JP2022039266A - Epoxy resin composition, intermediate substrate, tow preg, and fiber reinforced composite material - Google Patents

Abstract

To provide an epoxy resin composition which has excellent toughness and heat resistance while curable in a short time, and excellent storage property, an intermediate base material composed of the epoxy resin composition and a reinforcement fiber, and a fiber-reinforced composite material which is obtained by curing the intermediate base material and is excellent in long-term durability and durability under high temperature and high humidity environment.SOLUTION: An epoxy resin composition contains all of the following components [A] to [E], and satisfies all of conditions [I] to [III]. [A]: bifunctional epoxy resin that is liquid at 25°C. [B] core-shell rubber particles. [C] carboxyl group-terminated butadiene nitrile rubber. [D] dicyandiamide. [E]: aromatic urea. (I) molar number of active hydrogen of dicyandiamide/molar number of total epoxy group=0.40-0.53. (II) molar number of total epoxy group/molar number of urea group=15-55. (III) mass of carboxyl group-terminated butadiene nitrile rubber/mass of core-shell rubber particle=0.1-0.8.SELECTED DRAWING: None

Description

The present invention relates to an epoxy resin composition preferably used as a matrix resin for a fiber-reinforced composite material suitable for sports use and general industrial use, an intermediate base material such as tow preg and prepreg using the same as a matrix resin, and a fiber-reinforced composite. It is about materials.

Fiber-reinforced composite materials using reinforced fibers such as carbon fiber and glass fiber have been applied to many fields such as aerospace, automobiles, railroad vehicles, ships, civil engineering and construction and sporting goods due to their excellent lightness. There is. In particular, in applications where high performance is required, a fiber-reinforced composite material using continuous reinforcing fibers is used, and carbon fibers having excellent specific strength and specific elasticity are used as reinforcing fibers, and carbon fibers having excellent specific elasticity are used as thermosetting resins. , Epoxy resin is often used because of its excellent adhesion to carbon fiber, heat resistance, and mechanical strength.

In the production of the fiber-reinforced composite material, an intermediate base material in which the reinforcing fibers are impregnated in advance with a matrix resin is often used because of the ease of transportation and shape-impartment. The form of the intermediate base material is a narrow intermediate base material called a prepreg in which reinforcing fibers are arranged in a sheet shape, a tow prepreg in which a bundle of reinforcing fibers is impregnated with a thermosetting resin, a yarn prepreg, or a strand prepreg. Hereinafter, it will be referred to as a tow preg) and the like. In these intermediate base materials, the viscosity of the matrix resin is required to be stable over time in order to maintain good handleability.

With the expansion of application to intermediate base materials for general industrial applications such as automobile parts, it is desired to shorten the curing time from the viewpoint of improving the productivity of composite materials. To realize this, epoxy resin It is necessary to improve the curing rate of.

Further, in these applications, it is desired to improve the long-term durability of the fiber-reinforced composite material and the durability in a high temperature / high humidity environment. It is necessary to improve the property (glass transition temperature) and reduce the hygroscopicity. Further, in order to improve the heat resistance, it is necessary to improve the heat resistance not only as an epoxy resin but also as a fiber-reinforced composite material.

Patent Document 1 discloses a liquid epoxy resin composition excellent in fast-curing property using an aliphatic amine as a curing agent. Although such an epoxy resin composition is excellent in quick-curing property, prepreg Insufficient stability over time (pot life) of viscosity to use as an intermediate substrate such as towpreg and towpreg, could not be used.

Patent Document 2 discloses an epoxy resin composition capable of rapid curing by containing a large amount of dicyandiamide as a curing agent, and such an epoxy resin composition is excellent in rapid curing property and pot life. However, there are problems that the toughness of the cured resin product and the glass transition temperature of the fiber-reinforced composite material tend to decrease.

Japanese Patent Publication No. 2015-508125 Special Table 2016-500409 Gazette

In view of this background, the present invention comprises an epoxy resin composition that can be cured in a short time, has excellent toughness and heat resistance, and is also excellent in storage stability, and the epoxy resin composition. It is an object of the present invention to provide an intermediate base material made of reinforced fibers and a fiber-reinforced composite material obtained by curing the intermediate base material, which has excellent long-term durability and durability in a high temperature / high humidity environment.

The present invention employs the following means in order to solve such a problem. That is, the epoxy resin composition of the present invention is an epoxy resin composition containing all of the following components [A] to [E] and satisfying all of the conditions (I) to (III).
[A] Bifunctional epoxy resin liquid at 25 ° C. [B] Core-shell rubber particles [C] carboxyl group-terminated butadiene nitrile rubber [D] dicyandiamide [E] aromatic urea (I) number of active hydrogen moles of dicyandiamide / total epoxy group Number of moles = 0.40 to 0.53
(II) Number of moles of all epoxy groups / number of moles of urea groups = 15 to 55
(III) Mass of carboxyl group-terminated butadiene nitrile rubber / mass of core-shell rubber particles = 0.1 to 0.8

The epoxy resin composition of the present invention can be cured in a short time, has excellent toughness and heat resistance, and is also excellent in storage stability, so that it has excellent productivity, long-term durability, and high temperature. It is possible to obtain a fiber-reinforced composite material having excellent durability in a high humidity environment.

The present invention has the following configuration. That is, the epoxy resin composition of the present invention is an epoxy resin composition containing all of the following components [A] to [E] and satisfying all of the conditions (I) to (III).
[A] Bifunctional epoxy resin liquid at 25 ° C. [B] Core-shell rubber particles [C] carboxyl group-terminated butadiene nitrile rubber [D] dicyandiamide [E] aromatic urea (I) number of active hydrogen moles of dicyandiamide / total epoxy group Number of moles = 0.40 to 0.53
(II) Number of moles of all epoxy groups / number of moles of urea groups = 15 to 55
(III) Mass of carboxyl group-terminated butadiene nitrile rubber / mass of core-shell rubber particles = 0.1 to 0.8.

