LU86207A1 - FLEXIBLE METAL SHEET - Google Patents

Description

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The present invention relates to a flexible metal sheet intended in particular for the packaging industry and the food industry.

One of the aims of the present invention is to present a flexible metal sheet which can be used for. wide variety of applications, such as heat reflecting screens, no; combustible, easily deformable heat conducting sheets i but sufficiently rigid to be able to be maintained in a deformed form i without the need for special fixing means. It is therefore a metallic foil which is particularly suitable as a packaging or screen in the food sector.

To this end, the flexible metallic sheet according to the invention comprises a metallic film, preferably made of iron or an iron alloy, covered on at least one of its faces with a metallic protective film containing nickel, l tin, a zinc-nickel alloy, a nickel-chromium alloy, a nickel-iron alloy, chromium coated with an outer layer of chromium oxide, or zinc, this film possibly being coated with an intermediate layer of chromium followed by an outer layer of chromium oxide.

Advantageously, the film has a thickness of between 5 and 10 microns, preferably 5 and 40 microns.

The invention also relates to a method of manufacturing a flexible metal sheet of the aforementioned type.

This process is characterized by the fact that the metallic film, preferably made of iron or an iron alloy, is formed by an electrolytic deposition on a cathode of substantially conductive material.

i -3- | inert, this film is then separated from the cathode and the aforementioned metal protective film is deposited on at least one of the faces of the film.

According to a particular embodiment of the method according to the invention, the film is formed by an electrolytic deposit on a cathode consisting of an endless strip entering continuously on one side into an electrolyte bath and leaving the opposite side of the latter, where the formed film is removed, also continuously.

Finally, the invention also relates to an installation for implementing this method.

According to the invention, this installation comprises, for the formation of the metallic film, an electrolysis cell provided with | of a cathode made up of an endless conductive strip moving in contact with an electrolyte, means being provided for removing from a substantially continuous manner, as the strip moves, the film deposited on the latter under the action of the cathodic current I, this cell being followed by a section for the formation of a; protective film on said film.

According to a preferred embodiment of the invention, this installation comprises a thermal treatment device i i 20 known per se mounted downstream of the electrolysis cell in which the above-mentioned film is formed.

Other details and features of the invention i; l will emerge from the description given below, by way of examples not! limiting, of some particular embodiments of the sheet; flexible metal according to the invention and the method and installation for the manufacture of this sheet.

! 'Figure 1 is a block diagram of a first j) embodiment of an installation for the manufacture of the flexible metal sheet according to the invention.

i; Figure 2 is a similar block diagram of a second embodiment of such an installation.

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Figure 3 is, on a larger scale, one; longitudinal section of a detail of the installation according to these two embodiments.

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In the various figures, the same reference numbers relate to similar or identical elements.

The present invention relates to a flexible metallic sheet comprising a metallic film, preferably of iron 5 or of an iron alloy, which is covered on at least one of its faces with a metallic protective film making it possible to prevent corrosion. of this film.

It is more particularly a film which can be deformed somewhat in the same way as a sheet of paper, except that the memory effect is practically not present. Thus, when a given shape is given to the sheet, this shape remains without particular precautions having to be taken, such as bonding or the use of other fixing means.

This allows the sheet 15 to conform substantially exactly to the shape of an object, even if this shape is relatively complex.

It has been found, according to the invention, that a metal sheet having these properties can be obtained if it! comprises a film of iron or an iron alloy whose thickness is i r f I 20 between 5 and 100 microns and preferably between 5 and Ψ0 microns.

: In addition, the metallic protective film; contains nickel, tin, a zinc-nickel alloy, a Ni-Fe alloy, a nickel-chromium alloy, chromium coated with an outer layer of chromium oxide, or zinc, this film being possibly coated with a layer! 25 chromium intermediate followed by an outer layer of chromium oxide, the thickness of this film is such that it consists of 0.5 to 5 g / m2 of nickel, 0.3 to 2 g / m2 of tin, a zinc-nickel alloy, a nickel-chromium alloy, or zinc optionally coated with an intermediate layer I of 30 to 100 mg / m2 of chromium followed by an outer layer, 30 of 5 30 mg / m2 of chromium oxide, or 30 to 100 mg / m2 of chromium coated with 5 to 30 mg / m2 of chromium oxide.

More particularly, this film may consist of 1 to 2 g / m2 of nickel, of a zinc-nickel alloy or of a nickel-chromium alloy or of the order of 2 g / m2 of zinc, optionally coated i an intermediate layer containing around 70 mg / m2 of chromium and i • · - 5 - an outer layer containing approximately 15 mg / m2 of chromium oxide or alternatively around 70 mg / m2 of chromium, coated with a layer containing around 15 mg / m2 of chromium oxide.

