JP2001353820A - Stretch film for packaging food - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stretch film for packaging food satisfying required characteristics such as transparency or the like and having no problem from an aspect of disposal or food sanitation. SOLUTION: The surface layers (A-layers) on both sides of a laminated film comprising at least a three-layered structure comprise at least one kind of an ethylenic copolymer, which contains 5-25 wt.% of a monomer other than ethylene, selected from an ethylene/vinyl acetate copolymer, an ethylene/ethyl acrylate copolymer, an ethylene/methyl acrylate copolymer or the like and the layer (B-layer) on the center side of the A-layers comprises a composition containing crystalline polypropylene (B1) with an MFR of 0.1-10 g/10 min and a copolymer (B2) with an α-olefin content of 70-90 wt.% and a density of 0.910 g/cm3 or less. being a copolymer of ethylene and at least one kind of an α-olefin selected from 3-12C α-olefins.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretch film for food packaging, and more particularly to a film having a layer composed of a specific composition laminated thereon, which is transparent, glossy, transparent, stretchable, and heat-sealed. Excellent in properties and deformation recovery,
Further, the present invention relates to a stretch film for food packaging which has no problem in disposal property and food hygiene.

[0002]

2. Description of the Related Art In general, the following characteristics are required for a film in which foods such as fruits and vegetables, fresh fish, fresh meat, prepared foods and the like are stretch-wrapped directly or placed on a plastic tray. (1) Transparency, gloss, and transparency for improving product value (display effect) (2) Breathability and anti-fog properties for maintaining freshness and displaying effect of foods containing much moisture Water vapor permeability for preventing drying and maintaining freshness (4) Self-adhesiveness and heat sealing properties for maintaining tight packaging (5) Uniform elongation for obtaining tight packaging and elongation properties for recoverability (6) Suitability of packaging machine for improving workability of stretch packaging

Conventionally, a plasticized polyvinyl chloride film has been used as a film satisfying such characteristics. However, since the plasticized polyvinyl chloride film uses a large amount of a plasticizer, there is a problem that the water vapor permeability is large and the plasticizer easily migrates to the package. Also,
When the package is stored at a low temperature due to poor cold resistance, there is a disadvantage that the film is hard and brittle and easily broken.

[0004] Further, with respect to post-use processing of the film, the plasticized polyvinyl chloride film tends to cause the plasticizer to flow out of the film after being discarded, and the plasticizer that has flowed out may contaminate the sea or river. In addition, when incinerated at a garbage disposal site, hydrogen chloride gas is generated, so special treatment equipment is required for the incinerator.When incinerated at home, the released toxic gas is directly preferable to health. In addition, there is a problem that it contributes to promotion of acid rain.

As a composition suitable for a stretch film which solves these problems, a composition described in Japanese Patent Publication No. 59-38976 has been proposed. However, in the case of this composition, the most important transparency, gloss, and transparency are not sufficient and are not at a satisfactory level in the inflation method which is a conventionally known film forming method.
Also, the packaging workability is not sufficient. Further, JP-A-63-
No. 41550 has been proposed, but this composition satisfies several points required for a stretch film only by stretching, but the elongation and deformation when the most important film is stretched. The properties that are less recoverable and required as a stretch film are
It is far apart. Also, as a film,
Japanese Patent Publication No. 2-52624 has been proposed. However, since this film is also a stretched film, it has little elongation and deformation recovery when the most important film is stretched. Are far apart.

Further, a layer composed of an ethylene-vinyl acetate copolymer having a vinyl acetate unit content of 1 to 10% by weight, and a layer composed of an ethylene-vinyl acetate copolymer having a vinyl acetate unit content of 11 to 50% by weight. (Japanese Patent Laid-Open Publication No. 55-8 / 78).
No. 1155). However, for this food packaging film, there is still a problem that the temperature range in which heat sealing can be performed by an automatic packaging machine is narrow, so that a film other than the heat sealing portion is melted and perforated.
In addition, there is a problem that the cutting property of the film by the cutter blade in the automatic packaging machine, the slipperiness with the tray or the article to be packaged, and the rubber-like elasticity are inferior to the automatic packaging machine.

