Abstract: Novel precipitated calcium carbonate particles in clustered form, which when used as fillers impart improved strength, opacity and other advantages to paper, are prepared by a process involving adding lime and carbon dioxide to a reaction mixture containing seed material having a scalenohedral morphology, the lime and carbon dioxide being added simultaneously. The flow rates of the lime and carbon dioxide are adjusted to control the solution conductivity of the reaction minute to between about 2.0 and about 4.0 mS to form the clusters of calcite particles, the clusters having an average equivalent spherical diameter of between about 1.5 and 3.5 microns and a specific surface area of between about 2.0 and 9.0 m.sup.2 /g. At least about 25% of the particles of said clusters have a prismatic form.

Abstract: The disclosed invention relates to a composition comprising finely divided particles of an inorganic material treated with a cellulose derivative modified by or containing at least one ionic substituent. The disclosed invention further relates to a method of providing paper of improved brightness. The disclosed invention also relates to a method of providing finely divided particles of inorganic material, treating the particles with a cellulose derivative modified by or containing at least one ionic substituent, and adding the treated particles to cellulose fiber during an alkaline process for making paper. Also, an alkaline paper comprising the finely divided particles of inorganic material treated with the cellulose derivative is disclosed.

Abstract: The disclosed invention relates to a composition comprising finely divided cationically charged particles of an inorganic material treated with at least one of anionic polysaccharide or anionically modified polysaccharide. The disclosed invention further relates to a method of providing paper of improved strength. The method entails providing finely divided particles of inorganic material, treating the particles with at least one of anionic polysaccharide or anionically modified polysaccharide, and adding the treated particles to cellulose fiber during an alkaline process for making paper. Also, an alkaline paper comprising the finely divided particles of inorganic material treated with at least one of anionic polysaccharide or anionically modified polysaccharide is disclosed.