DE102004042968A1 - Heat-shrinkable multilayer film for use in a product-releasable cook-in-the-bag applications (especially with meat products) has a sealing layer provided with fluorine - Google Patents

Abstract

A heat-shrinkable, multilayer film with releasable adhesion to the product cooked in it and including (a) an outer layer, (b) a gas barrier layer and (c) a sealing layer is such that layer (c) is provided with 10-100 mu g/cm2> of fluorine. Independent claims are also included for a bag made from the multilayer film and for packaging cook-in-the-bag (especially protein-containing) foods.

Description

The present invention relates to a heat-shrinkable, cookable multilayer film with detachable product adhesion comprising at least one outer layer, at least one gas barrier layer and at least one sealing layer which is coated with 10 to 100 μg / cm ² fluorine, their preparation, their use as packaging material, preferably as shrink bags, and corresponding shrink bag packaging.

A Variety of foods are processed by the already packed goods elevated temperatures be exposed, for example by immersion in hot water or by treatment with water vapor. Films or packaging, the for Such a treatment are suitable as cooking films or Also referred to as a cookable film or cookable packaging.

A cookable film must one Meet a variety of requirements. So this must be Film elevated temperatures Stand up without being damaged to become. additionally must be for certain Applications heat-shrinkable cookable film and their liability to the packaged goods be large enough that the Packaging during the cooking process of the solidifying form of the packaged food adapts and this possible tightly encloses. This is to prevent that between the emerging food and the packaging film accumulates, for example, water.

Farther it is desirable that faces a cookable foil Oxygen impermeable is because the presence of oxygen in many goods, in particular Food, leads to oxidative spoilage. It is also desirable that a cookable foil for Impermeable to water vapor otherwise, the packaged goods will assist in the treatment increased Temperatures lose moisture.

A Another requirement for cookable multilayer films is that they a high seal strength at the cooking temperatures used guarantee, so that the packaging made from it remains tight.

The Foods that are packaged in a cookable foil and then put through Application of elevated temperatures can be finished then frozen, stored or already directly to the consumer be delivered. Since the finished, packaged food the Consumers are offered in an appealing way have to, It is also important that the packaging made from the Remove cooking film from the packaged food without any problems leaves. In particular, allowed no portions of the packaged food so strong on the foil adhere to being ripped out with the foil and thereby the visual appearance of the food is impaired.

Out the prior art (WO 2000/58093) is known that through a corona and / or plasma treatment the surface tension of foils leaves. heat shrinkable Foils with such a raised surface tension can when shrinking the packaged goods enclose better, so that no cavities between the packaged goods and the packaging form. The disadvantage, however, is that the corona and / or plasma treatment induced increase in the surface tension during storage of the film over a longer one Period decreases.

task It was therefore an object of the present invention to provide a cookable, gastight, heat-shrinkable multilayer film with detachable Product liability available to provide, preferably for the production of proteinaceous Foods, such as cooked ham, by cooking in a suitable Packaging is suitable, and their advantageous properties by a increased surface tension even with longer ones Storage time are still given.

When can be cooked according to the invention a film or packaging referred to in the treatment in hot water at a temperature of at least 65 ° C, preferably at least 75 ° C, more preferred of at least 85 ° C or with steam for a duration of at least 3 hours, preferably of at least 6 Hours, more preferably at least 8 hours, especially preferably at least 12 hours, remains undamaged.

The abovementioned object is achieved by providing the heat-shrinkable, multi-layer, heat-shrinkable film according to the invention with detachable product adhesion, which comprises at least one outer layer a), at least one gas barrier layer b) and at least one sealing layer c), the sealing layer c) having 10 to 100 μg / cm ^{2 of} fluorine is occupied.

The film according to the invention, the sealing layer is coated with fluorine, has over a entspre untreated film has an increased surface tension. This increased surface tension is permanent, so that even after a storage time of at least 28 days, preferably of at least 56 days, more preferably of at least 84 days, most preferably of at least 112 days, the film according to the invention meets all requirements for a heatable, heat-shrinkable multilayer film, such as they are described above, is sufficient.

In a preferred embodiment, the sealing layer c) is coated with 15 to 50 μg / cm ^{2 of} fluorine.

