JPH08198984A - Method for modifying surface of fluororesin film - Google Patents

Abstract

PURPOSE: To provide a method for modifying the surface of the fluororesin film to impart excellent adhesiveness to the surface, by applying a high electric voltage to the fluororesin film under specific conditions to generate corona discharge. CONSTITUTION: The method for modifying the surface of the fluororesin film comprises disposing the film of a fluororesin such as ethylene-tetrafluorethylene copolymer, polyvinyl fluoride, tetrafluoroethylene-perfluoroethylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer between a discharge electrode and a counter-electrode, and subsequently applying a high electric voltage having an average electrolytic strength of 40-200KV/cm, a pulse width of 1-50μmS, and a pulse frequency of 10-150pps to generate a corona discharge. Thus, the surface-modified film having a contact angle of <=80 degree with water is obtained. The average electrolytic strength is expressed by application voltage/interelectrode distance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-modified fluororesin film, a surface-modified fluororesin film and a method for adhering a fluororesin film.

[0002]

2. Description of the Related Art Fluororesin films have been used in various fields by taking advantage of their surface characteristics, but they have a problem of low adhesiveness to other materials. In order to solve this problem, attempts have been made to improve the adhesiveness by modifying the surface of the fluororesin film. Among them, the dry processes such as corona discharge and plasma treatment have been particularly noted because they do not require a cleaning step. However, a fluororesin film having sufficient adhesiveness has not yet been obtained by these treatments under normal pressure. JP-A-6-22
Japanese Patent No. 0231 discloses a method of plasma etching the surface of a fluororesin in a mixed gas atmosphere of hydrogen and nitrogen. Japanese Unexamined Patent Publication (Kokai) No. 5-43721 discloses a surface modification method for a fluororesin film in which corona discharge is performed in the presence of a rare gas, carbon dioxide and a saturated hydrocarbon. Either method can obtain a fluororesin film having excellent adhesiveness, but both require a special gas composition other than air, and in the former case, under reduced pressure, in the latter case, the degree of freedom of the gap between the electrodes is increased. Has problems such as low.

[0003]

SUMMARY OF THE INVENTION The present invention is intended to provide a technique for modifying the surface of a fluororesin film to impart excellent adhesiveness without using these industrially disadvantageous conditions. is there.

[0004]

According to the present invention, a fluororesin film is arranged between a discharge electrode and a counter electrode, and an average electric field strength represented by an applied voltage / a distance between electrodes is 40 to 200 kV / cm,
Pulse width is 1 to 50 μs and pulse frequency is 10 to 15
The present invention relates to a method of modifying the surface of a fluororesin film by applying a high voltage of 0 pps to generate corona discharge. Further, the present invention relates to a fluororesin film obtained by the method and a method for adhering the fluororesin film with an adhesive layer interposed between the modified surface of the film and the adherend surface of the adherend material.

An example of the fluororesin which can be surface-modified according to the present invention is ethylene-tetrafluoroethylene copolymer (ET
FE), polyvinyl fluoride resin (PVF), tetrafluoroethylene-perfluoroether copolymer (PFA),
Tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polytetrafluoroethylene (PTF
E), vinylidene fluoride resin (PVdF), trifluorochloroethylene resin (PCTFE), ethylene-trifluorochloroethylene copolymer resin (ECTFE) and the like.

The thickness of the fluororesin film used in the present invention is not particularly limited, but is 5 to 100 μm, and more generally 10 to 50 μm. When the thickness is more than 100 μm, the surface treatment is possible by the treatment of the present invention, but the cost of the film becomes high and it is not generally used. On the other hand, films thinner than 5 μm are difficult to obtain with current molding technology. The fluororesin film is preferably placed 0.1 to 7 cm, more preferably 0.1 to 2 cm, away from the corona discharge electrode. In addition, adhesion from the insulating layer of the counter electrode ~ 1
cm, more preferably in close contact.
The fluororesin film may be placed substantially in the center of the discharge electrode and the counter electrode, but it is preferably placed on the insulating layer in order to perform uniform treatment while keeping the distance between the film and the discharge electrode constant. In the present invention, the fluororesin film is inserted between the discharge electrode for corona discharge and the counter electrode. The atmosphere may be air, and no special inert gas or reactive gas such as carbon dioxide is used. Since the fluororesin film is modified on the side of the discharge electrode for corona discharge, the characteristic opposite to the fluororesin film is maintained as it is on the opposite surface.

