NO178722B - Thermoplastic composite film with profiled surface, method of manufacture and use thereof in the manufacture of packaging containers - Google Patents

Abstract

The invention relates to sheet metal coated with one or more layers (2) of possibly different resins, characterized by annular or disk-shaped bead-like thickenings (5) in at least one of the layers of resins. The invention also relates to processes for coating sheet metal, the thermoplastic composite films used to coat the sheet metal and the use of the coated sheet metal in the manufacture of packaging containers.

Description

The subject of the present invention is a thermoplastic composite foil as stated in claim 1's preamble, as well as a method for its manufacture and its use for coating sheet metal, especially for the manufacture of packaging containers.

For the production of a box or a closure device for use as a packaging material, especially for the packaging of foodstuffs, metal sheets are coated with white ink, chromated steel, such as ECCS ("electrolytic chromium-coated steel") and aluminum in sheet or strip form. The varnish layer acts as a protective layer to protect the metal from attack by the filler material and resulting corrosion on the one hand and on the other hand to prevent the filler material from being affected by corrosion products of the metal. Naturally, there should also be no influence or attack on the filler from the varnish layer itself, e.g. from dissolved varnish components, neither when attacking the filling material, the sterilization of the filling material which takes place in connection with the filling or during the subsequent storage of the packaged goods, especially foodstuffs.

Furthermore, the varnishes must be constructed in such a way that, during the processing of the coated metal sheets for cans or closure devices, they hold up against the mechanical stresses that occur, e.g. by forming, punching, folding, sealing and the like of the plates. In the manufacture of lids and bottoms of cans as well as closures, a sealing material is also necessary to induce tightness either between the metal parts or between metal and glass and the like. This sealing function is achieved by applying a sealing compound to the coated and already shaped packaging parts (bottom, lid, closing devices) as well as gel formation or drying of the sealant at higher temperatures. However, this production of lids and bottoms of cans as well as closure devices is associated with a high energy input, as varnish and sealant are burned in separately. Due to the high number of ready-made lids, bases and closure devices, this additional process step also constitutes a significant cost factor.

Moreover, it has to because of high solvent emissions

both when drying the varnish layer and when drying the sealant, measures are taken to keep these emissions and the associated environmental impact as small as possible.

Foil coating of metal sheets has proven to be an advantageous method for coating metal sheets which are particularly used for the production of food packaging. Thus, it is e.g. DE-OS 3128641 describes a method for the production of laminates for food packaging, whereby the metal plate and a thermoplastic resin film together with an adhesive applied between these layers based on a polyolefin containing a carboxyl group are heated to temperatures above the adhesive's melting point and then cooled together using pressure, whereby the metal-plastic composite is produced.

When manufacturing lids or bases as well as closure devices, however, the sealing compound must also be applied to the pre-formed lids and bases and hardened in a further process step.

Furthermore, laminates are also known from DE-OS 2912023, GB-A-2027391 and EP-B-31701 and food packaging containers, especially bags, produced from these laminates. The use of these laminates in the production of closure parts for packaging containers is admittedly not described.

From EP-B-41512, a method is now known for the manufacture of containers, whereby laminates are also used, i.e. for the manufacture of lids or bottoms of boxes or for the production of valve plates for aerosol cans. The polymer layer of these laminates then serves in the manufacture of containers at the same time as a seal and a protective layer, so that in this method the application of a sealing compound to the closing parts is not necessary. The disadvantage of this method is, of course, that in order to ensure the sealing function, a very high layer thickness of the laminated polymer layer is required, of approx. 200/im. The material consumption associated with this layer thickness leads to a strong increase in the production costs for the containers and thus constitutes a significant economic disadvantage of this method, above all when one takes into account that the containers are mass products with a very high unit price.

From patent application ZA-A-880198, it is known in the manufacture of cans to ensure the sealing of the connection between the can itself and the lid by inserting a sealing laminate between the lid and the can itself. This method also requires a lot of effort as the laminates that serve as sealing material must first be cut to size and then adapted to the closing part.

Finally, EP-B-167775 describes a method and a device for the continuous production of objects or coatings with complicated contours, e.g. for renewal of car tyres, whereby a liquid material is placed between at least two moving, endless, shaping surfaces and hardened. However, the production of thermoplastic composite foils or the use of the method in the production of metal sheets for use as closing parts on packaging containers is not described.

US-PS 3,265,785 describes a method for the production of closure parts on packaging containers, whereby a foamable vinyl resin plastisol is added as a sealant to the previously formed closure part, and it is shaped so that the plastisol layer exhibits an annular ("O-ring ") bead-like thickening. To achieve the sealing function, the plastisol is heated before, during or after shaping to a sufficiently high temperature to break down the foaming agent contained in the plastisol.

