JP4825651B2 - Solid flooring heat treatment method and solid flooring - Google Patents

Description

  The present invention relates to a heat treatment method for performing dimension stabilization processing on a solid floor material used for floor heating, and a solid floor material subjected to dimension stabilization processing.

  Solid wood made from natural wood has more residual stress than other wood materials, and it is greatly bent and distorted due to moisture absorption and desorption. It is ignored when solid wood is used as a building or furniture material. Inability to go wrong may occur. Since floor materials used in floor heating tend to undergo dimensional changes due to repeated temperature changes, solid floor materials are rarely used as floor materials for floor heating.

  As a dimensional stabilization process to suppress the dimensional change of the wood material, chemical treatment of immersing the wood material in the chemical like PEG treatment, or heating the wood material to microfibril (cellulose) and matrix (hemicellulose, The lignin is subjected to a heat treatment or the like which gives a thermochemical change (thermal decomposition). For example, in Patent Document 1, a wooden material is held in a sealed state between hot plates, the wooden material is heated at high frequency in that state, and moisture in the wooden material is pressurized and steamed to stabilize the size of the wooden material. A heat treatment method for performing the chemical treatment is described. Patent Document 2 describes a heat treatment method in which dimensional stability is imparted by performing high-frequency heat treatment on a wooden material in a compressed state.

JP-A-6-238615 Japanese Patent Laid-Open No. 2001-252909

  Dimensional stability can be imparted even to a solid material by a heat treatment method that has already been proposed. However, the method described in Patent Document 1 requires that the material to be processed be held in a sealed state, and the processing apparatus is somewhat complicated as a whole. The method described in Patent Document 2 also requires an apparatus for maintaining the material to be processed in a compressed state, and the processing apparatus is complicated as a whole.

  The present invention has been made in view of the circumstances as described above, and applies a dimensional stabilization process to a solid flooring material for floor heating that is likely to undergo a dimensional change during use with a simpler apparatus. It is an object of the present invention to provide a heat treatment method that can be used, and a solid floor material that has been subjected to dimension stabilization treatment by the method.

  In order to solve the above problems, the present inventors have conducted a lot of research and experiments to irradiate solid wood with electromagnetic waves and so-called internal heating to relieve the residual stress of the solid wood. By performing the softening process, the required dimensional stability can be imparted without the need to maintain the solid flooring in a sealed state or in a compressed state during heat treatment, as previously thought. I discovered a new fact that I can. At the same time, solid materials are discolored by heating, but it is also found that by controlling the electromagnetic wave intensity and irradiation time, the required dimensional stabilization treatment can be completed without causing discoloration of the surface layer of the solid material. did.

  The present invention is based on the above knowledge applied to the dimensional stabilization treatment of a solid floor material, and the heat treatment method for a solid floor material according to the present invention irradiates the solid floor material with an electromagnetic wave to at least a part of the inner layer portion. By maintaining the temperature in the range of 170 ° C. to 250 ° C., only the inner layer portion is thermally decomposed and discolored, whereby the solid flooring is dimensionally stabilized.

  In the present invention, when the heating temperature of the inner layer part is less than 170 ° C., the solid material is not sufficiently softened and the relaxation of the residual stress does not proceed, so that sufficient dimensional stability may not be obtained. Absent. When the heating temperature of the inner layer portion exceeds 250 ° C., it is not preferable because the thermal decomposition of the wood becomes intense and the strength is reduced.

  By applying the above heat treatment to a solid floor material, it is possible to impart high dimensional stability to the solid floor material compared to the untreated one, and at the same time, the surface layer portion of the treated solid floor material. As for the color tone, the state before processing (that is, the color tone originally possessed by the solid flooring) is maintained almost as it is. Therefore, the solid flooring to which the heat treatment method according to the present invention has been applied is effectively used as a floor heating flooring that hardly undergoes a dimensional change even if moisture absorption and desorption is repeated due to repeated temperature changes. Moreover, since the color tone which a solid material has can be maintained in the surface layer part of a solid flooring, high designability can be exhibited as it is. Furthermore, since the surface layer portion is not subjected to high-temperature heat treatment that involves softening or decomposition, the bending strength of the surface layer portion can be maintained as it is, and the bending strength of the whole solid flooring is almost the same value as before the treatment. Can be maintained.

