Laminate, manufacturing method thereof, and prepreg

Abstract

A multilayer body according to the present invention comprises fibers, a matrix resin and a flame retardant filler. With respect to a cross-section of this multilayer body at an angle of 45° to the fiber direction, if the area occupied by the flame retardant filler in the entire cross-section at 45° is taken as 100%, the area occupied by the flame retardant filler in a range from one outermost surface of the multilayer body to the depth of 400 μm is 70% or more; and if A is the area of the flame retardant filler and B is the area of the matrix resin in the range from the outermost surface of the cross-section at 45° to the depth of 400 μm, the relational expression 0.01 < A / B < 0.15 is satisfied. A prepreg according to the present invention comprises fibers, a matrix resin and a flame retardant filler. With respect to a cross-section of this prepreg at an angle of 45° to the fiber direction, the uneven distribution rate of the flame retardant filler is 66% or more, and if A is the area of the flame retardant filler and B is the area of the matrix resin in the cross-section, the relational expression 0.01 < A / B < 0.15 is satisfied.

Description

[Technical Field]

[0001] The present invention relates to a laminate, a method for producing the same, and a prepreg. [Background technology]

[0002] Carbon fiber composite materials, which are made of reinforcing fibers, particularly carbon fibers, and a matrix resin, have excellent mechanical properties and are therefore used in a wide range of fields, including sporting goods 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, due to the electrical conductivity of carbon fibers in addition to their excellent mechanical properties, they have also been used in the housings of electronic and electrical devices such as laptop computers and video cameras, helping to reduce the thickness of the housings and the weight of the devices. Such carbon fiber reinforced composite materials are often obtained by laminating prepregs obtained by impregnating reinforcing fibers with thermosetting resins.

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

[0004] A widely used method for improving flame retardancy is to blend a flame retardant into a thermosetting resin (see, for example, Patent Document 1). However, the filler content must be reduced because it acts as a fracture initiation point and reduces the mechanical properties.

[0005] Therefore, a laminate technology has been disclosed in which prepregs mixed with a flame retardant filler are laminated on both surfaces of the surface layer (for example, Patent Document 2).Also disclosed is a prepreg technology in which a flame retardant filler is blended on one side of the prepreg and a cyanate ester resin with high flame retardancy is used on the other side (for example, Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2005 / 082982 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-231073 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-214547 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the technology of Patent Document 2, in which a flame retardant filler is laminated on both surfaces of the laminate, has problems of low flame retardancy and insufficient suppression of deterioration of physical properties that progresses from the vicinity of both surface layers. Also, the technology of Patent Document 3, in which a prepreg is mixed with a flame retardant filler on one side and a flame-retardant resin is used on the other side, achieves both flame retardancy and physical properties, but has problems with the moldability of the laminate, such as peeling due to differences in shrinkage because the resins on both sides of the prepreg are different.

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

[0009] The present invention, which has been made to solve the above problems, has the following configuration: That is, it is a laminate containing fibers, a matrix resin, and a flame retardant filler, characterized in that, in a cross section at 45° 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 within 400 μm from the outermost surface of one of the laminate is 70% or more, and when the area of ​​the flame retardant filler within 400 μm from the outermost surface in the 45° cross section is taken as A and the area of ​​the matrix resin is taken as B, the laminate satisfies the following relationship: 0.01

[0010] Furthermore, in a preferred embodiment of the laminate of the present invention, the thickness is 4 mm or more.

[0011] 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 is 60 μm or less.

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

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

[0014] In a preferred embodiment of the laminate of the present invention, part or all of the fibers are woven.

[0015] 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 within 400 μm from the outermost surface is 70% or more are woven fabrics.

[0016] The prepreg is characterized by comprising fibers, a matrix resin, and a flame retardant filler, in which the uneven distribution rate of the flame retardant filler in a cross section at 45° to the fiber direction is 66% or more, and in which the following relational expression holds when the flame retardant filler area in the cross section is A and the matrix resin area is B: ​0.01

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

[0018] 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] According to a preferred embodiment of the prepreg of the present invention, the matrix resin contains 1.5 to 25 parts by mass of a flame retardant filler per 100 parts by mass of the epoxy resin.

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

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

[0022] According to a preferred embodiment of the prepreg of the present invention, the matrix resin comprises 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] relative to 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] relative to 100 parts by mass of the epoxy resin [A].

[0023] The prepregs are laminated so that the side where the flame retardant filler is unevenly distributed becomes the outermost layer, thereby producing the laminate. [Effects of the Invention] ​

[0024] According to the present invention, it is possible to obtain an effect of achieving both flame retardancy and mechanical properties in a fiber-reinforced composite material such as a carbon fiber. The fiber-reinforced composite material, such as a laminate obtained from the laminate and prepreg of the present invention, is suitable for aircraft applications. DETAILED DESCRIPTION OF THE INVENTION

[0025] The laminate of the present invention is a laminate containing fibers, a matrix resin, and a flame retardant filler, and in a cross section at 45° 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 within a range of 400 μm from the outermost surface of one of the laminates is 70% or more, and when the flame retardant filler area within a range of 400 μm from the outermost surface in the 45° cross section is taken as A and the matrix resin area is taken as 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 the entire 45° cross section is taken as 100%, the area occupied by the flame retardant filler within 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 may be in any direction, but by cutting at 45° to a certain fiber direction, the fibers in the 0° and 90° directions have the same cross-sectional shape, making it possible to predict the abundance ratio of fiber, resin, and flame retardant filler without significant error. Having an area occupied by the flame retardant filler of 70% or more allows the laminate to efficiently exhibit its flame retardancy. The ratio of the flame retardant filler is evaluated according to the area measurement method described in the Examples.

[0027] ​In the laminate of the present invention, the formula (1) is 0.01

[0028] The laminate of the present invention preferably has a thickness of 4 mm or more. By having a thickness of 4 mm or more, the influence of the flame retardant filler in the surface layer on the mechanical properties is reduced, and the mechanical properties can be maintained while exhibiting excellent flame retardancy.

