JPS6154930A - Film for heat-shrinkable packaging and package using said film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is for heat-shrink packaging that does not cause the bag to break when it heat-shrinks processed meat products such as grilled pork chunks, but has excellent stress resistance. The present invention relates to a film and a package manufactured using the heat-shrinkable packaging film.

Furthermore, in detail, it is a heat-shrinkable packaging film that has excellent mechanical strength and oxygen barrier properties, and because it has specific shrinkage characteristics and sealing strength, it can be used to package contents with irregular shapes such as chunks of grilled pork. In addition, it can be packaged regardless of the size of the contents, and the bag does not break from the seal part of the package when heated in hot water or when removed from hot water and left to stand naturally. In addition, we use a heat-shrinkable packaging film that has been strained to produce a package that does not fully shrink due to heat-shrinking and is less likely to remain around the contents, has excellent tightness, and has a good appearance. The present invention relates to a package that is manufactured with excellent tightness and preserves its contents.

(Prior art) Recently, a heat shrink packaging method has been used in which roasted pork chunks, etc. are vacuum packaged in a bag made of a heat shrinkable film with oxygen barrier properties, and sterilized by heat shrinking in hot water. Ta. This packaging method has the feature that it can be packaged even if the shape is not uniform, such as a lump of grilled pork, and the contents can be preserved for a long time. Moreover, when processed meat products such as grilled pork chunks are packaged using this packaging method, after being heat-shrinked and sterilized in hot water, they are removed from the hot water.
It is possible to always tighten the contents with strong force until it is left alone, so the meat juices (referred to as drips) from roasted pork chunks, etc. do not accumulate between the package and the grilled pork chunks, etc. It has the great characteristic of being able to do things (this quality is called ``urgency'').

Moreover, when using conventional bags made of heat-shrink packaging film, the contents such as grilled pork chunks come in various sizes and shapes, so a bag that is appropriate for the size and shape is used.
If the size of the bag was too large relative to the size of the contents, a large amount of film would remain around the contents without being completely heat-shrinked, resulting in an unsightly appearance and a lack of tightness. Also, if the bag size is too small compared to the size of the contents, it will not only be difficult to fill the bag with the contents, but it will also be difficult to fill the bag with the contents. Take it out from
There were cases where the bag would break at the sealed part when left alone.

In this way, using conventional heat shrink packaging film, 1. When heat-shrink packaging contents with irregular shapes, such as chunks of grilled pork, the size and shape of the bag must be selected appropriately depending on the size and shape of the contents, otherwise the heating process in hot water, etc. There has been a complicated problem in that it is not possible to obtain a package that does not cause bag breakage at the sealing portion and has excellent tightness.

(Background of the Invention) The present inventors have investigated the conditions of a heat-shrinkable packaging film that imparts tightness to a heat-shrinkable packaging, and when the heat-shrinkable packaging is heat-shrinked in hot water or We conducted various experiments to find out why the bag breaks at the seal when it is taken out of the water and left to stand.

First, regarding the tightness of the heat-shrinkable packaging body, the maturation shrinkage rate in hot water of the heat-shrinkable packaging film used, the heat-shrinkage stress,
Various studies were conducted on the relationship between shrinkage stress and other factors when the material was heated in hot water and then left to stand naturally.

Next, regarding the cause of bag breakage at the seal part when the heat-shrinkable packaging is heat-shrinked in hot water, the relationship between the heat-shrinkage stress of the heat-shrinkable packaging film in hot water and the seal strength is explained. I looked into it. Also, take out the heat shrink packaging from hot water,
To determine the cause of bags breaking at the sealed part when left in the air, we investigated the relationship between the shrinkage stress and the 7-l strength when the heat-shrinkable packaging film was heated in hot water and left in the air. Ta.

The heat shrinkage rate, heat shrinkage stress, and seal strength of a heat shrink packaging film in hot water, or the shrinkage stress and seal strength when left naturally after heating in hot water, are as follows: It was measured as follows.

First, the heat shrinkage rate was determined by cutting a heat-shrinkable packaging film into a square of 100 mm in both the vertical and horizontal directions, and immersing the obtained sample in hot water at 80°C for about 3.0 seconds to shrink the film. , the amount of shrinkage in the vertical and horizontal directions is 100 of the length before shrinkage.
It was determined by the fraction.In addition, when measuring the ripening shrinkage rate, practical heat shrink packaging must be heated in hot water in the range of 80°C to 95°C, and 80°C or higher. Since a higher heat shrinkage rate can be obtained in hot water than that at 80°C, 80'
The heat shrinkage rate of C was determined.

