JP2009298119A - Multilayer film for shrink package and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer film for shrink package which satisfies both of heat-shrinking property and deformation recovery after shrink package, and to provide a manufacturing method of the multilayer film for shrink package. <P>SOLUTION: The multilayer film for shrink package includes a layer (A) and a heat sealing layer layered on the layer (A), wherein the heat sealing layer is a layer made of at least one kind of ethylene-α-olefin random copolymer (X) having a density of 0.900 to 0.930 g/cm<SP>3</SP>and the layer (A) is a layer made of a composition including at least one kind of ethylene-α-olefin random copolymer (Y) of a density of 0.900 to 0.930 g/cm<SP>3</SP>, by 30 to 80 mass% and at least one kind of ethylene-α-olefin block copolymer (Z) of a density of 0.860 to 0.890 g/cm<SP>3</SP>, by 20 to 70 mass%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a multilayer film for shrink wrapping and a method for producing the same.

  Conventionally, shrink wrapping (synonymous with shrink wrapping) is used to quickly and tightly package a plurality of products regardless of the shape and size of the package. Moreover, since the appearance of the obtained package is beautiful, the contents are kept hygienic, and visual quality control is easy, it is used for packaging food, sundries, and the like. Examples of a method for covering an object to be packaged with a packaging film include a method such as pillow shrink packaging and overlap packaging.

Shrink wrap is usually a tight and beautiful method in which the film is heat-shrinked with hot air in a shrink tunnel after the contents are primarily packaged by heat sealing, fusing sealing, etc. Finish is obtained.
Among such shrink wrapping, in pillow shrink wrapping, the film is required to have 1) heat shrinkability, 2) proper packaging machine, 3) optical properties, and 4) good deformation recovery after shrink wrapping. The

1) Regarding heat shrinkability, in a variety of container shapes, a package that has been primary packaged in advance with a specified margin using a film is finished tightly with no corner residue after passing through the hot air shrinkage tunnel, It is required to have a high shrinkage rate.
2) Regarding the suitability of the packaging machine, the slipperiness between the metal roll and the film in the packaging machine is good, the stretch property in the film width direction is good, and the resin falls off after sealing. There must be no (melt hole).
3) Regarding optical properties, when the film after shrinkage is transparent and the package is stored under freezing and refrigeration conditions, the adhesion of water droplets to the film surface is suppressed, and the contents are visible. Is required to be good.
4) With regard to deformation recovery after packaging, especially when prepared dishes, meat, etc. are placed on a tray without a lid and shrink-wrapped, the traces of the film stretched due to the stacking load between the packaging bodies are restored in a short time. Is needed.

  Practically, the required characteristics vary depending on the shape of the package, the distribution process, how it is handled during storage, and various environmental conditions, and it is essential that the heat shrink wrapping film meet this requirement. is there. On the other hand, as a result of considering environmental needs such as cost, resource saving, and waste reduction, usually, several types of film thickness are required as film thickness. As a film used for heat shrink packaging, a multilayer film using a polyolefin resin having excellent transparency is conventionally known.

  For example, in Patent Document 1, both surface layers composed of a mixture of linear low density polyethylene and an ethylene-α-olefin copolymer, and a core layer composed of a mixture of linear low density polyethylene and low density polyethylene having long chain branches. There is disclosed a polyethylene-based crosslinked shrink film that is crosslinked by irradiation with an electron beam.

  In Patent Document 2, both surface layers made of linear low density polyethylene, an inner layer made of ultra-low density polyethylene and an ethylene-α-olefin copolymer, and an ethylene-based polymer mainly composed of linear low density polyethylene are used. There is disclosed a polyethylene-based crosslinked shrink film having an inner layer and crosslinked by irradiation with an electron beam.

  Patent Document 3 discloses a low-temperature shrinkable film composed of an ethylene-α-olefin copolymer and an ethylene-based copolymer having a melting peak temperature below 110 ° C.

  In Patent Document 4, both surface layers are made of at least one resin selected from an ethylene-vinyl acetate copolymer resin and an ethylene-α-olefin resin, and are composed of a crystalline polypropylene resin and a thermoplastic elastomer. A heat shrinkable multilayer film comprising at least one layer is disclosed.

  Patent Documents 5 to 7 disclose a laminated film having at least one layer of an ethylene-α-olefin block copolymer.

Japanese Patent No. 3614810 JP 2007-118576 A International Publication No. 2005/049702 Pamphlet JP 2007-144741 A Special table 2007-529615 JP-T-2007-529616 JP-T-2007-529617

However, the polyethylene-based cross-linked shrink films disclosed in Patent Documents 1 and 2 have good packaging machine suitability and optical characteristics, but both have the disadvantage of insufficient deformation recovery after shrink wrapping. have.
Moreover, although the film for shrink wrapping disclosed in Patent Documents 3 and 4 has low-temperature shrinkage, further improvement in deformation recovery is desired.
Furthermore, regarding the laminated films described in Patent Documents 5 to 7, further improvement as a shrink wrapping film is desired.

  As described above, the film for shrink wrap disclosed in Patent Documents 1 to 7 has good packaging machine suitability and optical characteristics, but further improvement in deformation recovery after shrink wrap is desired. .

  The problem to be solved by the present invention is to provide a multilayer film for shrink wrapping which has both heat shrinkability and deformation recovery after shrink wrapping, and a method for producing the same.

  As a result of intensive studies to solve the above problems, the present inventors have determined that an ethylene-α-olefin random copolymer (Y) and an ethylene-α-olefin block copolymer (Z) having different density ranges. The present invention has been completed by finding that the above-mentioned problems can be solved by using the resin of the layer (A) on which the heat seal layer is laminated at a specific content.

