JPH06344505A - Covering of surface of metal with fluoroplastic film - Google Patents

Abstract

PURPOSE:To provide a novel film covering method capable of producing a fluoroplastic film covered steel plate excellent in film close adhesion. CONSTITUTION:A metal subjected to substrate treatment such as the coating with a primer if necessary is heated to 250-450 deg.C and a fluoroplastic film is temporarily bonded to the surface of the heated metal under pressure by a roll and the whole is reheated so that the interface temp. of the fluoroplastic film and the surface of the metal becomes 280 deg.C or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating a metal surface with a fluorine resin film containing a fluorine atom.

[0002]

2. Description of the Related Art Generally, a fluororesin film is excellent in properties such as corrosion resistance, stain resistance, adhesion resistance, heat resistance, and nonflammability. Since such characteristics can be added to the excellent strength and workability of the stainless steel sheet, a laminated steel sheet having excellent functionality can be obtained. With such laminated steel sheets, baking molds used for baking bread, cakes, confectionery, food cooking and food processing equipment, microwave oven inner plates, rice cooker inner pots, gas table tops, etc. It can be widely used for various cooking utensils, as well as materials for kitchen products such as materials for range hoods, and it has been desired to establish a technology for industrially producing such steel materials.

On the other hand, heretofore, JP-A-61-137534, JP-A-61-138567 and JP-B-63-11147 have been proposed.
Fluorine resin on so-called Al-plated steel sheet, which is proposed in Japanese Patent Publication No. 59-16836 and Japanese Patent Publication No. 59-16837, which are so-called stainless steel sheets and plated steel sheets coated with fluororesin. Or a so-called Al or Al alloy material, which is proposed in JP-B-54-24434, JP-B-59-10304 or JP-A-63-126728, is laminated with a fluororesin film. The development of materials has already been proposed.

[0004]

As described above, the steel sheet obtained by heat-sealing the fluororesin film is excellent in corrosion resistance, stain resistance, adhesion resistance, heat resistance, wear resistance and workability. . However, since the fluororesin film generally has a low surface tension and exhibits strong non-adhesion, it is difficult to laminate with an adhesive. Especially 4
One molecule unit such as fluorinated ethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), tetrafluoroethylene-6-fluoropropylene copolymer resin (FEP), tetrafluoroethylene-ethylene copolymer resin (ETFE) A fluororesin film containing two or more fluorine atoms therein has not been developed so far so that a suitable method for adhering it to a metal surface has been developed, and its practical application has been delayed.

In this respect, the present inventors first applied a mixture of a fluororesin and a heat resistant resin to an aluminum-based plated steel sheet, a zinc alloy-based plated steel sheet, and a stainless steel sheet,
A film of the same type of resin was pasted on it, and the roll was pressed down. During this roll pressing, a method was found in which the film-metal (steel plate) interface was heated to a temperature just above the melting point of the film to fuse it with the underlying resin layer. I proposed it as No. 3-327744,
Further improvements were desired. That is, the object of the present invention is excellent in heat resistance, durability, and adhesion, and
An object of the present invention is to propose a novel film coating method for producing a fluororesin film-coated steel sheet which is excellent in various properties such as corrosion resistance, stain resistance, adhesion resistance, wear resistance, workability and material rigidity.

[0006]

As means for solving the above-mentioned problems, in the present invention, any one of a phosphate treatment, a coating type chromate treatment, a primer coating containing a fluororesin and a heat-resistant resin, or a combination thereof is used as necessary. Treated Zn plated steel, Zn-Al alloy plated steel, Zn-Fe alloy plated steel, Zn-Ni alloy plated steel, Al plated steel,
When a metal surface such as Al-Si alloy plated steel material, 55% Al-Zn alloy plated steel material or stainless steel material is heated and the temperature of this metal surface is 250 to 450 ° C, PFA, FE
P, ETFE, etc., a fluororesin film containing two or more fluorine atoms in one molecular unit and having poor adhesion,
The step of temporarily pressure-bonding by roll pressing, and reheating so that the interface temperature between the metal surface on which the fluororesin film is temporarily pressure-bonded and the fluororesin film layer becomes 280 ° C or higher, the fluororesin film is metalized. We propose an advantageous method for coating the surface with high adhesion.

