JP2018012797A - Epoxy resin composition, prepreg, resin cured product and fiber-reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition for producing a prepreg having excellent curability to permit short-time curing and resin flowability and a fiber-reinforced composite material expressing high tensile strength.SOLUTION: An epoxy resin composition contains an epoxy compound [A], an episulfide compound [B] in which at least one oxirane ring of the epoxy compound is substituted with a thiirane ring, a curing agent [C] and a thermoplastic resin [D]. A content of [D] is 1-30 pts.mass relative to the total amount of [A] and [B], 100 pts.mass.SELECTED DRAWING: None

Description

  The present invention is an epoxy resin composition for producing a fiber-reinforced composite material having excellent curability and moldability that can be cured in a short time, and high tensile strength, and the reinforcing fiber is impregnated with the reinforcing fiber. The present invention relates to a prepreg, a cured resin obtained by curing an epoxy resin composition, and a fiber-reinforced composite material composed of an epoxy resin composition and reinforcing fibers.

  Conventionally, fiber-reinforced composite materials made of carbon fiber, glass fiber, and other reinforcing fibers and epoxy resins, phenol resins, and other thermosetting resins are lightweight, yet have mechanical properties such as strength and rigidity, heat resistance, and corrosion resistance. It has been applied to many fields such as aviation / space, automobiles, rail cars, ships, civil engineering and sports equipment. Especially in applications where high performance is required, fiber reinforced composite materials using continuous reinforcing fibers are used, carbon fibers with excellent specific strength and specific elastic modulus are used as reinforcing fibers, and thermosetting is used as a matrix resin. In particular, epoxy resins having adhesiveness to carbon fiber, heat resistance, elastic modulus and chemical resistance and minimal curing shrinkage have been used.

  Among them, aromatic amine curing agents, especially diaminodiphenylsulfone, are generally used in the matrix resins for composite materials for aerospace applications that require excellent strength characteristics and durability stability. ing. However, this diaminodiphenyl sulfone requires a high temperature close to 180 ° C. for curing, and the viscosity of the epoxy resin often becomes too low during molding.

  Then, the method of controlling the flow of resin by making this reaction start temperature low using a latent hardening accelerator and making it harden | cure at low temperature is proposed (patent document 1).

  In addition, as one method for imparting rapid curability to an epoxy resin, a method of blending an episulfide resin with an epoxy resin is known (Patent Documents 2 and 3).

  Furthermore, a method of blending a thermoplastic resin has been proposed in order to control the tackiness of the prepreg and to control the fluidity of the matrix resin when the prepreg is heat-cured (Patent Document 4).

International Publication No. 01/081445 International Publication No. 00/046317 Japanese Patent Laid-Open No. 11-222582 JP 2007-191633 A

  However, in the method described in Patent Document 1, in order to maintain the heat resistance of the cured resin, it is necessary to cure at a high temperature in two stages, resulting in a problem that the time required for molding becomes long.

  In addition, the techniques described in Patent Documents 2 and 3 are referred only to the curability of the resin composition and the stability at 20 ° C. to 25 ° C. at room temperature, both of which have thermal stability at 80 ° C., which is the prepreg manufacturing temperature. It was scarce. Moreover, there was no description about the moldability when using the fiber-reinforced composite material as a matrix resin and the mechanical properties of the obtained fiber-reinforced composite material, and the effect was unknown.

  Furthermore, in the method described in Patent Document 4, in order to obtain a resin composition having a desired viscosity, it is necessary to add a large amount of thermoplastic resin, and there is a problem that heat resistance and solvent resistance are lowered.

  Therefore, an object of the present invention is to provide an epoxy resin composition having excellent curability that cures in a short time, a prepreg excellent in moldability using the composition, and a fiber-reinforced composite material that exhibits high tensile strength. It is in.

The present invention employs the following means in order to solve such problems. That is, an epoxy resin composition including the following constituent elements [A] to [D] and 1 to 30 parts by mass of the constituent element [D] with respect to 100 parts by mass of the total amount of the constituent elements [A] and [B]. It is a thing.
[A]: Epoxy compound [B]: Episulfide compound in which at least one of the oxirane rings of the epoxy compound is substituted with a thiirane ring [C]: Curing agent [D]: Thermoplastic resin.

  Moreover, the prepreg of the present invention is obtained by impregnating reinforcing fibers with the above epoxy resin composition.

  Furthermore, the resin cured product of the present invention is obtained by curing an epoxy resin composition.

  The fiber-reinforced composite material of the present invention is obtained by curing the prepreg, or comprises the cured resin and the reinforcing fiber.

  According to the present invention, an epoxy resin composition having a high curability that can be molded in a short time and an appropriate resin flow amount during molding by blending an epoxy sulfide resin and a thermoplastic resin into the epoxy resin composition. Can provide. In addition, the fiber reinforced composite material obtained by curing the epoxy resin composition and the prepreg of the present invention can be molded in a shorter time than a conventional fiber reinforced composite material not containing an episulfide resin. It is possible to greatly reduce the molding time and molding cost of applied products such as wind turbine blades, automobile outer plates and computer trays such as IC trays and casings of notebook computers. In addition, the fiber reinforced composite material obtained by curing the epoxy resin composition and prepreg of the present invention can exhibit extremely high tensile strength as compared with the fiber reinforced composite material not containing conventional episulfide resin and thermoplastic resin. It becomes.

The epoxy resin composition of the present invention contains the following constituent elements [A] to [D], and the constituent element [D] is 1 to 1 part by mass with respect to 100 parts by mass in total of the constituent elements [A] and [B]. An epoxy resin composition containing 30 parts by mass.
[A]: Epoxy compound [B]: Episulfide compound in which at least one of the oxirane rings of the epoxy compound is substituted with a thiirane ring [C]: Curing agent [D]: Thermoplastic resin.

  The component [A] used in the present invention is preferably an epoxy resin having two or more glycidyl groups in one molecule. In the case of an epoxy resin having less than 2 glycidyl groups in one molecule, the glass transition temperature of a cured product obtained by heating and curing a mixture mixed with a curing agent described later is not preferable. Examples of the epoxy resin used in the present invention include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD type epoxy resins, bisphenol type epoxy resins such as bisphenol S type epoxy resins, and tetrabromobisphenol A diglycidyl ether. Novolak type such as brominated epoxy resin, epoxy resin having biphenyl skeleton, epoxy resin having naphthalene skeleton, epoxy resin having fluorene skeleton, epoxy resin having dicyclopentadiene skeleton, phenol novolac type epoxy resin, cresol novolac type epoxy resin Epoxy resin, N, N, O-triglycidyl-m-aminophenol, N, N, O-triglycidyl-p-aminophenol, N, N, O-triglycidyl 4-amino-3-methylphenol, N, N, N ′, N′-tetraglycidyl-4,4′-methylenedianiline, N, N, N ′, N′-tetraglycidyl-2,2′-diethyl Glycidylamines such as -4,4'-methylenedianiline, N, N, N ', N'-tetraglycidyl-m-xylylenediamine, N, N-diglycidylaniline, N, N-diglycidyl-o-toluidine Type epoxy resin, resorcin diglycidyl ether, triglycidyl isocyanurate and the like. Among these, in the case of aviation, spacecraft applications, etc., it is preferable to include a glycidylamine type epoxy resin from which a cured product having a high glass transition temperature and elastic modulus can be obtained.

