EP2142348B1 - Method for the production of bleached wood particles and wood materials ranging from light-toned to white - Google Patents

Method for the production of bleached wood particles and wood materials ranging from light-toned to white Download PDF

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Publication number
EP2142348B1
EP2142348B1 EP20080749657 EP08749657A EP2142348B1 EP 2142348 B1 EP2142348 B1 EP 2142348B1 EP 20080749657 EP20080749657 EP 20080749657 EP 08749657 A EP08749657 A EP 08749657A EP 2142348 B1 EP2142348 B1 EP 2142348B1
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EP
European Patent Office
Prior art keywords
wood
cellulose
weight
bleach
production
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Not-in-force
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EP20080749657
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German (de)
French (fr)
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EP2142348A1 (en
Inventor
Dieter SCHÖNHABER
Stefan Erren
Katerina Stieglitz
Eberhard Beckmann
Andres Carlos Garcia Espino
Norbert Jäger
Juliane Krüsemann
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BASF SE
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BASF SE
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Priority to EP20080749657 priority Critical patent/EP2142348B1/en
Priority to PL08749657T priority patent/PL2142348T3/en
Publication of EP2142348A1 publication Critical patent/EP2142348A1/en
Application granted granted Critical
Publication of EP2142348B1 publication Critical patent/EP2142348B1/en
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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
    • D21J—FIBREBOARD; MANUFACTURE OF ARTICLES FROM CELLULOSIC FIBROUS SUSPENSIONS OR FROM PAPIER-MACHE
    • D21J1/00—Fibreboard
    • 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
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/04—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides
    • 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
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/04—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides
    • D21C3/06—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites sulfites
    • 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
    • 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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/249921—Web or sheet containing structurally defined element or component
    • Y10T428/249924—Noninterengaged fiber-containing paper-free web or sheet which is not of specified porosity
    • Y10T428/249925—Fiber-containing wood product [e.g., hardboard, lumber, or wood board, etc.]