(About component [A])
The component [A] in the present invention is a bifunctional epoxy resin liquid at 25 ° C. The component [A] is necessary to adjust the viscosity of the epoxy resin composition to a range suitable for producing an intermediate base material without impairing a good balance between curing speed, toughness and heat resistance. Here, bifunctional means having two epoxy groups in one molecule. Examples of such epoxy resins include bisphenol type epoxy resins such as bisphenol A type and bisphenol F type, glycidylamine type epoxy resins such as glycidylaniline type, polyethylene glycol type, polypropylene glycol type, butanediol type, and neopentyl glycol type. , Hexadiol type, cyclohexanedimethanol type and other aliphatic epoxy resins and the like can be mentioned. These epoxy resins may be used alone or may be appropriately mixed and used.

Commercially available products of bisphenol type epoxy resin include "jER (registered trademark)" 825, "jER (registered trademark)" 828 (above, bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Co., Ltd.), and "EPICLON (registered trademark)". 830, "EPICLON (registered trademark)" 807 (above, bisphenol F type epoxy resin, manufactured by DIC Co., Ltd.), "jER (registered trademark)" 806 (bisphenol F type epoxy resin, manufactured by Mitsubishi Chemical Co., Ltd.) and the like can be mentioned. ..

Commercially available glycidyl amine type epoxy resins include GAN (N, N-diglycidyl aniline, manufactured by Nippon Kayaku Co., Ltd.), GOT (N, N-diglycidyl-o-toluidine, manufactured by Nippon Kayaku Co., Ltd.), etc. Can be mentioned.

Commercially available aliphatic epoxy resins include "Denacol (registered trademark)" EX-821, "Denacol (registered trademark)" EX-850 (above, polyethylene glycol type epoxy resin, manufactured by Nagase ChemteX Corporation), and "Denacol". (Registered Trademark) "EX-920," Denacol (Registered Trademark) "EX-941 (above, polypropylene glycol type epoxy resin, manufactured by Nagase ChemteX Corporation)," Denacol (Registered Trademark) "EX-214 (1,4) -Butanediol type epoxy resin, manufactured by Nagase ChemteX Corporation), "Araldite (registered trademark)" DY-026 (1,4-butanediol type epoxy resin, manufactured by Huntsman Japan Co., Ltd.), "Denacol (registered trademark)" "EX-212 (1,6-hexanediol type epoxy resin, manufactured by Nagase ChemteX Corporation)," Adecaledin (registered trademark) "ED-503 (1,6-hexanediol type epoxy resin, manufactured by ADEKA Co., Ltd.), "Denacol (registered trademark)" EX-211 (neopentyl glycol type epoxy resin, manufactured by Nagase ChemteX Corporation), "Adeca Resin (registered trademark)" ED-523 (neopentyl glycol type epoxy resin, manufactured by ADEKA Co., Ltd.), "Denacol (registered trademark)" EX-216 (cyclohexanedimethanol type epoxy resin, manufactured by Nagase ChemteX Corporation), "Ricaresin (registered trademark)" DME-100 (cyclohexanedimethanol type epoxy resin, manufactured by Shin Nihon Rika Co., Ltd.) ) And so on.

In the present invention, it is preferable that the aliphatic epoxy resin [A1] is contained as the component [A] in an amount of 3 to 20 parts by mass in 100 parts by mass of the total epoxy resin component. By including the component [A1] in such a range, the viscosity of the epoxy resin composition can be effectively reduced without impairing the good balance between the curing rate, toughness and heat resistance, and the range suitable for the production of towpreg can be obtained. In addition to being able to be adjusted, by using it in combination with the components [B] and [C] described later, it is specific compared to the case where each component is used alone or the two components are used in combination. The effect of improving the tensile elongation at break and the toughness value can be obtained. The reason why such an effect is obtained is not clear, but it is because the different tensile elongation at break and the mechanism for improving the toughness value of each of the components [A1], [B], and [C] work in concert. I'm guessing there is. Examples of the component [A1] include polyethylene glycol type epoxy resin, polypropylene glycol type epoxy resin, butanediol type epoxy resin, neopentyl glycol type epoxy resin, hexanediol type epoxy resin, cyclohexanedimethanol type epoxy resin and the like. Be done.

Further, among the components [A1], it is more preferable to contain a bifunctional epoxy resin having an alkylene skeleton having 4 to 10 carbon atoms because the increase in hygroscopicity of the matrix resin after curing can be suppressed. Examples of the bifunctional epoxy resin having an alkylene skeleton having 4 to 10 carbon atoms include a butanediol type epoxy resin (alkylene skeleton carbon number: 4) and a neopentyl glycol type epoxy resin (alkylene skeleton carbon number: 5). , A hexanediol type epoxy resin (carbon number of carbon of alkylene skeleton: 6), a cyclohexanedimethanol type epoxy resin (carbon number of carbon of alkylene skeleton: 8) and the like can be mentioned.

(About component [F])
In the present invention, 100 parts by mass of the total epoxy resin is used as an epoxy resin [F] which is at least one selected from the group consisting of a biphenyl type epoxy resin, a biphenyl aralkyl type epoxy resin, a dicyclopentadiene type epoxy resin and an oxazolidone type epoxy resin. It is preferable to contain 3 to 40 parts by mass thereof. By including the component [F] in such a range, the heat resistance can be further enhanced while maintaining a good balance between the curing rate, toughness and heat resistance, and the viscosity suitable for producing the intermediate base material.

