JP4812669B2 - Multilayer film - Google Patents

Description

  The present invention relates to a coextrusion stretched multilayer film. Specifically, the present invention relates to a coextrusion stretched multilayer film that can be used as a food packaging body or a film casing accompanied by a pressurized hot water sterilization treatment such as fish ham and sausage for retort.

  As a packaging method for processed products such as ham and sausage, dairy products such as cheese and butter, and confectionery such as yokan and jelly, there is a wide range of methods for heat-sealing films on envelopes and packaging the contents in cylinders. It's being used. Here, heat-sealing for envelope attachment means that when the contents are wrapped with a film in a cylinder slightly more than one round, the excess edge is overlapped with the other edge along the cylindrical side surface. In this case, it means that the lower surface of the upper film and the upper surface of the lower film are heat-sealed. Opening means such as an I notch, a V notch or a scar is often provided at one of the film edges of the heat-sealed portion in order to ensure the opening property. In addition, both ends corresponding to the cylindrical upper and lower bases are often sealed by ligating with metal wires or heat-sealing.

  Conventionally, a polyvinylidene chloride film has been used for such a cylindrical package, but recently there has been a tendency to demand other materials from the viewpoint of environmental load. Patent Document 1 proposes a multilayer film in which a heat-sealable polyolefin layer is disposed on both sides of a polyamide layer as a new material. However, since the strength of the film is stronger than that of the polyvinylidene chloride-based film, there is a drawback in that the openability of the package is significantly deteriorated.

  In Patent Document 2, in order to improve the unsealing property of a film having a similar composition, a multilayer film is formed as a composite film of three or more layers, and when it is formed into a cylindrical shape, between the outer layer film that becomes the outer layer and the intermediate layer film that becomes the intermediate layer There has been proposed a package body made of a composite resin film in which the peel strength is set to be smaller than the peel strength between the inner layer film and the intermediate layer film that are inside when the tube is formed into a cylindrical shape. However, although there are few specific descriptions, only examples of commercially available unstretched polypropylene and commercially available stretched nylon films as composite resin films by the dry lamination method are described, but it is difficult to set the peel strength, and retort treatment When performing, there is a problem that delamination occurs.

  In Patent Document 3, at least a polyamide resin layer (A) having a thickness of 5 to 50 μm and a polypropylene resin layer (B) having a thickness of 5 to 100 μm while maintaining transparency in a heat treatment at 120 ° C. ), And a heat shrinkable multilayer film having a heat shrinkage rate of 5 to 30% at 120 ° C. is disclosed and is introduced as being suitable for high temperature retort treatment. However, there is a problem in that the strength of the film is too strong and the opening performance is sacrificed.

  Patent Document 4 includes at least three layers of both outer layers made of the same type of polyolefin-based resin and a gas barrier intermediate layer made of polyamide-based resin, and the heat shrinkage stress at 50 ° C. is 2 MPa or less in both the vertical direction and the horizontal direction. A stretched multilayer film casing is disclosed in which a stretched multilayer film having a heat shrinkability of 5 to 20% at 0 ° C. is back-seamed with both outer layers. However, it is necessary to reduce the seal width to 0.1 to 1.5 mm in order to give easy-opening properties. According to this, the sealing strength is weakened, but the cylindrical inner film is likely to remain at the time of opening. There is a problem that it is difficult to take out things.

Further, Patent Document 5 discloses a polyolefin disposed to face the outer layer (1) through the outer layer (1) made of polyolefin resin, the intermediate layer (2) made of polyamide resin, and the intermediate layer (2). A laminated film composed of at least three layers of the other outer layer (3) made of a resin, wherein either one of the two outer layers is an easy peel layer, and the laminated film is used as an envelope sticker. A heat-shrinkable laminated film having a T peel force (T) in the range of 20 to 500 g / cm is disclosed. However, there is a problem that the sealing strength is weak and the bag is easily broken by retort processing.
JP-A-5-316933 JP 2002-219777 A JP-A-1-196338 JP 2000-37828 A JP 2001-009993 A

