15  4,118,377  16  an alkali metal salt of an organic Bronsted acid having a  pk$_{0 }$ in the range of about 4 to 6, an alkali metal cyanide  and an alkali metal carbonate.  7. The process of claim  6  wherein the reaction is 5  carried out in an aprotic solvent having a dielectric  constant in the range of  35 to 45.  8.  The process of claim  7  wherein the solution of the  bis-maleimide of increased molecular weight is treated  with a liquid which is a non-solvent for the bis-malei› mide to precipitate a solid product, and the solid prod› uct is isolated.  15.  The process of claim  13  wherein the bis-malei› mide has the formula: •  9.  The process of claim  1  wherein  n  is 0.  10.  The process of claim  1  wherein  n  is 1 to 20.  11.  The process of claim  1  wherein each  R$_{1 }$ is hydro- gen.  12.  The process of claim  1  wherein  Y  is  -0-.  13.  The process of claim  1  wherein each  R$_{1 }$ is hydro- gen and  Y  is  -0-.  14.  The process of claim  13  wherein the bis-malei› mide has the formula:  wherein  R$_{2 }$is -CH$_{2}$-, -0-, or -S0 2 - and  y  is a positive integer of 1 to 3.  * * * * *  0  0  II  II  [}-O<I  II  II  0  0 