JPS58102725A - Method of laminating fluoro plastic film to aluminum or aluminum alloy - Google Patents

Abstract

PURPOSE:To form a film, having a high adhesive power and uniform thickness, through processing of it in a short time, by a method wherein, after a specified 2-stage formation processing is conducted, a thermoplastic fluoro resin film is fusion-bonded by heat to a surface of an aluminum plate. CONSTITUTION:After a surface cleaning process is made on an aluminum (alloy) plate with a surface roughness of about 2mum or less, (i) a hydrarated oxide film is formed on the plate surface by immersing it in an aqueous solution, containing a basic organic compound, i.e., a triethanolamine aqueous solution of a density of about 0.2-1.5 volume %, at not lower than about 90 deg.C for about 1-15min. After it is washed with water, (ii) a resultant work is immersed in an aqueous solution, containing alkali silicate, i.e., a sodium silicate aqueous solution of a density of about 0.35-1.05 volume %, at not lower than about 90 deg.C for 1-15min to perform a formation process again. Then, a thermoplastic fluorine film is thermally fusion-bonded to the aluminum (alloy) plate, whereon said 2-stage clenical conversion process is carried out, by a hot press process.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for laminating a thermoplastic fluororesin film onto a plate of aluminum or aluminum alloy (hereinafter both will be referred to as aluminum). When applying a fluororesin dispersion, the method of applying a fluororesin dispersion, drying, and then baking is generally adopted. In order to achieve this, it is necessary to perform several overlapping operations to increase the film thickness. Furthermore, even with this layered coating, it cannot be said that there are no defects such as pinholes, so the original properties of the fluororesin are not exhibited.
For example, it has poor chemical resistance.

For this reason, in recent years, attempts have been made to obtain a healthy fluororesin film by contacting and collapsing a defect-free fluorine [W] film onto an aluminum plate. However, since fluororesin is non-adhesive in nature, it does not adhere closely to the aluminum plate by mere heat fusion. For this reason, methods such as bonding through adhesive properties, or chemically or electrochemically etching the aluminum of the substrate to create a 7-linker effect have been adopted, and as a base treatment for the wings. Methods have been proposed in which an anodic oxide film (alumite film) or a chemical conversion film (boehmite film) is used as a base.

Among these methods, methods using adhesives have the problem that the adhesive strength decreases as the weather resistance of the adhesive deteriorates, and the initial adhesive strength itself is not sufficient. - For the method of applying degradative or electrochemical etching treatment, a uniform fluoropolymer film layer is required, since there are thickness variations due to unevenness of the fluoropolymer film bonded to roughen the aluminum surface of the substrate. For example, it is unsuitable for applications that require electrical properties.On the other hand, the method of using an anodic oxide film or chemical conversion film as a base layer allows the fluororesin film to be adhered to the aluminum substrate with almost no damage. Therefore, this is a preferable method to maintain uniformity in the thickness of the fluororesin film, but the former method does not have sufficient adhesive strength, and the latter method also has problems in that it takes a long processing time and the adhesive strength is not sufficient. .

The present inventors have conducted various studies from the viewpoint of the smoothness (uniformity) of the fluororesin film, adhesive strength, and short processing time, which are the above-mentioned problems. A two-stage chemical conversion treatment was adopted in which a water-use oxide conversion film was formed by immersion in an aqueous solution, and then reconversion treatment was performed in an aqueous solution containing an alkali silicate. We have found a method that can produce a fluororesin film with high adhesive strength and uniform thickness in a short time by heat-sealing a thermoplastic fluororesin film onto the surface of a treated aluminum plate.

The present invention will be explained in more detail below.

The aluminum plate used in carrying out the present invention can be either a commercially available ordinary aluminum plate or an aluminum alloy plate, but the surface roughness of the plate should be 1μ or less to improve the uniformity of the thickness of the fluororesin film layer after lamination. It is preferable to maintain it. Note that the surface roughness referred to here is JI8B
It means the "maximum height" defined by θ6θ/.

The surface of this aluminum plate is preferably cleaned prior to chemical conversion treatment, and recommended methods include degreasing with a general organic solvent, alkaline degreasing, and electrolytic degreasing. Of these, alkaline degreasing requires caution, as unless it is a method using a weak alkaline bath, the aluminum surface will be roughened and the resulting fluororesin film laminate will have unfavorable results in uniformity of thickness.