The heat shrinkage stress is determined by applying a sample cut into a tanzak shape with a width of 1 (1+m) in each of the longitudinal and transverse directions of the heat-shrinkable packaging film to a chuck of 30mg+ at intervals without creating tension and without causing any slack. The stress generated between the chucks when the chucks are sandwiched between the chucks, fixed so that the chuck interval does not change, and immersed in the specified hot water for 5 minutes is the heat shrinkage stress in each direction in the hot water in units of g/Cm. In the heat shrinkage stress measurement described above, it was found that the heat shrinkage packaging film exhibits stronger heat shrinkage stress when the temperature of hot water is higher, and as mentioned above, the temperature of hot water in practical packaging is higher. is 80℃ to 95℃
Therefore, in practical packaging, the heat shrinkage stress is 8.
The lowest value is shown in 0°C hot water, and the highest value is shown in 95°C hot water. Therefore, the heat shrinkage stress in hot water at 80°C and 95°C was determined.

In addition, the shrinkage stress when left to stand naturally after heating in hot water is as follows. The stress between the chucks when left in a natural state for about 2 hours was determined in g/c+a units in both the longitudinal and lateral directions.

In addition, the shrinkage stress of a heat-shrinkable packaging film when it is left to stand naturally after being heated in hot water shows higher shrinkage stress when it is heated in high-temperature hot water. The shrinkage stress after Noni was heated in water was determined.

The seal strength of the heat-shrinkable packaging film when it is heated in hot water during bag making or vacuum packaging, or when it is left to stand naturally after heating, was determined by the following method. . First, the width of the heat-shrink packaging film including the sealing part is 10
A seal strength measurement sample cut into a tanzak shape of +u is rr-. The sample was heated to 30Ill as in the heat shrinkage stress measurement.
The chucks with the I1 interval are held between deaf ears without creating tension or slack, and are fixed so that the interval between the chucks does not change, and then immersed in hot water at 95°C for 5 minutes. After that, the chuck gap was opened at a speed of about 100 ma/sin in hot water, and the strength at which the seal part started to break was set at 95°C.
The seal strength in hot water was determined in units of g/c*. In addition, the seal strength when left to stand naturally after heating was determined by holding the sample in a chuck and immersing it in 95 °C hot water for 5 minutes, similar to the seal strength measurement in 95 °C hot water above. .

After that, it was taken out from the hot water without changing the chuck interval, and after being left to stand for about 2 hours, about looms/l
The chuck interval was opened at a speed of 1 liter, and the strength at which the seal portion started to break was determined in units of g/cra as the seal strength when the seal was heated in hot water at 95° C. and then allowed to stand.

The reason why the seal strength during heating was determined in hot water at 95°C is because heating of practical heat shrink packaging is carried out in hot water in the range of 80°C to 95°C, and the seal strength was determined in hot water at 95°C. This is because the seal strength decreases as the temperature increases, and the lowest seal strength is shown at 95°C. Furthermore, the seal strength when left naturally after being heated shows a weaker value after being heated at a high temperature, so the seal strength when left naturally after being heated in 95℃ hot water was evaluated. I asked for it.

Based on the results of various measurements of the properties of the heat-shrinkable packaging film based on the above conditions, we determined the conditions that give the heat-shrinkable packaging its tightness and the ability of the heat-shrinkable packaging to be heat-shrinked in hot water. This article describes the results of our investigation into the causes of bags breaking in the 7th part when the bag is taken out from hot water or left to stand naturally.

