JP2764421B2 - Curing agent composition for epoxy resin and method for curing epoxy resin using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a curing agent composition for an epoxy resin and a method for curing an epoxy resin. More specifically, it is composed of a specific aromatic diamine and thiosalicylic acid, cured at low temperatures and heat-resistant,
The present invention relates to a curing agent composition that gives an epoxy resin cured product having excellent chemical resistance, and a method for curing an epoxy resin using the curing agent composition.

2. Description of the Related Art Aromatic diamines are widely used as curing agents for epoxy resins, and provide cured epoxy resins having excellent heat resistance and chemical resistance. However, aromatic diamines cure epoxy resins at low temperatures at low temperatures, require high curing temperatures (typically at 100 ° C. to 200 ° C.), and have difficulty in workability. Various studies have been made to improve this disadvantage. For example, a method of mixing with an aliphatic amine (Japanese Unexamined Patent Publication No.
15528), a method of adding a curing accelerator (boron trifluoride ethylamine complex, benzoic acid, salicylic acid, 2,4,6-tris-dimethylaminomethylphenol, etc.) (edited by Hiroshi Kakiuchi, "New epoxy resin" Shokodo, Accelerated curing speed is being studied by 1985. However, mixing with an aliphatic amine lowers the heat resistance of the cured product, and the method of adding an accelerator often fails to provide a sufficient accelerating effect or lowers the physical properties of the cured product in many cases.

On the other hand, the aromatic diamine represented by the formula (1) (In the formula (1), R _{1 to} R ₄ each independently represent a C _{1 to} C ₃ alkyl or halogen.) In addition to the epoxy resin cured product having excellent heat resistance and chemical resistance, It is frequently used because of its low toxicity (no mutagenicity).

However, since the ortho position of the amino group is substituted by an alkyl group or a halogen atom, there is a disadvantage that curing is extremely slow at low temperatures due to steric hindrance of the alkyl group or the halogen atom.

In order to remedy this drawback, Japanese Patent Application Laid-Open No. 62-232429 discloses an aromatic diamine represented by the formula (1), monochloro-p-phenylenediamine, and a curing catalyst such as salicylic acid, benzoic anhydride, and alkyl of boron trifluoride. A curing agent composition containing a compound selected from an amine complex salt or an acetic acid complex has been proposed. According to them, although the curing speed is improved, the problem of using monochloro-p-phenylenediamine which is susceptible to oxidation and causes coloring of the cured product and the physical properties of the obtained epoxy resin cured product are not sufficient. Having.

Problems to be Solved by the Invention By using the aromatic diamine represented by the formula (1), it is possible to cure the epoxy resin at a sufficient curing rate even at a low temperature,
Further, development of a curing method that does not impair the physical properties of the obtained cured epoxy resin is desired.

Means for Solving the Problems The inventors of the present invention have intensively studied a method for curing an epoxy resin in order to solve the above-mentioned problems, and have found that a curing agent comprising an aromatic diamine represented by the formula (1) and thiosalicylic acid as a curing agent. By using the agent composition, it was found that an epoxy resin cured product having a sufficient curing rate even at a low temperature and having excellent heat resistance and chemical resistance was obtained, and the present invention was reached.

That is, the present invention provides an aromatic diamine represented by the formula (1) (In the formula (1), R _{1 to} R ₄ each independently represent an alkyl or halogen of C _{1 to} C ₃ ) and an epoxy resin curing agent composition comprising thiosalicylic acid, and a method of curing an epoxy resin using the curing agent composition I will provide a.

The curing agent composition and the curing method of the present invention will be described in detail. Specific examples of the aromatic diamine represented by the formula (1) include 4,4
4'-diamino-3,3 ', 5,5'-tetramethyldiphenylmethane, 4,4'-diamino-3,3', 5,5'-tetraethyldiphenylmethane, 4,4'-diamino- 3,3 ', 5,5'-tetraisopropyldiphenylmethane, 4,4'-diamino-3,3', 5,5'-tetra-n-propyldiphenylmethane, 4,4'-diamino-3 , 3'-Dimethyl-5,5'-diethyldiphenylmethane, 4,4'-diamino-3,3'-dimethyl-5,5'-diisopropyldiphenylmethane, 4,4 '
-Diamino-3,3'-dimethyl-5,5'-di-n-propyldiphenylmethane, 4,4'-diamino-3,3'-diethyl-5,5'-diisopropyldiphenylmethane, 4, 4'-
Diamino-3,3 ', 5,5'-tetrachlorodiphenylmethane, 4,4'-diamino-3,3', 5,5'-tetrabromodiphenylmethane, 4,4'-diamino-3, 3'-dichloro-5,
5'-dimethyldiphenylmethane, 4,4'-diamino-3,
3'-dichloro-5,5'-diethyldiphenylmethane, 4,
4'-diamino-3,3'-dichloro-5,5'-diisopropyldiphenylmethane, 4,4'-diamino-3,3'-dibromo-5,5'-dimethyldiphenylmethane, 4,4 '-Diamino-3,3'-dibromo-5,5'-diethyldiphenylmethane,4,4'-diamino-3,3'-dibromo-5,5'-diisopropyldiphenylmethane,4,4'-diamino −3,
3'-dichloro-5,5'-dibromodiphenylmethane and the like. These may be used alone or in combination of two or more.

