EP1678243A1

EP1678243A1 - Multi-layer foodstuff casing comprising an intermittently distributed organic substance in the outer layer

Info

Publication number: EP1678243A1
Application number: EP04765508A
Authority: EP
Inventors: Bernhard Feron; Ulrich Delius; Stefanie Stalberg; Christian Auf Der Heide; Dirk Auf Der Heide
Original assignee: Kalle GmbH and Co KG
Current assignee: Kalle GmbH and Co KG
Priority date: 2003-09-30
Filing date: 2004-09-22
Publication date: 2006-07-12
Also published as: DE10345839A1; WO2005033187A1

Abstract

The invention relates to a multi-layer, tubular foodstuff casing based on a thermoplastic plastic, comprising at least one polyamide and/or copolyamide-based layer. The outer layer of the casing contains at least one organic substance, which is intermittently distributed in the layer, producing a pigmentation. The outer surface of the casing has a matt appearance and resembles a natural intestine or a cellulose-fibre intestine. The casing is preferably used as an artificial sausage casing.

Description

Multilayer food casing with discontinuously distributed organic substance in the outer layer

The invention relates to a multilayer, tubular food casing based on thermoplastic material which comprises at least one layer based on polyamide and / or copolyamide.

Food casings, especially sausage casings, are traditionally made from natural casing,

Textiles, fiber-reinforced cellulose or made from collagen fibers. These casings still account for the largest share on the world market, especially for higher quality sausages. In second place follow the shells of thermoplastic materials, especially those made of polyamide or polyamide-polyolefin composite systems. In turn, the majority of the thermoplastic sheath becomes stretch oriented during manufacture resulting in thermal shrinkage and better mechanical properties. The collagen or skin fiber intestine is made from bovine skins after a very complex and polluting process. The tissue of the split skin is thereby digested with acids (eg lactic acid) up to the fibrils, the resulting highly viscous mass is then extruded and slowly and compactly precipitated and solidified with gaseous ammonia or ammonium hydroxide. During drying, crosslinking then takes place (hardening) in order to give the products sufficient stability so that they survive the brewing process without substantial loss of strength. However, natural casings as well as skin fiber casings are becoming increasingly less accepted by end users due to various incidents such as the BSE epidemic in cattle and the misuse of antibiotics. There are also legal restrictions. An alternative to the mentioned intestines is therefore desirable. Cellulose casings, even those with fiber reinforcement, can only do this task to a limited extent. Also, the manufacturing process is no less expensive and environmentally harmful than the collagen process. Advantage of the thermoplastic sausage casings is their simple, inexpensive production. However, the end user often has reservations about sausages in these cases. The naturally glossy surface of the plastic often gives the impression of lesser quality of the product. Added to this is the poor grip of the sausages when the plastic surface is moistened with moisture or grease.

In cases of natural casing, fiber-reinforced cellulose or collagen, the fibrous consistency provides a coarse textured, rough surface. The consumer, who has known this look for many decades, thus associates a higher value or traditional production of the sausage product.

For some years, ways have been known to produce blends of, for example, starch and synthetic polymers which have become thermoplastic articles for everyday use, e.g. B. can process films.

Thus, EP-A 596 437 describes mixtures of starch or thermoplastic starch with aliphatic polyesters or polyvinyl alcohol, which can be processed by thermoplastic extrusion into water-resistant, yet biodegradable films.

Similarly, WO 92/19680 discloses blends of a starch component and one or more synthetic polymers, especially homopolymers or copolymers of hydroxycarboxylic acids, polyurethanes, polyamides and vinyl alcohol copolymers. Furthermore, plasticizing aids such as

Be included glycerol.

