JP5705563B2 - Heat-shrinkable stretched laminated film, method for producing the same, top seal package, and pillow shrink package - Google Patents

Description

  The present invention relates to a heat-shrinkable stretched laminated film suitable for packaging by a packaging machine, and mainly suitable for use in the food packaging field where gas barrier properties and odor barrier properties are required, a method for producing the same, and a top seal package and The present invention relates to a pillow shrink package.

Various types of plastic packaging containers have been developed and proposed for packaging foods and drinks, pharmaceuticals, cosmetics, and the like.
Examples of the packaging method for covering food products include household wrap packaging, overlap packaging, twist packaging, bag packaging, skin packaging, pillow shrink packaging, stretch packaging, and top seal packaging. In particular, pillow shrink packaging and top seal packaging continuous packaging machines are becoming mainstream because they can package at high speed and provide a simple and clean finish.

  Furthermore, in recent years, due to consideration for the environment, awareness of reducing the amount of discarded foods sold at supermarkets and convenience stores has increased, and gas pack packaging for the purpose of long-term storage of foods and storage at normal temperatures has been attracting attention. Gas pack packaging is a tool that suppresses the growth of bacteria and the like by enclosing the container with nitrogen gas or carbon dioxide gas, and realizes long-term storage. The packaging film used has a gas barrier film with low oxygen permeability. Is suitable. As a gas barrier film, a film in which a polyamide resin, which is a barrier resin, and a polyolefin resin having a low-temperature sealing property are laminated is known.

For example, in Patent Document 1, at least one outer layer is a layer made of a polypropylene resin, and an intermediate layer is a layer made of a polyamide resin composition containing an aromatic diamine copolymer and an aromatic diamine polymer. A biaxially stretched film formed by laminating is disclosed.
In Patent Document 2, a sealing layer is a polyethylene resin layer having a tensile elastic modulus of 50 kg / mm ² or less, an intermediate layer is a rigid resin layer having a tensile elastic modulus of 120 to 400 kg / mm ² and a polyamide resin layer, and a surface layer is formed. A composite film formed by laminating as a layer made of an ethylene-vinyl alcohol copolymer is disclosed.
In Patent Document 3, a modified polyolefin resin layer, a polyamide resin layer, an ethylene-vinyl alcohol copolymer resin layer, a modified polyolefin resin layer, and an ethylene-α-olefin copolymer resin layer are laminated in this order. Thus, a stretched film that has been crosslinked to impart heat resistance is disclosed.

JP 2000-79669 A Japanese Utility Model Publication No. 57-11031 JP 2007-185910 A

However, as described in Patent Documents 1 to 3, when a film having a good barrier property, particularly a film having a nylon resin layer, is stretched, it is packaged when the packaged item is a soft item or a container with a strong strong heat shrinkage stress. Things may be deformed.
In Patent Document 1, the resin of both outer layers is substantially the same, and if the surface with which the heat seal bar contacts does not have heat resistance, the film is fused to the seal bar at the time of sealing, or the surface is roughened. The problem is that defects are likely to occur.
When a gas barrier ethylene-vinyl alcohol copolymer resin is used for the surface layer as in Patent Document 2, gas barrier performance deteriorates due to moisture absorption, which makes long-term storage difficult.
In Patent Document 3, heat resistance is imparted to the outer layer, which is a non-sealing surface, by applying electron beam crosslinking treatment, but there are cases where cost and maintenance work are required.

  The problem to be solved by the present invention is to achieve stable heat sealability and excellent barrier properties while suppressing deformation of the container in the heat shrinking process, and is suitable for both pillow shrink packaging and top seal packaging. Another object of the present invention is to provide a stretch stretch laminated film, a method for producing the same, and a top seal package and a pillow shrink package including the film.

