DE3323629A1 - SELF-SEALING OR SEALABLE, TRANSPARENT, COLD-EXPANDABLE FILM FOR PACKING FOODSTUFFS OR THE LIKE - Google Patents

Description

The invention relates to a self-sealing or sealable, transparent, cold-stretchable film for packaging (or wrapping) foodstuffs, e.g. fresh meat, fruits, vegetables and cheese, including 5 of the entire range of frozen foods. Such a slide can either be done by hand or used in semi-automatic or automatic devices and is for supermarkets, others Suitable for shops and packing centers.

10 The object of the invention is to create a film in which the problems caused by the possible Transfer of harmful or unpleasant substances

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occur from the packaging material on the food to be packaged, are eliminated.

This object is achieved according to the invention by a self-sealing, transparent film that can be stretched or stretched when cold, which has at least two superimposed different layers of adhesive, thermoplastic material, the first layer being a mixture of linear low density polyethylene (LLDP) and ethylene vinyl acetate (EVA) with a vinyl acetate content of about 12 % and the second layer of ethylene vinyl acetate (EVA) with a vinyl acetate content of about 30%, together with a percentage addition of ionomer resin (to vary the permeability properties) and an anti-fog material, as is usually the case with thermoplastic films used for food packaging includes.

Advantageously, the linear low density polyethylene of the first layer has a low melt index and a limited proportion may be conventional low density polyethylene of low melt index.

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A third layer can be arranged between the first and the second layer in order to prevent the passage to build a barrier against gases and vapors or to provide the composite film with precise permeability properties to rent. The intermediate layer is preferably a layer made of polyvinyl chloride or polyamide resin (Nylon).

The invention is described on the basis of exemplary embodiments and the following figures. Show it:

Fig. 1 is a section on a greatly enlarged scale part of a film of the invention;

Fig. 2 shows a section similar to that of FIG. 1 through. a film with an intermediate layer; and

3 and 4 each show a perspective view and a side view of a fresh meat processor

package wrapped with the film according to the invention, prior to sealing the package.

The film 1 shown in Fig. 1 consists of at least two layers 3 and 5, which are superimposed

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and adhere to one another over their entire surface so that it is impossible to separate the layers. The total thickness of the film is taking into account the Use of the film in the so-called "throw-away area" for packaging portions of fresh food, even of medium weight, low, e.g. B. usually in the range of 10 to 25 μπι. Bigger ones Thicknesses can be used, for example, for packaging of heavier weight and larger dimensions, or for reusable packaging Packaging and packaging that has a greater risk of tearing can be used. As The film of the invention can use stretch films made from the PVC used so far with a high proportion of plasticizers can be used for packaging foodstuffs which, as shown in FIGS. 3 and 4, in FIG an open small box 7} the foil can also be used without the box, e.g. B. for pieces of cheese with a relatively firm consistency.

In both cases, the film is on the surface of the food to be packaged in both directions (Width and length) stretched (manually by staff or by suitable devices or semi-automatically and automatic devices) and under the box or that

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Food with the solid consistency overturned by adding a certain length of its edge parts, such as. B. indicated by 9, 11 and 13, turned down or placed on top of each other. The edge parts are then with the help of a heating plate against the bottom 7F of the box (or against the underside of the piece with the relatively firm consistency) so that they adhere to one another. The slide is made that way held taut and sealed the packaging.

In order to meet the application requirements described at the outset, the films according to the invention with regard to extensibility and / or stretchability and adhesion properties, at least the properties of the plasticized PVC films used up to now

1.5 are similar, without having the disadvantages, to PVC regarding the possible transfer of harmful substances such as vinyl monomers and DCA or other plasticizers, on the packaged food itself in traces (to be estimated in ppm). Such Extensibility and adhesion is obtained by making two different layers 3 and 5, the first layer acting as a support that of the film

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imparts the required mechanical properties, d. H. the extensibility in connection with the tear or Peel strength, and the second layer provides the adhesiveness to make the film self-sealing make, as well as for the properties of the appropriate permeability for gases and vapors. To the satisfactory Storage of fresh food it is usually necessary that the packaging film is only partially gas and vapor tight while it is off For aesthetic reasons it is necessary that on the inside of the wrapping of the packaged food Film no condensates occur.