Accordingly contains a sealing layer c) 0.1 to 3.5 wt .-%, preferably 0.5 to 1.5 Wt .-%, based on the total weight of the sealing layer c), fluorine.

According to the invention Multilayer film, preferably the inside of a tubular film after their preparation according to the co-extrusion blown process treated with fluorine gas for occupancy with fluorine.

Preferably For this purpose, the sealing layer coming into contact with the product to be packaged is used c) with a mixture of 1 to 10% by volume, preferably 1.5 to 5% by volume, Fluorine gas and 90 to 99 vol .-%, preferably 95 - 98.5 vol .-%, of an inert gas at a temperature of 0 to 50 ° C, preferably at a temperature from 20 to 30 ° C, for 1 to 20 minutes, preferably for 2 to 10 minutes, fluorinated.

In a preferred embodiment the inert gas is a gas selected from the group comprising nitrogen, neon, argon and helium, especially preferably nitrogen.

advantageously, can by the composition of the gas mixture any change the surface tension can be reproducibly obtained by fluorination.

By the treatment of the surface the sealing layer c) with a gas mixture of inert gas and fluorine can in the surface the sealing layer material hydrogen atoms replaced by fluorine atoms become. For example, in a layer of polypropylene after a few minutes within a surface layer of the thickness of 10 - 30 nm at least 50% of all available Hydrogen atoms of the polymer exchanged for fluorine atoms. at The treatment with fluorine gas is for each exchanged hydrogen atom an equivalent Hydrogen fluoride released.

The Fluorination of the multilayer film according to the invention may preferably be in line with the production of the film, preferably continuously. This is the continuous slide in one Fluorination introduced, after evacuation with a gas mixture fluorine and preferably nitrogen, as described above, filled has been. The volume concentration of fluorine gas remains during the entire period of fluorination by subsequent addition of fluorine gas constant. The fluorination of the film is carried out so preferably continuously and preferably at a temperature of 20 to 30 ° C, without another energy input is necessary. At a production stop For example, the fluorination chamber can be evacuated and purged with air. The remaining fluorine gas is in a calcium carbonate absorber neutralized. The required safety measures for working with fluorine are taken into account in the construction of the equipment used, so that the corresponding MAK value (max Workplace concentration) for Fluorine of 0.1 ppm is never exceeded. The corresponding activities for this purpose are known in the art.

The outer layer a) the multilayer film according to the invention is based on a polymer selected from the group comprising polyolefins, olefin copolymers, polyesters and Polyamides.

Preferably, the outer layer a) is based on a polyethylene, more preferably on a polyethylene having a density of <0.92 g / cm ³ , a polypropylene, an ethylene copolymer, more preferably an ethylene-vinyl acetate copolymer, a propylene copolymer or a Polyamide.

Especially Preferably, the outer layer is based a) on a mixture of linear low density polyethylene (LLDPE) and ethylene-vinyl acetate copolymer.

The Use a mixture of LLDPE and ethylene-vinyl acetate copolymers for the Production of a heat-shrinkable Multilayer film is advantageous because this thermoplastic material has an excellent shrinkage behavior.

In a very particularly preferred embodiment, the outer layer a) is made of a mixture of 70 to 90 wt .-% LLDPE, 10 to 30 wt .-% ethylene-vinyl acetate copolymer and optionally up to 5 wt .-% of conventional additives, each based on the total weight of the outer layer a) with 100% constructed.

Under usual Additives are preferably anti-blocking agents, antistatic agents and / or Lubricant understood.

In a preferred embodiment seal the outer layer a) not at the necessary sealing temperatures, as these one at least 15 ° C, preferably one at least 20 ° C, more preferably a softening point at least 25 ° C higher than the sealing layer c). In this way it is prevented that while the sealing process to produce a packaging randomly overlapping areas of outer layers a) individual packaging seal against each other and thus no longer can be separated.

The outer layer a) has a melting temperature of 115 ° C to 200 ° C, preferably from 115 ° C to 175 ° C. The fat the outer layer is 5 - 50 microns, preferably 10-20 μm.

The Gas barrier layer b) is based on at least one polymer selected from the group comprising ethylene-vinyl alcohol copolymers, polyvinylidene chlorides, Polyesters and polyamides, preferably on an ethylene-vinyl alcohol Copolymer. The layer b) is intended for both oxygen and water vapor largely impermeable be. This property is essentially independent of temperature, so that too at elevated Temperatures the gas impermeability is maintained.

