Viscosity modifier for epoxy resin, epoxy resin composition, curable composition, prepreg and fiber-reinforced composite material

Abstract

To improve the strength of a composite material comprising an epoxy resin composition having resistance to a viscosity drop during heating.SOLUTION: A viscosity modifier for epoxy resin comprises a copolymer (A) comprising a monomer (a1) represented by general formula (1) and a monomer (a2) represented by general formula (2) as essential constituent monomers. Based on the total weight of the constituent monomers of the copolymer (A), the content of the monomer (a1) is 10-90 wt.% and the content of the monomer (a2) is 10-90 wt.%. The copolymer (A) preferably has a solubility parameter SPA of 9.8-12.5 (cal / cm3)1 / 2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a viscosity modifier for epoxy resins, an epoxy resin composition, a curable composition, a prepreg, and a fiber-reinforced composite material. [Background technology]

[0002] Typical prepregs are made by impregnating carbon fibers with epoxy resin. Hardening is prevented by storing them at low temperatures, and when manufacturing composite materials (molding), they are typically heated to 100-150°C for hardening. During molding, the resin is heated to a hardening temperature. However, if the viscosity of the epoxy resin drops significantly due to heating, the resin may flow out of the mold, resulting in unimpregnated areas in the cured product and disrupted fiber alignment. In light of these issues, Patent Document 1 proposes a technique for adding swelling particles (crosslinkable polymers) to epoxy resin, and Patent Document 2 proposes a technique for adding a thermoplastic resin that dissolves in epoxy resin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6663626 [Patent Document 2] Japanese Patent Application Publication No. 2019-89951 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the method of adding swelling particles described in Patent Document 1, the swelling particles may disrupt the fiber arrangement, which may result in a decrease in the strength of the composite material. Furthermore, in the method of adding a soluble thermoplastic resin described in Patent Document 2, the viscosity of the thermoplastic resin itself decreases as the temperature increases, so the effect of suppressing viscosity decrease is low and this can sometimes cause a decrease in the strength of the composite material.

[0005] An object of the present invention is to improve the strength of a composite material using an epoxy resin composition that suppresses a decrease in viscosity when heated. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. Specifically, the present invention relates to a viscosity modifier for epoxy resins, which contains a copolymer (A) having, as essential constituent monomers, a monomer (a1) represented by the following general formula (1) and a monomer (a2) represented by the following general formula (2), wherein the content of the monomer (a1) is 10 to 90% by weight and the content of the monomer (a2) is 10 to 90% by weight, based on the total weight of the constituent monomers of the copolymer (A); and an epoxy resin composition containing the viscosity modifier for epoxy resins and an epoxy compound (C) that is solid at 20°C, wherein when the epoxy resin composition contains the copolymer (A) and the epoxy compound (B), the solubility parameter SP of the copolymer (A) is 10 to 90% by weight. A and the solubility parameter SP of the epoxy compound (B). B and the average value SP of the solubility parameters SPc of the epoxy compounds (C) AV and the absolute value (ΔSP1) of the difference between the solubility parameter SP of the copolymer (A) and the solubility parameter SP of the epoxy resin composition is 0.2 to 1.1, and when the epoxy resin composition contains the copolymer (A) but does not contain the epoxy compound (B), the absolute value (ΔSP1) of the difference between the solubility parameter SP of the copolymer (A) and the solubility parameter SP of the epoxy resin composition is 0.2 to 1.1. A and the solubility parameter SPc of the epoxy compound (C), the absolute value of the difference (ΔSP2) between them is 0.2 to 1.1; a curable composition containing the epoxy resin composition and an epoxy resin curing agent and / or a curing accelerator; a prepreg containing the curable composition and at least one fiber selected from the group consisting of carbon fiber, glass fiber, aramid fiber, ceramic fiber, metal fiber, mineral fiber, rock fiber, slag fiber, and cellulose fiber; and a fiber-reinforced composite material containing the curable composition and at least one fiber selected from the group consisting of carbon fiber, glass fiber, aramid fiber, ceramic fiber, metal fiber, mineral fiber, rock fiber, slag fiber, and cellulose fiber.

[0007] [ka]

[0008] In formula (1), R 1 represents a hydrogen atom or a methyl group, and X 1 represents a group represented by -O- or -NH-, and R 2 represents an alkylene group having 2 to 4 carbon atoms, n is an integer of 0 to 20, and when n is 2 or more, R 2 may be the same or different, and R 3 represents a hydrogen atom or an alkyl group having 1 to 36 carbon atoms.

[0009] [ka]

[0010] In formula (2), R 4 represents an alkylene group having 1 to 4 carbon atoms, and R 5 and R 6 each independently represents a hydrogen atom or a methyl group, and X 2 represents a group represented by -O- or -NH-, and R 7 represents an alkylene group having 1 to 4 carbon atoms, and m is an integer of 0 to 3. [Effects of the Invention]

[0011] According to the present invention, it is possible to improve the strength of a composite material using an epoxy resin composition that is inhibited from decreasing in viscosity upon heating. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Viscosity modifier for epoxy resin] The viscosity modifier for epoxy resins of the present invention (hereinafter sometimes referred to as "viscosity modifier") contains a copolymer (A) having, as essential constituent monomers, a monomer (a1) represented by general formula (1) and a monomer (a2) represented by general formula (2). Among the constituent monomers constituting the copolymer (A), the monomer (a1) contained as an essential constituent monomer is a compound represented by the following general formula (1).

[0013] [ka]

[0014] In general formula (1), R 1 represents a hydrogen atom or a methyl group. 1 As X in the general formula (1), a methyl group is preferred. 1 represents a group represented by -O- or -NH-. X 1 is preferably a group represented by -O-.

[0015] R in general formula (1) 2 represents an alkylene group having 2 to 4 carbon atoms. Examples of the alkylene group having 2 to 4 carbon atoms include an ethylene group, a propylene group, a 1-methylethylene group, a 2-methylethylene group, a butylene group, a 1-methylpropylene group, a 2-methylpropylene group, a 3-methylpropylene group, a 1,2-dimethylethylene group, a 1,1'-dimethylethylene group, and a 2,2-dimethylethylene group. R 2 If there are two or more (n is 2 or more), multiple R 2 R may be one or different. 2 As the alkyl group, an ethylene group, a propylene group, a 1-methylethylene group and a 2-methylethylene group are preferred, and an ethylene group is more preferred.

[0016] In the general formula (1), n ​​is an integer of 0 to 20. n is R 2 n is the number of repeating units of O (an alkyleneoxy group having 2 to 4 carbon atoms).

[0017] R in general formula (1) 3 represents a hydrogen atom or an alkyl group having 1 to 36 carbon atoms. The alkyl group having 1 to 36 carbon atoms may be a straight-chain alkyl group or a branched alkyl group. Examples of the alkyl group having 1 to 36 carbon atoms include straight-chain alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, octadecyl, icosyl, tetracosyl, triacontyl, and hexatriacontyl groups, isopropyl, tert-butyl, trimethylheptyl, 2-methylnonyl, isodecyl, 2-ethylnonyl, and isopropyl. and branched alkyl groups such as 1-hexylundecyl, isododecyl, 2-ethyldodecyl, 2-ethyltridecyl, 2-methyltetradecyl, isohexadecyl, 2-octylnonyl, 2-hexylundecyl, 2-ethylpentadecyl, 2-(3-methylhexyl)-7-methyl-nonyl, isooctadecyl, 1-hexyltridecyl, 2-ethylheptadecyl, isoicosyl, 1-octylpentadecyl, 2-decyltetradecyl, and 2-tetradecyloctadecyl groups.

