JP2019116545A - Method for curing epoxy resin composition - Google Patents

Abstract

To provide a method for curing an epoxy resin composition for fiber-reinforced composite material which is excellent in dynamic characteristics of a molding while achieving impregnation property in prepreg production and storage stability.SOLUTION: In a method for curing an epoxy resin composition that contains an epoxy resin (A), dicyandiamide (B) and an imidazole-based curing assistant (C) as essential components, the epoxy resin composition having a heat generation start temperature of 135°C or higher is used as the imidazole-based curing assistant (C) when the epoxy resin composition is measured on the condition of a temperature-rise speed of 10°C/min by DSC, and the epoxy resin composition is pre-cured at 90-140°C.SELECTED DRAWING: None

Description

  The present invention relates to a method of curing an epoxy resin composition used for a fiber reinforced composite material.

  Conventionally, fiber-reinforced composite materials comprising reinforcing fibers such as carbon fiber and glass fiber and thermosetting resins such as epoxy resin and phenol resin 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 aerospace and space, automobiles, railway vehicles, ships, civil engineering buildings and sporting goods. In particular, in applications where high performance is required, a fiber-reinforced composite material using continuous reinforcing fibers is used, carbon fibers excellent in specific strength and specific elastic modulus as reinforcing fibers, and thermosetting as a matrix resin Resins, in particular epoxy resins having excellent adhesion to carbon fibers, are used in many cases. However, since epoxy resins (cured products) are generally brittle, that is, their toughness and elongation are low, the mechanical properties of the fiber-reinforced composite material using them as they are are not satisfactory.

  As a method of improving the toughness and elongation of the epoxy resin, a method of blending a rubber component having excellent toughness and a thermoplastic resin has been tried. For example, it has been studied since the 1970's that the toughness of the epoxy resin is improved by blending a rubber component such as acrylonitrile-butadiene rubber containing a carboxyl group into the epoxy resin, and it is generally well known. However, the rubber component causes a decrease in heat resistance and a decrease in elastic modulus, and in order to sufficiently obtain the toughness modifying effect by the rubber component, it is necessary to mix a large amount of the rubber component. Therefore, the heat resistance and mechanical properties inherent to the epoxy resin are lowered, and there is a disadvantage that a composite material having good physical properties can not be obtained.

The curing of the epoxy resin proceeds by addition polymerization or ring-opening polymerization accompanied by the ring-opening of the epoxy ring using a curing agent or a catalyst (curing agent). The curing agent is variously used, such as amine, acid anhydride, dicyandiamide, phenols, etc., and is appropriately selected and used according to the purpose and application.
Among them, since dicyandiamide is a solid crystal having a melting point of 200 ° C. or higher, it is known as a latent curing agent and is used in applications where storage stability is required. On the other hand, since the curing reaction starts by melting at 100 ° C. or higher, the curing temperature becomes high, and when using an epoxy resin in fiber reinforced composite material applications, even when the toughness of the obtained cured product does not satisfy the required physical properties. is there.

  Further, when curing the epoxy resin composition, an operation called pre-cure in which pre-curing is performed at a temperature equal to or lower than a predetermined curing temperature is generally performed. This is a technique used to shorten tacking time by shortening the curing time in the mold, control the heat generation of the cured product, or solidify to reduce tackiness and facilitate handling (Patent Document 1). , 2). However, the epoxy resin composition used for the fiber reinforced composite material has not been studied, and the influence on the physical properties of the cured product at that time is not mentioned.

Japanese Patent Application Laid-Open No. 10-279780 Japanese Patent Application Laid-Open No. 11-286026

  The present invention provides a fiber-reinforced composite material which is excellent in the impregnatability and storage stability at the time of producing a prepreg and is excellent in the mechanical properties of the shaped product by performing precure under specific conditions at the time of producing the shaped body. The present invention provides a curing method of an epoxy resin composition for fiber reinforced composite material that can be suitably used in the winding method.

