TECHNICAL FIELD

The disclosure relates to a method of producing a veneered element and such a veneered element.

TECHNICAL BACKGROUND

Floor coverings having a wooden surface may be of several different types. Solid wood flooring is formed of a solid piece of wood in form of a plank. Engineered wood flooring is formed of a surface layer of wood glued to a core. The core may be a lamella core or a wood-based panel such as plywood, MDF or HDF. The wooden surface layer may as an example have a thickness of 2-10 mm.

A wooden floor covering may also be formed by gluing a wood veneer to a core, for example, a wood-based panel such as particleboard, MDF or HDF. Wood veneer is a thin wood layer, for example having a thickness of 0.2-1 mm. A flooring with a separate surface layer glued to a core of for example HDF or plywood is more moisture stable than solid wood floorings.

Compared to solid wood and engineered wood floorings, wood veneer floorings can be produced to a lower cost since only a thin wood layer is used. However, a wood veneer layer cannot be sanded as a solid wood or engineered wood flooring can be.

As an alternative to wood floorings, laminate floorings are also available. Direct pressed laminated flooring usually comprises a core of a 6-12 mm fibre board, a 0.2 mm thick upper decorative surface layer of laminate and a 0.1-0.2 mm thick lower balancing layer of laminate, plastic, paper or like material.

A laminate surface conventionally comprise two paper sheets, a 0.1 mm thick printed decorative paper and a transparent 0.05-0.1 mm thick overlay intended to protect the decorative paper from abrasion. The transparent overlay, which is made of α-cellulose fibres, comprises small hard and transparent aluminium oxide particles, which gives the surface layer a high wear resistance.

The printed decorative paper and the overlay are impregnated with melamine resin and laminated to a wood fibre based core under heat and pressure. The two papers have prior to pressing a total thickness of about 0.3 mm and they are after pressing compressed to about 0.2 mm.

A wood veneer may have a lower impact resistance than laminate floorings and the production cost is high, compared to laminate floorings, when high quality veneers are to be used.

Recently new “paper free” floor types have been developed with solid surfaces comprising a substantially homogenous powder mix of fibres, binders and wear resistant particles referred to as WFF (Wood Fibre Floor). The mix is applied on a wood-based panel such as MDF or HDF, and subsequently applying heat and pressure to the mix to form a surface layer on the panel. Such a flooring and process are described in WO 2009/065769.

WO 2009/065769 also discloses a thin surface layer such as wood veneer layer, which is applied on a sub-layer comprising, for example, cork or wood fibres mixed with a binder. The sub-layer is applied on wood fibre based core.

U.S. Pat. No. 2,831,794 discloses a process for manufacturing veneer panels. A green veneer is applied on a mat of resin coated core particles of ligno-cellulose fibrous particles. Adhesive is applied on the veneer to bond the veneer to the fibrous core, and to form a dense surface zone in the fibrous core. The material of the core serves to fill knot holes or open flaws in the veneer. When heat and pressure is applied, the result is the formation of a panel, with the surface layer of the particles filling whatever flaws or holes would otherwise the present in the veneer.

U.S. Pat. No. 2,419,614 discloses a coated wood product wherein a plywood is coated by a covering or overlay material consisting of mixtures of sawdust and synthetic resin. The veneer layer is coated by the covering or overlay material such that the veneer is no longer visible. The covering forms the uppermost layer of the product.

In the above description, the different types of product have been described with reference to floorings. However, the same material and problems applies for other types of building panels such as wall panels, ceiling panels, and for furniture components.

SUMMARY

It is an object of at least embodiments of the disclosure to provide an improvement over the above described techniques and known art.

A further object of at least embodiments of the disclosure is to improve the wear resistance of a veneer surface.

A further object of at least embodiments of the disclosure is to reduce the cost for producing surface with an attractive design.

A further object of at least embodiments of the disclosure is to use veneers of low quality and/or thin thickness.

A further object of at least embodiments of the disclosure is to provide a wood veneer surface having the look of a solid wood surface.

A further object of at least embodiments of the disclosure is to provide a veneer surface having an attractive design.

A further object of at least embodiments of the disclosure is to control the design of a veneer surface.

