UV-stabilizers for siloxane systems

A process for producing UV-stabilizer comprising mixing and heating (A) a hydroxybenzotriazole conforming to

• where
• R1 denotes a member selected from the group consisting of H, C1-18-alkyl, C5-6-cycloalkyl and C6-12-aryl,
• R2 denotes a member selected from the group consisting of H, halogen and C1-12-alkyl,
• R3 denotes a member selected from the group consisting of a single bond, C1-12-alkylene, C5-6-cycloalkylene and phenylene
• R4 is a member selected from the group consisting of H, alkali metal, ammonium, alkaline earth metal, C1-12-alkyl, —CO-alkyl, C6-12-aryl, and —CO-aryl, and —CO-aryl, and
• (B) at least one hydrolyzable silane conforming to formula (2) or (3)
• where
• R5 is a divalent hydrocarbon residue having at most 9 carbon atoms or a divalent residue having at most 9 carbon atoms consisting of C, H and O atoms, wherein the O atom is present as an ether bond residue and
• R6 is an aliphatic hydrocarbon residue having at most 4 carbon atoms, an acyl residue having at most 4 carbon atoms or a residue of the formula (CH2CH2O)nZ, in which n is at least 1 and Z means an aliphatic hydrocarbon residue having at most 4 carbon atoms;
• m is 0 or 1, to at least 90° C. for at least 30 minutes to form a reaction product.