JP2022102349A - Resin composition for fiber-reinforced composite material, and fiber-reinforced composite material using the same - Google Patents

Abstract

To provide a resin composition for a fiber-reinforced composite material which is excellent in fracture toughness without impairing low viscosity and heat resistance, and a method for producing the same.SOLUTION: A two-pack type resin composition is composed of a main agent of an epoxy resin, and a curing agent, in which the main agent contains 30 wt.% or more of an epoxy resin (A) such as a bisphenol F type epoxy resin and a phenol novolac type epoxy resin, the curing agent contains 70 wt.% or more of an alicyclic diamine compound (B) represented by the following formula (2), a blending ratio of the main agent to the curing agent (weight of curing agent/active hydrogen equivalent of curing agent)/(weight of main agent/epoxy equivalent of main agent) is in a range of 0.90-1.30, and fracture toughness (K1c) of a cured product when cured at 150°C for 2 hours is 1.5 MPa/√m or more. In the formula (2), R1 and R2 independently represent H and CH3.SELECTED DRAWING: None

Description

The present invention relates to a resin composition for a fiber-reinforced composite material having low viscosity and excellent breaking toughness, a fiber-reinforced composite material using the same, and a method for producing a fiber-reinforced molded body using the same.

Fiber reinforced composite materials generally include reinforced fibers such as glass fiber, aramid fiber and carbon fiber, and heat such as unsaturated polyester resin, vinyl ester resin, epoxy resin, phenol resin, benzoxazine resin, cyanate resin and bismaleimide resin. Since it is composed of a curable matrix resin and is lightweight and has excellent mechanical properties such as strength, corrosion resistance and fatigue resistance, it is widely applied as a structural material for aircraft, automobiles, civil engineering and construction and sporting goods.

In recent years, due to growing environmental problems, conventional internal combustion engines that use gasoline, internal combustion engines that use natural gas with a lower environmental load, and fuel cell vehicles that use hydrogen gas that does not emit carbon dioxide have been put into practical use. ing. A pressure vessel in which a tank liner is reinforced with a fiber-reinforced composite material is used for a storage tank for natural gas or hydrogen gas mounted on a moving body such as an automobile because of its light weight. Glass fiber, carbon fiber, etc. can be used as the reinforcing fiber used here, but among them, carbon fiber has a high specific strength and has a great merit of reducing the weight of the pressure vessel, and is required to have higher pressure resistance than the natural gas storage tank. It is suitably used for storage tanks for hydrogen gas. The fiber-reinforced composite material used in this storage tank is required to have fiber strength, and the matrix resin is also required to have high fracture toughness and heat resistance.

The method for producing these fiber-reinforced composite materials is an autoclave molding method or a press molding method using a prepreg in which a thermosetting matrix resin is pre-impregnated in the reinforcing fibers, and a tow prepreg impregnated with the matrix resin is wound around a liner. It is carried out by a method such as a filament winding molding method for curing, a resin transfer molding method including a step of impregnating a reinforcing fiber with a liquid matrix resin and a molding step by thermosetting. Of these, the resin transfer molding method, in which impregnation and molding are performed without using a prepreg, is being studied as a molding method for improving productivity because the molding speed can be increased.

In this resin transfer molding method, in order to ensure high productivity, the viscosity of the matrix resin is required to be sufficiently low at the filling temperature in order to quickly impregnate the reinforcing fibers. Further, since it is required that the reinforcing fibers are impregnated with the matrix resin and then rapidly cured in order to increase the productivity, a matrix resin having a high curing rate is required. Furthermore, these molding methods include a step of removing the molded product from the mold after curing, and in order to ensure high productivity, a matrix that not only has a high curing speed but also has excellent mold removal properties. A resin composition is required.

Conventionally, in the resin transfer molding method, thermosetting resins such as unsaturated polyester resin, vinyl ester resin, urethane resin and epoxy resin have been used. Although unsaturated polyester resin and vinyl ester resin having radical polymerizable properties have low viscosity and excellent quick-curing property, they have a large curing shrinkage during molding, and the mechanical properties such as heat resistance, strength and toughness of the molded product are relatively good. There is a problem that it is low. Urethane resin is excellent in quick-curing property, and although a molded product having high strength and toughness can be obtained, there are problems that the heat resistance of the molded product is low and the water absorption rate is high. Epoxy resin has a problem that the curability is slow and the fracture toughness is not sufficient.

Although Patent Documents 1 and 2 make efforts to impart fast-curing properties of the resin composition by combining an epoxy resin and a specific phenol compound, the matrix resin of the fiber-reinforced composite material used for the storage tank is used. There is no description as to whether it has sufficient breaking toughness.

