Prepreg and method for manufacturing prepreg

Abstract

The present invention provides a prepreg which has good handling properties and little resin flow, thereby making work in the molding process easy and improving the dimensional accuracy of a molded body.　In order to achieve the above, the present invention provides a prepreg which comprises a fiber base material and a resin layer that is superposed on one surface of the fiber base material and contains a thermosetting resin composition that contains at least the constituents (A) and (B) described below, wherein: the fiber base material is impregnated with some of the thermosetting resin composition in the resin layer; if the resin layer-side surface of the fiber base material is taken as the resin surface and the surface on the reverse side is taken as the fiber base material surface, there is a difference between the tack force of the resin surface and the tack force of fiber base material surface; the complex viscosity η3*24 of the thermosetting resin composition at 24°C is from 20,000 Pa·s to 100,000 Pa·s and the complex viscosity η3*70 thereof at 70°C is from 100 Pa·s to 5,000 Pa·s; and if the mass of the entire prepreg is taken as 100% by mass, the volatilization amount of the thermosetting resin composition is 1% by mass or less. (A) a thermosetting resin (B) a curing agent for the component (A)

Description

[Technical Field]

[0001] This invention relates to a prepreg with excellent handling properties and low resin flow, and to a method for producing the same. [Background technology]

[0002] Products such as aircraft structural components, wind turbine blades, automobile body panels, and computer applications like IC trays and laptop casings require high structural performance. Molded articles for these products are obtained by curing prepregs under pressure and heat in an autoclave or press. Prepregs are manufactured by laminating a film-like resin material, consisting of a thermosetting resin composition such as epoxy resin, onto fibers, and then impregnating the fibers with the thermosetting resin composition by applying pressure and heating. Alternatively, a method exists in which a fiber base material is pre-laminated in a mold, sandwiched between film-like resin materials on both sides, and then cured under pressure and heat in the mold to obtain a molded article. This method is called resin film infusion (RFI) and allows for the production of molded articles in a short time.

[0003] In film-like resin materials and prepregs containing thermosetting resin compositions, the viscosity of the thermosetting resin composition is a very important property. For example, if the thermosetting resin composition has high viscosity at room temperature, the tack of the film-like resin material is low, and the adhesion of the resin to hands and the workplace during handling is suppressed. Tack refers to the stickiness or adhesion of film-like resin materials and prepregs; low tack means that they are less sticky and less likely to stick.

[0004] Furthermore, when a thermosetting resin composition has high viscosity during curing or molding of a prepreg, i.e., at high temperatures, resin flow can be suppressed, thereby reducing burrs that occur on the cured product or molded body, and reducing the loss of resin in the molded body. Resin flow refers to the flow of a thermosetting resin composition, such as a film-like resin material or a resin layer contained in a prepreg, and if the amount of resin flow is large, the thermosetting resin composition tends to spread to the surroundings.

[0005] On the other hand, in the manufacturing process of film-like resin materials and prepregs, the thermosetting resin composition is required to be adjusted to a low viscosity. This is because the lower the viscosity of the thermosetting resin composition, the easier it is to deform, and the easier it is to coat the release sheet that serves as the support for the film-like resin material with the thermosetting resin composition. In other words, if the thermosetting resin composition is designed to have high viscosity in order to make the film-like resin material low tack and low resin flow (low resin flow), the suitability of the manufacturing process for the film-like resin material and prepreg will be impaired, and problems will arise in the passage through the manufacturing process.

[0006] The above-mentioned methods for producing the film-like resin material include a wet method, in which a thermosetting resin composition is dissolved in an organic solvent selected from acetone, methyl ethyl ketone, and methanol to reduce its viscosity, coated onto a release sheet, and then the organic solvent is evaporated to obtain the film-like resin material; and a hot melt method, in which the viscosity is reduced by heating without using an organic solvent, and the film-like resin material is coated onto a release sheet.

[0007] Generally, when manufacturing film-like resin materials using the wet process, a solvent is used, making it easier to reduce the viscosity of the thermosetting resin composition. However, in the hot-melt process, which does not use a solvent, viscosity reduction is difficult because only heating is involved. Therefore, the hot-melt process often results in problems where high-viscosity thermosetting resin compositions cannot be formed into sheets during the manufacturing process to create film-like resin materials, and the passability through the manufacturing process is not good.

[0008] Patent Document 1 describes how excellent processability of film-like resin materials in the hot-melt method and excellent handling properties of prepregs can be achieved by blending a specific thermosetting resin, curing agent, and thermoplastic resin into a thermosetting resin composition. Patent Document 2 describes how excessive tackiness of prepregs can be eliminated by impregnating a fibrous substrate with a film-like resin material and then reacting the thermosetting resin composition with light to increase its viscosity. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2003-238657 [Patent Document 2] Patent No. 5733418 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] The wet process has several problems, including the need for subsequent solvent removal, the volatilization of solvents during the film-like resin material manufacturing process which harms the work environment, and the presence of residual solvent in the film-like resin material manufactured by the wet process, which causes voids in the subsequently manufactured molded fiber-reinforced composite material and degrades the mechanical properties of the fiber-reinforced composite material. Therefore, there is a demand for the manufacture of film-like resin materials with excellent process passability without the use of solvents, using high-viscosity thermosetting resin compositions, and for prepregs using these film-like resin materials. However, as mentioned above, manufacturing film-like resin materials by the hot-melt method and obtaining prepregs using them has been an extremely difficult challenge.

[0011] The technology disclosed in Patent Document 1 has low versatility because the raw materials used in the thermosetting resin composition are limited. Furthermore, in the technology disclosed in Patent Document 2, only the surface of the prepreg exposed to light becomes highly viscous, which may result in insufficient suppression of resin flow during molding.

[0012] Therefore, the problem that the invention aims to solve is to find a prepreg with low tack and low resin flow, and a method for manufacturing the same, without restrictions on the use of solvents or specific thermosetting resin composition raw materials. Furthermore, by realizing a prepreg with good handling properties and low resin flow, the work in the process of manufacturing molded articles will be made easier, and the dimensional accuracy of the molded articles will be improved. [Means for solving the problem]

[0013] The present invention has the following configuration in order to solve such problems. That is, A prepreg in which a resin layer containing a thermosetting resin composition containing at least the following components [A] and [B] is laminated on one surface of a fiber base material, A part of the thermosetting resin composition of the resin layer is impregnated into the fiber base material, When the surface on the resin layer side of the prepreg is defined as the resin surface and the opposite surface is defined as the fiber base material surface, There is a difference between the tack force of the resin surface and the tack force of the fiber base material surface, The complex viscosity at 24°C: η3*24 of the resin layer contained in the prepreg is 20,000 to 100,000 Pa·s, and the complex viscosity at 70°C: η3*70 is 100 to 5,000 Pa·s, A prepreg in which the volatile content of the thermosetting resin composition is 1% by mass or less when the total mass of the prepreg is 100% by mass. [A] Thermosetting resin [B] Curing agent for [A].

[0014] Further, the present invention provides a method for producing the following prepreg in order to solve such problems. That is, it has a treatment step of pre-curing a film-like resin material obtained by coating a thermosetting resin composition containing at least components [A] and [B] on a release sheet. In this pre-curing step, the viscosity of the thermosetting resin composition is such that the complex viscosity at 24°C: η2*24 is 20,000 to 100,000 Pa·s, and the complex viscosity at 70°C: η2*70 is 100 to 5,000 Pa·s to obtain a resin film, and the resin film after the pre-curing step is laminated on one surface of a fiber base material, and it is a method for producing a prepreg in which the thermosetting resin composition is impregnated into the fiber base material on one side. [A] Thermosetting resin [B] Curing agent for [A].

Effects of the Invention

[0015] The present invention provides a prepreg and a method for producing the same that eliminates restrictions on the raw materials of the thermosetting resin composition, has good passability through the manufacturing process, exhibits low tack at room temperature, and has low resin flow during molding. Furthermore, by realizing a prepreg with good handling properties and low resin flow, the work in the process of manufacturing molded articles is made easier, and the dimensional accuracy of the molded articles is improved. [Modes for carrying out the invention]

[0016] The prepreg of the present invention comprises a fibrous substrate and a resin layer laminated on one side of the fibrous substrate, the resin layer comprising a thermosetting resin composition containing at least [A] a thermosetting resin and [B] a curing agent, wherein a portion of the thermosetting resin composition of the resin layer is impregnated into the fibrous substrate. One side of the fibrous substrate has a thin resin layer laminated thereon, so that the resin layer covers one surface of the fibrous substrate. A portion of the thermosetting resin composition of the resin layer is impregnated into the fibrous substrate, and the degree of impregnation of the thermosetting resin composition into the fibrous substrate is such that one surface of the fibrous substrate is sufficiently impregnated, while the opposite side is not sufficiently impregnated, leaving all or part of the fibrous substrate exposed.

