Classifications

• • 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
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L97/00—Compositions of lignin-containing materials
  • C08L97/02—Lignocellulosic material, e.g. wood, straw or bagasse
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J197/00—Adhesives based on lignin-containing materials
  • C09J197/005—Lignin
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J197/00—Adhesives based on lignin-containing materials
  • C09J197/02—Lignocellulosic material, e.g. wood, straw or bagasse
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J5/00—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
  • C09J5/08—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers using foamed adhesives
• • 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 present invention relates to the manufacture of particle boards and similar wood-based products comprising lignocellulosic particles, fibers or flakes mixed with and bonded together with an adhesive binder.
• the present invention concerns novel lignin and/or carbohydrate -based adhesives and a preparation process thereof as well as particle boards manufactured using the adhesives.
• SSL As an adhesive for fiber board manufacture is its hygroscopicity. For this reason it cannot really compete with otner natural or synthetic adhesives.
• SSL When SSL is applied as an adhesive, it can be converted to an insoluble substance by curing. Chemically the curing of lignin is a cross-linking process, which leads to new carbon-carbon and ether bonds between different lignin molecules or within one macromolecule. Inter- as well as intramolecular cross-linking reactions decrease the solubility and swelling of lignin. Cross-links in lignin can be acnieved either by condensation or by radical coupling reactions.
• laccase enzymes and other peroxidases can be used as polymerization or curing catalysts of lignin (DE Patent No. 3 037 992, WO 96/03546).
• the enzymes for creating radical reaction have shown limited success so far.
• Fibers and wood chips used in the production of fiber boards contain 5 - 20 % water and the laccases used need some water to effectively catalyze the polymerization reaction needed for extensive bonding of the fiberboard.
• Kraft lignin like native lignin to its major part is, however, insoluble in water and thus two solid phases are formed on the production line. An uneven distribution of the solids cause spotting and major failure in the strength properties of the board formed in the pressing stage.
• a further problem relating to the use of isolated lignin is the high price of kraft lignin, which is near the limit for economical production of particle boards.
• the present invention aims at eliminating the problems relating to the prior art.
• lignin or lignin polymerized with oxidative enzymes or a soluble fraction of carbohydrates obtained from mechanical refining of lignocellulosic materials is added to and mixed with the fibers or chips or flakes used as lignocellulosic raw material of the wood-based product in the form of a foam to provide an even dispersion of the solids.
• Foamed UF and PF adhesives are known in the art. Said foams are used for improving process performance and product quality especially in adhesives with high solid contents.
• CA Patent Application No. 2,114,258 describes particle board production by using foamed mixtures of UF resins and animal blood.
• DE 3,644,067 describes the use of foamed materials in binding of fibers and flakes to produce a homogeneous adhesive application of fine particles (fibres or powders) on the furnish.
• T. Sellers describes in Forest Prod. J. 38
• the lignin-based adhesive composition according to the present invention comprises an aqueous suspension of lignin and/or carbohydrates obtained from a process of pulping lignocellulosic materials.
• the suspension has been foamed to 1.05 to 10, preferably 1.1 to 8, in particular to 1.2 to 5 times the volume of the liquid mixture.
• polymerized kraft lignin as the lignin component.
• natural lignin in wood fibers is used to replace a substantial part of the lignin in the adhesive binder intended for particle board production.
• the present adhesive binders comprise an aqueous mixture of fibers together with lignin and/or carbohydrates obtained from a process of pulping lignocellulosic raw materials.
• the fibers in the adhesive binder as well as the added lignin and/or other lignocellulosic material radical polymerize due to the effect of the enzyme in an even oxygen- containing foam matrix.
• the use of native lignin -containing fibers of MDF or TMP types leads to savings in adhesive use, and, however, to a corresponding strength.
• the foam will homogenize the solid phase and the liquid phase, increase the viscosity of the mixture and prevent the sedimentation of the solids.
• the oxygen-containing foamed structure will also provide more oxygen for the oxygen-dependent oxidase catalyzed lignin carbohydrate polymerization. Because of its large volume, the foam will cover more homogeneously the wood fibers and wood particles in the preparation of the boards. This will lead to better strength values and better control of the use of the adhesive in the production.
