WITH HIGH-FREQUENCY ELECTROMAGNETIC WAVES

Field of the invention

The present invention relates to a method for treating wooden material, particularly to methods for impregnation of wooden materials, for instance for protecting the materials against fire, insects, mould, rot or fungi or for dyeing the material.

Background of the invention

Traditionally, impregnation of wooden materials is performed by means of methods including the use of vacuum, pressure or vacuum-pressure systems or the like. These methods typically suffer from the problem that the impregnation solutions only penetrate the material to be impregnated to a certain depth, often only a few centimetres from the surface of the material.

For some wooden materials, such as for instance spruce, the impregnation depth is even smaller, in some cases almost non-existing.

Brief description of the invention

It is an object of the present invention to provide an improved method, which enables the impregnation solutions to completely penetrate the material to be impregnated, and which reduces the time needed for impregnating the material still using the well- known vacuum, pressure and vacuum-pressure systems.

The present invention relates to a method for treating a wooden material with high- frequency electromagnetic waves, said method comprising the step of heating the wooden material by exposing it to high-frequency electromagnetic waves. Heating the wooden material by means of high-frequency electromagnetic waves increases the susceptibility of the material for liquids, such as different types of impregnation solutions and enables for a complete penetration of the material of such liquids.

This means that the method makes it possible to impregnate the wooden material all the way through, even if it consists of heartwood of any species of wood, and not only to a certain limited penetration depth from the surface as is often the case when using methods known in the art. Thus, even spruce, which is almost non-impregnable with conventional methods, may be penetrated by the impregnation solution. The result is that wooden materials can be obtained, which are much more resistive to fire, algae, insects, mould, rot or fungi, and that it becomes possible to dye the material in any desired colour all the way through. In an embodiment of the invention, the wooden material is heated to a temperature of between 50 °C and 220 °C, depending on the species of the wood.

Experiments have shown that the optimum impregnation results are obtained if the wooden material is heated to a temperature within this range.

In an embodiment of the invention, the wooden material is heated using electromagnetic waves of a frequency between 10 MHz and 30 MHz, preferably 13.56 MHz. Experiments have shown that the optimum impregnation results are obtained if the wooden material is heated using electromagnetic waves of a frequency within this range. Due to legal requirements, a frequency of 13.56 MHz is preferred.

In an embodiment of the invention, the method further comprises the step of impregnating the wooden material with an impregnation solution. In a further embodiment of the invention, the wooden material is impregnated using a vacuum system, a pressure system or a vacuum-pressure system.

When the wooden material has been heated using high-frequency electromagnetic waves, the material may be impregnated using well-known vacuum, pressure and vacuum-pressure systems. The heating with electromagnetic waves means that deeper penetration and shorter impregnation times may be obtained without performing any changes to the impregnation systems. In an embodiment of the invention, the wooden material is kept at a substantially constant temperature between the step of heating the material and the step of impregnating the material.

In a further embodiment of the invention, the wooden material is kept at a substantially constant temperature from the step of heating the material and throughout the step of impregnating the material.

Experiments have shown that the optimum impregnation results are obtained if the wooden material is kept at the temperature, to which it is heated, throughout the impregnation process.

In an embodiment of the invention, the impregnation solution used for impregnating the wooden material is water glass. In a further embodiment of the invention, a dyeing colour is blended into the water glass.

When the wooden material is impregnated with water glass, it cannot burn and it complies with even the toughest requirements for fire protection and enables for building multi-storey buildings from wood. The water glass hardens and cannot be washed out or removed from the wooden material in any other way. The lifetime of the wooden material is significantly prolonged and almost no maintenance is needed. Furthermore, the water glass makes the wooden material much stronger and more dimensionally stable, and it is a very environmentally sound material. In an embodiment of the invention, the impregnation solution used for impregnating the wooden material is a fire retardant, such as Burnblock ^® or FT ^® Anti Burn.

When the wooden material is impregnated with a suitable fire retardant, it cannot burn and it complies with even the toughest requirements for fire protection and enables for building multi-storey buildings from wood. Many fire retardants, such as Burnblock ^® or FT ^® Anti Burn, are very environmentally sound materials.

