NO300451B1 - Metal-plastic foil laminate containing inorganic oxides, process for its preparation and its use for the manufacture of canned cans - Google Patents

Abstract

Inorganic oxide-containing metal-plastic film composite materials have at least 0.1 % by weight, preferably 0.5 to 8 % by weight, with respect to the total weight of the thermoplastic material constituting the plastic film and of the inorganic oxides, of a powder composed of zinc oxide and/or manganese oxide, incorporated into the plastic film and/or into the bonding or adhesive layers between the metal and the plastic film. The metal in the composite material is at least 0.08 mm thick. Also disclosed are a process for producing the metal-plastic film composite material and the use of the composite material to produce preserve cans.

Description

The present invention relates to metal-plastic laminates where a powder consisting of zinc oxide and/or manganese oxide is incorporated in the plastic foil and/or in the adhesive agent layer arranged between the metal and the plastic foil, respectively. adhesive layer, and where the metal in the laminate has a thickness of at least 0.08 mm, method for the production of these laminates, as well as their use in the production of cans.

For the production of a box or a wrapping device for use as packaging material, especially for packaging foodstuffs, tin is coated with tin, chromated steel, such as ECCS ("electolytic chromium-coated steel") and aluminum in plate or strip form. The varnish layer acts as a protective layer to protect the metal against attack by the filler material and the resulting corrosion on the one hand and on the other side to prevent an influence on the filler material by corrosion products from the metal. Of course, it must not be with the varnish layer itself, e.g. in the case of released lacquer components, there is an impact or deterioration of the filling material, neither during the sterilization of the filling material carried out in connection with the filling nor during the subsequent storage of the packaged goods, especially foodstuffs.

Furthermore, the varnishes must be structured in such a way that they hold up against the mechanical stresses that occur during the further processing of the coated tins into cans or packaging devices, e.g. by shaping, punching, bert1ing, sealing etc.

Foil coating of metal tin has proven to be a favorable method for coating tin which is particularly used for the production of food packaging. Thus, it is e.g. in DE-OS 3 128 641 describes a method for the production of laminates for food packaging, where the metal tin and a thermoplastic resin film together with an adhesive of a carboxyl group-containing polyolefin arranged between these layers are heated to temperatures above the adhesive's melting point and then cooled together using pressure, whereby the metal-plastic laminate is produced.

From EP-A-4633, plastic foils are known which are produced by co-extrusion and stretched biaxially, which plastic foils consist of a carrier foil and at least one heat-sealing layer. The opaque foils contain finely divided, solid particles in an amount of 1-25% by weight, calculated on the weight of the polymer. Due to the content of fillers and the biaxial stretching, micro-cavities occur, as the polymer matrix during the stretching process is torn up at the grain boundaries for the fillers incompatible with the plastic.

These microcavities cause the plastic films to have an opaque appearance. Metal-plastic foil laminates are not described in EP-A-4633.

EP-A-199 228 relates to laminate films containing two plastic films connected by adhesive, whereby at least one of the two films is provided on its inner surface with a metal layer, and whereby one of the two plastic films has an opaque appearance due to microcavities in the film , which cavities are formed by inorganic film substances, such as sulphates, carbonates, silicates, oxides. These are used in a proportion of 5-30% by weight, calculated on the total weight of the mixture of plastic and filler. The Lami night foils are recommended for the packaging of food and entertainment products that are sensitive to oxidation. The opaque plastic film, which mainly consists of plastic as the main component and filler, must be stretched coaxially. The transparent plastic film is preferably also stretched. According to EP-A-199 228, the opaque plastic film must necessarily be stretched biaxially, the transparent plastic films used as a cover layer are preferably stretched biaxially. However, the biaxial stretching is disadvantageous, as it is associated with a further work operation, and mechanical measures for carrying out the biaxial orientation are necessary.

The laminate foils known from EP-A-199 228 have good barrier properties, i.e. low light, water vapour, gas permeability and good aroma and odor substance density. These barrier properties can be traced back to the inorganic fillers and to the resulting microcavities, which act as a barrier to light and gases. Regarding the laminate systems, it concerns metallized laminate foils with a metal thickness of 20-1000 nm. It is therefore about flexible laminate systems that are suitable for e.g. for the production of biscuit and chocolate packaging. For the production of cans, the metallized laminate foil known from EP-A-199 228 is not suitable because of the low metal layer thickness.

