JP2000177076A - Stretch film for packaging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stretch film for packaging having processing stability, transparency, flexibility, cutting properties and high strength and excellent in heat fusion resistance and deformation restoring properties. SOLUTION: In a stretch film constituted of at least three layers, both surface layers are constituted of an ethylenic polymer characterized by that fusion calorie is 80-120 J/g and the fusion calorie ratio of 70 deg.C or lower to the total fusion calorie is 0-40% and melt tension at 180 deg.C is 1-10 g and at least one intermediate layer is constituted of a resin compsn. containing a propylene polymer of which the fusion calorie is 20 - below 80 J/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a stretch film for packaging comprising at least three layers. More specifically, as a soft film comparable to soft vinyl chloride resin film and vinylon film, processing stability, transparency,
The present invention relates to a stretch film for packaging, which has flexibility, cutability, and high strength, and is excellent in heat-sealing property and deformation recovery property.

[0002]

2. Description of the Related Art In recent years, soft vinyl chloride resin films containing a plasticizer have been widely used as soft films.
However, the soft vinyl chloride resin has social factors such as toxicity and transfer problems due to bleed out of plasticizers and monomers, acid rain problems due to generation of hydrogen chloride during incineration, and generation of dioxins.

On the other hand, as a soft film similar to the above-mentioned soft vinyl chloride resin film, there is a film made of a polymer mainly composed of ethylene such as an ethylene-vinyl acetate copolymer, a low-density polyethylene, and an ionomer. However, such a soft film composed of a polymer mainly composed of ethylene is inferior to a soft vinyl chloride resin film in terms of transparency, haze, gloss and the like, and is also inferior in heat resistance and stiffness.

[0004] For this reason, for example, Japanese Patent Application Laid-Open
No. 4 discloses a crystalline olefin-based resin or a resin layer comprising 10 to 90% by weight of a crystalline olefin-based resin and 90 to 10% by weight of an olefin-based thermoplastic elastomer. Monomers 5 to 4 selected from vinyl acetate ester units, aliphatic unsaturated carboxylic acids, and aliphatic unsaturated monocarboxylic acid alkyl esters
There has been proposed a film obtained by inflation molding a film having a copolymer resin surface layer of 0% by weight laminated thereon at a blow ratio of 8 to 20 times. In addition, Japanese Patent Application Laid-Open No. 9-15447
No. 9 has at least one layer containing a propylene polymer and a petroleum resin, and has a storage elastic modulus (E ′) of 5.0 × at a frequency of 10 Hz and a temperature of 20 ° C. by dynamic viscoelasticity measurement. 10 ^{8 to} 5.0 × 10 ⁹ dyn / c
Stretch films for food packaging having m ² and loss tangent (tan δ) in the range of 0.2 to 0.8 have been proposed.

[0005]

However, when these films are heated in a microwave oven or the like, the whole food-wrapped tray is made of a film and a paper bag that wraps a tray or chopsticks provided beside the tray. Heat-sealing properties, film processing stability, film flexibility, film cutability when packaging plastic trays containing food with an automatic packaging machine, deformation recovery when pressing the film on the tray with a finger Properties and high strength of the film were not all satisfactory.

SUMMARY OF THE INVENTION An object of the present invention is to provide a stretch film for packaging which has both processing stability, transparency, flexibility, cutability, and high strength, and is excellent in heat-sealing property and deformation recovery property.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies for the above purpose, and as a result, both surface layers are composed of an ethylene polymer having specific physical properties, and at least one of the intermediate layers has a specific property. The inventors have found that a film composed of at least three layers composed of a propylene-based polymer having physical properties achieves the above object, and completed the present invention.

