JP2019178224A - Epoxy resin, epoxy resin composition and fiber-reinforced composite material using the same - Google Patents

Abstract

To provide an epoxy resin which is excellent in adhesion and has a new oxazolidone structure, an epoxy resin composition and a fiber-reinforced composite material using the epoxy resin.SOLUTION: An epoxy resin has an oxazolidone structure has an epoxy equivalent of 220-480 g/eq and a softening point of 100°C or lower, and contains 0.25-2.5 wt.% of hydrolysis chlorine.SELECTED DRAWING: None

Description

  The present invention relates to an epoxy resin having a novel oxazolidone structure excellent in adhesiveness and an epoxy resin composition using the epoxy resin.

  Fiber reinforced composite materials include glass fibers, reinforced fibers such as aramid fibers and carbon fibers, and thermosetting matrices such as unsaturated polyester resins, vinyl ester resins, epoxy resins, phenol resins, benzoxazine resins, cyanate resins, and bismaleimide resins. Since it is made of resin and is lightweight and has excellent mechanical properties such as strength, corrosion resistance, and fatigue resistance, it is widely applied as a structural material for aircraft, automobiles, civil engineering and sports equipment.

  The fiber reinforced composite material manufacturing method includes an autoclave molding method, a sheet winding molding method, a press molding method, and a liquid matrix resin impregnated into a reinforcing fiber, using a prepreg in which a thermosetting matrix resin is impregnated in a reinforcing fiber in advance. There are techniques such as a wet lay-up molding method, a pultrusion molding method, a filament winding molding method, and an RTM method, which include a step of forming and a molding step by thermosetting.

  As one of the filament winding molding methods, there is a dry method using a tuprepreg in which a reinforcing fiber is impregnated with a resin in advance. The dry method is superior in terms of mass production of cylindrical or tank-shaped fiber-reinforced composite materials because it is excellent in shortening the winding speed and stability in the resin ratio.

  In order to improve the quality of the molded product obtained by the autoclave method and the dry method, the matrix resin used is required to have high elasticity, high strength and high glass transition temperature after curing, as well as toughness and high adhesion to reinforcing fibers. .

  There are various methods for increasing the toughness of the matrix resin, and examples thereof include addition of a low elastic modulus rubber-like polymer, block copolymer, core-shell type rubber particles, and thermoplastic resin. Although these techniques can increase the adhesiveness by increasing the toughness of the resin, they tend to cause a decrease in the elastic modulus and strength, and are difficult to adapt in applications where high rigidity is required for the fiber-reinforced composite material. Patent Document 1 proposes a resin composition using core-shell type rubber particles. While the fracture toughness is increased by the addition of the core-shell rubber, the elastic modulus is lowered.

  High elasticity and high strength have been studied with a focus on the structure of the epoxy resin as a technique to increase the toughness of the matrix resin, and attempts have been made to add novolac type epoxy, oxazolidone ring-containing epoxy, amine type epoxy, etc. .

  Patent Document 2 proposes a resin composition using an oxazolidone ring-containing epoxy. Patent Document 3 proposes a resin composition using an amine type epoxy. In these documents, an increase in strength is observed due to the introduction of an oxazolidone ring structure or a glycidylamine structure, but there is no mention of an increase in strength focusing on the amount of hydrolyzed chlorine in the epoxy resin.

  Patent Document 4 proposes an improvement in electrical characteristics with a focus on reducing the amount of hydrolyzed chlorine in the epoxy resin, and Patent Document 5 discloses an epoxy resin that is less colored at the time of heat molding due to the regulation of the amount of hydrolyzable chlorine. A resin composition comprising an acid anhydride has been proposed. On the other hand, there is no mention of improvement in strength and adhesion by paying attention to the amount of hydrolyzable chlorine.

  Regarding matrix resins for fiber reinforced composite materials, attempts have been made to improve the rigidity and strength of molded products and adhesion to adherends such as reinforcing fibers by adding rubber components and polyfunctionalizing epoxy resins. Further improvements are desired.

JP 2006-199673 A JP 2009-112626 A Japanese Patent No. 4811532 JP 2017-137374 A Japanese Patent No. 4752326

  The present invention relates to an epoxy resin, a curable resin composition, and an epoxy resin used as a matrix resin capable of obtaining a fiber-reinforced composite material having a high modulus of elasticity and adhesive strength obtained by curing and high rigidity. It aims at providing the used fiber reinforced composite material.

