Stabilization systems for polymeric material in pellet form

A stabilizing system for stabilizing polymeric materials against ultraviolet light and thermooxidative deterioration, the stabilizing system being in pellet form;

• the pellet being formed from a homogeneous mixture consisting essentially of a polymer stabilizing composition and a melt preventing compound which substantially prevents melting of the stabilizing composition during processing of the stabilizing composition and the melt preventing compound;
• the homogeneous mixture being substantially dry;
• the stabilizing composition comprising about 80% to about 98% by weight of the mixture and the melting preventing compound comprising about 2% to about 20% by weight of the mixture;
• the stabilizing composition being chosen from the group consisting essentially of (a) tris(2,4,di-tert-butylphenyl)phosphite, (b) pentaerythritol tetrakis 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, (c) dimethyl succinate polymer with 4-hydroxy-2,2,6,6-tetra methyl-1-piperidineethanol, and (d) N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine polymer with 2,4,6-trichloro-1,3,5-triazine and 2,4,4-trimethyl-1,2-pentanamine, and combinations thereof;
• the melt preventing compound being chosen from the group consisting essentially of (e) fatty alcohols and fatty acids, having a melting point of between 50.degree. C. and 100.degree. C., octadecyl 3,5-di-tert-butyl-4-hydroxy hydrocinnamate, glyceryl monostearate, and oleamide, (f) polyolefins having a particle size smaller than 100 .mu., and (g) calcium stearates having a particle size smaller than 100 .mu.;
• wherein the melt preventing compounds of group (e) comprising 3-10% by weight of the homogeneous mixture when used;
• the melt preventing compounds of group (f) comprising 3-15% by weight of the homogeneous mixture when used;
• and the melt preventing compounds of group (g) comprising 10-20% by weight of the homogeneous mixture when used;
• the stabilizing compounds remaining substantially unmelted during processing of the stabilizing compounds and melt preventing compounds.

A method of producing a stabilizer for polymeric materials in pellet form, wherein the pellet consists essentially of said stabilizer and a melt preventing compound which will substantially prevent melting of said stabilizer;

• the method comprising:
• dry mixing at least one stabilizing compound and said melt preventing compound to produce a homogeneous substantially dry mixture wherein said stabilizing compound remains substantially unmelted;
• the at least one stabilizing compound being chosen from the group consisting essentially of tris(2,4,di-tert-butylphenyl)phosphite, pentaerythritol tetrakis 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, dimethyl succinate polymer with 4-hydroxy-2,2,6,6-tetra methyl-1-piperidineethanol, and N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine polymer with 2,4,6-trichloro-1,3,5-triazine and 2,4,4-trimethyl-1,2-pentanamine, and combinations thereof;
• the melt preventing compound being chosen from the group consisting essentially of (a) fatty acids and fatty alcohols having a melting point of between 50.degree. C. and 100.degree. C., or octadecyl 3,5-di-tert-butyl-4-hydroxy hydrocinnamate, glyceryl monostearate, and oleamide, (b) polyolefins having a particle size of less than 100 .mu., and (c) calcium stearates having a particle size of less than 100 .mu.;
• the at least one stabilizing compound comprising approximately about 50% to about 98% by weight of the homogeneous mixture;
• the melt preventing compound comprising about 2% to about 50% by weight of the homogeneous mixture;
• introducing the homogeneous mixture into a pellet mill;
• operating the pellet mill to compress the homogeneous mixture into a product, the product having a pellet fraction and a powder fraction, the mill being operated so as to substantially prevent melting of the stabilizing agent;
• collecting a product from the pellet mill;
• and
• separating the pellet fraction from the powder fraction.