  That is, the present invention relates to a method of curing an epoxy resin composition comprising an epoxy resin (A), dicyandiamide (B) and an imidazole-based curing aid (C) as essential components, and as the imidazole-based curing aid (C) The epoxy resin composition is precured at 90 ° C. to 140 ° C. using an epoxy resin composition that has an exothermic onset temperature of 135 ° C. or higher when measured under conditions of a temperature rising rate of 10 ° C./min by DSC. It is a curing method of an epoxy resin composition characterized by the above.

  The above curing method is preferably performed by precuring at 90 ° C. to 140 ° C. for 30 to 180 minutes, and after precuring, preferably, the main curing reaction is performed at a temperature higher than the precuring temperature for 30 to 120 minutes.

  Another aspect of the present invention is an epoxy resin composition for fiber reinforced composite materials, which comprises an epoxy resin composition containing an epoxy resin (A), a dicyandiamide (B) and an imidazole-based curing aid (C) as essential components and a reinforcing fiber. Is a method for producing a fiber-reinforced composite material by curing the epoxy resin composition, which uses an exothermic start temperature of 135 ° C. or higher when measured under conditions of a temperature rise rate of 10 ° C./min by DSC as an epoxy resin composition And precuring the epoxy resin composition for fiber reinforced composite materials at 90.degree. C. to 140.degree. C. for producing a fiber reinforced composite material. Furthermore, it is a molded object obtained by the manufacturing method of the said fiber reinforced composite material.

  According to the curing method of the present invention, there is obtained an epoxy resin cured product for fiber reinforced composite material, which is excellent in the impregnatability at the time of producing a prepreg, and which achieves both high storage stability and high fracture toughness and elongation.

It is a graph which shows the exothermic start temperature calculated | required from a DSC chart, and the exothermic peak temperature.

Hereinafter, embodiments of the present invention will be described in detail.
The curing method of the present invention is a method of curing an epoxy resin composition containing an epoxy resin (A), dicyandiamide (B) and an imidazole-based curing aid (C) as essential components, and the epoxy resin composition is precured After preheating, curing is performed by two steps of main curing at a temperature higher than that of precure.
As the imidazole-based curing aid (C), an epoxy resin composition is used which has a heat generation start temperature of 135 ° C. or higher when measured under a condition of a temperature rising rate of 10 ° C./min by differential scanning calorimetry (DSC) Do.

When an epoxy resin, dicyandiamide and imidazole are present in the epoxy resin composition, the curing reaction mainly proceeds in a reaction of the epoxy resin and the imidazole and a reaction of the epoxy resin catalyzed by the imidazole and the dicyandiamide in concert. Furthermore, since the reaction between the epoxy resin and dicyandiamide proceeds, the reaction mechanism becomes very complicated.
Although the details are not clear, the epoxy resin cured product for fiber reinforced composites achieves high fracture toughness and elongation by controlling this curing reaction as a two-step curing of precure and main cure and controlling it at a specific temperature and time. You can get

  Pre-cure (pre-cure) suppresses heat generation during the main curing reaction, and controls the complex curing reaction of the present composition with temperature to advance the curing reaction with superiority in elongation and fracture toughness. To do. The precure is heated at any temperature of 90 to 140 ° C., preferably 100 to 130 ° C., more preferably 105 to 125 ° C., for any time in the range of 0.5 to 3 hours, preferably 0.5 to 2 hours To do. The heating condition may be one step, or may be a multi-step condition in which a plurality of heating conditions are combined. If the curing temperature is less than 90 ° C., the reaction is delayed, which is not preferable from the viewpoint of productivity, and similarly, a curing time exceeding 3 hours is also not preferred. Further, if the curing time is less than 0.5 hours, the effect of the precure is not sufficiently exhibited, and if the curing temperature is higher than 140 ° C., the elongation of the cured product is reduced.

  After pre-curing, main curing is carried out, and a desired curing product is obtained by a crosslinking reaction. In the main curing, the crosslinking reaction is allowed to proceed by heating at an arbitrary temperature above the precure temperature, preferably at a temperature higher by 10 ° C. or more, for an arbitrary time in the range of 0.5 to 2 hours, preferably 0.5 to 1 hours. To obtain a cured product. The main curing temperature is appropriately selected in a temperature range of 140 to 180 ° C., preferably 140 to 160 ° C., more preferably 145 to 155 ° C. The heating condition of the main curing may be one step, or may be a multistep condition combining a plurality of heating conditions, but a curing time exceeding 2 hours is not preferable from the viewpoint of productivity.

