DE202015103202U1 - Plywood with a coating on at least one ground surface - Google Patents

Abstract

Plywood comprising a number of veneers and a coating on at least one surface of the plywood, characterized in that the veneers are glued together with an adhesive or binder mixture, the surface of at least the other of the outermost veneers of the plywood sanded or and the coating is provided on the sanded surface, and in that the coating comprises a hydrophobic material and a coating material-comprising film, wherein the coating material comprises a plastic or a resin, and that, before the coating is provided on the sanded surface, the sanded surface is provided by using P40-P200 grade abrasive paper according to the ISO 6344 standard.

Description

FIELD OF THE INVENTION

The invention relates to a plywood having a number of veneers and a coating on at least one surface of the plywood.

BACKGROUND OF THE INVENTION

Plywood is a wood-based product that has multiple layers of thin wood joined together with adhesives or binder mixtures. These plywood layers or veneers are glued together with veneers having a fiber direction alternated at a specific angle with respect to adjacent layers. The inventors have recognized a need for a plywood that is protected against the effects of the surrounding atmosphere.

PURPOSE OF THE INVENTION

The purpose of the invention is to provide a new type of plywood having a number of veneers and a coating on at least one surface of the plywood.

SUMMARY

The plywood according to the present invention is characterized by the features of claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and to form a part of the specification, illustrate embodiments of the invention and, together with the description, help to understand the principles of the invention. In the drawings:

1 shows the rippling effect as a result of water that has entered through the coating on the plywood;

2 and 3 show the results of rippling measurements; and

4 and 5 show the results of rippling measurements.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a plywood having a number of veneers and a coating on at least one surface of the plywood, wherein the veneers are glued together with an adhesive or binder mixture, the surface of at least the other of the outermost veneers of the plywood is sanded and the coating is provided on the sanded surface, the coating comprising a hydrophobic substance and a coating material-comprising film, wherein the coating material comprises a plastic or resin.

The present invention relates to a plywood having a number of veneers and a coating on at least one surface of the plywood, wherein the veneers are glued together with a binder mixture, the surface of at least the other of the outermost veneers of the plywood is sanded, and the Coating is provided on the sanded surface, the coating comprising a hydrophobic material and a coating film, wherein the coating material comprises a resin, and wherein, before providing the coating on the sanded surface, the sanded surface by using an abrasive paper with a grain size from P40-P200 according to the Standard ISO 6344 provided.

The plywood may be treated or coated to protect its veneers against, for example, moisture, water and the adverse influence of the surrounding atmosphere. The operating value of such Coated plywood is reduced when holes appear in the coating. In such a case, the outermost or uppermost veneer would easily absorb moisture from the air or water. Plywood is also often used as a material for concrete forming and casting. In connection with the pouring, moisture from wet concrete can penetrate into the veneer through the holes that have appeared in the coating. From the holes in the coating, the moisture readily spreads in the direction of the wood grains and causes localized swelling of the fibers, ie rippling, and thereby blistering of the surface of the wood board.

A problem faced by processed wood products, such as plywood, is that the surfaces of the plywood are exposed to, as a result of the exposed process, such as hot pressing, often, for example, poor wettability as compared to freshly cut polar wood Have polar wood. The surface of the plywood may have a glazed appearance, indicating that it has been inactivated by pressing at high temperatures. In particular, during hot pressing, resinous extracts migrate to the surface, adhesives harden, and fabrics released from the pressure pad or pressure balance plate remain on the product surface, thus preventing the surface from being wetted. During the hot pressing, the plywood is subjected to a heat treatment whereby, as a result of plastification of lignin and / or loss of residual water, the plywood surface becomes more hydrophobic resulting in reorganization of lignocellulosic components of the wood. As a result of increased or increased hydrophobicity of the plywood, the wettability of the plywood is reduced. The poor wettability may then adversely affect the following treatments, such as the coating process.

The inventors have found that sanding the plywood surface on which the coating is applied results in roughness of the surface, which is suitable for good surface coating. As a result of the sanding, the surface roughness of the plywood surface has the advantage of allowing a planar and sufficient distribution of the hydrophobic substance across the surface by rolling and spraying.

The inventors also found, surprisingly, that sizing the plywood surface to which the coating is applied has the beneficial effect of penetrating the hydrophobic material into the voids of the wood material, and particularly into the vessels and cells with wide cell lumens. When the hydrophobic substance, such as a wax, fills the cell lumens, the rate of water absorption into the plywood is reduced.

