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
  • D21B1/02—Pretreatment of the raw materials by chemical or physical means
  • D21B1/021—Pretreatment of the raw materials by chemical or physical means by chemical means
• • 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
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/1005—Pretreatment of the pulp, e.g. degassing the pulp
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/1063—Bleaching ; Apparatus therefor with compounds not otherwise provided for, e.g. activated gases
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/1084—Bleaching ; Apparatus therefor with reducing compounds
  • D21C9/1089—Bleaching ; Apparatus therefor with reducing compounds with dithionites

Definitions

• the present invention relates to a process for the production of bleached wood pulp, a process for the production of paper or light wood materials, bleached wood pulp and the use of bleached wood pulp for the production of paper or wood-based materials, each as defined in the claims.
• Wood pulp also referred to in the art and herein as "pulp" is an important and abundant source material for the manufacture of certain types of paper, such as newsprint, magazine paper or paperboard.
• hardwoods or hardwoods or softwoods or softwoods are usually debarked, crushed into smaller, usually about 5 cm x 5 cm pieces (in the art and also referred to herein as "wood chips"), and then in a grinder ( in the art and also referred to herein as a "refiner"), usually at elevated temperature of, for example, 100 to 160 ° C, ground.
• a grinder in the art and also referred to herein as a "refiner”
• suitable such hardwoods or deciduous woods as well as suitable softwoods or softwoods are described, for example, in Lönnberg, Chapter (Chapter) 5, in particular Section 2. or Section 2.1.1 (Softwoods), for example spruce, fir, pine, pine or Section 2.1. 2 (Hardwoods), for example poplar such as Populus tremula, Populus tremuloides.
• TMP thermomechanical pulp
• the TMP is bleached in a subsequent step with bleaching chemicals in order to obtain as white paper as possible in the following processing.
• bleaching chemicals used are oxidatively active substances such as hydrogen peroxide, salts of inorganic or organic peracids, for example percarbonate, or reductive substances such as sulfinic acids, salts of sulfurous acid (sulfites) or salts of dithionic acid (dithonites).
• TMP Temporal Pulping
• Object of the present invention was to reduce the energy consumption - preferably in the refiner in the production of bleached wood pulp while increasing the whiteness of the pulp as possible without further important properties of the paper made of wood pulp - for example, mechanical properties - negative change.
• Wood pulp and its production is known and described for example in Lönnberg, in particular in the chapters (Chapters) 4, 6, 7, 8 and 15 described.
• the starting material for the wood pulp according to the invention are hardwoods, hardwoods and softwoods or softwoods. These woods are for example in Lönnberg, Chapter (Chapter) 5, in particular paragraph 2 or 2.1.1 (softwoods), such as spruce, fir, pine, pine or item 2.1.2 (Hardwoods), for example beech, birch, eucalyptus or Poplar as Populus tremula, Populus tremuloides described and well suited for the inventive method.
• larger wood particles preferably of debarked deciduous or coniferous wood, generally in a size of about (15-50) mm x (15-50) mm x approx (6 - 12) mm, prepared by conventional mechanical methods, for example by chopping.
• chips or chips.
• the woodchips or chips can, before further processing with chemicals, for example Sodium hydrogen sulfite (NaHSO 3 ), sodium sulfite (Na 2 SO 3 ) and / or water are pretreated.
• the chips are then delaminated in step a).
• the chips are usually first (i) subjected to mechanical pressure and / or shearing forces and then (ii) ground under relatively mild conditions, usually in a refiner.
• the chips produce "modified wood particles” (also referred to herein), usually loose fiber bundles, usually with a longitudinal dimension in the range of 5 cm to 0.3 cm, which generally greatly increase in size compared to the chips employed Have surface.
• a refiner is usually a grinding unit with rotating and possibly fixed knives or preferably slices for grinding fibrous materials and preferably consists of one or two radially-relief metal discs, which are close together and form a gap between them.
• the refiner operates at atmospheric or overpressure.
• Refiners are well known and extensively described in Lönnberg, especially in Chapters 6 and 7.
• the above step a) (i) is usually carried out in a screw press, which usually serves for dewatering and at the same time for the pre-fiberization of the larger wood particles.
• a well-suited device for carrying out the above-mentioned step a) (i) is, for example, the "Impressafiner" from Andritz AG, Austria.
• step a) (ii) is usually carried out in a refiner or other suitable milling unit under relatively mild conditions, for example in a single-disc refiner at a disc rotation number of 1800 rpm and a pressure of 2.4 bar.
• the energy consumption and / or pressure in the refiner of stage a) (ii) are lower than the corresponding parameters for the refiner in step b).
• the energy consumption in the refiner is generally determined inter alia by the Refineriminnaviere and the gap width between the Refinerimin.