As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, the present invention is as follows.
1. A surface layer (A) containing an ethylene-α-olefin copolymer having a melting point of 95 to 125 ° C;
An adhesive layer (B);
A core layer (C) containing an aromatic polyamide copolymer;
An adhesive layer (D);
A surface layer (E) containing a propylene-based copolymer having a melting point of 130 to 150 ° C .;
Is a heat shrinkable stretched laminated film comprising
The heat shrinkage rate measured according to the measuring method ASTM-D2732 is 5 to 20% at 100 ° C. and 40% or more at 160 ° C.
A heat shrinkable stretched laminated film having a maximum heat shrinkage stress in the TD direction measured in accordance with a measuring method ASTM-D2838 of 0.4 N / cm or less in a temperature range of 100 to 160 ° C.
2. 1. The tensile elastic modulus of the core layer (C) is 3000 MPa or more, and the thickness of the core layer (C) is 1 to 5 μm. The heat shrinkable stretched laminated film described in 1.
3. 1. Tensile elastic modulus is 700 to 1600 MPa and thickness is 10 to 25 μm. Or 2. The heat shrinkable stretched laminated film described in 1.
4). 1. ~ 3. A method for producing a heat-shrinkable stretched laminated film according to any one of
A laminate in which the surface layer (A), the adhesive layer (B), the core layer (C), the adhesive layer (D), and the surface layer (E) are laminated by a coextrusion method is used in an MD direction and a TD direction. A production method in which biaxial stretching is performed at a stretching ratio of 5.0 to 8.0.
5. 1. ~ 3. A top seal package comprising the heat-shrinkable stretched laminated film according to any one of the above.
6). 1. ~ 3. A pillow shrink package comprising the heat-shrinkable stretched laminated film according to any one of the above.

  According to the present invention, since the heat-shrinkable stretched laminated film has the above-described configuration, it is possible to use one surface layer (heat-resistant layer) containing a resin having a relatively high melting point as a film surface with which the heat seal bar contacts. In addition, it is possible to increase the difference in melting point between the other surface layer (sealing layer, sealant layer) containing a resin having a relatively low melting point and the heat-resistant layer. It is possible to reduce the sealing trouble in the automatic packaging machine. Furthermore, this invention can carry out pillow shrink packaging and top seal packaging, suppressing a deformation | transformation of a tray container in a heat contraction process because a heat shrinkable stretched laminated film has a low shrinkage stress. In addition, the present invention is excellent in rigidity, airtight sealability, heat sealability, pinhole resistance, alcohol resistance, and antifogging properties while being tight and beautifully finished. Furthermore, since this invention is excellent in barrier property, it is suitable for packaging of food with strong smell and gas pack packaging.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

  The heat-shrinkable stretched laminated film of this embodiment includes a surface layer (A), an adhesive layer (B), a core layer (C), an adhesive layer (D), and a surface layer (E) in this order.

  The surface layer (A) is composed of an ethylene-α-olefin copolymer having a melting point of 95 to 125 ° C. The surface layer (A) functions as a seal layer when heat-sealing. When the melting point of the ethylene-α-olefin copolymer exceeds 125 ° C., the heat sealing temperature is set high, and small wrinkles and pinholes are likely to occur, and power consumption is also likely to increase. On the other hand, when the melting point is less than 95 ° C., the productivity of the film is reduced, and blocking between the films is likely to occur and the slipperiness is likely to be reduced. The melting point of the ethylene-α-olefin copolymer is more preferably 100 to 125 ° C.

  The ethylene-α-olefin copolymer of the surface layer (A) is generally polymerized using a single-site catalyst or a catalyst called a multi-site catalyst. It is preferable because it is excellent in hot tack sealability. Examples of the α-olefin used as the monomer of the ethylene-α-olefin copolymer include propylene, 1-butene, 4-methyl-pentene, 1-pentene, 1-hexene, and 1-octene. It is not specifically limited to these.

The ethylene-α-olefin copolymer of the surface layer (A) has a melt flow rate value (hereinafter also referred to as MFR _{190 ° C.} ) measured according to JIS-K-7210 (temperature 190 ° C., load 2.16 kgf). In view of excellent extrudability, stretching stability, and kneadability of the antifogging agent, 0.5 to 6.0 is preferable.

The density of the ethylene-α-olefin copolymer is preferably 0.900 to 0.930 g / cm ³ . If the density is 0.900 g / cm ³ or more, it is easy to suppress blocking between films, and an appropriate rigidity can be imparted to the film, so that it can be easily applied as a cover material for top seal packaging. On the other hand, when the density is 0.930 g / cm ³ or less, the stretchability of the film is excellent, and the transparency of the film after stretching is excellent. The density of the ethylene-α-olefin copolymer is more preferably 0.905 to 0.926 g / cm ³ .

  The ethylene-α-olefin copolymers having a melting point of 95 to 125 ° C. may be used alone or in combination of two or more. In the surface layer (A), an ethylene-α-olefin copolymer having a melting point of less than 95 ° C. or more than 125 ° C., or a high-pressure method low-density polyethylene or linear low-density polyethylene may be added. The content of the ethylene-α-olefin copolymer having a melting point of 95 to 125 ° C. is preferably 60 to 100% by weight based on the entire surface layer (A), and 70 to 100% by weight from the viewpoint of excellent properties and airtight sealing properties. % Is more preferable, and 80 to 100% by weight is still more preferable.

