Method for producing a multilaminar wood board resisting atmospheric agents

Abstract

A method is disclosed for producing a multilaminar wood board resisting atmospheric agents. The method consists of the steps of: gluing a plurality of wood sheets to form a multilaminar wood board; drying the multilaminar wood board to obtain a dried multilaminar wood board; impregnating the dried multilaminar wood board with a mixture for treating wood by immerging the dried multilaminar wood board in the mixture for treating wood and subjecting the dried multilaminar wood board to a vacuum and pressure cycle to obtain an impregnated multilaminar wood board; drying the impregnated wood board to obtain a multilaminar wood board resisting atmospheric agents.

Description

Method for producing a multilaminar wood board resisting atmospheric agents

[0001] The invention relates to a method for producing multilaminar wood boards resisting atmospheric agents, in particular resisting in a maritime environment, suitable for an application in a nautical environment.Background of the invention

[0002] As known, in outdoor environments, and in particular in a nautical environment, it is necessary to use materials that are able to resist atmospheric agents and, in particular, humidity, UV rays, temperature variations and saltiness. Most wood-based products do not have features that are such as to confer resistance in an outdoor environment and in a maritime environment.

[0003] In particular, types of wood that are easily procurable at relatively low costs, such as poplar or African whitewood, are not suitable for applications in an outdoor environment, nor are such types of wood suitable for solid wood boards or even for use for example in glued laminated wood boards, plywood boards or other products obtained using these types of wood.

[0004] Also, wood boards obtained by cutting a block of wood sheets, obtained by known procedures, in particular gluing together a plurality of wood sheets, are not suitable for applications in outdoor environments and in maritime environments. For example, a block of wood sheets is disclosed in patent document EP1275481A2.

[0005] Until today, teak is normally used in the wood industry in outdoor uses, because of the great resistance of teak to atmospheric agents and to the maritime environment.

[0006] Nevertheless, one drawback linked to the use of teak is the scarcity thereof and import difficulties. In fact, teak grows in natural forests of the Indian peninsula, whereas other plantations have been laid out until today in Africa and in Central America.

[0007] Further, owing to the scarcity thereof, teak has high costs.Summary of the invention

[0008] One object of the present invention is to provide a wood-based material that is able to overcome the drawbacks of the prior art.

[0009] A further object of the present invention is to provide a method for producing multilaminar wood boards resisting atmospheric agents and the maritime environment that has moderate costs.

[0010] One advantage of the present invention is to make multilaminar wood boards resisting atmospheric agents, using types of wood such as poplar or African whitewood.

[0011] These and other objects are achieved by a method as specified in the first of the claims appended to this description.Brief description of the drawings

[0012] The invention can be better understood and implemented with reference to the enclosed drawings that illustrate embodiments by way of non-limiting examples, in which: Figure 1 illustrates schematically a block of wood sheets;Figure 2 illustrates an enlarged portion of Figure 1 in which the layers of the glued sheets of wood are visible;Figure 3 illustrates schematically a wood board obtained by sawing the block of wood sheets of Figure 1;Figure 4 illustrates an enlarged portion of Figure 3.Detailed description

[0013] The present invention provides a method for producing multilaminar wood boards resisting atmospheric agents, water, and humidity for use in a maritime environment

[0014] In particular, the multilaminar wood boards obtained by the method according to the present invention possess a dimensional variation, following exposure to water, comparable to that of teak.

[0015] The method involves using wood sheets. The wood sheets can be stained sheets or bleached and stained.

[0016] The sheets can be obtained from African whitewood or poplar or from any other type of wood.

[0017] The wood sheets can have a thickness comprised between 0.2 and 5 mm, in particular comprised between 0.4 and 5 mm.

[0018] The method includes a step of gluing a plurality of wood sheets to form a multilaminar block of wood sheets. In this phase, the wood sheets are glued, in particular hot-glued, by a glue that comprises one or more of melamine glue, melamine-urea-formaldehyde glue, polyurethane glue. These glues confer resistance to the atmospheric agents. Lastly, the presence of this glue between the layers constituted by the wood sheets acts as a physical and chemical barrier to the proliferation of mould, fungi, and other microorganisms.

[0019] During the step of gluing, the glue is spread by rollers onto the wood sheets. The wood sheets are then superimposed and subsequently pressed, with a single or multichamber press. In particular, the superimposed sheets are pressed at a pressure comprised between 2 and 20 kg / cm2, more in particular between 5 and 15 kg / cm2, for a time comprised between 1 and 7 hours, more in particular between 2 and 5 hours, at a temperature comprised between 20 and 110°C, more in particular between 60 and 100°C, still more in particular between 80 and 100°C.

[0020] The block of sheets obtained can be sawn in order to obtain one or more multilaminar wood boards of desired dimensions.