At least some of these and other objects and advantages that will be apparent from the description have been achieved by a method of producing a veneered element, comprisingproviding a substrate,applying a sub-layer on a first surface of the substrate,applying a veneer layer on the sub-layer, andapplying pressure to the veneer layer and/or the substrate, such that at least a portion of the sub-layer permeates through the veneer layer.

Said at least a portion of the sub-layer may permeate partly through, the veneer layer, or may permeate completely through the veneer layer.

Preferably, the method further comprises controlling a design of the veneer layer by determining a level of permeation of the sub-layer through the veneer layer. Determining a level of permeation may involve selecting or adjusting the permeation. This may involve selecting or adjusting a fluid pressure of the sub-layer when applying pressure.

By determining is, for example, meant determining by visual impression of the design of the veneer layer.

Preferably, at least a portion of the sub-layer is visible at the surface of the veneer layer facing away from the substrate.

The substrate is preferably a pre-fabricated substrate. Preferably, the substrate is manufactured in a preceding manufacturing process.

An advantage of at least certain embodiments is that the surface design of the veneered element may be changed or altered by a portion of the sub-layer permeating through the veneer. By applying pressure to the veneer layer and/or the substrate, a part of the sub-layer flows through pores, or cracks or holes, of the veneer such that a part of the sub-layer becomes visible at the surface of the veneer facing away from the substrate. Thereby, the design of the veneer is changed, especially if the sub-layer comprises pigments. A new design can be created, or features of the veneer such as cracks and knots can be intensified by the sub-layer being visible at the surface of the veneer.

The veneer layer forms the visible surface of the veneered element. The design of the veneer layer, permeated by at a least a portion of the sub-layer, forms the design of the veneered element.

The veneer layer may also be reinforced by being arranged on the sub-layer. Further, the veneer layer may obtain improved wear resistant properties by being at least partly impregnated by the sub-layer. The sub-layer arranged under the veneer layer may also improve impact resistance properties of the veneer. The sub-layer may comprise a binder or lacquer giving the veneer improved wear resistant properties. The sub-layer may also comprise wear resistant particles.

Since the sub-layer also flows into the substrate during pressing, the sub-layer provides improved impact, surface soundness, adhesive capacity, reduced swelling, etc.

Furthermore, an advantage of at least certain embodiments is that the sub-layer may fill any cracks, holes, or knots of the veneer layer. Thereby, there is no need, or at least a reduced need, to putty cracks, holes or knots of the veneer layer. Thereby, a costly operation often made by hand is eliminated or at least reduced by arranging the veneer layer on a sub-layer when pressing the veneer to the substrate.

By arranging the veneer on the sub-layer, and by at least a part of the sub-layer flowing through the veneer such that cracks, cavities or knots are filled by the sub-layer, a thinner veneer may be used, or a veneer of lower quality may be used, for example, containing more irregularities and defects.

Furthermore, by including pigments in the sub-layer, the veneer may be coloured. A glazing effect, a lazuring effect and/or staining effect may be obtained.

By including additives to the sub-layer, the properties of the veneer layer may be changed. For example, sound-absorbing fillers, such as cork particles, may be added to the sub-layer to improve the sound absorbing properties of the veneered element. Anti-static agents may be added to the sub-layer. Additives improving the heat transfer of the veneered element may also be added.

In an embodiment wherein the substrate is a core, the core and the veneered element being bonded to the core form a building panel or a furniture component. The building panel may be a floor panel, a ceiling panel, a wall panel, a door panel, a worktop, skirting boards, mouldings, edging profiles, etc.

In an embodiment, the veneered element is formed as a separate element, which later may be adhered to a component. The substrate may be a carrier for the veneer layer and the sub-layer, or may be a temporary carrier from which the veneer layer and the sub-layer later are removed.

The method may further comprise controlling permeation of the sub-layer through the veneer layer. Thereby, the design and appearance of the surface may be varied and controlled by varying and controlling fluid pressure, binder concentration, type of binder, filler concentration, veneer properties, etc. By controlling these parameters, the amount of the sub-layer which permeates the veneer layer can be controlled, and thereby the design of the veneer layer can be changed in a controlled manner.

The method may further comprise processing the veneer layer by abrasive machining prior to applying pressure to the veneer layer and/or the substrate. The method may further comprise brushing the veneer layer prior to applying pressure to the veneer layer and/or the substrate. By abrasive machining the veneer layer, material from the veneer layer is mechanically removed.

