HRP20010938A2 - Process for impregnating wood - Google Patents

Abstract

Impregnation of wood comprises: immersion of the wood in a preheated dispersion containing impregnating oil and water soluble polymers; extracting water from the wood; creating a shear force in the dispersion to split the polymers and create a greater surface area for drawing in additional water; and then pressurizing the emulsion into the wood in one or more cycles. A dispersion is created in a tank (1) by combining impregnating oil and water soluble polymers. The dispersion is preheated to 100 [deg]C and pumped into an impregnation tank (13) containing wood to be treated. The dispersion temperature is raised to 100-130 [deg]C while continuously circulating and water extracted from the wood is partially combined with the polymers. A shear force is then created in the dispersion to split the polymers and create a greater surface area for drawing in additional water. The emulsion is then pressurized into the wood in one or more cycles. An independent claim is also included for the process plant comprising a dispersion forming tank (1) and an impregnation tank with a unit (26) for producing a shear force in the dispersion.

Description

The invention relates to a process for impregnating wood in a soaking boiler using an impregnating agent, which contains impregnating oil, and at the very least, water-soluble polymers as a thickening agent, and also relates to a device for implementing this process.

In accordance with the usual process for wood impregnation, in the pre-impregnation process, the introduced oil for impregnation is heated to a temperature of over 100°C, and maintained at that temperature, in order to evaporate all the remaining water from the wood. The evaporated water is removed as condensate from the boiler. Such a procedure, for example, the so-called improved "Rüping procedure", which is an existing procedure according to the rules of the German Federal Railways (Bundesbahn) or the German Post (Bundespost). This procedure is described, inter alia, in "Holzlexikon" 3rd edition, volume 1, DRW-Verlag Stuttgart, page 636, paragraph b). The disadvantage in this process is the fact that the resulting condensate, which is drained off, cannot be further used, and must be removed as waste, which results in a large loss of heat.

From the document US 5 098 472, a process is known in which an impregnation emulsion is produced from impregnation oil, pigment and water-soluble polymers, with the addition of water, in an emulsification tank. For wood impregnation, the impregnation emulsion is fed into the soaking boiler. The disadvantage of this procedure lies in the fact that for the production of a stable, i.e., storable, emulsion, new substances must be introduced, which, again, prevent the possibility of oil penetration. All in all, producing an emulsion in this way is a difficult and time-consuming process. In addition to other things, the water phase inside the finished impregnation emulsion is very sensitive to temperature and tends to boil quickly during the impregnation process, even at temperatures of 90°C and above, so that unwanted pigmentation occurs during and after impregnation. In addition, the impregnation emulsion described here is not able to impregnate damp or wet wood, because this leads to disturbances in the oil/water balance in the emulsion, which destroys it. As a rule, with this procedure, the wood needs to be dried beforehand in a special pre-procedure, which again represents an increase in costs.

From the document DE 198 12 407 A1, we also know the process in which, with the addition of water, an emulsion for impregnation is produced from impregnation oil, pigments and water-soluble polymers. There, an additional agent is introduced in the water or oil phase, with the action of shearing forces, that is, an emulsion is first created with the joining of the water and oil phases, after which an additional substance is added to the emulsion with the action of shearing forces. The described procedure enables the introduction of additional substances, in a less expensive and more flexible way, already during the production of impregnation agents.

The task of this invention is to implement a procedure that will enable the impregnation of damp and even wet wood, without the need to dry the wood and drain the condensate in the preliminary procedure.

This task is solved in accordance with patent claim 1, as well as by means of a device in accordance with patent claim 12. The further implementation of this invention can be seen from the other mentioned patent claims.

After impregnation oil, pigments and water-soluble polymers are placed in the dispersion tank, dispersion is carried out there, this dispersion is heated, then it is introduced into the soaking boiler, in which the wood for impregnation is located, with a temperature of at least 100°C, and a temperature of 100 to 130°C is maintained there during the heating phase, with constant rolling, during which water is extracted from the wood and partially binds to the polymers. After the dispersion is subjected to a shearing force, the polymers are split due to the shearing force. Namely, the surface of the polymer expands, so that it can absorb an even larger amount of water, and the impregnation agent is pressed into the wood by means of one or more pressing cycles, and thus it is possible to extract water from the wood in a single step during the process, introduce water into the agent for introduce the impregnation and impregnation agent into the wood. From the resulting effect, where the water that comes out of the wood cells is squeezed out of the pores of the wood, and which binds to the polymers under the action of shearing forces, a great advantage arises, because now the bound water from the cells can be introduced into the wood, and there in approx. the same amount of volume of evaporated water, drawn into the impregnation agent. Cell water is thus, without any prior preparation, used in an ideal way for impregnation, in such a way that it introduces pigments into the wood, in the finest distribution, together with impregnation oil. Among other things, the anatomical properties of wood are used in such a way that the wood itself makes available the amount of water from the cell, which corresponds to the same amount of impregnation agent, which should be introduced into the wood. Thus, for example, during dehydration, more cellular water comes out of chips and REIFHOLZ wood than in the case of KERNHOLZ wood. In accordance with the process of the invention, it is possible to introduce this cell water in the same amount into the wood during impregnation in a favorable way.

