IT201800003227A1 - COATED WOOD PANEL, ITS USES AND RELATED PRODUCTION PROCESS. - Google Patents

Description

COATED WOODEN PANEL, ITS USES AND RELATIVE

PRODUCTION PROCESS

The present invention relates to a coated wooden panel and the related preparation process. This panel is particularly suitable as a substrate in the production of ennobled panels. The present invention also relates to a faced panel obtained starting from the aforementioned coated wooden panel as well as a production process of said faced panel.

As is known, the faced wood panels are obtained by applying a finishing layer (or finishing layer), such as a sheet of paper pre-impregnated with a thermosetting resin (so-called finishing paper) or a sheet of polymeric material (e.g. PVC ), on one or both sides of a wooden base (substrate) in order to impart a smooth and / or decorated surface to the finished panel. The finishing can also give the panel properties of resistance to moisture, wear and / or make it more easily paintable and further decoratable.

The faced panels are used in various industrial sectors, including: the furniture sector, for example for the production of furniture, doors, flooring and window coverings; the construction sector, for example for the production of formworks or for the preparation of light walls; the naval and motor vehicle sector (eg. caravans, trailers, etc.), for example for the preparation of interior environments.

The wooden bases used for the manufacture of melamine panels are, for example, plywood bases, chipboard bases, ligno-cellulosic fiber bases and solid wood bases.

In order for the faced panels to have adequately smooth surfaces, it is essential that the face of the wooden base below the finishing layer has a surface that is as smooth and free of defects as possible. In the presence of surface defects, in fact, the coating materials (e.g. finishing paper and polymeric film) do not adhere perfectly to the wooden base or, even where they adhere well, do not completely hide the defects of the wooden base, which are therefore visible. also on the melamine panel.

This technical problem is particularly felt in the case of faced panels in which the wooden base is a plywood base. As is known, plywood is a product formed by a multiplicity of thin layers of wood (so-called, peeled; in English, veneers), held together by an adhesive composition.

In the case of the ennobling of plywood panels, in the state of the art, in order to overcome the problem of surface defects of the plywood base which are visible even after the finishing, we generally resort to the use of plywood made with high quality veneers (e.g. veneer quality class I according to the UNI-EN 635-1 standard). In particular, for this purpose, veneers of exotic wood essences are generally used, such as ilomba, fromager, etc., which however have a relatively high cost and are often not easily available on the market. Depending on the quality required for the faced panel, where possible the high quality veneer is used to form only the outermost layers of the plywood base, while the internal layers are made up of lower quality veneers.

As an alternative to the use of high quality veneers, to obtain defect-free ennobled panels, in the state of the art it is also known to repair surface defects of the plywood base, before applying the finishing layer. The repair can be carried out in different ways, for example: (i) by filling the defects with polymeric compositions; (ii) by removing the defective portion of the surface and subsequent gluing of a joint or a patch made of flawless veneer. The plywood repair operations, however, being carried out manually, make the production process of the faced panels complex, time-consuming and expensive.

In consideration of the aforementioned state of the art, the Applicant has set itself the primary objective of providing a wooden panel, usable as a substrate for the manufacture of a faced panel, having one or both sides of a quality suitable for receiving an ennobling treatment. , such as the application of a sheet of finishing paper or a sheet of polymeric material, without necessarily having to use first choice wood materials or to carry out preliminary repairs of the base to be refined.

The Applicant has also set itself the goal of providing a process for the production of the aforementioned base and a process for its ennobling, which are simple to implement and economically convenient.

The Applicant has found that these and other objects, which will be better illustrated in the following description, can be achieved by forming on at least one face of a wood base a coating layer of a polyurethane polymer having certain characteristics of density and surface hardness. This coating layer has a smooth surface and has a substantially uniform density over its entire thickness, thus being particularly suitable for receiving a subsequent finishing treatment.

Furthermore, the polyurethane coating layer according to the present invention covers the defects of the wood surface very well, so that these are not visible on the faced panel. By using the coated panels according to the present invention as substrates it is possible to manufacture high quality faced panels, even using relatively low quality wood bases and without carrying out preliminary repairs.

