EP1771605A1

EP1771605A1 - Method for producing coated aluminium alloy strips for producing photographic quality decorations by dry transfer

Info

Publication number: EP1771605A1
Application number: EP05778636A
Authority: EP
Inventors: Laura Cecchetto; Gianfranco Maggi
Original assignee: Traitement des Metaux et Alliages (Satma)
Current assignee: Traitement des Metaux et Alliages (Satma)
Priority date: 2004-06-18
Filing date: 2005-06-16
Publication date: 2007-04-11
Also published as: CN1969066A; JP2008502801A; FR2871814A1; WO2006008371A1; KR20070026618A; US20070184213A1; BRPI0512203A; FR2871814B1; RU2007101711A; MXPA06014163A

Abstract

The invention relates to a method for continuously producing an aluminium alloy strip for transferring a sublimable decoration from a temporary carrier consisting in using the aluminium alloy strip having a gloss and high-gloss quality, in anodising and sealing said strip and in coating the anodised strip with a transparent lacquer consisting of a polyester and polyurethane mixture. Said anodisation and sealing are substitutable by a HELIA process under EP 0 745 703 patent in order to form a compact oxide barrier whose thickness ranges from 140 to 200 nm. The thus produced aluminium alloy strip for sublimation transfer and a strip or sheet decorated after said transfer from the temporary carrier are also disclosed.

Description

Process for manufacturing coated aluminum alloy strips for making photographic quality decorations by dry transfer.

Field of the invention

The invention relates to a process for the continuous industrial production of aluminum alloy strips coated with a varnish, particularly suitable for obtaining photographic quality decors according to the technique of sublimation dry transfer from a support. and strips produced by this process.

State of the art

The dry transfer of decors by sublimation from a temporary support has found its first important applications in the textile industry, natural and synthetic.

According to this method, the image to be transferred is, in most cases, printed on a paper medium according to traditional printing techniques. To carry out the transfer, said support is pressed against the material on which it is desired to transfer the sublimable image, for about 30 seconds at temperatures generally from 200 to 230 ° C. The constituents of the inks composing the image then pass directly from the solid state to the gaseous state and migrate towards the support to be printed on which they condense and are absorbed. During cooling, the ink vapors return directly to the solid state. The application then spread to other materials including polymers and metals. In the case of aluminum alloys, in order to obtain the maintenance of the transferred decor, anodizing treatment prior to transfer is mainly practiced.

US Pat. No. 3,484,342 (Martin-Marietta Corp.), filed in 1966, describes the process of transferring sublimation decorations from a temporary substrate (paper according to claim 6) to alloys coated with a porous anodic layer, to allow the penetration of the various pigments into the pores, and clogged (by treatment with boiling water, or boehmitage, according to claim 6) after transfer to fix said pigments on their new substrate.

Claim 4 preferably refers to anodizing in a sulfuric medium; the description in column 4, lines 63 to 66 states that, after clogging for half an hour in boiling water, an operation known as boehmitage, the quality and clarity of the hue remain "acceptable".

Among the disadvantages of this method, it can indeed be emphasized that, according to their size, not all the pigments penetrate the same way in the pores, some causing dusting by accumulating on the surface, which is detrimental to the definition of the image, and above all, causes a change or loss of color after clogging.

What is more, we often observe the transfer not only of the image of the decoration, but also other parasitic elements (weft of the paper, ...) on the non-clogged layers. In addition, the handling between anodizing and transfer as well as between transfer and clogging must be carried out with particular care to avoid easy deterioration of the pores.

On the other hand, the transfer must be carried out in a short and relatively constant time after the anodization (preferably chained to the anodization) the pores clogging naturally by formation of hydrated alumina (Al ₂ O ₃ , (H ₂ 0) x).

