JP7707559B2 - Coatings and intermediate substrates - Google Patents

Description

The present invention relates to a spray or hand-applied coating agent made of an epoxy resin composition with excellent light resistance, and to an intermediate substrate in which the coating agent is applied to the surface of a metal or the like.

Prepregs, which are made by impregnating reinforcing fibers such as carbon fibers with thermosetting resins such as epoxy resins, are often used in products that require high structural performance, such as aircraft structural components, wind turbine blades, automobile exterior panels, and computer applications such as IC trays and laptop computer cases. However, fiber composite materials obtained by curing typical prepregs have low light resistance (UV resistance), and their surfaces deteriorate and degrade when exposed to light. As a result, there has been an increasing demand in recent years to impart light resistance to the surfaces of fiber composite materials.

Patent Document 1 discloses a sheet material with UV blocking properties as a surface protection film for fiber composite materials. Patent Document 2 discloses a combination of an epoxy resin that does not contain aromatic rings, a carboxylic acid anhydride that also does not contain aromatic rings, and an ultraviolet absorber as a resin composition with UV resistance. Non-aromatic epoxies generally have low molecular weights and weak intermolecular interactions, which gives them the characteristics of low viscosity and easy volatility.

Special table 2015-507648 publication International Publication No. 2003/002661

However, the technology disclosed in Patent Document 1 has the problem that the epoxy resin composition used as the film material contains aromatic rings, and the film material itself has poor UV resistance. In addition, the technology disclosed in Patent Document 2 uses a carboxylic acid anhydride as a curing agent for the epoxy resin composition, which causes problems with the ease of handling as a surface protection material, the control of resin flow, and the low degree of design freedom in suppressing volatilization during curing.

Therefore, the challenge is to develop a surface protection material that is highly UV resistant, can protect the surface of the prepreg base material, can prevent UV-induced deterioration of fiber-reinforced composite materials and prevent defects during painting, can control the resin flow, and has a low volatilization rate when cured.

In order to solve the above problems, the present invention has the following configuration: That is, the coating agent of the present invention is a spray or hand-applied coating agent made of an epoxy resin composition containing at least the components [A] to [D], and is characterized in that it contains 90 to 100 parts by mass of [A], 15 to 75 parts by mass of [B], 0.05 to 75 parts by mass of [C], and 0.1 to 10 parts by mass of [D] relative to 100 parts by mass of the total epoxy resin.
[A] a non-aromatic epoxy resin; [B] a pigment having an average particle size of 0.1 to 10 μm; [C] a non-aromatic thermoplastic resin; and [D] a cationic or anionic curing agent.

The intermediate substrate of the present invention is formed by applying the above-mentioned coating agent to the surface of a metal, a carbon fiber reinforced composite material precursor, or a carbon fiber reinforced composite material.

According to the present invention, a coating agent using an epoxy resin composition having excellent light resistance can be provided . In addition, by applying the coating agent to the surface of a metal, a carbon fiber reinforced composite material precursor, or a carbon fiber reinforced composite material and integrating the coating agent therewith, an intermediate substrate having a light resistance on the surface can be provided.

The coating agent of the present invention has the following composition:

A coating agent for spraying or hand application, which comprises an epoxy resin composition containing at least components [A] to [D], and contains 90 to 100 parts by mass of [A], 15 to 75 parts by mass of [B], 0.05 to 75 parts by mass of [C], and 0.1 to 10 parts by mass of [D] relative to 100 parts by mass of total epoxy resin.
[A] a non-aromatic epoxy resin; [B] a pigment having an average particle size of 0.1 to 10 μm; [C] a non-aromatic thermoplastic resin; and [D] a cationic or anionic curing agent.

The component [A] according to the present invention is a non-aromatic epoxy resin. Here, "aromatic" refers to a compound containing an aromatic hydrocarbon or a conjugated unsaturated heterocyclic compound in its chemical structure, and the rest is "non-aromatic". In other words, a non-aromatic epoxy resin refers to an epoxy resin that does not contain an aromatic hydrocarbon group or an unsaturated heterocyclic ring in its chemical structure. Examples of non-aromatic epoxy resins include alicyclic epoxy resins (epoxy resins containing a cycloalkane ring), such as tetrahydroindene diepoxide, vinylcyclohexene oxide, (3',4'-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate, dipentene dioxide, bis(3,4-epoxycyclohexylmethyl) adipate, dicyclopentadiene dioxide, bis(2,3-epoxycyclopentyl)ether, and 1,2-epoxy- 4-(2-oxiranyl)cyclohexane adduct, epoxidized butanetetracarboxylic acid tetrakis-(3-cyclohexenylmethyl) modified epsilon-caprolactone, bi-7-oxabicyclo[4.1.0]heptane, dodecahydrobisphenol A diglycidyl ether, dodecahydrobisphenol F diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, hexahydrophthalic acid diglycidyl ester, hexahydroterephthalic acid diglycidyl ester, 2,2-bis(4-hydroxycyclohexyl) Specific examples of epoxy resins that do not contain any of an aromatic ring, an amine nitrogen atom, a cycloalkane ring, and a cycloalkene ring include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol glycidyl ether, 1,6-hexanediol diglycidyl ether, neopentylene glycol diglycidyl ether, glycerol polyglycidyl ether, and diglycerol polyglycidyl ether. Specific examples of monofunctional epoxy compounds that do not contain any aromatic rings or amine nitrogen atoms (epoxy compounds that contain only one oxirane ring) include trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, 1,4-bis(2-oxiranyl)butane, pentaerythritol polyglycidyl ether, 4-tert-butyl glycidyl ether, butyl glycidyl ether, 1-butene oxide, 1,2-epoxy-4-vinylcyclohexane, and 2-ethylhexyl glycidyl ether.

From the viewpoint of heat resistance, alicyclic epoxy resins are preferably used as non-aromatic epoxy resins.

The non-aromatic epoxy resin may be a commercially available product. For example, "Celloxide (registered trademark)" 2021P, "Celloxide (registered trademark)" 8010, "Celloxide (registered trademark)" 2000, "Epolead (registered trademark)" GT401, "Celloxide (registered trademark)" 2081, EHPE3150 (manufactured by Daicel Chemical Industries, Ltd.), THI-DE (manufactured by JXTG Energy Corporation), TTA21, AAT15, TTA22 (manufactured by Sun Chemical Co., Ltd.), etc. ), Ex-121, Ex-211, Ex-212, Ex-313, Ex-321, Ex-411 (manufactured by Nagase Chemtec Corporation), "Epolite (registered trademark)" 4000 (manufactured by Kyoeisha Chemical Co., Ltd.), ST-3000, ST-4000 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), YX8000 (manufactured by Mitsubishi Chemical Corporation), EPALOY5000 (manufactured by HUNTSMAN), etc.

By using at least two of the above non-aromatic epoxy resins, the reactivity of the epoxy resin composition can be controlled, and a good balance between the fast curing property and the pot life of the epoxy resin composition can be obtained.

By including 90% by mass or more of the above non-aromatic epoxy resin in the entire epoxy resin composition, high light resistance (UV resistance) can be obtained.

In addition, when only alicyclic epoxy resins are used in the epoxy resin composition, it is possible to obtain a cured epoxy resin product that has UV resistance and a high glass transition temperature.

Component [B] is a pigment (average particle size 0.1 to 10 μm). Examples of pigments include barium sulfate, zinc sulfide, titanium oxide, molybdenum red, cadmium red, chromium oxide, titanium yellow, cobalt green, cobalt blue, ultramarine, barium titanate, carbon black, iron oxide, red phosphorus, and copper chromate. The average particle size of the pigment must be 0.1 to 10 μm, preferably 0.1 to 5 μm, and more preferably 0.3 to 5 μm, to obtain an epoxy resin composition with high UV shielding properties. The average particle size here is measured using LA-950 (manufactured by Horiba, Ltd.) using a laser diffraction scattering method. The volumetric conversion results measured using "Araldite (registered trademark)" GY282 (component: bisphenol F type epoxy resin, manufactured by Huntsman Japan Co., Ltd.) as a dispersion medium are adopted as the particle size distribution measurement results, and the particle size (median diameter) at 50% in the cumulative curve of the obtained particle size distribution is taken as the average particle size.

