Film consisting of at least two layers

Abstract

The disclosure relates to a film having a longitudinal direction, which consists of at least two layers, an aluminium layer and a layer of heat-sealable coating, wherein the coating covers the surface of the film differently, optionally only in some parts. The disclosure is characterised in that - the coating is applied in stripes which extend at an angle to the longitudinal direction, - adjacent stripes of the coating have different coating thicknesses, - the coating thickness of the thin stripes is between 0µm and 1.5µm, preferably between 0.8µm and 1.3µm, and - the coating thickness of the thick stripes is approximately 2.5µm to 3.5µm. The stripes preferably extend less than 45° to the longitudinal direction; they can be in a straight line and / or wave-shaped and / or zig-zag-shaped. The film, embossed or unembossed (smooth aluminium layer), can be used for packaging purposes.

Description

[0001] Film made of at least two layers

[0002] The disclosure relates to a film having a longitudinal direction which consists of at least two layers, an aluminum layer and a layer of heat-sealable lacquer, and which is intended in particular for packaging objects, and here again in particular foodstuffs, such as chocolate and the like.

[0003] The aluminum layer, which is a continuous material with a longitudinal direction, can consist of so-called soft or hard aluminum, as are well known in the prior art. Heat seal lacquer (HSL) in its various variants is also well known; reference is made to DE 10 2001 086 372 A, EP 0 574 803 B, WO 2011 / 017 388 A, DE 102 56 493 A, and JP 2010-132 911 A, which relate to so-called aqueous HSL. Solvent-based HSL are also included; although they are increasingly avoided in the food industry, they are advantageous or at least accepted in numerous other applications; reference is made to DE 10 2011 112 951 A.

[0004] In the technical field of this disclosure, there has long been a desire to use as little heat-sealing lacquer as possible. This is not only for economic reasons, in order to save on sealing lacquer, but also for ecological reasons, since, on the one hand, this allows for savings in the use of natural raw materials during production, and, on the other hand, a reduction in environmental impact corresponding to the overall reduction in mass can be achieved when recycling the film. It should be noted here that in this disclosure, the terms heat-sealing lacquer, HSL, sealing lacquer, lacquer, and also simply "material" are used synonymously and are synonymous.

[0005] Common films for the above purposes have a coating weight (grammage) of at least 3g / m 2(containing the "3,000...", technical point of view, not mathematical). The varnish is applied evenly over the entire surface of the continuous material in the form of an aluminum foil, which has a thickness of, for example, 10 μm, in special cases between 7 μm and 50 μm, including the limit values. As an example in connection with such an effort to save HSL, reference can be made to WO 2017 / 089919 A1, which proposes arranging diagonally running, parallel strips of alternating cold-seal material and heat-seal material along the continuous aluminum web. This arrangement is specifically used to individually wrap objects such as candies or sweets, with the protruding ends being twisted and finally the twisted ends being glued "into themselves."Since the use of cold seal varnishes on continuous material, which is common practice and cannot be avoided, is very unpleasant, as it tends to stick together and become unusable when wound up, or at the latest during longer storage, in the rolled-up state, and therefore commercial use on a larger scale is not possible.

[0006] The reason for applying the stripes diagonally to the continuous material is primarily that the thickness differences of the entire film do not cause problems when winding the continuous material; this applies to both longitudinal and transverse stripes, despite the marginal thickness of the varnish application and the resulting small thickness differences of the entire film composite.

[0007] There have also been attempts to apply the heat seal lacquer only in the form of parallel, spaced-apart stripes, without stripes of cold seal lacquer in between, but such "patterns" of heat seal lacquer have not produced a reliably tight package when, for example, they are folded around a piece of chocolate and then sealed along the three open sides. These attempts will be discussed in more detail below.

[0008] In another context, WO 2021 / 144687 A1 discloses applying adhesive only point by point to a label to allow easy removal from the object to which it is adhered. KR 101 320 300 B1 aims to create a multilayer film with air-permeable channels within it. It achieves this goal by applying pressure-sensitive adhesive (PSA) between two adjacent layers of the film in a special strip shape. At least one of the two layers is embossed with a special pattern to form the channels.

[0009] US 2017 / 0081569 Al concerns a circuit board (lid) for a coffee capsule, in which the focus is on compressive strength rather than on saving HSL, and in which the lacquer is applied over the entire surface.