Furthermore, DE-OS 19 03 783 describes a method for coating substrates with a thermoplastic film, whereby the thermoplastic film exhibits a pre-selected profile of zones of different thickness. This method serves for the production of coated box or cardboard inserts that are used for packaging liquids, such as e.g. milk or juice. These coated box or cardboard sections show in the area around the sealing resp. the weld seams increased thickness to prevent leakage.

The thermoplastic composite foil according to the invention is characterized by what is stated in the characterizing part of claim 1. Further features are apparent from requirements 1-5.

The thermoplastic composite foil according to the invention can be used for the production of coated metal sheets which are suitable for use as packaging material. Especially when using these coated metal sheets as closing parts, such as e.g. can lids, can bases, valve plates and screw lids, packaging containers can be produced using a simple and cost-effective method, whereby this method does not exhibit the aforementioned disadvantages from the state of the art. Furthermore, these coated metal sheets fulfill the aforementioned requirements regarding mechanical properties and regarding tolerance and protective effect towards the filling material.

In a surprising way, this task was solved with a thermoplastic composite foil consisting of at least one primer layer and at least one further thermoplastic layer arranged on the primer layer, characterized in that the thermoplastic composite foil exhibits ring- or disk-shaped bead-like thickenings on the primer and/or cover layer, and that the bead-like thickenings form a pattern that repeats both in the transverse and longitudinal directions.

The advantages of coating metal sheets are mainly to be seen in that they are excellently suited for the production of closing parts for packaging containers, such as e.g. lids, bottoms and closing mechanisms, whereby it is a particular advantage that due to the integrated sealing function of the coated metal plates, the process step of applying a sealing compound, which is otherwise necessary when manufacturing closing parts, is omitted. By using the coated metal sheets, it is therefore possible to produce packaging containers using a simple and, above all, cost-effective method.

In the following, the materials that are suitable for the production of coated metal sheets are now described in more detail.

Metal plate:

As metal sheets, metal sheets with a thickness of 0.04-1 mm made of black tin, white tin, aluminum and various steel alloys are suitable, which may be equipped with a passivation layer based on nickel, chrome and zinc compounds.

These metal sheets are coated with one or more, possibly different resin layers, whereby it is essential that the coated metal sheet exhibits the bead-shaped thickenings that take over the sealing function.

Particularly preferred metal plates are obtained, however, when thermoplastic composite foils are used for coating the metal plates, which consist of at least one primer layer and at least one additional layer, on the primer

layer arranged thermoplastic layer.

The thermoplastic cover layer of the composite foil:

The thermoplastic resin foils or films which, according to the invention, are used as cover layers include polyolefins, polyamides, polyesters, polyvinyl chloride, polyvinylidene chloride and polycarbonates, either in the form of a foil or a film. They also include composite foils and films (composite foils and films), such as e.g. obtained by joint extrusion of at least two of the above-mentioned har-pix. The preferred thermoplastic foil or the preferred thermoplastic film which forms the innermost layer (ie the layer which is in contact with the filler) of the metal plastic composites 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 in a large selection in the trade.

Such polyolefin foils are produced according to known methods (the blowing method, the "chili-roll" method, etc.) from granules of homopolymers of ethylene and propylene as well as copolymers. Mention may be made of copolymers with low density (PE-LD), medium density (PE-MD), high density (PE-HD), "linear low" and "linear very low density" polyethylenes (PE-LLD, PE-VLD) polypropylene , their copolymers with ethylene as well as the copolymers of ethylene with one or more co-monomers from the group of vinyl esters, vinyl alkyl ethers, unsaturated mono- and dicarboxylic acids, their salts, anhydrides and esters.

These polyolefins are e.g. available in the trade under the following brand names: Escorene, Lupolen, Lotader, Lacqtene, Orerac, Lucalen, Dowlex, Primacor, Surlyn, Admer, Novatec, Sclair, Stamylan and others.

Examples of polyamides that are suitable as a cover layer 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 made from cj-aminoundecanoic acid) and Polyamide 12 (polyamide made from <o-aminolauric acid or from lauryl lactam). Examples for commercial products are Grilon, Sniamid and Ultra-mid.

Polyesters that are preferably used are polyethylene terephthalate, polyethylene terephthalate and polyesters based on terephthalic acid, ethylene and butylene glycol. 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 polymerisation.

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

Primer layer on the thermoplastic composite foil

Polymers that are used as primer layers in the method according to the invention can be both copolymers, terpolymers, graft copolymers and ionomers, provided that they exhibit carboxyl or anhydride groups or groups that are hydrolyzable to carboxyl groups, and that the melt index for the polymers measured at 190°C and a load of 2.1 kg is between 0.1 and 30 g/10 min, preferably between 0.2 and 25 g/10 min and particularly preferred between 0.5 and 30 g/10 min.

