JP2003260764A - Polyolefin resin heat-shrinkable multi-layer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyolefin resin heat-shrinkable multi-layer film having excellent properties of restoration from deformation in a range from a chilled zone of approximately 0°C to a refrigeration zone of approximately -10°C. <P>SOLUTION: The polyolefin resin heat-shrinkable multi-layer film is composed of at least three layers, and its heat-shrinkage factor at 80°C is 20-50%. The film has following characteristics as described from (1) to (3). (1) A peak temperature of tanδ of the film measured by dynamic viscoelasticity measurement is -10 to 2°C. (2) In a secondary melting behavior of the film measured by a differential scanning calorimeter (DSC), a peak is at least in a range of 155°C±15°C, and a heat of crystal fusion at 125°C or higher is 10 to 20 J/g. (3) A lengthwise tear strength of the film is at least 0.05 N or greater, and a ratio of lengthwise and widthwise tear strength is lengthwise/widthwise = 1.2 to 5.0 times. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat shrinkable multi-layer film of a polyolefin resin for shrink wrapping, and particularly stretch shrink wrapping and pillow type automatic wrapping machines by an automatic wrapping machine such as a bump type or a straight type. Stretched film suitable for shrink wrapping.

[0002]

2. Description of the Related Art Conventionally, shrink wrapping has the feature that it does not depend on the shape and size of the article to be packaged, and at the same time, it can quickly and tightly package a plurality of products. It is often used for packaging foods, sundries, etc. because it has a beautiful appearance, exhibits a display effect, enhances the product value, keeps the contents hygienic, and allows visual confirmation of quality.

A typical example of such shrink-wrapping is a method of heat-shrinking the film with hot air or the like after the contents are primarily wrapped with a little room left in the film, for example, pillow shrink packaging. Generally, food items such as food stored in containers and trays are covered with a film in a tubular shape, and then a center roller device such as a rotating roller is used so that the seal line is on the back side of the items. After heat sealing, both open ends of the tubular film are heat sealed to form a bag, which is heat-shrinked. For this pillow shrink packaging, there is a method other than the above, such as a method of heat-shrinking a bag-like film that is sealed on three sides or four sides.

Further, as in the conventional stretch wrapping, the film is wrapped in a tensioned state to some extent, the end of the film is folded into the bottom of the article to be wrapped, and the folded portion is primarily adhered to the film by self-adhesion or heat fusion. After packaging, there is a method such as a stretch shrink method in which heat shrinkage treatment is similarly applied to remove local tarmi and wrinkles of the film, and all of them have a tight and beautiful finish. On the other hand, in recent years, the speed of wrapping by automatic wrapping machines and the diversification of items to be packed have advanced, and the quality required for packaging as a product has become more and more sophisticated. Is in the process of higher performance and higher functionality.

Conventionally, as a film suitable for a shrink wrapping film, a surface layer (A) containing 50% by weight or more of an ethylene α-olefin copolymer resin and a propylene as an inner layer are disclosed in JP-A-10-34848. Mixed resin layer (B) of a polymer-based polymer and a polybutene-1 resin, a layer having a density different from that of the surface layer and containing 50% by weight or more of an ethylene α-olefin copolymer resin having a specific MFR (C) A multilayer shrink film in which the thickness ratio of each layer including is specified is disclosed.

According to the above-mentioned publication, the surface layer (A) is intended to provide the surface of the multilayer film with transparency, luster, (low temperature) heat sealability, antifogging property and the like, and has a linear low density. The use of a resin such as an ethylene-vinyl acetate copolymer (hereinafter EVA) as a resin containing 50% by weight or more of an ethylene α-olefin copolymer resin such as polyethylene is exemplified. Further, the layer (C) has an effect of imparting high puncture strength to the film, and contains 50 parts by weight of an ethylene α-olefin copolymer resin such as linear low density polyethylene having a higher density than the surface layer (A). The use of a resin such as EVA as an example of a resin containing at least 100% by weight is illustrated.

The layer (B) mainly has a role of imparting heat resistance and deformation recovery to the entire multilayer film, and a mixed composition of a propylene polymer and polybutene-1 is exemplified. And the multilayer film original fabric which consists of four or more layers of layer (A), layer (B), and layer (C) is stretched at an area stretching ratio of 3 to 50 times at a temperature of 40 to 120 ° C., resulting in heat resistance. It is possible to obtain a high-strength film having a thickness of 7 to 20 μm, which has excellent properties, low-temperature shrinkage, puncture resistance, tear resistance, and deformation recovery.

However, the above-mentioned Japanese Laid-Open Patent Publication No. 10-3484.
The film disclosed in Japanese Patent No. 8 had a property that the deformation recovery property was poor in a chilled region around 0 ° C to a frozen region around -10 ° C. For this reason, when the frozen product is thawed at around 0 ° C., the film cannot follow the volume change phenomenon of the contents, and the film is slackened, resulting in a bad appearance. Further, when the packaged product is refrigerated and transported, there is a problem in that the film itself is slackened or wrinkled due to the vibration itself or the movement of the content due to the vibration, which significantly deteriorates the appearance of the product. Furthermore, when the film of the tray package displayed in the refrigerated open showcase at the store is pushed in with a finger, there is a problem that the film cannot follow and the finger mark remains and the film is dented and impairs the appearance. Was there.

Further, in a packaged object having sharp protrusions or edges in a frozen or chilled state, a film breakage once generated during packaging propagates in the longitudinal direction (flow direction during film formation, hereinafter referred to as MD). However, it is necessary to stop the wrapping machine and reset the film, restart the film, or the like, and depending on the wrapping machine, the cuttability of the film is not stable and the cut film edge is torn off. become,
After that, there were problems that the foldability of the film was poor and the appearance of the package was impaired.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polyolefin resin heat-shrinkable multilayer film which is excellent in deformation recovery from a chilled region around 0 ° C to a frozen region around -10 ° C. .

