CN109996444B - Moisture-proof casing folded into rigid self-supporting bar form and method for producing same - Google Patents

Abstract

The invention discloses a molten (co) extruded tubular moisture barrier casing for food products, which is transformed into the form of a rigid self-supporting corrugated stick, wherein the tubular casing has a layer in contact with the food contents, characterized in that the tubular casing has a reduced adhesion to the contents, wherein the outer surface of the tubular casing has at most 10g/m²Wherein the outer surface of the tubular casing further has a hydrophobic component which reduces the bond strength and comprises at least one liquid organic and/or organoelement compound which is substantially non-volatile at room temperature and substantially water-insoluble, wherein the compound has a total surface concentration outside the casing which is greater than the bonding polymer and is in the range of from 50 to 500mg/m²(ii) a And the corrugated rod has the following characteristics: after being left in a free state on a smooth surface at 20 ℃ and RH 75% for 24 hours, its longitudinal compressibility under a force of 1N is not more than 0.5%; the corrugated rod is characterized by not having macroscopic elastic bending deformation as a cantilever support under its own weight; and the corrugated rod is irreversibly broken when the bending moment is 60 to 400N-mm; and the crumple bar is characterized in that it is capable of being de-crumpled at a speed of not less than 1.5m/sec at a temperature of 20 ℃ and RH 60% without the casing wall breaking.

Description

Moisture-proof casing folded into rigid self-supporting bar form and method for producing same

Technical Field

The invention relates to a tubular moisture-proof casing essentially based on synthetic resin, which is converted into the form of a corrugated stick and which is suitable for the high-speed automatic filling of sausage meat, in particular sausage meat emulsions like frankfurters, and also for removal from processed sausages by means of an automatic stripper. The corrugated rod of the present invention is characterized by being rigid and does not require support, such as a special tubular mesh, to maintain its shape and size. The invention also relates to a method for producing such a wrinkled casing.

Background

Sausage casings in compact pleated form are commonly used to fill meat emulsions during the manufacture of ham and sausages, including frankfurters, wiener sausages, hot dogs or bukker sausages. Even if casings are supplied to sausage manufacturers in the form of a roll on a flat tubular film, they usually first fold individual portions of the casing onto a filling tube and then fill the casing with only meat emulsion. It is more practical to use pre-crimped casings in the form of compact sticks (also known as "tubes", "tubes" or "caterpillars") which are about 0.5 metres in length, including up to tens of metres of tubular casings. However, if any significant portion of the operating time is wasted on replacing the corrugated bars, since the bars, which are usually made of plastic casing, cannot maintain their shape and dimensions without support, they are packed in special tubular nets for transport and use.

The person skilled in the art knows adhesive-based casings (reinforced and non-reinforced) which can be processed into mechanically stable self-supporting corrugated bars. This is caused by the specific characteristics of the cellulose film, which are irreversible in bending and indentation deformation. Because of its mechanical stability, the folded cellulose casing is used in an automatic filling process for making frankfurters or wiener sausages. The same type of casing can be removed from processed sausages in an industrial peeling process by a high speed peeler. Due to the constructional features of high-capacity filling automatic machines, such as for example Townsend Frank-a-Matic or Townsend SuperMatic RT7, a plurality of corrugated bars can be fed into the hopper, which can then be filled one by one with meat emulsion of frankfurters or wiener sausages.

However, the production of casings based on viscose is associated with environmentally unfriendly "wet" technology, accompanied by the formation of waste water containing toxic sulphides. Moreover, such casings do not provide a satisfactory water vapour barrier, and consequently the sausages packaged therein lose weight rapidly during heat treatment.

Some previous attempts have been made to provide stable self-supporting corrugated rods from synthetic polymer based tubular casings. For example, european patent No. 1659868, published on 7/1/2009, discloses a method for manufacturing a self-bearing mechanically stable pleated tubular casing made of substantially synthetic resin. The method is based on the breakdown of the elasticity of the casing in the pleat pleats caused by lengthening its shape setting (up to 24 hours). To increase its mechanical stability, the casing can be sprayed with pure water or an oil-in-water emulsion during or directly before the creasing process. For the same purpose, the inventors recommend corona treatment of the casing.

Corrugated rods made in accordance with the invention exhibit observable mobility when subjected to bending or tensile deformation. This can cause serious problems during its transport and when it is used as an automatically filled casing material in sausage production. Furthermore, the disclosed method may cause spontaneous adhesion (or, in other words, clogging) of the casing in the form of a corrugated rod, due to the formation of spots of monolithic polymeric material in the interface between the corrugations of the corrugated rod. This is believed to be the result of non-valent interactions between macromolecules located on different sides of the pleat. Thus, attempts to de-wrinkle such a wrinkled rod result in multiple breaks in the casing; it cannot be used for the filling process. As shown below, this failure occurs more frequently if the casing is wet and if its outer layer is made of a hydrophilic polymeric material such as polyamide or blends thereof with water soluble polymers. Another factor that increases the risk of clogging is corona treatment of the casing surface.

Us patent No. 7803437, published on 28.9.2010, discloses a corrugated stick including an adhesive between the corrugations of a corrugated casing. Bonding is achieved by water soluble polymers, such as carboxymethyl cellulose (CMC), which are typically applied as an aqueous solution to one or both surfaces of the tubular casing during the pleating process. The casing comprises a layer and is made of a blend of polyamide and a hydrophilic, in particular water-soluble, polymer. Similar casings are known in the art and are disclosed, for example, in patent RU No. 2182107, published 5/10/2002, where they are described as membranes having high water vapor and smoke (smokable) permeability. The production method of such a corrugated rod disclosed in the same patent US7803437 can only be achieved by the high water vapor permeability of the casing. Due to the moisture absorption of the hydrophilic polymer component of the casing, adhesive joints between the folds are formed without forced drying. Preferably, the adhesive bonding is achieved by applying a water-soluble polymer only on the inner surface of the tube. A hydrophobic liquid, such as mineral oil, may also be applied as a lubricant on the inner or outer surface of the tube. Furthermore, such liquid may be applied on the inner surface of the casing to provide enhanced peelability. However, as highlighted in the description of the invention, their concentration must be lower than that of the water-soluble polymer.

It is clear that the production method disclosed in this document for corrugated rods is not likely to be applicable to multilayer intermediate moisture-permeable (comprising only polyamide-based layers) casings or moisture-proof casings (e.g. comprising a moisture-impermeable, e.g. polyolefin-based layer), even if they comprise a hydrophilic polymer in one of their layers (further referred to as "moisture-absorbing layer"). Due to the hydrophilic polymer absorption of the casing, the removal of water from the binding polymer solution is greatly limited, because the volume of the outer hygroscopic layer is reduced compared to a single casing; or it is absolutely impossible due to the presence of a moisture barrier between the sticky surface of the tubular casing and the hygroscopic layer. Meanwhile, in many traditional gourmets around the world, frankfurters of small diameter are not suitable for smoking. In this case, it is very advantageous if the casing for such sausages has certain moisture-proof properties, since it prevents an undesired weight loss when the sausage is subjected to heat treatment.

Closest to the present invention is patent RU No. 2131670, published on 20.6.1999, which discloses a wrinkled casing extruded from a (co) polyamide based composition (i.e. from a moderately moisture permeable and hygroscopic material) and having additional layers comprising water soluble film forming polymers on both its outer and inner surfaces. In this case, the inner adhesive non-drying layer is generally composed of a water-soluble polymer and a liquid, substantially hydrophobic substance and provides the casing with reduced adhesion to the sausage meat, while the outer layer serves as a mechanical protective agent for the polyamide layer. The document also teaches that these coatings can be applied to the casing during the creping process, while the resulting creped stick is stable and suitable for automatic filling of casings.

However, the bond strength between the casing folds of the pleated stick is too high, since the outer layer of water-soluble polymer is continuous. This leads to sporadic cracking of such casing walls at a high de-wrinkling rate during high-throughput filling. The behavior of such a wrinkled casing is largely dependent on the environmental conditions in the working chamber where filling is done; first, it depends on the relative humidity of the air and the lower the air humidity, the higher the average frequency of cracking. Furthermore, the inner, substantially liquid layer prevents the corrugated pleats from being sufficiently densely stacked and makes it impossible to manufacture a corrugated rod with a high degree of compression. Furthermore, for certain types of meat emulsions, particularly those rich in collagen or polysaccharides, such as starch, the inner layer of such casing does not provide the desired peelability (or sufficiently low meat adhesion strength).

Thus, there remains a need for a wrinkled moisture barrier casing with reduced adherence to food contents suitable for high speed automated filling with sausage meat and automated removal of thermally processed sausages by industrial strippers.

In view of the foregoing, it is an object of the present invention to provide a single-or multilayer moisture-resistant casing which has reduced adhesion to food products, in particular to sausage meat and meat emulsions of frankfurters, which is creased in the form of a rigid self-supporting stick, which has a balanced strength, on the one hand, which maintains the integrity of the creased stick during its transport and filling, and on the other hand, which can be passed through a high-speed dewrinkling process without breaking.

In the following, the term "rigid" (rigid) as applied to a corrugated rod is understood to mean the ability of the rod to break irreversibly under bending or tensile deformation forces that significantly exceed its weight. The term "self-supporting" as applied hereinafter to corrugated bars is to be understood as the ability of the bar to maintain its integrity and shape without additional shape-retaining mechanisms, such as external tubular meshes or rods with plugs, under moderately applied loads, such as inertial forces occurring during its transportation and handling.

It is a further object of the invention to provide a method for efficiently manufacturing such a wrinkled casing.

Description of the invention

Terms and definitions

In the following, including the specification and claims, unless otherwise indicated, in describing compositions or formulations, the symbol "%" denotes weight percent based on the total weight of the composition or mixture (blend).

Further, in the following, words including bracketed prefixes and/or endings are used to denote concepts also denoted by the word with or without such prefixes and/or endings. For example, the word (co) polyamide simultaneously means a polyamide (homopolymer), or copolyamide, or a blend of some polyamides and/or copolyamides.

In addition, in the description of the copolymers, the first-mentioned monomers, unless otherwise specified, are predominant in terms of their molar percentages, for example, in copolymers of ethylene and of an α -olefin, ethylene units predominate and in copolymers of propylene and ethylene, propylene units predominate.

The terms "polymer" and "polymer", as well as molecular fragments thereof (e.g., in the context of "polymeric chain" or "polymeric segment"), may be used expressly in the context in its limiting sense (as a term associated with homopolymers) and in its broader sense (as a term associated with high molecular weight species in general).

Brief description of the invention

After intensive research, the inventors have surprisingly found that the object of the invention can be achieved by a wrinkled casing for food products, in the form of a rigid self-supporting stick and in the form of a molten (co-) extruded tubular moisture barrier casing, having a layer in contact with said food product, which layer has a reduced adhesion to such food product, wherein the outer surface of the wrinkled tubular casing has at least 10g/m²At least one water-soluble or water-dispersible binding (co) polymer providing adhesive joints between the pleats of the pleated rod, wherein

-the wrinkled casing outer surface also has an adhesion strength reducing hydrophobic component being at least one liquid organic and/or organo-element (organoelement) compound, substantially non-volatile and substantially water-insoluble at room temperature, and having a total surface concentration greater than the surface concentration of the binding polymer, and said total surface concentration being from 50 to 500mg/m²Wherein the corrugated rod is characterized by the following features:

-a longitudinal compressibility under a force of 1N of not more than 0.5% after being kept in a free state on a smooth surface for 24 hours at 20 ℃ and a relative humidity (hereinafter RH) of 75%;

-when the corrugated bar is supported as a cantilever, there is no macroscopic elastic bending deformation under its own weight; and

-irreversible rupture of the corrugated bars at a bending moment of 60 to 400N · mm; and

the crumpling bar is capable of being de-crumpled at a temperature of 20 ℃ and RH 60% at a speed of not less than 1.5m/sec without the casing wall breaking.

Typically, the average wall thickness of the casing is 15 to 45 μm. The thickness range of the casing wall is based on the fact that: if the thickness is less than 15 μm, the mechanical property of the casing is too weak; if the thickness is higher than 45 μm, it may only be transformed into a folded bar that is too long, and furthermore, the process of making a connected section of frankfurter using such casing is hindered due to the poor stability of the twisted areas between the individual sausages.

In general, the casings are characterized by a water vapor transmission rate (water vapor diffusion flow density) of not more than 40, preferably less than 20, and most preferably less than 10g/m, measured according to DIN 53122 at 23 ℃ and RH 85%²The day is.

The adhesion strength of the pleats of the pleat bar can be estimated by the pleat bar bending strength and if the value of the bending moment is less than 60N · mm, this usually means that the pleat bar will be difficult to transport and will break in the hopper of the filling machine, and if the value of the bending moment is greater than 400N · mm, this usually means that the adhesion joints between the pleats of the pleat bar are too strong, or "jamming" between the pleats of the casing can occur; in any case, the crumple bar cannot be de-crumpled in the event of a rupture, at least in automated filling processes with high productivity.

If left unconstrained on a smooth plane at 20 ℃ and RH 75% for about one day, the crumpled bar is characterized by a longitudinal compressibility under a force of 1N of greater than 0.5%, which generally means that under the above-mentioned environmental conditions (roughly those corresponding to the heating chamber), the crumpled bar tends to spontaneously crumple and is therefore not stable enough under storage conditions.

Due to the high surface concentration of components, reduced adhesive strength (hereinafter CDAS), which are liquid, substantially non-volatile at room temperature and substantially water-insoluble, the adhesive joints between the folds of the wrinkled casing according to the invention appear to be of discrete character and the adhesive polymer may be distributed between different locations on the outer surface of the tubular casing. This distribution allows achieving the desired balance of mechanical strength of the crumpled bar that it needs for use in a high-productivity automated filling process.

Another object of the invention relates to a process for the manufacture of moisture-resistant casings which are creased in the form of rigid self-supporting creased bars, this object being achieved by a process comprising a production stage of a tubular casing based on a substantially synthetic resin which, among other features, provides a casing with low permeability to water vapour and the inner layer of the tube has reduced adhesion to the food contents, which process comprises (co) extruding the tubular casing, optionally followed by oriented stretching and possibly heat-setting, which is subsequently converted into creased rigid self-supporting bars, wherein the conversion process comprises the following operations:

(i) applying an aqueous system comprising a binding polymer and CDAS onto the outer surface of the moisture barrier casing such that the total surface concentration of CDAS is higher than the surface concentration of the binding polymer and is from 50 to 500mg/m²；

(ii) After the folding process, directly fixing the shape of the folding rod by a shape fixing tool;

(iii) forcibly drying the corrugated rod in a fixed state for 0.5 to 20 minutes, wherein the preferred surface temperature of the corrugated rod reaches 45 to 75 c,

(iv) cooling it to room temperature, and;

(v) the shape-fixing tool is removed and a rigid self-supporting corrugated rod is obtained.

Typically, the volume of aqueous system applied to the surface of the tubular casing (i.e., water and binding components dissolved or dispersed therein) is greater than the CDAS. However, the binding polymer concentration in the aqueous system is selected such that its surface concentration is less than the surface concentration of the CDAS. In practice, the aqueous system and CDAS may be applied to the surface of the casing as an oil-in-water or water-in-oil emulsion, or the two separate liquids may be sprayed by two separate sprayers.

Detailed description of the invention

Tubular moisture barrier casings (co) extruded from substantially synthetic resins are suitable for producing the wrinkled casing according to the invention, as is known in the art. Typically they may comprise from 1 to 9 (co) extruded layers. Such casings may be non-oriented, uniaxially oriented, but preferably they are biaxially oriented and heat set.

Typically, tubular moisture barrier casings suitable for pleating have at least one moisture barrier layer comprising at least one resin having moisture barrier properties, such as a vinylidene chloride (co) polymer, a non-functionalized olefin (co) polymer, or in other words a (co) polyolefin; and also (co) polyolefins functionalized by groups, generally chosen from anhydride, acid or epoxy groups. The non-functionalized (co) polyolefin may comprise a propylene homopolymer, a (co) polymer of propylene and at least one alpha-olefin having from 2 to 12 carbon atoms, an ethylene homopolymer, a copolymer of ethylene and at least one alpha-olefin having from 3 to 12 carbon atoms, a copolymer of ethylene and at least one ethylenically unsaturated monomer selected from vinyl esters and alkyl (meth) acrylates. The functionalized (co) polyolefin may comprise a copolymer comprising units of ethylene and at least one ethylenically unsaturated monomer, such as an ethylenically unsaturated carboxylic acid, a salt of an ethylenically unsaturated carboxylic acid, a cyclic anhydride of an ethylenically unsaturated carboxylic acid, a glycidyl ester of an ethylenically unsaturated carboxylic acid, and optionally, one or more ethylenically unsaturated monomers selected from vinyl esters and alkyl (meth) acrylates. Further, the functionalized (co) polyolefin may include any of the above-described non-functionalized (co) polyolefins grafted with at least one ethylenically unsaturated monomer, such as ethylenically unsaturated carboxylic acids, glycidyl esters of ethylenically unsaturated carboxylic acids, and cyclic anhydrides of ethylenically unsaturated dicarboxylic acids.

As can be seen from the prior art, a (co) extruded layer of any of the above materials having a thickness of at least about 2 μm can generally provide no more than 40g/m²Water vapor transmission rate per day.

Conditions that reduce adhesion to food (e.g., sausage meat) also impose certain limitations on the composition of the casing layer that can be in contact with the food.

It is well known from the prior art that polar substances such as proteins are difficult to adhere to materials having low surface energy (hereinafter referred to as "ζ"), e.g., the above-mentioned (co) polyolefins (functionalized and non-functionalized polyolefins), as well as silicone (co) polymers and fluorine-containing (co) polymers, that is, the free energy of the surface, normalized to the surface area, and numerically equal to the surface tension coefficient. In this case, casings extruded from the (co) polymers comprising an inner layer are characterized by a zeta of their inner surface, measured according to DIN 53364, of generally not more than 35 dynes/cm.

Since the polyolefin is also a moisture barrier resin, this inner layer can be the only layer of the casing. If so, the most suitable material for extruding a single layer casing is a crystallizable copolymer of a homopolymer of propylene or a blend thereof, in terms of its stress-strain properties and heat resistance.

Further, the tubular casing having a low zeta value on its inner surface may be multilayered. In this variant of the casing, at least one or more layers, preferably extruded from a material different from the polyolefin, for example a material based on (co) polyamide, (co) polyester or vinylidene chloride (co) polymer, are not in contact with the food product, in particular the meat emulsion. Thus, the casing may comprise two, three or more layers. Preferably, the outer layer of such a multilayer tubular casing is extruded from a non-polyolefin resin, and the layer in direct contact with the former comprises the above-mentioned functionalized (co) polyolefin. For example, the casing may comprise an inner layer of tubular structure made of a blend of functionalized (co) polyolefin and non-functionalized (co) polyolefin, and an outer layer, directly in contact with the former and mainly of a polyamide-based material. Alternatively, instead of a layer based on a single composition of polyolefin, the casing may comprise two adjacent layers, one of which comprises a functionalized polyolefin and which is adjacent to the polyamide layer, the second of which comprises a non-functionalized polyolefin and which is the inner layer of the tubular structure.

The polyamide-based layer typically comprises predominantly aliphatic (co) polyamides. Such (co) polyamides comprise in their macromolecules units of at least one such monomer (i): gamma-aminobutyric acid, delta-aminopentanoic acid, epsilon-aminocaproic acid, iota-aminoundecanoic acid, kappa-aminolauric acid, tetramethylenediamine, hexamethylenediamine, dodecanediamine, adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid; and optionally, not more than 15 wt.% of at least one monomer selected from group (ii): isophthalic acid, terephthalic acid, m-xylene diamine, and p-xylene diamine. The aliphatic (co) polyamides which are substantially most preferably used are products such as PA6, PA 66, PA 6/66. Furthermore, the (co) polyamide constituting the enteric coating may comprise a partially aromatic (co) polyamide prepared by polycondensation of at least one aliphatic diamine and at least one aromatic dicarboxylic acid, or vice versa, at least one aromatic diamine and at least one aromatic dicarboxylic acid, such as PA6I/6T or PAMXD 6.

Any of the polyamide-based layers mentioned hereinafter, irrespective of the enteric layered structure and layer arrangement (outer, inner or core layer with respect to the tubular structure), may comprise the same (co) polyamide.

The above-mentioned outer polyamide-based layer, other than the (co) polyamide, may also comprise up to 40% of at least one (co) polymer chosen from semi-aromatic (co) polyesters and olefinic (co) polymers.

In particular, the casing to be wrinkled may comprise two layers, wherein the outer or outer layer of the tubular structure mainly comprises a polyamide and the inner layer of the tubular structure comprises a functionalized (co) polyolefin optionally blended with a non-functionalized (co) polyolefin. Another variant of its layered structure may imply the following arrangement: wherein the outer layer predominantly comprises polyamide and the core layer comprises a functionalized (co) polyolefin, optionally blended with a non-functionalized (co) polyolefin; the inner layer comprises predominantly at least one thermoplastic (co) polymer, for example a non-functionalized olefin (co) polymer; olefin (co) polymers (functionalized with, for example, anhydride groups, acid groups or epoxy groups); and silicone (co) polymers or fluorine-containing (co) polymers.

Furthermore, we have found that an inner layer with reduced adhesion to its food contents can be extruded from a resin, characterized by a sufficiently high zeta value, measured according to DIN 53364, for example above 35 dynes/cm, i.e. the resin can be identified as a hydrophilic resin. Surfaces with such high zeta values have previously generally been considered to have enhanced adsorption of polar materials. Typically, such resins are polymer blends based on (co) polyamides. As at least one blend component other than (co) polyamide, the total content thereof is generally from 2 to 45% and may be selected from non-functionalized (co) polyolefins, semi-aromatic (co) polyesters and water-soluble polymers, such as polyvinyl alcohol (hereinafter PVA). Typically, the olefin (co) polymer and/or semi-aromatic (co) polyester content in these blends is from 2 to 25% and the water-soluble (co) polymer content is from 25 to 45%.

Suitable polyvinyl alcohols preferably have a saponification degree of not more than 88 mol%, the semi-aromatic (co) polyester being selected from the group consisting of poly (ethylene terephthalate), poly (1, 4-butylene terephthalate) and poly (1, 3-propylene terephthalate).

It is clear that such casings with an inner surface of ζ >35 dynes/cm must be multilayered and should furthermore have at least one moisture barrier which is not an inner layer of the tubular structure. This layer or layers essentially comprise the above-mentioned non-functionalized and/or functionalized (co) polyolefins, or PVdC (co) polymers, and one of these layers may be the outer layer of the tubular structure. For example, the casing may comprise two layers, wherein the outer layer of the tubular structure comprises predominantly a functionalized (co) polyolefin, optionally blended with a non-functionalized (co) polyolefin. As a variant, it may comprise three layers, wherein the outer layer of the tubular structure comprises mainly a non-functionalized (co) polyolefin and the core layer comprises a functionalized (co) polyolefin, optionally blended with a non-functionalized (co) polyolefin.

However, it is most preferred if the casing essentially has an inner layer based on polyamide (ζ >35 dynes/cm), the at least one moisture barrier layer located between the inner and outer layers also mainly comprising polyamide. In this case, the outer polyamide-based layer may additionally comprise a polyester, such as poly (ethylene terephthalate) (PET) or poly (butylene terephthalate) (PBT) and a (co) polyolefin, typically in a concentration of not more than 40%. In particular, the casing may comprise three layers, wherein the outer layer of the tubular structure is selected from the outer polyamide-based layers described above, and the core layer comprises a functionalized (co) polyolefin, optionally blended with a non-functionalized (co) polyolefin.

Any layer of the casing may further comprise up to 10% of at least one component selected from the group consisting of pigments, colorants, finely or coarsely dispersed fillers, plasticizers, lubricants, stretching aids, foaming agents, and any mixtures thereof.

According to the invention, any of the above-described tubular casings can be converted into a corrugated stick.

In a preferred embodiment of the invention, the binding (co) polymers that bind the pleats of the pleat bars together are selected such that they have a weight average molecular weight of no less than about 15 kDa. In general, the molecular weight of the polymer required to provide the desired strength of the adhered joint depends on the chemical nature of the polymer. For example, polymers of N-vinylpyrrolidone, preferably having a weight average molecular weight of at least 15kDa, are suitable as binders. On the other hand, polymers of ethylene oxide (ethylene glycol) achieve adhesive and cohesive properties while having a molecular weight greater than about 40kDa, preferably greater than 100 kDa.

The binding polymer material may comprise (alone or in any combination) water soluble polymers including PVA, polyvinylpyrrolidone (hereinafter PVP), polyacrylamide, solid polymers of ethylene oxide (polyethylene oxide or PEO) having an average molecular weight above 40kDa, cellulose ethers, starch, modified starch, natural gums, carrageenan, alginate, agar.

The molecular weight of suitable polyethylene oxides is particularly specified, since it is well known that such polymers having a molecular weight below about 40kDa are moderately viscous liquids (molecular weight range 0.2-0.6kDa), or brittle waxy substances (molecular weight range 0.7-40kDa) at room temperature; and in the intermediate molecular weight range they have the consistency of thickening lubricants and therefore they cannot be used as binders when used alone. Such ethylene oxide polymers (e.g., PEG grade, available from Clariant AG) may be used, however, as plasticizers for the binding polymers listed above, including high molecular weight PEO (e.g.,

mw of about 600-4000kDa, available from Dow Chemical Co.).

In addition, the polymer providing pleat bonding to the pleat bars may comprise a water dispersible polymer, such as polyvinyl acetate, butadiene rubber, butadiene-styrene rubber, and any mixtures thereof.

The above CDAS is preferably selected from non-volatile and water-insoluble liquids, such as paraffin oil, silicone oil, liquid vegetable oil, liquid substantially non-volatile fatty acids, or any mixture thereof.

In addition toIn addition to the binding polymer and CDAS, the outer surface of the wrinkled tubular casing may have water soluble components (hereinafter WSCDAS) which reduce the adhesive strength, water soluble plasticizers including water soluble or water dispersible polymers, such as glycerol, 1, 3-propanediol, liquid polyethylene glycols (molecular weight range of about 0.2 to 15kDa), triethanolamine, monoethanolamine, mono-, di-or triacetin, and additional water soluble salts such as alkali or alkaline earth metal or ammonium chlorides, phosphates, sulfates or acetates, and mixtures thereof, and at a total surface concentration of 2 to 200mg/m². The plasticizers for soluble or dispersible polymers can soften the adhesive joints and soluble salts reduce the activity of water in the applied solution or dispersion, thereby preventing "blocking" of the wrinkles in the wrinkled casing.

The surface of the wrinkled moisture-proof tubular casing may also be provided with functional additives, such as antimicrobial agents, which prevent damage of the applied solution and the adhesive joints by microorganisms.

The preferred length ratio (degree of compression) of the initial tubular casing and the resulting corrugated stick is at least 100.

Tubular moisture barrier casing precursors based on substantially synthetic resins can be prepared by extrusion blow molding or triple bubble processes comprising stages of (co) extrusion molding, uniaxial or biaxial orientation stretching and heat setting. In both cases, the tubular casing should be cooled, folded and wound into a roll at the end of the production process. Thus, the casing precursor is in the form of a roll.

If the production process of the tubular casing comprises an oriented stretching stage, the following heat setting is preferably carried out in such a way: an oriented casing is prepared characterized by minimal horizontal shrinkage due to moisture measured at room temperature and at elevated temperature. This shrinkage behaviour enables drying of the corrugated bars at high temperatures without the risk of deformation of their geometry, which in turn allows a reduction of the production cycle time.

The web casing prior to creasing may be provided with a printed image by some rotogravure printing method (e.g., by flexography). Furthermore, if the casing has a single or external coextruded resin layer with a low zeta value, for example polypropylene, corona discharge treatment may be used beforehand to strengthen the adhesive joint between the folds of the corrugated rod.

Typically, the CDAS and binding polymer solution or dispersion (e.g., latex) with or without WSCDAS may be applied to the outer surface of the casing in the form of a pre-prepared oil-in-water or water-in-oil emulsion, followed by a creping process.

However, in a preferred embodiment of the process according to the invention, both liquids are applied directly in the corrugating machine by spraying. In this case, components such as WSCDAS and functional additives may be added to these solutions or dispersions in advance.

The creasing process itself (creasing of tubular casings) is well known in the art. Among industrially used crimping methods, the so-called "thread method" is most preferable. This technique and the corresponding machine allow the folding of the folded rods to be overlapped and packed in the most compact way.

The corrugated rod is then fixed in the tool, forcing its geometry. Such means may be selected from:

-a tubular plastic or cotton web provided with clips, the diameter of which is approximately equal to the outer diameter of the corrugated rod, or;

the combination of such a mesh and smooth rod, with a diameter smaller than the inside diameter of the corrugated rod (rod opening diameter);

-a rigid wire cylinder, the internal geometry of which corresponds to the desired shape of the corrugated rod and is equipped with fixable top and bottom parts, or;

a threaded rod equipped with a welded disc-shaped stop at the end opposite the thread, wherein the stop limits the corrugated rod; a washer freely movable along the rod as another moving disc-shaped stopper; and a nut that is screwed on the thread and presses the moving washer against the corrugated bar.

The casing is converted into a tool-mounted corrugated rod and further dried by one of the known methods, including convection drying, hot air flow drying, vacuum drying, radiant heat (IR) drying and induction drying. Regardless of the method used, the maximum temperature of the surface during drying of the corrugated rod is generally no more than 75 ℃.

The drying process of the fixed corrugated rod usually takes 0.5 to 20 minutes, depending on the method of application.

The drying step is very important for the desired relaxation and mechanical properties of the corrugated rod. In particular, due to this step, rigidity determined by the shape and size of the internal space of the shape fixing tool and a dimensionally stable shape are imparted to the corrugated rod. This relates in particular to its constant length, which practically coincides with the distance between the limiters of the shape-fixing means (the clips on the net, the top and bottom parts of the cylinder, the stop of the rod means).

After drying, the corrugated rod may be cooled, non-actively, substantially in still air; or cooled in a forced manner, for example in an air stream. The cooled corrugated rod is pulled out of the shape-fixing tool and packed for subsequent transport.

The following examples, which disclose the most preferred embodiments of the invention, are intended to illustrate the invention only and not to limit the scope of the invention as defined by the claims.

Examples

Test method

Determination of the type of inner surface of a tubular casing (hydrophobic or hydrophilic type)

The tubular casing inner surface type is nominally determined in terms of a surface energy (ζ) value, so surfaces having ζ ≦ 35mN/m (mN/m ═ dyne/cm) are considered to be nominally hydrophobic, and surfaces having ζ >35mN/m are nominally hydrophilic.

A length of approximately 200mm of de-wrinkled casing is carefully rolled out or cut longitudinally. If the interior of the casing is in contact with the lubricant during extrusion or/and pleating, the inner surface to be tested is degreased by a filler wetted with hexane or ethanol, depending on whether the lubricant is a hydrocarbon or a siloxane. The casing was then dried at room temperature for at least 3 hours. The surface type was determined along its entire width by applying a liquid composition comprising 35 vol% formamide and 65 vol% 2-ethoxyethanol (ethyl cellosolve) on a test surface of a flat and smooth sample and observing the liquid behavior. If no liquid spreading occurs during 3 seconds (liquid stays at the initial boundary or breaks down into individual droplets, ζ ≦ 35mN/m according to DIN 53364, the surface is considered to be nominally hydrophobic; ζ >35mN/m if liquid spreading occurs, the surface is considered to be nominally hydrophilic.

Measurement of the surface concentration of CDAS on the outside of tubular casings

The equipment and chemicals used in the measurements were: a scale with 1mm pitch on a scale, an analytical balance with an accuracy of 0.01mg, a 500ml round bottom flask, a rotary evaporator, a drying oven and a solvent (hexane or ethanol). A pre-measured section comprising approximately 2m of de-wrinkled casing was cut from a wrinkled rod of known compressibility and then carefully turned out. One end of the section is knotted; a certain distance of about 1.5-1.7m from the knot was measured, marked with ink and recorded. Thereafter, about 200ml of solvent (hexane for extracting paraffin oil, liquid vegetable oil, substantially nonvolatile liquid fatty acid and ethanol for extracting silicone oil, and liquid polyethylene glycol) was put into the tubular casing, and the other end of the segment was knotted at the ink mark. The filled tubular casing (air bubbles) is then shaken and repeatedly turned over within 2-3 minutes, and its inner surface is washed with a solvent. After which a knot is cut and the bubble contents are replaced into a pre-weighed round bottom flask with an accuracy of 0.1 mg. The flask with contents was placed in a rotary evaporator to remove the major portion of the solvent. The flask was then transferred to a drying oven, heated to a temperature of 105 ℃, where it was dried to constant weight, cooled in a drying atmosphere of a desiccator, and weighed again with an accuracy of 0.1 mg. Surface concentration of CDAS on the outer surface of the casing (C)_CDAS) In mg/m²Expressed, the calculation is as follows:

C_CDAS＝M/HL＝(M₂–M₁)/HL，

where M is the weight of CDAS, equal to M₂–M₁Wherein M is₂And M₁Is the weight of the flask, with the contents and the empty flask expressed in mg, respectively. H is the width of the flat tube in meters and L-measures the length of the tube in meters.

Measurement of surface concentration of water-soluble polymers outside tubular casings

The equipment and chemicals used in the measurements were:

a scale with a scale pitch of 1mm, an analytical balance with an accuracy of 0.01mg, a laboratory scale grade Vivacell 250 ultrafiltration device (available from Sartorius AG, Germany) equipped with a 15kDa molecular weight cut-off membrane, a 500ml round-bottom flask, a rotary evaporator, a drying oven, double distilled water.

Tubular casings were treated with solvent in the same manner as the previous test method, except that double distilled water was used as the solvent. The tube washed to no CDAS resulting from the above test can also be used as a casing section of smaller length. After treating the stage with solvent, the contents of the stage were replaced into a 250ml cell of an ultrafiltration apparatus. After the first filtration, with a 5-fold decrease in solution volume, double distilled water was added to the cell until approximately the initial volume was reached. The filtration-dilution cycle was repeated 10 times, while the ultrafiltrate was collected in a separate vessel. The solution washed free of low molecular weight polymer was then replaced in a pre-weighed round bottom flask. Washing the pool with 3 to 80ml of double distilled water; the rinse water was poured into the same flask. The flask contents were concentrated by evaporation and dried as in the previous experiment except that the drying temperature was maintained at a level of 120 ℃. Then, the flask with the contents was cooled in a dry atmosphere of a desiccator and weighed again to an accuracy of 0.1 mg. The weight of the water-soluble polymer can be obtained from the measurement value by subtracting the weight of the empty flask.

The water-soluble polymer surface concentration can be calculated using the same previous test formula by subtracting the corresponding weight and length values.

The above test method is independent of its chemical properties>General procedure for 15kDa molecular weight water soluble polymer. Meanwhile, the bubble content (bubble content) can be tested by any other analysis procedure designed for previously known polymers. For example, certain polymers may be selectively extracted by a suitable non-aqueous solvent (e.g., PVP may be selectively dissolved by chloroform or acetone), and thenConcentrated gravimetric analysis was performed by evaporating and drying the extract. Photometric analysis of the coloured complex of this or some other polymer is also suitable, for example PVP-Congo Red (patent SU No. 1599727 published 10, 15.1990) and PVA-I can be used₂And (c) a complex. In the last case, no ultrafiltration procedure is required.

Crumple bar compressibility test

The equipment used in the test was:

a vernier caliper with a scale interval of 0.1 mm; the dryer was equipped with a movable platform with a diameter exceeding the length of the pleat rod by at least 1cm, and slightly wet sodium chloride was placed in the space under the platform, keeping RH ≈ 75%; an air thermometer; a retort support with a stainless steel vertical rod having a diameter of no more than 10 mm; a polyethylene washer having an inner diameter exceeding the rod diameter by about 1mm and an outer diameter substantially corresponding to the outer diameter of the corrugated rod; a set of steel washers of the same diameter and a total mass of about 102g (weight of about 1N).

The corrugated rod was placed on a platform and cured in the atmosphere at room temperature on wet salt in a desiccator with a lid for 24 hours. Then, it is pulled out and the distance between its two ends is measured by a vernier caliper (short sections of non-wrinkled casing are omitted). The rod is then inserted into the cavity of the corrugated rod with its convex end facing upwards, and the rod is then dropped until its concave end makes firm contact with the holder base. A polyethylene gasket and a steel gasket having a total weight of about 102g were successively dropped on the upright bar. The resulting assembly was left motionless for about 10 minutes, after which the distance between the ends of the corrugated rods compressed by a gravity force of 1N was measured with the same vernier caliper.

Compressibility (x) is taken as

Wherein L is₁Is the free pleat rod length, L₂Is the compressed corrugated rod length.

Flexural Strength test of corrugated bars

The equipment used in the test was:

a set of analytical balance weights; a pre-weighed lightweight basket for weighing, with threads attached with knots on its handle; a set of smooth cylindrical metal rods with a through hole at one of their ends, as attachment points for threads and cuts or ink marks 50-100mm from the other end; the scale is divided into 1mm intervals; a distiller's stand with a ring binder.

A smooth cylindrical rod for testing is selected from the group so that its diameter is 1-5mm smaller than the inside diameter of the corrugated rod and the distance of the cut or ink mark from the end with the hole is approximately equal to half the length of the corrugated rod being tested. The exact value of this distance is measured and recorded. A rod is attached at the other end of the screw and the basket is used for weighing. The free end of the rod selected passes through the opening of the corrugated rod for testing, starting from its concave end until said end coincides with the cut or ink mark, so that the thread also partially passes through the opening. The rod is then secured to the holder by means of a ring clamp, the edge of which is adjacent to the cut/mark and the concave end of the rod. Thereafter, the weight was carefully and gently placed in the basket in 10 gram steps until the crimped rod broke, and the total mass of the weight in the basket was recorded.

Breaking bending moment (M) in Newton millimeter (N.mm)_{Fracture of}) Calculated from the following formula:

M_{fracture of}＝0.0098·(L_Stick–L_Marking)·M，

Wherein L is_StickIs the length of the corrugated bar, L_MarkingIs the distance from the end of the rod with the hole to the cut or mark (in millimeters), M is the total mass of the weight at break of the basket in grams, and 0.0098 is the conversion factor (in units of force) from grams force to newtons.

Evaluation of the ability of a crumple bar to crumple without rupture at a given rate of crumpling

The test device used was located in a chamber, in which a constant temperature of about 20 ℃ and an RH of about 60% were maintained; the device is a semi-industrial aggregate, comprising:

an industrial electric winder for casings equipped with a linear speed regulator, and

firmly fixed to a suitable support and a horizontally oriented metal hollow cylindrical support, the internal diameter of which is greater than about 1mm of the external diameter of the corrugated bar, one rear base of the cylinder being fully open and the other base (facing the winding roller) having a concentric opening, the diameter of which is greater than the internal diameter of the corrugated bar and less than its external diameter. The bracket device exceeds the bracket rolling line. The distance between the nearest base of the cylindrical support and the winder reel is about 400 mm. This support has almost the same structural features as the crumple bar support of a machine set for the automatic filling of frankfurters,

a long length of plastic bath, consisting of a small slope, so that its highest part is located under the cold tap. The length of the bath is slightly greater than the maximum length of the de-wrinkled casing removed from the bar.

All of the corrugated bars to be tested were kept in room air for about one day at all times.

The sausage casing sections of about 0.5m length were manually de-wrinkled. The free end of which passes through the opening of the support and is fixed to a winder while the corrugated rod itself is placed in the support. For each bar, one of the following linear velocity values is preset: 0.5, 1, 1.5, 2 and 2.5m/sec (or respectively, 30, 60, 90, 120 and 150 m/min). Winding then begins and continues until the rod is completely de-crimped. If the process is not accompanied by visible rupture of the tubular casing, the roll with the wound casing is removed from the apparatus and moved into a bath. The free end of which is placed on the junction of the funnel fixed below the faucet and held in place by a ring clamp. The casing was then wrapped completely around the bath and its second end was twisted and squeezed with an aluminum wire clamp. The casing is then filled with water by a laminar flow without air bubbles. When the casing is filled (including its vertical part), the water supply is stopped and the casing integrity is checked for a first time for damage, i.e. the point of leakage seen by the naked eye. If no leakage is found, the casing is disconnected from the funnel and connected to the tap joint by means of a ring clamp in such a way as to avoid air bubbles being present in the water-filled tube. Water is then added at low pressure to start the inflation of the casing. When its diameter increases by 10% from the initial diameter (typical stretching of synthetic casings filled with sausage meat in general), the water supply is stopped. After this, a repeated inspection of the blown casing was performed to find leaks.

Starting from the maximum rolling speed (linear speed of 2.5m/sec) and completing the test.

The inspection results lay the foundation for concluding that the crumpled bar can or cannot be crumpled without rupture at a given de-crumpling rate. If the casing fails the test, all the process is repeated at a lower winding line speed. If the cause of the rupture is suspect, a controlled leak test with an initial (non-wrinkled) tubular casing is performed.

Performance testing of wrinkled casings by industrial equipment of the sausage factory

Fill test

For the crimped rods prepared according to the embodiments of the examples of the invention, as well as for the acceptably stable crimped rods prepared according to the comparative examples, they were vacuum-packed and sealed in commercially available gas-and moisture-proof bags immediately after cooling to room temperature, and then transported to a sausage manufacturing plant. The bags were opened in the factory and the crumpled sticks were fed into the hopper of a filling machine of the Handtmann VF 616 grade (Albert Handtmann Holding GmbH & co. kg, Germany) with the highest production rate of 3600kg meat emulsion per hour, equipped with chains representing the chain sausage Handtmann PLH 216. The filling of the casings with the meat emulsion of frankfurters continuously increases the machine productivity from low values (1000kg/h) to medium levels (2000kg/h) to high values (3500 kg/h). According to the test results, the filling behaviour of the wrinkled stick (mechanical stability/instability of the wrinkled stick and preservation of the casing integrity) was recorded.

Peel test

Frankfurters filled into test casings were subjected to standard cooking procedures and then cooled with a cold water shower; thereafter, the casing was removed from the sausage by an automatic high speed machine (peeler) Townsend SP 2600. By reference to the test results, the peeling behaviour of frankfurters (retention of sausage surface integrity, availability of maximum peeling rate) was recorded.

Materials mentioned in the examples and tables and their abbreviations:

random propylene-based copolymer, grade Moplen RP210G (vicat softening point about 135 ℃), available from Lyondell-Basell co.

A terpolymer of propylene, ethylene and butene, grade Adsyl 7BC 39F, available from Lyondell Basell Industries n.v. -TP.

High pressure (low density, branched) polyethylene, grade PVD15803, available from PJSC KazanOrgSintz-PE.

Maleated copolymers, grades, of propylene

50E561, available from E.I.duPont de Nemours and Co. -Ad 1.

Maleated low density polyethylene, grade

4200 available from e.i. dupont de Nemours and co. -Ad 2.

Polyamide 6, grade

B33, available from BASF SE-PA.

Copolyamide 6/66 grade

C33, available from BASF SE-CPA.

Aromatic copolyamide 6I/6T, grade

PA3426, available from e.i. dupont de Nemours and co.

Poly (butylene terephthalate), grade

B4500, available from BASF SE-PBT.

Polyvinyl alcohol, grade BC-5, available from Chang Chun Petrochemical Co., Ltd-PVA.

Polyvinylpyrrolidone, weight average molecular weight 28000 and 34000, grade

25, from BASF SE-PVP.

Sodium carboxymethyl cellulose with a moderate degree of etherification and a viscosity number in 2% aqueous solution of 10P, grade

C10000P 2, available from Clariant AG-CMC.

Medicinal white paraffin oil

82 from ExxonMobil Fuels&Lubricants–POi。

Chemically pure oleic acid, purchased from Sigma-Aldrich co.

Chemically pure glycerol, purchased from Sigma-Aldrich co.

Abbreviations used in the tables:

o. -non-oriented casing;

a cart-like cassette;

c-convection (drying);

IR-infrared radiation (dry);

a-aging at room temperature;

'+' -is;

'-' -no.

Example 1

The wrinkled sticks were prepared using a single layer non-oriented tubular casing having an average wall thickness of about 30 μm and a diameter of about 20mm, having a zero shrinkage value after immersion in water at 85 ℃, made of PP by extrusion blow moulding technique and air cooling.

Two hours before the creasing operation, the outer surface of the casing was activated by corona treatment by means of a discharger arranged on a printing press until a surface energy of 42 dynes/cm was reached. However, no print image is applied.

The G-6PA 9 type (ZDen ě k) is adopted

Co.,Czech Republic) equipped with a corrugation screw and a single spray system. By means of a spraying system before the wrinkling itself, the outside of the casing was sprayed with an emulsion prepared by mixing and stirring 1% aqueous solution (15: 1 by volume) of PVP and POi. At an emulsion feed rate of 16ml/min, the casing was moved inside the machine at a speed of 100m/min and then transformed into corrugated bars, each comprising 25m tubular casing. The resulting wet and loose corrugated rods are moved into shape-fixing tools made in the form of boxes with the above-mentioned threaded rods, each equipped with two washers and nuts. After the nut was tightened, the length of each corrugated rod was reduced by a factor of about 1.5 and became equal to about 250 mm. Thereafter, the box with the wrinkled stick was placed in a room temperature drying oven at 60 ℃ and an air circulation rate of 8m/sec and maintained therein for 5 minutes. The surface temperature of the freshly withdrawn rod was about 58 ℃. The crumpled bars were then cooled at room temperature for 45 minutes, removed from the shape fixing tool, and after sampling tests, they were packaged, shipped to a sausage manufacturer and tested for performance, including the fill and peel tests described above. All important parameters of the production process of the wrinkled casing and their characteristics are shown in tables 1 and 2.

Comparative example 1

The tubular casing used in example 1 treated with corona discharge was processed into wet, wrinkled sticks according to example 1 and dried, except that tap water was used instead of the above emulsion. The parameters of the production process of the wrinkled casing and the characteristics thereof are shown in tables 1 and 2.

Example 2

The tubular casing to be processed into the corrugated stick is:

a double-layer biaxially oriented casing having an average wall thickness of about 20 μm, a diameter of about 20mm and a shrinkage value of 1% after immersion in water in the longitudinal and transverse directions at 85 ℃, wherein the layer has an inner layer (a) in contact with the food contents and an outer layer (B) in contact with the environment, shown below, and the layer thickness percentages in brackets, based on the total wall thickness of the casing, shown below:

a (30%): TP-40% and Ad 1-60%;

b (70%): PA-95%, APA-3% and PBT-2%; this layer is indicated in table 2 as (PA).

The casing without corona discharge pretreatment was processed into a crumpling bar by a crumpling machine equipped with a crumpling screw and two spraying systems and by these two spraying systems the outer surface of the casing was sprayed with a 1% aqueous solution of PVP and paraffin oil, respectively, supplied at a volumetric flow rate of 15 and 1ml/min, respectively, and the speed of the casing was the same as in example 1, before crumpling itself. The resulting wet and loose corrugated rods of approximately the same length as in example 1 were then placed in a shape-fixing tool comprising once a tubular plastic mesh, the ends of which were pressed by clamps until the length was approximately 234mm when each corrugated rod had been compacted by a factor of approximately 1.6, and the compacted rods were dried under the same conditions as in example 1. The parameters of the production process of the wrinkled casing and the characteristics thereof are shown in tables 1 and 2.

Comparative example 2

The tubular casing of example 2 was used. Two hours before its pleating, it was corona-discharge treated using the same printer without the application of a printed image, and then processed into a pleated rod according to example 2, except that tap water was used instead of the PVP solution described above. Fixing and drying of the corrugated rod were also performed in the same manner as in example 2. The parameters of the production process of the wrinkled casing and the characteristics thereof are shown in tables 1 and 2.

Example 3

The casing precursor of the crimped rod was provided by a three-layer biaxially oriented tubular casing having the same wall thickness, diameter and shrinkage characteristics as in example 2. The casing has layers represented by: inner layer (a) in contact with the food contents and outer layer (C) in contact with the environment, and the percentage of layer thickness in brackets shown below, based on the total wall thickness of the casing:

A(20％)：TP；

B(10％)：Ad1；

c (70%): PA-95%, APA-3% and PBT-2%; this layer is indicated in table 2 as (PA).

After pretreatment with a corona discharge, the casing is coated with a printed image using flexographic printing techniques.

It was then processed into pleated rods in the same way as in example 2, except that a mixture of paraffin oil and oleic acid (volume ratio 1:1) was used as CDAS, corresponding to a volumetric flow rate of 15ml/min and 1.5ml/min for the aqueous PVP solution and the paraffin-oleic acid mixture.

As described in example 1, the corrugated rods held in the box were tunnel dried for 5 minutes by an infrared oven with a maximum surface temperature of 68 ℃, and then they were cooled for 10 minutes by a stream of room temperature air. The following operation was performed according to example 1 of the present specification. The parameters of the production process of the wrinkled casing and the characteristics thereof are shown in tables 1 and 2.

Comparative example 3

The tubular casing used in example 3 was pre-treated with corona discharge without application of a printed image, processed into a wet corrugated stick and dried according to example 3, except that the feed of PVP solution had been deactivated. The parameters of the production process of the wrinkled casing and the characteristics thereof are shown in tables 1 and 2.

Example 4

The casing precursor of the crimped rod was provided by a three-layer biaxially oriented tubular casing having the same wall thickness, diameter and shrinkage characteristics as in example 2. The casing has layers represented by: inner layer (a) in contact with the food contents and outer layer (C) in contact with the environment, and the percentage of layer thickness in brackets shown below, based on the total wall thickness of the casing:

a (20%): CPA-65% and PE-35%;

B(10％)：Ad2；

c (70%): PA-95%, APA-3% and PBT-2%; this layer is indicated in table 2 as (PA).

The casing was processed into a wrinkled stick and further dried in the same manner as in example 2. The parameters of the production process of the wrinkled casing and the characteristics thereof are shown in tables 1 and 2.

Comparative example 4a

The tubular casing used in example 4 was converted into a corrugated rod by the apparatus used in example 2 according to patent RU No. 2131670. The pleating step itself was directly preceded by spray treatment of the tubular casing outer surface with a 4% aqueous PVP solution at a volumetric flow rate of 15ml/min, with no CDAS added, and the inner surface with an emulsion of 10.0% oleic acid in a 2.0% aqueous PVP solution. The wet crimped rod can only be compressed 1.3 times. The following operation was achieved in the same manner as in example 1 of the present specification. The parameters of the production process of the wrinkled casing and the characteristics thereof are shown in tables 1 and 2.

Comparative example 4b

The tubular casing used in example 4 was converted into a wrinkled stick in the same manner as in example 2, except that the PVP concentration in the aqueous system was increased to 4% and the volumetric flow rate of the oil was reduced to 0.5 ml/min.

Example 5

The casing precursor of the crimped rod was provided by a three-layer biaxially oriented tubular casing having the same wall thickness, diameter and shrinkage characteristics as in example 2. The casing has layers represented by: inner layer (a) in contact with the food contents and outer layer (C) in contact with the environment, and the percentage of layer thickness in brackets shown below, based on the total wall thickness of the casing:

a (20%): CPA-60%, PVA-34% and G1-6%; this layer is indicated in table 2 as (CPA + PVA).

B(10％)：Ad2；

C (70%): PA-95%, APA-3% and PBT-2%; this layer is indicated in table 2 as (PA).

The casing was wrinkled and dried in the same manner as in example 3, except that the aqueous system was a solution containing 1% CMC. The parameters of the production process of the wrinkled casing and the characteristics thereof are shown in tables 1 and 2.

Comparative example 5

A casing according to example 5 was converted to a wrinkled stick in the same manner as example 5, except that the CMC concentration in the aqueous system was increased to 5% and the CDAS volumetric flow rate was reduced to 0.5 ml/min; and unlike forced drying, the corrugated rods were kept in the shape-fixing box for 15 minutes at room temperature. The parameters of the production process of the wrinkled casing and the characteristics thereof are shown in tables 1 and 2.

TABLE 1 casing layered structure and production process parameters thereof

Where the number of columns corresponds to the following representation:

i-example number or comparative example number, the latter being denoted as number C.

II-casing layered structure (layers shown from inside to outside).

III-Corona discharge treatment.

IV-liquid used directly for pretreatment before the pleating step.

IV₁-water (H)₂O) or an aqueous polymer solution; concentration (wt.%); volumetric flow rate (ml/min).

IV₂-CDAS, component, concentration (vol.%); volumetric flow rate (ml/min).

A V-shape fixing tool.

VI-drying (setting in tool for aging).

VI₁-dry type.

VI₂-maximum surface temperature of the corrugated bar, ° c.

VI₃-time, minutes.

TABLE 2 characteristics of the crimped bars

Where the number of columns corresponds to the representation:

i-example number or comparative example number, the latter being denoted as number C.

II-type of inner surface of casing (c ζ ≦ 35 denoted NPb-nominally hydrophobic; c ζ >35 denoted NP 1-nominally hydrophilic).

III-compressibility of casing in the form of wrinkled sticks-length ratio of the initial tubular casing and the wrinkled sticks produced (in the box).

IV-componentSurface concentration of (2), mg/m²。

IV₁-a polymer.

IV₂-CDAS。

V-compressibility,%.

VI-breaking bending moment, N.mm.

VII-Stable De-wrinkling Rate, m/sec.

VIII-casing filling behavior.

^aNo buckling of the rod occurred.

^bThe crimped rod undergoes a noticeable dot-like "jamming" with a relatively low strength.

After its cooking (scalding) and cooling, all frankfurter-type sausages, the casings of which have proven to withstand the filling test, were successfully detached from the casings at the maximum operating speed of the detacher, according to the detachment test described above, without the integrity of the sausage surface being damaged. Thus, all casings tested had reduced adhesion to the food contents.

A comparison of the above-described embodiment examples and comparative examples can only lead to the following definitive conclusions:

the invention discloses a wrinkled, single-or multi-layered moisture-proof casing with reduced adhesion to foodstuffs, which casing is converted into a self-supporting, mechanically stable, rigid, wrinkled stick, which can be transported and filled with sausage meat using highly efficient automatic filling equipment, without the occurrence of technical problems, including impairment of its integrity and shape.

An essential prerequisite for achieving these features of the corrugated stick is the disclosed composition applied to the outer surface of the casing before the corrugation step itself, and the combination of the mass ratios of the components, which can provide a bonding of the corrugations of the corrugated stick with balanced adhesive strength. Another prerequisite for this is the application of the method of the invention. The components and their amounts and other options for the production process of the corrugated rods made from such precursor casings result in the resulting rods being so mechanically weak that they can hardly be considered self-supporting; or they are so strongly bonded that they cannot be de-wrinkled at a sufficiently high rate without casing cracking.

The process of the invention for preparing moisture-proof casings in the form of corrugated sticks allows the manufacture of products with a desired combination of properties and with cycle times which are significantly shorter than the processes known from the prior art.

Claims (38)

1. A wrinkled casing in the form of a rigid self-supporting stick for food, the wrinkled casing being a melt-extruded moisture-proof casing having a tubular structure, the casing having a layer in contact with and having reduced adhesion to food contents, the casing having an outer surface with at least 10g/m²Of (a) at least one water-soluble or water-dispersible binding polymer or copolymer that provides adhesive joints between pleats in the form of pleated rods, wherein:

-the outer surface of the wrinkled casing further has a hydrophobic component reducing the adhesive strength; the hydrophobic component is at least one liquid organic compound, is non-volatile at room temperature and is insoluble in water; and the total surface concentration of the organic compounds is greater than the surface concentration of the binding polymer or copolymer and the total surface concentration is from 50 to 500mg/m²And wherein the corrugated rod has the following characteristics:

-the longitudinal compressibility of the corrugated rod is not more than 0.5% under a force of 1N after 24 hours of holding in a free state on a smooth surface at 20 ℃ and RH 75%;

-as a cantilever support, the corrugated rod under its own weight is free from macroscopic elastic bending deformations; at the same time, when the bending moment reaches 60-400 N.mm, the corrugated rod is irreversibly broken; and

-at a temperature of 20 ℃ and RH 60%, the crumpling bar is capable of being de-crumpled at a speed of not less than 1.5m/sec without the casing wall breaking.

2. A wrinkled casing according to claim 1, wherein DIN 53122 is at 23 ℃ and at relative humidityA water vapor transmission value measured at 85% of not more than 40g/m²The day is.

3. A wrinkled casing according to claim 1 wherein the weight average molecular weight of the binding polymer or copolymer is not less than 15 kDa.

4. A wrinkled casing according to claim 3 wherein the water soluble adhesive polymer or copolymer is selected from the group comprising: polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyethylene oxide having an average molecular weight of more than 40kDa, cellulose ethers, starch, modified starch, natural gums, carrageenan, alginate, agar, or any mixture thereof.

5. A wrinkled casing according to claim 3 wherein the water dispersible binding polymer or copolymer is selected from the group comprising: polyvinyl acetate, butadiene rubber, butadiene-styrene rubber, or any mixture thereof.

6. A wrinkled casing according to claim 1 wherein the organic compound which is non-volatile and water insoluble at room temperature is selected from the group comprising: paraffin oil, silicone oil, liquid vegetable oil, liquid non-volatile acid, or any mixture thereof.

7. A wrinkled casing according to claim 1, wherein the wrinkled casing outer surface further has water soluble components reducing adhesive strength and comprises at least one compound selected from the group comprising: water-soluble plasticizers, water-soluble salts of water-soluble or water-dispersible binding polymers or copolymers; and the surface concentration of the water-soluble component is 2 to 200mg/m²Within the range of (1).

8. A wrinkled casing according to claim 7 wherein the water soluble plasticizer is selected from the group comprising: glycerol; 1, 3-propanediol; polyethylene glycol having a molecular weight of 0.2 to 15 kDa; triethanolamine; monoethanolamine; mono-, di-or triacetin.

9. A wrinkled casing according to claim 7 wherein the water soluble salt is selected from the group comprising: chlorides, phosphates, sulfates or acetates of alkali or alkaline earth metals or ammonium.

10. A wrinkled casing according to claim 1 wherein the wrinkled casing has 1 to 9 extruded layers.

11. A wrinkled casing according to claim 1, wherein the casing is non-oriented or is monoaxially or biaxially oriented heat set.

12. A wrinkled casing according to claim 1 wherein the casing comprises at least one moisture barrier layer predominantly comprising a polymer selected from the group comprising: vinylidene chloride polymers or copolymers; a non-functionalized olefin polymer or copolymer; a polymer or copolymer of an olefin functionalized by a group, typically selected from an anhydride group, an acid group or an epoxy group.

13. A wrinkled casing according to claim 1, wherein the surface energy value of the inner surface of the tubular casing is at most 35 dynes/cm measured according to DIN 53364.

14. A wrinkled casing according to claim 13 wherein the layer in contact with food contents generally comprises at least one thermoplastic polymer or copolymer selected from the group comprising: a non-functionalized olefin polymer or copolymer; an olefin polymer or copolymer functionalized by a group, typically selected from an anhydride group, an acid group or an epoxy group; a silicone polymer or copolymer; a fluoropolymer or copolymer; or mixtures thereof.

15. A wrinkled casing according to claim 12 or 14, wherein the non-functionalised olefin polymer or copolymer is selected from the group comprising: a propylene homopolymer; copolymers of propylene and at least one alpha-olefin having from 2 to 12 carbon atoms; an ethylene homopolymer; copolymers of ethylene and at least one alpha-olefin having from 3 to 12 carbon atoms; a polymer or copolymer of ethylene and at least one ethylenically unsaturated monomer selected from the group consisting of vinyl esters and alkyl (meth) acrylates.

16. A wrinkled casing according to claim 12 or 14 wherein the functionalised olefin polymer or copolymer is selected from the group comprising: (i) a copolymer comprising units of ethylene and at least one functionalized ethylenically unsaturated monomer selected from ethylenically unsaturated carboxylic acids, salts of ethylenically unsaturated carboxylic acids, cyclic anhydrides of ethylenically unsaturated carboxylic acids, glycidyl esters of ethylenically unsaturated carboxylic acids; and also (ii) any non-functionalized polyolefin or co-olefin grafted with at least one functionalized ethylenically unsaturated monomer selected from the group consisting of ethylenically unsaturated carboxylic acids, glycidyl esters of ethylenically unsaturated carboxylic acids, and cyclic anhydrides of ethylenically unsaturated dicarboxylic acids.

17. A wrinkled casing according to any of the claims 12-14, wherein the casing has a single layer, typically made of a crystallizable propylene polymer or copolymer.

18. A wrinkled casing according to claim 12 wherein at least one moisture barrier is not an inner layer of the tubular casing.

19. A wrinkled casing according to claim 13 wherein at least one layer of the casing is a layer not in contact with food contents and comprises predominantly at least one aliphatic polyamide or copolyamide.

20. A wrinkled casing according to claim 19 wherein the aliphatic polyamide or copolyamide comprises in its macromolecules at least one monomer unit selected from: gamma-aminobutyric acid, delta-aminopentanoic acid, epsilon-aminocaproic acid, iota-aminoundecanoic acid, kappa-aminolauric acid, tetramethylenediamine, hexamethylenediamine, dodecanediamine, adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid.

21. A wrinkled casing according to claim 20 wherein the aliphatic polyamide or copolyamide comprises in its macromolecules up to 15% of at least one monomer unit selected from: isophthalic acid, terephthalic acid, m-xylene diamine, and p-xylene diamine.

22. A wrinkled casing according to claim 19 wherein at least one layer comprises predominantly at least one aliphatic polyamide or copolyamide and also up to 40% of at least one polymer or copolymer selected from the group consisting of semi-aromatic polyesters or copolyesters and olefinic polymers or copolymers.

23. A wrinkled casing according to any of the claims 19-22 wherein the casing comprises two layers wherein the outer layer of the tubular structure comprises mainly polyamide and the inner layer of the tubular structure is a functionalized polyolefin or co-olefin mixed with a non-functionalized polyolefin or co-olefin.

24. A wrinkled casing according to any of the claims 19-22, wherein the casing comprises three layers, wherein the outer tubular casing layer comprises mainly polyamide and the core layer is a functionalized polyolefin or co-polyolefin; and the inner layer of the tubular structure comprises predominantly at least one thermoplastic polymer or copolymer selected from the group comprising: a non-functionalized olefin polymer or copolymer; olefin polymers or copolymers functionalized by groups; silicone polymers or copolymers and fluoropolymers or copolymers; the group is selected from an anhydride group, an acid group or an epoxy group.

25. A wrinkled casing according to claim 1 wherein the surface energy value of the inner surface of the tubular casing is greater than 35 dynes/cm measured according to DIN 53364.

26. A wrinkled casing according to claim 25 wherein the tubular casing inner layer comprises a blend comprising at least one thermoplastic aliphatic polyamide or copolyamide and 2 to 45% of at least one polymer or copolymer selected from polyvinyl alcohol, semi-aromatic polyesters or copolyesters and olefinic polymers or copolymers.

27. A wrinkled casing according to claim 26 wherein the aliphatic polyamide or copolyamide comprises in its macromolecules at least one monomer unit selected from: gamma-aminobutyric acid, delta-aminopentanoic acid, epsilon-aminocaproic acid, iota-aminoundecanoic acid, kappa-aminolauric acid, tetramethylenediamine, hexamethylenediamine, dodecanediamine, adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid.

28. A wrinkled casing according to claim 27 wherein the aliphatic polyamide or copolyamide further comprises not more than 15% of at least one monomer unit selected from: isophthalic acid, terephthalic acid, m-xylene diamine, and p-xylene diamine.

29. A wrinkled casing according to claim 26 wherein the polyvinyl alcohol has a degree of saponification of at most 88 mol%.

30. A wrinkled casing according to claim 26 wherein the semi-aromatic polyester or copolyester is selected from the group comprising: poly (ethylene terephthalate), poly (1, 4-butylene terephthalate), and poly (1, 3-propylene terephthalate).

31. A wrinkled casing according to any of the claims 26-30 wherein the casing comprises two layers wherein the outer layer of the tubular structure comprises predominantly a functionalised polyolefin or co-polyolefin.

32. A wrinkled casing according to any of the claims 26-30 wherein the casing comprises three layers wherein the outer layer of the tubular structure comprises predominantly a non-functionalized polyolefin or co-polyolefin; and the core layer comprises a functionalized polyolefin or co-olefin.

33. A wrinkled casing according to any of the claims 26-30, wherein the casing comprises three layers, wherein the outer layer of the tubular structure comprises predominantly at least one polyamide; and a core layer comprising a functionalized polyolefin or co-olefin.

34. A wrinkled casing according to claim 1 wherein any of the extruded layers of the tubular casing contains not more than 10% of at least one component selected from the group comprising: pigments, colorants, finely or coarsely dispersed fillers, plasticizers, lubricants, stretching aids, foaming agents, or any mixtures thereof.

35. A method of manufacturing casing comprising converting a wrinkled casing according to any of claims 1-34 into rigid self-supporting wrinkled sticks, the method comprising an extrusion stage of a synthetic resin based tubular casing; orientation stretching and heat setting stages; and a wrinkling stage after application of an aqueous system onto the outer surface of the casing, the aqueous system comprising a binding polymer or copolymer, wherein

-also applying a hydrophobic component reducing the adhesive strength on the outer surface of the casing and comprising at least one liquid organic compound which is non-volatile at room temperature and insoluble in water, such that the total surface concentration of this compound on the outside of the casing is greater than the binding polymer or copolymer and said total surface concentration is between 50 and 500mg/m²；

-the method comprises a corrugated rod shape fixing phase by means of a shape fixing tool;

-the method comprises a stage of forced drying of the corrugated bar in a shape-fixed condition for 0.5-20 minutes, wherein the surface temperature of the corrugated bar is between 45 and 75 ℃;

-the method comprises a stage of cooling the corrugated rod to room temperature and releasing the corrugated rod from the shape fixation tool, thereby obtaining the rigid self-supporting corrugated rod.

36. The method of claim 35, wherein a hydrophobic component that reduces adhesion strength is emulsified in the aqueous system.

37. The method of claim 35 wherein the hydrophobic adhesion strength reducing component is applied separately to the casing in the form of an organic compound or a mixture of such compounds that is liquid, non-volatile at room temperature and water insoluble.

38. The method of claim 35, wherein the aqueous system further comprises a water soluble component that reduces adhesion strength.