[0017] In other words, when the side of the prepreg with the resin layer is considered the resin surface and the opposite side is considered the fiber substrate surface, the thermosetting resin composition does not completely impregnate the outermost surface of the fiber substrate surface, or even if it does, the amount of impregnation is insufficient, so the fiber substrate is not completely covered. Furthermore, the tack strength of the prepreg is lower compared to the thermosetting resin composition before curing, and there is a difference between the tack strength of the resin surface and the tack strength of the fiber substrate surface. The tack strength of the resin surface covered by the thermosetting resin composition is high, while the tack strength of the fiber substrate surface, which is not completely covered by the resin surface, is low.

[0018] Such prepregs are obtained by pre-curing a film-like resin material of the thermosetting resin composition in order to create a difference in the amount of impregnation of the thermosetting resin composition. The pre-cured resin film, which has an increased complex viscosity of the thermosetting resin composition, is then laminated onto one side of a fiber substrate and impregnated on one side. If the film-like resin material of the thermosetting resin composition is impregnated directly into the fiber substrate, the complex viscosity of the thermosetting resin composition is low, so both the surface of the fiber substrate and the opposite surface are sufficiently impregnated, and both surfaces of the fiber substrate are covered with a resin layer. In other words, the prepreg of the present invention has a prepreg configuration that cannot be obtained by impregnation of a normal thermosetting resin composition.

[0019] Furthermore, in the process of manufacturing the film-like resin material, even with a low-viscosity thermosetting resin composition, a pre-cured resin film is laminated onto a fiber substrate before impregnation into the prepreg, making it possible to obtain a high-viscosity thermosetting resin composition. In other words, the process suitability of the hot-melt method, which requires a low-viscosity thermosetting resin composition, is met, and the resulting prepreg can achieve low tack and low resin flow.

[0020] The prepreg is characterized in that the complex viscosity (η3*24) of the resin layer contained in the prepreg at 24°C is 20,000 to 100,000 Pa·s, and the complex viscosity (η3*70) at 70°C is 100 to 5,000 Pa·s, and the volatilization amount of the thermosetting resin composition is 1% by mass or less when the total mass of the prepreg is 100% by mass.

[0021] The complex viscosity η3*24 of the prepreg resin layer at 24°C is an important property related to the handling and impregnation of the prepreg. Higher viscosity results in lower tack force and better handling. The complex viscosity η3*70 of the prepreg resin layer at 70°C is a property related to the resin flow of the prepreg. Higher viscosity results in lower resin flow, less flow of the resin composition in the prepreg, and improved dimensional accuracy of the molded product. Both η3*24 and η3*70 are lower than the complex viscosity of the thermosetting resin composition before curing. A volatilization amount of 1% by mass or less is a characteristic possessed only by prepregs that are made by forming a film of the thermosetting resin composition using a hot melt method without solvents, and then impregnating one side of the fiber substrate with a pre-cured resin film from which volatile components have been removed before impregnation.

[0022] The film-like resin material and prepreg of the present invention will be described in detail.

[0023] <Film-like resin materials and prepregs> In this invention, the thermosetting resin composition is handled in various forms and states from kneading to impregnation into the prepreg. First, the names of the thermosetting resin composition in each step will be explained. The thermosetting resin composition is obtained by kneading [A] thermosetting resin and [B] curing agent for [A], and may also include resins other than [A] and [B]. The thermosetting resin composition can be made into a film-like resin material by coating it onto a release sheet, for example. In this invention, the material in which the thermosetting resin composition is coated onto a release sheet is called a "film-like resin material with a release sheet," and the sheet-like thermosetting resin composition alone is called a "film-like resin material." The coating of the thermosetting resin composition onto the release sheet is performed by the hot melt method.

[0024] The resin composition obtained by pre-curing the resulting film-like resin material is called the "pre-cured resin film." Pre-curing is a heat treatment of a thermosetting resin composition at a temperature lower than the curing temperature. The degree of pre-curing is evaluated and adjusted to a predetermined degree of curing. The production of this "pre-cured resin film" is carried out separately before the production of the prepreg. Furthermore, the "pre-cured resin film" is laminated to one side of a fiber substrate, the release sheet is removed, and the resulting thermosetting resin composition laminated to the fiber substrate is called the "resin layer." A portion of the thermosetting resin composition in the "resin layer" is impregnated into the fiber substrate, forming the prepreg.

[0025] The complex viscosity η* of the thermosetting resin composition of the present invention changes depending on the degree of curing and the measurement temperature. Complex viscosity η* is an important indicator in each of the above-described steps. Complex viscosity, also called complex viscosity ratio, is obtained from viscoelastic measurements related to flow properties. By subjecting the thermosetting resin composition to periodic deformation (strain) and detecting the resulting stress and phase difference, the storage modulus of elasticity G' (elastic term), the loss modulus of elasticity G'' (viscous term), and the complex viscosity η* (viscosity term) can be determined. In the present invention, the characteristics of the complex viscosity η* at each measurement temperature are important. Here, the complex viscosity of the kneaded thermosetting resin composition is denoted as "η1*", the complex viscosity of the resin film after pre-curing is denoted as "η2*", and the complex viscosity of the resin layer of the prepreg is denoted as "η3*". The measurement temperature is added to the end of the notation. The complex viscosity of the kneaded thermosetting resin composition at 70°C is notated as "η1*70".

[0026] The complex viscosity of the kneaded thermosetting resin composition at 70°C, i.e., η1*70, is a viscosity that affects the passability of the manufacturing process in the process of forming the kneaded thermosetting resin composition into a film-like resin material. The complex viscosity of the pre-cured resin film at 24°C, η2*24, is an important viscosity in the process of laminating the pre-cured resin films to manufacture a prepreg. Higher viscosity results in lower tack force and better handling. The complex viscosity of the resin layer of the prepreg at 24°C, η3*24, is an important viscosity for handling the prepreg. Higher viscosity results in lower tack force and better handling. Higher viscosity also means that less of the resin layer is impregnated into the fiber substrate, resulting in weaker resin impregnation into the fiber substrate.

[0027] The complex viscosity η2*70 of the pre-cured resin film at 70°C and the complex viscosity η3*70 of the resin layer of the prepreg are important viscosities when laminating the pre-cured resin film and impregnating it into the prepreg. Higher viscosity results in smaller resin flow. Also, at the curing temperature, the amount of resin impregnated into the resin layer decreases, weakening the resin impregnation into the fiber substrate, and preventing the resin composition from completely covering the fiber substrate. Note that the η2*24 of the pre-cured resin film of the present invention is slightly lower than the η3*24 of the prepreg. Furthermore, the η2*70 of the pre-cured resin film is slightly lower than the η3*70 of the prepreg.

[0028] The prepreg of the present invention is constructed by laminating a resin layer containing a thermosetting resin composition onto a fiber substrate, and impregnating the fiber substrate with a portion of the thermosetting resin composition in the resin layer. The impregnation is one-sided, with the impregnation occurring from one side of the fiber substrate. When the side of the prepreg facing the resin layer is considered the resin surface and the opposite side the fiber substrate surface, the thermosetting resin composition does not completely penetrate to the outermost surface of the fiber substrate surface, or if it does, the amount is insufficient. Therefore, the fiber substrate is not completely covered by the thermosetting resin composition. Furthermore, the tack strength of the prepreg is lower compared to the pre-cured state of the thermosetting resin composition, and there is a difference between the tack strength of the resin surface and the tack strength of the fiber substrate surface. The tack strength of the resin surface covered by the resin is high, while the tack strength of the fiber substrate surface not completely covered by the resin surface is low.

[0029] The tack and resin flow of the prepreg of the present invention depend on the viscosity of the resin layer contained in the prepreg. The method for evaluating the viscosity of the resin layer is as follows: First, the prepreg is sandwiched between two release sheets, and heat and pressure are applied with an iron or the like to partially separate the resin layer contained in the prepreg from the fiber substrate, and the resin layer contained in the prepreg that adheres to the release sheets is sampled.

[0030] The complex viscosity η3* can be measured using a dynamic viscoelastic device, ARES-2KFRTN1-FCO-STD (manufactured by T.A. Instruments Co., Ltd.). Using parallel plates with a diameter of 40 mm as upper and lower measuring fixtures, the resin layer of the prepreg is placed between the upper and lower fixtures so that the distance between the fixtures is 1 mm. The complex viscosity is then measured in torsion mode (measurement frequency: 0.5 Hz) while increasing the temperature from 20°C to 150°C at a rate of 2°C / min. Here, the complex viscosity of the resin layer at 24°C is denoted as η3*24, and the complex viscosity at 70°C is denoted as η3*70.

[0031] A Pa·s of η3*24 is preferably 20,000 to 100,000. When η3*24 is 20,000 Pa·s or higher, the tack of the prepreg is low, and the resin layer contained in the prepreg is less likely to stick to hands or the work surface during handling, making it easier to handle. When η3*24 is 100,000 Pa·s or lower, the impregnation of the resin layer contained in the prepreg into the fiber substrate is good, which is preferable because it maintains high adhesion to the lamination target during prepreg lamination. A Pa·s of η3*24 of 25,000 to 90,000 is more preferable, and a Pa·s of 40,000 to 90,000 is even more preferable.

