WO2004009307A2

WO2004009307A2 - A method of treating timber and other cellulosic material

Info

Publication number: WO2004009307A2
Application number: PCT/ZA2003/000096
Authority: WO
Inventors: Andre Bakkes; Cedric Eldrid Puckrin
Original assignee: Andre Bakkes; Cedric Eldrid Puckrin
Priority date: 2002-07-18
Filing date: 2003-07-18
Publication date: 2004-01-29
Also published as: ZA200501287B; WO2004009307A3; AU2003275497A1; AU2003275497A8

Abstract

The invention provides a method of treating timber. The method includes the step of immersing a sawn end of a freshly felled timber in a fluid having a viscosity suitable to permit drawing of the fluid through a part of a xylem capillary system of the timber as a result of a pressure differential existing between the sawn end and opposing end region of the freshly felled timber. The pressure differential may be caused by any one or combination of transpiration, photosynthesis and a suction induced by a vacuum pump connected to the opposing end region of the timber.

Description

A METHOD OF TREATING TIMBER AND OTHER CELLULOSIC MATERIAL

INTRODUCTION

This invention relates to a method of treating timber and timber so treated, to a device for treating timber and to a fluid for treating timber.

BACKGROUND TO THE INVENTION

Untreated wood whether in the form of poles or lumber may be subject to infestation, for instance by fungi and insects inter alia, particularly when used outside or when planted

in the soil. Treatment for such wood has conventionally involved treatment of only the exterior of the wood. Conventional methods include the simple expedient of painting or spraying on various substances, or alternatively the immersion of the wood in a large autoclave in a particular fluid such as creosote or chrome copper arsenic and then subjecting the wood to high pressure (and in the case of creosote) high temperature. The latter method allows the fluid to penetrate the outer layers of the wood to an extent of a few millimetres. These conventional methods, whilst being effective in the short term are not effective indefinitely nor do these methods prevent the cracking of the timber. Indeed, these methods of treatment described above are invariably conducted after the timber has already dried and cracked. The impregnation of wood with substances such as creosote or CCA cannot take place if the wood has a high moisture content. A good example of a treatment of wood which has to be repeated at regular interval is the varnishing of the exterior of sawn timber articles such as window frames, doors and the like. If such articles are subjected to the elements and particularly ultra violet rays, it is inevitable that the treatment will have to be repeated from time to time. Furthermore, the application of high pressure and high temperature to the fluid and the timber in some of the methods aforementioned it is a very expensive and potentially hazardous form of treatment.

A further form of treatment which is well known but which does not relate to preservation of the wood is that of staining timber so that it takes on a colour other than its natural colour. Conventionally, such staining is effected only after the timber has been sawn and dried. Once again the stain only penetrates the timber to a limited extent. Stain so applied also tends to obliterate the natural grain of the wood. Most stains do not endure indefinitely and have to be repeated on a regular basis, particularly when the wood is open to the elements.

Examples of processes for treating wood with preservative are disclosed in United States Patent No 6,235,403 in the names of Vinden et al.

It has been known since the work of Joly in 1894 that water is normally transported under tension which implies that it is pulled and not pushed up the stem of a tree. The most obvious mechanism which causes this is the capillary action within the stem when the available pressure is only sufficient to move water approximately a metre up the stem of a tree. The remaining energy which is necessary to pull water up the stem of very tall trees, begins as the leaves lose water through their stomata and the internal cells become drier pulling water from the next driest cell and so on until the suction reaches a vein and exerts tension on the water in the xylem of the tree. The effect is that the tension is passed on down the tree and has the effect of pulling a continuous column of water up through the xylem tubes. Such columns can be lifted over 450 metres and certainly sufficiently high to reach the top of the tallest trees which are in the vicinity of 120 metres. Water can thus be moved up trees in large quantities by a combination of tension and cohesion. It is estimated that the tension required to move water to the top of very tall trees is in the order of -30 atmospheres. There are other theories about subsidiary mechanisms that assist in the movement of water up a tree and it has been suggested by Conny (1995) that the living cells in the trunk may exert pressure on the xylem system. This is known as the compensating pressure theory.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a method of treating timber, which method includes the step of immersing a sawn end of a freshly felled timber piece in a fluid having a viscosity suitable to permit drawing of the fluid through a part of a xylem capillary system of the timber as a result of a pressure differential existing between the sawn end and opposing end region of the freshly felled timber. The pressure differential may be caused by any one or combination of transpiration, photosynthesis and a suction induced by a vacuum pump connected to the opposing end region of the timber. It is to be appreciated that adhesion, cohesion and/or capillary actions in the timber may be assisted by transpiration and/or photosynthesis which continue for a period after felling the timber.

