Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
  • D21B1/00—Fibrous raw materials or their mechanical treatment
  • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
  • D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
  • D21B1/14—Disintegrating in mills
  • D21B1/16—Disintegrating in mills in the presence of chemical 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
  • 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
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/47—Condensation polymers of aldehydes or ketones
  • D21H17/48—Condensation polymers of aldehydes or ketones with phenols
• • 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
  • D21H17/63—Inorganic compounds
  • D21H17/66—Salts, e.g. alums
• • 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
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/04—Addition to the pulp; After-treatment of added substances in the pulp
  • D21H23/06—Controlling the addition
  • D21H23/14—Controlling the addition by selecting point of addition or time of contact between components
  • D21H23/16—Addition before or during pulp beating or refining

Definitions

• the present invention relates to a process for making board according to what is commonly referred to as the wet method. More specifically, the invention concerns an improved process for making board, by adding the binder at an early stage of the process. Insulation board, building board and hardboard, for instance, can be produced by this process.
• a stock is prepared from fibres produced from a fibrous raw material, such as chips and sawdust, by mixing the fibres with water in several steps.
• a binder is added to bind the fibres in the board, whereupon the stock is dewatered and the fibre pulp is pressed.
• the binder is added to the stock and, if water-soluble, is precipitated and fixed to the fibres by acidification of the stock, e.g. by alum or acid.
• the binder may be added at a site where the stock concentration is about 5-15%, e.g. in the level box, whereupon precipitation and fixation by acidification take place where the stock concentration is about 2-3%, e.g. in the machine chest.
• both the addition of the binder and the precipitation thereof on to the fibres may take place in the machine chest.
• the binder when precipitated, deposits not only on the fibres, but also on the remaining material in the stock.
• the stock contains fibre fragments, i.e. what is commonly referred to as fines, as well as dissolved carbohydrate material and, to a certain extent, ligneous substance in dissolved and colloidal form. Since the water in the process is at least partly recycled by using, in the preparation of the stock, the white water from the dewatering step, the contents of these by-products will be comparatively high. As a portion of the binder deposits on these components, this portion will be of no avail to the fibre matrix. It has thus become necessary to increase the amount of binder added, which nevertheless has not given the desired result in certain cases.
• the dosage of resin is also restricted by the fact that dewatering of the stock is rendered more difficult if the amount of resin exceeds a certain level (about 6-8%).
• many board manufacturers in Europe have made their processes more or less closed for environmental reasons (reduced discharge of COD-consuming materials to recipients). As a result, the contents of fines and dissolved substances in the white water have increased even further.
• the present invention largely obviates these disadvantages.
• One object of the invention is, therefore, to utilize the adhesive on the fibre matrix more effectively in the making of board. Another object of the invention is to enable dosage of the desired amount of resin on the fibres without affecting the subsequent dewatering.
• a process for making board according to the wet method in which a stock is prepared from fibres produced from a fibrous raw material, such as chips and sawdust, and a binder is added prior to dewatering and pressing, the binder being added to the fibres before the preparation of the stock. It has surprisingly been found that the binder can be utilized far more effectively if added to the fibres early in the process, before the supply of water for preparing the stock, resulting in improved properties of the board. Also, it has become possible to add very large amounts of binder without adversely affecting the subsequent process.
• the wood raw material is conducted, by preheating with steam, to a defibrator for disintegration.
• the resulting fibre pulp is conveyed through a blow line to chests where the stock is prepared.
• Fresh water and/or white water is added to the chests, resulting in a stock having a content of about 5-15%.
• This stock is conducted to a refiner for final adjustment of the beating degree. From the refiner, the stock is conveyed to a machine chest, where the final dilution with water/white water is performed. At this stage, the stock has a content of about 2-3%.
• This stock is conducted to a wet machine to be dewatered, pressed and dried/press-dried (hot press).
• the binder may be added to the fibres at any time before the site where a substantial amount of water is added for preparing the stock.
• the binder is suitably added in the blow line from the defibrator.
• the fibres have a dry solids content of about 40-60% by weight. This constitutes a preferred embodiment of the invention.
• the binder may also be added to the fibres before the defibrator.
• binders as are predominant in the art. These are curing organic or inorganic binders, such as phenolic resins, amino resins, silicates or mixtures thereof.
• Water-soluble binders are generally used. When water-soluble resins are employed, they have to be precipitated and fixed to the fibres, which is brought about by acidification, e.g. by means of alum or acid. Preferably, acidification is performed in connection with the preparation of the stock or prior thereto, and in that case also prior to the addition of the binder.
• the precipitating reagent may be added to the first dilution chest, where the stock concentration is about 1-15% by weight, usually 5-15% by weight.
• the present invention it is also possible to "control" the penetration of resin into the fibre.
• the properties of the board can be influenced in different directions, e.g. internal bond strength and modulus of rupture versus swelling and water absorption. If a sparingly soluble or concentrated resin is used, penetration is reduced and the resin is concentrated on the fibre surfaces. This enhances the possibility of obtaining active glue joints between the fibres, resulting in higher strength.
• penetration increases, resulting in lower swelling and, above all, lower water absorption.
• Penetration may also be reduced by adding alum/acid before the defibrator or before the site where the binder is added. Thus, the binder will be precipitated directly on the surface of the acid fibre, and penetration is reduced to a minimum. Consequently, the present invention enables several ways of controlling in a given direction the properties of the end product.
• the process according to the invention enables the addition of very large amounts of binder without rendering dewatering on the wet machine more difficult.
• the prior-art process restricts the dosage of the binder to about 6-8%, requiring at that the aid of certain flocculating chemicals. If the dosage exceeds this level, dewatering from the wire is impeded to such an extent that there is a risk of crushing the sheet in the press section.
• there are no dosing problems with contents of from about 0.5% by weight to about 40% by weight (based on dry resin on a dry fibre matrix), suitably up to about 15-20% by weight.
• the binder is used in an amount of about 0.5-10% by weight, preferably 1-5% by weight.
• the binder can be added through a simple connecting tube on the blow line after the defibrator.
• the amount of binder is adjusted by a dosing pump.
• the binder can be precipitated in e.g. a first dilution chest at a stock concentration of about 10% by means of alum. Then, the sized stock is allowed to continue in the process via a refiner, a dilution chest, a machine chest and a wet machine in conventional manner.
• the process according to the invention is fairly easy to incorporate in existing processes.
• Phenolic resin having a concentration of 40% by weight was applied by so-called blow-line dosage immediately after the defibrator through an insert pipe centered in the blow line.
• the phenolic resin was applied to concentrated hot fibre having a temperature of about 150°C (a dry solids content of about 50% by weight).
• the resin was dosed by a suitable dosing pump, and was precipitated and fixed to the fibre at a high stock concentration (8-10%) immediately after the cyclone in the first dilution chest.
• Precipitation was brought about by the addition of an alum solution to the diluting water.
• the sized fibre (the stock) was then conducted further in the process via refiners, machine chests and a wet machine in conventional manner.
• the board thickness was 13 mm.
• Dosing process Phenolic resin dosage % MOR MPa IB MPa Swelling 2 h % Water abs. 2 h % According to the invention 5 6.5 0.26 1.9 12.4 Added in machine chest typical values* 5 3.0-3.5 0.08-0.12 2.3-3.5 18-30 Standard board 0 2.7 0.11 7.0 173 *) An addition of wax forms part of this grade.
• the process according to Example 1 was repeated, the only difference being that use was here made of concentrated phenolic resin of 43% by weight, i.e. having higher viscosity than the resin used in Example 1.
• Dosing process Phenolic resin dosage % MOR MPa IB MPa Swelling 2 h % Water abs. 2 h % According to the invention 5 4.0 0.16 3.2 15 Added in machine chest 2 2.2 0.07 3.5 22 *) An addition of wax (2%) forms part of this grade.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Mechanical Engineering (AREA)
• Inorganic Chemistry (AREA)
• Paper (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Laminated Bodies (AREA)
• Cell Separators (AREA)
• Battery Electrode And Active Subsutance (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Magnetic Record Carriers (AREA)
• Machines For Manufacturing Corrugated Board In Mechanical Paper-Making Processes (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

