JPH0745121B2 - Bonding method for thin wooden boards - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for adhering a thin wooden plate to a core material,
In particular, a film adhesive layer in a dry state made of a thermoplastic resin adhesive is formed on the surface of the core material, and the temperature corresponding to 95 to 80% of the melting point indicated by the absolute temperature of the adhesive forming the film adhesive layer. By applying heat and pressure treatment in the range and adhering the thin wooden board, it is possible to prevent the exudation of the adhesive on the surface of the thin wooden board and the cracking of the thin wooden board, and to obtain high adhesion performance in a short time. It is a thing.

[Prior Art] Generally, as a method for adhering a thin wooden plate such as a veneer to a core material such as a metal plate or a wood plywood, for example, i) applying a liquid adhesive material such as SBR / melamine resin onto the core material surface. , A method of adhering a thin wooden plate on it by drying and curing, or ii) arranging the thin wooden plate on the surface of the core material via a hot-melt type adhesive film such as polyolefin, Method of performing hot-melting treatment at a temperature higher than the melting point of, and then performing melt-bonding, or iii) via a prepreg sheet which is semi-cured by impregnating a surface of a core material with a thermosetting resin such as epoxy resin There is a method of arranging a thin wooden plate, heat-pressing it to cure a prepreg sheet, and integrally bonding.

[Problems to be Solved by the Invention] However, in the above method i), when the thin wooden plate is very thin, such as a veneer, the adhesive exudes through the conduit of the veneer and spoils the appearance. There is a problem that ends up. Further, when this method is applied to a core material made of a metal plate or resin-impregnated paper, there is no place for the water content of the liquid adhesive to escape during drying and curing, and therefore, adhesion is impossible.

Further, in the above method ii), since the adhesive film is heated to a temperature higher than the melting point and melt-bonded, the resin forming the adhesive film remarkably melts and flows, and the veneer cracks or the wood thin plate surface is accompanied by this flow. There is a problem that the resin liquid oozes out. Further, there is also a problem that the jig for hot pressing is significantly contaminated with the flow of the resin.

In addition, the method iii) has a problem in workability, such as a high temperature and a long-time hot-pressing treatment when curing the prepreg sheet.

In the present invention, the problems described above are solved, and exudation of the adhesive to the surface of the thin wooden board and the occurrence of cracks in the thin wooden board due to the flow motion of the resin are prevented, and good adhesion performance is achieved by heat and pressure treatment for a short time. It is an object of the present invention to provide a method for adhering a thin wooden plate that can obtain a composite material having

[Means for Solving the Problems] This invention forms a film adhesive layer made of a polyurethane-based or polyester-based thermoplastic resin-based adhesive on the surface of a core material, and superimposes a wooden thin plate on the film adhesive layer. After combining, solve the problem that the thin wood plate is bonded to the core material by hot pressing in the temperature range corresponding to 95 to 80% of the melting point indicated by the absolute temperature of the adhesive forming the film adhesive layer. The means.

[Operation] By thus setting the temperature of the heat and pressure treatment within the above range, the adhesive is bonded in the temperature range in which the fluidity is appropriate, and the exudation of the adhesive on the surface of the thin wooden board and It is possible to suppress the occurrence of cracks in a thin wooden plate and obtain a composite material having an excellent appearance by a hot press treatment for a short time. In addition, since a dry film adhesive layer made of an adhesive is used, workability during hot pressing is good and contamination of the jig is small. There is also a convenience that any form of adhesive may be used.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 to 5 show an example of a method of adhering a thin wooden board of the present invention in the order of steps.

Reference numeral 1 in the figure is a core material. For the core material 1, wood plywood,
Any plate such as an aluminum plate, a metal plate such as a steel plate, or a resin-impregnated paper laminate may be used depending on the purpose and application.

On the surface (both sides or one side) of the core material 1, a film adhesive layer 3 in a dry state composed of a thermoplastic resin adhesive 2 is formed. As the adhesive 2, a polyurethane-based or polyester-based thermoplastic resin is used, and its form is a solution-like one prepared by dissolving it in an appropriate solvent or a dispersion-like one prepared by dispersing it in a solvent. It may be present, or may be in the form of powder or film. The effect of the present invention can be obtained even if a cross-linking agent is added to the thermoplastic resin within the range of having the original property of thermoplasticity. Then, a specific method for forming the film adhesive layer 3 in a dry state by using the adhesive 2 in each form will be described below.

When a solution type or dispersion type adhesive is used as the adhesive 2, first, the adhesive 2 is applied by an appropriate method (FIG. 2), and then dried to form a film (third). Figure) method is adopted. The coating method is not particularly limited, and a spray coating method, a brush coating method, a spin coater coating method, an electrostatic coating method, or the like may be selected and used according to the type and form of the adhesive 2. The coating amount is not particularly limited as long as sufficient adhesiveness can be obtained, but is usually about 10 to 100 g / m ² (one side) in terms of solid content. The method of drying the applied adhesive 2 is not particularly limited, but a method of heating and drying at about 50 to 80 ° C. in a normal heating furnace is often used.

