Additives for protection of polymers against ultraviolet light

A process of preparing an ultraviolet light absorber additive for protecting polymers from ultraviolet radiation, comprising providing silica particles having silanol groups (SiOH) on their surface;

• reacting the silanol groups with a vinyl compound of the formula (H2C═CH)iSi(OCjH2j+1)4−i wherein 1≤i≤3 and 1≤j≤3, thereby covalently attaching the vinyl compound to the silica surface via the surface silanol groups, thereby introducing onto the surface of the silica particles a first functional group which is a carbon-carbon double bond, reacting the so-formed inorganic oxide particles modified with the carbon-carbon double bond group with a spacer having a plurality of a second functional group,
• wherein the spacer is an organosilicon compound having silicon hydride (SiH) functional groups, wherein the number of SiH groups in the organosilicon compound is denoted by n, where n is an integer equal to or greater than 4, wherein one SiH group participates in a bond formation reaction with the carbon-carbon double bond group present on the surface of the silica particles, thus having n−1 SiH groups available for bond formation reaction with a UV light absorbing compounds;
• reacting the so-formed particles having n−1 SiH groups available for bond formation reaction, with a UV light absorbing compound;
• and isolating from the reaction mixture said ultraviolet light absorber additive.