JPH09286086A - Heat-shrinkable multilayered barrier film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-shrinkable multilayered barrier film adapted to the heat shrinkage vacuum packing of various contents, especially, foods to be utilized in the formation of a package, having low temp, shrinkability and gas barrier properties, wide in a superposing seal temp. range and having inner surface oil resistance and pravical transparency. SOLUTION: In a heat-shrinkable multilayered barrier film, a seal layer is composed of a polyethylene resin containing 10-25wt.% of at least one kind of olefin selected from 4-12C α-olefins and having density of 0.860-0.910g/cm<3> and a gas barrier layer is composed of a polyvinylidene chloride resin and containing vinyl chloride in a ratio of 11-28wt.% as a copolymer component as a constituent unit of a structure wherein the average polymerization chain length of vinyl coloride is 1.2-2.5 and the number of chains thereof is 30-35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat shrinkable multilayer barrier film for vacuum packaging, which uses a specific polyethylene resin for a sealing layer and a specific polyvinylidene chloride resin for a gas barrier layer. is there. Also,
The heat-shrinkable barrier film obtained by the present invention is also effective in the field of packaging raw meat.

[0002]

2. Description of the Related Art When a vinylidene chloride resin (vinylidene chloride-vinyl chloride copolymer) is used for a gas barrier layer in a conventional heat-shrinkable multilayer barrier film, it is disclosed in, for example, JP-A-6-33978. The polyvinylidene chloride resin layer has a barrier property and the other resin layers have a heat shrinkage property. However, even if the other layers are improved to improve the heat shrinkage performance, the gas barrier layer using the polyvinylidene chloride resin (vinylidene chloride-vinyl chloride copolymer) has a low heat shrinkage rate, so this gas barrier The result is that the layers tend to interfere with the heat shrink performance of the multilayer film. Due to this, it was not possible to obtain a heat-shrinkable multilayer barrier film having high shrinkage performance.

Further, since the shrinkage rate of the layer having shrinkage performance and the vinylidene chloride resin layer are extremely different, peeling phenomenon occurs at the interface even if a seal layer is present between the layers, and the film is whitened. , The transparency was sometimes lowered. Further, in the conventional heat-shrinkable multi-layer barrier film, when a packaged object is put in and sealed, there is a case where a sealing defect easily occurs depending on a vacuum packaging machine in an overlapping portion of the films.

That is, in the prior art, the heat-shrinkable multilayer barrier film for vacuum packaging has a good heat-shrinkability, a good sealability (sealing property in a superposed state, foreign matter sealing property (oil, dust, etc.)), and actual use. There was room for improvement on the transparency above.

[0005]

The present invention has high low-temperature heat shrinkage performance, high barrier properties, and properties suitable for vacuum packaging, that is, good sealing properties (sealing property in a superposed state, foreign substance sealing property). (Oil and dust, etc.)), and an object thereof is to provide a heat-shrinkable multilayer barrier film having transparency in actual use. Another object of the present invention is to provide a heat-shrinkable multilayer barrier film for vacuum packaging which is also useful for packaging raw meat.

[0006]

In order to solve the above-mentioned problems, the inventors of the present invention have found that, as a result of their studies, they use polyvinylidene chloride and a specific polyethylene, which have more heat-shrinkability than before, in a heat-shrinkable multilayer barrier film. As a result, a film having a high heat shrinkage property, a good sealing property, and a transparency in practical use was found, and the present invention was completed.

That is, according to the present invention, in the heat-shrinkable multi-layer barrier film, the sealing layer is α-containing 4 to 12 carbon atoms.
A polyethylene resin containing 10 to 25% by weight of at least one olefin selected from olefins, and the density of the polyethylene resin is 0.860 g / c.
m ^{3 to} 0.910 g / cm ³ , the gas barrier layer is made of vinylidene chloride resin, and the copolymerization component of the vinylidene chloride resin is vinyl chloride, and the composition ratio of vinyl chloride is 11% by weight. A heat-shrinkable multi-layer barrier film having a structural unit of ˜28% by weight, an average polymerization chain length of vinyl chloride of 1.2 to 2.5, and a chain number of vinyl chloride of 30 to 35. .