Next, a method for forming a chemical conversion film will be described. As the first stage of t-1, the Fluss Miniram plate whose surface has been cleaned as described above is placed in an aqueous solution containing a basic organic compound in a nearly boiling state above θ°C. It is immersed for 7j minutes, preferably 3 to 7 minutes, to form a water utilization oxidation promoting film on the surface. The basic organic compound mentioned here specifically includes amines such as triethanolamine, jetanolamine, monoethanolamine, etc., and these are added to ion-exchanged water (specific resistance jθθ × lθΩm or more) at 0. .7! ~i, sv-1, preferably θ, 3~θ', 7vo13 are dissolved in a weakly alkaline aqueous solution.

After washing the aluminum plate chemically formed in the above bath, it was subsequently soaked in an aqueous solution containing an alkali silicate at θ.
7 to 75 minutes at almost boiling temperature above °C, preferably 3
Soaked for ~7 minutes and reconverted. Examples of alkali silicates include 8102/ known as water glass.
Sodium silicate with a molar ratio of Na2O in the range of 20 to
Sodium metasilicate with a mole ratio of O can be used.

The concentration of these alkali silicates is O, SS ~ /, V (
θ, j~/, jwt), preferably θ, j~0. δ4
It is preferable to prepare an aqueous solution in which twtqlr(θ, 7~/, 2 wt%) is dissolved.

The aluminum plate that has been subjected to the two-stage chemical conversion treatment is washed with water, dried, and a thermoplastic fluororesin film is placed on the surface and heat-sealed. Examples of the thermoplastic fluororesin film here include a tetrafluoroethylene resin film, a tetrafluoroethylene-hexafluoropropylene copolymer resin film, and an ethylene-tetrafluoroethylene copolymer resin film.

The method of heat-sealing the thermoplastic fluororesin film and the aluminum plate is not particularly limited, but a hot press method or a hot roller method is usually recommended. Moreover, the conditions for thermal fusion may be selected by combining the three elements of temperature, pressure, and time to ensure that the fluororesin film is sufficiently fused to the aluminum plate, and the individual conditions are not particularly limited.

The film obtained by heat-sealing the fluororesin film laminated aluminum plate wire as described above has a high adhesive strength, has a uniform thickness, and is sound without pinholes or cracks.

The reason why the chemical conversion treatment, which is a feature of the present invention, is performed in two stages will be described below.

Chemically converting an aluminum plate in a weakly alkaline aqueous solution containing a basic organic compound in a nearly boiling state is a commonly known method for forming a water-conserving oxide conversion film (boehmite film), and the The structure of the chemical conversion film shows the growth of relatively dense needle-like crystals even when observed under an electron microscope. However, when these films are heat-sealed to, for example, a fluororesin film, their density is insufficient (IJ), and sufficient peel strength cannot be obtained in a peel test of the heat-sealed fluororesin film. This is thought to be due to insufficient density of the tentacles of the chemical conversion coating crystals that contribute to adhesion to the fluororesin film, and insufficient strength of the chemical conversion coating itself.

Therefore, in the present invention, the chemical conversion film formed as described above is further subjected to a chemical conversion treatment in an aqueous solution containing an alkali silicate in the second stage to transform it into a chemical film with a denser film strength. It is something to do. In this case, for example, compared to the case where the chemical conversion treatment is performed in only one stage, the time required for each of the first and second stages of the chemical conversion treatment can be shortened, and therefore a short processing time is also possible.

When a fluororesin film is heat-sealed to an aluminum plate that has been subjected to two-stage chemical conversion treatment in this way, the chemical conversion film does not break in a peel test, and compared to the peel strength of a conventional chemical conversion film that has been treated in one stage, It is possible to obtain values approximately - times or more.

Next, examples of the present invention will be shown and the main features will be explained by comparing them with comparative examples as appropriate, but the present invention is not limited by these examples.

Example/Thickness θ, Doug-aluminum plate (/θjθ-H2 material)
After degreasing with a weak alkaline solvent, the specific resistance jθθ×
Dissolve triethanolamine θ, jvoA% in ion-exchanged water of /θ'Otm and adjust the pH to /θ WII! It was chemically treated by immersing it in a slightly alkaline aqueous solution at 5° C. for 5 minutes. After washing with water, a molar ratio of 8102/Na2O was added to ion-exchanged water with a specific resistance of Sθθ×/θ4QcIn of 3. /
1 of sodium silicate was added and dissolved in an aqueous solution of 0.7 VQJL%, and the sample was immersed for 5 minutes in an aqueous solution at 25''C, the pH of which was adjusted to /θ, to carry out reconversion treatment.

