JPH0520242B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] This invention relates to a method for producing modified wood used as building materials and the like. [Background technology] As a method for modifying wood, it is possible to produce flame retardant (fire retardant),
Methods for imparting dimensional safety, antiseptic/insect repellent properties, mechanical strength, etc. are being researched and developed. In general, modification methods for imparting flame retardancy to wood are broadly classified based on the following flame retardant mechanisms. (a) Covering with inorganic substances (b) Promoting carbonization (c) Inhibiting chain reaction in flaming combustion (d) Generating nonflammable gas (e) Absorbing heat due to decomposition and releasing crystal water (f) Insulating with foam layer Here, The modification method of including an insoluble, nonflammable inorganic substance in wood is expected to have the effects of (a), (b), (c), and (d) described below. Moreover, once this insoluble, nonflammable inorganic substance is fixed in the wood structure, there is little risk of it leaching out of the wood, so there is little worry that its effects will diminish, making it an effective method. In the above, (a) coating with an inorganic substance means that even if the material is flammable, it can be made flame retardant by combining it with a non-flammable inorganic substance at an appropriate blending ratio. For example, the conventionally known wood chip cement board is made by mixing combustible wood with noncombustible cement at a weight ratio of approximately 1:1 and forming it into a board shape. It is recognized as. The carbonization promotion in (b) has the following mechanism. In other words, when wood is heated, it thermally decomposes and generates flammable gas, which causes flaming combustion. At this time, if phosphoric acid or boric acid is present, the thermal decomposition, or carbonization, of the wood is promoted. A carbonized layer is quickly formed. This carbonized layer acts as a heat insulating layer and provides a flame retardant effect. Therefore, when the insoluble nonflammable inorganic substance contains a phosphoric acid component or a boric acid component, the flame retardant effect of the modified wood becomes even higher. The inhibition of the chain reaction in flaming combustion in (c) is contributed by halogen, and as a result of the halogen acting as a chain transfer agent in the radical oxidation reaction in the flame, the oxidation reaction is inhibited. This is the mechanism by which the flame retardant effect occurs. Therefore, if the insoluble, nonflammable inorganic substance contains a halogen, these effects can also be obtained. Finally, the generation of nonflammable gas (d) will be explained. This is because compounds such as carbonates and ammonium salts generate nonflammable gases such as carbon dioxide, sulfur dioxide, and hydrogen halides through thermal decomposition, but these gases dilute flammable gases and prevent combustion. It is. Therefore, if the insoluble nonflammable inorganic substance contains something that can generate the above-mentioned nonflammable gases, such as carbonate, a flame retardant effect due to this mechanism can also be obtained. Next, the antiseptic and insect repellent effects of wood containing this insoluble, noncombustible inorganic substance will be explained. When fungi cause wood to rot, hyphae first invade the inner cavity of the wood, but if foreign matter is present in the lumen of the wood, this prevents the mycelium from entering, and as a result, the wood becomes less likely to rot. . The foreign matter in the wood lumen does not have to be a particularly antiseptic agent (preservative), and may be anything as long as it does not provide nutrients for the mycelium. Insect repellents are the same as preservatives, and as long as they have medicinal effects, they are no different, and it is preferable to use ones that are poorly digestible, non-digestible, or repellent to insects. . Therefore, if an insoluble, nonflammable inorganic substance that satisfies these conditions is included in the internal cavity of wood, it is effective for preventing wood from rotting and insects. Furthermore, for dimensional stabilization and mechanical strengthening of wood, if wood can be swollen with water and some substance can be fixed in the wood cell walls in that state, then
Both of the above effects can be obtained due to the bulk effect. In other words, if the inside of the wood cell wall is occupied by the filler, the wood itself becomes less likely to expand or contract, and at the same time, various mechanical strengths, especially hardness, are improved. Here, as the fixing substance, inorganic substances that are difficult to dissolve in water can also be used, so the effect can be obtained by fixing an insoluble, nonflammable inorganic substance in the wood cell wall. As described above, the method of incorporating insoluble nonflammable inorganic substances is very effective in modifying wood, including flame retardation, but it has the following problems. Generally, for example, an insoluble nonflammable inorganic substance is directly dispersed in a solvent such as water, and this dispersion (processing liquid) is