In order to impart antifogging properties to the heat-shrinkable stretched laminated film of the present embodiment, a glycerin fatty acid ester can be added to the surface layer (A). When the glycerin fatty acid ester is added, the content is preferably 0.1 to 5.0% by weight based on the entire surface layer (A).
Examples of glycerin fatty acid esters include mono-fatty acid esters of glycerin, di-fatty acid esters, tri-fatty acid esters, poly fatty acid esters, etc., and mono-glycerin esters, diglycerin esters of saturated or unsaturated fatty acids having 8 to 18 carbon atoms, A triglycerin ester, a tetraglycerin ester, etc. are mentioned. Among them, diglycerin oleate, diglycerin laurate, glyceryl stearate, glycerin monooleate, or a mixture thereof is preferable because it is difficult to inhibit the slipperiness and optical properties of the film and is easy to use.

  Furthermore, you may add liquid additives, such as antioxidant, an antistatic agent, petroleum resin, and mineral oil, to the surface layer (A) to such an extent that antifogging property is not impaired.

The adhesive layer (B) is a layer having a function of adhering the surface layer (A) and the core layer (C). As the adhesive resin used for the adhesive layer (B), a known resin that can adhere an ethylene-α-olefin copolymer resin and a polyamide-based resin can be used.
Examples of the adhesive resin include modified polyethylene resins and modified polypropylene resins obtained by grafting a polyolefin resin and at least one monomer selected from α, β-unsaturated carboxylic acids and derivatives thereof, and mixtures thereof. .

  The core layer (C) is composed of an aromatic polyamide copolymer. The aromatic polyamide copolymer used for the core layer (C) may be used alone or in combination of two or more. The aromatic polyamide copolymer means crystalline nylon (polyamide) having an aromatic ring in the main chain. Specific examples thereof include, for example, metaxylylene adipamide (MXD6Ny), metaxylene Examples include polycondensates of range amine, adipic acid and isophthalic acid. Aromatic polyamide-based copolymers have better gas barrier properties and odor barrier properties than aliphatic nylons such as nylon 6 and nylon 6/66, and have strength such as pinhole resistance, stretchability, and moldability. It is good, suppresses changes in color tone and deterioration of the object to be packaged by light, and further has high rigidity, and is therefore suitable as a material constituting the core layer (C). The content of the aromatic polyamide-based copolymer is preferably 90 to 100% by weight based on the entire core layer (C).

  The tensile modulus of the core layer (C) composed of the aromatic polyamide copolymer is preferably 3000 MPa or more. In this case, even if the core layer (C) is thinned, the rigidity as a lid for the tray container can be maintained. Moreover, since there exists a tendency which becomes weak with respect to an impact when a tensile elasticity modulus is too large, it is preferable that the tensile elasticity modulus of a core layer (C) is 5000 Mpa or less. In addition, a tensile elasticity modulus can be measured based on ASTM-D882.

  The thickness of the core layer (C) is preferably 1 to 5 μm. In general, a barrier resin such as a polyamide resin is more expensive than a polyolefin resin, and thus the manufacturing cost can be reduced by setting the thickness to 5 μm or less. Further, by setting the thickness to 1 μm or more, it is easy to have rigidity and oxygen barrier performance necessary for gas pack packaging.

The adhesive layer (D) is a layer having a function of adhering the core layer (C) and the surface layer (E). As the adhesive layer (D), a known adhesive resin capable of adhering a polypropylene resin and a polyamide resin may be used.
Examples of the adhesive resin include modified polyethylene resins and modified polypropylene resins obtained by grafting a polyolefin resin and at least one monomer selected from α, β-unsaturated carboxylic acids and derivatives thereof, and mixtures thereof. .

  The surface layer (E) is a heat-resistant layer containing a propylene-based copolymer having a melting point of 130 to 150 ° C., and is preferably a layer having a melting point different from that of the surface layer (A). The difference in melting point between the surface layer (A) and the surface layer (E) is preferably as large as possible, and the difference in melting point is preferably 10 ° C. or higher, more preferably 20 ° C. or higher. In addition, melting | fusing point of surface layer (A) and surface layer (E) can be measured with a differential scanning calorimeter (DSC), respectively.