  In the present invention, when a package or the like for wrapping the contents is formed, there is no delamination or bag breakage from the seal portion even if retorting is performed, and the original function of protecting the contents is achieved for several months. It is an object of the present invention to provide a film in which wrinkles are not generated in the film even after a certain degree of storage, and the package or the like can be opened stably and easily.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found the present invention. That is, the present invention is as follows.
1. At least five layers of the surface layer (A), the easy release layer (B), the gas barrier layer (C), the adhesive layer (D), and the surface layer (E) are laminated in the order described above, and the following condition (1) Coextruded stretched multilayer film characterized by satisfying (5).
(1) The surface layer (A) is composed of 5 to 40 wt% of a propylene homopolymer and 60 to 95 wt% of a propylene-based copolymer.
(2) The easy release layer (B) is composed of 20 to 50 wt% of a propylene-based copolymer and 50 to 80 wt% of a propylene-based acid-modified product.
(3) The gas barrier layer (C) is made of polymetaxylylene adipamide.
(4) The adhesive layer (D) is made of a propylene-based acid-modified product.
(5) The surface layer (E) is composed of 20 to 50 wt% of a propylene homopolymer and 50 to 80 wt% of a propylene-based copolymer.
2.1. A film casing comprising the coextrusion stretched multilayer film as described above and being for pressurized hot water sterilization.
3. The co-extrusion stretched multilayer film has a thickness of 30 to 50 μm. The film casing as described.
4.1. A package comprising the coextruded stretched multilayer film described above.
5. 3. The package is formed by providing a heat seal portion, and at least a pair of notches having a distance of 10 to 20 mm is provided in a part of the heat seal portion. The package described.

  The co-extrusion stretched multilayer film of the present invention has an original function of protecting the contents without forming a delamination or a bag breakage from the seal portion even when the retort treatment is performed when forming a package that wraps the contents. In addition, the film does not wrinkle even after being stored for several months, and the package and the like can be opened stably and easily.

Embodiments of the present invention will be described in detail below. The film of the present invention is a multilayer in which at least five layers of a surface layer (A), an easily peelable layer (B), a gas barrier layer (C), an adhesive layer (D), and a surface layer (E) are laminated in the order described above. It is a film. Each layer will be described in turn.
1. About surface layer (A)

  A surface layer (A) is located in the outermost layer of a film, and plays the role of the sealing layer for heat-sealing. In addition, it plays a role of preventing the performance of the gas barrier layer (C) from being deteriorated due to moisture entering from outside air. In order to satisfy the performance required for this, the resin used for the surface layer (A) comprises 5 to 40 wt% of a propylene homopolymer and 60 to 95 wt% of a propylene-based copolymer.

  Here, the propylene homopolymer is a polymer composed only of propylene. Examples of the propylene-based copolymer include a random or block copolymer of propylene and ethylene or an α-olefin having 4 to 8 carbon atoms. These may be used singly or in combination of two or more. Among these, a propylene-ethylene copolymer and a propylene-ethylene-1-butene copolymer can be preferably used. Moreover, as a propylene-type copolymer, the value represented by a weight average molecular weight / number average molecular weight is 1.5-3.5, More preferably, the thing of 1.5-3.0 can be used. .

  When the surface layer (A) is made of only a propylene-based copolymer, the stretchability is good but the water barrier property is insufficient. Therefore, after retorting the package, the gas barrier layer (C) is exposed to moisture from the outside after several months. Performance may decrease and contents may cause oxidative degradation.

On the other hand, in the case of a propylene homopolymer, it shows a sufficient water barrier property even after several months after retorting the package without degrading the performance of the gas barrier layer (C). There is a problem that the temperature becomes high and the film shrinks at the time of sealing, so that a sufficient sealing strength cannot be obtained, or the stretchability is deteriorated and stable film formation cannot be performed. According to the configuration of the surface layer (A), any of these problems can be avoided and necessary characteristics can be ensured.
2. About easy release layer (B)

  The easily peelable layer (B) plays the role of being opened by peeling between the easily peelable layer (B) and the gas barrier layer (C) when the package is opened. Moreover, the role which prevents the performance fall by the water | moisture content of a gas barrier layer (C) is also played simultaneously like a surface layer (A) and a surface layer (E). The resin used for the easy release layer (B) is composed of 20 to 50 wt% of a propylene copolymer and 50 to 80 wt% of a propylene acid-modified product.

  As a propylene-type copolymer, it can select from the propylene-type copolymer of the same range as what was shown by description regarding surface layer (A). The propylene-based copolymer of the easily peelable layer (B) may be the same as or different from the propylene-based copolymer of the surface layer (A), but the surface layer (A) and the easily peelable layer are the same. From the viewpoint of adhesive strength with (B), it is preferable. Examples of the propylene-based acid-modified products include propylene homopolymers, propylene-ethylene copolymers, propylene-ethylene-1-butene copolymers, unsaturated carboxylic acids such as maleic acid and fumaric acid, or acid anhydrides. And a modified polymer obtained by graft copolymerization. Among these, an acid-modified product obtained by graft copolymerizing maleic anhydride with a propylene-ethylene copolymer is preferable.