When a powdery adhesive is used as the adhesive 2, a predetermined amount of the adhesive 2 is applied to the surface of the core 1 by an electrostatic coating method or the like (FIG. 2). In this case, it is desirable to adjust the particle size to about 100 to 150 mesh pass in advance of coating so that appropriate fluidity can be obtained in the hot-pressing process described later. After the adhesive 2 is applied, the adhesive 2 is once heated in the hot-air oven to a temperature equal to or higher than the melting point to melt-flow the adhesive 2, and then the adhesive 2 is cooled and cured to form a film adhesive layer 3 having a uniform film thickness. It is better to form.

When an adhesive film is used as the adhesive 2, it may be simply placed on the surface of the core material 1. In this case,
Since the adhesive film 3 which has been formed into a dry film in advance is used, the step of applying the adhesive 2, the step of drying and the step of forming a film can be omitted.

Next, the thin wooden board 4 is superposed on the dried film adhesive layer 3 (FIG. 4). The wood thin plate 4 is a wood veneer made of natural wood or artificial wood such as beech, oak, hippo, duck, sen, pine, cedar, cypress, lauan, and teak cut to a thickness of about 0.2 mm by various cutting methods. Depending on the desired wood grain pattern or the like, a grain veneer plate by rotary cutting (round peeling) or half rotary cutting, a grain veneer plate by slice cutting (planing), etc. are appropriately selected and used.

Next, this superposed product is subjected to a heat and pressure treatment to obtain a target composite material 5 (Fig. 5). The temperature of the hot pressing is within a temperature range corresponding to 95 to 80% of the melting point of the adhesive 2 used, which is expressed in absolute temperature. Here, the temperature of the hot pressing is displayed as an absolute temperature. Moreover, the reason why the hot pressing treatment temperature is set to the above range is that the degree of fluidity of the adhesive 2 becomes optimum at a temperature within this range, and the melting point of the adhesive 2 is 80% or less.
If the temperature is lower than the temperature corresponding to%, the fluidity of the adhesive 2 is insufficient, and the heat and pressure treatment requires a long time, and in the temperature range exceeding the temperature corresponding to 95% of the melting point, the adhesive 2 Since the fluidity becomes too large, the adhesive 2 exudes to the surface of the thin wooden plate 4 at the time of bonding, and the thin wooden plate 4 is cracked as the adhesive 2 flows.

Moreover, the pressure of the hot press treatment is 0.1 MPa or more, more preferably 1
Approximately 2 MPa, and the heat and pressure treatment time is preferably 0.5 to 10 minutes. Further, during the hot pressing, it is desirable to degas by repeating hot pressing and depressurizing several times.

In such a bonding method, as described above, the adhesive 2
Since the heat and pressure treatment is carried out in the temperature range where the fluidity is moderate,
The composite material 5 has a good appearance, with no exudation of the adhesive 2 on the surface of the thin wooden plate 4 and no cracking of the thin wooden plate 4.
Can be obtained. Further, since various properties such as adhesiveness and bendability of the obtained composite material 5 are also excellent, it is possible to further perform a forming process such as a bending process. Also,
Since the film adhesive layer 3 in a dry state is formed in advance prior to the heat and pressure treatment, workability during the heat and pressure treatment is improved,
The wood thin plates can be bonded by a short time hot pressing without contaminating the jig or the like.

Hereinafter, the present invention will be described in more detail with reference to examples.

Example I 1) Core material: 0.15 mm thick aluminum alloy (A5086 H1)
9) treated with phosphoric chromic acid was used.

2) Adhesives: The following four types of adhesives were prepared.

A: Dispersion type adhesive made by dispersing thermoplastic urethane resin in water. (Melting point 484.4K) Coating method; electrostatic coating (coating amount; solid content 20 g / m ² (one side)) Drying method; heating at 80 ° C for 15 minutes.

The following adhesive was formed under the above conditions, and the melting pattern of the adhesive A in this adhesive was measured by thermal analysis (TMA). The details of the measuring method are described below.

First, a coating film made of the adhesive A was formed on the surface of the core material by electrostatic coating, and then dried under the above conditions to form a film to form an adhesive body. Then, a probe was placed on the coating film of the adhesive sample obtained by cutting the adhesive into 5 × 5 mm ² squares and heated. The probe is a glass rod having a diameter of 2.0 mm, the end face of which is cut at right angles to the rod axis and flat, and the surface of which is polished.

Therefore, the subsidence amount (depth) of the probe with respect to the heating temperature of the adhesive sample in the heated state was measured. This data means the variation (reduction amount) in the thickness of the coating film made of the adhesive A.

Then, a graph in which the vertical axis represents the ratio of the film thickness of the coating film made of the adhesive A at 296 K (23 ° C. = room temperature) to 1 and the horizontal axis represents the heating temperature (K) is shown in FIG. It was

As shown in FIG. 6, the adhesive A used in this test was 36
At 1.7K (heat distortion temperature), the softening and flow of the thermoplastic urethane resin (adhesive component) begins, and when it reaches around 461.2K, the softening and flow of the resin component increases more rapidly, and the adhesive A exceeds 461.2K. When the resin component expands due to foaming caused by evaporation of the residual solvent such as water, the amount of sinking decreases, and the temperature is further raised, the thickness of the adhesive layer made of the adhesive A becomes the thickness at room temperature. It turns out that it will be thicker than. Then, at 484.4 K (melting point), the adhesive A starts melting.