From US-A-4,681,816, metal-plastic laminates are known, where the plastic foil contains an inorganic filler, such as e.g. zinc oxide (cf. D2, column 3, lines 22-34). The laminates known from D2, however, contain 10-400 parts by weight of the inorganic filler, calculated on 100 of the plastic in the plastic film. This corresponds to a content of inorganic fillers of 9-80% by weight. calculated on the total weight of filler and plastic. The metal-plastic laminates according to claim 1, on the other hand, contain significantly less zinc oxide and/or manganese oxide, namely only 0.1-8% by weight of the zinc oxide and/or manganese oxide powder, calculated on the total weight of filler and plastic.

When it comes to tin cans based on iron- and tin-containing metal tin that are punched from metal-plastic foil laminates and sterilized after filling, the problem arises that clear signs of corrosion and marbling appear on the can, which can presumably be traced back to iron sulphide formation or zinc sulphide formation. These signs of corrosion and marbling manifest themselves in the darkening of the cans. As plastic foils, especially in a non-biaxially stretched state, exhibit a certain gas and thus also sulphide permeability, undesirable metal sulphide formations occur in the can during sterilization.

The task on which the present invention is based therefore consists in providing metal-plastic foil laminates for the production of cans which exhibit excellent barrier properties, i.e. low gas permeability, and especially low sulphide permeability, without the plastic foil necessarily having to be stretched biaxially . The cans made from the metal-plastic foil laminates must not show signs of corrosion and marbling, and they must be suitable for packaging delicate goods, such as e.g. meat products, vegetables and ready meals. As metal tin, especially tin containing iron and tin must be suitable, such as e.g. tin of black tin, white tin and ECCS ("elec-trolytic chromium-coated steel").

The task that forms the basis of the invention is surprisingly solved by a metal-plastic foil laminate of the kind indicated at the outset. This is characterized by the fact that preferably 0.5-8% by weight, calculated on the total weight of the thermoplastic in the plastic film and of the inorganic oxides and the zinc oxide and/or the manganese oxide, is incorporated.

The laminates according to the invention are produced by mixing a thermoplastic with zinc oxide powder and/or powdered manganese oxide, coextruding together with an adhesive agent, and the produced plastic film is coated on a metal sheet, and/or a thermoplastic is coextruded with a mixture of adhesive agent and zinc oxide powder and/or manganese oxide powder and the produced plastic foil is coated on a metal sheet, or by incorporating the zinc oxide powder and/or manganese oxide powder into a solvent-containing or aqueous adhesive, the adhesive is applied to a heated metal sheet, and a thermoplastic foil is coated on the metal sheet. Furthermore, it is possible from a mixture of thermoplastics and zinc oxide powder and/or manganese oxide powder to extrude a plastic film which is applied to a metal sheet with the aid of a solvent-containing or aqueous adhesive, which may also contain zinc oxide and/or manganese oxide powder. According to the invention, the zinc oxide powder and the manganese oxide powder can therefore be incorporated into the plastic foil in the adhesive-acting plastic that is extruded together with the thermoplastic, or in the adhesive layer arranged between the metal sheet and the plastic foil.

The plastic films are produced by extrusion of thermoplastics. The extrusion of thermoplastics is a well-known process that does not need to be described in more detail here.

It is advantageous to introduce the inorganic powder into the plastic melt when side coating the extruder. Double spiral extruders are preferably used. It is preferred to carry out a multi-stage extrusion for the production of the plastic films, whereby the organic powder is extruded together with part of the plastic during the production of a film with a high filler content in the first extrusion stage, and in a second stage the granules obtained from the film are extruded with a further thermoplastic powder. In this way, a better homogenization of the mixture of plastic and filler is achieved.