[0029] In the laminate of the present invention, the average particle size of the flame retardant filler is preferably larger than the fiber diameter and 60 μm or less. When the average particle size is larger than the fiber diameter, the flame retardant filler is less likely to penetrate the fiber layer when the fiber layer is impregnated with resin, remaining in the surface layer and exhibiting high flame retardancy. Furthermore, when the average particle size is 60 μm or less, the total surface area of ​​the flame retardant filler is sufficiently large, allowing for a high flame retardant effect to be exhibited. 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] In the laminate of the present invention, the flame retardant filler preferably contains phosphorus atoms. When the flame retardant filler contains phosphorus atoms, harmful gases are less likely to be generated during combustion, and a high flame retardant effect can be achieved.

[0031] In the laminate of the present invention, the flame retardant filler preferably contains 60% by mass or more of red phosphorus, which increases the phosphorus concentration per unit area of ​​the filler and enables the laminate to exhibit a higher flame retardant effect.

[0032] In the laminate of the present invention, it is preferable that some or all of the fibers are woven. When the fibers are in the woven form, the mechanical properties are less affected even when a flame retardant filler is added, and flame retardancy can be improved.

[0033] ​ In the laminate of the present invention, the fibers contained in the outermost layer on the side where the flame retardant filler occupies 70% or more of the area within 400 μm from the outermost surface are preferably woven fabric. Here, the outermost layer refers to the layer disposed on the outermost side of the laminate. When the fibers contained in the outermost layer are woven fabric, the addition of the flame retardant filler is less likely to affect the mechanical properties, and flame retardancy can be improved.

[0034] Next, the matrix resin that can be used in the laminate will be described.

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

[0036] Examples of the epoxy resin 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, glycidyl ether type epoxy resin such as aliphatic epoxy resin, glycidyl amine type epoxy resin, and glycidyl ester type epoxy resin. , Go In the present invention, the term "liquid" refers to a material that exhibits fluidity at 25°C.

[0037] The curing agent is an amine-based curing agent, which is a compound having a nitrogen atom in the molecule.

[0038] Such a curing agent is not particularly limited as long as it contains a nitrogen atom in the molecule, but examples thereof include aromatic polyamine compounds having active hydrogen such as 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, m-phenylenediamine, m-xylylenediamine, and diethyltoluenediamine, and fatty acids having active hydrogen such as diethylenetriamine, triethylenetetramine, isophoronediamine, bis(aminomethyl)norbornane, bis(4-aminocyclohexyl)methane, and dimer acid esters of polyethyleneimine. Examples of the active hydrogen-containing amines include aromatic amines, modified amines obtained by reacting these amines having active hydrogen with compounds such as epoxy compounds, acrylonitrile, phenol and formaldehyde, and thiourea, tertiary amines having no active hydrogen such as N,N-dimethylaniline, N,N-dimethylbenzylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and monosubstituted imidazoles, dicyandiamide, tetramethylguanidine, polycarboxylic acid hydrazides such as adipic acid hydrazide and naphthalenecarboxylic acid hydrazide, and Lewis acid complexes such as boron trifluoride ethylamine complex.

[0039] The amine curing agent preferably has thermally activated latency for the purposes of stability during the resin compounding process, storage stability at room temperature, and stability against the thermal history experienced during the process of impregnating fibers such as carbon fibers with a matrix resin. Here, thermally activated latency refers to the property of being in a low activity state as is, but undergoing a phase change or chemical change to become highly active when subjected to a certain thermal history.

[0040] The matrix resin may further contain a thermoplastic resin in order 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 containing at least two components selected from aromatic vinyl monomers, vinyl cyanide monomers, and rubbery polymers, polyamides, polyesters, polycarbonates, polyarylene oxides, polysulfones, polyethersulfones, polyimides, phenoxy resins, etc. Among these, polyvinyl formals and polyethersulfones 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, the thermoplastic resin component is preferably contained in an amount of 5 to 20 parts by mass per 100 parts by mass of the epoxy resin, which allows for both drapeability of the prepreg and flame retardancy in the carbon fiber reinforced composite material.

[0043] Next, the flame retardant filler will be described.

[0044] As the flame retardant filler, phosphorus-containing compounds, red phosphorus, nitrogen-containing compounds, metal hydroxides, and metal oxides can be preferably used.

[0045] As the red phosphorus, a crushed product, a product processed so that the highly active cleavage plane does not appear on the surface, a product coated to enhance stability, or various other commercially available products may be used.

[0046] Examples of the nitrogen-containing compound include melamine, melamine derivatives such as melamine cyanurate and melamine isocyanurate.

[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 properties of the cured product of the thermosetting resin composition, and red phosphorus is particularly preferred because it has a high flame retardant effect even when added in a small amount. It is also possible to use red phosphorus in combination with other phosphorus-containing compounds, or to use multiple types of non-halogen flame retardants in combination, such as red phosphorus and a metal hydroxide, red phosphorus and a phosphate ester, or red phosphorus and a nitrogen-containing compound.

[0050] Here, red phosphorus used is not only untreated red phosphorus, but also red phosphorus whose surface has been coated with a metal hydrate and a resin to enhance stability. Examples of metal hydrates include aluminum hydroxide, magnesium hydroxide, zinc hydroxide, and titanium hydroxide. While there are no particular limitations on the type of resin or the amount of coating, preferred resins include phenolic resins, epoxy resins, and polymethyl methacrylates, which have a high affinity with the epoxy resins. Furthermore, to prevent 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. In terms of stability, the greater the amount of coating, the better. However, from the viewpoint of flame retardancy, it is preferable that the amount of coating does not exceed 40% by mass.

[0051] The 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 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 as the carbon fiber, but preferably, the carbon fiber has a strand modulus of elasticity of 200 GPa or more and 450 GPa or less in a strand tensile test, which is a test performed in accordance with JIS R7601 (1986).

