Process of controlled chemical reaction of a solid filler material surface and additives to produce a surface treated filler material product

A surface treated filler material product comprising:

• a) at least one calcium carbonate-containing filler material, having
• i) a weight median particle size d50 value in the range from 0.1 μm to 7 μm,
• ii) a top cut (d98)≤15 μm,
• iii) a specific surface area (BET) of from 0.5 to 150 m2/g as measured by the BET nitrogen method, and
• iv) a residual total moisture content of 1 wt.-%, based on the total dry weight of the at least one calcium carbonate-containing filler material, and
• b) a treatment layer on the surface of the at least one calcium carbonate-containing filler material comprising at least one mono-substituted succinic anhydride and an optional at least one mono-substituted succinic acid, and/or salty reaction product(s) thereof,
• wherein the surface treated filler material product comprises the treatment layer in an amount of from 0.1 to 3 wt. %, based on the total dry weight of the at least one calcium carbonate containing filler material

A process for preparing a surface treated filler material product with succinic anhydride(s), the process comprising at least the steps of:

• a) providing at least one calcium carbonate-containing filler material having
• i) a weight median particle size d50 value in the range from 0.1 μm to 7 μm,
• ii) a top cut (d9s) of 15 μm,
• iii) a specific surface area (BET) of from 0.5 to 150 m2/g as measured by the BET nitrogen method, and
• (iv) a residual total moisture content of from 0.01 wt.-% to 1 wt.-%, based on the total dry weight of the at least one calcium carbonate-containing filler material,
• b) providing at least one mono-substituted succinic anhydride and optionally at least one mono-substituted succinic acid in an amount of from 0.1 to 3 wt.-%, based on the total dry weight of the at least one calcium carbonate-containing filler material of step a),
• c) contacting the surface of the at least one calcium carbonate-containing filler material of step a) under mixing, in one or more steps, with the at least one mono-substituted succinic anhydride and the optional at least one mono-substituted succinic acid of step b) such that a treatment layer comprising the at least one mono-substituted succinic anhydride and the optional at least one mono-substituted succinic acid and/or salty reaction product(s) thereof is formed on the surface of said at least one calcium carbonate-containing filler material of step a),
• wherein the temperature before and/or during contacting step c) is adjusted such that the temperature is at least 2° C. above the melting point of the at least one mono-substituted succinic anhydride and the optional at least one mono-substituted succinic acid.