Heat-sealable aluminum alloy strip for beverage can lids

Abstract

The invention relates in particular to an aluminium alloy strip for producing beverage can ends, which aluminium alloy strip has an aluminium alloy type AA5xxx. The object of defining an aluminium alloy strip made of an aluminium alloy type AA5xxx for producing beverage can ends, which allows a secure and cost-effective fixing of a plastic element to the manufactured beverage can end, is achieved by an aluminium alloy strip having on one or both sides a heat-sealable coating containing a polyolefin.

Description

[Technical Field]

[0001] The present invention relates to an aluminum alloy strip for producing beverage can ends, the aluminum alloy strip having an aluminum alloy type AA5xxx. Additionally, the present invention relates to a method for producing the aluminum alloy strip, the method comprising casting a rolled ingot or cast strip from an aluminum alloy type AA5xxx, homogenizing the rolled ingot or cast strip, hot rolling the rolled ingot or cast strip to a hot rolled strip, and cold rolling the hot rolled strip to a final thickness, with or without at least one intermediate annealing. Finally, the present invention relates to uses of the aluminum alloy strip, a resealable beverage can end, and a beverage can with a resealable beverage can end. [Background technology]

[0002] Beverage cans are an important type of packaging for beverages. Typically, a beverage can consists of a beverage can body and a beverage can lid, which are hermetically connected to each other, for example, by a flange method. The beverage can body is primarily used to hold the beverage and may also be formed in multiple parts. On the one hand, the beverage can lid serves the purpose of reliably closing the cavity formed by the beverage can body, thereby preventing, for example, leakage of the beverage when the unopened beverage can is stored or transported. On the other hand, however, the beverage can lid is typically also designed in such a way that an opening can be made on the beverage can lid for intended removal of the beverage by the consumer.

[0003] In addition to tinplate, aluminum alloys are commonly used as materials for the manufacture of beverage cans. Beverage can bodies and beverage can lids are typically made of different aluminum alloys due to the different requirements for each material. For beverage can bodies, aluminum alloys of type AA3xxx have primarily been used due to their good forming properties, while for beverage can lids, aluminum alloys of type AA5xxx are typically used, which have improved mechanical properties due to their higher magnesium content. This allows for higher internal pressure stability of the beverage can lid, thereby preventing undesired expansion of the beverage can lid due to, for example, carbonated drinks.

[0004] Most beverage can lids in use today have a mechanism for irreversibly creating an opening for accessing the beverage. For example, the opening is created by pressing in a portion of the beverage can lid defined by a pre-punched, predetermined break line. Such mechanisms do not provide for resealing the created opening, which has several disadvantages. First, this exposes the beverage in a relatively unprotected manner to environmental influences, such as dirt, dust, and insects. Second, the beverage is not protected against spillage, for example, when the beverage can is violently moved or turned upside down. Third, carbon dioxide can easily escape from the beverage.

[0005] Mechanisms capable of creating a resealable opening for beverage can lids are known, for example from US Pat. No. 5,629,499. An additional rotatable cover made of sheet metal is provided to close the created opening and reopen it when necessary. However, sheet metal has the disadvantage that it can have sharp edges, which present a considerable risk of injury to the consumer when activating the resealable mechanism.

[0006] Therefore, it has been considered to realize a resealable opening for a beverage can lid by attaching an element made of plastic to the beverage can lid. According to this approach, the plastic element is intended to ensure that the opening created for removing the beverage can be closed and reopened when necessary without significant risk of injury to the consumer from sharp metal edges. However, a problem in realizing this approach is the reliable and cost-effective fixation of the plastic element to the beverage can lid. This unresolved problem currently prevents further development and market release of resealable openings for beverage can lids based on plastic elements. For example, if the connection between the plastic element and the beverage can lid is not sufficiently strong, the plastic element may become detached, causing the mechanism for resealing the beverage can lid to no longer function. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] German Utility Model No. 29 812 116(U1) Summary of the Invention [Means for solving the problem]

[0008] Against this background, the object of the present invention is to define an aluminium alloy strip made of an aluminium alloy of type AA5xxx for producing beverage can lids, which allows a secure and cost-effective fixation of a plastic element to the manufactured beverage can lid. The invention also has the object of providing a method for producing such an aluminium alloy strip, and of defining advantageous uses of the aluminium alloy strip. Finally, the invention has the object of defining a resealable beverage can lid and a corresponding beverage can, to which a plastic element can be securely and cost-effectively fixed.

[0009] According to a first teaching of the present invention, the above-mentioned object for an aluminum alloy strip for producing beverage can ends, which involves an aluminum alloy strip having an aluminum alloy of type AA5xxx, is achieved by an aluminum alloy strip having a heat-sealable coating containing a polyolefin on one or both sides.

[0010] As part of the present invention, it has been found that a heat-sealable coating containing a polyolefin allows for secure, cost-effective fastening of a plastic element to an aluminum alloy strip having an aluminum alloy type AA5xxx. Because the coating of the aluminum alloy strip according to the present invention is heat-sealable, a plastic element can be fastened to a beverage can lid made from the aluminum alloy strip according to the present invention by a simple, proven heat-sealing method. Generally, plastic parts are connected together during heat sealing by heating the joining surfaces of the parts to be connected and pressing them together so that they fuse together. The heat-sealable coating of the aluminum alloy strip according to the present invention can also provide a corresponding joining surface so that a plastic element can be connected to the aluminum alloy strip according to the present invention by the heat-sealable coating. As can be further shown within the scope of the present invention, the connection established by heat sealing between the heat-sealable coating of the aluminum alloy strip and the plastic element of a resealable beverage can lid fastened thereto can durably provide the adhesive force required for a secure connection. The heat-sealable coating acts as an adhesion promoter between the aluminum alloy of the beverage can lid and the plastic element. Because the heat-sealing method also allows for efficient mass production, cost-effective fastening of the plastic element is also achieved.

[0011] Because the heat-sealable coating for aluminum alloy strip according to the present invention contains polyolefins, the coating also has a high degree of health compatibility, which means that the coating complies with applicable food safety regulations. In particular, the heat-sealable coating for aluminum alloy strip according to the present invention does not contain formaldehyde, bisphenol A (BPA), melamine, polytetrafluoroethylene (PTFE), or styrene. Because these substances have harmful effects on health, their use in the food sector is restricted to strict limits or completely banned in many countries. However, the heat-sealable coating for aluminum alloy strip according to the present invention is based on polyolefins that are not problematic in this regard and does not contain any of the aforementioned substances, so the coating has a high degree of health compatibility and complies with food safety regulations.

[0012] It has further been found that the heat-sealable coating of aluminium alloy strip according to the invention is easily adaptable to the manufacturing process of beverage can ends, and in particular the forming processes required therefor.

