JP7213620B2 - Epoxy resin composition, prepreg, carbon fiber reinforced composite material and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to an epoxy resin composition, a prepreg obtained by impregnating a reinforcing fiber base material with this epoxy resin composition, and a method for producing a fiber-reinforced composite material using this prepreg. In particular, the present invention relates to a prepreg that uses a reinforcing fiber base material having a heavy weight per unit area and can adopt a wide range of molding conditions, and a method for producing a fiber-reinforced composite material using the same.

Fiber-reinforced composite materials (hereinafter referred to as "FRP") are lightweight, high-strength, and high-rigidity, so they are used in a wide range of fields, including sports and leisure applications such as fishing rods and golf shafts, and industrial applications such as automobiles and aircraft. It is A method of using a prepreg, which is an intermediate material obtained by impregnating a resin-impregnated fiber reinforcing material made of long fibers such as reinforcing fibers, is preferably used for the production of FRP. A molded article made of FRP can be obtained by cutting the prepreg into a desired shape, shaping it, and curing it under heat and pressure.

In recent years, from the viewpoint of reducing the manufacturing cost of FRP, towpreg and towpreg, which are made by impregnating a reinforcing fiber bundle in which several thousand to tens of thousands of reinforcing fiber filaments are arranged in one direction with a matrix resin composition, have been used as intermediate materials for FRP. , SMC (sheet molding compound) in which a matrix resin composition is impregnated in a sheet-shaped material using short fibers as a reinforcing material, a woven fabric with a heavy weight per unit area, and a multi-layered woven fabric in which a matrix resin composition is impregnated. woven fabric prepreg is used.

However, in the hot-melt method used in conventional prepreg production, the viscosity of the matrix resin composition is high, making it difficult to impregnate the prepreg as described above.

Conventionally, low-viscosity unsaturated polyester resins and vinyl ester resins have been widely used as matrix resins for SMC. There are some
For example, unsaturated polyester resins and vinyl ester resins exhibit large cure shrinkage. Cure shrinkage causes warpage, sink marks, cracks, and the like in molded products. In some cases, a low-shrinkage agent is added to reduce curing shrinkage, but the addition of a low-shrinkage agent causes a decrease in heat resistance and strength.
Another problem is that it is difficult to control the viscosity of the resin. Generally, in the method of manufacturing a prepreg using an unsaturated polyester resin or a vinyl ester resin, the viscosity of the resin composition impregnated into the reinforcing fibers is increased to the target viscosity using a thickener such as magnesium oxide or isocyanate. Although tack is suppressed, the viscosity after thickening varies greatly due to the effects of moisture, temperature, and the amount of thickener added, making it difficult to control stable tack.
Furthermore, unsaturated polyester resins and vinyl ester resins generally contain styrene as a reactive diluent, and in molding workshops where uncured resin compositions are handled, volatilized styrene deteriorates the working environment. Therefore, development of an intermediate material for FRP using epoxy resin as a base resin is desired.

As the epoxy resin composition, for example, the following have been proposed.
An epoxy resin composition containing an epoxy resin, an amino compound such as bis-(4-aminocyclohexyl)methane, 1,3-bis-(aminomethyl)-cyclohexane, isophoronediamine, dicyanamide, and an imidazole compound (Patent Document 1) .
An epoxy resin composition, a molding material, and a fiber-reinforced composite material having a long B-stage pot life by using a reactive diluent comprising a specific aliphatic epoxy compound and an alicyclic diamine having a specific structure (Patent Document 2).

The resins used in the prepregs described in Patent Documents 1 and 2 have low viscosity and good impregnation properties into the fiber-reinforced base material, but it is difficult to control the viscosity of the B-stage after impregnation, and the B-stage state is difficult. change significantly. Therefore, since the B-stage state is not stable, when the intermediate material of the B-staged FRP is press-molded in a short time, the resin may flow too much or the fluidity is low, resulting in poor appearance of the FRP after molding. produces

In addition, Patent Documents 3 to 5 describe prepregs for high-cycle press molding that are improved in handleability at room temperature, do not lower Tg and curing speed, and suppress resin flow. The resins used in the prepregs described in Patent Documents 3 to 5 are obtained by dissolving a thermoplastic resin in a liquid epoxy resin to increase the resin viscosity. However, due to the high viscosity of the resin, the impregnability of the resin into the reinforcing fiber base material layer decreases during the production of towpreg, SMC, and multi-layered woven fabric prepreg, and voids may occur in the molded FRP.

Patent Literature 6 discloses an epoxy resin composition and a prepreg that can employ a wide range of molding conditions by blending thickening particles. However, in some cases, the impregnation of the reinforcing fiber base material with the epoxy resin composition is not sufficient, and in some cases, the prepreg molding conditions cannot be said to be wide enough.

JP-A-6-166742 WO2017/150521 Japanese Patent Application Laid-Open No. 2009-292976 JP 2009-292977 A JP 2010-248379 A WO2016/159147

When molding FRP using towpreg, SMC, or multi-layered fabric prepreg, the resin composition whose viscosity is lowered by heating is pressurized, causing the resin composition to flow violently inside and on the surface of the prepreg. . As a result, the resin composition flows out from the inside of the prepreg, and the interior and surface of the obtained FRP are not impregnated with the resin composition (withered resin). Moreover, the arrangement of the reinforcing fiber substrate is disturbed due to the flow of the resin composition. As a result, the appearance and physical properties of the obtained FRP deteriorate. Furthermore, when a resin composition having high mechanical properties such as heat resistance and impact resistance is used, the performance of the resulting FRP tends to vary, and the original high mechanical properties cannot be stably obtained.

An object of the present invention is to allow the resin composition to be sufficiently impregnated into the reinforcing fiber base material layer, which has a heavy weight per unit area, to improve the handling of the prepreg at room temperature, and to suppress the resin flow during molding. It is to provide a resin composition that That is, it is an object of the present invention to provide a resin composition capable of suppressing resin flow during molding while maintaining high resin impregnability and prepreg handleability. Another object of the present invention is to provide a resin composition that undergoes little change in viscosity with respect to changes in temperature during resin impregnation or molding. Another object of the present invention is to provide a resin composition from which an FRP having high heat resistance, high impact resistance, and high mechanical properties can be stably produced. Another object of the present invention is to provide a prepreg obtained by impregnating a reinforcing fiber base material layer with these resin compositions, and a method for manufacturing an FRP using the prepreg.

The present inventors have found that an epoxy resin composition that constitutes a prepreg contains an epoxy resin, a curing agent that reacts with the epoxy resin at low temperatures, and a curing agent that reacts with the epoxy resin at high temperatures. The present inventors have found that the above problems can be solved by adding thickening particles that increase the viscosity of the epoxy resin composition to control the viscosity of the epoxy resin composition, and have completed the present invention.

The present invention for solving the above problems is described below.

[1] At least the following [A] component to [D] component [A] component: epoxy resin,
[B] component: epoxy resin curing agent,
[C] component: a first compound that undergoes a curing reaction with the [A] component at a temperature of 40°C or less;
[D] component: a second compound that thickens the [A] component at a temperature of 45 ° C. or higher;
An epoxy resin composition comprising
When the viscosity at 40°C immediately after preparation of the epoxy resin composition is (a), and the viscosity at 40°C after 48 hours at 40°C after preparation is (b),
(a) = 0.05 to 5 Pa s
(b) = 200 to 200,000 Pa·s
An epoxy resin composition characterized by being

The invention described in [1] above comprises component [A], components [B] and [C] that are curing agents thereof, and component [D] that is a compound that increases the viscosity of component [A]. consists of Component [C] undergoes a curing reaction with component [A] at a relatively low temperature to increase the viscosity of the epoxy resin composition. The [D] component increases the viscosity of the epoxy resin composition at a predetermined temperature in the epoxy resin composition. The [B] component reacts with the [A] component at a relatively high temperature and cures to give a cured epoxy resin composition.

