JP2006035435A - Wood drying method and wood drying equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wood drying method adaptable to the drying of wood represented, for example, by a floor heating flooring material, achieving high quality and low in cost, and wood drying equipment capable of performing this method. <P>SOLUTION: Wood, which is processed into a required dimension and has a heat-resistant coating film formed on its surface, is heated to a drying temperature or above in a drying process to evaporate and diffuse the moisture in the wood. The heat-resistant coating film is preferably a coating film made of a polyurethane resin or a coating film made of ceramic. Further, in the drying process, a drying means using a heating medium oil, which is constituted of at least one kind of oils and fats such as mineral oil, vegetable oil, animal oil and used waste oil, is desirably employed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for drying wood and a drying facility, and more particularly, to a drying method capable of obtaining wood exhibiting high durability and stability against changes in the use environment, and a drying facility for carrying out the method. Is.

Usually, various artificial drying methods employed as a method for drying wood are mainly intended to remove moisture in the wood before it is used as a building material. For example, in the case of a recently popular flooring material (flooring material), the board material processed to the required size is dried to a moisture content of about 10 to 20% or less in the drying process, and then the surface is painted with an appropriate wood paint. A coating film is formed and shipped as a product.
There is no problem in using it in a relatively small place such as home use, but when using flooring in a large area such as a gymnasium, the number of flooring used is large, so it is resistant to environmental changes in temperature and humidity. The shrinkage and expansion of wood is a problem. For example, the floor material contracts during the dry season, creating a gap between the floor materials, and the floor material expands and floats during high humidity. Further, in recent years, floor heating systems tend to gradually increase as winter heating means, but the same situation as described above also occurs in the flooring material used for this floor heating. In particular, when the water content is about 10% or more, shrinkage in the width direction at a high temperature becomes a problem, and it cannot be actually used.

  Flooring materials for floor heating are preferably about 7% or less in terms of moisture content, but with the current drying method, it is quite difficult to dry to below this moisture content and maintain this moisture content. Even if it is realized, it must be expensive. Accordingly, there has been a strong demand for the development of a drying method that can reduce the moisture content to a desired level and maintain the moisture content and supply a floor material that is inexpensive in terms of cost.

A wide variety of conventional drying methods have been proposed, but the drying method disclosed in Patent Document 1 developed by the present applicant can be said to be extremely advantageous in consideration of cost, drying time, target moisture content, and the like. . In the drying method shown in Patent Document 1, wood is immersed in a heat medium oil having no affinity for moisture and dried to a moisture content of 20% or less through a heating step, an equilibrium step, and an oil drying step. Is the content.
Patent No. 3044039 publication

However, according to the drying method according to Patent Document 1 described above, there is an advantage that it can be reached in a very short time compared to the previous drying method according to the target moisture content, but because it is directly immersed in the heat medium oil, Since oil permeates the surface of the wood after drying to a small extent, depending on the purpose of use of the wood, a cleaning treatment of the surface layer may be required. For example, when this oil drying method is applied to drying flooring materials for floor heating as described above, the moisture content should be finally reduced to 7% or less, the moisture content can be maintained after drying, and it is inexpensive in terms of cost. However, although the advantage in this respect is recognized, the above-mentioned surface cleanliness still has a problem.
The present invention has been made in consideration of the above points, and can be applied to, for example, a wood product represented by a flooring flooring material, achieves a high quality and can be produced at a low cost, and a method for drying wood. It is an object to provide a drying facility that can effectively carry out this method. In particular, when a drying method using a heat medium oil is employed, an object is to provide a drying method capable of efficiently obtaining high-quality wood while making the most of its advantages.