[0010] The paint application itself is known in many different ways from the state of the art and will only be dealt with briefly and roughly here for the purpose of explanation.

[0011] This can be achieved, for example, through a painting or printing process, particularly screen printing. The HSL can be applied to the aluminum sheets, which are usually already printed on the visible side, with sufficient precision in terms of surface coverage and tolerances, either partially or fully, or with a particularly limited layer thickness.

[0012] Another type of application is via a two-roller system or a three-roller system:

[0013] In the three-roller system, a smooth or slightly rough roller, the transport roller (or dipping roller), dips into the varnish in a trough, which it carries along on its casing as it rotates. A doctor blade ensures that the thickness of the varnish on this transport roller is as even as possible. By roughly linear contact, the varnish is transferred to a second, equally smooth roller, the applicator roller. The ratio of the rotational speeds of the two rollers determines the application rate. The continuous material is pressed against the applicator roller by the third roller, the counter roller, which is often rubber or plastic coated and smooth. In the two-roller system, the applicator roller dips directly into the trough and thus also acts as the dipping roller. Cup-like depressions (cups) are machined into its casing, into which the varnish is applied; the excess is wiped off with a doctor blade.The varnish is applied from the cups onto the continuous material; the cup size and cup depth determine the application quantity; the second roller is the counter roller.

[0014] On the continuous material, the cup-shaped application immediately blurs and runs to a virtually uniform thickness. All of this is state-of-the-art and requires no further explanation.

[0015] It is the aim and task of the disclosure to make such an improvement that, with possible economical use of lacquer, a reliable, tight seal is achieved even with different sizes of the wrapped objects (chocolate bars, etc.).

[0016] It should be noted here that packers pack objects with different geometric dimensions, yet always want to use the same film because this simplifies storage and also simplifies the conversion of the packaging station to objects with different geometric dimensions because no changes need to be made to the roll of continuous material.

[0017] In another technical field, the sealing of yogurt cups and the like with a circuit board, it is known from EP 3 263 477 B1 to apply a heat-sealing layer and a layer of anti-adhesion material to a base layer on the circuit board, wherein the heat-sealing layer has stripes of varying thickness due to periodic changes in the density of fillers and is arranged beneath the adhesion-reducing layer. The manufacturing costs are exorbitant, and the film is completely unusable for packaging of the type mentioned above. In yet another technical field, it is known from DE 10 2012 107 407 A1 to apply adhesive only to certain areas of the continuous material for packaging individual objects of the same size (and shape), and to use different grammages (applied mass / m 2). Application in the form of stripes or dots is also disclosed. Apart from the complex production of the continuous material, the main disadvantage, as briefly mentioned above, is that a single roll of continuous material can only be used to package items with exactly the same, specified dimensions. This is only accepted by customers in exotic, special cases due to storage requirements and the adjustments required when changing the items to be packaged.

[0018] There is therefore a need for a packaging material that enables trouble-free, tight packaging of objects of different sizes while reducing the coating weight as much as possible. The following story presents a solution to this problem.

[0019] The solution is to apply the heat-sealing lacquer in the form of parallel stripes (or bands, as you wish) of alternating thicknesses, i.e. different grammage, diagonally to the longitudinal direction of the continuous aluminum material.

[0020] When the HSL is applied using the two-roller system, the cups on the application roller are designed and / or arranged differently, resulting in the diagonal stripe pattern of the heat seal lacquer being formed on the continuous material.

[0021] The thin stripes preferably have a varnish thickness between 0.5 μm (actually: no application!) and 1.5 μm, preferably between 0.8 μm and 1.3 μm. The varnish thickness is preferably about 1 μm or just above. The thick stripes have a varnish thickness of about 3 μm (±10%). Naturally, the transitions from thick to thin are continuous, so the specified values ​​are averaged and must also be determined by averaging several measurements. This gives the total average grammage of the film of 3 g / m. 2 to 1.8g / m 2 reduced, which is particularly important considering the hundreds of millions of square meters of such films produced worldwide each year.

