JP2014168865A - Stretch film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stretch film in which each film is easy to be adhered though it is hard to be pasted to the object to be packaged, and having suitable stretchability and extensibility.SOLUTION: Provided is a stretch film 10 comprising: an inner layer 11 made of a resin material including: high density polyethylene polymerized with a metallocene catalyst; and an external layer 12 made of a resin material including linear low-density polyethylene having a density of below 0.92 g/cm.

Description

  The present invention relates to a stretch film.

Stretch films are widely used as films for packaging containers such as cans, goods, packages, and the like. For example, stretch films are used as films for household use, food packaging, integrated packaging, and the like.
If a stretch film is used, the packaged items can be protected and a plurality of items to be packaged can be packaged together, so that they can be easily integrated and pallet collapse can be prevented.

  When using a stretch film, the product is packaged while stretching the stretch film. Therefore, stretch properties, tensile strength, adhesiveness, and the like are required for stretch films, and stretch films having such physical properties have been proposed (for example, Patent Documents 1 and 2).

JP 2002-294007 A JP 2003-82121 A

  However, when a conventional stretch film as described in Patent Documents 1 and 2 is used and a plurality of articles to be packaged (for example, containers such as cans, glass bottles, and PET bottles) are packaged together, the stretch from the package is performed. When the film is peeled off (when unpacking), the packaged articles may stick to the film, and the packaged articles that are gathered together may be scattered. In particular, lightweight packages such as empty cans and plastic bottles were easy to stick to the film when the stretch film was peeled off, and the packages were easy to fall.

  In order to prevent the package from falling when the stretch film is peeled off from the package, it is important to reduce the adhesiveness of the stretch film and make the package difficult to adhere to the film. However, in a state where the packaged item and the film slide, the packaged item moves without being able to hold down the packaged item with the film during transportation, which may cause problems such as dropping when unpacked. A moderate stickiness is necessary.

Furthermore, when packaging an article to be packaged, the stretch film is usually wound several times. Therefore, in order to stably package the article to be packaged, the adhesiveness between the films is required to be good. However, when the adhesiveness of the stretch film is lowered, the adhesiveness between the films at the time of packaging the packaging object is also likely to be lowered.
When the stretch film is peeled off from the package, the film is usually cut in a direction perpendicular to the winding direction. At this time, if the stretch film is separated, it takes time to accumulate. Also, when the film is unpacked mechanically using an automatic unpacking machine, etc., if the unpacked film is scattered, the machine will not be able to grip the film, causing problems such as the machine stopping during unpacking. Become. If the films are adhered to each other, the stretch film will be unioned and peeled off from the package when unpacked.
As described above, the stretch film is required to have an appropriate tackiness that is difficult to stick to a package object, although the films adhere to each other.

As a method for reducing the adhesiveness of a stretch film, a method of adding a filler such as titanium, silica, or alumina to a resin material constituting the stretch film is known.
However, the stretch film obtained from the resin material containing the filler has a tendency to lower the adhesiveness and the stretchability. When the stretchability is lowered, the packaged goods move and troubles such as collapse of goods occur easily when the package is transported.
When packaging a relatively soft package such as an empty can or a plastic bottle, if the stretch property is too strong, the package may be clamped by the stretch film and deformed.
As described above, a problem occurs even if the stretch property is too strong or too weak. Therefore, the stretch film is required to have an appropriate stretch property.

  By the way, the stretch film is often used after being stretched in at least one of the flow direction and the width direction. This is because the film is oriented in the stretching direction by the stretching treatment and the strength is increased. Moreover, since a film becomes thin by extending | stretching process, the waste after use can be reduced in volume. Further, when packaging a tall package, it is effective to stretch the stretch film in the width direction in order to reduce the amount of stretch film used and the number of windings. Therefore, the stretch film is also required to have a performance (stretchability) that can be stretched in the width direction and the flow direction without impairing the properties of the film.

  The present invention has been made in view of the above circumstances, and is intended to provide a stretch film that is easy to adhere to each other and has appropriate stretch properties and stretchability, although it is difficult to adhere to an object to be packaged. .

