JPH0567646B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is an unsaturated ester-based heat-resistant resin containing a maleimide compound that has excellent moldability such as curability and workability, and provides a cured product with excellent stability and mechanical strength at high temperatures. The present invention relates to a method for stabilizing storage of a composition. (Prior Art) As resins with excellent stability under high temperatures, there are various heat-resistant resins represented by polyimide resins, polyamide-imide resins, and the like. but,
These heat-resistant resins have high melting points, so they require high temperatures or high pressures when molding, or require long periods of time under high temperatures and pressures for curing, or they require special high-boiling point solvents. Since it is necessary to dissolve the solvent before use, the process of removing the solvent by pressurizing or reducing pressure at high temperatures for a long time is required, resulting in major problems in moldability. Therefore, it is extremely difficult to manufacture large-sized molded products using these heat-resistant resins or to continuously manufacture molded products using pultrusion molding, extrusion molding, or the like. On the other hand, as resins with excellent moldability such as curability and workability, polyphenol type epoxy resins such as bisphenol type epoxy resins and novolac type epoxy resins, epoxy (meth)acrylates derived from (meth)acrylic acid, or Radical polymerizable resins such as unsaturated polyester are known, and these resins are usually blended with a radical polymerizable crosslinking agent such as styrene and are widely used as vinyl ester resins or unsaturated polyester resins. However, these resins do not necessarily reach a satisfactory level of thermal stability at high temperatures, which is a major obstacle in the development of new applications, and the emergence of resins with better thermal stability is a major hurdle. desired. (Problems to be Solved by the Invention) The present inventors have developed a cured product that is highly stable at high temperatures without impairing the excellent curability of radical polymerizable resins, moldability such as workability, and mechanical strength. As a result of various researches in order to develop a resin that gives a polybasic acid, an unsaturated resin obtained by reacting an epoxy compound having two or more epoxy groups in one molecule with an unsaturated monobasic acid and, if necessary, a polybasic acid. General formula for ester A and/or compounds having two or more phenolic hydroxyl groups in one molecule

[Chemical formula] (However, R ¹ and R ² are hydrogen or methyl groups independently.) A compound obtained by reacting a compound having an epoxy group and a radically polymerizable unsaturated bond in one molecule Saturated ester B, 1
It has been found that a resin composition containing a compound C having one or more maleimide groups in the molecule and optionally a polymerizable crosslinking agent D satisfies the above object. However, when the resin composition is blended and used within a relatively short period of time, it exhibits the above-mentioned excellent performance without any problems, but when the resin composition is stored for a long period of time, However, there was a problem in that the viscosity significantly increased or gelation occurred at room temperature even without the addition of a polymerization initiator, making it difficult to use. However, the present inventors have conducted various studies aimed at stabilizing the storage of the resin composition, and as a result, have arrived at the present invention. (Means and effects for solving the problems) The present invention is obtained by reacting an epoxy compound having two or more epoxy groups in one molecule with an unsaturated monobasic acid and, if necessary, a polybasic acid. General formula for unsaturated esters A and/or compounds having two or more phenolic hydroxyl groups in one molecule

[Chemical formula] (However, R ¹ and R ² are hydrogen or methyl groups independently.) A compound obtained by reacting a compound having an epoxy group and a radically polymerizable unsaturated bond in one molecule Saturated ester B, 1
A resin composition containing a compound C having one or more maleimide groups in the molecule and, if necessary, a polymerizable crosslinking agent D, has the general formula

[Chemical formula] (However, n is an integer of 1 to 8.) The resin composition is characterized in that a thiuram compound E and a copper-containing compound F having at least one atomic group in one molecule are added. This invention relates to a method for stabilizing the storage of products. The resin composition to be subjected to the storage stabilization method of the present invention (hereinafter simply referred to as heat-resistant resin composition) is:
It contains the aforementioned unsaturated ester A and/or unsaturated ester B, compound C, and if necessary, a polymerizable crosslinking agent D. The epoxy compound having two or more epoxy groups in one molecule (hereinafter simply referred to as a polyfunctional epoxy compound) used to obtain the unsaturated ester A in the present invention includes, for example, the general formula