[0013] The aluminum alloy strip according to the invention has a heat-sealable coating containing a polyolefin on one or both sides. In the case of a coating on one side, the heat-sealable coating is preferably applied to the side of the aluminum alloy strip corresponding to the outside of the beverage can lid, which is not intended to come into contact with the beverage contained therein before the beverage can is opened. In this way, a plastic element for a resealable beverage can lid can be fixed to the outside. In the case of a coating on both sides, the heat-sealable coating is preferably also applied to the side of the aluminum alloy strip corresponding to the inside of the beverage can lid, which is intended to come into contact with the beverage contained therein before the beverage can is opened. In this context, the heat-sealable coating of the aluminum alloy strip according to the invention has been shown to also act as a highly functional barrier between the aluminum alloy of the beverage can lid and the beverage. In particular, on the one hand, the heat-sealable coating protects the beverage against migration of aluminum from the can lid material. On the other hand, the aluminum alloy of the beverage can lid is also protected against attack by the beverage, for example when the beverage is carbonated. Additionally, the heat-sealable coating of the aluminum alloy strip according to the present invention also acts as a highly functional barrier on the outside of the beverage can lid, for example when the beverage comes into contact with the outside of the beverage can lid during or as a result of drinking.

[0014] In a preferred embodiment of the aluminum alloy strip according to the invention, the polyolefin is polyethylene or polypropylene or a mixture of both. Polyethylene (PE) and polypropylene (PP) are the two most widely used polyolefins and are particularly cost-effective. Preferably, the heat-sealable coating of the aluminum alloy strip according to the invention contains the same polyolefin from which the plastic element to be fastened is also made, because in this case, fusion during heat sealing occurs particularly reliably, thus creating a particularly secure connection.

[0015] In a preferred embodiment of the aluminum alloy strip according to the invention, the polyolefin is at least partially crosslinked. Crosslinking of polyolefins, and polymers in general, involves chemical reactions that link the polymer's chain-shaped macromolecules into a three-dimensional network. As a result of crosslinking, in particular the hardness and toughness of the polymer increase and its solubility decreases. This is advantageous for the production of beverage can ends, since it improves both the mechanical and chemical resistance of the heat-sealable coating.

[0016] In a preferred embodiment of the aluminum alloy strip according to the invention, the polyolefin is at least partially crosslinked with a hydroxyalkylamide. Preferably, the hydroxyalkylamide is N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide. Hydroxyalkylamides, especially the aforementioned N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide, have chemical properties that allow for effective crosslinking and are therefore highly suitable for crosslinking polyolefins. N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide as a crosslinking agent is suitable for use in the food sector, and the resulting crosslinked polyolefin also has the advantage of being highly resistant to weathering influences, such as ultraviolet radiation.

[0017] In a preferred embodiment of the aluminum alloy strip according to the present invention, the heat-sealable coating contains a wax. Preferably, this is a PTFE-free wax, such as carnauba wax, polyethylene wax, polypropylene wax, polyamide wax, or a mixture of the aforementioned waxes. Because the heat-sealable coating of the aluminum alloy strip according to the present invention contains a wax, the surface smoothness and surface hardness of the heat-sealable coating can be increased. This has an advantageous effect on the handling of the aluminum alloy strip and the beverage can ends produced therefrom during the production process, for example, when transported through a production line, and also improves the punchability (German: Stanzfaehigkeit, English: Stanzfaehigkeit) of the aluminum alloy strip. In addition, PTFE-free waxes are generally acceptable in terms of health compatibility and food safety regulations.

[0018] In a preferred embodiment of the aluminum alloy strip according to the invention, the heat-sealable coating is 1.0 g / m 2 ~20.0g / m 2 Preferably, the heat-sealable coating has a basis weight of 2.0 g / m 2 ~14.0g / m 2 Particularly preferably, the heat-sealable coating has a basis weight of 3.0 g / m 2 ~5.0g / m 2 or 6.0 g / m 2 ~12.5g / m 2 Most preferably, the heat-sealable coating has a basis weight of 3.5 g / m 2 ~4.5g / m 2 or 6.5 g / m 2 ~12.0g / m 2 The area weights specified are the dry weights. At a given mass density, the basis weight of the heat-sealable coating correlates with the thickness of the heat-sealable coating. The heat-sealable coating has a basis weight of 1.0 g / m2 ~20.0g / m 2 With a basis weight in the range of 2.0 g / m, a good compromise between adequate seal seam strength and using less material can be achieved. 2 ~14.0g / m 2 A particularly good compromise is achieved in the preferred range of 0.5 g / m. 2 ~5.0g / m 2 or most preferably 3.5 g / m 2 ~4.5g / m 2 Higher areal weights, especially 6.0 g / m², result in less material usage and therefore lower costs. 2 ~12.5g / m 2 or most preferably 6.5 g / m 2 ~12.0g / m 2 This results in a higher seal seam strength and thus a more secure fixation of the plastic element.

[0019] In a preferred embodiment of the aluminum alloy strip according to the present invention, the heat-sealable coating after heat sealing to a polypropylene film with a sealing force of 90 N, a sealing time of 1 second, and a sealing temperature of 180°C has a seal seam strength of at least 35 N at a sealing seam width of 15 mm. Preferably, the heat-sealable coating after heat sealing to a polypropylene film with the mentioned parameters of sealing force, sealing time, sealing temperature, and sealing seam width has a seal seam strength of at least 39 N. Particularly preferably, the heat-sealable coating after heat sealing to a polypropylene film with the described parameters has a seal seam strength of at least 42 N. For example, the seal seam strength can be determined according to DIN 55529. The term "seal seam strength" should be understood to be synonymous with the term "separation force" used in DIN 55529, where the separation force is always defined as an arithmetic mean value. To prevent the polypropylene film from tearing due to the relatively high sealing force required when determining the seal seam strength, it is necessary to ensure that a sufficiently thick polypropylene film is used during the heat sealing process. In this situation, for example, the thickness of the polypropylene film should be 200 pm or more. Since the heat-sealable coating of the aluminum alloy strip according to the present invention has a seal seam strength of at least 35 N under the aforementioned conditions, it is possible to achieve sufficient adhesive strength required for a secure connection between the heat-sealable coating and the plastic element to be secured. As a result, a properly secure fastening is achieved. With a higher seal seam strength, preferably at least 39 N or particularly preferably at least 42 N, a correspondingly higher adhesive strength can be provided, resulting in an even more secure fastening.