[0007]

According to the present invention, first, it is necessary to temporarily press-bond a heated fluororesin film to the surface of a metal (hereinafter, referred to as an example of "steel plate") by roll rolling. In this step of temporary pressure bonding, when the fluororesin film is roll-pressed onto the steel plate surface, it must be heated in advance so that the surface temperature of the steel plate surface or the primer-treated surface becomes 250 to 450 ° C. It should be noted that how much the surface temperature of the steel plate or the like at this time is set within the above range is controlled by the type and thickness of the film, the surface temperature of the pressure bonding roll, and the like. For example, in the case where a heat-treated steel sheet or a primer-treated steel sheet is passed through a tunnel furnace to be heated, and then rolled out of the furnace to roll down the film, it is necessary to heat the temperature to a higher temperature in advance by the temperature drop. is there. Experience has shown that the temperature drop is affected by factors such as plate thickness, plate speed, distance between the furnace and the draft roll, but is usually 10-50 ° C.
It is important to heat this portion extra.

The reason why the temperature of the steel sheet is limited to the above range is that when the temperature of the film adhered surface is less than 250 ° C., the adhesive surface of the fluororesin film does not melt so that the film and the steel sheet surface or the film and primer are not melted. This is because the adhesion with is insufficient. On the other hand, if the surface temperature exceeds 450 ° C., the film itself will be melted and cut during pressure bonding.

A general hot-air type tunnel furnace is used for heating the steel sheet. Alternatively, an electromagnetic induction heating furnace may be used. Rather, electromagnetic induction heating is preferred. The reason for this is that in electromagnetic induction heating, when a primer is used in the temporary pressure bonding step for heating the steel sheet,
This is because the primer is heated from the inside (steel plate side), so that the solvent remains less. Also, in the reheating step described below, the interface between the steel sheet and the film can be sufficiently heated, so that the adhesion of the film is improved.

In the research conducted by the present inventors, the adhesion of the film adhered through the above-mentioned temporary pressure bonding step was inspected and found to be still insufficient in practical use. Therefore, as a result of diligent research into a method for further improving the adhesiveness of the film, the film-coated steel sheet, which has undergone the provisional pressure bonding through the above steps, is reheated to a temperature of 280 ° C or higher to significantly increase the adhesive strength. The inventors have found that the number is increased and completed the present invention.

That is, in the reheating step, if the interface between the fluororesin film and the steel sheet temporarily pressed is reheated to a temperature of 280 ° C. or higher, the adhesive strength of the film is dramatically increased as described above. The reason why the adhesive strength of the film is improved by this reheating is that, when the film is roll-pressed to the heated steel plate surface, the interface is cooled to a temperature lower than the melting point of the film by heat transfer to the roll and the film. It is presumed that by reheating the interface, the interface becomes in a molten state again and the diffusion bonding action progresses this time, which improves the adhesive force between the two. When the reheating temperature is 280 ° C. or lower, there is almost no effect of improving the adhesive strength. On the other hand, the upper limit is not particularly limited, but the upper limit is a temperature at which the fluororesin film to be stuck is not thermally decomposed. For example, P, which has relatively high heat resistance
With FA film, the temperature is about 450 ° C. Further, when a primer is used, if it exceeds 450 ° C, there is a concern that the adhesiveness may be deteriorated due to the thermal decomposition of the primer resin, so that there is a limit on its own.

The reheating treatment may be carried out after the temporary pressure-bonding step, after once cooling to room temperature, or by heating the film immediately after the roll pressure is passed through the tunnel furnace. Just do it. In order to further improve the pressure bonding effect, the reheated film pressure bonding plate may be roll-pressed immediately after the reheating. After that, in the treatment after the reheating of the film-pressed steel plate, gradual cooling by standing cooling or rapid cooling such as water cooling is performed, but the effect on the adhesive strength can be neglected by any method of cooling.

