EA041144B1 - WOOD PROCESSING - Google Patents

Description

Technical field

The present invention relates to a method for processing wood-based materials. The present invention also relates to wood-based materials obtainable by the method of the invention. Also provided is the use of the method for obtaining processed wood materials. Wood materials obtained by the method of the present invention have a wide range of applications.

State of the art

Wood is a widely used material in numerous applications such as but not limited to flooring, building structures/houses, fencing, light poles and furniture. Various wood treatment technologies have been developed to improve the properties of wood in terms of, for example, mold resistance, durability, cracking and staining, resistance to wood-eating bugs and rot.

Such wood treatment technologies include pre-drying, for example by heating, after which the wood is impregnated with an impregnation liquid, the impregnating liquid being soaked into the wood by depressurizing the chamber in which the wood is placed (so-called vacuum impregnation). After this process, pressure is applied, either by generating hydraulic pressure with a pressure pump pumping additional liquid into the chamber, or by pressurizing air above the liquid level. Subsequently, the wood can be subjected to additional vacuum drying steps.

Other processing technologies can also be used. For example, EP 0612595 relates to a process for upgrading low quality wood to high quality wood, comprising the steps of: (a) softening the wood by electrical heating in the presence of an aqueous medium, (b) drying the softened wood, for example by electrical heating, (c) curing the dried wood and (d) wood cooling. In this method, ohmic or electrical heating is used in both the softening step and the drying step.

US 3,986,268 discloses a method and apparatus for accelerated drying of freshly sawn timber using high voltage dielectric heating at subatmospheric pressure to rapidly remove moisture from the wood without splitting, cracking, warping, internal cracking or similar damage to the wood structure. The method combines dielectric and vacuum drying. The use of subatmospheric pressure during the drying process also allows the introduction of suitable chemicals for fire retardant or other special wood treatments, making it possible to combine such treatments with wood drying in a single process.

From KR 20160124728 a method for treating wood is known. The method includes the step of placing wood in a vacuum chamber and evacuating air, followed by filling the vacuum chamber with flame retardant, and then applying pressure, followed by removing the flame retardant by pumping, dehydrating the chamber, and then drying the wood at a temperature of 65 to 80°C for from 2 to 4 days. When filling with fire retardant, it is possible to cause the fire retardant and wood to vibrate by means of ultrasonic waves. Air evacuation, filling with flame retardant, pressure increase and ultrasonic wave treatment are carried out at ambient temperature.

From JPH 04189503 a method for treating wood is known. The method includes the steps of placing wood in a sealed container and depressurizing the container, followed by pumping liquid and applying ultrasonic waves. After exposure to ultrasonic waves, pressure is increased inside the container. After approximately 30 minutes, the container is again pressurized to atmospheric pressure.

Although a number of technologies have been developed, they all still have some disadvantages of traditionally used technologies. For example, the wood may not be completely impregnated because it has been found difficult to ensure that the impregnating liquid reaches the deeper interiors of the wood logs, and thus the wood becomes susceptible to mold attack. In addition, wood that is not fully impregnated may not be suitable for a number of applications, which include further wood processing.

Brief description of the invention

The present invention relates to the use of ultrasound in the treatment of wood-based materials. Ultrasound is used when the wood material is covered with a liquid. The ultrasound is applied at a suitable pressure and a suitable temperature for a suitable period of time.

In particular, the method of processing wood materials includes:

(a) supplying a liquid to the wood material; and (b) sonicating the wood material at a suitable pressure at a temperature of 70 to 220° C. for a suitable period of time.

Ultrasonic treated wood materials have a more natural texture compared to wood material treated with conventional methods, including calorimetric, ohmic or dielectric heat treatment. Structural changes are caused by traditional methods, such as the decomposition of lignin in wood material, resulting in

- 1 041144 various impregnation components are absorbed by the wood material due to the softening of the wood material. By means of the present invention, the structure of the wood material is better preserved, thus offering advantages over known wood material.

More specifically, the present invention relates to a method for treating wood material, comprising the steps of:

a) vacuuming wood material;

b) supplying liquid to the wood material while maintaining a vacuum;

c) exposing the wood material to overpressure at a temperature between 70 and 220°C, at which the liquid does not reach its boiling point;

d) sonicating the wood material while maintaining excess pressure at a temperature of 70 to 220°C.

The present invention also relates to wood material obtained by the method described in this document.

The present invention contemplates various uses for the wood material produced by the process described herein. Such applications include, but are not limited to, indoor and outdoor flooring, buildings and fences, lighting poles and sculptures, and decorative finishes.

Brief description of the drawings

The invention is illustrated in the attached drawings. The drawings are not intended to limit the scope of the invention in any way.

In FIG. 1 shows a diagram of the process according to the invention.