[0020] In a preferred embodiment of the aluminium alloy strip according to the invention, the heat-sealable coating has a coating weight of 8 g / m 2 ~12g / m 2The heat-sealable coating has a porosity such that the measured current intensity in the "Enamelator" porosity measurement is 5 mA or less for a basis weight of the heat-sealable coating in the range of 1000 sq. m / s, where the "Enamelator" porosity measurement is performed with a DC voltage of 6.3 V and the current intensity is determined after a measurement time of 4 seconds. Preferably, the heat-sealable coating has a porosity such that the measured current intensity is 2 mA or less under these conditions. Particularly preferably, the heat-sealable coating has a porosity such that the measured current intensity is 1 mA or less. Preferably, the "Enamelator" porosity measurement is performed on beverage can lid shells made from aluminum alloy strip. The "Enamelator" porosity measurement is a common measurement method in the packaging industry for testing non-conductive coatings on metal materials, and it is performed on test specimens of the coated metal material. In the case of beverage can lids, so-called beverage can lid shells are used as test specimens. Here, the beverage can shell represents a preliminary beverage can lid that has already been punched and formed, but does not yet have the final shape of the beverage can lid or the pull tab for opening the beverage can lid. To perform the "Enamelator" porosity measurement, a test configuration is selected that places the coated side of the test specimen in contact with an electrolyte solution. The electrolyte solution is electrically contacted via a first electrode. A second electrode is connected to the metal layer of the test specimen. A DC voltage, typically 6.3 V, is then applied between the electrodes. Because the test specimen coating is an electrical insulator, the current between the electrodes via the electrolyte can only be generated by unlacquered spots or pores in the test specimen coating. Therefore, the measured current intensity is a measure of the area of ​​unlacquered spots or pores in the test specimen coating. The higher the measured current intensity, the greater the porosity. Because the measured current intensity does not usually reach a steady value immediately, the current intensity is determined after a measurement period, typically 4 seconds, during which a steady value is usually displayed. The measured current intensity also depends on the coating thickness and therefore on the basis weight, since unlacquered areas or pores are more likely to occur at smaller thicknesses than at larger thicknesses. 2~12g / m 2 For coating basis weights in this range, a current intensity of 5 mA or less, measured in an "enamelator" porosity measurement, can be considered to correspond to a sufficiently low porosity of the coating. Thus, in particular, a measured current intensity of 5 mA or less for the heat-sealable coating of an aluminum alloy strip according to the invention can achieve a sufficiently low porosity so that the heat-sealable coating can adequately perform its function as a highly functional barrier and adhesion promoter. At a measured current intensity of preferably 2 mA or less, particularly preferably 1 mA or less, a coating with a correspondingly lower porosity and thus improved properties as a highly functional barrier or adhesion promoter can be provided.

[0021] In a preferred embodiment of the aluminium alloy strip according to the invention, the aluminium alloy strip has an aluminium alloy of type AA5052 or AA5182. The aforementioned aluminium alloys have a high magnesium content and associated mechanical properties which make them particularly well suited for the manufacture of beverage can ends. In addition, they are easily adaptable to provide heat-sealable coatings.

[0022] In a preferred embodiment of the aluminum alloy strip according to the present invention, the aluminum alloy strip has a metal thickness of 0.1 mm to 0.3 mm, preferably 0.15 mm to 0.25 mm. The metal thickness does not include the thickness of a heat-sealable coating or other coatings. Because the aluminum alloy strip has a metal thickness of 0.1 mm to 0.3 mm, a good compromise can be achieved between sufficient mechanical strength on the one hand and reduced material usage and weight on the other hand. On the one hand, a smaller metal thickness results in less material usage, thus reducing costs. On the other hand, a smaller metal thickness also results in a lower weight of the beverage can end, which is particularly advantageous for the transportation of beverage cans. On the other hand, a larger metal thickness results in better mechanical strength, thus resulting in higher internal pressure stability, particularly for the beverage can end. In the preferred range of metal thickness of 0.15 mm to 0.25 mm, a particularly good compromise can be achieved between sufficient mechanical strength on the one hand and reduced material usage and weight on the other hand.

[0023] In a preferred embodiment of the aluminum alloy strip according to the present invention, the aluminum alloy strip additionally has a chromium-free conversion layer on one or both sides. Preferably, the chromium-free conversion layer on one or both sides is arranged directly on the metal layer of the aluminum alloy strip and is covered by a heat-sealable coating. Because the aluminum alloy strip according to the present invention has a conversion layer, improved corrosion protection can be achieved on the one hand, and improved adhesion of the heat-sealable coating can be achieved on the other hand. The chromium-free conversion layer is more suitable for contact with food than a chromium-containing conversion layer. Preferably, the chromium-free conversion layer contains zirconium phosphate. This makes it possible to achieve particularly good adhesion properties compared to heat-sealable coatings containing polyolefins. However, in principle, it is also possible to realize the aluminum alloy strip according to the present invention with a conversion layer containing other metal phosphates, such as titanium phosphate or chromium phosphate.

[0024] In a preferred embodiment of the aluminum alloy strip according to the present invention, the aluminum alloy strip has at least one further layer on one or both sides. For example, the aluminum alloy strip according to the present invention may have on one or both sides a further polymer layer, preferably a film made of a polyolefin, preferably a polyethylene film or a polypropylene film, or a film made of a mixture of both polymers. Such a polymer layer, both on the side of the aluminum alloy strip corresponding to the inside of the beverage can end and on the side corresponding to the outside, can be used to improve the mechanical properties of the aluminum alloy strip. This can particularly improve the internal pressure stability of beverage can ends made from the aluminum alloy strip according to the present invention. The inner polymer layer can, on the one hand, achieve better protection of the beverage against aluminum migration from the can end material, and, on the other hand, achieve better protection of the aluminum alloy of the beverage can end against attack by the beverage. The outer polymer layer can also be used for protection against external influences, such as mechanical stress.

[0025] According to a second teaching of the present invention, the above object is achieved with a method for producing an aluminum alloy strip, the method comprising: - Casting rolled ingots or cast strip from aluminum alloys of type AA5xxx, - homogenizing rolled ingots or cast strip; - hot rolling of rolled ingots or cast strip into hot rolled strip; - Cold rolling of hot-rolled strip to final thickness with or without at least one intermediate annealing The method includes: - further comprising producing a heat-sealable coating on one or both sides of the aluminum alloy strip that has been cold rolled to final thickness, the heat-sealable coating comprising a polyolefin.

[0026] Aluminum alloy strip made of type AA5xxx aluminum alloy can be reliably and efficiently produced by the method steps of casting a rolled ingot or cast strip from an aluminum alloy of type AA5xxx, homogenizing the rolled ingot or cast strip, hot rolling the rolled ingot or cast strip into hot-rolled strip, and cold rolling the hot-rolled strip to final thickness, with or without at least one intermediate annealing. When this method is carried out with at least one intermediate annealing, the strength in the rolled-hard state at final thickness can be reduced because solidification that occurs during cold rolling can be eliminated. However, in principle, this method can also be carried out without intermediate annealing. Optionally, the aluminum alloy strip may also be subjected to a final heat treatment after cold rolling, which may also eliminate solidification.

[0027] The method according to the invention comprises, as an additional method step, the production of a heat-sealable coating on one or both sides of the aluminum alloy strip that has been cold-rolled to its final thickness, which heat-sealable coating contains a polyolefin, so that the aluminum alloy strip can be provided with a corresponding heat-sealable coating having the advantages already described in connection with the first teaching. Thus, in particular, an aluminum alloy strip according to the first teaching of the invention is produced by a method according to the second teaching of the invention.

[0028] In a preferred embodiment of the method according to the invention, the heat-sealable coating is produced by applying and baking a lacquer, which makes it possible to provide a heat-sealable coating in a cost-effective and reliable manner, but in principle it can also be produced by other suitable methods, such as extrusion coating or lamination on an aluminium alloy strip that has been cold-rolled to the final thickness.

[0029] In a preferred embodiment of the method according to the present invention, the lacquer is water-based lacquer.Compared with traditional solvent-based lacquer, water-based lacquer has the advantage of being more environmentally friendly.In addition, water-based lacquer does not contain any aminoplasts, such as melamine or benzoguanamine, as reaction partners, so there are fewer problems with health compatibility and food safety regulations.

[0030] In a preferred embodiment of the process according to the invention, the lacquer contains a polyolefin dispersion. The fine distribution of the polyolefin in the dispersion makes it possible to produce a homogeneous heat-sealable coating upon application and baking of the lacquer.

