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
  • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/06—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to 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
  • B27K3/0271—Vapour phase impregnation
• • 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

Definitions

• the invention relates to treatment of resin-containing wood.
• the wood has an aesthetic appearing surface and of course good strength and durability. This is particularly relevant within the field of manufacturing window-frames and doors of wood. In such uses it is important that the wood appears substantially free of errors and free of cracks and knots. But in order to use as much as possible of the wood, without repairing all errors, a number of small cracks and small knots are normally allowed.
• the problem is enhanced with modern forestry where the trees are cut down all through the year including in the springtime where the turgescence is at the highest level.
• the methods of preservation may enhance the exudation of the resin, as preservation often includes use of organic solvents which will dissolve the resin and cause it to flow more easily.
• JP3166905A discloses a method where wood is impregnated with a melamine-based resin, followed by drying with high frequent heating (micro-waves) .
• Another method is immersion of the wood in hot water followed by immersion in an impregnating liquid which demobilizes the resin.
• the known methods all comprise application of at least one agent to the surface of the wood. This is a step in the production line which is costly and requires extra time. Moreover the known methods are often based on the use of chemical agents which are not environment- friendly, and may cause trouble when the wood is to be removed as waste-material.
• the sealing of the surface of the wood will loose its effect if the sealing, which is relatively thin, is destroyed. Hereby it is possible for the resin to exudates through the broken parts of the sealing.
• the object of the present invention is to provide a method for treating resin-containing wood, which will provide a permanent sealing of at least a part of the surface of the wood to prevent exudation of resin.
• Another object of the present invention is to provide a method for treating a resin-containing wood substrate which is cost effective and time saving to carry out.
• a further object of the present invention is to provide a method for treating resin-containing wood that does not require application of a sealing or a coating agent.
• the invention is based on the surprising finding that it is possible to harden the resin in a resin-containing wood substrate.
• the natural present resin is normally under pressure and exudes from the wood through small openings in the bark of the trees.
• the trees are cut down and de-barked for industrial use a lot of openings in form of canals, cracks and knots are laid open. This will of course heavily enhance the natural tendency of the wood to exude resin to the surface of the wood leaving sticky spots on the surface.
• the natural resin will harden and the stickiness will vanish, but the natural hardening of the resin is a process, which continues for several years.
• the hardened resin appears with a smooth relatively hard surface like the one of synthetic hard plastic.
• the natural present resins in wood are a relatively complex mixture of various substances including terpenes.
• the natural resin in wood comprises normally oleoresins like monoterpenoids, diterpenoids and parenchyma resin comprising triterponoids and steroids.
• the resins may comprise a mixture of non-volatile, partly unsaturated compounds including esters and free acids.
• the resin forms an extremely sticky gum which is capable of undergoing a certain slow hardening when exposed to the air.
• the hardening of the resin in particular the resin in the surface of the wood appears substantially instant. In fact the time for hardening is reduced to seconds or a few minutes.
• the method provides wood with a dry and relatively hard surface without any lose knots, indentations or holes and which has excellent properties for further treatment like application of paint or other coatings .
• the invention provides a method for treatment of resin- containing wood substrate, which method comprises the step of hardening at least a part of the resin in said wood substrate.
• the resin which is hardened, is the natural present resin in the wood substrate.
• the hardening of the resin will prevent the resin to exude from the wood substrate and hereby prevent the formation of sticky spots of resin on the surface of the wood substrate.