It is also an advantage that the dispersion can be subjected to a shearing force, when the water content, measured in the dispersion, reaches a water content of 20 to 30% by volume at the latest.

As a rule, pigments are added to the impregnation agent to close the pores of the wood. If possible, the addition takes place already in the dispersion tank, but alternatively it is possible to add the pigments in the soaking boiler.

In the further development of the invention, the possibility of adding additional water-soluble polymers and/or water to the impregnation agent is foreseen. In this way, it is possible to adjust the procedure to the appropriate content of the cellular water of the wood from the soaking boiler and during the impregnation itself. The addition of water-soluble polymers can be an advantage in this case, if it turns out that the content of cell water in the wood is higher than expected. The addition of water can be beneficial if the wood is impregnated with a degree of dryness that is higher than expected.

It will be especially good to produce the impregnation emulsion using shear force, when it comes to wood that can be soaked well (such as beech, birch, etc.), for optimal penetration in the soaking boiler. In this case, it will be necessary to expose the impregnation dispersion from the soaking boiler to increased shearing force, via the shearing unit.

During the further development of the invention, it is planned to add polyacrylic acid or polyacrylic saccharide as a water-soluble polymer to the impregnation agent, in a proportion of 0.03 to 05.0% by weight. Water-soluble polymers, which are used here, preferably polyacrylic acid, act as a dehydrating component, and help the excretion of cell water from the wood by binding water to itself. The more cell water is chemically bound, the faster the cell water comes out of the wood into the impregnation agent, without problems and without the formation of free water. The impregnation agent will be able to heat up faster than is the case with previous impregnation procedures, and it will be brought to the impregnation temperature, because there is no heat loss due to the now unnecessary draining of condensate. Here, the condensate acts to direct the carboxyl groups to the polyacrylic acids based on the dipole interaction between these groups and the water dipoles. Water is stored via dipole binding.

If dried wood, from which a little water is extracted during the impregnation process, needs to be impregnated, it would be good to add triethanolamine or a substance with a similar effect to the impregnation agent, in order to neutralize the polyacrylic acid. With the help of triethanolamine, the polymer structure is also established, which is the carrier of the pigment, such as polyacrylic acid. Alternatively, an aqueous admixture may follow.

During the further development of the invention, it is envisaged that the shearing force will be reduced during the action of the impregnation agent on the wood, to the extent that the impregnation emulsion breaks down and hydrophobic substances are added for hardening, and these substances act during the finishing treatment of the wood, to seal its surface. The fine pigment, which until then was stored in dispersion, now accumulates, which is more favorable, on the surface of the wood or on the outer grooves of the pores. It would be good to add waxes, silicones or polymers, which fix the fine pigment, that is, at the same time seal the surface of the wood.

A further advantage is that, after the impregnation is finished, the dispersion is led from the soaking boiler into the dispersion tank, so it can be used for further impregnation procedures. If possible, the preparation of the dispersion will follow in the dispersion container, where impregnation oil, water-soluble polymers and/or pigments are added and dispersed as necessary. Alternatively, it is possible to prepare the dispersion in a soaking boiler.

In a further development of the invention, it is planned to add a dispersion tank with a dispersion device to the device, and that at least one shear unit is added to the soaking boiler, into which the dispersion impregnation agent, prepared in the dispersion tank, is introduced. Preferably, the shear power of the shear unit assigned to the soaking boiler should be adjustable. In this way, the dispersion can be maintained and stabilized in the soaking boiler, as desired, or an emulsion can be produced, which is kept stable. This makes it possible to adapt the impregnation process to the appropriate requirements. It is desirable to add at least one inlet to the shearing unit for the introduction of additional substances, such as pigments or, for example, waxes and silicones.

