Paper and paperboard production process and corresponding novel retention aids, and papers and paperboards thus obtained
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Abstract
The invention relates to an improved paper production process according to which a cross-linked polymer prepared in reverse-phase emulsion and sheared before introduction into the fibrous mass is used as the main retention aid, and then bentonite is used as the secondary retention aid (a dual type system). The two additions are not separated by any mandatory stage for intense shearing of the fibrous suspension (or mass). The paper manufacturer can therefore be free from the constraints of shearing the pulp. A distinctly improved retention of the fines is obtained, and also a distinct improvement in drainage. In addition, the bentonite content in the white water is reduced. Lastly, excellent formation is maintained.
29 Citations
60 Claims
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1-34. -34. (canceled)
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35. Process for manufacturing a sheet of paper, paperboard or the like having improved retention and drainage properties, of the type which uses a dual system of an acrylic type polymer and bentonite or an optionally treated kaolin as the primary and secondary retention agents, respectively, characterized in that it incorporates operations comprised of adding to the suspension or fibrous mass to be flocculated, or paper pulp,
a) as the main retention agent, a (co)polyacrylamide that is cross-linked and exists in the form of a reverse phase or water-in-oil emulsion, or a solution of the powder obtained by drying said reverse phase emulsion, said emulsion or solution being sheared prior to introduction or injection into the fibrous mass; - wherein said (co)polyacrylamide is 20 mole % cationic or less, and
b) then a second retention agent, c) without a stage for intense shearing of the pulp between the additions a) and b), or with an “
optional”
shearing of the pulp between the additions a) and b);
wherein the active material concentration at the point in time when shear occurs is 3 to 15 g/l;
characterized in that the polymer used has an intrinsic viscosity i.v. as low as 1 to 3, which becomes an intrinsic viscosity i.v. as high as 3-7 or 8 after the application of the shearing; and
characterized in that the quantity of cross-linked polyacrylamide or of cross-linked acrylic (co)polymer introduced in the form of a reverse phase water-in-oil emulsion, Areversed@ in water, or in the form of the solution of the powder obtained by drying said emulsion, is between 0.03 and 1% o, or between thirty and one thousand grams/ton (30 and 1000 g/t) of dry pulp, optionally between 0.15 and 0.5% o (or between 150 and 500 g/t). - View Dependent Claims (36, 37, 38, 39, 40, 41, 42, 43, 44, 50, 51, 52, 53, 54, 55, 56, 57)
- wherein said (co)polyacrylamide is 20 mole % cationic or less, and
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45. Novel retention agent for the manufacture of a sheet of paper, paperboard or the like, characterized in that it comprises a sheared cross-linked polyacrylamide or a cross-linked acrylic (co)polymer in reverse phase or water-in-oil emulsion, or in the form of the sheared solution of the powder obtained by drying said emulsion, and optionally characterized in that the cross-linking agent is a cross-linking agent constituted by a polyfunctional compound having at least two reagent groups chosen from the group comprising the double bonds, the aldehyde bonds or the epoxy bonds, the cross-linking agents that can be incorporated comprising ionic cross-linking agents such as polyvalent metal salts, formaldehyde, glyoxal, or covalent cross-linking agents that will copolymerize with the monomers, optionally monomers with diethylenic unsaturation the family of diacrylate esters which can include the diacrylates of polyethylene glycol (PEG) or polyethylenic unsaturation, and optionally methylenebisacrylamide (MBA), and in that the cross-linking agent is introduced at a rate of five to two hundred (5 to 200) moles per million moles of monomers characterized in that the polymer used has an intrinsic viscosity i.v. as low as 1 to 3, which becomes an intrinsic viscosity i.v. as high as 3-7 or 8 after the application of the shearing;
- and characterized in that the quantity of cross-linked polyacrylamide or of cross-linked acrylic (co)polymer introduced in the form of a reverse phase water-in-oil emulsion, “
reversed”
in water, or in the form of the solution of the powder obtained by drying said emulsion, is between 0.03 and 1% o, or between thirty and one thousand grams/ton (30 and 1000 g/t) of dry pulp, optionally between 0.15 and 0.5% o (or between 150 and 500 g/t). - View Dependent Claims (46, 47, 48, 49, 58, 59, 60)
- and characterized in that the quantity of cross-linked polyacrylamide or of cross-linked acrylic (co)polymer introduced in the form of a reverse phase water-in-oil emulsion, “
Specification