• resin designate a chemical composition which, in the wet stages of the manufacture of, e.g. particle and fiber boards, provides adhesion between the particles or fibers. After heat compression during board manufacture, the composition containing polymerized resin works as a binder which keeps the particles or fibers or flakes bonded together.
• wood-based product denotes any lignocellulose-based product, such as particle boards, fiber boards (including high and medium density fiber boards, i.e. hard boards and MDF boards), flake boards, plywood and similar products constituted by particles, fibers or flakes of vegetable origin, in particular derived from wood or annular or perennial plants mixed with and bonded together with adhesive binders.
• the present invention is used for preparing particle boards and similar wood-based products in which wood particles can be crosslinked and joined together with the fibers of the adhesive composition, which will be attached to the particles by the lignin-based adhesive.
• fibers encompasses organic and inorganic fibers of any suitable material having a length-to-thickness ratio of more than 6, preferably more than 10, in particular more than 20. It is preferred to use lignin-containing fibers, because the lignin of the fibers will be oxidized in the presence of oxidases and work as an adhesive in mixtures of wood particles and the adhesive foam. Particularly preferred lignocellulosic fibers are derived from wood or annular or perennial plants. Such fibers can be obtained from mechanical refining of wood or plants by refiner mechanical pulping, pressurized refiner mechanical pulping, thermomechanical pulping, groundwood or pressurized groundwood pulping, or chemi- thermomechanical pulping. Furthermore, fibers from the preparation of fiber boards (e.g. medium density or high density fiber boards) can be used in the preparation of particle boards.
• fiber boards e.g. medium density or high density fiber boards
• cellulosic fibers In addition to the cellulosic fibers mentioned above, other natural fibers, such as cotton fibers, Abaca hemp fibers, sisal fibers, ramie fibers, flax fibers or jute fibers, can be used. Inorganic fibers such as glass fibers, carbon fibers, gypsum fibers, etc. can also be employed.
• oxidative enzymes capable of catalyzing oxidation of phenolic groups can be used. These enzymes are oxidoreductases, such as peroxidases and oxidases. "Peroxidases” are enzymes which catalyze oxidative reaction using hydrogen peroxide as their substrate, whereas “oxidases” are enzymes which catalyze oxidative reactions using molecular oxygen as their substrate.
• Phenoloxidases (EC 1.10.3.2 benzenediol: oxygen oxidoreductase) catalyze the oxidation of o- and p-substituted phenolic hydroxyl and amino/amine groups in monomeric and polymeric aromatic compounds.
• the oxidative reaction leads to the formation of phenoxy radicals and finally to the polymerization of lignin and possibly the carbohydrate matter.
• the enzyme used may be any of the enzymes catalyzing the biological radical formation and secondary chemical polymerization of low molecular weight lignins, such as laccase, tyrosinase, peroxidase or oxidase.
• oxidases As specific examples of oxidases the following can be mentioned: laccases (EC 1.10.3.2), catechol oxidases (EC 1.10.3.1), tyrosinases (EC 1.14.18.1) and bilirubin oxidases (EC
• Laccases are particularly preferred oxidases. They can be obtained from bacteria and fungi belonging to, e.g., the following strains: Aspergillus. Neurospora, Podospora, Botrytis, Lentinus, Polyporus, Rhizoctonia, Coprimis, Co iol s, Phlebia, Ple rotus, Fusarium and Trametes.
• Suitable peroxidases can be obtained from plants or fungi or bacteria.
• Preferred peroxidases are those which originate from plants, in particular horseradish peroxidase and soy bean peroxidase.
• surfactant or "surface active agent” are synonymously used to designate compounds which have affinity to water and to hydrophobic (e.g. fatty) materials, thus aiding the hydrophobic materials to suspend in water.
• lignin of different origins can be used as the adhesive component of the present foamed adhesive binders.
• isolated lignin of, e.g., the sulphate, sulphite, ORGANOSOLV and MILOX processes can be used.
• soluble wood fractions can also be employed.
• This fraction contains primarily the same chemical components as the fibers (carbohydrates, extractives and lignin).
