JP2020075407A - Polyethylene-based multilayer film for overlapping heat-shrinkable packaging - Google Patents

Abstract

To provide a polyethylene-based multilayer film for overlapping heat-shrinkable packaging capable of extending freshness holding period of fruits and vegetables after packaging, excellent in automatic packaging machine suitability, and hardly deteriorating beauty of a packaged article.SOLUTION: There is provided a polyethylene-based multilayer film for overlapping heat-shrinkable packaging constituted by 3 or more layers having 2 surface layers X and at least one inside layer Y arranged between these surface layers, in which 2 surface layers X and at least one inside layer Y are each independently a layer formed by a resin composition containing an ethylene resin of 94 to 99 pts.mass, zeolite of 0 to 2 pts.mass and an antifogging agent of 1 to 4 pts.mass, one or more layer in 2 surface layers X and at least one inside layer Y contains zeolite with a SiO/AlOmolar ratio of 100 or more, haze value is 5% or more, heat seal strength at 120°C is 1.5 N/cm or more, and heat shrinkage rate in an MD direction and a TD direction at 120°C are 55% or more respectively.SELECTED DRAWING: None

Description

  The present invention relates to a polyethylene-based multilayer film for overlapping heat shrink packaging.

Since fruits and vegetables cannot grow due to photosynthesis after harvesting, they decompose the stored substances such as carbohydrates by respiration and acquire the energy necessary for life support. Due to this breathing action, deterioration of fruits and vegetables progresses, the freshness of the fruits and vegetables deteriorates, and quality deterioration such as discoloration and wilting occurs.
It is known that the respiratory action is promoted by ethylene gas released from the fruits and vegetables themselves, cutting stress due to cutting when the fruits and vegetables are processed, and the like, which affects the freshness reduction.
Therefore, producers make various efforts to maintain freshness in order to deliver high-quality fruits and vegetables to the place of consumption, and one of the means of improvement is packaging of fruits and vegetables using a plastic film.

  As a fruit and vegetable packaging bag for keeping freshness, a fruit and vegetable freshness retaining packaging bag composed of a perforated synthetic resin film provided with one or more holes has been proposed (Patent Document 1). The fruit and vegetables freshness-keeping packaging bag is a so-called MA (Modified Atmosphere) packaging bag, and the oxygen concentration in the packaging bag is adjusted, and the water vapor permeation is controlled to control the respiration and water evaporation of the fruits and vegetables to maintain the freshness. It is the one that enhances sex.

  However, it is difficult to tightly wrap a packaged item in the fruit and vegetable freshness-keeping packaging bag proposed in Patent Document 1, and therefore when the packages are displayed at the store, the packages are not tightly packed due to excessive air in the packages. There is a problem that it is difficult to stack and stack due to slipping, and that the package is bulky when packed in a cardboard box and transport efficiency is not good.

  Therefore, in order to solve the above-mentioned problems, a heat shrinkable film (shrink film) is used to tightly overlap the fruits and vegetables to perform heat shrink wrapping. As a film, a heat-shrinkable plastic film composed of an ionomer resin, an amide lubricant, a silica antiblocking agent, and an inorganic antibacterial agent has been proposed (Patent Document 2).

  Further, it has a laminated structure having at least three layers of surface layer / center layer / back layer, the center layer is mainly composed of a polyamide resin, and the surface layer and the back layer are mainly composed of a single or mixed resin selected from polyolefin resins. Further, there is proposed a stretch shrink film for food packaging, wherein the 50% tensile elongation stress in the longitudinal direction of the film is in a predetermined range, and the 50% tensile elongation stress in the transverse direction of the film is in a predetermined range. (Patent Document 3).

