JPS61120745A - Multilayer packaging bag - 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 a multilayer packaging bag, and more particularly to a multilayer packaging bag that is made of a specific material, has excellent rigidity, low-temperature impact strength, etc., and has good surface properties.

Conventionally, films made of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and the like have been used as bags for packaging heavy items such as fertilizer, rice, and wheat. However, since the high-pressure LDPE film has low mechanical strength, it must be made thick. Furthermore, HDPE films do not have sufficient tear strength, have problems with sealing properties and strength against protrusions, and are not desirable in terms of appearance and slipperiness. In order to solve these problems, methods have been proposed in which rubbers are added to these films. Although the sealing properties of the film are improved by adding rubber, problems with mechanical strength and appearance have not yet been sufficiently resolved, and the film is insufficient for use as a packaging bag.

For this reason, various multilayer film bags have recently been proposed to solve the problem of making polyethylene bags and to reduce the wall thickness, especially from the standpoint of resource conservation. For example, fl) the outer layer is L
DPE, bag with inner layer made of HDPE, (2) outer layer made of HDPE
A bag consisting of a mixture of PE and linear low density polyethylene (LLDPE), the inner layer being LDPR, (3) one outer layer being LDP E, the middle layer being HDPE, and the other outer layer being L
A bag made of DPE, (4) a bag made of LLDPE in one outer layer, a mixture of HDPE and LLDPE in the middle layer, and LLDPE in the other outer layer have been proposed. However, although the bag in (1) has no particular problems in terms of mechanical strength or appearance, it does not have sufficient sealing performance, puncture strength, or practical drop strength, and the bag made of the film in (21) does not have sufficient rigidity and is Not suitable for packaging, and the inner layer is LDPE.
If so, the sealing performance will be insufficient and the appearance will be poor. Furthermore, although the bag of (3) has excellent optical properties, it lacks puncture strength and sealing performance when packaging heavy items. Although the bag (4) has a number of excellent features, it lacks sufficient drop strength during storage and handling at low temperatures, and its use has been limited to just its wide width. As described above, a fully satisfactory packaging bag has not yet been proposed.

Therefore, as a result of intensive research to develop a packaging bag with sufficient strength, surface characteristics, etc., the present inventor discovered that a multilayer packaging bag made of a specific material could achieve the above objectives.
The present invention was completed based on this knowledge.

That is, the present invention provides an outermost layer (hereinafter referred to as (A) layer) in a multilayer packaging bag consisting of at least two layers of film.

) has a density of 0.900g/cd or more and 0.940g/cm3
It is a layer made of the following ethylene polymer, and the inner layer (hereinafter referred to as (B) layer) has a density of 0.900 g/cd or more.
．． Linear ethyl 7-4-olefin copolymer (hereinafter referred to as (bl) component) with a density of less than 930 g/ad and linear ethylene-α- with a density of 0.930 g/- to 0.945 g/c+j Olefin copolymer (hereinafter referred to as (b2)
) ingredients. This is a multilayer packaging bag characterized by a layer made of a resin composition consisting of:

The layer (A) of the present invention forms the outermost layer of the bag, and has a density of 0.900 g/cd or more and 0.940 g/cm3.
Any of the following ethylene polymers may be used without particular limitation. Here, the ethylene polymer is
High pressure low density polyethylene (LDPR).

Ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, linear ethylene-α- as described below
Examples include olefin copolymers (LLDPE) and mixtures thereof. Here, the mixture includes the same type of comonomer, density, melt index (
Mixtures of resins with different Ml) are also included. Suitable ethylene polymers are LDPE, LLDPE and mixtures thereof.

Here, Ml of the ethylene polymer of layer (A) is o, i ~
20 g/10 minutes, preferably 0.2 to 10 g/10 minutes is used.

(A) The density of the ethylene polymer in the layer is 0.900 g/d
If it is less than 0,940, blocking will occur and
If it exceeds g/cn (), it is not preferable because it becomes slippery, the transportation and storage properties after packaging the contents, particularly the stackability, deteriorates, and the surface gloss also decreases.

