JP2016215419A - Woody board and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a woody board excellent in surface smoothness in spite of its lightness, and a method for producing the same.SOLUTION: Provided is a woody board 1 comprising: a core material layer 3 obtained by integrally adhering the first vegetable material into a planar shape with a binder; and a surface layer 5 located in the surface of the core material layer 3 and integrally adhering the second vegetable material with a binder. The first vegetable material being a core material of a bast vegetable not subjected to digestion treatment. This method includes: a step where the first vegetable material is integrated together with the binder to form the first integrated layer; a step where the second vegetable material is integrated together with a binder to form the second integrated layer; and a step where the first integrated layer and the second integrated layer are subjected to hot press together.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wooden board and a method for manufacturing the same. More specifically, the present invention relates to a wooden board formed by bonding plant materials together with a binder and a method for manufacturing the same.

  In recent years, development of wood boards that can substitute for natural wood has been promoted from the viewpoint of protecting and effectively utilizing natural resources. In such a wood board, wood materials such as thinned wood and offcuts discharged during wood processing are used as raw materials. The wood material is assembled and bonded using a binder such as a thermosetting resin to form a wood board. The following Patent Document 1 is known as a technique related to such a wood board.

JP 2008-188964 A

The wood board of Patent Document 1 is obtained by hot pressing a wood material provided with a binder. The wood board includes a core layer and a surface layer, and a wood piece is used for the core layer, while a fine and smooth surface is obtained using wood powder for the surface layer.
However, the wood board using such a piece of wood or wood powder has a problem that it becomes heavy when trying to obtain sufficient surface smoothness. This is because it is necessary to perform hot pressing to obtain surface smoothness, and the density of the wooden board is increased by the hot pressing. Naturally, the thickness of the wood board obtained is thinner at high pressure than at low pressure. For this reason, in order to obtain a wooden board having good surface smoothness and a target thickness, the amount of wood pieces and wood powder used must be increased and high press pressure must be applied. Therefore, if the wooden boards having the same thickness are compared, the wooden board having high surface smoothness becomes heavy.
However, if the pressing pressure is reduced in order to lighten the resulting wooden board, sufficient surface smoothness cannot be obtained. Thus, weight reduction and surface smoothness are contradictory, and it is difficult to achieve both of these characteristics.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wooden board that is lightweight and excellent in surface smoothness and a method for manufacturing the same.

In order to solve the above-mentioned problem, the wood board according to claim 1, the core material layer formed by laminating and bonding the first plant material in a plate shape with a binder,
A surface layer formed on the surface of the core material layer, the second plant material is assembled and bonded by a binder, and
The first plant material is a core material of a bast plant that has not been steamed,
The gist of the second vegetable material is a core material of a bast plant that has been steamed.

The wooden board according to claim 2, in the wooden board according to claim 1, the core material layer includes an outer layer located on a back side of the surface layer,
An inner layer separated from the surface layer than the outer layer, and
The gist of the invention is that the size of the first plant material constituting the outer layer is smaller than the size of the first plant material constituting the inner layer.

In order to solve the above-mentioned problem, the method for producing a wooden board according to claim 3, the first plant material, which is a core material of a bast plant that has not been steamed, is assembled together with a binder. A first laminated layer forming step of forming a layer;
A second laminated layer forming step of forming a second laminated layer by assembling the second plant material, which is a core material of the bast plant that has been steamed, together with a binder;
The hot press process of obtaining the wood board of Claim 1 by heat-pressing both the said 1st laminated layer and the said 2nd laminated layer is made into a summary.

  The method for producing a wooden board according to claim 4 is the method for producing a wooden board according to claim 3, wherein the second plant material pulverizes a steamed product obtained by steaming a core of a bast plant. This is the gist.

The wood board according to claim 1, wherein the first plant material is laminated and adhered in a plate shape with a binder, and the second plant material is gathered with the binder. And a surface layer formed by bonding. The first plant material is a core material of a bast plant that has not been steamed, and the second plant material is a core material of a bast plant that has been steamed.
By comprising in this way, it can be set as the wooden board excellent in surface smoothness while being lightweight. That is, by using a core material of a bast plant, a light wooden board can be obtained. Further, since the core material of the bast plant that has been steamed is used as the second plant material constituting the surface layer, a dense and smooth surface can be obtained.

