Green process for modifying wood

Abstract

The present invention relates to a process for modifying wood. The process involves treating wood with an impregnation solution containing an alkali metal (or alkaline earth metal) silicate under conditions sufficient to impregnate the wood with one or more components of the impregnation solution. The process can include an optional second impregnation with a second impregnation solution. The process also includes adding gaseous carbon dioxide to the treated wood under a pressure ranging from about 2 to about 12 bar, in the absence or presence of water, thereby lowering the pH of the treated wood to about 11 or below and stabilizing and / or fixing the components of the impregnation solution in the wood. The process is green and non-toxic, and the resulting modified wood or wood products can be used in all major construction and infrastructure applications.

Description

Technical Field

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 944,858, filed Dec. 6, 2019, and U.S. Provisional Patent Application No. 63 / 068,211, filed Aug. 20, 2020, both of which are hereby incorporated by reference in their entirety.

[0002] The present invention generally relates to a green (non-toxic) and environmentally sustainable process for modifying wood.

Background Art

[0003] The social and environmental benefits of all-green wood are important, including eliminating the need for toxic chemical treatments of wooden utility poles, railroad ties, residential construction, boardwalks, and decks, as well as enhancing the strength and fire resistance ratings suitable for use in fire-prone areas. Considering utility poles as an example, the economic and social disruptions of wildfires associated with utility companies are incalculable, especially in the western United States. In 2017 alone, wildfires in California resulted in dozens of deaths, thousands of homes and businesses destroyed, and tens of thousands of other assets damaged, with these losses estimated at $12 billion. In the record-breaking 2020 fire season, large-scale wildfires occurred in California and other western states. Since the beginning of 2020, over 5 million acres have burned in California, Colorado, Idaho, Montana, Oregon, and Washington. The cost of all wildfires in 2018 is estimated to exceed $20 billion, and a similar calculation could apply to the cost of wildfires in 2020. Affordable fire-resistant timber utility poles with fire-resistant cross-arms would have a substantial positive impact on these statistics. However, currently, there are no all-wood, low-cost, fully environmentally sustainable Class A fire-resistant industry-approved utility poles.

[0004] Timbers are treated with solutions of elements and compounds to improve their properties and extend their life cycle, with varying degrees of success. Treated wood typically refers to wood treated with preservatives. Typical treatment methods would include impregnating wood products with treatment chemicals that can result in fire-resistant, mold-resistant, and insect-resistant wood products. Many different chemicals, including arsenic- or copper-based compounds and many non-green toxic compounds such as pesticides, have been used for these purposes. The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) requires the EPA to register all pesticides sold or distributed in the United States. Most current wood chemical preservatives (either aqueous or oily) are registered pesticides regulated by the US EPA. Existing wood products are still made from treatment chemicals that are flammable, toxic to humans, and harmful to the environment.

[0005] U.S. Patent No. 7,955,711 describes an aqueous solution for the preservation of wood and wood products. However, the treatment solution contains chemicals for insect and termite repellents to achieve termite resistance and / or insect resistance. These chemicals are present at relatively high concentrations of about 1.5 to 9 wt%, which can potentially damage the environment. The '711 patent also uses about 1 to 10 wt% of an alkali metal carbonate (e.g., Na2CO3), which can leave a high level of Na2CO3 on the surface of the treated timber and cause efflorescence on the surface of the finished product.

[0006] U.S. Patent Nos. 6,303,234, 6,827,984, and 7,297,411 describe processes for making refractory products using sodium silicate solutions. However, these patents discuss the problems of water solubility and surface degradation due to exposure to air and moisture associated with the use of only sodium silicate, and wood samples treated with sodium silicate need to be further treated with a silicon oxide molecular coating to avoid the aforementioned problems. This surface molecular coating treatment particularly caused internal damage to the treated lumber after approximately 40 - 48 months in various applications at multiple locations. Furthermore, in these patents, since the flame retardancy tended to increase with the increase in concentration, a high concentration of sodium silicate exceeding 20% by weight was preferred.

[0007] U.S. Reissue Patent No. 40517 describes a process for making refractory and moisture-resistant products using a sodium silicate solution by applying energy to make sodium silicate water-insoluble. Similar to the above patents, in this patent too, since the flame retardancy tended to increase with the increase in concentration, a high concentration of sodium silicate exceeding 20% by weight was preferred.

[0008] U.S. Patent No. 6,146,766 describes a process for making refractory and moisture-resistant products using a sodium silicate solution by alternately applying vacuum and pressure to make sodium silicate water-insoluble. This patent does not discuss the concentration of the sodium silicate solution at all.

[0009] None of the aforementioned patents discuss the disadvantages associated with using higher concentration sodium silicate impregnation solutions. These patents also do not mention at all the weight ratio of (SiO2) / (Na2O) of sodium silicate in the impregnation solution and the advantages related to the control of this ratio. Furthermore, these patents do not employ gaseous CO2 fixation technology. Without a reliable fixation strategy, the treated wood may have problems related to the long-term life cycle protection of wood products. Additionally, these patents do not assume an additional impregnation stage, and the advantages are related to the additional process.

[0010] Therefore, there is a need to develop a cost-effective, all-green process for modifying wood that can eliminate toxic chemical treatments, meet or exceed the strength property improvements and high fire resistance ratings of internationally recognized building and construction material standards, while maintaining other desirable properties such as decay resistance, antibacterial properties, and insect resistance. This disclosure addresses that need. SUMMARY OF THE INVENTION

[0011] The object of the present invention is to design and manufacture a completely environmentally sustainable, green (free of toxic chemicals), and groundbreaking performance wood product that can be widely used across all major construction and infrastructure applications. The production process for producing the wood product utilizes the existing wood treatment infrastructure that previously used a manufacturing process mainly focused on toxic chemicals to employ a low-cost, scalable, and continuously improved manufacturing process. Since the existing infrastructure can be quickly converted into a sustainable wood modification facility with a very persuasive rate of return on investment, the entire conversion investment can be recovered within 12 months. As a result, while the existing log production and processing manufacturing facilities are maintained, the previous toxic chemical-centered environmentally destructive business is economically converted into a highly profitable and long-term sustainable "green" log business model. To the best knowledge of the inventors, a combination of all-green and low-cost high-performance wood products produced at a green tech wood treatment facility in the United States (using logs sourced domestically and harvested responsibly) has not been achieved so far.

[0012] This product is modified all-green wood supplied from the largest renewable forest in the United States, which uses special technologies and compounds in a scalable formulation and manufacturing process to improve the performance of wood for daily use. As a result, a single highly price-competitive product realizes a series of performance profiles that lead the industry. The main performance improvements include making the wood resistant to chemical leaching, inert, stronger, harder, decay-resistant, termite-resistant, electrically resistant, and, importantly, in the state of a Class A (highest level) fire-resistant material, compared to generally available and used alternatives that include both unsustainable conventional treated wood and some high-cost woods that are chemically sustainable and treatment-enhanced.

[0013] The inventors believe that using those processes, they can produce the first Class A fire-resistant, industry-approved utility poles that meet those criteria and can be manufactured at a price comparable to that of combustible ones treated with toxic chemicals currently in use, with a unique combination of the product performance attributes of the present invention and the ability to be used and approved by the power industry. This is an important step towards fire suppression in the electric utility industry, reducing the environmental damage caused by the highly toxic chemicals currently in use in utility poles where many wildfires start and float in the air, further endangering the safety of the first responders, the fire-fighting teams, and the surrounding communities.

[0014] Disclosed is a process for impregnating a lumber with a solution of an alkali metal salt, such as sodium silicate (Na2SiO3), along with the resulting product. Post-impregnation stabilization may also be provided. Disclosed are various methods of stabilization, such as by lowering the pH and by the addition of gaseous carbon dioxide (CO2) and application of any second impregnation treatment of the wood. Also disclosed is a heat treatment after impregnation. Such a process serves to fix and stabilize the impregnation of the lumber.

[0015] Accordingly, one aspect of the present invention relates to a process for modifying wood. The process includes treating the wood under conditions sufficient to impregnate the wood with one or more components of an impregnating solution that includes an alkali metal (or alkaline earth metal) silicate, wherein the weight ratio of SiO2 to the alkali metal (or alkaline earth metal) oxide in the alkali metal (or alkaline earth metal) silicate ranges from about 2.0 to about 4.0. The process also includes adding gaseous carbon dioxide to the treated wood under a pressure in the range of about 2 to about 12 bar, in the absence or presence of water, thereby lowering the pH of the treated wood to about 11 or less to stabilize and / or fix the components of the impregnating solution in the wood. The process is green and non-toxic as being carried out in the absence of pesticides or biocides or at environmentally safe boron levels in the impregnating solution of 1 wt% or less.

[0016] In one embodiment, the process is green and non-toxic as it is carried out in the absence of pesticides or biocides. In one embodiment, the process is green and non-toxic as it is carried out in the absence of mold repellents. In one embodiment, the process is green and non-toxic as it is carried out in the absence of toxic chemicals.

[0017] In certain embodiments, the alkali metal (or alkaline earth metal) silicate is sodium silicate, potassium silicate, or calcium silicate. Typically, the alkali metal silicate is sodium silicate or potassium silicate. In certain embodiments, the weight ratio of (SiO2) / (Na2O) of sodium silicate in the impregnating solution can range from about 2.1 to about 3.5, or from about 2.5 to about 3.5. In certain embodiments, the concentration of SiO2 in the impregnating solution ranges from about 3 wt% to about 15 wt%. In one embodiment, the concentration of SiO2 in the impregnating solution ranges from about 3 wt% to about 6 wt%.

[0018] In certain embodiments, the process further includes a step of pretreating the wood by drying the wood and / or applying a vacuum to the wood prior to the treating step to achieve a wood moisture content of less than about 20%.

[0019] In certain embodiments, the conditions sufficient to impregnate the wood in the treating step are the following conditions: the concentration of SiO2 in the impregnating solution ranges from about 3 wt% to about 15 wt%, the weight ratio of (SiO2) / (Na2O) of sodium silicate in the impregnating solution ranges from about 2.5 to about 3.5, applying a pressure of about 4 bar to about 20 bar, treating the wood at a temperature in the range of about 15 to about 100 °C, and / or treating the wood for a period of about 2 to about 4 hours, including two or more of these. The conditions sufficient to impregnate the wood in the treatment step may also include three, four, or all five of the above conditions.

[0020] In one embodiment, the conditions sufficient to impregnate the wood in the treatment step are the following steps: The concentration of SiO2 in the impregnation solution is in the range of about 5 wt% to about 10 wt%, and The weight ratio of (SiO2) / (Na2O) of sodium silicate in the impregnation solution is in the range of about 2.8 to about 3.2, and Applying a pressure of about 10 bar to about 20 bar, and Treating the wood at a temperature in the range of about 50 to about 80 °C, and Treating the wood for a period of about 2 to about 4 hours.

[0021] In one embodiment, the conditions sufficient to impregnate the wood in the treatment step are the following steps: The concentration of SiO2 in the impregnation solution is in the range of about 5 wt% to about 15 wt%, and The weight ratio of (SiO2) / (Na2O) of sodium silicate in the impregnation solution is in the range of about 2.8 to about 3.2, and Applying a pressure of about 10 bar to about 20 bar, and Treating the wood at a temperature in the range of about 20 to about 50 °C, and Treating the wood for a period of about 2 to about 4 hours.

[0022] In certain embodiments, gaseous carbon dioxide is added under a pressure in the range of about 6 to about 12 bar for a period of about 15 to about 60 minutes to lower the pH of the treated wood to about 9 or less. In one embodiment, gaseous carbon dioxide is added under a pressure in the range of about 2.4 to about 7 bar for a period of about 15 to about 60 minutes to lower the pH of the treated wood to about 9 or less.

[0023] In certain embodiments, the process further comprises, after the treating step, applying a vacuum to the treated wood to remove residual impregnation solution from the surface of the treated wood and preparing the treated wood for a post-treatment step.

[0024] In certain embodiments, the process further comprises heating the treated wood at a temperature in the range of about 50 to about 100 °C after the treating step. The heating step comprises heating the treated wood with dry air, saturated steam, or warm water. In one embodiment, the heating step has a duration of about 2 to about 6 days (or about 4 to about 6 days) and involves varying the rate at which the temperature is increased to a stable drying temperature and the rate at which the temperature is decreased to achieve the target moisture level.

[0025] Another aspect of the present invention relates to a process for modifying wood. The process comprises i) treating the wood under conditions sufficient to impregnate the wood with one or more components of a first impregnation solution comprising an alkali metal (or alkaline earth metal) silicate; ii) treating the wood with a second impregnation solution comprising an alkali metal (or alkaline earth metal) silicate at a higher concentration than the first impregnation solution for a shorter period than the treating step i); iii) performing one or more of the following post-treatment steps: adding gaseous carbon dioxide to the treated wood under a pressure in the range of about 2 to about 12 bar, in the absence or presence of water, thereby lowering the pH of the treated wood to about 11 or less, and / or heating the treated wood at a temperature in the range of about 50 to about 100 °C, to stabilize and / or fix the components of the first impregnation solution and / or the second impregnation solution in the wood; The post-treatment step iii) is performed after the treating step i), before the treating step ii), and / or after the treating step ii).

