DK149462B - PROCEDURE FOR TREATING PRODUCTS OF HIGH-RESPINE TREATMENT PRODUCTS - Google Patents

Description

1 149462

The invention relates to a process for treating products of high resin wood species, whereby the wood products are contacted with a solvent from the group of chlorinated hydrocarbons.

5 For many purposes, wood products are used in the form of veneers of various types of wood, including those containing, in the untreated condition, a considerable amount of resin, e.g. veneer of pine and other conifers. The resin content of a log can vary depending on various factors, e.g. the soil conditions at the growing site and the 10 latitude of the growing site. It can even vary greatly between different batches of one and the same cane. Excessive resin content complicates the processing of the veneer, among other things by frequent renewal of abrasive paper and uneven suction of the coating agent. The resin content can also cause a deterioration in the appearance of the product and thereby a lower market price. Therefore, there is a need for a method of eliminating or reducing these drawbacks by affecting the resin concentration in veneered wood varieties.

Swedish patent specification 51,590 discloses a process for the extraction of tanning substances, resins and other soluble constituents from solid wood products by treatment with acetone at very high pressure. However, as an extractant for resins, acetone is not overly effective, and in addition, acetone is a low boiling, highly flammable and explosive compound to work with.

From Chemical Abstracts, C A 46: 9866 f-g, it is known to recover resin from pine stumps that have been left in the soil several years after the trees have been felled, using dichloroethane as an extractant. It is stated that upon repeated extraction of the tree stumps in the form of cubes, it is possible to extract over 90% of the total resin content of the tree, and that the degree of extraction and rate is far better than using gasoline as an extractant. In this literature reference, however, the task is apparently only to extract as much of the resin as possible from the wood product in question and not to provide a wood product with a certain, low, uniform resin content, so that there is no specific indication as to how such a wood product is obtained.

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Further, from Chemical Abstracts, CA 52: 10572 d, it is known to extract pitch or resin substances from coarsely ground wood with dichloroethane at room temperature. It is stated that 96% of the resin can be extracted in 3-4 minutes. Thus, this literature site 5 also deals exclusively with obtaining the maximum possible yield of resin from a given wood product and not with the provision of a particularly useful and uniform wood product after extraction.

Finally, from Chemical Abstracts, CA 53: 12701 b, it is known that rosin with various properties can be obtained depending on the solvent used in the extraction of the rosin from the wood resin, including the use of dichloroethane.

Also, this literature site is intended solely for the preparation of resin or, rather, fractions thereof, and gives no instructions for the preparation of a particularly useful and uniform wood product after extraction.

In relation to the prior art mentioned above, the object of the present invention is almost the opposite, since the invention does not aim to extract resin in the greatest possible yield or with certain properties from given (waste) wood products, but 20 from high resin wood species that provide particularly useful wood products in the form of veneers with a predetermined low, uniform resin concentration. At the same time, it is an object that this is achieved by an energy-economical approach which is not associated with any particular fire or explosion risk.

This is achieved by the method according to the invention being characterized in that the wood products are introduced into a treatment container in the form of a large number of veneer leaves, and that the solvent is fed to the treatment container and caused to penetrate each veneer leaf from both sides of the leaf and into the heated. condition is dissolved to a portion of the resin contained therein, that the resin concentration in the solvent in the treatment vessel is kept below 2 wt.%, preferably less than 1 wt. In that the resin concentration in the veneer leaves is substantially everywhere brought below 1% by weight, preferably below 0.5% by weight, that the resinous solvent is removed from the treatment vessel and that the residual solvent remaining in the veneer leaves is maintained by maintaining a subatmospheric pressure in the vessel below. metilførsel.

3 149462

Preferably, methylene chloride, CH 2 Cl 2, is used as the solvent. Other halogenated hydrocarbons having a relatively low boiling point, preferably below 100 ° C, which, like methylene chloride, are not easily ignitable / can be used. These include 5 chloroform, trichloroethane and trichloroethene, dichloroethane and dichloroethene and carbon tetrachloride.