That is, this invention provides the following multilayer film for shrink wrapping, and its manufacturing method.
[1]
A multilayer film for shrink wrapping comprising a layer (A) and a heat seal layer laminated on the layer (A),
The heat seal layer is
A layer composed of at least one ethylene-α-olefin random copolymer (X) having a density of 0.900 to 0.930 g / cm ³ ;
The layer (A) is
30-80% by mass of at least one ethylene-α-olefin random copolymer (Y) having a density of 0.900 to 0.930 g / cm ³ ;
Shrinkage which is a layer formed of a composition containing 20 to 70% by mass of at least one ethylene-α-olefin block copolymer (Z) having a density of 0.860 to 0.890 g / cm ^3. Multi-layer film for packaging.
[2]
The multilayer film for shrink wrapping according to the above [1], wherein the density of the ethylene-α-olefin random copolymer (Y) is 0.900 to 0.920 g / cm ³ .
[3]
The multilayer film for shrink wrapping according to the above [1] or [2], wherein the ethylene-α-olefin random copolymer (Y) has a ratio of heat of fusion at 100 ° C. or lower of 30 to 80%.
[4]
The melting point of the ethylene-α-olefin block copolymer (Z) is 100 to 130 ° C, and the crystallization temperature is 80 to 100 ° C, according to any one of the above [1] to [3]. Multi-layer film for shrink wrapping.
[5]
The multilayer film for shrink wrapping according to any one of [1] to [4], wherein the heat of crystal fusion of the ethylene-α-olefin block copolymer (Z) is 10 to 50 J / g.
[6]
The multilayer film for shrink wrapping according to any one of [1] to [5], which is crosslinked by electron beam irradiation.
[7]
The multilayer film for shrink wrapping according to any one of [1] to [6], wherein the gel fraction of the entire shrink wrap film is 20 to 60% by mass.
[8]
The multilayer film for shrink wrapping according to any one of [1] to [7], wherein the heat seal layer is laminated on both surfaces of the layer (A).
[9]
A step of co-extruding the heat sealing layer and the raw material resin of the layer (A) from an annular die, and cooling the obtained tubular parison;
Re-heating in the stretching machine, the stretching start temperature is a temperature within the range of the melting point of the raw material resin used for the heat seal layer and the layer (A) to 150 ° C., and a magnification of 2 to 10 times in the flow direction and width direction. Stretching,
The manufacturing method of the multilayer film for shrink wrapping as described in any one of said [1]-[8] containing.
[10]
The method for producing a multilayer film for shrink wrapping according to [9], further including a step of performing crosslinking treatment by electron beam irradiation on the tubular parison.

By using the multilayer film for shrink wrapping of the present invention, it is possible to achieve both deformation recovery and shrinkage after shrink wrapping.
In particular, when a multilayered film for shrink wrapping according to the present invention is used for shrink wrapping by placing bulky sugar beets on a lidless tray, a tight packaging finish having a high shrinkage rate can be obtained. Movement of the packaged body in the tray can be suppressed. In addition, since the multilayer film for shrink wrapping of the present invention has deformation recovery properties, it is possible to maintain a beautiful package finish that is loosened and loosened by restoring the stretch marks of the film caused by product stacking. It becomes possible.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention.

The multilayer film for shrink wrapping of the present embodiment (hereinafter sometimes simply referred to as “film”) has a heat seal layer and a layer (A), and the heat seal layer is on the layer (A). A multilayer film for shrink wrapping which is laminated.
The heat seal layer of the film is a layer made of at least one ethylene-α-olefin random copolymer (X) having a density of 0.900 to 0.930 g / cm ³ .
The layer (A) of the film has at least one ethylene-α-olefin random copolymer (Y) having a density of 0.900 to 0.930 g / cm ³ and a density of 30 to 80% by mass. It is a layer which consists of a composition containing 20-70 mass% of at least 1 sort (s) of ethylene-alpha-olefin block copolymer (Z) which is 0.860-0.890 g / cm < ³ >.

(Heat seal layer)
In the present embodiment, the heat seal layer has at least one ethylene-α-olefin random copolymer (X) (hereinafter simply referred to as a random copolymer (X) having a density of 0.900 to 0.930 g / cm ^3. X) may be abbreviated as X)).
When the film has the heat seal layer, the packaging machine suitability, in particular, slipperiness, seal strength, and optical properties (glossiness) after shrink wrapping are improved.
By using the random copolymer (X) having a density of 0.900 g / cm ³ or more, there is less stickiness on the film surface, and the slipperiness with the packaging machine is good. By using the random copolymer (X) having a density of 0.930 g / cm ³ or less, the glossiness of the film becomes good.
In the present embodiment, the density of the ethylene-α-olefin random copolymer (X) is preferably 0.905 to 0.930 g / cm ³ from the viewpoint of slipperiness and gloss.

The ethylene-α-olefin random copolymer (X and Y) used in the present embodiment is a random copolymer of ethylene and at least one monomer selected from α-olefins having 3 to 18 carbon atoms. The α-olefin in the ethylene-α-olefin copolymer is propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1 -Dodecene and the like.
The ethylene-α-olefin random copolymer may be polymerized using either a multi-site catalyst or a single-site catalyst, but when packaging contents that require transparency, a single-site catalyst is used. It is preferable to use one polymerized with a catalyst. In this case, from the viewpoint of transparency, it is preferable to use one having a molecular weight distribution (Mw / Mn) measured by GPC of 3.5 or less.
The melt flow rate of the ethylene-α-olefin random copolymer is preferably 0.2 to 7.0 g / 10 min. When the melt flow rate is 0.2 g / 10 min or more, it is preferable in terms of obtaining film strength, and when it is 7.0 g / 10 min or less, it is preferable in terms of obtaining stability in the stretching step.

  You may mix | blend resin other than random copolymer (X) with the heat seal layer in the range which does not impair the characteristic as a film of this Embodiment. Other resins include ethylene-vinyl acetate copolymer resin, ethylene-ethyl acrylate copolymer resin, ethylene-acrylic acid copolymer resin, ethylene-methyl methacrylate copolymer resin, ethylene-methacrylic acid. Copolymer resin, ionomer resin, high pressure method low density polyethylene, high density polyethylene, and α-olefin copolymer having a crystallinity of 30% or less by X-ray method different from the above random copolymer (X) Examples thereof include soft resins, resins obtained by modifying these resins by acid modification, polybutene resins, crystalline 1,2-polybutadiene resins, amorphous polypropylene resins, and the like.

  The ratio of the other resin in the heat seal layer is not particularly limited as long as it does not impair the characteristics of the film of the present embodiment, but it is 50% by mass or less in the resin of the heat seal layer. It is preferable that it is 40 mass% or less. When the ratio of the resin other than the random copolymer (X) in the heat seal layer is 50% by mass or less, it is preferable in terms of improving the glossiness of the film.

  The thickness ratio of the heat seal layer to the entire multilayer film for shrink wrapping is not particularly limited as long as it does not impair the characteristics of the film of the present embodiment, but is preferably 10 to 50%. More preferably, it is 15 to 40%. When the ratio of the heat seal layer is 10% or more, it is preferable in that the sealing strength is good, and when it is 50% or less, it is preferable in that the stretching stability is good.

(Layer (A))
In the present embodiment, the layer (A) contains 30 to 80% by mass of at least one ethylene-α-olefin random copolymer (Y) having a density of 0.900 to 0.930 g / cm ³ , It is a layer formed of a composition containing 20 to 70% by mass of an ethylene-α-olefin block copolymer (Z) having a density of 0.860 to 0.890 g / cm ³ .