Definitions

  • the present invention relates to a process for producing bleached wood particles and to a process for producing light to white wood materials made from the bleached wood particles.
  • MDF medium density fibreboard
  • HDF high density fibreboard
  • MDF and HDF boards can be processed like conventional chipboard. Due to their uniform structure, they are also suitable for the production of profiled parts and are therefore becoming increasingly popular in furniture construction. Thus, for example, furnishings for rooms and for decorative purposes (for example, in trade fair construction), but also higher-quality furniture made from these plates and then, in order to preserve the wood-like structure visible, only colorless or coated with overlay.
  • wood-based panels are of particular interest.
  • the light inherent color is achieved by the use of bleached wood fibers and optionally the addition of a white pigment and / or an optical brightener.
  • the coloring constituents of the wood particles are destroyed or rendered ineffective by oxidizing and / or reducing chemicals.
  • the wood fibers are usually bleached in bleach towers in countercurrent or during the processing of the wood chips usually used as raw material in the preheater or in the digester.
  • the plasticized woodchips are subsequently defibrated in the refiner and the fibers are blown out of the refiner via the so-called blowline.
  • both oxidatively acting substances such as hydrogen peroxide and salts of inorganic and organic peracids (for example, percarbonate) are used as well as reductive substances such as sulfinic acids, sulfites and dithionites.
  • the bleaching of the wood fibers in bleaching towers is an additional process step in their production, which increases the expenditure on equipment. It is therefore useful to lay the bleaching of wood fibers in the process of their production, as in the WO 2006/042651 A1 is described.
  • the bleaching agents must be carefully selected since bleaches incorporated in the process, as well as their reaction and degradation products, generally remain on the wood fibers and the product steps made therefrom.
  • the bleaching agents must be particularly suitable, they must have appropriate stabilities, redox potentials and reaction times. You should also take any adverse consequences.
  • hydrogen peroxide is unsuitable as a bleaching agent because it must be worked in alkaline, leading to swelling of the wood fiber and later yellowing, which is undesirable in the final products.
  • oxygen and ozone are used in the bleaching of pulp, bleaching of lignin-containing wood requires long reaction times. Sulphites and many organic bleaches have under the given conditions too low redox potentials, are in this case too weak as a bleaching agent.
  • sodium dithionite is highly reactive, it decomposes at temperatures above 80 to 100 ° C. The resulting and remaining in the wood fibers degradation products include hydrogen sulfide and thiosulfate, which are noticeable in the final product as an unpleasant odor.
  • the object of the present invention is therefore an alternative process for producing bleached wood particles, in which neither unwanted or disadvantageous compounds originating from the bleaching agent remain on or in the wood particles, with which a good bleaching action is achieved and which does not require extensive apparatus Processes for the production of wood fibers can be integrated.
  • the object is achieved by a method for producing bleached wood particles according to the present claim 1.
  • the wood particles are carried out in step b) via a blowline.
  • the comminuted, cellulose-containing raw materials are pretreated in a digester before they are used in step a) of the process according to the invention.
  • the wood particles are carried out in step b) via a blowline.
  • the comminuted, cellulose-containing raw materials are pretreated in a digester before they are used in step a) of the process according to the invention.
  • the process according to the invention for the production of bleached wood particles can be incorporated into existing processes for the production of wood particles without great expenditure on apparatus.
  • the bleach compositions to be used according to the invention have the great advantage of not being broken down prematurely in the refiner or in the blowline and, despite the very short to short residence times of the wood particles, which are in the range of minutes in the case of the refiner in the range of milliseconds and in the blowline To develop good to good bleaching effect, without leaving behind harmful or even harmful compounds on or in the wood particles.
  • the wood materials produced by the process according to the invention surprisingly have a greater brightness compared to wood materials produced from wood particles bleached in the digester or preheater.
  • wood particles are understood to mean small-particle, cellulose-containing particles. These include, for example, fibers and chips made of wood and other cellulosic materials.
  • all fibrous materials to be obtained from plants can serve as the base material for the wood particles and wood materials according to the invention.
  • wood is usually used as a raw material, but it is also possible to obtain suitable cellulosic particles from palms as well as from annual plants such as begasse or straw.
  • Another source is agricultural waste products.
  • Preferred base materials are light wood species, especially spruce or pine, but darker woods such as beech or eucalyptus can also be used.
  • the cellulose-containing raw materials are first comminuted and optionally washed. This may possibly be followed by a pretreatment. For example, wood is first chopped up, washed and the water-moist pieces of wood (wood chips) preheated first.
  • the comminuted, cellulosic raw materials are pretreated in a so-called digester. Usually, this is carried out at a pressure of 2 to 5 bar and a temperature of 100 to 180 ° C. The exact temperatures and pressures depend on the raw materials used. Lower annual temperatures are usually lower enough for digestion of annual plants than for the digestion of multi-annual plants such as wood.
  • step a) the optionally pretreated, comminuted, cellulose-containing raw materials are transferred to a so-called refiner and ground there to form wood particles.
  • a refiner is usually a grinding unit with rotating and possibly fixed knives / discs for grinding fibrous materials and preferably consists of two radially-provided with metal discs which are close to each other. One of these two discs can move, but both can rotate in opposite directions. Usually, the refiner works with overpressure.
  • the grinding of optionally pretreated, comminuted, cellulose-containing raw materials can also be carried out in other devices suitable for this purpose.
  • step b) the wood particles are carried out of the refiner.
  • the wood particles are blown out of the refiner by a so-called blowline.
  • a blowline is usually understood a blow pipe, through which the wood particles are carried out by the pressure prevailing in the refiner overpressure.
  • the wood particles are bleached in the refiner or when the wood particles are removed from the refiner by adding a bleach composition containing at least one bleach. If the wood particles are carried out via a blowline according to a preferred embodiment, the addition of the bleaching composition can take place in the refiner or in the blowline.
  • the wood particles are bleached reductively.
  • reducing sulfur compounds such as dithionites, disulfites, sulfites or sulfur dioxide
  • sulfinic acids and their salts in particular the alkali metal salts and especially the sodium salts and hydroxycarboxylic acids such as citric acid and malic acid are suitable.
  • bleaching compositions containing at least one bleaching agent selected from the group of stabilized sulfites and sulfinic acids and their salts are used hydroxymethylsulfinic acid being preferred as the sulfinic acid.
  • the stabilization of the sulfites is carried out by the addition of basic salts.
  • the bleaching composition may contain, in addition to the at least one bleaching agent and optionally its stabilizers, further auxiliaries such as complexing agents, for example EDTA or polyphosphates.
  • the alkali metal salts can be used, preferred are sodium and potassium hydrosulfite, particularly preferred is sodium hydrosulfite.
  • the alkali metal salts can be used, preferred are sodium and potassium sulfite, particularly preferably sodium sulfite.
  • the basic salts can be selected from the group of carbonates and bicarbonates, the alkali metal carbonates are preferred, sodium carbonate is particularly preferred.
  • Tripolyphosphatsalze potassium and sodium tripolyphosphate can be used, preferred is sodium tripolyphosphate.
  • the bleaching composition is added to the cellulose-containing raw material or the wood particles during their production.
  • the addition takes place in the refiner or when carrying out the wood particles.
  • the wood particles are carried out via a blowline.
  • the bleach composition containing at least one bleach is in this embodiment in the refiner or in the blowline, preferably added in the refiner or at the beginning of the blowline, particularly preferably in the refiner.
  • the bleaching composition is metered so that the amount of bleaching agent is from 0.1 to 6 wt .-%, preferably 0.5 to 5 wt .-% and particularly preferably 1 to 3 wt .-% of atro (absolutely dry) fibers.
  • the bleaching compositions are usually added to the wood particles in the refiner or in the blowline in the form of aqueous solutions, the concentration of bleaching composition in the aqueous solution being from 1 to 25% by weight, preferably from 5 to 20% by weight and more preferably from 10 to 15 wt .-% is enough.
  • the bleached wood particles can be further processed directly, they can also be dried and further processed in a dried state. Also, the dried wood particles can be stored before further processing.
  • a preferred possibility for further processing of the bleached wood particles is the production of wood-based materials, in particular directly after the bleaching step.
  • the wood particles are carried out in step b) via a blowline.
  • the comminuted, cellulose-containing raw materials are pretreated in a digester before they are used in step a) of the process according to the invention.
  • the wood-based materials produced according to the invention may be MDF, HDF, chipboard or OSB boards. Preference is given to MDF and HDF boards, particularly preferred MDF boards.
  • MDF, HDF, OSB and chipboard are also referred to as wood-based panels. They are preferably prepared by gluing coated fibers or shavings into mats, optionally cold precompressed and pressed in heated presses at temperatures of 170 to 240 ° C to plates.
  • the binder used as the sizing agent is usually urea-formaldehyde resins partially reinforced with melamine, urea-melamine-formaldehyde resins, melamine-formaldehyde resins, phenol-melamine resins and phenol-formaldehyde resins.
  • urea-melamine-formaldehyde resins partially reinforced with melamine
  • urea-melamine-formaldehyde resins melamine-formaldehyde resins
  • phenol-melamine resins phenol-formaldehyde resins
  • phenol-formaldehyde resins phenol-formaldehyde resins.
  • the wood particles can according to the invention directly, d. H. still wet, glued in the blowline.
  • Another possible method for gluing is in the so-called dry gluing, while the dried wood particles are sprayed with glue.
  • wood particles are glued in the blowline, they then pass through a dryer in which they are dried to moistures of 8 to 15 wt .-%.
  • the glued and optionally dried wood particles are then poured into mats, optionally precompressed cold and pressed in heated presses at temperatures of 170 to 240 ° C to plates.
  • the further processing of the bleached wood particles takes place immediately after the bleaching.
  • the bleached wood particles are bleached after bleaching according to the invention by adding a bleach composition in the refiner or at the beginning of the blowline in the blowline, then dried in a dryer to a residual moisture content of 8 to 15 wt .-% and further processed into wood materials.
  • At least one white pigment is added to the wood particles during the production process. This results in a mass coloration of the resulting wood material.
  • white pigment encompasses both inorganic pigments such as titanium dioxide (rutile, CI Pigment White 6), calcium carbonate and calcium / magnesium mixed carbonates (eg dolomite), zinc oxide, zinc sulfite, lithopone and sodium aluminum silicates, as well as white-dyeing, strongly light-scattering Plastic emulsions and dispersions.
  • inorganic white pigments are preferred, and titanium dioxide is particularly preferred. It is also possible to use mixtures of white pigments.
  • the white pigments are preferably used in the form of aqueous dispersions in which they are finely divided, since they can be introduced directly into the production process of the wood materials via the blowline, separately from or together with the glue.
  • These pigment dispersions may contain other customary auxiliaries, in particular wetting and dispersing agents, defoamers and biocides, anti-settling agents, water retention agents and rheology modifiers and are preferably prepared by wet milling of all components, for example in a stirred ball mill.
  • concentrations of the white pigment in the finished wood material are usually at 0.5 to 15% per atro wood fiber, preferably at 1 to 6% per atro wood fiber.
  • a further increase in whiteness can be achieved by the addition of optical brighteners, which compensate for their bluish fluorescence (complementary color) graying and yellowing.
  • optical brighteners can be introduced in the form of aqueous dispersions or solutions separately or together with the glue in the production process for the wood-based materials.
  • the concentration in the finished wood material is generally from 0.01 to 1% per atro wood fiber, preferably 0.08 to 0.2% per atro wood fiber.
  • wood-based materials of the invention in which both at least one white pigment and at least one optical brightener are combined, since the individual contributions are potentiated by synergy effects to a maximum overall degree of whiteness.
  • any resulting from the inventive measures changes in the physical properties of the pressed wood-based panel can be controlled by selecting the glue quality and amount of glue.
  • the selection of the corresponding parameters is familiar to the person skilled in the art.
  • Another object of the present invention are bleached wood particles, prepared by the process according to the invention for the production of bleached wood particles.
  • Another object of the present invention are light to white wood materials, prepared according to one of the inventive method described above.
  • the present invention will be illustrated by the production of MDF boards in Examples.
  • the MDF production process is carried out as usual with a throughput of 28 to 30 kg / h, the wood chips are shredded by the refiner, the fibers obtained are discharged through the blowline and continuously glued in the blowline with the glue batch listed in the examples.
  • the glued wood fibers are dried in the subsequent continuous dryer to a residual moisture content of about 9 wt .-% and then poured discontinuously to a mat, cold precompressed and at 190 ° C with a pressing time factor of 15 s / 2mm to a 16 mm thick plate pressed.
  • Wood chips from spruce wood were used as the cellulosic raw material.
  • the fibers were fiberized without the addition of a bleach composition and were continuously glued in the blowline with the glue formulation listed in Table 1.
  • Table 1 glue batch Urea-melamine-formaldehyde resin, 66.5% by weight in water 100.0 parts by weight Paraffin dispersion, 60% strength by weight in water 4.0 parts by weight water 33.8 parts by weight Solid resin content of the liquor 48% Solid resin / atro fibers 14% Fleet on 100 kg of atro fibers 29.2 kg
  • Spruce wood chips are used during the MDF production process in the refiner with a 15% strength by weight aqueous hydrosulfite solution, corresponding to 5% by weight. Bleach per atro fibers, offset. In the blowline, the fibers are glued with the glue batch listed in Table 1.
  • Spruce wood chips are added during the MDF production process in the refiner with a 15 wt .-% aqueous solution of bleach compositions listed in Table 3 1a to 1c, corresponding to 5 wt .-% bleach per atro fibers.
  • the resulting fibers are glued continuously in the blowline with the glue batch listed in Table 1.
  • An MDF board was prepared analogously to the procedure described in Example 1, but without the addition of the bleach-containing compositions.
  • Table 3 the obtained whiteness of Examples 1 a, 1 b and 1 c, expressed in the brightness difference .DELTA.L based on the comparative example V3 is listed as a standard.
  • Table 3 Bleaching compositions 1a to 1c example 1a 1b 1c V3 Hydrosulfite [% by weight] 85 80 70 - Sodium sulfite [% by weight] 7.5 12 13 - Soda (Na 2 CO 3 ) [% by weight] 7.5 5 14 - Sodium tripolyphosphate [% by weight] - 3 1 - .DELTA.L 5.1 6.7 5.0 -
  • Wood chips from spruce wood were fiberized in the refiner and treated with a 15 wt .-% aqueous solution of the bleaching composition listed under Example 1b, corresponding to 5 wt .-% bleach per atro fibers. Subsequently, the fibers in the blowline were glued with the glue batch listed in Table 1. The glued fibers were then pressed into an MDF board.
  • An MDF plate was prepared analogously to the procedure described in Example 2, but without the addition of a bleach-containing composition.
  • Table 4 shows the whiteness achieved, expressed in the brightness difference ⁇ L, based on the comparative example V4 as standard.
  • Wood chips from spruce and beech wood were added in the refiner with a 15 wt .-% aqueous bleach composition according to Example 1b, corresponding to 5% bleach atro fibers.
  • the fibers were in the blowline continuously with the in table 5 glued, containing the white pigment containing titanium dioxide glue batch, dried and pressed into MDF boards.
  • an MDF board was prepared.
  • a glue formulation according to Table 5 was used, with the titanium dioxide preparation being replaced by the same amount of water.
  • Table 6 the obtained whiteness, expressed in the brightness difference .DELTA.L, based on the comparative example V5 is listed as a standard. Table 6 example .DELTA.L 3 4.7 V5 -
  • An MDF board was prepared analogously to the procedure described in Example 5, but using the glue formulation listed in Table 8, which contains a combination of the white pigment titanium dioxide and optical brightener.
  • Table 8 glue batch Urea-melamine-formaldehyde resin, 66.5% by weight in water 100.0 parts by weight Paraffin dispersion, 60% strength by weight in water 4.0 parts by weight Titanium dioxide preparation, 50 wt .-% in water, containing 2 wt .-% of a commercial optical brightener 47.5 parts by weight Solid resin content of the liquor 44% Solid resin / atro fibers 14% Titanium dioxide / atro fibers 5% optical brightener / atro fibers 0.2% Fleet on 100 kg of atro fibers 31.8 kg
  • An MDF board was prepared analogously to the procedure described in Example 4, but without the addition of the bleach-containing composition in the refiner.
  • Wood chips from spruce wood were treated in the refiner with a 15% strength by weight aqueous solution of hydroxymethanesulfinic acid, corresponding to 5% bleach-free fibers.
  • the bleached fibers were glued with the glue formulation listed in Table 1.
  • Table 10 the obtained whiteness, expressed in the brightness difference ⁇ L, based on the comparative example V7 as a standard, is listed.
  • Poplar wood chips were treated during the MDF production process in the refiner with a 15% by weight aqueous bleaching composition according to Example 1b, corresponding to 5% bleach per atro fibers.
  • the resulting fibers were coated in the blowline continuously with the glue formulation listed in Table 1.
  • An MDF board was prepared analogously to the procedure described in Example 8, but without the addition of the bleach-containing composition.
  • Table 11 shows the whiteness achieved, expressed in the difference in brightness ⁇ L, based on the comparative example V8 as standard.
  • Spruce wood chips were treated during the MDF production process in the refiner with a solution containing 15% by weight aqueous bleach according to Example 1b, corresponding to 5% bleach per atro fibers.
  • the resulting fibers were glued in the blowline with the glue formulation listed in Table 1.
  • the glued wood fibers were dried and pressed into a plate.
  • the plate was then exposed for 24 hours in a Sun tester and the whiteness expressed in terms of the difference in brightness ⁇ L with respect to the unexposed plate was measured.
  • Table 12 lists the results. Table 12 example .DELTA.L 9 exposed - 2 9 unexposed -
  • Spruce wood chips were treated during the MDF production process in the refiner with a 15% by weight aqueous hydrosulfite solution corresponding to 5% bleach per atro fibers.
  • the resulting fibers were coated in the blowline continuously with the glue formulation listed in Table 1.
  • the dried glued wood fibers were pressed into MDF boards.
  • Table 13 shows the whiteness achieved. example .DELTA.L V9 exposed - 4,5 V9 unexposed -
  • Wood chips from spruce wood were added during the MDF production process in the refiner with a 15 wt .-% aqueous solution containing bleach composition according to Example 1b, corresponding to 5% bleach per atro fibers.
  • the resulting fibers were coated in the blowline continuously with the glue formulation listed in Table 1.
  • an MDF board was prepared.
  • Table 14 shows the whiteness achieved, expressed in the difference in brightness ⁇ L, transverse tensile strength, swelling, and the sensorially determined odor of the plates, each referred to as comparative example V10 as standard.
  • the transverse tensile strength of the resulting MDF boards was measured according to DIN 319, particleboard and fiberboard, determination of tensile strength, perpendicular to the board plane.
  • the swelling was measured in accordance with DIN EN 317, particleboard and fiberboard, determination of thickness swelling and water absorption.
  • Table 14 example .DELTA.L Transverse tensile strength [N / mm 2 ] Swelling 24 h [%] odor 10 6.3 0.85 6.67 woody V10 - 1.04 6.33 woody

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

The present invention relates to a process for the production of bleached wood particles and a process for the production of pale to white wood-base materials which are produced from the bleached wood particles.

Description

Die vorliegende Erfindung betrifft ein Verfahren zur Herstellung von gebleichten Holzpartikeln sowie ein Verfahren zur Herstellung heller bis weißer Holzwerkstoffe, die aus den gebleichten Holzpartikeln hergestellt sind.The present invention relates to a process for producing bleached wood particles and to a process for producing light to white wood materials made from the bleached wood particles.

Im Bereich der Holzwerkstoffe ist der Markt an so genannten mitteldichten Faserplatten (Medium density fibreboard, MDF-Platten) und hoch verdichteten Faserplatten (high density fibreboard, HDF-Platten) stark im Anstieg begriffen. Die Produktionsmengen haben sich in den letzten zehn Jahren mehr als verdreifacht.In the field of wood-based panels, the market for medium density fibreboard (MDF) and high density fibreboard (HDF) is growing rapidly. The production volumes have more than tripled in the last ten years.