[0007] Further, ethylene and α-
A random copolymer of at least one α-olefin selected from olefins and propylene,
An ethylene having a vinyl acetate unit content of 5 to 25% by weight on both surfaces of a layer mainly containing a resin having an olefin unit content of 4 to 19% by weight and a melt flow rate of 1 to 10 g / 10 minutes; A stretch packaging film having a total thickness of 6 to 40 μm, in which a layer mainly composed of a vinyl acetate copolymer resin is laminated (JP-A-61-446).
No. 35). However, this film for stretch packaging is inferior in transparency and gloss of the film, in particular, it is difficult to balance the physical properties of the film in the vertical and horizontal directions, is inferior in cutability, and does not sufficiently have uniform elongation characteristics.

Further, the layer containing butene-1 resin as a main component has an ethylene-based resin having a vinyl acetate content of 5 to 25% by weight.
There has been proposed a film for stretch packaging in which a layer mainly composed of a vinyl acetate copolymer resin is laminated (see JP-A-61-89040). However, the stretch packaging film has a relatively good vertical and horizontal balance of physical properties of the film, but is inferior in transparency and gloss, particularly transparency and uniform elongation characteristics of the film.

As described above, many stretch packaging films have been proposed. However, a stretch film for food packaging that satisfies the above-mentioned required characteristics and has no problem in disposal treatment and food hygiene has not yet been proposed. Is the current situation.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to provide excellent transparency, gloss, transparency, elongation characteristics, deformation recovery, suitability for packaging machines, workability, etc., and problems with disposal and food hygiene. The object of the present invention is to provide a stretch film for food packaging.

[0011]

SUMMARY OF THE INVENTION The present inventor has solved the above-mentioned problems of the conventional film, has uniform elongation characteristics of the film, and is excellent in transparency, gloss, and transparency. The heat sealable temperature range is wide enough and the packaging workability is excellent, and it also satisfies the requirements for the stretch packaging property of foods, and furthermore, it does not cause environmental problems in the processing after use, and it is a problem in food hygiene. We continued our research to develop a stretch film without any. As a result, they have found that a laminate having a layer composed of a specific composition is a film that meets the above-mentioned object. The present invention has been completed based on such findings.

That is, the present invention relates to a laminated film having at least a three-layer structure, wherein the surface layer (A layer) on both sides of the film has a content of a monomer other than ethylene of 5 to 2 or less.
5% by weight of ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene- The surface layer (A) comprises at least one ethylene-based copolymer selected from methyl methacrylate copolymer, ethylene-ethyl methacrylate copolymer, and ionomer resin.
The layer (layer B) closer to the center than the layer (layer B) is composed of a crystalline polypropylene (B ₁ ) having a melt flow rate of 0.1 to 10 g / 10 min and at least ethylene and carbon number of 3 to 12
At least one α selected from α-olefins
A copolymer with an olefin having an α-olefin content of 70% by weight or more and 90% by weight or less and a density of 0.1% or less.
A stretch film for food packaging characterized by comprising a composition containing a copolymer (B ₂ ) of 910 g / cm ³ or less.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The stretch film for food packaging of the present invention is a laminated film having at least a three-layer structure, wherein the surface layers on both sides are (A layer), and the layer on the center side of this (A layer) layer. Is (B layer). That is, the basic structure of the stretch film for food packaging of the present invention is (layer A) /
(B layer) / (A layer), but a plurality of layers may be provided between (A layer) and (B layer) or between (B layer).

The ethylene-based copolymer used in the surface layer (layer A) of the present invention is an ethylene-vinyl acetate copolymer having a content of a monomer other than ethylene of 5 to 25% by weight, an ethylene-acrylic copolymer. Ethyl acid copolymer, ethylene-
Methyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-
It is at least one polymer selected from a methyl methacrylate copolymer, an ethylene-ethyl methacrylate copolymer, and an ionomer resin. Among them, an ethylene-vinyl acetate copolymer is most preferred. The content of the monomer other than ethylene is more preferably 7 to 25% by weight, further preferably 10 to 20% by weight. If the content of the monomer other than ethylene is less than 5% by weight, the sealing property, transparency, flexibility, etc. may not be sufficiently obtained,
If it exceeds 25% by weight, the strength properties may be reduced and blocking may occur.

Further, the ethylene copolymer constituting the surface layer (layer A) has a melt flow rate at 190 ° C. of preferably 0.1 to 10 g / 10 min, more preferably 0.5 to 10 g / 10 min.
５5 g / 10 min. This melt flow rate is
If the amount is less than 0.1 g / 10 minutes, there is a possibility that there is a problem in extrudability. If the amount exceeds 10 g / 10 minutes, there is a possibility that strength properties are reduced and molding stability cannot be obtained.