The coating, which includes a hydrophobic cloth and a coating film, is located on at least one outwardly facing surface of the plywood. In one embodiment of the present invention, the coating comprising a film comprising a hydrophobic substance and a coating material is located on at least one side of the plywood. In one embodiment of the present invention, the plywood has a coating on both of its outermost veneers. In one embodiment of the present invention, the plywood is surrounded by a coating.

In one embodiment of the present invention, the plywood has a coating on the surfaces of both the outermost veneers of the plywood. In one embodiment of the present invention, the plywood has a coating comprising a paint-containing film, the paint comprising a resin, on the surfaces of both the outermost veneers of the plywood. In one embodiment of the present invention, the plywood comprises a coating comprising a hydrophobic and a paint-containing film, the paint comprising a resin, on the surfaces of both the outermost veneers of the plywood.

The coating provided on the at least one surface of the plywood has the advantage of preventing swelling of the outermost veneer upon contact with, for example, water or moisture. The use of the hydrophobic fabric has the added benefit of being able to penetrate the wood grain or fibers of the plywood. As a result of this effect, spreading of water through possible holes formed in the coating of the plywood and swelling of the fibers of the uppermost veneer can be prevented.

In one embodiment of the present invention, the veneers are glued together with a binder mixture. In one embodiment of the present invention, the veneers are glued together with an aqueous binder mixture. The water present in the binder mixture leads advantageously to a swelling of the cell wall, which allows the effect of a smoother way for the binder mixture to penetrate into the cell wall, and thus allows impregnation of the binder mixture in the surface of the veneers.

In one embodiment of the present invention, the veneers are glued together under the influence of pressure or by applying pressing pressure with a binder mixture. The use of pressing has the added benefit of allowing a guide of the binder mixture into the veneers. In one embodiment of the present invention, pressing comprises cold pressing, followed by hot pressing. Cold pressing has the effect of passing the binder mixture into the veneers even before the curing process is started. Cold pressing in particular helps to allow smaller molecules to penetrate deeper into the veneers, which can increase the amount of binder mixture.

In one embodiment of the present invention, the resin-containing coating material and the aqueous binder mixture are one and the same material. In one embodiment of the present invention, the dry solids content of the aqueous binder mixture for gluing together the veneers is 40-60% by weight and preferably 45-55% by weight.

The veneers are bonded together with a binder mixture, with the surface of at least the other of the outermost veneers of the plywood being sanded, and the coating comprising a hydrophobic substance and a coating material with resin is provided on the sanded surface. In one embodiment of the present invention, the two surfaces of the outermost veneers of the plywood are sanded.

The inventors of the present invention surprisingly found that the use of a liquid binder mixture for gluing together the veneers and sands of the plywood surface on which the coating comprising the hydrophobic and coating material film is provided, the impregnation of the hydrophobic Influenced substance advantageous. The sanding opens routes or ways for the impregnation of the hydrophobic substance. On the other hand, the use of an aqueous binder mixture has the added benefit of preventing the hydrophobic substance from penetrating too far into the outermost veneer.

In one embodiment of the present invention, in the grinding step, prior to providing the coating on the sanded surface, the sanded surface is formed by using an abrasive paper having a grain size of P40-P200, preferably a grain size of P50-P150, and more preferably a grain size of P60-P120 according to the Standard ISO 6344 provided. The use of an abrasive paper with this type of grain size results in a surface into which the hydrophobic substance readily adsorbs. By using a finer grain size, the surface might remain so-called occluded for the adsorption of the hydrophobic substance, and the use of a coarser grain size could result in a non-uniform distribution of the major part of the hydrophobic substance, with the hydrophobic substance in the wells or depressions of the surface remains, while the so-called peaks or elevations or peaks would remain uncovered.

In one embodiment of the present invention, the surface of at least the other of the outermost veneers of the plywood is sanded in a direction substantially transverse to the grain direction of the veneer. This has the advantageous effect that most of the grains or fibers on the surface of the plywood, and many discernible or specific points of a fiber, are sanded and opened so that the hydrophobic substance easily penetrates into the grain or fibers or absorbed. In particular, when sanding the surface of birch veneers, the rather long vascular cells of the birch veneer receive multiple openings through which the hydrophobic material will penetrate at a good rate.

In one embodiment of the present invention, the plywood comprises a number of veneers and a coating on at least one surface of the plywood, wherein the veneers are glued together with a binder mixture, the surface of at least the other of the outermost veneers of the plywood substantially in the transverse direction Relative to the grain direction of the veneer, and the coating comprising a hydrophobic substance and a coating material comprising film, wherein the coating material comprises a resin, is provided on the sanded surface.

