JP2513375B2 - Laminated bag for food packaging - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a food packaging laminated bag which can be opened by hand, and more specifically,
The present invention relates to a laminated bag for food packaging in which both sides of the package can be cut with the same strength when opened and the cuts on both sides of the laminate are neatly aligned.

[0002]

2. Description of the Related Art Polyolefin is a material suitable as a layer (hereinafter referred to as an inner layer) which comes into contact with the food contained in a heat-sterilized food package because it has excellent heat-sealing properties and solvent extraction resistance and heat resistance. However, there is a problem that mechanical strength such as impact resistance is poor. Therefore, conventionally, a polyolefin film is stretched to improve its mechanical strength and is laminated with an aluminum foil or the like to be used as a laminated bag for food packaging.

In general, a resin film is stretched biaxially in the machine direction (MD direction) and at a right angle direction (TD direction), and this stretch improves mechanical strength and cuttability of the film. It has also become possible to provide a laminated bag that can be easily opened by hand.

[0004]

However, in the case of forming a bag in which the polyolefin thus stretched is laminated with aluminum foil or the like, the laminate is folded in two and the three sides where the laminate is overlapped are heat-sealed. Although it is sealed to form a laminated bag, by folding the laminated body in two, the stretching directions of the front surface and the back surface of the polyolefin film forming the inner layer of the laminated bag do not face the same direction.

Such a phenomenon is described, for example, in Japanese Patent Laid-Open No. 62-62.
It can be understood from the disclosure in Japanese Laid-Open Patent Publication No. 96066 or Japanese Laid-Open Patent Publication No. 1111664. That is,
The film extruded from the T-die is biaxially stretched while being transferred. As a result, the center of the film is stretched in the longitudinal direction, but the transverse stretching may be performed at right angles to the longitudinal direction. Instead, it is oriented obliquely with the central part as a boundary.

If this stretched film is cut into a bag and folded in two, the two sides will be oriented in different directions on the front side and the back side. Therefore, the three sides are heat-sealed as they are. When configured as a bag, even if a notch is formed and an attempt is made to open from that portion, when the laminated bag is cut by hand, for example, one surface is cut slightly above the notch for starting cutting. Then, the other surface will be cut slightly downward from the notch, so the cutting edges will not be aligned at the same height, and the tearing direction of the front surface and the back surface will deviate slightly There was also a problem in terms of ease.

On the other hand, the tearability and the impact strength of the film are in a contradictory relationship. When the film is stretched to obtain the tearability (easy to open), the drop impact strength of the film is lowered depending on the stretching ratio. There was also the problem of doing. Therefore, an object of the present invention is to provide a laminated bag which is excellent in impact resistance, drop impact strength, etc., is easy to open by hand, and has clean cuts.

[0008]

According to the present invention, a finely stretched polyolefin film (a) is used as a layer (inner layer) in contact with a food product, and a metal foil (b) is used as an intermediate layer. In the laminated bag for food packaging in which the polyolefin (c) stretched in the machine direction (MD direction) is laminated as an outer layer, the orientation direction of the polyolefin film (a) is 0.1 < L ≦ 0.5 (Equation 1) 0.5 <N ≦ 0.9 (Equation 2) (wherein L represents the orientation in the direction parallel to the film formation direction, and N represents the in-plane non-orientation). A laminated bag for food packaging is provided, which satisfies the range and has a melt index of 0.5 to 10.0 g / 10 min. The term "(a) finely stretched" in the present invention means a low degree of stretching with a stretching ratio of about 0.05 to 0.5.

According to the present invention, the polyolefin (a) used in the inner layer is polyethylene or ethylene-propylene random having an ethylene content of 2 to 20 mol% or a block copolymer having an ethylene content of 2 to 15 mol%. A laminated bag for food packaging is provided.

According to the present invention, the orientation direction of the polyolefin (c) used in the outer layer is 0.2 <L ≦ 1.0 (formula 3) 0 <M ≦ 0. 4 (Equation 4) 0 <N ≦ 0.8 (Equation 5) (In the equation, L is an orientation in a direction parallel to the film formation direction, N is an in-plane non-orientation, and M is perpendicular to the film formation direction. A laminated bag for food packaging is provided which satisfies the range (representing orientation in direction).

[0011]

DETAILED DESCRIPTION OF THE INVENTION An important technical feature of the present invention is that in a laminated bag for food packaging, a layer (inner layer) in contact with the content food.
A specific polyolefin having a low degree of stretching is used for the outer layer, and a laminate using a polyolefin highly stretched in the MD direction is used as the outer layer.

