JP2009172787A - Method for producing heat-treated lumber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a heat-treated lumber in which the occurrence of breaking, deformation, and warpage is prevented and which is improved in durability against decay, termite repelling properties, and safety. <P>SOLUTION: The heat-treated lumber is produced by passing in turn through the first process in which lumber having a large cross section and a water content of at least 15% selected from a log having a sectional diameter of at least 50 mm, a square bar having the minimum side in the cross section of at least 50 mm, and a board having the minimum side in the cross section is at least 50 mm, by the use of at least one heating medium selected from superheated steam, microwaves, and heating oils, is dried to make its water content 12% or below while the temperature of the lumber is kept at 50-130°C and the second process in which the lumber dried in the first process, by the use of at least one heating medium selected from superheated steam and heating oils, is heat-treated for 4-24 hours while the temperature of the lumber is kept at 180-250°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing heat-treated wood with improved decay durability, ant repellency, and safety.

  Conventionally, iron, plastics, and concrete have been used as building materials, but 1) iron is vulnerable to corrosion, so it is indispensable to paint its surface with a corrosion-resistant paint. 2) Because plastics have low weather resistance, they are considered to have a short useful life in outdoor use, and 3) concrete may have an unexpectedly short useful life due to alkali-aggregate reaction, etc. It is supposed to be. Therefore, iron, plastic, and concrete are subjected to appropriate protection treatment and appropriate maintenance and management for long-term use.

  Since wood has a higher specific strength than metal, concrete, and plastic, it has characteristics such as being easy to process, being able to fix carbon dioxide, and being able to be regenerated. It can be said that it is the only building material that can be used continuously, but because it is a biological resource, it tends to be a bait for decaying fungi and termites, and if it is not properly protected like other materials, its useful life is very high. It has the disadvantage of being short. Therefore, in the past, in order to extend the service life of wood, chemicals are injected and infiltrated into the wood by a method such as a decompression method or a pressurization method, but these methods are the most expected life of wood. Recognized worldwide as a technology to lengthen

  In the treatment of the wood, a new drug with excellent safety is currently used on a global scale, but since such a new drug is a chemical substance, it is a housing member, deck, fence, exterior material, etc. Some customers who use wood products understand the fact that chemical-treated wood has good durability, but dare avoid treated wood and use natural, highly durable tree species Is increasing. This tendency is particularly strong in Europe, and products made of larch heartwood and highly durable hardwood are used rather than drug-treated wood. In addition, acetylation treatment, furfuryl, in which components other than chemicals classified as so-called bactericides, insect repellents, and ant repellents, that is, acetic anhydride or furfuryl alcohol are injected into wood and then chemically reacted to fix Wood treatment such as chemical treatment is beginning to be commercialized. However, the method of injecting the liquid into the wood has the same problem as the conventional medicine injection, that is, the durability performance of the product is greatly affected by the difficulty of wood permeability.

Heat treated wood (see Patent Documents 1 and 2) is attracting attention by methods other than injecting these liquids into wood. This “heat-treated wood” is obtained by treating hemicellulose in wood when the wood is treated for a long time while maintaining a wood temperature much higher than the temperature range normally used for drying wood (up to 120 ° C.) at 180 to 250 ° C. Is a commercialization of the theory that the crystallization of cellulose is promoted and the crystallization of cellulose is promoted so that the wood is no longer decayed by decaying fungi. In the manufacture of such conventional heat treated wood, a heating medium such as vegetable oil, high-temperature nitrogen, and water vapor is used. Moreover, in the manufacture of such heat treated wood, not only heating the wood but also a method of blocking oxygen in order to suppress excessive carbonization of the wood is considered at the same time. The production of heat-treated wood has become full-fledged in Europe since around 2001, and has recently been about 200,000 cubic meters.
JP-A-3-162902 Japanese Patent No. 2717713

  Since wood retains a large amount of moisture in its tissue immediately after logging, when using wood as a material, the moisture content is removed by drying and the equilibrium moisture content (region, season) is the most stable in size. However, in the Kanto region, the average is 15%.) When wood is dried, it is necessary for free water that exists unevenly throughout the wood to move from inside the tissue to outside the tissue. The point at which this free water disappears from the tissue and becomes only bound water is called the fiber saturation point. Defects such as cracking, twisting, and warping occur at each part from the time when the moisture content of the wood is below the fiber saturation point. These are disadvantages that occur when the wood structure has different shrinkage rates depending on the length direction, the radial direction, and the tangential direction, so that stress is generated to eliminate strain on the structure. The technique of drying wood has been developed from an effort to maximize economic efficiency by minimizing the disadvantages that occur during such drying processes.