[0031] In a preferred embodiment of the method according to the present invention, the polyolefin dispersion is a polyethylene dispersion or a polypropylene dispersion, or a mixture of both. Thus, the polyolefin contained in the resulting heat-sealable coating is polyethylene or polypropylene, or a corresponding mixture. Polyethylene (PE) and polypropylene (PP) are the two most widely used polyolefins and are therefore particularly cost-effective. Preferably, the polyolefin dispersion is the same polyolefin dispersion that also produces the plastic element of the resealable beverage can lid to be fixed. In this case, fusion occurs particularly reliably during heat sealing, resulting in a particularly secure connection.

[0032] In a preferred embodiment of the method according to the invention, the lacquer contains a crosslinking agent, as a result of which, as already explained in connection with the first teaching, the polyolefin is at least partially crosslinked, thereby achieving an improvement in both the mechanical and chemical resistance of the heat-sealable coating.

[0033] In a preferred embodiment of the method according to the present invention, the lacquer contains a hydroxyalkylamide as a crosslinking agent. Preferably, the hydroxyalkylamide is N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide. As already mentioned in connection with the first teaching, by using a hydroxyalkylamide as a crosslinking agent, in particular N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide, effective crosslinking of polyolefins, suitability for use in the food sector, and high weather resistance can be achieved.

[0034] In a preferred embodiment of the method according to the present invention, the lacquer contains a wax. Preferably, this is a PTFE-free wax, such as carnauba wax, polyethylene wax, polypropylene wax, polyamide wax, or a mixture of the aforementioned waxes. Because the lacquer contains a wax, the surface smoothness and surface hardness of the heat-sealable coating can be increased, thereby improving the punchability, especially of aluminum alloy strips. In addition, PTFE-free waxes are generally acceptable in terms of health compatibility and food safety regulations.

[0035] In a preferred embodiment of the method according to the present invention, the water-based lacquer contains 1 to 15% by weight, preferably 2 to 6% by weight, of an aqueous solution of a hydroxyalkylamide; 1 to 20% by weight, preferably 5 to 11% by weight, of a PTFE-free wax; and the remainder, an aqueous polyolefin dispersion. The aqueous polyolefin dispersion may have a solids content of up to 60% by weight, preferably 40 to 50% by weight. Furthermore, the aqueous polyolefin dispersion may preferably be an aqueous polyethylene dispersion or an aqueous polypropylene dispersion. The aqueous solution of the hydroxyalkylamide may be a solution of preferably 10 to 90% by weight, preferably 20 to 40% by weight, of N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide in deionized water, or a slightly alkaline solution containing 0.1 to 0.5% by weight of N,N-dimethylethanolamine (DMEA). The PTFE-free wax may be, for example, carnauba wax, polyethylene wax, polypropylene wax, polyamide wax, or a mixture of the aforementioned waxes. By means of the defined composition of the water-based lacquer, it can be achieved on the one hand that the heat-sealable coating is produced cost-effectively and on the other hand that the advantageous properties of the heat-sealable coating are reliably established.

[0036] In a preferred embodiment of the method according to the invention, the lacquer is applied by a coil coating method on one or both sides. In this method, the aluminum alloy strip to be coated is unwound from one coil, coated, and rewound onto another coil. This allows for easy handling of the aluminum alloy strip for coating purposes. However, in principle, the method according to the invention can also be implemented with other methods for handling the aluminum alloy strip.

[0037] In a preferred embodiment of the method according to the present invention, the lacquer is applied using a roll coating method on one or both sides. In the roll coating process, the coating is applied to the aluminum alloy strip by rolling a roller on one or both sides. This allows the coating thickness or basis weight to be set very accurately even at high coating speeds, so that a reliable coating can be achieved. However, in principle, the method according to the present invention can also be implemented by other coating methods. For example, the coating can also be applied by spraying, preferably electrostatic spraying.

[0038] In a preferred embodiment of the method according to the invention, the lacquer is baked in such a way that a maximum metal temperature in the range of 200°C to 300°C, preferably in the range of 220°C to 260°C, is reached. The specified range of maximum metal temperatures allows reliable through-hardening of the heat-sealable coating without significant softening of the aluminum alloy strip. The baking time, i.e., the duration of the heating process until the maximum metal temperature is reached, can be, for example, in the range of 5 to 35 seconds, preferably in the range of 8 to 25 seconds.

[0039] According to a further preferred embodiment of the method, after application and baking of the heat-sealable coating, a further polymer layer is applied in the form of a heat-sealable film made of polyolefin, preferably a polyethylene or polypropylene film. The surface coating of the strip, especially in strip form, with a polyolefin film, preferably a polyethylene or polypropylene film, or a film made of a mixture of the two polymers, can be carried out in a particularly economical manner by applying a corresponding polyolefin film, for example by lamination or hot lamination.

[0040] In a preferred embodiment of the method according to the invention, the rolled ingot or cast strip is cast from an aluminium alloy of type AA5052 or AA5182, which, as already explained in connection with the first teaching, have particularly advantageous mechanical properties.

[0041] In a preferred embodiment of the method according to the invention, the hot-rolled strip is cold-rolled to a final thickness of a maximum metal thickness of 0.1 mm to 0.3 mm, preferably 0.15 mm to 0.25 mm. The metal thickness does not include the thickness of any heat-sealable or other coatings. As already explained in connection with the first teaching, with a metal thickness in the mentioned range a good compromise can be achieved between sufficient mechanical strength and low material usage and weight.

[0042] In a preferred embodiment of the method according to the present invention, the aluminum alloy strip is subjected to a chromium-free phosphating treatment on one or both sides. Preferably, the chromium-free phosphating treatment is carried out using zirconium phosphate. The chromium-free phosphating treatment, preferably using zirconium phosphate, can produce a chromium-free conversion layer, preferably containing zirconium phosphate, on one or both sides of the aluminum alloy strip, the advantages of which have already been described in connection with the first teaching. However, in principle, other metal phosphates, such as titanium phosphate or chromium phosphate, can also be used for the phosphating treatment instead of zirconium phosphate. Preferably, the phosphating treatment is carried out so that the conversion layer produced on one or both sides is placed directly on the metal layer of the aluminum alloy strip and is then covered by a subsequently applied heat-sealable coating. Particularly preferably, the phosphating treatment can be carried out in conjunction with a coil coating method for applying a lacquer, i.e., "in-line." This results in better process efficiency by eliminating the need to wind and unwind the aluminum alloy strip. The phosphating treatment is preferably carried out in a rinse-free process, in which the phosphating agent is applied to the aluminum alloy strip and dried, so that no rinsing step is required. Compared to the phosphating process with a rinse step, the rinse-free process is more economical and environmentally friendly.

[0043] According to a third teaching of the present invention, the above-mentioned object of the use of an aluminum alloy strip is achieved in the manufacture of a resealable beverage can lid using an aluminum alloy strip according to the first teaching. In this context, the aluminum alloy strip according to the first teaching, in particular due to the heat-sealable coating containing a polyolefin, allows a reliable and cost-effective fixation of a plastic element of the resealable beverage can lid to the aluminum alloy strip by a simple and proven heat-sealing method. For further configurations and advantages of the use according to the present invention, reference is also made to the description relating to the first teaching.

