초록 ▼

The present invention relates to a process for manufacturing paper or board, wherein paper or board pulp is diluted with acidic water and wherein the pH value of the pulp is raised with an alkali simultaneously with increasing the solids content of the pulp by filtration, compression and evaporation

The present invention relates to a process for manufacturing paper or board, wherein paper or board pulp is diluted with acidic water and wherein the pH value of the pulp is raised with an alkali simultaneously with increasing the solids content of the pulp by filtration, compression and evaporation on the wire, press and drying sections, and, at the same time, filler is precipitated from the acidic water into the paper or board structure. The invention also relates to moistening of paper or board, with a dry matter content of over 40%, in acidic water, after which the pH value is raised with an alkali, and the paper or board is dried, or it is dried after the moistening without raising the pH value.

대표청구항 ▼

1. A process for manufacturing paper or board from paper or board pulp in a papermaking machine having a headbox, wire section, press section, and drying section, the process comprising: i) diluting the pulp to a defined consistency range with a water-based composition, the water-based composition c

1. A process for manufacturing paper or board from paper or board pulp in a papermaking machine having a headbox, wire section, press section, and drying section, the process comprising: i) diluting the pulp to a defined consistency range with a water-based composition, the water-based composition comprising colloidal carbonate particles and bicarbonates and other carbonate compounds in process water, or a mixture of process water and additional water, at a pH value of less than 8.3, and ii) raising the pH value of the diluted pulp with an alkali substantially simultaneously with increasing the solids content of the pulp, whereby a carbonate filler is precipitated from the water-based composition into the paper or board structure. 2. The process according to claim 1, wherein chemical, mechanical or chemi-mechanical pulp, fibre pulps prepared with alkalis, recycled fibre, deinked fibre, nanocellulose pulp, or a mixture of these pulps, are used. 3. The process according to claim 1, wherein the pulp is diluted with the water-based composition in such a way that the consistency of the pulp is at least 1.5% after the dilution. 4. The process according to claim 1, wherein the pH value is raised with an alkali substantially simultaneously with increasing the solids content of the pulp by filtration, compression and/or evaporation on the wire section, the press section and/or drying section of the paper or board machine. 5. The process according to claim 1, wherein the water-based composition is generated from calcium and/or magnesium ions and forms of carbonate in an aqueous solution in such a way that the pH value of the aqueous solution during the generation remains essentially below 8.3, while the pulp is in the headbox. 6. The process according claim 1, wherein the water-based composition used for diluting the pulp has a content of carbonate compounds which is 0.01%, calculated from the weight of the solids of the pulp to be diluted. 7. The process according to claim 1, wherein the average particle size of the carbonate forms is less than 300 nanometers. 8. The process according to claim 1, wherein the carbonate compound contained by the water-based composition is mainly calcium carbonate, magnesium carbonate, or a composite or mixture thereof. 9. The process according to claim 1, wherein the water-based composition is prepared in such a way that oxide or hydroxy slurry and carbon dioxide are added into a flowing aqueous solution in such a way that substantially no precipitates are formed in the composition used for diluting the paper or board pulp, while the pH value is kept below 8.3. 10. The process according to claim 9, wherein the oxide or hydroxy slurry is calcium oxide, magnesium oxide, calcium hydroxide, magnesium hydroxide or a mixture of some or all of these. 11. The process according to claim 9, wherein the aqueous solution into which the water-based composition is prepared is a flowing and substantially fibre-free process water of a paper or board machine, or a mixture of this process water and additional water. 12. The process according to claim 1, wherein the alkali is sodium hydroxide, sodium bicarbonate, sodium carbonate, calcium hydroxide, potassium hydroxide, alkaline bicarbonate, sodium silicate, potassium silicate or a mixture thereof. 13. The process according to claim 1, wherein pressure is applied to the water-based composition in the headbox, on the wire, press and/or drying sections. 14. The process according to claim 1, wherein a chemical is used in manufacturing the paper or board, selected from flocculants, coagulants, or micro particles, aluminium compounds, beater-sizing glues, surface-sizing glues, colours, starch, optical clarifying agents, natural and synthetic polymers. 15. The process according to claim 1, wherein one or more charged polymers and/or one or more inorganic chemicals and/or one or more different micro-particles are added directly into the process water and/or into the water-based composition which is prepared from this process water, after which dilution of the pulp is carried out with the prepared water-based composition. 16. The process according to claim 15, wherein charged polymer and/or inorganic chemical and/or micro-particles are added into the pulp to be diluted, simultaneously with its dilution with the water-based composition. 17. The process according to claim 15, wherein the charged polymer is a natural polymer, synthetic polymer, copolymer, terpolymer or a mixture of two or more of such polymers, selected from polyacryl amide, polyethylene imine, starch, polydadmac, polyamine, polyethylene oxide, polyvinyl amine, dicyanide amide, a copolymer or terpolymer of any of the above, or a mixture of two or more of such polymers, copolymers and/or terpolymers. 18. The process according to claim 15, wherein the inorganic chemical is talc, sodium montmorillonite, bentonite, saponite, sepiolite, hectorite, smectite, zeolite, amorphous magnesium silicate, alum, aluminium chloride, polyaluminium chloride, sodium aluminate, iron sulphate, iron chloride, polyphosphate, polysulphonate, zirconium salt complex or a mixture of two or more chemicals. 19. The process according to claim 15, wherein the quantity of charged polymers and/or inorganic chemicals is smaller than 20%, calculated from the weight of the solids of the pulp to be diluted. 20. The process according to claim 15, wherein the micro-particles are sols, gels, microgels, silicic acids, polysilicic acids, containing bentonites or silicon dioxide, or a mixture thereof. 21. The process according to claim 1, wherein a water-soluble aluminium-containing compound is added into the pulp, substantially simultaneously with the addition of the charged polymer and/or inorganic chemical and/or micro-particles. 22. The process according to claim 1, wherein essentially no coated broke nor filler has been added into the paper or board pulp.