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Title:
METHOD FOR TREATING WOOD
Document Type and Number:
WIPO Patent Application WO/2019/145606
Kind Code:
A1
Abstract:
The present invention relates to a novel method of treating wood, in which method wood material is kept in hot liquid in a temperature from 100 to 260 °C, the treated wood material is dried and liquid treatment substance is impregnated into the wood material in a pressure from 5 to 20 bar, The liquid treatment substance can be e.g. alkaline silicate or copper-containing treatment substance, especially soluble glass.

Inventors:
HEINONEN, Markku (Yläneentie 183, Hinnerjoki, 27600, FI)
Application Number:
FI2019/050051
Publication Date:
August 01, 2019
Filing Date:
January 22, 2019
Export Citation:
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Assignee:
TAMMISTON PUU OY (Yläneentie 183, Hinnerjoki, 27600, FI)
International Classes:
B27K1/00; B27K3/02; B27K3/20; B27K5/00; B27K5/06
Foreign References:
GB566766A1945-01-12
CN107088941A2017-08-25
Attorney, Agent or Firm:
SEPPO LAINE OY (Itämerenkatu 3 A, Helsinki, 00180, FI)
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Claims:
CLAIMS

1. A method of treating wood, in which method:

- keeping wood material in hot liquid in a temperature from 100 to 260 °C,

- drying the wood material, and

- impregnating liquid treatment substance into the wood material in pressure from 5 to

20 bar,.

2. A method according to claim 1 , wherein the liquid treatment substance is alkaline silicate or copper-containing treatment substance.

3. A method according to claim 2, wherein the liquid treatment substance is soluble glass.

4. A method according to any of the above claims, wherein the wood material is dried subsequent to hot liquid treatment in a pressure lower than the ambient pressure.

5. A method according to any of the above claims, wherein the wood material is treated with hot water. 6. A method according to any of the above claims, wherein the wood material is treated with hot liquid in pressurized conditions.

7. A method according to any of the above claims, wherein the wood material is treated in a pressure lower than ambient pressure subsequent to drying after the treatment with hot liquid,

8. A method according to any of the above claims, wherein the wood material is post- dried subsequent to the pressure treatment with liquid treatment substance. 9. A method according to any of the above claims, wherein the wood material to be treated is solid wood.

10. A method according to any of the previous claims, characterized in that the wood material is softwood, such as pine or spruce.

11. A method according to any of the above claims, wherein the hot liquid contains base, especially lye.

12. A method according to any of the above claims, wherein least one liquid treatment material contains at least one metal salt from group of: calcium sulphate or -chloride, magnesium sulphate or chloride or barium sulphate or chloride or pine oil.

Description:
METHOD FOR TREATING WOOD TECHNICAL FIELD

[0001] The present invention relates to treating wood in order to alter its utilization properties. Specifically the invention relates to treating wood in order to improve the rot and fire resistance properties thereof. In more detail the invention relates to an apparatus according to the preamble of claim 1 for a method of treating wood..

BACKGROUND

[0002] Methods of treating wood with e.g. soluble glass, impregnation substances and copper compounds are known in prior art. Soluble glass is used to improve fire resistance and rot resistance, copper and copper compounds are mainly used to improve rot resistance. Soluble glass is sodium silicate xSi02 * Na20. The use of soluble glass for impregnating wood in atmospheric pressure has been researched since the early 19th century. Boric acid and borax have been used in connection with the impregnation. The use of soluble glass as a fire resistant material is known since the 1970’s. Patent US 4,612,050 describes the use of soluble glass for petrifying wood, i.e. transforming wood material so as to correspond to petrified wood. Wood material treated with soluble glass can be treated with citric acid or malic acid. The publication ’’Fire Resistance of Wood Impregnated with Soluble Alkaline Silicates; Hindawi Publishing Corporation, Research Letters in Materials Science, Volume 2007, Article ID 31956, 4 pages” researches the fire resistance properties of wood treated with alkaline silicates. In this publication the wood is impregnated in pressurized conditions.

Publication EP 2 646 208 describes a method using post-drying in elevated

temperatures .