Next, layer (B) laminated on the outermost layer has a density of 0.90.
Linear ethylene-α-olefin copolymer (b+ acid component and density 0.930 g/cn or more and less than 0.945 g/ad) It is a resin composition consisting of an olefin copolymer (bz acid component).

Here, the linear ethylene-α-olefin copolymer is usually made to have a density of about 0.900 to 0.945 GLAL, called linear low-density polyethylene (LLDPE), and is shortened by introducing side chains. Manufactured by creating a chain-branched structure.

In the present invention, the α-olefin content in the two types of low-density LLDPEs, components (b,) and (b2), should normally be 1 to 20% by weight, and within this range, the content of the two types of LLDPEs should be between 1 and 20% by weight. The α-olefin content may vary or may be exactly the same.

In addition, in the above two types of LLDPE, the same α-olefin may be used to copolymerize with ethylene,
Alternatively, a different one may be used. α-olefins having 3 to 20 carbon atoms, preferably 4 to 15 carbon atoms are used, and specific examples include propylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, 1, decene-1, dodecene-1, and the like.

Furthermore, M+ of the above two types of LLDPEs may be the same or different, but is usually 0.1 to
20 g/l 0 min, preferably 0.2-10 g/10
It's a minute. Since these two types of LLDPE are of the same quality, they have extremely good kneading properties and can be mixed uniformly.

In the present invention, the mixing ratio of the above-mentioned two components of LLDPE is not particularly limited, and may be determined by taking into consideration the intended use of the bag (use temperature, etc.), size, suitability for automatic packaging, etc. 10% by weight, preferably 85-4
0% by weight, component (b2) 10 to 90% by weight, preferably 15 to 60% by weight.

The inner layer of the present invention basically consists of the above two components (b,) and (b2), but if necessary, high-pressure method L
DPE, ethylene-vinyl acetate copolymer, etc. can be added.

The multilayer packaging bag of the present invention has a small amount (both (A) and (B)
) layer, but if the composition of the (B) layer tends to cause blocking during molding or bag making, another layer (hereinafter referred to as (C) layer) may be added inside the (B) layer as necessary. ) may be laminated. (C) Layer has sealing properties.

There is no particular restriction as long as it has excellent blocking resistance. Usually LDPE, LLI)PE as mentioned above
Alternatively, a mixture of LLDPEs having different physical properties may be used.

Examples of the method for laminating the multilayer film of the present invention include T-die coextrusion and inflation coextrusion, with inflation coextrusion being particularly preferred. In this case, the blow ratio is between 1.0 and 5.0, preferably between 1.6 and 3.0.

During lamination, the layer ratio of each layer is appropriately determined depending on the intended use of the bag, the size of the bag, suitability for automatic packaging, etc.

When consisting of two layers (A) layer and (B) layer, (A) layer: (B) layer = 2-80: 98-20. Preferably 2-6
0:98-40. If the ratio of the layer (A) is less than 2, it is not preferable because the drop bag strength, especially the drop bag strength at low temperatures, will decrease and the surface properties will also deteriorate. Also, (A)
When the layer ratio exceeds 60, the stiffness of the film is noticeably lowered and the suitability for automatic filling is lowered, making it impractical.

In addition, in the case of three layers: (A) layer, (B) layer, and (C) layer, (A) layer: (B) layer: (C) layer = 2 to 60
:10-70:2-60, preferably 2-50:2
0-50: 2-50. Here, the ratio of layer (B) is 1
When the ratio is less than 0, the stiffness of the film becomes noticeable and the automatic filling suitability decreases, and when the ratio of layer (B) exceeds 70,
This is undesirable because the bag drop properties, especially the thin layer strength at low temperatures, deteriorate.

In the present invention, the thickness of the multilayer film may be determined in consideration of the intended use, but is usually 10 to 300μ, preferably 2
Approximately 0 to 200μ is suitable.

