Manufacture of dihydroxy aromatic compounds by alcoholysis of flame retardant-containing polycarbonate compositions

Patent metadata

Field	Value
Publication number	US-9428627-B2
Application number	US-201314440162-A
Country	US
Kind code	B2
Filing date	Dec 11, 2013
Priority date	Dec 21, 2012
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

The disclosure provides a method for recovering a dihydroxy aromatic compound and a dialkyl carbonate from a polycarbonate-containing composition comprising a polycarbonate and a phosphorus-containing flame retardant. The method comprises heating the composition in the presence of an alcohol and a transesterification catalyst having non-neutralizable groups at a temperature of 70° C. to 200° C. and a pressure of 50 mbar to 40 bar for a time sufficient to depolymerize the polycarbonate producing a dihydroxy aromatic compound and a dialkyl carbonate.

First claim

What is claimed is:

1. A method for recovering a dihydroxy aromatic compound and a dialkyl carbonate from a composition comprising a polycarbonate and a phosphorus-containing flame retardant, the method comprising
heating the polycarbonate-containing composition in the presence of an alcohol and a transesterification catalyst, having non-neutralizable groups, selected from the group consisting of a tin compound, a zinc compound, a titanium compound, an aluminum compound, or a combination thereof, at a temperature of 70° C. to 200° C. and a pressure of 50 mbar to 40 bar for a time sufficient to depolymerize the polycarbonate to provide a dihydroxy aromatic compound and a dialkyl carbonate;
wherein the catalyst is present in an amount from 0.01 wt. % to 1 wt. % based upon the total weight of the polycarbonate-containing composition and the alcohol.

2. The method of claim 1 , wherein the composition further comprises acrylonitrile-butadiene-styrene.

3. The method of claim 2 , wherein the method further comprises separating the dihydroxy aromatic compound and the dialkyl carbonate from acrylonitrile to butadiene-styrene by filtration.

4. The method of claim 1 , further comprising separating a blend of the alcohol and the dialkyl carbonate from the dihydroxy aromatic compound by distillation.

5. The method of claim 1 , wherein the polycarbonate is bisphenol A polycarbonate, the dihydroxy aromatic compound is bisphenol-A, and the dialkyl carbonate is dimethyl carbonate.

6. The method of claim 5 , wherein the alcohol is a C 1-10 alcohol.

7. The method of claim 6 , wherein the alcohol is methanol.

8. The method of claim 6 , wherein the alcohol is ethanol or n-butanol.

9. The method of claim 8 , wherein the dialkyl carbonate is diethyl carbonate or dibutyl carbonate.

10. The method of claim 1 , wherein the phosphorus-containing flame retardant is bisphenol A bis(diphenyl phosphate), resorcinol bis(diphenyl phosphate), or a combination thereof.

11. The method of claim 1 , wherein the catalyst is tetra(isopropyl)titanate, titanate-phosphate complex, dibutyltin oxide, aluminum isopropoxide, a metal phenoxide, or a combination comprising at least one of the foregoing.

12. The method of claim 1 , wherein the catalyst is a catalyst purge stream from a diphenyl carbonate product unit.

13. The method of claim 1 , wherein the catalyst is a titanium-based catalyst, and wherein the method further comprises removing the catalyst by adding a sufficient amount of water to a blend of dihydroxy aromatic compound, the dialkyl compound and the alcohol to convert the catalyst to titanium dioxide and filtering to remove titanium dioxide.

14. The method of claim 1 , wherein the catalyst is present in an amount from 0.01 wt. % to 1 wt. % based upon the total weight of the polycarbonate-containing composition and the alcohol.

15. The method of claim 14 , wherein the catalyst is present in an amount from 0.01 wt. % to 0.1 wt. % based upon the total weight of the polycarbonate-containing composition and the alcohol.

16. The method of claim 1 , wherein the alcohol is present in an amount of 200 weight percent to 600 weight percent based upon the weight of polycarbonate-containing composition.

17. The method of claim 1 , wherein the alcohol is added as a methanol stream containing from 0 to 50 weight percent dimethyl carbonate.

18. The method of claim 1 , wherein the method further comprises: polymerizing the recovered dihydroxy aromatic compound and a carbonyl source to provide the polycarbonate.

19. The method of claim 1 , further comprising recovering the dialkyl carbonate; and reacting the recovered dialkyl carbonate with phenol to provide diphenyl carbonate.

20. The method of claim 1 , further comprising
recovering the dihydroxy aromatic compound and the dialkyl carbonate;
reacting the recovered dialkyl carbonate with phenol to provide diphenyl carbonate;
polymerizing the recovered dihydroxy aromatic compound and diphenyl carbonate to provide the polycarbonate.

Assignees

• Sabic Global Technologies Bv

Inventors

• Bell Philip Wesley
• Fernandez Vic Ignacio
• Bhotla Venkata Ramanarayanan Ganapathy
• Gunale Tukaram
• Stanislaus Alexander
• Jayanna Darshan

Classifications

• C08J2369/00

  Characterised by the use of polycarbonates; Derivatives of polycarbonates · CPC title

• C08L69/00

  Compositions of polycarbonates; Compositions of derivatives of polycarbonates · CPC title

• C07C37/0555

  being esterified hydroxy groups · CPC title

• C08G64/307

  and phenols · CPC title

• Y02W30/706

  Cross-Sectional Technologies · mapped topic