Even if you try to soak the wood in it and let the liquid penetrate into the wood, almost all that penetrates is the solvent, such as water. This is because the narrowest part of the passage through which the treatment liquid permeates into the wood is the pit membrane, where the pore diameter is approximately 0.1 μm, while the dispersed particles The particle size of the insoluble, nonflammable inorganic material is usually 0.1μ
This is because it is much larger than m. Therefore, the inventors have first developed a method that can solve this problem. That is, two types of aqueous solutions are prepared that separately contain cations and anions that react to produce insoluble, nonflammable inorganic substances when mixed, and both are sequentially impregnated into raw wood to cause both ions to react inside the wood. This is a method for producing modified wood that fixes insoluble, nonflammable inorganic substances (Japanese Patent Application No. 1989-089423). If you do this,
Although extremely large amounts of insoluble, nonflammable inorganic substances can be efficiently incorporated into wood, on the other hand,
Even now, the following problems remain. First, conventionally, prior to impregnation, raw wood is subjected to water saturation treatment to ensure that the wood is sufficiently saturated with water (for example, a high water content state of 70% or more). Ta. This is because the ions in the treatment liquid will diffuse quickly using the water in the wood as a medium, and the impregnation time can be shortened. Here, the above-mentioned water saturation treatment methods include underwater wood storage, steaming, impregnation under reduced pressure,
Examples include impregnation under pressure, and in any case, it takes several hours to several tens of hours. This is not desirable in terms of improving overall processing efficiency. Second, when immersion treatment is performed, during the second and subsequent immersion, the components that were previously impregnated into the wood flow out and react not only inside the wood but also outside the wood, that is, in the treatment bath. However, there was a problem in that insoluble and nonflammable inorganic substances were produced. Since these contaminate the bath and lead to an increase in the amount of chemicals used, it is important to suppress their formation outside the wood as much as possible, and to generate a sufficient amount of insoluble, nonflammable inorganic substances almost exclusively within the wood. It is preferable. To this end, efforts have been made so far to make the concentration of the treatment liquid for later impregnation equal to or higher than the concentration of the treatment liquid for earlier impregnation, or to provide a sufficient impregnation time. However, when wood is treated under these conditions, the components that are subsequently impregnated exceed the amount necessary to react with the components previously contained in the wood to form insoluble, non-combustible minerals. Inevitably, too much was injected, which caused the third problem. In other words, the unreacted ions and soluble inorganic substances left in the wood in this way absorb a large amount of water and moisture, and depending on the type, may exhibit deliquescent properties. Therefore, if too many of these remain in the wood, the water absorption and hygroscopicity of the wood will become too high. As a result, the resulting modified wood has a sticky feel,
Under high humidity conditions, the surface of the wood becomes wet, making it unsuitable for use as building materials. Therefore, leaching treatment is usually performed after impregnation treatment to remove these soluble components remaining inside the wood and improve the water resistance and weather resistance of the wood. This leaching treatment is carried out by providing a post-treatment bath and immersing the material in water for a long time, or leaving it in running water for washing. On the other hand, regarding the appearance of modified wood, that is, its wood texture, when it is dried after treatment, the insoluble and nonflammable inorganic substances generated near the wood surface precipitate white, making the entire wood white as if it had been dusted with powder. There was also the problem that it would wear out and its appearance would be damaged.
To this end, in the past, treated wood was washed to remove inorganic substances from the surface to maintain its appearance. However, as a new issue, some of the soluble inorganic substances removed by the above leaching process,
Depending on the type, it is also nonflammable and contains many components that can contribute to not only flame retardant wood but also mechanical strengthening and dimensional stabilization, so this soluble inorganic material is simply removed. In the end, these effective ingredients are completely wasted, and a large amount of chemicals are consumed, leading to an increase in manufacturing costs, and the above-mentioned performance of the wood is also reduced accordingly. This is a very important issue in view of the current situation where ever higher standards are required in terms of mechanical strength, dimensional stability, and especially flame retardancy, and it is difficult to meet these demands. On the other hand, there is a large loss of time due to the long leaching process, and the cost of the water required cannot be underestimated. As mentioned above, in the past, in order to obtain modified wood with excellent performance, various processes such as saturated water treatment, soaking treatment, leaching treatment, and washing treatment were required for a long