The subject of WO 95/004108 are biodegradable thermoplastic films containing hydrophobically modified starch esters and biodegradable polyesters such as polylactides, polycaprolactone or polyhydroxyalkanoate. These films are distinguished from conventional starch-containing materials by improved water resistance, processability and mechanics. EP-A 479964 discloses moisture-insensitive multilayer films having a central layer of thermoplastic starch and additives to which a layer of polyolefin or a polyolefin-starch blend is attached on both sides. The trapped starch layer should cause a low gas permeability. The primary consideration in this as well as in many other publications is the biodegradability of the material or of the films produced therefrom.

In EP-A 709030 thermoplastic starch is described for the first time as a material for sausage casings. This application provides that native strength under

Addition of aggregates such as glycerol and with the supply of mechanical and thermal energy destructured and then mixed with additives such as fibers, proteins, crosslinking agents and optionally with synthetic polymers. Due to their high water vapor permeability, single-layer sausage casings obtained from these blends are of primary importance

Production of salami suitable. The problem, however, is that the necessary for a sausage casing mechanical properties, such as strength, elasticity and shrinkage capacity, are not yet fully achieved.

It was therefore the task of a tubular food casing

To provide polymer base, which is similar to rough on the outside as a cellulose fibrous or natural gut. The shell should have a correspondingly low gloss. It should have the properties required for a sausage casing, such as strength, elasticity and shrinkage, also be easy and inexpensive to produce.

The problem is solved with a multi-layered polymer shell whose outer layer contains organic particles.

The invention accordingly provides a multilayer, tubular

Food casing based on thermoplastic material which comprises at least one layer based on polyamide and / or copolyamide and thereby characterized in that the outer layer contains at least one organic substance which is discontinuously distributed in the layer.

The organic substance is preferably a polysaccharide, a protein or a high-temperature-stable synthetic fiber or a high-temperature-stable plastic powder. This outer layer modified in this way forms an extremely rough, matt surface during the production of the hoses, which surface is very close in optical as well as haptic terms to the surfaces of cellulose fiber casings or collagen casings. Thus, the outside of the casing according to the invention has a gloss value of less than 20, preferably less than 15, more preferably less than 8, in each case at an irradiation angle of 60 ° (determined according to DIN 67 530).

The further layers bring about the mechanical properties typical of plastic casings, such as tensile strength and elasticity, and, if appropriate, also high gas and water vapor tightness.

These layers are preferably based on (co) polyamides, polyolefins, ethylene / vinyl alcohol copolymers (EVOH), vinylidene chloride (co) polymers, optionally also (co) polymers having adhesion-promoting properties. The casing according to the invention comprises at least one layer based on polyamide and / or copolyamide (abbreviated to (co) polyamide).

The polyamide layer (hereinafter abbreviated to "A") may contain one or more aliphatic (co) polyamides, moreover also partially aromatic (co) polyamides. Examples include: aliphatic polyamides: PA6, PA66, PA12; aliphatic copolyamides: PA4 / 6, PA6 / 66, PA6 / 69, PA6 / 9, PA6 / 10, PA6 / 12 polyetheramides, polyesteramides, polyetheresteramides, polyamide urethanes, poly (ether-block-amides); partially aromatic polyamides: PA6-I, nylon-MXD6 (polycondensate of m-xylylenediamine and adipic acid); partially aromatic copolyamides: PA 6-1 / 6-T, PA 6 / 6-1.

Preferred are PA 6, PA 66, PA 12, PA 6/66, nylon MXD6 and PA 6-I / 6-T as well

Mixtures of two or more of these polyamides. The proportion of partially aromatic (co) polyamides is generally not more than 40% by weight, based on one layer (A).

In addition, (A) may contain other polymers, for example olefinic

Copolymers such as EMAA (ethylene-methacrylic acid copolymer), derived therefrom ionomers, EVOH or (hot) water-soluble synthetic polymers such as polyvinyl alcohol (partially and completely saponified), copolymers of vinyl alcohol with propen-1-ol, polyalkylene glycols, polyvinylpyrrolidone, copolymers from vinylpyrrolidone and at least one .alpha.,. beta.-olefinically unsaturated monomer, polymers of N-vinylalkylamides or (co) polymers of acrylic acid and / or acrylamide. The proportion of the other polymers is preferably not more than 35 wt .-% based on layer (A). In addition, layers (A) may also contain pigments and / or other plastic-typical additives. The thickness of these layers is generally 15 to 85 microns, preferably 25 to 65 microns.