The discharge is performed by a high voltage pulse, and a preferable pulse width is 1 to 50 μs. When the pulse width is less than 1 μs, the surface treatment effect on the fluororesin film is insufficient, resulting in extremely low energy efficiency. If the pulse width becomes too long, harmful sparks are likely to occur, and
It consumes more power than necessary.

The applied voltage for corona discharge is the average electric field strength.
(Applied voltage (peak value) / distance between poles) 40 to 200 kv
/ Cm, preferably 60 to 150 kv / cm, more preferably 80 to 120 kv / cm. When the average electric field strength is less than 40 kv / cm, effective corona discharge is unlikely to occur and the surface treatment effect becomes poor. If the average electric field strength exceeds 200 kv / cm, sparks are likely to occur, which is not preferable.

The applied voltage is defined by the waveform value of the voltage actually applied between the discharge electrode and the counter electrode. Therefore, the applied voltage is represented by the peak value of the waveform of the high voltage pulse between the discharge electrode and the counter electrode.

The distance between the electrodes means the distance between the discharge electrode and the counter electrode, and specifically, it is preferably 1 to 200 mm. Particularly preferably, it is 1 to 100 μm. If it is less than 1 mm, it is difficult to take space in the insulating layer. If it exceeds 200 mm, the discharge region does not reach the film surface and cannot be treated. Pulse frequency is 10 to 150 pps, more preferably 50 to 150 pps
ps. If the pulse frequency is less than 10 pps, the effective treatment energy per unit time is insufficient and the surface treatment time is long, which is not preferable. It is technically difficult to generate a high-voltage pulse having a pulse frequency exceeding 150 pps with the pulse width and the average electric field strength as described above. Attempting to obtain a pulse frequency of 300 pps or more is not preferable because the high-voltage generator becomes very large, the equipment cost becomes excessive, and the profit becomes industrially unprofitable.

As the high voltage pulse generator, basically, the high voltage pulse generator in the conventional corona discharge treatment method can be used.

It is necessary to interpose a dielectric between the counter electrode and the fluororesin film. This makes it possible to prevent the generation of harmful sparks even when the applied voltage (peak value) is high and the average electric field strength is high. As the dielectric material, vinyl chloride resin, Teflon resin, and other general dielectric materials can be arbitrarily used. The thickness of the dielectric is
The range is 1 mm or more, preferably 5 to 20 mm. If the thickness of the dielectric is less than 1 mm, the spark prevention effect is insufficient. There is no difference in the effect of the treatment even if it is thicker than 20 mm. The dielectric and the counter electrode may be in close contact with each other or may be separated by about 100 mm. When a relatively thin dielectric layer is formed on the surface of the counter electrode, it is preferable to use a plate material having a thickness of 0.1 mm or more, preferably 1.6 mm or more as the counter electrode in order to obtain sufficient mechanical strength and durability. A thin film or foil of a conductive material such as copper or aluminum formed on the back surface of the dielectric may be used as the counter electrode. In this case, in order to have mechanical strength, it is preferable to make the thickness of the dielectric material thicker, for example, about 5 mm or more. In order to perform the corona discharge treatment continuously and uniformly, it is preferable to convey the fluororesin film at a constant speed. The structure of the counter electrode that can be used in the present invention may be such that the film can be transported uniformly and the discharge is not concentrated on a part of the dielectric, but in order to maintain the durability of the dielectric, the counter electrode is It is desirable to have a structure in which it is rolled and rotates at the same speed as the film is conveyed.

The surface of the fluororesin film is modified by the method of the present invention, and the wettability with respect to water and organic solvents is remarkably improved. For example, the contact angle with water is 80 degrees or less,
Further, it can be set to about 70 to 40 degrees. Therefore, the adhesiveness to other substances, which has been conventionally regarded as a drawback of the fluororesin film, is improved. On the other side, which is not subjected to electric discharge treatment, the properties peculiar to the fluororesin are maintained, so the surface of the material to which the film is adhered has excellent properties such as water repellency, stain resistance, and chemical resistance. can do. The degree of surface modification can be performed by measuring the contact angle with water.