In the woody board of claim 2, the core material layer has an outer layer located on the back surface side of the surface layer, and an inner layer separated from the surface layer rather than the outer layer. And the magnitude | size of the plant material which comprises an outer layer is made small compared with the magnitude | size of the plant material which comprises an inner layer.
By comprising in this way, it becomes the structure by which the magnitude | size of vegetable material becomes small toward the outer side in order of the inner layer of a core material layer, and the outer layer of a core material layer. Thereby, it can be made the wooden boat which was further excellent in surface smoothness while being lightweight.

  According to the method for producing a wooden board according to claim 3, it is possible to produce a wooden board that is lightweight and excellent in surface smoothness. That is, a lightweight wooden board can be manufactured by using the core material of a bast plant. Furthermore, since the core material of the bast plant that has been steamed is used as the second plant material constituting the second laminated layer, a wooden boat having a dense and smooth surface can be produced.

According to the method for producing a wooden board of claim 4, a material obtained by pulverizing a steamed product such as a core of a bast plant is used as the second vegetable material.
Such boiled bast plants have brittle cell walls and can be easily crushed. In addition, the material obtained by pulverizing the steamed product can be made smaller than the material obtained by pulverizing the bast plant that has not been steamed and then steaming. For this reason, the wood board which has a smoother surface can be manufactured by using the 2nd vegetable material obtained by grind | pulverizing after a steaming process.

The present invention will be further described in the following detailed description with reference to the drawings referred to, with reference to non-limiting examples of exemplary embodiments according to the present invention. Similar parts are shown throughout the several figures.
It is sectional drawing explaining an example of this wood board. It is sectional drawing explaining the other example of this wood board. It is a perspective view explaining the 2nd laminated layer formation process in this method. It is a perspective view explaining the 1st laminated layer formation process in this method. It is a perspective view explaining the 2nd laminated layer formation process in this method. It is a perspective view explaining the hot press process in this method. It is sectional drawing explaining manufacture of the wooden board of an Example. It is sectional drawing explaining the process following FIG. 7 about manufacture of the wooden board of an Example.

  The items shown here are for illustrative purposes and exemplary embodiments of the present invention, and are the most effective and easy-to-understand explanations of the principles and conceptual features of the present invention. It is stated for the purpose of providing what seems to be. In this respect, it is not intended to illustrate the structural details of the present invention beyond what is necessary for a fundamental understanding of the present invention. It will be clear to those skilled in the art how it is actually implemented.

The present invention will be described in detail below.
[1] Wood board The wood board (1) (see FIG. 1) of the present invention has a core layer (3) in which the first plant material is assembled and bonded in a plate shape with a binder. The 1st vegetable material used for a core material layer (3) is a core material of the bast plant which is not cooked. The core material of a bast plant is a material obtained by making the core of a bast plant or the core of a bast plant fine. Since the core material of the bast plant has a small specific gravity, its characteristics are reflected, and a core material layer (3) that is lighter than when using a woody material such as wood chips can be obtained.

Furthermore, this wooden board (1) is provided with a surface layer (5) on the surface of the core material layer (3). The surface layer (5) may be provided on only one surface of the core material layer (3), or may be provided on both the front and back surfaces.
Further, the surface layer (5) is a layer in which the second plant material is assembled and bonded with a binder. The second plant material is a core material of the bast plant that has been steamed. The core material of the bast plant subjected to the steaming process is a material obtained by making the core of the bast plant steamed or the core of the bast plant steamed.

  The core of the bast plant is a porous material and has a low specific gravity and it is difficult to obtain strength as a structural material. Furthermore, since the fiber length is short, it is difficult to function as a reinforcing material like bast fibers. For this reason, it is scarcely used, and there have been cases where it has been conventionally discarded as the remaining part of collecting bast fibers. However, with this woody board, the core of the bast plant can be used effectively by taking advantage of its low density.

  Furthermore, this wooden board (1) is usually obtained by hot pressing the assembled plant material. The smoothness of the surface of the obtained wooden board is improved as the pressing pressure during the hot pressing is increased. However, on the other hand, the density of the resulting wood board is increased. On the other hand, the density of the wood board obtained can be reduced as the pressing pressure during hot pressing is reduced. However, on the other hand, the surface smoothness of the resulting wooden board is reduced. That is, when the press pressure is increased to improve the smoothness of the surface, the obtained wooden board becomes heavier at the same thickness, and when the weight is reduced by reducing the press pressure and reducing the density of the wooden board, Surface smoothness will fall. Thus, the lightness and surface smoothness of the wooden board are in a contradictory relationship.