MDF- und HDF-Platten können wie herkömmliche Spanplatten verarbeitet werden. Durch ihren gleichmäßigen Aufbau sind sie aber auch zur Herstellung von profilierten Teilen geeignet und setzen sich deshalb verstärkt im Möbelbau durch. So werden beispielsweise Einrichtungsgegenstände für Räume und für dekorative Zwecke (z.B. im Messebau), aber auch schon höherwertige Möbel aus diesen Platten gefertigt und anschließend, um die holzartige Struktur sichtbar zu erhalten, nur noch farblos lackiert oder mit Overlay beschichtet.MDF and HDF boards can be processed like conventional chipboard. Due to their uniform structure, they are also suitable for the production of profiled parts and are therefore becoming increasingly popular in furniture construction. Thus, for example, furnishings for rooms and for decorative purposes (for example, in trade fair construction), but also higher-quality furniture made from these plates and then, in order to preserve the wood-like structure visible, only colorless or coated with overlay.

Naturgemäß besitzen diese Platten, je nach verwendeter Holzart, eine mehr oder weniger ausgeprägte braune Färbung, die für eine Anwendung im Möbelbereich nur von geringem ästhetischem Wert ist.Naturally, these boards, depending on the type of wood used, a more or less pronounced brown color, which is of little aesthetic value for an application in the furniture sector.

Durch Massefärbung mit den aus der WO-A 04/35276 bekannten Pigment und Farbstoff enthaltenden Farbmittelzubereitungen kann die Eigenfärbung der Holzfasern kompensiert werden. Auf diese Weise sind bunte, vollständig durchgefärbte, lichtechte und damit ästhetisch hochwertige MDF-Platten zu erhalten, die zur Herstellung langlebiger Artikel, z.B. von Möbeln für den Wohnbereich, geeignet sind.By mass coloring with those from the WO-A 04/35276 known pigment and dye-containing colorant preparations can be compensated for the inherent color of the wood fibers. In this way, colorful, completely colored, lightfast and therefore aesthetically high-quality MDF boards are obtained, which are suitable for the production of durable articles, for example of furniture for the living area.

Für die Herstellung von Möbeln und Innendekorationsobjekten, z.B. für Küche oder Bad sind helle oder gar weiße Holzwerkstoffe, insbesondere Holzwerkstoffplatten von besonderem Interesse.For the manufacture of furniture and interior decoration objects, e.g. for kitchen or bathroom light or even white wood materials, especially wood-based panels are of particular interest.

In der WO 2006/042651 werden helle bis weiße Holzwerkstoffplatten beschrieben, deren helle Eigenfarbe durch die Verwendung von gebleichten Holzfasern sowie gegebenenfalls dem Zusatz eines Weißpigments und/oder eines optischen Aufhellers erreicht wird. Bei der chemischen Bleiche werden die färbenden Inhaltsstoffe der Holzpartikel durch oxidierende und/oder reduzierende Chemikalien zerstört oder unwirksam gemacht. Die Holzfasern werden üblicherweise in Bleichtürmen im Gegenstrom oder bei der Verarbeitung der üblicherweise als Rohstoff eingesetzten Holzhackschnitzel im Vorerwärmer oder im Kocher gebleicht. Die plastifizierten Holzhackschnitzel werden im Anschluss im Refiner zerfasert und die Fasern über die sogenannte Blowline aus dem Refiner ausgeführt. Als Bleichmittel werden sowohl oxidativ wirkende Substanzen wie Wasserstoffperoxid und Salze anorganischer und organischer Persäuren (zum Beispiel Percarbonat) verwendet als auch reduktiv wirkende Substanzen wie Sulfinsäuren, Sulfite und Dithionite.In the WO 2006/042651 Light to white wood-based panels are described, the light inherent color is achieved by the use of bleached wood fibers and optionally the addition of a white pigment and / or an optical brightener. In the chemical bleaching, the coloring constituents of the wood particles are destroyed or rendered ineffective by oxidizing and / or reducing chemicals. The wood fibers are usually bleached in bleach towers in countercurrent or during the processing of the wood chips usually used as raw material in the preheater or in the digester. The plasticized woodchips are subsequently defibrated in the refiner and the fibers are blown out of the refiner via the so-called blowline. As a bleaching agent both oxidatively acting substances such as hydrogen peroxide and salts of inorganic and organic peracids (for example, percarbonate) are used as well as reductive substances such as sulfinic acids, sulfites and dithionites.

Das Bleichen der Holzfasern in Bleichtürmen ist ein zusätzlicher Prozessschritt bei deren Herstellung, der den apparativen Aufwand erhöht. Es ist deshalb sinnvoll, das Bleichen der Holzfasern in den Prozess ihrer Herstellung zu verlegen, wie dies in der WO 2006/042651 A1 beschrieben wird. Allerdings müssen die Bleichmittel sorgfältig ausgewählt werden, da in den Prozess eingebrachten Bleichmittel sowie ihre Reaktions- und Abbauprodukte im Allgemeinen auf den Holzfasern und den daraus hergestellten Produktschritten verbleiben. Um in bereits bestehenden Anlagen zur Herstellung von Holzfasern eingesetzt werden zu können, müssen die Bleichmittel besonders geeignet sein, sie müssen entsprechende Stabilitäten, Redoxpotentiale und Reaktionszeiten aufweisen. Sie sollten zudem keine nachteiligen Folgereaktionen eingehen.The bleaching of the wood fibers in bleaching towers is an additional process step in their production, which increases the expenditure on equipment. It is therefore useful to lay the bleaching of wood fibers in the process of their production, as in the WO 2006/042651 A1 is described. However, the bleaching agents must be carefully selected since bleaches incorporated in the process, as well as their reaction and degradation products, generally remain on the wood fibers and the product steps made therefrom. To be able to be used in existing plants for the production of wood fibers, the bleaching agents must be particularly suitable, they must have appropriate stabilities, redox potentials and reaction times. You should also take any adverse consequences.

So ist beispielsweise Wasserstoffperoxid als Bleichmittel ungeeignet, da im Alkalischen gearbeitet werden muss, dies führt zum Quellen der Holzfaser und späterem Vergilben, was in den Endprodukten unerwünscht ist. Sauerstoff und Ozon werden zwar bei der Bleiche von Zellstoff eingesetzt, das Bleichen von Lignin-haltigem Holz erfordert jedoch lange Reaktionszeiten. Sulfite und viele organische Bleichmittel haben unter den vorgegebenen Bedingungen zu geringe Redoxpotentiale, sind in diesem Fall also als Bleichmittel zu schwach. Natriumdithionit hingegen ist zwar hochreaktiv, zersetzt sich jedoch bei Temperaturen oberhalb von 80 bis 100 °C. Die dabei entstehenden und in den Holzfasern verbleibenden Abbauprodukte sind beispielsweise Schwefelwasserstoff und Thiosulfat, die sich im Endprodukt als unangenehmer Geruch bemerkbar machen.For example, hydrogen peroxide is unsuitable as a bleaching agent because it must be worked in alkaline, leading to swelling of the wood fiber and later yellowing, which is undesirable in the final products. Although oxygen and ozone are used in the bleaching of pulp, bleaching of lignin-containing wood requires long reaction times. Sulphites and many organic bleaches have under the given conditions too low redox potentials, are in this case too weak as a bleaching agent. While sodium dithionite is highly reactive, it decomposes at temperatures above 80 to 100 ° C. The resulting and remaining in the wood fibers degradation products include hydrogen sulfide and thiosulfate, which are noticeable in the final product as an unpleasant odor.

Aufgabe der vorliegenden Erfindung ist daher ein alternatives Verfahren zum Herstellen von gebleichten Holzpartikeln, bei dem weder unerwünschte oder nachteilig wirkende, aus dem Bleichmittel stammende Verbindungen auf oder in den Holzpartikeln zurückbleiben, mit dem eine gute Bleichwirkung erzielt wird und das ohne großen apparativen Aufwand in bestehende Prozesse zur Herstellung von Holzfasern integriert werden kann.The object of the present invention is therefore an alternative process for producing bleached wood particles, in which neither unwanted or disadvantageous compounds originating from the bleaching agent remain on or in the wood particles, with which a good bleaching action is achieved and which does not require extensive apparatus Processes for the production of wood fibers can be integrated.

Die Aufgabe wird gelöst durch ein Verfahren zur Herstellung von gebleichten Holzpartikeln gemäß dem vorliegenden Anspruch 1.The object is achieved by a method for producing bleached wood particles according to the present claim 1.

In einer bevorzugten Ausführungsform werden die Holzpartikel in Schritt b) über eine Blowline ausgeführt.In a preferred embodiment, the wood particles are carried out in step b) via a blowline.

In einer ebenfalls bevorzugten Ausführungsform werden die zerkleinerten, cellulosehaltigen Rohstoffe in einem Kocher vorbehandelt, bevor sie in Schritt a) des erfindungsgemäßen Verfahrens eingesetzt werden.In a likewise preferred embodiment, the comminuted, cellulose-containing raw materials are pretreated in a digester before they are used in step a) of the process according to the invention.

Weiterhin wurde ein Verfahren zur Herstellung von hellen bis weißen Holzwerkstoffen gemäß dem vorliegenden Anspruch 6 gefunden.Furthermore, a process for the preparation of light to white wood materials according to the present claim 6 has been found.

In einer bevorzugten Ausführungsform werden die Holzpartikel in Schritt b) über eine Blowline ausgeführt.In a preferred embodiment, the wood particles are carried out in step b) via a blowline.

In einer ebenfalls bevorzugten Ausführungsform werden die zerkleinerten, cellulosehaltigen Rohstoffe in einem Kocher vorbehandelt, bevor sie in Schritt a) des erfindungsgemäßen Verfahrens eingesetzt werden.In a likewise preferred embodiment, the comminuted, cellulose-containing raw materials are pretreated in a digester before they are used in step a) of the process according to the invention.

Das erfindungsgemäße Verfahren zur Herstellung von gebleichten Holzpartikeln lässt sich in bestehende Prozesse zur Herstellung von Holzpartikeln ohne großen apparativen Aufwand eingliedern. Die erfindungsgemäß einzusetzenden Bleichmittelzusammensetzungen besitzen den großen Vorteil, im Refiner beziehungsweise in der Blowline nicht vorzeitig abgebaut zu werden und trotz der sehr kurzen bis kurzen Verweilzeiten der Holzpartikel, die beim Refiner im Bereich von Millisekunden und bei der Blowline im Bereich von Minuten liegen, eine sehr gute bis gute Bleichwirkung zu entfalten, ohne dabei nachteilige oder sogar schädliche Verbindungen auf oder in den Holzpartikeln zurückzulassen.The process according to the invention for the production of bleached wood particles can be incorporated into existing processes for the production of wood particles without great expenditure on apparatus. The bleach compositions to be used according to the invention have the great advantage of not being broken down prematurely in the refiner or in the blowline and, despite the very short to short residence times of the wood particles, which are in the range of minutes in the case of the refiner in the range of milliseconds and in the blowline To develop good to good bleaching effect, without leaving behind harmful or even harmful compounds on or in the wood particles.

Wenn der gleiche Rohstoff für die Holzpartikel eingesetzten wird, weisen die nach dem erfindungsgemäßen Verfahren hergestellten Holzwerkstoffe im Vergleich zu Holzwerkstoffen, die aus im Kocher oder Vorerwärmer gebleichten Holzpartikeln hergestellt wurden, überraschenderweise eine größere Helligkeit auf.When the same raw material is used for the wood particles, the wood materials produced by the process according to the invention surprisingly have a greater brightness compared to wood materials produced from wood particles bleached in the digester or preheater.