That is, the present invention relates to a film comprising at least three layers, wherein the film has a heat of fusion of 80 to 120.
J / g, an ethylene polymer (A) in which the ratio of the heat of fusion at 70 ° C. or less to the total heat of fusion is 0 to 40%, and the melt tension at 180 ° C. satisfies 1 to 10 g
To form both surface layers, and the heat of fusion is 20 J / g or more and 8
A stretch film for packaging, wherein at least one of the intermediate layers is composed of a resin composition (E) containing a propylene-based polymer (B) of less than 0 J / g. Hereinafter, the present invention will be described in detail.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The packaging stretch film of the present invention is a film having at least three layers composed of both surface layers and at least one intermediate layer. The ethylene polymer (A) used for the surface layer has a heat of fusion of 80 to 120 J / measured by a differential scanning calorimeter (DSC).
g, preferably 90 to 115 J / g, more preferably 9
5 to 110 J / g, and the ratio of the heat of fusion at 70 ° C. or less to the total heat of fusion is 0 to 40%, preferably 0 to 30%.
%, More preferably 0 to 20%, and an ethylene polymer satisfying a melt tension at 180 ° C. of 1 to 10 g, preferably 1.5 to 5 g. Heat of fusion is 80 J /
If it is less than g, heat-fusibility is poor, and if it exceeds 120 J / g, flexibility is poor. When the ratio of the heat of fusion at 70 ° C. or less to the total heat of fusion exceeds 40%, the heat-fusing property is poor. Also, 1
If the melt tension at 80 ° C. is less than 1 g, bubble stability during inflation processing is poor, and if it exceeds 10 g, drawdown properties during film processing are poor.

The amount of heat of fusion measured by a differential scanning calorimeter (DSC) and the ratio of the amount of heat of fusion at 70 ° C. or less were determined by using an RDC220 manufactured by Seiko Electronics Co., Ltd. 150 ° C at ° C / min
After maintaining the temperature at 150 ° C for 5 minutes, the temperature was lowered at 10 ° C / min to -100 ° C, and after maintaining at -100 ° C for 5 minutes, the temperature was raised to 200 ° C at 10 ° C / min and the melting curve was measured. did. The base line on the high-temperature side of the melting curve is extended linearly to the low-temperature side, the heat of fusion is determined from the total area of the portion surrounded by the straight line and the melting curve, and the total area is divided into two at 70 ° C.
The area ratio of the portion at 70 ° C. or less to the total area was defined as the ratio of the heat of fusion at 70 ° C. or less.

The melt tension was measured by using a melt tension tester manufactured by Toyo Seiki Seisakusho as an apparatus at a temperature of 180 ° C.
A resin extruded at a shear rate of 7.4 sec ^-1 from an orifice having a nozzle diameter of 2.1 mm and a nozzle length of 8 mm at ℃,
The tension at the time of winding at 20 m / min was measured.

The ethylene polymer (A) used for the surface layer has a shear stress of 2.0 × 10 ⁶ dynes at a shear rate of 102 sec ⁻¹ measured by a melt viscosity at 200 ° C.
/ Cm ² or less, preferably 1.5 × 10 ⁶ dy
More preferably, it is ne / cm ² or less.

The shear stress was measured at a temperature of 200.degree. C. using an orifice having a nozzle diameter of 1.53 mm and a nozzle length of 50.83 mm at a temperature of 200.degree.
The shear stress when the resin was extruded at c ^-1 was measured.

The ethylene polymer (A) used for the surface layer is a polymer having a content of repeating units derived from ethylene usually exceeding 50% by weight, for example, low-density polyethylene, linear low-density polyethylene. , Linear ultra-low-density polyethylene, medium-density polyethylene, high-density polyethylene and a copolymer containing ethylene as a main component, that is, a homopolymer of ethylene, ethylene and propylene,
Butene-1, pentene-1, hexene-1, heptene-
1, α-olefins having 3 to 8 carbon atoms such as octene-1; vinyl esters such as vinyl acetate and vinyl propionate; unsaturated carboxylic esters such as methyl acrylate, ethyl acrylate, methyl methacrylate and ethyl methacrylate And ionomers thereof; vinyl aromatic compounds such as styrene and α-methylstyrene; butadiene;
Diene compounds such as isoprene, 1,3-pentadiene and 2,5-norbornadiene; 2-norbornene, 5-
Copolymers or multi-component copolymers with one or more comonomers selected from cyclic olefins such as methyl-2-norbornene, hydrogenated products thereof, and compositions thereof are exemplified.

Among these ethylene polymers (A), at least one ethylene polymer selected from low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene and high-density polyethylene is used. preferable.

