Classifications

• • 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
  • B27K3/02—Processes; Apparatus
  • B27K3/0207—Pretreatment of wood before impregnation
  • B27K3/0221—Pore opening
• • 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
  • B27K5/001—Heating
• • 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
  • B27K5/003—Treating of wood not provided for in groups B27K1/00, B27K3/00 by using electromagnetic radiation or mechanical waves
  • B27K5/0055—Radio-waves, e.g. microwaves

Definitions

• the present invention relates to a method and a device for heat treatment and impregnation, essentially by immersion, of wood or similar woody materials.
• the effectiveness of an impregnation treatment can be assessed by both the amount and the depth of penetration of the preservative absorbed into the piece of wood.
• the processes ensuring a shallow penetration depth let us cite in particular: the external application of the preservative using a brush, by spraying or spraying, by direct immersion in the treatment solution containing the preservation.
• Increasing penetration depth and impregnated quantities is generally obtained from an autoclave treatment such as the process described in the document "Guide to the preservation of wood", Michel RAYZAL, March 1998, Technical Center for Wood and Furniture (CTBA) - 75012 PARIS, pages 62-67.
• the autoclave treatment times are also long (several hours) and require long equipment downtimes.
• the object of the present invention is to propose an improved process for treating wood and a device allowing its implementation.
• the present invention also aims to remedy, at least in part, the drawbacks of the known methods.
• the invention is based on the generation of a high pressure drop in the wood fabrics (induced by intense vaporization) in the presence of high densities of heat flux and of a higher material temperature or equal to the boiling temperature of water at working pressure.
• This first step is followed by the fastest possible contact with the treatment solution at a temperature much lower than the boiling temperature of water.
• the internal overpressure of the first stage is followed by a depression during the second stage which is used for the impregnation of the pores and vessels of the piece of wood by capillary flow of the treatment solution in contact with its external surface.
• this transfer must be carried out in less than 30 seconds, in particular in less than 10 seconds, for example in less than 3 or 5 seconds.
• This effect can, if necessary, be limited or even avoided by waterproofing or covering the ends of the part to be treated where the longitudinal fibers of the wood are flush and which offer low pressure drops to gases and liquids; this further promotes the internal suppression of the piece of wood by heating.
• the parts to be treat are not dry; it is essential that the parts to be treated have a humidity higher than 25%, in particular of the order of 40% to 80% (mass / dry mass); for this purpose the parts can if necessary be re-humidified before treatment by prolonged immersion in a tank of liquid water at room temperature.
• the latter is carried out in a liquid medium in the treatment solution at a temperature much lower than that of the surface of the heated piece of wood.
• the difference between these last two temperatures is generally chosen to be greater than 40 ° C., in particular greater than 60 ° C.
• the piece of wood is heated for this purpose to a temperature higher than the boiling temperature of the surface water (of the order of 1 10 to 180 ° C. if the operation is carried out at atmospheric pressure) and at a core temperature close to the boiling temperature of water (which depends on the working pressure and the internal overpressure).
• the temperature of the bath is maintained, by means of a cooling unit, at a temperature generally less than 90 ° C.
• the treatment bath in which the rapid cooling of the immersed parts to be treated is carried out, can essentially consist of an aqueous phase added with hydrophilic preservatives (such as copper - chromium-arsenic), by creosotes diluted in petroleum, by an emulsion or a dispersion of these same agents in aqueous or hydrophobic phases, by one or a mixture of organic solvents.
• hydrophilic preservatives such as copper - chromium-arsenic
• Cooling in an oil bath makes it possible to greatly reduce the costs of the treatment solution and to ensure rapid cooling, of around fifty degrees in less than 30 minutes, in particular in less than 10 minutes, under conditions of natural convection (oils are very thermodilatable fluids).
• a tangential movement of the cold treating medium with respect to the pieces is induced, either by displacement of the pieces, or by flow of the bath, or by a combination of these means (moving the pieces of wood on rails or carpets combined with a re-circulation of the treatment solution in the cooling tank).
• the total duration of the treatment does not exceed four hours; for example, the duration is of the order of 30 min to 1 hour (depending on the dimensions and the initial water content of the parts to be treated.
• the desired quality objective quantitative impregnated and / or depth of penetration