SUMMARY

[0003] The present invention relates to treatment of wood with alkaline silicates, such as soluble glass, or copper compounds. The treatment allows improvement of the rot resistance of the wood and with soluble glass and other alkaline silicates allow improving the fire resistance of the wood. With soluble glass wood can be treated so as to be quite fire resistant. At the same time rot resistance and other weather resistance are considerably improved, whereby the method is suitable for production of wood material used in wood structures requiring weather resistance.

[0004] The invention is characterized by what is disclosed in the characterizing part of the independent claim.

[0005] According to a first feature of the invention the wood material is kept in hot liquid at a temperature from 100 to 260 °C, the wood material is dried and liquid treatment substance is impregnated thereto at a pressure of 5 to 20 bar.

[0006] According to a second feature of the invention the liquid treatment substance is alkaline silicate or copper-containing treatment substance.

[0007] According to a third feature of the invention the liquid treatment substance is soluble glass.

[0008] According to a fourth feature of the invention the wood material is dried in partial vacuum (pressure lower than ambient pressure) subsequent to treatment with hot liquid.

[0009] According to a fifth feature of the invention the wood material is treated with hot water.

[0010] According to a sixth feature of the invention the wood material is treated with hot liquid in pressurized conditions.

[0011] According to a seventh feature of the invention the wood material is treated in pressure lower than ambient pressure subsequent to drying.

[0012] According to an eighth feature of the invention the wood material is post-dried subsequent to pressure treatment with a liquid treatment substance.

[0013] According to a ninth feature of the invention the wood material is solid wood.

[0014] According to a ninth feature of the invention the wood material is softwood, such as pine or spruce.

[0015] According to a tenth feature of the invention the hot liquid contains a base, such as lye.

[0016] According to an eleventh feature of the invention the at least one liquid treatment material contains at least one metal salt from group of: sodium sulphate or - chloride, magnesium sulphate or chloride or barium sulphate or chloride or pine oil.

BRIEF DESCRIPTION OF DRAWINGS

[0017] In the following, some embodiments of the invention are disclosed in more detail by means of reference to the appended drawings, in which:

FIGURE 1 is a flow diagram showing a method according to at least one embodiment. EMBODIMENTS

[0018] DEFINITIONS

[0019] In this context the term“solid wood” means wood consisting of one piece.

[0020] Wood material means wood-based materials consisting of a number of pieces, such a pieces of solid wood attached to each other, veneers, battens, boards, wood chips and combinations thereof, but not limiting thereto.

[0021] Ambient pressure and temperature mean a general temperature in the production plant, standard room temperature to be more precise, and pressure on sea level.

[0022] In this method wood material is treated by first keeping it in a hot liquid. The purpose of the treatment with hot liquid is to provide space into the cell structure of the wood for other materials to be impregnated thereto. The treatment substances can be alkaline silicates, copper or copper-containing impregnation substances. The aim of liquid treatment is to improve the penetration rate and amount of treatment substance being transferred to the wood material. The end result is, depending on the treatment substance, e.g. a very fire-resistant and/or a rot-resistant wood product.

[0023] Figure 1 shows the method according to one embodiment as a flow chart. The first step of the method is treatment of wood material with hot liquid. Preferably the liquid is water. Additives can be added to water for enhancing the treatment. Such an additive could be a hemicellulose-dissolving washing agent. The washing agent can be lye or other corresponding strong base. By removing hemicellulose or by reducing the amount thereof the porosity and pore size of the cell structure of the wood can be increased, whereby it is possible to transfer more liquid treatment substance into the cell structure of the wood during the impregnation step.

The liquid used in the hot treatment must be hot enough for opening the cell structure, but the intention is not to cause cell changes in the wood material. From 100 to 260 °C is a suitable temperature range. The duration of the heat treatment must be sufficiently long. The length of the treatment time depends on the desired strength of the treatment and the thickness of the piece to be treated. Typically the treatment time ranges from 0.5 to 8 hours.

[0024] Subsequent to the treatment with hot liquid the liquid must be removed from the wood material to be treated. As the wood material has been heated during the treatment, it will dry by itself after being taken away from the hot liquid, but it is preferable to enhance the drying by means of partial vacuum or heat, A sufficient circulation of air can naturally be used for enhancing drying both in ambient

temperature as well as elevated temperature or partial vacuum. It is of course possible to use combinations of these. Subsequent to the drying taking place in the second step a separate vacuum treatment can be made in a third step, i.e. the wood material can be treated in pressure lower than the ambient pressure for removing air and other gases. The lowest treatment pressure can be very low, for example technical vacuum.

