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
  • B27N7/00—After-treatment, e.g. reducing swelling or shrinkage, surfacing; Protecting the edges of boards against access of humidity
• • 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

Definitions

• the invention relates to a method for reducing the release of formaldehyde from chipboard and fiber board veneered with finishing layers, the chipboard or fiber board belonging to emission class E1.
• Wood chipboards are wood chip boards that are hot pressed with a synthetic resin glue binder. Due to the size, shape and arrangement of the chips and the amount of synthetic resin, which is generally in the range of 5 to 10%, the properties of the chipboard can be varied widely.
• the chipboard can be coated with decorative films, primer films and veneers, for example with valuable woods.
• Urea resins or aminoplastics are by far the most widely used particle board binders. They are characterized by a favorable price and high strength of the gluing and also enable very short pressing times.
• the urea resins have the great disadvantage that they release formaldehyde during the use of the particle board, which not only has an unpleasant odor but is also harmful to health, and therefore the use of urea resins as binders is subject to certain restrictions.
• isocyanates have only been used to a small extent as binders for particle boards.
• Diphenylmethane diisocyanate in particular has proven to be an excellent binder with which plates of high durability can be produced.
• the price of these products has so far prevented wider use.
• the published European patent application 0 012 169 describes multilayer, predominantly aminoplast-bonded chipboard or fiberboard which, in an interior, preferably in the middle layer, has an adhesive which does not belong to the group of aminoplasts, for example diisocyanate, as a binder and which is characterized by it that only those binders are used for this interior, the hardening of which is not impaired by the presence of additional formaldehyde-reactive substances, these additional substances in the form of ammonia, ammonium carbonate, ureas, thioureas, melamine or dicyandiamide which are mixed with the binder the formaldehyde still present or released after pressing the plate under the influence of moisture and / or heat, possibly also indirectly via fission products, reacting it to set.
• an adhesive which does not belong to the group of aminoplasts, for example diisocyanate
• these additional substances in the form of ammonia, ammonium carbonate, ureas, thioureas, melamine or
• European patent application 0 006 486 relates to a process for reducing the release of formaldehyde from aminoplast-bonded chipboard or fiberboard, in which urea or other ammonia-releasing substances in the form of an aqueous solution on the surface of the boards in the hot state immediately after their removal from the heating press be applied.
• these E1 panels are in many cases veneered with finishing layers, for example with mahogany, for example for the manufacture of panels. It is common in the plywood industry to use urea-formaldehyde resins with a high formaldehyde content (molar ratio urea: formaldehyde 1: 1.6 to 1: 1.8) as veneers between the veneer and the board. Heat-curing formaldehyde-rich urea-formaldehyde resins are also used in the application of plastic surfaces for furniture construction.
• binders can increase the release of formaldehyde from the veneered or otherwise coated panels, depending on the type of coating, type of wood, thickness, direction of cut, and manufacturing conditions, so that the legal requirements are no longer met.
• the formaldehyde-reducing effect of the barrier (for example due to the veneer) is lost and is completely masked (cf. Marutzky, R., Mehlhorn, L. and Wenzel, W., 1981: "Recommendations for the use of chipboard in furniture construction", lecture , held on the occasion of the symposium of Mobil Oil AG in Grainau on September 18, 1981). This is particularly true when the formats of the veneered panels or panels are very small (see ETB guidelines).
• the present invention is therefore based on the object of providing a method according to which it is possible to reduce the formaldehyde release from chipboard and fibreboard with applied finishing layers, the panels themselves belonging to emission class E1, the finishing layers being particularly valuable veneer woods and have been applied using high formaldehyde urea-formaldehyde resins.
• the above object can be achieved in that the P pale releasing compounds are treated prior to veneering in a conventional manner with aqueous solutions of urea and / or other ammonia and that subsequently in a known manner, the Finishing layers are applied.
• the boards treated according to the invention are preferably veneered with mahogany wood.
• urea and / or other compounds which release ammonia are used as formaldehyde-reactive substances.
• ammonia such as, for example, ammonium carbonate
• the process according to the invention is not intended to reduce the formaldehyde release of the raw panels themselves, since the process according to the invention uses plates of emission class E1, the use of which in construction does not require any further reduction in their formaldehyde emissions.
• the chipboard acts as a carrier for the formaldehyde scavenger. Due to the spatial separation between the urea-formaldehyde resin and the formaldehyde scavenger, the hardening of the resin takes place undisturbed, while the free formaldehyde is trapped in the plate (cf. discussion of the prior art in DE-PS 28 51 589).
• aqueous solutions of urea and / or other compounds which release ammonia are used.
• the aqueous solutions can have concentrations in the range from 5% to 60%, preferably from 30% to 50%. They are easily manufactured by dissolving the corresponding compounds in water.
• Ammonium carbonate, ammonium bicarbonate can be used as compounds which release ammonia. Urea mixed with ammonium carbonate is preferably used.
• the field of application of the present invention is not restricted to chipboard of the emission class E1, bonded with aminoplast resin, but the process according to the invention can be successfully applied to chipboard bonded to isocyanate and chipboard bonded to phenol-formaldehyde resin, which does not give off any formaldehyde at all, but does so by veneering with aminoplast resin as a binder gain in formaldehyde release potential.
• Low-emission fiberboard can also be treated in accordance with the process.
• a chipboard of emission class E1 [perforator value 8.0 mg (iodometric) or 6.1 mg (photometric) / 100 g dry plate] was coated with 220 g / m 2 of a 50% urea-formaldehyde resin solution (molar ratio 1: 1 , 6) and then coated with a veneer (mahogany, thickness 0.6 mm).

Landscapes

• 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)
• Laminated Bodies (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (3)

Family

ID=6216269

Family Applications (1)

Country Status (3)

Cited By (6)

Families Citing this family (3)

Citations (4)

• 1983
  • 1983-12-07 DE DE3344239A patent/DE3344239C2/de not_active Expired
• 1984
  • 1984-12-06 DE DE84114876T patent/DE3486202D1/de not_active Expired - Fee Related
  • 1984-12-06 AT AT84114876T patent/ATE93444T1/de not_active IP Right Cessation
  • 1984-12-06 EP EP84114876A patent/EP0144985B1/fr not_active Expired - Lifetime

Patent Citations (4)

Non-Patent Citations (1)

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