Laminate, method for manufacturing the same, and prepreg

Abstract

The present invention aims to provide a lightweight laminate that exhibits excellent flame retardancy while maintaining mechanical properties, a method for manufacturing the same, and a prepreg. [Solution] A laminate comprising fibers, a matrix resin containing a cured product of epoxy resin and a curing agent, and a flame retardant filler containing phosphorus atoms, wherein, in a cross section at a 45° angle with respect to the fiber direction, when the area occupied by the flame retardant filler in the entire 45° cross section is taken as 100%, the area occupied by the flame retardant filler in the range of 400 μm from the outermost surface of one of the laminates is 70% or more, and the average particle size of the flame retardant filler is greater than the fiber diameter and 60 μm or less, and when the area of ​​the flame retardant filler in the range of 400 μm from the outermost surface in the 45° cross section is A and the area of ​​the matrix resin is B, the following relationship holds true for the laminate. 0.01

Description

[Technical Field]

[0001] This invention relates to laminates, methods for manufacturing the same, and prepregs. [Background technology]

[0002] Carbon fiber composite materials, consisting of reinforcing fibers, particularly carbon fibers, and matrix resins, are widely used in various fields due to their excellent mechanical properties. These include sports equipment such as golf clubs, tennis rackets, and fishing rods, as well as structural materials for aircraft and vehicles, and reinforcement of concrete structures. In recent years, in addition to their excellent mechanical properties, carbon fibers have also been used in the casings of electronic and electrical equipment such as laptop computers and video cameras because they are electrically conductive, contributing to thinner casings and reduced weight. Such carbon fiber reinforced composite materials are often obtained by laminating prepregs, which are made by impregnating reinforcing fibers with thermosetting resins.

[0003] Among the various applications of carbon fiber reinforced composite materials, there is a strong demand for flame retardancy in materials to prevent ignition and combustion in the event of a fire, particularly in structural and interior materials for aircraft and vehicles. Furthermore, in applications for electronic and electrical equipment, flame retardancy is required to prevent accidents where casings or components ignite and burn due to heat generated from within the device or exposure to high external temperatures.

[0004] A widely used method to improve flame retardancy is to incorporate a flame retardant into a thermosetting resin (for example, Patent Document 1). However, since the filler acts as a fracture initiation point and reduces the mechanical properties, it is necessary to reduce the amount of filler mixed in.

[0005] Therefore, a technology for laminates in which a prepreg mixed with a flame retardant filler is laminated on both sides of the surface layer has been disclosed (for example, Patent Document 2). In addition, a technology for prepregs in which a flame retardant filler is incorporated on one side of the prepreg and a cyanate ester resin with high flame retardant effect is used on the other side has been disclosed (for example, Patent Document 3). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2005 / 082982 [Patent Document 2] Japanese Patent Publication No. 2007-231073 [Patent Document 3] Japanese Patent Publication No. 2008-214547 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, the laminate described in Patent Document 2, in which a flame retardant filler is laminated on both surfaces, has the problem of low flame retardancy and insufficient suppression of the deterioration of physical properties that progresses from near both surface layers. Furthermore, the prepreg described in Patent Document 3, in which a flame retardant filler is mixed on one side and a flame retardant resin is used on the other side, can achieve both flame retardancy and physical properties, but the fact that both sides of the prepreg are made of different resins presents challenges in the moldability of the laminate, such as delamination due to differences in shrinkage.

[0008] The present invention aims to solve the problems of the prior art described above and to provide a laminate that is a lightweight fiber-reinforced composite material that can maintain mechanical properties while exhibiting excellent flame retardancy, and also to provide a prepreg suitable for obtaining such a fiber-reinforced composite material. [Means for solving the problem]

[0009] The present invention for solving such problems has the following configuration. That is, a laminate containing fibers, a matrix resin, and a flame retardant filler, wherein in a cross-section at 45° with respect to the fiber direction, when the area occupied by the flame retardant filler in the entire cross-section of 45° is taken as 100%, the area occupied by the flame retardant filler in the range of 400 μm from one outermost surface of the laminate is 70% or more, and when the area of the flame retardant filler in the range of 400 μm from the outermost surface in the cross-section of 45° is A and the area of the matrix resin is B, it is a laminate in which the following relational expression holds. 0.01 < A / B < 0.2

[0010] Moreover, according to a preferred embodiment of the laminate of the present invention, the thickness is 4 mm or more.

[0011] Moreover, according to a preferred embodiment of the laminate of the present invention, the average particle size of the flame retardant filler is larger than the fiber diameter and 60 μm or less.

[0012] Moreover, according to a preferred embodiment of the laminate of the present invention, the flame retardant filler contains a phosphorus atom.

[0013] Moreover, according to a preferred embodiment of the laminate of the present invention, the flame retardant filler contains 60% by mass or more of red phosphorus.

[0014] Moreover, according to a preferred embodiment of the laminate of the present invention, part or all of the fibers are a woven fabric.

[0015] Moreover, according to a preferred embodiment of the laminate of the present invention, the fibers contained in the outermost layer on the side where the area occupied by the flame retardant filler in the range of 400 μm from the outermost surface is 70% or more are a woven fabric.

[0016] Also, a prepreg containing fibers, a matrix resin, and a flame retardant filler, wherein the uneven distribution rate of the flame retardant filler in a cross-section at 45° with respect to the fiber direction is 66% or more, and when the area of the flame retardant filler in the cross-section is A and the area of the matrix resin is B, it is a prepreg in which the following relational expression holds. 0.01 < A / B < 0.15.

[0017] Also, according to a preferred embodiment of the prepreg of the present invention, the flame retardant filler contains a phosphorus atom.

[0018] Also, according to a preferred embodiment of the prepreg of the present invention, the flame retardant filler contains 60% by mass or more of red phosphorus.

[0019] Also, according to a preferred embodiment of the prepreg of the present invention, 1.5 to 25 parts by mass of the flame retardant filler is contained per 100 parts by mass of the epoxy resin in the matrix resin.

[0020] Also, according to a preferred embodiment of the prepreg of the present invention, the average particle diameter of the flame retardant filler is larger than the fiber diameter and 60 μm or less.

[0021] Also, according to a preferred embodiment of the prepreg of the present invention, the fiber form is a woven fabric.

[0022] Also, according to a preferred embodiment of the prepreg of the present invention, the composition of the matrix resin consists of an epoxy resin [A], an amine-based curing agent [B], a flame retardant filler [C], and a thermoplastic resin [D], and one side of the prepreg satisfies the following conditions [a] and [b], and the other side satisfies the following conditions [a] and [c]. [a] When the total amount of the epoxy resin [A] is 100 parts by mass, the epoxy resin [A] contains 30 to 100 parts by mass of a glycidylamine-type epoxy resin [A1]. [b] The matrix resin contains 3 to 50 parts by mass of the flame retardant filler [C] and 10 to 20 parts by mass of the thermoplastic resin [D] per 100 parts by mass of the epoxy resin [A]. [c] The matrix resin contains 10 to 20 parts by mass of the thermoplastic resin [D] per 100 parts by mass of the epoxy resin [A].

[0023] Also, the above laminate is manufactured by laminating the above prepreg so that the side where the flame retardant filler is unevenly distributed becomes the outermost layer.

