Polysiloxane-polycarbonate copolymers and method for production thereof

1. A method for preparing a polysiloxane-polycarbonate copolymer comprising:

(a) contacting a dihydroxyaromatic compound with a continuous supply of phosgene under interfacial reactions conditions, in aqueous-organic solvent at a pH of 9-12, in the presence of at least one tertiary amine, to form a mixture;

(b) combining a monohydroxyaromatic compound with the mixture to produce an oligomeric aromatic polycarbonate mixture, with additional introduction of phosgene, wherein the amount of phosgene added in steps (a) and (b) is not more than 30% by weight of the total phosgene employed in the method;

(c) combining a mixture of a polyorganosiloxane bis(aryl)chloroformate in aqueous-organic solvent with the oligomeric aromatic polycarbonate mixture, with additional introduction of phosgene, before 65% of the total weight of phosgene is added, to form a reaction mixture; and

(d) adding the remainder of the phosgene to the reaction mixture, while stirring, to afford a polysiloxane-polycarbonate copolymer of a desired molecular weight;

wherein the % solids for preparing the polysiloxane-polycarbonate copolymer is 12% to 18%,

a molded plaque prepared from the polysiloxane-polycarbonate copolymer has a haze value of less than 1%, as measured according to ASTM D1003-07; wherein hydroxylaryl terminated polydiorganosiloxane oligomers used to produce the polyorganosiloxane bis(aryl)chloroformate have a polydispersity of less than 3.0 determined using a cross-linked styrene-divinylbenzene column with an ultraviolet-diode array detector set to detect at 254 nm.

2. The method of claim 1 , wherein the dihydroxyaromatic compound is bisphenol A (BPA).

3. The method of claim 1 , wherein the monohydroxyaromatic compound is selected from the group consisting of phenol, and para-cumylphenol (PCP), or a combination thereof.

4. The method of claim 1 , wherein the polyorganosiloxane bis(aryl)chloroformate has formula (X)

wherein

A is an unsubstituted or substituted divalent aryl group,

R 6 is a divalent C 2-8 alkyl group,

each R is independently a C 1-8 alkyl group, and

E is an average of 2 to 200.

5. The method of claim 1 , wherein the polyorganosiloxane bis(aryl)chloroformate has formula (Y)

wherein E is an average of 10 to 90.

6. The method of claim 1 , wherein the polyorganosiloxane bis(aryl)chloroformate is prepared by introducing into a reactor a solution of formula (Z)

wherein E is an average of 10 to 90;

the solution comprising methylene chloride, an aqueous solution of sodium hydroxide, and phosgene, said phosgene being introduced at a rate such that the ratio of phosgene to the formula (Z) OH groups is in a range between 2.5 and 6 moles of phosgene per mole of formula (Z) OH group, said aqueous solution of sodium hydroxide having a concentration of at least 5 percent by weight sodium hydroxide, said aqueous solution of sodium hydroxide being introduced at a rate such that the molar ratio of metal hydroxide to phosgene is in a range between 3.5 and 6.

7. The method of claim 1 , wherein the polysiloxane-polycarbonate copolymer is a siloxane block co-polycarbonate comprising, by weight, 1% siloxane to 20% siloxane.

8. The method of claim 1 , wherein the polysiloxane-polycarbonate copolymer is

a PCP end-capped BPA polycarbonate-polydimethylsiloxane copolymer comprising 6 wt % siloxane, having an average polydimethylsiloxane block length of 45 units, and having a Mw of 17,000 g/mol to 35,000 g/mol, as determined by GPC using BPA polycarbonate standards.

9. The method of claim 1 , wherein the polyorganosiloxane bis(aryl)chloroformate is added to the oligomeric aromatic polycarbonate.

10. The method of claim 1 , wherein a molded plaque with 3.18 mm thickness prepared from the polysiloxane-polycarbonate copolymer has a db* value of less than 3, as measured according to ASTM D2244-09b.

11. The method of claim 1 , wherein the cycle time for preparing the polysiloxane-polycarbonate copolymer is at least 18 minutes but less than 40 minutes.

12. The method of claim 1 , wherein the % solids for preparing the polysiloxane-polycarbonate copolymer is 15% to 18%.

13. The method of claim 1 , wherein the hydroxylaryl terminated polydiorganosiloxane oligomers used to produce the polyorganosiloxane bis(aryl)chloroformate have a polydispersity of less than 2 determined using a cross-linked styrene-divinylbenzene column with an ultraviolet-diode array detector set to detect at 254 nm.

14. The method of claim 1 , wherein the cycle time for preparing the polysiloxane-polycarbonate copolymer is at least 23 minutes.

15. The method of claim 1 , wherein the hydroxylaryl terminated polydiorganosiloxane oligomers used to produce the polyorganosiloxane bis(aryl)chloroformate have a polydispersity of less than 2 determined using a cross-linked styrene-divinylbenzene column with an ultraviolet-diode array detector set to detect at 254 nm, and wherein the cycle time for preparing the polysiloxane-polycarbonate copolymer is at least 23 minutes.