JPH03156281A - Drying method for wood or the like - Google Patents

Abstract

PURPOSE:To prevent wood or the like from cracking at the time of drying by sensing AE generated upon variation of a wood structure as a signal, information-processing the signal to presume crack of the wood, and heating it with temperature and moisture as operation factors. CONSTITUTION:Various vegetable wood or the like such as log, wood material, bamboo, etc., is immersed in organic impregnant of oxyethers such as polyethy lene glycol, methyl cellosolve, etc., polyvalent alcohols, phenols, natural rubber or synthetic rubber, or combination thereof, and thermally chemically reacted. An AE sensor is mounted on the immersed wood, AE generated upon variation of wood structure is sensed as a signal, the signal is information-processed to presume crack of the wood, heat treated at 100 deg.C or lower under normal pressure while controlling the atmosphere to eliminate crack of the wood with temperature and moisture as operation factors based on presumption information to be dried. Even in a drying step, the AE signal is observed to always grasp the advancing state on the way of drying of the wood.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention is a method for heating and drying various processed vegetable materials (hereinafter referred to as "wood, etc.") such as logs, processed wood, and bamboo materials to prevent them from cracking. Regarding how to process.

``Prior Art'' Wood is usually subjected to drying treatment in order to prevent it from deforming when used and to improve workability, paintability, and adhesion. This drying method can be roughly divided into two types: natural drying and artificial drying. In recent years, there has been a demand for drying a large amount of water in a short period of time, and for evenly drying to a low moisture content that is difficult to obtain naturally. Most of them use the dry method.

In such wood drying treatment, the most important problem is to prevent cracking. especially,
In the case of the so-called artificial drying method, which uses forced heating and drying, cracking is more likely to occur due to the harsh drying conditions, and if zero cracking occurs, the quality will deteriorate significantly and the product value will be lost. However, if it takes many days to carefully avoid cracking, the processing efficiency will be too low and it will not be viable as a business.

For this reason, during wood drying treatment, while preventing cracking,
Techniques to shorten drying time are being researched in various fields, but no decisive method has yet been developed.

Therefore, while investigating the causes of R-cracking in wood during heat treatment and researching methods to prevent it, we found that since cracking due to drying is a type of solid-state fracture, acoustic emissions must be emitted. Considering that this is the case, we have begun research into technology that can detect ``R cracks'' and predict ``cracks'' caused by drying by observing this AE. At the same time, when we investigated technical literature regarding the relationship between r-cracks in wood and AE, we found that there was a known technology called ``Dry Crack Prediction and Prevention Device for Wood'' (Japanese Patent Publication No. 7317/1983).

In addition, we recently discovered that it is possible to transform wood into a material with plasticity similar to plastic through a simple chemical reaction.

Taking these as hints, the present inventors conducted research aimed at preventing cracking during drying of wood, etc., and completed the present invention.

``Problem to be Solved J'' The causes of cracks occurring in wood etc. when heat-treated are thought to be mainly due to moisture movement during the heating and drying process and tissue shrinkage.

First of all, we learned the following about the cracking of wood etc. due to moisture movement and tissue shrinkage during the drying process. The moisture contained in wood usually includes free water and bound water.
During drying, first only free water disappears and is removed from the surface layer, and then, as drying progresses, bound water also begins to be removed.

The movement of free water in the former is dominated by capillary action, and the movement of bound water in the latter is due to diffusion. In this way, free and bound water in the surface layer of the wood moves and dries;
The inner layer will still have a high water content. The dry part then tends to shrink, and the water-containing part resists shrinkage.

As a result, in the first half of drying, tensile stress acts on the surface layer and compressive stress acts on the inner layer. Furthermore, as drying progresses, these stresses increase and the shrinkage spreads inside, but the surface layer is always under large tensile stress.
Permanent deformation occurs without proper contraction. After that, as the inside dries, the surface layer attempts to contract normally, and as a result, the positive and negative stresses are reversed, and in the latter half, the surface layer is subjected to compressive stress and the inner layer is subjected to tensile stress. For this reason,
If the tensile stress exceeds the tensile strength of the wood part, end cracks or surface cracks along the surface fibers will occur during the first half of drying, and internal cracks will occur during the second half of drying. In addition, defects called surface hardening and depression occur with drying, and it has been found that these are both directly related to the magnitude of the gradient of the moisture content distribution inside the wood. In heat drying, it is necessary to shorten the drying time by increasing the gradient of the moisture content distribution inside the wood as much as possible without causing defects such as the various cracks mentioned above. It is important to understand the moisture content distribution inside the wood from time to time, and it is necessary to dry the wood while adjusting the temperature and humidity according to the moisture content of the wood during drying. However, the structure of wood is complex, and its thermal properties are affected by humidity and moisture content, as well as differing depending on the species of wood.
It is difficult to theoretically grasp the moment-by-moment moisture content distribution inside wood. In addition, the mechanical strength and thickness of the material also play a role in the occurrence of cracks that occur with drying, so it is important to clarify the conditions under which defects occur in a highly anisotropic and complex wood structure. is extremely difficult.

