PURPOSE: To improve the impregnating property between windings by hardening in a short period by a method wherein, after methyltetrahydrophthalic anhydride has been brought into a stereoisometric state as an acid anhydride, an insulating treatment is conducted at the room temperature obtained by bringing into a structurally stereoisometric state using a composition in which a liquid acid anhydride mixture is used.
CONSTITUTION: By heating methyltetrahydrophthalic anhydride (Me-THPA) in a non-catalytic state or in a state having a basic catalizer, the Me-THPA can be brought into a three-dimensional geometric somerism without generation of the movement of double coupling. Subsequently, said Me-THPA is heated up together with an acid catalyst, and it is brought into a structually stereoisometric state by moving the double coupling of a cyclohexane ring. After the Me-THPA has been brought into a stereoisometric state, it is an indispensable condition that the Me-THPA is formed into a state of structural isomerization, and when the order of isomerization is reversed, the impregnating property of the material is deteriorated, its hardening becomes non-uniform, it is partially colored, the irregularity is generated in physical properties, and the above-mentioned reverse order is undesirable.
AKIMA TOSHIO
URUNO MICHIO
NAKAHARA TAKESHI
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