# US 9,752,284 B2 · Method for treating a fibre stock for making of paper, board or the like and product > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,752,284 B2 - Document ID: US9752284B2 - Status: Granted - Kind: B2 - Application number: 14/442,182 - Filed: 2013-11-12 - Published: 2016-10-06 - Granted: 2017-09-05 - Earliest claimed: 2012-11-12 - Assignees: Kemira Oyj - Applicants: Kemira Oyj - Inventors: Matti Hietaniemi; Mikko Virtanen; Emmi Saranpää - Web page: https://patentgrep.com/patent/US9752284B2 ## CPC - D21H 21/18: Reinforcing agents - D21H 17/29: cationic - D21H 17/375: {Poly(meth)acrylamide} - D21H 23/04: Addition to the pulp; After-treatment of added substances in the pulp - D21H 27/30: Multi-ply (for surface covering D21H27/18; making on paper-making machines D21F9/00, D21F11/00) - D21H: PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR ## Abstract The invention relates to a method for treating a fiber stock for making of paper, board or the like. The method comprises obtaining a fiber thick stock and adding to the fiber thick stock at least one cationic first agent, and adding separately to the fiber stock and after the addition of the cationic first agent, at least one anionic second agent, which is an water-soluble anionic copolymer of acrylamide, methacrylamide or acrylonitrile, in such amount that the ratio of the added absolute cationic charge to the added absolute anionic charge is from 1:0.1 to 1:0.95. The invention relates also to the product prepared by using a fiber stock, which is treated by using the method. ## Claims ### Claim 1 A method for treating a fibre stock for making of paper or board, the method comprising obtaining a fibre thick stock, adding, to the fibre thick stock, at least one cationic first agent, selected from the group consisting of: cationic starch having a charge density of 0.1-2 meq/g; cationic copolymers of acrylamide or methacrylamide, having a charge density of 0.2-5 meq/g; and any of their mixture; and adding separately to the fibre stock and after adding the at least one cationic first agent, at least one anionic second agent, which is a water-soluble anionic copolymer of acrylamide, methacrylamide or acrylonitrile, and which has an anionic charge of 0.4-5 meq/g in such amount that a ratio of an added absolute cationic charge to an added absolute anionic charge is from 1:0.1 to 1:0.95, whereby the cationic first agent is allowed to interact with the fibres in the thick stock before the anionic second agent is added. ### Claim 2 (depends on 1) The method according to claim 1, characterised in that the at least one cationic first agent and the at least one anionic second agent are added to the fibre stock in amount such that the ratio of the added absolute cationic charge to the added absolute anionic charge is from 1:0.1 to 1:0.5. ### Claim 3 (depends on 1) The method according to claim 1, characterised in that the at least one cationic first agent and the at least one anionic second agent are added to the fibre stock in amount such that the ratio of the added absolute cationic charge to the added absolute anionic charge is from 1:0.55 to 1:0.95. ### Claim 4 (depends on 1) The method according to claim 1, characterised in that the cationic first agent is added to the fibre thick stock having consistency of at least 2%. ### Claim 5 (depends on 1) The method according to claim 1, characterised in that the cationic first agent and the anionic second agent are added consecutively after each other to the fibre thick stock and the fibre thick stock is diluted with short loop white water of paper or board machine before a web formation. ### Claim 6 (depends on 1) The method according to claim 1, characterised in that the cationic first agent is added before a shear stage, in which mixing of the cationic first agent and the fibre thick stock is conducted. ### Claim 7 (depends on 1) The method according to claim 1, characterised in that the anionic second agent is added to the fibre thick stock at the latest at a head box of a paper machine or a board machine. ### Claim 8 (depends on 1) The method according to claim 1, characterised in adding two or more cationic first agents to the fibre thick stock as a single mixture or successively one after another. ### Claim 9 (depends on 1) The method according to claim 1, characterised in that the cationic first agent is cationic starch, which has