Method of producing a chromium-free conversion coating on a surface of an aluminium or aluminium alloy strip
专利汇可以提供Method of producing a chromium-free conversion coating on a surface of an aluminium or aluminium alloy strip专利检索，专利查询，专利分析的服务。并且In a method of producing an aluminium or aluminium alloy strip with a heat-seal lacquer on a first surface and an epoxide based stove lacquer on the second surface, a chromium-free conversion coating is produced on the first and second surface of the aluminium or aluminium alloy strip in a continuous production line before applying the hot seal lacquer and the stove lacquer, the chromium-free conversion coating is produced by
(A) a no-rinse process by treatment with a solution of silanes in a polar organic solvent, or
a no-rinse process by treatment with an aqueous solution of 5 to 10 wt.-% hexafluorotitanic acid (H 2 TiF 6 ) and 2.5 to 5 wt.-% hexafluorozirconic acid (H 2 ZrF 6 ), or
(B) a rinse process by treatment with an aqueous solution of 4 ) 2 Mo 2 O 7 ) and 5 to 10 wt.-% hexafluorozirconic acid (H 2 ZrF 6 ).，下面是Method of producing a chromium-free conversion coating on a surface of an aluminium or aluminium alloy strip专利的具体信息内容。
The invention relates to a method of producing an aluminium or aluminium alloy strip with a heat-seal lacquer on a first surface and an epoxide based stove lacquer on the second surface.
In particular, the invention relates to the preparation of cleaned surfaces with good adhesion properties of the aforementioned organic coatings on aluminium or aluminium alloy strips intended for the manufacturing of lacquered and deep-drawn capsules closed with a heat-sealed membrane lid for packaging portions of coffee.
So-called "rinse" and "no-rinse" processes are generally known in the chemical treatment of metal surfaces, for example for the subsequent application of paints, adhesives and/or plastics. In rinse and no-rinse processes, the metal surfaces are freed from oil, dirt and other residues in a first stage. Any residues of chemicals from this first stage are removed by rinsing with water. In the next stage of the rinse process, the clean metal surface is wetted with an aqueous bath solution which is rinsed off. In the non-rinse process the clean metal surface is wetted with an aqueous bath solution which is not rinsed off, but instead is dried in situ on the metal surface and, in the process, is converted into a solid film of the bath ingredients. Coatings such as these can significantly improve the surface quality of covering layers subsequently applied, particularly with respect to corrosion control and adhesion. Originally, treatment solutions containing hexavalent chromium ("yellow chromating") were often proposed in the extensive relevant prior art literature. On account of the toxic character of Cr(VI), these processes or rather the rinsing waters accumulating therein require expensive wastewater treatment. Even processes which only use trivalent chromium were not entirely satisfactory on account of increasing demands for the complete absence of chromium.
The chromium-free conversion treatment of aluminum surfaces with fluorides of boron, silicon, titanium zirconium or molybdenum alone or in conjunction with organic polymers for obtaining permanent protection against corrosion and for producing a base for subsequent painting is known in principle:
- a) 10 to 16 g/I of polyacrylic acid or homopolymers thereof,
- b) 12 to 19 g/I of hexafluoro zirconic acid,
- c) 0.17 to 0.3 g/I of hydrofluoric acid and
- d) up to 0.6 g/l of hexafluoro titanic acid.
- a) 0.5 to 10 g/l of polyacrylic acid or an ester thereof and
- b) 0.2 to 8 g/l of at least one of the compounds H2 ZrF6, H2TiF6 and H2SiF6, the pH value of the solution being below 3.5, and an aqueous concentrate for regenerating the treatment solution containing:
- a) 25 to 100 g/l of polyacrylic acid or an ester thereof,
- b) 25 to 100 g/l of at least one of the compounds H2 ZrF6, H2TiF6 and H2SiF6
and
- c) a source of free fluoride ions supplying 17 to 120 g/I of free fluoride.
- a) phosphate ions in a concentration of 1.1x10-5 to 5.3x10-3 moles/I, corresponding to 1 to 500 mg/l,
- b) 1.1 x 10-5 to 1.3 x 10-3 moles/l of a fluoroacid of an element of the group consisting of Zr, Ti, Hf and Si (corresponding to 1.6 to 380 mg/l, depending on the element) and
- c) 0.26 to 20 g/I of a polyphenol compound obtainable by reacting poly(vinylphenol) with aldehydes and organic amines.
