JP3249005B2 - Easily peelable composite sheet, lid material and container using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer easily peelable composite sheet for a cover material which can be easily peeled off and opened for use.

[0002]

2. Description of the Related Art Conventionally, containers made of synthetic resin used for food packaging and the like have a problem in that, when the containers are used, dust adheres to the outer surface of the containers in a standing environment, and contamination by microorganisms or the like occurs. Often, contaminants are wiped off or washed before use, which poses a problem in food hygiene. As countermeasures against this, double packaging in which the entire packaging container is covered with a film or a bag, or covering only the lid portion for taking out or opening the contents with a film or covering with a cap has been taken.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a multi-layer easily peelable composite sheet for a lid material which can be easily peeled off, opened and used. The present inventors have conducted intensive studies on the easily peelable composite sheet for the lid material, and as a result, have arrived at a co-extruded easily peelable composite sheet for the lid material which can be used by peeling off the surface layer at the time of use and opening. Thus, the present invention has been completed.

[0004]

That is, the first aspect of the present invention is as follows.
The invention of (1) a surface layer containing the following (A) 98 to 70% by weight and the following (B1) 2 to 30% by weight or less,
(2) The following (C) 98 to 70% by weight and the following (B2)
A coextruded composite sheet comprising at least two base layers containing 2 to 30% by weight or less, wherein the thickness of the surface layer is 50 to 3
(A) a polyolefin-based resin (B1) a modified polyolefin-based resin or a modified polyolefin-based resin and a styrene-based block, wherein the base material layer has a thickness of 250 to 1500 μm. Copolymer (B2) Styrene-based block copolymer or styrene-based block copolymer and modified polyolefin-based resin (C) Styrene-based resin Also, when the total of the resin components in each layer is 100% by weight.
Can, as the surface layer (1), the (A) ninety-four to eighty-three
6 to 17% by weight (B1), and the base material layer (2)
(C) is 90-84% by weight (B2)
A composite sheet containing 16% by weight is particularly preferred. On the other hand, the 180-degree peel strength between the surface layer and the base material layer is JIS-
This is an easily peelable composite sheet for a lid material having a weight of 15 to 300 g / 20 mm as measured by the K6854 method. Further, a lid material made of this sheet, a lid material having a tab and a drinking spout,
Furthermore, it is a container having this lid material, and is suitable as a beverage container.

Hereinafter, the present invention will be described in more detail.

Examples of the polyolefin resin constituting the surface layer of the easily peelable composite sheet for a lid material of the present invention include ordinary polypropylene resins and polyethylene resins.
Examples of the polypropylene resin include a normal polypropylene homopolymer and 30% by weight or less of ethylene or butene.
There are random copolymers and block copolymers with α-olefins such as 1, pentene-1, 4-methylpentene-1, and hexene-1. The melt index of these polypropylene resins is generally 0.1 to 15 g.
/ 10 minutes, more preferably 0.5 to 10 g / 10 minutes. If the melt index is out of these ranges, it is not preferable because of melt extrudability and thermoformability. As the polyethylene resin, high-density polyethylene, low-density polyethylene, and linear low-density polyethylene can be used. The melt index of these polyethylene resins is usually 0.02 to 10 g / 10 min, preferably 0.03 to 5 g.
/ 10 minutes. If the melt index is out of these ranges, it is not preferable because of melt extrudability and thermoformability.

[0007] The polystyrene resin constituting the base layer of the easily peelable composite sheet for a lid material of the present invention contains 2 to 15% by weight of a rubber component such as general-purpose polystyrene or polybutadiene.
Impact-resistant polystyrene. The melt index of this polystyrene resin is in the range of 0.5 to 8 g / 10 min, preferably 1 to 6 g / 10 min, from the viewpoint of melt extrudability and thermoformability. The composition of these styrenic resins includes not only 70% by weight or more of styrene monomer but also 30% by weight of α-methylstyrene, acrylonitrile, methyl methacrylate, acrylic acid, n-butyl acrylate and the like. It is also possible to use a styrene copolymer resin with a monomer.