The stretch film of the present invention includes an inner layer made of a resin material containing a high-density polyethylene polymerized with a metallocene catalyst and a high-density polyethylene polymerized with a nonmetallocene catalyst, and a linear chain having a density of less than 0.92 g / cm ^3. And an outer layer made of a resin material containing low-density polyethylene.
Moreover, it is preferable that mass ratio of the high density polyethylene polymerized by the metallocene catalyst and the high density polyethylene polymerized by the nonmetallocene catalyst is 30:70 to 70:30.

  Although the stretch film of the present invention is difficult to stick to an object to be packaged, the films are easy to adhere to each other and have appropriate stretch properties and stretchability.

It is sectional drawing which shows an example of the stretch film of this invention.

Hereinafter, an example of the stretch film of the present invention (hereinafter sometimes simply referred to as “film”) will be described with reference to FIG.
The stretch film 10 of this example has an inner layer 11, an outer layer 12, and an intermediate layer 13 provided between these layers.
In FIG. 1, for the convenience of explanation, the dimensional ratio is different from the actual one.

<Inner layer>
The inner layer 11 is a layer that comes into contact with the package object when the package object is packaged.
The inner layer 11 is made of a resin material (inner layer resin material) containing high-density polyethylene (metallocene HDPE) polymerized with a metallocene catalyst and high-density polyethylene (non-metallocene HDPE) polymerized with a non-metallocene catalyst.
Here, “high density polyethylene” refers to polyethylene having a density of 0.942 g / cm ³ or more.
In the present invention, the density of polyethylene is a value measured according to JIS K6760-1981.

The metallocene HDPE plays a role of reducing the adhesive strength of the inner layer 11. In addition, the mechanical strength is high, and the tensile breaking elongation (stretchability) in both the flow direction (MD direction) and the width direction (TD direction) of the stretch film 10 is assisted. Metallocene HDPE can be obtained by homopolymerizing ethylene or copolymerizing ethylene and α-olefin in the presence of a metallocene catalyst.
Examples of the α-olefin include α-olefins having 3 to 12 carbon atoms, specifically, propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, nonene-1, decene. -1, dodecene-1, 4-methyl-pentene-1, 4-methyl-hexene-1, vinylcyclohexane, vinylcyclohexene, styrene, norbornene, butadiene, isoprene and the like.

Examples of the metallocene catalyst include a catalyst comprising a metallocene compound, an organoaluminum compound and / or an ionic compound.
As the metallocene compound, a transition metal compound having a group having a cyclopentadiene type skeleton, usually, in the general formula ML a _{X n-a (wherein,} M is a transition of Group 4 or lanthanide series of the Periodic Table of the Elements L is a group having a cyclopentadiene skeleton or a group containing a hetero atom, and at least one of them is a group having a cyclopentadiene skeleton, and a plurality of L may be bridged with each other. X is a halogen atom, hydrogen, or a hydrocarbon group having 1 to 20 carbon atoms, n is a valence of a transition metal atom, and a is an integer of 0 <a ≦ n. Can be mentioned. A metallocene type compound may be used individually by 1 type, and may use 2 or more types together.

Examples of organoaluminum compounds include alumoxane compounds.
On the other hand, examples of the ionic compound include trityl borate and anilinium borate.
In addition, the metallocene compound, organoaluminum compound, and ionic compound are combined with a particulate carrier comprising an inorganic carrier such as SiO ₂ and Al ₂ O ₃ and an organic polymer carrier such as an olefin polymer such as ethylene and styrene. It may be used.

The melt flow rate (MFR) of metallocene HDPE is preferably 1.0 to 10.0 g / min. When the MFR is less than 1.0 g / min, the distribution of the metallocene HDPE in the inner layer 11 is difficult to be uniform. On the other hand, if the MFR exceeds 10.0 g / min, the fluidity becomes too high and film formation may be difficult.
MFR is a value measured according to JIS K6760-1981.

  A commercially available product may be used as the metallocene HDPE. As a commercially available product, for example, “Creolex” series manufactured by Asahi Kasei Chemicals Corporation is suitable.

