RU2340195C2 - Food product multilayer hose casing with outer layer of nonuniform thickness and ribbed fibrous-reticular structure - Google Patents

Abstract

FIELD: food industry.

SUBSTANCE: casing comprises at least two layers; the outer layer is of ribbed fibrous-reticular structure which is formed by alternating thickening and thinning sectors with maximum layer thickness in a thickening sector equal to 80 mcm. The outer layer can be broken in some sectors of the casing, i.e. it is not solid. It can be made from polymer or a mixture of polymers whereas melt flow index of each polymer amounts to 0.2-15 g/10 minutes measured according to ASTM D 1238 A.

EFFECT: casing is characterised by low tendency to rupture in case its surface is broken, has pleasant appearance and facilitates clips fixation, especially during clipping of cooked sausage products.

9 cl, 5 dwg, 1 tbl, 9 ex

Description

The present invention relates to a multilayer coextruded sleeve casing for food products, in particular sausages and processed cheeses, with an external layer of inhomogeneous thickness, having a relief fiber-mesh structure, which gives the casing an attractive appearance.

In recent decades, artificial sausage casings based on synthetic polymers, mainly polyamide, have become widespread. Such membranes have several advantages compared to previously used natural, artificial protein and cellulose membranes. Synthetic sausage casings are distinguished by greater mechanical strength, better barrier properties with respect to moisture and oxygen, which increases the possible shelf life of sausages, impermeability to pathogenic microorganisms. In addition, they are produced using simple and high-performance extrusion technologies that do not involve the formation of toxic effluents, such as the production of cellulose casings.

However, the shells based on synthetic polymers in their appearance are very different from the usual for the consumer natural or artificial protein shells. They are characterized by a smooth glossy surface with an unnatural gloss, while natural shells, as a rule, differ in a dull surface, and artificial proteins - in a fibrous structure. Usually, synthetic shells are given additional appeal by means of a printed image deposited on their surface. However, such a printed image usually covers only part of the surface of the casing, since its continuous sealing presents a serious technical problem, associated with the difficulty or inability to apply a decorative layer to the edges of the folded casing, with constant contamination of the image drum, etc.

Another way to change the appearance of synthetic shells is to introduce fillers into the polymer material of the film.

In the patent of the GDR No. 247830, publ. 07/22/1987, the claimed sausage casing, suitable for both raw and smoked, and cooked sausages. The sausage casing according to the invention is made of polyurethane with starch as a filler. The thermoplastic composition consists of 60-90 wt.%, Preferably 70-95 wt.% Polyurethane and 2-40 wt.%, Preferably 5-30 wt.%, Starch. The claimed sausage casing can also be made from a polyurethane-cellulose composition with the introduction of starch. Starch disperses well in polyurethane components or polyurethane melt, so the mixture has no inclusions. The gas-vapor-permeability of the shell depends on the starch content. According to the invention, an extrudable, non-clumping film is obtained having a natural appearance and high gas and vapor permeability. The disadvantages of the claimed films include their large thickness - 0.1 mm, which leads to an increase in the cost of sausage casings.

The sausage casing of polyurethane elastomer, the properties of which are similar to those of the natural gut, is claimed in GDR patent No. 257384, publ. 15. 06. 1988, the Polyurethane composition contains 70-98 wt.%, Preferably 80-95 wt.% Polyurethane, 2-30 wt.%, Preferably 5-20 wt.%, Microcrystalline cellulose. The inventive shell during filling does not form folds and passes air, smoke and water vapor well, has a good ability to shrink and an appearance similar to the properties of a natural gut, physiologically harmless. The sausage casing is suitable for raw and hard smoked, as well as for cooked sausages. However, in the above examples, the film thickness is quite large and amounts to 70-150 μm, in addition, prior compounding of the thermoplastic mixture is required, which also increases the cost of the final product.