The surface layer (layer A) of the present invention can use the above resin alone or as a composition of two or more kinds. Further, the surface layer (A layer) of the present invention is composed of the above-mentioned resin composition, and further has a suitable slip property, self-adhesive property,
Additives can be added to obtain antistatic properties and antifogging properties. Specifically, sorbitan fatty acid esters,
Sorbitan monooleate such as glycerin fatty acid ester and polyglycerin fatty acid ester, sorbitan monolaurate, sorbitan monobehenate, sorbitan monostearate, glycerin monooleate, glycerin monostearate, glycerin monolaurate, glycerin monobehenate, diglycerin Monolaurate, diglycerin monostearate, diglycerin monooleate,
Examples include, but are not limited to, tetraglycerin monooleate, tetraglycerin monostearate, hexaglycerin monolaurate, hexaglycerin monooleate, decaglycerin monolaurate, decaglycerin monostearate, decaglycerin monooleate, and the like. Absent. These fatty acid esters are used singly or as a mixed composition, and the amount of addition is usually 0.1 to 5.0% by weight, preferably 0.5 to 3.0% by weight. If the addition amount is less than 0.1% by weight, the effect of modifying the film is not sufficient. If the addition amount exceeds 5.0% by weight, the amount of protrusion on the film surface is large, and the film is sticky. In addition to the above, there is a possibility that problems such as contamination of the packaged object may occur.

Next, the layer (layer B) closer to the center than the surface layer (layer A) has a melt flow rate of 0.1 to 10 g / 1.
A copolymer of crystalline polypropylene (B ₁ ) for 0 minutes and at least one kind of α-olefin selected from ethylene and α-olefins having 3 to 12 carbon atoms, wherein α-olefin And a copolymer (B ₂ ) having a content of 70% by weight or more and 90% by weight or less and a density of 0.910 g / cm ³ or less.

The first component, crystalline polypropylene (B
₁ ) is a copolymer with polypropylene or other resin units produced by a conventionally known method, and has a melt flow rate at 230 ° C. of 0.1 to 10 g / 10 min, preferably 0.2 to 5 g. / 10 minutes, more preferably 0.5 to
It is 3.0 g / 10 minutes. If the melt flow rate at 230 ° C. is less than 0.1 g / 10 minutes, there is a problem in molding stability, and if it exceeds 10 g / 10 minutes, the strength of the film is insufficient and there is a problem in molding stability. Also preferably, a copolymer of ethylene and at least one α-olefin selected from α-olefins having 4 to 12 carbon atoms and propylene, more preferably,
It is a copolymer of ethylene or butene-1 and propylene. Here, the content of the α-olefin is 1
0 wt% or less, preferably 2 wt% to 10 wt%, more preferably 4 wt% to 8 wt%. When the content of α-olefin exceeds 10% by weight,
There is a possibility that heat sealability may be reduced.

The first component, crystalline polypropylene (B
₁ ) plays an important role in solving the problem that holes are formed by melting at the time of heat sealing in an automatic packaging machine, and in a specific range to prevent uneven stretching during stretching. It is important to mix. That is, the content of the crystalline polypropylene (B ₁ ) in the composition forming the layer (B layer) is preferably from 10% by weight to 50% by weight, though it depends on other components. When the content of the crystalline polypropylene (B ₁ ) is less than 10% by weight,
There is a possibility that the effect of improving the heat sealability may not be sufficiently obtained, and the appropriate temperature range in which the heat seal can be performed is narrow. A problem arises in that the temperature is changed. In order to prevent the problem, the temperature condition must be changed in accordance with the change in the weight of the contents, and the workability may be significantly reduced. On the other hand, if the content exceeds 50% by weight, the elongation characteristics of the film are deteriorated, so that there is a problem that the tray is deformed at the time of performing the stretch packaging, so that a tight packaging cannot be obtained. There is a risk of causing wrinkling in the package due to excessive elongation.