  These epoxy resins may be used alone or in combination as appropriate. Mixing an epoxy resin exhibiting fluidity at an arbitrary temperature and an epoxy resin not exhibiting fluidity at an arbitrary temperature is effective in controlling the fluidity of the matrix resin when the resulting prepreg is thermoset. For example, if the fluidity shown until the matrix resin is gelled at the time of thermosetting is large, the orientation of the reinforcing fibers is disturbed or the matrix resin flows out of the system, so that the fiber mass content is predetermined. As a result, the mechanical properties of the resulting fiber-reinforced composite material may be reduced. Further, combining a plurality of epoxy resins exhibiting various viscoelastic behaviors at an arbitrary temperature is also effective for making the tackiness and draping properties of the obtained prepreg appropriate.

  In the epoxy resin composition of the present invention, a monoepoxy compound having only one epoxy group in one molecule or an alicyclic epoxy is used as long as the heat resistance and mechanical properties are not significantly reduced. Resins and the like can be appropriately blended.

  Component [B] in the present invention is an episulfide compound in which at least one of the oxirane rings of the epoxy compound is substituted with a thiirane ring. Such an episulfide compound may be either a compound having only a thiirane ring in the molecule or a compound having both an intramolecular thiirane ring and an oxirane ring.

  The basic skeleton of the component [B] used in the present invention is not particularly limited, but an episulfide compound having a skeleton similar to the epoxy compound as shown in the component [A] is preferably exemplified. For example, bisphenol A type episulfide resin, bisphenol F type episulfide resin, bisphenol AD type episulfide resin, bisphenol type episulfide resin such as bisphenol S type episulfide resin, brominated episulfide resin, episulfide resin having biphenyl skeleton, episulfide resin having naphthalene skeleton, Episulfide resins having a fluorene skeleton, episulfide resins having a dicyclopentadiene skeleton, novolak-type episulfide resins such as phenol novolak-type episulfide resins, cresol novolak-type episulfide resins, thiiranes of N, N, O-triglycidyl-m-aminophenol N, N, O-triglycidyl-p-aminophenol thiirane, N, N, O-to Thiairanide of glycidyl-4-amino-3-methylphenol, thiirane of N, N, N ′, N′-tetraglycidyl-4,4′-methylenedianiline, N, N, N ′, N′-tetra Thiairanide of glycidyl-2,2′-diethyl-4,4′-methylenedianiline, thiirane of N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, N, N-diglycidylaniline And thiiranes of N, N-diglycidyl-o-toluidine, resorcin diglycidyl ether, and triglycidyl isocyanurate.

  When an episulfide compound having a structure in which a glycidylamino group represented by the general formula (I) (wherein X is an oxygen atom or a sulfur atom) is thiiraned is used as the component [B], an epoxy resin composition In addition to being able to impart excellent quick curability to the resin, a cured resin product having excellent heat resistance and elastic modulus can be obtained, which is preferable.

  Moreover, it is preferable to use an episulfide compound having a structure obtained by thiirane-forming a glycidyl ether group represented by the general formula (II) as the constituent element [B] because the excellent thermal stability of the epoxy resin composition can be obtained.

  These episulfide compounds may be used singly or may be appropriately blended and used. Mixing an episulfide resin exhibiting fluidity at an arbitrary temperature and an episulfide resin not exhibiting fluidity at an arbitrary temperature is effective in controlling the fluidity of the matrix resin when the resulting prepreg is thermoset. For example, if the fluidity shown until the matrix resin is gelled at the time of thermosetting is large, the orientation of the reinforcing fibers is disturbed or the matrix resin flows out of the system, so that the fiber mass content is predetermined. As a result, the mechanical properties of the resulting fiber-reinforced composite material may be reduced. Further, combining a plurality of epoxy resins exhibiting various viscoelastic behaviors at an arbitrary temperature is also effective for making the tackiness and draping properties of the obtained prepreg appropriate.

  In the epoxy resin composition of the present invention, a monoepisulfide compound having only one episulfide group per molecule, or an alicyclic episulfide, as long as the heat resistance and mechanical properties are not significantly reduced. Resins and the like can be appropriately blended.

  The component [B] of the present invention can be produced by various methods. For example, a method of producing a thiirane ring by reacting an oxirane ring of an epoxy compound with a thialating agent. The thialating agent is not particularly limited as long as it is a compound that reacts with an oxirane ring to form a thiirane ring. For example, a thiating agent selected from the group consisting of thiocyanates such as thiureas, sodium thiocyanate, potassium thiocyanate, and ammonium thiocyanate may be used alone, or two or more types may be used in combination. .

In the episulfide compound of the component [B], the ratio of the number of thiirane rings to the total number of oxirane rings and thiirane rings (hereinafter also referred to as the thiirane conversion rate) is obtained by the following formula (1).
Rate of thiirane of episulfide compound = (number of thiirane rings in episulfide compound / (number of oxirane rings in episulfide compound + number of thiirane rings in episulfide compound)) × 100 (1)

Here, the number of oxirane rings and thiirane rings in the episulfide compound can be measured by ¹ H-NMR. That is, a 10 mg sample was placed in a sample bottle, and a solution of 1 g added with chloroform-d (manufactured by Wako Pure Chemical Industries, Ltd.) was transferred to an NMR tube having a diameter of 5 mmφ, and a Fourier transform nuclear magnetic resonance apparatus Spectrospin 400 type ( ¹ H-NMR measurement is performed under the conditions of frequency 400 MHz, nuclide H, and the number of integrations of 200 times. In the obtained spectrum, the integrated value of the peak derived from the oxirane ring and the integrated value of the peak derived from the thiirane ring are obtained, and the ratio is set as the ratio of the number of oxirane rings and the number of thiirane rings, respectively.

  Although the rate of thiirane formation of the component [B] is not particularly limited, it is preferably 5 to 100%, more preferably 20 to 100%, still more preferably 30 to 100% from the viewpoint of the curing rate. As the thiirane conversion rate of the constituent element [B] is higher, excellent quick curability can be imparted to the resulting epoxy resin composition even if the blending amount is small, and the productivity is excellent. The rate of thiirane formation of the component [B] can be arbitrarily controlled, for example, by changing the amount of the thialating agent used in the reaction for converting the oxirane ring of the epoxy compound to a thiirane ring, or the thialation reaction time. Can do.