The Gas barrier layer b) has a thickness of 2 to 15 microns, preferably from 3 to 10 μm, on.

The Sealing layer c) is based on at least one polymer selected from the group comprising polyolefins, olefin copolymers, polyesters and Polyamides, preferably selected from a mixture of polyolefins selected from the group consisting of metallocene polyethylene (m-PE), polyethylene high density (HDPE), low density polyethylene (LDPE), LLDPE, Polypropylene (PP) and propylene copolymers. The sealing layer materials are approved for contact with food.

In a preferred embodiment If the sealing layer c) consists of HDPE.

The Sealing layer c) preferably has a thickness of 5 - 50 microns, preferably from 10 to 30 μm, especially preferably from 14 to 25 μm. The Melting temperature of the sealing layer c) should preferably be 100 ° C to 160 ° C, especially preferably 100 ° C up to 140 ° C, be such that the sealing layer c) a by at least 15 ° C, preferably at least 20 ° C, most preferably at least 25 ° C, lower softening point as the outer layer a).

The inventive multilayer film may optionally have adhesion promoter layers d).

The Adhesive layers d) are preferably made of a mixture from modified polyolefins and / or olefin copolymers, preferably selected from the group comprising LDPE, HDPE, PP, ethylene-vinyl alcohol copolymer and / or ethylene-vinyl acetate copolymer and preferably have one Thickness of 5 - 50 microns, especially preferably from 5 to 15 μm.

The Thickness information is to be understood as the thickness of the respective layer of inventive multilayer film after the longitudinal and transverse orientation.

In a preferred embodiment is the gas barrier layer b) between two adhesion promoter layers d) embedded, which consist of the materials listed above.

The multilayer film according to the invention preferably has at least the following successive layers:
an outer layer a), a primer layer d), a gas barrier layer b), a primer layer d) and a sealing layer c).

In principle, each layer of the multilayer film according to the invention may additionally comprise conventional additives and assistants such as fillers, colorants, antistatic agents and stabilizers. The multilayer film according to the invention can be printed, wherein at least one layer of the multilayer film printed or by the addition of additives such as organic or inorganic dyes and pigments can be colored. The sealing layer c) can be equipped with the usual excipients such as antistatic agents, lubricants and / or Abstandshaltem.

The Production of the Multilayer Film According to the Invention can after a blowing, flat-film, Coating, extrusion, co-extrusion or equivalent Coating or laminating process done. Preferably the multilayer film according to the invention after the blown film process by co-extrusion such. B. in the No. 3,456,044. But that's it possible, first only the outer layer a) to extrude as a tube and the subsequent layers by co-extrusion or any sub-combination to extrude as tubular film and immediately afterwards with to extrude the remaining layers.

Provided the fluorination is not in line according to the preferred co-extrusion blown process takes place, the inventive, finished Foil also later with the help of a usual Foil processing device introduced into a fluorination are made by rolling the film roll into sheets and after fluorination is rewound into rolls.

Preferably the multilayer film is biaxially stretched. Thus, the multilayer film of the present invention is according to her Manufacturing process both in longitudinal as well as stretched in the transverse direction and has a stretch ratio in Longitudinally d. H. in the machine direction, from 1: 5 to 1: 3 and in the transverse direction, d. H. contrary to the machine direction, from 1: 5 to 1: 3. The multilayer films of the invention preferably have a shrinkage both in the longitudinal and in the transverse direction from 15 to 35%. You can if necessary, be crosslinked chemically or by irradiation.

The polymers used for layer construction are commercially available and described in the prior art. They are usually used for making the multilayer films according to the invention in the form of pellets or granules, if necessary in the usual way Mixed mixing equipment, and preferably by melting with Help of extruders in the desired Brought final shape. As already mentioned, the production is after the film blowing preferred, wherein as extruder those with Co-extrusion dies be used, which is the formation of a hose of several Ensure layers. The processing temperatures, in particular those in the extrusion, are known in the art and are with the provision of plastics in general.

The Multilayer film is preferably a tubular film whose innermost Layer is the sealing layer c).

The inventive multilayer films are great for the production of a tubular bag as packaging material.