JP, 2017-206311, A JP-A-3-126741 JP, 2007-15210, A

After the heat-shrinkable plastic film proposed in Patent Document 2, after heat-shrinkable packaging, moisture resulting from evaporation of fruits and vegetables as the contents becomes water drops on the inner surface of the heat-shrinkable plastic film, so-called clouding occurs, and the package There was a risk of spoiling the appearance. Further, in the heat-shrinkable plastic film of Patent Document 2, the heat-sealing strength of the film is apt to decrease, and pinholes and seal opening occur in the fusion-sealing portion during the overlap heat-shrink wrapping in the automatic fruit and vegetable wrapping machine. Since it is easy to perform, there is a concern that the aesthetic appearance of the fusing seal portion may be impaired.

  In addition, the stretch shrink film for food packaging proposed in Patent Document 3 has insufficient oxygen uptake from the outside of the bag-making product, so that the oxygen concentration in the bag-making product remarkably decreases as the breathing action of fruits and vegetables progresses. However, there was a problem that fruits and vegetables started to breathe anaerobicly without requiring oxygen and produced ethanol, acetaldehyde, etc., and caused an offensive odor.

  Therefore, the present invention can extend the freshness retention period of the fruits and vegetables after packaging in the form of heat-shrink packaging by overlapping the fruits and vegetables, and can automatically melt-seal and shrink finish in an automatic packaging machine. An object of the present invention is to provide a polyethylene-based heat-shrinkable multilayer film which is excellent in suitability for a packaging machine and does not impair the aesthetic appearance of the package.

As a result of earnest studies to solve such a problem, the present inventors have a layer including a zeolite having a specific SiO ₂ / Al ₂ O ₃ molar ratio (hereinafter, also referred to as SAR value), and specified. The polyethylene-based multilayer film for overlapping heat-shrink packaging that satisfies the physical properties of the product exhibits excellent freshness retention and transparency, and is also suitable for automatic packaging machines, especially for fusing sealability and shrink finish in automatic packaging machines. They have found that they are excellent and completed the present invention.

That is, the present invention is a polyethylene-based multilayer film for overlapping heat-shrink packaging, which is composed of three or more layers having two surface layers X and at least one inner layer Y provided between these surface layers. There
The two surface layers X and the at least one inner layer Y are each independently formed of a resin composition containing 94 to 99 parts by mass of an ethylene resin, 0 to 2 parts by mass of a zeolite, and 1 to 4 parts by mass of an antifogging agent. Is a layer that has been
One or more of the two surface layers X and the at least one inner layer Y comprises zeolite
The zeolite has a SiO ₂ / Al ₂ O ₃ molar ratio of 100 or more,
A polyethylene-based multilayer film that satisfies the following physical properties (a) to (c).
(A) The haze value is 5% or less (b) The heat seal strength at 120 ° C. is 1.5 N / cm or more (c) The heat shrinkage percentage in the MD direction and the TD direction at 120 ° C. is 55%. Be above

  The average particle size of the zeolite is preferably 0.5 to 10 μm.

  INDUSTRIAL APPLICABILITY The polyethylene-based multilayer film for overlapping heat-shrinkable packaging of the present invention has an effect of having excellent freshness retention and transparency.

  Further, the polyethylene-based multilayer film for overlapping heat-shrinkable packaging of the present invention has an effect that it is excellent in suitability for an automatic wrapping machine, in particular, melt-sealing property and shrink finish in the automatic wrapping machine.

Hereinafter, the present invention will be described in detail.
<Ethylene resin>
In the present invention, among the resin compositions used for forming the surface layer X and the inner layer Y, the ethylene-based resin is a homopolymer of ethylene and / or a copolymer of ethylene and a small amount of another monomer. Is. Other monomers as used herein are not particularly limited, but α-olefins such as propylene, butene-1, hexene-1, octene-1, 4-methyl-pentene-1, vinyl acetate, (meth) acrylic acid alkyl ester, Examples thereof include (meth) acrylic acid and metal ion neutralized products of (meth) acrylic acid.
In addition, in this specification, (meth) acrylic acid is a general term for acrylic acid and methacrylic acid, and refers to either or both of them.