Materials to be adhered to which the surface-modified fluororesin film can be adhered are metal plates such as cold rolled steel plate, stainless steel plate, aluminum steel plate, zinc plated steel plate, zinc / nickel plated steel plate, aluminum / zinc plated steel plate. , Polyolefins, maleic anhydride-modified polyolefins, ethylene-vinyl acetate copolymers, polyvinyl chloride and ethylene-acrylic copolymers, and other resins, as well as decorative boards, glass, cloth, non-woven fabrics, cushioning materials, etc. .

Examples of the adhesive include, but are not limited to, silicone-modified polyester resin, polyester resin, polyurethane resin and silicone resin. A polyester resin is an adhesive that gives particularly preferable results in combination with the surface-modified fluororesin film of the present invention.

In order to bond the material to be adhered and the fluororesin film, the above-mentioned adhesive is applied to the surface-modified surface of the material to be adhered and / or the fluororesin film, and after joining the both, heating is performed if necessary. Application includes all conventional application means such as brushing, rolling and spraying. The material coated with the adhesive may be heated immediately before joining. If the adhesive layer coated is a fluororesin film, 60-
It is suitable to heat to 180 ° C, and to 140 to 250 ° C in the case of a metal plate.

It is also possible to put it on the market with the adhesive applied to the modified surface of the fluororesin film. If the adhesive is soft and thermosetting, after applying it to the fluororesin film,
The adhesive surface may be coated with release paper. Alternatively, since it does not stick to the non-modified surface even when wound without a release paper, it may be put on the market as it is. Further, the adhesive may be a thermoplastic resin, or an adhesive adhesive may be used as an adhesive type covering material.

The present invention will be described below with reference to examples. Example A fluororesin film 1 was subjected to corona discharge treatment using a corona discharge treatment device whose outline is shown in FIG. In FIG. 1, 2 is a high voltage pulse generator, 3 is a corona discharge electrode, 4 is a counter electrode, 5 is an insulating layer, and 6 is a housing.

The fluororesin film 1 was used in close contact with the counter electrode 4, and the air inside the housing was made to flow with the atmosphere. Here, as the insulating layer 5, 1 mm-thick silicon rubber, which is a dielectric, was used. The treatment time was 5 seconds in all cases except the untreated comparative example. Other processing conditions are shown in each example. The contact angle of the treated surface of the obtained fluororesin film to water is also shown in each example.

Examples 1 to 6 and Comparative Examples 1 to 2 By using ETFE film (manufactured by Asahi Glass Co., Ltd., thickness: 38 μm), the gap distance, pulse width, and pulse frequency are kept constant, and the pulse peak value is changed. An example in which the average electric field strength was changed was shown. The results are shown in Table 1.

[0021]

[Table 1]

The water contact angle of Comparative Example 3 without surface modification is 113 °, but the water contact angle decreases as the average electric field strength increases. Average electric field strength is 30
Under the condition of KV / cm outside the range of the present invention, the treatment effect is recognized, but it cannot be said to be sufficient in practical use. The maximum average electric field strength obtained by the device used in this example is 200 KV.
Was / cm. Therefore, the average electric field strength capable of obtaining a sufficient treatment effect is 40 to 200 KV / cm.

Examples 7 and 8 and Comparative Example 3 These examples are examples in which the average electric field strength is changed by changing the distance between the electrodes while keeping the pulse crest value constant. Table 2 shows the results.

[0024]

[Table 2]

In the present embodiment, the processing effect is exhibited even if the average electric field strength is changed by changing the distance between the poles while keeping the crest value constant.

Clearly in this example, since the treatment effect is changed by the average electric field strength, which is represented by the crest value / interval distance, it is practically sufficient to set the changing electric field strength to 40 to 200 KV / cm. It is understood that various processing effects can be obtained.

Examples 9 to 12 and Comparative Examples 4 to 5 These examples are examples when the average electric field intensity pulse frequency is kept constant and the pulse width is changed.

[0028]

[Table 3]

As shown in Table 3, the pulse width is 1 to 10 μm.
No significant change in the contact angle is observed when the contact angle is changed within the range. Further, if the pulse width is widened, naturally the required electric power also increases and the economical efficiency decreases. Therefore, the effective pulse width is 1 to 50 μm.

Examples 13 to 18 and Comparative Examples 6 to 7 These examples are experimental examples in which the average electric field strength and the pulse width are kept constant and the pulse frequency is changed.

