DE102008030934A1 - Production of plastic film for packing such as butt-ended bags useful as food package for humans or animal and for dry, damp/liquid food, comprises stamping the plastic film in longitudinal direction to receive asymmetric groove structure - Google Patents

Abstract

The method for producing a plastic film (1) for packing such as butt-ended bags useful as a food package for humans or animal and package for dry, damp or liquid food, comprises stamping the plastic film in longitudinal direction to receive an asymmetric groove structure (2). The groove walls are located in an angle of 90-45[deg] C to the film surface. The structure is intercepted by bars (3), which have a length of 50-1000 mu m and the portion of the bars is less than 50% of the total length of the groove structure. The distance between the grooves and/or intercepted grooves is 0.05-0.5 mm. The method for producing a plastic film (1) for packing such as butt-ended bags useful as a food package for humans or animal and package for dry, damp or liquid food, comprises stamping the plastic film in longitudinal direction to receive an asymmetric groove structure (2). The groove walls are located in an angle of 90-45[deg] C to the film surface. The structure is intercepted by bars (3), which have a length of 50-1000 mu m and the portion of the bars is less than 50% of the total length of the groove structure. The distance between the grooves and/or intercepted grooves is 0.05-0.5 mm. The asymmetrical structure on the film top side has a width of 300-500mu m and a depth of 50-300 mu m. The grooves of the plastic film are arranged on the side turned to the layers. An independent claim is included for a plastic film for packing purposes.

Description

The Invention relates to a process for producing a plastic film, as well as the plastic film itself and its use, which by Embossing has an asymmetric structure.

STATE OF THE ART

From the DE 103 20 429 a composite film for tear-open packaging is known, which has a notch-shaped weakening line. In a preferred embodiment, such an inner film having such notch-like weakening lines is laminated as a strip to an outer film. The notch-like structuring takes place only on one side of the film, with the opposite side of the film remaining unchanged and flat.

Moreover are methods for laser perforation to improve the up and down Tear propagation behavior become known, which in addition to the elaborate technical realization on a production scale a destruction resulting in the continuous film surface, which is undesirable in a variety of particular packaging applications is.

DETAILED DESCRIPTION

Of the Invention is based on the object, a process for the preparation to provide a plastic film, with an easy on and tear-resistant plastic film is produced, the one preferred tear direction and optionally additional Has cracking effects.

The The object is achieved according to the invention, that the plastic film by embossing an asymmetric Structure receives. Due to the asymmetric structure of the embossing the tensile strength and direction of tear can be adjusted to the respective specifications adjust accordingly.

additionally becomes a special acoustic one due to the asymmetrical structure and haptic effect, which is an advantageous distinguishing feature can be, especially if it is the asymmetric structures around individual embossed structures and not through continuous groove structures is. These differences can also be used if For example, different structures on the roll width which are to areas with different tear behavior to lead.

By the choice of asymmetric structure can also be the Discharge or emptying behavior when using the plastic film affect the packaging of liquid media. The wetting surface At the crack edge can hereby to achieve the so-called lotus effect be educated.

in the The scope of the present invention means an asymmetric structure a structure that covers both the top of the film and the underside of the film changed, so that they are not plan anymore, the Extent of change, however, varies on the both sides. The following is called the top of the film, the page the film referred to, acts on the embossing tool or has acted. The lower side of the film consequently has a weaker one Embossing of the negative mold on.

Advantageous the embossing of the asymmetric structure takes place with the help of a structural or embossing calender. This calender features in a preferred embodiment over one another in height direction arranged, oppositely rotating rollers, with a distance are arranged to each other, wherein the provided with a structure plastic film supplied to the rollers and through the forming nip is passed. It goes without saying that the Gap width between the at least two rollers optionally set can be. One of the two rollers is doing with a comparatively hard surface, whereas the other roller has a comparatively less hard surface and for example of an elastic material, for example Rubber is formed. The harder of the two rollers carries in negative form to be impressed into the plastic film Template. The opposite of this roller other roller serves as a pressure roller and pushes the with a Structural or embossed pattern to be provided plastic film against the embossing roll. As a result, you get yourself a plastic film provided with an asymmetric structure.