[0011]

Means for Solving the Problems As a result of studies to solve the above problems, the present inventors have found that tan δ and melting behavior by dynamic viscoelasticity measurement of the film, and tear strength property of the film within a specific range. By adjusting it, the heat resistance, shrinkage property, optical property, and piercing resistance of the conventional film are maintained, while the cut property of the film during packaging is remarkably improved, and the chilled region around 0 ° C is -10 ° C. It was found that a shrink film having significantly excellent deformation recovery in the front and rear frozen regions can be obtained.

That is, the present invention is as follows.
1. A polyolefin resin heat-shrinkable multilayer film having a heat shrinkage rate of 20% to 50% at 80 ° C., which has at least three layers, and is characterized by the following (1) to (3): Multilayer film. (1) The peak temperature of tan δ measured by dynamic viscoelasticity of the film is −10 to 2 ° C. (2) 2nd. By the differential scanning calorimeter (DSC) measurement of the film. At least 155 ° C ± 1 in melting behavior
There is a peak in the range of 5 ° C, and the heat of fusion of crystals at 125 ° C or higher is 10 to 20 J / g. (3) The tear strength of the film is at least 0.05 N in the machine direction and the ratio of the tear strength in the machine direction and the tear strength in the machine direction is 1.2 to 5.0 times.

2. 20% by weight of propylene polymer (a)
-60% by weight, and 10% to 50% by weight of a polyolefin-based elastomer (b) having a Vicat softening point of less than 80 ° C.
And at least one inner layer composed of 10% by weight to 40% by weight of the polybutene-1 resin (c). The polyolefin-based resin heat-shrinkable multi-layer film as described in 1.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention, and particularly preferred embodiments thereof, will be described in detail below. The present invention is different from the prior art in that a polyolefin-based resin heat-shrinkable multi-layer film having at least a three-layer structure and having a heat shrinkage rate at 80 ° C. of 20% to 50% is measured by dynamic viscoelasticity measurement of the film. Tan δ, melting behavior by differential scanning calorimeter (DSC) measurement, and further the tear strength characteristics of the film are specified.

As a preferred embodiment that satisfies the above, there is a feature that at least one specific resin composition layer containing a polyolefin-based elastomer having a specific Vicat softening point is provided in the inner layer. First, the film of the present invention has a tan δ peak temperature of −10 to 2 ° C. measured by dynamic viscoelasticity. When the peak temperature of tan δ measured by dynamic viscoelasticity of the film exceeds 2 ° C, the deformation recovery property in the chilled region around 0 ° C to the frozen region around -10 ° C deteriorates. On the other hand, when the peak temperature of tan δ is less than −10 ° C., the film becomes too flexible and cannot be tightly bound, which causes Yumi and Talumi.

Next, the film of the present invention was measured by a differential scanning calorimeter (DSC) to have a 2nd. The melting behavior has a peak in the range of at least 155 ° C. ± 15 ° C., and
The heat of fusion of crystals at 125 ° C. or higher is in the range of 10 to 20 J / g. Differential scanning calorimeter (DSC) of film
2nd. If the melting behavior has a peak of less than 140 ° C., problems such as easy opening of holes during heat sealing tend to occur. On the other hand, when the peak exceeds 170 ° C, the deformation recovery property in the chilled region around 0 ° C to the frozen region around -10 ° C deteriorates.

Further, a film differential scanning calorimeter (DS
C) 2nd. In the melting behavior, if the amount of heat of melting at 125 ° C or higher is less than 10 J / g, the heat resistance becomes insufficient, so the running of the film becomes unstable during packaging, defective folding, and holes during heat sealing. Trouble such as easy opening is likely to occur. On the other hand, 1
If the heat of fusion at 25 ° C. or more exceeds 20 J / g, the peak temperature of tan δ of the film exceeds 2 ° C., and the deformation recovery property from the chilled region around 0 ° C. to the frozen region around −10 ° C. deteriorates.

The film of the present invention has a tear strength of at least 0.05 N in the longitudinal direction, and
The vertical and horizontal tear strength ratios are in the range of vertical / horizontal = 1.2 to 5.0 times. If the tear strength in the longitudinal direction is less than 0.05 N, tearing tends to occur during packaging. Further, the tear strength in the longitudinal direction is preferably less than 1.0 N from the viewpoint of easy opening.

Further, when the present film is used for packaging, examples of the packaging machine to be used include a linear packaging machine and a push-up packaging machine. Particularly, as an example of a high speed type linear packaging machine, Omori Machinery Co., Ltd. "STC-IIB" (trademark) manufactured will be described. In the film supply unit, while pulling the film in the lateral direction by a side belt at 5 to 10%,
The mechanism is to make the film into a tubular shape, cut the front of the tray (the direction of travel) with a cutter, and fold the film to the bottom of the tray while covering the film with the film on the tray. MD / TD If the ratio of the tear strength is less than 1.2 times, the minute tears that occur when packaging a packaged object having sharp protrusions or edges in the frozen or chilled state easily propagate to the MD up to the film supply section. This requires time and effort such as resetting and restarting the film, which is a major cause of packaging loss. On the other hand, if the tear strength ratio of MD / TD exceeds 5.0 times, due to protrusions of the packaged object during packaging,
The tear that has occurred propagates extremely laterally and causes packaging loss.

