WO2003086751A2

WO2003086751A2 - Multi-layer, tubular packaging casing

Info

Publication number: WO2003086751A2
Application number: PCT/EP2003/003565
Authority: WO
Inventors: Ekkehard Beer; Wolfram Goerlitz; Bernd Hoecker; Dieter Flieger
Original assignee: Ticona Gmbh
Priority date: 2002-04-12
Filing date: 2003-04-05
Publication date: 2003-10-23
Also published as: DE10216473B4; EP1497120A2; WO2003086751A3; DE10216473A1; AU2003229612A8; AU2003229612A1

Abstract

The invention relates to a multi-layer, tubular packaging casing for filling with a pasty product. The inventive packaging casing has a significantly reduced permeability to steam and atmospheric oxygen.

Description

Multi-layer, tubular packaging wrapper

description

The present invention relates to a multilayer, tubular packaging casing for pasty filling material, in particular artificial sausage casing based on a cycloolefinic copolymer. It essentially consists of an outer layer based on aliphatic polyamide, aliphatic copolyamide and / or cycloolefinic copolymer or a polymer mixture of at least one of these compounds, a middle layer which either consists of EVOH or else at least one partially crystalline polyolefin and from more than 5% by weight of at least one cycloolefinic copolymer and, if appropriate, adhesion-promoting component and an inner layer based on aliphatic and / or partially aromatic polyamides and / or aliphatic and / or partially aromatic copolyamides and / or cycloolefinic copolymer and, if appropriate, adhesion mediating layer between the outer and inner layer.

Casings based on polyamide are increasingly used for packaging food, in particular as artificial sausage casings. For this purpose, a casing material is required for different types of sausage, which has a low water vapor permeability, so that the weight loss when storing the sausage due to water release of the sausage mass remains as small as possible. The sausage then shows a wrinkle-free, tight-fitting casing even after prolonged storage; there are no gaps between the sausage mass and the inside of the casing, which leads to jelly sales of the sausage mass. For this purpose it is known to combine the polyamide layer with a polymer layer which has a lower water vapor permeability than the polyamide layer. In contrast, the oxygen permeability of this composite film is still too high for other foods. Sausage mass of the liver sausage type discolors due to the addition of oxygen, so that these casings are not suitable for these types of sausage. An oxygen barrier layer is therefore additionally required in the polyamide film to reduce the oxygen permeability. EP-A-0 305 959 describes a multilayer polyamide film which, for. B. is provided in the form of a heat sealable bag for packaging meat and poultry. It consists of a barrier layer for oxygen from a partially aromatic copolyamide (PA 6I / 6T), which consists of units of hexamethylenediamine, terephthalic acid and isophthalic acid. This copolyamide layer forms the core layer of the film. It is surrounded on both sides by polyolefin layers, which form a water vapor barrier, the inner polyolefin layer being intended to prevent the escape of moisture from the packaged food into the core layer made from copolyamide. Pure polyolefin layers, however, are disadvantageous as the inside of sausage casings because they lead to insufficient adhesion between the sausage mass and the inner wall of the sausage casing and promote jelly sales.

EP-A-0 127 296 (= US-A-4,606,922) has already attempted to solve this problem. There it has been proposed to provide a more ionic for the inside of a multilayer polyamide film and to treat the inside with ionized radiation. DE-A-38 16 942 (= US-A-4,888,223), in the case of a multilayer polyamide shell, to avoid the formation of wrinkles, teaches treating the inside layer of polyolefin resin with corona discharge and, if necessary, sprinkling it with starch powder. These proposals thus show the disadvantage that an additional pretreatment of the casing on the inside is required to prevent wrinkles and jelly deposits between the sausage mass and the casing inside.

EP-A-0 467 039 attempts to solve the disadvantages mentioned by means of a multilayer film structure based on polyamide, an outer layer consisting of aliphatic polyamide, aliphatic copolyamide or a polymer mixture. Another layer based on polyethylene or polypropylene or mixtures of these polymers is to take on the function of the water vapor barrier. It turns out, however, that these polymers only adequately fulfill the barrier effect against water vapor, alone or in a mixture, if they are present in such a film structure in a sufficient layer thickness. The increased layer thickness of these polymers is also necessary in order to give the tubular packaging envelope the necessary rigidity so that the pasty filling material remains in a defined shape. The present invention is therefore based on the object of providing a tubular packaging casing which, after being filled, has sufficient adhesion to the coated filling material, in particular sausage mass, has little or no jelly sales, and has sufficient rigidity to give the filling material in a defined form hold, the shirring process of the casing can be carried out without the addition of anti-blocking agents and no additional pretreatment of the inside of the casing is necessary. The casing should be easy to use as an artificial sausage casing, especially for cooked and cooked sausages. It should have a greatly reduced permeability with respect to water vapor and atmospheric oxygen. Sausages with this coating should not show any noticeable loss of moisture even after four to six weeks of storage, which is reflected in a decrease in the weight of the sausage and a wrinkled appearance, nor should peeling of the casing from the sausage mass between the casing wall and the sausage mass should result in jelly drop. The envelope is also intended for oxygen-tight packaging of air-sensitive goods, such as. B. sausage masses of the liver sausage type, be suitable so that they do not change during the storage period, especially not discolour in an unsightly manner.

