JP2002293368A - Packaging material and container thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, in a field of containers wherein a heat seal of a hermetic container is peeled for unsealing, a packaging material and a container which has an appropriate peeling strength, does not cause paper of-the container to peel even when the material is used as a lid of a paper container with a polyethylene coated on an innermost layer, and exhibits easiness in unsealing. SOLUTION: The packaging material comprises at least a base and a heat seal layer which has a lamination structure comprising, in the sequence from a side closer to the base, a resin layer (B) made of a low density polyethylene, and a resin layer (A) containing 55 to 75 pts.wt. of the low density polyethylene and 45 to 25 pts.wt. of a polybutene-1. The resin layer (A) and the resin layer (B) are adjacently laminated by a co-extrusion method. If the packaging material is heat-sealed as a lid of a paper cup container having a polyethylene with a melting point of 105 to 115 deg.C coated on the innermost layer, the resin layer (A) causes a cohesive failure when the container is unsealed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a packaging material and a container.

[0002]

2. Description of the Related Art Easy-open packaging materials having easy peelability are roughly classified into an interface peeling type, an interlayer peeling type, and a cohesive peeling type according to a difference in a peeling mechanism. Among these, the cohesive peeling type material exhibits easy peeling property by causing internal cohesive failure when the peel layer resin is opened. EVA-based materials blended with wax and binder, and incompatible polymer alloys such as polyolefin / polystyrene-based and polyethylene / polypropylene-based materials are known as cohesive-peeling type materials, and seal temperature stability of peel strength is known. It has the characteristic of being excellent in impurity sealing property and content resistance. Here, "excellent in foreign substance sealing properties" means that even when foreign substances having a relatively large particle size are mixed in the heat sealing material, good heat sealing performance is exhibited.

[0003]

However, the conventional easy-opening material belonging to the cohesive failure type is liable to cause a so-called "threading phenomenon" in which the peel layer resin remains on the peeled surface of the seal at the time of unsealing in a fiber-like state. There's a problem. Further, since it is difficult to control the peel strength, when the polyethylene-coated paper is used as an adherend, the paper of the adherend is broken because the peel strength is too strong, so-called "paper peeling phenomenon" is likely to occur. There are also problems.

Further, when a conventional easy-opening material is laminated on a base material such as paper, film, metal foil or the like by an extrusion laminating method or the like, the obtained easy-opening packaging material is liable to curl. There is also a problem that supply and handling during heat sealing often cause trouble.

An object of the present invention is to provide a lid for a paper container having an appropriate peel strength (peel strength) and a polyethylene coat on the innermost surface in the field of containers in which the heat-sealed portion of the hermetically sealed container is peeled and opened. An object of the present invention is to provide a packaging material and a container showing good easy-opening properties without causing paper peeling of the container even when used as a material.

[0006]

The easy-open packaging material according to the present invention comprises at least a base material and a heat seal layer provided on one side of the base material. A resin layer (B) made of low-density polyethylene and a resin layer (A) containing 55 to 75 parts by weight of low-density polyethylene and 45 to 25 parts by weight of polybutene-1 in this order from the side close to. It has a laminated structure provided, and the resin layer (A) and the resin layer (B) are laminated with each other by a co-extrusion method.

In the easy-open container according to the present invention, the packaging material is heat-sealed as a lid material of a paper cup container coated with polyethylene having a melting point of 105 to 115 ° C. on the innermost layer. ) Undergo cohesive failure.

Preferably, the thickness of the resin layer (A) is in the range of 5 to 15 μm, and the thickness of the resin layer (B) is not less than the thickness of the resin layer (A).

Preferably, the low-density polyethylene of the resin layer (A) is a high-pressure low-density polyethylene having a melting point of 110 ° C. or lower, and the polybutene-1 is a homopolymer having a melting point of 120 ° C. or higher.

[0010] It is preferable that the heat seal layer is laminated on the substrate by a co-extrusion lamination method.