By including 15 to 75 parts by mass, preferably 25 to 55 parts by mass, and more preferably 30 to 50 parts by mass of the above pigment relative to 100 parts by mass of the total epoxy resin contained in the epoxy resin composition, it is possible to obtain a good balance between the light shielding properties of the cured resin and the adhesion when applied by hand.

Component [C] is a non-aromatic thermoplastic resin. Here, "aromatic" refers to a resin that contains an aromatic hydrocarbon or a conjugated unsaturated heterocyclic compound in its chemical structure, and anything else is "non-aromatic." In other words, a non-aromatic thermoplastic resin refers to a thermoplastic resin that does not contain an aromatic hydrocarbon group or an unsaturated heterocyclic ring in its chemical structure. Examples of non-aromatic thermoplastic resins include polyvinyl alcohol, polyvinyl acetal, polyvinyl formal, polyvinyl acetoacetal, polyvinyl butyral, polyvinyl acetate, hydrogenated bisphenol A-pentaerythritol phosphite polymer, hydrogenated terpene, and hydrogenated terpene phenol.

In particular, polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, polyvinyl acetoacetal and polyvinyl vinyl acetate, which are highly soluble in non-aromatic epoxy resins, are preferred because they allow easy adjustment of the viscosity of the epoxy resin composition. Polyvinyl acetoacetal and polyvinyl butyral are more preferred because they improve the elongation of the cured epoxy resin composition. Here, elongation refers to the bending strain (%) when the cured epoxy resin composition is bent at three points in a specified shape.

These non-aromatic thermoplastic resins are preferably soluble in the epoxy resin of component [A]. For example, if at least 10 parts by mass of thermoplastic resin powder is added to 100 parts by mass of epoxy resin of component [A] and kneaded at 100 to 120°C for 1 hour, the thermoplastic resin powder is said to be soluble if it loses weight compared to the start of the kneading process. Weight loss refers to a case where the powder becomes so small that it cannot be optically observed, or when the remaining powder is collected, a mass reduction of 10% or more compared to the start of the kneading process is observed. From the viewpoint of dissolving in epoxy resin, it is preferable that the thermoplastic resin powder has an average particle size of at least 100 μm or less as measured by laser diffraction. In addition, an average particle size of more than 100 nm is preferable because it is easier to suppress agglomeration during storage and to mix with epoxy resin.

In addition, when the molecular weight of these non-aromatic thermoplastic resins is 5,000 to 70,000 g/mol, preferably 7,000 to 65,000 g/mol, and more preferably 10,000 to 60,000 g/mol, a good balance between the uniformity of dissolution in the epoxy resin composition and the resin flow suppression effect can be obtained. The molecular weight here means the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography using HLC-8420GPC (manufactured by Tosoh Corporation).

The non-aromatic thermoplastic resin may be a commercially available product. Examples include "J-POVAL (registered trademark)" (manufactured by Nippon Vinyl Acetate & Poval Co., Ltd.), "Vinylec (registered trademark)" (manufactured by JNC Corporation), "S-LEC (registered trademark)" (manufactured by Sekisui Chemical Co., Ltd.), "Ultrathene (registered trademark)" (manufactured by Tosoh Corporation), JPH-3800 (manufactured by Johoku Chemical Co., Ltd.), and YS Polystar UH130 (manufactured by Yasuhara Chemical Co., Ltd.).

When the epoxy resin composition is applied as a spray, the resin flow suppression effect can be obtained by including 0.05 parts by mass or more of the non-aromatic thermoplastic resin per 100 parts by mass of the total epoxy resin contained in the epoxy resin composition. Here, spraying refers to a method in which the epoxy resin composition is filled into a container and sprayed in a mist or foam form using high-pressure air or mechanical movement with a nozzle. When the epoxy resin composition is applied as a spray, it is preferable to include 0.05 to 1 part by mass, preferably 0.1 to 0.5 parts by mass of the non-aromatic thermoplastic resin, in order to maintain a large amount of spray per given time and to obtain a high resin flow suppression effect.

In addition, when applying the epoxy resin composition by hand coating, good adhesion can be obtained by including 1 to 75 parts by mass or less, preferably 5 to 65 parts by mass, and more preferably 10 to 55 parts by mass of the non-aromatic thermoplastic resin per 100 parts by mass of the total epoxy resin. Hand coating here refers to, for example, a method in which the epoxy resin composition is stored in a container, a brush or roller is dipped into the epoxy resin composition, and then the composition is applied to the target by hand with the brush or roller, or a method in which the epoxy resin composition is placed on the target and spread using a spatula or bar coater.

Component [D] is a cationic curing agent or an anionic curing agent. Examples of cationic curing agents include 1-naphthylmethylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate, 2-methylbenzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate, benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate, dimethyl-p-acetoxyphenylsulfonium hexafluoroantimonate, diaryliodonium salts, boron trifluoride piperidine, boron trifluoride monoethylamine, diaryliodonium salts, and sulfonium salts.

The cationic curing agent may be a commercially available product. For example, ADEKAOPTON (registered trademark) CP-77, ADEKAOPTON (registered trademark) CP-66 (manufactured by ADEKA Corporation), CI-2639, CI-2624 (manufactured by Nippon Soda Co., Ltd.), SAN-AID (registered trademark) SI-60, SAN-AID (registered trademark) SI-80, SAN-AID (registered trademark) SI-100, SAN-AID (registered trademark) SI-150, SAN-AID (registered trademark) SI-B4, SAN-AID (registered trademark) SI-B5 (manufactured by Sanshin Chemical Industry Co., Ltd.), TA-100, IK-1PC (80) (manufactured by San-Apro Co., Ltd.), boron trifluoride piperidine, boron trifluoride monoethylamine (manufactured by Stella Chemifa Co., Ltd.), etc. may be mentioned. The cationic curing agent is preferably a photothermal cationic curing agent or a thermal cationic curing agent. Photothermal cationic curing agents are those that become reactive when exposed to light below a certain wavelength, such as ultraviolet light or visible light, or heat above a certain temperature, while thermal cationic curing agents are those that become reactive due to heat. Photothermal cationic curing agents are preferred because they can be cured in a wide variety of environments, while thermal cationic curing agents are preferred because they can provide high storage stability through temperature control.

Examples of anionic hardeners include phosphorus hexafluoride, antimony hexafluoride, arsenic hexafluoride, tin hexachloride, iron tetrachloride, bismuth pentachloride, niobium hexachloride, etc.

By using at least two of the above curing agents, the reactivity of the epoxy resin composition can be controlled, and a good balance between the fast curing property and the pot life of the epoxy resin composition can be obtained.

The reactivity of the coating agent made of the epoxy resin composition can be controlled by the type and amount of the curing agent. When the coating agent made of the epoxy resin composition is applied to a fiber-reinforced composite material precursor such as a prepreg and molded, the epoxy resin composition cures faster than the resin of the fiber-reinforced composite material precursor during the molding process, and the fiber-reinforced composite material precursor resin does not mix with the epoxy resin composition after the epoxy resin composition cures, so this is preferable in that a high suppression effect can be obtained for the amount of resin of the fiber-reinforced composite material precursor mixed into the epoxy resin composition. Here, the DSC exothermic peak temperature of the coating agent depends on the curing temperature of the fiber-reinforced composite material precursor, but is preferably 40°C or more lower than the curing temperature of the fiber-reinforced composite material precursor, and more preferably 60°C or more lower. When the curing temperature of the fiber-reinforced composite material precursor is 180°C, it is also preferable from the viewpoint of handleability if the DSC exothermic peak temperature of the coating agent is in the range of 80 to 120°C.