This object is achieved by a multilayer, tubular packaging envelope for pasty filling material, characterized in that it is essentially composed of: an outer layer based on aliphatic polyamide, aliphatic copolyamide, and / or cycloolefinic copolymer or a polymer mixture containing at least one of these connections; a middle layer, which either consists of ethyl vinyl alcohol or contains at least a partially crystalline polyolefin and at least 5% by weight of a cycloolefinic copolymer and adhesion-promoting components if there is no adhesion-promoting agent between the outer and / or inner layer and the middle layer Layer is located; an inner layer based on aliphatic and / or partially aromatic polyamides and / or aliphatic and / or partially aromatic copolyamides and / or cycloolefinic copolymer and at least one adhesion-promoting layer which is located between the outer and / or inner layer and the middle layer if the middle layer contains no adhesion-promoting components.

The dependent claims indicate expedient developments of the shell. The casing shows a wall thickness which is comparatively very thin for multilayer packaging casings made of polyolefins and polyamide with good barrier properties, which is essentially due to the use of the cycloolefinic copolymer. It is preferably 30 to 60, in particular 40 to 50, micrometers. The lower limit is around 25 to 30 micrometers. The hose caliber is adapted to the intended use. When using the casing for cooked and cooked sausages, the tube caliber is generally 30 to 160, in particular 40 to 135 mm. The proportion of the outer layer in the total thickness of the shell is 45 to 80%, the middle layer 15 to 75% and the inner layer 2 to 35%. The proportion of optional additional adhesion-promoting layers is between 0 and 35%.

The packaging wrapper consists of at least three layers, namely an outer, a middle and an inner layer, the outer and the inner layer made of polyamides, optionally and / or cycloolefinic copolymer, and the middle layer made of a polymer mixture of a cycloolefinic copolymer and another, partly crystalline Polyolefins exist. If necessary, the three-layer structure is expanded to a five- or multi-layer structure in which there is at least one layer around the middle layer that improves the adhesion of the middle layer to the inner and outer layer or other intermediate layers.

The middle layer usually has the greatest thickness compared to the other layers. The thickness is generally 10 to 50 μm with a total thickness of the film of 25 to 60 μm. This layer can therefore generally be regarded as the actual carrier layer of the multilayer casing.

The middle layer of the packaging envelope shows practically no water and water vapor absorption and, above all, practically no water vapor permeability. For for this purpose, the middle layer should have a minimum thickness of 2 μm. In general, a thickness of 5 to 25 μm is sufficient to achieve the water vapor impermeability required for sausage casings for scalded and cooked sausages. The middle layer consists of a mixture of a cycloolefinic copolymer and partially crystalline polyolefin and optionally an adhesion-promoting component, which improves the adhesion between the inner or outer layer with the middle layer. This adhesion-promoting component is either largely homogeneously distributed over the entire cross section of the middle layer or forms a separate layer which forms an inner interface with the adjacent layers and encloses the middle layer. In the first case, the middle layer is made up of a single layer, in the second case the middle layer preferably consists of a polyolefin core and in each case a layer of polyolefin / adhesion promoter or only adhesion promoter on the surfaces of the polyolefin core, so that in the first case one a total of three layers, in the second case a total of five layers, of the shell wall. Due to the use of a cycloolefinic copolymer in the mixture with partially crystalline polyolefins, depending on the selected mixing ratio, the barrier effect against water vapor as well as the mechanical stiffness, in contrast to the use of conventional alpha-olefins at a given thickness, can be increased or increased significantly, e.g. greater than 25% the layer containing the cycloolefinic copolymer can be made significantly thinner in order to achieve the same barrier effect against water vapor and mechanical rigidity.

When using the cycloolefinic copolymer, the glass transition temperature Tg is preferably matched to the melting points of the other, partially crystalline polymers in order to be able to ensure a homogeneous melting of the polymer mixtures.

In one embodiment as a three-layer film structure, in which the total thickness of the tube wall can be kept particularly thin and takes into account the fact that some manufacturers of multilayer, tubular packaging casings only have systems for three-layer film structures, the adhesion-promoting component is incorporated into the middle layer , This increases the binding force between the middle layer and the adjacent layers with a sufficient amount of the adhesion-promoting component, so that at The coextrusion of the three layers creates a firm bond, which does not experience any separation of layers even when exposed to hot water when the sausage is scalded.

In this embodiment, the proportion of the adhesion-promoting components is generally 5 to 50% by weight, in particular 10 to 35% by weight, based on the polymer mixture present in the middle layer. It should be noted, however, that the water vapor permeability of the middle layer increases somewhat due to the functional groups of the adhesion promoter, which is why this addition should be as small as possible in a three-layer film structure. In general, 20 to 25% by weight, based on the polymer mixture of the middle layer, is therefore sufficient.

In the case of a five-layer embodiment, the problem of reducing the barrier effect against water vapor in the middle layer can be avoided in that the component imparting the adhesion forms its own layer. Furthermore, this layer which improves the adhesion can be made so thin that, in relation to the necessary addition of the adhesion promoter in the middle layer, smaller amounts of the adhesion promoter can be used, so that the entire film structure becomes less expensive.

