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
  • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
  • D21H25/02—Chemical or biochemical treatment
• • 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
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
  • D21H21/18—Reinforcing agents
  • D21H21/20—Wet strength agents
• • 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
  • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
  • D21H11/14—Secondary fibres
• • 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
  • D21H17/005—Microorganisms or enzymes
• • 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
  • D21H17/03—Non-macromolecular organic compounds
  • D21H17/05—Non-macromolecular organic compounds containing elements other than carbon and hydrogen only
  • D21H17/09—Sulfur-containing compounds
• • 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
  • D21H17/03—Non-macromolecular organic compounds
  • D21H17/05—Non-macromolecular organic compounds containing elements other than carbon and hydrogen only
  • D21H17/14—Carboxylic acids; Derivatives thereof
  • D21H17/15—Polycarboxylic acids, e.g. maleic acid

Definitions

• the present invention relates to a process for producing paper materials such as paper, linerboard or corrugated linerboard from unbleached and semi-bleached chemical or semichemical pulp or pulp from recycled fibres.
• Linerboard and corrugated medium used for making corrugated paperboard and corrugated cartons, are commonly made from a suspension of unbleached chemical or semichemical pulp or pulp from recycled fibres .
• the pulp is treated in a screening process, refined, then mixed with paper making additives in the stock preparation section before the pulp suspension is de-watered on the paper/board machine, and the drained water (so-called white water) is recycled back into the process for dilution of the screened stock.
• the white water will normally contain high amounts of wood fibers/fines, sterol esters, resin acids, lignans, and lignin fragments typically in concentrations of 100-500 ppm or higher; all of this material will have phenolic or phenol-like groups.
• Strength is an important mechanical property of the unbleached board grades used to make corrugated boxes: linerboard and corrugated linerboards. Due to new governmental rules in some countries giving an alternative specification based on combined board edge crush and since combined edge crush can be tied directly to the compression strength of the board's components it is now possible to sell board on a performance per square meter basis rather than only by weight. Clearly, the wet strength of unbleached board grades used to make corrugated boxes is also of importance.
• EP 429,422 discloses reduction of energy consumption in the refining stages by use of laccase during pulp preparation between the first and second refining stage; the document indicates that some increase of paper strength is also obtained.
• WO 93/23606 discloses a process for treating a mechanical pulp with a phenol-oxidizing enzyme system to increase the strength of the produced paper.
• WO 95/09946 discloses a process for producing linerboard or corrugated medium having increased strength by treating pulp with a phenol-oxidizing enzyme.
• WO 95/07604 discloses a process for producing fibreboard having improved mechanical properties by treating a slurry or suspension of a lignin-containing wood fibre material with a phenol-oxidizing enzyme.
• US 4,687,745 discloses a process for enhancing the strength properties and brightness stability of mechanical pulp by treating the pulp with ligninolytic enzymes.
• the wet strength of paper materials may be enhanced by adding wet strength resins to the pulp.
• these resins will enhance the strength of the paper material in such a way that re-use of the paper material will become difficult.
• the present inventors have now surprisingly found that the wet strength of paper materials can be increased by treating a pulp suspension with a phenol-oxidizing enzyme system prior to the paper machine. It has also been found that the wet strength can be further improved by a combined enzyme/mediator treatment . The wet strength may be even further improved by additional applying a heat treatment .
• the present invention relates to a process for producing paper materials with improved wet strength, comprising:
• the process water from step (c) is recycled, and step (a) comprises dilution of the pulp with the recycled process water.
• the enzymatic treatment of the pulp and white water suspension will to a large extent polymerize the aromatic materials present in the white water (lignans, resin acids, sterol esters, lignin-like compounds, fibres and fines) so that they are retained in the paper sheet, leading to an increased yield and a decreased COD (chemical oxygen demand) load and toxicity of the effluent . Said polymerization is also believed to contribute to strengthening of the linerboard or corrugated medium.
• the paper material is heated after the completion of step c) .
• the present invention relates to a process for making corrugated paperboard or corrugated boxes using the linerboard and/or corrugated linerboard produced by the process of the invention.
• the present invention relates to the use of a phenol-oxidizing enzyme in combination with a mediator to produce a paper material with improved wet strength.
• Figure 1 shows the wet tensile strength of the sheets produced in Example 1. Data is taken from Table 1. Vertical bars indicate the 95% confidence limit.
• Figure 2 shows the wet strength after immersion into distilled water for 24 hours of paper subjected to different treatments as described in Example 2.
• the following abbreviations have been used:
• ⁇ paper material refers to products, which can be made out of pulp, such as paper, linerboard, corrugated paperboard, corrugated container or boxes .
• ⁇ ' improved wet strength indicates that the wet strength of the paper material is increased/enhanced in comparison to the paper material which has not be treated according to the invention.
• the pulp to be used in the process of the invention is a suspension of unbleached or semi-bleached chemical or semichemical pulp or pulp from recycled fibres.
• Unbleached or semi-bleached pulp is characterised by containing lignin, which is used as substrate for the enzyme system.