Hereinafter, the present invention will be described in detail. First,
A method of using the heat-shrinkable multilayer barrier film in the vacuum packaging process will be described. In the vacuum packaging process, the article to be packaged is first put in a tubular heat-shrinkable multilayer barrier film for vacuum packaging. This is set in a vacuum packaging machine and packaged. More specifically, (1) The tubular film containing the article to be packaged is placed in the decompression chamber with the opening protruding from the decompression chamber.

(2) The decompression chamber is closed, and at the same time, the film protruding from the decompression chamber is cut off. (3) The vacuum pump operates and the decompression chamber is in a decompressed state. (4) In this state, the opening is sealed. (5) Finally, the decompression chamber is returned to atmospheric pressure, the decompression chamber is opened, and the packaged object wrapped with the film is taken out.

In the above (3), wrinkles are likely to occur near the opening of the film depending on the state of (1) placed and the shape of the packaged object, and the sealing is performed in the state where the films are overlapped in (4). There are many cases. Surprisingly, by forming the sealing layer from the polyethylene resin having the constitution of the present invention, even if the film is folded and folded, it is possible to perform sealing without leakage.
Further, since the seal layer of the present invention also has shrinkability, it is possible to improve the shrinkage performance more than ever before.

The polyethylene resin constituting the seal layer of the present invention must contain 10 to 25% by weight of at least one olefin selected from α-olefins having 4 to 12 carbon atoms, and has a density. 0.860 g / cm
It should be between ^{3 and} 0.910 g / cm ³ . further,
It is preferable to contain 10 to 25% by weight of at least one olefin selected from α-olefins having 4 to 8 carbon atoms, and have a density of 0.880 g / cm ^{3 to} 0.
It is preferably 905 g / cm ³ .

The density of this polyethylene resin is 0.91.
Α greater than 0 g / cm ³ and copolymerized with ethylene
-If the content of the olefin is 11 weight or less, the sealing property in the folded state of the film deteriorates. Further, when the density is less than 0.860 g / cm ³ and the content of α-olefin copolymerized with ethylene is more than 25% by weight, blocking is apt to occur, which makes it difficult to put an object to be packaged in the film and vacuum packaging. Workability in the process is reduced.

The polyethylene resin used in the present invention is a resin obtained by copolymerizing one or more α-olefins such as butene-1, hexene-1, 4 methylpentene-1 and octene-1 with ethylene. Etc. When the same type of polyethylene resin as the above-mentioned seal layer is used for the outer surface layer of the barrier film of the present invention, the effect becomes more remarkable.

Next, in the polyvinylidene chloride resin constituting the gas barrier layer of the present invention, the composition ratio of vinyl chloride is 11% by weight to 28% by weight, and the average polymerization chain length of vinyl chloride is 1.2. It is necessary to use a structure of ˜2.5 and a chain number of 30 to 35 as a constitutional unit. When the composition ratio of this vinyl chloride is less than 11% by weight, the average polymerization chain length of vinyl chloride is less than 1.2, and the value of the number of chains is less than 30, the required sufficient shrinkage performance cannot be obtained. Further, when the content of vinyl chloride exceeds 28% by weight, the compatibility of vinylidene chloride and vinyl chloride deteriorates, and coloring tends to occur. further,
When the average polymerization chain length of vinyl chloride exceeds 2.5, it is difficult to obtain a heat-shrinkable multilayer barrier film that sufficiently satisfies the required properties from the viewpoint of gas barrier properties.

