JP7139572B2 - Epoxy resin compositions, fiber reinforced composites, moldings and pressure vessels - Google Patents

Description

The present invention relates to epoxy resin compositions, fiber reinforced composites, moldings and pressure vessels.

Epoxy resins are widely used in industrial fields such as paints, adhesives, electrical and electronic information materials, and advanced composite materials, taking advantage of their excellent mechanical properties. In particular, epoxy resins are frequently used in fiber-reinforced composite materials composed of reinforcing fibers such as carbon fibers, glass fibers, and aramid fibers and matrix resins.

As a method for manufacturing the fiber-reinforced composite material, a construction method such as a prepreg method, a hand lay-up method, a filament winding method, a pultrusion method, an RTM (Resin Transfer Molding) method, or the like is appropriately selected. Among these construction methods, the filament winding method, the pultrusion method, and the RTM method, which use liquid resin, have been actively applied to industrial applications such as pressure vessels, electric wires, and automobiles.

In general, fiber-reinforced composite materials produced by the prepreg method exhibit excellent mechanical properties because the arrangement of reinforcing fibers is precisely controlled. On the other hand, in response to the growing interest in the environment in recent years and the movement to control greenhouse gas emissions, there is a demand for even higher strength in fiber-reinforced composite materials using liquid resins other than prepregs.

Patent Literature 1 discloses a resin for filament winding that uses acrylamide or phthalimide to increase adhesion to reinforcing fibers, thereby providing a fiber-reinforced composite material with excellent torsional strength.

Patent Document 2 discloses a resin for RTM that uses a substituted phenylglycidyl ether and provides a fiber-reinforced composite material with excellent workability and mechanical strength.

Patent Document 3 discloses a resin composition that uses substituted phenylglycidyl ether and nanosilica fine particles to improve elastic modulus and heat resistance.

Patent Document 4 discloses a resin composition for RTM that uses an alicyclic amine compound and a reactive catalyst and can be cured at low temperature for a short period of time.

Patent Document 5 discloses an epoxy resin composition containing a monofunctional epoxy resin, a polyfunctional epoxy resin and a core-shell polymer and having excellent elastic modulus and fracture toughness.

Patent Document 6 discloses a prepreg resin composition that contains a monofunctional epoxy having a biphenyl skeleton and provides a fiber-reinforced composite material having excellent strength and elongation.

US Pat. No. 5,300,001 discloses low viscosity epoxy resin compositions using monofunctional epoxies as reactive diluents.

JP-A-2000-212254 JP 2005-120127 A JP 2010-174073 A Japanese Patent Publication No. 2015-508125 JP 2011-46797 A JP 2006-265458 A Japanese Patent Publication No. 2009-521589

However, although Patent Document 1 improves torsional strength and compressive strength, the tensile strength utilization factor of the fiber-reinforced composite material cannot be said to be sufficient. Although Patent Document 2 discloses a resin having low viscosity and heat resistance, it cannot be said that the tensile strength utilization rate of the fiber-reinforced composite material is sufficient. Patent Document 3 is effective in improving compressive strength, but the utilization rate of tensile strength is not sufficient. Although the resin composition disclosed in Patent Document 4 can be cured at a low temperature, the tensile strength utilization factor of the fiber-reinforced composite material was not sufficient.

Furthermore, although Patent Document 5 is effective in improving impact resistance, the utilization rate of tensile strength was not sufficient. In Patent Document 6, although a fiber-reinforced composite material having excellent heat resistance can be obtained, the tensile strength utilization factor cannot be said to be sufficient. Although Patent Document 7 can obtain a low-viscosity resin composition, it cannot be said that the tensile strength utilization factor of the fiber-reinforced composite material is sufficient.

Furthermore, the resin compositions disclosed in Patent Documents 3 and 6 have high viscosity for prepreg and cannot be applied to processes using liquid resins.

Accordingly, the present invention provides an epoxy resin composition that has an appropriate curing rate and provides a fiber-reinforced composite material exhibiting excellent tensile strength utilization, and a fiber having excellent tensile strength utilization using the composition as a matrix resin. The object is to provide reinforced composites, moldings and pressure vessels.

As a result of intensive studies aimed at solving the above problems, the inventors of the present invention have found an epoxy resin composition having the following constitution, and have completed the present invention. That is, the epoxy resin composition of the present invention has the following constitution.

An epoxy resin composition containing the following components [A] to [C], wherein the component [B] is the following component [b1] and/or the following component [b2] and the following component [b1] and a bifunctional or higher aromatic epoxy resin other than the component [b2], the component [C] is the following component [c1] or the following component [c2], and the rotorless curing test An epoxy resin composition having a gel time of 15 to 100 minutes at 80° C. using a machine, and a cured product obtained by curing the epoxy resin composition having a rubber state elastic modulus of 10 MPa or less in dynamic viscoelasticity evaluation.
[A] A monofunctional epoxy resin that is a phenylglycidyl ether substituted with a tert-butyl group, sec-butyl group, isopropyl group, or phenyl group
[B] Bifunctional or higher aromatic epoxy resin
[b1] optionally substituted diglycidylaniline (wherein the substituent is a group selected from an alkyl group having 1 to 4 carbon atoms, a phenyl group and a phenoxy group).
[b2] Tetraglycidyldiaminodiphenylmethane [C] Curing agent [c1] Acid anhydride curing agent [c2] Aliphatic amine curing agent.

Also, the fiber-reinforced composite material of the present invention comprises a cured product of the epoxy resin composition and reinforcing fibers.

Further, the molded article and pressure vessel of the present invention are made of the fiber-reinforced composite material.

The epoxy resin composition of the present invention has an appropriate curing rate, and the fiber-reinforced composite material, molded article and pressure vessel of the present invention using the epoxy resin composition as a matrix resin exhibit excellent tensile strength utilization. have.