[0054] The number of carbon fiber filaments is preferably 2,000 to 50,000, more preferably 2,500 to 40,000, from the viewpoints of preventing meandering of the fiber arrangement and facilitating resin impregnation during prepreg production or molding.

[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 produced, for example, through the following process. A spinning dope containing polyacrylonitrile obtained from a monomer mainly composed of acrylonitrile is spun by a wet spinning method, a dry-wet spinning method, a dry spinning method, or a melt spinning method. The solidified yarn after spinning is subjected to a spinning process to produce a precursor, which is then subjected to processes such as flame retardation and carbonization to obtain carbon fibers.

[0056] Commercially available carbon fibers include "TORAYCA (registered trademark)" T700G-24K, "TORAYCA (registered trademark)" T300-3K, and "TORAYCA (registered trademark)" T700S-12K, each with a tensile modulus of 230 GPa, "TORAYCA (registered trademark)" T800G-24K and "TORAYCA (registered trademark)" T800S-24K, each with a tensile modulus of 294 GPa, and "TORAYCA (registered trademark)" T1100G-24K, each 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 unidirectionally aligned long fibers, woven fabrics, etc., but 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 continuous fibers such as unidirectionally aligned long fibers (fiber bundles) or woven fabrics, etc. The term "long fibers" as used here refers to fiber strands with an average length of 10 mm or more.

[0058] The carbon fiber bundles used in the laminate of the present invention preferably have a single fiber fineness of 0.2 to 2.0 dtex, more preferably 0.4 to 1.8 dtex, from the viewpoint of preventing damage to the carbon fiber bundles during twisting or in the resin composition impregnation treatment step, and of sufficiently impregnating the carbon fiber bundles with the resin composition.

[0059] The laminate of the present invention can be obtained by laminating prepregs obtained by impregnating long carbon fibers or woven fabrics, etc., which are unidirectionally aligned, with a mixture of a matrix resin and a flame retardant filler, and then curing the laminate.

[0060] Such prepregs can be produced by various known methods, such as a wet method in which a matrix resin is dissolved in an organic solvent selected from acetone, methyl ethyl ketone, methanol, etc. to reduce the viscosity and then impregnated into reinforcing fibers, or a hot melt method in which a matrix resin is heated to reduce the viscosity without using an organic solvent and then impregnated into reinforcing fibers.

[0061] In the wet method, a prepreg can be obtained by immersing reinforcing fibers in a liquid containing a matrix resin, then removing them, and evaporating the organic solvent using an oven, etc. In the hot melt method, a matrix resin whose viscosity has been reduced by heating is directly impregnated into the reinforcing fibers, or a release paper sheet with a resin film (hereinafter sometimes referred to as a "resin film") is first prepared by coating the matrix resin onto release paper, etc., and then the resin film is placed on both or one side of the reinforcing fibers, and the reinforcing fibers are impregnated with the matrix resin by heating and pressurizing.

[0062] As a method for producing the prepreg, a hot melt method in which the matrix resin is impregnated into the reinforcing fibers without using an organic solvent is preferably used, since substantially no organic solvent remains in the prepreg.

[0063] The prepreg in the present invention has a reinforcing fiber amount per unit area of ​​70 to 2000 g / m 2The amount of reinforcing fibers is preferably 70 to 2000 g / m 2 Within this range, the drapeability of the prepreg is excellent, and when molding a fiber reinforced composite material, the number of prepreg layers required to obtain a predetermined thickness is appropriate, resulting in excellent workability.

[0064] The mass content of the reinforcing fibers in the prepreg is preferably 30 to 90 mass%, more preferably 35 to 85 mass%, and even more preferably 40 to 80 mass%. When the mass content of the reinforcing fibers in the prepreg is 30 mass% or more, a fiber-reinforced composite material excellent in specific strength and specific modulus can be obtained, and the amount of heat generated during curing when molding the fiber-reinforced composite material can be suppressed. Furthermore, when the mass content of the reinforcing fibers in the prepreg is 90 mass% or less, the reinforcing fibers are sufficiently impregnated with the matrix resin, and a void-free laminate can be obtained.

[0065] The laminate of the present invention can be produced, for example, by laminating the above-described prepregs in a predetermined form and applying heat and pressure to cure the matrix resin. Methods for applying heat and pressure include press molding, autoclave molding, bagging molding, and internal pressure molding.

[0066] Furthermore, laminates can also be produced without using prepregs by directly impregnating the reinforcing fibers with the matrix resin described above and then heat-curing the impregnated fibers, using molding methods such as 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 flame retardant filler is the outermost layer on one side. The reason for this is that combustion progresses from the outermost surface of the laminate, so increasing the flame retardancy of this outermost surface is most effective. Furthermore, although there are no particular limitations on the configuration of the laminate, when the thickness of the laminate is 4 mm or less, it is desirable for the fibers and matrix resin to be symmetrical in the thickness direction to prevent deformation due to differential shrinkage during cooling of the resin after curing.

[0068] In order to achieve the object of the present invention, it is preferable to distribute the flame retardant filler unevenly 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 containing fibers, a matrix resin, and a flame retardant filler, in which the uneven distribution rate of the flame retardant filler in a cross section at 45° 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 relational expression holds true: 0.01

[0070] In the prepreg of the present invention, the uneven distribution rate of the flame retardant filler in a cross section at 45° to the fiber direction is 66% or more, preferably 75% or more, and more preferably 80% or more. When the uneven distribution rate of the flame retardant filler is 66% or more, the flame retardancy of the laminate can be efficiently exhibited. The uneven distribution rate is evaluated according to the area measurement method described in the Examples.

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

[0072] In the prepreg of the present invention, the flame retardant filler preferably contains phosphorus atoms, which allows the flame retardant filler to exhibit a high flame retardant effect without generating harmful gases during combustion.

[0073] ​​In the prepreg of the present invention, the flame retardant filler preferably contains 60% by mass or more of red phosphorus. 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 the epoxy resin contained in the matrix resin. If the flame retardant filler is 1.5 parts by mass or more, sufficient flame retardancy can be achieved. While the greater the amount of flame retardant filler, it is preferable to control the amount so that the upper limit is 25 parts by mass.