The sawn end of the timber may be immersed until the fluid has been drawn up at least a substantial length of the timber.

Freshly felled timber will be understood to mean timber which has not dried substantially since it was felled and preferably wherein the timber may have a moisture content above

a fibre saturation point thereof. Timber will further be understood to include any stem part of any plant, such as bamboo.

The inventors have found that by using the natural mechanisms that cause water to rise up the stem of a tree other fluids can be infused into the stem of a tree such as the

preservative and colouring fluids which have been discussed herein before. Simple experiments with saplings have demonstrated that if the butt end of a tree is immersed

within a receptacle containing the fluid desired to be infused immediately after being cut, the mechanisms of the tree continue to suck up the desired fluid for a period of up to two weeks. It is theorised that at the beginning the transpiration in the leaves continues and thereafter, after the leaves have died and are no longer capable of photosynthesis, capillary action continues whilst there is still water within the tree moving up the vessels in the tree. The inventors believe that when a tree is cut into segments or poles, if the butt or lower end of such poles are immediately or soon thereafter immersed in a receptacle containing the desired fluid and a suction pump device is connected in an airtight fashion to the opposing end of the pole so as to increase a pressure differential across the length of the pole, the increased pressure differential may improve the flow of fluid through the xylem. Although this method of infusing the desired fluid will probably only work in poles which are less than approximately 10 metres long, this is no real disadvantage as timber is rarely required in longer lengths.

The desired fluids may not be limited to aqueous solutions. The inventors have found that oils move with facility up the stem of a tree by using one or more of the aforesaid processes, provided that the viscosity is not too great to gain ingress into the vessels of the tree. The viscosity of, for example creosote, which is a thick hydrocarbon, may be brought to the desired level by mixing it with various organic solvents such as for instance turpentine. It has been found that timber of say 2 metres (being the length of the average fencing pole) may be thoroughly impregnated with a creosote and turpentine mixture of equal parts and that such infusion can be accomplished within two hours after the felling of the tree and thereafter cutting it into poles. Aqueous colourants have also been so infused. Oils which are conventionally used for the treatment of wood such as raw linseed oil, have also been infused into timber using the above described processes. In this specification, a solution will be understood to include an emulsion. In other words, an aqueous solution may include oil suspended in water and an oil solution may include water suspended in oil.

The fluid may be selected from an aqueous solution, which includes any one or more of a dye; a resin; a flame retardant; a flame enhancer; a poison; and a glue.

Instead, the fluid is selected from an oil based solution, which includes any one or more of:- a dye;

a resin; a flame retardant; a flame enhancer; a poison; and a glue.

The fluid may include a curable resin and the method may include the step of curing the resin in the timber. Depending on the resin, it may be cured by an acid, peroxide, a base, heat, micro waves or naturally over time.

According to a further aspect of the invention there is provided timber treated by means of a method as described above.

According to a further aspect of the invention, there is provided a device for treating timber by means of a method as described above, which device includes a suction means and a connection means for inter connecting and end of a sawn timber in a substantially airtight manner to the suction means.

The timber so treated can of course be used as poles in the round (in the case of creosote treated fencing poles for instance) or may be cut by conventional means after treatment in order to make lumber and the like. It has been found that the introduction of conventional oils used for treatment of wood within the timber itself prevents excessive splitting which often occurs when timber dries out. Such cracking is caused by the fact that the drying process is not uniform throughout the timber and concomitantly there is a differential in the expansion and contraction of various parts of the timber. As the abovementioned processes replace much of the water in the timber with oil which does not evaporate, the cracking or splitting of the timber is reduced to a minimum.