The epoxy resin composition of the present invention is an epoxy resin composition containing the following components [A] to [C], wherein the component [C] is the following component [c1] or the following component [c2]. A gel time at 80° C. measured by a rotorless curing tester is 15 to 100 minutes, and a cured product obtained by curing the epoxy resin composition has a rubber state elastic modulus of 10 MPa or less in dynamic viscoelasticity evaluation.
[A] Phenyl glycidyl ether substituted with a tert-butyl group, sec-butyl group, isopropyl group, or phenyl group [B] Difunctional or higher aromatic epoxy resin [C] Curing agent [c1] Acid anhydride curing Agent [c2] Aliphatic amine curing agent.

The epoxy resin composition of the present invention contains the constituent elements [A] to [C].

The phenylglycidyl ether substituted with any one of tert-butyl group, sec-butyl group, isopropyl group, or phenyl group, which is the constituent element [A] of the present invention, has an appropriate curing speed and excellent utilization of tensile strength. It is a necessary component to obtain a fiber-reinforced composite material with a high modulus. The tensile strength utilization rate is an index of how much the fiber-reinforced composite material utilizes the strength of the reinforcing fibers. Even among fiber composite reinforcing materials using the same type and amount of reinforcing fibers, the fiber reinforced composite material having a higher tensile strength utilization rate exhibits a higher tensile strength.
Examples of such phenylglycidyl ethers, that is, epoxy resins include o-phenylphenolglycidyl ether, p-tert-butylphenylglycidyl ether, p-sec-butylphenylglycidyl ether, p-isopropylphenylglycidyl ether, and the like. .

Component [B] is a bifunctional or higher functional epoxy resin containing an aromatic ring. A bifunctional or higher epoxy resin is a compound having two or more epoxy groups in one molecule. Examples of such epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, epoxy resin containing a dicyclopentadiene skeleton, fluorene type epoxy resin, Novolak type epoxy resins such as phenol novolak type epoxy resins and cresol novolak type epoxy resins, biphenylaralkyl type and Zyroc type epoxy resins, N,N,O-triglycidyl-m-aminophenol, N,N,O-triglycidyl -p-aminophenol, N,N,O-triglycidyl-4-amino-3-methylphenol, N,N,N',N'-tetraglycidyl-4,4'-methylenedianiline, N,N, glycidyl such as N',N'-tetraglycidyl-2,2'-diethyl-4,4'-methylenedianiline, N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline; Amine-type epoxy resins and the like are included. These may be used singly or in combination.

Component [C] is a curing agent and is component [c1] or component [c2] below.
[c1] Acid anhydride curing agent [c2] Aliphatic amine curing agent.

Component [c1] is an acid anhydride curing agent. An acid anhydride-based curing agent is a compound having one or more acid anhydride groups in the molecule. Acid anhydride curing agents include, for example, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, methylnadic anhydride, maleic anhydride, and succinic anhydride.

Component [c2] is an aliphatic amine curing agent. An aliphatic amine-based curing agent is a compound having one or more primary or secondary amino groups in its molecule. Examples of aliphatic amine curing agents include isophoronediamine, diethylenetriamine, triethylenetetramine, hexamethylenediamine, N-aminoethylpiperazine, 4,4′-methylenebiscyclohexylamine, 2,2′-dimethyl-4,4 '-methylenebiscyclohexylamine, cyclohexanediamine, 1,3-bisaminomethylcyclohexane, and aliphatic polyamines having an alkylene glycol structure. Alkylene glycol structures include polyoxyethylene, polyoxypropylene, copolymers of polyoxyethylene and polyoxypropylene, and the like.

The rubber state elastic modulus obtained by dynamic viscoelasticity evaluation of the cured product obtained by curing the epoxy resin composition of the present invention is 10 MPa or less. By setting the rubbery state elastic modulus within this range, the resulting fiber-reinforced composite material exhibits an excellent tensile strength utilization factor. In addition, in the present invention, the tensile strength of the fiber-reinforced composite material is evaluated by the tensile strength utilization factor. Here, the rubber state elastic modulus is an index that is correlated with the crosslink density, and generally, the lower the crosslink density, the lower the rubber state elastic modulus. The tensile strength utilization rate is indicated by the tensile strength of the fiber-reinforced composite material/(strand strength of reinforcing fiber x fiber volume content) x 100, and a high value indicates that the performance of the reinforcing fiber is being drawn out higher. It can be said that the weight reduction effect is large.

The gel time of the epoxy resin composition of the present invention at 80° C. measured by a rotorless curing tester (curastometer) is 15 to 100 minutes. Within this range, there is no retardation in the curing speed observed when a monofunctional epoxy is applied, and an epoxy resin cured product with excellent productivity can be obtained.

The epoxy resin composition of the present invention preferably contains 5 to 40 parts by mass of component [A] based on 100 parts by mass of the total epoxy resin. By setting the content of the component [A] within the above range, an epoxy resin composition that provides a fiber-reinforced composite material having an excellent balance between curing speed and tensile strength utilization can be obtained.

The epoxy resin composition of the present invention preferably contains two or more of the component [A]. Intermolecular motion is further suppressed by introducing steric hindrance of different structures or substitution positions.

In the epoxy resin composition of the present invention, the component [B] is preferably the following component [b1] or the following component [b2].
[b1] optionally substituted diglycidylaniline [b2] tetraglycidyldiaminodiphenylmethane.

Component [b1] is an optionally substituted diglycidylaniline. Examples of substituents include alkyl groups having 1 to 4 carbon atoms, phenyl groups, and phenoxy groups. Alkyl groups having 1 to 4 carbon atoms are preferable because they suppress the viscosity increase of the epoxy resin. Examples of such epoxy resins include diglycidylaniline, diglycidyltoluidine, N,N-diglycidyl-4-phenoxyaniline and the like.

Component [b2] is tetraglycidyldiaminodiphenylmethane.

Component [A] is preferable because, when combined with component [b1] or component [b2], both curing speed and tensile strength utilization rate can be achieved at a higher level, and heat resistance is also excellent. .

