Process to prepare high heat polycarbonates
View Patent ↗A catalyzed interfacial phosgenation process with controlled feed ratios and controlled reaction pH levels allows for the formation of high heat polycarbonate random copolymers having high loadings of bis (4-hydroxyphenyl)-2-phenylisoindolin-1-one (“PPPBP”) or a structurally related comonomer. The process produces a polycarbonate copolymer having improved hydrolytic stability.
1. A method for preparing polycarbonate copolymer by an interfacial method, comprising
phosgenating a mixture comprising an aromatic dihydroxy compound, water, an organic solvent substantially immiscible with water, and a condensation catalyst to form a reaction mixture;
cofeeding an aqueous high heat comonomer feed to the reaction mixture during the phosgenation step, wherein during phosgenation, a ratio of high heat comonomer/phosgene weight/weight dry basis is about 1.75 to about 9; and
maintaining the pH of the reaction mixture during the phosgenation step at greater than 7 to less than 11,
to form a polycarbonate copolymer comprising greater than about 30 mole % structural units derived from the high heat comonomer.
2. The method of claim 1 , wherein the aqueous high heat comonomer feed is a slurry feed, a solution feed, or a combination comprising at least one of the foregoing feeds.
3. The method of claim 1 , wherein the ratio of high heat comonomer/phosgene is about 1.75 to about 6 weight/weight dry basis.
4. The method of claim 1 , wherein the ratio of high heat comonomer/phosgene is about 1.75 to about 4 weight/weight dry basis.
5. The method of claim 1 , wherein the pH of the reaction mixture during the phosgenation step is maintained at about 8 to about 10.
6. The method of claim 1 , wherein the pH of the reaction mixture during the phosgenation step is maintained using a caustic.
7. The method of claim 1 , wherein the pH of the reaction mixture during the phosgenation step is maintained using an alkali metal hydroxide, an alkaline earth hydroxide, or an alkaline earth oxide.
8. The method of claim 1 , wherein the pH of the reaction mixture during the phosgenation step is maintained using aqueous sodium hydroxide.
9. The method of claim 1 , wherein the aromatic dihydroxy compound is a compound according to
wherein R a and R b are each independently a halogen, C 1-12 alkoxy, or C 1-12 alkyl; i and j are each independently integers of 0 to 4; and X a is single bond, —O—, —S—, —S(O)—, —S(O) 2 —, —C(O)—, or a C 1-18 organic group; or
wherein each R h is independently a halogen atom, a C 1-10 alkyl, a halogen-substituted C 1-10 alkyl, a C 6-10 aryl, or a halogen-substituted C 6-10 aryl; and h is 0 to 4.
10. The method of claim 1 , wherein the aromatic dihydroxy compound is bisphenol A.
11. The method of claim 1 , wherein the high heat comonomer is a compound according to Formula (1a), Formula (1b), or a combination comprising at least one of the foregoing:
wherein R 1 is C 1-12 alkyl, C 6-12 aryl optionally substituted with 1 to 5 C 1-10 alkyl groups, or benzyl optionally substituted with 1 to 5 C 1-10 alkyl groups; R 2 is a C 1-12 hydrocarbyl group or a halogen; R 3 and R 4 are each independently a halogen, C 1-12 alkoxy, or C 1-12 alkyl; n is 0 to 2; and p and q are each independently 0 to 4.
12. The method of claim 1 , wherein the high heat comonomer is 3,3-bis(4-hydroxyphenyl)-2-phenylisoindolin-1-one (“PPPBP”).
13. The method of claim 1 , wherein the condensation catalyst is an organic tertiary amine.
14. The method of claim 1 , wherein the mixture further comprises a chelating agent.
15. The reaction of claim 1 , performed in the absence of a phase transfer catalyst.
16. The method of claim 1 , wherein the polycarbonate copolymer comprises about 30 to about 70 mole % structural units derived from the high heat comonomer.
17. The method of claim 1 , wherein the polycarbonate copolymer is hydrolytically stable and has a glass transition temperature of about 180 to about 250° C.
18. The method of claim 1 , wherein the polycarbonate copolymer retains greater than or equal to 90% of an initial Mw after 48 hours at 60° C. as determined using gel permeation chromatography.
19. The method of claim 1 , wherein the polycarbonate copolymer has a low creaming on the centrifuges, wherein the creaming is less than 5% on each of the centrifuges, wherein the creaming percent is determined by the following formula:
creaming
%
=
volume
organic
phase
+
volume
emulsion
volume
aqueous
phase
+
volume
organic
phase
+
volume
emulsion
)
*
100.
20. A method for preparing polycarbonate copolymer by an interfacial method, comprising
phosgenating a mixture comprising an aromatic dihydroxy compound, water, an organic solvent, and a condensation catalyst to form a reaction mixture, wherein organic solvent is selected from methylene chloride, 1,2-dichloroethane, chlorobenzene, and toluene;
cofeeding an aqueous high heat comonomer feed to the reaction mixture during the phosgenation step at a ratio of about 1.75 to about 9 high heat comonomer/phosgene weight/weight dry basis; and
maintaining the pH of the reaction mixture during the phosgenation step at greater than 7 to less than 11,
to form a polycarbonate copolymer comprising greater than about 30 mole % structural units derived from the high heat comonomer.