Bisphenol methylene chloride phase

The terminal R groups can be aromatic or aliphatic. Typically, they are derivatives of monohydric phenoHc compounds including phenol and alkylated phenols, eg, /-butylphenol. In iaterfacial polymerization, bisphenol A and a monofunctional terminator are dissolved in aqueous caustic. Methylene chloride containing a phase-transfer catalyst is added. The two-phase system is stirred and phosgene is added. The bisphenol A salt reacts with the phosgene at the interface of the two solutions and the polymer "grows" into the methylene chloride. The sodium chloride by-product enters the aqueous phase. Chain length is controlled by the amount of monohydric terminator. The methylene chloride—polymer solution is separated from the aqueous brine-laden by-products. The facile separation of a pure polymer solution is the key to the interfacial process. The methylene chloride solvent is removed, and the polymer is isolated in the form of pellets, powder, or slurries. 

Preparation of siloxane-carbonate segmented copolymers by interfacial polymerization involves the reaction of carboxypropyl-terminated siloxane oligomers with bisphenol-A and phosgene, in the presence of a strong base and a phase transfer catalyst, in water/methylene chloride solvent system l50 192), as shown in Reaction Scheme XIV. 

At the start of interfacial polymerization, bisphenol A is dissolved in methylene chloride, then introduced into a reactor. Phosgene is injected into the reactor as a liquefied gas together with an aqueous solution of sodium hydroxide. The methylene chloride and the aqueous solutions are immiscible polymerization occurs at the interface between them. The reactants are combined in a rapidly stirred reactor as shown in Fig. 20.7. The sodium hydroxide neutralizes the hydrochloric acid that is generated by polymerization, while the organic phase serves as a solvent for the polymer. The organic phase is separated and washed to remove traces of the base or salts after which the solvent is removed. 

The reaction between a dihydroxy compound (bisphenol) and phosgene, which is performed on an industrial scale, proceeds even at room temperature.The reaction is generally carried out in a biphasic medium consisting of methylene chloride (with dissolved phosgene) and aqueous sodium hydroxide (with dissolved bisphenol sodium salt) and a phase transfer catalyst (e.g.triethylamine).The procedure is termed interfacial polycondensation (see Sect.4.1.2.3 and Examples 4-5,4-12,and 4-13). 

Today, most polycarbonate is produced by an interfacial adaptation of the reaction in equation 4 (7 ). The bisphenol plus 1-3 raol% monofunctional phenol, which controls molecular weight, is dissolved or slurried in aqueous sodium hydroxide methylene chloride is added as a polymer solvent, a tertiary amine is added as a catalyst, and phosgene gas is dispersed in the rapidly stirred mixture. Additional caustic solution is added as needed to maintain basicity. The growing polymer dissolves in the methylene chloride, and the phenolic content of the aqueous phase diminishes. 

This polymer can be prepared by the interfacial polycondensation of bisphenol A alkali salt dissolved in the water phase and phosgene (COQj) dissolved in methylene chloride. It can be used either as the pure polymer or in blends, particularly with acrylonitrile-butadiene-styrene (ABS) copolymers. The bisphenol A structure appears in other combinations, e.g., in a polysulfone copolymer (see Table 15.10) and in aromatic polyesters with phthalic acid moieties... 

An aromatic polyformal was also prepared from bisphenol-A and methylene chloride by phase-transfer-catalyzed etherification in the presence of 2-(p-hydroxyphenyl)-2-oxazoline as an encapping agent. A polyformal with two oxazoline chain ends was obtained. When a mixture of DMSO and CH2CI2 was used as a solvent rather than only CH2CI2, a pol3nner with both oxazoline and... 

We learned later that Bayer was practicing a form of tertiary base catalyzed interfacial polymerization. This process consisted of metering phosgene and caustic solution into a stirred slurry of bisphenol-A and tertiary amine catalyst in a water/methylene chloride solvent mixture. The polymer forms at the aqueous/organic solvent interface and remains in the organic phase. The formed sodium chloride accumulates in the aqueous phase. The polymer may be recovered in a manner similar to that employed in solution polymerization. 

In this method a solution of bisphenol A in aqueous sodium hydroxide is dispersed in an organic solvent such as methylene chloride by rapid stirring. A small quantity of tertiary amine (e.g., triethylamine) or quaternary ammonium base (e.g., tetramethylammonium hydroxide) is added to the system as catalyst and then phosgene is passed in at about 25°C. When reaction is complete the organic phase, which contains the polymer, is separated and the polymer is isolated as in the solution method described above. 

In the interfacial process, bisphenol A is dissolved in the aqueous sodium hydroxide phase of a two-phase system with methylene chloride. As phosgene is pumped into the mixture, the sodium chloride condensation by-product dissolves in the aqueous phase, and the growing polymer dissolves in the organic phase. A tertiary amine is used as the catalyst. When the reaction is complete, the methylene chloride solution is extracted with acid to remove basic components and then washed with water. The solvent is then flashed off and recycled, leaving the solid. 

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