RU2442425C2 - Synthetic sausage polyamide-based cover filled without stretching and method of its production - Google Patents

Abstract

FIELD: food industry.

SUBSTANCE: invention refers to single or multilayer synthetic heat shrinkable sausage covers as well as to their production method. At least one polyamide cover layer is made on the basis of at least one aliphatic (co)polyamide chosen of polyamide 6 and/or polyamide 66 or copolyamide 6/66. Cover in the state ready to be filled has next characteristics: Young modulus at least 400 MPa in cross direction and at least 300 MPa in lengthwise direction. At exposure to air with relative humidity of 60% and temperature of 25°C within 5 days its contraction is within 2% both lengthwise and crosswise. At exposure to water of 40°C within 2 hours its constriction amounts to 4-10% crosswise and 3-10% lengthwise. At exposure to water of 80°C within 30 minutes its constriction amounts to 9-18% crosswise and 8-15% lengthwise. The sausage cover production method includes extrusion of single or multilayer extrudate, orientation stretching and thermal fixation of oriented sleeve film with further additional treatment. Additional treatment consists in that the thermally fixed sleeve film with temperature of 60-140°C is stretched 4-10% crosswise and 3-8% lengthwise, cooled in stretched state to the temperature no more than 57°C and wind up into roll. This stage of technological process can be included into one production line with preceding stages of cover production or is fulfilled at separate machine.

EFFECT: sausage covers made according to the invention are filled with mince with no preliminary damping and almost without stretching and production of tightly filled sausage links.

38 cl, 3 tbl, 4 ex

Description

Field of Invention

The present invention relates to a single or multi-layer synthetic sausage casings, filled without pre-wetting and practically without stretching, but allowing you to get a tightly filled package, such as sausage loaf. In addition, this invention relates to a method for producing such shells.

State of the art

Synthetic casings for sausage products such as sausages, sausages, ham, pastes and the like are well known in the art. They are technological in manufacture and allow to receive packaged products attractive to consumers. In particular, such casings make it possible to obtain pleasant to the touch, tightly filled loaves of sausages without wrinkles. Such loaves not only have an attractive appearance, but are also a guarantee that there will be no liquid or gel (so-called broth or fat swelling) between the shell and the meat.

To obtain tightly filled loaves, several possible approaches are usually used. The first of them involves the use of shrinkage in the manufacture of sausages in plastic casings. Using this approach, a casing with heat-shrink properties is filled with sausage meat under low pressure or without it at all so that it is practically not subjected to stretching. Then the sausage is cooked using water or hot steam. During cooking, the forcemeat expands in volume. Under the influence of internal pressure, the shell stretches and during cooling, the new dimensions of the shell are fixed, since it cools earlier than the stuffing remaining in the expanded state. Therefore, immediately after cooling the sausage product, the shell does not fit tightly and may even form wrinkles. Obtaining tightly filled loaves is achieved by the fact that the loaf after complete cooling is additionally quickly heated, usually by treatment with hot steam or hot water. In this case, thermal shrinkage of the shell occurs, and it tightly tightens the loaf. As polymeric materials for the production of such shells, which can be single or multilayer, traditionally used are: polyvinylidene chloride (hereinafter - PVDC), polyolefins: polypropylenes (PP) and polyethylene (PE) of various types, polyesters such as polyethylene terephthalate, polybutylene terephthalate, etc. ., as well as polyamides. Heat-shrinkable shells are obtained by orientational drawing with subsequent incomplete heat setting or without it at all. In this case, oriented polymers are characterized by an unstable crystalline phase with a large number of small and imperfect crystallites capable of breaking at relatively low temperatures. When they are destroyed (in fact, melting), an additional amorphous phase forms, which, due to the thermal motion of the polymer chains, tends to leave the oriented state, causing the appearance of shrink forces. When these processes occur during the cooking of sausages in heat-shrinkable casings, these forces are not allowed to be realized by the expansion of minced meat, and when the shell is cooled, the crystalline phase is restored, which causes the fixation of the new shell geometry. With subsequent short-term heating, everything repeats, but now nothing is opposed to the shrink forces and the shell shrinks. Obviously, this approach, associated with additional heat treatment of sausages after cooling, requires additional energy and working time when preparing sausages.

European patent application EP No. 0974452 A2, published on January 26, 2000, discloses a multilayer elongated shell having the necessary level of heat shrinkage and a reduced heat shrink voltage. The sleeve shell contains a core layer of polyamide and two peripheral layers of polyolefins. In the manufacture of the casing according to the usual scheme for the production of oriented sleeve films, low-temperature thermofixation with steam or hot water (60-98 ° C) is used. This leads to the fact that such a shell exhibits a heat shrink voltage at 50 ° C of a maximum of 2 MPa in both longitudinal and transverse directions and a shrink value of 5-20% in hot water at 90 ° C. This shell is filled with minced meat, including manually. The resulting sausage product is cooked by conventional technology, cooled, and then dipped in hot water for several seconds. The restriction of heat shrink voltage, according to the inventors, is necessary so that when cooking sausages there is no violation of the tightness of the package (rupture of the shell, its welds, etc.).

The second approach is based on the use of the elastic properties of plastic shells. However, in this case, the range of applicable materials is much narrower. For their manufacture, for example, thermoplastic polyurethanes or various special block copolymers having the properties of thermoplastic elastomers can be used. Such materials, as a rule, are very expensive and difficult to process. Therefore, the most common materials for the manufacture of shells exhibiting elastic properties are aliphatic polyamides. They are used both as the base material of single-layer shells and as the material of one of the layers (most often the thickest) in multilayer shells. Such casings usually have good moisture and oxygen barrier properties, which make it possible to store products packaged in them for a sufficiently long time.

Commercial aliphatic polyamides, such as polycaprolactam (hereinafter referred to as polyamide 6 or PA 6), polyhexamethylene adipamide (hereinafter referred to as polyamide 66 or PA 66) and other aliphatic polyamides, in a non-oriented (molded) state do not have elasticity, on the contrary, they are prone to irreversible deformations. To give them elastic properties, a technology is used that includes the extrusion of a cast tubular film from a single or multilayer extrudate, followed by orientation drawing and, if possible, the most complete heat setting. Such technology is described, for example, in US patent No. 4303711, publ. December 1, 1981. It allows you to get shells with the ability to large reversible deformations, i.e. elasticity, and in addition, remarkable strength and dimensional stability. In addition, they exhibit relatively low thermal shrinkage, measured when the casing is immersed in water at 80 ° C, at about 5-10% in both directions.

Dry film based on conventional commercial polyamides is too stiff (elastic modulus or Young's modulus is approximately 400-500 MPa (40-50 kgf / mm ² )) in both directions and cannot be stretched to the required level when filling using traditional sausage filling equipment . Therefore, before stuffing, i.e. filling with sausage meat under pressure, which leads to a stretching of the shell, it is moistened, usually soaking for a while in a bath with water. In this case, the elastic modulus of the shell drops to values of about 200-250 MPa in both directions. With the correct selection of the diameters and thicknesses of the shells, such a Young's modulus provides, on the one hand, the ability to stretch the shell under the forcemeat pressure to the required values, and on the other hand, to prevent the sausage loaves from being deformed by their own weight. After wetting, the shell is stuffed with minced meat on the stuffing unit (syringe and clipper) so that its diameter (caliber) increases by about 8-12% relative to the original value. Typically, this stretching is sufficient to provide the sausage with an elastic consistency. It should be noted that when filling with minced meat, the shell usually stretches unequally in the longitudinal and transverse directions, and this, in turn, leads to a distortion of the printed image applied to it. In addition, as a result of printing and subsequent operations, the casing undergoes significant alternating deformations (tension-compression), which weaken the adhesion between it and printing inks and can lead to partial peeling of the printed image.

As a rule, when soaking, the water contacts both the external and internal surfaces of the sleeve. This operation can lead to contamination of the inner surface of the shell by pathogenic microorganisms or their spores, as well as toxic products of their vital activity or decay, which, ultimately, can get on the surface of the stuffing.

In addition to the technology for stuffing sleeve casings, there is a method for producing sausages on packaging machines that carry out the operations of forming sleeve sections, filling them with minced meat and finally brewing sausage products using long flat films as the starting material. With this technology, it is impossible to stretch the shell and, therefore, obtaining a tightly filled loaf is impossible without additional operations, such as the aforementioned short-term steam treatment of the already cooled loaf.

Sheaths are known which are delivered to sausage plants after being wetted in advance under controlled conditions. So, in US patent No. 4897295, publ. On January 30, 1990, a single-layer oriented tubular sheath of polycaprolactam (PA 6) and / or polyhexamethylene adipamide (PA 66) with or without an ionomer was added, which, when finished, is moistened with excess hot sterile water placed inside the sleeve. In this state, the shell is held for some time until the polyamide is saturated with water, and then, when this sleeve is rewound from roll to roll, excess water is removed. Then the shell is corrugated. Such an operation is extremely low-productivity and requires the organization of a separate workplace. In addition, it is known that a polyamide sleeve shell saturated with moisture is inclined to stick together with its internal surfaces when stored in rolls.

