Prepreg for fiber-reinforced composite materials and method for manufacturing the same

Abstract

To provide a prepreg which enables production of a fiber-reinforced composite material that enables long-term storage, and is excellent in tensile strength and penetration resistance.SOLUTION: A prepreg is composed of a fiber substrate and a curable resin uncured product, wherein 10-100 wt.% of a curable resin is contained in the prepreg with respect to the fiber substrate, the curable resin uncured product is composed of a main agent and a curing agent, and in the curable resin uncured product, the main agent is an epoxy compound having a hydroxyl group and / or a polyol compound, the curing agent is block isocyanate, and a weight ratio of the main agent to the curing agent is 10:90 to 80:20.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a prepreg for fiber-reinforced composite materials and a method for producing the same. [Background technology]

[0002] Fiber-reinforced composite materials (hereinafter also referred to as composite materials), which consist of reinforcing fibers and matrix resin, are characterized by their light weight, high strength, and high modulus of elasticity, and are widely applied in aircraft, automobiles, sports and leisure, and general industry. These composite materials are often manufactured via prepregs, in which the reinforcing fibers and matrix resin are integrated beforehand.

[0003] This prepreg is made by impregnating reinforcing fibers with a matrix resin, such as epoxy resin, and can be manufactured by several methods. For example, a hot melt method can be used in which a resin-coated film, in which a matrix resin is coated onto release paper or release film, and reinforcing fibers are arranged in a sheet-like manner, and the resin side of the resin-coated film is placed on both sides or one side of the reinforcing fiber sheet, and the resin is impregnated between the reinforcing fibers by heating and pressurizing (Patent Document 1).

[0004] This hot-melt method requires special equipment and effort to prepare the resin coating film in advance. Furthermore, when using thermosetting resins, even if the resin is heated to soften it in order to properly impregnate the reinforcing fibers of the coating film, overheating will cause the resin to harden, making it difficult to sufficiently reduce its viscosity. As a result, impregnation takes a long time, and productivity is poor.

[0005] To achieve good impregnation, it is often necessary to use thin reinforcing fiber sheets with a low basis weight. As a result, a large number of reinforcing fiber sheets must be laminated in the prepreg during the molding process, which leads to lower productivity of the composite material.

[0006] To address the challenges of the hot-melt method, there is a wet method in which the resin composition is diluted with an organic solvent to reduce its viscosity and become a solution, reinforcing fibers are immersed in the solution to impregnate them with the resin composition, and then the fibers are dried (Patent Document 2).

[0007] In the wet process using organic solvents, the organic solvent contained in the resin composition impregnated into the substrate must be removed during the prepreg manufacturing process. This process generates a large amount of organic solvent vapor, which not only severely deteriorates the working environment but also poses a risk of fire and explosion. Furthermore, the above method inevitably includes a highly wasteful step in terms of resources and energy: the heating and removal of the organic solvent.

[0008] To address the challenges of the wet method using organic solvents, methods have been investigated for producing prepregs by impregnating epoxy resin with an aqueous epoxy resin emulsion containing an epoxy resin, a curing agent, and a curing accelerator using water as a dispersion medium, and then drying the impregnation. A specific example of this is a method using dicyandiamide as a curing agent in an aqueous epoxy resin emulsion (Patent Document 3).

[0009] As described above, there are many methods for manufacturing prepregs, but in any process, the selection of resin and curing agent requires that the mixture of resin and curing agent, or its solution or emulsion, be stable and can be stored for a long period of time before impregnation into the fiber substrate; that the prepreg, with the resin impregnated into the fiber substrate, can be stored for a long period of time; that it hardens quickly when heated in the subsequent molding process; and that the cured product becomes a resin cured body that satisfies the expected properties of the composite material. All of these requirements must be met for industrial production. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 10-231372 [Patent Document 2] Japanese Patent Publication No. 2001-72783 [Patent Document 3] Patent No. 3581857 [Overview of the project] [Problems that the invention aims to solve]