In the application WO 03/073861 A1, publ. 09/12/2003, describes a food-permeable shell for water vapor and smoke, especially suitable for uncooked smoked sausages such as salami. It is made of a thermoplastic mixture that contains at least one aliphatic polyamide and / or copolyamide, one inorganic and / or organic filler, and one aliphatic and / or aromatic copolyamide having glycol and / or polyglycol units. As a filler, carbohydrates are used, which may consist of a natural polysaccharide and / or its derivative, as well as branched and cross-linked polysaccharides and their derivatives. Synthetic thermostable fibers or polymer based powders may be used. Inorganic fillers or reinforcing materials such as fiberglass, glass fibers, mineral wool fibers, talc, clay, etc. are also suitable. Organic fillers cause increased permeability of the shell for gas and water vapor. By varying the grain size of the filler, its type and mass fraction, it is possible to control the surface roughness of the shell, as a result of which the shell takes on a silky matte appearance resembling parchment and making it look like a natural intestinal membrane.

A similar solution is given in the patent application WO 03/073862 A1, publ. 09/12/2003, for a single and multilayer shell with a matte, rough surface, giving the impression of a natural one. This shell is the closest to the claimed. For its manufacture, the composition of the thermoplastic mixture is used, the same as in the application WO 03/073861. In a preferred embodiment, the thermoplastic mixture consists of at least one (co) polyamide and at least one organic and / or inorganic filler. The proportion of (co) polyamide in this case is 50-99 wt.%, Preferably 65-98 wt.%, And the total proportion of organic and / or inorganic filler is 1-50 wt.%, Particularly preferably 2-35 wt.% From total weight of thermoplastic mixture. As an organic filler, the authors declare plant powders and fibers, synthetic thermostable fibers or powders based on fluoropolymers, polysulfones, polyethersulfones, polyethersetones, polyphenylene sulfides, polyaramides, polyimides, aromatic polyesters, polyquinoxalines, polyquinolines, polybenzimidazoles, and also. Suitable inorganic fillers are fibers or spherical particles of glassy materials. In a particularly preferred embodiment, the length of the organic fibers or the grain size of such substances is 15-500 microns, the length of inorganic fibers is 1-250 microns. Introduced fillers create a rough microrelief of the shell surface. The method for producing such films involves two stages. First, the granulate is prepared from a mixture of organic material and filler, then the granulate is processed into a sleeve film by blown extrusion or by a biaxial orientation drawing method. Multilayer shells are made by coextrusion using a head for coextrusion of multilayer films, and the layer containing the filler forms the outer layer. Such a casing is used as a sausage casing, especially for cooked sausages, however, its surface has only a slight roughness. In addition, such films do not have sufficiently good tensile strength along / across, and with an increase in the number of fillers, the shell acquires the ability to tear like paper.

At the same time, such polyamide shells, like other known shells with an outer layer of polyamide, are prone to breaks during packing, heat treatment and cooling.

The aim of the present invention is to create a shell that differs in its appearance from the known polymer shells and does not have a characteristic gloss for them, and is also pleasant to the touch.

In addition, it should have a reduced tendency to tear if its surface is disturbed.

Polymeric sausage casings are traditionally made of polyamide. In multilayer sausage casings, the outer layer is most often a biaxially oriented polyamide, which is a brittle material and, even if slightly injured, easily breaks in the direction of the orientation axes. In addition, this layer should be sufficiently thin, otherwise the shell will not have the required degree of elasticity. Injury to the shells can occur at various stages of its production and use with insufficiently fine-tuned equipment, for example, when printing, crimping, stuffing with minced meat, clipping. At the same time, if obvious malfunctions of the equipment, leading to injury to all layers of the shell, are usually obvious and easily eliminated, then minor injuries that damage only the outer layer are not always detected, which leads to rupture of the shell during heat treatment of the sausage, and, accordingly , to the loss of meat in meat processing plants. In addition, if the sausage loaf during the sale is cut into separate pieces, damage to its surface often also occurs, which leads to longitudinal cracking of the shell and loss of presentation.

One of the known methods used to protect the external polyamide layer from damage is the application (lamination, coextruding) on its surface of a polyolefin layer. In this case, an improvement in puncture and tear resistance is actually achieved. However, in this case, the casing has a smooth glossy surface, in addition, the polyolefin layer has a reduced adhesion to the clip, as a result of which technological problems arise during the operations of clip-cutting, precipitation and cooking of sausages. The clip may shift during packing of the casing, as well as during roasting or cooling, leading to a deviation of the shape of the sausage bar from the cylindrical ("pear") or injury to the casing, or it may completely slip off the casserole.

