JPS6320252B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention comprises an epoxy resin internally plasticized with caprolactone, a polycarboxylic acid anhydride,
The present invention relates to an epoxy resin curable composition having excellent flexibility and comprising a curing accelerator. It is well known that a polycarboxylic acid anhydride is blended into an epoxy resin and then heated and cured using a curing accelerator such as amines. This cured product generally has excellent chemical properties, mechanical properties, and thermal properties, and is used in many industrial fields, mainly in electrical parts. However, these cured products are very hard and suffer from a large shrinkage strain during curing, resulting in a lack of flexibility. Therefore, various attempts have been made to provide flexibility.
For example, methods of adding polybutadiene oligomers having carboxyl groups at both ends, acid-type polyester resins having carboxyl groups, polyethers, polyesters, polyamide resins, etc. having hydroxyl groups as flexibility-imparting agents, methods of adding polyether polyols and epichlorohydrin, etc. Various attempts have been made, including the addition of flexible epoxy resins, such as glycidyl ethers. However, all of them result in a decrease in heat resistance, a decrease in chemical resistance, and a decrease in mechanical strength, and cannot be said to be fully satisfactory. The inventors of the present invention have conducted intensive studies on curable epoxy resin compositions having excellent flexibility, and found that by heating and curing epoxy resins modified with caprolactone and polycarboxylic acid anhydrides with a curing accelerator, The inventors have discovered that a curable composition having excellent flexibility can be obtained and have arrived at the present invention. That is, the present invention is a lactone-modified epoxy resin obtained by ring-opening polymerization of 3 to 95 parts by weight of ε-caprolactone to 97 to 5 parts by weight of hydroxyl groups in an epoxy resin having hydroxyl groups, and a polycarboxylic anhydride. The present invention relates to a curable composition containing a curing accelerator. The lactone-modified epoxy resin used in the present invention is extremely flexible because ε-caprolactone undergoes ring-opening polymerization to the hydroxyl groups present in the epoxy resin itself and is directly bonded to the epoxy resin as a polycaprolactone side chain. In addition, it has excellent characteristics as polycaprolactone, such as heat resistance, water resistance, low temperature resistance, and compatibility.
In the case of other additive-type flexibility-imparting agents, compatibility with epoxy resins may be a problem, but in the present invention, any epoxy resin having a hydroxyl group can be used with ε-caprolactone. Denaturation is possible. Therefore, the usefulness of the present invention is extremely large in that flexibility can be imparted to epoxy resin curable compositions used in all industrial fields. Any epoxy resin can be used as long as it has a hydroxyl group in the resin. For example, bisphenol A diglycidyl ether represented by the following structural formula () produced from bisphenol A and epichlorohydrin, An epoxy resin produced from bisphenol A and β-methylepichlorohydrin and represented by the following structural formula (), Furthermore, a flame-retardant epoxy resin produced from 2,6-dibromobisphenol A and epichlorohydrin or β-methylepichlorohydrin, an alicyclic epoxy resin represented by the following structural formula (), (n≧1, R = alkylene group, aromatic group) diglycidyl ester shown by the following structural formula () synthesized from dicarboxylic acid and epichlorohydrin, (n≧1, R=alkylene group, aromatic group) Furthermore, instead of bisphenol A, a glycidyl ether type epoxy resin made from bisphenol F synthesized from formalin and phenol and epichlorohydrin, etc. can be used. The ε-caprolactone reacted with these hydroxyl group-containing epoxy resins is industrially produced by the Bayer-Villiger reaction of cyclohexanone with peracid. It is also possible to copolymerize other cyclic lactones, such as trimethylcaprolactone and valerolactone, with ε-caprolactone, as long as the characteristics of the present invention are not impaired. The ratio of reacting epoxy resin and ε-caprolactone is ε to 97 to 5 parts by weight of epoxy resin.
- 3 to 95 parts by weight of caprolactone, preferably 95 to 30 parts by weight of epoxy resin, 5 to 95 parts by weight of ε-caprolactone
It is 70 parts by weight. If the amount of modification of ε-caprolactone is too small, sufficient flexibility cannot be imparted to the cured product, and if it is too large, the cured product becomes soft. To react ε-caprolactone with an epoxy resin, the temperature is preferably 100 to 240°C, preferably 120°C in the presence of a catalyst.
Perform at ~200°C. This is because if it is lower than 100°C, the reaction rate is low, and if it is higher than 240°C, ε-caprolactone will boil and escape from the reaction system. A catalyst is required for the ring-opening addition reaction of ε-caprolactone to the secondary hydroxyl group of the epoxy resin. Examples of catalysts include titanium compounds such as tetrabutyl titanate, tetrapropyl titanate, and tetraethyl titanate, organic tin compounds such as tin octylate, dibutyltin oxide, and dibutyltin laurate, and stannous chloride, stannous bromide, and stannous iodide. A stannous halide such as 1 tin can be used. In particular, when it is desired to obtain a material with a narrow molecular weight distribution, stannous halides are preferred. The amount of catalyst used varies depending on the reaction temperature, but is generally 0.01 to 1000 ppm, preferably 0.2 to 500 ppm.