  The content of the ethylene-based resin in the resin composition used for forming the surface layer X and the inner layer Y is 94 to 99 parts by mass. The ethylene-based resin has a function of imparting excellent characteristics such as shrink finish and fusing and sealing property in an automatic packaging machine. Regarding the antifogging agent and the zeolite in the resin composition used for forming the surface layer X and the inner layer Y, from the viewpoint of the content necessary for imparting a function due to them, the ethylene resin is within the range. Content is required.

<Zeolite>
In the present invention, of the resin compositions used for forming the surface layer X and / or the inner layer Y, zeolite is a general term for crystalline aluminosilicate, and as a general formula, M _{2 / n 2} O.Al _{It is represented by 2} O ₃ .xSiO ₂ .yH ₂ O. Here, M means a metal cation, n means a valence of the metal cation, and x and y mean the number of moles of SiO ₂ and H ₂ O, respectively.
The zeolite here is not particularly limited and is selected from the group of generally classified synthetic zeolite, artificial zeolite, and natural zeolite.
Zeolite absorbs ethylene gas released from fruits and vegetables, thereby suppressing the respiration of fruits and vegetables and imparting a freshness-retaining property.

The zeolite in the resin composition used for forming the surface layer X and / or the inner layer Y has a SAR value of 100 or more. If the SAR value is less than 100, the transparency of the multilayer film may be reduced, and the aesthetics of the package may be impaired. The reason for this decrease in transparency is presumably because the lower the SAR value of the zeolite, the higher the hydrophilicity of the zeolite, and the lack of dispersibility of the zeolite in the hydrophobic polyethylene matrix.
Further, as the above-mentioned zeolite, the average particle size measured using a laser diffraction particle size distribution measuring device (for example, Mastersizer 3000 manufactured by Malvern Panalytical) is 0.5 to 1
It is preferably 0 μm. If the average particle size exceeds 10 μm, the transparency of the multilayer film may be deteriorated and the aesthetics of the package may be impaired. Therefore, if the average particle size is less than 0.5 μm, the production cost of zeolite increases. However, the cost performance of the multilayer film is lowered, which is not preferable.

  In the present invention, in the resin composition used for forming the surface layer X and the inner layer Y, the content of zeolite is 0 to 2 parts by mass from the viewpoint of compatibility between freshness retention of fruits and vegetables and aesthetics of the package. And at least one of the two surface layers X and at least one inner layer Y always contains zeolite. If the desired freshness of fruits and vegetables is not obtained without containing zeolite, and if the surface layer X and / or the inner layer Y contains more than 2 parts by mass, the transparency of the multilayer film decreases, It may impair the aesthetics of the package.

<Anti-fog agent>
In the present invention, among the resin compositions used for forming the surface layer X and the inner layer Y, the antifogging agent includes sorbitan fatty acid ester, glycerin fatty acid ester, glycerin fatty acid succinic acid ester, polyglycerin fatty acid ester, and sorbitan-glycerin. -Type condensed fatty acid ester, sorbitan-diglycerin-type condensed fatty acid ester, pentaerythritol fatty acid ester, dipentaerythritol fatty acid ester and other polyhydric alcohol partial fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyethylene glycol fatty acid ester Ethylene oxide adducts such as polyoxyethylene sorbitan fatty acid ester and polyoxyethylene glycerin fatty acid ester, and sorbitol derivatives obtained by adding propylene oxide and ethylene oxide to sorbitol and then esterifying, alkylamine, alkylamide, alkylethanolamine Amines such as fatty acid diethanolamide, amides and their ethylene oxide adducts, nonionic surfactants such as polyalkylene glycols, cationic surfactants, anionic surfactants and other known ones. Be done.
The antifogging agents can be used alone or in combination of two or more.

When wrapping fruits and vegetables in an overlapping manner, the plastic film made of an ethylene-based resin has a hydrophobic surface, so the water adhering to the plastic film surface is fogged as water drops due to transpiration from the fruits and vegetables. Decrease the distinguishability of the packaged item.
On the other hand, the present invention, by using an antifogging agent, the presence of the antifogging agent on the plastic film surface, by making the surface of the plastic film hydrophilic, it is possible to form a water film instead of water droplets, It is possible to suppress the occurrence of fogging and obtain an appropriate appearance as a multilayer film for wrapping an article to be packaged.

