JP2016087816A - Production method of molded plywood - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wood product having functionality, being excellent in designability and having a three-dimensional curved surface without causing cracks and breakage caused when molding a molded plywood using woody veneers.SOLUTION: In a molded plywood where a plurality of woody veneers are layered and bonded, the woody veneers 10, 11, 13, 14, 16, 17 and 18 orthogonal to a wood grain (fiber) direction before hand are mutually bonded with the adhesive, cured and formed to flat plate plywoods 12, 15 and 19, the adhesive is coated on each flat plate plywood and layered to be orthogonal to the wood grain direction, and then the plywood is produced by curing the adhesive while forming a three-dimensional curved surface with molding presses 20, 21.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing molded plywood, and more particularly to a method for producing molded plywood suitable for furniture such as chairs and tables, and wooden products used for benches.

Molded plywood is used for furniture such as chairs and tables. The manufacturing method is to apply an adhesive to a 1 mm to 2 mm thick wood veneer, stack the multiple wood veneers so that the fiber directions of the wood are orthogonal to each other, fit into a mold, and form the plywood by high frequency heating press processing To manufacture. It is common that the adhesive is cured and molded simultaneously by heating.

As woody veneer used tree species, there are many hardwood beech (beach) that have been widely used for bending since ancient times, and even beech plywood has been used because it is easy to mold. In recent years, the use of domestic beech wood is low, and most use mainly imported beaches. Molded plywood has traditionally been a traditional technology, and its manufacturing method has not changed much. However, depending on the type of tree, the thickness of the wood veneer, the thickness of the molding (lamination), and the curvature of the molded plywood, there is a problem that the wood veneer at the time of molding is not cracked or damaged. The reason is that wood has anisotropy with respect to dimensional change and strength. In terms of strength, the tensile strength is extremely low in the tangential direction (perpendicular to the grain), approximately 1/20 of the fiber direction, and cracking occurs when stress exceeding the allowable strength is applied.

Regarding the molded plywood using hardwood, for example, there are those shown in Patent Documents 1-3. The manufacturing method of the molded plywood shown in Patent Document 1 is a three-dimensional method in which a decorative wood veneer and a core material are formed in advance, and the decorative wood veneer (0.2 mm) during molding is torn and wrinkled. A plywood having a curved surface is formed. This is because the decorative wood veneer is thin and easily torn, and a resin impregnated paper laminate having strength is used as a prevention method. The manufacturing method disclosed in Patent Document 2 is a method for forming a molded plywood having a low curvature, and prevents damage to a decorative wood veneer that makes use of the properties of an adhesive. In the manufacturing method disclosed in Patent Document 3, a plurality of wood veneers are polymerized via thermosetting resin and heat-sensitive adhesive, and this polymer is heated and pressed by a flat plate press molding machine. Molded in a semi-hardened or softened state according to the performance of the adhesive.

While hardwood imported overseas is used as the main material of molded plywood, the use of domestic timber is not widespread as mentioned above. In recent years, the use of forests in Japan has been called out, and measures to increase the timber self-sufficiency ratio in Japan are being implemented in unison with the public and private sectors. In particular, conifers such as cypress and cedar, which have abundant forest stocks, are being used mainly for pillars and beams of housing structural materials. However, conifers are rarely used for familiar plywood such as furniture and benches. Compared with broad-leaved trees, the structure of coniferous trees is simple.Most tree species are almost occupied by temporary canals, and the arrangement of the cells is orderly, and the porosity between the cells that make up the trees is large and the density is high. This is because it is low.