The Creation of the negative form of the structure to be impressed (ie, for example, the embossing roller) is carried out according to those skilled in the art known and customary methods, depending on the structure and materials specific processes may be particularly advantageous can.

Usually and to the preferred straight forwarding of the crack the embossing roll a parallel and perpendicular to the roll axis Arrangement of the structures to be impressed on the formative Roller area on. However, there are also deviations from z. B. the vertical arrangement conceivable to meet specific requirements (tearing off a Packaging corner) to meet.

In principle, the structures on the embossing roll can either have a continuous structure or else as an interrupted structure (sequence of individual embossed structures), wherein a combination of both structures is also possible.

The respective structures on the embossing roll can have a variety of geometric shapes, depending on intended asymmetric structure of the plastic film.

A Possibility for a continuous asymmetric Structure is a groove structure with the groove walls perpendicular or even at an acute angle to the film surface can stand, for example, at an angle of 90 ° to 45 ° to the film surface. Also, the groove bottom in addition to the parallel to the film surface alignment in the concave shape, up to a spritz tapered notch shape taking.

interrupted Asymmetric structures are derived from the general ones described Groove shape by the groove more or less pronounced Has webs. Depending on the geometry of the webs then arise in the supervision, for example, rectangular, round, oval or pointed tapered single embossed structures. The webs can for example, have a length of up to one centimeter, preferred is a length of 0.001 mm to 10 mm and especially preferably a length of 50 microns to 1000 microns. The proportion of webs in the total length of the groove structure is at most 50%, preferably from 5% to 45% and especially preferably from 10% to 40%. Preferably, the webs are in uniform Interspersed, but it can also be alternating Distances are provided.

advantageously, have, for example, arranged in parallel, interrupted, Asymmetrical structures, the webs from one to the adjacent structure offset in order to forward the crack in the desired To ensure direction.

Of the Distance between the asymmetrically arranged preferably in parallel Structures (grooves or interrupted grooves) is preferably from 0.01 mm to 10 mm and more preferably from 0.05 mm to 0.5 mm.

It has according to a further embodiment of the Invention also proved to be extremely advantageous if the asymmetric structure on the top of the film has a width from 50 μm to 1000 μm, preferably from 300 μm up to 500 microns.

Also it is very advantageous if the asymmetric structure measured from the top of the film, a depth of at most the thickness, preferably from 10 to 90% of the thickness, more preferably from 50 to 90% of the thickness Has thickness of the film. Depending on the film thickness Thus, preferably result structures with a depth, measured from the top of the film, from 10 μm to 1000 μm, preferably from 50 microns to 300 microns.

With such a dimensioning of the asymmetric structure becomes produces an excellent tear behavior.

It has according to a further embodiment of the Invention proved to be advantageous when the embossing of the asymmetric structure takes place in the film longitudinal direction. This allows the plastic film very easily and continuously, for example, by the embossing calender described above, provided with the asymmetric structure.

A further, very advantageous embodiment according to the invention consists in a heat supply to the plastic film, so that the asymmetric imprint on a heated Plastic film is performed. The heat supply can in this case on the rollers, such as the embossing roller leading rollers for film guidance, done or but done by warm air or heat radiator. Depending on the type the plastic film has temperatures of 40 to 90 ° C, for example, for polyethylene (PE) or polypropylene films (PP), proven.

A further, very advantageous embodiment according to the invention also lies in the fact that the film produced by the glass process becomes. The glass process has proved to be a very good option for cheap but high-quality film production proved.

Also It is very advantageous if the film in their production until is cooled in its crystalline temperature range. This has to endure that the plastic film so produced is easily tear-resistant.

A further, inventive advantageous embodiment is in that the plastic film is cooled on both sides, d. H. in the blown film production both on the outside than also on the inside of the plastic film tube. It has also proved to be very beneficial when cooling off takes place by means of tempered air. This is possible control the cooling behavior very accurately, with the cooling with different temperatures on the inside and the outside the plastic tube can be done advantageously. Especially advantageous It is also when the cooling with a defined cooling gradient he follows. By specifying a defined cooling gradient the achieved properties of the film are particularly good adjust and the tear propagation behavior even further improve. The molecular chains can thereby be specifically arranged or fixed.

A further advantageous embodiment of the invention is characterized in that that the cooling downstream of a so-called annealing zone is.

