JPH10120747A - Woody fiber board and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a woody fiber board extremely low in formaldehyde radiation amount even in a severe serving condition without losing various strength and water resistance and to provide a process producing the same. SOLUTION: This woody fiber board consists of a phenol resin comprising formaldehyde(F) and phenol(P) in a molar ration (F/P) of 1.0-3.0 and a formaldehyde scavenger contained in all the obverse surface and rear surface layers or the inner layer or any one layer of them to give the woody fiber board excellent in water resistance and extremely low in formaldehyde radiation amount and the woody fiber board is produced by mixing woody fiber with phenol resin. In this case, the molar ratio of formaldehyde(F) to phenol(P) of the phenol resin is adjusted to 1.0-3.0, and the formaldehyde scavenger is mixed with the woody fiber of all the obverse surface and rear surface layers or the inner layer of the woody fiber board or any one layer of them before mixing with an amino resin, and then pressed and molded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wood fiberboard produced using a phenolic resin and a method for producing the same. More specifically, it is a plate-like, flake-like, fibrous, powdery wood fiber bonded to a binder and molded into a plate shape, and is a wood fiber board composed of multiple layers, and has good water resistance, and The present invention relates to a wood fiberboard that emits very little formalin from a fiberboard and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, when these wood fiber boards are bonded and formed, a formaldehyde resin such as a phenol resin is mainly used to obtain a water-resistant wood fiber board.

[0003] However, wood fiberboard using formaldehyde resin uses formaldehyde as a part of the raw material, and unreacted formaldehyde remains in the wood fiberboard when cured by heat and pressure. Formaldehyde is released by the progress of hydrolysis and condensation reaction. These formaldehyde move to the surface of the wood fiber board and are released from the board surface and side surfaces. This is the so-called formalin odor, which causes irritation and discomfort. In order to solve these problems of formaldehyde, various measures for reducing formaldehyde in resins have been studied.

However, it is difficult to achieve a good balance between the formaldehyde emission and the performance such as water resistance, and it is not perfect. In addition, a method of storing plywood in a well-ventilated place and diffusing it over time, a method of applying a compound capable of reacting with formaldehyde to the surface of the molded wood fiber board, and treating the formed fiber board in an ammonia gas chamber Although methods and the like have been proposed, the post-process is complicated and the sustainability of the formaldehyde reduction effect is insufficient.

[0005] Furthermore, a method of reducing the amount of formaldehyde emission such as a method of finishing the paint can be considered, but it is sometimes difficult in practical use, but it is a temporary measure and not a fundamental measure. Therefore, it is conceivable to use a urethane resin containing no formaldehyde at all, an aqueous vinyl urethane resin, or the like. However, it is obviously difficult to use it as a general-purpose resin in practice, and it will greatly increase the cost.

[0006]

DISCLOSURE OF THE INVENTION The present invention does not require complicated treatment of a wood fiber board, does not lose various strengths and water resistance of the wood fiber board, and can be used in a severe use environment. It is an object of the present invention to provide a wood fiber board having a very low amount of emitted formaldehyde and a method for producing the same.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve these objects, and as a result, using a phenolic resin having a specific composition as a binder in a multi-layered wood fiber board, It has been found that by mixing a scavenger which can react with formaldehyde into water, the water resistance is good and the amount of emitted formaldehyde can be controlled for a long period even under severe conditions.

That is, in the present invention, the molar ratio (F / P) of formaldehyde (F) to phenols (P) is 1.
A phenolic resin of 0 to 3.0 and a woody material having good water resistance and a very small amount of released formalin by using a formaldehyde scavenger in all or any of the front and back layers and the core layer of the wood fiberboard In a method for producing a wood fiber board by mixing a phenol resin with a fiber board and wood fiber, the molar ratio (F / P) of formaldehyde (F) to phenols (P) of the phenol resin is 1.0 to 3. 0, mixed with wood fibers, and mixed with a formaldehyde scavenger before or after mixing the amino resin with wood fibers in all or any of the front and back layers and the core layer of the wood fiber board. The present invention also relates to a method for producing a wood fiber board having good water resistance and an extremely small amount of released formalin, characterized by being pressed and molded.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The wood fibers referred to in the present invention include wood, stems of Graminaceae, coconut family and the like. In the present invention, a wood fiber is formed into a plate shape, a piece shape, a fiber shape, a powder shape, and formed into a plate shape with an adhesive. .