In FIG. 2 shows, from left to right, untreated Scandinavian spruce (1); traditionally impregnated Scandinavian spruce (2); Scandinavian spruce (3) treated with the method according to the invention; Scandinavian spruce (4) treated with the method according to the invention; Scandinavian spruce (5) treated with the method according to the invention; Scandinavian spruce (6) treated with the method according to the invention; untreated Spanish eucalyptus (7); Spanish eucalyptus (8) treated with the method of the invention; untreated Danish oak (9) and Danish oak (10) treated with the method of the invention.

In FIG. 3 shows, from left to right, Scandinavian spruce (11) treated with the method according to the invention; pine (12) treated with the method according to the invention; Scandinavian spruce (13) treated with the method of the invention; Scandinavian spruce (14) treated with the method according to the invention; and Scandinavian spruce (15) treated with the method according to the invention.

In FIG. 4 schematically shows an apparatus for carrying out the method according to the invention.

In FIG. 5 is a close-up of a sealed container with a log of wood material and an ultrasonic generator.

Detailed description of the invention

In the following, various aspects and embodiments of the present invention are described in more detail.

According to the present invention, the method relates to the processing of wood material, including:

a) supplying liquid to the wood material;

b) exposing the wood material to excessive pressure at a temperature of 70 to 220°C;

c) sonicating the wood material at 70 to 220°C for a suitable period of time.

A liquid is supplied to the wood material, after which the pressure is increased to reach an overpressure. The temperature is from 70 to 220°C in both stages. Wood material is exposed to ultrasound while maintaining excess pressure and temperature from 70 to 220°C.

The combination of heat and ultrasound provides improved impregnation as well as controlled coloring of the wood material. In particular, the depth of impregnation can be adjusted, and thus, if required, the wood material can be completely impregnated without leaving untreated parts of the wood material. Moreover, the method makes it possible to at least reduce the use of impregnation agents harmful to the environment.

In the present method, the liquid is supplied in such a way that the wood material is completely covered with the liquid.

Suitable pressures, temperatures and times are detailed below.

In the context of the present description, the term woody material includes materials obtained from trees of various species. Non-limiting examples of tree species include pine, cedar, cypress, fir, larch, spruce, oak, birch, beech, aspen, alder, elm, lime, eucalyptus, ash, mahogany, cherry, poplar, chestnut, maple, and redwood. The wood material may suitably be selected from the heartwood and the outer zone of the wood.

In the context of the present description, ultrasound is defined as having frequencies from 1 kHz to 1 MHz. In general, for the purposes of this invention, the frequency of the ultrasound is such that it is suitable for the purposes of the present invention, while still allowing the wood material to be treated to improve the properties of the wood material. For example, the frequency may be from 1 to 120 kHz. It should be understood that the frequency may in particular be 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 or 110 kHz, including any non-integer value between the indicated values. Moreover, different frequencies can be used during the application of ultrasound. The frequency may depend on the type of wood material (e.g. heartwood or outer zone of wood) and its water content, oily components, the shape and thickness of the wood material, as well as the time period during which the ultrasound is applied and the temperature at which the ultrasound is applied. , and it can be adjusted according to these parameters. The intensity of ultrasound can be changed depending on the number of sources of ultrasound. In general, exposure to ultrasound should be selected from 1 to 20 watts per liter of liquid. Ultrasound is able to knock on the wood material without destroying or disturbing the structure of the wood material. The ultrasound may be applied for a suitable period of time, for example, from 1 minute to 15 hours. A suitable period of time may be, for example, 1, 5, 15, 30-45 minutes, 8, 9, 10, 11, 12, 13, 14, or 15 hours, including any integer or non-integer values between the indicated values. In one embodiment, ultrasound is applied for 1 minute to 15 hours, such as 5 minutes to 12 hours, or for 2 hours.

The ultrasound is provided by ultrasound sources placed at suitable positions relative to the wood material. One or more ultrasound sources may be used. The number of ultrasound sources may depend, for example, on the amount and shape of the wood material to be treated.

More specifically, the present invention relates to a method for treating wood material, comprising the steps of:

a) vacuuming wood material;

b) supplying a liquid to the wood material while maintaining a vacuum;

c) exposing the wood material to overpressure at a temperature between 70 and 220°C, at which the liquid does not reach its boiling point;

d) exposure of wood material to ultrasound while maintaining excess pressure at a temperature of from 70 to 220°C.

When vacuuming the wood material, it is easier to remove air and moisture from the wood material. The temperature during this stage can be chosen to be suitable in relation to the applied vacuum, as well as in relation to the amount, condition and/or type of wood material. To do this, the wood material is placed in a sealed container equipped with a vacuum pump to ensure vacuum. The sealed container may be additionally provided with valves for regulating the pressure in the sealed container.

