JP2779962B2 - Drying method for wood etc. - Google Patents

Description

[Detailed Description of the Invention] [Industrial application field] The present invention relates to heat-drying of various plant-based processed materials (hereinafter, referred to as "wood and the like") such as logs, processed wood, bamboo and the like so as not to cause cracking. How to process.

"Prior art" Wood prevents mess when using it, processability,
It is common to carry out a drying treatment in order to improve paintability and adhesiveness. This drying method is roughly classified into two types, natural drying and artificial drying. In recent years, there has been a demand for a large amount of drying treatment in a short period of time, uniform drying to a low moisture content that is difficult to obtain by natural drying, etc. Most employ a drying method.

The most important problem in such a wood drying process is to prevent cracking. In particular, in the case of the so-called artificial drying method in which the heat drying treatment is forcibly performed, cracks are likely to occur as the drying conditions are severe. If cracking occurs, the quality will be extremely deteriorated or the commercial value will be lost, and if you take long days carefully so as not to crack, the processing efficiency is too bad, It is not easy as a business.

For this reason, in the wood drying treatment, techniques for shortening the drying time while preventing cracks have been studied in various fields, but a decisive method has not yet been developed.

Therefore, while exploring the causes of "cracks" in wood and the like during heat treatment and studying methods to prevent them, cracks due to drying are a kind of solid destruction,
We thought that acoustic emission should have appeared, and started research on technology to detect "cracking" by observing this AE and to predict "cracking" due to drying. At the same time, we investigated the technical literature on the relationship between AE and the "crack" of wood, and noticed that there was a known technique called "a device for predicting and preventing dry cracking of wood" (Japanese Patent Publication No. 63-7317).

In addition, it has recently been discovered that wood can be converted into a material having the same plasticity as plastic by a simple chemical reaction.

The present inventors have conducted studies with these as hints for the purpose of preventing cracks in the drying treatment of wood or the like, and completed the present invention.

"Technical issues to be solved"
It is roughly considered that there is a movement of water during the heating and drying process and a contraction of the tissue.

First, the following was found regarding cracking of wood and the like due to moisture movement and tissue shrinkage during the drying process.
The water contained in wood usually has free water and bound water, but during drying, only free water is first eliminated and removed from the surface layer, and then the bound water is removed as drying progresses . The former movement of free water is dominated by capillary action, and the latter movement of bound water is by diffusion. In this way the free and bound water of the surface layer of the wood migrates and dries, but the inner layer still has a high moisture content. The dry portion then tries to shrink and the wet portion resists shrinkage. As a result, in the first half of drying, a tensile stress acts on the surface layer and a compressive stress acts on the inner layer. Furthermore, as the drying proceeds, these stresses increase and the shrinkage also spreads inside. However, since the surface layer is constantly subjected to a large tensile stress, permanent deformation occurs without regular shrinkage. Then, as the interior dries, the positive and negative stresses reverse, as the surface layer attempts to shrink normally,
In the latter half, the surface layer receives compressive stress and the inner layer receives tensile stress. For this reason, if the tensile stress exceeds the tensile strength of the wooden part, cracks in the mouth or surface cracks along the surface fibers occur in the first half of drying, and internal cracks occur in the second half of drying. In addition, it is also found that defects such as surface hardening and depression occur with drying, but these are all directly related to the magnitude of the gradient of the water content distribution inside the wood. In heating and drying, it is required that defects such as the above-mentioned various cracks do not occur, and that the drying time is shortened by increasing the gradient of the water content distribution inside the wood as much as possible. It is important to grasp the water content distribution every moment inside the wood, and it is necessary to dry the wood while adjusting the temperature and humidity according to the water content of the wood during drying. However, since the wood structure is complicated and the thermal properties are affected by humidity and moisture content, and also differ depending on the wood species, it is necessary to theoretically grasp the moisture content distribution inside the wood every moment. It is difficult. In addition, the mechanical strength and thickness of the material are also involved in the occurrence of cracks due to drying, so it is necessary to clarify under what conditions defects occur in complex wood structures with large anisotropy. Is extremely difficult.

Therefore, in the conventional drying process, it is the current situation that the user enters the room during drying, visually confirms cracks, and adjusts the atmosphere inside the room. However, this method cannot predict before cracks occur and cannot find cracks that occur inside.