[Chemical formula] (However, A is an alkylene group containing 1 to 4 carbon atoms, SO ₂ , S or O, R ³ is hydrogen or a methyl group, X is hydrogen or a halogen, and l is O or an integer in the range of 1 to 15.) Bisphenol type epoxy resin represented by the general formula

embedded image (However, R ⁴ , R ⁵ , and R ⁶ are hydrogen or alkyl groups, and they may be the same or different, and m is an integer in the range of 1 to 15. ); glycidylamine type epoxy resins such as triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, N-tetraglycidyl-diaminodiphenylmethane, polyglycidyl metaxylylene diamine; Examples include isocyanuric acid type epoxy resins such as glycidyl isocyanurate; tetrahydroxyphenylethane type epoxy resins; hydantoin type epoxy resins; alicyclic epoxy resins, and these can be used alone or in a mixture of two or more types. Commercially available products include, for example, Ciba Geigy's Araldite GY250, Araldite GY260, Araldite 6071, Araldite 8011, EPN1138,
EPN1139, ECN1235, ECN1273, ECN1280,
ECN1299, Araldite MY720; Epicote 828, Epicote 1001, Epicote 1004 manufactured by Ciel Chemical Co.; DER330, DE manufactured by Dow Chemical Company
R.331, DER662, DER542, DEN431, D.
EN438; Epotote YD-127 manufactured by Toto Kasei Co., Ltd.
Epotote YD-011, Epotote YDB-400, Epotote YDB-500, Epotote YDF-170, Epotote YDF-2001, YDCN-701, YDCN-
702, YDCN−703, YDCN−704, YDPN−638,
YDPN−601, YDPN−602, YDM−120, YH
-434, ST-110, etc. Furthermore, for example, glycidyl ether of a condensate of an unsaturated aldehyde and a phenol, an adduct of a polyvalent phenol compound and an epoxy compound containing an average of two or more epoxy groups in one molecule, a polyvalent phenol and a monovalent Although there are glycidyl etherified products of phenol co-condensates, the polyfunctional epoxy compounds used in the present invention are not limited to these epoxy compounds, and include compounds containing an average of two epoxy groups in one molecule. Any epoxy compound containing the above may be used, and these can be used alone or in combination of two or more. Examples of unsaturated monobasic acids to be reacted with polyfunctional epoxy compounds include unsaturated dibasic acids such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, oleic acid, linoleic acid, linolenic acid, maleic acid, and fumaric acid. There are half-esterified products of
Of course, these can be used alone or in combination of two or more. In addition, examples of polybasic acids used as necessary in the present invention include unsaturated acids such as maleic acid, fumaric acid, itaconic acid, and citraconic acid;
Saturated acids such as phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, trimellitic acid, and pyromellitic acid, as well as polybutadiene containing carboxyl groups at both ends and butadiene-acrylonitrile copolymer containing carboxyl groups at both ends, etc. Alternatively, any of two or more types can be used. When reacting a polyfunctional epoxy compound with an unsaturated monobasic acid and, if necessary, a polybasic acid to obtain unsaturated ester A, the amount of unsaturated monobasic acid per mole of epoxy group contained in the polyfunctional epoxy compound is The total carboxyl groups contained in the basic acid and the polybasic acid used as necessary are 0.7 to 1.3 mol, preferably
Use in a proportion of 0.8 to 1.2 moles. In addition, when using a polybasic acid in combination with an unsaturated monobasic acid, it is best to keep the number of moles of the polybasic acid equal to or less than the number of moles of the unsaturated monobasic acid to develop excellent mechanical strength. preferred above. The above esterification reaction is carried out in an inert solvent or without a solvent, heated to 60 to 150°C, preferably 70 to 130°C, and preferably in the presence of air. In order to prevent gelation due to polymerization during the reaction, it is preferable to use known and commonly used polymerization inhibitors such as hydroquinones such as methylhydroquinone and hydroquinone; benzoquinones such as p-benzoquinone and p-torquinone. Further, in order to shorten the reaction time, it is preferable to use an esterification catalyst, and examples of the esterification catalyst include tertiary amines such as N,N-dimethylaniline, pyridine, triethylamine, hexamethylene diamine, and their base salts; Bromates; quaternary ammonium salts such as tetramethylammonium chloride and triethylbenzylammonium chloride; sulfonic acids such as para-toluenesulfonic acid; sulfoxides such as dimethylsulfoxide and methylsulfoxide; sulfonium salts such as trimethylsulfonium chloride and dimethylsulfonium chloride ; Phosphines such as triphenylphosphine and tri-n-butylphosphine; and metal halides such as lithium chloride, lithium bromide, stannous chloride, and zinc chloride. Known and commonly used phosphines can be used. Toluene, xylene, etc. can be used as the inert solvent, but since the solvent needs to be removed after the reaction, these should not be used, especially when a polymerizable crosslinking agent that is liquid at room temperature is used in the final composition. Advantageously, a polymerizable crosslinking agent of 100% is used as the solvent. Examples of the compound having two or more phenolic hydroxyl groups in one molecule (hereinafter simply referred to as a polyfunctional phenol compound) used to obtain the unsaturated ester B in the present invention include diphenolmethane (bisphenol F ), diphenol ethane, diphenol propane (bisphenol A), diphenolsulfone (bisphenol S), 4,4'-thiobisphenol, 4,4'-sulfinylbisphenol, 2,3'-oxy Bisphenol, bisphenol tetrachloride A, bisphenol tetrabromide A, 1,1-bis-(4-hydroxyphenyl)-1-phenylethane, 1,1-bis-(4-hydroxyphenyl)-1, 1-dimethylmethane, phenol novolak, brominated phenol novolak, cresol novolak, brominated cresol novolak, resorcinol novolak,
Brominated resorcinol novolak, hydroquinone,