• the soluble fraction of softwood chips contains some 40 to 70 % carbohydrates, 10 to 25 % lignin and 1 to 10 % extractives, whereas hardwood pulping process water contains some 20 to 60 % carbohydrates, 10 to 25 % lignin and 10 to 40 % extractives.
• this soluble lignin/carbohydrate fraction obtainable from mechanical or chemimechanical pulping is particularly useful as an additive or adjuvant for gluing of particles boards, fiber boards and other similar wood-based composite products. Particularly good gluing is achieved if this fraction (as is the case with lignin) is polymerized with laccase (or similar) oxidase enzyme(s). The results are on the same level as those obtainable with conventional phenol or urea formaldehyde resins. It should be noticed that a similar soluble fraction can be obtained by treating lignocellulosic raw material, such as wood fibers or saw dust, with hydrolases, e.g. cellulases, hemicellulases and pectinases.
• hydrolases e.g. cellulases, hemicellulases and pectinases.
• the present invention relates to foam-based technology for providing good dispersion of the different solids.
• efficient contact during economical production of particle board is achieved using adhesive binders based on oxidase-activated lignin and/or carbohydrates together with wood fibers or other lignocellulosic fibers.
• 0.1 to 50 %, preferably 0.5 to 30 % and in particular about 1 to 10 % by weight of the kraft lignin or similar lignin is replaced by fibers in the foam-based, oxidase-activated adhesive formulation.
• lignin and the fibers are activated by oxidases are mixed with the chips in the form of a foam that provides a good viscose suspending medium to form an even dispersion of the solids and hence improves substantially the quality of the particle board formed.
• the use of the foamed adhesives as described in this invention leads also to better control of the application and to substantial savings in adhesive use.
• the foam is produced by the use of a surface active agent.
• the foamed, activated fiber and lignin/carbohydrate dispersion can be produced separately from the chips, which are mixed into the foam by known mixing technology, e.g. by extruding or spraying the foam onto the fibers or chips.
• the foam can also be produced simultaneously by mixing the fibers and chips with the foam chemicals, the lignin/carbohydrates and the laccase.
• the foam is produced by dispersing the mixture of lignin and fibers into water to form a suspension and bubbling a gas through the suspension to form bubbles having a medium diameter of 0.001 to 1 mm, in particular about 0.01 to 0.1 mm.
• the foam is produced by the use of a surface active agent that can be anionic, cationic or non-ionic.
• the surfactant can be selected from the group consisting of alkylsulfonate or alkyl benzene sulfonate, Tween® and other commercial compounds, fatty acid soaps, lignosulfonates, sarcosinates, fatty acid amines or amines or poly(oxyetylene alcohol)s and wood and plant extractives.
• Foam stabilizers and solid surfactants such as CMC, gelatin, pectin, wood extractive and similar compounds, can be used to produce and enhance the foam stability.
• a small amount of the surface active compounds is needed, i.e. about 0.01 to 10 %, in particular about 0.05 to 5 %.
• the foam can be produced by foaming in a static foamer or in a turbulent foam cell by using known mixing technology.
• any gas can be used for foaming, it is preferred to use oxygen-containing gases, such as air, oxygen enriched air, oxygen or pressurized systems of these. The importance of using oxygen-containing gases is discussed in further detail below.
• the foam produced is essentially stable during handling, storage, transport and manufacture of wood-based products and it has a density in the range of 0.1 to 0.9 kg/1, in particular about 0.2 to 0.7 kg/1, and a medium foam bubble diameter in the range of 0.005 to 0.1 mm, in particular about 0.01 to 0.1 mm, preferably about 0.02 mm.
• the method according to the present invention can be used for all oxidase-catalyzed, previously unsuccessfully suggested enzyme-catalyzed glueing processes using oxidases
• the enzyme used can be any of the enzymes catalyzing the oxidation and polymerization of aromatic compounds or lignins, such as laccase, tyrosinase, or other oxidases, as mentioned above.
• the amount of enzyme used varies depending on the activity of the enzyme and on the amount of dry matter content of the composition.
• the oxidases are used in amounts of 0.001 to 10 mg protein/g of dry matter, preferably about 0, 1 to 5 mg protein/g of dry matter.