In one embodiment, controlling permeation of the sub-layer through the veneer layer may comprise abrasive machining the veneer layer prior to applying pressure to the veneer layer and/or the substrate.

In one embodiment, controlling permeation of the sub-layer through the veneer layer may comprise brushing the veneer layer prior to applying pressure to the veneer layer and/or the substrate.

By abrasive machining and/or brushing the veneer layer, holes, cavities and/or cracks are formed in the veneer layer. Abrasive machining and/or brushing the veneer layer may enlarge existing holes, cavities and/or cracks, and/or form new holes, cavities and/or cracks. By forming, or enlarging existing, holes, cavities, and cracks, the sub-layer permeates more easily through the veneer layer. Thereby, the permeation of the sub-layer through the veneer layer is increased, and the design of the veneer layer can be controlled and changed.

The veneer layer may be brushed prior to being applied on the sub-layer, or when being applied on the sub-layer. The same applies to abrasive machining of the veneer layer.

Abrasive machining of the veneer layer may be performed by an abrasive tool. The abrasive tool may be a brushing device. The abrasive tool may be brush filaments, abrasive strips, sanding belts, sanding disks, grinding wheels, cutting tools such as water jet, etc.

The veneer layer may be processed by an abrasive tool such that veneer material with low density is removed while veneer material with higher density remains. The abrasive tool may be harder than at least portions of the veneer layer.

Both surfaces, or only one of the surfaces, of the veneer layer, may be machined abrasively. A lower surface of the veneer layer adapted to face the sub-layer may be machined. An upper surface of the veneer layer adapted to facing upwards may be machined. By machining abrasively the upper surface of the veneer layer, flowing of the sub-layer in a direction parallel to the surface of the veneer layer is increased. By machining abrasively the lower surface of the veneer layer, the sub-layer may fill cavities formed in the lower surface of the veneer layer.

Machining abrasively may be performed at different levels in the veneer layer. Cavities, holes and/or cracks may be extending through the veneer layer, or may extend partly through the veneer layer. The depth of the cavities, holes and/or cavities may substantially equal the thickness of the veneer layer, or may be less than the thickness of the veneer layer.

Machining the veneer layer prior to applying pressure may also be combined with machining performed after pressure has been applied to form the veneered element.

The abrasive machining and/or processing of the veneer layer may, for example, include brushing, sanding, grinding, blasting, local compressing, tearing, splitting, compressed air, etc.

Controlling permeation of the sub-layer through the veneer layer may comprise processing the veneer layer prior to applying pressure to the veneer layer and/or the substrate. Such processing may include heating, for example, by thermal radiation, convective heating, and/or conductive heating, steaming, and/or drying veneer prior to applying pressure to the veneer layer and/or the substrate. Permeation may also be controlled by applying additives to the veneer layer adjusting the permeation of the sub-layer through the veneer layer. As an example, an additive reducing permeation of the sub-layer through the veneer layer, for example, by blocking permeation, may be applied. Alternatively or in combination, an additive degrading the veneer layer, thus increasing permeation may also be applied on the veneer layer.

Controlling permeation of the sub-layer through the veneer layer may comprise compressing the veneer prior to applying the veneer on the sub-layer. By compressing the veneer, the density of at least portions of the veneer is increased, thus reducing permeation of the sub-layer through at least portions of the veneer layer during pressing. Compressing may be performed by pressing plates and/or rollers with embossings. The compression, preferably combined with heating, preferably heating to a temperature exceeding 100° C., may result in a remaining increase in density.

Controlling permeation of the sub-layer through the veneer layer may comprise controlling a fluid pressure of the sub-layer during pressing. A fluid pressure of the sub-layer is formed by applying pressure to the veneer layer and/or the substrate. In one embodiment, the sub-layer may be in fluid form when applied on the substrate, or may be transformed into fluid form by applying heat and pressure, such as the case for a thermosetting binder applied in powder form. By increasing the fluid pressure, a larger amount of the sub-layer permeates through the veneer layer, and/or longer way through the veneer layer, and/or permeates into the veneer layer in a direction parallel to a plane of the veneer layer, such that larger spots of the sub-layer are visible from the surface of the veneer layer. Furthermore, when the sub-layer includes a thermosetting binder, the cross-linking reaction results in forming of condensation water, transforming into steam under the applied heat and pressure, thereby increasing the fluid pressure. The cross-linking also results in solidification of a part of the sub-layer, thus further pressing remaining uncured binder of the sub-layer.