Commercially available products of the biphenyl type epoxy resin which is the component [F] include "jER (registered trademark)" YX4000, "jER (registered trademark)" YX4000H, and "jER (registered trademark)" YL6121H (all manufactured by Mitsubishi Chemical Corporation). And so on.

Examples of commercially available products of the biphenyl aralkyl type epoxy resin as the component [F] include NC-3000-L, NC-3000, NC-3100 (all manufactured by Nippon Kayaku Co., Ltd.) and the like.

Commercially available products of the dicyclopentadiene type epoxy resin which is the component [F] include "EPICLON (registered trademark)" HP-7200L, "EPICLON (registered trademark)" HP-7200, and "EPICLON (registered trademark)" HP-7200H. (The above is manufactured by DIC Corporation), XD-1000-2L, XD-1000, XD-1000H (above, manufactured by Nippon Kayaku Co., Ltd.) and the like.

Examples of commercially available products of the oxazolidone-type epoxy resin as the component [F] include "DER (registered trademark)" 858 (manufactured by Olin Corporation).

Among the components [F], since the balance between heat resistance and viscosity is the best, it is more preferable to contain a dicyclopentadiene type epoxy resin, and further, it is a bifunctional type having two epoxy groups in one molecule. preferable. Examples of commercially available products of such a bifunctional dicyclopentadiene type epoxy resin include "EPICLON (registered trademark)" HP-7200L (manufactured by DIC Corporation).

(About other epoxy resins)
Epoxy resins other than the component [A] and the component [F] can be contained as long as the effects of the present invention are not impaired. The epoxy resin is not particularly limited, and is, for example, a bisphenol type epoxy resin such as solid bisphenol A type, solid bisphenol F type, and solid bisphenol S type, diaminodiphenylmethane type, diaminodiphenylsulfone type, aminophenol type, and metaxylene diamine. Type, glycidylamine type epoxy resin such as 1,3-bisaminomethylcyclohexane type, isocyanurate type, hydantin type, phenol novolac type, orthocresol novolac type, bisnaphthalene type, trishydroxyphenylmethane type and tetraphenylol ethane type Epoxy resin and the like. These epoxy resins may be used alone or may be appropriately mixed and used.

(About component [B])
The component [B] in the present invention is a core-shell rubber particle. The component [B] is a component necessary for improving the toughness of the cured resin product. Here, the core-shell rubber particles are particles in which a part or the whole of the surface of the particulate core component is coated with the shell component. As the component [B], for example, a core shell structure is used in which rubber fine particles such as acrylic rubber fine particles, butadiene rubber fine particles, butadiene-styrene rubber fine particles, and silicone rubber fine particles are used as the core component, and the surface thereof is coated with a dissimilar polymer. There are things that you have. These rubber components may be used alone or may be appropriately mixed and used.

Commercially available products of such component [B] include "Kaneace (registered trademark)" MX-125, "Kaneace (registered trademark)" MX-150, "Kaneace (registered trademark)" MX-154, and "Kaneace (registered trademark)". "MX-257," Kaneace (registered trademark) "MX-267," Kaneace (registered trademark) "MX-416," Kaneace (registered trademark) "MX-451," Kaneace (registered trademark) "MX-EXP (HM5) ) (The above is manufactured by Kaneka Co., Ltd.), "PARALOID (registered trademark)" EXL-2655, "PARALOID (registered trademark)" EXL-2668 (above, manufactured by Dow Chemical), and the like.

(About component [C])
The component [C] in the present invention is a carboxyl group-terminated butadiene nitrile rubber. The component [C] is a component necessary for improving the toughness of the cured resin product. Commercially available products of such component [C] include "Hypro (registered trademark)" 1300X31, "Hypro (registered trademark)" 1300X13, "Hypro (registered trademark)" 1300X13NA, and "Hypro (registered trademark)" 1300X8 (hereinafter, CVC). (Manufactured by Thermoset Specialties) and the like. These may be used alone or may be appropriately mixed and used.

In the present invention, it is necessary to use the component [B] and the component [C] together. As a result, a specifically excellent toughness improving effect can be obtained as compared with the case where each of the component [B] and the component [C] is used alone, and both quick curing and excellent toughness can be achieved.

Further, in the present invention, the mass ratio (mass of carboxyl group-terminated butadiene nitrile rubber / mass of core-shell rubber particles) obtained by dividing the mass of the component [C] by the mass of the component [B] is 0.1 to 0. It is necessary to be 0.8. By setting the content of the component [C] with respect to the component [B] in such a range, it is possible to effectively obtain specifically excellent toughness and to achieve both heat resistance.

Further, since a better toughness improving effect and a viscosity suitable for manufacturing an intermediate base material can be obtained, the content of the component [B] is 5 to 30 parts by mass with respect to 100 parts by mass of the total epoxy resin component. It is preferably 5 to 15 parts by mass, and more preferably 5 to 15 parts by mass.

From the same viewpoint, the content of the component [C] is preferably 0.5 to 15 parts by mass, more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the total epoxy resin component. preferable. The sum of the content of the component [B] and the content of the component [C] is preferably 5 to 45 parts by mass, and 9 to 35 parts by mass with respect to 100 parts by mass of the total epoxy resin component. Is more preferable.

