JPH02242746A - Easily tearable bag - Google Patents

Abstract

PURPOSE:To provide a bag which can be opened by being smoothly torn from its back seal notch part by providing a tear notch in the back seal part formed of the material laminating in layers a laterally uniaxial stretched plastic film and a plastic film having a specific ability of an easily cohesive failing and peeling. CONSTITUTION:A tear notch 3 is provided in a back seal part 1 formed of the material laminating in layers a laterally uniaxial stretched plastic film A and a plastic film B having an easily cohesive failing and peeling ability at a heat sealing strength of 0.5-2.0kg/15mm. By imposing a stress on the same line in reverse directions from (a) and (b) with the notch 3 as a center, a tear takes place in the width direction (c) of the back seal part and continues toward a sealing field (d), i.e. since the stress is worked on the tear deviation instead of a cohesive failing force, a suitable stress causes the tear to restart at the tear deviation and progress toward (d1) and (d2), leading to a smooth bag opening. This provides a bag which can be opened by being smoothly torn from the back seal notch part.

Description

DETAILED DESCRIPTION OF THE INVENTION A1.Objective of the invention (industrial application field) The present invention provides a heat-sealable layer used for packaging paste products such as sausages, yokan, kamaboko, and cheese, as well as other general foods. It is related to a bag that has.

(Prior art) Conventionally, in bags having vertical and raw bag back seals,
A technique is disclosed in Japanese Utility Model Application Publication No. 136964/1983 in which a notch is inserted into the back seal portion and the bag is torn from this portion so that the bag begins to tear from the notch portion and can be opened.

This product is made of a material in which two or more layers of horizontally uniaxially stretched film are laminated in the same stretching direction, and has a back seal part.
The bag has an easy-to-tear notch in the back seal.

In order to improve tearability, the material of the bag is often one in which a horizontally uniaxially stretched film is used as the outermost layer, middle layer, or seal layer of the bag.

Polypropylene, polyethylene, etc. are often used as the material for the horizontally uniaxially stretched film.

(Problem to be solved by the invention) However, in these cases, when the sealant is torn from the notch of the back seal and reaches the nose of the back seal, the sealant thickens due to the heat and pressure of heat sealing. It has the disadvantage that it is difficult to tear properly due to the strong heat sealing and the deterioration of tearability due to the heat sealing and hot pressure of the transversely uniaxially stretched film.

In order to overcome these drawbacks, some ideas have been proposed to improve tearability by configuring two or more horizontally uniaxially stretched films, but the material is too hard for applications that require flexibility. Further, such a configuration has the disadvantage of high cost.

It is an object of the present invention to provide a bag that does not suffer from such drawbacks and can be torn open smoothly from the back seal notch.

8. Structure of the Invention (Means for Solving the Problems) The means of the present invention for achieving the above-mentioned object is to apply a transversely uniaxially stretched plastic film with a heat seal strength of 0.5 to 2.5 kg between surfaces. The easily tearable bag has a back seal portion made of a laminated plastic film having a cohesive failure peelability of /15II11 and is provided with an opening notch.

The horizontally uniaxially stretched film of the present invention having the above structure is a polyethylene film (Toyobo, Baylene P-1567,
25μ thick), polyethylene film (Toyo Kagaku, Karalyan Y, 18μ thick), etc. can be used.

In addition, the easily peelable film of the present invention having the above-mentioned structure can be a film obtained by suitably blending polypropylene with polyethylene and polybutene, a coextrusion film of a blend of polypropylene, polyethylene and polybutene, or a coextrusion film of a blend of high density polyethylene, polypropylene and ethylene. -A wide range of products are available, including coextruded films of blends with vinyl acetate copolymers.

In either case, the heat seal strength between the surfaces is 0.
It is necessary to have easy cohesive failure and peelability of 5 to 2.5 kg/15 mm.

Easily peelable films can be laminated by forming the film in a separate process and bonding it to the base material using an adhesive, or by using an anchor coating agent on the base material and directly extrusion laminating it on top. Available.

(Function) The four functions that occur when the bag configured as described above is opened will be explained with reference to the drawings.

Figures 1 and 2 are configuration examples of the present invention. A: A horizontally uniaxially stretched plastic film B: Paper, aluminum foil, biaxially stretched plastic film, etc. C: A plastic film that is easy to cohesively break and peel. However, a film having excellent barrier properties such as polyvinylidene chloride or ethylene vinyl alcohol may be used as the intermediate layer.

3 and 4 show the action of tearing the bag constructed according to the present invention from the back seal notch 3, and FIG. 3 shows stress applied in opposite directions a and b on the same line centering on the back seal notch s3. As a result, it is torn in the back seal width direction C and moves toward the seal field d.

1 indicates the back seal portion, and 2 indicates the top seal.

Figure 4 shows left and right opposite directions a, centering on the back seal notch part 3;
By applying stress to b, tearing similar to that shown in FIG. 3 occurs.

