JPH0524483Y2 - - Google Patents

Description

[Detailed explanation of the idea]

<Industrial Application Field> The present invention relates to building materials, and more particularly to a novel building material that has an excellent effect of preventing dry cracking of decorative veneers. <Prior art and its problems> Decorative plywood is known in which decorative thin veneers are laminated and bonded to the surface of the plywood using an adhesive so that the fiber direction is parallel to the fiber direction of the surface veneer. . In such decorative plywood, dry cracking has been a problem for some time. This is because, although the expansion and contraction of the plywood itself due to moisture absorption and release is relatively small, intensive drying cracking occurs in the surface layer due to behavior caused by conduit grooves, back cracks, etc. The decorative thin veneer of the car caused countless dry cracks,
This caused a decline in quality and surface design. This cracking phenomenon was particularly noticeable in the direction perpendicular to the fiber arrangement, which was not constrained by the plywood substrate. Although some techniques have been proposed to prevent dry cracking, no fundamental solution has yet been found. <Means for solving the problems> The present invention was created to solve the above objectives,
More specifically, it was invented based on the knowledge that drying cracks in the decorative thin veneer can be prevented by completely restraining the drying cracking phenomenon in the surface layer of the plywood substrate and preventing it from being transmitted to the decorative thin veneer. In the case where a decorative thin veneer is laminated and bonded to the surface of a plywood substrate, the effects of expansion and contraction that occur in the surface layer of the plywood substrate due to absorption and release of moisture may affect the decorative thin veneer. This building material is characterized by interposing a wood fiber board, especially a medium density fiberboard with a specific gravity of 0.4 to 0.8, as a restraining material that can prevent the spread of the disease. <Example> An example of the building material according to the present invention is shown in the accompanying drawings. This is formed by adhering a wood fiber board 2 to the surface of a plywood substrate 1 via an adhesive, further applying an adhesive thereon, laminating a decorative thin veneer 3, and then press-bonding it. The wood fiber board 2 acts as a restraining material that prevents the effects of expansion and contraction caused by absorption and release of moisture from the substrate 1 from reaching the decorative thin veneer on the surface. Wood fiberboards exhibit very little expansion and contraction due to absorption and release of moisture, and do not cause intensive drying and cracking, so they can effectively restrain the expansion and contraction of the board. Furthermore, since this wood fiberboard is made of the same wood as the plywood that is the substrate and the decorative thin veneer that is the surface, it is preferable for use as a restraining material from the viewpoint of adhesion and the like. Among wood fiber boards, so-called medium-density fiberboard with a specific gravity of 0.4 to 0.8 is particularly suitable because it has appropriate rigidity and flexibility. Those with specific gravity less than 0.4 are
It is too flexible and easily dents when localized compression is applied to the surface of the building material. Also, 0.8
If it is larger, the weight per unit volume is large, making the building material heavy and difficult to handle. Also, although it is strong against compression, it lacks flexibility and is brittle, so it has the disadvantage of being easily broken by impact. <Test Example> In order to confirm the effectiveness of the present invention in preventing drying and cracking of building materials, a comparative test was conducted as follows. The test materials were (A) 12mm plywood with 0.3mm thick oak veneer pasted on top, (B) 12mm plywood with Japanese paper pasted on top, and 0.4mm thick oak veneer on top of that. (C) 12mm plywood with 0.3mm thick cover wood veneer applied with WPC processing, (D) 9mm plywood with 3mm thick fiberboard (product name) We prepared four types: Nodabest Wood P type) and then a 0.3mm thick oak veneer on top. The adhesives used were all phenol-based. These test materials were subjected to a water resistance test and a cold/heat cycle test, and the number and size of dry cracks that occurred were visually measured. The water resistance test involves immersing the product in warm water at 60℃ for 1 hour and then drying it at 60℃ for 2 hours, repeated in two cycles.The cold/heat cycling test involves drying the product at 80℃ for 2 hours and then cooling it to -20℃. The process of holding the sample for 2 hours was repeated for 2 cycles and 8 cycles, and each of these tests was conducted twice. The results are shown in the table below.

[Table] As is clear from the results shown in this table, it was found that test material D according to the present invention had no or almost negligible drying cracks in all tests, and In particular, it was confirmed that this function substantially completely restrains the expansion and contraction caused by moisture absorption and release, and effectively prevents drying cracks in the decorative thin veneer. <Effects of the invention> When the invention is adopted, the wood fiber board completely restrains dry cracks in the surface layer of the plywood substrate that occur due to expansion and contraction due to moisture absorption and release, and eliminates the effect on the decorative thin veneer on the surface. Therefore, the occurrence of dry cracks in the decorative thin veneer is effectively prevented.

[Brief explanation of drawings]

The accompanying drawing is a sectional view showing an embodiment of the building material according to the present invention. Explanation of symbols: 1...Plywood board, 2...Wood fiber board, 3...Decorative thin veneer.

Claims (1)

[Claims for Utility Model Registration] 1. Decorative thin veneer is laminated and bonded on the surface of a plywood substrate via a wood fiberboard, and the wood fiberboard absorbs and releases moisture in the surface layer of the plywood substrate. A building material characterized by acting as a restraining material to prevent the effects of expansion and contraction from being propagated to the decorative thin veneer. 2. The building material according to claim 1, wherein the wood fiber board is a medium density fiberboard with a specific gravity of 0.4 to 0.8.