In the cured product of the epoxy resin composition, the aromatic ring of the component [b1] interferes with the tert-butyl group, sec-butyl group, isopropyl group, or phenyl group of the component [A] as a steric hindrance, and the molecule Limit chain movement. As a result, high heat resistance is exhibited even when the crosslink density derived from covalent bonds is low. In addition, component [b2] is a component that generally increases the crosslink density and improves heat resistance. Since this becomes a reaction and further steric hindrance, the motion of the molecular chain is restricted in a state where the crosslink density is low, similarly to the component [b1]. That is, the epoxy resin cured product cured by the combination of component [A], component [b1] or component [b2], and component [c1] or component [c2] has an appropriate curing speed. However, in addition to having a high tensile strength utilization rate, a fiber-reinforced composite material having excellent heat resistance can be obtained.

In the epoxy resin composition of the present invention, component [B] preferably contains component [b1] and component [b2] at the same time. It is easy to obtain a fiber-reinforced composite material which is excellent in workability as a liquid resin and which has an excellent balance among curing speed, heat resistance and tensile strength utilization rate.

The epoxy resin composition of the present invention further contains an epoxy resin other than the constituent elements [A], the constituent elements [b1], and the constituent elements [b2] within a range that does not impair the effects of the present invention, particularly within an allowable viscosity range. can contain Epoxy resins other than component [A], component [b1] and component [b2] are adjusted according to the purpose for the balance of mechanical properties, heat resistance, impact resistance, etc., and process suitability such as viscosity. and is preferably used.

Examples of such epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, aminophenol type epoxy resin, phenol novolac type epoxy resin, dicyclo Epoxy resins containing a pentadiene skeleton, phenylglycidyl ether type epoxy resins other than the component [A], reactive diluents having an epoxy group, and the like. These may be used singly or in combination.

Component [A] is a monofunctional epoxy resin having a substituent with high steric hindrance. A monofunctional epoxy suppresses the formation of a network and greatly reduces the crosslink density of the cured epoxy resin. That is, the rubber state elastic modulus can be greatly reduced, and the tensile strength utilization rate of the molded product is improved. On the other hand, ordinary monofunctional epoxies are slow to gel and slow to cure because they suppress network formation. Furthermore, the heat resistance of the cured resin is lowered. The reason why the component [A] suppresses the delay in the curing speed is not clear, but the steric hindrance group of the component [A] interferes with the network during the curing process, resulting in the formation of pseudo-crosslinks. , presumably to suppress the delay in curing rate seen in ordinary monofunctional epoxy resins. As a result, it is possible to achieve both an appropriate cure rate and a low rubbery state modulus, and to provide a fiber-reinforced composite material exhibiting excellent tensile strength utilization in a normal curing process.

That is, the epoxy resin composition of the present invention overcomes the problem that the lower the rubbery state elastic modulus, the higher the tensile strength utilization rate of the fiber-reinforced composite material, and the slower the curing rate.

The epoxy resin composition of the present invention preferably has a compressive shear strength of 50 to 120 MPa in a compression test of a cured product obtained by curing the epoxy resin composition. By setting the compressive shear strength within this range, the interlaminar shear failure of the fiber-reinforced composite material made of the epoxy resin composition is suppressed, which is preferable. In particular, in a pressure vessel made of a fiber-reinforced composite material, the interlaminar shear fracture between the helical layer and the hoop layer is suppressed, which is preferable.

Here, the compressive shear strength is obtained by cutting out a test piece having a thickness of 6 mm, a width of 6 mm, and a length of 6 mm from the epoxy resin cured product, and performing a compression test at a test speed of 1.0 mm/min using a universal testing machine, according to JIS K7181. (1994), the compressive yield stress is measured and divided by two.

In the epoxy resin composition of the present invention, the component [A] is preferably phenylglycidyl ether substituted with a tert-butyl group or a sec-butyl group. The tert-butyl group or sec-butyl group, which is a substituent, is likely to interfere with the epoxy network and has a greater effect as a steric hindrance group. It becomes easier to obtain a fiber-reinforced composite material having an excellent tensile strength utilization rate.

In the epoxy resin composition of the present invention, component [C] is preferably component [c1]. The acid anhydride-based curing agent, which is the component [c1], is preferable because it can achieve both low viscosity of the epoxy resin composition and heat resistance of the cured resin in a well-balanced manner.

Acid anhydride curing agents include, for example, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, methylendomethylenetetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, methylbicyclo heptanedicarboxylic anhydride, bicycloheptanedicarboxylic anhydride, maleic anhydride, succinic anhydride, and the like.

In the epoxy resin composition of the present invention, the component [c1] preferably contains a norbornene skeleton or a compound having a norbornane skeleton. In the epoxy resin composition of the present invention, a norbornene skeleton or an acid anhydride having a norbornane skeleton increases interference with the molecular chain due to the steric hindrance of the skeleton, resulting in a better balance between curing speed and tensile strength utilization rate. It is preferable because a fiber-reinforced composite material can be obtained. Specific examples of acid anhydrides having a norbornene skeleton or a norbornane skeleton include methylendomethylenetetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, methylbicycloheptanedicarboxylic anhydride, and bicycloheptanedicarboxylic anhydride. .

When an acid anhydride is used as a curing agent, it is generally used together with a curing accelerator. As curing accelerators, imidazole compounds, 1,8-diazabicyclo[5.4.0]-7-undecene (hereinafter referred to as DBU) salts, tertiary amine compounds, Lewis acids and the like are used.
Among these, the epoxy resin composition of the present invention preferably contains an imidazole compound or a tertiary amine compound as a curing accelerator. Such a curing accelerator is preferably used because of its high reactivity and excellent productivity. Examples of imidazole compounds include 2-ethyl-4-methylimidazole and 1-cyanoethyl-2-ethyl-4-methylimidazole. Tertiary amine compounds include dimethylbenzylamine and tris(dimethylaminomethyl)phenol.