Therefore, in the conventional drying process, the current situation is to enter the room during drying, visually check for cracks, and readjust the indoor atmosphere. However, this method cannot predict cracks before they occur, nor can it detect cracks that occur internally.

Therefore, the present inventors have developed a known technique (Japanese Patent Publication No. 1983-1983-1) that predicts dry cracks in wood using AE detection technology and prevents cracks by controlling the temperature and humidity around the wood.
7317). However, this known document only describes that initial cracking during drying treatment is predicted based on the cumulative number of AEs and the rate of AE occurrence. In other words, even in the case of the drying process, the initial cracks during drying are predicted, and the cracks in the latter stages of the drying process are not considered.
All you have to do is know the cumulative number and AE occurrence rate, and when the AE occurrence rate reaches a limit value, activate the control equipment to relax the drying conditions and prevent cracking.

In this conventional technology, the correlation between the cumulative number of AEs, the AE incidence rate, and cracking is valid to some extent for cracking in the early stage of drying, but it does not necessarily show a correlation in the middle or late drying stage, and it depends on the individual situation of the wood to be treated. It has been found that the AE has disadvantages such as the generated AE has a lot of noise, making it easy to make mistakes in judgment.0 The inventor observed and analyzed the occurrence of wood cracks and AE signals, and discovered that wood cracks Noticing that there is a close correlation with the amplitude of the AE multiplied signal, we focused on the amplitude of the electrical signal and discriminated and detected the effective signal directly connected to the crack. If it is large, it is considered a danger signal for cracking, and while monitoring the cumulative number of AE events with large amplitudes and the AE incidence rate online, we constantly identify whether the drying state is in the early, middle, or late stage. The purpose is to predict cracks during the treatment process by making a comprehensive judgment while comparing with preset reference values at each treatment stage. The temperature and humidity are then manipulated based on the predictive information obtained in this way to control the atmosphere so as not to cause cracks in the wood or the like.

Furthermore, although wood impregnation techniques have been widely adopted, there are no known examples of using impregnating agents in advance to prevent cracking during drying or heat treatment. We learned that when wood, etc. is impregnated with a specific organic solvent and then heat treated, a chemical reaction occurs internally, resulting in internal plasticization, giving the material thermal fluidity, and we applied this knowledge. The present invention was developed based on the idea that thermal fluidization inside the wood could prevent cracking during heat treatment. That is, the interior of the wood is plasticized by impregnating it with a specific organic solvent and performing a hydrothermal chemical reaction. This ensures that it will not crack even if subjected to artificial drying treatment under severe heat treatment conditions.

Means to Solve the Problem The present invention solves the technical problem of preventing cracking during the drying process, such as in the case of diagonal cracking, by combining the following technical means.

As a result of research into cracks caused by heat drying of wood, etc., the inventor found that cracks occur due to moisture movement, tissue shrinkage, and cellulose decomposition due to high heat. Dry cracking of wood is a form of solid state destruction, and we believe that acoustic emission (AE) must be generated.If we can detect this and know its frequency and signal strength, we can use this information. I thought it would be possible to predict cracks in advance by treating them. As a result of research, wood cracking is A.
We noticed that there is a close correlation between the occurrence rate and the amplitude of the E signal, so we focused on the amplitude of the electrical signal to distinguish and detect effective signals that are directly linked to cracks. As a result, it has become possible to understand that - when the amplitude of the AE flaw signal is large, it is a danger signal for cracking. Moreover, by online monitoring of the cumulative AE events with amplitudes that are effective for crack prediction and the AE incidence rate, it is possible to identify whether the drying condition is in the early, middle, or late stages, and to Analyze and consider the meaning of the detected AE flaw signal while comparing it with the empirically predetermined reference value to predict cracks during the processing process, and based on this predictive information, manipulate temperature and humidity to treat wood, etc. Atmospheric conditions are relaxed and controlled to prevent cracks from occurring. Since cracks in wood, etc. are caused by the movement of moisture during drying and heating treatments and the denaturation of the material by heat, it has been found that cracking can be sufficiently prevented by adjusting temperature and humidity as operating factors.