In a preferred embodiment of the film of the present invention, a propylene-based polymer (a), a polyolefin-based elastomer (b) having a Vicat softening point of less than 80 ° C., and a polybutene-1-based resin (c) are used in its inner layer. At least one specific resin composition layer (hereinafter referred to as D layer) to be constituted
It has a layer. The propylene polymer (a) is preferably a propylene homopolymer (homotype), propylene, and at least one α such as ethylene and butene.
-Copolymer with olefin (random type, block type). From the viewpoint of heat resistance, more preferable propylene-based polymers are propylene homopolymers and propylene-ethylene random copolymers having a melting point of 150 ° C or higher. The propylene-based polymer has a melt flow rate (hereinafter referred to as MFR) of 0.2 to 15 g / 10.
It is for the minute. What is MFR JIS-K-7210-1
It is a value measured according to 995, and the MFR of the propylene-based polymer is measured under the conditions of 230 ° C. and 2.16 kgf. MF of propylene polymer (a)
If R is less than 0.2 g / 10 minutes, the extrusion power during extrusion will increase and the surface smoothness of the extruded raw fabric will decrease.
The orientation is strongly applied to the MD, the tear strength of the MD is weakened, and the film easily breaks during packaging. Also, MFR is 15g
If it exceeds / 10 minutes, the stretchability tends to deteriorate, and even if a film is obtained, only those having poor mechanical properties such as deformation recovery and puncture strength tend to be obtained.

The proportion of the propylene polymer (a) in the D layer is 20% by weight to 60% by weight. If the amount exceeds 60% by weight, -10 ° C from the chilled region around 0 ° C.
The deformation recovery property in the front and rear frozen regions becomes poor, and the MD tear strength decreases when the content is less than 20% by weight, and the MD / TD tear strength ratio becomes less than 1.2 times, resulting in sharp protrusions in the frozen or chilled state. Micro breakage that occurs when a packaged object having edges or edges is easily propagated to the MD, which is not preferable. Furthermore, since the film becomes too soft and becomes less stiff, and the heat resistance becomes insufficient, problems such as easy opening of holes during heat sealing tend to occur.

Next, the polyolefin-based elastomer (b) having a Vicat softening point of less than 80 ° C. has an MFR of 0.2 to 15 g.
/ 10 minutes. The Vicat softening point referred to in the present invention is a value measured by JIS-K-7206 (test load 1 kg, heating rate 50 ° C./hour). When the Vicat softening point is 80 ° C or higher, the softening of the propylene-based polymer becomes insufficient and the stretched film forming stability deteriorates, and the deformation recovery property in the chilled region around 0 ° C to the frozen region around -10 ° C decreases. To do. Further, the Vicat softening point of the polyolefin-based elastomer (b) is preferably less than 80 ° C., more preferably less than 60 ° C., but its lower limit is difficult to specify by the above-mentioned measuring method, Is room temperature (23 ℃)
And solid.

The above polyolefin elastomer (b)
MFR of JIS-K-7210-1995 (230
C., 2.16 kgf).
The polyolefin-based elastomer (b) has an MFR of 0.
If it is less than 2 g / 10 minutes, the extrusion power during extrusion will increase and the surface smoothness of the extruded raw material will decrease, or the MD will have a strong orientation, the MD tear strength will be weak and the film will easily break during packaging. Become. On the other hand, if the MFR exceeds 15 g / 10 minutes, the stretchability is lowered, and even if a film is obtained, only those having poor mechanical properties such as deformation recovery and puncture strength can be obtained.

The density of the polyolefin elastomer (b) is 0.860 to 0.910 g / cm ³ . The density referred to in the present invention is a value at 23 ° C. measured according to JIS-K-7112. 0.860g density
If it is less than / cm ³ , the resin tends to be blocked, so that the storage temperature must be controlled, which is an obstacle to handling.
Further, if the density exceeds 0.910 g / cm ³ , the softening of homo PP becomes insufficient and the stretching becomes unstable, and the deformation recovery property from the chilled region around 0 ° C to the frozen region around -10 ° C decreases. To do.

Next, the proportion of the polyolefin elastomer (b) in the D layer is 10% by weight to 50% by weight.
Is. If it exceeds 50% by weight, the tear strength of MD is lowered and the tear strength ratio of MD / TD is less than 1.2 times, and when propagating a product with protrusions, tear propagation easily occurs in the vertical direction, which is not preferable. . Further, the film becomes too soft and loses its rigidity, and the heat resistance becomes insufficient, and troubles such as easy opening of holes during heat sealing tend to occur. Below 10% by weight the tan of the film
The peak temperature of δ exceeds 2 ° C., and the deformation recovery from the chilled region around 0 ° C. to the frozen region around −10 ° C. deteriorates.

Specific examples of the polyolefin elastomer (b) include propylene and one or more kinds of α-olefins (having 4 to 8 carbon atoms in addition to ethylene).
In addition to those copolymerized with conventional catalysts such as Ziegler-Natta catalyst, those copolymerized with metallocene-based catalysts are also included, and copolymers with a high concentration of up to about 70% by weight. The rubber component may be uniformly dispersed, or an amorphous poly-α-olefin or an ethylene-butylene copolymer may be used, and at least one of them may be used and a blend of two or more thereof may be used.

Alternatively, it is a random copolymer of ethylene and at least one monomer selected from α-olefins having 3 to 18 carbon atoms, and α-olefins include propylene, butene-1 and pentene-1. , 4-methyl-pentene-1, hexene-1, octene-1, decene-
1, dodecene-1, etc., and a hydrocarbon having a polyene structure, for example, dicyclopentadiene, 1,4
-Hexadiene, norbornene-based monomers (eg ethylidene norbornene) and the like may be copolymerized. The ethylene content in the copolymer is usually 40 to 95% by weight, preferably 50 to 90% by weight, more preferably 60 to 85% by weight.
belongs to. The resin may be polymerized with either a multi-site catalyst or a single-site catalyst.

