JP2000052320A - Manufacture of wood panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a wood panel which shows excellent nailing properties and nail retaining strength and the minimization of warpage and twist attributed to a humidity change, by which the wood panel is manufactured at a low cost. SOLUTION: A wood fiber with 5 wt.% or less moisture content is used for forming a skin layer 3 and the wood fiber with 6-20 wt.% moisture content is used for forming a cover layer 2. In addition, a binder is applied to the wood fiber and the skin layer 13 is integrally combined together with the core layer 2 on at least one of the face sides of the core layer 2 by molding the wood fiber with the applied binder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a wood panel.
In particular, the present invention relates to a wood panel suitable for use as a gauge board of a pachinko machine.

[0002]

2. Description of the Related Art Wood panels are used for various purposes, and one of the uses is a gauge plate of a pachinko machine. Plywood is used as a wood panel used for this purpose, and as this plywood, there is beech plywood or plywood using beech and southern seawood. However, the production of these plywood is problematic due to lack of wood resources and protection of forests. Another example of the wood panel is a wood fiber board made of wood fiber, but the wood fiber board has a hard surface layer and is not good in nailing property. Other examples of the wood panel include a particle board made of small pieces of wood, and a laminated piece of wood flakes (O).
SB), but because they are heterogeneous, nails are difficult to hit straight. Acetylated MDF is expensive.

[0003] In Japanese Patent Application Laid-Open No. 10-128711, the sizes of acetylated wood fibers and / or the wood powder obtained by pulverizing the acetylated wood fibers are selected and made uniform. A wood panel is disclosed in which a binder is applied to wood fibers and / or wood powder and molded and integrated. In the case of the wood panel,
The process required for the acetylation treatment is required, and the production cost of the wood panel is high.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides nailing properties,
An object of the present invention is to provide a method of manufacturing a wood panel which has excellent nail holding power, reduces warpage and twist caused by a change in humidity, and can manufacture a wood panel at low cost.

[0005]

According to the present invention, a wood fiber having a water content of 5% by weight or less is used for forming a surface layer, and a wood fiber having a water content of 6 to 20% by weight is used for forming a core layer. Used, and adhere a binder to these wood fibers,
This is a manufacturing method in which these wood fibers to which a binder is attached are formed and the surface layer is integrated on at least one side of the core layer.
In the method for manufacturing a wood panel, it is preferable that the back sheet is integrated on at least one surface layer, and the binder is preferably a polyurethane resin.

[0006]

FIG. 1 is a sectional view showing an example of a wooden panel manufactured by the method of the present invention. The wood panel uses wood fibers having a water content of 5% by weight or less to form the surface layer 3, uses wood fibers having a water content of 6 to 20% by weight to form the core layer 2, and uses the wood material. A binder is attached to the fibers, and the wood fibers to which the binder for forming the surface layer 3 is located on both outer surfaces of the wood fibers to which the binder for forming the core layer 2 is attached. The fiber is formed and the surface layer 3 is formed on both sides of the core layer 2.
It is a wood panel manufactured by integrating the above. That is,
The wood panel comprises a core layer 2 in which wood fibers are bonded by a binder, and a surface layer 3 in which wood fibers are bonded by a binder integrated with both surfaces of the core layer 2. It is a wood panel integrated with 2.

Wood fibers for forming the surface layer 3 and the core layer 2 are produced as follows. That is, as the wood fiber, wood obtained by turning wood such as hardwood or conifer into chips with a chipper and defibrating the obtained chips is used. For fibrillation, a method of steaming with high-pressure steam at about 150 ° C. and then fibrillating with a disc refiner or the like is used. This wood fiber can be used as it is without acetylation, or it can be used after acetylation. As the wood fibers used in the present invention, powdery wood fibers obtained by crushing the wood fibers using a crusher are preferable.

The preferred wood fiber for use is diameter (thickness)
It has a length of about 2 to 300 μm and a length of about 1 to 30 mm.
Wood fibers having such a size can be obtained by passing the above-mentioned powdery wood fibers through a sieve having an opening of 500 μm. When wood fibers passed through a sieve having a mesh size exceeding 500 μm are used, it is difficult to nail nails straight into the wood panel. When substantially only wood fibers passed through a sieve having a mesh size of 500 μm are used, nails are easily straightened on the wood panel.

In the present invention, wood fibers having a water content of 5% by weight or less, preferably 0.5 to 3% by weight for forming the surface layer 3, and 6 to 20% by weight, preferably 8 to 15% for forming the core layer. Wood fibers having a moisture content of% by weight are used. Wood fibers having such a water content can be obtained by selecting drying conditions and drying the wood fibers. When the surface layer 3 is formed using wood fibers having a water content of more than 5% by weight, a rock layer is easily formed on the surface layer 3 and nailing performance is deteriorated. The bedrock layer refers to a layer in which wood fibers are dense and hard, and are hard to nail. The water content of the wood fiber is a water content determined according to Japanese Industrial Standards, JIS A5905. That is, the water content (% by weight) is (m ₁ −m ₀ ) × 100 /
m ₀ . Here, m ₁ is the mass (g) of the wood fiber sample before drying, and m ₀ is the mass of the wood fiber sample when the wood fiber sample is put into a 103 ° C. air dryer and becomes constant weight ( g).

