JP2023149613A - Curable resin composition and tow prepreg using the same - Google Patents

Abstract

[Problems] A fiber-reinforced composite material matrix with a viscosity that allows for good impregnation into reinforcing fibers, excellent viscosity stability during the impregnation process and tow prepreg storage, and high strength of molded products obtained by curing. A curable resin composition suitably used as a resin is provided. [Solution] A curable resin composition containing as essential components an epoxy resin (A) that is liquid at 25°C, an oxazolidone epoxy resin (B), dicyandiamide or its derivative (C), and a solid curing accelerator (D). The oxazolidone epoxy resin (B) has a viscosity of 8 Pa·s or less at 100°C, and the amount of the oxazolidone epoxy resin (B) is 100 parts by mass in total of components (A) and (B). 10 to 35 parts by mass, and the curable resin composition has a viscosity of 4 to 40 Pa·s at 25°C. [Selection diagram] None

Description

The present invention relates to an epoxy resin composition that provides high strength upon curing, and tow prepreg using the same.

Fiber-reinforced composite materials consist of reinforcing fibers such as glass fibers, aramid fibers, and carbon fibers, and thermosetting matrices such as unsaturated polyester resins, vinyl ester resins, epoxy resins, phenolic resins, benzoxazine resins, cyanate resins, and bismaleimide resins. Composed of resin, it is lightweight and has excellent mechanical properties such as strength, corrosion resistance, and fatigue resistance, so it is widely used as a structural material for aircraft, automobiles, civil engineering construction, sports equipment, etc.

Manufacturing methods for fiber-reinforced composite materials include autoclave molding and press molding, which use prepreg in which reinforcing fibers are pre-impregnated with thermosetting matrix resin, and processes in which reinforcing fibers are impregnated with liquid matrix resin and thermosetting. There are methods such as a wet layup molding method, a pultrusion molding method, a filament winding molding method, an RTM method, etc.

One of the filament winding molding methods is a dry method using tow prepreg in which reinforcing fibers are pre-impregnated with resin. The dry method is superior in reducing the winding speed and stabilizing the resin ratio, so it is advantageous in achieving high productivity and stabilizing the quality of fiber-reinforced composite materials, and is particularly applied as a manufacturing method for high-pressure gas tanks. ing.

In the dry method, in order to improve the quality of the tow prepreg, the matrix resin used is within a preferred viscosity range and has a small rate of increase in viscosity in order to ensure stable impregnation and handling properties during winding. Furthermore, in order to increase the rigidity and strength of the fiber-reinforced composite material in the molded article after curing, the matrix resin is desired to have high elastic modulus and strength, and also to have high heat resistance from the viewpoint of long-term reliability.

Examples of curing agents for epoxy resin-based matrix resins include liquid polyamines, solid polyamines, liquid acid anhydrides, hydrazide compounds, imidazole compounds, and boron complex compounds. Although liquid polyamines and liquid acid anhydrides have low viscosity and can yield resin compositions with excellent impregnating properties, they have a high viscosity increase rate and are not suitable as matrix resins for tow prepregs, so the viscosity increase rate of the matrix resin is reduced. Therefore, solid polyamines such as dicyandiamide and diaminodiphenylsulfone are often used as curing agents.

Patent Document 1 and Patent Document 2 describe the use and addition of an aliphatic epoxy resin as a method for lowering the viscosity of a matrix resin. However, these methods reduce heat resistance.

Patent Documents 3 to 5 describe studies using oxazolidone-type epoxy resins obtained by reacting epoxy resins and isocyanate compounds as a method for increasing the strength of matrix resins, but Insufficient consideration.

One way to increase the strength of matrix resins is to increase their elasticity by using polyfunctional epoxy resins. Although this method can increase strength and Tg, it causes an increase in viscosity increase rate and a decrease in toughness due to high crosslinking density (Patent Document 6).

For fiber-reinforced composite materials, especially matrix resins for tow prepregs, there is a need for a method that has low viscosity, excellent impregnability, low viscosity increase rate, and can achieve high strength and heat resistance after curing.

Japanese Patent Application Publication No. 11-302507 Japanese Patent Application Publication No. 2019-189750 Patent No. 4674988 JP2009-112626A Patent No. 6073284 Japanese Patent Application Publication No. 2016-148022

The present invention is a matrix resin for tow prepreg that has a low viscosity and excellent impregnating properties into reinforcing fibers, and can be used to obtain a fiber-reinforced composite material with excellent strength and heat resistance of the molded product obtained by curing. The purpose of the present invention is to provide a resin composition for use in the present invention.

