Manufacturing method for a high durability, high insulating composite timber member and a composite timber member

Abstract

The present invention describes a method for thermo-treatment of wood, where said method comprises the following steps: a) selecting the wood to be as free from knots as possible b) introducing the wood to a temperature increase up to approximately 173° C.; c) maintaining the wood at an ambient temperature of 173° C. for 3-5 hours; d) decreasing the temperature to approx. 20° C.; e) introducing the wood into an autoclave wherein a mixture of linseed oil and mineral oil is applied to the wood, and allowing the mixture to penetrate the wood f) retrieving and storing the treated wood. Furthermore a timber member made with wood treated according to the method is disclosed.

Claims

1. Manufacturing method for obtaining an increased durability, increased insulating composite timber member, where said method comprises the following steps: a. Introducing wood to be treated into a treatment unit, selecting substantially knot-free wood to be treated; b. Increasing the temperature and/or pressure to a first elevated level inside the treatment unit and maintaining said first elevated temperature for a pre-determined period of time, wherein said first elevated temperature level is in a range of about 170° C. to 175° C. for between 45 minutes and up to 6 hours; c. Decreasing the temperature and/or pressure to a certain lower level for a certain pre-determined period of time, wherein said lower level is in a range of about 20° C. to 60° C. and introducing the wood into an autoclave or into the treatment unit, and applying a mixture of linseed oil and mineral oil to the wood, and allowing the mixture to penetrate the wood; and d. Retrieving and storing the treated wood.

2. The method according to claim 1, wherein before or at the same time as step b, replacing the air and vapor inside the treatment chamber with an inert gas.

3. The method according to claim 2, wherein the pressure of the inert gas introduced into the treatment unit is maintained at a pressure higher than the vapor pressure inside the wood to be treated.

4. The method according to claim 3, wherein the pressure of the inert gas introduced into the treatment unit is maintained at a pressure higher than a pressure at the boiling point of the water in the wood.

5. The method according to claim 2, wherein the pressure of the inert gas introduced into the treatment unit is maintained at a pressure higher than a pressure at the boiling point of the water in the wood.

6. The method according to claim 1, wherein the linseed oil has been distilled prior to being applied in step c and wherein nutrients and/or waxes have been removed from the linseed oil.

7. The method according to claim 1, wherein linseeds from which the linseed oil is made is selected from linseeds grown at latitudes between 40° to 70°.

8. The method according to claim 7, wherein the linseed from which the oil is made is selected from linseeds grown at latitudes between 50° to 65°.

9. The method according to claim 1, wherein the wood to be treated in the method is sideboards.

10. The method according to claim 1, wherein method step b and/or step c and/or step d and/or step e is carried out at a pressure between 3 to 15 bars.

11. The method according to claim 10, wherein method step b and/or step c and/or step d and/or step e is carried out at a pressure between 5 to 13 bars.

12. The method according to claim 1, wherein the temperature in steps b and c is maintained at 173° C.

13. The method according to claim 1, wherein the temperature increase to the first elevated level in method step c or b is achieved by circulating steam containing air inside the treatment unit, where inside said treatment unit high temperature and high pressure steam is mixed with the steam containing air from the treatment unit, and said mixture is recirculated into the treatment unit by means of nozzles, where said nozzles are directed at the wood to be treated in such a manner that any gasses evaporating from the wood is quickly ventilated away from said wood; wherein the time in step c is maintained until no more gas evaporates from the wood.

Description

DESCRIPTION OF THE DRAWING

(1) The invention will now be described with reference to the accompanying drawings in which

(2) FIG. 1 illustrates schematically the heat treatment which the selected wood according to the present invention is subjected to

(3) FIG. 2 illustrates a schematic overview of the method according to the present invention

(4) FIG. 3 illustrates a timber member

(5) FIG. 4 illustrates microscopic pictures of untreated pinewood and pinewood exposed to a heat treatment

DETAILED DESCRIPTION OF THE INVENTION

(6) In FIG. 1 is schematically illustrated the heat treatment which the selected wood according to the present invention is subjected to. The selected wood is introduced into a chamber and during a period of 6-16 hours the temperature is increased up to a temperature in the range of 170 to 175° C., preferably constant around 173° C. At this temperature level any excess moisture in the wood will evaporate such that the moisture content will be approx. 5-6%. At the same time chemical changes will take place in the wood structure such that a much more orderly structure is achieved, see FIG. 4. The changes in the wood are both physical, but also chemical in that as already mentioned above most of the changes are caused by thermic degrading of hemi-celluloses. By maintaining the temperature at 173° C. for approximately 3-5 hours as indicated by the curve 10 the wood will change its structure both chemically and physically such that any irregularities or cracks and the like in the wood do not turn into major deficiencies which could otherwise cause the wood item to be discarded. The milder heat treatment slowly transforms the wood into a heat treated wood and the following impregnating process with the oil mixture where the advantages and characteristics of the present invention, among others an increased insulating property without losing its integrity, durability or strength, is obtained.

