JPH04164602A - Manufacture of modified wood - Google Patents

Abstract

PURPOSE:To manufacture the modified wood excellent in dimensional stability and water resistance, etc., by a simple operation by a method in which wooden construction is impregnated with an organic compound containing at least three carboxyl groups in a molecule or an aqueous solution of the anhydride or the solution of an organic solvent corresponding thereto. CONSTITUTION:In the manufacture of modified wood, the organic compound containing at least three carboxyl group in a molecule or the organic compound containing anhydride groups of the number corresponding thereto is used. As the organic compound containing at least three carboxyl group in a molecule, e.g. 1,2,3-propane tricarboxylic acid and 1,2,3,4-butane-tetracarboxylic acid, etc., are used. The wood is dipped in the solution obtained by dissolving said organic compound, or the wood is coated with said solution, whereby the wooden construction is impregnated with the solution. In order to effect a crosslinking reaction between the carboxyl group of the organic compound with which the wood is impregnated and the hydroxyl in the wooden construction, heat- treatment is carried out, whereby the modified wood excellent in water resistance and dimension stability may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing modified wood. More specifically, the present invention relates to a method for producing wood with excellent dimensional stability, water resistance, etc. by reacting wood with an organic compound having three or more carboxyl groups in the molecule.

(Prior Art) Wood is a material that has been widely used in the fields of building materials, furniture, and the like. However, since the main component of wood is cellulose, which is extremely hydrophilic, it is easily affected by moisture in the air (when the humidity is high, it absorbs moisture and expands in volume, and conversely, when the humidity is low, it contracts). This phenomenon occurs, and as a result, the wood has the disadvantage of warping, warping, cracking, etc.In addition, because it is not sufficiently water resistant, decomposing bacteria activity occurs within the wood in water or in a high temperature atmosphere, causing the wood to deteriorate. The disadvantage is that it rots.

Improving the various properties of wood is very important for the effective use of wood, and many attempts have been made to impart dimensional stability and water resistance to wood.

For example, there is a method of imparting hydrophobicity and bulk to wood by esterifying the hydroxyl groups present in the molecules of wood components such as cellulose, hemicellulose, and lignin using fatty acids. However, the reactivity between the carboxyl groups of fatty acids and the hydroxyl groups in wood tissue is low, and esterification through direct dehydration reaction hardly occurs, and the esterification reaction does not proceed sufficiently even at high temperatures.

Therefore, fatty acid halides or fatty acid anhydrides have been used as highly reactive esterification reagents.

However, when acid halides are used, the wood itself deteriorates due to large amounts of hydrogen halide produced during the reaction, so amines or basic substances are usually added to neutralize the hydrogen halide produced. The process of removing by-product salt is extremely difficult. On the other hand, there is a method of reacting fatty acid anhydrides, but since the same amount of fatty acids as the reacted fatty acids are produced as by-products, it is necessary to remove the by-product fatty acids, and the operation is very complicated.

In addition, a method of reacting an alkyl ketene dimer with wood has been proposed as one of the esterified wood products (Mokugyo, Vol. 44. No., IO, P476-480, 1989, 1). This method produces by-products. Although this is an excellent method in that it does not react with hydroxyl groups, it has a very low reactivity with hydroxyl groups in the wood structure compared to the acid halides mentioned above, so a large amount of unreacted substances remain, making it necessary to remove them and making the operation complicated. It is.

In other words, as mentioned above, all methods of modifying wood by introducing hydrophobic groups are complicated to operate, and adding hydrophobicity may significantly impair the inherent properties of wood such as adhesiveness and paintability. However, it has not been put into practical use.

Another modification method is to inject polyethylene glycol into wood, but since polyethylene glycol is a hydrophilic polymer, there are problems with painting workability, and there are also problems with the rot resistance of the resulting modified wood. Not satisfied.

In addition, a method has been proposed in which the hydroxyl groups in the wood structure are reacted with formaldehyde in the presence of an acidic catalyst, and the two hydroxyl groups are crosslinked with acetal1, thereby imparting dimensional stability and water resistance to the wood. Although this method is excellent in that it does not impair the inherent properties of wood, it is harmful and dangerous because it uses formaldehyde in gaseous form.
Furthermore, there is the disadvantage that the reactor is large-scale.
It has not yet been put into practical use.

