JPH0610224B2 - Method for stabilizing storage of vinyl ester resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a specific vinyl ester which is excellent in moldability such as curability and workability, and gives a cured product excellent in stability at high temperature and mechanical strength. The present invention relates to a method for stabilizing storage of a resin composition.

(Prior Art) As a resin having excellent stability at high temperatures, there are various heat-resistant resins represented by a polyimide resin and a polyamide-imide resin. However, these heat resistant resins are
Since it has a high melting point, it requires high temperature or high pressure for molding, or it takes a long time at high temperature and high pressure for curing, and it is necessary to dissolve the resin in a special high boiling point solvent before use. However, there is a serious problem in moldability such as requiring a step of removing the solvent by pressurizing or depressurizing at high temperature for a long time. Therefore, it is extremely difficult to manufacture a large-sized molded product using these heat-resistant resins, or to continuously manufacture a molded product such as by drawing or extrusion molding.

On the other hand, as a resin having excellent moldability such as curability and workability, a polyhydric phenol type epoxy resin such as bisphenol type epoxy resin or novolac type epoxy resin and an epoxy (meth) acrylate derived from (meth) acrylic acid or Radical polymerization type resins such as saturated polyester are known, and these resins are generally used as vinyl ester resins or unsaturated polyester resins by incorporating a radical polymerizable crosslinking agent such as styrene. However, these resins do not always reach a satisfactory level in terms of thermal stability at high temperatures, which is one of the major obstacles to the development of applications, and the emergence of resins with more excellent heat stability Is desired.

(Problems to be Solved by the Invention) The present inventors have found that the radical curable resin has excellent curability,
As a result of repeated research to develop a resin that gives a cured product with high stability at high temperatures without impairing moldability such as workability and mechanical strength, the results of the general formula [However, R ¹ is independent of each other (Wherein R ³ and R ⁴ are independently of each other hydrogen or a methyl group), hydrogen, and at least one of R ¹ is (Provided that R ³ and R ⁴ are hydrogen or a methyl group independently of each other), and R ² is an atom or an organic group selected from the group consisting of hydrogen, halogen, a methoxy group, and an alkyl group having 1 to 5 carbon atoms. , M is 0 or an integer of 1 to 10. ] Unsaturated ester compound (A) and /
Or general formula [However, the formulas R ⁵ are independent of each other. (Wherein R ³ and R ⁴ are independently of each other hydrogen or a methyl group), hydrogen, and at least one of R ⁵ is (Provided that R ³ and R ⁴ are independently of each other hydrogen or a methyl group), and R ⁶ is an atom or an organic group selected from the group consisting of hydrogen, halogen, a methoxy group, and an alkyl group having 1 to 5 carbon atoms. , N is 0 or an integer of 1 to 10, and when n is 0, Is a divalent organic group selected from the group consisting of
X is independent of each other in the case of an integer of 10 It is a divalent organic group selected from the group consisting of. It was found that the vinyl ester resin composition containing the unsaturated ester compound (B) represented by the formula (1) and the polymerizable cross-linking agent (C) meets the above object.

However, when the resin composition is produced and used within a short period of time, it exhibits the above-mentioned excellent performance without any problem, but when the resin composition is stored for a long period of time, it is polymerized. Even if an initiator is not added, the viscosity will increase significantly at room temperature or gelation will occur,
There was a problem that its use became difficult.

However, the present inventors have reached the present invention as a result of various researches aimed at stabilizing the storage of the resin composition.