(7) The traditional thermo wood treatment is illustrated in the dashed line 20, and it is clear that the treatment involves more severe changes which although improving the wood's characteristics do not obtain the same advantages as with the present invention.

(8) In FIG. 2 is illustrated a schematic overview of the method according to the present invention. In step 1 wood is selected 1. The selection criteria for the wood are not very harsh, but it is desirable to treat wood with as few knots as possible and without severe cracking or other defects.

(9) As opposed to the advice given in the thermo wood handbook mentioned above, it is also possible with the present invention to treat sideboards which are a special selection of wood deriving from the manner in which the timber logs are cut at the sawmill. With the thermo wood procedure described in the thermo wood handbook sideboards are discouraged from treatment in that the treatment may cause bending, skewing or other defects giving the thermo wood method a high percentage of defects when sideboards are treated. However, with the present milder treatment method the advantages of the present invention are obtained without generating a high percentage of boards that need to be discarded.

(10) After selection of the wood for treatment the wood is introduced into the thermo treatment facility 2. In this stage the wood is treated as explained with reference to FIG. 1 where the temperature is controlled to follow the curve 10.

(11) After having gone through the thermo treatment as discussed above with reference to FIG. 1 the thermo treated wood is introduced into an autoclave 3. At the same time a mixture of linseed oil and mineral oil is also introduced into the autoclave 3 where the mixture 5 is derived by taking regular linseed oil 6, distilling and refining the linseed oil in a step 7 and mixing it with a mineral oil 8 to obtain the mixture 5 which is added to the autoclave 3 in the method of impregnating the thermo treated wood.

(12) Once the wood has undergone the treatment method in the autoclave 3 it is taken out of the autoclave and stored at 9. At this stage the wood has obtained the advantages, i.e. high durability, wearability and insulation properties due to the thermo treatment, and furthermore has been deeply impregnated with an environment-friendly impregnating agent such that the wood has overall improved characteristics.

(13) In this connection it should be noted that the impregnating agent, i.e. the mixture of refined/cleaned linseed oil and mineral oil, is relatively slow to harden as compared to raw linseed oil, and in this manner during the autoclave method it is possible to obtain a deeper penetration into the wood of the impregnating agent, i.e. the mixture derived at 5 as compared to regular impregnating agents.

(14) After the wood has stored at 9 and the linseed/mineral oil mixture 5 has been allowed to cure, the wood may be used in a sandwich construction in order to obtain a timber member 11 as illustrated with reference to FIG. 3. The sandwich member is made from a layer of wood 12 treated according to the method described above with reference to FIG. 2. This wood 12 will typically be used in timber members which are exposed to the ambient environment, i.e. the exterior on a house, for example built into a door frame, window frame or the like.

(15) In order to break the thermo bridge the timber member 11 is provided with an insulating layer 13. This insulating layer may be chosen from any suitable organic or inorganic material, but preferred materials are cork, polyurethane foam or other insulating materials.

(16) Finally, the other side of the sandwich may be constituted by regular wood 14, but naturally also wood treated according to the invention may be positioned on the opposite side of the sandwich.

(17) The sandwich is adhered together, and the skilled person will select a suitable adhesive/glue according to circumstances.

(18) In FIG. 4 are illustrated microscopic pictures of untreated pinewood 20 and pinewood exposed to a heat treatment 21. It is clear that the structure of the heat treated pinewood 21 is much more structured and regular than the untreated pinewood 20.

(19) The invention has now been explained in detail with reference to the accompanying drawings, but it is clear that the advantages obtained by the heat treatment and impregnating method using the inventive impregnating agents according to the present invention may be utilized in a number of applications, particularly in the construction industry, where it is desirable to retain the aesthetic properties of wood, but obtain a better durability and insulating properties than achievable with regular wood.

(20) In this connection particularly the impregnating method and the insulating properties of the wood in combination with the sandwich layer construction as described with reference to FIG. 3 provide particular advantages for construction elements such as timber members used in the manufacture of doors, door frames, window frames etc.

(21) All units are listed as metric units (meters, degrees Celcius etc).