The blending ratio of thiirane rings contained in the epoxy resin composition of the present invention (hereinafter also referred to as thiirane ring blending ratio) is determined by the following formula (2).
Mixing ratio of thiirane rings in the epoxy resin composition = (number of thiirane rings in the epoxy resin composition / (number of oxirane rings in the epoxy resin composition + number of thiirane rings in the epoxy resin composition)) × 100 · -Formula (2).

Here, the number of oxirane rings and thiirane rings in the epoxy resin composition can be measured by ¹ H-NMR in the same manner as for the episulfide compound.

  It is preferable that the thiirane ring compounding rate of the epoxy resin composition of this invention is 5 to 40%, More preferably, it is 5 to 30%, More preferably, it is 10 to 30%. By setting the blend ratio of the thiirane ring in such a range, it is possible to balance the rapid curability of the obtained epoxy resin composition and the thermal stability of the epoxy resin composition during the resin kneading process and the prepreg manufacturing process. By improving the thermal stability, it is possible to suppress poor impregnation of the reinforcing fibers and a decrease in tackiness of the prepreg due to an increase in the viscosity of the epoxy resin composition. The thermal stability here refers to the viscosity stability of the epoxy resin composition in a low temperature region such as room temperature to 80 ° C. As an evaluation method, it can confirm by evaluating the viscosity change of an epoxy resin composition when it maintains at 80 degreeC for 2 hours, for example by a dynamic viscoelasticity measurement.

  In the epoxy resin composition of the present invention, it is preferable to blend 30 to 90 parts by mass of a compound having 3 or more functional groups in a total amount of 100 parts by mass of the component [A] and the component [B], more preferably 40. -90 mass parts, More preferably, it is 50-80 mass parts. The number of functional groups referred to here is the total number of oxirane rings and thiirane rings contained in one molecule of component [A] or component [B]. By making the compounding quantity of a compound with 3 or more functional groups into such a range, it is preferable since the heat resistance and elastic modulus of the resulting epoxy resin composition can be made excellent. If the compounding amount of the compound having 3 or more functional groups contained in the epoxy resin composition is within a range, the component [A] may contain a composition having 3 or more functional groups or the component [B]. In the case where only the composition having 3 or more functional groups is included, any of the cases in which both the component [A] and the component [B] include a composition having 3 or more functional groups may be used.

  Component [C] in the present invention is a curing agent for thermally curing the epoxy resin composition of the present invention. Such a curing agent is not particularly limited as long as it cures an epoxy resin composition, and includes amines such as aromatic amines and aliphatic amines, acid anhydrides, polyaminoamides, organic acid hydrazides, and phenol resins. , Isocyanates, and dicyandiamides. These may be used alone or in combination.

  It is preferable to mix an aromatic amine compound as the component [C] because the cured resin obtained is excellent in mechanical properties and heat resistance. Examples of the aromatic amine compound include 3,3′-diisopropyl-4,4′-diaminodiphenylmethane, 3,3′-di-t-butyl-4,4′-diaminodiphenylmethane, and 3,3′-diethyl. -5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-diisopropyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5 , 5′-dimethyl-4,4′-diaminodiphenylmethane, 3,3 ′, 5,5′-tetraethyl-4,4′-diaminodiphenylmethane, 3,3′-diisopropyl-5,5′-diethyl-4, 4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, 3,3 ', 5,5'-tetra Sopropyl-4,4′-diaminodiphenylmethane, 3,3′-di-t-butyl-5,5′-diisopropyl-4,4′-diaminodiphenylmethane, 3,3 ′, 5,5′-tetra-t- Butyl-4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, m-phenylenediamine, m-xylylenediamine, diethyltoluenediamine Etc.

  In particular, in the case of aviation, spacecraft applications, etc., 4,4′-diaminodiphenylsulfone and 3,3 ′ are obtained which are excellent in heat resistance and elastic modulus, and can obtain a cured product with small reduction in heat resistance due to linear expansion coefficient and water absorption. -Diaminodiphenyl sulfone is preferably used. These aromatic amine compounds may be used singly or may be appropriately blended and used. When mixing with other components, either powder or liquid form may be used, and powder and liquid aromatic amine compounds may be mixed and used.

  In the present invention, the compounding amount of the component [C] is the active hydrogen of the component [C] with respect to 1.0 equivalent of the total amount of oxirane ring and thiirane ring contained in the component [A] and the component [B]. It is preferable that the total amount is 0.6 to 1.3 equivalents, more preferably 0.7 to 1.2 equivalents, and even more preferably 0.7 to 1.1 equivalents. It is to be. Here, active hydrogen means a highly reactive hydrogen atom bonded to nitrogen, oxygen, or sulfur in an organic compound. For example, the active hydrogen of an amino group is two. When the ratio of the total amount of oxirane rings and thiirane rings and the active hydrogen of the curing agent is within the predetermined range, it is preferable because the obtained cured resin has excellent heat resistance and elastic modulus.

  In addition to the component [C] in the present invention, the epoxy resin composition may be used in combination with another curing accelerator as long as the heat resistance and thermal stability of the epoxy resin composition are not impaired. Examples of other curing accelerators include tertiary amines, Lewis acid complexes, onium salts, imidazole compounds, urea compounds, and hydrazide compounds. The blending amount of the other curing accelerator needs to be adjusted as appropriate depending on the type to be used, but is 10 parts by mass or less, preferably 5 parts by mass or less with respect to 100 parts by mass of the total epoxy resin. When the blending amount of the other curing accelerator is within the above range, a decrease in thermal stability of the resulting epoxy resin composition can be suppressed.

  Component [D] in the present invention is the viscosity control of the resulting epoxy resin composition, the tackiness of the prepreg, the flowability of the matrix resin when the prepreg is heat-cured, and the heat resistance of the resulting fiber-reinforced composite material It is added to impart toughness without impairing properties and elastic modulus and increase tensile strength. Such a thermoplastic resin has a bond selected from the group consisting of carbon-carbon bond, amide bond, imide bond, ester bond, ether bond, carbonate bond, urethane bond, thioether bond, sulfone bond and carbonyl bond in the main chain. Thermoplastic resins are preferred. Among them, a thermoplastic resin composed of a polyaryl ether skeleton is preferable, and examples thereof include polysulfone, polyphenylsulfone, polyethersulfone, polyetherimide, polyphenylene ether, polyetheretherketone, and polyetherethersulfone. These thermoplastic resins composed of a polyaryl ether skeleton may be used alone or may be appropriately blended and used. Among these, polyethersulfone can be preferably used because it can impart toughness without deteriorating the heat resistance and mechanical properties of the resulting fiber-reinforced composite material.