About the molded plywood using a conifer, there exist some which were disclosed by patent documents 4, 5. According to the manufacturing method disclosed in Patent Document 4, the laminated material in which timbers such as cedar, straw, and pine are assembled is sliced to a thickness of 0.2 mm to form a wooden thin plate, and the two pieces are bonded with the grain direction aligned. It is shown that the two laminated plates made in this way are stacked with a cross-cut wooden sheet sandwiched between them. This technology deals with wooden thin plates sliced from laminated timber and is not a plywood layered with wood veneer obtained by peeling katsura. Moreover, in patent document 5, in the manufacturing method of a laminated veneer, even if a large amount of deformation occurs when the laminated veneer is molded and pressed with a die against a cedar wood veneer having a thickness of 0.2 to 0.8 mm. As a molding method in which cracks and cracks are unlikely to occur, there is a method in which a laminated single plate is vapor-irradiated and the single plate is softened to be bent. This is widely used as a method for manufacturing bent trees.

Japanese Patent Laid-Open No. 4-91901 JP-A-61-205102 JP-A-2-98401 JP 2006-315397 A JP 2000-43003 A

Let us consider manufacturing a flip-up type seat board 1 of a wooden chair shown in FIG. 1 using molded plywood. In FIG. 1A, the horizontal direction of the paper surface is the x direction, the vertical direction is the y direction, the front and back directions are the z direction, and the vertical and horizontal lengths are 475 mm. The seat plate 1 is formed with a cylindrical curved surface in the x direction having a radius of 1663 mm having a center on the front side of the paper surface at the reference numeral 2, and a radius of 100 mm having a center on the back side of the paper at the reference numeral 3. A cylindrical curved surface in the x direction is formed (see FIG. 1B). At a location indicated by reference numeral 4, a y-direction cylindrical curved surface having a center at the back side of the paper and having a radius of curvature of 50 mm is formed, and at a location indicated by reference numeral 5, a y-direction having a center at the front side of the paper and a radius of curvature of 1486 mm. A cylindrical curved surface is formed (see FIG. 1C). The seat plate 1 is three-dimensionally formed by combining two cylindrical curved surfaces in the x and y directions.

FIG. 3 shows an example in which a molded plywood is produced by a conventional manufacturing method disclosed in Patent Document 5. First, a molded plywood seat plate having a three-dimensional curved surface shape is formed using a wood veneer of a conifer cypress 1.3 mm. First, a cypress 1.3 mm veneer was cut into a 50 cm square. Subsequently, an adhesive is applied to one side of each single plate of hinoki 1.3 mm, and 7 sheets are laminated (thickness: about 9.0 mm) so that the wood grain (fibers) G are alternately orthogonal to each other to form a mold. Inserted and pressurized (1.2 MPa) with a flat press. The pressure was maintained for 2 hours for curing and fixing the adhesive. After 2 hours, the pressure was released and the mold was taken out of the mold. As a result, cracks C due to the transverse tensile force against the grain of the molding press occurred on the surface layer portion, the inner layer and the back side indicated by S of the seat plate 1. These areas indicated by S are areas where cylindrical curved surfaces in the x and y directions are combined. On the other hand, even in the same three-dimensional molding, as shown in FIG. 3B, cracks C were not observed at the portions deformed only by the cylindrical curved surfaces R50 and R1486 in the y direction. In the figure, m is a mark representing one corner of the seat plate 1. 3D is the back side of FIG. 3C, and FIG. 3E is an enlarged view of a portion of FIG. 3C. Next, when the same procedure was performed using 13 wood veneers of 1.8 mm of broad-leaved Mizunara, which are widely used for furniture and flooring, noticeable cracks C were generated at similar locations.
In the wood veneer obtained by peeling off the log, if the thickness is 1.0 mm or more, a fine crack will occur on the surface of the wood veneer which becomes the center side of the log, and this crack will occur when the thickness increases. Becomes prominent. In the production of a three-dimensional curved shape molded plywood, this is considered to cause cracks. On the other hand, a thin wood veneer having a thickness of 0.8 mm or less is difficult to handle, and the number of laminated layers greatly increases to obtain a molded plywood having a desired thickness.

Thus, in the production of a molded plywood having a three-dimensional curved surface shape, it is not possible to prevent damage during molding such as cracking and tearing by simply applying an adhesive to a wood veneer, laminating it, and molding pressing. In other words, it is necessary to provide means that does not cause damage such as cracking or tearing in the veneer in the process of applying, laminating, and forming the adhesive to the wood veneer.