  In the past, small cross-section timber with a minimum side of less than 50 mm could be dried without causing cracks to a moisture content of 12% or less. For logs of 50 mm or more, it was extremely difficult and substantially impossible to dry without causing cracks.

  In the manufacture of conventional heat-treated wood, a large cross section selected from a log having a diameter of 50 mm or more in a cross section, a square member having a minimum side of 50 mm or more in a cross section, and a plate material having a minimum side of 50 mm or more in a cross section. When heat treatment is performed for a long time while maintaining the wood temperature at 180 to 250 ° C. on wood having a moisture content of 15% or more, cracking, twisting, warping, etc. occur in the obtained heat treated wood. There was a problem that could not be commercialized. Therefore, conventionally, only heat-treated wood having a relatively small cross section that does not cause cracking, twisting, warping, etc. has been put into practical use even if heat treatment is performed for a long time while maintaining the wood temperature at 180 to 250 ° C. It was. Therefore, the use of heat-treated wood having such a small cross section has been limited to deck boards, flower pots, house outer wall materials, window frames, bathtubs, wooden bathroom unit materials and the like having a cross section of 10 to 40 mm.

  The present invention aims to solve this problem.

  That is, the present invention provides a method for producing a heat-treated wood that is prevented from cracking, deforming and warping, and having improved durability against decay, ant repellency and safety even with heat-treated wood having a large cross section. It is intended to provide.

  The inventor has a moisture content of 15 having a large cross section selected from a log having a diameter of 50 mm or more in a cross section, a square member having a minimum side of 50 mm or more in a cross section, and a plate having a minimum side of 50 mm or more in a cross section. % Of wood is dried to a moisture content of 12% or less using at least one heating medium selected from superheated steam, microwave and heating oil while maintaining the wood temperature at 50-130 ° C. The heat-treated wood having a large cross section is obtained by heat-treating the obtained wood with at least one heating medium selected from the superheated steam and heating oil while maintaining the wood temperature at 180 to 250 ° C. for 4 to 24 hours. To produce heat-treated wood that is prevented from cracking, deformation and warping, and has improved anti-corrosion, ant-repellency and safety I have found that you can, and have completed the present invention.

  That is, in order to achieve the above object, the invention described in claim 1 is a log having a diameter of 50 mm or more in a cross section, a square bar having a minimum side of 50 mm or more in a cross section, and a minimum side in a cross section. The wood temperature is maintained at 50 to 130 ° C. using at least one heating medium selected from superheated steam, microwave and heating oil for wood having a water content of 15% or more having a large cross section selected from a plate material of 50 mm or more. While maintaining the wood temperature at 180 to 250 ° C. using the first step of drying to a moisture content of 12% or less and the wood dried in the first step using at least one heating medium selected from the superheated steam and heating oil And a second step of heat-treating for 4 to 24 hours in sequence.

  The invention described in claim 2 is characterized in that, in the invention described in claim 1, superheated steam is used as a heating medium in the second step.

  The invention described in claim 3 is characterized in that, in the invention described in claim 1, heating oil is used as a heating medium in the second step.

  According to the first aspect of the present invention, a log having a cross-sectional diameter of 50 mm or more, a square member having a minimum side of 50 mm or more in a cross-section, and a plate member having a minimum side of a cross-section of 50 mm or more is selected. A wood having a large cross section with a water content of 15% or more is maintained at a wood temperature of 50 to 130 ° C. using at least one heating medium selected from superheated steam, microwave and heating oil, and the water content is reduced to 12% or less. A first step of drying, and heat treatment of the wood dried in the first step for 4 to 24 hours while maintaining the wood temperature at 180 to 250 ° C. using at least one heating medium selected from the superheated steam and heating oil And the second step to prevent the occurrence of cracking, deformation and warping even with heat-treated wood having a large cross section,朽 durability can termite and safety is to provide a method of manufacturing enhanced heat treated wood.

  According to the second aspect of the present invention, since superheated steam is used as the heating medium in the second step, it is possible to heat-treat wood in an almost oxygen-free atmosphere, and furthermore, the thermal efficiency is very good. Heat-treated wood can be produced in a short time of 4 to 12 hours in a temperature range of 250 ° C.