  The epoxy resin composition used for the curing method of the present invention contains an epoxy resin (A), dicyandiamide (B) and an imidazole-based curing aid (C) as essential components. Moreover, it is preferable to contain a rubber component as (D) component. Hereinafter, epoxy resin (A), dicyandiamide (B), imidazole-based curing auxiliary (C), core-shell rubber (D) are respectively included in (A) component, (B) component, (C) component and (D) component Say.

The compounding amount of the epoxy resin (A) used in the present invention is 40 to 75 parts by mass, preferably 40 to 70 parts by mass, and more preferably 50 to 50 parts by mass in total 100 parts by mass of the components (A) to (C). 70 parts by mass. When it also contains (D) component, it is a similar compounding quantity with respect to a total of 100 mass parts of (A)-(D) component.
As an epoxy resin, bisphenol A epoxy resin having two epoxy groups in one molecule, bisphenol F epoxy resin, bisphenol E epoxy resin, bisphenol S epoxy resin, bisphenol Z epoxy resin, isophorone bisphenol epoxy resin Etc., halogens, alkyl-substituted products, hydrogenated products of these bisphenol-type epoxy resins, polymer products having a plurality of repeating units as well as monomers, glycidyl ethers of alkylene oxide adducts, phenols Novolak epoxy resin such as novolac epoxy resin, cresol novolac epoxy resin, bisphenol A novolac epoxy resin, 3,4-epoxy-6-methylcyclohexylmethyl-3,4-e Cycloaliphatic epoxy resins such as xyl-6-methylcyclohexane carboxylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 1-epoxyethyl-3,4-epoxycyclohexane, and trimethylol Aliphatic epoxy resins such as propane polyglycidyl ether, pentaerythritol polyglycidyl ether, polyoxyalkylene diglycidyl ether, glycidyl esters such as phthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, dimer acid glycidyl ester, Tetraglycidyldiaminodiphenylmethane, tetraglycidyldiaminodiphenylsulfone, triglycidylaminophenol, triglycidylaminocresol, tetraglycidylki Glycidyl amines such as Rirenjiamin like can be used. Among these epoxy resins, an epoxy resin having two epoxy groups in one molecule is preferable from the viewpoint of viscosity increase rate, and a polyfunctional epoxy resin having more epoxy groups is not preferable. Among them, bisphenol F epoxy resin is most preferable. One of these may be used alone, or two or more of these may be used in combination.

  The epoxy resin (A) used in the present invention preferably has a viscosity in the range of 5 to 30 Pa · s measured using an E-type viscometer (cone plate type) at 25 ° C., more preferably 6 to 25 Pa · s. And more preferably 7 to 20 Pa · s. As a result, it has good impregnating properties to reinforcing fibers, and even after impregnation, dripping of resin from the fibers hardly occurs. The epoxy resin (A) may be a mixture of several types, and the viscosity of the mixture is preferably in the above range.

  In the epoxy resin composition, dicyandiamide (B) is used as a curing agent. Dicyandiamide is a curing agent that is solid at room temperature and hardly dissolves in epoxy resin at room temperature, but dissolves when heated to 180 ° C or more, and has excellent storage stability at room temperature, which has the property of reacting with epoxy groups It is a curing agent. The amount to be used is preferably in the range of 0.2 to 0.8 equivalent (calculated as 1 equivalent of dicyandiamide as 4 equivalents) with respect to the epoxy equivalent of the epoxy resin (A). More preferably, it is 0.2 to 0.5 equivalent. If the amount is less than 0.2 equivalent to the epoxy equivalent, the crosslink density of the cured product becomes low and fracture toughness tends to be low, and if it exceeds 0.8 equivalent, unreacted dicyandiamide tends to remain, so the mechanical properties deteriorate. There is a tendency.