As described above, the metallocene HDPE plays a role of reducing the adhesive strength of the inner layer 11. Therefore, when the stretch film is peeled off from the package (when unpacking), the package becomes difficult to stick to the film, and the packages can be prevented from separating. In particular, even if the packaged item is lightweight, such as an empty can or a plastic bottle, the packaged item can be prevented from sticking to the stretch film and dropping at the time of unpacking. In addition, the tensile elongation at break is as high as 600% or more in both the MD direction and the TD direction, and plays a role of assisting mechanical strength during biaxial stretching.
However, when only metallocene HDPE is used as the resin constituting the inner layer 11, the adhesive strength of the inner layer 11 is excessively reduced. When packaging an article to be packaged, the stretch film is usually wound several times, so that the outer layer 12 of the stretch film and the inner layer 11 of the stretch film wound next come into contact with each other. When the adhesive strength of the inner layer 11 is excessively reduced, the adhesiveness between the outer layer 12 and the inner layer 11, that is, the adhesiveness between the films is extremely reduced, and it becomes difficult to wrap the article to be packaged.

Therefore, nonmetallocene HDPE is used in order to prevent the adhesive strength of the inner layer 11 from excessively decreasing.
Non-metallocene HDPE has an appropriate level of adhesive strength that does not impair the effects of metallocene HDPE (that is, the effect of preventing the packaged items from sticking to the film during unpacking and preventing the packaged items from separating from each other). 11 plays a role. Therefore, the balance between the non-adhesiveness to the article to be packaged and the adhesiveness of the inner layer 11 and the outer layer 12 (adhesiveness between films) becomes good. Therefore, when packaging an article to be packaged, the films adhere appropriately to each other, so that the packaging is easy, and it is difficult for the article to be packaged to stick to the film when unpacked. .

Nonmetallocene HDPE is obtained by homopolymerizing ethylene or copolymerizing ethylene and an α-olefin in the presence of a nonmetallocene catalyst.
Examples of the α-olefin include the α-olefins exemplified above in the description of the metallocene HDPE.
The nonmetallocene catalyst is a catalyst other than the metallocene catalyst, and a known catalyst used for the production of high density polyethylene such as a Phillips catalyst or a Ziegler catalyst can be used.

The MFR of nonmetallocene HDPE is preferably 1.0 to 10.0 g / min. When the MFR is less than 1.0 g / min, the distribution of the nonmetallocene HDPE in the inner layer 11 becomes difficult to be uniform. On the other hand, if the MFR exceeds 10.0 g / min, the fluidity becomes too high and film formation may be difficult.
The MFR of nonmetallocene HDPE is a value measured in the same manner as metallocene HDPE.

  A commercially available product may be used as the nonmetallocene HDPE. As the commercially available products, for example, “Suntech” series manufactured by Asahi Kasei Chemicals Corporation, “Hi-Zex” series manufactured by Prime Polymer Co., Ltd. and the like are suitable.

As described above, the metallocene HDPE serves to reduce the adhesive strength of the inner layer 11 and also assists the stretchability of the film. On the other hand, the nonmetallocene HDPE plays a role of imparting appropriate adhesive strength to the inner layer 11. Therefore, the adhesive force of the inner layer 11 can be easily adjusted while maintaining the stretchability by adjusting the mass ratio of the two.
The mass ratio of the metallocene HDPE to the nonmetallocene HDPE in the inner layer resin material is preferably metallocene HDPE: nonmetallocene HDPE = 30: 70 to 70:30, more preferably 40: 60: 60: 40. When the ratio of the metallocene HDPE is less than the above range, the adhesive strength of the inner layer 11 is increased, and the packaged articles stick to the film at the time of unpacking, and the packages to be packaged tend to be easily separated. Moreover, the mechanical strength at the time of extending | stretching falls, and malfunctions, such as a fracture | rupture, may generate | occur | produce. On the other hand, when the ratio of the metallocene HDPE is larger than the above range, the adhesive strength of the inner layer 11 is excessively lowered, and the adhesiveness between the films is lowered when the packaged item is packaged, and the packaged item tends to be difficult to package. It is in.