• the term wood substrate designates a substrate for the hardening process which may be a typically shaped wood article, structural wood, timber, poles, etc., but encompasses also material comprising comminuted wood such as chips or building plates, etc.
• the resin is hardened in a layer extending from the surface of the wood substrate and at least some distance into the wood, preferably said layer has a thickness between 0,001 - 5,0 cm, more preferably a thickness between 0,01 - 1,0 cm.
• the resin is hardened in a layer extending from the surface of the wood substrate and at least some distance into the wood substrate.
• at least a surface layer of the wood substrate comprises hardened resin.
• the surface layer seals the surface and prevents un-hardened resin within the wood substrate to exude to the surface of the wood substrate.
• substantially all resin present in the wood substrate is hardened. This method will be advantageous, if the wood substrate is to be subjected to a further treatment like cutting or drilling. Although such treatments lay new surfaces of the wood substrate open, no resin will exude to these surfaces .
• the resin present in canals and/or cracks and/or knots in the wood substrate is hardened.
• the natural present resin in wood is flowing in canals or resin canals from which in unhardened condition it may penetrate to the surface of the wood substrate e.g. via cracks or knots in the wood substrate.
• the resin is hardened by cross-linking of monomers and/or polymers in the resin by use of UV- radiation, IR-radiation, high frequent heating, laser- radiation, corona treatment, plasma treatment and/or heat-treatment in fluid bed.
• the resins are cross-linked at elevated temperatures.
• UV light may be applied with wave-lengths within 250 to 400 nm and 300 - 600 WPI lamps is useful.
• the treatment of the surface disclosed above may be in combination with or subsequently followed by a treatment of the surface with a suitable gas, e.g. oxygen or ozone.
• a suitable gas e.g. oxygen or ozone.
• the surface to be treated is moved in the longitudinal direction with a speed from 0,5m pr. minute and up till i.e. over 30 m/min.
• the amount, size and position of knots are being recorded using standard wood- recognition equipment equipped with standard image processing and evaluation equipment. If the knots or cracks identified in the wood surface are of the potential dangerous kinds, i.e. of the sticky or exudating type a signal is sent to a treatment station
• the beam can be of different types such as UV radiation (UV light), a laser, or IR or microwave type.
• UV radiation UV light
• a laser or IR or microwave type.
• the requirement is that it has the ability to accelerate the natural bonding (cross-linking) taking place in natural resin when exposed to normal weather conditions i.e. daylight and air. This effect will mainly be caused by the locally heating process of the resin and thus accelerate the natural ageing processes within the surface of the resin facing the exterior of the wooden profile of the resin.
• the hardening of the resin may be enhanced by subjecting the monomers and/or polymers in the resin to a treatment that will increase the number of free radicals significantly. Hereby it is possible to reduce the time required for hardening the resin significantly.
• the base monomer is isoprene like in natural rubber, therefore the different polymers contain double bonds which can be the basis for derivatisation in the form of oxidation, coupling, addition of other groups, etc.
• the isoprene-type double bonds are the basis for cross- linking and hardening of the resin.
• the resin is hardened by cross-linking of monomers and/or polymers in the resin by applying a reactive chemical, preferably selected among sulphur, sulphur trioxide, peroxide, nitrogen-oxides, phosphor, halogens or ozone.
• a reactive chemical preferably selected among sulphur, sulphur trioxide, peroxide, nitrogen-oxides, phosphor, halogens or ozone.
• the reactive chemical is preferably applied in a gaseous or vapour state.
• the resin-containing wood substrate is subjected to a heat-treatment step after a reactive chemical has been applied.
• The- heat treatment may be heating by IR-light, microwaves or by hot steam e.g. under pressure.
• the cross- linking is initiated by reactive chemicals, whereby the resin is vulcanised to provide a smooth and hard surface.
• the resin is further cross-linked to the natural present cellulose in the wood substrate.
• a double vulcanisation is created as the resin is cross-linked to resin and cellulose of the wood substrate.
• the bondings may be formed via double bonds in the resin and free OH-groups of the cellulose. It is possible to obtain strong bindings between resin and cellulose and an effective sealing of the surface can be achieved.
