WO2013149695A1

WO2013149695A1 - Plastic bag with printable inner face

Info

Publication number: WO2013149695A1
Application number: PCT/EP2013/000681
Authority: WO
Inventors: Rudolf Haimerl; Thomas Rethschulte; Alfons Stahl
Original assignee: Bischof + Klein Gmbh & Co. Kg
Priority date: 2012-04-05
Filing date: 2013-03-08
Publication date: 2013-10-10
Also published as: HRP20151372T1; EP2744721B1; DE202012003520U1; ES2550235T3; DK2744721T3; HUE026265T2; EP2744721A1; SI2744721T1; RS54255B1; PL2744721T3

Abstract

The invention relates to a plastic bag (1) with at least two walls (2, 3) which are connected by seams (4, 12) and which are made of a polyethylene monofilm or a layered film with a polyethylene layer on the inner face of the bag (1). The inner face is modified by a corona treatment or a similar printing pretreatment of the surface in order to improve the printability. The bag is designed to be usable with respect to the problematic heat sealability of printing-pretreated polyethylene surfaces to one another for the purpose of a machine-adapted processing with quick work cycles, such as the processing which is already used for unpretreated surfaces, by forming at least one seam between the pressure-pretreated inner faces of the walls (2, 3) as a sealing seam (12) with an intermediate layer (14) as a film made of a polyolefin which is not modified in the surface and the melting point of which does not lie above the melting point of the film of the plastic bag.

Description

Plastic bag with printable inside

The invention relates to a plastic bag according to the preamble of claim 1.

Plastic bags of this type are usually formed from sheets or pieces of flat films which obtain an at least partially closed bag shape by means of seams, in which films to be bonded are brought to a softening temperature and then sealed together with pressure. Because of the rapid and simple heating, use is made to a large extent of the low-melting polyethylene material, which is formed as a uniform film (mono-film) or as a layered film with at least one exposed polyethylene layer. The layer film also benefits from the good heat-sealability of the polyethylene, when it is to be connected to one another by way of another layer film via the polyethylene layers.

However, polyethylene is inherently poorly printable material. If polyethylene mono-film or a polyethylene surface of a film layer to be printed, usually a pressure pretreatment with a corona treatment is provided. The changed surface is then easy to print, but more difficult to seal.

The desire to lay the printing of packaging material such as the plastic bags considered here on the inside of the bag to the printed image with it To protect against abrasion, scratches or dirt during the delivery, storage or consumption of the packaged goods is becoming increasingly greater. Moreover, with a clear plastic film, a gloss effect can be achieved for the printed image, which otherwise can only be achieved with a "fair print" on the outside with a lacquer coating. However, a pressure on the inside of the bag or just a pressure-preparing surface treatment of the inside creates problems for the seaming of the bag walls, which are regularly sealed with the inside superimposed.

The problems in heat-sealing pressure-pretreated polyethylene surfaces occur in particular in sealing seams in the area, so if the film is not to be severed. Edge seams are reliably executed as separating seams in which the entire film thickness is cut with a hot tool. Any pressure pre-treatment is not critical in the case of dividing seams, since the foils are integrated into the sealing process over the entire thickness. More critical is the connection with a seam at such seams, which run in the area and which should receive only a superficial connection of the films.

This problem is conventionally taken into account that the seams with increased sealing temperature, extended sealing time, increased pressure and / or repeatedly performed, as mentioned for example in EP 2 324 992 A1 as a multi-stage welding. However, these measures are quite critical in terms of the necessary settings and could easily thermally melt through the film or mechanically overload. Especially at thin films and even with thin layers results in a problematic processing of the films, whereby a general development of the packaging films to always low wall thicknesses of, for example, about 40 μιη is observed. This is a development which is aimed at saving material and reducing packaging waste, but makes processing more difficult.

The object of the invention is accordingly to improve and simplify seam formation by heat sealing in polyethylene films or laminated films with a polyethylene layer, although these have poorly sealable surfaces which are modified in the seam area for better printability, the concerns of machine processability and the fast stroke in the production of such plastic parts with cutting of the film and seam formation are taken into account.

According to the invention, this object is achieved by a plastic bag according to the preamble of claim 1, starting with the characterizing features of claim 1.