(Means and Actions for Solving Problems) The present invention has the general formula [However, R ¹ is independent of each other (Wherein R ³ and R ⁴ are independently of each other hydrogen or a methyl group), hydrogen, and at least one of R ¹ is (Provided that R ³ and R ⁴ are hydrogen or a methyl group independently of each other), and R ² is an atom or an organic group selected from the group consisting of hydrogen, halogen, a methoxy group, and an alkyl group having 1 to 5 carbon atoms. , M is 0 or an integer of 1 to 10. ] Unsaturated ester compound (A) and /
Or general formula [However, the formulas R ⁵ are independent of each other. (Wherein R ³ and R ⁴ are independently of each other hydrogen or a methyl group), hydrogen, and at least one of R ⁵ is (Provided that R ³ and R ⁴ are independently of each other hydrogen or a methyl group), and R ⁶ is an atom or an organic group selected from the group consisting of hydrogen, halogen, a methoxy group, and an alkyl group having 1 to 5 carbon atoms. , N is 0 or an integer of 1 to 10, and when n is 0, Is a divalent organic group selected from the group consisting of
X is independent of each other in the case of an integer of 10 It is a divalent organic group selected from the group consisting of. ] The vinyl ester resin composition containing the unsaturated ester compound (B) represented by (However, 1 is an integer of 1 to 8.) The vinyl compound characterized in that a thiuram compound (D) having at least one atomic group represented by the formula (1) in one molecule and a copper-containing compound (E) are added. The present invention relates to a method for stabilizing the storage of an ester resin composition.

Unsaturated ester compound used as a component of the vinyl ester resin composition which is the object of the storage stabilization method of the present invention
The (A) or unsaturated ester compound (B) can be produced, for example, as follows.

As the first manufacturing method, the general formula (However, R ² is hydrogen, a halogen, a methoxy group, a carbon number of 1 to
5 is an atom or an organic group selected from the group consisting of 5 alkyl groups, and m is 0 or an integer of 1-10. ) Aromatic polyamine (a) or general formula (However, in the formula, R ⁶ is an atom or an organic group selected from the group consisting of hydrogen, a halogen, a methoxy group, and an alkyl group having 1 to 5 carbon atoms, n is 0 or an integer of 1 to 10, and n If is 0 Is a divalent organic group selected from the group consisting of
X is independent of each other in the case of an integer of 10 It is a divalent organic group selected from the group consisting of. ) The aromatic diamine (b) represented by (However, in the formula, R ³ and R ⁴ are independently of each other hydrogen or a methyl group.) A method of reacting an epoxy group and a compound (c) having a radically polymerizable unsaturated bond in one molecule is there.

The aromatic polyamine (a) is represented by the above general formula. For example, an aniline derivative is neutralized with hydrochloric acid to give an aniline derivative hydrochloride solution, and formaldehyde is added in an amount of 0.25 to 1.0 mol per mol of the aniline derivative. It can be obtained by reacting formaldehyde so that Examples of the aniline derivative include aniline and p-
(M or o-) chloraniline, p- (m or o
-) Toluidine, p- (m or o-) ethylaniline, p- (m or o-) iso-propylaniline, p
-(M or o-) n-propylaniline, p- (m or o-) methoxyaniline and the like can be used alone or as a mixture of two or more kinds. Further, poly (phenylene methylene) polyamine obtained by the reaction of aniline and formaldehyde is industrially produced as a polyurethane raw material, for example, MDA-220, MDA.
-150 (all manufactured by Mitsui Toatsu Chemicals, Inc.) can be directly used as the aromatic polyamine (a) in the present invention.

The aromatic diamine (b) is represented by the above general formula, for example, 4,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfone, 3,
3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2,2-bis (4-aminophenyl) propane, 2,2-bis (4-aminophenyl) hexafluoropropane , 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene,
2,2-bis [4- (4-aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, 1- (p-aminobenzoyl) -4
-(P-aminobenzyl) benzene, 1- (p-aminobenzoyl) -4- (m-aminobenzyl) benzene,
1- (m-aminobenzoyl) -4- (p-aminobenzyl) benzene, 1- (m-aminobenzoyl) -4-
(M-aminobenzyl) benzene, 1,4-bis (m-
Aminobenzoyl) benzene, 1,4-bis (p-aminobenzoyl) benzene, 1,3-bis (m-aminobenzyl) benzene, 4,4'-bis (m-aminobenzoyl) diphenylmethane, 4,4'- Bis (p-aminobenzoyl) diphenylmethane, 4,4'-bis (m-
Aminobenzyl) diphenylmethane or a halogen of aromatic hydrogen of these compounds, a methoxy group or a substituted alkyl group having 1 to 5 carbon atoms and the like can be used alone or in combination of two or more kinds.

