Polycarbonates and method of preparing same
View Patent ↗Polycarbonates incorporating terminal carbonate groups derived from ester-substituted activated carbonates, for example terminal methyl salicyl carbonate (TMSC) derived from the use of BMSC as the activated carbonate in a transesterification process, have unfavorable properties with respect to color, hydrolytic stability and thermal stability, particularly when the polycarbonate containing such end groups is molded. The number of activated carbonate end groups formed during the melt transesterification formation of polycarbonate can be reduced, however, without sacrificing the benefits of using an activated diaryl carbonate, and without requiring a separate reaction or additional additives by reacting a dihydroxy compound with an activated diaryl carbonate in the presence of an esterification catalyst to produce a polycarbonate, wherein the molar ratio of activated diaryl carbonate to dihydroxy compound is less than 1 when expressed to at least three decimal places, for example 0.996 or less.
1. A method for preparing a polycarbonate comprising reacting a dihydroxy reaction component comprising a dihydroxy compound with carbonate reaction component comprising an activated diaryl carbonate in the presence of an esterification catalyst to produce a polycarbonate, wherein carbonate reaction component and the dihydroxy reaction component are reacted in a molar ratio of less than 1 when expressed to at least three decimal places.
2. The method of claim 1 , wherein the dihydroxy compound is an aromatic dihydroxy compound.
3. The method of claim 2 , wherein the activated diaryl carbonate is an ester-substituted diaryl carbonate.
4. The method of claim 3 , wherein the molar ratio is 0.996 or less.
5. The method of claim 3 , wherein the molar ratio is between 0.962 and 0.996, inclusive.
6. The method of claim 3 , wherein the molar ratio is between 0.968 and 0.996, inclusive.
7. The method of claim 3 , wherein the molar ratio is between 0.971 and 0.994, inclusive.
8. The method of claim 3 , wherein the ester-substituted diaryl carbonate is bis(methyl salicyl)carbonate.
9. The method of claim 1 , wherein the activated diaryl carbonate is an ester-substituted diaryl carbonate.
10. The method of claim 9 , wherein the molar ratio is 0.996 or less.
11. The method of claim 9 , wherein the molar ratio is between 0.962 and 0.996, inclusive.
12. The method of claim 9 , wherein the molar ratio is between 0.968 and 0.996, inclusive.
13. The method of claim 9 , wherein the molar ratio is between 0.971 and 0.994, inclusive.
14. The method of claim 9 , wherein the ester-substituted diaryl carbonate is bis(methyl salicyl)carbonate.
15. The method of claim 1 , wherein the dihydroxy compound is bisphenol A.
16. The method of claim 15 , wherein the activated diaryl carbonate is an ester-substituted diaryl carbonate.
17. The method of claim 16 , wherein the molar ratio is 0.996 or less.
18. The method of claim 16 , wherein the molar ratio is between 0.962 and 0.996, inclusive.
19. The method of claim 16 , wherein the molar ratio is between 0.968 and 0.996, inclusive.
20. The method of claim 16 , wherein the molar ratio is between 0.971 and 0.994, inclusive.
21. The method of claim 16 , wherein the ester-substituted diaryl carbonate is bis(methyl salicyl)carbonate.
22. The method of claim 1 , wherein the dihydroxy reaction component comprises two or more dihydroxy compounds.
23. The method of claim 1 , wherein the polycarbonate is a poly(carbonate-co-ester) and the dihydroxy reaction component comprises a diacid compound.
24. The method of claims 1 , wherein the polycarbonate is a poly(carbonate-co-ester) and the carbonate reaction component comprises a diester compound.
25. The method of claim 1 , wherein the polycarbonate is prepared in a continuous process.
26. A polycarbonate made in accordance with the method of claim 1 .
27. A molded article molded from the polycarbonate of claim 26 .
28. A polycarbonate having less than 0.5 mole % of terminal alkyl carbonate end groups, less than 1000 ppm of Fries rearrangement products, and free salicylate in the range of from 1 to 500 ppm, said polycarbonate containing free non-salicylate OH groups and carbonate end groups of the formula
wherein X is one or more electron-withdrawing groups in the ortho or para positions, and wherein the free non-salicylate OH groups and carbonate end groups are present in a ratio of at least 0.1.
29. The polycarbonate of claim 28 , wherein the polycarbonate has a number average molecular weight measured relative to polystyrene standards, Mn, of from 10,000 to 160,000 g/mol.
30. The polycarbonate of claim 28 , wherein the polycarbonate comprises residues from a dihydroxy compound selected from the group consisting of hydroquinone, resorcinol, methylhydroquinone, butylhydroquinone, phenylhydroquinone, 4-phenylresorcinol and 4-methylresorcinol.
31. The polycarbonate of claim 28 , wherein the free salicylate comprises methyl salicylate.
32. The polycarbonate of claim 28 , wherein the carbonate end groups comprise ends groups of the formula
wherein R is alkyl, phenyl or benzyl.
33. The polycarbonate of claim 28 , wherein the carbonate end groups comprise end groups of the formula
wherein Me is methyl.
34. A molded article molded from the polycarbonate of claim 28 .