[0018] As the monomer (a1) represented by the general formula (1), from the viewpoint of viscosity adjusting function, R 3 is an alkyl group having 1 to 6 carbon atoms; 3 is an alkyl group having 12 to 36 carbon atoms, and R 3 is a hydrogen atom. In this specification, (meth)acrylic acid means acrylic acid and / or methacrylic acid.

[0019] R in general formula (1) 3is an alkyl group having 1 to 6 carbon atoms [hereinafter also referred to as "monomer (a11)"], examples of which include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, and 2-ethoxyethyl (meth)acrylate. Of these, methyl (meth)acrylate and ethyl (meth)acrylate are preferred, and methyl methacrylate and ethyl methacrylate are more preferred. These monomers may be used alone or in combination of two or more.

[0020] R in general formula (1) 3 is an alkyl group having 12 to 36 carbon atoms [hereinafter also referred to as "monomer (a12)"], examples of the monomer (a12) include dodecyl (meth)acrylate, tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, eicosyl (meth)acrylate, 2-decyltetradecyl (meth)acrylate, and 2-tetradecyloctadecyl (meth)acrylate. Of these, 2-decyltetradecyl (meth)acrylate and 2-tetradecyloctadecyl (meth)acrylate are preferred, and 2-decyltetradecyl methacrylate and 2-tetradecyloctadecyl methacrylate are more preferred. These monomers may be used alone or in combination of two or more.

[0021] R in general formula (1) 3 is a hydrogen atom [hereinafter also referred to as "monomer (a13)"], examples of which include (meth)acrylic acid, 2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate. Of these, 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate are preferred, and 2-hydroxyethyl methacrylate is more preferred. These monomers may be used alone or in combination of two or more.

[0022] Among the constituent monomers constituting the copolymer (A), the monomer (a2) contained as an essential constituent monomer is a compound represented by the following general formula (2).

[0023] [ka]

[0024] In general formula (2), R 4 represents an alkylene group having 1 to 4 carbon atoms. Examples of the alkylene group having 1 to 4 carbon atoms include a methylene group, an ethylene group, a propylene group, a 1-methylethylene group, a 2-methylethylene group, a butylene group, a 1-methylpropylene group, a 2-methylpropylene group, a 3-methylpropylene group, a 1,2-dimethylethylene group, a 1,1'-dimethylethylene group, and a 2,2-dimethylethylene group. R 4 As the alkyl group, a methylene group, an ethylene group, a propylene group, a 1-methylethylene group and a 2-methylethylene group are preferred, and a methylene group is more preferred.

[0025] In general formula (2), R 5 and R 6 R each independently represents a hydrogen atom or a methyl group. 5 is preferably a methyl group, and R 6 is preferably a hydrogen atom. In general formula (2), X 2 represents a group represented by -O- or -NH-. X 2 is preferably a group represented by -O-.

[0026] In general formula (2), R 7 represents an alkylene group having 1 to 4 carbon atoms, and m is an integer of 0 to 3. 7 As the alkylene group having 1 to 4 carbon atoms, R 4 The same groups as those listed above can be mentioned, and the preferred groups are also the same. m is preferably an integer of 0 to 2, and more preferably an integer of 0 to 1.

[0027] Examples of the monomer (a2) represented by general formula (2) include glycidyl (meth)acrylate, 4-hydroxybutyl acrylate glycidyl ether, and 2-methylglycidyl (meth)acrylate. Among these, glycidyl (meth)acrylate is preferred, and glycidyl methacrylate is more preferred.

[0028] The content of monomer (a1) is 10 to 90% by weight, and the content of monomer (a2) is 10 to 90% by weight, based on the total weight of the constituent monomers of copolymer (A). By containing monomer (a1) and monomer (a2) in the above proportions, copolymer (A) obtained by polymerizing constituent monomers containing these monomers as essential constituent monomers can adjust the viscosity by suppressing a decrease in viscosity when an epoxy resin composition containing said copolymer is heated, and can improve the strength of a composite material using said epoxy resin composition.

[0029] The content of the monomer (a1) based on the total weight of the constituent monomers of the copolymer (A) is preferably 15% by weight or more, more preferably 20% by weight or more, and is preferably 70% by weight or less, more preferably 60% by weight or less. The content of the monomer (a2) based on the total weight of the constituent monomers of the copolymer (A) is preferably 30% by weight or more, more preferably 40% by weight or more, and is preferably 85% by weight or less, more preferably 80% by weight or less.

[0030] The constituent monomers constituting the copolymer (A) may contain a monomer (a3) ​​other than the essential constituent monomers [monomer (a1) and monomer (a2)]. Examples of the other monomer (a3) ​​include monomers having a (meth)acryloyl group other than the monomer (a1) and the monomer (a2). Examples of the monomer having a (meth)acryloyl group include (meth)acrylic acid and (meth)acrylamides having an alkyl group having 10 to 24 carbon atoms [e.g., N-decyl(meth)acrylamide, N-dodecyl(meth)acrylamide, N-tridecyl(meth)acrylamide, N-tetradecyl(meth)acrylamide, N-pentadecyl(meth)acrylamide, N-hexadecyl(meth)acrylamide, and N,N-dodecyl(meth)acrylamide].

[0031] The copolymer (A) can be obtained, for example, by polymerizing a monomer component containing the monomers constituting the copolymer (A) [monomer (a1), monomer (a2), and other monomers (a3) ​​used as needed] in a solvent or in an epoxy compound (B) that has a viscosity of 0.01 to 10 Pa s at 30°C and is liquid at 20°C. The copolymer (A) can also be obtained by a method other than the above solution polymerization (for example, bulk polymerization, emulsion polymerization, or suspension polymerization). The polymerization mode of the copolymer (A) may be either random addition polymerization or alternating copolymerization, or may be either graft copolymerization or block copolymerization.

[0032] Among the above polymerization methods, a method in which a monomer component containing a monomer constituting the copolymer (A) is polymerized in a solvent or in the epoxy compound (B) is preferred, and a method in which the monomer component is polymerized in the epoxy compound (B) is more preferred. Polymerizing the monomer component in the epoxy compound (B) can produce a viscosity modifier containing the copolymer (A) and the epoxy compound (B). In the following description, the "monomer component containing a monomer constituting the copolymer (A)" will also be referred to as the "monomer component."

[0033] Examples of the solvent used in the method of polymerizing the monomer components in a solvent include aromatic solvents such as toluene, xylene, or alkylbenzenes having 9 to 10 carbon atoms; aliphatic hydrocarbons (having 6 to 18 carbon atoms) such as n-hexane, n-heptane, cyclohexane, and octane; alcohol solvents (having 3 to 8 carbon atoms) such as 2-propanol, 1-butanol, or 2-butanol; ketone solvents such as methyl ethyl ketone; mineral oils (solvent refined oils, paraffin oils, high viscosity index oils containing isoparaffin, high viscosity index oils obtained by hydrocracking isoparaffin, and naphthenic oils); and synthetic oils (hydrocarbon synthetic lubricating oils (poly-α-olefin synthetic lubricating oils, etc.) and ester synthetic lubricating oils, etc.).

[0034] The epoxy compound (B) used in the method of polymerizing the monomer components in the epoxy compound (B) is preferably an epoxy compound having a viscosity of 0.02 to 8 Pa·s at 30° C., more preferably 0.025 to 7 Pa·s. The viscosity at 30° C. can be measured in accordance with the method specified in JIS-K7233.