[0026] In certain embodiments, the treating step ii) is performed under the following conditions: The second impregnating solution contains an alkali metal (or alkaline earth metal) silicate at a concentration of about 10 to 15% by weight, and the wood is treated for a period of about 10 to about 60 minutes, a pressure of about 2 to about 12 bar is applied, and the wood is treated at a temperature in the range of about 20 to about 70 °C.

[0027] In certain embodiments, the process is green and non-toxic as being carried out in the absence of pesticides or biocides, or at environmentally safe boron levels in the first impregnating solution or the second impregnating solution of 1% by weight or less.

[0028] In one embodiment, the process is green and non-toxic as being carried out in the absence of pesticides or biocides. In one embodiment, the process is green and non-toxic as being carried out in the absence of fungicides. In one embodiment, the process is green and non-toxic as being carried out in the absence of toxic chemicals.

[0029] In certain embodiments, the alkali metal (or alkaline earth metal) silicate is sodium silicate, potassium silicate, or calcium silicate. Typically, the alkali metal silicate is sodium silicate or potassium silicate. In certain embodiments, the weight ratio of (SiO2) / (Na2O) of sodium silicate in the first impregnating solution and / or the second impregnating solution can range from about 2.0 to about 4.0, from about 2.1 to about 3.5, or from about 2.5 to about 3.5.

[0030] In certain embodiments, the concentration of SiO2 in the first impregnating solution ranges from about 3% to about 15% by weight. In one embodiment, the concentration of SiO2 in the first impregnating solution ranges from about 3% to about 6% by weight. The concentration of SiO2 in the second impregnating solution ranges from about 10% to about 15% by weight.

[0031] In certain embodiments, the process further includes a step of pretreating the wood by drying the wood and / or applying a vacuum to the wood prior to step i) of the process to achieve a moisture content of the wood of less than about 20%.

[0032] In certain embodiments, the conditions sufficient to impregnate the wood in step i) of the process are the following conditions: The concentration of SiO2 in the first impregnation solution is in the range of about 3 wt% to about 15 wt%, The weight ratio of (SiO2) / (Na2O) of sodium silicate in the first impregnation solution is in the range of about 2.5 to about 3.5, Applying a pressure of about 4 bar to about 20 bar, Treating the wood at a temperature in the range of about 15 to about 100 °C, and / or Treating the wood for a period of about 2 to about 4 hours, including two or more of the above.

[0033] The conditions sufficient to impregnate the wood in step i) of the process may also include three, four, or all five of the above conditions.

[0034] In one embodiment, the conditions sufficient to impregnate the wood in step i) of the process are the following steps: The concentration of SiO2 in the first impregnation solution is in the range of about 5 wt% to about 10 wt%, and The weight ratio of (SiO2) / (Na2O) of sodium silicate in the first impregnation solution is in the range of about 2.8 to about 3.2, and Applying a pressure of about 10 bar to about 20 bar, and Treating the wood at a temperature in the range of about 50 to about 80 °C, and Treating the wood for a period of about 2 to about 4 hours, including.

[0035] In one embodiment, the conditions sufficient to impregnate the wood in step i) of the process are the following steps: The concentration of SiO2 in the first impregnation solution is in the range of about 10 wt% to about 15 wt%, and The weight ratio of (SiO2) / (Na2O) of sodium silicate in the first impregnation solution is in the range of about 2.8 to about 3.2, and applying a pressure in the range of about 10 bar to about 20 bar, and treating the wood at a temperature in the range of about 20 to about 50 °C, and treating the wood over a period of about 2 to about 4 hours.

[0036] In certain embodiments, post-treatment step iii) includes adding gaseous carbon dioxide to the treated wood under a pressure in the range of about 2 to about 12 bar, in the absence or presence of water, thereby lowering the pH of the treated wood to about 11 or less.

[0037] In certain embodiments, gaseous carbon dioxide is added over a period of about 15 to about 60 minutes under a pressure in the range of about 6 to about 12 bar to lower the pH of the treated wood to about 9 or less. In one embodiment, gaseous carbon dioxide is added over a period of about 15 to about 60 minutes under a pressure in the range of about 2.4 to about 7 bar to lower the pH of the treated wood to about 9 or less.

[0038] In certain embodiments, post-treatment step iii) includes heating the treated wood at a temperature in the range of about 50 to about 100 °C. The heating step includes heating the treated wood with dry air, saturated steam, or warm water. In one embodiment, the heating step has a duration of about 2 to about 6 days (or about 4 to about 6 days) and includes varying the rate at which the temperature is increased to a stable drying temperature and the rate at which the temperature is decreased to achieve the target of the desired moisture level.

[0039] Another aspect of the present invention relates to wood (or wood products) modified by all of the above aspects related to the process for modifying wood and the processes discussed in all of the above embodiments.

[0040] In certain embodiments, the wood is a lumber, a lumber board, a wooden post, a laminated lumber, a laminated veneer lumber, a plywood, a particle board, or a fiber board. The lumber may be a softwood or a coniferous species, such as a southern yellow pine, a radiata pine (pinus radiata), a hemlock, or a fir.

[0041] In certain embodiments, the modified wood (or wood product) is inert, decay-resistant, fire-resistant, termite-resistant, bacteria-resistant, and / or fungus-resistant. The modified wood (or wood product) also has improved strength compared to unmodified wood, characterized in that the modulus of elasticity (MOE) measured by ASTM D143-14 is increased by at least 35%, and the modulus of rupture (MOR) is increased by at least 4%. The modified wood also has improved strength compared to wood treated by a conventional phosphate-based impregnation process, and when measured by ASTM D143-14, the modulus of elasticity (MOE) is increased by at least 100%, and the modulus of rupture (MOR) is increased by at least 15%.

[0042] The resulting product is inert, i.e., neither chemically nor biologically reactive, does not decompose, is decay-resistant, fire-resistant, termite-resistant, bacteria-resistant, and / or fungus-resistant, and has excellent strength properties compared to untreated stabilized wood, resulting in an extended lifespan. The resulting product is also non-toxic and completely environmentally safe. Lumber for residential / commercial construction, railways (for sleepers) and telephone / electric utilities (for utility poles) and other applications may be made according to the disclosed process. In some examples, significant carbon sequestration is provided.

[0043] Embodiments of the present invention also provide fire-resistant wood (or wood products) modified by all of the above aspects related to the process for modifying wood and by the processes discussed in all of the above embodiments.

[0044] In certain embodiments, the fire-resistant wood (or wood product) modified by the process according to the present invention meets the Class A fire resistance rating as measured by the ASTM E84 10-minute combustion test. In this test, the fire-resistant wood modified by the process according to the present invention does not exceed a flame spread limit of 6 feet (a total of 10.5 feet from the burner according to the ASTM E84 standard with an additional 4.5 feet at the burner position). The fire-resistant wood modified by the process according to the present invention has a 170% improvement compared to wood treated by a conventional phosphate-based impregnation process (for a flame spread limit of 6 feet (a total of 10.5 feet from the burner according to the ASTM E84 standard with an additional 4.5 feet at the burner position)).

[0045] In certain embodiments, the fire-resistant wood (or wood product) modified by the process according to the present invention meets the Class A fire resistance rating as measured by the ASTM E2768 30-minute combustion test. In this test, the fire-resistant wood modified by the process according to the present invention does not exceed a flame spread limit of 6 feet (a total of 10.5 feet from the burner according to the ASTM E2768 standard with an additional 4.5 feet at the burner position). The fire-resistant wood modified by the process according to the present invention has a 350% improvement compared to wood treated by a conventional phosphate-based impregnation process (for a flame spread limit of 6 feet).

[0046] In certain embodiments, the modified wood (or wood product) can be used in the manufacture of all-green, fire-resistant, high-performance railroad ties, which are another major infrastructure need.

[0047] In certain embodiments, the modified wood (or wood product) has excellent strength properties, insect resistance, and decay resistance compared to toxic chemically treated wood and can be used in a variety of construction products including framing, siding, structural supports, handrails, landscaping, and all areas where lumber and plywood are utilized. FIG. 30 shows the construction uses within the comprehensive scope of the present invention. The resulting products also have an important immediate use for partnering with CLT (cross-laminated timber) in new generation low-carbon sustainable housing construction, which is an urgent and growing need in the United States. The all-green and high-performance wood reduces the carbon impact, dependence on oil, exposure to toxic leaching chemicals in water and wetlands, and is sourced entirely from responsibly managed sustainable U.S. forests.

Brief Description of the Drawings

[0048]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6a

Figure 6b

Figure 7a

Figure 7b

Figure 8a

Figure 8b

Figure 9

Figure 10a

Figure 10b

Figure 11

Figure 12a

Figure 12b

Figure 13a

Figure 13b

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

Figure 32a

Figure 32b

Figure 33

Figure 34

Figure 35

Figure 36A

Figure 36B

[0049] Aspects of the present invention relate to making soluble alkali metal silicate solutions, such as sodium silicate solutions, insoluble in wood (lumber) and other cellulosic materials, optionally under vacuum and / or pressure, optionally injecting the soluble alkali metal silicate solutions into the wood (lumber) and other cellulosic materials, and optionally applying post-injection carbon dioxide addition and / or heat treatment for post-impregnation stabilization, for the purpose of enhancing the mechanical properties, decay resistance, insect resistance, and / or fire resistance of the wood (lumber) and other cellulosic materials.

[0050] Modification Process Disclosed is a procedure for impregnating cellulosic materials, such as Southern Yellow Pine (Pinus taeda and Pinus elliotii) species, in the form of dimension lumber, plywood, cross-laminated timber (CLT), KD19 kiln-dried lumber, and railway ties, utility poles, pole cross-arms, and green untreated lumber, for the purpose of improving some or all of the performance characteristics of the above wood raw materials.

[0051] Embodiments of the present invention include various wood modification processes by single or double impregnation with alkali silicate solutions such as sodium silicate or calcium silicate.

[0052] The National Forest Service Library of the United States Department of Agriculture defines modified wood as "wood that has been treated by chemical treatment, compression, or other means, with or without heat, to give it permanently different properties from the original wood." The purpose of modified wood is to overcome the drawbacks of standard wood. Conventional wood treatments typically use unsustainable chemicals, including the commonly used EPA-registered preservatives today. In contrast, the wood modification processes described in various aspects of the present invention are environmentally friendly, and the modified wood materials can be safely and easily disposed of at the end of the product life cycle.

[0053] Various processing conditions for modifying wood include, but are not limited to, the following aspects.

[0054] Impregnation The concept of "less is more". Alkali salt impregnation typically uses a relatively high concentration of sodium silicate (+15 wt% when measured as silicon dioxide content) for the purpose of improving the properties of wood. The concentration of SiO2 in the impregnation solution during the impregnation process can be controlled in the range of about 3 wt% to about 35 wt%, about 3 wt% to about 15 wt%, about 5 wt% to about 15 wt%, about 5 wt% to about 10 wt%, or about 3 wt% to about 6 wt%. In certain embodiments, the process utilizes a lower concentration (3 wt% to 15 wt%) to better penetrate the lumber and provide the desired basic protective properties. The lower concentration means a beneficially low viscosity, as higher concentrations can negatively affect the impregnation process. Additionally, at higher concentrations and temperatures of impregnation, the alkali metal (or alkaline earth metal) silicate solution tends to form a thin silicate film on the wood sample, known as efflorescence, which can negatively affect the impregnation process. The "less is more" approach of using low specific silicon dioxide concentration levels enables both products with excellent performance, including long-term environmental attributes, and, equally importantly, a small amount of sustainable treatment solution used in the new production method, as well as a small amount of infrastructure for manufacturing costs and thus a small amount of depreciation costs (quick recovery conversion from an exclusive design to an all-greenwood plant in an existing facility), resulting in a much more affordable and competitive price for the product. Combining these factors is fundamental and revolutionary, enabling the adoption of all-green high-performance modified wood in large-scale price-sensitive construction and infrastructure industries and, thereby, having a significantly positive impact on the product (and process) with respect to the environment and their ability to realize the full potential of the present invention to improve the planet. Furthermore, the new all-green high-performance wood can utilize readily available sustainable sources of US lumber, further reducing transportation costs and the negative carbon impact of imported products from long-distance sources.

[0055] The impregnation time may be selected so that the alkali metal (or alkaline earth metal) silicate can enter the cell structure of the wood material. The impregnation time varies depending on the dimensions of the lumber to be treated. The reaction time during the impregnation process may range from about 20 minutes to about 10 hours, from about 20 minutes to about 120 minutes, from about 45 minutes to about 5 hours, from about 0.5 hour to about 4 hours, or from about 1.5 hours to about 4 hours. For example, in the case of conventional 2x4 lumber boards, decking materials and fencing materials, and other lumber of smaller dimensions, the impregnation time may be about 45 minutes to 5 hours, depending in part on the size of the lumber. For certain large pieces of lumber, the reaction time can be extended to about 10 hours.

