JPS6244012B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an epoxy resin curing agent comprising an acid anhydride mixture.

Conventionally, alicyclic or aromatic polycarboxylic acid anhydrides have been frequently used as curing agents for epoxy resins, but these cannot impart flexibility to cured products.

In addition, 4-ketopimelic acid dilactone has the formula [] The Journal of Applied Polymer Science (J.APPLID POLYM.SCI.) is an example of using only this compound as a curing agent for epoxy resin and examining the shrinkage of the cured product.
Reported in Vol. 10, p. 887 (1966). However, when dilactone 4-ketopimelate is used alone as a curing agent for an epoxy resin, although the volume shrinkage during the curing reaction is small, the hardness of the cured product is extremely low and it is extremely susceptible to scratches, making it impractical.

The first object of the present invention is to solve such problems.

Furthermore, dilactone 4-ketopimelate is a crystal with a melting point of 65°C, so when using it alone as a curing agent for epoxy resin, it must be heated above its melting point in order to mix uniformly with the epoxy resin. As a result, it has the disadvantage of a short pot life.

A second object of the present invention is to solve such problems.

The present invention solves the above problems,
An object of the present invention is to provide an epoxy resin curing agent which exhibits the effect that a cured product obtained by reacting with an epoxy resin has good hardness and can impart flexibility to the cured product, which has not been previously known.

That is, the present invention relates to an epoxy resin curing agent comprising an acid anhydride mixture containing 95 to 30% by weight of an alicyclic or aromatic polycarboxylic acid anhydride and 5 to 70% by weight of dilactone 4-ketopimelate.

The alicyclic or aromatic polycarboxylic acid anhydride of the present invention includes hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride,
Examples include 3,6-endomethylenetetrahydrophthalic anhydride, methyl-3,6-endomethylenetetrahydrophthalic anhydride, phthalic anhydride, pyromellitic anhydride, and the like.

The alicyclic or aromatic polycarboxylic acid anhydride of the present invention is preferably liquid at room temperature.

Examples of alicyclic or aromatic polycarboxylic acid anhydrides that are liquid at room temperature include methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and methylendomethylenetetrahydrophthalic anhydride. There are some known compounds, and these can be used alone or in a mixture of two or more. There are also eutectic mixtures of hexahydrophthalic anhydride, tetrahydrophthalic anhydride, phthalic anhydride, chlorendic acid, and the like.

The above alicyclic polycarboxylic acid anhydride, which is liquid at room temperature, is a stereoisomer mixture or a structural isomer mixture, and the stereoisomer mixture is the cis form and trans form of the above alicyclic polycarboxylic anhydride. It can be obtained mainly by heating the cis-isomer in the presence or absence of a basic catalyst or by hydrogenating methyltetrahydrophthalic anhydride. The ratio of the cis isomer to the trans isomer is preferably 7/3 to 3/7, particularly preferably 6/4 to 4/6. Structural isomer mixtures can be obtained by heating methyltetrahydrophthalic anhydride (particularly 3- or 4-methyl- ^Δ4 -tetrahydrophthalic anhydride) in the presence of an acidic catalyst or a noble metal catalyst. can. This structural isomer mixture is a mixture of structural isomers that differ in the position of the double bond in the six-membered ring.

As the basic catalyst, dibutylaniline,
There are alkali metal compounds, etc. Examples of the alkali metal compound include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, and alkali metal oxides such as lithium oxide, sodium oxide, and potassium oxide.

The above acidic catalysts include phosphoric acid, polyphosphoric acid,
There are silica alumina catalysts, etc.

The above-mentioned noble metal catalyst includes palladium black and the like.

Catalysts that can be used during the above hydrogenation include palladium, nickel, and the like.