[0035] The epoxy compound (B) is an epoxy compound that is liquid at 20°C. In this specification, "liquid at 20°C" means that, at a temperature of 20°C, an object is placed in a container, and the object flows and changes shape within 10 seconds after the container is tilted. "Before tilting the container" refers to a state in which the container is placed on a horizontal table, and "when the container is tilted" refers to a state in which the container placed on a horizontal table is tilted by 10° or more from before tilting.

[0036] Examples of the epoxy compound (B) include glycidyl ethers of compounds having a hydroxyl group per molecule and epichlorohydrin condensates of compounds having a hydroxyl group per molecule. Examples of compounds having a hydroxyl group per molecule include aliphatic alcohols (e.g., ethanol, butanol, etc.), aliphatic alkanediols (e.g., (poly)ethylene glycol, (poly)propylene glycol, etc.), alicyclic alcohols (e.g., cyclohexaneethanol, cyclohexanepropanol, butylcyclohexanol, isopropylcyclohexanol, etc.), alicyclic diols (e.g., 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.), aromatic ring-containing phenols (e.g., nonylphenol, etc.), aromatic ring-containing dihydric phenols (e.g., bisphenol A, bisphenol F, etc.), and polymers obtained by polymerizing alkylene oxides having 2 to 4 carbon atoms (e.g., copolymers of propylene oxide (PO) and ethylene oxide (EO)). These may be used alone or in combination of two or more.

[0037] The epoxy equivalent of the epoxy compound (B) is preferably 100-400, and more preferably 160-300. In the present invention, the epoxy equivalent of the epoxy compounds (epoxy compound (B) and epoxy compound (C)) refers to the mass of the compound containing one equivalent of an epoxy group, and can be measured by the method specified in JIS K 7236. When two or more epoxy compounds are used, the epoxy equivalent of a mixture containing two or more epoxy compounds can be calculated as follows. For example, when W1 g of epoxy compound 1 having an epoxy equivalent of EE1 and W2 g of epoxy compound 2 having an epoxy equivalent of EE2 are used, the epoxy equivalent EEm of the mixture of epoxy compound 1 and epoxy compound 2 can be calculated by the following formula (X). EEm=(W1+W2) / {(W1 / EE1)+(W2 / EE2)} (X)

[0038] The number average molecular weight (Mn) of the epoxy compound (B) can be measured by gel permeation chromatography (GPC). The Mn of the epoxy compound (B) is preferably 300 to 600, and more preferably 310 to 520. The Mn of the epoxy compound (B) can be measured, for example, under the following conditions. (Mn measurement conditions) Model: HLC-8220GPC [Tosoh Corporation, liquid chromatograph] Column: TSK gel SuperH4000 TSK gel SuperH3000 TSK gel SuperH2000 (All manufactured by Tosoh Corporation) Column temperature: 40℃ Detector: RI Solvent: tetrahydrofuran Flow rate: 0.6ml / min Sample concentration: 0.25% by weight Injection volume: 10μl Standard material: Polystyrene [TSK STANDARD manufactured by Tosoh Corporation]

[0039] In the present invention, commercially available products can also be used as the epoxy compound (B). Examples of commercially available products include "Glycier PP-300P" (epoxy equivalent: 295, Mn: 540) manufactured by Sanyo Chemical Industries, Ltd., "jER828" (epoxy equivalent: 189, Mn: 370) manufactured by Mitsubishi Chemical Corporation, and "jER807" (epoxy equivalent: 167, Mn: 315) manufactured by Mitsubishi Chemical Corporation.

[0040] The amount of the epoxy compound (B) used in the method of polymerizing the monomer component in the epoxy compound (B) is preferably 50 parts by weight or more, more preferably 150 parts by weight or more, and preferably 500 parts by weight or less, more preferably 400 parts by weight or less, per 100 parts by weight of the monomer component.

[0041] When polymerizing the monomer components, a polymerization catalyst (E), a chain transfer agent (F), and the like can be used as needed. Examples of the polymerization catalyst (E) include azo catalysts [e.g., 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2-azobisisobutyrate], and peroxide catalysts [e.g., t-butyl peroxypivalate, t-hexyl peroxypivalate, t-butyl peroxyneoheptanoate, t-butyl peroxyneodecanoate, t-butyl peroxy 2-ethylhexanoate, t-butyl peroxyisobutyrate, t-amyl peroxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutyl peroxy 2-ethylhexanoate, dibutyl peroxytrimethyladipate, benzoyl peroxide, cumyl peroxide, and lauryl peroxide]. Among these, azo catalysts are preferred, and at least one of 2,2'-azobis(2-methylbutyronitrile) and 2,2'-azobis(2,4-dimethylvaleronitrile) is more preferred, and it is particularly preferred to use both 2,2'-azobis(2-methylbutyronitrile) and 2,2'-azobis(2,4-dimethylvaleronitrile).

[0042] When a polymerization catalyst (E) is used in polymerizing the monomer components, the amount used is preferably 0.01 part by weight or more, more preferably 0.02 part by weight or more, and preferably 0.5 part by weight or less, more preferably 0.3 part by weight or less, per 100 parts by weight of the monomer components.

[0043] Examples of the chain transfer agent (F) include alkyl mercaptans (having 2 to 20 carbon atoms), etc. As the chain transfer agent (F), mercaptans having 10 to 20 carbon atoms are preferred, and dodecyl mercaptan is more preferred.

[0044] When a chain transfer agent (F) is used during polymerization of the monomer components, the amount used is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, and preferably 5 parts by weight or less, more preferably 3 parts by weight or less, per 100 parts by weight of the monomer components.

[0045] The reaction temperature during polymerization of the monomer components is preferably 50 to 140°C, more preferably 60 to 120°C.

[0046] Solubility parameter SP of copolymer (A) contained in viscosity modifier A is 9.8 to 12.5 (cal / cm3) from the viewpoint of exerting excellent viscosity adjusting ability with a small amount of addition. 3 ) 1 / 2 It is preferable that the viscosity is 9.8 to 10.7 (cal / cm 3 ) 1 / 2 or 10.3 to 12.5 (cal / cm 3 ) 1 / 2 It is more preferable that:

[0047] Solubility parameter SP of copolymer (A) A is 9.8 to 10.7 (cal / cm 3 ) 1 / 2 In this case, the monomer (a1) which is an essential constituent monomer of the copolymer (A) is R 3 is an alkyl group having 1 to 6 carbon atoms, and R 3 and a monomer (a12) which is an alkyl group having 12 to 36 carbon atoms. Solubility parameter SP of copolymer (A) A is 10.3 to 12.5 (cal / cm 3 ) 1 / 2 In this case, the monomer (a1) which is an essential constituent monomer of the copolymer (A) is R 3 It is preferable that the monomer (a13) contains a monomer (a13) in which is a hydrogen atom.

[0048] The SP value (solubility parameter) in this specification (unit: cal / cm 3 ) 1 / 2] is a value calculated by the method described in formula (28) on page 153 of the Fedors method (Polymer Engineering and Science, February 1974, Vol. 14, No. 2, pp. 147-154) using the values ​​(heat of vaporization and molar volume at 25°C of atoms or functional groups) described on page 152 (Table 5). Specifically, Δe i and Δv i It can be calculated by substituting the values ​​of the above into the following formula (Y) using the values ​​corresponding to the types of atoms and atomic groups in the molecular structure. SP value = (ΣΔe i / ΣΔv i ) 1 / 2 (Y) ΣΔe in the above formula (Y) i (unit: cal / mol) is the cohesive energy density (unit: cal / mol), and ΣΔv i is the molecular volume (unit: cm 3 In this specification, the unit of the SP value is (cal / cm 3 ) 1 / 2 Sometimes the symbol is omitted and only the numerical value is given.