[0044] According to the fourth and fifth teachings of the present invention, the above-mentioned objects for a resealable beverage can lid and a beverage can with a resealable beverage can lid are achieved in that the beverage can lid is manufactured from an aluminum alloy strip according to the first teaching. Here again, the aluminum alloy strip according to the first teaching allows for a secure and cost-effective fixation of the plastic element of the resealable beverage can lid. For further configurations and advantages of the resealable beverage can lid and the beverage can according to the present invention, reference is also made to the embodiments relating to the first teaching.

[0045] In the following, the invention will be explained in more detail by describing exemplary embodiments in connection with the drawings. [Brief explanation of the drawings]

[0046] [Figure 1A] 1 is a schematic cross-sectional view showing an exemplary embodiment of an aluminum alloy strip according to the present invention according to the first teaching; FIG. [Figure 1B] 1 is a schematic cross-sectional view showing an exemplary embodiment of an aluminum alloy strip according to the present invention according to the first teaching; FIG. [Figure 2A] 3 is a schematic diagram illustrating an exemplary embodiment of the method according to the present invention according to the second teaching; [Figure 2B] 3 is a schematic diagram illustrating an exemplary embodiment of the method according to the present invention according to the second teaching; [Figure 3] 1 is a schematic diagram showing an example of a beverage can according to the fifth teaching with a beverage can lid according to the fourth teaching; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0047] 1A and 1B each show, in a schematic cross-section, exemplary embodiments of an aluminum alloy strip 10, 11 according to the invention. To this end, firstly, FIG. 1A shows an aluminum alloy strip 10 having a metal layer 12 and a heat-sealable coating 13 applied to one side. The aluminum alloy strip 10 is particularly suitable for producing resealable beverage can ends, since a plastic element for realizing the resealable beverage can end can be reliably and cost-effectively fixed to the heat-sealable coating 13 by a heat-sealing method. In addition, the polyolefin-containing heat-sealable coating 13 is also highly compatible with health and does not pose any problems with regard to currently applicable food safety regulations.

[0048] The metal layer 12 of the aluminum alloy strip 10 is made of an aluminum alloy of type AA5xxx, here AA5182 for example. This aluminum alloy has a high magnesium content and is therefore strong, making it highly suitable for the manufacture of beverage can ends. Furthermore, the metal layer 12 has a thickness of, for example, 0.2 mm. This thickness, in particular, ensures sufficient internal pressure stability of the beverage can end. At the same time, the weight of the beverage can end and the material used for its manufacture are reasonably limited.

[0049] The heat-sealable coating 13 of the aluminum alloy strip 10 contains, for example, polypropylene as a polyolefin and a PTFE-free wax. The polypropylene is crosslinked using a hydroxyalkylamide, here N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide as an example. As a result of the crosslinking, the mechanical and chemical resistance of the heat-sealable coating 13 is improved. In this context, the hydroxyalkylamide is highly suitable as a crosslinking agent for polyolefins due to its chemical properties. In addition, the N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide used as an example here is suitable for use in the food industry. Similarly, the PTFE-free wax contained in the heat-sealable coating 13 increases the surface smoothness and surface hardness of the heat-sealable coating 13, thereby improving the punchability of the aluminum alloy strip 10 in particular.

[0050] The basis weight of the heat-sealable coating 13 is 1.0 g / m 2 ~20.0g / m 2 in the range of 2.0 g / m 2 ~14.0g / m 2 , whereby a good compromise can be achieved between a sufficiently secure fixation of the plastic element and a small amount of material usage. Furthermore, the seal seam strength of the heat-sealable coating 13 after heat sealing to a polypropylene film with a sealing force of 90 N, a sealing time of 1 second and a sealing temperature of 180°C is at least 35 N at a sealing seam width of 15 mm. This allows the plastic element to be sufficiently securely fixed. Finally, the heat-sealable coating has a sealing force of 8 g / m 2 ~12g / m 2The porosity of the heat-sealable coating 13 is such that the current intensity measured in the "Enamelator" porosity measurement is 5 mA or less for heat-sealable coating basis weights in the range of 100 sq. m / s, where the "Enamelator" porosity measurement is performed with a DC voltage of 6.3 V and the current intensity is determined after a measurement time of 4 seconds. This ensures that the porosity of the heat-sealable coating 13 is sufficiently low so that the heat-sealable coating 13 adequately fulfills its properties as an adhesion promoter and functional barrier.

[0051] 1B also shows in a schematic cross-section a further exemplary embodiment of an aluminum alloy strip 11 according to the invention, which also has a metal layer 12 and a heat-sealable coating 13 on both sides. With regard to the metal layer 12 and the heat-sealable coating 13 of the aluminum alloy strip 11, the above explanations regarding the aluminum alloy strip 10 shown in FIG. 1A apply analogously.

[0052] However, unlike the aluminum alloy strip 10 of Figure 1A, the aluminum alloy strip 11 shown in Figure 1B is provided with a heat-sealable coating 13 on both sides. In the case of a beverage can end made from the aluminum alloy strip 11, the upper heat-sealable coating 13 primarily serves the purpose of securing the plastic element to achieve a resealable beverage can end. On the other hand, the lower heat-sealable coating 13 primarily serves the role of a highly functional barrier. In this function, the heat-sealable coating 13 protects the beverage against aluminum migration from the end material on the one hand, and the aluminum alloy of the beverage can end against attack by the beverage on the other hand.

[0053] Additionally, the aluminum alloy strip 11 shown in FIG. 1B has a conversion layer 14 on both sides in addition to the metal layer 12 and the heat-sealable coating 13 on both sides. The exemplary conversion layer 14 shown is chromium-free and preferably contains zirconium phosphate, and is disposed directly on the metal layer 12 so that each is covered by the heat-sealable coating 13. In addition to protecting against corrosion, the conversion layer 14 provides improved adhesion, particularly of the heat-sealable coating 13. Because the conversion layer 14 does not contain any harmful chromium, it is highly suitable for contact with food. The preferred inclusion of zirconium phosphate also ensures particularly good adhesion of the heat-sealable coating 13, which contains a polyolefin.

[0054] In principle, further layers may also be present on the aluminium alloy strips 10, 11 shown in Figures 1A and 1B. For example, the side of the aluminium alloy strip 11 in Figure 1B corresponding to the inside of the beverage can lid may have a polymer layer as a barrier layer and / or to improve the internal pressure stability of the beverage can lid. Additionally or alternatively, the aluminium alloy strip 11 may have a polymer layer on one side corresponding to the outside of the beverage can lid as protection against external influences and / or to also improve the internal pressure stability of the beverage can lid.

[0055] 2A and 2B now show in schematic diagrams an exemplary embodiment of a method according to the invention for producing an aluminum alloy strip, in particular for producing an aluminum alloy strip according to the invention. Figure 2A shows method steps 20a, which include casting a rolling ingot through to cold rolling the hot rolled strip to final thickness. Figure 2B shows method step 20b for coating the aluminum alloy strip after cold rolling.

