JPH07214507A - Building material - Google Patents

Abstract

PURPOSE:To prevent the effect of expansion and shrinkage corresponding to moisture absorption and moisture discharge in the surface layer part of plywood from being transmitted to a fancy veneer on the surface and to prevent the dry crack phenomena of the fancy veneer in the fancy plywood constituted by laminating the fancy veneer on the base plate of plywood. CONSTITUTION:Building material is constituted by interposing a ligneous fiber board 2 between the base plate 1 of plywood and a fancy veneer 3 and integrally laminating and bonding them. While making full use of the excellent characteristics of the base plate of plywood, heterogeneous expansion and shrinkage in the surface layer part thereof are completely restricted by the homogeneous ligneous fiber board. A dry crack of the fancy veneer is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a building material, and more particularly to a novel building material having an excellent effect of preventing dry cracking of a decorative veneer.

[0002]

2. Description of the Related Art Plywood is used as a substrate, and its surface has a fiber direction parallel to the fiber direction of the surface veneer of the plywood substrate.
A so-called decorative plywood, which is formed by laminating decorative thin veneers through an adhesive, is known.

[0003]

In such decorative plywood, cracking has been a problem in the past. this is,
Although the expansion and contraction of the plywood itself due to the absorption and release of water is relatively small, a concentrated cracking phenomenon occurs due to the behavior caused by conduit grooves, back cracks, etc. in the surface layer part, and the cracking phenomenon occurs on the surface This caused numerous cracks in the veneer, resulting in deterioration of quality and deterioration of surface design. This cracking phenomenon was particularly remarkable in the direction orthogonal to the fiber arrangement that was not constrained by the plywood substrate.

Although some technologies for preventing dry cracking have been proposed, a drastic solution has not been found yet.

[0005]

The present invention was devised to solve the above-mentioned object, and more specifically, it is necessary to completely restrain the cracking phenomenon in the surface layer portion of the plywood substrate so that it is not transmitted to the surface-coated thin veneer. It was created based on the knowledge that cracking in the surface decorative thin veneer can be prevented, and the decorative thin veneer is sequentially formed on the surface of the plywood substrate via a wood fiber board thinner than the plywood substrate. Laminated and adhered, the wood fiber board serves as a restraining material for preventing the influence of expansion and contraction occurring in the surface layer portion of the plywood substrate due to absorption and release of water from being propagated to the decorative thin veneer. It is a building material characterized by working.

[0006] The wood fiber board prevents the influence of expansion and contraction due to the absorption and release of water, particularly on the surface veneer of the plywood substrate, from reaching the thin veneer on the surface.

The wood fiberboard has excellent expansion and contraction characteristics due to absorption and release of water, is homogeneous throughout, and does not cause intensive dry cracking. Therefore, the expansion and contraction of the plywood board can be effectively restrained. it can. Further, since this wood fiber board is a wood-based material of the same quality as the plywood which is the substrate and the decorative thin veneer on the surface, it is preferable to be used as a restraining material from the viewpoint of adhesiveness and the like.

Among the wood fiberboards, the specific gravity is 0.4 to 0.8
The so-called medium-quality fiberboard of (3) has appropriate rigidity and flexibility, and is particularly suitable for use as a restraint material in the building material of the present invention. If the specific gravity is less than 0.4, it is too soft and dents easily occur when the surface of the building material is locally compressed. If it is larger than 0.8,
Since the weight per unit volume is large, the resulting building material increases in weight and becomes difficult to handle.
Further, although it is strong against compression, it lacks flexibility and becomes brittle, so that it has a drawback that it is easily cracked by impact.

The function and function of the wood fiberboard interposed between the plywood substrate and the decorative thin veneer in the building material of the present invention will be described in detail below.

That is, comparing the contraction and expansion rates of plywood and wood fiberboard, generally, the average contraction and expansion rate per water content of 1% for the entire plywood is 0.02% in the direction parallel to the fibers of the surface veneer. 0.03% in the direction perpendicular to the fibers of the surface veneer
On the other hand, the shrinkage / expansion rate per 1% of the water content of the wood fiberboard is 0.03 to 0.04%, which is uniform throughout, and is more uniform than the shrinkage / expansion rate of the plywood in the direction perpendicular to the fiber direction. The contraction and expansion rate of the plate is larger.

However, the shrinkage and expansion rate of the plywood is
The shrinkage and expansion rate of the whole plywood laminated by crossing the fiber directions of a plurality of veneers with each other, and when observing each veneer constituting the plywood, there are parts where the fibers are clogged and where the fibers are rough, etc. The shrinkage / expansion rate when the water content changes is non-uniform due to the state of such fibers, and a very large shrinkage portion and a portion where little shrinkage occurs are mixed.

Since the veneer having the non-uniform shrinkage characteristic is also present in the surface layer portion of the plywood, there is a portion where a change larger than the shrinkage amount of the wood fiberboard occurs locally in the direction perpendicular to the fiber direction. However, the uneven shrinkage causes cracks in the thin veneer on the surface.

