JPH0839676A - Sandwich welding method - Google Patents

Abstract

PURPOSE:To weld polyethylene or polypropylene by a hot air welding method simply at a low cost. CONSTITUTION:Binders 2a, 2b comprised of a polymer compound having segments of styrene and rubber are formed on the surfaces of polyethylenes 1a, 1b (or polypropylene) of base materials. The binder is interposed between the polyethylenes 1a, 1b and the three parties are heated and melted at the same time at almost 200 deg.C, through which they are made to unify in a sandwiched state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for welding various molded articles made of polyethylene or polypropylene.

[0002]

2. Description of the Related Art For example, in order to weld base materials made of vinyl chloride, the base materials are pressed while the welding rod is melted with hot air between the base materials.

On the other hand, in order to weld the base materials made of polyethylene or polypropylene together, a welding rod made of the same material as the base material is overheated and melted in a welding machine, and the base material is slowly mixed with the base material while being extruded from the tip of the nozzle. The method of putting them into practice, or the method of interposing a metal net or the like between the base materials and heating them by high frequency in this state to fuse them has been put into practical use.

[0004]

In the case of polyethylene or polypropylene, reliable welding can be performed by using the above-mentioned conventional method. However, this method requires the use of a special welder.

Therefore, even in the case of polyethylene or polypropylene, it is desired to adopt the simple hot-air welding method of the above-mentioned conventional example like general thermoplastic resins such as polyvinyl chloride, polyester, etc. Molten polyethylene or polypropylene did not fuse at all, and after peeling off after cooling, almost 0.5 kg /
It peels off neatly with a force of less than cm.

Various theoretical reasons have been given to this characteristic property of polyethylene and polypropylene. One of them is that the surface of polyethylene or polypropylene is always fragile, and polyethylene or polypropylene is the same when melted, or polypropylene. There is a theory that there is an extremely thin layer that acts to prevent the fusion of fellows. Alternatively, there is a theory that justifies it by the polarity and crystallinity of polyethylene and polypropylene, but it is unclear whether these theories are correct. However, it is generally said that all adhesives such as epoxy, urethane, SGA, etc. have no effect on the adhesion of polyethylene and polypropylene, and that a fragile layer is formed on the surface by observing the surface with an electron microscope. Is accepted. Certain facts are
It means that adhesives do not work for polyethylene and polypropylene, and hot-air welding fails almost 100%.

The present inventor has conducted various tests and studies to solve the above conventional problems, and
Alternatively, the inventors have found a joining material that improves the poor fusion property of polypropylene, and intend to provide a sandwich welding method that enables easy and low-cost welding by hot air welding by using this joining material. Is.

[0008]

Means for Solving the Problems The technical means of the present invention for achieving the above object is to provide a base material made of polyethylene or polypropylene between a base material and a thermoplastic resin of a different kind, or It is composed of the compound, and a bonding material having the property of removing or suppressing the adhesion inhibiting factor existing on the surface of the base material is interposed, and the three members are simultaneously heated and melted so as to be integrated in a sandwich form. It was done.

Then, as the above-mentioned joining material, a polymer compound having a segment of styrene and rubber, for example, a block polymer compound or a graft polymer compound is used.

The above-mentioned joining material does not adhere even if it is simply melted on the surface of polyethylene or polypropylene and cannot be a so-called adhesive, but if the surface of polyethylene or polypropylene is pushed up by the hot air above the melting temperature and pressed, it will bond. The force rises sharply and has sufficient strength for practical use. In other words, it is conjectured that some of the welding-inhibiting factors that occurred in the case of polyethylene and polypropylene were removed or their generation was suppressed by the presence of these inclusions. Therefore, the heating temperature of the bonding material is 145 ° C to 2 ° C.
The temperature can be set to 50 ° C., and preferably around 200 ° C.

[0011]

According to the above technical means, the joining material is interposed between the base materials made of polyethylene or polypropylene, and the three materials can be integrated into a sandwich by heating and melting them at the same time. . In this way, welding can be performed by the hot air welding method.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are explanatory views showing a sandwich welding method in a first embodiment of the present invention.