Controlling the fluid pressure of the sub-layer may comprise adjusting a concentration of a binder in the sub-layer. By increasing the concentration of the binder in the sub-layer, the part of the sub-layer that flows when heat and pressure are applied increases, and thereby a larger part of the sub-layer may permeate through the veneer layer. When the binder flows, the binder brings any pigments to upper parts of the veneer.

Controlling the fluid pressure of the sub-lay may comprise adjusting the type of binder used in the sub-layer. Different binders have different properties, such as how fast the binder cures and hardens. When using a binder that cures rapidly, less permeation of the sub-layer occurs compared to a binder that cures more slowly, thus being in liquid form over a longer time and allowing permeation through the veneer layer.

The design of the veneered element may also be performed by controlling a ratio between pigment and binder of the sub-layer. By adjusting the binder concentration, and the ratio pigment/binder, the amount of pigment permeating through the veneer layer can be controlled. The binder brings the pigments when the binder flows during pressing. The amount of pigment that permeates through the veneer layer may also be controlled and adjust by choosing the size of the pigment particles. Smaller pigment particles permeate more easily through the veneer layer than larger pigment particles.

Controlling the fluid pressure may comprise adjusting the moisture content of the sub-layer. By increasing the moisture content of the sub-layer, more steam is formed when heat and pressure is applied, which forms an increased fluid pressure and thereby increased permeation of the sub-layer through the veneer layer. Contrary, if less permeation is desired, the moisture content of the sub-layer may be decreased, for example by drying before pressing.

Controlling the fluid pressure may comprise adjusting the pressure applied to the veneer layer and/or the substrate. By increasing the pressure, the fluid pressure of the sub-layer is increased. By increasing the fluid pressure, a larger amount of the sub-layer permeates through the veneer layer as described above.

Controlling the fluid pressure may comprise generating a gas pressure in the sub-layer. The gas pressure increases the fluid pressure of the sub-layer, thus resulting in that the sub-layer permeates through the sub-layer in an increased extent.

Generating the gas pressure may comprise including chemical and/or physical blowing agents in the sub-layer. When reacting, the chemical and/or physical blowing agents form a gas pressure in the sub-layer.

Controlling permeation of the sub-layer through the veneer layer may comprise including fillers in the sub-layer. By increasing the amount of fillers in the sub-layer, the less the sub-layer permeates through the veneer layer. The fillers may reduce flowing of the sub-layer such that the sub-layer permeates more difficult through the veneer layer. Furthermore, some fillers, for example, wood particles, absorb the binder to a certain degree, thereby reducing the amount of free binder, which may permeate through veneer layer, and thereby also reduce the fluid pressure. The fillers may comprise wood particles such as lignocellulosic and/or cellulosic particles. The wood particles may be at least partially bleached.

Controlling the permeation of the sub-layer through the veneer layer may comprise adjusting the thickness of the sub-layer, for example by adjusting the amount of the sub-layer applied. If the sub-layer is applied as a powder, controlling the permeation of the sub-layer through veneer layer may be controlled by adjusting the amount of powder applied for forming the sub-layer. By applying a larger amount of powder for forming the sub-layer, the sub-layer permeates through the veneer layer to an increased extent.

Controlling permeation of the sub-layer through the veneer layer may comprise forming holes and/or cracks in the veneer layer. The holes and/or cracks facilitate the sub-layer to permeate through the veneer layer. Forming holes and cracks reduces resistance for the sub-layer for permeating through the veneer layer. Forming holes, cavities and/or cracks may be performed by brushing prior to applying pressure to the veneer layer and/or the substrate. The holes, cracks and cavities may be pre-existing but enlarged, and/or may be newly formed holes, cracks and cavities.

Controlling permeation of the sub-layer through the veneer layer may comprise controlling a thickness of the veneer layer. The thinner veneer layer, the less distance for the sub-layer to travel until the sub-layer is visible on the top surface of the veneer layer.

