EP2076379A1

EP2076379A1 - Tubular bag consisting of a multi-layered film

Info

Publication number: EP2076379A1
Application number: EP07818442A
Authority: EP
Inventors: Markus Bevilacqua; Sven Jacobsen
Original assignee: Alcan Technology and Management Ltd
Current assignee: 3A Composites International AG
Priority date: 2006-09-28
Filing date: 2007-09-26
Publication date: 2009-07-08
Also published as: WO2008037441A1; EP1905577A1

Abstract

The invention relates to a tubular bag consisting of a multi-layered film. At least one part of the layers of said multi-layered film is a 3B film having a maximum shrinkage degree of no more than 2%.

Description

Tubular bag made of a multilayer film

The invention relates to a tubular bag made of a multilayer film.

Tube bags for vertical and horizontal filling on so-called FFS (Form-Fill-Seal) systems are known. For continuous production of the tubular bag, a flat strip is guided from a packaging laminate over a forming shoulder and thereby formed into a tube. The tube thus formed is formed by attaching a longitudinal seam and a transverse seam to a bag, which is closed after filling with a second transverse seam and separated from the hose. This process, forming the tube - filling the bag formed - sealing the longitudinal and transverse seams, repeats clocked in quick succession. Typical laminates for tubular bags are usually adhesive-laminated and / or extrusion-laminated or coated, wherein the outer layer usually consists of an oriented plastic film or paper and serves as a print carrier and / or carrier for a barrier coating, offers a glossy surface and a good Has thermoresistance. Depending on the field of use, there is optionally a further oriented or unoriented polymer film or a metallic film as barrier layer carrier or as a layer for improving mechanical properties, such as strength, in the middle. The inner layer usually consists of a non-oriented, for example by blow or cast method, produced mono- or coextruded, heat-sealable film. In the manufacturing process via a Kleberkaschierung the individual films with solvent-based or solvent-free 2-component Kleberπ are connected in part firmly in several steps to the laminate. This process has several disadvantages: Before the bag is made, a residence time is required for curing the adhesive, which binds circulating capital. Furthermore, the Kleberkaschierprozess is not safe because of solvent consumption and recovery from an economic and environmental point of view. Another risk factor is, for example, primary aromatic amines that can migrate into the packaged goods if the adhesive has not completely reacted. It would therefore be desirable to have a process that does not have a residence time needed and does not contain any reactive chemistry. A partial solution to this problem is the production process via extrusion lamination or coating. Here, a polymer melt applied between the oriented plastic films of the outer layers or the paper and the metal layer assumes the adhesive function, either PE or a PE PE-based acid, acid anhydride or acrylate-based copolymer is used as the adhesion promoter. Further, the sealing layer is partially applied as an extrusion film on the inside of the composite. For higher demands on the laminate, so-called solvent-based primers, which complicate the process from the raw materials logistics, as a primer necessary. A major disadvantage compared to the adhesive laminating is a significant limitation of the sealing film functionality, as can be achieved, for example, with coextruded cast or blown films. It would therefore be desirable to have a process which produces a composite structure exclusively from the melt in one operation, without having to handle raw materials from the solution.

The prepackaging properties, such as haptics, dimensional stability, strength, etc., are achieved by appropriate combination of the layers in terms of arrangement and thickness, wherein in the region of the oriented films the range of variation, e.g. in terms of available thicknesses and versatility. For example, biaxially oriented PET films having a thickness of less than 12 .mu.m can not be produced sufficiently economically using conventional methods. This leads to solutions which, while functioning technically but which provide the necessary packing property, e.g. a heat-resistant outer layer, sealability u.a.m., required material use is disproportionately high. It is therefore desirable to have film structures which are suitable for tubular bags and which can be produced in one operation with a flexibly adjustable layer structure both in order and layer thickness in order to achieve the desired prepackaging properties.

Biaxially stretched polymer films can inter alia via a blown film extrusion under Formation of two or three bubbles to be made. In English, the terms "double bubble (2B) process" and "triple bubble (3B) process" are used. The 3-bubble blown film extrusion discussed below is also referred to herein as the 3B process and the 3B process films are also referred to as 3B films.