[0056] The temperature in the impregnation of the alkali metal (or alkaline earth metal) silicate during the impregnation process may range from about 15°C to about 100°C, from about 15°C to about 80°C, or from about 50°C to about 80°C. As the concentration and temperature of the impregnation increase, the alkali metal silicate solution tends to form a thin silicate film on the wood sample, known generally as efflorescence, which can interfere with the impregnation process because silicate particles accumulate on the impregnated surface of the wood sample.

[0057] The impregnation of the alkali metal (or alkaline earth metal) silicate solution is carried out with the liquid being pushed in by natural infiltration and pressure being applied to the pores of the untreated lumber. The pressure applied during the impregnation process may be about 0.5 bar or more, for example, about 4 to about 20 bar, about 10 to about 20 bar, or about 6 bar (about 100 psi) to about 18 bar (about 250 psi).

[0058] Prior to the impregnation process, during the selection and preparation of the raw material, the wood may be pretreated to achieve a moisture content in the range of, for example, about 12% to about 40%, less than about 20%, or 18 to 20%, so as to maximize the efficiency and performance of the impregnation process. The pretreatment step may include drying the wood and / or applying a vacuum to the wood to achieve the desired moisture content.

[0059] The ratio of SiO2 / Na2O in the impregnation of sodium silicate during the impregnation process can range from about 2.0 to about 4.0, from about 2.0 to about 3.5, from about 2.0 to about 3.5, from about 2.5 to about 3.5, or from about 2.8 to about 3.2. The ratio of SiO2 / Na2O can be an important factor in the impregnation process in terms of minimizing efflorescence (Na2CO3) on the surface of the finished product by controlling the pH, the level of impregnation control, and the level of Na2CO3 remaining on the surface of the treated wood.

[0060] The pH of the impregnation solution in the impregnation process can be controlled in the range of about 9.0 to about 13.5, about 11 or less, from about 9 to about 11, or about 9 or less so as to maximize the efficiency and performance of the impregnation in the sodium silicate process. Increasing the pH of the impregnation solution may cause aggregation and polymerization of silicon dioxide. One way to lower the pH of the impregnation solution is by adjusting the ratio of SiO2 / Na2O in the impregnation solution as described herein. Another way to lower the pH is by applying carbon dioxide to the treated wood as described herein.

[0061] The longitudinal to radial impregnation of sodium silicate in the wood sample and the wood production during the impregnation process may be controlled, at least in part, based on the dimensions of the wood being impregnated.

[0062] The impregnation solution can further contain an environmentally safe biocide or preservative (or an environmentally safe amount of a biocide or preservative). For example, the biocide or preservative can optionally include boron or a boron-containing compound, a microbicide, a fungicide, or a combination thereof.

[0063] Boron or boron-containing compounds suitable for addition to the impregnating solution include boron, boric acid, boron oxide, borates, borate ions, borax, or fluoroborates. Adding a boron-based biocide to the impregnating solution improves the decay resistance and termite resistance of the impregnated wood. Boron is typically added as boric acid, added to an alkaline salt mixture, and mixed into a homogeneous liquid for use as the impregnating solution. However, when adding boron or boron-containing compounds, they are added at very low concentrations (environmentally safe, less than 1 wt%). One of ordinary skill in the art will understand that if the boron level exceeds 1 wt%, it is not considered to be completely environmentally safe. In one embodiment, the boron or boron-containing compound is added at 0.75 wt% or less, or 0.5 wt% or less. These levels are considered to be in full compliance with remaining consistent with the product's claim of being all green and non-toxic to the environment and humans. Boron has a tendency to leach from wood in conventional treatment processes, but the combination of alkaline salts and boron, and the post-impregnation stabilization process of the present invention prevent this. Thus, and importantly, the impregnated wood is suitable for use in indoor and outdoor environments.

[0064] This process may include stabilization / fixation of SiO2 within the wood impregnated with the sodium silicate solution using one or more of the following steps.

[0065] Fixation of carbon dioxide After the first impregnation step and / or the second impregnation step(s), if any, CO2 can be applied to the treated wood to stabilize or fix the SiO2 within the pores of the wood. CO2 can be added to the treated wood under pressure, in the absence or presence of water, to lower the pH of the host cells of the wood, precipitate the SiO2, and form a solid gel-like substance within the pore structure, resulting in a significant improvement in strength properties and providing a solid matrix that makes the wood more resistant to fire, decay, termite attack, and mold. Carbon dioxide is typically added in gaseous form and is compressed into the impregnation cylinder at a pressure of about 2 to 12 bar, about 6 to about 12 bar, or about 2.4 to about 7.0 bar. The residence time of this gas exposure can be 15 minutes to 60 minutes, or about 20 to about 45 minutes, depending on the type of wood used.

[0066] Previous methods of exposing impregnated wood to CO2 were carried out at atmospheric pressure for a long period of about 8 hours or for several minutes at high pressures of 300 - 800 psi. In the CO2 fixation discussed herein, a much lower pressure of about 2 to 12 bar (i.e., less than 180 psi) was used over a period of 15 - 60 minutes. These ranges of pressure and fixation duration can ensure better control of pH and better results in wood resistance.

[0067] Heat treatment After the impregnation step(s), if any, a slow heat treatment can be applied to the treated wood to dry and cure the SiO2 impregnated in the wood. The heating step can be carried out by heating the treated wood with dry air (e.g., in a drying kiln), by heating the treated wood with hot water, or by heating the treated wood with saturated steam. For example, the impregnated wood can be passed through a second drying kiln (the first being for moisture adjustment of the wood before impregnation) with a lower temperature range in the drying sequence (hardwood regime). The heat treatment after impregnation can typically be over a temperature range of about 50 to about 150 °C, or about 50 to about 100 °C, for a period of about 2 to about 6 days, e.g., a period of 72 hours to 120 hours.

[0068] The previous patent process described above used intensive heating such as microwave heating to provide sufficient energy. Such a process may have created a solid surface layer, but it did not address the problem of internal moisture. Only the surface veneer was fixed by microwave treatment, which could cause the overall structure of the product to break down after 40 - 48 months for sleepers and structural applications.

[0069] The heat treatment described in this specification involves slower drying at lower temperatures and for longer periods to enable consistent and uniform drying throughout the cross - section of the wood. Furthermore, the heating schedule can include rapidly increasing the temperature to a stable drying temperature and then rapidly decreasing the temperature, thereby changing the rate of temperature increase and decrease to achieve the target of the desired moisture level.

[0070] When gaseous carbon dioxide is added after impregnation, the wood modification process is improved by reducing the pH due to the precipitation of alkaline salts in the wood, thereby preventing excessive leaching and product deterioration after impregnation. In combination with the second drying step (the first drying step is before impregnation to optimally condition the wood), this causes the alkali metal silicate within the pores of the modified wood to solidify.

[0071] Second impregnation Certain embodiments of the present invention relate to a double - impregnation process for modifying wood. In the case of a double - impregnation process, after the first impregnation process (and related pre - impregnation and post - impregnation treatments), for example, before and / or after the carbon dioxide stabilization / fixation step, a second shorter - duration impregnation process can be continued.

[0072] All of the above descriptions regarding the impregnation process and various reaction conditions, as well as pre - impregnation and post - impregnation treatments, will apply to the first impregnation process (and related pre - and post - impregnation treatments) in these embodiments.

[0073] The second impregnation step is typically carried out using a second impregnation solution containing an alkali metal (or alkaline earth metal) silicate at a higher concentration than the concentration of the first impregnation solution over a shorter period than the first impregnation step. For example, the first impregnation solution can contain an alkali metal (or alkaline earth metal) silicate at a concentration of about 5 to about 10 wt%, and the second impregnation solution can contain an alkali metal (or alkaline earth metal) silicate at a concentration of about 10 to about 15 wt%. For example, the second impregnation step can be carried out using an alkali metal (or alkaline earth metal) silicate solution of about 10 to about 15 wt% SiO₂) over a period of about 10 to about 60 minutes, about 20 to about 60 minutes, or about 20 to about 30 minutes. The second impregnation step can be carried out at an operating temperature of about 20 to about 70 °C under a pressure of about 2 to about 12 bar (for example, about 6 to about 12 bar).

[0074] The purpose of this second impregnation step is to provide additional surface protection to the wood, such as adding an additional fire barrier. As shown in the following examples, this optional second impregnation step can enhance the fire resistance of the lumber, improve the resistance to decay and termite attack, and in some cases also enhance the strength properties. In particular, Example 2 shows that double impregnation of the lumber can result in fire resistance properties of Class "A" (significantly improved compared to conventional phosphate-based flame retardants).

[0075] According to an embodiment of the present invention, the above parameters and processing conditions enable both single impregnation processes and double impregnation processes, provide both fire resistance and termite repellency protection properties to the modified lumber, and improve strength and decay resistance by the drying process after impregnation.

[0076] As described below, an exemplary implementation of the processing process is shown in FIG. 1. 1. Mixing of sodium silicate and make-up water in a mixing tank. 2. Addition (optional) of boron as a biocide to this mixing tank. 3. Pumping of the mixture into a heated stirring container known as a working tank. 4. Transportation of unprocessed timber to the impregnation vessel / autoclave. 5. Placement of the autoclave under vacuum. 6. Addition of the liquid mixture from the working tank. 7. Application of pressure to the autoclave. 8. Depressurization and placement of the autoclave under vacuum. 9. If an optional second impregnation step is added, which includes the addition of a second, more concentrated impregnation solution to the autoclave, it will typically be carried out after step 8. If the optional second impregnation step is not added, step 10 will follow step 8. 10. Addition of gaseous carbon dioxide to the autoclave. 11. Removal of the treated timber from the autoclave. 12. Heating of the treated timber in a conventional sawmill kiln.

[0077] Alternatively, an optional second impregnation step can be added after step 10. If the optional second impregnation step is added, a further step of adding gaseous carbon dioxide to the autoclave can be made, similarly, before step 9.

[0078] Preparation of the solution Water and an aqueous alkali metal silicate such as sodium silicate (Na2SO3) are supplied to a mixing tank and mixed. Both sodium silicate and make-up water are pumped from separate storage tanks. The water is clean drinking water.

[0079] Sodium silicate is composed of both sodium oxide (Na2O) and silicon dioxide (SiO2) and is purchased from chemical suppliers in a certain ratio. This ratio can vary from 2.0 to 4.0. However, this ratio can be controlled within the range of about 2.0 to about 3.5, or about 2.5 to about 3.5.

[0080] The concentration of silicon dioxide in the mixture within the mixing tank may be, for example, from about 5% to about 35% (by weight). When preparing the impregnation solution for single impregnation, the concentration used is typically in the range of 3% to 15% by weight, or about 3% to about 6% by weight.

[0081] Optional addition of biocide An environmentally safe biocide (or an environmentally safe amount of biocide) is optionally added to the mixing tank to provide additional protection against insects, bacteria, and / or fungi in the final product. The biocide may be, for example, boron or a boron-containing compound. A trace amount (less than about 1% by weight of the mixture, or less than about 0.5% by weight) may be added.

[0082] Pumping to the working tank Next, the mixture containing SiO2, water (and optionally biocide) is pumped into the working tank. A heating element stirrer is inserted into this tank, which raises the temperature of the impregnation solution to the desired autoclave temperature (about 20°C to about 80°C). Stirring ensures uniform mixing and eliminates layering of the various chemicals.

[0083] Preparation of the timber In one embodiment, the timber for modification is selected. In one example, the timber is radiata pine. In another example, the timber is southern yellow pine. The timber may be in the form of, for example, a timber board without defects and knots. The timber may be in other forms, and other types of timber may be used.

[0084] The timber is dried in a conventional sawmill kiln until the water content is 19% or less (commonly known as KD19, or kiln-dried 19%). The timber may be dried to a water content of, for example, about 12% to about 19%.

[0085] The timber is typically placed on a pallet strapped together before being transferred to the autoclave.

[0086] Application of vacuum to the autoclave Next, the untreated lumber bundled with straps can be placed in the autoclave under vacuum conditions for a period of approximately 20 to 60 minutes (depending on the amount of lumber or other factors). The purpose of applying vacuum is to remove the free water in the wood and prepare the pores of the wood for chemical impregnation.

[0087] The applied vacuum is 22 inches Hg (or -1.2 bar). This vacuum can vary by 20% in either direction (depending on the amount of lumber or other factors).

[0088] Pumping the liquid into the autoclave When the vacuum in the autoclave is released, the heated homogeneous liquid from the working tank is pumped into the autoclave. This container is completely filled and completely surrounds all the lumber.

[0089] Impregnation process Next, the pressure in the impregnation pressure vessel may be increased. The pressure may be increased to, for example, a pressure of about 4 bar to about 20 bar. The impregnation of the sodium silicate solution is carried out with the liquid being pushed in by natural infiltration and pressure being applied to the pores of the untreated lumber.