[0049] [Table 1]

[0050] The method for calculating the SP value will be described below, taking as an example the method for calculating the SP value of copolymer (A-1) (a copolymer of methyl methacrylate, 2-decyltetradecyl methacrylate, and glycidyl methacrylate) used in Example 1 described later. First, the SP value is calculated by counting the atoms or functional groups of each of the structural units (methyl methacrylate, 2-decyltetradecyl methacrylate, and glycidyl methacrylate) that make up the copolymer (A-1). Let us explain about methyl methacrylate. The repeating unit of the polymer of methyl methacrylate is -CH3(Δe i =1125, Δv i=33.5), two -CH2-(Δe i =1180, Δv i =16.1) and one >C<(C, Δe i =350, Δv i =-19.2) and one -COO-(Δe i =7630, Δv i =52.4). Therefore, ΣΔe i becomes 8080, and ΣΔv i is 81.9, so the SP value (SPa1) of methyl methacrylate is 9.9. When the SP values ​​of other monomers (2-decyltetradecyl methacrylate and glycidyl methacrylate) are calculated in the same manner, the SP value (SPa2) of 2-decyltetradecyl methacrylate is 8.77, and the SP value (SPa3) of glycidyl methacrylate is 10.73. Next, the SP value of copolymer (A-1) is calculated using the SP values ​​of each structural unit calculated by the above method. In this specification, the SP value of copolymer (A-1) can be calculated using the SP value of each structural unit alone in the copolymer and the ratio (weight ratio) of the amounts used. When the weight ratio of the structural units constituting the copolymer (methyl methacrylate: 2-decyltetradecyl methacrylate: glycidyl methacrylate) is m1:m2:m3, the SP value of the copolymer is as follows: SP value of copolymer = (SPa1 × m1 + SPa2 × m2 + SPa3 × m3) / (m1 + m2 + m3)

[0051] The weight average molecular weight (Mw) of the copolymer (A) is preferably 10,000 to 900,000, and more preferably 19,000 to 820,000. The Mw of the copolymer (A) can be adjusted by the polymerization temperature, the monomer concentration, the amount of the catalyst, the amount of the chain transfer agent, etc. The Mw of the copolymer (A) was determined by GPC and converted into polystyrene. In the examples, the Mw was determined by GPC under the following measurement conditions. <Conditions for measuring Mw of copolymer (A)> Device: "HLC-802A" [manufactured by Tosoh Corporation] Column: "TSK gel GMH6" [Tosoh Corporation] 2 pieces Measurement temperature: 40℃ Sample solution: 0.5% by weight tetrahydrofuran solution Solution injection volume: 200μl Detector: Refractive index detector Reference material: 12 standard polystyrenes (TSK standard POLYSTYRENE) (molecular weights: 500, 1,050, 2,800, 5,970, 9,100, 18,100, 37,900, 96,400, 190,000, 355,000, 1,090,000, 2,890,000) [manufactured by Tosoh Corporation]

[0052] As described above, when an epoxy compound (B) is used in polymerizing a monomer component containing a monomer constituting the copolymer (A), a viscosity modifier containing the copolymer (A) and the epoxy compound (B) is obtained. On the other hand, when a solvent is used in polymerizing the monomer component without using the epoxy compound (B), a viscosity modifier containing the copolymer (A) but not the epoxy compound (B) is obtained.

[0053] In an embodiment in which the viscosity modifier contains an epoxy compound (B), the preferred ranges of the epoxy equivalent and Mn of the epoxy compound (B) are as described above.

[0054] In an embodiment in which the viscosity modifier contains an epoxy compound (B), the amount of the epoxy compound (B) is preferably 50 parts by weight or more, more preferably 150 parts by weight or more, and preferably 500 parts by weight or less, more preferably 400 parts by weight or less, per 100 parts by weight of the copolymer (A).

[0055] The content of copolymer (A) in the viscosity modifier is 15% by weight or more, more preferably 18% by weight or more, based on the weight of the viscosity modifier, and is preferably 70% by weight or less, more preferably 65% ​​by weight or less.

[0056] The viscosity modifier may contain other components in addition to the copolymer (A) and the optional components [epoxy compound (B), catalyst (E), and chain transfer agent (F)], such as organic solvents, antioxidants, and ultraviolet absorbers.

[0057] The viscosity modifier of the present invention can be obtained, for example, by polymerizing a monomer component containing a monomer constituting the copolymer (A) in a solvent or in the epoxy compound (B). A preferred method for producing the viscosity modifier is to polymerize the monomer component in the epoxy compound (B). The polymerization conditions for the method for polymerizing the monomer component in the epoxy compound (B) are the same as those described for the polymerization method of the monomer component, and a catalyst (E) and a chain transfer agent (F) are used as needed.

[0058] The viscosity modifier of the present invention is used by adding it to an epoxy resin composition. The mechanism by which the viscosity modifier of the present invention suppresses a decrease in viscosity that may occur when the epoxy resin composition is heated is presumed to be as follows. The copolymer (A) contained in the viscosity modifier of the present invention is insoluble in the epoxy resin composition at room temperature (20 to 30°C) and exists in a dispersed state in the composition, but when heated (for example, to 50°C or higher), it dissolves and the polymer chains extend, which is thought to suppress a decrease in the viscosity of the epoxy resin composition.

[0059] [Epoxy resin composition] The epoxy resin composition of the present invention contains the viscosity modifier for epoxy resins of the present invention and an epoxy compound (C) that is solid at 20°C. In this specification, "solid at 20°C" means that when an object is placed in a container and the container is tilted at a temperature of 20°C, the object does not flow or change shape after 10 seconds. "Before tilting the container" refers to a state in which the container is placed on a horizontal table, and "when the container is tilted" refers to a state in which the container placed on a horizontal table is tilted by 10° or more from before tilting.

[0060] The epoxy compound (C) is a solid epoxy compound at 20°C. Examples of the epoxy compound (C) include epichlorohydrin condensates of bisphenols (such as bisphenol A and bisphenol F), novolaks (such as phenol novolak and cresol novolak), and biphenyls, which have an epoxy equivalent of more than 400. The epoxy compound (C) is preferably an epichlorohydrin condensate of bisphenol A. The epoxy compounds (C) may be used singly or in combination of two or more.

[0061] The epoxy equivalent of the epoxy compound (C) is preferably more than 400 and 950, and more preferably 450-930.

[0062] The number average molecular weight (Mn) of the epoxy compound (C) is preferably 600 to 2000, more preferably 630 to 1800. The Mn of the epoxy compound (C) can be measured by the same method as that of the epoxy compound (B).

[0063] In the present invention, commercially available products may be used as the epoxy compound (C). Examples of commercially available products include bisphenol A epichlorohydrin condensates "jER1001" (epoxy equivalent: 479, Mn: 900), "jER1002" (epoxy equivalent: 650, Mn: 1200), and "jER1004" (epoxy equivalent: 911, Mn: 1650), all manufactured by Mitsubishi Chemical Corporation.

[0064] The amount of the epoxy compound (C) contained in the epoxy resin composition is preferably 5% by weight or more, more preferably 10% by weight or more, and preferably 85% by weight or less, more preferably 80% by weight or less, based on the weight of the epoxy resin composition.

[0065] The amount of viscosity modifier contained in the epoxy resin composition is preferably 10% by weight or more, more preferably 20% by weight or more, and preferably 60% by weight or less, more preferably 50% by weight or less, based on the weight of the epoxy resin composition.

[0066] The content of copolymer (A) in the epoxy resin composition is 2.25% by weight or more, more preferably 3.6% by weight or more, based on the weight of the epoxy resin composition, and is preferably 42% by weight or less, more preferably 32.4% by weight or less.