(About component [D])
The component [D] of the present invention is dicyandiamide. Dicyanodiamide is a heat-active latent curing agent. That is, although the activity is low below a predetermined temperature, it has the property of changing to a high activity state by undergoing a phase change or a chemical change by receiving a certain thermal history. The component [D] imparts stability to the epoxy resin composition and has an effect of preventing thickening of the epoxy resin composition during the preparation process of the epoxy resin composition, the manufacturing process of the intermediate base material, and the storage period of the intermediate base material. It is a component necessary to achieve both the effect of rapidly advancing the curing reaction under heating conditions. Examples of commercially available products of such dicyandiamide include "jER Cure (registered trademark)" DICY7 and "jER Cure (registered trademark)" DICY15 (all manufactured by Mitsubishi Chemical Corporation).

The content of the component [D] in the present invention is a molar ratio (of the dicyandiamide) obtained by dividing the number of moles of active hydrogen of the dicyandiamide by the number of moles of the epoxy groups of all the epoxy resin components contained in the epoxy resin composition. The number of moles of active hydrogen / the number of moles of all epoxy groups) needs to be 0.40 to 0.53. Here, in the present invention, it is assumed that one molecule of dicyandiamide reacts with four epoxy groups, and the active hydrogen equivalent is 21 g / eq. Treat as. The content of the component [D] corresponding to the above range varies depending on the type and content of the epoxy resin component, and is not limited to the following range, but is 4 to 4 to 100 parts by mass of the total epoxy resin component. 6 parts by mass is a guide. The range of the content of the component [D] is necessary for obtaining a resin composition which can be cured in a short time, has excellent toughness and heat resistance, and is also excellent in storage stability. be. Further, in general, the glass transition temperature of the fiber-reinforced composite material is lower than the glass transition temperature of the cured resin product, but the range of the content of the component [D] is particularly limited to the fiber-reinforced composite with respect to the cured resin product. It is necessary to suppress a decrease in the glass transition temperature of the material and to obtain a fiber-reinforced composite material having excellent heat resistance.

(About component [E])
The epoxy resin composition used for the tow preg of the present invention needs to contain an aromatic urea as a component [E]. By using the component [E] in combination with the component [D], the balance between the viscosity of the epoxy resin composition over time and the curing rate can be improved. Here, the aromatic urea refers to a compound having a structure in which a urea group is bonded to an aromatic ring, and specifically, 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU), 3 -(4-Chlorophenyl) -1,1-dimethylurea, phenyldimethylurea (PDMU), 2,4-toluenebis (3,3-dimethylurea) (TBDMU) and the like can be mentioned. These may be used alone or may be appropriately mixed and used.

Commercially available products of such component [E] include DCMU99 (DCMU, manufactured by Hodogaya Chemical Industry Co., Ltd.), "Omicure (registered trademark)" 24 (TBDMU, manufactured by Chori GLEX Co., Ltd.), and "Dyhard (registered trademark)" UR505 (registered trademark). 4,4'-Methylenebis (phenyldimethylurea), manufactured by AlzChem) and the like can be mentioned.

Among the components [E], TBDMU is preferably used because a cured resin product having excellent heat resistance can be obtained.

Further, in the present invention, the molar ratio (the number of moles of all epoxy groups / the number of moles of urea groups) obtained by dividing the number of moles of all epoxy groups by the number of moles of urea groups needs to be 15 to 55. It is preferably 15 to 30. The content of the component [E] corresponding to the above range varies depending on the type and content of the epoxy resin component, and is not limited to the following range, but is 1 to 1 to 100 parts by mass of the total epoxy resin component. 5 parts by mass is a guide. The range of the content of the component [E] is necessary for obtaining a resin composition having excellent toughness and heat resistance while being able to be cured in a short time.

Further, in the present invention, the ratio of the number of moles of urea groups to the number of moles of active hydrogen of dicyandiamide (number of moles of urea groups / number of moles of active hydrogen of dicyandiamide) is preferably 0.035 to 0.17. By satisfying the range in which the content ratio of the component [D] and the component [E] is satisfied, an epoxy resin composition having an excellent balance between curing speed and heat resistance can be obtained.

(About other additives)
The epoxy resin composition used for the tow preg of the present invention has various additions such as viscosity modifiers such as thermoplastic resins and rocking agents, defoaming agents, stabilizers, flame retardants, pigments, etc., as long as the effects of the present invention are not lost. Can contain agents. The thermoplastic resin is preferably a thermoplastic resin that is soluble in the epoxy resin. Examples of the thermoplastic resin soluble in the epoxy resin include polyvinyl acetal resins such as polyvinyl formal and polyvinyl butyral, polyvinyl alcohol, phenoxy resin, polyamide, polyimide, polyvinylpyrrolidone, and polysulfone. Shaking modification agents include organic substances such as amido wax and hydrogenated castor oil, silica, alumina, mixed oxides of aluminum and silicon, titanium oxide, light calcium carbonate, and smectite clay minerals (montmorillonite, bidelite, bentonite). , Hectorite, saponite, etc.), sepiolite, carbon black, and other inorganic substances. Examples of the defoaming agent include non-silicon polymer-based defoaming agents and silicon-based defoaming agents.

The epoxy resin composition of the present invention preferably has a viscosity at 25 ° C. of 1 to 150 Pa · s, more preferably 1 to 110 Pa · s, and even more preferably 1 to 50 Pa · s. By setting the viscosity in such a range, it is possible to improve the liquid feedability, the impregnation property into the reinforcing fibers, the handleability, etc. of the epoxy resin composition at the time of manufacturing the intermediate base material.

