Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N1/00—Pretreatment of moulding material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
  • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
  • B27N3/02—Manufacture of substantially flat articles, e.g. boards, from particles or fibres from particles

Definitions

• the invention relates to a process for the production of wood fiber boards, such as MDF boards, and to a method for the production of wood fibers.
• MDF medium density fiberboard
• HDF high density fiberboard
• Wood of different types is used, mainly conifers such as spruce and pine are used. Other types of wood such as beech or eucalyptus can be used.
• the wood for fiber production is debarked and shredded into chips. Subsequently, the wood chips are shredded to wood particles in a grinding unit, the so-called refiner.
• the refiner is preferably made of two metal discs provided with radial relief, which are close to each other. One of these discs can move, and both can rotate in opposite directions.
• the refiner usually work under pressure. The wood chips are shredded between these two disks, with the fineness of the fibers depending on the grinding gap between the disks.
• the defibration of wood chips consumes a lot of energy.
• the energy consumption in the refiner is up to 400 KW / h per ton of wood.
• the energy cost of defibration can be up to 20% of the cost of manufacturing an MDF board.
• the chips are subjected to a hydrothermal pretreatment.
• the wood chips are pretreated in a digester at temperatures of 100 to 180 ° C and a pressure of up to 10 bar. This treatment softens the middle lamella and facilitates defibering in the refiner.
• EP 1255630 mentions the use of chemicals such as acids, bases or surfactants or combinations of these products in the production of fiber boards from recycled fiber boards.
• the chemicals have the task to facilitate the degradation of the polymeric binder in the recycled fiberboard during the pretreatment in the preheater.
• the chemicals and surfactants are not described in detail.
• EP 2168738 describes the use of surfactants in the production of wood fiber boards.
• the object of the surfactants is to prevent the penetration of an impregnating liquid into raw fibreboard facilitate. In this way, a predetermined final moisture is to be achieved.
• the type of surfactants used is not described in detail.
• US 8262852 describes a formulation consisting of wetting agent, complexing agent, hydrotrope and reducing agent or oxidizing agent.
• the formulation should reduce the proportion of fines and splinters, increase the brightness and save energy.
• the object of the invention is to provide a method for the production of wood fiber boards, which has a lower energy consumption.
• the surfactants can be supplied to the wood chips either in the pre-steaming container or else at the feed screw in front of the refiner.
• the amounts used of the surfactants are 0.05 wt .-% to 5 wt .-%, preferably 0.1 wt .-% to 3 wt .-%, based on absolutely dry (dry) wood.
• the surfactants used may be anionic or nonionic. Combinations of several different surfactants can also be used.
• the anionic surfactants may be sulfates, sulfonates or phosphates of branched or unbranched fatty alcohols or oxoalcohols, branched or unbranched fatty alcohol alkoxylates or oxoalcohol alkoxylates. Sulfates, sulfonates or phosphates of naphthyl alcohol or ethoxylated naphthyl alcohol, arylalkyl alcohols or arylalkyl ethoxylates are also possible.
• Preferred anionic surfactants are fatty alcohol ether sulfates with branched or unbranched C 8 -C 20 -alkyl chains and 2 to 50 ethylene oxide (EO) units. Particularly preferred are fatty alcohol ether sulfates having a C 8 -C 14 alkyl chain and 2 to 12 ethylene oxide units.
• fatty alcohol ether sulfates having a C 8 -C 14 alkyl chain and 2 to 12 ethylene oxide units.
• Preferred nonionic surfactants are branched or unbranched C 8 to C 15 alkyl ethoxylates having 3 to 20 ethylene oxide units.
• Preferred nonionic surfactants are branched or unbranched C 8 - to C 15 -alkylethoxy-late with 3 to 20 ethylene oxide units.
• the nonionic surfactants may be PO / EO block copolymers.
• the nonionic surfactants may be C 5 -buttoned or C 6 -ugar-based alkylpolyglucosides or mixtures thereof, preferably of the general formula (IIa) or (IIb) R 1 O (R 2 O) b (Z) a (IIa) R 1 O (Z) a (R 2 O) b H (IIb)
• R 1 linear or branched C 4 -C 30 -alkyl
• R 2 C 2 -C 4 -alkylene
• a 1 - 15, even broken numbers are possible.