The inventive method is further improved if in the blown film production the expansion ratio between extrusion nozzle diameter and finished film tube diameter less than 2.5, preferably less than 1.8. As also very beneficial it has turned out, if according to the invention Deduction ratio, d. H. the quotient of extrusion gap and film thickness at least 1, preferably at least 20 and especially preferably at least 35.

According to one advantageous embodiment of the invention is a plastic film manufactured, which in the finished state has a thickness of 10 microns to 1500 microns, preferably from 40 microns to 400 microns having.

Especially Advantageously, the method is used when the plastic film made from a badly tearing plastic. When using a poorly tearing plastic ensures that it does not overlap different tear properties comes, but this exclusively by the asymmetric structure according to the present invention Be determined invention.

According to the invention It is very beneficial if the plastic film turns out to be a bad one tearing PP is made. It has been shown that a variety of polypropylenes are badly tearing. Another advantageous embodiment of the invention Method is characterized in that the plastic film is produced as a monofilm of PP homopolymer. Also very beneficial is it. if according to another embodiment the inventive method, the plastic film as monofilm from blends of PP homopolymer with ethylene-propylene Block copolymer and or random PP is produced. One too very advantageous embodiment of the invention Method is characterized in that the plastic film is produced in the coextrusion process, wherein at least one the coextruded layers consists of PP homopolymer. Another very advantageous embodiment of the invention is also in that the PP homopolymer or the PP copolymer nucleases is. It is also extremely advantageous if the melt flow index (MFI) of the film material greater 0.5, preferably greater than 1.5. Through both Measures become the desired film properties improved again.

In Another embodiment of the invention is the plastic film made of polyethylene (PE). It has been shown that a Variety of polyethylenes are badly tearing. A further advantageous embodiment of the method according to the invention is characterized in that the plastic film of HDPE or also especially from poorly known known LDPE, LLDPE or MDPE will be produced.

According to Another embodiment relates to the present invention also plastic films, which by embossing an asymmetric Structure have. For these inventive Plastic films are as above for the manufacturing process described preferences and particular embodiments in analog Wise.

According to Another embodiment relates to the present invention also the use of the inventive plastic film for packaging purposes. By imprinting the asymmetric Structure, the formed packaging can be opened easily and defined.

It has proven to be advantageous when the inventive Plastic film joined together with other packaging material layers is.

there it is very advantageous according to the invention, if the plastic film laminated together with other packaging materials is.

In order to can be adapted very well to the respective application Form packaging.

According to one further embodiment, it is extremely advantageous if the plastic film according to the invention the tear behavior the packaging determined.

Thereby can not only tear the plastic film defined, but also the whole packaging, which consists of several different ones Packaging materials may be formed.

One possible use of the films according to the invention is the use for the production of flexible packaging, for example of stand-up pouches. Here, the packaging is usually closed at both sides by welds. In a weld seam then a notch can be arranged, which serves as a tear-open. If the packaging is torn open at the notch, it tears along a predetermined line. Depending on the asymmetric embossing and the packaging material or packaging structure used, lighter or heavier tear properties can be set. By embossing individual structures, the acoustic and haptic effects can be varied over a wide range. The tearing ent Long of a predetermined line or contour is generated by the embossing of the asymmetric structure, as described above, and again exemplified in the exemplary embodiment.

to Production of this plastic film are usually bad tearing Plastic materials used, so that the tear behavior the finished plastic film by their asymmetric structure and whose production process is determined and no undesirable, material-related effects occur. That is why it is also conceivable that a nucleated polypropylene homopolymer or copolymer with a MFI greater than 2 on a blown film line is extruded. The gap width of the extruder blower head is thereby for example, set to 2 mm. The trigger and the expansion the film tube can be adjusted so that the Expansion ratio is 1.6. Shortly after the extrusion the film tube is cooled. Cooling can be for example through inner and or outer Cooling air supply done. It is conceivable that the cooling down is not only fast, but also in several stages, which, for example, the orientation the molecules are frozen down. It is also conceivable that the cooling over a given gradient, so that the film, for example linear to approximately room temperature within 30 seconds is cooled. It is also conceivable that through Supply of different tempered cooling air not only the gradient of cooling, but also the Temperature difference between film and cooling influenced will improve the tear properties. It can also still a different cooling on the inside and the outside of the film tube are provided by, for example, different tempered cooling air is supplied. But it is also conceivable that the Foil is produced in the cast process and there the two sides of the film analog be treated. Possible cast methods are in particular the casting of the melt on a correspondingly structured chilli roll, casting into an embossing gap and inline embossing in a subsequent, correspondingly structured calender. It can also be followed by an annealing zone in which the film is reheated, resulting in not only the flatness of the film and the roll quality can positively influence, but also the tearing properties improve again and have it changed in a defined way. The resulting films usually have a thickness between 10 μm and 1500 μm, preferably between 40 μm and 400 microns and can as monofilms from the above raw material, blends thereof or else as coexfolien with be formed at least one such layer.