In view of this, the present inventors have proposed a known technique (for example, Japanese Patent Publication No. 63-73) that predicts dry cracking of wood using AE detection technology and controls the temperature and humidity around the wood to prevent cracking.
17). However, the known document only describes that the initial cracks in the drying process are predicted based on the cumulative number of AEs and the AE occurrence rate. That is, even in the case of the drying process, it is a prediction of the initial crack of the drying, and the crack of the latter stage of the drying process is not recalled. In addition, the method of predicting initial cracking is only to know the cumulative number of AEs and the AE occurrence rate immediately before cracking of the wood, and when the AE occurrence rate reaches the limit value, operate the control equipment to relax the drying conditions and prevent cracking. is there.

In this conventional technology, the correlation between the cumulative number of AEs and the AE occurrence rate and cracking is valid to some extent in the early drying cracks, but does not necessarily show a correlation in the middle and late drying stages, depending on the individual situation of the wood to be treated. It was found that the generated AE had drawbacks such as increased noise and erroneous judgment. The inventor observed and analyzed the cracking of the wood and the occurrence of the AE signal, and noticed that the cracking of the wood had a close correlation with the amplitude of the AE signal, and focused on the amplitude of the electrical signal. Then, the effective signal directly linked to the crack is detected and detected, and if even one AE signal has a large amplitude,
Cumulative AE with a large amplitude, considered as a danger signal for cracking
While monitoring the number of events and the AE occurrence rate online, constantly identifying whether the dry state is in the initial, middle or late stage, and comparing it with the preset reference value for each identified processing step It is intended to make a comprehensive judgment to predict cracks in the process. The temperature and humidity are manipulated based on the prediction information obtained in this way, and the atmosphere is controlled so that cracks do not occur in wood and the like.

Although the technique of impregnating wood is widely used, there is no known example of using an impregnant in advance for the purpose of preventing cracking during drying or heat treatment. The inventor
When a specific organic solvent is impregnated into wood or the like from among various impregnating agents and then heat-treated, a chemical reaction takes place inside, and internal plasticization occurs, giving the knowledge that the material is given thermal fluidity. The inventors of the present invention have developed the present invention by thinking that if the knowledge is applied, heat fluidization inside the wood during heat treatment can prevent cracks. That is, the interior of the wood is plasticized by impregnating with a specific organic solvent and performing a hydrothermal chemical reaction. Thus, even if an artificial drying process is performed under severe heat treatment conditions, the material is not broken.

"Means to Solve the Problems" The present invention solves the technical problem of preventing cracks during the drying process as described above by combining the following technical means.

The inventors of the present invention have studied cracks caused by heat drying of wood or the like, and have found that the cracks occur due to moisture movement, tissue shrinkage, and decomposition of cellulose by high heat. Dry cracking of wood is a form of solid destruction. We believe that acoustic emission (AE) should be generated, and if this can be detected and its frequency and signal strength can be known, this information can be used. We thought that cracks could be predicted in advance by processing. As a result of the research, we noticed that cracks in wood have a close correlation with the amplitude of the AE signal and the amplitude, and we focused on the amplitude of the electrical signal and discriminated effective signals directly linked to cracking. Detected. As a result, when one AE signal has a large amplitude, it can be understood as a danger signal for cracking.
In addition, while monitoring the cumulative number of AE events and the AE occurrence rate of the amplitude that are effective for predicting this crack online, while identifying whether the dry state is in the initial, middle or late stages,
Analyzing the meaning of the detected AE signal while comparing it with empirically predetermined reference values at each identified processing stage, predicting and determining cracks in the processing process studied, and based on this prediction information, Is operated to relax and control the atmospheric conditions so that cracks do not occur in the wood and the like. Cracks in wood and the like are caused by moisture transfer due to drying treatment and heat treatment and denaturation of the material due to heat. It has been found that cracking can be sufficiently prevented by adjusting temperature and humidity as operating factors.

Furthermore, before the drying treatment, the organic impregnating agent is impregnated in advance, and when it is put into high-temperature water of 100 ° C or less, the wood part chemically changes to a state of thermoplasticity (thermofluidity) by a hydrothermal chemical reaction. In the heat-drying process, the wood is deformed according to the difference between the tensile stress and the compressive stress between the surface layer and the inner layer caused by heating. ).

