JPS60171147A - Laminate - 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 The present invention has excellent transparency, hygiene and gas barrier properties,
The present invention relates to a laminate useful as a packaging film for foods, drinks, medicines, etc.

Conventional flexible packaging materials for foods have various strict requirements depending on the purpose, such as hygiene, gas barrier properties, moisture proof properties, ultraviolet barrier properties, water resistance, and hot water resistance. In order to meet these demands, a laminated film made of 41 materials laminated is used.

BACKGROUND OF THE INVENTION Polyester films, particularly bolier and ethylene terephthalate films (hereinafter also referred to as PET), are widely used as food packaging materials because of their excellent properties. but.

It is used as a laminated film formed by forming a redene shoulder by coating, or laminating aluminum foil, polyvinyl alcohol film, or saponified ethylene/vinyl acetate copolymer film.

However, aluminum foil has drawbacks such as the inability to see the contents, which reduces the attractiveness of the product, and the method of forming a polyvinylidene chloride layer by coating has problems in terms of workability, so recently Laminated films in which a saponified layer of ethylene/vinyl acetate copolymer is provided on PET have come into use. However, P.E.
T and saponified ethylene/vinyl acetate copolymer cannot be laminated without the use of an adhesive, and the commonly used urethane adhesives require an aging period after adhesion. Problems remain, including the possibility of low molecular weight compounds migrating into food.

The present invention aims to solve the problems of the laminate of PET and saponified ethylene/vinyl acetate copolymer as described above, and to laminate the laminate without using an adhesive. That is, the present invention provides a laminate in which a polyester sheet is subjected to low-temperature plasma treatment, and a saponified ethylene/vinyl acetate copolymer layer is laminated on the treated surface.

In the present invention, the polyester film is preferably commercially available as polyethylene terephthalate, and may be an unstretched film or a uniaxially or biaxially stretched film.

In the present invention, the ethylene content of the saponified ethylene/vinyl acetate copolymer is 20 to 50 mol%.

Those having a degree of saponification of 90% or more are preferred from the viewpoint of gas barrier properties.

In the present invention, the conditions for low temperature plasma treatment include l
Discharge value of 100 W or more, 0.01 seconds, preferably t L < Ha 0.
It is about 1 to 10 seconds. Note that low-temperature plasma is plasma caused by gas glow discharge under a gas pressure lower than atmospheric pressure, and is completely different from the energy rays emitted from high-temperature plasma, which is known from Japanese Patent Application Laid-Open No. 14759/1983. In the invention, as a method for laminating a saponified ethylene/vinyl acetate copolymer layer on a polyester sheet that has been subjected to low-temperature plasma treatment,
The most common method is to melt the saponified vinyl acetate copolymer and extrusion laminate it, but the saponified ethylene/vinyl acetate copolymer is processed into a film or sheet, and if necessary, it can be used on one or two wheels. There is a method of stretching and heat-sealing lamination.

Since the laminate according to the present invention has almost the same stretchable temperature range for polyester (polyethylene terephthalate) and saponified ethylene/vinyl acetate copolymer, the laminate is further subjected to uniaxial or biaxial stretching treatment. Is possible. Stretching treatment can improve mechanical strength, gas barrier properties, and further improve moisture permeability.
It has been confirmed that there is no problem with adhesion.

Further, this laminate can be used as a material for squeeze-molded containers for foods such as miso and mayonnaise by a known method such as vacuum forming.

It is obvious that the laminate of the present invention can be used as a composite film or sheet in which other packaging materials are further laminated as required.

For example, polyolefin, nylon, or the like can be further laminated on the saponified ethylene/vinyl acetate copolymer layer of the laminate of the present invention with or without a known adhesive. in this case.

As the adhesive, a urethane adhesive, a carboxyl group-containing polyolefin, or a polyolefin adhesive further blended with a metal compound can be used.

Example 1 Unstretched polyethylene terephthalate sheet (thickness 10
10-2T on 100u, 350W, 0.1 seconds
A low-temperature plasma treatment was performed in a nitrogen gas atmosphere. On this treated surface, a saponified ethylene/vinyl acetate copolymer (EVAL EPE-101, trade name, (■Kuraray) was laminated with XTR-SILON to a thickness of 150 μm using a conventional method.The adhesive strength of this laminate was T-type. As a result of measurement using a peeling method, it was 2 kg/cm or more.

Furthermore, if this laminate is biaxially stretched to approximately 9 times the area ratio, a sheet with excellent transparency can be obtained, the adhesive strength of this sheet is 1.5 kg/am, and the oxygen gas permeability is Oi 1
'ml/trr, 24hr, fresh at 25°C.

Example 2 Two-wheel stretched polyethylene terephthalate sheet (thickness 1
2 μm) was subjected to low-temperature plasma treatment in 120 Torr argon gas at 350 W for 1 second. A uniaxially stretched 7 ethylene/vinyl acetate copolymer saponified film (thickness 15 μrn) was applied to this treated surface.

Eval EF-! I, product name, ■Kuraray) 180
℃.

Heat seal lamination was performed at a linear pressure of 5 kg/■.

The adhesive strength of the obtained laminate was 1.5 kg/cm.

Example 3 In the same manner as in Example 1, an unstretched polyethylene terephthalate sheet was subjected to low-temperature plasma treatment, and a saponified ethylene/vinyl acetate copolymer was extrusion laminated on the treated surface. The saponified polymer layer was heat-sealed at 180°C and a linear pressure of 5 kg/cm with the treated surfaces of unstretched polyethylene terephthalate sheets that had been subjected to the same low-temperature plasma treatment facing each other to form a 3-layer laminate. Obtained. This laminate was pressure-molded at 120° C. to obtain a cylindrical container with a diameter of 7 cm and a depth of 12 cm.

The interlayer adhesion strength of the wall of this container is 1.85 kg/
ctm, and the oxygen gas permeability is 0.8 ml/rr
r, 24 hr, 25°C.

Example 4 A carboxyl group-containing polyolefin (Liocene M-1063, trade name, Toyo Ink ■) was added to the saponified ethylene/vinyl acetate copolymer layer of the laminate obtained in Example 2 to a thickness of 10 μm and an unstretched polypropylene film ( thickness 7
0μm, Torefan 3701゜Product name, Toshigren) 3
The layers were heat-sealed and laminated at 180° C. and a linear pressure of 5 kg/c111 to obtain a laminate.

The oxygen gas permeability of this laminate is 0.1 ml/nr
, 24 hours at 25°C, and a 4% acetic acid aqueous solution was filled into a flat bag made by a conventional method using this laminated sheet I.

After retorting at 125℃ for 10 minutes, the interlayer adhesion strength was 1.
．． It was 3 kg/cm.

patent applicant Toyo Ink Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. A laminate obtained by subjecting a polyester sheet to low-temperature plasma treatment, laminating a saponified ethylene/vinyl acetate copolymer layer on the treated surface, and uniaxially or biaxially stretching as required.