Thiosalicylic acid acts as a curing accelerator, and the benzene nucleus may be substituted with chlorine or an alkyl group. The mixing ratio of thiosalicylic acid in the curing agent composition according to the present invention is as follows.
It is 1 to 30 parts, more preferably 5 to 10 parts, per 100 parts by weight.

The aromatic diamine represented by the formula (1) and thiosalicylic acid are simply physically mixed, or more preferably, the mixture of the two is melted once to be uniform, and then cooled and solidified.
By pulverizing, the curing agent composition of the present invention is obtained.

The temperature at which the curing agent composition of the present invention is mixed with the epoxy resin to cure the epoxy resin is arbitrarily determined depending on the purpose of use, but is usually in the range of 5 ° C to 100 ° C.

Although the curing agent composition of the present invention can be used in an arbitrary ratio to the epoxy resin to be cured, the ratio of the epoxy equivalent to the amine equivalent of the aromatic diamine represented by the formula (1) is usually 0.1.
Preferably, it is used so as to be 7 to 1.3.

The epoxy resin and the curing agent composition of the present invention are kneaded using a roll, a kneader, or the like, or are dissolved and mixed in a solvent as necessary, and then are cured while removing the solvent as necessary. .

Examples of solvents that can be used in this case include acetone, methyl ethyl ketone, toluene, xylene, ethyl acetate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, dimethylformamide, N-
Methylpyrrolidone and the like.

Specific examples of the epoxy resin to which the curing agent composition of the present invention can be applied include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin,
Glycidyl ester type epoxy resin, glycidylamine type epoxy resin, alicyclic epoxy resin, brominated bisphenol A type epoxy resin, brominated phenol novolak type epoxy resin, and the like are exemplified. In addition, fine powder inorganic fillers, pigments, carbon black and the like can be added to the epoxy resin as long as the properties are not lost.

The epoxy resin can be cured at a low temperature by the curing agent composition of the present invention, and a cured epoxy resin having excellent heat resistance and chemical resistance can be obtained.

Examples The present invention will be described more specifically with reference to examples.

Example 1. 100 parts of 4,4'-diamino-3,3 ', 5,5'-tetraethyldiphenylmethane and 10 parts of thiosalicylic acid were dissolved by heating at 85 ° C and uniformly mixed. The mixture was cooled, solidified and pulverized to obtain a curing agent composition of the present invention.

Examples 2 to 4. The curing agent composition of the present invention was prepared in the same manner as in Example 1. Table 1 shows the composition ratio, the melting point of the composition, and the amine equivalent. Table 1 also shows comparative examples.

Examples 5 to 8 Using the curing agent compositions of Examples 1 to 4 and Comparative Examples 1, 2, and 3, epicoat 828 (manufactured by Yuka Shell Epoxy Co., Ltd., bisphenol A type epoxy resin) at a heating bath temperature of 55 ° C. A curing reaction with an epoxy equivalent of 190) was performed. The results are shown in Table 2.

As is clear from the table, rapid curing (gelation) was observed even at a relatively low temperature such as 55 ° C. The obtained epoxy cured product shows a high glass transition temperature, heat resistance,
The chemical resistance was good.

Although the salicylic acid used in Comparative Example 1 has a curing acceleration effect, the heat resistance of the cured epoxy resin is reduced.

Effects of the Invention A curing agent composition and a curing method that provide a cured epoxy resin having a sufficient curing rate even at a low temperature and excellent heat resistance have been found.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yasuo Nakano 7-20-1-1-1108 Arakawa, Arakawa-ku, Tokyo (72) Inventor Masaki Fujimoto 1090 Kamiochiai, Yono-shi, Saitama (56) References JP-A-63-186728 (JP, A) JP-A-62-184012 (JP, A) JP-A-61-218624 (JP, A) JP-A-50-138099 (JP, A) JP-A-62-232429 (JP, A) JP-A-61-159417 (JP, A) JP-A-1-284578 (JP, A) JP-B-47-13394 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08G 59 / 00-59/72 C08L 63/00-63/10 C08K 3/00-13/08

Claims (2)

(57) [Claims] An aromatic diamine represented by the general formula (1) (Wherein R _{1 to} R ₄ each independently represent C _{1 to} C ₃ alkyl or halogen) and a thiosalicylic acid curing agent composition for epoxy resin 2. A method for curing an epoxy resin, comprising using the epoxy resin curing agent composition according to claim 1.