The treatment is conveniently carried out on a number of bundles of loosely bonded veneer sheets, between which the solvent can readily penetrate, so that the veneer sheets are contacted quickly and from both sides 10 of the individual veneer sheets.

During the soaking phase, the solvent should be circulated in the treatment vessel, e.g. using one or more agitators. The solvent is preferably used for at least two tanks, one of which is connected to circulate the solvent, while the other is available for recovery of the solvent by stripping and recirculation. The resin remaining after evaporation is removed from the tank and may be disposed of for special purposes.

After the liquid solvent has been removed from the treatment vessel, the remaining solvent in the veneer blades is expelled appropriately by lowering the gas pressure and by heat supply. The pressure in the container should be below approx.

600 mm Hg, suitably between 250 and 500, and preferably between 350 and 450 mm Hg when the solvent is methylene chloride.

The solvent vapor may be condensed or absorbed in an activated carbon absorber and recycled to the process. Recycling entails economic and environmental benefits.

In order to speed up the process, the solvent may be preheated upon delivery to the treatment vessel, conveniently near the boiling point, e.g. to between 35 and 40 ° C for methylene chloride. The residence time of the solvent in the treatment vessel should be limited to a maximum of approx. 30 minutes, although this is not a condition for the successful completion of the process. Equally, 35, the evaporation of solvent vapors from the veneer blades should be possible at a maximum of approx. 30 minutes, without this being considered a necessary condition. During stripping, heat should be supplied to the treatment container, conveniently by means of electrical resistance heating elements or from the outside by means of a heating jacket around one or more portions of the treatment container.

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The resin content of the veneer blades should be reduced almost everywhere to a maximum of 1%, and preferably to a maximum of 0.5%.

During the treatment, in addition to extraction of resin from the veneer blades, there is a redistribution of the resin concentration 5 in the leaves, whereby parts of a veneer leaf which initially exhibit a low resin concentration may appear after the treatment exhibit an elevated resin concentration, which is acceptable, however. as long as the resin content still does not exceed the prescribed value.

10 To ensure the intended result, the resin content of the circulating solvent must be checked regularly. At a too high resin content, pure solvent can be added or another tank with cleaner solvent may be added. The resin content of the solvent in the solvent is at most 2%, suitably at most 1% and preferably at most 0.5%.

When using methylene chloride and other water-soluble resin extractants, the moisture content of the veneer sheets is not affected or only negligible during the treatment process, which is most often an advantage. On the one hand, the always necessary conditioning of the veneer blades with regard to the moisture content can take place in the usual way without being disturbed by the process of removing the resin, and secondly, in the latter process, veneers can be treated with any moisture content, also conditioned accordingly.

In practical experiments with the method according to the invention, the resin content of veneer blades was examined in a bundle of such, whereby some veneer blades were first removed from the bundle and examined separately for the resin content while the others were subjected to the treatment according to the invention, after which their resin content was determined. In the more important steps of the process, the following times were used. The solvent was CHgCl2 · 5 min.

Pumping of preheated solvent into 38 ° C in treatment container filled with a veneer bundle 10 5 Resin extraction with circulating solvent 60

Draining the container and draining solvent from the veneer leaves 30 10 Removing the solvent from the veneer leaves at 300-400 mm Hg during heat supply (max, temp. 75 ° C) _60

The above times can probably be shortened by optimum execution of the process.

15 For different bundles of veneer sheets, the following results were obtained.

Resin content%

Bundle Number of veneer sheets examined (average) 20 no ._ubehandl._behandl._ubehandl. treat.

1 2 21 5.7 0.52 2 2 14 2.5 1.1 32 14 6.2 0.50 _4_2_8_2j3_0.30 25

Methylene chloride and similar halogen-substituted hydrocarbons, due to their good resin solubility due to their high flammability, have shown other common solvents clearly superior to the purposes of the invention.

By the method according to the invention, substantially improved surface properties of veneer from resin-rich woods are obtained with a corresponding increase in the value of the products. In addition, veneer portions which should have been previously discarded due to too high resin content can now be used as intended after a treatment according to the invention.

