TW201943772A - Prepreg and fiber-reinforced composite material using same - Google Patents

Abstract

To provide a prepreg having both high elastic modulus and high strength with respect to the tensile, compressive, and bending properties of a fiber-reinforced composite material, and a fiber-reinforced composite material using the prepreg. A prepreg obtained by impregnating reinforcing fibers with a resin composition containing as main components the following [A], [B], [C], and amine curing agent [D], in which components [A], [B], and [C] are 1-20 weight parts, 45-80 weight parts, and 20-55 weight parts, respectively; [A] carboxyl group-containing polyvinyl formal resin, [B] epoxy resin that is solid at 25 DEG C, [C] epoxy resin that is liquid at 25 DEG C.

Description

Prepreg and fiber-reinforced composite material using the same

The invention relates to a prepreg and a fiber-reinforced composite material.

A fiber-reinforced composite material formed by laminating a prepreg impregnated with a matrix resin in a unidirectional parallel sheet of carbon fiber or a woven fabric, etc., on a golf club, fishing rod, or racket frame And other sports and leisure areas are widely used. Furthermore, in recent years, its use has been expanding in industrial fields such as automobiles and aerospace fields.

So far, a resin composition containing a thermoplastic resin such as a polyvinyl butyral resin has been used in the epoxy resin for the purpose of improving the properties of the epoxy resin, which is a matrix resin. However, the compatibility between polyvinyl butyral and epoxy resin is also not good. Therefore, when the composition is cured, phase separation may occur and the strength may decrease. In contrast, it is known that a fiber-reinforced composite material formed by laminating a prepreg containing a resin composition containing a polyvinyl formal can suppress phase separation to a certain degree, and relatively The tensile strength at 90 ° in the fiber direction is improved (Patent Document 1).

Patent Document 2 discloses that a thermoplastic resin is added to a prepreg for the purpose of controlling resin flow during molding or imparting toughness to a cured resin. In Patent Document 2, phenoxy resins are cited as thermoplastic resins in addition to polyvinyl formal. Furthermore, Patent Document 3 describes that when a fiber-reinforced composite material is used in a tubular shaped body such as a fishing rod or a golf club, polyethylene is preferably used as a thermoplastic resin suitable for improving properties such as compressive strength. Formal or phenoxy resin.

Regarding carbon fiber composite materials (CFRP), in order to reduce weight and reduce manufacturing costs, thin plates are used as members for sporting goods, industrial goods, and the like. Therefore, improvements in strength and elastic modulus are required.
There have been no examples of thermoplastic resins added to CFRP matrix resins that have high strength and high modulus of elasticity in terms of tensile, compression, and bending properties. Polyvinyl formal, which is one of the thermoplastic resins added to CFRP's matrix resin, improves the strength of CFRP in terms of tensile properties, but has the disadvantage of lowering the coefficient of elasticity.
[Prior Art Literature]
[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 62-169829
[Patent Document 2] Japanese Patent Laid-Open No. 2017-2202
[Patent Document 3] International Publication No. 1998/044017

[Problems to be Solved by the Invention]
An object of the present invention is to provide a prepreg having a high coefficient of elasticity, high strength, and impact resistance in terms of tensile, compression, and bending characteristics of a fiber-reinforced composite material, and a fiber-reinforced composite material using the same.
[Means for solving problems]

Previously, the polyvinyl formal added to the matrix resin (epoxy resin) of the carbon fiber composite material had the following disadvantages: Although the strength of the composite material was improved in terms of tensile and bending characteristics, the elastic coefficient decreased. Furthermore, in addition to these characteristics, it does not have impact resistance. Therefore, the present inventors have actively studied not only the tensile properties but also the bending and compressive properties to achieve high strength and high coefficient of elasticity, and to improve impact resistance. As a result, they have found that A prepreg is produced by reacting an oxetanyl group and interacting with a functional group containing oxygen such as a hydroxyl group or a carboxyl group on the surface of a carbon fiber to prepare a prepreg, which solves all of the problems described above, and is completed. this invention.

The constitution of the present invention is as follows.
[1] A prepreg comprising the following components [A], [B], [C], and an amine hardener [D] as main components, and each component of [A], [B], and [C] 1 to 20 parts by weight, 45 to 80 parts by weight, and 20 to 55 parts by weight of a resin composition impregnated in a reinforcing fiber;
[A] Polyvinyl formal resin containing carboxyl group
[B] Solid epoxy resin at 25 ° C
[C] Liquid epoxy resin at 25 ° C.
[2] The prepreg according to [1], wherein the polyvinyl formal resin containing a carboxyl group [A] includes a constituent unit a, a constituent unit b, a constituent unit c, and a constituent unit d;
[Chemical 1]






(In the formula constituting unit d, R ^{1 is} independently hydrogen or an alkyl group having 1 to 5 carbon atoms).
[3] The prepreg according to [1] or [2], wherein the softening point of the solid epoxy resin [B] is 60 ° C or higher.
[4] The prepreg according to [1] or [2], wherein the liquid epoxy resin [C] is liquid at 150 ° C.
[5] The prepreg according to [1] or [2], wherein the amine hardener [D] is dicyandiamine or a derivative thereof.
[6] The prepreg according to [1] or [2], wherein the reinforcing fiber is carbon fiber, aromatic polyamide fiber, glass fiber, graphite fiber, silicon carbide fiber, boron fiber, alumina fiber, stainless steel Any of the fibers.
[7] The prepreg according to [1] or [2], wherein the reinforcing fibers are carbon fibers, the carbon fibers have a tensile strength of 4.4 GPa to 6.5 GPa, a tensile elongation of 1.7% to 2.3%, and a tensile strength. The coefficient of elasticity is 230 GPa to 400 GPa.
[8] The prepreg according to [1] or [2], in which the amine hardener [D] is contained in all rings including solid epoxy resin [B] and liquid epoxy resin [C]. The oxygen resin component is in a range of 1 to 10 parts by weight based on 100 parts by weight.
[9] The prepreg according to [1] or [2], wherein the impregnation amount of the reinforcing fibers in the prepreg is such that the volume of the prepreg including the reinforcing fibers is 100 vol% In this case, the fiber volume content (Vf) is 40% to 90%.
[10] A fiber-reinforced composite material using the prepreg according to [1] to [9].
[Effect of the invention]

The fiber-reinforced composite material produced by laminating a prepreg to which a polyvinyl formal-containing polyvinyl formal is added is stretched in comparison with other thermoplastic resins or previous fiber-reinforced composite materials containing polyvinyl formal. In terms of compression, compression and bending characteristics, it shows a high elastic coefficient, high strength and also shows impact resistance.

Hereinafter, although the embodiment of this invention is described in detail, this invention is not limited to these descriptions.

The prepreg of the present invention includes the following components [A], [B], [C], and an amine hardener [D] as main components, and each component of [A], [B], and [C] is separately The resin composition is 1 to 20 parts by weight, 45 to 80 parts by weight, and 20 to 55 parts by weight by impregnating a reinforcing fiber.
[A] Polyvinyl formal resin containing carboxyl group
[B] solid epoxy resin
[C] Liquid epoxy resin

Resin composition The resin composition includes a carboxyl group-containing polyvinyl formal resin of component [A], a solid epoxy resin of component [B], and a liquid epoxy resin of component [C]. The component [C] may contain a reactive diluent.
The content of the carboxyl group-containing polyvinyl formal resin of the component [A] in the resin composition is 1 to 20 parts by weight, and preferably 3 to 10 parts by weight. It is more preferably 4 parts by weight to 7 parts by weight.

When the content of the carboxyl group-containing polyvinyl formal resin of the component [A] is 1 part by weight or more, it is not only dissolved in the matrix resin constituting the prepreg, but also by laminating and heating the prepreg. When a fiber-reinforced composite material is produced by curing, the carboxyl group of the polyvinyl formal containing carboxyl groups is crosslinked with epoxy resin on the one hand, and functional groups containing oxygen such as hydroxyl groups or carboxyl groups on the surface of the carbon fiber are mutually Effect, while showing the toughening of the composite material. When the content of the carboxyl group-containing polyvinyl formal resin of the component [A] is 20 parts by weight or less, the resin can be sufficiently coated on the release paper, and the reinforcing fibers can be well impregnated when the prepreg is produced. Resin.

