JP2007015210A - Stretch shrink film for food packaging - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stretch shrink film that is good in suitability for packaging and tensity after packaging and can be provided with gas barrier property or smell barrier property. <P>SOLUTION: The film comprises a laminated makeup having at least three layers of a front layer, a center layer and a back layer. The center layer is composed chiefly of a polyamide resin, and the front and back layers are composed mainly of a single or mixed resin selected from polyolefin resins. The stress at 50% tensile elongation to the film machine direction is in the range of ≥20 MPa and ≤80 MPa, and the stress at 50% tensile elongation to the transverse direction of the film is in the range of >10 MPa and ≤50 MPa. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention mainly relates to a stretch shrink film for food packaging having properties suitable for prepackages of fresh foods and processed foods, and overlap shrink film applications.

  Polyvinyl chloride (PVC) and polyolefin (PO) are best known as examples of the raw material resin used for the shrink film having heat shrinkage in the above applications. This is because a shrink film made of PVC or PO-based material satisfies a wide range of user requirements, including practical properties such as mechanical strength, rigidity, optical properties, shrinkage properties, and cost.

  However, among these, a film made of PVC has a problem of waste disposal, and therefore, a shrink film made of a material other than PVC has been desired. Therefore, in the present application, at present, the shrink film made of a PO-based material occupies the market.

  Moreover, the shrink film in this use is roughly divided into two according to the use. One is a high-shrink type shrink film used for overlapping shrink packaging of containers with lids such as lunch boxes and side dishes at convenience stores, and the other is mainly fresh foods and processed foods. This is a method in which a lidless tray made of the same foamed polystyrene or polypropylene material as that of stretch packaging is used as a container and wrapped with a shrink film.

In the former, a fusing and sealing type packaging machine called a horizontal pillow type is mainly used as a packaging method. In this packaging system, in the middle of the film transport, the rolls with needles are passed mainly, holes are formed in the film at a constant pitch, and the film is formed in a tunnel shape so as to wrap the container, and at the bottom of the container The film is pressure-bonded with a roller in the longitudinal direction and heat-sealed, then the front and back of the container are fused and sealed, then passed through a shrink tunnel, and the expanded air interposed between the container and the film is externally passed through the needle hole of the previously formed film. This is a method of shrink wrapping while releasing. In this application, in order to obtain a tight packaging finish corresponding to containers of various shapes and sizes, a film that does not tear at a high shrinkage rate (generally at 120 ° C, 50% or more in both the vertical and horizontal directions) and needle holes. Physical properties are required.
In order to satisfy this required quality, in the production of a film, the material structure is devised and crosslinking by an electron beam is performed in the film production process, but the film cost is generally high.

  On the other hand, in the latter, the packaging form of the container is exactly the same as that of normal stretch packaging, and is a system in which the tray is overlapped with a film and the film is folded at the bottom of the tray. In this method, the same horizontal pillow type folding type as a stretch packaging machine or a folding type packaging machine called a push-up type is usually used.

  However, push-up packaging machines are originally designed on the assumption that the packaging mechanism uses stretch film. When shrink film is used, the film is difficult to stretch and the tear strength is weak. However, there are few examples of the combination of the push-up type packaging machine and the shrink film due to the problem of generation of tears caused by tearing of the film during packaging, and most are used in pillow packaging machines. The reason for using shrink film and the biggest feature compared to stretch film is that it has heat shrinkability, so it can remove wrinkles after packaging by passing through the shrink tunnel, and the film is difficult to stretch even after shrinkage Therefore, a tight and tight packaging finish can be obtained.

  In addition, the packaging of fresh products is roughly divided into those that are packaged at a pack center and delivered to each store, and those that are packaged in-store and displayed directly in the store. In terms of efficiency, the in-store packaging ratio is decreasing and the packaging ratio at pack centers is increasing. Here, in packaging at the pack center, about 2 to 4 packs of packed products are stacked, packed in containers, and delivered to each store by a cold truck, so in normal stretch packaging, vibration during transportation and friction between products For example, the film may be broken or stacked due to stacking after delivery, which may reduce the display effect of the product in the store after delivery, or may require repacking and increase incidental work. There's a problem.

