JPS631162B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing bent wood products used for furniture, decorative materials, and construction materials.

Conventionally, in order to manufacture such bent wood materials, it has been common practice to steam or boil the wood material to increase the plasticity of the material and then bend it. Since plasticization occurs gradually from the surface layer of the wood, it takes a long time to fully plasticize the inside, which reduces productivity, and the wood tends to discolor due to steaming. Furthermore, since the bending process was performed under high moisture content, it took a long time to dry after the process.

In addition, when bending wood materials, compressive stress and tensile stress act on the inner and outer surfaces of the bent part, so depending on the wood type, buckling may cause wrinkles or breaks on the compression side. On the tensile side, cracks are likely to occur due to tensile fracture, and especially when the cross-sectional shape of the wood material becomes large, the rate at which this phenomenon occurs increases, making it difficult to obtain bent products with a good appearance. It was hot.

In order to eliminate such conventional drawbacks and problems, the present invention has been developed by laminating wooden boards together using an adhesive that has boiling resistance and softens when heated, and also by making the wooden boards retain moisture. By irradiating the wood with microwaves to raise the temperature of the laminated wood while softening the adhesive, and then performing the bending process in this state, efficient production can be achieved without causing cracks even during bending processes with a small radius of curvature. The present invention provides a method for manufacturing a bent product obtained by the present invention.

The method of the present invention will be described in detail with reference to the drawings. A plurality of wood boards 1, 1...1 made of wood boards such as beech veneer, particle board, wood fiber board, or other wood materials are attached to an adhesive layer 2. Thus, the mutually opposing surfaces are bonded and integrated to form the laminated wood material A.

This adhesive has boiling resistance to the extent that the wooden boards will not peel off when the laminated wood material A is boiled, and it also heat softens when heated to around 100°C (specifically within the range of 80 to 120°C). For example, a phenol-resorcinol synthetic resin adhesive or a water-based vinyl urethane adhesive is used. The temperature at which the above adhesive heat softens is 80°C.
℃ or lower, as long as it has a heat softening property that softens as the wood board is heated by microwave irradiation that will be performed later.

Next, the wood material A thus laminated and integrated is subjected to soaking, sprinkling, or steaming treatment to retain moisture.

This moisture treatment is necessary for the wooden material A to obtain sufficient plasticity through microwave irradiation, and it is preferable to absorb water to the center of the wooden material A. Specifically, the moisture content Use by absorbing water to a concentration of 20% or more.

In addition, when forming wood material A from raw wood,
Since the material contains a large amount of water, it may be used as is without being treated to contain water.

Next, the wet laminated wood material A is placed in a microwave irradiation furnace and the wood material A is irradiated with microwaves to raise the temperature of the wood material A to a certain temperature or higher.

This temperature increase due to microwave irradiation utilizes the heat generation phenomenon caused by dielectric loss when a polar material is placed in a high frequency electric field, and microwaves (300MHz to 300KMHz) are used as the high frequency.

The reason why microwaves were used here is that when wood material A is irradiated with microwaves, heat can be generated evenly from inside wood material A, unlike hot air heating or heating between hot plates. The moisture retained in wood material A actively moves not only in the surface layer of wood material A but also in the center of wood material A.
This is because the plasticizing phenomenon can be caused throughout, and at the same time, the adhesive layer 2 between the wooden boards 1 and 1 can also be uniformly softened.

Also, the reason we used microwaves instead of normal high frequencies (10MHz to 100MHz) is because the frequency at which the dielectric loss factor of wood A in a wet state is at its maximum is in the microwave region, so the dielectric loss factor and frequency are different. This is because the amount of heat involved in the product is significantly larger in the microwave range than in the normal high frequency range, and the heat generation is rapid, making it possible to soften the adhesive layer 2 and plasticize the wood material A in a short time. .

When microwaves are irradiated in this way, the wood components and moisture in wood material A absorb the microwaves, causing rapid heat generation due to dielectric loss, and the temperature of wood material A rises to over 100℃, causing the wood material to As the wood components such as hemicellulose and lignin soften, the moisture in the wood rapidly evaporates from inside, and the entire wood becomes plasticized. The time required for this depends on the cross-sectional shape of the wood material A, but if the wood material is 1 x 2 cm, the output will be 2KW.
It can be plasticized in microwave for about 1 minute.

Moreover, at the same time, the adhesive layer 2 between the wooden boards 1 and 1 is heated to a temperature of around 100°C by the heat generated by the wood material A, and becomes softened, and slippage is likely to occur on the bonded surfaces of the wooden boards 1 and 1. state.

In this way, the temperature of the wooden material A is raised by microwave irradiation, the adhesive layer 2 is softened, and in this state, an external force is applied in a direction perpendicular to the adhesive layer 2 to bend the wooden material A. However, this bending process may be performed inside a microwave irradiation furnace while irradiating microwaves, or may be performed outside the microwave irradiation furnace after temporarily stopping microwave irradiation.

The method for bending the wood material A is not particularly limited, and may be performed by appropriate means such as applying pressure using a shape or using a bending machine.

At this time, wood material A made by laminating and bonding wood boards 1
Since the bending deformation is performed while causing slippage in the adhesive layer 2, the stress generated in the wooden material A is dispersed to each wooden board 1, and bending can be performed with a small force. The tensile and compressive stresses on both the front and back sides are relaxed, allowing for smooth bending without cracks or wrinkles due to buckling. In addition, when using a wood veneer for the wood board 1 constituting the laminated wood material A, the fiber direction is
The veneer structure of the laminated wood material A may be laminated in either parallel or orthogonal directions, and is not particularly limited, but the veneer structure of the laminated wood material A is arranged so that the fiber directions of at least the outermost veneers on the front and back sides are parallel to each other, An appropriate number of veneers perpendicular to the fiber direction of the veneers are arranged between these veneers, and the total thickness of each veneer in the perpendicular fiber direction is the total thickness of the laminated wood material A. 50% of the
The number of plies and the thickness of the veneer are adjusted and formed as above, and then the above-mentioned microwave irradiation is performed to bend the laminated wood material A in the direction that the wood fibers of the front and back veneers expand and contract. It is preferable to perform the bending process easily with a small amount of force, and moreover, the occurrence of cracks and wrinkles in the front and back layer veneers is small, and beautiful bent products can be efficiently produced.

That is, when forming laminated wood material A using wood veneers, it is possible to adjust the plastic range for bending deformation of the entire laminated material by considering the fiber direction of each veneer, and it is possible to adjust the plastic range for bending deformation of the entire laminated material. By placing a large number of veneers in the middle layer, the plasticity range is widened and bending products with a small radius of curvature can be obtained without causing fracture. The overall thickness of the veneer subjected to lateral compression is
If the bending process is performed with a bending ratio of 50% or more, the force required for the bending process will be small, and breakage during processing can be significantly reduced.

After bending in this manner, the wood material A is dried and solidified in a deformed state, and is then cooled to room temperature to harden the adhesive layer 2 and fix the entire wood material.

Next, examples of the present invention and comparative examples will be shown.

Example A 5-ply beech plywood was formed by laminating and integrating 2 mm thick beech veneers with their fibers facing in the same direction using a water-based vinyl urethane adhesive, and then submerging the plywood in water. After immersion to reach an average moisture content of 90%, 2450MHz, output
The temperature of the plywood was raised to 100℃ by irradiating it with 2.4KW microwave for 1 minute in the irradiation furnace, and then the plywood was taken out from the microwave irradiation furnace and immediately bent using an appropriate bending machine as shown in Figure 2. When the bending process was performed, even when the radius of curvature was 3 cm, no cracks occurred on the front side (the side where tensile force is applied to the fibers), and no wrinkles appeared on the back side (the side where compressive force acts on the fibers). Smooth bending was possible without any occurrence.

Comparative Example 1 When a 1 cm thick wooden board made of beech wood was bent by irradiating microwaves under the same conditions as in the above example, no abnormality was observed up to a radius of curvature of 7 cm. When it reached 3 cm, as shown in Figure 3, cracks occurred on the front side (tensile side) due to tensile fracture, and many wrinkles due to bending occurred on the back side (compression side).

Comparative Example 2 When a wooden board made of the same beech wood as in Comparative Example 1 was bent after being steamed for 1 minute, plasticization was insufficient and cracking immediately occurred, making bending impossible.

Multiple wood boards with boiling resistance and 80 to 120
The laminated wood materials are integrated through an adhesive layer that softens at a temperature of ℃, and microwaves are irradiated with this laminated wood material retaining moisture to raise the temperature of the laminated wood materials and soften the adhesive layer. Since this relates to a method for manufacturing a bent product, which is characterized by bending the wood boards into an arbitrary shape while causing slippage on the adhesive surfaces of the wood boards in this state, it is possible to bend the wood boards into an arbitrary shape by irradiating them with microwaves The material is plasticized in a short period of time, allowing for efficient bending, and the adhesive softens as the temperature of the laminated wood increases, preventing slippage in the adhesive layer during bending. Each laminated wood board is bent independently via an adhesive layer, so even when bending with a small radius of curvature, the front and back surfaces of the board are bent with a beautiful appearance without cracks or wrinkles. Processed products can be obtained easily.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a cross-sectional view of a wooden material made by laminating and bonding a plurality of wooden boards, FIG. 2 is a perspective view of the wood after it has been bent, and FIG. FIG. 2 is a perspective view of a bent product formed by a conventional bending method. 1...Wood board, 2...Adhesive layer, A...Wood material.

Claims (1)

[Claims] 1 Multiple wooden boards with boiling resistance and 80~
The laminated wood materials are integrated through an adhesive layer that softens at a temperature of 120°C, and microwaves are irradiated with this laminated wood material retaining moisture to raise the temperature of the laminated wood materials and soften the adhesive layer. A method for manufacturing a bent product, characterized by bending the wood boards into an arbitrary shape while causing slippage on the adhesive surfaces of the wood boards in this state.