The liquid is fed into the wood material such that the wood material is covered with the liquid. This can suitably be done by sucking liquid into a sealed container containing wood material from another container containing liquid by means of an established vacuum. The liquid is supplied to the wood material at a suitable rate while maintaining a vacuum. The temperature of the liquid is selected such that it is appropriate in relation to the vacuum in the sealed container, as well as the amount, condition and/or type of wood material. In one embodiment of the present invention, the temperature of the liquid supplied is the same as or close to the temperature of the wood material during the vacuuming step. The liquid may suitably be supplied to the sealed container containing the wood material from another container interconnected with the sealed container by a valve. Due to the presence of vacuum in the sealed container, the liquid is diverted into the sealed container from another container. The liquid is withdrawn into the sealed container until the sealed container is filled with liquid and the wood material is covered with liquid. In addition, both the sealed container and the other container may be provided with heating means (heaters) and/or cooling means (coolers) for heating or cooling the liquid before or after being supplied to the sealed container.

After adding the liquid, the vacuum pump of the sealed container is turned off and the pressure pump connected to the sealed container is set to a suitable overpressure value and started. By means of this, the wood material is subjected to an overpressure. The excess pressure makes it easier for the liquid to be absorbed into the wood material. By means of excess pressure, the boiling point of the liquid also increases compared to the boiling point at atmospheric pressure. In this way, the temperature of the wood material and the liquid can be significantly increased relative to the possible temperature at atmospheric pressure without causing the liquid to boil, thereby facilitating the impregnation of the wood material, i.e. the liquid is absorbed into the wood material. The temperature and pressure are chosen to be appropriate in relation to the quantity, condition and/or type of wood material as well as in relation to the liquid and possible components present in the liquid. The liquid can be suitably circulated/contacted with heating means (heating device) during heating to ensure that the desired temperature is maintained at all times. Thus, the liquid can be continuously heated to the desired temperature during the impregnation process.

Wood material is exposed to ultrasound while maintaining elevated temperature and excess pressure. The wood material is exposed to ultrasound for a suitable period of time. The time of exposure to temperature, overpressure and ultrasound is chosen so that it is appropriate in relation to the amount, condition and/or type of wood material as well as in relation to the liquid and possible components present in the liquid, and also depending on the frequency of the applied ultrasound . The ultrasound is usually applied by means of an ultrasonic generator or a plurality of ultrasonic generators located in a sealed container. The combination of overpressure and ultrasound makes it easier for the wood material to absorb the liquid. In fact, liquid absorption can be twice that of traditional pressure impregnation of wood-based materials. Moreover, the liquid penetrates deeper into the wood material, thereby providing an increased depth of impregnation. This significantly increases the durability of the wood material. Since the impregnation of the wood material is improved, the method according to the invention further makes it possible to use impregnating agents (liquid or substances contained in the liquid) that are more environmentally friendly.

After sonication is completed, it may be preferable to first turn off the ultrasound source(s) and then lower the temperature (either via natural cooling by turning off the heat or forced cooling) before depressurizing to atmospheric pressure. If the excess pressure is released before the temperature is low enough, it can cause the liquid to boil due to the temperature of the liquid. Atmospheric pressure can suitably be generated by means of a valve or valves in a sealed container.

As noted above, the wood material is usually placed in a sealed container suitable for both vacuum and overpressure. The sealed container can be additionally connected to another container for heating and supplying liquid. The sealed container and/or other container may be additionally provided with heating and/or cooling means (devices) to control the temperature in accordance with the required conditions. The sealed container, as well as the other container, may be of any shape and size suitable for carrying out the method. Suitable containers are generally known in the art.

The wood material may be stacked or otherwise placed in an airtight container, possibly by means for arranging pieces or logs of the wood material.

In the context of the present description, the term liquid means a liquid that is suitable for coating wood material and further for the application of ultrasound. The liquid used in the method of the invention may be, for example, water, oil, or mixtures of water and another solvent, and may in some embodiments also suitably include wood treatment compounds such as impregnation agents, for example alum, boric acid solution, copper, oils such as linseed oil, tree resin and the like, fire retardants, biocides, fungicides and/or pigments and dyes, and combinations thereof. It should be understood that one or more wood treatment compounds may be present in the liquid in an amount suitable for the intended effect and application, but this amount may depend on the type of wood material and its content of air and moisture. Compounds for wood treatment, as well as the amounts used, are generally known in the art. In particular, the fire retardant may be a gaseous fire suppressant suitable for extinguishing a fire, such as argon or freon.