The inventors of the present invention surprisingly found that sanding increases the surface roughness and wettability of plywood, which advantageously reduces the surface roughness and wettability of plywood Application or use of the hydrophobic substance and the coating material having film influences. As a result of the sanding, the hydrophobic substance can be provided evenly on the surface of the plywood. Wettability is an indication of how easily and effectively any liquid expands over a wood surface. The moistening process of wood by a liquid, such as water, involves the spreading and penetration of a liquid drop or drops. The wettability can be assessed by measuring the contact angle (CA) of a drop, as well as by assessing its propagation rate. Sanding the plywood surface opens paths for the applied hydrophobic material to penetrate into the cell lumens and especially into vascular cells, special water-conducting cells in a birch tree. The above-mentioned rippling phenomenon is caused, for example, by water that first penetrates through the vascular cell lumens and then further into the vascular cell walls, resulting in swelling of the cell wall. By filling the lumens with the hydrophobic substance, the liquid absorption rate into the cell walls is hindered, resulting in reduction or prevention of the rippling phenomenon.

In one embodiment of the present invention, the veneers are glued together to form cross-bonded or cross-laminated plywood. In cross-linked or cross-laminated plywood, the veneers have alternating grain orientation throughout the structure.

In one embodiment of the present invention, the veneers are glued together so that the outermost veneer having the sanded surface has a cross grain direction in relation to the grain direction of its adjacent veneers.

In one embodiment of the present invention, the veneers are glued together so that the four first veneers, from the surface of the plywood on which the coating is located, form a cross-linked or cross-laminated structure. In one embodiment of the present invention, the veneers are glued together so that the four outermost veneers, when calculated from both sides of the plywood, form a cross-linked or cross-laminated structure.

In one embodiment of the present invention, the veneers of the plywood are glued together so that all the veneers except a pair of veneers in the middle of the plywood, which have a substantially parallel grain direction to one another, form a cross-linked or cross-laminated structure.

In one embodiment of the present invention, the veneers are glued together with a binder mixture such that the first outermost veneer of the plywood with the sanded surface has a cross grain direction in relation to the grain direction of the adjacent veneer, and the following two, three or four veneers, which follow the first outermost veneer, have a substantially parallel grain direction with respect to each other, and are followed by a veneer having a crosswise grain direction relative to the grain direction of the following two, three or four veneers.

In one embodiment of the present invention, the third veneer, calculated from the first outermost veneer, with its adjacent veneers, by providing the binder mixture on at least one side of the veneer in an amount of 10-50 g / m ² and preferably in an amount of 20-40 g / m ² , glued together. In one embodiment of the present invention, the third veneer, calculated from the first outermost veneer, is its adjacent veneers, by providing the binder mixture on both sides of the veneer in an amount of at least 50 g / ^m2 and preferably in an amount of at least 100 g / m ² , glued together. The inventors of the present invention surprisingly found that application of the binder mixture to the so-called third veneer calculated from the first outermost veneer, the dimensional stability and strength, as a result of increased amount of binder mixture in the surface layers of the plywood, increased. Increasing the dimensional stability increases the ability of the plywood to resist swelling and shrinkage caused by penetrating water or moisture. The increased amount of binder mixture in the surface veneer layers thus prevents the entry of water through the structure of the plywood according to the present invention. The binder mixture used to glue the veneers together has the added benefit that some of the binder mixture can penetrate into the cell wall of the wood material and advantageously affects the ability of the plywood to withstand the adverse effects of the water.

In one embodiment of the present invention, the veneers are glued together so that the outermost veneer having the sanded surface has a cross grain direction in relation to the grain direction of its adjacent veneer, and the following two, three, or four veneers following the outermost veneer have a substantially parallel grain direction with respect to each other and are followed by a veneer having a cross grain direction in relation to the grain direction of the following two, three or four veneers, and this structure is repeated from the other side of the plywood calculated from the outermost veneer.

In one embodiment of the present invention, the plywood has an even number of veneers, with the two veneers in the center of the plywood having a substantially parallel grain direction.

