Abstract: An acrylonitrile solution of maleimide manifesting transparency, precluding coloration and opacification during the course of handling, and excelling in stability, a method for the preparation of the acrylonitrile solution, and an acrylonitrile based copolymer obtained by using the acrylonitrile solution are provided.The acrylonitrile solution of maleimide is such that, when it is subjected to a forced coloration test, the differences .DELTA.L, .DELTA.a, and .DELTA.b values (invariably as absolute values) each between L, a, and b values before and after the test are respectively not more than 5, not more than 5, and not more than 10. The acrylonitrile solution of maleimide is prepared by lowering the water content in the acrylonitrile solution to a level of not more than 0.

Abstract: The present invention provides a process for producing a ketone represented by a general formula RCOR' (wherein R is a C.sub.1 -C.sub.17 alkyl group, a C.sub.7 -C.sub.12 aralkyl group, a C.sub.7 -C.sub.12 aryl group or a C.sub.5 -C.sub.8 cycloalkyl group; R' is a C.sub.1 -C.sub.17 alkyl group, a C.sub.7 -C.sub.12 aralkyl group, a C.sub.7 -C.sub.12 aryl group or a C.sub.5 -C.sub.8 cycloalkyl group; R and R' may the same), which process comprises reacting a carboxylic acid represented by a general formula RCOOH (wherein R has the same definition as given above) with a carboxylic acid represented by a general formula R'COOH (wherein R' has the same definition as given above) in a gas phase in the presence of a catalyst containing at least either of MgO and CaO.The process allows for production of an intended ketone at a high yield at high productivity.

Abstract: A process for producing a high-molecular-weight polydioxolane, which includes the steps of: polymerizing 1,3-dioxolane using a polymerization catalyst comprising a heteropolyacid and a ketone; and neutralizing the resulting polymerization reaction product using an organic amine and/or ammonia. A hydrophilic film, which includes a resin including a polydioxolane and having a particular molecular weight and has a particular crystallinity and a particular spherulite's size. A film crumbly in cold water is produced by forming a film under particular forming conditions from a resin including a polydioxolane and having a particular molecular weight, or by subjecting an already formed film to particular thermal hysteresis.