• a well-suited apparatus for carrying out the aforementioned step a) (ii) is the Andritz 36-1 CP Single Disk Refiner from Andritz AG, Austria.
• step b) the modified wood particles from step a) are then ground in a refiner, usually under harsher conditions, for example higher output and / or higher pulley speed and / or higher pressure, than in step a) (ii).
• Step b) is usually carried out in a refiner under the following conditions, for example in a single-disk refiner at a disk revolution number of 2300 rpm and a pressure of 5.2 bar.
• the energy consumption in the refiner is generally determined inter alia by the Refineriminnaviere and the gap width between the Refinerimin.
• a well-suited apparatus for carrying out the aforementioned step b) is the Andritz 36-1 CP Single Disk Refiner from Andritz AG, Austria.
• Step b) may be followed by a further milling step or may be followed by a plurality of milling steps in a refiner in analogy to step b).
• step b) The substance obtained in step b) is optionally treated in a following step c) with reductive or oxidative bleaches using otherwise customary methods known from wood fiber production, for example in the bleaching tower.
• Bleaching agents and bleaching processes in the production of wood pulp are described in detail, for example, in Lönnberg, in particular in Chapter 11.
• Suitable oxidative bleaching agents which are suitable for the process according to the invention are those having a peroxy grouping, for example hydrogen peroxide, alkali metal peroxides.
• Suitable reductive bleaches for step c) of the process according to the invention are, for example, salts of the dithionic acid H 2 S 2 O 4 , salts of sulfurous acid and the like, preferably the composition Z, particularly preferably the components Z 1 or Z 2 or Z 3 .
• a salt of the dithionic acid H 2 S 2 O 4 Z 1
• the salt of the dithionic acid (Z1) are preferably the alkali metal salts, preferably lithium, sodium, potassium salts or alkaline earth metal salts, preferably calcium, magnesium salts of dithionic acid or mixtures thereof, the forms are of course included with water of crystallization or similar adducts.
• alkali metal salts preferably lithium, sodium, potassium salts or alkaline earth metal salts, preferably calcium, magnesium salts of dithionic acid or mixtures thereof
• the forms are of course included with water of crystallization or similar adducts.
• sodium dithionite Na 2 S 2 O 4
• lye for example sodium hydroxide (NaOH in water) in question.
• component (Z3) are: a salt, preferably an alkali metal salt, preferably lithium, sodium, potassium salt or alkaline earth metal salt, preferably calcium, magnesium salt of sulfurous acid (H 2 SO 3 ), ergo sulfites, or mixtures thereof, wherein the forms are of course included with water of crystallization or similar adducts, each in combination with sodium tetraborohydride.
• a salt preferably an alkali metal salt, preferably lithium, sodium, potassium salt or alkaline earth metal salt, preferably calcium, magnesium salt of sulfurous acid (H 2 SO 3 ), ergo sulfites, or mixtures thereof, wherein the forms are of course included with water of crystallization or similar adducts, each in combination with sodium tetraborohydride.
• Na 2 SO 3 sodium sulfite
• NaBH 4 sodium tetraborohydride
• Component (Z4) is one or more of the following components (1) to (4), and optionally further additives: (1) complexing agents, for example EDTA, polyphosphates, for example sodium tripolyphosphate and / or potassium tripolyphosphate; (2) basic compounds, preferably basic salts such as carbonates or bicarbonates, for example basic salts such as carbonates or bicarbonates of the alkali metals or alkaline earth metals, preferably lithium, sodium, potassium carbonate or alkaline earth metal carbonate, preferably calcium, magnesium carbonate, more preferably sodium carbonate (Na 2 CO 3 ), the forms of course being included with water of crystallization or similar adducts; (3) an alkali metal salt, preferably lithium, sodium, potassium salt or alkaline earth metal salt, preferably calcium, magnesium salt of the disulfurous acid (H 2 S 2 O 5 ); (4) an alkali metal salt, preferably lithium, sodium, potassium salt or alkaline earth metal salt, preferably calcium, magnesium salt of sulfurous acid (H 2 SO 3 ),
• Suitable further additives of component (Z4) are: surface-active substances such as anionic, cationic or nonionic or glucose-containing surfactants, usually in the proportion of from 1% by weight to 10% by weight, based on the composition Z; further anti-scale or anti-fouling substances such as polyacrylates in the proportion in the range of 1 wt .-% to 10 wt .-%, based on the composition Z.
• the composition Z comprises a salt of the dithionic acid H 2 S 2 O 4 (Z1), preferably a sodium salt, potassium salt, calcium salt, magnesium salt of the dithionic acid, including mixtures of these salts, particularly preferably sodium dithionite , the components (Z1) described above, in each case particularly preferably in the range from 20 to 95% by weight, very particularly preferably from 60 to 95% by weight, in each case based on the composition Z.