In the 3B process, a polymer mass is extruded as a monolayer or multilayer film through a ring die into a thick tube, calibrated to a precise diameter upon exiting the die, and then immediately quenched with water.

Subsequently, the tube is heated to a suitably selected stretching temperature and inflated in a further stage to form a second bubble between two pairs of withdrawal rollers to expand the bubble diameter again with air or other suitable gas and thereby stretched in the transverse direction or transverse direction. The stretching in the longitudinal direction or machine direction takes place by setting a different rotational speed of the take-off rolls delimiting the bubble in its longitudinal direction. The tube expanded into a bladder is thus conveyed at a higher speed in comparison to the extrusion speed, so that its orientation in the transverse or machine direction is maintained.

To remove the biaxial orientation introduced and frozen reset tension of the film or tube is expanded to a third bladder and fixed in the inflated state while maintaining a controlled temperature and a controlled internal bladder pressure. This heat treatment of the third bubble contributes in addition to the reduction of residual stresses, especially in multi-layer films at a flat position, all while maintaining the biaxial orientation achieved high stability and good mechanical strength. EP 1 410 902 A1, WO 2004/080805 A2, WO 01/03922 A1 and WO 2004/110755 A1 disclose multilayer films produced by the 2B and 3B methods as so-called shrink films for the airtight packaging of foods, wherein the film in the shrinkage process without forming microcavities containing air closely conforms to the product to be packaged. In particular for the packaging of large pieces of meat together with bone, a tube manufactured continuously in the 2B or 3B method is subdivided into individual tube sections. At the tube sections, one of the two tube openings is first closed by means of a heat seal. The thus formed, unilaterally still open bag is airtight after filling the goods to be packaged over a second Heisssiegelung and then shrunk under the action of heat until the bag film completely rests against the contents. The degree of shrinkage of the multilayer films is typically about 20 to 60%.

Because of the severe shrinkage of 3B films at a temperature impact, their use in the packaging sector to date has been confined to the aforementioned targeted use of shrinking for packaging products where a positive head-less wrap is desired.

The invention has for its object to provide a tubular bag of the type mentioned, in which the multilayer film without the methods of the prior art adhering disadvantages can be produced. In particular, a tubular bag should be made of a multilayer film having the above properties due to its layer number, order and thickness.

For the inventive solution of the problem results in that at least a part of the layers of the multilayer film is present as a 3B film with a maximum degree of shrinkage of at most 2%. The aim is a practically negligible shrinkage. Preferably, the allowable maximum shrinkage degree of the 3B film is at most 1%.

The 3B films of the multilayer films used according to the invention are thermally stabilized or fixed. This ensures that the films practically do not shrink during further possible processing steps, such as laminating or printing or during a subsequent sterilization process, in which high temperatures sometimes act on the films for a relatively long time.

A significant advantage of the 3B films used according to the invention in comparison with conventionally produced films or laminates is that the 3B coextrusion process can be used to produce films having substantially lower thicknesses of the biaxially oriented layers, which leads to substantial material savings. Thus, with the 3B process, films with a biaxially oriented PET layer having a thickness of, for example, 2 to 12 μm are possible.

Another important advantage results from the combination of two thin biaxially oriented layers with good rigidity, such as e.g. biaxially oriented PET, with a cheap intermediate layer as spacer or spacer. In this way, it is possible to inexpensively produce rigid films which are necessary for achieving a sufficient standing ability of the tubular bag, with great material savings.

Additional advantages result from the higher operating safety and improved environmental conditions resulting from the saving of process costs in the absence of reactive adhesive and solvents during production.