  To improve the water barrier property, do not cause delamination or breakage during retort treatment, and peel between the easy-peeling layer (B) and the gas barrier layer (C) when opened, a propylene copolymer And propylene-based acid-modified product must be mixed and the propylene-based copolymer alone is insufficient because the delamination strength (X) between the easily peelable layer (B) and the gas barrier layer (C) is weak. The propylene-based acid-modified product alone has insufficient water barrier properties, increases the delamination strength (X), and tends to fail to open.

  The propylene-based acid-modified product can be adjusted in adhesive strength with polymetaxylylene adipamide (MXD6 nylon) by adjusting the acid modification ratio. Increasing the acid modification ratio increases the adhesive strength, but also develops adhesion to metal surfaces such as extruder screws and dies, causing the resin to stay and cause the generation of foreign substances such as carbon due to gel and burning It is easy to become. Decreasing the acid modification rate reduces resin stagnation, but weakens the adhesive strength.

If the acid-modified product is used alone or a mixture of acid-modified products is used, the water barrier property will be insufficient, and moisture will escape from the contents of the package, making it easy for wrinkles to occur in the package in several months. . This is because the film shrinks due to the retort treatment, and the fixed thing in a tense state is reduced in volume as the moisture of the contents evaporates with time, and the film cannot keep the original tense state. It is guessed that.
3. About gas barrier layer (C)

The gas barrier layer (C) is a layer for inhibiting oxygen permeation of the film and preventing oxidative deterioration of the contents for several months. The resin used for the gas barrier layer (C) is made of polymetaxylylene adipamide (MXD6 nylon). Polymetaxylene adipamide obtained by polycondensation of metaxylylenediamine and adipic acid has better gas barrier properties and lower water absorption than aliphatic nylon such as 6 nylon and 6/66 nylon. There is little deterioration in gas barrier properties. Moreover, since strength, such as pinhole resistance, and stretchability are also favorable, it is preferable.
4). Adhesive layer (D)

  The adhesive layer (D) is a layer for adhering the gas barrier layer (C) and the surface layer (E), and exhibits an interlayer adhesive strength (Y). The resin used for the adhesive layer (D) is made of a propylene-based acid-modified product. The propylene-based acid-modified product can be selected from propylene-based acid-modified products in the same range as that shown in the explanation relating to the easily peelable layer (B). The propylene-based acid-modified product of the adhesive layer (D) may be the same as or different from the propylene-based acid-modified product of the easily peelable layer (B), but the same is used from the viewpoint of adjusting the peel strength. preferable.

In order to peel between the easy-peeling layer (B) and the gas barrier layer (C) at the time of opening, it is necessary that the delamination strength (X) <the delamination strength (Y). Therefore, in the easily peelable layer (B) and the adhesive layer (D) sandwiching the gas barrier layer (C), the propylene-based acid-modified product is used in all, and a certain proportion of the propylene-based material is used in the easily peelable layer (B). A copolymer is used in combination so that a difference in delamination strength between the two occurs.
5. About surface layer (E)

  The surface layer (E) plays the same role as the surface layer (A), but the surface layer (E) is also a layer in contact with the contents. Therefore, the water barrier property of the surface layer (E) that is in contact with the contents is equivalent to the water barrier property of the surface layer (A) that is not in contact with the contents in order to prevent wrinkles due to water loss after months after retorting. It is preferable to make it higher. Water evaporation of the contents is prevented by the surface layer (E), and moisture ingress from outside air is prevented by the surface layer (A). Compared to the outside air, the contents have higher water content and higher humidity, so that the water barrier property of the surface layer (E) is preferably higher than that of the surface layer (A), and mixing of the propylene homopolymer of the surface layer (E) The ratio is preferably higher than that of the surface layer (A).