Regarding the tightness of heat-shrinkable packaging, the first condition is the heat-shrinkage rate of the heat-shrinkable packaging film used, which must shrink by 10% or more in both the vertical and horizontal directions in hot water at 80°C. It is. If the heat shrinkage rate is less than 10%, the diameter of the heat shrink packaging bag should be set to a size that is easy to insert compared to the outer shape of the contents, so that the temperature is lower for practical packaging. 8
In hot water at 0'C, 1ffi is not enough to hold the contents, it is not possible to maintain the contents tightly, walnuts form on the heat shrink packaging, and drips accumulate in the case of pieces of grilled pork etc. Put it away. In other words, the result is a heat-shrinkable package that lacks tightness. Also, if you try to reduce the diameter of the bag and obtain a package with tightness by heating shrinkage in 80°C hot water,
Inserting the contents becomes very difficult. Moreover, if the heat shrinkage rate exceeds 10%, it is necessary to use a bag with a diameter that allows the contents to be inserted easily, and then the packaging for puko can be carried out at a lower temperature of 80°C.
Even when heat-shrinked in hot water (C), a heat-shrinkable package with sufficient tightness can be obtained. In addition, when heat-shrinking in hot water of 80°C or higher, the heat-shrinkable packaging film exhibits a higher heat-shrinkage rate than when heat-shrinking in hot water of 80°C.
If the above-mentioned conditions for the shrinkage rate in hot water of 80° C. are satisfied, a good heat-shrinkable package with excellent tightness can always be obtained in hot water of 80° C. or higher.

Next, the second condition is the heat shrinkage stress of the heat shrink packaging film to be used, which is 50g in both the vertical and horizontal directions in hot water at 80°C.
/am or more is required.

For items with heat shrinkage stress of less than 50 g/cm, even if the heat shrinkage rate exceeds 10%, the contents cannot be held tightly during heat shrinkage in 80°C hot water. , a film that does not fully shrink remains around the contents, resulting in walnuts on the package. This is because the heat-shrinkable packaging film is in close contact with the contents during vacuum packaging, so if the film's heat-shrinkage stress is weak, it will not be able to fully shrink.

That is, it is thought that this is because the heat-shrinkable packaging film that has come into close contact with the contents due to vacuum packaging does not have the force to pull the wavy-shaped film toward further heat-shrinking. Moreover, if the heat shrinkage stress exceeds 50 g/cm, film walnuts will not occur in the package due to heat shrinkage in hot water, and a film that has not been completely heat-shrinked will tend to remain around the contents. This results in a heat-shrinkable package with excellent tightness. This is because the heat shrinkage stress of the shrink wrapping film is strong, so even though the packaging (() tightly tightens the contents, it leaves a film that does not fully shrink around the contents as described in 11). Because there is no such thing, it seems that it is more tense.

The third condition is to reduce the shrinkage stress of the heat-shrinkable packaging film when it is taken out from the hot water and left to stand naturally after being heat-shrinked in hot water. It is necessary to make the stress stronger than the heat shrinkage stress in order to maintain the tightness of the package over time. That is, when the contents such as pieces of grilled pork are heated, they expand to some extent, and in this expanded state, the tightness during heating contraction is maintained. Moreover, when the heat-shrinkable package is taken out of the hot water and cooled, the contents such as roasted pork chunks will shrink and the volume will become somewhat smaller. Therefore, if the heat-shrinkable packaging film has the ability to shrink as the volume of the contents decreases, the heat-shrinkable packaging can maintain its tightness even after cooling.

First, regarding the causes of bag breakage at the seal part of heat shrink packaging,
The reason why the heat-shrinkable package breaks when it is heat-shrinked in hot water is considered to be as follows. That is, the seal strength of a heat-shrinkable packaging film decreases significantly when heated in hot water, and the higher the heating temperature, the more the seal strength decreases. In particular, in hot water at a temperature higher than the melting point of the sealant material, the decrease is remarkable. When the heat-shrinkable packaging is heat-shrinked in hot water, if the sealing strength of the heat-shrinkable packaging in hot water becomes weaker than the heat-shrinkage stress of the film, it will be torn at the sealing part and the bag will break. This is thought to occur. Therefore, in order to prevent the bag from breaking at the sealed portion when the heat-shrinkable package is heated in hot water, it is necessary to meet the following conditions. In the temperature range of 80°C to 95°C, which is the temperature range of hot water used for heat-shrink packaging of pieces of pounded and grilled pork, etc., the sealing strength is the lowest in the 95°C hot water. Stress shows the highest value.

Therefore, it is necessary to make the seal strength in 95°C hot water stronger than the heat shrinkage stress in 95°C hot water to prevent bag breakage over the entire hot water temperature range. be. Furthermore, as described in 1i4, the heat shrinkage stress of the heat shrink packaging film must satisfy the above conditions in order to impart tightness to the package.