  If the mass ratio of the metallocene HDPE and the nonmetallocene HDPE is within the above range, the inner layer 11 showing an appropriate adhesive strength can be formed. Therefore, the films adhere to each other when packaging the package, and it becomes easy to obtain the stretch film 10 having appropriate tackiness when the package is difficult to stick at the time of unpacking.

  The resin material for the inner layer may contain one or more other resins and additives as long as it does not impair the effects of the present invention. However, when a filler such as titanium, silica, alumina or the like is added, the stretch property of the stretch film 10 is lowered. Therefore, the inner layer resin material preferably does not contain a filler.

Examples of the other resins include polyolefin resins such as low density elastomers used for improving impact strength.
Examples of the additive include a stabilizer (antioxidant), a lubricant, an antistatic agent, a processability improving agent, an antiblocking agent, and a pigment.

Examples of the stabilizer include 2,6-di-t-butyl-p-cresol (BHT), tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (commercially available). Examples of the product include “IRGANOX1010” manufactured by BASF Japan Ltd.), n-octadecyl-3- (4′-hydroxy-3,5′-di-t-butylphenyl) propionate (commercially available products include, for example, BASF Japan Phenol stabilizers typified by “IRGANOX1076” manufactured by Co., Ltd.), bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite, tris (2,4-di-t-butylphenyl) A phosphite stabilizer represented by phosphite and the like, 6- [3- (3-t-butyl-4-) having both performances Droxy-5-methyl) propoxy] -2,4,8,10-tetra-t-butyldibenz [d, f] [1,3,2] -dioxaphosphepine (commercially available products include, for example, Sumitomo Chemical Co., Ltd.) Examples thereof include phosphorus-containing phenolic stabilizers represented by “Sumilyzer GP” manufactured by the company.
Examples of the lubricant include higher fatty acid amides and higher fatty acid esters.
Examples of the antistatic agent include glycerin esters and sorbitan acid esters of fatty acids having 8 to 22 carbon atoms, alkyl dialkanol amides of fatty acids having 8 to 22 carbon atoms, and polyethylene glycol esters.
Examples of the processability improver include fatty acid metal salts such as calcium stearate.

  The thickness of the inner layer 11 is preferably 5 to 50% of the total thickness of the stretch film 10, and more preferably 10 to 30%. If the thickness is less than 5%, the effect of preventing unraveling during unpacking may be insufficient. Moreover, the stretchability of the film may be reduced. On the other hand, if the thickness exceeds 50%, the stretch property of the stretch film 10 becomes insufficient, and packaging failure may occur.

<Outer layer>
The outer layer 12 is a layer that comes into contact with the inner layer 11 when the stretch film 10 is wrapped around and wrapped around the article to be packaged.
The outer layer 12 is made of a resin material (outer layer resin material) including linear low density polyethylene (LLDPE-1) having a density of less than 0.92 g / cm ³ .

LLDPE-1 plays a role of imparting adhesiveness and stretchability to the outer layer 12.
Polyethylene tends to increase its tackiness and stretchability as the density decreases. Therefore, if the density is less than 0.92 g / cm ³ , the tackiness and stretchability required for the stretch film 10 can be expressed. Moreover, since the outer layer 12 becomes easy to adhere to the inner layer 11 when the stretch film 10 of the present invention is wrapped around and wrapped in the package (that is, the films adhere well), the package is stabilized. Can be packaged.
The lower limit of the density of LLDPE-1 is preferably 0.88 g / cm ³ or more considering that the strength of the outer layer 12 can be maintained satisfactorily and is easily available as a material.

LLDPE-1 is obtained by copolymerizing ethylene and an α-olefin in the presence of a catalyst.
Examples of the α-olefin include the α-olefins exemplified above in the description of the metallocene HDPE.
As the catalyst, known catalysts used for the production of linear low density polyethylene such as Ziegler catalyst and metallocene catalyst can be used.

The MFR of LLDPE-1 is preferably 1.0 to 10.0 g / min. When the MFR is less than 1.0 g / min, the distribution of LLDPE-1 in the outer layer 12 becomes difficult to be uniform. On the other hand, if the MFR exceeds 10.0 g / min, the fluidity becomes too high and film formation may be difficult.
The MFR of LLDPE-1 is a value measured in the same manner as metallocene HDPE.