  According to the third aspect of the present invention, since heated oil is used as the heating medium in the second step, the thermal efficiency is improved, and therefore, heat-treated wood can be produced in a short time. For example, the heat-treated wood can be produced in a short time of 4 to 12 hours in a temperature range of 200 to 250 ° C.

  The method for producing heat-treated wood according to the present invention is a large cross section selected from a log having a diameter of 50 mm or more in a cross section, a square member having a minimum side of 50 mm or more in a cross section, and a plate having a minimum side of 50 mm or more in a cross section. The wood having a water content of 15% or more having a water content is dried to a water content of 12% or less using a heating medium selected from superheated steam, microwave and heating oil while maintaining the wood temperature at 50 to 130 ° C. A first step and a second heat treatment of the wood dried in the first step for 4 to 24 hours while maintaining the wood temperature at 180 to 250 ° C. using at least one heating medium selected from the superheated steam and heating oil. And a process sequentially.

  Thus, a moisture content of 15% having a large cross section selected from a log having a cross section diameter of 50 mm or more, a square member having a minimum side section of 50 mm or more, and a plate member having a minimum side section of 50 mm or more. A first step of drying the above wood to a moisture content of 12% or less while maintaining the wood temperature at 50 to 130 ° C. using at least one heating medium selected from superheated steam, microwave and heating oil; A second step of sequentially heat-treating the wood dried in one step for 4 to 24 hours while maintaining the wood temperature at 180 to 250 ° C. using at least one heating medium selected from the superheated steam and heating oil. This prevents cracking, deformation, and warping, even for heat-treated wood with a large cross section, as well as durability against decay, ant-repellency and safety. There can be provided a method for producing enhanced heat treated wood.

  As in the present invention, when moisture containing wood (ordinary undried wood) is irradiated with microwaves under conditions of 6 to 12 kw for about 15 to 30 minutes, for example, the moisture contained in the wood tissue is 100. As a result of being heated to a temperature higher than 0 ° C. and becoming high-pressure (pressurized) steam, which is discharged to the outside of the wood, the moisture content of the wood rapidly decreases and the wood is dried. Since the water vapor generated in the tissue is confined inside the tissue, the pressure is increased, so that the wood is heated to become pressurized water vapor or high-pressure water vapor. The wood is dried at a temperature of 100 ° C. or higher generated according to the pressure.

  In the present invention, superheated steam is preferably used as the heating medium in the second step. Superheated steam here is not pressurized superheated steam that raises the temperature under pressurized conditions, but steam that is generated in a boiler is further heated at normal pressure by a heater or the like to increase the temperature. It is an epoch-making heating medium that can raise the temperature up to 1200 ° C. This product using superheated steam has recently been marketed as a cooking device to replace a microwave oven, but in the wood-related industry, machinery using superheated steam has not yet been developed and commercialized. Thus, when superheated steam is preferably used as the heating medium in the second step, water droplets are less likely to form than steam generated from a normal boiler, so the amount of heat given to the wood increases and heat treated wood can be processed in a very short time. Can be manufactured.

  Further, in the present invention, the type of heat source that secondarily heats the water vapor produced by the boiler is not limited, but an IH heater that is easily temperature-controlled by electricity is desirable. It has been reported that hemicellulose is involved as a wood component involved in the anti-corrosion effect of heat-treated wood against wood decay fungi. It is said that the significant reduction or disappearance of hemicellulose is related to the fungi-inhibiting effect of wood-rotting fungi.

  From the experiment results of the present inventor, it is directly understood that the treatment temperature and treatment time of the heat-treated wood affect the decay-preventing effect of the wood-rotting fungi. If the temperature of the second step is 200 ° C. or higher, the untreated cedar sapwood is usually 30 when the treatment is performed for 4 to 96 hours according to the thermal efficiency of the medium (unit time and amount of heat applied per unit area of wood). We know that the mass loss is 0% under the condition of mass loss due to -50% decay.

  Among the heat mediums, heated steam has the best thermal efficiency. Heated steam can produce heat-treated wood in the shortest time by the treatment at the same temperature among the superheated media of the present invention.