Furthermore, in consideration of the substantial absence of surface defects that characterizes the polyurethane coating according to the present invention, the finishing layer used for any finishing (e.g. pre-impregnated papers) can be of reduced thickness compared to the thickness of the finishing layers. generally used in the state of the art.

Furthermore, the use of the coated wooden bases according to the present invention makes the production process of the faced panels simpler, quicker and cheaper, as it does not require the preliminary carrying out of repair operations of the surface defects and at the same time reduces , the production of waste.

In accordance with a first aspect, the present invention therefore relates to a coated wooden panel comprising:

- at least a wooden base having at least a first face and at least a second face opposite to said first face;

- at least a first layer of polyurethane coating having a hardness in the range 20 - 100 Shore D and density in the range 400 - 1,200 kg / m <3>, on said first face.

In accordance with a second aspect, the present invention relates to a faced panel comprising the aforementioned surface-coated wooden panel and at least one finishing layer, which is applied on at least said first polyurethane coating layer having a hardness in the range of 20 - 100 Shore. D and density in the range 400-1,200 kg / m <3>, said finishing layer being selected from: finishing paper, elastomeric polyurethane layer, polymeric material sheet.

In accordance with a third aspect, the present invention relates to a process for preparing a coated wood panel comprising:

to. providing at least a wooden base having at least a first face and at least a second face opposite to said first face;

b. depositing on at least said first face a polyurethane polymerizable composition comprising at least one organic polyisocyanate and at least one polyol;

c. polymerize said polyurethane polymerizable composition to form a first layer of polyurethane coating having a hardness in the range 20 - 100 Shore D and density in the range 400 - 1,200 kg / m <3>.

In accordance with a fourth aspect, the present invention relates to a process for producing a faced panel comprising:

the. supply the aforementioned coated wood panel;

ii. form on said first layer of polyurethane coating having a hardness in the range 20 - 100 Shore D and a density in the range 400 - 1.200 kg / m <3>, at least one finishing layer chosen from: finishing paper, polyurethane layer elastomeric, sheet of polymeric material.

In particular, if the finishing layer is a sheet of finishing paper or a sheet of polymeric material, the aforementioned step (ii) can comprise:

ii-a. overlapping said first layer of polyurethane coating with at least one finishing layer chosen from: sheet of finishing paper or a sheet of polymeric material;

ii-b. pressing said panel while said panel is heated.

In a preferred embodiment, the coated wood panel according to the invention comprises a second layer of polyurethane coating having a hardness in the range 20 - 100 Shore D and density in the range 400 - 1,200 kg / m <3>, on the second face of the wooden base, opposite to said first face.

The polyurethane coating layer that forms the aforementioned first and, optionally, second coating layer preferably has a hardness in the range 40 - 100 Shore D, more preferably in the range 60 - 100.

The surface hardness properties of the polyurethane coating layer make the coated panel processable in a similar way to wood, being able to be subjected, for example, to mechanical processing (e.g. milling, sanding, calibration, insertion of nails or screws, etc.) or the application of further coatings (eg paints).

The characteristics of density and surface hardness of the two coating layers in polyurethane material can be the same or different from each other.

For the purposes of the present invention, the Shore D and Shore A hardness values are intended to be determined in accordance with the DIN ISO 7619-1 standard.

The density of the coating layer is chosen according to the characteristics of the wood base. Preferably, the density value of the polyurethane polymer used for the coating layer is close to that of the wood base.

Preferably, the polyurethane coating layer has a density in the range 600 - 1,100 kg / m <3>, more preferably in the range 800 - 1,000 kg / m <3>.

The thickness of the polyurethane coating layer is generally chosen according to the quality of the surface of the wooden base to be coated. On surfaces with less pronounced defects, the polyurethane layer can be applied in reduced thicknesses compared to surfaces with more pronounced defects. Preferably, the coating layer in polymeric material has a thickness in the range 0.2 - 3 mm.

The polyurethane coating layer, in addition to having the aforementioned hardness characteristics, preferably has a tensile strength (DIN 53504) in the range of 1 - 20 MPa, preferably in the range of 5 - 10 MPa.