Suitable co- or terpolymers can be prepared by copolymerization of ethylene with a, jS-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. methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclohexyl, heptyl, octyl and 2-ethylhexyl esters of the indicated acids. The corresponding salts of the specified carboxylic acids can also be used, e.g. the sodium, potassium, lithium, magnesium, calcium, zinc and ammonium salts. The carboxylic acids and their anhydrides are preferably used.

During the copolymerization, further monomers can be used which are copolymerizable with ethylene and the unsaturated carbonyl compounds. Suitable is e.g. α-olefins with 3 to 10 C atoms, vinyl acetate and vinyl propionate. The amounts of the monomer used are then chosen so that the resulting polymer has a carboxyl group content of 0.1 to 30% by weight, preferably 2 to 20% by weight, and that the content of ethylene units in the polymer is between 99.9% by weight, preferably between 75 and 95% by weight.

Suitable graft copolymers can be prepared 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 monomer, of at least one monomer from the group of α,/3-unsaturated carboxylic acids, their anhydrides, their esters or salts in the presence or absence of peroxides. Examples of suitable polyolefins are the polyolefins already mentioned in connection with the description of the cover layers on page 6 of this description. Examples of suitable carbonyl compounds are the carbonyl compounds indicated above in the description of the copolymer-based primers.

The ionomers used as primer layers can be produced by the already described copolymerization of ethylene and possibly further monomers with salts of α,β-unsaturated carboxylic acids or by partial neutralization of the already described carboxyl-containing copolymers, terpolymers and grafted 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 amount of basic compound is thereby chosen so that the degree of neutralization of the polymer is between 0.1 and 99%, preferably between 0.1 and 75% and very particularly preferred between 0.1 and 40%.

Both the primer layer and the thermoplastic cover layer can also contain common additives, such as e.g. internal and external lubricants, anti-blocking agents, stabilizers, antioxidants, pigments, crystallization aids and the like. These additives are added in quantities that are necessary for production, processing, packaging and use in the form of powders, powders, beads or in the form of a concentrate that is incorporated directly into the corresponding polymer. Further details of the quantities that are usually used, and examples of suitable additives can be found in e.g. Gåchter-Miiller, "Plastic additives", Car 1-Hanser Verlag. These additives are preferably incorporated into the cover layer.

Production of composite foils with a structured surface: For the production of composite foils with a structured surface, which are made up of the materials described above, there are different possibilities: 1. When extruding over wide slot nozzles or ring nozzles, mono foils or multi-layer composite foils are produced. These flat foils are then reshaped using heat and pressure so that one surface of the foil is flat, and the other surface exhibits the bead-like thickenings of the invention which preferably repeat periodically. This shaping is possible with the help of a mask that is placed on the foil, or a positioned profiled plate, using a press or a roller. Rolls are preferably used, as it is thus possible to continuously produce the structured foil. Of course, it is also possible to use presses with a profiled plate, preferably with an exchangeable, surface-structured press plate, and rollers with a - preferably exchangeable - structured surface. It is also preferred that the press or the roller is temperable, preferably able to be heated, to shape the foil at the required temperature. The temperature used during forming naturally depends on the pressing pressure of the roller or the press and lies e.g. between 50°C and the foil's melting temperature, whereby the temperature is higher the lower the pressure. The pressure is, for example, between 1 and 400 bar.

Such a structured foil is then coated with a primer or a co-extruded, layered polymer composite with the same or a different primer on both surfaces of the polymer composite in the form of a film or a melt. Thereby, a temperature is selected at which the primer forms a firm and stable connection with the structured mono- and composite foil, without the structured foil melting or losing its distinct structure. 2. Analogous to the method just described, it is also possible to transform a flat mono- or composite foil with a press or roller so that one surface shows the invention's bead-like thickenings which preferably repeat periodically (the positive form), while the other the surface shows the corresponding geometric pattern in negative form, i.e. in the form of depressions. This structured foil is then coated analogously to method 1, also on the negative side with a primer, so that the embossed structure (positive side) is maintained. 3. In addition to the multi-step methods 1 and 2, the thermoplastic composite foil can also be produced by extruding one (in the case of a mono-foil) or several (in the case of multi-layer composite foils) using a resp. several extruders through a wide-slit die, a "dual-slit" die or a "feedblock" die directly on a thermostatizable roll with - preferably replaceable - structured surface and thus directly obtain a foil with a structured surface. The lamination, casing or coating is then carried out with a primer film, a primer melt or a possibly melt-flowing, layer-shaped polymer composite film, whereby it must be ensured that the surface structure of the thermoplastic layer is maintained. This application of the primer layer can either take place on the melt-flowing, smoothed surface facing the structured surface of the thermoplastic cover layer in the area of the surface-structured roller or on the smoothed, cooled surface of the cover layer. Thermoplastic composite foils are obtained that correspond to the foils produced according to method 1. 4. The thermoplastic composite foil with a structured surface can also be produced by coextruding the thermoplastic cover layer together with the primer layer over wide-slit nozzles or ring nozzles. The flat thermoplastic composite foil thus obtained is then reshaped using the device described in method 1 so that one surface is flat, and the other surface shows the bead-like thickenings of the invention which preferably repeat periodically. 5. However, it is also possible to connect a planar thermoplastic monofilm or a composite with a primer layer or a polymer composite, in which at least one surface consists of a primer layer, and to reshape the planar thermoplastic composite film thus obtained analogously to method 4 so that

one surface is flat, and the other exhibits the bead-like thickenings of the invention which preferably repeat periodically.

