| 摘要 |
PURPOSE:A low-thermal expansion resin material which, like inorganic materials such as metal, ceramics, glass, has an extremely low coefficient of thermal expansion and excellent mechanical properties, comprising a polyimide having specified chemical structural units. CONSTITUTION:A low-thermal expansion polyimide having chemical structural units of formula I [wherein Ar1 is a bivalent organic group selected from the groups of formula II (wherein R is alkyl, fluoroalkyl, alkoxy, fluoroalkoxy, acyl or halogen, l is 0-3 and m is 0-2), Ar2 is a tetravelent organic group selected from the groups of formula III (wherein R, l and m are as defined above and n is 0-4)]. This polyimide can be obtained by reacting an aromatic diamine or diisocyanate (e.g., 2,5-diaminopyridine or its diisocyanate) with an aromatic tetracarboxylic acid or its derivative (e.g., pyromellitic acid or its anhydride, chloride or ester).
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