In the present invention, the base metal to be treated is the above-mentioned steel plate, for example, zinc-plated steel material, zinc-aluminum alloy plated steel material, zinc-iron alloy plated steel material, zinc-nickel alloy plated steel material, aluminum. A plated steel material, an aluminum-silicon plated steel material, a 55% aluminum zinc alloy plated steel material, a stainless steel material, or the like is preferably used. When the metal is a steel plate among these metals, the thickness is preferably about 0.2 to 1.6 mm, but is not particularly limited. For example, an aluminum-plated steel plate or a stainless steel plate is suitable for applications with high heat resistance requirements such as a gas stove top plate. Also, PFA
In order to obtain high film adhesion with a high melting point fluororesin film such as above, reheating will also be a high temperature of around 400 ° C, and in such requirements, the galvanized steel sheet etc. will dissolve the plating layer. Cannot be manufactured.

Next, in the present invention, as the fluororesin film to be coated on the above metal material, a fluororesin film containing two or more fluorine atoms in one molecule unit having particularly poor adhesion, for example, tetrafluoride. Ethylene-perfluoroalkoxyethylene copolymer resin (PFA) film,
Tetrafluoroethylene-6-fluoropropylene copolymer resin (F
EP) tetrafluoroethylene-ethylene copolymer resin (ET
It is effective when using a thermoplastic resin film such as FE). The thickness of this fluororesin film is not particularly limited, but is preferably 10 to 100 μm. Note that these films are originally colorless and transparent, but those in which pigment powder is blended for coloring, those containing additives for imparting functionality, and those which have been subjected to any treatment can be similarly used. .

Further, in the present invention, an undercoating treatment is carried out, if necessary, before the temporary pressure-bonding step of the film. This base treatment is performed by applying a primer. When the primer is not applied as the base treatment, other pretreatment methods include polishing with shot blasting or wire brushing, followed by a general method of pickling or electrolytic etching, or a coating type chromate treatment. May be. Further, in the case of stainless steel plate, not only the primer treatment but also the coating type chromate treatment and then the primer treatment can significantly improve the film adhesive strength, heat resistance and durability.

Next, as a primer for the base treatment of the base steel sheet, polytetrafluoroethylene (PTFE), 4
Fluorinated ethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), 4-fluoroethylene-6-fluoropropylene copolymer resin (FEP), 4-fluoroethylene-ethylene copolymer resin (ETFE), polychlorotrifluoroethylene, Fluororesin powder selected from polyvinylidene fluoride and polyether sulfone (PE
S), polyphenylene sulfide (PPS), a heat resistant resin selected from polyimide, polyamide imide, epoxy resin, silicone resin, phenol resin, and the like, and a water-solvent or organic-solvent primer of a mixed resin thereof is preferably used. . The mixing ratio of the fluororesin and the heat resistant resin is preferably in the range of 1:99 to 95: 5 by weight.

The film thickness of the primer is 3 to 3 after drying.
15 g / m ² is preferable, and when 3 g / m ² or less, the effect of improving the adhesive strength as a primer is poor, and when 15 g / m ² or more, the effect saturates, and the film adhesion during processing and primer decrease. It is not preferable because it causes cracking due to medium residual gas.

[0018]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. Examples 1 to 10 Fluororesin films were heat-sealed to various steel sheets provided with a primer containing a mixed resin of PFA and PES and PPS of 1: 2: 1 to obtain products. Examples 11 to 12 Fluororesin films were heat-sealed to various steel sheets provided with a primer containing a mixed resin of FEP and PES of 1: 2 to obtain products. Examples 13 to 16 Products were obtained by heat-sealing a fluororesin film to various steel plates that had been subjected to a base treatment by a coating type chromate treatment. Comparative Examples 1-5 As a comparison with the above examples, various steel sheets of Comparative Examples 1-5 were heat-sealed with a fluororesin film to obtain products. The respective production conditions are also shown in Table 1. Table 2 shows the performance test results of the temporary adhesion, wear resistance, heat resistance / durability, and corrosion resistance of each product.

