 1) The prepared resin composition 1 was applied onto release paper using a film coater, at a rate of 48 g / m². 2 A sheet (resin film) of resin composition 1 was prepared.

[0191] (Preparation of resin composition 2) In a mixing device, TGDDM (70 parts by mass), DGBPA (25 parts by mass), and GAN (5 parts by mass), all epoxy resins, were mixed with PES (15 parts by mass), an epoxy resin-soluble thermoplastic resin, 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. After that, the resin temperature was cooled to 80°C or below to prepare the epoxy resin composition. Subsequently, using a roll mill, the curing agents shown in Table 1 below (total 34 parts by mass) were added to the resin and mixed to prepare resin composition 2.

[0192] (Preparation of a sheet of resin composition 2) The prepared resin composition 2 was applied onto the release paper using a film coater, at a rate of 48 g / m². 2 A sheet (resin film) of resin composition 2 was prepared.

[0193] (Preparation of thermosetting prepreg precursor sheets) Next, a carbon fiber sheet was prepared by arranging carbon fiber bundles (manufactured by Teijin, product name: IMS65) in one direction as reinforcing fibers. The sheet of resin composition 1 and the sheet of resin composition 2 prepared above were then placed on opposite sides of the carbon fiber sheet. Subsequently, the carbon fiber sheet was impregnated with resin composition 1 and resin composition 2 by heating and pressurizing it at 110°C and 15 N / cm using a hot roller, resulting in a carbon fiber basis weight of 190 g / m². 2 Then, a unidirectional prepreg precursor sheet (thermosetting prepreg precursor sheet according to Example 1) with a matrix resin mass fraction of 35.0% was prepared.

[0194] Two of the thermosetting prepreg precursor sheets prepared as described above are prepared, and the sides of their main surfaces impregnated with resin composition 1 are placed facing each other. The two precursor sheets are then heated and pressurized using a hot roller at 50°C and 15 N / cm to fuse them together, resulting in a carbon fiber basis weight of 380 g / m². 2 A unidirectional prepreg sheet (thermosetting prepreg according to Example 1) with a matrix resin mass fraction of 35.0% was then prepared. The evaluation results of the properties of the prepreg according to Example 1 are shown in Table 1 below.

[0195] A composite material was manufactured using the thermosetting prepreg described in Example 1. Specifically, 24 layers of the thermosetting prepreg described in Example 1 were laminated in a [45° / 0° / -45° / 90°] 3s configuration, and the composite material was manufactured by thermosetting treatment. The results of the property evaluation of the obtained composite material are shown in Table 1 below.

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

[0197] <Example 2B> A thermosetting prepreg according to Example 2B was manufactured in the same manner as in Example 2A, except that the amount of interlayer particles and the basis weight of resin compositions 1 and 2 were changed as shown in Table 1 below. A composite material was manufactured using the obtained thermosetting prepreg according to Example 2B in the same manner as in Example 1 above. The results of the property evaluation for the obtained prepreg and composite material are shown in Table 1 below.

[0198] <Example 3> A thermosetting prepreg according to Example 3 was manufactured in the same manner as in Example 1, except that the composition of the resin composition was changed to the types and amounts of additives listed in Table 1 below. A composite material was manufactured using the obtained thermosetting prepreg in the same manner as in Example 1 above. The results of the property evaluation for the obtained prepreg and composite material are shown in Table 1 below.

[0199] <Example 4> (Preparation of resin composition 1') In a mixing device, TGDDM (45 parts by mass), DGBPA (50 parts by mass), and GAN (5 parts by mass), all epoxy resins, were mixed with PES (20 parts by mass), an epoxy resin-soluble thermoplastic resin. The mixture was stirred at 120°C for 60 minutes using a planetary mixer to completely dissolve the PES in the epoxy resin. After that, the resin temperature was cooled to 80°C or below to prepare the epoxy resin composition. Subsequently, using a roll mill, the curing agents shown in Table 1 below (totaling 36 parts by mass) were added to the resin and mixed to prepare resin composition 1'.