The composition ratio of vinyl chloride is required to be 11% by weight to 28% by weight, as described above, from the viewpoint of the storability of the article to be packaged due to the barrier performance and the shrinkability of the gas barrier layer itself. More preferably 14% by weight to 28
% By weight. As described above, in the present invention, the polyethylene resin of the seal layer and the polyvinylidene chloride resin of the gas barrier layer are specified and combined to enhance the high shrinkage performance of the gas barrier layer at a low temperature, and the seal layer and the gas barrier layer. The effect of balancing the shrinkage performance of the above and preventing the deterioration of transparency and coloring due to the peeling phenomenon between the gas barrier layer and the seal layer, which has been a problem of the conventional gas barrier film, is brought about.

The weight average molecular weight of the vinylidene chloride resin used in the present invention is preferably 5,000 to 500,000, more preferably 20,000 to 200,000.
0 is good. The weight average molecular weight can be measured using a gel permeation chromatograph (GPC) method. More specifically, the copolymer is dissolved in tetrahydrofuran at 0.05%, and monodisperse polystyrene having a known molecular weight is measured as a standard substance. As a measuring device, 8000 series manufactured by Tosoh Corporation can be used.

Since the heat-shrinkable multilayer barrier film for vacuum packaging has improved heat-shrinkability as compared with the conventional one,
It can also be used for packaging raw meat from which water and blood exude after vacuum packaging. If the shrinkage is low, wrinkles are likely to occur when heat is shrunk, and water or blood accumulates on the wrinkles, impairing the appearance. The additive to each layer of the heat-shrinkable multilayer film for vacuum packaging of the present invention may be added, if necessary, to the extent that the object of the present invention is not impaired. For example, polyethylene-based resin used for the seal layer includes an antioxidant, a light stabilizer, a processing stabilizer, a lubricant, an antiblocking agent, an antifogging agent,
Various additives selected from antistatic agents and the like can be added.
Moreover, the additive of the polyvinylidene chloride resin used in the gas barrier layer is not particularly limited, and examples thereof include a plasticizer (one example: glycerin ester, etc.), a stabilizer (one example: epoxidized vegetable oil, ethylenediamine tetraacetate, amine). -Based or phenol-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, benzotriazole-based, benzophenone-based, benzoate- or cyanoacrylate-based light stabilizers, hindered piperidine-based light stabilizers, etc. ) And the like. All of these may be added, or one or several of them may be added as required. Furthermore, when adding a plasticizer, for example, the concentration to be added is preferably 0.1% by weight to 7% by weight from the viewpoint of shrinkability, extrudability and barrier property.

In the laminated film of the present invention, the thickness of all layers of the film is not particularly limited, but is 20 to 100 μm.
The range is preferably 40 to 80 μm.
Good range. If the thickness is less than 20 μm, the mechanical strength of the film will be insufficient, and if it exceeds 100 μm, the time required for heat sealing of the film will be undesirably long.
Further, in the layer structure, the thickness of the seal layer is not particularly limited, but the range of 2 to 50 μm is preferable, and the range of 5 to 40 μm is more preferable. 2μ thick
If it is less than m, the effect of hindering heat fusion between the outer surfaces of the bag is insufficient, and if it exceeds 50 μm, the laminated film is curled, which is not preferable.

Although the thickness of the gas barrier layer is not particularly limited, it is preferably in the range of 3 to 30 μm. More preferably, it is 5 to 15 μm. If it is less than 3 μm, the gas barrier property of the laminated film is lowered, and if it exceeds 30 μm, the abuse resistance of the laminated film is deteriorated, which is not preferable. Next, there are various manufacturing methods for obtaining the multilayer film of the present invention, and an example of a preferable manufacturing method will be described. The method for producing a laminated film of the present invention uses an annular multi-layer die to use the above-mentioned vinylidene chloride-based resin as a core layer, and further through the adhesive heat-shrinkable resin layer adjacent to both surfaces of the core layer, Polyethylene resin is used as the outermost layer and the innermost layer, and they are separately thermoplasticized by four extruders, fused and extruded in a five-layer annular multilayer die, and further extruded from the tip of the die to the downstream of the manufacturing process. Part is rapidly cooled with cold water of about 20 ° C. to form a tube-shaped raw material. After irradiating the original fabric with an electron beam, it is passed between a feed nip roll and a take-up roll faster than that, and heated during this period, and air is introduced into the interior as it is to continuously expand and stretch. Further, the stretching end region is cooled by an air ring from which cold air is blown, and then folded, taken up by a nip roll, and wound up as it is to obtain a predetermined film.