The polyolefinic layers (hereinafter abbreviated to "B") are generally composed of polyethylene, polypropylene and / or copolymers having units of ethylene, propylene and / or α-olefins having 4 to 8 C atoms and / or dienes. Also functionalized vinyl monomers, e.g. Vinyl acetate, (IVIeth) acrylic acid and

(Meth) acrylic acid esters are suitable as co-building blocks. Particularly suitable are C ₂ / C ₃ and C ₂ / C ₈ copolymers. The layers (B) primarily have the function of a moisture barrier, since polyolefins generally have a very low water vapor permeability. In addition, layers (B) may still contain pigments, such as those typically used for coloring or UV

Protection can be used. The layers (B) generally have a thickness in the range of 3 to 20 microns, preferably 4 to 15 microns. In order to additionally achieve a good barrier for oxygen and other gases, layers of plastics with corresponding blocking effect can be added (hereinafter referred to as "C"). Suitable plastics for this purpose are ethylene-vinyl alcohol copolymers (partially or completely saponified, "EVOH"), and vinylidene chloride copolymers (for example with vinyl chloride or methyl acrylate as comonomer, "PVDC"). These polymers may also be admixed with additives such as plasticizers and other polymers such as copolyamides or ionomers. The layer (C) generally has a thickness of 3 to 20 μm, preferably 5 to 15 μm.

It should be noted that layers corresponding to (A), (B) and (C) often do not adhere to one another in the film composite by themselves. Adhesion is achieved by incorporating additional primer interlayers ("HV") which adhere well to the two adjacent layers. Suitable adhesion promoters are, in particular, graft copolymers or linear copolymers (where copolymers also contain more than two types of monomer) with ethylene and / or propylene units and also components from the group consisting of (meth) acrylic acid, (meth) acrylic acid ester, vinyl acetate, maleic anhydride. Preferred are u.a. Maleic anhydride grafted polyethylene (LLDPE-g-MAA), ethylene / acrylic acid ester copolymers, and ethylene / vinyl acetate copolymers (EVA). The mentioned

Polymers may be included singly or in admixture in the HV layers. In addition, the HV layers may contain other polymers, e.g. Polyethylene and other additives or pigments. The adhesive layers are expediently relatively thin. Its thickness is generally 2 to 8 microns, preferably 3 to 6 microns.

Individual HV layers may also be eliminated if there is sufficient self-adhesion between the functional layers (e.g., between polyamide or EVOH) or by incorporating the adhesion promoter component into the components of the adjacent B layer.

The layer disposed on the outer surface of the shell (hereinafter referred to as "Z") generally consists of a blend of at least one poly saccharide and / or at least one high-temperature-stable synthetic fiber or powder and at least one thermoplastic. The polysaccharide may be of natural origin or chemically derivatized, it may be branched, crosslinked or linear.

Suitable polysaccharides of this type are, in particular, native or thermoplastic starch (TPS) or starch derivatives. In the area of underivatized starch, native or thermoplasticized corn and potato starch is preferred. Starch derivatives are, for example, starch esters (such as starch acetates, maleates, propionates, butyrates, lauroates or oleates), starch xanthates, phosphates, sulfates or nitrates, starch ethers (such as starch methyl ether, ethyl ether, propyl ether, butyl ether, alkenyl ether, hydroxyethyl ether, hydroxypropyl ether), grafted starches (eg grafted with maleic acid or succinic anhydride) or oxidized starches (such as dialdehyde starch, carboxy starch or starch degraded with persulfate).

