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BR-112021021922-B1 - METHOD FOR MANUFACTURING PAPER OR CARDBOARD

BR112021021922B1BR 112021021922 B1BR112021021922 B1BR 112021021922B1BR-112021021922-B1

Abstract

METHOD FOR MANUFACTURING PAPER OR CARDBOARD AND PAPER OR CARDBOARD OBTAINED BY THE METHOD AND USE OF CATIONIC EMULSION POLYMER IN THE MANUFACTURE OF PAPER OR CARDBOARD. The present invention relates to a method for manufacturing paper or cardboard, in which the method of an inverted solution of cationic polymer is added to the fiber suspension to provide enhanced retention without excessive flocculation of fiber stock and sheet destruction formation and/or improved drainage and enhancement or at least maintenance of the strength of the paper or cardboard. An inverted solution has a bulk viscosity of 50-150 mPas at 0.2 wt% cationic polymer concentration, and the inverted solution comprises the cationic polymer obtained by reverse-phase emulsion polymerization of a monomer mixture comprising nonionic monomers, 15-50 mol% cationic monomers, optionally a maximum of 50 ppm of a crosslinking agent, and a chain transfer agent, and the reverse-phase emulsion obtained from the cationic polymer is inverted into an aqueous solution.

Inventors

  • Yuping Luo
  • Jennifer RISER
  • Zheng DANG
  • Junhua Chen
  • Ronald Robinson
  • Andrew Pencek
  • Barbara Lukasik

Assignees

  • KEMIRA OYJ

Dates

Publication Date
20260310
Application Date
20200701
Priority Date
20190805

Claims (11)

  1. 1. A method for manufacturing paper or cardboard, wherein a fiber web is formed from an aqueous fiber suspension, characterized in that it comprises: - providing an aqueous fiber suspension, comprising at least 50% by weight of recycled fiber material and/or coated waste, based on dry paper or cardboard; - optionally diluting the aqueous fiber suspension; - releasing the aqueous fiber suspension to a headbox, draining the aqueous fiber suspension onto a wire screen to form a wet fibrous web; and - pressing and drying the wet fibrous web to obtain a paper or cardboard web, in which an aqueous solution of a cationic reverse-phase polymer emulsion, wherein the cationic polymer reverse-phase emulsion is inverted in an aqueous solution, is added to the fiber suspension having a consistency above 20 g/l before releasing the fiber suspension to a headbox, wherein the aqueous solution of a cationic reverse-phase polymer emulsion has a bulky viscosity of 50-150 mPas at 0.2% by weight of cationic polymer concentration and comprises a reverse-phase emulsion of the cationic polymer having a standard viscosity of 1.5 - 3.5 mPas measured by a Brookfield viscometer with UL adapter at 25°C in a 0.1% by weight polymer solution in 1 M NaCl, and said cationic polymer is obtained by reverse-phase emulsion polymerization of a mixture of monomers comprising ethylenically unsaturated non-ionic monomers, ethylenically unsaturated cationic monomers of 20 - 40% molar, and a maximum of 50 ppm of a crosslinking agent, in the presence of a chain transfer agent, wherein the cationic polymer is branched or unbranched.
  2. 2. Method according to claim 1, characterized in that a net cationic charge of the cationic polymer is in the range of 1.1 - 4.5 meq/g (dry), preferably 1.5 - 4.5 meq/g (dry), and more preferably 3.5 - 4.5 meq/g (dry), at pH 7.
  3. 3. Method, according to claim 1 or 2, characterized in that the reverse phase emulsion of the cationic polymer has a standard viscosity of 1.7 - 3.3 mPas, preferably 1.7 - 3.0 mPas, more preferably 1.7 - 2.5 mPas and even more preferably 1.7 - 2.0 mPas measured by a Brookfield viscometer with a UL adapter at 25°C in a 0.1% by weight polymer solution in 1M NaCl.
  4. 4. A method, according to any of the preceding claims, characterized in that the amount of crosslinking agent is preferably in the range of 5–30 ppm.
  5. 5. A method, according to any of the preceding claims, characterized in that the cationic monomers comprise one or more selected from diallyldimethylammonium chloride (DADMAC); acryloyloxyethyltrimethylammonium chloride; methacrylates of N,N-dialkylaminoalkyl compounds; and quaternary compounds and their salts, such as N,N-dimethylaminoethylacrylate methylchloride salt; N,N-dialkylaminoalkyl (meth)acrylamide monomers; and their salts and quaternary compounds, such as N,N-dialkylaminoethylacrylamides; methacrylamidopropyltrimethylammonium chloride; 1-methacryloyl-4-methylpiperazine and the like.
  6. 6. A method, according to any of the preceding claims, characterized in that the nonionic monomers comprise one or more selected from acrylamide; methacrylamide; N-alkyl acrylamides, such as N-methylacrylamide; N,N-dialkylacrylamides, such as N,N-dimethylacrylamide; methyl acrylate; methyl methacrylate; acrylonitrile; N-vinylmethylacetamide or formamide; N-vinyl acetate or vinylpyrrolidone and the like.
  7. 7. A method, according to any of the preceding claims, characterized in that the fiber suspension comprises at least 60% by weight, preferably at least 70% by weight, or more preferably at least 80% by weight or 100% by weight, of recycled fibrous material and/or coated waste, based on dry paper or cardboard.
  8. 8. A method, according to any of the preceding claims, characterized in that said inverted solution is added to a fiber suspension having a consistency above 30 g/l.
  9. 9. A method, according to any of the preceding claims, characterized in that a portion of the inverted solution is added to a fiber suspension having a consistency below 20 g/l.
  10. 10. A method, according to any of the preceding claims, characterized in that said inverted solution is added to the fiber suspension before washing and/or cleaning and/or thickening of the fiber suspension.
  11. 11. A method, according to any of the preceding claims, characterized in that said inverted solution is added to a fiber suspension having a consistency above 20 g/l in an amount of 0.9 - 2.72 or 1.36 - 2.72 kg (as is)/ton of paper or cardboard produced.

