METHOD FOR PRODUCING POLYCARBONATE OLIGOMERS

Abstract

A process for producing an oligomer comprising contacting a dialkyl carbonate and a dihydroxy compound in a reaction zone in the presence of an oligomerization catalyst under oligomerization conditions to form the oligomer wherein the molar ratio of dihydroxy compound to dialkyl carbonate in the reaction zone is at least 2:1.

Claims

1. A process for producing an oligomer comprising contacting a dialkyl carbonate and a dihydroxy compound in a reaction zone in the presence of an oligomerization catalyst under oligomerization conditions to form the oligomer wherein the molar ratio of dihydroxy compound to dialkyl carbonate in the reaction zone is at least 2:1.

2. The process of claim 1, wherein the dialkyl carbonate is selected from the group consisting of dimethylcarbonate, diethylcarbonate and mixtures thereof.

3. The process of claim 1, wherein the dihydroxy compound is selected from the group consisting of aliphatic diols, acids and dihydroxy aromatics.

4. The process of claim 1, wherein the dihydroxy compound is selected from the group consisting of bisphenols, dihydroxy benzenes and dihydroxy naphthalenes.

5. The process of claim 1, wherein the ratio of dihydroxy compound to dialkyl carbonate in the reaction zone is at least 5:1.

6. The process of claim 1, wherein the ratio of dihydroxy compound to dialkyl carbonate in the reaction zone is at least 10:1.

7. The process of claim 1, wherein the ratio of dihydroxy compound to dialkyl carbonate in the reaction zone is in the range of from 2:1 to 100:1.

8. The process of claim 1, further comprising removing at least a portion of unreacted dihydroxy compound from the oligomer.

9. The process of claim 1, wherein an alcohol is formed during the oligomerization.

10. The process of claim 9. wherein the oligomerization conditions comprise a temperature and pressure at which at least a portion of the alcohol is in the vapor phase.

11. The process of claim 1, wherein the oligomerization conditions comprise a pressure of less than 2.03 MPa.

12. The process of claim 1, wherein the oligomerization conditions comprise a temperature in the range of from 110 to 330 C.

13. The process of claim 1, wherein the oligomerization conditions comprise a temperature in the range of from 160 to 300 C.

14. The process of claim 1, wherein the oligomerization is carried out in a plurality of reactors.

15. The process of claim 1, wherein the oligomerization reaction is carried out as a batch process.

16. The process of claim 1, further comprising contacting the oligomer with additional dialkyl carbonate in a separate reaction zone.

17. The process of claim 1, wherein the oligomerization catalyst is heterogeneous.

18. The process of claim 1, wherein the oligomerization catalyst is homogeneous.

19. The process of claim 1, wherein the oligomerization catalyst is selected from the group consisting of sodium hydroxides, sodium carbonates, lithium hydroxide, lithium carbonates, tetraalkylammonium hydroxides, tetraalkylammonium carbonates and titanium alkoxides.

Description

EXAMPLES

Example 1

[0044] BPA (38.7 g/170 mmol) and DEC (1.65 g/14 mmol) were mixed with 0.056 g of Ti(OEt).sub.4, resulting in a mixture that contained about 290 ppm of Ti. The reaction mixture was heated in an autoclave batch reactor at 180 C. under constant stirring. After one hour, the reaction mixture was cooled to ambient temperature and analyzed using GC and FTIR. The analysis showed that about 15%of the DEC was converted to di-BPA-carbonate. In addition, some of the DEC was converted to ethyl-BPA-carbonate.

Example 2

[0045] In yet another example, transesterification between BPA and DMC is performed, and the reaction by product methanol is removed from the reaction system via molecular sieves 4 A. The reaction was performed by refluxing a mixture of BPA (41.2 g/180 mmol) and DMC (1.48 g/16 mmol) in the presence of 0.061 g Ti(OEt).sub.4 (about 300 ppm Ti), methanol was continuously removed over a 5 g molecular sieves 4 A in a Soxhlet extractor. After 1 hr at 180 C., about 26% DMC was converted into di-BPA-carbonate. In addition, some of the DMC was converted to methyl-BPA-carbonate.