It is. The reaction may be carried out without a solvent, or with toluene,
The reaction may be carried out in a solvent without active hydrogen such as xylene. Solvents with ester bonds are not preferred. This is because, during the reaction, a transesterification reaction occurs between the ester bond of the polycaprolactone chain and the solvent, producing polycaprolactone that is not bonded to the epoxy resin. Any polycarboxylic anhydride may be used in the curable composition of the present invention, but commonly used ones include phthalic anhydride, (methyl)tetrahydrophthalic anhydride, (methyl)hexahydrophthalic anhydride, Examples include methylnadic anhydride, chlorendecic anhydride, trimellitic anhydride, pyromellitic anhydride, dodecenylsuccinic anhydride, and the amount used is 0.5 per equivalent of epoxy group.
~1.0 equivalent is used. Any curing accelerator may be used as long as it has a catalytic effect, but commonly used ones include benzyldimethylamine, benzyldiethylamine, cyclohexyldimethylamine,
It is a tertiary amine such as tris(dimethylaminomethyl)phenol, and is used in an amount of 0.05 to 5.0 parts by weight per 100 parts by weight of epoxy resin. In addition, water, alcohols having active hydrogen, carboxylic acids, primary and secondary amine compounds, etc. can also be added as substances having a curing accelerating effect. Furthermore, inorganic compounds such as alumina and silica may be mixed into this mixture as fillers. Further, a flexibility imparting agent known in the art, such as butadiene-acrylonitrile copolymer oligomer, polybutadiene dicarboxylic acid, polycaprolactone, dimer acid, polyether polyol, etc., is further added to this epoxy resin curable composition. You can also. The present invention will be explained in detail with reference to examples below, but the present invention is not limited thereto. In addition, parts in the examples mean parts by weight. Synthesis Example 1 In a four-necked flask equipped with a nitrogen inlet tube, thermometer, cooling tube, and stirring device, epoxy resin Araldite GY-250 (trade name of Ciba Geigy, epoxy equivalent: 180 to 190) manufactured from bisphenol A and epichlorohydrin was used. ) 2000 copies, ε-caprolactone
200 parts and 0.022 parts of tetrabutyl titanate were charged and reacted at 170°C for 8 hours under a nitrogen stream. Unreacted ε-caprolactone was 0.62%. The obtained resin was a viscous liquid having an epoxy equivalent of 207, a viscosity (Gardna) of Z ₄ , an acid value of 0.06, and a hue (Gardna) of 1 or less. Synthesis Example 2 Araldite GY- in the same equipment as Synthesis Example 1.
1,800 parts of 250, 360 parts of ε-caprolactone, and 0.022 parts of tetrabutyl titanate were charged, and the mixture was reacted at 170°C for 8 hours under a nitrogen stream. Unreacted ε-caprolactone was 0.48%. The obtained resin had an epoxy equivalent of 225, a viscosity (Gardna) of Z ₄ , an acid value of 0.05,
It was a viscous liquid with a hue (Gardna) of 1 or less. Example 1 50 parts of the lactone-modified epoxy resin obtained in Synthesis Example 1 was added with methyltetrahydrophthalic anhydride (trade name: Rikaside MH-700, manufactured by Shin Nippon Chemical Co., Ltd.) as a curing agent.
36.5 parts, benzyldimethylamine 0.43 as catalyst
Blend the parts and pre-cure at 100℃ for 2 hours, and then
A curing reaction was carried out at 160°C for 5 hours. Table 1 shows the heat distortion temperature, elongation at break, and strength at break of the cured product.
Shown below. Example 2 Methyltetrahydrophthalic anhydride was added as a curing agent to 50 parts of the lactone-modified epoxy resin obtained in Synthesis Example 2.
33.6 parts, benzyldimethylamine 0.42 as catalyst
The mixture was cured under the same conditions as in Example 1. Table 1 shows the properties of the cured product. Comparative Example 1 40.9 parts of methyltetrahydrophthalic anhydride and 0.45 parts of benzyldimethylamine were blended with 50 parts of Araldite GY-250, an epibis type epoxy resin not modified with ε-caprolactone, and cured under the same conditions as in Example 1. Table 1 shows the properties of the cured product. Comparative Example 2 50 parts of Araldite GY-250, an Epibis type epoxy resin not modified with ε-caprolactone, 40.9 parts of methyltetrahydrophthalic anhydride, and polycaprolactone triol (trade name Plaxel 308, Daicel Chemical Industries) as a flexibility imparting agent. Co., Ltd. products)
12.5 parts of verzyl dimethylamine and 0.52 parts of verzyl dimethylamine were blended, and the mixture was cured under the same conditions as in Example 1. Table 1 shows the properties of the cured product.

[Table] As shown in the Examples and Comparative Examples above, the cured composition of the lactone-modified epoxy resin of the present invention not only has excellent flexibility, but also has better flexibility than when a flexibility-imparting agent is simply added. It has a high heat distortion temperature.

Claims (1)

[Claims] 1 Polycarboxylic acid anhydride and a curing accelerator are added to a lactone-modified epoxy resin obtained by ring-opening polymerization of 3 to 95 parts by weight of ε-caprolactone to 97 to 5 parts by weight of hydroxyl groups in an epoxy resin having hydroxyl groups. An epoxy resin curable composition.