JP2002225175A - Lid material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sealable lid material having no problem in adhesiveness even if bonded to a surface having unevenness. SOLUTION: The lid material consists of aluminum, a resin layer and a heat sealer layer. The resin layer comprises at least one kind of a resin selected from high density polyethylene, medium density polyethylene, straight chain low density polyethylene, polypropylene, an ionomer, an ethylene acrylic acid copolymer resin and an ethylene methacrylic acid copolymer resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lid material for a food container or the like.

[0002]

2. Description of the Related Art Aluminum foil is excellent in aesthetics and barrier properties, so that yogurt, jam, cheese, butter,
It is used as a lid for containers for ice cream and other foods. For example, as shown in FIG. 1, a flange portion 2 is provided at an upper opening of the main body 1, and an aluminum lid 3 having a heat seal lacquer applied to the flange portion is heat-sealed and hermetically closed.

However, some containers have irregularities such as steps on the bonding surface of the flange. For example, in the case of a paper container, as shown in FIG. 1, a superposed portion 4 is inevitably produced in manufacturing, and this portion becomes uneven. Irregularities may occur even in a resin container due to its shape or the parting line of a mold. In such a case, the bonding pressure of the aluminum lid material is reduced at the irregularities during heat sealing,
Adhesive strength is weakened, and in extreme cases, it is impossible to follow irregularities and a gap is generated, which may cause a problem in airtightness.

In order to solve this problem, there is a lid material which extrudes and laminates aluminum, low density polyethylene (LDPE) and an adhesive resin, and heat seals. As the adhesive resin, an ethylene-vinyl acetate copolymer resin is usually used. In this case, at the time of bonding, LDPE plays a cushion-like role, the bonding pressure does not decrease so much, and no gap is formed in the seal portion. However, the ethylene-vinyl acetate copolymer-based resin is liable to generate gels and foreign substances, which lowers its value as a commercial product. In addition, there is a characteristic resin smell.

[0005] Instead of the adhesive resin, it is conceivable to apply a polypropylene heat seal lacquer as an adhesive layer to the LDPE layer. Such a lid material is easily broken when the lid is peeled off. Furthermore, a lid material in which heat seal lacquer is applied to a laminated material of aluminum and polyester resin is conceivable.However, polyester resin has high rigidity, cannot follow irregularities on the sealing surface, has poor adhesiveness, and also when peeling off the lid Easy to tear.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sealable lid material which has no problem in adhesiveness even when it is bonded to a surface having irregularities and hardly breaks when peeled off. It is to provide.

[0007]

Means for Solving the Problems The present inventor has conducted extensive studies on a laminated material of various resins and an aluminum foil. As a result, when a specific resin layer is laminated on the aluminum foil, the resin layer functions as a cushion layer and adheres. The inventors have found that unevenness in pressure hardly occurs, the adhesive strength does not decrease, and that there is no breakage when peeled off, and the present invention has been reached.

That is, the present invention relates to a lid material comprising aluminum, a resin layer and an outermost heat sealer layer, wherein the resin layer is made of high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, polypropylene, ionomer. And a lid material characterized by being at least one member selected from the group consisting of ethylene-acrylic acid copolymer resin and ethylene-methacrylic acid copolymer resin.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 2, a laminated structure of a lid member according to the present invention comprises aluminum 6, resin 7, and heat sealer 8 layers. The aluminum foil may be either soft or hard and the type thereof is not particularly limited. Also, the thickness of the aluminum foil is not particularly limited, but is preferably 9 to 100 μm, more preferably 20 to 50 μm, in view of demands for formability, strength, and weight reduction.

The resin layer is made of high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, polypropylene, ionomer, ethylene acrylic acid copolymer resin or ethylene methacrylic acid copolymer resin. Other resins cannot follow irregular surfaces such as steps during heat sealing, resulting in uneven bonding pressure and a problem in bonding strength. Preferred resins are high density polyethylene and polypropylene, particularly preferably high density polyethylene. The resin layer may be a single layer or a combination of a plurality of resin layers. The thickness of the resin layer is not particularly limited as long as it can absorb irregularities on the adhesive surface of the container and hardly causes pressure unevenness during heat sealing.
５０50 μm.

The heat sealer may be any one which is used as a heat seal adhesive for polyethylene-coated paper or resin. For example, a solvent type heat seal lacquer or an aqueous type heat seal lacquer can be preferably used. As the solvent type, for example, a type in which a polypropylene-based resin is mainly used and dispersed in a solvent is used, and as the aqueous type, a polyethylene-based or acrylic-based resin such as an ionomer, an ethylene acrylic acid copolymer resin or an ethylene methacrylic acid copolymer resin is used. A resin mainly composed of the above resin and dispersed or emulsified in an aqueous solvent can be preferably exemplified. The lid material of the present invention may have other layers laminated as necessary. For example, an aluminum foil may be further laminated between the resin layer and the heat sealer layer.