Here, the hydrothermal chemical reaction means a chemical reaction using an aqueous solution at a high temperature and a high pressure (supercritical or subcritical aqueous solution). The properties of such supercritical or subcritical aqueous solutions are physically or chemically distinctive from ordinary-temperature water.

In the case of the present invention, when wood or the like is subjected to a hydrothermal chemical reaction with a high-temperature and high-pressure aqueous solution (supercritical or subcritical aqueous solution) in a closed vessel, cleavage of benzyl ether in lignin components constituting the wood, cellulose, Thermoplasticity (thermofluidity) is obtained by cutting the cellulose chain by hydrolysis of the hemicellulose component.
The organic impregnating agent is more easily permeated and impregnated into the fine structure portion of the decomposed wood. Such a phenomenon,
This effect is essentially different from the impregnation effect of a simple organic impregnating agent.

Therefore, these three ideas, namely, first, to prevent dry cracking by converting to chemically modified wood by impregnation with an organic impregnating agent, and second, to detect AE signals and to process wood, etc. Third, preventing cracks by controlling the atmosphere using temperature and humidity as operating factors based on the prediction information. By appropriately combining the above, wood and the like can be dried efficiently and uniform It is intended to process and provide a large amount of dry wood.

Hereinafter, the invention for which a patent is sought will be described in detail.

The first invention for which a patent is sought is, firstly, oxyethers such as polyethylene glycol and methyl cellosolve, polyhydric alcohols, etc. on various plant-processed woods (woods, etc.) such as logs, processed woods and bamboos. , A natural rubber or a synthetic rubber or a combination thereof is impregnated with such an organic impregnating agent to cause a hydrothermal chemical reaction.

The processing target range of the present invention is wood and the like, which includes all kinds of plant-processed materials such as logs, processed wood, and bamboo regardless of the type of plant.

The specific organic impregnating agent to be impregnated is an oxyether such as polyethylene glycol or methyl cellosolve, a polyhydric alcohol such as 1,4-butanediol, a natural rubber or a synthetic rubber, or a combination thereof. I just need. Next, a description will be given of a change in wood quality caused by the impregnation process.

Chemically, wood is 40-50% cellulose, 15-
Consists of 25% hemicellulose, 20-30% lignin and other accessory ingredients. In addition, in the cell wall constituting the wood, a bundle of aggregates of cellulose molecular chains passes through a network existing in a sponge shape, and the components are compounded in such a manner that the gap between the two is filled with hemicellulose.
Furthermore, the bundle of the aggregate of the cellulose molecular chains is regularly arranged to form crystals. This is a linear polymer having a regular configuration and having a large number of hydroxyl groups (-OH), so that regular hydrogen bonds between hydroxyl groups are likely to occur between adjacent molecules. And that's up to 70% of the total cellulose. Since the cellulose has a high melting temperature of crystals and undergoes thermal decomposition before flowing even when heated, it does not eventually cause thermal flow. It is considered that such properties of wood and the like facilitate cracking due to water movement, tissue shrinkage, and thermal decomposition of cellulose. However, the hydroxyl group of cellulose (-OH) acetyl (-COCH ₃₎ or a nitro group, a benzyl group, if not chemically modified substituting the lauroyl group or the like, occurs internally plasticized wood, thermal fluidity gives Can be That is, it was thought that if the cellulose was changed to a derivative and the degree of hydrogen bonding was reduced, the lumber would have thermal fluidity. As described above, if the cellulose crystal is caused to flow, even if the cellulose crystal is heated and dried under fairly severe conditions, shrinkage cracks and moisture transfer cracks do not occur.

As a specific method, the use of the fact that wood becomes a state having thermofluidity (thermoplasticity) due to a hydrothermal chemical reaction was recalled. In other words, as a pretreatment step, raw wood is impregnated with a specific organic impregnant, put into high-temperature water of 100 ° C or higher to cause a hydrothermal chemical reaction, and dissolve a part of cellulose, lignin, etc. in wood. Then, some of the chemical bonds were partially cleaved, or the esters in the resins were alcoholized to make the woody portion have a thermofluidity (thermoplasticity).