[0022] It is necessary to point out one peculiarity here: Packers usually require that the finished film be embossed (usually around 60% of the ordered areas of such films worldwide are embossed). The reason for this is purely aesthetic: Embossing eliminates the inevitable dents, edges, and other technically insignificant, but visually noticeable, defects in the smoothness of unembossed films. The embossing itself (which takes place after the application of the varnish) is also as unobtrusive as possible, but despite the minimal embossing depth, it means that when the thin strips are reduced to zero thickness, reliable bonding no longer occurs. Therefore, the lower grammage limit for the thin strips is the above-mentioned 0.8g / m 2However, if a packer uses unembossed film, known in jargon as "smooth" (despite the differences in the thickness of the finished continuous material), then the thickness of the thin strips can be reduced to zero (in effect, no order!), thus increasing the savings.

[0023] When embossing is provided, the lacquer thickness of the thin strips is preferably between 0.8 pm and 1.3 pm (including the respective limits).

[0024] Interestingly, the grammage does not require any change when applied to thicker or thinner aluminum foils than the usual 10pm stated above.

[0025] Examples of usable HSL systems include the following, without limiting the usability of the numerous HSLs:

[0026] Water-based varnish based on EAA (ethylene-acrylic acid copolymer)

[0027] Solid content: 25% (25-30%)

[0028] Kinematic viscosity (20°C): 100-150 mm 2 / s Water-based varnish based on EMA (ethylene-methyl acrylate copolymer)

[0029] Solid content: 27% (25-30%)

[0030] Kinematic viscosity (20°C): 100-150 mm 2 / s

[0031] The above applies in particular to food packaging, the following to other items:

[0032] Solvent-based varnish based on VC-VA acid (vinyl chloride-vinyl acetate acid copolymer)

[0033] Solid content: 28% (25-30%)

[0034] Kinematic viscosity (20°C): 100-150 mm 2 / s

[0035] To illustrate the production of such a film using an example, the following possible dimensions of the individual cells, produced by conventional etching, measured on the application roller, are given using the two-roll system:

[0036] For the application of the 3g / m2 HSL (technically understood, not mathematically, thus ±10%) of the thick strips 60 square cells / cm are provided, across this also 60 / cm (results in 3600 cells / cm 2 ), with a depth of 65 pm. For the thin stripes, 80 cells / cm are planned in both directions, with a depth of 15 pm. The cell depths are to be understood with a ±10% tolerance.

[0037] The width of the thin stripes (measured perpendicular to the direction of the stripe on the surface of the film) is, for the frequently occurring sealing jaw width of 10 mm (to be understood as technically precise, not mathematical, thus ±10%), practically between 4 mm and 6 mm, around 5 mm is optimal, and the width of the thick stripes is between 1 mm and 3 mm, here 2 mm is optimal. The thick stripes are therefore narrower than the thin stripes. For sealing jaws of other widths, these values ​​must be adjusted, which poses no problems for the person skilled in the art with knowledge of the disclosure. The lacquer or its thickness then runs approximately sinusoidally in the direction perpendicular to the stripe direction, with the thickness of the thin stripes of 0 mm with a flattening almost to zero, which still enables tight sealing with a smooth film.

[0038] It is advantageous if the cells on the roller are arranged at an angle so that their edges run in the direction of the strip or perpendicular to it.

[0039] For production using a printing technique as described above, the person skilled in the art can easily determine the appropriate parameters for the printing process using this information.

[0040] Surprisingly, it has proven advantageous to maintain a narrow, free gap on the applicator roller between a thick stripe and each adjacent thin stripe, preferably with a width (measured perpendicular to the stripe direction) that corresponds to 0.5 to 1.5 times the dimension of the "thick" cups in this direction. This results in gaps of l / 120cm (=> 0.083mm) to l / 40cm (=> 0.25mm) using the above values. This also simplifies the manufacture of the applicator rollers; these values ​​are to be understood as technical specifications, not mathematical ones, and are therefore ±10%.

[0041] Especially when the varnish is applied by printing, this can be done in two separate steps: In one step, the varnish is applied over the entire surface in the thickness of the thin stripes, and in a separate step, the varnish for the thick stripes is applied in stripes with a different thickness. The order of the steps is irrelevant.

[0042] The angle between the longitudinal direction (of the continuous material) and the direction of the strips is between 30° and 60° (including the boundaries), preferably between 40° and 50° (including the boundaries), and particularly preferably 45° (±2°). At 45° (±2°), the orientation of rectangular items to be packaged relative to the longitudinal direction is irrelevant during packaging and sealing.