If, in addition to the normal barrier action of the partially crystalline polymers and cycloolefinic copolymers, a special barrier to oxygen is required, a five- or seven-layer embodiment is preferred in which EVOH is used in the middle layer or in one of the layers on the inside. The layers around the EVOH layer consist of a mixture of partially crystalline polymers and cycloolefinic copolymer. In the seven-layer embodiment, the adhesion-promoting layers are in a separate form above these layers. In the five-layer embodiment, the adhesion-promoting component may be in the layer in which the cycloolefinic copolymers and partially crystalline polymers are located. The outer and inner layers based on aliphatic polyamide, aliphatic copolyamide and / or cycloolefinic copolymer or a polymer mixture of at least one of these compounds are located above these layers or the adhesion-promoting layers. The middle layer is a mixture containing a cycloolefinic copolymer and a partially crystalline polyolefin.

Homopolymers of z. B. ethylene or propylene or a copolymer of linear alpha-olefins having 2 to 8 carbon atoms or a mixture of these polymers. Suitable copolymers are C ₂ / C ₃ and C ₃ / C ₄ copolymers and C ₂ / C ₃ / C ₄ terpolymers, e.g. B. a mixture of C ₃ / C copolymer and C ₂ / C ₃ / C terpolymer. The homopolymers of ethylene or propylene, copolymers of linear and / or cyclic alpha-olefins having 2 to 8 carbon atoms or mixtures of these polymers, or copolymers with units of ethylene / propylene, ethylene / propylene / butylene or Propylene / butylene or from mixtures of these polymers. Suitable materials are known in principle to the person skilled in the art and are described, for example, in Sachtling, Plastic Pocket Book, 27th Edition 1998 on pages 375 to 415, to which reference is made.

The cycloolefinic copolymer has a glass transition temperature of greater than 60 ° C., which is matched to the glass or melting temperature of the other polymers, and an average molecular weight Mw of 500 to 500,000, preferably 3,000 to 150,000. The cycloolefinic copolymer is advantageously a copolymer of ethylene and / or an alpha-olefin and a cyclic, bicyclic or polycyclic olefin. The cycloolefinic copolymer derived from at least one cyclic or polycyclic olefin of the formula I to VII is particularly advantageous

CH

( IN THE )

R

(V)

HC

(CH-7.) _R

wherein the radicals R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ^{8 of} the formulas I to VI may be the same or different, and H, C ₆ -C ₂ o-aryl, Cι -C ₂₀ alkyl, F, Cl, Br, I mean, n is an integer from 0 to 5, and m is an integer from 2 to 10, in particular copolymers of one or more of the cyclic or polycyclic olefins of the formula I to VII with ethylene. The cycloolefinic copolymer is very particularly advantageously a copolymer of ethylene and norbornene. The cycloolefinic copolymer is present in the middle layer in an amount of more than 5% by weight, particularly advantageously in amounts of 5 to 100% by weight, in particular 5 to 50% by weight.

The adhesion-promoting component is an agent as is known for the production of coextruded composites from polar and non-polar plastics such as polyamide and polyolefin. It usually consists of a polyolefin resin modified with functional groups, which is composed of ethylene and / or propylene units, optionally also further linear alpha-olefins having 3 to 10 carbon atoms. The olefinic chain ensures compatibility with the polyolefin of the middle layer and the extrudability of the adhesion-promoting component. The functional groups are in particular units of vinyl acetate, vinyl alcohol, ethylenically unsaturated carboxylic acids such as acrylic acid and methacrylic acid, and the esters and salts, in particular Na and Zn salts, and also also ethylenically unsaturated carboxylic acid anhydride groups. They lead to a sufficient the wettability of the polyamide and polyolefin melt during coextrusion, so that a firmly adhering bond is created.

Suitable adhesion promoters also consist of graft polymers, copolymers or terpolymers with ethylene or propylene units with at least one comonomer from the group comprising (meth) acrylic acid, (meth) acrylic acid esters (esters of n-alkanols with 1 to 6 carbon atoms, e.g. butyl acrylate), ethylene vinyl acetate and / or maleic anhydride. The proportion of units with functional groups is usually 3 to 12% by weight, based on the weight of the adhesion-promoting polymer. The modified polyolefin resins also include rubber modified polyethylene. The adhesion-promoting component is present in the middle layer in an amount of 0 to 50% by weight, advantageously 5 to 50% by weight, in particular 10 to 35% by weight.

If the casing is to be colored, it is expedient to incorporate the dye or the color pigments into the middle layer so that they do not come into direct contact with the filling material. This measure has the advantage that the stretching process is not disturbed by the nucleating effect of color pigments. It has also been shown that color pigments can be dispersed particularly easily and uniformly in the middle layer.

The outer layer usually has an equal or less thickness in relation to the middle layer, but in special embodiments it can also be thicker than the middle layer. The thickness is generally greater than 5 μm to 50 μm with a total thickness of the film of, for example, 25 to 60 μm. This

The layer can thus either serve as a cover layer or, owing to its share of the total thickness, can sometimes assume a certain carrier function, the middle layer, as a result of the selection of the polymers, in particular the cycloolefinic copolymer and thus also the rigid polymer, generally also the carrier function of the Whole film is inside, if it should be thinner than other layers in a special embodiment. Usually the outer layer is made up of a single layer and shows a higher water absorption than the middle layer The outer layer absorbs water when the sausage is scalded or boiled, which is gradually released again when the sausage is cooled and stored. As a result, the outer layer shrinks when drying, so that the sausage casing lies tightly against the cooled sausage mass and without wrinkles. Since the casing is practically waterproof and impermeable to water vapor through the middle layer, the outer layer cannot absorb moisture from the sausage mass. The outer layer consists essentially of an aliphatic polyamide, aliphatic copolyamide and / or cycloolefinic copolymer or a polymer mixture of at least one of these compounds. Polyamides of this type are known to the person skilled in the art and are described, for example, in Sachtling, Kunststoff-Taschenbuch, Hanser Verlag, 27th edition 1998 on pages 465 to 478, to which reference is made.

