DE1492511C3 - Process for drying wood impregnated with a solution of preservatives - Google Patents

Description

The invention relates to a method to protect wood and other organic materials against rot and insects to preserve and also to cause drying of the impregnated material and in connection with the drying process, to add certain substances to the wood that give it the desired properties to lend.

The impregnation solution intended for the process is pressed into the wood under pressure. To the To facilitate subsequent drying, no more solvents should be added to the wood than necessary. When impregnating, therefore, it is better not to use full impregnation, but rather it is preferable the Lowry or Rüping method is used.

With full impregnation, the wood is first exposed to a vacuum before the solution is injected under pressure. In this way, maximum absorption of the solution in the wood is obtained, ie not only the walls of the wood cells, but also their cavities are completely filled with solution. As an example it can be mentioned that when fully impregnated, Swedish pine usually absorbs about 300 liters of preservation solution per m ^{3 of} wood.

In the Lowry process, on the other hand, the process starts without a fore-vacuum. The solution is pressed directly into the wood. After this has taken place and the solution has then been withdrawn from the cylinder, a vacuum is applied, with part of the impregnating solution supplied being sucked out of the wood with the aid of the air compressed in the wood during the pressure period. When treating Swedish pine in the Lowry process, about 150 liters of solution per m ^{3 are} usually absorbed by the wood, and this quantity is then very well distributed in the wood.

The Rüping process goes one step further and exerts air pressure on the wood before the solution is injected. This has the consequence that an increased quantity of air is compressed in the wood when the solution is then introduced into the wood under increased pressure. During the subsequent vacuum period, even more solution can be sucked out than with the Lowry process. When treating Swedish pine according to the Rüping method, a maximum of 100 liters of solution per m ³ are usually added to the wood. In this context, the Rüping process has certain technical advantages. The apparatus for its use, however, is so expensive that the Lowry process is usually preferable despite the somewhat higher absorption.

In the present case, the preservation agents

agent primarily uses aqueous solutions of agents that are fixed after impregnation, preferably those in which the protective substances are dissolved with the help of ammonia and ammonium salts are. Solutions of this kind are described in Swedish patents 182404 and 182477. They have the important property that they are sufficient for the Lowry and Rüping processes Own durability.

Because different quantities of solution are added to the wood in the various impregnation processes a suitably concentrated solution is used for each process, so that the wood per Volume unit always receives the correct (same) amount of preservative.

The invention now relates to a method for drying with a solution of preservatives Substances impregnated wood, which is characterized in that the impregnated wood in the Heat at up to 80 to 90 ° C in a high-boiling liquid that is immiscible with the solvent, preferably high-boiling oil, treated in vacuo and while maintaining the vacuum that Treatment medium removed.

The wood is then ready for use. It has now received protection against wood destroyers, as well as is dried, and eventually the heavy oil penetrated the surface layer of the wood, which makes the wood water-repellent and less prone to swelling and shrinking.

From Mahlke-Troschel »Handbook of Wood Conservation« 1950, pp. 239 to 240, it is known to dry the wood in an oil that is used as a protective agent is used, and after the oil has dried, the protective agent penetrates the wood in large proportions Press in pressure.

In contrast, according to the present process, an impregnation salt is first applied to the wood, whereupon the wood is dried in a high-boiling oil and the oil under vacuum is deducted. So the vacuum is maintained. According to the method of the invention the oil treatment is limited to the surface. This is a very important measure since makes it possible, suitable - sometimes very costly-

playful - to use oils to make the surface water-repellent, or a protective layer against To train fire. Without restricting the absorption of the oil products on the surface of the Wood would produce a heavy wood and the color pigments would separate as it penetrated will. The wood would continue to absorb a lot of oil, both technically and economically Point of view cannot be accepted.

In addition, wood impregnated with salts is much more difficult to dry than not impregnated wood. The salts have a tendency to absorb moisture. Many of them are hygroscopic.

The oil, such as B. Paraffin oil, with which the wood is heated, various substances can be added to give it various desirable properties, or the oil can be replaced by some

such substances are replaced. Chlorinated paraffin can be mentioned as an example. This gives the fabric certain fire protection properties, which is desirable in many cases. The chlorinated paraffin can be used in high boiling points Oil can be used dissolved or it can be used alone. If the chlorine content is high, it is the chlorinated paraffin is so viscous that it is difficult to use without mixing it with oil. Other organic Substances that contain chlorine and phosphorus have fire-protective properties and can have similar properties Way to be used. A phosphorus-containing substance of this type is commercially available under the name Phosgard available. If the oil consists entirely or partially of a drying oil, ζ. B. linseed oil, so can a harder surface of the wood can be obtained; the same effect is achieved if resin is in the oil is resolved. When wax is dissolved in the oil, it can create different types of water repellent properties can be achieved, etc. Of course, color can be added to the oil, so that the wood in Connection with drying is colored.