Content of the solid epoxy resin of a component [B] is 45 weight part-80 weight part, Preferably it is 50 weight part-60 weight part. When the content of the solid epoxy resin of the component [B] is 45 parts by weight or more, the viscosity of the prepreg becomes good, and when it is 80 parts by weight or less, the application of the resin to the release paper caused by the increase in viscosity can be prevented. Poor application or impregnation of reinforcing fibers during prepreg.

The content of the liquid epoxy resin of the component [C] is 20 to 55 parts by weight, and preferably 40 to 50 parts by weight. When the content of the liquid epoxy resin of the component [C] is 55 parts by weight or less, the compatibility with the carboxyl group-containing polyvinyl formal and the viscosity of the prepreg will be improved, and the liquid ring will not be caused. The increase in the crosslinking density of the oxyresin results in a decrease in impact resistance. If it is 20 parts by weight or more, it is possible to prevent poor application of the resin to the release paper due to an increase in viscosity or poor impregnation to the reinforcing fibers during prepreg.
Hereinafter, each component is demonstrated.

Component [A] The carboxyl group-containing polyvinyl formal resin The component [A], the carboxyl group-containing polyvinyl formal resin preferably has a constituent unit a, a constituent unit b, a constituent unit c, and a constituent unit d. A carboxyl group-containing polyvinyl formal resin is obtained by introducing a carboxyl group as a crosslinkable group into a polyvinyl formal resin. If a resin composition added thereto is used, the toughness or transparency of the cured product can be improved. Sex, etc. The introduced carboxyl group becomes a cross-linking point, and the carboxyl group and the epoxy resin are cross-linked directly or via a hardener, and a physical complexation of the close-molecular molecular chains of the two polymers based on the cross-linking point is generated. By this mechanism, a soft polyvinyl formal resin is incorporated into a network of epoxy resins that are network-bonded.
[Chemical 2]

In the formula constituting the unit d, R ^{1 is} independently hydrogen or an alkyl group having 1 to 5 carbon atoms.
The total content of the constituent units a to d in the carboxyl group-containing polyvinyl formal resin is preferably 80% by weight to 100% by weight with respect to all the constituent units.
Examples of other constituent units that may be contained in the carboxyl group-containing polyvinyl formal resin include intermolecular formal units or hemiformal units. The content of other constituent multi-units is preferably less than 20% by weight.

[Chemical 3]



(R represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms)

In the polyvinyl formal resin containing a carboxyl group, the constituent units a to d may be arranged regularly (block copolymer, alternating copolymer, etc.) or may be arranged randomly (random copolymerization). Materials), but preferably arranged in disorder.

The structural unit a is a structural unit having a formal, and can be formed by a reaction between a continuous polyvinyl alcohol chain unit and an aldehyde (HCHO).
The structural unit b is a structural unit including a vinyl acetate chain.
The structural unit c is a structural unit including a vinyl alcohol chain.

The structural unit d is a chain having a carboxyl group, and R ¹ in the structural unit d is hydrogen or an alkyl group having 1 to 5 carbons, and more preferably hydrogen or an alkyl group having 1 to 3 carbons.

As for each constituent unit in the carboxyl group-containing polyvinyl formal resin, the content rate of the constituent unit a is preferably 49.9 mol% to 80 mol%, and the content rate of the constituent unit b is 0.1 mol% to 49.9 mol%. The content rate of the structural unit c is 0.1 mol% to 49.9 mol%. When the structural unit d is included, the content rate of the structural unit d is preferably from 0.1 mol% to 49.9 mol%. More preferably, the content rate of the constituent unit a is 49.9 mol% to 80 mol%, the content rate of the constituent unit b is 1 mol% to 30 mol%, and the content rate of the constituent unit c is 1 mol% to 30 mol%. When the structural unit d is included, the more preferable range of the content rate of the structural unit d is 1 to 30 mol%.

In order to fully obtain the chemical resistance, flexibility, abrasion resistance, and mechanical strength of the carboxyl group-containing polyvinyl formal resin, the content of the constituent unit a is preferably 49.9 mol% or more. In addition, the structural unit a in the carboxyl group-containing polyvinyl formal resin is formed by formalizing a vinyl alcohol chain portion continuously present in a molecular chain. That is, it is difficult to formalize a discontinuous vinyl alcohol chain in a molecular chain (for example, one vinyl alcohol chain sandwiched between two vinyl formal chains). Therefore, in the synthesis, the content rate of the constituent unit a is preferably 80.0 mol% or less.

When the content rate of the structural unit b is 0.1 mol% or more, the solubility of the polyvinyl acetal resin containing a carboxyl group in a solvent or the solubility in an epoxy resin becomes good. When the content rate of the structural unit b is set to 49.9 mol%, the chemical resistance, flexibility, abrasion resistance, and mechanical strength of the carboxyl group-containing polyvinyl formal resin are less likely to decrease, so it is preferable.

In consideration of solubility in a solvent or solubility in an epoxy resin, the content rate of the constituent unit c is preferably set to 49.9 mol%. Furthermore, when the polyvinyl alcohol chain is formalized in the production of a polyvinyl formal resin, the content rate of the structural unit c is preferably 0.1 mol% in order to bring the structural unit b and the structural unit c into a balanced relationship. the above.
In the case where the carboxyl group-containing polyvinyl formal resin contains the constituent unit d, considering the solubility to the epoxy resin and the viscosity after dissolution, the content rate of the constituent unit d is preferably 49.9 mol% the following. In addition, in order to maintain the heat resistance (glass transition temperature) by smoothly carrying out the cross-linking reaction between the side chain carboxyl group and the epoxy resin, and to obtain a resin that is strengthened and toughened with cross-linking, it is stretched, bent, In terms of compressive properties, a fiber-reinforced composite material exhibiting a high elastic modulus, high strength, and impact resistance, and the content rate of the constituent unit d is preferably 0.1 mol% or more.

The respective proportions of the constituent units a to c in the carboxyl group-containing polyvinyl formal resin can be measured and determined in accordance with Japanese Industrial Standards (JIS) K6729.
The content rate of the structural unit d in the carboxyl group-containing polyvinyl formal resin can be measured by the method described below.
In a 1 mol / l sodium hydroxide aqueous solution, a polyvinyl formal resin having a carboxyl group introduced by copolymerization was heated at 80 ° C for 2 hours. In this way, a polymer obtained by adding sodium to a carboxyl group and adding sodium carboxylate was obtained. After excess sodium hydroxide is extracted from this polymer, it is dehydrated and dried. After that, it was carbonized and subjected to atomic absorption analysis to determine the amount of sodium addition and quantify it.

In addition, in the analysis of the constituent unit b (vinyl acetate chain), the constituent unit d is quantified as a vinyl acetate chain. Therefore, the constituent unit b is subtracted from the constituent unit b measured in accordance with JIS K6729, and the constituent unit b is corrected. .

In addition, in order to change the proportion of each of the constituent units in the carboxyl group-containing polyvinyl formal resin, for example, an alkyl acrylate or a methyl group may be arbitrarily changed with respect to the vinyl acetate monomer of the main raw material. The ratio of the alkyl acrylate is adjusted by adjusting the amount of water and acid catalyst to be hydrolyzed and the amount of aldehyde compound to be formalized.

The weight average molecular weight of the carboxyl group-containing polyvinyl formal resin is preferably 5,000 to 200,000, and more preferably 10,000 to 150,000. When the weight-average molecular weight of the polyvinyl formal resin is 5,000 or more, the solubility to the epoxy resin becomes high, and the toughening effect of the polyvinyl formal resin containing a carboxyl group can be obtained, which is preferable. When the weight-average molecular weight of the polyvinyl formal resin is 150,000 or less, the viscosity when dissolved in an epoxy resin does not increase excessively, so it is preferable in terms of workability when molding into a fiber-reinforced composite material.

