JPH0468122B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention particularly relates to a method for producing modified wood having excellent dimensional stability and weather resistance, which is industrially very advantageous. [Conventional technology] Wood is light, strong, and easy to process, so
Since ancient times, it has been used as building materials and furniture materials,
Although it is used for a wide range of other purposes, it has the disadvantage of being susceptible to dimensional changes due to increase or decrease of bound water in the wood. In addition, wood used for outdoor purposes such as exterior wall materials, eaves, and rain shutters is susceptible to deterioration due to ultraviolet rays in sunlight, moisture, oxygen, etc., and has problems in weather resistance. As a means to improve the dimensional stability and weather resistance of the wood, chemical substances are injected into the wood and subjected to a heating reaction.
Methods of modifying wood are being used. However, such heat treatment methods mainly apply heat from the outside of the object to be heated, first heating the surface and then heating the inside by heat conduction. Therefore, when heat treating large pieces of wood such as planks or pillars, even if the surface of the wood can be treated, it takes a long time to process the inside of the wood as much as possible, and during that time the surface is heated. However, there were problems with discoloration and deterioration. Further, in this case, since the chemical treatment is performed from the surface, there is a problem that it becomes difficult to remove the unreacted solution inside the wood during the process of collecting the unreacted solution by suction and vacuum. [Problems to be solved by the invention] The present invention chemically treats large pieces of wood, such as planks and pillars, to the inside as much as possible, so that the surface does not discolor, deteriorate, or crack, and has particularly excellent dimensional stability and weather resistance. The object of the present invention is to provide a method for producing modified wood that is industrially very advantageous. [Means for Solving the Problems] In view of the above-mentioned circumstances, the inventors of the present invention have conducted repeated research with the aim of finding an industrially advantageous method of obtaining modified wood with excellent performance. Impregnating the wood with a reaction solution consisting of a basic acid anhydride and an epoxy compound, then separating the wood impregnated with the reaction solution and the excess reaction solution that was not impregnated into the wood during the impregnation process,
Afterwards, the wood impregnated with the reaction solution is treated with high frequency.
By heating the wood to a temperature of 40 to 160°C and alternately adding a polybasic acid anhydride and an epoxy compound to the hydroxyl groups of the wood components present in the wood, chemical modification is effectively carried out from within the wood. They discovered that modified wood with excellent dimensional stability and weather resistance can be obtained industrially advantageously. In addition, by heating the wood impregnated with the reaction solution using high frequency and applying a vacuum while or after chemically modifying the wood, the unreacted solution is heated from the inside, efficiently vaporized, and recovered. By allowing oligomers of polybasic acid anhydrides and epoxy compounds, which are produced as side reaction products during the above-mentioned heating, to be present in the treated wood, it is possible to produce modified wood that has even better effects, especially in terms of dimensional stability, and is more economical. It was discovered that this can be advantageously obtained. That is, in the present invention, when the wood is impregnated with the reaction solution prior to chemical modification, the excess reaction solution that is not impregnated is separated, which improves the long-term stability of the separated and recovered reaction solution. It has the characteristic of allowing continuous or cyclical use of the reaction solution.Also, by using high frequency, it is possible to treat large pieces of wood such as planks and columns as deep as possible, with good thermal efficiency and a reaction solution. Modified wood that takes less time, and because the temperature at the center of the wood is somewhat higher than the surface layer, unreacted solution can be easily recovered by suction and vacuum with less damage such as cracks. This provides a manufacturing method suitable for industrial production. The wood used in the present invention is one that retains the tissue structure of wood. Various shapes are used, such as columnar, plate-like, or block-like, and are particularly suitable for large pieces of wood such as planks and columns. There are also no particular restrictions on tree species. In addition, there are no particular limitations on the polybasic acid anhydride, but specific examples include phthalic anhydride, maleic anhydride, succinic anhydride, tetrahydrophthalic anhydride,
Examples include hexahydrophthalic anhydride, itaconic anhydride, hectic anhydride, and pyromellitic anhydride. Particularly preferred are phthalic anhydride, maleic anhydride, succinic anhydride, etc., which are industrially advantageous and inexpensive, and among them, phthalic anhydride is particularly preferred because it has a large wood-modifying effect. The epoxy compounds used in the present invention are not particularly limited, but include epichlorohydrin, methyl glycidyl ether, ethyl glycidyl ether, allyl glycidyl ether, glycidyl methacrylate, phenyl glycidyl ether, styrene oxide, olefin oxide, butyl glycidyl ether, Examples include cresyl glycidyl ether, bisphenol A glycidyl ether, and glycerin diglycidyl ether. Particularly preferred are epichlorohydrin, methyl glycidyl ether, ethyl glycidyl ether, allyl glycidyl ether, glycidyl methacrylate, and styrene oxide, which are industrially produced in large quantities and have relatively small molecular weights and low boiling points. Among them, epichlorohydrin is used for wood modification. It is highly effective and preferred. Next, the manufacturing method of the present invention will be explained step by step. First, wood in the form of columns, plates, or blocks is preferably used with a wood moisture content of 15% or less in order to facilitate chemical modification and in relation to the chemicals used. On the other hand, a mixed solution of a polybasic acid anhydride and an epoxy compound is used as the reaction solution. The mixing ratio is preferably adjusted so that the molar ratio of the polybasic acid anhydride to the epoxy compound is 1:1 to 30. The reason why such an epoxy compound is used in excess compared to the polybasic acid anhydride is that the epoxy compound acts as a solvent for the polybasic acid anhydride, and also that the esterified wood side that is generated in the intermediate stage of chemical treatment is This is because it has the effect of increasing the degree of addition of the epoxy compound to the carboxyl group of the chain and lowering the acid value of the modified wood. In addition, the mixed solution is generally
Although it can be prepared without a solvent, it may not be possible to dissolve it depending on the type of polybasic acid anhydride. In that case, it is preferable to prepare using a solvent such as dimethylformamide or dimethyl sulfoxide. In addition, the ring-opening esterification reaction between the hydroxyl group in wood and the polybasic acid anhydride, and the addition esterification reaction between the side chain carboxyl group and the epoxy compound generated by this ring-opening esterification reaction are both non-existent. The reaction proceeds well under a catalyst, but in order to accelerate the reaction, an acidic catalyst such as sulfuric acid, perchloric acid, para-toluenesulfonic acid, or sodium carbonate, etc.
Basic catalysts such as dimethylbenzylamine and pyridine may also be used. In order to impregnate wood with the reaction solution prepared as described above, for example, the wood is immersed in the reaction solution, or the reaction solution is applied to the wood under reduced pressure, under increased pressure, or under reduced pressure. A method such as injection can be used. Next, the reaction solution-impregnated wood obtained by the above method and the excess reaction solution that was not impregnated into the wood are separated, and then only the reaction solution-impregnated wood is placed in a high-frequency heating device, electrode plates are placed on the top and bottom, and a frequency 5
It is heated by applying high frequency waves at ~27MHz.
In this heating method, the reaction solution impregnated into the wood itself generates heat, so the wood is heated from the inside and can be uniformly modified, and the heat efficiency is very high, so the reaction time can be shortened. Heating should be done at 40-160°C. This is because if the temperature is less than 40°C, the above reaction will hardly proceed, and if it exceeds 160°C, disadvantages such as discoloration and deterioration of the wood will occur. The heating time varies depending on the type of polybasic acid anhydride or epoxy compound, the reaction temperature, and the shape and dimensions of the wood, but it can be considerably shorter than the external heating method. After the wood impregnated with the reaction solution is heated and chemically modified, the inside of the reaction vessel is vacuumed and depressurized, for example, with a degree of vacuum higher than 50 mmHg to lower the boiling point of the unreacted solution in the treated wood and vaporize it. The unreacted solution is collected by cooling and liquefying it outside. In the high-frequency heating method, the temperature of the central part of the wood is slightly higher than that of the surface layer, so the unreacted solution can be efficiently recovered by suction and vacuum. Also, there is less damage such as cracking of the wood. After suctioning for a predetermined period of time, the modified wood taken out from the reaction vessel becomes a product as it is, and there is no need to wash or dry it again. In the modified wood obtained in this way,
Its acid value is a small value. This is because the molar concentration of the epoxy compound is higher than that of the polybasic acid anhydride present in the reaction solution, so that most of the side chain carboxyl groups in the esterified wood obtained at the intermediate stage of this chemical treatment are simultaneously This indicates that an addition esterification reaction occurred with the epoxy group in the compound. In addition, in the infrared absorption spectrum of the modified wood, characteristic absorptions of adducts of polybasic acid anhydrides and epoxy compounds were clearly seen, which also indicates that ring-opening esterification and addition esterification reactions occurred. It shows. As mentioned above, the purpose of adding an epoxy compound to a carboxyl group is to add a highly hydrophobic epoxy compound residue to a hydrophilic carboxyl group, thereby reducing its hydrophilicity. [Effects of the Invention] As described above, in the production method of the present invention, when impregnating the wood with the reaction solution prior to chemical modification, in order to separate the excess reaction solution that was not impregnated,
The stability of the reaction solution is good, making it possible to reuse or circulate it, and because the impregnated wood is chemically modified using high frequency, it is possible to treat the inside more uniformly than with conventional external heating methods. , has good thermal efficiency and can shorten reaction time. Furthermore, since the temperature of the central part of the wood is somewhat higher than that of the surface layer, it is easy to recover unreacted solution by suction and vacuum, and there is little damage such as cracking, making this a very advantageous method industrially. On the other hand, the modified wood obtained by the manufacturing method of the present invention has particularly excellent dimensional stability, has a lower swelling rate due to moisture absorption than untreated wood, and has a very high anti-swelling (anti-shrinkage) rate (ASE). It has excellent long-term dimensional stability. The reason for its excellent dimensional stability is that it reduces the number of hydroxyl groups by esterifying and blocking the hydroxyl groups in the wood, which have moisture adsorption ability, and that the swelling of the wood is caused by the structure of the cell wall. This is due to the effect that when the bulky substituents of polybasic acid anhydrides and epoxy compounds enter the water-permeable portion of the wood, the space for adsorbed water to enter is reduced. Furthermore, in terms of weather resistance, the modified wood of the present invention is superior to untreated wood, with very little discoloration and deterioration. The reason for this excellent weather resistance is the same as mentioned above. In the modified wood obtained by the manufacturing method of the present invention, without impairing the excellent characteristics of wood,
Suppresses dimensional changes due to moisture, which is a drawback of wood,
It has become possible to suppress deterioration caused by ultraviolet rays, moisture, oxygen, etc. in sunlight. Further, as a derivative effect, it can be expected to prevent or suppress wood decay and termite damage caused by various wood-decaying fungi and termites. As described above, the modified wood having excellent properties obtained by the production method of the present invention is suitable for construction materials, furniture materials, and many other fields, such as pillars, beams, foundations, and base materials. , floor, soffit,
It is used for shutters, exterior wall materials, desks, bookshelves, etc. [Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but it goes without saying that the present invention is not limited to the Examples. Example 1 Dried Japanese cypress wood (hereinafter referred to as dried wood) measuring 3 cm in the tangential direction x 3 cm in the radial direction x 12 cm in the fiber direction was treated with 24.1 g of phthalic anhydride and epichlorohydrin.
Immersed in a reaction solution consisting of 225.8 g (molar ratio of phthalic anhydride and epichlorohydrin 1:15),
Suction was carried out under reduced pressure (25 mmHg) for 1 hour, and then injected under increased pressure (12.5 Kg/cm ² ) for 30 minutes to impregnate the wood with the reaction solution. Next, this impregnated wood was taken out of the reaction solution, placed in a high-frequency reactor, with electrode plates placed above and below, and high-frequency waves were applied at a frequency of 6.7 MHz and an output of 3 Kw. Internal temperature 80℃, 3
After heating at 110℃ for 3 hours,
The unreacted solution was removed by suctioning and reducing the pressure at 50 mmHg while heating for a period of time to obtain modified wood. The weight increase rate of phthalic anhydride and epichlorohydrin in this modified wood was 33.3% by weight based on the wood. Example 2 The injection conditions of Example 1 were changed to 1 under reduced pressure (20 mmHg).
time, and further for 1 hour under pressure (6.5Kg/cm ² ),
In addition, modified wood was obtained in the same manner as in Example 1 except that the heating conditions were changed to an internal temperature of 110° C. for 2 hours. The weight increase rate of phthalic anhydride and epichlorohydrin in this modified wood is based on the wood.
It was 33.1% by weight. Example 3 Dry wood was immersed in a reaction solution consisting of 18.5 g of phthalic anhydride and 231.1 g of epichlorohydrin (molar ratio of phthalic anhydride and epichlorohydrin 1:20), and suction was applied under reduced pressure (20 mmHg) for 10 minutes. The mixture was further injected for 20 minutes under pressure (20 kg/cm ² ) to impregnate the wood with the reaction solution. Next, this impregnated wood was taken out of the reaction solution, placed in a high-frequency reactor, with electrode plates placed above and below, and high-frequency waves were applied at a frequency of 6.7 MHz and an output of 3 Kw. After heating at an internal temperature of 110° C. for 1 hour, suction and vacuum were applied at 50 mmHg while further heating at 110° C. for 6 hours to remove unreacted solution to obtain modified wood. The weight increase rate of phthalic anhydride and epichlorohydrin in this modified wood is 34.0% based on the wood.
It was in weight%. Example 4 Dry wood was immersed in a reaction solution consisting of 13.5 g of maleic anhydride and 235.7 g of allyl glycidyl ether (mole ratio of maleic anhydride and allyl glycidyl ether 1:15) and heated under reduced pressure (20 mmHg).
Suction was carried out for 1 hour ^at
The mixture was injected for 1 hour to impregnate the wood with the reaction solution. Next, this impregnated wood was taken out of the reaction solution, placed in a high-frequency reactor, with electrode plates placed above and below, and high-frequency waves were applied at a frequency of 6.7 MHz and an output of 3 Kw. After heating at an internal temperature of 120°C for 30 minutes, a 50mm
The unreacted solution was removed by vacuuming with Hg to obtain modified wood. The weight increase rate of maleic anhydride and allylglucidyl ether in this modified wood was 23.7% by weight based on the wood. Comparative Example 1 Dry wood was immersed in a reaction solution consisting of 24.1 g of phthalic anhydride and 225.8 g of epichlorohydrin (molar ratio of phthalic anhydride and epichlorohydrin 1:15), and suction was applied under reduced pressure (20 mmHg) for 1 hour.
The mixture was further injected under pressure (6.5 kg/cm ² ) for 1 hour to impregnate the wood with the reaction solution. Next, this impregnated wood was taken out of the reaction solution, placed in a reaction container, and heated using an external heating method at 110°C for 3 hours, and then further heated at 110°C for 6 hours while vacuuming at 20 mmHg. I went. Thereafter, it was thoroughly dried using air drying and a hot air dryer at 105°C to obtain modified wood. The weight increase rate of phthalic anhydride and epichlorohydrin in this modified wood was 35.3% by weight based on the wood. Comparative Example 2 Untreated dried wood was used as a comparative example. (Physical property test of modified wood) The modified wood obtained in Examples 1 to 4, the wood modified by the external heating method of Comparative Example 1, and the untreated wood of Comparative Example 2 were subjected to a physical property test. The weight increase rate was expressed as the total amount of the polybasic acid anhydride and the epoxy compound in % by weight based on the wood. The moisture absorption test was conducted as follows. That is, after measuring the weight and dimensions of a completely dry specimen in a hot air dryer at 105°C, it was placed in a desiccator at 23°C (75% RH) containing a saturated aqueous solution of NaCl to absorb moisture until a constant weight was reached. The moisture absorption and swelling rates (tangential and radial directions) of the pieces were determined. The dry water repeated test was conducted as follows. That is,
After drying completely in a hot air dryer at 105°C and measuring the dimensions of the test piece, it was immersed in distilled water, reduced pressure (20 mmHg) for 30 minutes, and left for 22 hours. After that, these were taken out and the dimensions of the water-absorbed test pieces were measured.
The anti-swelling rate was determined. Next, these water-absorbed test pieces were dried at 40°C for 4 hours and then at 105°C for 20 hours, and the dimensions of the test pieces were measured to determine the anti-shrinkage ratio. Note that the anti-swelling (anti-shrinkage) rate (ASE) is defined by the following formula. ASE = Vc - Vt / Vc x 100 (%) where Vc is the volumetric swelling (shrinkage) of untreated wood.
The rate, also Vt, represents the volumetric swelling (contraction) rate of the treated wood.