Preferably, the liquid may be present in an amount sufficient to ensure that it is suitably absorbed by the wood material. The amount of liquid generally depends on the amount (size, weight, shape) of the wood material, the content of air and moisture in the wood material, the type of wood material (e.g. beech, birch, pine, spruce, oak, mahogany, and heartwood, outdoor part of the stem, etc., as noted above), as well as processing conditions, such as applied pressure and temperature. The amount of liquid can be additionally adapted to the required impregnation depth.

In one embodiment, the method of the present invention includes the use of ultrasound at a frequency of 1 kHz to 1 MHz, such as 1 to 120 kHz. In another embodiment, the frequency is from 20 to 40 kHz. In a specific embodiment, the frequency is 30 kHz. Other suitable frequencies are defined above.

In another embodiment, the method according to the present invention includes the application of ultrasound for from 1 minute to 15 hours. It should be understood that the time during which ultrasound is applied may depend on other parameters, such as, for example, the type, shape, size, weight of the treated wood material, the content of air and moisture in it, as well as the liquid and the frequency of the applied ultrasound. It should also be understood that the frequency of the ultrasound can be varied during the time the ultrasound is applied. It should also be understood that ultrasound can be applied intermittently, ie. there may be periods of time with and without the application of ultrasound. In one embodiment, ultrasound is applied for 1 to 3 hours. In another embodiment, ultrasound is applied for 2 hours.

First, the wood material is subjected to a vacuum. Vacuum is a pressure below atmospheric pressure. Accordingly, the vacuum can be as low as 0 mbar.

Typical examples of vacuum include, but are not limited to, 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100% of atmospheric pressure, as well as any integer or non-integer values between these values. It should be understood that vacuum can also be defined in units of mbar. As a general rule, a value of 1000 mbar (0.1 MPa) is considered equal to atmospheric pressure, which means that, for example, 50% of atmospheric pressure corresponds to a pressure of 5000 mbar (50 kPa). In this document, vacuum can be stated interchangeably in both % and mbar. A decrease in pressure below atmospheric pressure suggests that the solvents boil at a lower temperature. For example, water present in wood material can evaporate (boil away) more easily under vacuum.

In one embodiment, the method of the present invention is one in which the vacuum is from 1 to 100% of atmospheric pressure, such as 80% (about 800 mbar (80 kPa)) or 50% of atmospheric pressure (about 500 mbar (50 kPa)) .

The vacuum should be chosen so as to obtain the required evaporation of the water contained in the wood material. Thus, the temperature during the evacuation step can be adjusted in terms of, for example, the size, weight, density, shape of the wood material and its air and moisture content. Therefore, the temperature during the evacuation step can be suitably chosen to be 1 to 100°C, eg 20 to 70°C, or room temperature.

In general, the vacuum is maintained for 1 minute to 2 hours, such as 5, 10, 15, 20, 30, 40, 45, 50 minutes, 1 hour, 1 hour and 10 minutes, 1 hour and 20 minutes, 1 h and 30 min, 1 h and 40 min, 1 h and 50 min, or 2 h. In one embodiment, the vacuum is maintained for 5 min to 2 h, or 15 to 45 min. In one embodiment, the vacuum is maintained for 30 minutes. Thus, the period of time can be adjusted according to the size, weight, density, shape of the wood material and its water content.

Subsequently, after maintaining the vacuum for a certain period of time, the container containing the wood material is supplied with a liquid under vacuum pressure from another container containing the liquid. The amount of liquid required may depend on the amount of wood material present, the size, weight, density, shape of each piece or log of wood material and its air and moisture content and type, as well as the size and shape of the containers used. In general, the amount of liquid should be supplied to ensure that the wood material is completely covered with liquid and the wood container is filled with liquid.

The temperature during and after the addition of the liquid is chosen to be suitable for supplying the liquid while maintaining the liquid below its boiling point at the pressure being used. Typical temperatures may be, for example, from 20 to 70°C. In one embodiment, the temperature during the evacuation step is 70°C and a liquid having a temperature of 70°C is supplied to the wood material.

The temperature and vacuum are maintained for a suitable period of time, in one embodiment, this period of time varies from minutes to hours, for example from 5 minutes to 5 hours, for example 20, 45 minutes, 2 or 3 hours. Examples of suitable temperature and vacuum are given above.

The wood material is then subjected to an overpressure. This may occur after pressurization from vacuum to atmospheric pressure by means of a pressure pump, as described above. The required temperature during the overpressure phase is that at which the liquid does not reach its boiling point. This temperature depends on the applied overpressure and on the supplied liquid. The temperature and pressure are maintained for a suitable period of time, usually varying from 1 minute to 15 hours, for example for 1, 5, 15, 30, 45 minutes, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 hours, including integer or non-integer values between the specified values. Usually the temperature is from 70 to 220°C. In some embodiments, the temperature may be 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, or 220° C., including integer or non-integer values between these values.