[0032] Furthermore, η3*70 is preferably 100 to 5,000 Pa·s. When η3*70 is 100 Pa·s or higher, the resin flow is reduced, which is preferable as it suppresses burrs during prepreg molding. When η3*70 is 5,000 Pa·s or lower, the adhesion of the prepreg to the lamination target after molding is improved, which is preferable. When η3*70 is 500 to 4,000 Pa·s, it is more preferable, and when η3*70 is 2,000 to 4,000 Pa·s, it is even more preferable.

[0033] Furthermore, the preferred ranges for the complex viscosities η2*24 and η2*70 of the pre-cured resin film are close to those of η3*24 and η3*70, with η2*24 preferably ranging from 20,000 to 100,000 Pa·s and η2*70 preferably ranging from 100 to 5,000 Pa·s. Single-sided impregnation can be achieved by controlling the complex viscosity η2*24 of the pre-cured resin film to be considerably higher than the complex viscosity η1*24 of the thermosetting resin composition (kneaded).

[0034] The prepreg in this invention can be laminated one or more sheets together or with different materials and then molded. The prepreg or laminate using the prepreg can be molded into a molded body (referred to as a fiber-reinforced composite material) by autoclave molding, press molding, oven curing, etc.

[0035] The volatilization amount of the prepreg in this invention is less than 1% by mass, which reduces the impact of chemical substances being released into the environment where the prepreg is handled. Furthermore, since the resin flow of the prepreg in this invention is less than 10% by mass, the resin-to-fiber substrate content ratio and curing thickness of the molded product can be set as desired, and there is also the advantage that there are fewer burrs on the molded product, making burr trimming easier.

[0036] The basis weight of the film-like resin material according to the present invention is 10 to 300 g / m². 2 Preferably, the basis weight of the film-like resin material is 10 g / m². 2This is preferable because it allows for sufficient impregnation of the reinforcing fibers, enabling the fiber-reinforced composite material to fully exhibit its mechanical properties such as compression and tensile strength, and reduces the number of prepreg layers required to obtain the desired thickness during fiber-reinforced composite material molding, thus improving work efficiency. The basis weight of the resin film is 300 g / m². 2 The following conditions are preferable because, when molding as a prepreg, the heat generated by the curing of the thermosetting resin composition is suppressed, and the prepreg tends to have good drapeability. Drapability refers to the flexibility of deformation of the prepreg and is a characteristic that affects the shapeability on the mold during lamination. If the drapeability is low, it is difficult to shape it onto a curved surface, and if the drapeability is too high, it tends to wrinkle easily.

[0037] The basis weight of the prepreg of the present invention is preferably 65 to 450 g / m². 2 More preferably, 80-400 g / m² 2 And more preferably 90-300 g / m² 2 The basis weight of the prepreg is 65 g / m². 2 This is preferable because it allows for a smaller number of prepreg layers relative to the desired thickness of the molded product, thereby improving work efficiency. The prepreg basis weight is 450 g / m². 2 This is preferable because it tends to result in good drape properties for the prepreg.

[0038] In the present invention, the fiber mass content of the prepreg is preferably 10 to 90% by mass, with the prepreg being 100% by mass. More preferably, the fiber mass content of the prepreg is 60 to 85% by mass, with the prepreg being 100% by mass, and even more preferably 70 to 80% by mass. When the fiber mass content is 10% by mass or more, the advantage of the prepreg is easily obtained, as it provides a fiber-reinforced composite material with excellent specific strength and specific modulus due to the high reinforcing fiber content. Furthermore, when the fiber mass content is 90% by mass or less, impregnation defects of the thermosetting resin composition are less likely to occur, and the resulting composite material tends to have fewer voids, which is preferable.

[0039] As the reinforcing fibers of the fiber reinforced composite material, various carbon fibers, graphite fibers, glass fibers, PET fibers, nylon fibers, aramid fibers, etc. are preferably used. Among these, it is preferable to use carbon fibers from which a lightweight and high-rigidity fiber reinforced composite material can be obtained.

[0040] The form of the fiber base material by the reinforcing fibers is not particularly limited, and examples include long fibers aligned in one direction, tow, woven fabric, mat, knit, braided cord, blade, non-woven fabric, etc. The fiber base material may be used alone or in two or more types.

[0041] When the fiber base material is 5 to 200 g / m 2 the handling property of the prepreg becomes good. When the basis weight of the fiber base material is 5 g / m 2 or more, the fiber base material is difficult to break during handling, and when it is 200 g / m 2 or less, it is preferable in terms of good shaping property of the prepreg.

[0042] The curing temperature of the prepreg of the present invention depends on the thermosetting resin used, the curing agent used, and the curing catalyst, but it is preferably carried out at a temperature of 100 to 200 °C from the viewpoint of suppressing the generation of distortion and wrinkles due to thermal stress.

[0043] The tack of the prepreg of the present invention can be evaluated by attaching the surface of the prepreg to the surface of an FEP film, further pressing it firmly with a 2kg roller for one pass, and then measuring the load when peeling the prepreg off at a 30° angle using an adhesion / film analysis device. A tack of 1mN / mm or more is preferable because it provides excellent adhesion to the object to be attached, and a tack of 15mN / mm or less is preferable because it makes it easy to peel off the object to be attached, allowing for repositioning and reattachment after peeling. Furthermore, the prepreg of the present invention is characterized by having a difference in tack on both sides (the impregnated side of the prepreg is called the resin side, and the unimpregnated side is called the fiber substrate side). The fiber substrate side of the prepreg is preferably 0 to 10mN / mm. A tack higher than 0mN / mm is preferable because it provides good adhesion to the material to be attached to the fiber substrate side, and a tack of 10mN / mm or less is preferable because it makes it easy to distinguish between the resin side and the fiber substrate side of the prepreg. Furthermore, a tack of 0 to 0.5 mN / mm on the fiber substrate surface is particularly preferable, as it allows the resin layer contained in the prepreg to be handled without sticking to the hands from the fiber substrate surface.

[0044] The prepreg in this invention contains a thermosetting resin composition on one side of a fiber substrate, has a difference in tack between the upper and lower surfaces, with η3*24 being 20,000 to 100,000 Pa·s and η3*70 being 100 to 5,000 Pa·s, and a volatilization amount of 1% by mass or less. As a result, the tack of the fiber substrate surface is low, making it difficult for the thermosetting resin composition contained in the prepreg to stick to the hands when handled, and it is easy to distinguish which side is the fiber substrate side and which is the resin side, resulting in good handling. Resin flow during molding is suppressed, reducing the loss of thermosetting resin composition and burrs in the resulting molded product, and voids during molding are also suppressed. Therefore, the prepreg in this invention has good handling properties, and its use allows for the design of molded product dimensions with high precision without compromising mechanical properties, which is an excellent feature.

[0045] Component [A] of the present invention is a thermosetting resin. A thermosetting resin refers to a resin material that reacts and forms crosslinks upon heating. Examples of thermosetting resins include epoxy resins, phenolic resins, polyurethane resins, isocyanate resins, polyimide resins, polyester resins, cyanate ester resins, and bismaleimide resins. Epoxy resins are preferably used from the viewpoint of heat resistance, dimensional stability after molding and curing, and adhesiveness. An example of an epoxy resin is a bisphenol-type epoxy resin, which is not particularly limited as long as it is obtained by reacting two phenolic hydroxyl groups of a bisphenol compound with epichlorohydrin to convert them into glycidyloxy groups. Bisphenol A type, bisphenol F type, bisphenol AD ​​type, bisphenol S type, or halogen, alkyl substituted, or hydrogenated versions of these bisphenols can be used. Furthermore, high molecular weight compounds having multiple repeating units can also be preferably used, not just monomers.

[0046] Commercially available amine-type epoxy resins include, for example, tetraglycidyldiaminodiphenylmethane, tetraglycidyldiaminodiphenylsulfone, triglycidylaminophenol, triglycidylaminocresol, tetraglycidylxylylenediamine, glycidylaniline, diglycidyltoluidine, and halogen- and alkyl-substituted versions thereof, as well as hydrogenated versions. Other epoxy resins include tetrahydroindenide diepoxide, vinylcyclohexene oxide, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylic acid, dipentene dioxide, bis(3,4-epoxycyclohexylmethyl) adipate, dicyclopentadiene dioxide, bis(2,3-epoxycyclopentyl) ether, 1,2-epoxy-4-(2-oxyranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol, tetrakis-(3-cyclohexenylmethyl) modified epsilon-caprolactone, bi-7-oxabicyclo[4.1.0]heptane, dodecahydrobisphenol A diglycidyl ether, dodecahydrobisphenol F diglycidyl ether, and 1,4-cyclohexanedimethanol diglycidyl ether. Examples include diglycidyl ether, hexahydrophthalate diglycidyl ester, hexahydroterephthalate diglycidyl ester, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol glycidyl ether, 1,6-hexanediol diglycidyl ether, neopentylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, 1,4-bis(2-oxyranyl)butane, pentaerythritol polyglycidyl ether, 4-tert-butyl glycidyl ether, butyl glycidyl ether, 1-butene oxide, 1,2-epoxy-4-vinylcyclohexane, and 2-ethylhexylglycidyl ether.