[2] The [C] component is an amine and/or an acid anhydride, and the content of the [C] component is such that the active hydrogen and/or acid anhydride equivalent is 0 per the total amount of epoxy groups in the [A] component. .The epoxy resin composition according to [1], wherein the amount is 1 to 0.4 equivalents.

[3] The epoxy resin composition according to [1] or [2], wherein the component [D] is thickening particles.

[4] The epoxy resin composition according to any one of [1] to [3], wherein component [B] is one or more compounds selected from dicyandiamide, urea compounds, and imidazole compounds.

[5] The epoxy resin composition according to any one of [1] to [4], wherein the reaction initiation temperature between the [A] component and the [B] component is 100 to 150°C.

[6] The epoxy resin composition according to any one of [1] to [5], wherein the pot life of component [A] and component [C] at 25°C is 30 to 360 minutes.

[7] Any one of [1] to [5], wherein the component [D] starts to swell at 80 to 110°C when the temperature of the component [A] and the component [D] is increased at 2°C/min. The epoxy resin composition described.

[8] The epoxy resin composition according to any one of [1] to [7], wherein component [C] is an alicyclic diamine and/or aromatic diamine having a viscosity of 10 to 500 mPa·s at 25°C. .

[9] Component [D] is a polymer having one or more polymerized units selected from the group consisting of methacrylic acid ester compounds, acrylic acid ester compounds and vinyl compounds [1] to [8] The epoxy resin composition according to any one of [8].

[10] a reinforcing fiber base material;
the epoxy resin composition according to any one of [1] to [9] impregnated in the reinforcing fiber base;
A prepreg consisting of
A prepreg formed by reacting part of the component [A] with part or all of the component [C].

The invention described in [10] above is obtained by impregnating a reinforcing fiber base material with the epoxy resin composition described in [1] above. The unreacted epoxy resin composition impregnated in the reinforcing fiber base material is in a state of having increased viscosity due to reaction with part of the [A] component and the [C] component thereafter.

[11] The prepreg of [10], wherein the reinforcing fiber base material is a carbon fiber strand and has the form of a tow prepreg.

[12] The prepreg according to [10], wherein the reinforcing fiber base material is a mat formed of short fibers having a fiber length of 5 to 100 mm, and is in the form of a sheet molding compound.

[13] The prepreg of [10], wherein the reinforcing fiber base material is a woven fabric or multi-layered woven fabric, and has the form of a woven fabric prepreg.

[14] A prepreg characterized by impregnating a reinforcing fiber base material with the epoxy resin composition according to any one of [1] to [9], followed by heat treatment at a temperature of 50° C. or less for 8 hours or more. manufacturing method.

[15] A method for producing a fiber-reinforced composite material, comprising heating and pressing the prepreg according to any one of [10] to [13] in a mold at a temperature of 130 to 170° C. and a pressure of 0.2 to 10 MPa for 1 to 20 minutes. .

The epoxy resin composition of the present invention has a low viscosity when the components [A] to [C] are unreacted and the viscosity is not increased by the component [D]. Therefore, it is possible to manufacture a prepreg that has extremely excellent impregnating properties with respect to the reinforcing fiber base material and that has an extremely small amount of unimpregnated portions. By heat-treating the epoxy resin composition impregnated into the reinforcing fiber base material under predetermined conditions, the [A] component and the [C] component react to increase the viscosity.
This epoxy resin composition contains the [D] component. Component [D] increases the viscosity of the epoxy resin composition at a predetermined temperature. Therefore, the epoxy resin composition contained in the prepreg has a temperature range in which the viscosity of the resin rises due to the action of the component [D] when heated during molding, and the change in viscosity with respect to temperature changes is small. By molding in a temperature zone in which the change in viscosity is small, the quality of FRP can be stabilized without precisely controlling the temperature and pressure conditions during molding.
Furthermore, in the prepreg produced using the epoxy resin composition of the present invention, the component [A] reacts with the component [C] and the viscosity increases even before the thickening by the component [D] starts. there is Therefore, it is possible to widen the temperature zone in which the change in viscosity with respect to temperature change is small.

A prepreg produced using the epoxy resin composition of the present invention is less prone to excessive flow of the resin during heat and pressure molding. As a result, appearance defects, performance defects, mold operation defects, etc. of the obtained FRP are suppressed. In addition, it is possible to stably produce a high-performance FRP that reflects the high heat resistance and high impact properties of the epoxy resin composition.

The prepreg of the present invention is particularly suitable for short-time molding. Therefore, the FRP production method of the present invention using the prepreg of the present invention has high productivity.

The epoxy resin composition of the present invention comprises the following [A] component to [D] component [A] component: epoxy resin,
[B] component: epoxy resin curing agent [C] component: a first compound that undergoes a curing reaction with the [A] component at a temperature of 40° C. or less;
[D] component: a second compound that thickens the [A] component at a temperature of 45 ° C. or higher;
comprising
When the viscosity at 40°C immediately after preparation of this epoxy resin composition is (a), and the viscosity at 40°C after 48 hours at 40°C after preparation is (b), the following relationship (a) = 0.05 ~5Pa.s
(b) = 200 to 200,000 Pa·s
equip. Further, in the present invention, it is preferable to satisfy the relationship of (b)/(a)=200 to 200,000.
Unless otherwise specified, the viscosity in this specification refers to the viscosity when the temperature is raised at a rate of 2° C./min.

When the viscosity (a) is 0.05 to 5 Pa·s, the reinforcing fiber base material can be sufficiently impregnated with the epoxy resin composition. The lower limit of viscosity (a) is preferably 0.06 Pa·s or more, more preferably 0.08 Pa·s or more, and even more preferably 0.10 Pa·s or more. If the viscosity (a) is too low, the epoxy resin composition may flow within the prepreg during heat treatment of the prepreg, which will be described later, and the component [D] dispersed within the epoxy resin composition may be unevenly distributed within the prepreg. The upper limit of the viscosity (a) is preferably 4.8 Pa·s or less, more preferably 4.5 Pa·s or less, and even more preferably 4.0 Pa·s or less. If the viscosity (a) is too high, the impregnation of the reinforcing fiber base material tends to deteriorate.

When the viscosity (b) is 200 to 200,000 Pa·s, it is suitable for operations such as cutting and laminating prepregs, and resin flow can be suppressed during press molding of prepregs. The lower limit of viscosity (b) is preferably 250 Pa·s or more, more preferably 400 Pa·s or more, and even more preferably 500 Pa·s or more. If the viscosity (b) is too low, the prepreg becomes sticky, making it difficult to cut and laminate, and the epoxy resin composition tends to flow out of the prepreg during press molding of the prepreg, which will be described later. The upper limit of viscosity (b) is preferably 180,000 Pa·s or less, more preferably 150,000 Pa·s or less, and even more preferably 120,000 Pa·s or less. If the viscosity (b) is too high, press molding may become difficult.

The above viscosities (a) and (b) have the following relationship (b) / (a) = 200 to 100,000
is preferably provided. The lower limit of (b)/(a) is more preferably 220 or more, even more preferably 250 or more. The upper limit of (b)/(a) is more preferably 80,000 or less, even more preferably 70,000 or less.

(1-1) Component [A] As the component [A], an epoxy resin is used, and an epoxy resin that is liquid at 25°C is more preferable. Epoxy resins include bifunctional epoxy resins such as bisphenol type epoxy resins, alcohol type epoxy resins, biphenyl type epoxy resins, hydrophthalic acid type epoxy resins, dimer acid type epoxy resins, and alicyclic type epoxy resins; tetrakis(glycidyloxyphenyl) glycidyl ether-type epoxy resins such as ethane and tris(glycidyloxyphenyl)methane; glycidylamine-type epoxy resins such as tetraglycidyldiaminodiphenylmethane; naphthalene-type epoxy resins; phenol novolac-type epoxy resins, which are novolak-type epoxy resins; type epoxy resin and the like.

