JP2000169597A - Easily breakable film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easily breakable film manufactured by a simple process, balanced in easily breakable property and bag breaking strength, having a good heat sealing property and beautiful surface, SOLUTION: This film is prepared by extruding with a T dye method a resin compsn. comprising 80-98 wt.% polyolefin resin and 2-20 wt.% ionic copolymer. Or it is a multi-layered film prepared by extruding with a T dye method a resin compsn. comprising at least one surface layer of a resin compsn. mainly composed of a linear low density polyethylene having a density of 0.890-0.920 g/cm3 or an ethylene/vinyl acetate copolymer, and at least one layer of a resin compsn. comprising 40-95 wt.% polyolefin resin and 5-60 wt.% ionic copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easily tearable film, and more particularly to an easily tearable film suitably used as a packaging material having excellent tearability.

[0002]

2. Description of the Related Art In recent years, hermetically sealed packaging with a plastic film has been widely used due to hygiene, economy, and ease of handling. Examples of plastic films used for such packaging include low-density polyethylene and ethylene-vinyl acetate copolymer resin films having excellent flexibility, and linear low-density polyethylene films having excellent seal strength and the like.

[0003] Such a sealed package made of a plastic film is made of a transparent type having an enhanced content visibility, an opaque type such as an aluminum vapor-deposited film having an enhanced fragrance retention, other gas barrier properties and light shielding properties, and the like. There are various types such as those with vivid printing, but in particular, containers used for retort pouch food can be opened by easily tearing from the notch provided at the end without using a blade. It is required to be something.

Means for imparting tear resistance to a plastic film include, for example, a method of stretching a plastic film in one direction and orienting it, a method of using a unidirectionally oriented plastic film for a specific layer of a multilayer plastic film, A method of blending incompatible thermoplastic resins, for example, low-density polyethylene and high-density polyethylene to form a film (Japanese Patent Application Laid-Open Nos. 9-111060 and 4-19137) and the like can be mentioned. In the former, a special stretching machine is required to produce an easily tearable plastic film, and the molding must be performed under extremely poor molding stability conditions, such as a high stretching ratio and a low molding temperature. In the latter case, there is a possibility that it is difficult to balance the tear strength and the bag breaking strength in the flow direction of the mixed resin, and it is difficult to produce a stable easily tearable plastic film in any case.

A polyolefin layer and an ionic copolymer layer are co-extruded under an inflation method under a specific condition, and a shrinkable thermoplastic plastic film provided with easy tearability so as to be linearly torn in a direction perpendicular to the extrusion direction ( Japanese Patent Application Laid-Open No. 6-55632) is disclosed. However, the co-extrusion method based on the inflation method may be used for applications such as shrink-packing a plurality of canned products or bottled products only with the above-mentioned shrinkable thermoplastic film, but may be used for retort pouch foods and the like. In the field of light packaging, the degree of easy tearing needs to be even more sensitive, and in particular, there is a problem that productivity is poor and economical.

[0006] Furthermore, plastic film bag making means and sealing means are widely used because heat sealing is simple and reliable, and easy tearing films are also required to have good heat sealing properties. But,
Making the plastic film easily tearable, as a result of taking measures to make the heat sealing property worse such as the above-described stretching orientation treatment and mixing of the incompatible thermoplastic resin, thereby, when the heat sealing property becomes poor, However, it was necessary to partially or entirely laminate a film having good heat sealability by a part coating method or another laminating method.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above facts, and its object is to
An object of the present invention is to provide an easily tearable film having a beautiful surface with a good balance between easy tearability and bag breaking strength, which has a simple manufacturing process and good heat sealability.

[0008]

According to a first aspect of the present invention, there is provided an easily tearable film formed by extruding a resin composition comprising 80 to 98% by weight of a polyolefin resin and 2 to 20% by weight of an ionic copolymer by a T-die method. It is characterized by being formed.

The easily tearable film according to the second aspect of the present invention comprises:
A multilayer film extruded by a T-die method, wherein at least one surface layer is made of low-density polyethylene,
The resin composition is mainly composed of a linear low-density polyethylene having a density of 0.890 to 0.920 g / cm ³ or an ethylene-vinyl acetate copolymer resin, and at least one other layer is formed of a polyolefin resin 40 to It is characterized by comprising a resin composition comprising 95% by weight and 5 to 60% by weight of an ionic copolymer.

The polyolefin resin used in the present invention means an α-olefin homopolymer or a copolymer of an α-olefin and one or more other monoethylenic monomers. Examples of the α-olefin include ethylene, propylene, 1-butene, 1-hexene, 4-methylpentene-1, 1-octene, and the like.Other monoethylenic monomers include, for example, vinyl acetate, Styrene, (meth) acrylic derivatives and the like can be mentioned.