Finally, to obtain an acceptable color intensity, that is to say pores of sufficient size, the thickness of the anode layer must be relatively large (more than 2 to 3 μm, or even 7 μm for blue and black) and of the sublimation operation by heating, it is common to see a cracking of this type of layer. The patent application FR 2,230,794 (Sublistatic Holding SA) filed in 1974 describes the application of this process, at a temperature between 140 and 300 ° C, preferably 180 to 230 ^° C, on any rigid material made up or previously coated with epoxy resins, transparent or colored. Aluminum is cited, among a large amount of other media, through home appliances, furniture, automotive sheets, but without any indication of the surface treatment prior to allow adhesion of said epoxy resins. Since this is known to be difficult in the case of aluminum, the treatment in question consists of either conventional anodizing or chemical conversion. to obtain in order to fix the resin, a porous layer at least at the surface, with all the disadvantages already described as to this type of surface.

It is also known that the surfaces, made of aluminum alloy, "bare" or naturally coated with a thickness of a few nm oxide, by nature irregular, varnished without further treatment, are fragile and in particular very sensitive to scratching . Patent EP 0 012 831 B1 (Fromson, Howard A.), filed in 1979, describes a sublimatic transfer process, at a temperature preferably between 121 and 218 ^° C., on an aluminum substrate comprising a porous oxide layer not clogged and coated with a transparent or colored polymer. The pigments pass through the polymer material and condense in this coating as well as in the pores of the anode layer.

The disadvantages already reported, related to the fixing of the pigments in the pores of the anodic layer and the usual thickness thereof remain in fact.

Problem

The Applicant has therefore sought to obtain a resistant support (both scratches and corrosion and aging in particular) allowing transfer by sublimation without cracking or visible modification of the color and the definition of the transferred image (so-called photographic quality ) with a non-limiting palette of pigments, and allowing subsequent folding or shaping operations without apparent deterioration.

Object of the invention

The subject of the invention is a method of continuously manufacturing an optimized surface aluminum alloy strip for transferring a sublimable decoration from a temporary support, comprising:

1. The preparation of a high-reflectivity aluminum alloy strip of "brilliant" or "high gloss" quality,

2. The possible degreasing and the chemical or advantageously electrolytic polishing of said strip,

3. The creation of a nonporous surface layer, either by conventional anodization, to form an oxide layer of thickness less than or equal to 1 μm, followed a sealing operation, in particular by boehmitage, or, advantageously, by electrolytic micro-polishing, that is to say by anodization in mineral acid, organic or mixed, to form a compact layer of the barrier type of a thickness preferably comprised between 140 and 200 nm, 4. The coating of the anodized clogged or barrier-type strip of a clear lacquer based on a blend of polyester and polyurethane.

In the case of the formation of a barrier-type layer, this step may be preceded by deoxidation, also called selective etching, in a phosphochromic medium of the previously formed oxide layer. Advantageously, the selective pickling and electrolytic polishing steps can be repeated.

Preferably, the varnish is glossy, of the BASF type CI49-0005, or matt, of the type

BASF CI49-0004.

The subject of the invention is also the strip treated and coated according to the process or its variants above, thus prepared for application, after any cutting into sheets of said strip, to the transfer by sublimation, as well as the strip or sheet decorated after said transfer from a temporary support.

Description of the invention

The invention consists in using aluminum alloy strips of "brilliant" or "high gloss" quality, subjecting them continuously, after optional degreasing and chemical or electrolytic polishing, to a thin-layer anodizing treatment. thickness less than 1 micron followed by a pore-sealing operation by continuous immersion preferably in boiling water, operation known as boehmitage, before coating, preferably continuously according to the coating technique of the type known by the person skilled in the art, under the name "coil coating", of a transparent varnish based on a mixture of polyester and polyurethane. The anodic layer with a non-porous surface, obtained before final varnishing, can advantageously be a compact layer of the barrier type obtained by the HELIA® process, which is the subject of patent EP 0 745 703 of the Applicant, applied to strips of "brilliant" or "high gloss" quality and whose main phases, after possible degreasing, are recalled below:

A first step of conventional polishing chemically or preferably electrolytic and then a water wash, optionally a deoxidation step or selective etching for example in a phospho-chromic medium (H ₃ PO ₄ + CrOs) and then a wash at the water, A final step, as described in detail in patent EP 0 745 073, micro-polishing by anodizing organic mineral acid, or mixed, to form a barrier layer with a thickness preferably between 100 and 500 nm and better between 140 and 200 nm.

