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1. WO2020115707 - POLYCARBONATE COMPOSITIONS WITH IMPROVED OXIDATION STABILITY AND METHODS OF MANUFACTURING THE SAME

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CLAIMS

1. A method of preparing a polycarbonate composition in a polymerization system, wherein the polymerization system comprises a monomer mixing unit, an oligomerization section, and a polymerization section, the method comprising:

melt polymerizing a dihydroxy compound with a diaryl carbonate compound in the presence of a quaternary phosphonium catalyst to produce the polycarbonate composition comprising a phosphorus -containing byproduct of at least one of the quaternary phosphonium catalyst or of the diaryl carbonate compound;

recycling a recycle stream comprising the phosphorus-containing byproduct into the monomer mixing unit of the polymerization system; and

removing the polycarbonate composition from the polymerization system;

wherein the recycle stream has a phosphorus concentration of greater than or equal to 40, preferably greater than or equal to 50 ppm.

2. The method of claim 1, wherein the phosphorus-containing byproduct comprises phosphate ester of formula:


3. A method of preparing a polycarbonate composition in a polymerization system, the method comprising:

melt polymerizing a dihydroxy compound with a diaryl carbonate compound in the presence of a quaternary phosphonium catalyst;

recycling phosphorus-containing byproduct into the polymerization system; and wherein the recycle stream has a phosphorus -containing byproduct concentration of greater than or equal to 280 ppm, preferably greater than or equal to 350 ppm, such as 280 ppm to 3,500 ppm, or 280 to 1,750 ppm; and

wherein the phosphorus-containing byproduct comprises phosphate ester of formula:


4. The method of any one or more of the preceding claims, wherein the quaternary phosphonium catalyst comprises tetrabutyl phosphonium acetate.

5. The method of any one or more of the preceding claims, wherein the dihydroxy compound is bisphenol A and the diaryl carbonate compound is diphenyl carbonate.

6. The method of any one or more of the preceding claims, wherein the quaternary phosphonium catalyst is present in amount of 5 to 500 moles of the quaternary phosphonium catalyst per total mole of the dihydroxy compound.

7. The method of any one or more of the preceding claims, wherein the melt polymerizing is further in the presence of an ionic catalyst.

8. The method of any one or more of the preceding claims, wherein the polymerization system further comprises an extraction column that extracts phenol from the oligomerization section and returns at least one of the dihydroxy compound or the diaryl carbonate compound to the oligomerization section.

9. The method of claim 8, wherein the recycle stream comprises phenol, bisphenol A, diphenyl carbonate, tributyl phosphine oxide, and phosphate esters.

10. The method of claims 8 and 9, wherein the recovery system further comprises a first extraction column and a second extraction column, and wherein a top stream of the second extraction column comprises from 80 to 99 wt. % of diphenyl carbonate and from 200 to 1000 ppm of tributyl phosphine oxide.

11. The method of claim 9, wherein the diphenyl carbonate contains from 10 to 100 ppm of tributyl phosphine oxide in the recovery system.

12. The method of claims 8 to 11, wherein extracting of the phosphoms-containing byproduct of the quaternary phosphonium catalyst is by a side draw from at least one of the first extraction column and the second extraction column.

13. The method of any one or more of the preceding claims, wherein the recycle stream has a phosphorus concentration of 40 to 150 ppm, preferably 50 to 100 ppm, or 50 to 70 ppm.

14. The method of any one or more of the preceding claims, wherein the phosphorous concentration the recycle stream is 40 to 500 ppm, or 40 to 250 ppm, or 50 to 250 ppm, preferably 50 to 150 ppm, or 50 to 100 ppm, and yet or 50 to 70 ppm.

15. The method of any one or more of claims 1-13, wherein the phosphorous concentration the recycle stream is greater than or equal to 50 ppm.

16. A polycarbonate prepared by the method of any one or more of the preceding claims.

17. An article comprising the polycarbonate of claim 16.

18. The article of claim 17, wherein the article is a sheet, a film, a multilayer sheet, a multilayer film, a molded part, an extruded profile, a fiber, a coated part, or a foam.