In the ethylene polymer (A), at least one ethylene polymer selected from linear low-density polyethylene, linear ultra-low-density polyethylene and high-density polyethylene is used in an amount of 80 to 20% by weight. % And low-density polyethylene from 20 to 80% by weight are most preferred.

The method for producing the ethylene polymer (A) is not particularly limited, and may be a known polymerization method using a known olefin polymerization catalyst, for example, a Ziegler polymer.
Using a Natta type catalyst, a slurry polymerization method, a solution polymerization method,
Examples include a bulk polymerization method and a gas phase polymerization method, and a bulk polymerization method and a solution polymerization method using a radical initiator.

The ethylene polymer (A) constituting the surface layer may contain various additives as required, for example, an antioxidant, an antifogging agent, an antistatic agent, a lubricant, a nucleating agent, and the like. Can be.

The propylene polymer (B) used for the intermediate layer of the present invention is a propylene polymer having a heat of fusion of 20 J / g or more and less than 80 J / g as measured by a differential scanning calorimeter (DSC). Preferably, the heat of fusion is 30 to
It is a propylene polymer having a weight of 70 J / g. When the heat of fusion is less than 20 J / g, heat resistance is poor, and when it is 80 J / g or more, flexibility is poor. The propylene unit content of the propylene-based polymer usually exceeds 50% by weight.

The amount of heat of fusion measured by a differential scanning calorimeter (DSC) was measured by using an RDC220 device manufactured by Seiko Denshi Kogyo Co., Ltd., packing about 5 mg of a sample in an aluminum pan, and increasing the temperature to 230 ° C. at 100 ° C./min. Warm and 230 ° C for 5
After holding for 10 minutes, the temperature was lowered to -50 ° C at 10 ° C / minute,
After holding at 50 ° C. for 5 minutes, the temperature was raised to 230 ° C. at 10 ° C./min, and the melting curve was measured. The point at which the melting curve returned to the base line on the high temperature side and the point at 0 ° C. in the melting curve were connected with a straight line. ,
The heat of fusion was determined from the total area of the portion surrounded by this straight line and the melting curve.

The propylene polymer (B) is a propylene homopolymer (B-1) or a propylene-α-olefin copolymer (B-1) having a propylene unit content of 100 to 50% by weight. No. Examples of the α-olefin include ethylene, butene-1, pentene-1, hexene-1, heptene-1, and octene-1.
And α-olefins having 2 to 4 carbon atoms, such as

The propylene polymer (B) may be a crystalline propylene homopolymer (B-1) having a propylene unit content of 100 to 90% by weight or a crystalline propylene-α-olefin copolymer. Coalescing (B-1)
A propylene-based resin mixture containing 85 to 20% by weight and 15 to 80% by weight of an amorphous polyolefin (B-2) having a content of propylene unit and / or butene-1 unit of 50% by weight or more is preferable. Examples of the α-olefin include ethylene, butene-1, pentene-
Α-olefins having 2 to 4 to 10 carbon atoms, such as 1, hexene-1, heptene-1 and octene-1. In the present invention, the term “amorphous” refers to a xylene-soluble component (FD)
A standard, CFR21, §177.1520 (d) (4)
(1) is 60% by weight or more.

Specific examples of the amorphous polyolefin (B-2) include polypropylene, polybutene-1, and propylene-ethylene copolymers having a content of the propylene unit and / or butene-1 unit of 50% by weight or more. Coalescing,
Butene-1-ethylene copolymer, propylene-butene-
1 copolymer, propylene-butene-1-ethylene terpolymer, propylene-hexene-1-ethylene terpolymer, butene-1-hexene-1-ethylene terpolymer and the like. And amorphous polyolefins.

The propylene polymer (B) can be prepared by a known polymerization method using a known olefin polymerization catalyst, for example, a slurry polymerization method using a Ziegler-Natta type catalyst,
It can be produced by a solution polymerization method, a bulk polymerization method, a gas phase polymerization method, or the like.

The preparation method when the propylene polymer (B) is a polymer mixture is not particularly limited, and may be a known method, for example, a kneader such as a kneader, a Banbury mixer, a roll, a uniaxial or a kneader. Heat melting and kneading can be performed using a twin screw extruder or the like. Further, various resin pellets may be dry-blended. Further, the polymer may be blended by multi-stage polymerization.

