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
  • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
• • 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
  • B27N3/002—Manufacture of substantially flat articles, e.g. boards, from particles or fibres characterised by the type of binder

Definitions

• the wood particles for example wood fibers or wood chips, with an organic Glue glued under pressure and at elevated temperature.
• the most important binders for fiber board production are urea-formaldehyde resins (UF) resins.
• UF urea-formaldehyde resins
• PF resins phenol-formaldehyde resins
• MF resins pressed wood panels
• MDF and HDF fibreboards Another disadvantage of these reactive resins is evident in the production of MDF and HDF fibreboards: in the production of MDF boards (Medium Density Fibreboard) and HDF boards (High Density Fibreboard) the fibers are in a refiner system pretreated hydrothermally in a first step, that means cooked and ground under heat and steam pressure. Subsequently after grinding, the fibers are still under steam pressure and at temperatures from 120 ° C to 150 ° C, by injection from aqueous dispersions of the adhesives to a cooled one Glued valve in the expansion tube. The one at a flow rate Distribute turbulence from 200 to 500 m / s the binder evenly on the fiber surface.
• the glued fibers are dried evenly stored and pressed into sheets at temperatures of 150 to 250 ° C.
• the problem is that when gluing in this process the reactive resins due to the thermal load already in Relax tube react and up to 25% of their binding potential get lost during pressing.
• Formaldehyde-free, thermally curable, aqueous binders for Manufacture of pressed wood panels are for example from WO-A 97/31059 known, in which we use a mixture of carboxyl functional Copolymer and an alkanolamine with at least two hydroxyl groups used.
• Aqueous adhesive compositions made from polycarboxylic acid and hydroxyalkyl group substituted aminoaliphatics are described in WO-A 97/45461.
• WO-A 99/02591 relates Compositions of carboxyl functional copolymer and long chain Amines. A disadvantage of these systems, which are crosslink an esterification reaction that crosslinking only in the anhydrous state, takes place during drying.
• the invention was therefore based on the object of a method for Manufacture of pressed wood panels to provide largely premature reaction of functional groups is prevented and in which the emission of pollutants how formaldehyde is avoided, but still a high quality Gluing is obtained.
• Suitable two-component binders contain as a component A) a copolymer of one or more comonomer units the group comprising vinyl esters of unbranched or branched Alkyl carboxylic acids with 1 to 18 carbon atoms, acrylic acid esters or Methacrylic acid esters of branched or unbranched alcohols with 1 to 15 carbon atoms, dienes, olefins, vinyl aromatics and vinyl halides, and from 0.1 to 50% by weight, based on the total weight of the copolymer, one or more units which contain carboxyl, Contain hydroxy or NH groups.
• Suitable NH-functional comonomers are (meth) acrylamide, diacetone acrylamide, maleimide, maleic and fumaric acid monoalkyl ester amide, maleic and fumaric acid diamide, glutaric and succinic acid monovinyl ester amide, glutaric and succinic acid monoallylesteramide.
• the NH-functional units can also be added to the copolymer A) as amino-functional oligomers with primary or secondary NH groups, preferably with primary NH groups such as Jeffamine.
• the proportion of functional units in copolymer A) is preferably 1 to 30% by weight, particularly preferably 5 to 20% by weight, in each case based on the total weight of the copolymer.
• polyester or polyether resins which contain hydroxyl, amine or carboxyl groups.
• Suitable crosslinkers B) are non-thermoplastic compounds such as bisphenol A type epoxy crosslinkers, that is to say condensation products of bisphenol-A and epichlorohydrin or methylepichlorohydrin.
• epoxy crosslinkers are commercially available, for example available under the trade names Epicote or Eurepox.
• Diisocyanates, if appropriate blocked, are also suitable Oligo- or polyisocyanates, for example common commercial products such as m-tetramethylxylene diisocyanate (TMXDI), methylene diphenyl diisocyanate (MDI), toluene diisocyanate, isophorone diisocyanate, Dimethyl-meta-isopropenyl.
• TXDI m-tetramethylxylene diisocyanate
• MDI methylene diphenyl diisocyanate
• toluene diisocyanate isophorone diisocyanate
• Suitable crosslinkers B) are also connections with two or more groups from the series Aldehyde, keto, reactive CH group such as glutaraldehyde, terephthalaldialdehyde; Bisacetoacetates of ethylene, propylene, butylene, Hexadienglykols; Compounds with multiple aziridine, carbodiimide or oxazoline groups.
• crosslinker B Also suitable as crosslinker B) are copolymers which contain epoxy, NMethylol, Ethylene carbonate or isocyanate groups or combinations of these groups included.
• the polymer compositions for crosslinkers B) are suitable as those for copolymer A) described comonomers.
• (Meth) acrylic acid esters are also particularly preferred here.