[0043] Regarding the stripes, it should be noted that, for reasons of practicality, they preferably run in a straight line from the edge of the continuous material to the opposite edge. However, for optical reasons, which often play a major role in packaging of all kinds, it is possible to give the stripes a wavy and / or zigzag shape, so that a fictitious line averaged over the length of the stripes defines the oblique direction (central strip direction). It is clear to the person skilled in the art that, with such an arrangement, special consideration must be given to the width of the sealing jaw, which, given the disclosure, does not pose any problems. The angles specified above can serve as a guideline for the maximum deviation from the central strip direction.

[0044] The width of the sealing jaw, its temperature, the applied sealing pressure, the width, the spacing, and possibly the shape of the strips result in a continuous, curved / bent, sealed longitudinal area (sealing strip, not to be confused with the strips used for HSL application!) being created during sealing along the entire sealing length. This area has a minimum width throughout, which is specified by the packer based on the material and the desired tightness and robustness of the packaging. Based on this data, the specialist, with knowledge of the description and the HSL used, can easily determine the strips on the continuous material and thus the application details depending on the technique used.

[0045] Of course, further layers can be provided on the continuous material, especially on the outer side (display side); the disclosure does not change this; this is in line with the prior art and requires no explanation.

[0046] In summary, we can say:

[0047] The disclosure relates to a film with a longitudinal direction consisting of at least two layers, an aluminum layer and a layer of heat-sealable lacquer, the lacquer covering the surface of the film differently, optionally only partially, wherein the lacquer is applied in stripes which run obliquely to the longitudinal direction, that adjacent strips of the lacquer have different lacquer thicknesses, that the lacquer thickness of the thin stripes lies between 0m and 1.5pm, including the limit values, and that the lacquer thickness of the thick strips is approximately 2.5pm to 3.5pm, the limit values ​​being variable by ±10% in each case.

[0048] If the foil remains unembossed, in jargon “smooth”, the lacquer thickness of the thin stripes can be between 0.5 pm and 0.5 pm, including the lower limit, the upper limit can be varied by ±10%, so that in extreme cases only thick stripes are actually applied.

[0049] If the foil is embossed, the lacquer thickness of the thin stripes can be between 0.8 pm and 1.3 pm, the limits can be varied by ±10%.

[0050] The width of the thin strips is between 4mm and 6mm, the limit values ​​can be varied by ±10%, preferably 5mm, ±10%.

[0051] The width of the thick strips is between 1mm and 3mm, the limit values ​​can be varied by ±10%, preferably 2mm, ±10%.

[0052] If the film is produced with a two-roller system, good results are obtained if the application roller, measured in the direction longitudinal and normal to the stripes, has 60 square cells / cm for the thick stripes, and also 60 / cm across them. 2 , with a depth of the cells of 65pm, ±10%, for the thin strips 80 square cells / cm are provided in both directions, the depth of which is 15pm ±10%.

[0053] In this case, the application roller preferably has a distance in the form of a flat area between the stripes of the different cells, measured in the direction normal to the stripe direction, which is from l / 120cm (=> 0.083mm) to l / 40cm (=> 0.25mm), the limit values ​​being variable by ±10% in each case.

[0054] If the varnish is applied in two steps, particularly by means of a printing process, it is preferable to apply the varnish in the thickness of the thin stripes over the entire surface in one step and to apply the varnish for the thick stripes in stripes of the difference in thickness in a separate step. This leads to more repeatable results than the other way around, which is also possible, especially if you do not push the varnish to the limit.

[0055] The angle between the longitudinal direction and the strip direction is preferably between 30° and 60°, the limit values ​​each variable by ±10%, particularly preferably between 40° and 50°, the limit values ​​each variable by ±10% and very particularly preferably at 45°±2°.

[0056] The film can have stripes in a wavy or zigzag shape, in which case a mean stripe direction applies depending on the stripe shape.

[0057] Further explanations for professionals:

[0058] In the description and claims, unless otherwise stated, "substantially" means a deviation of up to 10% of the stated value, if physically possible both upwards and downwards, otherwise only in the reasonable direction; for degrees (angle and temperature) this means ± 10°.