  In the method of the present invention, it is preferable that the region in which the heating temperature is maintained in the range of 170 ° C. to 250 ° C. includes the central portion of the solid floor material, whereby a more uniform dimensional stabilization process proceeds throughout the entire solid floor material. To do.

  In the present invention, an electromagnetic wave is used as a heating source. When a substance is irradiated with an electromagnetic wave, the substance is converted into heat energy inside the substance, the substance causes internal heating, and the substance is usually placed in an open space. In this case, the inner layer portion of the substance is heated to a temperature higher than that of the surface layer portion. In the present invention, the electromagnetic wave is a general term for electromagnetic waves conventionally used as high-frequency heating or microwave heating, and more specifically, a high frequency of 1 to 300 MHz, particularly preferably 13. Examples include a high frequency of 56 MHz, 27.12 MHz, 40.14 MHz, a microwave of 300 MHz to 300 GHz, more preferably a microwave of 2450 MHz.

  As described above, the wood material is generally composed of microfibrils (cellulose) and a matrix (hemicellulose, lignin), and heat decomposition causes the matrix to soften and soften. In the case where residual stress due to drying or growth remains in the material, it is released when the matrix is softened. If it is cured while maintaining a stress-free state, a material with less residual stress inside the material can be produced, and dimensional changes such as bending will be reduced even if the environment changes. Such softening varies depending on the tree species, but usually starts above about 140 ° C.

  In our experiments, solid wood such as oak and beach changes color when heated to around 170 ° C. Although this discoloration is also caused by many factors, the main chain of the cellulose is broken (thermal decomposition phenomenon), and water, carbon monoxide, carbon dioxide, etc. are released along with a decrease in the degree of polymerization (softening phenomenon) due to the bond cutting. , Carbonyl, carboxyl, hydroperoxide, etc. are generated, and it is said to be blackened or browned visually, and at higher temperatures such as 260 ° C, carbon content in carbides due to oxidative decomposition The amount suddenly increases and turns in the direction of charcoal production, reducing the strength.

  FIG. 7a shows the result of measurement of dynamic thermomechanical measurement values at oak and beach at a frequency of 10 Hz. The degree of polymerization (softening) of the beach material increases from around 180 ° C. and peaks at 210 to 230 ° C. ing. Moreover, the degree of polymerization reduction (softening) in oak increases from around 170 ° C. and peaks at 200 to 220 ° C. Moreover, FIG. 7 b shows the weight change due to thermal decomposition in oak and beach, and it can be seen that the decomposition of the beach starts at around 240 ° C. and the oak decomposes from around 230 ° C. In the present invention, the temperature of at least a part of the inner layer portion of the solid flooring is maintained in the range of 170 ° C. to 250 ° C. for the above reason, and the solid flooring is maintained in this temperature range. By doing so, discoloration occurs in the heated area and dimensional stability is imparted to the solid flooring.

  The time for maintaining the temperature of at least a part of the inner layer portion in the range of 170 ° C. to 250 ° C. varies depending on the intensity of the electromagnetic wave to be irradiated, the initial species moisture content of the tree species, the solid flooring, and the like. If the maintenance time is short, sufficient dimensional stability cannot be obtained. If the maintenance time is too long, as described above, the temperature of the inner layer portion exceeds 250 ° C., and carbonization proceeds to cause a decrease in strength of the solid flooring. Therefore, in the present invention, a longer maintenance time is set in a range in which discoloration does not occur in the surface layer portion while performing a preliminary experiment.