[0075] In the prepreg of the present invention, the average particle size of the flame retardant filler is preferably larger than the fiber diameter and 60 μm or less. When the average particle size is larger than the fiber diameter, the flame retardant filler does not penetrate the fiber layer when the fiber layer is impregnated with resin, remaining in the surface layer, thereby exhibiting high flame retardancy. Furthermore, when the average particle size is 60 μm or less, the total surface area of ​​the flame retardant filler is sufficiently large, allowing a high flame retardant effect to be exhibited. The average particle size of the flame retardant filler is evaluated according to the calculation method described in the Examples.

[0076] The prepreg of the present invention preferably has a woven fiber form, which allows the addition of a flame retardant filler to enhance flame retardancy without affecting mechanical properties.

[0077] The laminate produced using the prepreg of the present invention is preferably laminated so that the side where the flame retardant filler is unevenly distributed is the outermost layer. By having the side where the flame retardant filler is unevenly distributed as the outermost layer, combustion that starts from the surface layer can be significantly suppressed.

[0078] The prepreg of the present invention preferably has a matrix resin composition comprising 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 preferably satisfies the following conditions [a] and [b], and the other side preferably 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].

[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 concentrated 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 component [A] contains a glycidylamine-type epoxy resin [A1], which is preferably a tetraglycidylaminodiphenylmethane resin.

[0082] In the matrix resin, when the total amount of [A] is 100 parts by mass, [A] contains 30 to 100 parts by mass of [A1]. This allows the matrix resin to be combined with fibers such as reinforcing fibers to form a prepreg, and when the prepreg is heat-cured to form a fiber-reinforced composite material, it is possible to impart high mechanical properties.

[0083] The above [A1] is, for example, a tetraglycidylaminodiphenylmethane resin.

[0084] Commercially available tetraglycidylaminodiphenylmethane resins include ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), Araldite (registered trademark) MY720, Araldite (registered trademark) MY721, Araldite (registered trademark) MY9512, and Araldite (registered trademark) MY9663 (all manufactured by Huntsman Advanced Materials, Inc.), and Epotohto (registered trademark) YH-434 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.).

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

[0086] The epoxy resin [A] in the present invention may contain an epoxy resin other than the epoxy resin [A1], such as a liquid bisphenol A type epoxy resin, a liquid bisphenol F type epoxy resin, a solid bisphenol A type epoxy resin, a solid bisphenol S type epoxy resin, a glycidyl ether type epoxy resin such as an aliphatic epoxy resin, a glycidyl ester type epoxy resin, a glycidyl amine type epoxy resin, or a rubber-modified epoxy resin. In the present invention, the term "liquid" refers to a resin that exhibits fluidity at 25°C.

[0087] Component [B] in the present invention is an amine-based curing agent, which is a compound having a nitrogen atom in the curing agent molecule.

[0088] Such a curing agent is not particularly limited as long as it contains a nitrogen atom in the molecule, but examples thereof include aromatic polyamine compounds having active hydrogen such as 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, m-phenylenediamine, m-xylylenediamine, and diethyltoluenediamine, and fatty acids having active hydrogen such as diethylenetriamine, triethylenetetramine, isophoronediamine, bis(aminomethyl)norbornane, bis(4-aminocyclohexyl)methane, and dimer acid esters of polyethyleneimine. Examples of the active hydrogen-containing amines include aromatic amines, modified amines obtained by reacting these amines having active hydrogen with compounds such as epoxy compounds, acrylonitrile, phenol and formaldehyde, and thiourea, tertiary amines having no active hydrogen such as N,N-dimethylaniline, N,N-dimethylbenzylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and monosubstituted imidazoles, dicyandiamide, tetramethylguanidine, polycarboxylic acid hydrazides such as adipic acid hydrazide and naphthalenecarboxylic acid hydrazide, and Lewis acid complexes such as boron trifluoride ethylamine complex.

[0089] The amine curing agent [B] in the present invention preferably has thermally activated latency in order to ensure stability during the resin compounding process, storage stability at room temperature, and stability against the thermal history experienced during the process of impregnating fibers such as carbon fibers with a matrix resin. Here, thermally activated latency refers to the property of being in a low activity state as is, but undergoing a phase change or chemical change when subjected to a certain thermal history, thereby changing into a highly active state.

[0090] The amine-based curing agent [B] preferably has a diphenyl sulfone skeleton. By using a curing agent having a diphenyl sulfone skeleton, a cured resin having good heat resistance and a good flexural modulus can be obtained. In particular, various isomers of diaminodiphenyl sulfone are the most suitable curing agents because they can provide a cured resin having good heat resistance and a good flexural modulus.

[0091] The isomers of diaminodiphenyl sulfone include 3,3'-diaminodiphenyl sulfone and 4,4'-diaminodiphenyl sulfone.

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

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

[0094] As the red phosphorus, a crushed product, a product processed so that the highly active cleavage plane does not appear on the surface, a product coated to enhance stability, or various other commercially available products may be used.

[0095] Examples of the nitrogen-containing compound include melamine, melamine derivatives such as melamine cyanurate and melamine isocyanurate.

[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 properties of the cured product of the thermosetting resin composition, and red phosphorus is particularly preferred because it has a high flame retardant effect even when added in a small amount. It is also possible to use red phosphorus in combination with other phosphorus-containing compounds, or to use multiple types of non-halogen flame retardants in combination, such as red phosphorus and a metal hydroxide, red phosphorus and a phosphate ester, or red phosphorus and a nitrogen-containing compound.

[0099] Here, red phosphorus used may be not only untreated red phosphorus, but also red phosphorus whose surface has been coated with a metal hydrate and a resin to enhance stability. Examples of metal hydrates include aluminum hydroxide, magnesium hydroxide, zinc hydroxide, and titanium hydroxide. While there are no particular limitations on the type of resin or the amount of coating, preferred resins include phenolic resins, epoxy resins, and polymethyl methacrylate, which have high affinity with the epoxy resin used in the present invention. Furthermore, to prevent 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. In terms of stability, the greater the amount of coating, the better. However, from the standpoint of flame retardancy, it is preferable that the amount of coating does not exceed 40% by mass.