[0056] Initially, in step 22, a rolled ingot 21a is produced from a type 5xxx aluminum alloy. As shown schematically here, the rolled ingot 21a is produced, for example, by a discontinuous direct chill (DC) casting process. However, other casting processes may alternatively be used, such as continuous strip casting (not shown). After casting, in step 23, the rolled ingot 21a is homogenized using a homogenization furnace 28a. In step 24, the rolled ingot 21a is then hot rolled into a hot rolled strip 21b. Hot rolling 24 may be performed in a reversing stand (shown) and / or a tandem stand with multiple passes (not shown). In step 25a, the hot rolled strip 21b is then cold rolled to a final thickness to form a cold rolled strip 21c. During cold rolling 25a, at least one optional intermediate annealing 25b can be performed, here using a chamber furnace 28b as an example, or alternatively using a continuous flow furnace (not shown). This at least one optional intermediate annealing 25b achieves softening of the cold-rolled strip 21c. As a result, following the at least one optional intermediate annealing 25b, further cold-rolling steps 25a can be performed until the cold-rolled strip 21c reaches a final thickness of 0.2 mm as an example. A final heat treatment is also possible, which also serves to soften the cold-rolled strip 21c so that it can be better further processed, if necessary. For this purpose, the cold-rolled strip having its final thickness, e.g., in coil form, is subjected to a heat treatment, e.g., in a chamber furnace.

[0057] Method step 20b, which follows cold rolling 25a, is shown in FIG. 2B. The starting point for method step 20b is a cold-rolled, optionally final heat-treated, cold-rolled strip 21c. As described below, this cold-rolled strip 21c is first provided with an optional conversion layer and then with a heat-sealable coating. In this example, the optional conversion layer and heat-sealable coating are formed on one side, but this should be understood as merely an example. Similarly, a conversion layer and / or a heat-sealable coating can be formed on both sides of the cold-rolled strip 21c. The application of a conversion layer should also be understood as an example, and a conversion layer can generally be omitted on one or both sides.

[0058] To produce the conversion layer, the cold-rolled strip 21c is unwound from the coil and sent to, for example, a phosphating step 26, which is configured as a one-side roll coating process. Alternatively, the phosphating solution can be sprayed, for example, by electrostatic spraying 26a. Furthermore, phosphating can also be performed by passing the cold-rolled strip 21c through a bath containing the phosphating solution (not shown). However, the advantage of the roll coating method is that the application of the phosphating solution can be precisely adjusted, even at high processing speeds. The phosphating step 26 is a preferred no-rinse method, in which the phosphating agent (zirconium phosphate in this case) remains on the cold-rolled strip 21c, so no rinsing step is required. For this purpose, the cold-rolled strip 21c that has been subjected to the phosphating solution is guided through a drying oven 28c, where the phosphating agent dries. As already mentioned above, the phosphating step 26 is not absolutely necessary to realize the method according to the invention. However, the phosphating step 26 on one or both sides makes it possible to produce a conversion layer on one or both sides of the cold-rolled strip 21d, which not only provides protection against corrosion but also particularly improves the adhesion of a subsequently applied heat-sealable coating. Preferably, a chromium-free phosphating step 26 is carried out, so that the conversion layer produced on one or both sides does not contain any chromium that is harmful to health and is more suitable for contact with food.

[0059] In process step 27, a polyolefin-containing heat-sealable coating is finally applied to the cold-rolled strip 21d, which has already been provided with a conversion layer (for example). Here, the heat-sealable coating is applied by applying a water-based lacquer to the cold-rolled strip 21d and then baking it. The lacquer contains, for example, a polypropylene dispersion as the polyolefin dispersion. Additionally, the lacquer contains, for example, N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide as a crosslinking agent and a PTFE-free wax. Similar to the phosphating step 26, the lacquer is also applied in a one-side roll coating process. Alternatively, the lacquer can be sprayed, particularly electrostatically sprayed (27a), or, as a further alternative, passed through a lacquer bath (not shown). To bake the lacquer, the cold-rolled strip 21d, coated on one side with the lacquer, is sent to a baking oven 28d. The baking process is carried out in such a way that a maximum metal temperature in the range of 200°C to 300°C is reached. The baking time is, for example, in the range of 5 to 35 seconds. As a result of baking, a cold-rolled strip 21e is obtained that is provided with a heat-sealable coating on one side and is then wound into a coil for easier storage or transportation.

[0060] The aluminum alloy strip according to the invention, produced, for example, by the method according to the invention described herein, can be used in particular to produce resealable beverage can lids. The aluminum alloy strip according to the invention is particularly suitable for this purpose, since a plastic element for realizing the resealable beverage can lid can be reliably and cost-effectively fixed by heat sealing in the heat-sealable coating of the aluminum alloy strip according to the invention. The production of at least one resealable beverage can lid can be carried out, for example, by punching at least one beverage can lid from the aluminum alloy strip according to the invention using suitable equipment, followed by forming if necessary. A plastic element for realizing the resealable mechanism can then be fixed to the at least one punched beverage can lid by heat sealing.

[0061] FIG. 3 shows, by way of example, a schematic view of a beverage can 30 according to the invention with a beverage lid 32 according to the invention, manufactured by the use according to the invention of the aluminum alloy strip according to the invention described herein. In addition to the beverage lid 32, the beverage can 30 also has a beverage body 31, which is hermetically connected to the beverage lid 32 by means of a flange (German: Boerdelung, English: beading). Instead of a flange, other suitable connection methods, such as adhesive bonding, are also conceivable. Although in this example the beverage body 31 is designed as a single part, the beverage body 31 can also basically be designed in multiple parts, in particular in two parts. Although only diagrammatically shown, an element 33 for realizing a resealable mechanism can be provided on the beverage lid 32. This element 33 can then be fixed by heat sealing to a heat-sealable coating on the outside of the beverage lid 32. Additionally, the beverage can lid 32 in this example also has a heat-sealable coating on its inside, which acts as a highly functional barrier to both protect the beverage from aluminum migration from the beverage can lid 32 and protect the aluminum alloy of the beverage can lid 32 from attack by the beverage.

[0062] Within the scope of the present invention, laboratory tests were also conducted to investigate the dependence of the seal seam strength of the heat-sealable coating on aluminum alloy strip according to the present invention on various influencing parameters, particularly the basis weight of the coating. For this purpose, two test specimens, each measuring 290 mm x 210 mm, were cut from aluminum alloy strip of type AA5182. The aluminum alloy strip was produced by carrying out the method steps described in connection with FIG. 2A, namely, casting a rolling ingot, homogenizing the rolling ingot, hot-rolling the rolling ingot into hot-rolled strip, and cold-rolling the hot-rolled strip to the final thickness with optional intermediate annealing. Additionally, the aluminum alloy strip was pretreated on both sides with chromium-free phosphating using zirconium phosphate to produce a corresponding conversion layer on the aluminum alloy strip. The metal thickness of the aluminum alloy strip was 0.224 mm.

[0063] Next, in the laboratory, a polyolefin-containing heat-sealable coating was produced on one side of the two test specimens described herein. To this end, a water-based lacquer was first applied to one side of the test specimen. The water-based lacquer contained 2-6 wt. % of an aqueous solution of a hydroxyalkylamide, 5-11 wt. % of a PTFE-free wax, and the remainder was an aqueous polyolefin dispersion. The aqueous polyolefin dispersion was, for example, an aqueous polypropylene dispersion with a solids content of 40-50 wt. %. The aqueous hydroxyalkylamide solution was a 30 wt. % solution of N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide in slightly alkaline water containing 0.3 wt. % DMEA. When the water-based lacquer was applied to the two test specimens, the target basis weight of the resulting heat-sealable coating was 4 g / m for the first test specimen. 2 and 12 g / m for the second test sample. 2 It was.