The aliphatic polyamide is a homopolycondensate of aliphatic primary diamines, in particular with 4 to 8 C atoms, and aliphatic dicarboxylic acids, in particular with 4 to 10 C atoms, or a homopolymer of omega-aminocarboxylic acids with 8 to 12 C atoms or their lactams. The aliphatic copolyamide contains the same units and is e.g. a polymer based on one or different aliphatic diamines and one or different aliphatic dicarboxylic acids and / or one or different omega

Aminocarboxylic acids or their lactams. Examples of suitable dicarboxylic acids are adipic acid, azelaic acid, sebacic acid and dodecanedicarboxylic acid, suitable diamines are tetra-, penta-, hexa- and octa-methylenediamine, and hexamethylenediamine is particularly preferred. An example of omega-aminocarboxylic acids is 11-aminoundecanoic acid, examples of lactams are epsilon-caprolactam and omega-laurolactam. Particularly preferred aliphatic polyamides are polycaprolactam (PA 6) and polyhexamethylene adipinamide (PA 66) or mixtures of these polyamides. The aliphatic copolyamide contains various of the units mentioned. A preferred aliphatic copolyamide consists of caprolactam, hexamethylene diamine and adipic acid units (PA 6/66).

The outer layer of the tubular packaging casing has a higher water absorption capacity than the middle layer and, in a preferred embodiment, also as the inner layer, so that it functions well as a sausage casing before the filling process water and shows the required suppleness. The middle layer with the reduced water absorption and water vapor permeability, on the other hand, enhances the barrier properties with respect to the inner layer. PA 6 and PA 66, which are also in a mixture with other water-absorbent polymers, including polyester, are therefore particularly suitable for the outer layer. The addition of polyester facilitates the biaxial stretching of the tube, ie the required stretching force is surprisingly reduced, and the strength of the envelope is also increased overall.

Suitable polyesters are condensation products of diols and aromatic dicarboxylic acids, in particular terephthalic acid and optionally additionally isophthalic acid. Polyesters are known to the person skilled in the art and are described, for example, in Sachtling, Kunststoff-Taschenbuch, Hanser Verlag, 27th edition 1998 on pages 478 to 495, to which reference is made. To a small extent, the polyester can be modified with aliphatic dicarboxylic acids, such as adipic acid. The diols are in particular aliphatic compounds of the formula HO- (CH ₂ ) n-OH (n = 2-8), such as ethylene glycol, 1,4-butylene glycol, 1,3-propylene glycol or hexamethylene glycol, and alicyclic compounds such as 1, 4-cyclohexanedimethanol. Polybutylene terephthalate is preferably used in the polymer mixture. The proportion of the polyester ester is usually 5 to 15% by weight, based on the polymer mixture of the outer layer of the packaging casing.

In individual cases, it is advisable to modify the outer polyamide layer by adding other polymers which are compatible with the polyamide or with the polyamide mixture up to a proportion of 25% by weight. Suitable, additional polymers are, for example, polyolefins, ie homopolymers or copolymers of alpha-olefins having 2 to 8 carbon atoms, in particular ethylene, propylene and butylene, preferably polyethylene, in particular LDPE and LLDPE, and also modified polyolefins with functional groups, such as those used in the middle layer as a suitable adhesion-promoting component, for example polyolefins with carboxyl radicals, that is to say groups which consist of acids, esters, anhydrides and salts of carboxylic acids and / or cycloolefinic copolymers. The polyolefin and the modified polyolefin improve the adhesion of the outer layer to the middle layer and increase the smoothness of the casing. However, they are generally A maximum of only 3 to 10% by weight is present in the outer layer in order not to significantly impair the water absorption capacity and the strength of the outer layer. The outer layer may contain conventional additives, for example matting agents, in order to reduce the gloss. Furthermore, the outer layer shows good color adhesion and can be printed on the entire surface without any problems.

In one embodiment, the inner layer consists of aliphatic polyamide, aliphatic copolyamide and / or cycloolefinic copolymer or a polymer mixture of at least one of these compounds. Other polymers, e.g. Polyolefins, polyesters or ionomers can be present in the inner polyamide layer in a proportion of up to 15% by weight. This layer thus consists of a polymer or a polymer mixture, as has already been described above for the outer layer. However, the aliphatic polyamide of the inner layer preferably shows a lower water absorption capacity than the aliphatic polyamide of the outer layer. For the inner layer, therefore, aliphatic polyamides with relatively long methylene chains such as. B. PA 11 or PA 12 or copolyamides used with these units. The adhesion of the inner layer to the sausage mass can be improved by adding ionomers to the aliphatic polyamide. The layer of aliphatic polyamide or copolyamide prevents direct contact between the polyolefin and the sausage mass. The oxygen barrier property of this inner layer is comparatively low. If the shell is to have a reduced oxygen permeability, the inner layer consists of a partially aromatic polyamide and / or partially aromatic copolyamide or of ethyl vinyl alcohol. The partially aromatic polyamide or copolyamide consists of aliphatic and aromatic units.