This protective film is provided on one, but preferably on both sides of the film.

The metal sheet according to the invention can be obtained by forming the film by electrolytic deposition on a cathode of substantially inert conductive material, then separating this film from the cathode and depositing on at least one of the faces of this film. the metallic protective film.

More particularly, in a continuous process, this film is formed on a cathode consisting of an endless strip entering at a substantially constant speed and continuously from one side into an electrolyte bath and leaving from the opposite side of this where the film formed is then removed, also continuously.

The anode used ‘may be soluble or insoluble, although preference is generally given for the use of a soluble anode. This can be constituted by a casting die of suitable dimensions or by scrap metal contained in a basket immersed in the electrolyte.

The protective film is also preferably obtained by electrolytic deposition in one or more electrolysis cells, this depending on the nature and the composition of the film.

In most cases it is useful to subject the film to a heat treatment generally known per se.

This heat treatment can take place either before the protective film is deposited on the film, or after this deposit, or even even simultaneously before and after the deposit.

Finally, this protective film can be covered with a non-metallic coating, preferably with an organic coating, such as a varnish.

Such a coating has the advantage of giving additional protection to the sheet against corrosion and, moreover, of allowing printing inscriptions and the like.

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This can therefore be particularly useful when the sheet is used as a means of packaging products.

The process according to the invention can also comprise certain conventional treatments, such as rinsing with water after electrolysis and drying before applying the non-metallic coating.

It may also prove useful to provide for stripping of the film after the heat treatment followed by rinsing and possibly drying before the metal protective film is deposited.

Figures 1 to 3 schematically show 1q two particular embodiments of an installation for the implementation of a method of manufacturing a flexible metal sheet according to the invention.

It is more particularly a continuous installation.

Thus, FIG. 1 shows an installation comprising successively an electrolysis cell 1 for the formation of the flexible metallic film, a first rinsing section 2 for eliminating the electrolyte entrained by the film, a heat treatment device i, generally known per se, a pickling section 4, followed by a second rinsing section 5, a second electrolysis cell allowing the deposition of the protective film on one or both sides of the film, a third rinsing section 7, a drying section S, a varnishing section 9 and a winding section 10.

The electrolysis cell 1 is advantageously a belt cell, that is to say in which the cathode consists of an endless conductive strip moving in contact with an electrolyte. Such a cell, which was the subject of Luxembourg patent No. 80,496 of September 9, 1978, has been shown in more detail in FIG. 3.

In this figure, the endless conducting strip 5Q 11, which therefore constitutes the cathode, is driven around two cylinders 12 and 13 in the direction of arrow 14.

The portion 15 of the endless belt 11 extending tangentially below the cylinders 12 and 13 forms the upper wall of an electrolytic bath 16 in which an electrolyte circulates in a direction opposite to that of this portion 15. Thus, as shown by an arrow 17, - »- 7 - the electrolyte is introduced into the electrolytic bath 16 by a line 18 on the rear side of the cell and leaves this bath by a line 19 provided on the opposite side of the electrolytic bath, as indicated by arrow 20.

The endless strip 11 cooperates with a cathode current supply 5 comprising a series of contacts, such as brushes 21, mounted in parallel on brush holders 22 distributed substantially uniformly on the face 23 of the portion 15 of the opposite strip 11 to that directed towards the electrolytic bath 16.

The portion 15 thereof extends substantially j0 parallel to an anode 24 which is, in the embodiment shown in Figure 3, consisting of a soluble anode. It is more particularly an ingot of iron casting. This ingot can therefore move in the direction of arrow 25, between walls 26 and 27 of the cell, as it is consumed as a result of the electrolysis. j <> An electrolytic deposit is formed on the face of 1 the portion 15 of the endless belt 11 oriented towards the electrolytic bath 16 which thickens as this portion advances in the direction of the arrow 28.

'When, at the end of the electrolytic bath 20 16, the strip moves away from the electrolytic bath, the electrolytic deposit 29 thus formed constitutes the aforementioned film and is detached from this strip to be directed, for example by means of a roller 30, towards the first rinsing section 2, as shown in FIG. 1.

After the heat treatment in the device 25 3, the film passes into the pickling section 4 where it can be e.g.

treated with a solution of formic, hydrochloric or sulfuric acid.

For the formation of the metallic protective film on this film 29, the electrolysis cell 6 used may, for example, be a cell of the type which is the subject of Luxembourg patent 30 No. 85.086 of 11 November 1983. This cell enables a substantially uniform metallic film to be produced at high current density simultaneously on each of the two faces of the film 29.

Figure 2 relates to a second embodiment of an installation for the manufacture of a flexible metal sheet according to the invention.