[0067] The epoxy resin composition may contain, as a component other than the viscosity modifier and the epoxy compound (C), an epoxy compound that has a viscosity of 0.01 to 10 Pa s at 30°C and is liquid at 20°C [referred to as a second liquid epoxy compound (B2)]. In this specification, in order to distinguish between the second liquid epoxy compound (B2) and the epoxy compound (B) that may be contained in the viscosity modifier, the epoxy compound (B) that may be contained in the viscosity modifier may be referred to as the "first liquid epoxy compound (B1)."

[0068] Examples of the second liquid epoxy compound (B2) include compounds similar to the epoxy compound (B) [first liquid epoxy compound (B1)] that may be contained in the viscosity modifier. When the epoxy resin composition contains the second liquid epoxy compound (B2) and the viscosity modifier contains the first liquid epoxy compound (B1), the second liquid epoxy compound (B2) and the first liquid epoxy compound (B1) may be the same compound or different compounds. In addition, in an embodiment in which the epoxy resin composition contains a viscosity modifier that does not contain the first liquid epoxy compound (B1), the epoxy resin composition of this embodiment may contain the second liquid epoxy compound (B2). The second liquid epoxy compound (B2) is preferably a bisphenol A epichlorohydrin condensate. As the second liquid epoxy compound (B2), one compound may be used, or two or more compounds may be used in combination.

[0069] When the epoxy resin composition contains the second liquid epoxy compound (B2), the content thereof is preferably 5% by weight or more, more preferably 10% by weight or more, and preferably 65% ​​by weight or less, more preferably 60% by weight or less, based on the weight of the epoxy resin composition.

[0070] When the epoxy resin composition contains the copolymer (A) and the epoxy compound (B) [at least one of the first liquid epoxy compound (B1) and the second liquid epoxy compound], the solubility parameter SP of the copolymer (A) A and the solubility parameter SP of the epoxy compound (B). B and the average value SP of the solubility parameter SPc of the epoxy compound (C) AV The absolute value of the difference (ΔSP1) between is preferably 0.13 to 1.3, and more preferably 0.2 to 1.1, from the viewpoint of exerting excellent viscosity adjusting ability.

[0071] Solubility parameter SP of epoxy compound (B) B The solubility parameter SPc of the epoxy compound (C) is the solubility parameter SP of the copolymer (A). A The same method as in (the number of atoms or functional groups in the compound was extracted, and the Δe i , Δv i The value of (Y) can be calculated by the above formula (Y).

[0072] Solubility parameter SP of epoxy compound (B) B and the average value SP of the solubility parameter SPc of the epoxy compound (C) AV can be calculated by weighted averaging. For example, if the epoxy resin composition has a solubility parameter of SP B1 M1 part by weight of a first liquid epoxy compound (B1) having a solubility parameter of SP B2 M2 parts by weight of a second liquid epoxy compound (B2) having a solubility parameter of SP C1 When M3 parts by weight of epoxy compound (C) is contained, the average value SP of the solubility parameter SPB of epoxy compound (B) and the solubility parameter SPc of epoxy compound (C) is AV can be calculated using the following formula: SP AV =(SP B1 ×M1+SP B2 ×M2+SP C1 ×M3) / (M1+M2+M3)

[0073] When the epoxy resin composition contains the copolymer (A) but does not contain the epoxy compound (B) [both the first liquid epoxy compound (B1) and the second liquid epoxy compound], the solubility parameter SP of the copolymer (A) A and the solubility parameter SPc of the epoxy compound (C), the absolute value (ΔSP2) of the difference is preferably 0.13 to 1.3, more preferably 0.2 to 1.1, from the viewpoint of exerting excellent viscosity adjusting ability. In this embodiment, when the epoxy resin composition contains two or more epoxy compounds (C), the solubility parameters SPc of the epoxy compounds (C) can be calculated as a weighted average.

[0074] Solubility parameter SP of epoxy compound (B) B is preferably 5 to 15, and more preferably 9 to 13. The solubility parameter SPc of the epoxy compound (C) is preferably 5-15, and more preferably 9-13.

[0075] From the viewpoint of suppressing a decrease in viscosity upon heating, the viscosity of the epoxy resin composition at 30°C is preferably 10 to 10,000 Pa·s, more preferably 50 to 5,000 Pa·s, and even more preferably 70 to 1,600 Pa·s. When the epoxy resin composition contains the viscosity modifier of the present invention and the epoxy compound (C) that is solid at 20°C, the viscosity at 30°C can be adjusted to the above range.

[0076] The epoxy resin composition may contain other components in addition to the viscosity modifier for epoxy resins, the epoxy compound (C), and the second liquid epoxy compound (B2) that is optionally contained, such as an organic solvent, an antioxidant, and an ultraviolet absorber.

[0077] The epoxy resin composition of the present invention can be prepared by uniformly mixing the epoxy resin viscosity modifier, epoxy compound (C), optional second liquid epoxy compound (B2), and other components using a device selected from a stirring defoamer, pot mill, ball mill, bead mill, roll mill, homogenizer, super mill, homodisper, universal mixer, Banbury mixer, kneader, etc. Among these, the method using a stirring defoamer is preferred. The mixing conditions (mixing time, mixing temperature) can be set taking into account the components and their amounts contained in the epoxy resin composition.

[0078] The epoxy resin composition of the present invention, containing the viscosity modifier of the present invention, exhibits the effect of suppressing viscosity reduction due to heating, and therefore can prevent the resin from leaking out from a mold, etc., when curing a curable composition obtained by adding a curing agent to the epoxy resin composition. Thus, the epoxy resin composition of the present invention is useful as a material for curable compositions.

[0079] [Curable composition] The curable composition of the present invention contains the epoxy resin composition of the present invention and an epoxy resin curing agent (G) and / or a curing accelerator (H). Hereinafter, the "epoxy resin curing agent" may be simply referred to as the "curing agent."

[0080] Examples of the epoxy resin curing agent (G) and the curing accelerator (H) include polyamine compounds, amide compounds, acid anhydrides, phenolic hydroxyl group-containing resins, phosphorus compounds, imidazole compounds, imidazoline compounds, urea compounds, organic acid metal salts, Lewis acids, and amine complex salts. Specific examples of these include those described in Japanese Patent No. 6721855. An example is shown below.

[0081] Examples of polyamine compounds include aliphatic amine compounds (e.g., trimethylenediamine, ethylenediamine, etc.), alicyclic and heterocyclic amine compounds (e.g., piperidine, piperazine, menthanediamine, isophoronediamine, methylmorpholine, ethylmorpholine, etc.), aromatic amine compounds (e.g., phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, benzylmethylamine, dimethylbenzylamine, m-xylenediamine, pyridine, etc.), and modified amine compounds (e.g., epoxy compound-added polyamines). Examples of the amide compound include dicyandiamide and polyamidoamine (e.g., those obtained by reacting an aliphatic dicarboxylic acid such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, or azelaic acid, a carboxylic acid compound such as a fatty acid or dimer acid with an aliphatic polyamine or a polyamine having a polyoxyalkylene chain). Examples of acid anhydrides include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride. Examples of the phenolic hydroxyl group-containing resin include phenol novolac resin, cresol novolac resin, aromatic hydrocarbon formaldehyde resin-modified phenol resin, and dicyclopentadiene phenol addition type resin. Examples of the phosphorus compound include alkyl phosphines such as ethylphosphine and butylphosphine, primary phosphines such as phenylphosphine, dialkyl phosphines such as dimethylphosphine and dipropylphosphine, secondary phosphines such as diphenylphosphine and methylethylphosphine, and tertiary phosphines such as trimethylphosphine, triethylphosphine and triphenylphosphine. Examples of the imidazole compound include imidazole, methylimidazole, and ethylimidazole. Examples of the imidazoline compound include 2-methylimidazoline and 2-phenylimidazoline. Examples of the urea compound include aromatic dimethylurea compounds (p-chlorophenyl-N,N-dimethylurea, 3-phenyl-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-N,N-dimethylurea, and N-(3-chloro-4-methylphenyl)-N',N'-dimethylurea).