• the chemical pulp may be unbleached kraft pulp, and the semichemical pulp may be NSSC (neutral sulfite semichemical) pulp.
• the pulp from recycled fibres may be made from a chemical pulp, such as unbleached kraft pulp.
• a specific example of recycled fibres made from a chemical pulp includes OCC (old corrugated containers) .
• the preparation of the pulp suspension may comprise beating or refining of the pulp, depending on the type of pulp.
• Phenol ox dising enzyme system Phenol ox dising enzyme system
• the enzyme system used in the invention consists of a suitable oxidase together with 0 2 or a suitable peroxidase together with H 2 0 2 .
• Suitable enzymes are those, which oxidize and polymerize aromatic compounds such as phenols and lignin.
• Suitable enzymes are catechol oxidase (EC 1.10.3.1), laccase (EC 1.10.3.2), bilirubin oxidase (EC 1.3.3.5) and peroxidase (EC 1.11.1.7) and haloperoxidases.
• the peroxidase may be derived from a strain of Coprinus, e.g. C. cinerius or C. macrorhizus , or of Bacillus, e.g. B . pumilus, from soy bean or horse radish. It may be preferable to use two different phenol oxidizing enzymes together.
• Suitable laccases may, for example, be derived from a strain of Polyporus sp., in particular a strain of Polyporus pinsi tus (also called Tra etes villosa) or Polyporus versicolor, or a strain of Myceliophthora sp., e.g. M. thermophila or a strain of Rhizoctonia sp., in particular a strain of Rhizoctonia praticola or Rhizoctonia solani , or a strain of Scytalidium sp. , in particular S. thermophilium, or a strain of Pyricularia sp., in particular Pyricularia oryzae, or a strain of Coprinus sp., such as a C. cinereus .
• the laccase may also be derived from a fungus such as Collybia, Forties, Lentinus, Pleurotus, Aspergillus, Neurospora, Podospora, Phlebia, e. g. P. radiata (WO 92/01046), Coriolus sp., e. g. C. hirsi tus (JP 2-238885) , or Botr tis.
• a fungus such as Collybia, Forties, Lentinus, Pleurotus, Aspergillus, Neurospora, Podospora, Phlebia, e. g. P. radiata (WO 92/01046), Coriolus sp., e. g. C. hirsi tus (JP 2-238885) , or Botr tis.
• the laccase is derived from a strain of Polyporus sp . , especially the Polyporus pinsi tus laccase (in short: PpL) .
• the amount of peroxidase should generally be in the range 10- 10,000 PODU per g of dry substance (PODU unit of peroxidase activity defined below) .
• the amount of laccase should generally be in the range 0.001-1000 units per g of dry substance (unit of laccase activity defined below) .
• a suitable amount of H 2 0 2 will usually be in the range 0.01-10 M, particularly 1-10 M.
• redox mediator is sometimes in literature referred to as "an enhancing agent”.
• an enhancing agent in the present context the term “mediator” will be used.
• a “mediator” is an agent capable of enhancing the activity of phenol-oxidizing enzymes.
• the mediator may be a phenolic mediator or a non-phenolic mediator. Which mediator is preferred depends of the purpose.
• mediators capable of enhancing the activity of phenol- oxidizing enzymes include the compounds described in WO 95/01426, which is hereby incorporated by reference, and described by the general formula I:
• RI to RIO and A groups can be found in WO 95/010426 (see pp. 9 to 11) .
• Specifically contemplated compounds within the above formula I include the following: 2 , 2 ' -azino-bis (3-ethylbenzothiazoline-6- sulfonate (ABTS); 6-hydroxy-2-naphtoic acid; 7-methoxy-2-naphtol ; 7-amino-2-naphthalene sulfonic acid; 5-amino-2-naphthalene sulfonic acid; 1, 5-diaminonaphthalene; 7-hydroxy-l, 2-naph- thimidazole,- 10-methylphenothiazine; 10-phenothiazine-propionic acid (PPT) ; N-hydroxysuccinimide-10-phenothiazine-propionate; benzidine; 3,3' -dimethylbenzidine; 3,3' -dimethoxybenzidine;
• -C 16 alkyl preferably a alkyl, which alkyl may be saturated or unsaturated, branched or unbranched and optionally substituted with a carboxy, sulfo or amino group; and B and C may be the same or different and selected from CHa ⁇ * ..; ⁇ m ⁇ 5.
• Suitable mediators are vanillic acid, NHA, HOBT, PPO and violoric acid. Process conditions
• the enzyme treatment can be done at conventional consistency, e.g., 0.5-25% (particularly 0.5-10%) dry substance, at temperatures of 20-90°C and at a pH of 4-10. Furthermore, the enzyme (and mediator) treatment may be carried out at atmospheric pressure.
• the enzyme activity when using a laccase is 0.001-1000 LACU per gram of dry substance.
• PODU peroxidase activity
• Peroxidase activity is determined from the oxidation of 2,2'- azinobis (3-ethylhenzo-thiazoline-6-sulfonate) (ABTS) by hydrogen peroxide. The greenish-blue color produced is photometered at 418 nm.