Next, an AE sensor is attached to the impregnated wood, etc., and the wood, etc., detects the AE generated as the wood structure changes as a signal, and processes the signal to predict cracks in the wood, etc. Based on the prediction information, the temperature and humidity are used as operating factors, and a drying process is performed by performing a heating process at 100 ° C. or less at normal pressure while controlling the atmosphere so that cracks do not occur in wood and the like.

The installation of the AE sensor is performed via a wave guide in consideration of temperature and humidity. The mounting position of the wave guide was a test piece opening. Then, the AE generated by the change in the structure of the wood is detected as an electric signal, and the information is analyzed to predict cracks in the wood.

As described above, even in the drying process, by observing the AE signal, it is possible to always grasp the progress of the wood or the like during drying.

The signal sent from the sensor attached to wood etc. is amplified by the preamplifier, the signal below the set value is cut off by the cracking monitor, the AE event of specific amplitude is detected after amplification, and this specific amplitude AE event data is It is recorded (Fig. 14). FIG. 15 shows this as the cumulative AE energy. By performing such an experiment and collecting a large number of cases and performing statistical processing, a standard AE pattern in the wood drying process as shown in FIG. 3 can be obtained.

From the standard AE pattern in this drying process, the following empirical rules for predicting cracks in wood and the like were obtained.

If an AE signal with a certain amplitude exceeding the empirically determined value appears, it is considered as a precursor to cracking.

The drying process has three stages, an initial stage, a middle stage, and a late stage, and it is important to change the criteria for each stage.

The first stage (I) is considered to be a stage in which steam penetrates into the center of wood or the like, the temperature and the water content become uniform, and drying gradually proceeds. The moisture content in the first and second stages is 25%, corresponding to the fiber saturation point (about 30-25%). Above the fiber saturation point, liquid water is present in the wood. At this stage, sufficient care must be taken because cracks are easily generated.

The second stage (II) is considered to be the stage in which the water absorbed in the form of bound water in the fibers breaks the bonds and begins to evaporate. Therefore, the energy required for lowering the water content is higher than in the first stage. At this stage, the tensile strength of the wood will increase sharply, and it will be possible to end the harsh drying conditions from the first stage. Therefore, severe drying conditions can be given from the first stage. That is, in the second stage, severe drying conditions are applied, thereby shortening the drying time. The boundary between the second and third stages corresponds to a water content of about 15%. This water content of about 15% is considered to correspond to the equilibrium water content, and corresponds to the air-dry state.

In the third stage, since there are many AEs with small amplitudes, it is considered that the crystallization water inside the cells is reduced to detach from the cells. However, since the AE having the small amplitude has no relation to the drying crack, the drying condition may be set regardless of the number of AE events. Therefore, in the third stage, it is possible to set more strict drying conditions than in the second stage, and here it is possible to further shorten the drying time.

As described above, when the drying state progresses and the water content becomes 10% or less, the AE having a small amplitude also decreases.

Therefore, the method of predicting “cracking” in the drying process was determined empirically while identifying the current drying stage while monitoring the AE occurrence rate and the cumulative number of AE events of a specific amplitude online. Compare the standard AE occurrence situation (AE occurrence rate and AE cumulative number of events) with the crack alert reference value to predict and judge cracking during the processing process.

Next, the temperature condition and the humidity condition are manipulated based on the optimal control pattern at that stage empirically determined based on the crack prediction information to relax and control the atmospheric conditions so that cracks do not occur in wood and the like. And strict temperature and humidity conditions so that there is no loss in processing efficiency. In this way, cracks are predicted by analysis of the AE signal, and drying is performed while controlling the atmosphere using temperature and humidity as operating factors until the moisture content of the wood or the like becomes 10% or less.

That is, the present invention first impregnates, predicts cracks in wood or the like based on the AE signal, and controls temperature and humidity based on the prediction information to dry while controlling the atmosphere so that cracks do not occur in the wood or the like. Is performed.

FIG. 1 is a flow chart of the drying control in the case where the drying process is performed while controlling the atmosphere, and FIG.
FIG. 3 is a schematic diagram of a standard AE generation pattern when temperature and humidity control is performed in a drying process.

The second invention for which a patent is sought is to impregnate wood or the like with an organic impregnating agent according to oxyethers such as polyethylene glycol and methyl cellosolve, polyhydric alcohols, natural rubber or synthetic rubbers or a combination thereof. This is a method for drying wood or the like, which is characterized in that it is subjected to a hydrothermal chemical reaction after being subjected to a treatment and then heated and dried.

