AT520566B1 - Foil with a visually recognizable marking - Google Patents

Abstract

The invention relates to a composite material, at least comprising a substrate and a polyolefin layer, wherein the polyolefin layer has at least one optically detectable marking which covers a geometric area of the surface. The invention is characterized in that the geometric region of the marking has undergone a different thermal treatment, preferably cooling, in relation to the geometric surrounding region. The thermal treatment is preferably carried out by the polyolefin layer is applied to the substrate by an extrusion coating process and cooled by contact with a cooling roller, wherein on the opposite side of the cooling roller is a pressure roller in contact with the substrate, and that the Allpresswalze the mark in Form of depressions or recesses, elevations or deposits made of a material with a coefficient of thermal conductivity better or better than the environment, or a combination thereof.

Description

The invention relates to a film which has an optically detectable marking, according to the preamble of claim 1 and a method for producing an optically detectable marking on a film consisting of a substrate and at least one polyolefin layer, according to the preamble of claim 5.

Films consisting of a substrate and a layer of polyolefin are known in the art.

Thus, DE 10 2015 109 974 discloses such a laminate in which the substrate is metal-containing, and in which the layers brought together are treated with electromagnetic waves, whereby it comes to the composite. In order to obtain different binding force over the surface, it is provided to allow the electromagnetic waves to act correspondingly differently. Preference is given to using an adhesion promoter which becomes active at a temperature at which the other layers do not show any change. Numerous embodiments are given, it is also stated on the chill rolls without giving reasons that they can be smooth or structured.

DE 600 06 066 T2, corresponding to EP 1 146 170, seeks to provide for packaging purposes such a composite material with a smooth substrate surface for applying a pressure and a rough polyolefin surface to avoid blocking when singulating and proposes to use the cooling roll for the polyolefin rough. The same measure is also taken by EP 1 010 641.

From US 2017/0225444 an extrusion method is known in which the liquid (pasty) plastic material is applied to a cooled roller before the gap, so that its later free surface already cools, while the contact surface to the substrate still warm. There are numerous variants and designs.

Optically recognizable in the description and in the claims understood that visible to the naked eye markings on the side of the composite material on which the polyolefin layer is formed.

As a substrate may preferably be an aluminum foil, meant in the technical sense, not in the chemically pure sense of so-called hard or soft aluminum, preferably in a thickness of 10pm to 70pm used. Also composite materials consisting of plastic films, with or without aluminum, can be used.

For example, as examples of substrates without aluminum PET films, such as boPET = biaxially oriented polyethylene terephthalate, with titanium dioxide white colored PET but also metallized PET, or the like, as well as polypropylene films, such as CPP (= produced in cast film process) or boPP (= biaxially oriented) polypropylene films, which in turn may consist of several coextruded layers according to the prior art, or other films, ultimately also paper.

The substrates mentioned are in the subject of the application application of the invention, this is an extrusion coating process, coated with a polyolefin coating. The coating may consist of one or more coextruded layers according to the prior art. In this case, a co-extruded adhesion promoter (for example of ethylene / acrylic acid copolymer for adhesion to aluminum foil) can be used to achieve the required adhesion. Equally possible is the use of a previously applied to the substrate or otherwise applied adhesive primer.

The most important polyolefins that can be used for coating are polyethylene and polypropylene types. For the purposes of the application, all the various types covered by the named materials are understood. The term polyethylenes includes all various types, LDPE, LLDPE, HDPE, metallocene PE, etc. Also known in the art are polyethylene / copolymers (e.g., ethylene / vinyl acetate (EVA) or / 6

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Ethylene / methyl acrylate (EMA)).

Also, polypropylene (PP homopolymers) and polypropylene copolymers are useful, beyond other, in particular sealable, thermoplastic polyolefinic materials, as they are known in the packaging industry.

The coatings may, as is common practice, contain additives for improving the sliding properties or antiblocking additives or other additives commonly used in plastics processing. It is also quite possible that active-action additives (e.g., antimicrobial action) are incorporated into the coating. It has also been found that the optical effect according to the invention is also clearly visible in filled layers (for example with 30% talc in PE).