[0200] (Preparation of a sheet of resin composition 1') The prepared resin composition 1' was applied onto release paper using a film coater, resulting in a density of 68 g / m². 2 A sheet of resin composition 1' was prepared.

[0201] (Preparation of resin composition 2') In a mixing device, TGDDM (45 parts by mass), DGBPA (50 parts by mass), and GOT (5 parts by mass), all epoxy resins, were mixed with PES (20 parts by mass), an epoxy resin-soluble thermoplastic resin, 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. After that, the resin temperature was cooled to 80°C or below to prepare the epoxy resin composition. Subsequently, using a roll mill, the curing agents shown in Table 1 below (total 32 parts by mass) were added to the resin and mixed to prepare resin composition 2'.

[0202] (Preparation of a sheet of resin composition 2') The prepared resin composition 2' was applied onto release paper using a film coater, resulting in a density of 68 g / m². 2 A sheet of resin composition 2' was prepared.

[0203] (Preparation of thermosetting prepreg precursor sheets) Next, a carbon fiber sheet was prepared by arranging bundles of carbon fibers (manufactured by Teijin, product name: IMS65) as reinforcing fibers in one direction. The sheet of resin composition 1' and the sheet of resin composition 2' prepared above were then placed on opposite sides of the carbon fiber sheet. Subsequently, the carbon fiber sheet was impregnated with resin composition 1' and resin composition 2' by heating and pressurizing it at 110°C and 15 N / cm using a hot roller, resulting in a carbon fiber basis weight of 260 g / m². 2 Then, a unidirectional prepreg precursor sheet (thermosetting prepreg precursor sheet according to Example 4) with a matrix resin mass fraction of 35.0% was prepared.

[0204] Two prepared thermosetting prepreg precursor sheets were overlapped such that the sides impregnated with the resin composition 1' faced each other among their main surfaces, and the two precursor sheets were integrated by heating and pressing under the conditions of 80 °C and 50 N / cm using a hot roller, and a unidirectional prepreg sheet (thermosetting prepreg according to Example 4) with a carbon fiber basis weight of 520 g / m 2 was produced, in which the mass fraction of the matrix resin was 35.0%.

[0205] A composite material was produced using the thermosetting prepreg according to Example 4. Specifically, 16 layers of the thermosetting prepreg according to Example 4 were laminated with a stacking configuration of [45° / 0° / -45° / 90°] 2s and subjected to a thermosetting treatment to produce a composite material. 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 above, except that the content of the curing agent was changed as shown in Table 1 below. Using the prepared thermosetting prepreg, a composite material (composite) 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 and dried on a release paper using a film coater to form a sheet, peeled off from the release paper, and two sheets of the resin composition 1 with a basis weight of 96 g / m 2 were produced.

[0209] Next, two sheets of the resin composition 1 prepared above were placed on both sides of a carbon fiber sheet, which had carbon fiber bundles of carbon fiber (manufactured by Teijin, product name: IMS65) arranged in one direction as reinforcing fibers. Then, the resin composition 1 was impregnated into the carbon fiber sheet by heating and pressurizing it at 110°C and 15 N / cm using a hot roller, resulting in a carbon fiber basis weight of 380 g / m². 2 A unidirectional prepreg sheet (thermosetting prepreg related to Comparative Example 2) was prepared, with a matrix resin mass fraction of 35.0%. The evaluation results of the properties of the prepreg related to Comparative Example 2 are shown in Table 1 below.

[0210] Using the thermosetting prepreg prepared for Comparative Example 2, a composite material was manufactured in the same manner as in Example 1 above, and its properties were evaluated. 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 above, except that a sheet of resin composition 2 was used instead of a sheet of resin composition 1. A composite material was manufactured using the prepared thermosetting prepreg in the same manner as in Example 1 above. 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 preferred handling properties (impregnation level and tackiness) due to the resin with a smaller equivalent ratio of curing agent, as well as preferred mechanical properties (compression properties and post-impact compression properties) due to the resin with a larger equivalent ratio of curing agent, compared to the thermosetting prepregs of Comparative Examples 2 and 3, which were manufactured using only one resin composition.

