Stabilizer compositions containing substituted chroman compounds and methods of use

1. A method for enhancing processing stability of polypropylene homopolymer, the method comprising adding to said polypropylene from 0.01% to 10% by weight based on the total weight of the polypropylene of a stabilizer composition comprising vitamin E acetate and zinc stearate; wherein amounts of the vitamin E acetate and zinc stearate in the stabilizer composition are selected to enhance processing stability of the polypropylene even in the absence of antistatic agents and organic phosphites and phosphonites by improving retention of melt index (MI) of the polypropylene when subjected to multi-pass extrusion.

2. A method according to claim 1 , wherein the stabilizer composition further comprises at least one organic phosphite or phosphonite selected from the group consisting of triphenyl phosphite, diphenyl alkyl phosphites, phenyl dialkyl phosphites, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol phosphite, tris(2,4-di-tert-butylphenyl) phosphite, tris(nonylphenyl) phosphite, a compound of formulae (A), (B), (C), (D), (E), (F), (G), (H), (J), (K) and (L):

2-butyl-2-ethyl-1,3-propanediol 2,4,6-tri-t-butylphenol phosphite, bis-(2,6-di-t-butyl-4-methlphenyl) pentaerythritol diphosphite, 2-butyl-2-ethyl-1,3-propanediol 2,4-di-cumylphenol phosphite, 2-butyl-2-ethyl-1,3-propanediol 4-methyl-2,6-di-t-butylphenol phosphite, and bis-(2,4,6-tri-t-butyl-phenyl) pentaerythritol diphosphite.

3. A method according to claim 1 , wherein the stabilizer composition further comprises at least one hindered phenol compound having a molecular fragment according to one or more of Formula (IVa), (IVb), or (IVc):

wherein:

R 18 in Formula (IVa), (IVb), and (IVc) is chosen from hydrogen or a C 1-4 hydrocarbyl;

each of R 19 and R 20 in Formula (IVa), (IVb), and (IVc) is independently chosen from hydrogen or a C 1 -C 20 hydrocarbyl; and

R 37 in Formula (IVa), (IVb), and (IVc) is chosen from a C 1 -C 12 hydrocarbyl.

4. A method according to claim 3 , wherein the at least one hindered phenol compound is selected from the group consisting of (1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione, 1,1,3-tris(2′-methyl-4′-hydroxy-5′-t-butylphenyl)butane, triethylene glycol bis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate], 4,4′-thiobis(2-t-butyl-5-methylphenol), 2,2′-thiodiethylene bis[3-(3-t-butyl-4-hydroxyl-5-methylphenyl)propionate], octadecyl 3-(3′-t-butyl-4′-hydroxy-5′-methylphenyl)propionate, tetrakismethylene(3-t-butyl-4-hydroxy-5-methylhydrocinnamate)methane, N,N′-hexamethylene bis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionamide], di(4-tertiarybutyl-3-hydroxy-2,6-dimethyl benzyl) thiodipropionate, and octadecyl 3,5-di-(tert)-butyl-4-hydroxyhydrocinnamate.

5. A method according to claim 1 , wherein the stabilizer composition further comprises a light stabilizer selected from the group consisting of hindered amine light stabilizers, hindered hydroxyl benzoates, nickel phenolates, ultraviolet light stabilizers, and combinations thereof.

6. A method according to claim 5 , wherein the light stabilizer is a hindered amine light stabilizer compound comprising a molecular fragment according to:

(a) Formula (VI):

wherein:

R 62 is selected from the group consisting of hydrogen, OH, C 1 -C 20 hydrocarbyl, —CH 2 CN, C 1 -C 12 acyl, and C 1 -C 18 alkoxy;

R 65 is selected from the group consisting of hydrogen and C 1 -C 8 hydrocarbyl; and

each of R 60 , R 61 , R 63 , and R 64 is independently chosen from a C 1 -C 20 hydrocarbyl, or R 60 and R 61 and/or R 63 and R 64 taken together with the carbon to which they are attached form a C 5 -C 10 cycloalkyl; or

(b) Formula (VIa)

wherein:

m is an integer from 1 to 2;

R 39 is selected from the group consisting of hydrogen, OH, C 1 -C 20 hydrocarbyl, —CH 2 CN, C 1 -C 12 acyl, and C 1 -C 18 alkoxy; and

each of G 1 -G 4 is independently chosen from a C 1 -C 20 hydrocarbyl.

7. A method according to claim 5 , wherein the light stabilizer comprises an ultraviolet light absorber selected from the group consisting of a 2-hydroxybenzophenone compound, a 2-(2′-hydroxyphenyl)benzotriazole compound, a 2-(2′-hydroxyphenyl)-1,3,5-triazine compound, and combinations thereof.

8. A method according to claim 1 , wherein the stabilizer composition further comprises at least one N,N-dihydrocarbylhydroxylamine selected from the group consisting of N,N-dibenzylhydroxylamine, N,N-diethylhydroxylamine, N,N-dioctylhydroxylamine, N,N-dilaurylhydroxylamine, N,N-didodecylhydroxylamine, N,N-ditetradecylhydroxylaamine, N,N-dihexadecylhydroxylamine, N,N-dioctadecylhydroxylamine, N-hexadecyl-N-tetradecylhydroxylamine, N-hexadecyl-N-heptadecylhydroxylamine, N-hexadecyl-N-octadecylhydroxylamine, N-heptadecyl-N-octadecylhydroxylamine, and N,N-di(hydrogenated tallow)hydroxylamine.

9. A method according to claim 1 , wherein 0.15% of the vitamin E acetate and 0.05% of the zinc stearate are present based on the total weight of the polypropylene.

10. A method according to claim 1 , wherein the stabilizer composition further comprises vitamin E.

11. A method according to claim 10 , wherein 0.075% of the vitamin E acetate, 0.075% of the vitamin E, and 0.05% of the zinc stearate are present based on the total weight of the polypropylene.

12. A method according to claim 1 , wherein the vitamin E acetate is a chroman-based compound according to Formula (Va):

or isomers and/or mixtures thereof, including mixtures of said isomers.

13. A method according to claim 1 , wherein the amounts of vitamin E acetate and zinc stearate are further selected to enhance processing stability of the polypropylene by improving elongation retention of the polypropylene when subjected to extrusion followed by compression molding.