JPH03187743A - Nylon multiple layer packaging body and method and device for its manufacture - Google Patents

Abstract

PURPOSE: To exactly package a foodstuff charged in a package by forming the package from a tubular melt-molded polymeric laminate having an outer layer of moisture-containing crystallized nylon and an inner moistureproof layer and crystallizing nylon under heating to moisten the same at the same time. CONSTITUTION: A nylon layer of a package comprises nylon having water absorbability of at least about 8% and capable of being crystallized by heating, for example, like nylon 4, 6 or 66. While a tube 12 of a generation period is lightly pulled from a die, a multilayered package is co-extruded into a tubular form through a usual die. The tube of the generation period is lightly pulled on a sizing mandrel 15 between cooling means 16 by nip rollers 14. The roll of the package is heat-treated under a temp. and time condition sufficient to crystallize the amorphous nylon layer in the package in the presence of humidity. This heat treatment is performed by immersing the filled roll in a hot water bath.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates generally to tubular food packages made of laminated films, and more particularly to tightly enclosing food products extruded or stuffed into the package. The present invention relates to a package that can be used as a packaging material.

PRIOR ART AND THE PROBLEM TO BE SOLVED BY THE INVENTION Many processed foods are packed into packages during their processing, i.e., 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 means that during pressure filling the package undergoes uniform radial deformation 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 hold tightly onto the shrunken roll of food contained within the package as the packaged food product cools or tightens. It also means that the dimensional memory is sufficient to hold the package in a uniformly stretched state.

Typically, such packages are generally packaged under U.S. Patent Box 4.02
In some cases, various synthetic polymers may be used to provide the necessary composite properties for a particular application, such as low oxygen and water vapor permeability, as exemplified by No. 6.985. It consists of a fibrous web of non-woven paper, which is impregnated with or laminated with. In use, these cellulosic packages are processed prior to 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 immersed in hot water for a short period of time. There are a number of disadvantages to the use of this type of packaging, in that it requires hot water immersion and therefore it is not possible to preserve the soaked packaging in the event of a work stoppage. . In addition, water becomes a source of pollution, and
Due to the 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 by the present invention, which consists of a tubular melt-formed polymeric laminate having a strong bond to crystallized and moistened nylon and an inner moisture barrier layer. The solution is a closely conforming food packaging characterized in that the nylon is heat-crystallized from a substantially amorphous state and simultaneously moistened.

The present invention further comprises: a) melt-forming the polymeric laminate with functional groups having strong bonds to the nylon, and b) rendering the nylon substantially amorphous;
C) heat treating the tubular laminate to substantially crystallize the nylon; and d) moistening the nylon. A method of manufacturing a package for

The present invention further provides a means for melt forming a polymeric laminate with a functional group having a strong bond to the nylon, and b) rendering the nylon substantially amorphous. Cooling the base laminate a1. ．． ．． ．． ．． ．． C) means for solidifying the nylon; C) heat treating the tubular laminate; c) means for substantially crystallizing the nylon; d) means for moistening the nylon. 4. A manufacturing apparatus for a strictly conforming food package Z and body is provided. 3. The packaging body of the present invention has no risk of causing brittle 1 fracture;
Even if the package is inappropriately filled beyond its elastic limit, the packed food should have extremely uniform plastic deformation that will not spill out. On the other hand, the increased apparent elasticity should be
) E1, it δ, -Therefore, a tight, -layer uniform fit can be obtained by state.

Moreover, the package 13 of the present invention can be thoroughly moistened prior to filling, and even in a moist state it appears to be 1° dry. However, even if the package has completely dried out during storage, it can be re-soaked and therefore used again.

Thus, the package of the present invention includes a tubular laminate of non-fibrous polymer that exhibits a strong bond to the crystallized nylon, thereby maintaining a plastic failure mode. In order to maximize the elastic range and elastic limit of the package, the package should be kept in a humid environment to prevent complete drying of the strong bond to the nylon. 3. In another method that allows complete drying during storage, the nylon layer is first applied before packing the food. The package is filled with the food, and then
In order to ensure that the radial deformation of the upper is uniform along the length of the tubular wrapper, a packing load is applied that is less than the elastic limit of the wrapper.