Further examples include polyfunctional epoxy resins such as phenol type epoxy resins. Various modified epoxy resins such as urethane-modified epoxy resins and rubber-modified epoxy resins can also be used.

In particular, an epoxy resin having an aromatic group in the molecule is preferred, and an epoxy resin having either a glycidylamine structure or a glycidyl ether structure is more preferred. Alicyclic epoxy resins can also be suitably used.

Examples of epoxy resins having a glycidylamine structure include N,N,N',N'-tetraglycidyldiaminodiphenylmethane, N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-m- Various isomers of aminophenol, N,N,O-triglycidyl-3-methyl-4-aminophenol and triglycidylaminocresol are exemplified.

Examples of epoxy resins having a glycidyl ether structure include bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, and phenol novolak-type epoxy resins.

These epoxy resins may optionally have a non-reactive substituent on the aromatic ring structure or the like. Examples of non-reactive substituents include alkyl groups such as methyl, ethyl and isopropyl; aromatic groups such as phenyl; alkoxyl groups; aralkyl groups; and halogen groups such as chlorine and bromine.

Bisphenol type epoxy resins include bisphenol A type resin, bisphenol F type resin, bisphenol AD type resin, bisphenol S type resin and the like. Specifically, jER815, jER828, jER834 and jER807 (trade names) manufactured by Mitsubishi Chemical Corporation are exemplified.

Examples of alicyclic epoxy resins include Araldite CY-179, CY-178, CY-182 and CY-183 (trade names) manufactured by Huntsman.

Examples of phenolic novolac epoxy resins include jER152 and jER154 (trade names) manufactured by Mitsubishi Chemical Corporation; DEN431, DEN485 and DEN438 (trade names) manufactured by Dow Chemical Company.

Examples of epoxy resins having a glycidylamine structure include Sumiepoxy ELM434, Sumiepoxy ELM120, and Sumiepoxy ELM100 (trade names) manufactured by Sumitomo Chemical Co., Ltd.; Araldite MY9634, Araldite MY9663 (trade name); jER604, jER630 (trade name) manufactured by Mitsubishi Chemical Corporation; Bakelite EPR494, Bakelite EPR495, Bakelite EPR496, Bakelite EPR497 (trade name) manufactured by Bakelite AG; Araldite MY0500, Araldite MY0510, Araldite MY0600 (trade name) manufactured by Material Co., Ltd., and the like can be mentioned.

Examples of various modified epoxy resins include Adeka Resin EPU-6 and EPU-4 (trade names) manufactured by Asahi Denka Co., Ltd. as urethane-modified bisphenol A epoxy resins.

These epoxy resins can be appropriately selected and used singly or in combination of two or more.

In order to increase the heat resistance of the resin, it is preferable to use an epoxy resin having a glycidylamine structure. The amount of the epoxy resin having a glycidylamine structure is preferably 25 to 85 parts by mass, more preferably 30 to 80 parts by mass, per 100 parts by mass of component [A]. If the amount of the epoxy resin having a glycidylamine structure is less than 25 parts by mass, sufficient heat resistance may not be obtained. If it exceeds 85 parts by mass, the heat resistance is sufficient, but the resin becomes brittle, and an FRP with sufficient impact resistance cannot be obtained.
Moreover, from the viewpoint of not lowering the heat resistance of the resin, it is preferable not to use an aliphatic epoxy resin that mainly acts as a reactive diluent. Aliphatic epoxy resins have a low viscosity at 25° C. and are used to promote impregnation into reinforcing fiber base materials, but have the problem of reducing the heat resistance of cured resins. Therefore, the [A] component is preferably an epoxy resin that does not contain an aliphatic epoxy resin.

(1-2) Component [B] Component [B] is an epoxy resin curing agent. The epoxy resin curing agent may generally have any structure as long as it can cure the epoxy resin. Examples thereof include amines, acid anhydrides (carboxylic acid anhydrides), phenols (novolac resins, etc.), mercaptans, Lewis acid amine complexes, onium salts, imidazoles and the like.
Among these, one or more compounds selected from dicyandiamide, urea compounds, and imidazole compounds are preferably used as the epoxy resin curing agent used in the present invention. Dicyandiamide (DICY), which is an amide-based curing agent, and imidazole compounds are preferred from the viewpoint of excellent curability and physical properties after curing.

Specific examples of dicyandiamide (DICY) include jER Cure DICY7 and DICY15 (trade name) manufactured by Mitsubishi Chemical Corporation.

Moreover, when using DICY, it is more preferable to use together with a urea compound. Since DICY does not have a high solubility in epoxy resin, it needs to be heated to a high temperature of 160° C. or higher in order to dissolve it sufficiently. However, the dissolution temperature can be lowered by using it together with a urea compound.
Urea compounds include, for example, phenyldimethylurea (PDMU) and toluenebisdimethylurea (TBDMU).

The amount of component [B] in the epoxy resin composition is preferably 6 to 15 parts by mass per 100 parts by mass of component [A]. When the amount of component [B] is 6 parts by mass or more, the crosslink density is sufficient and a sufficient curing speed is obtained. When the amount of the component [B] is 15 parts by mass or less, it is possible to suppress problems such as deterioration of the mechanical properties of the cured resin and turbidity of the cured resin due to excessive presence of the [B] component.

The reaction initiation temperature between the [A] component and the [B] component is preferably 100 to 150°C, more preferably 100 to 130°C.

When DICY and a urea compound (PDMU, TBDMU, etc.) are used together as component [B], the blending amount thereof is 3 to 7 parts by mass of DICY and 3 parts by mass of urea compound per 100 parts by mass of component [A]. It is preferably to 8 parts by mass (provided that the total amount of DICY and the urea compound is 6 to 15 parts by mass).

Examples of imidazole compounds include imidazole compounds in which the 5-position hydrogen of 1H-imidazole is replaced with a hydroxymethyl group and the 2-position hydrogen is replaced with a phenyl group or a toluyl group. Examples of such imidazole compounds include 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4-benzyl-5-hydroxymethylimidazole, 2- para-toluyl-4-methyl-5-hydroxymethylimidazole, 2-meth-toluyl-4-methyl-5-hydroxymethylimidazole, 2-meth-toluyl-4,5-dihydroxymethylimidazole, 2-para-toluyl-4,5-dihydroxymethylimidazole exemplified. Among them, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-paratoluyl-4-methyl-5-hydroxymethylimidazole, 2-methatoyl-4-methyl -5-Hydroxymethylimidazole, 2-methatolyl-4,5-dihydroxymethylimidazole, and 2-paratoluyl-4,5-dihydroxymethylimidazole are more preferred.

Further, examples of imidazole compounds include 1-(2-hydroxy-3-phenoxypropyl)-2-methylimidazole and an adduct compound obtained by reacting a glycidyl ether type thermosetting resin with 2-methylimidazole. is mentioned. In particular, an adduct compound obtained by reacting an aryl glycidyl ether type thermosetting resin with 2-methylimidazole is preferable because it can provide excellent physical properties of a cured product of the epoxy resin composition. When an imidazole compound is used as component [B], the amount of imidazole compound is preferably 2 to 20 parts by mass, more preferably 3 to 15 parts by mass, per 100 parts by mass of component [A].

(1-3) Component [C] Component [C] is not particularly limited as long as it is a compound that undergoes a curing reaction with component [A] at a temperature of 40° C. or lower. In the present invention, the [C] component is preferably an amine and/or an acid anhydride, and is preferably a compound that is liquid at 25°C. Examples of amines include various isomers of aliphatic amines, alicyclic amines, and aromatic amine curing agents.