[0059] All quantities and proportions stated without a specific indication, in particular those used to delimit the disclosure, unless they relate to concrete examples, are to be understood as having a tolerance of ± 10%, thus, for example: 11% means: from 9.9% to 12.1%. For ranges, the limit values ​​are included. In terms such as “a solvent,” the word “a” is not to be regarded as a numeral, but as an indefinite article or pronoun, unless the context indicates otherwise. The term “combination” or “combinations” stands, unless otherwise stated, for all types of combinations, starting from two of the components in question up to a plurality or all of such components; the term “containing” also stands for “consisting of.”

[0060] The term "smooth" poses particular difficulties because, upon closer inspection, the foils so described are not truly smooth due to the patterned lacquer coating. In this context, as well as in previously published documents concerning foils consisting of at least one layer of aluminum and a layer of heat-sealing lacquer (HSL), this term always means that they are not embossed; therefore, the aluminum layer is smooth, but the entire foil is not.

[0061] The discrepancy between the activity "becoming" and the state "are," evident to meticulous experts in this story, becomes clear when one considers the chronological sequence of production and use: The manufacturer knows from the order whether the foil will ultimately be embossed, and depending on this, he applies the HSL, as described above, in the appropriate thickness (thickness, grammage) and distribution—an activity. When it is finished, the state is achieved.

[0062] The features and variants specified in the individual embodiments and examples can be freely combined with those of the other examples and embodiments and can be used, in particular, to characterize the disclosure in the claims without necessarily including the other details of the respective embodiment or example.

[0063] The present disclosure also relates to an invention, but goes beyond it and in no way limits it, which is why disclosure or narrative or similar euphemisms have been used throughout.

Claims

Patent claims:

1. A film with a longitudinal direction consisting of at least two layers, an aluminum layer and a layer of heat-sealable lacquer, the lacquer covering the surface of the film differently, optionally only partially, characterized in that the lacquer is applied in stripes which run obliquely to the longitudinal direction, that adjacent strips of the lacquer have different lacquer thicknesses, that the lacquer thickness of the thin stripes is between 0m and 1.5pm, including the limit values, and that the lacquer thickness of the thick strips is approximately 2.5pm to 3.5pm, the limit values ​​being variable by ±10% in each case.

2. Film according to claim 1, characterized in that it is unembossed and thus the aluminum layer is smooth, and that the lacquer thickness of the thin strips is between 0.5 pm and 0.5 pm, including the lower limit, the upper limit being variable by ±10%.

3. Film according to claim 1, characterized in that it is embossed and that the lacquer thickness of the thin stripes is between 0.8 pm and 1.3 pm, the limit values ​​each being variable by ±10%.

4. Film according to one of claims 1 to 3, characterized in that the width of the thin strips is between 4 mm and 6 mm, the limit values ​​each being variable by ± 10%, preferably 5 mm, ± 10%.

5. Film according to one of claims 1 to 4, characterized in that the width of the thick strips is between 1 mm and 3 mm, the limit values ​​each being variable by ± 10%, preferably 2 mm, ± 10%.

6. Film according to one of the preceding claims, which is produced with a two-roller system, characterized in that, measured in the direction longitudinal and normal to the stripes, the application roller has 60 square cells / cm for the thick stripes, and also 60 / cm transversely thereto 2, with a depth of the cells of 65 pm, ±10%, and that for the thin stripes in both directions 80 square cells / cm are provided, the depth of which is 15 pm ±10%.

7. Film according to claim 6, characterized in that the application roller is arranged between the strips of the different cells, measured in the direction normal to the strip direction, has a distance in the form of a flat area ranging from l / 120cm (=> 0.083mm) to l / 40cm (=> 0.25mm), the limit values ​​each varying by ±10%.

8. Film according to one of claims 1 or 3, characterized in that the lacquer is applied, in particular by means of a printing process, in two steps, in that in one step the lacquer is applied over the entire surface in the thickness of the thin strips, and in that in a separate step the lacquer for the thick strips is applied in stripes in the difference thickness.

9. Film according to one of the preceding claims, characterized in that the angle between the longitudinal direction and the strip direction is between 30° and 60°, the limit values ​​in each case being variable by ±10%, preferably between 40° and 50°, the limit values ​​in each case being variable by ±10%, and particularly preferably at 45°±2°.

10. Film according to one of the preceding claims, characterized in that strips have a wave shape and / or zigzag shape.

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