Process for the production of paper
View Patent ↗The present invention relates to a process for producing paper which comprises: (vii) providing an aqueous suspension comprising cellulosic fibres, (viii) adding to the suspension after all points of high shear: a first polymer being a cationic polymer having a charge density above 2.5 meq/g; a second polymer; and a third polymer being an organic or inorganic anionic polymer; and (ix) dewatering the obtained suspension to form paper.
1. A process for producing paper which comprises:
(i) providing an aqueous suspension comprising cellulosic fibres,
(ii) adding to the suspension after all points of high shear at least:
a first polymer being a water-soluble cationic acrylamide-based polymer having a charge density above 2.5 meq/g and a molecular weight above 2,000,000;
a second polymer being a water-soluble acrylamide-based polymer having a molecular weight above 5,000,000; and
a third polymer being an inorganic anionic polymer selected from silicic acid or silicate based polymers, with the proviso that the third polymer is not bentonite;
wherein the first and second acrylamide-based polymers are formed from a reaction mixture which is free from polyfunctional crosslinking agents; and
(iii) dewatering the obtained suspension to form paper.
2. The process of claim 1 , wherein the second polymer is cationic.
3. The process of claim 1 , wherein the second polymer is anionic.
4. The process of claim 1 , wherein the third polymer comprises colloidal silica-based particles.
5. The process of claim 4 , wherein the silica-based particles comprise aggregated particles and have an average particle size in the range of from 1 to 10 nm.
6. The process of claim 1 , wherein the third polymer is an inorganic anionic silica-based polymer prepared by condensation polymerization of siliceous compounds.
7. The process of claim 6 , wherein the third polymer is in the form of an aqueous colloidal silica sol.
8. A process for producing paper which comprises:
(i) providing an aqueous suspension comprising cellulosic fibres,
(ii) adding to the suspension after all points of high shear at least:
a first polymer being a water-soluble cationic acrylamide-based polymer having a charge density above 3.0 meq/g and a molecular weight above 2,000,000;
a second polymer being a water-soluble acrylamide-based polymer having a molecular weight above 5,000,000 and higher than the molecular weight of the first polymer and a charge density of less than 2.0 meq/q; and
a third polymer being an inorganic anionic polymer selected from silicic acid or silicate based polymers, with the proviso that the third polymer is not bentonite;
wherein the first and second acrylamide-based polymers are formed from a reaction mixture which is essentially free from polyfunctional crosslinking agents; and
(iii) dewatering the obtained suspension to form paper.
9. The process of claim 8 , wherein the second polymer is cationic.
10. The process of claim 8 , wherein the second polymer is anionic.
11. The process of claim 8 , wherein the third polymer comprises colloidal silica-based particles.
12. The process of claim 11 , wherein the silica-based particles comprise aggregated particles and have an average particle size in the range of from 1 to 10 nm.
13. The process of claim 8 , wherein the third polymer is an inorganic anionic silica-based polymer prepared by condensation polymerization of siliceous compounds.
14. The process of claim 13 , wherein the third polymer is in the form of an aqueous colloidal silica sol.