[0082] Commercially available curing agents (G) and curing accelerators (H) may be used, such as dicyandiamide (manufactured by Mitsubishi Chemical Corporation under the trade name "DICY7") and aromatic dimethylurea (manufactured by San-Apro Co., Ltd. under the trade name "U-CAT 3512T").

[0083] The curing agent (G) is preferably at least one compound selected from the group consisting of aromatic amine compounds, acid anhydrides, imidazole compounds, and dicyandiamide, and more preferably contains dicyandiamide. The curing accelerator (H) preferably contains a urea compound, more preferably aromatic dimethylurea.

[0084] When the curing agent (G) is used in the present invention, the amount used is preferably from 0.5 to 60% by weight, more preferably from 1 to 30% by weight, based on the weight of the curable composition. When a curing agent having a functional group capable of reacting with an epoxy group is used as the curing agent (G), it is preferable to use the curing agent so that the amount of the functional group in the curing agent is in the range of 0.4 to 1.0 mole per mole of epoxy group in the epoxy compound component [epoxy compound (C) and the first liquid epoxy compound (B1) and the second liquid epoxy compound (B2) contained as needed].

[0085] In the present invention, when the curing accelerator (H) is used, the amount used is preferably from 0.1 to 10% by weight, more preferably from 1 to 7% by weight, based on the weight of the curable composition.

[0086] The curable composition of the present invention may contain components other than the epoxy resin composition, the epoxy resin curing agent (G), and the curing accelerator (H). Examples of other components include organic solvents, ultraviolet absorbers, antioxidants, silicon-based additives, fluorine-based additives, flame retardants, plasticizers, silane coupling agents, organic beads, inorganic fine particles, inorganic fillers, rheology control agents, defoamers, anti-fogging agents, and colorants. These components can be added in any amount depending on the desired performance.

[0087] The curable composition of the present invention can be prepared by uniformly mixing the epoxy resin composition, the epoxy resin curing agent (G) and / or the curing accelerator (H), and, if necessary, the other components described above, using an apparatus selected from a stirring defoamer, a pot mill, a ball mill, a bead mill, a roll mill, a homogenizer, a super mill, a homodisper, a universal mixer, a Banbury mixer, a kneader, etc. The mixing conditions (mixing time, mixing temperature) can be set taking into consideration the components contained in the curable composition and their amounts.

[0088] The curable composition of the present invention contains the epoxy resin composition of the present invention, which contains a viscosity modifier that inhibits viscosity reduction due to heating, and a curing agent and / or a curing accelerator. Therefore, when curing the curable composition, it is possible to prevent the resin from leaking out of a mold or the like. Therefore, the curable composition of the present invention is suitable for use in prepregs and fiber-reinforced composite materials. The curable composition of the present invention may also be used by placing the composition itself in a mold or the like and curing it as is. In this case, a cured product can be produced by placing the curable composition in a mold or the like of a desired shape and heating it at 120 to 140°C for 1 to 3 hours to cure it. The temperature conditions and heating time when producing the cured product can be selected taking into account the type and amount of resin contained in the curable composition, the type and amount of curing agent, etc.

[0089] [Prepreg] The prepreg of the present invention contains at least one fiber selected from the group consisting of carbon fiber, glass fiber, aramid fiber, ceramic fiber, metal fiber, mineral fiber, rock fiber, slug fiber, and cellulose fiber, and the curable composition of the present invention.

[0090] The prepreg of the present invention can be produced by impregnating fibers with a curable composition that has been thermally melted (melting temperature: 60 to 150°C) or diluted with a solvent (acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, ethyl acetate, etc.). When a solvent is used, it is preferable to remove the solvent by drying the prepreg.

[0091] The weight ratio of the curable composition to the fibers (curable composition / fibers) is preferably 10 / 90 to 90 / 10, more preferably 20 / 80 to 70 / 30, and particularly preferably 30 / 70 to 60 / 40, from the viewpoint of molded body strength, etc. When a catalyst is contained, the content (wt %) of the catalyst relative to the curable composition is preferably 0.01 to 10, more preferably 0.1 to 5, and particularly preferably 1 to 3, from the viewpoint of molded body strength, etc.

[0092] [Fiber-reinforced composite materials] The fiber-reinforced composite material comprises at least one fiber selected from the group consisting of carbon fiber, glass fiber, aramid fiber, ceramic fiber, metal fiber, mineral fiber, rock fiber, slug fiber, and cellulose fiber, and the curable composition of the present invention.

[0093] The fiber-reinforced composite material of the present invention can be obtained by stacking multiple sheets of the prepreg of the present invention, if necessary, and then heat-molding and curing them. Curing does not need to be complete, but it is preferable that the molded product is cured to an extent that allows the molded product to maintain its shape. After molding, the prepreg may be further heated to achieve complete curing. The heat-molding method is not particularly limited, and examples include a filament winding molding method (a method in which prepreg sheets are wound around a rotating mandrel under tension and then heat-molded), a press molding method (a method in which prepreg sheets are stacked and then heat-molded), an autoclave method (a method in which prepreg sheets are pressed against a mold under pressure and then heat-molded), and a method in which chopped fiber or milled fiber is mixed with a curable composition and then injection-molded.

[0094] According to a fiber-reinforced composite material using the curable composition of the present invention, it is possible to improve the strength of the composite material while using an epoxy resin composition that is inhibited from decreasing in viscosity upon heating, and the mechanism by which this effect is exhibited is presumed to be as follows. As described above, the copolymer (A) contained in the viscosity modifier of the present invention is insoluble in the epoxy resin composition at room temperature (20 to 30°C) and exists in a dispersed state in the epoxy resin composition, but it dissolves when heated (for example, to 50°C or higher), and the polymer chains extend, presumably suppressing viscosity reduction. The polymer chains contain glycidyl groups derived from the monomer of general formula (2), and it is presumed that the glycidyl groups are incorporated into the crosslinked structure of the epoxy resin after the curable composition is cured, thereby improving the strength of the composite material. [Example]

[0095] The present invention will be further explained below with reference to examples and comparative examples, but the present invention is not limited to these.

[0096] [Production Example 1: Production of POEO block copolymer (b1) used in Production Example 3] 200 parts by weight of polypropylene glycol ("Newpol PP-200" [manufactured by Sanyo Chemical Industries, Ltd.]) and 0.9 parts by weight of potassium hydroxide were placed in a pressure-resistant reactor equipped with a stirrer, a heating / cooling device, and a dropping bomb, and the atmosphere was replaced with nitrogen. The temperature was raised to 110°C, and 200 parts by weight of ethylene oxide was added dropwise over 10 hours while adjusting the pressure to 0.5 MPa or less, followed by aging at 120°C for 4 hours. The contents were then cooled to 60°C, and the catalyst residue was neutralized with a 90% by weight aqueous phosphoric acid solution to obtain a PO / EO block copolymer (b1).