Description

Field of Invention [001] The present invention relates to a method for the manufacture of paper or cardboard and the use of an inverted solution comprising a cationic polymer reverse-phase emulsion in the manufacture of paper and/or cardboard according to the independent claims set forth below to improve retention and/or drainage. Background of the Invention [002] Recycled fiber material is commonly used as raw material for paper or cardboard. Recycled fibrous material contains, in addition to fibers, a number of other substances. The particulate foreign material is separated from the pulp in the pulper or sieve. Some substances are naturally retained in the fibers and do not interfere with the process. Other substances, such as adhesives, can be separated from the pulp during sieving and at least partially removed from the process. [003] Typically, recycled fiber material comprises starch, which has a low molecular weight. This starch originates from the sizing of the surface of paper or cardboard. Starch is poorly retained in the fibers, as it usually has no charge or a slightly anionic charge, and due to its small size, it is also not effectively separated by sieving. Thus, low molecular weight starch remains in the water circulation of the pulping process or is removed along with the screen effluent for wastewater treatment. In the water circulation, starch increases the risk of microbial growth, as it is a suitable nutrient for various microbes. Microbes can affect the functioning of the papermaking chemistry and the quality of the final product. High microbial activity can lower the pH and have a marked effect on the wet end chemistry. The formation of slime, biofilms, on the surfaces of tanks and machine structures leads to paper defects such as stains and holes, or web breaks when slime pieces are detaching. The amount of low molecular weight starch in recycled fiber material can be relatively high, for example 1-3% of the total weight of the recycled fiber. When starch is lost to water circulation during the pulp preparation process, the process yield naturally decreases. Therefore, a process that avoids starch enrichment for water circulation and assists its retention in recycled fibers would provide numerous advantages. [004] The use of recycled fiber material as raw material is also the main source of hydrophobic substances, the so-called stickies, in the manufacture of paper and cardboard. Although some or even most of these hydrophobic substances are removed during the pulping of the recycled fiber raw material, substantial amounts are still carried over into the paper or cardboard manufacturing process. The hydrophobic substances that were not removed in the deinking or other processing step of recycled fiber, and that are not trapped by the screens, enter the paper or cardboard machine and circulate in the process waters. Due to increased environmental awareness and regulations, paper manufacturing processes have become increasingly closed and use less fresh water. This results in a strong accumulation of interfering substances, including hydrophobic substances, in the fiber suspension and in the process waters. These substances can agglomerate into larger hydrophobic particles, capable of forming deposits. [005] In addition to recycled fiber material, the recycling of coated waste can also cause problems similar to those described above for recycled fiber material. The deposition of contaminants from coated waste in papermaking systems can cause serious operational problems if not controlled. Coated waste is repulped and used as a feedstock in most coated fine paper mills. The most difficult problem involved with the recycling of coated waste stems from the binder materials, sometimes in combination with pigments or fillers, since these polymers and the materials to which they are attached are the source of sticky deposits. These sticky deposits cause difficulties when recycled back into the paper machine operation. [006] Modern paper manufacturing processes with high-speed machines are very sensitive to interference. One of the important factors limiting productivity on a high-speed paper machine is the formation of deposits. Deposits can cause web breaks, so as a precaution, the most affected surfaces, such as drying cylinders, calenders, wires and felts, are regularly washed and cleaned, which leads to stoppages and production losses. [007] Circulating hydrophobic substances can be controlled by adding chemicals to the papermaking process in order to build a boundary layer of hydrophilic material around the hydrophobic particles to decrease their tendency to deposit, i.e., to make them less sticky. The colloidal stability of small hydrophobic particles can be increased by surfactants and dispersants, which prevent their agglomeration and deposition on surfaces. High-charge cationic polymers, such as diallyldimethylammonium chloride (DADMAC) homopolymers, are conventionally used as fixati