Next, when the heat-shrinkable package that has been heat-shrinked in hot water is taken out from the hot water and left to stand, the reason why the bag breaks at the sealed portion is considered to be as follows. That is, when the heat-shrink packaging film is heated in hot water and then left to stand, the shrinkage stress of the heat-shrink packaging film when placed under the same conditions is lower than the shrinkage stress when the film is heated in hot water and then left to stand. It is thought that this is due to the weak strength of the bag, which causes the bag to break. The reasons for this are that the sealant layer of the heat-shrinkable packaging film has poor ripening resistance and water resistance, and the sealing strength decreases after heating in hot water. It is thought that the shrinkage stress gradually increases when the product is left to stand naturally after heating. Due to the shrinkage stress, heating in high temperature hot water shows stronger shrinkage stress. On the other hand, the seal strength shows a weaker seal strength when heated in hot water at a higher temperature. From the above, in light of practical packaging, it is necessary to ensure that the shrinkage stress when heated in hot water at 95°C and left to stand naturally does not become stronger than the seal strength under the above conditions. As mentioned above, the shrinkage stress gradually increases when a heat-shrinkable packaging film is heated in hot water and then taken out from the hot water and left to stand. This is due to the stress of the heat-shrinkable packaging. This is a necessary characteristic.

(Summary of the Invention) The first invention of the present application comprises at least one polyamide resin layer (A), at least one thermoplastic resin layer (B) with excellent oxygen barrier properties, and a heat-sealable thermoplastic resin layer on at least one surface. A film laminated with a plastic resin layer (C), which has a heat shrinkage rate in hot water of 80°C of 10% or more in both the longitudinal and horizontal directions, and has a heat shrinkage stress in hot water of 80°C. is 50 g/cn or more in both the longitudinal and lateral directions, and the seal strength of the film in 95°C hot water is 95 g/cn or more.
It is stronger than the heat shrinkage stress in hot water at 5°C, and furthermore, the seal strength when the film is left to stand after being heated in hot water at 95°C is This is a heat-shrinkable packaging film that is characterized by having a stronger shrinkage stress than when it is left to stand naturally after being heated. Also, the second application
The invention comprises at least one polyamide resin layer (A)
, at least one thermoplastic resin layer (B) with excellent oxygen barrier properties, and a heat-sealable thermoplastic resin layer (C) on at least one surface, the film comprising:
Thermal shrinkage rate in hot water at 80℃ is 10 in both vertical and horizontal directions.
5 or more, the irises shrinkage stress in hot water at 80°C is 508/am or more in both the longitudinal and transverse directions, and the film has a
The sealing strength in 5°C hot water is stronger than the heat shrinkage stress of the film in 95°C hot water, and furthermore, when the film is left naturally after being heated in 95°C hot water. A bag is made using a heat-shrinkable packaging film whose sealing strength is stronger than the shrinkage stress when the film is heated in hot water at 95°C and then left to stand, and the bag is filled with the packaged item. , a package characterized by being vacuum-packed and then heat-shrinked and sterilized in hot water.

The heat-shrinkable packaging film of the first invention of the present application and the heat-shrinkable packaging film used for the package of the second invention of the present application (these films are collectively referred to hereinafter simply as the "heat-shrinkable packaging film of the present application") In order to increase the mechanical strength and heat shrinkage stress, a polyamide resin layer is included as a layer component of the film structure. In this case, nylon-6 and nylon = 6
It is desirable to include a copolymer layer with 6.

In this case, as shown in claim 5, if a polyamide resin layer is included in the outermost layer, the Ilf result can be obtained.The biggest reason for doing so is that This is because after heating the heat-shrinkable packaging film in duck water, 1. Take out the white shoes from clear water, and if you leave them for a while, the shrinkage stress will gradually increase. This is particularly preferred in terms of the tightness of the heat-shrinkable package.

This gradual increase in shrinkage stress is thought to be due to the fact that the polyamide resin layer evaporates the moisture it has absorbed when it is soaked in hot water, and the shrinkage stress increases as it dries.

Furthermore, the heat-shrinkable packaging film of the present invention can preserve contents such as roasted pork chunks for a long time. It is made to contain.

The curl strength of the mature shrink packaging film in hot water is as follows:
It is largely influenced by the type of Norant material. That is, the Nolant material has excellent water resistance, and therefore, it is preferable that the Nolant material has a higher melting point because it will have a stronger Nourant strength in hot water. In particular, if the temperature of the hot water exceeds the melting point of the hot water, the strength of the steel will drop sharply, so it is preferable that the melting point of the hot water is higher than the temperature of the hot water. Therefore, since heat shrink packaging in practical use is shrinked and sterilized in hot water in the temperature range of 80°C to 95°C, a resin with a melting point of 95°C or higher is used as the sealant material layer; 1- is necessary.