For Packaging is often laminated PET, aluminum, polyethylene, Polypropylene and other comparable materials used. such Composite films are often used only packaging in which to open the packaging particularly light and defined should be. It is important that the tearing only along a desired line or at least approximately takes place along this line. Such a tear behavior is often complicated by paints, labels or other aids generated. In addition, in these known films often still a laser perforation in one of the film layers attached, to support this tearing behavior. One such behavior is known as easy-tear behavior. The inventive On the one hand, plastic film is able to replace such film composites and on the other hand to optimize so that this in a simple way and obtain the desired tear properties, without relying on tearing aids. It will be by the plastic film according to the invention the Tear properties improved again. On perforations can be dispensed with.

According to Another embodiment relates to the present invention also packaging, which using the inventive plastic film produced.

Especially Advantageously, the packaging is food packaging for food for humans or animals. The inventive Plastic film makes it possible to dry in addition to the packaging Food also especially the packaging more moist or liquid Food.

The Invention will be illustrated with reference to an embodiment.

Embodiment

1 shows a section through a plastic film according to the invention.

The plastic film 1 is provided with an asymmetrical structure consisting of a plurality of parallel aligned grooves 2 consists, in addition to a continuous groove structure and an interrupted arrangement of individual embossed structures is possible, as described above. In a packaging structure consisting for example of a PET cover layer and an aluminum foil layer, the grooves 2 in the direction of the surface facing away from the other layers of the plastic film 1 be aligned. Other structures are also conceivable. So it is conceivable that individual grooves 2 are provided, which need not necessarily be linear and / or parallel to each other. It is also conceivable that the plastic film 1 between two layers of the Packing structure is arranged. It is also conceivable that the grooves 2 are arranged on the other layers of the packaging structure facing side. If a package consisting of, among other things, the plastic film shown is torn open, the crack along one of the grooves 2 directed. For example, if the crack breaks out of this groove due to material inhomogeneity or the like 2 it will pass through the next groove 2 directed. The grooves 2 are so pronounced that they are able to conduct the crack despite possible further layers of other, even undefined tearing packaging materials. The grooves 2 have a width of 50 microns to 1000 microns, preferably from 300 microns to 500 microns on the top of the film. The between the grooves 2 arranged webs 3 (Distance between two grooves) have a width of 10 .mu.m to 10000 .mu.m, preferably from 50 .mu.m to 500 .mu.m. The depth of the grooves 2 , measured from the plastic film top, is between 10 .mu.m and 1000 .mu.m, preferably between 50 .mu.m and 300 .mu.m. Such a plastic film which determines the breaking behavior of a package can be produced by providing it with the asymmetrical structure after the film has been produced. The structure is impressed into the film and can be oriented in a continuous production in the film longitudinal direction.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10320429 [0002]

Claims (38)