time, and a large amount of chemicals and chemicals were used. It's been time consuming. Therefore, it is currently desired to further improve not only the quality of modified wood but also the treatment efficiency. [Objective of the Invention] In view of the above circumstances, the present invention utilizes the chemicals necessary for the modification treatment without wasting it, fixes a large amount of insoluble, non-combustible inorganic substances in wood, and improves its antiseptic and insect repellent properties, mechanical strength, and The purpose of the present invention is to provide a method for efficiently producing modified wood that has excellent dimensional stability, hygroscopicity, etc., highly flame retardant properties, and good appearance. [Disclosure of the Invention] In order to achieve the above object, the present invention provides a treatment solution containing two or more types of anions and a treatment solution containing cation, which produce insoluble, non-combustible inorganic substances by mixing two or more types of anion-containing treatment liquid and a caotine-containing treatment liquid for raw material wood to be modified. A method for producing modified wood in which the inorganic substances are generated and fixed in the wood structure by impregnating each of the above-mentioned inorganic substances individually, wherein both of the processing solutions are impregnated alternately by immersion three times or more in total, and The gist of the present invention is a method for producing modified wood, characterized in that the first impregnation is carried out by vacuum impregnation, and the final impregnation is carried out with an anion-containing treatment liquid having a higher concentration than the previously used anion-containing treatment liquid. This invention will be explained in detail below. The raw material wood for modification used in this invention is not particularly limited, and examples include raw logs, sawn timber products, sliced veneers, and plywood. There are no limitations on these tree species either. Insoluble, nonflammable inorganic substances that are generated in wood and dispersed and fixed in the wood tissue are not particularly limited, and include, for example, borates, phosphates, hydrogen phosphates, carbonates, sulfates, and hydrogen sulfate. Examples include salts, silicates, nitrates, fluorides, bromides, hydroxides, etc., and two or more types of inorganic substances may coexist in the wood. Further, one type of insoluble nonflammable inorganic substance may contain two or more types of each of the following cation moiety and/or anion moiety. As the elements constituting the cationic moiety of the inorganic compound (salt) as described above, alkali metal elements such as Na and K, alkaline earth metal elements such as Mg, Ca, Sr, and Ba, Zn and Al can be used. Preferably, but not limited to, for example,
Transition elements such as Mn, Ni, and Cd and carbon group elements such as Si and Pb can also be used. The anion part is composed of BO ₃ ,
Preference is given to using PO ₄ , CO ₃ , SO ₄ and OH anions. However, it is not limited to these, and includes, for example, F, Cl, Br, O, NO ₃ ,
It may be SiO ₃ anion or the like. BO ₃ , PO ₄
For anions, the effect is due to the flame retardant mechanism (b), and for CO ₃ anions, the effect is due to the same mechanism (d), F, Cl,
Br anions are more suitable because the effects of (c) and (d) can be expected. The cation moiety and the anion moiety may be used alone or in combination. Here, not all combinations of the two are possible, and there are restrictions due to the ionic radius and the like. In view of such conditions, both of them are arbitrarily selected, and water-soluble inorganic substances containing them are respectively dissolved in water to form a cation-containing treatment liquid (X) and an anion-containing treatment liquid (Y). Prepare an aqueous solution of more than one type of water-soluble inorganic substance. Two or more types means that X and Y may each have the same composition, or X ₁ , X ₂ , X ₃ , etc. with different compositions, and
Y ₁ , Y ₂ , Y ₃ ... may also be prepared. Here, it goes without saying that there may be a plurality of types of cations or anions contained in one type of aqueous solution. In addition, as described above, so that an insoluble nonflammable inorganic substance containing two or more types of the above cation or anion moieties is generated,
A treatment liquid may be included. For example, the above-mentioned halogen and OH anion may be contained together in a cation-containing treatment solution and/or an anion-containing treatment solution containing other anions, so that apatite or the like is produced in the wood. It's good. Prior to impregnation with such a treatment liquid, raw material wood was conventionally subjected to water saturation treatment, but in the production method according to the present invention, this pretreatment can be omitted. That is, one of the features of this invention is that the processing liquid to be initially injected is
Impregnation is carried out by a reduced pressure method, and according to this reduced pressure impregnation method, the wood does not need to be saturated with water, but rather is preferably in a normal dry state. This is because in this method, the pressure is reduced in the voids inside the wood, and the treatment liquid is injected into the area where the pressure is low.