Furthermore, if the organic impregnating agent is pre-impregnated with an organic impregnating agent before drying and then placed in high-temperature water below 100°C, a hydrothermal chemical reaction (hydrolysis) will occur, causing the wood to become thermoplastic (thermofluid). Even during heat drying, cracks do not occur because the surface layer deforms in response to the difference in tensile stress and compressive stress between the surface layer and the inner layer. (
It was found that there is a chemical change to a state with thermal fluidity.

Therefore, we came up with these three ideas: first, to prevent dry cracking by chemically modifying wood by impregnating it with an organic impregnant, and second, to detect AE flaw signals and process that information to improve wood quality. The third step is to prevent cracks by controlling the atmosphere using temperature and humidity as operating factors based on this predicted information.By appropriately combining the above, wood, etc. can be dried efficiently and evenly. The aim is to process and provide large quantities of dried wood.

The invention for which a patent is sought will be explained in detail below.

The first invention for which a patent is sought is a log,
Processed wood, organic impregnation of various vegetable processed materials such as bamboo, oxyethers such as polyethylene glycol and methyl cellosolve, polyhydric alcohols, phenols, natural rubber or synthetic rubber, or a combination of these. The material is impregnated with the agent and subjected to a hydrothermal chemical reaction (hydrolysis).

The scope of treatment of the present invention is wood, etc., but this includes all types of processed plant materials such as logs, processed wood, and bamboo, regardless of the type of plant.

In addition, the specific organic impregnating agent to be impregnated includes oxyethers such as polyethylene glycol and methyl cellosolve, polyhydric alcohols such as 1,4-butanediol, phenols such as phenol, natural rubber or synthetic rubber, or these. Any combination of the above may be used.

Next, changes in wood quality caused by the impregnation treatment will be explained.

Chemically, wood contains 40-50% of the amount of cellulose, 1
It is composed of 5-25% hemicellulose, 20-30% lignin and other accessory components, and in the cell walls that make up wood, bundles of aggregates of cellulose molecular chains pass through the sponge-like network. The components are combined in such a way that hemicellulose fills the gap between the two. Furthermore, the bundles of aggregates of cellulose molecular chains are regularly arranged to form crystals. This is a linear polymer with a regular steric configuration and has many hydroxyl groups (-OH), so regular hydrogen bonds between hydroxyl groups are likely to occur between adjacent molecules. Moreover, this amount reaches 70% of the total cellulose. This cellulose has a high melting temperature of crystals, and even when heated, it undergoes thermal decomposition before it starts to flow, so in the end it does not cause thermal flow.This property of wood, etc., is due to moisture movement, tissue shrinkage, and cellulose. It is thought that cracking is likely to occur due to thermal decomposition. However, the hydroxyl group (−
By chemically modifying wood by substituting an acetyl group (-COCH3), nitro group, benzyl group, lauroyl group, etc., internal plasticization occurs in the wood, giving it thermal fluidity. In other words, he thought that by changing cellulose to a derivative and weakening the degree of hydrogen bonding, it would be possible to create a material with thermofluidity in lumber. In this way, if the cellulose crystals are made to flow, shrinkage cracks and moisture migration cracks will not occur even if the cellulose crystals are heated and dried under fairly severe conditions.

As a specific method, we thought of utilizing the fact that wood becomes thermofluid (thermoplastic) due to a hydrothermal chemical reaction. In other words, as a pretreatment process, raw wood is impregnated with a specific organic impregnating agent, and this is placed in high-temperature water below 100°C to cause a hydrothermal chemical reaction (hydrolysis), which removes cellulose, lignin, etc. in the wood. By dissolving some of the chemical bonds and partially cleaving some of the chemical bonds, by alcoholizing the esters in the resins, and by replacing the lignin aromatic nucleus with halogen to produce chlorinated lignin, the wood becomes thermally fluid. This resulted in a state in which it has properties (thermoplasticity).

Next, an AE sensor is attached to this impregnated wood, etc., and the AE sensor that is generated as the wood structure changes.
is detected as a signal, and the signal is processed to predict cracks in wood, etc. Based on the prediction information, temperature and humidity are used as operating factors to control the atmosphere to prevent cracks in wood, etc. at normal pressure. A drying process is performed by performing a heat treatment at 100° C. or lower.

The AE sensor was installed via a wave guide in consideration of temperature and humidity, and the wave guide was installed at the end of the test piece.