  In the present invention, heated oil is preferably used as the heating medium in the second step. A preferred heating oil used in the present invention is that the temperature range in which smoke is generated from the heating oil is as high as possible when heated. If possible, the fuming temperature is desirably 200 ° C. or higher. Further, it is desirable to use an oil that is maintained at a high temperature for a long time and is difficult to become a liquid having a high viscosity and no fluidity due to the influence of oxidation by oxygen in the air and components discharged from wood. Although general vegetable oils can be used, sunflower oil, rapeseed oil or oils obtained by esterifying these are desirable, although the stability against thermal oxidation and the smoke generation temperature differ depending on the type of plant used as a raw material. An industrially synthesized inert oil having excellent thermal stability can also be used. Since heated oil has the second highest thermal efficiency after superheated steam, heat-treated wood can be produced in a relatively short time even at the same temperature. According to the present invention, it is possible to produce heat-treated wood provided with sufficient anti-corrosion performance of wood-rotting fungi at 200 to 250 ° C. for 4 to 12 hours.

Example 1
A cycle in which 20 cedar squares having a large cross section of 120 mm × 120 mm × 2000 mm with an average initial moisture content of 98% were irradiated for 30 minutes using 10 KW microwaves and then transferred to a curing room and kept at 60 ° C. for 30 minutes. A first step of repeating the process once and drying to a finished average moisture content of 11.5%, and a second step of immersing the wood dried in the first step in sunflower oil and heat-treating it at a temperature of 220 ° C. for 8 hours. The heat-treated wood was obtained sequentially.

(Example 2)
Ten cedar logs having a large cross section with a diameter of 150 mm × 2000 mm having an average initial moisture content of 102% are heated at 130 ° C. for 8 hours, at 120 ° C. for 4 hours, and at 100 ° C. for 4 hours using superheated steam. A first step of heating sequentially for a time and drying to an average moisture content of 10%, and a second step of heat treating the wood dried in the first step at a temperature of 220 ° C. for 8 hours using superheated steam. After that, heat-treated wood was obtained.

(Example 3)
A first step of immersing 15 cypress logs having a large cross section of 150 mm × 2000 mm in diameter with an average initial moisture content of 87% in rapeseed oil and heating them at a temperature of 130 ° C. for 24 hours, followed by drying to an average moisture content of 8.3% Then, the wood dried in the first step was immersed in rapeseed oil and the second step of heat treating at 220 ° C. for 8 hours to obtain heat treated wood.

Example 4
5 cycles of 10 cypress squares having a large cross section of 150 mm × 150 mm × 2000 mm with an average initial moisture content of 110% were irradiated for 30 minutes using 12 KW microwaves, then transferred to the curing room and kept at 60 ° C. for 30 minutes. Repeatedly, the first step of drying to a finished average moisture content of 11.3% and the second step of heat-treating the wood dried in the first step for 12 hours at a temperature of 220 ° C. using superheated steam After that, heat-treated wood was obtained.

(Example 5)
The first step of immersing 20 larch squares having a large cross section of 120 mm × 120 mm × 2000 mm with an average initial moisture content of 87% in sunflower oil and heating them at a temperature of 130 ° C. for 24 hours, followed by drying to an average moisture content of 11% And the 2nd process of heat-treating the wood dried at the said 1st process at the temperature of 220 degreeC for 8 hours using superheated steam was obtained in order, and the heat-treated wood was obtained.

(Example 6)
15 larch logs having a large initial cross section with a diameter of 150 mm × 2000 mm with an average initial moisture content of 98%, using superheated steam for 8 hours at a temperature of 130 ° C., 4 hours at a temperature of 120 ° C., and 2 at a temperature of 100 ° C. After heating for hours and hours, the first step of irradiating with 9 KW microwave for 30 minutes to finish and drying to an average moisture content of 10%, and the wood dried in the first step at a temperature of 220 ° C. using rapeseed oil The heat-treated wood was obtained through the second step of heat-treating for 48 hours.

(Example 7)
Ten cedar logs having a large cross-section with a diameter of 150 mm × 2000 mm with an average initial moisture content of 105%, using superheated steam for 8 hours at a temperature of 130 ° C., 4 hours at a temperature of 120 ° C., and 4 at a temperature of 100 ° C. After heating for 1 hour, the first step of irradiating with 9 KW microwave for 30 minutes and drying to an average moisture content of 10.3%, and the wood dried in the first step at 220 ° C. using superheated steam The heat-treated wood was obtained through the second step of heat-treating at the temperature of 8 hours in sequence.

