Multilayer bi-elastic shell of artificial material having high barrier properties

FIELD: packaging materials.

SUBSTANCE: sleeve-like shell is composed of inner layer A, central layer E and outer layer G. Inner layer A tightly fits the contents and mainly consists of aliphatic polyamide or copolyamide and/or polyamide or copolyamide including aromatic links. Central layer E is mainly formed of aliphatic polyamide or copolyamide and/or polyamide or copolyamide including aromatic links. Outer layer G is also formed of aliphatic polyamide or copolyamide and/or polyamide or copolyamide including aromatic links. Located between inner layer A and central layer E is polyolefin intermediate layer C preventing water vapors from penetrating through the layer. Connected with layer A is adhesive layer B. Layer E is coated with adhesive layer D. Oxygen-barrier intermediate layer F is located between outer layer G and central layer E.

EFFECT: increased impenetrability for water vapor and oxygen, increased shelf life of products packed in above shell.

11 cl, 2 tbl, 8 ex

The present invention relates to multi-layered, stretched along two axes artificial shell of material based on polyamide, free from polymerizate polyvinylidenechloride mixture (PVDC-free), which shows a high degree of barrier properties against oxygen and water vapor and provides, in particular, during long-term storage without refrigeration, preventing the loss of weight and effect Pomerania filling.

Casings for sausages and cooked sausages that could practically be used, must meet a wide range of specific requirements.

These requirements mainly include the following:

- high strength shell, such that there was no residual plastic deformation or breaks in the internal pressure developed during filling or cooking;

- correct the cylindrical shape of the finished sausage, such that it had an attractive appearance and, moreover, was well packaged in a large packing containers, such as cartons;

elasticity of sausages, such as to ensure a snug fit shell filling without folds and that the sausage having a good appearance, was equipped with secure locks (clips);

- thermal stability at temperatures of sterilization;

- very high defence is rnie properties against penetration of water vapor to reduce weight loss, so, in order to prevent wrinkling of the product;

- high capacity for adhesion to the sausage meat in order to avoid the formation of gel precipitate between the shell and filling;

- the ability to easily be removed and well cut;

- good ability to capture the various ways of capturing (axial feed, feed screw);

- good ability to thermal deformation to give the shell an annular shape in the conventional ring forms (A-, b-and C-rings), as well as the natural shape of the shell;

security in accordance with the legal regulations relating to food products (indications EG, Public service health protection of consumers and veterinary medicine, BGVV, Control food and drug administration - FDA), as well as compliance with environmental requirements in the absence of halogen compounds and heavy metals;

reliable adhesion to the printing ink;

- low cost of manufacture.

Single layer and multilayer shell existed in the technique before. However, previously developed shell never answered the whole set of necessary requirements.

In the German patent application DE 2850181 described single-layer, stretched along two axes shell made from a polymer mixture of aliphatic polyamide and about Edinboro copolymer. Although when mixed olefin copolymers it is possible to achieve a significant reduction of the penetration of water vapor, but, in particular, PVDC not provided with barrier properties against water vapor. Insufficient barrier properties against water vapor lead to the fact that during storage occur weight loss due to water evaporation. This not only reduces the profit earned for the sausage product, but further leads to the fact that the products become wrinkled and unattractive.

In Japanese patent application JP 1014032 described stretched along two axes, sextravaganza tubular film serving as a casing for sausages and cooked sausages and consisting of three polymer layers, with the outer, surrounding the filling layer is made of aliphatic polyamide (PA), a domestic adjacent to the filling layer is made of copolymers of ethylene with acrylic acid. Layer located between the outer and inner layers and consisting of a polymer based on propylene or ethylene, serves as an intermediate means for adhesion. The internal layer of copolymer of ethylene and acrylic acid provides adhesion to the meat. According to subsequent British patent application GB 2205273, adhesion to the meat of the inner layer of linear low density polyethylene (LLDPE) improve by Dragostea is its impact on the internal side of the tubular film pre-processing in the field of corona discharge. Although thanks to this structure, the film can achieve good barrier properties against moisture, the consumer discovers nevertheless these flaws concerning stability during storage, as too high tear resistance, poor adhesion to the meat and POSELENIE surface sensitive to the action of oxygen and light filling in the retention period.