[0011] Conventional combinations of resins and hardeners result in poor storage stability of the prepreg, and the resulting cured resin is brittle, particularly in terms of puncture resistance and impact resistance of composite materials. The object of the present invention is to provide a fiber-reinforced composite material prepreg that can provide a fiber-reinforced composite material that can be stored for a long period of time and also has excellent tensile strength and puncture resistance. [Means for solving the problem]

[0012] In other words, the present invention is Weight: 300-1000g / m 2 Aramid fiber fabric and a prepreg consisting of an uncured curable resin, wherein the prepreg contains 10 to 100% by weight of the curable resin relative to the fiber substrate, and the uncured curable resin consists of a main component and a curing agent, wherein the main component is Sorbitol polyglycidyl ether The prepreg for fiber-reinforced composite materials is characterized in that the curing agent is a dimethylpyrazole (DMP) block, and the weight ratio of the main component to the curing agent is 10:90 to 80:20. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a fiber-reinforced composite material prepreg that can be stored for a long period of time and also provides a fiber-reinforced composite material with excellent tensile strength and puncture resistance. [Modes for carrying out the invention]

[0014] The present invention will be described in detail below.

[0015] [Textile base material] The prepreg of the present invention consists of a fibrous substrate and an uncured curable resin. As the fibers of the fiber substrate used in the present invention, examples thereof include organic fibers such as polyolefin fibers, polyester fibers, polyarylate fibers, vinylon fibers, rayon fibers, aliphatic polyamide fibers, semi-aromatic polyamide fibers, wholly aromatic polyamide (aramid) fibers, and polyparabenzobisoxazole fibers, and inorganic fibers such as glass fibers, basalt fibers, and carbon fibers. From the viewpoints of tensile strength and heat resistance, preferably, para-aramid fibers, glass fibers, basalt fibers, and carbon fibers are used. From the viewpoints of puncture resistance and impact resistance, para-aramid fibers are particularly preferably used.

[0016] Para-aramid fibers are polymers composed of an aromatic dicarboxylic acid component and an aromatic diamine component, or an aromatic aminocarboxylic acid component, or aromatic copolyamide thereof, and examples thereof include polyparaphenylene terephthalamide and copolyparaphenylene·3,4'-oxydiphenylene terephthalamide.

[0017] When high flame retardancy is required, it is preferable to use para-aramid fibers and inorganic fibers in combination. As a method of using para-aramid fibers and inorganic fibers in combination, a fiber substrate composed of blended spun yarn or mixed filament yarn of para-aramid fibers and inorganic fibers can be used, or a woven fabric substrate that is mixed can be used. Further, prepregs of para-aramid fibers and inorganic fibers are respectively manufactured, and the prepregs can be laminated and used in combination during the production of the composite material.

[0018] The shape of the fiber substrate can be, for example, paper, non-woven fabric, unidirectional sheet, woven fabric, knitted fabric, and non-crimp fabric. From the viewpoints of tensile strength, puncture resistance, impact resistance, and productivity, a woven fabric is preferable. In the case of a woven fabric, the weave is, for example, plain weave, twill weave, or satin weave, and from the viewpoints of tensile strength, puncture resistance, and impact resistance, plain weave is preferable.

[0019] The basis weight (weight) of the fiber substrate is preferably 300 to <0000>1000 g / m from the viewpoint of achieving both impregnation properties of the resin raw material into the fiber substrate and productivity. [[ID=ID=19]] 2Therefore, the weight is 300-1000g / m². 2 Para-aramid fiber fabrics are particularly preferred.

[0020] [Uncured curable resin] The uncured curable resin consists of a main component and a curing agent. In the uncured curable resin, the main component is an epoxy compound and / or polyol compound having a hydroxyl group, and the curing agent is a blocked isocyanate.

