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US-12617120-B2 - Wood protecting methods and wood products produced with the methods

US12617120B2US 12617120 B2US12617120 B2US 12617120B2US-12617120-B2

Abstract

Disclosed herein is an environmentally friendly wood protecting method against biological deterioration such as fungal, bacterial and insect damage and non-biological wood deterioration such as weathering. The method comprises contacting a wood material with an aqueous solution of a zirconium salts which is followed by a heat treatment step, providing durable protection of wood against biodegradation and improving several other properties of the treated wood.

Inventors

  • Juhanes AYDIN
  • Salman HASSANZADEH
  • Lidija GLAVAS

Assignees

  • ORGANOWOOD AB

Dates

Publication Date
20260505
Application Date
20201214
Priority Date
20191213

Claims (18)

  1. 1 . A method of improving degradation resistance of a wood product, comprising: contacting a wood material with a water-based composition containing no biocide and consisting essentially of one or more zirconium salts selected from the group consisting of zirconium acetate, ammonium zirconium carbonate, zirconium bromide, zirconium chloride, zirconium hydroxynitrate, zirconium nitrate, zirconium oxide diperchlorate octahydrate, zirconium oxychloride, zirconium oxynitrate, zirconium sulfate, zirconium sulfate tetrahydrate, zirconyl chloride, zirconium acetate hydroxide, zirconium orthosulphate and zirconium sulphamate, and optionally at least one or more of: a wetting agent, a defoamer, a conservative, a dye, a pigment, a rheology modifier, and/or a UV stabilizer; and heat treating the wood material at a temperature of between 115°° C. to 200° C., wherein the one or more zirconium salts create physical and chemical bonds with hydroxyl and/or carboxyl groups of the wood material and wherein the one or more zirconium salts are selected so that a protonated counter ion to zirconium in the zirconium salt has a boiling point that is lower than the temperature of heat treating the wood material.
  2. 2 . The method according to claim 1 , wherein the contacting comprises contacting the wood material with the water-based composition comprising 0.01% to 30% (w/w) of zirconium ions from the one or more zirconium salts.
  3. 3 . The method according to claim 1 , wherein the contacting comprises contacting the wood material with the water-based composition comprising 70% to 99.99% (w/w) water and optionally at least one or more of: the wetting agent, the defoamer, the conservative, the dye, the pigment, the rheology modifier, and/or the UV stabilizer.
  4. 4 . The method according to claim 1 , wherein the contacting comprises contacting the wood material with the water-based composition having a pH value of 2 to 13.
  5. 5 . The method according to claim 1 , further comprising: drying the wood material to a moisture content of less than 20% before heat treating the wood material.
  6. 6 . The method according to claim 1 , further comprising: drying the wood material to less than 40% moisture content before contacting the wood material with the water-based composition.
  7. 7 . The method according to claim 1 , further comprising: heating the wood material to temperatures of 5° C. to 250° C. before contacting the wood material with the water-based composition.
  8. 8 . The method according to claim 1 , further comprising: heating the water-based composition to a temperature of less than 100° C. before contacting the wood material with the water-based composition.
  9. 9 . The method according to claim 7 , wherein the heating comprises heating both the wood material and the water-based composition before contacting the wood material with the water-based composition.
  10. 10 . The method according to claim 1 , wherein the heat treating comprises heat treating the wood material at a temperature of between 135° C. to 185° C.
  11. 11 . The method according to claim 1 , wherein the contacting comprises contacting the wood material with the water-based composition comprising 0.1% to 15% (w/w) of zirconium ions from the one or more zirconium salts.
  12. 12 . The method according to claim 1 , wherein the contacting comprises contacting the wood material with the water-based composition comprising 0.2% to 6% (w/w) of zirconium ions from the one or more zirconium salts.
  13. 13 . The method according to claim 1 , wherein the contacting comprises contacting the wood material with the water-based composition, the water-based composition containing no biocide and consisting essentially of the one or more zirconium salts and at least one or more of: the wetting agent present in amounts of less than 7% (w/w), the defoamer, the conservative, the dye present in amounts of less than 7% (w/w), the pigment present in amounts of less than 7% (w/w), the rheology modifier present in amounts between 0.5% to 5% (w/w), and/or the UV stabilizer present in amounts of less than 7% (w/w).
  14. 14 . The method according to claim 1 , wherein the contacting comprises contacting the wood material with the water-based composition having a pH value of 2 to 11.
  15. 15 . The method according to claim 1 , wherein the contacting comprises contacting the wood material with the water-based composition having a pH value of 2 to 9.
  16. 16 . The method according to claim 1 , wherein the contacting comprises contacting the wood material with the water-based composition having a shelf life of more than 1 month at temperatures ranging from 0° C. to 65° C.
  17. 17 . The method according to claim 1 , wherein the contacting is performed by soaking, impregnating, padding, foularding, dipping, spraying, brushing, coating, rolling, or foam-application.
  18. 18 . The method according to claim 17 , wherein the contacting is performed by vacuum pressure impregnation.

