A process for industrially producing a colorless, transparent polycarbonate with a high molecular weight efficiently by the melt polycondensation of a dihydroxy compound with a carbonic diester through transesterification, which comprises preparing a polycarbonate prepolymer in the first-stage reaction and conducting the polycondensation thereof either under the condition of a residence time ranging from 15 to less than 60 minutes or by using at least one self-cleaning twin-screw paddle extruder in the second-stage reaction.

Process for producing polycarbonate

A crystallized aromatic polycarbonate having a weight average molecular weight of from 6,000 to 200,000 and having a terminal hydroxyl group content of not greater than 0.03% by weight based on the weight of the polycarbonate is effectively produced by first heating a mixture of a dihydroxydiaryl compound comprising at least 85 mole % of a dihydroxydiaryl alkane with a diaryl carbonate to prepare a prepolymer having a weight average molecular weight of from 2,000 to 20,000 and having terminal aryl carbonate groups in an amount of greater than 50 mole %, based on the total number of moles of all the terminal groups of the prepolymer, secondly crystallizing the prepolymer and finally subjecting the crystallized prepolymer to solid-state polymerization. The crystallized aromatic polycarbonate does not contain impurities, is colorless and has excellent properties such as resistance to heat and to boiling water. Therefore, the polycarbonate is advantageously used as engineering plastics.

Method for producing a crystallized aromatic polycarbonate, and a crystallized aromatic polycarbonate obtained thereby

It is a task of the present invention to provide a method for producing a high quality, high performance aromatic polycarbonate (which is colorless and has excellent mechanical properties) from a molten aromatic polycarbonate prepolymer obtained by reacting an aromatic dihydroxy compound with a diaryl carbonate, wherein the polycarbonate can be stably produced on a commercial scale at 1 to 50 t/hr for a long time. In the present invention, this task has been accomplished by a method for producing an aromatic polycarbonate by the melt transesterification process, in which the prepolymer is polymerized by a guide-wetting fall polymerizer device having a specific structure, whereby a high quality, high performance aromatic polycarbonate as mentioned above can be stably produced on a commercial scale at 1 to 50 t/hr for a long time (more than several thousand hours, e.g., more than 5,000 hours) without fluctuation of the molecular weight thereof.

Method for producing an aromatic polycarbonate

A method for producing an aromatic polycarbonate comprises feeding to a feeding zone (having a foraminous plate) at least one polymerizing material selected from the group consisting of a) a molten monomer mixture of an aromatic dihydroxy compound and a diaryl carbonate, and b) a molten prepolymer obtained by a process comprising reacting an aromatic dihydroxy compound with a diaryl carbonate, and allowing the polymerizing material to pass downwardly through the foraminous plate and fall along and in contact with a wire through a wire-wetting fall polymerization reaction zone, thereby effecting polymerization of the polymerizing material during the wire-wetting fall thereof. Colorless and high quality aromatic polycarbonates are thus stably produced at a high polymerization rate for a prolonged period of time, using an apparatus which has excellent sealing properties under high vacuum and maintenance of which is easy.

Wire-wetting fall polymonization process for the production of polycarbonates

Disclosed herein are zeolite compositions comprising structural units of the formulae: 
wherein “B” and “C” are spacer groups comprising C 2 to C 20 hydrocarbyl groups; and R 1 and R 2 independently of each other comprise alkali metal, hydrogen, or C 1 to C 20 alkyl groups. The zeolite compositions further comprise structural units derived from a heteropolyacid compound of the formula: (M 3 ) 3 (M 4 )(M 5 ) 12 O 40 ; where M 3 comprises hydrogen or an alkali metal; M 4 comprises phosphorus or silicon, and M 5 comprises tungsten or molybdenum. Methods for preparing these zeolite compositions are also disclosed. The zeolite compositions are useful as catalysts for producing bisphenols.

Functionalized zeolite compositions and methods for their preparation and use

A process for preparing aromatic polycarbonates from diphenyl carbonate and bisphenol A which comprises effecting preliminary polymerization under limited operational conditions to produce specific polycarbonate prepolymers and then subjecting the specific prepolymers to further polymerization for a shorter residence time thereby obtaining high molecular weight polycarbonates.

Process for preparing aromatic polycarbonates

In a process for producing a stabilized oxymethylene copolymer by heat-melting, at a temperature ranging between the melting point of the copolymer and a temperature 100° C. higher than the melting point in a degassing apparatus in the presence of a heat stabilizer, a crude oxymethylene copolymer of trioxane with a cyclic acetal or cyclic ether, to decompose and eliminate the instable portions of the copolymer, the improvement which comprises using as the degassing apparatus in heat stabilizing the crude oxymethylene copolymer a combination of (A) an extruder and (B) a surface renewing-type mixer, and carrying out the operation by first feeding a crude oxymethylene copolymer to said extruder (A) to heat-melt and decompose 30-90% by weight of the instable portions of the crude copolymer, removing the decomposed gas via a vent provided in said extruder, and thereafter introducing the molten resin continuously to said surface renewing-type mixer (B) where substantially all of the remaining instable portions of the oxymethylene copolymer are heat-decomposed until the content of the instable portions falls below about 2 wt. %, thereby heat stabilizing the copolymer; said extruder (A) having a single or a plurality of shafts, said surface renewing-type mixer functioning to mix and knead the resin thereby constantly renewing the surface of the resin to volatize the volatiles contained therein.

Furusawa Tomotaka

Papers

Process for preparing aromatic polycarbonates

Process for heat stabilizing oxymethylene copolymers

Verfahren zur herstellung aromatischer polycarbonate

Verfahren zur stabilisierung von oxymethylencopolymeren gegen waerme