Specific examples of aliphatic amines include alkylenediamines having 2 to 6 carbon atoms (ethylenediamine, propylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, etc.), polyalkylenes (2 to 6 carbon atoms) polyamines (diethylenetriamine , iminobispropylamine, bis(hexamethylene)triamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, etc.), alkyl- or hydroxyalkyl-substituted products thereof (dialkylaminopropylamine, trimethylhexamethylenediamine, aminoethylethanol amines, methyliminobispropylamine, etc.), alicyclic- or heterocyclic-containing aliphatic polyamines such as 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro [5, 5] Undecane and the like, such as xylylenediamine and tetrachloro-p-xylylenediamine.
Alicyclic amines include, for example, 1,3-diaminocyclohexane, isophoronediamine, menzenediamine, 4,4′-methylenedicyclohexanediamine (hydrogenated methylenedianiline), bis(4-amino-3-methyldicyclohexyl) methane and the like.
Examples of aromatic amines include diaminodiphenylmethane, m-phenylenediamine, diaminodiphenylsulfone, diethyltoluenediamine, trimethylenebis(4-aminobenzoate), polytetramethyleneoxide-di-p-aminobenzoate and the like.
Heterocyclic amines include, for example, piperazine, 1-aminoethylpiperazine, 1,4-diaminoethylpiperazine, 3-aminopyrrolidine, 2-(2-aminoethyl)pyrrolidine, 4,4'-bipiperazine, 4,4' -ethylenedipiperidine, 4,4′-trimethylenedipiperidine, 4-(aminomethyl)piperidine, 3-(4-aminobutyl)piperidine and the like.
Examples of acid anhydride curing agents include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, Methylhexahydrophthalic anhydride and the like can be mentioned.

As component [C], it is preferable to use an alicyclic diamine and/or aromatic diamine having a viscosity of 10 to 500 mPa·s at 25° C., more preferably 20 to 400 mPa·s. By using the [C] component with such a viscosity, it is possible to enhance the impregnation into the reinforcing fiber base material.

When an amine and/or an acid anhydride is used as the [C] component, the amount of the [C] component contained in the epoxy resin composition is the total amount of epoxy groups of the [A] component blended in the epoxy resin composition. The active hydrogen or acid anhydride equivalent is preferably 0.1 to 0.4 equivalent per unit. The amount of component [C] is more preferably 0.15 to 0.35 equivalents, more preferably 0.2 to 0.35 equivalents. By blending the [C] component in an amount within this range, the epoxy resin composition can be appropriately thickened. If the amount is less than 0.1 equivalent, the epoxy resin composition will not be sufficiently thickened in the prepreg, and the viscosity will decrease significantly before the component [D] described below starts to swell during press molding, resulting in resin flow. or the [D] component may be unevenly distributed in the prepreg. If it exceeds 0.4 equivalents, the curing reaction with the component [A] may proceed too much, making press molding difficult.

The pot life of the components [A] and [C] at 25° C. is preferably 30 to 360 minutes, more preferably 60 to 300 minutes. The usable time of the [A] component and the [C] component is the time when the [A] component and the [C] component are mixed, 100 g is left at 25 ° C., and the resin viscosity reaches twice the initial value. It's time.
If the usable time at 25° C. is less than 30 minutes, the curing reaction may be too rapid, the viscosity of the resin may increase, and impregnation of the reinforcing fiber base material with the resin may be insufficient. If the pot life at 25° C. exceeds 360 minutes, the viscosity of the epoxy resin composition in the prepreg is not sufficiently increased, so that the viscosity significantly increases before the component [D] described below starts to swell during press molding. It may decrease to cause resin flow, or the [D] component may be unevenly distributed in the prepreg.

(1-4) [D] Component As the [D] component, a compound that increases the viscosity of the [A] component at a temperature of 45° C. or higher is used. Thickening particles are preferably used as such a compound. In the present invention, the thickening particles are particles that increase the viscosity without a curing reaction with the [A] component, and a mixture of the [A] component and the thickening particles is heated to a temperature range of 45 ° C. or higher. By doing so, it means a particle that swells and thickens the mixture. That is, the epoxy resin curing agent and the thermoplastic resin described later are not the thickening particles of the present invention. The thickening particles are preferably particles that thicken the mixture in an amount of 3 to 20 parts by mass per 100 parts by mass of component [A]. Examples of thickening particles include particles obtained by copolymerizing single or multiple unsaturated compounds and a crosslinkable monomer. Although not particularly limited, it is desirable to include a resin having at least one monomer unit of an acrylic acid ester compound, a methacrylic acid ester compound, and a vinyl compound.

The acrylic acid ester compound used for the thickening particles refers to compounds having an acrylic acid ester structure and derivatives thereof, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate.

The methacrylic acid ester compound used for the thickening particles refers to compounds having a methacrylic acid ester structure and derivatives thereof, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, and n-hexyl methacrylate. , cyclohexyl methacrylate.

The vinyl compound used for thickening particles refers to a compound having a polymerizable vinyl structure. Substituted compounds are included.

Further, the thickening particles may be a polymer composed of polymerized units of one or more of methacrylic acid ester compounds, acrylic acid ester compounds, and vinyl compounds, and two or more resins having different structures. It may be a resin mixed with moreover,
(i) a polymer comprising at least one of an acrylic acid ester compound, a methacrylic acid ester compound, and a diene compound;
(ii) a polymer comprising an acrylic acid ester compound or a methacrylic acid ester compound and a radically polymerizable unsaturated carboxylic acid;
(iii) It may be a composite resin ionically crosslinked by adding metal ions.

The thickening particles are preferably polymers composed of one or more polymer units selected from the group consisting of methacrylic acid ester compounds, acrylic acid ester compounds and vinyl compounds, and alkyl methacrylate polymers are preferred. more preferred.

The thickening particles preferably have an average degree of polymerization of 4,000 to 40,000.

As the thickening particles, it is also preferable to use commercially available products made of alkyl methacrylate polymers such as Zephiac F325 and Zefiac F320 (both of which are available from Aica Kogyo Co., Ltd.).

The particle size of the thickening particles is not particularly limited, but the average particle size is preferably 0.3 to 10 μm, more preferably 0.5 to 8 μm. The content of component [D] is preferably 3 to 20 parts by mass, more preferably 4 to 18 parts by mass, and 5 to 15 parts by mass relative to 100 parts by mass of component [A]. is particularly preferred.

The [D] component dispersed in the [A] component swells in the epoxy resin composition upon heating. The swelling of the [D] component progresses with temperature and time, and the viscosity of the epoxy resin composition rises rapidly as the [D] component swells.
Specifically, when the epoxy resin composition is heated at a rate of 2°C/min, the component [D] preferably begins to swell at 80 to 110°C, and more preferably at 85 to 105°C. .

Since the epoxy resin composition has a low viscosity before the [D] component swells, it is excellent in impregnation into the reinforcing fiber base material layer. When the [D] component swells and the viscosity of the epoxy resin composition increases in the reinforcing fiber base material layer, resin flow during molding is suppressed. As a result, both resin impregnability and suppression of resin flow can be achieved at a high level.

(1-5) Thermoplastic resin The epoxy resin composition of the present invention may contain a thermoplastic resin in addition to the above components [A] to [D]. Thermoplastic resins include polysulfone, polyetherimide, polyphenylene ether, polyamide, polyacrylate, polyaramid, polyester, polycarbonate, polyphenylene sulfide, polybenzimidazole, polyimide, polyethersulfonepolyketone, polyetherketone, polyetheretherketone, polyvinyl A group of thermoplastic resins belonging to engineering plastics such as formal are more preferably used. Polyimides, polyetherimides, polysulfones, polyethersulfones, polyvinyl formals, and the like are particularly preferably used because of their excellent heat resistance, toughness, and handleability.