Advantages of the Invention

[0024] According to the present invention, it is possible to achieve both flame retardancy and mechanical properties in fiber-reinforced composite materials such as carbon fibers. Fiber-reinforced composite materials such as laminates and laminates obtained from prepregs of the present invention are suitable for aircraft applications. [Modes for carrying out the invention]

[0025] The laminate of the present invention is a laminate comprising fibers, a matrix resin, and a flame retardant filler, wherein, in a cross section at a 45° angle with respect to the fiber direction, when the area occupied by the flame retardant filler in the entire 45° cross section is taken as 100%, the area occupied by the flame retardant filler in a range of 400 μm from the outermost surface of one of the laminates is 70% or more, and when the area of ​​the flame retardant filler in the range of 400 μm from the outermost surface in the 45° cross section is A and the area of ​​the matrix resin is B, the following relationship holds. 0.01

[0026] In the laminate of the present invention, when the area occupied by the flame retardant filler in a cross-section at a 45° angle to the fiber direction is taken as 100%, the area occupied by the flame retardant filler in a range of 400 μm from the outermost surface of one of the laminates is 70% or more, preferably 80% or more, and more preferably 90% or more. The cross-section can be in any direction, but by cutting at a 45° angle to a certain fiber direction, the fibers in the 0° and 90° directions will have the same cross-sectional shape, and the ratio of fibers, resin, and flame retardant filler can be predicted with little error. The flame retardant filler area being 70% or more allows the laminate to efficiently exhibit flame retardancy. The ratio of such flame retardant filler is evaluated according to the area measurement method described in the examples.

[0027] ​The laminate of the present invention has equation (1) equal to 0.01

[0028] The laminate of the present invention preferably has a thickness of 4 mm or more. A thickness of 4 mm or more reduces the influence of the flame retardant filler on the mechanical properties, allowing for the maintenance of mechanical properties while exhibiting excellent flame retardancy.

[0029] In the laminate of the present invention, it is preferable that the average particle size of the flame retardant filler is larger than the fiber diameter and 60 μm or less. Because the particle size is larger than the fiber diameter, when the resin is impregnated into the fiber layer, the flame retardant filler is less likely to penetrate the fiber layer and remains on the surface, resulting in high flame retardancy. Furthermore, if the particle size is 60 μm or less, the total surface area of ​​the flame retardant filler is sufficiently large, enabling a high flame retardant effect. The fiber diameter and the average particle size of the flame retardant filler are evaluated according to the calculation method described in the examples.

[0030] The laminate of the present invention preferably contains phosphorus atoms as a flame retardant filler. The inclusion of phosphorus atoms in the flame retardant filler reduces the generation of harmful gases during combustion, thereby achieving a high flame retardant effect.

[0031] The laminate of the present invention preferably contains 60% by mass or more of red phosphorus as a flame retardant filler. By containing 60% by mass or more of red phosphorus as a flame retardant filler, the phosphorus concentration per unit area of ​​the filler is increased, and a higher flame retardant effect can be achieved.

[0032] In the laminate of the present invention, it is preferable that some or all of the fibers are woven. Because the fibers are woven, the addition of flame retardant fillers does not significantly affect the mechanical properties, thereby enhancing flame retardancy.

[0033] ​ In the laminate of the present invention, it is preferable that the fibers contained in the outermost layer on the side where the flame retardant filler occupies 70% or more of the area in the range of 400 μm from the outermost surface are woven fabric. Here, the outermost layer is the outermost layer of the laminate. Because the fibers contained in the outermost layer are woven fabric, the addition of flame retardant filler does not significantly affect the mechanical properties, and flame retardancy can be enhanced.

[0034] Next, we will describe the matrix resins that can be used in the above-mentioned laminate.

[0035] The matrix resin described above includes an epoxy resin and a curing agent.

[0036] Preferably, the epoxy resins used include liquid bisphenol A type epoxy resin, liquid bisphenol F type epoxy resin, solid bisphenol A type epoxy resin, solid bisphenol S type epoxy resin, aliphatic epoxy resin, glycidyl ether type epoxy resin, glycidyl amine type epoxy resin, glycidyl ester type epoxy resin, and rubber-modified epoxy resin. In this invention, "liquid" refers to a material that exhibits fluidity at 25°C.

[0037] The curing agent described above is an amine-based curing agent. An amine-based curing agent is a compound that contains a nitrogen atom in its curing agent molecule.

[0038] Such curing agents are not particularly specified as long as they contain nitrogen atoms in their molecules, but examples include aromatic polyamine compounds with active hydrogen such as 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, m-phenylenediamine, m-xylylenediamine, and diethyltoluenediamine, and fatty acids with active hydrogen such as diethylenetriamine, triethylenetetramine, isophoronediamine, bis(aminomethyl)norbornane, bis(4-aminocyclohexyl)methane, and dimer acid esters of polyethyleneimine. Examples include amines, modified amines obtained by reacting these amines with epoxy compounds, acrylonitrile, phenol, and compounds such as formaldehyde and thiourea, tertiary amines without active hydrogen such as N,N-dimethylaniline, N,N-dimethylbenzylamine, 2,4,6-tris(dimethylaminomethyl)phenol and monosubstituted imidazoles, dicyandiamides, tetramethylguanidine, polycarboxylic acid hydrazides such as adipic acid hydrazides and naphthalenecarboxylic acid hydrazides, and Lewis acid complexes such as boron trifluoride ethylamine complexes.

[0039] The above-mentioned amine-based curing agent preferably has thermal latent properties for reasons such as stability in the resin compounding process, storage stability at room temperature, and stability against thermal history during the process of impregnating fibers such as carbon fibers with matrix resin. Here, thermal latent properties refer to the property that, although it is in a low-activity state as is, undergoes a phase change or chemical change after being subjected to a certain thermal history, and changes to a high-activity state.

[0040] The matrix resin described above can be further blended with a thermoplastic resin to control viscoelasticity and impart toughness.

[0041] Examples of such thermoplastic resins include polymethyl methacrylate, polyvinyl acetals such as polyvinyl formal and polyvinyl butyral, polyvinylpyrrolidone, polymers composed of at least two components selected from aromatic vinyl monomers, vinyl cyanide monomers, and rubbery polymers, polyamides, polyesters, polycarbonates, polyarylene oxides, polysulfones, polyethersulfones, polyimides, and phenoxy resins. Among these, polyvinyl formal and polyethersulfone are preferred because they have good compatibility with many types of epoxy resins and are highly effective in controlling the fluidity of the matrix resin.

[0042] In the matrix resin described above, the thermoplastic resin component is preferably present in an amount of 5 to 20 parts by mass per 100 parts by mass of epoxy resin. Within this range, both the drape properties of the prepreg and the flame retardancy of the carbon fiber reinforced composite material can be achieved.

[0043] Next, we will discuss the flame retardant filler mentioned above.

[0044] Preferably, phosphorus-containing compounds, red phosphorus, nitrogen-containing compounds, metal hydroxides, and metal oxides can be used as the above-mentioned flame retardant fillers.

[0045] As red phosphorus, you may use pulverized products, products processed so that the highly active cleavage surface is not exposed on the surface, products coated to enhance stability, or any other commercially available products.

[0046] Examples of nitrogen-containing compounds include melamine, melamine cyanurate, melamine isocyanurate, and other melamine derivatives.

[0047] Examples of metal hydroxides include aluminum hydroxide, magnesium hydroxide, calcium hydroxide, tin hydroxide, and zirconium hydroxide.

[0048] Examples of metal oxides include magnesium oxide and aluminum oxide.

[0049] Among these, phosphorus atom-containing compounds and red phosphorus are preferred because they have little effect on the cured product properties of the thermosetting resin composition, and red phosphorus is particularly preferred because it provides a high flame retardant effect even with a small amount of addition. It is also possible to use red phosphorus in combination with other phosphorus-containing compounds, for example, using multiple types of non-halogen flame retardants such as red phosphorus and metal hydroxides, red phosphorus and phosphate esters, or red phosphorus and nitrogen-containing compounds.