  By setting the melting point of the propylene-based copolymer to 130 ° C. or more, the heat resistance of the surface layer (E) is improved, and the surface roughness generated during heat sealing with which the seal bar comes into contact, and the seal bar and the surface layer (E) Packaging troubles such as sticking by heat fusion can be suppressed. In addition, when the melting point of the propylene copolymer exceeds 150 ° C., the stretching stability during film formation is lowered, and furthermore, the heat shrinkage stress of the obtained film is increased, so that the obtained film is used for packaging. In this case, the container of the package may be deformed.

  Here, specific examples of the propylene copolymer of the surface layer (E) include a copolymer of propylene and ethylene, a copolymer of propylene and an α-olefin having 4 to 8 carbon atoms, propylene, ethylene and carbon. Copolymers with α-olefins of several 4 to 8 are mentioned, and any of random copolymers and block copolymers may be used.

  Specific examples of the α-olefin having 4 to 8 carbon atoms include 1-butene, 4-methyl-pentene, 1-pentene, 1-hexene and 1-octene, but are not particularly limited thereto. These copolymerization components may be used alone or in combination of two or more. Among these, a propylene-ethylene copolymer and a propylene-ethylene-1-butene copolymer are preferable because they are relatively inexpensive and easy to produce a film of good quality with little thickness variation.

The MFR _{230 ° C.} of the propylene-based copolymer of the surface layer (E) is preferably 0.5 to 8.0 in that a sufficient heat shrinkage rate is obtained and the productivity of the film is excellent. Moreover, the value represented by the weight average molecular weight (Mw) / number average molecular weight (Mn) in the propylene-based copolymer of the surface layer (E) is preferably 1.5 to 9.0 from the viewpoint of excellent stretchability. 2.0 to 8.0 is more preferable. The weight average molecular weight (Mw) and the number average molecular weight (Mn) are measured by gel permeation chromatography (GPC) and converted to values using a standard polystyrene calibration curve.

  The propylene-based copolymer used for the surface layer (E) may be used alone or in combination of two or more as long as the above conditions are satisfied. Is preferably used. The content of the propylene copolymer having a melting point of 130 to 150 ° C. is preferably 50 to 100% by weight, more preferably 60 to 100% by weight, based on the entire surface layer (E), from the viewpoint of excellent heat resistance. More preferred is ˜100% by weight.

  Moreover, you may add the modifier of a polypropylene resin to the surface layer (E). Examples of the polypropylene resin modifier include 1-butene, ethylene elastomer, and propylene elastomer. By adding the modifier, when the film is formed by biaxial stretching, the stretching orientation degree of the surface layer (E) can be suppressed, and heat shrinkage stress can be suppressed.

  Each of the layers (A) to (E) described above may contain various additives such as a plasticizer, an antioxidant, a colorant, an ultraviolet absorber, a lubricant, an inorganic filler, and a crystal nucleating agent.

  In the heat-shrinkable stretched laminated film of this embodiment, the heat shrinkage rate measured according to the measurement method ASTM-D2732 is 5 to 20% at 100 ° C and 40% or more at 160 ° C. Generally, in order to obtain a tightly finished package in top seal packaging, it is sufficient that the heat shrinkage rate at 100 ° C. is 5% or more. However, if the heat shrinkage rate exceeds 20%, the tray container is deformed. On the contrary, the finish of the package is lowered. On the other hand, in a pillow shrink packaging, a high heat shrinkage rate is preferable, and in particular, if the heat shrinkage rate is 40% or more at 160 ° C., a tight and clean finished package can be obtained. The heat-shrinkable stretched laminated film of the present embodiment is a film characterized in that the heat shrinkage rates at 100 ° C. and 160 ° C. are greatly different, and depending on the packaging form, the heat shrinking process after packaging (heat shrinking process) By adjusting the heating temperature at, it can be suitably used for both top seal packaging and pillow shrink packaging. The thermal shrinkage rate is preferably 10 to 20% at 100 ° C, and preferably 50 to 70% at 160 ° C.

  Moreover, the heat shrinkable stretched laminated film of the present embodiment has a maximum heat shrinkage stress in the TD direction (lateral direction) measured according to the measurement method ASTM-D2838 of 0.4 N in a temperature range of 100 to 160 ° C. / Cm or less, and 0.35 N / cm or less is preferable. The reason why the temperature is set to 100 to 160 ° C. is that it is a practical temperature of a shrink tunnel that causes film shrinkage in the field of top seal packaging and pillow shrink packaging. The “TD direction” refers to the direction perpendicular to the film flow direction, that is, the width direction of the original roll, and the “MD direction” described later refers to the film flow direction, ie, the original roll. Point the winding direction.