Thermoplastic composite foils with a structured surface, on which at least one layer consists of a foamed plastic

In the method of the invention, it is also possible to use thermoplastic composite foils with a structured surface, on which at least one layer consists of a foamed plastic. Such composite foils are e.g. possible to produce by the following methods: In an extruder, a polymer is melted in the presence of a chain misc (thermally decomposing compound, such as e.g. azodicarbonamide, sodium dicarbonate) or a physical fuel (propellant gas, such as e.g. freon, carbon dioxide, butane) and extruded on a tempered roller with - in advance exchangeable - structured surface. The non-structured surface of the foam film is smoothed,

if necessary, with a squeegee or a roller and then a primer film or a primer foil or a polymer composite foil is cased or extruded or -film, which has on at least one surface a primer layer, on the polymer film.

i II a) Analogous to method I, a polymer is melted in an extruder in the presence of a chemical or physical fuel and extruded on a smooth roller and then coated, after any smoothing of the surface, analogous to method I, with a primer layer or a polymer composite foil.

This unstructured, planar composite foil is then transformed, as described in method 1 for the foil production, between one- or two-sided heated presses or rollers into a composite with bead-like thickenings on the foamed surface layer.

II b) A composite foil with at least one surface of a primer or a primer foil is coated with a foamed polymer film. The foamed surface layer is transformed as described in II a) in presses or rollers.

II c) A coextruded composite foil with a foamed surface layer and a primer as a second surface is transformed between one- or two-sided heated presses or rollers into a composite with bead-like thickenings on the foamed surface layer.

III A composite foil is produced that corresponds to the composite foil produced according to method II, so that a flat thermoplastic foamed monofoil or composite foil with at least one foamed surface layer is first transformed into a foil with the bead-like thickenings according to the invention on the foamed surface layer between tempered rollers (e.g. embossing) with a two- or one-sided structured surface, and then the primer layer is applied, or a composite with at least one primer layer on the surface, on the non-structured surface so that the structured surface is retained.

IV The depressions of a temperable roller (W) are filled with a foaming resin, and excess material is removed with a squeegee or a roller. Directly thereafter, a heated cashier foil or a melt film of either a primer or of a coextruded polymer composite with a primer layer is pressed onto at least one of its surfaces with a roller. The composite is torn off after a partial wrapping of the roll (W) in the range of 40-90% of the roll's (W) extent.

Use of coated metal sheets for the production of packaging containers

Metal plates coated with thermoplastic composite foil according to the invention are used for the production of packaging containers, especially 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-INTERPACK 1969, pages 600-606; W. Panknin, A. Breuer, M. Sodeik, "Abstreckziehen als Verf ahren zum Herstellen von Dosen aus Wei/Sblech" ; SHEET METAL INDUSTRIES, August 1976: W. Panknin, Ch. Schneider, M. Sodeik, "Plastic Deformation of Tinplate in Can Manufacturing; Verpackungs-Rundschau, Hefte 11/1971, pages 450-458; M. Sodeik, I . Siewert, "Die sinachaste Dose aus Wei/3blech"; Verpackungs-Rundschau, hefte 11/1975, pages 1402-1407; M. Sodeik, K. Haa/?, I. Siewert, "Herstellen von Dosen aus Wei/Sblech durch Tief ziehen"; Arbeitsmappe fiir den Verpackungspraktiker, Metalle, Teil II, Gruppe 2, WeijS-blech, Lfd. No. 220.042 to 220.048 in neue Verpackung 12/87, page B 244 to B 246 and neue Verpackung 1/88, pages B 247 to B 250).

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

The invention is now explained in more detail with the help of drawings.

Fig. 1 shows a section of a structured thermoplastic composite foil (1) consisting of a thermoplastic layer (2) and a primer layer (3), where the thermoplastic layer (2) exhibits bead-like thickenings. Such a composite foil can be produced according to method 1 which

is explained in the present description.

