JP2012006307A - Method for controlling humidity of wood, method of manufacturing veneer, and veneer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling humidity of wood, along with a method of manufacturing veneer and the veneer, capable of controlling variations after the moisture content of the wood is adjusted in a constant range.SOLUTION: The wood humidity control method includes: a heating step of heating the wood 6 so as to have substantially uniform distribution of temperature, by supplying a high pressure steam J into a container 2 where the wood 6 is stored; a cooling step of cooling the wood 6, which is processed by the heating step, such that the temperature distribution of a surface layer section 10 is lower than the temperature of the center layer section 11; and a decompression drying step of drying the wood 6 by decompressing the interior of the container 2 storing the wood 6 where the temperature of the surface layer section 10 becomes to have the distribution of temperature lower than the temperature of the center layer section 11.

Description

  The present invention relates to a humidity control method for wood, a method for manufacturing a veneer, and a veneer.

  Conventionally, the timber after cutting is sufficiently dried before being processed into a product, so that the moisture content is adjusted to be uniform (see, for example, Patent Document 1).

  The reason why the moisture content is made close to uniform is as follows. Since the moisture content of each timber after logging is not uniform and varies, the expansion rate differs depending on the site. This is because if the processing is performed in a state where the expansion coefficient differs depending on the part, a difference in the contraction rate occurs depending on the part due to drying after the processing, and problems such as warping and cracking occur.

JP 2004-1237 A

  However, the wood dried by the method disclosed in Patent Document 1 has a low moisture content due to sufficient drying, and is hard because it contains almost no moisture. Therefore, the problem of increasing the mechanical burden during product processing occurs.

  Therefore, as a method for adjusting the moisture content uniformly without excessive drying in order to reduce the mechanical burden during product processing, boiling or wet heat treatment with high-pressure steam can be mentioned. However, according to this heat treatment with boiling or high-pressure steam, the moisture content of wood becomes too high, so that during cutting, cutting parts (cutting parts) adhere to each other and workability is reduced. There was a problem.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to adjust the moisture content of wood, which can suppress the variation after adjusting the moisture content of the wood to a certain range. It is to provide a method, a method for manufacturing a veneer, and a veneer.

  The method for conditioning moisture of a wood according to the present invention includes a heating step of heating the wood to have a substantially uniform temperature distribution by supplying high-pressure steam into a container in which the wood is accommodated, and the heating step. A cooling step of cooling the timber so that the temperature of the surface layer portion has a temperature distribution lower than the temperature of the central layer portion, and after the cooling step, the temperature of the surface layer portion is lower than the temperature of the central layer portion And a reduced-pressure drying step of drying the wood by decompressing the inside of the container in which the wood having a low temperature distribution is accommodated.

  In this wood humidity control method, the cooling step is preferably to cool the wood with cooling water.

  Moreover, the method for producing a veneer according to the present invention includes a heating step of heating the wood so as to have a substantially uniform temperature distribution by supplying high-pressure steam into a container in which the wood is accommodated, and the heating step. A cooling step of cooling the treated wood so that the temperature of the surface layer portion is lower than the temperature of the central layer portion; and after the cooling step, the temperature of the surface layer portion is the temperature of the central layer portion Pressure reducing the inside of the container in which the wood having a temperature distribution lower than this is contained, and drying the wood, slicing the wood treated by the reduced pressure drying step to a predetermined thickness, And a processing step of generating a single plate by cutting into a predetermined size.

  In addition, the veneer of the present invention is cooled so that the wood heated using high-pressure steam so as to have a substantially uniform temperature distribution has a temperature distribution in which the surface layer portion has a temperature lower than that of the central layer portion. In this state, the conditioned wood produced by drying under reduced pressure is sliced to a predetermined thickness and cut into a predetermined size.

  According to the wood moisture conditioning method, veneer manufacturing method, and veneer of the present invention, the moisture content of the wood can be adjusted to a certain range, and variations thereof can be suppressed.

It is the schematic explaining the flow of each process of one Embodiment of this invention. It is a schematic block diagram which shows the wood moisture content adjusting device of this embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows an outline of a wood moisture conditioning method of the present embodiment, and FIG. 2 shows an outline of a wood moisture content adjusting device of the present embodiment.