  Here, when the tray container is top-sealed and pillow-shrink-wrapped, the TD direction of the film is usually aligned with the horizontal direction of the tray container (the short side direction in the rectangular container, the short axis direction in the elliptical container). In this case, at the time of heat shrink (heat shrink), the tray container tends to be largely deformed in the lateral direction due to the structure of the tray container. In the heat-shrinkable stretched laminated film of the present embodiment, the maximum heat-shrinkage stress in the TD direction is 0.4 N / cm or less in the temperature range of 100 to 160 ° C., so in any of the top seal packaging and the pillow shrink packaging. In addition, the deformation of the tray that occurs during heat shrinkage can be suppressed to a level that does not cause a problem in practice.

  The thickness of the heat-shrinkable stretched laminated film of this embodiment is preferably 10 to 25 μm. Since the heat shrinkage stress is almost proportional to the thickness, the thicker the film is, the more the heat shrinkage stress increases and the tray container is easily deformed at the time of heat shrinkage. Therefore, the film thickness is preferably 25 μm or less, more preferably 20 μm or less. . Moreover, if the thickness of a film is 10 micrometers or more, it will become moderate rigidity and is excellent in the touch feeling after packaging.

  The tensile elastic modulus (rigidity) of the heat-shrinkable stretched laminated film of this embodiment is preferably 700 to 1600 MPa. When the tensile elastic modulus is 1600 MPa or less, resistance due to rigidity is small during heat shrinkage, and sufficient shrinkage is easily obtained. When the tensile modulus is 700 MPa or more, it is easy to obtain an appropriate rigidity as a cover material for the top seal packaging. The tensile elastic modulus is more preferably 1000 to 1600 MPa. In addition, a tensile elasticity modulus can be measured based on ASTM-D882.

  The method for forming the heat-shrinkable stretched laminated film of the present embodiment is first extruded from a die by a known co-extrusion method such as a T-die type co-extrusion method or a circular die type co-extrusion method (A) to ( After laminating each layer of E), it is rapidly cooled to extract an unstretched original fabric (laminate).

  Next, the raw material on which the layers (A) to (E) are laminated as described above is heated and biaxially stretched under a temperature condition suitable for imparting orientation to form a multilayer film. The stretching temperature is preferably 100 to 130 ° C, more preferably 100 to 120 ° C, and the stretching ratio is preferably set to 5.0 to 8.0 times in the MD direction and the TD direction, respectively.

In addition, after stretching, heat treatment such as hot air blowing, hot roller, or indirect heating such as an infrared heater may be performed alone or in combination. The above-mentioned heat treatment tends to suppress the occurrence of curling of the film that deteriorates usability when used in a continuous packaging machine.
Furthermore, in order to improve printing suitability, surface treatment such as corona treatment or plasma treatment may be performed after stretching.

  Next, an example of a process for obtaining a top seal package using the heat-shrinkable stretched laminated film of the present embodiment as a packaging film will be described. First, the top surface of a plastic container (tray container) filled with an article to be packaged is directly covered with a packaging film, heat sealed with a heat seal bar, and simultaneously cut with a cutter blade to obtain individual packages. Next, a tightly finished package is obtained by heat-shrinking the film with a hot-air shrink tunnel whose temperature is adjusted in the vicinity of 100 ° C. in advance. When the object to be packaged is in contact with the film, the contacted part is not shrunk with hot air, so steam or hot water may be used in combination.

  Next, an example of a process for obtaining a pillow shrink package using the heat-shrinkable stretched laminated film of the present embodiment as a packaging film will be described. First, a process of covering the plastic container (tray container, packaged body) filled with the packaged object in a cylindrical shape is performed, and then a seal line is placed on the back surface of the packaged object with a rotary roller type center heat seal device. The process of sending it into a cylinder while performing a palm seal is performed. Subsequently, heat sealing is performed so as to close the front and rear of the film cylinder while cutting the front and rear of the cylindrical film surrounding the package with a saw blade cutter or the like, thereby obtaining individual packages. Next, a tightly finished package is obtained by thermally shrinking the film with a hot-air shrink tunnel whose temperature is adjusted to 150 to 160 ° C. in advance. When the object to be packaged is in contact with the film, the contacted part is not shrunk with hot air, so steam or hot water may be used in combination.