By including 0.5 to 10 parts by mass, preferably 1 to 5 parts by mass, and more preferably 1 to 3 parts by mass of the above curing agent relative to 100 parts by mass of the total epoxy resin contained in the epoxy resin composition, it is possible to obtain a fast curing property, an effect of suppressing resin flow and volatilization during molding, and a good balance of fast curing property, pot life, and UV resistance.

The epoxy resin composition of the present invention may further contain a thixotropy-imparting agent as component [E]. Examples of thixotropy-imparting agents include silicon dioxide, magnesium silicon sodium fluoride hydroxide oxide, alkyl quaternary ammonium salts, synthetic hectorite, clay minerals, modified bentonite, and mixtures of minerals and organically modified bentonite.

The thixotropic agent may be a commercially available product, and examples include fumed silica (Aerosil (registered trademark) (manufactured by Nippon Aerosil Co., Ltd.)), OPTIGEL (registered trademark), OPTIBENT (registered trademark), GARAMITE (registered trademark), LAPONITE (registered trademark), TIXOGEL (registered trademark), CRAYTONE (registered trademark), CLOISITE (registered trademark) (manufactured by BYK Corporation), Somasif (registered trademark) ME-100, Micromica MK (manufactured by Katakura Coop Agri Co., Ltd.), etc.

By including the thixotropy-imparting agent in an amount of preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the total epoxy resin contained in the epoxy resin composition, a good balance can be obtained between the effect of suppressing resin flow during molding and adhesion properties.

Furthermore, the epoxy resin composition of the present invention may contain a curing aid as component [F]. Examples of the curing aid include 4-hydroxyphenyldimethylsulfonium methylsulfate, 4-(methylthio)phenol, etc.

The above curing aids can be commercially available products, examples of which include "San-Aid (registered trademark)" SI-S and "San-Aid (registered trademark)" S-ME (manufactured by Sanshin Chemical Industry Co., Ltd.).

By including the curing aid in an amount of preferably 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and even more preferably 0.1 to 2.5 parts by mass, per 100 parts by mass of the total epoxy resin contained in the epoxy resin composition, a good balance between the fast curing property and the pot life of the epoxy resin composition can be obtained.

The epoxy resin composition of the present invention may contain rubber as a component [G]. Examples of rubber include natural rubber, diene rubber, and non-diene rubber. Examples of diene rubber include styrene-butadiene rubber, isoprene rubber, butadiene rubber, chloroprene rubber, and acrylonitrile-butadiene rubber. Examples of non-diene rubber include butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, urethane rubber, silicone rubber, and fluororubber. As the content of the epoxy resin composition of the present invention, non-diene rubber is preferable. Among them, ethylene-propylene rubber, ethylene-propylene-diene rubber, silicone rubber, and fluororubber, which do not have double bonds in the polymer main chain, are particularly preferable because they have high light resistance and have little effect on the UV resistance of the epoxy resin composition of the present invention. In addition, as for the shape of the rubber, powder form is particularly preferable because it has excellent dispersibility in the epoxy resin composition.

When the epoxy resin composition is applied as a spray, the inclusion of 0.05 parts by mass or more of the above rubber relative to 100 parts by mass of the total epoxy resin contained in the epoxy resin composition provides excellent resin flow suppression effects and elongation of the cured epoxy resin composition, thereby preventing cracking after coating. Here, elongation refers to the bending strain (%) when the cured epoxy resin composition is bent at three points in a specified shape, and spray refers to a method in which the epoxy resin composition is filled into a container and sprayed in a mist or foam form using high-pressure air or mechanical movement using a nozzle. It is preferable to include 0.05 to 1 part by mass of the above rubber relative to 100 parts by mass of the total epoxy resin contained in the epoxy resin composition in order to maintain a large amount of spray per certain time and to obtain a high resin flow suppression effect.

In addition, when applying the epoxy resin composition by hand coating, the content of the rubber is preferably 1 to 50 parts by mass per 100 parts by mass of the total epoxy resin. A rubber content of 1 part by mass or more per 100 parts by mass of the total epoxy resin is preferable because it provides a resin flow suppression effect and excellent elongation of the epoxy resin composition after curing, thereby preventing cracking after painting, and a rubber content of 50 parts by mass or less is preferable because it provides excellent adhesion between the target and the epoxy resin composition. Hand coating here refers to, for example, a method in which the epoxy resin composition is stored in a container, a brush or roller is dipped into the epoxy resin composition, and then the epoxy resin composition is applied to the target by hand with the brush or roller, or a method in which the epoxy resin composition is placed on the target and spread using a spatula or bar coater.

The above rubbers can be commercially available products, examples of which include KMP-598, KMP-600, KMP-601, KMP-602, and KMP-605 (manufactured by Shin-Etsu Chemical Co., Ltd.), "Cevian (registered trademark)" (manufactured by Daicel Miraize Co., Ltd.), JSR N215SL, JSR N222SH, JSR N238H, JSR N241H, JSR N250S, PN30A, PN20HA, and N280 (manufactured by JSR Corporation).

From the viewpoints of the working environment and accurate control of thickness after molding, it is preferable that the amount of evaporation of the spray or hand-applied coating agent made of the epoxy resin composition of the present invention is 10% or less after being placed in an environment of 180°C for 1 hour.

From the viewpoint of UV resistance, it is preferable that no discoloration is observed after the cured product of the epoxy resin composition according to the present invention is irradiated with 1000 kJ/ ^m2 of UV rays having a wavelength of 300 to 400 nm, and it is possible to protect the coated object from UV. In the present invention, no discoloration is observed means that the color difference ΔE*ab before and after UV irradiation is 4 or less, and the color difference ΔE*ab can be determined by measuring the colorimetric value of the cured product of the epoxy resin composition before and after irradiation with 1000 kJ/ ^m2 of UV rays having a wavelength of 300 to 400 nm using a multi-light source spectrophotometer.

The coating agent for spraying or hand application made of the epoxy resin composition of the present invention can be applied to a metal surface and then cured by heat, or can be applied to the top surface of uncured prepreg, RTM material, or resin film infusion (RFI) material (also referred to as "fiber-reinforced composite material precursor" in the present invention) generally used for fiber-reinforced composite materials, and both can be cured by heat in the applied state. Here, the prepreg is a fiber-reinforced composite material precursor made by impregnating a thermosetting resin such as an epoxy resin into a reinforcing fiber, the RTM material is a fiber-reinforced composite material precursor made by stacking a reinforcing fiber substrate in a mold and injecting a liquid thermosetting resin therein to impregnate the reinforcing fiber substrate, and the RFI material refers to a fiber-reinforced composite material precursor made by stacking a thermosetting resin film on a reinforcing fiber substrate and impregnating the reinforcing fiber substrate with the thermosetting resin by heating and pressurizing the laminate. When applying to a metal surface, a silane coupling agent may be applied to the metal surface before application, and the epoxy resin composition may be applied to the metal surface after treating it with a light source or heat. By treating with a silane coupling agent, the silane coupling agent acts as a bridge between the metal surface and the coating agent of the epoxy resin composition of the present invention, and it is possible to obtain the effect of improving the adhesion between the metal surface and the coating agent and the effect of improving the wettability of the coating agent to the metal surface. By curing, the cured product of the epoxy resin composition covers the surface of the cured fiber-reinforced composite material precursor, and an integrated fiber-reinforced composite material can be obtained.

As reinforcing fibers in fiber-reinforced composite material precursors, various carbon fibers, graphite fibers, glass fibers, aramid fibers, etc. are preferably used.

The spray or hand-applied coating agent made of the epoxy resin composition of the present invention is effective when applied to a fiber-reinforced composite material precursor and then thermally cured together, but the epoxy resin composition may be applied by spraying, or may be hand-applied using a brush or a bar coater. After hand application, it is also possible to increase the adhesion between the spray or hand-applied coating agent made of the epoxy resin composition of the present invention and the fiber-reinforced composite material precursor by vacuuming using a release film or the like.