This is because it is better if there are voids in the wood that can create a low pressure, that is, it is better if it is somewhat dry. This reduced pressure impregnation is performed, for example, by the following operation. First, the raw material wood is fixed in a vacuum container and the pressure is reduced. Once the pressure has been reduced to a predetermined pressure, the pressure is maintained for about half an hour to reduce the pressure inside the wood. Then, a treatment liquid is introduced into the container, and the wood is Once it is completely immersed in the liquid, return it to normal pressure. Alternatively, the treatment may be carried out by first introducing the treatment liquid into the container and soaking the wood in it, then reducing the pressure from that state and holding it for about an hour when the predetermined pressure is obtained, and then releasing it to atmospheric pressure. . Conventional immersion under normal pressure requires immersion for several tens of hours to achieve sufficient impregnation, but with this reduced pressure impregnation, sufficient effects can be obtained with immersion for a few minutes to several tens of minutes. . The reduced pressure state is not particularly limited, but is preferably 50 mmHg or less in order to efficiently perform sufficient impregnation. In this way, the raw material wood is first impregnated with the treatment liquid X or Y under reduced pressure, and then the wood is impregnated with both treatment liquids separately and alternately. Then, the final anion-containing treatment liquid Y′ is
A feature of this invention is that it has a higher concentration than any of the Y used previously. There are no particular limitations on the concentration of other treatment liquids, the number of times of impregnation, the order of impregnation, etc., and can be set as appropriate depending on the purpose. For example, impregnation methods include YXY′,
Examples include YXY...XY', XY...XY', etc., and X, Y, and Y' may be of the same type or different types, respectively. Here, if we start with impregnation with anion-containing treatment liquid Y, at least 3
Effective impregnation according to the present invention can be achieved in 10 times,
This is preferable because it is more efficient than impregnating from the cation-containing treatment liquid X. The immersion time in each bath is not particularly limited, but from the second bath onwards, the ions diffused into the wood react to form insoluble and nonflammable inorganic substances, and the immersion time in each bath includes the process in which ions that have already been formed react. Since the inorganic substances contained in the water may impede penetration, it is also effective to gradually lengthen the immersion time in order to further satisfactorily impregnate the ions. After the above impregnation treatment is completed, the wood is dried to obtain modified wood. Note that in order to further improve the water resistance of the wood after the impregnation treatment, a leaching treatment may be performed as a post-treatment, or washing with water or the like may be performed. The method for producing modified wood according to the present invention includes, firstly,
Since the immersion treatment is performed three or more times in total, it has the following advantages. That is; wood can be sufficiently impregnated with a large amount of inorganic substances. Secondly, the use of a highly concentrated anion-containing treatment solution for the final impregnation provides the following advantages. In other words; the diffusion rate of anions into the wood becomes faster, and the cationic components contained within the wood react inside the wood without leaking out to the outside, so that insoluble and nonflammable inorganic substances The generation is controlled, and it becomes possible to generate and fix a large amount of insoluble, nonflammable inorganic substances within the wood.
In other words, it is possible to prevent the loss of inorganic substances outside the wood, utilize chemicals efficiently, reduce manufacturing costs, and obtain modified wood with highly superior performance. Anion components can remain as ions remaining in the wood. This anion component is
Usually, it has higher performance in terms of fire retardancy than cationic components, so it greatly contributes to making the modified wood flame retardant. In this way, soluble components can be effectively utilized without performing leaching treatment, and at the same time, the processing time for this is shortened.
Processing baths, processing liquids, etc. are also not required. Insoluble and nonflammable inorganic substances present on the wood surface are
It is eluted by a treatment solution containing a high concentration of anions. In other words, the surface of the wood is cleaned by the final impregnation, and it is possible to obtain modified wood with an excellent appearance that retains its wood feel without the need for a separate cleaning process after the impregnation treatment. Thirdly, since the vacuum method is adopted for the initial impregnation, the following advantages are also obtained. In other words; the conventional saturated water treatment can be omitted, which not only significantly shortens the overall treatment time, but also the time required for vacuum impregnation itself to reach the specified amount of impregnation is significantly reduced compared to the conventional method. Because it becomes shorter,
Processing efficiency will be further improved. Insoluble and nonflammable inorganic substances can be generated and fixed deep into the wood, further enhancing the performance of modified wood. Next, examples and comparative examples of the present invention will be described. Example of manufacturing method for modified wood 1 A 3 mm thick rotary veneer of hemlock wood was depressurized to about 30 mmHg in a processing container, and 3.5 mol of diammonium hydrogen phosphate [(NH ₄ ) ₂ HPO ₄ ] and orthophosphorous were added per 1 water. An anion-containing treatment liquid (first bath) in which 4.0 mol of acid [H ₃ BO ₃ ] was dissolved was injected to perform vacuum impregnation. Next, soak this veneer in 1 part of water.