When exposed and the outer layer of nylon dries, the multilayered wrapper surprisingly shrinks evenly, thus tightening even more elastically over the mouth of the stuffed squares inside. It will be in a stretched state. This shrinkage upon drying actually gives an apparent increase in the elasticity of the package.32 When the food filling is hot, this delayed shrinkage offsets the thermal shrinkage of the food filling as it cools; This gives a neat packaging without wrinkles.

The laminated structure of the present invention is a multilayer tubular food package having an outer nylon layer bonded onto one or more inner layers including a moisture barrier layer of "layers"-1, e.g., nylon (outer layer)/
Adhesive/barrier (inner layer) construction. Typically, nylon is present in food packaging laminates to serve as an oxygen barrier to prevent inward diffusion of oxygen and to impart relatively high strength to the laminate, while
For example, polyolefins such as polyethylene, EVA.

Saran, or nylon and their copolymers and terpolymers, have been used as inner surfaces that are relatively moisture impermeable and often chemically inert to many food products. However, the above composite arrangement is an example;
It is important to note that, depending on the basic features of the invention, the packaging of the invention can also include a number of inner layers, which can be chosen to achieve the desired composite performance as required in the application. It is. As will be discussed below, it is important that the nylon layer forms a strong bond to the package so as to be responsive to the selected heat treatment, humidification and drying conditions. In a particularly advantageous aspect of the invention, the nylon is further characterized by a selected crystalline microstructure developed by the selected processing steps. This selected microstructure, as revealed by selected stress strain curves, also discussed below, retains a plastic non-brittle failure mode with large plastic elongation in the wet state, while retaining a conventional Exhibits increased yield point, elastic elongation and hygroscopicity compared to tubular food packaging. Of general interest on the issue of selected stress strain curve development in tubular food packaging is the packaging of U.S. Pat. No. 4.303.71.1, which describes Discloses expanding the elastic region of the body to near maximum stress by selected processing steps including biaxial orientation, thereby reducing the susceptibility of the package to irreversible plastic deformation during pressure filling. ing.

The nylon layer of the package of the present invention is, for example, nylon 4.6
Advantageously, it comprises a heat-crystallizable nylon having a water absorption of at least about 8%, more preferably about 15%, such as 66 or 66. 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 the aforementioned U.S. Pat.
No. 7, No. 4,087.588 and No. 4,303,711. 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. Plexor 3
are preferred in said embodiments, comprising high density polyethylene blended with one or more homopolymers of ethylene, copolymers of ethylene and alpha olefins, or polyethylene resins consisting of any or all of these; It consists of a blend of graft copolymers of various unsaturated fused ring carboxylic acid anhydrides. More generally, adhesives suitable in the present invention have a strong affinity for nylon and are described, for example, in U.S. Pat. No. 4,233.
, 367, each chemically modified by providing the polymer with a functional group that forms a strong bond to the nylon under the heat and pressure of coextrusion.
It consists of a chemically modified polyolefin selected from the group consisting of ethylene-vinyl acetate copolymer, high density polyethylene and rubber modified high density polyethylene. An alternative, but less preferred, construction is based in part on the techniques described in U.S. Pat. ing. 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 the olefin in the adhesive and the olefin in the polyolefin layer are the same. I need that.