An important feature of the above invention is that it is possible to infuse into the timber by one of the aforementioned methods material which can strengthen the timber significantly. Thus, for instance, a long chain polymer or some other plastic material may be made in a liquid form and infused into the timber by the aforesaid methods. Once such fluid has set and become solid within the timber, it is axiomatic that the timber will take on some of the physical properties of the infused material. Where the material is a long chain polymer which has high tensile or compressive strength, the load-bearing characteristics of the timber are enhanced significantly. Such strengthening materials might also be used for instance in other plant material such as bamboo or reeds. An article which may be manufactured from such strengthened timber may be a mine prop. This invention also extends to an article manufactured from timber treated in accordance with the invention.

It is yet a further object of the invention to identify various fluids which are suitable for treating wood in order to preserve the timber, prevent cracking thereof, to colour it, to strengthen the timber element or to retard or enhance the flammability of the timber so treated, said fluids having a viscosity which enable them to flow through the xylem capillaries of a freshly sawn timber.

According to an even further aspect of the invention, there is provided an aqueous solution for the treatment of timber by means of a method which includes the step of immersing a sawn end of a freshly felled timber in a fluid having a viscosity suitable to permit drawing of the fluid through a part of a xylem capillary system of the timber as a result of a pressure differential existing between the sawn end and opposing end region of the freshly felled timber, the solution including any one or more of:- a dye; a resin; a flame retardant;

a flame enhancer; a poison; and a glue.

It will be appreciated that aqueous solutions will normally have a suitable viscosity.

According to another aspect of the invention, there is provided an oil based solution for the treatment of timber by means of a method which includes the step of immersing a sawn end of a freshly felled timber in a fluid having a viscosity suitable to permit drawing of the fluid through a part of a xylem capillary system of the timber as a result of a pressure differential existing between the sawn end and opposing end region of the freshly felled timber, the solution including any one or more of:- a dye;

a resin; a flame retardant; a flame enhancer; a poison; and a glue.

Although the aforesaid objects have been demonstrated in relation to wood derived from trees, it should be understood that the methods and fluids hereinafter described can also be applied to cellulosic material derived from such plants as bamboo and the like.

According to another aspect of the invention there is provided a device for treating timber which device includes a suction means and a connection means for inter connecting an end of a sawn timber in a substantially airtight manner to the suction means.

The method may take seasons into consideration. For example, the timber may be immersed in the fluid for a shorter time in summer than in winter.

Yet another feature of the invention is the use of two fluids mixed together in which one of the fluids comprises a catalyst or a setting agent for the other. In this embodiment the fluid is infused into the timber whilst still in a liquid form and after a period the fluid changes to a solid state. Heat or any other radiation may be applied to the timber to enhance such a change of state in the fluid infused, or to increase infusion within the timber. The desired fluid may also be heated.

A further feature of the invention is to infuse timber which is to be used as fire wood with a fuel, such as a liquid hydrocarbon (for instance diesel oil or paraffin) so as to enhance the calorific value and/or combustion characteristic of the timber.

The invention is not limited to the precise constructional or functional features as hereinbefore described and may cover timber elements which have been treated by any of the aforegoing methods.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described by way of reference to the following non-limiting examples.

In one embodiment of the invention, a series of poles are placed lying down in a row

within the forest immediately after having been cut. A cup-shaped element connected to a mobile tank containing the desired fluid is placed over the butt-end of the pole so that the butt-end is in contact with the suitable fluid which is fed by gravity to the cup-shaped element. A similar cup-shaped element is then fitted to the top end of each pole connected by pressure hose or pipe to a suction pump which provides the necessary pressure differential. Once the desired level of infusion is attained, the cup-shaped elements are removed and the next row of poles can be treated.

In another embodiment of the invention, a series of poles are placed upright in an open container against a tree within the forest immediately after having been cut. The open container contains a suitable fluid. Once the desired level of infusion is attained, the cup-shaped elements may be removed and the next row of poles may be treated.