• wood particles are understood to mean small-particle cellulose-containing particles. These include, for example, fibers and chips made of wood and others cellulose-containing materials.
• the base material for the wood particles and fiberboard can be all fibrous materials available from plants. 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.
• the wood materials are comminuted in step a) of the process according to the invention and optionally washed. This is followed by a hydrothermal pretreatment of wood chips with steam.
• step b) of the process according to the invention the comminuted wood materials are pretreated in a pre-steaming container (cooker) with steam. This is preferably carried out at a pressure of 1 to 10 bar and a temperature of 100 to 180 ° C. The exact temperatures and pressures depend on the raw materials used. Lowering temperatures for annual plants are usually lower than crushing multi-annual plants such as wood.
• step c) the hydrothermally pretreated, comminuted wood material is transferred to a so-called refiner and ground there to finely divided wood particles.
• a refiner is usually a grinding unit with rotating and possibly fixed knives or discs for grinding fibrous materials and preferably comprises two radially-provided with metal discs, which are close to each other. One of these discs can move and the other can be fixed, but both discs can rotate in opposite directions. Usually, the refiner works with overpressure.
• the grinding of the pretreated, comminuted wood materials can also be carried out in other devices suitable for this purpose.
• the production of wood fibers for MDF boards in the refiner generally takes place at temperatures of 150 to 180 ° C, preferably at about 170 ° C.
• the temperature in the refiner is significantly higher than in the TMP process for producing pulp for papermaking, which is about 140 ° C. Due to the higher temperature, there is an increased softening of the lignin in the wood, which reduces the energy expenditure during defibering.
• the lignin is more widely distributed over the fiber surface at higher temperature, thereby lowering the bondability of the fibers to one another. This is a disadvantage in the manufacture of paper, but no disadvantage in the production of fiberboard, since the fiber bond is achieved here by the addition of glue.
• the fine wood particles are further processed by conventional methods to HDF or MDF boards.
• the energy requirement in the refiner can be reduced by up to 20%.
• the surfactants are added to the wood chips in the pre-steaming container (cooker). Subsequently, the mixture is transported via a screw conveyor in the refiner. It is also possible to dose the surfactants directly into the refiner.
• the amount used of the surfactants is 0.05 wt .-% to 5 wt .-%, preferably 0.1 wt .-% to 3 wt .-%, based on absolutely dry (dry) wood.
• surfactants has no detrimental effect on the process and properties of the wood particles and wood fiber boards made therefrom.
• bleaching of the wood particles can be carried out in addition to energy saving.
• the wood particles are additionally bleached reductive.
• 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.
• the stabilization of the dithionites, sulfites and hydrosulfites takes place 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 addition of the bleach composition takes place in the refiner or during the discharge of the fine wood particles from the refiner.
• the wood particles are discharged via a so-called blowline, preferably the containing Bleach composition added in this embodiment in the refiner or in the blowline, more preferably in the refiner or at the beginning of the blowline, in particular in the refiner.
• the bleach composition is metered such that the amount of bleach is 0.1 to 6 wt.%, Preferably 0.5 to 5 wt.% And more preferably 1 to 3 wt.%, Based on atro (absolutely dry) fibers , is.
• the bleaching compositions are usually added to the wood particles in the refiner or blowline in the form of aqueous solutions, the concentration of the bleaching composition in the aqueous solution generally being from 1 to 25% by weight, preferably from 5 to 20% by weight, and more preferably from 10 to 15% by weight.
• step d) of the process according to the invention the fine wood particles are glued and dried, wherein the drying of the wood particles can also take place before gluing.
• the wood particles are carried out by the overpressure existing in the refiner via a blowline (blowing line) from the refiner.