As described above, stretching the resin film improves the mechanical strength and tearability of the film, but on the other hand, depending on the degree of stretching, the strength against drop impact tends to decrease. In the present invention, when the degree of stretching of the polyolefin used for the inner layer is lowered and the stretching direction is measured by the fluorescent orientation method, the above (formula 1)
And the range of (Equation 2) is satisfied, and the melt index is 0.5 to 10.0 g / 10 min, especially 1.0
To 4.0 g / 10 min of polyolefin, and by using as the outer layer a polyolefin that is strongly stretched in the MD direction, it has excellent impact resistance and drop impact strength, and is easy to open by hand and has a cut edge. It was completed based on the finding found by the present inventor that it can be formed into a neatly arranged laminated bag.

That is, an important feature of the present invention is that the orientation direction of the polyolefin film (a) in the laminated bag for food packaging having the above-mentioned constitution is measured by a fluorescent orientation method, and 0.1 <L≤0. 5 (Equation 1) 0.5 <N ≦ 0.9 (Equation 2) (where, L represents the orientation in the direction parallel to the film formation direction, and N represents the in-plane non-orientation). And the melt index is 0.5 to 10.0 g / 10 min.

In the laminated bag for food packaging of the present invention, as is clear from the results of Examples and Comparative Examples described later, the orientation direction of the polyolefin (c) used in the outer layer is 0 by the fluorescent orientation method. .2 <L ≦ 1.0 (Equation 3) 0 <M ≦ 0.4 (Equation 4) 0 <N ≦ 0.8 (Equation 5) (In the equation, L is in the direction parallel to the film formation direction. Orientation, N is in-plane non-orientation, and M is orientation in a direction perpendicular to the film formation direction).

The fluorescent orientation method for defining the stretching direction in the present invention is a method for obtaining the orientation state of a polymer amorphous chain, and when the two deflecting plates P1 and P2 are parallel, I.parallel. In this method, I⊥ is set as time, and the angular distribution of these fluorescence deflection component intensities is obtained as a function of the rotation angle ω of the sample.

I / (ω) = Kφ (Lcos ⁴ ω + Msin ⁴ ω + 3 /
8 · N) (Equation 6) L + M + N = 1
In (Equation 7), L is an orientation in a direction parallel to the film forming direction (direction to MD), M is an orientation in a direction perpendicular to the film forming direction (TD direction), and N is in-plane non-orientation. These are parameters shown respectively. If L = M = 0, no in-plane orientation is obtained. If M = N = 0, then perfect uniaxial orientation is obtained, and L = M,
If N = 0, it means perfect orthogonal biaxial orientation.

In the present invention, the polyolefins that can be used in the inner layer and the outer layer are not limited to these, but include polyethylene, polypropylene and ethylene-
It is a propylene copolymer or the like, and is particularly a polyethylene or an ethylene-propylene random copolymer having an ethylene content of 2 to 20 mol% or an ethylene-propylene block copolymer having an ethylene content of 2 to 15 mol%. Is preferred.

As the metal foil that can be used as the intermediate layer, aluminum foil, steel foil, iron foil, tin foil and the like can be used, and among them, aluminum foil can be preferably used. The thickness of the metal foil is generally 5 to 50 μm, especially 6
It is preferably in the range of 20 to 20 μm.

In the present invention, not only the above three-layered structure including the inner layer, the intermediate layer and the outer layer, but also a protective layer such as a thermoplastic polyester may be provided on the surface of the outer layer. Also in such a protective layer, the film or sheet to be used preferably has cuttability, and for example, biaxially stretched polyethylene terephthalate or the like can be preferably used.

Each layer does not have to have a specified thickness, but the inner layer is generally 20 to 100 μm.
m, especially in the range of 40 to 70 μm, and the outer layer is 9 to 25 μm, especially 12 to 16 μm
It is preferable to be in the range. Further, these inner layer, outer layer, metal foil and, if necessary, the outermost layer can be adhered by a known means to form a laminate.

For example, each of these layers can be adhered by an adhesive. In this case, known adhesives such as isocyanate adhesives, epoxy adhesives, adhesives made of thermosetting resins such as isocyanate-epoxy adhesives, synthetic rubber adhesives and adhesives made of thermoplastic resins are used. Any adhesive can be used.