From the above, the resin for the sealant material layer is low-density polyethylene with excellent water resistance and a melting point of 95°C or higher, linear low-density polyethylene, ethylene-vinyl acetate copolymer,
Alternatively, an ionomer resin or the like is used. Furthermore, when the heat-shrinkable packaging film of the present application is produced by coextrusion v1 stretching, modified low-density polyethylene, modified linear low-density polyethylene in which polar groups are graft copolymerized from the viewpoint of productivity, or modified linear low-density polyethylene, It is preferable to use a modified ethylene-vinyl acetate copolymer or the like.

In addition, the heat shrinkage rate and heat shrinkage stress of the heat-shrinkable packaging film of the present invention are determined by the production method, the type of resin constituting the heat-shrinkable packaging film, and the like. Due to smudges etc., furthermore, stretching 13
It can be appropriately selected depending on stretching conditions such as ratio and stretching temperature, or heat treatment conditions such as heat treatment temperature and relaxation rate.

The method for producing the mature shrink packaging film of the present invention is not particularly limited, but it is considered preferable to produce it by the following method. Specifically, a multilayer sheet having the structure of the heat-shrinkable packaging film of the present invention is coextruded from a laminated goo using multiple extruders, the multilayer sheet is cooled and solidified, and then reheated to a temperature at which it can be stretched. vertically,
The ratio is at least 6.2.0 times greater in both the horizontal direction. The tenter method or the inflation method can be used as a method, but it is preferable that bags for packaging roasted pork chunks, etc. be made from a duplex film, and that they can be used in both the vertical and horizontal directions. The inflated method is more preferable because it is easy to adjust the amount of contraction to the same degree. In view of the above, it is preferable that the multilayer notebook before stretching is extruded into a tube shape using a multilayer circular die and laminated so that the outermost layer is a polyamide resin layer. Furthermore, it is natural from the viewpoint of bag manufacturing that the sealant material layer is the innermost layer. Furthermore, when a saponified ethylene-vinyl acetate copolymer is used as the oxygen-barrier resin, the resin can be melt-bonded with the polyamide resin;
It is difficult to melt-bond with resins such as low-density polyethylene resin, linear low-density polyethylene resin, or ethylene-vinyl acetate copolymer. Therefore, modified low-density polyethylene resin, modified linear low-density polyethylene resin, or modified ethylene-vinyl acetate copolymer, etc., in which polar groups are graft-copolymerized, is used as the sealant material layer. The above-mentioned resin is provided as a sealant material layer via. Furthermore, if the stretched coextruded laminated stretched film is left to naturally stand, deformation and surface condition will deteriorate over time due to natural shrinkage of the film.

Therefore, in order to prevent this, heat treatment is performed to an extent that does not deviate from the range of heat shrinkage rate and heat shrinkage stress that are the requirements of this application.
It is more preferable not to reduce the amount of natural shrinkage, and the total thickness of the film for heat-shrinkable packaging of the present invention is suitable for use as packaging for processed meat products such as chunks of grilled pork. If 30 Il to l 0
0 It is appropriate.

The package using the heat-shrinkable packaging film of the second invention of the present application is preferably packaged by the following method. After the inside is degassed, the opening is heat-sealed.Then, the Shun package is heated to 80℃.
immersed in hot water at 95°C for 5 to 20 minutes,
After performing heat shrinkage and heat sterilization at the same time, it is taken out of the hot water and cooled with water.

(Effects of the Invention) The heat-shrinkable packaging film of the present invention can easily heat-shrink-wrap contents with irregular shapes, such as chunks of grilled pork, and the heat-shrinkable packaging film heat-shrinks to form the contents. Since the film adheres closely and there are no creases or creases in the film, they are very small, resulting in a package with a good appearance. Furthermore, the heat-shrinkable packaging film of the present invention has excellent oxygen release properties.
This is combined with the fact that the contents are sterilized by heating in the step of heating and shrinking the package in hot water, making it possible to preserve the contents for a period of time.

In particular, the packaging body using the shrink packaging film of this invention has excellent tightness after heat shrinkage and discharging, even if the packaging bag is made larger so that it can be easily filled with contents. Moreover, it has the great feature that it does not shrink completely and does not remain around the contents, so it looks good.