  In the present invention, the content of the antifogging agent in the resin composition used for forming the surface layer X and the inner layer Y is 1 to 4 parts by mass from the viewpoint of achieving both antifogging property and extrusion moldability of the multilayer film. Is. If the content in the surface layer X and the inner layer Y is less than 1 part by mass, the desired antifogging effect may not be sufficiently obtained, and if it exceeds 4 parts by mass, the extrusion moldability may decrease. is there.

  In the present invention, additives such as a lubricant, an antiblocking agent, an antistatic agent, and an antioxidant are appropriately added for the purpose of exerting their respective effective performances, as long as they are within the range not hindering the object of the present invention. Can be used.

  In the present invention, the resin composition used for forming the inner layer Y may be mixed with the resin composition used for forming the surface layer X as long as the object of the present invention is not impaired. The resin composition used for forming the inner layer Y may be mixed with the resin composition used for forming the surface layer X. As a result, it is possible to adjust various physical properties according to the required characteristics, and it is also possible to mix and use recycled resins such as trims and nonstandard products generated during film production.

  The layer structure of the present invention comprises three or more layers having two surface layers X and at least one internal layer Y provided between the surface layers, and for example, X / Y / X, X / X + Y / X. And a 5-layer structure such as X / X + Y / Y / X + Y / X and X / Y / X + Y / Y / X. Among them, the layer structure provided with the X + Y layer is preferable because it is easy to adjust various physical properties and to mix and use the recycled resin. The layers other than the inner layer Y and both surface layers X are not particularly limited as long as they do not hinder the object of the present invention.

  The thickness composition ratio of each layer of the present invention is not particularly limited as long as the object of the present invention is achieved. The total thickness of the multilayer film of the present invention is not particularly limited, but it is preferably 7 to 35 μm for heat shrinkable packaging material use.

Regarding the physical properties of the multilayer film of the present invention, the haze value is 5% or less, the heat seal strength at 120 ° C. is 1.5 N / cm or more, and the heat shrinkage rates at 120 ° C. in the MD direction and the TD direction are 55, respectively. % Or more must be satisfied.
If the haze value exceeds 5%, the transparency required for easily identifying the packaged item and not reducing the commercial value may not be obtained. Heat seal strength at 120 ° C is 1.5N
If it is less than / cm, the fusing sealing property at the time of automatically packaging fruits and vegetables may be deteriorated, and pinholes and openings may occur in the fusing sealing portion, and the appearance of the package may be impaired. In addition, when the thermal shrinkage percentages in the MD direction and the TD direction at 120 ° C. are less than 55%, the shrink finish in automatic packaging of fruits and vegetables may be deteriorated, and the appearance of the package may be impaired.

  Regarding the packaging form of fruits and vegetables using the multilayer film of the present invention, using the multilayer film of the present invention, uncut fruits and vegetables or fruits and vegetables cut into two or more are overlapped and heat-shrink wrapped. It is preferable from the viewpoints of suitability for stacking and stacking packages at stores and transportation efficiency of packages.

For example, the multilayer film of the present invention can be used in a packaging machine such as a vegetable wrapping machine PAW-6000B or PAW-9000B manufactured by Japan Polyster Co., Ltd. to wrap fruits and vegetables for heat shrink wrapping. .. Thereby, since the multilayer film of the present invention can tightly package the object to be packaged, when the package is displayed at the store, it can be stacked, and when the package is packed in a cardboard box, Since it is not bulky, it also has an effect of excellent transport efficiency.
The packaging machine illustrated above is a pillow packaging three-way heat-sealed bag-making system in which the vertical seal is a knurl and the horizontal seal is a seal-and-cut heat-sealing system. In addition, the packaging machine employs a system (PAMS) that automatically measures the vertical size of the packaged object and automatically sets the cut length of the film to a preset extra length. Even an article to be packaged can be automatically packaged into a bag-making size most suitable for the article to be packaged. A heat-shrinkable tunnel is attached to this packaging machine to perform heat-shrinkable wrapping, whereby a shrinkable wrapping body having a tight shrinkage finish can be manufactured.