(Problems to be Solved by the Invention) As described above, various methods are known for improving the hygroscopicity and water resistance of wood and imparting dimensional stability, but none of them are economically and technically satisfactory. However, the current situation is that it has not yet been put into practical use. Therefore, an object of the present invention is to provide a method for producing modified wood having various properties such as dimensional stability and water resistance through simple operations.

(Means for Solving the Problems) The present inventors intended to solve the problems of the above-mentioned 2 prior art techniques by crosslinking the hydroxyl groups in the wood structure. Therefore,
As a result of intensive studies focusing on the fact that the hydroxyl group easily undergoes an esterification reaction with acid anhydride groups, we have developed a book on organic compounds having three or more carboxyl groups in the molecule or the corresponding acid anhydride in 6 liquids or When the organic bath medium is impregnated into the wood structure and then heat-treated, at least two acid anhydride groups derived from the organic compound are formed, crosslinking the hydroxyl groups in the wood structure, resulting in dimensional stability. The present inventors have discovered that modified wood with extremely good properties in terms of water-based properties and water-based properties can be obtained, leading to the completion of the present invention.

That is, the present invention impregnates wood tissue with an aqueous solution or an organic hot medium solution of an organic compound having three or more carboxyl groups in the molecule or a corresponding acid anhydride,
The present invention relates to a method for producing modified wood, which is characterized in that it is then subjected to heat treatment.

In the present invention, it is essential to use an organic compound having three or more carboxyl groups in one molecule or an organic compound having a corresponding number of acid anhydride groups. The organic compound crosslinks hydroxyl groups in the wood structure, giving the wood water resistance and
Used as a crosslinking agent to impart dimensional stability.

The reason why it is essential that the organic compound has three or more carboxyl groups or a corresponding number of acid anhydride groups in the molecule is as follows.

That is, since the free carboxyl group in -V hardly undergoes an esterification reaction with the hydroxyl group in the wood structure, the hydroxyl group cannot be easily crosslinked by simply reacting an organic compound having two carboxyl groups. In other words, an organic compound having two carboxyl groups can easily undergo a half-esterification reaction with the hydroxyl groups in the wood tissue by forming two acid anhydride groups in the molecule through heat treatment, but the half-esterification reaction Since the resulting carboxyl group itself hardly undergoes an esterification reaction with the hydroxyl group as described above, in any case, it is difficult to crosslink with the hydroxyl group with an organic compound having two carboxyl groups.

On the other hand, for example, in the case of an organic compound having three carboxyl groups in the molecule, one acid anhydride group is first formed by heat treatment, and then one acid anhydride group is formed by a half-esterification reaction with the hydroxyl group. One more acid anhydride group is formed by the carboxyl group and the remaining carboxyl group that did not participate in the formation of the acid anhydride group, so essentially two acid anhydride groups are formed in the same molecule. It turns out. Therefore, an organic compound having three or more carboxyl groups in a molecule or an acid anhydride corresponding thereto, has two or more acid anhydride groups formed in substantially the same molecule by heat treatment. acts as an effective crosslinking agent that easily crosslinks the hydroxyl groups in the wood structure.

For the above reasons, organic compounds having three carboxyl groups on IJ in the molecule of the present invention are those that easily form two or more acid anhydride groups or those that already have two or more acid anhydride groups. Applicable to what is being formed. That is, the organic compound preferably has at least two or more sets of horizontal groups in which two arbitrarily selected carboxyl groups are bonded to the same carbon, adjacent carbons, or carbons separated by one carbon. Specifically, for example, ], ]2.3-propanetricarboxylic acid, 1.2.3.4-butanetetracarboxylic acid, tetracarboxylmethane, 1°1.2.2-ethanetetracarboxylic acid, J, 2 Examples include 3-benzenetricarboxylic acid, 1.2.4.5-benzenetetracarboxylic acid, benzenehexacarboxylic acid, citric acid, and acid anhydrides thereof.

The type of wood used in the present invention is not particularly limited, and any type of wood can be used, including coniferous trees such as pine, cedar, and cypress, and broad-leaved trees such as birch, oak, and lauan. Furthermore, these woods can be used not only as square timbers and boards, but also as small pieces or wood powder.

Next, the processing method of the present invention will be explained step by step. first,
The solution is impregnated into the wood tissue by immersing the wood in the antiseptic solution prepared by dissolving the organic compound under normal pressure, reduced pressure, or pressurization, or by applying the solution to the wood with a brush or the like. The number of times these processes are performed is arbitrary, and the processes can be divided into several stages.

Said? The solvent used for the @ solution is not particularly limited as long as it dissolves the organic compound, and may be either water or an organic solvent, but water is preferably used from the viewpoint of solubility of the organic compound. Examples of organic solvents include ethers such as diethyl ether, diisopropyl ether, tetrahydrofuran, and dioxane; esters such as ethyl acetate and butyl acetate; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; methanol, ethanol, and 1-propanol. , 2-propertool, l-butanol, and the like. These solvents can be added in any proportion within the range of solubility of the organic compound, but the concentration is usually about 5 to 40% by weight.

The amount of the organic compound (solid content) impregnated varies depending on the shape, size, treatment method, etc. of the wood, so it is important to know which organic compound to use. The concentration of fllfi is adjusted appropriately. - For boat fishing, the amount is about 01 to 80 parts by weight, preferably 1 to 30 parts by weight, per 100 parts by weight of wood. If it is less than 0.01 part by weight, dimensional stability and water resistance will not be sufficiently improved;
Even if it exceeds 0 parts by weight, no more can be impregnated, and there is no point in using it in excess. Note that the remaining solution that is not injected into the wood can be reused as is, which is economically advantageous.

The treatment time varies significantly depending on the type, shape, size, and pressure of the wood, but in the case of immersion treatment, it is usually 0.1 to 7 hours.
The time is about 2 hours, preferably 1 hour to 30 hours.

If it is less than 0.1 hour, impregnation is insufficient, and if it exceeds 72 hours, it is a waste of time since impregnation can be carried out for any longer than 72 hours.

Moreover, the 7M degree at the time of witnessing is usually about 0°C to 60°C, preferably 15°C to 50°C. If the temperature is below 0°C, the viscosity of the processing liquid increases or it freezes, making processing difficult. Furthermore, even if it is carried out at a temperature that can reach 60°C, the impregnation effect is only about the same as that obtained when it is carried out at a temperature lower than 60°C, which is meaningless.

Through the operations described above, wood can be impregnated with the organic compound. When impregnated by the immersion method, remove the wood from the container and remove any exudate remaining on the surface as necessary. Subsequently, a heat treatment is performed to cause a crosslinking reaction between the carboxyl group of the organic compound impregnated into the wood and the hydroxyl group in the wood structure. This temperature is usually 40℃~300℃
°C, preferably 50 °C to 250 °C. If the temperature exceeds 300 degrees Celsius, the wood deteriorates, which is undesirable. 40℃
If it is less than this, the crosslinking reaction will not proceed sufficiently. Further, the conditions are similar to those described above in the case of coating treatment.

The esterification reaction between the organic compound and wood in the present invention proceeds satisfactorily even in the absence of a catalyst, but in order to further accelerate the esterification reaction, amines such as triethylamine, dimethylbenzylamine, dimethylaniline, pyridine, etc. It is also possible to use catalysts such as phosphoric acid, phosphorous acid, hypophosphorous acid, metaphosphoric acid, polyphosphoric acid, or alkali metal salts or alkaline earth metal salts thereof. These catalysts are preferably present at the same time when the wood is impregnated with the organic compound.

The rate of introduction of the organic compound into wood can be determined from the weight increase rate of the obtained wood before and after treatment.

(Examples) The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 Beech wood dried at 100°C for 2 hours was heated to 1.2°3.4-
It was immersed in a 20% by weight aqueous solution of butanetetracarboxylic acid at room temperature and normal pressure for 12 hours. Next, the surface was wiped with filter paper to remove excess solution, and then heat treated and dried at 200°C for 4 hours.
Modified wood shown in Table 1 was obtained.

Example 2 Beech wood dried at 100°C for 2 hours was heated to 1.2°3.4-
It was immersed in an aqueous solution containing 20% by weight of butanetetracarboxylic acid and 5% by weight of triethylamine at room temperature and normal pressure for 12 hours. Next, the surface was wiped with a filter paper to remove excess liquid, and then heat treated and dried at 180° C. for 4 hours to obtain the modified wood shown in Table 1.