An intermediate layer of a non-modified in the surface (not pre-treated) polyethylene reduces the sealing problems of druckvorbehandelten and / or printed polyethylene surfaces considerably by the fact that now not two pre-printed and / or printed surfaces must be superimposed and connected to each other On one side of the seam joint a regularly good sealable polyethylene for material pairing is available. In addition, the liner creates already by the introduction of additional material has an advantage in terms of the robustness of the films in the seam area, which are less susceptible to overstress even when subjected to the film material with greater heat, exposure time or pressing force of the sealing tools. This is especially true for foils minimized thickness of about 40 m, which can now be reduced even further, so that despite additional film strip material can be saved.

Advantageously, the polyethylene of the intermediate layer may have a melting point below 120 ° C. Overall, it is advantageous if the material of the intermediate layer has a relatively low melting point, in particular a lower melting point than the polyethylene material of the wall-forming film. The intermediate layer can then be melted on the surface responsible for seam formation all the more easily, especially since its heating must take place during heat sealing from the outside through the wall-forming film.

Although EP 2 188 438 B1 discloses an intermediate layer for joining a sealing layer made of polyethylene with a fabric layer of drawn polymer strips, the intermediate layer does not serve for the sealability of the fabric, but only for the combination of sealing layer and fabric. The production of films or fabrics is also not the production of plastic bags by heat sealing, folding, cutting and the like, in particular the machining, Zufallende work step, but a previous stage. Advantageously, the polyethylene of the liners with a melt index, the so-called MFR value, of more than 2 g / 10 min can be selected to facilitate seaming to the intermediate layer from both sides.

As a material for the intermediate layer is preferably a polybutene into consideration.

For the connection of films and the like, materials which are applied as an adhesive in molten form, for example, are already widely known. In DE 72 28 831 U there are overlap longitudinal seams for tube formation for bags, formed with heated extruded compound material. DE 2 263 624 A also provides for the application of reinforcing and adhesive threads for edge reinforcements on bags. A sealable liner is usually easier to process during bag production than a liquid entry of melt material.

Preferably, the polyethylene film for the walls material-saving with a film thickness of at most 40 μιτι specified while the liner receives a film thickness of over 40 μιη. From the point of view of easy sealing processing, significantly greater thicknesses can also be specified for the intermediate layer, wherein the material expenditure remains justifiable if the intermediate layer is reduced to the narrower region of the seam or seams to be produced.

A reduction of the intermediate layer to the requirements required for the sealing is advantageously taken into account with a strip shape in which the sealing strips are formed with a width which overlaps the width of the sealing seam. For the overall width, the machine tolerances or working tolerances in the production will be taken into account in the first place. In accordance with slight displacements between the sealing strips and the film or the placement areas of the sealing tools, the width of the sealing strips must be sufficiently specified beyond the sealing seam width.

In addition, an intermediate layer or a sealing strip in areas of a plastic packaging, which can often be obtained for shaping, fixing and also for stiffening sealing seams in the interior, can also be designed as a stiffening element, as in the case of bags made from easily sealable films, for example in DE 20 2008 008 471 U1 is shown. This applies in particular with regard to an extremely thin wall material of the plastic bag with a correspondingly low dimensional stability. In particular, in the case of a pouch equipped with a grip area, which delimits the area between the packaging and the handle, and which in turn is thoroughly loaded during filling and handling, a seam can advantageously be provided with a strong or wide sealing strip, both from a strength point of view and from a form stiffness point of view ,

An embodiment of the invention is illustrated in the drawing and will be described in more detail below. In drawing show in a schematic simplification:

Fig. 1 is a side view of a substantially flat folded packaging bag with a handle area and Fig. 2 section along line II-II in Fig. 1st

A generally designated 1 plastic bag is in its basic form of known type and for example in EP 2 361 842 A1 of the present applicant - there with a particularly contoured cut seam on the handle - described. The illustrated bag provides still open empty packaging for relatively lightweight products such as toilet paper rolls and similar pulp products, which are accordingly often supplied in large containers. The bag accordingly comprises two large walls 2 and 3, which are connected on the underside by a dividing seam 4 which is readily loadable on the underside and which merge integrally with each other on one (transverse) side with a folded side fold wall, while an opening 6 is initially formed on the opposite side is left between an edge region 7 of the wall 2 and a projecting over the wall 2 stacking edge 8 with pin stacking holes 9 for stacking and for machine handling. The empty bag is therefore to be filled from the opening 6 ago, where he is exposed there in particular by Aufspreizwerkzeuge and also by the injected contents considerable loads.