The weight average molecular weight of the carboxyl group-containing polyvinyl formal resin can be measured by a gel permeation chromatography (GPC) method. Specific measurement conditions are as follows.
Device: LC-4000 series (manufactured by JASCO Corporation)
Detector: RI-4030
Oven: CO-4060
Pump: PU-4180
Separation column: Shodex KF-805L x 2 pieces Temperature: 40 ° C
Mobile phase: Chloroform Standard sample: Polystyrene As such a carboxyl-containing polyvinyl formal resin, commercially available Vinylec ((registered trademark) grade ( grade): PVF-C) and so on.

Component [B] Solid epoxy resin As component [B], a solid epoxy resin is used. The solid epoxy resin may be solid at 25 ° C during use, and preferably has a softening point of at least 60 ° C.
Component [B] is preferably used as the matrix resin of the prepreg, and it is preferable to use a ring having strong adhesion to reinforcing fibers such as carbon fibers, aromatic polyamide fibers, boron fibers, and glass fibers, and having excellent strength, elastic coefficient, and heat resistance. Oxygen resin.

As the matrix resin of the prepreg, an epoxy resin having strong adhesion to reinforcing fibers such as carbon fibers, aromatic polyamide fibers, boron fibers, and glass fibers, and having excellent strength, modulus of elasticity, and heat resistance is preferably used.
When the epoxy resin is combined with the matrix resin, the polyvinyl formal resin including the carboxyl group-containing polyvinyl formal resin of the component [A] has high compatibility with the epoxy resin, and is laminated and hardened. When a prepreg is obtained, it is expected that the resin is strengthened and toughened by crosslinking with the epoxy resin.
By using the solid epoxy resin and the liquid epoxy resin together, the component [A] in the preparation of the resin composition can be uniformly dissolved.

For example, if the softening point of the solid epoxy resin is 60 ° C or higher, the polyvinyl formal resin including the carboxyl-containing polyvinyl formal resin of the component [A] can be dissolved in advance at 130 ° C or higher. After the component [C] is in the liquid epoxy resin, the solid epoxy resin of the component [B] is easily dissolved by lowering the temperature to 80 ° C to 90 ° C.

Regarding the type of the solid epoxy resin, in order to easily dissolve it in the preparation of the resin composition, the softening point is preferably 60 ° C or higher.
Specifically, the solid epoxy resin is a compound having two or more epoxy groups in the molecule, and bisphenol epoxy resin, phenol novolac epoxy resin, cresol novolac epoxy resin, Benzene type epoxy resin, naphthalene type epoxy resin, fluorene type epoxy resin, etc. Furthermore, in order to further improve the adhesion between the reinforcing fiber and the matrix resin, a solid epoxy resin having an oxazolidone ring structure can be used. These epoxy resins can be used individually or in combination of 2 or more types.

Regarding the bisphenol epoxy resin, there are bisphenol A epoxy resin, bisphenol F epoxy resin, and brominated bisphenol A epoxy resin.
As a bisphenol A type solid epoxy resin, products of Mitsubishi Chemical Co., Ltd. include, for example, jER1001, jER1002, jER1003, jER1004, jER1055, jER1007, jER1009, jER1010.

As bisphenol F-type solid epoxy resins, products of Mitsubishi Chemical Corporation include, for example, jER4004P, jER4005P, jER4007P, and jER4010P.
Examples of brominated bisphenol A type solid epoxy resin include jER5046B80, a product of Mitsubishi Chemical Corporation.

As phenol novolak type solid epoxy resins, it includes jER152 and jER154 products of Mitsubishi Chemical Corporation.
As cresol novolac type solid epoxy resins, the products of Nippon Kayaku Co., Ltd. EOCN-1020, EOCN-102S, EOCN-104S, etc. are included.

As the biphenyl type solid epoxy resin, jER YX4000, jER YX4000H, jER YL6121H, etc. are products of Mitsubishi Chemical Corporation.
Examples of naphthalene-type solid epoxy resins include NC-7000L and NC-7300L, products of Nippon Kayaku Co., Ltd.

Examples of the 茀 -type solid epoxy resin include oncoat EX-1010, EX-1011, and EX-1012 manufactured by Nagase ChemteX.
Examples of the solid epoxy resin having an oxazolidone ring structure include AER4152, a product of Asahi Kasei Chemicals Co., Ltd., and DER858 manufactured by Dow Co., Ltd. and the like.
Among these, in the case where the softening point is at least higher than the temperature, the component [B] is selected.

Component [C] Liquid epoxy resin Liquid epoxy resin is only required to be liquid at 25 ° C during use. However, when a liquid epoxy resin is used as a matrix resin, a polymer containing a carboxyl group is used. Polyvinyl formal resins typified by vinyl formal resins have high compatibility with epoxy resins. Therefore, the type of the epoxy resin is preferably a liquid at 150 ° C. The reason for this is that the melting temperature of polyvinyl formal to a liquid epoxy resin is usually 130 ° C to 150 ° C. Here, the liquid state means a state in which it is liquid at normal temperature (25 ° C) and contains no solids. The viscosity of the liquid epoxy resin is preferably 1.5 Pa · s to 15 Pa · s at 25 ° C.

The carboxyl-containing polyvinyl formal resin is particles having a large number of pores (pore volume (representative value); 0.71 ml / g). If the polyvinyl acetal particles containing a carboxyl group are mixed with a liquid epoxy resin in advance Refining and filling the epoxy resin with fine pores improves the solubility, dissolves in the epoxy resin at least at 100 ° C, and shortens the dissolution time if it is 130 ° C to 150 ° C.
The liquid epoxy resin can be obtained by using one liquid epoxy resin or by mixing two or more liquid epoxy resins.

Examples of the liquid epoxy resin include a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, an alicyclic epoxy resin, and a glycidylamine type epoxy resin.
Examples of the bisphenol A type liquid epoxy resin include jER827, jER828, and the like, among products of Mitsubishi Chemical Corporation.
Examples of the bisphenol F-type epoxy resin include jER806, jER807, and the like, among products of Mitsubishi Chemical Corporation.

As the alicyclic epoxy resin, there are Cellel 2021P and Celloxide 2081, which are products of Daicel Chemical Industry Co., Ltd.
Examples of glycidylamine epoxy resins include ELM434 from Sumitomo Chemical, YH-434L from Ciba specialty chemicals, jER630, jER604 from Mitsubishi Chemical Corporation, or Huntsman Advanced Materials) araldite MY0600, GAN and GOT products of Nippon Kayaku Co., Ltd.

The liquid epoxy resin is a liquid compound having at least one oxetanyl group. It may also be a liquid compound having a lower molecular weight than a general liquid epoxy resin and a viscosity at 25 ° C of 2 mPa · s to 100 mPa · s. Such a liquid compound is preferably used to reduce the viscosity of one of the liquid epoxy resins.

Examples of the liquid compound include monoepoxides. Examples of monoepoxides include alcohol-based allyl glycidyl ether, n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and higher glycidyl ether. Examples of the phenol type include phenyl glycidyl ether, p-third butyl phenyl glycidyl ether, Cresyl Glycidyl Ether, and phenol (EO) 5 glycidyl ether (Phenol (EO) 5 Glycidyl Ether), second butylphenyl glycidyl ether, cardanol DiGlycidyl Ether, dibromophenyl glycidyl ether, and the like.

Examples of other compounds include glycidyl methacrylate, styrene oxide, and glycidyl tertiary carboxylic acid. Examples of diepoxides include N, N'-diglycidylaniline, N, N. -Diglycidyl-O-toluidine, hexahydrophthalic anhydride diglycidyl ester, polyethylene glycol diglycidyl ether (n = 2 to 13), ethylene glycol diglycidyl ether, polypropylene glycol di Glycidyl ether (n = 3 ～ 11), neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, diglycidyl-O-o-phenylene Diformate, dibromo neopentyl glycol diglycidyl ether and the like.

Examples of the triepoxides include glycerol polyglycidyl ether and trimethylolpropane polyglycidyl ether.

By using component [B] and component [C] together, it is possible to prevent the resin from leaking out of the mold caused by the decrease in resin viscosity during thermal curing when forming into a carbon fiber composite material, and to prevent the adjustment of the viscosity of the prepreg or heat A decrease in toughness due to an increase in crosslinking density during hardening.

