JPH0155293B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a laminated material containing aluminum foil and polyolefin film with excellent workability.

In recent years, packaging materials, especially food packaging materials, and building materials, are often used as laminated materials that take advantage of the characteristics of multiple materials. In particular, polyolefins, which are hygienic and have heat sealability, are used as materials. The combination of film and aluminum foil, which has excellent barrier properties, is used as one of the most excellent food packaging materials.

However, since polyolefin film has poor adhesion to aluminum foil, polyurethane resin is generally used as an adhesive.
There are some problems, such as the possibility of low molecular weight compounds in polyurethane adhesives migrating to food, a reduction in commercial value due to foaming of the adhesive, and variations in adhesive strength. For this reason, it has been proposed to use an ionomer resin as the adhesive (patent application
52-116110).

Conventionally, methods for laminating a polyolefin film and aluminum foil using this ionomer resin include (1) a method in which the ionomer resin is previously formed into a film shape and then laminated by heating and pressurizing;
(2) Sand-German tiramination using a heated roller was considered. however,
Method (1) has economical and operational problems such as a large number of steps and the use of large amounts of expensive ionomer resin, while method (2)
Due to the high MI value of the ionomer resin, the fluidity of the resin changes drastically at the start of work or due to small changes in heating conditions, which causes the ionomer resin to spread too much and stick to the heating roller. This is an industrially unavoidable problem in which work-related accidents occur frequently in which the extruded resin breaks or the extruded resin breaks, significantly deteriorating work efficiency, and also easily causing variations in adhesive strength and increasing the defective rate. There was a problem that needed to be solved.

In view of the above-mentioned current situation, the inventors of the present invention have conducted intensive research on a method of using ionomer resin as an adhesive without causing any industrial problems, and have discovered that molten resin is one of the techniques for laminating dissimilar materials such as various plastic films. The first step is a method known per se called so-called side-deutsche lamination, in which a film is extruded between different materials from an extruder, cooled on a cooling roller, and rolled up. The inventors have discovered that a method of applying pressure while heating is extremely useful, leading to the present invention.

That is, the present invention involves bonding aluminum foil or an aluminum foil lined with a heat-resistant resin layer and a polyolefin film by sandwich lamination using a polyolefin composition prepared by heating and blending a carboxyl group-containing polyolefin and a metal compound as an adhesive. The object of the present invention is to provide a method for producing a laminated material, which comprises laminating the polyolefin composition in a cold state, and then heating and pressurizing the polyolefin composition to a temperature higher than the melting temperature.

In the present invention, the melt-extruded polyolefin composition is stably formed as a uniform layer through the first step of cold sandwich lamination as described above. However, in this first step alone, the adhesive force with the polyolefin film is a temporary bond that can be easily peeled off by hand, and it cannot be put to practical use as it is. Next, in a second step of applying pressure while heating the polyolefin composition of the intermediate adhesive layer to a temperature higher than the melting temperature, a desired laminate having high adhesive strength is obtained.

In the present invention, since aluminum foil generally has low mechanical strength, it is preferable to use one that is lined with a heat-resistant film such as polyamide or polyester in advance, and the heat-resistant resin layer and aluminum foil are preferably lined in advance. An appropriate printed layer may be formed between the layers. The structure of the laminate thus obtained is polyester (polyamide) layer/printed layer/aluminum foil/polyolefin composition adhesive layer/polyolefin film, with the polyester (polyamide) layer as the outer layer and the polyolefin film as the inner layer. It can be used as a flexible packaging material.

The polyolefin film used in the present invention is made from polyethylene, polypropylene, polybutene, ethylene-propylene copolymer, etc. by a conventional method and has a thickness of about 20 to 150 microns.

The polyolefin composition used as an adhesive in the present invention is a mixture of a carboxyl group-containing polyolefin and a metal compound under heating. Carboxyl group-containing polyolefins include olefinic monomers such as ethylene, propylene, or butene, and α,β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, and maleic anhydride. It is obtained by polymerization or graft polymerization. The amount of the α,β-unsaturated carboxylic acid is preferably 0.01 to 30 parts by weight per 100 parts by weight of the olefin component. If the amount is less than 0.01 parts by weight, the effect on adhesion will be weak, and on the contrary, if it is more than 30 parts by weight, no improvement in the effect on adhesion will be observed.

Metal compounds include carbonates, sulfates, acetates of sodium, potassium, magnesium, calcium, zinc, iron, aluminum, copper, nickel, etc.
Oxides, hydroxides, organic compounds, etc. are used. Note that metal compounds of magnesium and aluminum are preferred for food-related fields. The metal compound is blended in an amount of 0.05 to 10 parts by weight per 100 parts by weight of the carboxyl group-containing polyolefin. If less than 0.05 parts by weight is used, it is difficult to obtain high adhesive strength after contact with a hot roll for a short time; conversely, if more than 10 parts by weight is used, not only is no improvement in adhesive strength observed, but the polyolefin resin is When heated and melted, problems arise such as foaming, which makes it impossible to uniformly coat the base material, so it is unsuitable.