  The wood moisture content adjusting device of the present embodiment adjusts the moisture content of the wood 6 before machining to a desired value in the range of approximately 40 to 100%, and suppresses the variation so as to be substantially uniform. It is a device. As shown in FIG. 2, this wood moisture content adjusting device includes a pressure vessel 2 in which wood 6 is accommodated, a steam supply means 3 for supplying high-pressure steam into the pressure vessel 2, and pressurizing the inside of the pressure vessel 2. Alternatively, a pressurizing / depressurizing unit 4 for depressurizing and a cooling unit 5 for cooling the wood 6 in the pressure vessel 2 are provided. Further, the wood moisture content adjusting device includes a control device for controlling these operations of the steam supply means 3, the pressurizing / depressurizing means 4, and the cooling means 5.

  The pressure vessel 2 has an opening 21 serving as a carrying-in portion and a carrying-out portion for the wood 6, and the opening 21 is closed by a door 22 that can be opened and closed. When the door 22 is closed, the inside of the pressure vessel 2 becomes a sealed space, and the pressure inside the pressure vessel 2 can be freely adjusted by the pressurizing / depressurizing means 4. The pressure vessel 2 is connected to an air vent pipe 23 communicating with the atmosphere, and an air vent valve 24 made of an electromagnetic valve is connected to the air vent pipe 23. By opening the air vent valve 24, the pressure inside the pressure vessel 2 that has been pressurized or depressurized is returned to atmospheric pressure. The pressure vessel 2 is connected to a drain pipe 25 that communicates with an external drainage facility. A drain drain electromagnetic valve 26 that is an electromagnetic valve is connected to the drain pipe 25. The drain pipe 25 can discharge the condensed water generated when the steam is condensed, the remaining water of the cooling water 51 used as the cooling means 5, and the like.

  The pressure vessel 2 is provided with a pressure sensor 27 for measuring pressure and a temperature sensor 28 for measuring temperature, which are connected to a control device.

  The steam supply means 3 is a part for supplying high-pressure steam into the pressure vessel 2, and supplies high-temperature and high-pressure saturated water vapor into the pressure vessel 2 in this embodiment. The steam supply means 3 includes a boiler 31 that generates high-pressure saturated steam at least above atmospheric pressure, and a steam supply pipe 32 that connects the boiler 31 and the pressure vessel 2 in communication with each other. A steam supply valve 33 configured by an electromagnetic valve that closes the supply of steam from the boiler 31 is connected. While the steam supply valve 33 is open, the steam continues to be supplied to the pressure vessel 2, so that the internal pressure gradually increases.

  The pressurizing / depressurizing means 4 is for adjusting the pressure of the pressure vessel 2 to a desired pressure. The pressurizing / depressurizing means 4 has a pressure increasing device 41 composed of a pressure pump 42 for increasing the pressure inside the container 2 and a pressure reducing device 43 consisting of a vacuum pump 44 for reducing the pressure inside the container 2. Further, the pressurizing / depressurizing means 4 has a pressure regulating valve 45 that is branched and connected from a pipe on the upstream side of the decompressing device 43, and this pressure regulating valve 45 finely adjusts the pressure value of the pressure vessel 2. Make it possible.

  The cooling means 5 is for cooling the wood 6 accommodated in the pressure vessel 2. In this embodiment, the cooling means 5 is a water cooling type cooling means 5 for circulating the cooling water 51 in the pressure vessel 2. . The cooling means 5 includes a water temperature adjusting device 52 that adjusts the temperature of the tap water to generate the cooling water 51, a water supply pipe 53 that connects the water temperature adjusting device 52 and the pressure vessel 2, and cooling water in the pressure vessel 2. And a drain pipe 54 for discharging 51. A water supply electromagnetic valve 55 and a drainage electromagnetic valve 56 are connected to the water supply pipe 53 and the drainage pipe 54, respectively. The cooling means 5 has a circulation device 57 that circulates the cooling water 51 in the pressure vessel 2. As the circulation device 57, for example, an injection nozzle having a cooling water outlet facing in one direction so as to create a constant water flow in the cooling water 51 in the pressure vessel 2, an inlet, an outlet nozzle and an inlet What is provided with the circulation path which has a circulation pump while connecting is mentioned.

  The control device includes opening / closing operations of the above-described various valves (the air vent valve 24, the drain drain electromagnetic valve 26, the steam supply valve 33, the pressure adjusting valve 45, the water supply electromagnetic valve 55, the drain electromagnetic valve 56), and the pressurizing / depressurizing means 4 And the operation of the cooling means 5 are controlled. The various valves are controlled by comparing the measured values of the temperature sensor 28 and the pressure sensor 27 with the set pressure value and set temperature value set by the user, and performing necessary valve opening / closing control. Depending on the situation, valve opening / closing control is performed. The control device is constituted by a computer whose main component is a microprocessor.