In order to solve this problem, there is a tendency to increase the use of the above-described shrinkable film having heat-shrinkability, which can provide the film strength and tight tension of the packed product as compared with the stretch film.
In this method, the packaging machine is the same as a normal stretch wrapping machine, only a shrink tunnel is added to the post-packaging process, and the tray shape is not as diverse as a bento container. Is not required, and a sufficiently good packaging finish can be obtained with a small shrinkage rate. Rather, since the contents are fresh food, a shrinkage rate (low temperature shrinkage) at a relatively low temperature is required. The shrink film for such a use is called a stretch shrink film because the packaging form and the packaging machine to be used are the same as those for the stretch film and the stretch property is maintained to some extent.
As the stretch shrink film, films having various configurations are shown in the following Patent Documents 1 to 4 and the like.

JP-A-8-230122 Japanese Patent Laid-Open No. 10-272747 JP-A-11-99600 JP-A-12-272069

However, each of the stretch shrink films disclosed in Patent Documents 1 to 4 is composed of a single layer or a laminated structure mainly composed of a polyolefin-based resin, and has an oxygen permeability of 5.0 × 10 ^−11. (Mol / m ² · sec · Pa) or more.

Therefore, among fresh products, fruits and vegetables that are relatively active in respiration and transpiration, and the breathing action causes condensation on the inner surface of the packed product, resulting in water droplets adhering to it and impairing the display effect on the appearance. There is a problem that the freshness of the product which is the contents deteriorates.
In addition, when foods with relatively strong odors such as sugar beet and processed foods are packaged, the odor of the food permeates to the outside through the film, and when stored in the refrigerator, there is a problem that the odor is transferred to other foods. It was.

  Accordingly, an object of the present invention is to provide a stretch shrink film that can provide a film with good packaging properties and good tension after packaging, and can provide gas barrier properties and odor barrier properties, and solve the above-mentioned problems. It is in.

(1) The stretch shrink film for food packaging of the present invention has a laminated structure having at least three layers of a surface layer / a center layer / a back layer, the center layer is mainly composed of a polyamide-based resin, and the surface layer and the back layer are polyolefin-based. The main component is a single or mixed resin selected from resins, and the 50% tensile elongation stress in the longitudinal direction of the film is in the range of 20 MPa or more and 80 MPa or less, and the 50% tensile elongation stress in the lateral direction of the film is from 10 MPa. It is large and is in the range of 50 MPa or less.
(2) Further, the stretch shrink film for food packaging of the present invention preferably has a heat shrinkage ratio of 20 to 70% in both the vertical and horizontal directions of the film measured in an oil bath at 100 ° C. for 10 seconds. .
(3) Furthermore, it is preferable that the total film thickness is 5 to 20 μm, and the thickness ratio of the central layer is 5 to 40% of the total film thickness.
(4) Moreover, it is preferable that the oxygen permeability of a film is 3.0 * 10 < ^-11 > (mol / m < ² > * sec * Pa) or less.
(5) Furthermore, the stretch shrink film for food packaging of the present invention can be used for pillow type packaging.

  As an effect of the present invention, when the contents are fruits and vegetables, the effect of suppressing the breathing action of the product, maintaining the antifogging property and prolonging the freshness maintaining effect is great. In addition, when foods with relatively strong odors such as sugar beet and processed foods are packaged, the odor of the food permeates to the outside through the film, and when stored in the refrigerator, the odor will be transferred to other foods. It is effective to prevent.

Next, an embodiment of the invention will be specifically described.
In the present invention, the longitudinal direction of the film means the film take-up direction (MD) during film formation, and the lateral direction of the film means a direction (TD) orthogonal to the longitudinal direction.
In addition, the expression “main component” in the present invention includes the intention to allow other components to be contained within a range that does not interfere with the function of the main component, unless otherwise specified. However, it preferably accounts for 50% by mass or more, more preferably 70% by mass or more, and particularly preferably 90% by mass or more (including 100%) in the composition.