A method for drying wood according to the present invention for achieving the above-mentioned object is the method of heating a wood having a heat-resistant coating film formed on a surface thereof to a drying temperature or higher in a drying process, and processing the required dimensions. It is characterized by evaporating and diffusing moisture.
In the above method, the heat-resistant coating film is preferably a polyurethane resin coating film or a ceramic coating film, and these coating films have a drying temperature of wood (approximately 100 ° C. to 130 ° C.) or higher. Even if it does not change in quality, the form as the coating film can be maintained.
In the drying step, it is desirable to perform drying by immersing wood in a heat medium oil composed of one or more oils such as mineral oil, vegetable oil, animal oil, or used waste oil. .
On the other hand, the drying equipment according to the present invention comprises a plurality of wood blocks, which are processed to a required size and are clamped and fixed from the outside by sandwiching a pierced piece between woods having a heat-resistant coating film formed on the surface. It is characterized by heating the wood above the drying temperature by dipping in it.
In the above drying equipment, the heat medium oil tank is any one of a drying tank that can continuously move the wood block, an oil tank that immerses the wood block, or a cylindrical tank that enables the injection and discharge of the heat medium oil. Should be selected.

According to the method for drying wood according to the present invention, it is possible to easily obtain low-moisture wood at low cost, and to use wood with low moisture content without performing special moisture content maintenance treatment. It becomes possible to do. Therefore, according to the present invention, it is possible to provide a floor heating flooring material with low deformation (especially expansion and contraction in the width direction) and low cost, which has been impossible in the past.
Moreover, according to the drying equipment which concerns on this invention, it is possible to implement the above-mentioned method effectively and to obtain the wood of the target moisture content efficiently.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the illustrated example, drying of a flooring material is shown as a specific example.
FIG. 1 shows the basic steps of a drying method according to the present invention. First, as a flooring processing step A, a desired cross-section and length of a required size are processed from a raw wood and subjected to surface finishing. Get the flooring master. At this time, the log is dried in advance by a known drying method (appropriate artificial drying method such as natural drying or steam drying) to a moisture content that allows the required processing. The moisture content in advance is, for example, 25% for pillar materials, 20% for interior materials, and 10% for flooring materials for special floor heating. These are 20% or less, 15% or less, and 7%, respectively. It is a goal of the present invention to dry to a moisture content of: In consideration of the shrinkage of the wood when the target moisture content is reached, the width of the original plate can be reduced by about 1% when processing into the final dimensions.

The next painting step B is a step of uniformly painting the surface of the original plate that has been processed to the required dimensions. In the present invention, the paint used in this coating step is required to have a property (heat resistance and durability) that does not change at the heating temperature in the drying step described later. Since the drying temperature is about 100 ° C. to 130 ° C., the heat resistance temperature of the paint must withstand higher temperatures. Any paint is acceptable as long as this condition is met, but polyurethane resin paints with excellent wear resistance and chemical resistance, which are widely used as paints for flooring, are most preferred, and ceramic paints can also be used. is there. In addition, it is desirable to perform UV (Ultra Violet) processing after the application of the polyurethane resin paint. In the UV treatment, the coating film is cured by irradiating with ultraviolet rays, and more excellent wear resistance, flexibility, beauty, etc. are exhibited.
The coating needs to be applied evenly over the entire surface of the wood, but the coating means may be appropriately selected from known methods such as spraying, roll coater, and brush coating. After the coating is finished, the coating film is subjected to post-treatment such as hot air drying to form a desired coating film on the surface of the wood, and then sent to the next drying step.

In the next drying step C, the painted wood is heated to a temperature of 100 ° C. or higher to discharge the moisture in the wood to the target moisture content. As a drying means, a heat medium oil drying method, a steam drying method, etc. Any known method such as a vacuum (vacuum) drying method, a microwave or high-frequency heating drying method, or the like may be employed. In the present invention, the drying process using a heat medium oil immersion method, which is advantageous in terms of operation and cost, will be described, but the present invention is not limited to this.
When the wood is heated to 100 ° C or higher, the moisture in the wood becomes vapor and is discharged outside the wood, and further passes through the coating film covering the wood surface and is discharged outside. It does not enter the wood through the coating. The coating film does not change even at a temperature of 100 ° C. or higher, and vapor that is a gas molecule is allowed to pass through, but heat medium oil and water that are liquids are not allowed to pass through. When the target moisture content is reached, the drying process is completed, but since the coating film is maintained on the entire surface of the wood removed from the drying process, moisture in the air does not enter the wood, and the wood There is little deformation and the moisture content does not fluctuate.
As an example of the heating pattern in the drying step C, as disclosed in Patent Document 1, wood is immersed in a heat medium oil, and the temperature of the heat medium oil is increased to heat the wood to a drying temperature or higher. A step of temporarily stopping the temperature increase of the heat transfer medium oil near the drying temperature and maintaining the temperature at this temperature for a certain period of time, and a drying step of increasing the temperature of the heat transfer medium oil again to vaporize moisture in the wood. The following pattern can be adopted. Of course, the present invention is not limited to such a heating pattern, and any other heating pattern may be used as long as the target moisture content can be reached in a short time. A heating pattern can also be employed. What is necessary is just to select the optimal heating pattern according to conditions, such as a kind of wood, and cross-sectional size.