In the epoxy resin composition of the present invention, the component [C] is the component [c2], and the carbon atom adjacent to the carbon atom having an amino group has a substituent 2,2'-dimethyl-4, It preferably contains 4'-methylenebiscyclohexylamine . In the epoxy resin composition of the present invention, the application of 2,2'-dimethyl-4,4'-methylenebiscyclohexylamine having a substituent at the carbon atom adjacent to the carbon atom having an amino group is the component [A] The combination with component [b1] or component [b2] is preferable because the restraint of molecular chains due to steric hindrance is increased, and a fiber-reinforced composite material having a better balance between curing speed and tensile strength utilization can be obtained .

These aliphatic amine-based curing agents, which are component [c2], can be used alone or in combination.

In the epoxy resin composition of the present invention, component [C] preferably further contains an aliphatic polyamine having an alkylene glycol structure as component [c2]. 2,2'-Dimethyl-4,4'-methylenebiscyclohexylamine having a substituent on the carbon atom adjacent to the carbon atom having an amino group and an aliphatic polyamine having an alkylene glycol structure are used in combination to obtain an epoxy resin. It is preferable because the balance between the viscosity of the composition and the rubber state elastic modulus of the cured product is easily improved, and the tensile strength utilization rate of the fiber-reinforced composite material is easily improved. Alkylene glycol structures include polyoxyethylene, polyoxypropylene, copolymers of polyoxyethylene and polyoxypropylene, and the like. Among them, aliphatic polyamines having amino groups at their terminals are preferably used because they have excellent reactivity with epoxy resins, are easily incorporated into networks with epoxy resins, and improve the tensile strength utilization rate of fiber-reinforced composite materials. . Aliphatic polyamines having terminal amino groups include aliphatic polyamines having a 2-aminopropyl ether structure, a 2-aminoethyl ether structure, or a 3-aminopropyl ether structure.

In the epoxy resin composition of the present invention, component [C] preferably further contains isophoronediamine as component [c2]. Adding isophoronediamine in addition to 2,2′-dimethyl-4,4′-methylenebiscyclohexylamine in which the carbon atom adjacent to the carbon atom having an amino group has a substituent provides fiber reinforcement with excellent tensile strength utilization rate. In addition to obtaining composite materials, process stability is improved. This is because the addition of isophoronediamine suppresses the phenomenon in which amine in the resin bath forms a salt with carbon dioxide in the air (amine blush), thereby improving process stability.

These aliphatic amine-based curing agents, which are the component [c2], can be used in combination other than the above.

The total amount of component [C] is preferably 0.6 to 1.2 equivalents in terms of active hydrogen equivalents or acid anhydride equivalents relative to the epoxy groups of all the epoxy resin components contained in the epoxy resin composition. Within this range, it becomes easier to obtain a resin cured product that gives a fiber-reinforced composite material having an excellent balance between heat resistance and mechanical properties.

The gel time in the present invention was measured by weighing 2 mL of the epoxy resin composition, using a rotorless curing tester (curastometer V type, manufactured by Nichigo Shoji Co., Ltd.) at a measurement temperature of 80 ° C., with a sine wave vibration waveform. The curing behavior is measured under conditions of a frequency of 100 cpm and an amplitude angle of ±1°, and the time until the torque value of the epoxy resin composition reaches 0.02 N·m.

The rubber state elastic modulus in the present invention was measured by cutting out a test piece having a thickness of 2 mm, a width of 12.7 mm and a length of 45 mm from the cured product obtained by curing the epoxy resin composition, and using a viscoelasticity measuring device (ARES, T.A.In.) (manufactured by Strument), under the conditions of a torsional vibration frequency of 1.0 Hz and a temperature increase rate of 5.0 ° C./min, DMA measurement was performed in the temperature range of 30 to 250 ° C., and the glass transition temperature and rubber state elastic modulus were measured. to read. The glass transition temperature is the temperature at the intersection of the tangent line in the glassy state and the tangent line in the transition state on the storage modulus G' curve. In addition, the rubber state elastic modulus is the storage elastic modulus in the area where the storage elastic modulus becomes flat in the temperature range above the glass transition temperature. and

In addition, it is preferable to set the glass transition temperature of the cured product obtained by curing the epoxy resin composition to 95° C. or higher. A fiber-reinforced composite material with excellent environmental friendliness can be obtained.

Conditions for curing the epoxy resin composition of the present invention are not particularly specified, and are appropriately selected according to the properties of the curing agent.

The epoxy resin composition of the present invention is suitably used for fiber-reinforced composite materials produced by liquid processes such as the pultrusion method and filament winding. The epoxy resin composition must be liquid in order to improve the impregnating properties of the reinforcing fiber bundles. Specifically, the epoxy resin composition of the present invention preferably has a viscosity of 2000 mPa·s or less at 25°C. When the viscosity is within this range, the reinforcing fiber bundles can be impregnated with the epoxy resin composition without requiring a special heating mechanism for the resin bath or dilution with an organic solvent or the like.

More preferably, the viscosity is 200 to 1000 mPa·s. By setting the viscosity within this range, it is possible to suppress resin sagging during the molding process and further improve the impregnation of the reinforcing fiber bundles with the epoxy resin composition.

The viscosity and thickening ratio in the present invention are measured using an E-type viscometer (TVE-30H, manufactured by Toki Sangyo Co., Ltd.) equipped with a standard cone rotor (1 ° 34' × R24), and in accordance with JIS Z8803 (1991). According to "Method for Measuring Viscosity Using a Cone-Plate Rotational Viscometer", measurement is performed at a measurement temperature of 25°C and a rotation speed of 50 revolutions/minute. The initial viscosity is the viscosity after 5 minutes from the start of measurement. In the present invention, the term "viscosity" refers to the initial viscosity. Further, the value obtained by dividing the viscosity after 90 minutes at 25°C by the initial viscosity is defined as the thickening ratio.