[Method for producing polyethylene-based multilayer film for heat shrink packaging]
Next, a method for producing the multilayer film of the present invention will be exemplified.
The multilayer film produced using the above resin composition is stretched by a known vertical / horizontal simultaneous biaxial stretching method. The stretching ratio is preferably 3 to 7 times in both length and width. When it is less than 3 times, the heat shrinkage rate of the obtained multilayer film is low, and satisfactory shrink finish may not be obtained, which is not preferable, and when it exceeds 7 times, the tear strength of the multilayer film may decrease. Therefore, it is not preferable.
Further, within the range not hindering the object of the present invention, for the purpose of imparting heat resistance to the multilayer film to improve shrink finish, etc., the multilayer film is appropriately subjected to crosslinking treatment by electron beam or the like. May be.

Hereinafter, the case of the five-layer laminated annular film-forming stretching will be described as an example.
First, a layer formed from a resin composition containing an ethylene resin, a zeolite and an antifogging agent on both surface layers, a layer formed from a resin composition containing an ethylene resin and an antifogging agent on both intermediate layers, A five-layered ring which is melt-kneaded by three or five extruders and joined to the tip of the extruder so that a layer formed from a resin composition containing an ethylene resin and an antifogging agent becomes a core layer. A tubular unstretched multilayer film is produced by coextruding in a ring form from a die and then rapidly solidifying without stretching. Then, both sides of the tubular unstretched multilayer film are irradiated with an electron beam by an electron beam irradiation device to prepare a crosslinked tubular unstretched multilayer film. The obtained crosslinked tubular unstretched multilayer film is supplied to a tubular stretching apparatus, reheated in a temperature range capable of being highly oriented, and a gas pressure is applied to the inside of the tube to expand and stretch it, thereby stretching at a stretching ratio of 3 in both length and width. Approximately 7 times causes simultaneous biaxial orientation. The multilayer film taken out from the stretching device can be heat-treated or annealed as desired, and thus natural shrinkage during storage can be suppressed.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
The methods of measurement and evaluation in Examples and Comparative Examples were performed as shown below.
1. Film thickness: Measured according to JIS-Z1709.
2. Thickness ratio: Measured by observing the cross section of the film with a microscope.
3. Haze value: measured according to JIS-K7105.
4. Heat-sealing strength: Using a heat-sealing tester (model: TP-701-B) manufactured by Tester Sangyo Co., Ltd., a two-layered film was gauged with a heat-sealing bar having a width of 10 cm and controlled at 120 ° C. Sealing was performed at a pressure of 0.8 kgf / cm ² and a sealing time of 1.0 second. Then, the film was cut into a width of 15 mm, mounted on a gripping tool of a tensile tester so as to peel off the seal portion, and the seal strength was measured according to JIS-Z1707.
5. Heat shrinkage ratio: Measured at 120 ° C. according to ASTM-D1204.