Therefore, another objective of the invention is to improve the fastening of the clip during clipping on the surface of the shell, which is particularly suitable for the manufacture of cooked sausages.

As a result of the studies carried out by the authors of the present invention, it was found that the tasks can be solved by creating a synthetic tubular casing for food products containing at least two layers, while the coextruded outer layer has a relief fibrous-mesh structure.

The embossed fiber-mesh structure of the outer layer is formed by alternating regions of thickenings and thinning,

thickening regions have linear dimensions from 0.1 mm to 250 mm in the longitudinal direction and from 0.1 mm to 15.0 mm in the transverse direction, more preferably from 0.1 mm to 100.0 mm in the longitudinal direction and from 0, 1 mm to 3.0 mm in the transverse;

the thinning regions have linear dimensions from 0.1 mm to 100.0 mm in the longitudinal direction and from 0.1 mm to 30.0 mm in the transverse direction, more preferably from 0.1 mm to 40.0 mm in the longitudinal direction and from 0.1 mm to 15 mm in the transverse;

the maximum thickness of the layer in the area of thickening is 80 microns;

in this case, the coextruded outer layer can be made continuous or with violations of the integrity (continuity) of the layer, that is, non-continuous;

the outer layer of the shell can be made of a polymer or a mixture of polymers, each of which has a melt flow index of 0.2 to 15 g / 10 min, measured according to ASTMD1238A.

The shell can be made straight, curved or spiral;

uniaxially or biaxially oriented;

in addition, it can be cut along one or two edges with the formation of one or two strips of a polymer film, respectively or across the shell, and make packages for food packaging using known methods.

Moreover, any layer or layers of the shell may additionally contain pigment and / or dye, and / or matting additives;

in addition, the outer layer may contain anti-blocking additives and / or glidants and / or matting additives; It can be painted in a color contrasting with the color of the previous painted layer.

In addition, the synthetic sleeve casing according to the invention can be obtained by blown extrusion or biaxial orientation drawing.

Thus, the result of this study was the creation of a sleeve shell for food products, which lacks the gloss inherent in synthetic shells and has a relief fibrous-mesh structure. The embossed fibrous-mesh structure of the shell is visually perceived as a grid deposited on the surface of the shell, while the length of the mesh cells can vary in different ranges: from fine-mesh to coarse-mesh, and even resemble fibers that are parallel to the longitudinal direction of the shell. The absence of gloss on the surface of the shell and the presence of a relief fiber-mesh structure immediately distinguish it from the previously known synthetic shells and make it attractive to the consumer. In addition, the shell is pleasant to the touch.

The creation of an outer layer having a embossed fiber-mesh structure is possible on all polymer sausage casings having a different structure, from one or more layers to their reasonable amount and combination.

The number of polymer layers, their sequence and the choice of materials for the manufacture of the layers are entirely determined by the functional purpose of the shell. The shells intended for long-term storage of food products are made in the form of a multilayer structure in which layers alternating provide barrier properties to water vapor, for example polyolefin, and polymer layers providing barrier properties to the membrane with respect to oxygen, in particular polyamides, copolymers ethylene and vinyl alcohol, polyurethanes, etc. For the manufacture of single- and multi-layer casings for food products that undergo smoking or microbiological maturation during the production process, thermoplastic materials are selected that provide a sufficiently high gas and vapor permeability of the casing, as well as permeability with respect to smoke components of the smoke.

The thermoplastic materials used in the framework of the present invention for the manufacture of the outer layer and subsequent layers must be technologically compatible in the process of coextrusion, that is, they must have intersecting processing temperature ranges, while for the adjustment (adjustment) of the temperature ranges, the use of technological additives, plasticizers, etc. .d.

The thermoplastic materials used for the manufacture of the inner layers must have a melt flow index (hereinafter - IGR) of the layer in the range from 1 to 4 g / 10 min at the extrusion temperature; plasticizers, glidants, nucleating agents, etc. can be used to adjust the value of the melt flow index.

The lower boundary of the melt viscosity is associated with the stability of the technological process of drawing polymer material in the form of a film. The use of thermoplastic materials with a MFI of a layer of less than 1 g / 10 min leads to local disturbances in the continuity of the layer and, as a consequence, frequent breaks in the sleeve. The upper limit of viscosity is determined by the uneven thickness of the film layer. The use of thermoplastic materials, the MFI layer of which is higher than 4 g / 10 min, leads to a non-uniformity of the sleeve thickness of more than 15%. If a polymer mixture is used as a thermoplastic material, the necessary melt viscosity is achieved using polymers with MFI in the range from 0.2 to 15 g / 10 min, measured according to ASTM D 1238 A.