Besonders vorteilhaft ist die Herstellung der Holzwerkstoffe im direkten Anschluss an die erfindungsgemäße Herstellung der gebleichten Holzpartikel, da hier ohne weiteren apparativen Aufwand helle bis weiße Holzwerkstoffe erhalten werden.Particularly advantageous is the production of wood-based materials in direct connection to the inventive production of bleached wood particles, since light to white wood materials are obtained without further equipment expense.

Im Rahmen der vorliegenden Erfindung werden unter "Holzpartikel" kleinteilige, cellulosehaltige Partikel verstanden. Dazu zählen beispielsweise Fasern und Späne aus Holz und anderen cellulosehaltigen Materialien. Als Basismaterial für die erfindungsgemäßen Holzpartikel und Holzwerkstoffe können im Prinzip alle aus Pflanzen zu gewinnenden faserigen Materialien dienen. So wird üblicherweise Holz als Rohstoff eingesetzt, jedoch können auch aus Palmen sowie aus einjährigen Pflanzen wie Begasse oder Stroh geeignete cellulosehaltige Partikel gewonnen werden. Eine weitere Quelle stellen landwirtschaftliche Abfallprodukte dar. Bevorzugte Basismaterialien sind helle Holzarten, insbesondere Fichte oder Kiefer, jedoch können auch dunklere Holzarten wie Buche oder Eukalyptus verwendet werden.In the context of the present invention, "wood particles" are understood to mean small-particle, cellulose-containing particles. These include, for example, fibers and chips made of wood and other cellulosic materials. In principle, all fibrous materials to be obtained from plants can serve as the base material for the wood particles and wood materials according to the invention. For example, wood is usually used as a raw material, but it is also possible to obtain suitable cellulosic particles from palms as well as from annual plants such as begasse or straw. Another source is agricultural waste products. Preferred base materials are light wood species, especially spruce or pine, but darker woods such as beech or eucalyptus can also be used.

Die cellulosehaltigen Rohstoffe werden zunächst zerkleinert und gegebenenfalls gewaschen. Daran kann sich gegebenenfalls eine Vorbehandlung anschließen. Holz wird beispielsweise zunächst klein zerhackt, gewaschen und die wasserfeuchten Holzstücke (Hackschnitzel) zunächst vorgewärmt.The cellulose-containing raw materials are first comminuted and optionally washed. This may possibly be followed by a pretreatment. For example, wood is first chopped up, washed and the water-moist pieces of wood (wood chips) preheated first.

In einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens werden die zerkleinerten, cellulosehaltigen Rohstoffe in einem sogenannten Kocher vorbehandelt. Üblicherweise wird dies bei einem Druck von 2 bis 5 bar und einer Temperatur von 100 bis 180 °C durchgeführt. Die genauen Temperaturen und Drücke hängen von den jeweils eingesetzten Rohstoffen ab. Zum Aufschluss von Einjahrespflanzen reichen üblicherweise niedrigere Temperaturen aus als beim Aufschluss von Mehrjahrespflanzen wie Holz.In a preferred embodiment of the method according to the invention, the comminuted, cellulosic raw materials are pretreated in a so-called digester. Usually, this is carried out at a pressure of 2 to 5 bar and a temperature of 100 to 180 ° C. The exact temperatures and pressures depend on the raw materials used. Lower annual temperatures are usually lower enough for digestion of annual plants than for the digestion of multi-annual plants such as wood.

In Schritt a) werden die gegebenenfalls vorbehandelten, zerkleinerten, cellulosehaltigen Rohstoffe in einen sogenannten Refiner überführt und dort zu Holzpartikeln zermahlen. Ein Refiner ist üblicherweise ein Mahlaggregat mit rotierenden und gegebenenfalls feststehenden Messern/Scheiben zur Mahlung von Faserstoffen und besteht vorzugsweise aus zwei mit radialem Relief versehenen Metallscheiben, die sich dicht aneinander befinden. Von diesen beiden Scheiben kann sich eine bewegen, es können sich aber auch beide in entgegengesetzem Sinn drehen. Üblicherweise wird im Refiner mit Überdruck gearbeitet. Das Zermahlen der gegebenenfalls vorbehandelten, zerkleinerten, cellulosehaltigen Rohstoffe kann auch in anderen, für diesen Zweck geeigneten Vorrichtungen durchgeführt werden.In step a), the optionally pretreated, comminuted, cellulose-containing raw materials are transferred to a so-called refiner and ground there to form wood particles. A refiner is usually a grinding unit with rotating and possibly fixed knives / discs for grinding fibrous materials and preferably consists of two radially-provided with metal discs which are close to each other. One of these two discs can move, but both can rotate in opposite directions. Usually, the refiner works with overpressure. The grinding of optionally pretreated, comminuted, cellulose-containing raw materials can also be carried out in other devices suitable for this purpose.

In Schritt b) werden die Holzpartikel aus dem Refiner ausgeführt. In einer bevorzugten Ausführungsform der vorliegenden Erfindung werden die Holzpartikel dabei aus dem Refiner durch eine sogenannte Blowline hinausgeblasen. Unter einer Blowline wird üblicherweise eine Blasleitung verstanden, durch die die Holzpartikel durch den im Refiner herrschenden Überdruck ausgeführt werden.In step b) the wood particles are carried out of the refiner. In a preferred embodiment of the present invention, the wood particles are blown out of the refiner by a so-called blowline. Under a blowline is usually understood a blow pipe, through which the wood particles are carried out by the pressure prevailing in the refiner overpressure.

Erfindungsgemäß werden die Holzpartikel im Refiner oder beim Ausführen der Holzpartikel aus dem Refiner durch Zugabe einer mindestens ein Bleichmittel enthaltenden Bleichmittelzusammensetzung gebleicht. Werden die Holzpartikel gemäß einer bevorzugten Ausführungsform über eine Blowline ausgeführt, kann die Zugabe der Bleichmittelzusammensetzung im Refiner oder in der Blowline stattfinden.According to the invention, the wood particles are bleached in the refiner or when the wood particles are removed from the refiner by adding a bleach composition containing at least one bleach. If the wood particles are carried out via a blowline according to a preferred embodiment, the addition of the bleaching composition can take place in the refiner or in the blowline.

Erfindungsgemäß werden die Holzpartikel reduktiv gebleicht. Für die reduktive Bleiche sind zum Beispiel reduzierende Schwefelverbindungen wie Dithionite, Disulfite, Sulfite beziehungsweise Schwefeldioxid, Sulfinsäuren und deren Salze, insbesondere die Alkalimetallsalze und vor allem die Natriumsalze und Hydroxycarbonsäuren wie Zitronensäure und Äpfelsäure geeignet. Gemäß der vorliegenden Erfindung werden Bleichmittelzusammensetzungen eingesetzt, die mindestens ein Bleichmittel ausgewählt aus der Gruppe der stabilisierten Sulfite und der Sulfinsäuren und deren Salze, enthalten wobei als Sulfinsäure Hydroxymethylsulfinsäure bevorzugt ist.According to the invention, the wood particles are bleached reductively. For the reductive bleaching, for example, reducing sulfur compounds such as dithionites, disulfites, sulfites or sulfur dioxide, sulfinic acids and their salts, in particular the alkali metal salts and especially the sodium salts and hydroxycarboxylic acids such as citric acid and malic acid are suitable. According to the present invention, bleaching compositions containing at least one bleaching agent selected from the group of stabilized sulfites and sulfinic acids and their salts are used hydroxymethylsulfinic acid being preferred as the sulfinic acid.

Die Stabilisierung der Sulfite erfolgt durch die Zugabe basischer Salze.The stabilization of the sulfites is carried out by the addition of basic salts.

Die Bleichmittelzusammensetzung kann neben dem mindestens einen Bleichmittel und gegebenenfalls dessen Stabilisatoren noch weitere Hilfsmittel enthalten wie Komplexbildner, beispielsweise EDTA oder Polyphosphate.The bleaching composition may contain, in addition to the at least one bleaching agent and optionally its stabilizers, further auxiliaries such as complexing agents, for example EDTA or polyphosphates.

Bevorzugt werden die Holzpartikel erfindungsgemäß mittels der nachfolgend aufgeführten Bleichmittelzusammensetzung gebleicht. Die erfindungsgemäße Bleichmittelzusammensetzung enthält

  1. a) 60 bis 95 Gew.-% eines oder mehrerer Hydrosulfitsalze
  2. b) 1 bis 25 Gew.-% eines oder mehrerer Sulfitsalze
  3. c) 1 bis 10 Gew.-% eines oder mehrerer basischer Salze
Preferably, the wood particles are bleached according to the invention by means of the bleaching composition listed below. The bleaching composition of the invention contains
  1. a) 60 to 95 wt .-% of one or more hydrosulfite salts
  2. b) 1 to 25 wt .-% of one or more sulfite salts
  3. c) 1 to 10 wt .-% of one or more basic salts

Als Hydrosulfitsalze können die Alkalisalze eingesetzt werden, bevorzugt sind Natrium- und Kaliumhydrosulfit, besonders bevorzugt ist Natriumhydrosulfit.As hydrosulfite salts, the alkali metal salts can be used, preferred are sodium and potassium hydrosulfite, particularly preferred is sodium hydrosulfite.

Als Sulfitsalze können die Alkalisalze eingesetzt werden, bevorzugt sind Natrium- und Kaliumsulfit, besonders bevorzugt ist Natriumsulfit.As sulfite salts, the alkali metal salts can be used, preferred are sodium and potassium sulfite, particularly preferably sodium sulfite.

Die basischen Salze können ausgewählt werden aus der Gruppe der Carbonate und Hydrogencarbonate, bevorzugt sind die Alkalicarbonate, besonders bevorzugt ist Natriumcarbonat.The basic salts can be selected from the group of carbonates and bicarbonates, the alkali metal carbonates are preferred, sodium carbonate is particularly preferred.

Als Tripolyphosphatsalze können Kalium- und Natriumtripolyphosphat eingesetzt werden, bevorzugt ist Natriumtripolyphosphat.As Tripolyphosphatsalze potassium and sodium tripolyphosphate can be used, preferred is sodium tripolyphosphate.

Gemäß der vorliegenden Erfindung wird die Bleichmittelzusammensetzung dem cellulosehaltigen Rohstoff oder den Holzpartikeln während deren Herstellung zugesetzt. Die Zugabe erfolgt im Refiner oder bei Ausführen der Holzpartikel. Gemäß einer bevorzugten Ausführungsform werden die Holzpartikel über eine Blowline ausgeführt, erfindungsgemäß wird die mindestens ein Bleichmittel enthaltende Bleichmittelzusammensetzung bei dieser Ausführungsform im Refiner oder in der Blowline, bevorzugt im Refiner oder am Beginn der Blowline, besonders bevorzugt im Refiner zugegeben.According to the present invention, the bleaching composition is added to the cellulose-containing raw material or the wood particles during their production. The addition takes place in the refiner or when carrying out the wood particles. According to a preferred embodiment, the wood particles are carried out via a blowline. According to the invention, the bleach composition containing at least one bleach is in this embodiment in the refiner or in the blowline, preferably added in the refiner or at the beginning of the blowline, particularly preferably in the refiner.

Die Bleichmittelzusammensetzung wird so dosiert, dass die Menge Bleichmittel bei 0,1 bis 6 Gew.-%, bevorzugt 0,5 bis 5 Gew.-% und besonders bevorzugt 1 bis 3 Gew.-% auf atro (absolut trockene) Fasern liegt.The bleaching composition is metered so that the amount of bleaching agent is from 0.1 to 6 wt .-%, preferably 0.5 to 5 wt .-% and particularly preferably 1 to 3 wt .-% of atro (absolutely dry) fibers.