(Elongation characteristics)
Regarding the above-described elongation characteristics, the 50% tensile elongation stress in the longitudinal direction of the film is preferably in the range of 20 MPa or more and 80 MPa or less. More preferably, it is 40 MPa or more, and 60 MPa or less is preferable. If it is 20 MPa or more, a packed product can be given a sufficient tight feeling and tightness. Moreover, if it is 80 Mpa or less, a crack and deformation | transformation of a tray will not be generated at the time of packaging.
Moreover, regarding the horizontal direction of a film, the range whose 50% tensile elongation stress is larger than 10 Mpa and below 50 Mpa is suitable. More preferably, it is 15 MPa or more, and 30 MPa or less is preferable. If it is larger than 10 MPa for the same reason as in the longitudinal direction, it is possible to give a packed product a sufficient tight feeling and tightness. On the other hand, if it is 50 MPa or less, the film will not be sufficiently stretched and wrinkles and tarmi will not remain at the time of packaging, and the tray will not crack or deform.

(Heat shrinkage)
As the heat shrinkage rate, it is preferable that the heat shrinkage rate in both the vertical and horizontal directions of the film at 100 ° C. for 10 seconds measured with an oil bath is 20 to 70%. The lower limit is preferably 30% or more, and the upper limit is further preferably 60% or less.
By setting the shrinkage rate in the vertical direction to 20% or more, it is possible to remove wrinkles generated after packaging by passing through the shrink tunnel, and depending on the shrinkage stress, the shrinkage rate should be 70% or less. In this case, there is no problem that the tray is deformed or curled when the film folded into the bottom of the tray is heat-sealed. In addition, the stretch shrink film used for pillow packaging does not require a large shrinkage as described above.

(Laminated structure)
In the present invention, it has a laminated structure having at least three layers of a surface layer / a center layer / a back layer, the center layer is mainly composed of a polyamide resin, and the surface layer and the back layer are single or mixed resins selected from polyolefin resins. As the main component.
As long as it has at least three layers of surface layer / center layer / back layer, other layers may be provided between these layers. For example, surface layer / adhesive resin layer / center layer / adhesive resin layer / back layer A three-kind five-layer structure consisting of these is suitable.

(Surface and back layers)
The material constituting the surface layer and the back layer (hereinafter referred to as “front and back layer”) is mainly composed of a single or mixed resin selected from polyolefin resins.
Since the shrink film in this application is required to have an appropriate elongation, a film having low crystallinity to some extent is preferable. The material used for the front and back layers is preferably a material having a melting point of at least 10 ° C., preferably 20 ° C. or more higher than the melting point of the material used for the center layer. A chain low density polyethylene or the like), a copolymer of ethylene and α-olefin, or a copolymer of other comonomer can be preferably used.
When the bottom seal part of the packed product is heat-sealed by a hot plate after packaging because the melting point of the front and back layer material is lower than the melting point of the center layer, the resin of the front and back layers is fused, and the center layer has a melting point. Therefore, the temperature range suitable for heat sealing without melting and opening can be expanded.
Examples of the α-olefin include propylene, butene-1, pentene-1, hexene-1, 4-methyl-pentene-1, octene-1, and the like, and other comonomers include vinyl acetate such as unsaturated ester, acrylic Examples include methyl acid, propyl acrylate, methyl methacrylate, and ethyl methacrylate. In addition, soft polypropylene materials can be arbitrarily combined by simple substance and blend. That is, as a low crystalline polypropylene material, a crystalline polypropylene blended with amorphous polypropylene or a low crystalline material, or a so-called reactor TPO, a mixture of a crystalline portion and an amorphous portion in a polymerization stage is mixed. It may be polymerized. Alternatively, it may be a single crystal of low crystalline polypropylene polymerized by a metallocene catalyst or a blended composition.

