FIELD: polymer materials. SUBSTANCE: invention concerns thermal stabilizers for compositions containing halogenated polymers, in particular polyvinylchloride, and proposes calcium or magnesium acetylacetonate partially coated with compatibility-imparting agent. Preparation procedure: calcium or magnesium acetylacetonate. Or their mixture is brought into contact with at least one compatibility-imparting agent optionally in presence of solvent and/or dispersant. EFFECT: avoided problem of inhomogeneities arising during formation of polymer compositions stabilized by calcium or magnesium acetylacetonate. 22 cl, 3 tbl, 6 ex
