Abstract: A solid stabilizer composition for organic polymers is formed by a solid, continuous phase and by a dispersed phase in said continuous phase, wherein the continuous phase is constituted by amorphous tetrakis-[3-(3,5-di-tert.-butyl-4-hydroxyphenyl)-propionyloxymethyl]-metha ne and the dispersed phase is constituted by an either amorphous or crystalline organic phosphite, in the form of particles with a particle size of from 10 .mu.m to 2 mm, with the weight ratio of said continuous phase to said dispersed phase being comprised within the range of from 9:1 to 1:9.The processes for preparing said solid stabilizer composition and its use in the stabilization of organic polymers are disclosed.

Abstract: Stabilizers for organic polymers, consisting of one or more phosphorus-containing compounds of the family of alkyl- and/or phenyl-phosphites, alkyl- and/or phenyl-phosphonites, alkyl- and/or phenyl-diphosphonites, are directly added to the reaction mixture during the (co)polymerization of .alpha.-olefins or of mixtures thereof with other unsaturated monomers.The so-obtained polymeric compositions result perfectly stabilized, and show a thermo-oxidative resistance higher than that of the same polymeric compositions to which the same antioxidants have been added by a traditional route.

Abstract: Solid organic phosphites in powder form, used to endow organic polymers with stability characteristics are made resistant to hydrolysis by treating said powder phosphites with a silane containing in its molecule at least two alkoxy groups and causing the silane to hydrolyze, and the formation and deposition of a siliconic polymer on the surface of powder particles to occur.