  As a result of investigations to solve the above-mentioned problems, the present inventors obtained an epoxy containing an oxazolidone ring while paying attention to the hydrolyzable chlorine amount of the epoxy resin, that is, the amount of the chlorohydrin group, and then the curing agent and It discovered that the resin composition which gives a high intensity | strength and an elasticity modulus to a molded object by mixing and hardening was obtained, and came to complete this invention.

  That is, the present invention is an epoxy resin having an oxazolidone structure characterized by containing hydrolyzed chlorine having an epoxy equivalent of 220 to 480 g / eq, a softening point of 100 ° C. or less and 0.25 to 2.5% by weight.

（式中、ｎは０〜５を表し、Ｒはそれぞれ独立して炭素数１〜８の二価の炭化水素残基であり、Ｇはそれぞれ独立して下記式（２）、下記式（３）または下記式（４）で表される基である）

The present invention is represented by the following general formula (1), an epoxy equivalent of 165 to 245 g / eq, an epoxy resin (a) containing 0.3 to 3.0% by weight of hydrolyzed chlorine, and toluene diisocyanate. Or it is an epoxy resin which has said oxazolidone structure obtained by making it react with diphenylmethane diisocyanate.

(In the formula, n represents 0 to 5, each R is independently a divalent hydrocarbon residue having 1 to 8 carbon atoms, and G is independently represented by the following formula (2) or the following formula (3 Or a group represented by the following formula (4))

（式中、ｍは０〜５を表し、Ｒ^１はそれぞれ独立して炭素数１〜８の二価の炭化水素残基であり、Ｙはそれぞれ独立して単結合、下記式（１２）若しくは式（１３）で表される基又はこれらの組み合わせであり、式（１２）及び式（１３）で表される基を複数含んでもよく、Ｙの１５モル％以上は式（１２）で表される基を含む。Ｇはそれぞれ独立して上記式（２）、式（３）または式（４）で表される基である。）

（式中、Ｒ^２、Ｒ^３は炭素数１〜８の二価の炭化水素残基であり、Ａは炭素数４〜１６の二価の炭化水素残基である。） Furthermore, this invention is an epoxy resin which has an oxazolidone structure of Claim 1 represented by following General formula (11).

(Wherein, m represents 0 to 5, R ¹ is independently a divalent hydrocarbon residue having 1 to 8 carbon atoms, Y each independently represent a single bond, the following equation (12) or It is a group represented by the formula (13) or a combination thereof, and may contain a plurality of groups represented by the formula (12) and the formula (13), and 15 mol% or more of Y is represented by the formula (12). G is independently a group represented by the above formula (2), formula (3) or formula (4).

(In the formula, R ² and R ³ are divalent hydrocarbon residues having 1 to 8 carbon atoms, and A is a divalent hydrocarbon residue having 4 to 16 carbon atoms.)

  Moreover, this invention is a manufacturing method of the epoxy resin characterized by making the said epoxy resin (a) react with toluene diisocyanate or diphenylmethane diisocyanate in manufacturing the epoxy resin which has said oxazolidone structure.

Moreover, this invention is an epoxy resin composition formed by mix | blending a hardening | curing agent (B) with said epoxy resin.
Preferred examples of the curing agent (B) include dicyandiamide or a derivative thereof and a polyamine that is liquid at 40 ° C.

Furthermore, this invention is a fiber reinforced composite material characterized by mix | blending a reinforced fiber with said epoxy resin composition. As the fiber reinforced composite material, there is a prepreg in which the reinforcing fiber is a carbon fiber.
Moreover, this invention is a molded object obtained by hardening said fiber reinforced composite material.

  A molded product obtained by curing using the epoxy resin of the present invention or an epoxy resin composition containing the epoxy resin exhibits high strength and elastic modulus. The epoxy resin of this invention or the epoxy resin composition containing this is used suitably for the fiber reinforced composite material formed by mix | blending a reinforced fiber.

  Hereinafter, embodiments of the present invention will be described in detail.

  The epoxy resin of the present invention is an epoxy resin having an oxazolidone structure having an epoxy equivalent (g / eq) of 220 to 480, a softening point of 100 ° C. or less, and containing 0.25 to 2.5% by weight of hydrolyzed chlorine. is there.

  The epoxy resin having the oxazolidone structure can be an epoxy resin represented by the general formula (11) or an epoxy resin containing this as a main component.

  The epoxy resin having this oxazolidone structure is represented by the above general formula (1), has an epoxy equivalent of 165 to 245, and contains 0.3 to 3.0% by weight of hydrolyzed chlorine (a) And toluene diisocyanate or diphenylmethane diisocyanate can be obtained.