In the present invention, as in the first invention, raw wood is impregnated with a specific organic impregnating agent, thereby converting cellulose into a derivative and reducing the degree of hydrogen bonding. It becomes something. As described above, if the cellulose crystal is caused to flow, even if the cellulose crystal is heated and dried under fairly severe conditions, shrinkage cracks and moisture transfer cracks do not occur. Based on such a principle, it is a method of drying wood or the like so as not to cause cracks even when subjected to a heat drying treatment.

As a specific method, the wood is made to have a thermofluidity (thermoplasticity) by a hydrothermal chemical reaction. In other words, as a pretreatment step, raw wood is impregnated with a specific organic impregnating agent, put into high-temperature water of 100 ° C or lower to cause a hydrothermal chemical reaction, and dissolve a part of cellulose and lignin in wood. Then, some of the chemical bonds are partially cleaved, or the ester in the resin is alcoholized, so that the woody part has a state of having a heat fluidity (thermoplasticity).

In the present invention, if the impregnation treatment is performed in this manner, the heating and drying treatment is not particularly limited, and the heating and drying cracks do not occur in most cases under the conventionally performed heating and drying conditions. Of course, depending on the individual characteristics of the wood to be treated and the special heating conditions, it can not be said that there is no cracking, but for example, according to Example 1. Even in the case where the degree of drying was increased by heating (if necessary, a nonflammable atmosphere was required), cracking hardly occurred. (Fig. 4, Fig. 6, Fig. 8, Fig. 10) Therefore, the standard heating and drying temperature (30 to
If it is a general drying process performed at 100 ° C.), this does not cause cracking. That is,
As long as the impregnation treatment is performed as the pretreatment, cracks during the drying treatment can be reduced at least drastically as long as the drying treatment is performed under conventional common-sense heating conditions.

In the wood drying method of the first invention, in the drying process of wood after the above-described hydrothermal chemical reaction, an AE signal is obtained, a crack is predicted by analyzing the AE signal, and the crack prediction information is used. Using temperature and humidity as operating factors,
The drying process is performed while controlling the atmosphere. The drying process is as follows.

An AE sensor is attached to wood, etc., and the detected AE signal is
Paying attention to the amplitude, only a specific signal effective for crack prediction is discriminated and extracted. The specific mounting method of the AE sensor and the recording method of the AE signal are the same as those described in the first invention.

Based on the selected specific-amplitude AE signal, the cumulative number of AE events and AE occurrence rate are processed and monitored to recognize the progress of drying in real time. To identify

There are three stages in the drying process, and it is important to change the criteria for each stage.

Crack prediction is determined by comparing the preset number of accumulated AE events and the reference value of the AE occurrence rate in each processing stage, which is identified from the real-time AE occurrence information, with the crack warning reference value.

The standardized temperature and moisture content during the wood drying process, the cumulative AE energy at that time, and the model pattern of the AE generation rate are 3rd.
As shown in the figure.

Based on the crack prediction information, the atmosphere condition is controlled by operating the temperature condition and the humidity condition on the basis of the optimum control pattern empirically determined at that stage so that cracks do not occur in the wood or the like.

FIG. 1 is a flow chart of the drying control in the case where the drying process is performed while controlling the atmosphere, and FIG.
FIG. 7 is a schematic diagram of a standard AE generation pattern when temperature and humidity control is performed in a drying process.

Moreover, from the results of many experiments, it was found that the following should be considered when examining the optimal work process in the wood drying.

(A) Drying must be considered in three stages.

(B) In the first stage, a sufficient amount of steam is required.

At this stage, sufficient steam is used because cracks are likely to occur, and care is taken to obtain a uniform moisture content and temperature distribution inside the wood.

Further, since the occurrence of cracks is very sensitive to changes in the drying conditions, when the drying conditions are strict, it is necessary to gradually perform the drying.

If AE indicates a sign of cracking, introduction of a large amount of steam is effective.

(C) In the second stage, it is possible to make the drying conditions stricter at high temperature and low humidity compared to the first stage. Therefore, it is possible to further accelerate the drying speed.

(D) In the third stage, more severe drying conditions are possible than in the second stage, and even if it is considerably difficult, cracks are unlikely to occur. Therefore, this step can minimize the drying time.

As described above, considering the most efficient drying schedule based on the fact that the state of drying differs for each stage, the following is obtained.

Crack detection is performed with an AE measuring device. In the measurement system used in this experiment, the precursor of cracking is detected by the total number of AE events of 0.5 V or more, and the drying conditions are controlled so that this total number of events does not exceed a certain value. The control of the drying conditions is basically performed by the temperature and the relative humidity. The first, second and third steps are distinguished by the rate of increase of the accumulated AE energy.

The specific control method is as shown in the flow chart of the drying control shown in FIG. Set the amount of steam that seems to be approximately appropriate and start drying at the temperature that is expected to be appropriate. When the number of AE events of 0.5 V or more per minute exceeds a certain value Nc (pieces / minute), a large amount of steam is injected temporarily to prevent cracking, and at the same time, the temperature setting of ΔTd1 ° C is lowered. If the number of AE events of 0.5 V or more is equal to or less than No for a certain period of time (about 10 minutes), the temperature set value is increased by ΔTu1 ° C. in order to tighten the drying conditions. By this repetition, the temperature settles to a constant value (Tc). However, the upper temperature limit suitable for wood drying is empirically dependent on the species. If the temperature is too low, the drying efficiency will decrease. As described above, when Tc is not in the desired temperature range, the steam amount is adjusted, and control is performed so that Tc falls within an appropriate temperature range. If it is determined that the transition to the second stage from the increase rate of the cumulative AE energy, ΔTu2,
ΔTd2 is used to control the temperature rise and fall. Here, ΔTu1 <ΔTu2, and control is performed in the same manner as in the first stage.
Further, if it can be judged from the shift to the third stage and the increase rate of the accumulated AE energy, the temperature control parameters ΔTu3, Td
Control is performed using 3. It is expected that ΔTu2 <Tu3Δ, and the drying conditions will be more severe than the second stage. The temperature control parameters ΔTu1, ΔTd1, ΔTu2, ΔTd2, ΔTu3, and ΔTd3 need to be determined for each tree species.

"Example"<Example1> A natural raw wood log material (length: 200 mm x diameter: 80 mm) prepared by natural drying (water content: 30%) was prepared, and this was first decompressed at room temperature to obtain wood. The inside was degassed, and then the resin solution polyethylene glycol was injected under pressure at 3 to 5 atm with a pressure pump. Thereafter, the impregnated wood is placed in high-temperature water of 100 ° C. or lower to cause a hydrothermal chemical reaction. The log material thus pre-treated and the same log material which had not been pre-treated were placed in a heat treatment room, and an AE sensor was attached to these materials via a wave guide. Specifically, the terminal inside the heat treatment chamber of the wave guide is fixed to the test opening with wood screws,
The wave guide was extended to the outside through the measurement hole provided in the heat treatment room, an AE sensor was attached to the outside of the wave guide, and a preamplifier, a cracking monitor and a personal computer installed nearby were connected. Next, air is degassed from the heat treatment chamber, and nitrogen gas is injected from a nonflammable gas injection part to make a 97% nonflammable gas atmosphere. Then, while operating the thermocouple of the heating unit to increase the temperature in the heat treatment chamber, steam is injected from the steam injection unit to adjust the humidity inside. As shown in FIG. 4, the temperature is raised to 150 ° C. at a stretch, heated at a high temperature of about 150 to 160 ° C. for 22 hours, and then lowered to room temperature in about 2 hours.
Processing was completed in 24 hours. We observed the AE occurrence during that time. FIG. 5 shows the AE event status for each amplitude class of the unimpregnated material at that time. FIG.
It is a record showing the AE event occurrence status for each amplitude of the impregnated material. In these figures, it is not possible to identify at which point the crack occurred, so the amplitude was set to 80 dB within one minute.
When the AE of 1V or more was specified and recorded, the AE event occurrence of untreated material was as shown in Fig. 7, and the AE event occurrence of impregnated material was as shown in Fig. 8. Now you can recognize. According to this report, in both the untreated and impregnated materials, large amounts of AE were generated in the initial stage when the temperature in the heat treatment chamber was rising, and in the intermediate stage almost no AE was generated. There is a tendency for AE events to occur. However, the occurrence situation is totally different between untreated material and impregnated material,
In the impregnated material, almost no AE is generated. In other words, it is clear that the untreated material cracked at the early stage of heating, but the impregnated material did not crack. This can be more clearly recognized by comparing FIG. 9 (untreated material) and FIG. 10 (impregnated material) showing the accumulated AE energy.

Therefore, when heating wood at a high temperature so as not to crack wood that is in a low crack state like untreated wood, it is necessary to predict cracking and control the atmosphere. Fig. 11 shows the control model. That is, AE is detected as an electrical signal, and information processing such as recording and analyzing the data with a personal computer is performed, and a crack of wood or the like is predicted by comparing with a reference value set empirically in advance. For example,
Within 1 minute, record an AE with an amplitude of 1 V or more with an amplification factor of 80 dB,
If the cumulative number of events exceeds the reference value or the amplitude exceeds the reference, it is determined that the crack has become a warning zone, and the steam injection unit is activated to inject a large amount of steam into the heat treatment chamber in a short time. In addition to adjusting the humidity inside the heat treatment room and controlling the operation of the heating unit to adjust the temperature inside the heat treatment room (heat treatment room), no AE is generated from wood, etc., or the AE signal is below a predetermined standard The atmosphere was controlled so as to maintain the state, and the heating section was operated while controlling the atmosphere to gradually increase the temperature in the heat treatment chamber, thereby realizing high-temperature heating and drying such that cracks did not occur in wood and the like.

As a result, the impregnated high-temperature heat-dried material had a degree of dryness of about 2% and had no cracks, whereas the unimpregnated high-temperature heat-treated material had many radial cracks.

<Example 2> A test piece of 493 × 101 × 30 mm of rice hiba was raised at a stretch to 55 ° C., heated and dried at 55 to 65 ° C. for 105 hours, and then cooled to room temperature to complete. 12). We observed the AE occurrence during that time. FIG. 13 shows the AE event status for each amplitude class of the unprocessed material at that time. As a result, it was dried from a water content of 45.5% to 13.2% (FIG. 16). No crack was observed in this drying treatment.

As shown in FIG. 12, the drying treatment conditions in the present embodiment become stricter in the latter half of drying. The number of AE events shows a sharp increase after 100 hours (Fig. 14,
(Fig. 15). However, when classified by level, they are as shown in Fig. 13, and when AEs of 0.5V or more are cut, they are less organized as shown in Fig. 14. Therefore, an AE signal of 0.5 V or less
It is not considered to be involved in the generation of cracks. From these graphs, it can be seen that the drying conditions may be stricter in the latter half of the drying, but it is not clear from which point the latter half is indicated.

However, as shown in Fig. 15, the cumulative AE energy can be divided into three stages of drying. That is, about 45 hours from Fig. 15 showing the accumulated AE energy,
Since the gradient of the accumulated AE energy changes clearly at 95 hours, it can be classified into the first stage up to 45 hours, the second stage from 45 to 95 hours, and the third stage after 95 hours.

In this way, in wood drying, it is important to analyze the AE signal and grasp the drying stage.By setting the drying conditions according to each stage, it is possible to dry so as not to crack, and the drying period Can be shortened.

[Effects] The first invention of the present application involves impregnating wood or the like with a specific organic impregnating material and subjecting the impregnated wood or the like to heat drying after a hydrothermal chemical reaction. During the drying process, the wood and other materials are detected as a signal to detect the acoustic emission generated due to the change in the structure of the wood, and the cracks in the wood and the like are predicted, and the temperature and humidity are used as operating factors to prevent the wood and the like from cracking. This is a method of drying wood or the like, which performs drying while controlling. By impregnating the organic impregnant, wood can be given thermoplasticity, and during heating and drying, atmosphere control is performed using AE as a signal and temperature and humidity as operating factors. Cracking during processing can be almost completely prevented even when processing from raw wood, and moreover, the drying time has been reduced as much as possible and efficient drying can be performed. As a result, it was possible to overcome the conflicting technical demands of preventing the yield from lowering in the conventional drying treatment and short-time drying treatment.

The second invention of the present application is a wood drying method in which wood or the like is impregnated with a specific organic impregnating material, subjected to a hydrothermal chemical reaction, and then heated and dried. The heating and drying treatment here is not particularly limited as long as it is a conventional general heating and drying treatment method. It is not always necessary to detect the AE signal and grasp the dry state in real time.