Process for producing a plastic film, characterized in that the plastic film is given an asymmetrical structure by embossing. Method according to claim 1, characterized in that that the structure is a groove structure. Method according to claim 1 or 2, characterized that the groove walls at an angle of 90 ° to 45 ° to Slide surface stand. Method according to one of claims 1 to 3, characterized in that the structure is interrupted by webs Groove structure is. Method according to claim 4, characterized in that that the webs maximally a length of one centimeter and the proportion of webs less than 50% of the total length the groove structure is. Method according to claim 4 or 5, characterized that the webs have a length of 50 microns to 1000 microns exhibit. Method according to one of claims 1 to 6, characterized in that the distance between the grooves or interrupted grooves of 0.01 mm to 10 mm. Method according to one of claims 1 to 7, characterized in that the distance between the grooves or interrupted grooves of 0.05 mm to 0.5 mm. Method according to one of claims 1 to 8, characterized in that the asymmetric structure on the Film top has a width of 50 microns to 1000 microns having. Method according to one of claims 1 to 9, characterized in that the asymmetric structure on the Film top has a width of 300 microns to 500 microns having. Method according to one of claims 1 to 10, characterized in that the asymmetric structure, measured from the top of the film, a depth of 10 to 90% of the thickness the film has. Method according to one of claims 1 to 11, characterized in that the asymmetric structure, measured from the top of the film, a depth of 10 microns to 1000 microns having. Method according to one of claims 1 to 12, characterized in that the asymmetric structure, measured from the top of the film, a depth of 50 microns to 300 microns having. Method according to one of claims 1 to 13, characterized in that the asymmetric structure in the film longitudinal direction is impressed. Method according to one of claims 1 to 14, characterized in that the plastic film made of polypropylene (PP) blends of PP homopolymer with ethylene-propylene block copolymer and / or Random PP, coextruded layers of PP homopolymer or PP copolymer or PP homopolymer or PP copolymer which is nucleated, will be produced. Method according to one of claims 1 to 14, characterized in that the plastic film made of polyethylene (PE) such as HDPE, LDPE, LLDPE or MDPE is produced. Use of one of claims 1 to 16 produced plastic film, characterized in that the plastic film is used for packaging purposes. Use according to claim 17, characterized in that the plastic film ( 1 ) is joined together with other packaging material layers such as PET and / or an aluminum foil. Use according to claim 18, characterized in that the grooves ( 2 ) of the plastic film ( 1 ) are arranged on the side facing away from the further layers. Use according to one of claims 17 to 18, characterized in that the packaging is a stand-up pouch packaging is. Use according to one of claims 17 to 20, characterized in that the packaging as food packaging intended for food for humans or animals is. Use according to one of claims 17 to 21, characterized in that the packaging as packaging for dry, moist or liquid food is determined. Plastic film, characterized in that it by embossing has an asymmetric structure. Plastic film according to claim 23, characterized that the structure is a groove structure. Plastic film according to claim 23 or 24, characterized in that the groove walls in at an angle of 90 ° to 45 ° to the film surface. Plastic film according to one of the claims 23 to 25, characterized in that the structure is a through Webs broken groove structure is. Plastic film according to claim 26, characterized in that that the webs maximally a length of one centimeter and the proportion of webs less than 50% of the total length the groove structure is. Plastic film according to claim 26 or 27, characterized characterized in that the webs have a length of 50 microns have up to 1000 microns. Plastic film according to one of the claims 23 to 28, characterized in that the distance between the Grooves or interrupted grooves of 0.01 mm to 10 mm. Plastic film according to one of the claims 23 to 29, characterized in that the distance between the Grooved or interrupted grooves from 0.05 mm to 0.5 mm. Plastic film according to one of the claims 23 to 30, characterized in that the asymmetric structure on the film top a width of 50 microns to 1000 microns having. Plastic film according to one of the claims 23 to 31, characterized in that the asymmetric structure on the upper side of the film has a width of 300 microns to 500 microns having. Plastic film according to one of the claims 23 to 32, characterized in that the asymmetric structure, measured from the top of the film, a depth of 10 to 90% the thickness of the film has. Plastic film according to one of the claims 23 to 33, characterized in that the asymmetric structure, measured from the top of the film, a depth of 10 microns up to 1000 microns. Plastic film according to one of the claims 23 to 34, characterized in that the asymmetric structure, measured from the top of the film, a depth of 50 microns has up to 300 microns. Plastic film according to one of the claims 23 to 35, characterized in that the asymmetric structure is impressed in the film longitudinal direction. Plastic film according to one of the claims 23 to 36, characterized in that the plastic film made of polypropylene (PP) blends of PP homopolymer with ethylene-propylene block copolymer and / or random PP, coextruded layers of homopolymer PP or PP copolymer or PP homopolymer or PP copolymer which nucleates is produced. Plastic film according to one of the claims 23 to 36, characterized in that the plastic film made of polyethylene (PE) such as HDPE, LDPE, LLDPE or MDPE is produced.