  In the general formula (1), n represents 0 to 5, and each R is independently a divalent hydrocarbon residue having 1 to 8 carbon atoms, preferably an alkylene group or alkylidene group having 1 to 4 carbon atoms. . Since R is a group derived from the epoxy resin (a), it is understood from the description of the epoxy resin used.

  G is each independently a group represented by the above formula (2), (3) or formula (4). The epoxy resin (a) contains 0.3 to 3.0% by weight, preferably 0.5 to 2.5% by weight of hydrolyzed chlorine. Since the group represented by the formula (3) contains hydrolyzed chlorine, the amount of hydrolyzed chlorine can be adjusted by changing the amount thereof.

In the general formula (11), m represents 0 to 5, ^{R 1} represents a divalent hydrocarbon residue having 1 to 8 carbon independently. Preferred examples are the same as R in the general formula (1). Y is a single bond, a divalent group represented by the above formula (12) or formula (13), or a combination thereof, and may contain a plurality of groups represented by formula (12) and formula (13), 15 mol% or more of Y contains group represented by Formula (12). For example, when the group represented by the formula (12) is E1, and the group represented by the formula (13) is E2, Y may contain both E1 and E2 as in E1-E2-E2, and only one of them. , E1 and E2 may be included, or a single bond not including E1 and E2 may be used. Usually, it is preferable that the total of those containing a single bond or one of E1 and E2 is 25 mol% or more of Y, and the length of Y is also limited from the epoxy equivalent. However, 30 mol% or more, preferably 20 to 50 mol%, of Y is a group containing E1 having an oxazolidone ring. If it exceeds 50 mol%, the softening point of the resulting resin may be too high. G is the same as the general formula (1).

In the formulas (12) and (13), R ² and R ³ are divalent hydrocarbon residues having 1 to 8 carbon atoms, and preferred examples are the same as R in the general formula (1). A is a divalent hydrocarbon residue having 4 to 16 carbon atoms, and is preferably a hydrocarbon residue having 1 to 2 aromatic rings. Since A is a residue of diisocyanate, it is understood from the description of diisocyanate. Although m is 0-5, it is preferable that the component of 0-2 is a main component (50 mol% or more). In the formulas (12) and (13), most of the left end binds to O in the general formula (11) and the right end binds to G, but a part of the left end of the formula (12) or the formula (13) Join to the end. A line marked with * at the end represents a bond. The same applies to the left end line of Formula (2) to Formula (4).

  In the method for producing an epoxy resin having an oxazolidone structure according to the present invention, the epoxy resin (a) is reacted with toluene diisocyanate or diphenylmethane diisocyanate. An epoxy resin (a) containing a predetermined amount of hydrolyzed chlorine is commercially available. If the epoxy resin being used meets the requirements, it can be used. However, epoxy resins are usually used for electronic materials and have a low content of hydrolyzed chlorine. For this reason, an epoxy resin having a desired hydrolyzed chlorine concentration is produced by changing the reaction conditions in the step of epoxidizing the hydroxy compound with epichlorohydrin, or a commercially available epoxy resin is modified to produce the desired hydrolyzed resin. It is preferable to use an epoxy resin having a decomposed chlorine concentration. Preferably, the epoxy resin having a desired hydrolyzed chlorine concentration is obtained by reacting an epoxy resin having a low hydrolyzed chlorine content with hydrochloric acid. By reacting with hydrochloric acid, a part of the epoxy group is considered to be changed to groups represented by the formulas (3) and (4).

  When a part of G in the general formula (1) is a group represented by the formula (3) or the formula (4), it is found that an oxazolidone ring is not generated and remains as a terminal group. It has been found that the presence of a certain amount of end groups improves physical properties such as improved adhesion and strength of the molded product. It is considered that this is because the end group exhibits an effect of improving the adhesion, and an increase in physical properties of the molded product due to the influence of the molecular weight at the end stop.

  The epoxy resin (a) has an epoxy equivalent of 165 to 245 and contains 0.3 to 3.0% by weight of hydrolyzed chlorine. In this range, the epoxy resin (A) having an oxazolidone structure obtained by reacting with toluene diisocyanate or diphenylmethane diisocyanate is cured using a curing agent (B), so that heat resistance, strength elastic modulus, adhesion A resin composition that is a molded article having excellent properties can be obtained. When the epoxy equivalent of the epoxy resin (a) is less than 165, the crosslink density becomes high, so that brittleness is developed and the adhesiveness is lowered, and when it exceeds 245, the crosslink density is lowered and the heat resistance is lowered.