[0097] [Production Example 2: Production of Epoxy Compound (B-2)] A reaction vessel equipped with a stirrer, temperature control measures, and a wet grinder (attached to the outside of the reaction vessel) was charged with 400 parts by weight of polyethylene glycol ("PEG-400" [manufactured by Sanyo Chemical Industries, Ltd.]), 278 parts by weight of epichlorohydrin, and 30 parts by weight of cyclohexane. The reaction vessel was conditioned under a nitrogen atmosphere (oxygen concentration: 730 ppm), and 112 parts by weight of granular potassium hydroxide in a nitrogen atmosphere at 19°C was added intermittently over 5 hours at 19 to 29°C. The mixture was then reacted and aged for 5 hours at 25 to 29°C, resulting in glycidyl etherification of the polyethylene glycol. The vessel was then cooled to 16°C, and 370.4 parts by weight of 23°C water was added at 20-28°C. The mixture was stirred for 0.5 hours. After allowing the mixture to stand at 17°C for 0.5 hours, the lower (aqueous) layer was removed. To the remaining upper (organic) layer, 12 parts by weight of Kyoward 600 (Kyowa Chemical Industry Co., Ltd.; alkali adsorbent) was added and the mixture was stirred at 80°C for 0.5 hours. After filtration using Radiolite #700 (Kyowa Chemical Industry Co., Ltd.; diatomaceous earth filter aid), the mixture was heated to 110°C under reduced pressure (-0.1 MPa) and the epichlorohydrin and cyclohexane mixture was distilled off to obtain epoxy compound (B-2). The epoxy equivalent, Mn, and SP values ​​of epoxy compound (B-2) are shown in Table 2.

[0098] [Production Example 3: Production of epoxy compound (B-3)] Epoxy compound (B-3) was obtained by the same procedure as in Production Example 2, except that 400 parts by weight of the PO / EO block copolymer (b1) produced in Production Example 1 was used instead of 400 parts by weight of polyethylene glycol. The epoxy equivalent, Mn, and SP value of epoxy compound (B-3) are shown in Table 2.

[0099] [Example 1: Preparation of viscosity modifier (Y-1)] Into a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, a nitrogen inlet tube, and a pressure reducing device, 152.4 parts of the epoxy compound (B-2) obtained in Production Example 2 was placed, and in another glass beaker, 38 parts by weight of the monomer (a11-1) (methyl methacrylate), 14 parts by weight of the monomer (a12-1) (2-decyltetradecyl methacrylate), and 48 parts by weight of the monomer (a2-1) (glycidyl methacrylate). Parts of monomer components (100 parts by weight in total), 1.6 parts by weight of chain transfer agent (F-1) (dodecyl mercaptan), 0.042 parts by weight of polymerization catalyst (E-1) [2,2-azobis(2,4-dimethylvaleronitrile)], and 0.2 parts by weight of polymerization catalyst (E-2) [2,2-azobis(2-methylbutyronitrile)] were charged, and the mixture was stirred and mixed at 20°C to prepare a monomer solution, which was then charged into the dropping funnel. After replacing the gas phase of the reaction vessel with nitrogen (gas phase oxygen concentration: 100 ppm or less), the monomer solution was added dropwise over 3 hours while maintaining the temperature of the system at 70-85°C under sealed conditions. After aging at 85°C for 2 hours after the completion of the addition, the temperature was raised to 120-130°C and the unreacted monomer was removed at the same temperature under reduced pressure (0.027-0.040 MPa) over 2 hours to obtain viscosity modifier (Y-1) containing 40 wt% of copolymer (A-1). The Mw and SP values ​​of copolymer (A-1) contained in viscosity modifier (Y-1) are shown in Table 2.

[0100] [Production of Viscosity Modifiers of Examples 2 to 16 and Comparative Examples 1 and 2] The same operations as in Example 1 were carried out, except that the type and amount of epoxy compound (B), the type and amount of monomer components [monomer (a11), monomer (a12), monomer (a13) and monomer (a2)], the amount of chain transfer agent (F-1), the amount of polymerization catalyst (E-1) and the amount of polymerization catalyst (E-2) were changed as shown in Table 2, to obtain viscosity modifiers (Y-1) to (Y-8) and (Y-1) to (Y-2) containing copolymers (A-2) to (A-8) or (A-1) to (A-2). The Mw and SP values ​​(SP) of the obtained copolymers (A-2) to (A-8) and (component A-1) to (component A-2) were A ) are shown in Table 2.

[0101] The components used in the examples and comparative examples are as follows. Monomer (a1) (a11-1): Methyl methacrylate (SP value: 9.9) (a11-2): Butyl methacrylate (SP value: 9.45) (a12-1): 2-decyltetradecyl methacrylate (SP value: 8.77) (a12-2): 2-tetradecyl octadecane methacrylate (SP value: 8.71) (a13-1): 2-hydroxyethyl methacrylate (SP value: 13.47) Monomer (a2) (a2-1): Glycidyl methacrylate (SP value: 10.73) Epoxy compound (B) (B-1): Glycidylated polypropylene glycol ["Glycier PP-300P" manufactured by Sanyo Chemical Industries, Ltd., epoxy equivalent 295, Mn 540] (B-2): Epoxy compound obtained in Production Example 2 (epoxy equivalent: 280, Mn: 510) (B-3): Epoxy compound obtained in Production Example 3 (epoxy equivalent: 285, Mn: 515) (B-4): Bisphenol A epichlorohydrin condensate ["jER828" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 189, Mn: 370] (B-5): Bisphenol F epichlorohydrin condensate ["jER807" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 167, Mn: 315] Epoxy Compound (C) (C-1): Bisphenol A epichlorohydrin condensate ["jER1001" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 479, Mn: 900] (C-2): Bisphenol A epichlorohydrin condensate ["jER1002" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 650, Mn: 1200] (C-3): Bisphenol A epichlorohydrin condensate ["jER1004" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 911, Mn: 1650] Polymerization catalyst (E) (E-1): 2,2-azobis(2,4-dimethylvaleronitrile) (E-2): 2,2-azobis(2-methylbutyronitrile) Chain transfer agent (F) (F-1): Dodecyl mercaptan Hardener (G) (G-1): Dicyandiamide Curing accelerator (H) (H-1): Aromatic dimethylurea [U-CAT 3512T, manufactured by San-Apro Co., Ltd.] In the "Epoxy equivalent" column of "Physical properties of epoxy compound (B)" in Table 2, when one type of compound is used, the epoxy equivalent of the compound is recorded, and when two or more types of compounds are used, the epoxy equivalent of the mixture of two or more types of compounds (calculated using the method described above) is recorded.

[0102] [Table 2]

[0103] [Preparation of Epoxy Resin Compositions of Examples 9 to 18 and Comparative Examples 3 to 5] The types of viscosity modifiers [(Y-1) to (Y-8), ratios (Y-1) to (Ratio Y-2)], second liquid epoxy compound (B2) [(epoxy resin (B-4)], and the types of epoxy compounds (C) [(C-1) to (C-3)] listed in Table 3 were mixed in the amounts listed in Table 3 to obtain epoxy resin compositions (Z-1) to (Z-10) and (Ratio Z-1) to (Ratio Z-3) of Examples 9 to 18 and Comparative Examples 3 to 5. Mixing was carried out using a stirring defoamer (THINKY, ARV-930TWIN) at 1400 rpm and 100°C for 3 minutes. The average SP values ​​(SP AV ), ΔSP1 or ΔSP2, viscosity at 30°C and viscosity index (see below for measurement method) are shown in Table 3.