  The epoxy resin composition can be prepared by various known methods. For example, there is a method of kneading each component with a kneader. Alternatively, kneading may be performed using a twin-screw extruder. The dicyandiamide (B) is dispersed in each component as it is in a solid state, but when all the components are kneaded at one time, the dicyandiamide may aggregate to cause poor dispersion. An epoxy resin composition with poor dispersion is not preferable because it causes uneven physical properties in the cured product and causes poor curing. Therefore, it is preferable to use a portion of the epoxy resin in the dicyandiamide as a master batch by pre-kneading with a three-roll mill.

  The compounding amount of the imidazole-based curing auxiliary (C) contained in the epoxy resin composition is preferably 50 to 250 parts by mass, more preferably 50 to 100 parts by mass with respect to 100 parts by mass of dicyandiamide (B). . When the amount of the imidazole-based curing aid is less than 50 parts by mass, it is difficult to develop fast curing, and when it is more than 250 parts by mass, the cured product tends to become brittle although there is no change in rapid curing.

As an imidazole series curing adjuvant (C), in order to improve suppression (storage stability) of a viscosity increase rate, when it is set as the epoxy resin composition of (A), (B) and (C), DSC (a differential Scanning calorimetric analysis) Use one having an exothermic onset temperature of 135 ° C. or higher. Preferably, the temperature is 137 ° C. or more, more preferably 140 ° C. or more. If the heat generation start temperature is lower than 135 ° C., not only the storage stability at room temperature is lowered, but also the curing reaction proceeds at the time of impregnation and the flowability improvement effect is not sufficiently expressed. The DSC heat generation start temperature is the condition of a temperature rising rate of 10 ° C./minute for the epoxy resin composition of (A), (B) and (C) which is blended with an imidazole based curing aid (C) as a curing catalyst It is a temperature represented by extrapolation of the calorific value per time when measured by DSC, and its measurement method is shown in FIG.
In FIG. 1, for the epoxy resin compositions of (A), (B) and (C), the calorific value per time is extrapolated, the intersection is defined as the calorific start temperature, and the temperature showing the maximum calorific value As the exothermic peak temperature.

  Furthermore, as the imidazole-based curing aid (C), the DSC exothermic peak temperature when used as an epoxy resin composition is preferably 145 ° C. to 160 ° C., more preferably 148 ° C. It is preferable that the temperature is 155 ° C. When the exothermic peak temperature is lower than 145 ° C., not only the storage stability at room temperature is lowered, but also the curing reaction proceeds at the time of impregnation, and the fluidity improvement effect is not sufficiently expressed. Further, if it exceeds 160 ° C., it is not preferable because abnormal heat generation and decomposition of the resin itself occur due to curing heat generation during curing. The DSC exothermic peak temperature is a exothermic peak temperature when an epoxy resin composition containing an imidazole-based curing aid (C) as a curing catalyst is subjected to DSC measurement under a condition of a temperature rising rate of 10 ° C./min.

  In order to further satisfy the heat resistance at the time of curing, in addition to the impregnating properties to the reinforcing fiber of the epoxy resin composition as an imidazole-based curing aid (C), 2,4-diamino-6- [2′-ethyl] Preferred is -4'-methylimidazolyl- (1 ')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenyl-4-methyl-5-hydroxymethylimidazole. In addition, other imidazole compounds may be used alone or in combination as a part of a curing assistant component, as long as the composition exhibits a heat generation peak temperature of 145 ° C. or higher. For example, as these other imidazole-based curing assistants (C1), 2-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-undecylimidazole Imidazoles such as 2-heptadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl 6-4 ', 5'-dihydroxymethylimidazole, 1-cyanoethyl-2-ethyl-4methylimidazole It is preferable to use a system compound. Furthermore, as an imidazole compound containing a triazine ring, for example, 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine, 2,4-diamino-6- [4 2'-undecylimidazolyl- (1 ')]-ethyl-s-triazine etc. are mentioned.

  Since the imidazole-based curing aid (C) is also solid, it tends to cause poor dispersion and, like the dicyandiamide (B), a part of the epoxy resin is used, pre-kneaded with a triple roll, and used as a master batch It is preferable to do.