[0025] The treatment with liquid treatment substance takes place in the fourth step. Soluble glass is one of these treatment substances. Soluble glass can be used for improving fire resistance and weather resistance. Depending on the amount of soluble glass used the result can be wood material with slightly improved fire resistance or petrified wood with very good fire and weather resistance. All intermediate forms are naturally also possible. As the aim of the hot liquid treatment is to increase the penetration rate of the liquid treatment substance into the wood and the amount thereof remaining in the wood, it is most preferable in products in which the aim is to add great amounts of treatment substance in relation to the mass of the wood material to be treated. In addition to soluble glass other additives worth mentioning are other water- soluble alkaline silicates, especially commercially available sodium and boric silicates, allowing producing properties like those corresponding to soluble glass especially as far as fire resistance is concerned. Rot resistance can be improved with copper or copper compounds.

[0026] If a vacuum treatment is made before the treatment with liquid treatment substance, it is preferable to maintain the wood material in reduced pressure until it is submerged into the liquid treatment material. Such a procedure can be carried out in the same treatment vessel in which the pressure can be changed so as to be higher or lower than the ambient pressure. The pressure in the vessel or tank can be changed by known methods using vacuum pumps, compressors or liquid pumps. The invention can be carried out by means of known apparatuses from wood processing industry, such as driers and impregnators, suitable modified when necessary.

[0027] The invention can be applied to all kinds of wood-based construction materials.

Hot water treatment can, however, weaken the properties of glued or bonded materials, whereby the method is more effective in the treatment of solid wood. Hemicellulose can be removed from wood material by means of the method. Usually the removal of hemicellulose is an expensive procedure, and at least some of the hemicellulose can be inexpensively removed from the wood material by means of the invention. The wood material to be treated is preferable softwood, as it is more porous than hardwood, and larger amounts of treatment substance can be introduced into the softwood by means of the treatment. Pine and spruce can be mentioned as examples of wood species suitable for treatment.

[0028] Acid addition can be used for enhancing the polymerization of soluble glass.

This acid can be added in hot state into the liquid or the liquid treatment substance or the acid treatment can be a separate step subsequent to impregnation with liquid treatment substance. The acid substances of the wood material itself, such as resins, also cause forming chains. Acid treatment is described in the publications disclosed in the preamble of this description.

[0029] In the following the method steps of figure 1 are described in chronological order.

1. Opening the cell structure of the wood material with hot liquid. Preferably the liquid is water. Treatment temperature range 100 to 260 °C

2. In step 2 the wood material is dried in partial vacuum or by some conventional means. The heat transferred into the wood during liquid treatment enhances drying.

3. In step 3 it is possible to perform an optional vacuum treatment for removing air from the wood material. The aim of this step is to increase penetration rate and the amount of transferred material. In this step the wood material is in a gaseous atmosphere, in a pressure lower than the ambient pressure.

4. The treatment with liquid treatment material is performed in step 4, in a pressure from 5 to 20 bar. Depending on the size and impregnation amount the treatment time can be from minutes (2 to 10 minutes) to up to 48 hours.

Elevating the temperature lowers viscosity and thereby increases the penetration rate. Reference literature is available for carrying out this step.

5. Finally the treated wood can be dried to remove excess liquid.

[0030] In addition to those listed above, the liquid treatment substance can be a salt of metal, preferably from the group calcium sulphate or chloride, magnesium sulphate or chloride or barium sulphate or chloride or pine oil and combinations thereof. These salts and pine oil can be added or used as liquids and also in connection with the treatment by means of hot liquid.

INDUSTRIAL APPLICABILITY

[0031] Fire and weather resistant wood-based materials can be produced by means of the invention for various application requiring such resistance. LIST OF REFERENCES

Patent literature

US 4,612,050

EP 2 646 208

Other publications

Fire Resistance of Wood Impregnated with Soluble Alkaline Silicates; Hindawi Publishing Corporation, Research Letters in Materials Science, Volume 2007, Article ID 31956, 4 pages




 
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