JPH1158585A - Manufacture of laminated film and the laminated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To laminate films in the state of satisfactory combination of the films so far impossible to be satisfactorily laminated in the case of laminating the films by using a solventless type adhesive. SOLUTION: In the method for manufacturing a laminated film 33 comprising the steps of coating a first base material 31 with a solventless type adhesive 34, then press bonding it to a second base material 32 to laminate them, the adhesive 34 is used under the condition that coating viscosity becomes 50 cps or less, and the films are laminated. In the case of using a polyester film as the material 31 and aluminum vapor deposited polypropylene film as the material 32, as the adhesive 34, the adhesive having a viscosity of 500 cps or less at liquid temperature of 90 deg.C or lower is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a laminated film obtained by laminating two substrates with a non-solvent type adhesive, and particularly to a polyester film which has conventionally been considered to cause poor appearance. /adhesive/
The present invention relates to a method for producing a laminated film having a layer structure composed of an aluminum vapor-deposited polypropylene film and capable of suppressing occurrence of poor appearance.

[0002]

2. Description of the Related Art Conventionally, as a laminating method for obtaining a flexible composite packaging material, an adhesive dissolved in an organic solvent is applied to the surface of a plastic film, and the solvent is evaporated to a dry state by hot air or heating, followed by bonding. There is known a dry lamination method in which films to be laminated are laminated and heated and pressed. Although this method is more costly than the wet lamination method in which the adhesive is bonded while the adhesive is in a wet state, the bonding can be performed efficiently at a high speed, and the type of the adhesive and its application amount can be reduced. By selection, it can be applied to almost all films, so that various laminated films having various properties required for packaging materials can be produced.

FIG. 1 shows a schematic configuration of a laminator for performing the dry lamination method. In the figure, 1 is a first base material, 2
Is a second substrate, 3 is a laminated film, 4 is an adhesive, 5
Is a coating section, 6 is a drying zone, 7 is a laminating section, and 8 is a cooling roll. The outline of the dry lamination process will be described with reference to FIG. 1. After applying the adhesive 4 to the first substrate 1 through the coating portion 5 (generally employing a gravure coating method), the first substrate 1 ,
The first base material 1 is passed through a drying zone 6 to dry the adhesive 4 (generally, a hot-air spraying method at 80 to 120 ° C. is employed), and then the first adhesive which has become a tacky state through a drying step. By nipping the adhesive surface of the base material 1 and the second base material 2 with the rubber roll 7a and the heated metal roll 7b,
Thermocompression bonding at 80 ° C. Thereafter, it is cooled by a cooling roll 8 and wound up. The wound laminated film 3 is subjected to an aging treatment at a temperature of 35 to 45 ° C. in order to accelerate the curing of the adhesive.

[0004] Among the laminated films manufactured through such a process, those used as food packaging materials employ a film having a high elastic modulus, heat resistance and dimensional stability as an outer film, As the inner film, an aluminum vapor-deposited film having a heat sealing property that softens at a relatively low temperature and a gas barrier property for preventing a solvent from leaking to the contents side is employed. FIGS. 2 (a) and 2 (b) show a laminate film which occupies the mainstream as such a packaging material for food. In both films 11, 21, the inner films 12, 22 and the outer films 13, 23 are bonded together via the adhesive layers 14, 24, and the inner films 12, 22 are aluminum-evaporated polypropylene (VMCPP) films. The films 13 and 23 are a polyester (PET) film and a biaxially oriented polypropylene (OPP) film, respectively. Here, the PET film in the laminated film 11 of FIG. 2A has excellent heat resistance and dimensional stability, and has properties of high rigidity and high strength. Compared with the PET film for such properties, the OPP film is inferior, but has advantages such as excellent moisture proofness and low cost. Therefore, the laminated film 21 of FIG. It is frequently used for packaging and the like.

[0005] On the other hand, the dry lamination method using an adhesive containing an organic solvent as described above involves problems of environmental pollution, fire protection law, and solvent cost (e.g., equipment cost for the solvent) due to the organic solvent. ) And other problems. In the field of food packaging,
There is a background that a laminated film using a solvent-type adhesive has a residual solvent smell, which is not preferable. Therefore, in recent years, adhesives that do not contain organic solvents,
A so-called solventless adhesive is provided by a manufacturer, and a part of a food packaging material using a laminated film bonded via such an adhesive is on the market. Since this type of laminated film has various advantages such as energy saving, resource saving, environmental problems, and no residual solvent odor, a laminated film using a solventless adhesive is a laminate using a solvent type adhesive. It is thought that it will further increase in the future while coexisting with the film.