  On the other hand, when using the second plant material that has been steamed, compared to the case of using a plant material that has not been steamed, even with the same press pressure, the smoothness was superior. A surface can be obtained. This is because the core of the bast plant that has been steamed is made brittle and can be pulverized more easily than the plant material that has not been steamed, and the size of the pulverized product obtained is reduced. Thus, a smoother surface can be obtained when the surface layer is formed using a plant material having a smaller size.

In addition, various components such as cellulose, hemicellulose, and lignin that constitute the core of the bast plant, and components in which these components are changed by the steaming treatment, become adhesive components having thermosetting properties. For this reason, the 2nd plant material is hardened by hot press, and surface smoothness can further be improved.
That is, in the present wood board, the surface of the second plant material that has been steamed is used as a surface layer, so that the surface smoothness is high even at a low press pressure compared to the case of using the plant material that has not been steamed. Sex can be obtained. Thereby, the characteristics which the lightness and surface smoothness conflict can be made to make compatible.

Moreover, it can be set as the form provided with the outer layer (7) and the inner layer (9) in the core material layer (3) of this wooden board (1) (refer FIG. 2). Among these, an outer layer (7) is a layer arrange | positioned more outside in a core material layer (3), and is a layer located in the back surface side of a surface layer (5). Moreover, an inner layer (9) is a layer arrange | positioned more inside in a core material layer (3), and is a layer located in the back surface side of an outer layer (7). That is, the inner layer (9) is located farther from the surface layer (5) than the outer layer (7).
And when a core material layer (3) has these outer layers (7) and inner layers (9), the magnitude | size of the 1st vegetable material which comprises an outer layer (7) comprises an inner layer (9). The size is preferably smaller than the size of the first plant material. That is, it is preferable to use a plant material having a smaller size in the outer layer.
In this way, in the core material layer (3) of the wood board (1), the smoother surface is obtained in the outer layer by using the plant material having a smaller size in the outer layer. be able to. For this reason, the unevenness | corrugation of the surface of the layer located inside can be relieved by the outer layer.

  As described above, the size of the first plant material constituting the outer layer (7) may be smaller than the size of the first plant material constituting the inner layer (9). The size is not particularly limited. For example, when the first plant material constituting the inner layer (9) is on a sieve of a circular plate having a predetermined mesh, the first plant material constituting the outer layer (7) is the same. It can be used as a sieve under a circular hole plate sieve. The aperture of the circular plate sieve is preferably 0.5 to 5 mm, more preferably 0.5 to 3 mm, and particularly preferably 0.5 to 1.5 mm. Moreover, the 1st vegetable material which normally comprises an inner layer (9) is on the sieve of a 1.0 mm aperture plate. On the other hand, the first plant material constituting the outer layer (7) may be a material having a small size, but is usually under a sieve of a round plate having a mesh size of 0.1 mm.

Further, the thickness of each of the inner layer (7) and the outer layer (9) is not particularly limited, but the inner layer (9) is usually formed thicker than the outer layer (7). That is, the thickness of the inner layer (9) and _{D A,} the thickness of the outer layer (7) in the case of the _{D B,} a _D A> D _B. More specifically, in order to effectively relieve the surface of the inner layer (9) with the outer layer (7), it is preferable that 0.01 ≦ D _B / D _A <1. ≦ D _B / D _A ≦ 0.1 is more preferable, and 0.05 ≦ D _B / D _A ≦ 0.1 is particularly preferable. Furthermore, _{D B,} for example, be a _{0.1 ≦ D B (mm) ≦} 3.0.

Moreover, the core material layer (3) can include not only two layers of the outer layer (7) and the inner layer (9) but also three or more layers. Also in this case, for the reasons described above, it is preferable to use a plant material having a smaller size as the layer is located on the outer side. Further, in a case comprising two or more layers of the outer layer (7) also, the thickness of each outer layer (7) and D _B, the inner layer thickness (9) in the case of the D _A, each of the outer layer (7) However, the range of D _B / D _A can be applied as it is.