An even more important feature is that the package does not break at the sealed portion when the package is heat-shrinked in hot water or when it is left to stand naturally after being heat-shrinked. So,
There is no need to make too many selections of bag sizes, etc., and there is an effect that packaging can be carried out smoothly.

Example 1 Copolymer of nylon-6 and nylon-66 (Toshikumai)
Amilan CM-6041), saponified ethylene-vinyl acetate copolymer (Soaseal ET, manufactured by Nippon Gosei Kagaku Kogyo (Aji)), and modified linear low-density polyethylene (Atomer NF350, manufactured by Mitsui Petrochemical Industries, Ltd.). A laminated unstretched tube was obtained using an extruder L1 made by Ohdai and a multilayer surgical die in which the resin was arranged in the order from the outermost layer. The unstretched tube was subjected to lamination HA stretching by a conventional inflation biaxial stretching method to obtain a heat-shrinkable packaging film having a thickness configuration of each layer of 12μ/8μ/20μ from the outermost layer. A packaging test was conducted by vacuum packaging roasted pork chunks in a bag made from the heat-shrinkable packaging film, and heat-shrinking and sterilizing the bag in 90°C hot water for 20 minutes. As a result, the package has excellent tightness, with the heat-shrinkable packaging film and the contents being in close contact with each other, the film having no folds and wrinkles, and no film that has not been completely heat-shrinked remaining around the contents. It was. Furthermore, when heating the package in hot water, or when removing it from the hot water and releasing it naturally, remove the torn bag from the seal 11. There was no.

The heat shrinkage rate of the heat-shrinkable packaging film in 80°C hot water is 0.23% and 22%, respectively. The a-stress was 78 g/cm and 74 g/cm in the longitudinal and transverse directions, respectively.Furthermore, the sealing strength of the heat-shrinkable packaging film in hot water at 95°C was 176 g/am; Heat shrinkage stress in vertical and horizontal directions in water: 125 g/c+n and 117 g
/cm. In addition, the seal strength of the heat-shrinkable packaging film when left to stand after being heated in hot water at 95°C is 1740 g/cm; The shrinkage stress in the longitudinal and transverse directions was 360 g/cm and 340 g/cm, respectively.

Example 2 Amiran CM-1021 made by Nylon-6 (Toshiku Co., Ltd.)
), saponified ethylene-vinyl acetate copolymer, modified linear low-density polyethylene, and linear low-density boethylene (Tsurtozex 2020 manufactured by Mitsui Petrochemical Industries, Ltd.)
Using an extruder with a die of L) and a multilayer surgical die, a laminated unstretched tube was obtained in which the resin was arranged in the order from the outermost layer to the outermost layer. The unstretched tube was treated as in Example 1,
Laminated and stretched in an inflator 7-uniaxial stretching direction θ4,
Layer thickness configuration is 12μ/8μ15μ/20 from the outermost layer
A heat-shrinkable packaging film of /Z was obtained. Using the obtained packaging film, a heat yield i11 packaging test was carried out on grilled pork chunks in 95° C. hot water for 5 minutes in the same manner as in Example 1. As a result, as in Example 1, a package was obtained that had a slightly different tightness and had a good appearance.

And 1. When heating approximately in water, or 1. When the package was taken out of water and left to stand naturally, the package did not break at the sealed portion.

The heat shrinkage rate of the heat shrink packaging film J1 in 80"C hot water is 16% and 14%, respectively, and the heat shrinkage rate in 80"C hot water is 16% and 14%, respectively. The stresses were 03 g/am and 511 g/cm in the longitudinal and transverse directions, respectively.

Furthermore, the sealing strength of the heat-shrinkable packaging film in hot water at 95°C is 340 g/cm, and the heat shrinkage stress in the longitudinal and lateral directions in hot water at 95°C is 108 g/cm. !
= IO2g/am. In addition, the sealing strength of the heat-shrinkable packaging film when left to stand naturally after being heated in 95°C hot water is strong, with a rating of 2170°C.
g/cca, shrinkage response in longitudinal and transverse directions when left to stand after heating in hot water at 95°C: 1240 g/ca
+ and 240 g/cm.

Comparative Example 1 A 15μ thick heat-shrinkable film made of nylon-6, a 10μ thick unstretched ethylene-vinyl acetate copolymer saponified film, and a 35μ thick low-density polyethylene (Sumitomo Chemical Co., Ltd.) Sumikasen F-208) film was laminated by a conventional dry lamination method in the above film order to obtain a heat-shrinkable packaging film.