In the present embodiment, the density of the ethylene-α-olefin random copolymer (Y) (hereinafter sometimes simply referred to as random copolymer (Y)) is 0.900 to 0.930 g / cm. ³ , preferably 0.900 to 0.920 g / cm ³ . When the density is 0.900 g / cm ³ or more, the runnability of the film is stable, and when the density is 0.930 g / cm ³ or less, low-temperature shrinkage is imparted to the film.

  In this Embodiment, the ratio as a component in the layer (A) of a random copolymer (Y) is 30-80 mass%, and 40-80 mass% is preferable. When the ratio is 30% by mass or more, stretching stability is obtained, and when it is 80% by mass or less, flexibility is obtained.

The ratio of the heat of fusion at 100 ° C. or less of the random copolymer (Y) is preferably 20 to 90%, more preferably 30 to 80%. When the ratio of the heat of fusion at 100 ° C. or less is 20% or more, it is preferable in that low-temperature shrinkage is imparted to the film. When the ratio of the heat of fusion at 100 ° C. or less is 90% or less, the dimensional stability of the film Is preferable in that it is obtained.
In the present embodiment, the ratio of the heat of fusion of 100 ° C. or less is 2nd. Measured by a differential scanning calorimeter (hereinafter sometimes simply referred to as “DSC”). In the melting behavior, it means the ratio of the heat of fusion at 100 ° C. or less to the heat of crystal fusion (ΔHm), which can be determined by the method described in the following examples.

  In the present embodiment, the ethylene-α-olefin random copolymer (Y) may be the same as or different from the ethylene-α-olefin random copolymer (X) used in the heat seal layer. Good.

In the present embodiment, the ethylene-α-olefin block copolymer (Z) (hereinafter sometimes simply referred to as a block copolymer (Z)) has a density of 0.860 to 0.890 g / cm. ³ .

  The block copolymer (Z) is preferably a block copolymer of ethylene and at least one monomer selected from α-olefins having 3 to 18 carbon atoms, and α in the ethylene-α-olefin copolymer is preferable. Examples of the olefin include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene and the like.

The density of the block copolymer (Z) is 0.860 to 0.890 g / cm ³ , and preferably 0.865 to 0.880 g / cm ³ . When the density is 0.860 g / cm ³ or more, the runnability of the film in the packaging machine is stable, and when the density is 0.890 g / cm ³ or less, the film has good deformation recovery.

  In this Embodiment, the ratio as a component in the layer (A) of a block copolymer (Z) is 20-70 mass%, and 20-60 mass% is preferable. When the ratio is 20% by mass or more, flexibility is obtained, and when it is 70% by mass or less, stretching stability is obtained.

The melting point of the block copolymer (Z) is preferably 100 to 130 ° C, and more preferably 105 to 125 ° C. When the melting point is 100 ° C. or higher, heat resistance can be imparted to the film, and when the melting point is 130 ° C. or lower, stretching stability is obtained.
In the present embodiment, the melting point means a melting point measured by a differential scanning calorimeter.

The crystallization temperature of the block copolymer (Z) is preferably 80 to 100 ° C, and more preferably 85 to 100 ° C. When the crystallization temperature is 80 ° C. or higher, the dimensional stability of the film is good, and when the crystallization temperature is 100 ° C. or lower, stretch stability is obtained.
In the present embodiment, the crystallization temperature means a crystallization temperature measured with a differential scanning calorimeter.

The heat of crystal fusion of the block copolymer (Z) is preferably 10 to 50 J / g, more preferably 15 to 45 J / g. When the heat of crystal fusion is 10 J / g or more, it is preferable from the viewpoint of imparting heat resistance, and when the heat of crystal fusion is 50 J / g or less, it is preferable from the viewpoint of good deformation recovery.
In the present embodiment, the heat of crystal melting means the heat of crystal melting measured by a differential scanning calorimeter.

The ratio of the heat of fusion at 100 ° C. or less of the block copolymer (Z) is preferably 50% or less, more preferably 40% or less. When the ratio of the heat of fusion of 100 ° C. or less is 50% or less, it is preferable in terms of heat resistance.
In the present embodiment, the ratio of the heat of fusion of 100 ° C. or less is 2nd. Measured with a differential scanning calorimeter. In the melting behavior, it means the ratio of the heat of fusion at 100 ° C. or less to the heat of crystal fusion (ΔHm), which can be determined by the method described in the following examples.

  In the present embodiment, the block copolymer (Z) is composed of (I) a first olefin polymerization catalyst and (II) a polymer prepared by the first olefin polymerization catalyst under equivalent polymerization conditions. In the presence of a composition comprising a mixture or reaction product obtained by combining a second olefin polymerization catalyst capable of preparing polymers having different properties or physical properties and (III) a chain shuttling agent, ethylene And a block copolymer formed by polymerizing α-olefin. Specific methods for producing the ethylene-α-olefin block copolymer (Z) useful in the present embodiment are disclosed in JP-T-2007-529615, JP-T-2007-529616, JP-T-2007-529617. All of which are incorporated herein by reference.

In the present embodiment, the melting point, crystallization temperature, and crystal melting calorie can be defined by measuring using a differential scanning calorimeter.
Specifically, the sample amount is 5 to 10 mg, the measurement atmosphere is a nitrogen atmosphere, and indium is used as a calorific value standard. As a heating program, the sample was first heated from 0 ° C. to 200 ° C. at a temperature rising rate of 10 ° C./min (1st. Melting behavior), left at 200 ° C. for 1 minute, and then heated at a temperature decreasing rate of 10 ° C./min. The solution was cooled from 0 ° C. to 0 ° C. and left at 0 ° C. for 1 minute (1st. Crystallization behavior). Thereafter, the temperature was raised from 0 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min (2nd. Melting behavior). The melting point is 2nd. In the specific heat curve obtained from the melting behavior, the temperature indicates the maximum endothermic amount. The crystallization temperature is 1st. In the specific heat curve obtained by the crystallization behavior, the temperature indicates the maximum calorific value. 2nd. The amount of heat of crystal melting can be obtained using a straight line obtained by extrapolating the specific heat curve of the completely melted state obtained by the melting behavior directly to the low temperature side as a baseline. Further, the ratio of heat of fusion at 100 ° C. or lower can be obtained by dividing the heat of fusion at 100 ° C. or lower by the heat of crystal fusion.

  In the present embodiment, the layer (A) is blended with a resin other than the random copolymer (Y) and the block copolymer (Z) as long as the characteristics of the film of the present embodiment are not impaired. May be. Other resins include ethylene-vinyl acetate copolymer resin, ethylene-ethyl acrylate copolymer resin, ethylene-methacrylic acid copolymer resin, ionomer resin, high pressure method low density polyethylene resin, high density polyethylene resin, Examples thereof include resins obtained by modifying these resins by acid modification, propylene homopolymer resins, propylene-ethylene copolymer resins, propylene-ethylene-butene copolymer resins, amorphous polypropylene resins, and the like.

