PAPER PRODUCTION METHOD Russian patent published in 2020 - IPC D21F11/12 B82B3/00 B82Y40/00 

FIELD: pulp and paper industry.

SUBSTANCE: method includes preparation of waste paper stock, milling of prepared raw materials to degree of grinding 36–40 °SR to produce fibrous mass, mixing a strengthening agent, which is an aqueous solution of a cationic polymer, with an aqueous dispersion of nanofibrillar cellulose, having a zeta potential from minus 36 mV to minus 200 mV, taken in amount of 2.0–4.5 kg/t in terms of dry weight of cellulose and waste paper stock. Said mixture is held at 50–60 °C for 5–10 minutes to produce flocculated reinforcing agent. Sizing agent is mixed with aqueous dispersion of nanofibrillar cellulose, having zeta potential from minus 36 mV to minus 200 mV, taken in amount of 1.5–3.5 kg/t in terms of dry weight of cellulose and waste paper stock, thereby obtaining modified sizing agent. Fibrous mass is then mixed with a flocculated reinforcing agent and a modified sizing agent to obtain a paper mass. Latter is subjected to dehydration, pressing, drying and calendering to produce the target product.

EFFECT: achieved technical result consists in formation of complex flocculas in paper mass, providing binding of dissolved starch and aggregation of fine fiber in paper mass, as well as enhancing the sedimentation resistance of the reinforcing agent, which results in more uniform distribution of the hardening agent in the fibrous mass and, as a result, higher homogeneity and mechanical properties of the obtained paper.

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