In accordance with a more favorable example of execution, a shearing unit was added to one feed leading to the soaking boiler as a bypass. At the same time, it is an advantage if the shear power can be adjusted, which is supplied by the shearing unit to the soaking boiler.

In the following content, the invention will be explained in more detail on the basis of examples of implementation. The drawing shows the device for wood impregnation in the soaking boiler, schematically shown in Figure 1.

The device shown in the drawing shows the dispersion tank 1, which is connected to the heat exchanger 4 by pipelines 2 and 3. In pipeline 2 there is one transport pump 5. Pipeline 2 can be closed using valves 6 and 7. Pipeline 3 is led as a return flow supply dispersion tank 1. A valve 9 is located in front of the entrance 8 to the dispersion tank l.

In the pipeline 3, in front of the heat exchanger 4, there is a valve 10 for closing the pipeline 3. From the heat exchanger 4, the pipeline 11, in which the pump 12 is located, leads to the soaking boiler 13. In the pipeline 11, there are valves 14, 15 and 16 The distribution pipelines 17, with nozzles 18, are connected to the pipeline 11, in the soaking boiler 13, along its entire length.

From the soaking boiler 13, the suction line 19, in which the pump 20 is located, leads to the heat exchanger 4. In the soaking boiler 13, a distribution pipeline 21 is connected to the suction line 19, on which the suction nozzles 22 are located. Two valves 23 and 24, which are placed in the suction line 19, enable the closing of that line.

From pipeline 11, which leads to the soaking boiler 13, it branches off as a bypass, pipeline 25, in which the shearing unit 26 is located. In pipeline 25, valves 27 and 28 are added on both sides to the shearing unit 26. If necessary, it can more shearing units 26 can also be allocated. The shearing unit 26 has two inlets 29, through which additional substances, such as pigments or, for example, waxes and silicones, are introduced.

In order to carry out the process in terms of the invention, the device, according to the shape in the drawing, can be applied in such a way that an impregnating agent is introduced into the dispersion tank l, i.e. impregnating oil, pigment and water-soluble polymers, as thickening agents without additives of water, and a dispersion is created there by activating the dispersion device 1a. The dispersion is heated and transported, after opening the valves 7, 6 and 10, and with the adjustment of the transport pump 5, through lines 2 and 3, along the heat exchanger 4. After opening the valves 14, 15 and 16, the dispersion arrives, preheated to at least 100°C , through the inlet 11 to the soaking boiler 13. In the soaking boiler 13, the dispersion is redistributed to the distribution pipelines 17 with output nozzles 18. Before introducing the dispersion, wood is introduced into the soaking boiler 13, which is not shown in the drawing.

By preheating the dispersion, crystallization of the impregnation oil, supplied to the soaking boiler 13, is prevented when passing through the pipelines and valves. During one phase of the subsequent heating, the dispersion is pumped, after opening the valves 24 and 23 of the suction line 19 by means of the pump 20, in one circular flow, for the purpose of heating, through the heat exchanger 4 and through the inlet 11, back to the soaking boiler 13. Before after that, the valve 10 of the pipeline 3 above the heat exchanger 4 is closed. In this heating phase, the temperature rises from 100 to 130°C and is maintained at that temperature.

During the heating phase, water is released from the wood into the dispersion. At the latest when the proportion of water in the dispersion is 39% by volume, and after closing the valve 15 and opening the valves 27 and 28, the pipeline 25, which leads to the shearing unit 26, is opened, and the shearing unit 26 is adjusted. By means of the shearing unit 26, water is drawn into the dispersion, whereby the dispersion is additionally stabilized, because the pigments, as well as the water-soluble polymers, are kept in a fine distribution. Using the shearing unit 26, an emulsion can be prepared, which in its known way enables deep penetration of the pigment into the wood, especially if we impregnate wood that is well permeated by soaking, as is the case with beech and birch. This will produce an effect that allows the introduced shear energy to be further utilized in the temperature control process. If you need to impregnate wood, which is difficult to soak, such as, for example, oak, it is often enough to impregnate such wood only with a dispersion. After all, at the end of the wood heating phase, there is pressure to introduce the dispersion, prepared in the soaking boiler, i.e. introducing the emulsion into the tree.