• Z1 a salt of the dithionic acid H 2 S 2 O 4 (Z1), preferably a sodium salt, potassium salt, calcium salt, magnesium salt of the dithionic acid, including mixtures of these salts, particularly preferably sodium dithionite , the components (Z1) described above, in each case particularly preferably in the range from 20 to 95% by weight, very particularly preferably from 60 to 95% by weight, in each case based on the composition Z.
• the composition Z contains, on the one hand, a salt of the dithionic acid H 2 S 2 O 4 (Z 1), preferably a sodium salt, potassium salt, calcium salt, magnesium salt of the dithionic acid, including mixtures of these salts, particular preference is given to sodium dithionite, the components (Z1) described above, in each case particularly preferably in the range from 60 to 95% by weight, based in each case on the composition Z and secondly the component (Z4), more preferably of which (1) complexing agent polyphosphates, ( 2) basic salts such as carbonates or bicarbonates the alkali metals or alkaline earth metals, such as sodium carbonate; (3) an alkali metal salt of the dibasic acid (H 2 S 2 O 5 ); (4) an alkali metal salt of sulfurous acid (H 2 SO 3 ), preferably (Z1) in the range of 60 to 95% by weight and (Z4) in the range of 5 to 40% by weight, based on the composition Z, is included.
• the composition Z comprises 60 to 95% by weight of a sodium salt (Z1), preferably sodium dithionite; 1 to 25% by weight of a sulfite Z4 (4), preferably sodium sulfite; 1 to 10 wt .-% of a carbonate and / or a hydrogen carbonate, in each case the alkali metals Z4 (2), preferably sodium carbonate; 0 to 10% by weight of a complexing agent Z4 (1), preferably sodium tripolyphosphate; in each case based on the composition Z and wherein the sum of said components gives 100%.
• a sodium salt (Z1) preferably sodium dithionite
• a sulfite Z4 (4) preferably sodium sulfite
• 1 to 10 wt .-% of a carbonate and / or a hydrogen carbonate in each case the alkali metals Z4 (2), preferably sodium carbonate; 0 to 10% by weight of a complexing agent Z4 (1), preferably sodium tripolyphosphate; in each case
• the composition Z contains, in addition to one or more of the components (Z1) to (Z3) and one or more components Z4 (1), Z4 (3) and Z4 (4), such an amount of basic compounds Z4 (2), preferably basic salts such as carbonates or bicarbonates, for example basic salts such as carbonates or bicarbonates of the alkali metals or alkaline earth metals, preferably lithium, sodium, potassium carbonate or alkaline earth metal carbonate, preferably calcium, magnesium carbonate, particularly preferably sodium carbonate, that these basic Compounds act as an acid buffer.
• basic salts such as carbonates or bicarbonates
• the alkali metals or alkaline earth metals preferably lithium, sodium, potassium carbonate or alkaline earth metal carbonate, preferably calcium, magnesium carbonate, particularly preferably sodium carbonate, that these basic Compounds act as an acid buffer.
• the composition Z contains, in addition to the component (Z1) - preferably a sodium salt, potassium salt, calcium salt, magnesium salt of dithionic acid, including mixtures of these salts, particularly preferably sodium dithionite - and one or more components Z4 (1), Z4 (3) and Z4 (4) such an amount of basic compounds Z4 (2), preferably basic salts such as carbonates or bicarbonates, for example basic salts such as carbonates or bicarbonates of the alkali metals or alkaline earth metals, preferably lithium, sodium -, potassium carbonate or alkaline earth metal carbonate, preferably calcium, magnesium carbonate, particularly preferably sodium carbonate, that these basic compounds act as acid buffer.
• basic salts such as carbonates or bicarbonates
• basic salts such as carbonates or bicarbonates of the alkali metals or alkaline earth metals, preferably lithium, sodium -, potassium carbonate or alkaline earth metal carbonate, preferably calcium, magnesium carbonate, particularly preferably sodium carbonate, that these basic compounds act as acid buffer.
• composition Z is used in the inventive method in the form of a solution or suspension, but it can also be used without further solvents or diluents as pure substance.
• Suitable solvents or dispersants dissolve or disperse the composition Z without its active ingredient or active ingredients, in particular component Z1, by decomposition or otherwise rendering ineffective or greatly reducing their action.
• water-containing solvents or dispersants for example mixtures of water and protic or aprotic organic solvents, for example alcohols, or ethers, ketones.
• a preferred solvent or dispersant is water.
• the concentration of the composition Z in such solutions or dispersions is generally in the range of 1 to 30 wt .-%, preferably 5 to 20 wt .-%, each based on the mass of the solution or dispersion.