• the wood particles can then be glued directly, that is still wet, in the blowline. Then they go through a dryer, where they are dried to a residual moisture of 8 to 15%.
• the wood particles are first dried and glued in the dry state and further processed.
• the wood-based materials produced according to the invention may be MDF, HDF, Span 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 produced by pouring glued fibers or shavings into mats, optionally precompressed cold 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, some of which are reinforced with melamine, urea-melamine-formaldehyde resins, melamine-formaldehyde resins, phenol-melamine resins and phenol-formaldehyde resins.
• urea-melamine-formaldehyde resins some of which are reinforced with melamine, urea-melamine-formaldehyde resins, melamine-formaldehyde resins, phenol-melamine resins and phenol-formaldehyde resins.
• isocyanates are used, these are usually based on polymethylene diisocyanate.
• the wood particles can be glued directly, ie still moist, in the blowline.
• the gluing in mixers is particularly preferred in chipboard and OSB board production, for the production of HDF and MDF boards takes the Glueing preferred in the blowline instead.
• 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 a residual moisture of 8 to 15 wt .-%.
• step e) of the process according to the invention optionally precompressed cold and pressed in heated presses at temperatures of 170 to 240 ° C to plates.
• Wood chips were fiberized in a refiner at a temperature of about 180 ° C, a pressure of about 9 bar and a grinding gap of 0.12 mm.
• the residence time in the digester before the refiner was 3 to 4 minutes. During the grinding process the necessary energy was measured.
• the unit for the fiberization energy is kWh / t atro. Atro means "absolutely dry wood".
• Example 2 wood chips from spruce wood were defibered in the presence of C 8 -C 10 -alkylpolyglucoside.
• the surfactant was dosed directly into the refiner.
• additive additional amount defibration C 8 -C 10 alkyl polyglucoside 0.2% of the amount of wood 109 kWh / t atro
• Wood chips from spruce wood were fiberized in the presence of C 8 -C 14 alkyl polyglucoside.
• the surfactant was dosed directly into the refiner.
• additive additional amount defibration C 8 -C 14 alkyl polyglucoside 0.2% of the amount of wood 114 kWh / t atro
• Wood chips from spruce wood were fiberized in the presence of C 13 -oxo alcohol ethoxylate with 12 EO units.
• the surfactant was dosed directly into the refiner. additive additional amount defibration C 13 oxo alcohol ethoxylate + 12 EO units 0.2% of the amount of wood 115 kWh / t atro
• Wood chips from spruce wood were fiberized in the presence of fatty alcohol ether sulfate with 12 EO units of sodium salt.
• the surfactant was dosed directly into the refiner. additive additional amount defibration Fatty alcohol ether sulfate with 12 EO units, Na salt 0.2% of the amount of wood 111 kWh / t atro
• Wood chips from spruce wood were fiberized in the presence of C 8 -C 10 alkyl polyglucoside.
• the surfactant was metered into the predampening tank.
• additive additional amount defibration C 8 -C 10 alkyl polyglucoside 0.2% of the amount of wood 111 kWh / t atro
• Wood chips from spruce wood were fiberized in the presence of C 8 -C 10 alkyl polyglucoside.
• the surfactant was dosed directly into the refiner. additive additional amount defibration C 8 -C 10 alkyl polyglucoside 0.1% of the amount of wood 115 kWh / t atro
• Wood chips from spruce wood were fiberized in the presence of C 8 -C 10 alkyl polyglucoside.
• the surfactant was dosed directly into the refiner. additive additional amount defibration C 8 -C 10 alkyl polyglucoside 1% of the amount of wood 105 kWh / t atro
• Woodchips made of beech wood were ground without addition in a refiner. additive additional amount defibration No addition - 136 kWh / t atro
• Beech wood chips were ground in the presence of C 8 -C 14 alkyl polyglucoside additive additional amount defibration C 8 -C 14 alkyl polyglucoside 0.5% 109 kWh / t atro
• the wood chips from example 2 were glued in the blowline with a urea-melamine-formaldehyde resin, dried and pressed into MDF boards.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Paper (AREA)

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Cited By (6)

Citations (8)

• 2015
  • 2015-02-23 EP EP15156069.5A patent/EP3059056A1/fr not_active Withdrawn

Patent Citations (9)

Non-Patent Citations (2)

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