The epoxy resin composition according to the present invention can be applied to a target by various methods. For example, the epoxy resin composition can be filled into a container and sprayed in a mist or foam form using high-pressure air or mechanical movement from a nozzle, or a roller or brush can be dipped into the coating agent of the present invention and applied to the target. Furthermore, the coating agent of the present invention can be applied to a target by using a bar coater or a spatula. In either method, the epoxy resin composition can be applied while heating it as necessary to reduce its viscosity.

As described above, the coating agent for spraying or hand application made of the epoxy resin composition of the present invention can be applied to a target by various methods, but the preferred method of application depends on the room temperature viscosity of the epoxy resin composition. When the room temperature viscosity of the epoxy resin composition is 100 to 500 mPa·s, application by spraying is preferred. When applying by spraying, if the room temperature viscosity is 100 mPa·s or less, resin flow at room temperature can be suppressed and the thickness of the coating agent can be maintained uniform, while if the room temperature viscosity is 500 mPa or less, the epoxy resin composition can be applied without clogging when sprayed, which provides good workability.

When the room temperature viscosity of the epoxy resin composition is 0.5 to 30 Pa·s, hand application using a roller, brush, etc. is preferable. If the room temperature viscosity of the epoxy resin composition is 0.5 Pa·s or more, dripping during application can be suppressed, which is preferable, and if it is 30 Pa·s or less, the brush or roll can be easily immersed in the epoxy resin composition, resulting in good workability.

When the room temperature viscosity of the epoxy resin composition is 30 to 30,000 Pa·s, hand application using a spatula, bar coater, etc. is preferred. When applying by hand, it is preferred that the room temperature viscosity of the epoxy resin composition is 30 Pa·s or more, since the resin flow suppression effect of the epoxy resin composition during the curing process is high. It is also preferred that the room temperature viscosity of the epoxy resin composition is 30,000 Pa·s or less, since the adhesion between the epoxy resin composition and the fiber reinforced composite material precursor is high, and the adhesion between the epoxy resin composition and the fiber reinforced composite material after curing is high.

When the coating agent for spraying or hand application comprising the epoxy resin composition of the present invention is applied to a fiber-reinforced composite material precursor, the basis weight is preferably 30 to 300 g/ ^m2 . When the basis weight of the epoxy resin composition is 30 g/ ^m2 or more, the surface of the fiber-reinforced composite material can be covered without being visible through, and sufficient light resistance can be exhibited. In addition, when the basis weight of the epoxy resin composition is 300 g/ ^m2 or less, heat generation during curing of the epoxy resin composition is suppressed when it is molded together with the fiber-reinforced composite material, which is preferable.

As a method for molding the coating agent for spraying or hand application made of the epoxy resin composition of the present invention and the fiber-reinforced composite material, it is preferable to apply it to the outermost surface of the fiber-reinforced composite material precursor and then cure both. The coating agent made of the epoxy resin composition of the present invention described above is applied in a predetermined form to the outermost surface of the fiber-reinforced composite material precursor, and pressurized and heated to cure the coating agent made of the epoxy resin composition of the present invention and the resin contained in the fiber-reinforced composite material precursor, thereby producing a fiber-reinforced composite material. Examples of methods for applying heat and pressure include press molding, autoclave molding, bagging molding, wrapping tape, and internal pressure molding.

The present invention will be described in detail below with reference to examples. However, the scope of the present invention is not limited to these examples. In addition, measurements of various characteristics were performed in an environment with a temperature of 23°C and a relative humidity of 50%, unless otherwise noted.

Materials used in the Examples and Comparative Examples
(1) Aromatic epoxy resin/bisphenol A type epoxy resin ("jER (registered trademark)" 828, manufactured by Mitsubishi Chemical Corporation) epoxy equivalent: 175 (g/eq.).

(2) Component [A] Non-aromatic epoxy resin
(3',4'-epoxycyclohexane) methyl 3,4-epoxycyclohexane carboxylate ("Celloxide (registered trademark)" 2021P, manufactured by Daicel Corporation) Epoxy equivalent: 136 (g/eq.)
1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol ("EHPE3150", manufactured by Daicel Corporation)
Epoxidized butanetetracarboxylic acid tetrakis-(3-cyclohexenylmethyl) modified epsilon-caprolactone ("Epolead (registered trademark)" GT401, manufactured by Daicel Corporation)
Diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane (YX8000, manufactured by Mitsubishi Chemical Corporation).

(3) Component [B] Pigment titanium oxide (rutile type) ("Ti-Pure (registered trademark)" R-960, manufactured by Chemours, Inc., average particle size 0.5 μm).

(4) Component [C] Non-aromatic thermoplastic resin - polyvinyl formal ("Vinylec (registered trademark)" K, manufactured by JNC Corporation, calculated molecular weight 40,000 to 54,000 g/mol)
Polyvinyl formal ("Vinylec (registered trademark)" E, manufactured by JNC Corporation, calculated molecular weight 95,000 to 134,000 g/mol)
Polyvinyl acetoacetal ("S-LEC (registered trademark)" KS-10, manufactured by Sekisui Chemical Co., Ltd., calculated molecular weight 17,000 g/mol)
Polyvinyl butyral ("S-LEC (registered trademark)" BX-L, manufactured by Sekisui Chemical Co., Ltd., calculated molecular weight 18,000 g/mol).

(5) Component [D] Cationic curing agent: Dimethyl-p-acetoxyphenylsulfonium hexafluoroantimonate "San-Aid (registered trademark)" SI-150, manufactured by Sanshin Chemical Industry Co., Ltd.
Benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate "San-Aid (registered trademark)" SI-100, manufactured by Sanshin Chemical Industry Co., Ltd.

(6) Component [E] Thixotropic agent, fumed silica ("AEROSIL (registered trademark)" RY200S, manufactured by Nippon Aerosil Co., Ltd.)
Alkyl ammonium clay ("GARAMITE (registered trademark)" 1958, manufactured by BYK Corporation).

(7) Component [F] Curing aid: 4-hydroxyphenyldimethylsulfonium methyl sulfate (SAN-AID (registered trademark) SI-S, manufactured by Sanshin Chemical Industry Co., Ltd.)
4-(Methylthio)phenol ("Sanaide (registered trademark)" S-ME, manufactured by Sanshin Chemical Industry Co., Ltd.).

(8) Component [G] Rubber: Silicone rubber powder (KPM-601, manufactured by Shin-Etsu Chemical Co., Ltd.).

<Methods for producing and evaluating epoxy resin compositions and fiber-reinforced composite materials>
The epoxy resin compositions of the examples and comparative examples were measured by the following methods.

(1) Preparation of epoxy resin composition An epoxy resin corresponding to component [A] (including aromatic epoxy resins in Examples 33 and Comparative Examples 1 and 8) corresponding to component [A] in Tables 1 to 8, a pigment corresponding to component [B], and if necessary, a thixotropy imparting agent [E] and a rubber [G] were charged into a three-roll mill and mixed at an arbitrary roll rotation speed to obtain a powder mixture precursor. The powder mixture precursor and a non-aromatic thermoplastic resin corresponding to component [C] in Tables 1 to 8 were charged into a mixer, and heated and mixed to dissolve the non-aromatic thermoplastic resin. Next, while continuing the kneading, the temperature was lowered to 60°C or lower, and the cationic curing agent [D] and the curing assistant [F], if necessary, described in Tables 1 to 8, were added and stirred to obtain an epoxy resin composition.

(2) Room-temperature viscosity measurement of epoxy resin composition The room-temperature viscosity of the epoxy resin composition prepared in (1) above was measured using a dynamic viscoelasticity device ARES-2KFRTN1-FCO-STD (manufactured by TA Instruments) with flat parallel plates of 40 mm diameter as upper and lower measuring jigs, the epoxy resin composition was set so that the distance between the upper and lower jigs was 1 mm, and then it was measured in torsion mode (measurement frequency: 0.5 Hz) at an isothermal measurement temperature of 23° C. for 10 minutes. The average value of the viscosity during measurement times from 2 to 10 minutes was regarded as the room-temperature viscosity of the epoxy resin composition.

