Classifications

• • 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
  • 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

Definitions

• the present invention relates to the preparation of particle boards, fiber boards, flake boards, plywood and similar wood-based products comprising lignocellulosic particles, fibers, flakes or veneer mixed and bonded together with an adhesive binder.
• the present invention concerns novel lignin-based adhesives and a preparation process thereof as well as particle boards, fiber boards and flake boards manufactured by using the adhesives.
• SSL As an adhesive for fiber board manufacture is its hygroscopicity. For this reason it cannot really compete with other natural or synthetic adhesives.
• SSL When SSL is applied as an adhesive, it has to 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 macromoiecule. Inter- as well as intramolecular cross-linking reactions decrease the solubility and swelling of lignin.
• Cross-links in lignin can be achieved either by condensation or by radical coupling reactions. For the condensation reactions, either high temperatures and long heating times or mineral acids are required, which cause structural changes or charring in the wood particles.
• cross-linking of the lignosulphonate molecules by radical combinations has been developed.
• additional cross-linking agents for lignin are necessary, such as epoxides, polyisocyanates, polyols, poly(acryl amide)s, poly(ethylene imine) and aldehydes.
• laccase enzymes and other peroxidases can be used as polymerization or curing catalysts of lignin (DE Patent No. 3 037 992, WO 96/03546).
• Fibers and wood chips used in the production of the fiber board 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 causes spotting and major failure in the strength properties of the board formed in the pressing stage.
• the present invention aims at eliminating the problems relating to the prior art.
• lignin or lignin polymerized with oxidative enzymes, 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. 2J 14,258 describes particle board production by using foamed mixtures of UF resin and animal blood. Also DE 3,644,067 describes the use of foamed materials for binding of fibers and flakes to produce a homogeneous adhesive application of fine particles (fibers or powders) on the furnish.
• T. Sellers describes in Forest Prod. J. 38
• the lignin-based adhesive binder composition according to the present invention comprises an aqueous suspension of lignin isolated from a process of pulping lignocellulosic raw materials.
• the suspension has been foamed to 1.05 to 10, preferably, 1 J to 8, in particular to 1.2 to 5 times the volume of the liquid mixture. It is preferred to use polymerized kraft lignin as the lignin component.
• the foam will homogenize the solid phase and the liquid phase, increase the viscosity of the mixture and prevent sedimentation of the solids.
• the oxygen required by the lignin adhesive binder is introduced into the adhesive binder in the form of an evenly divided, homogenous foam with small bubbles.
• the oxygen-containing foamed structure will also provide more oxygen for the oxygen-dependent oxidase catalyzed lignin polymerization. Because of its large volume, the foam will cover more homogeneously the wood fibres and wood particles during the preparation of the boards. This will lead to better strength values and better control of the use of the adhesive binder in the production of wood-based products.
• Figure 1 shows the effect of oxygen supply to glueing efficiency of lignin-based adhesive binders in particle board glueing
• Figure 2 shows the bubble size distribution in foamed lignin-based adhesive binders without dispersing agents
• Figure 3 shows the bubble size distribution in foamed lignin-based adhesive binders containing 5 % of CMC
• Figure 4 shows the bubble size distribution in foamed lignin-based adhesive binders containing 5 % of wood extractive (a lignin carbohydrate fraction called "anionic trash” obtained from the MDF process); and
• Figure 5 shows the swellings of MDF boards, small scale tests.
• 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, fibers or flakes. 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 products, 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.
• 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 J0.3.2 benzenediol: oxygen oxidoreductase) catalyze the oxidation of o- and p-substituted phenolic hydroxyl and amino/amine groups in monomeric and polymeric aromatic compounds.
• the 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 JO.3.2), catechol oxidases (EC 1J0.3J), tyrosinases (EC 1J4J8J) and bilirubin oxidases (EC 1.3.3.5). 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, Coprinus, Coriolus, Phlebia, Pleurotus, 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 and decrease surface tension, thus aiding the hydrophobic materials to suspend in water and providing a sufficient stability for the suspension and the foam.
• 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 or even better as those obtainable with conventional phenol or urea formaldehyde resins.
• 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.
• a lignin and/or carbohydrate-based adhesive is produced by dispersing lignin and/or carbohydrate matter into water to form a suspension and bubbling a gas through the suspension such that bubbles having a medium diameter of 0.001 to 1 mm, in particular about 0.01 to 0J mm, are formed.
• 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.
• the foam can be produced by foaming in a static foamer or in a turbulent foam cell by using known mixing technology. 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 OJ to 0.9 kg/1, in particular about 0.2 to 0.7 kg/1, and a medium 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 foam can be produced separately from the fibers and chips, which are mixed with the foam by extruding or spraying the foam to the fibers or chips.
• the foam can also be produced simultaneously by mixing the fibers or chips with the foam chemicals, the lignin and the enzyme (e.g. the laccase).