In European patent application EP-A 0216094 by mixing copolymers of ethylene and vinyl alcohol (EVON) with aliphatic RA achieve improved the ability of single-layer RA-shells to serve as a barrier to the penetration of oxygen while ensuring a high degree of passage of smoke flavouring substances. But, although infused EVON is possible to achieve a significant reduction of permeability to oxygen, it is not enough to effectively suppress the process Pomerania the surface of the filling during storage. Further, insufficient thermal stability EVON results in co-extrusion with their RA at high temperatures to the stitching EVON that interferes with the process of manufacture of the shell. Poor barrier properties against water vapor lead to the shrinkage of the sausage during storage.

In the German patent application DE-A 4141292 described single-layer, oriented along two axes of the tubular RA-shell PI is of evich products, which consists mainly of aliphatic polyamide, copolyamid containing aromatic units, modified acid polyolefin and fine-grained pigment. The shell is intended to create a barrier against light, but the barrier properties against moisture and oxygen is insufficient.

German patent application DE-A 4128081 describes a multi-layered, stretched along the two axes of the tubular film, which contains as a Central layer of at least one layer that serves as a barrier to the passage of oxygen and is made of EVON, aromatic or aliphatic (co)polyamide and an inner layer, at least one layer that serves as a barrier to passage of water vapor and is made of aliphatic (co)polyamide. Such shell meets the requirements for reliable barriers to the penetration of water vapor, and also shows a good adhesion to the filling. At the same time during storage is the moisture transfer from the filling to the center layer that serves as a barrier to the passage of oxygen. As moisture accumulates in the Central layer and cannot pass through the outer polyolefin layer, which is a barrier to the penetration of water vapor barrier for the passage of oxygen during storage is always less reliable. Therefore, this shell does not go is designed for increased shelf life, especially for storage without refrigeration. Further, the outer polyolefin layer has the disadvantage that the film before tamping process should be subjected to, for example, processing in the field of corona discharge in order to ensure sufficient adhesion to the applied printing ink.

German patent application DE-A 4130486 describes a five-layer, coextruding, stretched along the two axes of the tubular film, which is assembled from at least three polyamide layers constituting the Central, inner and outer layers. Between these layers are layers of EVON or intermediate connection layers. When the Assembly of the tubular film one or two intermediate connecting layer consisting of a functionally modified polyolefins, act as barriers against the penetration of water vapor. Such modified polyolefins have through functional groups higher permeability to water vapor than the corresponding unmodified polyolefins, and therefore with the same thickness of the layer they act as barriers to water vapor is not achieved.

German patent application DE-A 0467039 A2 describes a multilayer tubular packaging casing based on polyamide, characterized in that it is formed from the outer layer on the basis of aliphatic polyamide, al is factual copolyamid or polymer mixture, at least one of these compounds, the middle layers of polyolefin and an intermediate connecting component, and the inner layer based on aliphatic polyamides and/or polyamides containing aromatic units. The outer layer is actually bearing layer of the multilayer shell and has a greater thickness in comparison with the two other layers. If you want to improve the barrier properties of the shell with respect to oxygen, the inner layer is made from a mixture of aliphatic polyamide and polyamide containing aromatic units. By doing the inner layer is very thin, it is not necessary to expect a particularly high ability to prevent the passage of oxygen. The middle layer serves as a barrier to the penetration of water vapor, consists of a mixture of polyolefin and a component that provides adhesion. Under component adhesion, refers to a polyolefin modified with functional groups. As modified polyolefins have a higher ability to pass water vapor than the corresponding unmodified polyolefins, through such mixing deteriorates the property of the polyolefin to be a barrier for the passage of water vapor. Next, the middle layer in comparison with a layer of clean material providing adhesion, shows a weaker extent the ü connection with polyamide layers, that can lead to the phenomenon of stratification. This means that shell still does not meet the requirements. Sausages Packed in such membranes, especially when stored without refrigeration, still find increased weight loss, discoloration of the surface of the filling and shrinkage of the product during the increase of storage period.