The present inventors conducted studies to solve the above-mentioned problems and found that a specific epoxy resin composition containing an oxazolidone-type epoxy resin as an essential component provides excellent impregnating properties to reinforcing fibers and high strength upon curing. It was discovered that a resin composition can be obtained, and the present invention was completed.

That is, the present invention provides a curable resin composition containing as essential components an epoxy resin (A) that is liquid at 25°C, an oxazolidone epoxy resin (B), dicyandiamide or a derivative thereof (C), and a solid curing accelerator (D). and the viscosity of the oxazolidone-type epoxy resin (B) at 100°C is 8 Pa·s or less, and the blending amount of the oxazolidone-type epoxy resin (B) is 100 parts by mass in total of components (A) and (B). The curable resin composition has a viscosity of 4 to 40 Pa·s at 25°C.

The oxazolidone epoxy resin (B) is obtained by reacting a bisphenol epoxy resin with toluene diisocyanate or diphenylmethane diisocyanate.

（式中、ｎは０～または１を表す。） The oxazolidone type epoxy resin (B) is obtained by reacting a bisphenol A type epoxy resin represented by the following general formula (1) with an epoxy equivalent of 165 to 175 g/eq and toluene diisocyanate.

(In the formula, n represents 0 to 1.)

A preferable form of tow prepreg in the present invention is that reinforcing fibers are blended at a volume content of 48 to 72%.

Another embodiment of the present invention is a fiber-reinforced composite material obtained by molding a tow prepreg prepared by blending reinforcing fibers into the above resin composition using a filament winding molding method.

The curable resin composition of the present invention has a low viscosity and excellent impregnating properties into reinforcing fibers, and molded products obtained by curing tow prepreg using the same exhibit high strength and heat resistance, and are particularly suitable for filament winding molding. It is suitably used for fiber-reinforced composite materials obtained by.

Embodiments of the present invention will be described in detail below.
The curable resin composition of the present invention contains an epoxy resin (A) that is liquid at 25°C, an oxazolidone epoxy resin (B), dicyandiamide or its derivative (C), and a solid curing accelerator (D) as essential components. . Hereinafter, epoxy resin (A), oxazolidone type epoxy resin (B), dicyandiamide or its derivative (C), and curing accelerator (D), which are liquid at 25°C, are used as component (A), component (B), and (C), respectively. ) component and (D) component.

The epoxy resin (A) that is liquid at 25°C is not particularly limited as long as it is an epoxy resin that is liquid at room temperature (25°C), but bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol E epoxy resin, Examples include bisphenol S-type epoxy resin, bisphenol Z-type epoxy resin, isophorone bisphenol-type epoxy resin, para-aminophenol-type epoxy resin, and meta-aminophenol-type epoxy resin.
Preferred are bisphenol A epoxy resins and bisphenol F epoxy resins, particularly preferably bisphenol A epoxy resins and bisphenol F epoxy resins, for example, 10 to 40 parts by weight of bisphenol A epoxy resin and bisphenol F epoxy resin. An epoxy resin can be blended in an amount of 40 to 80 parts by weight.
The epoxy equivalent of the epoxy resin (A) is preferably 90 to 250 g/eq, more preferably 150 to 200 g/eq.

The oxazolidone-type epoxy resin (B) is obtained by reacting an epoxy resin with an isocyanate compound, and an oxazolidone structure is formed by an addition reaction between the epoxy group of the epoxy resin and the isocyanate group of the isocyanate compound. In this reaction, side reactions such as self-polymerization of the isocyanate compound occur, so if you do not pay attention to the reactivity of the epoxy group and the isocyanate group, the molar ratio of the epoxy group to the isocyanate group, the type of catalyst, and the reaction temperature, side reactions may occur. Viscosity increases as the molecular weight increases.

The viscosity of component (B) of the present invention at 100° C. is 8 Pa·s or less. When the viscosity at 100° C. exceeds 8 Pa·s, the viscosity of the curable resin composition becomes high, impairing the impregnating properties of the reinforcing fibers. Preferably it is 3 Pa·s or less, more preferably 1 Pa·s or less.

The amount of component (B) contained in the curable resin composition is 10 to 35 parts by mass based on the total of 100 parts by mass of components (A) and (B). If component (B) is less than 10 parts by mass, no improvement in strength will be observed, and if component (B) is more than 35 parts by mass, the viscosity of the curable resin composition will increase, impairing the ability to impregnate reinforcing fibers. . More preferably, it is 15 to 30 parts by mass.