In one embodiment of the present invention, the first outermost veneer of the plywood is a birch veneer and meets quality grade III, and preferably grade II, according to Standard EN-635 ,

In one embodiment of the present invention, the veneers following the first outermost veneer of the plywood are birch veneers and meet quality classes K2, K3 or K4 according to the table below: Maximum diameter of the branch hole Maximum crack (width · length) Solid rot or "firm red" Peeling or peeling deficiency K1 6 3 x 300 not allowed not allowed K2 15 5 x 600 allowed not allowed K3 25 7 x 600 allowed not allowed K4 50 10 x 600 allowed allowed as far as extended or wide

The peel-off defect that may result from the rotary peel or rotary cutting process is considered to be an oblong scratch in the transverse direction as compared to the grain direction. The terms "hard red" or "sound red" could be used instead of the term "firm red".

In one embodiment of the present invention, the veneers of the plywood are made of softwood. In one embodiment of the present invention, the veneers of the plywood are made of hardwood.

In one embodiment of the present invention, the density of the wood material from which the veneer is formed is 320-750 kg / m ³ and preferably 390-650 kg / m ³ . In one embodiment of the present invention, the density of the wood material from which the veneer is formed is 390-550 kg / m ³ or 520-650 kg / m ³ . In one embodiment of the present invention, the density of the wood material from which the veneer is formed is 450-570 kg / m ³ . The above density values are in accordance with the Standards SFS-EN 384 and ISO 3131 measured ( SFS-EN 384 - Structural solid wood - Determination of characteristic values of mechanical properties and density (2010) , and ISO 3131 - Wood - Density Determination for Physical and Mechanical Tests (1975) ).

In one embodiment of the present invention, the veneers of the plywood are selected from a group consisting of pine veneer, poplar veneer, beech veneer, aspen veneer, spruce veneer and birch veneer.

In one embodiment of the present invention, at least the first outermost veneer of the plywood is a birch veneer, preferably at least the four, five or six first veneers of plywood, as counted from the first veneer, are birch veneers, and preferably all veneers of the plywood are birch veneers. In one embodiment of the present invention, at least the outermost veneer of the plywood, calculated from the surface of the plywood on which the coating is located, is a birch veneer, preferably at least the four, five or six first veneers of the plywood, calculated from the surface of the plywood on which the coating is located, birch veneers, and more preferably all veneers of plywood are birch veneers.

In one embodiment of the present invention, at least one veneer is made by either rotary cutting, flat blades, quarter knives, half rotary knives and rift blades. These methods are known as such in plywood manufacture, and various methods result in a slightly different appearance of the veneer. Circular cutting can also be referred to as rotary peeling, turning or rotation turning. In one embodiment of the present invention, the at least one veneer is produced by rotary cutting. In one embodiment of the present invention, all veneers of the plywood are made by rotary cutting. In one embodiment of the present invention, at least 80% and preferably 100% of the veneers of the plywood are made by rotary cutting.

In one embodiment of the present invention, the thickness of at least one veneer of the plywood is 0.5-4 mm, preferably 1-3.6 mm and more preferably 1.3-3.0 mm. In one embodiment of the present invention, the thickness of at least one veneer of the plywood is 1.3-3.0 mm. The thickness of the veneers of the plywood may be the same for each veneer or different from veneer to veneer. In one embodiment of the present invention, the veneers of the plywood have the same thickness. In one embodiment of the present invention, the veneers of the plywood have different thicknesses. In one embodiment of the present invention, at least 20% of the veneers of the plywood have a thickness of at least 0.2 mm and preferably at least 0.5 mm less or more than the thickness of the remaining veneers of the plywood. In one embodiment of the present invention, at least 20% of the veneers of the plywood have a thickness of at least 0.2-3.5 mm and preferably 0.5-2 mm less or more than the thickness of the remaining veneers of the plywood. In one embodiment of the present invention, all veneers are the same thickness with the accuracy of 0.2 mm.

The moisture percentages of the various veneers in plywood manufacture may vary. In one embodiment of the present invention, the average moisture percentage of the veneers used to make plywood prior to bonding is 1-9 and preferably 2-6. The above humidity values are in accordance with Standard SFS-EN 322 (Wood-Based Panels, Determination of Moisture Content (1993)) measured.

In one embodiment of the present invention, at least one veneer is modified by heat treatment, chemical treatment, mechanical treatment or a combination thereof. In one embodiment of the present invention, at least one veneer is modified by chemical treatment. If the veneers are modified or pretreated, their dimensional stability can be increased.