Field of application of the composites obtained according to the invention are customary flexible packaging materials, which can be made of these particular bag or stick packs. A special use is as a sealable masking tape, which is called as a sheet material or as a circuit board, also lid or lid, is present and in particular in connection with sensitive goods, thus in the field of pharmaceutical industry, electronics and the food industry, for closing cups , Cups, or other containers, usually by sealing. The use as a wrapping film, in particular, but without any limitation thereto, again on food and pharmaceutical products, including pharmaceutical equipment, disposable syringes, but also electronic components or the like, is to be mentioned. In the latter use, the sealing property of the olefin is in many cases irrelevant, the choice of the olefin is therefore particularly large.

The application of the polyolefinic coating to the substrate is preferably carried out according to the known from the prior art extrusion coating process, wherein the composite material between a cooling roll and a pressure roller, which usually interacts with at least one pressure transfer roller, substantially in the vertical direction from top to bottom is guided through the nip. In this case, on the side of the cooling roll, the molten shaped polyolefin film emerging from the extruder die is connected to the substrate by the contact pressure, while the material is cooled by the cooling roll and thereby "solidifies".

According to the invention, the inventively created markings are now achieved in such a method with the starting materials mentioned above, that on the surface of the pressure roller, which usually consists of steel and a plastic, rubber, polyurethane or rubber coating or a Coating of similar material, geometric patterns are formed with different heat transfer capacity. Thus, in a completely unexpected way, through the substrate, also over the surface of the coating film different heat dissipation is achieved because of the resulting different cooling rates, the morphological structure formation in the polyolefin layer varies and ultimately results in the formation of the optically recognizable geometric pattern on the side facing away from the roller of the film.

Polyolefins, as they were mentioned and are used according to the invention are semi-crystalline plastics, the structure of which is essentially dependent on the cooling rate, therefore, was also the word above: solidified under Gänsefüßchen set. If the cooling rate of the melt is sufficiently slow, the long molecular chains of the polymers can be partially ordered (one speaks of these (ordered) areas of (semi-) crystalline areas that form). The crystalline portions can be made to be better or better the slower the cooling, and the material subsequently has a milky-opaque appearance due to the light refraction properties and light scattering properties of the crystallites. If, on the other hand, a polyolefin is cooled very rapidly, so that the formation of ordered structures is suppressed, the plastic melt solidifies disorderly (glassy amorphous) and consequently has a clear, transparent

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AT 520 566 B1 2019-10-15 Austrian Patent Office optical appearance.

This different from place to place cooling can in principle be based on three causes on the surface of the pressure roller (also Anpresstrommel): It may be provided in the form of recesses or recesses, it may be in the form of elevations, or it may consist of a material with different thermal conductivity compared to the environment, possibly combinations of these measures. In all cases, when pressing the now coated with the hot melt film substrate to the cooling roller by these differences, possibly in combination with the different pressure from area to area contact pressure due to the depressions / elevations, which has an effect on the cooling rate, a different Abkühlhistorie leads to optical differences.

It is interesting that even when using one and the same pressure roller by different contact pressures and visually different results can be created. This is probably due to a change in heat dissipation when the contact pressure is changed.

If projections are chosen as active agents, and they are formed high enough, the affected areas of the film, substrate and polyolefin film, after cooling, by up to 50 pm and optionally more, can rise above the surrounding film surface. It is possible in this case, especially when using the film for boards, to use these bumps as a means against blocking when separating layers, as to the lower limit already 15 to 20 pm, depending on the structure of the film as a whole, sufficient.

When providing recesses or recesses, it may be on both sides by up to 5 pm to changes in the altitude of the surface (s), which are usually in every respect (print, adhesiveness, etc.) are irrelevant in the re-use; if inserts of other material are used, it depends on the position of the surface of the insert whether and to what extent geometric changes are made to the film.

By this measure according to the invention, the cooling rate of the olefin in the nip is sufficiently affected to crystallize at least partially and not only to harden like a glass can, resulting in the different visual appearance. The cooling rate can be additionally influenced by the process control, in particular by the difference between the melting temperature of the polyolefin (usually between 230-320 ° C) and the cooling roll temperature (usually between 15-60 ° C), and, as already mentioned, by varying the contact pressure the pressure roller.