The thermoplastics used according to the invention include polyolefins, polyamides, polyesters, polyvinyl chloride, polyvinylidene chloride, polyurethane and polycarbonates, in the form of a foil or a film. They also include composite foils and films (laminate foils and films), which are obtained, for example, by joint extrusion of at least two of the above-mentioned polymers. The preferred thermoplastic or the preferred thermoplastic film preferably comprises a foil or a film of a polyolefin, a polyester or a polyamide. Such foils and films are known and can be obtained on the market in a large selection.

Such polyolefin foils are produced according to known methods (the blowing process, the "Chill-roll" process, etc.) from granules of homopolymers of ethylene and propylene as well as copolymers. Mention may be made of polyethylene of lower density (PE-LD), medium density (PE-MD), higher density (PE-HD), "linear low" and "linear very low density polyethylene" (PE-LLD, PE-VLD), further polypropylene copolymers which are usually produced from 92-99% by weight propylene and 1-8% by weight, calculated on the total monomer weight, comonomers. Suitable comonomers are other (C 2 -C 4 )-α-monoolefins, preferably (C 2 -C 6 )-α-monoolefins, such as ethylene, butene-1, 4-methylpentene-1, hexene-1, n-octene -1, n-decene-1 and n-dodecene-1. Suitable polypropylenes and methods for their production are e.g. described in DE-A-37 30 022.

Further suitable thermoplastics from which the plastic foils according to the inventive metal-plastic foil laminates can be produced are copolymers of ethylene, e.g. with copolymers from the group of vinyl esters, vinyl alkyl ethers, unsaturated mono- and dicarboxylic acids, their salts, anhydrides and esters.

The polyolefin plastics are commercially available under the following brands: Escorene®, Lupolen®, Lotader®, Lacqtene®, Orevac®, Lucalen®, Dowlex®, Primacor®, Surlyn®, Admer®, Novolen®, Sclair®, Stamylan® etc. .

Examples of polyamides suitable for the thermoplastic are polyamide 6 (polyamide made from e-aminocaproic acid), polyamide 6.6 (polyamide made from hexamethylenediamine and sebacic acid), polyamide 66.6 (mixed polyamide consisting of polyamide 6 and polyamide 6 ,6), polyamide 11 (polyamide produced from w-aminoundecanoic acid) and polyamide produced from o-aminolauric acid or from lauryl lactam). Examples of commercial products are Grilon®, Sniamid® and Ultramid®.

Preferred polyesters are polyethylene terephthalate, polybutylene terephthalate. However, other polyesters based on terephthalic acid, isophthalic acid and phthalic acid and various polyols, such as e.g. polyethylene glycol and polytetramethylene glycols of different degrees of polymerization.

Examples of suitable commercial products are Hostaphan®, Melinex®, Hostadur® and Ultradur®.

An example of a suitable commercial product based on polyurethane is Elastolan® from the company BASF AG.

Plastic films obtained by extrusion of a statistical polypropylene copolymer are preferably used, particularly preferably of a polypropylene copolymer of 1-4% by weight ethylene and 96-99% by weight propylene, calculated on the total weight of the monomer composition.

The thickness of the thermoplastic plastic films is normally 15-200 nm, preferably 20-10 /nm.

The metal-plastic foil laminates according to the invention contain at least 0.1-8% by weight, preferably 0.5-8% by weight, calculated on the total weight of the thermoplastic in the plastic foil and the inorganic oxides, zinc oxide powder and/or manganese oxide powder. Preferably, the aforementioned powders are used in a proportion of 2-4% by weight, whereby it is particularly preferred to incorporate zinc oxide powder in a proportion of 2-4% by weight in the plastic foil in the metal-plastic foil laminate.

According to the present invention, the metal-plastic foil laminates contain at least 0.1-8% by weight, calculated on the total weight of the plastic used to produce the plastic foil, as well as of the zinc oxide and/or manganese oxide, of a powder consisting of zinc oxide and/or manganese oxide. The oxide powders are preferably used in a proportion of 0.5-8% by weight, calculated on the total weight of the plastic in the plastic film and the oxide powder. Zinc oxide and manganese oxide puylvers are commercially available in large quantities. Current as zinc oxide powder is e.g. the product available under the trade name "Zinkoxyd aktiv" from the company Bayer AG, as well as the product with the trade name "Zinkoxyd Harzsiegel NT/S" from the company Heubach.