The epoxy resin composition of the present invention preferably has a thickening ratio of 4 times or less after 90 minutes at 25°C. The thickening ratio is an index of the pot life of the epoxy resin composition. When the viscosity increasing ratio is within this range, the mass of the epoxy resin composition picked up by the reinforcing fibers can be stabilized in the pultrusion method or filament winding.

The epoxy resin composition of the present invention may contain a thermoplastic resin as long as the effects of the present invention are not lost. The thermoplastic resin may contain thermoplastic resin soluble in epoxy resin, organic particles such as rubber particles and thermoplastic resin particles, and the like.

Examples of thermoplastic resins soluble in epoxy resins include polyvinyl acetal resins such as polyvinyl formal and polyvinyl butyral, polyvinyl alcohol, phenoxy resins, polyamides, polyimides, polyvinylpyrrolidone, and polysulfone.

Examples of rubber particles include crosslinked rubber particles and core-shell rubber particles obtained by graft-polymerizing a different polymer on the surface of crosslinked rubber particles.

The epoxy resin composition of the present invention may be prepared by kneading using a machine such as a planetary mixer or mechanical stirrer, or by manually mixing using a beaker and a spatula.

The fiber-reinforced composite material of the present invention comprises a cured epoxy resin composition of the present invention and reinforcing fibers. The fiber-reinforced composite of the present invention containing the cured epoxy resin composition of the present invention as a matrix resin is obtained by combining the epoxy resin composition of the present invention prepared by the above method with reinforcing fibers and then curing the composition. materials can be obtained.

The reinforcing fibers used in the present invention are not particularly limited, and glass fibers, carbon fibers, aramid fibers, boron fibers, alumina fibers, silicon carbide fibers and the like are used. Two or more kinds of these fibers may be mixed and used. Among these, it is preferable to use carbon fiber, which yields a lightweight and highly rigid fiber-reinforced composite material.

The epoxy resin composition of the present invention can be suitably used for the filament winding method and the pultrusion method. The filament winding method is a molding method in which a reinforcing fiber is wound around a mandrel or liner while a resin is adhered thereon, and cured to obtain a molded product. The pultrusion method is a molding method in which resin is adhered to rovings of reinforcing fibers, and the resin is continuously cured while passing through a mold to obtain a molded product. In any construction method, the epoxy resin composition of the present invention can be used by putting it into a resin bath after preparation.

The fiber-reinforced composite material using the epoxy resin composition of the present invention is preferably used for pressure vessels, propeller shafts, drive shafts, electric wire cable core materials, structures of mobile bodies such as automobiles, ships and railway vehicles, and cable applications. .

The epoxy resin composition of the present invention is suitably used for manufacturing molded products by filament winding and pressure vessels. In general, monofunctional epoxy resins greatly reduce the viscosity of the resin composition and improve the workability of filament winding molding, etc., but since they are crosslinked ends, the viscosity increase during the curing process is slow, and as a result, the curing time is greatly increased. There is a problem that the heat resistance of the obtained molded article is lowered. However, the epoxy resin composition of the present invention is preferable because it has an appropriate gel time by using a specific monofunctional epoxy resin, so that a molded product having excellent moldability and excellent heat resistance can be obtained.

The molded article of the present invention comprises a fiber-reinforced composite material comprising a cured product of the epoxy resin composition of the present invention and reinforcing fibers.

A fiber-reinforced composite material, a molded product, and a pressure vessel comprising a cured product of the epoxy resin composition of the present invention and reinforcing fibers are preferable because they can be molded in a normal curing process and have an excellent tensile strength utilization rate. .

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the description of these examples. In the following, Examples 1-7, 11, 12 , 18-20 and 23 shall be read as Reference Examples 1-7, 11, 12, 18-20 and 23, respectively.

The components used in this example are as follows.

<Materials used>
Component [A]
・ “Denacol (registered trademark)” EX-146 (p-tert-butylphenyl glycidyl ether, manufactured by Nagase ChemteX Co., Ltd.)
・ “Epiol (registered trademark)” SB (p-sec-butylphenyl glycidyl ether, manufactured by NOF Corporation)
- "Denacol (registered trademark)" EX-142 (o-phenylphenol glycidyl ether, manufactured by Nagase ChemteX Corporation).

Component [B]
・GAN (N,N-diglycidylaniline, manufactured by Nippon Kayaku Co., Ltd.)
・GOT (N,N-diglycidyl orthotoluidine, manufactured by Nippon Kayaku Co., Ltd.)
・Px-GAN (N,N-diglycidyl-4-phenoxyaniline, manufactured by Toray Fine Chemicals Co., Ltd.)
・ “Sumiepoxy (registered trademark)” ELM434 (tetraglycidyldiaminodiphenylmethane, manufactured by Sumitomo Chemical Co., Ltd.)
- "Ogsol (registered trademark)" EG-200 (fluorene-based epoxy resin, manufactured by Osaka Gas Chemicals Co., Ltd.).
・ “ARALDITE (registered trademark)” MY0500 (triglycidyl-p-aminophenol, manufactured by Huntsman Japan Co., Ltd.)
・ “ARALDITE (registered trademark)” MY0610 (triglycidyl-m-aminophenol, manufactured by Huntsman Japan Co., Ltd.)
・ “SUMI (registered trademark)” ELM-100 (para-amino cresol type epoxy resin, manufactured by Sumitomo Chemical Co., Ltd.)
・ “TETRAD (registered trademark)”-X (N,N,N′,N′-tetraglycidyl-m-xylenediamine, manufactured by Mitsubishi Gas Chemical Company, Inc.)
・ “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)
・ “ARALDITE (registered trademark)” PY306 (Bisphenol F type epoxy resin, manufactured by Huntsman Japan Co., Ltd.)
· NC-7300L (naphthalene novolac type epoxy resin, manufactured by Nippon Kayaku Co., Ltd. ) .

Epoxy resin other than constituent elements [A] and [B] ・"Denacol (registered trademark)" EX-141 (phenylglycidyl ether, manufactured by Nagase ChemteX Co., Ltd.)
・ “Denacol (registered trademark)” EX-731 (N-glycidylphthalimide, manufactured by Nagase ChemteX Co., Ltd.)
- YED216 (1,6-hexanediol diglycidyl ether, manufactured by Yuka Shell Epoxy Co., Ltd.) .