Despite the rapid passage of the continuous material through the nip, the areas are clearly and optically clean separated from each other and allow the application of letters, symbols, images, etc., as otherwise allows only the embossing of such products by means of embossing rollers.

As a significant peculiarity is to be considered that the thus created optically recognizable areas, the markings, when heated to slightly above 60 ° C, depending on the considered polyolefin and the duration of holding at elevated temperature, disappear, without the material liquid or even just pasty. This (one-time) reversibility is based on molecular rearrangements (recrystallization), which is significantly below the crystallite melting temperature. This can be used as additional protection or feature when used as a security element of a packaging, since imitators must produce the imitating only by printing process, and thus the application of foreign substances, which can not be made to disappear by heating They usually do not have a coextrusion line available.

This complete abandonment of foreign materials is in addition to the ability to apply the features directly in the coextrusion another significant advantage that provides the invention. Especially when used as packaging material are Mar3 / 6

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Patent Office on the side facing the product (contents) side without the use of additional chemical substances particularly advantageous because no questionable for the consumer substances migrate from the material and can go into the product.

The equipping of the pressure roller to create the optical features can be done in different ways, has proven the application of thin Teflon tapes, rubber tapes, polyurethane tapes or the like, which have the optical features in the form of punched (holes). It is quite possible with only partial application of the features on the endless material, these bands, or rings seen in the axial direction of the roller, only partially applied to the pressure roller, since their low strength (usually between 50 to 250 microns), probably sufficient in order to modify the contact pressure and thus the cooling rate and also to influence sufficiently through the substrate by the cooling rate of the polymer, but insufficient to lead to a plastic deformation (embossing) of the substrate, with the abovementioned limit of a maximum of 5 pm, which is possible with such processing steps.

It is of course also possible in the upper of the pressure roller, which, as stated above, a steel roller with an elastic, or elastically deformable sheath is to create these areas, for example, by depressions, but this has the disadvantage that such a costly Roller can then only be used for one type of marking, thus worthwhile only at extremely large production quantities.

In comparison, one and the same pressure roller can be equipped by applying the appropriate Teflon tapes or other bands within a short time for different markings.

Another option is to apply the markers by means of flexographic printing plates or flexographic printing plates or flexographic printing plates, which are used to create recesses instead of the usual increase in the marks to be printed in a kind of reversal these are excluded from the pressure so that they are recessed and so for a slower cooling down. When creating low height projections, the "usual" method is used.

Elevations can of course be created by sticking the corresponding geometric pattern, but also by ablating the environment.

The use of inserts, as in a marquetry surface, is the most complex process in principle, but also allows to use a pressure roller, wherein the steel surface is the outermost surface and having the recesses, can be introduced into the inserts, which Recesses, protrusions, different materials or corresponding combinations. As a result, one and the same roller can be used for almost any number of variants.

As examples of composite materials which can be used according to the invention and which can be treated accordingly, mention may be made only of:

1) aluminum 12pm, coextrusion coating consisting of adhesion promoter (ethylene / acrylic acid copolymer), 4g and sealing layer of EVA 10g.

2) aluminum foil 30pm, adhesion promoter (EAA), 8g, sealing layer (PE filled) 19g, and top layer of PE 3g.

3) aluminum foil 20pm hard, primer (painted) to obtain adhesion of the coating, coating of PE (15g)

4) boPET (biaxially oriented polyethylene terephthalate) 36 or 50 pm, primer (paint), coextrusion coating consisting of PE (8 g) and EMA (12 g).

5) PET, metallized 23 g, adhesion promoter from EAA (on the metallised side) 5g, sealing / peeling layer from filled PE-compound 18g.

6) aluminum foil 58pm, adhesive primer (painted), coextrusion coating consisting of unfilled PP compound, 5g; PP-Compound with filler, 15g and PP unfilled, 3 g.

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AT 520 566 B1 2019-10-15 Austrian

Patent Office Unless otherwise indicated, all mass data are to be understood in each case as "per m ² ". When speaking of "mark,""band,""roll,""indent,""lead," and all other such objects and terms in the singular or plural, it is always meant plural or singular, and only for readability the tedious option information omitted.