  Specific examples of the epoxy resin (a) include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, bisphenol E type epoxy resin, bisphenol Z type epoxy resin, isophorone bisphenol type epoxy resin and the like. .

The epoxy resin having an oxazolidone structure is obtained by reacting the epoxy resin (a) with diisocyanate. As the diisocyanate, diisocyanate having an aromatic ring such as toluene diisocyanate or diphenylmethane diisocyanate is used. Since toluene diisocyanate and diphenylmethane diisocyanate have good reactivity with epoxy groups, an epoxy resin having a stable quality oxazolidone structure can be obtained. It is also economical.
In this case, the epoxy group of the epoxy resin reacts with diisocyanate to form a five-membered oxazolidone structure. However, not all of the epoxy groups are reacted, but only a part is reacted so as to have a predetermined epoxy equivalent. For this purpose, it is preferable to use less than the theoretical amount of diisocyanate and to react the whole so that no isocyanate groups remain.

  The epoxy resin having an oxazolidone structure of the present invention has an epoxy equivalent of 220 to 480 and a softening point of 100 ° C or lower. When the epoxy equivalent is in the range of 220 to 480, by mixing with a curing agent and curing, a resin composition that becomes a molded article excellent in heat resistance, strength elastic modulus, and adhesiveness is obtained. When the softening point is 100 ° C. or lower, a resin composition excellent in compatibility and fluidity can be obtained even when mixed with other components, and a molded article with stable quality can be obtained. Further, 0.25 to 2.5% by weight, preferably 0.4 to 2.0% by weight of hydrolyzed chlorine is contained. Since hydrolyzed chlorine is derived from hydrolyzed chlorine contained in the epoxy resin (a) used as a raw material, an approximate numerical value can also be calculated from the amount of hydrolyzed chlorine.

  The epoxy resin composition of the present invention contains the epoxy resin (A) having the oxazolidone structure and the curing agent (B) as essential components. Hereinafter, the epoxy resin (A) having an oxazolidone structure is also referred to as an epoxy resin (A) or (A) component, and the curing agent (B) is also referred to as a (B) component, and the epoxy resin composition is a curable resin composition. Therefore, it is also called a curable resin composition or a resin composition.

  The curable resin composition of the present invention can contain other components in addition to the epoxy resin (A) and the curing agent (B). Other epoxy resins may be included as long as the amount is less than 50 parts by mass with respect to 100 parts by mass of the epoxy resin (A) for the purpose of viscosity adjustment.

  Other epoxy resins include, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, bisphenol S type epoxy resin, bisphenol Z type epoxy resin having two or more epoxy groups in one molecule, Bisphenol-type epoxy resins such as isophorone bisphenol-type epoxy resins, or halogen, alkyl-substituted products, hydrogenated products, high-molecular weight products having a plurality of repeating units as well as monomers, glycidyl ethers of alkylene oxide adducts And novolac epoxy resins such as phenol novolac epoxy resin, cresol novolac epoxy resin, bisphenol A novolac epoxy resin, and 3,4-epoxy-6-methylcyclohexylmethyl-3 Alicyclic epoxy resins such as 4-epoxy-6-methylcyclohexanecarboxylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 1-epoxyethyl-3,4-epoxycyclohexane, Aliphatic epoxy resins such as trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, polyoxyalkylene diglycidyl ether, glycidyl esters such as diglycidyl phthalate, diglycidyl tetrahydrophthalate, and dimer acid glycidyl ester Tetraglycidyldiaminodiphenylmethane, tetraglycidyldiaminodiphenylsulfone, triglycidylaminophenol, triglycidylaminocresol, tetraglycidyl Glycidyl amines such as Gilles xylylenediamine and the like can be used. Among these epoxy resins, an epoxy resin having two epoxy groups in one molecule is preferable from the viewpoint of viscosity increase rate, and a trifunctional or higher polyfunctional epoxy resin is not preferable from the viewpoint of viscosity increase rate. These may be used alone or in combination of two or more.