The polyolefin-based elastomer (b) can be used alone to form a film or pellets by melt extrusion. For example, propylene used in the D layer and one or more α-
A copolymer with an olefin (having 4 to 8 carbon atoms in addition to ethylene) is produced by the following multistage polymerization method.
First, as a first step, polymerization is carried out in the presence of a titanium compound catalyst and an aluminum compound catalyst using a propylene monomer and optionally an ethylene monomer or an α-olefin monomer to obtain a first propylene resin. This first propylene-based resin is a propylene-based polymer, propylene-ethylene copolymer, propylene-
It may be an α-olefin copolymer or the like.

In the second step, the above-mentioned first propylene-based resin containing the titanium compound catalyst and the aluminum compound catalyst is copolymerized with an olefin monomer (for example, ethylene, propylene, or α-olefin). Thus, a second polyolefin resin is obtained.
The second polyolefin resin obtained by this two-step reaction is a propylene-ethylene copolymer, propylene-
It can be an α-olefin copolymer or an ethylene-α-olefin copolymer. The feature of this production method is that the polymerization is not completed in one step, but multi-step polymerization of two or more steps is performed.

From the above, it is possible to successively produce a plurality of types of polymers, and a blend type copolymer at a molecular level, which is completely different from ordinary polymer blends, is produced. High flexibility is included. Examples of the actual resin include "ADFLEX" (trademark) manufactured by Sun Allomer. Next, the polybutene-1 resin (c) preferably has an MFR of 0.2 to 10 g / 10 min, and the MFR of the polybutene-1 resin (c) is JIS-K-7210-1995 (190 ° C,
2.16 kg).

When the MFR is less than 0.2 g / 10 minutes, the compatibility with the propylene-based polymer (a) tends to be deteriorated, and the film tends to be whitened or the surface smoothness of the extruded raw sheet tends to be deteriorated. is there. When the MFR exceeds 10 g / 10 minutes, the stretchability is likely to be lowered, and mechanical properties such as deformation recovery and puncture strength may not be sufficient even if a film is obtained. As the polybutene-1 resin (c), homobutene-1, and a copolymer of butene-1 and ethylene or propylene having a butene-1 content of 70% by weight or more can be used. Polybutene-1 resin (c)
The ratio in the D layer is 10% by weight to 40% by weight. If it exceeds 40% by weight, the film becomes too soft,
In addition to lack of stiffness, heat resistance becomes insufficient, and problems such as easy opening of holes during heat sealing tend to occur.
Further, if it is less than 10% by weight, the stretchability and tear strength decrease.

Further, the film of the present invention may be
In addition to the D layer, another internal layer (F layer) that is further laminated with both surface layers (E layer) can be provided. Below, E layer,
The F layer will be described. The E layer secures airtightness as a package by heat sealing, adhesion, and the like, and in addition to transparency and gloss, bleeds additives such as antifogging agents, antistatic agents, and lubricants by an internal addition method. , A layer that exhibits the surface characteristics required as a film. As the resin used in the E layer, ethylene α-olefin copolymer resin,
EVA, ethylene-aliphatic unsaturated carboxylic acid copolymer,
At least one of polyethylene-based resins such as ethylene-aliphatic unsaturated carboxylic acid ester copolymer, or 2
More than one composition can be used. In the case of ethylene α-olefin copolymer resin, from the viewpoints of tear strength, puncture strength, deformation recovery property and stretching stability, α-olefin is 4-methyl-pentene-1, hexene-
1, octene-1 are preferred.

The F layer serves as a stretching assisting layer and is a polyethylene type resin such as ethylene α-olefin copolymer resin, EVA, ethylene-aliphatic unsaturated carboxylic acid copolymer and ethylene-aliphatic unsaturated carboxylic acid ester copolymer. At least one selected from resins and polypropylene-based resins is preferably used. Further, recycled resin obtained by pulverizing a stretched film and pelletizing after remelting can be used, but tear strength and puncture strength are also usable. In order to secure the deformation recovery property and the stretch film forming stability, the ethylene α-olefin copolymer preferably has a content of 20 to 60%.

Next, in the multilayer film of the present invention, the thickness ratio of each layer to all layers is 20 to 60% for the E layer and F layer for the heat sealing property, mechanical strength, deformation recovery property, heat resistance and the like. Is preferably 20 to 70% and the D layer is 10 to 40%, and the thickness of the multilayer film is usually 5 to 60 μm, preferably 6 to 40 μm. It is a thin region of ˜20 μm. The film of the present invention comprises an E layer forming a surface layer and an inner layer D
The layers are composed of at least 3 layers in total, and the layers are arranged, for example, in the case of 3 layers: E / D / E, in the case of 4 layers: E / F / D / E, in the case of 5 layers. : E / F / D / F /
E, E / D / F / D / E, 7 layers: E / F / D / F
Examples thereof include / D / F / E, E / D / F / D / F / D / E, etc., but it is also possible to use the same resin layer as the E layer as an inner layer. Besides, it can be composed of 6 layers, 8 layers, and more layers.

In the film of the present invention, a gas barrier layer using polyamide, thermoplastic polyester or ethylene-vinyl alcohol copolymer as an inner layer is also required as long as the original characteristics are not impaired. In addition, an adhesive layer made of an adhesive resin may be additionally provided. Furthermore, the film of the present invention has a heat shrinkage ratio at 20 ° C. of 20 to 50%. If this value is less than 20%, the low-temperature shrinkage is basically poor, and the fit after shrinking during packaging becomes insufficient, which causes wrinkles and lumps after packaging. On the other hand, if it exceeds 50%, there is a problem that dimensional shrinkage is likely to occur during storage and distribution processes (especially in the width direction, but in the case of a roll-shaped roll, the difference in width between the winding core and the outer surface). Is also a problem).

Each resin layer of the multi-layer film of the present invention contains an antifogging agent, a plasticizer, an antioxidant, a surfactant, a colorant, an ultraviolet absorber, a lubricant, in an amount that does not impair its original properties. Inorganic fillers may be added, and sucrose ester, various silicone emulsions, silicone oils, various surfactants, higher fatty acid metal salts, and known surface-modifying polymers such as polyvinyl alcohol may be added to the film surface. If necessary, the coating may be performed by appropriately diluting with a solvent.