(3) Pot life measurement of epoxy resin composition The viscosity of the epoxy resin composition prepared in (1) above was measured in a torsion mode (measurement frequency: 0.5 Hz) using a dynamic viscoelasticity measuring device ARES-2KFRTN1-FCO-STD (manufactured by TA Instruments Co., Ltd.) with flat parallel plates of 40 mm diameter as upper and lower measuring jigs, after setting the epoxy resin composition so that the distance between the upper and lower jigs was 1 mm. The viscosity η ^* ₂ when held at 65°C for 2 minutes and the viscosity η ^* _x at any time after holding at 65°C for 2 hours were measured, and the viscosity increase ratio at that time was calculated from η ^* _x ÷η ^* ₂ . The time until the viscosity increase ratio reached 3 was regarded as the pot life.

(4) Measurement of Volatilization Amount of Epoxy Resin Composition The epoxy resin composition prepared in (1) above was weighed out (mass: W2) onto a release paper (mass: W1) with a target weight of 3 g, and the epoxy resin composition and the release paper were placed in an oven at 180° C. for 1 hour. Thereafter, the epoxy resin composition and the release paper were removed from the oven and allowed to stand in a desiccator for 30 minutes, after which the combined mass of the epoxy resin and the release paper was measured (mass: W3), and the volatilization amount [%] in the present invention was calculated using the following formula:
{(W2-(W3-W1)}/W2×100[%]
A calculated volatilization amount of 5% or less was rated "good", and a calculated volatilization amount of more than 5% was rated "poor".

(5) Measurement of resin flow amount of epoxy resin composition The epoxy resin composition prepared in (1) above was weighed out to a target of 3 g on a release film cut into a 15 cm square (mass: W4). The epoxy resin composition was sandwiched between another release film cut into a 15 cm square, and then sandwiched between two 10 cm square metal plates (each 400 g), and molded in this state in an autoclave (6 atmospheres, 180°C, 2 hours, temperature increase 1.7°C/min). After molding, the cured product of the epoxy resin composition protruding from the 10 cm square metal plate was removed, and the mass of the remaining cured product of the epoxy resin composition was measured (mass: W5). The resin flow amount [%] of the epoxy resin composition in the present invention was calculated by the following calculation formula.
(W4-W5)/W4×100[%]
The resin flow amount was designated as A if it was 5% or less, B if it was more than 5% and 10% or less, C if it was more than 10% and 15% or less, and D if it was more than 15%.

(6) Adhesion of epoxy resin composition The epoxy resin composition prepared in (1) above was applied to an aluminum plate of any size (larger than 10 cm square) so that the epoxy resin composition was 80 μm thick, and a 10 cm square stainless steel plate (400 g) that had been sprayed with Daifree GA-3000 (manufactured by Daikin Industries) to perform a release treatment was placed on top of the composition and held for 30 seconds. Thereafter, the stainless steel plate was lifted up, and the aluminum plate was placed at an angle of 90° to the ground with the epoxy resin composition still in close contact with the aluminum plate. If the epoxy resin composition was still in close contact with the aluminum plate after 24 hours, the adhesion was evaluated as "good", and if even a part of the composition had peeled off, the adhesion was evaluated as "poor".

(7) UV irradiation test of epoxy resin composition The epoxy resin composition prepared in (1) above was applied onto a release film so that the epoxy resin composition had a thickness of 80 μm, and cured in an oven at 180° C. for 2 hours with a temperature rise of 1.7° C./min. The surface of the obtained cured product of the epoxy resin composition was covered with half of aluminum foil, and a metaling weather meter (M6T, manufactured by Suga Test Instruments Co., Ltd.) was used to set the irradiation wavelength to 300 to 400 nm and the cumulative illuminance to 1.55 kW/m ^2. Since the cured product of the epoxy resin composition of the present invention is expected to be exposed to sunlight outdoors on a yearly basis, the cured product was irradiated with UV light with a cumulative intensity of 1000 kJ/m ² , which is an approximate value of the amount of UV light in one month in Japan (summer). After irradiation, the aluminum foil was peeled off, and the appearance of the area covered with aluminum foil and the area not covered with aluminum foil was observed with the naked eye to confirm the presence or absence of discoloration of the cured epoxy resin before and after UV irradiation. The color difference of the cured product of the epoxy resin composition before and after irradiation was measured using a multi-light source spectrophotometer (MSC-P, manufactured by Suga Test Instruments Co., Ltd.). The epoxy resin composition was set in the multi-light source spectrophotometer, and the reflectance was measured under the measurement conditions of a wavelength range of 380 to 780 nm, reflection mode, C light source, 2° field of view, and 8° incidence. Furthermore, the color measurement value (L ^* 1a ^* 1b ^* 1) before UV irradiation in the L ^* a ^* b ^* discoloration system was obtained using a program attached to the device. Next, the color measurement value (L ^* 2a ^* 2b ^* 2) after UV irradiation was obtained. Furthermore, the color difference ΔE ^* ab of the cured product of the epoxy resin composition before and after UV irradiation was obtained by ΔE ^* ab=[(L ^* 1-L ^* 2) ² +(a ^* 1-a ^* 2) ² +(b ^* 1-b ^* 2) ² ] ^1/2 . When the determined ΔE ^* ab was 4 or less, the UV resistance was rated as "good", and when the ΔE ^* ab exceeded 4, the UV resistance was rated as "poor".

(8) Amount of resin of prepreg mixed into epoxy resin composition during molding process The epoxy resin composition prepared in (1) above was applied to the outermost surface of eight continuous fiber prepregs (T800S/3900-2B (manufactured by Toray Industries, Inc.)) laminated in a pseudo-isotropic manner (lamination structure: [+45°/0°/-45°/90°] _s ) to give a thickness of 80 μm. In this state, the composite material was molded in an autoclave under conditions of 6 atmospheres, 180° C. for 2 hours, and a temperature increase of 1.7° C./min. The cured product side of the epoxy resin composition was measured by ATR IR measurement (FT/IR-4000 manufactured by JASCO Corporation, prism: diamond, measurement wavelength: 400 to 4000 cm ⁻¹ , number of accumulations: 16 times) and normalized using the peak at 1715 cm ⁻¹ indicating the ester, and the peak at 1592 cm −1 indicating the benzene ring originating from the cured resin used in the prepreg was measured. By evaluating the value of the peak at ^{1592 cm −1} , it is possible to evaluate the amount of resin used in the prepreg mixed with the coating agent made of the epoxy resin composition during the molding process and exposed to the surface of the fiber reinforced composite material. If the value of the peak at 1592 cm ⁻¹ , which indicates the benzene ring caused by the cured resin used in the prepreg, is 0.6 or less, the UV resistance of the surface of the fiber reinforced composite material was judged to be good. In addition, in Examples 35 to 56 and Comparative Examples 9 to 11, IR measurement was performed by the ATR method in the same manner as above, and normalization using the peak at 1715 cm ⁻¹ , which indicates the ester, was not performed, and the value of the peak at 1592 cm ⁻¹ , which indicates the benzene ring caused by the cured resin used in the prepreg, was evaluated. In this case, if the value of the peak at 1592 cm ⁻¹ , which indicates the benzene ring caused by the cured resin used in the prepreg, is 1.0 or less, the UV resistance of the surface of the fiber reinforced composite material was judged to be good.

(9) Method of applying epoxy resin composition to prepreg surface When applying the epoxy resin composition by spraying, the epoxy resin composition was sprayed onto the prepreg surface using a spray gun W-2001-2 (manufactured by Anest Iwata Corp.).