  The resin used for the surface layer (E) is composed of a propylene homopolymer of 20 to 50 wt% and a propylene-based copolymer of 50 to 80 wt%. As a propylene homopolymer, it can select from the propylene homopolymer of the same range as what was shown by description regarding surface layer (A). The propylene homopolymer of the surface layer (E) may be the same as or different from the propylene homopolymer of the surface layer (A), but the same is the heat seal strength when forming a packaging bag. It is preferable from the viewpoint of ensuring. Moreover, as a propylene-type copolymer, it can select from the propylene-type copolymer of the same range as what was shown by description regarding the surface layer (A). The propylene copolymer of the surface layer (E) may be the same as or different from the propylene copolymer of the surface layer (A), but the heat seal strength when forming a packaging bag is the same. From the viewpoint of securing

In addition, the propylene-based copolymer alone has good stretchability but lacks water barrier properties. Storage for several months for pressurized hot water sterilization reduces the water content and wrinkles the package. . In addition, the performance of the gas barrier layer (C) is lowered due to moisture entering the gas barrier layer (C), and the contents are oxidized and deteriorated, so that the storage stability is deteriorated. On the other hand, with only a propylene homopolymer, the sealing temperature increases due to an increase in melting point, the film shrinks at the time of sealing, and sufficient sealing strength cannot be obtained, or the stretchability deteriorates and stable film formation is not possible. is there. In order to avoid these problems and secure the necessary characteristics, the structure of the surface layer (E) is suitable.
6). Layer structure of coextrusion stretched multilayer film

  The coextrusion stretched multilayer film includes at least five layers in this order: surface layer (A) / easy release layer (B) / gas barrier layer (C) / adhesive layer (D) / surface layer (E) (here, layer structure) The symbol “/” in FIG. 2 means that the layers on both sides thereof are stacked on each other). In order to improve the reliability of the gas barrier property or to perform printing, two or more coextrusion stretched multilayer films may be bonded together or two or more gas barrier layers (C) may be laminated. When two coextruded stretched multilayer films are laminated, A / B / C / D / E / A / B / C / D / E, or A / B / C / D / E / printing layer / A / A layer structure of B / C / D / E is preferable. By sticking together, the impact resistance and toughness are further improved. The pasting may be performed by self-adhesion between the surface layer resins, a known adhesive may be used, or the pasting may be performed by heat treatment. Further, by laminating two or more gas barrier layers (C), even if one gas barrier layer (C) has a defect, the gas barrier property can be secured by the other gas barrier layer (C ′). become.

  When printing on a coextrusion stretched multilayer film, for example, the two films are brought into close contact with each other by heating so as to be A / B / C / D / E / A / B / C / D / E. After printing on either side of layer A or layer E, the adhesive is applied to the same side, and two sheets are wound up. After winding up, the two layers can be peeled off so that the outer layer A, the layer, and E come into contact with each other and then rolled up again. Examples of the adhesive include urethane-based, acrylic-based, and epoxy-based adhesives.

Each layer (A), (B), (C), (D), (E) has a plasticizer, an antioxidant, a colorant, an ultraviolet absorber, a lubricant (wax, etc.) as long as the original properties are not impaired. Various additives such as inorganic fillers and crystal nucleating agents (talc and the like) can be added. The surface layer (E) is a layer in contact with the contents, and in order to improve the peelability from the contents, a surfactant such as sorbitan fatty acid ester, polyglycerin fatty acid ester, polyoxyethylene fatty acid ester is added. Also good.
7). Coextrusion stretched multilayer film thickness

  The thickness of the co-extrusion stretched multilayer film is preferably 30 to 50 μm in total from the point that the seal part does not peel even during retort processing and can be opened without applying excessive force. There is a trade-off relationship between the peeling (bag breaking) of the seal portion and the opening force in the retort processing. If the thickness is increased, the sealing strength becomes stronger and the bag breakage due to the retort treatment tends to decrease, but an excessive force is applied at the time of opening. Further, if the thickness is reduced, the sealing strength is weakened and can be opened with an appropriate force at the time of opening, but the bag breakage in the retort treatment tends to increase. The total thickness is preferably 30 to 50 μm in order to satisfy both the bag breaking and releasability in the retort treatment.

Further, the thickness of each layer is determined from the viewpoint of sealing strength and storage stability of about several months. The thickness ratio of the surface layer (A) and the surface layer (E) is 30 to 35% of the total, respectively, of the gas barrier layer (C). The thickness ratio is preferably 15 to 30% of the whole, and the easy peel layer (B) and the adhesive layer (D) are preferably 5 to 15% of the total thickness ratio, respectively.
8). Method for producing coextrusion stretched multilayer film

  The coextrusion stretched multilayer film is prepared by a coextrusion method from the viewpoint of productivity. The coextrusion is preferably made by a melt extrusion method, and the inflation method is particularly preferable. For example, the resin of each layer (A), (B), (C), (D), (E) is melted in each extruder, coextruded with a multilayer circular die, solidified by applying water or warm water, It is preferred to obtain a multilayer annular extrudate (parison). In order to stabilize the parison, it is preferable to provide a cylindrical cooling cylinder having a diameter equal to or smaller than the parison inner diameter by 1 to 2 mm, if necessary. When using a cooling cylinder, the surface is preferably mirror-finished, satin, Teflon or ceramic coated.

