Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • 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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/28—Starch
  • D21H17/29—Starch cationic

Definitions

• the invention relates to the chemistry of additives for paper making.
• the invention relates to a polymer stabilized with a polysaccharide and being generally used as an additive in the production of paper.
• Water soluble additives such as polyamides, polyamide-epichlorohydrin resins, melamin resins, urea-formaldehyde resins, polyacrylamides as well as preferably starch together with its derivatives are used to improve the strength properties.
• Starch is an advantageous and preferred raw material of natural origin. The amount of starch required to improve the strength properties is relatively large.
• starch As wood fiber is anionic in character, native starch has a quite low affinity thereto. Therefore, starch has been chemically modified into the cationic direction. Starch is cationized by attaching substituents having an ionic nitrogen group, such as primary, secondary, tertiary or quaternary ammonium groups, to the carbohydrate backbone. As a measure of the cationic character, the relative ratio of substituted to unsubstituted glucose units, i.e. a degree of substitution, is used. The cationic character can also be expressed as a percentage amount of ionic nitrogen based on the weight of the substituted starch.
• substituents having an ionic nitrogen group such as primary, secondary, tertiary or quaternary ammonium groups
• the dry strength properties of paper are usually improved by adding hydrogen bonds to OH groups of the fiber.
• the paper strengthening additives of this kind include hydrophilic, water-soluble polymers such as starch, carboxymethylcellulose or synthetic polymers. These include polyacrylamides of which anionic, cationic and amphoteric are used. Their use is limited by a relative high price.
• wet strength is usually meant the strength of a finished paper when it becomes wet, which strength is obtained by the formation of covalent bonds between the fibers. This property is of importance when making paper e.g. for filter paper or kitchen paper, and it can be be obtained through reactions between fibers and additives at a high temperature of the drying section of a paper machine.
• Another wet strength the strength of a wet web during the production of paper is of great importance for the runnability of the machine, especially when proceeding to a drying section, because the web has been fully supported up to that point. It has been tried to improve this property mainly by increasing the dry solids content of the web in the press section.
• starch In order to combine the properties of polyacrylamides and starches to improve the wet strength of paper, products have been prepared in which acrylamide or metacrylamide and an unsaturated organic acid are polymerized in the presence of starch. In this manner starch is formed to which polymerized side chains have been bound.
• the starch is preferably cationic, having typically a degree of substitution of 0.01 - 0.70.
• Japanese patent application JP 2-26944 discloses a polymer of an acrylamide or metacrylamide and methacrylamide acid, prepared in an aqueous solution containing a cationic polysaccharide. In addition to the tensile strength, attempts to improve the tear strength has been made. The cationic character of the polysaccharide is low, and the nitrogen content is 0.4%.
• a product is prepared by polymerizing 50 - 95 mol-% of (meth)acrylamide and 5 - 50 mol% of an ⁇ , ⁇ -unsaturated carboxylic acid in an aqueous solution containing 40 - 90 parts per weight of a cationic polysaccharide.
• a vinylic component to be polymerized is entirely in the form of amide, and after the polymerization, part of the amide groups is hydrolyzed to carboxylic groups.
• the number of the formed side chains of the starch is large in relation to the number of the cationic groups, because low cationic starch was used.
• additives are used in the production of paper to improve the complex of fiber and a binder.
• the runnability of paper in a machine can be improved by web wet strength improving agents.
• the present invention relates particularly to the wet strength of a web, i.e. to the strength of a paper or paperboard web during the production with a dry solids content of about 20 - 60%.
• copolymer stabilized by a cationic polysaccharide to be an advantageous additive in the production of paper and paperboard, in which copolymer acrylamide or metacrylamide, vinylic carboxylic acid and optionally other vinylic monomers, e.g. alkylaminoacrylate or metacrylate, are used as monomers.
• the additive according to the invention improves in addition to the wet strength of a web also the surface resistance of the product.
• the surface resistance is of particular significance for printing papers.
• a polysaccharide having a strong cationic character is used, which in an aqueous solution is ready for use, and no time-consuming cooking is needed.
• the degree of substitution of the cationic polysaccharide is about 0.02 - 0.50.