Examples include (iso)cyanuric acid and methylresorcinol. Furthermore, there are also condensates of unsaturated aldehydes and phenols, adducts of polyvalent phenol compounds and epoxy compounds, co-condensates of polyvalent phenol compounds and monovalent phenol compounds, etc., and the polyfunctional phenols used in the present invention The compound is not limited to these, but may be any compound having two or more weakly acidic so-called phenolic hydroxyl groups in one molecule, and these can be used alone or in a mixture of two or more. The compound having an epoxy group and a radically polymerizable unsaturated bond in one molecule (hereinafter simply referred to as an unsaturated glycidyl ester compound) to be reacted with a polyfunctional phenol compound is represented by the above general formula, for example: Examples include glycidyl methacrylate, glycidyl acrylate, 2-methylglycidyl methacrylate, and 2-methylglycidyl acrylate, and these can be used alone or in combination of two or more types. To obtain unsaturated ester B by reacting a polyfunctional phenol compound and an unsaturated glycidyl ester compound, a conventionally known ring-opening addition reaction may be followed.
For example, 0.5 to 1.5 equivalents, preferably 0.8 equivalents of unsaturated glycidyl ester compound per equivalent of phenolic hydroxyl group contained in the polyfunctional phenol compound.
The reaction mixture is mixed in an amount of ~1.2 equivalents and heated to 30 to 150°C, preferably 50 to 130°C, in an inert solvent or without a solvent, preferably in the presence of air.
In order to prevent gelation due to polymerization during the reaction, it is preferable to use known and commonly used polymerization inhibitors such as hydroquinones such as methylhydroquinone and hydroquinone; benzoquinones such as p-benzoquinone and p-torquinone. In addition, in order to shorten the reaction time, a ring-opening addition reaction catalyst can be used. Examples of ring-opening addition reaction catalysts include tertiary amines such as triethylamine and triethylenediamine, amines such as dimethylaminoethanol, and N-methylmorpholine. quaternary ammonium salts such as triethylbenzylammonium chloride and trimethyldodecylammonium chloride; 2-ethylimidazole, 2-
Imidazoles such as methyl-4-ethylimidazole; organic tertiary phosphines such as triphenylphosphine and tributylphosphine; tetraphenylboron salts such as triphenylphosphine tetraphenylborate and triethylamine tetraphenylborate; zinc chloride Known and commonly used metal halides such as tin chloride and the like can be used. As the inert solvent, for example, toluene, xylene, dimethylformamide, etc. can be used, but since the solvent needs to be removed after the reaction,
Particularly when a polymerizable crosslinking agent that is liquid at room temperature is used in the final composition, it is advantageous to use these polymerizable crosslinking agents as a solvent. Examples of the compound C having one or more maleimide groups in one molecule (hereinafter simply referred to as maleimide compound C) used in the present invention include N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide, N- -butylmaleimide,
N-cyclohexylmaleimide, N-phenylmaleimide, N-o-methylphenylmaleimide,
N-m-methylphenylmaleimide, N-p-methylphenylmaleimide, N-o-hydroxyphenylmaleimide, N-m-hydroxyphenylmaleimide, N-p-hydroxyphenylmaleimide, N-o-methoxy Phenylmaleimide, N
-m-methoxyphenylmaleimide, N-p-methoxyphenylmaleimide, N-o-carboxyphenylmaleimide, N-p-carboxyphenylmaleimide, N-o-chlorophenylmaleimide, N-m-chlorophenylmaleimide , N-p
- Monomaleimide compounds such as chlorophenylmaleimide; N,N'-ethylene dimaleimide, N,
N'-hexamethylene dimaleimide, N,N'-dodecamethylene dimaleimide, N,N'-m-phenylene dimaleimide, N,N'-p-phenylene dimaleimide, N,N'-(oxy- di-p-phenylene) dimaleimide, N,N'-(methylene-di-p-phenylene) dimaleimide, N,N'-2,
4-Tolylene dimaleimide, N,N'-2,6-
Tolylene dimaleimide, N,N'-m-xylylene dimaleimide, N,N'-p-xylylene dimaleimide, N,N'-oxydipropylene dimaleimide, ethylenedioxy-bis-N-propylmaleimide, oxy- Examples include polymaleimide compounds such as bis-N-ethylmaleimide, which can be used alone or in a mixture of two or more. Among these, monomaleimide compounds not only have good compatibility with unsaturated ester A and unsaturated ester B, but also have good compatibility with unsaturated ester A and unsaturated ester B and a polymerizable crosslinking agent D. It is also particularly preferred in terms of compatibility with. Polymerizable crosslinking agent D used as necessary in the present invention
Examples include styrene derivatives such as styrene, α-methylstyrene, p-methylstyrene, t-butylstyrene, vinyltoluene, and divinylbenzene;
(meth)acrylic acid ester monomers such as methyl methacrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, tricyclodecenyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate;
Trimethylolpropane tri(meth)acrylate, diethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, tris(2-hydroxyethyl)isocyanuric acid(meth)acrylate, 2,2-bis[ 4-(2-hydroxyethoxy)phenyl]
(meth)acrylates of polyhydric alcohols such as di(meth)acrylate of propane; general unsaturated polyester resins and vinyl compounds such as allyl compounds such as diallyl phthalate, diallyl isophthalate, diallyl terephthalate, triallyl isocyanurate, and triallyl cyanurate; Known and commonly used ester resins can be used alone or as a mixture of two or more. Unsaturated ester A and/or unsaturated ester B, maleimide compound C and polymerizable crosslinking agent D
There is no particular restriction on the blending ratio of unsaturated ester A and/or from the viewpoint of mechanical properties and heat resistance.
or unsaturated ester B30-90% by weight, maleimide compound C3-40% by weight, polymerizable crosslinking agent D0-67% by weight (however, the total of A, B, C and D components is
It is 100% by weight. ) is desirable. The thiuram compound E used in the present invention has the general formula