At the same time, for an external layer inhomogeneous in thickness, there are no such severe restrictions on the continuity and unevenness of the thickness; therefore, not only a mixture of polymers, but any polymer having a melt flow index of 0.2 to 15 g / can be used for its manufacture 10 min measured according to ASTM D 1238 A.

Such thermoplastic materials include all commonly used polymeric materials for the manufacture of synthetic sausage casings.

The thermoplastic material may be selected from the group consisting of polyamides, thermoplastic polyurethanes, block copolymers containing polyester blocks and polyamide blocks, olefin polymeric materials, (co) polyesters, thermoplastic elastomers based on styrene copolymers, thermoplastic cellulose ethers.

By polyamide is meant an aliphatic polyamide and / or an aliphatic copolyamide, and / or a partially aromatic copolyamide, and / or a polymer mixture, which includes at least one of these compounds. The aliphatic polyamide and / or copolyamide is selected from the group consisting of polyamide 6, polyamide 66, polyamide 610, polyamide 12, copolyamide 6.66, copodiamide 6.12. Manufacturers and trademarks of these polyamides are well known to those skilled in the art.

Partially aromatic copolyamide should be understood as copolyamides containing in the polymer chain at least 25% of aromatic units, for example, polyamide 6I, 6T, polyamide MXD6. They also include polyamide 61.6, polyamide 6I, 6T, 66, polyamide 6I, 66 and others.

Under olefin polymer material should be understood homopolymers of ethylene and / or propylene, copolymers of ethylene and / or propylene, ionomers. These also include copolymers of ethylene and / or propylene, additionally containing monomeric α-olefin residues with carbon numbers from 4 to 10, and / or unsaturated carboxylic acids, and / or cyclic anhydrides of unsaturated dicarboxylic acids, and / or vinyl alcohol esters .

The thermoplastic cellulose ethers used as the thermoplastic material contain ether residues of at least one of the acids selected from the group consisting of acetic, propionic, butyric acid.

An outer layer having a relief fiber network can be extruded together with a polyamide layer, optionally containing at least one water-soluble polymer selected from homopolymers and / or copolymers of vinylpyrrolidone, N-vinylalkylamide, alkyloxazoline, alkyl glycol, vinyl alcohol, acrylic, acrylic alkylene oxide, (meth-) acrylic acid, maleic acid and / or cellulose ether, and its proportion is 5-40% by weight. The outer layer may also be coextruded with a polyamide layer further comprising starches and / or dextrins and / or starch ethers. The shell made in this way, acquiring advantages in accordance with the objectives of the invention, does not lose its ability to pass smoke components of smoke.

A synthetic sleeve casing for food products with a non-uniform outer layer may contain an additional adhesive layer located between the outer and the underlying polymer layer, if these layers do not have mutual adhesion. As the adhesive material for the polyamide and olefin polymer material, an olefin polymer material modified with at least one grafted compound selected from the group consisting of unsaturated carboxylic acid, glycidyl ester of unsaturated carboxylic acid, cyclic dicarboxylic acid anhydride is selected. Adhesive layers can also be between other layers of shells, provided there is no mutual adhesion between them. At the same time, adhesives can be included directly in one of the adjacent (contiguous) layers. For a person skilled in the art it is quite obvious which adhesives should be used when combining those or other layers to achieve adhesion between them.

In accordance with the goals and objectives of the invention, it is obvious that the claimed shell may contain two or more layers, the main thing is that the outer layer has a relief fibrous-mesh structure. Depending on the purpose of the shell for the manufacture of various types of sausages (cooked sausages of various diameters, including sausages and sausages, as well as cooked smoked and raw smoked sausages), processed cheese, the design of the synthetic shell is chosen. As a rule, it is reasonable to use a shell consisting of 2 to 7 layers, but their number can be large. Additional layers can be layers, for example, based on polyolefins and / or copolymers of ethylene and vinyl alcohol (saponified copolymers of ethylene and vinyl acetate), and / or (co) polyamides, and / or polyesters, and / or polyurethanes with different arrangement sequences. Moreover, the layers may also contain mixtures of polymers belonging to any of the above classes, as well as to various classes. Between the layers may be thin adhesive layers, the thickness of which is mainly 1-5 microns.