• 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 0J to 5 mg protein g of dry matter.
• the activity of the oxidase is about. l to 100,000 nkat/g, preferably over 100 nkat/g.
• oxygen plays a decisive role in the enzymatic polymerization of lignin of any origin.
• water-soluble wood fractions containing carbohydrates, lignin and extractives 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.
• oxygen is needed in sufficient amounts.
• Oxygen can be supplied by various means, such as efficient mixing, air enriched with oxygen or by introducing oxygen by enzymatic or chemical means to the solution.
• Oxygen can be supplied by various means, such as efficient mixing, air enriched with oxygen or by introducing oxygen 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 lignin polymerization that continues with the fiber bound lignin due to the oxygen trapped in the foam and the dissolved enzyme.
• the foamed structure gives enough strength to the adhesive binder so as to prevent sedimentation of water-insoluble lignin or the polymerized lignin and carbohydrates from the adhesive binder, thus producing failure in the production and in the fiber board product.
• the present invention provides considerable advantages.
• the present method provides a good viscose suspending medium to form an even dispersion of the solids, which improves substantially the quality of the board formed.
• the use of the foamed adhesives as described in this invention leads also to better control of the applications and to substantial savings in adhesive use.
• particle boards, fiber boards or similar wood-based products comprising particles, flakes or fibres by mixing particles, flakes or fibers mixed with a foamed lignin/carbohydrate-based adhesive binder as described above so as to incorporate 2 - 20 % of the solids of the adhesive binder into the wood-based product.
• any known adjuvants to the boards and products according to the invention.
• wax including wax dispersions
• similar substances can be incorporated in amounts of 0.01 to 5 %, in particular about 0J to 2 % (calculated from the weight of the wood substance).
• the internal bonding (IB) of a particle board according to the present invention is typically greater than 0.9 MPa, and the tensile strength of a fiber board according to the invention typically greater than 38 MPa.
• particle board panels of the size of 50 mm x 50 mm x 2 mm were prepared by pressing for 2 min at a pressure of 30 kp/cnr and a temperature of 190 °C.
• MDF panels of the size of 90 mm x 90 mm x 2 mm were prepared by pressing for 2 min at a pressure of 50 kp/c ⁇ r and a temperature of 190 °C. 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 results are presented in Table 1.
• the components of the adhesive binder 192 g Indulin AT kraft lignin, 192 ml laccase culture concentrate (activity 4,000 nkat/ml) and 96 g 2M sodium acetate buffer of pH 4.5 were first mixed and then foamed with air to 1.3 times the original volume. Foaming was performed with an aeration loop which was inserted at the bottom of the mixing container during 30 min and at a temperature of 40 °C. The foamed mixture was then sprayed into a mixing drum. 1 % (wax d.w./wood d.w.) of hydrophobic wax dispersion (Mobilcer 60, 60 % dry matter) was also added to chips or fibers. Mixing time in the mixing drum was 30 min.
• MDF fibers were glued according to the procedures presented in example 1. Results are shown in Tables 3 and 4.
• Example 1 but the foaming times of the foamed adhesive varied from 1 to 30 min.
• Figure 1 shows the effect of oxygen supply on the glueing efficiency of lignin-based adhesive binders in particle board glueing.
• the tensile strength of a board containing foamed binder is 35 to 40 % greater than the corresponding strength of a reference board.
• a typical volume growth of the binder is about 25 %, varying from 10 to 80 %.
• Mean bubble size is 85 urn varying from 30 to 500 ⁇ m.
• Figure 2 shows the bubble size distribution in foamed lignin-based adhesive without dispersing agents.
• Figure 3 shows the bubble size distribution in foamed lignin-based adhesive containing 5 % of CMC
• Figure 4 shows the bubble size distribution in foamed lignin-based adhesive containing 5 % of wood extractive ("anionic trash" from the MDF process).
• volume growth and the bubble size of the foamed adhesive can be adjusted.
• volume growth in foamed lignin-based adhesive prepared according to the procedure presented in Example 1 was 50 %, mean bubble size being 50 ⁇ m, ranging from 20 to 300 ⁇ m.
• a wood extractive such as lyofilized anionic trash from the MDF process
• Mean bubble size was 20 ⁇ m, varying in the range of 10 to
• FIG. 5 shows the swelling results (24 h) of MDF boards in small scale tests (the relative swellings of boards manufactured in small size are greater than the swellings of standard boards), showing the effect of foamed adhesive on the relative swelling result as well as the effect of the surfactant used as an adjuvant in the foamed adhesive on the same result.
• the effect of the surfactant on the foam composition has been shown in Figures 2 and 3.

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

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• 1997
  • 1997-01-14 FI FI970159A patent/FI104834B/fi active
• 1998
  • 1998-01-14 PL PL98334529A patent/PL334529A1/xx unknown
  • 1998-01-14 HU HU0202099A patent/HUP0202099A2/hu unknown
  • 1998-01-14 NZ NZ336667A patent/NZ336667A/en unknown
  • 1998-01-14 SK SK947-99A patent/SK94799A3/sk unknown
  • 1998-01-14 KR KR1019997006387A patent/KR20000070161A/ko not_active Application Discontinuation
  • 1998-01-14 EP EP98900857A patent/EP0953029A1/en not_active Withdrawn
  • 1998-01-14 BR BR9806957A patent/BR9806957A/pt not_active IP Right Cessation
  • 1998-01-14 AU AU56644/98A patent/AU5664498A/en not_active Abandoned
  • 1998-01-14 CA CA002277285A patent/CA2277285A1/en not_active Abandoned
  • 1998-01-14 CN CN98803319A patent/CN1250464A/zh active Pending
  • 1998-01-14 WO PCT/FI1998/000025 patent/WO1998031763A1/en not_active Application Discontinuation

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