The styrenic block copolymer used in the present invention includes styrene, o-methylstyrene, m-
It is a block copolymer of an aromatic vinyl hydrocarbon such as methylstyrene, p-methylstyrene, ethylstyrene and dimethylstyrene and a diene compound such as butadiene, isoprene and pentadiene. As its structure,
Binary block copolymers such as polystyrene-polybutadiene (SB) and polystyrene-polyisoprene (SI), and ternary block copolymers such as polystyrene-polybutadiene-polystyrene (SBS) and polystyrene-polyisoprene-polystyrene (SIS). Styrene-ethylenebutylene-styrene (SEB) obtained by hydrogenating these block copolymers
S), styrene-ethylene propylene-styrene (SE
PS) and other saturated styrenic block copolymers. Although the styrene content in the styrene-based block copolymer is not particularly limited, a commercially available product containing an aromatic vinyl hydrocarbon such as styrene in a range of 10% by weight to 80% by weight, specifically, DENKA STR, DENKA-CLEAREN, manufactured by Kogyo Co., Ltd.
JSR-TR manufactured by Nippon Synthetic Rubber Co., Ltd., Asahi Kasei Corporation
Tufprene, Solprene, Asaflex, Tuftec, Philips Sorprene, K-resin, Califlex TR, Clayton G, Clayton G, Septon, Kuraray Co., Ltd. can be used.

The modified polyolefin resin used in the present invention includes ordinary ethylene vinyl acetate copolymers, ethylene acrylic acid copolymers, ethylene acrylate copolymers, ethylene propylene elastomers, and maleic acid. Polyolefin composition containing unsaturated carboxylic acid such as polypropylene, polyethylene modified with styrene or styrene-based polymer, ethylene-based elastomer, and the like. Specific product names are VMX, Modick, Mitsui, and Mitsui manufactured by Mitsubishi Yuka Corporation. Petrochemical Industry Co., Ltd.
Admer manufactured by Nippon Petrochemical Co., Ltd., and Plexar manufactured by Tosoh Corporation are included.

In the easily peelable composite sheet for a cover material of the present invention, at least one of the polyolefin-based surface layer and the polystyrene-based substrate layer has at least one layer selected from the above-mentioned styrene-based block copolymers and modified polyolefins.
It is necessary to contain 2 to 30% by weight of the type. If the content of the styrene-based block copolymer and / or the modified polyolefin is less than 2% by weight, the peel strength is too low and the surface layer is peeled off during the production of the composite sheet, or the lid material is cut around the lid material. It is not preferable because the feel when peeled off little by little from the surface or when peeled off by hand is too weak. 3
If it exceeds 0% by weight, the peel strength of the lid material is too high to be easily peeled off by hand, which is not suitable. Preferably, it is in the range of 5 to 20% by weight. These styrenic block copolymers and modified polyolefins may be used in at least one layer, or may be used in both layers.

If the thickness of the surface layer constituting the composite sheet is too small, the polyolefin-based surface layer is broken.
The range of m is preferred. On the other hand, if the thickness of the polystyrene-based base material layer is too small, the rigidity and strength of the lid material are insufficient, and if it is too large, it is not preferable in terms of moldability and economy, and 250 to 15
The range of 00 μm is preferable, and particularly preferably 400 to
It is in the range of 1200 μm.

If the contents of the container are required to have gas barrier properties, an ethylene-vinyl alcohol copolymer or polyacrylonitrile, which has been conventionally used as a base layer, may be used as an intermediate layer. A multi-layer sheet formed by a known method in which a layer of vinylidene chloride, nylon, polyethylene terephthalate, or the like is provided and an adhesive layer is formed on both sides can be used.

The easily peelable composite sheet for a lid material of the present invention may further contain a known coloring agent, filler, heat stabilizer,
Lubricants, plasticizers and the like can be blended.

The easily peelable composite sheet for a lid material of the present invention is not particularly limited, but can be easily formed by co-extrusion molding using a feed block method or a multi-manifold method with a plurality of ordinary extruders using a T-die method. Can be manufactured. The 180-degree peel strength of the surface layer and the base material layer of the easily peelable composite sheet for a lid material of the present invention, from the viewpoint of practicality of food containers and the like,
It is preferably 15 as measured by the JIS K-6854 method.
To 300 g / 20 mm, particularly preferably 20 to 2 g.
00 g / 20 mm.

The easily peelable composite sheet for a lid material of the present invention can be used as a lid material for a container by punching it into a predetermined shape as it is in the form of a sheet. A lid material having a desired shape can be formed and used by usual vacuum forming such as vacuum forming, air forming, hot plate forming or press forming. Further, there is a feature that the surface layer can be peeled off and used when necessary. Also,
A punch cut or a half cut can be provided only in the base material layer so that an opening such as a drinking mouth appears in the polystyrene base material layer after the surface layer is peeled off.