[0011]

FIG. 1 is a schematic sectional view showing an example of a layer structure of a packaging material of the present invention. FIG. 2 is a schematic sectional view showing another example of the layer structure of the packaging material of the present invention. 3A and 3B are conceptual diagrams illustrating a state in which the packaging material of the present invention is peeled off from an adherend. FIG. 3A is a state in which heat sealing is performed, and FIG. FIG. 4 shows an embodiment of a container using the packaging material of the present invention as a lid, (a) is a perspective view of the container,
(B) XX section sectional view, (c) partial section view of the seal portion,
(D) It is a fragmentary sectional view of a peel part when a lid material is peeled.

As shown in FIG. 1 or 2, the packaging material 1 of the present invention comprises at least a base material 3 and a heat seal layer 2, and the heat seal layer 2 is formed by laminating different resins. At least two layers (2A,
2B). In the example of FIG. 1, a heat seal layer is directly formed on a base material 3 such as paper by an extrusion coating method, and in the example of FIG.
Is formed into a film and bonded to a substrate such as a plastic film using an adhesive 4 by a dry laminating method or the like.

As the base material, a simple substance of paper, metal foil, plastic film, or a laminate of two or more of these can be used. The plastic film may be an evaporated film on which an oxide such as silica or alumina or a metal thin film such as aluminum is formed.

As shown in FIG. 1, the heat sealing layer 2 in the packaging material of the present invention is made of 55-55 low-density polyethylene.
A resin layer 2A in which 75 parts by weight and polybutene-1 are mixed at a ratio of 45 to 25 parts by weight, and a resin layer 2B made of low-density polyethylene are laminated by a co-extrusion method without using an adhesive layer. . The heat seal layer 2 is laminated with the resin layer 2B made of the low-density polyethylene disposed on the base material side in laminating with the base material 3. In other words, the heat seal layer 2 is laminated with the resin layer 2B side facing the base material.

The low-density polyethylene and polybutene-1
Forms a peel layer capable of causing cohesive failure when opened. Polybutene-1 is substantially incompatible with low density polyethylene, and mixtures thereof
Since a so-called "sea-island structure" is formed, the cohesive force of the peel layer is reduced, and the cohesive failure type easy peel property can be exhibited. The blending ratio of polybutene-1 is 25
If the content is less than 10% by weight, the peel strength is too strong, and when polyethylene-coated paper is used as an adherend, paper peeling occurs. If the blending ratio of polybutene-1 exceeds 45% by weight, the peel strength becomes insufficient, and threading tends to occur.

By providing the low-density polyethylene resin layer 2B adjacent to the peel layer, cohesive failure of the peel layer at the time of opening can be concentrated near the boundary between the 2A layer and the 2B layer, thereby stabilizing the peel strength. In addition, the occurrence of stringing can be suppressed. Further, providing the resin layer 2B of low-density polyethylene has an effect of increasing the lamination strength when the heat seal layer 2 is laminated with the base material 3 by, for example, a co-extrusion lamination method.

By laminating the 2A layer and the 2B layer, a heat seal layer can be easily formed at a predetermined layer ratio. As a method for laminating the heat seal layer 2 formed of the 2A layer and the 2B layer and the substrate 3, a dry lamination method, a sandwich lamination method, a co-extrusion lamination method, or the like can be used.

If the thickness of the heat-sealing layer 2A is less than 5 μm, the sealing strength tends to be unstable, and contaminant sealing becomes insufficient. Further, when the thickness of the 2A layer of the heat seal layer exceeds 15 μm, stringing tends to occur at the time of opening. On the other hand, the thickness of the 2B layer forming the heat seal layer is 2
When the heat seal layer is thinner than the layer A, the curl when the heat seal layer is laminated with the base material becomes large, and 2A by the co-extrusion method.
Lamination of the layer and the 2B layer also becomes difficult.

When the melting point of the low-density polyethylene contained in the 2A layer of the heat seal layer exceeds 110 ° C., the heat seal strength at low temperatures is weakened, and stringing tends to occur. In addition, linear low-density polyethylene, a copolymer of ethylene and α-olefin, so-called LLDPE
When used for the A layer, the sealing strength is increased and the paper is easily peeled off. The low-density polyethylene used for the 2A layer of the heat seal layer may have a density of 0.915 to 0.9.
920, MFR 0.5 to 50, preferably 20 to 50
Are preferred.