Description

TECHNICAL FIELD The present invention relates to an environmentally friendly wood protecting method against biological deterioration such as fungal, bacteria and insect damage and non-biological wood deterioration such as weathering. The method comprises contacting a wood material with an aqueous solution of a zirconium salts which is followed by a heat treatment step, providing durable protection of wood against biodegradation and improving several other properties of the treated wood. BACKGROUND OF THE INVENTION Structurally wood can be regarded as a porous and fibrous, hydrophilic and hard biocomposite composed mainly of cellulose, hemicellulose and lignin. Due to its nature, wood is vulnerable to environmental degradation including both physical and microbiological factors. Traditionally various biocides and pesticides are being used to preserve and protect wood against rot, fungus and insects. These compounds very often have a negative impact on human health and environment. For this reason, new avenues for obviating attacks from rot, fungus and insects have been attracting considerable amount of attention amongst researchers. There is a need for a solution for modifying wood with enhanced resistance to biodegradation without having a negative impact on nature and human health, especially when it comes to protecting wood in harsh conditions such as in ground contact. When it comes to wood not only is protection against wood destroying fungus, rot and insects a very important feature but also properties such as lowered water uptake, better dimensional stability, increased mechanical strength and enhanced protections against natural weathering are highly important factors that contribute to the expanded usage of wood as for example building material. Various protective technologies exist with different protection efficiencies both regarding economy and environmental impacts. Current technologies can be categorized to “surface” and “in-depth” protection. Beside any other problems, the surface protection technologies such as organic coatings suffer from their anisotropic protection and lack of protection mechanism for the whole mass and inner part of the wood, making surface protection vulnerable to physical damages to the thin surface coating. The “in depth” protection technologies are either “chemical impregnation” or “Thermal treatment”. But, most of the existing “in depth” protection technologies display major drawbacks. For example, there is a category of “chemical impregnation” based technologies using various biocides which display huge environmental issue (such as Ammoniacal Copper Quinolate with boron (ACQ-B), Copper Azole with boron (CBA), Chromated Copper Arsenate (CCA) and similar chemicals). Other technologies known as environmentally friendly also display shortcomings, for example: complex/expensive production of acetylated and furfurylated wood and decreased mechanical properties in heat treated wood. Zirconium as 20th element in abundance in the earth's crust lies in Group IVB of the periodic table. Zirconium exhibit a preferred oxidation state of 4 with not known redox chemistry under these conditions. Zirconium displays high charge to radius ratio and will hydrolysis and form polymeric species upon dissolution in water where the zirconium atoms are linked and bridged by hydroxyl groups. Further hydrolytic polymerization of these polymeric species can be happened by ageing, heating or by a reduction in acidity to form a polymer with a charged or neutral character. The polymeric species of zirconium in the aqueous solution can interact chemically and physically with different functional groups of organic polymers. The reaction of the aqueous zirconium species is known for example with carboxyl, hydroxyl, and amine groups. The reaction of the zirconium with functional groups of organic polymers can be controlled significantly by altering temperature, pH and chelating agents. The zirconium polymeric species based on the used amount, physical parameters and extent and type of the functionalities in the organic polymers can induce crosslinking bonds, improve adhesion properties of the treatments and surfaces and increase the resistance to the heat, scrubbing, water/solvents. Zirconium salts have previously been suggested as an agent to prevent microbial degradation of wood products, see US2011250359; WO9845053; GB809766; U.S. Pat. Nos. 3,547,688 and 5,612,094. However, none of these disclosures outline a process wherein zirconium salts can be further employed to improve other important characteristics of wood materials. Document U.S. Pat. No. 5,612,094 describes a method wherein wood material is contacted with a water-based composition comprising one or more zirconium salts, and drying the wood material. It is important to note that the document describes drying at low temperatures. To dry wood material at low temperatures is standard within the industry, as drying at high temperatures is known