• the polysaccharide used is preferably degraded starch.
• the starch may be any known starch, e.g. potato, corn, waxy maize, barley, wheat or tapioca starch.
• other useful polysaccharides are e.g. dextrine, amylopectin, amylose and mannose.
• vinylic monomers are used in the product according to this invention.
• the proportion of the monomers calculated on the dry solids content of the starting materials is not more than about 30%, preferably below 20%.
• at least about 95% of the molar amount of the monomer component is amide.
• polymerization initiators and pH adjusting agents are used as known in the art. Suitable initiators are e.g. cerium salts, persulfates, hydroperoxides alone or together with a reducing metal salt, or azo compounds.
• Cationic starch (20% aqueous solution) 860.0 g Water 55.0 g Acrylic acid (80% aqueous solution) 1.2g Acrylamide (50% aqueous solution) 38.0 g Tert-butyl hydroperoxide 5.3 g Water 18.3 g Sodium metabisulfite 3.9 g Water 18.3 g Dry solids content 20.0% Total amount 1000.0 g
• the cationic starch has a degree of substitution of 0.20; the cationization has been carried out by using a quaternary ammonium compound.
• the cationic starch and water are mixed together in a reactor.
• the pH of the solution is adjusted to 7 by using acetic acid, and 20% of both the tert-butyl hydroperoxide and the sodium metabisulfite aqueous solutions are added.
• the temperature is raised to 60°C, and a nitrogen atmosphere is arranged in the reactor for the duration of the reaction.
• the reaction is continued for 120 minutes at 60°C under agitation.
• the reaction can be initiated by various initiators, as in the above example by an oxidation-reduction-reagent pair, which includes i.a. a copper sulfate-hydrogen peroxide-pair, or e.g. by a cerium salt.
• the catalyst may also be a persulfate or another catalyst commonly used in emulsion polymerization.
• the wet tensile strength was determined freshly on wet sheets (about 35% dry solids).
• test product according to the invention improves the wet tensile strength of the sheets while the cationic starch alone does not.
• Laboratory sheets are prepared from a pulp consisting of 80% mechanical pulp and 20% chemical pulp. The additions of the additives are given in kg/t.
• the tested sheets were prepared using a fiber orientating sheeting mould in which the machine direction (MD) and the cross direction (CD) can be distinguished.
• MD machine direction
• CD cross direction
• the product according to the invention significantly improves the wet web strength both in the machine direction and in the cross direction.
• Laboratory sheets are prepared from a pulp consisting of 15% chemical pulp, 20% reject and 55% mechanical pulp, and as filler kaolin, so that the ash level will be 20%.
• the additions of the additives are given in kg/t of the dry solids of the pulp.
• the sheets were prepared to a basis weight of 70 g/m 2 .
• a conventional pulp starch (MT) was used which was added in the amount of 5 kg/t.
• Control point 1 2 3 Wet tensile strength MD kNm/kg Wet tensile strength CD kNm/kg IGT-pick m/s Zero point 0 2.1 1.2 2.27 Pulp starch 5 2.4 1.2 2.66 MT + Product of Example 1 5 + 1 2.4 1.2 2.82 MT + Product of Example 1 5 + 2 2.9 1.3 3.45
• the wet tensile strength was improved mainly in the machine direction when the test product was added in the amount of 2 kg/t.
• the IGT surface resistance was measured on these sheets, and a slight improvement could also be observed compared to the zero point as well as to the use of the pulp starch alone.
• the IGT picking indicates how the surface of a paper, which has been printed with a printing ink, is able to resist abrasion before the surface becomes flocked and the fibers can be seen on the surface.
• a product according to the invention may be used in paper and cardboard production, for example for stabilizing hydrophobic size dispersions.
• sizes are e.g. AKD (alkyl ketene dimer) and ASA ( alkenyl succinic anhydride).
• AKD alkyl ketene dimer
• ASA alkenyl succinic anhydride

Landscapes

• Paper (AREA)
• Extrusion Of Metal (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)
• Graft Or Block Polymers (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=8561260

Family Applications (1)

Country Status (9)

Families Citing this family (8)

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• 2001
  • 2001-05-23 FI FI20011085A patent/FI113968B/sv not_active IP Right Cessation
• 2002
  • 2002-05-20 ES ES02771660T patent/ES2340840T3/es not_active Expired - Lifetime
  • 2002-05-20 EP EP02771660A patent/EP1392919B1/en not_active Expired - Lifetime
  • 2002-05-20 AT AT02771660T patent/ATE459752T1/de active
  • 2002-05-20 US US10/478,138 patent/US20040149412A1/en not_active Abandoned
  • 2002-05-20 CA CA002448113A patent/CA2448113A1/en not_active Abandoned
  • 2002-05-20 PT PT02771660T patent/PT1392919E/pt unknown
  • 2002-05-20 DE DE60235539T patent/DE60235539D1/de not_active Expired - Lifetime
  • 2002-05-20 WO PCT/FI2002/000428 patent/WO2002095128A1/en not_active Application Discontinuation

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