The pressure during the overpressure stage may be from 0.1 to 3 MPa (1 to 30 bar). Accordingly, the excess pressure can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2 , 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2 .5, 2.6, 2.7, 2.8, 2.9 or 3 MPa (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 bar), including integer or non-integer values between the indicated values. In another embodiment, the pressure is 1 to 2.5 MPa (1 to 25 bar). In a specific embodiment, the pressure is 2.0 MPa (20 bar).

The wood material is then sonicated as defined in this document. The temperature during sonication may preferably be from 70 to 220°C. In some embodiments, the temperature may be 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200,

- 5 041144

210 or 220°C, including integer or non-integer values between the indicated values. In a specific embodiment, the temperature is from 170 to 220°C. In one embodiment, ultrasound is applied for 2 to 2.5 hours at 1.2 MPa (12 bar) or 2.0 MPa (20 bar).

The temperature during the various steps of the process according to the invention can be suitably controlled. By this, the impregnation of the wood material can be effectively controlled. In particular, the depth of impregnation depends on the conditions of temperature, vacuum, pressure, ultrasound and time, as well as on the properties and type of wood material. Some applications may require fully impregnated wood materials, while other applications may require wood materials only to a certain depth of impregnation.

It has been found and shown that the use of ultrasound at certain temperatures leads to a more uniform impregnation of the wood material. Moreover, it is generally possible to maintain a somewhat lower temperature than conventionally used methods, since the application of ultrasound facilitates the impregnation of the wood material. Moreover, heating combined with sonication enables better control of the coloring of the wood material. In general, the higher the temperature, the darker the color of the wood material. Moreover, by selecting the components of the liquid, the coloration of the veining of the wood material can be enhanced, thus making it possible to obtain more attractive impregnated wood materials, for example for decorative purposes.

The invention also relates to wood material obtained by the method described in this document. Such wood material has a number of applications, as mentioned above.

In FIG. 1 illustrates the method of the invention. Fig. 1 is intended to illustrate a specific embodiment of the invention and is not intended to limit the scope of the invention in any way. As can be seen in the drawing, the method according to the invention includes the processing of wood material in a vacuum from 0 mbar to atmospheric pressure (0.1 MPa (1000 mbar)) at room temperature. The vacuum is maintained for a certain period of time (in the example 45 minutes). Subsequently, the liquid is supplied while maintaining the vacuum. The liquid is supplied for a certain period of time (in the example 10 minutes). After that, the temperature and pressure are increased. Prior to this, the temperature and pressure may be adjusted to ambient temperature and ambient pressure (atmospheric pressure) (not shown). An overpressure of 1.5 MPa (15 bar) and an elevated temperature of 190°C are illustrated. For a period of time with overpressure and elevated temperature (illustrated by a time period of 120 minutes), the wood material is subjected to sonication. The ultrasound may be applied for a shorter period of time than the pressurization and elevated temperature period (shown), or the ultrasound may be applied for the entire pressurization and elevated temperature period (not shown). Ultrasound can be applied continuously (shown) or pulses of a certain length (not shown). The temperature and pressure can then be reduced so as to reach ambient temperature (room temperature) and ambient pressure (atmospheric pressure). This can be done by natural leveling (shown) or by forced leveling by ventilation or by means of a cooling device.

In FIG. 2 shows raw wood material, traditional pressure impregnated wood material and impregnated wood material obtained according to the method of the present invention.

In FIG. 3 shows wood products obtained according to the method of the present invention. The method of the present invention is further explained in the following non-limiting example.

Examples

Example 1. Device for carrying out the method according to the invention

Reference is made to FIG. 4. In FIG. 4 is a schematic representation of the device used to carry out the method according to the invention. Logs of wood material 31, having a suitable size, were placed in a sealed container 17 having a volume of approximately 1 m ³ . The sealed container 17 was chosen to be suitable for both pressurized and reduced pressure environments. Sealed container 17 was additionally equipped with an ultrasonic generator (not shown). The sealed container 17 was connected to a heating device 25 to heat the circulating liquid. Between the vacuum pump 20 and the valve 26 was a protective container 30 to protect the vacuum pump 20 from liquid. The sealed container 17 was connected to a vacuum pump 20 and a valve 26. The sealed container 17 was additionally provided with a valve 27 for safety reasons. The container 18 containing the liquid was connected to the container 16 by a circuit containing valves 23, 24, as well as to the pressure pump 28. The container 16 was also connected to the booster pump 19 and the valve 22. The container 16 was equipped with a heating/cooling device 21. The container 18 was only intended to hold liquid until use. To start the method of the invention, the liquid was pumped into container 16 and the connection between container 18 and container 16 was closed.

- 6 041144

In FIG. 5 shows part of a device for carrying out the method according to the invention. In FIG. 5 shows a sealed container 17, an ultrasonic generator 29 and a log of wood material 31.

