JPH0631808A - Bonding method - Google Patents

Abstract

PURPOSE:To provide a versatile bonding method by high frequency induction heating which is easily employed and particularly suitable for bonding a large and a long material to be bonded by applying a solvent which swells the material on its surface and applying high frequency to the surface with a high frequency induction heating apparatus. CONSTITUTION:A thermoplastic polymer such as chlorinated polyethylene and polyvinyl chloride is bonded by high frequency induction heating. In this method, a solvent including methylethyl ketone and toluene which swells a material 5 to be bonded is applied on its surface 2. High frequency is applied to the surface 2 with a high frequency induction heating apparatus including a high frequency welder based on a flat plate electrode and a high frequency sewing machine based on a roller current 3. The frequency generally used in this method is 40.68 or 27.12MHz of industrial allocation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining method for thermoplastic polymers, and more particularly to a joining method by high frequency dielectric heating.

[0002]

2. Description of the Related Art Conventionally, various types of joining by heat have been developed as a joining method for molded articles of thermoplastic polymers. Among them, the high frequency dielectric heating method can directly heat the bonding surface by utilizing internal heat generation due to the dielectric loss of the material to be bonded, and the bonding surface is clean and high bonding force can be obtained compared to other thermal bonding methods. It has been widely used.

[0003]

From the principle of high frequency dielectric heating, the longer the high frequency application time, the larger the amount of heat generated from the objects to be bonded and the higher the bonding force. In other words, increasing the high frequency output is the simplest method for increasing the joining speed and the joining force. However, when the high frequency output is increased, the high frequency dielectric heating device becomes very large due to the use of a high power oscillator or the like, and there are many cases where it is not suitable for practical use. In particular, the enlargement of the machine is not allowed in a small high-frequency induction heating device that moves a fixed object to be joined. Therefore, there is a demand for a method of extracting heat from the objects to be joined with high efficiency and joining them rapidly and strongly.

Therefore, various methods have been proposed to increase the heat generation efficiency during dielectric heating. JP-A-52-108
In No. 468, the object to be bonded or the electrode is heated by a means different from the high frequency dielectric heating to raise the internal temperature of the object to be bonded and the bonding is performed in a shorter time. Certainly, this method is effective, but it has a drawback that the equipment becomes large because a heating device and a temperature control device are added. From the same idea, in JP-A-62-297137, another dielectric sheet is sandwiched between the article to be joined and the electrode, and the heat is generated to uniformly heat the article to be joined to improve the efficiency of joining. A method has been proposed. However, according to the study by the present inventors, it was found that the material is significantly limited and that a sufficient heating effect cannot be obtained when the object to be bonded is thick.

A method has also been proposed in which a material having a large dielectric loss is sandwiched between objects to be joined and the objects to be joined are melted and joined by the heat generated (JP-A-62-50122).
It has been found that there is a problem in that a substance of another component enters between the objects to be joined, and in some cases a sufficient joining force cannot be obtained. Further, Japanese Patent Laid-Open No. 59-156714 proposes a method of impregnating a material to be bonded with a hygroscopic substance to increase the heat generation efficiency of the material to be bonded by moisture absorption. However, the objects to which this method can be applied are extremely limited and are generally difficult to use.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the conventional method, to provide a versatile, easy-to-use, and efficient method of joining by high-frequency induction heating. Especially. That is, according to the present invention, when joining a thermoplastic polymer by high frequency dielectric heating, a solvent having a swelling property with respect to an object to be joined is applied to the joining surface, and a high frequency is applied to this by a high frequency dielectric heating device. A joining method is provided.

The high frequency dielectric heating device used in the present invention is
Either a high frequency welder based on a flat plate electrode or a high frequency sewing machine based on a roller electrode may be used. Among them, the present invention has a great effect particularly in the case of continuously joining with a high-frequency sewing machine or in the case of performing joining work while moving a fixed object to be joined with a small-sized high-frequency dielectric heating device. The frequency used is not particularly limited, but is 40.68 MHz for industrial allocation, 2
7.12 MHz is generally preferred.