The above list of materials only confirms the possibility of their use in the framework of the present invention, but does not limit the use of other thermoplastic materials that satisfy the above criteria, and is not exhaustive.

In accordance with the objectives of the invention, one of the methods for creating the inventive synthetic shell for food is a coextruded method of manufacturing a shell with subsequent orientation. However, it differs from the known methods of manufacturing multilayer shells in that it provides for introducing into the thermoplastic material an outer layer of at least one blowing agent, followed by coextrusion of at least two layers of thermoplastic materials through an extrusion die with a ring die into a multilayer primary sleeve, cooling the primary sleeve, followed by heating, blowing and orientational drawing into the secondary sleeve, heat setting of the secondary sleeve and reeling. Then the shell can be subjected to printing, corrugation, ringing, bending into a spiral, etc.

Under the blowing agent in the present invention is meant a substance that is in a gaseous state at a melt temperature at the outlet of the head (nozzle) and atmospheric pressure or decomposes in an extruder with the release of a substance in a gaseous state, under the same conditions. In the latter case, the blowing agent and the extrusion conditions must be selected so that decomposition begins in any zone of the extruder, except the first, since otherwise gaseous matter may be lost. Organic and inorganic substances that decompose on heating can be used as blowing agents, in particular sodium hydrogen carbonate, potassium hydrogen carbonate, zinc carbonate, ammonium carbamate, urea, azodicarbonamide, citric acid, 5-phenyltetrazole, as well as substances containing residual moisture or containing water in the form of crystalline hydrates. To create a shell with an external layer having a relief fiber-mesh structure, it is advisable to introduce a foaming agent into the thermoplastic material of this layer in an amount of 0.1-5.0% by weight, more preferably 0.3-2.0% by weight. When leaving the head, a sharp expansion of gas occurs, leading to foaming of the thermoplastic material with the formation of open cells separated by partitions of the polymeric material. For the purposes of the present invention, it is preferable to use blowing agents in the form of a concentrate in a polymer carrier. The polymer carrier may be a polyolefin, polyamide or other thermoplastic material used to make the specified outer layer, while the polymer carrier may either be the same or different from the specific thermoplastic material of the outer layer. The specific distribution of the blowing agent concentrate and its concentration in the thermoplastic material, as well as the orientation of the shell (uniaxial or biaxial) and drawing coefficients, influence the distribution pattern of the inhomogeneities of the outer layer. The layer can be made as continuous, while the maximum thickness of the layer in the region of thickenings is 80 μm, and not continuous, that is, the layer in some places of the thinning disappears completely. Unlike the prototype, the implementation and use of such a heterogeneous layer thickness as a single-layer shell is impossible.

The use of such a method is illustrated by examples 3, 5-7.

Another way to create the inventive synthetic tubular sheath is also a method of coextrusion of layers of a polymer film using a multilayer head. The difference in the method in this case is the use of dies rotating in opposite directions to create the outer layer. The fibers of the thermoplastic material emerging from the openings of the spinnerets intersect and weld, forming a different structure (different textures) of the outer layer, from mesh to fiber-like.

The materials of the outer and lower layers can have the same nature, for example polyamide / polyamide or polyethylene / polyethylene, which provides good interlayer adhesion. The implementation of this method is shown in example 1. In the case of using materials of various nature, for example, a pair of polyolefin / polyamide, in order to ensure interlayer adhesion, an additional 50% by weight of the adhesive material should be added to the polyolefin layer. The coextruded outer layer made according to this method has the form of a grid, the thickness of the fibers and the cell sizes of which are determined by the technological parameters of the extrusion process, such as extruder productivity, angular rotation speed of the die, the ratio of longitudinal and transverse stretching. The thickness of the fibers of the mesh coating does not exceed 80 microns.