A composition comprising a block polymer having styrene and rubber segments, an additive, hexane and heptane was prepared, and first coated on a surface of a set of polyethylenes 1a and 1b as shown in FIG. After standing for a while, the solvent was evaporated to form the bonding materials 2a and 2b. Next, as shown in FIG. 2, a bonding material 2 for each polyethylene 1a, 1b
The polyethylenes 1a and 1b and the bonding material 2 are heated with hot air (see the arrow) at 200 ° C. (the temperature at which the surfaces of the polyethylenes 1a and 1b are sufficiently melted) so that the surfaces a and 2b face each other
Polyethylene 1a while heating and melting a and 2b at the same time,
By combining 1b and the bonding materials 2a and 2b, as shown in FIG. 3, it was possible to perform welding so as to be integrated into a sandwich.

As Comparative Example 1, under the same conditions as in the first embodiment, except that hot air at 120 ° C. (a temperature at which the dry coatings of the bonding materials 2a and 2b are sufficiently melted) was used for heating in FIG. Welded.

As a test example in the first embodiment of the present invention and the comparative example 1, as shown in FIGS. 1 to 3, the joining materials 2a, 2 are attached to the corresponding end portions of both polyethylenes 1a, 1b.
Welded polyethylene 1a, 1b, leaving the part without b
The end portions on the same side in which the bonding materials 2a and 2b were not interposed were clamped by clamps 3a and 3b as shown in FIG. 4, and T peeling was performed to test the peel strength. As a result, the first example of the present invention was 10 to 20 kg / cm, while the comparative example 1 was 0.05 to 0.2 kg / cm.

As another test example, as shown in FIG. 5, both polyethylenes 1a according to the first embodiment of the present invention and the comparative example 1,
Bonding materials 2a, 2 in polyethylene 1a, 1b welded leaving a portion without bonding materials 2a, 2b on the opposite side of 1b
As shown in FIG. 6, the opposite end where b was not interposed was clamped by clamps 4a and 4b of a tensile tester, and a tensile test was performed. As a result, the first embodiment of the present invention is 6
It was 0 kg / cm ² or more, while the comparative examples were 1 to 3
It was kg / cm ² .

Second embodiment of the present invention and its comparative example 2
As polypropylene, polypropylene is used in place of the polyethylene of the first embodiment and comparative example 1, and otherwise the first
Welding was performed in the same manner as in Example 1 and Comparative Example 1.

As a result of T peeling and testing the peel strength, the second example of the present invention was 5 to 10 kg / cm, while the comparative example 2 was 0.05 to 0.1 kg / cm. Met. Further, as a result of a tensile test using a tensile tester, polypropylene was broken in the second example of the present invention, while Comparative example 2 was 1 to 3 kg / cm ² .

As is apparent from the above test results, practical welding strength could be obtained by melting the surface of the base material made of polyethylene or polypropylene simultaneously with the joining material.

In addition, almost the same welding strength can be obtained by using the graft polymer compound having the styrene and rubber segments instead of the block polymer compound having the styrene and rubber segments in the above examples. It was

[0021]

In summary, according to the present invention, polyethylene or polypropylene can be welded by the hot air welding method, so that welding can be performed easily and at low cost.

[Brief description of drawings]

FIG. 1 is a perspective view showing a sandwich welding method according to a first embodiment of the present invention, in a state where a joining material is formed on a surface of polyethylene for a T peel test.

FIG. 2 is a perspective view showing the same welding method and in a state where polyethylene and a bonding material are heated with hot air.

FIG. 3 is a perspective view showing the same welding method in a welding completed state.

FIG. 4 is an explanatory diagram of a T-peeling test after completion of welding by the same welding method.

FIG. 5 is a perspective view showing the welding method, in which a bonding material is formed on the surface of polyethylene for a tensile test.

FIG. 6 is an explanatory diagram of a tensile test after completion of welding by the same welding method.

[Explanation of symbols]

 1a polyethylene 1b polyethylene 2a joining material 2b joining material

Claims (1)

[Claims] 1. A set of a base material made of polyethylene or polypropylene and a base material and a thermoplastic resin of a different type, or a mixture thereof, between a base material, which does not remove adhesion inhibiting factors existing on the surface of the base material. A sandwich welding method in which a joining material having a suppressing property is interposed and the above three members are simultaneously heated and melted to be integrated into a sandwich.