These last two steps can optionally be repeated to obtain an optimum optical reflectivity (greater than 80% without interferential iridescence or visible color variation). The Applicant has found that the barrier layer thus formed, although compact and having no pores in the sense that is meant for non-clogged layers, behaved like a thin anodic layer (less than 1 μm) with respect to the adhesion of the varnish and its resistance to scratching and tearing during subsequent folding or shaping operations. The varnish may be glossy, for example of the BASF CI49-0005 type, in order to keep on the final product a mirror-polished or matte appearance, for example of the BASF type CI49- 0004, for a satin appearance.

Finally, the Applicant has also found in all sublimation transfer tests images, a quality of the image that can be described as photographic both in terms of its definition and the return of colors, and this on a mirror-like support particularly favorable.

The explanation most probably lies in the absence of pores of both the sealed anodic layers and the barrier layers of the HELIA® process: all the pigments are homogeneously distributed in the varnish and on the anodized surface, without the accumulation phenomenon. surface of pigments too large and the diffusion of others in the pores, as in the case of porous layers; this characteristic acts as much on the fidelity of the colors restored compared to the initial substrate as on the definition and the clarity of the image (sharpness of the outlines); the eventual frame of the starting substrate does not appear on the final image either. the

This feature also expands the palette of usable inks or pigments.

Furthermore, the fineness of the anodic layer (conventional sealed or barrier) ensures the absence of visible cracking during the sublimation operation and also has a very positive influence on the characteristics of folding and shaping of the final product.

It is also proven to be very resistant to corrosion tested in salt spray. Finally, the handling of the tape reels before coating and before transfer by sublimation is quite conventional because of the absence of pores that could clog, and the good resistance of the varnish, after its application and before transfer; possible waiting times between anodic treatment of the tape coils and varnishing, as well as between coating and transfer, are here without any effect on the final quality of the product, which constitutes a serious advantage from the point of view of the industrial robustness of the process.

Examples

1) Alcan-Singen "1085 Surface 310" high gloss aluminum alloy coils and Amag "1085 126.2" coils were degreased and then treated using the HELIA® variant 1 of EP 0 745 703 (ie electrolytic polishing, phosphochromic deoxidation, micro polishing with barrier layer).

They were then coated with BASF gloss varnish CI49-0005 continuously on a so-called "coil coating" line 600 mm wide at a speed of 25 m / min, the temperature of the varnish drying oven being 24O ⁰ C; "Wet thickness" of the varnish was about 50 microns for a "dry thickness" of about 15 to 20 microns.

Characterizations included optical measurements, varnish adhesion and salt spray corrosion resistance. at. Optical measurements: they focused on the total reflectivity Rt and the diffuse reflectivity Rd by Ulbricht sphere according to DIN 5036, as well as on the specular reflectivity at 60 degrees in the long and rolling directions,

Rs60L and Rs60T, according to DIN 67530. b. Varnish Adhesion: The adhesion tests used are the grid tests defined by ISO 2409 (1992). vs. Salt spray: This is a hold for more than 1000 hours in a neutral salt spray chamber, tested to ASTM Bl 17, ASTM G85 Al and ISO / DP 9227 with the following parameters:

Fog temperature: 35 ⁰ C NaCl concentration of the solution: 50 g / l Ph of the solution: 7

Tilt of the samples in relation to the vertical: 15 degrees Fog flow: 1.5 cm3 / h collected with a funnel diameter 10 cm.

The same tests were carried out but using, in this case, BASF matt varnish CI49-0004.

Results:

at. Optical measurements:

Gloss lacquer: Rt = 85, Rd = 9, RsόOL = 76, RsόOT = 75 Matt varnish: Rt = 83, Rd = 69, Rs60L = 35, RsόOT = 35 After the glossy lacquer operation, the surface has all the characteristics mirror polish, ie high values of total and specular reflectivity, associated with a low value of diffuse reflectivity.