In order to achieve the properties described above, each layer is made up of different mixtures made of thermoplastic materials, the overall composition being the result of the predetermined Is components that are sized within a certain range of constituent parts.

The first layer of the film is (generally abbreviated LLDP) of a mixture of linear low density polyethylene and _t produced ethylene vinyl acetate (EVA) having a vinyl acetate content comparatively low, ie, about 12 wt.%. All percentages relate to weight.

The second layer is essentially made of an ethylene vinyl acetate (EVA) with a comparatively high vinyl acetate content, ie approximately 30 % ; this second layer can also consist of 100 % EVA, but for practical use the EVA is preferably used with a percentage of ionomer resin, for example SURLYN (registered trademark) and a percentage of anti-fog material, as is conventionally used in thermoplastic films for food packaging, mixed. The ionomer resin used in the mixture of the second layer is usually an ethylene copolymer with acrylic or methacrylic acid, in the molecules of which ionic bonds with zinc and sodium atoms are present. The ionomer resin gives the film more or less the aforementioned properties for the storage of fresh food in terms of gas and vapor permeability.

The linear low density polyethylene of the blend of the first layer should have a fairly low melt index (low grach), preferably grade 1. In addition, the linear polyethylene can partially through conventional low density polyethylene with properties suitable for the manufacture of thin films

and thus also replaced with a low melt index
to lower the cost of the product.

The areas between which the proportions of the
Components of the first and second layers varied
can be so that the film has both the cold expansion and self-sealing properties as well as the desired
Has permeability to gases and vapors
can be specified as follows:

First layer

linear low density polyethylene

with a low melt index 20 % to 50 %

conventional polyethylene lower

Low melt index density 0 % to 40 %

EVA with approximately 12 % vinyl acetate 20 % to 50 % second layer

EVA with approximately 30 % vinyl acetate 50 % to 90 % ionomer resin (e.g. SURLYN (registered

Trademarks) or the like) 0 % to 40 %

Anti-fog material 7 % to 12 %

Without taking costs into account, technically excellent results are obtained with the following percentages:

First layer

linear low density polyethylene

with low melt index 50 %

EVA with about 12% vinyl acetate 50 %

Second shift

EVA with about 30 % vinyl acetate 50 %

Ionomer resin (e.g. SURLYN (registered trademark) or similar) .40 %

Anti-fog material 10%

With the following percentages, good results are achieved from an economic point of view from the standpoint of function, especially for use in the packaging and storage of fresh food, which, together with the manufacturing costs, make the product competitive on the market: First layer

linear low density polyethylene

with low melt index 35 %

conventional low density polyethylene with low melt index 35 %

EVA with about 12% vinyl acetate 30 %

Second shift

EVA with about 30 % vinyl acetate 50 %

Ionomer resin (e.g. SURLYN (registered trademark) or similar) 40 %

Anti-fog material 10 %

The films according to the invention have corresponding proportions even in the percentages of the first layer good deformation properties at the lowest possible cost, whereas, as can be seen from the above the composition of the second layer is mainly with reference to the intended use the film is determined and only partially allows changes to reduce costs.

For example, cold stretch films of the invention can be made with three layers to provide one Creating a barrier against the passage of gases and vapors, d. H. with a layer 15 (Fig. 2) which is arranged between the two different layers described above. The intermediate layer with a The blocking function can be made up of a thin film made of polyvinyl chloride (PVDC) or a thin film Polyamide resin (e.g. nylon) can be formed.

The films of the invention, either with two layers or with an intermediate layer between the two layers, can according to conventional coextrusion processes for Manufacture of coextruded thin films will. However, such a film is preferably through

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a method and a device according to IT-PA 9426 A / 80, with a coextrusion and a blowing process, manufactured.

It can also be seen that the films of the invention with only two layers or with the additional intermediate layer can be produced in that the layers are produced separately and then by a conventional method and apparatus for making Composite foils are combined.

The films of the invention can be prepared by methods conventional in the food packaging field can be provided with heat-shrink properties.

The advantages of the films of the invention can be clearly seen; the foils effectively replace the Potash film made of PVC for the packaging of fresh products (or frozen) food without the disadvantages of the transmission of traces of harmful Components on the food that comes into contact with the film. The films of the invention

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are chemically inert and do not even transmit traces of any material. Even with the toughest test in which the transfer of film substances to vegetable oil is checked, there was absolutely no transfer detectable.