[0050] Here, the red phosphorus used includes not only untreated red phosphorus, but also red phosphorus whose surface has been coated with a metal hydrate and resin to enhance its stability. Examples of metal hydrates include aluminum hydroxide, magnesium hydroxide, zinc hydroxide, and titanium hydroxide. There are no particular limitations on the type of resin or the amount of coating, but as resins, phenolic resins, epoxy resins, and polymethyl methacrylates, which have high affinity with the epoxy resins mentioned above, are preferred. Furthermore, in order to suppress the generation of phosphine gas during high-temperature kneading, the amount of coating is preferably 1% by mass or more relative to the red phosphorus. While a larger amount of coating is preferable in terms of stability, it is preferable that it does not exceed 40% by mass from the viewpoint of flame retardancy.

[0051] Furthermore, the above-mentioned flame retardant filler may be used in combination with one or more other flame retardants to improve flame retardancy.

[0052] In the laminate of the present invention, it is preferable to use carbon fibers as the fibers. Hereinafter, the fibers may also be referred to as reinforcing fibers. By using carbon fibers as reinforcing fibers, the fiber-reinforced composite material can exhibit excellent flame retardancy, strength, and impact resistance.

[0053] Any known carbon fiber can be used, but those with a strand modulus of elasticity of 200 GPa or more and 450 GPa or less in the strand tensile test are preferred. The strand tensile test refers to the test performed in accordance with JIS R7601 (1986).

[0054] From the viewpoint of ensuring that the fiber arrangement does not meander and that resin impregnation is easy during prepreg production or molding, the number of carbon fiber filaments is preferably 2,000 to 50,000, and more preferably 2,500 to 40,000.

[0055] The carbon fibers used in the laminate of the present invention are classified into polyacrylonitrile-based, rayon-based, and pitch-based carbon fibers. Among these, polyacrylonitrile-based carbon fibers, which have high tensile strength, are preferably used. Polyacrylonitrile-based carbon fibers can be manufactured, for example, through the process described below. A spinning stock containing polyacrylonitrile obtained from a monomer mainly composed of acrylonitrile is spun by a wet spinning method, a wet-dry spinning method, a dry spinning method, or a melt spinning method. The coagulated yarn after spinning is used as a precursor through a spinning process, and then carbon fibers can be obtained through processes such as flame retardation and carbonization.

[0056] Commercially available carbon fiber products include "Torayca®" T700G-24K, "Torayca®" T300-3K, and "Torayca®" T700S-12K with a tensile modulus of 230 GPa, "Torayca®" T800G-24K and "Torayca®" T800S-24K with a tensile modulus of 294 GPa, and "Torayca®" T1100G-24K with a tensile modulus of 324 GPa (all manufactured by Toray Industries, Inc.).

[0057] The form and arrangement of the carbon fibers can be appropriately selected from long fibers aligned in one direction or woven fabrics, but in order to obtain a carbon fiber reinforced composite material that is lightweight and has a higher level of durability, it is preferable that the carbon fibers be in the form of long fibers (fiber bundles) aligned in one direction or continuous fibers such as woven fabrics. Here, long fibers refer to fibers with an average length of 10 mm or more per fiber strand.

[0058] In the laminate of the present invention, the carbon fiber bundles used are preferably 0.2 to 2.0 dtex, and more preferably 0.4 to 1.8 dtex, from the viewpoint of not damaging the carbon fiber bundles during twisting or the resin composition impregnation process, and of sufficiently impregnating the carbon fiber bundles with the resin composition.

[0059] The laminate of the present invention is obtained by laminating a prepreg, which is made by impregnating long carbon fibers or fabrics, in which carbon fibers are aligned in one direction, with a mixture of a matrix resin and a flame retardant filler, and then curing it.

[0060] Such prepregs can be manufactured by various known methods. For example, prepregs can be manufactured by a wet method, in which the matrix resin is dissolved in an organic solvent selected from acetone, methyl ethyl ketone, and methanol to reduce its viscosity and impregnate the reinforcing fibers, or by a hot melt method, in which the matrix resin is reduced in viscosity by heating without using an organic solvent and impregnates the reinforcing fibers.

[0061] In the wet method, reinforcing fibers are immersed in a liquid containing matrix resin, then removed, and the organic solvent is evaporated using an oven or the like to obtain a prepreg. In the hot melt method, methods can be used in which the matrix resin, whose viscosity has been reduced by heating, is directly impregnated into the reinforcing fibers, or in which a release paper sheet with a resin film (hereinafter sometimes referred to as "resin film") is first prepared by coating the matrix resin onto release paper, and then the resin film is placed on both sides or one side of the reinforcing fibers and heated and pressurized to impregnate the reinforcing fibers with the matrix resin.

[0062] As a method for producing the prepreg described above, a hot-melt method is preferably used, in which the matrix resin is impregnated into the reinforcing fibers without using organic solvents, because this method results in virtually no residual organic solvents in the prepreg.

[0063] The prepreg in this invention has a reinforcing fiber content of 70 to 2000 g / m² per unit area. 2It is preferable that the amount of reinforcing fiber is 70 to 2000 g / m². 2 Within this range, the prepreg exhibits excellent drape properties, and when forming fiber-reinforced composite materials, the number of prepreg layers required to obtain the desired thickness becomes appropriate, resulting in excellent workability.

[0064] The mass content of reinforcing fibers in the above prepreg is preferably 30 to 90% by mass, more preferably 35 to 85% by mass, and even more preferably 40 to 80% by mass. When the mass content of reinforcing fibers in the prepreg is 30% by mass or more, it is possible to obtain a fiber-reinforced composite material with excellent specific strength and specific modulus, and the amount of heat generated during curing when molding the fiber-reinforced composite material can be suppressed. Furthermore, when the mass content of reinforcing fibers in the prepreg is 90% by mass or less, the matrix resin is sufficiently impregnated into the reinforcing fibers, and a laminate without voids can be obtained.

[0065] The laminate of the present invention can be manufactured, for example, by laminating the above-mentioned prepregs in a predetermined form and curing the matrix resin by heating and pressurizing. Examples of methods for applying heat and pressure include press molding, autoclave molding, bagging molding, and internal pressure molding.

[0066] Furthermore, laminates can also be produced by directly impregnating the reinforcing fibers with the aforementioned matrix resin without using prepregs, followed by heat curing, such as by molding methods including hand lay-up, filament winding, and resin transfer molding.

[0067] When laminating prepregs, it is preferable to laminate them so that the prepreg mixed with the flame retardant filler is on the outermost layer of one side. This is because combustion proceeds from the outermost surface of the laminate, so increasing the flame retardancy of this outermost surface is most effective. In addition, there are no particular limitations on the composition of the laminate, but if the thickness of the laminate is 4 mm or less, it is desirable that the fibers and matrix resin be symmetrical in the thickness direction in order to prevent deformation due to differences in shrinkage when the resin cools after curing.

[0068] Furthermore, in order to achieve the objectives of the present invention, it is preferable to unevenly distribute the flame retardant filler in the prepreg on the outermost surface of the laminate. Next, the prepreg of the present invention will be described.

[0069] The prepreg of the present invention is a prepreg comprising fibers, a matrix resin, and a flame retardant filler, wherein the uneven distribution rate of the flame retardant filler in a cross section at a 45° angle to the fiber direction is 66% or more, and when the area of ​​the flame retardant filler in the cross section is A and the area of ​​the matrix resin is B, the following relationship holds. 0.01

[0070] The prepreg of the present invention has a flame retardant filler distribution rate of 66% or more, preferably 75% or more, and more preferably 80% or more, in a cross-section at a 45° angle to the fiber direction. A flame retardant filler distribution rate of 66% or more allows the laminate to efficiently exhibit flame retardancy. This distribution rate is evaluated according to the area measurement method described in the examples.

[0071] The prepreg of the present invention is more preferably 0.015 of formula (1).