Then, the AE generated by wood as the structure changes is detected as an electrical signal, and this information is analyzed to predict cracks in the wood.

In this way, even in the drying process, by observing the AE signal, it is possible to constantly grasp the progress of the drying process of wood, etc.

The signal sent from the sensor attached to the wood etc. is amplified by the preamplifier, and then the signal below the set value is cut by the cracking monitor.After amplification, an AE event with a specific amplitude is detected, and this specific amplitude AE event data is The accumulated AE energy is recorded (FIG. 14), and this is illustrated in FIG. 15 as the cumulative AE energy. By conducting such experiments, collecting a large number of cases, and performing statistical processing, it is possible to obtain a standard AE pattern in the wood drying process as shown in FIG.

From the standard AE pattern in this drying process, we were able to obtain the following empirical rule for predicting cracks in wood, etc.

■If an AE signal with an amplitude above a certain level determined empirically appears, it is considered to be a sign of cracking.

■The drying process has three stages: early, middle, and late, and it is important to change the judgment criteria for each stage.

In the first stage (I), the steam penetrates to the center of the wood, etc.
This is considered to be the stage where the temperature and moisture content become uniform and drying progresses gradually. The moisture content at the time of classification between the first stage and the second stage was 25%, which corresponds to the fiber saturation point (approximately 30 to 25%). Above the fiber saturation point, water exists in the wood in a liquid state. At this stage, cracks can easily occur, so care must be taken.

The second stage (II) is considered to be the stage in which the moisture absorbed into the fibers in the form of bound water breaks bonds and begins to evaporate. Therefore, the energy required to lower the water content increases from the first stage. At this stage, the tensile strength of the wood increases rapidly, and it is thought that it can withstand even more severe drying conditions than the first stage. Therefore, stricter drying conditions can be applied from the first stage. That is, in the second stage, severe drying conditions are applied, thereby making it possible to shorten the drying time. The boundary between the second and third stages corresponds to a water content of approximately 15%. This moisture content is approximately 15%
This is thought to correspond to the equilibrium moisture content, which corresponds to the air-dry state.

In the third stage, since there are many small-amplitude AEs, it is thought that crystal water inside the cells is reduced by leaving the cells. However, since this small amplitude AE has no relation to drying cracking, drying conditions can be set regardless of the number of ΔE events. Therefore, in the third stage, drying conditions must be set even more severely than in the second stage. , is possible;
Here, it is possible to further shorten the drying time.

In this way, as the drying state progresses and the moisture content becomes 10% or less, the small amplitude AE also decreases.

Therefore, the method for predicting "cracking" in the drying process is to identify the current drying stage by monitoring the AE incidence rate of a specific amplitude and the cumulative number of AE events online, and to determine it empirically. Standard AE occurrence situation (
AE occurrence rate, cumulative number of AE events), and crack warning reference values are compared to predict and judge cracks during the treatment process.

Next, based on this crack prediction information and based on the optimal control pattern for that stage determined empirically, temperature and humidity conditions are manipulated to relax and control the atmospheric conditions to prevent cracks from occurring in the wood, etc. or tighten temperature and humidity conditions to avoid loss of processing efficiency. In this way, cracks are predicted by AE multiplied signal analysis, and drying is performed while controlling the atmosphere using temperature and humidity as operating factors, and drying is performed until the moisture content of the wood, etc. becomes 10% or less.

That is, the present invention first performs an impregnation treatment, predicts cracks in the wood, etc. based on AE signals, and then dries while controlling the atmosphere so that the wood, etc. does not crack, using temperature and humidity as operating factors based on the prediction information. This is to ensure that the following is carried out.

Figure 1 is a drying control flowchart when drying is performed while controlling the atmosphere as described above, and Figure 2 is a typical AE generation diagram when temperature and humidity are controlled during drying. This is a schematic diagram of the pattern.

The second invention for which a patent is sought is to apply organic impregnating agents such as oxyethers such as polyethylene glycol and methyl cellosolve, polyhydric alcohols, phenols, natural rubber or synthetic rubber, or a combination thereof to wood, etc. This is a drying method for wood, etc., which is characterized in that it is heated and dried after an impregnation treatment that involves impregnation and hydrothermal chemical reaction (hydrolysis).

The present invention, similar to the first invention, impregnates raw material wood with a specific organic impregnating agent, thereby converting cellulose into a derivative and weakening the degree of hydrogen bonding. become something. Based on this principle, if the cellulose crystals are made to flow, shrinkage cracks and water migration cracks will not occur even if they are heated and dried under extremely harsh conditions. This is a drying method for wood, etc. that prevents cracking even after drying.