  Examples of the terminal functional groups of thermoplastic resins composed of these polyaryl ether skeletons include primary amines, secondary amines, hydroxyl groups, carboxyl groups, thiol groups, acid anhydrides and halogen groups (chlorine, bromine), etc. Can be used. Among these, in the case of a halogen group having a low reactivity with an epoxy resin, a prepreg excellent in storage stability can be obtained, while in the case of a functional group other than a halogen group, it has a high reactivity with an epoxy resin. It is preferable because an epoxy resin composition excellent in adhesion between the epoxy resin and the thermoplastic resin can be obtained.

  The glass transition temperature of the component [D] in the present invention is preferably 150 ° C. or higher, and more preferably 170 ° C. or higher. By setting the glass transition temperature of the constituent element [D] to 150 ° C. or higher, deformation due to heat can be suppressed when used as a molded body.

  The compounding amount of the component [D] in the present invention is in the range of 1 to 30 parts by mass, preferably 1 to 20 parts by mass with respect to 100 parts by mass in total of the component [A] and the component [B]. The range is more preferably 2 to 15 parts by mass. By making the compounding quantity of component [D] into such a range, the balance of the viscosity of an epoxy resin composition and the tack property of the obtained prepreg, and the mechanical characteristics of the obtained fiber reinforced composite material can be taken. In addition, surprisingly, the present inventors can effectively combine the component [B] and the component [D] in combination with the component [D] alone compared to the case of combining the component [D] alone. It was found that the viscosity of the epoxy resin composition increased. Thereby, only by mix | blending a small amount of structural element [D], the viscosity of the epoxy resin composition obtained and the tackability of a prepreg can be controlled, and the epoxy resin composition excellent in productivity is obtained.

When the epoxy resin composition of the present invention is used as a matrix resin for a prepreg, the viscosity at 25 ° C. of the epoxy resin composition is preferably 500 Pa · s or more, more preferably 1000 Pa · s or more. Here, the viscosity is a dynamic viscoelasticity measuring device (Rheometer RDA2: manufactured by Rheometrics or Rheometer ARES: manufactured by TA Instruments), a parallel plate having a diameter of 40 mm, a frequency of 0.5 Hz, It refers to the complex viscosity η ^* measured at Gap 1 mm. When the viscosity at 25 ° C. is in such a range, the prepreg has a tackiness suitable for handling during molding, in addition to making it difficult for the resin to flow at room temperature and suppressing variations in reinforcing fiber content. can get.

  When the epoxy resin composition of the present invention is used as a prepreg matrix resin, the initial viscosity at 80 ° C. of the epoxy resin composition is preferably in the range of 0.5 to 200 Pa · s from the viewpoint of tack and drape of the prepreg. . When the initial viscosity at 80 ° C. is 0.5 Pa · s or more, an excessive resin flow is less likely to occur during molding of the fiber-reinforced composite material, and variations in the reinforcing fiber content can be suppressed. In addition, when the initial viscosity at 80 ° C. is 0.5 Pa · s or more, the constituent element [C] is uniformly dispersed without being precipitated in the epoxy resin composition during the molding of the prepreg. A fiber reinforced composite material is obtained. On the other hand, when the initial viscosity at 80 ° C. is 200 Pa · s or less, the reinforced fiber can be sufficiently impregnated with the epoxy resin composition when producing the prepreg, and voids are less likely to occur in the obtained fiber-reinforced composite material. Moreover, the strength reduction of the fiber reinforced composite material can be suppressed. The initial viscosity at 80 ° C. of the epoxy resin composition is 0.5 to 200 Pa · s in order to produce a prepreg having a high fiber mass content because the epoxy resin composition is easily impregnated into the reinforcing fiber in the prepreg manufacturing process. It is preferable that it is in the range of 1 to 150 Pa · s, more preferably in the range of 5 to 100 Pa · s.

  In the epoxy resin composition of the present invention, the viscosity when held at 80 ° C. for 2 hours is preferably 2.5 times or less of the initial viscosity at 80 ° C., more preferably 2.0 times or less, and still more preferably It is 1.8 times or less, More preferably, it is 1.5 times or less. Here, the viscosity increase factor at 80 ° C. can be used as an index of the thermal stability of the epoxy resin composition in the kneading process of the epoxy resin composition or the manufacturing process of the prepreg. That is, the smaller the thickening factor at 80 ° C., the better the thermal stability at 80 ° C. or less. When the viscosity increase ratio when the epoxy resin composition is held at 80 ° C. for 2 hours is 2.5 times or less, the thermal stability of the epoxy resin composition is high, and the impregnation property of the resin to the reinforcing fiber in the prepreg manufacturing process Does not decrease, and voids hardly occur in the molded product. The initial viscosity at 80 ° C. means the viscosity when held at 80 ° C. for 1 minute.

The minimum viscosity of the epoxy resin composition of the present invention is preferably 0.1 to 50 Pa · s, more preferably 0.3 to 5 Pa · s, and still more preferably 0.3 to 1.5 Pa · s. . Here, the minimum viscosity refers to the minimum complex viscoelastic modulus η ^* _min of the epoxy resin composition measured by the method described in the column of “(3) Viscosity measurement of epoxy resin composition” described later. By setting the minimum viscosity of the matrix resin to 0.1 Pa · s or more, an increase in the fiber mass content of the fiber-reinforced composite material due to the outflow of the matrix resin during molding can be suppressed. Moreover, by setting the minimum viscosity to 50 Pa · s or less, fluidity is imparted to the matrix resin, and a decrease in mechanical strength of the fiber-reinforced composite material due to voids formed when the prepreg is laminated can be prevented.

  The epoxy resin composition of the present invention may contain thermoplastic resin particles that are insoluble in the epoxy resin composition as long as the heat resistance and fast curability are not significantly reduced. Here, insoluble in the epoxy resin means that the resin particles are not substantially dissolved in the epoxy resin when the epoxy resin in which the resin particles are dispersed is heated and cured. This means that the particles can be observed with a clear interface between the particles and the matrix resin without substantially reducing the original size in the cured epoxy resin using a microscope. The thermoplastic resin particles are blended to add the impact resistance of the fiber reinforced composite material obtained in the present invention. In general, a fiber reinforced composite material has a laminated structure. When an impact is applied to the fiber reinforced composite material, high stress is generated between the layers, and peeling damage occurs. Therefore, in the case of improving the impact resistance against external impact, a resin layer formed between layers of reinforcing fibers of the fiber reinforced composite material (hereinafter also referred to as “interlayer resin layer”) What is necessary is just to improve the toughness of. In the present invention, the component [D] is added to the epoxy resin which is a matrix resin to improve the toughness. In addition, in order to selectively increase the toughness of the interlayer resin layer of the fiber-reinforced composite material of the present invention. It is preferable to blend thermoplastic resin particles.

