EP0197674B1 - Procédé pour densifier des bois de basse densité - Google Patents

Procédé pour densifier des bois de basse densité Download PDF

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Publication number
EP0197674B1
EP0197674B1 EP86301862A EP86301862A EP0197674B1 EP 0197674 B1 EP0197674 B1 EP 0197674B1 EP 86301862 A EP86301862 A EP 86301862A EP 86301862 A EP86301862 A EP 86301862A EP 0197674 B1 EP0197674 B1 EP 0197674B1
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EP
European Patent Office
Prior art keywords
wood
ammonia
wood member
process according
thickness
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP86301862A
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German (de)
English (en)
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EP0197674A1 (fr
Inventor
Peter Favot
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Individual
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Individual
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Publication date
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Priority to AT86301862T priority Critical patent/ATE52958T1/de
Publication of EP0197674A1 publication Critical patent/EP0197674A1/fr
Application granted granted Critical
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    • 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
    • B27K1/00—Damping wood
    • 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
    • B27K3/16—Inorganic impregnating agents
    • B27K3/20—Compounds of alkali metals or ammonium
    • 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
    • B27K5/00—Treating of wood not provided for in groups B27K1/00, B27K3/00
    • B27K5/06—Softening or hardening of wood
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27M—WORKING OF WOOD NOT PROVIDED FOR IN SUBCLASSES B27B - B27L; MANUFACTURE OF SPECIFIC WOODEN ARTICLES
    • B27M1/00—Working of wood not provided for in subclasses B27B - B27L, e.g. by stretching
    • B27M1/02—Working of wood not provided for in subclasses B27B - B27L, e.g. by stretching by compressing