  Any curing agent for epoxy resins can be used as the curing agent (B), but dicyandiamide or a derivative thereof and a polyamine which is liquid at 40 ° C. are preferred. Dicyandiamide is a solid curing agent at room temperature, hardly dissolves in epoxy resin at room temperature, but dissolves when heated to 180 ° C or higher, and has the property of having excellent storage stability at room temperature. It is a curing agent. As the derivative, an N-substituted dicyandiamide derivative such as N-hexyl dicyandiamide described in JP-A-11-119429 can be used. The amount to be used is preferably in the range of 0.2 to 0.8 equivalents (calculated assuming 1 mol of dicyandiamide as 4 equivalents) per 1 equivalent of epoxy group of the epoxy resin (A). More preferably, it is 0.2-0.5 equivalent. If it is less than 0.2 equivalent to the epoxy equivalent, the crosslink density of the cured product is low, and fracture toughness tends to be low, and if it exceeds 0.8 equivalent, unreacted dicyandiamide tends to remain, resulting in poor mechanical properties. There is a tendency. From another viewpoint, the range of 0.01 to 7 parts by weight is preferable with respect to 100 parts by weight of the curable resin composition.

  The liquid polyamine at 40 ° C. is an amine compound having two or more amino groups in one molecule. Specific examples thereof include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, hexamethylenediamine, iminobispropylamine. , Polyamines such as bis (hexamethylene) triamine, polypropylene glycol diamine, polypropylene glycol triamine, bis (aminomethyl) cyclohexane, 1,3,6-trisaminomethylcyclohexane, 3,9-bis (3-aminopropyl) -2 , 4,8,10-tetraoxaspiro (5.5) undecane, bis (aminomethyl) norbornane, isophoronediamine, methylenebis (cyclohexylamine), etc., cycloaliphatic polyamines, metaxylile Diamine (MXDA), diethylene toluene diamine, bis (4-amino-3-ethylphenyl) polyamines having an aromatic ring such as methane, and derivatives thereof. Of these, triethylenetetramine, bis (aminomethyl) cyclohexane, bis (aminomethyl) norbornane, and isophoronediamine are particularly preferred in terms of fluidity and heat resistance.

  The curable resin composition of the present invention can use a curing accelerator such as a urea compound, an imidazole compound, a phenol compound, a phosphorus compound, or a tertiary amine compound for the purpose of adjusting the curing rate.

  Examples of urea compounds include 3- (3,4-dichlorophenyl) -1,1-dimethylurea, 3- (3,4-dichlorophenyl) -1,1-dimethylurea, 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, 1- (N, N-dimethylurea) -3- (N, N-dimethylureamethyl) -3,5,5-trimethylcyclohexane, N- (3-chloro- 4-methoxyphenyl) -N ′, N′-dimethylurea, N- (4-methyl-3-nitrophenyl) -N ′, N′-dimethylurea, 2,4-bis (N ′, N′-dimethyl) Ureid) Toru And methylene-bis (pN ′, N′-dimethylureidophenyl), among which 3- (3,4-dichlorophenyl) -1,1-dimethylurea, 3- (3,4 -Dichlorophenyl) -1,1-dimethylurea is preferred.

  Examples of imidazole compounds include 2-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, and 2-phenylimidazole. 2-phenyl-4-methylimidazole, 2-phenyl-6-4 ′, 5′-dihydroxymethylimidazole, 1-cyanoethyl-2-ethyl-4methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole 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 adduct, and the like. 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.

  Phenol compounds include catechol, 4-t-butylcatechol, pyrogallol, resorcin, hydroquinone, phlorogludinol, bisphenol A, bisphenol F, dihydroxybiphenyl, dihydroxynaphthalene 1,1,1-tris (4-hydroxyphenyl) ethane And compounds such as bis (4-hydroxyphenyl) sulfone, novolak-type or resol-type phenol resins, and phenolic polymers such as polyvinylphenol. It is. Of these, bisphenol F is preferred. The compounding quantity of the phenol compound as a phenol type hardening accelerator is 0.01-10 mass parts when the whole resin composition is 100 mass parts, Preferably it is 0.1-3.0 mass parts. By containing a curing accelerator within this range, the curing time due to curing acceleration during curing can be shortened, and a cured product having high heat resistance can be obtained.

  An antifoaming agent and a leveling agent can be added to the curable resin composition of the present invention for the purpose of improving the surface smoothness as an additive. These additives can mix | blend 0.01-3 mass parts with respect to 100 mass parts of the whole resin composition, Preferably 0.01-1 mass part can be mix | blended. Note that the calculation of the entire resin composition does not include fillers, fibers, and solvents that are not mixed homogeneously with the resin component.

  Moreover, another curable resin can also be mix | blended with the curable resin composition of this 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 plating organic particles, thermosetting resin particles, or inorganic fillers such as silica gel, nano silica, alumina fiber, and clay, A conductive filler can be blended. The conductivity of the cured resin or fiber reinforced composite material obtained by using conductive particles or conductive filler can be improved.

