JPH0341513B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to vulcanized adhesive formulations. More specifically, the present invention relates to a vulcanized adhesive formulation that is effectively used for adhesion between fluororubber and metal. Conventionally, organic silane-based adhesives have been used to bond fluorocarbon rubber and metals, but when this adhesive is used, there are problems with heat resistance after bonding, especially for secondary If the temperature of the subsequent vulcanization exceeds 200°C, hydrogen fluoride generated from the fluororubber will most likely cause peeling on the metal surface. The inventor has discovered that even if heat treatment is performed at high temperatures,
As a result of various studies in search of an adhesive formulation that would provide sufficient adhesive strength between fluorocarbon rubber and metal, we developed a vulcanized adhesive formulation containing polyamideimide resin, novolac type phenolic resin, and hexamethylenetetramine curing agent. It has now been discovered that the above object can be fully achieved. Therefore, the present invention relates to a vulcanized adhesive composition for adhesion between fluororubber and metal, which contains these components. In this way, when adhesion is carried out using the vulcanizable adhesive composition according to the present invention, various vulcanizing agents such as amine-based, polyol-based, peroxide-based, etc. Regardless of the type of agent used, it has stable adhesion and high heat resistance, and also effectively prevents corrosion of metals due to hydrogen fluoride generated from fluorine gas during heating. It has a remarkable effect of obtaining. Polyamide-imide resin is produced by introducing an amide bond into the main chain of the polyamide resin, and this bond adds flexibility to the polyimide resin and improves processability, and is produced, for example, as follows. Novolac-type phenolic resin is obtained as a rosin-like substance that is soluble in organic solvents such as alcohol and acetone by heating phenol and formalin in the presence of an acid catalyst, and adding hexamethylenetetramine as a curing agent to this. By heating, an insoluble and infusible phenolic resin is formed.
In the present invention, a two-stage phenolic resin having a melting point of about 100° C. and a molecular weight of about several tens of thousands is generally used. The vulcanized adhesive formulation according to the present invention contains such a polyamide-imide resin, a novolac-type phenolic resin, and hexamethylenetetramine as a curing agent thereof, and they contain a novolac-type phenolic resin based on 100 parts by weight of the polyamide-imide resin. The type ferol resin is about 5 to 50 parts by weight, preferably about 20 to 40 parts by weight.
Hexamethylenetetramine is used in a ratio of about 5 to 20 parts by weight per 100 parts by weight of novolak type phenolic resin. If the ratio of the novolac type phenolic resin to the polyamide-imide resin is less than this, the bonding force with fluorocarbon rubber etc. will be weak and the reactivity will be poor. This is because the curing speed of polyamide-imide resin is very slow, so before it starts bonding with rubber etc.
This is thought to be because the adhesive layer is fluidized. on the other hand,
If the proportion is higher than this, the proportion of the polyamide-imide resin will decrease, resulting in poor heat resistance. Further, the ratio of hexamethylenetetramine to the novolak type phenol resin is the same as that conventionally used as a curing agent, but it is preferable that the ratio used is as small as possible within that range. A vulcanized adhesive composition containing each of these ingredients is generally prepared and used in the form of an organic solvent solution. Any organic solvent can be used as long as it can dissolve these components, but it is particularly preferred to use dimethylformamide alone. For bonding, this vulcanized adhesive composition solution is applied to the metal, heated to approximately 130 to 150°C to dry, and then heated to approximately 230 to 250°C for approximately 10 to 30 minutes. Then, a baking process is performed. Thereafter, it is bonded to an unvulcanized compound of fluororubber, and is vulcanized under pressure using a mold or the like while heating to approximately 160 to 200°C, which is the vulcanization temperature of fluororubber. Metals include mild steel, aluminum, aluminum die-casting, yellow steel, stainless steel,
Zinc etc. are used. Further, as an unvulcanized compound of fluororubber, for example, the following compound is used. Compounding example A Fluororubber (DuPont product Viton E60C)
100 parts by weight Ca (OH) ₂ 6 〃 MgO 3 〃 MT Carbon Black 30 〃 Compounding example B Fluororubber (DuPont product Viton A)
100 parts by weight Resurge (lead oxide) 15 Vulcanizing agent (DuPont product Diamond No. 4)
3 〃 MT Carbon Black 20 〃 Compounding example C Fluorine rubber (Daikin product Daiel G902)
100 parts by weight vulcanizing agent (NOF Perhexa 25B40)
1.5 〃 Triallylisocyanurate 4 〃 MT Carbon Black 20 〃 The adhesive between fluororubber and metal obtained by the present invention does not cause peeling on the metal surface even when subjected to high heat treatment. It has the remarkable effect of almost no peeling on the metal surface, which often occurs with metals with low corrosion resistance, such as aluminum, copper, and zinc. Next, the effects of the present invention will be explained with reference to Examples. Example 1 Polyamide-imide resin (Mitsui Petrochemical Kerimide 500) 100 parts (weight, same hereinafter), novolac type phenolic resin (melting point 100°C, molecular weight several hundred ~
20 parts of a mixture of tens of thousands) and 2 parts of hexamethylenetetramine are dissolved in 120 parts of dimethyformamide,
This solution-form vulcanizable adhesive formulation was applied to a mild steel plate treated with a zinc phosphate coating. After drying at 130°C for 10 minutes, baking treatment was performed at 230°C for 10 minutes. The unvulcanized fluororubber compound of Formulation Example A was bonded to a mild steel plate treated as described above in accordance with the JISK-6301 90°C peel test method, and was then bonded to a mild steel plate treated as described above at 180°C using a mold. Pressure vulcanization was performed for 1 minute, and then the vulcanized adhesive was heat-treated at 200° C. for 22 hours. Example 2 In Example 1, polyamideimide resin 100
A solution vulcanizable adhesive formulation was used consisting of 40 parts of novolac-type phenolic resin, 4 parts of hexamethylenetetramine, and 40 parts of dimethylformamide. Comparative example In Example 1, polyamideimide resin 100
A resin solution consisting of 100 parts and 100 parts of dimethylformamide was used as the adhesive. For the adhesives of each of the above Examples and Comparative Examples, the peel force and remaining rubber area (excluding the remaining rubber, peeling between the adhesive and rubber) were measured according to the JISK-6301 90°C peel test method. did. The results obtained are shown in the following table. 【table】

Claims (1)

[Scope of Claims] 1. A vulcanized adhesive composition for bonding fluororubber and metal, comprising a polyamideimide resin, a novolak type phenolic resin, and a hexamethylenetetramine curing agent. 2. A vulcanized adhesive formulation according to claim 1 prepared in the form of an organic solvent solution.