The resin composition (E) used for the intermediate layer of the present invention
Is 95 to 55% by weight, preferably 85 to 65% by weight of the propylene-based polymer (B), and the content of ethylene unit is 9%.
0 to 60% by weight of an ethylene copolymer (C)
A resin composition containing 5% by weight, preferably 15 to 35% by weight, is preferred for flexibility and impact resistance.

The ethylene copolymer (C) includes:
For example, low density polyethylene, linear low density polyethylene,
Linear ultra-low density polyethylene, medium density polyethylene, high density polyethylene and copolymers based on ethylene,
That is, ethylene and propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1
Α-olefins having 3 to 8 carbon atoms such as vinyl esters; vinyl esters such as vinyl acetate and vinyl propionate; unsaturated carboxylic esters such as methyl acrylate, ethyl acrylate, methyl methacrylate and ethyl methacrylate; and ionomers thereof; Vinyl aromatic compounds such as styrene and α-methylstyrene; butadiene, isoprene, 1,3
Diene compounds such as pentadiene and 2,5-norbornadiene; copolymers or multi-component copolymers with one or more comonomers selected from cyclic olefins such as 2-norbornene and 5-methyl-2-norbornene Coalescing,
Examples thereof include hydrogenated products and compositions thereof.

Among these ethylene copolymers (C), linear low-density polyethylene, linear ultra-low-density polyethylene, low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer And at least one ethylene copolymer selected from ethylene-methacrylate copolymers.

In the ethylene copolymer (C), at least one ethylene copolymer selected from linear low-density polyethylene, linear ultra-low-density polyethylene and low-density polyethylene is particularly preferred. preferable.

The ethylene-based copolymer (C) has a heat of fusion of 20 to 20 from the balance of heat resistance, flexibility and high strength.
A copolymer of 120 J / g is preferred,
A copolymer having J / g is more preferred.

The method for producing the ethylene copolymer (C) is not particularly limited, and a known polymerization method using a known olefin polymerization catalyst, for example, Ziegler
Using a Natta type catalyst, a slurry polymerization method, a solution polymerization method,
Examples include a bulk polymerization method and a gas phase polymerization method, and a bulk polymerization method and a solution polymerization method using a radical initiator.

The resin composition (E) used in the intermediate layer of the present invention
Is 90 to 60% by weight, preferably 85 to 65% by weight, more preferably 80 to 70% by weight, and 10 to 40% by weight of petroleum resins (D), preferably 15 to 35% by weight. %, More preferably 20 to 30% by weight
Is preferred for cutability.

The petroleum resins (D) are rosin-based resins,
Examples include terpene resins, thermoplastic resins obtained by polymerizing and solidifying a cracked oil fraction generated by the thermal decomposition of petroleum, cumarone-indene resin, alkyl-phenol resin, and the like. Examples of the rosin resin include gum rosin, wood rosin, hydrogenated rosin, esterified rosin esterified with alcohol, and rosin phenol resin obtained by reacting phenol and rosin. As the terpene resin, α-pinene or β-pinene polymerized terpene resin,
Examples thereof include a terpene phenol resin obtained by reacting phenol and a terpene, an aromatic modified terpene resin imparted with polarity with styrene or the like, a hydrogenated terpene resin, and the like. The cracked oil fraction of polymerized thermoplastic resin is solidified to produce by pyrolysis of petroleum, aromatic petroleum that aliphatic petroleum resin obtained by the C ₅ fraction as a raw material, the C ₉ fraction as a raw material Examples thereof include a resin, an alicyclic petroleum resin obtained from dicyclopentadiene as a raw material, a copolymerized petroleum resin obtained by copolymerizing two or more of these, and a hydrogenated petroleum resin obtained by hydrogenating these. Specifically, commercial products such as Heylets and Petrozine manufactured by Mitsui Petrochemical Industries, Inc., Alcon manufactured by Arakawa Chemical Industries, Ltd., Clearon manufactured by Yashara Chemical Co., Ltd., and Escolets manufactured by Tonex Co., Ltd. are used. Can be.

