JPH0520243B2 - - 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 of imparting dimensional stability, 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 fungi. 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. The narrowest part of the passage through which the treatment liquid permeates into the wood is the pit membrane, and the pore diameter here is approximately 0.1 μm, whereas the diameter of the pores in the pit membrane is approximately 0.1 μm. The particle size of some insoluble, nonflammable minerals is typically 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, but in any case,
This took anywhere from several hours to several tens of hours. This is not desirable in terms of improving overall processing efficiency. Secondly, in the impregnation process, there was a problem in that unless a sufficient soaking time was allowed, it was not possible to impregnate a desired amount of insoluble and nonflammable inorganic material. For this purpose, it usually takes several tens of hours for each bath, and this is one of the factors that significantly reduces processing efficiency, leaving room for improvement. Third, conventionally, it has been difficult to obtain a high impregnation rate in a short time with aqueous solutions of water-soluble inorganic substances that have low solubility in water, and even if the ingredients are effective, they may not be fully utilized. Ta. In other words, when impregnating a component with low solubility, the processing time becomes long and problems arise in terms of efficiency, or the solubility is increased by heating before impregnation.
This was because it required a lot of effort, and even if it was dissolved by heating and impregnated into the wood, there was a problem that after impregnation, it would cool and precipitate within the wood. [Objective of the Invention] In view of the above circumstances, the present invention efficiently impregnates wood with a large amount of insoluble, non-combustible inorganic substances even if they are components with low solubility, and provides flame retardancy and other antiseptic properties.・The aim is to provide a method for producing modified wood that has excellent insect repellency, mechanical strength, dimensional stability, etc. [Disclosure of the Invention] In order to achieve the above object, the present invention impregnates the raw material wood to be modified with two kinds of water-soluble inorganic aqueous solutions that produce insoluble incombustible inorganic substances when mixed. A method for producing modified wood that generates and fixes the above-mentioned inorganic substances in the wood structure, the modification characterized by first impregnating under reduced pressure an aqueous solution of a water-soluble inorganic substance having a solubility of 30 or more at 25°C. The gist is the manufacturing method of wood. 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 cation portion of the above-mentioned inorganic compound (salt), 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 ₄ , SiO ₃ anion, or the like.
For BO ₃ and PO ₄ anions, the flame retardant mechanism is
The effect of (b), the effect of (d) for CO ₃ anions, and the effects of (c) and (d) for F, Cl, and Br anions are expected, so they are more suitable. 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 are arbitrarily selected and the water-soluble inorganic substances containing them are dissolved in water to prepare the cation-containing treatment liquid and the anaone-containing treatment liquid. Note that 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 liquid and/or an anion-containing treatment liquid containing other anions, and may be prepared to produce apatite etc. in the wood. It's good. Among the above cation- or anion-containing treatment solutions, the solute of the aqueous solution to be impregnated first, that is, the water-soluble inorganic substance containing the cation or anion moiety of the above-mentioned insoluble nonflammable inorganic substance, has a solubility of 30 or more at 25°C. One of the features of this invention is that it can be used. i.e. 25
An anhydrous compound that can be contained in an amount of 30 g or more in 100 g of a saturated aqueous solution at ℃ is used. Among such compounds, examples of compounds constituting the cation portion of an insoluble nonflammable inorganic substance, with their solubility listed in the box, include calcium chloride (45.3), maghesium chloride (35.5), and sodium bromide (48.61). ,
Potassium bromide (40.4) etc. constitute the anion moiety, including, but not limited to, potassium carbonate (52.85), diammonium hydrogen phosphate (41.0), ammonium sulfate (43.3), etc. . Conventionally, it has been difficult to impregnate a large amount efficiently. Even if it is an inorganic substance with low solubility, if it is used in combination with a component with high solubility (30 or more) as described above, and if the component with higher solubility is impregnated first, it can easily absorb a large amount of insoluble inorganic material. It becomes possible to generate nonflammable inorganic substances.
In other words, if a large amount of ions are impregnated into the wood in the first bath, even if the solubility of the solute in the aqueous solution in the second bath, that is, the solution concentration is low,
This is because the second bath ions always diffuse toward the inside of the wood, and insoluble and nonflammable inorganic substances are generated one after another within the wood. in this way,