6. Packaging evaluation: Using a vegetable automatic wrapping machine (model: PAW-9000B) manufactured by Nippon Polyster Co., Ltd., commercially available 1/4 cut Chinese cabbage was pre-packaged under an appropriate bag making margin condition, and the heat resistance limit of the film was 5 Let it stay in the shrinking tunnel set before ℃ for 5 seconds, then randomly select 10 pieces from the packaging sample after passing through the tunnel, and keep the freshness, fusing and sealing property, shrink finish and transparency according to the following criteria. evaluated.
<Freshness retention>
◯: The packaging sample was left still in an atmosphere of 10 ° C. immediately after packaging, and after 3 days, 8 or more out of 10 pieces of cabbage which was not packaged and showed no deterioration in freshness such as discoloration, wilting, and decay. .. Δ: The packaging sample was left still in an atmosphere of 10 ° C. immediately after packaging, and 3 days later, 3 to 7 out of 10 Chinese cabbage, which was an object to be packaged, showed no deterioration in freshness such as discoloration, wilting, and decay. Individual. X: The packaged sample is left still in an atmosphere of 10 ° C. immediately after packaging, and after 3 days, the cabbage to be packaged does not show a decrease in freshness such as discoloration, wilting, and spoilage, and 2 or less out of 10 .. <Fusing sealability>
◯: There is no pinhole or seal opening in the fusing seal part of the packaging sample, and there is a fusing seal temperature range in which good fusing sealability is obtained.
X: No pinhole or seal opening is found in the fusion-sealed portion of the packaging sample, and there is no fusing-sealing temperature range in which good fusion-sealing property is obtained.
<Shrink finish>
◯: Tightness between the shrink film and the object to be packaged is sufficient, and the four corners of the package sample are almost free of corners.
X: The tight feeling between the shrinkable film and the object to be packaged is insufficient, or the corners of the four corners of the packaging sample are large, and the appearance is impaired.
<Transparency>
◯: The transparency of the shrink film is good, and the objects to be packaged can be easily identified.
X: The transparency of the shrinkable film is poor, making it difficult to identify the object to be packaged, or even if it is possible, the appearance of the package is impaired, and the commercial value of the package is reduced.

Example 1
As shown in Table 1, the density is 0.913 g / cm ³ , the melt index (hereinafter, also referred to as MI) 2.4 g / 10 min, the linear low-density polyethylene (A1) 95.5 parts by mass, and the average particle size. 1.5 parts by mass of synthetic zeolite (B1) having a diameter of 1 μm and a SAR value of more than 2000 and an antifogging agent (C1) (mass ratio of glycerin fatty acid ester / polyglycerin fatty acid ester / polyoxyethylene alkyl ether = 20/70/10 Mixture) A resin composition consisting of 3 parts by mass is used as both surface layers and has a density of 0.920 g / cm ³ and an MI 0.5 g / 10 min of linear low density polyethylene (A2) 98 parts by mass and an antifogging agent (C2). (Mixture of glycerin fatty acid ester / polyglycerin fatty acid ester mass ratio = 50/50) A resin composition consisting of 2 parts by mass is used as both intermediate layers, and has a density of 0.905 g / cm ³ and an MI of 0.8 g / 10 min. A resin composition consisting of 98 parts by mass of density polyethylene (A3) and 2 parts by mass of antifogging agent (C2) (mixture of glycerin fatty acid ester / polyglycerin fatty acid ester mass ratio = 50/50) was used as a core layer, and three units were used. After melt-kneading with an extruder, the extrusion rate of each extruder was set so that the thickness ratio was 1/1/4/1/1, and coextrusion was performed downward with a 5-layer annular die. The five-layer tube thus formed was slid on the outer surface of a cylindrical cooling mandrel in which cooling water circulates, while the outer tube was cooled by passing through a water tank and taken out to obtain an unstretched multilayer film. .. Both sides of this tubular unstretched multilayer film were subjected to electron beam irradiation under an irradiation condition of 110 kGy using an electron beam irradiation device manufactured by Nisshin High Voltage Co., Ltd. The film was introduced into an axial stretching device, heated to a temperature near the melting point of the resin, and stretched 6 times in each of the length and width to obtain a biaxially stretched multilayer film having a film thickness of 10 μm.
The obtained film was good in all of the freshness-retaining property, the fusing sealing property, the shrinkable finish property and the transparency.