  As such a thermoplastic resin, polyamide or polyimide can be preferably used. Among them, polyamide is most preferable because it can greatly improve impact resistance due to excellent toughness. As the polyamide, polyamide 12, polyamide 11, polyamide 6, polyamide 66, polyamide 6/12 copolymer, semi-IPN (polymer interpenetrating network structure) in the epoxy compound described in Example 1 of JP-A-1-104624 is used. Polyamide (semi-IPN polyamide) and the like can be suitably used. The shape of the thermoplastic resin particles may be spherical particles, non-spherical particles, or porous particles, but the spherical shape is excellent in viscoelasticity because it does not deteriorate the flow characteristics of the resin, and there is no origin of stress concentration. This is a preferred embodiment in terms of giving high impact resistance.

  Examples of commercially available polyamide particles include SP-500, SP-10, TR-1, TR-2, 842P-48, 842P-80 (above, manufactured by Toray Industries, Inc.), “Orgasol (registered trademark)” 1002D. , 2001UD, 2001EXD, 2002D, 3202D, 3501D, 3502D (above, manufactured by Arkema Co., Ltd.), “Grillamide (registered trademark)” TR90 (manufactured by Mzavelke Co., Ltd.), “TROGAMID (registered trademark)” CX7321, CX9701 CX9704 (made by Degussa Co., Ltd.) and the like can be used. These polyamide particles may be used alone or in combination.

  In order to selectively increase the toughness of the interlayer resin layer of the fiber-reinforced composite material of the present invention, it is necessary to keep the thermoplastic resin particles in the interlayer resin layer. Therefore, the average particle diameter of the thermoplastic resin particles is It is good in the range of 5-50 micrometers, Preferably it is the range of 7-40 micrometers, More preferably, it is the range of 10-30 micrometers. By setting the average particle size to 5 μm or more, the particles can remain in the interlayer resin layer of the fiber-reinforced composite material obtained without entering the bundle of reinforcing fibers, and by setting the average particle size to 50 μm or less, the prepreg In the fiber reinforced composite material obtained by optimizing the thickness of the matrix resin layer on the surface, the fiber mass content can be optimized.

  The prepreg of the present invention is obtained by using the above-described epoxy resin composition as a matrix resin and combining this epoxy resin composition with reinforcing fibers. Preferred examples of the reinforcing fiber include carbon fiber, graphite fiber, aramid fiber, and glass fiber. Among them, carbon fiber is particularly preferable.

  The prepreg of the present invention can be produced by various known methods. For example, the matrix resin is dissolved in an organic solvent selected from acetone, methyl ethyl ketone, methanol, and the like to lower the viscosity, and the wet method in which the reinforcing fiber is impregnated, or the matrix resin is heated to lower the viscosity without using the organic solvent, A prepreg can be produced by a method such as a hot melt method for impregnating reinforcing fibers.

  In the wet method, the reinforced fiber is pulled up after being immersed in a liquid containing a matrix resin, and an organic solvent is evaporated using an oven or the like to obtain a prepreg.

  In the hot melt method, a matrix resin whose viscosity has been reduced by heating is impregnated directly into a reinforcing fiber, or a release paper sheet with a resin film once coated with a matrix resin on a release paper (hereinafter referred to as “resin”). The film may be referred to as “film” first), then a resin film is laminated on the reinforcing fiber side from both sides or one side of the reinforcing fiber, and the reinforcing fiber is impregnated with the matrix resin by heating and pressing. .

  The method for producing the prepreg of the present invention is preferably a hot melt method in which the reinforcing fibers are impregnated with a matrix resin without using an organic solvent, since substantially no organic solvent remains in the prepreg.

The prepreg preferably has a reinforcing fiber amount per unit area of 70 to 2000 g / m ² . When the amount of the reinforcing fibers is less than 70 g / m ^2, it is necessary to increase the number of laminated layers in order to obtain a predetermined thickness at the time of forming the fiber reinforced composite material, and the work may be complicated. On the other hand, when the amount of reinforcing fibers exceeds 2000 g / m ² , the prepreg drapability tends to deteriorate.

  The fiber mass content of the prepreg is preferably 30 to 90% by mass, more preferably 35 to 85% by mass, and further preferably 40 to 80% by mass. When the fiber mass content is less than 30% by mass, the amount of the resin is too large to obtain the advantages of the fiber reinforced composite material having excellent specific strength and specific elastic modulus, and it is hardened when molding the fiber reinforced composite material. Sometimes the amount of heat generated is too high. On the other hand, if the fiber mass content exceeds 90% by mass, poor resin impregnation may occur, and the resulting composite material may have many voids.

  The fiber-reinforced composite material of the present invention can be produced by taking, as an example, a method of laminating the above-described prepreg of the present invention in a predetermined form and curing the resin by pressurization and heating. As a method for applying heat and pressure, a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, an internal pressure molding method, or the like is employed.

  Further, without impregnating the prepreg, the reinforcing fiber is directly impregnated into the reinforcing fiber, followed by heat curing, such as a hand layup method, a filament winding method, a pultrusion method, a resin injection, A carbon fiber reinforced composite material can also be produced by a molding method such as a molding method or a resin transfer molding method.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the scope of the present invention is not limited to these examples. The unit “part” of the composition ratio means part by mass unless otherwise specified. Various characteristics (physical properties) were measured in an environment of a temperature of 23 ° C. and a relative humidity of 50% unless otherwise specified.

<Materials Used in Examples and Comparative Examples>
(1) Component [A]: Epoxy compound “Epiclon (registered trademark)” 830 (bisphenol F type epoxy resin, bifunctional, epoxy equivalent: 172, manufactured by DIC Corporation)
"Epiclon (registered trademark)" HP-4700 (epoxy resin having a naphthalene skeleton, tetrafunctional, epoxy equivalent: 162, manufactured by DIC Corporation)
"Ogsol (registered trademark)" CG-500 (epoxy resin having a fluorene skeleton, bifunctional, epoxy equivalent: 310, manufactured by Osaka Gas Chemical Co., Ltd.)
ELM434 (tetraglycidyldiaminodiphenylmethane, tetrafunctional, epoxy equivalent: 120, manufactured by Sumitomo Chemical Co., Ltd.)
"Araldite (registered trademark)" MY0610 (triglycidyl-m-aminophenol, trifunctional, epoxy equivalent: 100, manufactured by Huntsman Advanced Materials)
"Araldite (registered trademark)" MY0510 (triglycidyl-p-aminophenol, trifunctional, epoxy equivalent: 100, manufactured by Huntsman Advanced Materials)
-TORAY EPOXY PG-01 (diglycidyl-p-phenoxyaniline, bifunctional, epoxy equivalent: 167, manufactured by Toray Fine Chemical Co., Ltd.).