In the present invention, the phenolic resin is usually
An oligomer and / or polymer obtained by reacting one or more phenols such as phenol, resorcinol, cresol, xylenol, and bisphenol A with an aldehyde such as formaldehyde. The phenol resin has a molar ratio of formaldehyde to phenols (F / P) of 1.0 to 3.0. The molar ratio is 1.0
If it is less than the value, it is more advantageous for the purpose of reducing the amount of formaldehyde emission, but when it is cured as a binder, not only the curing is slow, but it is difficult to take a three-dimensional crosslinked structure after the curing reaction, and the strength and water resistance of the cured product are low. The wood fiberboard may lose its productivity, strength and water resistance. On the other hand, if it exceeds 3.0, it is unlikely that the productivity, strength and water resistance will be further improved, and the increase in the amount of formaldehyde emission tends to be a problem. The phenol resin may be a mixture of two or more phenols.

The phenolic resin may be mixed with other polymers such as polyvinyl alcohol and cellulose derivatives in order to impart various properties during the production of the phenolic resin. If necessary, a curing agent, a water-producing agent, a flame retardant, etc. , An insecticide, a preservative and the like.

The production method and properties of the phenolic resin used in the present invention are not particularly limited, and a production method generally applied may be used. Phenolic resins are
As a binder for a wood fiber board composed of multiple layers, it can be used for the front and back layers and the core layer. The phenol resin is preferable because it uses a catalyst or forms a cured product which is polymerized by heating and partially crosslinked to form a high-hardness adhesive layer because the bending strength and rigidity of the obtained wood fiber board are increased.

The scavenger capable of reacting with formaldehyde of the present invention is a substance which reacts with formaldehyde.
There is no particular limitation. In the wood fiberboard manufacturing process, those which volatilize or deteriorate and lose their reactivity with formaldehyde are not desirable because of their poor formaldehyde reducing function. Further, those having a low reaction rate with formaldehyde are not desirable. From this perspective,
It is preferable to use one or more of ammonium salts, a compound having an amino group, an amide group, or an imino group in a molecule, and / or a sulfite or a bisulfite.

Examples of the ammonium salts include ammonium nitrate, ammonium sulfate, ammonium hydrochloride, ammonium phosphate, ammonium carbonate, and ammonium acetate. Examples of the compound having an amino group, an amide group, and an imino group in the molecule include urea, thiourea, melamine,
Dicyandiamide, benzoguanamine and the like can be exemplified.
Furthermore, examples of the sulfite or bisulfite include sodium sulfite, sodium bisulfite, ammonium sulfite, and ammonium bisulfite.

These compounds can be added to the front and back layers, the innermost layer, or the wood fibers of the front and back layers and the innermost layer. The addition of the formaldehyde scavenger may be added before or after mixing the phenol. The amount of addition is preferably 5 to 40% by weight, more preferably 10 to 30% by weight, based on the solid content of the phenolic resin used as the binder for the wood fiber.

[0016]

Hereinafter, the present invention will be described in detail with reference to Examples.
The present invention is not limited to these examples. Parts and% represent parts by weight or% by weight unless otherwise specified. Example 1 A reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer was charged with 636 parts of phenol as phenol and 380 parts of paraformaldehyde (formaldehyde content of 80%) as formaldehyde. And 100 parts of water were added and reacted at a reaction temperature of 80 ° C. for 2 hours, and then cooled to obtain a phenol resin (hereinafter abbreviated as A1). For A1, the molar ratio of formaldehyde to phenol (F / P) was 1.5. The nonvolatile content was adjusted to 50%.

Next, a wood fiberboard was prepared using A1 under the following method and conditions. As a wood fiber, a lauan agent was made into a piece of wood using a flaker and dried to a moisture content of 4%. Next,
The mixture was sieved with a sieve having an opening of 1 mm, the material under the screen was used as the wood fibers for the front and back layers, and the material on the screen was used as the wood fibers for the core layer. Next,
300 parts of the prepared A1 resin, 10 parts of a 50% wax emulsion, and 50 parts of water were mixed, and the wood fibers 104 for the front and back layers were mixed.
0 parts were spray applied. The spraying rate of A1 on the absolutely dry wood fiber was 15%. 45 from wood fiber after application
0 parts were separated and used for the surface layer and the back layer. Next, 1040 parts of the core layer wood fiber and 15 parts of powdered urea were uniformly mixed to obtain a core layer wood fiber. In addition, prepared A1 resin 150
The mixture obtained by spraying 10 parts of a 50% wax emulsion and 20 parts of water was spray-coated on the wood fiber for the core layer. A1
Spray rate on the absolutely dry wood fiber was 7.5%.
The mixing ratio of the powdered urea was 20% in terms of A1 solid content. 1100 parts were collected from the wood fibers after application and used as a core layer. Next, the wood fiber for the back layer was uniformly applied in a frame of 38 cm square, and the fiber mat for the core layer and the surface layer was further sprayed and deposited.
It was pressed at a pressure of gf / cm ² for 6 minutes to obtain a wood fiber board having a thickness of 20 mm and a density of 750 kg / m ³ . Table 1 shows the physical property evaluation results.