  In the present invention, in order to heat-treat a solid floor material by irradiating electromagnetic waves, a known electromagnetic wave heat treatment apparatus can be appropriately used. An electromagnetic wave heat treatment apparatus provided with a hot plate capable of externally heating a solid floor material to be treated can also be used.

  In the present invention, the term “inner layer portion of the solid flooring” is used to indicate all the inner layer portions of the solid flooring excluding the surface layer. In addition, the term “thermally discolored by discoloration” is used in the same meaning as used in the technical field of wood, and as described above, heat decomposition and softening of hemicellulose, cellulose, lignin, etc. are caused by heating. It refers to all the discoloration that occurs and occurs as a result of thermal decomposition.

  In addition, when solid flooring is externally heated using a hot platen etc., the solid material has low thermal conductivity, so heat is not easily transmitted to the inner layer part.In the case of a thick material, the surface layer part and the inner layer part The temperature difference is likely to occur. When at least a part of the inner layer portion is heated to a temperature of 170 ° C. to 250 ° C. by external heating to cause thermal decomposition, the surface layer portion tends to become a temperature higher than that, and the carbonization of the surface layer portion may proceed. Will appear and the discoloration will increase. On the other hand, when the surface layer portion is heated to a temperature at which discoloration due to thermal decomposition does not occur due to external heating, heating of the inner layer portion does not proceed, so that sufficient dimensional stability cannot be obtained. Such inconvenience is solved by the heat treatment method according to the present invention.

  In the method for heat treating a solid floor material according to the present invention, as a step before irradiating with electromagnetic waves, a surface layer portion of the solid floor material may be externally heated in a range of 100 ° C to 170 ° C. Although the method of external heating is arbitrary, it is practical to sandwich the solid floor material to be treated between hot plates heated to a temperature of 100 ° C. to 170 ° C. and to heat by the heat from the hot platen. The temperature of the upper and lower hot plates may be the same or different. By heating the surface layer portion of the solid floor material to a temperature of 100 ° C. to 170 ° C. in advance, the heat treatment time with the electromagnetic wave can be shortened, and the thermal decomposition of hemicellulose in the surface layer portion proceeds, and the solid floor material The dimensional stability of the is further improved. However, no discoloration occurs in the surface layer within that temperature range.

  In the heat treatment method for a solid floor material according to the present invention, the step of irradiating electromagnetic waves may be performed in a state where the surface layer portion of the solid floor material is maintained in a range of 100 ° C. to 170 ° C. by external heating. Also in this case, the temperature of the upper and lower hot plates may be the same or different. This treatment can be easily performed by using an electromagnetic wave heat treatment apparatus provided with a hot plate capable of externally heating the solid floor material to be treated. Also by this method, since the surface layer part of the solid flooring is heated to a temperature of 100 ° C. to 170 ° C., the thermal decomposition of hemicellulose proceeds and the dimensional stability of the solid flooring is further improved. However, in the temperature range, no discoloration occurs in the surface layer portion, so that the design property of the treated solid flooring does not deteriorate. Furthermore, since heat radiation generated by electromagnetic waves is suppressed, the inner layer portion can be more uniformly thermally decomposed, and the dimensional stability is further improved.

  The present invention also discloses a solid flooring produced by the above heat treatment method. That is, the solid flooring according to the present invention basically has a thermal decomposition treatment by heating, and at least a part of the inner layer portion is discolored, and the surface layer portion is not discolored due to the thermal decomposition treatment. Features. More specifically, the solid flooring for floor heating is characterized in that the pyrolysis treatment is performed by irradiating with electromagnetic waves, and heat is generated by irradiating a high frequency as electromagnetic waves, particularly a high frequency of 13.56 MHz. Solid flooring for floor heating characterized by being subjected to decomposition treatment.