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This is essentially distinguished from the embodiment shown in FIG. 1 by the fact that the deposition of the protective film on the film 29 coming from the electrolysis cell 1 takes place before the heat treatment. In addition, the pickling section, which had been provided in the first embodiment after the heat treatment was omitted.

Thus, in this second embodiment, directly after the first rinsing section 2, the electrolysis cell 6 is provided for the formation of the protective metallic film 10. This electrolysis cell is then followed by the rinsing section 7.

As a result of the particular arrangement according to FIG. 2, diffusion in the solid state can occur during annealing, between the metallic protective film and the film. In this way, when this film is made of nickel, thanks to this diffusion effect, the nickel film! can be transformed, at least at the contact surface with the film, into a nickel-iron alloy.

In general, the electrolyte can advantageously contain between 40 and 150 g / J of Fe * "\ preferably in the form of FeCl 2, and the pH thereof is maintained between 0.5 and 4, eg by: adding a strong acid, such as hydrochloric acid.

The cathodic current density is advantageously between 100 and 300 A / dm2, for a circulation speed of the electrolyte of 2 to 4 m / sec and a temperature of the electrolytic bath between 25 70 and 95 ° C.

I If an insoluble anode is used, this is! . preferably formed of titanium coated with Ru02-Ti02. Furthermore, in this case, a regeneration of Fe ++ is necessary which can be obtained by an attack of iron metal by the Fe formed.

! 30 Example 1

This example relates to the continuous production of a sheet in the form of a strip whose film is made of iron and has a thickness of the order of 15 μ and a width of 2 m and whose protective film on both sides of the film consists of 2 g / m2 / per side of zinc coated with 40 mg / m2 / per side of zinc covered with 40 mg / nrr of chromium and 10 mg / m2 of oxide

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- 9 - chrome. In this respect, an installation was used comprising two electrolysis cells in series with a soluble anode, of the type shown in FIG. 3, of 2 m of useful length, therefore corresponding substantially to the length of the portion 15 of the strip 11. The current density was of the order of 200 5 A / dm2 and the line speed, that is to say the speed of movement of the strip 11, was of the order of 14 m / min.

The electrolytic bath 16 contained 60 g / l of Fe + * and the pH was of the order of 0.5.

This electrolysis was followed by rinsing the obtained film 29, which was then subjected to a heat treatment.

The zinc layer of the aforementioned protective film was formed in a first electrolysis cell of the type that is the subject of Luxembourg patent No. 85086.

In a second cell of the same type, after rinsing the surface of the zinc deposit, the successive deposition of the layers of chromium and chromium oxide was carried out. This deposit was also subjected to a rinsing which was then followed by drying to allow the covering of the film of

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protection thus obtained by a coating of varnish.

Example 2 ′ 20 This example relates to the continuous production of a flexible metallic sheet in the form of a strip with a width of 1.5 m, the film of which is made of iron and has a thickness of the order of 30 μ.

The installation used included six series electrolysis cells of the type shown in FIG. 3, with soluble anode, for the formation of the film.

The current density was of the order of 300 A / dm2 and the electrolytic bath had a concentration of Fe + of the order of 120 g / 1 and a pH of the order of 2.

The speed of the line or strip 11 in these cells was of the order of 30 m / min. These cells were followed by a rinsing section and an electrolytic deposition of a Ni-Cr alloy of 2 g / m2, of which about 70% consisted of nickel, in an electrolysis cell of the type making subject of Luxembourg patent 85086. The density of the cathode current was of the order of 200 A / dm2. After rinsing and drying, the film covered with the protective film thus formed was subjected to a heat treatment.

After cooling, the protective film was covered with a varnish. Example 3

This example relates to the continuous production of a flexible metal sheet 5 protected by a tin film and the iron film of which is identical to that of Example 2.

The installation used also corresponded to that of this example 2. The aforementioned tin film was formed by passing the film at a speed of the order of 20 m / min in a cell of the same type as that of 10 l. 'example' 2. The electrolyte was based on phenolsulfonic acid and contained around 20 g / l of Snz and 6 g / l of an organic inhibitor "ENSA". The bath temperature was of the order of 45 ° C and the cathodic current density of the order of 20 A / dm2, the cathodic current yield was 100%.

It is understood that the invention is not limited to the embodiments described above of the metal sheet (flexible, of the method and of the installation for the manufacture of this sheet, but that many variants can be envisaged without departing from the scope of the present invention.

20 Thus, the electrolytic deposition for the formation of both the film and the protective film can be carried out by a succession of several electrolysis cells of the same type or of different types with, if necessary, between two successive cells. a rinsing section.

Furthermore, in certain cases, the protective film may consist of nickel or tin covered with an intermediate layer of chromium and an outer layer of chromium oxide.

