Powder for the modification of thermoplastic resins

In a method for modifying a thermoplastic resin with an organopolysiloxane composition in order to improve the lubricity of said resin, the improvement comprising using as said organopolysiloxane composition a siloxane powder composition prepared by mixing

• (A) 100 parts by weight of a liquid polydiorganosiloxane;
• (B) 40 to 200 parts by weight of a silica powder that has a specific surface of at least 50 m.sup.2 /g using sufficient shear to prepare a powder in which the surface of component (B) is coated with component (A), and then mixing this powder with
• (C) 10 to 50 parts by weight of a polyorganosiloxane resin which is a solid at room temperature, said resin consisting essentially of (R.sub.3 SiO.sub.1/2) siloxane units and (SiO.sub.2) siloxane units in the molar ratio of 1:4 to 1:1, respectively,
• where R is selected from the group consisting of alkyl radicals and phenyl radical.