[0010] Examples of binders for binding wood fibers include urea resins, melamine resins, phenol resins, polyurethane resins, and epoxy resins. A solvent such as acetone may be mixed with these binders. A preferred binder to be used is a polyurethane resin, in particular, an isocyanate compound having two or more isocyanate groups in one molecule, a polyether polyol having two or more hydroxyl groups in one molecule, and reacting with water in the wood fiber. The resulting polyether-based polyurethane resin is preferable because of its softness. The polyether polyol preferably has a number average molecular weight of 200 to 4000. An example of an isocyanate compound is crude diphenylmethane-4,4 '
-A diisocyanate, an example of a polyether polyol is polypropylene glycol.

When the binder is a polyether-based polyurethane resin, the solid content of the polyurethane resin is 4 to 30 parts by weight, preferably 8 to 10 parts by weight, based on 100 parts by weight of the absolute dry weight of the wood fiber. 20 parts by weight. When the amount of the binder is less than 4 parts by weight, it is difficult to make a plate, and it is difficult to obtain a wood panel having sufficient performance. 30
When the amount exceeds the weight part, the bedrock is easily formed, and it is excessive and not economical.

When the binder is a polyether-based polyurethane resin, the polyether polyol is used in an amount of 15 to 150, preferably 30 to 100 parts by weight of the isocyanate compound.
It is preferable that the ratio is 100 parts by weight. If the proportion of the polyether polyol is less than 15 parts by weight, the wood panel becomes too hard and the nailing property is not good, and if it is more than 150 parts by weight, the nailing property of the wood panel is good, The nail holding force tends to be insufficient.

A wood fiber for forming the surface layer 3 is prepared by mixing a wood fiber whose water content is adjusted to 5% by weight or less, a binder and the like, and attaching the binder to the surface of the wood fiber. In addition, the wood fiber for forming the core layer 2 is prepared by mixing the wood fiber whose water content is adjusted to 6 to 20% by weight, a binder, and the like, and attaching the binder to the surface of the wood fiber. . The mixing of the wood fiber and the binder for forming the surface layer 3 and the core layer 2 is preferably performed by a spray method. For example, a method is preferable in which wood fibers whose moisture content is adjusted are put into a rotating drum rotating at a low speed, and a binder is spray-coated on the wood fibers when the wood fibers fall naturally in the rotating drum. When the binder is a polyether-based polyurethane resin, the isocyanate compound and the polyether polyol are dissolved in a solvent in advance to form a mixed solution, and the mixed solution may be applied to wood fiber by a spray method, or the isocyanate compound and the polyether polyol may be mixed. The ether polyol may be separately dissolved in a solvent to form a mixed solution, and the mixed solution may be separately applied to the wood fiber by a spray method. When using a spray device having good uniform dispersion, dilution with a solvent is unnecessary.

The wood fibers for forming the surface layer 3 and the wood fibers for forming the core layer 2 to which the binder has adhered are then dried by removing a solvent such as acetone contained in the binder, and then formed using a forming machine. It is preferable that the foam is formed into a mat. Thereby, a mat for forming the surface layer 3 and the core layer 2 in which the binder is attached to the wood fiber is obtained.

The mat for forming the surface layer 3 is positioned on one side or both sides of the mat for forming the core layer 2, preferably on both sides, and pressed (hot-press molding) so that the surface layer 3 is formed on one or both sides of the core layer 2. A wood panel integrated by hot pressing is obtained. The mat may be pre-pressed before pressing. By this hot pressing, the wood fibers in the mat for forming the core layer 2 are bonded by the hardened binder, and the wood fibers in the mat for forming the surface layer 3 are bonded by the hardened binder. And 3 are integrated by bonding with a cured binder. When the mat for forming the surface layer 3 is positioned on both the front and back surfaces of the mat for forming the core layer 2, the surface layer 3 is integrated on both surfaces of the core layer 2 as shown in FIG.
A wood panel 1 in which warpage hardly occurs is obtained.

The hot pressing temperature is about 150 to 200 ° C., depending on the kind of the binder. Further, the ratio F / C of the used amount F (kg / m ² ) of the mat for forming the surface layer 3 to the used amount C (kg / m ² ) of the mat for forming the core layer 2 is 80/2.
It is preferably 0 to 40/60. Therefore, the thickness ratio t ₃ between the thickness t ₃ of the surface layer 3 of the wood panel and the thickness t ₂ of the core layer 2.
₃ / t ₂ is 4.0 to 0.67, preferably 3.0 to 1.
It is preferably 0. The thickness ratio t ₃ / t ₂ is 0.67
When the thickness is less than the above, it is difficult to improve the nailing property, and when the thickness ratio t ₃ / t ₂ exceeds 4.0, the nail holding force tends to decrease.