In the present invention, the glass transition temperature of the cured resin product is preferably 120 to 160 ° C, more preferably 120 to 150 ° C. By setting the glass transition temperature of the cured resin product in such a range, the heat resistance and toughness of the cured resin product can be well balanced. Here, the cured resin product refers to a product obtained by curing the epoxy resin composition of the present invention under heating conditions. The curing conditions of the epoxy resin composition are not particularly limited. For example, the temperature is raised at a rate of 1 to 20 ° C./min and then heat-treated at 110 to 160 ° C. for 0.5 to 8 hours to carry out a curing reaction. Can be completed.

Various known methods can be used to prepare the epoxy resin composition of the present invention. For example, it may be kneaded using a machine such as a kneader, a planetary mixer, a mechanical stirrer, a dissolver, or a three-roll, or it may be mixed by hand using a beaker and a spatula.

The intermediate base material of the present invention is obtained by impregnating a reinforcing fiber bundle with the epoxy resin composition of the present invention. Here, as the reinforcing fiber bundle, a reinforcing fiber bundle composed of 1,000 to 70,000 filaments having a diameter of 3 to 100 μm is usually used.

Examples of the reinforcing fiber bundle used for the intermediate base material of the present invention include fiber bundles made of glass fiber, carbon fiber, aramid fiber, boron fiber, alumina fiber, silicon carbide fiber and the like. Two or more of these fiber bundles may be mixed and used. Among these, it is preferable to use a carbon fiber bundle that can obtain a lightweight and highly rigid fiber-reinforced composite material. Specific examples of the carbon fiber bundles include acrylic, pitch and rayon carbon fiber bundles, and acrylic carbon fiber bundles having particularly high tensile strength are preferably used.

The mass content (Rc) of the epoxy resin composition in the intermediate substrate of the present invention can be set without particular limitation depending on the intended purpose, but is preferably 20 to 40%, and more preferably 20 to 30%. It is preferable, 22 to 28% is most preferable. When the mass ratio of the epoxy resin composition to the reinforcing fiber bundle is 20% or more, it is possible to suppress the occurrence of defects such as unimpregnated portions and voids inside the obtained fiber-reinforced composite material. Further, if it is 40% or less, the volume content of the reinforcing fiber bundle can be increased, so that the mechanical properties of the fiber-reinforced composite material can be effectively exhibited and the weight can be reduced.

The intermediate substrate of the present invention can be produced by various known methods. That is, a method of impregnating the epoxy resin composition of the present invention into a low viscosity by heating without using an organic solvent and impregnating the reinforcing fiber bundle while immersing the reinforcing fiber bundle. It can be manufactured by forming a coating film on a release paper, then transferring it to one side or both sides of a reinforcing fiber bundle, and then applying pressure to impregnate it by passing it through a bending roll or a pressure roll.

In particular, in the case of producing a tow preg, it is preferable to include a step of bringing a rotary roll coated with the epoxy resin composition into contact with at least one side of the reinforcing fiber bundle because a high-quality tow preg can be produced. The tow preg is usually supplied in the form of a bobbin wound from hundreds to thousands of meters into a paper tube.

The fiber-reinforced composite material of the present invention can be obtained by heat-curing the intermediate substrate of the present invention. The intermediate substrate of the present invention can be used in many fields such as aerospace, automobiles, railroad vehicles, ships, civil engineering and sports equipment, and particularly for manufacturing hollow containers such as pressure vessels and cylinders. It can be suitably used.

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

<Materials used in Examples and Comparative Examples>
(1) Reinforcing fiber bundle, "Trading Card (registered trademark)" T720SC-36K (tensile strength 5,880 MPa, number of filaments 36,000, total fineness 1,650tex, density 1.8 g / cm ³ , manufactured by Toray Industries, Inc.) ..

(2) Component [A] (other than component [A1]): Bifunctional epoxy resin liquid at 25 ° C. "jER (registered trademark)" 828 (liquid bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
-"JER (registered trademark)" 806 (liquid bisphenol F type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
-GAN (N, N-diglycidyl aniline, manufactured by Nippon Kayaku Co., Ltd.).

(3) Ingredient [A1]: Aliphatic epoxy resin "Denacol (registered trademark)" EX-821 (polyethylene glycol type epoxy resin, manufactured by Nagase ChemteX Corporation)
-"Denacol (registered trademark)" EX-211 (neopentyl glycol type epoxy resin, carbon number of alkylene skeleton: 5, manufactured by Nagase ChemteX Corporation)
-"Denacol (registered trademark)" EX-212 (1,6-hexanediol type epoxy resin, carbon number of alkylene skeleton: 6, manufactured by Nagase ChemteX Corporation)
-"Denacol (registered trademark)" EX-216 (cyclohexanedimethanol type epoxy resin, carbon number of alkylene skeleton: 8, manufactured by Nagase ChemteX Corporation).

(4) Component [F]: At least one epoxy resin selected from the group consisting of biphenyl type epoxy resin, biphenyl aralkyl type epoxy resin, dicyclopentadiene type epoxy resin and oxazolidone type epoxy resin, "jER (registered trademark)". "YX4000 (biphenyl type epoxy resin, manufactured by Mitsubishi Chemical Co., Ltd.)
・ NC-3000-L (biphenyl aralkyl type epoxy resin, manufactured by Nippon Kayaku Co., Ltd.)
-"EPICLON (registered trademark)" HP-7200L (dicyclopentadiene type epoxy resin, manufactured by DIC Corporation)
"DER®" 858 (oxazolidone type epoxy resin, manufactured by Olin Corporation).

(5) Other epoxy resins ・ "Sumiepoxy (registered trademark)" ELM-434 (Tetraglycidyldiaminodiphenylmethane, manufactured by Sumitomo Chemical Co., Ltd.).