The heat medium oil used in the drying step C is preferably oil and fat having no affinity for water and having a high ignition point and flash point (above the drying temperature). Also, non-toxic or even very weak properties are desirable. On the premise of these conditions, the oil may be selected from mineral oil, vegetable oil, animal oil, used waste liquid, and the like. Depending on the case, a plurality of fats and oils may be mixed. As mineral oil, lubricating oil (for example, “Dyna Fresia” W-8, W-32, P-32, etc. of Idemitsu Kosan Co., Ltd.) is suitable and used as described in Patent Document 1. Used engine oil is the best waste liquid.
The wood dried to the target moisture content through the drying process C is finally cleaned in the cleaning process D by cleaning or wiping off dirt on its surface, and then shipped as a product.

Next, although the specific example of the drying equipment of this invention is demonstrated, the drying equipment of the heat medium oil immersion system is made into the Example for convenience.
FIG. 2 shows an example in which a large number of wood to be dried (painted wood) is enclosed and fixed as a single block body by a fixing pressing frame before being loaded into a drying facility. That is, a large number (in the figure, 24 in total) of timbers 1 are juxtaposed in a plurality of rows (four rows in the figure) and a plurality of rows (six rows in the figure) with the pier 2 between the upper and lower sides at regular intervals in the vertical and horizontal directions. At the same time, these are clamped and fixed from above and below by the press-clamping frame 3 to constitute one block body. These woods have a desired coating film formed on the surface by the above-described coating process. The reason for fixing with the pressing frame 3 is that when moisture is discharged from the wood after drying, the balance of moisture in the wood is broken and distortion occurs in the wood, which causes twisting, warping, and bending. In order to prevent this, the whole wood is fixed with a pressing frame. In the case of a plate material or a structural material, it is preferable to prevent the occurrence of twisting more effectively by increasing the number of piers and the number of fixing points.

FIG. 3 shows a belt-running drying facility for continuously drying a block of wood to be dried configured as described above. This method is effective for improving productivity, but can be employed when there is a sufficient space in the equipment.
In FIG. 3, 4 is a wood block formed in a block shape as shown in FIG. 2, 5 is a long drying tank, and the inside thereof is filled with a heat medium oil 6. Reference numeral 7 denotes a cleaning tank following the drying tank 5. In the illustrated example, a chain conveyor 8 is disposed at least along a line extending from the entry side of the drying tank 5 to the exit side of the washing tank 7, and the plurality of wood blocks 4 are arranged at arbitrary intervals on the chain conveyor 8. It is fixed and moved by (moves continuously or intermittently) and undergoes a drying process. The washing tank 7 is for washing the oil adhering to the coating surface during the drying process, and an appropriate solvent is used. What is necessary is just to control arbitrarily according to the kind of wood, size, etc., such as the temperature and quantity of the heat carrier oil in the drying tank 5, and the speed of a conveyor.

  FIG. 4 shows a batch-type drying facility with an oil tank, which is a system that can easily dry a certain amount of wood, although productivity is not high. In the oil tank 9 filled with the heat medium oil, a wood block 4 similar to the above is inserted and immersed, and at least one wood block is controlled while controlling the oil temperature by a heating device and a stirring device attached to the oil tank. 4. Oil drying is performed. Note that the heat medium oil may be filled after the wood block is charged into the empty oil tank 9. The upper lid of the oil tank 9 is openable and closable so that the closed state can be maintained when closed.