[0090] The impregnation time may be selected so that sodium silicate can enter the cell structure of the wood material. The impregnation time varies depending on the dimensions of the lumber to be treated. For example, in the case of conventional 2x4 lumber boards, decking materials, and fence materials, as well as other lumber of smaller dimensions, depending partially on the size of the lumber, the impregnation time may be set to a time of about 45 minutes to 5 hours. In this example, the impregnation time is set to 1.5 hours. For example, larger lumber products such as railroad ties and utility poles may be treated over a long period of up to 10 hours (depending on the amount of lumber or other factors).

[0091] When the impregnation is complete, the pressure may be lowered. The residual sodium silicate solution is discharged and returned to the working tank through a liquid filtration system, for example, to prevent contamination of the working tank.

[0092] Next, if necessary, additional replenishment may be added to the working tank from the mixing tank.

[0093] Vacuum after impregnation When the liquid is discharged from the autoclave, a vacuum may be reapplied to the container. This is at approximately 22 inches Hg (or -1.2 bar) plus or minus 20% (depending on the amount of wood or other factors) over a period of approximately 20 to 60 minutes (depending on the amount of wood or other factors). The purpose of this second vacuum treatment is to remove excess chemicals from the surface of the wood and prepare the wood for the post-impregnation fixation process.

[0094] Stabilization / fixation of carbon dioxide In one embodiment, after discharge, gaseous carbon dioxide (CO2) is compressed from the carbon dioxide supply tank into the impregnation container under pressure. The carbon dioxide may be maintained at a pressure of, for example, about 2 to about 12 bar, about 6 to about 12 bar, or about 2 to about 7 bar. The pressure may be maintained over a period of about 15 to about 45 minutes during which the carbon dioxide fixation takes place. This fixation process causes the liquid in the wood to precipitate into a gel solution, preventing subsequent leaching and improving various treatments. The carbon dioxide can lower the pH of the impregnated wood from about 11 after impregnation to about 9. This allows silicon dioxide to adhere better to the cell walls of the wood during impregnation and prevents leakage from the wood.

[0095] Carbon dioxide can react with water to form carbonic acid (H2CO3), a weak acid. Carbonic acid can further react with sodium silicate to produce silicon dioxide (SiO2) and sodium carbonate (Na2CO3). Sodium bicarbonate (NaHCO3) may also be produced, but due to the moderately acidic environment, sodium carbonate is more likely to be formed.

[0096] The better adhesion of silicon dioxide to the wood may be due to the polymerization of sodium silicate, which results in a phase change from a liquid to an amorphous structure. This coagulation process may be irreversible.

[0097] Most of the carbon dioxide in this process is isolated within the wood, and the remaining carbon dioxide (if any) may be recycled or reused when it is safely discharged from the container and the pressure drops to atmospheric pressure. This method is consistent with an environmentally friendly all-green process.

[0098] Optional second impregnation After the first impregnation step is completed, the wood is then optionally subjected to a second impregnation stage where a higher concentration impregnation solution (i.e., higher than the concentration of the impregnation solution in the first impregnation step) is pumped into the autoclave and held at a pressure of 2 - 12 bar and a temperature of 20 - 70 °C for a period of 20 - 60 minutes under pressure. This higher concentration solution (e.g., about 10 - about 15 wt% SiO₂) can be prepared in a second mixing tank and then pumped into one of the working tanks or arranged in sequence through the original mixing tank. Carefully controlling the time between the first and second times, and systematically eliminating other environmental impacts on the wood during processing are important for performance output, as is the solution concentration for each impregnation. And after the second impregnation step is completed, the carbon dioxide stabilization / fixation step is completed. The carbon dioxide stabilization / fixation step may be carried out after the first impregnation step and before the second impregnation. The carbon dioxide stabilization / fixation step may also be carried out both after the first impregnation step and before the second impregnation, as well as after the second impregnation step.

[0099] Removal of the wood from the autoclave Thereafter, the seal of the impregnation container can be broken and the wood can be removed.

[0100] Even after the carbon dioxide is isolated and discharged and the remaining part is recycled, stabilization may be continued. Solidification may continue to occur over the next 24 - 48 hours after discharge. Therefore, the wood is left on the discharge table for 24 - 48 hours to complete solidification and to drain the residual liquid from the wood to ensure the elimination of residual chemicals.

[0101] Heat treatment Once the lumber becomes stable on the drip tray storage system, it is transferred to and placed in a conventional sawmill kiln. Next, the lumber is heated at a temperature in the range of 50°C to 100°C (depending on environmental conditions and kiln design) for 4 days (2 to 6 days depending on environmental conditions and kiln design) according to a drying schedule that includes a series of parameters covering the time (number of days), temperature, and rate of increase and decrease while the operator controls the target of the optimal moisture level to a stable drying temperature. These conditions may vary depending on the kiln design, the lumber being processed, and the environmental conditions, with a residence time of 2 to 6 days and a temperature of 50°C to 100°C.

[0102] The residual moisture in the processed and dried lumber is approximately KD19 (19% moisture dried in the kiln). However, other moisture levels can be targeted by changing the drying schedule and other kiln set variables, as well as the requirements of the commercial market as needed.

[0103] Strength properties During the all-green high-performance wood modification process described herein, the strength properties of the processed wood are improved.

[0104] Compared to untreated or unmodified lumber, these improvements in mechanical and structural performance are significantly improved when measured by industry standards, such as ASTM D143 - 14, which is the Standard Test Methods for Small Clear Specimens of Timber.

[0105] In certain embodiments, these test methods include the following three tests, specifically, the standard tests for modulus of elasticity (MOE), modulus of rupture (MOR), and maximum tensile splitting load (Tensile). Example 3 below shows that, unlike conventional fire-retardant treatment processes (typically phosphate-based) that typically degrade the strength properties (from the perspective of tensile strength, MOR, MOE) of wood, the modification process described in the embodiments of the present invention not only does not degrade the strength properties compared to untreated SYP controls, but actually shows stability and, in some cases, significant improvement.

[0106] The modified wood products are not only stronger than non-sustainably treated fire-resistant lumber but also stronger than untreated lumber. For example, the MOE and MOR have been shown to be significantly improved, which allows the construction sector to use less lumber for the same production volume, while at the same time increasing design flexibility and reducing the constraints when using FRT lumber (in fact, the strength can increase compared to untreated lumber) that was considered to have compromised strength. This is a result unique to the inventors' process.

[0107] Unsustainably treated FRT lumber is the major form of FRT lumber used in current construction applications in the United States, such as treated lumber and treated plywood. The reduction values cited here are based on ANSI / AWC NDSI National Design Specification for Wood Construction (NDS). For other sustainable modified wood products, the inventors believe that the embodiments of the present invention provide the only FRT lumber that uses alkali metal silicate in combination with a gaseous carbon dioxide wood modification / treatment process, resulting in products with Class A rated FRT lumber, and that such a greenwood modification process produces wood products with termite resistance (subterranean termites), decay resistance (fungal decay), and superior structural properties compared to equivalent unmodified / untreated wood.

[0108] Fire resistance Embodiments of the present invention also provided wood (or wood products) specially treated for fire resistance.

[0109] Currently, there are no all-wood, low-cost, fully environmentally sustainable Class A fire-resistant utility poles approved in the industry. However, the inventors have demonstrated the Class A fire-resistant performance of wood modified by the process according to embodiments of the present invention, characterized by, for example, the E84 and E2768 tests (with successful combustion data for both), in Example 2 below.

[0110] In addition to use in utility poles and railroad ties, the modified wood products according to embodiments of the present invention can be used in various other applications such as construction lumber applications, e.g., for general dimension building and other infrastructure construction lumber applications that are low-cost, fully environmentally sustainable, stronger than untreated lumber or as strong, insect-resistant to building codes, and can meet Class A fire-resistant product or equivalent international standards.

[0111] "All-in-one" products and inventory and cost reduction This "all-in-one" product has all the important high-performance characteristics and can significantly reduce the required inventory levels held by lumber dealers and retailers at the major points of today's lumber distribution, with the potential to reduce the required on-hand inventory by 50% in certain cases (after detailed interviews with major lumber sellers and owners and managers of lumber yards in multiple locations in the United States regarding conventional lumber industry procurement and inventory procedures). This is a major revolutionary product attribute of All Green's high-performance lumber products compared to all competing companies. When comparing the wood produced by the All Green modified pressure treatment process described here with wood treated by industry standard processes, lumber dealers and lumber retailers selling standard products need to maintain two or three times the inventory investment (compared to the products of the present invention) to cover the possible demand for FRT lumber with at least one other important performance attribute, not to mention two or three performance attributes as in the case of the new invention.

[0112] None of the existing competing commercialized sustainable wood modification technologies, including acetylated (acetylation chemically modifies wood in a process where acetic anhydride reacts with the hydroxyl groups of polymers such as lignin and hemicellulose in the plant cell wall), furfurylated (wood impregnated with furfuryl alcohol (C5H6O2) generated from bio-based liquids), or heat-modified wood (heat modification uses heat to remove organic compounds from wood cells, so it does not absorb water, expand, contract, or provide nutrition to insects or fungi), have achieved a price-competitive product that can directly compete with the major unsustainable FRT (fire-retardant treated) wood products in the widely used market. Their price settings are typically two to three times higher than FRT wood. These processes produce products that exhibit some improved performance such as better dimensional stability and decay resistance, but none have achieved a Class A fire rating.

[0113] Changes to sustainable wood production facilities and optimization of ongoing processes The processing process described in this specification also enables the reuse of existing pressure treatment facilities (originally designed specifically for use with unsustainable chemicals) with minimal capital upgrade compared to the cost of a complete replacement, and enables the treatment of wood by using alkali metal silicate solutions and pore impregnation stabilization with CO2 and heat treatment. This change process may include re-piping and re-arranging of existing tanks, addition of agitation and heating coils, cladding of major equipment items, and addition of a CO2 gas supply system. Such a system may enable a rapid upgrade to a new all-greenwood system and a very rapid return on the capital invested.

[0114] Implementation of AI Artificial intelligence and machine learning can be integrated into the design of the facility. Some examples of impactful use cases are: 1) modernization and optimization of the wood treatment process to adapt to the unique profiles of wood raw materials, production environments, geographical locations, and meteorological conditions during production; 2) prediction and macro-variable modeling such as raw material prices and demand for housing or infrastructure products; 3) pricing and competitive intelligence; 4) optimization of the supply chain including wood and other input chemicals and resources; 5) renewable energy sources used in manufacturing; 6) back-office automation; and 7) predictive maintenance. Adjusting these variables can have a significant impact on metrics such as yield, quality, and overall cost. This is in line with the inventors' view that experiments have identified important parameters for the process of modifying wood to achieve all major inventive materials and high-performance characteristics. These variables can continue to be further improved using large datasets while applying the core theories and scientific knowledge developed by the inventors as outlined in the examples above and below.

Examples

[0115] The following examples are for illustrative purposes only and are not intended to limit the scope of the present invention in any way.

[0116] Example 1. An exemplary process for modifying a wood sample. Preparation of the wood sample. Radiator pine wood was purchased from SODIMAC S.A. in the Concepción region of Chile. All the selected wood pieces were physically similar. The wood was cut into samples of 7.5 mm x 4.5 mm x 2.5 mm and air-dried in a laboratory kiln at 50 °C for 48 hours. Next, the samples were stored in an air-conditioned room at 65% humidity and 25 °C. The weights of five randomly selected samples were constantly monitored until they reached a constant weight. The weight of the samples remained almost constant after 25 hours. Thus, it can be established without problem that the samples reach the equilibrium humidity in the air-conditioned room in about 25 to about 48 hours.

[0117] Preparation of the wood sample for impregnation and the impregnation process. After preparing the samples and storing them in an air-conditioned room, two types of samples were selected for the impregnation process. The first type of sample had annual rings perpendicular to the impregnation direction ("radial sample"), and the second type of sample had annual rings parallel to the impregnation direction ("longitudinal sample").

[0118] The samples were coated with epoxy resin on four larger surfaces to prevent impregnation from these surfaces, and the samples were cured in an air-conditioned room at 25 °C for 18 hours. The impregnation surfaces were not contaminated with epoxy resin or other waxy substances that could interfere with the process. Before the impregnation process, very thin slices were cut from both impregnation surfaces at both ends of the samples to confirm that they did not contain epoxy. Next, two radial samples and two longitudinal samples were loaded into the impregnation reactor. The samples were positioned in the impregnation vessel so that the impregnation surfaces were not blocked by the walls or surfaces of other samples. The impregnation reactor was a batch reactor with a capacity of 800 mL. The lid of the reactor had two openings, one for the vacuum inlet and the other for the fluid, which in the case of the inventors was for nitrogen and sodium silicate solution.

[0119] To remove air from the pores in the reactor and the sample, a vacuum was applied for 15 minutes. Next, 600 mL of a sodium silicate solution of a predetermined concentration was injected into the reactor. Subsequently, the pressure inside the reactor was raised to 12 bar using gaseous nitrogen (except when examining the influence of pressure during the impregnation process). Immediately after raising the pressure, the temperature of the reactor was raised to the desired value, and the reactor was left for a predetermined time to conduct the impregnation process.