Die Bleichmittelzusammensetzungen werden den Holzpartikeln im Refiner oder in der Blowline üblicherweise in Form wässriger Lösungen zugeben, wobei die Konzentration an Bleichmittelzusammensetzung in der wässrigen Lösung von 1 bis 25 Gew.-%, bevorzugt von 5 bis 20 Gew.-% und besonders bevorzugt von 10 bis 15 Gew.-% reicht.The bleaching compositions are usually added to the wood particles in the refiner or in the blowline in the form of aqueous solutions, the concentration of bleaching composition in the aqueous solution being from 1 to 25% by weight, preferably from 5 to 20% by weight and more preferably from 10 to 15 wt .-% is enough.

Die gebleichten Holzpartikel können direkt weiterverarbeitet werden, sie können auch getrocknet werden und in getrocknetem Zustand weiterverarbeitet werden. Auch können die getrockneten Holzpartikel vor der Weiterverarbeitung zwischengelagert werden. Eine bevorzugte Möglichkeit zur Weiterverarbeitung der gebleichten Holzpartikel ist die Herstellung von Holzwerkstoffen, insbesondere direkt im Anschluss an den Bleichschritt.The bleached wood particles can be further processed directly, they can also be dried and further processed in a dried state. Also, the dried wood particles can be stored before further processing. A preferred possibility for further processing of the bleached wood particles is the production of wood-based materials, in particular directly after the bleaching step.

Weiterer Gegenstand der vorliegenden Erfindung ist ein Verfahren zur Herstellung von hellen bis weißen Holzwerkstoffen, das die folgenden Schritte umfasst:

  1. a) Zermahlen der vorbehandelten zerkleinerten, cellulosehaltigen Rohstoffe in einem Refiner zu Holzpartikeln
  2. b) Ausführen der Holzpartikel aus dem Refiner und
  3. c) Verarbeitung der gebleichten Holzpartikel zu hellen bis weißen Holzwerkstoffen,
wobei die Holzpartikel in Schritt a) oder in Schritt b) durch Zugabe einer Bleichmittelzusammensetzung enthaltend mindestens ein Bleichmittel ausgewählt aus der Gruppe Sulfinsäure und ihre Salze und stabilisierte Sulfite.Another object of the present invention is a process for the preparation of light to white wood materials, comprising the following steps:
  1. a) grinding the pretreated comminuted cellulose-containing raw materials in a refiner to wood particles
  2. b) removing the wood particles from the refiner and
  3. c) processing the bleached wood particles into light to white wood-based materials,
wherein the wood particles in step a) or in step b) by addition of a bleaching composition containing at least one bleaching agent selected from the group consisting of sulfinic acid and its salts and stabilized sulfites.

Bevorzugt werden die Holzpartikel erfindungsgemäß in Schritt a) oder b) mit der nachstehend aufgeführten Bleichmittelzusammensetzung gebleicht:

  1. a) 60 bis 95 Gew.-% eines oder mehrerer Hydrosulfitsalze
  2. b) 1 bis 25 Gew.-% eines oder mehrerer Sulfitsalze
  3. c) 1 bis 10 Gew.-% eines oder mehrerer basischer Salze
  4. d) 0 bis 10 Gew.-% eines oder mehrerer Tripolyphosphatsalze.
According to the invention, the wood particles are preferably bleached in step a) or b) with the bleaching composition listed below:
  1. a) 60 to 95 wt .-% of one or more hydrosulfite salts
  2. b) 1 to 25 wt .-% of one or more sulfite salts
  3. c) 1 to 10 wt .-% of one or more basic salts
  4. d) 0 to 10 wt .-% of one or more Tripolyphosphatsalze.

In einer bevorzugten Ausführungsform zur Herstellung von hellen bis weißen Holzwerkstoffen werden die Holzpartikel in Schritt b) über eine Blowline ausgeführt.In a preferred embodiment for the production of light to white wood materials, the wood particles are carried out in step b) via a blowline.

In einer ebenfalls bevorzugten Ausführungsform werden die zerkleinerten, cellulosehaltigen Rohstoffe in einem Kocher vorbehandelt, bevor sie in Schritt a) des erfindungsgemäßen Verfahrens eingesetzt werden.In a likewise preferred embodiment, the comminuted, cellulose-containing raw materials are pretreated in a digester before they are used in step a) of the process according to the invention.

Bei den erfindungsgemäßen hergestellten Holzwerkstoffen kann es sich um MDF-, HDF-, Span- oder OSB-Platten handeln. Bevorzugt sind MDF- und HDF-Platten, besonders bevorzugt sind MDF-Platten.The wood-based materials produced according to the invention may be MDF, HDF, chipboard or OSB boards. Preference is given to MDF and HDF boards, particularly preferred MDF boards.

MDF-, HDF-, OSB- und Spanplatten werden auch als Holzwerkstoffplatten bezeichnet. Sie werden bevorzugt hergestellt, indem beleimte Fasern beziehungsweise Späne zu Matten geschüttet, gegebenenfalls kalt vorverdichtet und in beheizten Pressen bei Temperaturen von 170 bis 240 °C zu Platten gepresst werden.MDF, HDF, OSB and chipboard are also referred to as wood-based panels. They are preferably prepared by gluing coated fibers or shavings into mats, optionally cold precompressed and pressed in heated presses at temperatures of 170 to 240 ° C to plates.

Gemäß der vorliegenden Erfindung handelt es sich bei dem als Leim eingesetzten Bindemittel üblicherweise um Harnstoff-Formaldehydharze, die zum Teil mit Melamin verstärkt sind, um Harnstoff-Melamin-Formaldehydharze, Melamin-Formaldehydharze, Phenol-Melaminharze und Phenol-Formaldehydharze. Als weiteres Bindemittel werden Isocyanate verwendet, diese basieren üblicherweise auf Polymethylendiisocyanat.According to the present invention, the binder used as the sizing agent is usually urea-formaldehyde resins partially reinforced with melamine, urea-melamine-formaldehyde resins, melamine-formaldehyde resins, phenol-melamine resins and phenol-formaldehyde resins. As a further binder isocyanates are used, these are usually based on polymethylene diisocyanate.

Die Holzpartikel können erfindungsgemäß direkt, d. h. noch feucht, in der Blowline beleimt werden. Es können jedoch auch die vorher getrockneten Holzpartikel in Mischern, vorzugsweise kontinuierlich arbeitenden Mischern, beleimt werden. Die Beleimung in Mischern ist insbesondere bei der Span- und OSB-Platten-Herstellung bevorzugt, zur Herstellung von HDF- und MDF-Platten findet die Beleimung bevorzugt in der Blowline statt. Ein weiteres mögliches Verfahren zur Beleimung besteht in der sogenannten Trockenbeleimung, dabei werden die getrockneten Holzpartikel mit Leim besprüht.The wood particles can according to the invention directly, d. H. still wet, glued in the blowline. However, it is also possible to glue the previously dried wood particles in mixers, preferably continuously operating mixers. Blending in mixers is particularly preferred in chipboard and OSB board production, for the production of HDF and MDF boards, the gluing preferably takes place in the blowline. Another possible method for gluing is in the so-called dry gluing, while the dried wood particles are sprayed with glue.

Werden die Holzpartikel in der Blowline beleimt, durchlaufen sie anschließend einen Trockner, in dem sie auf Feuchten von 8 bis 15 Gew.-% getrocknet werden. Die beleimten und gegebenenfalls getrockneten Holzpartikel werden anschließend zu Matten geschüttet, gegebenenfalls kalt vorverdichtet und in beheizten Pressen bei Temperaturen von 170 bis 240 °C zu Platten gepresst.If the wood particles are glued in the blowline, they then pass through a dryer in which they are dried to moistures of 8 to 15 wt .-%. The glued and optionally dried wood particles are then poured into mats, optionally precompressed cold and pressed in heated presses at temperatures of 170 to 240 ° C to plates.

In einer besonders bevorzugten Ausführungsform der vorliegenden Erfindung findet die Weiterverarbeitung der gebleichten Holzpartikel direkt im Anschluss an das Bleichen statt. Dabei werden die gebleichten Holzpartikel nach dem erfindungsgemäßen Bleichen durch Zugabe einer Bleichmittelzusammensetzung im Refiner oder am Beginn der Blowline in der Blowline beleimt, anschließend in einem Trockner auf eine Restfeuchte von 8 bis 15 Gew.-% getrocknet und zu Holzwerkstoffen weiterverarbeitet.In a particularly preferred embodiment of the present invention, the further processing of the bleached wood particles takes place immediately after the bleaching. The bleached wood particles are bleached after bleaching according to the invention by adding a bleach composition in the refiner or at the beginning of the blowline in the blowline, then dried in a dryer to a residual moisture content of 8 to 15 wt .-% and further processed into wood materials.

In einer weiteren bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens zur Herstellung von hellen bis weißen Holzwerkstoffen wird während des Herstellungsprozesses den Holzpartikeln mindestens ein Weißpigment zugesetzt. Daraus resultiert eine Massefärbung des entstehenden Holzwerkstoffs.In a further preferred embodiment of the process according to the invention for producing light to white wood-based materials, at least one white pigment is added to the wood particles during the production process. This results in a mass coloration of the resulting wood material.

Der Begriff "Weißpigment" umfasst dabei erfindungsgemäß sowohl anorganische Pigmente wie Titandioxid (Rutil, C.I. Pigment White 6), Calciumcarbonat und Calcium/Magnesium-Mischcarbonate (z.B. Dolomit), Zinkoxid, Zinksulfit, Lithopone und Natriium-AluminiumSilikate, als auch weißfärbende, stark lichtstreuende Kunststoffemulsionen und - dispersionen. Bevorzugt sind die anorganischen Weißpigmente, besonders bevorzugt ist Titandioxid. Es können auch Mischungen von Weißpigmenten verwendet werden.The term "white pigment" according to the invention encompasses both inorganic pigments such as titanium dioxide (rutile, CI Pigment White 6), calcium carbonate and calcium / magnesium mixed carbonates (eg dolomite), zinc oxide, zinc sulfite, lithopone and sodium aluminum silicates, as well as white-dyeing, strongly light-scattering Plastic emulsions and dispersions. The inorganic white pigments are preferred, and titanium dioxide is particularly preferred. It is also possible to use mixtures of white pigments.

Die Weißpigmente werden bevorzugt in Form wässriger Dispersionen, in denen sie fein verteilt vorliegen, eingesetzt, da sie so über die Blowline, getrennt von oder zusammen mit dem Leim direkt in den Herstellungsprozess der Holzwerkstoffe eingebracht werden können. Diese Pigmentdispersionen können weitere übliche Hilfsstoffe, insbesondere Netz- und Dispergiermittel, Entschäumer und Biozide, Antiabsetzmittel, Wasserrückhaltemittel und Rheologiemodifizierer enthalten und werden vorzugsweise durch Nassmahlung aller Komponenten zum Beispiel in einer Rührwerkskugelmühle hergestellt.The white pigments are preferably used in the form of aqueous dispersions in which they are finely divided, since they can be introduced directly into the production process of the wood materials via the blowline, separately from or together with the glue. These pigment dispersions may contain other customary auxiliaries, in particular wetting and dispersing agents, defoamers and biocides, anti-settling agents, water retention agents and rheology modifiers and are preferably prepared by wet milling of all components, for example in a stirred ball mill.