Component [D] Amine hardener The amine hardener [D] is preferably dicyandiamine or a derivative thereof.
For example, there are aromatic amines such as diaminodiphenylmethane, diaminodiphenylsulfonium, aliphatic amines, imidazole derivatives, dicyandiamine, tetramethylguanidine, thiourea addition amines, and their Isomers, isomers, etc. Among these, dicyandiamine is particularly preferable from the viewpoint of excellent storability of the prepreg.
Examples of the derivative include a reactant with an epoxy resin, a reactant with an ethylene compound or an acrylic compound, and the like obtained by bonding various compounds to dicyandiamine.

Dicyandiamine is a particulate hardener and has the characteristics that it does not dissolve in the epoxy resin component at a temperature of 25 ° C, but maintains a state in which the particulate dispersed in the epoxy resin component is maintained. The contact area of the epoxy group in the resin component becomes small and hardly exhibits reactivity. Generally, when heated to 180 ° C. or higher, it dissolves in an epoxy resin and reacts with the epoxy group.

In order to maintain the storage stability of the obtained resin composition, the amount of heat generated when the prepreg is hardened, and the heat resistance of the hardened material within an appropriate range, the blending amount of the amine hardener [D] is relative to the components [B] and 100 parts by weight of all the epoxy resin components of the component [C] is preferably in the range of 1 to 10 parts by weight, and further preferably in the range of 2 to 8 parts by weight. By setting the compounding amount of the dicyandiamine to the above range, a good cured product can be obtained without causing a decrease in heat resistance or mechanical properties due to insufficient curing or excessive reaction heat generation. Examples of commercially available dicyandiamines include DICY-7 and DICY-15 (above, manufactured by Mitsubishi Chemical Corporation).

Furthermore, in order to improve the hardening activity of the amine hardener used in the preparation of the prepreg of the present invention, it is preferred to use a hardening aid in combination. For example, when the curing agent of epoxy resin is dicyandiamine, the curing aid is preferably 3-phenyl-1,1-dimethylurea, 3- (3,4-dichlorophenyl) -1 1,1-dimethylurea (DCMU), 3- (3-chloro-4-methylphenyl) -1,1-dimethylurea, 2,4-bis (3,3-dimethylfluorenil) ) Urea derivatives such as toluene. Generally, when dicyandiamine is used alone for curing, a temperature of 170 ° C to 180 ° C is required. However, if these curing aids are used, they can be hardened at 80 ° C to 150 ° C when used in combination with dicyandiamine.

Examples of commercially available ureas include: DCMU99 (manufactured by Powertech Technology Inc Japan), Omicure 24, Omicure 52, Omicure 94 ( The above are manufactured by CVC Specialty Chemicals, Inc.).

The method for producing the resin composition used in the production of the prepreg of the present invention is not particularly limited, and it can be constituted by using a general stirring heating device such as a kneader, a planetary mixer, and a stirring pressure heating device Each component of a composition is fully mixed and manufactured.
When manufacturing a resin composition, it is preferred that a polyvinyl formal resin including a carboxyl group-containing polyvinyl formal resin is first dissolved in a liquid epoxy resin at a temperature of 130 ° C or higher, and then the solid epoxy resin is Dissolve at 80 ° C to 90 ° C, and finally disperse the amine hardener at 50 ° C to 60 ° C.

The reinforcing fiber is not particularly limited as the reinforcing fiber, and it may be appropriately selected from known ones as a reinforcing fiber constituting the fiber-reinforced composite material according to the application and the like. As the reinforcing fiber used in the present invention, glass fiber is exemplified. , Carbon fiber, graphite fiber, aromatic polyamide fiber, boron fiber, alumina fiber and silicon carbide fiber. These reinforcing fibers may be used in combination of two or more kinds, but in order to obtain a lighter weight and more durable molded product, carbon fibers or graphite fibers are preferably used. In particular, in applications where material weight reduction or high strength is required, carbon fibers are suitably used because of their excellent specific elastic modulus.

Manufacturing method of prepreg The manufacturing method of the prepreg of this invention is not specifically limited. Examples include a hot melt method in which a resin composition is reduced in viscosity by heating and impregnated with a reinforcing fiber, or the resin composition is dissolved in a solvent such as methyl ethyl ketone or methanol to reduce the viscosity, and Contains a method (wet method) of impregnating the reinforcing fibers.
The wet method is a method in which a reinforcing fiber is immersed in a solution of a resin composition, and then the solvent is evaporated by using an oven or the like. The hot-melt method (dry method) is a resin composition having a reduced viscosity by heating. A method of directly impregnating a reinforcing fiber, or temporarily manufacturing a film obtained by coating a resin composition on a release paper or the like, and then superposing the film from both sides or one side of the reinforcing fiber, and heating and pressing, A method for impregnating a reinforcing fiber with a resin composition. According to the hot-melt method, since there is substantially no residual solvent in the prepreg, it is a preferable aspect in the present invention.

In the prepreg of the present invention, the fiber volume fraction (Vf) of the carbon fiber to be impregnated is preferably 40 vol% to 90 vol% when the volume of the prepreg including the carbon fiber is 100 vol%. It is more preferably 50 vol% to 80 vol%. When Vf is 50 vol% or more, the quality of the obtained composite material does not become excessively large, and the advantages of a fiber-reinforced composite material excellent in specific strength and specific elastic coefficient can be maintained. In addition, if Vf is 80 vol% or less, impregnation defects of the resin composition will not occur, and the obtained composite material will have fewer voids, and its mechanical properties will not be reduced.

Examples of the form of the reinforcing fiber used in the present invention include a shape in which continuous fibers are aligned in one direction, a form in which continuous fibers are interlaced to form a fabric, and a shape in which bundles are aligned in one direction and held by a horizontal line auxiliary line. 2. Forms in which a plurality of unidirectional reinforcing fiber sheets are superimposed in different directions and stitches are stitched with an auxiliary thread to form a fixed multiaxial warp knitted fabric; and a form in which the reinforcing fibers are made into a non-woven fabric However, in terms of exhibiting the strength of the hardened material, a form in which continuous fibers are aligned unidirectionally is preferred. The weight per unit area of the reinforcing fibers can be freely set according to the purpose of use of the fiber-reinforced composite material, but 50 g / m ² to 2000 g / m ² is a practically preferable range.

The carbon fibers that are preferably used in the present invention can use all kinds of carbon fibers depending on the application, but in terms of impact resistance, carbon fibers having a tensile elastic modulus of 230 GPa to 400 GPa are preferred. From the viewpoint of strength, a carbon fiber having a tensile strength of 4.4 GPa to 6.5 GPa is preferably used because a composite material having high rigidity and mechanical strength can be obtained. In addition, the tensile elongation is also an important factor, and high strength and high elongation fibers of 1.7% to 2.3% are preferred.

Examples of commercially available carbon fiber products include "Torayca (registered trademark)" T800G-24K, "Torayca (registered trademark)" T800S-24K, and "Torayca (registered trademark)" (Registered trademark) "T700G-24K," torayca (registered trademark) "T300-3K and" torayca (registered trademark) "T700S-12K (manufactured by Toray (stock) above), TR50S (Manufactured by Mitsubishi Rayon), etc.

The prepreg of the present invention is obtained by impregnating a reinforcing fiber with the resin composition of the present invention, and a fiber-reinforced composite material having excellent strength, heat resistance, and the like can be obtained by hardening.
As a method for producing the fiber-reinforced composite material, a known method can be used. As representative methods, there are a prepreg method, a filament winding method, and a resin transfer molding method. The viscosity of the resin composition applicable to the prepreg method ranges from 1 Pa · s to 10,000 Pa · s, and the viscosity of the resin composition applicable to the filament winding method ranges from 15 mPa · s to 30 Pa · s. The viscosity of the resin composition used for resin injection molding ranges from 350 mPa · s to 1 Pa · s.

Regarding the resin composition used in the prepreg of the present invention, the viscosity of the resin composition is increased by adding a carboxyl group-containing polyvinyl formal, so it is preferably applied to a prepreg method capable of coping with a high viscosity.
For example, when a fiber-reinforced composite material is produced using the prepreg, the prepreg sheet is aligned, laminated in a predetermined direction, and heated to integrate them, and finally heated and pressed to harden .

