Ionizing radiation stable thermoplastic composition, method of making, and articles formed therefrom

1. A thermoplastic composition comprising:

a sulfonate end-capped polycarbonate of formula:

Z-S(O) 2 —O-(-L-) m -O—S(O) 2 -Z

wherein each Z is independently an alkyl or aryl group, wherein -(-L-) m - is a polycarbonate linking group with m units of linking unit L, and wherein m is at least one, and

an ionizing radiation stabilizing additive comprising 2-methyl-2,4-pentanediol (hexylene glycol).

2. The thermoplastic composition of claim 1 , comprising 0.001 to 500 mmol/Kg of the sulfonate end-capped polycarbonate, based on the total weight of the thermoplastic composition.

3. The thermoplastic composition of claim 1 , comprising a blend of a polycarbonate and the sulfonate end-capped polycarbonate, wherein the sulfonate end-capped polycarbonate is used in an amount of 0.1 to 100 wt %, based on the total weight of the polycarbonate and sulfonate end-capped polycarbonate, with the proviso that the amount and type of sulfonate end-capped polycarbonate used is selected so that the overall concentration of sulfonate end groups is not greater than a molar concentration of 500 millimoles per kilogram (mmol/Kg), and is not less than 0.001 mmol/Kg, of the total weight of the sulfonate end-capped polycarbonate and any added polycarbonate.

4. The thermoplastic composition of claim 1 , wherein m is 1 to 500.

5. The thermoplastic composition of claim 1 , wherein each Z is a C 1 -C 20 alkyl group, substituted C 1 -C 20 alkyl group, C 6 -C 20 aryl group, or substituted C 6 -C 20 aryl group.

6. The thermoplastic composition of claim 1 , wherein L comprises carbonate units, ester units, poly(arylene ether) units, soft block units, or a combination comprising at least one of these; and wherein at least one L is a carbonate unit.

7. The thermoplastic composition of claim 6 wherein the poly(arylene ether) unit has the formula:

—(—Ar 1 —X—Ar 1 —O—) n —Ar 1 —X—Ar 1 —

wherein n is 0 to 200, wherein each Ar 1 is independently a substituted C 6 -C 20 arylene group or unsubstituted C 6 -C 20 arylene group; and wherein X is a bridging radical having one or two atoms that separate the Ar 1 groups.

8. The thermoplastic composition of claim 6 , wherein soft block units include polysiloxane units, polyalkylene oxide units, poly(alkylene ester) units, polyolefin units, or a combination comprising at least one of these.

9. The thermoplastic composition of claim 1 , wherein the ionizing radiation stabilizing additive further comprises an aliphatic alcohol, an aromatic alcohol, an aliphatic diol, an aliphatic polyol, an aliphatic ether, an esters, a diketone, an alkene, a thiol, thioethers, a cyclic thioether, a sulfone, a dihydroaromatic, a diether, a nitrogen compound, or a combination comprising at least one of the foregoing.

10. The thermoplastic composition of claim 9 wherein the aliphatic diol has the structure:

HO—(C(A′)(A″)) c -S—(C(B′)(B″)) d —OH

wherein A′, A″, B′, and B″ are each individually H or C 1 -C 6 alkyl; and wherein S is C 1 -C 20 alkyl, C 2 -C 20 alkyleneoxy, C 3 -C 6 cycloalkyl, or C 3 -C 6 substituted cycloalkyl; and wherein c and d are each 0 or 1, with the proviso that, where c and d are each 0, S is selected such that both —OH groups are not connected directly to a single common carbon atom.

11. The thermoplastic composition of claim 1 , further comprising hydrolysis stabilizer, impact modifier, filler, antioxidant, heat stabilizer, light stabilizer, ultraviolet light absorber, plasticizer, mold release agent, lubricant, antistatic agent, pigment, dye, flame retardant, anti-drip agent, or a combination comprising at least one of these.