The above-mentioned ionic copolymer means that a carboxyl group of a copolymer of an α-olefin and an α, β-ethylenically unsaturated carboxylic acid is partially or completely neutralized with a metal ion, and the molecular chain between Has a crosslinked structure, and exhibits properties as a crosslinked polymer in a solid state, and exhibits properties as an uncrosslinked thermoplastic polymer in a molten state. When the unsaturated carboxylic acid is a monocarboxylic acid, the ionic value of the metal ion is 1 to 3, and when the unsaturated carboxylic acid is a dicarboxylic acid, the ionic value of the metal ion is 1.

Among the above ionic copolymers, the α-olefin is ethylene, the α, β-ethylenically unsaturated carboxylic acid is a monocarboxylic acid or a dicarboxylic acid, the metal ion is a complexed metal ion, II, III,
Copolymers which are metal ions belonging to IV-A and VIII or metal ions of Group I of the periodic table, particularly alkali metal ions, are preferably used. These ionic copolymers are known per se, and include, for example, "Himilan" (trade name, manufactured by DuPont-Mitsui Polychemicals, Inc.).

The composition ratio of the ionic copolymer in the easily tearable film of the present invention is as follows.
It is 2 to 20% by weight with respect to 98% by weight. If the constituent ratio of the ionic copolymer is less than 2% by weight or more than 20% by weight, the resulting easily tearable film cannot have sufficient linear cut property and light tearability.

An easily tearable film composed of a resin composition comprising 80 to 98% by weight of a polyolefin resin and 2 to 20% by weight of an ionic copolymer can be used alone, but a layer composed of another resin composition is laminated. It can also be used as a laminated multilayer film. The tearable film,
In the case of a multilayer film extruded by the T-die method, at least one layer is made of low-density polyethylene,
It is composed of a resin composition mainly composed of a linear low-density polyethylene or an ethylene-vinyl acetate copolymer resin having a density of 0.890 to 0.920 g / cm ³ (hereinafter, abbreviated as a surface layer). One layer is composed of 40 to 95% by weight of polyolefin resin and 5 to 6 of ionic copolymer.
It is preferable that the resin composition is composed of 0% by weight (hereinafter, abbreviated as an easily tearable layer).

The easily tearable film layer of the multilayer film is
Low density polyethylene, density 0.890 ~ 0.920g
/ Cm ³ of a resin composition mainly composed of a linear low-density polyethylene or an ethylene-vinyl acetate copolymer resin. The low-density polyethylene having a density of 0.890-0.
Each of the surface layers extruded by the T-die method comprising a resin composition mainly composed of a linear low-density polyethylene of 920 g / cm ³ or an ethylene-vinyl acetate copolymer resin has good heat sealability, In addition, it has the necessary strength as a packaging material. In the above resin composition,
Linear low-density polyethylene has a density of 0.890 g
If it is less than / cm ³ , the films are likely to be blocked with each other, and the workability and the like will be reduced. If it is more than 0.920 g / cm ³ , the heat sealing property will be reduced.

When the content ratio of the ionic copolymer in the easily tearable film layer of the multilayer film is less than 5% by weight, the tearability is reduced, and it becomes difficult to tear straight.
If it exceeds 0% by weight, it becomes difficult to obtain the necessary strength as a packaging material, so that the content ratio is limited to the above. More preferably, the content ratio of the ionic copolymer is 10 to 30% by weight.

In the above multilayer film, the composition ratio of the thickness of the easily tearable film layer and the surface layer is preferably 12.5 to 75% of the total thickness of the surface layer. 25% or more. When the composition ratio of the thickness of the easily tearable film layer is less than 25%, the tearability is reduced, it is difficult to tear straight, and the composition ratio of the thickness of the surface layer is 1%.
If it is less than 2.5%, it is difficult to obtain the heat seal strength and the strength required as a packaging material. Further, in order to obtain good heat sealability, the absolute value of the thickness of the surface layer is preferably 5 μm or more.

The easily tearable film of the present invention or the easily tearable film layer and the surface layer of the above-mentioned multilayer film may contain, if necessary, an antiblocking agent, a slip agent, an antistatic agent, etc., without departing from the spirit of the present invention. Agents, inorganic fillers, coloring agents and the like may be added.

The easily tearable film of the present invention, whether it is a single-layer film or a multilayer film, is extruded by a T-die method. By the extrusion molding of the T-die method, the ionic copolymer in the easily tearable film layer is particularly easily oriented in the air gap portion, and is extremely easy to tear together with an appropriate setting of the drawdown ratio, and is uniform. It is possible to obtain a high quality easily tearable film which is gelled and has excellent heat sealing properties.

[0020]

(Example 1) Low density polyethylene (manufactured by Asahi Kasei Kogyo Co., Ltd., trade name "Suntech F1920"),
(Density 0.919 g / cm ³ , MFR 2.0 g / 10 min)
A resin composition comprising 5% by weight of an ionic copolymer (trade name "Himilan 1605", manufactured by DuPont-Mitsui Polychemicals Co., Ltd., density: 0.950 g / cm ³ , MFR: 2.8 g / 10 minutes) in a proportion of 95% by weight was subjected to a T-die method. Thickness 40μ
m was prepared.