It was immersed for 6 hours in a cation-containing treatment solution (second bath) in which 2.0 mol of barium chloride [BaCl ₂ ] and 2.0 mol of orthoboric acid were dissolved, and then immersed in 1 mol of water.
The wood was immersed for 17 hours in an anion-containing treatment solution (third bath) in which 8.0 moles of diammonium hydrogen phosphate and 6.0 moles of orthoboric acid were dissolved per wood, thereby producing insoluble, nonflammable inorganic substances within the wood. The veneer after this immersion treatment was washed with water and dried to obtain modified wood. Examples 2 to 5 In the same manner as in Example 1, veneers were treated under the conditions shown in Table 1 to produce each modified wood. Comparative Examples 1 to 3 In the first bath, impregnation under reduced pressure was not performed, but after saturated water treatment, immersion at normal pressure was performed in the same way as in the other baths. Each modified wood was manufactured by treating the veneer under the conditions shown in . Performance of Modified Wood The modified wood obtained above was examined for total impregnation rate of inorganic substances, flame retardancy (fire retardancy), and appearance. The above-mentioned total impregnation rate of inorganic substances is the total impregnated weight ratio of insoluble non-flammable inorganic substances and unreacted ions (ions that do not produce insoluble non-flammable inorganic substances) to the weight of bone dry wood without washing treatment. be. Flame retardancy is JIS standard
Flame retardant grade in A1321 is ◎, flame retardant grade is △,
The intermediate performance is ○, and the appearance is ◎, where no inorganic substances are observed on the wood surface, and △, where white, insoluble, nonflammable inorganic substances are observed over the entire wood surface. Those were marked as ○. The above results are shown in Table 1.

【table】

[Table] As shown in Table 1, the modified wood of the example that was impregnated under reduced pressure in the first bath was different from that of the comparative example.
It was found that although the treatment time was significantly shortened, a large amount of inorganic material was impregnated, resulting in improved flame retardancy and an excellent appearance. As mentioned above, the reduced pressure impregnation method is a very effective method for producing modified wood, but when applied to modifying thick board materials, a different kind of effect occurs. That is, it has been found that this method has an excellent effect of increasing wood hardness, and this will be explained below. In order to increase the hardness of soft wood such as coniferous wood, hard substances such as inorganic substances may be stuffed into voids such as conduits inside the wood and into the cell walls of the wood. Therefore, fixing the insoluble, nonflammable inorganic substance according to the present invention into wood simultaneously leads to an increase in hardness, but conventionally, when modifying thick board materials, favorable results in terms of hardness have not been achieved. I wasn't getting it. This is because, especially in the case of thick board materials, the effect of increasing hardness depends on the distribution of inorganic substances generated within the wood, and inorganic substances are densely generated near the surface layer of the wood. However, when impregnating a plate with the treatment liquid used in this invention, if normal pressure immersion is performed after saturated water treatment, the treatment liquid will be deeply impregnated near the center of the plate. This is because insoluble, nonflammable inorganic substances are distributed evenly within the wood. As a result of repeated studies, it was found that when the treatment liquid for impregnation is first injected using a reduced pressure method, insoluble, non-combustible inorganic substances are selectively and densely formed near the surface layer of the wood. That is, the raw material wood to be modified is individually impregnated with an aqueous solution of two or more water-soluble inorganic substances that produce insoluble, non-flammable inorganic substances when mixed to generate and fix the inorganic substances within the wood structure. In carrying out the method for producing modified wood, which is characterized in that when processing thick board materials, the aqueous solution to be impregnated is first impregnated by a vacuum impregnation method. It has been found that this method has the remarkable effect of increasing the hardness, especially the surface hardness, of thick plate materials while maintaining properties such as corrosion resistance, insect repellency, and dimensional stability. Here, if the thickness of the thick plate is about 1 mm or more, or even about 3 mm or more, the effect will be even more obvious. In the above thick plate modification method, vacuum impregnation is
This can be done in the same manner as already described in the disclosure of this invention. However, the treatment liquid impregnation method
The method is not limited to the dipping method; in other words, it may be performed by applying a treatment liquid, and the concentration of the treatment liquid, the order of impregnation, the number of times of impregnation, etc. can be set as appropriate. After impregnation, leaching treatment is performed as a post-treatment. It is also appropriate to remove soluble components. The mechanism by which insoluble and noncombustible inorganic substances are produced only in the surface layer of the plate by performing vacuum impregnation is still under investigation and has not been clarified, but an outline is provided below. Ions injected into dry planks using the vacuum method remain only in the surface layer of the wood and do not penetrate beyond that, but when wood is immersed in water after being saturated with water, the ions are absorbed into the wood. It enters the internal annual ring. Therefore, in the former case, the ions in the surface layer that have been impregnated first try to go out, and the ions that are impregnated later try to go inside and a reaction occurs in the surface layer, where insoluble and nonflammable inorganic substances are generated. However, in the latter case, inorganic substances are generated and fixed deep into the wood. Next, specific examples and comparative specific examples of the above-mentioned modification method for thick plate materials will be given. Specific example 1 A 15mm thick solid Douglas fir is fixed in a vacuum container and degassed using a vacuum pump to reduce the pressure inside the container.