If an emulsion is prepared in the soaking boiler 13, this results in the possibility of reducing the action of the shearing force of the shearing unit 26, which achieves the dissolution of the emulsion into a dispersion during the impregnation process. In this way, during the finishing treatment of the wood, with the simultaneous re-action of the pressure, additional hydrophobization of the wood can be achieved with the addition of, for example, hardening wax, silicone or polymer.

At the end of the impregnation, the dispersion is returned, after opening the corresponding valves 24, 23, 10 and 9, through the pipeline 19, 3 to the dispersion tank. There it is then possible to prepare the dispersion in such a form that, depending on the need, impregnation oil, water-soluble polymers and pigments are additionally added and dispersed.

The process according to the invention is characterized by the fact that it achieves a permanent connection of water into a dispersion, or emulsion, during the dehydration and impregnation of wood. Water can no longer be lost by boiling and serves, based on its association in the impregnation agent, as an optimal impregnation agent in terms of optimal distribution of pigments, as well as in terms of the subsequent moisture balance in the wood. The water can slowly dry out, after impregnation and thus conservation, with the oils and pigments remaining behind as a deep-acting sealing layer in the wood.

By means of the process in accordance with the present invention, and based on the high proportion of water, savings in soaking can be achieved. The high proportion of water enables the reduction of toxic contents and their good and even distribution in the wood. The water can later be squeezed out, whereby a very small proportion of toxic substances remains in the wood, in relation to the volume of the wood, which remains protected from any washing.

Claims (15)

1. Method for impregnating wood in the soaking boiler (13), using an impregnating agent, which contains impregnating oil and, at least as a thickening agent, water-soluble polymers, indicated by - that the impregnating oil and water-soluble polymers are placed in the dispersion tank (1), where the dispersion is carried out, - that the dispersion is heated, it is introduced into the soaking boiler (13), in which there is wood for impregnation with a temperature of at least 100°C, where then during the heating phase, with constant rolling, it is kept at a temperature of 100 to 130°C , whereby the water is extracted from the wood and partially binds to the polymers, - that the dispersion is exposed to a shearing force, whereby the polymers are split, due to the action of the shearing force, i.e. the surface of the polymers increases, so that they can absorb an additional amount of water, and - that the impregnation agent is then introduced into the wood, using one or more pressing cycles. 2. The method according to claim 1, characterized in that the proportion of water in the dispersion is measured and the dispersion is exposed to a shearing force, when the proportion of water in the dispersion of 20 to 30% by volume is reached. 3. The method according to at least one of the previous claims, characterized in that pigments are added to the impregnation agent. 4. The method according to at least one of the previous claims, characterized in that water-soluble polymers and/or water are added to the impregnation agent in the soaking boiler (13). 5. The method according to at least one of the previous claims, characterized in that the impregnation emulsion is produced in the soaking tank (13) using a shear force unit. 6. The method according to at least one of the previous claims, characterized in that polyacrylic acid or polysaccharide is added to the impregnation agent as a water-soluble polymer in a proportion of 0.03 to 0.5% by weight. 7. The method according to at least one of the previous claims, characterized in that triethanolamine is added to the polyacrylic acid as a neutralizer. 8. The method in accordance with at least one of the previous requirements, characterized by the fact that the effect of the shearing force during the action of the impregnation agent on the wood is reduced so that the impregnation emulsion breaks down, and hydrophobic substances are added, which during the final stage of wood processing act as a means of sealing the wood surface. 9. The method according to claim 8, characterized in that waxes, silicones or polymers are added as hydrophobic hardening agents. 10. The method according to at least one of the previous claims, characterized in that the dispersion, after completion of the impregnation, is removed from the soaking boiler (13) into the dispersion container (1) and is thus suitable for further use in impregnation procedures. 11. The method according to claim 9, characterized in that the preparation of the dispersion follows, whereby, depending on the need, impregnation oil, water-soluble polymers and/or pigments are additionally added and dispersed. 12. The method according to at least one of the previous claims, characterized in that a dispersion device (1a) is added to the dispersion tank (1), and a shearing unit (26) is added to the soaking boiler (13), whereby in the soaking boiler (13) introduces the dispersion agent for impregnation, prepared in the dispersion tank (1). 13. Device according to claim 12, characterized in that at least one supply line (29) is added to the shear force unit (26). 14. Device according to claim 12, characterized in that the shear force unit (26), which is added to the soaking boiler (13), is adjustable. 15. Device according to claim 12, characterized in that the shear force unit (26) is located on the pipeline (25) leading to the soaking boiler (13), added to said boiler as a bypass.