The forming method in the manufacturing method of the fiber-reinforced composite material of the present invention includes an autoclave forming method, a vacuum bag forming method, an oven forming method, a press forming method, a continuous press forming method, a drawing forming method, an inner pressure forming method, and a coating method. Sheet wrap forming method.

The fiber-reinforced composite material formed by laminating and thermosetting the prepreg of the present invention is suitably used in aircraft applications, general industrial applications, and sports applications. More specifically, in aerospace applications, primary structural materials such as main wing, tail and floor beam; aircraft passenger cabins, flaps, ailerons, cowls, Suitable for secondary structural materials such as fairing and interior materials; rocket motor housings and satellite structural materials. Among the aerospace applications, the impact resistance is particularly required, and it is exposed to low temperature during high flight. Therefore, it is an aircraft primary structural material application that requires tensile strength at low temperature, especially the fuselage surface or main wing. In the surface layer, the fiber-reinforced composite material of the present invention is particularly suitably used. Furthermore, in general industrial applications, it is used for structural materials of moving bodies such as automobiles, ships, and railway vehicles, drive shafts, leaf springs, windmill blades, various turbines, pressure vessels, flywheels, paper-making rolls, roofing materials, cables, and stiffeners. Suitable for use in civil and building materials such as restoration reinforcement. Furthermore, in sports applications, it is suitably used in racket applications such as golf clubs, fishing rods, tennis, badminton, and squash, bat applications such as hockey, and ski pole applications.

[Example]
Next, the present invention will be further described in detail through examples, but the present invention is not limited to these.

＜ Specific mass and composition of the used polyvinyl formal ＞
The carboxyl group-containing polyvinyl formal resin used in the examples is Vinylec (registered trademark) manufactured by JNC Corporation, grade: PVF-C. The weight average molecular weight Mw is 62000, the vinyl formal (constituting unit a) is 70.42 mol%, the vinyl acetate (constituting unit b) is 10.34 mol%, the vinyl alcohol (constituting unit c) is 16.09 mol%, and the acrylic acid (constituting unit) d) is 3.15 mol%.

The polyvinyl formal used in the comparative example was Vinylec (registered trademark), grade: PVF-K, PVF-E manufactured by JNC Corporation. Regarding PVF-K, the weight-average molecular weight Mw is 54000, the vinyl formal (constituting unit a) is 75.13 mol%, the vinyl acetate (constituting unit b) is 12.26 mol%, and the vinyl alcohol (constituting unit c) is 12.61 mol% .

Regarding PVF-E, the weight-average molecular weight Mw is 120,000, the vinyl formal (constituting unit a) is 74.80 mol%, the vinyl acetate (constituting unit b) is 12.66 mol%, and the vinyl alcohol (constituting unit c) is 12.54 mol% . PVF-K and PVK-E are polyvinyl formal resins to which no carboxyl group is introduced.

＜ Other thermoplastic resins used ＞
As another thermoplastic resin, a phenoxy resin (PKHP 200 Bar Industries) was used. Regarding PKHP200, the weight average molecular weight Mw was 52,000.

＜ Liquid epoxy resin used ＞
jER828: Bisphenol A epoxy resin average molecular weight 370 epoxy equivalent 184 ～ 194 manufactured by Mitsubishi Chemical (liquid at 25 ° C, viscosity (25 ° C): 12 Pa · s ～ 15 Pa · s)

＜ Solid epoxy resin used ＞
jER1001: Bisphenol A epoxy resin average molecular weight 900 epoxy equivalent 450 ~ 500 Manufactured by Mitsubishi Chemical (softening point: 64 ° C)

＜ Amine hardener used ＞
DICY7: Dicyandiamine manufactured by Mitsubishi Chemical

<Used hardening accelerator>
DCMU99: 3- (3,4-dichlorophenyl) -1,1-dimethylurea, manufactured by Powertech Technology Inc Japan

＜ Carbon fiber used ＞
TR50S15L: Mitsubishi Chemical's tensile strength of 4.9 GPa, tensile elastic modulus of 240 GPa, tensile elongation of 2%

＜ Measurement of resin viscosity ＞
Regarding the viscosity measurement of the resin composition, if an amine hardener is present, the reaction is performed at 80 ° C. and the viscosity rises. Therefore, a resin composition including component A, component B, and component C or a resin including component B and component C is prepared. Composition.
Using a rheometer (MCR-302 Anton Paar), the temperature-viscosity relationship was performed under conditions of a swing angle of 60%, a frequency of 0.5 Hz, a heating rate of 3 ° C / min, and a temperature of 30 ° C to 130 ° C. Determination.
Hereinafter, the preparation method of the resin composition used for viscosity measurement is shown. In the viscosity measurement, the same composition as in the examples and comparative examples was prepared except that the amine hardener was not included.

<Composition for measuring viscosity of Example 1>
A heating stirrer (manufactured by RCH-20L EYELA) with an aluminum block bath was used for heating, and a stirring motor (manufactured by BLh600 HEIDON) was used for the stirring.
Weigh 60g of liquid bisphenol A epoxy resin jER828 (manufactured by Mitsubishi Chemical) into a 200 mL beaker, and add vinylec ((trademark) grade: PVF-C manufactured by JNC Corporation. ) 7.2 g, dissolve at a temperature of 130 ° C, 120 rpm, and 120 minutes.
Next, the temperature was lowered to 90 ° C., and 60 g of solid bisphenol A epoxy resin jER1001 (manufactured by Mitsubishi Chemical) was added, and the mixture was heated and dissolved at 120 rpm. Finally, in a vacuum oven (manufactured by Vacuum Oven ADP300 Yamato), vacuum degassing was performed by a diaphragm pump (Diaphragm pump) at 90 ° C and 30 kPa.

<Composition for measuring viscosity of Comparative Example 1>
A heating stirrer (manufactured by RCH-20L EYELA) with an aluminum block bath was used for heating, and a stirring motor (manufactured by BLh600 HEIDON) was used for the stirring.
60 g of liquid bisphenol A epoxy resin jER828 (manufactured by Mitsubishi Chemical) was weighed into a 200 mL beaker, and 60 g of solid bisphenol A epoxy resin jER1001 (manufactured by Mitsubishi Chemical) was added, and the mixture was made at 90 ° C and 120 rpm. Heat to dissolve. Finally, in a vacuum oven (manufactured by Vacuum Oven ADP300 Yamato), vacuum degassing was performed by a diaphragm pump (Diaphragm pump) at 90 ° C and 30 kPa.

<Composition for measuring viscosity of Comparative Example 2>
A heating stirrer (manufactured by EYELA) with an aluminum block bath was used for heating, and a stirring motor (manufactured by BLh600 HEIDON) was used for stirring.
60 g of liquid bisphenol A epoxy resin jER828 (manufactured by Mitsubishi Chemical) was weighed into a 200 mL beaker, and 7.2 g of a phenoxy resin (PKHP200) manufactured by Bacon Co., Ltd. was added. The temperature was 130 ° C, 120 rpm, Let it dissolve in 40 minutes.
Next, the temperature was lowered to 90 ° C., and 60 g of solid bisphenol A epoxy resin jER1001 (manufactured by Mitsubishi Chemical) was added, and the mixture was heated and dissolved at 120 rpm. Finally, vacuum defoaming was performed in a vacuum oven (manufactured by Vacuum Oven ADP300 Yamato) at 90 ° C and 30 kPa.

<Composition for measuring viscosity of Comparative Example 3>
A heating stirrer (manufactured by EYELA) with an aluminum block bath was used for heating, and a stirring motor (manufactured by BLh600 HEIDON) was used for stirring.
Weigh 60 g of liquid bisphenol A epoxy resin jER828 (manufactured by Mitsubishi Chemical) into a 200 mL beaker, and add vinylec ((trademark) grade: PVF-K, manufactured by JNC Co., Ltd. ) 7.2 g, dissolve at a temperature of 130 ° C, 120 rpm, and 120 minutes.

Next, the temperature was lowered to 90 ° C., and 60 g of solid bisphenol A epoxy resin jER1001 (manufactured by Mitsubishi Chemical) was added, and the mixture was heated and dissolved at 120 rpm. Finally, vacuum defoaming was performed in a vacuum oven (manufactured by Vacuum Oven ADP300 Yamato) at 90 ° C and 30 kPa.