If the melting point of polybutene-1 is less than 120 ° C., the sealing strength is increased, and the peeling of the paper during peeling is liable to occur. When a copolymer obtained by copolymerizing butene-1 and another olefin with butene-1 as a main component is used, the sealing strength is increased and the paper is easily peeled off. Polybutene-1 has a density of 0.905 to 0.917, MFR
Is preferably in the range of 0.2 to 20.

When the melting point of the low-density polyethylene of the layer 2B of the heat seal layer is higher than that of the low-density polyethylene used for the layer 2A, stringing tends to occur at the time of opening. As the low-density polyethylene of the 2B layer of the heat seal layer, for example, the melting point is 105 ° C., the density is 0.92,
Those having an FR of about 5 to 30 can be used.

Hereinafter, opening of a container using the packaging material of the present invention will be described. As shown in FIG. 3A, the heat-sealing layer of the packaging material 1 of the present invention
The heat seal portion 13 is formed by facing the heat seal layer of No. 0 and heat sealing with the hot plate 30. When the heat seal portion 13 is peeled off (opened), as shown in FIG.
A cohesive failure 14 occurs in the layer, showing easy-opening properties, and a peeled surface without stringing is formed.

The substrate 3 on which the heat seal layer 2 is laminated is
In the case of paper, aluminum foil, or a plastic film such as polyethylene, the heat seal layer 2 composed of the 2A layer and the 2B layer can be directly laminated on the base material using a co-extrusion lamination method. This simplifies the manufacturing process.

As shown in FIG. 4 (a), the packaging material of the present invention can be suitably used as a lid 21 which is heat-sealed to a polyethylene-coated paper cup container 22. The paper container is formed by pressing the lip curl portion of the container body 22 to form a smooth flange 23 (see FIG. 2B), and the lid 21 is heat-sealed to the flange portion to be sealed. At the time of opening, the heat-sealed portion of the lid is peeled off. FIG. 4D shows a state in which the packaging material of the present invention was used as a lid material and peeled for opening. The paper container is widely used for foods such as instant noodles, yogurt, snacks, and natto. By using the packaging material of the present invention as a lid material of the paper container, excellent peelability can be imparted to the peel surface, and the occurrence of stringing on the peeled surface which has been conventionally observed in the paper container can be prevented. Was completed.

[0025]

EXAMPLES Next, the packaging material and the container of the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

Example 1 Low density polyethylene (melting point 1
05 ° C.) and 65 parts by weight of polybutene-1 (melting point 125
C.) with 35 parts by weight as a peel layer to form a first layer (thickness: 10 μm), low-density polyethylene (hereinafter referred to as “LDPE”) (melting point: 105 ° C., density =
0.92, MFR = 7) as a second layer (thickness: 20 μm), while applying an ozone treatment to the LDPE layer side, and extruding a corona-treated paper (basis weight: 100 g / m ² ) at an extrusion temperature of 300 ° C. Coextrusion lamination was performed to obtain a packaging material having the following configuration.

Paper (100 g / m ² ) / LDPE (20 μm)
m) / peel layer (10 μm)

Example 2 A mixture of 75 parts by weight of LDPE (melting point: 106 ° C.) and 25 parts by weight of polybutene-1 (melting point: 125 ° C.) was used as a peel layer to form a first layer (9 μm in thickness). 105 ° C, density = 0.92, MFR
= 7) as a second layer (thickness: 50 μm), while ozone treatment is performed on the LDPE layer side, paper (basis weight: 70 g / m ² ) and aluminum foil (thickness: 7 μm) are used as an intermediate layer by LDPE (thickness: 20 μm). ), A co-extrusion lamination is performed at an extrusion temperature of 280 ° C. on the aluminum foil surface (urethane-based primer coated) of the substrate bonded by an extrusion lamination method (so-called sandwich lamination method), and a packaging material having the following structure I got