[0006]

By the way, a laminated film manufactured by a laminating method using a solventless adhesive containing no organic solvent (hereinafter referred to as a solventless type laminated film) has a finished appearance of a solvent. There is a problem that it is not good as compared with the type laminate film. In other words, a state in which minute spot-like defects are generated on both the ground and the printed surface immediately after lamination is often observed, and these poor appearances often disappear after aging treatment, but fine defect portions remain depending on the type of film. The packaging material may exhibit poor appearance. In order to suppress such appearance defects, various improvements have been made on the operation side at the laminating site, but they have not been completely resolved, and in fact, a laminate combining a specific film with less visible appearance defects The film, specifically, the OPP film and the VM shown in FIG.
Since the appearance defect is not conspicuous in the laminate film combining the CPP film, the combination of the OPP film and the VMCPP film is mainly used as the solventless laminate film. On the other hand, a typical laminated film in which a specific film with a poor appearance is conspicuous is a P film shown in FIG.
A laminated film combining an ET film and a VMCPP film is exemplified. In the film of this type, minute spot-like defects are not resolved in a visible state, and as a result, the appearance is poor and the film cannot be used as a packaging material at present.

Therefore, as a solventless type laminated film, a laminated film composed of a combination of an OPP film and a VMCPP film, whose appearance is inconspicuous, has become the mainstream. Heat resistance along with market expansion,
There has been a demand for development of a laminate film in which a VMCPP film is combined with a PET film having excellent dimensional stability, high rigidity and high strength. Also,
In the current printing and laminating workplace where solvent-type laminated film and solvent-free type laminated film production coexist in the same factory, the material, namely PET
If the film could be shared, there is a great merit in that costs could be reduced for the entire factory.
For these reasons, PET film and VM have been considered difficult in the food packaging market.
Even in the case of a solvent-free type laminated film made of a CPP film, there is a need to finish the appearance as poor as a solvent-free type laminated film of an OPP film and a VMCPP film.

Various causes have been considered for the occurrence of the above-described poor appearance. One of them is that the initial adhesive strength is low, so that a kind of adhesion unevenness occurs (the adhesive is misaligned, the adhesive is displaced, the entire surface is not uniformly adhered, etc.), and a spot-like defect is generated. There is also the idea that after bonding is completed, the adhesive between the films reacts with gas, moisture, etc., which has penetrated due to the air permeability of the film, causing spot-like defects, but these ideas are only hypothetical. It does not escape and has not been proven. Various operational improvements have been made as measures to suppress the appearance failure. Specifically, the operational aspect is improved in the first direction to increase the initial adhesive strength and secondly in the direction to guide the aging processing conditions to more appropriate ones. Here, the first measure is explained.
The coating viscosity (approximately higher than the adhesive applied by lamination using a solvent type adhesive), which is considered to be about ps, is further increased (specifically, the molecular weight is increased). By increasing the initial adhesive strength, uneven adhesion itself is prevented from occurring.

An object of the present invention is to provide a PET film and a VM.
The purpose of the present invention is to derive truly appropriate lamination processing conditions that do not cause appearance defects in a solvent-free type laminating film made of a CPP film. From the viewpoint that it is more realistic that the lead time until the shipping of the packaging material does not become longer, it is more realistic to improve the adhesive (especially the coating conditions). I proceeded with the policy.

Further, the present inventors have found that the adhesive strength as a packaging material is not affected by the magnitude of the initial adhesive strength through normal aging, and that the adhesive strength cannot be used as a packaging material (for example, when the product is shipped as a product). From the viewpoint that the situation that the film on the outer side of the packaging bag is peeled off does not occur (the adhesive strength after coagulation can sufficiently endure product use even if the initial adhesive strength is small), An attempt was made to derive appropriate processing conditions in a wide range of viscosities from a small value to a large value without being limited to a conventional coating viscosity of around 1000 cps or more.

[0011]

SUMMARY OF THE INVENTION From the above viewpoint, PET
In order to derive truly proper laminating conditions that do not cause appearance defects in a solvent-free type laminating film consisting of a film and a VMCPP film, we conducted intensive experimental research in the direction of increasing the coating viscosity, and found that there was a problematic laminate. Film (PET / adhesive / VMCPP)
Increasing the coating viscosity of the adhesive at least has no correlation with the tendency of the occurrence of minute spot-like defects as described above (the appearance defects are reduced even if the coating viscosity is increased from 1000 cps). In other words, it was found that the cause of the appearance defect was not due to insufficient adhesive strength of the adhesive.