The compound (c) has an epoxy group and a radical-polymerizable unsaturated bond in one molecule represented by the above general formula, for example, glycidyl methacrylate, glycidyl acrylate, 2-methylglycidyl methacrylate, 2-
Methyl glycidyl acrylate or the like can be used alone or as a mixture of two or more kinds.

Unsaturated ester compound (A) by ring-opening addition reaction of aromatic polyamine (a) or aromatic diamine (b) and compound (c)
Alternatively, in obtaining the unsaturated ester compound (B), for example, aromatic polyamine (a) or aromatic diamine (b), aromatic polyamine (a) or aromatic diamine
0.2 to 1.5 equivalents of compound (c), preferably 0.3 to 1.0 equivalent to 1 equivalent of hydrogen atom directly linked to nitrogen atom contained in (b)
Add 3 parts by weight in an inert solvent or without solvent.
Heating to 0-150 ° C, preferably 50-130 ° C,
The reaction is preferably carried out 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-toluquinone.

Further, in order to shorten the reaction time, a ring-opening addition catalyst can be used, and examples of the ring-opening addition catalyst include water; alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol; phenol, t-butylcatechol and the like. Phenols; organic acids such as salicylic acid, citric acid and malic acid; organic acid salts such as zinc salicylate and tin octylate; boron trifluoride-monoethanolamine complex.

As the inert solvent, for example, toluene, xylene, dimethylformamide or the like can be used, but a catalyst itself such as ethyl alcohol or acetic acid can also be used as a reaction medium. Furthermore, since the solvent needs to be removed after the reaction, it is advantageous to use these polymerizable cross-linking agents as the solvent, especially when a polymerizable cross-linking agent which is liquid at room temperature is also used as the final composition.

Further, as the second production method, the aromatic polyamine (a) represented by the above general formula or the aromatic diamine (b) represented by the above general formula is added to the general formula (However, R ³ is hydrogen or a methyl group, and X is halogen.) An epihalohydrin (d) represented by the formula (I) is subjected to an addition reaction to produce N-halohydrin as an intermediate,
Next, the N-halohydrin is dehydrohalogenated with an alkali to be glycidylated to obtain an epoxy compound (hereinafter, referred to as an epoxy compound (a)), and further acrylic acid and / or methacrylic acid are ring-opened. The method of adding can be mentioned.

Epihalohydrin (d) is represented by the above general formula, for example, epichlorohydrin, epibromhydrin, epiiodohydrin, β-methylepichlorohydrin, β-methylepibromohydrin, β-methylepiodohydrin, etc. Is used.

The reaction for producing the epoxy compound (a) from the aromatic polyamine (a) or the aromatic diamine (b) and the epihalohydrin (d) is carried out by, for example, converting the aromatic polyamine (a) or the aromatic diamine (b) into the aromatic polyamine (a). 1 to 5 equivalents of epihalohydrin (d), preferably 2 to 1 equivalent of hydrogen atom directly connected to nitrogen atom in (a) or aromatic diamine (b)
3 equivalents are added and the addition reaction is performed at 40 to 100 ° C. for 5 to 30 hours, preferably at 70 to 90 ° C. for 7 to 15 hours, and then the alkali metal hydroxide is gradually added to the obtained reaction product. It can be carried out by adding and performing dehydrochlorination reaction at a temperature of 70 ° C. or lower for 2 to 10 hours.

Further, as one of such epoxy compounds (a),
A commercially available product from Ciba Geigy under the trade name of "Araldite MY-720" and from Toto Kasei Co., Ltd. under the trade name of "YH-434" can also be used in the present invention.

When the unsaturated ester compound (A) or the unsaturated ester compound (B) is obtained by reacting the epoxy compound (a) with acrylic acid and / or methacrylic acid, for example, the epoxy compound (a) is added to the compound (a). Acrylic acid and / or methacrylic acid are mixed in a proportion of 0.3 to 1.2 mol, preferably 0.5 to 1.1 mol, relative to 1 mol of the epoxy group contained in 60 to 15 mol in an inert solvent or no solvent.
The reaction is carried out at 0 ° C., preferably 70 to 130 ° C., 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-toluquinone.