  When core-shell rubber (D) is blended with the essential components (A) to (C), as the core-shell rubber (D), a particulate core component mainly composed of a crosslinked rubbery polymer or elastomer A part or the whole of the surface of the particulate core component is covered with the shell component by graft polymerizing a shell component polymer different from the core component on the surface.

  The blending amount of the core-shell rubber (D) is preferably 0.5 to 15 parts by mass in 100 parts by mass of the epoxy resin composition, and more preferably 1 to 10 parts by mass. If the compounding amount is 0.5 parts by mass or more, the fracture toughness required for the fiber-reinforced composite material after molding is easily obtained, and if the compounding amount is 15 parts by mass or less, the obtained fiber-reinforced composite Since the increase in viscosity of the material epoxy resin composition can be suppressed and the reinforcing fiber can be impregnated without difficulty, it is more suitable for fiber reinforced composite materials.

The epoxy resin composition may further contain other stabilizers, modifiers and the like. As a preferable stabilizer, a boric acid compound represented by B (OR) ₃ (wherein R represents a hydrogen atom, an alkyl group or an aryl group) is preferable. The compounding quantity of a boric acid compound is 0.01-10 mass parts with respect to 100 mass parts of whole resin compositions, Preferably it is 0.1-3 mass parts. If the addition amount is less than 0.01 parts by mass, the storage stability can not be secured, and if it exceeds 10 parts by mass, the effect of inhibiting the curing reaction becomes larger, and curing defects are induced, which is preferable. Absent.

  It is possible to add an antifoamer and a leveling agent to the epoxy resin composition as an additive for the purpose of improving surface smoothness. These additives may be blended in an amount of 0.01 to 3 parts by mass, preferably 0.01 to 1 parts by mass, per 100 parts by mass of the entire resin composition. If the compounding amount is less than 0.01 parts by mass, the effect of smoothing the surface does not appear, and if it exceeds 3 parts by mass, the additive bleeds out on the surface, which is not preferable because it causes the loss of smoothness. .

  The epoxy resin composition is prepared by uniformly mixing the components (A) to (C) described above. This epoxy resin composition has good impregnatability to reinforcing fibers, and even after impregnation, dripping of resin from the fibers does not easily occur. Furthermore, the viscosity is stable at room temperature of 23 ° C. and hardly changes in viscosity, and the viscosity increase rate after 72 hours is 20% or less under the conditions of temperature 40 ° C., air atmosphere or inert gas atmosphere, In addition to securing stable impregnating properties to reinforcing fibers at the time of production of the prepreg having the above, it does not thicken at the time of storage, so there are few voids at the time of curing due to poor resin flowability, and surface smoothness Fiber-reinforced composite materials are obtained.

  Other curable resins can also be blended with the epoxy resin composition. As such a curable resin, unsaturated polyester resin, curable acrylic resin, curable amino resin, curable melamine resin, curable urea resin, curable cyanate ester resin, curable urethane resin, curable oxetane resin, Examples thereof include, but are not limited to, curable epoxy / oxetane composite resins.

  The epoxy resin composition for fiber reinforced composite materials used in the curing method of the present invention preferably has a viscosity of 5 to 30 Pa · s / 25 ° C., more preferably 6 to 25 Pa · s, as measured using an E-type viscometer. / 25 ° C., particularly preferably 7 to 20 Pa · s / 25 ° C. When the viscosity is too high, the impregnating property to the carbon fiber is deteriorated, and when the viscosity is too low, sedimentation of dicyandiamide or an imidazole based curing aid is caused.