  In order to adjust the moisture content of the wood 6 using the wood moisture content adjusting device having such a configuration, the following operation is performed.

  First, the wood 6 (flitch material) placed on a carriage or the like is carried into the pressure vessel 2 from the opening 21 and the door 22 is closed to close the opening 21. And after maintaining the inside of the pressure vessel 2 in a sealed state, a heating process, a cooling process, and a reduced-pressure drying process are sequentially performed.

  The heating step is a step of heating the wood 6 by supplying high-pressure steam into the pressure vessel 2 in which the wood 6 is accommodated. When the heating process is started, the control device closes the air vent valve 24 and the drain drain electromagnetic valve 26 and opens the steam supply valve 33. Then, the supply of high-pressure steam (symbol J in FIG. 1) from the boiler 31 is started in the sealed pressure vessel 2. The control device keeps the steam supply valve 33 open until the value detected by the temperature sensor 28 reaches the set temperature value set by the user, and when the temperature sensor 28 detects the set temperature value, the steam supply valve 33. Occlude. That is, the temperature in the pressure vessel 2 rises to a set temperature value (140 ° C. in the example of FIG. 1), and then the steam supply valve 33 is closed to stop the temperature rise. The pressure vessel 2 is left in this state for a certain time (for example, 2 hours). At this time, when the internal temperature decreases, the control device opens the steam supply valve 33 again to increase the temperature in the pressure vessel 2 and keep the temperature at a constant value.

  The wood 6 that has undergone the heating process is in a high water content and high temperature state, and the water content and temperature distribution are substantially uniform.

  Next, a cooling step is performed. The cooling step is a step of cooling the wood 6 processed by the heating step so that the temperature of the surface layer portion 10 has a temperature distribution lower than the temperature of the central layer portion 11. Cooling by the cooling water 51 is employed in the cooling process in the present embodiment. In the cooling process, the control device causes the cooling water 51 to be supplied into the pressure vessel 2 immediately after the heating step, and circulates the cooling water 51 in the pressure vessel 2 for a certain period of time. Specifically, the temperature of the cooling water 51 is adjusted by operating the water temperature adjusting device 52 (55 ° C. in the example of FIG. 1), and the water supply electromagnetic valve 55 is opened and the drain electromagnetic valve 56 is closed. When the cooling water 51 is supplied until all of the wood 6 is immersed, the water supply electromagnetic valve 55 is closed and the circulation device 57 is driven. At this time, the inside of the pressure vessel 2 is preferably in a high pressure state (for example, 0.3 MPa). This high-pressure state may be formed by driving the booster 41, or may hold the high-pressure state in the heating process as it is. Then, after the circulation device 57 is driven for a predetermined time, the drain electromagnetic valve 56 is opened to bring the cooling water 51 in the pressure vessel 2 to the outside before the temperature of the surface layer portion 10 of the wood 6 falls below 50 ° C. Let it drain.

  The cooling process may be one in which the cooling water 51 is not used and is simply left after the heating process, or a cooling fan is provided in the pressure vessel 2 for cooling by air circulation. May be.

  The wood 6 that has undergone the cooling process has a temperature distribution in which the temperature of the surface layer portion 10 is lower than the temperature of the central layer portion 11, the moisture content is about 100 to 120%, and is almost uniform with little variation depending on the part. Become. The temperature of the surface layer portion 10 of the wood 6 at this time is 50 ° C. or higher and 95 ° C. or lower. In addition, since the cooling water 51 discharged | emitted outside was heat-exchanged with the timber 6 after a heating process, it becomes temperature (70 degreeC in the example of FIG. 1) higher than the water temperature before cooling.

  Next, a vacuum drying step is performed. The reduced-pressure drying step is a step of drying the wood 6 by reducing the pressure in the pressure vessel 2. In this vacuum drying step, the temperature of the surface layer portion 10 of the wood 6 in which the temperature of the surface layer portion 10 is lower than the temperature of the central layer portion 11 is 50 ° C. or higher (preferably 50 ° C. or higher and 95 ° C. or lower). ) Is processed. The control device opens the air vent valve 24 in the pressure vessel 2 immediately after finishing the cooling process, and once returns the pressure in the pressure vessel 2 to atmospheric pressure. Then, the air vent valve 24 is closed again, and the vacuum pump 44 of the decompression device 43 is driven. The control device continues to drive the vacuum pump 44 until the detection value of the pressure sensor 27 reaches a set pressure value (for example, −0.08 MPa), and stops the vacuum pump 44 when the pressure sensor 27 detects the set pressure value. Let And let it stand for a fixed time (for example, 3 minutes).