[0021] In particular, the block of sheets obtained is sawn (or cut) along one or more cutting planes T, T’ (where each cutting plane T, T’ means a plane coinciding with the plane on which the blade lies that is used to perform the cut, during cutting) that are transverse, for example tilted or perpendicular, to a plane P parallel to the faces of the glued sheets of wood. Tilted cutting planes T, T’ means planes that intersect the parallel plane P to form an angle that is greater than 0° and less than 90°. More in particular, the block of sheets is sawn to obtain multilaminar wood boards having a thickness comprised between 3 and 20 mm, more in particular between 5 andlO mm. Preferably, the cutting planes T, T’ for obtaining the wood boards made of multilayered wood are parallel to one another.

[0022] In this description, the term “board” also refers to strips.

[0023] For example, using wood sheets having a length of 2500 mm and a width of 650 mm, it is possible to have a block having the same length and width as the glued sheets of wood and a thickness of 50 mm. The block of sheets can be sawn to obtain strips having a length of 2500, a width of 50 mm (equal to the thickness of the block of sheets, with cutting planes T, T’ perpendicular to the faces of the glued sheets of wood) and thickness of 10 mm.

[0024] By cutting the block of sheets along the cutting planes T, T’ a multilaminar wood board is obtained that is illustrated in Figure 3, which shows on the face obtained by the cut, in the preceding embodiment, the face with a width of 50 mm, the layers of the glued sheets of wood. Aesthetically, this face has the “lined” veining that is typical of the teak slats used, for example, in a nautical environment. In Figure 4, an enlargement of the face of the multilaminar wood board is shown that is obtained by cutting the block of wood sheets.

[0025] Alternatively, the block of sheets can be subjected to the subsequent steps disclosed below without being cut, for example because the dimensions thereof correspond to the desired dimensions.

[0026] The method then involves a step of drying the multilaminar wood board to obtain a dried multilaminar wood board. In this step, the multilaminar wood board is dried until a dried multilaminar wood board is obtained having humidity comprised between 5 and 20%, in particular comprised between 9 and 12%.

[0027] Subsequently, the method includes a step of impregnating the dried multilaminar wood board with a mixture for treating wood, this mixture is a liquid mixture. In this step of impregnating, this board is immersed into the mixture for treating wood, which is also called an impregnating mixture, and is then subjected to a vacuum and pressure cycle. At the end of this step, an impregnated multilaminar wood board is obtained.

[0028] The mixture for treating wood comprises one of more of an alkyd resin water emulsion comprised between 2% and 25% by weight, in particular between 5 and 20% by weight; polysiloxane comprised between 2% and 25% by weight, in particular between 2.5 % and 10% by weight; iodopropynyl butylcarbamate (IPBC) comprised between 0.1 and 5% by weight, in particular between 0.5 % and 2% by weight and the appropriate amount of water at 100%. In particular, the mixture for treating wood comprises, in the percentages listed above, the emulsion of alkyd resin, the polysiloxane, and the iodopropynyl butylcarbamate (IPBC).

[0029] The alkyd resin water emulsion has particle dimensions comprised between 30 nm and 120 nm.

[0030] In one embodiment of the invention, the alkyd resin water emulsion can be replaced by a water emulsion of an acrylic copolymer, with particle dimensions comprised between 20 nm and 75 nm.

[0031] In a further embodiment of the invention, the alkyd resin water emulsion can be replaced by a water emulsion of a mixture of alkyd resin and of an acrylic copolymer.

[0032] In a still further embodiment of the invention, the polysiloxane can be replaced by a mixture of silanes.

[0033] In another embodiment of the invention, the iodopropynyl butylcarbamate (IPBC), can be replaced by a mixture of substances that are suitable for counteracting the proliferation of moulds and fungus.

[0034] The poly siloxane, or the mixture of silanes, generates a stable and durable water-repellent barrier, drastically reducing water absorption and facilitating cleaning of the treated surfaces.

[0035] This enables capillary water absorption to be reduced significantly, an increase in the surface contact angle to be obtained, an improvement in the resistance to weathering to be obtained and stability of the water-repellent effect to be obtained even after prolonged exposure to climatic agents.

[0036] The iodopropynyl butylcarbamate (IPBC) counteracts the proliferation of moulds and fungi, which are responsible for the aesthetic and structural deterioration of the wood, by exerting a preventive and protective action that preserves the compactness of wood and maintains the natural appearance thereof over time.

[0037] This enables the germination of fungal spores to be inhibited, the growth of surface and deep mycelia and moulds to be counteracted, the structural integrity of the wood to be preserved, reducing phenomena of biological degradation and the visual appeal of the product to be maintained unchanged even in very humid conditions.

[0038] The alkyd resin, the acrylic copolymer, or the mixture of alkyd resin and of acrylic copolymer, in a water emulsion, has high penetration capacity and becomes embedded in the microstructures of the wood, encompassing physically and chemically the water-repellent agent so as to promote the diffusion thereof inside the cellular wooden matrix. Further, the alkyd resin, the acrylic copolymer, or the mixture of alkyd resin and of acrylic copolymer water emulsion, acts as a consistent adsorption and release matrix of the anti-mould / anti-fungi agent, ensuring greater retention in the substrate, a reduction in leaching and extension of long-term biocide efficacy.

