Branched polycarbonate resins and processes to prepare the same

1. A method of increasing the branching and polydispersity of a polycarbonate comprising the steps of:

(a) including in the polycarbonate at least one species of an alkyl substituted monomer, and

(b) treating the polycarbonate at an elevated temperature and for a sufficient time to increase the branching and polydispersity relative to an otherwise equivalent polycarbonate without alkyl substituents

wherein treatment step (b) occurs during a compounding step at a temperature greater than 330° C. for greater than or equal to 20 minutes.

2. The method of claim 1 , wherein the at least one species of alkyl substituted monomer is selected from the group consisting of:

wherein each substituent Y is independently a hydroxy, an alcohol, an ester, or a carboxylic acid functional group, each substituent R is independently a C 1 to C 6 branched, linear, or cyclic aliphatic group, each x is an integer between 1 and 4 inclusive, and the sum of all x's is less than or equal to 4,

wherein each substituent Y is independently a hydroxy, an alcohol, ester or carboxylic acid functional group, each substituent R is independently a C 1 to C 6 branched, linear, or cyclic aliphatic group, each x is zero or an integer between 1 and 3 inclusive, and the sum of all x's is at least 1 and less than or equal to 6, and

wherein each substituent Y is independently a hydroxy, an alcohol, ester or carboxylic acid functional group, each substituent R is independently a C 1 to C 6 branched, linear, or cyclic aliphatic group, each x is zero or an integer between 1 and 4 inclusive, the sum of all x's is at least 1 and less than or equal to 8, and Z represents one of the groups of formula:

wherein R 1 , R 2 and R 3 are independently a C 1 to C 18 branched, linear, or cyclic aliphatic group, and R 4 is a C 3 to C 12 cyclic substituent.

3. The method of claim 2 , wherein each R substituent is independently a C 1 to C 4 branched or linear aliphatic group.

4. The method of claim 3 , wherein each R substituent is independently a C 1 or a C 2 aliphatic group.

5. The method of claim 1 , wherein at least one species of alkyl substituted monomer is selected from the group consisting of methylhydroquinone, tert-butylhydroquinone, DMBPC bis(3-methyl-4-hydroxyphenyl)cyclohexane, 2,2′-Thiobis (4-t-octylphenol), TMBPA (tetra-methyl-BPA), DMBPA (di-methyl-BPA), DEBPA (di-ethyl-BPA), di-ortho-isopropyl-BPA, di-ortho-sec-butyl-BPA, di-ortho-tert-butyl-BPA, bis-orthocresol flourene, methyl resorcinol, di-tert-butyl resorcinol, and di-tert-butyl hydroquinone.

6. The method of claim 5 , wherein at least one species of alkyl substituted monomer is tert-butyl hydroquinone.

7. The method of claim 1 , wherein alkyl substituted monomer is present in the polycarbonate in an amount greater than 10 mole percent based on the total moles of monomers in the polycarbonate.

8. The method of claim 7 , wherein the alkyl substituted monomer is present in the polycarbonate in an amount greater than 20 mole percent based on the total moles of monomers in the polycarbonate.

9. The method of claim 1 , wherein the step of treating the polycarbonate at an elevated temperature and for a sufficient time to increase the branching and polydispersity relative to an otherwise equivalent polycarbonate without alkyl substituents further occurs during a melt transesterification reaction to build molecular weight of the polycarbonate.

10. The method of claim 9 , wherein during the melt polymerization reaction the polycarbonate is treated at an elevated temperature and for a sufficient time to result in a polycarbonate having a polydispersity of greater than 2.3.

11. The method of claim 10 , wherein during the melt polymerization reaction the polycarbonate is treated at an elevated temperature and for a sufficient time to result in a polycarbonate having a polydispersity of greater than 2.5.

12. The method of claim 9 , wherein during the melt polymerization reaction the polycarbonate is treated at a temperature of greater than 330° C.

13. The method of claim 9 , wherein during the melt polymerization reaction the polycarbonate is treated at a temperature of greater than 340° C.

14. The method of claim 1 , wherein during the compounding step the polycarbonate is treated at an elevated temperature and for a sufficient time to increase the polydispersity of the polycarbonate by greater than 10 percent.

15. The method of claim 14 , wherein during the compounding step the polycarbonate is treated at an elevated temperature and for a sufficient time to increase the polydispersity of the polycarbonate by greater than 50 percent.

16. The method of claim 1 , wherein the compounding step occurs at a temperature greater than 340° C.

17. The method of claim 1 , wherein the compounding step occurs for greater than or equal to 40 minutes.

18. The method of claim 17 , wherein the compounding step occurs for greater than or equal to 60 minutes.

19. The method of any of claims 1 , wherein the step of treating the polycarbonate at an elevated temperature and for a sufficient time to increase the branching and polydispersity relative to an otherwise equivalent polycarbonate without alkyl substituents further occurs during a molding step.

20. The method of claim 19 , wherein during the molding step the polycarbonate is treated at an elevated temperature and for a sufficient time to increase the polydispersity of the polycarbonate by greater than 10 percent.

21. The method of claim 20 , wherein during the molding step the polycarbonate is treated at an elevated temperature and for a sufficient time to increase the polydispersity of the polycarbonate by greater than 50 percent.

22. The method of claim 19 , wherein the molding step occurs at an elevated temperature for a period of time greater than 10 minutes.

23. The method of claim 22 , wherein the molding step occurs at an elevated temperature for a period of time greater than 20 minutes.

24. The method of claim 1 , wherein the polycarbonate is treated at an elevated temperature and for a sufficient time to produce a polycarbonate having a broad NMR band centered at a chemical shift of between about 3.95 and 4.05 ppm in a proton NMR spectrum.