Said at least a portion of the sub-layer may permeate through pores of the veneer layer. A veneer is a porous structure, including pores in which the sub-layer may permeate.

Said at least a portion of the sub-layer may permeate through cracks and holes of the veneer layer.

The veneer layer may comprise a wood veneer, a cork veneer, or stone veneer. The veneer layer has a porous structure, and a portion of sub-layer may permeate through the veneer layer. The wood veneer may be cut veneer, sawn veneer, rotary cut veneer, and/or half-round cut veneer.

The sub-layer may comprise a binder.

The sub-layer may comprise a thermosetting binder. The thermosetting binder may be an amino resin such as melamine formaldehyde, urea formaldehyde, phenol formaldehyde, or a combination thereof. The thermosetting binder simultaneously bonds the veneer layer to the sub-layer. When heat and pressure is applied to the sub-layer, the thermosetting binder becomes fluid before cross-linking takes place. The applied heat and pressure results in curing of the thermosetting binder of the sub-layer, simultaneously as bonding the veneer layer to the sub-layer.

The sub-layer may comprise a thermoplastic binder. The thermoplastic binder may be polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polyurethane (PU), polyvinyl alcohol (PVOH), polyvinyl butyral (PVB), and/or polyvinyl acetate (PVAc), or a combination thereof. The thermoplastic binder simultaneously bonds the veneer layer to the sub-layer.

The sub-layer may be substantially formaldehyde free.

The sub-layer may further comprise pigments. Thereby, the veneer layer may be coloured by the parts of the sub-layer penetrating through the veneer layer. The sub-layer may be pigmented to one or several different colours. By using a sub-layer containing different colours, different parts of the veneer layer and/or different veneers may obtain different colours. The pigments may be brought by the flowable binder to an upper part of the veneer layer. The pigments may provide a colour being darker or lighter than the natural colour of the veneer. The pigment may be white, such as TiO2. White pigments, such as TiO2, may be combined with at least partially bleached wood particles, for example, to form a pale staining of the veneer.

The sub-layer may comprise wear resistant particles. Wear resistant particles which are brought by the binder of the sub-layer to an upper part of the veneer layer provide wear resistance to the veneer layer.

The substrate may be a wood-based board, for example, a wood-fibre based board such as MDF or HDF, or plywood. The substrate may be a Wood Plastic Composite (WPC). The substrate may be a mineral composite board. The substrate may be a fibre cement board. The substrate may be magnesium oxide cement board. The substrate may be a ceramic board. The substrate may be a plastic board such as a thermoplastic board.

The substrate may be a sheet such as paper sheet.

The fluid pressure may be uniformly distributed. Thereby, an essentially uniform permeation of the sub-layer through the veneer layer may be obtained, if the veneer layer has an essentially uniform structure. An essentially uniform colouring of the veneer layer may also be obtained, if the veneer layer has an essentially uniform structure.

The fluid pressure may be non-uniformly distributed. By the fluid pressure being non-uniformly distributed, the degree of permeation of the sub-layer may vary of the surface of the veneer and non-uniform pattern may be obtained.

The method may further comprise digital printing a pattern in the sub-layer prior to applying the veneer layer on the sub-layer. The method may further comprise digital printing a pattern on the veneer layer, prior or after pressing.

The veneer layer may be a continuous layer or a discontinuous layer of veneers. The veneer layer may be formed of several veneers pieces. The veneer layer may be formed of several pieces of veneer, forming a patchwork of veneers. The sub-layer may fill the gaps between the veneer pieces.

After pressure has been applied, the veneer layer may comprise embossed portions. A portion of the sub-layer may be more compressed under an embossed portion than under a non-embossed veneer layer portion.

The embossed portions may be naturally occurring after pressing. For wood veneers having a porous structure, such as hard wood (e.g., angiosperm), porous portions of the veneer form embossed portions after pressing, since these portions do not spring back from their compressed state when the pressure is released. These porous portions are filled with the binder of the sub-layer during pressing. Then the binder cures and/or hardens, the binder locks the position of the porous portions in the compressed state. The portions of veneer having high density, i.e. being non-porous, are compressed during pressing but spring back when the pressure is released, thus forming protrusions of the surface layer. The high-density portions do not absorb enough binder from the sub-layer to be locked by the hardened binder after pressing.