• the analytical conditions are 0.88 mM hydrogen peroxide, 1.67 mM ABTS, 0.1 M phosphate buffer, pH 7.0, 30°C, 3 minutes reaction.
• PODU 1 peroxidase unit
• Laccase activity was determined by a similar method without addition of hydrogen peroxide.
• 1 laccase unit (LACU) is defined as the amount of enzyme which under standard conditions (pH 5.5, 30°C) oxidizes 1 mmol syringaldazine per minute.
• a beaten and unbleached kraft pulp kappa 85 obtained from the Obbola mill in Sweden was disintegrated in a laboratory disintegrator and diluted to at consistency of 1%.
• As water phase was used either tap water or white water from the Obbola mill. pH was adjusted to 5.5 ⁇ 0.1 with 1 M sulphuric acid and this was maintained by further addition of acid.
• An enzyme dosage of 15 LACU/g dry pulp (laccase derived from Polyporus pinsi tus) was added and the suspension was stirred for 1 hour.
• Isotropic sheets with a specific weight of 150 g/m 2 were formed on a semiautomatic papermaker of the Rapid-Konthen type. When comparing the tensile strength of sheets subjected to different treatment it is of crucial importance that the sheets have the same density. Heat drying of a sheet increases its density, and to compensate for this, sheets to be air-dried were pressed to a higher density than sheets to be heat-dried.
• a trial was performed comprising the following variables: White water, laccase and heat drying.
• Test of tensile strength was performed after SCAN-P67 with 10 test strips. Permanent wet tensile strength was tested after immersion of the test piece into distilled water for 24 hr. For each of the 8 treatments, 5 sheets were made. The same batch of pulp and white water was used for all treatments, and the entire experiment was carried out on the same day. Data were analysed with the statistical software package SAS .
• Table 2 Main effect of variables (difference between means of the variables at high and low level ) . Significance at the 0 . 05 level is indicated by *** based on a T-test . Least significant differences (LSD) on the 0 . 05 level written in parentheses . All values are in Nm/g .
• the wet tensile strength was significantly affected by all variables . Heat drying had the highest impact on the wet tensile strength with almost 3 Nm/g followed by the laccase treatment with 0 . 8 Nm/g .
• a beaten and unbleached kraft pulp kappa 85 obtained from the Obbola mill in Sweden was disintegrated in a laboratory disintegrator and diluted to a consistency of 1%. pH was kept at 5.5 using a 0.05 M sodium acetate buffer. PpL laccase and a mediator were added and the slurry stirred for 1 hour at room temperature. The enzyme dosage was 10 LACU/g dry pulp in all experiments.
• Isotropic handsheets with a specific weight of 150 g/m2 were made of the modified pulp according to SCAN-P:26. In those experiments where the sheets was subjected to a heat treatment this was done to the wet sheets immediately after the second pressing step in a restrained dryer at 150°C for 5 min, and was then conditioned at 65% RH and 23 °C. All other sheets were dried in a conditioning chamber at 6 5 % RH and 21°C. The dry- and wet tensile strength were determined according to SCAN-P:38. Before measuring the wet tensile strength, the test strip was immersed in distilled water for 1 or 24 hour.
• the laccase mediator (PPT) treatment gives a significantly increase in the wet tensile strength of the linerboard, both when the paper is subjected to heat treatment (experiments Nos. 3 and 6) and when not subjected to heat treatment (Nos. 1 and 2).
• Heat treatment of paper is known to confer wet strength, possibly through generation of covalent bonds between cellulose chains, but the treatment of the pulp with laccase and PPT increased this effect by about 50%, cf. Figure 2.
• Table 3 shows the wet tensile strength of paper sheets made from kraft pulp oxidised with laccase and different mediators prior to sheets formation. Although the error within an experiment was low, the day-to-day variation was rather high, and therefore the effect of a given mediator should be evaluated by comparing all values to the control sheet within the same experiment . B y doing so, it becomes evident that PPT, followed by ABTS, yields the highest wet strength.
• Table 3 Wet strength of isotropic handsheets made of a kraft pulp oxidised with PpL (10 LACU/g) and a mediator. The wet tensile strength was tested after immersion into distilled water for 1 hour. In some of the experiments the control sheet did not have a measurable wet strength, and therefore this was set to maximum ⁇ 2.2, which is the lowest detection limit Under the right conditions, heat treatment of paper is known to increase the wet strength up to a value of 30% of the dry strength (Stenberg, E.L., Svensk Papperstidning 8:49-54, 1978).

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• Biochemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Paper (AREA)
• Machines For Manufacturing Corrugated Board In Mechanical Paper-Making Processes (AREA)

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• 2000
  • 2000-03-16 CA CA002372499A patent/CA2372499C/en not_active Expired - Fee Related
  • 2000-03-16 AU AU32736/00A patent/AU766409B2/en not_active Ceased
  • 2000-03-16 WO PCT/DK2000/000118 patent/WO2000068500A1/en active IP Right Grant
  • 2000-03-16 DE DE60023563T patent/DE60023563T2/de not_active Expired - Lifetime
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