  The bast plant used for the wooden board of the present invention refers to a plant from which bast fibers can be collected. Such bast plants include herbaceous bast plants such as kenaf, hemp, jute hemp, manila hemp, sisal hemp, okra, etc. , Stalk-resistant bast plants such as rice, bamboo, sugarcane (bagasse), straw, esparto, corn, papyrus, and surplus grass. These bast plants may use only 1 type and may use 2 or more types together. Among these, herbaceous bast plants are preferable, and kenaf is more preferable. The kenaf core has a characteristic suitable for reducing the weight of the wood board, in particular, its specific gravity is small. Kenaf is an annual plant that grows very fast and has excellent carbon dioxide absorption, so it can be expected to reduce the amount of carbon dioxide in the atmosphere and effectively use forest resources.

  Although this wood board can be used as it is, since it has excellent surface smoothness, it can be used with another member (for example, a skin layer) attached to the surface. In this case, since the surface layer of the wood board used as a foundation is smooth, the attached separate member can similarly obtain a smooth appearance. Further, even when such another member is stuck using an adhesive or the like, it is difficult for the adhesive to soak into the underlying surface layer, and the loss of the adhesive can be suppressed.

[2] Wood board manufacturing method The wood board manufacturing method of the present invention includes a first laminated layer forming step, a second laminated layer forming step, and a heat pressing step.

In the first laminated layer forming step (see FIG. 4), the first vegetable material (11), which is a core material of a bast plant that has not been steamed, is collected together with a binder, and the first laminated layer (13) Is a step of forming. The first laminated layer (13) then becomes a core material layer (3) through a hot pressing process.
The form of the first plant material (11) used in this step is not particularly limited. Examples include flakes, chips, fibers, and powders. These may use only 1 type and may use 2 or more types together.

As described above, when obtaining the core material layer (3) including the outer layer (7) and the inner layer (9), in order to obtain these layers in the first laminated layer forming step, the outer layer (7) An external first assembly layer forming step for forming an external first assembly layer, and an internal first assembly layer forming step for forming an internal first assembly layer serving as an inner layer (9). it can.
Further, in this case, the size of the first plant material used in the external first laminated layer forming step is smaller than the size of the first plant material used in the internal first laminated layer forming step. preferable. Specifically, the first first plant material constituting the outer layer (7) and the first plant material constituting the inner layer (9) are directly correlated to the size of the outer first assembly. The present invention can be applied to the correlation between the sizes of the first plant material used in the layer forming step and the first plant material used in the internal first laminated layer forming step.

The binder may be any material as long as it can assemble and adhere plant materials, but is preferably a thermosetting resin. The kind of this thermosetting resin is not specifically limited. For example, organic polyisocyanate-based thermosetting resin, formaldehyde-based thermosetting resin, epoxy-based thermosetting resin, and the like can be given. Examples of the organic polyisocyanate-based thermosetting resin include diphenylmethane diisocyanate, polymethylene polyphenylene polyisocyanate, and organic polyisocyanates using these modified products. Examples of the formaldehyde-based thermosetting resin include urea resin, melamine resin, and polyhydric phenol resin using formaldehyde. These may use only 1 type and may use 2 or more types together.
In the first laminated layer forming step, in addition to the first plant material and the binder, a curing agent, a water repellent, a flame retardant, an insecticide, an antiseptic, and the like can be blended as necessary.

In the second laminated layer forming step (see FIG. 3 and FIG. 5), the second plant material (15), which is the core material of the bast plant that has been steamed, is collected together with the binder, and the second laminated layer ( 17). Then, the second laminated layer (17) becomes a surface layer (5) through a hot press process.
The core material of the bast plant used for the first plant material (11) except that the core material of the bast plant used for the second plant material (15) is steamed. The materials described above can be used as they are. However, the core material of the bast plant used for the first plant material (11) and the core material of the bast plant used for the second plant material (15) may be the same or different. Good. Moreover, as a binder utilized at this process, the material mentioned above as a binder used at the said 1st laminated layer formation process can be utilized as it is. However, the binder in the first laminated layer forming step and the binder in the second laminated layer forming step may be the same or different.