In an embodiment of the invention, the impregnation solution used for impregnating the wooden material is a disinfectant, which is effective against algae, insects, mould, rot or fungi, such as Boracol ^® .

In a further embodiment of the invention, a dyeing colour is blended into the disinfectant. When the wooden material is impregnated with a suitable disinfectant, it cannot burn and it complies with even the toughest requirements for fire protection. Furthermore, the wooden material is protected against rot, fungi, termites and other insects, etc. The lifetime of the wooden material is significantly prolonged and almost no maintenance is needed. Many disinfectants, such as Boracol ^® , are very environmentally sound materials.

In an aspect of the invention, it relates to a wooden material, which has been impregnated with water glass using the method as described above. In an aspect of the invention, it relates to a wooden material, which has been impregnated with a fire retardant, such as Burnblock ^® or FT ^® Anti Burn, using the method as described above.

In an aspect of the invention, it relates to a wooden material, which has been impregnated with a disinfectant, which is effective against algae, insects, mould, rot or fungi, such as Boracol ^® , using the method as described above.

Figures

A few exemplary embodiments of the invention will be described in more detail in the following with reference to the figures, in which fig. 1 illustrates schematically a side view of an embodiment of a high- frequency electromagnetic heating device, which may be used for carrying out the method according to the invention, fig. 2 illustrates schematically an end view of an embodiment of a high- frequency electromagnetic heating device, which may be used for carrying out the method according to the invention, fig. 3a illustrates schematically an example of impregnation solution penetration obtained by using methods known in the art, and fig. 3b illustrates schematically the impregnation solution penetration, which may be obtained by using the methods according to the invention. Detailed description of the invention

Figs. 1 and 2 illustrate schematically a side view and an end view, respectively, of an embodiment of a high-frequency electromagnetic heating device 1, which may be used for carrying out the method according to the invention.

The wooden material 2 to be heated enters the heating device 1 on a conveyor comprising a first electrode and forming a fixed plane 4 onto which the wooden material 2 rests. When the wooden material 2 is in place in the heating device 1, a movable plane 3 comprising a second electrode is lowered until it is in contact with the upper surface of the wooden material 2. High-frequency electromagnetic waves are applied between the two electrodes, i.e. through the wooden material 2, by means of a high-frequency generator 6, resulting in the wooden material 2 being heated by the energy of the electromagnetic waves.

The temperature to which the wooden material 2 is to be heated and the time needed for heating the wooden material 2 depend on the species of the wood and of the desired quality of the wooden material 2 after the heating. When the desired temperature has been reached, the movable plane 3 is lifted from the wooden material 2, which leaves the heating device 1 on the conveyor. Preferably, the wooden material 2 moves into a heated chamber keeping it substantially at the temperature to which it was heated in the heating device 1. The heating device 1 may be used before any conventional system for impregnation of wooden materials, improving the efficiency with respect to penetration depth and time consumption of such a system. Obviously, heating devices 1 of many variations may be used, varying in size and dimensions as well as in complexity and level of automation. The impregnation of the wooden material 2 may, for instance, be done in a vacuum- pressure system, in which the air is removed from the wooden material 2 by means of vacuum before the impregnation solution is added and pressure is applied in order to facilitate the penetration of the impregnation solution into the wooden material 2.

In other simpler systems, the application of either the vacuum or the pressure may be omitted.

In any case, the time needed for the impregnation process depends very much on the species of wood and on the type of impregnation solution used.

Fig. 3b illustrates schematically how the impregnation solution (represented by the circles) is able to penetrate the wooden material 2 completely when the method according to the present invention is used, whereas, as indicated in fig. 3a, the impregnation solution typically only penetrates the wooden material 2 to a certain limited penetration depth from the surface of the material when more conventional impregnation methods are used.

It should be emphasized that the scope of the present invention is not restricted to the description above, which represents a few exemplary and illustrative embodiments only, whereas the scope of the invention is defined by the following claims.

List of reference numbers

1. High-frequency electromagnetic heating device

2. Wooden material to be impregnated

3. Movable plane with electrode

4. Fixed plane with conveyor and electrode

5. Cylinders or actuators for moving the movable plane up and down

6. High-frequency generator