Most often, wetting of polyamide shells, carried out by cold water irrigation, is combined with a corrugation operation. In this case, the shell can only come into contact with water on its outside, since enough time passes before it is stuffed with minced meat so that the moisture can be redistributed throughout its entire volume. To maintain the required humidity, the shell must be stored and transported tightly packed in a waterproof container. However, prolonged maintenance of humidity creates favorable conditions for the development of various microorganisms on the outer surface of the shell, which can spoil its presentation, forming colored colonies on it.

In German application DE No. 4128081 A1, publ. February 25, 1993, disclosed sleeve sausage casing, consisting of at least three layers. The outer layer is moisture barrier, made of olefin (co) polymers. The base layer - gas barrier - is made of copolymers of ethylene and vinyl alcohol (hereinafter - SEVS) or (co) polyamides such as MXD6 polyamide (polymethaxylylene adipamide) or copolyamide 6I / 6T (hexamethylene isophthalamide / terephthalamide). The inner layer is made of polyamide material. The shell is wetted at the stage of extrusion of the primary sleeve, cooled by water, both from the outside and from the inside and is kept moist when the shell is stored as a folded sleeve wound into a roll. However, if it comes in the form of corrugated "dolls", it requires additional packaging in a moisture barrier film. Therefore, in the manufacture of products in it, the shell is stuffed with sausage stuffing in the usual way, i.e. with stretching the shell.

In the patent of the Russian Federation No. 2189146, publ. On September 20, 2002, a shell was disclosed comprising a layer made of a mixture of polyamides and a block copolymer of polyamide and polyester. Such a block copolymer has a pronounced elasticity and imparts this property to its mixtures with polyamide. Therefore, the shell has a reduced modulus of elasticity (Young's modulus) and can be filled under a small pressure of minced meat and even manually. The shell according to this invention has a level of heat shrinkage (when immersed in water at 80 ° C), characteristic of traditional polyamide shells or only slightly exceeding it. It is made according to the usual scheme for producing single-layer or multi-layer shells based on polyamide. From the description of the invention it does not follow with clarity how such a shell is stretched during filling, and its degree of stretching cannot be estimated, since the specific values of the applied pressures are not reported. It is also not clear whether it needs to be moistened before filling, although all mechanical characteristics, including a tensile stress of 5%, proportional to Young's modulus, are given for a moistened shell. However, the use of casings with a lowered mechanical module can lead to serious problems during packing and intermediate operations associated with a noticeable deformation of sausages under their own weight, which leads to the sausage loaf becoming pear-shaped, unusual for sausages. In addition, the aforementioned block copolymers are very expensive products and their introduction into the composition of the shell greatly affects its cost.

The third - a mixed approach - is described in US patent No. 5549943 (publ. August 27, 1996), which proposes to simultaneously use the elastic and heat-shrink properties of the shell. The shell disclosed in this patent shows very high levels of heat shrink and heat shrink. In this case, due to the high values of the loaf compression forces arising from the heat shrinkage of such shells during cooking of sausages, the expansion of the stuffing can be partially (but not completely) suppressed. The heat-shrinkable multilayer sleeve sheath of this invention comprises a core layer of polyolefin and two peripheral layers of polyamide, as well as, in other embodiments, layers of a copolymer of ethylene and vinyl acetate (hereinafter referred to as SEVA) and SEVS. It is manufactured according to the usual scheme for producing oriented sleeve films using a heat setting procedure in which a shell in the form of a flat-layed sleeve in a dry or wet form is heated to 70-90 ° C. In accordance with the description, the values of shrinkage in water at 90 ° C are of the order of 25-30% and values of heat shrink forces of up to 96 kg / cm in the longitudinal and up to 186 kg / cm in the transverse direction are characteristic. The shell was filled with minced meat or in a moistened state manually, or in a dry form using a stuffing machine (example 8). Nevertheless, in both cases, after heat treatment of the sausages, a tightly packed sausage loaf was obtained. At the same time, it is not clear from the text of the document whether the shell was stretched during stuffing, although the traditional method of stuffing involves such stretching. The patent specification does not mention anywhere the possibility of filling the invented shells without stretching. At the same time, for such shells, the drawbacks described in the previous paragraph are characteristic, and in addition, for example, slipping of clips, which also occurs with strong shrinkage of the shell. In addition, with the described method of thermal fixation, it is impossible to achieve a satisfactory dimensional stability of the casing during storage, and in operations related to even moderate heating, for example, when drying inks after printing, such a casing will be guaranteed to undergo premature shrinkage.

DE Patent No. 2850182 (published June 4, 1980) also states that a single-layer polyamide shell based on PA 6 or PA 6/66, obtained by orientation drawing and heat setting at 120 ° C, can be filled with mincemeat without prior wetting and almost no pressure (manually). At the same time, tight sausage loaves in an unshriveled casing are obtained by shrinking the casing, which, however, is not illustrated by any specific figures. However, the same inventors in the description of the later US patent No. 4897295 (publ. January 30, 1990) recognize that it is impossible to obtain sausages of a satisfactory appearance in the casing according to DE patent No. 2850182 without first wetting (soaking) and using its elastic properties.

The shell, the closest in properties and application to the shell of the present invention, was proposed in US patent No. 4303711, publ. December 1, 1981 This biaxially oriented and thermofixed single-layer shell based on an aliphatic polyamide having, after absorption of moisture, a glass transition temperature of from -5 to + 3 ° C, contains zinc and / or calcium ionomer, and / or SEVA, and / or a modified polyolefin in an amount of from 1 to 50%. These are polymers that are easily deformable but immiscible with polyamide and do not affect its glass transition temperature. Thanks to these additives, the casing, already in dry form, acquires high extensibility comparable to that of moistened polyamide casings and can, in principle, be packed without preliminary soaking in water. The filling of the casing takes place at a pressure of 0.3-0.6 bar, which is typical for filling sausages into moistened casing, which, given its elastic properties, unambiguously assumes its similar stretching during filling. During cooking, the polyamide, which is part of the shell, acquires additional elasticity. As a result of this, the casing tightly fits the sausage product without the formation of wrinkles. The shell according to this invention undergoes a thorough heat setting (120 ° C for 3-5 minutes) and has, according to its inventors, shrink properties, however, the shrink characteristics of the shell are not specifically disclosed. The use of such a shell is also fraught with undesirable deformation of sausage loaves under the influence of its own weight, since immediately after filling, moisture begins to penetrate into the polyamide and lower its mechanical modulus. In addition, it cannot be used as a film for filling with minced meat on packaging machines.

A method of manufacturing a polyamide-based sleeve film closest to the invented method is described in US Pat. No. 4,560,520, publ. December 24, 1985 According to the invention disclosed therein, a single-layer polyamide film is obtained by multiaxial drawing of an extruded primary sleeve with an elongation of at least 1: 2.3 in the longitudinal direction and 1: 2.5 in the transverse direction and subsequent heat setting of the sleeve at temperatures from 90 up to 150 ° C with controlled sitting by 15-20% both in the longitudinal and in the transverse direction. In this case, heat setting at temperatures below 100 ° C is carried out in hot water. The shell obtained by this method has no shrinkage at either 40 or 80 ° C, so it is impossible to fill it with minced meat without stretching and at the same time get, ultimately, an unshriveled, tightly stuffed sausage loaf.

Therefore, the objective of the present invention is to develop a sausage casing devoid of the above disadvantages, namely:

- suitable for stuffing with minced meat using automatic stuffing equipment or packaging machines or manually without first wetting and stretching the shell when filling it and without requiring additional processing with steam or hot water after cooking and cooling the sausages to obtain tightly filled loaves,

- having sufficient rigidity in the wet state to withstand deformations arising under the influence of gravity in large sausages after stuffing,

- not creating excessive stresses during cooking,

- suitable for applying to it a printed image by flexography or other methods of high-performance printing,

- possessing sufficient dimensional stability during storage and transportation,

- possessing the necessary strength and barrier properties.

The next objective of the present invention is to develop an inexpensive and productive method of manufacturing such a shell.

Description of the invention

As a result of the studies, it was unexpectedly found that the tasks are achieved by creating a single or multi-layer synthetic heat-shrink sausage casing, which contains at least one polyamide layer made on the basis of at least one aliphatic (co) polyamide selected from the group consisting of polyamide 6, polyamide 66, copolyamide 6/66 or a mixture thereof, while the shell, when ready for filling, has a Young's modulus of at least 400 MPa in the transverse direction and at least 300 MPa in the longitudinal direction nii and its shrinkage:

- when exposed to air with a relative humidity of 60% and a temperature of 25 ° C for 5 days, it is no more than 2% both in the transverse and in the longitudinal direction;

- when holding in water with a temperature of 40 ° C for 2 hours is 4-10% in the transverse and 3-10% in the longitudinal direction;

- when holding in water with a temperature of 80 ° C for 30 minutes, it is 9-18% in the transverse and 8-15% in the longitudinal direction.