The thermoplastic resin may be mixed in any form. For example, a powdery thermoplastic resin may be kneaded and dispersed in the epoxy resin using a kneader or the like, or the thermoplastic resin may be dissolved in the epoxy resin by heating the epoxy resin. Also good. The epoxy resin composition of the present invention is preferably used by dissolving part of the thermoplastic resin in the epoxy resin and dispersing the remainder of the thermoplastic resin in the epoxy resin.

The particle size of the powdery thermoplastic resin is preferably 0.2 to 100 μm, more preferably 0.5 to 80 μm.

The blending amount of the thermoplastic resin is preferably 5 to 30 parts by mass, more preferably 5 to 20 parts by mass, based on 100 parts by mass of the epoxy resin.

(1-6) Other Additives The epoxy resin composition of the present invention may contain flame retardants, inorganic fillers and internal release agents.

Examples of flame retardants include phosphorus-based flame retardants. The phosphorus-based flame retardant is not particularly limited as long as it contains a phosphorus atom in the molecule. is mentioned. Organic phosphinic acid metal salts are particularly preferably used from the viewpoint of heat resistance.

Since the organic phosphinate metal salt has a high phosphorus content, it exhibits good flame retardancy. Moreover, since the decomposition temperature is high, the bleed-out phenomenon caused by pressure and heat during processing is less likely to occur. In addition, since it is a flame retardant that is insoluble in epoxy resin, the epoxy resin composition containing it contains a solid flame retardant or a liquid flame retardant that has a softening point or melting point of 150 ° C. or less, which is usually used. Compared with the epoxy resin composition, for example, the resin flow is reduced during press molding.
Examples of organic phosphinate metal salts include aluminum trisdiethylphosphinate, aluminum trismethylethylphosphinate, aluminum trisdiphenylphosphinate, zinc bisdiethylphosphinate, zinc bismethylethylphosphinate, zinc bisdiphenylphosphinate, and bisdiethylphosphine. titanyl acid, titanyl bismethylethylphosphinate, titanyl bisdiphenylphosphinate and the like. Among these, aluminum trisdiethylphosphinate and aluminum trismethylethylphosphinate are preferable in terms of obtaining an epoxy resin composition having high flame retardancy and moisture resistance.
These may be used individually by 1 type, and may be used in combination of 2 or more type.
Examples of commercially available organic phosphinate metal salts and complexes thereof include Exolit OP930, OP935, and OP1230 (manufactured by Clariant Japan KK), but are not limited thereto.
The average particle size of the organic phosphinate metal salt is preferably 50 µm or less, more preferably 20 µm or less, and even more preferably 10 µm or less. When the average particle size is 50 µm or less, sufficient flame retardancy is more easily exhibited.

Examples of inorganic fillers include aluminum borate, calcium carbonate, silicon carbonate, silicon nitride, potassium titanate, basic magnesium sulfate, zinc oxide, graphite, calcium sulfate, magnesium borate, magnesium oxide, and silicate minerals. is mentioned. In particular, it is preferable to use silicate minerals. Commercially available silicate minerals include THIXOTROPIC AGENT DT 5039 (manufactured by Huntsman Japan KK).

Examples of internal release agents include metal soaps, vegetable waxes such as polyethylene wax and carnauba wax, fatty acid ester release agents, silicone oils, animal waxes, and fluorine-based nonionic surfactants. The content of these internal release agents is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 2 parts by mass, per 100 parts by mass of the epoxy resin. Within this range, the release effect from the mold is favorably exhibited.

Commercially available internal release agents include "MOLD WIZ (registered trademark)" INT1846 (manufactured by AXEL PLASTICS RESEARCH LABORATORIES INC.), Licowax S, Licowax P, Licowax OP, Licowax PE190, Licowax PED (manufactured by Clariant Japan), Stearyl stearate (SL-900A; manufactured by Riken Vitamin Co., Ltd.).

(1-7) Method for Producing Epoxy Resin Composition The epoxy resin composition can be produced by mixing components [A] to [D]. The method for producing the epoxy resin composition is not particularly limited, and any conventionally known method may be used. For example, each component may be mixed at the same time to prepare a masterbatch in which the [A] component, the [B] component, and the [D] component are each appropriately dispersed in advance. good too. From the viewpoint of impregnation into the reinforcing fiber base material layer, a masterbatch in which the [A] component, [B] component, and [D] component are dispersed in advance is prepared, and 25% before impregnation into the reinforcing fiber base material. It is preferable to mix the [C] component at °C. After mixing the masterbatch resin and the [C] component, impregnation into the reinforcing fiber substrate is preferably performed within 180 minutes, more preferably within 120 minutes.

A conventionally known machine can be used as the mixing machine. Specific examples include roll mills, planetary mixers, kneaders, extruders, Banbury mixers, mixing vessels equipped with stirring blades, and horizontal mixing tanks. Mixing of each component can be performed in air or under an inert gas atmosphere. When mixing is performed in air, an atmosphere in which temperature and humidity are controlled is preferable. Although not particularly limited, for example, it is preferable to mix at a temperature controlled at a constant temperature of 30° C. or less or in a low-humidity atmosphere with a relative humidity of 50% RH or less.

(2) Prepreg The prepreg of the present invention comprises a reinforcing fiber base material and an epoxy resin composition. The epoxy resin composition is partially or wholly impregnated into the reinforcing fiber base material layer and integrated with the reinforcing fiber base material.

The shape of the prepreg of the present invention may be a towpreg in which the reinforcing fibers are formed in a strand shape, or may be an SMC in which the reinforcing fibers are short fibers having a fiber length of 5 to 100 mm. It may be a woven fabric prepreg formed of a woven fabric or multi-ply fabric.
Tow prepreg is obtained by impregnating a reinforcing fiber bundle in which several thousand to tens of thousands of reinforcing fiber filaments are arranged in one direction with a matrix resin composition and then winding it around a bobbin such as a paper tube. It is a narrow intermediate base material that can be In the present invention, a material wound around a bobbin in this way or a material unwound after being wound is called a "tow prepreg".

Since the prepreg of the present invention uses a resin composition that inherently has a low viscosity, it is easy to impregnate the reinforcing fiber base layer with the resin. After impregnating the reinforcing fiber base material with the epoxy resin, the reinforcing fiber base material is heated at 50° C. or lower for 8 hours or longer. Thereby, the [A] component and the [C] component are reacted to increase the viscosity of the epoxy resin composition. Furthermore, during heat molding, the viscosity of the epoxy resin composition is increased in a predetermined temperature range using thickening particles. Therefore, the epoxy resin composition has a temperature zone in which the change in viscosity becomes gentle, and by molding in this temperature zone, resin flow from the prepreg can be suppressed. As a result, the FRP produced using the prepreg of the present invention is less likely to have molding defects such as resin withering.

The content (RC) of the epoxy resin composition is preferably 25 to 70% by mass, more preferably 30 to 70% by mass, and 35 to 65% by mass, based on the total mass of the prepreg. is particularly preferred. If the content is less than 25% by mass, voids and the like may occur in the obtained FRP, degrading mechanical properties and the like. If the content exceeds 70% by mass, the reinforcing effect of the reinforcing fibers may be insufficient, and the mechanical properties of the obtained FRP may be deteriorated.

The content rate (RC) of the epoxy resin composition is determined by immersing the prepreg in sulfuric acid to elute the resin composition impregnated in the prepreg. Specifically, it is obtained by the following method.

First, a prepreg is cut into a size of 100 mm×100 mm to prepare a test piece, and its mass is measured. Next, the prepreg test piece is immersed in sulfuric acid and boiled if necessary. As a result, the resin composition impregnated in the prepreg is decomposed and eluted into the sulfuric acid. Thereafter, the remaining fibers are separated by filtration, washed with sulfuric acid, dried, and the mass of the fibers is measured. The content of the resin composition is calculated from the change in mass before and after the decomposition operation with sulfuric acid.