  Furthermore, the present invention provides a method in which at least a part of the inner layer part undergoes thermal decomposition treatment by irradiating the solid floor material with electromagnetic waves to maintain the temperature of at least a part of the inner layer part in a range of 170 ° C. to 250 ° C. Also disclosed is a solid flooring for floor heating, characterized in that at least a part of the part is discolored and the surface layer part is not discolored due to thermal decomposition treatment.

  As explained in the above method invention, the solid floor material according to the present invention is excellent in dimensional stability, and at the same time, the surface layer retains the same color tone as the surface layer surface of the solid floor material before treatment, and has high design properties. Secured. Therefore, the solid flooring according to the present invention is particularly suitable for use as a base material for flooring for floor heating.

  According to the present invention, a solid floor material that retains the color tone of the substrate surface as it is while the residual stress is released by softening the matrix (hemicellulose, lignin) by heat treatment and thereby improving dimensional stability is obtained. It is done. The solid flooring according to the present invention is particularly preferably used as a flooring for floor heating.

  Hereinafter, the present invention will be described based on embodiments with reference to the drawings. FIG. 1 shows an example of a solid floor material before heat treatment, and FIG. 2 is a diagram for explaining the heat treatment step. Moreover, FIG. 3 has shown typically the solid flooring after heat processing completion | finish. FIG. 4 shows two examples of a state where the solid flooring shown in FIG. 3 is actually processed.

  First, as shown in FIG. 1, a solid floor material 10 of an appropriate size made of, for example, beach material is prepared. In the illustrated example, the solid floor material 10 has a rectangular shape, but the shape is arbitrary as long as the shape can irradiate electromagnetic waves as required.

  In the next step, the solid flooring 10 is heated. In the illustrated example, an electromagnetic wave heat treatment apparatus 20 having upper and lower heating plates 21 and 22 is used, and the heating plates 21 and 22 are provided with heaters 23 and 23 as external heating sources. The heating plates 21 and 22 are connected to a high frequency generation circuit (not shown), and also function as a pair of electrode plates that generate electromagnetic waves (high frequency) of a required frequency.

  The heating plates 21 and 22 are preheated to a temperature of, for example, 100 ° C. to 170 ° C. by the heater 23, and the solid flooring 10 is placed on the lower heating plate 22. The upper heating platen 21 is lowered and brought into close contact with the solid flooring 10 as shown in FIG. 2b, and kept in that state for a certain period of time. Thereby, at least the surface layer portion of the solid flooring 10 is preheated to a temperature of approximately 100 ° C. to 170 ° C. However, the thermal conductivity of wood is low and it is difficult to heat to the same temperature up to the center. This preheating step can be omitted. In the region preheated to a temperature of 100 ° C. to 170 ° C., the thermal decomposition proceeds, but since the heating temperature is low, the color does not change.

  After the solid floor material 10 is preheated as necessary, the solid floor material 10 is irradiated with a high frequency (electromagnetic wave) of 13.56 MHz, for example. During irradiation, external heating by the heater 23 may be continued, or external heating may be stopped. Due to the high frequency irradiation, the inner layer portion of the solid flooring 10 gradually increases in temperature, and when the temperature reaches a predetermined temperature within the range of 170 ° C. to 250 ° C., the amount of high frequency irradiation is reduced or the output is reduced. Thus, the temperature is not further increased, and is maintained at a predetermined temperature within a temperature range of 170 ° C. to 250 ° C. for a certain period of time. As a result, thermal decomposition proceeds, and discoloration of the heated region also proceeds. The dimensional stabilization process of the solid flooring 10 proceeds by thermal decomposition in a temperature range of 170 ° C to 250 ° C. In the meantime, the surface layer portion of the solid flooring 10 is maintained at a temperature of 100 ° C. to 170 ° C., so that it does not change color. Before the discoloration occurs in the surface layer portion of the solid flooring 10, the irradiation of electromagnetic waves is stopped. The time point at which the irradiation of electromagnetic waves is stopped is obtained experimentally in advance.