Component [C]
・ "Baxxodur (registered trademark)" EC201 (isophorone diamine, manufactured by BASF Japan Ltd.)
・XTA-801 (1,4-bis (aminomethyl) cyclohexane, manufactured by Huntsman Japan Co., Ltd.)
- "Baxxodur (registered trademark)" EC331 (2,2'-dimethyl-4,4'-methylenebiscyclohexylamine, manufactured by BASF Japan Ltd.).
・ “JEFFAMINE (registered trademark)” D-230 (polypropylene glycol diamine, manufactured by Huntsman Japan Co., Ltd.)
・ HN-2200 (methyltetrahydrophthalic anhydride, manufactured by Hitachi Chemical Co., Ltd.)
・"KAYAHARD (registered trademark)" MCD (a mixed solution of methylendomethylenetetrahydrophthalic anhydride and endomethylenetetrahydrophthalic anhydride (in the table, the common name of methylnadic anhydride is described), manufactured by Nippon Kayaku Co., Ltd. ).
・ “jER Cure (registered trademark)” W (diethyltoluenediamine, manufactured by Mitsubishi Chemical Corporation)
・ 3,3'DAS (3,3'-diaminodiphenyl sulfone, manufactured by Mitsui Chemicals Fine Co., Ltd.)
- Seika Cure-S (4,4'-diaminodiphenyl sulfone, manufactured by Seika Co., Ltd.).

Curing accelerator "Kaolizer (registered trademark)" No. 20 (N,N-dimethylbenzylamine, manufactured by Kao Corporation)
・"U-CAT (registered trademark)" SA102 (2-ethylhexanoate of 1,8-diazabicyclo(5,4,0)undecene-7, manufactured by San-Apro Co., Ltd.)
- "Curamid®" CN (2-ethyl-4-methyl-1H-imidazole-1-propanenitrile, Borregaard).

<Method for preparing epoxy resin composition>
In a beaker, component [A], component [B] and, if necessary, other epoxy resins were added, heated to 80° C., and kneaded under heating for 30 minutes. Thereafter, the temperature was lowered to 30° C. or lower while kneading was continued, and the component [C] and, if necessary, other curing agents and curing accelerators were added and stirred for 10 minutes to obtain an epoxy resin composition.

Tables 1 to 5 show the compounding ratio of components in each example and comparative example.

<Method for evaluating gel time of epoxy resin composition>
2 mL of the epoxy resin composition was weighed and measured using a rotorless curing tester (curastometer V type, manufactured by Nichigo Shoji Co., Ltd.) at a measurement temperature of 80 ° C., the vibration waveform was a sine wave, the frequency of vibration was 100 cpm, and the amplitude angle was The curing behavior was measured under the condition of ±1°, and the gel time was defined as the time until the torque value of the epoxy resin composition reached 0.02 N·m.

<Method for measuring dynamic viscoelasticity of cured resin>
After defoaming the epoxy resin composition in a vacuum, it was cured at a temperature of 80° C. for 2 hours in a mold set to have a thickness of 2 mm with a 2 mm thick “Teflon (registered trademark)” spacer. It was cured at a temperature of 110° C. for 4 hours to obtain a plate-shaped resin cured product with a thickness of 2 mm.

A test piece having a width of 12.7 mm and a length of 45 mm was cut out from the obtained resin cured product, and measured using a viscoelasticity measuring device (ARES, manufactured by T.A. Instruments) at a torsional vibration frequency of 1.0 Hz. DMA measurements were performed in the temperature range of 30 to 250° C. at a temperature rate of 5.0° C./min to read the glass transition temperature and rubber state modulus. The glass transition temperature was taken as the temperature at the intersection of the tangent line in the glass state and the tangent line in the transition state in the storage modulus G' curve. In addition, the rubber state elastic modulus is the storage elastic modulus in the area where the storage elastic modulus becomes flat in the temperature range above the glass transition temperature. and

<Method for Evaluating Compressive Shear Strength of Cured Resin>
After defoaming the epoxy resin composition in a vacuum, it was cured at a temperature of 80° C. for 2 hours in a mold set to have a thickness of 6 mm with a 6 mm thick “Teflon (registered trademark)” spacer. It was cured at a temperature of 110° C. for 4 hours to obtain a plate-shaped resin cured product with a thickness of 6 mm.

A test piece with a width of 6 mm and a length of 6 mm was cut out from the obtained resin cured product, and a compression test was performed using a universal testing machine at a test speed of 1.0 mm / min. was measured, and the value obtained by dividing the compressive yield stress by 2 was taken as the compressive shear strength.

<Method for producing fiber-reinforced composite material>
Carbon fiber "Torayca (registered trademark)" T700S-12K-50C (manufactured by Toray Industries, Inc., 150 g/m ² of basis weight) was impregnated at room temperature to obtain an epoxy resin-impregnated carbon fiber sheet. After stacking eight of the obtained sheets so that the fiber direction is the same, they are sandwiched between a mold set to have a thickness of 1 mm with a metal spacer, and the mold is heated to 80 ° C. in a press for 2 hours to cure. carried out. After that, the mold was removed from the pressing machine, and heat-cured in an oven heated to 110° C. for 4 hours to obtain a fiber-reinforced composite material.

<Tensile strength measurement of fiber reinforced composite material>
From the fiber reinforced composite material produced according to the above <Method for producing fiber reinforced composite material>, a width of 12.7 mm and a length of 229 mm were cut out, and glass fiber reinforced plastic tabs of 1.2 mm in length and 50 mm in length were attached to both ends. Using the bonded test piece, the tensile strength was measured according to ASTM D 3039 using an Instron universal testing machine (manufactured by Instron) at a crosshead speed of 1.27 mm/min. The average value of the values measured with the number of samples n=6 was taken as the tensile strength.