Subsequently, in order to obtain a coextrusion stretched multilayer film, the parison obtained above is heated, and air is injected under a temperature condition suitable for imparting orientation to form bubbles to stretch. The stretching temperature is preferably 90 to 110 ° C. in view of bubble stability. The draw ratio is appropriately selected according to the heat shrinkage rate, heat shrinkage stress, and the like, but is preferably 10 to 30 times, more preferably 15 to 25 times in terms of area magnification. If necessary, before stretching, a crosslinking treatment may be performed by irradiation with an electron beam (acceleration voltage 150 to 250 kV, irradiation dose 50 to 120 kGy) or the like to impart stretchability and heat resistance, or during or after stretching. A heat set treatment can be performed by using a hot air blowing method, a heat roller method, an indirect heating method using a carbon heater or the like alone or in combination. Furthermore, in the case of enclosing printability or ham, sausage, etc. in the contents after stretching, corona treatment, plasma treatment, etc. are performed so that the wetting tension is about 30 to 45 dyn for the purpose of imparting fleshiness to the film. Surface treatment can be performed.
9. Film casing, packaging

  By heat-sealing the coextrusion stretched multilayer film, it is possible to produce a tubular film casing for packing foods such as ham and sausage that require sterilization under pressurized hot water, and packaging using the same. . At that time, the coextrusion stretched multilayer film is used so that the surface layer (E) is on the inner side in contact with the contents.

  The seal strength of the heat-sealed cylindrical film casing or the package using the same is preferably 6 to 10 N / 15 mm width so that the seal portion does not peel even during the retort process. Moreover, it is preferable that the delamination strength (X) of an easy peeling layer (B) and a gas barrier layer (C) is 0.5-1.0N / 15mm width, and a gas barrier layer (C) and an adhesive layer (D) The delamination strength (Y) is preferably 0.7 to 1.5 N / 15 mm width, and the delamination strength (X) <the delamination strength (Y). By these, peeling is easy to occur between the easy peeling layer (B) and the gas barrier layer (C) at the time of opening, and the contents can be reliably opened beyond the seal portion.

  In order to obtain a package from the co-extrusion stretched multilayer film, for example, an automatic filling and packaging machine (for example, “ADP (registered trademark)” manufactured by Asahi Kasei Life & Living Co., Ltd.) is flattened so that the surface layer (A) is on the outside. After the film is formed into a cylindrical shape, the part where the film is folded is heat-sealed with hot air or a seal bar, and a sealing wire of about 1 to 2 mm is sealed with one or two envelopes to form a film casing. It can be made by filling a film casing with a product that requires sterilization under hot water and ligating both ends with a metal clip such as an aluminum wire. When making this package, before heat sealing or after heat sealing, a pair of notches with a distance of 10 to 20 mm are made at the film end to create a notched package. By having such a pair of notches, it becomes a mark of the opening place when opening. Moreover, when the notch width is 10 to 20 mm, it can be opened with an appropriate force of 4 to 14 N at the time of opening, and it can be opened in a circular shape so as to peel off the tape, and the contents can be easily taken out. More preferable.

  In this packaging bag, when the film is torn in the circumferential direction from the heat seal portion, particularly from the notch portion of the heat seal portion, the surface layer (A) and the easily peelable layer (B) break at the heat seal portion, and easily peel off. The layer (B) peels off from the gas barrier layer (C) and can be easily opened by peeling to the overlapped unheat-sealed part.

The present invention will be specifically described based on the following examples. First, measurement methods used for evaluation of various physical properties and abbreviations of resins used in Examples and the like will be collectively described below.
(1) Retort suitability

The 200 packages were subjected to a retort treatment at 120 ° C. for 20 minutes, and the delamination and broken bag state due to the retort treatment were evaluated according to the following criteria.
○: No delamination occurred, and the number of broken bags was 0. x: Delamination occurred. Or the number of broken bags due to peeling of the seal part is 1 or more.

