The present disclosure relates to a method for preparing a polyalkylene carbonate. More specifically, provided is a method for preparing a polyalkylene carbonate in which after polymerization of polyalkylene carbonate, a mixture from which unreacted carbon dioxide and residual catalyst have been removed is charged into a stripper to remove the unreacted epoxide compound, and then heat-exchanged before removing the solvent to increase the temperature of the mixture stream to the maximum level, which is subjected to a heating step, following by a solvent removal step, whereby the amount of steam required in the heating step is reduced, side reactions due to unreacted epoxide compounds are prevented, and steam energy can be reduced in the solvent removal step.

The present application addresses the problem of providing a new method for producing a polycarbonate resin having excellent properties. This problem has been solved by providing a method for producing a polycarbonate resin containing a constituent unit derived from an aromatic dihydroxy compound represented by formula (1). The method includes polymerizing the aromatic dihydroxy compound represented by formula (1). During the polymerization, a raw material substance is used in which the concentration of compounds represented by formula (2), which are impurities, is 80 ppm or less relative to the total weight of the aromatic dihydroxy compound represented by formula (1) and the compounds represented by formula (2). (In formula (1) and formula (2), R.sub.1 to R.sub.3, X, a, b, m and n are as described in the description of the present application.)

##STR00001##

The invention provides a process for producing diol, characterized in that the process comprises the steps of (1-i) addition of alkylene oxide and carbon dioxide to an H-functional starter substance in the presence of a catalyst to obtain polyether carbonate polyol and cyclic carbonate, (1-ii) separation of the cyclic carbonate from the resulting reaction mixture from step (1-i), (1-iii) hydrolytic cleavage of the cyclic carbonate separated from step (1-ii) into carbon dioxide and diol, (1-iv) optionally distillative purification of the diol from step (1-iii), wherein (η) to the cyclic carbonate from step (1-ii) and/or to the diol a Lewis or Brønsted acid, excluding carboxylic acids having a pKa of >3.0, and optionally water are added and the reaction mixture obtained is optionally neutralized.

Alkylene carbonates are removed from polyether-carbonate polymers by contacting the polyether-carbonate with an absorbent at a temperature of 30 to 150° C. The process is effective and inexpensive. The purified polyether-carbonate is useful for making polyurethanes as well as in many other applications.

The present invention relates to a process for producing a polycarbonate from a diphenol or two or more different diphenols and a carbonyl halide by the interfacial process. It is a feature of the process according to the invention that it is carried out on the basis of a chlorohydrocarbon or a mixture of a mixture of two or more chlorohydrocarbons using an organic solvent. An organic solvent is also provided.

The present invention provides a process for removing gaseous constituents dissolved in liquid reaction mixtures in the copolymerization of alkylene oxide and carbon dioxide, characterized in that (η) prior to decompression the liquid reaction mixture has a pressure of 5.0 to 100.0 bar (absolute), wherein the following process stages are performed in the specified sequence: (i) decompression of the reaction mixture by at least 50% of the prevailing pressure, (ii) subsequent droplet separation with first defoaming and (iii) subsequent bubble separation with second defoaming to clarify the liquid phase, wherein the process stages (i) to (iii) are performed one or more times until the resulting reaction mixture has a pressure of 0.01 to <5.00 bar (absolute), and also a process for preparing polyethercarbonate polyols comprising the process stages (i)-(iii).

The present disclosure relates to a method for treating a solvent in wastewater generated in a polycarbonate production process. More specifically, the present disclosure relates to a method for treating a solvent in wastewater generated in a polycarbonate production process, which can easily recover a high purity solvent regardless of the concentration of the solvent by using a membrane distillation method to reuse it, and contribute to energy savings.

The present disclosure relates to a method for separating an organic zinc catalyst dispersed in a polyalkylene carbonate resin solution by filtering the polyalkylene carbonate resin solution using a composite filtering membrane, which is a composite material comprising a hydroxyl group-containing material and polyolefin material and has a form in which one or both surfaces of the polyolefin material is coated with the hydroxyl group-containing material.

A process for preparing polyol, wherein, in a first process stage, a diol is prepared by a process comprising: (1-i) adding alkylene oxide and carbon dioxide onto an H-functional starter substance in the presence of a catalyst to obtain polyethercarbonate polyol and a cyclic carbonate, (1-ii) separating the cyclic carbonate from the resulting reaction mixture from step (1-i), (1-iii) hydrolyzing the cyclic carbonate separated from step (1-ii) to carbon dioxide and diol, and (1-iv) optionally purifying the diol resulting from step (1-iii) by distillation.

The present invention relates to a process for producing a polycarbonate from a diphenol or two or more different diphenols and a carbonyl halide by the interfacial process. It is a feature of the process according to the invention that it is carried out on the basis of a chlorohydrocarbon or a mixture of a mixture of two or more chlorohydrocarbons using an organic solvent. An organic solvent is also provided.