Country Status (16)

Families Citing this family (3)

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• 1992
  • 1992-03-13 SE SE9200784A patent/SE470101B/sv not_active IP Right Cessation
• 1993
  • 1993-03-05 LT LTIP389A patent/LT3163B/lt not_active IP Right Cessation
  • 1993-03-09 RU RU9394040866A patent/RU2080429C1/ru active
  • 1993-03-09 AU AU37715/93A patent/AU665817B2/en not_active Ceased
  • 1993-03-09 AT AT93906930T patent/ATE144299T1/de not_active IP Right Cessation
  • 1993-03-09 EP EP93906930A patent/EP0663972B1/en not_active Expired - Lifetime
  • 1993-03-09 ES ES93906930T patent/ES2093417T3/es not_active Expired - Lifetime
  • 1993-03-09 NZ NZ251000A patent/NZ251000A/en unknown
  • 1993-03-09 CA CA002131525A patent/CA2131525A1/en not_active Abandoned
  • 1993-03-09 WO PCT/SE1993/000205 patent/WO1993018227A1/en active IP Right Grant
  • 1993-03-09 DE DE69305529T patent/DE69305529T2/de not_active Expired - Fee Related
  • 1993-03-13 LV LVP-93-183A patent/LV10657B/xx unknown
• 1994
  • 1994-09-09 FI FI944158A patent/FI96976C/sv active
  • 1994-09-12 NO NO943379A patent/NO301944B1/no unknown
  • 1994-11-17 EE EE9400251A patent/EE9400251A/xx unknown
• 1996
  • 1996-11-14 GR GR960403024T patent/GR3021653T3/el unknown

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