(2-1) Reinforcing fiber base material Reinforcing fiber base materials include carbon fiber, glass fiber, aramid fiber, silicon carbide fiber, polyester fiber, ceramic fiber, alumina fiber, boron fiber, metal fiber, mineral fiber, rock fiber and A substrate made of slag fibers is exemplified. Among these reinforcing fibers, carbon fibers, glass fibers, and aramid fibers are preferred. Carbon fiber is more preferable because it has good specific strength and specific elastic modulus, and provides a lightweight and high-strength FRP. Polyacrylonitrile (PAN)-based carbon fibers are particularly preferred because of their excellent tensile strength.

When PAN-based carbon fiber is used as the reinforcing fiber, its tensile modulus is preferably 100 to 600 GPa, more preferably 200 to 500 GPa, and particularly preferably 230 to 450 GPa. Also, the tensile strength is 2000 to 10000 MPa, preferably 3000 to 8000 MPa. The diameter of the carbon fiber is preferably 4-20 μm, more preferably 5-10 μm. By using such carbon fibers, the mechanical properties of the resulting FRP can be improved.

Examples of reinforcing fiber substrates include plain weaves, twill weaves, and satin weaves using reinforcing fiber bundles as warp and/or weft yarns, and unidirectional and bidirectional weaves composed of a set of reinforcing fiber bundles aligned in parallel. , multiaxial fabrics, and the like. Alternatively, it may be a non-woven fabric made of reinforcing fibers, a knit, a braid, a mat made of short fibers with a fiber length of 5 to 100 mm, or the like. Multiaxial woven fabric is a sheet of fiber reinforcement bundles aligned in one direction, laminated at different angles, and stitched with nylon yarn, polyester yarn, glass fiber yarn, etc. It is a woven fabric in which stitches are stitched back and forth along the surface direction between the front and back surfaces of the laminate, penetrating in the direction. Examples of preferred multiaxial fabrics include [+45/-45], [-45/+45], [0/90], [0/+45/-45], [0/-45/+45], [0/ +45/90/−45] and the like. 0, ±45, and 90 represent the lamination angle of each layer constituting the multiaxial fabric, and the fiber axis direction of the reinforcing fibers aligned in one direction is 0° and ±45° with respect to the length direction of the fabric. , 90°. The lamination angle is not limited to these angles and can be any angle.
It is preferable that the amount of reinforcing fibers per unit area is 300 to 1500 g/m ² . If the amount of reinforcing fibers in the prepreg is less than 300 g/m ² , it is necessary to increase the number of laminations in order to obtain a predetermined thickness when molding the prepreg for use as a fiber-reinforced composite material, which may complicate the work. If it exceeds 1500 g/m ² , the drapeability of the prepreg tends to deteriorate.

The fiber length of the mat formed of short fibers is preferably 5 to 50 mm, more preferably 10 to 50 mm. The amount of reinforcing fibers per unit area is preferably 300-1500 g/m ² , more preferably 300-1200 g/m ² . A mat formed of short fibers is used as an SMC (sheet molding compound) impregnated with a matrix resin composition.

(2-2) Method for producing prepreg The method for producing a prepreg of the present invention can be produced by impregnating a reinforcing fiber base material with an epoxy resin composition by a hot-melt method and then performing a predetermined heat treatment. can.

In the hot-melt method, a resin composition is applied in the form of a thin film on release paper to form a resin composition film, and the resin composition film is laminated on a reinforcing fiber substrate and heated under pressure. is a method of impregnating the reinforcing fiber base material layer with the resin composition.

A method for forming a resin composition film from a resin composition is not particularly limited, and any conventionally known method can be used. Specifically, using a die extrusion, an applicator, a reverse roll coater, a comma coater, etc., a resin composition film is obtained by casting the resin composition onto a support such as a release paper or a film. can be done. The resin temperature when producing the film is appropriately determined according to the composition and viscosity of the resin composition. Specifically, the same temperature conditions as the mixing temperature in the method for producing the epoxy resin composition described above are preferably used. The impregnation of the reinforcing fiber base material layer with the resin composition may be performed once or may be performed in multiple steps.

<Method for producing tow prepreg>
The tow prepreg of the present invention can be produced by preparing the epoxy resin composition, impregnating a reinforcing fiber bundle with the epoxy resin composition, and further winding it around a bobbin such as a paper tube. The reinforcing fiber bundle to be impregnated with the epoxy resin composition preferably has a widened and flattened shape because it has a large contact area with the resin composition.
Examples of methods for widening the reinforcing fiber bundle include rubbing with a cylindrical bar; applying vibration; and crushing.

<Method for manufacturing SMC>
The SMC of the present invention is produced by manufacturing a pair of films uniformly coated with the epoxy resin composition described above, randomly scattering reinforcing fiber bundles on the surface of one film coated with the resin composition, and coating the other film with the resin composition. Bonded to a surface, pressed and impregnated in a sheet form, and then thickened at room temperature or under heat due to the curing reaction of the [A] component and [C] component contained in the epoxy resin composition. can do.

When the epoxy resin composition film is impregnated into the reinforcing fiber substrate layer by hot melt method, the impregnation temperature is preferably in the range of 30 to 120°C. If the impregnation temperature is lower than 30° C., the epoxy resin has a high viscosity and may not be sufficiently impregnated into the reinforcing fiber base material layer. When the impregnation temperature exceeds 120° C., the curing reaction of the epoxy resin composition proceeds, and the resulting prepreg may have reduced storage stability and drape properties. The impregnation temperature is more preferably 40 to 100°C.
The impregnation pressure when the epoxy resin composition film is impregnated into the reinforcing fiber base material layer by the hot-melt method is appropriately determined in consideration of the viscosity and resin flow of the resin composition.

The prepreg of the present invention can be obtained by impregnating the reinforcing fiber base material with the epoxy resin composition, followed by heat treatment at a temperature of 50° C. or lower for 8 hours or longer. This heating is carried out to increase the viscosity of the epoxy resin composition by reacting the [A] component and the [C] component. The heating temperature is preferably 20 to 50°C, more preferably 25 to 45°C, even more preferably 25 to 40°C. The heating time is preferably 8 to 100 hours, preferably 12 to 80 hours, more preferably 24 to 72 hours.

(3) Fiber reinforced composite material (FRP)
An FRP can be obtained by curing the prepreg of the present invention by heating and pressurizing it under specific conditions. Examples of methods for producing FRP using the prepreg of the present invention include autoclave molding, press molding, internal pressure molding and vacuum-assisted air pressure molding.

As the method for producing the FRP of the present invention, a press molding method is preferable from the viewpoint of obtaining high-quality FRP with high productivity by taking advantage of the characteristics of the epoxy resin composition that constitutes the prepreg. The FRP is manufactured by the press molding method by heating and pressurizing the prepreg of the present invention or a preform formed by laminating the prepregs of the present invention using a mold. The mold is preferably preheated to the curing temperature.

The temperature of the mold during press molding is appropriately determined depending on the type of epoxy resin and curing agent used, and is not particularly limited, but is preferably 130 to 170°C. If the molding temperature is 130° C. or higher, a sufficient curing reaction can occur, and FRP can be obtained with high productivity. Moreover, if the molding temperature is 170° C. or lower, the resin viscosity does not become too low, and excessive flow of the resin in the mold can be suppressed. As a result, the outflow of the resin from the mold and meandering of the fibers can be suppressed, so that a high-quality FRP can be obtained.

The pressure during molding is 0.2-10 MPa. When the pressure is 0.2 MPa or more, the resin can be appropriately flowed, and appearance defects and voids can be prevented. In addition, since the prepreg is sufficiently adhered to the mold, FRP with a good appearance can be manufactured. If the pressure is 10 MPa or less, the resin is not caused to flow more than necessary, so that the resulting FRP is less likely to have poor appearance. In addition, since no excessive load is applied to the mold, deformation of the mold is less likely to occur.

