General Electric Company

Ryozo Sato

Tomoaki Shimoda

Takato Kimura

Satoru Omori

Gaylord M Kissinger

Akio Kanezawa

The specification provides a method for the manufacture of a high-quality optical polycarbonate that contains few inorganic or organic impurities or other microparticles, and that has a superior hue. Specifically, the specification provides a method for the manufacture of a polycarbonate by the melt polycondensation of a bisphenol and a carbonic diester, wherein the molten mixture of a bisphenol and a carbonic diester is filtered with a membrane filter made of a fluororesin, after which melt polycondensation is conducted.

Method for manufacturing polycarbonate for optical use

A process for producing a dihydric phenol preferably bisphenol-A consisting of the steps of (1) formulating reaction ingredients of phenol, acetone, recycle bisphenol A, impurities, an acid catalyst and water, (2) reacting the ingredients to form a product mix consisting of bisphenol-A, unreacted phenol, by-products, acetone and water, (3) crystallizing the product mix forming a slurry of bisphenol-A/phenol adduct crystals solid phase, (4) separating the solid phase from the liquid phase by filtration, (5) removing the phenol from the bisphenol-A/phenol adduct to obtain a crude bisphenol-A, and (6) purifying the crude bisphenol by fractional melt crystallization to obtain a bisphenol-A of at least 99.5% purity. Optionally, the process may include the steps of recycling the liquid phase from step (3) back to the reaction step after removal of the water of reaction, and further removing entrained phenol and acetone from the removed water of reaction which phenol and acetone is also recycled back to the reaction step.

Process for the manufacture of bisphenol-A

A phenol and a ketone are reacted to form bisphenol, and the liquid bisphenol obtained or a mixed solution of said solution and a phenol is filtered through a calcined metal filter to obtain bisphenol which makes it possible to efficiently obtain bisphenol which either does not contain fine particulate impurities or contains such impurities only in minute amounts, and a method for manufacturing polycarbonate using bisphenol obtained by this method. The filtration grade of the calcined metal filter should be 1.0 .mu.m or less. After filtering, the calcined metal filter can be backwashed or chemically washed and then reused. The bisphenol should preferably be bisphenol A.

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Murcia, Spain

Ryozo Sato