Another way to create a shell with a relief fiber-mesh structure of the outer layer is the coextrusion method of manufacturing the shell, the difference of which is the hot stamping of the primary sleeve during the coextrusion processing of thermoplastic materials into a multilayer shell with subsequent orientation drawing. The primary sleeve is heated to a temperature of 70 ° C and passed through a pair of heated metal shafts having an engraved pattern on the surface corresponding to the pattern of the outer layer inhomogeneous in thickness, after which it is inflated into the secondary sleeve. The method of heating the primary sleeve is determined by the material of the outer layer. For example, for polyamides and polyesters, infrared heating, a hot bath, or heating with hot steam to a glass transition temperature are used; for olefin polymers, heating by infrared radiation or heating with hot steam to Vick temperature is used. The temperature of the embossing rolls is also set depending on the material of the outer layer.

In addition, the claimed shell can be obtained by introducing into the thermoplastic material an outer layer of up to 25% by weight of an additional polymer, which is infinitely miscible in the melt with the original thermoplastic material, but is limited to be compatible with it in the solid state, and forming fibers (filaments) with a predominant content polymer in the outer layer. Due to spunbond drawing, areas of heterogeneous composition are oriented along the sleeve. When choosing an additional polymer material, a significant characteristic is the melting point. For the formation of extended fibrous regions, it is necessary that the melting points of the thermoplastic material and the additional polymer differ by at least 40 ° C.

Since the orientation hood is carried out when the primary sleeve is heated to softening temperature (polyolefins) or glass transition temperature (polyamides) of the base material, this determines one more criterion for choosing an additional polymer. It is necessary that the softening temperature or glass transition temperature of the additional polymer should differ from the temperature of the orientation drawing by at least 10 ° C. Subject to this condition, in the process of orientational drawing, regions with a predominant content of the main material are drawn into the film, and with the predominant content of the additional material, embossed fibers are formed in it. For the outer layer based on polyamide PA 66, a convenient additional material is polyamide PA 12; for the outer layer based on polyethylene, polypropylene is a convenient additional material.

The use of this method is illustrated by example No. 9.

Specialists may also suggest other methods of forming a layer non-uniform in thickness, which does not affect the essence of the technical effect achieved using the present invention, since it is due to the presence of a relief fibrous-mesh structure in the outer layer.

Shells made in accordance with the present invention have improved mechanical properties. Such violations of the polymer layer as scratches, punctures, scores do not spontaneously propagate and do not leave the mesh cell of the outer layer inhomogeneous in thickness. Artificial casings made from natural raw materials (for example, Belkozin, Kutizin) have, in contrast to synthetic sausage casings based on polyamide, lower strength under tensile loads. In some cases, to give strength under tensile loads to such artificial shells, they are glued or fused with a woven mesh. Obviously, a similar effect is observed in this case.

The physical quantity characterizing the mechanical resistance of the film to tearing when the surface is damaged is tear resistance, determined, for example, according to GOST 26128-84. The relevant data are given in the examples and in the table.

In addition, when making the outer layer of a thermoplastic polyolefin having the structure of the outer layer in accordance with the invention, slipping off the clip from the stick is less likely to occur compared to the same shell, but having a continuous polyolefin layer.

To assess the adhesion strength of the clip to the sheath, the following methodology was used:

- Pre-prepared sections of the shell are clipped together with a loop.

- On the shell below the clip, a marker is applied to the reference mark of its initial position.

- The loop of the clipped section of the shell is put on the hook of the device for testing samples, which is a platform in the center of which a pin with a hook is fixed perpendicular to its plane at the end. Depending on the caliber of the test shell, the weight of the device is selected: 3 kg with a shell gauge of 35-65 mm and 5 kg with a caliber of 66 or more.

- Slowly lift the shell by the unclipped end so that the platform is at a height of about 10 cm from the floor, and hold on weight for 5 seconds. The device is lowered, a sample is taken, inspected and the clip offset is measured.

Test results are considered positive if the shape of the clip does not change and there is no bias or slipping of the clip from the sample.

When testing 100 casing samples made according to Example 3 using this method, the clip moves and jumps off 4 segments, and when testing the same number of casing samples with a continuous outer layer (Example 4, comparative), the clip slides off 17 segments.

The caliber of the shell according to the invention can vary within wide limits: from 19 to 290 caliber.

For a person skilled in the art it is obvious that by known methods, the shell can be easily made curved, annular or spiral.