In one embodiment of the present invention, the hydrophobic material is selected from a group consisting of waxes, oils, alkyl ketene dimer (AKD), silicone, silicone oil, and combinations thereof. In one embodiment of the present invention, the hydrophobic substance is paraffin wax, microcrystalline wax, natural wax and / or slack wax. In one embodiment of the present invention, the hydrophobic substance is a natural oil. In one embodiment of the present invention, the hydrophobic substance is a paraffin wax, microcrystalline wax or alkyl ketene dimer. Alkylketene dimer is a waxy solid which is dispersed as a small particle in a solution. In one embodiment, the hydrophobic substance is a tall oil fatty acid. In one embodiment, the hydrophobic substance is stearin.

In one embodiment of the present invention, the coating comprises 10-150 g / m ² , preferably 20-100 g / m ² and more preferably 30-60 g / m ² of hydrophobic material, based on the total dry mass thereof.

In one embodiment of the present invention, the hydrophobic substance is provided on the at least one surface of the plywood as part of a mixture comprising the hydrophobic substance. In one embodiment of the present invention, the mixture is an emulsion containing water. In one embodiment of the present invention, a portion of the water contained in the emulsion is evaporated after the emulsion is applied to the plywood and before the coating comprising a coating material is applied. In one embodiment of the present invention, the mixture comprises an amount of 10-90% by weight and preferably 20-75% by weight of the hydrophobic substance. In one embodiment of the present invention, the mixture with a hydrophobic substance further comprises at least one additive and / or at least one filler.

In one embodiment of the present invention, the plywood has at least 20 g of the hydrophobic substance per square meter thereof. In one embodiment of the present invention, the plywood comprises at least 20 grams of paraffin wax per square meter thereof.

In one embodiment of the present invention, the plywood has a hydrophobic substance as a layer on the at least one surface of the plywood. In one embodiment of the present invention, the coating has a coating material-comprising film on the layer of the hydrophobic substance or the hydrophobic substance layer. In such a case, the hydrophobic fabric layer is on the at least one surface of the plywood, which is between the plywood and the film having a coating material. Providing the hydrophobic material layer on the at least one surface of the plywood sandwiched between the plywood and the coating material has the advantage that the hydrophobic material layer slows down the rate of water absorption into the plywood and thus swelling of the cell walls of the wood slows down. This is advantageous in the case that the film containing a coating material is damaged during, for example, storage or use.

In one embodiment of the present invention, the film comprising a coating material is coated with the hydrophobic material prior to being provided on the at least one surface of the plywood. In one embodiment of the present invention, the hydrophobic material is provided on one or both sides of the film comprising a coating material. In one embodiment of the present invention, the film comprising the coating material is provided with the hydrophobic substance on the at least one surface of the plywood so that the hydrophobic material is between the plywood and the film having a coating material.

In one embodiment of the present invention, the hydrophobic material is provided on the at least one surface of the plywood, and a coating film is provided on the hydrophobic fabric. In one embodiment of the present invention, the film comprising a coating material comprises a piece of paper having resin impregnated therein.

In one embodiment of the present invention, the film comprising a coating material has one or more film layers.

In one embodiment of the present invention, the thickness of the coating material film is 100-500 g / m ² , preferably 110-300 g / m ^2, and more preferably 120-220 g / m ² . In one embodiment of the present invention, the thickness of the film comprising a coating material is 100-150 g / m ² or 200-250 g / m ² .

The coating material comprises a plastic or a resin. In one aspect of the present invention, the resin is a phenolic resin, an amino resin or a combination of phenolic resin and amino resin. In one embodiment of the present invention, the resin is a phenolic resin. The phenolic resin may be prepared by the use of at least one polymerizable substance and a crosslinking agent, wherein at least a portion of the polymerizable substance is phenol. In one embodiment of the present invention, at least 50% by weight of the polymerizable substance is phenol. In one embodiment of the present invention, the polymerizable substance comprises lignin. In one embodiment, the crosslinking agent is formaldehyde. In one embodiment of the present invention, a catalyst and water are used to prepare the phenolic resin.

In one embodiment of the present invention, at least 80% by weight of the resin is based on phenol. In one embodiment of the present invention, the coating material consists of phenolic resin. In one embodiment of the present invention, the phenolic resin is a phenol-formaldehyde resin. In one embodiment of the present invention, the phenolic resin is modified by urea, melamine, lignin, resorcinol, modified phenols, cresols, bisphenols or other equivalent components.

In one embodiment of the present invention, the coating has one or more layers.

The embodiments of the invention hereinbefore described may be used in any combination with each other. Several of the embodiments may be combined together to form a further embodiment of the invention.

