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
  • B27N1/003—Pretreatment of moulding material for reducing formaldehyde gas emission
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
  • B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
  • B27K3/02—Processes; Apparatus
  • B27K3/15—Impregnating involving polymerisation including use of polymer-containing impregnating agents

Definitions

• the present invention relates to a process for formaldehyde emission reduction in wood-based materials by treatment with polyamines.
• Wood-based materials are a cost-effective and resource-saving alternative to solid wood, and have gained great importance especially in furniture construction and as building materials.
• starting materials serve wood layers of different thickness, wood strips, wood chips or wood fibers from different woods.
• wood parts or wood particles are usually pressed with natural and / or synthetic binders and optionally with the addition of further additives to plate or strand-shaped wood materials.
• Formaldehyde-containing resins or adhesives are often used as binders, for example UF resins (urea-formaldehyde resins) or melamine-containing urea-formaldehyde resins.
• the resins are produced by polycondensation of formaldehyde with urea or melamine. In order to obtain good adhesive properties, an excess of formaldehyde is generally added in this case. This means that there is free formaldehyde in the finished wood material that is released into the environment. Since the polycondensation proceeds slightly backwards, the back reaction is also a source of formaldehyde release.
• Formaldehyde may cause allergies, skin, respiratory or eye irritation above certain limits in humans.
• the reduction of formaldehyde emission in interior components is therefore an important concern.
• the formaldehyde emission can also be reduced by aftertreatment of the wood-based materials.
• the JP 2002-273145 A describes a method for reducing the formaldehyde release of wood composites, wherein several, each individually for Reduction of formaldehyde emission suitable measures can be combined.
• the described aqueous formaldehyde scavenger is composed of 20 to 50% by weight of urea, and a balance of a non-volatile amine, a means of increasing the permeability of the wood so that the urea and non-volatile amine can penetrate the composite, and a film-forming Solid which, upon drying, becomes a physical barrier to the formaldehyde on the wood composite. This film can affect the coatability of wood composites.
• the solution of the problem is based on the known methods for reducing the formaldehyde emission in wood materials by applying nitrogen-containing compounds.
• the process according to the invention is then characterized in that a mixture is applied to the wood material which contains at least one polyamine and optionally up to 20% by weight, based on the mixture, of urea.
• the mixture may be in aqueous form or without the addition of solvents.
• the aqueous polyamine solution contains preferably 10 to 50 wt .-% polyamine, in particular 15 to 45 wt .-% polyamine, particularly preferably 25 to 40 wt .-% polyamine, each based on the polymer solution.
• Polyamine (a) is understood as meaning compounds which have a molecular weight of at least 500 g / mol and at least 6 primary or secondary amino groups. Preference is given to using polyamines which have a molecular weight of at least 800 g / mol and at least 10 primary or secondary amino groups. As polyamines, preference is given to polyethyleneimine and polyvinylamine.
• the weight-average molecular weight of the polyvinylamine is preferably 5,000 to 350,000 g / mol, more preferably 5,000 to 100,000 g / mol, that of the polyethyleneimine is preferably 800 to 100,000 g / mol, more preferably 800 to 70,000 g / mol, most preferably 2,000 to 50,000 g / mol.
• Polyethyleneimine can be prepared by acid catalyzed polymerization of ethyleneimine and is obtained as an aqueous solution at levels of from 20 to 100% by weight, more preferably between 40 and 70% by weight of polyethylenimine.
• Polyvinylamine is prepared by polymerization of vinylformamide and subsequent hydrolysis and is obtained as an aqueous solution of 2 to 50 wt .-%, particularly preferably from 5 to 25 wt .-% of.
• the degree of hydrolysis can be adjusted by the reaction conditions and determines the ratio of amine groups to formamide groups.
• these solutions can be used directly as a basis for the polyamine solutions according to the invention.
• ionic and nonionic surfactants as used, for example, in US Pat H. Stache, "Tensid-Taschenbuch", Carl Hanser Verlag, Kunststoff, Vienna, 1981 . are used, in concentration of 0 to 5 wt .-%, preferably from 0 to 2 wt .-% are used.
• the pH can be adjusted by the following additives as optional component (c): mineral or organic acids such as sulfuric acid or formic acid.
• Component (c) may be added to the aqueous polymer solution from 0 to 30% by weight, preferably from 0 to 20% by weight.
• additives can be added to the aqueous polymer solution, for example, additives from the group of water repellents, e.g. Paraffin emulsions and waxes, fungicides, organic solvents or dyes.
• group of water repellents e.g. Paraffin emulsions and waxes, fungicides, organic solvents or dyes.
• the aqueous polyamine solution may contain up to 20% by weight of urea based on the polymer solution.
• the aqueous polymer solution contains less than 15% by weight of urea, preferably less than 10% by weight of urea and in particular less than 5% by weight of urea, in each case based on the polymer solution.
• the polymer solution is free of urea.
• a sufficient amount of polyamine solution is applied so that the amount of polyamine per m 2 surface of the wood material is between 1 g and 200 g, preferably between 2 g and 50 g, more preferably between 3 g and 30 g.