In the evaluation of retort suitability, the seal part of the package after the retort treatment in which delamination or bag breakage did not occur was made with a width of the distance between notches, 180 ° peeling and a tensile speed of 500 mm / min. ) Measured using a Tensilon universal testing machine RTC-1210 <trade name> manufactured by Orientec Co., Ltd., and an average value of 10 packaging bodies (measurement once / one) was adopted.
(3) Delamination strength

In the evaluation of retort suitability, the peelable package (B) and the gas barrier layer (C) of the package after the retort treatment that did not cause delamination or bag breakage, other than the seal part, were observed. The gas barrier layer (C) and the adhesive layer (D) are peeled off, and the width is 15 mm, the measurement length is 20 mm, and the tensile speed is 500 mm / min. The product was measured with a Tensilon universal testing machine RTC-1210 <product name> manufactured by Orientec Co., Ltd., and the average value of 10 packages ((n = 1) / 1) was obtained.
(4) Openability

In the evaluation of retort suitability, the package after retort treatment in which delamination or bag breakage did not occur was opened from the notch portion, and the opened state was evaluated according to the following criteria.
○: The opening force obtained above is 4 to 14 N, and it can be peeled off between the layers (B) and (C) and opened in a circumferential shape.
(Triangle | delta): Although the opening force calculated | required above is 4-14N and peels between a (B) layer and a (C) layer, it does not maintain a notch width to the last, it cuts in the middle and cannot open in a circumferential shape.
X: The opening force calculated | required above exceeds 14N, or peels between (D) layer and (C) layer, the contents cannot be taken out and cannot be opened.
(5) Preservability

In the evaluation of retort suitability, 20 packages after retort treatment that did not cause delamination or breakage were stored for 3 months at a temperature of 28 ° C. Was evaluated according to the following criteria by visual inspection.
○: Equivalent to the start of storage Δ: There is no tension (beam) of the package compared to the start of storage.
X: Wrinkles are generated as compared to the start of storage, and there is no tension (beam) of the package.
(6) Water barrier property (moisture permeability)

Using PERMATRAN W-200 <trade name> manufactured by MOCON, the moisture permeability was measured according to ASTM F1249. The value 3 hours after setting the sample in the apparatus was adopted. The measurement was performed under the conditions of 38 ° C. and 90% RH. The smaller the moisture permeability, the higher the water barrier property.
(7) Abbreviation of resin

The abbreviations and trade names of the resins used in the examples and comparative examples are summarized below.
PP1: Propylene homopolymer (Sun Allomer PL500A)
PP2: Propylene copolymer (Sun Allomer Co., Ltd. ADSYL5C37F)
PP3: propylene copolymer (Sun Allomer Co., Ltd. PC540R)
ad1: Propylene acid modified product (Mitsui Chemicals, Inc. Admer QF580)
ad2: Propylene acid modified product (Mitsui Chemicals, Inc. Admer QF551)
Ny1: MXD6 nylon (Mitsubishi Gas Chemical Co., Ltd. MX nylon 6007)
Ny2: 6 nylon (Mitsubishi Engineering Plastics NOVAMID1030)
[Example 1]

  From the outer A layer to the E layer, as shown in Table 1, the layer structure of the film was (a mixture of 5% by weight of PP1 and 95% by weight of PP3) / (50% by weight of ad1 and 50% of PP2). After melt coextrusion using an annular five-layer die so as to form five layers of (weight% mixture) / Ny1 / ad1 / (PP1 is 20 weight% and PP2 is 80 weight%), hot water at about 60 ° C. The parison was prepared so that the folding width was about 130 mm, the thickness was about 640 μm, and the thickness constitution ratio of each layer was 30/7/26/7/30 from the outside.

  Subsequently, after heating the parison to about 105 ° C. in the heating zone, air is injected into the inside of the stretching zone to form bubbles to continuously stretch, and the stretching ratio is about 4 times in the machine direction (MD direction). Simultaneously biaxially stretching about 5 times in the transverse direction (TD direction), and after heat treatment, a single-ply coextrusion stretched multilayer film having a final thickness of about 40 μm was obtained.

  Next, using an automatic filling and packaging machine ("ADP (registered trademark)" manufactured by Asahi Kasei Life & Living Co., Ltd.), the film having a width of 90 mm is formed into a cylindrical shape through a folder at a film speed of 46 m / min. Then, after notching the outside of the overlapping part of the film, hot air was blown to heat seal the envelope. Here, the temperature of the hot air was appropriately set at about 300 to 400 ° C. depending on the thickness of the film.