Example 2
As shown in Table 1, 97 parts by mass of linear low-density polyethylene (A1) having a density of 0.913 g / cm ³ and MI 2.4 g / 10 min, an average particle diameter of 6 μm, and a synthetic zeolite (B2) 1 having an SAR value of 400 2 parts by mass of a resin composition comprising 2 parts by mass of an antifogging agent (C1) (a mixture of glycerin fatty acid ester / polyglycerin fatty acid ester / polyoxyethylene alkyl ether mass ratio = 20/70/10) as both surface layers, density 0.920g ^/ cm 3, MI0.5g ^/ 10 min linear low density polyethylene (A2) 78 parts by mass, density 0.964g ^/ cm 3, MI5.2g ^/ 10 min density polyethylene (A4) 20 A resin composition consisting of 2 parts by mass of the antifogging agent (C2) (a mixture of glycerin fatty acid ester / polyglycerin fatty acid ester in a mass ratio of 50/50) is used as both intermediate layers, and the thickness ratio is 1/1/5. A biaxially stretched multilayer film having a film thickness of 10 μm was obtained in the same manner as in Example 1 except that the ratio was 1/1.
The obtained film was good in all of the freshness-retaining property, the fusion-sealing property, the shrink finish property and the transparency.

Example 3
As shown in Table 1, 98.5 parts by mass of linear low-density polyethylene (A1) having a density of 0.913 g / cm ³ , MI 2.4 g / 10 min, an average particle diameter of 3 μm, and a synthetic zeolite (B3 having a SAR value of 105). ) 0.5 parts by mass and 1 part by mass of an antifogging agent (C1) (a mixture of glycerin fatty acid ester / polyglycerin fatty acid ester / polyoxyethylene alkyl ether mass ratio = 20/70/10). A biaxially stretched multilayer film having a film thickness of 10 μm was obtained in the same manner as in Example 1 except that the surface layer was used and the thickness ratio was 1/1/3/1/1.
The obtained film was good in all of the freshness-retaining property, the fusing sealing property, the shrinkable finish property and the transparency.

Example 4
As shown in Table 1, 97 parts by mass of linear low-density polyethylene (A1) having a density of 0.913 g / cm ³ and MI 2.4 g / 10 min, an average particle size of 1 μm, and a synthetic zeolite (B1) having a SAR value of more than 2000. A resin composition consisting of 1 part by mass and 2 parts by mass of an antifogging agent (C1) (mixture of glycerin fatty acid ester / polyglycerin fatty acid ester / polyoxyethylene alkyl ether mass ratio = 20/70/10) as both surface layers A biaxially stretched multilayer film having a film thickness of 10 μm was obtained in the same manner as in Example 2 except for the above.
The obtained film was good in all of the freshness-retaining property, the fusing sealing property, the shrinkable finish property and the transparency.

Example 5
As shown in Table 1, 96 parts by mass of linear low-density polyethylene (A1) having a density of 0.913 g / cm ³ , MI 2.4 g / 10 min, an average particle size of 3 μm, and a synthetic zeolite of SAR value 105 (
B3) A resin composition comprising 1 part by mass and 3 parts by mass of an antifogging agent (C1) (mixture of glycerin fatty acid ester / polyglycerin fatty acid ester / polyoxyethylene alkyl ether mass ratio = 20/70/10) on both surfaces A biaxially stretched multilayer film having a film thickness of 10 μm was obtained in the same manner as in Example 1 except that the layers were used.
The obtained film was good in all of the freshness-retaining property, the fusing sealing property, the shrinkable finish property and the transparency.

Comparative Example 1
As shown in Table 2, 97 parts by mass of linear low-density polyethylene (A1) having a density of 0.913 g / cm ³ and MI 2.4 g / 10 min and an antifogging agent (C1) (glycerin fatty acid ester / polyglycerin fatty acid ester) / Mixture ratio of polyoxyethylene alkyl ether = 20/70/10) Biaxial with film thickness of 10 μm in the same manner as in Example 1 except that 3 parts by mass of the resin composition were used as both surface layers. A stretched multilayer film was obtained.
The obtained film was good in terms of fusing sealing property, shrink finish property, and transparency, but the result was insufficient freshness retention property.