(6) Ingredient [B]: Core shell rubber particles ・ "Kane Ace (registered trademark)" MX-150 (polybutadiene rubber type core shell rubber particles 40% liquid bisphenol A type epoxy resin masterbatch, manufactured by Kaneka Co., Ltd.)
-"Kane Ace (registered trademark)" MX-257 (polybutadiene rubber type core shell rubber particles 37% liquid bisphenol A type epoxy resin masterbatch, manufactured by Kaneka Corporation).

(7) Component [C]: Carboxyl group-terminated butadiene nitrile rubber- "Hypro®" 1300X13NA (terminal carboxyl group-modified butadiene nitrile rubber, manufactured by CVC Thermoset Specialties).

(8) Ingredient [D]: dicyandiamide, "jER cure (registered trademark)" DICY7 (epoxy resin curing agent, dicyandiamide, manufactured by Mitsubishi Chemical Corporation).
(9) Ingredient [E]: Aromatic urea "Omicure" (registered trademark) 24 (TBDMU, manufactured by Chori GLEX Co., Ltd.).

(10) Other additives- "BYK (registered trademark)" 1790 (defoaming agent, manufactured by Big Chemie Japan Co., Ltd.).

<Preparation method of epoxy resin composition>
After putting the components other than the component [D] and the component [E] into the beaker, the mixture was heated to 100 ° C. and stirred until uniform. Subsequently, after lowering the temperature of the resin to 25 to 60 ° C., the component [D] and the component [E] were added and stirred until uniform to obtain an epoxy resin composition. The component content ratios of Examples and Comparative Examples are shown in Tables 1 to 3.

<Measuring method of viscosity of epoxy resin composition at 25 ° C>
E-type viscometer (manufactured by Toki Sangyo Co., Ltd., TVE-) equipped with a standard cone rotor (1 ° 34'x R24) according to "Conical-Viscosity measurement method using flat plate type rotational viscometer" in JIS Z8803 (2011). 30H) was used and the rotation speed was measured as 5 to 20 rotations / minute. The inside of the sample cup was adjusted to the measurement temperature (25 ° C.), and after 1 minute or more had passed after the epoxy resin composition was added, the value was read when the displayed value became stable.

<Epoxy resin composition gelation time evaluation method>
Using a cure monitor LT-451 (manufactured by Lambient Technologies), the change over time in the ionic viscosity of the epoxy resin composition at 150 ° C. was measured. The ionic viscosity of the epoxy resin composition takes a minimum value at the start of curing, increases with the progress of the curing reaction, and then saturates with the completion. In the present invention, the percentage of the ionic viscosity value at a certain point in time with respect to the ionic viscosity at the completion of the curing reaction (the highest value obtained by measurement) is calculated as a cure index (Cd), and Cd reaches 20%. The time up to was taken as the gelation start time.

<Method of manufacturing resin cured plate>
The epoxy resin composition was defoamed in vacuum and then poured into a mold set to a thickness of 2 mm or 6 mm using a “Teflon®” spacer. Next, the temperature was raised from room temperature to 150 ° C. in a hot air oven by 2.5 ° C. for 1 minute, and then the temperature was maintained for 1 hour to cure the epoxy resin composition. Subsequently, the temperature was lowered to room temperature and the mold was removed from the mold to prepare a resin cured plate.

<Measurement method of glass transition temperature>
A test piece having a width of 12.7 mm and a length of 45 mm was cut out from a 2 mm thick resin cured plate, and a viscoelasticity measuring device (ARES, manufactured by TA Instruments) was used to obtain a torsional vibration frequency of 1.0 Hz. DMA measurement was performed in a temperature range of 30 to 250 ° C. under the condition of a heating rate of 5.0 ° C./min. The glass transition temperature (Tg) was defined as the temperature at the intersection of the tangent in the glass state and the tangent in the transition state in the storage elastic modulus G'curve.

<Measurement method of tensile elongation at break of epoxy resin cured product>
After cutting out from a 2 mm thick resin cured plate into a 1BA type dumbbell shape conforming to JIS K7161 (1994), set the chuck distance to 58 mm using an Instron universal testing machine (manufactured by Instron). , A tensile test was carried out at a test speed of 1 mm / min, and the tensile elongation at break was measured.

<Method for measuring fracture toughness of cured resin>
It was carried out according to the SENB (Single Edge Noched Bend) test method based on ASTM D5045. A test piece having a length of 60 mm and a width of 12.7 mm was cut out from a resin cured plate having a thickness of 6 mm, and then a pre-crack was introduced. Then, using an Instron universal testing machine (manufactured by Instron), the span spacing was 50.8 mm, the crosshead speed was 10 mm / min, the number of samples was n = 6, and the fracture toughness value ( _KIC ) was measured.

<Measurement method of water absorption rate of cured resin>
A resin cured plate processed to a thickness of 2 mm, a length of 60 mm, and a width of 10 mm is vacuum-dried at 60 ° C. for 24 hours, and then allowed to stand for 7 days under moist heat conditions of a temperature of 85 ° C. and a humidity of 95% RH. did. The water absorption rate was defined as the percentage of the mass change after exposure to moist heat conditions with respect to the dry mass of the test piece.

<How to make tow preg>
An epoxy resin composition adjusted to a temperature of 20 to 60 ° C. was applied to one side of the carbon fiber "Treca (registered trademark)" T720SC-36K using a tow preg manufacturing apparatus equipped with a creel, a kiss roll, a nip roll, and a winder. After that, the epoxy resin composition was impregnated into the inside of the reinforcing fiber bundle by passing it through a nip roll to obtain a tow preg having a resin content of 25% by mass. The bobbin of the tow preg was wound on a paper tube with an initial tension of 600 to 1,000 gf and a wind ratio of 6 to 10 so as to have a cylindrical shape with a winding width of 230 to 260 mm.