[Formula] (However, n is an integer of 1 to 8.) A compound having at least one atomic group in one molecule, such as tetramethylthiuram monosulfide, tetraethylthiuram monosulfide , tetrabutylthiuram monosulfide,
Bis(diethyleneoxyl)thiuram monosulfide, dipentamethylenethiuram monosulfide, bis(trimethylthiuram monosulfide)
Ethylene, tetramethylthiuram disulfide,
Tetraethylthiuram disulfide, tetrabutylthiuram disulfide, diphenyldimethylthiuram disulfide, diphenyldiethylthiuram disulfide, bis(diethyleneoxyl)thiuram disulfide, dipentamethylenethiuram disulfide, tetramethylthiuram disulfide Examples include, but are not limited to, tetrasulfide, dipentamethylenethiuram tetrasulfide, tetramethylthiuram trisulfide, tetramethylthiuram hexasulfide, bis(trimethylthiuram disulfide) ethylene, etc. They can be used alone or as a mixture of two or more. In addition, examples of the copper-containing compound F used together with the thiuram compound E in the present invention include copper acetate, copper citrate, copper oxalate, copper formate, copper naphthenate, copper oleate, copper acrylate, copper methacrylate, (2 -organic acid salts such as copper (hydroxyethyl) dithiocarbamate and copper dimethyldithiocarbamate; chelates such as copper acetylacetonate; complexes of cuprous chloride and triethyl phosphite;
Complex compounds such as complexes of cupric chloride and dicyclohexyl sulfoxide; cuprous chloride, cupric chloride, cuprous bromide, cupric bromide, cuprous oxide, cupric hydroxide, carbonic acid Examples include, but are not limited to, inorganic salts such as copper, copper nitrate, copper sulfate, copper phosphite, cupric phosphate, etc., used alone or in a mixture of two or more types. be able to. For storage stabilization of a heat-resistant resin composition, thiuram compound E or copper-containing compound F alone has no effect at all, or even if it has, it has only a slight effect, and thiuram compound E and copper-containing compound F
It is only when they coexist that significant effects can be produced. The amount of thiuram compound E and copper-containing compound F used is such that thiuram compound E is in a range of 0.0001 to 2.0 parts by weight, preferably 0.001 to 0.5 parts by weight, based on 100 parts by weight of the heat-resistant resin composition. And the copper-containing compound F is 0.00001 to 0.1 in terms of metallic copper.
Parts by weight, preferably in the range from 0.0001 to 0.05 parts by weight. The amount of thiuram compound E used is
If the copper-containing compound F is used in a small amount of less than 0.0001 parts by weight, the effect will be small even if an appropriate amount is used, and even if it is used in a large amount exceeding 2.0 parts by weight, no commensurate effect will be obtained. On the other hand, if the amount of copper-containing compound F used is small, less than 0.00001 part by weight in terms of metallic copper, even if an appropriate amount of thiuram compound E is used, there will be little effect.
If the amount exceeds 0.1 part by weight, polymerization will be significantly inhibited when the heat-resistant resin composition is cured, and physical properties such as heat resistance stability and mechanical strength of the resulting cured product will be reduced. Thiuram compound E and copper-containing compound F are
It can be added and blended into the heat-resistant resin composition by various methods. For example, at the start of production of unsaturated ester A or unsaturated ester B, a copper-containing compound F such as a relatively insoluble copper inorganic salt is added to the heat-resistant resin composition and gradually dissolved during the esterification reaction. There are methods of adding and blending thiuram compound E after producing the unsaturated ester, and methods of adding and blending thiuram compound E and copper-containing compound F at the same time when blending the heat-resistant resin composition. It goes without saying that the present invention is not limited by the method of addition and blending. Furthermore, in addition to the thiuram compound E and the copper-containing compound F used in the present invention, by adding a known and commonly used polymerization inhibitor such as hydroquinone or benzoquinone,