Comparative example 2
As shown in Table 2, 96 parts by mass of linear low-density polyethylene (A1) having a density of 0.913 g / cm ³ and MI of 2.4 g / 10 min, 2 parts by mass of metal fine particle antibacterial agent (D1) and antifogging agent ( C1) (a mixture of glycerin fatty acid ester / polyglycerin fatty acid ester / polyoxyethylene alkyl ether mass ratio = 20/70/10 mixture) 2 parts by mass, except that both surface layers were used as in Example 2. By the same method, a biaxially stretched multilayer film having a film thickness of 10 μm was obtained.
Although the obtained film had good freshness-retaining property and shrink finish property, it had a poor heat-sealing strength, so that the fusing-sealing property was insufficient, and the haze value was high, resulting in poor transparency.

Comparative Example 3
As shown in Table 2, 96 parts by mass of linear low-density polyethylene (A1) having a density of 0.913 g / cm ³ and MI 2.4 g / 10 min, a synthetic zeolite (B4) 1 having an average particle size of 4 μm and a SAR value of 30. A resin composition comprising 3 parts by mass of an antifogging agent (C1) (mixture of glycerin fatty acid ester / polyglycerin fatty acid ester / polyoxyethylene alkyl ether mass ratio = 20/70/10) was used as both surface layers. A biaxially stretched multilayer film having a film thickness of 10 μm was obtained in the same manner as in Example 3 except for the above.
The obtained film had good freshness retention, fusing sealing property and shrink finish, but had a high haze value and poor transparency.

Comparative Example 4
As shown in Table 2, 95 parts by mass of linear low-density polyethylene (A1) having a density of 0.913 g / cm ³ and MI 2.4 g / 10 min, an average particle diameter of 3 μm, and a synthetic zeolite (B5) 3 having an SAR value of 3 are used. A resin composition comprising 2 parts by mass of an antifogging agent (C1) (mixture of glycerin fatty acid ester / polyglycerin fatty acid ester / polyoxyethylene alkyl ether mass ratio = 20/70/10) was used as both surface layers. A biaxially stretched multilayer film having a film thickness of 10 μm was obtained in the same manner as in Example 4 except for the above.
The obtained film had good freshness retention, fusing sealing property and shrink finish, but had a high haze value and poor transparency.

Comparative Example 5
As shown in Table 2, a biaxially stretched multilayer film having a film thickness of 10 μm was obtained in the same manner as in Example 5 except that the stretching ratio was 2.5 times in each of the length and width.
The obtained film was good in terms of the freshness-retaining property, the fusing sealing property, and the transparency, but the shrink finish was insufficient because the heat shrinkage rate was low.

  The polyethylene-based multilayer film of the present invention is capable of extending the freshness-keeping period of the fruits and vegetables after packaging in a form in which the fruits and vegetables are overlapped and heat-shrink wrapped, and the fusing sealing property and shrink finish property in an automatic packaging machine are provided. It can be suitably used as a heat-shrinkable packaging material which is excellent in suitability for automatic packaging machines such as, and does not impair the appearance of the package.

Claims (2)

A polyethylene multilayer film for overlapping heat-shrink packaging, comprising three or more layers having two surface layers X and at least one inner layer Y provided between these surface layers,
The two surface layers X and the at least one inner layer Y are each independently formed of a resin composition containing 94 to 99 parts by mass of an ethylene resin, 0 to 2 parts by mass of a zeolite, and 1 to 4 parts by mass of an antifogging agent. Is a layer that has been
One or more of the two surface layers X and the at least one inner layer Y comprises zeolite
This zeolite is a polyethylene-based multilayer film having a SiO ₂ / Al ₂ O ₃ molar ratio of 100 or more and satisfying the following physical properties (a) to (c).
(A) The haze value is 5% or less (b) The heat seal strength at 120 ° C. is 1.5 N / cm or more (c) The heat shrinkage percentage in the MD direction and the TD direction at 120 ° C. is 55%. Be above   The polyethylene-based multilayer film for overlapping heat shrink packaging according to claim 1, wherein the zeolite has an average particle size of 0.5 to 10 μm.