• styrene polymers for example copolymers with n-butyl acrylate and / or 2-ethylhexyl acrylate; Copolymers of Methyl methacrylate with butyl acrylate and / or 2-ethylhexyl acrylate, and / or 1,3-butadiene; Styrene-1,3-butadiene copolymers and styrene (meth) acrylic acid ester copolymers such as styrene-butyl acrylate, styrene-methyl methacrylate-butyl acrylate or styrene-2-ethylhexyl acrylate, where n-, iso-, t-butyl acrylate are used as butyl acrylate can.
• the content of epoxy, N-methylol, ethylene carbonate and isocyanate functional Comonomers is 0.1 to 50% by weight, preferably 1 to 30% by weight, particularly preferably 5 to 20% by weight, in each case based on the total weight of the copolymer B).
• N-methylol-functional comonomers are N-methylol acrylamide (NMA), N-methylol methacrylamide, N-methylolallyl carbamate, Alkyl ethers such as the isobutoxy ether or ester of N-methylol acrylamide, N-methylol methacrylamide and N-methylolallyl carbamate.
• NMA N-methylol acrylamide
• N-methylol methacrylamide N-methylolallyl carbamate
• Alkyl ethers such as the isobutoxy ether or ester of N-methylol acrylamide, N-methylol methacrylamide and N-methylolallyl carbamate.
• Suitable crosslinkers B) in combination with carboxyl-functional Copolymers A) are di-, oligo- and polyamines such as diaminobutane, Hexamethylene diamine, polyalkylene amines such as triethylene tetramine, polyoxyalkylene amines (Jeffamine). More examples of suitable ones Crosslinker B) in combination with carboxyl-functional copolymers A) are compounds with two or more OH groups, such as ethylene glycol, Butanediol, pentaerythriol, polytetramethylene glycol, Bisphenol A and polyalkylene oxide adducts of ethylene glycol. Suitable as crosslinker B) for carboxyl-functional copolymers A) are also polyvalent metal ions such as aluminum, iron (III) - or Zinc chloride.
• Suitable crosslinkers B) in combination with hydroxy-functional Copolymers A) are compounds with two or more silanol or Alkoxysilane groups such as methyltriethoxysilane in monomeric or condensed form, as well as polyvalent metal ions such as aluminum, Iron (III) - or zinc chloride.
• Suitable crosslinkers B) in combination with NH-functional copolymers A) are di-, oligo- and polycarboxylic acids such as adipic acid, Polyacrylic acid.
• hydroxy and NH-functional copolymers A) can also be used that the crosslinker B) together with a crosslinking catalyst is added.
• crosslinking catalysts are citric acid, Oxalic acid, butanetetracarboxylic acid, quaternary phosphonium salts such as tetrabutylphosphonium salts, sodium hypophosphite and dibutyltin dilaurate.
• the copolymer A) together with component B) add first, and add the catalyst in the later step.
• carboxyl-functional copolymers are used as component A) , these can also be combined with a component B) be the reaction of the carboxyl group with the OH groups catalyzes the cellulose.
• a component B) be the reaction of the carboxyl group with the OH groups catalyzes the cellulose.
• Examples include citric acid, Oxalic acid, butanetetracarboxylic acid, quaternary phosphonium salts such as tetrabutylphosphonium salts, sodium hypophosphite and dibutyltin dilaurate.
• Di-, oligo- and polyamines such as diaminobutane, hexamethylene diamine, Polyalkylene amines such as triethylene tetramine or polyoxyalkylene amines (Jeffamine) can also be used as component A) then as component B) the above-mentioned, if appropriate blocked, diisocyanates, for example m-tetramethylxylene diisocyanate (TMXDI), methylene diphenyl diisocyanate (MDI), toluene diisocyanate, Isophorone diisocyanate, dimethyl-meta-isopropenylbenzyl isocyanate be used.
• TXDI m-tetramethylxylene diisocyanate
• MDI methylene diphenyl diisocyanate
• Isophorone diisocyanate dimethyl-meta-isopropenylbenzyl isocyanate
• 2-component systems are those which cross-linked polysiloxanes.
• Such systems contain as Component A) Dialkylpolysiloxanes with the same or different Alkyl radicals with 1 to 4 carbon atoms, which are optionally substituted can be, and which as terminal end groups hydroxyl or Contain vinyl groups.
• component B) in the case of Hydroxyl end group used silicic acid esters such as tetraethyl silicate.
• platinum catalysts are used used as component B) (RTV), or peroxides such as aroyl peroxides (Bis-2,4-dichlorobenzoyl peroxide, bis-4-methylbenzoyl peroxide) and alkyl peroxides (dicumyl peroxide, 2,5-di-t-butylperoxy-2,5-dimethylhexane) (HTV).
• aroyl peroxides Bis-2,4-dichlorobenzoyl peroxide, bis-4-methylbenzoyl peroxide
• alkyl peroxides dicumyl peroxide, 2,5-di-t-butylperoxy-2,5-dimethylhexane
• HTV alkyl peroxides
• Systems with an amino functional are also suitable Polysiloxane as component A) and an epoxy functional Polysiloxane as component B).