An object of the present invention is to provide a method for producing a molded plywood having a three-dimensional curved surface shape without causing a crack or tear of a single plate that occurs during molding press.

The present invention proposes a method for producing a molded plywood having a three-dimensional curved surface that makes it possible to use cypress, which is a conifer, as a tree species of the molded plywood. The method for producing a molded plywood according to the present invention is a method in which an adhesive is applied to a plurality of wood veneers and laminated with a molding die, and the adhesive is applied to a plurality of wood veneers, The first step of making multiple sets of flat plate plywood that are laminated and cured so as to be orthogonal to each other), the adhesive is applied to the multiple sets of flat plate plywood obtained in the first step, and each plate plywood is again orthogonal to the grain A second step of arranging and laminating in such a manner, and a third step of curing the adhesive by forming and pressing a flat plywood laminated by the second step into a three-dimensional curved shape by pressing with a molding press The above-mentioned object has been achieved.

In the first step, the present invention produces a flat plywood in which the adhesive is hardened by applying an adhesive to a wood veneer so that the grain is orthogonal. Thereby, the anisotropy of the tensile strength of the wood veneer which is weak to a lateral tension is improved, and the crack which arises at the time of a shaping press is suppressed. Next, in the second step, an adhesive is applied to the flat plywood and laminated so that the grain is orthogonal. At this time, the adhesive applied to the flat plywood gives slipperiness between the flat plywood during molding pressing, and suppresses cracks generated in the local portion. Next, in the third step, the flat plywood laminated with the adhesive applied in the second step is fitted into a mold and pressed to cure the adhesive to obtain a molded plywood. By providing a method for producing a molded plywood characterized by taking these three steps into consideration, the above object is achieved.

It is a figure which shows an example of a shaping | molding plywood. It is drawing which shows the manufacturing method of a shaping | molding plywood. It is drawing which shows the manufacturing method of the shaping | molding plywood by the conventional method.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In order to carry out the method for producing a molded plywood of the present invention, a three-dimensional curved mold and a press having a predetermined pressure are used. The seat plate 1 shown in FIG. 1 is created.

In each embodiment, the seat plate 1 is a laminate of a plurality of wood veneers, and the thickness of each wood veneer is 0.2 mm to 4.5 mm, preferably 1.0 mm to 2.0 mm. The wood veneer is manufactured using a rotary veneer with the raw wood peeled off, or a slice veneer obtained by flattening the raw wood with a flat or slicer. In this example, a rotary single plate having a wrinkle was used. The tree species used were Japanese timber coniferous cypress and broadleaf mizunara. Hinoki veneer and Mizunara veneer were cut to 50 cm square to match the wooden shape.

As the adhesive applied to the cypress veneer, a thermosetting resin adhesive is usually used for a high frequency press. However, in each Example, the water-based high molecular isocyanate adhesive which hardens | cures at normal temperature was used on the relationship of experiment equipment.

In FIG. 2, using a total of 13 cypress wood plates 10, 11, 13, 14, 16, 17, and 18 having a thickness of 1.0 mm, the plate plywood 12 for the front plate in the first step, and for the middle plate A flat plywood 15 and a flat plywood 19 for the back plate are made. An adhesive g of about 300 g / m ² is applied to the surface of the wood veneer 10 (the upper surface in the drawing, the same shall apply hereinafter), and the wood veneer 11 is overlaid so that the grain G is perpendicular to the two plies. To the first set. The surface 12 a of the flat plywood 12 (the surface of the wood veneer 11) is defined as the surface of the seat plate 1. Subsequently, the adhesive g is applied to the wood veneer 13 for the middle plate, and the wood veneer 14 is stacked thereon so that the wood grain G is perpendicular to form 4 sets of 2 sets of 2 plies. Finally, an adhesive g is applied to the wood veneer 16 for the flat plywood 19 for the back plate, and the wood veneer 17 coated with the adhesive g is stacked on the wood veneer so that the grain is perpendicular to the wood veneer. The plates 18 are stacked so that the grain is orthogonal, and a third set of 3 plies is made.

