Method for the production of paper, cardboard and card
A method for the production of paper, cardboard and card by adding a microparticle system consisting of a polymer retention agent having a molar mass M w of at least 2 million and a fine-part inorganic component in order to form a paper material having a material density of a 20 g/l maximum and by dewatering the paper material, wherein the paper material undergoes at least one shearing step prior to or after addition of the retention agent and wherein the retention agent is introduced in a dosed manner into the paper material in at least two places and the fine inorganic component is dosed prior to or after addition of the retention agent or between two dosing points for the retention agent.
1. A process for producing a paper, a board or a cardboard by adding a microparticle system comprising a cationic polymeric retention aid having a molar mass M w of at least 2 million and a finely divided inorganic component to a paper stock having a density of not more than 20 g/l and draining the paper stock, the paper stock being subjected, before or after the addition of the cationic polymeric retention aid, to at least one shear stage, wherein said adding comprises metering the cationic polymeric retention aid into the paper stock at least two places and metering the finely divided inorganic component after the addition of the cationic polymeric retention aid.
2. The process according to claim 1 , wherein the cationic polymeric retention aid is added after the last shear stage at least two successive places and thereafter the finely divided inorganic component is metered.
3. The process according to claim 1 , wherein the cationic polymeric retention aid is added after the last shear stage at least two places which are at equal distance from the shear stage, and thereafter the finely divided inorganic component is metered.
4. The process according to claim 1 , wherein the cationic polymeric retention aid is added before the last shear stage at least two places which are disposed in a plane perpendicular to the paper stock flow or successively, and the finely divided inorganic component is metered after the last shear stage.
5. The process according to claim 1 , wherein 25% to 75% by weight of the total amount of the cationic polymeric retention aid is metered before the last shear stage and the remaining fraction of the cationic polymeric retention aid is metered thereafter, and subsequently the finely divided inorganic component is added.
6. The process according to claim 1 , wherein the distance between the center point of the cationic polymeric retention aid metering places is at least 20 cm and wherein the distance between the center point of a metering place for the cationic polymeric retention aid and the center point of a metering place for the finely divided inorganic component is at least 20 cm.
7. The process according to claim 1 , wherein the distance between the center point of the cationic polymeric retention aid metering places is at least 50 cm and wherein the distance between the center point of a metering place for the cationic polymeric retention aid and the center point of a metering place for the finely divided inorganic component is at least 50 cm.
8. The process according to claim 1 , wherein the distance between the center point of the cationic polymeric retention aid metering places is 50 cm to 15 m and wherein the distance between the center point of a metering place for the cationic polymeric retention aid and the center point of a metering place for the finely divided inorganic component is at least 50 cm.
9. The process according to claim 1 , wherein the distance between the center point of the cationic polymeric retention aid metering places is 50 cm to 10 m and wherein the distance between the center point of a metering place for the cationic polymeric retention aid and the center point of a metering place for the finely divided inorganic component is 50 cm to 5 m.
10. The process according to claim 1 , wherein said cationic polymeric retention aid comprises at least one polymer selected from the group consisting of a nonionic polyacrylamide, a cationic polyacrylamide, an anionic polyacrylamide, a poly(N-vinylformamide), a polymer comprising a vinylamine unit, and a diallyldimethylammonium chloride.
11. The process according to claim 1 , wherein said cationic polymeric retention aid comprises at least one cationic polymer having a charge density of not more than 4 meq/g.
12. The process according to claim 1 , wherein said cationic polymeric retention aid comprises at least one polymer having a molar mass M w of at least 3 million.
13. The process according to claim 1 , wherein said cationic polymeric retention aid comprises at least one polyvinylamine obtained by hydrolyzing a polymer comprising a vinylformamide unit, the degree of hydrolysis of the vinylformamide unit being 5 to 100 mol %.
14. The process according to claim 1 , wherein the cationic polymeric retention aid is present in an amount of 0.005% to 0.5% by weight, based on a total weight of dry paper stock.
15. The process according to claim 1 , wherein the cationic polymeric retention aid is present in an amount of 0.001% to 0.25% by weight, based on a total weight of dry paper stock.
16. The process according to claim 1 , wherein said finely divided inorganic component of the microparticle system comprises at least one finely divided inorganic component selected from the group consisting of bentonite, colloidal silica, silicate, calcium carbonate and mixtures thereof.
17. The process according to claim 1 , wherein the finely divided inorganic component of the microparticle system is present in an amount of 0.01% to 2.0% by weight, based on a total weight of dry paper stock, and is metered into the paper stock flow at least two places disposed consecutively.
18. The process according to claim 1 , wherein the cationic polymeric retention aid is metered into the pulp flow at 3 to 5 places disposed successively.
19. The process according to claim 1 , wherein the finely divided inorganic component of the microparticle system is present in an amount of 0.1% to 1.0% by weight, based on a total weight of dry paper stock, and is metered into the paper stock flow at least two places disposed consecutively.
20. The process according to claim 1 , wherein the finely divided inorganic component of the microparticle system comprises an activated bentonite which is obtained by converting bentonite into a water-swellable form via treatment with an aqueous solution selected from the group consisting of an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, an aqueous solution of sodium carbonate, an aqueous solution of potassium carbonate, an aqueous solution of ammonia, and an aqueous solution of an amine.