Patent Document 3 proposes a method of adding a high toughness polymer compound such as a thermoplastic resin or rubber particles to the matrix resin as a method of increasing the fracture toughness of the matrix resin. However, although the toughness is increased by adding the polymer compound, the viscosity of the matrix resin composition is increased, so that it is difficult to apply to the resin transfer molding method and the liquid compression molding method.

Patent Document 4 proposes an epoxy resin that is excellent in resin impregnation property because the viscosity increase is small at a relatively low temperature of 60 ° C. or lower, and is a cured product that can be demolded in a short time within 1 hour. However, the purpose of this epoxy resin composition is to obtain a molded product with excellent design and high surface smoothness, and it has sufficient fracture toughness as a matrix resin of a fiber reinforced composite material used for a storage tank. There is no description as to whether it is.

Patent Document 5 describes that a curable composition containing an epoxy resin, an open chain polyamine, and an amine compound having a methylenebiscyclohexyl structure has high fracture toughness. However, since the fracture toughness shown in the examples is about 1.0 MPa / √m, it is insufficient to be used as a matrix resin for a fiber-reinforced composite material used in a storage tank, and a matrix having higher fracture toughness. Resin is required.

WO2019 / 171991 Japanese Patent No. 5576789 Japanese Unexamined Patent Publication No. 8-27360 Japanese Unexamined Patent Publication No. 2009-102563 Japanese Patent No. 6312711

An object of the present invention is to provide a resin composition for a fiber-reinforced composite material having excellent fracture toughness without impairing low viscosity and heat resistance. Further, it is an object of the present invention to provide a resin composition or a production method capable of obtaining a fiber-reinforced composite material and a fiber-reinforced molded product with high productivity.

As a result of studies to solve the above-mentioned problems, the present inventors have solved the above-mentioned problems by using a main agent containing an epoxy resin having a specific structure and an amine compound having a specific structure as a curing agent. It was found that the present invention was completed.

（式中、ｎは０以上の整数を表し、０～５である）

（式中、Ｒ_１、Ｒ_２は独立にＨ、ＣＨ_３を表す） That is, it is a two-component resin composition composed of a main agent of an epoxy resin and a curing agent, and the main agent contains 30% by weight or more of the epoxy resin (A) represented by the following formula (1), and the curing agent is Contains 70% by weight or more of the alicyclic diamine compound (B) represented by the following formula (2), and the blending ratio of the main agent and the curing agent (weight of the curing agent / active hydrogen equivalent of the curing agent) / (weight of the main agent / The epoxy equivalent of the main agent) is in the range of 0.90 to 1.30, and the breaking toughness (K1c) of the cured product when cured at 150 ° C. for 2 hours is 1.5 MPa / √m or more. It is a resin composition for a fiber-reinforced composite material.

(In the formula, n represents an integer of 0 or more and is 0 to 5)

(In the formula, R ₁ and R ₂ independently represent H and CH ₃ )

The resin composition for a fiber-reinforced composite material of the present invention is characterized in that the glass transition temperature of the cured product when cured at 150 ° C. for 2 hours is 120 ° C. or higher.

Another embodiment of the present invention is a fiber-reinforced composite material characterized by blending reinforcing fibers with the resin composition for a fiber-reinforced composite material. In this case, the volume content of the reinforcing fibers is preferably 45 to 70%.

The present invention is a method for producing a molded product, which comprises molding the fiber-reinforced composite material by a resin transfer molding method or a liquid compression molding method.

The resin composition for a fiber-reinforced composite material of the present invention has a low viscosity, good impregnation into reinforcing fibers, and exhibits curability in a relatively short time. Therefore, it is suitable as a resin composition for a fiber-reinforced composite material used for forming a fiber-reinforced composite material into a molded product by a resin transfer molding method. Further, the molded product obtained by curing has high fracture toughness and a high glass transition temperature.

Hereinafter, embodiments of the present invention will be described in detail.
The resin composition for a fiber-reinforced composite material of the present invention is made into a fiber-reinforced composite material by blending the reinforcing fibers with the resin composition, and by curing or molding the fiber-reinforced composite material, a cured product or a molded product is obtained. Hereinafter, the resin composition for a fiber-reinforced composite material is also referred to as a resin composition, and the fiber-reinforced composite material is also referred to as a composite material.

The resin composition of the present invention comprises a main agent containing an epoxy resin (A) represented by the above formula (1) and a curing agent containing an alicyclic diamine compound (B) represented by the above formula (2). It is a liquid-curable resin composition.