Plywood to which the invention relates may comprise at least one of the embodiments of the invention hereinbefore described.

An advantage of the plywood according to the present invention is that the sanded surface of the plywood on which the coating is applied results in the fact, for example, that the hydrophobic material enters the wooden vessels and the cells that are the result of the Grinding process can be "opened", absorbed or impregnated.

An advantage of the plywood according to the present invention is that because the surface of the plywood is sanded, the surface is less hydrophobic, which has the beneficial effect of uniform application of the hydrophobic substance, which otherwise forms droplets on the surface. would allow to make. An advantage of the plywood according to the present invention is that the sanded surface enables a uniform distribution of the hydrophobic substance into the cells of the wood material.

Examples

Embodiments of the present invention will now be described in detail to the embodiments of the present invention.

The description below discloses some embodiments of the invention in such detail that one skilled in the art will be able to practice the invention based on the disclosure. Not all steps of the embodiments are discussed in detail, as many of the steps will be apparent to those skilled in the art in this disclosure.

Example 1 - Forming plywood with a coating on one side of the plywood

In this example, a plywood coated with a number of birch veneers, each 1.4 mm thick, was coated with a coating comprising a film comprising a hydrophobic substance and a coating material. The panels were arranged so that the outermost veneer of the plywood on which the coating was formed had a cross grain direction in relation to the grain direction of its adjacent veneer, and the following three veneers following the first outermost veneer had a substantially parallel grain direction with respect to each other, and followed by a veneer having a cross grain direction in relation to the grain direction of the following three veneers. From the other side of the plywood, this structure was also repeated, and the veneers have a cross-linked structure between these structures. The manner in which the veneers were glued together with respect to their grain direction is shown below:
| - - - | - | - | - - - |

The veneers were glued together with an aqueous phenol-formaldehyde resin.

The surfaces of the plywood were made with a double belt grinder (abrasive belt roughness was P60 for one belt and P80 for the other belt).

The hydrophobic substance used was a paraffin wax and was used in the form of an emulsion. Two different concentrations were prepared, i. H. one of the emulsions had a dry wax content of 45% (wax emulsion 1 in the figure) and the other a dry wax content of 30% (wax emulsion 2 in the figure). The coating material was a phenolic resin.

First, the molded plywood panels were treated with the paraffin wax-containing emulsion. The paraffin wax was applied in an amount of 100 g / m ² on one side of the plywood. After the application or use of the paraffin wax, the panels were industrially dried in a drying plant consisting of three controllable drying zones of 40 ° C, 60 ° C and 60 ° C with a drying time of 40 seconds per stage. Thereafter, the phenol resin-containing film, ie, the phenol film coating, was applied thereon in an amount of 220 g / m ² . The phenol resin-containing film was applied at a temperature of 135 ° C under a maximum pressure of 1.8 MPa for 6 minutes.

Comparative or Comparative Example 1 (untreated)

In order to evaluate the influence of the emulsion with paraffin wax on rippling, plywood panels from the same plywood production batch used in the other examples were used with the same phenol resin-containing film, but without the use of the paraffin-containing emulsion coated.

Rippling test

Rippling is the effect that can occur when the coating formed on the plywood is damaged so that, for example, water can enter the coating and spread in the direction of the wood fibers, creating a swelling or shrinkage Swelling of the fibers, causing blistering of the coated surface (see 1 ).

In the rippling test, the swollen part or section, i. H. the rippling characteristic or figure, measured. Both the length (in the direction of grain) and the height of the formed shape are measured in millimeters.

In the test, a steel pin having a diameter of 1 mm and a length of 1.5 mm is pressed against the coated surface, so that a hole of the same diameter is formed on the coated wood surface. Then a moistened tissue or cloth is placed on the hole so that water can communicate with the surface to be tested, and the cloth remains on the surface for a defined time (2 hours, 4 hours and 6 hours). Thereafter, the dimensions or dimensions of the formed rippling characteristic are measured or measured. Three parallel measurements are performed.

The results of the performed rippling test of the plywood panels of Example 1 and Comparative Example 1 are in 1 and 3 shown. The number of rippling measurement points in these tests was 44-62 per panel.

