Additive mixtures for rheology modification of polymers

A composition comprising:

• (a) a compound of formula (1) or (2)
• wherein
• G1, G2, G3 and G4 are each independently of each other C1-C4 alkyl, or G1 and G2 together or G3 and G4 together are pentamethylene;
• G1′, G2′, G3′ and G4′ are each independently of each other C1-C4 alkyl, or G1′ and G2′ together or G3′ and G4′ together are pentamethylene;
• G5, G6, G5′ and G6′ are each independently of each other hydrogen or C1-C4 alkyl;
• and
• X and X′ are independently of each other hydrogen, C1-C18 alkyl, C2-C18 alkenyl, —O—C1-C18 alkyl, —NH—C1-C18 alkyl, —N(C1-C6 alkyl)2, phenyl, phenoxy or —NH-phenyl,
• m is 1 or 2, and
• when m is 1, R1 is C2-C8 alkylene, C2-C8 hydroxyalkylene or C4-C36 acyloxyalkylene, or
• when m is 2, R1 is (—CH2)2C(CH2—)2, and
• R1′ is hydrogen, C1-C8 alkyl, C1-C8 hydroxyalkyl or a group of formula —(C═O)—C1-C40 alkyl, or
• O—R1′ together with a —CH— group linking them are a group —(C═O)—,
• (b) a compound of formula (3)
• wherein
• A is based on an organic isocyanate, wherein radical(s) —S—R are introduced by reaction with isocyanate groups,
• R is C2-C40 alkyl which is optionally substituted and/or interrupted, and
• n is equal to or greater than 1, and
• (c) a polymeric substrate.