  The curing method of the epoxy resin composition of the present invention is suitably used for a tow prepreg fiber reinforced composite material. Although the manufacturing method of the tow prepreg used here is not particularly limited, the epoxy resin composition is dissolved in an organic solvent such as methyl ethyl ketone or methanol to lower the viscosity, and impregnated while immersing the reinforcing fiber bundle, and then the oven etc. Method to evaporate the organic solvent using to make a tow prepreg, or the epoxy resin composition whose viscosity is reduced by heating without using an organic solvent is filmed on a roll or a release paper, and then reinforced fiber bundle After transferring to one side or both sides of the film, a hot melt method in which pressure is applied to impregnate by passing through a bending roll or a pressure roll, the epoxy resin composition is reduced in viscosity by heating, and impregnated while immersing reinforcing fiber bundles. It can be manufactured by the filament winding method etc. and substantially no organic solvent remains in the tow prepreg. There, high quality tow prepreg high productivity since it can be produced, can be preferably used a filament winding method. By using such a production method, a resin-impregnated tow prepreg can be obtained.

  In the method of curing the epoxy resin composition of the present invention, as a reinforcing fiber to be used together with the epoxy resin composition, a fiber reinforced composite material is selected from glass fiber, aramid fiber, carbon fiber, boron fiber etc. It is preferred to use carbon fiber to obtain.

  In the molded article (fiber-reinforced composite material) formed of the epoxy resin composition obtained by the curing method of the present invention and reinforcing fibers (volume-reinforcing fibers), the volume content of reinforcing fibers is preferably 30 to 75%, more preferably 45 to 75 %, And in this range, a molded article with few voids and a high reinforcing fiber volume content can be obtained, so that a molding material of excellent strength can be obtained.

  Hereinafter, the present invention will be more specifically described by way of examples. In order to obtain the resin composition of each example, the following resin raw materials were used.

(A) Epoxy resin, liquid bisphenol F-type epoxy resin: YDF-170 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.)
(Epoxy equivalent weight 160 to 180 g / eq, viscosity 2 to 5 Pa · s)
Liquid bisphenol A epoxy resin: YD-128 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.)
(Epoxy equivalent weight 184 to 194 g / eq, viscosity 11 to 15 Pa · s)
(B) Dicyandiamide, dicyandiamide: DICYANEX1400F (manufactured by AIRPRODUCT)
(C) Imidazole-based curing aid · 2 MAOK-PW (manufactured by Shikoku Kasei Kogyo)
(D) Core shell rubber · MX-154 (manufactured by Kaneka Co., Ltd.): Epoxy master batch (core shell rubber compounded amount 40 wt%, BPA type epoxy resin compounded amount 60 wt%, average particle diameter 100 nm, manufactured by Kaneka Corporation)

The measurement method is shown below.
Epoxy equivalent: Measured in accordance with JIS K 7236 standard. Specifically, using a potentiometric titrator and using tetrahydrofuran as a solvent, a brominated tetraethylammonium acetic acid solution was added, and a 0.1 mol / L perchloric acid-acetic acid solution was used.
Viscosity: in accordance with JIS K7117-1. Specifically, the viscosity at 25 ° C. of the resin composition before curing was measured by an E-type viscometer.
Viscosity ratio: Measured according to JIS K 7177-1 after being left in a hot air circulating oven at 40 ° C. for 3 days.
Reaction peak temperature: When the calorific value per hour is maximized when measurement is performed with a differential scanning calorimeter (EXSTAR 6000 DSC 6200 manufactured by SII Nano Technology Inc.) under a temperature rising condition of 10 ° C./min. Expressed in temperature.
Reaction initiation temperature: This was expressed by extrapolation of the calorific value per time when measurement was carried out using a differential scanning calorimeter (EXSTAR 6000 DSC 6200 manufactured by SII Nano Technology Inc.) under a temperature rising condition of 10 ° C./min.
Tg: The temperature of a DSC extrapolation value when measured under a temperature rising condition of 10 ° C./min with a differential scanning calorimeter (EXSTAR 6000 DSC 6200 manufactured by SII Nano Technology Inc.).
Fracture toughness (K1c): according to ASTM E399. Specifically, a test piece having a width of 10 mm, a thickness of 4 mm and a length of 50 mm was prepared, and was measured at a room temperature of 23 ° C. and a crosshead speed of 0.5 mm / min.
Tensile modulus of elasticity, tensile strength, tensile elongation: in accordance with JIS K7161. Specifically, a universal material tester (Autograph AGS-H manufactured by Shimadzu Science Co., Ltd.) was used. A dumbbell specimen having dimensions of a total length of 215 mm, a width of 10 mm and a thickness of 4 mm including the grip portion at room temperature was 114 mm between chucks, a speed of 50 mm / min. The tensile strength, the tensile modulus, and the tensile elongation were determined from the obtained stress-strain diagram.