In a first embodiment of the partially aromatic polyamide, the diamine units predominantly or exclusively form the aromatic units. In contrast, the dicarboxylic acid units of this embodiment are predominantly or exclusively aliphatic and usually contain 4 to 10 C atoms. Preferred aliphatic dicarboxylic acid units are sebacic acid and azelaic acid, in particular adipic acid.

In a second embodiment of the partially aromatic polyamide, the diamine units predominantly or exclusively form the aliphatic units, while the Dicarboxylic acid units consist predominantly or completely of residues of aromatic dicarboxylic acids, in particular isophthalic acid and terephthalic acid. The aliphatic diamine units usually consist of 4 to 8 carbon atoms, preferably caprolactam and / or hexamethylene diamine units. The preferred partially aromatic copolyamide of the second embodiment consists of caprolactam and / or hexamethylenediamine units as well as terephthalic acid and / or isophthalic acid units, in particular PA 6I / 6T.

The first embodiment of the partially aromatic polyamide or copolyamide optionally contains up to 5 mol% of aliphatic diamine units and up to 5 mol% of aromatic dicarboxylic acid units. Likewise, the second embodiment of the partially aromatic polyamide or copolyamide can contain up to 5 mol% of aromatic diamine units and up to 5 mol% of aliphatic dicarboxylic acid units.

However, it has been shown that inner layers made of pure partially aromatic polyamide and / or pure partially aromatic copolyamide are relatively stiff and hard and lead to the fact that the inner sides of the flattened casing lying on top of one another tend to stick together.

It is therefore particularly advantageous when the casing is used as a sausage casing if the inner layer additionally contains aliphatic polyamides and / or copolyamides. In particular, if the partially aromatic polyamide or copolyamide consists of the second embodiment mentioned, the partially aromatic polyamide is present in a mixture with a saturated, linear aliphatic polyamide and / or a saturated linear, aliphatic copolyamide. A shell with an inner layer made of this polymer mixture is also particularly easy to stretch biaxially.

This additional aliphatic polyamide in the polymer mixture of the inner layer consists of the reaction product of an aliphatic dicarboxylic acid, preferably with 4 to 10 C atoms, with aliphatic primary diamines, preferably with 4 to 8 C atoms. Examples of suitable dicarboxylic acids are adipic acid, azelaic acid, sebacic acid and dodecanedicarboxylic acid, suitable diamines are tetra-, penta-, hexa- and octa-methylenediamine, hexamethylenediamine is particularly preferred. Furthermore, the additional aliphatic polyamide of the polyamide mixture can also be composed of units of omega-aminocarboxylic acids having 6 to 12 carbon atoms or their lactams, for example of 11- Amioundecanoic acids with 6 to 12 carbon atoms epsilon-caprolactam or omega-laurolactam. The aliphatic copolyamides in the mixture with the partially aromatic polyamide or copolyamide contain various of the units of the aliphatic polyamide mentioned. A preferred aliphatic copolyamide consists of caprolactam, hexamethylenediamine and adipic acid units. PA 6, PA 66, PA 6/66, PA 11 and PA 12 or mixtures of these polymers are particularly preferred as an additional component in addition to the partially aromatic polyamide and / or copolyamide in the inner layer.

The proportion of the partially aromatic polyamide and / or copolyamide in the inner

Layer is preferably 5 to 85, in particular 10 to 40 wt .-%, based on the polymer mixture of partially aromatic and aliphatic polyamides and copolyamides. In this range of the mixing ratio, a smooth, yet relatively oxygen-impermeable inner layer is achieved. On the other hand, as the proportion of the partially aromatic polyamide / copolyamide increases, the adhesion of the sausage mass to the inner wall of the casing increases, so that the casing properties can also be varied in this regard by increasing the proportion of the partially aromatic polyamide / copolyamide. The proportion of COC can also be varied from 0 to 25% by weight.

The tubular casing is preferably produced by coextrusion of the polymers forming the individual layers through an annular nozzle, for example using a system as described in EP-A-0 305 874. Due to the biaxial stretching, the shell is oriented and consequently shows excellent resistance to deformation and elastic elasticity. The stretching takes place at 70 to 95 ° C in a stretch ratio of 2.4 to 3.8, in each case in the longitudinal and transverse directions. The area stretch ratio is 7 to 12. To improve the dimensional stability, partial or complete heat setting may be carried out after stretching. This is usually done at 120 to 160 ° C. As a result of the heat setting, the film shows only a relatively small shrinkage of less than 20, in particular less than 15%, in the longitudinal and transverse directions when exposed to heat up to about 90 ° C. The packaging casing can be easily processed into sausage casings. The gathering process can surprisingly be carried out without the addition of inorganic or organic antiblocking agents. It is sufficient if only the usual gathering aids such as paraffin oil and water are used. The pleats are completely removed after the skin has been removed and filled and are no longer recognizable from the finished sausage.