(Center layer)
The polyamide resin used for the center layer is not particularly limited and is a 6 nylon resin, a 6-66 copolymer nylon resin fat, a 6-12 copolymer nylon resin, or an amorphous nylon resin alone or a blend thereof. Can be used. The polyamide resin used depends on the combination with the polyolefin resin used for the front and back layers, but in order to obtain appropriate flexibility and shrinkage, the copolymer has relatively low crystallinity as described above. It is preferable to use a mixed resin with a nylon resin or an amorphous nylon resin. Further, the polyamide-based resin has a relatively good oxygen barrier property, and suitably acts to suppress the respiratory action of fruits and vegetables. Moreover, it has a relatively good barrier property against odor, and can solve the above-mentioned problems.

(Thickness)
The total film thickness is preferably 5 to 20 μm, more preferably 7 to 15 μm.
If the total thickness of the film is 5 μm or more, tearing due to external force does not occur during packaging or after packaging, and if it is 20 μm or less, the elongation load of the film does not become too high. There is no deformation or cracking, and the bottom seal is not peeled off by repulsion against folding. Further, since the shrinkage force can be lowered, problems such as tray deformation after packaging do not occur.
The thickness ratio of the polyamide resin layer is preferably 5 to 40% of the total film thickness. More preferably, it is 15% or more, and 35% or less is preferable. If the thickness ratio is 5% or more, the oxygen barrier and odor barrier properties can be sufficient, and if it is 40% or less, the elastic modulus of the film is too high and the stretchability necessary for proper packaging is lost. And the problem that the bottom seal is easily peeled off does not occur.

  Depending on the selection of the front and back layer materials and the center layer material, sufficient adhesion may not be obtained by melting or coextrusion. In that case, generally used adhesive resins (polyolefin acid-modified graft copolymer resins, etc.) ) Is preferably used for interlayer adhesion. Furthermore, known anti-fogging agents, oils, and the like can be added to prevent slippage required when used in a packaging machine and fogging due to water droplets adhering to the inner surface of a packed product film.

(Manufacturing method of film)
Further, the film production method is not particularly limited as long as the above-described elongation characteristics and shrinkage characteristics are satisfied, but it is preferably stretched at least in the machine direction, biaxial stretching by a tenter method or a tubular method, or inflation. Examples thereof include a method of further longitudinal stretching after film formation without stretching by the method.

(Oxygen permeability of film)
The oxygen permeability of the stretch shrink film for food packaging of the present invention is preferably 3.0 × 10 ⁻¹¹ (mol / m ² · sec · Pa) or less. More preferably, it is 2.0 × 10 ⁻¹¹ (mol / m ² · sec · Pa) or less. If it is 3.0 × 10 ⁻¹¹ (mol / m ² · sec · Pa) or less, especially for fruits and vegetables, the respiratory action can be suppressed, and the adhesion of water droplets to the inner surface of the film due to transpiration can be reduced. In leafy vegetables, browning can be suppressed. Furthermore, in processed foods such as sugar beet, it is possible to maintain a state in which the odor of the contents has been prevented without permeating the odor of the contents to the outside for 1 day or more even at room temperature and for 4 days or more when refrigerated.

(Packaging method)
The stretch shrink film for food packaging of the present invention can be preferably used particularly for pillow type packaging. The reason for this is that the film of the present invention is a film that has little stretchability and is difficult to stretch due to its stretch characteristic range. This is because it is suitable for a packaging machine.

  Examples and examples will be described below, but the present invention is not limited thereto.

