Preparation of polyimide powder

PURPOSE: To prepare, with good reproducibility, polyimide powder suitable for heat compression molding, by heating an amide solvent solution of a biphenyltetracarboxylic acid component and an aromatic diamine component to a specified temp. under stirring. CONSTITUTION: Nearly equimolar amounts of a biphenyltetracarboxylic acid component and an aromatic diamine component are dissolved, at a temp. below 155°C, in an amide solvent in which the formed polyimide is soluble in less than 1wt%. The temp. of the resultant homogeneous solution with a low rotational viscosity is raised quickly to 160W300°C under stirring and is kept within the temp. range to form an aromatic polyimide with a logarithmic viscosity number of 0.2W1 (0.5g/100cc p-chlorophenol at 50°C) which is then precipitated as fine particles. The reaction soln. in which the aromatic polyimide has been precipitated may be aged at 160W300°C for 0.2W20hr to increase th logarithmic viscosity of the precipitated polyimide. COPYRIGHT: (C)1982,JPO&Japio