Next, the copolymer (B ₂ ) as the second component is
It is a copolymer of ethylene and at least one α-olefin selected from α-olefins having 3 to 12 carbon atoms having a density of 0.910 g / cm ³ or less. A hydrocarbon having a polyene structure, for example, dicyclopentadiene, 1,4-hexadiene, ethylidene norbornene, or the like may be further copolymerized. As the α-olefin used here, propylene, butene-1, hexene-1, heptene-1,
4-methyl-1-pentene, octene-1 and the like.
The content of the α-olefin in the copolymer (B ₂ ) is preferably from 70% by weight to 90% by weight. If it is less than 70% by weight or more than 90% by weight, the film may not have sufficient deformation recovery properties and elongation properties.

The copolymer (B ₂ ), which is the second component, plays an important role in enhancing the flexibility of the film and obtaining a tight packaging finish. It is important to mix in a specific range so as not to cause the problem of melting and puncturing during sealing. That is, although it depends on the components of the crystalline polypropylene (B ₁ ), the content is preferably 50% by weight or more and 90% by weight or less. When the copolymer (B ₂ ) is 50
If the amount is less than 90% by weight, the flexibility of the film may be insufficient, and the effect of improving the deformation recovery may not be sufficiently obtained. If the amount exceeds 90% by weight, the film may be easily broken at the time of packaging, and the heat resistance of the film may be reduced. Due to the shortage, the temperature range in which heat sealing can be performed is narrowed, and there is a possibility that a problem occurs in that the hole is formed by melting during heat sealing.

Further, a copolymer (B ₂ ) as the second component
Are copolymers (B ₂₁ ) having an α-olefin content of 70 to 90% by weight and copolymers (B ₂₁ ) having an α-olefin content of 10 to 70% by weight.
₂₂ ). More preferably, the α-olefin content of the copolymer (B ₂₁ ) is 75
The content of α-olefin in the copolymer (B ₂₂ ) is from 25% by weight to 60% by weight. The mixing ratio of the copolymer (B ₂₁ ) and the copolymer (B ₂₂ ) is such that the copolymer (B ₂₁ ) is 40% by weight to 90% by weight, and the copolymer (B ₂₂ ) is 10% by weight to 60% by weight. % By weight or less is preferred.

The layer (layer B) of the present invention is composed of the above-mentioned resin composition, and further has an appropriate sliding property, self-adhesive property, antistatic property and antifogging property for these resin components. In order to obtain, the same additives as in the above-mentioned surface layer (A layer) can be blended.

In the present invention, an ethylene-based copolymer (layer A) is provided on the surface layers on both sides of the film, and crystalline polypropylene (B ₁ ) and the copolymer are formed on the center side of the layer (layer A). (B layer) comprising a composition with (B ₂ )
The main purpose of providing is that a simple film made of an ethylene-based copolymer cannot provide a film having sufficiently satisfactory heat sealability, strength, and the like. Conversely, crystalline polypropylene (B ₁ ) and a copolymer ( The reason for this is that a single film composed of the composition of (B ₂ ) cannot provide sufficient flexibility, transparency, gloss, transparency, self-adhesion, deformation recovery, and the like. These problems are caused by providing an ethylene-based copolymer (layer A) on the surface layers on both sides of the film,
This problem can be solved for the first time by laminating a layer (B layer) composed of a composition of crystalline polypropylene (B ₁ ) and a copolymer (B ₂ ) on the layer closer to the center than the layer).

The stretch film for food packaging according to the present invention is provided with an ethylene copolymer (A layer) on the surface layers on both sides of the film, and a layer on the center side of the (A layer) is made of crystalline polypropylene (B). ₁ ) a laminated film having at least a three-layer structure provided with a (B layer) composed of a composition of a copolymer (B ₂ ), and the same composition is used for both sides (A layer). Alternatively, a composition belonging to the above-described composition but having a different component composition may be used. Such a laminated film can be produced by a method conventionally used using each of the above-described compositions, specifically, by an inflation method, a T-die method, an extrusion lamination method, or the like. Among them, an inflation method that has a good balance of properties in the vertical and horizontal directions is preferable.

The thickness of the stretch film for food packaging of the present invention is usually 8 to 30 μm, preferably 10 to 20 μm. The thickness of the film is 8 μm
If it is less than 30 μm, the handleability of the film will be significantly reduced due to a decrease in the strength and stiffness of the film, and if it exceeds 30 μm, the stress at the time of stretching the film will increase, which may cause a problem of deforming the tray and the packaged object. is there.