  The steaming process is a process of exposing the core of the bast plant to high-temperature steam. This steaming process is usually performed in a closed system. The exposure to water vapor is preferably performed, for example, in a pressure resistant container. Moreover, the temperature of the water vapor in the steaming treatment is not particularly limited, but is preferably 150 ° C. or higher. By setting the water vapor temperature to 150 ° C. or higher, the second vegetable material can be easily pulverized and the second vegetable material having a smaller size can be obtained compared to the case of using water vapor at a temperature lower than 150 ° C. easy. Moreover, the adhesive force of the second vegetable material can be increased. For these reasons, more excellent surface smoothness can be obtained by setting the water vapor temperature to 150 ° C. or higher. The upper limit of the water vapor temperature is not particularly limited, but is preferably 250 ° C. or lower. The water vapor temperature is more preferably 165 to 220 ° C, more preferably 170 to 200 ° C, and particularly preferably 170 to 190 ° C.

Moreover, the steam pressure at the time of performing a steaming process is not specifically limited. For example, the pressure can be 1.5 to 2.5 MPa, and preferably 1.7 to 2.0 MPa. In this range, it can be set as the 2nd vegetable material which was more excellent in adhesive force.
Furthermore, the cooking time in the cooking process (time for exposure to steam) is not particularly limited, but is usually 5 minutes or longer. By performing it for 5 minutes or more, the effect of the steaming treatment can be obtained more reliably. This cooking time is preferably 5 to 60 minutes, more preferably 7 to 40 minutes, and still more preferably 10 to 30 minutes.

Furthermore, after performing the steaming process, a water removal process for reducing the moisture content of the steamed second plant material can be performed. By removing moisture from the second plant material, the size of the second plant material can be pulverized smaller. Moreover, a hot press process can be performed more safely by performing moisture removal.
The amount of water to be removed in the water removal treatment is not particularly limited, but it is preferable to reduce the water content of the second plant material to 30% or less. By making this moisture content 30% or less, the obtained second plant material can be easily pulverized. Furthermore, the water content is preferably 10 to 30%.

Furthermore, it is preferable that the second plant material is obtained by pulverizing a steamed product obtained by steaming a core of a bast plant and / or a cut piece thereof. The second plant material can be obtained by performing a steaming treatment after previously pulverizing the plant material as a raw material. However, it is preferable that the plant material is pulverized after being steamed.
As described above, when the cooking process is performed on the plant material, the cell wall of the plant material becomes brittle and can be pulverized more easily than the plant material that has not been steamed. And the magnitude | size of the pulverized material obtained can also be made small compared with the plant material which has not been steamed. For this reason, compared with the case where the 2nd vegetable material pulverized and steamed is used, the direction which uses the 2nd vegetable material pulverized after the steaming process obtains superior surface smoothness. be able to.

  Moreover, any of the first laminated layer forming step and the second laminated layer forming step may be performed first, and can be in an appropriate order depending on the form of the wood board (1) to be obtained. . Specifically, when manufacturing the wooden board (1) having the surface layer (5) on both the front and back surfaces of the core material layer (3), as shown in FIGS. The step, the first laminated layer forming step, and the second laminated layer forming step can be performed in this order. That is, the second laminated layer forming step is performed twice, and the first laminated layer forming step is performed once, whereby the wood board (1) having the surface layer (5) on both the front and back surfaces of the core material layer (3) is obtained. Can be manufactured. Moreover, when manufacturing the wooden board (1) which has a surface layer (5) only in any one side of the front and back, after performing a 2nd laminated layer formation process, you may perform a 1st laminated layer formation process. Each step may be performed in the reverse order.

  The hot pressing step (see FIG. 6) is a step in which the first laminated layer (13) and the second laminated layer (17) are both hot pressed to obtain the wood board (1) of the present invention. In this step, the first assembly layer (13) and the second assembly layer (17) are hot-pressed in a stacked state. Thereby, the first plant material (11) in the first laminated layer (13) is glued and bonded by the binder to become the core layer (3). Further, the second plant material (15) in the second laminated layer (17) is laminated and bonded by the binder to form the surface layer (5).

Although the pressurization pressure in a hot press process is not specifically limited, It is preferable to set it as 1-10 Mpa, and it is more preferable to set it as 1-5 Mpa. Moreover, it is preferable to perform this pressurization normally for 30 seconds or more, and more preferably for 1 to 5 minutes.
Furthermore, although the heating temperature in a hot press process is not specifically limited, It is preferable that the temperature in a 2nd assembly layer (17) becomes 180 degreeC or more. By setting it as 180 degreeC or more, thermosetting components, such as a lignin contained in a 2nd vegetable material, can be functioned effectively. The heating temperature is preferably 195 to 255 ° C, more preferably 200 to 250 ° C.

