JPH026603B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for bonding the end of plywood.

The applicant previously filed Japanese Patent Application No. 54-207 and Patent Application No. 53-
No. 163346 was filed for an invention relating to a method for joining long plywood. As shown in this application, the conventional method for producing long plywood involves subjecting the end of the plywood to arbitrary processing such as scarf cutting, and applying room-temperature curing thermoplastic type or thermosetting type synthetic resin adhesive to the end of the plywood. After that, the butt ends of adjacent plywood boards were butted against each other and pressed and joined using cold press and hot press.

By the way, in the plywood production method in which veneers are bonded by cold press or hot press, as shown in Figure 1A (temperature distribution diagram of each veneer to be bonded in the case of room temperature curing or external heating), With the heating method, the temperature transfer to the core of the plywood is slow, so
Adhesive curing time is long, reducing work efficiency.

On the other hand, in order to improve the above-mentioned workability, there is also a method of applying high frequency power to the veneers to be bonded, internally heating them, and curing and bonding them. This bonding method that applies high-frequency power belongs to the internal heating method, as shown in Figure 1B (temperature distribution diagram of each veneer to be bonded in the case of high-frequency power heating), and it Although the temperature rise is slower, this method has the advantage that bonding can be performed in a shorter time than the external heating method. However, since the bonding method using high-frequency power is an internal heating method, high-frequency power energy is consumed to increase the temperature of the moisture in the adhesive and the moisture moved from the core near the outer surface, and the temperature increase near the outer surface is This results in slower curing of the adhesive on the outer surface and failure of adhesion on the surface layer due to evaporation of moisture.

The present inventor has discovered that when the external heat bonding method and internal heat bonding method are used in the end bonding method of plywood, etc.
As a result of various studies on how to eliminate the drawbacks of both of the above-mentioned bonding methods, it has been found that by using both of the above-mentioned methods in combination, the drawbacks of both methods can be offset.

Based on the above findings, the present invention employs a method for bonding the ends of plywood, etc., as described below, and provides a bonding method with short bonding time and high bonding strength.

Embodiments of the method of the present invention illustrated in the drawings will be described below.

(Description of Examples) As shown in FIG. 2, plywood 1 is formed by laminating and bonding a plurality of veneers cut to an arbitrary thickness so that the fiber directions are perpendicular to each other.

Plywood 1 is 3 ply, 4m/m thick, and has a moisture content of 10~
Finished at 15%. A slope at an arbitrary angle is formed on the end surface of the front veneer 2 in the fiber direction in a direction perpendicular to the fiber direction of the veneer 2. The length L of the slope 3 portion is preferably formed at an angle that is 2 to 15 times the thickness θ of the front veneer 2.

If the length L of the slope 3 portion is less than twice the thickness θ of the veneer 2, the adhesive area of the slope will be reduced and the bonding strength will be weakened. Also, the length L of the 3rd slope part is the length of the veneer 2
When the thickness θ is 15 times or more, actual cutting is difficult, and the bonding strength not only does not increase in proportion to the increase in length, but also decreases.

A slope 3' substantially parallel to the slope 3 formed on the front veneer 2 is formed on the back veneer 4. The slope 3' of the back veneer 4 forms a convex portion 5. The length L' of the slope 3' is approximately equal to the length L of the slope 3 of the table unit 2. On the veneer 6 laminated between the front and back veneers 2 and 4, an abutment surface 7 cut at an arbitrary angle is formed on the slopes 3 and 3'. Thus, the end surface of the plywood 1 has a Z-shaped end shape. On the other hand, the joint end surface of the adjacent plywood 1a is cut into a Z shape by fitting and butting against the Z shape end surface of the plywood 1. A room-temperature thermosetting or room-temperature thermoplastic type synthetic resin adhesive is applied to the joint end surfaces of the plywood boards 1 and 1a, and the end surfaces are butted against each other. When joining the Z-shaped end surfaces of the plywood boards 1 and 1a, the joints are pressed from above and below with hot platens 8, 8. The heating plate 8,
Reference numeral 8 also serves as a heating plate for external heating and an electrode plate for applying high frequency power for internal heating. In FIG. 3, 9 is a heating plate cord, and 10 is a high frequency power cord. External heating using the heating plate 8 is performed at 150° to 250° C. for a short time. In the method of the present invention, since internal heating is performed simultaneously with external heating, the temperature distributions of the front and back veneers 2, 4 and the intermediate veneer 6 are averaged. As a result, the moisture in the adhesive is instantaneously evaporated over the entire thickness of the plywood, while the moisture released from the core of the wood to the outside by the pressure of the hot plates 8, 8 is also evaporated from the inside and outside. Evaporates quickly on heating.
Therefore, moisture in the adhesive and the plywood does not remain in the joint and reduce the adhesive strength of the adhesive. 4
As a result of an experiment in which m/m thick plywood was bonded using vinyl acetate adhesive as described above, it was found that it took 4 seconds to bond when only high-frequency power was applied, but external heating was also used. In that case, it only took 3 seconds. Furthermore, as a result of an experiment by gluing plywood with a thickness of 12 m/m using vinyl acetate adhesive as described above, it was found that when only high frequency power was applied,
The time required for bonding was 30 seconds, but when external heating was also used, it took only 13 seconds.

Effects of the present invention: Since the plywood boards 1 and 1' are joined by both external heating and internal heating, the temperature distribution at the joint between the front and back veneers 2 and 4 and the intermediate veneer 6 is made uniform. As a result, the adhesive and moisture in the plate quickly evaporate, reducing the time required for bonding and increasing adhesive strength.

Since the joint end surfaces of the plywood boards 1 and 1a are O-shaped, no slipping occurs during joining. Therefore, the bonding can be performed reliably during bonding, and the high-frequency current for internal heating is reliably applied to the inside of the bonded portion, thereby increasing the bonding strength.

[Brief explanation of drawings]

Figure 1 A: Temperature distribution chart for room temperature curing and external heating when bonding plywood, Figure 1 B: Temperature distribution diagram during high-frequency power heating when bonding plywood, Figure 1 C: Adhesive resin curing time Comparison diagram, Figure 2: Cross-sectional view of plywood joint, Figure 3: Explanatory diagram of plywood joining method, 1, 1a...plywood, 2...front veneer, 3...upper slope, 3'...bottom Slope, 4...Back veneer, 5...Protrusion,
6...Middle veneer, 7...Abutting surface, 8...Heating plate, 9...External heating cord, 10...Internal heating cord.

Claims (1)

[Scope of Claims] 1. Processing the ends of boards such as plywood 1 and 1a to be joined into an appropriate shape, applying adhesive and butting them together, and using a heating plate for externally heating the joints of the ends from above and below. A method for joining plates such as plywood, characterized in that the joining portions are bonded by pressing with heating plates 8, 8 which also serve as electrode plates for applying high-frequency power for internal heating. 2 Cut the end surface of one plate such as plywood 1 to be joined into a Z-shape consisting of upper and lower slopes 3, 3' and a butt surface 7 between the slopes 3, 3', and The plywood according to claim 1, wherein the end surfaces to be joined are similarly cut into a Z shape so that they can fit into the end surfaces of the plywood 1, and the end surfaces of the plywood boards 1 and 1a are butted and bonded. How to join plates such as.