Paper (70 g / m ² ) / LDPE (20 μm)
m) / aluminum foil (7 μm) / LDPE (50 μm)
m) / peel layer (9 μm)

Example 3 First layer (9 μm thickness) of a mixture of 70 parts by weight of LDPE (melting point: 106 ° C.) and 30 parts by weight of polybutene-1 (melting point: 125 ° C.) as a peel layer.
LDPE (melting point 105 ° C., density = 0.92, MF
R = 20) as the second layer (thickness: 50 μm)
While applying ozone treatment to the layer side, paper (basis weight 70 g /
m ² ) and an aluminum foil (thickness: 7 μm) are bonded by wet lamination, and then the aluminum foil surface (urethane-based primer coated) is dry-laminated and biaxially cured using a two-component curable polyurethane-based adhesive. Coextrusion lamination was performed at an extrusion temperature of 260 ° C. on a PET film surface (corona discharge treated) of a substrate to which a stretched polyethylene terephthalate film (hereinafter, referred to as a PET film) (thickness: 12 μm) was adhered. Packaging material was obtained.

Paper (70 g / m ² ) / adhesive / aluminum foil (7 μm) / adhesive / PET film (12 μm)
/ LDPE (50 μm) / peel layer (9 μm)

Comparative Example 1 First layer (10 μm thick) as a peel layer, a mixture of 80 parts by weight of LDPE (melting point: 105 ° C.) and 20 parts by weight of polybutene-1 (melting point: 125 ° C.)
With EMAA (melting point 98 ° C.) as the second layer (thickness 20 μm), while exposing the EMAA layer to ozone, the sheet was extruded at a temperature of 30 g on corona-treated paper (100 g / m ² ).
Coextrusion lamination was performed at 0 ° C. to obtain a packaging material having the following structure.

Paper (100 g / m ² ) / EMAA (20 μm)
m) / peel layer (10 μm)

Comparative Example 2 A mixture of 50 parts by weight of LDPE (melting point: 105 ° C.) and 50 parts by weight of polybutene-1 (melting point: 125 ° C.) was used as a peel layer to form a first layer (10 μm). C.) as a second layer (20 μm), while extruding ozone on the EMAA layer side, and extruding at a temperature of 300 g on corona-treated paper (100 g / m ² ).
Coextrusion lamination was performed at ℃ to obtain a packaging material having the following composition.

Paper (100 g / m ² ) / EMAA (20 μm)
m) / peel layer (10 μm)

Comparative Example 3 Linear low-density polyethylene (hereinafter referred to as "LLDPE") (melting point 11
0 ° C) and 65 parts by weight of polybutene-1 (melting point 125 ° C)
A 35% by weight mixture as a peel layer, a first layer (thickness 10 μm), a second layer (thickness 20 ° C.) of EMAA (melting point 98 ° C.), and a corona treatment while applying ozone treatment to the EMAA layer side. was subjected to co-extrusion laminating at a temperature 300 ° C. extruded on paper (100g / m ²⁾ was subjected, to obtain a packaging material having the following constitutions.

Paper (100 g / m ² ) / EMAA (20 μm)
m) / peel layer (10 μm)

<Test> Cup base paper (2) extruded with a 20 μm thick low density polyethylene having a melting point of 106 ° C.
80 g / m ² ) was molded into a cup shape having a flange portion, and the packaging material prepared in Examples 1, 2, and 3 was used as a lid material for the flange portion, and heat-sealed at 150 ° C. for 0.6 sec. Thereafter, the package was opened and the cross section of the peeled surface was observed under a microscope. Since the peel layer of the lid material was observed on both the lid material side and the cup side, it was confirmed that the peel layer was cohesively broken at the time of opening.

The packaging prepared in each of Examples and Comparative Examples
The material is low-density polyethylene having a melting point of 106 ° C. (thickness: 20).
μm) is extruded and coated on a cup base paper (280 g
/ M ^Two) At 140 ° C, 98 kPa, 1 sec.
Heat sealing, peel strength and peeling
None was compared and evaluated.

The ease of opening (peel strength) and the occurrence of paper peeling in the examples and comparative examples were as follows.

[0041]

[Table 1]

The packaging materials of Examples 1, 2, and 3 exhibited an appropriate peel strength, and were satisfactory without causing paper peeling on the release surface.

In the packaging material of Comparative Example 1, since the blending ratio of polybutene-1 was too small, the peel strength was too strong and paper peeling occurred. The packaging material of Comparative Example 2 was polybutene-
Since the blending ratio of No. 1 was too large, no peeling of the paper occurred, but the peel strength was too weak, which was not preferable. Comparative Example 3
Packaging material is LLDPE instead of the first layer LDPE
Was used, the peel strength was too strong, and paper peeling occurred.

The packaging materials of Examples 1, 2 and 3 were prepared as follows: [paper (260 g / m ² ) / LDPE (20 μm) / aluminum foil (7 μm) / EMAA (12 μm) / LDPE
(13 μm)] when used as a lid material for a paper cup container for snacks formed using base paper having a layer structure of (13 μm), it had an appropriate peel strength, did not peel off paper on the release surface, and had good sealing properties and heat resistance. Thus, an easily-openable container having excellent properties was obtained.

[0045]

The packaging material of the present invention has a heat seal layer including a peel layer. When the heat-sealed portion sealed by the heat-sealing method is peeled and opened using this packaging material, cohesive failure occurs in the peel layer, and the easy-opening property is exhibited. In addition, paper peeling does not occur in the opening portion.

When this packaging material is used as a lid for a paper cup made of polyethylene on the inner surface, a sealed paper cup having easy opening is obtained. The container obtained in this way is very usable for the consumer.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a layer structure of a packaging material of the present invention.

FIG. 2 is a schematic sectional view showing another example of the layer structure of the packaging material of the present invention.

3A and 3B are conceptual diagrams illustrating a state in which the packaging material of the present invention is peeled from an adherend, wherein FIG. 3A is a state in which heat sealing is performed, and FIG.

FIG. 4 shows an embodiment of a container using the packaging material of the present invention as a lid material, wherein (a) is a perspective view of the container and (b)
X-X section view, (c) partial section view of seal portion, (d)
It is a fragmentary sectional view of a peel part when a lid material is peeled.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Packaging material 2 Heat seal layer 3 Base material 4 Adhesive layer 10 Adherend 11 Adherend heat seal layer 13 Heat seal part 14 Peeling part 20 Container 21 Cover 22 Container main body 23 Flange part 30 Hot plate

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 3E086 AB01 AD24 BA04 BA13 BA14 BA15 BB51 BB90 CA01 4F100 AB10 AB33 AK06B AK06C AK09C AK42 AK51G AL05C AT00A BA03 BA07 BA10A BA10C DG10 EH20B EH20C EH23Y15Y00 GB18J00

Claims (5)

[Claims] 1. A heat-sealing layer provided on at least one side of a base material, said heat-sealing layer being a resin layer (B) made of low-density polyethylene from a side close to said base material. And a resin layer (A) containing 55 to 75 parts by weight of low-density polyethylene and 45 to 25 parts by weight of polybutene-1 in this order, and the resin layer (A) And the resin layer (B) are laminated with each other by a co-extrusion method. 2. The method according to claim 1, wherein the thickness of the resin layer (A) is in a range of 5 to 15 μm, and the thickness of the resin layer (B) is not less than the thickness of the resin layer (A). The packaging material according to claim 1. 3. The low-density polyethylene of the resin layer (A) is a high-pressure low-density polyethylene having a melting point of 110 ° C. or lower,
The packaging material according to claim 1, wherein the polybutene-1 is a homopolymer having a melting point of 120 ° C. or higher. 4. The packaging material according to claim 1, wherein said heat seal layer is laminated on said base material by a co-extrusion lamination method. 5. The packaging material according to claim 1, wherein said packaging material has a melting point of 1.
An easily openable container, which is heat-sealed as a cover material of a paper cup container coated with polyethylene at the innermost layer at a temperature of from 05 to 115 ° C, and the resin layer (A) undergoes cohesive failure when opened.