Example 1
As the central layer, polyamide resin (Mitsubishi Engineering Plastics, 6.66 copolymer nylon (Novamid 2430A1, 66NY20 wt%, melting point 198 ° C.), and as the front and back layers, ethylene-vinyl acetate copolymer (Nihon Unicar, NUC-3758, melting point) 91.degree. C., vinyl acetate 15% by weight, MFR = 2.3 g / 10 min) 97% by weight, and a resin composition obtained by mixing 3% by weight of diglycerin oleate (Riken Vitamin, O-71DE) as an antifogging agent. In addition, an adhesive resin layer (Mitsui Chemicals, Admer NF556, MFR = 6.6 g / 10 min, melting point 120 ° C.) is arranged between the center layer and the front and back layers, and a downward water cooling method using a round die is performed by a co-extrusion method. Thus, the thickness ratio is surface layer / adhesive resin layer / center layer / adhesive resin layer / back layer = 36/12/24/12/36 μm, and the total thickness is 120 μm. After collecting the original tube of 3 types and 5 layers, the original tube was taken out by a low-speed nip roll, reheated by an infrared heater, air was injected inside, the bubble diameter was expanded, and air was blown into the bubble by an air ring. While being cooled and solidified, a take-up tubular biaxially stretched film was collected with a high-speed nip roll, and the draw ratio was adjusted by the speed ratio of the nip roll in the machine direction and by the ratio of the bubble diameter in the machine direction. The draw ratio in the transverse direction was 3.3 / 3.3 times, respectively, and the total film thickness at this point was 11.0 μm.
Subsequently, the film obtained was passed through an annealing roll set at 60 ° C. and subjected to relaxation treatment in the machine direction and the transverse direction, and the final draw ratio was 3.1 / 3.1 times, surface layer / adhesive resin layer / center. Layer / adhesive resin layer / back layer = 3.75 / 1.25 / 2.5 / 1.25 / 3.75 μm, a laminated film having a total film thickness of 12.5 μm was obtained.

(Example 2)
Finally, the thickness ratio of the original tube was as follows: surface layer / adhesive resin layer / center layer / adhesive resin layer / back layer = 30/12/36/12/30 μm and total thickness 120 μm. Surface layer / adhesive resin layer / center layer / adhesive resin layer / back layer = 3.1 / 1.25 / 3.8 / 1.25 / 3.1 μm, and a total film thickness of 12.5 μm was obtained.

(Example 3)
Low crystalline polypropylene resin (Mitsubishi Chemical, Wintech, WFX4T, MFR = 7.0 g / 10 min, melting point 125 ° C.) 97 wt% and diglycerin oleic acid as an antifogging agent polymerized on the front and back layers with a metallocene catalyst A film having a total film thickness of 12.5 μm was finally obtained in the same manner as in Example 1 except that a resin composition mixed with 3% by weight of ester (manufactured by Riken Vitamin, O-71DE) was disposed.

Example 4
A film having a total film thickness of 12.5 μm was finally obtained in the same manner as in Example 1 except that a polyamide resin (manufactured by Mitsubishi Engineering Plastics, 6NY resin (Novamid 1030, melting point 224 ° C.)) was used as the center layer.

(Comparative Example 1)
The thickness ratio of the original tube is surface layer / adhesive resin layer / center layer / adhesive resin layer / back layer = 18/12/60/12/18 μm, total thickness 120 μm, and finally the surface layer / adhesive resin layer / center layer / adhesion Resin layer / back layer = 1.9 / 1.25 / 6.2 / 1.25 / 1.9 μm A total film thickness of 12.5 μm was used in the same manner as in Example 1 to obtain a laminated film.

(Comparative Example 2)
As the center layer, linear low density polyethylene (manufactured by Nihon Unicar, TUF-2060: ethylene-hexene-1 copolymer, density 0.921 g / cm ³ , MFR = 2.6 g / min, melting point 120 ° C.) is arranged. As the front and back layers, a mixed resin composition of the same ethylene-vinyl acetate copolymer and antifogging agent as used in Example 1 is arranged, and the thickness ratio is the surface layer / center layer / back layer = 50/80 / An original tube having a thickness of 50 μm and a total thickness of 180 μm was collected. Thereafter, a tubular biaxially stretched film was collected in the same manner as in Example 1. The stretching ratio was adjusted by the nip roll speed ratio in the longitudinal direction and the bubble diameter ratio in the lateral direction, and the stretching ratio in the longitudinal / lateral direction was 4.5 / 4.0 times, respectively. The total film thickness at this point was 10.0 μm.
Subsequently, the film obtained was passed through an annealing roll set at 50 ° C., and both the MD and TD directions were subjected to relaxation treatment. The final draw ratio was 4.2 / 3.8 times, and the surface layer / center layer / back layer = A laminated film having a thickness of 3.1 / 5.0 / 3.1 μm and a total film thickness of 11.2 μm was obtained.