After the temperature dropped to below 40Torr, degassing was continued for another 2 hours. Then, while maintaining this pressure, pour
A barium chloride solution [BaCl ₂ .2H ₂ O, concentration 2 mol/water 1, PH 5-6] at 60° C. was injected. After the injection was completed, the wood was taken out and then immersed in diammonium hydrogen phosphate solution [(NH ₄ ) ₂ HPO ₄ , concentration 3.5 mol/water 1, pH 5-6] at 60° C. for 24 hours. The impregnated wood was immersed in water for 24 hours for leaching treatment, and then dried to obtain modified wood. Specific Examples 2 to 5 Wood was treated in the same manner as in Specific Example 1 under the conditions shown in Table 2 to produce each modified wood. Comparative Specific Examples 1 to 3 Table 2 is the same as in the above specific examples, except that the lumber was immersed in water for 24 hours and subjected to water saturation treatment, and was immersed in the first bath at normal pressure. Each modified wood was produced by treating the wood under the conditions shown in . In order to investigate the distribution position of the insoluble, nonflammable inorganic substances fixed on the modified wood obtained above, each modified wood was cut and exposed to soft X-rays. As a result, in the modified wood of the specific example, black shadows caused by insoluble and nonflammable inorganic substances were observed only in the surface layer within 1 to 2 mm from the wood surface. On the other hand, in the modified wood obtained in the comparative example, it was found that the inorganic substance was impregnated deep into the wood. Furthermore, the impregnation rate of insoluble and nonflammable inorganic substances and surface hardness of the obtained modified wood were investigated. The impregnation rate of inorganic substances is the ratio of the amount of insoluble incombustible inorganic substances impregnated to the weight of bone-dry wood, and the surface hardness is measured using a Barcall hardness meter.
I read the scale and compared it. Note that the hardness of untreated raw material wood is 0. The above results are shown in Table 2. In the table, specific example 1
The injection of the treatment liquid into the bath and the immersion operation are completed in a few minutes, so no particular description is given.

〔Effect of the invention〕

The method for producing modified wood according to the present invention is as described above, and in order to generate and fix an insoluble incombustible inorganic substance inside the wood, impregnating the wood with a treatment solution containing cations and anions alternately at least three times in total by dipping, In addition, the first impregnation is carried out by vacuum impregnation, and the final impregnation is carried out using an anion-containing processing solution with a higher concentration than the anion-containing processing solution used earlier, resulting in good mechanical strength, dimensional stability, etc. At the same time, it is possible to efficiently produce modified wood that has highly flame retardant properties and retains its wood texture.

Claims (1)

[Scope of Claims] 1. Raw material wood to be modified is impregnated with two or more types of anion-containing treatment liquid and cation-containing treatment liquid that produce insoluble, non-combustible inorganic substances when mixed, and the process is carried out within the wood structure. A method for producing modified wood in which the above-mentioned inorganic substances are generated and fixed in the wood, wherein both of the above-mentioned treatment solutions are impregnated alternately by immersion impregnation a total of three or more times, and the first impregnation is carried out by vacuum impregnation. A method for producing modified wood, characterized in that the final impregnation is carried out with an anion-containing treatment solution having a higher concentration than the previously used anion-containing treatment solution. 2. The method for producing modified wood according to claim 1, wherein the first impregnation is with an anion-containing treatment liquid. 3 At least one of the cation-containing treatment liquids that produce insoluble, nonflammable inorganic substances when mixed.
A solution containing at least one species selected from the group consisting of alkali metal, alkaline earth metal, zinc, and aluminum cations, and at least one of the anion-containing treatment liquids, Claim 1 or 2 is a solution containing at least one anion selected from the group consisting of BO ₃ , PO ₄ , CO ₃ , SO ₄ and OH anions.
Method for producing modified wood as described in Section 1.