  In the wood 6 that has been subjected to the vacuum drying process, the water impregnated in the cooling process evaporates preferentially from the central layer portion 11 having a higher temperature, while the surface layer portion 10 originally tends to evaporate. As a result, the water content is almost uniform with little variation (in the example of FIG. 1, about 70%). In addition, the temperature gradient generated by the cooling process has a substantially uniform temperature distribution with the passage of time (68 ° C. in the example of FIG. 1).

  After finishing the above steps, the control device opens the air vent valve 24 to return the pressure vessel 2 to the atmospheric pressure state. Thereafter, the humidity-controlled wood obtained after finishing each step can be taken out from the pressure vessel 2.

  The humidity-controlled wood thus obtained has a high moisture content of about 40 to 100%, and the moisture content varies little depending on the part. Therefore, it is possible to reduce the load on the machine during product processing, and it is also possible to reduce the deterioration of workability due to the attachment of the cut parts (cut parts). And since there is little dispersion | variation in a moisture content, even if it performs drying after a process, it will become a thing which does not produce a malfunction easily by the difference in shrinkage rate.

  The moisture-conditioned wood produced through each process goes through a post-processing process. The processing step is a step of slicing the humidity-controlled wood into a predetermined thickness and cutting it into a predetermined size to generate a single plate, which is performed by machining. In this processing step, a wood processing device that cuts wood thinly to produce a single plate of a predetermined size is used, and processing is performed by setting the humidity-controlling wood in the wood processing device. Here, as the wood processing apparatus, a known wood processing apparatus such as a wood slicer or a rotary race is used.

  Since the veneer produced | generated through the process process was produced | generated from the humidity control wood of the almost uniform moisture content with little dispersion | variation, it has the substantially uniform moisture content like the said humidity control wood. Therefore, after that, even if the veneer produced from the moisture-regulated wood is dried to a low water content of 20% or less by natural drying or artificial drying, a difference in shrinkage rate hardly occurs between the veneers. As a result, the veneer can reduce the occurrence of warpage and surface cracks.

(Example 1)
In this example, as the wood before moisture conditioning, a beech material having a moisture content of 65 to 90% and a size of 45 mm × width 120 mm × length 640 mm was used, and the above steps were performed in order. The heating process is carried out by raising the inside of the pressure vessel 2 to 140 ° C. with high-pressure steam and holding at that temperature for 2 hours. As the conditions for the cooling process, 55 ° C. cooling water 51 is used, the pressure in the pressure vessel 2 is kept at 0.3 MPa, and the circulating device 57 performs circulation cooling for 10 minutes. The conditions of the reduced pressure drying step are that after the cooling step is finished and the pressure is returned to the atmospheric pressure, the pressure is quickly reduced to -0.08 MPa and held in this state for 3 minutes.

  The wood after completion of the vacuum drying process was cut into seven equal parts, and the moisture content in each part was calculated by a total dry method. In addition, the total dry method indicates the ratio of the weight of moisture to the weight of wood in a completely dry state, and the following calculation formula is used.

   These results are shown in Table 1. In addition, the surface temperature of the wood after the cooling process in a present Example was 70 degreeC. As can be seen from Table 1, it can be seen that the moisture content is approximately uniform at around 70% in any part.

(Example 2)
In this embodiment, the cooling process was performed using cooling water 51 at 35 ° C., maintaining the pressure in the pressure vessel 2 at 0.3 MPa, and performing circulation cooling for 10 minutes by the circulation device 57. Other than that, it carried out similarly to Example 1, and implemented each process.

  These results are shown in Table 1. In addition, the surface temperature of the wood after the cooling process in a present Example was 50 degreeC. As can be seen from Table 1, it can be seen that the moisture content is substantially uniform at around 100% in any part.

