JPH09248807A - Manufacture of wood fiber board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for manufacture of a wood fiber board in order to manufacture easily the wood fiber board of which impact resistance is improved. SOLUTION: In a method for manufacture of a wood fiber board (MDF, HB, etc.) for which a formalin resin adhesive is used as an adhesive, that in which 5-50 pts.wt. emulsion of a polymer compound of ordinary temperature or lower Tg is added to a formalin resin is used as the adhesive. By modifying the rigid brittle formalin resin adhesive with the emulsion of a polymer compound of ordinary temperature or lower Tg, impact resistance of the manufactured wood fiber board is improved extremely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a wood fiberboard, and more particularly, to an improved wood fiberboard produced by heat-press molding defibrated plant fibers with a formalin resin adhesive. Manufacturing method.

[0002]

2. Description of the Related Art Wood fiberboards such as MDF (medium fiberboard) and HB (hardboard) mainly consist of plant fibers obtained by defibrating wood and the like, mainly formalin such as urea resin, melamine resin and phenol resin. A fiber mat is produced by using a system resin as an adhesive and heat-pressing it. Such a wood fiberboard has an appropriate weight and bending strength,
It is widely used alone or as a laminate with other wood materials such as plywood as a base material for decorative boards. However, the formalin-based resin is a thermosetting resin that is three-dimensionally cured, and the thermoset formalin-based resin has hard and brittle physical properties among synthetic resins. Therefore, the conventional wood fiberboard has a drawback that when an external force such as an impact force is applied to the fiber adhesive layer, the adhesive layer is broken, the wood fiberboard is chipped, and delamination easily occurs.

On the other hand, for the purpose of improving the bending resistance of the wood fiberboard, a thermosetting resin (for example, phenol resin) is coated on both sides of the wood fiberboard using a spreader, and then the phenol resin is By inserting the coated wood fiberboard between the upper and lower presses of the hot press and heating it, a resin impregnated layer in which the phenol resin has been impregnated and hardened is formed on the front and back surfaces of the wood fiberboard, which makes it lightweight. There is known a wood fiber board whose bending strength is strengthened as compared with that before heating (see JP-A-7-80810).

[0004]

As described above, in the wood fiberboard using formalin resin such as phenol resin as the adhesive, the adhesive layer is destroyed when external force such as impact force is applied to the fiber adhesive layer, Since the wood fiberboard is likely to be chipped or delaminated, the wood fiberboard or a composite board thereof is used as a base material, and a thin veneer or the like is adhered on the base material to manufacture a decorative board, especially in the flow direction. When the wood fiberboard or its composite board comes into contact with the guide rod or the like on the conversion line, or when other unexpected impact force is applied to the surface of the wood fiberboard, there is a drawback that the wood fiberboard is partially chipped. there were. When the chipping occurs partially, the base material is discarded as a defective product, which is one of the causes of cost increase.

When a caster test or the like is performed on a decorative board having a wood fiber board or a composite board thereof as a base material,
Alternatively, when a V groove or the like is formed on the surface of the decorative plate for the purpose of design, there is a drawback that the pressure contact portion such as the V groove portion is delaminated. Further, in the case of a flooring material or the like made of a wood fiber board as a base material, there is a possibility that the base material may be peeled off or chipped at a portion to which a local load is applied after being laid on the floor surface or the like.
For that reason, a wood fiberboard having high impact resistance has been conventionally demanded, but the fact is that an effective one has not been proposed yet.

In order to improve the bending strength of the above-mentioned wood fiber board, the one in which the front and back surfaces are impregnated with a thermosetting resin is treated in consideration of impact resistance, that is, chipping due to impact force is generated. No consideration was given,
Even when producing a decorative board using a wood base material having a wood fiberboard subjected to this kind of surface treatment as a surface layer,
The wood fiberboard may be partially chipped due to the impact force received on the production line.

Therefore, an object of the present invention is to provide a manufacturing method capable of easily manufacturing a wood fiberboard which has high impact resistance and does not cause chipping or delamination even when an impact force is applied. It is in.