[0021] The present invention is characterized by (1) using an epoxy compound and / or polyol compound having a hydroxyl group as the main component of the curable resin, and (2) using a blocked isocyanate as the curing agent.

[0022] Generally, hydroxyl groups (-OH groups) and isocyanate groups are highly reactive, so when they coexist, the reaction proceeds even at room temperature. In this invention, by using blocked isocyanate, in which the isocyanate group is blocked, as the curing agent, no reaction occurs even when the main agent and the curing agent are mixed, allowing for long-term storage in an uncured state.

[0023] In the process of heat-curing the prepreg into a desired shape, the prepreg undergoes a process in which the blocking agent first dissociates at high temperatures, followed by a rapid cross-linking reaction including urethane bonds, thereby forming a tough resin cured product. This allows for the production of composite materials with excellent tensile strength, puncture resistance, and impact resistance.

[0024] It is preferable to use an epoxy compound having a hydroxyl group as the main component. By using this compound having both a hydroxyl group and an epoxy group, when obtaining the composite material at high temperatures, the hydroxyl group and epoxy group react and self-crosslink, thereby improving the crosslink density. Furthermore, when using polymer fibers with functional groups having reactivity or affinity to epoxy groups in the polymer side chains as the fiber substrate, the epoxy group of the main component interacts with the fiber substrate, improving the adhesion strength at the interface between the fiber substrate and the curable resin cured product, thereby enhancing the mechanical properties of the fiber-reinforced composite material.

[0025] Epoxy compounds having hydroxyl groups preferably have a total of two or more hydroxyl groups and epoxy groups, more preferably three or more. Having a total of two or more hydroxyl groups and epoxy groups improves the crosslinking density when reacting with isocyanate groups, enabling the formation of a tough resin.

[0026] Furthermore, epoxy compounds containing a certain equivalent amount or more of hydroxyl groups have a high affinity for water, making them relatively easy to dissolve or disperse in water. For this reason, when impregnating a fiber substrate with the main agent and curing agent, they can be impregnated as an aqueous solution or aqueous dispersion.

[0027] Examples of epoxy compounds having a hydroxyl group include reaction products of polyhydric alcohols such as ethylene glycol, glycerol, sorbitol, pentaerythritol, and polyethylene glycol with halogen-containing epoxides such as epichlorohydrin; and reaction products of polyhydric phenols such as resorcinol, bis(4-hydroxyphenyl)dimethylmethane, phenol-formaldehyde resins, and resorcinol-formaldehyde resins with halogen-containing epoxides. Among these, the reaction product of a polyhydric alcohol and epichlorohydrin, i.e., a polyglycidyl ether compound of a polyhydric alcohol, is particularly preferred because it exhibits excellent performance.

[0028] [Blocked isocyanates] The blocked isocyanate used as a curing agent in this invention is an addition reaction product of an isocyanate compound and a blocking agent, which is a protecting group for the isocyanate group. Upon heating, the blocking component is released, producing an active isocyanate compound.

[0029] From the viewpoint of obtaining a tough resin cured product, a blocked isocyanate is used as the blocked isocyanate, which is a polyfunctional polyisocyanate compound having, preferably two or more, and more preferably three or more, isocyanate groups.

[0030] Examples of isocyanate compounds include aromatic isocyanates such as diphenylmethane diisocyanate (MDI) and tolylene diisocyanate (TDI), and aliphatic isocyanates such as hexamethylene diisocyanate (HDI).

[0031] Hexamethylene diisocyanate (HDI) is preferred as the isocyanate compound due to its excellent impregnation properties into fibrous substrates and its excellent handling characteristics, as it minimizes adhesion to metal rolls and other materials during the impregnation process. Polymers such as dimers and trimers of hexamethylene diisocyanate are particularly preferred.

[0032] Examples of blocking agents include phenols such as phenol, thiophenol, cresol, and resorcinol; aromatic secondary amines such as diphenylamine and xylidine; phthalimide; lactams such as caprolactam and valerolactam; oximes such as acetoxime, methyl ethyl ketoxime, and cyclohexanone oxime; and acidic sodium sulfite.