Definitions

  • This invention relates to an improved process for producing a densified solid wood product.
  • the invention provides a process for densifying solid wood which comprises the steps of:
  • Such wood will typically have a moisture of at least 50% and usually at least 80%.
  • the wood can be cut into planks having thicknesses of up to 2 inches (50 mm) or it can be in the form of a thin veneer, e.g. having a thickness of about inch (3 mm), or it can be in the form of a pre-glued wood laminate.
  • the plasticized agent is conveniently in the form of anhydrous ammonia.
  • Anhydrous ammonia is a strong, hydrogen bonding, low molecular weight solvent which penetrates not only into amorphous areas of the fiber cell wall but also into the lignin binding material of a wood member. Some of the hydrogen bonds responsible for the rigidity of wood are broken by the ammonia. This results in a softening or plasticizing of the fiber structure so that the wood assumes a sponge-like characteristic and can be compressed at moderate pressure. As the ammonia is removed from the wood, hydrogen bonds are again formed between the polymer chains, although not necessarily at the same locations on the polymer chains or between the same microfibrils, resulting in the wood member once again becoming rigid.
  • the wood member being impregnated with ammonia generally contains about 20-30% moisture, although moisture levels both above and below this range may be used. However, if the moisture content is too low, a proper plasticization will not be achieved.
  • the solid wood members are placed in a vacuum chamber and a negative pressure is applied.
  • a negative pressure typically a negative pressure of about one atmosphere (30" (750 mm) Hg.) may be used for about 15 to 20 minutes.
  • Ammonia gas may be added to the chamber while still under vacuum.
  • ammonia gas is pumped into the chamber, conveniently at room temperature, and at a pressure of preferably about 100 to 150 psi (690 to 1034 kPa). This ammonia pressure is maintained for usually about 2 to 8 hours depending on the thickness of the wood, the species, etc.
  • the chamber is vented and evacuated at a negative pressure for about 15 minutes.
  • This ammonia treatment stage may also conveniently be used for dyeing the wood.
  • the wood may be first impregnated with a dye which uniformly dyes the wood member throughout its thickness. Dyeing in this manner has the advantage that when the densified wood members are cut or planed, the newly exposed surfaces are of uniform color.
  • the cyclic press includes a bottom press member 10, the top face of which is in the form of a perforated plate 11 having perforations 15. Beneath perforated plate 11 is a drainage grid connected to drainage outlets 16.
  • top press member 12 which is connected to hydraulic cylinder 14 for vertical cyclic movement.
  • Press member 12 has a perforated bottom face plate 13 and above this face plate is a drainage grid connected to drainage outlets 17.
  • the wood member At the end of the pressing stage, the wood member remains in a compressed state of reduced thickness while still containing a considerable quantity of moisture.
  • the above cyclic pressing technique is particularly useful for densifying thick wood members, such as planks and pre-glued laminates.
  • densifying thin veneers e.g. 5 inch (3 mm) thick
  • steam formation is not a serious problem and so they can be densified by simpler pressing methods and at higher temperatures.
  • thin veneers can be densified at temperatures as high as 200°C and the densification can be carried out between rollers.
  • the first pair of rollers squeeze out water and ammonia, intermediate rollers fix the veneer at a predetermined reduced thickness and final heated rollers fully dry the veneer.
  • the product emerging from this drying stage is a permanently densified, high quality hardwood having substantially the same length and width as the original stock, but having a substantially reduced thickness.
  • the densification is consistent throughout the thickness of the wood member and it can be sanded, planed, routered, drilled, nailed, screwed and sawn similar to other hardwoods.
  • the product can be stained, polished and finished at least as well as regular hardwoods and has a very dense surface with minimum of texture and porosity, requiring very little preparation prior to finishing.
  • Roughly sawn planks of 1 and 2 inch (25 and 50 mm) thicknesses were cut from green poplar and alder.
  • the test planks had a width of 4 inches (100 mm), a length of H-2 feet (460-610 mm) and a moisture content of 80%.
  • the samples thus prepared were placed in a gas retort with spacers between the planks.
  • the chamber was evacuated with a negative pressure of approximately one atmosphere for 15 to 20 minutes, with ammonia gas being introduced into the chamber during that time.
  • the vacuum was discontinued and ammonia gas was pumped into the chamber at room temperature and a pressure of approximately 100-150 psi (690-1034 kPa). This pressure was maintained for approximately 6 hours.
  • the chamber was vented and evacuated at a negative pressure (vacuum) of one atmosphere for 15 minutes. Thereafter, the pressure was released, the door opened and overhead venting continued.
  • the plasticized wood samples thus obtained were placed in a cyclic press between perforated plates. While maintaining an elevated temperature below 100°C, a pressure of about 175 psi (1200 kPa) was applied with a cyclic pressing procedure consisting of 1 minute press cycles for a total period of 5 minutes. During each down cycle the perforated pressure plates reduced the thickness of the wood member by about 50%, were held in this position for approximately 45 seconds and then released. In this manner, the level of water in the wood was reduced from 80% down to about 20-30%, at the same time driving out dissolved ammonia, gaseous ammonia and water, thereby reducing the plasticization effect on the wood fibers. At the end of the cyclic pressing stage, wood samples were obtained having their thickness reduced to about 50% of their original thickness.
  • the poplar woodstock produced a walnut-looking hardwood, while the alder produced an ebony- looking hardwood.
  • the densified woods were approximately denser than the 3 natural hardwoods, with the densified poplar having a hardness near equal to the high quality natural hardwoods, while the densified alder had an hardness twice that of the high quality natural hardwoods.
  • the natural hardwoods have a class-III fire rating, while the densified poplar has a class-II fire rating and the densified alder has a class-III fire rating.
  • densified wood products Another important characteristic of the densified wood products is that they absorbed 40-50% less water during a 2 hour soak period than did the high quality natural hardwoods.
  • the strength properties of static bending and compressive strength for the densified wood products were approximately equal in most cases and in some cases were superior to the high quality natural hardwood. Abrasion tests indicated that the densified poplar wore down 3 times less than oak, while the densified alder wore down 1-a times less than oak, during the same period of time.
  • the densified wood products also showed excellent glueability and very good resistance to fungus.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Forests & Forestry (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Chemical And Physical Treatments For Wood And The Like (AREA)

Claims (10)