The casing can be filled with sausage mass plump and wrinkle-free without the filling pressure causing undesired bulging of the casing or delamination of the layers. Even with heavy sausages with one _. In the subsequent cooking process to a core temperature of 80 ° C., there is no formation of long corners, no pear-shaped deformations and no "bag-in-bag" formation. The sausages obtained are cylindrical and have a uniform cross section. Due to the high material strength and the excellent elastic resilience, there is no costly cooling of the sausages in cold water. A short, intermittent cooling shower with a subsequent cooling phase in air is sufficient.

Because of the increased water vapor barrier, a cooked sausage with the casing according to the invention can be stored for at least 8 weeks without serious weight loss and without wrinkling. In the case of veal sausage fillings, the graying of the sausage material occurs much later compared to stretch-oriented PA 6 casings (of the same film thickness), which can be attributed to an improved oxygen barrier.

Sausages with the casing according to the invention can be cut smoothly and without tearing. No layer separation occurs when the shell is peeled off in a spiral. The casing according to the invention is particularly suitable for use as a sausage casing, in particular as a casing for liver sausage, scalded sausage, meat sausage, blood sausage and cooked sausage. Such sausages are described, for example, in DE 298 03 965 U1, DE 299 14 336 U1, DE 198 37 733 A1, DE 29824273 U1, DE 20013974 U1, DE 20007988 U1, DE 02639177 C2 and DE 29517106 U1. The invention is illustrated by the following examples. Percentages are in percent by weight.

example 1

Using co-extrusion technology, a 5-layer pipe is constructed using 4 single-screw extruders and a downstream co-extrusion round die (state of the art according to EP-A-0 467 039):

Outer layer: 85% PA 4432-2 / 15% PA C35 adhesion promoter 100% Bynel 41E623 middle layer: blend of 80% ULDPE (Atane SL4102)

20% COC (TOPAS 9506)

Bonding agent 100% Bynel 41E623 inner layer: 85% PA 4432-2 / 15% PA C35

molded with a diameter of 30 mm and a total wall thickness of 0.33 mm. The individual layer thicknesses are:

Outer layer: 133 μm

Adhesion promoter 62 μm

Middle layer: 136 μm

Adhesion promoter 62 μm

Inner layer: 34 μm

This tube is brought to stretching temperature (about 80 ° C.) within 2 seconds by means of IR radiation.

By applying a pressure of about 1 bar inside the heated tube, it is stretched biaxially by an area factor of 7.33 and heat-set, laid flat and wound up in a second bubble.

The thickness of the resulting film is 58 μm. A determination of the individual layer thicknesses results in:

18.1 μm outer layer 8.5 μm adhesion promoter 18.6 μm middle layer 8.5 μm adhesion promoter 4.7 μm inner layer.

Example 1a

Analogous to example 1, but with 10% silver batch in the base layer:

Outer layer: 85% PA 4432-2 / 15% PA C35

Bonding agent 100% Bynel 41E623

Middle layer: blend of 70% ULDPE (Atane SL4102)

20% COC (TOPAS 9506)

10% silver color in LDPE

Bonding agent 100% Bynel 41E623 inner layer: 85% PA 4432-2 / 15% PA C35

Outer layer: 133 μm

Adhesion promoter 62 μm

Middle layer: 136 μm

Adhesion promoter 62 μm

Inner layer: 34 μm,

The thickness of the resulting film is 58 μm. A determination of the individual layer thicknesses gives: 18.1 μm outer layer 8.5 μm adhesion promoter

18.6 μm middle layer 8.5 μm adhesion promoter 4.7 μm inner layer.

Example 1b

Analogous to example 1, but with 10% silver batch in the base layer:

Outer layer: 80% PA 4432-2 / 15% PA C35 / 5% COC (TOPAS 9506)

Bonding agent 100% Bynel 41E623

Middle layer: blend of 70% ULDPE (Atane SL4102)

20% COC (TOPAS 9506)

10% silver color in LDPE

Adhesion promoter 100% Bynel 41E623 inner layer: 85% PA 4432-2 / 15% PA C35 / 5% COC (TOPAS 9506)

Outer layer: 133 μm

Adhesion promoter 62 μm

Middle layer: 136 μm bonding agent 62 μm

Inner layer: 34 μm.

This tube is brought to stretching temperature (about 80 ° C.) within 2 seconds by means of IR radiation. By applying a pressure of about 1 bar inside the heated tube, it is stretched biaxially by an area factor of 7.33 and heat-set, laid flat and wound up in a second bubble.

The thickness of the resulting film is 58 μm. A determination of the individual layer thicknesses gives: 18.1 -μm outer layer 8.5 μm adhesion promoter

18.6 μm middle layer 8.5 μm adhesion promoter 4.7 μm inner layer.

Example 2

Analogous to example 1a, but with a reduced PA outer layer:

Outer layer: 85% PA 4432-2 / 15% PA C35

Bonding agent 100% Bynel 41 E623

Middle layer: blend of 70% ULDPE (Atane SL4102)

20% COC (TOPAS 9506)

10% silver color in LDPE

Bonding agent 100% Bynel 41E623 inner layer: 85% PA 4432-2 / 15% PA C35

The thickness of the resulting film is 52 μm. A determination of the individual layer thicknesses results in:

1 1.8 μm outer layer 8.5 μm adhesion promoter 18.6 μm middle layer

8.5 μm adhesion promoter 4.7 μm inner layer.