[0120] Determination of the solid content ratio in the sodium silicate solution. The 38 Baume (°Be) sodium silicate solution was provided by QUIPASUR S.A. in Chile. To determine the solid content ratio present in the sodium silicate solution, five samples of approximately 1 g of the sodium silicate solution were taken in different watch glasses. Next, the dishes were kept in an oven at 105 °C for 24 hours and then cooled in a desiccator for 1 hour. Next, the weight of the dishes was measured to confirm the change in weight. The dishes were placed back in the 105 °C oven for 2 hours. It was found that the average solid content ratio in the sodium silicate solution was 41.81%.

[0121] Quantitative determination of SiO2 in the sodium silicate solution. The proportion of silicon dioxide in the original sodium silicate solution used during the experiment was determined. The specific gravity of the sodium silicate solution provided by QUIPASUR S.A. was 38 Be, and the range of the SiO2 / Na2O ratio was 3.2 - 3.5. To determine the amount of SiO2 in this solution, the procedure described in the instruction manual "Determination of Sodium Silicate in Impregnated Wood" was followed. According to this procedure, approximately 1 g of the sodium silicate solution provided by QUIPASUR S.A. was placed in a round-bottom flask. Subsequently, 40 mL of sulfuric acid and 30 mL of nitric acid were added. The sodium silicate solution tends to crystallize immediately upon contact with the acidic solution. The crystals were crushed finely using a glass rod, and the system was heated under reflux at 80 °C for 45 minutes. Next, the round-bottom flask was cooled, and the solution was diluted to 10 times its volume with distilled water. Then, the solution was filtered. The residue in the filter was washed with 500 mL of distilled water. After filtration, the residue was dried at 105 °C for 12 hours. Next, this was cooled in a desiccator and weighed. The difference indicates the amount of silicon dioxide in the sodium silicate solution. This operation was repeated 6 times. The results are shown in Table 1 below. The average amount of silicon dioxide in the sodium silicate solution provided by QUIPASUR S.A., determined by the above procedure, was 32.6 ± 0.21% grams, and the standard deviation was 0.51%.

Table 1

[0122] Determination of the proportion of residual solids after decomposition of wood by acid decomposition. The silicon dioxide content in the impregnated wood samples was determined using decomposition in an acidic medium. The wood contains inorganic materials that do not dissolve in the acid mixture used during decomposition. The residual inorganic substances may interfere with the proportion of silicon dioxide determined using this procedure. Therefore, the contribution of residual inorganic substances from the wood during the acid decomposition of wood samples impregnated with sodium silicate was quantified. To determine the amount of solid residue from radiata pine wood after decomposition with an acidic solution, the same procedure as described in the instruction manual "Determination of Sodium Silicate in Impregnated Wood" was followed.

[0123] Approximately 1 g of dry wood dried at about 105 °C for 12 hours was placed in a round-bottom flask. Subsequently, 80 mL of sulfuric acid and 60 mL of nitric acid were added, and the system was refluxed and heated at 80 °C for 45 minutes. Next, the round-bottom flask was cooled, and the solution was diluted 10-fold with distilled water to its volume. Next, the solution whose weight had been previously determined was filtered. The residue was filter-washed with 500 mL of distilled water. After filtration, the residue was dried at 105 °C for 12 hours. Next, this was cooled in a desiccator and weighed. The difference in its weight indicates the amount of solid remaining after the decomposition of radiata pine wood. This operation was repeated 6 times. The results are shown in Table 2 below.

Table 2

[0124] The results indicate that the contribution ratio of the solid residue of radiata pine wood after acid decomposition is relatively small. Therefore, this amount can be discarded in the calculation of the final residue after decomposing sodium silicate-impregnated radiata pine wood.

[0125] Effect of SiO2 concentration in the sodium silicate impregnating solution. To investigate the effect of the concentration of sodium silicate in the mixture during the impregnation of radiata pine wood with sodium silicate, a series of experiments were conducted under the following conditions.

Table 3

[0126] The samples were impregnated according to the procedure described in the instruction manual "Impregnation of Sodium Silicate into Pine Wood", then weighed and dried at 105 °C for 20 hours to confirm that the impregnated samples were free of moisture. Next, the completely dried samples were weighed and the increase in total mass was monitored. Figure 2 shows the effect of the silicon dioxide concentration on the total silicon dioxide (%) retained in the samples after drying the samples at 105 °C for 20 hours at each concentration.

[0127] As shown in Figure 2, in the case of wood samples impregnated in the longitudinal direction of the tree rings, the weight of the impregnated wood samples gradually increases as the concentration increases until the concentration of silicon dioxide in the impregnation solution reaches 20%, and then decreases rapidly. In the case of wood samples impregnated in the radial direction with respect to the tree rings, the weight of the impregnated wood samples increases for silicon dioxide concentrations of 5% to 10% and then gradually decreases. This decrease may be due to reaching the critical viscosity and / or critical particle size of sodium silicate as the concentration increases, which may have an adverse effect on the impregnation into the radiata pine wood matrix. This experiment supports the "less is more" principle of the present invention regarding the importance of using the appropriate solution concentration of sodium silicate for a given wood condition.

[0128] Subsequently, the silicon dioxide concentration in the impregnated wood samples was determined using gravimetric analysis by acid decomposition. The results of the average values of the retained silicon dioxide at different lengths along the impregnation direction, as shown in Figure 3, indicate that the retention rate of SiO2 in the wood matrix follows approximately the same trend as the increase in the mass of the impregnated samples shown in Figure 2.

[0129] To investigate the uniformity of the impregnation process, the concentration (%) of SiO2 in the impregnated samples was determined. For this purpose, as shown in Figure 3, the impregnated samples were cut into four equal parts and the silicon dioxide concentration was determined by acid decomposition by gravimetry.

[0130] The obtained results showed that the minimum difference in the average retention value of silicon dioxide between the outer parts (E1 and E2) and the inner parts (I1 and I2) was at a SiO2 solution concentration of 10 - 15%. This suggests that the most homogeneous distribution of the impregnation solution occurs somewhere between 10% - 15% liquid SiO2 concentration.

[0131] Effect of reaction time in the impregnation of sodium silicate into radiator pine wood matrix. To investigate the effect of reaction time in the impregnation of sodium silicate into radiate pine wood, a series of experiments were conducted under the following conditions.

Table 4

[0132] The completely dried samples obtained after impregnation and subsequent drying process at 10°C for 20 hours were weighed, and the increase in total mass was monitored. The increase in the weight of the impregnated wood samples is shown in Fig. 4. The upper solid line in Fig. 4 shows the increase in the mass percentage of the wood when impregnated with the longitudinal annual rings, and the lower line shows the increase in the mass percentage when impregnated with the radial annual rings.

[0133] This suggests that good results were obtained for samples impregnated radially and longitudinally over a period of 2 - 4 hours or more. In one example, for instance, the impregnation time was 3 hours.

[0134] Fig. 5 shows the increase in the total silicon dioxide content of the impregnated wood after drying the samples at 105°C for 20 hours. The error bars are the dispersions (standard deviations) observed with silicon dioxide along the length of the impregnated samples. The average silicon dioxide retained in the impregnated samples was determined using a wet gravimetric method involving acid decomposition. The results show that the silicon dioxide content impregnated into the wood samples remained almost constant within the error bars after a 2-hour impregnation period.

[0135] The uniformity of the silicon dioxide impregnation in the impregnated wood matrix was also determined using the same method as described above with respect to Figure 4. The results showed that among the samples impregnated for 2 hours, 3 hours, and 4 hours, there was no significant difference in the concentration of SiO2 along the length of the impregnated samples, indicating that it is preferable to exceed 2 hours.

[0136] Effect of temperature on the impregnation of sodium silicate into the radiator pipe wood matrix. Under a series of conditions shown in Table 5 below, wood samples were impregnated with radial annual rings with respect to the impregnation direction to determine the effect of temperature on impregnation. Other conditions were kept constant. The tests were conducted at temperatures of 20 °C, 60 °C, 80 °C, and 100 °C.

Table 5

[0137] The results in Figure 6a show that when the silicon dioxide content in the impregnation solution is 10% and 15%, the retention rate of the weight (%) of the impregnation solution increases with the increase in the impregnation temperature. As shown in Figure 6b, when the carbon dioxide content in the impregnation solution is 20%, the retention force decreases with the increase in the impregnation temperature. At higher concentrations and temperatures, it was observed that the sodium silicate solution tended to form a thin silicate film on the wood samples, which is generally known as efflorescence. Therefore, the decrease in the retention force of the impregnation solution when the silicon dioxide content is 20% at higher temperatures may be due to the deposition of silicate particles on the impregnated surface of the wood samples.

[0138] Additional tests were conducted at a silicon dioxide concentration of 5% with the weight increased to approach the above value of 10%.

[0139] Next, the wood samples were dried at 105 °C for 18 hours. Figure 7 shows the increase in the dry weight of the wood samples impregnated with sodium silicate when the silicon dioxide content in the impregnating solution was 10% and 15% at 20 °C, 40 °C, 60 °C, 80 °C, and 100 °C. The retention tendency of the impregnating solution in the wood samples seems to be proportional to the impregnation temperature, but the increase in dry weight, and thus the retention power of SiO2, does not follow the same trend. As shown in Figure 7a, for the 10% and 15% silicon dioxide mixtures, the increase in dry weight reaches a plateau at temperatures after 50 °C and seems to decrease at higher temperatures. This may be due to the tendency of the wood samples to delignify at the higher temperatures and pH (approximately 11.5 - 12) used in this investigation. In contrast, as shown in Figure 7b, the increase in the weight (%) of the wood samples with 20% silicon dioxide decreases from 20 °C to 80 °C and increases from 80 °C to 100 °C.

[0140] The wood samples dried at 105 °C for 18 hours were subjected to acid decomposition to determine the silicon dioxide content. Each wood sample was cut into four equal pieces of wood, including two inner parts and two outer parts. Figures 8a and 8b show the mass (%) of silicon dioxide along the wood samples determined after acid decomposition, with Figure 8a showing the case of 10% sodium silicate and Figure 8b showing the case of 15% sodium silicate.

[0141] The silicon dioxide content was not uniform in all impregnations, but the silicon dioxide content and the standard deviation of the silicon dioxide content along the wood samples were calculated.

[0142] Figures 8a and 8b show that the silicon dioxide content in the wood samples follows the same trend as the increase in dry weight shown in Figures 7a and 7b, but the non-uniformity of silicon dioxide in the wooden matrix, which decreases with increasing temperature, is greater.

[0143] However, as shown in Figure 9, the 20% silicon dioxide solution shows the opposite trend. This shows the weight percentage of silicon dioxide retained in the impregnated wood samples at different temperatures and 20% silicon dioxide concentration of the impregnation solution. The deposition of silicate particles on the impregnated surface of the wood samples may prevent impregnation.

[0144] Figures 10a and 10b show the average mass retained in the impregnated wood samples when the sodium silicate content in the impregnation solution is 10%, 15%, and 20%. Figure 10a shows that when the concentration of silicon dioxide in the impregnation solution is lower (10% and 15%), the average mass of silicon dioxide retained in the impregnated wood remains almost constant at temperatures above 50°C, while in the case of the 20% solution, as shown in Figure 10b, it decreases with temperature. These experiments confirm the importance of controlling the temperature setting for the sodium silicate solution according to the sodium silicate concentration used, and a specific range is necessary to achieve the modified wood performance results.

[0145] Effect of pressure on the impregnation of sodium silicate into the radiator pine wood matrix. To explain the effect of pressure when impregnating sodium silicate into the radiator pine wood, the wood samples were impregnated in the radial annual rings with respect to the impregnation direction at different external pressures. All other experimental conditions were kept constant. The experiments were carried out under a series of conditions shown in Table 6.

Table 6

[0146] Figure 11 shows the average retained mass of silicon dioxide in the radiator pine wood samples after impregnation at a 15% silicon dioxide concentration under pressures of 20°C, 0.5 bar, 10 bar, 15 bar, and 20 bar. The error bars indicate the non-uniformity of the mass ratio of silicon dioxide in the wooden matrix.

[0147] The results show that the retained mass of silicon dioxide increases linearly up to 10 bar and then levels off and becomes independent of pressure. This may be due to the presence of a limiting pressure where the pores in the wood exert a minimum resistance to the flow of fluid within the wood sample, and thus approximately the same amount of silicon dioxide is deposited. Most of the silicon dioxide was retained between approximately 10 bar and approximately 20 bar. In one example, 15 bar was used.

[0148] Effect of the ratio of SiO2 / Na2O in the impregnation of sodium silicate into the radiator pipe wood matrix. The effect of the weight ratio of silicon dioxide to sodium oxide (Na2O) was also measured. The ratio of Na2O to SiO2 in the impregnation solution was adjusted according to the instruction manual "Preparation of the impregnation solution of sodium silicate". All experimental conditions were kept constant except for the ratio of SiO2 / Na2O and the concentration of the impregnation solution. The experiments were carried out under a series of conditions shown in Table 7.

