Composite filler particles and process for the preparation thereof

Composite filler particles formed by the process comprising the steps of:

• (a) coating a particulate filler having a median particle size (D50) of from 1 to 1200 nm with a coating composition containing a film-forming agent forming a coating layer on the surface of the particulate filler, said coating layer displaying reactive groups on the surface of the coating layer, said reactive groups being selected from addition polymerizable groups and step-growth polymerizable groups, thereby forming a coated particulate filler;
• subsequently or concurrently
• (b) agglomerating the coated particulate filler, optionally in the presence of a further crosslinking agent and optionally in the presence of a further particulate filler not displaying reactive groups, for providing a granulation of the coated particulate filler wherein the granulation contains the coated particulate filler particles and the optional further particulate filler particles separated from and connected to each other by at least one coating layer, whereby the at least one coating layer may be crosslinked by crosslinking groups obtained by reacting the reactive groups and optionally a further crosslinking agent, whereby the agglomeration is carried out by spray agglomeration or growth agglomeration;
• (c) optionally milling, classifying and/or sieving the granulation of the coated particulate filler;
• and
• (d) optionally further crosslinking the granulation of the coated particulate filler;
• wherein the prepared composite filler particles have a median particle size (D50) of from 1 to 70 μm;
• wherein reactive groups are transformed into crosslinking groups obtained by reacting reactive groups and optionally a further crosslinking agent;
• and
• wherein the particulate filler is the main component by volume of the composite filler particles.

A dental composition comprising composite filler particles formed by the process comprising the steps of:

• (a) coating a particulate filler having a median particle size (D50) of from 1 to 1200 nm with a coating composition containing a film-forming agent forming a coating layer on the surface of the particulate filler, said coating layer displaying reactive groups on the surface of the coating layer, said reactive groups being selected from addition polymerizable groups and step-growth polymerizable groups, thereby forming a coated particulate filler;
• subsequently or concurrently
• (b) agglomerating the coated particulate filler, optionally in the presence of a further crosslinking agent and optionally in the presence of a further particulate filler not displaying reactive groups, for providing a granulation of the coated particulate filler wherein the granulation contains the coated particulate filler particles and the optional further particulate filler particles separated from and connected to each other by at least one coating layer, whereby the at least one coating layer may be crosslinked by crosslinking groups obtained by reacting the reactive groups and optionally a further crosslinking agent, whereby the agglomeration is carried out by spray agglomeration or growth agglomeration;
• (c) optionally milling, classifying and/or sieving the granulation of the coated particulate filler;
• and
• (d) optionally further crosslinking the granulation of the coated particulate filler;
• wherein the prepared composite filler particles have a median particle size (D50) of from 1 to 70 μm;
• wherein reactive groups are transformed into crosslinking groups obtained by reacting reactive groups and optionally a further crosslinking agent;
• wherein the particulate filler is the main component by volume of the composite filler particles;
• and
• wherein the dental composition is a dental composite, a dental cement or a resin reinforced dental cement.