The curable resin composition of the present invention has a viscosity of 4 to 40 Pa·s at 25° C. as measured by an E-type viscometer. If it is within this range, the impregnating properties of the reinforcing fibers will be good, and the outflow of the resin during molding will be suppressed, resulting in a good appearance of the fiber-reinforced composite material obtained. For practical use, it is desired that the viscosity increase rate be small; for example, the viscosity increase rate at 25° C. after 48 hours is preferably 120% or less, more preferably 105% or less.

ここで、ｎは、０又は１以上の整数であり、ジフェニルメタンジイソシアネートは、通常、単量体（ｎ＝０）と多量体（ｎ≧１）の混合物である。
これらの化合物はエポキシ基とイソシアネート基の反応性に優れ、オキサゾリドン構造の反応選択制を高めつつ得られるオキサゾリドン型エポキシ樹脂の粘度を低下できる。 Component (B) of the present invention is preferably obtained by, for example, reacting a bisphenol-type epoxy resin with toluene diisocyanate or diphenylmethane diisocyanate represented by the following structural formulas (2) and (3).

Here, n is an integer of 0 or 1 or more, and diphenylmethane diisocyanate is usually a mixture of a monomer (n=0) and a multimer (n≧1).
These compounds have excellent reactivity between epoxy groups and isocyanate groups, and can reduce the viscosity of the obtained oxazolidone-type epoxy resin while increasing the reaction selectivity of the oxazolidone structure.

（式中、ｎは０～または１を表す。） In addition, in the present invention, component (B) is obtained by reacting a bisphenol A type epoxy resin represented by the following general formula (1) and having an epoxy equivalent of 165 to 175 g/eq with toluene diisocyanate. This is preferable because the viscosity of the oxazolidone-type epoxy resin can be reduced while suppressing the oxidation and increasing the molar ratio of the oxazolidone structure.

(In the formula, n represents 0 to 1.)

In the curable resin composition of the present invention, the epoxy resin (A) or oxazolidone type epoxy resin ( It may contain epoxy resins other than B).

Examples of other epoxy resins include glycidyl ether of bisphenol alkylene oxide adducts, which have two or more epoxy groups in one molecule, phenol novolak epoxy resins, cresol novolac epoxy resins, and bisphenol A novolak epoxy resins. Novolak type epoxy resins such as 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate esters, alicyclic epoxy resins such as 1-epoxyethyl-3,4-epoxycyclohexane, glycidyl esters such as phthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, dimer acid glycidyl ester, and tetraglycidyl diamino Glycidyl amines such as diphenylmethane, tetraglycidyldiaminodiphenylsulfone, triglycidylaminophenol, triglycidylaminocresol, and tetraglycidylxylylene diamine can be used. These epoxy resins may be used alone or in combination of two or more.

In the resin composition of the present invention, dicyandiamide or a derivative thereof (C) is used as a curing agent. Dicyandiamide is a hardening agent that is solid at room temperature, and although it hardly dissolves in epoxy resins at room temperature, it dissolves when heated to 180°C or higher and reacts with epoxy groups.It has excellent storage stability and latent properties at room temperature. It is a hardening agent. Further, as a derivative thereof, an N-substituted dicyandiamide derivative such as N-hexyldicyandiamide described in JP-A-11-119429 can be used.

The amount of dicyandiamide or its derivative (C) contained in the curable resin composition of the present invention is the amount of active hydrogen groups contained in component (C) based on the number of moles of epoxy groups in the total epoxy resin in the composition. The molar ratio (H/E) is preferably 0.25 to 0.65, more preferably 0.35 to 0.55. From another point of view, the blending amount of component (C) is preferably in the range of 3.0 to 8.0 parts by weight based on 100 parts by weight of the total epoxy resin containing components (A) and (B).