Empfehlenswerte Konzentrationen des Weißpigments in den fertigen Holzwerkstoff liegen in der Regel bei 0,5 bis 15 % pro atro Holzfaser, bevorzugt bei 1 bis 6 % pro atro Holzfaser.Recommended concentrations of the white pigment in the finished wood material are usually at 0.5 to 15% per atro wood fiber, preferably at 1 to 6% per atro wood fiber.

Eine weitere Steigerung des Weißgrads lässt sich durch Zusatz von optischen Aufhellern erreichen, die durch ihre bläuliche Fluoreszenz (komplementäre Farbe) Vergrauungen und Vergilbungen kompensieren.A further increase in whiteness can be achieved by the addition of optical brighteners, which compensate for their bluish fluorescence (complementary color) graying and yellowing.

Geeignet sind grundsätzlich alle blau emittierenden Fluoreszenzfarbstoffe, besonders kommerziell zugängliche Produkte, z.B. Ultraphor® (BASF), Leucophor® (Clariant) oder Tinopal® (Ciba), aus den chemischen Substanzklassen der Stilbene, Distyrylbiphenyle, Cumarine, Naphthalsäureimide und über Doppelbindungen verknüpften Benzoxazol- und Benzimidazolsysteme.Principle, all blue-emitting fluorescent dyes, particularly commercially accessible products, including Ultraphor ® (BASF), Leucophor® ® (Clariant) or Tinopal ® (Ciba), from the chemical classes of stilbenes, distyrylbiphenyls, coumarins, naphthalimides and double bond linked benzoxazole and benzimidazole systems.

Die optischen Aufheller können in Form von wässrigen Dispersionen oder Lösungen getrennt oder zusammen mit dem Leim in den Herstellprozess für die Holzwerkstoffe eingeschleust werden.The optical brighteners can be introduced in the form of aqueous dispersions or solutions separately or together with the glue in the production process for the wood-based materials.

Wird ein optischer Aufheller eingesetzt, so liegt seine Konzentration in dem fertigen Holzwerkstoff im Allgemeinen bei 0,01 bis 1% pro atro Holzfaser, vorzugsweise bei 0,08 bis 0,2% pro atro Holzfaser.If an optical brightener is used, its concentration in the finished wood material is generally from 0.01 to 1% per atro wood fiber, preferably 0.08 to 0.2% per atro wood fiber.

Ganz besonders bevorzugt sind solche erfindungsgemäßen Holzwerkstoffe, bei denen sowohl mindestens ein Weißpigment und mindestens ein optischer Aufheller kombiniert sind, da die Einzelbeiträge durch Synergie-Effekte zu einem maximalen Gesamtweißgrad potenziert werden.Very particular preference is given to wood-based materials of the invention in which both at least one white pigment and at least one optical brightener are combined, since the individual contributions are potentiated by synergy effects to a maximum overall degree of whiteness.

Dabei ist es verfahrenstechnisch besonders vorteilhaft, die Weißpigmente und die optischen Aufheller zusammen in einer einzigen wässrigen Dispersion zu präparieren, die der Leimflotte hinzugefügt wird, bevor diese durch die Blowline in den Holzwerkstoff-Herstellprozess injiziert wird.It is procedurally particularly advantageous to prepare the white pigments and the optical brightener together in a single aqueous dispersion, which is added to the glue liquor before it is injected by the blowline in the wood material manufacturing process.

Etwaige aus den erfindungsgemäßen Maßnahmen resultierende Änderungen der physikalischen Eigenschaften der gepressten Holzwerkstoffplatte können durch Wahl der Leimqualität und Leimmenge kontrolliert werden. Die Auswahl der entsprechenden Parameter ist dem Fachmann geläufig.Any resulting from the inventive measures changes in the physical properties of the pressed wood-based panel can be controlled by selecting the glue quality and amount of glue. The selection of the corresponding parameters is familiar to the person skilled in the art.

Weiterer Gegenstand der vorliegenden Erfindung sind gebleichte Holzpartikel, herstellbar nach dem erfindungsgemäßen Verfahren zur Herstellung von gebleichten Holzpartikeln.Another object of the present invention are bleached wood particles, prepared by the process according to the invention for the production of bleached wood particles.

Weiterer Gegenstand der vorliegenden Erfindung sind helle bis weiße Holzwerkstoffe, herstellbar nach einem der vorstehend beschriebenen erfindungsgemäßen Verfahren.Another object of the present invention are light to white wood materials, prepared according to one of the inventive method described above.

Die vorliegende Erfindung wird anhand der Herstellung von MDF-Platten in Beispielen erläutert.The present invention will be illustrated by the production of MDF boards in Examples.

Der MDF-Herstellungsprozess wird wie üblich mit einem Durchsatz von 28 bis 30 kg/h durchgeführt, die Hackschnitzel werden durch den Refiner zerfasert, die erhaltenen Fasern werden durch die Blowline ausgetragen und in der Blowline kontinuierlich mit dem jeweils in den Beispielen aufgeführten Leimansatz beleimt.The MDF production process is carried out as usual with a throughput of 28 to 30 kg / h, the wood chips are shredded by the refiner, the fibers obtained are discharged through the blowline and continuously glued in the blowline with the glue batch listed in the examples.

Die beleimten Holzfasern werden in dem sich anschließenden kontinuierlichen Trockner auf eine Restfeuchte von etwa 9 Gew.-% getrocknet und dann diskontinuierlich zu einer Matte geschüttet, kalt vorverdichtet und bei 190 °C mit einem Presszeitfaktor von 15 s/2mm zu einer 16 mm dicken Platte gepresst.The glued wood fibers are dried in the subsequent continuous dryer to a residual moisture content of about 9 wt .-% and then poured discontinuously to a mat, cold precompressed and at 190 ° C with a pressing time factor of 15 s / 2mm to a 16 mm thick plate pressed.

Vergleichsbeispiel V1 (nicht erfindungsgemäß)Comparative Example C1 (not according to the invention)

Als cellulosehaltiger Rohstoff wurden Hackschnitzel aus Fichtenholz verwendet. Die Fasern wurden ohne Zusatz einer Bleichmittelzusammensetzung zerfasert und in der Blowline kontinuierlich mit dem in Tabelle 1 aufgeführten Leimansatz beleimt. Tabelle 1 Leimansatz Harnstoff-MelaminFormaldehydharz, 66,5 gew.-%ig in Wasser 100,0 Gewichtsteile Paraffin-Dispersion, 60 gew.-%ig in Wasser 4,0 Gewichtsteile Wasser 33,8 Gewichtsteile Festharzgehalt der Flotte 48% Festharz/atro Fasern 14% Flotte auf 100 kg atro Fasern 29,2 kg Wood chips from spruce wood were used as the cellulosic raw material. The fibers were fiberized without the addition of a bleach composition and were continuously glued in the blowline with the glue formulation listed in Table 1. Table 1 glue batch Urea-melamine-formaldehyde resin, 66.5% by weight in water 100.0 parts by weight Paraffin dispersion, 60% strength by weight in water 4.0 parts by weight water 33.8 parts by weight Solid resin content of the liquor 48% Solid resin / atro fibers 14% Fleet on 100 kg of atro fibers 29.2 kg

Vergleichsbeispiel V2 (nicht erfindungsgemäß)Comparative Example C2 (not according to the invention)

Hackschnitzel aus Fichtenholz werden während des MDF-Herstellungsprozesses im Refiner mit einer 15 gew.%igen wässrigen Hydrosulfit-Lösung, entsprechend 5 Gew.-% Bleichmittel pro atro Fasern, versetzt. In der Blowline werden die Fasern mit dem in Tabelle 1 aufgeführten Leimansatz beleimt.Spruce wood chips are used during the MDF production process in the refiner with a 15% strength by weight aqueous hydrosulfite solution, corresponding to 5% by weight. Bleach per atro fibers, offset. In the blowline, the fibers are glued with the glue batch listed in Table 1.

In Tabelle 2 ist der erzielte Weißgrad (ausgedrückt in der Helligkeitsdifferenz ΔL), bezogen auf das Vergleichsbeispiel V1 als Standard, aufgeführt. Tabelle 2 Beispiel ΔL V2 1,9 V1 - In Table 2, the obtained whiteness (expressed in the brightness difference ΔL), based on the comparative example V1 as a standard listed. Table 2 example .DELTA.L V2 1.9 V1 -

Beispiel 1 (erfindungsgemäß)Example 1 (according to the invention)

Hackschnitzel aus Fichtenholz werden während des MDF-Herstellungsprozesses im Refiner mit einer 15 gew.-%igen wässrigen Lösung der in Tabelle 3 aufgeführten Bleichmittelzusammensetzungen 1a bis 1c versetzt, entsprechend 5 Gew.-% Bleichmittel pro atro Fasern.Spruce wood chips are added during the MDF production process in the refiner with a 15 wt .-% aqueous solution of bleach compositions listed in Table 3 1a to 1c, corresponding to 5 wt .-% bleach per atro fibers.

Die erhaltenen Fasern werden in der Blowline kontinuierlich mit dem in Tabelle 1 aufgeführten Leimansatz beleimt.The resulting fibers are glued continuously in the blowline with the glue batch listed in Table 1.

Vergleichsbeispiel V3Comparative Example C3

Analog der in Beispiel 1 beschriebenen Vorgehensweise, jedoch ohne Zusatz der Bleichmittel enthaltenden Zusammensetzungen wurde eine MDF-Platte hergestellt.An MDF board was prepared analogously to the procedure described in Example 1, but without the addition of the bleach-containing compositions.

In Tabelle 3 ist der erzielte Weißgrad der Beispiele 1 a, 1 b und 1 c, ausgedrückt in der Helligkeitsdifferenz ΔL bezogen auf das Vergleichsbeispiel V3 als Standard aufgeführt. Tabelle 3 Bleichmittelzusammensetzungen 1a bis 1c Beispiel 1a 1b 1c V3 Hydrosulfit [Gew.-%] 85 80 70 - Natriumsulfit [Gew.-%] 7,5 12 13 - Soda (Na2CO3) [Gew.-%] 7,5 5 14 - Natriumtripolyphosphat [Gew.-%] - 3 1 - ΔL 5,1 6,7 5,0 - In Table 3, the obtained whiteness of Examples 1 a, 1 b and 1 c, expressed in the brightness difference .DELTA.L based on the comparative example V3 is listed as a standard. Table 3 Bleaching compositions 1a to 1c example 1a 1b 1c V3 Hydrosulfite [% by weight] 85 80 70 - Sodium sulfite [% by weight] 7.5 12 13 - Soda (Na 2 CO 3 ) [% by weight] 7.5 5 14 - Sodium tripolyphosphate [% by weight] - 3 1 - .DELTA.L 5.1 6.7 5.0 -

Beispiel 2 (erfindungsgemäß)Example 2 (according to the invention)

Hackschnitzel aus Fichtenholz wurden im Refiner zerfasert und mit einer 15 gew.-%igen wässrigen Lösung der unter Beispiel 1b aufgeführten Bleichmittelzusammensetzung versetzt, entsprechend 5 Gew.-% Bleichmittel pro atro Fasern. Anschließend wurden die Fasern in der Blowline mit dem in Tabelle 1 aufgeführten Leimansatz beleimt. Die beleimten Fasern wurden anschließend zu einer MDF-Platte verpresst.Wood chips from spruce wood were fiberized in the refiner and treated with a 15 wt .-% aqueous solution of the bleaching composition listed under Example 1b, corresponding to 5 wt .-% bleach per atro fibers. Subsequently, the fibers in the blowline were glued with the glue batch listed in Table 1. The glued fibers were then pressed into an MDF board.