  In the hot pressing step, any mold may be used, but it is preferable to use a mold having a mold release agent applied to the mold surface or a mold having a mold surface processed with a fluororesin. Thereby, it can suppress that lignin etc. which are contained in the 2nd vegetable material adhere to a metal mold | die, and can demold smoothly.

  The shape, size, thickness and the like of the wooden board (1) obtained by this method are not particularly limited. Further, its use is not particularly limited. These can be used as, for example, interior materials and exterior materials in buildings and furniture. More specifically, door cover materials, cover materials for various furniture (desks, chairs, shelves, bags, etc.), partition members, and the like can be mentioned. It can also be used as interior and exterior materials for automobiles, railway vehicles, ships and airplanes.

Hereinafter, the present invention will be described specifically by way of examples.
[1] Examples (1) First plant material preparation step A kenaf core was cut to a length of 30 mm and then cut using a knife ring flaker. The obtained kenaf core cut material was classified into a sieve top and a sieve bottom using a sieve having an opening of 1 mm.
And the thermosetting resin adhesive (binder) was spray-coated on the kenaf core on a sieve, and the 1st vegetable material (flaked shape) to which the binder was adhered was obtained.
Moreover, the thermosetting resin adhesive (binder) was spray-coated on the kenaf core under a sieve, and the powdery 1st plant material with which the binder was adhered was obtained.

(2) Second plant material preparation step Kenaf core was roughly pulverized using a pulverizer so as to have a shape smaller than about 2 mm square. Then, the obtained kenaf core pulverized product was carried into a pressure-resistant kettle, and steamed by exposing it to steam for 20 minutes while feeding steam at a temperature of 180 ° C. into the pressure-resistant kettle. Then, after stopping the feeding of steam, the inside of the pressure vessel was evacuated to reduce the moisture content of the steamed product to about 10%. The steamed product thus obtained was then pulverized using a hammer mill to obtain a pulverized steamed product having a shape smaller than about 0.5 mm square. Furthermore, a thermosetting resin adhesive (binder) was spray applied to the obtained pulverized steamed product to obtain a second plant material to which the binder was attached.

(3) Second laminated layer forming step The second plant material obtained in (2) above was dropped and sprinkled from above to form a second laminated layer 17 having a thickness of about 3 mm. (See FIG. 7).

(4) First laminated layer forming step (the outer first laminated layer 13A and the inner first laminated layer 13B)
The powdery first plant material obtained in (1) above is dropped onto the second laminated layer 17 obtained in (3) so as to be sprinkled and gathered, and the outside having a thickness of about 5 mm. A first laminated layer 13A (heat-pressed to become the outer layer 7 of the core material layer 3) was formed (see FIG. 7).
Further, the first flake-like plant material obtained in (1) above is dropped onto the outer first laminated layer 13A so as to sprinkle and gather, and the inner first laminated layer having a thickness of about 50 mm is collected. 13B (heat-pressed to become the inner layer 9 of the core material layer 3) was formed (see FIG. 7).
Next, the powdered first plant material obtained in (1) above is dropped onto the inner first laminated layer 13B so as to be sprinkled and gathered to form an outer first laminated layer having a thickness of about 5 mm. 13A (heat-pressed to become the outer layer 7 of the core material layer 3) was formed (see FIG. 7).

(5) Second laminated layer forming step On the laminate 19 (see FIG. 8) obtained up to (4) above, the second vegetable material obtained in (2) above is dropped and sprinkled. As a result, a second assembled layer 17 having a thickness of about 3 mm was formed (see FIG. 8).
In this way, a laminate 21 was obtained in which the second assembled layer 17, the outer first assembled layer 13A, the inner first assembled layer 13B, the outer first assembled layer 13A, and the second assembled layer 17 were stacked in this order ( (See FIG. 8).