Next, an example of a method for producing the multilayer shrink film of the present invention will be described. First, resins constituting various types (D, E, F layers and other layers used as necessary) are melted by respective extruders, coextruded by a multilayer die, and rapidly solidified to obtain a multilayer film original fabric. . The extrusion method is
A multi-layer T-die method, a multi-layer circular method or the like can be used, but the latter is preferable. The multilayer film stock thus obtained is heated to 30 to 100 ° C. and stretched. Examples of the stretching method include a roll stretching method, a tenter stretching method and an inflation (including a double bubble method) method, and a method of forming a film by simultaneous biaxial stretching is preferable. The stretching is performed in at least one direction at an area stretching ratio of 4 to 30 times, and the stretching ratio is appropriately selected according to the heat shrinkage ratio required depending on the application. If necessary, post-treatments such as heat setting for dimensional stability, corona treatment, and plasma treatment, as well as lamination with various films may be performed.

Further, in the film of the present invention, at least one layer thereof may be crosslinked, and the crosslinking treatment may be carried out by using an electron beam,
Conventionally known methods such as irradiation with energy rays such as γ-rays and ultraviolet rays and the use of peroxides are used. Hereinafter, the present invention will be described in more detail with reference to Examples. The measurement and evaluation methods used in the present invention and the resins used are as follows. (1) Stretching stability of film formation The continuous filming stability of the film when heat-stretched was evaluated according to the following criteria. (X / L when the variation range of the stretching start point is X with respect to the distance L from the stretching start point to the stretching end point) ◎: X / L is less than 2% (extremely stable) ○: X / L Is 3% or more and less than 5% (there are some fluctuations, but the stretching bubble does not shake) Δ: X / L is 6% or more and less than 10% (the stretching bubble shakes, but the bubble can be maintained) X: X / L is 10% or more (stretched bubbles sway greatly and it is difficult to maintain bubbles)

(2) A film sample having a heat shrinkage rate of 100 mm square is placed in an air oven type thermostatic chamber set to a predetermined temperature, and is shrunk freely to 3
After processing for 0 minutes, the amount of shrinkage of the film was obtained and expressed as a percentage of the value divided by the original size, and measured for both the vertical and horizontal directions. (3) tan δ Using a dynamic viscoelasticity tester, trademark “RSAII” (manufactured by Rheometric Scientific FE),
A strip sample having a width of 7 mm (TD) and a length of 40 mm (MD) is cut out, and the temperature is from −70 ° C. to +3 at a frequency of 1 Hz.
The temperature of the tan δ peak when the temperature was raised to 0 ° C. at 5 ° C./min was adopted.

(4) Differential Scanning Calorimeter (DSC) Measurement Using a differential scanning calorimeter DSC7 (manufactured by Perkin Elmer), the temperature was raised from -10 ° C to 200 ° C at 10 ° C / min (1st. Melting. behavior). After holding at 200 ° C. for 5 minutes, the temperature was lowered to −10 ° C. at 10 ° C./minute (1st. Crystallization behavior). Then, the temperature was again raised to 200 ° C. at 10 ° C./minute (2nd. Melting behavior), and the peak temperature at this time and 125
The heat of fusion (ΔH) above ℃ was adopted. Sample weight is 5
It was made to fall within the range of 10 mg. (5) Tear strength According to JIS-P-8116, a light load tear tester (manufactured by Toyo Seiki Co., Ltd.) was used to measure in each of the vertical direction and the horizontal direction. In addition, the reading of the measurement here is performed so as to be in the range of 20 to 60 on the scale, but when there is a difference in the measured value depending on the measurement range, the higher value is adopted.

(6) Deformation recovery-1 (mold recovery) A wooden frame having an outer size of 180 × 180 mm in a hollowed-out state is used as a film support, and the outer size is 82 at the center of the support. A box-shaped wooden mold of × 82 mm is made to project from the lower side of the support table by 10 mm from the upper surface of the outer support table so that the sides of the support table can be kept parallel, and in this state, the film is formed into the box-shaped tree pattern. The mold was covered over and the edge of this film was secured to the edge of the film support with double sided tape. At this time, the tension of the film was minimal, and the film was carefully fixed so as not to cause tarmi. Then, in this state, a hot air tunnel at 90 ° C. was passed for 3 seconds to shrink the film. After passing through the tunnel, leave them at 0 ° C and -10 ° C for 3 minutes, and then remove the box-shaped wooden mold from the film support.
The state of the surface of the film fixed on the support was visually observed after 5 minutes at 0 ° C. and −10 ° C. Talmi and wrinkles,
Or, there are slight local dents, but there is no problem in commercial property ○, clearly Talmi, wrinkles, local dents and problems in commercial property are marked ×, ○ and × The one of the intermediate level was marked with △.

(7) Deformation recovery-2 (indentation recovery) The outer dimensions of the hollowed-out state are 125 ± 125 mm,
A wooden frame having a depth of 50 mm was used as a film support, and the film was covered from above and the edge of this film was fixed to the edge of the film support with double-sided tape. At this time, the tension of the film was minimal, and the film was carefully fixed so as not to cause tarmi. Then, in this state, a hot air tunnel at 90 ° C. was passed for 3 seconds to shrink the film.
After passing through the tunnel for 3 minutes at 0 ° C and -10 ° C respectively, a SUS (stainless steel) push rod with a diameter of 15 mm, whose tip was processed into a spherical surface with a radius of 7.5 mm, was cut from the film at a speed of 1000 mm / min to 15 mm from the film. To the depth of
Pushed into the center of the support from above. After pushing in to a depth of 15 mm, hold down for 0 seconds and push the pushing bar in 10
It was pulled up at 00 mm / min. After that, the state of the surface of the film fixed to the support was visually observed after 1 minute at 0 ° C. and −10 ° C. Talmi, wrinkles, or local dents are slightly recognized, but there is no problem in productability. ○: Clearly talumi, wrinkles, or local dents remain, and productability is problematic. The ones with an intermediate level between ◯ and ◯ were marked with ∆.