As an alternative to or in combination with the above-listed starches or starch derivatives, it is also possible for other components from the family of polysaccharides to be present. In particular, vegetable powders or fibers (such as, among others, cellulose, cotton, kapok, flax, linen, hemp,

Jute, kenaf, ramie, sisal, peat, straw, wheat, potatoes, tomatoes, carrots, coconut, pineapple, apples, oranges, spruce, pine, cork, etc.). In addition, organic, synthetic, high temperature stable synthetic fibers or powders are also suitable, e.g. based on polyethylene, polypropylene, polyamide, polyacrylonitrile, polyesters, fluoropolymers, polysulfones, polyethersulfones,

Polyether ketones, polyphenylene sulfides, polyaramides, polyimides, aromatic polyesters, polyquinoxalines, polyquinolines, polybenzimidazoles or ladder polymers. Such components have also proven to be very effective for the production of a rough, textured surface in addition to the starches or starch derivatives and other polysaccharides.

The organic substance contained in the outer layer expediently has a Particle size of 1 to 200 microns, preferably from 15 to 100 microns. Fibrous organic substances generally arrange parallel to the shell surface, and therefore can be longer than the layer thickness. The length of such fibrous substances is generally 1 to 1000 μm, preferably 15 to 50 μm.

As a matrix-forming plastic component, in principle, all thermoplastic polymers are suitable which undergo a polar interaction with the discontinuously distributed organic substance with the aid of functional groups and their softening temperature is low enough to allow a Schmelzeompoundierung with her without the polysaccharide burns or the synthetic fiber or Synthetic fiber powder melts. Suitable are e.g. thermoplastic polyurethanes (= polyether urethanes), aliphatic (co) polyamides, aliphatic or partially aromatic (co) polyesters, polyester ether urethanes, besides vinyl copolymers such as ethylene / vinyl acetate copolymer. Among the polyurethanes are polyadducts, e.g. by reaction of tolylene diisocyanate (TDI), isophorone diisocyanate and / or

Hexamethylene diisocyanate with poly-1, 2-propanediol (PPG) and / or poly-1, 4-butanediol (PTMG) were prepared.

Among the polyamides, PA 6, PA 12, PA 6/66 and PA 6/12 are preferred. The copolymers mentioned are particularly suitable in that their melting points are below 220.degree. C. and thus permit thermally relatively gentle compounding with the polysaccharide component. When using high-temperature-stable synthetic fibers, PA 66 is also suitable as the polymer matrix.

Among the polyesters, preferred are polylactide, polycaprolactone, copolymers of aliphatic diols with aliphatic dicarboxylic acids and terephthalic acid, and poly (butylene glycol terephthalate).

Layer (Z) may further contain other high or low molecular weight components, e.g. softening substances such as glycerol, polyethylene glycols,

Glycerol carboxylic acid esters, phthalates, stabilizers and bactericidal and fungicidal substances. The preparation of the blend of the thermoplastic polymer matrix and the organic substance discontinuously dissolved therein for layer (Z) is generally carried out in a compounding step preceding the tube extrusion by methods known per se. If the discontinuously dissolved organic substance is starch, it may be thermoplastic

Form (TPS) enter into the compound. In this case, it is necessary to first destroy them (transfer from the native helix superstructure to the linear form). This step is already known and described in WO 90/05161 and WO 90/10019. The destructuring is done by supplying thermal and mechanical energy, e.g. by means of a heated kneader or a twin-screw extruder. As plasticizing aids, e.g. Water and / or glycerin proven.

The thermoplasticized (TPS) or native starch is continuously brought together with the intended plastic and unified with further supply of mechanical and thermal energy to a thermoplastic mass. It is advantageous if the plastic forms a continuous matrix in which the starch component is uniformly dispersed.

The above-mentioned additional substances (glycerol, polyethylene glycols,

Glycerincarbonsäureester, phthalic acid esters, stabilizers, bactericidal and / or fungicidal substances) are also added during the kneading or mixing process and incorporated equally.