The present invention will be described 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 nascent tube 12 out of the die, e.g., at about 25 to 80 feet/min (
7.6-24.4 m/min) into a tube. The nascent tube is lightly (pulled) by nip rollers 14 over a sizing mandrel 15 and between cooling means 16 which provide cooling by flowing water from a conventional water ring or by water injection or spraying. .The extrusion speed is
Enough is sufficient for the nascent tube to enter the cooling zone with the outer nylon layer remaining substantially amorphous. The cooling means 16 cools the nylon layer to a temperature below its glass transition temperature while maintaining the amorphous state within the nylon when extruded.
It has sufficient capacity to rapidly cool down to Preferably, the sized mandrel 15 is cooled internally, as shown by coolant lines 17, to increase the cooling rate. As explained further below, the diameter of the mandrel 15 is determined according to the desired final use diameter of the package.
That is, it is generally selected according to the desired diameter of the food roll to be placed inside. After cooling, the advancing package is squeezed 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 in the figure). Typically,
Such heat treatment is for about 1 to 12 hours, preferably about 1 to 4 hours, depending on the degree of crystallization desired.
Continue at temperatures ranging from about 180 to 212 degrees Fahrenheit (about 82 to 100 degrees Celsius) each time. Alternatively, heat treatment may be carried out by continuously passing the advancing tube directly through a heat treatment medium prior to winding onto a take-up roll, but in this case the nylon exposed to the heat treatment is relatively rapid. Depending on the response, a short time period of about 1 minute to 1 hour is generally acceptable. Previous: If, N force method, envelope R of the present invention
Forming like an older brother of i-body 6. It is particularly suitable for Alternative method '1? a: r,, suitable for you (:l
・Nixing 1 layer of single layer 1. and 1,2T molten part (molding, crystallization 2 layers, including 1%'1)
After laminating with the desired KvI, it is formed into a tubular shape with a 6" diameter.
Knee,! Gari:'kiru.

"Crystal ke 1.1" Terms (imaginary normal A!: ・f, I
! ,! , :(Used 6.゛long-range primary' within the material
Jit's picture of the arrangement, i', and the periodicity on the basic scale.
'3: a, i;・Meaning 4゛ru1, "amorphous 1. The term j (j also has the usual meaning (use no'13, synonymous with the expression "amorphous": y81L'8no) Su1, Shrine fee 6
．．゛、c+, which means 4゛, meaning the unfaithfulness of the periodicity of atoms in a wide range
The degree of IiQ arrangement is, for example, the radial atomic definite term ζ (
The density can be determined by the usual method such as X-ray radiation method δ, according to 5, first approximation and l, -7':'.

The melting temperature Ffv of the material is within the range 1]1. A material can be characterized as substantially crystalline if it is heated to 1,7C, and if the viscosity gradually decreases without exhibiting a constant melting point or range. , the material can be characterized as substantially amorphous (1) The package may be used for the final product (711) to form a roll (9), in which case, for example, if hot Melt cheese)) Place the food in the form of a pan to the desired length 6,
It is then cut into two parts and packed under pressure into a package that has been cut into two parts (with a 'clip' closed). The packaging is general! For example, for pretreatment of folded wrappers and bodies, U.S. Patent Section A in 1.7
, No. 307゜485), a conventional food filling device 1 is used for filling from a folded state, in this case,
It seems that the flexibility of the package is important for evenly filling the package. In the present invention, the unfilled package after the 11th heat treatment step is sufficiently moistened 4.
2", thus being in a relatively flexible state ζJ3, the packages can be bundled in a flat stack, cut, clamped together and stored in a substantially saturated moist environment to prevent desiccation. Alternatively, if the package is allowed to dry completely during storage, the package is re-packed before filling to restore its flexibility.

During packing, the cheese melt is placed under pressure (7) so that the package is subjected to stresses within its elastic range, thereby resulting in uneven filling and the formation of irregular cheese-tolls. The thickness of the layer is determined by the elastic range of the Kerr elongation curve of the package. The final 411 is selected to be at least approximately the same as the range of the filler.

The filled package is then clipped, cooled and dried. Shrinkage of the food product during cooling or heat treatment tends to loosen the fit of the food product's packaging.

However, for example about 0. Due to the complete drying of the nylon layer of the package that occurs in 5 hours, the package shrinks due to the remaining elasticity and drying: 7, thereby compensating for the thermal shrinkage of the cheese roll 4. The package can be said to have an increased elasticity beyond the normally defined range of elasticity, as described above. The second key result of the present invention is the relationship between the diameter of the mandrel 15 and the final diameter of the filled package, i.e., the diameter of the filled and dried package depends on the diameter of the selected mandrel 15.
This is related to the fact that it is approximately equal to the diameter of For example, using a mandrel with a diameter of 3.243 inches (about 82.37 mrn),
A package having a composite structure of Nylon 610.5 mil (about 0.013 mm) Plexor 3/1.5 mil (about 0.038 rnrn) LDPE (inner layer) is manufactured by the method described above. Fresh, saturated package after heat treatment is 3.104 inches (approximately 78.84 ROM)
It has a diameter of 3.024 inches (approximately 76.5 inches) after drying.
It has a diameter of 81 mm). Approximately 1 in a wet package
, 60°F (about 71.1°C) cheese melt at 3°27
Pack to a diameter of 5 inches (approximately 83.19 mrn). 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 wrinkles 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 was found to be dimensionally stable over its length, e.g.
The diameter after filling has been found to be within a tolerance of 0.02 inches, thus forming a substantially uniform cheese roll.