In a preferred embodiment of the invention, the shrinkage of the shell:

when it is exposed to air with a relative humidity of 60% and a temperature of 25 ° C for 5 days, it is no more than 1% both in the transverse and in the longitudinal direction; when kept in water with a temperature of 40 ° C for 2 hours it is 5-10% in the transverse and 4-10% in the longitudinal direction; when aged in water with a temperature of 80 ° C for 30 minutes, it is 10-15% in the transverse and 9-12% in the longitudinal direction.

The polyamide layer contains from 60 to 100% of at least one aliphatic (co) polyamide selected from the group consisting of polyamide 6 and / or polyamide 66 and / or copolyamide 6/66.

In addition, the polyamide layer may contain from 0 to 20% of at least one semi-aromatic (co) polyamide selected from the group consisting of copolyamide 6I / 6T, polyamide MXD6, or a mixture thereof.

In addition to the polyamide composition, the polyamide layer may contain from 0 to 20% of one polymer selected from the group consisting of polyester, olefin homopolymer, olefin copolymer, grafted olefin (co) polymer, ionomer, or a mixture thereof.

The shell can be made in the form of a sleeve, a half sleeve (when cutting a sleeve film along one edge) or an extended flat film (when cutting a sleeve film along both edges).

Such a shell can be obtained by a method consisting of successive stages, including extrusion of a single or multilayer extrudate in the form of a primary sleeve, orientational drawing of the primary sleeve to obtain an oriented sleeve film, heat-setting of an oriented sleeve film to obtain a heat-fixed oriented sleeve film. Further, according to the present invention, the thermofixed oriented sleeve film is subjected to further processing, consisting of successive steps of bringing it to a temperature of 60-140 ° C, stretching by 4-10% in the transverse and 3-8% in the longitudinal direction, and cooling in the stretched state to a temperature not higher than the glass transition temperature of the polyamide composition of the polyamide layer to obtain a ready-to-fill sausage casing, which is then wound into a roll in the form of a flat-layed sleeve.

The stage of thermal fixation is carried out by heating the shell, blown with air in the form of a bubble, to a temperature of 130-160 ° C, preferably 135-140 ° C, and holding it at this temperature for 3 to 5 seconds. In addition, in the process of heat setting, the shell is seated up to 10%, preferably 5-10%, both in the transverse and in the longitudinal direction.

In a preferred embodiment of the method, during further processing of the thermofixed oriented sleeve shell, it is stretched by 5-10% in the transverse direction and by 4-8% in the longitudinal direction.

In addition, during additional processing of the thermofixed oriented sleeve shell, the shell is stretched, preferably at a temperature of 70-130 ° C, and its cooling in the stretched state is carried out to a temperature of no higher than 45-57 ° C, depending on the composition of the polyamide layer.

At the same time, the stage of additional processing in various embodiments of the invention is carried out both on the same production line with the previous stages of the production of the shell, and on a separate installation.

The finished sausage casing can then be used as such or cut along one or both edges of the folded sleeve to produce a half sleeve or two extended flat films, respectively. In addition, the shell can be made in the form of a corrugated doll.

Obtaining a sausage product in a casing according to the present invention consists in filling the casing with virtually no pressure (an increase in the diameter of the loaf can be no more than 1.5%) with the formation of the sausage product, wet heat treatment of this sausage product and its subsequent cooling. In this case, preliminary wetting of the shell and additional heat treatment of the chilled loaf are not required.

The sausage product obtained according to the present invention is a tightly packed loaf.

Description of the shell of the present invention.

In the following description, conventional names for polymeric materials and abbreviations are used. The sign “%” denotes mass percentages of the total weight of the composition, unless expressly agreed otherwise or if a different interpretation obviously does not follow from the context. In the future, the words containing the prefix in parentheses are used to denote concepts that simultaneously include the concepts denoted by this word with this prefix and without it. For example, the word (co) polymer means both a polymer (homopolymer) and a copolymer.

The term "sausage casing in a ready-to-fill state" means a sausage casing that is used for filling immediately after opening the package, that is, without any preliminary operations. The package may be waterproof or other, depending on the specific structure and shape of the shell of the present invention.

The shell of the present invention, in a ready-to-fill state, has a Young's modulus characteristic of polyamide-based wetted and otherwise unplasticized shells. In other words, it is characterized by significant rigidity, completely atypical for shells at the time of filling, which, when pre-moistened, usually have a Young's modulus of 1.5-2.5 times lower.

At the same time, the casing retains its dimensional characteristics, in general, being packaged in a moisture-proof bag made, for example, of a polyethylene film, which ensures the humidity of the surrounding air at constant temperature differences during transportation. This property is evaluated by the so-called free shrinkage, measured after holding the casing in air at a temperature of 25 ° C and a relative humidity of 60% for 5 days. Under these conditions, free shrinkage does not exceed 2%, and in the preferred embodiment, 1%, both in the transverse and in the longitudinal direction. Such humidity conditions are created in a desiccator, on the bottom of which a suitable crystalline salt is placed, for example sodium bromide (NaBr) or its saturated solution.

In the shell of the present invention under the influence of temperatures of the order of 80-100 ° C and high humidity, i.e. in the conditions of cooking sausages, shrinkage forces develop which suppress the expansion of minced meat. If the shrinkage under these conditions is 9-18% in the transverse and 8-15% in the longitudinal direction, the tension force of the shell on the sausage stick is approximately equal to that which develops when cooking the stick in the shell that has not undergone additional processing in accordance with the present invention and filled with ordinary stretching. If the shrinkage value exceeds the upper values of the indicated ranges, this can cause excessive tension of the casing, which is associated with the risk of rupture or slipping of the clips. In the future, this type of shrinkage, the value of which is determined by holding the casing in water with a temperature of 80 ° C for 30 minutes, which approximately corresponds to the cooking conditions for sausages, will be referred to as “hot shrinkage”. Indeed, the magnitude of the hot shrinkage of the invented shell has these values, and in the preferred embodiment is 10-15% in the transverse and 9-12% in the longitudinal direction.

However, unlike the known casings having heat-shrink properties, in the casing of the present invention, a part of the shrink forces continues to act upon subsequent cooling of the sausage loaves. The condition for the activation of these residual shrinkage forces is only significant wetting of the polyamide layer, which is quickly achieved when cooking sausages. This shrink behavior of the casing occurs as a result of its additional processing in accordance with the present invention and determines the possibility of obtaining a tightly packed loaf in the invented casing without additional stretching when stuffing with minced meat and without additional heat treatment of the sausage product after it is cooled. These residual shrink forces can also be activated at lower temperatures, at which the remaining shrink forces are not yet included, due to changes in the crystalline phase of polyamide and other polymer shell components at high temperatures. It will be shown below that activation of this component of general shrinkage is possible when the inventive shell is moistened at temperatures from 20 to 50 ° C, and the value of the equilibrium (limiting at a given temperature) shrinkage does not depend on the temperature of the water within the range in which this test is placed shell, and depends only on the type of shell and the time of moisturizing. Above 50 ° C, activation of shrinkage forces associated with changes in the crystalline phase of polymers begins. In some embodiments of the shell of the present invention, it takes considerable time to hydrate its polyamide layer at temperatures close to room temperature (about 18-28 ° C), so it is advisable to measure its shrinkage characteristics at higher temperatures. For example, if the shell has outer layers or is made of a polyamide composition, its equilibrium shrinkage can be measured at 25 ° C for 1-2 hours. If it has at least one polyamide layer surrounded by layers of moisture barrier materials, either a very long soaking of the shell at room temperature is required or the same result is achieved at 40 ° C for 2 hours, as will be shown below (see table 3). In general, it is advisable to carry out this test at 40 ° C for 2 hours. This type of shrinkage will hereinafter be referred to as “wet shrinkage”. In order for the sausage to be cooked in the casing of the present invention to produce a tightly filled loaf, its shrinkage under such conditions should be 4-10% in the transverse direction and 3-10% in the longitudinal direction. Indeed, the values of wet shrinkage of the invented shell correspond to these values, and in the preferred embodiment, comprise 5-10% in the transverse direction and 4-10% in the longitudinal.

The shell can be either single-layer or multi-layer. The structure of the casing is selected in accordance with its shape and purpose, with the expected conditions of its storage and transportation, as well as in accordance with the expected storage periods of the sausage packed in it.

The shell of the present invention necessarily contains at least one polyamide layer, in which the total content of aliphatic (co) polyamides is at least 60%. As polyamides, conventional commercially available thermoplastic polyamides (nylons) are used that do not have special properties, such as, for example, high elasticity in a non-oriented (molded) state. However, such nylons as materials for sausage casings, of course, must be resistant to prolonged exposure to even hot water, that is, they must not dissolve, disperse or lose their mechanical strength in water. For the purposes of the present invention, aliphatic (co) polyamides, such as polyamide 6, polyamide 66, copolyamide 6/66, which are contained in this layer in an amount of from 60 to 100%, are used. Semi-aromatic (co) polyamides, such as copolyamide 6I / 6T, polyamide MXD6, the content of which in the polyamide layer is 0-20%, can also be used. The above polyamide layer, in addition to (co) polyamides, can contain up to 20% of other polymeric materials, such as polyesters, for example polyethylene terephthalate (PET), glycol-modified polyethylene terephthalate (PETG), polybutylene terephthalate (PBT), (co) olefin polymers, for example polyethylene, polypropylene, copolymers of propylene and ethylene (SPE), ionomers, etc. or a mixture thereof.