The thickness of the layer (layer B) of the stretch film for food packaging of the present invention is 20% of the total thickness of the film.
It is preferably 85% or less and specifically, 1.0 to 2%.
Those having a thickness of 5.0 μm, preferably 2.0 to 17.0 μm are suitable. Here, if the thickness of the layer (layer B) is less than 20% of the total thickness of the film, the effect of improving the heat sealability and the cutting property cannot be expected, and if it exceeds 85%, uniform elongation properties may be impaired.

[0028]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. (Example 1) As a resin for the surface layer (A layer), ethylene-
A vinyl acetate copolymer was used. Melt flow rate (hereinafter abbreviated as MFR) of this copolymer (JIS-K721)
0,190 ° C., load = 2.16 kg, MFR was 2.0 g / 10 min, except for temperature, and the vinyl acetate unit content was 16% by weight. A composition comprising 98.0% by weight of the ethylene copolymer and 2.0% by weight of diglycerin monooleate was used as a resin for the surface layer (A layer). As a resin for the layer (layer B) closer to the center than the surface layer (layer A), a propylene-ethylene random copolymer (ethylene content 4 wt%, MFR at 230 ° C.)
1.0 g / 10 min): 30% by weight, ethylene-propylene copolymer (ethylene content: 30% by weight, density: 0.87
0 g / cm ³ ): A composition comprising 70% by weight of 99% by weight and a composition comprising 1.0% by weight of diglycerin monooleate were used. MFR of this mixed composition at 230 ° C.
Was 0.5 g / 10 min.

Each of these resins has a diameter of 50 mm and an L / D of 26.
Are molded at a resin temperature of 190 ° C. and a blow-up ratio of 5.0 using an inflation molding machine comprising two extruders and a 100 mm annular three-layer die. Each layer has a thickness of 5 μm / 5.
A film having a thickness of 15 μm was obtained. Using this film, meat, fish, prepared foods, fruits, and the like were placed on an expanded polystyrene tray and packed by an automatic stretch packaging machine. The properties and measurement results of the film are shown in Tables 1 and 2 below.

Example 2 The same ethylene-vinyl acetate copolymer as in Example 1 was used as the resin for the surface layer (layer A).
Using a composition comprising 0% by weight and 2.0% by weight of diglycerin monooleate, as a resin for a layer (B layer) closer to the center than the surface layer (A layer), a propylene-ethylene random copolymer (containing ethylene) 4 wt%, MFR 1.0 g / 10 min at 230 ° C): 40 wt%, ethylene-propylene copolymer (ethylene content 20 wt%, density 0.880 g / cm ³ ): 45 wt%, ethylene-propylene Copolymer (ethylene content 70% by weight, density 0.
880 g / cm ³ ): A composition consisting of 99% by weight of a composition consisting of 15% by weight and a composition consisting of 1.0% by weight of diglycerin monooleate were used.

Example 1 was repeated except that these compositions were used.
And the thickness of each layer is 5 μm / 5 μm / 5
μm, and a film having a total thickness of 15 μm was obtained. Using this film, meat,
Fish, side dishes, fruits, etc. were placed and packed by a stretch automatic packaging machine. The properties and measurement results of the film are shown in Table 1 below.
And Table 2.

Example 3 As a resin for the surface layer (layer A), an ethylene-ethyl acrylate copolymer was used. The MFR of the copolymer was 6.0 g / 10 minutes, and the content of ethyl acrylate unit was 18% by weight. A composition comprising 98.0% by weight of the ethylene copolymer and 2.0% by weight of diglycerin monooleate was used as a resin for the surface layer (A layer).

The same procedure as in Example 1 was carried out except that this copolymer was used for the surface layer (A layer), and the thickness of each layer was 5 μm.
A film having m / 5 μm / 5 μm and a total thickness of 15 μm was obtained. Using this film, meat, fish, prepared foods, fruits, and the like were placed on an expanded polystyrene tray and packed by an automatic stretch packaging machine. The properties and measurement results of the film are shown in Tables 1 and 2 below.

Example 4 The same resin as in Example 1 was used for both the surface layer (layer A) and the layer on the center side (layer B), and the layer (layer B) was a portion that did not become a film product. Was collected, pulverized and continuously charged. The recovery rate of this film scrap was 8% by weight, and a film having a thickness of each layer of 4 μm / 6 μm / 4 μm and an overall thickness of 14 μm was obtained. Using this film, meat, fish, prepared foods, fruits, and the like were placed on an expanded polystyrene tray and packed by an automatic stretch packaging machine. The properties and measurement results of the film are shown in Tables 1 and 2 below.