(Comparative Example 3)
Propylene-ethylene random copolymer resin (manufactured by Sumitomo Chemical Co., Ltd., FH3315, ethylene 3.2 mol%, MFR = 3.0, melting point 150 ° C.) is arranged as the central layer, and the same ethylene as used in Example 1 is used as the front and back layers. -A mixed resin composition of a vinyl acetate copolymer and an antifogging agent was disposed, and an original tube having a thickness ratio of surface layer / center layer / back layer = 60/60/60 μm and a total thickness of 180 μm was collected. Thereafter, in the same manner as in Comparative Example 2, finally, a laminated film having a surface layer / center layer / back layer = 3.7 / 3.7 / 3.7 μm and a total film thickness of 11.1 μm was obtained.

  Table 1 summarizes the material configurations, stretch ratios, and thickness ratios used in the above Examples and Comparative Examples.

<Measurement method>
Using the film, the following items (1) to (3) were measured. The measurement results are shown in Table 2.

(1) Tensile elongation characteristics Using a commercially available tensile tester (Shimadzu Corp., AGS-H500N), a tensile test was conducted in both the longitudinal and lateral directions under the following conditions, and a 50% tensile load was read from the chart to determine the tensile stress. Converted.
(1-1) Sample size:
The film is cut out in both the vertical and horizontal directions in a strip shape having a width of 10 mm and a length of 100 mm.
(1-2) Distance between checks:
The cut film is set at a check interval of 40 mm, and a tensile test is performed at a pulling speed of 200 mm / min.
(1-3) Test data:
The test is performed three times in both the vertical and horizontal directions, and the average value is calculated.

(2) Thermal contraction rate by oil bath The shrinkage rate was measured under the following conditions in the longitudinal direction of the film using a commercially available oil bath.
(2-1) Sample size:
A film is cut out in both the vertical and horizontal directions in a strip shape having a width of 10 mm and a length of 140 mm.
Draw marked lines with an interval of 100 mm in the vicinity of the middle.
(2-2) Test conditions:
The temperature of the oil bath is adjusted to 100 ° C., the test sample is immersed in oil for 10 seconds, taken out, the length between the marked lines is measured, and the shrinkage rate is calculated.
(2-3) Test data:
The test is performed three times in both the vertical and horizontal directions, and the average value is calculated.

(3) Oxygen permeability The obtained film was measured by JIS K-7126 A method.

<Packaging test>
Using the following packaging machine, a pack sample for a packaging test using the above films was prepared.
Pillow type Omori Machine Co., Ltd .: Horizontal pillow type packaging machine (STN7500)

The tray used was an ordinary foamed styrene tray (length × width × height = 200 × 150 × 20 mm), and the film width was 400 mm.
The contents were 1 pack of 6 fresh shiitake mushrooms, 1 pack of about 70 g of cut lettuce, and 1 pack of 10 fresh dumplings, and each of the three products was packaged with films of Examples and Comparative Examples described later.
Then, it was shrunk using a shrink tunnel (C-300 type attached to a pillow packaging machine of Omori Machine Co., Ltd.) at a hot air temperature setting of 100 ° C. and a passage time of 3 seconds.
The packed sample was stored in a refrigerator at 5 ° C. for 4 days after packaging.