When a cell decorative sheet (not shown) having a thickness of, for example, 0.3 to 0.7 mm is affixed to one surface of the obtained wooden panel 1, the structure becomes asymmetric between the front surface and the back surface, and changes due to humidity change or the like. Warped wooden panel with cell decorative sheet,
Twisting easily occurs. This warping and twisting can be prevented by integrating the back sheet on the surface layer 3. The back sheet is placed on either the front surface or the back surface 3.
Preferably, it is integrated on the surface layer 3 on the front and back surfaces. It is preferable that the back sheet is laminated and integrated at least on the surface layer 3 on the side opposite to the surface on which the cell decorative sheet is affixed.
The backsheet-attached wood panel 10 shown in FIG. 2 is an example in which the backsheets 11 and 11 are integrated on the front and back surface layers 3 and 3. The cell decorative sheet is, for example, a sheet obtained by laminating paper on one side of a celluloid film.

Examples of the back sheet 11 include paper such as Japanese paper or nonwoven fabric such as vinylon nonwoven fabric and glass nonwoven fabric. When Japanese paper is used as the back sheet 11, the surface layer 3 and the back sheet (Japanese paper) 11 are firmly adhered to each other because the binder is easily impregnated into the Japanese paper at the time of hot-press molding. Preferred washi is a paper made of gin hull fibers such as cucumber, mitsumata, gambi and the like, and using paper thread in papermaking. Basis weight as the back sheet 11, preferably of about 20 to 200 g / m ^2, to a basis weight not be suppressed warpage is less than 20 g / m ^2, also liable strength becomes insufficient, exceed 200 g / m ² is economically Not a target.

Hereinafter, a method of manufacturing a wooden panel (hereinafter, referred to as a wooden molded board) integrated with a back sheet will be described. The wood-formed board 10 shown in FIG. 2 uses wood fibers having a water content of 5% by weight or less for forming the surface layer 3 and wood fibers having a water content of 6 to 20% by weight for forming the core layer 2. A binder is attached to these wood fibers, and a mat of wood fibers to which a binder for forming the surface layer 3 is located on both sides of the mat of wood fibers to which the binder for forming the core layer 2 is attached. Further, the backsheets 11 and 11 are positioned on both outer surfaces of the wood fiber mat to which the binder for forming the surface layer 3 is attached, and the mat and the backsheets 11 and 1 for forming the surface layer 3 and the core layer 2 are arranged.
1 can be manufactured by integrating by hot pressing. As shown in FIG. 2, this wood-formed board is laminated on both surfaces of the core layer 2 bonded by the binder in which the wood fibers are hardened, with the surface layers 3 and 3 in which the wood fibers are hardened by the binder being hardened. In addition to being integrated, the back sheet 11
Numeral 11 is laminated and integrated with the cured binder.

The total density of the wooden panel 1 and the wooden molded board 10 is 0.60 to 0.80 g / cm ³ , preferably 0.65 to 0.75 g / cm ³ .

[0021]

As described above, according to the present invention,
Since a wood fiber having a water content of 5% by weight or less is used for forming the surface layer, the surface layer of the wood panel is hardly plasticized during hot pressing, and a rock layer is hardly formed. The water content is 6 to 20% by weight.
Since the wood fibers are used for forming the core layer, the core layer tends to be dense during the hot pressing at the time of hot pressing, but it is difficult to form the bedrock layer. Therefore, according to the present invention, the nail is straightened by an automatic nailing machine excellent in nailing properties, and since the surface layer is not hard and the density of the core layer is not low, it has a nail holding force of 35 kg or more, Also, dimensional changes due to humidity changes, warpage,
A wood panel with little twist can be obtained. Therefore, the wood panel manufactured by the manufacturing method of the present invention is suitable as a gauge plate for a pachinko machine or the like.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a wooden panel according to a method of manufacturing a wooden panel of the present invention.

FIG. 2 is a cross-sectional view showing another example of a wood panel according to the method of manufacturing a wood panel of the present invention.

[Explanation of symbols]

1. Wood panel, 2. Core layer, 3. Surface layer, 10.
Wooden panel with integrated backsheet (wooden molded board), 11. Backsheet

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Murakami 10-1 Nakazawa-cho, Hamamatsu-shi, Shizuoka F-term in Yamaha Corporation (reference) 2B260 AA03 AA20 BA01 BA19 CB01 CD30 DA05 DC05 DD02 EA01 EA05 EB02 EB06 EB11 EB12 EB13 EB19 EB21

Claims (3)

[Claims] 1. A wood fiber having a water content of 5% by weight or less is used for forming a surface layer, a wood fiber having a water content of 6 to 20% by weight is used for forming a core layer, and these wood fibers are used. A method for producing a wood panel, comprising: attaching a binder to a core layer; forming a wood fiber to which the binder is attached; and integrating a surface layer on at least one side of the core layer. 2. The method for producing a wood panel according to claim 1, wherein a back sheet is integrated on at least one surface layer. 3. The method for producing a wood panel according to claim 1, wherein the binder is a polyurethane resin.