Example 3

Analogous to example 1, but with a reduced COC middle layer:

Outer layer: 85% PA 4432-2 / 15% PA C35

Bonding agent 100% Bynel 41 E623 Middle layer: blend of 70% ULDPE (Atane SL4102)

20% COC (TOPAS 9506)

10% silver color in LDPE

Bonding agent 100% Bynel 41 E623 inner layer: 85% PA 4432-2 / 15% PA C35

The thickness of the resulting film is 46 μm. A determination of the individual layer thicknesses results in:

14.7 μm outer layer

8.6 μm adhesion promoter

9.5 μm middle class

8.6 μm bonding agent, 4.8 μm inner layer

Example 4

Tubular film with a higher proportion (40% by weight) of COC in the middle layer:

Outer layer: 85% PA 4432-2 / 15% PA C35

Bonding agent 100% Bynel 41 E623

Middle layer: blend of 60% ULDPE (Atane SL4102)

40% COC (TOPAS 9506) adhesion promoter 100% Bynel 41 E623 inner layer: 85% PA 4432-2 / 15% PA C35

21.3 μm outer layer

8.1 μm bonding agent 9.4 μm middle layer 8.1 μm bonding agent 4.8 μm inner layer. Example 5

Analogous to example 4, tubular film with 100% by weight COC in the middle layer:

Outer layer: 85% PA 4432-2 / 15% PA C35

Bonding agent 100% Bynel 41 E623

Middle layer: 100% COC (TOPAS 9506) adhesion promoter 100% Bynel 41 E623

Inner layer: 85% PA 4432-2 / 15% PA C35

The thickness of the resulting film is 45 μm. A determination of the individual layer thicknesses results in:

22.0 μm outer layer

8.1 μm adhesion promoter

1.9 μm middle class

8.1 μm adhesion promoter 4.8 μm inner layer.

Example 6

3-layer tubular film with COC and adhesion promoter in the middle layer:

Outer layer: 85% PA 4432-2 / 15% PA C35

Middle layer: 80% COC (TOPAS 9506) 20% Bynel 41 E623

Inner layer: 85% PA 4432-2 / 15% PA C35

The thickness of the resulting film is 35 μm. A determination of the individual layer thicknesses results in: 21.3 μm outer layer 7.9 μm middle layer 5.2 μm inner layer.

Comparative Example 1

Using conventional coextrusion technology, a 3-layer pipe is constructed using 3 single-screw extruders and a downstream coextrusion round die (prior art according to EP-A-0 467 039):

Outer layer: PA 6 (Grilon F 47) Middle layer: Dry blend made from 80% HDPE (Lupolen 2411 D)

20% adhesion promoter based on LLDPE / methacrylic acid copolymer (Plexar OH 002)

Inner layer: FA 6 (Grilon F 47)

molded with a diameter of 23 mm and a total wall thickness of 0.35 mm. The individual layer thicknesses are:

Outer layer: 220 μm

Middle layer: 90 μm

Inner layer: 40 μm

By applying a pressure of about 1 bar inside the heated tube, the tube is stretched biaxially by an area factor of 8.6 and heat-set, laid flat and wound up in a second bubble.

The thickness of the resulting film is 40 μm. A determination of the individual layer thicknesses gives:

25 μm outer layer 10 μm middle layer 5 μm inner layer.

Comparative Example 2

A 3-layer pipe is made analogously to Example 1 with a structure of (also prior art according to EP-A-0 467 039):

Outer layer: PA 6 (Grilon F 47)

Middle layer: Dryblend made of 80% HDPE (Lupolen 2441 D) and 20% adhesion promoter based on LLDPE / methacrylic acid copolymer (Plexar OH 002). Inner layer: Dryblend made of 70% PA 6 (Grilon F 47) and 30% PA 61 / 6T (Grivory G 21)

produced and stretched to form a hose and heat-set as in Example 1. The layer thickness distribution corresponds to Example 1.

As comparative examples, a) a single-layer hose made of an oriented polyamide / polybutylene terephthalate blend (oPAx PBT blend according to DE-A-34 36 682, b) an unoriented single-layer blow hose made of polyamide-12 (PA-12) and c) a multi-layer cover with the structure of polyamide bonding agent-polyethylene

(PA / HV / PE) according to DE-A38 16 942.

Table 1 contains mechanical characteristics and the barrier properties of these sleeves. Table 2 shows the application comparison based on meat sausage or. Liverwurst fillings.

(The advantageous properties of the casings according to the invention were particularly evident in the application technology assessment.

5) The values of water vapor permeability WD and oxygen permeability were standardized to the film thickness of Comparative Example No. 1.

Claims

claims

1. Multi-layer, tubular packaging sleeve for pasty filling material, characterized in that it is essentially composed of: an outer layer based on aliphatic polyamide, aliphatic copolyamide, and / or cycloolefinic copolymer or a polymer mixture containing at least one of these compounds; a middle layer, which either consists of ethyl vinyl alcohol or contains at least a partially crystalline polyolefin and at least 5% by weight of a cycloolefinic copolymer and adhesion-promoting components, if there is between the outer and / or inner layer and the middle

Layer does not contain an adhesion-promoting layer; an inner layer based on aliphatic and / or partially aromatic polyamides and / or aliphatic and / or partially aromatic copolyamides and / or cycloolefinic copolymer, and - at least one adhesion-promoting layer which is between the outer and / or inner layer and the middle layer if the middle layer does not contain any adhesion-promoting components.