[0047] Commercially available epoxy resins can be used for the above-mentioned epoxy resins. For example, commercially available bisphenol A type epoxy resins include "jER(registered trademark)" 825, 828, 834, 1001, 1002, 1003, 1003F, 1004, 1004AF, 1005F, 1006FS, 1007, 1009, and 1010 (all manufactured by Mitsubishi Chemical Corporation). Brominated bisphenol A type epoxy resins include "jER(registered trademark)" 505, 5050, 5051, 5054, and 5057 (all manufactured by Mitsubishi Chemical Corporation).

[0048] Commercially available bisphenol F type epoxy resins include "jER(registered trademark)" 806, 807, 4002P, 4004P, 4007P, 4009P, and 4010P (all manufactured by Mitsubishi Chemical Corporation), and "Epotote(registered trademark)" YDF2001 and YDF2004 (both manufactured by Nippon Steel Chemical & Material Co., Ltd.). Examples of tetramethylbisphenol F type epoxy resins include YSLV-80XY (manufactured by Nippon Steel Chemical & Material Co., Ltd.).

[0049] Examples of bisphenol S type epoxy resins include "Epiclon®" EXA-1514 (manufactured by DIC Corporation).

[0050] As tetraglycidyldiaminodiphenylmethane, you can use "SumiEpoxy®" ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), YH434L (manufactured by Nippon Steel Chemical & Material Co., Ltd.), "jER®" 604 (manufactured by Mitsubishi Chemical Corporation), "Araldide®" MY720, MY721 (manufactured by Huntsman Corporation), etc. As tetraglycidyldiaminodiphenylsulfone, you can use TGDDS (manufactured by Konishi Chemical Co., Ltd.), etc. As triglycidylaminophenol or triglycidylaminocresol, you can use "SumiEpoxy®" ELM100, ELM120 (manufactured by Sumitomo Chemical Co., Ltd.), "Araldide®" MY0500, MY0510, MY0600 (manufactured by Huntsman Corporation), "jER®" 630 (manufactured by Mitsubishi Chemical Corporation), etc. As tetraglycidylxylylenediamine and its hydrogenated products, "TETRAD®"-X, "TETRAD®"-C (manufactured by Mitsubishi Gas Chemical Co., Ltd.), etc., can be used. As glycidylaniline, GAN (manufactured by Nippon Kayaku Co., Ltd.), etc., can be used. As diglycidyltoluidine, GOT (manufactured by Nippon Kayaku Co., Ltd.), etc., can be used.

[0051] Other epoxy resins include "Celoxide" (registered trademark) 2021P, "Celoxide" (registered trademark) 8010, "Celoxide" (registered trademark) 2000, "Epolid" (registered trademark) GT401, "Celoxide" (registered trademark) 2081, EHPE3150 (manufactured by Daicel Corporation), THI-DE (manufactured by JXTG Energy Corporation), TTA21, AAT15, TTA22 (manufactured by Sun Chemical Co., Ltd.). Examples include Ex-121, Ex-211, Ex-212, Ex-313, Ex-321, Ex-411 (manufactured by Nagase Chemtec Co., Ltd.), “Epolite” (registered trademark) 4000 (manufactured by Kyoeisha Chemical Co., Ltd.), ST-3000, ST-4000, ST5080, ST4000D, ST4100D, ST5100 (manufactured by Nippon Steel Chemical & Material Co., Ltd.).

[0052] Component [B] is the curing agent for [A]. Examples of curing agents include amine curing agents, alcohol compounds, phenol compounds, cationic curing agents, anionic curing agents, radical curing agents, acid anhydride compounds, and imidazole compounds. Examples of amine curing agents include dicyandiamide or its derivatives, and diaminodiphenylsulfone or its derivatives. Here, dicyandiamide can be used in combination with ureaamine curing agents or urea compounds to control the reactivity of the induced curing reaction.

[0053] Commercially available hardeners can be used. For example, commercially available dicyandiamides include DICY-7 and DICY-15 (both manufactured by Mitsubishi Chemical Corporation).

[0054] Diaminodiphenylsulfone has structural isomers depending on the position of the amino group. Commercially available 4,4'-diaminodiphenylsulfones include "Seikakyuka®"-S (manufactured by Wakayama Seika Kogyo Co., Ltd.) and "SumiCure®"-S (manufactured by Sumitomo Chemical Co., Ltd.). Commercially available 3,3'-diaminodiphenylsulfones include 3,3'-DAS (manufactured by Mitsui Chemicals Fine, Inc.). The amount of amine-based curing agent added is preferably 5 to 70 parts by mass per 100 parts by mass of component [A].

[0055] Examples of commercially available imidazole compounds include "Curezol" (registered trademark) 2MZ, 2PZ, and 2E4MZ (manufactured by Shikoku Chemicals Co., Ltd.).

[0056] Examples of cationic curing agents include 1-naphthylmethylmethylp-hydroxyphenylsulfonium=hexafluoroantimonate, 2-methylbenzylmethylp-hydroxyphenylsulfonium hexafluoroantimonate, benzylmethylp-hydroxyphenylsulfonium hexafluoroantimonate, dimethyl-p-acetoxyphenylsulfonium hexafluoroantimonate, diaryliodonium salts, boron fluoride piperidine, boron fluoride monoethylamine, diaryliodonium salts, and sulfonium salts.

[0057] Examples of commercially available cationic curing agents include "ADEKA-OPTON" (registered trademark) CP-77, "ADEKA-OPTON" (registered trademark) CP-66 (manufactured by ADEKA Corporation), CI-2639, CI-2624 (manufactured by Nippon Soda Co., Ltd.), "SUN-AID" (registered trademark) SI-60, "SUN-AID" (registered trademark) SI-80, "SUN-AID" (registered trademark) SI-100, "SUN-AID" (registered trademark) SI-150, "SUN-AID" (registered trademark) SI-B4, "SUN-AID" (registered trademark) SI-B5 (manufactured by Sanshin Chemical Industry Co., Ltd.), TA-100, IK-1PC(80) (manufactured by Sunapro Co., Ltd.), boron trifluoride piperidine, and boron trifluoride monoethylamine (manufactured by Stella Chemifa Co., Ltd.). The cationic curing agent is preferably a photothermal cationic curing agent or a thermal cationic curing agent. Photothermal cationic curing agents are those that become reactive when exposed to light of a certain wavelength or below, such as ultraviolet or visible light, or heat above a certain temperature, while thermal cationic curing agents are those that become reactive when exposed to heat. Photothermal cationic curing agents are preferred because they can be cured in a wide variety of environments, while thermal cationic curing agents are preferred because high storage stability can be obtained through temperature control.

[0058] Examples of anionic curing agents include phosphorus hexafluoride, antimony hexafluoride, arsenic hexafluoride, tin hexachloride, iron tetrachloride, bismuth pentachloride, and niobium hexachloride.

[0059] The above-mentioned cationic and anionic curing agents are preferably included in amounts of 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, and even more preferably 1 to 3 parts by mass, per 100 parts by mass of component [A] in the thermosetting resin composition, thereby providing rapid curing, suppression of resin flow and volatilization during molding, and a good balance of rapid curing, pot life, and UV resistance.

[0060] The above-mentioned cationic and anionic curing agents may be used with curing aids to control their reactivity. Examples of curing aids include 4-hydroxyphenyldimethylsulfonium methyl sulfate and 4-(methylthio)phenol. Commercial curing aids can also be used, such as "San-Aid" (registered trademark) SI-S and "San-Aid" (registered trademark) S-ME (manufactured by Sanshin Chemical Industry Co., Ltd.).

[0061] By including the above curing aid in an amount of preferably 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and even more preferably 0.1 to 2.5 parts by mass, per 100 parts by mass of component [A] in the thermosetting resin composition, a good balance between the rapid curing properties and pot life of the thermosetting resin composition can be obtained.

[0062] In the thermosetting resin composition related to the present invention, it is also preferable to include a thermoplastic resin. Examples of thermoplastic resins include polyamide, polycarbonate, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyarylate, polyester, polyamide-imide, polyimide, polyetherimide, polyimide having a phenyltrimethylindan structure, polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, polyaramid, polyethernitrile and polybenzimidazole, polyvinyl alcohol, polyvinyl acetal, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, polyvinyl acetate, hydrogenated bisphenol A-pentaerythritol phosphite polymer, hydrogenated terpenes, and hydrogenated terpene phenols.

[0063] These thermoplastic resins are preferably soluble in the thermosetting resin of component [A]. For example, if at least 10 parts by mass of thermoplastic resin powder is added to 100 parts by mass of thermosetting resin of component [A] and kneaded at 100-120°C for 1 hour, a reduction in the amount of thermoplastic resin powder from the starting point is observed, then the resin is considered soluble. A reduction in amount means that the amount becomes so small that it is not optically observable, or when the remaining powder is recovered, a decrease in mass of 10% or more from the starting point is observed. From the viewpoint of dissolving in the thermosetting resin, it is preferable that the volume-average particle size of the thermoplastic resin powder is 100 μm or less, at least as determined by laser diffraction. Furthermore, a volume-average particle size greater than 100 nm is preferable because it suppresses aggregation during storage and facilitates stirring into the thermosetting resin.

