JPS5864952A - Bag for packing - 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 packaging bag, and more particularly to a packaging bag that has excellent mechanical strength and low-temperature impact resistance, and is also suitable for automatic packaging.

Conventionally, low-density polyethylene, which has excellent sealing strength, has been widely used for bags for packaging single items such as fertilizer, rice, and wheat. However, low density polyethylene has tensile strength,
Since impact strength and rigidity are low, it must be thick-walled, which poses various problems from an economical and resource-saving standpoint.

Therefore, recently, various single-layer or laminated film bags have been proposed in response to requests for thinner bags from the standpoint of saving resources and energy. For example, (11) a bag made of high-density polyethylene with rubber added,
(2) A bag made of a laminated film with an outer layer of low-density polyethylene and an inner layer of high-density polyethylene; (3) A bag made of a mixed resin containing high-density polyethylene and a large amount of ethylene-α-olefin copolymer; A bag made of a laminated film with an inner layer of density polyethylene has been developed.

However, although the bag described in (1) above has improved seal strength, it has problems in terms of mechanical strength and appearance.
Although the bags in (3) are excellent in film strength and appearance, they are not necessarily satisfactory in terms of seal strength, puncture strength, and practical drop resistance.Furthermore, the bags in (3) 50 to 90% of the film layer thickness is low-density polyethylene, and since it is made by blending a large amount of ethylene-α-olefin copolymer with high-density polyethylene, it does not have sufficient rigidity and is not suitable for automatic packaging. Because low-density polyethylene is used for the inner layer, blocking tends to occur, resulting in poor mouthability and poor film formability.
The appearance is also not satisfactory.

The purpose of the present invention is to provide a bag that eliminates the drawbacks of the conventional bags mentioned above and is particularly suitable for heavy-duty packaging, and is composed of an outer layer made of a low-density ethylene polymer or copolymer, and an inner layer made of a high-density ethylene polymer or copolymer. This packaging bag is made of a resin mixture of 95 to 50% by weight of polyethylene and 5 to 50% by weight of ethylene-α-olefin copolymer.

The packaging bag of the present invention is composed of a laminated film of two layers, an outer layer and an inner layer, or three or more layers with a suitable intermediate layer interposed between these layers. Here, as the outer layer, a low-density ethylene polymer or copolymer method, that is, a low-density polyethylene or an ethylene-based copolymer is used. Specifically, the density is 0.91-0.94 g/c+m'', the melt index is 0.2-5.09 ZlO, preferably 0.3-3
．． It has a physical property of 0 g/10 min, and includes high-pressure low density polyethylene, ethylene-unsaturated ester copolymers such as ethylene-vinyl acetate co-polymer, and ethylene-α-olefin copolymer. The a-olefin in this ethylene-α-olefin copolymer is one having 3 to 20 carbon atoms, especially propylene, butene-
1, pentene-1, hexene-1,4-methylpentene-1, octene-1, nonene-1, etc. are preferred, and the content of α-olefin units in this copolymer is 1 to 1.
It should be 0 mole whisper.

Next, as the inner layer, a resin mixture of 95 to 50% by weight of high-density polyester and 5 to 50% by weight of ethylene-α-olefin copolymer is used.

Here, high density polyethylene has a density of 0.945 to 0.97.
09/C-”, Melt Inde 7ri x o, o 1-2.
0 g/10 minutes, preferably 0.0 to 1.0 g/710 minutes. On the other hand, ethylene-α-olefin copolymer is
Density 0.910-0.94097 cwt", preferably 0.915-0.935 g/c-, melt index 01-20 g ZlO min, preferably 0.2-1
This is for 09/1O. The α-olefin of this ethylene-α-olefin copolymer may be the same as those mentioned above, and the content of α-olefin units in the copolymer may be about 1 to 10 mol % as described above. The inner layer is composed of high-density polyethylene and ethylene-α-O,
As mentioned above, the mixing ratio with the reflexine copolymer should be in the range of 95 to 50% by weight of the high density polyester and 5 to 50% by weight of the ethylene-α-olefin copolymer. Here, the mixing ratio of the ethylene-α-olefin copolymer is 5
If the amount is less than 50% by weight, the puncture strength and sealing performance will not be sufficient, while if it exceeds 50% by weight, the film formability will deteriorate, the rigidity will decrease, and the suitability for automatic packaging will deteriorate, which is not desirable.

Further, the layer thickness ratio between the outer layer and the inner layer in the packaging bag of the present invention is not particularly limited and may be determined as appropriate, but usually the outer layer:
Inner layer = 1-45: Should be in the range of 99-55. Here, if the outer layer is too thick, the mechanical strength of the bag will be reduced,
On the other hand, if it is too thin, a uniform laminated film cannot be obtained.

There are various methods for forming the packaging bag of the present invention, but most commonly the outer layer and inner layer, or if necessary, the intermediate layer, are formed at a blowing ratio of 2.5 to 7.
Inflation coextrusion molding is performed at 0 to form a bag by laminating each layer in a state in which each layer is firmly bonded.

The bags obtained in this way are made of different materials.

The outer layers skillfully compensate for each other's deficiencies, resulting in an overall product with excellent physical properties. Specifically, this bag is stronger than a bag made of a single-layer low-density polyethylene film, so it can be made thinner, and it is also strong, so it has excellent suitability for automatic packaging. In addition, it has excellent low-temperature impact resistance, excellent blocking resistance, excellent printability, and beautiful appearance, so it is suitable for packaging various products, especially rice, fertilizer, broilers, etc. It can be suitably used as a packaging bag for heavy items.

Example 1 Next, the present invention will be explained in more detail with reference to Examples.
~5 Predetermined raw material resins for forming the outer layer and the inner layer were mixed uniformly at the compounding ratios shown in Table 1, and then melt-kneaded using respective extruders. Next, these were introduced into an in-die adhesive type circular die, and then inflation molded at a blow ratio of 4.3 to form a cylindrical two-layer structure with a layer thickness ratio of outer layer to inner layer of 1:4 and a total thickness of 50μ. Got the film.

One end of this cylindrical film is heated and placed in a packaging bag (340
11 Jl width x 570 chicken length) was obtained. Various physical property tests were conducted using this bag, and the results are shown in Table 1, along with moldability, properties, and overall evaluation. The method of physical property testing is as follows.

Tensile properties: According to JIS Z 1702 Tear strength: According to JIS P 8116 Impact strength: Measured using a film impact tester (*M* impact amount 20 kg・l, impact hammer diameter 1 inch) Bunture strength: According to JIS Z 8401 Compliant seal strength: ASTM D 1822 K Compliant Comparative Example 1.2 Bags were made in the same manner as in Example 1 except that the amount of ethylene-α-olefin copolymer constituting the inner layer was changed in Example 1. The results of the evaluation are shown in Table 1.

Comparative Example 3.4 High-pressure low-density polyethylene for general heavy bags (density 0.926
Table 1 shows the results of evaluation according to Example 1 using bags obtained from a film with a thickness of 50 μm or 80 μm.

Comparative Example 5 A bag was obtained in the same manner as in Example 1 except that the inner layer and outer layer of Example 3 were reversed, and the evaluation results are shown in Table 1.

1'- One-one-one-one

Claims (1)

[Claims] +1) The outer layer is a low-density ethylene polymer or copolymer, and the inner layer is a resin mixture of 95-50% high-density polyethylene and 5-50% by weight of ethylene-α-olefin copolymer. A packaging bag characterized by comprising: (2) The layer thickness ratio of the outer layer and the inner layer is 1 to 45:99 to
55. The packaging bag according to claim 1, which is No. 55.