The following definitions / abbreviations are used here: PO polyolefin PE polyethylene

PP polypropylene

PA polyamide

PA amorphous PA PA aromatic Aromatic PA oPA oriented polyamide

PET polyethylene terephthalate

PETam Amorphher PET

PLA Polylacqtique Acide (polylactic acid) TPS starch-based thermoplastic

PSA Self-adhesive layer (Pressure Sensitive Adhesive)

EVOH ethyl vinyl alcohol (barrier layer)

HV bonding agent

SBS styrene-butyl-styrene copolymer SEBS styrene-ethyl-butyl-styrene copolymer

SIS styrene-isoprene-styrene copolymer

AIu aluminum foil (barrier layer)

V2A stainless steel (barrier layer) with metallization of Alu (barrier layer) SiO _x ceramic coating of SiO _x (barrier layer)

Al ₂ O ₃ ceramic coating of Al ₂ O ₃ (barrier layer) i printing ink, printing (ink)

L lacquer layer (lacquer) a adhesive layer w white b black t transparent ma melt adhesive

PANMA Polyacrylonitrile Metacrylate Copoylmer coextruded

The 3B film may be provided with at least one further layer, in particular in the curtain coating or via a slot die coating method (Slot Die Coating).

The 3B film tube produced by the 3B process is cut after production, wound on a roll, and can be cut in a further step in-or offline to the required width, be processed directly into tubular bags. For other applications, additional coating, printing and / or another additional process step may be necessary to achieve technological and appearance properties. In this case, the 3B film tube produced by the 3B process is cut after production into a width required for carrying out the further process step, wound on a roll, fed to the process step, and then further processed directly into tubular bags.

Under certain circumstances, it may be useful to bond or coat the film produced by the 3B process with other films and / or by vapor deposition of metals and / or oxides with a barrier layer against water vapor, flavors, gases and migration of undesirable substances Mistake.

The 3B film or the at least one further layer can in particular be metallized with aluminum or coated with stainless steel or another metal.

The 3B film or the at least one further layer may be ceramic, in particular coated with SiO _x or with Al 2 O ₃ .

The 3B film or the at least one further layer can be printed and / or provided with a thermal protective varnish.

The 3B film or the at least one further layer can be made from completely biologically degradable polymers.

The 3B film preferably comprises at least one heat-sealable layer comprising a material selected from the group of polyolefins (PO), polyamides (PA), polyesters and their copolymers, and ionomers (ION). It is also possible to use hot melt adhesives based on EVA and other bases, as well as blends of the abovementioned materials.

Typical core layers used are polyamides, polyesters, polyolefins and their copolymers, cycloolefinic polymers, and also the adhesion promoters based on MAH, acrylate and carboxylic acids.

As barrier layers, EVOH, PVOH or aromatic polyamides can be used. Self-adhesive hot-melt adhesive layers made of SBS, SIS, SEBS and an adhesive resin can also be used.

As the outer layer, it is typically possible to use materials from the groups of the polyesters, polyamides, polyolefins and their copolymers, which have sufficient thermoresistance and are suitable for composition and additization for vacuum coating.

The tubular bags can preferably be used in the following fields of application:

- tubular bag for packaging moist, cleaning and facial tissues. For example, a 3B film suitable for this field of application may have the layer structure given in Table 1 for the films of Group 1 according to the invention.

- Tubular bag for packaging potato, corn and other chips, savory biscuits, protected or unprotected. For example, a 3B-FiIm suitable for this application can According to the invention, films of group 2 shown in Table 1 have a layer structure.

Tubular bag for packaging hard cheese. For example, a 3B film suitable for this field of application may have the layer structure given in Table 1 for the inventive films of group 3.

Tube bag for packaging cereals such as breakfast cereals and cereal bars. A 3B film suitable for this field of application may have, for example, the layer structure specified for the films according to the invention of group 4 in Table 1.

- tubular bag for packaging powder mixtures for drinks, bakery products, ground coffee and coffee beans. For example, a 3B film suitable for this field of application may have the layer structure given in Table 1 for the films according to the invention of group 5.

The 3B process allows a film build from fully biodegradable raw materials.

Further advantages, features and details emerge from the following description of preferred embodiments.

Table 1 compares the prior art laminates or films used for packaging products in tubular bags with the laminates or films provided in accordance with the invention. Depending on the type, the moisture content, the shelf life and other product properties, there are different requirements for the packaging materials, which can be divided into the following groups: Group 1: Agressive products Group 2: Salted biscuits + Chips Group 3: Hard cheese Group 4: Cereal products and muesli Group 5: Powder mixtures for beverages, bakery products, ground coffee and coffee beans, sugar confectionery

The examples of laminates according to the invention compiled in Table 1 have the advantages summarized in Table 2 in comparison with the corresponding laminates or films according to the prior art.

