Color improving stabilizing compositions comprising leucine

1. A color improving stabilizer composition for polyolefin-based thermoplastic polymers comprising

a) at least one sterically hindered phenol,

b) at least one phosphorus-containing secondary antioxidant, and

c) at least one Leucine compound,

wherein the weight ratio of component (a) to component (b) to component (c) is from 1:5:3 to 2:0.5:0.1.

2. A composition according to claim 1 wherein the weight ratio of component (a) to component (b) to component (c) is from 1:3:2 to 1:1:0.2.

3. A composition according to claim 1 wherein the Leucine compound is Leucine.

4. A composition according to any claim 1 , wherein the sterically hindered phenol is 2,2′-bis[3,5-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxoprop-oxy]methyl-1,3-propanediyl-3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepro-panoate; octadecyl-3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanoate; 1,3,5-tris[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]1,3,5,-triazine-2,4,6(1H,3H,5H)trione; 4,4′,4″-[2,4,6-trimethyl-1,3,5-benzenetriyl)tris-(methylene)-]tris[2,6-bis(1,1-dimethylethyl)-phenol; ethanediyl-3,5-bis(1,1-dimethylethyl)-4-hydroxy-thiodi-2,1-benzenepropanoate; 2:1 calcium salt of monoethyl-[[3,5-bis-(1,1-dimethylethyl)-4-hydroxyphenyl]-methyl]-phosphonic acid ester; 2-[3-[3,5-bis(1,1-dimethylethyl)-4-hydroxy-phenyl]-1-oxopropyl]-hydrazide-3,5-bis(1,1-dimethylethyl)-4-hydroxy-benzene-propanoic acid; 2,2′-oxamido-bis-[ethyl-3-(3,5-di-tert.-butyl-4-hydroxyphenyl)-propionate] or mixtures thereof.

5. A composition according to claim 1 , wherein the phosphorous-containing secondary antioxidant is triphenylphosphite, tris-isodecylphosphite; tris(nonylphenyl)phosphite; distearyl pentaerythritol diphosphite; 2,4,6-tri-tert.-butylphenyl-2-butyl-2-ethyl-1,3-propanediol phosphite; bis(2,4-di-tert.-butyl-phenyl)-pentaerythrityl diphosphite; 2,2′,2″-nitrilo triethyl-tris[3,3′,5,5′-tetra-tert.-butyl-1,1′-biphenyl-2,2′-diyl]phosphite; bis[2,4-di-tert.-butyl-6-methyl-phenyl]ethyl phosphite; 2,2′-ethylidene-bis-(4,6-di-tert.-butylphenyl)-fluorophosphite; tris(2,4-di-tert.-butylphenyl)phosphite; the 4,6-di-tert.-butyl-m-cresol condensation products with the Friedel-Crafts-reaction products of biphenyl and phosphorous trichloride; tetrakis [2,4-di-tert.-butylphenyl]-4,4′-biphenylenediphosphonite; or the condensation products of 2,4-di-tert.-butylphenol with the Friedel-Crafts-reaction product of biphenyl and PCl 3.

6. A method for enhancing the color stability of polyolefin-based thermoplastic polymers comprising the step of incorporating into the polyolefin-based thermoplastic polymer, before or during processing, a stabilizing quantity of the stabilizer composition according to claim 1 .

7. A method according to claim 6 wherein the stabilizer composition is added in an amount of from 0.001 to 5% by weight, based on the thermoplastic polymer.

8. A process for producing a stabilizer composition according to claim 1 , comprising mixing the components (a), (b) and (c) in the weight ratios given in claim 1 .

9. A masterbatch composition comprising a stabilizer composition according to claim 1 and a thermoplastic material, wherein the thermoplastic material is identical or compatible with a thermoplastic polymer to be stabilized.

10. A masterbatch composition according to claim 9 comprising 10 to 80% by weight of the stabilizer composition and 90 to 20% by weight of the thermoplastic material.

11. A method according to claim 6 , wherein the stabilizer composition is added in an amount from 0.01 to 1% by weight, based on the thermoplastic polymer.

12. A method according to claim 6 , wherein the stabilizer composition is added in an amount from 0.1 to 0.5% by weight, based on the thermoplastic polymer.

13. A masterbatch composition according to claim 9 , comprising 5 to 25% by weight of the stabilizer composition and 95 to 75% by weight of the thermoplastic material.

14. A thermoplastic article comprising the stabilizer composition of claim 1 .