Among the petroleum resins (D), hydrogenated derivatives such as hydrogenated rosin, hydrogenated terpene resins, and hydrogenated petroleum resins are preferred in terms of color tone and odor.

The resin composition (E) used in the intermediate layer of the present invention
Is 85 to 15% by weight of the propylene-based polymer (B),
The resin composition containing the ethylene copolymer (C) in an amount of 5 to 45% by weight and the petroleum resin (D) in an amount of 10 to 40% by weight has flexibility, impact resistance, cut properties and heat resistance. Preferred from a viewpoint. In particular, the propylene polymer (B) 70
To 30% by weight, the above-mentioned ethylene copolymer (C) 20 to 4
The resin composition (E) containing 0% by weight and 15 to 35% by weight of the petroleum resin (D) is preferable from the viewpoint of the balance between flexibility, impact resistance, cutability, and heat resistance.

The method for preparing the resin composition (E) used in the present invention is not particularly limited, and known methods, for example, kneaders such as kneaders, Banbury mixers, rolls, and single-screw or twin-screw extruders. And heat-melting and kneading. Further, various resin pellets may be dry-blended.

Further, the resin composition (E) constituting the intermediate layer
Can contain various additives and fillers, if necessary, for example, an antioxidant, an antifogging agent, an antistatic agent, a nucleating agent, a flame retardant and the like. Further, other resins can be blended and used within a range not to hinder the present invention.
For example, a recycled resin can be blended.

In the stretch film for packaging of the present invention, a recycled resin layer may be laminated and inserted as an intermediate layer, and another thermoplastic resin layer, for example, a polyamide resin or an ethylene / vinyl alcohol copolymer for providing a gas barrier. Coalescing,
A polyester resin or the like may be laminated and inserted. Further, in order to increase the adhesive strength between the layers, an adhesive or an adhesive resin layer may be laminated and inserted.

The thickness of each layer constituting the stretch film for packaging of the present invention is not particularly limited, and can be arbitrarily selected. Usually, each layer is about 2-100μ
m. Also, the thickness ratio of both surface layers to the total thickness of the film is not particularly limited, and can be arbitrarily selected. Usually, the total thickness of both surface layers is configured to be 20 to 90% of the total thickness of the film.

The method for producing the stretch film for packaging of the present invention is not particularly limited, and a known method, for example,
Co-extrusion laminating method by inflation method or casting method,
Extrusion lamination, sand lamination, dry lamination, and the like can be used. In the above manufacturing method, from the balance of the vertical and horizontal physical properties of the film,
The inflation method is preferred.

When the stretch film for packaging of the present invention requires shrinkability, it is preferably stretched at least uniaxially after film formation. Stretching can be uniaxial or biaxial. In the case of uniaxial stretching, for example, a commonly used roll stretching method is preferable. In the case of biaxial stretching, for example, a sequential stretching method in which biaxial stretching is performed after uniaxial stretching may be used, or a simultaneous biaxial stretching method such as tubular stretching may be used.

[0042]

As described in detail above, according to the present invention,
It is possible to provide a stretch film for packaging which has both processing stability, transparency, flexibility, cutability, and high strength, and is excellent in heat-sealing property and deformation recovery property. Further, the stretch film for packaging of the present invention is a soft film, and can be applied to various uses instead of a soft vinyl chloride resin film which is a social problem due to environmental pollution.

[0043]

Next, the present invention will be described based on examples, but the present invention is not limited to these examples.

First, methods for measuring physical properties in the following Examples and Comparative Examples will be described. (1) Content of Ethylene Unit The measurement was carried out by the IR method according to the method described on pages 593 to 594 of a Handbook for Polymer Analysis (1995, Kinokuniya Bookstore). (2) Content of Propylene Unit and Butene-1 Unit The measurement was carried out by an IR method according to the method described on pages 616 to 619 of a Handbook for Polymer Analysis (1995, published by Kinokuniya Bookstore). (3) Content of vinyl acetate unit The measurement was performed according to JIS K6730.