In the German patent application DE-A 4339337 described tubular film for packaging and filling a paste-like products consisting of five layers. This tubular film, in particular sausage casing based on polyamide differs in that it is made up of inner and outer layers made of the same nylon material consisting of at least one aliphatic polyamide and/or at least one aliphatic copolyamid and/or at least one copolyamid containing aromatic units; intermediate polyolefin layer and two layer providing adhesion and are made of the same material. The share of polyamides containing aromatic units, and/or copolyamids is from 5 to 60%, mainly from 10 to 50%, counting on the total weight of the mixture of polymers consisting of aliphatic polyamides and copolyamids and polyamides and copolyamids containing aromatic units. The disadvantage of this shell are bad bergern the properties against oxygen penetration, that are often the consequence of change (POSELENIE) color sensitive to oxidation filling. It is known that polyamides containing aromatic units have an improved ability to prevent the passage of oxygen compared to aliphatic polyamides, but not provide such a barrier properties, which are copolymers of ethylene and vinyl alcohol.

In European patent application EP-A 0879560 described multi-layered, stretched along two axes wrapper for food products, which has two layers serve as barriers to the passage of oxygen. As a result of implementation needed to achieve sufficient capacity for adhesion mixing polyolefin layer with a material providing adhesion, barrier properties of this layer due to the increased number of functional groups is significantly attenuated. Membranes made as described here, using detect shortcomings concerning the handling and barrier properties, mainly during long-term storage.

Described here as the characteristic of the prior art film structure find individual items of non-compliance of the above set. In particular, commercially available membranes show a lack of properties to be a barrier for water vapor, that is for oxygen. The combination of these barrier properties related requirements that are important for long term storage, is still not achieved.

Therefore, the challenge is to create a sausage casing based on polyamide, which primarily meets all requirements and, in particular, combines the properties to serve as a barrier to the passage of oxygen and water vapor.

In accordance with the invention, the elimination of these serious disadvantages of the known shells on their barrier properties, is achieved by manufacturing the multilayer stretched along the two axes of the tubular film from:

a) internal fitting the filling layer And which consists mainly of aliphatic polyamide or copolyamid and/or polyamide or copolyamid containing aromatic units;

b) a Central layer E, which consists mainly of aliphatic polyamide or copolyamid and/or polyamide or copolyamid containing aromatic units;

c) the outer layer G, which consists mainly of aliphatic polyamide or copolyamid and/or polyamide or copolyamid containing aromatic units, and

d) between the inner layer and the Central layer E lies polyolefin intermediate layer, having the ability to inhibit the passage of water vapor;

(e) on top of the layer And is not orestano associated with it, providing an adhesion layer, and on top of the E-layer is directly associated with providing the adhesion layer D, and

f) between the outer layer G and the Central layer E lies intermediate layer F, which has the ability to inhibit the passage of oxygen.

As the aliphatic polyamide and aliphatic copolyamid suitable are polyamides, as described in General terms the Handbook of artificial materials 3/4 "Polyamide", p.22 and subsequent pages, ed. Carl Hanser, Munich-Vienna, 1998. Aliphatic polyamide is homopolyamide of aliphatic primary diamines and aliphatic dicarboxylic acids or homopolymeric ω -aminocarbonyl acids or their lactams. Aliphatic polyamide contains the same parts and is, for example, a polymer based on one or more aliphatic diamines and one or more dicarboxylic acids and/or various ω -aminocarbonyl acids or their lactams. Aliphatic primary diamines contain mostly from 4 to 8 carbon atoms. Suitable diamines are Tetra-, Penta-, hexa - and octamethylene, particularly preferred hexamethylditin. Aliphatic dicarboxylic acids contain mostly from 4 to 12 carbon atoms. Examples of suitable dicarboxylic acids are adipic Ki the lot, azelaic acid, sabotinova acid and dodecadienol acid. ω -Aminocarbonyl acid or their lactams containing 6 to 12 carbon atoms. Example ω -aminocarbonyl acid is 11-aminoundecanoic. Examples of lactams are ε -caprolactam and ω -laurinlactam. Particularly preferred aliphatic polyamides are polycaprolactam (RA) and polyhexamethylenediamine (RA). The most preferred aliphatic polyamide is RA/66, which consists of parts of caprolactam, diamine and adipic acid.