[0104] (Viscosity measurement method at 30°C) The viscosity of the epoxy resin composition at 30°C was measured in accordance with the method specified in JIS-K7233. (Method for measuring viscosity index) The viscosity index of the epoxy resin composition was measured at 120°C and 50°C using the same method as for the viscosity at 30°C, and expressed as the logarithmic value of the viscosity at 120°C divided by the logarithmic value of the viscosity at 50°C. The larger the viscosity index, the greater the effect of suppressing viscosity reduction during heating. The viscosity index is preferably 0.55 or higher.

[0105] [Table 3]

[0106] [Preparation and Evaluation Tests of Curable Compositions of Examples 19 to 28 and Comparative Examples 6 to 8] (Preparation of Curable Composition) The types of epoxy resin compositions (Z-1) to (Z-10), (comparison Z-1) to (comparison Z-3) shown in Table 4, the curing agent (G-1), and the curing accelerator (H-1) were mixed in the amounts shown in Table 4 to obtain curable compositions of each example. Mixing was carried out using a stirring defoamer (THINKY Corporation, ARV-930TWIN) at 1400 rpm and 100°C for 3 minutes.

[0107] (Preparation and evaluation of cured products) The curable compositions of Examples 19 to 26 and Comparative Examples 6 to 8 were placed in a mold for preparing test specimens of the size specified in JIS K7111-1 (ISO179-1) and heated at 130°C for 1 hour to obtain a sheet-like cured product measuring 4 mm in thickness, 80 mm in length, and 10 mm in width. These cured products were used as test specimens. The flexural strength and impact resistance of these test specimens were evaluated using the methods described below. The results are shown in the "Physical properties of the cured product" column in Table 4.

[0108] (Evaluation test of the cured product) (1) Bending strength The bending strength (unit: N / mm) of the cured sheet was measured in accordance with the method specified in JIS K7074. 2 The larger the value, the better the bending strength. The bending strength was 130N / mm 2 It is preferable that this is equal to or greater than this. (2) Charpy impact strength The Charpy impact value (unit: J / m) was measured according to the method specified in JIS K-7111-1. The larger the value, the better the impact resistance. The Charpy impact strength is preferably 13 J / m or more.

[0109] (Fabrication and evaluation of fiber-reinforced composite materials) Carbon fiber bundles (fineness 800 tex, number of filaments 12,000) were aligned in one direction and placed in a mold. The curable compositions of Examples 19 to 26 and Comparative Examples 6 to 8 were added to the bundle, adjusting the amount of the carbon fiber bundle so that the fiber volume content was 55%. The curable compositions were then vacuum-impregnated into the carbon fiber bundles. After impregnation, the bundles were heated and cured at 130°C for 1 hour to obtain a cured product (fiber-reinforced composite material). The resulting cured product was cut using a diamond cutter into test specimens measuring 2 mm thick, 100 mm long, and 15 mm wide. The bending strength of the test specimens was evaluated according to the method specified in JIS K7074. The results are shown in the "Physical properties of CFRP" column in Table 4. The higher the bending strength value, the better the bending strength. The bending strength of fiber reinforced composite material is 1400N / mm 2 It is preferable that this is equal to or greater than this.

[0110] [Table 4]

[0111] As shown in Tables 2 to 4, the epoxy resin compositions containing the viscosity modifiers of the Examples were found to be highly effective in suppressing viscosity reduction during heating, and composite materials using epoxy resin compositions containing such viscosity modifiers with a high viscosity reduction suppression effect were found to have improved strength. This shows that the present invention can improve the strength of a composite material using an epoxy resin composition that is inhibited from decreasing in viscosity upon heating.

Claims

1. A viscosity modifier for epoxy resins, which is used for a prepreg containing a copolymer (A) consisting only of a monomer (a1) represented by the following general formula (1) and a monomer (a2) represented by the following general formula (2), wherein the content of the monomer (a1) is 10 to 90% by weight and the content of the monomer (a2) is 10 to 90% by weight, based on the total weight of the constituent monomers of the copolymer (A). 【Chemistry 1】 [In formula (1), R １ represents a hydrogen atom or a methyl group, and X １ represents a group represented by —O— or —NH—, R ２ represents an alkylene group having 2 to 4 carbon atoms, n is an integer of 0 to 20, and when n is 2 or more, R ２ may be the same or different, R ３ represents a hydrogen atom or an alkyl group having 1 to 36 carbon atoms.] 【Chemistry 2】 [In formula (2), R ４ represents an alkylene group having 1 to 4 carbon atoms, and R ５ and R ６ each independently represents a hydrogen atom or a methyl group; X ２ represents a group represented by —O— or —NH—, R ７ represents an alkylene group having 1 to 4 carbon atoms, and m is an integer of 0 to 3.

2. Solubility parameter SP of the copolymer (A) Ａ is 9.8 to 12.5 (cal / cm ３ ) １／２ 2. The viscosity modifier for epoxy resin used in the prepreg according to claim 1, wherein

3. Solubility parameter SP of the copolymer (A) Ａ is 9.8 to 10.7 (cal / cm ３ ) １／２ and the monomer (a1) is R ３ is an alkyl group having 1 to 6 carbon atoms, and R ３ and a monomer (a12) which is an alkyl group having 12 to 36 carbon atoms.

4. Solubility parameter SP of the copolymer (A) Ａ is 10.3 to 12.5 (cal / cm ３ ) １／２ and the monomer (a1) is R ３ The viscosity modifier for epoxy resins used in the prepreg according to claim 1 or 2, comprising a monomer (a13) in which

5. 3. The viscosity modifier for epoxy resins used in a prepreg according to claim 1, wherein the copolymer (A) has a weight average molecular weight of 10,000 to 900,000.

6. The viscosity modifier for epoxy resins used in the prepreg according to claim 1, further comprising an epoxy compound (B) that has a viscosity of 0.01 to 10 Pa·s at 30°C and is liquid at 20°C.

7. 7. The viscosity modifier for epoxy resins used in prepregs according to claim 6, wherein the epoxy compound (B) has an epoxy equivalent of 100 to 400.

8. 7. The viscosity modifier for epoxy resins used in prepregs according to claim 6, wherein the epoxy compound (B) has a number average molecular weight of 300 to 600.

9. An epoxy resin composition comprising the viscosity modifier for epoxy resins according to claim 1 and an epoxy compound (C) that is solid at 20°C, wherein the solubility parameter SP of the copolymer (A) is Ａ and the solubility parameter SP of the epoxy compound (C). Ｃ The epoxy resin composition used for the prepreg has an absolute value of the difference (ΔSP2) of 0.2 to 1.

1.

10. An epoxy resin composition comprising the viscosity modifier for epoxy resins according to claim 6 and an epoxy compound (C) that is solid at 20°C, Solubility parameter SP of the copolymer (A) Ａ and the solubility parameter SP of the epoxy compound (B). Ｂ and the solubility parameter SP of the epoxy compound (C) Ｃ Average value SP ＡＶ The epoxy resin composition used for the prepreg has an absolute value of the difference (ΔSP1) of 0.2 to 1.

1.

11. A curable composition for use in a prepreg, comprising the epoxy resin composition according to claim 9 or 10 and an epoxy resin curing agent and / or a curing accelerator.

12. The curable composition used in the prepreg according to claim 11, wherein the epoxy resin curing agent comprises dicyandiamide.

13. A prepreg comprising at least one fiber selected from the group consisting of carbon fiber, glass fiber, aramid fiber, ceramic fiber, metal fiber, mineral fiber, rock fiber, slag fiber, and cellulose fiber, and the curable composition according to claim 11.

14. A fiber-reinforced composite material comprising at least one fiber selected from the group consisting of carbon fiber, glass fiber, aramid fiber, ceramic fiber, metal fiber, mineral fiber, rock fiber, slag fiber, and cellulose fiber, and the curable composition according to claim 11.

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