The epoxy resin used as the main agent component contains a bifunctional or higher functional epoxy resin (A) represented by the above formula (1) as an essential component. Specific examples thereof include bisphenol F type epoxy resin and phenol novolac type epoxy resin. These may be used alone or in combination of two or more.

In addition to the epoxy resin (A) represented by the formula (1), other epoxy resins can be added to the main agent, if necessary. Specifically, bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol E type epoxy resin, bisphenol S type epoxy resin, bisphenol Z type epoxy resin, and isophoron bisphenol type epoxy resin, and halogens of these bisphenol type epoxy resins, In addition to alkyl substituents and hydrides, high molecular weight bodies having multiple repeating units, not limited to monomers, glycidyl ethers with alkylene oxide adducts, cresol novolak type epoxy resins, bisphenol A novolak type epoxy resins, and other novolak Type epoxy resin, 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 1, -Alicyclic epoxy resins such as epoxyethyl-3,4-epoxycyclohexane, aliphatic epoxy resins such as trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, and polyoxyalkylene diglycidyl ether, and diglycidyl phthalate. Epoxy, tetrahydrophthalic acid diglycidyl ester, glycidyl ester such as dimer acid glycidyl ester, tetraglycidyl diaminodiphenylmethane, tetraglycidyl diaminodiphenyl sulfone, triglycidyl aminophenol, triglycidyl aminocresol, tetraglycidyl xylylene diamine and the like. Examples include amines.

The main agent needs to contain 30% by weight or more of the epoxy resin (A) represented by the above formula (1). If the epoxy resin represented by the above formula (1) is less than 30% by weight, the fracture toughness (K1c) becomes low, and the performance as a fiber-reinforced composite material cannot be guaranteed. It is preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 70% by weight or more.

The curing agent component contains an alicyclic diamine compound (B) having a methylenebiscyclohexyl structure represented by the above formula (2) as an essential component. Specifically, it is 4,4'-methylenebis (cyclohexylamine) or 4,4'-methylenebis (2-methylcyclohexylamine). These diamine compounds may contain 2,4'-and 2,2'-isomers. Further, these may be used alone or in combination of two or more.

The curing agent containing the alicyclic diamine compound (B) can include an amine compound having another alicyclic structure. Specifically, there are isophoronediamine, bis (aminomethyl) -bicyclo [2.2.1] heptane, 1,2-cyclohexanediamine, 1,3-bisaminomethylcyclohexane and the like.

The curing agent needs to contain 70% by weight or more, preferably 90% by weight or more of the alicyclic diamine compound (B) represented by the above formula (2). If the alicyclic diamine compound (B) is less than 70% by weight, the fracture toughness (K1c) becomes low, and the performance as a fiber-reinforced composite material for a storage tank cannot be guaranteed.

The resin composition of the present invention is a two-component type of a main agent and a curing agent. The blending ratio of the main agent and the curing agent is determined by the ratio of the number of moles of the epoxy group in the main agent and the number of moles of the active hydrogen in the curing agent. This compounding ratio is indicated by a value calculated by (weight of curing agent / active hydrogen equivalent of curing agent) / (weight of main agent / epoxy equivalent of main agent) (hereinafter referred to as equivalent ratio), and the range of this value is 0. It needs to be .90 to 1.30, preferably 0.95 to 1.25, and more preferably 1.00 to 1.20. If this value is less than 0.90, the fracture toughness of the resin and the glass transition temperature tend to be low, and if it exceeds 1.30, the fracture toughness tends to be high but the glass transition temperature tends to be low.

The viscosity (25 ° C.) of the main agent is preferably 8500 mPa · s or less, more preferably 6500 mPa · s or less, and further preferably 3000 mPa · s or less. The viscosity (25 ° C.) of the curing agent is preferably 300 mPa · s or less, more preferably 200 mPa · s or less, still more preferably 150 mPa · s or less.
This is to make it easier to fill the resin in the fiber in the resin transfer molding method and the liquid compression molding method described later, and if the viscosity exceeds the above-mentioned viscosity, the viscosity after mixing the main agent and the curing agent also increases, so that the resin becomes It is not preferable because it causes poor filling in the fiber and further, poor filling in the molding die.

The resin composition of the present invention may contain other curing agent components, curing accelerators, or curing catalysts, if necessary. Examples of the other curing agent component, curing accelerator, and curing catalyst include tertiary amine, carboxylic acid, sulfonic acid, Lewis acid complex, onium salt, alcohols, phenol, phenol novolac, cresol, cresol novolak, and allylphenol. , Nitrophenol, paraaminophenol, metaaminophenol, mono-t-butylphenol, di-t-butylphenol and other compounds having one phenolic hydroxyl group. For these, one kind or two or more kinds may be used.