1 set of 2 plies is used for the front plate of the seat plate 1, 4 sets of 2 sets of 2 plies are used for the middle plate of the seat plate 1, and 3 plies are used as the back plate of the seat plate 1. A set is a set of one set.
Next, in order to harden the adhesive layer of each set coated with these adhesives g and form a flat plywood, each set of the first set, the second set, and the third set is stacked with a flat press and pressurized at 1 MPa. For 1 hour to form one set of flat plate plywood 12 and 19 and four sets of flat plate plywood 15. After the release, the adhesive was completely cured by curing for 24 hours. Thus, in a 1st process, the adhesive agent g is apply | coated to a wood single board, and the flat board plywood which bonded and hardened is manufactured. Thereby, the anisotropy of tensile strength is improved and the crack which arises locally at the time of shaping | molding press is suppressed.

Next, in the second step, the adhesive g is applied to the flat plate plywood 19 for the back plate of the seat plate 1 obtained in the first step, and the adhesive g is applied to the four flat plate plywoods 15 for the middle plate, Four sets are sequentially stacked so that the grain G appearing on the overlapping surface of each other is orthogonal. Finally, the plate plywood 12 for the front plate of the seat plate 1 is overlaid on the plate plywood 15 for the intermediate plate to which the adhesive g is applied. At this time as well, the overlapping is performed so that the grain G appearing on the overlapping surface of the flat plywood 12 and the flat plywood 15 is orthogonal. Thus, the flat plywoods 12, 15, 19 are laminated so that the adhesive g is applied and the grain is orthogonal. Since the adhesive g is uncured, the adhesive layer between the flat plate plywoods applied to the flat plate plywood at the time of molding is slippery and suppresses cracks generated in the local portions of the flat plate plywood.

In the third step, uncured and laminated flat plywoods 12, 15, and 19 are fitted into the molds 20 and 21, and the adhesive layer is cured and molded by pressing with a molding press at a pressure of 1.2 MPa for 2 hours. Release to obtain a molded plywood with a three-dimensional curved surface shape. The seat plate 1 was cut out from the obtained molded plywood and chamfered.

As a result, the seat plate 1 having a three-dimensional curved surface is not damaged such as a surface tear, a crack, a surface crack of the curved surface part, and a tear of the side surface part. It was satisfactory as a molded plywood for boards.

Since the back plate and the seat plate are separately flipped up, the surface of the seat plate 1 is required to have aesthetics and durability. It was created. Similarly, a flat plywood 19 having a quality that does not impair the aesthetic appearance of the back surface of the seat plate 1 was prepared. The middle plate allowed no bars or scratches that would not hinder molding. Further, in this embodiment, the flat plate plywood 19 for the back plate is made of three plies. However, one plate or a plurality of flat plate plywoods for the front plate or middle plate may be laminated in three plies or more. .

A plate plywood was prepared in the same manner as in the first step of Example 1 using 13 wood veneers of 1.8 mm broad-leaved mizunara. The configuration of the flat plywood is one set of two plies for the front plate of the seat plate 1, three sets of two plies for the middle plate, one set of three plies, and one set of two plies for the back plate. The second step is to apply 2 plies for the back plate, 2 plies for the middle plate, 3 plies for 1 set, 2 plies for 1 set, and finally 2 plies for the front plate for 1 plate. Stack one after another. At this time, each flat plywood is overlapped so that the grain is orthogonal. In the third step, the molded plywood having a three-dimensional curved surface shape was obtained by setting and pressing into a mold as in Example 1 and curing the adhesive between the flat plywoods. As a result, no damages such as local cracks and tears were observed, which was satisfactory.
In Example 1 above, the three-ply flat plywood is arranged in the outermost layer of the molded plywood. However, as in this example, the three-ply flat plywood is arranged in the middle layer of the molded plywood and sandwiched between the two-ply flat plywood. Also good. In the molding of the three-dimensional curved surface shape as shown in FIG. 1, since the stress applied to the middle layer of the molded plywood is smaller, it is desirable to provide a three-ply flat plywood that is thick and difficult to deform. In this case, the three-ply flat plywood and the two-ply flat plywood are arranged so that the grain of each wood single plate is alternately orthogonal when completed as a molded plywood.