The heat-shrinkable multi-layer barrier film obtained by the present invention is particularly suitable for food packaging because it has good low-temperature shrinkage and gas barrier properties.
Used for packing meat such as pigs, chickens, sheep and horses. Due to such characteristics, it can be used for various food packaging applications. For example, ham, sausage,
Processed meat products such as hamburgers, fish and fish fillets, shellfish such as shrimp and crab, processed products such as kamaboko and bamboo rings obtained from them, dried products of seafood, fruits and vegetables, grains such as rice and wheat, In addition, processed products obtained by processing them, cheese,
It is also used for dairy products such as butter, and processed foods such as various prepared foods. Further, it may be used as a packaging material for containers such as foods (for example, lunch boxes) and pharmaceuticals.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to Examples. The following measuring methods and polymers were used in the examples. (Measuring Method of Composition Ratio of Vinyl Chloride) The average polymerization chain length and the number of chains of vinyl chloride were measured by a high-resolution proton nuclear magnetic resonance analyzer: H-NMR (α-400 manufactured by JEOL Ltd.).

A solution prepared by dissolving 5% of a sample in deuterated tetrahydrofuran was measured at a measuring temperature of about 27 ° C.
It was measured by H-NMR of 0 MHz, and the chemical shift in the spectrum was 3.50 based on tetramethylsilane.
Up to 4.20 ppm, 2.80 to 3.50 ppm, 2.0
The integrated values obtained by subtracting the peak derived from the solvent from the peak between 0 and 2.80 ppm are (a), (b),
As (c), the vinyl chloride composition ratio of the vinylidene chloride resin was calculated by the following calculation formula.

Composition ratio of vinyl chloride (wt%) = {6
2.5 × ((c) + (b) / 2) × 100} / {97.
0 × ((a) + (b) / 2) + 62.5 × ((c) +
(B) / 2) (Measuring Method of Average Polymerization Chain Length and Number of Chains of Vinyl Chloride) The average polymerization chain length and number of chains of vinyl chloride are high-resolution proton nuclear magnetic resonance analyzer (H-NMR (α manufactured by JEOL Ltd.). -40
0).

A solution prepared by dissolving 5% of a sample in deuterated tetrahydrofuran was measured at a measuring temperature of about 23 ° C.
It was measured by 0-MHz H-NMR, and the chemical shift in the spectrum was 3.50 based on tetramethylsilane.
4.20 ppm, 2.80 to 3.50 ppm, 2.00
The integrated values obtained by subtracting the peak derived from the solvent from the peak between ˜2.80 ppm are (A), (B),
As (C), it was determined by the following calculation formula.

Average Polymer Chain Length of Vinyl Chloride = 1 + 2 (C) / (B) Number of Chains = 100 × (B) / ((A) + (B) + (C)) (Method for Measuring Density of Polyethylene Resin ) The density of the polyethylene resin used in the present invention is JIS-K7112.
A density gradient tube method specific gravity measuring device manufactured by Shibayama Scientific Instruments Co., Ltd. was used in conformity with the D method. An isopropyl alcohol / water system was used as the specific gravity liquid.

(Measurement Method of Polyethylene Resin Copolymer Composition Ratio) The composition is a carbon nuclear magnetic resonance absorption measuring device (1
3C-NMR). In a given spectrum obtained by 13 C-NMR measurement, it was calculated from the integrated value of the resonance intensity peak derived from the comonomer unit and the integrated value of the resonance intensity peak derived from the ethylene unit.