(6) Hot pressing step The laminated body 21 obtained up to the above (5) is hot pressed (temperature of about 180 ° C., pressure of 3 MPa) using a hot press machine having a die whose surface is processed with fluororesin. A wood board 1 having a thickness of about 15 mm and a density of about 0.3 g / cm ³ was obtained (see FIG. 8).
This wooden board 1 includes a core material layer 3 (using uncooked plant material) and a surface layer 5 (using cooked vegetable material) located on both front and back sides of the core material layer 3. Prepare. The core material layer 3 includes an outer layer 7 and an inner layer 9. The outer layer 7 is located on the back side of the surface layer 5. The inner layer is located on the back side of the outer layer 7.

[2] Comparative Example (1) Preparation of vegetable material In the same manner as in Example (1) above, a flake-like vegetable material with a binder attached and a powdery vegetable material with a binder attached were obtained. It was.

(2) Formation of Glue Layer The powdery plant material obtained in (1) above was dropped and sprinkled to form a gluing layer A having a thickness of about 5 mm.
Further, the flake-like plant material obtained in (1) above was dropped onto the laminated layer A so as to sprinkle and gathered to form a laminated layer B having a thickness of about 65 mm.
Next, the powdered plant material obtained in (1) above was dropped onto the laminated layer B so as to be sprinkled and gathered to form a laminated layer C having a thickness of about 5 mm.

(3) Hot pressing step The laminate (assembled layer A, assembled layer B, assembled layer C) obtained up to the above (2) is heated using a hot press machine having a die whose surface is processed with a fluororesin. Pressing (temperature: about 180 ° C., pressure: 3 MPa) yielded a wood board 1 having a thickness of about 15 mm and a density of about 0.3 g / cm ³ .

[3] Effect of Example The surface roughness Ra (μm) between the wooden board 1 which is the practical product obtained in the above [1] and the wooden board 1 which is a comparative product obtained in the above [2]. Measurements were made at 10 points at intervals of 5 mm, and the results are shown in Table 1 below.

From the results shown in Table 1, the average value of Ra of the products was 5.6 μm. The variation was 0.25. On the other hand, the average value of Ra of the comparative product was 6.9 μm. The variation was 0.55.
From this result, like the comparative product, a small-sized plant material is selected from the non-steamed plant material, and the steamed first plant material is used instead of providing a surface layer using this. It can be seen that excellent smoothness is obtained when the surface layer is provided.

  The foregoing examples are for illustrative purposes only and are not to be construed as limiting the invention. Although the invention has been described with reference to exemplary embodiments, it is to be understood that the language used in the description and illustration of the invention is illustrative and exemplary rather than limiting. As detailed herein, changes may be made in its form within the scope of the appended claims without departing from the scope or spirit of the invention. Although specific structures, materials and examples have been referred to in the detailed description of the invention herein, it is not intended to limit the invention to the disclosures presented herein, but rather, the invention is claimed. It covers all functionally equivalent structures, methods and uses within the scope of

  DESCRIPTION OF SYMBOLS 1; Wood board, 3; Core material layer, 5; Surface layer, 7; Outer layer (outer layer of core material layer), 9; Inner layer (inner layer of core material layer), 11; First vegetable material, 13, 13A, 13B; 1st laminated layer, 15; 2nd plant material, 17; 2nd laminated layer, 19; laminated body, 21; laminated body.

Claims (4)

A core layer in which the first plant material is assembled and bonded in a plate shape with a binder;
A surface layer formed on the surface of the core material layer, the second plant material is assembled and bonded by a binder, and
The first plant material is a core material of a bast plant that has not been steamed,
The woody board, wherein the second plant material is a core material of a bast plant that has been steamed. In the core material layer, an outer layer located on the back side of the surface layer,
An inner layer separated from the surface layer than the outer layer, and
The woody board according to claim 1, wherein a size of the first plant material constituting the outer layer is smaller than a size of the first plant material constituting the inner layer. A first assembly layer forming step of forming a first assembly layer by assembling together with a binder a first plant material that is a core material of a bast plant that has not been steamed;
A second laminated layer forming step of forming a second laminated layer by assembling the second plant material, which is a core material of the bast plant that has been steamed, together with a binder;
A method of manufacturing a wood board, comprising: a step of hot pressing both the first and second assembly layers to obtain the wood board according to claim 1.   The said 2nd plant material is a manufacturing method of the wooden board of Claim 3 formed by grind | pulverizing the steamed material obtained by steaming the core of a bast plant.

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