(4) Melt flow rate (MFR) In accordance with JIS K7210, measurement was made according to Condition 4 of Table 1 for ethylene polymers and according to Condition 14 of Table 1 for propylene polymers. (5) Melt tension A melt tension tester manufactured by Toyo Seiki Seisaku-sho, Ltd. was used, and a shear rate of 7.4 sec ^-1 from an orifice having a nozzle diameter of 2.1 mm and a nozzle length of 8 mm at a temperature of 180 ° C.
Was measured at the time of winding the resin extruded at 20 m / min. (6) Heat of fusion of propylene-based polymer (B) Using an RDC220 manufactured by Seiko Denshi Kogyo Co., Ltd. as an apparatus, about 5 mg of a sample was packed in an aluminum pan, and the temperature was raised to 230 ° C at 100 ° C / min. , The temperature was lowered to -50 ° C at 10 ° C / min, and the temperature was maintained at -50 ° C for 5 minutes, and then the temperature was raised to 230 ° C at 10 ° C / min, and the melting curve was measured. The point at which the melting curve returns to the base line on the high temperature side and the point at 0 ° C. of the melting curve were connected by a straight line, and the heat of fusion was determined from the total area of the portion surrounded by the straight line and the melting curve. (7) Heats of fusion of ethylene-based copolymers (A, C), ratio of heats of fusion Using an RDC220 manufactured by Seiko Denshi Kogyo Co., Ltd., about 5 mg of a sample is packed in an aluminum pan, and 150 ° C. at 100 ° C./min. After maintaining the temperature at 150 ° C for 5 minutes, the temperature was lowered at 10 ° C / min to -100 ° C, and after maintaining at -100 ° C for 5 minutes, the temperature was raised to 200 ° C at 10 ° C / min and the melting curve was measured. did. The base line on the high temperature side of the melting curve is extended linearly to the low temperature side, the heat of fusion is determined from the total area of this straight line and the area enclosed by the melting curve, and the total area is divided into two at 70 ° C. The area ratio of the portion at a temperature of not more than 70 ° C was defined as the ratio of the heat of fusion at a temperature of 70 ° C or less. (8) Shear stress The resin was extruded from an orifice having a nozzle diameter of 1.53 mm and a nozzle length of 50.83 mm at a temperature of 200 ° C. at an extrusion speed of 102 sec ⁻¹ using a capillary type melt viscosity measuring device, Capillograph 1B manufactured by Toyo Seiki Seisaku-sho, Ltd. The shear stress at the time of was measured.

(9) Transparency (Haze) The measurement was performed according to ASTM D1003. (10) Rigidity (1% SM) A 120 mm × 20 mm strip-shaped film test piece having a length in the film taking-up direction (MD) and the direction perpendicular to the taking-up direction (TD) is gripped by 60 mm and pulled at a speed of 5 m.
It was pulled at m / min and the stress at 1% elongation was measured. (11) Cutability When packaging a polystyrene foam tray using a commercially available push-up type tray automatic packaging machine (AW2600AT-III.PE manufactured by Teraoka Seiko Co., Ltd.), breakage of the broken portion of the film after cutting the film with a saw blade. Was determined as follows. ：: Very good without folding of the film. Δ: The film is slightly broken but good. X: The film is folded. (12) Deformation recovery property A circular sample film 1 having a diameter of 44.45 mm is fixed to a film fixing jig 2, and a tip of the center of the film has a radius of 6.3.
Using a load cell 4, push a 5 mm hemispherical pin 3 to a predetermined depth 5 at a speed of 100 mm / min, immediately pull it up at the same speed, and measure whether the push completely disappears within 30 seconds. did. The maximum indentation depth 5 at which the pressure disappears completely after the pressing was defined as the degree of deformation recovery. FIG. 1 is a plan view of an apparatus for measuring the degree of deformation recovery.