The shell according to the invention, depending on the number of layers included in it, is suitable for the manufacture of cooked sausages of any caliber, including sausages and sausages having both limited shelf life and long shelf life, as well as for sausages and processed cheeses having a taste and smell of smoking.

A brief description of the list of figures explaining the invention.

Figure 1-3, 5 shows photographs of the appearance of the shells obtained in accordance with examples 5-7, 9.

Figure 4 shows an optical micrograph of a transverse section of the shell obtained in accordance with example 6 (negative image).

Possible embodiments of the present invention are given in the following examples, which illustrate but do not exhaust the present invention.

In the embodiments of the present invention, the following material conventions were used (the brands of materials and manufacturers are shown in parentheses):

- PE ₁ - high density metallocene polyethylene (Finacene ER 2278, Atofina),

- PE ₂ - high pressure polyethylene (LDPE grade 15813-020, LLC Kazanorgsintez),

- SM - chalk superconcentrate (Aksoy 106123, Aksoy plastik),

- SP ₁ - blowing agent concentrate (Basko T0027, LLC PNF Bars-2),

- SP ₂ - blowing agent concentrate (Corducell ET 9520, NEMETZ Additive Plastic GmbH),

- Adg - LDPE grafted with maleic anhydride (Bynel 623, Du Pont),

- PA ₁ - polyamide 6 (Ultramid B4, BASF),

- PA ₂ - polyamide 6.66 (Ultramid C35, BASF),

- PA ₃ - partially aromatic polyamide 6I, 6T (Selar 3426, Du Pont),

- PA ₄ - polyamide MXD 6 (MX-Nylon 6007, Mitsubishi Gas Chemical Company, Inc.),

- PA ₅ - polyamide 12 (Grilamid L 25, EMS),

- SB - superconcentrate of white pigment (Schulman 8160, A. Schulman),

- CK - superconcentrate of red pigment in LDPE (Schulman 5330, A. Schulman),

- C3 - superconcentrate of golden pigment in PA 6 (Sicopas 30-1305, BASF).

Example 1

A mixture comprising 80% PA ₁ , 14% PA ₂ , 4% PA ₃ and 2% C3 is loaded into an extruder to make the outer layer. A mixture comprising 80% PA ₁ , 14% PA ₂ , 4% PA ₃ and 2% SK is loaded into an extruder for the manufacture of an adjacent polymer layer. The melts are fed into a multilayer head, through a ring die of which a continuous sleeve is formed from the material of the polymer layer, and through rotating dies, an outer layer non-uniform in thickness. Thus obtained primary sleeve is cooled to a temperature of 40 ° C, folded into a flat tape, then heated to a temperature of 70 ° C and subjected to biaxial orientation due to simultaneous inflation and longitudinal drawing. As a result of orientation, a secondary sleeve is obtained, which is subjected to heat setting for 15 seconds at a temperature of 150-165 ° C with simultaneous shrinkage of the sleeve by 20% along and 10% across. As a result, a finished sleeve is obtained, which is wound onto a roll.

The shell has a tear resistance of 0.39 kgf / mm

Example 2 (comparative)

A single-layer polyamide shell is made from a mixture of 80% PA ₁ , 14% PA ₂ , 4% PA ₃ and 2% SK using a single layer head with a ring die in accordance with example 1.

The tear resistance of the shell is 0.19 kgf / mm.

Example 3

For the manufacture of a three-layer shell using: a mixture of 59.3% PE ₁ , 30% SB, 10% SM and 0.7% SP ₁ for the outer layer; a mixture of 80% PA ₁ , 14% PA ₂ , 4% PA ₃ and 2% SK for another polymer layer and Bynel 623 adhesive (Du Pont) between them as the third layer. The compositions are loaded into extruders and extruded through a multilayer die head. The primary sleeve is cooled, folded into a flat tape, then heated to a temperature of 70 ° C and subjected to biaxial orientation due to simultaneous inflation and longitudinal drawing. The secondary sleeve is subjected to heat setting for 15 seconds at a temperature of 145-150 ° C with simultaneous shrinkage of the sleeve by 20% along and 10% across. As a result, a finished sleeve is obtained and wound onto a roll. The tear resistance of the shell is 0.62 kg / mm.