(8) HAZE after shrinkage ASTM-D was used by using a film obtained by passing through a hot air tunnel under conditions of 90 ° C. ± 3 seconds and shrinking 0% in area.
It was measured according to -1003-52. (9) The film 3 days after the formation of the antifogging film was further placed in an air oven type constant temperature bath at 23 ° C for 24 hours, and then the beaker containing water at 20 ° C was covered and sealed with the film. 5 ° C
After left in the refrigerator for 1 hour, the state of water attached to the film was visually evaluated according to the following criteria. 5: A transparent film with a water film formed in a mirror surface. 4: A slightly uneven water film, but there is almost no problem in checking the contents. 3: A spread water film is attached, but the contents can be confirmed and there is no practical problem. 2: Small water droplets are attached, and the shape of the contents can be seen, and it is difficult to check the details. 1: White and cloudy, and the presence of contents cannot be confirmed.

(10) Breakage during packaging Propagation M caused by sharp projections of the packaged object during packaging
Propagation in the D direction was evaluated using frozen shrimp. Chuo Kagaku's tray, trademark "Shrimp No. 24" beforehand-
Twelve frozen shrimps (280 g) stored at 30 ° C. were placed and each film was packaged using a packaging machine “STC-IIB” manufactured by Omori Machinery Co., Ltd. Each film was packaged in 10 packs, and the one that did not propagate the tear generated from the contact portion of the shrimp tail of the film was ○, the one that greatly propagated to the supply part of the packaging machine was X, and the intermediate one was Δ. .

(11) Resin used in Examples and Comparative Examples LL1: ethylene α-olefin copolymer (polymerized with a single-site catalyst, α-olefin = hexene-1, density = 0.904 g / cm ³ , MI = 4.0 g /
10 minutes) LL2: ethylene α-olefin copolymer (polymerized with a single-site catalyst, α-olefin = octene-1, density = 0.902 g / cm ³ , MI = 3.0 g /
10 minutes) LL3: ethylene α-olefin copolymer (polymerized with a single-site catalyst, α-olefin = hexene-1, density = 0.912 g / cm ³ , MI = 0.8 g /
10 minutes) EVA1: ethylene-vinyl acetate copolymer (vinyl acetate content = 15% by weight, MI = 2.2 g / 10 minutes)

PP1: propylene polymer (isotactic polypropylene (homopolymer)), density = 0.9
00 g / cm ³ , MFR = 4.0 g / 10 min, melting point (D
SC method maximum melting peak temperature) = 160 ° C. PP2: propylene-based polymer (propylene-ethylene random copolymer), density = 0.900 g / cm ³ , MF
R = 2.3 g / 10 min, melting point (DSC method maximum melting peak temperature) = 159 ° C. PP3: propylene polymer (propylene-ethylene random copolymer), density = 0.89 g / cm ³ , MFR
= 1.8 g / 10 minutes, melting point (DSC method maximum melting peak temperature) = 140 ° C.

TPO1: Polyolefin elastomer (random polypropylene type, EPR content 65% by weight), density = 0.880 g / cm ³ , MFR = 0.45
g / 10 minutes, Vicat softening point = 55 ° C. TPO2: polyolefin-based elastomer (TPO1 bisbreak product having EPR content of 65% by weight), density = 0.
890 g / cm ³ , MFR = 4.0 g / 10 min, Vicat softening point = 55 ° C. TPO3: Polyolefin elastomer (random polypropylene type, EPR content 90% by weight), density =
0.880 g / cm ³ , MFR = 1.5 g / 10 minutes, Vicat softening point ≦ 25 ° C.

TPO4: Polyolefin elastomer (ethylene-octene-1 copolymer polymerized with a single-site catalyst. Octene-1 content = 25% by weight, density =
0.870 g / cm ³ , MI = 1.0 g / 10 minutes, Mw
/Mn=2.7, Vicat softening point ≦ 25 ° C.) TPO5: Polyolefin elastomer (ethylene-octene-1 copolymer polymerized by a single site catalyst. Octene-1 content = 25% by weight, density = 0.868)
g / cm ³ , MI = 0.5 g / 10 min, Mw / Mn =
2.7, Vicat softening point ≤25 ° C)

TPO6: Polyolefin elastomer (homopolypropylene type, EPR content 65% by weight), density = 0.890 g / cm ³ , MFR = 3.0 g
/ 10 minutes (adjusted by mixing two kinds of MFR 0.8 g / 10 minutes and 30 g / 10 minutes), Vicat softening point = 68 ° C. TPO7: polyolefin elastomer (random polypropylene type, EPR content 50% by weight), density =
0.890 g / cm ³ , MFR = 6.0 g / 10 min, Vicat softening point = 81 ° C.

PB1: polybutene-1 resin (copolymer having propylene as a comonomer), density = 0.900 g
/ Cm ³ , MFR = 3.5 g / 10 minutes, melting point (DSC method maximum melting peak temperature) = 73 ° C. PB2: polybutene-1 resin (copolymer having propylene as a comonomer), density = 0.900 g / cm ³ , M
FR = 1.0 g / 10 minutes, melting point (DSC method maximum melting peak temperature) = 70 ° C.