On the other hand, although the wood fiberboard has a homogeneous property, as described above, the expansion and contraction due to moisture absorption and desorption is not small at all. A building material has also been proposed in which a wood fiberboard is used as a substrate and a decorative thin veneer is attached to its surface, but if it repeatedly expands and contracts over the years, the wood fiberboard that is the substrate will never expand or contract. Influences the decorative thin veneer on the surface and causes the decorative thin veneer to crack, warp, or twist. In this respect, it is rather inferior to the decorative plywood using plywood as a substrate.

However, according to the structure of the present invention, the plywood is used as the substrate and the decorative thin veneer is attached to the surface of the plywood via the wood fiberboard, and the excellent dimensional stability as the plate material of the plywood substrate, While maintaining the property that warpage is unlikely to occur as it is, the uneven contraction of the surface veneer of the plywood can be restrained by interposing the wood fiber board, and the influence on the decorative thin veneer can be eliminated.

On the other hand, looking at the wood fiberboard, the whole wood is constrained by the stable plywood substrate, which has a smaller average shrinkage amount than the wood fiberboard, so that the wood fiberboard alone can be used. The dimensional change is small and excellent as compared to the case where it is not.

That is, in the building material of the present invention, the excellent rigidity and dimensional stability of the plywood substrate are not deteriorated,
A wood fiberboard is used to prevent the influence of expansion and contraction of the surface veneer from being propagated to the thin veneer.

Therefore, the wood fiber board may have a thickness sufficient to exert the above-mentioned functions or functions, that is, it is thinner than the plywood board.
In particular, a wood fiber board having a thickness of about 1/3 of the thickness of the plywood substrate or less is used. This is
It should be understood from the relationship between the plywood used as the “substrate” and the wood fiberboard used as the “inclusion” in the building material of the present invention.

If the wood fiberboard is thicker than the plywood, it no longer departs from the concept of "decorative plywood" on the premise of the "plywood substrate", and the characteristics of the entire building material are The board will take the lead,
It is inferior in rigidity and dimensional stability and tends to cause cracks and the like on the decorative thin veneer attached to the surface.

[0019]

[Function] In the decorative plywood, by interposing the wood fiberboard between the plywood substrate and the decorative thin veneer, while maintaining the excellent properties of the plywood substrate, the influence of uneven expansion and contraction on the surface veneer is reduced. Prevents propagation to the plate.

[0020]

An embodiment of the building material according to the invention is shown in the accompanying drawings. This is because a 3 mm thick wood fiber board 2 (trade name: Nodabest Wood P type) is laminated on the surface of a 9 mm thick plywood substrate 1 via an adhesive, and an adhesive is further applied on the laminated wood fibrous board 2 (trade name: Nodabest Wood P type). It is obtained by laminating decorative thin veneers 3 made of oak material having a thickness of 3 mm and then pressure-bonding them.

A comparative test was conducted in the following manner in order to confirm the effect of preventing cracking of the building material according to the present invention.

As a test material, (A) a 12 mm plywood laminated with a 0.3 mm thick oak wood veneer
(B) A Japanese paper is pasted on a 12 mm plywood board, and further on it.
Veneer pasted with 4 mm thick oak wood veneer, and (C) 0.3 m with WPC processing on 12 mm plywood
As a comparative example, a building material of the present invention having the constitution of the illustrated example was designated as (D). The adhesives used are all phenolic.

A water resistance test and a cold repetition test were performed on these test materials to visually observe the number of cracks and their sizes. The water resistance test is carried out by repeating two cycles of a step of soaking in warm water of 60 ° C. for 1 hour and then drying at 60 ° C. for 2 hours, and a cold heat repeat test is dried at 80 ° C. for 2 hours and then cooled to −20 ° C. The step of holding for 2 hours was repeated for 2 cycles and 8 cycles, and these tests were performed twice each. The results are shown in Table 1 below.

[Table 1] As is clear from the results shown in this table, the test material D according to the present invention was found to have no cracking at all or to an extent that it can be neglected in any of the tests. It was confirmed that the expansion and contraction associated with the absorption and release of water is substantially completely restrained, and that it functions to effectively prevent dry cracking in the surface-coated thin veneer.

According to the present invention, the cracking in the surface layer of the plywood substrate caused by the expansion and contraction due to the absorption and release of water is prevented by the wood fiberboard interposed between the plywood substrate and the decorative thin veneer. The effect on the decorative thin veneer can be eliminated by restraining the veneer.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a building material according to the present invention.

[Explanation of symbols]

 1 Plywood board 2 Wood fiber board 3 Decorative thin veneer

Claims (2)

[Claims] 1. A laminated thin veneer is sequentially laminated and adhered to the surface of a plywood substrate via a wood fiberboard thinner than the plywood substrate, and the wood fiberboard is attached to the plywood substrate as the water is absorbed and released. A building material, which acts as a restraining material for preventing the influence of expansion and contraction occurring in the surface layer portion from being propagated to the decorative thin veneer. 2. The wood fiber board has a specific gravity of 0.4 to 0.8.
The building material according to claim 1, which is a medium quality fiberboard.