Catalyst removal process
View Patent ↗The present invention provides a process for producing polycarbonates in the presence of one or more alkali metal or alkaline-earth metal catalysts, and subsequently removing the catalyst residues by chelation, to yield a clear polycarbonate product that is free from catalyst residues, and is thus suitable for use as a binding material in the ceramics industry where residual amounts of catalysts in the binder are burdensome.
1. A process for producing a polycarbonate having the structure:
in which n is any number between about 5 and 50, R is any C 1 to C 20 alkyl group, whether straight-chain, cyclic, or branched, comprising the steps of:
a) reacting a reaction mixture comprising an aliphatic diol according to the formula: HO—R—OH in which R is any C 1 to C 20 alkyl group, whether straight-chain, cyclic, or branched and a linear organic carbonate having the formula:
in which R 1 and R 2 may independently be alkyl groups ranging from C 1 to C 4 , linear or branched, at a temperature of 60° C. to 180° C. in the presence of a catalyst selected from the group consisting of: one or more alkali or alkaline earth metal alkoxide, hydroxide, carbonate, or carboxylate salts, or mixtures of any of the foregoing;
b) supplying heat to said reaction mixture to cause distillation of alcohol by-product(s) produced from step a) above until said reaction mixture reaches a termination temperature of at least 150° C. to provide a semi-stripped crude product;
c) contacting said semi-stripped crude product from step b) with a chelating agent; to form a slurry; and
d) filtering said slurry from step c) to provide a clear liquid.
2. A process according to claim 1 wherein said semi-stripped crude product is mixed with an alcohol prior to its being contacted with a chelating agent or adsorbent.
3. A process according to claim 1 wherein said chelating agent is a magnesium silicate.
4. A process according to claim 1 wherein said termination temperature is in the range of 150° C. to 200° C.
5. A process according to claim 1 wherein said termination temperature is in the range of 160° C. to 200° C.
6. A process according to claim 1 wherein said termination temperature is in the range of 170° C. to 200° C.
7. A process according to claim 1 wherein said termination temperature is in the range of 180° C. to 200° C.
8. A process according to claim 1 wherein said termination temperature is in the range of 190° C. to 200° C.