Using the obtained heat-shrinkable packaging film, a heat-shrinkable packaging test was conducted on roasted pork chunks in hot water at 80°C in the same manner as in Example 1. As a result, in the package, the heat-shrinkable packaging film does not adhere to the contents sufficiently, the film has many folds and wrinkles, and moreover, a large amount of the film that has not been completely heat-shrinked remains around the contents, resulting in a poor appearance. It lacked urgency.

The heat shrinkage rates of the heat shrink packaging film in the 80°C hot water in the longitudinal and lateral directions are 8% and 7%, respectively, and the heat shrinkage stress in the 80°C hot water is The values were 32 g/am and 29 g/cm in the longitudinal and lateral directions, respectively, and both did not satisfy the conditions of each invention of the present application. Moreover, the seal strength in hot water at 95°C is 280 g/am, and the thermal shrinkage stress in the longitudinal and lateral directions in hot water at 95°C is 52 g/c111.
It shows a value stronger than 8g/cm, and the seal strength when left naturally after heating in 95℃ hot water is 18g/cm.
At 60 g/cm, the shrinkage stress in the longitudinal and transverse directions was 177 g/cm, which was stronger than the 165 g/an under the same conditions, and both values were similar to those in each invention of the present application.

Comparative Example 2 Copolymer of nylon-6 and nylon-66, saponified ethylene-vinyl acetate copolymer, and modified ethylene-
Vinyl acetate copolymer (Tubatic A manufactured by Mitsubishi Kasei Corporation)
I'-112E) was coextruded in the same manner as in Example 1, and 15μ/8μ/17
A heat-shrinkable packaging film having a thickness of μ was obtained. Using the obtained heat-shrink packaging film, as in Example I,
Heat shrink packaging tests were conducted on roasted pork chunks in hot water at 95°C and 90°C. As a result, the bag broke at the sealed portion during heat shrinkage not only at 95°C but also at 90°C.

The heat shrinkage stress of the heat shrink packaging film in the longitudinal and transverse directions in hot water at 95°C is 142 g/cm and 140 g/cm.
In terms of g/cm, the seal strength in hot water at 95° C. was weaker than the heat shrinkage stress and could not be measured because it broke when immersed in hot water. Furthermore, even in hot water at 90°C, the seal strength was weaker than the heat shrinkage stress and could not be measured. Furthermore, the thermal shrinkage rates in the longitudinal and transverse directions in hot water at 80°C are 25% and 24%, and the thermal shrinkage stress in the longitudinal and transverse directions in hot water at 80°C is 88 g/ c+n and 8
6 g/cm, which is the same value as in each invention of the present application. Furthermore, after heating in hot water at 95°C, the shrinkage stress in the vertical and horizontal directions when left to stand naturally was 179 g/Cff1 and 172 g/cra, respectively.
The seal strength could not be measured because it broke 11'r when immersed in hot water.

Comparative Example 3 A laminated heat-absorbing film 11 of a copolymer of nylon-6 and nylon-66 and a phenol compound of an ethylene-hinyl acetate copolymer was obtained by an inflation uniaxial stretching method. Ethylene-hinyl acetate copolymer (Sumitomo Chemical Co., Ltd. Ring Evati L-D-202) was added to the saponified ethylene-hinyl 61-acid copolymer layer on the top of the laminated heat-shrinkable film.
The film of 1F) was dry laminated to obtain a heat-shrinkable packaging film having a thickness of 15μ/15μ/20μ from the polyamide resin layer side. Using the obtained heat-shrinkable packaging film, a heat-shrinkable packaging test was conducted on roasted pork chunks in hot water at 95°C in the same manner as in Example 1. As a result, Comparative Example 2
Similarly, the bag broke at the sealed part during heat shrinkage in hot water.

The melting point of the ethylene-vinyl acetate copolymer film used for the heat-shrinkable packaging film was 95°C or lower.

In addition, the heat shrinkage stress of the heat shrink packaging film in 95°C hot water in the longitudinal direction and the groove direction is 102 g/cm and 97 g/c.
The seal strength in hot water at 95°C was weaker than the heat shrinkage stress and could not be measured. Moreover, the thermal shrinkage rates in the longitudinal and horizontal directions in hot water at 80°C are 18% and 20%, and the thermal shrinkage stress in the longitudinal and horizontal directions in hot water at 80°C is 68 g. /am and 71g/am, both of which showed the same numerical values as in each invention of the present application. Furthermore, 95
After being heated in hot water at ℃, the shrinkage stress in the vertical and horizontal directions is 145 g/cm and 150 g/cm, respectively.
However, it was not possible to measure the seal strength.

