The object of the invention is to provide a shoe press belt which has an excellent strength while the variation in strength among its parts being suppressed, and to provide a method for producing such a shoe press belt. Provided is a shoe press belt for use in a papermaking machine comprising at least one resin layer comprising polyurethane resin, wherein the polyurethane resin comprises as a component a polycarbonate diol comprising one or more unit(s) A expressed by the following formula (1) (wherein R.sup.1 is a branched alkylene group having 3 or more and 20 or less of carbon atoms): ##STR00001##

A polycarbonate resin comprising a structural unit represented by the following formula (1), wherein weight-average molecular weight Mw measured by size-exclusion chromatography using polymethyl methacrylate as a standard sample is 50,000 or larger and 500,000 or smaller:

##STR00001##

A polycarbonate resin comprising a structural unit represented by the following formula (1), wherein weight-average molecular weight Mw measured by size-exclusion chromatography using polymethyl methacrylate as a standard sample is 50,000 or larger and 500,000 or smaller:

##STR00001##

A polycarbonate resin having a high refractive index, a low Abbe number and a high moisture and heat resistance is provided. In an embodiment, a polycarbonate resin including a structural unit represented by general formula (1) below is provided.

##STR00001##

The invention relates to a composition comprising a titanium or zirconium alkoxide or aryloxide, wherein the alkoxy group in the titanium or zirconium alkoxide is a group of formula R-0.sup.− wherein R is an alkyl group having 1 to 4 carbon atoms and the aryloxy group in the titanium or zirconium aryloxide is a group of formula Ar-0.sup.− wherein Ar is an aryl group having 6 to 12 carbon atoms, and wherein the composition additionally comprises 0.1 to 50 wt. % of an organic carbonate, based on the total weight of the composition. Further, the invention relates to a process for preparing such composition, comprising blending such titanium or zirconium alkoxide or aryloxide with an organic carbonate in such amounts that the resulting composition comprises 0.1 to 50 wt. % of the organic carbonate, based on the total weight of the composition. Still further, the invention relates to a process for preparing an aromatic carbonate, such as a diaryl carbonate, using said composition comprising a titanium or zirconium alkoxide or aryloxide; and to a process for making a polycarbonate from the diaryl carbonate thus prepared.

The present invention relates to the use of an aromatic polycarbonate prepared by the transesterification of a bisphenol and a diaryl carbonate and having a viscosity average molecular weight, Mv, of from 22000 to 32000 g/mol, a polydispersity, defined as Mw/Mn, of from 1.8-3.2, a melt-flow index of from 3.0-10 g/10 min as determined in accordance with ASTM D 1238 (1.2 kg, 300° C.), an amount of Fries branching of from 750 to 2500 ppm, for the manufacture of bottles having a volume of at least 15 liter by means of an injection blow moulding or an extrusion blow moulding process.

The purpose of the present invention is to provide a thermoplastic resin that has a high refractive index and enables low birefringence and balanced heat resistance and moldability. This thermosetting resin includes repeating units represented by formula (1). (In the formula, the rings Z are the same or different and represent an aromatic hydrocarbon ring, R.sup.1 and R.sup.2 independently represent a C1-C12 hydrocarbon group optionally including a hydrogen atom, a halogen atom, and an aromatic group, Ar.sup.1 and Ar.sup.2 represent a C6-C10 aromatic group optionally having a substituent, L.sup.1 and L.sup.2 independently represent a divalent linking group, j and k independently represent an integer of 0 or more, m and n independently represent 0 or 1, and W is at least one selected from the groups represented by formulae (2) and (3).) (In the formula, X represents a divalent linking group.)

The purpose of the present invention is to provide a thermoplastic resin that has a high refractive index and enables low birefringence and balanced heat resistance and moldability. This thermosetting resin includes repeating units represented by formula (1). (In the formula, the rings Z are the same or different and represent an aromatic hydrocarbon ring, R.sup.1 and R.sup.2 independently represent a C1-C12 hydrocarbon group optionally including a hydrogen atom, a halogen atom, and an aromatic group, Ar.sup.1 and Ar.sup.2 represent a C6-C10 aromatic group optionally having a substituent, L.sup.1 and L.sup.2 independently represent a divalent linking group, j and k independently represent an integer of 0 or more, m and n independently represent 0 or 1, and W is at least one selected from the groups represented by formulae (2) and (3).) (In the formula, X represents a divalent linking group.)

The present disclosure provides a crystalline polythiocarbonate and a preparation method thereof. The crystalline polythiocarbonate is a random copolymer and includes five structural units L1 to L5 as shown in the following formula. The method includes carrying out a polymerization reaction natively or in solution using carbon disulfide, ethylene oxide, selectively added third monomer, initiator, Lewis acid, selectively added chain transfer agent, and selectively added solvent as raw materials. This method provides a new way for high value-added application of carbon disulfide and ethylene oxide by using inexpensive carbon disulfide and ethylene oxide as monomers; the product is a random copolymerized crystalline polythiocarbonate with novel structure, which has various chain link structures and excellent mechanical properties, processing properties and degradability.

In an embodiment, a melt polymerization process comprises melt polymerizing a carbonate compound and a dihydroxy compound in the presence of a catalyst composition to form a polycarbonate; and adding an end-capping agent comprising a mono-phenolic compound to the polycarbonate, wherein the adding of the end-capping agent comprises at least one of adding the end-capping agent just upstream of a final polymerization unit, adding the end-capping agent directly into the final polymerization unit, and adding the end-capping agent downstream of the final polymerization unit; wherein a molecular weight of the polycarbonate increases by less than 10% downstream of the final polymerization unit.