  A commercially available product may be used as LLDPE-1. As the commercially available products, for example, “Sumikasen” series manufactured by Sumitomo Chemical Co., Ltd., “Evolue” series, “Moretech” series manufactured by Prime Polymer Co., Ltd., and the like are suitable.

The outer-layer resin material may contain one or more other resins and additives as long as the effects of the present invention are not impaired. However, when a filler such as titanium, silica, or alumina is added, the stretch property of the stretch film 10 is lowered. Therefore, the outer layer resin material preferably does not contain a filler.
Examples of the other resins and additives include the other resins and additives exemplified above in the explanation of the resin material for the inner layer.

  The thickness of the outer layer 12 is preferably 10 to 60% of the total thickness of the stretch film 10, and more preferably 20 to 40%. If the thickness is less than 10%, sufficient adhesiveness cannot be expressed, and problems may occur during packaging. On the other hand, if the thickness exceeds 60%, the adhesive strength of the film becomes too strong, which may cause problems during packaging.

<Intermediate layer>
The intermediate layer 13 is a layer that is provided between the inner layer 11 and the outer layer 12 and imparts strength to the stretch film 10.
The intermediate layer 13 is made of a resin material (intermediate layer resin material) containing linear low-density polyethylene (LLDPE-2) having a density of 0.90 to 0.93 g / cm ³ . The density of LLDPE-2 is preferably different from the density of LLDPE-1 constituting the outer layer 12.
The intermediate layer 13 bears the mechanical strength of the entire stretch film 10 and greatly contributes to the manufacturing cost and processability of the film. Therefore, the intermediate layer 13 is required to be as inexpensive as possible, have high mechanical strength such as tensile elongation at break, and be excellent in workability.
LLDPE-2 can mainly improve the tensile rupture elongation in the TD direction among the tensile rupture elongation required for the stretch film 10. Therefore, by providing the intermediate layer 13 made of an intermediate layer resin material containing LLDPE-2 between the inner layer 11 and the outer layer 12, a durable stretch film 10 can be obtained even if the thickness of the entire film is reduced.

LLDPE-2 is obtained by copolymerizing ethylene and an α-olefin in the presence of a catalyst.
Examples of the α-olefin include the α-olefins exemplified above in the description of the metallocene HDPE.
As the catalyst, known catalysts used for the production of linear low density polyethylene such as Ziegler catalyst and metallocene catalyst can be used.

The MFR of LLDPE-2 is preferably 0.5 to 10.0 g / min, more preferably 1.2 to 3.0. If the MFR is out of the above range, it may be difficult to uniformly laminate the inner layer 11 and the outer layer 12 during film formation. In particular, LLDPE-2 having an MFR of 1.2 to 3.0 is suitable for processing with a T die.
The MFR of LLDPE-2 is a value measured in the same manner as metallocene HDPE.

A commercially available product may be used as LLDPE-2. As the commercially available products, for example, “Sumikasen” series manufactured by Sumitomo Chemical Co., Ltd., “Evolue” series manufactured by Prime Polymer Co., Ltd., and the like are suitable.
As described above, the intermediate layer 13 is required to be inexpensive and have high mechanical strength such as tensile elongation at break and excellent workability. Among the LLDPE-2, the “Sumikasen” series manufactured by Sumitomo Chemical Co., Ltd. is relatively inexpensive among general-purpose raw materials. In particular, among the “Sumikasen” series, “Sumikasen E FV203” and “Sumikasen E FV103” have a tensile elongation at break in the TD direction of 600% or more, and an MRF of 1.2 to 3.0 g / min. Particularly suitable as LLDPE-2.

The resin material for an intermediate layer may contain one or more other resins and additives as long as it does not impair the effects of the present invention. However, when a filler such as titanium, silica, or alumina is added, the stretch property of the stretch film 10 is lowered. Therefore, the intermediate layer resin material preferably does not contain a filler.
Examples of the other resins and additives include the other resins and additives exemplified above in the explanation of the resin material for the inner layer.