Particularly preferably, the average particle size of the zinc oxide powder and the manganese oxide powder is in the range 0.1-10 µm. The particle size in the oxide powder used naturally depends on the thickness of the layer in which the powder is incorporated.

According to the present invention, the oxide powders can be incorporated into the thermoplastic plastic foil in the metal plastic foil laminate. In this case, a mixture of the thermoplastic plastic and the zinc oxide powder and/or the manganese oxide powder together with further additives, such as lubricants, stabilizers, dyes, pigments, antistatic agents, antiblocking agents etc., is extruded into a plastic foil, whereby this is then laminated onto a metal sheet by using an aqueous or solvent-based adhesive or a co-extruded adhesive agent.

The plastic foils in the metal-plastic foil laminates according to the invention can advantageously contain additives, such as lubricants, stabilizers, dyes, pigments, antistatic agents, antiblocking agents and the like, in an effective amount. The additives are used in the quantities necessary for the production, processing, shaping and application in the form of powders, powders, beads or a concentrate incorporated directly into the polymer. Further details of the normally used amounts and examples of suitable additives can be found in e.g. Gåchter-Miiller, Plastic additive, Carl-Hanser-Verlag.

The above-mentioned additives can of course also be incorporated into the adhesive agent layer.

Copolymers can be used as adhesive agents,

terpolymers, graft copolymers and ionomers, provided that they exhibit carboxyl or anhydride groups or groups that can be hydrolysed to carboxyl groups, and that the melt index of the polymer, measured at 190°C and a load of 2.16 kg

lies between 0.1 and 30 g/10 min, preferably between 0.2 and 25 g/10 min, and particularly preferably between 0.5 and 20 g/10 min.

Suitable co-terpolymers, respectively terpolymers can be prepared by copolymerization of ethyls with a,j8-unsaturated carboxylic acids, such as e.g. acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid and fumaric acid, the corresponding anhydrides or the corresponding esters or half-esters with 1 to 8 C atoms in the alcohol residue, such as e.g. the methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclohexyl, heptyl, octyl and 2-ethylhexyl esters of the specified acids. Likewise, the corresponding salts of specified carboxylic acids can also be used, such as sodium, potassium, lithium, magnesium, calcium, zinc and ammonium salts. The carboxylic acids and their anhydrides are preferably used.

Furthermore, further monomers can be used in the copolymerization which are copolymerizable with ethylene and the unsaturated carbonyl compounds. Suitable are, for example, alpha olefins with 3 to 10 C atoms, vinyl acetate and vinyl propionate.

The quantity of the monomers used is thereby chosen so that the corresponding polymer exhibits a carboxyl group content of 0.1-30% by weight, preferably 2-20% by weight, and that the content of ethylene units in the polymer amounts to 99.9% by weight, preferably between 75 and 95% by weight.

Suitable graft copolymers can be produced by grafting at least one polymer from the group of polyolefins with up to 10% by weight, preferably up to 5% by weight, calculated on the total weight of the monomers, of at least one monomer from the group of a,j8-unsaturated carboxylic acids, their anhydrides, their esters or salts , in the presence or absence of peroxides. Examples of suitable polyolefins are polyolefins which are indicated above in the description of the plastics for the plastic foils. Examples of suitable carbonyl compounds are the carbonyl compounds indicated above in the description of adhesive agents on a copolymer basis.

The ionomers that are used as an adhesive intermediate layer can be produced by the above-described copolymerization of ethylene and possibly further monomers with salts of α,/S-unsaturated carboxylic acids or by partial neutralization of the above-described carboxylic acid-containing copolymers, terpolymers and graft polymers with salts, oxides and hydroxides of sodium, potassium, lithium, magnesium, calcium, zinc and ammonium. The neutralization can be carried out in melt or in solution. The amounts of basic compound are thereby chosen so that the degree of neutralization for the polymer is between 0.1 and 99%, preferably between 0.1 and 75%, and particularly preferably between 0.1 and 40%.

Polyurethane-based adhesive agents are also relevant.