Table 7

[0149] The impregnated samples were dried in an oven at 105 °C for 20 hours, and an increase in the mass of the dried impregnated samples was observed. The results show that the change in the mass percentage of the samples decreases with a decrease in the ratio of SiO2 / Na2O. Without limiting the present invention, this may be due to an increase in the pH of the impregnation solution due to an increase in the amount of sodium oxide, resulting in the aggregation and polymerization of silicon dioxide.

[0150] Next, the wood samples dried on a stove at 105°C for 20 hours were subjected to acid decomposition as described above to determine the silicon dioxide content. Each of the wood samples was cut into four equal pieces, and the outer parts were named E (E1 and E2), and the two inner parts were named I (I1 and I2). The average values of the outer and inner parts of the samples are shown in FIGS. 12a and 12b. FIG. 12a shows the increase in the mass (%) of the sodium silicate-impregnated wood sample when the silicon dioxide is 10%, and FIG. 12b shows the increase in the mass (%) of the wood sample impregnated with sodium silicate when the silicon dioxide is 15%. The red solid line shows the tendency for the mass percentage to decrease as the ratio of SiO2 / Na2O decreases.

[0151] FIGS. 13a and 13b show the average silicon dioxide retention values of the outer and inner parts of the wood samples impregnated with 10% silicon dioxide in FIG. 13a and 15% silicon dioxide in FIG. 13b. FIGS. 13a and 13b show that the liquid impregnation is not uniform in all wood samples and shows a high dispersion between the inner and outer segments. However, the impregnation process seems to be affected by the change in the ratio of SiO2 / Na2O of the impregnating solution (10% and 15% of SiO2) at both concentrations. The above-mentioned experiment can confirm the importance of controlling the pressure setting for solution impregnation while selecting the appropriate ratio of SiO2 / Na2O used.

[0152] Fixation of SiO2 inside the wood sample impregnated with sodium silicate solution. According to multiple strategies, the fixation of silicon dioxide inside the impregnated wood samples by thermal and chemical methods (pH reduction) was investigated. The durability of wood when exposed to humid conditions is closely related to the water solubility of the chemicals used. Sodium silicate is very soluble in water and is not very attractive for outdoor applications with high humidity.

[0153] In the heat treatment, the bound water is separated from the silicate, the number of cross-linked oxygen atoms decreases, and the equilibrium of silicon dioxide shifts to a form less soluble in water. Three different processes for heat treatment were investigated: 1) heat treatment with steam, 2) heat treatment with hot air, and 3) heat treatment with hot water. 1) In the heat treatment with steam, samples impregnated with 10% sodium silicate salt were treated with saturated steam at three different temperatures of 50 °C, 100 °C, and 150 °C for 2 hours and decomposed to determine the silicon dioxide content. 2) In the heat treatment with hot air, the impregnated samples were exposed to air heated to 50 °C, 100 °C, and 150 °C for 2 hours and further analyzed. 3) In the heat treatment with hot water, the impregnated samples were reacted with water at 50 °C, 100 °C, and 150 °C for 2 hours and further analyzed to determine the silica content in the treated samples.

[0154] Two different pH treatments were also investigated: 1) gaseous carbon dioxide (CO2) when the treated samples were exposed to carbon dioxide at three different pressures (3 bar, 6 bar, and 12 bar), and 2) water acidified with carbon dioxide when the treated samples were immersed in water in the reactor and the pressure of the reactor was increased to the desired value at 3 bar, 6 bar, and 12 bar for 2 hours.

[0155] For all the above treatments, the wood samples were impregnated with sodium silicate under the following conditions. TIFF0007713240000008.tif40149

[0156] For this purpose, 72 samples were prepared in a 10-liter reactor adjusted. The temperature inside the reactor was controlled by saturated steam circulating through an external jacket around the reactor. The samples obtained by impregnating the wood matrix with sodium silicate were subjected to the above heat treatment and pH treatment.

[0157] Next, the treated samples were subjected to acid decomposition to determine the silica content.

[0158] To evaluate the fixation of SiO2 inside the sodium silicate-impregnated wood samples, the leachability of sodium silicate was determined, and the silicon dioxide content was determined using an acid digestion method before and after each leaching cycle.

[0159] Heat treatment 1. Samples treated with hot air The impregnated samples were exposed to air heated to 50 °C, 100 °C, and 150 °C for 2 hours and then analyzed. The results of the decrease in the weight percentage of the samples with the leaching time are shown in Figure 14.

[0160] In Figure 14, the mass retention rate decreases with the passage of time. More mass is retained at 100 °C than at 50 °C, suggesting that mass retention at higher temperatures is better. However, at 150 °C, the mass retained was less.

[0161] It was observed that the samples released coloring substances during the leaching process. This may be due to the leaching of lignin and / or hemicellulose along with silicon dioxide and sodium hydroxide, resulting in more mass loss. Therefore, it can be concluded that the loss of lignin and hemicellulose is not significant at lower temperatures (50 °C and 100 °C).

[0162] To determine the amount of sodium silicate leached during the experiment, the silicon dioxide content in the samples was determined using an acid digestion method before and after the leaching test as described above. The mass percentages of silicon dioxide (SiO2) in the impregnated wood samples before (blue bars) and after (orange bars) the leaching test of samples treated with dry air at different temperatures are shown in Figure 15. The mass percentage of SiO2 did not change significantly. This also indicates that the mass loss of the samples observed during the leaching process is not due to silicon dioxide, but may be due to the loss of lignin, hemicellulose, and sodium hydroxide (NaOH), and sodium hydroxide is formed as a result of the reaction between water and sodium oxide (Na2O) present in sodium silicate.

[0163] 2. Samples treated with hot water In the heat treatment with hot water, the impregnated samples were reacted with water at 50 °C, 100 °C, and 150 °C for 2 hours, and further analyzed to determine the silica content of the treated samples. The mass reduction rate of the wood samples impregnated with sodium silicate during the leaching experiment is shown in Fig. 16.

[0164] First, the percentage of the retained mass decreased at almost the same rate until 10 hours and then diverged. At 150 °C, less mass was lost than at 50 °C and 100 °C. Most of the mass was lost at 50 °C. This may be due to the fact that most of the extracts from the samples had already been extracted during the hot water treatment process, and only a very small part of the remaining extracts was leached out during the leaching process, resulting in a gradual decrease in the mass of the samples over time. The percentage of the retained mass was higher at 50 °C, 100 °C, and 150 °C than the results of the hot air heat treatment shown in Fig. 14.

[0165] Fig. 17 shows the mass percentage of silicon dioxide (SiO2) retained in the impregnated wood samples before (blue bars) and after (orange bars) the leaching tests of the samples treated with hot water at different temperatures. The change in the mass percentage of SiO2 in the impregnated samples was similar in all cases.

[0166] The pH of the leachate was monitored after each leaching cycle. The pH of the leachate during the initial cycle was very high (the same order of magnitude as the sodium silicate solution) and gradually decreased with the increase in the leaching time.

[0167] 3. Samples treated with steam Fig. 18 shows the results of the leaching tests of the sodium silicate impregnated samples treated with saturated steam at 50 °C, 100 °C, and 150 °C. The mass loss of the impregnated wood samples was the least for the wood samples treated with steam at 100 °C and higher at 150 °C. The trend of the mass loss of the samples in Fig. 18 is the same as that observed in Fig. 14.

[0168] The changes in the mass percentage of silicon dioxide in the impregnated samples before (blue bars) and after (orange bars) the leaching test of samples treated with saturated steam at different temperatures are shown in Figure 19 below. The masses before and after leaching at different temperatures were substantially the same.

[0169] pH change of samples treated with gaseous CO2 under pressure 1. Samples treated with gaseous CO2 under pressure without water In these tests, the impregnated samples were treated with gaseous carbon dioxide under pressures of 3 bar, 6 bar, and 12 bar. Figure 20 shows the percentage of retained mass of sodium silicate-impregnated wood samples treated with gaseous carbon dioxide at different pressures over time during the leaching test. In the leaching test, heat-treated samples of size 2x2x2 cm were placed in 330 mL of distilled water in a 600 mL beaker and stirred for 8 hours. Next, the samples were dried at 60 °C for 16 hours. Four leaching cycles were performed for each sample.

[0170] As shown in Figure 20, increasing the treatment pressure reduces the mass loss from the samples during the leaching test. This indicates that as the treatment pressure increases, more carbon dioxide gas penetrates into the wood samples and reacts with the sodium silicate solution already present in the wood.

[0171] As described above, carbon dioxide reduces the pH of the impregnated wood from approximately 11 after impregnation to approximately 9 after CO2 treatment. This is due to carbon dioxide reacting with water to form carbonic acid (H2CO3), a weak acid. Carbonic acid further reacts with sodium silicate (Na2SO3) to produce silicon dioxide (SiO2) and sodium carbonate (Na2CO3). Sodium bicarbonate (NaHCO3) may also be produced, but due to the moderately acidic environment with a pH of 5.1 produced by distilled water, the formation of sodium carbonate is more likely. These reactions enable sodium silicate to adhere better to the cell walls of the wood during impregnation and prevent sodium silicate from leaking from the wood.

[0172] As shown in the above tests, the change in the mass of the sample may be due to the loss of lignin and sodium compounds at high temperatures, rather than due to the leached silicon dioxide. In this case, the loss of mass of the sample during the leaching process may be due to the loss of unreacted sodium hydroxide and sodium carbonate with low solubility in water at room temperature.

[0173] The silicon dioxide content of the leached samples and non-leached samples was also measured. Figure 21 shows the mass percentage of silicon dioxide in the impregnated wood before (blue bars) and after (orange bars) the leaching test of the samples treated with gaseous carbon dioxide at different pressures.

[0174] Figure 21 is consistent with the results of the tests on the leaching of the heat-treated samples, and there is essentially no change in the silicon dioxide content of the impregnated wood samples due to leaching.

[0175] 2. Samples Treated with Water in a CO2 Environment under Pressure The impregnated wood samples were immersed in water in an impregnation vessel and then treated with gaseous carbon dioxide at different pressures. The results obtained from these tests are summarized in Figure 22, which shows the percentage of the mass of the sodium silicate-impregnated wood samples retained during the leaching test.

[0176] When the impregnated samples were immersed in water at 6 bar and 12 bar, no significant difference was observed in the mass change. This may be due to the formation of an equal amount of sodium carbonate and / or the similar leaching rate of sodium carbonate together with sodium hydroxide. The change in the mass of the samples treated with water under a pressure of 3 bar was much greater than that at 6 bar and 12 bar. This may be due to the absence of the formation of sodium carbonate and sodium hydroxide that can be easily dissolved in water and easily leached.

[0177] The silicon dioxide contents of the leached samples and non-leached samples were also determined. The results are shown in Fig. 23. This indicates that the silicon dioxide content is substantially the same before and after leaching.

[0178] Comparison of Fixation Strategies A comparison between treatment strategies for fixing sodium silicate within wood samples is presented.

[0179] The heat-treated samples were subjected to acid decomposition. The results of samples heat-treated with dry air at 50 °C, 100 °C, 150 °C and samples heat-treated with steam at 150 °C were compared to determine the effect of heat treatment on the silicon dioxide content. The results are shown in Table 8 below.

Table 8

[0180] The leaching experiments were conducted according to the above method. Fig. 24 shows the mass reduction rates of wood samples impregnated with sodium silicate prepared with dry air at 50 °C, 100 °C, 150 °C, and steam at 150 °C. The weight reduction rates of the wood samples after each 16-hour drying process are shown in Fig. 24.

[0181] Fig. 24 shows that for all heat treatment strategies, the mass of the impregnated samples decreases over time. The maximum mass retained was provided by drying in dry air at 100 °C, followed by dry air at 50 °C, steam at 150 °C, and then dry air at 150 °C in that order. The results of the leaching tests indicate that heat treatment at 100 °C gives better results than samples treated with dry air at 50 °C. This may be due to more water being removed at higher air temperatures, and thus more precipitation of silicate due to a shortage of cross-linking oxygen.

[0182] It was observed that the samples released coloring substances during the leaching process. The coloring substances released during the leaching of these samples may be lignin together with sodium silicate, which indicates slight delignification. Therefore, the overall mass loss of the samples may not represent the loss of sodium silicate during the leaching process. Samples treated at a higher temperature (150 °C) by both dry air and water vapor lost more mass and were slightly delignified.

[0183] General comparisons in the heat treatment and pH change treatment of the impregnated samples before leaching are shown in Figures 25 and 26, respectively. Here, only the treatment process with the least mass loss of the samples during the leaching process is shown. Figure 25 compares the masses of the leached samples for the case of fixation with 12 bar of carbon dioxide gas and the case of fixation with carbon dioxide in water at 12 bar.

[0184] After 10 hours, when the fixation treatment was 12 bar of gaseous carbon dioxide, the retained mass was more.

[0185] Figure 26 compares the heat treatment with dry air at 100 °C and the heat treatment with 12 bar of gaseous carbon dioxide.

[0186] The retained mass was more in the pH change treatment with 12 bar of gaseous carbon dioxide than in the heat treatment with dry air at 100 °C. This tendency becomes more prominent at higher pressures. Due to the pH of the water (pH = 5.1) used in the initial impregnation treatment and the leaching process, it is considered that silicon dioxide has already polymerized and precipitated because the pH of the water is low.