The bag 1, which is to be worn in large dimensions, preferably in "landscape", has for this support position along an upper side a handle bar 10 with a handle 1 formed as a punched / welded. The handle strip 10 is separated by a sealing seam 12 from a filling space 13 of the bag. This sealing seam 12 extends to one side also on the two side fold halves of the side tenfaltenwand 5 and the other side to the end of the handle bar 10 and beyond this end on the edge region 7 of the wall 2, to connect there with the upper edge of the wall 3. The edge region 7 of the wall 2 is brought together after filling for closing the opening 6 with a sealing seam with the stacking edge 8 and sealed to then on the sealing seam projecting edge regions, in particular the stacking edge 8, separate.

In the area of the sealed seam 12, a narrow but also opposite to tolerances for the attachment of the sealing seam 12 in the width of security given sealing strips 14 between the wall 2 and the wall 3 is inserted. The seal is thus not between the walls 2 and 3 directly but each between the one and the other wall and the sealing strip 14. This additional sealing strip 14 is used for easier and more reliable attachment of the sealed seam 2. The present bag is made of a clear transparent polyethylene film produced on the inside a total pressure pretreatment and, at least in partial areas, has undergone printing.

The sealing strip 14 inserted between the walls 2, 3 to be joined together in the region of the sealing seam 12 avoids the difficult direct connection of two pressure-pretreated and / or printed insides and replaces them by two connections to be affixed to the sealing strip 14 on both sides with one side each of the non-pressure-pretreated sealing strip , Furthermore, the material of the sealing strip 14 is selected above all with regard to easy sealability. This includes a relation to the material of the remaining bag film lower melting point of at least less than 120 ° C. The use of a special polyethylene in the form of a polybuten is also advantageous. Furthermore, the thickness of the inserted sealing strip can be greater than that of the walls 2 and 3, without contributing significantly to the cost of materials.

But above all, the sealing strip 14 can contribute to the stiffening of the area between the handle bar 10 and the filling space 13, especially if it is designed to be stronger than the thickness of the walls 2 and 3. Since the area between the handle bar 10 and the remaining bag for the Formseifig speed and carrying capacity of the bag 1 has a key function, a reinforcement in this area with the sealing strip 14 is particularly advantageous and even allows the wall thickness of the film material for the walls 2 and 3 under the meanwhile common wall thickness of about 40 μιτι still significantly in the direction 30th to reduce μιη.

As shown in FIG. 1, the sealing strip 14 does not extend into the region of the inserted side gusset wall 5. The free end area is irrelevant to the load capacity and also to the protective function of the bag. The remaining opening opens from the filling chamber only in the handle bar. It goes without saying, however, that the sealing strip can be carried out with the side fold open on one side. A perfect finish at this point can be achieved by having corresponding seal strip pieces, in between on both sides used the walls 2 and 3 and the respective adjacent gusseted halves, even there can provide a degree.

Claims

claims

A plastic bag (1) having at least two walls (2, 3) connected by seams (4, 12) of a polyethylene mono-film or a laminated film with a polyethylene layer on the inside of the bag (1), the inside being defined by a Corona treatment or the like pressure pretreatment of the surface is changed for better printability, characterized in that at least one seam between the pressure-pretreated inner sides of the walls (2, -3) as a sealing seam (12) with an intermediate layer (14) as a film of a surface in not changed polyolefin whose melting point is not higher than that of the film of the plastic bag is formed.

2. Plastic bag according to claim 1, characterized in that the polyolefin of the intermediate layer (14) has a crystallite melting point of less than 120 ° C.

3. Plastic bag according to claim 1 or 2, characterized in that the polyethylene of the intermediate layer (14) has a melt flow rate (MFR value) of more than 2 g / 10 min.

4. Plastic bag according to claim 1, 2 or 3, characterized in that the intermediate layer (14) consists of a polyethylene, a polybutene or a polyethylene copolymer (eg EVA).

5. Plastic bag according to one of claims 1 to 3, characterized in that the intermediate layer is formed as a sealing strip (14) having a width of the sealed seam (12) cross-width.

6. Plastic bag according to one of claims 1 to 5, characterized in that the intermediate layer (14) has a film thickness which is substantially greater than that of the film of the walls (2, 3).

7. Plastic bag according to one of claims 1 to 6, characterized in that it is formed with a filling area (3) and a handle portion (10) against each other by a sealed seam (12) with a between the walls (2, 3) sealed intermediate layer (14) are delimited.

8. Plastic bag according to claim 7, characterized in that the intermediate layer (14) extends beyond the sealing seam (12) far into the grip area (10) that it surrounds the handle (1).