JPS61134251A - Composite film for cover having improved transparency - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] In a packaging form in which a composite film lid is heat-sealed to a polystyrene tray, heat-sealing is generally used as a lid that has heat-sealing properties and is easy to open. Ethylene layer
Products using vinyl acetate copolymers or modified products thereof are known. However, the heat seal strength of this lid material is temperature dependent, and due to variations in seal strength that occur during packaging, the contents may leak due to shock or vibration during the distribution stage, or conversely, the seal strength may become too strong. This not only makes it difficult to open, but furthermore, the film is opaque, making it difficult to see the contents and lacking in freshness.

The present invention relates to an easy-to-open lid material that solves the above problems, that is, a first layer and a second layer co-extruded with the first layer are grown, and the first layer has a film thickness of 0. This invention relates to a composite film for lids with improved transparency, characterized in that it is a styrene-butadiene block copolymer with a diameter of 5 to 10μ, and the second layer is an ethylene-vinyl acetate copolymer or a modified product thereof. It is possible to form a lid that is heat-sealable to a container made of polystyrene and is easy to open.

The present invention will be explained below with reference to the drawings. FIG. 1 is a cross-sectional view showing a state in which a lid made of a composite film for lids according to the present invention is heat-sealed to a container, and FIG. 2 shows a state in which the lid made of a composite film for lids according to the present invention is opened. FIG.

The first layer 1 is a styrene-butadiene block copolymer having a thickness of 0.5 to 10μ. The styrene-butadiene block copolymer used in the present invention is preferably K Resin KRO5J manufactured by Nippon Steel Chemical Co., Ltd. .Polystyrene may be mixed in the first layer 1 if necessary.If the mixing ratio of polystyrene increases, the first N1 becomes brittle and tends to generate small pieces when peeled, so the mixing ratio of polystyrene is 95% by weight or less. The polystyrene used in the present invention is preferably ``Dick Styrene CR2500J'' manufactured by Dainippon Ink Chemical Co., Ltd. or ``Estyrene G-32J manufactured by Nippon Steel Chemical Co., Ltd.''.

The second Nz coextruded with the first layer 1 is an ethylene-vinyl acetate copolymer or a modified product thereof. The ethylene-vinyl acetate copolymer has a vinyl acetate content of 5 to 3.
0%, and as the vinyl acetate content increases, the peel strength tends to increase. The modified ethylene-vinyl acetate copolymer is one modified by blending rosin, petroleum resin, etc. The ethylene-vinyl acetate copolymer used in the present invention is "Ultracene" manufactured by Toyo Soda, Sumitomo "Ebatate" manufactured by Kagaku Co., Ltd. and "Difuxerm" manufactured by Dainippon Ink Chemical Co., Ltd. as the modified ethylene-vinyl acetate copolymer are suitable.

In the composite film for lids according to the present invention, an incyanato adhesive is used as the third layer 3 on the second layer 2 as necessary, and two-wheel stretched polyethylene terephthalate film, biaxially stretched polypropylene film, cellophane, aluminum, etc. A base material such as foil or paper may be laminated together, or a thermoplastic resin such as low density polyethylene, high density polyethylene, or polypropylene may be coextruded onto the second layer 2 together with the first layer 1 and the second layer 2. Alternatively, low density polyethylene may be melt laminated on the second layer 2, and then the base material may be bonded as a fourth layer using an isocyanate adhesive.

The thickness of the composite film for lids is generally preferably 40 to 100 microns.

The container 4 to which the lid composite film can be heat-sealed includes a tray having a flange 5 around the opening formed from a polystyrene sheet by vacuum forming, pressure forming, etc., and a tray formed from polystyrene by injection molding, etc. Containers such as cups having a flange 5 around the opening, containers such as trays having a flange 5 around the opening formed of a composite sheet such as a laminated sheet of polypropylene and polystyrene with the polystyrene surface as the inner surface, or expanded polystyrene containers etc. can be mentioned.

To heat seal the lid composite film to the container 4 as a lid,
The first layer 1 of the composite film for lid is adhered to the flange 5 of the container 4, and the pressure is 1 to 3 kg/c+J and the temperature is 140 to 24.
Heat sealing may be performed at 0° C. for 0.2 to 2 seconds.

When the lid heat-sealed to the container 4 is pulled upward, the first layer 1 and the second layer 2 are separated from each other in the heat-sealed area 6 as shown in FIG. 2, making the lid extremely easy to open. can do.