The heating and pressurizing time during molding (time for molding at the above temperature and pressure) is not particularly limited, but is preferably 1 to 20 minutes, more preferably 2 to 18 minutes.

According to the manufacturing method of the present invention described above, it is possible to suppress defects in the mold during molding. In addition, it is possible to obtain high-quality FRP with reduced appearance defects, performance defects, etc., with high productivity.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the examples. Components and test methods used in the present examples and comparative examples are described below.

(Carbon fiber)
“Tenax (registered trademark)” STS40-24K: (tensile strength 4.2 GPa, tensile modulus 240 GPa, manufactured by Toho Tenax Co., Ltd.)

[A] Component “jER (registered trademark)” 807: (liquid bisphenyl A-type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
"jER (registered trademark)" 828: (liquid bisphenyl A type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
"jER (registered trademark)" 630: (p-aminophenol type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
“YH-404: (tetraglycidyldiaminodiphenylmethane type epoxy resin, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.)

[B] Component Dicy 7: (dicyandiamide, manufactured by Mitsubishi Chemical Corporation)
"Omicure (registered trademark)" 24: (2,4'-toluenebis (3,3-dimethylurea), manufactured by PIT Japan Co., Ltd.)
DCMU-99: (3,4-dichlorophenyl-1,1-dimethylurea, manufactured by Hodogaya Chemical Industry Co., Ltd.)
2P4MHZ-PW: (2-phenyl-4-methyl-5-hydroxymethylimidazole, manufactured by Shikoku Chemical Industry Co., Ltd.)

[C] Component “IPDA: (Isophoronediamine, manufactured by PII Japan Co., Ltd.)
“PACM: (Bis-para-aminocyclohexylmethane, manufactured by PII Japan Co., Ltd.)
“Etacure 100: (diethyltoluenediamine, manufactured by PTI Japan Co., Ltd.)
"1.3 BAC: (1,3-bis (aminomethyl) cyclohexane, manufactured by PII Japan Co., Ltd.)
"MHAC-P": (methyl-3,6 endomethylene-1,2,3,6-tetrahydrophthalic anhydride, manufactured by Hitachi Chemical Co., Ltd.)

Amines other than [C] component 4,4'-DDS: 4,4'-diaminodiphenylsulfone (aromatic amine curing agent manufactured by Wakayama Seika Co., Ltd.)

[D] Component “Zefiac (registered trademark)” F320: (Alkyl methacrylate polymer), average degree of polymerization 30,000, manufactured by Aica Kogyo Co., Ltd.)
“Zefiac (registered trademark)” F325: (Alkyl methacrylate polymer), average degree of polymerization 4,000, manufactured by Aica Kogyo Co., Ltd.)

(Thermoplastic resin)
"Ultrason (registered trademark)" E2020P: (Polyethersulfone, manufactured by BASF, weight average molecular weight 32,000, pulverized to an average particle size of 10 μm by laser diffraction method).

(Flame retardants)
"EXOLIT (registered trademark) OP930": (dialkylphosphinic acid aluminum salt, manufactured by Clariant Co., Ltd.)

(Examples 1 to 10, Comparative Examples 1 to 4)
(1) Preparation of Epoxy Resin Composition Epoxy resin groups [A], [B] components, [D] components, etc. were weighed in proportions shown in Table 1 and kneaded with a triple roll. This mixed resin was mixed with the [C] component in the ratio shown in Table 1 to obtain an epoxy resin mixture.

(2) Measurement of Gelation Time of Epoxy Resin Composition 3 g of epoxy resin composition was prepared as a sample, and cured at 40° C. for 48 hours. ) was used to measure the gelling time at a temperature of 150°C.

(3) Fabrication of Prepreg (3-1) Fabrication of Tow Preg Carbon fiber "STS40-24K" with 24,000 filaments was used as a reinforcing fiber bundle to fabricate a tow prepreg.
A specific preparation method is shown below. A reinforcing fiber bundle was sent out from a creel, passed through a fiber opening bar, and widened to a width of 10 to 15 mm. The widened reinforcing fiber bundle was brought into contact with a touch roll coated with an epoxy resin composition heated to about 40° C. to adhere the epoxy resin composition to the reinforcing fiber bundle. The reinforcing fiber bundle to which the epoxy resin composition is adhered is passed through an impregnating roll heated to about 80° C. to impregnate the reinforcing fiber bundle with the epoxy resin composition, and then wound around a paper tube with a winder. I took After that, heat treatment was performed at 40° C. for 48 hours to produce a tow prepreg.
The amount of resin adhered to the reinforcing fiber bundle was adjusted by adjusting the clearance between the doctor blade and the touch roll, and the carbon fiber content of the towpreg was 65% by mass. The towpreg width was about 8.5 mm.

(3-2) Production of SMC SMC was produced as follows. The epoxy resin composition obtained above was uniformly coated on one side of a polyethylene film so as to have a basis weight of 600 g/m ² to prepare a first resin sheet. Next, carbon fibers “STS40-24K” were cut into lengths of about 25 mm on the surface of the first resin sheet, and deposited two-dimensionally randomly so that the basis weight of the fibers was 1200 g/m ² . A sheet of reinforcing fiber bundles was prepared. Furthermore, on one side of a polyethylene film that serves as a second support, a resin having the same basis weight as that of the first resin sheet is applied to prepare a second resin sheet. A second resin sheet was attached. This was heated and pressurized at a temperature of 80° C. and a pressure of 0.5 MPa to obtain an SMC precursor. After that, this SMC precursor was heat-treated at 40° C. for 48 hours to prepare SMC. The carbon fiber content of this SMC was 50% by mass.

(3-3) Production of multiaxial woven fabric prepreg A multiaxial woven fabric prepreg was produced as follows. Using a reverse roll coater, the epoxy resin composition obtained above was applied onto release paper to prepare a resin film having a basis weight of 150 g/m ² . Next, using a carbon fiber multiaxial fabric (two layers laminated and stitched at an angle of 0/90, total basis weight of fabric base material 500 g/m ² ) made of carbon fiber “STS40-24K”, this carbon fiber The above resin films were stacked on both sides of the multiaxial woven fabric, and heated and pressed under conditions of a temperature of 80° C. and a pressure of 0.2 MPa. After that, the multiaxial fabric prepreg was heat-treated at 40° C. for 48 hours to produce a multiaxial fabric prepreg. The carbon fiber content of this multiaxial fabric prepreg was 63% by mass.

(4) Evaluation of Viscosity of Epoxy Resin Composition The viscosity of the epoxy resin composition immediately after preparation was measured within 1 hour after preparation using a rheometer ARES-RDA manufactured by Rheometrics.
After the preparation of the epoxy resin composition, the epoxy resin composition was allowed to stand at 40° C. for 48 hours, and then measured using a rheometer ARES-RDA manufactured by Rheometrics.
For viscosity evaluation, the thickness of the resin between parallel plates with a diameter of 25 mm was set to 0.5 mm. Viscosity was measured up to 150° C. at an angular velocity of 10 radian/second and a heating rate of 2° C./min.

