Highly filled sheets and method of preparation thereof

Claim 1

A method for preparing a sheet comprising: (I) providing an aqueous dispersion of from about 1 percent to about 30 percent of a water--dispersible fiber; (II) mixing therewith (A) from about 60 percent to about 95 percent of a finely-divided, substantially water-insoluble, non-fibrous, inorganic filler and (B) from about 2 percent to about 30 percent of a binder containing a film-forming, water-insoluble, organic polymer in the form of an ionically stabilized latex having not greater than 0.7 millieguivalent of bound charge per gram of polymer in the latex; (III) colloidally destabilizing the resulting mixture to form a fibrous agglomerate in aqueous suspension having the characteristics that at a concentration of 100 grams of solids in 13,500 milliliters, the suspension will drain in a time of from about 4 seconds to about 120 seconds in a 10-inch by 12-inch Williams Standard Sheet Mould having a 2-inch outlet and a 30-inch water leg and fitted with a 100-mesh, stainless steel screen having a wire diameter of 0.0045 inch to provide in one pass at least 85 percent retention of solids which contain at least 60 percent by weight of filler; (IV) distributing and draining the aqueous suspension on a porous support to form a wet web; and (V) drying the web; said ionically stabilized latex being devoid of sufficient non-ionic stabilization to interfere with formation of the fibrous agglomerate; said percentages being on a dry weight basis, calculated on the total dry weight.

Claim 2

A method for preparing a sheet comprising: (I) providing an aqueous dispersion of from about 1 percent to about 30 percent of a water--dispersible fiber; (II) mixing therewith (A) from about 60 percent to about 95 percent of a finely-divided, substantially water-insoluble, non-fibrous, inorganic filler and (B) from about 2 percent to about 30 percent of a binder containing a film-forming, water-insoluble, organic polymer in the form of an ionically stabilized latex having not greater than 0.7 millieguivalent of bound charge per gram of polymer in the latex; (III) colloidally destabilizing the resulting mixture to form a fibrous agglomerate in aqueous suspension having the characteristics that at a concentration of 100 grams of solids in 13,500 milliliters, the suspension will drain in a time of from about 4 seconds to about 120 seconds in a 10-inch by 12-inch Williams Standard Sheet Mould having a 2-inch outlet and a 30-inch water leg and fitted with a 100-mesh, stainless steel screen having a wire diameter of 0.0045 inch to provide in one pass at least 85 percent retention of solids which contain at least 60 percent by weight of filler; (IV) distributing and draining the aqueous suspension on a porous support to form a wet web; and (V) drying the web; said ionically stabilized latex being devoid of sufficient non-ionic stabilization to interfere with formation of the fibrous agglomerate; said percentages being on a dry weight basis, calculated on the total dry weight.