[0035]

[Table 1]

[0036]

[Table 2]

In Tables 1 and 2, measurement and evaluation of physical properties of each item were carried out by the following methods. 1) MFR; JIS K7210 2) Density; JIS K6760 3) Haze (transparency); JIS K6714 4) Gloss (glossy); JIS K7105 5) Clarity (transparency); Slit using Clarity Meter manufactured by Murakami Color Research Laboratory Measured at a width of 1 mm 6) Breaking strength; JIS Z1702 7) Elongation; JIS Z1702 8) Deformation recovery; A specimen of 15 mm in width and 100 mm in length is extended to 200 mm, immediately released, and after 30 seconds, the length of the specimen is reduced. It was measured and indicated by the length to which the specimen returned. 9) Elongation property: It was examined whether necking occurred when the film was stretched. 10) Self-adhesiveness: Two pieces of a sample having a length and width of 100 mm were overlapped, the ends of each film were fixed to upper and lower plates with a tape, and peeled up and down to measure. 11) Anti-fog property; water 10 at 20 ° C in a 300 ml beaker
When 0 ml was put, covered with a film and stored in a refrigerator at 1 ° C., the degree of cloudiness of the film was visually evaluated on a 5-point scale.
(The best was set to 5.) 12) Heat sealing property: The heater temperature of the hot plate of the automatic wrapping machine was set at 50 to 160 ° C., and the stretch-wrapped tray was allowed to rest on the hot plate for several seconds. Evaluation was made based on the sealing strength and the presence or absence of perforations, and the temperature was shown in a temperature range in which good sealing was possible. 13) Suitability for automatic packaging machine; Judgment was made as to whether stretch packaging was possible without problems such as generation of wrinkles, cracking and distortion of trays, unwinding property of film, and cutting property. 14) Cutting performance: Sensory evaluation of cutting performance by hand in the lateral direction,
Those that were cut straight in the horizontal direction were rated as 5, and those that could not be cut or those that were bent and cut were evaluated on a 5-point scale according to the degree.

(Comparative Example 1) As a resin for the center-side layer (layer B), a propylene-ethylene-butene-1-random copolymer (ethylene unit content 3% by weight, butene-1 unit content 9% by weight) 5.0 g / 1 MFR at 230 ° C.
0 minutes) A composition comprising 99% by weight and 1.0% by weight of diglycerin monooleate, and an ethylene-vinyl acetate copolymer (vinyl acetate unit content: 15% by weight, 190 ° C.) as a resin for the surface layer (A layer) 2.0 g / 10 in MFR
Min) 98.0% by weight; diglycerin monooleate 2.0
Using a composition consisting of 5% by weight, a film having a thickness of 5 μm / 5 μm / 5 μm and a total thickness of 15 μm was obtained. Packaging was performed using this film. The properties and measurement results of the film are shown in Tables 3 and 4 below.

Comparative Example 2 Ethylene-vinyl acetate copolymer (vinyl acetate unit content 15% by weight, MFR 2.0 g / 1 at 190 ° C.) as a resin for the center side layer (layer B)
0 minutes) 30% by weight; a composition consisting of 70% by weight of a propylene-ethylene random copolymer (ethylene unit content 7% by weight, MFR 2.0 g / 10 minutes at 230 ° C / 10 minutes) for the surface layer (A layer) Ethylene-vinyl acetate copolymer (vinyl acetate unit content 15% by weight, 190
2.0 g / 10 min MFR at 9 ° C) 98.5% by weight;
Using a composition comprising 1.5% by weight of diglycerin monooleate, a film was formed in the same manner as in Example 1 to obtain a film having a thickness of each layer of 5 μm / 5 μm / 5 μm; and a total thickness of 15 μm. Packaging was performed using this film. The properties and measurement results of the film are shown in Tables 3 and 4 below.