<Composition for measuring viscosity of Comparative Example 4>
A heating stirrer (manufactured by EYELA) with an aluminum block bath was used for heating, and a stirring motor (manufactured by BLh600 HEIDON) was used for stirring.
Weigh 60g of liquid bisphenol A epoxy resin jER828 (manufactured by Mitsubishi Chemical) into a 200 mL beaker, and add vinylec ((trademark) grade: PVF-E manufactured by JNC Corporation. ) 7.2 g, dissolve at a temperature of 130 ° C, 120 rpm, and 120 minutes.

Next, the temperature was lowered to 90 ° C., and 60 g of solid bisphenol A epoxy resin jER1001 (manufactured by Mitsubishi Chemical) was added, and the mixture was heated and dissolved at 120 rpm. Finally, vacuum defoaming was performed in a vacuum oven (manufactured by Vacuum Oven ADP300 Yamato) at 90 ° C and 30 kPa.

<Measurement of 90 ° tensile strength of fiber-reinforced composite materials>
A water-cooled composite material cutting machine (high-speed cutter AC) was used to prepare the fiber-reinforced composite material with a thickness of 2 mm and 320 cm × 320 cm so that the reinforcing fibers were aligned at 90 ° with respect to the longitudinal direction of the test piece. -500CF (manufactured by Maruto Seisakusho)) Cut out a test piece (length 250 mm × width 25 mm). An autograph (AG-IS 100 kN) manufactured by Shimadzu Corporation used a 5 kN load cell for this test piece at a test speed of 1 mm / min, 25 ° C, and 50% humidity. Next, a 90 ° tensile test was performed (based on JIS K7165). The strain (elongation) was measured using a video extensometer, and the modulus of elasticity was measured in accordance with JIS K7165. Make the distance between the marks 50 mm and the distance between the chucks 150 mm.

<Measurement of 0 ° compressive strength of fiber-reinforced composite materials>
From the produced fiber-reinforced composite material with a thickness of 2 mm and 320 cm × 320 cm, a water-cooled composite material cutter (high-speed cutter AC) was used to temporarily align the reinforcing fibers at 0 ° with respect to the longitudinal direction of the test piece. -500CF (manufactured by Maruto Seisakusho)) Cut out a test piece with a width of 98 mm and a length of 65 mm. Then, the portion of the test piece with the adhesive tab (adhesive sheet) and the bonding side of the tab were scratched with sandpaper having a particle size of 600 or 1000 to adhere the adhesive. However, the direction in which the scratches were made was a 90 ° direction with respect to the fiber direction on the CFPR test piece side. As the splice, a glass epoxy board cut out with a thickness of 2 mm, a width of 25 mm, and a length of 100 mm was prepared. A two-liquid type epoxy adhesive (three-bond) was used to bond the test piece to the test piece and left for two days. In addition, it was performed in a constant temperature room at 25 ° C. and a humidity of 50%.

Using a water-cooled composite cutter (manufactured by AC-500CF Maruto Manufacturing Co., Ltd.), the reinforcing fibers are aligned at 0 ° with respect to the longitudinal direction of the test piece. Length 55 mm × width 20 mm (20 mm in width and 15 mm in length in the measurement section). A strain gauge (model: KFGS-1-120-C1-11L1M2R manufactured by Kyowa Electric Co., Ltd.) was attached to both sides of the test piece. For the adhesive used for the attachment, an instant adhesive (for CC-33A Kyowa Denki Co., Ltd.) for strain gages was used.
This test piece was fixed to a compression test fixture according to Method 3 of JISK 7018, and an autograph (AG-IS 100 kN) manufactured by Shimadzu Corporation was used at a test speed of 1 mm / min, 25 ° C, and a humidity of 50. A 0 ° compression test was performed under the conditions of%. In addition, the strain was measured by a strain gauge, and the elastic coefficient was calculated in accordance with the elastic coefficient calculation method of JIS K7076.

<Measurement of 0 ° flexural strength of fiber-reinforced composite materials>
A water-cooled composite material cutter (high-speed cutter AC) was used to prepare the fiber-reinforced composite material with a thickness of 2 mm and 320 cm × 320 cm so that the reinforcing fibers were aligned at 0 ° with respect to the longitudinal direction of the test piece. -500CF (manufactured by Maruto Manufacturing Co., Ltd.) A test piece (length 100 mm × width 15 mm) was cut out, and a four-point bending jig (radius 3 mm indenter, fulcrum radius 3 mm, and upper fulcrum) Autograph (AG-IS 100 kN) manufactured by Shimadzu Corporation at a distance of 27 mm and a distance of 81 mm between the lower fulcrum points was implemented at 0 ° at a test speed of 5 mm / min, 25 ° C, and 50% humidity. Measurement of flexural strength (based on JIS K7074). The flexural modulus of elasticity is calculated by calculating the gradient of the initial straight portion of the measured load-displacement curve and calculating the flexural modulus of elasticity in accordance with the four-point bending test (method B) of JIS K7074.

<Measurement of impact resistance of fiber-reinforced composite materials>
A water-cooled composite material cutter (high-speed cutter AC) was used to prepare the fiber-reinforced composite material with a thickness of 2 mm and 320 cm × 320 cm so that the reinforcing fibers were aligned at 0 ° with respect to the longitudinal direction of the test piece. -500CF (manufactured by Maruto Seisakusho)) Cut out a test piece (length 80 mm × width 10 mm).
In a 25 ° C, 50% humidity environment, a Charpy impact tester (manufactured by Oji Measurement Equipment Co., Ltd.) was used to swing the hammer from a swing angle of 149.7 ° by a flatwise impact, and this test piece An impact test was performed by applying 2 J of energy (according to JIS K7077).

<Bending test piece of fiber-reinforced composite material, fracture surface observation of 90 ° tensile test piece>
A self-bending test piece and a 90 ° tensile test piece were used to cut a sample including a fracture surface using a cutter, and an electron microscope (apparatus: Hitachi High-technologies SU8020, analysis conditions: acceleration voltage 1 kv, current 10 μA) The fracture surface was observed as follows.
Before the electron microscope observation, the fracture surface of the bending test piece was observed in advance through a microscope (apparatus: Keyence VHX-2000, analysis conditions: side light), and the compression failure surface and tensile failure surface were observed. Confirm it (Figure 2).
When the fracture surface in FIG. 2 was observed, it was found that there was an interface between the compressed portion and the stretched portion during the bending test in the test piece, and the fracture surface stretched up to the interface was taken as the tensile failure. In the surface (A), the compressed fracture surface is referred to as a compression fracture surface (B), and the area of the fracture surface and each fracture surface is determined by image analysis.
The adhesion between the carbon fiber and the resin on the fracture surface of the bending test piece was evaluated by measuring the number of carbon fiber breaks in the tensile fracture surface of the fracture surface photographed by SEM. FIG. 3 shows an SEM photograph of the tensile fracture surface evaluated.
Regarding the adhesion between the carbon fiber and the resin on the fracture surface of the test piece of the 90 ° tensile test, the fracture surface photographed by the SEM was evaluated by observing the adhesion state of the resin on the carbon fiber surface with the following criteria. (Figure 4 and Table 5)
：: Adhesion of the resin to the carbon fibers was observed in a large amount. ○: Adhesion of resin to carbon fibers was observed.
Δ: A small amount of adhesion of the resin to the carbon fibers was observed. X: No adhesion to carbon fibers was observed.

[Example]
Example 1
<Preparation of resin composition>
As a machine for preparing the resin composition, a 10 L planetary mixer (PLM-15) manufactured by Inoue Manufacturing was used.

1.7 kg of liquid bisphenol A epoxy resin jER828 (manufactured by Mitsubishi Chemical) was added to the kettle, followed by vinylec ((registered trademark) grade: PVF- manufactured by JNC Co., Ltd. C) 204 g, at a temperature of 130 ° C, a rotation speed of 28 r / min and a rotation speed of 77 r / min, while decompressing (vacuum degree: 200 kPa), defoaming and mixing for 3 hours.