a charge density of 0.2-0.9 meq/g. ### Claim 10 (depends on 9) The method according to claim 9, characterised in that the cationic first agent is cationic starch, where at least 70 weight-% of the starch units have an average molecular weight (MW) over 700,000 Dalton. ### Claim 11 (depends on 9) The method according to claim 9, characterised in that the cationic first agent is cationic starch, which has a degree of substitution (DS) in a range of 0.01-0.20. ### Claim 12 (depends on 1) The method according to claim 1, characterised in that the cationic first agent is cationic starch, which has an amylopectin content in a range of 65%-90%, and the amylose content is in a range of 10%-35%. ### Claim 13 (depends on 1) The method according to claim 1, characterised in that the cationic first agent is a cationic copolymer of acrylamide or methacrylamide, the cationic copolymer having an average molecular weight (MW) of 300,000-3,000,000 g/mol. ### Claim 14 (depends on 1) The method according to claim 1, characterised in that the cationic first agent is a cationic copolymer of acrylamide or methacrylamide and at least one cationic monomer, which is selected from the group consisting of methacryloyloxyethyltrimethyl ammonium chloride, acryloyloxyethyltrimethyl ammonium chloride, 3-(methacrylamido) propyltrimethyl ammonium chloride, 3-(acryloylamido) propyltrimethyl ammonium chloride, diallyldimethyl ammonium chloride, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminopropylacrylamide, and dimethylaminopropylmethacrylamide. ### Claim 15 (depends on 14) The method according to claim 14, characterised in that the cationic first agent is a copolymer of acrylamide or methacrylamide with (meth)acryloyloxyethyltrimethyl ammonium chloride. ### Claim 16 (depends on 1) The method according to claim 1, characterised in that the charge density of the cationic copolymer of acrylamide or methacrylamide is 0.3-4 meq/g. ### Claim 17 (depends on 1) The method according to claim 1, characterised in that the anionic second agent is an anionic copolymer of acrylamide, methacrylamide or acrylonitrile comprising anionic groups attached to the polymer backbone. ### Claim 18 (depends on 17) The method according to claim 17, characterised in that the anionic second agent is a copolymer of acrylamide, methacrylamide or acrylonitrile and an ethylenically unsaturated monomer, which is selected from a group consisting of: acrylic acid, (meth)acrylic acid, maleic acid, crotonic acid, itaconic acid, vinylsulphonic acid, and 2-acrylamide-2-methylpropanesulfonic acid. ### Claim 19 (depends on 1) The method according to claim 1, characterised in that the anionic second agent has an average molecular weight of 200,000-2,000,000 g/mol, and/or an anionic charge of 0.5-4 meq/g. ### Claim 20 (depends on 1) The method according to claim 1, characterised in that a filtrate of the fibre stock has a cationic demand <300 μeq/l after addition of the cationic first agent. ### Claim 21 (depends on 1) The method according to claim 1, characterised in that a cationic demand of a fibre stock filtrate is increased less than 100 μeq/l after adding the at least one anionic second agent. ### Claim 22 A method for treating a fibre stock for making of paper or board, the method comprising obtaining a fibre thick stock, adding, to the fibre thick stock, at least one cationic first agent, selected from the group consisting of: cationic starch having a charge density of 0.1-2 meq/g; cationic copolymers of acrylamide or methacrylamide, having a charge density of 0.2-5 meq/q; and any of their mixture; and adding separately to the fibre stock and after adding the at least one cationic first agent, at least one anionic second agent, which is an water-soluble anionic copolymer of acrylamide, methacrylamide or acrylonitrile, and which has an anionic charge of 0.4-5 meq/q in such amount that a ratio of an added absolute cationic charge to an added absolute anionic charge is from 1:0.1 to 1:0.95, whereby the cationic first agent is allowed to interact with the fibres in the thick stock before the anionic second agent is added, and whereby adding the at least one cationic first agent increases original zeta potential value of the fibre stock to a first zeta potential value, which is in a range of −15-+10 mV, and adding the at least one anionic second agent decreases an obtained first zeta potential value by 1.5-10 mV.