  The ratio of the other resin in the layer (A) is not particularly limited as long as it does not impair the characteristics as the film of the present embodiment, but is preferably 50% by mass or less, More preferably, it is 40 mass% or less. When the ratio of the resin other than the random copolymer (Y) and the block copolymer (Z) in the layer (A) is 50% by mass or less, it is preferable in terms of improving the haze of the film.

  The thickness ratio of the layer (A) to the entire multilayer film for shrink wrapping is not particularly limited as long as it does not impair the characteristics of the film of the present embodiment, but may be 50 to 90%. Preferably, it is 50 to 80%. When the ratio of the layer (A) is 50% or more, stretching stability is obtained, and when the ratio of the layer (A) is 90% or less, the running property of the film is stabilized.

(Multilayer film for shrink wrapping)

The shrink-wrapping multilayer film of the present embodiment is a shrink-wrapping multilayer film comprising a layer (A) and a heat seal layer laminated on the layer (A), and the heat seal layer is It is a layer made of at least one ethylene-α-olefin random copolymer (X) having a density of 0.900 to 0.930 g / cm ³ , and the layer (A) has a density of 0.900 to is 0.930 g / cm ^3, and at least one ethylene -α- olefin random copolymer (Y) 30 to 80 wt%, a density of 0.860~0.890g / cm ^3, at least 1 It is a multilayer film for shrink wrapping, which is a layer made of a composition containing 20 to 70% by mass of a seed ethylene-α-olefin block copolymer (Z).

In order to give good anti-fogging property and slipperiness to the multilayer film for shrink wrapping, additives and the like may be blended. Examples of additives include fatty acid esters of polyhydric alcohols, polyoxyethylene alkyl ethers, polyalkylene glycol fatty acid esters, and the like.
Examples of fatty acid esters of polyhydric alcohols include mono-fatty acid esters, di-fatty acid esters, tri-fatty acid esters, and polyfatty acid esters of polyhydric alcohols, and monoglycerin esters of saturated or unsaturated fatty acids having 8 to 18 carbon atoms. , Diglycerin ester, triglycerin ester, tetraglycerin ester, sorbitan ester are preferred, more preferably monoglycerin ester, diglycerin ester, triglycerin ester, tetraglycerin ester of saturated or unsaturated fatty acid having 12 to 18 carbon atoms , A sorbitan ester. Specifically, glycerol monolaurate, glycerol monomyristate, glycerol monopalmitate, glycerol dipalmitate, glycerol monostearate, glycerol distearate, glycerol tristearate, glycerol monooleate, glycerol dioleate, glycerol trio Rate, glycerin monolinoleate, sorbitan laurate, sorbitan myristate, sorbitan palmitate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, sorbitan monooleate, sorbitan diolate, sorbitan trioleate, sorbitan linoleate, Diglycerol laurate, diglycerol myristate, diglycerol palmitate, diglycerol stearate, diglycerol oleate, Examples include glycerin linoleate, triglycerin laurate, triglycerin oleate, triglyceryl stearate, tetraglycerin laurate, tetraglycerin oleate, and tetraglyceryl stearate, but glycerin ester of lauric acid or oleic acid and diglycerin ester Is preferably used in order to achieve both antifogging properties and slipperiness.

As a layer which mixes an additive for imparting good antifogging property and slipperiness to the multilayer film for shrink wrapping, the heat seal layer and / or the layer (A), and the heat seal layer and the layer (A) When an intermediate layer exists between them, it is preferable to add to the heat seal layer and the intermediate layer. As a method of adding each layer to the resin, not only a method of diluting with a resin (master batch) containing a high concentration of the additive, but also a method of heating the additive to a molten state and directly injecting it into the resin is utilized. it can.
Other additives include fatty acid esters of polyhydric alcohols, polyoxyethylene alkyl ethers, surfactants other than polyalkylene glycol fatty acid esters, antioxidants, antistatic agents, and adhesives represented by low molecular weight petroleum resins. Liquid additives such as an agent and mineral oil can be added to each layer to such an extent that the antifogging property and slipperiness are not impaired.

  The multilayer film for shrink wrapping of the present embodiment has a heat seal layer composed of an ethylene-α-olefin random copolymer (X) and an ethylene-α-olefin random copolymer (Y ) And an ethylene-α-olefin block copolymer (Z) layer (A), an intermediate layer may be used. The intermediate layer (i) serves as an anti-fogging agent retaining layer for maintaining anti-fogging properties, and (ii) improves the adhesion between the heat seal layer and the layer (A) and suppresses delamination ( iii) It is preferably provided for reasons such as a recovered layer of the film in which the recovered resin is re-pelletized by an extruder, and the original characteristics are not impaired for the reasons (i), (ii) and (iii) above. Within the range, you may mix | blend other resin other than the copolymer used for a heat seal layer and a layer (A), an additive, etc. at 60 mass% or less. Other resins include polybutene resin, ethylene-vinyl acetate copolymer resin, ethylene-ethyl acrylate copolymer resin, ethylene-acrylic acid copolymer resin, ethylene-methyl methacrylate copolymer resin, ethylene -A methacrylic acid copolymer resin, an ionomer resin, a high pressure method low density polyethylene, a high density polyethylene, and a propylene homopolymer are mentioned.

In the present embodiment, the arrangement of the heat seal layer and the layer (A) is not particularly limited as long as the heat seal layer is laminated on the layer (A). For example, the heat seal layer (Hereinafter sometimes simply abbreviated as “S”) and layer (A) (hereinafter simply abbreviated as “A”): S / A, both surface layers Is a three-layered heat seal layer: S / A / S, a single intermediate layer (hereinafter sometimes referred to simply as “B”) is composed of three layers: S / B / A, S / A / B, when both surface layers are composed of a heat seal layer and consist of all four layers using one intermediate layer: S / B / A / S, all four layers using two intermediate layers Case: S / B / A / B, when both surface layers consist of a heat seal layer and consist of a total of five layers using two intermediate layers S / / A / B / S, and the like. Further, an intermediate layer different from the intermediate layer B (hereinafter sometimes simply referred to as “D”) may be used in combination, and S / B / A / D, S / D / A / B, S / D / B / A, S / B / D / A 4 layers, S / D / B / A / S, S / B / A / D / S, S / B / D / A / S 5 layers, 6 layers composed of S / B / D / A / B / S, 7 layers composed of S / B / D / A / B / D / S, and other layers such as 8 layers and more Can also be configured.
The arrangement of the layers in this embodiment is preferably composed of at least three layers such as S / B / A or S / A / S.