Comparative Example 4 The ethylene-vinyl acetate copolymer saponified layer side of the faFJ heat-shrinkable film obtained in Comparative Example 3 was coated with vinyl acetate resin Emultan Quib as a no-lant material to produce a heat-shrinkable packaging film. I got it. Using the heat-shrinkable packaging film, a heat-shrinkable packaging test was conducted on roasted pork chunks in hot water at 95°C in the same manner as in Example 1. As a result, the bag did not break from the /-ru part when it was heated and shrunk in hot water, but it did break from the sealed part when it was taken out from the hot water and left to stand naturally.

The shrinkage stress in the longitudinal and lateral directions of the heat-shrinkable packaging film when it is left to naturally after being heated in hot water at 95°C is 4.
At 40 g/cm and 420 g/cm, the seal strength under the same conditions was weaker than the shrinkage stress, and could not be measured because it could break when left alone. Moreover, 80°
The vertical and horizontal yields of C in hot water are 27% and 28%, and therefore, the vertical and horizontal yields of C in hot water at 80°C are J is 90g/am and 93g/c
m, and both showed the same number IM as in each invention of the present application.

Furthermore, the seal strength in 95℃ hot water is 220g/c.
m, the shrinkage stress in the longitudinal direction and the transverse direction was 186 g/cm and l 9 I g/cm, showing the same rXl value as in each invention of the present application.

Claims (1)

[Claims] 1. At least one polyamide resin layer (A) and at least one thermoplastic resin layer with excellent oxygen barrier properties (B)
and a heat-sealable thermoplastic resin layer (C) on at least one surface, the film having a heat shrinkage rate of 10% or more in both the longitudinal and transverse directions in hot water at 80°C, The heat shrinkage stress in hot water at 80°C is 50 g/cm or more in both the longitudinal and horizontal directions, and the seal strength of the film in hot water at 95°C is It is stronger than the heat shrinkage stress of the film at 95°C.
The sealing strength when the film is heated in hot water at 95°C and then left to stand is stronger than the shrinkage stress when the film is left to stand after being heated in hot water at 95°C. Shrink wrapping film. 2. The heat-shrinkable packaging film according to claim 1, wherein the polyamide resin layer (A) is a copolymer of nylon-6 and nylon-66. 3. Heat shrinkage according to claims 1 and 2, wherein the thermoplastic resin layer (B) with excellent oxygen barrier properties is a vinylidene chloride resin or a saponified ethylene-vinyl acetate copolymer. Packaging film. 4. Claim 1, wherein the heat-sealable thermoplastic resin layer (C) is low-density polyethylene with a melting point of 95°C or higher, linear low-density polyethylene, ethylene-vinyl acetate copolymer, or ionomer resin. A heat-shrinkable packaging film according to items 1 to 3. 5. The heat-shrinkable packaging film according to claims 1 to 4, wherein the polyamide resin layer (A) is the outermost layer. 6. Low-density polyethylene according to claim 4,
A patent claim that is linear low-density polyethylene or modified low-density polyethylene in which an ethylene-vinyl acetate copolymer is graft-copolymerized with a polar group, modified linear low-density polyethylene, or modified ethylene-vinyl acetate copolymer. A heat-shrinkable packaging film according to items 1 to 5. 7. At least one polyamide resin layer (A) and at least one thermoplastic resin layer with excellent oxygen barrier properties (B)
and a heat-sealable thermoplastic resin layer (C) on at least one surface, the film having a heat shrinkage rate in hot water of 80° C. of 10% or more in both the longitudinal and transverse directions, The heat shrinkage stress in hot water at 80°C is 50 g/cm or more in both the longitudinal and horizontal directions, and the seal strength of the film in hot water at 95°C is The seal strength is stronger than the heat shrinkage stress at
After heating the film in hot water at 95°C, a bag is made using a heat-shrink packaging film that is stronger than the shrinkage stress when left naturally, the bag is filled with the item to be packaged, and after vacuum packaging. ,
A package characterized by being heat-shrinked and sterilized in hot water.