[0064] The applied lacquer was then baked in a laboratory oven, which was heated to a temperature of 295°C and the two lacquered test specimens were placed in the oven for 21 seconds each, resulting in the test specimens heating up and reaching a maximum metal temperature of 243°C at the end of each heating process.

[0065] After baking the lacquer, the basis weight of the heat-sealable coating was determined for each of the two test specimens. For this purpose, a circular sample was punched out of the coated test specimen, this sample having a radius of 39.9 mm and therefore a diameter of 50.0 cm. 2 The coated samples were weighed using a laboratory precision balance. The heat-sealable coating was then removed from the samples by baking. For this purpose, the samples were placed in a laboratory oven at a temperature of 550°C for 15 minutes each, thereby pyrolyzing the heat-sealable coating. After baking, the samples were kept in water to cool and then rubbed with a cloth soaked in solvent to remove any residual lacquer residue from the surface. Finally, the uncoated samples were weighed again, and the basis weight of the heat-sealable coating was determined by forming the difference between the weight of the coated sample and the weight of the uncoated sample and dividing it by the area of ​​the sample. This resulted in a weight of 4.1 g / m for the first test specimen. 2 Therefore, for the second test sample, a basis weight of 11.7 g / m 2 The value of was determined.

[0066] Finally, the seal seam strength of the heat-sealable coating was determined for each of the two test samples. To this end, three test strips, each 15 mm wide, were cut from each of the two test samples using a sheet metal strip cutter. A strip of polypropylene film, also 15 mm wide, was then applied to one side of each of the six test strips by heat sealing. The polypropylene film was 200 μm thick.

[0067] Heat sealing was performed using a heat sealing machine with a sealing force of 90 N, a sealing time of 1 second, and a sealing temperature of 180°C. The seal seam strength for each of the six test strips was then determined in accordance with DIN 55529, where a 180° peel angle was used instead of the 90° peel angle specified in DIN 55529. Finally, the average seal seam strength was calculated as the average of the three test strips for each of the two test samples. The determined values ​​can be found in Table 1 below.

[0068] [Table 1]

[0069] As the table shows, the seal seam strength for both test samples is higher than the value of 35 N, which is already sufficient to provide a sufficiently secure connection between the heat-sealable coating of the resealable beverage can lid and the plastic element to be fixed. The seal seam strength for both test samples is even higher than the value of 39 N, which allows for an even more secure connection. In contrast to the first test sample, the second test sample reaches even a value higher than 42 N, which results in a particularly secure connection. The higher seal seam strength in the case of the second test sample can be attributed in particular to the higher basis weight of the heat-sealable coating.

[0070] Finally, laboratory tests were also carried out within the scope of the present invention to investigate the porosity of the heat-sealable coating of the aluminium alloy strip according to the invention. For this purpose, two further test samples 3 and 4 were cut out from aluminium alloy strip of type AA5182 in the same way as the two test samples 1 and 2 described above, and were provided with a heat-sealable coating on one side by baking a water-based lacquer. The two additional test samples were identical to the two test samples already described above, except for the basis weight of the heat-sealable coating, which was 8.0 g / m for the third test sample. 2 and 12.0 g / m for the fourth test sample. 2 It was.

[0071] To investigate the porosity, at least three beverage can lid shells were produced from test samples 3 and 4 by punching and molding. Then, the coated interior of the shells was subjected to "Enamelator" porosity measurements. For this purpose, a cylindrical test container mounted so that it could be rotated horizontally was filled with an electrolyte solution until approximately one-third of the test container volume was filled. The electrolyte solution consisted of 98.8% by weight deionized water, 1.0% by weight NaCl, and 0.2% by weight sodium dioctyl sulfosuccinate, the latter of which served to reduce interfacial tension and thereby allow any pores present to be better filled by the electrolyte solution. After filling the test container with the electrolyte solution, a shell for measuring the porosity of the heat-sealable coating was placed on top of the test container. The diameter of the test container was matched to that of the shell to ensure a precise fit. The shell was then pressed onto the test vessel and fitted into place due to the excess pressure of the laboratory environment, which was created by evacuating the test vessel through an opening located approximately midway along its outer surface. The test vessel was then rotated 180° horizontally, so that the shell faced downwards. In this position, the electrolyte solution in the test vessel contacted the coated interior of the shell. Furthermore, in this position, the first electrode, located inside the test vessel and contacted from the outside via a cable, was also immersed in the electrolyte solution. Finally, a metal pin acting as a second electrode was used to contact the metal layer of the shell.

[0072] Next, to actually perform the "enamelator" porosity measurement, a DC voltage of 6.3 V was applied to the two electrodes. After a measurement period of 4 seconds, the intensity of the current flowing between the two electrodes was measured. In this manner, the current intensity for each of the shells produced from test samples 3 and 4 was determined. Finally, the average current intensity of the porosity measurement for each test sample was calculated as the average value for at least three individual shells produced from each test sample. The determined values ​​are shown in Table 2 below.

[0073] [Table 2]

[0074] As the table shows, the average current strength measured for both test samples is not only less than 5 mA, but also less than 2 mA, and for the fourth test sample it is even less than 1 mA. These values ​​indicate that the 8 g / m 2 ~12g / m 2 Each heat-sealable coating having a basis weight in the range of 0.1 to 0.5 can be considered to have a sufficiently low porosity for application to beverage can ends. In particular, it can be achieved that the heat-sealable coating of the aluminum alloy strip according to the present invention adequately fulfills its properties as an adhesion promoter and a highly functional barrier for resealable beverage can ends.

[0075] Further embodiments also form part of this disclosure.

[0076] 1. An aluminium alloy strip for manufacturing beverage can ends, the aluminium alloy strip having an aluminium alloy of type AA5xxx; 1. An aluminum alloy strip having a heat-sealable coating containing a polyolefin on one or both sides. Aluminum alloy strip.

[0077] 2. An aluminum alloy strip according to embodiment 1, characterized in that the polyolefin is at least partially crosslinked by a hydroxyalkylamide, preferably N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide.

[0078] 3. An aluminum alloy strip according to embodiment 1 or 2, wherein the heat-sealable coating contains wax.

[0079] 4. Heat-sealable coating, 1.0 g / m 2 ~20.0g / m2 , preferably 2.0 g / m 2 ~14.0g / m 2 , particularly preferably 3.0 g / m 2 ~5.0g / m 2 or 6.0 g / m 2 ~12.5g / m 2 , most preferably 3.5 g / m 2 ~4.5g / m 2 or 6.5 g / m 2 ~12.0g / m 2 4. An aluminum alloy strip according to one of embodiments 1 to 3, characterized in that it has a basis weight of

[0080] 5. An aluminum alloy strip according to one of embodiments 1 to 4, wherein the heat-sealable coating has a seal seam strength of at least 35 N, preferably at least 39 N, particularly preferably at least 42 N at a sealing seam width of 15 mm after heat sealing to a polypropylene film with a sealing force of 90 N, a sealing time of 1 second, and a sealing temperature of 180°C.