A specific method is to make wood into a state where it has thermal fluidity (thermoplasticity) through a hydrothermal chemical reaction. In other words, as a pretreatment process, raw wood is impregnated with a specific organic impregnating agent, and this is placed in high-temperature water below 100°C to cause a hydrothermal chemical reaction (hydrolysis), which removes cellulose, lignin, etc. in the wood. By dissolving some of the chemical bonds and partially cleaving some of the chemical bonds, by alcoholizing the esters in the resins, and by replacing the lignin aromatic nucleus with halogen to produce chlorinated lignin, the wood becomes thermally fluid. It is in a state where it has properties (thermoplasticity).

In the present invention, if the impregnation treatment is carried out in this manner, heat-drying cracks will not occur in most cases even if the method of heat-drying treatment is not particularly limited and the conventional heat-drying conditions are used. Depending on the individual characteristics of the wood to be treated and special heating conditions, it cannot be said that cracking may occur.
For example, Example 1. According to , even when drying was increased by heating to a high temperature of about 150°C, which is no longer considered a normal drying process (it is necessary to create a nonflammable atmosphere if necessary), there was almost no cracking.

(Fig. 4, Fig. 6, Fig. 8, Fig. 10) Therefore, if it is a general drying process performed at a standard heating drying temperature (30 to 100°C) with mild heating conditions, this By,
No cracking will occur; in other words, as long as the impregnation treatment is performed as a pre-treatment, as long as the drying treatment is carried out under conventional, common sense heating conditions, cracking during the drying treatment can at least be dramatically reduced. It is something.

The third invention for which a patent is being sought is to attach an AE sensor to wood, etc., detect the AE generated by wood, etc. as a signal as the structure of the wood changes, and discriminate the amplitude of the signal to determine if the amplitude exceeds a predetermined value. The AE multiplication signal obtained was used as a danger signal for cracking, and the cumulative number of AE events and AE incidence rate were monitored online to constantly identify whether the drying state was in the early, middle, or late stages. Cracks are predicted by comparing preset cumulative AE event count and AE incidence rate criteria values at each processing stage with crack warning criteria values, and the optimal value for that stage is empirically determined based on the prediction information. This method of drying wood, etc. is characterized by controlling the atmosphere so as not to cause cracks in wood, etc. by manipulating temperature conditions and humidity conditions based on a control pattern.

In the drying process of wood, the present invention obtains an AE multiplied signal, predicts cracking by analyzing the AE multiplied signal, and performs the drying process while controlling the atmosphere using temperature and humidity as operating factors based on the splitting prediction information. The aim is to advance the process and reduce dry cracking as much as possible.

That is, the characteristic work steps of the wood drying method in the present invention are as follows.

■Attach an AE sensor to wood, etc., and focus on the detected AE multiplied signal and its amplitude to distinguish and extract only the specific signal that is effective for predicting cracks. The AE multiplied signal recording method is the same as that described in the first invention.

■Based on the selected specific amplitude AE signal, the cumulative AE
The number of events and AE incidence rate are processed and monitored to recognize the progress of drying in real time and identify whether the drying state is in the early, middle, or late stage.

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

(1) Predict and judge cracks by comparing the preset cumulative number of AE events and AE occurrence rate reference values at each processing stage identified from the full-time AE occurrence information with the crack warning reference value.

The model pattern of the standardized temperature and moisture content during wood drying treatment, the cumulative AE energy at that time, and the AE incidence rate is shown in Figure 3.

■Based on the crack prediction information, the temperature and humidity conditions are manipulated to control the atmosphere to prevent cracks from occurring in the wood, etc., based on the optimal control pattern for that stage determined empirically.

Figure 1 is a drying control flowchart when drying is performed while controlling the atmosphere as described above, and Figure 2 is a flowchart of standard AE light when temperature and humidity are controlled during drying. This is a schematic diagram of the occurrence pattern.

Moreover, when examining the optimal work process for wood drying mentioned above based on the results of many experiments, it was found that the following should be taken into consideration.

■Drying needs to be considered in three stages.

■ Sufficient amount of steam is required in the first stage.

Since cracks are likely to occur at this stage, care must be taken to use sufficient steam and to obtain a uniform moisture content and temperature distribution inside the wood.

Furthermore, since cracking is very sensitive to changes in drying conditions, it is necessary to gradually tighten drying conditions.