Example 4 (comparative)

A three-layer shell with a uniform thickness, smooth, continuous outer layer is made by coextrusion in accordance with Example 3, using a mixture of 60% PE ₁ , 30% SB and 10% CM, a mixture of 80% PA ₁ , 14% PA ₂ to make the outer layer , 4% PA ₃ and 2% SK for another polymer layer and Bynel 623 adhesive (Du Pont) between them.

When testing 100 samples of the shell made according to Example 3, the clip was displaced or slipped off in 4 segments, and when testing the same number of samples of the shell made according to Example 4, the clip shifts or slides off 17 segments.

Example 5-7.

The seven extruders attached to the seven-layer head, load the compositions shown in the table. A multilayer primary sleeve with a diameter of 26 mm is formed through an extrusion die. The primary sleeve is folded into a flat tape, then heated to a temperature of 70 ° C and subjected to biaxial orientation due to simultaneous inflation and longitudinal drawing. As a result of orientation, a secondary sleeve is obtained, which is subjected to heat setting for 15 seconds at a temperature of 145-150 ° C with simultaneous relaxation (shrinkage) of the sleeve by 20% along and 10% across. The result is a tertiary (finished) sleeve with a diameter of 80 mm, which is wound into a roll.

Photos of the appearance of the shells obtained in accordance with examples 5-7 are shown respectively in Fig.1-3. The photographs clearly show the embossed fiber-mesh structure of the outer layer obtained by using the described technology.

An optical micrograph (negative image) of a cross-section of a shell having a embossed fiber-mesh structure and obtained in accordance with Example 6 is shown in FIG. 4. In this photograph, the embossed nature of the outer layer of the shell, which arose due to the rupture of the bubbles, is clearly visible.

Example 8 (comparative).

The composition shown in the table is loaded into five extruders attached to a five-layer head, and a five-layer shell is obtained in accordance with the technology described in Example 5-7, with a uniform, thickness, smooth, continuous outer layer.

Example 9

A five-layer shell with an outer layer non-uniform in thickness, having a relief fibrous-mesh structure, is obtained in accordance with Example 8. Compositions for the manufacture of layers are shown in the table.

A photograph of the appearance of the shell is shown in Fig.5. The relief structure of the outer layer formed by the extended fibers of the polymer material is clearly visible in the photograph.

From the table it follows that the shell obtained in accordance with the present invention, are characterized by significantly better values of tear resistance.

The shell with a relief fiber-mesh structure in appearance clearly stands out from the number of known polymer shells. It does not have the sheen characteristic of traditional synthetic shells; alternating areas of thinning and thickening make it pleasant to the touch, and an unusual pattern of texture makes it recognizable and attractive to the consumer.

Claims (9)

1. Synthetic sleeve casing for food products containing at least two layers, characterized in that the coextruded outer layer has a relief fibrous-mesh structure formed by alternating regions of thickenings having linear dimensions from 0.1 to 250 mm in the longitudinal direction and from 0.1 to 15.0 mm in the transverse direction, and areas of thinning having linear dimensions from 0.1 to 100.0 mm in the longitudinal direction and from 0.1 to 30.0 mm in the transverse direction, while layer thickness in the region of thickening wish to set up to 80 microns. 2. The synthetic shell according to claim 1, characterized in that the region of thickenings have linear dimensions from 0.1 to 100.0 mm in the longitudinal direction and from 0.1 to 3.0 mm in the transverse direction. 3. The synthetic shell according to claim 1, characterized in that the region of thinning have linear dimensions from 0.1 to 40.0 mm in the longitudinal direction and from 0.1 to 15.0 mm in the transverse direction. 4. The synthetic shell according to any one of claims 1 to 3, characterized in that the coextruded outer layer having a embossed fiber-mesh structure is not continuous. 5. The synthetic shell according to claim 4, characterized in that the coextruded outer layer is made of a polymer or a mixture of polymers, each of which has a melt flow index of 0.2 to 15 g / 10 min, measured according to ASTM D 1238 A. 6. The synthetic shell according to claim 5, characterized in that it is obtained by the method of orientational drawing. 7. The synthetic shell according to claim 6, characterized in that it is made uniaxially or biaxially oriented. 8. The synthetic shell according to claim 7, characterized in that it is made straight, curved or spiral. 9. A bag for packaging food products, characterized in that it is made of a shell made according to any one of claims 1 to 8.

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