[0214] Furthermore, the thermosetting prepreg of Comparative Example 1 exhibited inferior mechanical properties compared to Examples 1-4. 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 that of the curing agent in the second resin composition impregnated in the outer region. Although there is no intention to limit the theory, it is thought that in Comparative Example 1, sufficient crosslinking density of the thermosetting resin in the central region could not be secured, resulting in insufficient mechanical properties.

[0215] <<Example 5>> A thermosetting prepreg according to Example 5 was manufactured and its physical properties were evaluated. In Example 5, only one fiber sheet was used to manufacture the prepreg as described below.

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

[0217] The prepared resin composition 1 is applied to release paper using a film coater, dried, and formed into a sheet. After peeling it off the release paper, it has a basis weight of 48 g / m². 2 Two sheets of 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. After peeling it off the release paper, it was processed to a basis weight of 48 g / m². 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, which had carbon fiber bundles of carbon fiber (manufactured by Teijin, product name: IMS65) arranged in one direction as reinforcing fibers. Then, the resin composition 1 was impregnated into the carbon fiber sheet by heating and pressurizing it at 110°C and 15 N / cm using a hot roller, resulting in a carbon fiber basis weight of 380 g / m². 2 Then, a unidirectional prepreg sheet with a matrix resin mass fraction of 20.5% was prepared.

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

[0222] Using the produced thermosetting prepreg according to Example 5, a composite material (composite) was manufactured in the same manner as in Example 1 above, and its properties were evaluated. The properties of the obtained composite material are described in Table 2 below.

[0223]

Table 2

[0224] As can be seen from Table 2, the prepreg according to Example 5, which was impregnated with the resin composition 1 having a relatively large curing agent equivalent ratio and then further impregnated with the resin composition 2 having a relatively small curing agent equivalent ratio, showed good prepreg properties and composite properties compared with Comparative Example 2 and Comparative Example 3 using only a single resin composition. Although not intended to be limited by theory, these effects of Example 5 are considered to be brought about by using two types of resin compositions with different curing agent contents, etc. In particular, in the prepreg of Example 5, the crosslink density of the thermosetting resin in the central region became relatively high, and as a result, it is considered that good mechanical properties were shown. In addition, when manufacturing Example 5, since the amount of the resin composition 1 impregnated into the fiber sheet was relatively reduced, the resin composition 2 was impregnated relatively well into the fiber sheet impregnated with the resin composition 1.

[0225] ≪Examples 6A and 6B and Examples 7 to 11≫ In Examples 6A and 6B, and Examples 7-11, the effects of adding a conductive material were evaluated.

[0226] <Example 6A> A thermosetting prepreg according to Example 6A was manufactured in the same manner as in Example 1, except that the resin composition was prepared with the components and quantities listed in Table 3 below, and the type of carbon fiber used as reinforcing fiber was changed (Teijin Corporation, product name: ITS55 E23 24K). A composite material was manufactured using the obtained thermosetting prepreg according to Example 6A in the same manner as in Example 1 above. The results of the property evaluation of the obtained prepreg and composite material are shown in Table 3 below.

[0227] <Example 6B> The basis weight M1 (g / m²) of the sheet-like resin composition 1. 2 ) and the basis weight M2 (g / m²) of the sheet-like thermosetting resin composition 2 2 Except for changing the ratio (M1 / M2) to 0.57, the thermosetting prepreg for Example 6B was manufactured in the same manner as in Example 6A, and evaluated in the same manner as in Example 6A. The results are shown in Table 3 below.