<Measurement method of glass transition temperature of fiber reinforced composite material (CFRP)>
First, the tow preg prepared according to the above <method for producing tow preg> is wound in one direction on a metal frame, and then sandwiched between a 20 mm wide mold set to have a thickness of 2 mm by a metal spacer. The die was heated at 150 ° C. for 1 hour using a press machine to cure the epoxy resin composition to prepare a fiber-reinforced composite flat plate.

Subsequently, a test piece having a width of 12.7 mm and a length of 45 mm was cut out from a 2 mm-thick fiber-reinforced composite flat plate, and torsionally vibrated using a viscoelasticity measuring device (ARES, manufactured by TA Instruments). DMA measurement was performed in a temperature range of 30 to 250 ° C. under the conditions of a frequency of 1.0 Hz and a heating rate of 5.0 ° C./min. The glass transition temperature (Tg) was defined as the temperature at the intersection of the tangent in the glass state and the tangent in the transition state in the storage elastic modulus G'curve.

(Example 1)
81.5 parts by mass of "jER (registered trademark)" 828 as component [A], 10 parts by mass of "jER (registered trademark)" 806, and 13 "Kaneace (registered trademark)" MX-257 as component [B]. .5 parts by mass (consisting of 8.5 parts by mass of epoxy resin which is one kind of component [A] and 5 parts by mass of component [B]), 4 parts by mass of "hypro (registered trademark)" CTBN1300X13 as component [C] , 4.4 parts by mass of "jER Cure (registered trademark)" DICY7 as component [D], 2.3 parts by mass of "Omicure (registered trademark)" 24 as component [E], and "BYK (registered)" as other additives. An epoxy resin composition was prepared according to the above <Method for preparing an epoxy resin composition> using 0.5 parts by mass of "1790". The viscosity of this epoxy resin composition at 25 ° C. was 21 Pa · s, and the gelation time at 150 ° C. was 3.1 minutes. The tensile elongation at break of the cured resin was 6.7%, the fracture toughness value ( _KIC ) was 2.3 MPa · m ^0.5 , the water absorption was 4.1%, and the glass transition temperature was 125 ° C. rice field.

Next, using this epoxy resin composition, a tow preg was obtained according to the above <method for producing a tow preg>. The glass transition temperature of the fiber-reinforced composite material obtained by using this tow preg was 115 ° C.

As mentioned above, good results were obtained in all the tests.

(Examples 2 to 5)
As shown in Table 1, the resin composition was changed, and an epoxy resin composition and toupreg were prepared and evaluated by the same method as in Example 1. The evaluation results are the viscosity of the resin composition at 25 ° C, the gelation time at 150 ° C, the tensile elongation at break of the cured resin, the fracture toughness value ( _KIC ), the water absorption rate, the glass transition temperature, and the glass of the fiber-reinforced composite material. Good results were obtained at all transition temperatures.

(Examples 6 to 12)
As shown in Tables 1 and 2, the resin composition was changed so as to contain the component [F], and an epoxy resin composition and towpreg were prepared and evaluated by the same method as in Example 1. The evaluation results are the viscosity of the resin composition at 25 ° C, the gelation time at 150 ° C, the tensile elongation at break of the cured resin, the fracture toughness value ( _KIC ), the water absorption rate, the glass transition temperature, and the glass of the fiber-reinforced composite material. Good results were obtained at all transition temperatures. In particular, the component [F] further improved the heat resistance of the cured resin product and the fiber-reinforced composite material while maintaining excellent toughness. Further, in Examples 6 to 7 and 9 to 12, in which the content of the component [C] is 5 to 30 parts by mass with respect to 100 parts by mass of the total epoxy resin component, an excellent toughness improving effect and production of tow preg are produced. It was possible to achieve both suitable viscosities.

(Examples 13 to 18)
As shown in Table 2, the resin composition was changed so as to contain the component [A1], and an epoxy resin composition and towpreg were prepared and evaluated by the same method as in Example 1. The evaluation results are the viscosity of the resin composition at 25 ° C, the gelation time at 150 ° C, the tensile elongation at break of the cured resin, the fracture toughness value ( _KIC ), the water absorption rate, the glass transition temperature, and the glass of the fiber-reinforced composite material. Good results were obtained at all transition temperatures. In particular, the component [A1] can effectively reduce the viscosity of the epoxy resin composition without impairing the good balance of curing speed, toughness, and heat resistance, and is used in combination with the component [B] and the component [C]. By doing so, a specific effect of improving the tensile elongation at break and the toughness value was obtained as compared with the case where each component was used alone or when the two components were used in combination. Further, Examples 14 to 18 using a bifunctional epoxy resin having an alkylene skeleton having 4 to 10 carbon atoms as the component [A1] were able to suppress an increase in hygroscopicity of the cured resin product as compared with Example 13. ..

(Comparative Example 1)
As shown in Table 3, the resin composition was changed, and only the component [B] was used without using the component [B] and the component [C] in combination. As a result of preparing and evaluating an epoxy resin composition and tow preg by the same method as in Example 1, the fracture toughness value ( _KIC ) of the cured resin product was 1.7 MPa · m ^0.5 , which was insufficient.

(Comparative Example 2)
As shown in Table 3, the resin composition was changed, and only the component [C] was used without using the component [B] and the component [C] in combination. As a result of preparing and evaluating an epoxy resin composition and tow preg by the same method as in Example 1, the fracture toughness value ( _KIC ) of the cured resin was 1.8 MPa · m ^0.5 , which was insufficient.