(Example 8)
First, 15 cypress logs having a large cross section with a diameter of 150 mm × 2000 mm having an average initial moisture content of 85% are immersed in sunflower oil, heated at a temperature of 130 ° C. for 24 hours, and finished to an average moisture content of 9.8%. The heat-treated wood was obtained through the process and the second process in which the wood dried in the first step was immersed in sunflower oil and heat-treated at a temperature of 220 ° C. for 8 hours.

Example 9
First step of immersing 15 larch logs having a large cross section with a diameter of 150 mm × 2000 mm having an average initial moisture content of 90% in rapeseed oil and heating them at a temperature of 130 ° C. for 24 hours, followed by drying to an average moisture content of 11.5% And the 2nd process of heat-treating the wood dried at the said 1st process at the temperature of 220 degreeC for 8 hours using superheated steam was obtained in order, and the heat-treated wood was obtained.

(Example 10)
Ten cedar squares having a large cross section of 150 mm × 150 mm × 2000 mm with an average initial moisture content of 95% are used at 130 ° C. for 8 hours, 120 ° C. for 4 hours and 100 ° C. using superheated steam. A first step of sequentially heating for 4 hours and finishing to an average moisture content of 11.5%; a second step of immersing the wood dried in the first step in rapeseed oil and heat-treating at 220 ° C. for 8 hours; The heat-treated wood was obtained sequentially.

(Example 11)
5 cycles of 10 cypress squares having a large cross section of 150 mm × 150 mm × 2000 mm with an average initial moisture content of 88% were irradiated for 30 minutes using 10 KW microwaves and then transferred to the curing room and kept at 60 ° C. for 30 minutes. The first step of drying to a final average moisture content of 11.3% and the second step of immersing the wood dried in the first step in sunflower oil and heat-treating at a temperature of 220 ° C. for 8 hours. The heat-treated wood was obtained sequentially.

Example 12
Five cycles of 15 larch logs having a large cross section with a diameter of 150 mm × 2000 mm with an average initial moisture content of 90% were irradiated for 30 minutes using 10 KW microwaves, then transferred to a curing room and kept at 60 ° C. for 30 minutes. Repeatedly, a first step of drying to a finished average moisture content of 10.5% and a second step of heat treating the wood dried in the first step at a temperature of 220 ° C. for 12 hours using superheated steam. Heat treated wood was obtained.

(Example 13)
15 cedar logs having a large cross section with a diameter of 150 mm × 2000 mm with an average initial moisture content of 90% are heated at 130 ° C. for 8 hours, at 120 ° C. for 4 hours, and at 100 ° C. for 2 hours using superheated steam. A first step of heating sequentially and drying to a final average moisture content of 10%, and a second step of heat treating the wood dried in the first step at a temperature of 220 ° C. for 8 hours using superheated steam. After that, heat-treated wood was obtained.

(Example 14)
Five cycles of irradiating 15 cypress logs with a large cross-section with a diameter of 150 mm × 2000 mm with an average initial moisture content of 88% using 10 KW microwave for 30 minutes and then moving to a curing room and keeping at 60 ° C. for 30 minutes Repeatedly, the first step of drying to a finished average moisture content of 9.8% and the second step of heat treating the wood dried in the first step for 4 hours at a temperature of 220 ° C. using superheated steam. Heat treated wood was obtained.

  As described above, the appearance (cracking) of the wood obtained by drying in the first step in Examples 1 to 14 was inspected. About said "crack", what exceeded 0.5 mm was determined to be a crack.

  Next, for the wood obtained in Examples 1 to 14, (1) the appearance (cracking) of the wood obtained by drying in the first step, and (2) the appearance (cracking) of the wood, 3) The cut surface of the center part of the wood was tested, and the following (4) decay durability test and (5) ant proof test were conducted.