The lid material of the present invention can be manufactured, for example, as follows. A laminated material of aluminum and a resin may be manufactured by a conventional method such as an extrusion lamination method, and a heat sealer dispersion may be applied to the aluminum surface and dried. The lid material of the present invention is used as a lid material for paper and various plastic containers, for example, by being adhered to a flange portion on the upper surface of the container by heat sealing, ultrasonic sealing, or the like.

[0013]

EXAMPLES The present invention will be described below with reference to examples. Example 1 Aluminum foil (AL foil) and high density polyethylene (HD)
PE) was laminated by extrusion lamination, and a carboxylic acid-modified polypropylene-based dispersion-type heat sealant was applied to the HDPE surface and dried to produce a lid material. Example 2 AL foil, HDPE and AL foil were laminated by extrusion lamination,
A carboxylic acid-modified polypropylene-based dispersion-type heat sealant was applied to one AL foil surface and dried to produce a lid material. Example 3 A lid material was produced in the same manner as in Example 2 except that HDPE was changed to polypropylene (PP).

Comparative Example 1 An AL foil, low-density polyethylene (LDPE), and an ethylene-vinyl acetate copolymer resin for adhesion were extrusion-laminated to form a lid material. Comparative Example 2 An AL foil was dry-laminated on both surfaces of a polyester (PET) film, and a heat sealant was applied and dried on one aluminum surface in the same manner as in Example 1 to produce a lid material. Comparative Example 3 A lid was prepared in the same manner as in Example 1 except that HDPE was changed to LDPE.

Table 1 shows the laminated structure of these lid members.
The following tests were performed on these lid materials.

[Seal strength and cut rate at peeling]
A lid sheet having the same outer shape is placed on a polypropylene sheet having a size of 7 mm × 50 mm and a thickness of 0.7 mm.
0 mm was heat-sealed under the conditions of a temperature of 200 ° C. and a pressure of 0.3 MPa for 1 second to obtain a test piece. This test piece was subjected to a tensile test in the direction of 180 ° at 100 mm / min to measure the seal strength (n = 10). Those whose lid material was broken during the measurement were excluded and regarded as seal strength. The breaking rate at the time of peeling was represented by the number of broken test pieces among 10 test pieces.

[Seal strength ratio of low pressure part to normal pressure part]
A test piece was prepared in the same manner as in the case of the seal strength, except that a polypropylene sheet having an outer shape of 25 mm × 50 mm, a thickness of 0.7 mm, and a step of 20 μm at the center in the longitudinal direction was used. The specimen was placed in a 90 ° direction at 10 °.
A tensile test was performed at 0 mm / min to measure the seal strength between the step portion and the normal portion, and the ratio was determined.

[0018]

[Table 1]

[0019]

The lid material using the ethylene-vinyl acetate copolymer resin adhesive of Comparative Example 1 is inferior in appearance due to inclusion of foreign matter and gel. The lid material using PET of Comparative Example 2 may be cut at the time of peeling, and the sealing strength of the low pressure part is low. The lid material using LDPE of Comparative Example 3 was severely cut when peeled. On the other hand, the lid material of the present invention using HDPE or PP has high sealing strength, does not cause cutting, and has no difference in sealing strength between the low pressure part and the normal pressure part. Especially HDP
In the case of E, these performances are excellent. in this way,
The lid material of the present invention is particularly suitable as a lid material for a container having irregularities at the rear.

[Brief description of the drawings]

FIG. 1 is a diagram showing a container and a lid member.

FIG. 2 is a diagram illustrating an example of a configuration of a lid member according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container main body 2 Flange part 3 Lid 4 Overlapping part 6 Aluminum foil 7 Resin layer 8 Heat seal layer

Continued on the front page F-term (reference) 3E084 AA02 AA12 AB01 AB10 BA01 BA06 BA08 BA09 CA01 CB03 CB04 FA09 FB01 GB08 GB12 GB17 HA01 HB01 HC08 HD01 KA14 KA15 4F100 AB10A AB10D AK04C AK05C AK07 AK07C01BA03B01 AK63C01A JL12B

Claims (4)

[Claims] 1. A lid material comprising an aluminum layer, a resin layer and an outermost heat sealer layer, wherein the resin layer is made of high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, polypropylene, ionomer, ethylene acrylic. A lid material comprising at least one selected from an acid copolymer resin and an ethylene methacrylic acid copolymer resin. 2. The lid material according to claim 1, wherein the aluminum layer and the heat sealer layer are formed with a resin layer interposed therebetween. 3. The lid material according to claim 1, wherein two aluminum layers are formed with a resin layer interposed therebetween, and the heat sealer layer is formed outside one of the aluminum layers. 4. The lid material according to claim 1, wherein the heat sealer layer comprises a solvent type heat seal lacquer or an aqueous type heat seal lacquer.