Table 1

Table 2

Claims

claims

1. tubular bag made of a multilayer film,

characterized in that

at least a portion of the layers of the multilayer film is present as a 3B film with a maximum degree of shrinkage of at most 2%.

2. tubular bag according to claim 1, characterized in that the 3B- FiIm has a maximum degree of shrinkage of at most 1%.

3. tubular bag according to claim 1 or 2, characterized in that the 3B-FiIm with at least one further layer, in particular curtain curtain coating (Curtain Coating) or a Schlitzdüsenbeschichtungs method (Slot Die Coating), coated.

4. tubular bag according to one of claims 1 to 3, characterized in that the 3B film and / or metallized at least one further layer, in particular coated with aluminum or stainless steel.

5. tubular bag according to one of claims 1 to 3, characterized in that the 3B film and / or the at least one further layer is ceramic, in particular with SiO _x or with Al ₂ O ₃ coated.

6. tubular bag according to one of claims 1 to 3, characterized in that the 3B-FiIm and / or the at least one further layer printed and / or provided with a thermal protective varnish.

7. tubular bag according to one of claims 1 to 6, characterized in that the 3B-FiIm and / or the at least one further layer of completely biodegradable polymers.

8. tubular bag according to one of claims 1 to 7, characterized in that the 3B FiIm an inner layer, a core layer and an outer layer having the following structure and is composed of the following materials:

Inner layer: heat-sealable layer comprising a material selected from the group of polyolefins (PO), polyamides (PA), polyesters and their copolymers, as well as ionomers (ION), hot melt adhesives, in particular based on EVA, and blends of the aforementioned materials.

Core layer: polyamides, polyesters, polyolefins and their copolymers, cycloolefinic polymers, and the bonding agents which bind them, in particular based on MAH, acrylate or carboxylic acids, EVOH, PVOH or aromatic polyamides as barrier layers, self-adhesive hot-melt adhesive layers of SBS, SIS, SEBS and an adhesive resin ,

Outer layer: Materials selected from the group of polyesters, polyamides, polyolefins and their copolymers, with sufficient thermoresistivity and suitability for vacuum coating.

9. Use of a tubular bag according to one of claims 1 to 8 for packaging of aggressive contents.

10. Use of a tubular bag according to one of claims 1 to 8 for the packaging of savory biscuits and chips.

11. Use of a tubular bag according to one of claims 1 to 8 for the packaging of hard cheese.

12. Use of a tubular bag according to any one of claims 1 to 8 for packaging cereals and muesli.

13. Use of a tubular bag according to one of claims 1 to 8 for the packaging of powder mixtures for drinks, bakery products, ground coffee and green coffee and sugar confectionery.

14. Use according to claim 9, characterized in that the 3B film is one of the layer structures

L / i / PET: HV: PPw: PE L / i / PET: HV: PE: PEw: PE LΛ / PET: HV: PPw: PP.

15. Use according to claim 10, characterized in that the 3B film has one of the layer structures oPP / i / a / met.PP: PP * L / i / PET: HV: PP: HV: PET: HV: PP * L / i / PP: PP: HV: EVOH: HV: PP: PP ^* * peelable or seal-resistant.

16. Use according to claim 11, characterized in that the 3B film is one of the layer structures

PA: HV: PE

PET: HV: PE: HV: PSA: HV: PE.

17. Use according to claim 12, characterized in that the 3B film is one of the layer structures

L / i / PP: PPpeel oPP / i / a / PA: HV: PE L / i / a / PET: HV: PE HDPE: ionomer having.

18. Use according to claim 13, characterized in that the 3B film has one of the layer constructions L / i / met.PET: HV: PP: PE * L / i / met.PET: HV: PP: HV: PET: HV: PE ^* L / i / PET: HV: PP: HV: PAam: HV: PE * L / i / met.PET: HV: PP: PP * L / i / PET: HV: PP: PP: PE ^* oPP / i / a / PA: HV: PP l_ / i / PP: HV: PA: PP: PE L / i / SiOx.PLA.HV: TPS * peelable or firmly sealed.