[Table] As is clear from the results in Table 1, Examples 1 to 4
The modified wood obtained by the production method of the present invention has less discoloration than the externally heat-treated wood of Comparative Example 1, and has better dimensional stability than the untreated wood of Comparative Example 1 and Comparative Example 2. It was clear that the effects of the present invention were recognized. Example 5 Dry wood measuring 10 cm in the tangential direction x 10 cm in the radial direction x 20 cm in the fiber direction was placed in a reaction solution consisting of 342.8 g of phthalic anhydride and 4282.5 g of epichloropidolic acid (molar ratio of phthalic anhydride and epichlorohydrin 1:20). The wood was soaked, suctioned under reduced pressure (20 mmHg) for 10 minutes, and then injected under increased pressure (20 Kg/cm ² ) for 20 minutes to impregnate the wood with the reaction solution. Next, this impregnated wood is taken out of the reaction solution and placed in a high frequency reactor with electrode plates sandwiched between the top and bottom.
A high frequency was applied at 6.7MHz and an output of 3Kw. After heating at an internal temperature of 110°C for 1 hour, suction and vacuum were applied at 50 mmHg while heating at 110°C for 15 hours to remove unreacted solution to obtain modified wood.
The weight increase rate of phthalic anhydride and epichlorohydrin in this modified wood is 32.1% by weight based on the wood.
It was hot. Comparative Example 3 Dry wood measuring 10 cm in the tangential direction x 10 cm in the radial direction x 20 cm in the fiber direction was immersed in a reaction solution consisting of 342.8 g of phthalic anhydride and 4282.5 g of epichlorohydrin (molar ratio of phthalic anhydride and epichlorohydrin 1:20), and the mixture was immersed under reduced pressure. Suction was performed for 10 minutes under pressure (20 mmHg), and then injected for 20 minutes under pressure (20 Kg/cm ² ).
The reaction solution was impregnated into the wood. Next, this impregnated wood was taken out of the reaction solution, placed in a reaction container, heated at 110°C for 1 hour using an external heating method, and then vacuumed at 50 mmHg while heating at 110°C for 20 hours. Ivy. Thereafter, it was thoroughly dried using air drying and a hot air dryer at 105°C to obtain modified wood. The weight increase rate of phthalic anhydride and epichlorohydrin in this modified wood was 49.7% by weight based on the wood. (Physical property test of modified wood) The results of the physical property test of the modified wood obtained in Example 5 and the wood treated by external heating of Comparative Example 3 are shown in Table 2.

[Table] As is clear from the results in Table 2, the modified wood obtained by the production method of the present invention in Example 5 had a low residual acid value on the surface and inside, the treatment was uniform, and oligomers were present. However, almost no unreacted solution remained. On the other hand, the wood treated by external heating in Comparative Example 3 had a high internal residual acid value, and a considerable weight loss was observed due to acetone extraction and cleaning.
This is thought to be due to the oligomer and a considerable amount of unreacted solution remaining inside the treated wood. In this way, the external heating method treats the wood from the surface, making it difficult to remove the unreacted solution inside, whereas the high-frequency heating method treats the wood uniformly from the inside, making it possible to remove the unreacted solution efficiently. It is clear that the effects of the present invention can be observed without any discoloration or cracking.

Claims (1)

[Claims] 1. Impregnating wood with a reaction solution consisting of a polybasic acid anhydride and an epoxy compound, and then separating the wood impregnated with the reaction solution and the excess reaction solution that was not impregnated into the wood during the impregnation process, Thereafter, the wood impregnated with the reaction solution is heated to a temperature of 40 to 160°C using high frequency to alternately add the polybasic acid anhydride and the epoxy compound to the hydroxyl groups of the wood components present in the wood. A method for producing modified wood. 2. Impregnating wood with a reaction solution consisting of a polybasic acid anhydride and an epoxy compound, then separating the wood impregnated with the reaction solution and the excess reaction solution that was not impregnated into the wood during the impregnation process, and then impregnating the wood with the reaction solution. The wood is heated to a temperature of 40-160℃ using high frequency,
While chemically modifying or after chemically modifying, the unreacted solution is vaporized and recovered by suctioning and reducing the pressure, and the oligomer of polybasic acid anhydride and epoxy compound produced as a side reaction product during the above heating is recovered. A method for producing modified wood, characterized in that it is present in the treated wood.