[0187] These results obtained from the above experiments show that the inventors' unique use of CO2 under pressure as the main fixation method of silicon dioxide (SiO2) is very effective in eliminating the problem of leaching, which may be common to many of the chemicals impregnated in the timber, using the form of a pressure-treated wood modification process.

[0188] The three heat treatment experiments outlined in detail below led to the following important findings: namely, that hot air treatment and hot water treatment were partially effective, but that use under gaseous CO2 pressure for fixation by the inventors was concluded to be far superior as outlined in the following section on gaseous CO2 experiments, the pH treated samples.

[0189] Example 2. Double impregnation process for further improving wood protection performance In this example, preparation of the wood sample, the impregnation process, and fixation by pH change treatment with gaseous CO2 under pressure as described above in Example 1 were carried out as the first step.

[0190] The second stage process described below involves using a second, shorter duration impregnation after the first stage CO2 fixation step. In this second stage, a higher concentration sodium silicate solution (i.e., a sodium silicate concentration higher than the sodium silicate concentration of the impregnation solution in the first stage, for example 10 - 15% SiO2) was applied to the wood in the autoclave at a pressure of about 2 - 12 bar and a temperature of about 20 - 70 °C over a period of about 20 - 30 minutes. The purpose of this second impregnation is to provide additional surface protection to the wood, such as adding an additional fire barrier.

[0191] This second impregnation shows an average weight increase of 104% compared to 98% in a single stage impregnation process, as shown in Table 9 and Figure 27 below. This additional 6% weight increase is considered important for additional wood protection characteristics.

Table 9

[0192] The concept of weight gain indicates that the first protective barrier in preparing pressure-treated lumber, i.e., the more chemicals retained after impregnation, the higher the likelihood that the wood can withstand fire, termite attack, decay, and rot. Impregnation is combined with the second protective barrier, i.e., fixing or stabilizing the chemicals impregnated in the wood to prevent leaching of the impregnated chemicals and the associated deterioration of the wood over time. The wood modification process shown in the examples strikes a balance between the first and second protective barriers, comprehensive chemical retention, and long-term chemical stability, both of which are achieved without reducing strength. This is a unique and important combination of key wood protection achievements comprehensively achieved in wood when using all sustainable chemical modification processes.

[0193] The results in Table 9 and Figure 27 show that double impregnation provides a better barrier against fire attack. As shown in Table 10 below, fixation with CO2 followed by a second impregnation treatment provides an additional protective layer to make the wood less flammable.

[0194] In this case, the 10-minute combustion test of E84 was applied to both lumber treated by the conventional method (phosphate-based treatment solution) and lumber treated by the double impregnation process of the present invention described above, and the spread of the corresponding flame was measured. These tests were carried out in an accredited ASTM fire testing laboratory using a 24-foot long Steiner tunnel and applying the standard combustion technique for the E84 test.

[0195] The samples used were untreated 2x4x8 lumber. #2 untreated lumber, 2 inches x 4 inches, 8 feet long, dried in a kiln to approximately 19% (KD19). This lumber was dried in a conventional sawmill kiln using an optimal drying schedule after undergoing the double impregnation process as described above. Next, these products were separated, packaged, and shipped to the ASTM test facility, where they were burned within one week of manufacture.

[0196] The maximum flame spread is a measure of the advance of the flame traveling down the tunnel, propagated by a methane burner, and measures the ability of the wood to resist the spread of the flame. The defined limit of 6.0 feet from the point of measurement (and 10.5 feet from the burner) is an industry standard to keep the burning of the wood from exceeding in order to obtain a Class "A" fire rating.

[0197] Two tests were conducted, one a 10-minute burn (ASTM E84) and the other a 30-minute burn (ASTM E2768). ASTM E-84: Standard Test Method for Surface Burning Characteristics of Building Materials. ASTM E2768: Standard Test Method for Long-Term Surface Burning Characteristics of Building Materials (30-Minute Tunnel Test). These are part of ASTM E119 or UL 263, which meet the world standards for fire ratings.

[0198] The results of the first test are shown in Table 10 and Figure 28.

Table 10

[0199] Here, the modified wood by the double impregnation process of the present invention resulted in a flame spread down the tunnel that was 170% smaller (compared to the 6-foot flame spread limit) compared to the wood produced by the conventional treatment process. A smaller flame spread directly corresponds to fire resistance and safety.

[0200] A more rigorous test for measuring the combustion characteristics of wood is to use the same Steiner tunnel but use the E2768 test over a 30-minute period. The results of this test are shown in Table 11 and Figure 29 below.

Table 11

[0201] This data again shows the superior performance of the modified wood by the double impregnation process of the present invention over a 30 - minute test period, compared to conventional treated products, and the ability of the wood modified by the double impregnation process of the present invention to meet or exceed the Class "A" fire - resistance standard as described. In this case, there is a 350% improvement compared to the 6 - foot limit in the 30 - minute test.

[0202] Example 3. Relative Strength Characteristics The change in the relative strength characteristics of wood is important, particularly from the perspective of FRT wood, which has hitherto been considered to require a strength compromise to achieve the safety necessary against fire risk. Conventional fire - resistant treatment processes (typically phosphate - based) have been shown to reduce the strength characteristics of wood (from the perspective of tensile strength, MOR, and MOE). However, as shown in Tables 12 and 13 below, for wood samples produced according to the modification process described in embodiments of the present invention (the impregnation by the inventors), the strength characteristics are not reduced but are actually stable and, in some cases, significantly improved compared to untreated SYP controls.

[0203] The dimensions of the sample wood were cut to 1 - inch width for each dimension thickness (approximately 1.5 inches). The span used in the test was 28 inches. The test speed was 0.5 inches per minute and was performed on an MTS electromechanical universal test frame equipped with a 2,000 - pound load cell. The strength characteristics were measured in accordance with ASTM D143 - 14, The Standard Test Methods for Small Clear Specimens of Timber. See Figure 31.

Table 12

[0204] The relative improvement in these strength properties, measured against SYP control (untreated) samples and typical conventional phosphate-treated wood, is shown in Table 13 below.

Table 13

[0205] The above data shows a significant improvement in strength properties. In particular, the MOE of the wood samples modified by our impregnation process was improved by more than 112% compared to conventional FRT wood and more than 30% compared to untreated SYP control wood. These results indicate a revolutionary paradigm change in the outlook for FRT wood, replacing conventional unsustainable FRT wood and using FRT wood for additional fire safety, which was previously an acceptable compromise with a reduction in strength and often a major hurdle for both design and cost issues. From both perspectives, it enables a fundamental consideration of the use of our all-green, excellent-strength fire-resistant wood products in many of the applications described herein.

[0206] This data is also summarized in Figures 32a and 32b. The improvement in the wood samples modified by the process according to an embodiment of the invention in MOE, and the MOR characteristics, are on average +36.9% (MOE) and +4.0% (MOR), respectively, compared to the untreated SYP control wood samples, and the Tensile is statistically similar.

[0207] Compared to unsustainable treated wood (conventional phosphate-treated wood), these performance improvements show significant improvements in MOE (+112%) and MOR (+18%). This factor is important in the lumber industry in that the additional improvement in strength and flexibility directly affects cost and design flexibility and usage.

[0208] Using unsustainably processed / modified Southern Yellow Pine (SYP) that is used in wall / bed environments and roof framing trusses, and using current industry leading processes and formulations that are not sustainable, for example, when testing these samples using industry standard tests as defined by ASTM D5664 (ASTM D5664 is a standard test method for evaluating the effects of fire retardant treatment and high temperature on the strength properties of fire retardant treated lumber) and ASTM D6841 (ASTM D6841 is a standard method for calculating the design value adjustment factor for fire retardant treated lumber), the adjustment factors for MOR and MOE are known to be approximately 0.80 to about 0.95 compared to untreated controls of Southern Yellow Pine (SYP). In comparison, the range for our modified lumber from the modification process described in embodiments of the present invention is expected to be from approximately 1.05 to exceeding 1.40 compared to untreated controls of Southern Yellow Pine (SYP) (as derived from test data used to prepare the samples shown in FIGS. 31 and 32a and 32b). This result is unprecedented and further is in contrast to other unsustainable modified wood products and their manufacturing / processing processes, particularly processes used in the preparation of fire retardant treated (FRT) lumber, where mechanical strength properties generally degrade during the impregnation process.

[0209] Furthermore, as shown in the widely referenced analysis of conventional FRT wood treatments, after exposure to natural elements such as temperature, microorganisms, and ultraviolet light, the strength properties of fire-resistant timber and other unsustainable chemically treated wood products significantly deteriorate over time. Therefore, starting from a very high range of strength parameters such as MOE and MOR of FRT products, as seen in all-green high-performance wood when used in construction environments exposed to degradation factors, is a major paradigm shift in the current outlook for FRT timber, and considering these results, it can be said that the implications for design, material use, and cost reduction for architects and contractors are significant. See Winandy and Rowell, "Chemistry of Wood Strength", Handbook of wood chemistry and wood components, pages 303 - 347 (CRC Press, Roca Raton, Florida, 2005).

[0210] Example 4. Decay resistance / Rot resistance All-green wood produced with a sodium silicate impregnation solution according to the modification process described in embodiments of the present invention provides an effective barrier against decay and termites while retaining the fire and strength benefits from the modification process. To support these findings, specific tests were conducted using appropriate species at major timber research and testing facilities in Chile and Uruguay. The results showed that while the combination of sodium silicate and sodium borate provided the best resistance profile against decay and rot, the modification process described in embodiments of the present invention using a sodium silicate impregnation solution has been shown to effectively protect wood from fungal degradation. However, boron at environmentally safe levels of less than 0.5 wt% in combination with sodium silicate in the impregnation solution would be more than sufficient to resist fungal attack.

[0211] Samples of wood were prepared according to the modification process described in the embodiments of the present invention using sodium silicate and other types of chemicals and tested according to ASTM D1413-07, "Standard Test Method for Wood Preservatives by Laboratory Soil-Block Cultures".

[0212] Furthermore, to provide more extensive results and provide management criteria, the samples were also evaluated according to European Standard EN 113, "Wood preservatives - Test method for determining the protective effectiveness against wood destroying basidiomycetes - Determination of the toxic values". All tests were carried out at the Tacuarembó headquarters of the University of the Republic of Uruguay using samples of Pinus radiata and Pinus taeda.

[0213] Results of decay tests compliant with standard D1413-07 Figure 33 shows a summary of the results of resistance to deterioration by exposure to the dry rot fungus Serpula lacrymans under standardized conditions. A summary of the observations is given below.

[0214] · Sodium silicate: The wood treated with sodium silicate showed a weight loss of 7.3%, which was significantly less than that of the untreated control sample, which showed a weight loss of 19.7%. This confirms that impregnation by the modification process described in the embodiments of the present invention with sodium silicate alone effectively protects the wood from deterioration by the dry rot fungus Serpula lacrymans.

[0215] · Sodium silicate + Bio-oil I and Sodium silicate + Bio-oil II: Different proportions of Bio-oil I (aqueous phase of pyrolyzed pine bark liquid) and Bio-oil II (oil phase of pyrolyzed pine bark liquid) were added to a sodium silicate solution containing 5.49% SiO₂. The results obtained with both reagents were similar, and no improvement in fungal resistance was observed. In fact, a slight increase in deterioration was seen.

[0216] · Sodium silicate + Sodium borate: Different proportions of sodium borate were added to a sodium silicate solution containing 5.49% SiO₂. This combination provided the best results for the observed weight loss. A weight loss of 0.6% - 7% (average 3.4%) was observed. This indicates a tendency for increased resistance to fungal attack with increasing boron concentration. Importantly, the inventors concluded that an environmentally safe level of boron of less than 0.5% is sufficient when used together with sodium silicate to resist fungal attack.

[0217] · Sodium silicate + Copper II salt: Different proportions of copper sulfate were added to a sodium silicate solution containing 5.49% SiO₂. Although copper 0 and copper 1 are known to be effective preservatives, copper II was tested because of its high water solubility, and as a result, a hypothesis was made that impregnation of wood would be more effective. The results show that the mass loss of the wood is slightly less than when impregnated with sodium silicate alone (average loss 6.7% vs average loss 7.3% respectively). Both results show an improvement over the untreated control sample, which shows an average weight loss of 19.7%.

[0218] · Sodium silicate + Copper I salt: Only two tests were carried out using copper (I) oxide, and this compound is known for its insolubility in water and difficulty in achieving efficient penetration. The results did not show promise, as evidenced by the greater weight loss in these test specimens.

[0219] Decay test according to standard EN 113 Table 14 shows the test results of samples subjected to white rot fungi and brown rot fungi (Trametes versicolor and Gloeophyllum separium, respectively) according to the European standard EN113 test.

[0220] In addition to the control specimens of Pinus taeda and Pinus radiata, three groups of test samples prepared according to the modification process described in the embodiments of the present invention were impregnated with a sodium silicate solution containing 5.49% SiO2 without other additives, a sodium silicate solution containing 5.49% SiO2 + 0.6% bio-oil I (aqueous phase of pyrolyzed pine bark solution), and a sodium silicate solution containing 5.49% SiO2 + 0.4% sodium borate, respectively. The results are shown in Table 14 and Table 15 below.