(Temperature width at which overlapping and sealing is possible) Fold width 40
Put beef (width approx. 250 mm, length approx. 300 mm, thickness approx. 150 mm) into two cylindrical bags of 0 mm length and 650 mm length and about 10 cm at the end of each bag.
2 bags are set at the same time in a vacuum packaging machine so that they overlap each other. Then, the decompression chamber was sealed, and after vacuuming,
Heat sealing is performed under a predetermined temperature condition to vacuum-pack the meat piece. Then, take out 2 bags from the vacuum packaging machine at the same time,
Dip in hot water at 0 ° C. for about 4 seconds to perform heat shrinkage, and then soak in cold water at 5 ° C. to cool.

The heat sealing temperature condition is 70 ° C. to 20 ° C.
Gradually raise it and check the seal on the inner surface of the bag with a seal checker (Ageless R seal checker (manufactured by Mitsubishi Gas Chemical Co., Inc.)) for the presence of pinholes. Let T1 be the temperature at which it is completely performed. Further, the temperature at which the two bags are heat-sealed and do not separate when immersed in cold water is defined as T2.

This (T1-T2) was overlapped to obtain a possible sealing temperature range. For vacuum packaging, use an impulse seal type FVM-WM machine manufactured by Furukawa Seisakusho for a sealing time of 2
Seconds and a cooling time of 2 seconds, and the sealing temperature was changed by changing the voltage. The sticker temperature was measured by sticking a thermo label (sticker for temperature measurement, manufactured by IP Giken Co., Ltd.) on the sticker bar.

Symbol Level value and evaluation ⊚: Overlap sealable temperature range of 60 ° C. or more: Very good superposition sealability. ◯: Overlap sealable temperature range of 40 ° C. or more and less than 60 ° C .: Overlap seal is excellent.

B: Overlap sealable temperature range of 20 ° C. or more and less than 40 ° C .: Overlap sealability is poor. (Low-temperature heat shrinkability) A film cut into squares of 10 cm in length and width is immersed in hot water at 70 ° C for 1 minute to shrink in a relaxed state, and shrinks by averaging the shrinkage ratio with respect to the original length and width. Rate

Symbol Level value and evaluation ⊚: Shrinkage is 33% or more: Very good low temperature heat shrinkability. ◯: Shrinkage rate is 28% to 33%: Excellent low temperature heat shrinkability. Δ: Shrinkage rate is 23% to 28%: Low temperature heat shrinkability is poor. X: Shrinkage rate is less than 23%: Low temperature heat shrinkability is very poor.

(Inner surface oil resistance) One end of the formed tubular film was heat-sealed under the condition that the maximum strength was obtained and cut along the heat-sealing line to manufacture a bag. After applying beef tallow to the bottom seal portion of the bag, raw beef meat was pushed in until it hit the bottom seal portion, and vacuum packaging was performed. This package 2
No. 0 was passed through a hot water shower at 90 ° C. for the time specified below, and the presence or absence of breakage of the bottom seal portion was examined to evaluate the oil resistance on the inner surface. If the number of breaks was one or less, it was considered good.

Symbol Level Value and Evaluation ◎: Good after 12 seconds: Very good oil resistance on the inner surface. ◯: Good after 8 seconds: Excellent inner surface oil resistance. B: Good after 4 seconds: Inner surface oil resistance is poor. ×: Poor even after 4 seconds: Very poor oil resistance on the inner surface.

(Gas Barrier Property) The gas barrier property of the film of the present invention is determined by the oxygen permeability as an index.
The measurement was performed according to D3985. Symbol Level value and evaluation A: Less than 30: Very excellent gas barrier property.