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, it has been found that the packages of the present invention have a typical plastic elongation of about 500%, as opposed to about 20% elongation for the conventional packages discussed above. The packaging of the invention is non-porous so that the food does not dry out significantly during storage (thereby providing a significant shelf life).The moisture state of the packaging of the invention is reversible. Therefore, if the package becomes completely dry during storage, it can be re-moistened before being filled with food.

Since this process is reversible for the packaging of the present invention,
Even if the food filling process is interrupted for a considerable period of time, waste of the package can be prevented.

Finally, because of the increased apparent elasticity of the wrapper that provides a snug, second-skin fit, the food product placed therein retains its appearance even after peeling the wrapper from the food roll. Has a good semi-gloss surface.

Figure 2 shows the Kerr elongation curve in the lateral direction in the elastic region.
An example of the above-mentioned packaging body of the present invention will be shown in comparison with a conventional non-woven fibrous packaging body. 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 below 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 mentioned above, the wraps of the present invention exhibit an increased apparent elastic range that is revealed when the wet outer nylon layer of the filled wrapper dries and contracts, thereby promoting a snug and uniform fit. have. 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 inadvertently overfilled, in which case the package ruptures plastically rather than brittle. The advantageous mechanical properties of the inventive package can be further enhanced by the manner in which the outer nylon layer is crystallized. First, in the preferred method:
Unlike crystallization from the melt, nylon is crystallized by reheating from a substantially solid amorphous cooled state. 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 present invention is the crystallization of the outer nylon layer to enhance mechanical properties in the elastic range, and to increase plastic flexibility and plastic extensibility while providing additional hydration of the nylon layer to provide an apparent elasticity, without 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 packaging laminate with four layers of nylon 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 12 above, so that each nylon layer was initially in a substantially amorphous state. The comparison is-・
The thermal filling temperature for boat fishing is 160°F (approximately 712.1.
'IC). The 5DX244 type package consists of a laminate with a structure of nylon 6 (outer layer)/adhesive/PE/adhesive/PE, the thickness of the nylon layer is 2 mils (approximately 0.051.rnm) The overall thickness was 4 mils (approximately 0°102rnrn). The sample of type 5DI246 is 4 mil (approximately 0°102rnr), same as the sample mentioned above.
The construction was PE/adhesive/nylon 6/adhesive/PE, with an overall thickness of n) and a nylon layer thickness of 2 mils. The data in the table are for state A, which is the dry state of unripe processing.

Yield strength and Elongation at yield: 4"-; The yield strength is determined by stretching the sample at a constant stretching rate and recording the force measurement along with the increasing elongation value. Measurements were made using a testing machine.The sample was a strip with a width of 1 inch (approximately 25.4rn>n) and a length of 4 inches (approximately 102 mm), and a constant crosshead speed of approximately 2 inches per minute (approximately 5078 VNM). s f) x 24 with nylon outer layer.
It can be seen that the Type 4 sample 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 can be seen that after 1 hour, further substantial increases in yield strength and elongation at yield are achieved.In contrast, for hydrothermal heat treatment The 5DX246 type sample chamber, which has an inner nylon layer that is not directly exposed, has virtually no effect within 1 minute.

It is recognized that some effect W occurs after 1 hour.

Essentially 5DI with a nylon outer layer according to the invention
It is observed that the Type 244 sample has a dramatic response to heat treatment in a very short period of 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,
Similar comparisons were made at 73°F (about 23°C) with similar general results.