[0031]

[Table 4]

According to the above results, the processing effect increases when the average electric field strength and the pulse width are kept constant and the pulse frequency is increased. Further, the processing effect becomes saturated when the pulse frequency is around 150 pps. Since the power required to increase the pulse frequency increases, the optimum range is 10
It is 150 pps.

Experimental Examples 19 to 22 and Comparative Examples 8 to 9 In these examples, the effects when the average electric field strength, the pulse width and the pulse frequency are changed will be described. The results are shown in Table 5.

[0034]

[Table 5]

Experimental Examples 23 to 27 and Comparative Examples 11 to 15 These examples are experimental examples in which a film made of an organic polymer was processed using the processing apparatus of the present invention. The results are shown in Table 6.

[0036]

[Table 6] From the above results, it can be seen that various fluorine-based films can be processed by the present invention.

Examples 28 to 34 and Comparative Examples 16 to 22 These examples show the relationship between the degree of corona discharge treatment and printability and adhesiveness. The test method was about 1μ of printing ink (Paramic Dainichiseika Co., Ltd.) on the film shown in the result table.
After coating with a bar coater for 1 m and leaving for 1 day, 6
What was dried and cured at 0 ° C was subjected to a peeling test with a cellophane tape and evaluated.

Further, the adhesion test was conducted by applying an adhesive (Power Tight C-200 to a galvanized steel plate having a thickness of 0.3 mm).
Nippon Paint Co., Ltd. polyester adhesive) was applied with a bar coater to a dry film thickness of about 10 μm and forcedly dried to a plate temperature of 220 ° C., and immediately the treated surface of the fluorine-based film was coated with an adhesive layer. Was superposed on each other and pressure-bonded with a silicon rubber roller at a pressure of 3 kg / cm ² , and allowed to stand for 1 day for testing. The adhesion was evaluated by measuring 180 peel strength with a width of 1 cm. The results are shown in Table 7.

[0039]

[Table 7] The above results show that sufficient ink adhesion and adhesion are obtained when the water contact angle is modified to 80 ° or less.

[0040]

According to the method of the present invention, the wettability of the fluororesin film can be improved under normal temperature and atmospheric conditions. As a result, it has become possible to easily improve the adhesiveness of the fluororesin film, which was difficult to adhere to in the past.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a corona discharge device used in the present invention.

[Explanation of symbols]

1: Fluororesin film, 2: High voltage pulse generator,
3: Corona discharge electrode, 4: Counter electrode, 5: Insulation layer,
6: Housing

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akinori Iwata 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Co., Ltd. Inside Paint Co., Ltd.

Claims (9)

[Claims] 1. A fluororesin film is disposed between a discharge electrode and a counter electrode, the average electric field strength expressed by applied voltage / distance between electrodes is 40 to 200 kV / cm, pulse width is 1 to 50 μs, and pulse frequency is 10. A method of modifying the surface of a fluororesin film by applying a high voltage of up to 150 pps to generate corona discharge. 2. The fluororesin film is selected from the group consisting of ethylene-tetrafluoroethylene copolymer, polyvinyl fluoride, tetrafluoroethylene-perfluoroether copolymer and tetrafluoroethylene-hexafluoropropylene copolymer. The method of claim 1. 3. A fluororesin film surface-modified by the method according to claim 1. 4. The surface-modified fluororesin film according to claim 3, which has a contact angle with water of not more than 80 degrees. 5. The fluororesin film is adhered by interposing an adhesive layer between the modified surface of the surface-modified fluororesin film obtained by the method according to claim 1 and the adherend surface of the adherend material. How to make. 6. The method according to claim 5, wherein heating is performed after interposing the adhesive layer. 7. The bonding method according to claim 5, wherein the bonding layer is selected from the group consisting of silicone-modified polyester resin, polyester resin, polyurethane resin and silicone resin. 8. The material to be adhered is a metal plate selected from the group consisting of cold rolled steel plate, stainless steel plate, aluminum plate, galvanized steel plate, zinc / nickel plated steel plate and aluminum / zinc plated steel plate. Method. 9. The material to be adhered is selected from polyolefin resin, maleic anhydride-modified polyolefin resin, ethylene-vinyl alcohol copolymer resin, ethylene-vinyl acetate copolymer resin, polyvinyl chloride resin and ethylene-acrylic copolymer resin. The method according to claim 5, which is a resin selected from the group consisting of: