Bisphenol reaction with, phosgene

Figure 14.4.4 The reaction of the sodium salt of bisphenol A with phosgene to produce the polycarbonate.

Aromatic polycarbonates are currently manufactured either by the interfacial polycondensation of the sodium salt of diphenols such as bisphenol A with phosgene (Reaction 1, Scheme 22) or by transesterification of diphenyl carbonate (DPC) with diphenols in the presence of homogeneous catalysts (Reaction 2, Scheme 22). DPC is made by the oxidative carbonylation of dimethyl carbonate. If DPC can be made from cyclic carbonates by transesterification with solid catalysts, then an environmentally friendlier route to polycarbonates using C02 (instead of COCl2/CO) can be established. Transesterifications are catalyzed by a variety of materials K2C03, KOH, Mg-containing smectites, and oxides supported on silica (250). Recently, Ma et al. (251) reported the transesterification of dimethyl oxalate with phenol catalyzed by Sn-TS-1 samples calcined at various temperatures. The activity was related to the weak Lewis acidity of Sn-TS-1 (251). 

Polycondensation of Bisphenols, II, with Phosgene. Polycondensation of siloxane-linked bisphenols, II, with phosgene is the most obvious synthetic approach leading to siloxane-modified poly(arylene carbonates) since the phosgene-bisphenol polycondensation is used in the synthesis of aromatic polycarbonates (1). This method was used initially to prepare polymer (as indicated in reaction 1) as well as for the attempted synthesis of polymers 2 and 5 ... 

Polycarbonate is a very hard and light plastic used for protection devices such as football helmets. It is made by reacting bisphenol A with phosgene in the reactions shown in Figure 1 1-... 

A knowledge of the chemistry of bisphenol-A oligomer carbonate synthesis is useful in the interpretation of GPC data. Bisphenol-A carbonate oligomers can be prepared by reaction of bisphenol-A with phosgene in the presence of an acid acceptor. The reaction can be conducted interfacially (6), in homogeneous pyridine solution (7), or by merely passing phosgene into an alkaline solution of bisphenol-A (8). The chemical reactions that occur in each of these systems are complicated and consist of multiple and competitive reactions. 

The reaction of bisphenol A with phosgene involves bubbling the phosgene into a solution of bisphenol A in pyridine at 20 to 35°C and isolation of the resulting polymer by precipitation in water or methanol. In the reaction of Bisphenol A with diphenyl carbonate, a prepolymer is formed initially by heating the mixture at 180 to 220°C in vacuum. Then the temperature is raised slowly to 280 to 300 C at reduced pressure to ensure the removal of the final traces of phenol. 

Arylene carbonate cyanoarylene ether copol5miers can be prepared by the reaction of a solution of a bisphenolic capped cyanoarylene ether oligomer with phosgene in the presence of a base. The reaction with phosgene is carried out in an inert atmosphere. The pol5mierization reaction is carried out at a subambient temperature so that the reaction proceeds at a controllable rate. ° The materials are useful as gas separation membranes. 

A further rapidly growing application for bisphenol A is the production of polycarbonates by reaction with phosgene. Polycarbonates are widely used as thermoplastic construction materials. 

The phase transfer method offers the possibility of conducting polymerization reactions in nonpolar, aprotic solvents using anionic initiators which ordinarily are not soluble in such media and are often too inactive to effect polymerization. We have discussed in Sect. 6.4 the condensation polymerization of bisphenol A with phosgene under phase-transfer conditions. The formation of polycarbonates by this method is one of the earliest and most important (from the industrial point of view) applications of the method. 

Polycarbonates are prepared commercially by two processes Schotten-Baumaim reaction of phosgene (qv) and an aromatic diol in an amine-cataly2ed interfacial condensation reaction or via base-cataly2ed transesterification of a bisphenol with a monomeric carbonate. Important products are also based on polycarbonate in blends with other materials, copolymers, branched resins, flame-retardant compositions, foams (qv), and other materials (see Flame retardants). Polycarbonate is produced globally by several companies. Total manufacture is over 1 million tons aimuaHy. Polycarbonate is also the object of academic research studies, owing to its widespread utiUty and unusual properties. Interest in polycarbonates has steadily increased since 1984. Over 4500 pubflcations and over 9000 patents have appeared on polycarbonate. Japan has issued 5654 polycarbonate patents since 1984 Europe, 1348 United States, 777 Germany, 623 France, 30 and other countries, 231. 

These materials have the general structure shown in Figure 20.11 and are prepared by reaction of bisphenol A with iso- and/or terephthalic acid and a carbonate group donor (e.g. phosgene or diphenyl carbonate). 

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. 

The synthesis of polycarbonate of bisphenol A begins with the reaction of bisphenol A and sodium hydroxide to obtain the sodium salt of bisphenol A, as in Fig. 14.4.3. The sodium salt of bisphenol A is then reacted with phosgene to... 

Polycarbonates are polyesters of carbonic acid. The most important commercial polycarbonate is that based on 2,2 -bis(4-hydroxyphenyl)propane(bisphenol A) [Freitag et al., 1988 Sehanobish et al., 1996]. It has been synthesized by the reaction of the dihydric phenol with phosgene or by ester interchange with diphenyl carbonate ... 

This method of transesterification is of high technical interest. Particularly the reaction of bisphenol A with diphenyl carbonate is a preferred phosgene-free process because biphenyl carbonate can be obtained directly from phenol and dimethyl carbonate.The latter is an industrial product made from CO and methanol. 

Bisphenol-A is present as the disodium salt in the aqueous phase of the two-phase mixture. Phosgene enters the system and dissolves in the organic phase. It is believed that the reaction between phosgene and bisphenol-A occurs at the organic-aqueous interface to form the monochloroformate—Reaction 1—or bischloroformate—Reaction 2— ester of bisphenol-A. The chloroformate esters that form grow to oligomers by reaction with additional bisphenol-A or by self-condensation —Reactions 3 and 4, respectively. 

Polycarbonates are a class of thermoplastic polymers that are used in the plastic lenses of eyeglasses and in the shells of bicycle helmets. A polycarbonate is made from the reaction of bisphenol A (BPA) with phosgene (COCl2) ... 

The so-called bisphenol A polycarbonate constitutes the largest outlet for the carbonate-based materials. It is prepared by reaction of phosgene with bisphenol A in an... 

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