JPS6227096B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to heat-curable epoxy resin compositions, particularly compositions useful for adhesives, paints, and the like. In recent years, adhesives and paints for steel plates are required to have active rust prevention functions in addition to their own functions. However, heavy metals such as lead and chromium contained in ordinary anti-rust pigments are a social problem from the standpoint of safety and health for the human body, and there is a trend towards not using them. Further, such rust-preventing pigments (for example, red lead, zinc chromate, etc.) are colored, and there is a problem in that their uses are limited. Therefore, the present inventors have developed a heat-curable epoxy resin composition (e.g., adhesive or paint) consisting of an epoxy resin and a latent curing agent that maintains the adhesive function, has low toxicity for human storage, and has a preventive effect. After conducting extensive research to develop a composition with excellent rust resistance, it was discovered that by incorporating heat-dehydrated phosphate, the above-mentioned problems could be overcome and the desired composition with excellent rust prevention properties could be obtained. This finding led to the completion of the present invention. That is, the present invention provides a heat-curable epoxy resin composition characterized in that a dehydrated phosphate is blended into a composition comprising an epoxy resin and a latent curing agent. As the epoxy resin used in the present invention, ordinary ones known in the art may be used, such as glycidyl ether type, glycidyl ester type,
Examples include glycidylamine type, linear aliphatic epoxide type, alicyclic epoxide type, etc., and one type or a mixture of two or more of these types is used.
In particular, glycidyl ether type liquids are preferred. In the case of solid epoxy resin, it can be used by dissolving it in a high boiling point plasticizer, but if it is dissolved in an organic solvent such as an ester or alcohol type, heating and curing it at 100℃ or higher will cause the organic solvent to volatilize. This causes foaming, which impedes the performance of the cured product. The latent curing agent used in the present invention is a normal curing agent that exhibits a curing effect when heated, and is generally
Those activated in the temperature range of 80 to 250°C may be used. Specific examples of such curing agents include dicyandiamide, 4,4'-diaminodiphenylsulfone, imidazole derivatives (2-n-heptadecyl imidazole, etc.), isophthalic acid dihydrazide, N·N-dialkyl urea derivatives, N·N- Examples include dialkylthiourea derivatives and melamine derivatives, and one or a mixture of two or more of these may be used depending on desired curing conditions and physical properties.
The amount used is usually selected in the range of 1 to 30 parts per 100 parts (parts by weight, the same applies hereinafter) of the epoxy resin. The dehydrated phosphate used in the present invention refers to a phosphate that has been heated in advance at a temperature of 100°C or higher to dehydrate the water in the molecule. Examples of the phosphate include aluminum salts, zinc salts, etc. Specifically, aluminum dihydrogen tripolyphosphate (AlH ₂ P ₃ O ₁₀・2H ₂ O) or zinc phosphate (Zn ₃ (PO ₄ ) ₂・nH ₂ O, n=2~
4) etc. By heating and dehydrating these hydrous phosphates in advance, it is possible to prevent foaming caused by volatilization of water during curing of the composition. Particularly preferred are those with a water content of 0.5% (weight %, hereinafter the same) or less that has been dehydrated by heating at a temperature of 150 to 200° C. for 30 minutes or more. The amount of these dehydrated phosphates to be used may be selected within the range of 5 to 30%, preferably 10 to 20%, based on the total amount of the composition. If it is less than 5%, there is a problem in rust prevention, and if it exceeds 20%, the cured physical properties tend to become weak. The heat-curable epoxy resin composition according to the present invention is composed of the above-mentioned epoxy resin, a latent curing agent, and a dehydrated phosphate in a predetermined ratio. calcium carbonate, clay, talc, silica, etc.), conductivity imparting agents (metal powder, carbon, ferrite, etc.),
Appropriate amounts of pigments and the like may be added and blended. According to the composition of the present invention having the above configuration,
At a curing temperature of 130 to 200℃, it is possible to obtain a cured product that does not foam due to water volatilization and has the desired physical properties with excellent rust prevention properties, and is mainly used for adhesives and paints for steel plates, as well as for base rust prevention treatment. It can be applied as an agent. In particular, when used as an adhesive, it is useful for bonding inner panel steel plates and outer panel steel plates, for example, in automobile body assembly and bonding. Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example 1 Compounding composition part Epoxy resin (manufactured by Yuka Ciel Epoxy Co., Ltd., Epicoat 828) ......80 Reactive diluent (manufactured by Nitto Kasei Co., Ltd., Eponite 012)
………20 Latent curing agent (dicyandiamide) ………7 Benzoguanamine ………10 Calcium carbonate ………10 Aluminum dihydrogen tripolyphosphate (180℃×30
Dehydrated by heating for 1 minute, moisture content 0.5% or less) ......10 Carbon Black ......5 The above components are sequentially put into a kneader, stirred and mixed, dispersed and mixed using three rolls, and then degassed under reduced pressure to form epoxy. Prepare a resin composition. Example 2 An epoxy resin was prepared in the same manner as in Example 1, except that 15 parts of zinc phosphate (heat-dehydrated at 200°C for 30 minutes, water content 0.4%) was used instead of 10 parts of heat-dehydrated aluminum dihydrogen tripolyphosphate. Prepare the composition. Comparative Example 1 An epoxy resin composition is prepared in the same manner as in Example 1, except that 15 parts of undried zinc phosphate with a moisture content of 2.0% is used instead of 10 parts of heat-dehydrated aluminum dihydrogen tripolyphosphate. Comparative Example 2 In Example 1, undried aluminum dihydrogen tripolyphosphate with a moisture content of 2.0% was used instead of 10 parts of heated and dehydrated aluminum dihydrogen tripolyphosphate.
An epoxy resin composition is prepared in the same manner except that 10 parts are used. The compositions of the above examples and comparative examples, respectively,
It is applied to a steel plate and then heated and cured at 190°C for 30 minutes to form a cured product. The cross section of the cured product was observed for foaming properties and tested for adhesion and rusting properties, and the results are shown in Table 1.

【table】

[Table] From the results in Table 1, it was confirmed that the compositions of the present invention according to Examples had excellent rust prevention properties, no foaming was observed in the cross section of the cured product, and desired physical properties were obtained without deterioration of physical properties. It will be done.

Claims (1)

[Scope of Claims] 1. A heat-curable epoxy resin composition characterized in that a dehydrated phosphate is blended into a composition comprising an epoxy resin and a latent curing agent. 2. The composition according to item 1, wherein the phosphate is selected from aluminum salts and zinc salts. 3. The composition according to item 1 or 2 above, wherein the amount of the dehydrated phosphate used is 5 to 30% by weight. 4. The composition according to item 1, 2 or 3, wherein the dehydrated phosphate has a water content of 0.5% by weight or less.