Example 2 - Forming plywood with a coating on one side of the plywood

In this example, a plywood coated with a number of birch veneers, each 1.4 mm thick, was coated with a coating comprising a film comprising a hydrophobic substance and a coating material. The panels were arranged so that the outermost veneer of the plywood on which the coating was formed had a cross grain direction in relation to the grain direction of its adjacent veneer, and the following three veneers following the first outermost veneer substantially parallel grain direction with respect to each other, and followed by a veneer having a cross grain direction in relation to the grain direction of the following three veneers. From the other side of the plywood, this structure was also repeated, and the veneers have a cross-linked structure between these structures. The manner in which the veneers were glued together with respect to their grain direction is shown below:
| - - - | - | - | - - - |

The veneers were coated with a thermoplastic resin, i. H. a polypropene resin, glued together.

The surfaces of the plywood were made with a double belt grinder (abrasive belt roughness was P60 for one belt and P80 for the other belt).

The hydrophobic substance used was a paraffin wax and was used in the form of an emulsion. Two different concentrations were prepared, i. H. one of the emulsions had a dry wax content of 45% and the other a dry wax content of 30%. The coating material was a phenolic resin.

First, the molded plywood panels were treated with the paraffin wax-containing emulsion. The paraffin wax was applied in an amount of 100 g / m ² on one side of the plywood. After the application or use of the paraffin wax, the panels were industrially dried in a drying plant consisting of three controllable drying zones of 40 ° C, 60 ° C and 60 ° C with a drying time of 40 seconds per stage. Thereafter, the phenol resin-containing film, ie, the phenol film coating, was applied thereon in an amount of 220 g / m ² . The phenol resin-containing film was applied at a temperature of 135 ° C under a maximum pressure of 1.8 MPa for 6 minutes.

Example 3 - Forming plywood with a coating on one side of the plywood

In this example, a plywood coated with a number of birch veneers, each 1.4 mm thick, was coated with a coating comprising a film comprising a hydrophobic substance and a coating material. The panels were arranged to have a cross-laminated structure as shown below:
| - | - | - | - | - | - |

The veneers were glued together with an aqueous phenol-formaldehyde resin.

The surfaces of the plywood were made with a double belt grinder (abrasive belt roughness was P60 for one belt and P80 for the other belt).

The hydrophobic substance used was a paraffin wax and was used in the form of an emulsion. The emulsion had a dry wax content of 30%.

First, the molded plywood panels were treated with the paraffin wax-containing emulsion. The paraffin wax was applied in an amount of 100 g / m ² or 120 g / m ² on one side of the plywood. After the application or use of the paraffin wax, the panels were industrially dried in a drying plant consisting of three controllable drying zones of 40 ° C, 60 ° C and 60 ° C with a total drying time of 1.5 to 2 minutes. Thereafter, the phenol resin-containing film, ie, the phenol film coating, was applied thereon in an amount of 220 g / m ² . The phenol resin-containing film was applied at a temperature of 135 ° C under a maximum pressure of 1.8 MPa for 6 minutes.

Rippling test

The above-described rippling test was performed in accordance with Example 3. The reference or comparative plywood panels were treated in the same way as those produced in Example 3, except that no paraffin wax was used. The results of the rippling exam are in 4 and 5 shown. The number of rippling measuring points was 44 per type of plywood panel (ie panels to be compared or compared, 100 g / m ² and 120 g / m ² )

Example 4 - Use of various hydrophobic substances and various forms thereof for coating plywood

The above-described procedure of Example 3 was repeated with a variation of the hydrophobic substance, the form thereof, and the amount of the hydrophobic substance (g / m ² ) used. The drying process of Example 3 was also replaced by drying the plywood with the hydrophobic substance applied to the surface at room temperature overnight. Results of the rippling test performed as described above after 4 hours are shown in Table 1.

The dry wax content of Wax Emulsion 1 was 30% and the dry wax content of Wax Emulsion 2 was 45%. The dry matter content of AKD was 15%. The number of rippling measurement points was six per plywood panel type. Table 1 sample Rippling result or result Height (mm) width (mm) Solid paraffin wax 50 g / m ² 0.08 9.00 Oil-wax mixture A 50 g / m ² 0.06 20.00 Oil-wax mixture B 50 g / m ² 0.08 35,00 Wax emulsion 1 100 g / m ² 0.04 9.00 Wax emulsion 1 50 g / m ² 0.04 20.00 Wax emulsion 2 100 g / m ² 0.04 7.92 Wax emulsion 2 50 g / m ² 0.07 19.13 AKD 0.06 38,20 Comparison or comparative 0.13 107.98

Example 5 - Forming plywood with a coating on both sides of the plywood

The procedure of Example 3 was repeated in this example except that both sides of the plywood were coated. Some of the plywood panels were coated with a coating as described in Example 3 on both sides of the plywood panel. Some of the plywood panels were coated with a coating as described in Example 3 on one side of the plywood panel and with a coating of paraffin wax on the other. Part of the plywood panels were coated with a coating as described in Example 1 on one side of the plywood panel and with a coating of phenolic resin on the other.