  The thickness ratio of the intermediate layer to the entire multilayer film for shrink wrapping is not particularly limited as long as the characteristics are not impaired, but is preferably 60% or less, more preferably 55% or less. When the ratio of the intermediate layer is 60% or less, it is preferable in that the stretching stability is good.

  The thickness of the multilayer film for shrink wrapping in the present embodiment is preferably 5 to 60 μm, more preferably 6 to 50 μm, and still more preferably 7 to 40 μm. When the thickness of the film is 5 μm or more, the rigidity of the film is improved and preferable in terms of workability at the time of packaging, and when it is 60 μm or less, the amount of heat required for the heat shrinkage of the film can be reduced, and the temperature can be reduced in a shorter time This is preferable in that heat shrinkage is possible.

The gel fraction of the multilayer film for shrink wrapping is obtained by immersing a sample put in a 150 mesh wire net in boiling p-xylene for 12 hours and calculating the ratio of the insoluble part from the following formula. It can be used as a scale.
Gel fraction (mass%) = (sample weight after extraction / sample weight before extraction) × 100
The gel fraction of the multilayer film for shrink wrapping is preferably 20 to 60% by mass, and more preferably 25 to 55% by mass. When a gel fraction is 20 mass% or more, it is preferable at the point to which heat resistance is provided to a film. When the gel fraction is 60% by mass or less, it is preferable in that the stretching stability is good.

The heat shrinkage rate of the multilayer film for shrink wrapping can be measured according to ASTM D-2732. Assuming pillow shrink packaging, the measurement temperature is evaluated at 120 ° C.
The heat shrinkage rate at 120 ° C. is preferably 50 to 80% in both the film flow and width directions in order to obtain a beautiful finish with no corner residue after shrink wrapping. When the heat shrinkage rate at 120 ° C. is 50% or more, it is preferable in that a beautiful packaging finish having no corner residue is obtained. Moreover, when the thermal shrinkage rate at 120 ° C. is 80% or less, it is preferable in that it can be shrink-wrapped at a lower temperature.

The heat shrink stress of the multilayer film for shrink wrapping can be measured according to ASTM D-2838. The measurement temperature is measured at 120 ° C., assuming the temperature at which the shrink wrap is actually performed. The heat shrinkage stress is necessary for quickly removing air from a small hole provided in advance using a needle or the like when a primary package having a specified film margin is heat shrunk by a shrink tunnel. Moreover, it is necessary in order to suppress the movement of the packaged body in the tray in the tray packaging without a lid.
Preferably the flow, at least one of the maximum thermal shrinkage stress in the width directions is 100~350gf / mm ² at 120 ° C. of the film, more preferably 120~330gf / mm ^2. When the heat shrinkage stress value is 100 gf / mm ² or more, it becomes easy to remove air from the small holes provided in advance when the film is shrunk, and a tight feeling is obtained in the package after shrinkage, and in the tray of the packaged body When the heat shrinkage stress value is 350 gf / mm ² or less, when the air inside the film is removed by the heat shrinkage stress, it is possible to suppress deformation of the tray made of expanded polystyrene.

(Manufacturing method of multilayer film for shrink wrapping)
The manufacturing method of the multilayer film for shrink wrapping according to the present embodiment includes a step of co-extruding the heat seal layer and the raw material resin of the layer (A) from an annular die, and cooling the obtained tubular parison, reheating in a stretching machine The stretching start temperature is a temperature in the range of the melting point to 150 ° C. of the raw material resin used for the heat seal layer and the layer (A), and the stretching is performed at a magnification of 2 to 10 times in the flow direction and the width direction, A method for producing the multilayer film for shrink wrapping.

  Examples of the manufacturing method of the shrink-wrapping multilayer film in the present embodiment include a single bubble inflation method, a double bubble inflation method, a triple bubble inflation method, and a tenter method. From the viewpoint of shrinkability, the single bubble inflation method, the double bubble The inflation method and the triple bubble inflation method are preferred. Among these, the double bubble inflation method is more preferable. The production method by the double bubble inflation method is described below.

  In the present embodiment, first, raw material resins used for each layer are melted from several types of extrusion machines, and each resin is coextruded from an annular die to obtain a tube-shaped unstretched parison. As a cooling method for the tube-shaped unstretched parison, the cooling medium is cooled and solidified from the outside of the tube-shaped parison, and the cooling medium is water from the outside, and the inside of the tube-shaped parison is passed with water. The surface may be blasted and roughened along a rough cooling mandrel, and may be cooled and solidified from both the inside and outside of the tubular parison, which may be rapidly cooled and solidified, and any method may be used.

  It is preferable to perform a crosslinking treatment by electron beam irradiation on the cooled and solidified tubular parison. Electron beam irradiation may be performed from one side or both sides of the film. The amount of electron beam irradiation is preferably 5 to 150 kGy, more preferably 10 to 130 kGy, from the viewpoints of stretching stability and heat resistance.

  Next, the tubular parison is guided into a stretching machine, and the temperature at the stretching start point is the heat-sealing layer, the ethylene-α-olefin random copolymer (X and Y) used for the layer (A), and the ethylene-α-olefin block. While heating so as to be equal to or higher than the melting point of the copolymer (Z) and equal to or lower than 150 ° C., air is injected between nip rolls provided with a speed difference, and from the viewpoint of stretching stability, the flow (MD) direction, Stretching is preferably performed in the width (TD) direction at a magnification of preferably 2 to 10 times, more preferably 3 to 9 times. The stretching start point refers to the position where the bubble starts to expand in the TD direction due to the internal pressure of the bubble, and the stretching start point temperature refers to the tubular parison surface temperature at that position.

If necessary, heat setting may be applied after stretching to adjust the dimensional stability and shrinkage stress. As a method of the heat setting treatment, an indirect heating step of blowing hot air to the stretched film or a direct heating step of bringing the stretched film into contact with a hot roll or the like can be selected.
Moreover, when surface treatments such as corona treatment, ozone treatment, and flame treatment are performed after stretching, a multilayer film for shrink wrapping suitable for printing applications can be obtained. It is preferable to slit the obtained film into a predetermined size.

Hereinafter, the present embodiment will be specifically described with reference to examples and comparative examples, but the present embodiment is not limited to only these examples.
The evaluation method and measurement method used in this embodiment are as follows.

<1. Density>
It measured according to JIS-K-7112 using the density gradient tube.

<2. Melt flow rate (MFR)>
The measurement was performed according to JIS-K-7210 under conditions of a temperature of 190 ° C. and a load of 2.16 kg.