[0228] <Examples 7-11> Thermosetting prepregs for Examples 7 to 11 were manufactured in the same manner as in Example 6A, except that the resin composition was prepared with the components and quantities listed in Table 3 below, and the conductive material (additional conductive material in Example 8) listed in Table 3 below was added. The conductive material was added to the resin after the amount of curing agent shown in Table 3 below was added using a roll mill. The results of the property evaluation of the obtained thermosetting prepregs for Examples 7 to 11, and the composite materials manufactured from these prepregs in the same manner as in Example 1 above, are shown in Table 3 below.

[0229] <Comparative Examples 4-5> Thermosetting prepregs for Comparative Examples 4 and 5 were prepared in the same manner as in Example 7, except that the resin composition was prepared with the components and quantities listed in Table 3 below. The results of the property evaluation of the obtained thermosetting prepregs for Comparative Examples 4 and 5, and the composite materials (composites) prepared 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 and 6B, and Examples 7-11, exhibited sufficient conductivity in the thickness direction. In particular, Examples 7-11, which contained conductive material, showed particularly good conductivity in the thickness direction compared to Example 6A, which did not contain conductive material. Furthermore, the thermosetting prepreg of Example 8, which contained additional conductive material of a relatively large size in addition to the conductive material, showed even better conductivity in the thickness direction compared to the case without additional conductive material.

[0232] Furthermore, Examples 7-11 exhibited conductivity equivalent to or better than Comparative Examples 4 and 5, and showed higher composite properties than Comparative Examples 4 and 5. In Comparative Example 4, the curing agent equivalent ratios of the first resin composition and the second resin composition were the same, and there was no difference between the curing agent equivalent ratio in the outer region of the prepreg and the curing agent equivalent ratio in the central region. 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 large curing agent equivalent ratio being located in the outer region of the prepreg. In contrast, in Examples 7-11, a resin composition with a relatively high curing agent equivalent ratio (the first resin composition) was located in the central region of the prepreg. Although there is no intention to limit the theory, it is considered that the composites according to Examples 7-11 showed 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 constituting the composite.

[0233] Furthermore, as can be seen in Table 3, in Example 6B, where the basis weight ratio (M1 / M2) of the resin film used in manufacturing the prepreg was 0.57, superior conductivity in the thickness direction was confirmed compared to Example 6A, where this ratio was 1.00. [Explanation of Symbols]

[0234] 100 Thermosetting prepreg 110, 210, 310 fiber sheets 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 sheets 314 1st main surface 316 2nd main surface 320 Sheet of the first thermosetting resin composition 330 Sheet of the second thermosetting resin composition 340 Intermediate Laminate A outer area B central area A' Second outer region of the fiber sheet B' First outer region of the fiber sheet T thickness direction

Claims

1. A method for producing a thermosetting prepreg, including the following: (a) To provide a thermosetting prepreg precursor sheet, wherein the precursor sheet comprises a fiber sheet and first and second thermosetting resin compositions impregnated in the fiber sheet and each comprising a thermosetting resin and a curing agent, respectively, 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 of the 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. 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.

2. A method for producing a thermosetting prepreg precursor sheet, To provide a fiber sheet, To provide a first thermosetting resin composition comprising a thermosetting resin and a curing agent, To provide a second thermosetting resin composition comprising a thermosetting resin and a curing agent, The first thermosetting resin composition is placed on one main surface of the fiber sheet. The second thermosetting resin composition is placed on the other main surface of the fiber sheet, and The first thermosetting resin composition and the second thermosetting resin composition are impregnated into the fiber sheet, at least partially. Includes A method wherein 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.

3. The basis weight (g / m²) of the sheet-like first thermosetting resin composition ２ ) The basis weight (g / m²) of the sheet-like second thermosetting resin composition of M1 ２ The method according to claim 2, wherein the ratio to M2 (M1 / M2) is 0.25 to 4.

0.

4. The method according to claim 2 or 3, wherein the second thermosetting resin composition further comprises resin particles.

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