Vergleichsbeispiel V4Comparative Example V4

Analog der in Beispiel 2 beschriebenen Vorgehensweise, jedoch ohne den Zusatz einer Bleichmittel enthaltenden Zusammensetzung wurde eine MDF-Platte hergestellt.An MDF plate was prepared analogously to the procedure described in Example 2, but without the addition of a bleach-containing composition.

In Tabelle 4 ist der erzielte Weißgrad, ausgedrückt in der Helligkeitsdifferenz ΔL, bezogen auf das Vergleichsbeispiel V4 als Standard, aufgeführt. Tabelle 4 Beispiel ΔL 2 5,1 V4 - Table 4 shows the whiteness achieved, expressed in the brightness difference ΔL, based on the comparative example V4 as standard. Table 4 example .DELTA.L 2 5.1 V4 -

Beispiel 3 (erfindungsgemäß)Example 3 (according to the invention)

Hackschnitzel aus Fichten- und Buchenholz wurden im Refiner mit einer 15 gew.-%igen wässrigen Bleichmittelzusammensetzung gemäß Beispiel 1b, entsprechend 5 % Bleichmittel atro Fasern versetzt. Die Fasern wurden in der Blowline kontinuierlich mit dem in Tabelle 5 aufgeführten, das Weißpigment Titandioxid enthaltenden Leimansatz beleimt, getrocknet und zu MDF-Platten verpresst. Tabelle 5 Leimansatz Harnstoff-MelaminFormaldehydharz, 66,5 gew.-%ig in Wasser 100,0 Gewichtsteile Paraffin-Dispersion, 60 gew.-%ig in Wasser 4,0 Gewichtsteile Titandioxid-Präparation, 70 gew.-%ig in Wasser 47,5 Gewichtsteile Festharzgehalt der Flotte 44% Festharz/atro Fasern 14% Flotte auf 100 kg atro Fasern 31,8 kg Wood chips from spruce and beech wood were added in the refiner with a 15 wt .-% aqueous bleach composition according to Example 1b, corresponding to 5% bleach atro fibers. The fibers were in the blowline continuously with the in table 5 glued, containing the white pigment containing titanium dioxide glue batch, dried and pressed into MDF boards. Table 5 glue batch Urea-melamine-formaldehyde resin, 66.5% by weight in water 100.0 parts by weight Paraffin dispersion, 60% strength by weight in water 4.0 parts by weight Titanium dioxide preparation, 70% strength by weight in water 47.5 parts by weight Solid resin content of the liquor 44% Solid resin / atro fibers 14% Fleet on 100 kg of atro fibers 31.8 kg

Vergleichsbeispiel V5Comparative Example V5

Analog der in Beispiel 3 beschriebenen Vorgehensweise, jedoch ohne Zusatz des Weißpigments Titandioxid, wurde eine MDF-Platte hergestellt. Zur Beleimung wurde ein Leimansatz gemäß Tabelle 5 eingesetzt, wobei die Titandioxid-Präparation durch die gleiche Menge Wasser ersetzt wurde.Analogous to the procedure described in Example 3, but without the addition of the white pigment titanium dioxide, an MDF board was prepared. For gluing, a glue formulation according to Table 5 was used, with the titanium dioxide preparation being replaced by the same amount of water.

In Tabelle 6 ist der erzielte Weißgrad, ausgedrückt in der Helligkeitsdifferenz ΔL, bezogen auf das Vergleichsbeispiel V5 als Standard aufgeführt. Tabelle 6 Beispiel ΔL 3 4,7 V5 - In Table 6, the obtained whiteness, expressed in the brightness difference .DELTA.L, based on the comparative example V5 is listed as a standard. Table 6 example .DELTA.L 3 4.7 V5 -

Beispiel 4 (erfindungsgemäß)Example 4 (according to the invention)

Zur Herstellung einer MDF-Platte wurden Hackschnitzel aus Buchenholz im Refiner mit einer 15 gew.-%igen wässrigen Bleichmittelzusammensetzung gemäß Beispiel 1b, entsprechend 5% Bleichmittel pro atro Fasern versetzt. In der Blowline wurden die erhaltenen Fasern kontinuierlich mit dem in Tabelle 7 aufgeführten Leimansatz beleimt. Nach der Trocknung wurden die beleimten Fasern zu MDF-Platten verpresst. Tabelle 7 Leimansatz Harnstoff-MelaminFormaldehydharz, 66,5 gew.-%ig in Wasser 100,0 Gewichtsteile Paraffin-Dispersion, 60 gew.-%ig in Wasser 4,0 Gewichtsteile Wasser 47,5 Gewichtsteile Festharzgehalt der Flotte 44% Festharz/atro Fasern 14% Flotte auf 100 kg atro Fasern 31,8 kg For the production of an MDF board wood chips from beech wood in the refiner were mixed with a 15% strength by weight aqueous bleaching composition according to Example 1b, corresponding to 5% bleach per atro fibers. In the blowline, the resulting fibers were continuously glued with the glue formulation listed in Table 7. After drying, the glued fibers were pressed into MDF boards. Table 7 glue batch Urea-melamine-formaldehyde resin, 66.5% by weight in water 100.0 parts by weight Paraffin dispersion, 60% strength by weight in water 4.0 parts by weight water 47.5 parts by weight Solid resin content of the liquor 44% Solid resin / atro fibers 14% Fleet on 100 kg of atro fibers 31.8 kg

Beispiel 5 (erfindungsgemäß)Example 5 (according to the invention)

Analog der in Beispiel 4 beschriebenen Vorgehensweise, jedoch unter Einsatz des in Tabelle 5 aufgeführten, das Weißpigment Titandioxid enthaltenden Leimansatzes, wurde eine MDF-Platte hergestellt.Analogous to the procedure described in Example 4, but using the listed in Table 5, the white pigment containing titanium dioxide glue batch, an MDF plate was prepared.

Beispiel 6 (erfindungsgemäß)Example 6 (according to the invention)

Analog der in Beispiel 5 beschriebenen Vorgehensweise, jedoch unter Verwendung des in Tabelle 8 aufgeführten Leimansatzes, der eine Kombination des Weißpigments Titandioxid und optischem Aufheller enthält, wurde eine MDF-Platte hergestellt. Tabelle 8 Leimansatz Harnstoff-Melamin-Formaldehydharz, 66,5 gew.-%ig in Wasser 100,0 Gewichtsteile Paraffin-Dispersion, 60 gew.-%ig in Wasser 4,0 Gewichtsteile Titandioxid-Präparation, 50 gew.-%ig in Wasser, enthaltend 2 Gew.-% eines handelsüblichen optischen Aufhellers 47,5 Gewichtsteile Festharzgehalt der Flotte 44% Festharz/atro Fasern 14% Titandioxid/atro Fasern 5% optischer Aufheller/atro Fasern 0,2% Flotte auf 100 kg atro Fasern 31,8 kg An MDF board was prepared analogously to the procedure described in Example 5, but using the glue formulation listed in Table 8, which contains a combination of the white pigment titanium dioxide and optical brightener. Table 8 glue batch Urea-melamine-formaldehyde resin, 66.5% by weight in water 100.0 parts by weight Paraffin dispersion, 60% strength by weight in water 4.0 parts by weight Titanium dioxide preparation, 50 wt .-% in water, containing 2 wt .-% of a commercial optical brightener 47.5 parts by weight Solid resin content of the liquor 44% Solid resin / atro fibers 14% Titanium dioxide / atro fibers 5% optical brightener / atro fibers 0.2% Fleet on 100 kg of atro fibers 31.8 kg

Vergleichsbeispiel V6Comparative Example V6

Analog der in Beispiel 4 beschriebenen Vorgehensweise, jedoch ohne den Zusatz der Bleichmittel enthaltenden Zusammensetzung im Refiner wurde eine MDF-Platte hergestellt.An MDF board was prepared analogously to the procedure described in Example 4, but without the addition of the bleach-containing composition in the refiner.

In Tabelle 9 sind die erzielten Weißgrade, ausgedrückt in der Helligkeitsdifferenz ΔL, bezogen auf das Vergleichsbeispiel V6 als Standard, aufgeführt. Tabelle 9 Beispiel ΔL 4 3,1 5 6,2 6 7,0 V6 - In Table 9, the obtained whiteness, expressed in the brightness difference ΔL, based on the comparative example V6 as a standard listed. Table 9 example .DELTA.L 4 3.1 5 6.2 6 7.0 V6 -

Beispiel 7 (erfindungsgemäß)Example 7 (according to the invention)

Hackschnitzel aus Fichtenholz wurden im Refiner mit einer 15 gew.-%igen wässrigen Lösung von Hydroxymethansulfinsäure, entsprechend 5% Bleichmittel atro Fasern, behandelt. In der Blowline wurden die gebleichten Fasern mit dem in Tabelle 1 aufgeführten Leimansatz beleimt.Wood chips from spruce wood were treated in the refiner with a 15% strength by weight aqueous solution of hydroxymethanesulfinic acid, corresponding to 5% bleach-free fibers. In the blowline, the bleached fibers were glued with the glue formulation listed in Table 1.

Vergleichsbeispiel V7Comparative Example V7

Analog der in Beispiel 7 beschriebenen Vorgehensweise, jedoch ohne Zusatz einer Bleichmittel enthaltenden Lösung wurde eine MDF-Platte hergestellt.Analogous to the procedure described in Example 7, but without the addition of a bleach-containing solution, an MDF board was prepared.

In Tabelle 10 ist der erzielte Weißgrad, ausgedrückt in der Helligkeitsdifferenz ΔL, bezogen auf das Vergleichsbeispiel V7 als Standard, aufgeführt. Tabelle 10 Beispiel ΔL 7 5,2 V7 - In Table 10, the obtained whiteness, expressed in the brightness difference ΔL, based on the comparative example V7 as a standard, is listed. Table 10 example .DELTA.L 7 5.2 V7 -

Beispiel 8 (erfindungsgemäß)Example 8 (according to the invention)

Hackschnitzel aus Pappel wurden während des MDF-Herstellungsprozesses im Refiner mit einer 15 gew.-%igen wässrigen Bleichmittelzusammensetzung gemäß Beispiel 1b, entsprechend 5% Bleichmittel pro atro Fasern behandelt. Die erhaltenen Fasern wurden in der Blowline kontinuierlich mit dem in Tabelle 1 aufgeführten Leimansatz beleimt.Poplar wood chips were treated during the MDF production process in the refiner with a 15% by weight aqueous bleaching composition according to Example 1b, corresponding to 5% bleach per atro fibers. The resulting fibers were coated in the blowline continuously with the glue formulation listed in Table 1.