  Moreover, in the manufacturing method of the package of this embodiment, immediately before packaging with the heat-shrinkable stretched laminated film, nitrogen gas, carbon dioxide gas, or a mixed gas thereof is blown toward the packaged object and immediately packaged. And sealed in a gas pack. Gas pack packaging can prevent oxidative deterioration of the packaged item and has the effect of extending the shelf life of food.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited only to these Examples. The tensile elastic modulus, heat shrinkage rate, maximum heat shrinkage stress, oxygen barrier property, heat sealability, and finish of the package body of the laminated films of Examples and Comparative Examples were measured and evaluated by the following methods.

[Tensile modulus]
The entire laminated film and the tensile elastic modulus of the core layer (C) were measured according to ASTM-D882. The tensile elastic modulus of the core layer (C) was measured by obtaining a single layer film of the core layer (C) by sampling the laminated film with a tape or the like. It measured about MD direction (longitudinal direction) and TD direction (lateral direction), respectively, and the average value was used as a tensile elasticity modulus.

[Heat shrinkage]
In accordance with ASTM-D2732, the laminated film was shrunk at a temperature of 100 ° C. and 160 ° C. for 10 minutes, and the thermal shrinkage rate of the laminated film was measured. It measured about MD direction and TD direction, respectively, and the average value was used as a heat contraction rate.

[Maximum heat shrinkage stress]
Based on ASTM-D2838, the heat shrink stress of 100 to 160 ° C. in the TD direction of the laminated film was measured. The measurement was performed continuously for 5 minutes, and the maximum value among the measured values in the above temperature range was used as the maximum heat shrinkage stress.

[Oxygen barrier properties]
Using an oxygen permeation analyzer manufactured by MOCON (OX-TRAN (registered trademark 2 / 21SH)), the oxygen transmission rate was measured at an oxygen condition of 65% RH and a measurement temperature of 23 ° C., and the measurement started for 3 hours. The oxygen barrier property was evaluated based on the value of oxygen permeability afterwards. The unit of measurement of oxygen permeability is “cc / m ² / MPa / day”.

[Heat sealability]
The obtained laminated film was slit to a predetermined width, and a packaging speed of 30 using a TL-3000S manufactured by Ibaraki Seiki Co., Ltd. and an elliptical tray container for polypropylene top seal with 200 g of clay inside. Packaging was performed under the conditions of pack / min and heat seal pressure 0.4 MPa. The TD direction of the laminated film was aligned with the minor axis direction of the tray container for packaging. The heat sealability was evaluated based on the following criteria by visually evaluating the surface roughness of the seal portion and the presence or absence of pinholes.
<Evaluation criteria>
◯: At the lower limit heat seal setting temperature at which the seal strength is 2 N / 15 mm width or more, the surface of the seal portion is not rough and no pinhole is generated.
X: At the lower heat seal setting temperature at which the seal strength is 2 N / 15 mm width or more, the surface of the seal portion is roughened or pinholes are generated.

[Package finish]
"Top seal packaging"
The obtained laminated film was slit to a predetermined width, and a packaging speed of 30 using a TL-3000S manufactured by Ibaraki Seiki Co., Ltd. and an elliptical tray container for polypropylene top seal with 200 g of clay inside. Packaging was done at packs / minute. The TD direction of the laminated film was aligned with the minor axis direction of the tray container for packaging. BOT-600S manufactured by K & U System Co., Ltd. was used as the hot air tunnel, and the hot air temperature was set to 100 ° C. The finish of the package was visually evaluated by evaluating the appearance of the tray container according to the following criteria.
"Pillow shrink packaging"
The obtained laminated film was slit to a predetermined width, and packaged at a packing speed of 30 packs / minute using a polystyrene tray container with 200 g of clay inside using VSP-2000 manufactured by Ibaraki Seiki Co., Ltd. It was. The TD direction of the laminated film was aligned with the minor axis direction of the tray container for packaging. FB-800 manufactured by K & U System Co., Ltd. was used as the hot air tunnel, and the hot air temperature was set to 160 ° C. The finish of the package was visually evaluated by evaluating the appearance of the tray container according to the following criteria.
<Evaluation criteria>
○: No deformation (distortion or warping) is observed in the tray container, and there is little corner residue.
X: Deformation (distortion or warping) is recognized in the tray container, or there are many corners remaining due to insufficient shrinkage.

  Table 1 shows the abbreviations of the synthetic resins used in Examples and Comparative Examples.