[0064] The above thermoplastic resin can be a commercially available product. For example, commercially available polyethersulfone products such as "Sumika Excel" (registered trademark) PES3600P, "Sumika Excel" (registered trademark) PES5003P, "Sumika Excel" (registered trademark) PES5200P, "Sumika Excel" (registered trademark) PES7600P (all manufactured by Sumitomo Chemical Co., Ltd.), "VIRANTAGE" (registered trademark) VW-10700RFP (manufactured by Solvay Advanced Polymers Co., Ltd.), a copolymer oligomer of polyethersulfone and polyethersulfone, and a commercially available polyetherimide product such as "Ultem" ( Examples include registered trademark 1000, "Ultem" (registered trademark) 1010, "Ultem" (registered trademark) 1040 (all manufactured by SABIC Innovative Plastics), and other thermoplastic resins such as "J-POVAL" (registered trademark) (manufactured by Nippon Vinegar Vinegar Co., Ltd.), "Vinylec" (registered trademark) (manufactured by JNC Corporation), "Eslec" (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), "Ultrasen" (registered trademark) (manufactured by Tosoh Corporation), JPH-3800 (manufactured by Johoku Chemical Industry Co., Ltd.), and YS Polystar UH130 (manufactured by Yasuhara Chemical Co., Ltd.).

[0065] A prepreg with good tack properties can be obtained by including the above thermoplastic resin in an amount of 1 to 60 parts by mass, more preferably 10 to 55 parts by mass, and even more preferably 30 to 55 parts by mass, per 100 parts by mass of component [A] in the thermosetting resin composition.

[0066] When polyethersulfone is used as a thermoplastic resin, polyethersulfone with a molecular weight of 10,000 to 60,000 g / mol is more preferably used, even more preferably with a molecular weight of 12,000 to 50,000 g / mol, and particularly preferably with an average molecular weight of 15,000 to 30,000 g / mol. When the molecular weight is within the above preferred range, the tack of the prepreg is appropriate and easy to handle, and the toughness of the cured product of the thermosetting resin composition does not decrease easily. On the other hand, when dissolved in a thermosetting resin, the viscosity of the thermosetting resin composition is appropriate and prepreg formation is easy. In particular, when dissolving polyethersulfone with a high heat resistance and a molecular weight of 15,000 to 30,000 g / mol into a thermosetting resin, a large amount of thermoplastic resin can be dissolved into the thermosetting resin within a range that does not cause problems in the prepreg formation process. Furthermore, high toughness can be imparted to the cured product of the thermosetting resin composition while maintaining the flexural modulus, and high tensile and compressive strength can be imparted to the resulting fiber-reinforced composite material. Here, molecular weight refers to the weight-average molecular weight in polystyrene terms, measured by gel permeation chromatography using HLC-8420GPC (manufactured by Tosoh Corporation) (the same applies hereinafter).

[0067] Furthermore, when the molecular weight of polyvinyl acetal, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, polyvinyl acetate, hydrogenated bisphenol A-pentaerythritol phosphite polymer, hydrogenated terpenes, and hydrogenated terpene phenol is preferably 5,000 to 70,000 g / mol, more preferably 7,000 to 65,000 g / mol, and even more preferably 10,000 to 60,000 g / mol, a good balance can be obtained between uniformity of dissolution in the thermosetting resin composition and the resin flow suppression effect. Examples of commercially available products with different molecular weights include polyvinyl formal ("Vinirec" (registered trademark) K, manufactured by JNC Corporation, molecular weight 40,000-54,000 g / mol), polyvinyl formal ("Vinirec" (registered trademark) E, manufactured by JNC Corporation, molecular weight 95,000-134,000 g / mol), and polyvinyl acetal ("Esrec" (registered trademark) KS-10, manufactured by Sekisui Chemical Co., Ltd., molecular weight 17,000 g / mol). <Prepreg manufacturing method> The prepreg of the present invention can be manufactured by coating the thermosetting resin composition according to the present invention onto, for example, a release sheet to form a film-like resin material, pre-curing the film-like resin material with the release sheet using light or heat (in the present invention, the film-like resin material and the pre-cured film-like resin material with the release sheet are referred to as "resin film" and "resin film with release sheet," respectively), and impregnating a fibrous substrate with the resin film from one side. Here, the release sheet is a material that facilitates the release of the resin film, the resin film, and the cured resin film, and examples include release paper and release film. Paper (release paper) is preferred as the release sheet from the viewpoint of strength and ease of handling.

[0068] The coating of the thermosetting resin composition onto the release sheet is performed by the hot melt method. In the production of film-like resin materials with release sheets using the hot melt method, the viscosity of the thermosetting resin composition is important. The viscosity of the thermosetting resin composition can be measured using a dynamic viscoelastic device ARES-2KFRTN1-FCO-STD (manufactured by T.A. Instruments Co., Ltd.). Using parallel plates with a diameter of 40 mm as upper and lower measuring fixtures, the thermosetting resin composition is set between the upper and lower fixtures so that the distance between the upper and lower fixtures is 1 mm. Then, the complex viscosity is measured while raising the temperature from 20°C to 150°C at a rate of 2°C / min in torsion mode (measurement frequency: 0.5 Hz). Here, the complex viscosity of the thermosetting resin composition at 24°C is denoted as η1*24, and the complex viscosity at 70°C is denoted as η1*70. It is preferable for process passability that η1*70 is between 1 and 500 Pa·s. A value of η1*70 of 1 Pa·s or more is preferable because it allows the film-like resin material to remain on the release sheet without flowing, and a value of η1*70 of 500 Pa·s or less is preferable because it allows the production of a film-like resin material with a stable basis weight and no defects on the release sheet.

[0069] A resin film can be produced by pre-curing the film-like resin material according to the present invention. In this invention, when simply referred to as "resin film," it refers to the pre-cured resin film. Pre-curing of the film-like resin material is performed by heating the sheet-like or roll-like film-like resin material with a release sheet in an oven or by irradiating the film-like resin material with light. This pre-curing process is performed on the film-like resin material alone before lamination onto a fibrous substrate. The complex viscosity η2*24 of the pre-cured resin film at 24°C is 20,000 to 100,000 Pa·s, and the complex viscosity η2*70 at 70°C is 100 to 5,000 Pa·s.

[0070] Pre-curing can be performed by heating the film-like resin material with a release sheet using an IR heater or by bringing the release paper surface of the film-like resin material with a release sheet into contact with a heating plate. The temperature of the oven, furnace, IR heater, or heating plate during pre-curing is preferably 40 to 200°C. A temperature of 40°C or higher can shorten the pre-curing time, while a temperature of 200°C or lower allows for uniform pre-curing of the film-like resin material. When pre-curing the film-like resin material by irradiating it with light, there are no particular limitations on the wavelength of the light, but ultraviolet light in the 100 to 400 nm range, which is absorbed by general photocuring agents, is more preferable. Depending on the curing temperature and the illuminance of ultraviolet / visible light, pre-curing for 0.005 to 24 hours is preferable from the viewpoint of film uniformity. Curing by light or heat may be performed until the fluidity of the film-like resin material surface is lost, or the degree of curing may be arbitrarily adjusted to leave a certain degree of fluidity.

[0071] As the fluidity of the film-like resin material surface decreases, the resin flow of the prepreg decreases. Furthermore, when combining a prepreg with a different material such as a fiber-reinforced composite material precursor (an uncured intermediate material in which a thermosetting resin such as a prepreg has impregnated reinforcing fibers), it is preferable because it can suppress the amount of each thermosetting resin mixed during the molding process. It is also preferable to arbitrarily adjust the degree of curing to retain a certain degree of fluidity in order to improve the adhesion between prepregs or between prepregs and other materials, and the adhesion between materials that were already in contact before molding in the fiber-reinforced composite material obtained by molding them.

[0072] The degree of curing of the resin film can be calculated by determining the ratio of the residual exothermic peak after pre-curing to the exothermic peak before pre-curing by measuring the temperature rise of the DSC of the film-like resin material and the resin film before and after pre-curing. The degree of curing after pre-curing is preferably 1 to 70%. If it is 1% or more, the tack, resin flow, and volatilization of the resin film can be designed to be low, and if it is 70% or less, impregnation of the resin film into the reinforcing fibers becomes easy, which is preferable.

[0073] Furthermore, the resin film according to the present invention can be used as a resin film infusion (RFI) material. The resin film can be laminated without excessive adhesion to the fibrous substrate preformed in the mold during lamination in the pre-molding preparation of RFI, and has excellent handling properties. In addition, since the resin flow of the resin film during molding is low, at 10% by mass or less, the design of the resin and fibrous substrate content of the molded body becomes very easy, and there is also the advantage that there is less burr in the fiber-reinforced composite material, making burr trimming easier.

[0074] A prepreg can be produced by impregnating a fibrous substrate with a resin film related to the present invention by heating and pressurizing. One or more of these prepregs can be laminated together or on different materials and molded. A molded body (referred to as a fiber-reinforced composite material) can be obtained from the prepreg or laminate using the prepreg by autoclave molding, press molding, oven curing, etc.