The solid curing accelerator (D) is preferably one that can accelerate the reaction with component (C) and suppress the viscosity increase rate of the mixed curable resin composition, and solid aromatic urea compounds and solid curing accelerators are preferred. Imidazole compounds and the like are used.
Examples of solid aromatic urea compounds include 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, and N-phenyl-N' , N'-dimethylurea, N-(4-chlorophenyl)-N',N'-dimethylurea, N-(3,4-dichlorophenyl)-N',N'-dimethylurea, N-(3-chloro- 4-methylphenyl)-N',N'-dimethylurea, N-(3-chloro-4-ethylphenyl)-N',N'-dimethylurea, N-(3-chloro-4-methoxyphenyl)- N',N'-dimethylurea, N-(4-methyl-3-nitrophenyl)-N',N'-dimethylurea, 2,4-bis(N',N'-dimethylureido)toluene, methylene- Examples include bis(p-N',N'-dimethylureidophenyl), among which 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(3,4-dichlorophenyl)- 1,1-dimethylurea is preferred. These may be used alone or in combination of two or more, and are not limited to the above as long as they are chemically stable and do not dissolve in the epoxy resin at room temperature.
Solid imidazole compounds include 2-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2- Phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl6-4',5'-dihydroxymethylimidazole, 1-cyanoethyl-2-ethyl-4methylimidazole, 2-phenyl-4-methyl-5-hydroxy It is preferable to use imidazole compounds such as methylimidazole.
Furthermore, imidazole compounds containing a triazine ring can also be preferably used, such as 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6 -[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-S - triazine isocyanuric acid adducts, etc. These may be used alone or in combination of two or more, and are not limited to the above as long as they are chemically stable and do not dissolve in the epoxy resin at room temperature.
The amount of component (D) used is preferably 0.1 to 7 parts by weight based on 100 parts by weight of the total epoxy resin containing components (A) and (B). When the amount exceeds 7 parts by weight, the viscosity increase rate during storage of the curable resin composition increases. If the amount is less than 0.1 part by weight, a problem arises in that the curing reaction is not promoted. More preferably, it is 1 to 5 parts by weight.

It is possible to add an antifoaming agent and a leveling agent to the curable resin composition of the present invention as additives for the purpose of improving surface smoothness. These additives can be blended in an amount of 0.01 to 3 parts by weight, preferably 0.01 to 1 part by weight, based on 100 parts by weight of the entire resin composition.

The curable resin composition of the present invention is produced by uniformly mixing the above components (A), (B), (C), (D), and the like. The resulting resin composition has a viscosity in the range of 4 to 40 Pa·s as measured using an E-type viscometer cone plate type at 25°C. If it is within this range, the impregnating properties of the reinforcing fibers will be good, and the outflow of the resin during molding will be suppressed, resulting in a good appearance of the fiber-reinforced composite material obtained.

Moreover, other curable resins can also be further blended into the curable resin composition of the present invention. Such curable resins include unsaturated polyester resins, curable acrylic resins, curable amino resins, curable melamine resins, curable urea resins, curable cyanate ester resins, curable urethane resins, curable oxetane resins, Examples include, but are not limited to, curable epoxy/oxetane composite resins.

The curable resin composition of the present invention includes a coupling agent, conductive particles such as carbon particles and metal-plated organic particles, thermosetting resin particles, or inorganic fillers such as silica gel, nanosilica, alumina fiber, and clay. A conductive filler can be blended. By using conductive particles or conductive fillers, the conductivity of the resulting cured resin or fiber-reinforced composite material can be improved.

Examples of the conductive filler include carbon black, carbon nanotubes, fullerene, and metal nanoparticles, which may be used alone or in combination. Among these, the blending of carbon nanotubes is widely known not only to improve conductivity but also to increase the impact strength of fiber-reinforced composite materials even at a blending amount of less than 1 wt%. , can be suitably used.

The curable resin composition of the present invention is impregnated into reinforcing fibers or bundles to produce tow prepreg. A known method may be used to form tow prepreg. The tow prepreg thus obtained is suitably used for fiber-reinforced composite materials obtained by filament winding molding.

Although the method for producing a fiber-reinforced composite material by processing the curable resin composition of the present invention into tow prepreg is not particularly limited, it is preferably applied as a method for producing a pressure vessel using a filament winding method. By wrapping the tow prepreg around a metal or resin liner and then thermally curing it, a molded article is obtained in which a layer of fiber-reinforced composite material is formed to cover the liner. After this, the liner may be removed if necessary. Further, the present invention is desirably applied as a method for producing hollow fiber-reinforced composite materials in the form of circular injections, such as shaft- or roll-shaped molded articles, by the filament winding method. A molded product is obtained by wrapping the tow prepreg around a metal or resin mandrel and heat-forming it, and the mandrel may be removed depending on the purpose.