Fig. 2 shows a section of a structured thermoplastic composite foil (1) which consists of a thermoplastic cover layer (2) and a primer layer (3), where the primer layer (3) exhibits bead-like thickenings. Such a composite foil can be produced by method 2, which is explained in the present description. Fig. 3 shows a section of a structured thermoplastic composite foil (1) consisting of a primer layer (3) and a thermoplastic cover layer (4) of foamed plastic. Such a composite foil can be produced according to method IV which is explained in the present description. Fig. 4 shows a section of a coated metal sheet with bead-like thickenings (5) of the cover layer (2) in ring form in a perspective representation. Furthermore, a part punched out of the metal ink is shown which is necessary for the production of a closing part. Fig. 5 shows a section along the line A-B. You can see the metal plate (6), the primer layer (3) and the cover layer (2) with the bead-like thickenings (5).

In fig. 4 and fig. 5, the following typical parameter was used as a basis for the coated sheet metal:

Height of the thickening = 0.05 mm

Width of the thickening = 4 mm

Thickness of the composite foil = 0.1 mm Metal plate thickness = 0.2 mm

Lid diameter = 73 mm

Distance between neighboring thickenings = 1 mm

In the following, the invention is explained in more detail with the help of design examples. All indications of parts and percentages are weight indications if nothing else is expressly stated.

I, Production<g> of thermoplastic composite foils

1. 1 Production<g> of the thermoplastic composite foil 1

A coextruded film of a 0.20 mm thick layer of a high density polyethylene (density = 0.960 g/cm<3>, melt index, measured at 190°C and a load of 2.16 kg (short MFI 190/ 2.16) = 8 g/10 min, melting point 135°C) and et

0.05 mm thick layer of an ethylene acrylic acid copolymer (density = 0.931 g/cm<3>, MFI 190/2.16 = 6 g/10 min, 6.5 wt% acrylic acid) is formed in a heated embossing plant. The embossing roller is heated to a temperature of 5 to 20°C below the melting point of the polyethylenes, the smooth impression roller to 40°C below the temperature of the embossing roller. The embossing roll is wrapped to 80% of its extent by the coextruded film to enable an optimal heat transfer. The press roller has a Teflon or rubber coated surface to prevent too strong adhesion. The embossing roller has annular depressions (0.05 mm depth, 5 mm width). The pressing force is 200 N/mm gap length.

1. 2 Production<g> of the thermoplastic composite foil 2

An embossed polyamide foil (Polyamide 6, 0.06 mm foil thickness) with raised ring-shaped structures (0.06 mm height) on one side is coated in a coating plant on the side facing away from this profile,"with ethylene acrylic acid copolymer (density = 0.938 g /cm<3>, MF I 190/2.16 = 10 g/10 min, 10% by weight acrylic acid).

Mass temperature: 180°C, coating speed 150 m/min, temperature for "chill-roll" 5°C, thickness of the layer 0.1 mm.

1. 3 Production<g> of the thermoplastic composite foil 3

An embossed polyamide foil (Polyamide 6, 0.06 mm thickness) with ring-shaped structures (0.02 mm height) on one side is coated in a coating plant on the side facing away from this profile with a coextruded polymer film of 0.02 mm Zn -ionomers (density = 0.940 g/cm<3>, MF I 190/2.16 = 2 g/10 min, 1.7 wt% Zn acrylate and 6.8 wt% acrylic acid), 0.06 mm LDPE - "low density polyethylene" - (density = 0.934 g/cm<3>, MF I 190/2.16 = 0.3 g/10 min) and 0.03 mm Zn ionomer.

Mass temperature 170°C, coating speed 100 m/min, temperature for "chill-roll" 5°C, thickness of the layer 0.11 mm.

1. 4 Production<g> of the thermoplastic composite foils 4-6

HDPE - "high density polyethylene" - (density 0.952 g/cm<3>, MFI 190/2.16 = 6 g/10 min, grafted LLDPE - "linear low density polyethylene" - (density 0.920 g/cm<3> , MF I 190/2.16 = 4 g/10 min, 0.3 wt% maleic anhydride) and ethylene vinyl alcohol copolymer (density 1.19 g/cm<3>, MF I 190/2.16 =

1.3 g/10 min, 30 mol% ethylene) is coextruded using a "feed-block" die into a surface-structured composite foil. The HDPE layer of the composite is structured by extruding the melt (290°C, 150 m/min) on a "chill-roll" (15° C) with removable surface parts. The removable

parts are 2 mm thick, chrome-plated half-cups in which the annular recesses (width 7 mm and 3 mm, depth on foil 4 0.15 mm, on foil 5 0.1 mm and on foil 6 0.01 mm) were placed using of spark erosion before the chrome plating. The composite is composed of 0.1 mm HDPE, 0.02 mm g-LLDPE, 0.05 mm ethylene vinyl alcohol copolymer and 0.03 mm g-LLDPE.