Corrosion durability test The "corrosion durability test" was measured based on JISK1571. That is, five test materials (2 × 2 × 9 cm) were collected from all the woods that had been subjected to the heat treatment, dried at 60 ° C. for 3 days, and the mass was measured. The same number of untreated cedar sap material test materials (2 × 2 × 9 cm) were prepared for all the heat treatment test materials, and similarly dried at 60 ° C. for 3 days to measure the mass. Fix the treated test material and the untreated test material at two locations with a stapler, place the cedar sapwood (4 × 1 × 7 cm) in a 450 mL culture bottle, add 100 mL of tap water, and add the test material (untreated pair) One set) was stored, the lid was closed, steam sterilized and allowed to cool, and then inoculated with P. japonica and cultured for 3 months in a thermostat. The test material was taken out from the culture bottle after the culturing period, and extraneous matters such as excess mycelia were removed, dried at 60 ° C. for 3 days, and the mass was measured. The mass reduction rate was calculated from the difference in mass before and after the decay test.

Ant protection test The "ant protection test" was measured based on JISK1571. That is, five test materials (2 × 2 × 1 cm) were collected from all the woods that had been subjected to the heat treatment, dried at 60 ° C. for 3 days, and the mass was measured. Sea sand used in JISK1571 was uniformly spread over a container with a lid to a thickness of 1 cm, and water was sprayed. A pine sapwood having a thickness of 1 cm was placed thereon, and a test material was placed thereon. Ten untreated test materials were arranged at random with respect to 50 treated test materials. About 10,000 termites were collected from the nest and released into containers. After 3 months, the test material was removed, and the contaminants were cleaned from the test material, washed with water, dried at 60 ° C. for 3 days, and the mass was measured. The mass reduction rate was calculated from the difference in mass before and after the termite feeding damage test.

  In the test, with respect to the “crack”, a crack exceeding 0.5 mm was determined as a crack. In JISK1571, the mass reduction rate up to 3.4% is considered to be an error. Therefore, in the “rotation durability test” and the “ant-proof test”, the mass reduction rate is 3%. The following test timbers were judged acceptable.

  The test results are shown in Table 1 below.

  Next, Comparative Examples 1 to 11 will be described. In Comparative Examples 1 to 11, the heat treatment conditions in the first step are the schedule 1 (medium temperature condition) and schedule 2 (shown in the following Tables 1 to 3). Medium and high temperature conditions) and Schedule 3 (high temperature conditions).

(Comparative Example 1)
A first step of steaming 20 cedar squares having a large cross section of 120 mm × 120 mm × 2000 mm based on Schedule 1 and drying to an average moisture content of 21.5%, and heating the steam dried wood in the first step The heat treatment wood was obtained through the second step of heat treatment for 48 hours at a temperature of 220 ° C. using

(Comparative Example 2)
A first step of heating 10 cedar logs having a large cross section with a diameter of 150 mm × 2000 mm based on schedule 3 by steam heating and drying to an average moisture content of 15.5%, and superheated steam from the wood dried in the first step The heat-treated wood was obtained through the second step of heat treatment at a temperature of 220 ° C. for 8 hours.

(Comparative Example 3)
A first step of heating 15 cedar logs having a large cross section with a diameter of 150 mm × 2000 mm with steam based on Schedule 3 and drying to an average moisture content of 13.5%, and immersing the wood dried in the first step in rapeseed oil The heat-treated wood was obtained through the second step of heat-treating at a temperature of 220 ° C. for 8 hours.

(Comparative Example 4)
A first step of heating 10 cedar squares having a large cross-section of 150 mm × 150 mm × 2000 mm by steam based on Schedule 2 and drying them to an average moisture content of 12.8%, and superheated steam from the wood dried in the first step The heat-treated wood was obtained through the second step of heat-treating at a temperature of 220 ° C. for 12 hours using

(Comparative Example 5)
A first step of heating 20 larch squares having a large cross section of 120 mm × 120 mm × 2000 mm according to schedule 1 by steam heating and drying to an average moisture content of 15.8%, and superheated steam from the wood dried in the first step The heat-treated wood was obtained through the second step of heat-treating at a temperature of 220 ° C. for 12 hours using

(Comparative Example 6)
A first step of heating 15 larch logs having a large cross-section of 150 mm diameter x 2000 mm with steam based on Schedule 3 to dry to an average moisture content of 12.3%, and the wood dried in the first step to sunflower oil A heat treated wood was obtained through the second step of immersing and heat treating at 220 ° C. for 8 hours.

(Comparative Example 7)
A first step of heating 10 cedar logs having a large cross section with a diameter of 150 mm × 2000 mm with steam based on Schedule 3 and drying them to an average moisture content of 18.7%, and superheated steam from the wood dried in the first step The heat-treated wood was obtained through the second step of heat treatment at a temperature of 220 ° C. for 12 hours.