It will be apparent to one skilled in the art that as the technology advances, the basic idea of the invention can be implemented in various ways. Therefore, the invention and the embodiments thereof are not limited to the examples described above and may instead vary within the scope of the claims.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• Standard ISO 6344 [0010]
• Standard ISO 6344 [0023]
• Standard EN-635 [0035]
• Standards SFS-EN 384 [0039]
• ISO 3131 [0039]
• SFS-EN 384 - Solid wood for design - Determination of characteristic values of mechanical properties and density (2010) [0039]
• ISO 3131 - Wood - Density Determination for Physical and Mechanical Tests (1975) [0039]
• Standard SFS-EN 322 (Wood Based Panels Determination of Moisture Content (1993)) [0044]

Claims (16)

Plywood comprising a number of veneers and a coating on at least one surface of the plywood, characterized in that the veneers are glued together with an adhesive or binder mixture, the surface of at least the other of the outermost veneers of the plywood sanded or and the coating is provided on the sanded surface, and in that the coating comprises a hydrophobic material and a coating material-comprising film, wherein the coating material comprises a plastic or a resin, and that, before the coating is provided on the sanded surface, the sanded surface is provided by using P40-P200 grade abrasive paper according to the ISO 6344 standard. Plywood according to claim 1, wherein the veneers are bonded together with an aqueous binder mixture and preferably with an aqueous phenolic resin. Plywood according to claim 1 or 2, wherein prior to providing the coating on the sanded surface, the sanded surface is provided by using an abrasive paper preferably having a grain size of P50-P150, and more preferably a grain size of P60-P120 according to the ISO 6344 standard. Plywood according to one of claims 1 to 3, wherein the surface of at least the other of the outermost veneers of the plywood is sanded in a substantially transverse direction in relation to the grain direction of the veneer. Plywood according to one of claims 1 to 4, wherein the veneers are glued together, so that the outermost veneer with the sanded surface has a cross grain direction in relation to the grain direction of its adjacent veneer. A plywood according to any one of claims 1 to 5, wherein the veneers are glued together so that the outermost veneer having the sanded surface has a cross grain direction in relation to the grain direction of the adjacent veneer, and the following two, three or four veneers corresponding to the veneer first outermost veneer, having a substantially parallel grain direction with respect to each other, and followed by a veneer having a cross grain direction in relation to the grain direction of the following two, three or four veneers. A plywood according to any one of claims 1 to 6, wherein at least the outermost veneer of the plywood, from the surface of the veneer on which the coating is located, is a birch veneer, preferably at least the four, five or six first veneers of the plywood, Calculated from the surface of the veneer on which the coating is located, birch veneers, and preferably all plywood veneers are birch veneers. Plywood according to one of claims 1 to 7, wherein the thickness of at least one veneer of the plywood is 0.5-4 mm, preferably 1-3.5 mm and more preferably 1.3-3.0 mm. A plywood according to any one of claims 1 to 8, wherein the hydrophobic substance is selected from a group consisting of waxes, oils, alkylketene dimer, silicone, silicone oil and combinations thereof. Plywood according to one of claims 1 to 9, wherein the hydrophobic substance is paraffin wax, microcrystalline wax, natural wax and / or Parackingatsch or Slack Wax. A plywood according to any one of claims 1 to 10, wherein the hydrophobic substance is paraffin wax, microcrystalline wax, natural wax or alkyl ketene dimer. A plywood according to any one of claims 1 to 11, wherein the coating comprises a hydrophobic substance on the sanded surface of the plywood, and the coating material-containing film is provided on the hydrophobic substance. A plywood according to any one of claims 1 to 12, wherein the coating comprises 10-150 g / m ² , preferably 20-100 g / m ² and more preferably 30-60 g / m ^{2 of} the hydrophobic substance based on the total dry matter thereof , Plywood according to any one of claims 1 to 13, wherein the resin is a phenolic resin, an amino resin or a combination of phenolic resin and amino resin. A plywood according to any one of claims 1 to 14, wherein the resin is a phenolic resin. A plywood according to any one of claims 1 to 15, wherein the thickness of the coating material film is 100-500 g / m ² , preferably 110-300 g / m ^2, and more preferably 120-220 g / m ² .

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