Abstract: The present invention provides a preparation method of polyimide, comprising the following steps: a) carrying out a dehydration polymerization reaction on a diamine and an anhydride of an organic acid in a non-polar solvent to obtain a mixture, the non-polar solvent being one or more of arene, aliphatic hydrocarbon, halogenated arene and halogenated aliphatic hydrocarbon, and the anhydride of the organic acid being one or more of dianhydride and single anhydride: and b) filtering the mixture obtained in step a) and drying to obtain the polyimide. In the present invention, the dehydration polymerization reaction between the diamine and the anhydride of the organic acid can be carried out directly in the non-polar solvent to obtain the polyimide which cannot be dissolved in the non-polar solvent. Therefore, polyimide powder with fine particles can be obtained by directly filtering and drying the reaction mixture without washing.

Abstract: The present invention provides a preparation method of polyimide, comprising the following steps: a) carrying out a dehydration polymerization reaction on a diamine and an anhydride of an organic acid in a non-polar solvent to obtain a mixture, the non-polar solvent being one or more of arene, aliphatic hydrocarbon, halogenated arene and halogenated aliphatic hydrocarbon, and the anhydride of the organic acid being one or more of dianhydride and single anhydride: and b) filtering the mixture obtained in step a) and drying to obtain the polyimide. In the present invention, the dehydration polymerization reaction between the diamine and the anhydride of the organic acid can be carried out directly in the non-polar solvent to obtain the polyimide which cannot be dissolved in the non-polar solvent. Therefore, polyimide powder with fine particles can be obtained by directly filtering and drying the reaction mixture without washing.

Abstract: Polythioetherimides and a producing method thereof. The method is comprised of using monosubstituted phthalic anhydride isomer as raw material, reacting it with disubstituted amine to produce disubstituted phthalimide, allowing coupling reaction between the obtained phthalimide and an alkali metal sulfide or sulfur to produce polythioetherimides.

Abstract: The present invention discloses a process for preparing dibasic salt of bisphenol from bisphenol and alkali, wherein the bisphenol and the alkali are reacted in a reaction medium consisting of an organic solvent or an aqueous inorganic salt solution, and then through filtration, a highly pure dibasic salt of bisphenol is directly obtained at a yield of higher than 90%.

Abstract: Biphenyl tetracarboxlic acid esters and derivatives thereof are prepared by the coupling reaction of 4-halogen substituted o-benzenedicarboxylic acid ester, carried out in an aprotic polar solvent in the presence of a pre-prepared triphenylphosphine-nickel chloride or trialkylphosphine-nickel chloride catalyst, zinc powder as the reducing agent, and an alkali metal halide promoting agent. The ester may be hydrolyzed in basic solution to afford the corresponding acid. The acid may be heated or boiled with acetic anhydride to afford the biphenyl dianhydride.