If a sign of cracking is found by AE, it is effective to introduce a large amount of steam.

■In the third stage, compared to the first stage, it is possible to make the drying conditions stricter, such as high temperature and low humidity.

Therefore, it is possible to further accelerate the drying rate.

■ In the third stage, even more severe drying conditions than in the second stage are possible, and even if the conditions are quite severe, cracks do not occur (therefore, this stage can shorten the drying time the most).

As mentioned above, the most efficient drying schedule is considered as follows, taking into account that the drying process differs at each stage.

Detection of cracks is carried out using an AE measurement device, and the measurement system used in this experiment detects signs of cracking as the total number of AE events of 0.5 V or higher, and the drying conditions are controlled so that the total number of events does not exceed a certain value. . Drying conditions are basically controlled by temperature and relative humidity.

The first, second and third stages are distinguished by the rate of increase in cumulative AE energy.

The specific control method is as shown in the drying control flowchart shown in FIG. Set the amount of steam that you think is appropriate, and start drying at the temperature that you think is appropriate. 0.5V every minute
If the number of AE events exceeds a certain value Nc (numbers/min), a large amount of steam is temporarily injected to prevent cracking.
At the same time, lower the ΔTdl"C temperature setting. If the number of AE events of o, 5V or more is less than NO for a certain period of time (about 10 minutes), the drying conditions will be made stricter.
' Increase the temperature set point by 'C. By repeating this process, the temperature settles to a constant value (Tc).The upper limit of the temperature suitable for drying wood depends on the tree species based on experience. Furthermore, if the temperature is too low, the drying efficiency will decrease. In this way Tc
If T is not within the desired temperature range, adjust the amount of steam and
c is controlled so that it stays within an appropriate temperature range. Cumulative AE
If it is determined that the second stage has been reached based on the energy increase rate, ΔTu2゜△Td2, which is different from the first stage, is determined.
is used to control the temperature rise and fall, where ΔT
If ul < ΔTu2 and it can be determined from the rate of increase in cumulative AE energy that the control is performed in the same way as in the first stage and that the third stage has been entered, the temperature control parameter ΔT
Control is performed using u3 and Ta2, ΔTu2 <Tu
3Δ, which means that the drying conditions will be even more severe than those in the second stage.

Temperature control parameter ΔTul ΔTdlΔTu2. Δ
Td2, ΔTu3, and ΔTd3 need to be determined for each tree species.

"Example"<Example1> Natural live maple log material (length 200mm x diameter 80φ
) is air-dried (moisture content 30%), and this is first depressurized at room temperature to degas the wood, and then the resin liquid polyethylene glycol is pressurized at 3 to 5 atmospheres using a pressure pump. Injected. Thereafter, the impregnated wood is placed in high temperature water of 100°C or less to cause a hydrothermal chemical reaction. The thus pretreated log material and the same log material without pretreatment were placed in a heat treatment chamber, and an AE sensor was attached to these materials via a waveguide. Specifically, the terminal inside the heat treatment chamber of the waveguide is fixed to the test end with wood screws, the waveguide is extended to the outside through a measurement hole provided in the heat treatment chamber, and the AE sensor is installed outside the waveguide. I installed it and connected it to a nearby preamplifier, cracking monitor, and computer.

Next, air is degassed from the heat treatment chamber and nitrogen gas is injected from the nonflammable gas injection part to create a 97% nonflammable gas atmosphere. Then, the thermocouple in the heating section is activated to raise the temperature inside the heat treatment chamber, and the internal humidity is adjusted by injecting steam from the steam injection section. As shown in Figure 4, the temperature was raised to 150°C in -air, heated at a high temperature of approximately 150 to 160°C for 22 hours, and then the temperature was lowered to room temperature in about 2 hours, and the treatment was completed in about 24 hours. . We observed the occurrence of AE during that time. FIG. 5 shows the AE event situation for each amplitude class of the unimpregnated treated material at that time. FIG. 6 is a record showing the occurrence of AE events for each amplitude of the impregnated material. In these figures, it is not possible to specify at what point the crack occurred, so if the amplification factor is 80 dB and the amplitude is 1 V or more within 1 minute,
After identifying and recording E, the AE event occurrence situation for the untreated material is shown in Figure 7, and the AE event occurrence situation for the impregnated material is shown in Figure 8.The AE multiplication signal related to cracking can be recognized quite clearly. Became. Reading this, it can be seen that for both untreated and impregnated materials, a large amount of AE is generated in the initial stage when the temperature inside the heat treatment chamber increases, and almost no AE light is generated in the middle stage, and then again when the temperature starts to drop. A.E.
There is a tendency for events to occur. However, the situation in which AE occurs is completely different between the untreated material and the impregnated material, with almost no AE occurring in the impregnated material.