Table 1: Properties at 160°F YS: Lateral Yield Strength, psi and (Standard Deviation) SD
X244 YS 1670 (40) 207
0 (120) 2250 (6O) (outer layer nylon) E 21 (4) 19 (4) >25
DI246 (inner layer nylon) ys 141o (140) 1400 (22O)
1840 (30)E 23 (2) 22
(7) >25 Condition A: Unheated, Dry Condition B: Hydrothermal treated, 180°F, 1 minute Condition C: Hydrothermal treated, 180°F, 1 hour YS: Transverse yield strength, psi and ( Standard deviation t) SDX244
YS 2770 (70) 2990 (30)
3130 (24)E 14 >25
24 (1) SDX246 YS 28
00 (90) 2470 (190) 218G
(9O)E 9 24(0) 25
Although this invention has been described in terms of preferred embodiments, those skilled in the art will readily appreciate that modifications and changes can be made without departing from the principle and scope of the invention. You should understand. Therefore, such modifications and changes may be practiced within the scope of the appended claims.

[Brief explanation of drawings]

FIG. 1 is a conceptual flow diagram of a preferred method of manufacturing a package of the present invention. FIG. 2 is a stress strain diagram comparing dry and soaked packaging and conventional fibrous packaging. iφC(″

Claims (1)

[Scope of Claim] 1. Comprising a tubular melt-formed polymeric laminate having an outer layer of crystallized, moistened nylon and an inner moisture barrier layer, the nylon being heated from a substantially amorphous state. A closely conforming food packaging characterized in that it is crystallized and simultaneously moistened. 2. The package of claim 1, wherein the thickness of the outer layer of nylon is selected such that the elastic range of the Kerr elongation curve of the package is at least approximately the same as the range of end-use fill. 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 nylon crystallizable by heating and has a water absorption rate 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 package according to claim 6, wherein the nylon is nylon 6 or nylon 66. 8. The polyolefin consists of polyethylene, and the adhesive respectively imparts functional groups to the polymer that have a strong affinity for nylon and form a strong bond to nylon once 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, chemically modified by packaging. 9. The package according to claim 6, wherein the outer and inner surfaces are coated with a lubricant. 10. a) melt forming a nascent tubular polymeric laminate having an outer layer of nylon; b) so as to render the nylon substantially amorphous;
cooling and solidifying the nascent tubular laminate; c) heat treating the tubular laminate to substantially crystallize the nylon; and d) moistening the nylon. A method for manufacturing strictly compliant food packaging. 11. The method of claim 10, wherein said heat treatment and wetting treatment are performed simultaneously and before substantially natural ripening of said nylon occurs. 12. The method of claim 11, wherein the heat treatment and moistening treatment are carried out 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 nascent tubular laminate is cooled while passing over a mandrel of approximately a predetermined final use diameter. 16. The method according to claim 15, wherein the cooling is water cooling. 17. The method of claim 10, wherein said melt forming is by coextrusion. 18. The method of claim 10, wherein the heat treatment is performed at about 180°F to about 212°F to 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 the tubular laminate has an inner moisture barrier layer. . 21. The method of claim 20, wherein the tubular laminate comprises nylon (outer layer)/adhesive layer/polyolefin layer (inner layer). 22. The method of claim 21, wherein said nylon comprises nylon 6 or nylon 66. 23. The polyolefin consists of polyethylene, and the adhesive respectively imparts 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, chemically modified by 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 nascent tubular polymeric laminate having an outer layer of nylon; and b) means for melt forming the nascent tubular laminate so as to render the nylon substantially amorphous. c) means for heat treating the tubular laminate to substantially crystallize the nylon; and d) means for moistening the nylon. Manufacturing equipment for strictly conforming food packaging. 26. The apparatus of claim 25, comprising means for simultaneously heat treating the nylon and moistening the nylon. 27. At the same time as cooling the nascent tubular laminate,
26. The apparatus of claim 25, including means for rendering the laminate approximately equal in diameter to a predetermined end use diameter. 28. The apparatus of claim 25, wherein said means for melt forming comprises a coextrusion device. 29. The apparatus of claim 27, wherein said means for bringing the laminate to a diameter approximately equal to a predetermined end use diameter comprises a mandrel having approximately a predetermined end use diameter. 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. ”