Thereafter, a 2Jμ thick polytetrafluoroethylene-hexafluoropropylene copolymer resin film was glued onto the surface of this aluminum plate, and a pressure of 70% 7cm was applied using a hot press for S minutes at a temperature of 3θO°C. .

Obtained from nine fluororesin supported aluminum plate, width, 23
m, length
D? When the peel strength was measured according to θ3-data,
Yu3$/,2! ; The film showed a value of attack width and film breakage occurred in all cases.

The aluminum plate used in Comparative Example/Example/ was degreased in the same manner as in Example/, and after death, triethanolamine was added to ion-exchanged water with a specific resistance of SθOx/θ4Ω.
fA was added and dissolved, pI was adjusted to /Q, and chemical conversion treatment was performed by immersing it in a weakly alkaline aqueous solution of j''C for 75 minutes.

Thereafter, the fluororesin film was subjected to pressure bonding and peeling tests in exactly the same manner as in Example, except that the reconversion treatment in an aqueous sodium silicate solution was not performed, and the peel strength was 7.3~/, 7$. 72jws width and its value varied. This is thought to be caused by peeling at the interface between the film and the chemical conversion coating or destruction of the chemical conversion coating itself.

Comparative Example After degreasing the aluminum plate used in Example/ in the same manner as in Example/, triethanolamine θ,! ; vo-6,
% and molar ratio of 5i02/Na2O3. Add and dissolve sodium silicate θ and 7voA at the same time.
Did you adjust H to /θ? 7 in a slightly alkaline aqueous solution of j″C.
A chemical conversion treatment was performed by immersing the sample for 0 minutes.

In this way, the chemical conversion treatment was carried out in only one step, and after that, the pressure bonding and peeling tests of the fluororesin film were conducted in exactly the same manner as in the example, and the peel strength was /
-3b/, 2jsII widths, all of which were damaged due to interfacial peeling with the chemical conversion coating.0 Example co An aluminum plate of the same type that had been subjected to the same degreasing treatment as Example/ was immersed in ion-exchanged water with a specific resistance of jθθ×/θ4Ω. A chemical conversion treatment was carried out by dissolving 0.5 voA of ethanolamine, adjusting the pH to 1, and immersing it in a slightly alkaline aqueous solution at 5° C. for 3 minutes. Then wash with water, resistivity jθθ×/θ4
Add and dissolve sodium metasilicate with a molar ratio of 51o2/Na2o/into ion-exchanged water from Ω country.
9J”C with H adjusted to //.

The fluororesin film was immersed in an aqueous solution for 3 minutes to undergo reconversion treatment.Then, the fluororesin film was hot press-bonded using the method described in Example/1 and Ichikawa, and the peel strength was measured. ! ; The value of wx width was obtained.

Example 3 The aluminum plate to be used was continuously fed by a coil, subjected to degreasing treatment and chemical conversion treatment under the same conditions as in Example/1, and then transferred to a thermocompression roll together with tetrafluoroethylene and hexafluoropropylene. A synthetic resin film was laminated and supplied at the same time, and thermocompression bonding was performed.

As a result, a fluororesin nuclide aluminum plate having adhesive strength equivalent to that of the example was obtained. Relationship of Patent Applicant Address: 5-15 Kitahama, Higashi-ku, Osaka City, Column 5 of "Detailed Description of the Invention" of the Specification, Contents of Amendment 2) "rl-15 minutes" on page 5, line 16. "1
~15 minutes”.

3) #6N [[0,5 to 0,84 wt%] in the 17th line is corrected to [0,5 to 0.84 vol, %].

that's all

Claims (1)

[Claims] An aluminum or aluminum alloy plate is immersed in a weak alkaline aqueous solution containing a basic organic compound or at a temperature of 0°C or higher to form a water-conserving oxide conversion film, and then treated with an alkali silicic acid group-containing solution θ°C. A method for laminating a fluororesin film onto an aluminum or aluminum alloy plate, the method comprising immersing it in the above aqueous solution to perform reconversion treatment, and then heat-sealing a thermoplastic fluororesin film to the surface of the plate.