A multilayer packaging bag having layer (A) as the outermost layer is obtained from the film thus obtained. The bag may be manufactured by any conventional method, and preferably, for example, a method in which a cylindrical film is manufactured and then the bottom is heat-sealed.

The multilayer packaging bag of the present invention has high strength and can therefore be made thinner, which is advantageous from the standpoint of resource saving. It also has high low-temperature impact strength and good practical low-temperature drop characteristics. Furthermore, it has excellent surface properties, with good sealing properties and blocking resistance on the inner surface, and excellent gloss and slip resistance on the outer surface. Moreover, since it has good rigidity, it has good packaging suitability, and is particularly suitable for automatic packaging.

As described above, the multilayer packaging bag of the present invention is extremely useful as a packaging bag, especially as a bag for packaging heavy items such as fertilizer, rice, and wheat.

Next, the present invention will be explained in detail with reference to examples.

Examples 1 to 7 and Comparative Examples 1 and 2 Predetermined raw material resins shown in Table 1 constituting each layer of the multilayer film were melt-kneaded using two or three 401 mφ extruders, and bonded in the die. The mixture was introduced into a circular die (die diameter: 200 mmφ, lip gap: 21 mm, die temperature: 180° C.) and extruded, and inflation molded at a blow ratio of 1.7 to obtain a 140 μm multilayer film. Table 1 shows the evaluation results of various physical property tests of the multilayer film thus obtained. This multilayer cylindrical film was bottom-sealed (sealing temperature: 180°C) to obtain a packaging bag.

The test method was based on the following method.

(1) Tensile properties JIS Z 1702 (2) Tear strength JIS Z 1702 (3) Bunture strength J
ISP 8134 (4) Heat seal strength
JIS Z 1707 (5) Low-temperature drop test A 400×660 IllI bag was filled with 20 kg of chemical fertilizer, heat-sealed at 200°C, cured at the specified test temperature for 10 hours, and then dropped horizontally from a height of 1.2 m. The bag was dropped five times on each side, and the condition of the bag being torn was observed. The test results are shown in Table 1 as the percentage of unbroken bags.

Comparative Example 3 In Example 1, high pressure LDPE1 was used as the raw material.
A single-layer film with a thickness of 200 μm was obtained in the same manner as in Example 1, except that a single layer was used. The evaluation results are shown in Table 1.

*...LLDPH (A): Ethylene-octene-l
Copolymer, density 0.920 g/cd, M r 1.
1 g/10 min (manufactured by DSM, product name "Stamilex 1016 J") LLDPE (B): Ethylene-octene-1 copolymer, density 0.940 g/cd, MI 1.0 g/
10 minutes (manufactured by DSM, product name: Stamilex 4016 J) LDPE: High pressure low density polyethylene, density 0.
920 gIci, M I 0.3g/10 minutes (
Manufactured by Toyo Soda ■, product name [Petrosen 172J] HDPE: High density polyethylene, density 0.950
g/cnl, MI 0.05g/10 min (manufactured by Idemitsu Petrochemical ■, product name [Idemitsu Polyethylene 640 UFJ)]

Claims (2)

[Claims] (1) In a multilayer packaging bag made of at least two layers of film, the outermost layer (A) is a layer made of an ethylene polymer having a density of 0.900 g/cm^3 or more and 0.940 g/cm^3 or less, and the inner layer (B) has a density of 0.900g/cm^
Linear ethylene of 3 or more and less than 0.930g/cm^3
α-olefin copolymer and density 0.930g/cm
A multilayer packaging bag characterized by having a layer made of a resin composition made of a linear ethylene-α-olefin copolymer having a weight of 3 or more and 0.945 g/cm or less. (2) The layer ratio of the outermost layer (A) and the inner layer (B) is the outermost layer (
The multilayer packaging bag according to claim 1, wherein the ratio of A) to inner layer (B) is 2 to 80:98 to 20.