[0081] 6. Heat-sealable coating, 8g / m 2 ~12g / m 2 6. An aluminum alloy strip according to one of embodiments 1 to 5, characterized in that the porosity is such that the current intensity measured in the "Enamelator" porosity measurement for a basis weight of the heat-sealable coating in the range of 1 to 5 is 5 mA or less, preferably 2 mA or less, particularly preferably 1 mA or less, wherein the "Enamelator" porosity measurement is performed with a voltage of 6.3 V and the current intensity is determined after a measurement time of 4 seconds.

[0082] 7. An aluminum alloy strip according to one of embodiments 1 to 6, wherein the aluminum alloy strip has an aluminum alloy of type AA5052 or AA5182.

[0083] 8. The aluminum alloy strip according to one of embodiments 1 to 7, wherein the aluminum alloy strip has a metal thickness of 0.1 mm to 0.3 mm, preferably 0.15 mm to 0.25 mm.

[0084] 9. Aluminum alloy strip according to one of embodiments 1 to 8, characterized in that the aluminum alloy strip additionally has a chromium-free conversion layer on one or both sides, the chromium-free conversion layer preferably containing zirconium phosphate.

[0085] 10. A method for producing an aluminum alloy strip, in particular an aluminum alloy strip according to one of the embodiments 1 to 9, comprising: - Casting rolled ingots or cast strip from aluminum alloys of type AA5xxx, - homogenizing rolled ingots or cast strip; - hot rolling of rolled ingots or cast strip into hot rolled strip; - Cold rolling of hot-rolled strip to final thickness with or without at least one intermediate annealing and wherein the method comprises: - producing a heat-sealable coating on one or both sides of the aluminum alloy strip that has been cold-rolled to final thickness, wherein the heat-sealable coating contains a polyolefin; method.

[0086] 11. The method according to embodiment 10, wherein the heat-sealable coating is produced by applying and baking a lacquer.

[0087] 12. The method according to embodiment 10 or 11, characterized in that the baking of the lacquer is carried out in such a way that a maximum metal temperature in the range of 200 ° C to 300 ° C, preferably in the range of 220 ° C to 260 ° C, is reached.

[0088] 13. Use of an aluminum alloy strip according to one of embodiments 1 to 9 for producing a resealable beverage can lid.

[0089] 14. A resealable beverage can lid, characterized in that the beverage can lid is made from an aluminum alloy strip according to one of embodiments 1 to 9.

[0090] 15. A beverage can having a resealable beverage lid, characterized in that the beverage lid is made of an aluminum alloy strip according to one of embodiments 1 to 9.

Claims

1. An aluminium alloy strip for manufacturing beverage can ends, the aluminium alloy strip having an aluminium alloy of type AA5xxx; the aluminum alloy strip has on one or both sides a heat-sealable coating containing a polyolefin, the polyolefin being at least partially crosslinked with a hydroxyalkylamide, preferably N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide, and the heat-sealable coating containing a wax; Aluminum alloy strip.

2. The heat-sealable coating has a coating thickness of 1.0 g / m ２ ~20.0g / m ２ , preferably 2.0 g / m ２ ~14.0g / m ２ , particularly preferably 3.0 g / m ２ ~5.0g / m ２ or 6.0 g / m ２ ~12.5g / m ２ , most preferably 3.5 g / m ２ ~4.5g / m ２ or 6.5 g / m ２ ~12.0g / m ２ 2. The aluminum alloy strip of claim 1, having a basis weight of

3. 3. Aluminium alloy strip according to claim 1 or 2, characterized in that the heat-sealable coating has a seal seam strength of at least 35 N, preferably at least 39 N, particularly preferably at least 42 N at a sealing seam width of 15 mm after heat sealing to a polypropylene film with a sealing force of 90 N, a sealing time of 1 second and a sealing temperature of 180°C.

4. The heat-sealable coating has a thickness of 8 g / m ２ ~12g / m ２ 4. Aluminium alloy strip according to claim 1, characterized in that the aluminium alloy strip has a porosity such that the current intensity measured in an "Enamelator" porosity measurement for a basis weight of the heat-sealable coating in the range of 0.05 to 0.5 s is 5 mA or less, preferably 2 mA or less, particularly preferably 1 mA or less, wherein the "Enamelator" porosity measurement is carried out with a voltage of 6.3 V and the current intensity is determined after a measurement time of 4 seconds.

5. An aluminium alloy strip according to any one of claims 1 to 4, characterized in that the aluminium alloy strip has an aluminium alloy of type AA5052 or AA5182.

6. Aluminium alloy strip according to any one of claims 1 to 5, characterised in that the aluminium alloy strip has a metal thickness of 0.1 mm to 0.3 mm, preferably 0.15 mm to 0.25 mm.

7. 7. Aluminium alloy strip according to any one of claims 1 to 6, characterised in that the aluminium alloy strip additionally comprises a chromium-free conversion layer on one or both sides, said chromium-free conversion layer preferably containing zirconium phosphate.

8. A method for producing an aluminium alloy strip, in particular for producing an aluminium alloy strip according to any one of claims 1 to 7, said method comprising the steps of: - Casting rolled ingots or cast strip from aluminium alloys of type AA5xxx; - homogenizing the rolled ingot or the cast strip; - hot rolling said rolled ingot or said cast strip into a hot rolled strip; - cold rolling said hot rolled strip to final thickness with or without at least one intermediate annealing; wherein the method comprises: - further comprising producing a heat-sealable coating on one or both sides of said aluminum alloy strip that has been cold rolled to final thickness, said heat-sealable coating comprising a polyolefin; The heat-sealable coating is produced by applying and baking a lacquer, the lacquer containing a polyolefin dispersion, a hydroxyalkylamide, preferably N,N,N',N'-tetrakis(2-hydroxyethyl)adipamide, as a crosslinking agent, and a wax. A method characterized by:

9. 9. The method according to claim 8, characterized in that the lacquer is a water-based lacquer, the lacquer contains a polyolefin dispersion, the polyolefin dispersion being preferably a polyethylene dispersion or a polypropylene dispersion or a mixture of both.

10. 10. The method according to claim 8 or 9, characterized in that the wax is preferably a PTFE-free wax, particularly preferably carnauba wax, polyethylene wax, polypropylene wax, polyamide wax or a mixture of said waxes.

11. 11. The method according to any one of claims 8 to 10, characterized in that the water-based lacquer contains 1 to 15% by weight, preferably 2 to 6% by weight, of an aqueous solution of hydroxyalkylamide, 1 to 20% by weight, preferably 5 to 11% by weight, of a PTFE-free wax, and the remainder an aqueous polyolefin dispersion, the aqueous polyolefin dispersion preferably having a solids content of up to 60% by weight, preferably 40 to 50% by weight.

12. Method according to claim 10 or 11, characterized in that the baking of the lacquer is carried out in such a way that a maximum metal temperature is reached in the range of 200°C to 300°C, preferably in the range of 220°C to 260°C.

13. Use of an aluminium alloy strip according to any one of claims 1 to 12 for producing resealable beverage can lids.

14. A resealable beverage can lid, characterized in that the beverage can lid is manufactured from an aluminium alloy strip according to any one of claims 1 to 7.

15. A beverage can having a resealable beverage lid, characterized in that the beverage lid is manufactured from an aluminium alloy strip according to any one of claims 1 to 7.

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