The presence or absence of an influence on molding was verified by the difference between the thickness of the wood veneer and the laminated thickness.
Using seven cypress 1.3mm wood veneers, a three-dimensional curved plywood is made. As in Example 1, the first step consists of one set of 2-ply flat plywood for the front plate, one set of 2-ply flat plywood for the middle plate, and one set of 3-ply flat plywood for the back plate, An adhesive is applied to each wood veneer and the adhesive is cured with a flat press to form a flat plywood. In the second step, the adhesive is applied to the three-ply flat plate plywood for the back plate obtained in the first step, and the adhesive is applied to the two-ply flat plate plywood for the intermediate plate, and laminated in the same manner as in Example 1. Subsequently, finally, a two-ply plate plywood for a front plate is laminated in the same manner as in Example 1 on the surface of the plate plywood to which the adhesive is applied. In the third step, as in Example 1, the molds 20 and 21 were fitted and pressed to cure the adhesive between the flat plywoods to obtain a molded plywood having a three-dimensional curved surface shape. As a result, a molded plywood for a seat plate having a thickness of about 9 mm and a three-dimensional curved chair having no problem as in Example 1 was obtained.

Glyoxal resin that imparts durability is poured into a wood veneer to make it a seat plate with performance for outdoor use. A cypress wood veneer was dipped in a resin solution in a vacuum pressurizing apparatus, and the inside of the can was decompressed at 80 Torr for 2 hours and pressurized at 1 MPa for 1 hour. After injecting approximately 700 kg / m ³ of resin into the wood veneer, the wood veneer is dried to a moisture content of about 10% in a heater. The wood veneer after drying produces a molded plywood having a three-dimensional curved shape in the same manner as in Example 1. Next, since the resin remaining on the molded plywood is uncured, it must be reacted and cured at a high temperature. For curing, the temperature in the dryer is increased from 120 ° C. to 150 ° C. to cure and fix the molded plywood. This time, the molded plywood was subjected to reaction hardening with hot air at 100 ° C. to 150 ° C. in a heater to impart durability. In general, a molded plywood is manufactured by heating to 120 ° C. to 130 ° C. by high-frequency heating press processing to cure the adhesive in a short time. By using a high frequency, the resin can be cured by reaction simultaneously in a short time, and a three-dimensional curved plywood can be manufactured. The resin to be injected may be impregnated with a thermoplastic resin such as an acrylic resin and a thermosetting resin such as a melamine resin or a phenol resin.

1 Seat plate 10, 11, 13, 14, 16, 17, 18 Wood veneer 12, 15, 19 Flat plywood 20, 21 Mold

Claims (2)

In a method of applying an adhesive to a plurality of wood veneers and laminating them with a mold,
A first step of applying a plurality of wood veneers to form a plurality of sets of flat plywood laminated and cured so that the grain (fibers) are orthogonal;
A second step in which an adhesive is applied to a plurality of sets of flat plywood obtained in the first step, and each flat plywood is arranged again so that the grain is orthogonal, and the adhesive is laminated uncured;
A method for producing a molded plywood comprising the third step of fitting and pressing the flat plywood laminated in the second step with a molding press to form a three-dimensional curved surface and curing the adhesive.
The wood veneer to which the adhesive is applied in the first step is impregnated with thermoplastic resin such as acrylic resin, thermosetting resin such as melamine resin and phenol resin, glyoxal resin, etc. 2. The method for producing a molded plywood according to claim 1, wherein the molded plywood is laminated and cured perpendicularly to the grain direction (fiber) direction.