  The upper heating platen 21 is raised and the wood board 10 after heat treatment is taken out. As shown in FIG. 3, the inner layer portion of the solid floor material 10 after the heat treatment is a region 12 discolored due to thermal decomposition as indicated by the oblique lines in the figure, and the surface layer portion has the color tone of the original solid material. Remains. As shown in the following examples, the solid flooring thus heat-treated has greatly improved dimensional stability.

  FIG. 4 shows a flooring 11 in which actual processing is performed around the solid flooring 10 made as described above. In this example, the end face of the solid flooring 10 is cut off, and a male fruit 13 and a female fruit 14 are formed on the long side. By performing such processing, a portion (region) 12 discolored due to thermal decomposition appears around, but this portion is inconvenient because it is not touched by human eyes when the flooring 11 is spread on the floor base. There is no. In addition, since the color tone of the surface of the solid material remains as it is as the base material, the solid floor material has high dimensional stability and high design characteristics, especially suitable for floor heating flooring. Can be obtained.

Hereinafter, the present invention will be described with reference to examples and comparative examples.
[Example 1]
As a solid floor material of the test body, a 30 mm thick, 83 mm wide, 1840 mm long beach grid material is prepared, and it is divided in the thickness direction to test a pair of 12 mm thick x 83 mm wide x 1840 mm long. The body. About one test body, it heat-processed by irradiating the high frequency (electromagnetic wave) with a frequency of 13.56 MHz using the electromagnetic wave heat processing apparatus provided with the heating board with the heater of the form shown in FIG. The temperature at the center of the solid floor was actually measured with an optical fiber sensor.
In the heat treatment, the upper and lower hot platen temperatures were set to 100 ° C. and the test piece was sandwiched between the hot plates, and then high frequency was irradiated at a watt density of 3.7 W / cm ² . A cycle of high frequency 15 seconds irradiation, no 5 seconds irradiation was repeated for 7 minutes. The maximum temperature reached in the center was 230 ° C.

[Example 1-1]
The actual floor processing as shown in FIG. 4 was performed on the solid floor material after the heat treatment, and it was spread on a hot water mat equipped with a hot water pipe to construct an experimental hot water heating floor structure. The surface of the solid flooring that was laid down was almost the same as the background color of solid wood. After the construction, it was left in an environment of 20 ° C. and 65% RH for 1 week, and then hot water passing through the hot water mat was continued for 1100 hours. When the gap fluctuation amount at a plurality of points between the long sides of adjacent solid floor materials after 1100 hours of hot water was passed through the following equation and the average gap fluctuation amount was calculated, it was 0.50 mm.
Formula: Clearance fluctuation amount = gap amount after 1100 hours of hot water-gap amount before hot water flow

[Comparative Example 1]
Using the other specimen of the pair of specimens used in Example 1, the same solid flooring was processed without heat treatment. An experimental hot water heating floor structure was constructed using the same as in Example 1-1. After construction, hot water passing through the hot water mat was continued for 1100 hours. It was 1.17 mm when the average gap | interval fluctuation | variation amount between the long sides of the adjacent solid flooring after passing hot water for 1100 hours was measured like Example 1-1.

[Discussion]
From Example 1-1 and Comparative Example 1, it can be seen that the solid flooring subjected to the heat treatment according to the present invention has higher dimensional stability than the untreated one. In addition, the surface of the solid floor material according to the present invention has almost the same background color as that of the solid material, and high design properties can be obtained.