Other components such as plasticizers, dyes, organic pigments and inorganic fillers, polymer compounds, coupling agents, surfactants and solvents can be appropriately added to the main agent and the curing agent. When these are blended, they are blended in either the main agent or the curing agent in consideration of reactivity. However, if both the main agent and the curing agent are not reactive, they can be blended in either the main agent or the curing agent.

The resin composition of the present invention may also contain a curable resin different from the epoxy resin. Examples of such curable resins include unsaturated polyester resins, curable acrylic resins, curable amino resins, curable melamine resins, curable urea resins, curable cyanate ester resins, curable urethane resins, and curable oxetane resins. Examples thereof include, but are not limited to, a curable epoxy / oxetane composite resin. These can be blended in any of them in consideration of the reactivity with the components contained in the main agent and the curing agent, the viscosity and the like.

The resin composition of the present invention preferably has a glass transition temperature of 120 ° C. or higher when cured at 150 ° C. for 2 hours. If the glass transition temperature is less than 120 ° C., deformation is likely to occur when the mold is removed from the mold during molding.

The resin composition of the present invention has a fracture toughness (K1c) of 1.5 MPa / √m or more when cured at 150 ° C. for 2 hours. It is useful as a matrix resin used as a fiber-reinforced composite material for hydrogen gas storage tanks and the like. The fracture toughness (K1c) of the cured product is preferably 1.7 MPa / √m or more.

The reinforcing fiber used in the fiber-reinforced composite material of the present invention is selected from glass fiber, aramid fiber, carbon fiber and the like, but it is preferable to use carbon fiber in order to obtain a fiber-reinforced composite material having excellent strength. ..

The fiber-reinforced composite material of the present invention contains the above resin composition and reinforcing fibers. The volume content of the reinforcing fiber in the fiber-reinforced composite material is preferably in the range of 30 to 75%, more preferably 45 to 75%. Within this range, a molded product having few voids and a high volume content of the reinforcing fibers can be obtained, so that a molding material having excellent strength can be obtained.

The fiber-reinforced composite material is preferably cured by injecting the main agent into a mold or the like in which fibers are arranged in advance at a temperature in the range of 50 to 90 ° C. and a curing agent in the temperature range of 20 to 60 ° C. Primary curing is performed by heating and curing at 100 to 140 ° C. for 5 to 15 minutes, preferably 7 to 10 minutes. After the completion of the primary curing, the molded product is taken out from the mold, and then post-cured at a temperature of 120 to 160 ° C., preferably 140 to 150 ° C. for 10 to 120 minutes, preferably 15 to 30 minutes. The desired fiber-reinforced composite material can be obtained. At this time, the main agent and the curing agent may be injected into the mold at the same time within the range of the above-mentioned compounding ratio, but in order to improve the uniformity, it is desirable to mix them immediately before injection. However, it may be poured into the mold without mixing and mixed in the presence of fibers. The mixing method is not particularly limited, such as collision mixing and static mixer method, but a collision mixing method that completes uniform mixing in a short time is preferable.
Further, if the temperature at which the resin is injected into the mold is too low, the fluidity decreases, and poor filling into the mold and fibers occurs, which is not preferable. On the other hand, if the injection temperature is high, burrs will occur, or the resin will start to cure at the time of injection, and the resin will cure faster in the tank or molding mold. It is not preferable because it causes defects. Further, if the molding time including the primary curing time in the mold is too short, the molded product is not sufficiently filled, and further, the molded product may be deformed at the time of demolding due to poor curing, and if it is too long, the productivity is lowered. Not preferable because it happens. If the post-curing temperature is too low, curing does not proceed sufficiently, and the predetermined mechanical properties and glass transition temperature may not be exhibited, and if it is too high, oxidative deterioration and thermal deterioration of the resin may occur.

The method for producing the fiber-reinforced composite material or the molded product from the resin composition of the present invention is not particularly limited, but a resin transfer molding method or a liquid compression molding method is preferable.
In the resin transfer method, a fiber base material or preform made of reinforcing fibers is placed in a molding die, and a liquid resin composition for a fiber-reinforced composite material is injected into the molding die to impregnate the reinforcing fibers. This is a method in which a fiber-reinforced composite material is obtained and then heated to cure the fiber-reinforced composite material to obtain a molded product. As the curing conditions, the conditions described in the above-mentioned curing of the resin composition are suitable.
The liquid compression molding method is to impregnate and mold by installing a fiber base material or preform made of reinforcing fibers that have been preliminarily blended with resin in the molding die with the molding pressure released, and then molding the molding die. This is a method of obtaining a molded product by simultaneously performing the process to obtain a fiber-reinforced composite material and then heating a mold to cure the fiber-reinforced composite material. As the curing conditions of the liquid compression molding method, the conditions described in the above-mentioned curing of the resin composition are also suitable.