  The thickness of the intermediate layer 13 is preferably 30 to 70% and more preferably 40 to 60% of the total thickness of the stretch film 10. If the thickness is less than 30%, it may be difficult to obtain sufficient film strength (mechanical strength). On the other hand, if the thickness exceeds 70%, the adhesiveness of the film and the effect of preventing the unraveling during unpacking may be insufficient. Moreover, since the thickness of the inner layer 11 and the outer layer 12 becomes thin, the characteristic of each layer is not fully demonstrated and a packaging defect may generate | occur | produce.

<Manufacture of stretch film>
The stretch film 10 can be manufactured as follows, for example.
First, each resin material is prepared. When the resin material contains other resins and additives, they may be previously melt-kneaded, may be individually dry blended, or may be dry blended into one or more master batches.
Each resin material is coextruded from a T-die in a flat shape to form an inner layer 11, an intermediate layer 13, and an outer layer 12, and these layers are laminated to obtain the stretch film 10. The obtained stretch film 10 is wound around a paper tube with the inner layer 11 inside and the inner layer 11 and the outer layer 12 in contact with each other, and is stored as a wound object.

  Further, each resin material is coextruded from a round die into a tubular shape to form an inner layer 11, an intermediate layer 13, and an outer layer 12, and after obtaining an annular body in which these layers are laminated in a tubular shape, the annular body is cut open to form a flat shape. The stretch film 10 may be manufactured by the method described above.

  The stretch film 10 thus obtained preferably has an overall thickness of 5 to 50 μm, and more preferably 8 to 30 μm.

  In addition, the stretch film of the present invention is not limited to the above-described ones. For example, the stretch film may not have an intermediate layer, and may have other layers between an inner layer and an intermediate layer, and an intermediate layer and an outer layer. It may be. However, from the viewpoint of strength and thickness, the stretch film preferably has a three-layer structure in which an inner layer, an intermediate layer, and an outer layer are sequentially laminated.

  As described above, according to the present invention, by using both metallocene HDEP and nonmetallocene HDEP as the resin constituting the inner layer, the balance between the non-adhesiveness to the package and the adhesiveness between the films is good. It becomes. In addition, by using LLDPE-1 as the resin constituting the outer layer, it is possible to express the tackiness, stretchability, and stretchability required for the stretch film, and when the stretch film is wound around the package, the film Easy to stick to each other.

Accordingly, the stretch film of the present invention has appropriate adhesiveness, stretchability, and stretchability that the films adhere to each other when the packaged object is packaged, and the packaged object is difficult to stick when unpacked. Therefore, it is possible to stably package the objects to be packaged, and to prevent the objects to be packaged from separating from each other during unpacking.
Moreover, since the stretch film of this invention has the moderate adhesiveness mentioned above, it is not necessary to add a filler to the resin material which comprises each layer. Therefore, the stretchability can be maintained well.

  Further, if an intermediate layer is provided between the inner layer and the outer layer, strength is imparted to the stretch film, so that a durable stretch film can be obtained even if the thickness of the entire film is reduced.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to an Example.
The measurement method and evaluation method implemented in each example are shown below.

(1) Measurement of density The density of polyethylene was measured according to JIS K6760-1981.

(2) Measurement of MFR The MFR of polyethylene was measured under the conditions of a load of 2.16 kg and a temperature of 190 ° C. in accordance with JIS K6760-1981.

(3) Adhesive evaluation 1 (Adhesiveness to package)
Empty cans with a capacity of 200 mL were arranged without gaps so as to be 18 vertical x 20 horizontal (first stage). On top of this, empty cans were similarly arranged through a paper separate sheet (second stage). The same operation was repeated until the height of the empty can reached 15 levels. Next, the stretch film was mechanically stretched 1.5 times in the TD direction and 1.2 times in the MD direction, and this was immediately wrapped four times around the empty cans stacked in 15 steps and packaged. After a certain period of time in this state, check whether the empty can has fallen when the stretch film is cut in a direction perpendicular to the winding direction and the film is peeled off (when unpacked). The tackiness was evaluated according to the evaluation criteria.
○: An empty can cannot be dropped when unpacked.
Δ: Five or less empty cans dropped when unpacked.
×: Six or more empty cans dropped during unpacking.