[0051]

Example 1 Ethylene α-olefin copolymer LL1 =
60% by weight, ethylene-vinyl acetate copolymer EVA1 =
1.5% by weight of a mixture of 50% by weight of diglycerin oleate and 50% by weight of glycerin monooleate to 40% by weight.
The E layer was included, and 5% by weight of the polyolefin-based elastomer TPO5 and 50% by weight of the ethylene α-olefin copolymer LL1 were added to the F layer, and EVA1 was added to obtain 10%.
A resin composition adjusted to 0% by weight was mixed with 2.3% by weight of a mixture of 50% by weight of diglycerin oleate and 50% by weight of glycerin monooleate.

Further, as the D layer, the propylene polymer PP
40% by weight of 1 and 30% by weight of a polyolefin elastomer TPO1 having a Vicat softening point of less than 80 ° C. and 30% by weight of a polybutene-1 type resin PB1 are used as a mixed resin, and the layer arrangement is E / F / D / After being extruded using an annular five-layer die so as to have five layers of F / E, it was cooled and solidified with cold water to prepare a tube-shaped original fabric having a folding width of 270 mm and a thickness of 100 μm and uniform thickness accuracy.

At this time, a 6% sodium oleate aqueous solution was enclosed inside the tube, and the inner surface was coated by squeezing with a nip roll. The thickness ratio of each layer is 10% / 27.5% / 25% / 2 from the outside of the tube.
It was adjusted to be 7.5% / 10%. Then, this raw fabric is passed between two pairs of differential nip rolls, heated to about 50 ° C., air is forced into the inside to form bubbles for continuous stretching, and cold air at 20 ° C. is blown to fold the bubbles. Then, a film having a thickness of 11 μm was simultaneously stretched at a stretching ratio of 3.2 times and a width of 2.8 times. Table 1 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film. From Table 1, the stretch film forming stability, tear strength, puncture strength, transparency after shrinkage, and deformation recovery are all excellent, and tear propagation during packaging does not occur, and packaging machine suitability is also excellent. I understand.

[0054]

Example 2 The film obtained in Example 1 was fragmented and passed through an extruder to prepare recycled pellets. This pellet was added to the F layer in an amount of 50% by weight and LL1 of 43%, and the amount of LL1 in the F layer was the same as the amount of LL1 in Example 1, 4% of TPO5 was further added, and EVA1 was added. 1
It was adjusted to 00% by weight. Otherwise, the same operations as in Example 1 were carried out to obtain a film having a thickness of 11 μm. Using the obtained film, the same recycling operation as above was repeated 3 times. Table 1 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film.
The stretched film forming stability and tear strength, puncture strength, transparency after shrinkage, and deformation recovery are almost the same as those of the film obtained in Example 1, and tear propagation during packaging does not occur, and it is also suitable for a packaging machine. And was excellent in recyclability.

[0055]

Example 3 A film having a thickness of 11 μm was obtained in the same manner as in Example 1 except that TPO2 was used instead of the polyolefin-based elastomer having a Vicat softening point of less than 80 ° C. in the D layer. Table 1 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film.

[0056]

Example 4 A film having a thickness of 11 μm was obtained in the same manner as in Example 1 except that TPO3 was used instead of the polyolefin-based elastomer having a Vicat softening point of less than 80 ° C. in the D layer. Table 1 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film.

[0057]

Example 5 A film having a thickness of 11 μm was obtained by the same procedure as in Example 1 except that the polyolefin elastomer having a Vicat softening point of less than 80 ° C. in the D layer in Example 1 was changed to TPO4. Table 1 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film.

[0058]

Example 6 The propylene-based polymer PP was added to the D layer of Example 1.
The same operation as in Example 1 except that 30% by weight of 1 and 40% by weight of a polyolefin-based elastomer TPO5 having a Vicat softening point of less than 80 ° C. and 30% by weight of a polybutene-1 type resin PB1 were used as a mixed resin of three kinds. The thickness of 11 μm
I got a film of. Resin composition used for D layer and D layer, E
Table 1 shows the resin composition ratio of the layers and the evaluation results of the obtained film.

[0059]

Example 7 Propylene-based polymer PP of layer D of Example 1
1 was changed to 50% by weight, the polyolefin-based elastomer TPO1 having a Vicat softening point of less than 80 ° C. was changed to 20% by weight, and the polybutene-1 type resin PB1 was changed to 30% by weight. A film having a thickness of 11 μm was obtained. Table 1 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film.

[0060]

[Example 8] Propylene-based polymer PP of layer D of Example 1
The same operation as in Example 1 was performed except that 1 was changed to 30% by weight, polyolefin elastomer TPO1 having a Vicat softening point of less than 80 ° C. was changed to 40% by weight, and polybutene-1 resin PB1 was changed to 30% by weight. A film having a thickness of 11 μm was obtained. Table 1 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film.

[0061]

Example 9 The same operation as in Example 1 was carried out except that the PP polymer in the D layer in Example 1 was changed to PP2, and the thickness was 11 μm.
m film was obtained. The resin composition used for the D layer and the D layer,
Table 1 shows the resin composition ratio of the E layer and the evaluation results of the obtained film.

[0062]

Example 10 A film having a thickness of 11 μm was obtained by performing the same operation except that the E layer in Example 1 was changed to EVA1.
Table 1 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film.

[0063]

Example 11 40% by weight of LL1 in the E layer of Example 1
The same operation was performed except that EVA1 was changed to 60% by weight to obtain a film having a thickness of 11 μm. Table 1 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film.

[0064]

[Table 1]

From Table 1, the above Examples 3 to 11 are the same as Example 1.
Similar to the above, it is excellent in stretch film forming stability and tear strength, puncture strength, transparency after shrinkage, and recovery from deformation, and does not cause tear propagation during packaging and is also suitable for packaging machines. I understand.