When synthesizing the polyolefin resin according to the present invention by heat compounding, a third compound such as polybutadiene, etc.
It is also possible to use components in combination. However, it is necessary to select a third component that does not adversely affect adhesive properties.

The polyolefin composition used as an adhesive in the present invention is prepared by heating the aforementioned carboxyl group-containing polyolefin and a metal compound to a temperature of about 120 to 220°C and uniformly mixing them for about 5 to 120 minutes.
Alternatively, it is also possible to heat and mix the polyolefin, α,β-unsaturated carboxylic acid, and metal compound simultaneously to carry out graft polymerization.

The laminate obtained by the present invention can be advantageously used as a packaging material for foods, etc. When used for retort foods, it is desirable to select high-density polyethylene or polypropylene, which has relatively high heat resistance, as the polyolefin.

The present invention will be explained in more detail below based on the drawings.

FIG. 1 is an example of a process diagram of an apparatus seen from a side view for explaining the method for manufacturing a laminate according to the present invention.

In FIG. 1, an aluminum foil 1, which may be lined with a heat-resistant resin layer, is transferred from an unwinding roller (not shown) to a cooling roller 3 via a guide roller 2, and a polyolefin film 4 is transferred from an unwinding roller (not shown) to a cooling roller 3. It travels from a delivery roller (not shown), passes through a guide roller 5, and comes into contact with a nip roller 6. The above-mentioned polyolefin composition used as an adhesive is heated and melted in an extruder (not shown), extruded from a T-shaped die 7 into a film, and passed between a cooling roller 3 and a nip roller 6 for about 1 hour.
A laminate 8 is obtained in which the aluminum foil 1 and the polyolefin film 3 are temporarily bonded together by applying pressure to ~5 Kg/cm ² .

Since the polyolefin composition is at a high temperature of 160° C. or more, the elastic rubber material on the surface of the nip roller 6 is heated and the surface becomes sticky, so a cooling back up roller 9 is brought into contact with the nip roller 6 to cool it. is preferred.

The cooling roller 3 or the cooling back-up roller 9 is cooled by a known method such as passing a coolant such as water inside.

The temporarily bonded laminate 8 is heated and pressed between a heating roller 11 and a nip roller 12 via a guide roller 10. In this case as well, it is better to install a cooling back-up roller 13 as well. The heating temperature is above the melting temperature of the polyolefin composition, i.e., approximately
120℃~130℃ or higher, preferably 140~250℃
The pressurization is approximately 0.2 to 5 kg/cm ² , preferably 1
~4Kg/ ^cm2 . The laminated material 14 heated and pressurized in this way is passed through appropriate steps such as reheating, pressurizing, pressurizing, pre-cooling, cooling, etc., as necessary, and is transferred from the guide roll 15 to the laminated material 14. take-up roller (not shown)
is wound up.

Examples are shown below. Parts in the examples are parts by weight.

Example 1 1.0 part of aluminum hydroxide was blended with 100 parts of a carboxyl group-containing polyolefin obtained by graft polymerizing about 0.2% by weight of maleic anhydride to polypropylene, thoroughly mixed with a Henschel mixer, and heated to 180°C. It is heated and melted in an extruder and taken out as pellets.

Using the equipment shown in Figure 1, 9μ aluminum foil lined with polyester film and
A polyolefin composition prepared by melting the above pellets into a 70μ polypropylene film at about 200 to 230°C was extruded through a T-shaped die. The peripheral speed of the cooling roller 3 is about 70 m/min, and each film has the same speed.
Water flows inside the cooling roller 3, and its surface temperature is approximately
It is 30℃.

The melt-extruded polyolefin composition was uniformly sanded, and there were no accidents such as extrusion or cutting, and the workability was good.

Thereafter, the adhesive strength of the laminated material, which was brought into contact with a heating roller 11 whose surface was heated to 220° C. for 0.5 seconds to be pressurized to approximately 0.5 kg/cm ² and allowed to cool, was approximately 1150 g/15 mm, which was sufficient adhesive strength.

On the other hand, the temperature of the cooling roller 3 in Fig. 1 is approximately 222℃.
When similar operations were performed using a heating roller, the polyolefin composition extruded due to a slight increase in the heating temperature at the start of work protruded, staining the heating roller or causing it to break, resulting in extremely poor workability. It was hot.

[Brief explanation of drawings]

FIG. 1 shows a process diagram of an apparatus viewed from the side for explaining the method for manufacturing a laminate according to the present invention, and the main symbols in the diagram are as follows. 1... Aluminum foil, 3... Cooling roller, 4
... Polyolefin film, 6, 12 ... Nip roller, 11 ... Heating roller, 9 ... Cooling back-up roller.

Claims (1)

[Claims] 1. Aluminum foil or aluminum foil lined with a heat-resistant resin layer and polyolefin film are laminated in cold by Sand-German lamination using a polyolefin composition prepared by heating and blending a carboxyl group-containing polyolefin and a metal compound as an adhesive. and then heating and pressurizing the polyolefin composition to a temperature higher than the melting temperature thereof.