Table 14

Table 15

[0221] Table 14 shows the obvious advantages provided by the wood modification treatment of the present inventors against white rot decay and brown rot decay. In the case of the white rot fungus (Trametes vesicolor), the modification process of the present invention using a sodium silicate impregnation solution showed weight losses of 4.01% (without other additives), 9.49% (with bio-oil I), and 5.92% (with sodium borate), compared with the controls of Pinus taeda and Pinus radiata showing weight losses of 16.81% and 19.98% respectively. In the case of the brown rot fungus (Gloeophyllum separium), the modification process of the present invention using a sodium silicate impregnation solution showed weight losses of 4.91% (without other additives), 6.63% (with bio-oil I), and 4.12% (with sodium borate), compared with the controls of Pinus taeda and Pinus radiata showing weight losses of 26.18% and 30.37% respectively.

[0222] Table 15 shows an increase in advantages in relation to two controls. A large three-digit improvement in the improved weight loss can be confirmed in the range of 77% to 637% depending on the treatment solution and the comparison control variable.

[0223] Figures 34a to 34e show that the test pieces treated with the sodium silicate treatment solution delayed fungal decay and limited damage to the cell wall. Figures 34a and 34b show the first and second months respectively of test pieces treated with the process of the present inventors (5.49% SiO2 + 0.6% bio-oil I) exposed to G. separium, showing that despite the increased toxicity of this fungus and the increased affinity for brown dry rot disease in coniferous forests, the damage to the cell wall was delayed.

[0224] In comparison, Figure 34c shows a cross-section of a control sample taken from the center of the test piece, showing the progression of cell wall deterioration and fungal proliferation.

[0225] Figure 34d shows a test piece treated with a sodium silicate solution containing 5.49% SiO2 + 0.4% concentration of sodium borate. Figure 34e shows a test piece treated with a sodium silicate solution containing 5.49% SiO2 without additional additives. Both test pieces show a high ability to delay fungal progression and cell wall degradation.

[0226] Example 5. Termite resistance Termites are essential agents for carbon recycling in tropical ecosystems but are serious household pests in urban environments. Conventional termite management mainly relied on the use of biocides, which did not require in-depth knowledge of organisms. Due to legal and socio-economic pressures, many of the most effective (but at the same time environmentally harmful) poisons have been driven out of the market.

[0227] The original environmentally persistent (persistent organic pollutants, POPs) termiticides (organochlorine compounds) were effective, provided decades of protection, and were usually applied before construction. Next, they were replaced by less effective soil termiticides and insecticides used as barriers, in an approach ranging from killing most of the termite population to killing some of the population around the treatment boundary, causing secondary repellence from necrophobia. These had to be applied more frequently than organochlorine compounds. Additional approaches, including physical barriers, biological control, physical control, and various baiting techniques, were added. Most of these have resulted in complex outcomes and continue to have an adverse impact on the environment. Furthermore, construction timber has been pressure-treated with various unsustainable chemicals as an additional method of termite control, resulting in the long-term consequence that the chemicals eventually leach into the environment and lose their efficacy, thereby requiring additional treatment on-site. Woodrow and Grace, "Termite Control from the Perspective of the Termite: a 21 stSee "Century Approach", ACS Symposium Series, Vol. 982, American Chemical Society (April 2, 2008), which is incorporated herein by reference in its entirety.

[0228] The inventors focused their termite control strategy on a sustainable combination of chemicals in wood that achieve stable termite resistance without termite removal and without long-term harmful leaching of toxic chemicals into the environment. The inventors were able to achieve both important results according to the modification processes described in embodiments of the present invention, thereby creating natural barrier products within the cellulose structure of the wood itself so that termites do not want to forage on the wood. This combination uniquely makes the inventors' modified wood approach effective against termites.

[0229] The following experiments were conducted to evaluate the effectiveness of the process of the present invention against termites in the field.

[0230] A termite test field site composed of SYP piles was created. These were 18 two-inch x four-inch x 18-inch (half modified using the process of the present invention and half untreated), and 18 one-inch x one-inch x 18-inch (half modified using the process of the present invention and half untreated), which is a standard piling method of industry practice sizes. These samples were planted in a managed field site in Appling, Georgia and monitored monthly. At this date, the two-inch x four-inch piles had been in the ground for approximately 12 months and the one-inch x one-inch piles for approximately 6 months. To date, there has been no termite attack on any of the modified pile samples of 2x4 or 1x1. As shown in Figure 35, the test pieces treated with the process of the present invention in the termite field test area (one-inch x one-inch x 18-inch piles) after 6 months have shown no evidence of termite attack since measurements began.

[0231] No other methods were applied to prevent termite colonies from the outdoor area.

[0232] Example 6. TGA Test In this example, TGA (thermogravimetric analysis) tests were used to pyrolyze eight wood samples and four conventional treated wood samples made according to the modification process described in the embodiments of the present invention. Samples of 2x4 modified wood (by the modification process according to the embodiments of the present invention) were sent to a reliable university research institute in North Carolina, where TGA tests were performed on the wood compared to control (untreated) SYP samples and also compared to wood treated by conventional methods (phosphate-based).

[0233] The data is shown in Table 16 and FIGS. 36A and 36B. [Table 16] Thermograms of the modified wood and the conventionally treated wood of the inventors

[0234] FIGS. 36A and 36B show the average thermograms of samples taken from the surface and core of the inventors' modified wood samples and conventionally treated wood samples. In the case of the outermost surface (FIG. 36A), the inventors' modified wood samples showed a slightly higher level of residual char (37.1% vs. 34.9%) than the conventionally treated samples, indicating slightly better fire resistance performance. Both treatments showed better performance than the untreated control. The residual char levels of the samples taken from the core (FIG. 36B) were significantly different, and the inventors' modified wood samples showed much better performance than the conventionally treated samples (35.9% vs. 18.7% char residue). The cores of the inventors' modified wood samples all showed better performance than the control, while the conventionally treated samples showed performance similar to the control.

[0235] These results indicate that the modifications by the inventors to the lumber samples taken from the surface and core increased the residual char, which is an initial indicator of fire resistance. These results also show that the conventional treated samples taken from the core and exposed to a nitrogen or air atmosphere at 700 °C are more prone to degradation than the inventors' core samples. Thus, those results explain that the modification process provided an impregnation that penetrated the 2x4 samples more than the conventional treatment.

Claims

1. A process for modifying wood, comprising directly treating the untreated pores of the wood with an impregnating solution containing sodium silicate under conditions sufficient to impregnate the wood with one or more of the components of the impregnating solution, said sufficient conditions including applying a pressure of 4 bar to 20 bar, treating at a temperature in the range of 15 to 100 °C, and treating the wood for a period of 2 to 4 hours, wherein the weight ratio of (SiO₂) / (Na₂O) of the sodium silicate is in the range of 2.5 to 3.5, and the concentration of SiO₂ in the impregnating solution is in the range of 3 wt% to 15 wt%, directly treating the untreated pores of the wood, adding gaseous carbon dioxide to the treated wood under a pressure in the range of 2 to 12 bar in the absence or presence of water, thereby lowering the pH of the treated wood to 11 or less to stabilize and / or fix the components of the impregnating solution in the wood, wherein the process is green and non-toxic as being carried out in the absence of pesticides or biocides or at an environmentally safe boron level in the impregnating solution of 1 wt% or less, process.

2. The process according to claim 1, wherein the process is green and non-toxic as being carried out in the absence of pesticides or biocides.

3. The concentration of SiO in the impregnation solution ２ is in the range of 3% to 6% by weight, the process according to claim 1.

4. The process according to claim 1, further comprising a step of pretreating the wood by drying the wood and / or applying a vacuum to the wood to achieve a water content of less than 20% of the wood before the step of treating.

5. The sufficient conditions for impregnating the wood in the step of treating are The concentration of SiO in the impregnation solution ２ is in the range of 5% by weight to 10% by weight, and The weight ratio of (SiO ２ ) / (Na ２ O) in the impregnating solution is in the range of 2.8 to 3.2, and applying a pressure of 10 bar to 20 bar, treating the wood at a temperature in the range of 50 to 80 °C, and treating the wood for a period of 2 to 4 hours, the process according to claim 1.

6. The sufficient conditions for impregnating the wood in the step of treating are The concentration of SiO in the impregnation solution ２ is in the range of 10% by weight to 15% by weight, and The weight ratio of (SiO ２ ) / (Na ２ O) in the impregnating solution is in the range of 2.8 to 3.2, and applying a pressure of 10 bar to 20 bar, treating the wood at a temperature in the range of 20 to 50 °C, and treating the wood for a period of 2 to 4 hours, the process according to claim 1.

7. The process according to claim 1, further comprising, after the step of treating, applying a vacuum to the treated wood to remove residual impregnation solution from the surface of the treated wood and preparing the treated wood for the post-treatment step.

8. The process according to claim 1, further comprising heating the treated wood at a temperature in the range of 50 to 100 °C after the step of treating, and the step of heating comprises heating the treated wood with dry air, saturated steam, or warm water.

9. The step of heating has a duration of 2 to 6 days and includes varying the rate at which the temperature is raised to a stable drying temperature and the rate at which the temperature is lowered to achieve a target of a desired moisture level, the process according to claim 8.

10. A process for modifying wood, i) directly treating the untreated pores of the wood with a first impregnation solution containing sodium silicate under conditions sufficient to impregnate the wood with one or more components of the first impregnation solution, the sufficient conditions including applying a pressure of 4 bar to 20 bar, treating at a temperature in the range of 15 to 100 °C, and treating the wood for a period of 2 to 4 hours, the weight ratio of (SiO₂) / (Na₂O) of the sodium silicate being in the range of 2.5 to 3.5, and the concentration of SiO₂ in the impregnation solution being in the range of 3 wt% to 15 wt%, characterized in that treating the untreated pores of the wood with the first impregnation solution; ii) treating the wood with a second impregnation solution containing sodium silicate at a higher concentration than the concentration of the first impregnation solution for a period shorter than the step of treating i), the weight ratio of (SiO₂) / (Na₂O) of the sodium silicate being in the range of 2.5 to 3.5, and the concentration of SiO₂ in the second impregnation solution being 10 to 15 wt%, characterized in that treating with the second impregnation solution; iii) performing one or more of the following post-treatment steps for stabilizing and / or fixing the components of the first impregnation solution and / or the second impregnation solution in the wood, the post-treatment step being In the absence or presence of water, gaseous carbon dioxide is added to the treated wood under a pressure in the range of 2 to 12 bar, thereby lowering the pH of the treated wood to 11 or less, and / or heating the treated wood at a temperature in the range of 50 to 100 °C, wherein the post-treatment step iii) is carried out after the treatment step i), before the treatment step ii), and / or after the treatment step ii), a process.

11. The treatment step ii) is carried out under the following conditions: treating the wood for a period of 10 to 30 minutes; applying a pressure of 2 to 12 bar; treating the wood at a temperature in the range of 20 to 70 °C, the process according to claim 10.

12. The process is carried out in the absence of pesticides or biocides or at an environmentally safe boron level in the first impregnating solution or the second impregnating solution of 1 wt% or less, and is green and non-toxic, the process according to claim 10.

13. The post-treatment step iii) comprises adding gaseous carbon dioxide to the treated wood under a pressure in the range of 2 to 12 bar in the absence or presence of water, thereby lowering the pH of the treated wood to 11 or less, the process according to claim 10.

14. The gaseous carbon dioxide is added under a pressure in the range of 6 to 12 bar for a period of 15 to 60 minutes to lower the pH of the treated wood to 9 or less, the process according to claim 13.

15. The post-treatment step iii) comprises heating the treated wood at a temperature in the range of 50 to 100 °C, and the heating step comprises heating the treated wood with dry air, saturated steam, or warm water, the process according to claim 10.

16. The modified wood obtained by the process according to claim 1 or 10.

17. The wood is sawn timber, sawn timber board, sawn timber column, laminated sawn timber, laminated veneer lumber, plywood, particle board, or fiber board, the modified wood according to claim 16.

18. The modified wood is inert, decay-resistant, fire-resistant, termite-resistant, bacteria-resistant, and / or fungus-resistant, the modified wood according to claim 16.

19. The modified wood has improved strength compared to unmodified wood, and when measured by ASTM D143-14, the modulus of elasticity (MOE) has increased by at least 35% and the modulus of rupture (MOR) has increased by at least 4%. The modified wood according to claim 18.

20. The modified wood has improved strength compared to wood treated by a conventional phosphate-based impregnation process, and when measured by ASTM D143-14, the modulus of elasticity (MOE) has increased by at least 100% and the modulus of rupture (MOR) has increased by at least 15%. The modified wood according to claim 18.

21. Fire-resistant wood obtained by the process according to claim 1 or 10, which satisfies the Class A fire resistance rating measured by the 10-minute combustion test of ASTM E84 and / or the 30-minute combustion test of ASTM E2768.

Images