[Example 2]
One of the paired test bodies used in Example 1 was used, and each test body was heat-treated in the same manner as in Example 1. However, the high-frequency heating was controlled so that the maximum reached temperature at the center of the solid flooring was three types of 220 ° C, 205 ° C, and 190 ° C.
Each solid floor material after the heat treatment was subjected to actual processing having the shape shown in FIG. 5, and three types of experimental hot water heating floor structures were constructed in the same manner as in Example 1-1. In all cases, the surface of the solid flooring that had been laid out had almost the same background color as that of the solid wood.
After the construction, it was left in an environment of 20 ° C. and 65% RH for 1 week, and then hot water passing through the hot water mat was continued for 1100 hours. The amount of fluctuation of the slant gap h in FIG. 5 formed between the long sides of adjacent solid floor materials after 1100 hours of hot water is measured by the following equation at a plurality of points, and the average value of the slant gap average fluctuation amount As a result, the average fluctuation amount of the slant gap in the warm water heating floor structure constructed with a solid floor material treated at 220 ° C. is 0.13 mm, and the mean slant gap in the warm water heating floor structure constructed with a solid floor material treated at 205 ° C. The variation amount was 0.28 mm, and the average variation amount of the slant gap was 0.28 mm in the warm water heating floor structure constructed with a solid floor material treated at 190 ° C.
Diagonal gap variation = slant gap after 1100 hours of hot water-diagonal gap before hot water

[Discussion]
The solid floor material in Example 2 has a value smaller than the average gap fluctuation amount of 1.17 mm in the untreated solid floor material in Comparative Example 1, and is high in the solid floor material according to the present invention. It is shown that dimensional stability is obtained.

[Example 3]
As a solid floor material of the test body, a plurality of 30 mm thick, 83 mm wide, and 1840 mm long beach grid materials are prepared and divided in the thickness direction into a pair of 12 mm thick x 83 mm wide x 1840 mm long. It was set as the test body. One test specimen was subjected to an external heating process in the range of 100 ° C. to 170 ° C. for 300 seconds using an electromagnetic wave heating apparatus equipped with a heating plate having the heater shown in FIG. A heat treatment was performed by repeating a cycle of irradiation with a high frequency (electromagnetic wave) of 56 MHz for 15 seconds and no irradiation for 15 seconds over 5 minutes. When the temperature at the center of the solid flooring was actually measured with an optical fiber sensor, the maximum temperature reached was 205 ° C.

  The surface of the heat-treated specimen had almost the same background color as that of the solid material. The heat-treated specimens were continuously placed in the environment described in Table 1, and the bending at each time point was measured as follows to determine the maximum bending fluctuation amount. The results are shown in Table 1. Note that the maximum bending fluctuation amount in Table 1 is an average value of a plurality of curves.

ａ．曲がり量の測定：試験体の片側にガイドを当て、ガイドの材との間の隙間を測定して曲がり量とした。
ｂ．曲がり変動量：２０℃６５％で２週間放置した平衡状態を基準とし、そこからどれだけ変化したかを曲がり変動量として次式により求めた。
曲がり変動量（ｍｍ）＝各環境下での曲がり量（ｍｍ）−２０℃６５％平衡状態での曲がり量（ｍｍ）

a. Measurement of bending amount: A guide was applied to one side of the test specimen, and the gap between the guide material was measured and used as the bending amount.
b. Bending fluctuation amount: Based on the equilibrium state left at 20 ° C. and 65% for 2 weeks as a reference, the amount of change from there was determined as the bending fluctuation amount by the following equation.
Bending fluctuation amount (mm) = Bending amount under each environment (mm)-Bending amount at 20 ° C 65% equilibrium (mm)

  In addition, the amount of bending was measured at a plurality of points for each material and also measured on both sides. Then, the bending fluctuation amount was calculated for each, and the maximum value was shown in Table 1 as the maximum bending fluctuation amount (mm).

[Comparative Example 2]
Using the other test specimen of the pair of test specimens used in Example 3, the maximum bending fluctuation amount was measured in the same manner as in Example 3 without performing heat treatment. The results are shown in Table 1 as a comparative material.

[Evaluation]
As shown in Table 1, the test body (Example material) subjected to the heat treatment according to the present invention has a smaller value of the maximum bending variation even after the moisture release treatment, compared to the comparative material, It can be seen that the material has excellent dimensional stability.

