Sodium carbonate, from polycarbonates

FIGURE 17.8 SEM of amorphous PLA 8302D (NatureWorks, 10% D-lactic acid content) foamed with 0.5% endothermic CFA (BIH40 from Boehringer Ingelheim Chemicals, which is sodium salt of polycarbonic acid + carbonate compounds) at 40rpm (a) 30 x and (b) 70 x magnifications [86]. 

A method of converting polycarbonate (PC) to bishydroxyethyl ether of bisphenol A (BHE-BPA) was studied, with a view to recycling PC plastic wastes. Treating PC in ethylene glycol with a catalytic amount of sodium hydroxide produced the monohydroxyethyl ether of bisphenol A (MHE-BPA, 42%), BHE-BPA (11%) and BPA (42%). BHE-BPA was produced quantitatively when 1.6 mol. equiv. ethylene carbonate was added to this reaction system. The reaction of BPA with EC produced both BHE-BPA and MHE-BPA, indicating that ethylene carbonate was formed as an intermediate in the base catalysed reaction of PC with ethylene glycol. A large proportion of this ethylene carbonate formed from PC was, however, lost by decarboxylation so additional ethylene carbonate must be provided for the quantitative preparation of BHE-BPA. 12 refs. 

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). 

Tsuge et al. [263] showed that Py-GC can be used to determine the molecular weight of polycarbonates from the terminal groups. Py-GC has also been shown to be applicable to the determination of the degree of cross-linking of carbon exchange resins in the hydrogen and sodium fonns on the basis of these copolymers [264]. The application... 

Linear and cyclic structures of polycarbonates from bisphenol-A, from bisphenol-Z, and from 4,4 -dihydroxydiphenyl-3,3-pentane, were determined by PSD MALDI-TOF experiments. It was foimd that the fragmentation behavior of these polycarbonates depends on the substituents boimd to the central carbon atom of the bisphenol unit. The cleavage of the polymer backbone is suppressed, and the spectra are dominated by the loss of side groups. PSD MALDl spectra of these polycarbonates could be acquired only from Li adduct ions, because the sodium or potassium cationized adduct ions yield only dissociation of the cation from the polymer. ... 

Technical processes for the production of diphenyl carbonate (DPhC) 885 from phenol and phosgene are covered in many patent applications (for the production of polycarbonates on optical storage of electronic data, see Section 4.3.3.7). Such processes are carried out in the presence of sodium hydroxide [643], pyridine derivatives [644], Ti02 and AI2O3 [645], or Hf02 [646]. 

The potential release of the toxic BPA from the polymer is driving the search for an alternative monomer. Diphenolic acid (DPA) is a potential substitute for BPA in polymer synthesis. The synthesis of polycarbonates involves a two-step process. First, DPA is treated with NaOH to produce a sodium diphenoxide. This intermediate reacts with phosgene (COCy to start the polymerisation. A disadvantage of this process is the toxicity of phosgene (phosgene was used as a chemical weapon during World War 1). An alternative route to polycarbonates consists of the transesterification of DPA with diphenyl carbonates. DPA can also be copolymerised using the same reaction route. 

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