A film casing having a folding width of 38 mm thus obtained was filled with surimi fish meat, and both ends were ligated with aluminum wires at intervals of 200 mm to obtain a package. About the obtained package, retort suitability, opening force, delamination strength, opening property, storage stability, and moisture permeability were evaluated, and the results are shown in Table 1. All evaluations were good.
[Example 2]

From the outside, the layer structure is (a mixture of 40% by weight of PP1 and 60% by weight of PP2) / (a mixture of 50% by weight of ad1 and 50% by weight of PP3) / Ny1 / ad1 / (50% by weight of PP1 and PP3 50% by weight of the mixture), and a film was prepared in the same manner as in Example 1 except that each layer thickness component ratio was changed to 35/5/20/5/35 from the outside. A single-ply coextrusion stretched multilayer film having a final thickness of about 40 μm was obtained. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.
[Example 3]

From the outside, the layer structure is (mixture of 30 wt% PP1 and 70 wt% PP2) / (mixture of 80 wt% ad1 and 20 wt% PP2) / Ny1 / ad1 / (30 wt% PP1 and PP2 70% by weight of the mixture) and the thickness of each layer is 30/5/30/5/30 from the outside, except that the film thickness is changed to 30/5/30/5/30. And a single-ply coextrusion stretched multilayer film having a final thickness of about 40 μm was obtained. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.
[Example 4]

Layer structure from outside (PP1 is 20 wt%, PP2 is 40 wt% and PP3 is 40 wt%) / (ad1 is 75 wt% and PP3 is 25 wt%) / Ny1 / ad1 / (PP1 is Example 5 except that the thickness of each layer was changed to 30/10/20/10/30 from the outside so as to be 5 layers of a mixture of 30 wt% and PP3 of 70 wt%) Thus, a film was prepared to obtain a single-ply coextrusion stretched multilayer film having a final thickness of about 40 μm. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.
[Example 5]

From the outside, the layer structure is (mixture of PP1 30 wt% and PP2 70 wt%) / (ad1 80 wt% and PP2 20 wt% mixture) / Ny1 / ad1 / (PP1 30 wt% and PP3 70% by weight of the mixture), except that the parison thickness was about 560 μm and each layer thickness component ratio was changed to 34/6/20/6/34 from the outside. Thus, a film was prepared to obtain a single-ply coextrusion stretched multilayer film having a final thickness of about 35 μm. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.
[Example 6]

From the outside, the layer structure is (mixture of PP1 30 wt% and PP2 70 wt%) / (ad1 80 wt% and PP2 20 wt% mixture) / Ny1 / ad1 / (PP1 30 wt% and PP3 70% by weight of the mixture), the parison thickness was about 720 μm, and each layer thickness component ratio was changed to 27/13/20/13/27 from the outside. Thus, a film was prepared to obtain a single-ply coextrusion stretched multilayer film having a final thickness of about 45 μm. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.
[Comparative Example 1]

Layer structure from outside (PP1 is 30% by weight and PP3 is 70% by weight) / (ad1 is 40% by weight and PP2 is 60% by weight) / Ny1 / ad1 / (PP1 is 30% by weight and PP3 is A film was prepared in the same manner as in Example 1 except that the thickness was changed to 5 layers of a 70 wt.% Mixture) to obtain a single-ply comparative film having a final thickness of about 40 μm. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2. Delamination occurred and the retort suitability was poor.
[Comparative Example 2]

Layer structure from outside (PP1 is 30 wt% and PP3 is 70 wt%) / (ad1 is 90 wt% and PP2 is 10 wt%) / Ny1 / ad1 / (PP1 is 15 wt% and PP3 is A film was prepared in the same manner as in Example 1 except that the thickness was changed to 5 layers of a mixture of 85% by weight to obtain a single-ply comparative film having a final thickness of about 40 μm. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2. Both openability and storage were inferior, and moisture permeability was high.
[Comparative Example 3]

Layer structure from outside (PP1 is 50% by weight and PP3 is 50% by weight) / (ad1 is 50% by weight and PP2 is 50% by weight) / Ny1 / ad1 / (PP1 is 60% by weight and PP3 is A film was prepared in the same manner as in Example 1 except that the composition was changed to 5 layers of a 40% by weight mixture). However, an unstretched part was partially generated, and the film could not be stably formed. .
[Comparative Example 4]