[0033] Due to its relatively low dissociation temperature and high reactivity after dissociation, dimethylpyrazole (DMP) block is preferred as the blocked isocyanate. Blocked isocyanates are generally insoluble in water, but can be used as aqueous dispersions. By mixing them in aqueous dispersion form with epoxy compounds and / or polyol compounds having hydroxyl groups (-OH), and impregnating a fibrous substrate with the mixture, a prepreg for fiber-reinforced composite materials can be obtained.

[0034] The curable resin is contained in an amount of 10 to 100% by weight, preferably 20 to 60% by weight, relative to the fiber substrate. This means that in the fiber-reinforced composite material prepreg of the present invention, the curable resin is contained in an amount of 10 to 100% by weight, preferably 20 to 60% by weight, relative to 100% by weight of the fiber substrate. If the amount is less than 10% by weight, it becomes difficult to sufficiently impregnate the fiber substrate with the curable resin. The matrix resin needs to impregnate at least between the multifilaments constituting the fiber substrate and play a role in connecting them. Preferably, it is preferable that it also impregnates between the single filaments (monofilaments) constituting the multifilaments. On the other hand, if the weight of the curable resin exceeds 100% by weight relative to 100% by weight of the fiber substrate, the amount of resin adhering becomes excessive, the volume fraction occupied by the fiber substrate, which has excellent mechanical properties, decreases, and the mechanical properties of the composite material become inferior.

[0035] The weight ratio of the main component to the curing agent in the uncured curable resin is 10:90 to 80:20. If the ratio of the main component is less than 10 or greater than 80, the crosslinking reaction will be slower, resulting in lower productivity.

[0036] [Flame retardant] The fiber-reinforced composite material prepreg of the present invention may contain additives to further impart functionality. For applications requiring flame retardancy, it is preferable to add a flame retardant. In particular, for applications in aircraft, automobiles, and electrical and electronic equipment, flame retardancy is desirable, and it is preferable to add a flame retardant. In this case, the flame retardant is contained in the uncured curable resin. That is, in a preferred embodiment of the present invention, the uncured curable resin further contains a flame retardant.

[0037] Halogenated flame retardants and non-halogenated flame retardants can be used as flame retardants. In particular, phosphorus-based flame retardants are preferred because they have low toxicity to the environment and human health and excellent flame retardancy. Phosphorus-based flame retardants exhibit flame retardancy by forming a carbonized layer on the surface of molded products, thereby blocking heat and oxygen and preventing the propagation of flames. Examples of phosphorus-based flame retardants include phosphate ester compounds such as triphenyl phosphate, tricresyl phosphate, trimethyl phosphate, triethyl phosphate, cresyl diphenyl phosphate, xylenyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate, and other aromatic phosphate esters, as well as halogen-containing phosphate ester compounds such as trisdichloropropyl phosphate, trischloroethyl phosphate, and trischloropropyl phosphate, condensed phosphate ester compounds, polyphosphates, and red phosphorus compounds. These may be used individually or in combination of two or more.

[0038] [Additives] In addition, depending on the application, fillers such as mica, talc, kaolin, vermiculite, hydrotalcite, sericite, bentonite, xonotlite, sepiolite, smectite, montmorillonite, warlastenite, silica, calcium carbonate, glass beads, glass flakes, glass microballoons, clay, molybdenum disulfide, titanium dioxide, zinc oxide, antimony oxide, calcium polyphosphate, graphite, barium sulfate, magnesium sulfate, zinc borate, calcium borate, aluminum borate, whiskers, potassium titanate whiskers, and polymer compounds may be added; conductive agents such as metallic, metal oxide, carbon black, and graphite powders; pigments, dyes, lubricants, release agents, compatibilizers, dispersants, plasticizers such as phosphate esters; heat stabilizers, antioxidants, color inhibitors, UV absorbers, flow modifiers, foaming agents, antibacterial agents, vibration dampers, deodorants, sliding modifiers, and antistatic agents such as polyether ester amides may be added.