[0008]

[Means for Solving the Problems] The inventors of the present invention have conducted many experiments and studies in order to obtain a wood fiberboard which eliminates the above disadvantages of the wood fiberboard produced by using a formalin-based resin adhesive. As a result, Tg was added to the formalin resin adhesive.
It has been found that the above object of the present invention can be achieved by adding an appropriate amount of an emulsion of a soft polymer compound having a (glass transition point) below room temperature to modify a hard and brittle formalin resin adhesive. Then, the present invention was completed.

That is, according to the present invention, in the method for producing a wood fiber board in which defibrated plant fibers are heat-pressed using a formalin-based resin adhesive, as the adhesive,
The gist is to use a polymer compound emulsion having a Tg of not higher than room temperature added to a formalin resin.
As the defibrated plant fiber according to the present invention, any defibrated plant fiber conventionally used in the production of wood fiberboard can be optionally used.Other than hardwood fiber and softwood fiber, plants other than wood such as bagasse can be used. Fiber etc. are mentioned.

Examples of the formalin-based resin adhesive include urea resin adhesive, urea melamine resin adhesive, phenol resin adhesive, urea adhesive modified with guanamines, urea melamine resin adhesive modified with guanamines, and alkylphenol modification. It may be like a phenol resin adhesive and is not particularly limited.

The Tg of a polymer compound emulsion added to a formalin-based resin adhesive is room temperature (20 to 25 ° C.).
It is necessary that the following, for example, acrylic modified vinyl acetate resin, ethylene modified vinyl acetate resin,
Examples thereof include acrylic resin, styrene-butadiene rubber (SBR), nitrobutadiene rubber (NBR), and the like. From the viewpoint of reactivity with formalin-based adhesives, styrene-butadiene rubber and modified acrylic resin are particularly effective. Further, the polymer compound preferably has a functional group, because the polymer compound reacts with the formalin-based adhesive to be integrated.

In the present invention, a polymer compound having a Tg higher than room temperature is not preferable because it is hard at room temperature and the brittleness of the formalin-based adhesive cannot be improved, and it is preferably -30 ° C to 20 ° C. -30 ° C or lower, especially -5
If the temperature is 0 ° C. or lower, there is a disadvantage that the peel strength becomes weak.

The polymer compound may be emulsion polymerized to form an emulsion (latex), and various additives such as a protective colloid agent and a cross-linking agent may be used, if necessary. In the present invention, the polymer compound emulsion is added in an amount of 5 to 50 parts by weight, preferably 20 to 30 parts by weight, based on 100 parts by weight of the formalin-based resin, and is used as an adhesive for defibrated plant fibers. If the amount added is more than 50 parts by weight, the thermocompression molding time becomes unnecessarily long, and if it is less than 5 parts by weight, the impact resistance of the fiber board cannot be sufficiently improved.

According to the production method of the present invention, a hard and brittle formalin-based resin adhesive is modified with an emulsion of a polymer compound having a Tg of not higher than room temperature, so that the impact resistance of a molded wood fiber board is significantly increased. Can be improved. As a result, it is possible to avoid the occurrence of chipping or delamination of the adhesive layer due to the impact force during processing or after the product is formed into a product.

[0015]

The present invention will be described below with reference to examples. [Example 1] Tg of -5 using acetaldehyde-modified Poval as a protective colloid was -5 with respect to 100 parts by weight of urea resin.
Using an adhesive to which 50 parts by weight of acrylic modified polyvinyl acetate resin emulsion at 0 ° C was added, the adhesive was added to Lauan fiber in an amount of 15% in the resin solid part, and a 3 mm thick MDF (medium fiber board) was added. It was produced by a conventionally known dry method.

Example 2 An adhesive obtained by adding 50 parts by weight of a carboxyl-modified SBR having a Tg of 0 ° C. to 100 parts by weight of a urea resin was used. 30% added, 3 mm thick HB
(Hard board) was produced by a conventionally known dry method.

Example 3 An adhesive obtained by adding 50 parts by weight of carboxyl-modified SBR having a Tg of 10 ° C. to 100 parts by weight of a urea resin was used. 30% was added, and MDF was produced in the same manner as in Example 1.