Polyamides from aromatic components are also described in the Handbook of artificial materials 3/4 "Polyamide", str and subsequent pages, ed. Carl Hanser, Munich-Vienna, 1998. For the extrusion mainly suitable polyamides and copolyamids. The polyamides and copolyamids containing aromatic units can be formed or in the overwhelming number of links diamine or exclusively of aromatic units in the same time units of dicarboxylic acids are mainly or exclusively of aliphatic nature, or parts of the diamine are mainly or exclusively of aliphatic nature, and the links of the dicarboxylic acid will be mainly or exclusively aromatic. Examples of the first form of execution are polyamides and with oleamide, containing aromatic units, in which the aromatic parts of the diamine and the aromatic parts of dicarboxylic acids consist of xylylenediamine and phenylenediamine. Aliphatic chains dicarboxylic acid in this form of execution typically contain from 4 to 10 carbon atoms, in particular, adipic acid, sabotinova acid and azelaic acid. In addition to the aromatic parts of the diamine and aliphatic parts of dicarboxylic acids may also contain, depending on the circumstances, up to 5 mol.% aliphatic parts of the diamine and the aromatic parts of dicarboxylic acid. Especially preferred form of execution consists of links of methoxylamine and parts of adipic acid. This polyamide (PA-MXD6) manufactured by Mitsubishi Gas Chemical Company Inc. under the name of the MX Nylon. Examples of the second form of execution are polyamides and copolyamids, including aromatic units, in which the aliphatic diamines containing from 4 to 8 carbon atoms. Under aromatic dicarboxylic acids are understood to be preferably isophthalic acid and terephthalic acid. In addition to the aliphatic parts of the diamine and the aromatic parts of dicarboxylic acids may also contain, depending on the circumstances, up to 5 mol.% aromatic parts of the diamine and aliphatic parts of dicarboxylic acid. Especially preferably the I form of execution consists of links diamine, isophthalic acid and terephthalic acid. This polyamide (PA6I/6T) is, for example, Fa.Du Pont De Nemours under the name Selar PA. Adding polyamide PA6I/6T containing aromatic units, mostly in amounts of from 2 to 40 wt.% on the layer, preferably from 5 to 20 wt.%. Adding polyamide PAMXD/6 containing aromatic units, mostly in amounts of from 5 to 40 wt.% on the layer, preferably from 10 to 30 wt.%.

The composition of the individual layers a, E and G may be different or the same. In a particularly preferred form of execution of the layers a and G is based primarily on the aliphatic homopolyamide RA 6, and the Central layer E - aliphatic copolyamide RA 66/6. The addition of polyamide RO/6T containing aromatic units, mostly in amounts of from 2 to 40 wt.% on the layer, preferably from 5 to 20 wt.%. Adding polyamide PAMXD/6 containing aromatic units, mostly in amounts of from 5 to 40 wt.% on the layer, preferably from 10 to 30 wt.%.

The thickness of the inner layer And in the preferred form of execution is between 2 and 12 micrometers, in particular between 3 and 8 micrometers.

Suitable polyolefins are homopolymers of ethylene or propylene or copolymers of linear α -olefins containing from 2 to 8 carbon atoms, or mixture is these homopolymers or copolymers. In addition, can be used metallocene polyolefins. Here we are talking about the polyolefins, which are obtained from the use of metallocene catalysts and which have the advantages of polyolefin obtained in the usual way. So, they find increased tear resistance and good barrier properties. The idea of metallocene polyolefins give Bohn and Fleiβ ner in "Kunstoffe" 88 (1998), str-1870, ed. Verlag, Munich.

Layers b and D, promoting adhesion, mainly composed of the modified polyolefin. This refers to modified Homo - and copolymers of ethylene or propylene and further, if necessary, other linear α -olefins containing from 3 to 8 carbon atoms, which include monomers from the group α ,β unsaturated dicarboxylic acids such as maleic acid, fumaric acid, taconova acid or their anhydrides, esters, amides or imides. Further suitable are inomer copolymerizate of ethylene and propylene, as well as, in certain cases, linear α -olefins containing from 3 to 8 carbon atoms, which include α ,β unsaturated dicarboxylic acids such as acrylic acid, methacrylic acid, and/or metal salts and/or alkilany ether or the corresponding graft polymers obtained by grafting the above monomers naprimer, or partially saponified copolymerizate ethylene and vinyl ester, which, if necessary, will polimerizuet inoculation with the monomer of the above acids. The thickness of the layers b and D, providing adhesion, in a preferred form of execution is between 1 and 6 microns. The composition of the layers b and D can be different and equal.