According to the present invention, the oxide powders can also be incorporated into the adhesive agent layer, whereby for the production of the laminate a mixture of adhesive agent plastic and the zinc oxide powder and/or the manganese oxide powder is first prepared, this mixture is coextruded together with the plastic specified for the thermoplastic plastic foil, and the coex foil is cased onto a metal sheet .

Instead of an adhesive agent layer, an aqueous or solvent-based adhesive can also effect the adhesion between the plastic foil and the metal sheet. The adhesives are preferably applied by applying solutions or dispersions in water or organic solvents. The solutions or dispersions usually have an adhesive content of approx. 5 to 60% by weight. The amount of adhesive applied usually amounts to 1 to 10 g/m<2> surface. Particularly suitable adhesives are the synthetic adhesives consisting of thermoplastic resins, such as cellulose esters, cellulose ethers, alkyl or acrylic esters, polyamides, polyurethanes and polyesters, of thermosetting resins, such as epoxy resins, urea/formaldehyde resins, phenol/formaldehyde resins and melamine-formaldehyde resins or of synthetic rubbers. It is also possible to incorporate the zinc oxide powder and/or the manganese oxide powder into the adhesive layer which is arranged between the thermoplastic plastic foil and the metal. This is done in such a way that the oxide powder is mixed with the aqueous or solvent-containing adhesive, the resulting adhesive is applied to a heated metal sheet, and a thermoplastic plastic foil is coated on the metal sheet.

Relevant metal sheets in the metal-plastic foil laminates according to the invention are all iron and tin-containing sheets, e.g. metals of black tin, white tin, iron and of similar alloys, which are optionally equipped with a passivation layer. Suitable metallization processes are electroplating, spraying and vacuum evaporation. To achieve good adhesion of the metal layer to the surface to be metallized, the surface is first exposed to a corona treatment. According to the present invention, such sheet metal comes into question which has a thickness of at least 0.08 mm. Sheet metal with a thickness of 0.08 to 1 mm is preferred. Depending on the purpose of application, thicknesses of more than 1 mm are also suitable.

The present invention also relates to methods for the production of the above-described metal-plastic foil laminates, which methods are characterized by the fact that a thermoplastic plastic is co-extruded with an adhesive agent, and the resulting foil is coated on a metal sheet, whereby the zinc oxide powder and/or the manganese oxy powder is incorporated into the thermoplastic plastic foil and/or in the adhesive agent layer, or a thermoplastic plastic foil is coated on a metal sheet using a solvent-based or aqueous adhesive, whereby the zinc oxide powder and/or manganese oxide powder has been incorporated into the thermoplastic plastic foil and/or in the adhesive layer.

It is therefore possible to mix the thermoplastic plastic used for the production of the plastic foils with zinc oxide and/or manganese oxide powder, and co-extrude this mixture with an adhesive agent, whereby the co-extruded foil is then coated on the metal sheet. Of course, however, the oxide powder can also be mixed with the adhesion promoter plastic, and this adhesion promoter composition is co-extruded with the thermoplastic plastic, which may optionally also contain zinc oxide and/or manganese oxide powder. When using an adhesive agent which is co-extruded with the thermoplastic plastic, the sheet metal is coated with the co-extruded foil in such a way that the adhesive agent layer of the co-extruded foil touches the metal surface. By applying pressure and heat, the metal-adhesive agent-plastic foil laminate is produced either by means of a temperable press or in a roller gap on a rolling mill or a calender by means of temperable rollers. The pressure and temperature must then be chosen in such a way that, on the one hand, the adhesive agent forms a firm and stable connection with the metal foil or metal sheet, respectively, and on the other hand, the thermoplastic plastic foil must not melt.

The production of a metal-plastic foil laminate with a solvent-containing or aqueous adhesive is likewise a well-known process. One then usually proceeds in such a way that the adhesive is applied to a heated metal tin, and then the plastic foil is covered over the heated tin. In this case, a mixture of thermoplastic plastic and zinc oxide and/or manganese oxide powder can be extruded, and the resulting foil can be glued to the sheet metal using an aqueous and/or solvent-containing adhesive, which can also contain zinc oxide and/or manganese oxide powder. In addition, however, it is also possible to incorporate the oxide filler only in the adhesive layer.