In other words, it clearly shows that the untreated material cracked at the initial stage of heating, but the impregnated material did not. This can be more clearly recognized by comparing FIG. 9 (untreated material) and FIG. 10 (impregnated material), which show the cumulative AE energy.

Therefore, when heating wood that is easily brittle, such as untreated wood, at high temperatures to prevent it from cracking, it is necessary to predict cracking and control the atmosphere. If you create a control model for this, it will look like the one shown in Figure 11.

In other words, AE is detected as an electrical signal, this data is recorded on a computer, and information processing such as analysis is performed, and compared with a standard value set empirically in advance to predict cracks in wood, etc. , amplification factor 80d within 1f
If an AE with an amplitude of 1■ or more is recorded as B, and the cumulative number of events exceeds the standard value or the amplitude exceeds the standard, it is determined that the warning area for cracking has been reached, and the steam injection unit is activated to perform heat treatment. A large amount of steam is injected into the room in a short period of time to adjust the humidity in the heat treatment chamber, and the operation of the heating section is controlled to adjust the temperature in the heat treatment chamber (heat treatment chamber) to remove A from wood, etc.
The atmosphere is controlled so that E does not occur or the AE multiplier signal is generated below a predetermined standard, and while controlling the atmosphere, the heating section is operated to gradually raise the temperature in the heat treatment chamber to treat the wood. We were able to achieve high-temperature heating drying that did not cause cracks in the materials.

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

<Example 2> A test piece of rice cypress wood measuring 493 x 101 x 30 mm was heated to 55°C in -air, heated and dried at 55 to 65°C for 105 hours, and then the temperature was lowered to room temperature to complete the drying process (see Figure 12). ), we observed the occurrence of AEs during that period. Figure 13 shows the A for each amplitude class of the untreated material at that time.
This shows the E-event status. As a result, the moisture content was dried from 45.5% to 13.2% (Figure 16), and no cracks were observed in this drying process.

As shown in FIG. 12, the drying conditions of this example become more severe as the latter half of the drying progresses.

The number of AE events shows a rapid increase after 100 hours (Figs. 14 and 15). However, when classified by level, it becomes as shown in Fig. 13. A
When E is cut, it is organized into fewer parts as shown in Figure 14. Therefore, it is considered that the AE multiplied signal of 0.5v or less is not involved in the occurrence of cracks. From the graph below, it can be seen that the drying conditions can be made stricter in the latter half of drying.
It is not clear at what point the second half begins.

However, as shown in FIG. 15, when looking at the cumulative AE energy, it is possible to divide the drying into three stages. In other words, since the gradient of cumulative AE energy clearly changes at about 45 hours and about 95 hours from the figure showing the cumulative AE energy, the period up to 45 hours is the first stage, the period from 45 to 95 hours is the second stage, and 95 hours. The subsequent stages can be classified as the third stage.

In this way, when drying wood, it is important to analyze the AE signal and understand the drying stages.By setting the drying conditions according to each stage, it is possible to dry the wood without cracking and to determine the drying period. can be shortened.

"Effect" The first invention of the present application impregnates wood, etc. with a specific organic impregnating material, causes a hydrothermal chemical half reaction (hydrolysis), and then heat-dries the impregnated wood, etc. The system detects as a signal the acoustic emissions that occur as a result of changes in the structure of wood during the heating and drying process, predicts cracks in the wood, etc., and uses temperature and humidity as operating factors to predict cracks in the wood. This is a drying method for wood, etc., in which the atmosphere is controlled to ensure that the wood is not contaminated. Impregnation with an organic impregnating agent imparts thermoplasticity to the wood, and during the heating drying process, the atmosphere is controlled using temperature and humidity as operating factors using AE as a signal, so the combination of these factors results in a high moisture content. It is now possible to almost completely prevent cracking during processing even when processing raw wood, and moreover, it has become possible to carry out efficient drying processing in which the processing time is shortened as much as possible. As a result, it was possible to overcome the contradictory technical demands of preventing a decrease in yield in conventional drying processes and short-time drying processes.

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 half reaction (hydrolysis), and then heated and dried. The heat drying treatment referred to herein may be any conventional heat drying treatment method, and is not particularly limited. It is not necessary to detect the AE signal and grasp the dry state in real time.