In order to shorten the reaction time, it is preferable to use an esterification catalyst. Examples of the esterification catalyst include tertiary amines such as N, N'-dimethylaniline, pyridine and triethylamine and their hydrochlorides or bromates. Quaternary ammonium salts such as tetramethylammonium chloride and triethylbenzylammonium chloride; Sulfonic acids such as paratoluene sulfonic acid; Sulfoxides such as dimethyl sulfoxide and methyl sulfoxide; Sulfonium salts such as trimethylsulfonium chloride and dimethylsulfonium chloride; Triphenyl Phosphines such as phosphine and tri-n-butylphosphine; lithium chloride, lithium bromide, primary chloride
Known and conventional metal halides such as tin and zinc chloride can be used.

As the inert solvent, for example, toluene, xylene and the like can be used, but since the solvent needs to be removed after the reaction, particularly when the final composition is used in combination with a polymerizable crosslinking agent which is liquid at room temperature. It is preferable to use these polymerizable crosslinking agents as a solvent.

Examples of the polymerizable crosslinking agent (C) used in the present invention include styrene, α-methylstyrene, p-methylstyrene,
Styrene derivatives such as t-butylstyrene, vinyltoluene and divinylbenzene; methyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, tricyclodecenyl (meth) acrylate, 2-hydroxyethyl ( Meta)
(Meth) acrylic acid ester monomers such as acrylates; trimethylolpropane tri (meth) acrylate, diethylene glycol di (meth) acrylate, 1,
4-butanediol di (meth) acrylate, tris (2-hydroxyethyl) isocyanuric acid (meth) acrylate, di (meth) acrylate of 2,2-bis [4- (2-hydroxyethoxy) phenyl] propane, etc. (Meth) acrylates of polyhydric alcohols; diallyl phthalate, sialyl isophthalate, diallyl terephthalate, triallyl isocyanurate, triallyl cyanurate, and other allyl compounds such as general unsaturated polyester resins and vinyl ester resins known and commonly used Can be used alone or as a mixture of two or more kinds.

The mixing ratio of the unsaturated ester compound (A) and / or the unsaturated ester compound (B) and the polymerizable cross-linking agent (C) is not particularly limited, but the unsaturated ester compound is preferred from the viewpoint of mechanical strength and heat resistance. (A) and / or unsaturated ester compound
It is preferable that the proportion of (B) is 30 to 95 parts by weight and the amount of the polymerizable cross-linking agent (C) is 5 to 70 parts by weight.

The thiuram compound (D) used in the present invention has the general formula A compound having at least one atomic group represented by in one molecule, for example, 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 tetrasulfide, dipentamethylene thiuram tetrasulfide, Tetramethyl thiuram trisulfide, tetramethyl thiuram hexasulfide, bis (trimethyl disulfide) but such ethylene including but without limitation, can be used alone or as a mixture of two or more.

Further, as the copper-containing compound (E) used together with the thiuram compound (D) in the present invention, for example, copper acetate, copper citrate, copper oxalate, copper formate, copper naphthenate, copper oleate, copper acrylate, methacrylic acid. Acid salts, organic acid salts such as copper (2-hydroxyethyl) dithiocarbamate and copper dimethyldithiocarbamate; chelate compounds such as copper acetylacetonate; complexes of cuprous chloride and triethyl phosphite; cupric chloride and dicyclohexyl Complex compounds such as sulfoxide complexes; cuprous chloride, cupric chloride, cuprous bromide, cupric bromide, cuprous oxide, cupric hydroxide, copper carbonate, copper nitrate, sulfuric acid Examples thereof include inorganic salts such as copper, copper phosphite, cupric phosphate, etc., but are not limited thereto, and they may be used alone or in a mixture of two or more kinds.

For storage stabilization of a vinyl ester resin composition containing an unsaturated ester compound (A) and / or an unsaturated ester compound (B) and a polymerizable crosslinking agent (C), a thiuram compound (D) is used. Alternatively, each of the copper-containing compounds (E) alone has no effect, or if any, is insignificant, and the thiuram compound (D) and the copper-containing compound (E) coexist to bring about a remarkable effect. .