In the above, the reaction in the presence of a basic catalyst is
It is preferable to carry out the hydrogenation at 150℃ or higher, or 200℃ or higher without a catalyst.
It is preferable to carry out the reaction at 130-180°C using a nickel catalyst. The structural isomerization reaction is preferably carried out at 150°C or higher. Note that when palladium black is used, a disproportionation reaction also occurs at the same time.

Examples of the above eutectic mixture include a mixture of about 80% by weight of hexahydrophthalic anhydride and about 20% by weight of tetrahydrophthalic anhydride, a mixture of about 50% by weight of hexahydrophthalic anhydride, about 25% by weight of tetrahydrophthalic anhydride and phthalic anhydride. Examples include mixtures containing about 25% acid by weight.

The 4-ketopimelic acid dilactone used in the present invention is disclosed in Ann. Vol. 253, p. 206 (1890) and West German Publication No. 2136886 (1973).
As shown in 2003, succinic anhydride can be obtained by heating succinic anhydride in the presence of an alkali catalyst and causing a decarboxylation condensation reaction.

In the present invention, the alicyclic or aromatic polycarboxylic anhydride and 4-ketopimelic acid dilactone are used in a weight ratio of 95/5 to 70/30, preferably 85/15 to 60/40. It is blended into. If this ratio exceeds 95/5, the flexibility of the cured product obtained by reacting with the epoxy resin will decrease, and if it is less than 30/70, even if the cured product has flexibility, the hardness will decrease. easy to be hurt.

Since 4-ketopimelic acid dilactone has a melting point of 65°C, in order to make the acid anhydride mixture of the present invention liquid, it is preferable to use an alicyclic or aromatic polycarboxylic acid anhydride that is liquid at room temperature. preferable. In this case, if too much 4-ketopimelic acid dilactone is present, it will not be completely dissolved, so the liquid alicyclic or aromatic polycarboxylic acid anhydride and 4-ketopimelic acid dilactone are mixed at a weight ratio of 6.
It is preferable to mix it so that it becomes 5/35 or more.

Other acid anhydrides may be mixed with the acid anhydride mixture according to the present invention. Examples of such acid anhydrides include dodecenyl succinic anhydride, diisobutenyl succinic anhydride, polyazelaic acid polyanhydride, and succinic anhydride. The amount thereof in the acid anhydride mixture is preferably 10% by weight or less, particularly preferably 5% by weight or less. If the amount of such acid anhydride is too large, the mechanical strength of the cured product with the epoxy resin tends to decrease.

In particular, succinic anhydride is a raw material for dilactone 4-ketopimelate, and is often included depending on the degree of purification of dilactone 4-ketopimelate. When the acid anhydride mixture of the present invention is in a liquid state, this succinic anhydride will crystallize and precipitate during storage if a large amount is present, resulting in a non-uniform mixture. Therefore, it is preferable that the amount of succinic anhydride present in the acid anhydride mixture according to the present invention is adjusted to 1% by weight or less. For this purpose, dilactone 4-ketopimelate may be produced and then sufficiently purified. Purification methods include distillation and extraction with organic solvents such as chloroform.

The epoxy resin curing agent according to the present invention has a weight ratio of epoxy resin and the latter/former of 100/30 to 100/150.
A cured product of the epoxy resin can be obtained by blending the epoxy resin so as to have the following properties, further blending a curing accelerator as necessary, and heating. Here, as the epoxy resin, a compound having two or more epoxy groups in one molecule is used, including an epibis type epoxy resin represented by diglycidyl ether of bisphenol A, and an alicyclic resin represented by a cyclohexene oxide derivative. Examples include novolac type epoxy resins which are glycidyl ether compounds such as formula epoxy resins, phenol novolacs, and cresol novolacs. In addition, curing accelerators include tertiary amines, their salts, quaternary ammonium compounds, alkali metal alcoholates, fatty acid metal salts, and examples of these include benzyldimethylamine, 2,4,6-tris Examples include (dimethylaminomethyl)phenol, 2-ethyl-4-methylimidazole, triamylammonium phenolate, sodium hexanetriol, 1,8-diazabicyclo[5.4.0]-undecene-7, and tin octylate.

Next, examples of the present invention will be shown.

Example 1 Liquid 4-methylhexahydrophthalic anhydride (4-methyl-Δ ⁴ -tetrahydrophthalic anhydride hydrogenated at 150°C in the presence of Raney Nickel catalyst) and liquid 3-methylhexahydrophthalic anhydride. acid (3-methyl- ^Δ4 -tetrahydrophthalic anhydride in the presence of Raney-nickel catalyst)
Hydrogenated at 150℃) 70% by weight each
33 g of 4-ketopimelic acid dilactone containing 0.5 wt % succinic anhydride was added to 67 g of liquid methylhexahydrophthalic anhydride containing 30 wt % and uniformly mixed at 70°C to obtain a liquid acid anhydride mixture. The viscosity of this product at 20°C was 170 centipoise.

Furthermore, 100 parts by weight of the obtained liquid acid anhydride mixture was added to 100 parts by weight of Epicote 828 (trade name of Ciel Chemical Co., Ltd., Epibis type epoxy resin, epoxy equivalent weight 185), and 2-ethyl chloride was added as a curing accelerator. -1.0 parts by weight of 4-methylimidazole was added, mixed well, and heated at 120°C for 3 hours and at 150°C.
A cured product was obtained by heating at ℃ for 15 hours. The obtained cured product was subjected to a tensile test using a No. 1 test piece based on JISK 7113 tensile test method for plastics. As a result, the elongation was 14.5% and the tensile strength was
It was 910Kg/ ^cm2 . Further, the hardness was 42 according to the Barcol hardness tester (GY943-1).

Example 2 Liquid methyltetrahydrophthalic anhydride (4-
A mixture of 61% by weight of methyl- ^{Δ 4 -tetrahydrophthalic} anhydride and 39% by weight of 3-methyl-Δ 4 -tetrahydrophthalic anhydride was added to 190% by weight in the presence of polyphosphoric acid.
33 g of 4-ketopimelic acid dilactone containing 0.5% by weight of succinic anhydride was added to 67 g (obtained by heating at 70° C. for 3 hours) and mixed uniformly at 70° C. to obtain a liquid acid anhydride mixture. The viscosity of this product at 20°C was 185 centipoise, and no crystal precipitation was observed even after it was left at room temperature for one week. Furthermore, 100 parts by weight of the obtained liquid acid anhydride was added to 100 parts by weight of Epicote 828, and a cured product was prepared in exactly the same manner as in Example 1, and a tensile test was conducted. As a result, the growth was 13.1%. The tensile strength was 890Kg/ ^cm2 .

The barcol hardness was 41.

Comparative Example 1 A cured product was prepared in exactly the same manner as in Example 1, except that polyazelaic acid polyanhydride (melting point 56°C) was used in place of 4-ketopimelic acid dilactone, and a tensile test was conducted. As a result, the growth was 9.7%. The tensile strength was 670Kg/ ^cm2 . The Bacall hardness was 16.

The epoxy resin curing agent according to the present invention can impart sufficient hardness and flexibility to the epoxy resin curing agent.

Claims (1)

[Scope of Claims] 1. An epoxy resin curing agent comprising an acid anhydride mixture containing 95 to 30% by weight of an alicyclic or aromatic polycarboxylic acid anhydride and 5 to 70% by weight of dilactone 4-ketopimelate. 2. The epoxy resin curing agent according to claim 1, wherein the alicyclic or aromatic polycarboxylic acid anhydride is liquid. 3. The epoxy resin curing agent according to claim 2, wherein the alicyclic polycarboxylic anhydride is methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, or a mixture thereof. 4. The epoxy resin curing agent according to claim 2, wherein the succinic anhydride contained in the acid anhydride mixture is 1% by weight or less.