X: 1000 or more: Very poor gas barrier property. (Polymer used in this example and comparative example) PE1: ethylene-butene-1 copolymer, density 0.90
2 g / cm ³ , copolymer content 12% by weight PE2: ethylene-hexene-1 copolymer, density 0.9
02 g / cm ³ , copolymer content 15% by weight PE3: ethylene-butene-1 copolymer, density 0.91
6 g / cm ³ , copolymer content 7% by weight PVD1: vinylidene chloride-vinyl chloride copolymer, vinyl chloride content 15% Average polymerization chain length 1.3, chain number 33.0 PVD2: vinylidene chloride-vinyl chloride copolymer, Vinyl chloride content 27 weight Average polymer chain length 2.4, chain number 34.1 PVD3: vinylidene chloride-vinyl chloride copolymer, vinyl chloride content 10 weight Average polymer chain length 1.2, chain number 24.6 PVD4: vinylidene chloride Vinyl chloride copolymer, vinyl chloride content 29% by weight EVA1: ethylene-vinyl acetate copolymer, density 0.9
36 g / cm ³ , vinyl acetate content 15% by weight

[0037]

Example 1 PE was used as a seal layer by using four extruders.
1, a layer made of PVD1 as a gas barrier layer, a layer made of EVA1 between the seal layer and the gas barrier layer, and a layer made of PE1 on the outside of the gas barrier layer with a layer made of EVA1 interposed therebetween. Using each layer from the sealing layer PE1: EVA1: PVD1: EVA1: PE1
(= 20%: 40%: 10%: 20%: 10%) 5-layer structure was extruded from a circular multilayer die.

The extruded laminate was quenched with cold water at 20 ° C. and folded to obtain a parison with a folding width of 100 mm and a thickness of 660 μm. This parison has ENERGYSCIEN
CEINC. Electrocurtain <registered trademark> (non-scanning type) manufactured by Japan, using an accelerating voltage of 175 KV and an irradiation dose of 12
The electron beam irradiation was performed under the condition of megarad. Air is injected into the cross-linked parison, which is further heated, and inflation is biaxially stretched to obtain a folding width of 400 mm and an average thickness of 60 μm.
A tubular film of m was obtained.

Then, one end of the obtained tubular film was heat-sealed under the condition that the maximum strength was obtained, cut along the heat-sealing line, and the folding width was 400 mm and the length was 650 mm.
I made a bag.

[0040]

Example 2 The same procedure as in Example 1 was repeated except that PE2 was used for the seal layer in Example 1, to obtain a tubular film having a folding width of 400 mm and an average thickness of 60 μm. Furthermore, the folding width of 400 m from the obtained film
A bag having a length of m and a length of 650 mm was manufactured.

[0041]

Comparative Example 1 A tubular film having a folding width of 400 mm and an average thickness of 60 μm was obtained by repeating the same procedure as in Example 1 except that PE3 was used as the seal layer in Example 1. Furthermore, the folding width of 400 m from the obtained film
A bag having a length of m and a length of 650 mm was manufactured.

Table 1 collectively shows the evaluation results of the above Examples 1, 2 and Comparative Example 1. That is, as can be seen from the evaluation results of Examples 1 and 2, even if the kind of the polyethylene resin copolymer used in the seal layer is changed within the range of C4 to C8, the structure of the above range is obtained. By forming the seal layer with a polyethylene resin, a film having low-temperature shrinkability, a temperature range capable of overlapping and sealing, and oil resistance on the inner surface can be obtained. As shown in Comparative Example 1, when a polyethylene-based resin out of the above range is used, the low-temperature shrinkability and the temperature range over which superposition sealing is possible become extremely poor.

[0043]

Example 3 PVD was used for the gas barrier layer in Example 1.
The same procedure as in Example 1 was repeated except that 2 was used to obtain a tubular film having a folding width of 400 mm and an average thickness of 60 μm. Further, from the obtained film, a folding width of 4
A bag having a length of 00 mm and a length of 650 mm was manufactured.