Example 2 Treatment of wood material according to the invention

The wood material logs 31 were placed in the sealed container 17 described in Example 1, and the method of the invention was carried out as follows.

Stage(s) - evacuation

The pressure in the sealed container 17 with wood material 31 (one log of wood material) was reduced to 50% of atmospheric pressure (50 kPa (500 mbar)) using a vacuum pump 20 connected to a valve 26 on top of the sealed container 17. Vacuum at 50 kPa ( 500 mbar) was maintained for 30 min. Thereby, the air contained in the wood material was removed from the wood material.

Step (b) - adding liquid

The liquid (1000 l) intended to be supplied to the wood material was preheated in vessel 16 to a temperature of 70°C. The preheated liquid was supplied to the sealed container 17 using the valve 23. Since the pressure in the sealed container was 50% of atmospheric pressure (50 kPa (500 mbar)), the liquid was easily pumped into the sealed container 17 by vacuum. Vacuum was maintained during the addition of the liquid by means of the vacuum pump 20 until the sealed container 17 was filled with the liquid and the wood material was covered with the liquid. After that, the vacuum pump 20 was turned off. The filling of sealed container 17 was checked by the presence of liquid in container 30.

Stage (c) - overpressure and heating

The pressure pump 19 was set at a pressure of 2.0 MPa (20 bar) and started. The liquid in the sealed container was maintained at the desired temperature of 70 to 220°C (see Table 2 below for specific temperatures) by circulating the liquid through the heating device 25 using the pressure pump 19. Thus, the liquid was recirculated (see See table 2 for specific fluids) to maintain the required temperature.

Stage (d) - sonication

When a pressure of 2.0 MPa (20 bar) and the required temperature were reached, ultrasound at a frequency of 30 kHz was applied for 2 or 3 hours (see Table 2 for specific times). The pressure was maintained at 2.0 MPa (20 bar) during sonication. The desired temperature was maintained during sonication. After sonication, a pressure of 2.0 MPa (20 bar) was maintained until the temperature in the sealed container 17 (and the temperature of the liquid and wood material 28) was reduced to 100° C. to avoid boiling of the liquid if water-based. In the case where the liquid is an oil or an oil mixture, a temperature below 100° C. was preferred for safety reasons. When the required temperature was reached, the pressure was reduced to atmospheric pressure through the valve 26, the liquid was drained and the wood material 28 was removed from the sealed container 17.

It has been demonstrated that, through the use of a combination of heat and ultrasound, the liquid is efficiently absorbed into the wood material.

- 7 041144

Table 1. Wood material

Sample number Wood material size (cm x cm x cm) Initial moisture content,% wood material 1 120x9x4.5 17 Scandinavian spruce 2 120x9x4.5 17 Scandinavian spruce 3 120 x 9 x 4.5 17 Scandinavian spruce 4 120 x 9 x 4.5 17 Scandinavian spruce 5 120 x 9 x 4.5 17 Scandinavian spruce 6 120 x 9 x 4.5 17 Scandinavian spruce 7 35x9x4 17 spanish eucalyptus 8 35x9x4 17 spanish eucalyptus 9 40 x 10x5 7 Danish oak 10 40 x 10x5 7 Danish oak eleven 120x9x4.5 17 Scandinavian spruce 12 120x9x4.5 17 Pine 13 120 x 9 x 4.5 17 Scandinavian spruce 14 120 x 9 x 4.5 17 Scandinavian spruce 15 120 x 9 x 4.5 17 Scandinavian spruce 16 120x9x4.5 17 Pine 17 120x9x4.5 17 Scandinavian spruce 18 120x9x4.5 17 Danish oak 19 120x9x4.5 17 Asian redwood 20 120x9x4.5 17 Scandinavian spruce 21 120x9x4.5 17 Danish oak 22 120 x 9 x 4.5 17 Asian redwood 23 120 x 9 x 4.5 17 Scandinavian spruce 24 120 x 9 x 4.5 17 Danish oak 25 120 x 9 x 4.5 17 Asian redwood 26 120 x 9 x 4.5 17 Pine 27 120 x 9 x 4.5 17 Danish oak 28 120 x 9 x 4.5 17 Asian redwood 29 120 x 9 x 4.5 17 Pine thirty 120 x 9 x 4.5 17 Danish oak 31 120 x 9 x 4.5 17 Asian redwood 32 120 x 9 x 4.5 17 Pine 33 120 x 9 x 4.5 17 Scandinavian spruce 34 120x9x4.5 17 Danish oak 35 120 x 9 x 4.5 17 Asian redwood 36 120 x 9 x 4.5 17 Pine 37 120 x 9 x 4.5 17 Scandinavian spruce 38 120 x 9 x 4.5 17 Danish oak 39 120 x 9 x 4.5 17 Asian redwood 40 120 x 9 x 4.5 17 Pine 41 120 x 9 x 4.5 17 Scandinavian spruce 42 120 x 9 x 4.5 17 Danish oak 43 120 x 9 x 4.5 17 Asian redwood

In table. 1, sample numbers 1-15 refer to the logs shown in FIG. 2 and 3, respectively.