• the aqueous polymer solution can be applied to the wood material by various measures known to those skilled in the art. These include, for example, spraying, rolling, dipping, knife coating, brushing, curtain coating, preferably the amine solution is applied by spraying.
• Wood-based materials are all materials which are made of wood strips, such as, for example, fun board or plywood boards, wood-based materials produced from wood chips, for example chipboard or OSB boards, and wood-fiber materials such as LDF, MDF and HDF boards. These wood-based materials are produced from the corresponding wood particles with the addition of natural and / or synthetic binders by hot pressing.
• wood materials containing formaldehyde-containing binders are treated by the process according to the invention.
• OSB, wood fiber and chipboard Preference is given to OSB, wood fiber and chipboard.
• the wood-based materials can be surface-treated after pressing by grinding.
• the application of the polyamines according to the invention can be carried out before or after the grinding, preferably after grinding.
• the wood-based material may have an elevated temperature during application or at room temperature are located.
• the wood-based material can also be heat-treated after application, for example by infrared radiation, heated rollers or in a heat channel.
• the polyamines can be applied on one side or on both sides, preferably on both sides.
• the polyamine solution is preferably applied at a pH of from 3 to 12, preferably from 7 to 11, particularly preferably at a pH of from 9 to 11, it also being possible for protonation of the polyamines to occur in the less preferred acidic range.
• the invention also relates to the wood materials produced by the process according to the invention, in particular wood-containing materials containing formaldehyde-containing binders. Particular preference is given to particleboards and fibreboards treated according to the invention.
• the wood-based materials obtained by the process can then be surface-finished.
• the surface finishing can be done by coating with different materials. For example, a painting, funcing, lamination or lamination can be performed.
• Such surface-treated wood materials are also the subject of the invention.
• the wood-based materials according to the invention can be used for the production of furniture, packaging materials, in building construction, in dry construction or in interior work, for example as a laminate, insulation or support.
• a 30% aqueous solution of a polyethyleneimine having an average molecular weight of 5,000 g / mol was sprayed on the chipboard so that 40 g / m 2 of polyethylenimine was applied to the chipboard. Subsequently, the surface was heated to 60 ° C within 150 sec and then stored for 1 day at 20 ° C / 65% humidity.
• Formaldehyde emission with or without aftertreatment was determined in accordance with the DIN standard DIN EN717-2 (Determination of Formaldehyde Release Part 2: Formaldehyde Release by the Gas Analysis Method) from 1994 and DIN Standard DIN EN717-1 (Determination of Formaldehyde Release Part 1 : Formaldehyde release according to the test chamber method) from the year 2004 in a 1 m 3 chamber.
• the air flow is set to 60 1 / h.
• the escaping air is collected in a gas wash bottle containing an aqueous solution of acetylacetone and ammonium acetate.
• Formaldehyde reacts in aqueous solution with ammonium ions and acetylacetone to diacetyldihydrolutidine (DDL). This reaction is highly specific for formaldehyde.
• the DDL has an absorption maximum at 412 nm and can be quantitatively detected by spectroscopy. To determine the formaldehyde concentration, the values for the last 3 hours are averaged.
• test specimens with the dimensions 0.5 x 0.5 x thickness xm 3 with 0.75 m open edge are placed in a test chamber with a volume of 1 m 3 .
• the measurement is carried out for at least 10 to a maximum of 28 days at 23 ° C and a relative humidity of 45 +/- 3%.
• the air intake and exhaust is chosen so that the entire air is replaced once within 1 hour.
• 120 l of air are passed at a rate of 2 l / min into a gas scrubber bottle filled with aqueous ammonium acetate and acetylacetone solution.
• the formaldehyde concentration is also determined spectroscopically.
• the formaldehyde emission results from this method from a compensation curve, while 4 consecutive values may vary by no more than 5%. If this condition is not fulfilled after 28 days, the last 4 values are used for averaging.
• the chipboards A-C were coated after 24 h in standard atmosphere (20 ° C / 65% humidity) as follows:
• a white decorative paper (80 g / m 2 ) was impregnated with 100 g / m 2 of a resin liquor of Kauramin impregnating resin 792 and hardener 529 (100: 0.3) and dried in the oven at 160 ° C. The resulting film is placed on the surface of the chipboard and pressed (190 ° C, 25 bar, 35 s). To stabilize the test piece, a counter pull film is simultaneously pressed on the back side.
• a lattice test is carried out. For this purpose, two times four parallel line-shaped cuts (distance 0.5 cm) are made through the surface with a razor blade so that a diamond-shaped pattern is created. In the corners of the diamonds, there is a partial flaking of the coating. The percentage of destroyed surface is determined. The smaller the value, the better the coatability of the chipboard.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)

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Citations (5)

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• 2006
  • 2006-01-17 EP EP06100479A patent/EP1808278A1/de not_active Withdrawn
• 2007
  • 2007-01-12 CN CN200780002439.6A patent/CN101370626B/zh not_active Expired - Fee Related
  • 2007-01-12 UA UAA200810446A patent/UA95792C2/ru unknown

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Non-Patent Citations (7)

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