<3. Melting point, crystallization temperature, heat of crystal fusion>
Measurement was performed using an input-compensated differential scanning calorimeter “Diamond DSC (registered trademark)” manufactured by PerkinElmer. The sample amount was 5 to 10 mg, the measurement atmosphere was a nitrogen atmosphere, and indium was used as the calorie standard. As a heating program, the sample was first heated from 0 ° C. to 200 ° C. at a temperature rising rate of 10 ° C./min (1st. Melting behavior), left at 200 ° C. for 1 minute, and then heated at a temperature decreasing rate of 10 ° C./min. The solution was cooled from 0 ° C. to 0 ° C. and left at 0 ° C. for 1 minute (1st. Crystallization behavior). Further, the temperature was raised from 0 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min (2nd. Melting behavior). Melting point is 2nd. In the specific heat curve obtained from the melting behavior, the temperature indicating the maximum endotherm was used. The crystallization temperature is 1st. In the specific heat curve obtained by the crystallization behavior, the temperature indicating the maximum calorific value was used. 2nd. The heat of crystal melting (ΔHm) was determined using the straight line obtained by extrapolating the specific heat curve in the completely molten state obtained by melting behavior directly to the low temperature side as a baseline.
As the ratio of the heat of fusion of 100 ° C. or less, a value (%) obtained by dividing the heat of fusion at 100 ° C. or less by the heat of crystal fusion (ΔHm) in the same manner as the above-mentioned heat of crystal fusion was used.

<4. Gel fraction>
A sample placed in a 150-mesh wire mesh in boiling p-xylene was immersed for 12 hours, and the ratio of the insoluble portion was expressed by the following formula and used as a measure of the degree of crosslinking of the film.
Gel fraction (mass%) = (sample weight after extraction / sample weight before extraction) × 100

<5. Thermal shrinkage>
Measured according to ASTM D-2732. The film was sampled so as to be 10 cm × 10 cm in the flow (MD) direction and the width (TD) direction, respectively, and contracted at a temperature of 120 ° C. for 30 minutes using a hot air dryer. Five films were shrunk, the dimensional change was calculated | required, and the average value was calculated | required in both MD and TD directions, respectively.

<6. Thermal shrinkage stress>
Measured according to ASTM D-2838. The maximum heat shrinkage stress value at 120 ° C. was evaluated using an oil bath. The film was sampled to a width of 10 mm x a length of 50 mm, the peak value when immersed in an oil bath set at each temperature was measured, and the average value was obtained by measuring three times in each of the MD direction and the TD direction. .

<7. Packaging test>
7-1. Package Appearance The obtained film was slit to a width of 390 mm and packaged at 30 packs / minute using “FW-3451A-αV (registered trademark)” manufactured by Fujikikai Co., Ltd. The tray uses a tray “CK20-11E (registered trademark)” manufactured by Chuo Kagaku Co., Ltd., packs 30 packs with 100 g of clay placed on the tray, and heat-treats for 5 seconds in a shrink tunnel set at 130 ° C. After the film was shrunk, the packaging finish was evaluated.
〔Evaluation criteria〕
◯: There were no small wrinkles or corner residue around the seal before and after the package, and there was no air accumulation between the film and the package.
Δ: There were small wrinkles around the seal before and after the package, but there was no corner residue and no air accumulation.
X: The film did not shrink completely and an air pocket remained.

<8. Optical properties>
8-1. Haze degree Measured according to ASTM D-1003. <7. Pillow shrink packaging was performed under the same conditions as in the packaging test>, and the film on the tray upper surface of the obtained package was cut into 50 mm × 50 mm and evaluated.
8-2. Glossiness Measured according to ASTM D-2457. <6. Pillow shrink packaging was performed under the same conditions as in the packaging test>, and the film on the tray upper surface of the obtained package was cut into 50 mm × 50 mm and evaluated.
When the haze is 2.5% or less and the glossiness is 140% or more, the film has a high-class feeling and can be evaluated to have a very high commercial value.

<9. Deformability recovery (indentation load, recovery time)>
As described above, <7. Pillow shrink wrapping was performed under the same conditions as in the packaging test>, and evaluation was performed by the following method using the resulting package.
A metal round bar with a diameter of 15 mm (a hemisphere with a radius of 7.5 mm at the tip) is pushed into the center of the pillow shrink package at a constant speed of 1000 mm / min to a depth of 20 mm from the top of the tray, and then pulled out at a speed of 1000 mm / min. It was. The load when 20 mm was pushed in was defined as the indentation load. Immediately after the round bar was pulled out (3 seconds after the round bar came into contact with the film), the time required to eliminate the imprint formed on the film by the indentation was taken as the restoration time. The clay inside moved to the corner of the tray so as not to contact the film during pressing.

9-1 Indentation load [Evaluation criteria]
○: 400 gf or more: Very high load resistance, a level in which the film is not easily stretched due to the stacking of packages, and indentation marks are not easily generated.
Δ: 300 to 400 gf: Excellent load resistance, but depending on conditions, the film is stretched due to stacking of the package, etc., and a level of indentation is generated.
X: 300 gf or less: The level with which load resistance is inferior and the film is stretched due to the stacking of the package, etc., and indentation marks are easily generated.

9-2 Restoration time [Evaluation criteria Restoration time]
○: Restoration time less than 180 seconds: Very good deformation / deformability after packaging, and Yurmi and wrinkles are unlikely to remain even after the package is transported.
Δ: Restoration time 180 seconds or more and less than 300 seconds: excellent in deformation / replication properties after packaging, but depending on conditions, Yurumi and wrinkles remain after transporting the package.
X: 300 seconds or more: a level at which Yurumi and wrinkles remain in the transportation of the package, because the deformation / replication property after packaging is not good.

<10. Appearance after transportation>
<6. As described above, except that the packaging body was changed from 100 g of clay to about 240 g of a water-kneaded product (disk-shaped tempura × 4 pieces) stored in a refrigerator at 0 ° C. Pillow shrink wrapping was performed under the same conditions as in the packaging test> to obtain a package. Subsequently, the obtained packaged products were stacked in three rows to form two rows, placed in cardboard, and transported back and forth by a distance of about 400 km one way. The temperature at the time of transportation shall be the refrigeration temperature (0 to 10 ° C), and a cardboard board is inserted between the tray stacked in three stages and another tray stacked in the cardboard so as not to buffer each other. I made it. The cushioning material was put between the top tray and the cardboard lid so that there was no gap.
〔Evaluation criteria〕
○: There is no looseness or wrinkles, the film has a tight feeling, and the packaged body is not moved compared to the pre-transport state.
Δ: Although there is looseness and wrinkles, the overall appearance is good when the packaged body is not moved compared to the state before transportation.
X: Loose or wrinkled, and an unfavorable appearance state in which the packaged body is moving compared to the state before transportation.