12. The thermoplastic composition of claim 1 , wherein the sulfonate end-capped polycarbonate includes sulfonate end-capped polycarbonate homopolymers, sulfonate end-capped polycarbonate copolymers, sulfonate end-capped polyester-polycarbonate, sulfonate end-capped polysiloxane-polycarbonate, sulfonate end-capped polysiloxane-co-(polyester-polycarbonate), sulfonate end-capped poly(aiylene ether)-co-polycarbonate, sulfonate end-capped poly(arylene ether)-co-(polyester-polycarbonate), sulfonate end-capped poly(alkylene ester)-co-polycarbonate, sulfonate end-capped poly(alkylene ester)-co-(polyester-polycarbonate), sulfonate end-capped poly(alkylene ether)-co-polycarbonate, sulfonate end-capped poly(alkylene ether)-co-(polyester-polycarbonate), sulfonate end-capped polyolefin-co-polycarbonate, sulfonate end-capped poly(olefin)-co-(polyester-polycarbonate), or a combination comprising at least one of these.

13. The thermoplastic composition of claim 1 , wherein the sulfonate end-capped polycarbonate is tosyl end-capped poly(bisphenol-A carbonate).

14. The thermoplastic composition of claim 1 , wherein a molded article having a thickness of 3.2± 0.12 millimeters and consisting of the sulfonate end-capped polycarbonate, a polycarbonate resin, and an effective amount of each of an aliphatic diol, a mold-release agent, and an antioxidant has, after exposure to a total gamma radiation dose of 83 kGy and when measured according to ASTM D1925-70, an increase in yellowness index (dYI) of less than or equal to 36, when compared to the unexposed article.

15. A thermoplastic composition comprising:

a sulfonate end-capped polycarbonate of formula:

Z-S(O) 2 —O-(-L-) m -O—S(O) 2 -Z

wherein each Z is independently an alkyl or aryl group, wherein -(-L-) m - is a polycarbonate linking group with m units of linking unit L, and wherein m is at least one;

wherein a molded article having a thickness of 3.2±0.12 millimeters and consisting of the sulfonate end-capped polycarbonate, a polycarbonate resin, and an effective amount of each of an aliphatic diol, a mold-release agent, and an antioxidant has, after exposure to a total gamma radiation dose of 83 kGy and when measured according to ASTM D1925-70, an increase in yellowness index (dYI) of less than or equal to 36, when compared to the unexposed article.

16. A thermoplastic composition comprising:

a sulfonate end-capped polycarbonate of formula:

Z-S(O) 2 —O-(-L-) m -O—S(O) 2 -Z

wherein each Z is independently an alkyl or aryl group, and -(-L-) m - is a polycarbonate linking group with m units of linking unit L, wherein m is at least one; and

a polycarbonate,

wherein the sulfonate end-capped polycarbonate is present in an amount of 0.1 to 100 wt %, based on the total weight of the sulfonate end-capped polycarbonate and any added polycarbonate, with the proviso that the amount and type of sulfonate end-capped polycarbonate used is selected so that the overall concentration of sulfonate end groups is not greater than a molar concentration of 500 millimoles per kilogram (mmol/Kg), and is not less than 0.001 mmol/Kg, of the total weight of the thermoplastic composition.

17. A thermoplastic composition comprising:

a sulfonate end-capped polycarbonate of formula:

Z-S(O) 2 —O-(-L-) m -O—S(O) 2 -Z

wherein each Z is independently an alkyl or aryl group, and -(-L-) m - is a polycarbonate linking group with m units of linking unit L, wherein m is at least one; and

a polycarbonate,

wherein a molded article having a thickness of 3.2±0.12 millimeters and consisting of the sulfonate end-capped polycarbonate, the polycarbonate, and an effective amount of each of an aliphatic diol, a mold-release agent, and an antioxidant has, after exposure to a total gamma radiation dose of 83 kGy and when measured according to ASTM D1925-70, an increase in yellowness index (dYI) of less than or equal to 36, when compared to the unexposed article.