When applying the epoxy resin composition by hand using a brush, the epoxy resin composition was collected in a container, the brush was dipped into it, and then the composition was applied directly to the object.

When applying the epoxy resin composition by hand using a bar coater, the epoxy resin composition was placed on the surface to be coated and then spread with the bar coater to apply it to the object.

(10) Method for measuring exothermic peak temperature of epoxy resin composition Using a differential scanning calorimeter (DSC Q2500: manufactured by TA Instruments), an exothermic curve of the epoxy resin composition was obtained in a nitrogen atmosphere at a temperature rise rate of 5°C/min. In the obtained exothermic curve, the temperature at the apex of the exothermic peak having a heat release of 100 mW/g or more was calculated as the exothermic peak temperature. When there are two or more exothermic peaks having a heat release of 100 mW/g or more, the temperature at the apex of the peak on the lower temperature side was calculated as the DSC exothermic peak temperature in the present invention. Regarding the evaluation of fast curing property, in Tables 1 to 4, an exothermic peak temperature of 100°C or less is indicated as A, more than 100°C and 120°C or less is indicated as B, more than 120°C and 140°C or less is indicated as C, and more than 140°C is indicated as D.

(11) Bending test of cured epoxy resin composition After degassing in a vacuum, the uncured epoxy resin composition was cured for 2 hours at 180°C in a mold set to a thickness of 2 mm using a 2 mm thick Teflon (registered trademark) spacer. The resulting 2 mm thick cured epoxy resin was cut to a width of 10±0.1 mm and a length of 60±1 mm to obtain a test piece. Using an Instron universal testing machine (manufactured by Instron), three-point bending was performed with a span of 32 mm according to JIS-K7171 (1994), and the elastic modulus and bending strain (elongation) were measured. The number of measurements was N=6, and the average value was calculated.

<Examples 1 to 32 and Comparative Example 1>
In Examples 1 to 32, when an epoxy resin composition was used as component [A] consisting of only (3',4'-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate, or a combination of a non-aromatic epoxy resin with a 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol or an epoxidized butanetetracarboxylic acid tetrakis-(3-cyclohexenylmethyl) modified epsilon-caprolactone, no discoloration was observed even after curing, and good results were obtained. On the other hand, Comparative Example 1, which did not contain the non-aromatic epoxy resin component [A] and contained only an aromatic epoxy resin, was judged to be poor in the UV resistance test, indicating low UV resistance.

<Examples 1 to 2>
In Examples 1 and 2, the type of component [D] was changed and compared. As a result, it was shown that when benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate was used as a cationic curing agent, the curing rate was higher than when an iodonium salt was used as a cationic curing agent, and there was a tendency to suppress all of the volatility, resin flow, and the amount of resin of the prepreg mixed into the coating agent made of the epoxy resin composition during the molding process, but the pot life was shortened.

<Examples 2 to 6, 21 to 23, 26 to 28, 34, and Comparative Examples 4 to 5>
In Examples 2 to 3, in which the application method was a spray, the type of component [C] was changed, and as a result of comparison, it was shown that the use of polyvinyl acetoacetal had a higher effect of suppressing the amount of resin flow than polyvinyl formal. In addition, in Examples 4 to 6, in which the application method was also a spray, the amount of polyvinyl acetoacetal added was changed, and it was shown that the effect of suppressing the amount of resin flow improved as the amount was increased.

On the other hand, in Comparative Example 4, when component [C] was not included, the amount of resin flow was large, and the amount of prepreg resin mixed into the coating agent made of the epoxy resin composition of the present invention during the molding process was excessive, and it was judged to be defective.

In addition, in Examples 21 to 22, in which the application method was hand application using a brush, and in Examples 23 and 26 to 28, in which the application method was hand application using a bar coater, the amount of polyvinyl formal in component [C] was changed, and it was shown that in these cases too, the effect of suppressing the amount of resin flow improved as the amount of component [C] increased.

On the other hand, in Example 28, when the amount of polyvinyl formal in component [C] was 75 parts by mass, it was shown that the adhesion was good, whereas when the amount of polyvinyl formal was 80 parts by mass as in Comparative Example 5, the room temperature viscosity was high and the adhesion was judged to be poor.

In addition, in Example 34, when Vinylec E (calculated molecular weight 95,000-134,000 g/mol), which has a higher calculated molecular weight than Vinylec K (calculated molecular weight 40,000-54,000 g/mol) and S-LEC KS-10 (calculated molecular weight 17,000 g/mol), was used as component [C], the resin flow suppression effect was high, and the effect of suppressing the amount of prepreg resin mixed into the cured resin during the molding process was shown, but the room temperature viscosity was excessive and the adhesion was judged to be poor.

<Examples 23 to 25, 33, and Comparative Example 8>
In Example 23, 100 parts by mass of (3',4'-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate was used as component [A], whereas in Example 24, 30 parts by mass of 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol and 30 parts by mass of epoxidized butanetetracarboxylic acid tetrakis-(3-cyclohexenylmethyl)-modified epsilon-caprolactone were added to 70 parts by mass of (3',4'-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate. As a result, the epoxy resin compositions in Examples 23 to 25 had good adhesion and good UV resistance. Therefore, it was shown that, as long as the epoxy resin is a non-aromatic epoxy resin, it is possible to obtain an epoxy resin composition having good physical properties both when one type of epoxy resin is used and when two or more types of epoxy resins are used.

In addition, in Example 33, 90 parts by mass of non-aromatic epoxy resin and 10 parts by mass of aromatic epoxy resin were used in combination, and the UV resistance was evaluated and determined to be good. Therefore, it was shown that the UV resistance is good in the case of an epoxy resin composition containing 10% by mass of aromatic epoxy resin among the epoxy resins.

On the other hand, in Comparative Example 8, 80 parts by mass of non-aromatic epoxy resin and 20 parts by mass of aromatic epoxy resin were used in combination, and the UV resistance was evaluated and determined to be poor. This shows that the UV resistance of an epoxy resin composition containing 20% by mass of aromatic epoxy resin among the epoxy resins is poor.

<Examples 1, 2, 7 to 10, Comparative Examples 6 and 7>
In Example 7, the amount of iodonium salt, which is the cationic curing agent (component [D]), was increased compared to Example 1. The fast curing property of the epoxy resin composition of Example 7 was increased compared to Example 1, while the pot life was decreased. However, it was shown that there was a high effect of suppressing the amount of volatilization, the amount of resin flow, and the amount of resin of the prepreg mixed into the coating agent made of the epoxy resin composition of the present invention during the molding process.

Similarly, in Example 8, the amount of benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate, the cationic curing agent of component [D], was increased compared to Example 2. The fast curing property of the epoxy resin composition of Example 8 was increased compared to Example 2, while the pot life was decreased, but it was shown to have a high effect of suppressing the amount of volatilization, the amount of resin flow, and the amount of resin in the prepreg mixed into the coating agent made of the epoxy resin composition of the present invention during the molding process.

In Examples 9 and 10, two types of cationic curing agents, dimethyl-p-acetoxyphenylsulfonium hexafluoroantimonate and benzylmethyl-p-hydroxyphenylsulfonium hexafluoroantimonate, which are the component [D], were used in combination as curing agents. In Example 9, the fast curing property was decreased compared to Example 8, but the pot life was increased. In Example 10, the amount of methyl-p-acetoxyphenylsulfonium hexafluoroantimonate was increased from that in Example 9. In Example 10, the fast curing property was improved compared to Example 9, but the pot life was decreased. Therefore, it was shown that the balance between the fast curing property and the pot life of the epoxy resin composition can be controlled by the addition ratio of the cationic curing agent of component [D], or the mixing ratio when two types are added.

In Comparative Example 6, 0.05 parts of dimethyl-p-acetoxyphenylsulfonium hexafluoroantimonate, which is the cationic curing agent (component [D]), was added. Comparative Example 6 had low fast curing properties, and was judged to be poor in terms of the amount of volatilization and the amount of resin in the prepreg mixed into the epoxy resin composition during the molding process.

On the other hand, in Comparative Example 7, 15 parts by mass of benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate was added. Although the fast curing property was high, the pot life was significantly reduced. In addition, the evaluation of the amount of resin of the prepreg mixed into the coating agent made of the epoxy resin composition during the molding process was judged to be poor, and in Comparative Example 7, the epoxy resin composition after curing after UV irradiation of 1000 kJ/ ^m2 was judged to be poor in the UV resistance test, indicating that the UV resistance was low.

<Examples 11 to 12, Examples 29 to 30, Comparative Examples 2 and 3>
In Examples 11 and 12, the amount of titanium oxide in component [B] was changed and compared, and as a result, Example 12, which contains a larger amount of titanium oxide, showed a lower rapid curing property and an improved pot life compared to Example 11, indicating that the reactivity of the epoxy resin composition can be controlled by the amount of titanium oxide. Also, it was shown that Example 12, which contains a larger amount of titanium oxide, is more effective than Example 11 in suppressing the amount of prepreg resin mixed into the epoxy resin composition during the molding process.

In Examples 29 and 30, the amount of titanium oxide in component [B] was 15 parts by mass and 75 parts by mass, respectively. Example 30 showed a lower cure rate compared to Example 29, demonstrating a high effect in suppressing and improving the amount of volatilization. In addition, the UV resistance of both examples and the amount of resin in the prepreg mixed into the epoxy resin composition during the molding process were judged to be good.

On the other hand, when titanium oxide of component [B] was set to 10 parts by mass as in Comparative Example 2, the amount of prepreg resin mixed into the epoxy resin composition during the molding process was large, and it was judged to be defective.

In addition, when 100 parts by mass of titanium oxide of component [B] (II) was added as in Comparative Example 3, the rapid curing was poor, and the amount of volatilization after 1 hour at 180°C was judged to be poor.

<Examples 8, 13 to 15, 23, and 31>
In Examples 13 to 15, in which the application method was spraying, a curing aid of the component [F] was applied. In Example 13, 0.2 parts by mass of the curing aid 4-hydroxyphenyldimethylsulfonium=methylsulfate was applied as the component [F], and as a result, an improvement in pot life was observed compared to Example 8. In Example 15, the amount of 4-hydroxyphenyldimethylsulfonium=methylsulfate was increased to 1.0 part, and as a result, a further improvement in pot life was observed compared to Example 13. Similarly, in Example 14, the type of the curing aid of the component [F] was changed to 4-(methylthio)phenol, and 0.2 parts was applied, and as a result, an improvement in pot life was observed compared to Example 8. In addition, in Examples 13 to 15, all of the volatility, UV resistance, and amount of resin of the prepreg mixed into the coating agent made of the epoxy resin composition during the molding process were judged to be good.

In addition, in Example 31, in which the coating method was hand-coating using a bar coater, 0.2 parts by mass of 4-hydroxyphenyldimethylsulfonium methyl sulfate was used as component [F], and as a result, an improvement in pot life was observed compared to Example 23, in which the coating method was also hand-coating using a bar coater. Therefore, it was shown that the pot life improvement effect can be obtained by applying component [F] to an epoxy resin composition, regardless of the coating method.

<Examples 8, 16 to 18, 23, and 32>
Examples 16 to 18, which are applied by spraying, use the thixotropy imparting agent (component [E]). In Examples 16 to 17, 4 parts each of fumed silica and alkylammonium clay are applied to Example 8, which is also applied by spraying, and the effect of suppressing the amount of resin flow and the amount of resin from the prepreg mixed into the epoxy resin composition during the molding process is shown without impairing the fast curing property and UV resistance. In Example 18, 4 parts each of both fumed silica and alkylammonium clay are applied to Example 8, and the effect of suppressing the amount of resin flow and the amount of resin from the prepreg mixed into the epoxy resin composition during the molding process is shown to be higher than in Examples 16 to 17.

In addition, when both fumed silica and alkylammonium clay were applied to component [E] in Example 32, which was applied by hand using a bar coater, it was shown to be more effective in suppressing the amount of resin flow and the amount of prepreg resin mixed into the epoxy resin composition during the molding process than in Example 23, which was also applied by hand using a bar coater.

Therefore, it was shown that applying component [E] to an epoxy resin composition, regardless of the application method, can suppress the amount of resin flow and increase the amount of prepreg resin mixed into the epoxy resin composition during the molding process.

<Examples 8, 19 to 20>
In Examples 19 to 20, in which the application method was spraying, both the component [E] the thixotropy imparting agent and the component [F] the curing aid were used, and compared with Example 8, in which the application method was also spraying, it was shown that there was an effect of suppressing the amount of resin flow and the amount of prepreg resin mixed into the epoxy resin composition during the molding process, and furthermore, the pot life was excellent. Therefore, it was shown that a synergistic effect can be obtained by using the components [E] and [F] simultaneously.

In addition, when both the component [E] thixotropy imparting agent and the component [F] curing aid were applied in Example 32, which was applied by hand using a bar coater, there was an effect of suppressing the amount of resin flow and the amount of prepreg resin mixed into the epoxy resin composition during the molding process, and furthermore, the pot life was shown to be excellent, compared to Example 23, which was also applied by hand using a bar coater.

Therefore, it was shown that applying both component [E] and component [F] to an epoxy resin composition, regardless of the application method, can suppress the amount of resin flow and increase the amount of prepreg resin mixed into the epoxy resin composition during the molding process.

<Examples 8, 35 to 45, Comparative Examples 9 to 10>
In Examples 35 to 37, diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane was used as the non-aromatic epoxy resin of the component [A], and one each of polyvinyl formal, polyvinyl acetoacetal, and polyvinyl butyral were used as the non-aromatic thermoplastic resin of the component [C]. In the order of Examples 35, 36, and 37, a decrease in elastic modulus and an increase in bending strain were observed in the cured product of the epoxy resin composition. In addition, comparing Example 35 with Example 8, Example 35 had a lower exothermic peak temperature, but showed a long pot life, indicating that it is possible to control reactivity by changing the type of component [A]. Therefore, it was shown that it is possible to control reactivity by changing the type of component [A], and it is possible to adjust the balance between fast curing and pot life, i.e., the effect of suppressing the amount of resin flow during the molding process and the amount of resin in the prepreg mixed into the cured resin, and process passability.

In Examples 38 to 39, silicone rubber powder was used as the rubber component [G]. Increasing the content of component [G] reduced the elastic modulus of the cured epoxy resin composition, improved bending strain, and suppressed the amount of resin flow. On the other hand, when the amount of component [G] was too small, as in Comparative Example 9, the effect of suppressing the amount of resin flow was not fully exerted, and the amount of resin in the prepreg mixed with the cured resin during the molding process was excessive, and it was judged to be defective. Furthermore, when the amount of component [G] was excessive, as in Comparative Example 10, the epoxy resin composition clogged the nozzle when spraying, making it impossible to apply.

In Examples 40 to 41, two types of non-aromatic epoxy resins, (3',4'-epoxycyclohexane) methyl 3,4-epoxycyclohexane carboxylate and diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane, were used as the non-aromatic epoxy resin of component [A]. Comparing Examples 35 and 40 to 41, it was shown that the higher the content of (3',4'-epoxycyclohexane) methyl 3,4-epoxycyclohexane carboxylate, the lower the exothermic peak temperature, and the resin flow amount and the amount of resin in the prepreg mixed into the resin cured product during the molding process were suppressed. Example 8, which used only one type of (3',4'-epoxycyclohexane) methyl 3,4-epoxycyclohexane carboxylate as component [A], was shown to have excellent fast curing properties, and Example 35, which used only one type of diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane, was shown to have excellent pot life, and when two types of the above are used as in Examples 40 to 41, it is possible to achieve both excellent fast curing properties and excellent pot life. Therefore, it was shown that by using two types of non-aromatic epoxy resins in the component [A], it is possible to control the reactivity of the epoxy resin composition, and it is possible to adjust the balance between the fast curing property, the pot life, i.e., the effect of suppressing the amount of resin flow during the molding process and the amount of resin in the prepreg mixed into the cured resin, and the processability. Here, a comparison of Examples 8 and 35 shows that the bending strain of the cured epoxy resin is higher in Example 35, which uses diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane, than in Example 8, which uses (3',4'-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate as the non-aromatic epoxy resin in the component [A]. A comparison of Examples 40 to 41 shows that the bending strain of the cured epoxy resin is higher when the proportion of diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane used as the non-aromatic epoxy resin in the component [A] is higher.

In Example 42, (3',4'-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate was used as the non-aromatic epoxy resin of component [A], and in Example 43, (3',4'-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate and diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane were used, and in both cases, 4-hydroxyphenyldimethylsulfonium methyl sulfate was used as the curing aid of component [F]. Compared with Example 35 and Example 41, Example 42 and Example 43 each had an improved exothermic peak temperature, indicating that the inclusion of component [F] makes it possible to control the reactivity of the epoxy resin composition.

In Example 44, (3',4'-epoxycyclohexane) methyl 3,4-epoxycyclohexane carboxylate was used as the non-aromatic epoxy resin of component [A], and in Example 45, (3',4'-epoxycyclohexane) methyl 3,4-epoxycyclohexane carboxylate and diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane were used. In both cases, fumed silica was used as the thixotropy imparting agent of component [E], 4-hydroxyphenyldimethylsulfonium = methyl sulfate was used as the curing aid of component [F], and silicone rubber powder was used as the rubber of component [G]. When Example 44 is compared with Example 35, and Example 45 is compared with Example 41, it was shown that the reactivity of the epoxy resin composition can be controlled by the inclusion of component [F] in each of Examples 44 and 45. In addition, when Example 44 is compared with Example 42, and Example 45 is compared with Example 43, it is found that the resin flow amount is suppressed in Examples 44 and 45 by containing the component [E] and the component [G], and the amount of resin in the prepreg mixed into the cured resin during the molding process is also suppressed. When Example 44 is compared with Example 35, and Example 45 is compared with Example 41, it is found that Examples 44 and 45 each contain the component [F] to further improve the pot life of the epoxy resin composition.

<Examples 23, 46 to 56, Comparative Example 11>
In Examples 46 to 48, diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane was used as the non-aromatic epoxy resin of component [A], and one each of polyvinyl formal, polyvinyl acetoacetal, and polyvinyl butyral were used as the non-aromatic thermoplastic resin of component [C]. Examples 46, 47, and 48 showed an increase in room temperature viscosity, a decrease in elastic modulus in the cured product of the epoxy resin composition, and an increase in bending strain in that order. In addition, comparing Example 46 with Example 23, Example 46 showed a lower exothermic peak temperature, but a longer pot life. Thus, it was shown that reactivity can be controlled by changing the type of component [A], and the balance between fast curing and pot life, i.e., the effect of suppressing the amount of resin flow during the molding process and the amount of resin in the prepreg mixed into the cured resin, and process passability can be adjusted.

In Examples 49 to 50, silicone rubber powder containing the rubber component [G] was used. Increasing the content of component [G] improved the room temperature viscosity, reduced the elastic modulus of the cured epoxy resin composition, improved bending strain, and suppressed the amount of resin flow. On the other hand, when the amount of component [G] was excessive, as in Comparative Example 11, the room temperature viscosity was also excessive, and the adhesion was judged to be poor.

In Examples 51-52, two types of non-aromatic epoxy resins, (3',4'-epoxycyclohexane) methyl 3,4-epoxycyclohexane carboxylate and diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane, were used as the non-aromatic epoxy resin of component [A]. Comparing Examples 46 and 51-52, it was shown that the higher the content of (3',4'-epoxycyclohexane) methyl 3,4-epoxycyclohexane carboxylate, the lower the exothermic peak temperature, and the resin flow amount and the amount of resin in the prepreg mixed into the resin cured product during the molding process were suppressed. Example 23, which used only one type of (3',4'-epoxycyclohexane) methyl 3,4-epoxycyclohexane carboxylate as component [A], was shown to have excellent fast curing properties, and Example 46, which used only one type of diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane, was shown to have excellent pot life, and when two types of the above are used as in Examples 51-52, it is possible to achieve both excellent fast curing properties and excellent pot life. Therefore, it was shown that by using two types of non-aromatic epoxy resins in the component [A], it is possible to control the reactivity of the epoxy resin composition, and it is possible to adjust the balance between the fast curing property, the pot life, i.e., the effect of suppressing the amount of resin flow during the molding process and the amount of resin in the prepreg mixed into the cured resin, and the processability. Here, a comparison of Examples 23 and 46 showed that the bending strain of the cured epoxy resin was higher in Example 46, which used diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane, than in Example 23, which used (3',4'-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate as the non-aromatic epoxy resin in the component [A], and a comparison of Examples 51 and 52 showed that the bending strain of the cured epoxy resin was higher when the proportion of diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane used as the non-aromatic epoxy resin in the component [A] was higher.

In Example 55, (3',4'-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate was used as the non-aromatic epoxy resin of component [A], and in Example 56, (3',4'-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate and diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane were used. In both cases, fumed silica was used as the thixotropy imparting agent of component [E], 4-hydroxyphenyldimethylsulfonium=methylsulfate was used as the curing aid of component [F], and silicone rubber powder was used as the rubber of component [G]. When Example 55 is compared with Example 46 and Example 56 with Example 52, Examples 55 and 56 each showed the effect of further improving the pot life of the epoxy resin composition by including component [F].

Claims (10)

A coating agent for spraying or hand application , which comprises an epoxy resin composition containing at least components [A] to [ E ] and is used for applications in which the coating agent is applied to the surface of a fiber-reinforced composite material precursor and then heat-cured together, the coating agent containing 90 to 100 parts by mass of [A], 15 to 75 parts by mass of [B], 0.05 to 75 parts by mass of [C], 0.1 to 10 parts by mass of [D], and 0.5 to 10 parts by mass of [E] relative to 100 parts by mass of the total epoxy resin.
[A] Non-aromatic epoxy resin [B] Pigment having an average particle size of 0.1 to 10 μm [C] Non-aromatic thermoplastic resin [D] Cationic or anionic curing agent [E] Thixotropy imparting agent The coating agent according to claim 1 , wherein the epoxy resin composition further comprises a component [F] a curing aid. The coating agent according to claim 2 , wherein the curing aid component [F] is 4-hydroxyphenyldimethylsulfonium methylsulfate or 4-(methylthio)phenol. The coating agent according to any one of claims 1 to 3 , wherein the non-aromatic thermoplastic resin as component [C] is at least one selected from the group consisting of polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, polyvinyl acetoacetal, and polyvinyl acetate. The coating agent according to any one of claims 1 to 4 , wherein the DSC exothermic peak temperature is 80 to 120°C. The coating agent according to any one of claims 1 to 5 , which has a volatilization amount of 5 % or less. The coating agent according to any one of claims 1 to 6 , wherein a color difference ΔE ^* ab value is 4 or less after a cured product of the epoxy resin composition is irradiated with 1000 kJ/ ^m2 of ultraviolet light having a wavelength of 300 to 400 nm. 8. An intermediate substrate comprising a fiber-reinforced composite material precursor made of a thermosetting resin and coated with the coating agent according to claim 1 . A fiber-reinforced composite material comprising a carbon fiber-reinforced composite material using a thermosetting resin, the surface of which is coated with a cured product of the coating agent according to any one of claims 1 to 7 . A fiber-reinforced composite material comprising a cured product of the coating agent according to any one of claims 1 to 7 coated on the surface of a carbon fiber-reinforced composite material (excluding those for printed circuit assembly use) using a thermosetting resin.