• Other examples are Dimethylpolysiloxanes as component A) and condensation catalysts such as
• compositions with carboxyl functional Styrene-n-butyl acrylate and / or styrene-methyl methacrylate-n-butyl acrylate copolymer as component A) and with glycidyl methacrylate Styrene-n-butyl acrylate and / or styrene-methyl methacrylate-n-butyl acrylate copolymer as component B).
• components A) and B) can be in dry, powdered form Form (dry gluing), in the form of an aqueous dispersion or an aqueous solution (wet gluing).
• the Components A) and B) can both be powder or both can be used as an aqueous solution or aqueous dispersion. Powders, aqueous solutions or aqueous dispersions can also be used are used, which each contain a component, can be used in any combination.
• the binder components A) and B) are generally separated as a 2-component system used. When using powdered binder if necessary, the fibers with water or a Olefin wax emulsion to be moistened. 2 to 10% by weight Water (olefin wax emulsion), based on binder, on the Sprayed on fibers or chips.
• the binder composition is shown in an amount of 2 to 30% by weight, preferably in an amount of 7 up to 15% by weight, based on wood (solid / solid).
• Wood chips are used to manufacture MDF or HDF fibreboards usually via a hopper and a Snail transported into the refiner system cooker. There will be the wood chips for a few minutes, generally 5 to 15 minutes, at a water vapor pressure of 1 to 8 bar and a temperature from 120 to 200 ° C. Then they are softened Schnitzel, for example by means of another snail, conveyed to the mill of the refining plant, usually one Disc refiner, where the wood chips between grinding discs be frayed. For gluing, the fibers are still under steam pressure and at temperatures from 120 ° C to Conveyed 150 ° C into the expansion pipe (blow-line) of the refiner system.
• Spruce wood chips were refined at 5 bar and 147 ° C for 5 min cooked and with grinding wheel spacing 0.1 mm with a power consumption of approximately 20 kW.
• the fibers were glued without Dried to 2% residual moisture and temporarily stored without compression.
• the glued fibers were evenly spread by hand in a 50 x 50 cm 2 , 40 cm high frame and compacted at room temperature. This mat was removed from the frame and placed in a flat press and pressed to a nominal density of 3 mm at 200 ° C. for up to 50 bar. The hot plate was placed in an insulation box to complete the crosslinking reaction and kept warm for 12 hours, then cut to size and subjected to the property tests.
• Spruce wood chips were refined at 5 bar and 147 ° C for 5 min cooked and with grinding wheel spacing 0.1 mm with a power consumption of approximately 20 kW.
• the glued Fibers were then dried to 2% residual moisture and temporarily stored without compression.
• the glued fibers were evenly spread by hand in a 50 x 50 cm 2 , 40 cm high frame and compacted at room temperature. This mat was removed from the frame and placed in a flat press and pressed for 180 seconds at 200 ° C. with a pressure of up to 50 bar to a target density of 3 mm. The plate was then cut to size and subjected to property tests.
• Spruce wood chips were cooked in the refiner at 5 bar and 147 ° C for 5 min and ground with a grinding wheel spacing of 0.1 mm with a power consumption of approx. 20 kW.
• an aqueous dispersion of a styrene-butyl acrylate-acrylic acid copolymer with a Tg> 50 ° C. was added in an amount of 9% by weight (solid / solid).
• the glued fibers were then dried to 2% residual moisture, and the dried fibers were mixed with 6% by weight of powdered styrene-butyl acrylate-glycidyl methacrylate copolymer with a Tg> 50 ° C.
• Comparative example 1 shows high transverse tensile and bending strength, as well as low water swelling. Since the phenolic resin was not added in the refiner, but at room temperature on dry fibers, full crosslinking was available during pressing. The subsequent long thermal treatment is disadvantageous in order to allow the crosslinking reaction to proceed to completion. Another disadvantage is the high risk of splintering of the press plates, due to the high degree of crosslinking and the low flexibility of the resin. This is particularly undesirable in automotive applications because of the risk of injury in the event of an accident. The plate was colored yellow-brown and had a distinct unpleasant smell.
• Comparative example 2 leads to similar strengths and swelling values like comparative example 1. Particularly striking is the bending tests the deflection of more than 29 mm without a plate break to get. Because the binder after the fiber drying full networking capacity has been added.
• Comparative example 3 was bonded via wet sizing with the same resin as comparative example 2 via dry sizing.
• wet gluing the resin is generally distributed more evenly on the fiber surface due to the stronger turbulence and the long mixing section. A stronger bond of the fibers in the press plate is expected.
• a comparison of the values shows, however, that wet gluing is slightly weaker than dry gluing. The cause of the loss of binding is that some of the networking already takes place in the refiner. When pressing, the resin then flows poorly and can no longer set as well.
• Example 4 shows the best strengths.
• only one component with thermally stable functional groups was introduced in the wet gluing and an optimal binder distribution was achieved.
• the second component with crosslinkable, thermally unstable groups was added by means of dry gluing at short-term and low thermal loads. This means that the full networking capacity is available for pressing.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Die Bonding (AREA)
• Optical Couplings Of Light Guides (AREA)

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