1. 5 Production of the thermoplastic coposit foil 7

A polypropylene of density 0.908 g/cm<3> and melt index MFI 23 0/2.16 = 11 g/10 min is melted in a screw extruder (ø = 45 mm, length of the screw L = 30 D (D = ø) , mass temperature 290°C) and extruded on a "chill-roll" cylinder (surface temperature 15°C). On the surface of the "chill-roll" a 2.5 mm thick Teflon film was attached which showed annular depressions (0.05 mm depth and 5 mm width). The polypropylene film (thickness 0.15 mm) extruded on this surface is smoothed with the help of a press roller and torn off after half a turn of the cylinder. Using technically known methods (electrical discharge, Corona and plasma treatment, flame treatment), the flat surface of the structured film is pre-treated so that there is a surface tension of 45 to 65 mN/m.

This textured surface polypropylene film is coated with a coextruded film (0.05 mm thickness) of an ethylene vinyl acetate copolymer (28 wt% vinyl acetate, MFI 190/2.16 = 20 g/10 min, 0.01 mm thickness) and an ethylene acrylic acid copolymer (8 wt% acrylic acid, MFI 190/2.16 = 17 g/10 min, 0.04 mm thickness) so that the ethylene vinyl acetate copolymer layer is placed on the polypropylene film. The mass temperature is 205°C, the coating speed 100 m/min.

1. 6 Production<g> of the thermoplastic composite foil 8

Analogous to composite foil 7, a thermoplastic composite foil 8 is produced, with the only difference compared to the production of composite foil 7, that now the ring-shaped depressions in the Teflon film from the "chill-roll" have a depth of 0.03 mm (instead of 0.05 mm) .

1. 7 Production<g> of the thermoplastic composite foil 9

Analogous to composite foil 7, a thermoplastic composite foil 9 is produced, with the only difference being that now the annular depressions in the Teflon film from the "chill-roll" have a depth of 0.005 mm instead of 0.05 mm.

1. 8 Production<g> of the thermoplastic composite foil 10

A polypropylene (density = 0.898 g/cm<3>, MFI 230/2.16 =

5 g/10 min) is coextruded together with a grafted Random Polypropylene (density = 0.89 g/cm<3>, MFI 230/2.16 = 12 g/10 min, melting point 158°C, 0.21 wt% maleic anhydride ) on a "chill-roll" with attached Teflon foil (2 mm thickness, ring-shaped recess 0.1 mm, 5 mm width, internal ø 73 mm). At a mass temperature of 250°C and a speed of 120 m/min, the recesses are filled, and a composite foil of 0.24 mm thickness (0.2 mm polypropylene, 0.04 mm graft copolymer) with 0.08 mm high bead-shaped thickenings on the polypropylene side. 1. 9 Production<g> of the thermoplastic composite foil 11

The graft copolymer side of composite foil 10 is coated with a 0.05 mm thick layer of a copolymer (87% ethylene, 9% butyl acrylate, 4% acrylic acid, MFI 190/2.16 = 7 g/10 min) at a mass temperature of 270° C.

1. 10 Production<g> of the thermoplastic composite foil 12

A polyester film (commercial product Melinex<®> 870 from the company ICI) with 0.012 mm thickness) is equipped in a heated deep-drawing tool (T = 150°C) with ring-shaped structures

(0.04 mm depth, outer ø 11.57 cm, inner ø 10.57 cm). This film is coated with grafted PE-LLD (linear low density polyethylene density: 0.918 g/cm<3>, MFI 190/2.16 = 4 g/10 min, 0.27 wt% maleic anhydride). Mass temperature 290°C, application strength 50 g/m<3>.

Example 1

A polyethylene (PE) with a density of 0.918 g/cm<3> and a melt index MFI 190/2.16) of 1.7 g/10 min is melted in an extruder (ø.60, L = 25 D). The mass temperature is 220°C. In a second extruder (ø 35, L = 25 D) an ethylene acrylic acid copolymer (8 wt% acrylic acid, density = 0.935 g/cm<3>, MFI 190/2.16 = 7 g/10 min) is melted at a temperature of 210 °C. Both melt streams are brought together in the "feedblock" nozzle and extruded on a smooth "chill-roll" (temperature 15°C). The 0.2 mm thick film consists of 0.15 mm polyethylene and 0.05 mm copolymer. In a second work step, this film is placed with the copolymer side on a degreased steel plate (0.3 mm ECCS, "electrolytic chromium coated steel", chrome-plated steel). On the polyethylene side, a Teflon foil (2 mm thickness) equipped with ring-shaped recesses is laid. The rings have an inside diameter of 54 mm and 59 mm outside with different depths of 0.003, 0.01, 0.05 and 0.1 mm. Under slight pressure

< 0.5 kg/cm<2> is first pressed for 1 minute at 200°C, then 3 minutes at a pressure of 5 kg/cm<2> and finally cooled under pressure to room temperature. The ring-shaped recesses are completely filled. In the peeling test according to ASTM D 1876 (angle 90°), an adhesion of 45 N/15 mm band width is measured (cf. table 1). The adhesion of the primer layer to other substrates is indicated in table 2.