It is necessary to impregnate the wood with a certain amount of ions in the first bath, but for this purpose, it is necessary to use a water-soluble inorganic substance with a solubility of at least 30 or higher, and to impregnate it by vacuum impregnation as described below. Prior to impregnation with the treatment liquid, raw material wood was conventionally subjected to a water saturation treatment, but in the manufacturing method according to the present invention, in order to impregnate the treatment liquid in the first bath by a reduced pressure method, Processing can be omitted. According to this vacuum impregnation method, the wood does not need to be saturated with water; rather, it is preferable that the wood be in its 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 low-pressure area, so it is better to have voids in the wood that can create a low pressure. In other words, it is better to keep it dry to some extent. 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 impregnated with the first treatment liquid under reduced pressure, and then impregnated with the other liquid. Here, it goes without saying that the solubility of the solute contained in the other liquid is not particularly limited. Note that the impregnation is performed by immersion, and the immersion time in each bath is not particularly limited. After the above impregnation treatment is completed, the wood is dried to obtain modified wood. In addition, in order to improve the water resistance of the impregnated wood, the wood may be subjected to leaching treatment as a post-treatment to remove soluble components, or may be washed with water or the like. Here, the soluble component is
Unreacted ions left in the wood and soluble inorganic substances as by-products absorb a large amount of water and may exhibit deliquescent properties depending on the type of wood. If too much remains in the wood, the water absorption and hygroscopicity of the wood will become too high. As a result, the resulting modified wood will have a sticky feel, and under high humidity conditions the wood surface will appear wet, so leaching treatment is performed in addition to impregnation treatment to improve the water resistance of the wood. It can also improve weather resistance. 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. However, on the other hand, some of these soluble components are nonflammable and can contribute to improving the flame retardance, mechanical strength, dimensional stability, etc. of wood, so they may be left in place if necessary. One solution is to do so. The method for producing modified wood according to the present invention first impregnates the wood with an aqueous solution in which the solute has a solubility in water of 30 or more, so it has the following advantages. That is: Even if the wood is then impregnated with an aqueous solution of an inorganic substance having low solubility, a large amount of the inorganic substance can be efficiently impregnated into the wood in a short period of time. On the other hand, since the vacuum method is adopted for the initial impregnation, the following advantages are also obtained. In other words; the conventional water saturation 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 shorter than conventional methods. Therefore, processing efficiency is 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 diammonium hydrogen phosphate [(NH ₄ ) ₂ HPO ₄ , solubility 41.0] 3.5 per 1 water was added. Mol and orthoboric acid [H ₃ BO ₃ ]
Anion-containing treatment liquid in which 4.0 mol was dissolved (first
Impregnation was carried out under reduced pressure. Next, this veneer was mixed with barium chloride [BaCl ₂ ,
Solubility 27.1] 2.0 mol and orthoboric acid 2.0 mol were dissolved in the cation-containing treatment solution (second bath).
The wood was soaked for a period of time to form insoluble, non-combustible minerals within the wood. The veneer after this immersion treatment was washed with water and dried to obtain modified wood. Examples 2 to 4 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, the veneer after the saturated water treatment was subjected to normal pressure immersion impregnation in the same way as in the second bath. Each modified wood was manufactured by treating the veneer under the same conditions. Performance of Modified Wood The modified wood obtained above was examined for total impregnation rate of inorganic substances and flame retardancy (fire retardancy). 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.
According to JIS standard A1321, the flame retardant grade is ◎, the flame retardant grade is △, and the intermediate performance is ○. The above results are shown in Table 1.

〔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 nonflammable inorganic substance inside the wood, first, an aqueous solution of a water-soluble inorganic substance having a solubility of 30 or more at 25°C is impregnated under reduced pressure. Therefore, even if a water-soluble inorganic substance with low solubility is used as an aqueous solution for later impregnation, a large amount of insoluble, non-combustible inorganic substance will be generated within the wood in a short period of time, resulting in excellent flame retardance etc. This makes it possible to efficiently produce modified wood with high performance.

Claims (1)

[Scope of Claims] 1. Raw material wood to be modified is individually impregnated with two types of aqueous solutions of water-soluble inorganic substances that produce insoluble non-flammable inorganic substances when mixed to produce the inorganic substances within the wood structure. 1. A method for producing modified wood for fixation, the method comprising first impregnating under reduced pressure an aqueous solution of a water-soluble inorganic substance having a solubility of 30 or more at 25°C. 2. One of the two types of water-soluble inorganic aqueous solutions that produce an insoluble nonflammable inorganic substance by mixing at least one of the cations selected from the group consisting of alkali metals, alkaline earth metals, zinc, and aluminum cations. and the other 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. A method for producing modified wood according to item 1.