However, at 484.4K, the expansion was beyond the measurement range, so the measurement was stopped.

A ₁ ; Adhesive A freeze-dried, crushed while being cooled with liquid nitrogen, and added with 1% by weight of Aerosil to make it free-flowing, and further made into a powder of 150 mesh pass . (Melting point 484.4K) Coating method: Electrostatic coating (Coating amount: 50g / m ² (one side)) Drying method: Melt flow in a hot air oven at 503K, then cool and cure.

B: Olefinic hot melt type thermoplastic adhesive film. (Melting point 373K) C; Epoxy resin prepreg (100g / m ² ) (Melting point 370K) 3) Wooden thin plate; 0.20mm thick cover rotary veneer 4) Bonding conditions (hot pressure treatment conditions); Step 1; XK, Y ₁ MPa, Z ₁ minute.

Step 2; decompression, degassing.

Step 3; XK, Y ₂ MPa, Z ₂ minutes.

Step 4; decompression, finishing.

According to each condition shown in Table 1, a core material and a wood thin plate are adhered to manufacture a composite material, and the composite materials are manufactured in Examples 1 to 8, respectively.
It was set as Comparative Examples 1-15. Each temperature XK in Table 1 is the adhesive A
Corresponding to the melting pattern of No. 3, it is shown in FIG.

Using the composite materials obtained in Examples (8 examples) and Comparative examples (15 examples), the exudation and appearance of the adhesive on the surface of the veneer, the appearance of the veneer, the bendability, and the adhesive performance were evaluated. . The results are also shown in Table 2. In the table, "○" means that no problem occurred and can be used, "△" means that problem occurred and limited use was possible, "X" means that problem occurred and cannot be used, and "-" means not tested. It is possible.

As is clear from Table 2, in the examples, there was no bleeding of the adhesive or cracking of the veneer, and it was possible to obtain a composite material having good bendability and adhesive performance. On the other hand, the comparative example 1, in which the hot-pressing treatment temperature was lower than the temperature range of the present invention,
In 2 and Comparative Examples 4 and 5, although exudation of the adhesive and cracking of the veneer were not observed, since the fluidity of the resin was insufficient, a composite material having sufficient bendability and adhesiveness was obtained. I couldn't do it. Further, in Comparative Examples 3 and 6 in which this temperature was set to a temperature exceeding the range of the invention, the fluidity of the resin became too large, and the exudation of the adhesive and the cracking of the veneer occurred. Further, in Comparative Examples 7 to 13 in which the hot-melt type thermoplastic film was used as the adhesive and the heat-pressing treatment was performed at a temperature lower than the temperature range of the present invention, those satisfying the above characteristics were not obtained, and particularly, It was not even possible to test the bendability and the adhesive performance of the materials that were bonded at a high temperature of 403K or higher. Further, even in the comparative example using the epoxy resin prepreg, the one having similarly sufficient characteristics was not obtained.

Example II

In Example I, the core material and the wooden thin plate were bonded in the same manner except that a film-shaped thermoplastic polyester resin (melting point 433K) was used as the adhesive. The adhesion conditions at that time are as shown in Table 3. Table 4 shows the evaluation results of the obtained composite materials.

From the results shown in Tables 3 and 4, it is understood that the same effect can be obtained even when the thermoplastic polyester resin is used as the adhesive.

[Effects of the Invention] As described above, the method for adhering a thin wooden plate of the present invention is such that a dry film adhesive layer made of a polyurethane-based or polyester-based thermoplastic resin adhesive is formed on the core material surface, Since the wood thin plate is adhered by heat and pressure treatment in a temperature range corresponding to 95 to 80% of the melting point indicated by the absolute temperature of the adhesive forming the film adhesive layer, the adhesive is appropriately used. Since the bonding is performed in the flowing region, the adhesive does not exude to the surface of the veneer and the veneer does not crack, and a composite material having an excellent appearance can be obtained. Also, since a dry adhesive film is used,
Good workability and less contamination during hot pressing. Further, it is convenient that any shape of adhesive can be used, and the hot pressing treatment time can be shortened. In this way, even a very thin veneer can be easily bonded without backing, and its application range is expanded, such as providing a composite material for bending.

[Brief description of drawings]

1 to 5 are cross-sectional views illustrating an example of the method of adhering a thin wooden plate of the present invention in the order of steps, and FIG. 6 is a graph showing a melting pattern of an adhesive used in Examples. 1 ... Core material, 2 ... Adhesive, 3 ... Film adhesive layer, 4 ... Wood thin plate.

Claims (1)

[Claims] 1. A film adhesive layer made of a polyurethane-based or polyester-based thermoplastic resin adhesive is formed on the surface of a core material, and a wood thin plate is superposed on the film adhesive layer. A method of adhering a thin wooden plate to a core material by heat-pressing it in a temperature range corresponding to 95 to 80% of a melting point expressed by an absolute temperature of the layered adhesive.