Method for production of paper
AssigneeKemira Chemicals, Inc.
InventorsJonni Ahlgren, Kimmo Strengell
Life of this patent
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Abstract
The invention relates to a method for the production of paper or board, wherein retention aids are added to the stream of stock. Improved retention and more effective dewatering are achieved by adding to the stream of stock a cationic polymer solution and a suspension-form microparticle mixture composed of a swellable clay of the smectite group and a colloidal synthetic metal silicate in which the prevalent cation is magnesium.
Claims11
A method for the production of paper or board in such a manner that retention aids are added to the stream of stock passing to the paper machine headbox, the stream of stock is directed to the wire, the stock is dewatered in order to form a paper web, and the paper web is dried, characterized in that the retention aids used are a solution of a water-soluble cationic polymer and, in the form of a suspension, a microparticle mixture containing a swellable clay of the smectite group and a colloidal synthetic metal silicate, the prevalent cation of the colloidal synthetic metal silicate being magnesium, wherein the microparticle mixture contains the swellable clay of the smectite group in an amount of 85-99% by weight and the colloidal synthetic metal silicate in an amount of 1-15% by weight,
The method according to any of the preceding claims, characterized in that the said retention aids are added in steps by first adding a solution of the cationic polymer, whereafter there follows a shearing process step to break up flocs, and thereafter the microparticle mixture in suspension form is added.
The method according to any of the preceding claims, characterized in that the said cationic polymer is a copolymer of acrylamide or methacrylamide and a cationic monomer.
The method according to any of the preceding claims, characterized in that the molecular weight of the cationic polymer is at minimum 500,000.
The method according to any of the preceding claims, characterized in that the said cationic polymer is used in an amount of at minimum 0.02%, preferably 0.03-0.05%, of the dry solids weight of the stock.
The method according to any of the preceding claims, characterized in that the said microparticle mixture is used in an amount of at minimum 0.05%, preferably 0.1-0.25%, of the dry solids weight of the stock.
The method according to any of the preceding claims, characterized in that the suspension-form micropartcle mixture is prepared on site from a swellable clay of the smectite group and a solid colloidal synthetic metal silicate.
The method according to any of the preceding claims, characterized in that the stock contains cellulose, mechanical pulp or recycled fiber, or various combinations of these, as well as filers and additives commonly used in the production of paper.
Dependencies are inferred from the claim text.