- 8 041144

Sample No. 1

Sample #2

Sample #3

Sample No. 4

Sample No. 5

Sample No. 6

Sample No. 7

Sample No. 8

Sample No. 9

Sample No. 10

Sample No. 11

Sample No. 12

Sample No. 13

Sample No. 14

Sample #15 is untreated Scandinavian spruce.

is a traditionally impregnated (copper impregnated) Scandinavian spruce.

is a Scandinavian spruce treated according to the process of the invention.

is a Scandinavian spruce treated according to the process of the invention.

is a Scandinavian spruce treated according to the process of the invention.

is a Scandinavian spruce treated according to the process of the invention.

is untreated eucalyptus.

is a eucalyptus treated according to the method of the invention and cut after treatment.

is untreated Danish oak.

is Danish oak treated according to the method of the invention and cut after treatment.

is a Scandinavian spruce treated according to the process of the invention.

is a pine treated according to the method according to the invention.

is a Scandinavian spruce treated according to the process of the invention.

is a Scandinavian spruce treated according to the process of the invention.

is a Scandinavian spruce treated according to the process of the invention.

- 9 041144

Table 2. Processing of wood material

Sample number Liquid Stage temperature (s) Temperature/time of exposure to ultrasound in step (d) 3 Demineralized water (calcium-free) 170°C 170°C/2 hours 4 Demineralized water (calcium-free) 180°C 180°С/2 hours 5 1:1 linseed oil : tree resin 190°С 190°C/2 hours 6 1:1 linseed oil : tree resin 200°С 200°С/2 hours 8 1:1 linseed oil : tree resin 200°С 200°С/2 hours 10 1:1 linseed oil : tree resin 220°С 220°С/2 hours eleven 5% solution of alum in demineralized water (calcium-free) 70°С 70°C/3 hours 12 10% solution of alum in demineralized water (calcium-free) 70°С 70°C/3 hours 13 20% solution of alum in demineralized water (calcium free) 70°С 70°C/3 hours 14 20% solution of alum in demineralized water (calcium free) 70°C 70°C/3 hours 15 20% boron solution in demineralized water (calcium-free) 70°C 70C/3 hours 16 Water (calcium-free) with colored pigment (579 kg/m ³ ) 70°С 70°C/3 hours 17 Water (calcium-free) with color pigment (478 kg/m ³ ) 70°C 70°C/3 hours 18 Water (calcium-free) with color pigment 70°C 70°C/3 hours 19 Water (calcium-free) with color pigment (307 kg/m ³ ) 70°С 70°C/3 hours 20 5% solution of alum in demineralized water (calcium-free) 70°C 70°C/3 hours 21 5% solution of alum in demineralized water (calcium-free) 70°C 70°C/3 hours 22 5% solution of alum in demineralized water (calcium-free) 70°C 70°C/3 hours 23 10% solution of alum in demineralized water (calcium-free) 70°С 70°C/3 hours 24 10% solution of alum in demineralized water (calcium-free) 70° 70°/3 hours

- 10041144

25 10% solution of alum in demineralized water (calcium-free) 70°C 70°C/3 hours 26 20% solution of alum in demineralized water (calcium free) 70°C 70°C/3 hours 27 20% solution of alum in demineralized water (calcium free) 70°С 70°C/3 hours 28 20% solution of alum in demineralized water (calcium free) 70С° 70°C/3 hours 29 20% boron solution in demineralized water (calcium-free) 70°С 70°C/3 hours thirty 20% boron solution in demineralized water (calcium-free) 70°C 70°C/3 hours 31 20% boron solution in demineralized water (calcium-free) 70°С 70°C/3 hours 32 1:1 linseed oil : tree resin 170°C 170°C/2 hours 33 1:1 linseed oil : tree resin 170°C 170°C/2 hours 34 1:1 linseed oil : tree resin 170°С 170°C/2 hours 35 1:1 linseed oil : tree resin 170°С 170°C/2 hours 36 wood resin 220°C 220°С/2 hours 37 wood resin 220°C 220°С/2 hours 38 wood resin 220°C 220°С/2 hours 39 wood resin 220°C 220°С/2 hours 40 Copper (Celcure AC800) 70°С 70°C/3 hours 41 Copper (Celcure AC800) 70°С 70°C/3 hours 42 Copper (Celcure AC800) 70°C 70°C/3 hours 43 Copper (Celcure AC800) 70°C 70°C/3 hours

As can be seen from FIG. 2, traditionally impregnated Scandinavian spruce is impregnated only on the surface. Further, the impregnation is uneven, and the depth of impregnation is at most approximately 0.5 cm. Thus, the log remains mostly unimpregnated. Moreover, the use of copper-based impregnations is undesirable because these compounds are harmful to the environment and are also harmful to humans.