Example 2

A coated steel plate is produced according to the method described in example 1, where, unlike example 1, polyethylene with a thickness of 0.924 g/cm<3> and a melt index of MFI 190/2.16 = 7 g/10 min and ethylene acrylic acid copolymer is now used with the density 0.932 g/cm<3> and the melt index MFI 190/2.16 = 7 g/10 min and a content of 4% by weight acrylic acid and 8% by weight butyl acrylate. The thickness distribution in the composite foil is 0.20 mm polyethylene to 0.05 mm copolymer. The copolymer adheres to 0.2 mm white tin E 5.6/5.6 with 69 N/15 mm. The results of further adhesion tests with the primer layer on other substrates are shown in table 2.

Example 3

An unstructured coextruded film of a lower thickness LDPE polyethylene (thickness = 0.918 g/cm<3>, MFI 190/2.16 = 7 g/10 min, thickness 0.1 mm) and an ethylene copolymer (thickness = 0.940 g/ cm<3>, MFI 190/2.16 = 11 g/10 min, 16 wt% vinyl acetate, 0.6 wt% maleic anhydride, 0.02 mm thickness) is bonded in an embossing machine at a pressure force of 100 N/mm and a speed of 10 m/min with a pre-heated white tin belt while simultaneously embossing the LDPE layer. The embossing roller exhibits regular ring-shaped depressions of 5 mm width and 0.1 mm depth. The temperature of the foil's preheating roller is 80°C, and the temperature of the embossing roller and pressure roller is 15°C. The metal sheet track is preheated to 150°C. The results of the adhesion tests are listed in Tables 1 and 2.

Example 4

Polyethylene glycol terephthalate (density 1.41 g/cm<3>, melting point: 255°C, glass transition temperature: 75°C) is coextruded together with an ethylene vinyl acetate-maleic anhydride terpolymer (8 wt% vinyl acetate, 3 wt% maleic anhydride, MFI 190/2, 16 = 6 g/10 min) at 270°C. The composite consists of 0.01 mm polyester and 0.07 mm terpolymer. This film is placed in a second work step with the copolymer side on a degreased steel plate (0.2 mm TFS). On the polyester side, a steel plate equipped with ring-shaped recesses (0.2 mm thickness) is placed. The rings have a cross-section inside of 25 mm and 32 mm outside with different depths of 0.01 and 0.05 mm. Under a slight pressure of < 0.5 kg/cm<2>, first press for 1 minute at 250°C, then 3 minutes at a pressure of 5 kg/cm<2> and finally cool under pressure to room temperature. -The ring-shaped recesses are completely filled. The results of various adhesion tests are given in Tables 1 and 2.

Examples 5 to 15 (method a)

A 35 cm wide metal strip is heated to a temperature between the primer's melting temperature and 250°C (for the individual temperatures see also tables 1 and 2) using suitable methods (HF heating, gas flame etc), coated with the primer side on a 35 cm wide partial web of the composite foils 1 to 11 and joined between the rollers on an embossing machine to form a metal-plastic laminate. The press roller is rubberized, and the press force (< 50 N press force per mm gap length) is chosen so that the reduction of the structure height is less than 10% of the original height. A peeling test according to ASTM D 1876 was carried out on some selected composites. The test results are shown in Tables 1 and 2.

Examples 16 to 21 (method b)

A 35 cm wide metal strip is coated with the primer side of a 35 cm wide partial web of the composite foils 1 to 11, the metal side is heated using suitable methods (HF heating, gas flame etc.) to a temperature that is higher than the melting point of the primer (for the individual temperatures see table 1), and this laminate is pressed between a smooth metal roller and a rubber roller (structured polymer side) on an embossing machine into a metal-plastic laminate. The pressure force is set so that the reduction of the structure height is less than 10% of the original height. A peeling test according to ASTM D 1876 was also carried out on some selected composites. The test results are shown in Tables 1 and 2.

Examples 27 to 37 (method c)

A 35 cm wide metal strip is heated to a temperature higher than 300°C (for the individual temperatures see table 1) using suitable methods (HF heating, gas flame etc.) and joined in the roll gap of an embossing mill with the primer side on one of the composite foils 1 to 11 to a metal-plastic laminate. The pressure roller is rubberized, and the pressing force (< 100 N pressing force per mm gap length) is chosen so that the reduction of the structure height is less than 10% of the original height. A peeling test according to ASTM D 1876 was also carried out on some selected composites. The test results are shown in tables 1 and 2.

Example 38

Using the thermoplastic composite foil 12, coated metal sheets are produced, using method b. A peeling test was also carried out on some composites according to AS TM 1876. The test results are shown in tables 1 and 2.