<11. Overall evaluation>
〔Evaluation criteria〕
○: All are ○, and can be used suitably.
△: Some are △, others are evaluated as ◯, practical level.
X: x is present and not at a practical level.

Resins used in Examples and Comparative Examples are as follows.
<Ethylene-α-olefin random copolymer>
・ X1: Ethylene-α-olefin random copolymer (Ube Industries, Ltd. Umerit 0520F)
(Polymerized with a single site catalyst, α-olefin: 1-hexene, density: 0.904 g / cm ³ , melt flow rate (hereinafter referred to as “MFR”): 2.0 g / 10 min, melting point: 112 ° C. Crystallization temperature: 97 ° C., heat of crystal fusion: 70 J / g, ratio of heat of fusion below 100 ° C .: 70%)
* X2: ethylene-α-olefin random copolymer (Ube Industries, Ltd. Umerit 1520F)
(Polymerized with a single site catalyst, α-olefin: 1-hexene, density: 0.914 g / cm ³ , MFR: 2.0 g / 10 min, melting point: 113 ° C., crystallization temperature: 97 ° C., heat of crystal melting : 96 J / g, ratio of heat of fusion of 100 ° C. or lower: 55%)
* X3: ethylene-α-olefin random copolymer (Umerit Corp. Umerit 215FA)
(Polymerized with a single site catalyst, α-olefin: 1-hexene, density: 0.914 g / cm ³ , MFR: 2.0 g / 10 min, melting point: 113 ° C., crystallization temperature: 97 ° C., heat of crystal melting : 96 J / g, ratio of heat of fusion of 100 ° C. or lower: 55%)
X4: ethylene-α-olefin random copolymer (Sumitomo Chemical Co., Sumikasen E FV201)
(Polymerized with a single site catalyst, α-olefin: 1-hexene, density: 0.916 g / cm ³ , MFR: 2.3 g / 10 min, melting point: 114 ° C., crystallization temperature: 101 ° C., heat of crystal melting : 103 J / g, ratio of heat of fusion of 100 ° C. or lower: 56%)
X5: ethylene-α-olefin random copolymer (dowchemical 2032)
(Polymerized with multi-site catalyst, α-olefin: 1-octene, density: 0.926 g / cm ³ , MFR: 2.0 g / 10 min, melting point: 121 ° C., crystallization temperature: 105 ° C., crystal melting (Amount of heat: 128 J / g, ratio of heat of fusion below 100 ° C .: 26%)
X6: ethylene-α-olefin random copolymer (Ube Industries, Ltd. Umerit 2525F)
(Polymerized with a single site catalyst, α-olefin: 1-hexene, density: 0.926 g / cm ³ , MFR: 2.5 g / 10 min, melting point: 118 ° C., crystallization temperature: 105 ° C., heat of crystal fusion : 104 J / g, ratio of heat of fusion of 100 ° C. or lower: 37%)

<Ethylene-α-olefin block copolymer>
Z1: ethylene-α-olefin block copolymer (Infuse D9107.15 manufactured by Dow Chemical Co.)
(Α-olefin: 1-octene, density: 0.866 g / cm ³ , MFR 1.0 g / 10 min, melting point: 120 ° C., crystallization temperature: 91 ° C., heat of crystal fusion: 18 J / g, heat of fusion of 100 ° C. or less Ratio: 7%)
Z2: ethylene-α-olefin block copolymer (Infuse D9100.05 manufactured by Dow Chemical Co.)
(Α-olefin: 1-octene, density: 0.877 g / cm ³ , MFR 1.0 g / 10 min, melting point: 120 ° C., crystallization temperature: 96 ° C., heat of crystal fusion: 37 J / g, heat of fusion of 100 ° C. or less Ratio: 4%)

<Low density ethylene-α-olefin random copolymer>
Y1: ethylene-α-olefin random copolymer (engage 8100 manufactured by Dow Chemical Co., Ltd.)
(Α-olefin: 1-octene, density: 0.870 g / cm ³ , MFR: 1.0 g / 10 min, melting point: 59 ° C., crystallization temperature: 42 ° C., heat of crystal melting: 17 J / g, 100 ° C. or less Ratio of heat of fusion: 100%))
Y2: ethylene-α-olefin random copolymer (engage 8150 manufactured by Dow Chemical Company)
(Α-olefin: 1-octene, density: 0.868 g / cm ³ , MFR: 0.5 g / 10 min, melting point: 57 ° C., crystallization temperature: 42 ° C., heat of crystal melting: 18 J / g, 100 ° C. or less Ratio of heat of fusion: 100%))
・ LD1
High-pressure low-density polyethylene (Suntech LD M2004 manufactured by Asahi Kasei Chemicals)
(Density: 0.921 g / cm ³ , MFR: 0.4 g / 10 min, melting point: 109 ° C., crystallization temperature: 95 ° C., heat of crystal fusion: 110 J / g, ratio of heat of fusion below 100 ° C .: 49%)
・ LD2
High pressure low density polyethylene (Suntech LD M2102, Asahi Kasei Chemicals)
(Density: 0.922 g / cm ³ , MFR: 0.2 g / 10 min, melting point: 110 ° C., crystallization temperature: 97 ° C., heat of crystal fusion: 106 J / g, ratio of heat of fusion below 100 ° C .: 46%)

  As Examples 1 to 13 and Comparative Examples 1 to 10, shrinkable multilayer films having the arrangement of layers as shown in Table 1 and Table 2 were produced. Further, in Examples 1 to 13 and Comparative Examples 1 to 10, diglycerin oleate (Riken Vitamin Riquemar (registered trademark) O-71-DE) and glycerin monooleate (Riken Vitamin Ricamar (registered trademark) OL-) 100-E) was used as an antifogging agent.