The polyurethane coating layer according to the present invention can be obtained by applying a polymerizable polyurethane composition, on one or both surfaces of the wood base, and subsequent polymerization of the applied composition. The coating layer can be adjacent to the wood base, i.e. in direct contact with it, or in contact with an intermediate coating layer (e.g. a primer).

Preferably, the polyurethane polymerizable composition comprises at least one organic polyisocyanate having two or more isocyanate groups and at least one organic compound having two or more hydrogen atoms reactive towards the isocyanate (H-reactive) groups, such as a polyol.

The polymerizable polyurethane composition can optionally comprise one or more of the following components: catalyst, chain extender (or cross-linker), water or organic solvent, blowing agent (in the case of foams), additives (e.g. pigments, surfactants, flame retardants, rheology modifiers, etc.).

Preferably, the polymerizable polyurethane composition is a two-component composition, although it is not excluded to also use single-component polyurethane compositions.

Preferably, the two-component polyurethane polymerizable composition comprises: at least a first component (component A) containing at least one polyol; at least a second component (component B) containing at least one polyisocyanate or a prepolymer having free isocyanate groups.

Preferably, component A and component B are mixed together to form the polymerizable composition to be applied on the wood base, generally just before application.

Preferably, the polyisocyanate is reacted with the polyol in a mol NCO / mol H-reactive ratio in the range from 0.2: 1 to 10: 1.

The organic polyisocyanates can be aliphatic or aromatic organic compounds. Examples of polyisocyanates usable for the purposes of the present invention are: 2,2'-diphenylmethane diisocyanate (MDI), 2,4'-diphenylmethane diisocyanate (MDI), 4,4'-diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDMI) and isophorone diisocyanate (IPDI)

The organic compounds having two or more reactive hydrogen atoms are preferably polyols, in particular polyether polyols and polyester polyols.

The aforementioned polyisocyanates, polyols and their preparation processes are known to those skilled in the art.

Examples of catalysts that can be used for the purposes of the present invention are: amines (e.g. triethylamine, dimethylcyclohexylamine, tetramethylethylenediamine, etc.), organo-metallic compounds (e.g. organotin compounds, such as tin (II) acetate, tin (II) octanoate, dibutyl tin dilaurate) and mixtures thereof. The quantity of catalyst present in the polyurethane composition depends on the type of catalyst used and, generally, is in the range 0.01 - 10 phr (part per hundred rubber), where for phr we mean parts by weight of catalyst per 100 parts by weight of polyol .

Advantageously, the polyurethane composition can also comprise at least one filler consisting, for example, of wood powder (e.g. poplar powder).

The polyurethane compositions which, once polymerized, form a coating having the characteristics of density and surface hardness according to the present invention are known to those skilled in the art and commercially available. In a preferred embodiment, rigid polyurethane foams can be used, such as for example the foams used to make so-called "imitation wood" products.

Preferably, components A and B of the polyurethane composition have a viscosity in the range of 400 - 1500 cPs (measured at 25 ° C, according to ASTM D4878–15 (component A) or ASTM D1786–16 (component B)).

These viscosity values of the polymerizable composition during the application phase allow the surface of the wood base to be optimally covered, filling the surface defects of the latter and at the same time creating a smooth surface with homogeneous density throughout the entire thickness of the coating.

The polymerizable polyurethane composition can be applied on the surface of the wood base, for example, by spraying, with a brush, with a spatula or by means of a roller or other device suitable for applying fluid compositions on a wood surface.

In some cases, before applying the coating layer, an intermediate coating layer consisting of a primer can be applied to the surface of the wood, to facilitate the formation of a more coherent, uniform and homogeneous polyurethane coating layer. The primer also favors the application of the polymerizable polyurethane composition, making the wood surface smoother and more receptive. For the purposes of the present invention, the primers known to those skilled in the art and commercially available can be used, preferably the primers based on: polyurethane, acrylic, polyurethane-acrylic, vinyl or epoxy. Primers can be water based or organic solvent based. Generally, the intermediate primer layer has a thickness in the range of 1 - 300 micrometers, preferably in the range of 50 - 150 micrometers. Preferably, the hardness of the primer layer is in the range 40 - 70 Shore A.