(2) Component [B]: Episulfide compound in which at least one of the oxirane rings of the epoxy compound is substituted with a thiirane ring. Episulfide compound A synthesized by the following method (bifunctional, thiirane equivalent: 172)
4.0 mol of “Epiclon (registered trademark)” 830 was added to 6.0 L of chloroform and stirred. A solution prepared by dissolving 4.0 mol of thiourea in 6.0 L of methanol was added, and the mixture was stirred at room temperature for 24 hours. Further, 4.0 L of water was added and stirred for 10 minutes, and then the operation of removing the water / methanol mixed layer was repeated 10 times. After adding 500 g of magnesium sulfate to the chloroform layer and dehydrating the solution, the magnesium sulfate was filtered, and the filtrate was concentrated by an evaporator. The obtained concentrated liquid was dried under reduced pressure at room temperature for 15 days to obtain episulfide compound A. ^{From the 1} H-NMR measurement, the thiirane conversion rate was 100%.

Episulfide compound B synthesized by the following method (bifunctional, total equivalent of epoxy group and thiirane group: 172)
4.0 mol of “Epiclon (registered trademark)” 830 was added to 6.0 L of chloroform and stirred. A solution in which 2.0 mol of thiourea was dissolved in 6.0 L of methanol was added, and the mixture was stirred at room temperature for 24 hours. Further, 4.0 L of water was added and stirred for 10 minutes, and then the operation of removing the water / methanol mixed layer was repeated 10 times. After adding 500 g of magnesium sulfate to the chloroform layer and dehydrating the solution, the magnesium sulfate was filtered, and the filtrate was concentrated by an evaporator. The obtained concentrated liquid was dried under reduced pressure at room temperature for 15 days to obtain episulfide compound B. ^{From the 1} H-NMR measurement, the thiirane conversion rate was 50%.

Episulfide compound C synthesized by the following method (tetrafunctional, total equivalent of epoxy group and thiirane group: 162)
8.0 mol of “Epicron (registered trademark)” HP-4700 was added to 8.0 L of dichloromethane and stirred. A solution in which 4.0 mol of thiourea was dissolved in 8.0 L of methanol was added, and the mixture was stirred at room temperature for 48 hours. Further, after adding 3.0 L of water and stirring for 10 minutes, the operation of removing the water / methanol mixed layer was repeated 15 times. After adding 500 g of magnesium sulfate to the dichloromethane layer and dehydrating the solution, the magnesium sulfate was filtered, and the filtrate was concentrated by an evaporator. The obtained concentrate was dried under reduced pressure at 80 ° C. for 5 hours to obtain episulfide compound C. ^{From the 1} H-NMR measurement, the thiirane conversion rate was 50%.

  Episulfide compound D (“Ogsol (registered trademark)” CS-500, episulfide resin having a fluorene skeleton, bifunctional, 100% thiirane conversion, thiirane equivalent: 304, manufactured by Osaka Gas Chemical Co., Ltd.)

Episulfide compound E synthesized by the following method (tetrafunctional, total equivalent of epoxy group and thiirane group: 120)
4.0 mol of ELM434 was added to 6.0 L of chloroform and stirred. A solution in which 2.0 mol of thiourea was dissolved in 6.0 L of methanol was added, and the mixture was stirred at room temperature for 24 hours. Further, 4.0 L of water was added and stirred for 10 minutes, and then the operation of removing the water / methanol mixed layer was repeated 10 times. After adding 500 g of magnesium sulfate to the chloroform layer and dehydrating the solution, the magnesium sulfate was filtered, and the filtrate was concentrated by an evaporator. The obtained concentrated liquid was dried under reduced pressure at room temperature for 15 days to obtain episulfide compound E. ^{From the 1} H-NMR measurement, the thiirane conversion rate was 50%.

Episulfide compound F synthesized by the following method (trifunctional, total equivalent of epoxy group and thiirane group: 100)
"Araldite (registered trademark)" MY0610 3.0 mol was added to chloroform 6.0 L and stirred. A solution in which 1.0 mol of thiourea was dissolved in 6.0 L of methanol was added and stirred at room temperature for 24 hours. Further, 4.0 L of water was added and stirred for 10 minutes, and then the operation of removing the water / methanol mixed layer was repeated 10 times. After adding 500 g of magnesium sulfate to the chloroform layer and dehydrating the solution, the magnesium sulfate was filtered, and the filtrate was concentrated by an evaporator. The obtained concentrated liquid was dried under reduced pressure at room temperature for 15 days to obtain episulfide compound F. ^{From the 1} H-NMR measurement, the thiirane conversion rate was 33%.

-Episulfide compound G synthesized by the following method (trifunctional, total equivalent of epoxy group and thiirane group: 100)
"Araldite (registered trademark)" MY0510 3.0 mol was added to 6.0 L of chloroform and stirred. A solution in which 1.0 mol of thiourea was dissolved in 6.0 L of methanol was added and stirred at room temperature for 24 hours. Further, 4.0 L of water was added and stirred for 10 minutes, and then the operation of removing the water / methanol mixed layer was repeated 10 times. After adding 500 g of magnesium sulfate to the chloroform layer and dehydrating the solution, the magnesium sulfate was filtered, and the filtrate was concentrated by an evaporator. The obtained concentrated liquid was dried under reduced pressure at room temperature for 15 days to obtain episulfide compound G. ^{From the 1} H-NMR measurement, the thiirane conversion rate was 33%.

Episulfide compound H synthesized by the following method (bifunctional, thiirane equivalent: 167)
4.0 mol of TRAY EPOXY PG-01 was added to 6.0 L of chloroform and stirred. A solution prepared by dissolving 4.0 mol of thiourea in 6.0 L of methanol was added, and the mixture was stirred at room temperature for 24 hours. Further, 4.0 L of water was added and stirred for 10 minutes, and then the operation of removing the water / methanol mixed layer was repeated 10 times. After adding 500 g of magnesium sulfate to the chloroform layer and dehydrating the solution, the magnesium sulfate was filtered, and the filtrate was concentrated by an evaporator. The obtained concentrated liquid was dried under reduced pressure at room temperature for 15 days to obtain episulfide compound H. ^{From the 1} H-NMR measurement, the thiirane conversion rate was 100%.

Episulfide compound I synthesized by the following method (bifunctional, total equivalent of epoxy group and thiirane group: 172)
5.0 mol of “Epiclon (registered trademark)” 830 was added to 6.0 L of chloroform and stirred. A solution prepared by dissolving 1.5 mol of thiourea in 6.0 L of methanol was added, and the mixture was stirred at room temperature for 24 hours. Further, 4.0 L of water was added and stirred for 10 minutes, and then the operation of removing the water / methanol mixed layer was repeated 10 times. After adding 500 g of magnesium sulfate to the chloroform layer and dehydrating the solution, the magnesium sulfate was filtered, and the filtrate was concentrated by an evaporator. The obtained concentrated liquid was dried under reduced pressure at room temperature for 15 days to obtain episulfide compound I. ^{From the 1} H-NMR measurement, the thiirane conversion rate was 30%.

(3) Component [C]: Curing agent / Seikacure S (4,4′-diaminodiphenylsulfone (4,4′-DDS), manufactured by Seika Corporation, amine equivalent: 62)
3,3′-DAS (3,3′-diaminodiphenylsulfone, manufactured by Mitsui Chemicals Fine Co., Ltd., amine equivalent: 62)
・ Lonza Cure DETDA80 (diethyltoluenediamine, Lonza Japan Co., Ltd., amine equivalent 45)
"Adeka Hardener (registered trademark)" EH-3895 (alicyclic polyamine, manufactured by ADEKA Corporation, amine equivalent 80)
“Novacure (registered trademark)” HX-3722 (imidazole-modified microcapsule, manufactured by Asahi Kasei E-Materials Co., Ltd.).

(4) Component [D]: Thermoplastic resin “Sumika Excel (registered trademark)” PES 5003P (polyethersulfone, manufactured by Sumitomo Chemical Co., Ltd., glass transition temperature: 230 ° C.)
"VIRANAGE (registered trademark)" VW-10700RFP (terminal hydroxyl group polyethersulfone, manufactured by Solvay Specialty Polymers, Inc., glass transition temperature: 216 ° C)
“Nanostrength (registered trademark)” M22N (a block copolymer made of butyl acrylate (Tg: −54 ° C.) and methyl methacrylate (Tg: 130 ° C.), manufactured by Arkema Co., Ltd.)

(5) Carbon fiber "Torayca (registered trademark)" T800S-24K-10E (24,000 fibers, fineness: 1,033 tex, tensile modulus: 294 GPa, density 1.8 g / cm ³ , manufactured by Toray Industries, Inc.) .

<Various evaluation methods>
The following measurement methods were used to measure the epoxy resin composition and prepreg of each example.

(1) Measurement of glass transition temperature of cured epoxy resin After injecting the epoxy resin composition into a mold, the temperature is increased from 30 ° C. at a rate of 1.5 ° C./min in a hot air dryer, and heat cured at 180 ° C. for 2 hours. Then, the temperature was lowered to 30 ° C. at a rate of 2.5 ° C./min to produce a 2 mm thick resin cured plate. After cutting out a test piece having a width of 12.7 mm and a length of 55 mm from the produced cured resin plate, the glass transition temperature was determined by the DMA method according to SACMA SRM18R-94. In the storage elastic modulus G ′ curve, the intersection temperature value between the tangent in the glass state and the tangent in the transition state was defined as the glass transition temperature. Here, the measurement was performed at a heating rate of 5 ° C./min and a frequency of 1 Hz.

(2) Measurement of gel time of epoxy resin composition The curing reactivity of the epoxy resin composition was evaluated from the change over time of the rotational torque with a curast meter. Here, using Rubber Process Analyzer RPA2000 (manufactured by ALPHA TECHNOLOGIES), the temperature was raised from 40 ° C. to 180 ° C. at a rate of 1.7 ° C./min and heated at 180 ° C. for 2 hours. The gel time was the time from the start of heating at 40 ° C. until the torque exceeded 1 dNm.

(3) Viscosity Measurement of Epoxy Resin Composition The viscosity of the epoxy resin composition is measured by using a dynamic viscoelastic device ARES-2KFRTN1-FCO-STD (manufactured by T.A. Instruments Co., Ltd.). A 40 mm flat parallel plate was used, and the epoxy resin composition was set so that the distance between the upper and lower jigs was 1 mm, and then measured in the torsion mode (measurement frequency: 0.5 Hz). The temperature was raised from 20 ° C. to 150 ° C. at a rate of 2 ° _C./min, and the lowest complex viscosity was defined as η ^* _min .

(4) Definition of 0 ° of carbon fiber reinforced composite material As described in JIS K7017 (1999), the fiber direction of the unidirectional fiber reinforced composite material is defined as the axial direction, and the axial direction is defined as the 0 ° axis. The direction perpendicular to the axis was defined as 90 °.

(5) Measurement of resin flow during molding of prepreg After prepreg produced by impregnating a matrix resin into a reinforced fiber by hot melt method is cut into a size of 100 mm x 1010 mm and laminated in four directions, a vacuum bag And cured using an autoclave at a temperature of 180 ° C. and a pressure of 6 kg / cm ² for 2 hours to obtain a unidirectional reinforcing material (carbon fiber reinforced composite material). The reinforcing fiber containing part of this unidirectional reinforcing material was cut with a width of 100 mm and a length of 100 mm, the cured resin flowed around the unidirectional material was removed, and the weight of the flowed resin was measured. The resin flow rate at the time of prepreg molding was calculated by dividing the weight of the resin that flowed at the time of molding by the amount of resin contained in the prepreg before curing. Here, the flow characteristic determination of the resin was evaluated in the following two stages.
A: A fiber-reinforced composite material having a low resin flow rate of 0 to 5% and a desired fiber content was obtained.
B: The resin flow rate is larger than 5%, and the fiber content of the fiber reinforced composite material is greatly changed.

(6) Measurement of 0 ° tensile strength of carbon fiber reinforced composite material Cut unidirectional prepreg into a predetermined size, laminate 6 sheets in one direction, perform vacuum bag, use autoclave, temperature 180 ° C, pressure It was cured at 6 kg / cm ² for 2 hours to obtain a unidirectional reinforcing material (carbon fiber reinforced composite material). This unidirectional reinforcing material was cut to a width of 12.7 mm and a length of 230 mm, and a glass fiber reinforced plastic tab having a length of 1.2 mm and a length of 50 mm was bonded to both ends to obtain a test piece. This test piece was subjected to a 0 ° tensile test according to the standard of JIS K7073 (1988) using an Instron universal testing machine.

(7) Thiirane ring blending ratio measurement of epoxy resin composition 10 g of epoxy resin composition was added chloroform-d (manufactured by Wako Pure Chemical Industries, Ltd.) to 1 g, and the solution was transferred to an NMR tube having a diameter of 5 mmφ and Fourier ¹ H-NMR measurement was performed with a conversion nuclear magnetic resonance apparatus Spectrospin 400 type (manufactured by Bruker) under the conditions of a frequency of 400 MHz, a nuclide H, and an accumulation count of 200 times. From the formula (2), the integrated value of the peak derived from the oxirane ring and the integrated value of the peak derived from the thiirane ring in the obtained spectrum are obtained, and the ratio is the ratio of the number of oxirane rings and the number of thiirane rings, respectively. The thiirane ring content was calculated.
Mixing ratio of thiirane rings in the epoxy resin composition = (number of thiirane rings in the epoxy resin composition / (number of oxirane rings in the epoxy resin composition + number of thiirane rings in the epoxy resin composition)) × 100 · -Formula (2).

<Example 1>
(Preparation of epoxy resin composition)
An epoxy resin composition was prepared by the following method.

  In the kneading apparatus, the epoxy resin and the constituent element [D] corresponding to the constituent element [A] shown in Table 1 are charged, the temperature is raised to 160 ° C., and the mixture is heated and kneaded at a temperature of 160 ° C. for 1 hour. Element [D] component was dissolved. Next, while continuing kneading, the temperature was lowered to a temperature of 55 to 65 ° C., the component [B] shown in Table 1 was added, and the mixture was heated and kneaded to the melting temperature. Thereafter, while continuing kneading, the temperature was lowered to a temperature of 55 to 65 ° C., the constituent element [C] shown in Table 1 was added, and the mixture was stirred for 30 minutes to obtain an epoxy resin composition.

  The obtained epoxy resin composition was measured in accordance with “(1) Measurement of glass transition temperature of cured epoxy resin” in the various evaluation methods described above. As a result, the glass transition temperature of the cured product was 195 ° C.

  Moreover, when the gel time was measured according to "(2) Gel time measurement of epoxy resin composition" of the various evaluation methods described above for the obtained epoxy resin composition, it was 91 min. The gel time was shortened by 5% or more as compared with Comparative Example 1 (when component [B] was not blended) described later, and sufficient rapid curability was confirmed.

  The obtained epoxy resin composition was subjected to viscosity measurement according to “(3) Viscosity measurement of epoxy resin composition” in the various evaluation methods described above. As a result, the minimum viscosity was 1.1 Pa · s, which was good as described later. Resin flow characteristics were obtained.

(Preparation of prepreg)
The epoxy resin composition obtained in above was applied onto release paper using a knife coater, a resin weight per unit area were prepared two sheets of resin films of 51.2 g / m ^2. Next, on the carbon fibers arranged in one direction so as to form a sheet having a fiber basis weight of 190 g / m ² , ^two obtained resin films are stacked from both sides of the carbon fiber, the temperature is 130 ° C., and the maximum pressure is 1 MPa. The prepreg was obtained by impregnating the epoxy resin composition by heating and pressing under the conditions described above.

The configuration of the constituent elements [A] to [D] in the obtained prepreg was as follows.
-Component [A];
“Epiclon (registered trademark)” 830: 25 parts,
“Araldite (registered trademark)” MY0610: 50 parts,
-Component [B];
Episulfide compound A: 25 parts
-Component [C];
Seica Cure S: 44 parts,
-Component [D];
“VIRANAGE (registered trademark)” VW-10700RFP: 2 parts,
At this time, the active hydrogen group contained in the constituent element [C] was 0.9 equivalent with respect to 1.0 equivalent of the total amount of the oxirane ring and the thiirane ring contained in the constituent element [A] and the constituent element [B]. .

(Evaluation of prepreg characteristics)
With respect to the obtained prepreg, the resin flow characteristics of the prepreg were evaluated in accordance with “(5) Measurement of resin flow amount during prepreg molding” in the various evaluation methods described above. The produced prepreg had a resin flow rate of 2.6, and a composite material having a desired fiber content was obtained.

(Evaluation of fiber reinforced composite materials)
When the obtained prepreg was measured according to “(6) Measurement of 0 ° tensile strength of carbon fiber reinforced composite material” in the various evaluation methods described above, the tensile strength was 3286 MPa, and good tensile strength was obtained. Surprisingly, it was found that the tensile strength of the fiber-reinforced composite material was improved by adding the constituent element [B] as compared with Comparative Example 1 described later.

<Examples 2 to 24>
Except for changing the composition as shown in Tables 1 to 5, an epoxy resin composition was prepared in the same manner as in Example 1, and a prepreg was prepared by a hot melt method, and various measurements were performed.

  The results of various measurements are as shown in Tables 1-5. In Examples 2 to 24, as in Example 1, excellent rapid curability, resin flow characteristics, and high tensile strength were exhibited.

<Comparative Examples 1-5>
Except for changing the composition as shown in Table 6, an epoxy resin composition was prepared in the same manner as in Example 1, a prepreg was prepared by a hot melt method, and various measurements were performed. The results of various measurements are as shown in Table 6.

  In Comparative Example 1, an epoxy resin composition was prepared in the same manner as in Example 1 except that the constituent element [B] was not included. Comparing Comparative Example 1 and Example 1, it was found that the component [B] was not blended in Comparative Example 1, so that the resulting epoxy resin composition had a long gel time and poor fast curability.

  Comparative Examples 2-4 produced the epoxy resin composition by the method similar to Examples 1-24 except not including component [D]. Comparative Examples 2 to 4 do not contain the constituent element [D], and the viscosity control of the epoxy resin composition was insufficient, so the resin flow rate during molding was 5% or more, and the fiber content of the fiber reinforced composite material varied greatly. have done.

  In Comparative Example 5, the amount of component [D] is greater than the specified range. Therefore, the minimum viscosity of the epoxy resin composition became too high, voids remained in the fiber-reinforced composite material after molding, and the tensile strength decreased. Moreover, since the compounding quantity of the thermoplastic resin in a composition was large, the glass transition temperature of resin cured material fell.

Claims (11)

An epoxy resin composition comprising the following components [A] to [D] and 1 to 30 parts by mass of the component [D] with respect to 100 parts by mass of the total amount of the components [A] and [B].
[A]: Epoxy compound [B]: Episulfide compound in which at least one oxirane ring of the epoxy compound is substituted with a thiirane ring [C]: Curing agent [D]: Thermoplastic resin Component [D] has a bond selected from the group consisting of carbon-carbon bond, amide bond, imide bond, ester bond, ether bond, carbonate bond, urethane bond, thioether bond, sulfone bond and carbonyl bond in the main chain. The epoxy resin composition according to claim 1. The epoxy resin composition of Claim 1 or 2 whose minimum viscosity is 0.1-50 Pa.s. The epoxy resin composition in any one of Claim 1 to 3 whose glass transition temperature of component [D] is 150 degreeC or more. The epoxy resin composition in any one of Claim 1 to 4 whose thiirane ring compounding rate is 5 to 40% with respect to the sum total of the oxirane ring and thiirane ring contained in an epoxy resin composition. The epoxy resin composition according to any one of claims 1 to 5, wherein the constituent element [B] includes an episulfide compound having a structure represented by the general formula (I).

(In general formula (I), X is an oxygen atom or a sulfur atom.) The epoxy resin composition according to any one of claims 1 to 6, wherein the constituent element [B] includes an episulfide compound having a structure represented by the general formula (II).

A prepreg obtained by impregnating a reinforcing fiber with the epoxy resin composition according to any one of claims 1 to 7. A fiber-reinforced composite material obtained by curing the prepreg according to claim 8. A cured resin obtained by curing the epoxy resin composition according to claim 1. A fiber-reinforced composite material comprising the cured resin according to claim 10 and reinforcing fibers.