One Another object of the invention are therefore cookable tubular bag from the multilayer film according to the invention and their use for food packaging of proteinaceous foods, more preferably of meaty foods Food. Most preferably, the cookable are Tubular bag made of the multilayer film according to the invention for packaging of meat-containing foods selected from the group comprising Meatloaf, Pies and cooked ham, preferably finished in the package become.

Also An object of the present invention are tubular bag packaging the multilayer film according to the invention.

The Packaging may consist of the multilayer films of the invention at all the packaging machines known to the person skilled in the art are produced, for example, horizontal as well as vertical, automatically running packaging machines or on bag machines.

Surprisingly is the seal strength of a package of a multilayer film according to the invention not affected by the fluorination of the sealing layer c).

Another object of the present invention is a method for packaging foods, preferably of proteinaceous foods, more preferably of meat-containing foods, most preferably meat-containing foods selected from the group comprising Leberkäse, pies and cooked ham according to the possibly still be ready to put Food is filled into a tubular bag and the tubular bag by sealing or by clipping, preferably with a metal clip, closed and, if necessary, cooked, whereby the protein-containing food, preferably a cooked ham, a pate or a Leberkäse, is completed.

Preferably has that in a package of the invention modified Multi-layer film finished food, especially the finished protein foods, at most after cooking 2% by weight, preferably at most 1.5 wt .-%, based on the total weight of packaging material and finished food, a water accumulation between the food and packaging material.

Examples

Treatment of a multilayer film with fluorine gas and determination of the surface tension of the multilayer film

example 1

• a) Außenschicht aus einer Mischung aus 81 Gew.-% LLDPE (Stamylex^® der Firma DexPlastomers) mit einer Dichte von 0,911 g/cm³; 15 Gew.-% eines Ethylen-Vinyacetat-Copolymerisats mit 28 Mol-% Vinylacetat-Einheiten (Novex^® VO7 E460 der Firma BP Chemicals) und 4 Gew.-% eines Antiblockmittels, wobei die Schicht eine Dicke von 15 μm hatte;
• d) Haftvermittlerschicht aus einer Mischung aus 40 Gew.-% eines Maleinsäureanhydridmodifizierten Ethylen-Vinyacetat-Copolymerisats (Bynel^® 3930 der Firma Du Pont), 18 Gew.-% eines Maleinsäureanhydrid-modifizierten linearen Polyethylens geringer Dichte (Bynel^® 41E710 der Firma Du Pont) und 42 Gew.-% eine Ethylen-Vinyacetat-Copolymerisats (Elvax^® 3135 X der Firma Du Pont), wobei die Schicht eine Dicke von 9 μm hatte;
• b) Gasbarriereschicht aus einem Ethylen-Vinylalkohol Copolymerisats mit 44 Mol-% Ethylen-Einheiten (EVAL^® ES 104B der Firma Eval), die Schicht eine Dicke von 6 μm hatte;
• d) weitere Haftervermittlerschicht aus einer Mischung aus 40 Gew.-% eines Maleinsäureanhydrid-modifizierten Ethylen-Vinyacetat-Copolymerisats (Bynel^® 3930 der Firma Du Pont), 18 Gew.-% eines Maleinsäurenhydrid-modifizierten linearen Polyethylens geringer Dichte (Bynel^® 41E710 der Firma Du Pont) und 42 Gew.-% eine Ethylen-Vinyacetat-Copolymerisats (Elvax^® 3135 X der Firma Du Pont), wobei die Schicht eine Dicke von 12 μm hatte;
• c) Siegelschicht aus HDPE (Eltex^® P KS 341 der Firma Solvay) mit einer Dicke von 18 μm.

