Process for the production of paper
View Patent ↗The present invention relates to a process for producing paper which comprises: (i) providing an aqueous suspension comprising cellulosic fibers, (ii) 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 (iii) dewatering the obtained suspension to form paper.
1. A process for producing paper which comprises:
(i) providing an aqueous suspension comprising cellulosic fibres,
(ii) dding to the suspension after all points of high shear at least:
a first polymer being a polyaluminium compound;
a second polymer being a water-soluble acrylamide-based polymer; 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; and wherein the second acrylamide-based polymer is formed from a reaction mixture which is essentially free from polyfunctional crosslinking agents
(iii) dewatering the obtained suspension to form paper.
2. The process of claim 1 , wherein the polyaluminium compound is selected from the group consisting of polyaluminium chloride, polyaluminium sulphate, polyaluminium compounds containing both chloride and sulphate ions, polyaluminium silicate-sulphate, and mixture thereof.
3. The process of claim 1 , wherein the second polymer is a cationic water-soluble acrylamide-based polymer.
4. The process of claim 1 , wherein the second polymer has a weight average molecular weight above about 2,000,000.
5. The process of claim 1 , wherein the second polymer has a weight average molecular weight above about 5,000,000.
6. The process of claim 1 , wherein the second polymer has a weight average molecular weight above about 5,000,000 up to about 50 million.
7. The process of claim 1 , wherein the second polymer has a charge density in the range of from 0.5 to 10.0 meq/g.
8. The process of claim 1 , wherein the second polymer has a charge density in the range of from 1.0 to 4.0 meq/g.
9. The process of claim 1 , wherein the third polymer is an inorganic anionic polymer selected from silicic acid or silicate based polymers comprising colloidal silica-based particle.
10. The process of claim 1 , wherein the third polymer is an inorganic anionic polymer selected from silicic acid or silicate based polymers comprising colloidal silica-based particle, the silica-based particles comprising aggregated particles having an average particle size in the range of from 1 to 10 nm.
11. The process of claim 1 , wherein the points of high shear are selected from fan pumps, pressure screens, and centri-screens.
12. The process of claim 1 , wherein the first, second and third polymers are added subsequent to a centri-screen being the last point of high shear.
13. 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 polyaluminium compound having a charge density above about 2.5 meq/g;
a second polymer being a cationic water-soluble acrylamide-based polymer having a weight average molecular weight of above about 500,000; 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; and wherein the second acrylamide-based polymer is formed from a reaction mixture which is essentially free from polyfunctional crosslinking agents; and dewatering the obtained suspension to form paper.
14. The process of claim 13 , wherein the first polymer has a charge density of above about 4.0 meq/g.
15. The process of claim 13 , wherein the polyaluminium compound is selected from the group consisting of polyaluminium chloride, polyaluminium sulphate, polyaluminium compounds containing both chloride and sulphate ions, polyaluminium silicate-sulphate, and mixture thereof.
16. The process of claim 13 , wherein the polyaluminium compound is selected from the group consisting of polyaluminium chloride, polyaluminium sulphate and mixtures thereof.
17. The process of claim 13 , wherein the second polymer has a weight average molecular weight of above about 2,000,000.
18. The process of claim 13 , wherein the first, second and third polymers are added subsequent to a centri-screen being the last point of high shear.
19. 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 polyaluminium compound selected from the group consisting of polyaluminium chloride, polyaluminium sulphate and mixtures thereof;
a second polymer being a cationic water-soluble acrylamide-based polymer having a weight average molecular weight of above about 5000,000, and a charge density in the range of from 0.5 to 4.0 meq/g; and
a third polymer being an inorganic anionic polymer selected from silicic acid or silicate based polymers comprising colloidal silica-based particle, the silica-based particles comprising aggregated particles having an average particle size in the range of from 1 to 10 nm, the particles being present in a sol having an S-value in the range of from 8 to 50%, with the proviso that the third polymer is not bentonite; and wherein the second acrylamide-based polymer is formed from a reaction mixture which is essentially free from polyfunctional crosslinking agents; and
dewatering the obtained suspension to form paper.
20. The process of claim 19 , wherein the first polymer has a charge density above about 4.0 meq/g.
21. The process of claim 19 , wherein the second acrylamide-based polymer is formed from a reaction mixture which is free from polyfunctional crosslinking agents.