Classifications

• • 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
  • C08L97/005—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
  • C09J197/005—Lignin

Definitions

• This invention relates to a method of preparing a solution of lignin at high concentration, to a method of preparing a binder using said solution, and to a method of producing a wood composite using said binder.
• lignin is only sparingly soluble in water at weakly acidic to neutral pH.
• solubility of lignin can be increased by incorporating a surfactant.
• the invention provides a method of increasing the solubility of lignin, characterized by incorporating a surfactant and a lignin solution, characterized by comprising a surfactant. Further, the invention also provides a method for producing a binder for wood products from lignin, characterized by comprising treatment of such a lignin solution with a phenol oxidizing enzyme system. Finally, the invention provides a method of producing a wood composite from wood fibre material, characterized by comprising production of a binder in this way, coating the wood fibre material with said binder, followed by pressing and heating.
• the invention is applicable to any quality of lignin, particularly non- sulfonated lignin such as indulin which results in a strong binder when treated with a phenol-oxidizing system, but has a low solubility in water at weakly acidic to neutral pH where these enzymes are mostly active.
• Lignin can be used in an amount of 25-250 g/1, and solutions containing above 100 g/l of lignin can be obtained.
• the surfactant used in the invention may be nonionic, anionic, cationic or zwitterionic (amphoteric).
• suitable nonionics are alkyl glycosides, alkyl glycoside esters and ethoxylated alcohols and phenols.
• the alkyl glycoside (ester) used in the invention consists of an alkyl group linked to a saccharide moiety through a glycosidic bond.
• the saccharide moiety may optionally be esterified.
• the saccharide moiety is a mono- or oligosaccharide, preferably a mono-, di- or trisaccharide, preferably consisting of hexose units, particularly of aldose units.
• Some preferred saccharide moieties are of the type G n where G is a glucose group, n is 1 , 2 or 3, and the glucose units are linked through ⁇ - 1 ,4 bonds, i.e. glucose, maltose or maltotriose.
• the alkyl glycoside preferably contains a straight-chain saturated unsubstituted C 6 -C 18 alkyl, particularly C ⁇ -C 12 .
• the alkyl glycoside ester is preferably a monoester and preferably contains a C.-C 4 alkyl group and a straight-chain saturated unsubstituted C 6 -C 1 ⁇ acyl group, particularly C ⁇ -C 12 .
• the ester group is preferably attached to the C atom in the 6- position of a glucose moiety.
• the glycoside bond may be in the a- or ⁇ - conformation, or a mixture of the two may be used.
• Suitable anionic surfactants are linear alkylbenzene sulfonate (LAS), alcohol ether sulfate (AES) and alkyl ether phosphate.
• suitable cationic surfactants are quaternary ammonium salts:
• suitable zwitterionic (amphoteric) surfactants are substituted betaines, e.g. alkylamide propyl betaine.
• the surfactant is generally added in an amount of 5-100 g/l.
• Phenol oxidizing enzyme system The enzyme system used in the invention consists of a suitable oxidase together with 0 2 or a suitable peroxidase together with H 2 0 2 .
• Suitable enzymes are those which oxidize and polymerize aromatic compounds such as phenols and lignin.
• Suitable enzymes are catechol oxidase (EC 1.10.3.1), laccase (EC 1.10.3.2) and peroxidase (EC 1.11.1.7).
• Some preferred enzymes are peroxidase derived from a strain of Coprinus, e.g. C. cinereus or C. macrorhizus, peroxidase from Bacillus, e.g. ⁇ . pumilus and laccase from Trametes, e.g. T. versicolor (previously called Polyporus). It may be preferable to use two different phenol oxidizing enzymes together.
• the amount of enzyme should generally be in the range 10-10,000
• H 2 0 2 Molecular oxygen from the atmosphere will usually be present in sufficient quantity.
• a suitable amount of H 2 0 2 will usually be in the range 0.01 -10 mM, particularly 1-10 mM.
• Suitable conditions for the enzymatic treatment of lignin to produce binder are known in the art. Typical conditions are 20-60°C and pH 5-6 for laccase, and 20-60°C and pH 7-8 for peroxidase.
• the binder to wood fibre material and pressing under heat to produce a wood composite can be done by methods known in the art.
• a typical example is production of particle board from wood particles.
• the binder is applied by spraying in an amount of 40-100 g/kg of wood fibre material, and pressing is typically done by compressing for 2-4 minutes at a pressure of 20-40 kg/cm 2 (2-4 Pa) with temperature rising form 35 to 190°C in 20 seconds.
• APG increases the lignin solubility 5 particularly at acid pH, and glucose-C 10 particularly at alkaline pH.
• Fig. 1 shows the solibility of indulin in the 20 presence of surfactants as a function of pH. It appears that at pH 7, the solubility of indulin is 12.7 mg/ml in the absence of surfactant, and 39, 45 and 29 mg/ml in the presence of 5% Empigen, 5% Nansa 1169/P and 5% APG, respectively.
• EXAMPLE 3 shows the solibility of indulin in the 20 presence of surfactants as a function of pH. It appears that at pH 7, the solubility of indulin is 12.7 mg/ml in the absence of surfactant, and 39, 45 and 29 mg/ml in the presence of 5% Empigen, 5% Nansa 1169/P and 5% APG, respectively.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)

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Cited By (4)

Citations (3)

• 1992
  • 1992-06-12 DK DK77492A patent/DK77492D0/da not_active Application Discontinuation
• 1993
  • 1993-06-10 WO PCT/DK1993/000199 patent/WO1993025622A1/en active Application Filing
  • 1993-06-10 AU AU43114/93A patent/AU4311493A/en not_active Abandoned

Patent Citations (3)

Non-Patent Citations (2)

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