[0072] The prepreg of the present invention preferably contains phosphorus atoms as a flame retardant filler. By containing phosphorus atoms as a flame retardant filler, a high flame retardant effect can be achieved without generating harmful gases during combustion.

[0073] ​​The prepreg of the present invention preferably contains 60% by mass or more of red phosphorus in the flame retardant filler. By containing 60% by mass or more of red phosphorus in the flame retardant filler, the phosphorus concentration per unit area of ​​the filler is increased, and a higher flame retardant effect can be achieved.

[0074] The prepreg of the present invention preferably contains 1.5 to 25 parts by mass, more preferably 2 to 23 parts by mass, and even more preferably 2.5 to 20 parts by mass of the flame retardant filler per 100 parts by mass of epoxy resin contained in the matrix resin. Sufficient flame retardancy can be achieved if the amount of flame retardant filler is 1.5 parts by mass or more. While a larger amount of flame retardant filler is preferable, it is preferable to control it so that the upper limit is 25 parts by mass.

[0075] In the prepreg of the present invention, it is preferable that the average particle size of the flame retardant filler is larger than the fiber diameter and 60 μm or less. Because the particle size is larger than the fiber diameter, when the resin is impregnated into the fiber layer, the flame retardant filler does not penetrate the fiber layer but remains on the surface, resulting in high flame retardancy. Furthermore, if the particle size is 60 μm or less, the total surface area of ​​the flame retardant filler is sufficiently large, enabling a high flame retardant effect. The average particle size of such flame retardant filler is evaluated according to the calculation method described in the examples.

[0076] The prepreg of the present invention preferably has fibers in the form of a woven fabric. Because the fibers are woven, flame retardancy can be enhanced without affecting the mechanical properties even when flame retardant fillers are added.

[0077] In laminations manufactured using the prepreg of the present invention, it is preferable to laminate the material so that the side with unevenly distributed flame retardant fillers is the outermost layer. By having the side with unevenly distributed flame retardant fillers as the outermost layer, combustion starting from the surface can be significantly suppressed.

[0078] The prepreg of the present invention preferably has a matrix resin composition consisting of epoxy resin [A], amine-based curing agent [B], flame retardant filler [C], and thermoplastic resin [D], and preferably one side of the prepreg satisfies the following conditions [a] and [b], and the other side satisfies the following conditions [a] and [c]. [a] When the total amount of epoxy resin [A] is 100 parts by mass, epoxy resin [A] contains 30 to 100 parts by mass of glycidylamine-type epoxy resin [A1]. [b] The matrix resin contains 3 to 50 parts by mass of the flame retardant filler [C] and 10 to 20 parts by mass of the thermoplastic resin [D] per 100 parts by mass of epoxy resin [A]. [c] The matrix resin contains 10 to 20 parts by mass of the thermoplastic resin [D] with respect to 100 parts by mass of the epoxy resin [A].

[0079] By having one side of the prepreg satisfy conditions [a] and [b], and the other side satisfy conditions [a] and [c], the flame retardant filler can be unevenly distributed on the burning side, resulting in high flame retardancy.

[0080] Next, the matrix resin used in the prepreg of the present invention will be described.

[0081] The above component [A] includes a glycidylamine-type epoxy resin [A1]. Here, the glycidylamine-type epoxy resin [A1] is preferably a tetraglycidylaminodiphenylmethane resin.

[0082] In the matrix resin described above, when the total amount of [A] is 100 parts by mass, [A] contains 30 to 100 parts by mass of [A1]. This allows for the formation of a prepreg by combining the matrix resin with reinforcing fibers, and then by heat curing the prepreg to form a fiber-reinforced composite material, thereby imparting high mechanical properties.

[0083] Examples of the above [A1] include tetraglycidylaminodiphenylmethane resin.

[0084] Commercially available tetraglycidylaminodiphenylmethane resins include ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), "Araldite®" MY720, "Araldite®" MY721, "Araldite®" MY9512, "Araldite®" MY9663 (all manufactured by Huntsman Advanced Materials Co., Ltd.), and "Epotote®" YH-434 (manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.).

[0085] [A1] may be used alone or in mixture with other epoxy resins.

[0086] The epoxy resin [A] in the present invention may contain epoxy resins other than the epoxy resin [A1], for example, liquid bisphenol A type epoxy resin, liquid bisphenol F type epoxy resin, solid bisphenol A type epoxy resin, solid bisphenol S type epoxy resin, aliphatic epoxy resin, glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, rubber-modified epoxy resin, etc. In the present invention, "liquid" means a substance that exhibits fluidity at 25°C.

[0087] In this invention, component [B] is an amine-based curing agent. An amine-based curing agent is a compound that has a nitrogen atom in its curing agent molecule.

[0088] Such curing agents are not particularly specified as long as they contain nitrogen atoms in their molecules, but examples include aromatic polyamine compounds with active hydrogen such as 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, m-phenylenediamine, m-xylylenediamine, and diethyltoluenediamine, and fatty acids with active hydrogen such as diethylenetriamine, triethylenetetramine, isophoronediamine, bis(aminomethyl)norbornane, bis(4-aminocyclohexyl)methane, and dimer acid esters of polyethyleneimine. Examples include amines, modified amines obtained by reacting these amines with epoxy compounds, acrylonitrile, phenol, and compounds such as formaldehyde and thiourea, tertiary amines without active hydrogen such as N,N-dimethylaniline, N,N-dimethylbenzylamine, 2,4,6-tris(dimethylaminomethyl)phenol and monosubstituted imidazoles, dicyandiamides, tetramethylguanidine, polycarboxylic acid hydrazides such as adipic acid hydrazides and naphthalenecarboxylic acid hydrazides, and Lewis acid complexes such as boron trifluoride ethylamine complexes.

[0089] In the present invention, the amine-based curing agent [B] preferably has thermally activated latent properties for reasons such as stability in the resin compounding process, storage stability at room temperature, and stability against thermal history during the process of impregnating fibers such as carbon fibers with matrix resin. Here, thermally activated latent properties mean that it is in a low-activity state in its current state, but undergoes a phase change or chemical change after being subjected to a certain thermal history, and changes to a high-activity state.

[0090] The above amine-based curing agent [B] preferably has a diphenylsulfone skeleton. By using a curing agent having a diphenylsulfone skeleton, a resin cured product with good heat resistance and flexural modulus of elasticity can be obtained. In particular, various isomers of diaminodiphenylsulfone are the most suitable curing agents because they produce resin cured products with good heat resistance and flexural modulus of elasticity.

[0091] Isomers of diaminodiphenylsulfone include 3,3'-diaminodiphenylsulfone and 4,4'-diaminodiphenylsulfone.

[0092] Commercially available amine-based curing agents [B] include 4,4'-DABAN, 3,4'-DABAN (both manufactured by Nippon Junryo Pharmaceutical Co., Ltd.), Seika Cure S (manufactured by Wakayama Seika Kogyo Co., Ltd.), MDA-220 (manufactured by Mitsui Chemicals, Inc.), “jER Cure®” W (manufactured by Mitsubishi Chemical Corporation), and 3,3'-DAS (manufactured by Mitsui Chemicals, Inc.), “Lonzacure®” M-DEA, “Lonzacure®” M-DIPA, “Lonzacure®” M-MIPA, and “Lonzacure®” DETDA 80 (all manufactured by Lonza Co., Ltd.).

[0093] As the above-mentioned flame retardant filler [C], phosphorus-containing compounds, red phosphorus, nitrogen-containing compounds, metal hydroxides, and metal oxides can be preferably used.

[0094] As red phosphorus, you may use pulverized products, products processed so that the highly active cleavage surface is not exposed on the surface, products coated to enhance stability, or any other commercially available products.

[0095] Examples of nitrogen-containing compounds include melamine, melamine cyanurate, melamine isocyanurate, and other melamine derivatives.

[0096] Examples of metal hydroxides include aluminum hydroxide, magnesium hydroxide, calcium hydroxide, tin hydroxide, and zirconium hydroxide.

[0097] Examples of metal oxides include magnesium oxide and aluminum oxide.

[0098] Among these, phosphorus atom-containing compounds and red phosphorus are preferred because they have little effect on the cured product properties of the thermosetting resin composition, and red phosphorus is particularly preferred because it provides a high flame retardant effect even with a small amount of addition. It is also possible to use red phosphorus in combination with other phosphorus-containing compounds, for example, using multiple types of non-halogen flame retardants such as red phosphorus and metal hydroxides, red phosphorus and phosphate esters, or red phosphorus and nitrogen-containing compounds.

[0099] Here, the red phosphorus used includes not only untreated red phosphorus, but also red phosphorus whose surface has been coated with a metal hydrate and resin to enhance its stability. Examples of metal hydrates include aluminum hydroxide, magnesium hydroxide, zinc hydroxide, and titanium hydroxide. There are no particular limitations on the type of resin or the amount of coating, but as resins, phenolic resins, epoxy resins, and polymethyl methacrylates, which have high affinity with the epoxy resin used in this invention, are preferred. Furthermore, in order to suppress the generation of phosphine gas during high-temperature kneading, the amount of coating is preferably 1% by mass or more relative to the red phosphorus. While a larger amount of coating is preferable in terms of stability, it is preferable that it does not exceed 40% by mass from the viewpoint of flame retardancy.

[0100] Furthermore, the matrix resin used in the present invention may be combined with one or more other flame retardants to improve flame retardancy.

[0101] The matrix resin used in this invention may contain a [D] thermoplastic resin for viscoelasticity control and toughness enhancement.

[0102] Examples of such thermoplastic resins include polymethyl methacrylate, polyvinyl acetals such as polyvinyl formal and polyvinyl butyral, polyvinylpyrrolidone, polymers composed of at least two selected from aromatic vinyl monomers, vinyl cyanide monomers, and rubbery polymers, polyamides, polyesters, polycarbonates, polyarylene oxides, polysulfones, polyethersulfones, polyimides, and phenoxy resins. Among these, polyvinyl formal and polyethersulfone are preferred because they have good compatibility with many types of epoxy resins and are highly effective in controlling the fluidity of the matrix resin for fiber-reinforced composite materials. A commercially available polyvinyl formal is "Vinirec®" K (manufactured by JNC Corporation), and a commercially available polyethersulfone is "Sumika Excel®" PES5003P (manufactured by Sumitomo Chemical Co., Ltd.).

[0103] In the matrix resin used in the present invention, the thermoplastic resin component is preferably present in an amount of 10 to 20 parts by mass per 100 parts by mass of epoxy resin. Within this range, both the drape properties of the prepreg and the flame retardancy of fiber-reinforced composite materials such as carbon fibers can be achieved.

[0104] In the prepreg of the present invention, it is preferable to use reinforcing fibers such as carbon fibers as the fibers. By using carbon fibers as the fibers, the fiber-reinforced composite material can exhibit excellent flame retardancy, strength, and impact resistance.

[0105] The above matrix resin can be used in combination with fibers to form a fiber-reinforced composite material. Carbon fibers are preferably used as the fibers, and any known carbon fiber can be used, but those with a strand modulus of elasticity of 200 GPa or more and 450 GPa or less in the strand tensile test are preferably used. The strand tensile test refers to the test performed in accordance with JIS R7601 (1986).

[0106] From the viewpoint of ensuring that the fiber arrangement does not meander and that resin impregnation is easy during prepreg production or molding, the number of carbon fiber filaments is preferably 2,500 to 50,000, and more preferably 2,800 to 40,000.

[0107] The carbon fibers used in this invention can be classified as polyacrylonitrile-based, rayon-based, and pitch-based carbon fibers. Among these, polyacrylonitrile-based carbon fibers, which have high tensile strength, are preferably used. Polyacrylonitrile-based carbon fibers can be manufactured, for example, through the process described below. A spinning stock containing polyacrylonitrile obtained from a monomer mainly composed of acrylonitrile is spun by a wet spinning method, a wet-dry spinning method, a dry spinning method, or a melt spinning method. The coagulated yarn after spinning is used as a precursor through a spinning process, and then carbon fibers can be obtained through processes such as flame retardation and carbonization.

[0108] Commercially available carbon fiber products include "Torayca®" T700G-24K, "Torayca®" T300-3K, and "Torayca®" T700S-12K with a tensile modulus of 230 GPa, "Torayca®" T800G-24K and "Torayca®" T800S-24K with a tensile modulus of 294 GPa, and "Torayca®" T1100G-24K with a tensile modulus of 324 GPa (all manufactured by Toray Industries, Inc.).

[0109] The form and arrangement of the carbon fibers can be appropriately selected from long fibers aligned in one direction or woven fabrics, but in order to obtain a carbon fiber reinforced composite material that is lightweight and has a higher level of durability, it is preferable that the carbon fibers be in the form of long fibers (fiber bundles) aligned in one direction or continuous fibers such as woven fabrics. Here, long fibers refer to fibers with an average length of 10 mm or more per fiber strand.

[0110] In the present invention, the carbon fiber bundles used are preferably 0.2 to 2.0 dtex, and more preferably 0.4 to 1.8 dtex, from the viewpoint of not damaging the carbon fiber bundles during twisting or the resin composition impregnation process, and ensuring sufficient impregnation of the carbon fiber bundles with the resin composition.

[0111] The prepreg of the present invention can be manufactured by various known methods. For example, the prepreg can be manufactured by a wet method, in which the matrix resin used in the prepreg of the present invention is dissolved in an organic solvent selected from acetone, methyl ethyl ketone, and methanol to reduce its viscosity and impregnate it into fibers, or by a hot melt method, in which the matrix resin is reduced in viscosity by heating without using an organic solvent and impregnated into fibers.

[0112] In the wet method, fibers are immersed in a liquid containing matrix resin, then removed, and the organic solvent is evaporated using an oven or the like to obtain a prepreg. In the hot melt method, a method can be used in which the matrix resin, whose viscosity has been reduced by heating, is directly impregnated into the fibers, or a method can be used in which a release paper sheet with a resin film (hereinafter sometimes referred to as "resin film") is first prepared by coating the matrix resin onto a release paper or the like, and then the resin film is placed on both sides or one side of the fibers and the fibers are impregnated with matrix resin by heating and pressing.

[0113] As a method for producing the prepreg of the present invention, a hot melt method is preferably used, in which the matrix resin is impregnated into the fibers without using an organic solvent, because there is virtually no residual organic solvent in the prepreg.

[0114] The prepreg of the present invention has a fiber content of 70 to 2000 g / m² per unit area. 2 It is preferable that the fiber content is 70-2000 g / m². 2 Within this range, the prepreg exhibits excellent drape properties, and when forming fiber-reinforced composite materials, the number of prepreg layers required to obtain the desired thickness becomes appropriate, resulting in excellent workability.

[0115] The mass content of fibers in the prepreg of the present invention is preferably 30 to 90% by mass, more preferably 35 to 85% by mass, and even more preferably 40 to 80% by mass. When the mass content of fibers in the prepreg is 30% by mass or more, it is possible to obtain a fiber-reinforced composite material with excellent specific strength and specific modulus, and to suppress the amount of heat generated during curing when molding the fiber-reinforced composite material. Furthermore, when the mass content of fibers in the prepreg is 90% by mass or less, the matrix resin is sufficiently impregnated into the fibers, and a fiber-reinforced composite material without voids can be obtained.

[0116] Laminates manufactured using the prepreg of the present invention can, for example, be manufactured by laminating the prepreg of the present invention described above in a predetermined form and curing the matrix resin by heating and pressurizing. Examples of methods for applying heat and pressure include press molding, autoclave molding, bagging molding, and internal pressure molding.

[0117] Furthermore, fiber-reinforced composite materials can also be produced by directly impregnating the above-mentioned matrix resin into fibers without using prepregs, followed by heat curing, such as by molding methods including hand lay-up, filament winding, and resin transfer molding.

[0118] When laminating prepregs, it is preferable to concentrate the flame retardant filler on the outermost surface. This is because combustion proceeds from the outermost surface of the laminate, and therefore, enhancing the flame retardancy of this outermost surface is most effective. To place the flame retardant filler on the outermost surface, the surface with the concentrated flame retardant filler should face outwards. This can be achieved by using this method for the first and last layers when laminating the laminate.

[0119] The laminate obtained by laminating and curing the laminate or prepreg of the present invention (a laminate of fiber-reinforced composite material) (as flame retardancy measured at a thickness of 2 mm) exhibits a maximum heat release rate of 100 kW·m² in a heat release test (OSU method) in accordance with FAR25.853 (Appendix F, Part IV). -2 The value is less than 100 kW·min·m³, and the average value of the total heat generated during the first two minutes is 100 kW·min·m³. -2 It possesses the following high level of flame retardancy. [Examples]

[0120] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are as follows.

[0121] <Component [A1]: Glycidylamine-type epoxy resin> • ELM434 (tetraglycidylaminodiphenylmethane resin, manufactured by Sumitomo Chemical Co., Ltd.). GAN (N,N-diglycidylaniline resin, manufactured by Nippon Kayaku Co., Ltd.).

[0122] <Other epoxy resin components> • “jER(registered trademark)” 825 (liquid bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation).

[0123] <Component [B]: Amine-based curing agent> • "SeikaCure (registered trademark)"-S (4,4'-diaminodiphenylsulfone, manufactured by Wakayama Seika Kogyo Co., Ltd.).

[0124] <Ingredients [C]: Flame retardant filler> • "NovaRed (registered trademark)" 120UF (surface coating red phosphorus, phosphorus content 75% by mass, manufactured by Phosphorus Chemical Industry Co., Ltd.). • "EXOLIT®" AP462 (ammonium polyphosphate salt, phosphorus content 29-31% by mass, manufactured by Clariant Co., Ltd.).

[0125] <Component [D]: Thermoplastic resin> · 10 parts by mass of "Sumika Excel (registered trademark)" 5003P (polyethersulfone, manufactured by Sumitomo Chemical Co., Ltd.).

[0126] <Carbon fiber> · "Torayca (registered trademark)" T800SC-24K (tensile strength 5.9 GPa, tensile modulus 294 GPa, fiber specific gravity 1.80, manufactured by Toray Industries, Inc.).

[0127] <Fiber fabric> Carbon fiber fabric (Toray's "Torayca" cross CO6343B) Carbon fiber: Torayca T300B (3K) Weave pattern: Plain weave Warp density: 12.5 threads / 25 mm, Weft density: 12.5 threads / 25 mm Areal density: 198 g / m 2 Thickness: 0.23 mm.

[0128] <Prepreg sheet> Prepreg sheet: "Torayca" (registered trademark) prepreg sheet P2352W-19 Reinforcing fiber: T800S Matrix resin: 3900-2B Volume content of reinforcing fiber: 56%.

[0129] <Heat release test (OSU method)> The laminate produced in (4) or (10) described below was subjected to a heat release test (OSU method) in accordance with FAR25.853 (Appendix F, Part IV) such that the combustion surface became the prepreg produced in (3) or (8) described below, and the average values of the maximum heat release rate and the total heat release amount in the first 2 minutes were evaluated. Note that as the judgment criteria, when the maximum heat release rate is 100 kW·m -2 or less and the average value of the total heat release amount in the first 2 minutes is 100 kW·min·m -2 or less, it is judged as qualified, and otherwise it is judged as unqualified.

[0130] The basic production of the laminates in Examples 1 to 8 and Comparative Examples 1 to 4 was carried out as follows.

[0131] (1) Method for preparing matrix resin After adding the epoxy resin and thermoplastic resin corresponding to Table 1 to the kneading apparatus, heating and kneading were performed. Next, the temperature was lowered to below 60°C, and the amine-based curing agent corresponding to Table 1 was added and stirred to ensure uniform dispersion, thereby obtaining a matrix resin.

[0132] (2) Method for preparing flame retardant filler mixed matrix resin After adding epoxy resin, thermoplastic resin, and flame retardant filler corresponding to Table 1 to a mixing device, heating and mixing were performed. Next, the temperature was lowered to below 60°C, and an amine-based curing agent corresponding to Table 1 was added and stirred to ensure uniform dispersion, thereby obtaining a flame retardant filler mixed matrix resin.

[0133] (3) Preparation of prepregs Using the matrix resin prepared in (1) and (2) above, 66 g / m 2 A resin film was prepared by coating a release paper with the resin. This resin film was set in a prepreg making machine, and the resin film was layered onto a carbon fiber fabric from both sides of the "Torayca" (registered trademark) cloth CO6343B so that both sides were a film of the matrix resin prepared in (1) and both sides were a film of the flame retardant filler mixed matrix resin prepared in (2). The fabric was then heated and pressurized to impregnate the matrix resin, and a prepreg with a matrix resin mass fraction of 40% by mass was prepared.

[0134] (4) Fabrication of laminates of carbon fiber reinforced composite materials "Toreca" (registered trademark) prepreg sheet P2352W-19 was laminated in 11 or 21 plies using cross-ply lamination. On one side, a prepreg prepared in (3), where both sides are a film of the matrix resin prepared in (1), was laminated, and on the other side, a prepreg prepared in (3), where both sides are a film of the matrix resin prepared in (2), was laminated, creating laminates with an overall thickness of 2 mm (2.4 mm) or 5 mm (5.0 mm). From these laminates, pieces were cut to a width of 150 mm and a length of 150 mm.

[0135] (5) Method for evaluating the amount of flame retardant filler mixed in the laminate The laminate obtained in (4) was embedded in an epoxy resin prepared by mixing EpoKwick FC Resin (Buehler) as the main component and Epokwick FC Hardener (Buehler) as the hardener. After curing at room temperature, the cross section at a 45° angle to the fiber axis was wet-polished. A 2 mm length of the exposed laminate cross section was observed at a total magnification of 500x using a 50x objective lens of an optical microscope.

[0136] The area ratio of the flame retardant filler within a 400 μm range from the outermost surface of one of the laminates, when the area occupied by the flame retardant filler is set to 100%, was determined by calculating the area occupied by the flame retardant filler and the area A occupied by the flame retardant filler within a 400 μm range from the outermost surface of one of the laminates, respectively, from the cross-sectional microscope image of the polished surface. The Trainable WEKA Segmentation plugin of the image analysis program FIJI was used for the analysis. First, separate classifiers were determined to identify the region divisions of fibers, matrix resin, and flame retardant filler in the cross-sectional image, and applied to the entire cross-sectional image to determine the area At occupied by the flame retardant filler. Next, the portion within 400 μm from the outermost surface where the flame retardant filler is present was cut out from the entire cross-sectional image, and the area A occupied by the flame retardant filler was determined in the same manner to derive the area ratio.

[0137] The ratio A / B, which is the ratio of the total cross-sectional area A of the flame retardant filler to the cross-sectional area B of the matrix resin in the 400 μm range from the outermost surface of the laminate, was determined by calculating the resin cross-sectional area B and the flame retardant filler cross-sectional area A using the Trainable WEKA Segmentation plugin of the image analysis program FIJI, in the 400 μm range of the surface where the flame retardant filler is mixed in, from the cross-sectional microscope image of the polished surface.

[0138] The fiber diameter was determined by identifying and deriving it from region segmentation of cross-sectional images within a 400 μm range from the outermost surface where the flame retardant filler is present, using the Trainable WEKA Segmentation plugin of the image analysis program FIJI mentioned above. In detail, the area F of each fiber was determined. i (i=1~n: number of fibers in the cross-sectional image) is derived for each, and the fiber diameter f is derived from this value. i The following was calculated. Assuming that the fiber cross-section of a plane perpendicular to the fiber axis is a circle, the cross-sectional area F i Considering that the angle is 45° with respect to the fiber direction, the fiber diameter f i It can be calculated as follows: f i =(F i (π × 2√2) 0.5 The fiber diameters f1~f were derived in this way. n The average value was used as the fiber diameter.

[0139] The average particle size of the flame retardant filler was determined from the average value A / N of the cross-sectional areas A obtained by the method described above. Here, assuming the shape of the flame retardant filler is a sphere, the cross-sectional area of ​​the flame retardant filler obtained by the method described above will be any circle perpendicular to the axis passing through the center of the sphere. Therefore, the expected value S of the cross-sectional area can be calculated by dividing the volume of the sphere by the diameter of the central axis, 2r, where r is the radius of the flame retardant filler assumed to be a sphere, and using the following formula. S = 2 / 3 × π × r 2 Here, using S=A / N, the average particle size 2r of the flame retardant filler was calculated using the following formula. 2r = (6 × A / (π × N)) 0.5 .

[0140] (Examples 1-4) As component [C], "NovaRed®" 120UF was blended to match the area occupied by the flame retardant filler in the range of A / B and 400 μm from the outermost surface of one of the laminates as shown in Table 1, and the matrix resin as shown in (2) above was prepared, and a prepreg was made using "Torayca"® cloth CO6343B. Furthermore, a 2 mm thick laminate was made by combining this prepreg with "Torayca"® prepreg sheet P2352W-19. From cross-sectional observation of this laminate, the ratio A / B of the flame retardant filler area to the resin area was calculated. A heat release test (OSU method) was also performed, and the flame retardancy was good.

[0141] (Examples 5 and 6) Laminates of carbon fiber reinforced composite material were prepared in the same manner as in Examples 1 to 4, except that "EXOLIT®" AP462 was blended as a flame retardant filler so that the flame retardant filler occupied an area of ​​400 μm from the outermost surface of each of the A / B laminates shown in Table 1. A heat release test (OSU method) was also performed, and the flame retardancy was good.

[0142] (Example 7) A laminate was prepared in the same manner as in Example 2, except that the matrix resin contained the components listed in Table 1. A heat release test (OSU method) was also performed, and the flame retardancy was good.

[0143] (Example 8) The laminate was fabricated in the same manner as in Example 2, except that the laminate thickness was set to 5 mm. A heat release test (OSU method) was also performed, and the flame retardancy was good.

[0144] (Comparative Example 1) Laminates were fabricated in the same manner as in Examples 1-3, except that they did not contain flame retardant fillers. A heat release test (OSU method) was also performed, and the flame retardancy was found to be insufficient.

[0145] (Comparative Example 2) The laminate was prepared in the same manner as in Comparative Example 1, except that the laminate thickness was set to 5 mm. A heat release test (OSU method) was also performed, and the flame retardancy was found to be insufficient.

[0146] (Comparative Example 3) When a prepreg was prepared as described in (3) above, in the same manner as in Examples 1 to 3, except that "NovaRed (registered trademark)" 120UF was blended as a flame retardant filler so that the flame retardant filler occupied an area of ​​400 μm from the outermost surface of one of the A / B laminates shown in Table 1, the flame retardant effect was low and the flame retardancy was insufficient.

[0147] (Comparative Example 4) When a prepreg was prepared as described in (3) above, in the same manner as in Examples 1 to 3, except that "EXOLIT®" AP462 was blended as a flame retardant filler so that the flame retardant filler occupied an area of ​​400 μm from the outermost surface of one of the A / B laminates shown in Table 1, the flame retardant effect was low and the flame retardancy was insufficient.

[0148] [Table 1]

[0149] The basic fabrication of the laminates in Examples 9-14 and Comparative Examples 5-7 was carried out as follows.

[0150] (6) Method for preparing matrix resin After adding the epoxy resin corresponding to component [A] and the thermoplastic resin corresponding to component [D] listed in Table 2 to a mixing apparatus, heating and mixing were performed to dissolve component [D]. Next, the temperature was lowered to below 60°C, and the amine-based curing agent corresponding to component [B] listed in Table 1 was added and stirred to ensure uniform dispersion, thereby obtaining a matrix resin for carbon fiber reinforced composite materials.

[0151] (7) Method for preparing flame retardant filler mixed matrix resin An epoxy resin corresponding to component [A], a flame retardant filler corresponding to component [C] listed in Table 2, and a thermoplastic resin corresponding to component [D] were added to a mixing apparatus, and then heated and kneaded to dissolve component [D]. Next, the temperature was lowered to below 60°C, and an amine-based curing agent corresponding to component [B] was added and stirred to uniformly disperse, thereby obtaining a matrix resin for carbon fiber reinforced composite materials.

[0152] (8) Preparation of prepregs Using the matrix resin prepared in (6) and (7) above, 66 g / m 2 A resin film was prepared by coating a release paper with the resin. This resin film was set in a prepreg making machine, and the resin film was placed on both sides of the carbon fiber fabric "Torayca" (registered trademark) cloth CO6343B so that one side was the matrix resin film prepared in (6) and the other side was the matrix resin film prepared in (7). The resin was then impregnated by heating and pressurizing, and a prepreg with a matrix resin mass fraction of 40% by mass was prepared.

[0153] Then, using the matrix resin prepared in (6) above, 66 g / m 2 A resin film was prepared by coating a release paper with the resin. This resin film was set in a prepreg making machine, and the resin film was layered onto a carbon fiber fabric from both sides of the "Torayca" (registered trademark) cloth CO6343B so that both sides would be the matrix resin film prepared in (6). The fabric was heated and pressurized to impregnate the resin, and a prepreg with a matrix resin mass fraction of 40% by mass was prepared. This prepreg was used in Comparative Example 5, which will be described later.

[0154] Furthermore, using the matrix resin prepared in (7) above, 66 g / m 2A resin film was prepared by coating a release paper with the resin. This resin film was set in a prepreg making machine, and the resin film was layered onto a carbon fiber fabric from both sides of the "Torayca" (registered trademark) cloth CO6343B so that both sides would be the matrix resin film prepared in (7). The fabric was heated and pressurized to impregnate the resin, and a prepreg with a matrix resin mass fraction of 40% by mass was prepared. This prepreg was used in Comparative Example 7, which will be described later.

[0155] (9) Method for evaluating the amount of flame retardant filler mixed in the prepreg One sheet of prepreg obtained in (8) was cured in an autoclave at 180°C for 90 minutes under a pressure of 0.6 MPa and a heating rate of 2.5°C / min. This cured prepreg was embedded in epoxy resin prepared by mixing EpoKwick FC Resin (Buehler) as the main component and Epokwick FC Hardener (Buehler) as the curing agent. After curing at room temperature, the cross section at a 45° angle to the fiber axis was wet-polished. A 2 mm length of the exposed prepreg cross section was observed using a 50x objective lens on an optical microscope at a total magnification of 500x. The ratio A / B, which is the ratio of the total cross-sectional area A of the flame retardant filler to the cross-sectional area B of the matrix resin, was calculated by determining the resin cross-sectional area B and the flame retardant filler cross-sectional area A from the cross-sectional microscope images of the polished surface. The Trainable WEKA Segmentation plugin of the image analysis program FIJI was used for the analysis. In the cross-sectional image, separate classifiers were determined to identify the regional divisions of fibers, matrix resin, and flame retardant filler, and applied to the entire cross-sectional image. The distribution ratio is calculated using the following formula, where Am and An are the flame retardant filler areas in each of the two equally divided images in the thickness direction of the prepreg cross-sectional image. (Distribution rate (%)) = Am / (Am + An) × 100, where Am > An.

[0156] The average particle size of the flame retardant filler is determined from the average value A / N of the cross-sectional areas A obtained by the method described above. Here, assuming that the shape of the flame retardant filler is a sphere, the cross-sectional area of ​​the flame retardant filler obtained by the method described above will be any circle perpendicular to the axis passing through the center of the sphere. Therefore, the expected value S of the cross-sectional area can be calculated by dividing the volume of the sphere by the diameter of the central axis, length 2r, where r is the radius of the flame retardant filler assumed to be a sphere, and using the following formula. S = 2 / 3 × π × r 2 Here, using S=A / N, the average particle size 2r of the flame retardant filler was calculated using the following formula. 2r = (6 × A / (π × N)) 0.5 .

[0157] (10) Fabrication of carbon fiber reinforced composite laminates The prepreg prepared in (8) above and the "Torayca" (registered trademark) prepreg sheet P2352W-19 were laminated in a 9-ply configuration (prepreg prepared in (8) / 0 / 90 / 0 / 90 / 90 / 0 / 0 / prepreg prepared in (8)) to create a laminate with a thickness of 2 mm (1.9 mm). The laminate was formed in an autoclave at a temperature of 180°C for 90 minutes under a pressure of 0.6 MPa and a heating rate of 2.5°C / min to create a unidirectional laminate with a thickness of 2 mm (1.9 mm). Pieces were cut from the laminate to a width of 150 mm and a length of 150 mm.

[0158] (Examples 9-12) As component [C], "NovaRed®" 120UF was blended to achieve the A / B ratio and distribution ratio shown in Table 2 to prepare the matrix resin as described in (2) above, and a prepreg was fabricated using "Torayca"® cloth CO6343B. The ratio of resin area to flame retardant filler area was calculated from cross-sectional observation of this prepreg. Furthermore, a laminate was fabricated using this prepreg together with "Torayca"® prepreg sheet P2352W-19. A heat release test (OSU method) was also performed, and the flame retardancy was good.

[0159] (Example 13) Laminates of carbon fiber reinforced composite material were prepared in the same manner as in Examples 9-11, except that "EXOLIT®" AP462 was blended as component [C] to the A / B ratio and distribution ratio shown in Table 2. A heat release test (OSU method) was also performed, and the flame retardancy was good.

[0160] (Example 14) A laminate of carbon fiber reinforced composite material was prepared in the same manner as in Example 10, except that an epoxy resin corresponding to component [A] listed in Table 2 was used as component [A]. A heat release test (OSU method) was also performed, and the flame retardancy was good.

[0161] (Comparative Example 5) Laminates of carbon fiber reinforced composite material were prepared in the same manner as in Examples 9-11, except that they did not contain component [C]. A heat release test (OSU method) was also performed, and the flame retardancy was found to be insufficient.

[0162] (Comparative Example 6) When a prepreg was prepared as described in (8) above, in the same manner as in Examples 9 to 11, except that "NovaRed®" 120UF was blended as component [C] to the A / B ratio and distribution ratio shown in Table 2, the flame retardant effect was low and the flame retardancy was insufficient.

[0163] (Comparative Example 7) When a prepreg was prepared as described in (8) above, in the same manner as in Examples 9 to 11, except that "NovaRed®" 120UF was blended as component [C] to the A / B ratio and distribution ratio shown in Table 2, the flame retardant effect was low and the flame retardancy was insufficient.

[0164] [Table 2]

[0165] The content values ​​in Table 1 represent parts by mass. In the evaluation, A indicates a pass, and B indicates a fail.

[0166] For the laminates produced in Examples 9 to 14, when the area occupied by the flame retardant filler in the entire 45° cross-section with respect to the fiber direction was taken as 100% by the method described in (4) above, and the area occupied by the flame retardant filler in the range of 400 μm from the outermost surface of one laminate was evaluated, all were 90% or more. And when the area of the flame retardant filler in the range of 400 μm from the outermost surface in the 45° cross-section was A and the area of the matrix resin was B, all satisfied 0.01 < A / B < 0.2. In particular, Examples 9 to 11 and 13 to 14 also satisfied 0.02 < A / B < 0.16. Note that Comparative Examples 6 and 7 had 0.01 > A / B and 0.01

Claims

1. A laminate comprising fibers, a matrix resin containing a cured product of epoxy resin and a curing agent, and a flame retardant filler containing phosphorus atoms, wherein, in a cross section at a 45° angle with respect to the fiber direction, when the area occupied by the flame retardant filler in the entire 45° cross section is taken as 100%, the area occupied by the flame retardant filler in a range of 400 μm from the outermost surface of one of the laminates is 70% or more, and the average particle size of the flame retardant filler is greater than the fiber diameter and 60 μm or less, and when the area of ​​the flame retardant filler in the range of 400 μm from the outermost surface in the 45° cross section is A and the area of ​​the matrix resin is B, the following relationship holds true for the laminate. 0.01<A / B<0.2

2. The laminate according to claim 1, wherein the thickness is 4 mm or more.

3. The laminate according to claim 1 or 2, wherein the flame retardant filler contains 60% by mass or more of red phosphorus.

4. The laminate according to any one of claims 1 to 3, wherein some or all of the aforementioned fibers are woven fabric.

5. The laminate according to any one of claims 1 to 4, wherein the fibers contained in the outermost layer on the side where the area occupied by the flame retardant filler in the range of 400 μm from the outermost surface is 70% or more are woven fabric.

6. A method for manufacturing a laminate comprising laminating a prepreg containing fibers, an epoxy resin and a curing agent, and a flame retardant filler containing phosphorus atoms, wherein the uneven distribution of the flame retardant filler in a cross section at a 45° angle to the fiber direction is 66% or more, the average particle size of the flame retardant filler is larger than the fiber diameter and 60 μm or less, and the following relationship holds when the flame retardant filler area in the cross section is A and the matrix resin area is B, the prepreg is laminated such that the side with uneven distribution of the flame retardant filler is the outermost layer. 0.01<A / B<0.15

7. The method for producing a laminate according to claim 6, wherein the flame retardant filler contains 60% by mass or more of red phosphorus.

8. A method for manufacturing a laminate according to claim 6 or 7, wherein the flame retardant filler is contained in an amount of 1.5 to 25 parts by mass per 100 parts by mass of epoxy resin contained in the matrix resin.

9. A method for manufacturing a laminate according to any one of claims 6 to 8, wherein the form of the fiber is a woven fabric.

10. A method for manufacturing a laminate according to any one of claims 6 to 9, wherein the composition of the matrix resin consists of an epoxy resin [A], an amine-based curing agent [B], a flame retardant filler [C], and a thermoplastic resin [D], and one side of the prepreg satisfies the following conditions [a] and [b], and the other side satisfies the following conditions [a] and [c]. [a] When the total amount of epoxy resin [A] is 100 parts by mass, epoxy resin [A] contains 30 to 100 parts by mass of glycidylamine type epoxy resin [A1]. [b] The matrix resin contains 3 to 50 parts by mass of the flame retardant filler [C] and 10 to 20 parts by mass of the thermoplastic resin [D] per 100 parts by mass of epoxy resin [A] [c] The matrix resin contains 10 to 20 parts by mass of the thermoplastic resin [D] with respect to 100 parts by mass of the epoxy resin [A].

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