The layer (Z) can be combined with the other layer types mentioned to form different multilayer structures. It is always essential that layer (Z) is arranged on the outer tube surface and that there is at least one layer with a mechanical bearing function underneath. Preferred layer structures are: (for the abbreviations see above): Hose outer side: Hose inner side 1) Z / A 2) Z / A / B 3) Z / HV / A 4) Z / HV / C 5) Z / A / HV / A 6) Z / A / HV / C 7) Z / HV / A / HV 8) Z / HV / C / HV 9) Z / HV / A / HV / A 10) Z / A / HV / B / HV / A 11) Z / A / HV / C / HV / A 12) Z / HV / A / HV / B / HV / A 13) Z / HV / A / HV / C / HV / A

Structures according to 3), 5) and 11) are particularly preferred.

The preparation of the food casing according to one of the structures described is effected by coextrusion and subsequent tube blowing or biaxial tube stretching. Corresponding methods are familiar to the person skilled in the art.

The blend of the discontinuously dissolved organic substance and the plastic matrix, and the other polymers or mixtures provided, are melted and plasticized in separate extruders and subsequently combined in a heated coextrusion ring die. The emerging annular melt film can now either be inflated directly to a Fol ienschlauch or be performed by a biaxial stretching process with optionally downstream heat setting. In the latter process, the melt film is solidified by rapid cooling to an amorphous pre-hose and this biaxially by subsequent reheating (about 80 ° C) and by means of an enclosed between two nip rolls air cushion stretched. The subsequent thermosetting can be done by the stretched tube is passed through a further heating zone, optionally with stabilization with a second air cushion. In this way, the thermal shrinkage tendency of the shell can be reduced to practical values (ie to about 5 to 20% shrinkage in the longitudinal and transverse directions, measured after 20 minutes storage in 80 ° C warm water).

The food casing according to the invention generally has a total thickness of from 35 to 140 μm, preferably from 50 to 110 μm. The outer layer has expediently a proportion of 15 to 85 μm, preferably from 25 to 65 μm. Because it is made using a ring nozzle, it is seamless. The shell has, depending on the intended use, a diameter of 10 to 300 mm, preferably from 15 to 210 mm.

The food casing according to the invention is particularly suitable as an artificial

Sausage casing.

The following examples serve to illustrate the invention. Percentages are by weight unless otherwise indicated or apparent from the context. "LLDPE" stands for "Linear Low Density Polyethylene",

"MSA" for maleic anhydride.

example 1

(Bladder with outer layer based on polyamide and starch) With the help of the coextrusion technique, a three-layer bladder over three

Single-screw extruder and downstream coextrusion ring made with

a) an inner layer consisting of PA12 ^(® Grilamid L25), b) a middle layer consisting of 80% of a polyethylene LDPE (Lupolen ^® 3020D) was mixed with 20% of a maleic anhydride grafted LLDPE as an adhesive agent Admer NF358E) and c) an outer layer consisting of a thermoplasticized kneader on a conventional two-shaft compound prepared from 50% of copolyamide PA 6/12 (Grilon® CF6S ^®) and 50% starch (TPS) - the latter in turn consisting of 66.6% native corn starch (Cerestar ^® Gel 03402) and 33.3% glycerol and water as softening and destructuring aids.

The total wall thickness of the envelope was 80 μm to 125 μm, its diameter 105 mm. The inner layer had a share of 50%, the middle layer of 10% and the outer layer of 40%. This shell construction corresponds to the structure Z / HV / A described above. The outer layer corresponds to the outer layer Z. It is particularly rough and provides extremely low surface gloss. The surface properties of the hose are listed in the table.

Example 2

(biaxially stretched and heat-set shell with outer layer on base of starch and PA 6/12)

With the help of the coextrusion technique, a three-layer primary tube was produced by means of three single-screw extruders and a downstream coextrusion ring die

a) an inner layer consisting of 80% PA6 ^(® Grilon F34) nd 20% PA 6l / 6T ^(® Grivor G21), b) a middle layer consisting grafted of an adhesion promoter on the basis of MSA LLDPE ^(® Modic-AP L513) and c) an outer layer consisting thermoplasticized from a prepared on a twin-screw kneader compound of 70% copolyamide PA 6/12 ^(® Grilon CF6S) and 30% starch (TPS) - the latter in turn consisting of 50% native corn starch ^(® Cerestar gel 03402) and 50 % Glycerin and water as softening and destructuring aids. The primary tube was cooled rapidly to about 20 ° C and then heated to about 80 ° C and biaxially stretched at this temperature at a Flächenstreck- ratio of 9.25. In a further heating zone, the tube was then heat-set, so that the thermal shrinkage measured in water at 80 ° C was still about 10 to 12%. The diameter of the heat-set

Hose was 108 mm with a total wall thickness of 75 microns to 95 microns. It accounted for 40% on the inner layer, 5% on the middle layer and 55% on the outer layer. The latter corresponds to a layer Z described above. It is characterized among other things by an extremely low surface gloss (see following table).

Example 3

(Blown tube with outer layer based on crystalline cellulose powder and

PA6 / 12)

As described in Example 1, a blown tube was coextruded with the difference that the outer layer Z of a made on a twin kneader compound of 87.5% copolyamide PA 6/12 Grilon CF6S) and 12.5% crystalline cellulose powder ( ^® Jelucel PF60 ) consists.

The total wall thickness of the shell was 105 .mu.m to 140 .mu.m and a diameter of 40 mm. The inner layer had an average proportion of 50%, the middle layer of 10% and the outer layer of 40%. The natural-intestine-like surface properties of this shell reflect the table.

Example 4

(biaxially stretched and heat-set shell with outer layer based on starch and thermoplastic polyurethane) I As described in Example 2, a biaxially stretched thermo-fixed three-layer hose with a diameter of 108 mm was produced at a total wall thickness of 75 .mu.m to 90 .mu.m. In contrast to the above, the outer layer Z consisted of one produced on a twin-screw kneader Compound of 50% aromatic thermoplastic polyurethane ( ^® lrogran VP456 / 40) and 50% thermoplasticized starch (TPS). The latter, in turn, consisted of 70% native maize starch Cerestar Gel 034O2) and 30% of a mixture of glycerine and water as softening and destructuring aids. The outer layer Z was also characterized by a particularly low surface gloss - see table.

Comparative Example V1

(biaxially stretched and heat-set shell without carbohydrate additive in the outer layer)

In the same way as Example 2, a biaxially stretched thermo-set three-layer hose was made consisting of

a) an inner layer consisting of 85% of PA 6 ^(® Grilon F34) and 15% PA 6l / 6T (Grivory G21), b) a middle layer consisting of 50% of a polyethylene LDPE ^(® Escorene LD165BW) mixed with 50% of a MSA grafted LLDPE as an adhesive agent Admer NF518E) and c) an outer layer consisting of 80% PA 6 (Grilon ^® F34) and 10% PA 6I / 6T (Grivory ^® G21) and 10% brown pigment.

The total wall thickness here was 50 microns with a diameter of 80 mm. The inner layer portion was 20%, the middle layer portion 40% and the outer layer portion 40%. The surface is very smooth and shiny in spite of the pigmentation compared to the described inventive sheaths as shown in the table below.

The table shows how clearly the food casing according to the invention by the externally arranged layer (Z), which is a dispersed organic

Contains substance, differ from conventional sheaths in terms of their surface properties.

The roughness values and roughness depths were measured according to DIN 4768.

The average roughness value R _a is the arithmetic mean of all deviations of the roughness profile from the center line within the total measurement distance.

The average roughness R _z is the average value of the individual roughness depths of five consecutive individual measuring sections in the roughness profile.

The maximum roughness R _max is the largest of the five single roughness depths.