18. A method of preparing a sulfonate end-capped polycarbonate, comprising condensing:

a dihydroxy compound,

a reactive sulfonic acid derivative, and

an activated carbonyl compound,

in a biphasic medium at a pH of about 9 to about 11 and in the presence of a phase transfer catalyst having the formula (R) 4 Q + X, wherein each R is the same or different, and is a C 1-10 alkyl group; Q is a nitrogen or phosphorus atom; and X is a halogen atom or a C 1-8 alkoxy group or C 6-18 aryloxy group.

19. The method of claim 18 wherein the activated carbonyl compound is phosgene, diphosgene, triphosgene, a dichloroformate, or a combination comprising at least one of these.

20. The method of claim 18 wherein the dihydroxy compound comprises a dihydroxy aromatic compound, a dihydroxy poly(arylene ether), a dihydroxy soft-block compound, or a combination comprising at least one of these.

21. The method of claim 18 , wherein the activated carbonyl compound is phosgene, wherein the phase transfer catalyst is methyl tri-n-butyl ammonium chloride; wherein the dihydroxy compound is bisphenol-A, and wherein the reactive sulfonic acid derivative is p-toluenesulfonyl chloride.

22. The method of claim 18 wherein the sulfonate end-capped polycarbonate prepared by the method has a polydispersity (Mw/Mn) of less than or equal to 2.4, as determined using molecular weights determined by GPC using a crosslinked styrene-divinylbenzene column calibrated with polystyrene or polycarbonate standards.

23. The method of claim 18 wherein the sulfonate end-capped polycarbonate prepared by the method has less than 5 percent by weight of residual reactive sulfonic acid derivative based on the total weight of the sulfonate end-capped polycarbonate.

24. The method of claim 18 , wherein the sulfonate end-capped polycarbonate has sulfonate end groups, and wherein the sulfonate end groups are present in amount of 0.01 to 10 mole-percent (mol %), per the total number of moles of repeating unit L present in the sulfonate end-capped polycarbonate.

25. A method of making a thermoplastic composition comprising melt-blending:

a sulfonate end-capped polycarbonate of formula:

Z-S(O) 2 —O-(-L-) m -O—S(O) 2 -Z

wherein each Z is independently an alkyl or aryl group, and -(-L-) m - is a polycarbonate linking group with m units of linking unit L, wherein m is at least one; and

a polycarbonate,

wherein a molded article having a thickness of 3.2±0.12 millimeters and consisting of the sulfonate end-capped polycarbonate, the polycarbonate, and an effective amount of each of an aliphatic diol, a mold-release agent, and an antioxidant has, after exposure to a total gamma radiation dose of 83 kGy and when measured according to ASTM D1925-70, an increase in yellowness index (dYI) of less than or equal to 36, when compared to the unexposed article.

26. An article comprising the thermoplastic composition of claim 1 .

27. A thermoplastic composition comprising:

a blend of

a polycarbonate, and

a sulfonate end-capped polycarbonate of formula:

Z-S(O) 2 —O-(-L-) m -O—S(O) 2 -Z

wherein each Z is independently an alkyl or aryl group, -(-L-) m - is a polycarbonate linking group with m units of linking unit L, and m is at least one,

wherein the amount and type of sulfonate end-capped polycarbonate is selected so that the overall concentration of sulfonate end groups is not greater than a molar concentration of 500 millimoles per kilogram (mmol/Kg), and is not less than 0.001 mmol/Kg, of the total weight of the sulfonate end-capped polycarbonate and the polycarbonate.

28. The thermoplastic composition of claim 1 , comprising a blend of a polycarbonate and the sulfonate end-capped polycarbonate, wherein the sulfonate end-capped polycarbonate is used in an amount of 1 to 80 wt %, based on the total weight of the polycarbonate and sulfonate end-capped polycarbonate, with the proviso that the amount and type of sulfonate end-capped polycarbonate used is selected so that the overall concentration of sulfonate end groups is not greater than a molar concentration of 500 millimoles per kilogram (mmol/Kg), and is not less than 0.001 mmol/Kg, of the total weight of the sulfonate end-capped polycarbonate and any added polycarbonate.