Example 4 A carboxyl-modified SBR having a Tg of −20 ° C. was added to 50 parts by weight of 100 parts by weight of a urea resin.
Using an adhesive added in an amount of 20 parts by weight, the adhesive was added to Lauan fiber in a resin solid content of 20%, and an MDF was produced in the same manner as in Example 1.

Comparative Example 1 The same urea resin as in Example 1 was added to Lauan fiber in an amount of 15% in the resin solid portion, and a MDF having a thickness of 3 mm was produced in the same manner as in Example 1.

Comparative Example 2 The same urea resin 10 as in Example 1
An adhesive containing 30 parts by weight of an acrylic resin emulsion having a Tg of 60 ° C. with respect to 0 parts by weight was used.
In the same manner as in Example 1, a 3 mm thick MDF was manufactured.

Comparative Example 3 The same urea resin 10 as in Example 2
An adhesive containing 30 parts by weight of an acrylic resin emulsion having a Tg of 60 ° C. with respect to 0 parts by weight was used.
HB having a thickness of 3 mm was manufactured in the same manner as in Example 2.

A MDF composite plate and an HB composite plate were prepared by bonding a 9 mm thick softwood plywood to the MDF and HB of Examples 1 to 4 and Comparative Examples 1 to 3. SBR + urea melamine resin adhesive is applied on the surface of MDF or HB of the composite board at 9 g / scale ² , and a 0.3 mm-thick oak veneer is stuck at 120 ° C. for 7 hours.
It was pressed for 60 seconds at kg / cm ² . Urethane paint was applied to the surface of the veneer-attached composite plate at 7 g / square ² to produce an MDF composite decorative plate and an HB composite decorative plate. A caster test and a plane tensile test were performed for each. Table 1 shows the results.

In addition, the caster test is carried out on the caster.
After applying a load of 5 kg and reciprocating the test piece 3000 times at a distance of 100 mm in that state, visually observing the presence or absence of peeling of the decorative veneer, coating film, etc., and using a dial gauge, The maximum dent is measured to 1/100 mm, and at this time, the test piece makes one revolution in about 17 reciprocations and returns to the original position.

The plane tensile test complies with JAS (special plywood), and one side is 20 m on the surface of the test piece.
A metal plate having a square m-shaped bonding surface was bonded using a cyanoacrylate-based adhesive, and a cut having a depth reaching a wood fiberboard such as MDF was attached to the periphery, and then a plane tensile test was performed.

[0025]

[Table 1]

As can be seen from Table 1, the composite decorative boards of the examples clearly show improved peeling by the caster test as compared with the comparative examples. Also, the value in the plane tensile test is greatly improved. Although the peeling state in the plane tensile test was delamination of MDF and HB in all cases, the values when the peeling occurred were high in all of the examples, and were manufactured by the manufacturing method according to the present invention. The resulting wood fiberboard shows significantly improved impact resistance. This may cause chipping on the wood fiberboard that is the base material during the manufacturing process of the decorative board, or peeling or chipping on the base material when a local load is applied to the obtained decorative board. Will be resolved.

[0027]

According to the present invention, a hard and brittle formalin-based resin adhesive is modified with an emulsion of a polymer compound having a Tg of not higher than room temperature to significantly improve the impact resistance of the wood fiberboard produced. Can be made. As a result, it is possible to avoid the occurrence of chipping or delamination of the adhesive layer due to impact force during processing or after the product is manufactured, and as a result, the production cost of the wood fiber board is reduced.

Claims (3)

[Claims] 1. A method for producing a wood fiberboard in which defibrated plant fibers are heated and pressed using a formalin-based resin adhesive, and an emulsion of a polymer compound having a Tg of room temperature or lower is used as the adhesive. A method for producing a wood fiber board, characterized by using a material added to a formalin resin. 2. The production of a wood fiberboard according to claim 1, wherein an emulsion of a polymer compound having a Tg of 20 ° C. to 25 ° C. or less, preferably −30 ° C. to 20 ° C. is added. Method. 3. The emulsion of the polymer compound is added in an amount of 5 to 50 parts by weight based on 100 parts by weight of the formalin resin.
The method for producing a wood fiber board according to claim 1, wherein the content is preferably 20 to 30 parts by weight.