(4) Adhesive evaluation 2 (adhesiveness between films)
An empty can was packed with a stretch film in the same manner as in Evaluation 1 for tackiness. And the adhesiveness between films when the stretch film was cut | disconnected in the direction perpendicular | vertical with respect to the winding direction and the film was peeled (at the time of unpacking) was evaluated with the following evaluation criteria.
○: The film is peeled together as one when unpacked.
(Triangle | delta): A film scatters and peels at the time of unpacking.
X: At the time of unpacking, three or more films are separated and peeled off.

(5) Evaluation of stretch property It carried out similarly to the evaluation 1 of adhesiveness, and the empty can was packaged with the stretch film, and the fixed distance was transferred in this state. The presence or absence of deformation of the empty can before unpacking and the presence or absence of movement were confirmed, and the stretch properties were evaluated according to the following evaluation criteria.
○: The empty can is not deformed and does not move.
Δ: At least a part of the empty can is slightly deformed and / or moved slightly.
X: At least a part of the empty can is clearly deformed and / or is clearly moving.

(6) Evaluation of film stretchability In the same manner as the adhesive evaluation 1, the film stretch state in the MD direction and the TD direction when packaging an empty can with a stretch film is confirmed. Evaluated.
◯: The film is not broken even when stretched in the MD direction and the TD direction.
Δ: When stretched in the MD direction and TD direction, the film is broken.
X: The film is broken when stretched in the MD direction and the TD direction.

(7) Comprehensive evaluation From the evaluation results of the above (3) to (6), comprehensive evaluation was performed according to the following evaluation criteria.
○: All evaluation results are “◯”.
Δ: “△” is present in the evaluation result, but “×” is not present.
X: The evaluation result includes “x”.

The polyethylene used in each example is as follows.
H-1: Metallocene HDPE (Asahi Kasei Chemicals Corporation, “Creolex QT-4750”, density: 0.947 g / cm ³ , MFR: 5.0 g / min)
H-2: Non-metallocene HDPE (Asahi Kasei Chemicals Corporation, “Suntech S-360”, density: 0.952 g / cm ³ , MFR: 1.0 g / min)
L-1: linear low density polyethylene (LLDPE) (manufactured by Sumitomo Chemical Co., Ltd., “Sumikasen E FV203”, density: 0.913 g / cm ³ , MFR: 2.0 g / min)
L-2: LLDPE (manufactured by Sumitomo Chemical Co., Ltd., “Sumikasen E FV103”, density: 0.904 g / cm ³ , MFR: 1.3 g / min)
L-3: LLDPE (Exxon Mobil Chemical Company, “EXCEED 2018”, density: 0.918 g / cm ³ , MFR: 2.0 g / min)
L-4: LLDPE (manufactured by Prime Polymer Co., Ltd., “Moretech 0238CN”, density: 0.916 g / cm ³ , MFR: 2.3 g / min)
L-5: LLDPE (manufactured by Prime Polymer Co., Ltd., “MORETECH 0278G”, density: 0.939 g / cm ³ , MFR: 2.1 g / min)
L-6: LLDPE (manufactured by Prime Polymer Co., Ltd., “MORETECH 0398CN”, density: 0.907 g / cm ³ , MFR: 3.0 g / min)
L-7: LLDPE (manufactured by Sumitomo Chemical Co., Ltd., “Sumikasen L FS140”, density: 0.919 g / cm ³ , MFR: 1.0 g / min)
L-8: LLDPE (manufactured by Dow Chemical Japan, “ATTANE 4404G”, density: 0.904 g / cm ³ , MFR: 4.0 g / min)
L-9: Low-density polyethylene (LDPE) (manufactured by Asahi Kasei Chemicals Corporation, “Suntech LD F200-0”, density: 0.924 g / cm ³ , MFR: 2.0 g / min)
A-1: Lubricant (manufactured by Sumitomo Chemical Co., Ltd., “Sumikasen A-10”)
A-2: Anti-blocking material (manufactured by Sumitomo Chemical Co., Ltd., “Sumikasen A-20”)