The glabellar peelable lid material of the present invention has reliable heat sealing properties because it is heat-sealed with the same resin as the other tray, and the glabellar peelable material is made of ethylene-vinyl acetate copolymer or its modified product. Therefore, the temperature dependence of the sealing strength is small and stable peeling strength can be obtained.Another effect of the present invention is that the tearing of the lid material reduces the energy that destroys the first layer of the heat-sealing layer, and furthermore, the peeling between the eyebrows. Because it requires energy to move, it is resistant to shock and vibration, and is effective in preventing accidents such as leaks during transportation. In addition, the composite film for lids according to the present invention can form lids that are easy to open even after being heat-sealed and boiled in hot water, so it can be used to store heat-solidified and heat-sterilized foods such as filled tofu and egg tofu. It can be suitably used as a lid for a container.

Next, the present invention will be specifically explained with reference to Examples.

Example 1 Styrene-butadiene block copolymer (Nippon Steel Chemical Co., Ltd. II K Resin KRO5, density 1.04 g/d, melt index 60) 251% by weight and polystyrene (Dainippon Ink Chemical Co., Ltd. Dick Styrene CR2500, density 1.05 g /-, melt index 27) 75% by weight
The first layer 1 with a film thickness of 3μ consists of a mixed system of ethylene-
l1lJ made of modified vinyl acetate copolymer (Dicktherm E L 8B manufactured by Dainippon Ink Chemical Co., Ltd., density 0.94 g/aj, melt index 12, melting point 80°C)
1.10μ second layer 2 and low density polyethylene (density 0
．． 920g/aj, melt index 7.0, melting point 1
A coextruded three-layer film having a third layer 3 having a thickness of 25 μm and consisting of 0.05° C.) is produced. The third coextruded three-layer film
After corona discharge treatment was applied to the surface of layer 3, an isocyanate adhesive (main agent manufactured by Dainippon Ink Chemical Co., Ltd., EPS-415,
Using a two-component adhesive with hardening agent KT-75, the film thickness is 1.
Two-wheel stretched polyester film having a diameter of 2μ is laminated to form a composite film for a lid.

Sheet made of styrene-butadiene copolymer (thickness 2
fi) on the periphery of the opening formed by secondary molding using a vacuum forming machine.
Soy milk 15 is placed in a square tray 4 having a flange 5 of 11 cm.
0g, the first layer 1 of the composite film for lid is brought into contact with the flange 5 of the square tray 4, and the temperature is 210, 220, 23.
Heat sealing is carried out under the conditions of 0 or 240°C, a pressure of 2 kg/csi, and a time of 1 second. Square tray 4 containing this soy milk
When the lid was sterilized by boiling at 85° C. for 1 hour, and then cooled at 15° C. for 1 hour, the lid could be opened cleanly, as shown in FIG. 2, with no remaining lid pieces or tears.

In addition, the peel strength before boiling and after boiling cooling under the conditions of temperature 23°C, tensile speed 300 m/win %, sample width 15 cranes, and 180' peeling is as follows, and both have easy opening properties. Ta.

As a comparative example, styrene-butadiene graft copolymer (
Dick Styrene GH6300 manufactured by Dainippon Ink Chemical Co., Ltd.
, density 1.05 g/c+J, melt index 1
1) and modified ethylene-vinyl acetate copolymer (Example 1)
(same as in Example 1) and low density polyethylene (same as in Example 1), a first layer 1 with a thickness of 3μ made of a styrene-butadiene graft copolymer, and a modified ethylene-vinyl acetate copolymer. A coextruded three-layer film is produced having a second layer 2 having a thickness of 10μ and a third layer 3 having a thickness of 25μ made of low density polyethylene. After corona discharge treatment of the surface of the third layer 3 of the coextruded three-layer film, the film thickness was 12 μm using an isocyanate adhesive (same as in Example 1).
The two-wheel stretched polyethylene terephthalate film is laminated to form a composite film for a lid.

A comparison of the transparency of the composite film for lids according to the present invention and the composite film for lids of the comparative example is as follows:
The composite film for lids according to the present invention had extremely excellent transparency.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a lid made of a composite film for lids according to the present invention heat-sealed to a container, and FIG. 2 is a sectional view showing a lid made of a composite film for lids according to the present invention in an unsealed state. FIG. 1-----1st layer, 2-----1st layer.

Claims (1)

[Claims] The composite film for lids has a first layer and a second layer coextruded with the first layer, and the first layer has a film thickness of 0.5 to 10 μm.
is a styrene-butadiene block copolymer of
A composite film for a lid with improved transparency, characterized in that the layer is an ethylene-vinyl acetate copolymer or a modified product thereof.