(13) Tensile properties A strip-shaped film test piece having a width of 50 mm was gripped by a distance of 5 m.
m, the film was pulled in a direction perpendicular to the direction in which the film was pulled (TD) at a tensile speed of 200 mm / min, and the breaking elongation and breaking strength were measured. (14) Heat-resistant fusing property As a device, a heat seal tester manufactured by Tester Sangyo Co., Ltd. was used.
The film and the tracing paper (40 g / m ² ) were heat-sealed under the conditions of a sealing pressure of 0.5 kg / cm 2 for 2 seconds, and the strength when the sealing interface was peeled off at a speed of 300 mm / min was measured. (15) Processing stability Bubble stability during film processing was determined as follows. ○: There is no wobble in the bubble, no wrinkles in the film,
Small thickness unevenness. X: The bubble is wobble or meandering, the film is wrinkled, and the thickness unevenness is large. (16) Film appearance The film surface was visually judged as follows. ：: There is no rough pattern on the film surface, and the film appearance is good. ×: A rough pattern is observed on the film surface, and the film appearance is poor.

Example 1 [Preparation of Surface Layer Resin Composition] As the resin composition constituting the surface layer, an ethylene-butene-1 copolymer (Esprene SPO N0355, MFR, manufactured by Sumitomo Chemical Co., Ltd.) was used.
(190 ° C.) = 5 g / 10 min, butene-1 unit content = 10% by weight) 60% by weight, low-density polyethylene (Sumikasen CE2573, manufactured by Sumitomo Chemical Co., Ltd., MFR (1
90 ° C.) = 2 g / 10 min) 40 parts by weight and 1 part by weight of an anti-fogging agent (STO-405 manufactured by Marubishi Yuka Kogyo Co., Ltd.) per 100 parts by weight of the ethylene polymer mixture was melt-kneaded with a Banbury mixer. The prepared resin composition was used. [Preparation of Intermediate Layer Resin Composition] As the resin composition (E) constituting the intermediate layer, a propylene-ethylene random copolymer which is a crystalline propylene-α-olefin copolymer (B-1) (Sumitomo Chemical Co., Ltd.) Noblen WF73 manufactured by Kogyo Co., Ltd.
2-1, MFR (230 ° C.) = 5.5 g / 10 min, propylene unit content = 97% by weight) 50% by weight and amorphous polyolefin (B-2) (Ube Tack UT2780 manufactured by Ube Lexen Co., Ltd.) 50% by weight of a propylene-based resin mixture (B) melt-kneaded with a Banbury mixer, and 50% by weight of an ethylene-butene-1 copolymer (C) (MFR
(190 ° C.) = 7 g / 10 min, butene-1 unit content = 22% by weight, heat of fusion = 47 J / g) 30% by weight;
Petroleum resins (D) (Alcon P1 manufactured by Arakawa Chemical Industry Co., Ltd.)
25) A resin composition prepared by melt-kneading 20% by weight with a single screw extruder was used. [Production of Film] A 13 μm-thick two-layer three-layer laminated film having a surface layer / intermediate layer / surface layer composition ratio of 38/24/38 was processed at a processing temperature of 200 using a Placo three-layer blown film processing machine. C. and a blow-up ratio of 4.5. Table 1 shows the evaluation results of the obtained films.
And Table 2.

Comparative Example 1 The resin composition constituting the surface layer was MFR (190 ° C.) = 2 instead of the ethylene polymer used in Example 1.
Example 1 except that an ethylene-butene-1 copolymer (Sumikacene-L CL2080, manufactured by Sumitomo Chemical Co., Ltd.) having a g / 10 minute butene-1 unit content of 9% by weight was used.
In the same manner as in the above, a laminated film was formed. Tables 1 and 2 show the evaluation results of the obtained films.

Comparative Example 2 As the resin composition constituting the surface layer, an ethylene-vinyl acetate copolymer (MFR (190 ° C.) = 2 g / 10 min, instead of the ethylene polymer used in Example 1) A laminated film was formed in the same manner as in Example 1 except that the content of vinyl acetate units = 15.8% by weight) was used. Tables 1 and 2 show the evaluation results of the obtained films.