[Example 1]
As a resin material for the inner layer, a mixture of H-1 and H-2 (mass ratio (H-1: H-2) = 70: 30), and as a resin material for the intermediate layer, L-1, L-2, L-3 ( Mass ratio (L-1: L-2: L-3) = 40: 40: 20), L-4 was used as the resin material for the outer layer, and a three-layer coextrusion machine equipped with a T die (Modern Machinery Co., Ltd.) Manufactured, both ends φ65 mm extruder, central 75 mm extruder, feed block type), a stretch film having a thickness of 10 μm, in which an inner layer, an intermediate layer, and an outer layer are sequentially laminated, has an inner layer on the inner side, and the inner layer and the outer layer are It was wound on a paper tube in contact. In addition, when the thickness of each layer was measured, the inner layer was 4 μm, the intermediate layer was 5 μm, and the outer layer was 1 μm.
About the obtained stretch film, adhesiveness, stretch property, and stretchability were evaluated. The results are shown in Table 1.

[Examples 2 to 7]
A stretch film was produced and evaluated in the same manner as in Example 1 except that the type and mass ratio of polyethylene constituting each resin material were changed as shown in Table 1. The results are shown in Table 1.

[Comparative Examples 1 to 7]
A stretch film was produced and evaluated in the same manner as in Example 1 except that the type and mass ratio of polyethylene constituting each resin material were changed as shown in Table 2. The results are shown in Table 2.

As is clear from Table 1, the stretch film obtained in each example had appropriate tackiness, stretchability, and stretchability.
As described above, the mass ratio of the metallocene HDPE to the nonmetallocene HDPE in the inner layer is preferably 30:70 to 70:30, and in particular, the mass ratio of the metallocene HDPE to the nonmetallocene HDPE is 50:50. The stretch film had good results for Adhesive Evaluation 1 and Adhesive Evaluation 2 and had sufficient stretch properties.

On the other hand, as is clear from Table 2, the stretch film of Comparative Example 1 using only the metallocene HDPE having a density of 0.947 g / cm ³ without using nonmetallocene HDPE as the resin constituting the inner layer is an empty can. When packaging the film, the adhesiveness between the films was poor and the packaging was difficult.
In the stretch film of Comparative Example 2 using LDPE having a density of 0.924 g / cm ³ as the resin constituting the inner layer, the empty can easily moved and the stretchability was insufficient.
The stretch film of Comparative Example 3 using LLDPE having a density of 0.916 g / cm ³ as the resin constituting the inner layer and using a lubricant and an anti-blocking material easily moves the empty can and has insufficient stretchability. there were.
The stretch film of Comparative Example 4 using LLDPE having a density of 0.939 g / cm ³ as the resin constituting the inner layer had insufficient stretchability.
The stretch film of Comparative Example 5 using LDPE having a density of 0.924 g / cm ³ as the resin constituting the inner layer and using an anti-blocking material together has insufficient stretchability.
The stretch film of Comparative Example 6 using only non-metallocene HDPE having a density of 0.952 g / cm ³ without using metallocene HDPE as the resin constituting the inner layer has insufficient adhesion to the package. It was.
The stretch film of Comparative Example 7 using only LLDPE having a density of 0.939 g / cm ³ as the resin constituting the outer layer had insufficient adhesion and stretchability between the films.

10: Stretch film, 11: Inner layer, 12: Outer layer, 13: Intermediate layer.

Claims (2)

A resin comprising a high-density polyethylene polymerized with a metallocene catalyst and a resin layer comprising a high-density polyethylene polymerized with a non-metallocene catalyst, and a linear low-density polyethylene having a density of less than 0.92 g / cm ³ A stretch film comprising an outer layer made of a material.   The stretch film according to claim 1, wherein a mass ratio of the high-density polyethylene polymerized with the metallocene catalyst and the high-density polyethylene polymerized with a nonmetallocene catalyst is 30:70 to 70:30.

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