  Examples of the conductive filler include carbon black, carbon nanotube, fullerene, metal nanoparticles, and the like, and they may be used alone or in combination. Of these, carbon nanotube blending is widely known not only for improving electrical conductivity, but also for improving the impact strength of the fiber reinforced composite material even with a blending amount of less than 1 wt% with respect to the fiber reinforced composite material. Can be preferably used.

The fiber-reinforced composite material of the present invention is obtained by blending reinforcing fibers with the curable resin composition of the present invention.
The curable resin composition of this invention is used suitably for the fiber reinforced composite material obtained by PCM method (Pre-preg Compression Molding).
Here, the production method of the prepreg used in the PCM method is not particularly limited, but the curable resin composition is heated to about 70 to 90 ° C. in advance and the viscosity is lowered to a predetermined thickness on the release paper. By applying, a sheet-like resin composition is created. This application method is not particularly limited, and it is possible to apply using a knife coater, a reverse roll coater, or the like. A prepreg as a fiber-reinforced composite material impregnated with resin by sandwiching reinforcing fibers with the obtained sheet-like curable resin composition and then heating and pressing with a roll or the like (usually 80 to 100 ° C.) Obtainable.

  A method for producing a fiber-reinforced composite material by processing from the curable resin composition of the present invention to a prepreg or a tuprepreg is not particularly limited, but production by an autoclave method or a press molding method is desirably applied.

  The reinforcing fiber used in the prepreg or tuprepreg of the present invention is selected from glass fiber, aramid fiber, carbon fiber, boron fiber, etc., but carbon fiber is used to obtain a fiber-reinforced composite material having excellent strength. Is preferred.

  Next, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples unless it exceeds the gist. The part which shows a compounding quantity is a mass part unless there is particular notice. The unit of epoxy equivalent is g / eq.

(Measurement of hydrolyzable chlorine content)
For the measurement of hydrolyzable chlorine, about 0.2 g of sample was dissolved in 30 mL of dioxane, 25 mL of a methanol solution in which caustic potassium was dissolved so as to be 0.1 mol / L was added, and reacted at 70 ° C. for 40 minutes. 30 mL of acetone, 10 mL of water, and 3 mL of acetic acid were added, and an approximately 0.01 mol / L silver nitrate aqueous solution was titrated to measure the potential difference and calculated using the titration when the inflection point was detected. The calculation formula of the amount of hydrolyzable chlorine (Z) is shown below.
Z (% by weight) = 100 × (X × Y × 35.5) / (1000 × W)
Here, X is the silver nitrate aqueous solution titration (mL) when the inflection point is detected, Y is the concentration (mol / L) of the silver nitrate aqueous solution, and W is the sample collection amount (g).

The abbreviations of the components used in the synthesis examples and examples are as follows.
YD-128: Bisphenol A type epoxy resin (manufactured by Nippon Steel & Sumikin Chemical, epoxy equivalent 187, hydrolyzable chlorine content 0.019% by weight)
YDF-170: Bisphenol F type epoxy resin (manufactured by Nippon Steel & Sumikin Chemical, epoxy equivalent 169, hydrolyzable chlorine content 0.004% by weight)
YDPN-6300: phenol novolac type epoxy resin (manufactured by Nippon Steel & Sumikin Chemical, epoxy equivalent 173, hydrolyzable chlorine amount 0.007% by weight)
DICY: Dicyandiamide IPDA: Isophoronediamine
DCMU: 3- (3,4-dichlorophenyl) -1,1-dimethylurea 2MZA: 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine

Synthesis example 1
A glass separable flask equipped with a stirrer, thermometer, fraction collection condenser tube, and nitrogen gas introduction device was charged with 210 parts of YD-128 and 10 parts of 37% hydrochloric acid, and stirred while introducing nitrogen gas. While heating, the temperature was raised to 80 ° C. Furthermore, the reaction temperature was kept at 80 ° C. for 3 hours. Thereafter, the temperature was raised to 130 ° C. while reducing the pressure, and water was volatilized into the fraction collection tank to obtain 207 parts of an epoxy resin having an epoxy equivalent 201 and a hydrolyzable chlorine content of 1.6% by weight. This epoxy resin is designated as a-1.