- a) 2.2 to 22.0 g/l of Zr(IV) and/or 1.4 to 14.0 g/I of Ti(IV),
- b) 2.4 to 24.0 g/l of orthophosphate,
- c) 3.0 to 30.0 g/l of fluoride,
- d) 0.15 to 1.5 g/l of a water-soluble or homogeneously water-dispersible organic film former, and the solutions are dried on the surface without rinsing after a contact time of 1 to 40 seconds at temperatures of 50°C to 125°C.
An object of the present invention is to provide a method of the type mentioned at the beginning with a good adhesion of the aluminium or aluminium alloy strip with a heat-seal lacquer on a first surface and an epoxide based stove lacquer on the second surface and the epoxide based stove lacquer without the need of a Cr(III) conversion coating. In particular, the aluminium or aluminium alloy strip manufactured with the method according to the present invention shall be qualified for the manufacture of deep-drawn capsules for packaging portions of coffee, the capsules having a heat-seal lacquer on the inner surface of the capsule and an epoxide based coloured stove lacquer on the outer surface of the capsule.
A further object is to provide a method of producing a chromium-free conversion coating on a surface of an aluminium or aluminium alloy strip in a continuous production line, the chromium-free conversion coating having good adhesion properties of a heat-seal lacquer on a first surface and an epoxide based stove lacquer on the second surface of the aluminium or aluminium alloy strip intended for the manufacturing of lacquered and deep-drawn capsules closed with a heat-sealed membrane lid for packaging portions of coffee.
The first of the aforementioned objectives is achieved by way of the invention in that a chromium-free conversion coating is produced on the first and second surface of the aluminium or aluminium alloy strip in a continuous production line before applying the heat-seal lacquer and the stove lacquer, the chromium-free conversion coating is produced by
- (A) a no-rinse process by treatment with a solution of silanes in a polar organic solvent, or
a no-rinse process by treatment with an aqueous solution of 5 to 10 wt.-% hexafluorotitanic acid (H2TiF6) and 2.5 to 5 wt.-% hexafluorozirconic acid (H2ZrF6), or
- (B) a rinse process by treatment with an aqueous solution of < 1 wt.-% diammonium dimolybdate ((NH4)2Mo2O7) and 5 to 10 wt.-% hexafluorozirconic acid (H2ZrF6).
The second of the aforementioned objectives is achieved by way of the invention in that the method comprises the steps of
continuous uncoiling of a rolled aluminium or aluminium alloy strip from a first coil;
continuous annealing of the uncoiled strip;
continuous cleaning and degreasing of the surface of the annealed strip; continuous washing of the cleaned and degreased surface of the strip; continuous pickling of the surface of the washed strip;
continuous washing of the surface of the pickled strip;
drying of the surface of the washed strip;
continuous production of a chromium-free conversion coating on the surface of the dried conversion coated strip by
- (A) a no-rinse process by treatment with a solution of silanes in a polar organic solvent, or
a no-rinse process by treatment with an aqueous solution of 5 to 10 wt.-% hexafluorotitanic acid (H2TiF6) and 2.5 to 5 wt.-%hexafluorozirconic acid (H2ZrF6), or
- (B) a rinse process by treatment with an aqueous solution of < 1 wt.-% diammonium dimolybdate ((NH4)2Mo2O7) and 5 to 10 wt.-% hexafluorozirconic acid (H2ZrF6);
optional washing of the surface of the conversion coated strip;
continuous drying of the surface of the conversion coated and optionally washed strip;
continuous coiling of the dried strip onto a second coil.
Cleaning and degreasing is preferably made by spraying the strip with an aqueous solution of 5 to 50 g/I, preferably 15 to 25 g/I, of an initial solution comprising 0.10 to 1.0 wt.% bisoctyl dimethyl ammonium chloride, 5 to 10 wt.-% potassium hydroxide, 5 to 10 wt.-% phosphate (P) and < 5 wt.-% cationic tenside.
In a first embodiment of the invention, pickling is preferably made by spraying the strip with an aqueous solution of 5 to 50 g/I, preferably 15 to 25 g/I, of an initial solution comprising 65 to 80 wt.-% ortho phosphoric acid.
In a second embodiment of the invention, pickling is preferably made by spraying the strip with an aqueous solution of 5 to 30 g/l, preferably 8 to 15 g/I, of a first initial solution comprising 25 to 50 wt.-% sulphuric acid and 5 to 15 wt.-% non ionic tenside, and 0.1 to 10 g/l, preferably 1 to 3 g/I, of a second initial solution comprising 5 to 7 wt.-% hydrofluoric acid.
In a first embodiment of the invention, the conversion coating is preferably made by spraying the strip with a solution of 50 to 200 g/l, preferably 80 to 120 g/l, of an initial solution comprising silane and 10 to 25 wt.-% ethanol.