[0075] The volatile content of the prepreg produced by this invention is less than 1% by mass, thus minimizing the impact on the environment in which the prepreg is handled. Furthermore, the resin flow of the prepreg is less than 10% by mass, making it very easy to design the resin and fiber substrate content of the fiber-reinforced composite material. In addition, there is an advantage in that there is less burr in the fiber-reinforced composite material, making burr trimming easier.

[0076] The basis weight of the film-like resin material and resin film according to the present invention is 10 to 300 g / m². 2 It is preferable that the basis weight of the resin film is maintained even after pre-curing. The basis weight of the film-like resin material and the resin film is 10 g / m². 2 This is preferable because it allows for sufficient impregnation of the reinforcing fibers, enabling the fiber-reinforced composite material to fully exhibit its mechanical properties such as compression and tensile strength, and reduces the number of prepreg layers required to obtain the desired thickness during fiber-reinforced composite material molding, thus improving work efficiency. The basis weight of the resin film is 300 g / m². 2The following conditions are preferable because, when molding as a prepreg, the heat generated by the curing of the thermosetting resin composition is suppressed, and the prepreg tends to have good drapeability. Drapability refers to the flexibility of deformation of the prepreg and is a characteristic that affects the shapeability on the mold during lamination. If the drapeability is low, it is difficult to shape it onto a curved surface, and if the drapeability is too high, it tends to wrinkle easily.

[0077] The basis weight of the prepreg according to the present invention is preferably 65 to 450 g / m². 2 More preferably, 80-400 g / m² 2 And more preferably 90-300 g / m² 2 The basis weight of the prepreg is 65 g / m². 2 This is preferable because it allows for a smaller number of prepreg layers relative to the desired thickness of the molded product, thereby improving work efficiency. The prepreg basis weight is 450 g / m². 2 This is preferable because it tends to result in good drape properties for the prepreg.

[0078] The fiber mass content of the prepreg produced according to the present invention is preferably 10 to 90% by mass, more preferably 60 to 85% by mass, and even more preferably 70 to 80% by mass, when the total mass of the prepreg is considered as 100% by mass. When the fiber mass content is 10% by mass or more, the advantage of the prepreg, which is that it can provide a fiber-reinforced composite material with excellent specific strength and specific modulus, is easily obtained because the reinforcing fiber content is high. Furthermore, when the fiber mass content is 90% by mass or less, impregnation defects in the resin layer contained in the prepreg are less likely to occur, and the resulting composite material tends to have fewer voids, which is preferable.

[0079] Preferably, various carbon fibers, graphite fibers, glass fibers, PET fibers, nylon fibers, and aramid fibers are used as reinforcing fibers in fiber-reinforced composite materials. Among these, carbon fibers are preferred as they provide a lightweight and highly rigid fiber-reinforced composite material.

[0080] The form of the fiber base material made of reinforcing fibers is not particularly limited and can include long fibers aligned in one direction, tow, woven fabric, mat, knit, braid, braid, nonwoven fabric, etc. One type of fiber base material or two or more types may be used.

[0081] The fiber base material is 5-200g / m 2 This improves the handling properties of the prepreg. The basis weight of the fiber base material is 5 g / m². 2 If the amount is greater than 200g / m, the fiber base material will be less likely to tear during handling. 2 The following is preferable because it results in better moldability of the prepreg.

[0082] The curing temperature of the prepreg produced according to the present invention depends on the main component of the thermosetting resin used, the curing agent, and the curing catalyst used, but it is preferable to cure it at a temperature of 100 to 200°C from the viewpoint of suppressing the occurrence of distortion and wrinkles due to thermal stress.

[0083] The tack of the prepreg manufactured according to the present invention can be evaluated by attaching the surface of the prepreg to the surface of an FEP film, further pressing it firmly with a 2kg roller for one pass, and then measuring the load when the prepreg is peeled off at a 30° angle using an adhesion / coating analyzer. A tack of 1mN / mm or more of the prepreg manufactured according to the present invention is preferable because it has excellent adhesion to the object to be attached, and a tack of 15mN / mm or less is preferable because it is easy to peel off from the object to be attached, and it is possible to correct the position after peeling it off and reattach it. Furthermore, the manufacturing method of the present invention allows for a difference in tack between the two sides of the prepreg. The impregnated side of the prepreg is called the resin side, and the unimpregnated side is called the fiber substrate side. The fiber substrate side of the prepreg is preferably 0 to 10mN / mm. A tack higher than 0mN / mm of the fiber substrate side is preferable because it has good adhesion to the material to be attached to the fiber substrate side, and a tack of 10mN / mm or less is preferable because it is easy to distinguish between the resin side and the fiber substrate side of the prepreg. Furthermore, a tack of 0 to 0.5 mN / mm on the fiber substrate surface is particularly preferable, as it allows the resin layer contained in the prepreg to be handled without sticking to the hands from the fiber substrate surface.

[0084] The tack force, resin flow, manufacturing process passability, and quality of the prepreg produced by this invention depend on the viscosity of the pre-cured resin film produced by this invention. The viscosity of the pre-cured resin film produced by this invention can be measured using a dynamic viscoelastic device ARES-2KFRTN1-FCO-STD (manufactured by T.A. Instruments). Using parallel plates with a diameter of 40 mm as upper and lower measuring fixtures, the pre-cured resin film produced by this invention is set between the upper and lower fixtures so that the distance between the upper and lower fixtures is 1 mm. The complex viscosity η2* is then measured while increasing the temperature from 20°C to 150°C at a rate of 2°C / min in torsion mode (measurement frequency: 0.5 Hz) to determine the viscosity.

[0085] The complex viscosity η2*24 of the thermoset resin film manufactured according to the present invention at 24°C is preferably 20,000 to 100,000 Pa·s. When η2*24 is 20,000 Pa·s or higher, the resin layer contained in the prepreg or the tack of the prepreg is low, and the resin layer contained in the prepreg is less likely to stick to hands or the workplace when handling the prepreg, thus providing good handling. When η2*24 is 100,000 Pa·s or lower, the impregnation of the resin layer into the fiber substrate becomes easier. It is also preferable in that high adhesion to the lamination target is maintained when the prepreg is laminated. When η2*24 is 25,000 to 90,000 Pa·s, it is more preferable, and when η2*24 is 40,000 to 90,000 Pa·s, it is even more preferable.

[0086] Furthermore, the complex viscosity at η70°C, η2*70, is preferably 100 to 5,000 Pa·s. A η2*70 of 100 Pa·s or higher is preferable because it reduces the resin flow of the prepreg and suppresses burrs during molding of the prepreg. The higher the complex viscosity, the less resin flow there is. A η2*70 of 5,000 Pa·s or lower is preferable because it improves the adhesion of the prepreg to the lamination target after molding. A η2*70 of 500 to 4,000 Pa·s is more preferable, and a η2*70 of 2,000 to 4,000 Pa·s is even more preferable. [Examples]

[0087] The present invention will be described in detail below with reference to examples. However, the scope of the present invention is not limited to these examples. Furthermore, unless otherwise noted, the various characteristics were measured under conditions of 24°C and 50% relative humidity.

[0088] <Materials used in the examples and comparative examples> (1) Component [A] Thermosetting resin • Bisphenol A type epoxy resin ("jER(registered trademark)" 828, manufactured by Mitsubishi Chemical Corporation) Epoxy equivalent: 175 (g / eq.) Tetraglycidyldiaminodiphenylmethane ("Araldite" (registered trademark) MY721, manufactured by Huntsman Corporation), epoxy equivalent: 120 (g / eq.). • 3,4-Epoxycyclohexanecarboxylic acid 3,4-epoxycyclohexylmethyl ("Celoxide" (registered trademark) 2021P, manufactured by Daicel Corporation) Epoxy equivalent: 136 (g / eq.).

[0089] (2) Hardener of component [B] [A] • 3,3'-Diaminodiphenylsulfone (3,3'-DAS, manufactured by Mitsui Chemicals Fine, Inc.) • Benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate ("San-Aid®" SI-100, manufactured by Sanshin Chemical Industry Co., Ltd.).

[0090] (3)Thermoplastic resin • Polyvinyl formal ("Vinirec" (registered trademark) K, manufactured by JNC Corporation) • Polyethersulfone ("Sumika Excel®" PES5003P, manufactured by Sumitomo Chemical Co., Ltd.).

[0091] (4) Fiber base material • C06142 (T300 carbon fiber fabric (plain weave), fabric weight: 119g / m²) 2 (Manufactured by Toray Industries, Inc.)

[0092] <Method for preparing thermosetting resin compositions and prepregs> The thermosetting resin compositions and prepregs for each example and comparative example were prepared using the following method.

[0093] (I) Preparation of resin film In a kneader, predetermined amounts of [A] and thermoplastic resin listed in Tables 1-4 were added, and the mixture was heated to 150°C while kneading. Kneading at 150°C for 1 hour yielded a viscous liquid. The mixture was then cooled to 80°C while kneading, and [B] was added at 70°C or below. Further kneading yielded a thermosetting resin composition (kneaded). Subsequently, a film-like resin material was prepared. The prepared thermosetting resin composition was coated at a rate of 100 g / m² using a knife coater. 2 A film-like resin material was prepared by applying it to release paper with the specified basis weight. The quality of the prepared film-like resin material was also visually inspected. Poor quality can be caused by streaks or droplets of the thermosetting resin composition not being applied to the release paper, areas where the thermosetting resin composition is applied in an island-like pattern, the basis weight of the film-like resin material deviating by more than 10% from the target basis weight, or the thermosetting resin composition not passing through the knife coater. Good quality of the film-like resin material means that none of the above problems are present.