[0039] The vacuum and pressure cycle involves applying a vacuum degree comprised between -0.5 and -0.99 bar, in particular -0.8 bar, and pressure comprised between 5 and 18 bar, in particular between 10 and 12 bar inclusive. The application of the vacuum degree has a duration comprised between 20 min and 5 hours, in particular between 30 min and 3 hours. Applying the pressure has a duration comprised between 4 and 24 hours, in particular between 6 and 8 hours.

[0040] In particular, the step of impregnating is performed in an autoclave in which the table is immersed in the mixture for treating wood and is then subjected to the vacuum and pressure cycle. In the autoclave, it is possible to impregnate simultaneously a plurality of dried multilaminar wood boards. The internal volume of the autoclave is occupied by one or more dried multilaminar wood boards and by the impregnating mixture.

[0041] During the vacuum and pressure cycle, the mixture for treating wood is maintained at a temperature comprised between 25 and 35°C, in particular at a temperature of30 ± 2°C.

[0042] After the pressure and vacuum are applied, the impregnated multilaminar wood board is left to drip. Further, again after applying the vacuum and pressure, for example before the board is left to drip, the method can include the step of subjecting to brushing the impregnated multilaminar wood board, wherein the impregnated multilaminar wood board, in particular exiting the autoclave, is subjected to brushing, in particular rotational brushing, in order to push inside the wood pores the maximum possible quantity of the mixture for treating wood that at the end of the vacuum and pressure cycle covers the impregnated multilaminar wood board.

[0043] Subsequently, the method includes a step of drying the impregnated multilaminar wood board. The impregnated multilaminar wood board is dried to humidity comprised between 5 and 20%, in particular comprised between 9 and 12%.

[0044] The inventors have discovered that owing to the present method, and in particular owing to the synergic effect of the glue and of the impregnating substance that are used, wood boards are obtained that resist atmospheric agents and are suitable for use in a maritime environment. In fact, a multilaminar wood board obtained with the present method starting from wood sheets of African whitewood has the following features: swelling, after the test according to ISO 13061-15, in the slat thickness below 2.5%, in particular 1.97%, less than 2.5 % in width, in particular 1.64%. A multilaminar wood board obtained with the present method starting with poplar wood sheets has the following features: swelling, after the test according to ISO 13061-15, in slat thickness less than 3%, in particular 2.45%, less than 2.5 % in width, in particular 1.42%.

[0045] It is accordingly clear that this method achieves the set objects, enabling multilaminar wood boards to be obtained that resist atmospheric agents and are suitable for use in a nautical environment.

Claims

CLAIMS1. Method for producing a multilaminar wood board resisting atmospheric agents, said method comprising the steps of:- gluing a plurality of wood sheets to form a multilaminar wood board;- drying said multilaminar wood board to obtain a dried multilaminar wood board; - impregnating said dried multilaminar wood board with a mixture for treating wood, said impregnating comprising immersing said dried multilaminar wood board in said mixture for treating wood and subjecting to a vacuum and pressure cycle to obtain an impregnated multilaminar wood board;- drying said impregnated wood board to obtain a multilaminar wood board resisting atmospheric agents, characterized in that said mixture for treating wood comprises:- a water emulsion of alkyd resin, or of an acrylic copolymer, or of a mixture of alkyd resin and an acrylic copolymer, with a percentage comprised between 2% and 25%, in particular between 5% and 20%- polysiloxane, or a mixture of silanes, with a percentage comprised between 2% and 25%, in particular between 2.5 % and 10%- iodopropynyl butylcarbamate, with a percentage comprised between 0.1 and 5%, in particular between 0.5 % and 2%.

2. Method according to claim 1, wherein said gluing comprises gluing with a glue comprising one or more of: melamine glue, melamine-urea-formaldehyde glue, polyurethane glue.

3. Method according to claim 1, or 2, wherein said vacuum and pressure cycle comprises applying a vacuum degree between -0.5 and -0.99 bar.

4. Method according to claim 3, wherein said vacuum degree is applied for a period of time comprised between 20 minutes and 5 hours.

5. Method according to any one of the preceding claims, wherein said vacuum and pressure cycle comprises applying pressure comprised between 5 and 18 bar.

6. Method according to claim 5, wherein said pressure is applied for a period of time comprised between 4 and 24 hours.

7. Method according to any one of the preceding claims, comprising maintaining said mixture for treating wood at a temperature comprised between 25 and 35°C during said impregnating.Method according to any one of the preceding claims, comprising, after said impregnating, subjecting to brushing said impregnated multilaminar wood board to push inside the pores of said multilaminar wood board said mixture for treating wood that, after said impregnating, covers said impregnated multilaminar wood board.

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