Next, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded. The portion indicating the blending amount is a mass portion unless otherwise specified.

The abbreviations of each component used in Examples and Comparative Examples are as follows.
YD-127: Bisphenol A type epoxy resin (manufactured by Nittetsu Chemical & Materials Co., Ltd.)
YDF-1500: Bisphenol F type epoxy resin (manufactured by Nittetsu Chemical & Materials Co., Ltd.)
PACM: 4,4'-methylenebis (cyclohexylamine)
MACM: 4,4'-methylenebis (2-methylcyclohexylamine)
NBDA: Bis (aminomethyl) -bicyclo [2.2.1] heptane (also known as norbornane diamine)

The measurement or test method for each physical property is as follows.
(Epoxy equivalent)
Measurements were carried out in accordance with JIS K7236.
(Active hydrogen equivalent in the curing agent)
After determining the amine value by a method according to JIS K7234, the active hydrogen equivalent was calculated.
(viscosity)
The viscosities of the main agent and the curing agent were measured at 25 ° C. using an E-type viscometer cone plate type (manufactured by Toki Sangyo: RE80H), and the value 60 seconds after the start of the measurement was taken as the viscosity value.
(Mechanical characteristics)
Measurements were carried out in accordance with JIS K7162.
(Fracture toughness)
Measurements were performed according to ASTM D5045.
(Glass-transition temperature)
According to JIS K7121, the measurement was performed twice in a temperature range of 20 to 200 ° C. and a heating rate of 20 ° C./min, and the second measured value was taken as the glass transition temperature.

Example 1
100 g of YDF-1500 as the main agent and 31.1 g of PACM as the curing agent were taken in a plastic container, and stirring was carried out at 2000 rpm for 20 seconds using a rotation / revolution vacuum mixer. The obtained resin composition was poured into a mold having a space of 160 mm × 160 mm × 2 mm thick preheated to 150 ° C. in advance in an oven, and the cured product was obtained as it was at 150 ° C. for 2 hours. Test pieces were cut out from the obtained cured product plate using a CNC milling machine, and each measurement was carried out. The results are shown in Table 1.

Examples 2-8
A cured product was prepared and measured in the same procedure as in Example 1 except that the resin composition was blended at the blending ratio shown in Table 1. The results are shown in Table 1.

Example 9
A cured product was prepared and measured in the same procedure as in Example 1 except that the curing conditions were set to 150 ° C. for 20 minutes. The results are shown in Table 1.

Comparative Examples 1 to 6
A cured product was prepared and measured in the same procedure as in Example 1 except that the resin composition was blended at the blending ratio shown in Table 2. The results are shown in Table 2.

Claims (6)

A two-component resin composition consisting of an epoxy resin main agent and a curing agent, wherein the main agent contains 30% by weight or more of the epoxy resin (A) represented by the following formula (1), and the curing agent is the following formula. It contains 70% by weight or more of the alicyclic diamine compound (B) represented by (2), and the compounding ratio of the main agent and the curing agent (weight of the curing agent / active hydrogen equivalent of the curing agent) / (weight of the main agent / of the main agent). The epoxy equivalent) is in the range of 0.90 to 1.30, and the breaking toughness (K1c) of the cured product when cured at 150 ° C. for 2 hours is 1.5 MPa / √ m or more. Resin composition for fiber-reinforced composite materials.

(In the formula, n represents an integer of 0 or more and is 0 to 5)

(In the formula, R ₁ and R ₂ independently represent H and CH ₃ ) The resin composition for a fiber-reinforced composite material according to claim 1, wherein the glass transition temperature of the cured product when cured at 150 ° C. for 2 hours is 120 ° C. or higher. A fiber-reinforced composite material, which comprises blending reinforcing fibers with the resin composition for a fiber-reinforced composite material according to claim 1 or 2. The fiber-reinforced composite material according to claim 3, wherein the volume content of the reinforcing fibers is 30 to 75%. A cured product of the fiber-reinforced composite material according to claim 3 or 4. A method for producing a molded product, which comprises molding the fiber-reinforced composite material according to claim 3 or 4 by a resin transfer molding method or a liquid compression molding method.