- Method for preparing aromatic bischloroformate compositions
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Bischloroformate oligomer compositions are prepared by passing phosgene into a heterogeneous aqueous-organic mixture containing at least one dihydroxyaromatic compound, with simultaneous introduction of a base at a rate to maintain a specific pH range and to produce a specific volume ratio of aqueous to organic phase. By this method, it is possible to employ a minimum amount of phosgene. The reaction may be conducted batchwise or continuously. The bischloroformate composition may be employed for the preparation of cyclic polycarbonate oligomers or linear polycarbonate, and linear polycarbonate formation may be integrated with bischloroformate composition formation in a batch or continuous process.
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- Bischoloroformate preparation method with phosgene removal and monochloroformate conversion
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Aqueous bischloroformates are prepared by the reaction of a dihydroxyaromatic compound (e.g., bisphenol A) with phosgene in a substantially inert organic liquid (e.g., methylene chloride) and in the presence of an aqueous alkali metal or alkaline earth metal base, at a pH below about 8. After all solid dihydroxyaromatic compound has been consumed, the pH is raised to a higher value in the range of about 7-12, preferably 9-11, and maintained in said range until a major proportion of the unreacted phosgene has been hydrolyzed. At the same time, any monochloroformate in the product may be converted to bischloroformate.
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- Cyclic monocarbonate bishaloformates
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Cyclic monocarbonate bischloroformates are prepared by the reaction of a carbonyl halide such as phosgene with a bridged substituted resorcinol or hydroquinone such as bis(2,4-dihydroxy-3-methylphenyl)methane or bis(2,5-dihydroxy-3,4,6-trimethylphenyl)methane in the presence of aqueous alkali metal hydroxide. The cyclic monocarbonate bischloroformates may be used for the preparation of linear or cyclic polycarbonates containing cyclic carbonate structural units, which may in turn be converted to crosslinked polycarbonates.
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- Dihydric phenols
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Novel polycarbonates are provided which exhibit rubbery and elastomeric properties which are the polymerized reaction products of: (i) a carbonate precursor; and (ii) at least one dihydric phenol represented by the general formula STR1 wherein R is selected from straight chain alkyl radicals containing from 8 to about 30 carbon atoms; each R1 is independently selected from halogen monovalent hydrocarbon, and monovalent hydrocarbonoxy radicals; each R2 is independently selected from halogen, monovalent hydrocarbon, and monovalent hydrocarbonoxy radicals; and n and n' are independently selected from whole numbers having a value of from 0 to 4 inclusive.
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