(Comparative Example 8)
A first step in which 15 cypress logs having a large cross-section of 150 mm in diameter and 2000 mm in diameter are heated by steam according to schedule 3 and dried to an average water content of 16.8%, and the wood dried in the first step is turned into sunflower oil A heat treated wood was obtained through the second step of immersing and heat treating at 220 ° C. for 8 hours.

(Comparative Example 9)
A first step of heating 10 larch logs having a large cross section with a diameter of 150 mm × 2000 mm according to schedule 3 by steam heating to an average moisture content of 12.7%, and heating the wood dried in the first step with superheated steam The heat-treated wood was obtained through the second step of heat treatment at a temperature of 220 ° C. for 12 hours.

(Comparative Example 10)
A first step of heating 10 cedar squares having a large cross section of 150 mm × 150 mm × 2000 mm with steam based on schedule 2 and drying them to an average moisture content of 12.0%, and the wood dried in the first step to sunflower oil The heat treatment wood was obtained through the second step of heat treatment at 220 ° C. for 8 hours.

(Comparative Example 11)
A first step of heating 10 cypress squares having a large cross section of 150 mm × 150 mm × 2000 mm with steam based on Schedule 2 and drying them to an average water content of 12%, and dipping the wood dried in the first step in rapeseed oil The heat treatment wood was obtained through the second step of heat treatment at 220 ° C. for 8 hours in sequence.

  As described above, the appearance (cracking) of the wood obtained by drying in the first step in Comparative Examples 1 to 11 was inspected. About said "crack", what exceeded 0.5 mm was determined to be a crack.

  Next, the wood obtained in Examples 1 to 11 was tested for (1) the appearance (cracking) of the wood obtained by drying in the first step, and (2) the appearance (cracking) of the wood ( 3) The cut surface of the central part of the wood was tested, and (4) decay durability test and (5) ant protection test were tested in the same manner as in Examples 1-11.

  The test results are shown in Table 5 below.

  As seen from Table 1, in Examples 1 to 14, a log having a cross-sectional diameter of 50 mm or more, a square member having a minimum side of 50 mm or more in the cross-section, and a plate member having a minimum side of 50 mm or more in the cross-section. The wood having a large cross section and having a water content of 15% or more has a water content of 10 while maintaining the wood temperature at 50 to 130 ° C. using at least one heating medium selected from superheated steam, microwave and heating oil. % Of the wood dried in the first step and at least one heating medium selected from the superheated steam, high-pressure steam (pressurized steam) and heated oil, the wood temperature is 180 to The second step of heat treatment for 4 to 24 hours while maintaining the temperature at 250 ° C. is sequentially processed, so that the generation of cracks is prevented and the durability against decay is improved. It can be seen that produce heat treatment timber termite resistance is improved. Moreover, in Examples 1-14, when it heat-processes for 4 to 24 hours, maintaining at 180-250 degreeC, irrespective of the kind of heating medium, it is almost that decay by a wood decay fungus has disappeared (mass reduction rate is 3%). I understand below.

  However, from Table 5, in Comparative Examples 1-14, since the steam dryer used conventionally is used, the log in which the diameter in a cross section is 120 mm or more, and the minimum side in a cross section is 120 mm or more. As a raw material in the manufacture of heat-treated wood, square wood and wood with a moisture content of 15% or more having a large cross section selected from a plate material having a minimum side of 120 mm or more in cross section are prone to cracking when dried. It turns out that it cannot be used at all.

Claims (3)

  A wood having a moisture content of 15% or more having a large cross section selected from a log having a cross section diameter of 50 mm or more, a square member having a minimum side of 50 mm or more in the cross section, and a plate member having a minimum side of 50 mm or more in the cross section. A first step of drying to a moisture content of 12% or less while maintaining the wood temperature at 50 to 130 ° C. using at least one heating medium selected from superheated steam, microwave and heating oil; and drying in the first step And a second step of sequentially heat-treating the finished wood for 4 to 24 hours while maintaining the wood temperature at 180 to 250 ° C. using at least one heating medium selected from the superheated steam and heating oil. A method for producing heat-treated wood.   The method for producing heat-treated wood according to claim 1, wherein superheated steam is used as the heating medium in the second step.   The method for producing heat-treated wood according to claim 1, wherein heated oil is used as the heating medium in the second step.