Comparative Example 3 A propylene-ethylene random copolymer (ethylene unit content: 4% by weight, MFR: 1.0 g at 230 ° C.) as a resin for the center layer (layer B)
/ 10 min) 70% by weight; butene-1-ethylene copolymer (butene-1 content 97% by weight, density 0.895 g / c)
m ³ , MFR 2.0 g / 10 min at 190 ° C.) 30
A resin composition for the surface layer (layer A) was used as the resin for the surface layer (A layer), and an ethylene-vinyl acetate copolymer (vinyl acetate unit content 15% by weight, MFR 2.0 g at 190 ° C.) was used.
/ 10 min) 98.5% by weight; a composition consisting of 1.5% by weight of diglycerin monooleate was used to form a film in the same manner as in Example 1, and the thickness of each layer was 5 μm / 5 μm / 5 μm.
m: A film having a total thickness of 15 μm was obtained. Packaging was performed using this film. The properties and measurement results of the film are shown in Tables 3 and 4 below.

Comparative Example 4 Example 1 was obtained using a commercially available plasticized polyvinyl chloride stretch film (thickness: 15 μm).
In the same manner as in the above, packaging was performed by a stretch automatic packaging machine. The properties and measurement results of the film are shown in Tables 3 and 4 below.

[0042]

[Table 3]

[0043]

[Table 4]

In Tables 3 and 4, physical properties of each item were measured and evaluated in the same manner as in the examples.

[0045]

As described above, the stretch film for food packaging of the present invention is excellent in transparency, gloss and transparency.
It has uniform elongation characteristics when the film is stretched,
It has excellent heat sealing properties in an automatic packaging machine, has sufficient elongation and deformation recovery properties, is suitable for packaging machines, and has excellent workability. In addition, air permeability, anti-fog property, water vapor permeability required for stretch films for food packaging,
Physical properties such as self-adhesiveness are also good. Furthermore, there is no problem of disposal property after use like a conventional plasticized polyvinyl chloride stretch film, and there is no problem in food hygiene. Therefore, the stretch film for food packaging of the present invention is expected to be widely used as a film for stretch packaging various foods such as fruits and vegetables, fresh fish, fresh meat, and prepared foods.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B65D 65/40 BSN B65D 65/40 BSN BSQ BSQ C08L 23/02 C08L 23/02 23/10 23/10 (72) Invention Taita Kinoshita 2 Onaka Research Center, Oita City, Oita Prefecture Showa Denko Co., Ltd. Oita Research Laboratories (72) Inventor Satoshi Iwamoto Oita City, Oita City Oita City, Oita City 2 Oita Research Laboratories Showa Denko Co., Ltd. 2 Oita-shi, Oita City, Oita Prefecture Showa Denko KK Oita Research Laboratories F term (reference) GB23 JA06C JA11C JA13C JD02 JK08 JL00 JL01 JL07 JL12 JN01 JN21 YY00A YY00B YY00C 4J002 BB122 BB141 BB151 BB152 BB171 GF00 GG02

Claims (4)

[Claims] 1. A laminated film having at least a three-layer structure, wherein a surface layer (A layer) on both sides of the film has an ethylene-acetic acid content of 5 to 25% by weight of a monomer other than ethylene. Vinyl copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer,
At least one kind of ethylene selected from ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl methacrylate copolymer, and ionomer resin The layer (B layer), which is made of a copolymer and is closer to the center than the surface layer (A layer), has a melt flow rate of 0.1 to 10 g /
A copolymer of crystalline polypropylene (B ₁ ) for 10 minutes and at least ethylene and at least _one α-olefin selected from α-olefins having 3 to 12 carbon atoms; Olefin content is 70% by weight
A stretch film for food packaging, comprising a composition containing at least 90% by weight or less and a copolymer (B ₂ ) having a density of 0.910 g / cm ³ or less. 2. Layer (B) of crystalline polypropylene (B)
₁ ) is a copolymer of ethylene and at least one α-olefin selected from among α-olefins having 4 to 12 carbon atoms and propylene, wherein the content of α-olefin is 10% by weight or less. , Melt flow rate is 0.1-1
The stretch film for food packaging according to claim 1, wherein the stretch film is 0 g / 10 minutes. 3. The food packaging material according to claim 1, wherein the content of the crystalline polypropylene (B ₁ ) in the composition constituting the layer (B layer) is 10% by weight or more and 50% by weight or less. Stretch film. 4. A layer (layer B) of crystalline polypropylene (B)
₁₎ and the copolymer (B ₂₎ and stretch film for food packaging according to claim 1, wherein the melt flow rate is 0.1 to 10 g / 10 min of the composition of the.