As wood is plasticized by impregnation,
Even if the wooden layer shrinks or is pulled by the heating, it deforms in response to the stress and prevents cracking.
For this reason, cracks do not occur in most cases if the conventional general heat drying treatment method is employed. That is, although the crack prevention rate is not as reliable as that of the first invention, the cracks in the drying treatment can be prevented with much higher probability than the conventional drying method.

[Brief description of the drawings]

FIG. 1 is a drying control flow chart when performing a drying process while controlling the atmosphere using the AE according to the first invention of the present application.
FIG. 2 is a schematic diagram of temperature and humidity control and AE generation in the drying process. FIG. 3 is an AE generation model pattern during wood heating and drying process. FIG. 4 is a temperature change of the high temperature heating process in Example 1. 5 is a graph in which the number of AE events (occurrence rate) for each amplitude class of the untreated material of Example 1 is recorded, and FIG. 6 is a graph showing each amplitude of the impregnated material of Example 1. FIG. 7 is a graph in which the number of AE events (occurrence rate) for each class is recorded. FIG. 7 is a graph in which the AE occurrence rate of the untreated material of Example 1 having an amplitude of 1 V or more is recorded. FIG. FIG. 9 is a graph in which the AE generation rate of the processed material having an amplitude of 1 V or more is recorded, FIG. 9 is a graph in which the accumulated AE energy of the unprocessed material having the amplitude of 1 V or more is recorded in Example 1, and FIG. This graph records the accumulated AE energy of the processed material with an amplitude of 1 V or more.
FIG. 12 is a graph showing an AE generation model pattern at the time of high-temperature heat treatment in Example 1 and a crack limit control criterion based on cumulative AE.
FIG. 13 is a graph in which the temperature and the relative humidity change in the high-temperature heat treatment in Example 2 are recorded. FIG. 13 is a graph in which the number of AE events (occurrence rate) of each amplitude class of the untreated material in Example 2 is recorded. FIG. 14 is a graph in which the temperature of the drying process and the AE occurrence rate with an amplitude of 1 V or more in Example 2 are recorded, and FIG. 15 is a graph in which the cumulative AE energy of the drying process with an amplitude of 1 V or more in Example 2 is recorded. FIG. 16 shows a change in water content and a change in weight in the drying treatment in Example 2.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kiyoshi Sato 1-28-4 Midorigaoka, Taishiro-ku, Sendai, Miyagi Prefecture (72) Inventor Satoshi Yume 3-27-22, Nankodai, Izumi-ku, Sendai-shi, Miyagi (72) Inventor Isuzu Suzuki 18-18 Kodaira-cho, Aoba-ku, Sendai, Miyagi Prefecture (72) Inventor Katsumi 3-22, Ipponsugi-cho, Wakabayashi-ku, Sendai, Miyagi Prefecture (72) Inventor Yasuo Suzuki 68, Maedazawa, Takagi, Matsushima-cho, Miyagi-gun, Miyagi Prefecture, Japan 56) References JP-A-58-156176 (JP, A) JP-A-51-136803 (JP, A) JP-B-63-7317 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , (DB name) F26B 7/00 F26B 9/06

Claims (2)

(57) [Claims] 1. Various kinds of plant-based processed materials (hereinafter referred to as "wood and the like") such as logs, processed woods and bamboos, oxyethers such as polyethylene glycol and methyl cellosolve, polyhydric alcohols, natural rubber and synthetic rubber. After an impregnation treatment to impregnate the organic impregnating agent according to the class or a combination thereof, a hydrothermal reaction is performed, and then an AE sensor is attached to the impregnated wood and the like. The generated AE is detected as a signal, the signal is processed to predict cracks in wood, etc., and temperature and humidity are used as operating factors based on the prediction information while controlling the atmosphere so that cracks do not occur in wood, etc. A method for drying wood or the like, wherein a heat treatment at a pressure of 100 ° C. or less is performed. 2. An impregnating treatment for impregnating wood or the like with an organic impregnating agent according to an oxyether such as polyethylene glycol or methyl cellosolve, a polyhydric alcohol, a natural rubber or a synthetic rubber, or a combination thereof. A method for drying wood or the like, characterized in that it is heated and dried after a hydrothermal chemical reaction.