Vergleichsbeispiel V8Comparative Example V8

Analog der in Beispiel 8 beschriebenen Vorgehensweise, jedoch ohne Zusatz der Bleichmittel enthaltenden Zusammensetzung wurde eine MDF-Platte hergestellt.An MDF board was prepared analogously to the procedure described in Example 8, but without the addition of the bleach-containing composition.

In Tabelle 11 ist der erzielte Weißgrad, ausgedrückt in der Helligkeitsdifferenz ΔL, bezogen auf das Vergleichsbeispiel V8 als Standard, aufgeführt. Beispiel ΔL 8 4,9 V8 - Table 11 shows the whiteness achieved, expressed in the difference in brightness ΔL, based on the comparative example V8 as standard. example .DELTA.L 8th 4.9 V8 -

Beispiel 9 (erfindungsgemäß)Example 9 (according to the invention)

Hackschnitzel aus Fichte wurden während des MDF-Herstellungsprozesses im Refiner mit einer 15 gew.-%igen wässrigen Bleichmittel enthaltenden Lösung gemäß Beispiel 1b, entsprechend 5 % Bleichmittel pro atro Fasern, behandelt. Die erhaltenen Fasern wurden in der Blowline mit dem in Tabelle 1 aufgeführten Leimansatz beleimt.Spruce wood chips were treated during the MDF production process in the refiner with a solution containing 15% by weight aqueous bleach according to Example 1b, corresponding to 5% bleach per atro fibers. The resulting fibers were glued in the blowline with the glue formulation listed in Table 1.

Die beleimten Holzfasern wurden getrocknet und zu einer Platte gepresst. Die Platte wurde anschließend 24 h in einem Sun-Testgerät belichtet und der Weißgrad, ausgedrückt in der Helligkeitsdifferenz ΔL, bezogen auf die unbelichtete Platte, gemessen.The glued wood fibers were dried and pressed into a plate. The plate was then exposed for 24 hours in a Sun tester and the whiteness expressed in terms of the difference in brightness ΔL with respect to the unexposed plate was measured.

In Tabelle 12 sind die Ergebnisse aufgeführt. Tabelle 12 Beispiel ΔL 9 belichtet - 2 9 unbelichtet - Table 12 lists the results. Table 12 example .DELTA.L 9 exposed - 2 9 unexposed -

Vergleichsbeispiel V9Comparative Example V9

Hackschnitzel aus Fichte wurden während des MDF-Herstellungsprozesses im Refiner mit einer 15 gew.-%igen wässrigen Hydrosulfitlösung, entsprechend 5 % Bleichmittel pro atro Fasern, behandelt. Die erhaltenen Fasern wurden in der Blowline kontinuierlich mit dem in Tabelle 1 aufgeführten Leimansatz beleimt. Die getrockneten beleimten Holzfasern wurden zu MDF-Platten gepresst.Spruce wood chips were treated during the MDF production process in the refiner with a 15% by weight aqueous hydrosulfite solution corresponding to 5% bleach per atro fibers. The resulting fibers were coated in the blowline continuously with the glue formulation listed in Table 1. The dried glued wood fibers were pressed into MDF boards.

Ein Teil der Platten wurde anschließend 24 h in einem Sun-Testgerät belichtet und der Weißgrad, ausgedrückt in der Helligkeitsdifferenz ΔL, bezogen auf die unbelichtete Platte, gemessen.A portion of the plates were then exposed for 24 hours in a Sun tester and the whiteness, expressed in the difference in brightness ΔL, with respect to the unexposed plate, measured.

In Tabelle 13 ist der erzielte Weißgrad aufgeführt. Beispiel ΔL V9 belichtet - 4,5 V9 unbelichtet - Table 13 shows the whiteness achieved. example .DELTA.L V9 exposed - 4,5 V9 unexposed -

Beispiel 10 (erfindungsgemäß)Example 10 (according to the invention)

Hackschnitzel aus Fichtenholz wurden während des MDF-Herstellungsprozesses im Refiner mit einer 15 gew.-%igen wässrigen, Bleichmittelzusammensetzung enthaltenden Lösung gemäß Beispiel 1b, entsprechend 5 % Bleichmittel pro atro Fasern, versetzt. Die erhaltenen Fasern wurden in der Blowline kontinuierlich mit dem in Tabelle 1 aufgeführten Leimansatz beleimt.Wood chips from spruce wood were added during the MDF production process in the refiner with a 15 wt .-% aqueous solution containing bleach composition according to Example 1b, corresponding to 5% bleach per atro fibers. The resulting fibers were coated in the blowline continuously with the glue formulation listed in Table 1.

Vergleichsbeispiel V10Comparative Example V10

Analog der in Beispiel 4 beschriebenen Vorgehensweise, jedoch ohne die Behandlung der Holzfasern im Refiner mit einer bleichmittelhaltigen Zusammensetzung, wurde eine MDF-Platte hergestellt.Analogous to the procedure described in Example 4, but without the treatment of the wood fibers in the refiner with a bleach-containing composition, an MDF board was prepared.

In Tabelle 14 ist der erzielte Weißgrad, ausgedrückt in der Helligkeitsdifferenz ΔL, Querzugsfestigkeit, Quellung sowie der sensorisch bestimmte Geruch der Platten, jeweils auf das Vergleichsbeispiel V10 als Standard bezogen, aufgeführt.Table 14 shows the whiteness achieved, expressed in the difference in brightness ΔL, transverse tensile strength, swelling, and the sensorially determined odor of the plates, each referred to as comparative example V10 as standard.

Die Querzugsfestigkeit der erhaltenen MDF-Platten wurde gemäß DIN 319, Span- und Faserplatten, Bestimmung der Zugfestigkeit, senkrecht zur Plattenebene gemessen.The transverse tensile strength of the resulting MDF boards was measured according to DIN 319, particleboard and fiberboard, determination of tensile strength, perpendicular to the board plane.

Die Quellung wurde gemäß DIN EN 317, Span- und Faserplatten, Bestimmung der Dickenquellung und Wasseraufnahme, gemessen. Tabelle 14 Beispiel ΔL Querzugsfestigkeit [N/mm2] Quellung 24 h [%] Geruch 10 6,3 0,85 6,67 Holzig V10 - 1,04 6,33 Holzig The swelling was measured in accordance with DIN EN 317, particleboard and fiberboard, determination of thickness swelling and water absorption. Table 14 example .DELTA.L Transverse tensile strength [N / mm 2 ] Swelling 24 h [%] odor 10 6.3 0.85 6.67 woody V10 - 1.04 6.33 woody

Claims (11)

  1. A process for the production of bleached cellulose-containing particles comprising the steps
    a) milling of optionally pretreated comminuted, cellulose-containing raw materials in a refiner to give cellulose-containing particles and
    b) removal of the cellulose-containing particles from the refiner,
    the cellulose-containing particles being bleached in step a) or in step b) by addition of a bleach composition or at least one bleach,
    wherein the bleach composition comprises
    i) from 60 to 95% by weight of one or more hydrosulfite salts
    ii) from 1 to 25% by weight of one or more sulfite salts
    iii) from 1 to 10% by weight of one or more basic salts
    and the
    bleach is selected from the group consisting of sulfinic acids and their salts and stabilized sulfites.
  2. The process according to claim 1, wherein the bleach composition comprises up to 10% by weight of one or more tripolyphosphate salts.
  3. The process according to claim 1 or 2, wherein the cellulose-containing particles are removed via a blowline in step b).
  4. The process according to any of claims 1 to 3, wherein the comminuted, cellulose-containing raw materials are pretreated in a digester before they are used in step a).
  5. The process according to any of claims 1 to 4, wherein wood, bagasse or straw is used as raw material for the cellulose-containing particles.
  6. A process for the production of pale to white wood-base materials, comprising the steps
    a) milling of optionally pretreated comminuted, cellulose-containing raw materials in a refiner to give cellulose-containing particles and
    b) removal of the cellulose-containing particles from the refiner, and
    c) processing of the cellulose-containing particles to give pale to white wood-base materials,
    the cellulose-containing particles being bleached in step a) or in step b) by addition of a bleach composition or at least one bleach,
    wherein the bleach composition comprises
    i) from 60 to 95% by weight of one or more hydrosulfite salts
    ii) from 1 to 25% by weight of one or more sulfite salts
    iii) from 1 to 10% by weight of one or more basic salts
    and the bleach is selected from the group consisting of sulfinic acids and their salts and stabilized sulfites.
  7. The process according to claim 6, wherein step b) is followed directly by step c).
  8. The process according to claim 6 or 7, wherein at least one white pigment is added during the production of the pale to white wood-base materials.
  9. The process according to any of claims 6 to 8, wherein at least one optical brightener is added during the production of the pale to white wood-base materials.
  10. The process according to any of claims 6 to 9, wherein at least one white pigment and at least one optical brightener are added during the production of the pale to white wood-base materials.
  11. The process according to any of claims 6 to 10, wherein the pale to white wood-base materials are MDF boards, HDF boards, OSB boards or particle boards.
EP20080749657 2007-04-24 2008-04-23 Method for the production of bleached wood particles and wood materials ranging from light-toned to white Not-in-force EP2142348B1 (en)

Priority Applications (2)

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EP20080749657 EP2142348B1 (en) 2007-04-24 2008-04-23 Method for the production of bleached wood particles and wood materials ranging from light-toned to white
PL08749657T PL2142348T3 (en) 2007-04-24 2008-04-23 Method for the production of bleached wood particles and wood materials ranging from light-toned to white

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP07106804 2007-04-24
EP20080749657 EP2142348B1 (en) 2007-04-24 2008-04-23 Method for the production of bleached wood particles and wood materials ranging from light-toned to white
PCT/EP2008/054879 WO2008129048A1 (en) 2007-04-24 2008-04-23 Method for the production of bleached wood particles and wood materials ranging from light-toned to white

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EP2142348A1 EP2142348A1 (en) 2010-01-13
EP2142348B1 true EP2142348B1 (en) 2013-12-25

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EP (1) EP2142348B1 (en)
JP (1) JP5371955B2 (en)
CN (1) CN101678557B (en)
BR (1) BRPI0810574B1 (en)
CL (1) CL2008001199A1 (en)
ES (1) ES2447870T3 (en)
PL (1) PL2142348T3 (en)
WO (1) WO2008129048A1 (en)

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KR101207845B1 (en) * 2010-11-05 2012-12-04 (주)지바이오텍 Wood Particles, Manufacturing Method for paper of using the Same
KR101178727B1 (en) * 2011-12-01 2012-08-31 한솔제지주식회사 Paper comprising bleached wood flour and preparation method thereof
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DE102022134621A1 (en) 2022-12-22 2024-06-27 Siempelkamp Maschinen- Und Anlagenbau Gmbh Method for producing particles for the production of a material plate and material plate

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WO2008129048A1 (en) 2008-10-30
JP2010524738A (en) 2010-07-22
US8784607B2 (en) 2014-07-22
US20100132898A1 (en) 2010-06-03
CN101678557A (en) 2010-03-24
PL2142348T3 (en) 2014-05-30
EP2142348A1 (en) 2010-01-13
BRPI0810574B1 (en) 2018-10-23
CN101678557B (en) 2014-07-02
BRPI0810574A2 (en) 2014-10-29
ES2447870T3 (en) 2014-03-13
CL2008001199A1 (en) 2010-01-11
JP5371955B2 (en) 2013-12-18

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