[0039] [Method for manufacturing prepregs for fiber-reinforced composite materials] The present invention also relates to a method for producing a prepreg, comprising an impregnation step of impregnating a fiber substrate with an uncured curable resin, wherein the impregnation step is performed by impregnating the fiber substrate with an aqueous dispersion of the uncured curable resin, the uncured curable resin consists of a main component and a curing agent, the main component of the uncured curable resin is an epoxy compound and / or polyol compound having a hydroxyl group, the curing agent is a blocked isocyanate, and the weight ratio of the main component to the curing agent is 10:90 to 80:20, characterized in that the method for producing a prepreg for fiber-reinforced composite materials is also related to the present invention.

[0040] The prepreg of the present invention can preferably be manufactured by this method. The impregnation process is carried out by impregnating the fibrous substrate with an aqueous dispersion of uncured curable resin. The aqueous dispersion used in this impregnation process can be obtained by mixing and stirring an aqueous dispersion containing the main component with an aqueous dispersion containing the curing agent. If flame retardants or other additives are used, they can also be added as part of the aqueous dispersion.

[0041] In the aqueous dispersion used in the impregnation process, the total concentration of the hydroxyl group-containing epoxy compound and / or polyol compound (the main component) and the blocked isocyanate (the curing agent) is preferably 20 to 60% by weight. If it is less than 20% by weight, the concentration of the active ingredient is low, making it difficult to adhere a sufficient amount to the fiber substrate. On the other hand, if it exceeds 60% by weight, the stability of the aqueous dispersion decreases.

[0042] The impregnation temperature when impregnating the fibrous substrate with an aqueous dispersion is, from the viewpoint of the stability of the aqueous dispersion, for example, 20 to 50°C, preferably 20 to 40°C. As an impregnation method, for example, a method can be used in which an aqueous treatment agent is placed in a dip container and the fibrous substrate is immersed in it. After immersing the fiber substrate, the amount of water-based treatment agent adhering to the substrate during impregnation can be controlled by squeezing out excess water-based treatment agent with a nip roll or removing it with pressurized air or vacuum.

[0043] After impregnating the fibrous substrate with an aqueous dispersion, the moisture is dried. This drying may be carried out under non-heating conditions, for example at room temperature, but from the viewpoint of production efficiency, manufacturing stability, partial curing of the resin, and adjustment of the fluidity of the resin, it is carried out under heating conditions, for example at a temperature of 60 to 200°C, preferably 100 to 180°C.

[0044] In this process, since the dissociation temperature differs depending on the type of blocking agent used for the blocked isocyanate, it is preferable to adjust the temperature and time conditions so that the blocking agent completely dissociates and hardening does not progress. It is acceptable for the resin to partially harden due to the dissociation of a portion of the blocking agent. Low-temperature drying and high-temperature drying may be used in combination as needed. After the water has dried, the uncured curable resin impregnated into the fiber base material will exhibit adhesive properties. Therefore, it is preferable to wind it onto a roll or similar while sandwiched between release paper and store it as a prepreg.

[0045] [Method for manufacturing composite materials] The fiber-reinforced composite material prepreg of the present invention can be made into a fiber-reinforced composite material by press-molding the prepreg at a high temperature. In this case, a single prepreg may be used, or a prepreg laminate made by stacking multiple prepregs may be used.

[0046] In this case, the fiber base material of the fiber-reinforced composite material may be the same or different for all prepregs constituting the prepreg laminate. For example, only aramid fiber fabric may be used as the fiber base material, or aramid fiber fabric and other fiber fabrics may be used.

[0047] Other fibrous materials can be used, such as inorganic fibers, and glass fibers are preferred from the viewpoint of puncture resistance and impact resistance. When using aramid fiber base material and glass fiber fabric in combination, it is preferable to have a weight ratio of 5:95 to 95:5 in order to bring out the characteristics of each.

[0048] The temperature used for pressure molding at high temperatures is the temperature at which the blocking agent of the blocked isocyanate dissociates, and the maximum temperature is, for example, 130 to 250°C, preferably 160 to 220°C. A higher maximum temperature results in a faster curing speed, but if it is too high, the resin will decompose.

[0049] From the viewpoint of obtaining composite materials with appropriate plate thickness and few voids, the maximum molding pressure should be, for example, 1 to 50 kg / cm². 2 Preferably 2-50 kg / cm³ 2 The molding time at the maximum temperature is, for example, 10 to 360 minutes, preferably 15 to 180 minutes.

[0050] The boiling point of the block agent after dissociation varies depending on the type of block agent. It may remain in the composite material after dissociation, or it may volatilize. To speed up the pressure molding cycle, or to reduce voids caused by the volatilization of the block agent, heat treatment without pressure may be performed as a post-curing step after pressure molding.

[0051] [Panels for air cargo containers] The fiber-reinforced composite material prepreg of the present invention can be suitably used as an aircraft container panel by, for example, molding it into a flat plate. In other words, according to the present invention, a panel for an aircraft container is provided, which is made of a fiber-reinforced composite material obtained by curing the above-mentioned fiber-reinforced composite material prepreg.

[0052] A particularly preferred embodiment of this aircraft container panel is an aircraft container panel made of a fiber-reinforced composite material obtained by curing a laminate of the above-mentioned fiber-reinforced composite material prepreg and an inorganic fiber sheet substrate. [Examples]

[0053] The present invention will be described in more detail below with reference to examples. Note that "parts" refers to parts by weight.

[0054] (1) Weight of prepreg We measured the weight of a composite material measuring 300mm x 300mm, and m 2 It was converted to a per-unit weight.

[0055] (2) Weight of composite material We measured the weight of a composite material measuring 250mm x 250mm, and m 2 It was converted to a per-unit weight.

[0056] (3) Thickness of composite material For a composite material measuring 250mm x 250mm, the thickness was measured at eight points, and the average value was calculated.

[0057] (4) Tensile strength of composite materials A Type 1B type B test specimen, as specified in JIS K 7164, was used, with a width of 25 mm and a length of 250 mm. The thickness was measured as the thickness of the molded composite material. The test speed was 2 mm / min. Other conditions were measured in accordance with JIS K 7164.

[0058] (5) Puncture resistance per unit weight of composite materials The penetration resistance was measured in accordance with ISO 12236, and then calculated by dividing it by the weight obtained in (1) above.

[0059] (6) Vertical flammability of composite materials The measurements were performed in accordance with the U.S. Federal Aviation Regulation FAR25 Vertical Bunsen Burner Test for Cabin and Cargo Compartment Materials. The test specimen size was 75 mm wide and 300 mm long, and the ignition time was 12 seconds. The evaluation was performed according to the following criteria. ○: Ignition for 12 seconds, then extinguished in less than 5 seconds. △: After ignition for 12 seconds, the fire extinguished after 5 seconds or more, or spread to a length of 300 mm over 60 seconds or more. ×: After ignition for 12 seconds, the fire spread over a length of 300 mm in less than 60 seconds.

[0060] [Example 1] (Fiber base material) This plain weave fabric, woven using para-aramid fiber (Teijin Aramid BV, Twaron® T2200) 3360dtex2000 filament yarn, has a warp density of 68 threads / 10cm and a weft density of 70 threads / 10cm, resulting in a weight of 470g / m². 2 The textiles were prepared.