For wood veneer having a non-porous structure, such as soft wood (e.g., gymnosperm), the summer wood annual rings (also called late wood annual rings), having high density, are not compressible during pressing. Instead, the summer wood annual rings are pressed into the sub-layer such that the sub-layer is compressed. The summer wood annual rings form embossed portions of the surface layer. The spring wood annual rings (also called early wood annual rings) are compressible during pressing. During pressing, the spring wood annual rings are compressed. Then the pressure is released, the spring wood annual rings spring back, and form protrusions.

The embossed portions of the surface layer may also be formed by pressing by an embossed pressing device, such as an embossed press plate.

The method may further comprise applying a balancing layer on a surface of the substrate being opposite the veneer layer. The balancing layer may be a powder based balancing layer being applied as a powder. The powder based balancing layer may comprise wood particles such as lignocellulosic and/or cellulosic particles and a binder, preferably a thermosetting binder such as an amino resin. The balancing layer may be a resin impregnated paper, preferably impregnated with a thermosetting binder.

A second aspect of the disclosure relates to a veneered element. The veneered element comprises a substrate, a sub-layer arranged on the substrate, and a veneer layer arranged on the sub-layer, wherein at least a portion of the sub-layer is permeated through the veneer layer.

At least a portion of the sub-layer may be visible at the surface of the veneer facing away from the substrate.

The sub-layer may further comprise pigments.

The sub-layer may comprise fillers. The fillers may be particles or fibres, for example wood fibres or particles, or mineral particles or fibres. The wood particles may be lignocellulosic particles and/or cellulosic particles. The wood particles may be at least partially bleached.

The sub-layer may comprise wear resistant particles.

The substrate may be a wood-based board.

The at least a portion of the sub-layer may be permeated through pores of the veneer layer.

The veneer layer may comprise a wood veneer, a cork veneer, or a stone veneer.

The veneer layer may comprise embossed portions. A portion of the sub-layer may be more compressed under an embossed portion than under a non-embossed veneer layer portion.

The embossed portions may be naturally occurring after pressing. For wood veneers having a porous structure, such as hard wood (e.g., angiosperm), porous portions of the veneer form embossed portions after pressing, since these portions do not spring back from their compressed state when the pressure is released. These porous portions are filled with the binder of the sub-layer during pressing. Then the binder cures and/or hardens, the binder locks the position of the porous portions in the compressed state. The portions of veneer having high density, i.e. being non-porous, are compressed during pressing but spring back when the pressure is released, thus forming protrusions of the surface layer. The high-density portions do not absorb enough binder from the sub-layer to be locked by the hardened binder after pressing.

For wood veneer having a non-porous structure, such as soft wood (e.g., gymnosperm), the summer wood annual rings (also called late wood annual rings), having high density, are not compressible during pressing. Instead, the summer wood annual rings are pressed into the sub-layer such that the sub-layer is compressed. The summer wood annual rings form embossed portions of the surface layer. The spring wood annual rings (also called early wood annual rings) are compressible during pressing. During pressing, the spring wood annual rings are compressed. Then the pressure is released, the spring wood annual rings spring back, and form protrusions.

The embossed portions of the surface layer may also be formed by pressing by an embossed pressing device, such as an embossed press plate.

The method may further comprise applying a balancing layer on a surface of the substrate being opposite the veneer layer. The balancing layer may be a powder based balancing layer being applied as a powder. The powder based balancing layer may comprise wood particles such as lignocellulosic and/or cellulosic particles and a binder, preferably a thermosetting binder such as an amino resin. The balancing layer may be a resin impregnated paper, preferably impregnated with a thermosetting binder.

The veneered element according to the second aspect of the disclosure incorporates all the advantages of the method, which previously has been discussed, whereby the previous discussion is applicable also for the veneered element.

According to a third aspect of the disclosure, a method of producing an element is provided. The method comprisesproviding a substrate,applying a sub-layer on a first surface of the substrate,applying a surface layer having a porous structure on the sub-layer, andapplying pressure to the surface layer and/or the substrate, such that a least a portion of the sub-layer is permeating through the porous structure of the surface layer.