After confirming that Vinylec was dissolved, 1.7 kg of solid epoxy resin was put in several times and defoamed while decompressing (vacuum degree: 200 kPa) at 90 ° C for 30 minutes while rotating at 28 r / min. 2. Rotate at 77 r / min for mixing.

After the solid epoxy resin was dissolved, the temperature was lowered to 50 ° C. Add 204 g of dicyandiamine (DICY7) and 80 g of 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU99) as hardeners and reduce the pressure (vacuum degree: 200 kPa ), Then start stirring, mix at 50 ° C for 90 minutes, rotate speed: 28 r / min revolution, 77 r / min rotation.

＜ Production of resin sheet ＞
The temperature was set on the basis of the viscosity measurement results of FIGS. 1 and 6.
The resin composition prepared by the method was added to an oven in advance and heated to 65 ° C. The resin composition was added to a liquid bank heated to 65 ° C in a coating device, and coated on a release paper by a coating roller at a roll temperature of 60 ° C and a coating width of 290 mm to produce a unit area weight of 26.96 g / m ² of resin sheet.

＜ Production of unidirectional prepreg sheet ＞
Carbon fibers arranged unidirectionally in sheet form (15,000 filaments, unit weight 1.000 g / m, monofilament diameter 6.8 μm, tensile strength 4900 MPa, tensile modulus of elasticity 240 GPa, tensile elongation 2 %) The above-mentioned produced resin sheet was superimposed, and the resin composition was impregnated by heating and pressing to prepare a prepreg sheet having a fiber volume content rate of 55%, a unit volume weight of 76.96 g / m ² , and a slit width of 260 mm. material. The heating was set based on the viscosity measurement results in FIGS. 1 and 6.

＜ Production of fiber-reinforced composite material by autoclave method ＞
The unidirectional prepreg sheet produced according to the above contents was laminated in such a way that the fiber-reinforced composite material had a thickness of 2 mm and a thickness of 320 mm × 320 mm, and was unified at 130 ° C in an autoclave. , 2 hr, 0.5 MPa, heat-pressed and hardened to produce a fiber-reinforced composite material.

[Comparative example]
Comparative Example 1
<Preparation of resin composition>
As a machine for preparing the resin composition, a 10 L planetary mixer (PLM-15) manufactured by Inoue Manufacturing was used.

1.8 kg of liquid bisphenol A epoxy resin jER828 (manufactured by Mitsubishi Chemical) was added to the kettle, and 1.8 kg of solid epoxy resin was added in several times, while decompressing (vacuum degree: 200 kPa) while defoaming, and rotating at a speed : Revolving at 28 r / min and rotating at 77 r / min at 90 ° C for 30 minutes.
After the solid epoxy resin was dissolved, the temperature was lowered to 35 ° C. Add 200 g of dicyandiamine (DICY7) and 80 g of 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU99) as hardeners and reduce the pressure (vacuum degree: 200 kPa ), Then start stirring, knead at 35 ° C for 90 minutes, rotating speed: 28 r / min revolution, 77 r / min rotation.

＜ Production of resin sheet ＞
The temperature was set on the basis of the viscosity measurement results of FIGS. 1 and 6.
The resin composition prepared by the method was added to an oven in advance and heated to 55 ° C. The resin composition was added to a liquid bank heated to 55 ° C by a coating device, and coated on a release paper by a coating roller at a roll temperature of 50 ° C and a coating width of 290 mm to produce a weight per unit area of 26.92 g. / m ² of resin sheet.

＜ Production of unidirectional prepreg sheet ＞
On a unidirectional sheet of carbon fibers (15,000 filaments, unit weight 1.000 g / m, monofilament diameter 6.8 μm, tensile strength 4900 MPa, tensile modulus of elasticity 240 GPa, tensile elongation 2%) The produced resin sheet was superimposed, and the resin composition was impregnated by heating and pressing to prepare a prepreg sheet having a fiber volume content rate of 55%, a unit volume weight of 76.92 g / m ² , and a slit width of 260 mm. The heating was set based on the viscosity measurement results in FIGS. 1 and 6.

＜ Production of fiber-reinforced composite material by autoclave method ＞
The unidirectional prepreg sheet produced according to the above contents was laminated in such a way that the fiber-reinforced composite material had a thickness of 2 mm and a thickness of 320 mm × 320 mm, and was unified at 130 ° C in an autoclave. , 2 hr, 0.5 MPa, heat-pressed and hardened to produce a fiber-reinforced composite material.

Comparative Example 2
<Preparation of resin composition>
As a machine for preparing the resin composition, a 10 L planetary mixer (PLM-15) manufactured by Inoue Manufacturing was used.
1.7 kg of liquid bisphenol A-type epoxy resin jER828 (manufactured by Mitsubishi Chemical) was added to the kettle, followed by 204 g of phenoxy resin (PKHP200) manufactured by Bar Industries Co., Ltd., at a temperature of 130 ° C, rotation speed: 28 revolutions r / min, rotation 77 r / min, while decompressing (vacuum degree: 200 kPa), defoaming and mixing for 1 hour.

After confirming the dissolution of the phenoxy resin, 1.7 kg of solid epoxy resin was put in several times, and the pressure was reduced (vacuum degree: 200 kPa) while defoaming at 90 ° C for 30 minutes. Rotation speed: 28 r / min, revolution Rotate at 77 r / min for mixing.
After the solid epoxy resin was dissolved, the temperature was lowered to 50 ° C. Add 204 g of dicyandiamine (DICY7) and 80 g of 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU99) as hardeners and reduce the pressure (vacuum degree: 200 kPa ), Then start stirring, knead at 50 ° C for 60 minutes, rotating speed: 28 r / min revolution, 77 r / min rotation.

＜ Production of resin sheet ＞
The temperature was set on the basis of the viscosity measurement results of FIGS. 1 and 6.
The resin composition prepared by the method was added to an oven in advance and heated to 62 ° C. The resin composition was added to a liquid bank heated to 62 ° C in a coating device, and coated on a release paper by a coating roller at a roll temperature of 57 ° C and a coating width of 290 mm to produce a weight per unit area of 26.90 g / m ² of resin sheet.

＜ Production of unidirectional prepreg sheet ＞
On a unidirectional sheet of carbon fibers (15,000 filaments, unit weight 1.000 g / m, monofilament diameter 6.8 μm, tensile strength 4900 MPa, tensile modulus of elasticity 240 GPa, tensile elongation 2%) The prepared resin sheet was superimposed, and the resin composition was impregnated by applying heat and pressure to prepare a prepreg sheet having a fiber volume content rate of 55%, a unit volume weight of 76.90 g / m ² , and a slit width of 260 mm. The heating was set based on the viscosity measurement results in FIGS. 1 and 6.

＜ Production of fiber-reinforced composite material by autoclave method ＞
The unidirectional prepreg sheet produced according to the above contents was laminated in such a way that the fiber-reinforced composite material had a thickness of 2 mm and a thickness of 320 mm × 320 mm, and was unified at 130 ° C in an autoclave. , 2 hr, 0.5 MPa, heat-pressed and hardened to produce a fiber-reinforced composite material.

Comparative Example 3
<Preparation of resin composition>
As a machine for preparing the resin composition, a 10 L planetary mixer (PLM-15) manufactured by Inoue Manufacturing was used.
1.7 kg of liquid bisphenol A epoxy resin jER828 (manufactured by Mitsubishi Chemical) was added to the kettle, followed by vinylec ((registered trademark) grade: PVF- manufactured by JNC Co., Ltd. K) 204 g, at a temperature of 130 ° C, a rotation speed of 28 r / min and a rotation speed of 77 r / min while decompressing (vacuum degree: 200 kPa) and defoaming for 2 hours.

After confirming that Vinylec was dissolved, 1.7 kg of solid epoxy resin was put in several times and decompressed (vacuum degree: 200 kPa) while defoaming at 90 ° C for 30 minutes while rotating at 28 revolutions per revolution. min, rotation 77 r / min for mixing.
After the solid epoxy resin was dissolved, the temperature was lowered to 50 ° C. Add 204 g of dicyandiamine (DICY7) and 80 g of 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU99) as hardeners and reduce the pressure (vacuum degree: 200 kPa ), Then start stirring, and mix at 50 ° C for 30 minutes, rotating speed: 28 r / min, 77 r / min.

