JPS6198783A - Bonding of wood with water-soluble thermosetting adhesive - Google Patents

Abstract

PURPOSE:To prevent the foaming of an adhesive almost completely, to increase the adhesive strength, and to shorten the heating time, by applying a water-soluble thermosetting adhesive to a wood material, sealing the circumference of the bonding surface of the material airtightly, and introducing high-pressure gas to the system to effect the thermal setting of the adhesive. CONSTITUTION:A water-soluble thermosetting adhesive is applied to the wood material 3 such as veneer, wood, lamina, chip, etc. and the circumference of the bonding face is sealed airtightly with the member 4. A high-pressure gas such as compressed air having higher pressure than the saturated steam pressure proportional to the heating temperature of the adhesive is introduced through the inlet 6 into the airtight chamber 5 to effect the thermal setting of the adhesive under high pressure.

Description

[Detailed description of the invention] 7 (The invention uses a water-soluble thermosetting adhesive.

This article relates to a bonding method for bonding wood materials such as veneer intermediate boards, wood, lamina, and chips.

Conventionally, when bonding wood materials such as veneer veneer, wood, lamina, chips, etc., 1, for example, [Plywood adhesive using hop phase] (Subun I+? (Publication No. 55-389'98), [Birch・Production method of Ikuruhoto" (Japanese Patent Publication No. 59-15'059) In response to the,
Water φ increase (water soluble 8 made by adding desired amount of ψ agent, curing agent, etc.)
It is well known that curable adhesives are widely used, and the curing reaction of the resins, for example, urea resin, is
After OO''C1iii, the heating temperature of the adhesive is set at a temperature below the boiling point of water in the -he state, since the heating temperature of the adhesive is effectively and rapidly accelerated at high temperatures, such as around 130°C for phenolic resins. It is said that it is preferable to set it to .

On the other hand, as a heating method for heating and curing the water-soluble thermosetting adhesive that adheres to the adhesive surface of the wood material to be bonded, for example, the ``weight type accumulator in a multi-stage press'' (Utokosho 54- 40545) etc., it was heated to the desired heating temperature! The adhesive was heated internally using a disc or indirectly via a wooden material. In addition to the most general-purpose hot plate heating method, there is also a
There are known high-frequency heating methods in which heating is performed by applying high-frequency current, etc., as disclosed in Japanese Patent Publication No.
In any of the conventionally known heating methods, at least a portion of the adhesive surface during heating is directly exposed to the atmosphere, or has air permeability between it and the atmosphere due to the presence of conduits peculiar to wood materials. and is essentially open to the atmosphere.

However, by the conventionally known heating method as described above, the water-soluble thermosetting adhesive that adheres to the bonding surface of the wood material to be bonded is heated at a temperature higher than the boiling point of water in normal conditions, and is cured. During the course of developing the present invention, it was discovered that when wood materials are bonded, the curing of the adhesive is significantly adversely affected.

That is, when the temperature of the adhesive rises to a temperature higher than the boiling point of wood under normal conditions (nearly 100"C) due to heating, the water contained in the adhesive boils and foams in the adhesive. It will happen.

However, as mentioned above, at least a portion of the adhesive surface is open to the atmosphere, so the generated steam always gradually leaks into the atmosphere either directly or through conduits in the wood material or gaps in the adhesive surface. , a pressure difference constantly occurs between the adhesive surface and the atmosphere, and the foaming continues even during the curing reaction of the adhesive, resulting in the adhesive penetrating into the interior of the wood material more than necessary.
Alternatively, the adhesive may protrude from the bonding surface, or even the adhesive remaining on the bonding surface may harden into a thin carmela shape, and the strength that it should originally have cannot be fully exhibited.

However, it is possible to avoid foaming of the adhesive by limiting the heating temperature of the adhesive to a temperature higher than the boiling point of water under normal conditions.

In that case, not only does the time required for heating become extremely long, but depending on the adhesive, the adhesive may harden without achieving an effective degree of hardening of 1ε, resulting in problems with adhesive strength, which is not practical.

As a result, in the past, the amount of adhesive used tends to be excessive, and the temperature of the adhesive tends to rise slowly due to latent heat loss due to steam leakage, and the heating time tends to become longer.

The present invention was developed in order to solve the problems caused by the conventional heating method, and the water-soluble thermosetting 5! When bonding the wood materials by heating the adhesive at an appropriate heating temperature higher than the boiling point of water in a coma and curing the adhesive, at least an appropriate range that includes the adhesive surface is applied to the adhesive surface. By airtightly closing the surrounding area, and introducing high-pressure gas such as compressed air having a pressure higher than the saturated vapor pressure proportional to the heating temperature into the air chamber formed due to the blockage, It is constructed so that the adhesive is cured under high pressure.