The solvent used may contain additives for special purposes, e.g. color pigments of various kinds, such as aniline dyes, substances for increasing the fire resistance of the products, wood preservatives and other wood modifying substances.

In the accompanying drawing is shown a system for carrying out the method according to the invention. The system is shown schematically and 5 viewed from the side as well as partly in section.

On. a site limited by walls 1 has a veneer leaf treatment container 3 installed. The container is elongated, e.g. ca. 3-4 m, and may have a circular cross section with a diameter of e.g. 0.5-1 m. Other cross-sectional shapes are of course possible. At one end 5 of the container, the container is open and accessible for insertion of an elongated trough 9, partially shown in section, showing that its interior exhibits a plurality of longitudinally extending compartments 11, each of which is intended to record a number of veneer sheets, e.g. 10-30. The trough may conveniently be arranged to run on wheels rolling on longitudinal support rails not shown in the drawing.

Heating caps 13 may be arranged around the container 3. The figure also shows a solvent collection tank 15 and two tanks 17 and 19 for substantially resin-free solvent. The drawing also shows a container 21 with no connections shown, which container is intended to be supplied with container liquid from the tank 15 for evaporating solvent, which can be fed to the tanks 17 and 19, whereby the resin can be removed from the container 21 in a manner known per se. manner. The drawing 25 also shows a number of conduits and valves for routing fluid between the units in the system in a suitable manner according to the invention. 23 represents a three-way valve I inserted between the container 3 and the tank 15 and connected to the tanks 17 and 19 via valves 25 and 27. By 29, a valve is denoted in a conduit which extends from the tank 15 and leads to the tanks 17 and 19 via valves 35 and 37. New solvent is supplied to the tanks through a conduit via valves 43, 31 and 33.

The system according to the drawing is used as follows.

After the compartments 11 of the trough 9 have been provided with loose bundles 35 of veneer leaves, the trough is inserted into the container 3, after which solvent is filled and the treatment is started. During the treatment, the solvent is circulated by means of one or more agitators, as indicated by 8. After the prescribed time, the solvent is drained onto the tank 15 and after the solvent has run out of the veneer blades, it is expelled! leaving residual solvent by vacuum. In order that the temperature should not become too low and the evaporation in the path, the container is heated electrically by means of heating caps 13. After the solvent has disappeared from the veneer leaves, the trough 9 is withdrawn and charged with a new team of untreated veneer leaves. Solvent used in the tank 15 is directed to distillation in the tank 21 in a manner previously described.

Claims (7)

A process for treating products of high resin wood species, whereby the wood products are contacted with a solvent from the group of chlorinated hydrocarbons, characterized in that the wood products are introduced into a treatment container in the form of a large number of veneer leaves and the solvent is fed. causing the resin concentration in the solvent in the treatment container to be kept below 2 wt.%, preferably below 1 wt.%, of the treatment container and caused to penetrate each veneer sheet from both sides of the blade and in heated state 10. and that the time of solvent contact with the veneer blades as well as the pressure and temperature of the treatment vessel is controlled or selected in such a way that the resin concentration in the veneer blades is substantially everywhere lower than 1 wt.%, preferably below 0.5 wt.%, that the resinous solvent is removed from treatment vessels. n, and that solvent remaining in the veneer leaves is removed by maintaining a subatmospheric pressure in the vessel during heat application. Process according to claim 1, characterized in that the solvent is methylene chloride, Method according to any one of the preceding claims, characterized in that the treated veneer sheets 25 are made of pine veneer. Process according to any one of the preceding claims, characterized in that, during the soaking of the veneer leaves, the solvent is recycled between the treatment vessel and a tank for the solvent. Process according to Claim 3, characterized in that the gas pressure during removal of the solvent from the veneer blades using methylene chloride as solvent is maintained between 250 and 500 mm Hg, preferably between 350 and 450 mm Hg. Process according to any one of the preceding claims, characterized in that the solvent is supplied to the treatment vessel in a preheated state, suitably heated to a temperature slightly below the boiling point of the solvent. Process according to any one of the preceding claims, characterized in that the solvent is kept in contact with the veneer blades for a maximum of 30 minutes.