Abstract: The process contemplates the use of a sizing dispersion that comprises an aqueous dispersion of rosin material, a synthetic sizing agent and a aluminum compound selected from the group formed by aluminum sulfate and aluminum polymers of formulas [Al(OH)x(A)(3−x)]n  (1) or [Al(OH)x(H3PO4)y(A)(3−x)]n  (2) where A=Cl−, NO3−, HCOO−, CH3COO−; or [Al(OH)x(H3PO4)y(SO4)(3−x/2)]n  (3) where “x” ranges from 0.03 to 2.7, and “y” ranges from 0.01 to 0.8 and n≧2; and by mixtures thereof.

Abstract: A sizing composition and a method of sizing a cellulosic fiber material are disclosed. The sizing composition comprises an aqueous dispersion of a rosin material and a polyaluminium compound, and is characterised in that the polyaluminium compound is a polyaluminium phosphate sulphate compound. The polyaluminium phosphate sulphate compound should comprise at least 5% by weight, calculated as aluminium on the amount of rosin material in the composition. It is preferred that the sizing composition also comprises a synthetic sizing agent in addition to the rosin material. The dispersion preferably also includes a dispersing agent and has a dry content of at least 1% by weight. The sizing composition is used for the sizing of cellulosic fibre materials, such as paper, board or paper board by adding 0.