Reference Example An epoxy resin composition used to measure the exothermic onset temperature and the reaction peak temperature was prepared according to the following.
YD-128 (A) / dicyandiamide (B) / imidazole-based curing aid-2MAOK-PW (C), respectively, in a composition (wt%) of 93.7 / 5.3 / 1 and kneaded to obtain epoxy It was set as a resin composition. The heat generation start temperature and heat generation peak temperature of the imidazole-based curing aid were 143 ° C. and extrapolated from the calorific value around time when measurement was performed under a temperature rising condition of 10 ° C./min with a differential scanning calorimeter. It was 154 ° C.

Examples 1 to 7 and Comparative Examples 1 and 2
(1) Preparation of Epoxy Resin Composition YDF-170 (A) / DICYAnex 1400 F (B) / 2 MAOK-PW (C) / MX-154 (D), each of 69.7 / 5.3 / 3/25 The composition (parts by weight) was added, and the mixture was kneaded for 6 minutes under the conditions of 2000 rpm and 4.0 mmhg using THINKY PLANETARY VACUUM MIXER (manufactured by Shinky Co., Ltd.) to prepare an epoxy resin composition. (B) The dicyandiamide used what pre-kneaded with a part of epoxy resin (A), and used the masterbatch which disperse | distributed the core-shell rubber also to epoxy resin (A) in the manufacture process of core-shell polymer. The rubber content of the prepared epoxy resin composition was 10% by weight. The initial viscosity was 6.8 mPa · s / 25 ° C., and the viscosity after 40 ° C. for 3 days was 7.2 mPa · s / 25 ° C., and the viscosity ratio was 5.9%.
The prepared epoxy resin composition had a low viscosity and a low thickening rate, and was excellent in the impregnating ability at the time of producing a prepreg and the storage stability.

(2) Preparation of test piece The epoxy resin composition prepared in the above (1) is heated to a temperature of 80 ° C., injected into a mold, and raised to a predetermined temperature at 3 / min in an oven at a temperature of 50 ° C. After warming, curing was carried out under the conditions of various pressure temperatures and times and post curing (main curing) temperatures and times shown in Table 1 to prepare a plate of epoxy resin cured product having a thickness of 4 mm. Next, the obtained epoxy resin cured product plate was cut out and used for test analysis. The results are shown in Table 1 together.

Claims (5)

  A curing method of an epoxy resin composition comprising an epoxy resin (A), a dicyandiamide (B) and an imidazole-based curing aid (C) as essential components, wherein the epoxy resin composition is DSC as the imidazole-based curing aid (C) Epoxy resin composition characterized in that the epoxy resin composition is precured at a temperature of 90 ° C. to 140 ° C. using a resin whose heat generation start temperature is 135 ° C. or higher when measured under conditions of a temperature rising rate of 10 ° C./min. Method of curing the composition.   The method according to claim 1, wherein the pre-curing is performed at 90 ° C to 140 ° C for 30 to 180 minutes.   The method according to claim 1 or 2, wherein after the precure, the main curing reaction is carried out at a temperature higher than the precure temperature for 30 to 120 minutes.   An epoxy resin composition containing an epoxy resin (A), dicyandiamide (B) and an imidazole-based curing aid (C) as essential components, and an epoxy resin composition for fiber reinforced composite materials including reinforcing fibers are cured to obtain a fiber reinforced composite material The epoxy resin composition is an epoxy resin composition which has an exotherm onset temperature of 135 ° C. or higher when measured under conditions of a temperature rise rate of 10 ° C./min. A method for producing a fiber reinforced composite material, comprising precuring the resin composition at 90 ° C to 140 ° C. The molded object obtained by the manufacturing method of the fiber reinforced composite material of Claim 4.

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