c 2 mmhg 146 u00b0 c 2 mmhg str14 while operating under nitrogen 6 3 g of pyromellitic dianhydride and 34 8 g of a mixture of n n dimethylacetamide and xylene mixing ratio 95 5 by weight were introduced into a flask equipped with stirrer addition funnel and thermometer and were stirred the addition funnel was charged with 11 1 g of the organosilicon compound prepared in example 1 and 34 8 g of a mixture of n n dimethylacetamide and xylene mixing ratio 9 5 by weight this diaminosiloxane solution was added dropwise from the addition funnel over a period of 29 minutes during which time the reaction temperature varied from 29 u00b0 c to 37 u00b0 c this was followed by stirring for 3 5 hours at 37 u00b0 c to 26 u00b0 c a dean stark receiver was installed and an azeotropic dehydration was run for 8 minutes at 144 u00b0 c to 146 u00b0 c cooling to room temperature and filtration yielded 77 3 g of a polyimide solution when the infrared absorption spectrum of this solution was measured the sih signal at 2130 cm 1 and the imide group signals at 1780 cm 1 and 1720 cm 1 were observed when this polyimide solution was held for 6 months at room temperature it remained a homogeneous solution and did not manifest such changes as gel production precipitate development or viscosity increase this polyimide solution was coated on a silicon wafer glass plate and aluminum sheet and in each case a polyimide film was produced by curing for 3 hours in a 160 u00b0 c oven a pressure cooker test was then run for 20 hours at 121.