• Heating can be obtained by different processes which can be combined if necessary: radiation (infrared, high frequencies, ultra high frequencies), exposure to very hot air (eg combustion gas) or superheated steam , immersion in a fluid at high temperature (between 1 10 and 300 ° C at atmospheric pressure) whose boiling temperature is much higher than that of liquid water; in the latter case, the parts are preferably immersed in a bath of a similar nature to that used for cooling, in particular an oil bath maintained at a temperature between 1 10 and 250 ° C. at atmospheric pressure.
• radiation infrared, high frequencies, ultra high frequencies
• very hot air eg combustion gas
• superheated steam immersion in a fluid at high temperature (between 1 10 and 300 ° C at atmospheric pressure) whose boiling temperature is much higher than that of liquid water; in the latter case, the parts are preferably immersed in a bath of a similar nature to that used for cooling, in particular an oil bath maintained at a temperature between 1 10 and 250 ° C. at atmospheric pressure.
• oils animal, vegetable or mineral origin, in particular used vegetable oils, by-products of the food industry such as oils. used frying. These inexpensive products are thermodegraded and therefore rich in surfactants (free fatty acids); they make it possible to use either hydrophilic or hydrophobic preservation products in the cooling bath.
• the use, for the cooling step, of an oil or of a treatment solution having the same hydrophobic character makes it possible to greatly reduce the costs of the impregnation solution and to protect the treated wood from subsequent rewetting and its effects when used outdoors (drying-rewetting cycles). These effects are responsible for the appearance and propagation of cracks on the periphery of the treated wood and constitute preferential pathways for the penetration of biological agents of wood degradation.
• the oil is used for its excellent heat transfer fluid properties in a two-phase medium (ie in the presence of steam) during the first stage.
• this first step can be accompanied by the strong fixation of fatty acids from the bath on the celluloses and hemicelluloses of the wood, a very favorable reaction to the preservation of the wood.
• the impregnation of the material with thermodegraded substances such as frying oils very greatly reduces the biological availability of the wooden substrate for microorganisms and insects.
• the use of oils offers outlets for by-products from the agro-food industry that are not highly valued and allows the material to be impregnated with biodegradable substances which will allow better compatibility of the materials produced with the environment during their use or recycling.
• the immersion step in a bath brought to a temperature above the boiling temperature of water is interesting for the impregnation process proposed by what it allows:
• the invention consists of a wood treatment device which comprises:
• each container receiving the bath comprises means for keeping the pieces of wood in immersion total (the buoyancy of the material depending on the composition of the material and in particular on its water content).
• immersion total the buoyancy of the material depending on the composition of the material and in particular on its water content.
• These devices can be fixed or mobile, in the latter case they also serve to move the parts in the bath.
• the two containers (or bins) should preferably be contiguous; they can be obtained by equipping a tank with a partition separating physically and thermally the heating bath from the cooling bath. This separation can be total or partial.
• the transfer of the parts from the first to the second bath can be obtained without contact with the gaseous atmosphere present above the baths; for this purpose, the device may include an airlock (or "lock") provided with devices for maintaining the parts in immersion during their transfer.
• the tanks are preferably covered, at least in part, by a cover making it possible to reproduce a confinement enclosure under slight overpressure.
• the invention consists of a piece of wood , which can be obtained, directly or indirectly, by a process according to the invention, at least part of which (or peripheral layer) is impregnated with a preservative; said part or layer is impregnated with an impregnation vector chosen from mineral oils, animal oils, vegetable oils, solvents (creosotes, tars, mineral oils resulting from the fractionation of petroleum products, plant extracts in mineral solvents or no) ; in addition, a surface part (layer) can be roasted (partial charring), as a result of surface heating, in particular in an oil bath at high temperature (between 1 10 and 250 ° C at atmospheric pressure).
• the average water content of the part will be less than 0.3 kg or 0.4 kg of water per kg of non-oily dry matter, in particular less than 0.1 kg / kg.
• the average content of impregnation solution (in particular oil) of said impregnated layer will generally be of the order of 0.05 to 2 kg of oil per kg of non-oily dry matter.
• the thickness of the impregnated layer is of the order of 1 to 100 mm in the cutting direction of the pieces of wood relative to the orientation of the cellular elements of the wood, in particular of the order of 5 to 50 mm for a log 200 mm in diameter.