The amount of the thiuram compound (D) and the copper-containing compound (E) used is
The thiuram compound (D) is 0.0001 to 2.0 parts by weight, preferably 0.001 part by weight, relative to 100 parts by weight of the vinyl ester resin composition.
1 to 0.5 parts by weight, and a copper-containing compound
(E) is in the range of 0.00001 to 0.1 part by weight, preferably 0.0001 to 0.05 part by weight, calculated as metallic copper. If the amount of the thiuram compound (D) used is less than 0.0001 parts by weight, the effect is small even if the copper-containing compound (E) is used in an appropriate amount, and even if it is used in a large amount exceeding 2.0 parts by weight, the corresponding effect can be obtained. Absent. On the other hand, when the amount of the copper-containing compound (E) used is a small amount of less than 0.00001 parts by weight in terms of metallic copper, the thiuram compound
The effect is small even if (D) is used in an appropriate amount, and in a large amount exceeding 0.1 part by weight, polymerization inhibition becomes remarkable when the vinyl ester resin composition is cured, and the resulting cured product has heat resistance stability and mechanical strength. Reduce the physical properties of.

The thiuram compound (D) and the copper-containing compound (E) can be added / blended to the vinyl ester resin composition by various methods. For example, unsaturated ester compound (A)
Or at the start of the production of unsaturated ester compound (B) to the vinyl ester resin composition, a copper-containing compound (E) such as a relatively poorly soluble inorganic salt of copper is added and gradually dissolved during the reaction, A method of adding and blending the thiuram compound (D) after the production of the vinyl ester, a method of adding and blending the thiuram compound (D) and the copper-containing compound (E) at the same time when blending the vinyl ester resin composition, etc. There are these additions
It goes without saying that the present invention is not limited by the compounding method.

In addition to the thiuram compound (D) and the copper-containing compound (E) used in the present invention, addition of a known and commonly used polymerization inhibitor such as hydroquinone or benzoquinone does not influence the method of the present invention.

(Effect of the Invention) According to the method of the present invention, a specific vinyl containing the unsaturated ester compound (A) and / or the unsaturated ester compound (B) and the polymerizable crosslinking agent (C) as described above. It is possible to easily solve the problems of viscosity increase and gelation during storage in the ester resin composition, without impairing the moldability such as excellent curability and workability of the vinyl ester resin composition at high temperature. It is possible to stably supply a cured product having excellent stability and mechanical strength below. Therefore, the method of the present invention remarkably enhances the practicability of the vinyl ester resin composition for which a satisfactory storage stabilizing effect has not been obtained with a conventionally known polymerization inhibitor or the like. The unique synergistic effect of thiuram and copper-containing compounds on storage stabilization is surprising.

(Examples) The present invention will be specifically described below with reference to Reference Examples, Examples and Comparative Examples, but the present invention is not limited to the following Examples. Further, all parts below are based on weight.

Reference Example 1 In a reaction vessel equipped with a thermometer, a reflux condenser, an air suction tube and a stirrer, 128 parts of glycidyl methacrylate and polymethylene polyaniline MDA-150 represented by the following formula.
(Mitsui Toatsu Chemicals, Inc., amino content 15.8%) 59
Part, 75 parts vinyltoluene, Methylhydroquinone (0.3 parts) and zinc salicylate (0.45 parts) were charged and heated at 110 ° C. for 8 hours with stirring in an air stream. The nuclear magnetic resonance absorption spectrum of the reaction product confirmed that glycidyl methacrylate was completely reacted, and was unsaturated. A vinyltoluene solution of the ester compound was obtained. Further, 25 parts of vinyltoluene was mixed to obtain a resin composition (1).

Reference Example 2 In the same reaction vessel used in Reference Example 1, 2,2-bis [4
-(4-Aminophenoxy) phenyl] propane 71.2
Part, 78.8 parts of glycidyl methacrylate, 80 parts of p-methylstyrene, 0.2 part of methylhydroquinone and 0.5 part of triethylamine were charged and heated at 115 ° C. for 5 hours while stirring in an air stream, and glycidyl was determined by nuclear magnetic resonance absorption spectrum of the reaction product. When it was confirmed that the methacrylate had completely reacted, a resin composition (2) was obtained.