<Packaging finish evaluation method>
Regarding the preparation of the pack sample, the following items (1) to (3) were evaluated by each packaging machine. The evaluation results are shown in Table 3.
The following evaluation results were all evaluated based on the following criteria.
×: Completely practical failure level △: Level is better than × but practically failed level ○: Almost practically acceptable level ◎: Very good, no problem level

(1) State immediately after packaging The state immediately after packaging and before passing through the shrink tunnel was evaluated for the top and bottom surfaces.
Upper surface: x: Wrinkles and sagging occur on the entire surface, which is very unsightly.
Or the deformation | transformation of a tray is large or the crack of the tray has arisen.
(Triangle | delta): A wrinkle sagging is in the state which is a little unsightly in about a half.
○: Wrinkles are slightly around the tray.
A: There is almost no wrinkle on the top surface of the tray and the appearance is good.
Bottom: X: A state where there is little film fusion and it is stiff, with a lot of turning and peeling.
(Triangle | delta): The state in which the overlap of a film and a melt | fusion state are inadequate.
○: The film overlap and fusion state are almost good.
A: The film is neatly folded over the entire bottom surface of the tray.

(2) Evaluation of tension after passing through shrink tunnel Upper surface: ×: Wrinkles and sagging occur all over the surface and very unsightly Δ: Wrinkled sagging is about half of the whole and slightly unsightly.
Or there is a large deformation or cracking of the tray.
○: Wrinkles are slightly around the tray.
A: There is almost no wrinkle on the top surface of the tray and the appearance is good.
Bottom: X: A state where there is little film fusion and it is stiff, with a lot of turning and peeling.
(Triangle | delta): The state in which the overlap of a film and a melt | fusion state are inadequate.
○: The film overlap and fusion state are almost good.
A: The film is neatly folded over the entire bottom surface of the tray.

(3) Evaluation after the elapsed time of the contents (after storage at 5 ° C for 4 days)
The shiitake pack products were visually evaluated for the degree of water drops and the degree of deterioration.
X: It is unsightly because of water drops. Some corruption is ongoing.
Δ: Water droplets are attached and some are slimy.
○: There are few water droplets and there is almost no deterioration of the product. ◎: There are almost no water droplets. There is almost no change immediately after packing.
The cut lettuce pack product was visually evaluated for discoloration (brown color) of the cut surface.
X: It is quite discolored and unsightly. Some corruption is ongoing.
Δ: Slightly discolored and looks fresh.
○: Slight discoloration is observed, but hardly noticeable.
A: Almost no discoloration, almost no change immediately after packing.
About the dumpling pack goods, the smell was smelled from the exterior of the pack goods, and the grade was evaluated as follows.
X: It smells considerably.
Δ: Smell slightly ○: Almost no odor ◎: No smell at all

(4) Comprehensive evaluation It evaluated comprehensively as a stretch shrink film for food packaging from the evaluation result of said (1) to (3).
×: Cannot be used due to practical problems in packaging finish or changes in contents after storage.
Δ: There is a problem in practical use and the level is unacceptable.
A: Overall excellent as a stretch shrink film.
A: Overall excellent as a stretch shrink film.

Claims (5)

It consists of a laminated structure having at least three layers of a surface layer / center layer / back layer, the center layer is mainly composed of a polyamide-based resin, and the surface layer and the back layer are based on a single or mixed resin selected from polyolefin resins, Further, the food has a 50% tensile elongation stress in the longitudinal direction of the film in the range of 20 MPa or more and 80 MPa or less, and a 50% tensile elongation stress in the lateral direction of the film in the range of more than 10 MPa and 50 MPa or less. Stretch shrink film for packaging. The stretch shrink film for food packaging according to claim 1, wherein the film has a heat shrinkage rate of 20 to 70% in both the vertical and horizontal directions measured at 100 ° C. for 10 seconds in an oil bath. The stretch shrink film for food packaging according to claim 1 or 2, wherein the total thickness of the film is 5 to 20 µm, and the thickness ratio of the center layer is 5 to 40% of the total thickness of the film. The stretch shrink film according to any one of claims 1 to 3, wherein the film has an oxygen permeability of 3.0 x 10 ^-11 (mol / m ² · sec · Pa) or less. The stretch shrink film according to any one of claims 1 to 4, wherein the stretch shrink film is used for pillow packaging.