[0016]

Embodiments of the present invention will be described below. Examples 1 to 6 Using the raw materials shown in Table 1, the components for the surface layer and the components for the base material layer shown in the composition of Table 2 were used, and the width was 550 m.
m using a two-layer T-die, extrusion temperature 160-210 ° C,
By a co-extrusion molding method at a take-up speed of 10 m / min, a two-layer composite sheet comprising a surface layer and a base material layer having the thickness constitution shown in Table 2 was produced. The 180-degree peel strength (20 mm width) between the surface layer and the base material layer of the obtained two-layer composite sheet was measured according to JIS K-6.
It was measured at a pulling speed of 200 mm / min according to 854. The resulting two-layer composite sheet is provided with a release tab (5) on a polyolefin-based surface layer (2) shown in FIG. 1 by a vacuum forming machine, and a drinking spout (6) on a polystyrene-based substrate layer (3). A lid material (1) with a diameter of 70 mm with a cut and cut was formed, and the feel and state when the tab portion was gripped by hand and peeled were evaluated. Those which could not be peeled off or peeled off were marked X. Table 2 shows the results of these evaluations.

Comparative Examples 1 to 5 A composite sheet was prepared and evaluated in the same manner as in Example 1 except that the components for the surface layer and the components for the base material layer shown in Table 3 were used. Table 3 shows the results of these evaluations. In Comparative Examples 1 and 2, the polyolefin-based surface layer was broken when the lid material was peeled off by hand, and in Comparative Example 3, the rigidity of the polystyrene-based substrate layer was insufficient, so that it was unsuitable as a lid material.
Comparative Example 4 had too much added styrene-based block copolymer or modified polyolefin, so the peeling feeling as a lid material was too strong, and Comparative Example 5 had insufficient added styrene-based block copolymer or modified polyolefin, resulting in poor releasability. Both are too weak and bad.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

As described above, with the easily peelable composite sheet for a lid material of the present invention, it is possible to obtain a container with a lid material which can be easily peeled off and opened without breaking the surface layer. As it can remove dust and the like adhering to the outside of the container, as specific applications, lactic acid bacteria drinks and juices,
It is useful as various packaging containers, including beverage containers for coffee, tea, water and the like.

[Brief description of the drawings]

FIG. 1 is a perspective view of a lid member formed from an easily peelable composite sheet for a lid member of the present invention.

FIG. 2 is a perspective view showing a state in which a polyolefin-based surface layer has been partially peeled off with a lid formed from the easily peelable composite sheet for a lid according to the present invention.

FIG. 3 is a perspective view of a beverage container using a lid formed from the easily peelable composite sheet for a lid according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 lid material 2 surface layer mainly composed of polyolefin resin 3 base material layer mainly composed of polystyrene resin 4 container body 5 tab for peeling surface layer 6 tap that cuts and opens base material layer Part of

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-93248 (JP, A) JP-A-2-274529 (JP, A) JP-A-4-189135 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 B65D 43/00-43/26

Claims (7)

(57) [Claims] 1. A surface layer containing the following (A) 98 to 70% by weight and the following (B1) 2 to 30% by weight:
(2) The following (C) 98 to 70% by weight and the following (B2)
A coextruded composite sheet comprising at least two base layers containing 2 to 30% by weight, wherein the thickness of the surface layer is 50 to 300.
An easily peelable composite sheet for a cover material, wherein the thickness of the base material layer is 250 to 1500 µm. (A) Polyolefin resin (B1) Modified polyolefin resin or modified polyolefin resin and styrene block copolymer (B2) Styrene block copolymer or styrene block copolymer and modified polyolefin resin (C) Styrene resin 2. The total weight of the resin components in each layer is 100% by weight.
% (A) 94-83% by weight of (A) and (B)
A surface layer containing 6 to 17% by weight of (1), (2) (C)
2. The easily peelable composite sheet for a cover material according to claim 1, comprising 90 to 84% by weight of (B2) and 10 to 16% by weight of (B2). 3. The 180-degree peel strength between the surface layer and the substrate layer is J.
15 to 300 g / 20 as measured by the IS-K6854 method
3. The easily peelable composite sheet for a lid material according to claim 1, wherein 4. A lid comprising the easily peelable composite sheet for a lid according to any one of claims 1 to 3. 5. The lid according to claim 4, which has a tab and a drinking spout. 6. A container having the lid according to claim 4. 7. A beverage container having the lid material according to claim 4.