Surface-treated magnesium hydroxide-comprising material

A surface-treated magnesium hydroxide-comprising material having a weight median particle size d50 value in the range from 0.25 μm to 15 μm,

• wherein the magnesium hydroxide-comprising material has been treated with at least one surface treatment agent that is a compound according to Formula (I),
• wherein R1 is a hydrolysable alkoxy group, and R2, R3 and R4 are independently from each other selected from the group consisting of hydrogen, a hydroxyl group, an alkyl group, a vinyl group, an alkoxy group, an acyloxy group, an acryloxy group, a methacryloxy group, an ethacryloxy group, a carboxyl group, an epoxy group, an anhydride group, an ester group, an aldehyde group, an amino group, an ureido group, an azide group, a halogen group, a phosphonate group, a phosphine group, a sulphonate group, a sulphide group or disulphide group, an isocyanate group or masked isocyanate group, a thiol group, a phenyl group, a benzyl group, a styryl group, a benzoyl group and a fully or partially halogenated alkyl group having from 1 to 20 carbon atoms, and u, v and w are independently from each other an integer from 0 to 24,
• and wherein the surface-treated magnesium hydroxide-comprising material has a specific surface area (BET) of from 15 to 150 m2/g as measured using nitrogen and the BET method according to ISO 9277:2010, a moisture pick-up susceptibility of from 0.1 to 10 mg/g, and a moisture pick-up susceptibility to specific surface area (BET) ratio of 0.001 to 0.5 mg/m2;
• and wherein the moisture content of the surface-treated magnesium hydroxide-comprising material is in the range from 0.05 to 5 wt.-% based on the total weight of the surface-treated magnesium hydroxide-comprising material.