[0044]

Comparative Example 2 PVD was used as the gas barrier layer in Example 1.
The same procedure as in Example 1 was repeated except that 3 was used to obtain a tubular film having a folding width of 400 mm and an average thickness of 60 μm. Further, from the obtained film, a folding width of 4
A bag having a length of 00 mm and a length of 650 mm was manufactured.

[0045]

COMPARATIVE EXAMPLE 3 PVD was used as the gas barrier layer in Example 1.
The same procedure as in Example 1 was repeated except that No. 4 was used to obtain a tubular film having a folding width of 400 mm and an average thickness of 60 μm. Further, from the obtained film, a folding width of 4
A bag having a length of 00 mm and a length of 650 mm was manufactured.

[0046]

Comparative Example 4 PE1 was used as the gas barrier layer in Example 1.
The same procedure as in Example 1 was repeated except that the above was used to obtain a tubular film having a folding width of 400 mm and an average thickness of 60 μm. Further, from the obtained film, a folding width of 4
A bag having a length of 00 mm and a length of 650 mm was manufactured.

The evaluation results of Example 1, Example 3, Comparative Example 2, Comparative Example 3 and Comparative Example 4 are summarized in Table 2.
As can be seen from the evaluation results of Example 1, Comparative Example 1 and Comparative Example 2, the low temperature shrinkability is the characteristic of the polyethylene resin used for the seal layer and the characteristic of the polyvinylidene chloride resin used for the gas barrier layer. By having both of them, it is possible to obtain a film having remarkably high performance.

That is, conventionally, the film in this field has shrinkage performance, sealing performance, and barrier performance in each layer,
Films with each performance have been manufactured by making them multi-layered, but the shrinkage rate of the polyvinylidene chloride resin layer, which is the gas barrier layer, is significantly lower than other layers, and it has shrinking performance. Even if the layer was improved, the polyvinylidene chloride resin layer could not follow the film of other layers, and it was difficult to obtain high shrinkage performance at low temperature. Therefore, in the present invention, it is possible to obtain a film having a high shrinkage performance at a lower temperature than before by making the polyethylene resin for the seal layer, particularly the polyvinylidene chloride resin used for the gas barrier layer, capable of largely shrinking even at a low temperature. did it.

When a layer made of a polyvinylidene chloride resin outside the scope of the present invention is used as shown in Comparative Examples 2 and 3, the shrinkage rate is low and the layer is colored, so that it cannot be used as a product. .

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

EFFECTS OF THE INVENTION According to the present invention, a heat shrinkage, a gas barrier property, a wide sealing seal temperature range, an oil resistance on the inner surface, and a transparency in practical use, which are particularly suitable for packaging fresh meat, are used. A shrinkable multilayer barrier film can be obtained.

Claims (3)

[Claims] 1. A heat-shrinkable multi-layer barrier film, wherein the sealing layer is made of a polyethylene resin containing 10 to 25% by weight of at least one olefin selected from α-olefins having 4 to 12 carbon atoms. The density of the system resin is 0.860 g / cm ^{3 to} 0.910
g / cm ³ , the gas barrier layer is made of vinylidene chloride-based resin, and the copolymerization component of the vinylidene chloride-based resin is vinyl chloride, and the composition ratio of the vinyl chloride is 11% by weight to 28% by weight, The average polymerization chain length of vinyl chloride is 1.2 to 2.5, and the number of chains of vinyl chloride is 30 to 3
A heat-shrinkable multilayer barrier film having the structure of 5 as a constituent unit. 2. A polyethylene resin containing 10 to 25% by weight of at least one olefin selected from α-olefins having 4 to 8 carbon atoms, and the density of the polyethylene resin is 0.88 g / cm 2. ^{3 to} 0.905 g
The heat-shrinkable multi-layer barrier film according to claim 1, wherein the heat-shrinkable multi-layer barrier film has a thickness of 1 / cm ³ . 3. The heat-shrinkable multilayer barrier film for vacuum packaging according to claim 1, which is used for vacuum packaging of raw meat.