[Example 4]
The solid floor material after the heat treatment treated in the same manner as in Example 1 was conditioned at 20 ° C. and 65% RH, and gradually dehumidified in the environment shown in Table 2, and the moisture content (%) in each environment. The change of was measured. The results are shown in Table 2.

  Further, the bending amount at each time point was measured in the same manner as in Example 3, and the maximum bending fluctuation amount was calculated. The result was shown as a processing material in the graph of FIG. 6 with the change of the moisture content. In addition, the moisture content in Table 2 and the maximum bending fluctuation amount in FIG. 6 are average values of a plurality.

[Comparative Example 3]
Using the other test piece of the pair of test pieces used in Example 4, the maximum bending fluctuation amount was measured in the same manner as in Example 4 without performing heat treatment. The results are shown in Table 2 as a comparative material and in FIG. 6 as a blank.

[Evaluation]
As shown in Table 2 and FIG. 6, the test piece subjected to the heat treatment according to the present invention has a smaller value of the maximum bending variation even after the moisture release treatment in this example as compared with the comparative material. It can be seen that the material has excellent dimensional stability.

The figure which shows an example of the solid flooring before heat processing. The figure for demonstrating the heat processing process. The figure which shows typically the solid flooring after heat processing completion. The figure which shows the state which gave the actual process to the solid flooring shown in FIG. The figure which shows the actual shape in Example 2. FIG. The graph which shows the change of the moisture content in Example 4 and the comparative example 3, and the maximum bending fluctuation amount. The graph for demonstrating the characteristic with respect to the heat | fever of wood.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Solid floor material, 12 ... Area discolored due to thermal decomposition, 11b ... Floor material, 13 ... Male fruit, 14 ... Female fruit, 15 ... Groove, 20 ... Electromagnetic wave heat treatment apparatus, 21 ... Upper heating board, 22 ... Lower heating panel, 23 ... Heater

Claims (10)

  A heat treatment method for a solid floor material, in which at least a part of the inner layer part is thermally decomposed by irradiating the solid floor material with electromagnetic waves and maintaining a temperature of at least a part of the inner layer part in a range of 170 ° C. to 250 ° C. The solid flooring heat treatment method, wherein the solid flooring is subjected to dimensional stabilization treatment.   The heat treatment method for a solid floor material according to claim 1, wherein the region maintained in the range of 170 ° C to 250 ° C includes a central portion of the solid floor material.   The method for heat-treating a solid floor material according to claim 1 or 2, wherein as a step before irradiating the electromagnetic wave, the solid floor material is externally heated in a range of 100 ° C to 170 ° C.   The solid floor material according to any one of claims 1 to 3, wherein the step of irradiating the electromagnetic wave is performed in a state where a surface layer portion of the solid floor material is maintained in a range of 100 ° C to 170 ° C by external heating. Heat treatment method.   The heat treatment method for a solid flooring according to any one of claims 1 to 4, wherein a high frequency of 13.56 MHz is used as the electromagnetic wave.   A solid flooring for floor heating, characterized in that at least a part of the inner layer portion is discolored as a result of thermal decomposition treatment by heating, and the surface layer portion is not discolored due to the thermal decomposition treatment.   A solid floor material for floor heating according to claim 6, wherein the floor material is pyrolyzed by irradiation with electromagnetic waves.   The solid floor material for floor heating according to claim 7, wherein the floor material is subjected to thermal decomposition treatment by irradiation with high frequency.   The solid floor material for floor heating according to claim 8, wherein the floor material is pyrolyzed by irradiating a high frequency of 13.56 MHz.   By irradiating the solid floor material with electromagnetic waves and maintaining the temperature of at least a part of the inner layer part in a range of 170 ° C. to 250 ° C., the thermal decomposition process proceeds in at least a part of the inner layer part and at least a part of the inner layer part Solid flooring for floor heating, in which the color changes and the surface layer is not discolored due to thermal decomposition.

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