| 摘要 |
<p>PURPOSE:To obtain the titled film which has good heat resistance, electrical and mechanical properties and is suitable for use in electronic parts etc., by casting an uncyclized polyamic acid solution of a specified intrinsic viscosity on a base material, requlation its concentration, cyclizing it partially for molding and increasing a cyclization ratio by heating after solvent removal. CONSTITUTION:A film is formed by casting a stock solution principally comprising a solution of a 10-45wt% concentration composed of a polar amide solvent (e.g. dimethylacetamide) and a substantially uncyclized polyamic acid (e.g. a reaction product of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride) of an intrinisic viscsity of at least 0.4dl/g on a base material, removing part of the solvent to increase the polymer concentration to at least 50% and the cyclization ratio of the polymer to at least 30%. Then, the solvent is further removed in an aqueous medium to lower the solvent content below 10% and the film is heated above 200 deg.C to raise the cyclization ratio above 90%, thereby obtaining the purpose film.</p> |