[Example 1]
First, it melt-coextruded using the cyclic | annular 5-layer die with the layer structure shown in Table 2, Then, it solidified with the cold water of about 15 degreeC, and produced the tube-shaped unstretched original fabric of about 700 micrometers in total thickness. Next, this unstretched original fabric is heated to 110 ° C., biaxially stretched at a stretch ratio shown in Table 2 by an inflation method, and then heat-treated with a heating roll at 90 ° C., so that a final thickness of 20 μm is obtained. An extruded stretched laminated film was obtained.
The evaluation results of the obtained laminated film are shown in Table 2. The obtained laminated film was excellent in rigidity, had a low maximum thermal shrinkage stress in the TD direction, and had a good finish after packaging.

[Examples 2 to 7]
Coextrusion and biaxial stretching were carried out in the same manner as in Example 1 except for the resin component of each constituent layer to obtain a 20 μm coextruded stretched laminated film having the layer constitution shown in Table 2.
The evaluation results of the obtained laminated film are shown in Table 2. The obtained laminated film was excellent in rigidity, had a low maximum thermal shrinkage stress in the TD direction, and had a good finish after packaging.

[Example 8]
Coextrusion and biaxial stretching were carried out in the same manner as in Example 1 except for the resin component and the stretching ratio of the core layer (C) to obtain a 17 μm coextruded stretched laminated film having the layer constitution shown in Table 2.
The evaluation results of the obtained laminated film are shown in Table 2. The obtained laminated film was excellent in rigidity, had a low maximum thermal shrinkage stress in the TD direction, and had a good finish after packaging.

[Comparative Example 1]
Coextrusion and biaxial stretching were carried out in the same manner as in Example 1 except for the resin component and stretching ratio of the core layer (C) to obtain a 20 μm coextruded stretched laminated film having the layer constitution shown in Table 3.
Table 3 shows the evaluation results of the obtained laminated film. It was easy to puncture so that bubbles were broken in the stretching process, and the obtained laminated film had a high heat shrinkage rate of 100 ° C., and when it was made into a top seal package, the container was deformed and was inappropriate as a packaging film. .

[Comparative Example 2]
Except for the resin component of the surface layer (A) and the draw ratio, it was coextruded in the same manner as in Example 1, and then the unstretched original fabric was heated to 95 ° C. and biaxially stretched by the inflation method, as shown in Table 3. A 20 μm coextrusion stretched laminated film having a layer structure was obtained.
Table 3 shows the evaluation results of the obtained laminated film. In the obtained laminated film, the film stretchability was lower than in Examples 1 to 8 and Comparative Examples 1, 3, 5 and 6, so that the thickness accuracy was lowered and the inflation bubble was easily punctured. Stability was inferior. Moreover, since the obtained laminated film had a high maximum thermal shrinkage stress in the TD direction, container deformation occurred when it was formed into a package, which was inappropriate as a packaging film.

[Comparative Example 3]
Coextrusion and biaxial stretching were performed in the same manner as in Example 1 except for the resin component of the surface layer (E) to obtain a 20 μm coextrusion stretched laminated film having the layer structure shown in Table 3.
Table 3 shows the evaluation results of the obtained laminated film. When the obtained laminated film was heat-sealed, the surface of the seal portion was rough and inferior in beauty, and pinholes were partially generated, which was impractical as a gas pack packaging film.

[Comparative Example 4]
Coextrusion and biaxial stretching were carried out in the same manner as in Example 1 except for the resin components of the surface layer (A) and surface layer (E) to obtain a 20 μm coextruded stretched laminated film having the layer constitution shown in Table 3.
Table 3 shows the evaluation results of the obtained laminated film. In the obtained laminated film, since film stretchability was reduced as compared with Examples 1 to 8 and Comparative Examples 1, 3, 5, and 6, thickness accuracy and transparency were lowered, and inflation bubbles were easily punctured. The film formation stability was inferior. Moreover, since the obtained laminated film had a high thermal shrinkage stress in the TD direction, the container was deformed when formed into a package, and was inappropriate as a packaging film.

[Comparative Example 5]
Coextrusion and biaxial stretching were carried out in the same manner as in Example 1 except for the draw ratio to obtain a 20 μm coextruded stretched laminated film having the layer structure shown in Table 3.
Table 3 shows the evaluation results of the obtained laminated film. Since the heat shrinkage rate of the laminated film was small, the package obtained by the top seal packaging and the pillow shrink packaging both had looseness and slackness of the film, and a tight finish could not be obtained.