The allocation of respectively the metal sheet and the thermoplastic laminate oil normally exhibit a total dry film thickness of less than 500 µm, preferably 10-200 nm. The thickness of the adhesive layer, resp. the adhesive layer is then between 0.5 and 100 µm. The thickness of the deck gasket thus has values between 10 and 499.5 fim.

According to the present invention, metal-plastic foil laminates also mean laminates where the metal sheet is coated with a plastic foil on both sides.

The invention likewise relates to the metal-plastic foil laminates produced according to the inventive method. These are stopped e.g. for cans, glass closure devices, crown cap or valve plate carriers for aerosol cans.

The metal-plastic foil laminates according to the invention are used for the production of packaging containers, in particular for the production of bottoms or lids on cans, valve plates on aerosol cans and closing devices. The production of the closing parts takes place according to usual methods (cf. e.g. VR-INTERPAK 1969, pages 600-606: W. Panknin, A. Breuer, M. Sodeik, "Abstreckziehen als Verfahren zum Herstellen von Dosen aus Wei/3blech"); SHEET METAL INDUSTRIES, August 1976: W. Panknin, Ch. Schneider, M. Sodeik, "Plastic Deformation of Tinplate in Can Manufacturing"; Verpackungs-Rundschau, Hefte 4/1971, pages 450-458: M. Sodeik, I. Siewert , "Die sinachaste Dose aus Wei/3blech"; Verpackungs-Rundschau, hefte 11/1975, page 1402-1407: M. Sodeik, K. Haa/3, I. Siewert, "Herstellen von Dosen aus WeijSblech durch Tiefziehen"; Arbeitsmappe fur den Verpackungspraktiker, Metalle, part II, group 2, WeijSblech, serial no. 220.042 to 220.048 in neue Verpackung 12/87, page B 244-B 246 and nue Verpackung 1/88, page B 247-B 250).

Regarding further details, reference is therefore made to the literature.

On cans that are punched from the laminates according to the invention and sterilized after filling, no signs of corrosion or marbling appear on the cans. This can presumably be attributed to the fact that the zinc oxide and manganese oxide powders used are transferred to colorless zinc sulphides, respectively. manganese sulphides, by sulphide formation. The dark coloring or marbling signs that appear without the addition of resp. zinc oxide powder and manganese oxide powder, can probably be attributed to iron sulphide formation and tin sulphide formation. By incorporating the oxide powder into the foil and/or adhesive agent or into the adhesive layer, the formation of iron or tin sulphide in the can is effectively prevented.

In the following, the invention is illustrated by means of design examples.

Example 1

Polypropylene granules (Novolen 3225 MCX from BASF AG) are mixed with 0.1, 0.5, 1, 2, 4, 6 and 8% by weight of ZnO powder (zinc oxide active from the company Bayer), calculated on the total weight of polypropylene and zinc oxide powder (caution : explosion hazard) and is melted at approx. 180°C roll temperature (double roll apparatus) and homogenized. The mixtures are pressed into foils and laminated onto white tin using a 2K polyurethane adhesive or an adhesive agent (adhesive agent based on polypropylene grafted with maleic anhydride) and punched into cans or lids.

The thickness of the foils is varied and amounts to 30, 50, 100, 200 /xm.

Several tins are produced, respectively. lid, which is

coated with foil on one or both sides, and they are filled with different solutions, e.g. NaCl, acetic acid, NaCl and lactic acid solution, animal feed ("Shappi", "Sheba"), tomato paste and the like and close. The cans are sterilized with wood

121°C for 30 min or at 130°C for 1 hour, then opened and examined for marbling (blackening of the material), or examined for any signs of corrosion.

Result: In all the experiments, no marbling is observed, resp. signs of corrosion, while in the corresponding tests without zinc oxide powder, clear marbling signs can be observed on the box.

Example 2

The procedure is as in example 1, with the difference that the zinc oxide powder is not mixed with the polypropylene granulate, but is added to the polypropylene melt during extrusion by means of an automatic powder dosing device. In this way, an explosion is excluded. The results regarding marbling or signs of corrosion correspond to the results from example 1.