The tensile strength utilization rate was calculated by dividing the tensile strength of the fiber-reinforced composite material/(strand strength of reinforcing fiber×fiber volume content)×100.

For the fiber volume content, a value measured according to ASTM D 3171 was used.

(Example 1)
20 parts by mass of "Epiol (registered trademark)" SB as component [A], 80 parts by mass of "jER (registered trademark)" 828 as component [B], and 20 parts by mass of XTA-801 as component [C]. Using 0 parts by mass, an epoxy resin composition was prepared according to the above <Method for preparing epoxy resin composition>. The gel time at 80° C. of this epoxy resin composition was 10 minutes.

Next, the epoxy resin composition was cured by the above method to prepare a cured product, and dynamic viscoelasticity evaluation was performed. Met. Furthermore, the glass transition temperature was 128° C., and the heat resistance was also good.

From the obtained epoxy resin composition, a fiber-reinforced composite material was produced according to <Production method of fiber-reinforced composite material> to obtain a fiber-reinforced composite material having a fiber volume content of 66%. The tensile strength of the obtained fiber-reinforced composite material was measured by the above method, and the tensile strength utilization rate was calculated to be 76%.

(Examples 2 to 27)
An epoxy resin composition, a cured epoxy resin, and a fiber-reinforced composite material were produced in the same manner as in Example 1, except that the resin composition was changed as shown in Tables 1 to 3. All of the epoxy resin cured products obtained exhibited good low-temperature short-time curability and rubber-like elastic modulus. The tensile strength utilization rate of the resulting fiber-reinforced composite material was also good.

(Comparative example 1)
An epoxy resin composition, an epoxy resin cured product, and a fiber-reinforced composite material were produced in the same manner as in Example 1, except that the resin composition was changed as shown in Table 4. The gel time was as slow as 98 minutes, and the rubber state elastic modulus was as high as 14.0 MPa. As a result, the fiber-reinforced composite material had an insufficient tensile strength utilization rate of 68%.

(Comparative example 2)
An epoxy resin composition, an epoxy resin cured product, and a fiber-reinforced composite material were produced in the same manner as in Example 1, except that the resin composition was changed as shown in Table 4. The gel time was 12 minutes and the curability was good, but the rubber state elastic modulus showed a high value of 15.5 MPa. As a result, the fiber-reinforced composite material had an insufficient tensile strength utilization rate of 66%.

(Comparative Example 3)
An epoxy resin composition, an epoxy resin cured product, and a fiber-reinforced composite material were produced in the same manner as in Example 1, except that the resin composition was changed as shown in Table 4. The gel time was 46 minutes and the curability was good, but the rubber state elastic modulus showed a high value of 12.2 MPa. As a result, the fiber-reinforced composite material had an insufficient tensile strength utilization rate of 70%.

(Comparative Example 4)
An epoxy resin composition, an epoxy resin cured product, and a fiber-reinforced composite material were produced in the same manner as in Example 1, except that the resin composition was changed as shown in Table 4. The gel time was 29 minutes and the curability was good, but the elastic modulus in the rubber state was as high as 12.5 MPa. As a result, the fiber-reinforced composite material had an insufficient tensile strength utilization rate of 72%.

(Comparative Example 5)
An epoxy resin composition, an epoxy resin cured product, and a fiber-reinforced composite material were produced in the same manner as in Example 1, except that the resin composition was changed as shown in Table 4. The gel time was 3 minutes and the curability was good, but the rubber state elastic modulus showed a high value of 17.1 MPa. As a result, the fiber-reinforced composite material had an insufficient tensile strength utilization rate of 65%.

(Comparative Example 6)
An epoxy resin composition, an epoxy resin cured product, and a fiber-reinforced composite material were produced in the same manner as in Example 1, except that the resin composition was changed as shown in Table 4. Here, "Denacol (registered trademark)" EX-141 used instead of the component [A] is a monofunctional epoxy resin having no steric hindrance. The elastic modulus in the rubber state showed a low value of 6.7 MPa, but the gel time was 175 minutes, which was slow and insufficient.

(Comparative Example 7)
An epoxy resin composition, a cured epoxy resin, and a fiber-reinforced composite material were produced in the same manner as in Example 1, except that the resin composition was changed as shown in Table 5. Here, "Denacol (registered trademark)" EX-731 used instead of component [A] is a monofunctional epoxy resin. The gel time was 75 minutes, which was slow and insufficient, and the rubber state elastic modulus was as high as 12.0 MPa. As a result, the fiber-reinforced composite material had an insufficient tensile strength utilization rate of 72%.

(Comparative Example 8)
An epoxy resin composition, a cured epoxy resin, and a fiber-reinforced composite material were produced in the same manner as in Example 1, except that the resin composition was changed as shown in Table 5. The gel time was 38 minutes and the curability was good, but the rubber state elastic modulus was a high value of 14.1 MPa. As a result, the fiber-reinforced composite material had an insufficient tensile strength utilization rate of 69%.

(Comparative Example 9)
An epoxy resin composition, a cured epoxy resin, and a fiber-reinforced composite material were produced in the same manner as in Example 1, except that the resin composition was changed as shown in Table 5. Here, the curing agent used instead of component [C] is an aromatic amine curing agent. The gel time was 190 minutes, which was slow and insufficient, and the elastic modulus in the rubbery state was as high as 16.5 MPa. As a result, the fiber-reinforced composite material had an insufficient tensile strength utilization rate of 67%.

(Comparative Example 10)
An epoxy resin composition was prepared in the same manner as in Example 1, except that the resin composition was changed as shown in Table 5. Here, the curing agent used instead of component [C] is an aromatic amine curing agent. At 80° C., gelation did not occur even after 200 minutes or more, and a cured product could not be produced.

(Comparative Example 11)
An epoxy resin composition was prepared in the same manner as in Example 1, except that the resin composition was changed as shown in Table 5. At 80° C., gelation did not occur even after 200 minutes or more, and a cured product could not be produced.