Synthesis example 2
In the same apparatus as in Synthesis Example 1, 500 parts of YDF-170 and 10 parts of 37% hydrochloric acid were charged, heated while stirring while introducing nitrogen gas, and heated to 80 ° C. Furthermore, the reaction temperature was kept at 80 ° C. and the reaction was carried out for 2 hours. Thereafter, the temperature was raised to 130 ° C. while reducing the pressure, and the water was volatilized into the fraction collection tank to obtain 501 parts of an epoxy resin having an epoxy equivalent of 177 and a hydrolyzable chlorine content of 0.6 wt%. This epoxy resin is designated as a-2.

Synthesis example 3
In the same apparatus as in Synthesis Example 1, 180 parts of YDPN-6300 and 12 parts of 37% hydrochloric acid were charged, heated while stirring while introducing nitrogen gas, and heated to 100 ° C. Furthermore, the reaction temperature was kept at 100 ° C. for 2 hours. Thereafter, the temperature was raised to 140 ° C. while reducing the pressure, and the water was volatilized into the fraction collection tank to obtain 174 parts of an epoxy resin having an epoxy equivalent of 202 and a hydrolyzable chlorine content of 2.1 wt%. This epoxy resin is designated as a-3.

Example 1
In the same apparatus as in Synthesis Example 1, 100 parts of a-1 and 0.2 part of tris- (2,6-dimethoxyphenyl) phosphine were charged, and the temperature was raised to 150 ° C. while stirring. Next, using a dropping funnel, 18 parts of toluene diisocyanate was dropped over 3 hours to carry out the reaction. Furthermore, the reaction temperature was kept at 150 ° C., and the reaction was performed for 3 hours to obtain 115 parts of an epoxy resin having an oxazolidone structure having an epoxy equivalent of 385, a hydrolyzable chlorine content of 1.4% by weight, and a softening point of 80 ° C. This epoxy resin is designated as A-1.

Example 2
A device similar to Synthesis Example 1 was charged with 100 parts of a-2 and 0.2 part of tetrabutylammonium bromide and heated to 140 ° C. while stirring. Next, 20 parts of toluene diisocyanate was added in portions over 4 hours to carry out the reaction. The reaction temperature was further maintained at 140 ° C. for 3 hours to obtain 116 parts of an epoxy resin having an oxazolidone structure having an epoxy equivalent of 351, a hydrolyzable chlorine content of 0.5% by weight, and a softening point of 91 ° C. This epoxy resin is designated as A-2.

Example 3
A device similar to Synthesis Example 1 was charged with 100 parts of a-3 and 0.2 part of tetrabutylammonium bromide and heated to 140 ° C. while stirring. Next, 15 parts of diphenylmethane diisocyanate was added in portions over 3 hours to carry out the reaction. Furthermore, the reaction temperature was kept at 140 ° C., and the reaction was carried out for 3 hours to obtain 105 parts of an epoxy resin having an oxazolidone structure having an epoxy equivalent of 294, a hydrolyzable chlorine content of 1.8% by weight, and a softening point of 79 ° C. This epoxy resin is designated as A-3.

Comparative Example 1
In the same apparatus as in Synthesis Example 1, 100 parts of YD-128 and 0.2 part of tris- (2,6-dimethoxyphenyl) phosphine were charged and heated to 150 ° C. while stirring. Next, using a dropping funnel, 18 parts of toluene diisocyanate was dropped over 3 hours to carry out the reaction. Furthermore, the reaction temperature was kept at 150 ° C., and the reaction was carried out for 3 hours to obtain 113 parts of an epoxy resin having an oxazolidone structure having an epoxy equivalent of 356, a hydrolyzable chlorine content of 0.05% by weight and a softening point of 86 ° C. This epoxy resin is designated as B-1.

Example 4
(A) 57 parts of A-1 as component, 37 parts of YD-128 as an epoxy resin component other than (A) component, 3.5 parts of DICY as component (B), 2.8 DCMU as a curing accelerator The mixture was placed in a 150 mL plastic container and mixed using a vacuum mixer (Awatori Netaro, manufactured by Shinky Corporation) at room temperature for 5 minutes with stirring to obtain a curable resin composition.

Examples 5-11, Comparative Examples 2-7
A curable resin composition was obtained under the same mixing conditions as in Example 4 except that each raw material was used in the composition described in Tables 1 and 2.

  Using the obtained curable resin composition, test pieces for measuring glass transition temperature, bending test, and adhesive shear strength were prepared.