Claims (22)

1. Flexible metallic sheet, characterized in that it comprises a metallic film, preferably made of iron or an iron alloy, covered on at least one of its faces with a metallic protective film containing nickel, tin, a zinc-nickel alloy, a nickel-chromium alloy, a nickel-iron alloy, chromium coated with an outer layer of chromium oxide, or zinc, this film possibly being coated with an intermediate layer of chrome followed by an outer layer of chromium oxide. 2. Sheet according to claim 1, character-ized in that this film contains, on at least one of the faces of the film, between 0.5 and 5 g / m2 of nickel, 0.5 to 2 g / m2 d tin, a zinc-nickel alloy, a nickel-chromium alloy, zinc, this film being optionally coated with an intermediate layer of 30 to 100 mg / m2 of chromium followed by an outer layer of 5 to 30 mg / m2 of chromium oxide coated with 15 5 to 30 mg / m2 of chromium oxide. 3. Sheet according to claim 2, characterized in that this film contains, on at least one of the faces of the film, between 1 and 2 g / m2 of nickel, a zinc-nickel alloy, or an alloy of nickel-chromium or of the order of 2 g / m2 of zinc, this film being optionally coated with an intermediate layer containing on the order of 70 mg / m2 of chromium and with an outer layer containing of the order of 15 mg / m 2 of chromium oxide or alternatively of the order of 70 mg / m 2 of chromium coated with a layer containing of the order of 15 mg / m 2 of chromium oxide. 4. Sheet according to any one of claims 1 to 3, characterized in that the film has a thickness of between 5 and 100 μ, preferably between 5 and 40 μ. 5. Sheet according to any one of claims 1 to 4, characterized in that it has a non-metallic exterior coating, preferably an organic coating, such as a varnish. 6. Flexible metal sheet, as described above. ** "," - 12 - „'7. A method of manufacturing a flexible metal sheet according to any one of claims 1 to 6, characterized in that the metal film, preferably made of iron or an iron alloy, is formed by a deposit electrolytic on a cathode of substantially inert conductive material 5, this film is then separated from the cathode and the metal protective film is deposited on at least one of the faces of the film. 8. Method according to claim 7, characterized in that the film is formed by an electrolytic deposit on a cathode constituted by an endless strip entering continuously on one side into an electrolyte bath and leaving on the opposite side thereof, where the formed film is removed, also continuously. 9. Process according to either of Claims 7 and 8, characterized in that an electrolytic cell with a soluble anode is used to form the film by electrolytic deposition. 10. Process according to either of Claims 1 to 9, characterized in that the protective film,,,, f, mentioned above, is formed by an electrolytic deposit in at least one electrolysis cell. 11. Method according to any one of claims 7 to 10, characterized in that the film is subjected to a heat treatment. 12. Method according to claim 11, characterized in that the protective film is formed on the film after the heat treatment. 13. Method according to claim 11, characterized in that the protective film is formed on the film before i heat treatment. 14. Method according to any one of claims 7 to 13, characterized in that the protective film is covered with a non-metallic coating, preferably an organic coating, such as a varnish. 15. Method according to any one of claims 7 to 14, characterized in that the film is subjected to pickling before the deposition of the metal protective film. w. - 13 - island ! ; ^ 16. Process for manufacturing a sheet | flexible metal, as described above or illustrated by the accompanying drawings. 17. Installation for the implementation of. process according to any one of claims 7 to 16, characterized in that it comprises, for the formation of the metallic film, an electrolysis cell provided with a cathode constituted by an endless conductive strip moving in contact with an electrolyte, means being provided for removing, in a substantially continuous manner, as the i | displacement of this strip, the film deposited on the latter under | jq the action of the cathode current, this cell being followed by a section for J the formation of a protective film on said film. i 18. Installation according to claim 17, j characterized in that the aforementioned section comprises at least one second cell ′lectrolysis through which the film can move in a substantially continuous manner in contact with an electrolyte containing, i metal ions, of which the protective film is made. ], 19. Installation according to either of claims 17 and 18, characterized in that it comprises a heat treatment device mounted downstream of the electrolysis cell in which the film is formed. . • I 20. Installation according to claim 19, i / j characterized in that the heat treatment device is mounted after! the section for the formation of the protective film on the film. i ·! 21. Installation according to claim 19, characterized in that the heat treatment device is mounted before; the section for the formation of the protective film on the film. i 22. Installation for the manufacture of a flexible metallic sheet i covered with a metallic protective film, such as! ' described above or shown in the accompanying drawings. f i · j i î'i Der-sr-s: .......... <3, · ·, ·; - ---- é.J. ':. .. Λ. S j; * 3 · ij / _: · - v 1; ? _