(5) Resin flow of prepreg Cut the multiaxial fabric prepreg obtained above into a size of 150 mm × 150 mm and laminate it into two layers of [0 ° / 90 °] / [90 ° / 0 °] to make a preform. Obtained. The upper and lower molds of the press are preheated to 150°C, the preform is placed on the lower mold, the upper mold is immediately lowered, the press is closed, and the pressure is maintained at 0.1 MPa for 30 seconds, and then at 2 MPa. It was cured by applying pressure and heating and pressurizing for 5 minutes, and after curing, it was removed from the press to obtain a molded article. The burrs of the resin that flowed out to the end of the molded product were removed, the mass before and after molding was measured, and the resin flow amount (%) of the prepreg was calculated.
W1; mass of preform before molding (g)
W2; mass (g) of molded product after molding (after removing resin burrs)
Prepreg resin flow amount (%) = (W1-W2)/W1 x 100
Determination of resin flow ○: Good: Resin flow amount is less than 5.0% ×: Poor: Resin flow amount is 5.0% or more

(6) CFRP internal defect The CFRP cured product after measuring the resin flow of the multiaxial woven prepreg obtained above is measured using an ultrasonic flaw detector (SDS-3600: manufactured by Nippon Krautkramer Co., Ltd.) using a double transmission method. Measurements were made at 5 Hz and an amplification of 19 dB. The ratio of the threshold value of 50% or less was calculated with respect to the measured area, and the internal defect of the CFRP molding was evaluated.
Judgment of internal defects ○: Very good: Less than 1.0% of the threshold value is 50% or less △: Good: 1.0% or more and less than 3.0% of the threshold value is less than 3.0% ×: Bad : Percentage of 50% or less threshold is 3.0% or more

(7) Glass transition temperature The glass transition temperature of the carbon fiber reinforced composite material was measured according to the ASTM D7028 method for the CFRP cured product after measuring the resin flow of the multiaxial fabric prepreg obtained above. The molded plate was processed into a test piece having a length (fiber direction) of 55 mm and a width of 6 mm. The storage modulus E' was measured up to the elastic region. Log E′ was plotted against temperature, and the temperature obtained from the intersection of the approximate straight line of the flat region of log E′ and the approximate straight line of the transition region of E′ was recorded as the glass transition temperature (Tg).

(8) UL-94V combustion test (carbon fiber composite plate)
The multiaxial fabric prepregs were laminated at [0°/90°]/[90°/0°]. This laminate was placed in a bag, heated in an autoclave at a rate of 2° C./min, heated at 150° C. for 10 minutes, and cured to produce a molded plate (carbon fiber reinforced composite material).
The resulting carbon fiber composite material with a thickness of 1.0 mm was processed into a test piece (length 127 mm×width 12.7 mm) and subjected to a combustion test according to the UL-94V standard using a combustion tester manufactured by Suga Test Instruments. The longest burning time (max) [seconds], the total burning time [seconds], and the judgment results [V-0, V-1, V-2 and fail] among the burning times of each test piece were recorded. The results are shown in Table 1.

(9) Evaluation of bending properties of multiaxial woven prepreg Laminated. This laminate was placed in a bag, heated in an autoclave at a rate of 2° C./min, heated at 150° C. for 10 minutes, and cured to produce a molded plate (carbon fiber reinforced composite material).
The resulting 2 mm thick carbon fiber composite material was processed into a test piece (length 100 mm x width 15 mm) and subjected to three-point bending in an environment of a temperature of 23 ° C. and a humidity of 50% RH according to the ASTM D790 method. A bending test was performed using a tool, and bending strength, bending elastic modulus and bending elongation were calculated. The results are shown in Table 1.
The distance between supports in the bending test was set to 64 mm, which is 32 times the thickness.

(Examples 11-12)
An SMC was obtained with the resin composition shown in Table 2, except that the form of the reinforcing fiber base material was a mat of short fibers.

(10) Manufacture of fiber-reinforced composite material using SMC material 2 ply of the SMC obtained above is laminated, and the molding die is charged at a charge rate (ratio of SMC area to die area) of 65%. The epoxy resin composition was cured by heat compression for 5 minutes at a mold temperature of 150° C. and a pressure of 5 MPa to obtain a fiber-reinforced composite material having a thickness of about 2 mm and a size of 300 mm square.

(11) Evaluation of flexural properties of fiber-reinforced composite material using SMC material The 2 mm-thick carbon fiber composite material obtained above was processed into a test piece (length 100 mm x width 25 mm), and tested according to the ASTM D790 method. Accordingly, a bending test was performed using a three-point bending jig under an environment of a temperature of 23° C. and a humidity of 50% RH, and bending strength, bending elastic modulus and bending elongation were calculated. The results are shown in Table 2.
The distance between supports in the bending test was 32 mm, which is 16 times the thickness.

(Examples 13-14)
A towpreg was obtained with the resin composition shown in Table 3, except that the form of the reinforcing fiber base material was a tow of reinforcing fiber bundles.

(12) Production of fiber-reinforced composite material using towpreg The towpreg obtained above is arranged on a flat plate at intervals of 8.5 mm and laminated into five layers of 0°/90°/0°/90°/0° A preform of 150 mm×150 mm was obtained.
The obtained preform was subjected to the resin flow evaluation of (6) and CFRP internal defect of (7), and the results are shown in Table 3.

Claims (12)

At least the following [A] component to [D] component [A] component: an epoxy resin that is liquid at 25 ° C. ,
[B] component: epoxy resin curing agent,
Component [C]: a first compound that is liquid at 25°C and undergoes a curing reaction with component [A] at a temperature of 40°C or lower;
Component [D]: An epoxy resin composition containing a second compound that thickens component [A] at a temperature of 45° C. or higher and is not thickened by component [D] ,
(a) is the viscosity at 40°C measured at a temperature increase rate of 2°C/min within 1 hour after preparation of the epoxy resin composition, and (b) is the viscosity at 40°C after 48 hours at 40°C after preparation. ), then
(a) = 0.05 to 5 Pa s
(b) = 200 to 200,000 Pa·s
(b)/(a) = 200 to 100,000
and
The [C] component is an amine and/or an acid anhydride, and the content of the [C] component is such that the active hydrogen and/or acid anhydride equivalent is 0.1 to 0.1 per the total amount of epoxy groups in the [A] component. is an amount that will be 0.4 equivalents,
Component [D] is a polymer having one or more polymerized units selected from the group consisting of methacrylic acid ester compounds, acrylic acid ester compounds and vinyl compounds, and contains component [D]. An epoxy resin composition characterized in that the amount is 3 to 20 parts by mass per 100 parts by mass of component [A]. 2. The epoxy resin composition according to claim 1, wherein the [B] component is one or more compounds selected from dicyandiamide, urea compounds, and imidazole compounds. 3. The epoxy resin composition according to claim 1 or 2, wherein the reaction initiation temperature of component [A] and component [B] is 100 to 150°C. 4. The epoxy resin composition according to any one of claims 1 to 3, wherein the pot life of component [A] and component [C] at 25°C is 30 to 360 minutes. 5. The epoxy according to any one of claims 1 to 4, wherein when the temperature of component [A] and component [D] is raised at 2°C/min, component [D] starts to swell at 80 to 110°C. Resin composition. The epoxy resin composition according to any one of claims 1 to 5, wherein the component [C] is an alicyclic diamine and/or an aromatic diamine having a viscosity of 10 to 500 mPa·s at 25°C. a reinforcing fiber base material;
The epoxy resin composition according to any one of claims 1 to 6, which is impregnated in the reinforcing fiber base material;
A prepreg consisting of
A prepreg formed by reacting part of the component [A] with part or all of the component [C]. A prepreg according to claim 7, wherein the reinforcing fiber substrate is carbon fiber strands and has the form of a tow prepreg. 8. The prepreg according to claim 7, wherein the reinforcing fiber base material is a mat formed of short fibers having a fiber length of 5 to 100 mm, and is in the form of a sheet molding compound. The prepreg according to claim 7, wherein the reinforcing fiber substrate is a carbon fiber woven fabric or multi-layer woven fabric and has the form of a woven prepreg. A method for producing a prepreg, comprising impregnating a reinforcing fiber base material with the epoxy resin composition according to any one of claims 1 to 6, followed by heat treatment at a temperature of 50°C or less for 8 hours or more. . A method for producing a fiber-reinforced composite material, comprising heating and pressing the prepreg according to any one of claims 7 to 10 in a mold at a temperature of 130 to 170°C and a pressure of 0.2 to 10 MPa for 1 to 20 minutes.