＜ Production of resin sheet ＞
The temperature was set on the basis of the viscosity measurement results of FIGS. 1 and 6.
The resin composition prepared by the method was added to an oven in advance and heated to 65 ° C. The resin composition was added to a liquid bank heated to 65 ° C in a coating device, and coated on a release paper by a coating roller at a roll temperature of 60 ° C and a coating width of 290 mm to produce a unit area weight of 26.96 g / m ² of resin sheet.

＜ Production of unidirectional prepreg sheet ＞
On a unidirectional sheet of carbon fibers (15,000 filaments, unit weight 1.000 g / m, monofilament diameter 6.8 μm, tensile strength 4900 MPa, tensile modulus of elasticity 240 GPa, tensile elongation 2%) The prepared resin sheet was superimposed and heated and pressurized to impregnate the resin composition, and a prepreg sheet having a fiber volume content rate of 55%, a unit volume weight of 76.96 g / m ² , and a slit width of 260 mm was produced. The heating was set based on the viscosity measurement results in FIGS. 1 and 6.

＜ Production of fiber-reinforced composite material by autoclave method ＞
The unidirectional prepreg sheet produced according to the above contents was laminated in such a way that the fiber-reinforced composite material had a thickness of 2 mm and a thickness of 320 mm × 320 mm, and was unified at 130 ° C in an autoclave. , 2 hr, 0.5 MPa, heat-pressed and hardened to produce a fiber-reinforced composite material.

Comparative Example 4
<Preparation of resin composition>
As a machine for preparing the resin composition, a 10 L planetary mixer (PLM-15) manufactured by Inoue Manufacturing was used.
1.7 kg of liquid bisphenol A epoxy resin jER828 (manufactured by Mitsubishi Chemical) was added to the kettle, followed by vinylec ((registered trademark) grade: PVF- manufactured by JNC Co., Ltd. E) 204 g, at a temperature of 150 ° C, a rotation speed of 28 r / min and a rotation speed of 77 r / min, while decompressing (vacuum degree: 200 kPa), defoaming and mixing for 3 hours.

After confirming that Vinylec was dissolved, 1.7 kg of solid epoxy resin was put in several times and decompressed (vacuum degree: 200 kPa) while defoaming at 90 ° C for 30 minutes while rotating at 28 revolutions per revolution. min, rotation 77 r / min for mixing.
After the solid epoxy resin was dissolved, the temperature was lowered to 60 ° C. Add 204 g of dicyandiamine (DICY7) and 80 g of 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU99) as hardeners and reduce the pressure (vacuum degree: 200 kPa ), Then start stirring, knead at 60 ° C for 65 minutes, rotating speed: 28 r / min revolution, 77 r / min rotation.

＜ Production of resin sheet ＞
The temperature was set on the basis of the viscosity measurement results of FIGS. 1 and 6.
The resin composition prepared by the method was added to an oven in advance and heated to 70 ° C. The resin composition was added to a liquid bank heated to 70 ° C. of the coating device, and coated on a release paper at a roll temperature of 66 ° C. and a coating width of 290 mm by a coating roller to produce a weight per unit area of 26.96 g. / m ² of resin sheet.

＜ Production of unidirectional prepreg sheet ＞
On a unidirectional sheet of carbon fibers (15,000 filaments, unit weight 1.000 g / m, monofilament diameter 6.8 μm, tensile strength 4900 MPa, tensile modulus of elasticity 240 GPa, tensile elongation 2%) The prepared resin sheet was superimposed and heated and pressurized to impregnate the resin composition, and a prepreg sheet having a fiber volume content rate of 55%, a unit volume weight of 76.96 g / m ² , and a slit width of 260 mm was produced. The heating was set based on the viscosity measurement results in FIGS. 1 and 6.

＜ Production of fiber-reinforced composite material by autoclave method ＞
The unidirectional prepreg sheet produced according to the above contents was laminated in such a way that the fiber-reinforced composite material had a thickness of 2 mm and a thickness of 320 mm × 320 mm, and was unified at 130 ° C in an autoclave. , 2 hr, 0.5 MPa, heat-pressed and hardened to produce a fiber-reinforced composite material.

[Example 1, Comparative Example 1 to Comparative Example 4]
Tables 1 to 5 show the evaluation results of the compositions prepared in Comparative Examples 1 to 4. As shown in Tables 1 and 2, according to a comparison between Example 1 and Comparative Examples 1 to 4, the fiber-reinforced composite material produced using the prepreg of the present invention has 90 ° tensile properties and 0 ° bending properties. , 0 ° compression characteristics show high coefficient of elasticity, high strength, and also show high impact resistance.
As one of the main reasons for the improvement of the 90 ° tensile property and the 0 ° bending property of the fiber-reinforced composite material in Example 1 compared with Comparative Examples 1 to 4, according to the electrons in FIGS. 3 and 4 and Tables 3 to 5 As a result of microscopic observation, the adhesion improvement effect between the carbon fiber and the resin due to the carboxyl-containing polyvinyl formal was considered.

[Table 1]
Table 1

[Table 2]
Table 2

[table 3]
table 3

[Table 4]
Table 4

[table 5]
table 5

[TABLE 6]
Table 6
E is the exponent, which means a power of 10.

no

FIG. 1 shows changes in viscosity due to temperature in the resin compositions prepared in Examples and Comparative Examples.

FIG. 2 shows an electron microscope photograph of a fracture surface of a bending test piece evaluated in Examples and Comparative Examples.

FIG. 3 shows an electron microscope photograph showing the breaking of carbon fibers in the tensile failure surface of the fracture surface of the bending test piece evaluated in the examples and comparative examples.

FIG. 4 shows an electron microscope photograph obtained by observing the adhesion state of the resin between the carbon fiber and the resin in the 90 ° tensile test fracture surface evaluated in the examples and comparative examples.

Claims (10)

A prepreg comprising the following [A], [B], [C] and an amine hardener [D] as main components, and each component of [A], [B], and [C] is 1 part by weight -20 parts by weight, 45 parts by weight-80 parts by weight, 20 parts by weight-55 parts by weight of a resin composition impregnated in a reinforcing fiber; [A] Polyvinyl formal resin containing carboxyl group [B] Solid epoxy resin at 25 ° C [C] Liquid epoxy resin at 25 ° C. The prepreg according to item 1 of the scope of the patent application, wherein the polyvinyl formal resin [A] containing a carboxyl group includes a structural unit a, a structural unit b, a structural unit c, and a structural unit d; In the formula constituting the unit d, R ^{1 is} independently hydrogen or an alkyl group having 1 to 5 carbon atoms. The prepreg according to item 1 or item 2 of the scope of patent application, wherein the softening point of the solid epoxy resin [B] is 60 ° C or higher. The prepreg according to item 1 or item 2 of the scope of patent application, wherein the liquid epoxy resin [C] is liquid at 150 ° C. The prepreg according to claim 1 or claim 2, wherein the amine hardener [D] is dicyandiamine or a derivative thereof. The prepreg according to item 1 or item 2 of the scope of the patent application, wherein the reinforcing fibers are carbon fibers, aromatic polyamide fibers, glass fibers, graphite fibers, silicon carbide fibers, boron fibers, alumina fibers, and stainless steel Any of the fibers. For example, the prepreg of item 1 or item 2 of the patent application scope, wherein the reinforcing fiber is carbon fiber, the tensile strength of the carbon fiber is 4.4 GPa to 6.5 GPa, the tensile elongation is 1.7% to 2.3%, and the tensile elasticity It is 230 GPa to 400 GPa. The prepreg according to item 1 or item 2 of the scope of patent application, wherein the amine hardener [D] is contained in all rings including solid epoxy resin [B] and liquid epoxy resin [C]. The oxygen resin component is in a range of 1 to 10 parts by weight based on 100 parts by weight. The prepreg according to item 1 or 2 of the scope of application for a patent, wherein the impregnation amount of the reinforcing fibers in the prepreg is such that the volume of the prepreg including reinforced carbon fibers is 100 vol% In this case, it is 40 vol% to 90 vol% in terms of fiber volume content (Vf). A fiber-reinforced composite material using the prepreg according to any one of claims 1 to 9 of the scope of patent application.