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.