From the outside, the layer structure is PP2 / (mixture of ad1 50% by weight and PP2 50% by weight) / Ny1 / ad1 / PP2, and the parison thickness is about 400 μm. A film was prepared in the same manner as in Example 1 except that the thickness was changed to 30/8/24/8/30 to obtain a single-ply comparative film having a final thickness of about 25 μm. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2.
[Comparative Example 5]

The layer configuration is PP2 / ad2 / Ny1 / ad1 / PP2 from the outside, the parison thickness is about 880 μm, and the layer thickness composition ratio is 20/20/20/20/20 from the outside. A film was prepared in the same manner as in Example 1 except that the film was changed to a single ply comparative film having a final thickness of about 55 μm. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2.
[Comparative Example 6]

From the outside, the layer constitution is (a mixture of PP1 of 30% by weight and PP3 of 70% by weight) / (a mixture of ad1 of 50% by weight and PP2 of 50% by weight) / Ny1 / ad1 / PP2, A film was prepared in the same manner as in Example 1 except that the thickness composition ratio of each layer was changed to 35/10/10/10/35 from the outside to obtain a single-ply comparative film having a final thickness of about 40 μm. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2.
[Comparative Example 7]

Changed to be 5 layers of PP2 / (ad1 50% by weight and PP2 50% by weight) / Ny1 / ad1 / (PP1 20% by weight and PP3 80% by weight) from outside. A film was prepared in the same manner as in Example 1 except that a single-ply comparative film having a final thickness of about 40 μm was obtained. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2.
[Comparative Example 8]

Changed from the outside so that the layer structure is 5 layers (mixture of 30% PP1 and 70% PP3) / ad1 / Ny1 / ad1 / (mixture of 30% PP1 and 70% PP3). A film was prepared in the same manner as in Example 1 except that a single-ply comparative film having a final thickness of about 40 μm was obtained. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2.
[Example 7]

Layer structure from outside (PP1 is 30 wt% and PP2 is 70 wt%) / (ad1 is 50 wt% and PP2 is 50 wt%) / Ny1 / ad1 / (PP1 is 30 wt% and PP2 is 70% by weight of the mixture), the parison thickness was about 320 μm, and each layer thickness component ratio was changed to be 35/5/20/5/35 from the outside. A film was prepared and stretched to obtain a single-ply coextrusion stretched multilayer film. After that, the two single ply films are overlapped so that the outside and inside are in contact, passed through two 260φ heat rollers at about 130 ° C. for a total of about 7 seconds, and then a double ply with a final thickness of about 40 μm. A coextrusion stretched multilayer film was obtained. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 3.
[Comparative Example 9]

  From the outside, the layer structure was changed to be 5 layers of PP2 / (ad1 is 50% by weight and PP2 is 50% by weight) / Ny2 / ad1 / PP2, and two single-ply comparative films were obtained. A film was prepared in the same manner as in Example 7 except that heat treatment was performed so that the inner sides were in contact with each other, and a double-ply comparative film having a final thickness of about 40 μm was obtained. Further, a package was produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 4.

Claims (5)

At least five layers of the surface layer (A), the easy release layer (B), the gas barrier layer (C), the adhesive layer (D), and the surface layer (E) are laminated in the order described above, and the following condition (1) Coextruded stretched multilayer film characterized by satisfying (5).
(1) The surface layer (A) is composed of 5 to 40 wt% of a propylene homopolymer and 60 to 95 wt% of a propylene-based copolymer.
(2) The easy release layer (B) is composed of 20 to 50 wt% of a propylene-based copolymer and 50 to 80 wt% of a propylene-based acid-modified product.
(3) The gas barrier layer (C) is made of polymetaxylylene adipamide.
(4) The adhesive layer (D) is made of a propylene-based acid-modified product.
(5) The surface layer (E) is composed of 20 to 50 wt% of a propylene homopolymer and 50 to 80 wt% of a propylene-based copolymer.   A film casing comprising the co-extrusion stretched multilayer film according to claim 1 and being for pressurized hot water sterilization.   The film casing according to claim 2, wherein the thickness of the coextrusion stretched multilayer film is 30 to 50 μm.   A package comprising the coextrusion stretched multilayer film according to claim 1.   5. The package according to claim 4, wherein the package is formed by providing a heat seal part, and at least a pair of notches having an interval of 10 to 20 mm is provided in a part of the heat seal part. body.