• the cross-linking process can be initiated by UV-light, high frequent heating, reactive chemicals, etc., as described above
• the canals, cracks and knots can be identified using a known wood sorting system like WoodEye from the company Innovativ Vision AB, Sweden. Once the canals, cracks and knots are identified, the resin present herein can be hardened e.g. by subjecting the canals, cracks or knots to UV-light or high frequent heating which will initiate the cross-binding and hardening process of the resin. The process can be controlled by a computer and run automatically.
• the hardening by cross-linking of the resin naturally present in the canals, cracks and/or knots is done by use of UV-radiation.
• a preferred embodiment of the method according to the invention further comprises the step of coating said resin-containing wood substrate with a coating material e.g. shellac or paint.
• a coating material e.g. shellac or paint.
• the first step comprises hardening of the resin naturally present in the wood substrate.
• the surface of the wood substrate is coated with a coating material, which are allowed to harden or dry.
• the resin-containing wood substrate is coated with a coating material wood and the resin in the wood substrate and is hardened and the coating material is hardened dried simultaneously.
• the entire wood substrate may be coated or the coating may be limited to the canals, cracks and/or knots in the wood substrate.
• Coating of the wood substrate may be an advantage when the wood substrate is designated for use in wet environments with changing temperatures .
• the invention also relates to a resin-containing wood substrate wherein at least a part of the resin is hardened according to the above-described method.
• Embodiments of the invention are illustrated in the following examples.
• a resin containing wood substrate constituted by a lath of pinewood having the dimensions 4 x 8 x 50 cm is subjected to manual inspection were openings of resin canals and/or cracks and/or knots is visually identified and marked with a red ink.
• the identified resin canals and/or cracks and/or knots are subjected to a treatment with UV light.
• the marked spots on the surface of the wood are subjected to a treatment with UV-light from a medium pressure mercury vapour lamp (300 WPI, approx 365 n ) from a distance between 10 and 15 cm for 20 to 40 seconds. It is observed that the naturally occurring resin in the treated spots are hardened in a thickness extending from the surface and into the wood from 0,2 mm to 0,8 mm.
• a medium pressure mercury vapour lamp 300 WPI, approx 365 n
• a resin containing wood substrate constituted by a lath of pinewood having the dimensions 4 x 8 x 50 cm is subjected to a treatment with UV light on one surface.
• the surface which is subjected to treatment has the dimensions 8 x 50 cm.
• the surface is moved in the longitudinal direction with a speed of approximately 0.5 m/min and exposed to UV light from a fixed UV lamp.
• the UV lamp is a medium pressure mercury vapour lamp (300 WPI, approx 365 nm) placed at a distance of approximately 10 cm over the moving surface, which is treated.
• a wood substrate constituted by a lath of pinewood with a resin filled crack having the dimensions of 4 x 2 mm was subjected to a treatment of an UV radiation source. With an intensity level of 500 mW/cm 2 at 450 +/- 25 nm, and an exposure time of 40 sec and a distance between the source and the substrate at 1,5 mm. This specimen had a measured mean shear-peel bond strength at 12,3 MPa.
• Example 3B A wood substrate constituted by a lath of pinewood with a resin filled crack having the dimensions of 4 x 2 mm was subjected to a treatment of an argon laser source. With an intensity level of 500 mW/cm 2 , and an exposure time of 5 sec and a distance between the source and the substrate at 1,5 mm. This specimen had a measured mean shear-peel bond strength at 11,8 MPa.

Landscapes

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

Priority Applications (1)

Applications Claiming Priority (3)

Publications (2)

Family

ID=8159544

Family Applications (1)

Country Status (5)

Families Citing this family (2)

Family Cites Families (4)

• 2001
  • 2001-06-07 AT AT01940231T patent/ATE260741T1/de not_active IP Right Cessation
  • 2001-06-07 EP EP01940231A patent/EP1294546B1/de not_active Expired - Lifetime
  • 2001-06-07 WO PCT/DK2001/000392 patent/WO2001094086A2/en not_active Ceased
  • 2001-06-07 AU AU2001273872A patent/AU2001273872A1/en not_active Abandoned
  • 2001-06-07 DE DE60102240T patent/DE60102240T2/de not_active Expired - Lifetime

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events