1. Procédé pour densifier du bois massif, comprenant les opérations consistant à:
a) imprégner un bois massif à forte teneur en humidité d'un agent plastifié contenant de l'ammoniac, de manière à plastifier la pièce de bois jusqu'à obtention d'une forme semblable à une éponge saturée d'eau et d'ammoniac,
b) placer la pièce de bois plastifiée entre des plateaux perforés de serrage d'une presse à mouvement cyclique et, tout en maintenant la température de la pièce de bois plastifiée au-dessous de 100°C, la soumettre à une pluralité de cycles de compression pour comprimer la pièce de bois à une épaisseur prédéterminée, la maintenir à cette épaisseur pendant une courte durée et la desserrer pendant chaque cycle, de manière que l'eau et l'ammonic soient exprimés de la pièce de bois à travers les perforations des plateaux de serrage, jusqu'à ce que la teneur en humidité soit inférieure à 30% afin d'obtenir une pièce de bois humide d'une épaisseur réduite prédéterminée, et
c) sécher la pièce de bois comprimé, humide, pour obtenir un produit de bois massif sec, densifié de façon permanente.
2. Procédé selon la revendication 1, dans lequel le bois massif est un bois de faible masse volumique et de basse qualité.
3. Procédé selon la revendication 2, dans lequel le bois est un bois vert.
4. Procédé selon la revendication 1, 2 ou 3, dans lequel le bois contient au moins 50% d'humidité environ.
5. Procédé selon la revendication 4, dans lequel le bois vert contient au moins 80% d'humidité environ.
6. Procédé selon l'une quelconque des revendications précédentes, dans lequel le bois massif est sous la forme d'une planche ayant une épaisseur pouvant atteindre deux pouces (50 mm).
7. Procédé selon l'une quelconque des revendications précédentes, dans lequel on imprègne la pièce de bois massif d'ammoniac en soumettant premièrement la pièce de bois à une évacuation sous vide, pendant que la pièce de bois est amenée en contact avec du gaz ammoniac et, deuxièmement, en traitant la pièce de bois ayant subi l'évacuation avec du gaz ammoniac à une pression supérieure à la pression atmosphérique.
8. Procédé selon l'une quelconque des revendications précédentes, dans lequel on effectue le pressage cyclique pendant une durée totale pouvant atteindre 5 minutes environ, avec une durée d'environ une demie à une minute pour chaque cycle.
9. Procédé selon l'une quelconque des revendications précédentes, dans lequel on effectué le séchage final à une température inférieure à 100°C, en maintenant fermement la pièce de bois comprimée entre des plateaux pendant la séchage afin d'empêcher le gauchissement.
10. Procédé selon l'une quelconque des revendications précédentes, dans lequel ou soumet la pièce de bois à une vibration pendant la pressage cyclique.
EP86301862A 1985-03-15 1986-03-14 Procédé pour densifier des bois de basse densité Expired - Lifetime EP0197674B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT86301862T ATE52958T1 (de) 1985-03-15 1986-03-14 Verfahren zur verdichtung von hoelzern mit niedriger dichte.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA000476650A CA1236255A (fr) 1985-03-15 1985-03-15 Methode de densification des bois legers
CA476650 1985-03-15

Publications (2)

Publication Number Publication Date
EP0197674A1 EP0197674A1 (fr) 1986-10-15
EP0197674B1 true EP0197674B1 (fr) 1990-05-23

Family

ID=4130037

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86301862A Expired - Lifetime EP0197674B1 (fr) 1985-03-15 1986-03-14 Procédé pour densifier des bois de basse densité

Country Status (4)

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EP (1) EP0197674B1 (fr)
AT (1) ATE52958T1 (fr)
CA (1) CA1236255A (fr)
DE (1) DE3671403D1 (fr)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2658750A1 (fr) * 1990-02-26 1991-08-30 Ober Ind Procede de fabrication, partant de bois massif ou de placage, scie, tranche ou deroule, de panneaux densifies et durs.
AU3898193A (en) * 1992-04-04 1993-11-08 Woodform Design Ltd. Bending and shaping mdf
GB2265914A (en) * 1992-04-04 1993-10-13 Hoffman Thornwood Plc Method of plasticising medium density fibre board
DE69400417T2 (de) * 1993-04-29 1997-02-13 Shell Int Research Verfahren zur Verbesserung von Holz niedriger Qualität
FR2796586B1 (fr) 1999-07-20 2001-10-12 Frederic Voisin Procede et dispositif de compression, cintrage et jointage de douelles pour fabriquer des futs ou des barriques
CZ304024B6 (cs) * 2008-12-02 2013-08-28 Mendelova zemedelská a lesnická univerzita v Brne Zpusob rovnomerného plosného zhustování dreva, zejména smrkového
SE534884C2 (sv) * 2010-04-28 2012-01-31 Mb Aedeltrae Ab Metod för behandling av en skiva samt ett skivelement
JP6530865B2 (ja) * 2016-07-01 2019-06-12 公立大学法人北九州市立大学 集成材の製造方法

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3282313A (en) * 1964-11-24 1966-11-01 Research Corp Method of forming wood and formed wood product
FI43008B (fr) * 1969-06-10 1970-09-02 Neste Oy
AT326339B (de) * 1971-09-14 1975-12-10 Inst Khim Drevesiny Akademii N Verfahren zum verdichten von vollholz

Also Published As

Publication number Publication date
DE3671403D1 (de) 1990-06-28
EP0197674A1 (fr) 1986-10-15
CA1236255A (fr) 1988-05-10
ATE52958T1 (de) 1990-06-15

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