[0066]

Comparative Example 1 Japanese Patent Laid-Open No. 10-34848, which is a prior art.
According to the first embodiment described in Japanese Patent Publication No.
A layer of LL2, an F layer of LL3, and a D layer of 70% by weight of PP3 and 30% by weight of PB2 were used.
I got a film of. Resin composition used for D layer and D layer, E
Table 2 shows the resin composition ratio of the layers and the evaluation results of the obtained film. From Table 2, in Comparative Example 1, the amount of the propylene-based polymer in the D layer was large, so that the peak temperature of tan δ did not decrease and the deformation recovery property was inferior.

[0067]

[Comparative Example 2] The composition of the layer D of Example 1 was 70% by weight of the propylene polymer PP1 and 3% of the polybutene-1 resin PB1.
Example 1 except that the polyolefin-based elastomer having a Vicat softening point of less than 80 ° C. was not used.
The same operation as above was performed to obtain a film having a thickness of 11 μm.
Table 2 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film. From Table 2, in Comparative Example 2, since the amount of the propylene-based polymer in the D layer was large, t
The peak temperature of an δ did not decrease, resulting in poor deformation recovery.

[0068]

[Comparative Example 3] The composition of the D layer of Example 1 was 30% by weight of the propylene-based polymer PP1 and 7% of the polybutene-1 resin PB1.
Example 1 except that the polyolefin-based elastomer having a Vicat softening point of less than 80 ° C. was not used.
The same operation as above was performed to obtain a film having a thickness of 11 μm.
Table 2 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film. From Table 2, in Comparative Example 3, the amount of propylene-based polymer was small and the peak temperature of tan δ was lowered, but there was no polyolefin-based elastomer having a Vicat softening point of less than 80 ° C., so that the deformation recovery was inferior.

[0069]

[Comparative Example 4] 70% by weight of a polyolefin-based elastomer TPO6 having a Vicat softening point of 80 ° C or less and a polybutene-1-based resin PB1 were used without using a propylene-based polymer in the D layer.
Was changed to 30% by weight and the same operation as in Example 1 was performed to obtain a film having a thickness of 11 μm. Table 2 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film. From Table 2, Comparative Example 4 has tan δ
Although the peak temperature was low and the deformation recovery was good, the MD tear strength was low due to the absence of the propylene polymer, and the tear propagation during packaging was large.

[0070]

[Comparative Example 5] The same procedure as in Example 1 was carried out except that TPO7 was used instead of the polyolefin-based elastomer in the layer D of Example 1. Table 2 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film. From Table 2, Comparative Example 4 has a high Vicat softening point of the polyolefin-based elastomer in the D layer, so that the stretching stability is poor,
On the other hand, the tan δ peak temperature was high, and the deformation recovery tended to be poor.

[0071]

Comparative Examples 6 to 8 The same procedure as in Example 1 was carried out except that the mixing ratio of the resin used in the D layer in Example 1 was changed. Table 2 shows the resin composition used for the D layer, the resin composition ratio of the D layer and the E layer, and the evaluation results of the obtained film. From Table 2, Comparative Example 6 is D
Since the amount of the polyolefin-based elastomer in the layer was small, the deformation recovery property was inferior. In Comparative Example 7, the amount of the propylene-based polymer was small, so that the tear strength ratio was low and the tear propagation during packaging was inferior. Has a sufficient amount of the polyolefin-based elastomer in the D layer, but has a large amount of the propylene-based polymer,
Since the peak temperature of an δ is high, the deformation recovery property is poor, and the tear strength ratio is also low, which results in large tear propagation during packaging.

[0072]

[Table 2]

[0073]

The film of the present invention comprises at least three layers and has a heat shrinkage ratio of 20% to 50% at 80 ° C. and has various excellent properties of the film, that is, heat resistance, shrinkability, optical properties and breakthrough resistance. Tear strength M while maintaining the anti-fog property
Good balance between D and TD, from chilled area around 0 ℃-
Since it was possible to achieve both the deformation recovery property in the freezing region around 10 ° C., the film performance was dramatically improved and the market was satisfied. The film of the present invention can, of course, be used for various shrink packaging applications,
It can also be used for various packaging materials such as household and commercial wrap films.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29L 9:00 B29L 9:00 F term (reference) 4F100 AK03A AK03B AK03C AK07B AK09B AK62 AK62A AK62B AK62C AK66A AK66B68AK66C AK66B6866 AL05B AL09B BA03 BA04 BA05 BA06 BA07 BA10A BA10C BA16 EH20 EJ38 GB15 GB23 JA03 JA04 JA04B JJ03 JK03 JK07 JK14 JL01 JL04 JL07 JN00 YY00 YY00B 4F210 AA08 AA10 AA12 AA45 AB19 AG01 AG02 RA03 RC02 RC02 RA03 RC02

Claims (2)

[Claims] 1. A polyolefin resin heat-shrinkable multi-layer film comprising at least three layers and having a heat shrinkage rate at 80 ° C. of 20% to 50%.
(3) A polyolefin resin heat-shrinkable multi-layer film characterized by: (1) The peak temperature of tan δ measured by dynamic viscoelasticity of the film is −10 to 2 ° C. (2) 2nd. By the differential scanning calorimeter (DSC) measurement of the film. At least 155 ° C ± 1 in melting behavior
There is a peak in the range of 5 ° C, and the heat of fusion of crystals at 125 ° C or higher is 10 to 20 J / g. (3) The tear strength of the film is at least 0.05 N in the machine direction and the ratio of the tear strength in the machine direction and the tear strength in the machine direction is 1.2 to 5.0 times. 2. Propylene polymer (a) 20% by weight to
60% by weight and 10% by weight to 50% by weight of a polyolefin-based elastomer (b) having a Vicat softening point of less than 80 ° C.
And a polybutene-1 resin (c) in an amount of 10% by weight to 40% by weight, at least one inner layer comprising the polyolefin resin heat-shrinkable multilayer film according to claim 1.