In a second embodiment of the invention, the conversion coating is preferably made by spraying the strip with an aqueous solution of 10 to 160 g/l, preferably 30 to 50 g/I, of a first initial solution comprising 5 to 10 wt.-% hexafluorotitanic acid and 2.5 to 5 wt.-% hexafluorozirconic acid, and 1 to 10 g/l, preferably 7 to 9 g/I, of a second initial solution comprising 20 to 21 wt.-% silica.
In a third embodiment of the invention, the conversion coating is preferably made by spraying the strip with an aqueous solution of 5 to 50 g/l, preferably 15 to 25 g/I, of a first initial solution comprising < 1 wt.-% diammonium dimolybdate and 5 to 10 wt.-% hexafluorozirconic acid, and 0.01 to 0.3 g/l, preferably 0.1 to 0.3 g/I, of a second initial solution comprising 10 to 25 wt.-% ammonium fluoride and 10 to 25 wt.-% ammonium hydrogen difluoride.
In a third embodiment of the invention, the conversion coating is preferably made by spraying the strip with an aqueous solution of 5 to 50 g/l, preferably 15 to 25 g/I, of a first initial solution comprising < 1 wt.-% diammonium dimolybdate and 5 to 10 wt.-% hexafluorozirconic acid, and 0.01 to 0.3 g/l, preferably 0.1 to 0.3 g/l, of a second initial solution comprising 10 to 25 wt.-% ammonium fluoride and 10 to 25 wt.-% ammonium hydrogen difluoride, and 0 to 2 g/I, preferably 0.05 to 0.2 g/I, of a third initial solution comprising 25 wt.-% polycarboxylic acid in water.
In the preferred no rinse process according to the invention, a conventionally cleaned and rinsed metal surface, after rinsing with deionized water and drying and/or removal of the water film by squeegees, is wetted in any manner with the solution of silanes in the polar organic solvent aqueous treatment solution in such a quantity that around 2 to 20 ml and preferably around 5 to 10 ml of the polar organic treatment solution are applied per square meter of surface area.
The treatment solutions in the preferred no rinse process according to the invention may be applied to the precleaned metal strips by any method which is capable of producing a uniform, defined liquid film on the metal surface in the quantity ranges indicated. The roller application process using two to four rollers ("chemcoater") has proved to be particularly effective, although wetting of the strip by spraying or immersion and subsequent removal of the excess liquid film, for example by plastic-coated equalizing rollers or an adjustable air knife, is also suitable. The temperature of the treatment solution may be in the range from 15°C to 30°C and is preferably in the range from 20°C to 25°C.
The liquid film applied to the metal surface is allowed to react thereon for about 1 to 40 seconds, after which the film is dried and heat-treated at elevated temperature. However, the process steps of contact with the metal surface and drying may also be combined. After drying, a formable, water-insoluble solid film with a weight per unit area of around 5 to 50 mg Si/m2 and preferably around 10 to 30 mg Si/m2 is left on the metal surface. The drying and/or heat treatment of the liquid film applied to the metal surface, or rather of the chemicals applied with it, may be carried out at temperatures of around 80°C to 140°C, temperatures in the range from 110°C to 120°C being preferred.
Both acidic and alkaline cleaners are suitable for the cleaning pretreatment of the metal surfaces to be wetted in accordance with the invention. The layers obtained with the treatment solution according to the invention provide a uniform finish of the substrate. In combination with suitable organic coatings subsequently applied, they satisfy the requirements of the food packaging industry.
The following example relates to a no-rinse process with a conversion coating by treatment with a solution of silanes in ethanol.
- 1. cleaning and degreasing with surfactant-containing alkaline or acidic cleaners -- for example GARDOCLEAN S 5664, 20 g/I -- applied by spraying at a treatment temperature of 50°C to 65°C for treatment times of 2 to 5 s,
- 2. rinsing with process water,
- 3. pickling with an aqueous solution of 20 g/I phosphoric acid (H3PO4) or 10.6 g/I sulfuric acid (H2SO4) with 2 g/l hydrofluoric acid (HF) applied by spraying at a treatment temperature of 50°C to 60°C for treatment times of 2 to 5 s,
- 4. rinsing with deionized water,
- 5. drying,
- 6. application of the pretreatment -- for example 100g/l OXSILAN® MM-0705using a coater at a treatment temperature of 18°C to 25°C, 20 mg Si/m2
- 7. drying (with OXSILAN® at 110°C to 120°C)
Chemical composition, broad and preferred of treatment solutions for the process steps of degreasing, pickling and conversion related to rinse and no rinse processes are included in the following tables.
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