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 &Dgr;L, &Dgr;a, &Dgr;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 0.1% by weight, or causing the acrylonitrile solution to permit coexistence therein of a polymerization inhibitor and lowering the water content in the acrylonitrile solution to a level of not more than 0.3% by weight.

Abstract: In manufacturing a thermoplastic copolymer by copolymerizing an aromatic vinyl monomer, a vinyl cyanide monomer, and, when necessary, a vinyl monomer (a) copolymerizable with the above two monomers, at least a part or all of the vinyl cyanide monomer is put in a reactor and copolymerizing reaction is started, and a weight of an unreacted portion of the aromatic vinyl monomer is caused to become greater than a weight of an unreacted portion of the vinyl cyanide monomer when all the monomer components are put in the reactor. By doing so, a ratio of the vinyl cyanide monomer in a structural unit of a thermoplastic copolymer produced at latter stages of the copolymerizing reaction is lowered. Thus, the present invention is capable of providing a thermoplastic copolymer which has excellent physical properties such as good heat resistance and good mechanical strength and is hard to discolor, as well as a manufacturing method thereof.

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: This invention provides a maleimide-based copolymer in which, because its molecular weight-retention ratio at high temperature is high, deterioration of physical properties by heating is little. Also, this invention provides a process wherein a maleimide-based copolymer is arranged so as not to heat more than necessity and thereby a maleimide-based copolymer containing only a small amount of residual volatile components is efficiently obtained without deterioration of physical properties. The maleimide-based copolymer is such as having a glass transition temperature of 170.degree. C. or higher, a weight-average molecular weight of 100,000 to 500,000, and a molecular weight-retention ratio of 90% or more when heated at 280.degree. C. for 10 minutes.

Abstract: A desulfurization process for hydrogen sulfide-containing gases, which comprises contacting an alkaline aqueous medium containing a naphthoquinone sulfonate, a water-soluble compound of at least one polyvalent metal selected from the group consisting of iron, manganese, vanadium and copper, and a water-soluble high molecular compound having weight-average molecular weight of from 300 to 50,000 with a hydrogen sulfide-containing gas thereby causing the hydrogen sulfide in said gas to be absorbed by said aqueous medium and subsequently contacting said aqueous medium now containing the absorbed hydrogen sulfide with a molecular oxygen-containing gas thereby separating elementary sulfur from said hydrogen sulfide.