After application, the polymerizable polyurethane composition is polymerized to form the coating layer. Polymerization can occur as a result of exposure to air, preferably at room temperature or at a temperature in the range of 40 - 70 ° C. Generally, the polymerization can be considered finished 12 hours after the application of the polymerizable composition.

Once the coating layer has been made on the first face of the wooden base, if it is desired to obtain a panel coated on both faces, a second aliquot of polyurethane composition can be applied on the second face of the base, repeating the deposition and polymerization operations described. previously.

Preferably, the coating layer covers in a substantially uniform and complete manner at least the surface of the wooden base which is intended to receive the finishing layer.

For the purposes of the present invention, wooden bases having different structures can be used. Preferably, the wood base is chosen from: plywood base, chipboard wood base, wood fiber base and solid wood base.

Examples of types of wood that can be used for the purposes of the present invention are: poplar, fir, birch, beech, okumè, sycamore, walnut, ash, mahogany, etc.

In a particularly preferred embodiment of the present invention, the wood base is a plywood base. As is known, plywood is a wood product comprising a multiplicity of wood veneers held together by an adhesive composition; the veneers are superimposed on each other so that the grain of one veneer is rotated by a certain angle (up to 90 °) with respect to the grain of the adjacent sheets.

In the case of plywood bases, the use of a layer of polyurethane coating as a substrate on which to apply an ennobling layer allows the use of wood veneers of even relatively low quality to form the wood base. In particular, in the faced plywood panels according to the present invention, the most external wood veneer, which is in contact with the polyurethane coating layer, can be a class II, III or IV wood veneer (UNI EN 635-1) , even not subjected to repairs. The present invention therefore allows to avoid the use of ilomba, fromager or other high quality exotic essences, as is instead necessary in the state of the art. However, it is not excluded that, before the application of the polyurethane coating layer, the surface of the wood base may be subjected to repair operations, for example in the event that the surface of the outermost wood veneer has large surface defects.

Preferably, the plywood used as a wood base comprises from 3 to 17 layers of veneer, more preferably from 5 to 13 layers of veneer.

The finishing layers that can be used for the purposes of the present invention are known to those skilled in the art and commercially available.

The finishing papers essentially consist of sheets of paper pre-impregnated with thermosetting resins, such as melamine, urea, phenolic, formaldehyde resins or their mixtures.

Finishing layers consisting of sheets of polymeric material (for example, PVC sheets) or sheets of a multilayer plastic laminate can also be used for the finishing. These finishing layers can be applied to the polyurethane coating layer in a conventional way, for example with the aid of adhesive compositions (eg. Vinyl glues).

In a further preferred embodiment, the finishing layer can also be a layer of elastomeric polyurethane, in particular a layer of relatively low density, preferably in the range of 150 - 500 kg / m3. Preferably the surface hardness of the elastomeric polyurethane layer is in the range 15 - 70 Shore D. The finishing layer in elastomeric polyurethane, in addition to having a decorative function, can also give the final product other desired properties. For example, in the case of a faced panel intended to be used as the seat of a chair, an elastomeric polyurethane finishing layer gives a certain degree of surface softness and, at the same time, resistance to wear from rubbing.

Preferably, the elastomeric polyurethane finishing layer is obtained from aliphatic polyisocyanates, which give the coating greater resistance to degradation caused by exposure to UV radiation, which can cause yellowing of the finishing layer.

The finishing layer in elastomeric polyurethane, in addition to being able to perform the function of "visible" decorative layer, also contributes to increasing the sound-absorbing properties of the panel.

The finishing layer in elastomeric polyurethane can be prepared and applied with the same techniques and devices described above for the polyurethane coating layer applied on the wood base.