When wood is impregnated, it becomes plasticized, so even if the wood layer shrinks or is stretched by heating, it deforms to accommodate the stress and prevents cracking. For this reason, if the conventional general heat drying treatment method is used, cracking will not occur in most cases.In other words, although the first invention does not have a reliable cracking prevention rate, it is better than the conventional drying method. can dramatically prevent drying cracking with high probability.

The third invention of the present application does not perform an impregnation process, but in the drying process, detects and analyzes AE as a signal, predicts cracks, and performs a heating drying process while controlling the atmosphere to prevent cracks. As a result, it has become possible to industrially and efficiently mass-produce high-quality dried wood with good yield and no cracking.

[Brief explanation of the drawing]

Figure 1 is a drying control flowchart when drying is performed while controlling the atmosphere using the AE according to the first and third inventions of the present application, and Figure 2 is a drying control flowchart in which temperature and humidity control and AE generation are performed in the drying process. Fig. 3 is a schematic diagram of the AE generation model pattern during wood heat drying treatment, Fig. 4 is a graph recording temperature changes during high temperature heat treatment in Example 1, and Fig. 5 is a graph showing the AE generation model pattern during wood heat drying treatment. This is a graph recording the number of AE events (occurrence rate) for each amplitude class of the treated material. Figure 6 is a graph recording the number of AE events (occurrence rate) for each amplitude class of the impregnated treated material of Example 1. , FIG. 7 is a graph recording the incidence of AE with an amplitude of 1 V or more in the untreated material of Example 1, and FIG. 8 is a graph recording the incidence of AE with an amplitude of 1 V or more in the impregnated material of Example 1. , FIG. 9 is a graph recording the cumulative AE energy of the untreated material of Example 1 with an amplitude of 17 or more, and FIG. 10 is a graph recording the cumulative AE energy of the impregnated material of Example 1 with an amplitude of 17 or more.
FIG. 11 is a graph recording the E energy.
AE generation model pattern and cumulative AE during high temperature heat treatment
Figure 12 is a graph recording the temperature and relative humidity changes during high-temperature heat treatment in Example 2, and Figure 13 is a graph showing the cracking limit control criteria for each amplitude class of untreated material in Example 2. These are graphs recording the number of AE events (occurrence rate). Figure 14 is a graph recording the temperature and incidence of AEs with amplitude IV or higher in the drying process in Example 2. Figure 15 is a graph recording the number of AE events (incidence rate) in the drying process in Example 2. FIG. 16 is a graph recording cumulative AE energy with an amplitude of IV or more, and shows a change in moisture content and a change in weight in the drying process in Example 2.

Claims (3)

[Claims] (1) Various processed plant materials such as logs, processed wood, and bamboo materials (
(hereinafter referred to as "wood, etc.") is impregnated with an organic impregnating agent such as oxyethers such as polyethylene glycol or methyl cellosolve, polyhydric alcohols, phenols, natural rubber or synthetic rubber, or a combination thereof, and a hydrothermal chemical reaction is performed. An AE sensor is attached to this impregnated wood, etc., and the AE generated by the wood, etc. as a signal is detected as a signal, and the signal is processed as information and the wood etc. It is characterized by predicting cracks in the wood, and based on the predicted information, using temperature and humidity as operating factors, heat treatment is performed at a temperature of 100°C or less at normal pressure while controlling the atmosphere to prevent cracks from occurring in the wood, etc. Drying method for wood, etc. (2) Wood, etc. is impregnated with organic impregnating agents such as oxyethers such as polyethylene glycol and methyl cellosolve, polyhydric alcohols, phenols, natural rubber or synthetic rubber, or a combination of these, and a hydrothermal chemical reaction (hydration 1. A method for drying wood, etc., characterized in that the material is impregnated to cause decomposition) and then heated and dried. (3) Attach an AE sensor to wood, etc., detect the AE generated by wood, etc. as a signal as the wood structure changes, distinguish the amplitude of the signal, and detect A with an amplitude above a predetermined value.
The E signal is used as a danger signal for cracking, and the cumulative A
Monitoring the number of E-events and AE incidence on-line, always identifying whether dry conditions are in early, middle, or late stages, and preset empirically established cumulative AEs at each identified treatment stage. By comparing the number of events, the standard value of AE occurrence rate, and the crack warning standard value, cracks during the treatment process are predicted, and the temperature A method for drying wood, etc., characterized in that the atmosphere is controlled by manipulating conditions and humidity conditions so that cracks do not occur in the wood, etc.