Example 3 Beech wood dried at 100°C for 2 hours was heated to 1.2°3.4-
A methanol extract containing 20% by weight of butanetetracarboxylic acid and 10% by weight of sodium dihydrogen phosphate was heated at room temperature.
It was immersed for 12 hours at normal pressure.

Next, wipe the surface of 1 with filter paper to remove excess solution, and then
The wood was heat-treated and dried at 80° C. for 2 hours to obtain the modified wood shown in Table 1.

Example 4 Modified wood shown in Table 1 was obtained in the same manner as in Example 3, except that sodium dihydrogen phosphate was replaced with sodium dihydrogen hypophosphite.

Example 5 Beech wood dried at 100°C for 2 hours was heated to 1.2°3.4-
12% by weight of butanetetracarboxylic acid and 10% by weight of sodium dihydrogen phosphate at room temperature and normal pressure.
Soaked for an hour. Next, one surface was wiped with a filter paper to remove excess solution, and then heat treated and dried at 180° C. for 2 hours to obtain the modified wood shown in Table 1.

Example 6 Beech wood dried at 100°C for 2 hours was heated to 1.2°3.4-
1 in an aqueous solution containing 50% by weight of butanetetracarboxylic acid and 10% by weight of sodium dihydrogen phosphate at room temperature and normal pressure.
Soaked for 2 hours. Next, one surface was wiped with a filter paper to remove excess solution, and then heat treated and dried at 180° C. for 2 hours to obtain the modified wood shown in Table 1.

Example 7 Beech wood dried at 100°C for 2 hours, ], 2°3.4-
Butanetetracarboxylic acid 20% water by weight? @Liquid at room temperature,
It was immersed for 12 hours at 8 kg/cm2. Next, the surface was wiped with a filter paper to remove excess solution, and then heat treated and dried at 200° C. for 4 hours to obtain the modified wood shown in Table 1.

Example 8 The modified wood shown in Table 1 was prepared in the same manner as in Example 3 except that 1,2,3,4-butanetetracarboxylic acid was replaced with 1,2,3-propanetricarboxylic acid. Obtained.

Example 9 The same procedure as in Example 3 was carried out except that 1.2,3.4-butanetetracarboxylic acid was replaced with 1.2,4.5-benzenetetracarboxylic acid, and the modifications shown in Table 1 were carried out. Obtained quality wood.

Comparative Example 1 The same procedure as in Example 3 was carried out except that 1.2,3,4-butanetetracarboxylic acid in Example 3 was replaced with succinic acid.
The modified wood shown in the table was obtained.

Comparative Example 2 The same procedure as in Example 3 was carried out except that 1.2.3.4-butanetetracarboxylic acid in Example 3 was replaced with phthalic acid.
The modified wood shown in the table was obtained.

The modified wood obtained in these Examples and Comparative Examples was JTS
The moisture absorption amount was measured by the method of No. 22105.

Moisture absorption 1g/crn2) = (W2411-Wo
h) / A1! . 7. Weight when equilibrated at 40°C and 75% humidity and temperature condition (N Ig) W24fi・Weight after 24 hours minus the weight of paraffin is 1g) A: Moisture absorption area fcm21 In addition, a 25°C hot water tank After 7 days immersion in
The formula for AsEl was determined.

Anti-swelling rate 1AsEl = (V,, -Vl) /V.

vo・Volume swelling rate of untreated material V'1: Volumetric swelling rate of treated material These results are shown in Table 1.

[Margins below] Table 1 (Effects of the Invention) According to the present invention, the crosslinking agent used to crosslink hydroxyl groups in the wood tissue is used in a solution state, so that the crosslinking agent can be easily impregnated into the wood. It is safe and has advantages during manufacturing, such as not producing by-products. Furthermore, it is possible to easily provide modified wood that has excellent water resistance and dimensional stability while retaining the properties inherent in wood. Therefore, by using the modified wood obtained by the method of the present invention, peeling and cracking can be effectively prevented when used for wood panels and decorative veneers, and furthermore, it can withstand use outdoors and around water. It is also recommended as a material for musical instruments that are sensitive to fourths, and has various effects such as vine.

Patent applicant: Arakawa Chemical Industry Co., Ltd.

Claims (1)

[Claims] 1. Production of modified wood characterized by impregnating wood tissue with an aqueous solution or an organic solvent solution of an organic compound having three or more carboxyl groups in the molecule or a corresponding acid anhydride, and then heat-treating. Method.