(Example 3)
In this example, as the wood before humidity control, a birch material having a moisture content of 50 to 80% and a size of 45 mm in thickness, 120 mm in width, and 640 mm in length was used to sequentially perform the above steps. The heating process is carried out by raising the inside of the pressure vessel 2 to 140 ° C. with high-pressure steam and holding at that temperature for 2 hours. The condition of the cooling process is that the cooling water 51 is not used, the supply of high-pressure steam is simply stopped and left for 30 minutes. At this time, the temperature in the pressure vessel 2 is about 116 ° C. The conditions of the reduced pressure drying step are that after the cooling step is finished and the pressure is returned to the atmospheric pressure, the pressure is quickly reduced to -0.08 MPa and held in this state for 3 minutes.

  These results are shown in Table 1. As can be seen from Table 1, it can be seen that the moisture content is substantially uniform at around 50% in any part.

   As can be seen from Examples 1 to 3, by carrying out the heating process, cooling process, and reduced-pressure drying process in this order on the wood, the moisture content is high in the range of about 40 to 100% and almost uniform with little variation. Humidity-controlling wood with a high moisture content can be obtained. Moreover, it turns out that the moisture content of the moisture-conditioned wood finally obtained falls, so that the temperature of the wood at the time of starting a reduced pressure drying process (namely, after a cooling process) becomes high temperature. However, if the temperature of the wood at the start of the vacuum drying process is high, cracks are likely to occur in the wood, so the lower limit of the target moisture content of the moisture-conditioned wood finally obtained should be about 40%. Is preferred.

  In addition, since the water impregnated in the wood is less likely to evaporate than usual, it is desirable that the pressure in the reduced pressure drying step is lower than −0.06 MPa.

  In the heating process in the above embodiment, high-temperature saturated steam is used as the high-pressure steam. However, the heating process of the present invention is to heat the inside of the container after supplying the steam to bring the inside of the container into a high-temperature and high-pressure state. The present invention is not limited to the embodiment. In the cooling process in the above embodiment, the wood is cooled by water cooling. However, the cooling process of the present invention may cool the wood by air cooling, and is not limited to only water cooling.

  Moreover, it becomes possible to effectively prevent surface dry cracking of wood by using saturated steam in the heating process or adopting a water cooling system in the cooling process. For this reason, it can be said that it is preferable to use both saturated steam and water cooling, or selectively use either one for a material that is prone to surface dry cracking.

DESCRIPTION OF SYMBOLS 10 Surface layer part 11 Center layer part 2 Container 21 Opening part 22 Door 23 Air vent pipe 24 Air vent valve 25 Drain pipe 26 Drain drainage electromagnetic valve 27 Pressure sensor 28 Temperature sensor 3 Steam supply means 31 Boiler 32 Steam supply pipe 33 Steam supply valve 4 Addition Pressure / pressure reducing means 41 Pressure raising device 42 Pressure pump 43 Pressure reducing device 44 Vacuum pump 45 Pressure adjusting valve 5 Cooling means 51 Cooling water 52 Water temperature adjusting device 53 Water supply pipe 54 Drain pipe 55 Water supply electromagnetic valve 56 Drain electromagnetic valve 57 Circulating device 6 Wood

Claims (4)

A heating step of heating the wood so as to have a substantially uniform temperature distribution by supplying high-pressure steam into the container containing the wood;
A cooling step of cooling the wood treated by the heating step so that the temperature of the surface layer portion has a temperature distribution lower than the temperature of the central layer portion;
A vacuum drying step of drying the wood by decompressing the inside of the container in which the wood in which the temperature of the surface layer portion has a temperature distribution lower than the temperature of the central layer portion is stored after the cooling step. A method of conditioning moisture of wood characterized by the above.   The wood conditioning method according to claim 1, wherein the cooling step cools the wood with cooling water. A heating step of heating the wood so as to have a substantially uniform temperature distribution by supplying high-pressure steam into the container containing the wood;
A cooling step of cooling the wood treated by the heating step so that the temperature of the surface layer portion has a temperature distribution lower than the temperature of the central layer portion;
After the cooling step, the reduced pressure drying step of drying the wood by depressurizing the inside of the container containing the wood in which the temperature of the surface layer portion is lower than the temperature of the central layer portion,
A method of manufacturing a veneer comprising: a step of slicing wood treated by the reduced-pressure drying step to a predetermined thickness and cutting the wood into a predetermined size to generate a veneer. The wood heated with high-pressure steam so as to have a substantially uniform temperature distribution is dried under reduced pressure in a state where the temperature of the surface layer portion is cooled to a temperature distribution lower than the temperature of the central layer portion. A veneer formed by slicing the generated humidity-controlled wood into a predetermined thickness and cutting it into a predetermined size.

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