  FIG. 5 shows a pressure cooker type drying facility that facilitates efficient work and maintenance. One end of the cylindrical main body 10 is a lid 11 that can be opened and closed, and the main body 10 has a heating medium. Appropriate means for injecting and discharging oil are provided. In the drying operation, the lid 11 is opened and the above-described wood block 4 is carried into the main body, the lid is closed and sealed, and then a desired heat medium oil is injected into the main body to dry the painted wood oil. . Oil temperature control may be performed after injection. After the drying is finished, the oil is discharged, the lid 11 is opened, and the wood is taken out.

  The wood targeted by the present invention is particularly suitable for floor heating flooring materials, but is not limited to this, and other wood materials such as plate materials, pillar materials, beam materials, logs, log materials for other purposes. Of course, it can be applied to all.

[Conditions]
(1) Wood to be dried: Original 12 mm long x 75 mm wide x 1818 mm long, flooring flooring material used (2) Coating conditions: Wood polyurethane resin paint is sprayed on the entire surface of the original plate, Thereafter, UV treatment was performed.
(3) Drying conditions: The drying tank is an immersion tank of the type shown in FIG. 4, and the inside of the tank can be heated to 130 ° C.
(4) Heat transfer oil: “Dyna Fresia” (trade name) W-32 from Idemitsu Kosan Co., Ltd.
[Result]
For the above-mentioned original plate, the above-mentioned coating was applied to the five sheets whose moisture content before coating was changed (No. 1 to No. 5 example of the present invention), and the two original plates were not coated (No. .6, No. 7 Comparative Example), and Table 1 shows the results of measuring the weight, width, and moisture content of each plate before and after oil drying.

As shown in Table 1, in the present invention examples (Nos. 1 to 5), the weight difference is -10 g or more before and after drying. This is due to the evaporation of moisture from the wood during drying, and due to the presence of the coating film. This weight did not change thereafter. On the other hand, in the comparative examples (Nos. 6 and 7), since there is no coating film, a part of the heat medium oil saturates during drying and the weight increases. In the present invention and the comparative example, the moisture content can be lowered in both the present invention and the comparative example, and this moisture content was not changed by the presence of the coating film in the present invention and the presence of the oil film on the surface in the comparative example. For this reason, although there is no big difference also about board width before and behind drying, the thing of the comparative example was not beautiful as the surface, and was rejected as a flooring.
In addition, when it is dried to the same moisture content by other drying methods with the original plate as it is, moisture is absorbed after drying, so the plate width shrinkage exceeds 1 mm, and for floor heating It was a failure.

It is process drawing which shows the basic process of the drying method which concerns on this invention. It is the front view (a) and side view (b) of the to-be-dried wood block for charging to the drying equipment of this invention. 1 is an overall schematic diagram showing one embodiment of a drying facility according to the present invention. It is explanatory drawing which shows the other Example of the drying equipment which concerns on this invention. It is the whole schematic which shows the further another Example of the drying equipment which concerns on this invention.

Explanation of symbols

A Processing Process B Painting Process C Drying Process 1 Painted Wood 2 Crosspiece 3 Clamping Frame 4 Wood Block 5 Drying Tank 6 Heat Transfer Oil 7 Washing Tank 8 Chain Conveyor 9 Oil Tank 10 Main Body 11 Lid

Claims (5)

  A method for drying wood, comprising: heating a wood having a heat-resistant coating film on a surface thereof having a heat-resistant coating film to a drying temperature or higher in a drying step to evaporate and diffuse moisture in the wood.   2. The method for drying wood according to claim 1, wherein the heat-resistant coating film is a polyurethane resin coating film or a ceramic coating film.   The drying step is performed by immersing wood in a heat medium oil composed of one or more kinds of oils such as mineral oil, vegetable oil, animal oil or used waste oil. 3. A method for drying wood according to 1 or 2.   A plurality of wood blocks that have been processed to the required dimensions and have a heat-resistant coating film on the surface and sandwiched and fixed from the outside with a pierced timber are immersed in a heat medium oil bath to bring the wood above the drying temperature Wood drying equipment, characterized by heating to   5. The heat medium oil tank is a drying tank capable of continuously moving the wood block, an oil tank in which the wood block is immersed, or a cylindrical tank capable of injecting and discharging the heat medium oil. The drying equipment described.

Images