A multilayer film of the invention having the following structure was produced by a coextrusion blow molding process:

• a) outer layer of a mixture of 81 wt .-% LLDPE (Stamylex ^® DexPlastomers) with a density of 0.911 g / cm ³ ; 15 wt .-% of an ethylene-vinyl acetate copolymer with 28 mol% vinyl acetate units (Novex ^® VO7 E460 from BP Chemicals) and 4 wt .-% of an antiblocking agent, wherein the layer had a thickness of 15 microns;
• d) adhesion promoting layer of a mixture of 40 wt .-% of a maleic anhydride modified ethylene-Vinyacetat copolymer (Bynel ^® 3930 from Du Pont), 18 wt .-% of a maleic anhydride modified linear low density polyethylene (Bynel ^® 41E710 by DuPont ) and 42 wt .-% ethylene-Vinyacetat copolymer (Elvax ^® 3135 X of the company Du Pont), which layer had a thickness of 9 microns;
• b) Gas barrier layer of an ethylene-vinyl alcohol copolymer with 44 mol% ethylene units (EVAL ^® ES 104B Eval), the layer had a thickness of 6 microns;
• d) further Haftervermittlerschicht of a mixture of 40 wt .-% of a maleic anhydride-modified ethylene-Vinyacetat copolymer (Bynel ^® 3930 from Du Pont), 18 wt .-% of a Maleinsäurenhydrid-modified linear low density polyethylene (Bynel ^® 41E710 the Du an ethylene Vinyacetat copolymer (Elvax ^® 3135 X of the company Du Pont), said layer having a thickness of 12 .mu.m had Pont), and 42 wt .-%;
• c) sealing layer of HDPE (Eltex ^® P KS 341 from Solvay) microns with a thickness of 18th

• a) 5 Vol.-% Fluorgas, 95 Vol.-% Stickstoff,
• b) 2 Vol.-% Fluorgas, 98 Vol.-% Stickstoff,

innerhalb der Fluorierungskammer für a) 10 Minuten oder b) 3 Minuten jeweils bei 25 °C behandelt. Die Volumenkonzentration Fluorgas wurde durch Nachdosierung von Fluorgas über den gesamten Zeitraum konstant gehalten.The coextruded film tube was transported to a fluorination chamber of the company "Fluor Technik System GmbH" (Lauterbach, Germany) and exchanged for a mixture of the atmosphere

• a) 5% by volume fluorine gas, 95% by volume nitrogen,
• b) 2% by volume of fluorine gas, 98% by volume of nitrogen,

within the fluorination chamber for a) 10 minutes or b) for 3 minutes each at 25 ° C. The volume concentration of fluorine gas was kept constant by adding fluorine gas over the entire period.

The Continuous fluorination of the film was achieved by the film is transported from one roll to another roll being, while being the transport in each of the above periods the Passing fluorination chamber with the gas mixture. After completion of production the chamber was subsequently connected evacuated the fluorination and rinsed with air. The remaining fluorine gas was neutralized in a calcium carbonate absorber.

The surface tension the fluorinated invention Multilayer films were then determined according to DIN 53 364.

In Table 1 below shows the values of the measured surface tension given in mN / m.

Table 1.

A non-fluorinated, identically constructed multilayer film had in the entire storage period of 112 days an unchanged surface tension of 28 mN / m.

Comparative Example 1

The surface tension a plasma or corona-treated multilayer film with the following structure was determined as indicated under Example 1.

Film structure:

• a) outer layer from a mixture of 94% by weight of polyethylene and 6% by weight of one Ethylene vinyl acetate copolymer, wherein the layer thickness was 23 microns;
• d) Primer layer of a mixture as in Example 1, which had a thickness of 4 μm;
• b) gas barrier layer of an ethylene-vinyl alcohol copolymer;
• d) further adhesion promoter layer of a mixture as in Example 1, which had a thickness of 13 microns; another layer from a mixture of 82% by weight of polyethylene and 18% by weight of one Ethylene vinyl acetate copolymer, wherein the layer has a thickness of 13 μm would have;
• c) and a sealing layer of polypropylene.

The Oberflächspannung was 36 mN / m directly after the plasma or corona treatment. To 112 days of storage, a value of 32 mN / m was measured.

Out Example 1 shows that a multilayer film according to the invention a) has a surface tension of 58 mN / m directly after fluorination, the much higher is considered the surface tension of a non-fluorinated multilayer film (28 mN / m) or a plasma or corona-treated film (34.5 mN / m). Even after storage of 112 days, the value of the multilayer film a) according to the invention is still significantly higher (51 mN / m) than the value of an untreated film (28 mN / m) or a plasma or corona treated film (32.5 mN / m).

completion a food in a tubular bag and checking the product liability

Example 2

A meaty paste, as starting material for the production served by boiled ham was in tubular bag from the multilayer film according to the invention according to example 1, slide a) and the full bag was sealed. Subsequently was the packaging at 72 ° C for one Duration of two hours kept in a water bath; then 15 Minutes cold and quenched for stored for at least 15 hours in the refrigerator at 4 ° C.