FIG. 5 shows that the tearing stress in the sealing field d of the back seal portion 1 is ideally aligned with Cr on the left and right.

Although the figure shows propagation in the c8 direction, in actual opening, such ideal opening is impossible when the contents are filled.

That is, as shown in FIG. 7, this part becomes thinner due to the heat pressure of the heater par 4 during back sealing, and the sealing area d becomes thicker by this amount, making this part less likely to be torn. Therefore, as shown in FIG. 6, the tear propagation from the sealing field d in the back seal tearing direction C is always d r , d
A discrepancy occurs like a sophist. If the stress caused by this misalignment is due to the strong heat-sealing strength of ordinary sealants, the tensile strength will be so high that it may not be possible to tear it, or even if it can be torn, more stress than necessary will be applied to the seal. Since the tearing direction of the transversely uniaxially stretched film after the opening is largely deviated, the result is that the package is opened in a very dirty state.

In the bag configured according to the present invention, since a sealant having a surface-to-surface heat-sealing strength of O, S ~ 2.5 kg/15 mm and easy cohesive failure peelability is used, the stress due to the displacement replaces the cohesive failure force. By being able to handle this, the tear propagates again from the portions d, dz shown in FIG. 6 by applying appropriate stress, and the package is opened smoothly. A diagram of the package being opened is shown in FIG.

(Example) Examples of the easily tearable bag of the present invention will be described below.

Example Axial oriented polyester film (Toyobo).

Ester F5100.12 μm thick) and horizontally uniaxially stretched polypropylene film [Toyobo, Baylene P-1567,
25 μm thick] using a urethane adhesive, and then polypropylene (d part 0.90. MF I
= 15at230℃) 70% by weight, polyethylene (
d part 0°92, MI=7at190°C) 15% by weight,
Polybutene (d part 0.915, M I =3.Oa
t190°C) 15% by weight of the blend resin was extrusion laminated to a thickness of 25 μm at an extrusion temperature of 260°C to obtain a composite film having a structure as shown in FIG.

The heat-sealing strength of this composite film at a heat-sealing temperature of 190'C and a heat-sealing pressure of 2.0kg/cya'' was 1.8 with cohesive failure in the heat-sealed part.
It showed a value of kg/15mm.

A vertical billow bag with a back seal was made from this base material at a heat sealing temperature of 198°C, then filled and sealed with kneading cake and solidified in a steamer as shown in Figures 3 and 4. Using this method, I tore the bag from the notch in the circumferential direction, but even though the d part was slightly misaligned in the heat-sealed part, I was able to tear and open the bag smoothly and without any trouble.

Furthermore, by pressing downward from this opening, the rectangular kneading cake could be taken out without losing its shape.

Comparative Example I The blending ratio of the sealant of Example I was 8.5% polypropylene.
Weight%, polyethylene 7.5% by weight, polybutene 7.5%
When I changed it to weight%, the heat seal strength between surfaces was 2.
．． 5 kg / 15 mm was shown, and as a result of tearing and opening in the same way, I managed to open it, but
When the weight percentage of polypropylene was increased more than this, the tearing at the heat-sealed part d became unstable, and as a result, the shape of the kneaded cake was distorted.

On the other hand, if the heat-sealing strength is less than 0.5 kg/715 mm, the heat-sealed portion will peel off while being torn, resulting in unstable opening performance in this case as well.

C1 Effects of the Invention The easily tearable bag according to the present invention can be torn open with a small stress without significantly impairing the tearability of the transversely uniaxially stretched film in the transverse direction, no matter how it is torn from the back seal notch. Sausage, which can be opened by
Contents that are relatively easy to lose their shape, such as yokan, kamaboko, and cheese, can be taken out without losing their shape.

It is convenient and sanitary because even the elderly and children can easily tear it open and eat it one after another by pressing from below the opening.

High-temperature sterilization treatments such as boiling and retorting are also possible, extending the shelf life.

Furthermore, the economical effect is great due to the rational configuration.

It has an exceptional effect.

[Brief explanation of drawings]

FIGS. 1 and 2 are sectional views showing a part of the configuration of the bag according to the present invention, and FIGS. 3 to 6 are explanatory views showing the same torn state. FIG. 7 is a sectional view showing the back seal state of the same as above. FIG. 8 is a perspective view showing the same as the above in an unsealed state. In the figure, A is a horizontally uniaxially stretched plastic film;
C is a plastic film with easy cohesive failure and peelability;
1 is a back seal portion, and 3 is an opening notch. The first Ling

Claims (1)

[Claims] A notch for opening was provided in the back seal part, which is made of a material laminated with a plastic film that is easily peelable due to cohesive failure and has a heat seal strength of 0.5 to 2.5 kg/15 mm on a horizontally uniaxially stretched plastic film. An easily tearable bag characterized by: