JPH0443783B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD OF THE INVENTION This invention relates generally to tubular food packages made of laminated films, and more particularly to packages capable of tightly enclosing food products extruded or stuffed into the package. . PRIOR ART AND PROBLEMS TO BE SOLVED BY THE INVENTION Many processed foods are packed into packages during their processing, that is, flowed under pressure into tubular packages while the food is in a fluid state. I am made to do so. The food product may be further processed while contained in the package, or may be stored within the package until further processing or sale. For example, cheese rolls are commonly formed by pressure filling a heated cheese melt or solid curd cheese into a tubular food package. The wrapped cheese is then allowed to solidify or tighten; under ideal conditions, the package is evenly filled to form a cheese roll of uniform diameter. Ideally, these tubular packages have material properties that are said to form a "close fit." This is due to the uniform radial deformation of the package during pressure filling so that the roll of food product formed within the package has a substantially uniform diameter along its length. It means that. Furthermore, radially non-uniform deformations which could weaken the package and encourage its tearing and extrusion of the food product are prevented. Furthermore, the term "close fit" means that an ideal package would allow the shrinkage of the package to cling onto the shrunken food roll contained within the package as the packaged food product cools or tightens. It is also meant to have a dimensional memory sufficient to hold the package in a uniformly stretched state. Typically, such packaging is generally referred to as U.S. Pat.
As exemplified by No. 4026985,
Nonwoven paper fibers, in some cases impregnated or laminated with various synthetic polymers to provide the required composite properties for specific applications, such as low oxygen and water vapor permeability. Consists of the web. In use, these cellulosic packages are briefly blanched before filling to bring them from a wrinkled state to a sufficiently flexible and elastic state for uniform filling, and to wash away preservatives. Must be soaked in hot water for an hour. Because it requires hot water immersion,
The use of this type of packaging has a number of disadvantages, in that it is not possible to save the soaked packaging in the event that the operation is stopped. Furthermore,
Because water is a source of contamination and because of its relatively high moisture permeability, the shelf life of packages filled with food must be relatively short to prevent the food from drying out. The potential for these filled packages to break due to brittle fracture is also a significant problem. Means for Solving the Problems The above problems are solved in accordance with the present invention, which comprises a tubular melt-formed polymeric laminate having an outer layer of crystallized, moistened nylon and an inner moisture barrier layer, the nylon is solved by a closely conforming food packaging which is characterized in that it is heated and crystallized from a substantially amorphous state and simultaneously moistened. The invention further comprises: a) melt forming a tubular polymeric laminate having an outer layer of nylon, and b cooling the nascent tubular laminate so as to render the nylon substantially amorphous. c. heat treating the tubular laminate to substantially crystallize the nylon; and d. wetting the nylon. The invention further provides: a) means for melt forming a tubular polymeric laminate having an outer layer of nylon; and b) forming the nascent tubular laminate so as to render the nylon substantially amorphous. a means for cooling and solidifying; c) means for heat treating the tubular laminate to substantially crystallize the nylon; and d) a means for moistening the nylon. An apparatus for manufacturing a packaging body for use in a vehicle is provided. The packaging of the present invention is free from the risk of brittle fracture, and even if the packaging is improperly filled beyond its elastic limit, it will undergo extremely uniform plastic deformation without spilling of the packed food. , can provide increased apparent elasticity, thereby promoting a tighter, more uniform fit. Furthermore, the packaging of the present invention can be well moistened prior to filling and yet appears dry even when wet. However, even if the package becomes completely dry during storage, it can be soaked again and therefore used again. Thus, the package of the present invention includes a tubular laminate of non-fibrous polymer with an outer layer of crystallized and moistened nylon, thereby increasing the elasticity of the package while maintaining a plastic failure mode. Maximize range and elastic limit. In one method of use, the package is stored in a humid environment to prevent complete drying of the nylon outer layer. In another method, which allows complete drying during storage, the nylon layer is moistened to the maximum before packaging the food product. The package is stuffed with the food product, with a stuffing load approximately below its elastic limit so that the radial deformation is uniform along the length of the tubular package. When the exposed outer layer of nylon dries,
The multilayer packaging surprisingly shrinks uniformly and thus becomes more elastically taut over the roll of stuffed food contained therein. This shrinkage upon drying actually provides an apparent increase in the elasticity of the package. When the food stuffing is hot, this delayed shrinkage offsets the thermal shrinkage of the food stuffing as it cools, thereby providing a tight, wrinkle-free package. The laminate structure of the present invention comprises a multilayer tubular food package having an outer nylon layer bonded onto one or more inner layers including one or more moisture barrier layers, e.g. nylon (outer layer)/adhesive/barrier. (inner layer) structure. Typically, nylon is present in food packaging laminates to serve as an oxygen barrier to prevent oxygen from diffusing inward and to impart relatively high strength to the laminate, whereas for example polyethylene Polyolefin, EVA, etc.
Saran, or nylon and their copolymers and terpolymers, have been used as inner surfaces that are relatively moisture impermeable and chemically inert to many food products. However, it should be noted that the composite arrangement described above is an example, and that the packaging of the invention can be chosen to achieve the desired composite performance as needed in the application, depending on the basic features of the invention. Importantly, it can also include as many internal layers as possible. As will be discussed below, it is important that the nylon layer be formed as the outer layer of the package so as to be responsive to the selected heat treatment, humidification and drying conditions. In a particularly advantageous manner of the invention, the nylon is further characterized by a selected crystalline microstructure developed by the selected processing steps. This selected microstructure, also explained below, is revealed by selected stress-strain curves, while retaining a plastic non-brittle failure mode with large plastic elongation in the wet state. Exhibits increased yield point, elastic elongation and hygroscopicity compared to conventional tubular food packaging. Of general interest in the question of the development of selected stress-strain curves in tubular food packages is the package of U.S. Pat. It is disclosed that selected processing steps, including axial orientation, can increase near maximum stresses, thereby reducing the susceptibility of the package to irreversible plastic deformation during pressure filling. The nylon layer of the package of the present invention comprises at least about 8%, such as nylon 4, 6 or 66,
More preferably, it is made of nylon which can be crystallized by heating and has a water absorption of about 15%. A preferred laminate construction for the package is nylon 6 or 66/plexer/polyethylene. Adhesive Plexor™ is commercially available from Chemplex Corporation. Various varieties of Plexor are described in US Pat. No. 4,087,587, which is hereby incorporated by reference.
Nos. 4087588 and 4303711. Plexer 2 is generally of the type consisting of a blend of a graft copolymer of high density polyethylene and at least one unsaturated fused ring carboxylic acid anhydride, and a resin copolymer of ethylene and one or more ethylenically unsaturated esters. It is characterized as an adhesive. Plexer 3 is preferred in the embodiment, and
This is a high-density polyethylene blended with one or more homopolymers of ethylene, copolymers of ethylene and alpha olefin, or polyethylene resins consisting of any or all of these, and at least one unsaturated fused ring carboxylic acid anhydride. It consists of a blend of graft copolymers of More generally, adhesives suitable in the present invention have a strong affinity for nylon and exhibit strong bonding to nylon under the heat and pressure of coextrusion, as shown for example in U.S. Pat. No. 4,233,367. ethylene-vinyl acetate copolymers, high-density polyethylene, and rubber-modified high-density polyethylene, each chemically modified by donating functional groups to the polymer to form It is made of modified polyolefin. Although less preferred, an alternative construction partially adapts the technology described in US Pat. No. 4,104,404 for "Crosslinked Amide/Olefin Polymer Tubular Film Coextrusion Laminate." This patent, incorporated herein by reference, discloses amide/olefin films that have relatively high peel resistance when used in heated conditions. The adhesive used has a monomer unit that can be crosslinked by irradiation and is mainly composed of olefin units, and furthermore, the olefin in the adhesive and the olefin in the polyolefin layer are the same. need something. The present invention will be explained in detail below based on the drawings. FIG. 1 conceptually illustrates a preferred method for manufacturing the packaging of the present invention. As shown at 13, the multilayer package is passed through a conventional die 11 while gently pulling the tube 12 out of the die, e.g.
At a speed of feet/min (approx. 7.6 to 24.4 m/min),
Coextrude into a tube. The tube 12 is pulled lightly by a nip roller 14 over a sized mandrel 15 and between cooling means 16 which provide cooling by running water from a conventional water ring or by water injection or spraying. The extrusion speed is sufficient to allow the tube 12 to enter the cooling zone while keeping the outer nylon layer substantially amorphous. The cooling means 16 has sufficient capacity to rapidly cool the nylon layer below its glass transition temperature while preserving the amorphous state within the nylon as extruded. Preferably, the sized mandrel 15 is cooled internally, as shown by coolant lines 17, to increase the cooling rate. As will be explained further below, the diameter of the mandrel 15 is determined according to the desired final use diameter of the package, i.e. according to the desired diameter of the food roll placed therein.
Generally selected. After cooling, the advancing package is crushed and pulled between nip rollers 14 and then continuously fed to take-up rolls 18. The roll of wrapper is then heat treated in the presence of moisture at a temperature and time sufficient to substantially crystallize the amorphous nylon layer in the wrapper. Preferably, the heat treatment is carried out by immersing the filled roll in a hot water bath (not shown). Typically, such heat treatment is for about 1 to 12 hours, preferably about 1 to 4 hours, depending on the degree of crystallization desired.
over an hour and approximately 180~212〓 (approximately 82~100℃)
Continue at temperatures in the range of. Alternatively, the heat treatment may be carried out by continuously passing the advancing tube directly through the heat treatment medium before winding onto a take-up roll, but in this case the nylon exposed to the heat treatment Due to the rapid response, short processing times of about 1 minute to 1 hour are generally appropriate. The method described above is particularly suitable for the integral shaping of the packaging according to the invention. Alternatively, although less preferred, the nylon layer can be melt-formed as a single layer sheet, crystallized and moistened, laminated with the desired substrate, and then formed into a tube. The term "crystalline" is used in its conventional sense and refers to the presence of long-range three-dimensional atomic arrangements or periodicity on the atomic scale within a material. "Amorphous"
The term is also used in its usual sense and is synonymous with the expression "amorphous", meaning the absence of long range atomic periodicity within the material. The degree of atomic alignment can be determined by conventional methods, such as by X-ray diffraction methods for measuring the radial atomic probability density. As a first approximation, a material can be characterized as substantially crystalline if it has a constant melting temperature or range, whereas a material can be heated gradually without exhibiting a constant melting point or range. If the viscosity decreases,
The material can be characterized as substantially amorphous. The package is ultimately used to form a roll of food, in which case a pasty food product, such as a hot cheese melt, is cut into the desired length and clipped into the package. Pack under pressure. Packages are generally filled from the folded state using conventional food filling equipment, such as that shown in US Pat. No. 4,307,489 for pre-treatment of folded packages. In this case, the flexibility of the package appears to be important for uniform filling of the package. In the present invention, the unfilled package after the heat treatment step described above is sufficiently moist and thus in a relatively flexible state. Preferably, the packages are bundled, cut and secured in a flat stack and stored in a substantially saturated, humid environment to prevent desiccation. Alternatively, if the package is allowed to dry completely during storage, the package can be rewetted to restore flexibility before filling. When packing, when the cheese melt is put under pressure, the package is subjected to stresses within its elastic range, thereby causing uneven plasticity of the package with uneven filling and the formation of irregular cheese rolls. extruded into the package in such a way as to prevent physical deformation. The thickness of the nylon layer is selected such that the elastic range of the force-elongation curve of the package is at least approximately the same as the range of the end-use fill. The filled package is then clipped, cooled and dried. Shrinkage of the food product upon cooling or heat treatment tends to loosen the fit of the package on the food product. However, complete drying of the nylon layer of the package, which occurs for example in about 0.5 hours, causes the package to shrink due to residual elasticity and dryness, thereby offsetting the thermal shrinkage of the cheese roll and making it tighter. Maintains a wrinkle-free fit. Thus, the package can be said to have increased apparent elasticity beyond the normally defined elastic range. As previously mentioned, a key result of the present invention is the relationship between the diameter of the mandrel 15 and the diameter of the final filled package, i.e. the diameter of the filled and dried package depends on the selected mandrel 1.
This is related to the fact that it is approximately equal to the diameter of 5. For example, using a mandrel with a diameter of 3.243 inches,
A package having a composite structure of Nylon 6/0.5 mil Plexor 3/1.5 mil LDPE (inner layer) is manufactured by the method described above. The fresh saturated package after heat treatment has a diameter of 3.104 inches and after drying has a diameter of 3.024 inches. Approximately 160〓 (approximately 71.1℃) in a damp package
of cheese melt to a diameter of 3.275 inches. After cooling and drying, the filled package has a diameter of 3.25 inches. The diameter of the final filled package is thus very similar to the diameter of the sizing mandrel 15. Additionally, it should be noted that the package exhibits a substantial amount of drying shrinkage of about 3% relative to the elastic range of the package. Moreover, it is observed that the multilayer package performs this contraction in a unitary manner, ie, the entire package follows the outer nylon layer without wrinkling or separation between the component layers. Additionally, the packaging of the present invention has been found to have significant other advantages over conventional fibrous packaging. The need for immersion in water immediately before filling is eliminated, thereby removing water on the surface of the package. Even when the nylon is saturated, it does not appear visually wet, thereby eliminating damp conditions around the area of the filling device. The package is found to be dimensionally stable over its length,
For example, the diameter after filling is 0.02 inch (approximately 0.51 mm)
has been found to be within tolerances of , thus forming substantially uniform cheese rolls. Even if the elastic range of the package is exceeded during filling, the package will not stretch plastically and cause brittle fracture, and therefore the food will not blow out of the package and become waste. For example, the wraps of the present invention have an elongation of about 20% for the conventional wraps mentioned above.
It is recognized to have a typical plastic elongation of 500%. Since the packaging body of the present invention is non-porous, the food will not dry out significantly during storage.
This provides a considerable shelf life. The moisture content of the packaging according to the invention is reversible, so that if the packaging has completely dried out during storage, it can be re-moistened before being filled with food. Since this process is reversible for the packaging of the present invention, waste of the packaging can be prevented even if the food filling process is interrupted for a considerable period of time. lastly,
Because of the increased apparent elasticity of the wrapper that provides a tight second skin-like fit, the food product placed therein remains in an aesthetically pleasing semi-finished state even after the wrapper is removed from the food roll. It has a glossy surface. FIG. 2 shows the lateral force-elongation curves in the elastic region for the embodiment of the inventive package described above in comparison with a conventional non-woven fibrous package. Curves A and B show the elastic response of conventional packaging in dry and wet conditions, respectively. Conventional packages must be packed wet and are therefore relatively prone to bursting due to overfilling, given that curve B is significantly lower than curve A. Curve C is the elasticity curve of a typical wet package of the invention, which is found to be comparable to the extremely high strength of conventional packages in the dry state. There are several features of the invention that are worth highlighting. As noted above, the wrappers of the present invention exhibit increased apparent density that is revealed as the wet outer nylon layer of the filled wrapper dries and shrinks, thereby promoting a tight and uniform fit. It has an elastic range. Another feature is the increased yield strength and increased elastic range produced by the crystallization heat treatment as described above. These increases each extend the elastic range of the package, thereby increasing its dimensional stability during filling, i.e. reducing the susceptibility of the filled package to uneven plastic and irreversible deformation or bulging. I work to make people do what they want. This increase in elastic range, however, does not come at the expense of plastic elongation, even if the package is bent and overfilled, in which case the package ruptures plastically rather than brittlely. The advantageous mechanical properties of the packaging according to the invention can be further enhanced by the manner in which the outer nylon layer is crystallized. First, in a preferred manner, the nylon is crystallized by reheating from a substantially solid, amorphous, cooled state, as opposed to crystallizing from a melt. At least in that the properties of the nylon immediately before heat treatment are constant, it provides a highly reproducible method for manufacturing the packaging. Second, the heat treatment for crystallization is preferably carried out in the presence of moisture, which appears to influence the manner of crystallization and the desirable enhancement of high water absorption and plasticity of the nylon. More generally, a broad feature of the invention is the crystallization of the outer nylon layer to enhance mechanical properties in the elastic range, and to enhance plastic flexibility as well as plastic extensibility and additional drying properties. Including hydration of the nylon layer to provide apparent elasticity, with the overall result that the multilayer package substantially uniformly exhibits these properties of the nylon outer layer. Table 1 shows a comparison of mechanical properties between a package sample with an outer nylon layer and a sample with a nylon layer on the inside of the packaging laminate. The package samples were manufactured substantially in accordance with the preferred method described above, so that each nylon layer was initially in a substantially amorphous state. The comparison was made at a common hot filling temperature of 160㎓ (approximately 71.7°C). The SDX244 package consists of a laminate with a structure of nylon 6 (outer layer)/adhesive/PE/adhesive/PE, with the nylon layer having a thickness of 2 mils (approximately 0.051 mm) and a total thickness of the laminate. The diameter was 4 mils (approximately 0.102 mm).
The SDX246 type sample is 4 mil (approx.
0.102mm) overall thickness and 2 mils (approximately 0.051mm)
The thickness of the nylon layer is
It was PE/adhesive/nylon 6/adhesive/PE. The data in the table are for state A, which is a dry state without heat treatment, state B, which shows heat treatment for 1 minute in a hot water bath at 180〓 (about 82 °C), and 180〓 (about 82 °C), respectively.
The yield strength and elongation at yield are shown for condition C, which shows heat treatment for 1 hour in hot water at a temperature of 0.05 °C.
The term "yield strength" is used in its usual meaning,
shall indicate the stress value that causes a small irreversible deformation or permanent set in the test material. Yield strength was determined using a conventional force-elongation tensile tester of the Instron type that stretches the sample at a constant extension rate and records the force measurements with increasing elongation values. The sample is 1 inch wide (approximately 25.4 mm) and 4 inches long (approximately 102
mm), and approximately 2 inches (approximately 50.8 mm) per minute.
It was pulled at a constant crosshead speed of mm). It can be seen that the SDX244 type sample with the nylon outer layer responds quickly to heat treatment, ie within 1 minute, as evidenced by the comparison of Conditions A and B. If the heat treatment is continued further, it is observed that a further substantial increase in both yield strength and elongation at yield is achieved after 1 hour. In contrast, in samples of type SDX246, which has an inner nylon layer that is not directly exposed to hydrothermal heat treatment,
There is virtually no effect within 1 minute. It is observed that some effect occurs after 1 hour. essentially having a nylon outer layer according to the invention
It is observed that samples of type SDX244 have a dramatic response to heat treatment in a very short time. It should be noted that the standard deviations for each test condition shown in parentheses have a narrow statistical spread indicating that the behavior of the samples is relatively unchanged. In Table 2, a similar comparison was made at 73°C (approximately 23°C) with similar general results.

[Table] Iron)

Claims (1)

Claims: 1. Consisting of a tubular melt-formed polymeric laminate having an outer crystallized and moistened nylon and an inner moisture barrier layer, the nylon is heated from a substantially amorphous state to crystallized. 1. A tightly conforming food packaging, characterized in that it is moistened and moistened at the same time. 2 The thickness of the nylon outer layer is determined by the force of the package -
A package according to claim 1, wherein the elastic range of the elongation curve is selected to be at least approximately the same as the end-use fill range. 3. The package of claim 1, wherein the package exhibits uniform shrinkage when the nylon outer layer dries. 4. The package of claim 1, wherein the nylon is previously rendered substantially amorphous while imparting a predetermined end-use diameter to the tubular laminate. 5. The package of claim 1, wherein the nylon is a heat-crystallizable nylon having a water absorption of at least about 8%. 6. The package according to claim 5, wherein the tubular laminate is composed of nylon (outer layer)/adhesive layer/polyolefin layer (inner layer). 7 The nylon is nylon 6 or nylon 66
A package according to claim 6, comprising: 8. The polyolefin consists of polyethylene, and the adhesive is prepared by imparting functional groups to the polymer that have a strong affinity for nylon and form a strong bond to nylon under the heat and pressure of coextrusion. Claim 7 comprising a chemically modified polyolefin selected from the group consisting of ethylene-vinyl acetate copolymer, high density polyethylene and rubber modified high density polyethylene. packaging. 9. The package according to claim 6, wherein the outer and inner surfaces are coated with a lubricant. 10 a. melt forming a tubular polymeric laminate having an outer layer of nylon; b. cooling and solidifying the tubular laminate so as to render the nylon substantially amorphous; c. A method of manufacturing a closely conforming food packaging comprising: heat treating a laminate to substantially crystallize the nylon; and d moistening the nylon. 11. The method of claim 10, wherein the heat treatment and wetting treatment are performed simultaneously and before substantially natural ripening of the nylon occurs. 12. The method of claim 11, wherein the heat treatment and moistening treatment are performed in a hot water bath. 13. The method of claim 10, further comprising storing the tubular laminate in a moist environment until use. 14. The method of claim 10, wherein said cooling is performed simultaneously while providing said tubular laminate with a diameter approximately equal to a predetermined end-use diameter. 15. The method of claim 14, wherein the tubular laminate is cooled while passing over a mandrel of approximately a predetermined final use diameter. 16 The cooling is water cooling according to Claim 1
The method described in Section 5. 17. The method of claim 10, wherein said melt forming is by coextrusion. 18 The heat treatment is carried out at a temperature of about 180°C (about 82°C) to about
11. The method according to claim 10, wherein the method is carried out at a temperature of about 100° C. for about 1 minute to 12 hours. 19. The method of claim 15, wherein the mandrel is internally cooled. 20. The method of claim 10, wherein the nylon comprises a heat-crystallizable nylon having a water absorption of at least about 8%, and wherein the tubular laminate has an inner moisture barrier. 21 The tubular laminate is made of nylon (outer layer)/
21. The method according to claim 20, comprising an adhesive layer/polyolefin layer (inner layer). 22 The nylon is nylon 6 or nylon 6
22. The method of claim 21, comprising: 6. 23 The polyolefin consists of polyethylene, and the adhesives are each made by imparting functional groups to the polymer that have a strong affinity for nylon and form a strong bond to nylon under the heat and pressure of coextrusion. Claim 22 comprising a chemically modified polyolefin selected from the group consisting of ethylene-vinyl acetate copolymer, high density polyethylene and rubber modified high density polyethylene. the method of. 24. The method of claim 21, wherein the outer and inner surfaces are coated with a lubricant. 25 a means for melt forming a tubular polymeric laminate having an outer layer of nylon; b means for cooling and solidifying the tubular laminate so as to render the nylon substantially amorphous; An apparatus for manufacturing a tightly conforming food packaging, comprising: c) means for heat-treating the tubular laminate to substantially crystallize the nylon; and d) means for moistening the nylon. 26. The apparatus of claim 25, comprising means for simultaneously heat treating the nylon and moistening the nylon. 27. The apparatus of claim 25, comprising means for simultaneously cooling the tubular laminate and bringing the laminate to a diameter approximately equal to a predetermined end use diameter. 28. The apparatus of claim 25, wherein said means for melt forming comprises a coextrusion device. 29. The means for rendering the laminate approximately equal to the predetermined final use diameter comprises a mandrel having approximately the predetermined final use diameter.
The device according to item 7. 30. The apparatus of claim 29, wherein said cooling means comprises water cooling means. 31. The apparatus of claim 29, wherein the mandrel is internally cooled.