Example 3

The procedure is as in example 1, with the difference that instead of the polypropylene Novolen 3225 MCX from BASF AG, a 1:1 mixture of the polypropylene Novolen 110 and Novolen 1125 (both from the company BASF AG) is used.

The results regarding marbling and corrosion to

corresponds to the results from examples 1 and 2.

Example 4

Monofoils and laminate films consisting of several layers are produced, whereby the polyethylene Lupolen® (BASF AG), the polyamide Ultramid® (BASF AG), the polybutylene terephthalate Ultradur® (BASF AG) and 1:1 mixtures of the various plastics are used as the carrier material . As the adhesive agent, the material known under the trade name Lucalen® (BASF AG) is coextruded together with the carrier material.

Zinc oxide powder (commercially available under the name "Zinkoxid Harzsiegel NT/S" from the company Heubach) is incorporated in proportions of 0.1, 0.5, 1.0, 2.0, 4.0, 6.0 and 8% by weight , calculated on the total weight of the carrier material and the zinc oxide pillar, both in the carrier layer and in the adhesive agent. The foils laminated on white tin are punched into cans. The cans are filled with the solutions mentioned in example 1 and closed. The cans are sterilized at 121°C for 30 min or at 130°C for 1 hour, opened and examined with respect to marbling and signs of corrosion.

Result: In all tests, no marbling is observed, resp. signs of corrosion, while in similar tests without zinc oxide powder, clear signs of marbling appear.

Claims (6)

1. Metal-plastic foil laminate where a powder consisting of zinc oxide and/or manganese oxide is incorporated in the plastic foil and/or in the adhesive agent layer arranged between the metal and the plastic foil, respectively. adhesive layer, and where the metal in the laminate has a thickness of at least 0.08 mm, characterized in that 0.1-8% by weight, preferably 0.5-8% by weight, calculated on the total weight of the thermoplastic in the plastic foil and of the inorganic oxides and the zinc oxide and/or the manganese oxide are incorporated. 2. Metal-plastic foil laminate according to claim 1, characterized in that 2-4% by weight of zinc oxide, calculated on the total weight of the thermoplastic in the plastic foil and the inorganic oxides, is incorporated into the plastic foil. 3. Metal-plastic foil laminate according to claim 1 or 2, characterized in that the average particle size of the zinc oxide and the manganese oxide is in the range 0.1-10 µm. 4. Metal-plastic foil laminate according to claims 1-3, characterized in that the plastic foil is obtained by extrusion of statistical polypropylene copolymer, preferably by extrusion of polypropylene copolymer of 1-4% by weight ethylene and 96-99% by weight propylene, calculated on the total weight of the monomer composition. 5. Procedure for the production of metal-plastic foil laminates where a powder, consisting of zinc oxide and/or manganese oxide, is incorporated in the plastic foil and/or in the adhesive agent layer arranged between the metal and the plastic foil, respectively. adhesive layer, and where the metal in the laminate has a thickness of at least 0.08 mm, characterized by a thermoplastic coex is coated with an adhesive agent, and the produced foil is coated on a metal sheet, whereby 0.1-8% by weight, preferably 0.5-8% by weight, calculated on the total weight of the thermoplastic in the plastic foil and of the inorganic oxides and the zinc oxide and/or the manganese oxide , has been incorporated into the thermoplastic foil and/or into the adhesive agent layer or that a thermoplastic foil is coated onto a metal sheet using a solvent-based or aqueous adhesive, whereby 0.1-8% by weight, preferably 0.5-8% by weight, has been incorporated, calculated on the total weight of the thermoplastic in the plastic film and the inorganic oxides, the zinc oxide and/or the manganese oxide, in the thermoplastic film and/or the adhesive layer. 6. Use of a metal-plastic foil laminate, where a powder consisting of zinc oxide and/or manganese oxide is incorporated in the plastic foil and/or in the adhesive agent layer arranged between the metal and the plastic foil, respectively. adhesive layer, and where the metal in the laminate has a thickness of at least 0.08 mm, whereby 0.1-8% by weight, preferably 0.5-8% by weight, has been incorporated, calculated on the total weight of the thermoplastic in the plastic foil and of the inorganic oxides and the zinc oxide and/or the manganese oxide, for the production of cans.