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Claims (12)

GLAWE, DELFS, MOLL & PARTNER · ·:. ··. . · -, .- PATENTANWÄLTE 3323629 \. :: .. "*: ..: '' .EiJROP ^ AtJPATENTATTORNEYS RICHARD GLAWE KLAUS DELFS DR ING DlPLHNG ULRICH MENGDEHL WALTER MOLL DIPL-CHEM OR.RER NAT DIPL-PHYS DR- RER NAT HEINRICH NIEBUHR - OFF BEST INTERPRETER DIPL-PHYS DR PHiL HABlL Piero Francesconi Via Pico della Mirandola 12 Firenze, Italy 80O0 Munich 26 2000 Hamburg POST BOX 162 POST BOX 25 LlEBHERRSTR. 20 ROTHENBAUM- self-sealing or sealable, transparent 4 <o89) cold stretchable film for packaging food or the like MUNICH A 38 claims 1. Self-sealing or sealable, transparent, cold-stretchable film, characterized by at least two superimposed, different layers of adhesive thermoplastic material, the first layer being a mixture of linear low-density polyethylene (LLDP) and ethylene vinyl acetate (EVA) with a vinyl acetate content of approximately 12 %, and the second layer comprises ethylene vinyl acetate (EVA) with a vinyl acetate content of approximately 30% together with a percentage of ionomer resin (to vary the permeability properties) and an anti-fog material known per se in thermoplastic films for the packaging of foodstuffs. CR = SCNER BANK. HAMBURG, 4030 «8 .RLZ 2003CxJQOj POSTSCHECK HAMBjRG 1476C 2" O-BlZ 200-M20) TELEGRAM SPECHTZ'r.5 2. Film according to claim 1, characterized in that the linear polyethylene is lower Density of the first layer has a low melt index and a limited proportion by a conventional one Is replaced by low density polyethylene with low melt index. 3. Film according to claim 1 or 2, characterized in that the mechanical properties z. B. extensibility, flexibility at low temperatures and tear resistance, and the properties with regard to the adhesiveness for the purpose of self-sealing and the relative gas and vapor permeability can be achieved through the following ranges of percentage contents of the components: First layer linear low density polyethylene with a low melt index 20 % to 50 % conventional polyethylene lower Density 0 % to 40 % EVA (with approximately 12 % vinyl acetate) 30 % to 50 % second layer EVA (with about 30 % vinyl acetate) 50 % to 90 % Ionomer resin 0 % to AO % Anti-fog material 7 % to 12 % 4. Film according to any one of the preceding claims, characterized by the following percentage contents of the various components: First layer linear low density polyethylene with low melt index 50 % EVA (with about 12 % vinyl acetate) 50 % Second shift EVA { with about 30 % vinyl acetate) 50 % Ionomer resin. 40 % Anti-fog material 10 % 5. Film according to any one of claims 1, 2 or characterized by the following percentage contents of the components: First layer linear low density polyethylene with low melt index 35 % conventional low density polyethylene 35 % EVA (with approximately 12 % vinyl acetate) 30 % second layer EVA (with about 30 % vinyl acetate) 50 % Ionomer resin 40 % Anti-fog material 10 % 6. Film according to any one of the preceding claims, characterized in that a third layer is placed between the first and second layers to provide an additional barrier to prevent the passage of gases and vapors or to create precise permeability properties for the film to rent. 7. Film according to claim 6, characterized in that the intermediate layer is a film is made of polyvinyl chloride. 8. Film according to claim 6, characterized in that the intermediate layer is a film made of polyamide resin (nylon). 9. A method for producing the film according to any one of the preceding claims by coextruding the film materials to form the composite film. 10. A method for producing a film according to any one of claims 1 to 8, characterized in that the film is produced by coextrusion and a blow molding process is produced in which the method and the device according to IT-PA 9426 A / 80 is used. 11 .. A method for producing a film according to any one of claims 1 to 8, characterized through the steps of forming the film of the first and second layers and the intermediate layer and the joining and gluing of these layers to form a composite film. 12. A method for producing a film according to any one of claims 1 to 8, characterized in that the composite film by means of a conventional method is provided with heat shrink properties. -V