The thermoplastic polymer which can be used in the present invention may be any one capable of high frequency dielectric heating such as chlorinated polyethylene, polyvinyl chloride, polyvinylidene chloride, or polyamide, which has a large dielectric loss. The form may be a film, a sheet, a non-woven fabric, a woven or knitted fabric, or the like, or may be one obtained by laminating or coating a cloth or the like with a thermoplastic polymer having a large dielectric loss.

The solvent to be applied to the joint surface has a completely different purpose from the usual application for degreasing and must have a swelling property for the objects to be joined. There are various solvents for this purpose, among aromatic hydrocarbons, petroleum hydrocarbons, halogenated hydrocarbons, ketones, esters, ethers, alcohols and the like. For example, for chlorinated polyethylene, methyl ethyl ketone and toluene are particularly preferable. The amount of solvent applied must be determined according to the degree of solvent absorption and swelling in the article. The article to be joined may be appropriately subjected to high-frequency dielectric heating after applying the solvent. However, when the solvent is applied to the object to be bonded, the object to be bonded becomes tacky during the process of adsorption, diffusion and swelling of the solvent. Therefore,
If tackiness is required, an appropriate open time may be taken and the objects to be joined may be pasted together when the desired tackiness is exhibited.

[0010]

According to the present invention, an efficient method of joining by high frequency induction heating is provided. This effect is considered as follows. When the solvent molecules penetrate into the amorphous phase of the object to be bonded, the interaction between the amorphous molecules is reduced, and as a result, the mobility of the amorphous molecules is increased and the molecular orientation is reduced. further,
Regarding crystals, incomplete crystals existing at the crystal / amorphous interface are gradually dissolved and transformed into an amorphous phase. From the above points, the melting point of the object to be joined is lowered and the dielectric loss tangent (t
It is understood that the maximum value of an δ) rises. That is, a decrease in the melting point of the object to be bonded means that the amount of heat required for melting decreases, and an increase in the maximum value of the dielectric loss tangent means that the amount of heat obtained from the object to be bonded increases. . Due to the above synergistic effect, even if the same high-frequency dielectric heating device is used, it is possible to efficiently take out the amount of heat generated from the objects to be joined and perform the joining. That is,
If the heating time is the same, the bonding force will be high, and if the bonding force is the same, high-speed bonding will be possible. Further, when the solvent is absorbed by the object to be bonded, the bonding surface has an adhesive property, so that the adhesive force can be used to temporarily fix the object to be bonded. This is particularly effective for large and long objects to be joined.

[0011]

EXAMPLES The present invention will be described in detail below with reference to FIG. 1 by way of examples. After a solvent is applied to the joint surface 2 of the chlorinated polyethylene sheet 1 having a thickness of 3 mm, two sheets of this are superposed. The superposed sheets were passed through the roller electrode 3 of a small high-frequency induction heating device (output: 80 W, frequency: 40.68 MHz) and the pressure / cooling roller 4 and joined. Table 1 shows the results obtained by changing the solvent and changing the bonding speed. It should be noted that when there is a sufficient joining force, it is ◯, when the joining force is partially insufficient, it is Δ, and when the joining force is completely insufficient, it is x. Experiment No. When an appropriate solvent having a swelling property is applied to the article to be joined as in Nos. 1 and 2, the joining is sufficiently performed even if the joining speed is increased, while the experiment No. It can be seen that the bonding efficiency is low when a solvent having no swelling property such as Nos. 3 and 4 is used or nothing is applied.

[0012]

[Table 1]

[Brief description of drawings]

FIG. 1 is a schematic view of a case in which a solvent-coated object to be bonded is bonded by a high-frequency dielectric heating device.

[Explanation of symbols]

 1 Object to be bonded before bonding 2 Bonding surface to which solvent is applied 3 Roller electrode of high frequency dielectric heating device 4 Pressure / cooling roller 5 Object to be bonded after bonding

Claims (1)

[Claims] 1. When joining a thermoplastic polymer by high-frequency dielectric heating, a solvent having a swelling property with respect to an article to be joined is applied to the joining surface, and a high frequency is applied to this with a high-frequency dielectric heating device. Characteristic joining method.