The layers may be adhered by extrusion coating instead of using an adhesive. In this case, it is preferable to apply an anchoring agent such as a titanate ester or an isocyanate compound to the surface of the substrate to be coated, for example, the aluminum foil. The polyolefin forming the inner and outer layers of the laminate of the present invention,
Known additives such as natural rubber, plasticizers, lubricants, fillers, colorants, stabilizers, antistatic agents and the like can be added at any time as long as the achievement of the object of the present invention is not impaired.

In the present invention, the laminated body having the above-mentioned structure can be formed by a method of folding the laminated body in two so that the inner layers face each other and heat-sealing so as to form a peripheral edge of a desired bag. Heat sealing can be performed by a conventionally known method, for example, a method of heating a required portion from the outside of a laminated seal such as a heating bar, a heating knife, a heating wire or an impulse seal, or an ultrasonic sealing or an induction heating sealing. A method by internal heating such as can be used.

The bag obtained as described above is filled with the content food and, if necessary, vacuum deaeration, hot filling deaeration, steam deaeration, steam injection deaeration, or pressure deaeration. In any of the methods, the inside of the bag is deaerated, or the content food is sterilized by heating, and then the content food filling port is heat-sealed to seal the content food.

The package filled with the content food and sealed is suitable for heat sterilization or HTST sterilization.
The heat sterilization treatment is carried out at a temperature of 115 to 160 ° C., and the temperature of HTST heating is 130 to 160 ° C. The bag made of the laminate of the present invention allows a very wide range of food products to be sealed and sterilized.

[0026]

EFFECTS OF THE INVENTION According to the present invention, a specific polyolefin having a low degree of stretching is used for the layer (inner layer) which is in contact with the food, and a laminate is used for the outer layer which is a polyolefin which is strongly stretched in the MD. As a result, it is possible to provide a laminated bag which has excellent impact resistance and drop impact strength, is easy to open by hand, and has clean cuts.

[0027]

The present invention is described in detail in the following examples. 12 μm thick polyethylene terephthalate film as the outermost layer, 20 μm thick polyolefin shown in Table 1 as the outer layer, 7 μm thick aluminum foil or nylon film, and the polyolefin or other resin film shown in Table 1 as the inner layer 170 mm in length and 1 in width from a 4-layer laminated sheet made of 70 μm film
A 30 mm bag was made, filled with 180 g of water / oil suspension and then sealed. In the outer layer of Table 1, H-PP represents homopolypropylene and B-PP in the inner layer represents block polypropylene. In Comparative Example 6, nylon was used instead of the aluminum foil.

Retort treatment (121 ° C, 30 minutes)
Then, immediately after boiling for 5 minutes (product temperature 98 ° C.), a sensory test of the openability was carried out by 20 panelists to evaluate the ease of opening and whether the cuts at the time of opening are the front and back. ◯ indicates good overall, Δ indicates good but less than half, and x indicates defective overall. Separately, the temperature of the product in the bag is kept at room temperature (20 ° C.), and the product is dropped vertically from the height of 1.2 m onto the concrete floor. Each of 100 bags was dropped 5 times in total, and the number of broken bags was examined. The results are shown in Table 1.

[0029]

[Table 1]

Claims (3)

(57) [Claims] 1. A film (a) composed of a finely stretched polyolefin is used as a layer (inner layer) in contact with a food product.
Moreover, the metal foil (b) is used as the intermediate layer, and the flow direction (MD
Direction), the orientation direction of the polyolefin film (a) is 0.1 <L ≦ 0.5 in the laminated bag for food packaging in which the polyolefin (c) is laminated as an outer layer. (Equation 1) 0.5 <N ≦ 0.9 (Equation 2) (wherein L represents an orientation in a direction parallel to the film formation direction, N represents an in-plane non-orientation), A laminated bag for food packaging, which has a melt index of 0.5 to 10.0 g / 10 min. 2. A polyolefin (a) used for the inner layer
2. The laminated bag for food packaging according to claim 1, wherein is polyethylene or ethylene-propylene random having an ethylene content of 2 to 20 mol%, or a block copolymer having an ethylene content of 2 to 15 mol%. 3. The orientation direction of the polyolefin (c) used in the outer layer is 0.2 <L ≦ 1.0 (formula 3) 0 <M ≦ 0.4 (formula 4) 0 as measured by a fluorescent alignment method. <N ≦ 0.8 (Equation 5) (In the equation, L represents an orientation parallel to the film formation direction, N represents no in-plane orientation, and M represents an orientation perpendicular to the film formation direction. The laminated bag for food packaging according to claim 1, which satisfies the range (1).