The procedure is, as mentioned above, in the first place suitable for drying wood that has been impregnated with aqueous solutions. On the other hand, can it can also be used in cases where the impregnant is dissolved in organic solvents is. Wood that has been impregnated in this way is in a high-boiling oil in which the organic solvents are not soluble, "dried". That is when the wood is "dried" in gas form outgoing solvent can easily be condensed and recovered. Such organic solvents, not in z. B. Paraffin oil are dissolved, for example, alcohols and organic acids.

The following example shows a preferred embodiment of the invention without being limited thereto.

example

Pine wood was impregnated with an ammoniacal solution containing 0.6% copper, 0.3% chlorophenol, 1.2% ammonia and 2.5% carbonic acid. Here and in the following are percentages by weight. The impregnation solution was pressed into the wood at 8 kg overpressure for 90 minutes, after which the solution was removed from the impregnation cylinder and a strong vacuum was applied for 30 minutes, a large part of the solution being evacuated from the wood and pumped away from the cylinder. While maintaining the strong vacuum, the cylinder was filled with 40 degree paraffin oil in which a brown dye had been dissolved. The oil was allowed to circulate through the cylinder and also passed a heating unit, which gradually increased the temperature of the oil to 80 to 90 ° C in just under an hour. At this final oil temperature, the wood was dried for 3 hours. The oil was then removed from the cylinder, holding the vacuum until all of the oil was removed. The wood was then taken out of the cylinder and was then finished treated with regard to impregnation, drying, water-repellent effect and coloring. Water added in the form of solution during the impregnation was practically removed. The amount of paraffin oil absorbed was relatively low and was about 60 kg per m ^{3 of} wood. It was found in the surface of the wood.

An interesting variant of the invention is the treatment of moist (raw) wood. Impregnation can be done in the form of a diffusion process and this can be done for practically everyone Woods are used. In this case too, ammonia and ammonium salts are advantageous Solvents are used, as this can be used to obtain agents that diffuse as well as after

ίο the drying can be fixed. As suitable Solution for treating wood by the diffusion method can e.g. B. an aqueous solution with a Content of 1.2% copper, 0.6% arsenic pentoxide, 4% ammonia and 5% carbonic acid are mentioned. One can also use solutions with the same or slightly higher copper content, the copper acetate or formate, mixed with a little ammonium acetate or formate, go out.

The process is carried out so that the moist Wood is surrounded with the preservation solution for a certain period of time, with the agent in the Wood diffused into it. The time for this treatment varies with the dimension and type of wood. Single-inch wood is usually treated for a week, while masts are treated for a month. After a sufficient amount of preservative has diffused into the wood, the impregnation solution is drained and the wood is during an equal time as the diffusion took, prevented from drying. Here is the Agent distributed in the wood. The dehydration can be prevented by leaving the wood during the distribution period is surrounded with oil. If you keep the oil a little warm, around 40 to 50 ° C, in this way the distribution of the remedy is quicker and this period can then be shortened. Then takes place the above-described drying in oil, after which the wood is finished.

When treating damp wood, pressure treatment - in this case full impregnation is preferable - or open-tank treatment can be used instead of long storage in the solution in order to effect the penetrating diffusion. This is particularly preferable in cases where the wood is already a bit dry and therefore not completely raw. With these treatment methods, more preservatives are usually added to the wood than with diffusion treatment, which is why a weaker solution can be used, e.g. a solution with half the content of the additives that have been specified for the diffusion solution. Spruce and pine were treated with such a solution. After the felling, the wood had been stored for _{about two months under winter conditions.} The wood was subjected to a strong vacuum in the treatment cylinder, whereupon the solution was introduced and pressed into the wood under 8 kg overpressure. The solution was then removed and a paraffin oil was introduced into the cylinder instead, which was heated in circulation to a final temperature of 80 to 90 ° C. over the course of one hour, while a strong vacuum was applied to the cylinder at the same time. The warm oil was circulated around the wood for 8 hours while maintaining the vacuum, drying the wood. The process was interrupted by pulling the oil out of the cylinder while maintaining the vacuum

S. 6th

was pumped away. Drying lasted a certain time, so can

When impregnating damp wood, pressure impregnation should have such a good penetration

can be obtained from various impregnation-technical green and distribution that the drying

use the methods that set a maximum water - without a distribution period - in motion immediately

bring about or assume water content in the wood. 5 can be set as indicated in the above

This delays the subsequent drying. Has the attempt been made.

Claims (2)

Patent claims: 1. Method of drying impregnated with a solution of preservatives Wood, characterized in that the impregnated wood in the heat at up to 80 to 90 ° C in a high-boiling liquid immiscible with the solvent, preferably high-boiling oil, treated in vacuo and, while maintaining the vacuum, the Treatment medium removed. 2. The method according to claim 1, characterized in that there is paraffin oil or a oil drying oil, preferably linseed oil, is used.