According to the bonding method according to the present invention configured as described above, even if the temperature of the adhesive rises to a temperature higher than 8 points of water under normal conditions due to heating, saturation is proportional to the heating temperature. Since the pressure is higher than the steam pressure, boiling of water contained in the adhesive is suppressed, and the adhesive hardens while preventing or significantly reducing foaming, thereby preventing the adhesive from foaming. Alternatively, as a result of curing while significantly reducing the adhesive strength, the adhesive strength of the adhesive is significantly improved compared to conventional adhesives, and the water boiling point is
l! Along with the prevention of WI heat loss due to the suppression of heat generation, the temperature rise of the adhesive is effectively promoted, and the heating time tends to be shortened compared to the conventional method.

The present invention will be described in more detail below based on an example of implementation illustrated in the drawings.

The method for adhering wood materials according to the present invention is as follows: 1. As illustrated in FIG. ,
For example, a work consisting of a fluid cylinder, etc. 5) A water-soluble thermosetting adhesive is interposed at a desired position between the heat sinks 1 and 2 which are arranged in parallel so as to be separated from each other by a J mechanism (disclosure omitted). At least a plurality of laminated veneer veneers 3 are inserted, pressed and heated from the front and back sides, and the veneer veneers 3 are bonded together with +ii+ strong adhesive! When performing pipework, it is possible to press an elastic airtight member 4 made of silicone rubber, fluororubber, etc., to the r-side heating plate 2 at a position corresponding to the vicinity of the veneer on the bottom surface of the upper 8-plate 1. When the veneer veneer 3 is pressed, the area around the veneer veneer 3 is closed off in an airtight manner, and the airtight chamber 5 formed by the heated aluminum 2 and the airtight member 4 is filled with 1: Through the high-pressure gas introduction hole 6, which is drilled to communicate from the side of the heating platen 1 to the vicinity of the inside of the airtight member 4, the saturated steam pressure, which is proportional to the heating temperature of the heating platen 1-2, is A high-pressure gas such as compressed air is introduced to cure the adhesive under high pressure.

For example, according to the above-mentioned bonding method, as the mature board 1.2 is heated, the temperature of the adhesive that adheres to the bonding surface of the veneer veneer 3 rises to a temperature higher than that of water under normal conditions. temperature, i.e. 1
Even if the temperature reaches around 00°C, the pressure is higher than the saturated steam pressure, which is proportional to the heating temperature, so boiling of the water contained in the adhesive is suppressed, and the adhesive does not foam. As a result, the adhesive strength of the adhesive is significantly improved compared to conventional methods; the temperature of the adhesive is also increased by preventing latent heat loss due to suppression of water boiling aS generation, etc. The increase in temperature is effectively promoted, and the heating time tends to be shortened compared to conventional methods.

In addition, a common water-soluble thermosetting adhesive for plywood, which is mainly composed of melamine and urea co-condensed resin and added with a water extender, etc. in a typical mixing ratio, was applied in the usual amount (30 g/square).
A large number of plywood coated using the conventional adhesive method and a large number of plywood coated using the adhesive method according to the present invention were manufactured, and a similar penetration peeling test was conducted to compare the adhesive strength of the latter. This was an average improvement of more than 20%. Therefore,
As another comparative example, a large number of plywoods were prepared using the bonding method according to the present invention, which reduced the amount of adhesive applied by approximately 6%, and plywood was obtained using the bonding method according to the present invention, which reduced the pressing and heating time by approximately 9%. When they were manufactured and compared with ordinary plywood using conventional adhesive methods, both products were able to obtain adhesive strength that exceeded that of conventional adhesives. In still other experiments.

On average, the moisture content exceeds the appropriate moisture content for plywood by more than 10%. relatively r-45
When we produced a large number of plywood using the bonding method according to the present invention and plywood using the conventional bonding method using the same coating and heating time for veneer veneers with a moisture content, we found that in this case as well. I was able to obtain communication skills that surpassed the conventional contact-6 method.

In addition, in the embodiment illustrated in FIG. 2, Todoroki's water-soluble thermosetting adhesive is applied to the circumferential surfaces of each meter, and the adhesive is placed on the caul plate 7 so that the surface layer is fine and the center layer is rough. A holding member made of metal, hard synthetic resin, etc. is used when manufacturing a particle board by inserting a large number of tacked chips 8 between the mature plates 1 and 2, pressing and heating them, and curing the adhesive. An elastic airtight member 4 made of silicone rubber, purified fluororubber, etc. is disposed in a position corresponding to the vicinity of the chip periphery of the upper 8 board 1 so as to be able to be pressed against the caul board 7 via the chip 8. At the time of pressing, the vicinity of the tip 8 is closed airtightly, and the hot plate 1, the coal plate 7 and the holding member 9 are closed together with the closing.
and into the airtight chamber 5 formed by the airtight member 4, - through the high-pressure gas introduction hole 6 bored so as to communicate from the side of the upper heating platen 1 to the vicinity of the inside of the holding member 9, the heating plate lφ2. A high-pressure gas such as compressed air with a pressure higher than the saturated steam pressure, which is proportional to the heating temperature, is introduced to cure the adhesive under high pressure. Curing was effectively promoted, and a particle board that was stronger than conventional products was obtained.