2. Cover according to claim 1, characterized in that the cover contains further internal layers based on aliphatic and / or cycloolefinic polymers or copolymers of polyolefin or polyamide.

3. Shell according to claim 1 or 2, characterized in that the layers containing cycloolefinic copolymer contain 5 to 100 wt .-% cycloolefinic copolymer and the partially crystalline polyolefin essentially from one

Homopolymers of ethylene or propylene, copolymers of linear and / or cyclic alpha-olefins with 2 to 8 carbon atoms or mixtures of these polymers.

4. Shell according to one or more of the preceding claims, characterized in that the layers containing cycloolefinic copolymer contain 5 to 50 wt .-% cycloolefinic copolymer.

5. Shell according to one or more of the preceding claims, characterized in that the cycloolefinic copolymer has a glass transition temperature of greater than 60 ° C.

6. Shell according to one or more of the preceding claims, characterized in that the cycloolefinic copolymer has an average molecular weight Mw of 500 to 500,000, preferably 3,000 to 150,000.

7. Shell according to one or more of the preceding claims, characterized in that a cycloolefin copolymer and / or a cycloolefinic polymer is used as the cycloolefinic copolymer.

8. Shell according to one or more of the preceding claims, characterized in that a copolymer of ethylene and / or an α-olefin and a cyclic, bicyclic or polycyclic olefin is used as the cycloolefinic copolymer.

9. Shell according to one or more of the preceding claims, characterized in that the cycloolefinic copolymer is derived from at least one cyclic or polycyclic olefin of the formula I to VII

IT

IR ¹

HC CH

(CH _9. ) _R

wherein the radicals R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ^{8 of} the formulas I to VI may be the same or different, and H, C ₆ -C ₂ o-aryl , C * ι-C ₂ o-alkyl, F, Cl, Br, I mean, n is an integer from 0 to 5, and m is an integer from 2 to 10

10. Shell according to one or more of the preceding claims, characterized in that a copolymer of ethylene and norbomene is used as the cycloolefinic copolymer.

11. Shell according to one or more of the preceding claims, characterized in that the partially crystalline polyolefin consists of copolymers with units of ethylene / propylene, ethylene / propylene / butylene or propylene / butylene or mixtures of these polymers.

12. Shell according to one or more of the preceding claims, characterized in that the middle layer, which contains the cycloolefinic copolymer, contains a mixture of the partially crystalline polyolefin, the cycloolefinic copolymer and 5 to 50% by weight of the adhesion-promoting component.

13. Case according to one or more of the preceding claims, characterized in that the adhesion-promoting component forms a separate intermediate layer between the middle and the / the outer and inner layer.

14. Case according to one or more of the preceding claims, characterized in that the adhesion-promoting component of the middle layer or intermediate layer is based on polyolefin resin modified with functional groups.

15. Shell according to one or more of the preceding claims, characterized in that the outer layers essentially of a polyamide or copolyamide with aliphatic dicarboxylic acid units with 4 to 10 carbon atoms and aliphatic diamine units with 4 to 8 carbon atoms and / or units of omega-aminocarboxylic acids with 6 to 12 carbon atoms or their lactams or from a polymer mixture with at least one of these polyamides and / or copolyamides.

16. Cover according to one or more of the preceding claims, characterized in that the outer layer made of a mixture of polyamide and / or

Copolyamide and up to 25 wt .-% of a further polymer or linear or cycloolefinic copolymer, based on the polymer mixture of ionomers or polyester.

17. Cover according to one or more of the preceding claims, characterized in that the inner layer is composed of one or more partially aromatic polyamides and / or partially aromatic copolyamides, of linear aliphatic polyamide and / or aliphatic copolyamide or, if appropriate, additionally of cycloolefinic copolymers.

18. Shell according to one or more of the preceding claims, characterized in that the inner layer of one or more partially aromatic polyamides and / or partially aromatic copolyamides and aliphatic dicar- bonic acid units and / or aliphatic copolyamide and / or is additionally composed of cycloolefinic copolymers.

19. Shell according to one or more of the preceding claims, characterized in that the entire proportion of the partially aromatic polyamide and / or

Copolyamids 5 to 85 wt .-% based on the mixture of partially aromatic and aliphatic polyamides and copolyamides of the inner layer and the proportion of cycloolefinic copolymer is between 0 to 50 wt .-%.

20. Shell according to one or more of the preceding claims, characterized in that the inner layer contains as a linear aliphatic polyamide or copolyamide one of the polymers mentioned in claim 15.

21. Cover according to one or more of the preceding claims, characterized in that its wall thickness is 30 to 60, preferably 40 to 50, micrometers, the proportion of the outer layer being 45 to 80%, the middle layer being 15 to 75%, the inner layer is 2 to 35% and the proportion of the additional adhesion-promoting layers is 0 to 35%.

22. Use of a casing according to one or more of claims 1 to 21 as a sausage casing.

23. Sausage, characterized in that it contains a casing according to one or more of claims 1 to 21.

24. Sausage according to claim 23, characterized in that it is a liver sausage, scalded sausage, meat sausage, blood sausage or cooked sausage.