DETAILED DESCRIPTION 1.
A process for the production of paper which comprises: i) providing an aqueous suspension containing cellulosic fibres, and optional fillers; ii) adding to the suspension at least 0.
001% by weight, based on dry cellulosic fibres and optional fillers, of at least one cationic or amphoteric organic polymer and at least 0.
001% by weight, calculated as SO2 and based on dry cellulosic fibres and optional fillers, of an aqueous silica-based sol comprising anionic silica-based particles and an organic nitrogen containing compound having molecular weight less than 1,000; and iii) forming and draining the obtained suspension on a wire.
2.
The process of claim 1, wherein the cationic or amphoteric organic polymer has a molecular weight of at least 1,000,000.
3.
The process of claim 1, wherein the cationic or amphoteric organic polymer is selected from the group consisting of amphoteric starch, cationic starch, amphoteric guar gum, cationic guar gum, amphoteric acrylamide-based polymer, cationic acrylamide-based polymer, cationic poly(diallyl-dimethyl ammonium chloride), cationic polyethylene imines, cationic polyamines, cationic polyamidoamines, cationic vinylamide-based polymers, cationic melamine-formaldehyde, cationic ureaformaldehyde resins, and mixtures thereof.
4.
The process of claim 3, wherein the cationic or amphoteric organic polymer is cationic starch.
5.
The process of claim 3, wherein the cationic or amphoteric organic polymer is a cationic acrylamide-based polymer.
6.
The process of claim 1, wherein the aqueous silica-based sol has a molar ratio of SO2 to N from 1:1 to 50:1.
7.
The process of claim 1, wherein the nitrogen-containing organic compound contains at least one oxygen atom.
8.
The process of claim 1, wherein the nitrogen-containing organic compound is an amine containing from 2 to 12 carbon atoms.
9.
The process of claim 1, wherein the nitrogen-containing organic compound is selected from the group consisting of triethanolamine, diethanolamine, dipropylamine, aminoethylethanolamine, 2-methoxyethylamine, N,N-dimethylethanolamine, choline hydroxide, choline chloride, tetramethylammonium hydroxide, tetramethylammonium hydroxide, tetraethanol ammonium hydroxide, and mixtures thereof
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Manufacturing Materials 