(Comparative Example 12)
An epoxy resin composition was produced according to the method described in Example 1 of Patent Document 2 (JP-A-2005-120127). The cured resin obtained had a rubber state elastic modulus of 25.0 MPa, which is a very high value (Table 6). This epoxy resin composition had a high viscosity, and the resin did not impregnate the fibers in <Method for Producing Fiber-Reinforced Composite Material>, resulting in a large amount of voids in the fiber-reinforced composite material. Therefore, the epoxy resin composition was heated to 70° C. for impregnation to obtain an epoxy resin-impregnated carbon fiber sheet. Thereafter, a fiber-reinforced composite material was obtained in the same manner as in the above <Method for producing fiber-reinforced composite material>. The fiber-reinforced composite material obtained had an insufficient tensile strength utilization rate of 61%.

(Comparative Example 13)
With reference to the epoxy composition of Example 5 of Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2010-174073), the resin composition was set as shown in Table 5, and an epoxy resin composition and a cured resin were produced. Table 5 shows the evaluation results. The rubber state elastic modulus showed a high value of 14.0 MPa. As a result, the fiber-reinforced composite material obtained had an insufficient tensile strength utilization rate of 69%.

(Comparative Example 14)
An epoxy resin composition was prepared according to the method described in Example 13 of Patent Document 5 (JP-A-2011-46797). The rubber-state elastic modulus of the cured resin obtained by curing this was as high as 12.0 MPa (Table 6). Since this epoxy resin composition had a very high viscosity, an epoxy resin-impregnated carbon fiber sheet was produced in the same manner as in Comparative Example 12. Thereafter, a fiber-reinforced composite material was obtained in the same manner as in the above <Method for producing fiber-reinforced composite material>. The fiber-reinforced composite material obtained had an insufficient tensile strength utilization rate of 70%.

(Comparative Example 15)
An epoxy resin composition was produced according to the method described in Example 3 of Patent Document 6 (Japanese Patent Application Laid-Open No. 2006-265458). The rubber-state elastic modulus of the cured resin obtained by curing this was as high as 11.4 MPa (Table 6). Using the obtained epoxy resin composition, a fiber-reinforced composite material was obtained according to the above <Method for producing fiber-reinforced composite material>. The fiber-reinforced composite material obtained had an insufficient tensile strength utilization rate of 71%.

(Comparative Example 16)
An epoxy resin composition was prepared according to the method described in Example 1 of Patent Document 7 (Japanese Patent Publication No. 2009-521589). The rubber-state elastic modulus of the resin cured product obtained by curing this showed a high value of 10.5 MPa (Table 6). Using the obtained epoxy resin composition, a fiber-reinforced composite material was obtained according to the above <Method for producing fiber-reinforced composite material>. The fiber-reinforced composite material obtained had an insufficient tensile strength utilization rate of 72%.

INDUSTRIAL APPLICABILITY The epoxy resin composition of the present invention can be cured under normal conditions and is preferably used as a matrix resin for producing fiber-reinforced composite materials, molded articles and pressure vessels having excellent tensile strength utilization.

Moreover, the epoxy resin composition and fiber-reinforced composite material of the present invention are preferably used for general industrial applications.

Claims (15)

An epoxy resin composition containing the following components [A] to [C], wherein the component [B] is the following component [b1] and/or the following component [b2] and the following component [b1] and a bifunctional or higher aromatic epoxy resin other than the component [b2], the component [C] is the following component [c1] or the following component [c2], and the rotorless curing test An epoxy resin composition having a gel time of 15 to 100 minutes at 80° C. using a machine, and a cured product obtained by curing the epoxy resin composition having a rubber state elastic modulus of 10 MPa or less in dynamic viscoelasticity evaluation.
[A] A monofunctional epoxy resin which is a phenylglycidyl ether substituted with a tert-butyl group, sec-butyl group, isopropyl group or phenyl group
[B] bifunctional or higher aromatic epoxy resin [b1] optionally substituted diglycidylaniline (wherein the substituent is a group selected from an alkyl group having 1 to 4 carbon atoms, a phenyl group and a phenoxy group) be.)
[b2] Tetraglycidyldiaminodiphenylmethane [C] Curing agent [c1] Acid anhydride curing agent [c2] Aliphatic amine curing agent 2. The epoxy resin composition according to claim 1, comprising 5 to 40 parts by mass of component [A] in 100 parts by mass of the total epoxy resin. 3. The epoxy resin composition according to claim 1, wherein the component [A] is a phenylglycidyl ether substituted with a tert-butyl group or a sec-butyl group. 4. The epoxy resin composition according to any one of claims 1 to 3, comprising two or more of the components shown in component [A]. The epoxy resin composition according to any one of claims 1 to 4, wherein component [C] is component [c1]. 6. The epoxy resin composition according to claim 5, wherein the component [c1] contains a norbornene skeleton or a compound having a norbornane skeleton. 7. The epoxy resin composition according to claim 5, which contains an imidazole compound or a tertiary amine compound as a curing accelerator. 2. The epoxy resin composition according to claim 1, wherein component [C] contains an aliphatic polyamine having an alkylene glycol structure as component [c2]. 2. The epoxy resin composition according to claim 1, wherein component [C] contains isophorone diamine as component [c2]. The epoxy resin composition according to any one of claims 1 to 9 , which has a viscosity of 2000 mPa·s or less at 25°C. 11. The epoxy resin composition according to claim 10 , which has a thickening ratio of 4 times or less after 90 minutes at 25[deg.]C. The epoxy resin composition according to any one of claims 1 to 11 , wherein a cured product obtained by curing the epoxy resin composition has a compressive shear strength of 50 to 120 MPa in a compression test . A fiber-reinforced composite material comprising a cured epoxy resin composition according to any one of claims 1 to 12 and reinforcing fibers. A molded article made of the fiber-reinforced composite material according to claim 13 . A pressure vessel comprising the fiber-reinforced composite material according to claim 13 .