[Examples 1 to 13]
The raw materials used in each layer are melted from three extruders, and the respective resins are coextruded from an annular die. In Example 1, a tube-shaped unstretched raw material having a two-layer structure including a one-side heat seal layer and a layer (A) is used. Got anti. In Examples 2 to 13, a layer (A) and a tube-shaped unstretched raw material having a three-layer structure in which both surface layers are heat seal layers were obtained. Each extrusion amount was set so that each layer had a predetermined ratio, and the layer configuration was confirmed by cross-sectional observation. In addition, it cooled and solidified using the water for the cooling medium from the outer side of the tubular raw fabric.
Moreover, in Examples 1-13, with respect to the resin raw material which uses the mixture which is mass ratio 1: 1 of diglycerol oleate and glycerol monooleate as an anti-fogging agent in a heat seal layer and a layer (A), for each layer, 2.0% by mass was added. As an addition method, a liquid injection method was used in which the antifogging agent was injected with a high-pressure pump before the compression portion of the screw of the extruder.
Next, the tube-shaped unstretched raw fabric cooled and solidified was guided to an electron beam irradiation apparatus, and subjected to crosslinking treatment at an acceleration voltage of 750 kV so as to obtain a predetermined irradiation dose from both sides of the tube-shaped original fabric. Subsequently, an ethylene-α-olefin random copolymer (X and Y) used for the heat seal layer, the layer (A), and an ethylene-α-olefin block copolymer are introduced into the stretching machine and the temperature at the stretching start point is used for the layer (A). (Z) While being heated to a melting point of 150 ° C. or less, air is injected between two pairs of nip rolls provided with a speed difference, bubbles are formed by the internal pressure, and the bubbles are deflator parts. After folding, the film was wound up by a winder to collect the original film. The draw ratio in the flow direction (MD) was adjusted by the speed ratio between the speed of the heated nip roller and the speed of the winder. And the ratio of the film original fabric width | variety and parison width | variety of a winder was made into the draw ratio of the width direction (TD). The MD stretch ratio and TD stretch ratio were 7.0 × 7.0, and a film having a film thickness of 11 μm was obtained.
While cutting both ends of the obtained tube-shaped film, it was cut into a size of 390 mm in width to form two films, each of which was a single film, having a width of 450 mm, an inner diameter of 76.2 mm, and a thickness of 10 mm. The film was wound with a length of 200 m with a tension that does not cause wrinkles in the cigarette, and a multilayer film for shrink wrapping for evaluation was obtained.

[Comparative Examples 1 to 10]
In the same manner as in Examples 1 to 13, a multilayer film for shrink wrapping was obtained and evaluated using polymers as shown in Comparative Examples 1 to 10 in Table 2.

  Table 3 shows the evaluation results of Examples and Comparative Examples.

As is clear from the results in Table 3, the multilayer films for shrink wrapping of Examples 1 to 13 have a heat shrinkage ratio, heat shrinkage stress, package appearance, haze, glossiness, deformation recovery, and appearance after transportation. It was excellent in terms. In particular, the shrink-wrap multilayer films of Examples 1 to 13 were excellent in deformation recovery.
On the other hand, in Comparative Examples 1 and 2, the layer (A) has a density comparable to that of the ethylene-α-olefin random copolymer (X3) and the ethylene-α-olefin block copolymer (Z). Although the composition which consists of an ethylene-alpha-olefin random copolymer (y1, y2) was used, although the obtained film is excellent in heat shrinkability, deformation | transformation recoverability (restoration time) is 300 second or more. There was a shortage, and the appearance of the package after transportation deteriorated.
In Comparative Example 3, the ratio of the ethylene-α-olefin random copolymer (y1) of the layer (A) was increased with respect to Comparative Example 1, but as in Comparative Example 1, deformation recovery (restoration time) However, the appearance of the package after transportation deteriorated.
In Comparative Examples 4, 5, and 6, the same procedure as in Examples 5, 7, and 10 was performed except that the low-density ethylene-α-olefin random copolymer (y1) was used for the layer (A). Compared to, the time required for deformation recovery (restoration time) was 300 seconds or more, and the appearance of the package after transportation deteriorated.
Comparative Examples 7 to 9 were carried out in the same manner as in Examples 11 to 13 except that the low density ethylene-α-olefin random copolymer (y1) was used for the layer (A). Compared to, the time required for deformation recovery (restoration time) was 300 seconds or more, and the appearance of the package after transportation deteriorated.
In Comparative Example 10, the same procedure as in Example 11 was performed except that the layer (A) was an ethylene-α-olefin block copolymer (Z2) alone, but the obtained film was flexible and deformable. The load required for (indentation load) was 300 gf or less, and the appearance of the package after transportation deteriorated.
The multilayer film for shrink wrapping of Examples 1 to 13 was a multilayer film for shrink wrap having both heat shrinkability and deformation recovery after shrink wrapping.

  By using the multilayer film for shrink wrapping of the present invention, it is possible to achieve both heat shrinkability and deformation recovery, which has not been achieved with conventional films, and a beautiful finish with no corner residue in various container shapes. In addition to being obtained, even when a load is applied to the package, the stretch marks of the film can be quickly restored, and the beautiful finish of the shrink package can be maintained even after transportation.

Claims (10)

A multilayer film for shrink wrapping comprising a layer (A) and a heat seal layer laminated on the layer (A),
The heat seal layer is
A layer composed of at least one ethylene-α-olefin random copolymer (X) having a density of 0.900 to 0.930 g / cm ³ ;
The layer (A) is
30-80% by mass of at least one ethylene-α-olefin random copolymer (Y) having a density of 0.900 to 0.930 g / cm ³ ;
Shrinkage which is a layer formed of a composition containing 20 to 70% by mass of at least one ethylene-α-olefin block copolymer (Z) having a density of 0.860 to 0.890 g / cm ^3. Multi-layer film for packaging. The multilayer film for shrink wrapping according to claim 1, wherein the ethylene-α-olefin random copolymer (Y) has a density of 0.900 to 0.920 g / cm ³ .   The multilayer film for shrink wrapping according to claim 1 or 2, wherein the ethylene-α-olefin random copolymer (Y) has a ratio of heat of fusion of 100 ° C or lower of 30 to 80%.   The melting point of the ethylene-α-olefin block copolymer (Z) is 100 to 130 ° C, and the crystallization temperature is 80 to 100 ° C, for shrink wrapping according to any one of claims 1 to 3. Multilayer film.   The multilayer film for shrink wrapping according to any one of claims 1 to 4, wherein the ethylene-α-olefin block copolymer (Z) has a heat of crystal fusion of 10 to 50 J / g.   The multilayer film for shrink wrapping according to any one of claims 1 to 5, which is crosslinked by electron beam irradiation.   The multilayer film for shrink wrapping according to any one of claims 1 to 6, wherein the gel fraction of the entire film for shrink wrapping is 20 to 60% by mass.   The multilayer film for shrink wrapping according to any one of claims 1 to 7, wherein the heat seal layer is laminated on both surfaces of the layer (A). A step of co-extruding the heat sealing layer and the raw material resin of the layer (A) from an annular die, and cooling the obtained tubular parison;
Re-heating in the stretching machine, the stretching start temperature is a temperature within the range of the melting point of the raw material resin used for the heat seal layer and the layer (A) to 150 ° C., and a magnification of 2 to 10 times in the flow direction and width direction. Stretching,
The manufacturing method of the multilayer film for shrink wrapping as described in any one of Claims 1-8 containing these.   The manufacturing method of the multilayer film for shrink wrapping of Claim 9 which further includes the process of performing the crosslinking process by electron beam irradiation to the said tubular parison.