[Comparative Example 6]
Coextrusion and biaxial stretching were carried out in the same manner as in Example 1 except for the resin component of the core layer (C) to obtain a 20 μm coextrusion stretched laminated film having the layer structure shown in Table 3.
Table 3 shows the evaluation results of the obtained laminated film. The obtained laminated film has a low tensile elastic modulus, so that sufficient rigidity as a cover material for a top seal package cannot be obtained. Further, since the oxygen permeability is high, the laminated film is inappropriate as a gas pack packaging film.

  As shown in Table 2, each of the laminated films of Examples 1 to 8 has a heat-shrinkable stretch that achieves a tight packaging finish without causing container deformation when the top seal packaging and pillow shrink packaging are performed. It is a laminated film. In addition, the laminated films of Examples 1 to 8 are heat-shrinkable stretched laminated films having both stable heat sealability, rigidity, and oxygen barrier properties necessary for gas pack packaging.

On the other hand, it can be seen from the results of Comparative Example 1 that if the draw ratio is too high, the bubble is easily broken so that the bubble is broken, and the productivity is inferior. In addition, the obtained laminated film has a maximum heat shrinkage stress in the TD direction of 0.4 N / cm or less, but because the heat shrinkage rate at 100 ° C. is too high, the container is not deformed in the heat shrinking process of the top seal packaging. It turns out that it occurs.
From the results of Comparative Example 2, it can be seen that if the melting point of the ethylene-α-olefin copolymer resin of the surface layer (A) which is the sealing layer is too low, the film forming stability is inferior and the productivity and quality are lowered. Furthermore, since the maximum heat shrinkage stress in the TD direction in the obtained laminated film becomes large, it can be seen that the container deformation of the package occurs as in Comparative Example 1.
From the result of Comparative Example 3, if the surface layer (E) is a propylene-based copolymer resin having a melting point of less than 130 ° C., the heat resistance of the surface layer (E) decreases, so the surface layer (E) is welded to the seal bar. It can be seen that the surface is rough and pinholes are generated, which is impractical.
From the results of Comparative Example 4, it can be seen that when the surface layer (E) is a polypropylene resin having a melting point exceeding 150 ° C., the film forming stability is inferior and thus the productivity and quality are lowered. Furthermore, since the maximum heat shrinkage stress in the TD direction in the obtained laminated film becomes large, it can be seen that the container deformation of the package occurs as in Comparative Example 1.
From the results of Comparative Example 5, since the shrinkage rate is too low when produced at a low film stretch ratio, the shrinkage in the heat shrinking process becomes insufficient, and the package after heat shrinkage is loosened and loosened, resulting in poor finish. I understand that
From the results of Comparative Example 6, it can be seen that when aliphatic polyamide is used as the polyamide resin of the core layer (C), the feel as a lid material is inferior due to low rigidity. Furthermore, since oxygen barrier property is low compared with aromatic polyamide, it turns out that it is not suitable for gas pack packaging.

  The present invention is suitable for packaging by an automatic packaging machine, and is suitable for use in top-seal packaging or pillow shrink packaging of foods and drinks, pharmaceuticals, cosmetics, and the like.

Claims (5)

A surface layer (A) containing an ethylene-α-olefin copolymer having a melting point of 95 to 125 ° C;
An adhesive layer (B);
A core layer (C) containing an aromatic polyamide copolymer;
An adhesive layer (D);
A surface layer (E) containing a propylene-based copolymer having a melting point of 130 to 150 ° C .;
Is a heat shrinkable stretched laminated film comprising
The heat shrinkage rate measured according to the measuring method ASTM-D2732 is 5 to 20% at 100 ° C. and 40% or more at 160 ° C.
Maximum thermal shrinkage stress in the TD direction as measured according to the measuring method ASTM-D2838 is, Ri 0.4 N / cm der less in a temperature range of 100 to 160 ° C.,
The tensile modulus of the core layer (C) is not less than 3000 MPa, and the thickness of the core layer (C) is Ru 1~5μm der, heat-shrinkable stretched laminate film. The heat-shrinkable stretched laminated film according to claim 1, having a tensile modulus of 700 to 1600 MPa and a thickness of 10 to 25 µm. A method for producing a heat-shrinkable stretched laminated film according to claim 1 or 2 ,
A laminate in which the surface layer (A), the adhesive layer (B), the core layer (C), the adhesive layer (D), and the surface layer (E) are laminated by a coextrusion method is used in an MD direction and a TD direction. A production method in which biaxial stretching is performed at a stretching ratio of 5.0 to 8.0. Claim 1 or 2 comprising a heat-shrinkable stretched laminated film according to, top seal packaging. Claim 1 or 2 comprising a heat-shrinkable stretched laminated film according to, pillow shrink packaging.