The invention may be variously modified, the individual features mentioned may be combined with each other in any combination other than in the explanations or examples, as long as only the label has been applied by the geometrically different thermal treatment of the polyolefin. For this it is also possible, for example, to cool the pressure roller. It is interesting that the effect according to the invention also occurs in poorly heat-conductive substrate, such as paper.

Finally, it is not necessary to carry out the coextrusion process set forth in detail, the marking can according to the invention also on a finished composite material by applying a stamp for heating and then applying one with the pattern (increase, depression, intarsia, as in the roller) provided Stamp for differentiated cooling are performed. This is especially suitable for small quantities or individual pieces.

In summary, it can be said that the invention relates to a composite material, at least comprising a substrate and a polyolefin layer, wherein the polyolefin layer has at least one optically detectable marking which covers a geometric area of the surface. It is characterized in that the geometric region of the marking has undergone a different thermal treatment, preferably a different cooling rate, relative to the geometric surrounding region.

In summary, the invention also relates to a method for providing a marked composite material in which the polyolefin layer is applied to the substrate by an extrusion coating process and cooled by contact with a cooling roll, wherein on the opposite side of the cooling roll, a pressure roller is in contact with the substrate is characterized in that the pressure roller the marking in the form of a recess, or a recess, or a projection, or an insert of a material with poorer or better heat conduction than that of the surrounding material, or a combination of these possibilities, having.

Claims (10)

A composite material, at least comprising a substrate and a polyolefin layer, wherein the polyolefin layer has at least one optically detectable marking which covers a geometric area of the surface, characterized in that the geometric area of the marking has undergone a different thermal treatment with respect to the geometric surrounding area , 2. Composite material according to claim 1, characterized in that the thermal treatment is a cooling. 3. The composite material according to claim 1 or 2, characterized in that the substrate is an aluminum foil, a PET film, for example of boPET and / or colored with titanium dioxide white, or a metallized PET film, a polypropylene film such as CPP or boPP film, respectively single layer or consisting of several coextruded layers, or paper, is. 4. The composite material according to claim 1 or 2, characterized in that the polyolefin is selected from the following group: polyethylene in the most diverse types such as: LDPE, LLDPE, HDPE, metallocene PE, polyethylene / copolymers, such as ethylene / vinyl acetate ( EVA), ethylene / methyl acrylate (EMA); Polypropylene in a variety of types such as PP homopolymers, polypropylene copolymers and other sealable thermoplastic polyolefinic materials known in the packaging industry. 5. A method for producing a composite material according to any one of claims 2 to 4, wherein the polyolefin layer is applied to the substrate by an extrusion coating method and cooled by the contact with a cooling roller, wherein on the opposite side of the cooling roller is a pressure roller in contact with the substrate , characterized in that the pressure roller has the marking in the form of recesses or recesses. 6. A method for producing a composite material according to any one of claims 2 to 4, wherein the polyolefin layer is applied to the substrate by an extrusion coating process and cooled by contact with a cooling roll, wherein on the opposite side of the cooling roll, a pressure roller is in contact with the substrate , characterized in that the pressure roller has the marking in the form of inserts made of a material with a poorer or better coefficient of thermal conductivity than the environment. 7. A method for producing a composite material according to any one of claims 2 to 4, wherein the polyolefin layer is applied to the substrate by an extrusion coating method and cooled by contact with a cooling roll, wherein on the opposite side of the cooling roll, a pressure roller is in contact with the substrate , characterized in that the pressure roller has the marking in the form of elevations. 8. The method according to claim 7, characterized in that the elevations protrude by more than 25 pm over the surrounding surface. 9. The method according to any one of claims 5 to 8, characterized in that the pressure roller is wound with at least one band made of plastic, in particular Teflon, made of rubber, or of rubber, or of polyurethane, the marking in the form of recesses or recesses, of elevations or deposits of a material having a coefficient of thermal conductivity better or better than the environment, or a combination thereof. 10. The method according to claim 9, characterized in that the pressure roller is a flexographic printing roll, which has the marking in the Flexodrucksleeve or Flexodruckklischee. No drawings for this