(Glass transition temperature, preparation of bending test specimens)
Molding plate for measurement by pouring the curable resin composition into a 120 mm long by 120 mm wide mold provided with a 4 mm thick spacer cut into a flat plate shape, and curing at 120 ° C. for 2 hours and then at 150 ° C. for 2 hours (Test specimen 1) was used for measurement of flexural modulus and flexural strength, and measurement of fracture toughness.

(Preparation of adhesive shear strength test piece)
The curable resin composition is applied to the end of a cold rolled steel sheet of 100 mm × 25 mm × thickness 2 mm to 12.5 mm × 25 mm × thickness 0.2 mm, and the same two steel sheets are bonded together at 120 ° C. After 2 hours, it was cured at 150 ° C. for 2 hours to obtain a test plate for measurement (test piece 2), which was used for measuring the adhesive shear strength.

(Processing for glass transition temperature measurement specimens, measurement of glass transition temperature)
The test piece 1 was cut into a size of 2.5 mm × 2.5 mm with a table band saw, and further polished to a thickness of about 0.8 mm using a belt disk sander. Using a differential scanning calorimeter, measurement was performed under a nitrogen atmosphere at a temperature increase rate of 10 ° C./min. The point of intersection with the tangent in the temperature range 20-30 ° C lower was defined as the glass transition temperature Tg.

(Measurement of bending test piece, bending elastic modulus, bending strength, adhesive shear strength)
The test piece 2 was cut into a size of 80 mm × 10 mm with a table-top band saw, and the bending test piece was subjected to a bending test under a temperature condition of 23 ° C. in accordance with JISK7171, thereby calculating the bending elastic modulus and bending strength.
Moreover, the test based on JISK6850 was implemented on the temperature conditions of 23 degreeC, and the adhesive shear strength was computed.

  The composition and test results are shown in Table 1 and Table 2, respectively.

Claims (10)

  An epoxy resin having an oxazolidone structure having an epoxy equivalent of 220 to 480 g / eq, a softening point of 100 ° C. or less, and containing 0.25 to 2.5% by weight of hydrolyzed chlorine. An epoxy resin (a) represented by the following general formula (1) having an epoxy equivalent of 165 to 245 g / eq and containing 0.3 to 3.0% by weight of hydrolyzed chlorine, and toluene diisocyanate or diphenylmethane diisocyanate. The epoxy resin which has an oxazolidone structure of Claim 1 obtained by making it react.

(In the formula, n represents 0 to 5, each R is independently a divalent hydrocarbon residue having 1 to 8 carbon atoms, and G is independently represented by the following formula (2) or the following formula (3 Or a group represented by the following formula (4))

The epoxy resin which has an oxazolidone structure of Claim 1 represented by following General formula (11).

(In the formula, m represents 0 to 5, R ¹ is each independently a divalent hydrocarbon residue having 1 to 8 carbon atoms, Y is independently a single bond, the following formula (12) or It is a divalent group represented by the formula (13) or a combination thereof, and may contain a plurality of divalent groups represented by the formula (12) and the formula (13). (Including the group represented by (12), each G is independently a group represented by the following formula (2), formula (3) or formula (4)).

(In the formula, R ² and R ³ are divalent hydrocarbon residues having 1 to 8 carbon atoms, and A is a divalent hydrocarbon residue having 4 to 16 carbon atoms.)

An epoxy resin (a) represented by the following general formula (1) having an epoxy equivalent of 165 to 245 g / eq and containing 0.3 to 3.0% by weight of hydrolyzed chlorine, and toluene diisocyanate or diphenylmethane diisocyanate. The method for producing an epoxy resin having an oxazolidone structure according to claim 1 or 2, wherein the reaction is performed.

(In the formula, n represents 0 to 5, each R is independently a divalent hydrocarbon residue having 1 to 8 carbon atoms, and G is independently represented by the following formula (2) or the following formula (3 Or a group represented by the following formula (4))

  The epoxy resin composition formed by mix | blending a hardening | curing agent (B) with the epoxy resin in any one of Claims 1-3.   The epoxy resin composition according to claim 5, wherein the curing agent (B) is dicyandiamide or a derivative thereof.   The epoxy resin composition according to claim 5, wherein the curing agent (B) is a polyamine which is liquid at 40 ° C.   A fiber-reinforced composite material comprising a reinforcing fiber blended in the epoxy resin composition according to any one of claims 5 to 7.   The fiber-reinforced composite material according to claim 8, wherein the reinforcing fiber is a carbon fiber, and the fiber-reinforced composite material is a prepreg. The molded object obtained by hardening the fiber reinforced composite material of Claim 8 or 9.