[0061] (Resin composition water dispersion) 70 parts of sorbitol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, EX614B, active ingredient concentration 100% by weight), a water-soluble epoxy resin; 830 parts of an aqueous dispersion of a dimethylpyrazole-blocked hexamethylene diisocyanate-based blocked isocyanate (manufactured by Lanxess, Trixene aqua BI201, active ingredient concentration 40% by weight); and 100 parts of an aqueous dispersion of ammonium polyphosphate (manufactured by Nikka Chemical Co., Ltd., Nikka Finon HF36D, active ingredient concentration 40% by weight), a phosphorus-based flame retardant, were mixed to obtain an aqueous dispersion of a flame retardant component containing an active ingredient concentration of 44% by weight.

[0062] (Prepreg) The above-mentioned aqueous dispersion of the flame retardant component-containing resin composition was impregnated into the above-mentioned fiber substrate. Then, it was dried at 150°C for 5 minutes to remove moisture, and the mixture was sandwiched between release paper to obtain a para-aramid fiber prepreg. The composition and weight of the obtained prepreg are shown in Table 1.

[0063] (composite material) After removing the release paper from the above-mentioned para-aramid fiber prepreg and stacking two sheets, the resin was partially cured by heat treatment at 200°C for 20 minutes. Then, it was pressure molded at 0.5 MPa for 10 minutes. Post-curing was then performed in a dryer under a nitrogen atmosphere at 200°C for 30 minutes to obtain the composite material. Post-curing removed most of the blocking agent. Additionally, because the resin fluidized during pressure molding, causing some resin to flow towards the edges of the composite material, resulting in slightly more resin adhesion at the edges, 25 mm from each side was trimmed. The properties of the obtained composite material are shown in Table 1.

[0064] [Example 2] In Example 1, a para-aramid fiber prepreg was obtained in the same procedure as in Example 1, except that the following resin composition aqueous dispersion was used instead of the resin composition aqueous dispersion containing a flame retardant component. The composition and weight of the obtained prepreg are described in Table 1. Further, a composite material was obtained in the same procedure as in Example 1. The properties of the obtained composite material are described in Table 1.

[0065] (Resin composition aqueous dispersion) The resin composition aqueous dispersion was obtained as follows. 70 parts of sorbitol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, EX614B, active ingredient concentration 100% by weight), which is a water-soluble epoxy resin, 830 parts of an aqueous dispersion of a blocked isocyanate of hexamethylene diisocyanate blocked with dimethylpyrazole (manufactured by Lanxess, Trixene aqua BI201, active ingredient concentration 40% by weight), and 100 parts of water were mixed to obtain a resin composition aqueous dispersion with an active ingredient concentration of 40% by weight.

[0066] 〔Example 3〕 As a fiber base material, a glass fiber fabric with a basis weight of 210 g / m 2 (manufactured by Arisawa Manufacturing Co., Ltd., K7628 S650) was prepared separately from the para-aramid fiber fabric. In the same procedure as in Example 2, a para-aramid fiber prepreg and a glass fiber prepreg were obtained. The composition of the obtained prepreg is described in Table 1.

[0067] Also, after removing the release paper of the para-aramid fiber prepreg and the glass fiber prepreg, three sheets were stacked in the order of one glass fiber prepreg, one para-aramid fiber prepreg, and one glass fiber prepreg, and then compression molded at 200 °C for 30 minutes under a pressure of 0.5 MPa. Then, post-curing was performed at 200 °C for 30 minutes in a dryer under a nitrogen atmosphere to obtain a composite material. The ends, each 25 mm in the up, down, left, and right directions, were cut off. The properties of the obtained composite material are described in Table 1.

[0068] 〔Example 4〕 A para-aramid fiber prepreg was obtained using the same procedure as in Example 2. The composition and weight of the obtained prepreg are shown in Table 1. Subsequently, the release paper was removed from the para-aramid fiber prepreg, and one sheet was pressure-molded at 0.5 MPa for 30 minutes at 200°C. Afterward, post-curing was performed in a dryer under a nitrogen atmosphere at 200°C for 30 minutes to obtain the composite material. 25 mm from each end (top, bottom, left, and right) was trimmed. The properties of the obtained composite material are shown in Table 1.