To check the Product liability, the packaging was withdrawn from the boiled ham. The packaging settled it easily without tearing of meat pieces from the surface of the Peel cooked ham completely off this.

Claims (23)

Heat-shrinkable, cookable multilayer film with detachable product adhesion comprising at least the following layers an outer layer a), a gas barrier layer b) and a sealing layer c), characterized in that the sealing layer c) is coated with 10 to 100 ug / cm ^{2 of} fluorine. Multilayer film according to claim 1, characterized in that the sealing layer c) is coated with 15 to 50 μg / cm ^{2 of} fluorine. Multilayer film according to claim 1 or 2, characterized characterized in that the sealing layer c) 0.1 to 3.5 wt .-%, preferably 0.5 to 1.5 wt .-%, based on the total weight of the sealing layer c) contains fluorine. Multilayer film according to one of claims 1 to 3, characterized in that the outer layer a) on a polymer selected from the group comprising polyolefins, olefin copolymers, polyesters and polyamides based. Multilayer film according to one of claims 1 to 4, characterized in that the outer layer a) on a mixture based on linear low density polyethylene (LLDPE) and ethylene vinyl acetate copolymer. Multilayer film according to one of claims 1 to 5, characterized in that the outer layer a) not sealable is. Multilayer film according to one of claims 1 to 6, characterized in that the outer layer a) one at least 15 ° C, preferred at least 20 ° C, most preferably at least 25 ° C higher softening point than the sealing layer c). Multilayer film according to one of claims 1 to 7, characterized in that the gas barrier layer b) on at least a polymer selected from the group comprising ethylene-vinyl alcohol copolymers, polyvinylidene chlorides, Polyesters and polyamides, preferably on an ethylene-vinyl alcohol Copolymer, based. Multilayer film according to one of claims 1 to 8, characterized in that the sealing layer c) on at least a polymer selected from the group comprising polyolefins, olefin copolymers, polyesters and polyamides, preferably selected from a mixture of polyolefins selected from the group consisting of metallocene polyethylene (m-PE), polyethylene high density (HDPE), low density polyethylene (LDPE), LLDPE, Polypropylene and propylene copolymers based. Multilayer film according to one of claims 1 to 9, characterized in that the gas barrier layer b) between two adhesion promoter layers d) is embedded. Multilayer film according to claim 10, characterized in that the adhesion promoter layers d) are made from a mixture of modified Polyolefins and / or olefin copolymers exist. Multilayer film according to claim 10 or 11 comprising at least the successive layers an outer layer a) a primer layer d), a gas barrier layer b) a bonding agent layer d) and a sealant layer c). Multilayer film according to one of claims 1 to 12, characterized in that the multilayer film biaxially stretched is. Multilayer film according to one of claims 1 to 13, characterized in that the more layer film has a stretching ratio in the longitudinal direction of 1: 5 to 1: 3 and in the transverse direction of 1: 5 to 1: 3. Multilayer film according to one of claims 1 to 14, characterized in that the multilayer film is a tubular film is. Use of a multilayer film according to a the claims 1 to 15 for producing a tubular bag. Cookable tubular bag made of a film according to a the claims 1 to 15. A tubular bag according to claim 17 for packaging of foods, preferably of proteinaceous foods, particularly preferred of meat-containing foods. A tubular bag according to claim 17 or 18 for packaging of meat-containing foods selected from the group comprising Meatloaf, Pies and cooked ham. Tubular bag packaging from a multilayer film according to one the claims 1 to 15. Method for packaging food, preferred of proteinaceous foods, characterized in that a) the possibly still finished food in a tubular bag according to claim 17 filled, b) the tubular bag sealed by sealing or by cliffs and c) if necessary subsequently is cooked. Method according to claim 21 for packaging meat-containing foods, preferably meat-containing Food selected from the group comprising Leberkäse, Pies and cooked ham. Method according to claim 21 or 22, characterized that by cooking the finished proteinaceous food, preferably cooked ham, pate or meatloaf.