(Comparative Example 3)
As shown in Table 3, the resin composition was changed and the component [B] and the component [C] were used in combination, but the mass ratio of the component [B] to the component [C] was 0.03, which was 0.1. Also made smaller. As a result of preparing and evaluating an epoxy resin composition and tow preg by the same method as in Example 1, the fracture toughness value ( _KIC ) of the cured resin product was 1.7 MPa · m ^0.5 , which was insufficient.

(Comparative Example 4)
As shown in Table 3, the resin composition was changed and the component [B] and the component [C] were used in combination, but the mass ratio of the component [B] to the component [C] was 1.0 and 0.8. Also made larger. As a result of preparing and evaluating an epoxy resin composition and _towpreg by the same method as in Example 1, the fracture toughness value (KIC) of the cured resin was 2.7 MPa · m ^0.5 , which was an excellent value. The glass transition temperature of the cured resin product was 109 ° C., and the glass transition temperature of the fiber-reinforced composite material was 96 ° C., which were insufficient.

(Comparative Example 5)
As shown in Table 3, the resin composition was changed so that the ratio of the number of moles of active hydrogen of dicyandiamide to the number of moles of the total epoxy group was 0.30, which was smaller than 0.4. As a result of preparing and evaluating an epoxy resin composition and tow preg by the same method as in Example 1, the gelation time at 150 ° C. was as long as 7.1 minutes, and the fracture toughness value ( _KIC ) of the cured resin product was 1.6 MPa. The glass transition temperature of the ^cured resin product was 112 ° C, and the glass transition temperature of the fiber-reinforced composite material was 97 ° C, which were insufficient.

(Comparative Example 6)
As shown in Table 3, the resin composition was changed so that the ratio of the number of moles of active hydrogen of dicyandiamide to the number of moles of the total epoxy group was 0.63, which was larger than 0.53. As a result of preparing and evaluating an epoxy resin composition and tow preg by the same method as in Example 1, the gelation time at 150 ° C. was 4.2 minutes, and the glass transition temperature of the cured resin product was 130 ° C., showing excellent values. However, the glass transition temperature of the fiber-reinforced composite material was as low as 96 ° C, which was insufficient.

(Comparative Example 7)
As shown in Table 3, the resin composition was changed to make the ratio of the number of moles of urea groups to the number of moles of total epoxy groups 8 and smaller than 15. As a result of preparing and evaluating an epoxy resin composition and tow preg by the same method as in Example 1, the gelation time at 150 ° C. showed an excellent value of 1.2 minutes, but the glass transition temperature of the cured resin product was 105. The temperature was low at ℃, which was insufficient.

(Comparative Example 8)
As shown in Table 3, the resin composition was changed so that the ratio of the number of moles of urea groups to the number of moles of total epoxy groups was 65, which was larger than 55. As a result of preparing and evaluating an epoxy resin composition and towpreg by the same method as in Example 1, the gelation time at 150 ° C. was as long as 8.3 minutes, which was insufficient. The glass transition temperature of the cured resin product was 133 ° C., which was an excellent value, but the glass transition temperature of the fiber-reinforced composite material was 104 ° C., which was insufficient.

Claims (11)

An epoxy resin composition containing all of the following components [A] to [E] and satisfying all of the conditions (I) to (III).
[A] Bifunctional epoxy resin liquid at 25 ° C. [B] Core-shell rubber particles [C] carboxyl group-terminated butadiene nitrile rubber [D] dicyandiamide [E] aromatic urea (I) number of active hydrogen moles of dicyandiamide / total epoxy group Number of moles = 0.40 to 0.53
(II) Number of moles of all epoxy groups / number of moles of urea groups = 15 to 55
(III) Mass of carboxyl group-terminated butadiene nitrile rubber / mass of core-shell rubber particles = 0.1 to 0.8 The epoxy resin composition according to claim 1, wherein the content of the component [B] is 5 to 30 parts by mass with respect to 100 parts by mass of the total epoxy resin. The epoxy resin composition according to claim 1 or 2, which satisfies the following condition (IV).
(IV) Number of moles of urea group / Number of moles of active hydrogen of dicyandiamide = 0.035 to 0.17 The epoxy resin composition according to any one of claims 1 to 3, which has a viscosity at 25 ° C. of 1 to 150 Pa · s. The epoxy resin composition according to any one of claims 1 to 4, wherein the cured resin has a glass transition temperature of 120 to 160 ° C. The epoxy resin composition according to any one of claims 1 to 5, which contains the following component [F] in an amount of 3 to 40 parts by mass in 100 parts by mass of the total epoxy resin.
[F] At least one epoxy resin selected from the group consisting of a biphenyl type epoxy resin, a biphenyl aralkyl type epoxy resin, a dicyclopentadiene type epoxy resin and an oxazolidone type epoxy resin. The epoxy resin composition according to any one of claims 1 to 6, wherein the following component [A1] is contained as the component [A] in an amount of 3 to 20 parts by mass in 100 parts by mass of the total epoxy resin.
[A1] Aliphatic epoxy resin The epoxy resin composition according to claim 7, wherein the component [A1] contains a bifunctional epoxy resin having an alkylene skeleton having 4 to 10 carbon atoms. An intermediate base material obtained by impregnating a reinforcing fiber with the epoxy resin composition according to any one of claims 1 to 8. A tow preg obtained by impregnating a reinforcing fiber with the epoxy resin composition according to any one of claims 1 to 8. A fiber-reinforced composite material obtained by curing the intermediate substrate according to claim 9 or 10.