Furthermore, although not shown in the drawings, various experiments have been carried out, such as gluing a plywood veneer for chemical tJ1 on the surface of particle board, or gluing a metal plate on one side of 1F plywood. We also confirmed the adhesion of materials to each other and the adhesion of materials other than wood to wood, and found that the desired effect could be obtained with both methods. It was confirmed that there is no practical problem in bonding using a plastic adhesive in combination, but in any case, following the conventional method, the process from the time the adhesive adheres to the adhesive surface of the wood material until the time of heating. Providing an arbitrary residence time in between, or once cold-pressing the objects to be adhered together prior to heating, was effective in improving adhesiveness.

When sealing the area around the bonding surface of the wood material to be bonded, as exemplified in the above two embodiments, it is best to airtightly close the area around the entire object to be bonded, including the bonding surface. Although it is convenient, it can be used, for example, when gluing the end surface of a piece of wood 10 with extremely dense fibers, as illustrated in FIG. 3, or when gluing the sides of lamina, wood, etc. As is clear from Fig. 3, if there is substantially no air permeability between the adhesive surface of the wood material and the atmosphere,
Appropriate form I with airtightness! ! There is no practical problem even if the closing member 11 of , is used to locally close only the vicinity of the adhesive surface of the wooden material in an airtight manner.

Furthermore, as exemplified in the first and second embodiments, if an elastic material is applied to at least a part of the member used for closing, it is possible to adapt to the non-uniformity of the shape of the original wooden material. Alternatively, it is convenient because it makes it possible to follow the deformation of the wood material due to compaction, etc., but the introduction of high-pressure gas Φ
In order to prevent gas from leaking to Mars due to deformation caused by heating, etc., it is preferable that the material properties such as I61 thermal properties and rigidity and shape of the material used for the closure be selected appropriately, and materials that do not have thermal properties or elasticity should be selected. Although it is not impossible to block the air using wood, and utilizing the elasticity of wood materials is also effective in improving airtightness, in any case, even if the blockage is such that a small amount of high-pressure gas leaks, There is no practical problem as long as the desired high pressure state can be maintained in the airtight chamber at all times by continuously introducing high-pressure gas.1 Occlusion in the present invention is not necessarily limited to a strictly airtight state. .

In addition, as a means for heating the welding agent, see iii.
Numbers 11 and 21 are illustrated in the example of the eye.

Although it is possible to use an 8-plate heated by an appropriate heat source, 1.For example, a method in which a high-frequency current is applied using a high-frequency current oscillator or the like to heat the adhesive is effective because the thickness of the wood material is comparatively high. Any heating means may be used as long as it is suitable for the production of molded plywood or for the production of molded plywood, and is capable of heating the adhesive.
Theory I, for example on one side of a thick particle port? In cases where there is a bias in the heating position or heat conductivity, such as when bonding a thin plywood veneer or a metal plate on one side of plywood, it is necessary to unilaterally apply heat only from a specific direction. It is also possible to use a form in which it is heated to a certain temperature.

Although compressed air is cheap, simple, and effective as a high-pressure gas to be introduced into the gas chamber formed due to blockage, it is also possible to use various inert gases, heated gas, etc. In addition, the high-pressure gas may be introduced into the closed room at an appropriate time immediately before foaming occurs in the adhesive, but preferably when using a heated atmosphere, the moisture content is relatively low. The best time to introduce a dry heated bath into an airtight room is relatively quickly after the blockage.
J, and furthermore, it is desirable that the high-pressure gas be removed to the outside of the airtight chamber before the blockage is released.

As is clear from the above, the method for bonding wood materials according to the invention can be implemented in various forms, but in any case, the effects of its implementation are extremely large, such as reducing bonding costs and increasing productivity. This contributes to the improvement, etc.

[Brief explanation of the drawing]

The drawings are for explaining the invention. Fig. 1 is a partially cutaway side view for explaining an embodiment of gluing a plurality of veneer veneers together according to the present invention, and Fig. 2 is an explanatory side view showing an embodiment of gluing a large number of chimps according to the present invention. FIG. 3 is a partially cutaway side view for explaining another embodiment of the method for adhering wood materials according to the present invention. 1, 2Φ-・Heat plate, 3・Warp/Veneer veneer, 4・Fist・Airtight member, 5・Air chamber, 6・Introduction hole for heavy pressure gas, 7
... Call plate, 8... Chip, 9... Holding member,
10...Gravel wood, 11...Closing member patent applicant Meinan Seisakusho Co., Ltd. Procedures Amendment (voluntary) October 24, 1980

Claims (1)

[Claims] When bonding the wood materials by heating the water-soluble thermosetting adhesive that adheres to the bonding surface of the wood materials to be bonded at an appropriate heating temperature higher than the boiling point of water under normal conditions and curing the adhesive, at least the above-mentioned Within an appropriate range that includes the adhesive surface, the area around the adhesive surface is closed in an airtight manner, and a pressure higher than the saturated steam pressure proportional to the heating temperature is applied to the airtight chamber formed due to the closure. A method for bonding wood materials using a water-soluble thermosetting adhesive, characterized in that the adhesive is cured under high pressure by introducing high-pressure gas such as compressed air.