Example 2 477 parts of phenol and 11% of 48% aqueous sodium hydroxide solution
A phenol resin was obtained in the same manner as in Example 1 except that the amount was changed to 2 parts and water to 80 parts (hereinafter abbreviated as A2). The molar ratio (F / P) of A2 was 2.0. Non-volatile content is 50%
And a wood fiber board was obtained in the same manner as in Example 1. Table 1 shows the physical property evaluation results.

Example 3 A2 is used as the phenol resin, and the wood fibers 104 for the front and back layers are used.
0 parts and 30 parts of powdered urea were uniformly mixed to obtain a wood fiber board in the same manner as in Example 1 except that the wood fiber for the front and back layers was used and the wood fiber for the core layer was not powdered urea. Table 1 shows the physical property evaluation results.

Example 4 381 parts of phenol and 90% of 48% aqueous sodium hydroxide solution
Phenolic resin was obtained in the same manner as in Example 1 except that the amount of phenolic resin was changed to 60 parts by weight (hereinafter abbreviated as A3). The molar ratio (F / P) of A3 was 2.5. Non-volatile content is 50%
And a wood fiber board was obtained in the same manner as in Example 1. Table 1 shows the physical property evaluation results.

Comparative Example 1 The procedure of Example 1 was repeated except that 15 parts of the powdered urea were omitted. Table 2 shows the physical property evaluation results.

Comparative Example 2 The procedure of Example 1 was repeated except that 15 parts of powdered urea were removed. Table 2 shows the physical property evaluation results.

Comparative Example 3 The procedure of Example 1 was repeated except that 15 parts of powdered urea were removed. Table 2 shows the physical property evaluation results.

Comparative Example 4 1059 parts of phenol and 9% of 48% aqueous sodium hydroxide solution
A phenol resin was obtained in the same manner as in Example 1 except that the amount was changed to 0 parts and water was changed to 200 parts (hereinafter abbreviated as B1). The molar ratio (F / P) of B1 was 0.9. The non-volatile content is 50
%, And a wood fiberboard was obtained in the same manner as in Example 1. Table 2 shows the physical property evaluation results.

Comparative Example 5 298 parts of phenol and 70% of 48% aqueous sodium hydroxide solution
Phenol resin was obtained in the same manner as in Example 1 except that the amount was changed to 40 parts by weight and water was changed to 40 parts (hereinafter abbreviated as B2). The molar ratio (F / P) of B2 was 3.2. Non-volatile content is 50%
And a wood fiber board was obtained in the same manner as in Example 1. Table 2 shows the physical property evaluation results.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

According to the present invention, even in extremely severe use conditions, the use of a phenolic resin binder having a specific composition and a scavenger capable of reacting with formaldehyde in a wood fiberboard, which has not been achieved by the prior art, makes it possible to obtain a water-resistant material. It has become possible to obtain a wood fiber board which has good properties and can control the amount of formaldehyde emitted for a long period of time even under severe conditions.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Nobuhiko Koto 7-1-1, Hikoshimasako-cho, Shimonoseki-shi, Yamaguchi Pref.

Claims (4)

[Claims] 1. A phenol resin having a molar ratio (F / P) of formaldehyde (F) to phenols (P) of from 1.0 to 3.0, and a total of front and back layers and a core layer of a wood fiber board. A wood fiber board which has good water resistance and a very small amount of released formalin, using a formaldehyde scavenger for one or any of the layers. 2. A wood fiber mixed with a phenolic resin,
In the method for producing a wood fiber board, a molar ratio (F / P) of formaldehyde (F) and phenols (P) of the phenol resin is adjusted to 1.0 to 3.0, mixed with wood fiber, and mixed. A formaldehyde scavenger is mixed with or before and after mixing the amino resin with the wood fibers of all or any of the front and back layer portions and the core layer portion of the wood fiber board, followed by pressing and molding. A method for producing a wood fiber board having good water resistance and an extremely small amount of released formalin. 3. The wood fiber board according to claim 2, wherein the formaldehyde scavenger comprises at least one or more of ammonium salts, compounds containing an amino group, an amide group and an imino group and / or sulfites or bisulfites. Manufacturing method. 4. The wood fiberboard produced in claim 2.