• the average thickness of the roasted surface layer characterized by an alteration of the hemicellulose and amorphous cellulose molecules (significant reduction in the number of hydroxyl groups associated with partial crosslinking) and the appearance of pyrolysis products, may be of 0.5 to 2 cm (it depends very much on the processing times and temperatures).
• Figures from 1 to 6 schematically show 6 examples of embodiments of the method according to the proposed invention
• Figure 7 shows a schematic cross section of a piece of wood treated according to the invention.
• Each of the devices 1 comprises a tank 2 containing the bath 3 for heating the pieces 4 of wood, and a tank 5 containing the bath 6 for cooling and treating these same pieces.
• the tank 2 is equipped with a heat exchanger 7 connected by conduits 50 to a heating device (not shown) of a heat transfer fluid circulating in the exchanger 7 and the conduits 50.
• the tank 5 is equipped with a heat exchanger 8 connected by conduits 51 to a cooling unit (not shown) of a refrigerant fluid circulating in the exchanger 8 and the conduits 51.
• each tank 2, 5 is respectively equipped with a member 10, 12 ensuring immersion.
• This member 10, 12 can be fixed and be in the form of a rail flush with the surface of the bath or immersed in it; alternatively this member can be mobile and can be in the form of a belt, chain or cable conveyor; in this case, it can be fitted with projecting members forming fingers capable of driving the parts 4 in movement in the baths, as schematically represented by the arrows 11, 13.
• such a conveyor 14a partially immersed in the bath 3 is used to move (arrow 55) the pieces 4 along an inclined wall 54 of the tank 2, so as to cause them to fall ( arrow 56) in the bath 6.
• a single conveyor 14 the central part of the longitudinal profile of which is curved so as to extend substantially parallel to the inclined walls 54, 57 by which the tanks are connected, fulfills both the drive function in movement of the parts 4 in the baths 3, 6, of keeping these parts immersed in these baths, and of transferring the parts from the first to the second bath.
• one or more pumps and / or agitators can contribute to the relative movement of the pieces of wood with the treatment solution.
• a cover 16 equipped with a nozzle 18 for injecting (arrow 58) a hot gas covers the zone 9 for transfer between the tanks.
• the heating of the parts 4 can be obtained and / or supplemented by the action of a device as marked 1 7 which diffuses into the treatment enclosure 59 delimited by the cover 16 and the tanks 2, 5, microwaves or infrared radiation.
• the transfer from one tank to the other is obtained by pivoting 60 along the axis 61 (perpendicular to the plane of the figure), from a basket 62 mounted at the end of an arm 63.
• this transfer is obtained by a similar pivoting of a partially submerged airlock comprising four flaps 64 whose transverse profiles form a cross; the ends of the two flaps located in the lower part slide, during the pivoting of the airlock, along a wall 65 in the form of a portion of cylinder of horizontal axis, which wall extends at the upper end of a partition 66 separating the tanks 2, 5; the space 67 delimited by the two lower flaps and the wall 65 is adapted to receive one or more pieces 4; the rotation of the airlock flaps according to the arrow (anti-clockwise) causes the transfer of parts from bath 3 to bath 6 without emersion.
• rapeseed oil maintained respectively at 1 80 ° C and 35 ° C at atmospheric pressure.
• the stakes were immersed, the ends of which had been previously waterproofed by soaking in tar, in the heating bath for 60 minutes, taking care to allow easy circulation of the oil between the posts by natural convection and to ensure a effective compensation for the drop in bath temperature.
• the stakes clamped at their ends by metal frames were kept submerged in the bath by means of chains and removed from the bath by the same device. Transfer to the cooling bath was carried out with a passage in the air of the order of 5 seconds.
• the material remained immersed in the treatment solution for about thirty minutes, taking care to limit the heating of the cooling bath below 50 ° C.
• This bath colored red in Sudan red contained pyrethrums as a preservative.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Mechanical Engineering (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)

Applications Claiming Priority (3)

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• 1999
  • 1999-11-22 FR FR9914672A patent/FR2801241B1/fr not_active Expired - Fee Related
• 2000
  • 2000-11-22 CA CA002392159A patent/CA2392159C/fr not_active Expired - Fee Related
  • 2000-11-22 EP EP00981456A patent/EP1232047B1/de not_active Expired - Lifetime
  • 2000-11-22 WO PCT/FR2000/003245 patent/WO2001038055A1/fr active IP Right Grant
  • 2000-11-22 DE DE60012564T patent/DE60012564T2/de not_active Expired - Lifetime
  • 2000-11-22 AT AT00981456T patent/ATE271959T1/de not_active IP Right Cessation
  • 2000-11-22 ES ES00981456T patent/ES2225274T3/es not_active Expired - Lifetime
  • 2000-11-22 AU AU18698/01A patent/AU1869801A/en not_active Abandoned

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