Examples of suitable fluids

(It should be understood that that examples are not limiting in any way)

1. Water mixed with fabric dye such as fabric dye sold under the trade name "Dylon" as per instructions for fabric dying procedures. Any colour can be used to colour the timber as desired.

2. Creosote diluted with toluol in a ratio of 1:1 in order to give it a suitable viscosity to be drawn up the timber. Creosote is both an insecticide and a fungicide.

3. Keto aldehyde resin as is or diluted 1 :1 with water, which strengthens the wood. The resin may be cured by conventional methods, such as heating.

4. Phenolic resin as is or diluted 3:1 with water, which strengthens the wood. The resin may be cured by conventional methods, such as heating.

5. Amino resin diluted 1 :1 with water, which strengthens the wood and may be cured by conventional methods such as heating. 6. Furniture oil, such as teak furniture oil diluted 1 :1 with turpentine. The infused oil serves the same function as that of normally applied oil. Infused oil is more efficient than applied oil.

7. Copper chrome cyanide solution as used for conventional methods of treatment of timber as an insecticide and a fungicide.

8. Tetra ethylene silicon as is as a flame retardant.

9. Paraffin as is as a flame enhancer.

10. Commercial cold wood glue diluted 1:10 with water to strengthen the timber.

11. Turpentine as a flame enhancer.

12. Artificial ligno-hemi cellulose polymer to strengthen the wood.

Claims

1. A method of treating timber, which method includes the step of immersing a sawn end of a freshly felled timber piece in a fluid having a viscosity suitable to permit drawing of the fluid through a part of a xylem capillary system of the timber as a result of a pressure differential existing between the sawn end and opposing end region of the

freshly felled timber.

2. A method as claimed in Claim 1 , wherein the pressure differential is caused by any one or combination of transpiration, photosynthesis and a suction induced by a vacuum pump connected to the opposing end region of the timber.

3. A method as claimed in Claim 1 or Claim 2, wherein the sawn end of the timber is immersed until the fluid has been drawn up at least a substantial length of the timber.

4. A method as claimed in any one of the previous claims, where in the fluid is selected from an aqueous solution, which includes any one or more of:- a dye; a resin; a flame retardant; a flame enhancer; a poison; and a glue.

5. A method as claimed in any one of the previous claims 1 to 3, wherein the fluid is selected from an oil based solution, which includes any one or more of:- a dye; a resin; a flame retardant; a flame enhancer;

a poison; and a glue.

6. A method as claimed in any one of the previous claims, wherein the fluid includes a curable resin and the method includes the step of curing the resin in the

timber.

7. Timber treated by means of a method as claimed in any one of claims 1 to

6.

8. A device for treating timber by means of a method as claimed in any one of claims 2 to 6, which device includes a suction means and a connection means for inter connecting and end of a sawn timber in a substantially airtight manner to the suction means.

9. An aqueous solution for the treatment of timber by means of a method which includes the step of immersing a sawn end of a freshly felled timber in a fluid having a viscosity suitable to permit drawing of the fluid through a part of a xylem capillary system of the timber as a result of a pressure differential existing between the sawn end and opposing end region of the freshly felled timber, the solution including any one or more of:- a dye; a resin; a flame retardant; a flame enhancer; a poison; and a glue.

10. An oil based solution for the treatment of timber by means of a method which includes the step of immersing a sawn end of a freshly felled timber in a fluid having a viscosity suitable to permit drawing of the fluid through a part of a xylem capillary system of the timber as a result of a pressure differential existing between the sawn end and opposing end region of the freshly felled timber, the solution including any one or more of a dye; a resin; a flame retardant; a flame enhancer; a poison; and a glue.

11. An article manufactured from timber treated according to the method as

claimed in any one of claims 1 to 6.

12. A method of treating timber, substantially as described herein.

13. Timber, substantially as described herein.

14. A device for treating timber, substantially as described herein.

15. An aqueous solution for the treatment of timber, substantially as described herein.

16. An oil based solution for the treatment of timber, substantially as described

herein.

7. 'An article manufactured from timber, substantially as described herein.