The method of the invention is not subject to this. (Effects of the Invention) According to the method of the present invention, the problems of viscosity increase and gelation during storage in unsaturated ester-based heat-resistant resin compositions containing maleimide compounds can be easily solved, and the heat-resistant It becomes possible to stably supply a cured product with excellent stability at high temperatures and mechanical strength without impairing the moldability such as the excellent curability and workability of the resin composition. Therefore, the method of the present invention can significantly improve the practicality of unsaturated ester-based heat-resistant resin compositions containing maleimide compounds, for which satisfactory storage stabilization effects have not been obtained with conventionally known polymerization inhibitors. The unique synergistic effect of the thiuram compound and the copper-containing compound on storage stabilization of the heat-resistant resin composition is surprising. (Examples) The present invention will be specifically explained below using reference examples, examples, and comparative examples, but the present invention is not limited to the following examples. In addition, all parts and percentages below are based on weight. Reference Example 1 Into a reaction vessel equipped with a thermometer, reflux condenser, air blowing tube, and stirrer, 88 parts of methacrylic acid, cresol novolac epoxy resin ECN-1280 (manufactured by Ciba Geigy, epoxy equivalent 227, average per molecule) were added.
227 parts (containing 5.1 epoxy groups), 130 parts vinyltoluene, 0.34 parts hydroquinone and 13.0 parts triethylamine were heated at 115°C for 8 hours with stirring under a stream of air to form a vinyltoluene solution with an acid value of 5. An unsaturated ester was obtained, and 127 parts of vinyltoluene was further added to obtain an unsaturated ester resin a. Mix 20 parts of N-cyclohexylmaleimide with 100 parts of the obtained unsaturated ester resin a,
A resin composition (1) was obtained. Reference Example 2 In the same reaction vessel as used in Reference Example 1, phenol novolak (softening point 85°C, 0H equivalent 103) was added.
parts, glycidyl methacrylate 142 parts, styrene
66 parts of methylhydroquinone, 0.2 parts of methylhydroquinone, and 0.85 parts of triethylamine were heated at 115°C for 8 hours with stirring under a stream of air, and complete reaction of glycidyl methacrylate was confirmed by nuclear magnetic resonance absorption spectrum of the reactants. Further, 90 parts of styrene and 45 parts of tris(2-hydroxyethyl)isocyanuric acid acrylate were added to obtain unsaturated ester resin b. 15 parts of N-phenylmaleimide was mixed with 100 parts of the obtained unsaturated ester resin b to obtain a resin composition (2). Reference Example 3 In the same reaction vessel as used in Reference Example 1, 88 parts of methacrylic acid, 185 parts of bisphenol type epoxy resin Araldite GY250 (manufactured by Ciba Geigy, epoxy equivalent: 185), 0.084 part of hydroquinone, and 0.024 part of cuprous chloride. and 1.0 part of triethylamine were charged, and the mixture was heated at 115° C. for 6 hours with stirring under a stream of air to obtain an unsaturated ester with an acid value of 7. To 55 parts of this unsaturated ester, 35 parts of p-methylstyrene and 10 parts of trimethylolpropane trimethacrylate.
These parts were mixed to obtain unsaturated ester resin c. 25 parts of N-cyclohexylmaleimide was mixed with 100 parts of the obtained unsaturated ester resin C to obtain a resin composition (3). Examples 1 to 3 After adding the thiuram compound and copper-containing compound shown in Table 1 to 100 parts of the resin composition (1), 1 kg of each of the resulting resin compositions was placed in a tin can with a volume of 1 and sealed. and stored at a temperature of 40°C. The conditions after storage were observed and the results are summarized in Table 1. Comparative Examples 1 to 3 Comparative resin compositions obtained by adding only one of a thiuram compound or a copper-containing compound, or adding neither of them, to 100 parts of the resin composition (1) as shown in Table 1. Examples 1 to 3
It was sealed in a tin can and stored at a temperature of 40°C. The observation results of the condition after storage are summarized in Table 1.