Layer F, which has the ability to inhibit the passage of oxygen, in particular, consists mainly of copolymers of ethylene and vinyl alcohol obtained by saponification of a copolymer of ethylene and vinyl acetate. The ethylene content preferably ranges from 25 to 47 wt.%, especially between 29 and 38 wt.%. The thickness of the layer F in the preferred form of execution is between 2 and 8 μm, in particular between 3 and 6 microns.

The sum of the thicknesses of the layers coextruding shell is from 30 to 80 μm, preferably from 35 to 65 μm. Shell demonstrate ability to free shrink, at least in one direction, measured at 100° after 15 min and equal to 5-25%, mostly 10-20%. At 40° With free shrinkage is less than 3%, which guarantees the necessary stability thermofixing membranes during storage.

Made shell can be painted in one or more layers mainly in the supply of masterbatches. It is preferable staining of the outer layer but it is still possible, in contrast or in addition, to paint and other layers, in particular the Central layer E and/or polyolefin layer C. To optimize the processing and opening of the shell into the inner layer and/or the outer layer can be introduced additives. For this, first of all, be suitable additives antibioticsa and providing the sliding. They are the basis, for example, silicon oxide.

In order to reduce the impact on the filling of light, especially when using unpainted or partially painted shells, you can enter in the individual layers of the additive that absorbs ultraviolet rays. In particular, it can be applied to fine-grained inorganic pigments such as zinc oxide, titanium oxide, iron oxide or silicon dioxide. In a particularly preferred form of execution of inorganic fine-grained pigment is introduced into the film with the fallopian mix with a carrier material which is compatible with the base layer. The amount of pigment is from 0.1 to 5 wt.%, preferably from 0.5 to 2.5 wt.%, counting on the total weight of the shell.

The next object of the invention is the use of these membranes as wrappers for food products or shells animal feed. They are especially suitable for packaging sausages, but also used for packaging of cheeses, test masses or other Pasto is different or liquid food products.

The emergence of a tubular film according to the invention allows the user the ability to manufacture the product, which for extremely long periods of storage, and storage without refrigeration, almost does not lose weight (moisture) through the membrane or lose a little and not undergoing Pomerania due to infiltration of outside air oxygen. Known still shell did not differ sufficiently combination of barrier properties against oxygen and water vapor, particularly during prolonged storage. These drawbacks are eliminated by a tubular casing according to the invention.

Production of tubular casings according to the invention is carried out mainly by way of a "double bubble" or "blown bubble", in accordance with which the first extrudate in the form of a tubular shell subjected to intensive cooling for solidification, and then, in the further course of the manufacturing process, thus obtained initial thick-walled tube (300-600 micrometers) again heated to a temperature that provides the tension of the solid product, so after that stretch both in the transverse and longitudinal directions between two closely interlocked pairs of rollers through the application of pneumatic pressure cushions. Reheat the initial t of the skirts can be carried out in one or several stages, for example, hot air, hot steam, in a water bath with controlled temperature and/or in the infrared emitters. After the first stage stretching is the second camera to do a reverse shrinkage (reduction in diameter) bubble guts again between the two pressing rollers applying pressure pneumatic pillows and simultaneously re-stretching in the longitudinal direction. Varying the degree of air pressure during the subsequent heat-setting, you can adjust the diameter of the tubes. By heat-setting can be precisely set the desired magnitude of shrinkage through the parameters of the inverse shrinkage (quotient of the difference between the thickness stretch and thickness when cured thickness when cured), the heat-setting temperature and time of exposure. To achieve greater flexibility, heat setting may be carried out in the presence of water or in moist air. Before winding the stretched along the two axes of the tubular film it should have sufficient cooling to prevent activation of shrinkage stresses on the package. For cooked sausage products are made stretched along the two axes of the tubular film, a typical outside diameters of which are from 25 to 220 mm, mainly from 30 to 150 mm

Important properties described below sausage, Obolo the EC established by the following method.

Assessment of sausages made in different shells, carried out after cooling the finished sausages to the temperature of the refrigeration room. For manufacturing samples of sausage in each case used the same standardized sausage stuffing. The pressure during the filling has set specific for each sausage casings. A subjective assessment of the individual criteria in the test was carried out with the use of school scores, namely from 1, which represents the best indicator to 6 that indicates the worst performance.

Adhesion to the filling

Subjective assessment of the amount of filling, adhering to the intestine after removing the shells.

Barrier properties

Barrier properties evaluated by assessing the loss of weight during long-term storage (duration 6 months, at 23° C, 75% relative humidity) and subjective visual judgments about the appearance of a gray color on the surface of the filling.

Along with this, take into account technical data measuring the ability to pass water vapor and oxygen:

pass oxygen in cm³·m^-2·d^-1·bar^-1measured at 23° C and 75% relative humidity IT. DIN 53 380;

pass water vapor in g· m^-2·d^-1measured at 23° C and 85% relative humidity IT. DIN 53 122.

The ability is ü be removed

To assess the ability of the shell to pull the intestine is separated from the sausage and cut with a sharp knife. Very good assessment suggests that the intestine is separated from the sausage in a spiral in the form of strips (width of about 3-5 mm), without hooks or cracking. If the gut to pull in any direction, it should mainly grub also in the transverse direction and in any case not take place predominantly in the longitudinal direction. In particular, it reduces the possibility of delamination.

Cylindrical form

Under the cylindrical refers to the constancy of the size of sausages along its length.

The object of the invention is explained in more detail using the following examples.

Examples:

The following examples were carried out using stretched along the two axes of the tubular film with a diameter of 60 mm

Shell received by sextravaganza from different layers according to the invention, and shell in the reference examples are summarized as follows:

In these examples, the thickness of the individual layers relate to the final product, i.e. stretched tubular casings.

Technical and operational assessment of the membranes produced according to embodiments of the invention and reference examples, are summarized in the following tables:

1. Multi-layered, stretched along the two axes of the tubular sheath made of

a) internal fitting the filling layer a, which mainly consists of aliphatic polyamide or copolyamid and/or polyamide or copolyamid containing aromatic units; (b) the Central layer E, which mainly consists of aliphatic polyamide or copolyamid and/or polyamide or copolyamid containing aromatic units; (c) the outer layer G, which mainly consists of aliphatic polyamide or copolyamid and/or polyamide or copolyamid containing aromatic units, and (d) between the inner layer and the Central layer E lies polyolefin an intermediate layer, having the ability to inhibit the passage of water vapor; (e) on top of the layer And is directly associated with providing the adhesion layer, and on top of the E-layer is directly associated with providing the adhesion layer D, and f) between the outer layer G and the Central layer E lies intermediate layer is F, possessing the ability to inhibit the passage of oxygen.

2. The tubular casing according to claim 1, characterized in that the aliphatic polyamides used in the layers a, E, and G are linear (RA) RA 6, PA 66, PA 11, PA 12 and/or linear copolyamide 6.66 PA, PA 6.6, PA 6.8, PA 6.9, PA 6.10, PA 6.11, PA 6.12, or a mixture of the above-mentioned polyamide and copolyamid.

3. The tubular casing according to claim 1, characterized in that the layers a, E and G polyamide or copolyamide containing aromatic units, formed from the elements of the meta-xylylenediamine and adipic acid and/or link diamine, isophthalic acid and terephthalic acid.

4. The tubular casing according to claim 1, characterized in that are used when assembling the layers a, E and G are made different.

5. The tubular casing according to claim 1, wherein providing the adhesion layers b and D consist of a polyolefin modified with functional groups.

6. The tubular casing according to claim 1, characterized in that the polyolefin layer is made of polyethylene, polypropylene, copolymers of ethylene and propylene and/or copolymers based on propylene or mixtures thereof.

7. The tubular casing according to claim 1, characterized in that the layer F, which has the ability to inhibit the passage of oxygen, consists of a copolymer of ethylene and vinyl alcohol with ethylene content elements 25-47 wt.%.

8. TRU is striated shell in one of the preceding paragraphs, characterized in that the total thickness of the layers coextruding shell is 30-80 microns, mainly 35-65.

9. The tubular shell in one of the preceding paragraphs, characterized in that it is subjected to heat-setting.

10. The tubular shell in one of the preceding paragraphs, characterized in that the free shrink, at least in one direction of orientation of the shell, measured at 100° after 15 min, 5 to 25%, mostly 10-20%.

11. The tubular shell in one of the preceding paragraphs, characterized in that one or more colored layers, and the color is preferably occurs when submitting masterbatches.