Comparative Example 3 As the resin composition constituting the intermediate layer, a propylene-ethylene random copolymer (Noblen S131 manufactured by Sumitomo Chemical Co., Ltd., MFR (230 ° C.) = 1.3 g / 10
Propylene unit content = 95% by weight), and a laminated film was formed in the same manner as in Comparative Example 2 except that 100% by weight was used. Table 1 and Table 2 show the evaluation results of the obtained films.
Shown in

[0052]

[Table 1]

In the table, PE: ethylene polymer (A) or (C) LD: low-density polyethylene LL: linear low-density polyethylene or linear ultra-low-density polyethylene EVA: ethylene-vinyl acetate copolymer PP: propylene -Based resin composition (B) C-PP: crystalline propylene-α-olefin copolymer (B-1) APO: amorphous polyolefin (B-2) STO-405: antifogging agent (Marubishi Yuka Kogyo Co., Ltd.) STO manufactured by
-405) P125: Petroleum resin (D) (Alcon P125 manufactured by Arakawa Chemical Industries, Ltd.)

[0054]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a plan view of an apparatus for measuring a degree of deformation recovery of a film.

[Description of Signs] 1 ... Circular sample film, 2 ... Film fixing jig, 3 ... Pin 4 ... Load cell, 5 ... Indentation depth

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F100 AK01C AK04A AK04B AK06 AK07C AK62A AK62B AK63A AK63B AK64 AK65 AK66C AK67C AL03 AL05C BA03 BA04 J05A06 BA07 BA10A BA10B GB15 J06A JA10B GB20 YY00B YY00C

Claims (10)

[Claims] 1. A film comprising at least three layers, having a heat of fusion of 80 to 120 J / g, a ratio of a heat of fusion of 70 ° C. or less to a total heat of fusion of 0 to 40%, and 180 ° C. Resin composition containing a propylene polymer (B) having both surface layers composed of an ethylene polymer (A) having a melt tension of 1 to 10 g and having a heat of fusion of 20 J / g or more and less than 80 J / g. Stretch film for packaging, characterized in that at least one of the intermediate layers is composed of the product (E). 2. The packaging according to claim 1, wherein the ethylene polymer (A) has a shear stress of not more than 2.0 × 10 ⁶ dyne / cm ² at a shear rate of 102 sec ⁻¹ as measured by a melt viscosity at 200 ° C. For stretch film. 3. The ethylene-based polymer (A) is at least one ethylene polymer selected from linear low-density polyethylene, linear ultra-low-density polyethylene, high-density polyethylene, and low-density polyethylene. Item 10. The stretch film for packaging according to item 1. 4. An ethylene polymer (A) comprising 80 to 20% by weight of at least one ethylene polymer selected from linear low density polyethylene, linear ultra low density polyethylene and high density polyethylene, and Low density polyethylene 2
The stretch film for packaging according to claim 1, which is a resin composition containing 0 to 80% by weight. 5. A propylene homopolymer (B-1) or a propylene-α-olefin copolymer (B-1) wherein the propylene polymer (B) has a propylene unit content of 100 to 50% by weight. The stretch film for packaging according to claim 1, which is: 6. The propylene polymer (B) is a crystalline propylene homopolymer (B-1) or a crystalline propylene polymer having a propylene unit content of 100 to 90% by weight.
85 to 20% by weight of an α-olefin copolymer (B-1) and 15 to 80% by weight of an amorphous polyolefin (B-2) having a content of propylene units and / or butene-1 units of 50% by weight or more. The stretch film for packaging according to claim 1, which is a propylene-based resin mixture containing 0.1% by weight. 7. The resin composition (E) has a propylene polymer (B) content of 95 to 55% by weight and an ethylene unit content of 90%.
5 to 45% by weight of an ethylene-based copolymer (C),
The stretch film for packaging according to claim 1, which is a resin composition containing the resin composition in an amount of 1% by weight. 8. A resin composition (E) comprising 90 to 60% by weight of a propylene polymer (B) and 10 to 4% of a petroleum resin (D).
The stretch film for packaging according to claim 1, which is a resin composition containing 0% by weight. 9. The resin composition (E) has a propylene polymer (B) content of 85 to 15% by weight and an ethylene unit content of 90%.
5 to 45% by weight of an ethylene-based copolymer (C),
The stretch film for packaging according to claim 1, which is a resin composition containing 10% by weight and 10 to 40% by weight of a petroleum resin (D). 10. The ethylene copolymer (C) is at least one ethylene polymer selected from linear low-density polyethylene, linear ultra-low-density polyethylene and low-density polyethylene. 10. The stretch film for packaging according to 9.