[0100] The matrix resin used in the present invention may contain one or more other flame retardants in combination to improve flame retardancy.

[0101] The matrix resin used in the present invention may contain a thermoplastic resin [D] in order to control viscoelasticity and impart toughness.

[0102] Examples of such thermoplastic resins include polymethyl methacrylate, polyvinyl acetals such as polyvinyl formal and polyvinyl butyral, polyvinylpyrrolidone, polymers containing at least two components selected from the group consisting of aromatic vinyl monomers, vinyl cyanide monomers, and rubbery polymers, polyamides, polyesters, polycarbonates, polyarylene oxides, polysulfones, polyethersulfones, polyimides, and phenoxy resins. Among these, polyvinyl formals and polyethersulfones are preferred because they have good compatibility with many types of epoxy resins and are effective in controlling the flow properties of matrix resins used in fiber-reinforced composite materials. Commercially available polyvinyl formals include "Vinylec®" K (manufactured by JNC Corporation), and commercially available polyethersulfones include "Sumikaexcel®" PES5003P (manufactured by Sumitomo Chemical Co., Ltd.).

[0103] In the matrix resin used in the present invention, the thermoplastic resin component is preferably contained in an amount of 10 to 20 parts by mass per 100 parts by mass of the epoxy resin, which allows for both the drapeability of the prepreg and the flame retardancy of the fiber-reinforced composite material such as carbon fiber.

[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, it is possible to impart excellent flame retardancy, strength, and impact resistance to the fiber-reinforced composite material.

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

[0106] The number of carbon fiber filaments is preferably 2,500 to 50,000, more preferably 2,800 to 40,000, from the viewpoints of preventing meandering of the fiber arrangement and facilitating resin impregnation during prepreg production or molding.

[0107] The carbon fibers used in the present invention can be those classified as polyacrylonitrile-based, rayon-based, or pitch-based carbon fibers. Among these, polyacrylonitrile-based carbon fibers, which have high tensile strength, are preferably used. Polyacrylonitrile-based carbon fibers can be produced, for example, through the following process. A spinning dope containing polyacrylonitrile obtained from a monomer containing acrylonitrile as the main component is spun by a wet spinning method, a dry-wet spinning method, a dry spinning method, or a melt spinning method. The solidified yarn after spinning is subjected to a spinning process to produce a precursor, which is then subjected to processes such as flame retardation and carbonization to obtain carbon fibers.

[0108] Commercially available carbon fibers include "TORAYCA (registered trademark)" T700G-24K, "TORAYCA (registered trademark)" T300-3K, and "TORAYCA (registered trademark)" T700S-12K, each with a tensile modulus of 230 GPa, "TORAYCA (registered trademark)" T800G-24K and "TORAYCA (registered trademark)" T800S-24K, each with a tensile modulus of 294 GPa, and "TORAYCA (registered trademark)" T1100G-24K, each 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 unidirectionally aligned long fibers, woven fabrics, etc., but 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 continuous fibers such as unidirectionally aligned long fibers (fiber bundles) or woven fabrics, etc. The term "long fibers" as used here refers to fiber strands with an average length of 10 mm or more.

[0110] The carbon fiber bundles used in the present invention preferably have a single fiber fineness of 0.2 to 2.0 dtex, more preferably 0.4 to 1.8 dtex, from the viewpoint of preventing damage to the carbon fiber bundles during twisting or in the resin composition impregnation treatment step, and of sufficiently impregnating the carbon fiber bundles with the resin composition.

[0111] The prepreg of the present invention can be produced by various known methods, such as 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, methanol, etc. to reduce the viscosity and then impregnated into fibers, or a hot melt method in which the matrix resin is heated to reduce the viscosity without using an organic solvent and then impregnated into fibers.

[0112] In the wet method, a prepreg can be obtained by immersing fibers in a liquid containing a matrix resin, then removing them, and evaporating the organic solvent using an oven, etc. In the hot melt method, a matrix resin whose viscosity has been reduced by heating is directly impregnated into fibers, or a release paper sheet with a resin film (hereinafter sometimes referred to as a "resin film") is first prepared by coating the matrix resin onto release paper, etc., and then the resin film is placed on both or one side of the fibers and heated and pressurized to impregnate the fibers with the matrix resin.

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

[0114] The prepreg of the present invention has a fiber amount per unit area of ​​70 to 2000 g / m 2 The amount of fiber is preferably 70 to 2000 g / m 2 Within this range, the drapeability of the prepreg is excellent, and when molding a fiber reinforced composite material, the number of prepreg layers required to obtain a predetermined thickness is appropriate, resulting in excellent workability.

[0115] The mass content of fibers in the prepreg of the present invention is preferably 30 to 90 mass%, more preferably 35 to 85 mass%, and even more preferably 40 to 80 mass%. When the mass content of fibers in the prepreg is 30 mass% or more, a fiber-reinforced composite material with excellent specific strength and specific modulus can be obtained, and the amount of heat generated during curing when molding the fiber-reinforced composite material can be suppressed. Furthermore, when the mass content of fibers in the prepreg is 90 mass% or less, the fibers are sufficiently impregnated with the matrix resin, and a void-free fiber-reinforced composite material can be obtained.

[0116] A laminate produced using the prepreg of the present invention can be produced, for example, by laminating the above-mentioned prepregs of the present invention in a predetermined form and applying heat and pressure to cure the matrix resin. 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 without using prepregs by directly impregnating the fibers with the matrix resin and then heat-curing them, using molding methods such as hand layup, filament winding, and resin transfer molding.