The process of ennobling the panel coated with the polymeric material can be carried out with the devices and techniques known to the skilled in the art. For example, in the case of laminating paper sheets and polymeric material sheets, the finishing can be achieved by superimposing a finishing layer on the polyurethane coating layer and, subsequently, applying pressure to the panel, while the panel is heated. This operation can be performed, for example, by means of a conventional heated plate press.

To facilitate the adhesion of the finishing layer to the panel, a layer of an adhesive composition (for example, a vinyl glue) can be advantageously interposed between the polyurethane coating layer and the finishing layer.

In consideration of the high quality that characterizes the surface of the polyurethane coating layer (degree of smoothness and flatness) obtainable according to the present invention, said surface can be processed to impart further desired properties to the surface of the finished product, before applying the layer of finish. For example, the coated panel according to the present invention can be subjected to painting or a printing process.

Before applying the finishing layer, the panel coated with the polyurethane layer can optionally be subjected to a calibration process to remove, for example, any excesses of polymeric material and / or give greater flatness or uniformity to the surface.

For the purposes of this description and the related claims, the verb "to understand" and all terms derived from it, as used herein in the description and claims, also include the meaning of the verb "to consist" and the terms derived from it.

Claims (12)

CLAIMS 1. Coated wood panel comprising: - at least a wooden base having at least a first face and at least a second face opposite to said first face; - at least one first layer of polyurethane coating having a hardness in the range 20 - 100 Shore D and a density in the range 400 - 1,200 kg / m <3>, on said first face. 2. Panel according to claim 1, comprising at least a second layer of polyurethane coating having a hardness in the range 20 - 100 Shore D and a density in the range 400 - 1,200 kg / m <3>, on said second face. 3. Panel according to any one of the preceding claims, in which the material that forms said polyurethane coating has a hardness in the range 40 - 100 Shore D, preferably in the range 60 - 100 Shore D. 4. Panel according to any of the preceding claims, in which the material that forms said polyurethane coating has a density in the range 600 - 1,100 kg / m <3>, preferably in the range 800 - 1,000 kg / m <3>. 5. Panel according to any one of the preceding claims, in which said coating layer has a thickness in the range of 0.2 - 3 mm. 6. Panel according to any one of the preceding claims, wherein said wooden base is selected from: plywood base, chipboard base, wood fiber base, solid wood base. 7. Panel according to the preceding claim, wherein said wooden base is a plywood base comprising a plurality of wood veneers stacked on top of each other and glued together by means of an adhesive composition, where the wood veneer adjacent to said layer of polyurethane coating is a class II, III or IV wood veneer (UNI EN 635-1). 8. Faceted panel comprising a coated wooden panel according to claim 1 and at least one finishing layer, which is applied on said first polyurethane coating layer having a Shore D hardness in the range 20 - 100 and a density in the range 400 - 1,200 kg / m <3>, said finishing layer being chosen from: finishing paper, elastomeric polyurethane layer, polymeric material sheet. A process for preparing a coated wood panel according to claim 1, which comprises: a. providing at least a wooden base having at least a first face and at least a second face opposite to said first face; b. depositing on at least said first face a polyurethane polymerizable composition comprising at least one organic polyisocyanate and at least one polyol; c. polymerize said polyurethane composition to form a first layer of polyurethane coating having a hardness in the range of 20 - 100 Shore D and a density in the range of 400 - 1,200 kg / m <3>. 10. Process according to the preceding claim comprising: d. repeat steps b. and c. on said second face of said wooden base to form a second layer of polyurethane coating having a hardness in the range 20 - 100 Shore D and a density in the range 400 - 1,200 kg / m <3>. 11. Process for producing a faced panel comprising: the. providing a coated wood panel according to claim 1; ii. form on said first layer of polyurethane coating having a hardness in the range 20 - 100 Shore D and a density in the range 400 - 1.200 kg / m <3>, at least one finishing layer chosen from: finishing paper, polyurethane layer elastomeric, sheet of polymeric material. 12. Process according to the preceding claim, wherein said step ii. comprehends: ii-a. overlapping said first layer of polyurethane coating with at least one finishing layer chosen from: finishing paper or a sheet of polymeric material; ii-b. pressing said panel while said panel is heated.