[Table] Examples 4 to 6 After adding the thiuram compound and copper-containing compound shown in Table 2 to 100 parts of resin composition (2), each of the resulting resin compositions was treated in the same manner as in Examples 1 to 3. It was then sealed in a tin can and stored at a temperature of 40°C. The observation results of the condition after storage are summarized in Table 2. Comparative Examples 4 to 6 Comparative resin compositions obtained by adding only one of a thiuram compound or a copper-containing compound, or adding neither of them, to 100 parts of resin composition (2) as shown in Table 2. Examples 1 to 3
It was sealed in a tin can and stored at a temperature of 40°C. The observation results of the condition after storage are summarized in Table 2.

[Table] Examples 7 to 9 After adding the thiuram compounds shown in Table 3 to 100 parts of the resin composition (3) (the copper-containing compound was prepared by adding cuprous chloride during the synthesis of the unsaturated ester). ), and each of the obtained resin compositions was prepared in Example 1.
It was sealed in a tin can and stored at a temperature of 40°C as in 3. The observation results of the condition after storage are summarized in Table 3. Comparative Example 7 For comparison, 100 parts of the resin composition (3) was sealed in a tin can as in Examples 1 to 3 and stored at a temperature of 40°C. The observation results of the condition after storage are shown in Table 3.

【table】

Claims (1)

[Claims] 1. Unsaturated ester A and/or one molecule obtained by reacting an epoxy compound having two or more epoxy groups in one molecule with an unsaturated monobasic acid and, if necessary, a polybasic acid. Radical polymerization with an epoxy group in one molecule of a compound having ^two or more phenolic hydroxyl groups in ^one molecule represented by the general formula A resin composition containing an unsaturated ester B obtained by reacting a compound having a sexual unsaturated bond, a compound C having one or more maleimide groups in one molecule, and optionally a polymerizable crosslinking agent D. , characterized by adding a thiuram compound E and a copper-containing compound F having at least one atomic group represented by the general formula [formula] (where n is an integer of 1 to 8) in one molecule. A method for stabilizing storage of the resin composition.