Example 2 An easily tearable film was produced in the same manner as in Example 1 except that the content ratio of the ionic copolymer in Example 1 was changed to 20% by weight.

Example 3 Low-density polyethylene (manufactured by Tosoh Corporation, trade name "Petrocene 175R", density 0.920)
g / cm ³ , MFR 0.6 g / 10 min) 20 parts by weight and linear low density polyethylene (manufactured by Idemitsu Petrochemical Co., Ltd., trade name “Moretech 0238CN”, density 0.920 g /
cm ³ , 2.0 g / 10 min MFR) and 80 parts by weight of ionic copolymer (trade name “Himilan 1705”, manufactured by DuPont-Mitsui Polychemicals, density 0.9)
An easily tearable film having a thickness of 40 μm was prepared by a T-die method using a resin composition mixed with 5% by weight (60 g / cm ³ , MFR 5.0 g / 10 min).

Example 4 An easily tearable film was prepared in the same manner as in Example 3 except that the content ratio of the ionic copolymer in Example 3 was changed to 20% by weight.

Comparative Example 1 A film was produced by the T-die method in the same manner as in Example 1 except that the ionic copolymer of Example 1 was not used.

Comparative Example 2 A film was produced by the T-die method in the same manner as in Example 3 except that the ionic copolymer of Example 3 was not used.

Comparative Example 3 Example 1 was repeated except that the content of the ionic copolymer in Example 1 was changed to 1% by weight.
An easily tearable film was prepared in the same manner as described above.

(Example 5) 20 parts by weight of low-density polyethylene (trade name "Petrocene 175R" manufactured by Tosoh Corporation) and 80 parts by weight of linear low-density polyethylene (trade name "Moretech 0238CN" manufactured by Idemitsu Petrochemical Industries, Ltd.) And a low-density polyethylene (trade name "Suntech F192" manufactured by Asahi Kasei Corporation).
0 ") in 80 parts by weight of ionic copolymer (trade name" Himilan 1605 "manufactured by DuPont-Mitsui Polychemicals)
An easily tearable film consisting of a two-layer film in which a 30-μm-thick easily tearable layer of a resin composition consisting of 20 parts by weight was laminated with T
It was produced by a die method using a multilayer extruder.

Table 1 shows that low-density polyethylene is L
DPE and linear low-density polyethylene are abbreviated as LLDPE, and only the product number at the end of the product name is described for the type.

In order to evaluate the performance of the obtained multilayer film, tearability and appearance quality were evaluated by the following methods. The evaluation results are shown in Table 1.

1. Tear load (unit: gf) The trouser tear strength was measured in accordance with JIS K 7127, and the tear load in the film forming direction was evaluated.

2. Straight cutability (unit: mm) A notch of 5 mm was formed in the film forming direction, and the film was torn by 200 mm in the film forming direction. The magnitude of the deviation in the direction perpendicular to the vertical direction in the film forming direction of the film having the notch at the tear end position was measured.

3. Using a heat sealer with a width of 5 mm and a length of 100 mm,
A heat seal test was performed at a heat seal bar temperature of 150 ° C. Evaluation is visually evaluated the quality of the finish of the seal portion, and further, whether the material is destroyed by pulling the seal portion in the width direction or whether the seal portion is peeled off,
：: Good finish of the seal portion and strong heat sealing indicating material destruction was performed. ×: Defective seal strength such as dirty finish of the seal portion or peeling of the seal portion. 、 And 総 合 × were evaluated comprehensively.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

According to the tearable film of the present invention, since it is constituted as described above, the manufacturing process is simple, and it has a beautiful surface with a good balance between tearability and bag strength. It has excellent heat sealing properties, and is suitably used as a food packaging container material for retort pouches and the like.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hirochika Shibata 2-2 Umihara, Ogawa-shi, Higashiura-cho, Chita-gun, Aichi Pref. 4F100 AK03A AK03J AK06B AK24A AK24J AK63B AK68B AL01A AL05A AL05B BA02 EH17A EJ05J GB15 JA13B JB12J JK03 YY00B 4J002 BB031 BB061 BB071 BB101 BB121 BB141 BB171 BB232 BB232

Claims (2)

[Claims] 1. 80 to 98% by weight of a polyolefin resin
And a resin composition comprising 2 to 20% by weight of an ionic copolymer and extruded by a T-die method. 2. A multilayer film extruded by a T-die method, wherein at least one surface layer is made of low-density polyethylene and has a density of 0.890 to 0.920 g / cm ^3.
A low-density polyethylene or a resin composition mainly composed of an ethylene-vinyl acetate copolymer resin, and at least one other layer comprises a polyolefin resin 40 to 9
An easily tearable film comprising a resin composition comprising 5% by weight and 5 to 60% by weight of an ionic copolymer.