Explanations for table 1:

1) Method used in the production of the composite of metal plate and thermoplastic composite foil 2) The surface temperature of the metal plate in the production of the composite of metal plate and thermoplastic composite foil

3) TFS "tin free steel"

ECCS = "electrolytic chromium-coated steel"

4) Tinplate E 5.6/5.6 (DIN 1616)

Explanations for table 2:

1. Method described for producing a composite of a metal plate and a primer layer according to example 1.

2. Abbreviations:

E = ethylene

BA = butyl acrylate

AA = acrylic acid

ZnAA = zinc acrylate

g = grafted

PE-LLD = "linear low density polyethylene"

PP = polypropylene

VA = vinyl acetate

MSA = maleic anhydride

3. The surface temperature of the metal plate during the production of the composite of metal plate and primer layer.

4. TFS = "tin free steel"

ECCS = "electrolytic chromium-coated steel"

5. Tinplate E 5.6/5.6 (DIN 1616)

Examples 3 9 to 42

From the plastic-metal composites from examples 15, 19, 20 and 21 produced according to the method a-c, can lids were punched, and their suitability for use as can material was examined in a short trial. The examination showed good resistance to the usual test solutions (lactic acid, acetic acid, common salt solution, H20) under sterilization conditions of 121°C for 30 minutes.

Examples 43 to 44

With the composites from examples 1 and 3, small bowls were made with a cross section of 33 mm and a height of 25 mm. Methylene chloride was then allowed to act on the bowls. The adhesiveness was examined before and after 72 hours with the Tesa test. No reduction in adhesiveness was observed.

Examples 45 to 47

From the composites from examples 6, 17 and 28 prepared according to method A-C, a bowl with cross-section 33 mm, height 25 mm was prepared and then it was stored in isopropan-ol, xylene, "Solvent naphtha 100", "Solvent", "Naphtha 150 ". Before starting and after 72 hours, the adhesiveness was examined with the Tesa test. No reduction in adhesiveness was observed.

Examples 48 and 49

Beverage cans were punched out of the composites from examples 4 and 38. These were sterilized for 30 minutes at 78°C and 100°C in water. The investigation showed that the composite was completely resistant (no water absorption, no loss of adhesiveness).

Claims (7)

1. Thermoplastic composite foil, consisting of at least one primer layer (3) and at least one additional thermoplastic layer (2) arranged on the primer layer, characterized in that the thermoplastic composite foil exhibits ring- or disk-shaped bead-like thickenings on the primer and/or cover layer and that the bead-like thickenings form a pattern that repeats both in the transverse and longitudinal direction. 2. Thermoplastic composite foil according to claim 1, characterized in that the bead-like thickenings have a thickness of at least 2 µm, preferably at least 50 µm. 3. Thermoplastic composite foil according to one of claims 1 or 2, characterized in that the thermoplastic composite foil has a total thickness of less than 500 µm, preferably from 10-300 µm. 4. Thermoplastic composite foil according to one of claims 1-3, characterized in that the thickness of the primer layer on the thermoplastic composite foil is between 0.5 fim and 100 fim, preferably between 1 fim and 70 fim, and that the thickness of the covering layer of the thermoplastic composite foil is between 10 µm and 499.5 µm, preferably between 10 µm and 200 µm. 5. Thermoplastic composite foil according to one of claims 1-4, characterized in that the cover layer (4) of the thermoplastic composite foil consists of a foamed polymer. 6. Procedure for the production of a thermoplastic composite foil consisting of at least one primer layer (3) and at least one further, on primer the middle layer comprises a thermoplastic layer (2), characterized in that one A) 1. extrudes a thermoplastic foil or a multi-layer composite foil of primer and cover layer and during or after the extrusion shapes it so that one surface of the foil exhibits ring- or disk-shaped bead-like thickenings that form a pattern that repeats both in the transverse and longitudinal direction, and the other surface is either flat or contains the bead-like thickenings in negative form, i.e. as recesses, and 2. coats the thus produced surface-structured foil on its flat surface or on the surface with the recesses with a primer or a co-extruded layer-shaped polymer composite with the same or different primer layers on both surfaces of the polymer composite so that the surface structure of the thermoplastic cover layer is maintained, or B) the thermoplastic composite foil is produced by co-extrusion of the primer and cover layer and subsequent shaping of it thermoplastic composite foil such that the covering layer exhibits the aforementioned bead-like thickenings, or C) the thermoplastic composite foil is produced by first joining a planar thermoplastic monofoil or a composite with a primer layer or a polymer composite, where at least one surface consists of a primer layer, and then shaping it thus obtained flat thermoplastic composite foil so that one surface becomes flat and the other exhibits the aforementioned bead-like thickenings. 7. Use of a thermoplastic composite foil, consisting of at least one primer layer (3) and at least one additional thermoplastic layer (2) arranged on the primer layer, where the thermoplastic composite foil exhibits ring- or disk-shaped bead-like thickenings on the primer and/or cover layer and that the bead-like thickenings form a pattern that repeats both transversely and longitudinally, for coating sheet metal especially for the manufacture of packaging containers.