Matte varnish offers an interesting alternative corresponding to a satin aspect but with a high value of total reflectivity. b. Adhesion of the varnish: The adhesion of the coating to the substrate corresponds in both cases to the ISO 2409 (1992) class 0: perfectly smooth incisions edges, none of the grid squares detached.

. c Salt fog:

The samples were recovered intact after more than 1000 hours. the

2) Other "high gloss" quality aluminum alloy coils of the type

"1085 Surface 210" of Alcan-Singen, the rolling mills underwent continuous degreasing and electrochemical polishing, anodizing also continuously, in a bath based on sulfuric acid, and in a thin layer with a thickness of about 0.8 microns, followed by an operation to seal the pores by immersion, always continuous, in boiling water, operation known as boehmitage.

Half of them were coated with BASF glossy varnish CI49-0005 and the other half with BASF matt varnish CI49-0004, continuously on a so-called coil coating line with a width of 600 mm at a speed of 25 m. min, the temperature of the drying oven of the varnish being 240 ° C; "Wet thickness" of the varnish was about 50 microns for a "dry thickness" of about 15 to 20 microns.

The characterizations included the same optical measurements, adhesion of the varnish and resistance to salt spray corrosion.

Results:

at. Optical measurements:

Gloss varnish: Rt = 85, Rd = 13, Rs60L = 76, Rs60T = 76

Matt varnish: Rt = 84, Rd = 77, Rs60L = 27, Rs60T = 26 After the glossy lacquer operation, the surface has as before all the characteristics of the mirror polish, namely high values of the total and specular reflectivity, associated with a low value of diffuse reflectivity.

Matt varnish offers, in the same way as for the previous tests, an interesting alternative corresponding to a satin aspect but with a high value of the total reflectivity. b. Adhesion of the varnish:

The adherence of the coating to the substrate corresponds in both cases to ISO 2409 (1992) class 0: perfectly smooth incisions edges, none of the squares of the detached grid. vs. Salt spray :

The samples were recovered intact after more than 1000 hours. In conclusion, the tests proved to be quite positive, as well as the various sublimation transfers carried out at 215 ° C for 30 to 40 seconds: many images, differing both in nature and in the density of patterns and colors, been reproduced with a sharpness and definition quite remarkable.

Claims

claims

A method of continuously manufacturing an optimized surface aluminum alloy strip for transferring sublimable decor from a temporary support, comprising: a. The preparation of a high-reflectivity aluminum alloy strip of "brilliant" or "high gloss" quality, b. The optional degreasing and the chemical or advantageously electrolytic polishing of said strip, c. The creation of a non-porous surface layer, either by conventional anodization, to form an oxide layer of thickness less than or equal to 1 μm, followed by a sealing operation, in particular by boehmitage, or, advantageously, by electrolytic micro-polishing, that is to say by anodization in mineral acid, organic or mixed, to form a compact layer of the barrier type with a thickness of preferably between 140 and 200 nm, d. The coating of the sealed anodized band or the barrier type of a transparent varnish based on a mixture of polyester and polyurethane.

2. Method according to claim 1, with formation of a barrier layer, characterized in that the electrolytic micro-polishing step is preceded by a deoxidation also called selective etching, in phosphochromic medium, of the oxide layer. previously formed during chemical or electrolytic polishing.

3. Method according to claim 2 characterized in that the steps of selective etching and electrolytic micro polishing are repeated.

4. Method according to one of claims 1 to 3 characterized in that the varnish is brilliant BASF type CI49-0005

5. Method according to one of claims 1 to 3 characterized in that the varnish is matte type BASF CI49-0004

6. A coated aluminum alloy strip manufactured according to the method described in one of claims 1 to 5.

7. A method of manufacturing a decorated strip or sheet comprising: a. The preparation of the web according to one of claims 1 to 5, b. Optionally the sheet metal cutting of the strip thus prepared, c. The dry transfer of a sublimable decor from a temporary support.