[0118] When laminating prepregs, it is preferable to distribute the flame retardant filler unevenly on the outermost surface. The reason for this is that combustion progresses from the outermost surface of the laminate, so increasing the flame retardancy of this outermost surface is most effective. In order to distribute the flame retardant filler on the outermost surface, the surface on which the flame retardant filler is unevenly distributed is arranged to be the outside. This can be achieved by using these on the first and last sheets when laminating the laminate.

[0119] The laminate of the present invention or the laminate obtained by laminating and curing the prepreg of the present invention (a laminate of a fiber-reinforced composite material) (as flame retardancy measured at a thickness of 2 mm) has a maximum heat release rate of 100 kW m in a heat release test (OSU method) in accordance with FAR25.853 (Appendix F, Part IV). -2 and the average total heat generation rate for the first 2 minutes is less than 100 kW min m -2 It has high flame retardancy of 1000 MPa or less. [Example]

[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 epoxy resin, manufactured by Mitsubishi Chemical Corporation).

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

[0124] <Component [C]: Flame retardant filler> "Nova Red (registered trademark)" 120UF (surface coating red phosphorus, phosphorus content 75% by mass, manufactured by Rin Kagaku Kogyo Co., Ltd.). "EXOLIT (registered trademark)" AP462 (ammonium polyphosphate, phosphorus content 29-31% by mass, manufactured by Clariant).

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

[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] <Textile fabric> Carbon fiber fabric (Toray "Torayca" cloth CO6343B) Carbon fiber: Torayca T300B (3K) Weave: Plain weave Longitudinal density: 12.5 lines / 25mm Latitude density: 12.5 lines / 25mm Weight: 198g / m 2 Thickness: 0.23mm.

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

[0129] <Heat release test (OSU method)> The laminates prepared in (4) or (10) below were subjected to a heat release test (OSU method) in accordance with FAR25.853 (Appendix F, Part IV) with the prepreg prepared in (3) or (8) below as the burning surface, and the maximum heat release rate and the average total heat release value for the first 2 minutes were evaluated. The evaluation criteria were a maximum heat release rate of 100 kW m -2 or less and the average total heat generation rate for the first 2 minutes is 100 kW·min·m -2 The test was deemed to have passed if the following conditions were met, and failed if not.

[0130] The laminates in Examples 1 to 8 and Comparative Examples 1 to 4 were basically produced as follows.

[0131] (1) Preparation method of matrix resin The epoxy resin and thermoplastic resin shown in Table 1 were placed in a kneading device and then heated and kneaded. The temperature was then lowered to 60°C or less, and the amine-based curing agent shown in Table 1 was added and stirred to disperse uniformly, yielding a matrix resin.

[0132] (2) Preparation method of flame retardant filler mixed matrix resin An epoxy resin, a thermoplastic resin, and a flame retardant filler corresponding to Table 1 were placed in a kneading device and then heated and kneaded. Then, the temperature was lowered to 60°C or less, and an amine-based curing agent corresponding to Table 1 was added and stirred to disperse uniformly, thereby obtaining a flame retardant filler mixed matrix resin.

[0133] (3) Prepreg fabrication Using the matrix resins prepared in (1) and (2) above, 66 g / m 2 This resin film was placed in a prepreg-making machine, and the resin film was placed on both sides of the carbon fiber fabric, with the "TORAYCA" (registered trademark) cloth CO6343B so that both sides were films of the matrix resin prepared in (1) and both sides were films of the flame retardant filler-mixed matrix resin prepared in (2). The fabric was then heated and pressurized to be impregnated with the matrix resin, producing a prepreg with a matrix resin mass fraction of 40% by mass.

[0134] (4) Fabrication of carbon fiber reinforced composite laminates 11 or 21 plies of Torayca® prepreg sheet P2352W-19 were cross-laminated, and on one side was laminated the prepreg prepared in (3) with both sides being films of the matrix resin prepared in (1), and on the other side was laminated the prepreg prepared in (3) with both sides being films of the matrix resin of (2), to produce a laminate with an overall thickness of 2 mm (2.4 mm) or 5 mm (5.0 mm), respectively. This laminate was cut into a piece 150 mm wide and 150 mm long.

[0135] (5) Evaluation method for 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 base resin and Epokwick FC Hardener (Buehler) as the hardener, and after curing at room temperature, the cross section at a 45° angle to the fiber axis was wet polished. A 2 mm long section of the exposed laminate cross section was observed at a total magnification of 500x using an optical microscope with a 50x objective lens.

[0136] The area ratio of the flame retardant filler within a 400 μm range from the outermost surface of one laminate, assuming the area occupied by the flame retardant filler as 100%, was calculated by calculating the area occupied by the flame retardant filler in a cross-sectional microscope image of the polished surface and the area A occupied by the flame retardant filler within a 400 μm range from the outermost surface of one laminate. The analysis was performed using the Trainable WEKA Segmentation plugin in the image analysis program FIJI. First, separate classifiers were determined to distinguish between the fiber, matrix resin, and flame retardant filler regions in the cross-sectional image. These were then applied to the entire cross-sectional image to calculate the area At occupied by the flame retardant filler. Next, a 400 μm section from the outermost surface where the flame retardant filler was present was cut out from the entire cross-sectional image, and the area A occupied by the flame retardant filler was calculated in the same manner to derive the area ratio.

[0137] 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 within 400 μm from the outermost layer of the laminate, was determined by calculating the resin cross-sectional area B and the flame retardant filler cross-sectional area A in the outermost 400 μm range of the side where the flame retardant filler was mixed in, using the Trainable WEKA Segmentation plug-in of the image analysis program FIJI.

[0138] The fiber diameter was determined by segmenting the cross-sectional image within a range of 400 μm from the outermost surface where the flame retardant filler is present, using the Trainable WEKA Segmentation plugin of the image analysis program FIJI. i (i = 1 to n: number of fibers in the cross-sectional image) are calculated, and the fiber diameter f i Assuming that the cross section of the fiber perpendicular to the fiber axis is a circle, the cross-sectional area F i Considering that the angle is 45° to the fiber direction, the fiber diameter f i can be calculated as follows: f i =(F i / π×2√2) 0.5 The fiber diameters f1 to f n The average value was taken as the fiber diameter.

[0139] The average particle size of the flame retardant filler was calculated from the number average value A / N of the cross-sectional area A calculated using the above method. If the flame retardant filler is assumed to be spherical, the cross-sectional area of ​​the flame retardant filler obtained using the above method will be any circle perpendicular to the axis passing through the center of the sphere. Therefore, if the radius of the flame retardant filler, assumed to be spherical, is taken as r, the expected value S of the cross-sectional area is the volume of the sphere divided by the diameter of the central axis, 2r, and can be calculated using the following formula. S=2 / 3×π×r 2 Here, assuming 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 to 4 As component [C], Novaled® 120UF was blended to the ratios A / B shown in Table 1 and the area occupied by the flame retardant filler within 400 μm from the outermost surface of one of the laminates to prepare the matrix resin described in (2) above, and a prepreg was then produced using Torayca® cloth CO6343B. This prepreg was then combined with Torayca® prepreg sheet P2352W-19 to produce a 2 mm thick laminate. The ratio A / B, the ratio of the flame retardant filler area to the resin area, was calculated from cross-sectional observation of this laminate. A heat release test (OSU method) was also performed, revealing good flame retardancy.

[0141] (Examples 5 and 6) Carbon fiber reinforced composite laminates were prepared in the same manner as in Examples 1 to 4, except that "EXOLIT (registered trademark)" AP462 was blended as the flame retardant filler so that the area occupied by the flame retardant filler was within 400 μm from the outermost surface of the laminate A / B and one of the laminates shown in Table 1. A heat release test (OSU method) was also conducted, and the flame retardancy was found to be good.

[0142] Example 7 A laminate was produced in the same manner as in Example 2, except that the components listed in Table 1 were blended as the matrix resin. A heat release test (OSU method) was also carried out, and the flame retardancy was found to be good.

[0143] Example 8 Except for changing the thickness of the laminate to 5 mm, a laminate was produced in the same manner as in Example 2. A heat release test (OSU method) was also carried out, and the flame retardancy was found to be good.

[0144] (Comparative Example 1) Except for not containing the flame retardant filler, a laminate was produced in the same manner as in Examples 1 to 3. A heat release test (OSU method) was also carried out, and the flame retardancy was found to be insufficient.

[0145] (Comparative Example 2) Except for changing the thickness of the laminate to 5 mm, a laminate was produced in the same manner as in Comparative Example 1. A heat release test (OSU method) was also carried out, and the flame retardancy was found to be insufficient.

[0146] (Comparative Example 3) Prepregs were prepared as in (3) above in the same manner as in Examples 1 to 3, except that "Novaled (registered trademark)" 120UF was used as the flame retardant filler so that the area occupied by the flame retardant filler was within 400 μm from the outermost surface of A / B and one of the laminates shown in Table 1. However, the flame retardant effect was low and the flame retardancy was insufficient.

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

[0148] [Table 1]

[0149] The laminates in Examples 9 to 14 and Comparative Examples 5 to 7 were basically produced as follows.

[0150] (6) Method for preparing matrix resin In the kneading device, 2 After adding the epoxy resin corresponding to component [A] and the thermoplastic resin corresponding to component [D], the mixture was heated and kneaded to dissolve component [D]. The temperature was then lowered to 60°C or lower, and the amine-based curing agent corresponding to component [B] listed in Table 1 was added and stirred to disperse uniformly, yielding a matrix resin for carbon fiber reinforced composite materials.

[0151] (7) Preparation method of flame retardant filler mixed matrix resin In a kneading device, an epoxy resin corresponding to component [A], 2After adding the flame retardant filler corresponding to component [C] and the thermoplastic resin corresponding to component [D], the mixture was heated and kneaded to dissolve component [D]. The temperature was then lowered to 60°C or less, and the amine-based curing agent corresponding to component [B] was added and stirred to disperse uniformly, thereby obtaining a matrix resin for carbon fiber reinforced composite materials.

[0152] (8) Prepreg production Using the matrix resins prepared in (6) and (7) above, 66 g / m 2 This resin film was placed in a prepreg-making machine, and the resin film was placed on both sides of a carbon fiber fabric, Torayca (registered trademark) Cloth CO6343B, so that one side was a film of the matrix resin prepared in (6) and the other side was a film of the matrix resin prepared in (7). The machine was then heated and pressurized to impregnate the resin, producing a prepreg with a mass fraction of the matrix resin of 40 mass%.

[0153] Then, using the matrix resin prepared in (6) above, 66 g / m 2 The resin film was coated on release paper to produce a resin film. This resin film was set in a prepreg production machine, and the resin film was placed on both sides of the carbon fiber fabric, "TORAYCA" (registered trademark) cloth CO6343B, so that both sides were films of the matrix resin prepared in (6). The fabric was then heated and pressurized to impregnate the fabric with the resin, producing a prepreg with a matrix resin mass fraction of 40 mass%. 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 2 The resin film was coated onto release paper to produce a resin film. This resin film was set in a prepreg production machine, and the resin film was placed on both sides of the carbon fiber fabric, "TORAYCA" (registered trademark) cloth CO6343B, so that both sides were films of the matrix resin prepared in (7). The fabric was then heated and pressurized to impregnate the fabric with the resin, producing a prepreg with a matrix resin mass fraction of 40 mass%. This prepreg was used in Comparative Example 7, which will be described later.

[0155] (9) Evaluation method for the amount of flame retardant filler mixed in prepreg One prepreg obtained in (8) was cured in an autoclave at 180°C for 90 minutes under 0.6 MPa pressure at a heating rate of 2.5°C / min. This cured prepreg was embedded in an epoxy resin prepared by mixing EpoKwick FC Resin (Buehler) as the base resin and Epokwick FC Hardener (Buehler) as the hardener. After curing at room temperature, a cross section at 45° to the fiber axis was wet-polished. A 2mm length of the exposed prepreg cross section was observed at a total magnification of 500x using an optical microscope with a 50x objective lens. The ratio of the total cross-sectional area of ​​the flame retardant filler, A, to the cross-sectional area of ​​the matrix resin, B, was calculated from the cross-sectional micrograph of the polished surface by calculating the cross-sectional area of ​​the resin, B, and the cross-sectional area of ​​the flame retardant filler, A. The analysis was performed using the Trainable WEKA Segmentation plugin in the image analysis program FIJI. Separate classifiers were determined to distinguish between fiber, matrix resin, and flame retardant filler regions in the cross-sectional image, and these were applied to all cross-sectional images. The uneven distribution rate was calculated using the following formula, where the prepreg cross-sectional image was divided into two equal parts in the thickness direction, and the flame retardant filler areas in each divided image were Am and An. (Distribution rate (%)) = Am / (Am+An) × 100, where Am>An.

[0156] The average particle size of the flame retardant filler is calculated from the number average value A / N of the cross-sectional area A calculated using the above method. If the flame retardant filler is assumed to be spherical, the cross-sectional area of ​​the flame retardant filler calculated using the above method will be any circle perpendicular to the axis passing through the center of the sphere. Therefore, if the radius of the flame retardant filler, assumed to be spherical, is taken as r, the expected value S of the cross-sectional area is the volume of the sphere divided by the diameter of the central axis, 2r, and can be calculated using the following formula. S=2 / 3×π×r 2 Here, assuming 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 Nine plies of the prepreg prepared in (8) above and Torayca® prepreg sheet P2352W-19 were laminated together in a configuration of (prepreg prepared in (8) / 0 / 90 / 0 / 90 / 0 / 90 / 0 / prepreg prepared in (8)) to produce a 2 mm (1.9 mm) thick laminate. The laminate was molded in an autoclave at 180°C for 90 minutes under a pressure of 0.6 MPa at a heating rate of 2.5°C / min to produce a unidirectional laminate with a thickness of 2 mm (1.9 mm). A piece 150 mm wide and 150 mm long was cut from the laminate.

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

[0159] Example 13 Laminates of carbon fiber reinforced composite materials were prepared in the same manner as in Examples 9 to 11, except that "EXOLIT (registered trademark)" AP462 was blended as component [C] so as to achieve the A / B ratio and uneven distribution rate shown in Table 2. A heat release test (OSU method) was also conducted, and the flame retardancy was found to be good.

[0160] Example 14 A laminate of a carbon fiber reinforced composite material was produced in the same manner as in Example 10, except that component [A] was blended with an epoxy resin corresponding to component [A] shown in Table 2. A heat release test (OSU method) was also carried out, and the flame retardancy was found to be good.

[0161] (Comparative Example 5) A laminate of a carbon fiber reinforced composite material was produced in the same manner as in Examples 9 to 11, except that it did not contain component [C]. When a heat release test (OSU method) was also conducted, the flame retardancy was insufficient.

[0162] (Comparative Example 6) A prepreg was produced as in (8) above in the same manner as in Examples 9 to 11, except that "Novaled (registered trademark)" 120UF was blended as component [C] so as to have the A / B and the uneven distribution rate shown in Table 2. As a result, the flame retardant effect was low and the flame retardancy was insufficient.

[0163] (Comparative Example 7) A prepreg was produced as in (8) above in the same manner as in Examples 9 to 11, except that "Novaled (registered trademark)" 120UF was blended as component [C] so as to have the A / B and the uneven distribution rate shown in Table 2. As a result, the flame retardant effect was low and the flame retardancy was insufficient.

[0164]

Table 2

[0165] The contents in Table 1 are represented in parts by mass. In the determination, a qualified case is represented by A and a non-qualified case is represented by B.

[0166] Regarding the laminates produced in Examples 9 to 14, by the method described in (4) above, 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 at 45° was taken as 100%, the area occupied by the flame retardant filler in the range of 400 μm from the outermost surface of one laminate was evaluated. As a result, 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 cross-section at 45° 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. Regarding Comparative Examples 6 and 7, 0.01 > A / B and 0.01

Claims

1. A laminate comprising fibers, a matrix resin containing a cured product of an epoxy resin and a curing agent, and a flame retardant filler containing phosphorus atoms, wherein, in a cross section at 45° 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 within a range of 400 μm from the outermost surface of one of the laminate is 70% or more, and the average particle size of the flame retardant filler is larger than the fiber diameter and 60 μm or less, and when the flame retardant filler area within a range of 400 μm from the outermost surface in the 45° cross section is taken as A and the matrix resin area is taken as B, the laminate satisfies the following relationship: 0.01<A / B<0.2

2. 2. The laminate according to claim 1, having a thickness of 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. 4. The laminate according to claim 1, wherein a part or all of the fibers are woven.

5. 5. The laminate according to claim 1, wherein the fibers contained in the outermost layer on the side where the area occupied by the flame retardant filler within 400 μm from the outermost surface is 70% or more are woven fabrics.

6. A method for manufacturing a laminate by laminating prepregs containing fibers, a matrix resin containing an epoxy resin and a curing agent, and a flame retardant filler containing phosphorus atoms, wherein the prepregs have a flame retardant filler uneven distribution rate of 66% or more in a cross section at 45° to the fiber direction, and the average particle size of the flame retardant filler is greater than the fiber diameter and is 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, so that the side with the unevenly distributed flame retardant filler becomes 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. 8. The method for producing a laminate according to claim 6, wherein the flame retardant filler is contained in an amount of 1.5 to 25 parts by mass per 100 parts by mass of the epoxy resin contained in the matrix resin.

9. The method for producing a laminate according to any one of claims 6 to 8, wherein the fibers are in the form of a woven fabric.

10. 10. The method for producing a laminate according to any one of claims 6 to 9, wherein the matrix resin has a composition comprising an epoxy resin [A], an amine-based curing agent [B], a flame retardant filler [C], and a thermoplastic resin [D], and one surface of the prepreg satisfies the following conditions [a] and [b], and the other surface 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].

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