[0094] The obtained film-like resin material was pre-cured to obtain a pre-cured resin film. The pre-curing method was as follows: The film-like resin material coated on the release film was pre-cured at a temperature lower than the curing temperature. The degree of pre-curing was adjusted by the degree of curing, but the appropriate pre-curing temperature and processing time were determined in advance from the ratio of the exothermic peaks associated with thermal curing during heating, as measured by DSC before and after pre-curing. Specifically, the prepared film-like resin material was pre-cured by placing it in a hot air dryer (PVH-330, manufactured by ESPEC Corporation) at the temperatures and times listed in Tables 1 to 4, and a pre-cured resin film was obtained. The resin film is the one that has undergone pre-curing.

[0095] (II) Method for preparing prepregs One pre-cured resin film prepared in (I) was placed on one side of the fiber substrate C06142, and the film was heated and pressurized to impregnate it with a thermosetting resin composition, thereby obtaining a fiber fabric prepreg. The obtained prepreg consisted of a fiber substrate and a very thin resin layer containing the thermosetting resin composition laminated on one side of the fiber substrate, with a portion of the thermosetting resin composition in the resin layer impregnating the fiber substrate. Here, the degree of impregnation of the thermosetting resin composition into the fiber substrate was not sufficient, as pre-curing had increased the complex viscosity, and the resin did not completely penetrate to the opposite side of the fiber substrate, or even if it did, the amount was insufficient. In other words, the side on which the resin film was laminated had a greater amount of impregnation of the thermosetting resin composition compared to the fiber substrate side on the opposite side. The side on which the pre-cured resin film impregnated the reinforcing fibers is called the resin side, and the opposite side is called the fiber substrate side.

[0096] <Method for characterizing prepregs> Sampling of the resin layer from the prepreg Sampling was performed from the obtained prepreg for characterization. The prepreg prepared in (II) was sandwiched between two release papers, and heat and pressure were applied using an iron set to 120°C to partially separate the resin layer contained in the prepreg from the fiber substrate. The resin layer contained in the prepreg that adhered to the release sheet was sampled and used as the target for measurement of the (D) complex viscosity η3*24 and η3*70 of the prepreg. There was no significant difference in the complex viscosity of the resin layer contained in the prepreg sampled from the pre-cured resin film and the resin film sampled from the prepreg, but the complex viscosity of the resin layer sampled from the prepreg was higher than that of the resin film.

[0097] (A) Measurement of the volatility of the prepreg The prepreg sample was cut into 8cm squares, its mass was measured (mass: W1), and it was placed on release paper and placed in a 180°C oven for 1 hour. After that, the prepreg and release paper were removed from the oven and left in a desiccator for 30 minutes, and then its mass was measured again (mass: W2). The amount of volatilization [mass%] in this invention was calculated using the following formula. (W1-W2) / W1×100 [mass%].

[0098] (B) Prepreg resin flow measurement The prepreg sample was cut into 10cm squares, and four 10cm square prepreg sheets were stacked. The mass of the resulting stack was measured (W3). The stack was sandwiched between two 15cm square release films, and then between two 10cm square metal plates (400g each). In this state, it was molded in an autoclave (6 atmospheres, 180°C for 2 hours, heating rate 1.7°C / min). After molding, the prepreg portion that protruded from the 10cm square metal plates was removed, and the mass of the hardened 10cm square prepreg stack was measured (mass: W4). The resin flow [mass%] in this invention was calculated using the following formula. (W3-W4) / W3×100 [mass%].

[0099] (C) Prepreg tack measurement The prepared prepreg sample was cut to 30 cm in length and 2 cm in width. The side to be measured for tack was attached to an FEP film of the same size (Toyoflon (50 μm thickness), manufactured by Toray Film Processing Co., Ltd.). The prepreg and FEP film were then sandwiched between two sheets of release paper, and a 2 kg roller was applied with one back-and-forth load to ensure adhesion. Using an adhesion / coating analyzer (VPA-2, manufactured by Kyowa Interface Science Co., Ltd.), the average load was measured when the prepreg was peeled from the FEP film at a 30° angle at a speed of 200 mm / min, and the tack was determined by calculating the average value. The average load per unit width (unit: mN / mm) was calculated. Tack force was measured on both the resin side and the fiber base surface of the prepreg.

[0100] (D) Viscosity measurement of resin layers contained in thermosetting resin compositions, resin films, and prepregs The viscosities of three types of materials—the thermosetting resin composition (kneaded) prepared in (I), the pre-cured resin film, and the resin layer contained in the prepreg sampled in (II)—were measured using a dynamic viscoelastic device ARES-2KFRTN1-FCO-STD (manufactured by T.A. Instruments Co., Ltd.). A parallel plate with a diameter of 40 mm was used for the upper and lower measuring fixtures. The thermosetting resin composition was placed between the upper and lower fixtures so that the distance between them was 1 mm, and then measured in torsion mode (measurement frequency: 0.5 Hz). The temperature was increased from 20°C to 150°C at a rate of 2°C / min, and η1*24, η1*70, η2*24, η2*70, η3*24, and η3*70 were determined. The complex viscosity of the thermosetting resin composition (kneaded) is denoted as η1*, the complex viscosity of the resin film after pre-curing, i.e., laminated onto the fiber substrate, is denoted as η2, and the complex viscosity of the resin layer contained in the prepreg sampled from the prepreg is denoted as η3*. The number after * indicates the measurement temperature.

[0101] (E) Evaluation of the results of one-sided impregnation of the prepreg The impregnation state of the thermosetting resin composition was evaluated using a microscope. The impregnation state was evaluated using the following ranks.

[0102] Defect: Complete impregnation from the resin side to the fiber substrate side, with a resin surface layer covering the entire surface of the fiber substrate side. Good: The resin side is impregnated, but the surface layer on the fiber substrate side either has no resin surface or has resin partially present.

[0103] <Examples 1-8> Examples 1-8 involved preparing thermosetting resin compositions by applying 3,3'-diaminodiphenylsulfone as a curing agent to a thermosetting resin prepared by using bisphenol A type epoxy alone or a mixture of bisphenol A type epoxy and tetraglycidyldiaminodiphenylmethane. A film-like resin material was then produced, followed by the preparation of a resin film by pre-curing the film-like resin material, and finally, a prepreg was prepared by impregnating one side of a fibrous substrate with the resin film. The viscosity of the thermosetting resin composition was adjusted by the amount of thermoplastic resin added.

[0104] In all of the examples 1 to 8, η1*70 was 500 Pa·s or less. Film-like resin materials were prepared at 70°C, and the quality of the film-like resin materials was shown to be good by visual inspection and basis weight measurement.

[0105] The thermosetting resin compositions of Examples 1 to 7 were pre-cured at 90°C, and Example 8 was pre-cured at 80°C for the times shown in Table 1, to obtain resin films.

[0106] The resin films of Examples 1-8 were impregnated on one side of a fiber substrate to produce prepregs. A difference in tack was observed between the fiber substrate side and the resin side of each prepreg, indicating that the prepregs of Examples 1-8 had good handling properties. It was shown that the higher the complex viscosity η2*24 and η3*24, the lower the tack on both the resin side and the fiber substrate side, respectively. Examples 3, 5, 7, and 8 had a tack of 0 mN / mm on the fiber substrate side and were prepregs with tack only on the resin side, demonstrating particularly favorable handling properties.

[0107] The η2*70 and η3*70 values ​​for Examples 1-8 were all between 100 and 5,000 Pa·s. The η2*70 and η3*70 values ​​for Examples 1, 4, and 6 were below 500 Pa·s, indicating a higher resin flow compared to Examples 2, 3, 7, and 8. However, burrs and resin loss during molding were small, demonstrating no significant problems. On the other hand, the η2*70 and η3*70 values ​​for Examples 3, 5, 7, and 8 exceeded 500 Pa·s, with the η3*70 value for Example 2 exceeding 500 Pa·s. The prepregs of Examples 2, 3, 7, and 8 were shown to be particularly preferable because they exhibited lower resin flow and further suppressed burrs and resin loss during molding compared to Examples 1, 4, and 6.

[0108] Furthermore, the prepregs of Examples 3, 7, and 8, where the η2*70 value exceeded 500 Pa·s, were shown to be preferable to the prepregs of Examples 1, 2, 4, and 6, where the η2*70 value was below 500 Pa·s, as they exhibited better prepreg manufacturing process and improved process passability of the resulting prepregs. The passability of the pre-cured resin film through the process was good in all examples.

[0109] The one-sided impregnation of the prepregs described in Examples 1 to 8 was successful, as there was either no resin present on the surface layer on the fiber substrate side, or only a partial presence of resin, and there was no resin layer on the surface layer on the fiber substrate side.