The inventive shell may contain more than one polyamide layer, while their total thickness should generally be at least 40%, and preferably at least 45% of the total shell thickness. Moreover, the total shell thickness is from 18 to 120 microns.

In addition to the above polyamide layer (s), the shell may have one or more layers, mainly containing other thermoplastic polymers, such as (co) polyamides other than the polyamide components of the above polyamide layer, including polyamide 9, polyamide 10, polyamide 610, polyamide 12, polyamide 612, copolyamide 6/66/10, copolyamide 6/66/12, (co) olefin polymers grafted with maleic anhydride (co) olefin polymers, polyvinylidene chloride, ethylene vinyl alcohol copolymers, thermoplastic polyurethanes. These layers may also contain mixtures of the aforementioned thermoplastic polymers belonging to both one and various types. Polyamide components of the above polyamide layer (s): polyamide 6, polyamide 66, copolyamide 6/66, copolyamide 6I / 6T and polyamide MXD6 can also be part of these additional layers in an amount not exceeding 40%, for example, in the form of a mixture with a copolymer ethylene and vinyl alcohol. The use of rigid polymer materials, such as polyesters, for example PET as raw materials for individual layers, is undesirable for the purposes of the present invention, since they give the shell rigidity that does not disappear when wet.

The shell, made in the form of a sleeve, may have a layer in contact with the meat, made of any material approved for direct contact with food products. However, in a preferred embodiment, it consists of (co) polyamide or linear polyurethane, because these materials without additional processing provide good adhesion of the shell to minced meat. In the most preferred embodiment of the tubular sheath, this layer is made on the basis of (co) polyamide. If the material of this layer does not have inherent adhesion to the stuffing, this property can be given to it in a known manner, for example by corona treatment.

If the shell is made in the form of a sleeve or an extended flat film and is intended to be filled on a packaging machine, the layer in contact with the stuffing is made of any heat-sealable material that can be welded on a particular packaging machine by a specific welding method and has a hygienic tolerance to direct contact with food products and ensures during welding the formation of a sufficiently durable weld under sausage heat treatment. It is preferable that the heat-sealable polymer material has a melting point in the range of 101-160 ° C. Suitable for these purposes are (co) polymers of olefins, ionomers, as well as thermoplastic polyurethanes or polyamides, for example copolyamide 6/66/12, Grilon CF6N or Grilon CF7N (manufactured by EMS Co). In preferred embodiments, this layer is made of ionomer, SEVA, metallocene polyethylene (linear low density polyethylene - hereinafter LLDPE, very low density linear polyethylene - hereinafter LLPEONP, etc.), a copolymer of ethylene and (meth) acrylic acid or PVDC or a mixture thereof . In order to ensure the necessary adhesion of such a layer to the stuffing, you can use the techniques known from the prior art, namely, treating this layer with plasma, corona discharge or high-energy radiation (UV, γ radiation, electron beams, etc.). The most preferred method for treating such a layer is corona treatment. If it is assumed that when forming the package, the film or the half sleeve will be overlapped, the layer facing the environment should also be made of heat-sealable material.

For the casing of the present invention, prolonged contact of the polyamide layer (s) with humid atmospheric air during storage, which adversely affects its dimensional stability, is undesirable. Therefore, if such a shell is supposed to be stored and transported outside a moisture-proof package, the polyamide layer (s) are preferably insulated from the atmosphere by layers made of a material that is barrier to water vapor. If the casing is delivered to the consumer in the form of a flat sleeve wound onto a roll, one such outer layer is sufficient. If the shell is supplied in the form of a corrugated doll and the air flows freely inside the sleeve, it is desirable that at least the thickest of the polyamide layers be insulated on both sides with layers of a moisture barrier material. To adjust the sensitivity of the polyamide layer to moisture, semi-aromatic (co) polyamides 6I / 6T and / or MXD6 can be introduced into it, which increase the glass transition temperature of aliphatic polyamides in the wet state, as well as (co) polyolefins, ionomers, or polyesters such as PET, PETG or PBT.

As the material of the moisture barrier layer, it is preferable to use the following thermoplastic polymers: polypropylene, a copolymer of propylene and ethylene, with a content of monomer residues of propylene of at least 80 mol%, high pressure polyethylene (HDPE), low pressure polyethylene (HDPE), metallocene LLDPE, metallocene LLDPE, SEVA as well as the products of grafting maleic anhydride on these polymers, PVDC and mixtures of the above polymers.

Any of the layers or several layers of the shell of the present invention may additionally contain from 0 to 10% by weight of the total composition of the layer of at least one of the low molecular weight additives selected from the group including dyes, pigments, fillers, lubricants, processing aids, foaming agents additives, glidants, matting additives.

The casing of the present invention may be intended for packaging sausages with different shelf life. Packaging intended for short-term storage can be made as, for example, a single-layer shell. Packaging for longer storage should prevent the contents from drying out and prevent oxygen from entering from outside, which causes it to spoil (rancidity of fats, etc.). Therefore, such a shell contains layers made of materials having moisture and oxygen barrier properties.

Polyamides themselves, such as polyamide 6 or polyamide 66, have fairly high oxygen-barrier properties, but their oxygen permeability substantially depends on their moisture content. Therefore, it is desirable that during storage of the sausage product, at least the thickest (main) of the polyamide layers remain relatively dry. This is achieved when the main polyamide layer is in contact with atmospheric air and is separated from the moist stuff by a layer of moisture barrier material. However, in this case, the condition of isolation of the polyamide from atmospheric air, which is highly desirable for storing the shell itself, is not achieved. Therefore, it is most preferable that the main polyamide layer is simultaneously insulated from both atmospheric air and moist minced meat with layers of moisture barrier materials, but in such a way that the transmission rate of water vapor (SPV) in the second of the mentioned moisture barrier layers is significantly lower than in the first. If these moisture barrier layers are made of materials with close vapor permeability coefficients, this condition is achieved by an appropriate simple selection of layer thicknesses. It is desirable that the total thickness of the moisture barrier layers between the polyamide layer and the stuffing be significantly higher than that of the layers separating it from atmospheric air. In addition, the oxygen permeability of a polyamide layer made predominantly of an aliphatic polyamide, such as polyamide 6 or polyamide 66, can be made less sensitive to moisture by adding up to 20% of semi-aromatic (co) polyamide 6I / 6T or polyamide MXD6 to this layer.

In addition to polyamide layers, protection from oxygen penetration can be provided by additional layers of oxygen-barrier materials, such as PVDC or SEVS. The gas permeability of PVDC does not depend on its moisture; therefore, the position of this layer in the shell structure does not matter. If it is desirable that the layers based on polyamide and PVDC act simultaneously, it is necessary that the PVDC layer, which has powerful moisture-barrier properties, be closer to the stuffing than the polyamide layer. SEVS is also sensitive to moisture, and the dependence of its oxygen-barrier properties on its moisture content is even stronger than that of polyamides. Therefore, it is desirable that in the package a layer of this material should be located as close to the atmosphere as possible, but not external.

For bonding layers made of materials of various nature that do not have inherent mutual adhesion, adhesive layers of maleic anhydride grafted (o) olefin polymers can be used. Most often, the corresponding (co) polymers grafted with maleic anhydride are used as adhesive materials for bonding layers of polar polymers, such as polyamide or SEVS, with layers of olefin (co) polymers. These adhesive materials can be contained in the shell both as separate layers and as components of a layer mainly containing an olefin (co) polymer compatible with a particular adhesive material.

The shell can be made in the form of a sleeve, a half sleeve or an extended flat film. It depends on whether it is intended to be filled on stuffing equipment (sleeve) or on a packaging machine (half sleeve or long flat film). A printed image can be applied to the casing in any of these forms, and the sleeve casing can also be corrugated. In addition, the casing of the present invention is suitable for applying a printed image to it by flexography or other high-performance printing methods.

Possible shell structures of the present invention are shown in Tables 1 and 2.

Table 1. Embodiments of the casing of the present invention used as a filling sleeve on stuffing equipment. Shell structure (from minced meat to air - from left to right) The need for packaging during storage The need for corona processing Barrier properties in relation to O ₂ H ₂ O pairs PA Yes no the choir beats PA | PO + A roll no no unfortunate the choir (PA | A | ON) doll Yes no ON | A | PA Yes Yes ex the choir PO1 | A | PA | PO2 + A no Yes the choir the choir (PO1 | A | PA | A | PO2) ^ab PA | PO1 + A | PA | PO2 + A roll no no the choir the choir (PA | PO1 | A | PA | PO2 + A) (PA | PO1 + A | PA | A | PO2) doll Yes (PA | PO1 | A | PA | A | PO2) ^a PA | PO1 + A | PA | SEVS | PO2 + A roll no no ex the choir (PA | PO1 | A | PA | SEVS | PO2 + A) (PA | PO1 + A | PA | SEVS | A | PO2) doll Yes (PA | PO1 | A | PA | SEVS | A | PO2) ^a PA | A | PVDC | A | PA | PO + A roll no no ex ex (PA | A | PVDC | A | PA | A | PO) doll Yes

PA is a polyamide composition containing mainly polyamide 6, polyamide 66 or copolyamide 6/66 or a mixture thereof, and, if necessary, (co) polyamide 6I / 6T and / or MXD6;

PO - polyolefin (PP, SPE, LDPE, HDPE, LLDPE, LLPEONP), SEVA, a copolymer of ethylene and (meth) acrylic acid, an ionomer or a mixture thereof;

A is an adhesive material, preferably a polyolefin grafted with maleic anhydride;

PO + A - a mixture of PO and A;

SEVS is a copolymer of ethylene and vinyl alcohol with an ethylene residue content of 32 to 44%;

PVDC is a thermoplastic copolymer of vinylidene chloride with vinyl chloride and / or vinyl acetate, with a content of vinylidene chloride residues from 75 to 90%.

In the designation PO1, PO2 - the number corresponds to the serial number of the polyolefin layer in the polymer film, if there are several such layers, in the direction from the stuffing to the air.

^a The layer PO1 (PO1 + A) is preferably substantially thicker than the layer PO2 (PO2 + A).

^b The option of the inner layer PO1 + A is not considered, since adhesive polymers often do not have hygienic tolerance for direct contact with sausage products.

Table 2. Embodiments of the sheath of the present invention used in the form of a sleeve or flat long film for filling on packaging machines. Shell structure (from minced meat to air - from left to right) Location of welded edges Welding method Barrier properties in relation to O ₂ H ₂ O pairs ON | A | PA ^ab butt contact ex the choir PVDC | A | PA butt contact or induction ex ex PO1 | A | PA | PO2 + A butt or lap contact the choir the choir (PO1 | A | PA | A | PO2) ^ab PO1 | A | PA | SEVS | PO2 + A ^ab butt or lap contact ex the choir PVDC | A | PA | PO + A butt contact or induction ex ex (PVDC | A | PA | A | PO) ^c lap contact PVDC1 | A | PA | A | PVDC2 butt or lap contact or induction ex ex

All shells require special treatment (plasma, radiation or corona) of the food contact layer and all but the first two do not require additional packaging;

PA is a polyamide composition containing mainly polyamide 6, polyamide 66 or copolyamide 6/66 or a mixture thereof, and, if necessary, (co) polyamide 6I / 6T and / or MXD6;

PO - polyolefin (PP, SPE, LDPE, HDPE, LLDPE, LLPEONP), SEVA, a copolymer of ethylene and (meth) acrylic acid, an ionomer or a mixture thereof;

A is an adhesive material, preferably a polyolefin grafted with maleic anhydride; SEVS is a copolymer of ethylene and vinyl alcohol with an ethylene residue content of 32 to 44%;

PVDC is a thermoplastic copolymer of vinylidene chloride with vinyl chloride and / or vinyl acetate, with a content of vinylidene chloride residues from 75 to 90%.

In the designation PO1, PO2 (PVDC1, PVDC2) - the number corresponds to the serial number of the polyolefin layer (PVDC layer) in the polymer film, if there are several such layers, in the direction from the stuffing to the air.

^a The PO1 layer (PVDC1) is preferably thicker than the PO2 layer (PO2 + A, PVDC2).

^b The option of the inner layer PO1 + A is not considered, since adhesive polymers often do not have hygienic tolerance for direct contact with sausage products.

The thickness of the PVDC layer is chosen so that its SPVV is significantly lower than that of the PO layer (PO + A).

Description of a method for producing a shell of the present invention.

The first three stages described above of the method for producing the casing of the present invention, including the extrusion of a single or multilayer extrudate in the form of a primary sleeve, the orientation hood of the primary sleeve to obtain an oriented sleeve film, the heat setting of the oriented sleeve film to obtain a heat-fixed oriented sleeve film, are typical for the technology for producing traditional sausage shells, which is often exhausted by them. The traditionally used subsequent operations, such as printing and / or corrugation, change only the appearance and shape of the shell, but not its properties. At the extrusion stage, a molded “blank” of the tubular sheath is formed. At this stage, the extrudate molded by means of an annular die in the form of a sleeve is cooled, preferably abruptly, to form the so-called primary sleeve. As a cooling medium, it is preferable to use water. This technology prevents premature crystallization of the polyamide and facilitates subsequent orientation drawing.

The drawing stage is preceded by heating of the primary sleeve to approximately 70-80 ° C. This operation can be carried out in an air oven, in an infrared heater or in a bath with hot water. The sleeve shell is drawn by blowing up the primary sleeve with air in the form of a bubble (secondary sleeve or secondary bubble) and simultaneously drawing it in the longitudinal direction using two pairs of clamping shafts, due to the fact that the steam inlet sleeve rotates more slowly than the outlet one. In this case, the primary sleeve usually increases in diameter by 3.5-4 times and extends 2-3 times along in accordance with the ratio of the speeds of the pulling pairs. The hood results in a tubular film in an unstable oriented state, characterized by the presence of a crystalline phase in the form of many small imperfect and unstable crystallites in the polyamide layer.

The step of thermofixing an oriented sleeve film is preferably carried out by holding it in the form of an air-blown bubble (tertiary sleeve or tertiary bubble) at temperatures of 130-160 ° C, and preferably at 135-140 ° C, for 3-5 seconds. You can use an air oven or an infrared heater to heat the bubble. The use of the heat-setting method by treatment with hot steam or water, known from the prior art (see, for example, European patent No. EP 0974452), is in this case unacceptable, since the polyamide layer after the heat-setting stage, in accordance with the objectives of the present invention, must remain dry. During the heat-setting process, the oriented sleeve film shrinks up to 10%, and preferably from 5 to 10%, both in the transverse and longitudinal directions due to the selected air pressure in the bubble and the ratio of the speeds of the pairs of clamping shafts at the beginning and end of the bubble. By adjusting the temperature and time of heat setting within the specified limits, as well as the degree of bubble seating, it is possible to obtain tubular films with various degrees of "hot" shrinkage, which can be measured if the manufacture of the invented shell is made in two separate plants. This fraction of hot shrinkage will also be inherent in the finished shell of the present invention and approximately correspond to the difference between its hot shrinkage and its wet shrinkage after additional processing. However, if the heat-setting temperature is equal to or lower than 120 ° C, the resulting shell will have reduced dimensional stability and high thermal shrinkage. During thermal fixation, the formation of a stable crystalline phase of polyamide mainly occurs. The stability of the crystalline phase is manifested in the fact that it does not rebuild either spontaneously under storage conditions or involuntarily under moderate tensile deformations, for example, those that occur during filling of the shell.

Upon completion of the heat-setting stage according to traditional technology, the shell in the form of a flat-layed sleeve is fed to the cooling shaft and in a state cooled to about room temperature is wound into a roll.

Obtained using the first three stages, that is, by conventional technology, the shell has practically zero free shrinkage during storage, wet shrinkage, usually from 0 to 1.5% in both directions, and hot shrinkage, usually from 5 to 8% o in both directions.

The next step is the essence of the invented method for producing the shell of the present invention. The sleeve casing that has gone through the heat-setting stage, having a temperature higher than the glass transition temperature of the polyamide composition of the above-described polyamide layer, is stretched by 4-10% in the transverse and 3-8% in the longitudinal direction, preferably by 5-10% in the transverse direction and 4-8 % in longitudinal, followed by cooling in the expanded state to a temperature below the glass transition temperature of the polyamide composition. The glass transition temperature range of polyamides 6 and 66, which are contained in the predominant amounts of the polyamide composition, is (dry) about 47-60 ° C (Nylon Plastics Handbook ed. By Melvin I. Cohan, Cincinnati: Hanser / Gardner Publication, Inc, 1995, p. 147). The glass transition point (temperature) is usually understood as the lower value of this range. By incorporating the semi-aromatic (co) polyamides 6I / 6T and / or MXD6 into the polyamide composition, the glass transition temperature of the polyamide composition can be increased. For example, adding 20% copolyamide 6I / 6T (Selar® PA 3426 brand, manufactured by DuPont) to polyamide 6 increases the glass transition temperature of the latter by 10 ° C (see, for example, the DuPont ™ Selar® PA3426 Blends With Nylon 6 brochure - URL : http://www2.dupont.com/Selar/en_US/assets/downloads/selar_pa3426_nylon_blends.pdf Date of access: 03.24.09). The excess of the temperature at which the film is stretched above the glass transition temperature, chosen within reasonable limits, is not of fundamental importance and is determined solely by economic considerations. The temperature at which the film is stretched is in the range of 60-140 ° C, but preferably from 70 to 130 ° C. If the polyamide composition does not contain (co) polyamides 6I / 6T and / or MXD6, the stretched sleeve should be cooled to a temperature not exceeding 47 ° C, preferably to a temperature of 45 ° C, if 20% polyamide 6I / 6T is present in it , the sleeve can be cooled to a temperature not exceeding 57 ° C, preferably to a temperature of 55 ° C. The final cooling of the shell to room temperature can be done after flat folding of the sleeve, for example, using a cooling shaft. In a preferred embodiment, the sheath is stretched by simultaneously blowing it in the air in the form of a bubble and drawing it in the longitudinal direction with the help of two pairs of pulling shafts, in the same manner as with the orientation hood. This stage of the process can be carried out both on the same production line as in the previous stages, and on a separate installation consisting of a delivery shaft, a heater, two pairs of active clamping shafts, a cooling device and a winding shaft. Such an installation may be part of the same production line with a corrugating machine operating at a constant feed rate of the sleeve. As a heater, for example, an air oven or an IR heater can be used. The heater can be located up to the input pair of clamping shafts and heat up a flat-layed sleeve or between the input and output pairs and heat up the bubble. The cooling of the inflated bubble is preferably carried out by a stream of cold air using an annular blowing device. If the stage of additional stretching is carried out on the same production line with the previous stages, an additional heater is not required, since the shell is already sufficiently heated after the stage of heat setting, but the remaining nodes must be present. The additional stage of the present invention does not require significant time, so the length of the additional bubble, even on a high-performance line, does not exceed 1-3 m

It is advisable to carry out a separate stage of additional stretching outside the main production line if, for example, it is required to apply a printed image (marking) to a shell having an external polyamide layer using printing inks containing water or lower alcohols as a solvent. The application of such markings to the shell, which has undergone additional stretching, can cause its local shrinkage and distortion of a cylindrical shape. In this case, it is advisable to perform the operation of additional stretching after applying the marking, and the layout of the printed image should be developed taking into account previously known controlled image distortions arising from stretching.

If a shell in the form of a sleeve is required for end use, it can be supplied to the consumer in the form of rolls or in the form of corrugated dolls. In the latter case, it can be processed from a roll form into corrugated dolls using the well-known corrugation operation.

If the subsequent filling of the casing with minced meat is expected on packaging machines of vertical or horizontal type, it can be transformed from a sleeve form to the shape of a half sleeve or a flat extended film by cutting the sleeve along one or two of its edges, respectively. In the latter case, one roll of a sleeve will produce two rolls of a flat extended film. Such printed-printed products can be obtained both by marking them in finished form or by marking the tubular material before cutting it. In addition, a flat extended film can be obtained from a sleeve shell with a reduced thickness by gluing its halves together in a flat form with a suitable adhesive that does not contain solvent and does not require heating to cure, for example, UV-curable adhesive. Such an operation can be performed on an installation consisting of sequentially located nodes: a delivery shaft, two pairs of active clamping shafts, a UV emitter and a winding shaft. In this case, the liquid UV-curable adhesive is placed in the sleeve between the pairs of active clamping shafts and is cured in a thin layer between the halves of the flat-layed sleeve.

Shell filling on stuffing equipment. As mentioned above, the traditional technology of stuffing sausage stuffing with plastic casings based on polyamide involves their preliminary wetting, which usually takes from 30 minutes to 1 hour. For the shell of the present invention, this procedure is not needed. This is followed by packing the shell using a stuffing unit consisting of a syringe and a clipper. Usually it is accompanied by stretching the shell by 10-12% in diameter (caliber). When filling the invented shell, it is not stretched at all or stretched with a minimum degree of stretching of 0.5-1.5% in caliber. In principle, if the meat processor is pleased, the casing can be stretched during stuffing as much as a particular stuffing technique allows without compromising the quality of the final product and without causing excessive wear of the equipment. However, it is most preferable to fill the invented shell without stretching at all. Immediately after stuffing, the loafs can be slightly loose to the touch, except in the case when the main polyamide layer directly contacts the meat and contact with the moist environment causes shrinkage of the shell, its tension and tightening of the contents in a short time. The finished sausage product is always a tightly filled loaf using any embodiment of the casing of the present invention.

Shell filling on a packaging machine. In the case of filling the casing on a packaging machine, it is best to use a casing with maximum values of wet shrinkage. Filling in this case occurs according to the usual technological scheme.

Cooking sausage. In both cases, filling the shell cooking of sausage occurs according to the usual technological scheme. You can use steam cooking, boiling in boiling water or even in superheated water (autoclaving). During the cooking process, moisture penetrates into the polyamide layer and from this moment the forces compressing the shell around the stuffing begin to act.

Sausage cooling. The sausage product should be cooled so that the polyamide layer remains moist all the time. In the general case, for this it is most expedient to apply the method of irrigation with cold water (showering). If the main polyamide layer is core, cold air cooling can be used with caution, and if it comes in contact with minced meat, cold air cooling can be used without concern.

Subsequent operations. Subsequent operations are not required. Sausages immediately after cooling to room temperature are sent to the refrigerator.

Sausage product in the casing of the present invention.

Such a sausage is a tightly filled loaf. Its further use depends on the barrier properties determined by the composition and structure of the shell. For example, a sausage product in a casing containing a main polyamide layer in contact with minced meat without additional oxygen-barrier layers, it is most advisable to use sausages, sliced and packed in a barrier packaging material for subsequent manufacture. The remaining products can be stored in the refrigerator for a specified period in accordance with the conclusion of authorized institutions of the Ministry of Health.

The following examples of the invention show some variants of the shell of the present invention, as well as a method for its manufacture. These examples are purely illustrative and, of course, do not exhaust the scope of the claims established by the claims of the present invention.

Examples of the manufacture of the shell and its properties.

Comparative example 1.

As comparative example 1, a five-layered tubular sheath with a diameter of 65 mm and a thickness of 42-45 μm with a layered structure (from the layer in contact with food from left to right) was selected:

PA1 | A | PE1 | A | PA2

and relative layer thicknesses: 15% | 3% | 25% | 3% | 54%,

where PA1 is a mixture of 60% PA 6 (brand Ultramid B4), 35% PA 66 (brand Ultramid A4) (both of these polyamides are manufactured by BASF GmbH, Germany) and 5% PA 6I / 6T (brand Selar® PA 3426 manufactured by DuPont Co, USA);

A - adhesive polymer Modic 603 manufactured by Mitsubishi Chemical Co (Japan);

PE1 - LDPE (grade 15803-020 manufactured by Kazanorgsintez, Russia);

PA2 - a mixture of 55% PA 6 (brand Ultramid B4), 40% PA 66 (brand Ultramid A4) and 5% ionomer (brand Surlin 1652 manufactured by DuPont Co., USA).

This shell is made in accordance with the first three stages of the above technology. Granular polymeric materials are loaded into the hoppers of the five extruders of a multilayer extrusion plant in accordance with the above-described layered structure. Polymer materials are melted in extruders and fed into a five-layer extrusion head. They are then extruded through a ring die in the form of a multilayer molten tubular blank into a bath of cold water. This preform is cooled, and it hardens in the form of a multilayer primary sleeve with a diameter of about 20 mm and a thickness of about 320 microns. Then, the primary sleeve is fed into a tubular infrared heater using a system of pairs of active clamping shafts, where it is heated to a temperature of 80 ° C, and then subjected to orientational drawing with coefficients of longitudinal and transverse drawing of 2.5 and 3.7, respectively. Subsequent heat setting of the obtained oriented sleeve film is carried out in the form of an air tertiary sleeve in tubular infrared heaters at a temperature of 135-140 ° C for 3-5 seconds. In the process of thermal fixation with the help of appropriate adjustment of the rotation speeds of the inlet and outlet clamping pairs of active shafts that limit the tertiary bubble, the shell shrinks in the longitudinal direction with a coefficient of 1.10 while maintaining the bubble caliber at 66-67 mm. After thermofixing, the folded shell is passed through a cooling shaft, its temperature is brought to 25 ° C and wound into a roll.

The properties of the casing are shown in table 3. After sampling the casing for research, the coiled roll was packed in a plastic bag and sent for corrugation.

Example 1

The shell of the present invention is made by processing the shell, made in accordance with comparative example 1, in a separate installation.

On the shell, made in accordance with comparative example 1, using a flexographic printing machine, a printed image is applied with inks containing ethanol as a solvent. Then, a wrapped shell with a printed image is placed on the output shaft of the installation with a total length of 1.5 meters, which, in addition to the said shaft, includes a sequentially arranged IR heater with flat elements, inlet of a pair of clamping shafts, an annular air cooler, releasing a pair of clamping shafts, a cooling shaft and reeling shaft. The shell is passed through both pairs of shafts, the inlet pair is clamped, the sleeve is inflated to a diameter of 72-73 mm, the outlet pair is clamped, the end of the sleeve is passed through the cooling shaft and fixed on the sleeve mounted on the receiving shaft. Air is supplied to the air cooler and the rotation of all shafts is turned on. In this case, the rotation speeds of the output shaft and the incoming pair of shafts on the one hand, as well as the output pair and the receiving shaft on the other, coincide, but the ratio of the speeds of the incoming and outgoing pairs is 1: 1.04.

When rewinding, the temperature of the inflated bubble from the exit from the first pair of shafts to the cooling zone is from 70 to 80 ° C, and after this zone is 45 ° C. After passing through the cooling shaft, the temperature of the folded sleeve is 25 ° C. The last section of the shell with a length of 1.5 meters, the rewind field is cut off and discarded. The treated shell has a diameter of 71.5 mm (folded sleeve width 112-112.5 μm) and a thickness of approximately 35 μm. The properties of the casing are shown in table 3. After sampling the casing, the coiled roll is packaged in a plastic bag and sent to the corrugation.

Comparative Example 2

As a comparative example, a seven-layer shell with a layered structure is selected:

PA1 | A | PE2 | A | PA1 | A | PE3

and relative thicknesses of the layers: 13% | 3% | 29% | 3% | 39% | 3% | 10%,

where the composition of the layers PA1 and A corresponds to the composition specified in example 1,

PE2 - a mixture of 80% PE1 (according to example 1) and 20% brown pigment concentrate, with a pigment content of 48% (brand 1340 Brown manufactured by A. Schulman Inc., Germany),

and PE3 - PEONP (brand AFFINITY PL 1845G manufactured by Dow Chemical Co.).

The shell is made by the method described in comparative example 1, except that a seven-layer head is used for extrusion of the multilayer workpiece, and in the process of heat setting at 135-140 ° C, the shell is seated not by 10, but by 5% relative to the dimensional parameters of the secondary sleeve as in transverse and in the longitudinal direction. The finished shell has a thickness of about 40.5 μm and a diameter of 68-68.5 mm (width of the folded sleeve 107-107.5 mm). After sampling the shell samples, the coiled roll is packaged in a plastic bag and sent to the flexography site for printing with UV-curable printing inks. Another roll of the shell is packed and sent to the warehouse. The properties of the shell are shown in table 3.

Example 2

The shell is made on the same production line on which the shells are made in accordance with comparative examples 1 and 2, but characterized in that in the end of the line in front of the cooling shaft are added sequentially arranged: free path area of the flat-layed sleeve film, the first pair of active clamping shafts, two ring air coolers and a second pair of active clamping shafts. At the same time, the total length of the line increased by 3 meters. Accordingly, the manufacture of the sheath begins as in comparative example 1, but after the sleeve film exits from the pair of clamping shafts, which was the last in the manufacture of sheaths in accordance with the comparative examples, the sleeve passes in a flat-folded form to the free path, and then it is passed through the first pair of shafts. After that, it is inflated to a diameter of approximately 73 mm, the second pair of shafts is clamped, the end of the sleeve is passed through the cooling shaft and fixed to a sleeve mounted on the receiving shaft. Air coolers are supplied with air and a shell is wound around the sleeve. The ratio of the shaft rotation speeds in the first and second additional pairs is 1: 1.05, the film temperature at the entrance to the first pair of shafts is 105 ° C, after the first air cooler - 60 ° C, after the second - 48 ° C, and after the cooling shaft - 27 ° C. The finished shell has a thickness of about 35 μm and a diameter of 71.5 mm (folded sleeve width 112-112.5 mm). After sampling the shell samples, the coiled roll is packaged in a plastic bag and sent to the flexography site for printing with UV-curable printing inks. Another roll of the shell is packed and sent to the warehouse. The properties of the shell are shown in table 3.

Comparative example 3.

The shell has a layered structure the same as in example 2. Its manufacture was carried out in accordance with comparative example 1, except that the heat setting was carried out at 120 ° C for 2 seconds. This finished shell has the same diameter and the same thickness as the shell according to comparative example 1.

Comparative example 4.

The shell has a layered structure the same as in example 1. Its manufacture was carried out in accordance with comparative example 1, except that the heat setting was carried out at 90 ° C for 2 seconds, while the sleeve was not inflated. In the longitudinal direction, the shell was seated by 10%. As a result, a shell with a folded sleeve width of 98-99 μm and a thickness of about 47 μm was obtained. After sampling the sheath, the reeled-up roll was packed in a plastic bag and sent to the flexography site for printing with UV-curable printing inks. The properties of the shell are shown in table 3.

Print Stability Test

On the shells made according to examples 2 and comparative examples 3 and 4, 5 hours after their manufacture, a printed image was printed on a flexographic machine with UV-curable inks. After that, the rolls with these shells were packed in plastic wrap and stored at 25 ° C. After two weeks, the packaging was opened and the condition of the rolls and the printed image was evaluated. The casing of the present invention passed the test perfectly: the tension of the casing in the rolls was approximately the same as immediately after applying the printed image. The print image itself is not damaged.

In a roll with a casing made according to comparative example 3, a noticeable compression of the roll was observed, but there was no damage to the paint layer.

A roll with a shell made according to comparative example 4 was highly compressed, especially in the central part of its cylindrical surface. When unwinding the shell, it was found that the printed image partially switched to the opposite side of the sleeve in contact with it.

Table 3. The main characteristics of the resulting shells. Example No. Young's modulus, MPa Shrink% In air at 25 ° C and RH 60%, 2 weeks In water 25 ° C, 2 hours In water 25 ° C, 3 days In water 40 ° C, 2 hours In water 60 ° C, 0.5 hours In water 80 ° C, 0.5 hours vd pop. vd pop. vd pop. vd pop. vd pop. vd pop. vd pop. 1 comp. dry 513 514 <1 <1 one one one one one one 3 four four 5 1 comp. humid 196 261 H. H. H. H. H. H. H. H. H. H. H. H. 1 dry 521 532 one one 7 8 8 9 8 9 eleven 13 12 fourteen 2 comp. dry 382 345 <1 <1 one one one one one one 5 6 7 8 2 comp. humid 215 247 H. H. H. H. H. H. H. H. H. H. H. H. 2 dry 339 567 <1 <1 one one four 5 four 5.5 9 10 10 12 3 comp. dry 375 452 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 9 eleven eleven 13 4 comp. dry 412 435 5 7 H. H. H. H. H. H. H. H. H. H.

The Young's modulus was determined on an AUTOGRAPH AGS test machine manufactured by Shimadzu Co.

Exposure to air with a humidity of 60% at 25 ° C to determine free shrinkage was carried out in a closed desiccator with crystalline sodium bromide (NaBr) placed on the bottom, while the desiccator was in a thermostat with an appropriate set temperature.

Shrinkage tests in water at various temperatures (except 25 ° C for 2 hours) were then extended with a doubling of the holding period for each temperature and did not reveal further noticeable changes in the dimensional parameters of the shell.

OV - relative humidity; vd - along; pop. - across; cf. - comparative; dry - before determining the Young's modulus, the shell samples were not soaked; humid - before determining the Young's modulus, the shell samples were kept in water at 25 ° C for one hour; N. - the measurement was not carried out.

Shell usage examples.

Filling on the stuffing line.

The shells made according to examples 1 and 2, as well as comparative examples 1, 2 and 3, with a printed image in the form of corrugated dolls were delivered to the meat processing plant. There they are without pre-wetting on a production line consisting of a HANDTMANN VF618 syringe manufactured by Albert Handtmann Maschinenfabrik GmbH & Co. KG and automatic clipper FCA-3463 manufactured by Poly-Clip System GmbH & Co. KG, were filled with sausage meat so that the diameter of the resulting sausage loaf did not exceed the nominal diameter of the shell by more than 0.5%.

After that, the sausage loaves were sent to the cooking chamber, where they were subjected to steam treatment at a temperature of 100 ° C until the temperature inside the control loaf reached 70 ° C, which was about 40 minutes. During cooking, the shell on all the loaves looked taut. Then the loaves were cooled, and the loaves in the shells made according to comparative examples 1 and 2, and part of the loaves in the shells according to examples 1 and 2 were cooled by irrigation with water (showering), and the other part of the loaves in the shells according to examples 1 and 2 were cooled in a stream of air . As a result, by cooling by showering, tightly packed loaves were obtained only in both shells of the present invention. In the case of air cooling, tightly packed loaves turned out to be only in the shell according to Example 2. In all other cases, loosely filled loaves in a shriveled shell turned out.

Simulation of filling on a packaging machine

The outer surface of the sleeve shells made according to example 2 and comparative examples 2 and 3 was corona treated until a surface energy of 80 dyne / cm was achieved.

Then, sections of shells with a length of about 40 cm were cut along one of the edges of the sleeve and folded so that the sides of the half-sleeve containing the polyolefin layer were facing each other and butt-welded by resistance welding with a 2 mm wide longitudinal weld. After that, one end of each resulting sleeve turned out to be bundled and clamped with a clip of thick aluminum wire. Then the sleeve was tightly manually filled with minced meat and clamped with a clip from the second end. The obtained sausage loaves were cooked in boiling water for 30 minutes, and then were cooled in cold running water. As a result, the finished sausage loaf in the shell made according to Example 2 turned out to be tightly filled and had no wrinkles on the surface, and the shell made in accordance with comparative examples 2 and 3 turned out to be wrinkled on the surface of the finished loaf. In addition, after cutting both loaves under a shell made according to comparative example 2, gel-like deposits (the so-called broth swelling) were found.

Thus, tests of the shells show that only the shells made according to the present invention meet the objectives.

Claims (38)

1. A single or multi-layer synthetic heat-shrinkable sausage casing containing at least one polyamide layer based on at least one aliphatic (co) polyamide selected from the group consisting of polyamide 6, polyamide 66, copolyamide 6 / 66 or a mixture thereof, characterized in that:
i. in a state ready for filling, it has a Young's modulus of at least 400 MPa in the transverse and at least 300 MPa in the longitudinal direction;
ii. when exposed to air with a relative humidity of 60% and a temperature of 25 ° C for 5 days, its shrinkage is not more than 2%, both in the transverse and in the longitudinal direction;
iii. when aged in water with a temperature of 40 ° C for 2 hours, its shrinkage is 4-10% in the transverse and 3-10% in the longitudinal direction;
iv. when aged in water with a temperature of 80 ° C for 30 minutes, its shrinkage is 9-18% in the transverse and 8-15% in the longitudinal direction. 2. The synthetic shell according to claim 1, characterized in that its shrinkage when exposed to air with a relative humidity of 60% and a temperature of 25 ° C for 5 days is preferably not more than 1%, both transversely and in longitudinal direction. 3. The synthetic shell according to claim 1, characterized in that its shrinkage upon exposure to water at a temperature of 40 ° C for 2 hours is preferably 5-10% in the transverse and 4-10% in the longitudinal direction. 4. The synthetic shell according to claim 1, characterized in that its shrinkage upon exposure to water at a temperature of 80 ° C for 30 minutes is preferably 10-15% in the transverse and 9-12% in the longitudinal direction. 5. The synthetic shell according to claim 1, characterized in that the polyamide layer contains from 60 to 100% of at least one aliphatic (co) polyamide. 6. The synthetic shell according to claim 5, characterized in that the polyamide layer contains from 0 to 20% of at least one semi-aromatic (co) polyamide selected from the group consisting of copolyamide 6I / 6T, polyamide MXD6, or a mixture thereof. 7. The synthetic shell according to claim 1, characterized in that the polyamide layer contains from 0 to 20% of at least one polymer selected from the group consisting of polyesters, olefin homopolymers, olefin copolymers, ionomers, or a mixture thereof. 8. The synthetic shell according to claim 1, characterized in that it is made in the form of a sleeve. 9. The synthetic sheath according to claim 1, characterized in that it is made in the form of a half sleeve or an extended flat film. 10. The synthetic shell according to claim 1, characterized in that it further comprises from 1 to 11 layers of thermoplastic polymers. 11. The synthetic shell of claim 10, wherein the thermoplastic polymers are selected from the group consisting of (co) polyamides, (co) olefin polymers grafted with maleic anhydride (co) polymers of olefins, polyvinylidene chloride, ethylene vinyl alcohol copolymers, thermoplastic polyurethanes , as well as mixtures of these thermoplastic polymers belonging to both one and various types. 12. The synthetic shell according to claim 11, characterized in that (co) polyamides are polyamide 6, polyamide 66, copolyamide 6/66, polyamide 9, polyamide 10, polyamide 610, polyamide 12, polyamide 612, copolyamide 6/66 / 10, copolyamide 6/66/12, copolyamide 6I / 6T, polyamide MXD6. 13. The synthetic shell according to claim 11, characterized in that the (co) polymers of olefins are polypropylene, a copolymer of propylene and ethylene, with a content of monomer residues of propylene of at least 80 mol%, high pressure polyethylene, low pressure polyethylene obtained by polymerization on Ziegler-Natta catalysts, metallocene linear low density polyethylene, metallocene linear very low density polyethylene, ethylene vinyl acetate copolymer, ethylene acrylic or methacrylic acid copolymer and ionomer. 14. The synthetic shell according to claim 11, characterized in that the copolymers of ethylene and vinyl alcohol contain from 32 to 44 mol.% Ethylene residues. 15. The synthetic shell according to claim 11, characterized in that the polyvinylidene chloride is a copolymer of vinylidene chloride with at least one vinyl monomer selected from the group comprising vinyl chloride and vinyl acetate, with a content of vinylidene chloride monomer units in the range of 75-90 mol .%. 16. The synthetic shell according to claim 1, characterized in that any of its layers may additionally contain from 0 to 10% of the total mass of the layer composition of at least one of the low molecular weight additives selected from the group comprising dyes, pigments, fillers , lubricants, processing aids, blowing agents, glidants, matting additives. 17. The synthetic shell of claim 8, characterized in that its inner layer in contact with the meat, preferably consists of (co) polyamide or linear polyurethane, in the most preferred embodiment, this layer is a layer of (co) polyamide. 18. The synthetic shell according to claim 9, characterized in that its inner layer in contact with the meat, or both the inner and outer layers are made of heat-sealable polymeric material. 19. The synthetic shell according to p. 18, characterized in that the heat sealable polymer material contains at least one thermoplastic polymer with a melting point in the range of 101-160 ° C, selected from the group comprising metallocene linear low density polyethylene, metallocene linear polyethylene very low density, ethylene vinyl acetate copolymer, ethylene acrylic or methacrylic acid copolymer, ionomer, polyvinylidene chloride, copolyamide 6/66/12 and mixtures thereof. 20. The synthetic shell according to claim 1, characterized in that at least one polyamide layer is located between two moisture barrier layers. 21. The synthetic shell according to claim 20, characterized in that the moisture barrier layers contain at least one thermoplastic polymer material selected from the group consisting of polypropylene, a copolymer of propylene and ethylene, with a content of monomer residues of propylene of at least 80 mol.%, high pressure polyethylene, low pressure polyethylene, metallocene linear low density polyethylene, metallocene linear very low density polyethylene, ethylene vinyl acetate copolymer, maleic anhydride grafting products above numerical polymers, as well as polyvinylidene chloride and mixtures of the above polymers. 22. The synthetic shell of claim 10, characterized in that the layers made of materials of various nature that do not have immanent mutual adhesion are interconnected using adhesive layers of maleic anhydride grafted with (o) olefin polymers. 23. The synthetic shell according to claim 1, characterized in that the total thickness of the polyamide layers is from 40 to 100% of the total thickness of the shell, and mainly from 45 to 100% of the total thickness of the shell. 24. The synthetic shell according to claim 1, characterized in that its total thickness is from 18 to 120 microns. 25. The synthetic shell according to claim 2, characterized in that it is made in the form of a corrugated "doll". 26. The synthetic shell according to claim 1, characterized in that it is printed with a marking. 27. A method for producing a synthetic heat-shrinkable sausage casing according to any one of claims 1 to 26, consisting of successive stages, including extrusion of a single or multi-layer extrudate in the form of a primary sleeve, an orientation hood of the primary sleeve to obtain an oriented sleeve film, heat setting of an oriented sleeve film to obtain thermofixed oriented sleeve film, characterized in that the thermofixed oriented sleeve film is further subjected to further processing, in which a thermofixed oriented sleeve film having a temperature of 60-140 ° C is stretched by 4-10% in the transverse direction and by 3-8% in the longitudinal direction, cooled in the expanded state to a temperature not higher than the glass transition temperature of the polyamide composition of the polyamide layer and get ready to filling the sausage casing, which is then wound into a roll in the form of a flat-folded sleeve. 28. The method according to item 27, wherein the additional processing of the oriented sleeve film, it is preferably stretched by 5-10% in the transverse and 4-8% in the longitudinal direction. 29. The method according to item 27, wherein the heat setting is carried out by heating the shell, inflated with air in the form of a bubble, to a temperature of 130-160 ° C, preferably 135-140 ° C, and its exposure at this temperature for from 3 to 5 sec 30. The method according to clause 29, wherein the film is seated by up to 10%, preferably 5-10%, both in the transverse and in the longitudinal direction during the heat-setting process. 31. The method according to p. 30, characterized in that during further processing of the thermofixed oriented sleeve film, it is preferably stretched at a temperature of 70-130 ° C. 32. The method according to p, characterized in that during the additional processing, the cooling of the thermofixed oriented sleeve film in the stretched state is carried out to a temperature of not higher than 45-57 ° C, depending on the composition of the polyamide layer. 33. The method according to item 27, wherein the stretching during additional processing is carried out using air blown into the sleeve under excessive pressure, and two pairs of clamping shafts with an active drive rotating at different speeds. 34. The method according to item 27, wherein the additional processing is performed on the same production line as the operation for obtaining an oriented thermofixed sleeve film. 35. The method according to item 27, wherein the additional processing of oriented thermofixed sleeve film is performed outside the line of its production in a separate installation. 36. The method according to clause 35, wherein the additional processing of oriented thermofixed sleeve film is made after printing. 37. The method according to p. 35 or 36, characterized in that the additional processing is carried out in a separate installation with subsequent corrugation of the shell, and this separate installation is connected in one production line with a corrugating machine. 38. The method according to item 27, wherein the ready-to-fill sausage casing is cut along one or both edges of the folded sleeve to obtain, respectively, a half sleeve or an extended flat film.