[0069] [Comparative Example 1] Para-aramid fiber prepregs were obtained using the same procedure as in Example 1, except that the following resin composition aqueous dispersion was used instead of the flame retardant component-containing resin composition aqueous dispersion in Example 1. The composition and weight of the obtained prepreg are listed in Table 1. Furthermore, a composite material was obtained using the same procedure as in Example 4. The properties of the obtained composite material are listed in Table 1.

[0070] (Resin composition water dispersion) A resin composition aqueous dispersion was obtained as follows: 300 parts of sorbitol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, EX614B, active ingredient concentration 100% by weight), which is a water-soluble epoxy resin, and 700 parts of water were mixed to obtain a resin composition aqueous dispersion with an active ingredient concentration of 30% by weight.

[0071] [Comparative Example 2] Para-aramid fiber prepregs were obtained using the same procedure as in Example 1, except that the following resin composition aqueous dispersion was used instead of the flame retardant component-containing resin composition aqueous dispersion in Example 1. The composition and weight of the obtained prepreg are listed in Table 1. Furthermore, a composite material was obtained using the same procedure as in Example 4. The properties of the obtained composite material are listed in Table 1.

[0072] (Resin composition water dispersion) As an aqueous dispersion of the resin composition, an aqueous dispersion of a dimethylpyrazole-blocked hexamethylene diisocyanate-based blocked isocyanate (Lanxess, Trixene aqua BI201, active ingredient concentration 40% by weight) was prepared as a standalone product.

[0073] [Table 1]

[0074] As shown in Table 1, a composite material with excellent tensile strength and puncture resistance was obtained from the prepreg of the present invention. Furthermore, by adding flame retardants as needed, it was possible to obtain composite materials that also possessed flame-retardant properties.

[0075] When comparing the long-term storage properties of resin and curing agent mixtures at room temperature, curing progressed over time when unblocked isocyanate was used as the curing agent, whereas when blocked isocyanate was used, no curing was observed over the same period, and long-term storage at room temperature was possible. [Industrial applicability]

[0076] The composite material obtained from the prepreg of the present invention is suitably used in aircraft, automobiles, sports and leisure, and general industrial applications. In particular, it is suitably used as a panel material for aircraft containers where lightweight, high tensile strength, and puncture resistance are required.

Claims

1. A prepreg comprising an aramid fiber fabric with a basis weight of 300 to 1000 g / m² and an uncured curable resin, wherein the prepreg contains 10 to 100% by weight of curable resin relative to the fiber base material, the uncured curable resin consists of a main component and a curing agent, the main component of the uncured curable resin is sorbitol polyglycidyl ether, the curing agent is dimethylpyrazole (DMP) block, and the weight ratio of the main component to the curing agent is 10:90 to 80:20, characterized in that, a prepreg for fiber-reinforced composite materials.

2. The prepreg for fiber-reinforced composite materials according to claim 1, wherein the uncured curable resin further contains a flame retardant.

3. A panel for an aircraft container made of a fiber-reinforced composite material obtained by curing the prepreg according to any one of Claims 1 to 2.

4. A panel for aircraft containers, wherein the panel is made of a fiber-reinforced composite material obtained by curing a laminate of a prepreg according to any one of claims 1 to 2 and an inorganic fiber sheet substrate.

5. A method for producing a prepreg for fiber-reinforced composite materials, comprising an impregnation step of impregnating an aramid fiber fabric having a basis weight of 300 to 1000 g / m² with an uncured curable resin, wherein the impregnation step is performed by impregnating a fiber base material with an aqueous dispersion of the uncured curable resin, the uncured curable resin consists of a main component and a curing agent, the main component of the uncured curable resin is sorbitol polyglycidyl ether, the curing agent is dimethylpyrazole (DMP) block, and the weight ratio of the main component to the curing agent is 10:90 to 80:20.

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