• the amount of component (Z1) or (Z2) or (Z3), preferably of component (Z1), more preferably of sodium dithionite, per kilogram of wood material to be treated, for example chips or modified wood particles, is in the range of 1 to 50 grams, preferably in the range of 5 to 20 grams.
• solution or dispersion described above-including its preferred embodiments- is preferably prepared and used as fresh as possible, or it is stored with the most extensive possible exclusion of oxidizing media, for example atmospheric oxygen.
• composition Z is usually added before step a) (i), or before step a) (ii) or during the performance of step a) (i) and / or step a) (ii) and / or before step b) and / or during the performance of step b) with the corresponding wood particles or modified wood particles in contact.
• a solution or dispersion of the composition Z described in more detail above is introduced into the feed line for the wood particles to the corresponding devices in which the steps a) (i) a (ii) or b) are carried out, preferably in the flow direction of the wood particles or modified wood particles, shortly before the corresponding device dosed.
• a solution or dispersion of the composition Z which is described in greater detail above, can usually be metered directly into the space of the corresponding apparatuses in which steps a) (i), a (ii) or b) are carried out.
• a solution or dispersion of Z in water described in greater detail above-including its preferred embodiments- is metered into the refiner of stage a) (ii) and / or the refiner of stage b).
• the present invention also provides a process for the production of paper, preferably tissue, newsprint, magazine paper or paper for paperboard production, wherein, as described herein, a bleached wood pulp is made and this into paper, preferably tissue, newsprint, magazine paper or paper for paperboard production , usually with the known papermaking process, further processed.
• the present invention also provides a process for the production of bright wood materials, preferably HDF or MDF wood materials, which are as described herein bleached wood pulp and this, optionally with the addition of white pigments, glued and pressed to the wood materials.
• bright wood materials preferably HDF or MDF wood materials, which are as described herein bleached wood pulp and this, optionally with the addition of white pigments, glued and pressed to the wood materials.
• the present invention also provides a bleached wood pulp obtainable by a process as described herein.
• the present invention also provides the use of bleached wood pulp obtainable by the process as described herein for the production of paper or wood-based materials.
• the inventive method is characterized by the fact that the energy consumption in the refiner is reduced and the degree of bleaching of the wood pulp obtainable by the process according to the invention is higher than in the comparable prior art.
• the energy consumption in the refiner, the degree of bleaching of the wood pulp and other physical parameters were determined by the methods described in the examples.
• the corresponding wood was debarked and chopped into chips of approx. 5 cm x 5 cm x 1 cm using conventional mechanical methods.
• the chips were treated in a chip press (screw machine "Impressafiner” from Andritz AG, Austria) at a pressure of about 1.4 bar.
• the treated material was treated after leaving the screw machine with water and fed into a refiner (Andritz 36-1 CP Andritz AG, Austria), the so-called “Fiberizer” with a single grinding disc (diameter 0.91 m) where it converted into fibrous material at a grinding wheel speed of 1800 rpm and a pressure of 2.4 bar.
• the so-shredded material was fed into a first main refiner (Andritz 36-1 CP) and was there at a grinding wheel speed of 2300 U / min and a pressure of 5.2 bar in the presence of the composition Z, as described below, in Converted wood pulp.
• a first main refiner Engelhard 36-1 CP
• This wood pulp was further ground in a second main refiner with two grinding wheels (Andritz 401) at atmospheric pressure.
• the comparative experiments were carried out analogously to the inventive experiments (variant A)), but the inventive step a) was not carried out and the chips (see above) were directly in a first main refiner (Andritz 36-1 CP Andritz AG, Austria) at a pressure of 3.45 bar and a wheel speed of 1800 rev / min to wood pulp, in the presence of a solution described above under A) of the composition Z in water.
• This wood pulp was further ground in a second main refiner with two grinding wheels (Andritz 401 from Andritz AG, Austria) at atmospheric pressure.
• the Tensile Index was determined with Tappi T 456.
• the Tear Index was determined with Tappi T 414.
• the Tensile Energy Absorption (TEA) was determined with Tappi T 494.
• the Light Scattering Coefficient was determined with ISO 9416.
• Wood pulp fractionation was carried out with a Bauer Mc Nett Classifier.
• the Shives analysis was performed on a Pulmac Shive Analyzer fitted with a 0.10 mm sieve plate.
• the wood pulp produced according to the described variant A) with the wood of the black spruce was processed according to the standard TAPPI T 205 by means of a standard laboratory sheet to test paper and determined thereon mechanical properties, and the optical properties (for example, whiteness) were on paper sheets measured according to the TAPPI T 218 standard.
• wood pulp which was obtained according to the described variant B), as described above processed into test paper and investigated by the methods described above.
• wood pulp obtained according to the described variant B) from the wood of the turpentine pine was processed to test paper as described in Example 1 and investigated by the methods described in Example 1.

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• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Paper (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)

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