[0110] <Examples 9-12> Examples 9-12 involved preparing thermosetting resin compositions using 3,4-epoxycyclohexylmethyl epoxycyclohexanecarboxylic acid as the thermosetting resin and benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate as the curing agent. A film-like resin material was then prepared, followed by the preparation of a resin film by pre-curing the film-like resin material, and finally, a prepreg was prepared by impregnating one side of a fibrous substrate with the resin film. The viscosity of the thermosetting resin composition was adjusted by the amount of thermoplastic resin added.

[0111] In Examples 9-12, η1*70 was 500 Pa·s or less in all cases. Film-like resin materials were prepared at 70°C, and the quality of the film-like resin materials was shown to be good by visual inspection and basis weight measurement.

[0112] The film-like resin materials of Examples 9 to 12 were pre-cured at 70°C for the times shown in Table 2 to obtain resin films.

[0113] The resin films of Examples 9-12 were impregnated on one side of a fiber substrate to produce prepregs. A difference in tack was observed between the fiber substrate side and the resin side of each prepreg, indicating that the prepregs of Examples 9-12 had good handling properties. It was shown that the higher the η2*24 and η3*24 values, the lower the tack on the resin side and the fiber substrate side, respectively. Examples 9 and 10 had a tack of 0 mN / mm on the fiber substrate side and were prepregs with tack only on the resin side, demonstrating particularly favorable handling properties.

[0114] The η2*70 and η3*70 values ​​for Examples 9-12 were all between 100 and 5,000 Pa·s. The η2*70 and η3*70 values ​​for Examples 10-12 were below 500 Pa·s. Although the resin flow was higher compared to Example 9, the amount of burrs and resin loss during molding was small, indicating that there were no problems. On the other hand, the η2*70 and η*3 values ​​for Example 9 exceeded 500 Pa·s. The prepreg of Example 9 was shown to be particularly preferable because it had a low resin flow and further suppressed burrs and resin loss during molding.

[0115] Furthermore, the prepreg of Example 10, in which the η2*70 value exceeded 500 Pa·s, was shown to be preferable due to better process passability in the prepreg manufacturing process and the resulting prepreg. Process passability of the pre-cured resin film was good in all examples. The one-sided impregnation of the prepregs described in Examples 9 to 12 was successful, as there was either no resin present on the surface layer on the fiber substrate side, or only a partial presence of resin, and there was no resin layer on the surface layer on the fiber substrate side.

[0116] <Comparative Examples 1-2> Comparative Examples 1 and 2 involved preparing thermosetting resin compositions by applying 3,3'-diaminodiphenylsulfone as a curing agent to a thermosetting resin prepared by using bisphenol A type epoxy alone or a mixture of bisphenol A type epoxy and tetraglycidyldiaminodiphenylmethane, and then producing film-like resin materials. In Comparative Example 1, when the amount of thermoplastic resin added was 65 parts by mass, the η1*70 of Comparative Example 1 exceeded 500 Pa·s, indicating that the thermosetting resin composition could not pass through the knife coater, making it difficult to produce a film-like resin material of good quality. Therefore, pre-curing of the film-like resin material was not performed for Comparative Example 1. In addition, a prepreg was prepared by laminating the film-like resin material of Comparative Example 2 directly onto one side of a fiber substrate without pre-curing and impregnating it. The viscosity of the thermosetting resin composition was adjusted by the amount of thermoplastic resin added.

[0117] The η1*70 value described in Comparative Example 2 was 500 Pa·s or less. A film-like resin material was prepared at 70°C, and the quality of the film-like resin material was shown to be good by visual inspection and basis weight measurement.

[0118] Comparative Example 2 showed that the resin flow of the prepreg exceeded 10% by mass.

[0119] The prepreg in Comparative Example 2 had poor handling properties because it was excessively tacky, causing the resin contained in the prepreg to adhere to hands and the work surface. The single-sided impregnation of the prepreg described in Comparative Example 2 was unsatisfactory because the entire surface of the fiber substrate was covered with the thermosetting resin composition.

[0120] <Comparative Examples 3-4> Comparative Examples 3 and 4 involved preparing thermosetting resin compositions using 3,4-epoxycyclohexylmethyl epoxycyclohexanecarboxylic acid as the thermosetting resin and benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate as the curing agent, and then producing film-like resin materials. However, the η1*70 of Comparative Example 3 was less than 1 Pa·s, and the thermosetting resin composition could not remain on the release paper, making it impossible to produce a film-like resin material. Therefore, pre-curing of the film-like resin material was not performed for Comparative Example 3. In addition, the film-like resin material of Comparative Example 4 was laminated directly onto one side of a fiber substrate without pre-curing and impregnated to produce a prepreg. The viscosity of the thermosetting resin composition was adjusted by the amount of thermoplastic resin added.

[0121] In Example 4, η1*70 was 500 Pa·s or less. In Comparative Example 4, a film-like resin material was prepared at 70°C, and the quality of the film-like resin material was shown to be good by visual inspection and basis weight measurement. The prepreg of Comparative Example 4 was shown to have a volatilization amount exceeding 1% by mass.

[0122] Furthermore, the prepreg of Comparative Example 4 had poor handling properties because the resin contained in the prepreg adhered to hands and the work area due to excessive tackiness during handling. The single-sided impregnation of the prepreg described in Comparative Example 4 was unsatisfactory because the entire surface of the fiber substrate was covered with the thermosetting resin composition.

[0123] [Table 1]

[0124] [Table 2]

[0125] [Table 3]

[0126] [Table 4]

Claims

1. A prepreg comprising a fibrous substrate and a resin layer laminated on one side of the fibrous substrate, the resin layer comprising a thermosetting resin composition containing at least the following components [A] and [B], A portion of the thermosetting resin composition of the resin layer is impregnated into the fibrous substrate. When the side of the prepreg facing the resin layer is considered the resin surface and the opposite side is considered the fiber substrate surface, There is a difference between the tack force of the resin surface and the tack force of the fiber substrate surface. The complex viscosity of the resin layer contained in the prepreg at 24°C (η3*24) is 20,000 to 100,000 Pa·s, and the complex viscosity at 70°C (η3*70) is 100 to 5,000 Pa·s. A prepreg in which the volatile content of the thermosetting resin composition is 1% by mass or less when the total mass of the prepreg is taken as 100% by mass. [A] Thermosetting resin [B] [A] Hardener

2. The prepreg according to claim 1, wherein the tack force of the fibrous substrate surface is 0 to 0.5 mN / mm and the tack force of the resin surface is 1 to 15 mN / mm.

3. The prepreg according to claim 1 or 2, wherein the thermosetting resin composition further comprises 1 to 60 parts by mass of the following component [C] per 100 parts by mass of component [A]. [C] Thermoplastic resin

4. The prepreg according to any one of claims 1 to 3, wherein the component [A] is an epoxy resin.

5. The prepreg according to any one of claims 1 to 4, wherein component [B] is a cationic curing agent.

6. The prepreg according to any one of claims 1 to 5, wherein the η3*70 is 500 to 5000 Pa·s.

7. The prepreg according to any one of claims 1 to 6, wherein the fibrous base material is a nonwoven fabric.

8. The prepreg according to any one of claims 1 to 6, wherein the fiber base material is a woven fabric.

9. A prepreg according to any one of claims 1 to 8, wherein the resin flow is 10% by mass or less relative to 100% by mass of the prepreg.

10. The process includes a step of pre-curing a film-like resin material obtained by coating a thermosetting resin composition containing at least components [A] and [B] onto a release sheet, In the pre-curing step, the thermosetting resin composition is pre-cured to a complex viscosity at 24°C: η²*24 of 20,000 to 100,000 Pa·s and a complex viscosity at 70°C: η²*70 of 100 to 5,000 Pa·s, and the pre-cured resin film is laminated onto one side of the fiber substrate. A method for producing a prepreg, comprising impregnating a fibrous substrate with the aforementioned thermosetting resin composition on one side. [A] Thermosetting resin [B] [A] Hardener

11. The method for producing a prepreg according to claim 10, wherein the pre-curing treatment step is performed by heating.

12. A method for producing a prepreg according to claim 10 or 11, wherein a prepreg is obtained by impregnating a fibrous substrate with the thermosetting resin composition on one side, thereby obtaining a prepreg having a tack force of 0 to 0.5 mN / mm on one side and a tack force of 1 to 15 mN / mm on the other side.

13. A method for producing a prepreg according to any one of claims 10 to 12, wherein the thermosetting resin composition further comprises 1 to 60 parts by mass of the following component [C] per 100 parts by mass of component [A]. [C] Thermoplastic resin

14. A method for producing a prepreg according to any one of claims 10 to 13, wherein the component [A] is an epoxy resin.

15. A method for producing a prepreg according to any one of claims 10 to 14, wherein the component [B] is a cationic curing agent.

16. A method for manufacturing a prepreg according to any one of claims 10 to 15, wherein the η2*70 is 500 to 5000 Pa·s.

17. A method for manufacturing a prepreg laminate, characterized by laminating prepregs obtained by the prepreg manufacturing method described in any one of claims 10 to 16.

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