Reference Example 3 Methacrylic acid 7 was placed in the same reaction vessel used in Reference Example 1.
3 parts, Araldite MY720 (Ciba Geigy, N
-Tetraglycidyl-diaminodiphenylmethane, epoxy equivalent 125) 125 parts, styrene 50 parts, toluquinone 0.16 parts and triethylamine 0.65 parts were charged and heated under an air stream at 115 ° C for 6 hours with stirring to give a styrene solution having an acid value of 3.0. An unsaturated ester compound was obtained.

Further, 57 parts of vinyltoluene was mixed to obtain a resin composition (3)
Got

Examples 1 to 3 After adding the thiuram compound and the copper-containing compound shown in Table 1 to 100 parts of the resin composition (1), 1 kg of each resin composition obtained was placed in a tin can having a volume of 1 and sealed. And stored at a temperature of 40 ° C. The condition after storage was observed, and the results are summarized in Table 1.

Comparative Examples 1 to 3 Resin compositions (1) were obtained by adding only one of the thiuram compound and the copper-containing compound as shown in Table 1 or neither of them to the resin composition for comparison. Each of the products 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 state after storage are summarized in Table 1.

Examples 4 to 6 After adding the thiuram compound and the copper-containing compound shown in Table 2 to 100 parts of the resin composition (2), each of the obtained resin compositions was processed into tin cans in the same manner as in Examples 1 to 3. Sealed in and stored at a temperature of 40 ° C. The observation results of the state after storage are summarized in Table 2.

Comparative Examples 4 to 6 Resin compositions (2) obtained for comparison were obtained by adding only one of the thiuram compound and the copper-containing compound as shown in Table 2 or neither of them to the resin composition for comparison. Each of the items was sealed in tin cans as in Examples 1-3 and stored at a temperature of 40 ° C. The observation results of the state after storage are summarized in Table 2.

Examples 7 to 9 After adding the thiuram compound and the copper-containing compound shown in Table 3 to 100 parts of the resin composition (3), each of the obtained resin compositions was processed in the same manner as in Examples 1 to 3. Sealed in and stored at a temperature of 40 ° C. The results of observation of the state after storage are summarized in Table 3.

Comparative Examples 7 to 9 Resin compositions for comparison obtained by adding 100 parts of the resin composition (3) with only one of the thiuram compound and the copper-containing compound as shown in Table 3 or neither of them. Each of the items was sealed in tin cans as in Examples 1-3 and stored at a temperature of 40 ° C. The results of observation of the state after storage are summarized in Table 3.

Claims (1)

[Claims] 1. A general formula [However, R ¹ is independent of each other (Wherein R ³ and R ⁴ are independently of each other hydrogen or a methyl group), hydrogen, and at least one of R ¹ is (Provided that R ³ and R ⁴ are hydrogen or a methyl group independently of each other), and R ² is an atom or an organic group selected from the group consisting of hydrogen, halogen, a methoxy group, and an alkyl group having 1 to 5 carbon atoms. , M is 0 or an integer of 1 to 10. ] Unsaturated ester compound (A) and /
Or general formula [However, in the formula, R ⁵ is independent of each other. (Wherein R ³ and R ⁴ are independently of each other hydrogen or a methyl group), hydrogen, and at least one of R ⁵ is (Provided that R ³ and R ⁴ are hydrogen or a methyl group independently of each other), and R ⁶ is an atom or an organic group selected from the group consisting of hydrogen, halogen, a methoxy group, and an alkyl group having 1 to 5 carbon atoms. , N is 0 or an integer of 1 to 10, and when n is 0, Is a divalent organic group selected from the group consisting of
X is independent of each other in the case of an integer of 10 It is a divalent organic group selected from the group consisting of. ] The vinyl ester resin composition containing the unsaturated ester compound (B) represented by A method for stabilizing storage of a vinyl ester resin composition, which comprises adding a thiuram compound (D) having at least one atomic group represented by the formula (1) in one molecule and a copper-containing compound (E).