JPS6178644A - Multilayer film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to multilayer films, in particular mechanical strength,
In particular, it has excellent low-temperature impact resistance and can be made thinner.
Moreover, the present invention relates to a multilayer film having excellent properties such as heat sealability and blocking resistance.

Conventionally, low-density polyethylene films and high-density polyethylene films have been used as packaging materials for heavy items such as fertilizer, rice, and wheat. However, high-pressure low-density polyethylene film has low mechanical strength and must be thick, and high-density polyethylene film does not have sufficient tear strength and has problems with sealing performance and strength against protrusions. , which is not desirable in terms of appearance. Therefore, in order to eliminate these drawbacks of polyethylene films, methods of adding rubber or the like have been proposed. However, although this film has improved sealing properties, it has problems in terms of mechanical strength and appearance, and is not comprehensively sufficient as a packaging material.

Therefore, in order to solve the above-mentioned problems of polyethylene film, and especially in response to the demand for thinner films from the standpoint of resource conservation, various multilayer films consisting of two or three layers have been proposed recently. For example, (2) a layer made of a layer made of ot-density polyethylene and a layer made of high-density polyethylene; (2) a layer made of a resin mixed with high-density polyethylene and an ethylene/α-olefin copolymer and a layer made of low-density polyethylene; A film made of laminated layers or (
3) There is a three-layer laminated film formed by laminating high-density polyethylene as an intermediate layer and low-density polyethylene layers as outer layers on both sides.

However, although the film (1) has no 4GK problems in terms of mechanical strength and appearance, it is not necessarily satisfactory in terms of sealability, pay/f strength, and practical drop strength.

Furthermore, the film (2) does not have sufficient rigidity and is not suitable for automatic packaging.Moreover, if a bag with a low-density polyethylene inner layer is manufactured, it is easy to block, resulting in poor opening properties, as well as poor formability and appearance. The disadvantage is that it is inferior. Although the film (3) has excellent optical properties, it has the drawbacks of insufficient puncture strength and sealing properties for packaging heavy items, and is prone to blocking (in addition, it does not have sufficient moldability).

Therefore, in order to solve these conventional problems, the applicant of the present application has developed a resin composition made by already blending 100 parts by weight of high-density polyethylene and 10 to 100 parts by weight of an ethylene/α-olefin copolymer. proposed a laminated film in which the intermediate layer is laminated on both sides with an outer layer made of an ethylene/α-olefin copolymer (Japanese Unexamined Patent Publication No. 59-11).
No. 252).

Although this laminated film has a number of excellent *W properties, there is a limit to its low-temperature drop strength when used in severely cold regions or when packaging refrigerated items, which may limit its use.

The object of the present invention is to provide a multilayer film that has improved the above-mentioned problems.

That is, the present invention provides a multilayer film consisting of at least three layers with a density of 11[0,900 to 0.9409/ct
tt” linear ethylene/α-olefin copolymer 55
The middle layer was a layer made of a resin composition consisting of ~90 i weight and 45 to 10 weight high density polyethylene, and both outer layers were made of an ethylene polymer with a density of 0.900-0.9401/lcms. The present invention provides a multilayer film characterized by the following.

In the multilayer film of the present invention, as the intermediate layer, a resin composition of a Ui-like ethylene/α-olefin copolymer and high-density polyethylene as described above is used.

Here, the linear ethylene/α-olefin copolymer is medium-
It is a linear low density polyethylene obtained by a low pressure method, with a density of 0.900 to 0.940 gycttt3, js or 0.905 to 0.9301/cwt", and a melt index (MI) of 0.1 to 20. , 9/10 minutes, preferably 0.2 to 10 g/10 minutes.

Note that the α-olefin content in this copolymer is usually 1 to 1.
20″it, and as an α-olefin, it has 3 carbon atoms.
~20 substances are used, specifically haflopyrene, butene-1. Examples include pentene-1, hexene-1,4-methylpentene-1, octene-1, nonene-1, decene-1, and the like.

Also, high density polyethylene/ has a density of 0.945 to 0.97
0 J, false 3, preferably 0.948-0.9651/
cIIL3, MI of 0.01 to 201/l 0 min, preferably 0.02 to 10.9/l 0 min is used.

The blending ratio of the resin composition for the intermediate layer is linear ethylene.
α-olefin copolymer 55-9011i5, high-density polyethylene 45-10 weight 5, preferably the former 6
0 to 85% by weight, and the latter 40 to 15% by weight, which can be determined as appropriate considering the purpose of use of the multilayer film. If the blending amount is less than 55% by weight, the low-temperature impact resistance will be poor, and if it exceeds 90% by weight, the rigidity will decrease,
This is not preferable because the automatic filling characteristics deteriorate.

The intermediate layer in the multilayer film of the present invention basically consists of the above-mentioned linear ethylene/α-olefin copolymer and high-density polyethylene, but if necessary, high-pressure low-density polyethylene, ethylene-acetic acid Other resins such as vinyl copolymers may also be added. Here, the density of high pressure low density polyethylene is 0.910-0.94.
09/crn”, preferably 0.915 to 0.930
g/cyt”, MIo, 05~zo, o, y/lo min,
Preferably, 0.1 to 10 g/10 minutes is appropriate.

Next, both outer layers in the multilayer film of the present invention, that is, the inner layer and the outer layer of the intermediate layer, are made of an ethylene polymer. Here, the density of ethylene polymer is 0.90
0~0.94011/CI! L", linear ethylene/α-olefin copolymer, high pressure low density polyethylene, ethylene/vinyl acetate copolymer, ethylene/acrylic acid copolymer.

Ethylene/ethyl acrylate copolymer or a mixture thereof is used. Here, linear ethylene α-
The olefin copolymer is an α-olefin having 3 to 20 carbon atoms and having the same density and MI as the linear ethylene/α-olefin copolymer forming the intermediate layer.
The same material as that used in the intermediate layer may be used, or a different material may be used.

Furthermore, the above-described materials can be used as the high-pressure low-density polyethylene. That is, density 0.910-0.940
9/cIL3, preferably 0.915 to 0.930 p trowel 3, MI 0.05 to 20.09/10 min, preferably 0.1 to 1 o#/lo min. The high-pressure low-density polyethylene used in both outer layers may be the same as that blended into the intermediate layer, or a different one may be used.

Further, a mixture of a linear ethylene/α-olefin copolymer and a high-pressure low density polyethylene is preferably used for both outer layers, but the former: latter = 30 to 9
9:0 to 1, preferably in a ratio of 50 to 98:50 to 20.

Furthermore, the ethylene polymers used in both outer layers may be exactly the same, that is, those having exactly the same density and A different one may be used.

In addition, when high-pressure low-density polyethylene is used only in both outer layers, that is, either the inner layer or the outer layer of the intermediate layer, in other words, high-pressure low-density polyethylene alone or a resin composition containing high-pressure low-density polyethylene is used. When a layer consisting of the following is used only for either the inner layer or the outer layer, it is preferable to use this layer as the inner layer when molding by the inflation method. Furthermore, when high-pressure low-density polyethylene is used for both the inner and outer layers, it is preferable to mix more K in the inner layer than in the outer layer.

The multilayer film of the present invention consists of at least three layers, and other layers may be laminated in addition to the intermediate layer and both outer layers. For example, it is made of low density polyethylene, 7-density polyethylene, ethylene copolymers (e.g., ethylene/unsaturated ester copolymers such as ethylene/vinyl acetate copolymer, ethylene/ethyl acrylate copolymer, etc.). Place the resin layer in an appropriate position (between the middle layer and the outer layer) as necessary.

(Outside of the outer layer) K can also be laminated in layers.

When the multilayer film of the present invention is composed of the above-described three layers: the inner layer, the outer layer, and the intermediate layer, the layer thickness ratio of each layer is usually inner layer: intermediate layer: outer layer = 2 to 60: 96 to 10:
2-60, preferably 5-50:90-15:5-50
, more preferably 10-50:80-20:10-50
It is. When the thickness of the inner and outer layers increases, the intermediate layer becomes relatively thin (and the mechanical strength of the multilayer film decreases.On the other hand, when the thickness of the inner and outer layers becomes extremely thin, the sealing strength decreases). The thickness of the multilayer film is not particularly limited, and the total thickness is about 10 to 300 μm, preferably about 20 to 200 μm.

The multilayer film of the present invention is produced using an inflation method.

It can be manufactured by various methods such as the T-die method, but
In particular, it is desirable to manufacture by the following method, taking into consideration the use as a packaging bag.

First, the components constituting each layer described above are kneaded by melt kneading or the like, and then molded by a coextrusion die adhesion inflation method to produce the desired multilayer film. In this case, the blow ratio is usually 1 to 7, preferably 1.2 to 5.
Perform inflation molding.

The multilayer film of the present invention has high tensile strength and tear strength.

It has high mechanical strength such as impact strength, and particularly excellent low-temperature impact resistance. Furthermore, since it can be made thinner than conventional products, it can be manufactured at low cost and also contributes to resource saving. In addition, the surface properties are good, the heat sealability is good, the seal strength is high, and the seal shrinkage is small, so that no shrinkage is observed in the seal appearance. Furthermore, since it has good contaminant sealing properties, it is useful as a packaging bag for powder-containing materials. Furthermore, it has good anti-blocking properties and excellent opening properties. Moreover, since it has excellent rigidity, it also has good automatic filling characteristics. Furthermore, by appropriately selecting the resins used for the inner and outer layers, it is possible to obtain a film having surface characteristics optimal for the intended use.

Therefore, the multilayer film of the present invention is extremely useful for packaging, especially as a material for packaging heavy goods.

Next, examples of the present invention will be shown.

Examples 1 to 6 and Comparative Example 1 Predetermined raw material resins (parts by weight) shown in Table 1 constituting the intermediate layer and the inner and outer layers (inner layer, outer layer) were respectively melted using three extruders with a diameter of 40 mmφ. Knead, and then use a circular die with adhesive inside the die (die diameter 200 mm, lip gap 2 mm,
Die temperature: 180℃) and extrusion, blow ratio: 1.7
A multilayer film with a thickness of 140 μm was obtained by inflation molding.

Table 1 shows the evaluation results of various physical property tests of the multilayer film thus obtained. The test method was conducted in accordance with the following method.

Tensile properties JIS Z 1702 tear strength
JIS Z 1702 Bank Cheer - Strength JIS
P 8134 Low-temperature drop test A 440 m x 660 xx bag was filled with 20 yu of chemical fertilizer, heat-sealed at 200°C, and after curing at -10°C for 10 hours, the bag was dropped from a predetermined height onto a concrete floor and the bag was observed for breakage.

0 - No bag breakage Δ - Bag breakage of 50% or less × - Bag breakage of 50% or more
fl/(1K”.

MI 1.3 gZt 0 min) (manufactured by DSM, product name: Stamilex 1016) Book 2 LDPI High pressure low density polyethylene (density 0.920 P,
L", MIO-3g/10 min) (manufactured by Toyo Soda Co., Ltd., product name: Petrocene 172) Book 3 HDFIH High-density polyethylene (density 0.9509/ctn",
MI O,05I/10 minutes) (manufactured by Idemitsu Petrochemical Co., Ltd., product name: Idemitsu Polyethylene 640uF) *4 LLDPE (21 Ethylene-butene-1 copolymer (density 0.9219/c)
rrt'.

MI 3.7 g710 min) (manufactured by DSM, -Product name:
Stamilex 1048) Patent applicant Idemitsu Petrochemical Co., Ltd. Procedural amendment (voluntary) October 24, 1980

Claims (2)

[Claims] (1) In a multilayer film consisting of at least three layers, 55 to 90% by weight of linear ethylene/α-olefin copolymer with a density of 0.900 to 0.940 g/cm^3 and 45 to 10% by weight of high density polyethylene % is the middle layer, and both outer layers have a density of 0.900~
A multilayer film characterized by having a layer made of an ethylene polymer of 0.940 g/cm^3. (2), at least one layer of both outer layers is linear ethylene.
The multilayer film according to claim 1, which is a mixture of an α-olefin copolymer and high-pressure low-density polyethylene.