As can be seen from FIG. 2, the wood material logs were completely impregnated using the method according to the invention. There were no untreated pieces of wood material left. Moreover, streaks in the wood material stand out when colorants (eg, a combination of linseed oil and wood resin (liquid)) are used in combination with a liquid temperature that does not completely burn out the sugar components of the wood material. Thanks to this, the impregnated wood material looked more natural and attractive. A darker coloration of the wood material was obtained using a higher temperature during pressurization and sonication due to the burnout of the sugar constituents. Moreover, as can be seen, all types of wood material (from softer to harder material) have been completely impregnated using only environmentally friendly substances (linseed oil and resin are not considered harmful to the environment).

As can be seen from FIG. 3, both pine logs and Scandinavian spruce logs were completely impregnated using salts. Alum and boron are considered safe for the environment. Since the logs were completely impregnated, the flame-extinguishing effect can be considered enhanced. Moreover, even with the use of a 5% fire retardant solution, the wood material became completely impregnated. At higher concentrations, some precipitation of salts was observed. It was believed that this was due to the drying of the wood material. Precipitation has only an aesthetic effect.

All samples 16-43 were also fully impregnated. There were no areas where the wood material remained untreated, regardless of the type of wood material, the liquid used (eg water, wood resin, fire retardants and oils) and the temperature during steps (c) and (d).

In conclusion, it should be noted that wood-based materials obtained from several tree species were completely impregnated using the method according to the invention, i. no untreated/unimpregnated areas were observed. Thus, the method of the present invention is clearly superior to conventional methods. Moreover, environmentally friendly materials can be added to the liquid, and these additives completely penetrate the wood material, both in the case of softer and harder wood materials. This is an improvement over conventional impregnation methods.

List of symbols

- Wood material

- Wood material

- 11 041144

- Wood material

- Wood material

- Wood material

- Wood material

- Wood material

- Wood material

- Wood material

- Wood material

- Wood material

- Wood material

- Wood material

- Wood material

- Wood material

- capacity

- Capacity

- capacity

- Pressure pump

- Vacuum pump

- Heating/cooling device

- valve

- valve

- valve

- Heating/cooling device

- valve

- valve

- Pressure pump

- Ultrasonic generator

- capacity

- Wood material

Claims (11)

CLAIM 1. Method for processing wood material, characterized in that it includes the following steps: a) vacuuming wood material; b) supplying liquid to the wood material while maintaining a vacuum; c) exposing the wood material to overpressure at a temperature between 70 and 220°C, at which the liquid does not reach its boiling point; d) sonicating the wood material while maintaining excess pressure at a temperature of 70 to 220°C. 2. Method according to claim 1, characterized in that the ultrasound has a frequency of 1 kHz to 1 MHz, preferably 1 to 120 kHz. 3. Method according to claim 1 or 2, characterized in that the ultrasound has a frequency of 20 to 40 kHz, preferably 30 kHz. 4. Method according to any one of claims 1 to 3, characterized in that the ultrasound is applied for 1 minute to 15 hours, preferably 5 minutes to 12 hours. 5. Method according to any one of claims 1 to 4, characterized in that the temperature in steps (a) to (d) is controlled. 6. The method according to any one of claims 1 to 5, characterized in that the vacuum is from 0 to 100% of atmospheric pressure (from 0 to 0.1 MPa (from 0 to 1000 mbar)), preferably 80% of atmospheric pressure or less, preferably 50% of atmospheric pressure or less. 7. Method according to any one of claims 1 to 6, characterized in that the vacuum is maintained for 1 minute to 5 hours, for example 5 minutes to 2 hours, preferably 15 minutes to 45 minutes. 8. The method according to any one of claims 1 to 7, characterized in that the excess pressure is from 0.1 MPa (1 bar) to 3.0 MPa (30 bar), for example from 1.0 MPa (10 bar) to 2 .5 MPa (25 bar). 9. The method according to any one of claims 1 to 8, characterized in that the liquid is selected from water, oils, pigments and dyes, alum, for example at a concentration of 5, 10 or 20 vol.% solutions of boric acid, flame retardants, biocides, fungicides and copper, as well as combinations of these substances. 10. The method according to any one of claims 1 to 9, characterized in that the liquid is water, an aqueous solvent or an oil. 11. Method according to any one of claims 1 to 10, characterized in that the steps of the method are carried out in a sealed container.