[0019]

[Table 1]

[0020]

[Table 2]

Under the fluororesin film thermocompression bonding conditions of Examples 1 to 16 and Comparative Examples 1 to 5, the pressure bonding roll temperature was 150 ° C. and the roll linear pressure was 0.3 kg / cm. The treatment conditions for the coating type chromate are as follows: Chromium adhesion amount 30 mg / m ² ,
It was dried at 150 ° C for 30 seconds.

The test items, test methods and determination methods in the above examples were carried out under the following conditions. Adhesion test Performed according to the JIS Z 6744 well-type Erichsen test method. The test pieces used in the well-type Erichsen test method were prepared by preliminarily immersing them in boiling water for 1 hour and 2 hours, then naturally drying for 30 minutes and 3 types that were not immersed in boiling water. After extruding 6 mm with a machine, lift the film cut end of the extruded part with a knife, grab it with tweezers and forcibly peel the film. The evaluation criteria are as shown in Table 3, and the evaluation point was 5 when the film could not be floated for all three types.

[0023]

[Table 3]

Heat Resistance / Durability Test A test piece was prepared on the steel sheet obtained by the method of Examples and Comparative Examples according to the well-type Erichsen test method of JIS Z 6744, and extruded 6 mm with an Erichsen tester. After heating in an atmosphere of ℃, the cut end of the film in the extruded part is lifted with a knife every 10 hours until the test time of 100 hours, and the film is forcibly peeled by grasping it with tweezers. The evaluation was performed by the time until the film adhesion deteriorates and the film peels off. For tests of 100 hours or more, the same evaluation is performed every 50 hours, and
The test was conducted up to 00 hours.

Corrosion Resistance Test The steel plates obtained by the methods of Examples and Comparative Examples were used as test pieces of 70 × 150 mm, the cut end surface and the back surface of the test piece were sealed, and a cross cut until reaching the base material was made on the flat surface portion. Get in,
The test was performed according to the salt spray test of JIS Z 6744. Evaluation,
The state of the test piece after the 200-hour test was performed according to the following criteria. ◯: No rust, blister, film peeling Δ: Blister or film peeling, or rust occurred on cross-cut part ×: Blister or film peeling, rust occurred on cross-cut part

From the results of each test described above, the product obtained by first heating the fluororesin film according to the method of the present invention and then reheating the temporarily pressure-bonded steel plate to a temperature of 280 ° C. or higher has a large adhesive strength, In the case of a fluororesin-coated steel sheet obtained by reheating a fluororesin film heat-sealed to the surface of a steel sheet subjected to primer undertreatment with a mixed resin of fluororesin and heat-resistant resin, not only film adhesion and corrosion resistance, The product has excellent heat resistance, durability, and adhesion resistance.

[0027]

As described above, according to the fluororesin film-coated steel sheet according to the present invention, film adhesion,
In addition to excellent corrosion resistance, heat resistance, durability, and adhesion resistance, it also has excellent rigidity, which is a characteristic of steel plates, so it is a material for cooking processing equipment, kitchen equipment materials, microwave oven inner plates, gas table top plates, etc. In addition to the above-mentioned applications, it can be applied to fields such as materials for electronic parts and printed circuit boards, and it is possible to supply inexpensive and excellent materials suitable for a wide range of applications.

Claims (3)

[Claims] 1. A step of temporarily press-bonding a fluororesin film to a metal surface heated to a temperature of 250 to 450 ° C., and re-adjusting so that the interface temperature between the fluororesin film and the underlying metal surface becomes 280 ° C. or higher. A method of coating a metal surface with a fluororesin film, which comprises a heating step. 2. A primer made of a mixed resin of a fluororesin and a heat-resistant resin is applied on the surface of the steel plate in a weight of 3 to 15 g prior to the temporary pressure bonding of the fluororesin film to the steel plate.
The method for coating a fluororesin film on a metal surface according to claim 1, which is applied beforehand to a thickness of / m ² . 3. The fluororesin film according to claim 1, wherein at least one of heating of the metal surface, heating after applying a primer and heating after pressure bonding of the film is induction-heated. How to coat the surface.