The reinforcing fibers used in the tow prepreg of the present invention are selected from glass fibers, aramid fibers, carbon fibers, boron fibers, etc., but in order to obtain a fiber-reinforced composite material that is lightweight and has excellent rigidity and strength, carbon fibers It is preferable to use

In the tow prepreg composed of the curable resin composition of the present invention and reinforcing fibers, the volume content of the reinforcing fibers is preferably in the range of 48 to 72%, and more preferably in the range of 55 to 68% to reduce voids. , and a molded article with a high volume content of reinforcing fibers can be obtained, so a molding material with excellent rigidity and strength can be obtained.

In the present invention, a cured product obtained by curing a curable resin composition at a temperature of 160° C. for 1 hour has a flexural modulus of 2.8 GPa or more as measured according to JIS K7171, and a cured product according to JIS K7121. It is more preferable that the glass transition temperature (Tg) measured by the method is 120° C. or higher.

Next, the present invention will be specifically explained based on Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Parts indicating blending amounts are parts by mass unless otherwise specified. Moreover, the unit of epoxy equivalent is g/eq.

The abbreviations of each component used in the synthesis examples and examples are as follows.
(A) Component YD-128: Bisphenol A type epoxy resin, epoxy equivalent 187 (manufactured by Nippon Steel Chemical & Materials)
YD-8125: Bisphenol A type epoxy resin, epoxy equivalent weight 173 (manufactured by Nippon Steel Chemical & Materials)
YDF-170: Bisphenol F type epoxy resin, epoxy equivalent 170 (manufactured by Nippon Steel Chemical & Materials)
(B) Component YD-952: Oxazolidone type epoxy resin, epoxy equivalent: 335 (manufactured by Nippon Steel Chemical & Materials, viscosity at 100°C 54 Pa・s)
(C) Component DICY: dicyandiamide, active hydrogen group equivalent 21 g/eq
(D) Component DCMU: 3-(3,4-dichlorophenyl)-1,1-dimethylurea 2MZA: 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine

Synthesis example 1
171 parts of YD-128 and 0.2 parts of tris-(2,6-dimethoxyphenyl)phosphine were added to a glass separable flask equipped with a stirrer, a thermometer, a cooling tube with a distillate collection tank, and a nitrogen gas introduction device. After charging, the temperature was raised to 150°C while stirring. Next, 20 parts of toluene diisocyanate was added dropwise over 3 hours using a dropping funnel to carry out a reaction. Further, the reaction temperature was maintained at 160°C and the reaction was carried out for 3 hours to obtain 189 parts of an epoxy resin having an epoxy equivalent of 277, a viscosity at 100°C of 1.4 Pa·s, and an oxazolidone structure. This epoxy resin is referred to as OXA1.

Synthesis example 2
Into the same apparatus as in Synthesis Example 1, 149 parts of YD-128 and 0.2 parts of tetrabutylammonium bromide were charged, and the temperature was raised to 140°C while stirring. Next, 15 parts of diphenylmethane diisocyanate was added in portions over 4 hours to carry out a reaction. Further, the reaction temperature was maintained at 160° C. and the reaction was carried out for 3 hours to obtain 160 parts of an epoxy resin having an oxazolidone structure with an epoxy equivalent of 240 and a viscosity at 100° C. of 1.5 Pa·s. This epoxy resin is referred to as OXA2.

Synthesis example 3
199 parts of YD-8125 and 0.2 parts of tetrabutylammonium bromide were charged into the same apparatus as in Synthesis Example 1, and the temperature was raised to 150°C while stirring. Next, 20 parts of toluene diisocyanate was added dropwise over 3 hours to carry out a reaction. Further, the reaction temperature was kept at 160° C. and the reaction was carried out for 3 hours to obtain 208 parts of an epoxy resin having an oxazolidone structure with an epoxy equivalent of 236 and a viscosity at 100° C. of 0.6 Pa·s. This epoxy resin is referred to as OXA3.

Example 1
(A) 17 parts of YD-128, 67 parts of YDF-170, (B) 18 parts of OXA1, (C) 5.7 parts of DICY, and (D) 3 parts of DCMU. Four parts were used, and these were placed in a 150 mL plastic container and stirred for 5 minutes under reduced pressure using a vacuum mixer "Awatori Rentaro" (manufactured by Shinky Co., Ltd.) to obtain a curable resin composition.

Examples 2 to 11, Comparative Examples 1 to 3
A curable resin composition was produced in the same manner as in Example 1, except that each raw material was used as components (A) to (D) in the compositions listed in Tables 1 and 2.

(Viscosity measurement)
The viscosity value at 25° C. was measured using an E-type viscometer cone plate type. A curable resin composition was prepared, and 0.8 mL of it was used for measurement, and the value 90 seconds after the start of the measurement was taken as the viscosity value.
The viscosity value at 25° C. was measured using an E-type viscometer cone plate type. A curable resin composition was prepared, 0.8 mL of which was used for measurement, and the value 90 seconds after the start of the measurement was taken as the viscosity value at 25°C. In addition, the prepared resin composition for fiber-reinforced composite material was allowed to stand in a constant temperature water bath set at 40°C for 48 hours, and then the viscosity at 25°C was similarly measured using an E-type viscometer cone plate type. The 25°C viscosity value after 48 hours was taken as the value.
In addition, the viscosity increase rate was calculated using the formula 100 x (viscosity at 25°C after 48 hours/viscosity at 25°C).

(Measurement of bending modulus and bending strength)
The curable resin composition was poured into a 60 mm x 240 mm mold with a 4 mm thick spacer hollowed out into a flat plate shape, and cured at 150°C for 2 hours to form a molded plate for measurement, and the flexural modulus as described below was determined. It was used to measure bending strength and fracture toughness.
The obtained molded plate was cut into a size of 80 mm x 10 mm using a tabletop band saw, and the bending test piece was subjected to a bending test at a temperature of 23°C using a method based on JIS 7171, and the bending elastic modulus and bending strength were calculated. .

(Measurement of glass transition temperature)
The above molded plate was cut into a size of 2.5 mm x 2.5 mm using a tabletop band saw, and further polished to a thickness of approximately 0.8 mm using a belt disc sander. Measurement was performed using a differential scanning calorimeter under a nitrogen atmosphere at a heating rate of 10°C/min, and the tangent line at the inflection point of the DSC curve and the temperature at which the start of inflection was seen, that is, from the inflection point. The intersection with the tangent in the 20-30°C lower temperature range was defined as the glass transition temperature Tg.

(Measurement of interlayer shear peel strength)
The obtained curable resin composition was poured into a resin bath, and while threading carbon fiber Torayca T700SC-12K (manufactured by Toray Industries) through a roll coater at 2 m/min, 0.33 g of the curable resin composition was added per 1 m of carbon fiber. The tow prepreg laminate was coated and impregnated and wound using a bobbin traverse winder equipped with a plate-shaped mandrel until the laminate thickness reached 3 mm.
After that, the plate-shaped mandrel was removed and a flat plate part with a size of 200 mm in length x 100 mm in width was cut out from the tow prepreg laminate, and it was cured for 2 hours at 150°C using a vacuum press machine, resulting in a thickness of 3 mm with uniform fiber orientation in one direction. A plate of carbon fiber reinforced composite material having a volume content of 62% was molded.
A plate of carbon fiber reinforced composite material was cut using a milling machine to a size of 21 mm in the parallel direction of the fibers and 10 mm in the length in the vertical direction of the fibers, and a test piece was used for measuring fracture toughness. An interlayer shear peel test was conducted at a temperature of 23° C. using a method based on JIS K7078, and the interlayer shear peel strength was measured.

The physical properties and test results are shown in Tables 1 and 2, respectively.

Claims (5)

A curable resin composition containing as essential components an epoxy resin (A) that is liquid at 25°C, an oxazolidone-type epoxy resin (B), dicyandiamide or its derivative (C), and a solid curing accelerator (D), the composition comprising oxazolidone The viscosity of the epoxy resin (B) at 100°C is 8 Pa·s or less, and the amount of the oxazolidone epoxy resin (B) is 10 to 10 parts by mass per 100 parts by mass of the (A) component and (B) component. 35 parts by mass, and a curable resin composition characterized in that the viscosity of the curable resin composition at 25° C. is in the range of 4 to 40 Pa·s. The curable resin composition according to claim 1, wherein the oxazolidone-type epoxy resin (B) is obtained by reacting a bisphenol-type epoxy resin with toluene diisocyanate or diphenylmethane diisocyanate. Claim 1, wherein the oxazolidone type epoxy resin (B) is obtained by reacting a bisphenol A type epoxy resin represented by the following general formula (1) and having an epoxy equivalent of 165 to 175 g/eq with toluene diisocyanate. The curable resin composition described in .

(In the formula, n represents 0 to 1.) A tow prepreg characterized in that the curable resin composition according to any one of claims 1 to 3 is blended with reinforcing fibers at a volume content of 48 to 72%. A molded article obtained by molding the tow prepreg according to claim 4 by a filament winding molding method.