• the activity of the oxidase is about 1 to 100,000 nkat/g, preferably over 100 nkat/g.
• oxygen plays a decisive role in the enzymatic polymerization of lignin of any origin. This is important in particular for the production of adhesives for the manufacture of fiber boards, particle boards and flake boards and other similar wood-based products. Thus, in addition to the aromatic reactant, also oxygen is needed. The oxidative reaction leads to the formation of phenoxy radicals and finally to the polymerization of lignin.
• Oxygen can be supplied by various means, such as efficient mixing, air enriched with oxygen or introducing oxygen supplied by enzymatic or chemical means to the solution.
• Oxygen can be supplied by various means, such as efficient mixing, air enriched with oxygen or introducing oxygen supplied by enzymatic or chemical means to the solution.
• by foaming the suspension with an oxygen- containing gas it is possible to provide the oxygen needed for full polymerization of the lignin.
• the foamed structure gives enough strength to the adhesive so as to prevent sedimentation of water-insoluble lignin or the polymerized lignin from the adhesive thus producing failure in the production and in the board product.
• the foamed structure can be utilized in the preparation of particle boards of lignin and/or carbohydrates or polymerized lignin by utilizing the adhesive properties of the lignin or polymerized lignin, whereas the fibers work as crosslinkers between the particles.
• the foam will homogenize the inhomogenous solid phase and the liquid phase, increase the viscosity of the mixture and prevent the sedimentation of the solids and the fibers.
• the oxygen-containing foamed structure will also provide more oxygen for oxygen-enhanced oxidase catalyzed lignin/carbohydrate polymerization. Because of its large volume the foam will cover more homogeneously the wood fibres and wood particles in the preparation of the boards.
• the adhesive binder is evenly distributed throughout the wood-based product, about 0.02 ⁇ 0.002...0.2 ⁇ 0.02 g/cm 3 , preferably 0.04 to 0.08 g/cm 3 in any randomly selected volume unit of the product This leads to better strength values and better control of the use of the adhesive in the production.
• MDF fibers were prepared from hardwood (Swedish birch) by refining birch chips in a conventional TMP process at a refiner pressure of 4 bar.
• This Example describes the preparation of a foamed adhesive consisting of kraft lignin, laccase, wood fibre and the manufacture of particle boards from the adhesive.
• the test has been carried out on laboratory scale.
• Kraft lignin Indulin AT and 1 - 10 % of its weight substituted with the MDF fibers of Example 1 were used as a binder mixture in particle board test panel manufacture.
• particle board panels of the size of 50 mm x 50 mm x 2 mm were prepared by pressing 2 min in 30 kp/cm 2 of pressure and 190 °C of temperature. After pressing, the panels were then cut into four pieces (50 mm x 12 mm x 2 mm). These pieces were tested for parallel tensile strength with Zwick tensile strength testing equipment.
• the strength properties of particle boards prepared according to the present invention are quite comparable to those of conventional UF resin glued boards.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Dry Formation Of Fiberboard And The Like (AREA)
• Adhesives Or Adhesive Processes (AREA)

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• 1997
  • 1997-01-14 FI FI970160A patent/FI104835B/fi active
• 1998
  • 1998-01-14 PL PL98334548A patent/PL334548A1/xx unknown
  • 1998-01-14 NZ NZ336668A patent/NZ336668A/en unknown
  • 1998-01-14 HU HU0200620A patent/HUP0200620A2/hu unknown
  • 1998-01-14 ID IDW990681A patent/ID22657A/id unknown
  • 1998-01-14 CN CN98803315A patent/CN1250463A/zh active Pending
  • 1998-01-14 WO PCT/FI1998/000026 patent/WO1998031764A1/en not_active Application Discontinuation
  • 1998-01-14 KR KR1019997006390A patent/KR20000070164A/ko not_active Application Discontinuation
  • 1998-01-14 BR BR9806909-8A patent/BR9806909A/pt not_active Application Discontinuation
  • 1998-01-14 EP EP98900858A patent/EP0953030A1/en not_active Withdrawn
  • 1998-01-14 AU AU56645/98A patent/AU5664598A/en not_active Abandoned
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