The gloss values are determined according to DIN 67530 at the three different irradiation angles 20 °, 60 ° and 85 °.

Claims

claims

1. Multilayer, tubular food casing based on thermoplastic material, which comprises at least one layer based on polyamide and / or copolyamide, characterized in that the outer layer contains at least one organic substance dispersed in a polymer matrix.

2. Food casing according to claim 1, characterized in that the organic substance is a polysaccharide, a protein, a high-temperature stable synthetic fiber or a powder produced therefrom.

A food casing according to claim 2, characterized in that the polysaccharide is native or thermoplasticized starch or a starch derivative.

4. food casing according to one or more of claims 1 to 3, characterized in that its outer side has a gloss value of less than 20, preferably less than 15, more preferably less than 8, each determined at an angle of incidence of 60 °.

5. Food casing according to one or more of claims 1 to 4, characterized in that the matrix-forming polymer of the outer layer is a thermoplastic polyurethane, preferably a polyether urethane, an aliphatic (co) polyamide, an aliphatic or partially aromatic (co) polyester, a polyester ether-urethane and / or a vinyl polymer, preferably an ethylene / vinyl alcohol copolymer.

6. food casing according to claim 5, characterized in that the matrix-forming polymer has a melting point of less than 220 ° C up.

7. Food casing according to one or more of claims 1 to 6, characterized in that the melting point of the high-temperature-stable synthetic fiber is higher than that of the polymer matrix.

8. Food casing according to one or more of claims 1 to 7, characterized in that the polyamide layer contains at least one aliphatic (co) polyamide, optionally blended with at least one partially aromatic (co) polyamides.

9. Food casing according to claim 8, characterized in that the proportion of partially aromatic (co) polyamides up to 40 wt .-%, based on the weight of the polyamide layer.

10. Food casing according to one or more of claims 1 to 9, characterized in that the polyamide layer contains at least one further polymer, preferably an olefinic copolymer, an ethylene / ethyl alcohol copolymer, a polyvinyl alcohol, a vinyl alcohol / propen-1-ol - Copolymer, a polyalkylene glycol, a polyvinylpyrrolidone, a copolymer of vinylpyrrolidone and at least one α, ß-olefinically unsaturated monomer, a polymer of N-vinylalkylamides and / or a (co) polymer of acrylic acid and / or acrylamide.

11. Food casing according to claim 10, characterized in that the proportion of the at least one further polymer is up to 35 wt .-%, based on the total weight of the polyamide layer.

12. food casing according to one or more of claims 1 to 11, characterized in that it contains at least one polyolefin layer, preferably a layer of polyethylene, polypropylene and / or copolymers with units of ethylene, propylene and / or α-olefins with 4 to 8 carbon atoms and / or dienes.

13. Food casing according to one or more of claims 1 to 12, characterized in that it comprises at least one layer with barrier properties for oxygen or other gases, preferably a layer of a layer of ethylene / vinyl alcohol copolymers or PVDC.

14. Food casing according to one or more of claims 1 to 13, characterized in that it comprises at least one layer with adhesion-promoting properties, preferably a layer of a polyolefin, which is provided with functional groups.

15. Food casing according to one or more of claims 1 to 14, characterized in that it comprises not more than 7 layers, preferably not more than 6 layers.

16. Food casing according to one or more of claims 1 to 15, characterized in that it has a wall thickness of 35 to 140 microns, preferably from 50 to 110 microns.

17. Food casing according to one or more of claims 1 to 16, characterized in that it is stretched biaxially and has a residual shrinkage of 5 to 20% in the longitudinal and transverse directions, measured after storage for 20 minutes in 80 ° C warm water.

18. Food casing according to one or more of claims 1 to 16, characterized in that it is blow-molded and has a residual shrinkage of less than 5% in the longitudinal and transverse directions, measured after storage for 20 minutes in 80 ° C warm water.

19. Use of the food casing according to one or more of claims 1 to 18 as an artificial sausage casing.