[0012] Then, as a result of trying again in the direction of reducing the coating viscosity, the occurrence of poor appearance during bonding can be suppressed by lowering the coating viscosity of the solventless adhesive used for bonding. I found that. That is, it has been found that by setting a condition such that the coating viscosity is lower than a predetermined value, it is possible to perform bonding in a good state with a combination of films that has been considered impossible to bond. Was.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention, which has been deduced on the basis of the above findings, is to apply a solventless adhesive to a first base material,
In a method for producing a laminate film which is bonded to a base material by pressure bonding, the lamination is performed using a solventless adhesive under the condition that the coating viscosity is 500 cps or less.

When a polyester film is used as the first base material and an aluminum-deposited polypropylene film is used as the second base material, a solventless adhesive having a viscosity of 500 cps or less at a liquid temperature of 90 ° C. or less is used. Is preferred.

[0015]

EXAMPLES Lamination was carried out using an in-line laminator shown in FIGS. In FIG. 3, 31 is a first base material, 32 is a second base material, 33 is a composite film, 34 is a two-liquid mixed solventless adhesive, 35 is a coating part, and 36 is a laminating part. FIG. 4 shows a coating section 35 in FIG. 3 and an adhesive supply section 37 for supplying an adhesive 34 thereto.

The lamination process of this embodiment will be schematically described with reference to FIG. 3. The first base material 31 is passed through a coating section 35 (generally employing a four-roll coating method). After applying the adhesive 34 to the first base material 31, the second base material 32 is aligned with the adhesive surface of the first base material 31, and is nipped by a rubber roll 36 a and a heated metal roll 36 b to be heated and pressed at 40 to 65 ° C. Take up. The wound laminate film 33 is
Aging treatment is performed at a temperature of 35 ° C. to 45 ° C. in order to accelerate the curing of the adhesive.

The coating section 35 is an apparatus for applying an adhesive 34 whose viscosity has been adjusted to an appropriate value by heating to the first base material 31, and employs a known four-roll coating method as shown in FIG. The configuration includes, in order from the top, four rolls: a backup roll 35a (metal), a coating roll 35b (rubber), a metering roll 35c (metal), and an application roll 35d (rubber). An adhesive storage section is provided between the application roll 35d and the metering roll 35c, and a two-liquid mixed solventless adhesive 34 is supplied from the adhesive supply section 37 to the adhesive storage section. Then, the first base material 31 passes between the backup roll 35a and the coating roll 35b, and the adhesive 34 stored in the adhesive storage section is supplied to the first base material 3 via the metering roll 35c and the coating roll 35b.
1 is applied. Here, the backup roll 35a has a heating mechanism or the like, so that the temperature of the adhesive 34 applied to the opposite side of the first base 31 with the first base 31 therebetween can be adjusted. Further, by adjusting the interval between the rolls, the coating amount of the adhesive 34 (about 1 g / m ² ) can be adjusted.

Since the adhesive supply section 37 uses a two-liquid mixture type as the adhesive 34 this time, a system (tank, pump, piping for these) for supplying the main agent 34a of the adhesive 34 is used. 37b and a system (tank, pump, and piping thereof) 37b for supplying an auxiliary agent (hardening agent) 34b
And an application jig 37c for mixing and supplying the main agent 34a and the auxiliary agent 34b. Here, the application jig 37c is the application roll 35.
d and is located above between the metering roll 35c,
It has a structure capable of scanning in the width direction of both rolls, so that the viscosity of the adhesive 34 is reduced to some extent before supply to the adhesive storage section.

The above is the structure of the laminator using the two-liquid type non-solvent adhesive. In this embodiment, the first layer film to which the adhesive 34 is applied, that is, the first base material 31 is used. Is a PET (polyester) film, and a second layer film to be bonded thereto, that is,
An MCPP (aluminum-deposited polypropylene) film was used. This combination of films is a combination of films for which good bonding has been impossible in the past.

Then, several non-solvent type adhesives (A to C companies) were used, and the adhesives were bonded at different working temperatures, that is, at different coating viscosities. At the time of bonding, the tension applied to the two films 31 and 32 was 3 kg / cm ² , and the bonding speed was 200 m / min. And two films 3
1, 32 were laminated and wound up. Table 1 shows the results of observing the presence / absence of defective appearance in the laminated film thus manufactured.

[0021]

[Table 1]

As can be seen from Table 1, when bonding is performed under the condition that the coating viscosity is 500 cps or less,
No appearance defect occurred.

FIG. 5 shows the structure of a laminate film manufactured through the steps of the present invention. As for the structure, FIG.
And has the same layer configuration as the laminated film 11 described in
2 is an aluminum vapor-deposited polypropylene (VMCPP) film, and the outer film 43 is a polyester (PET) film. Here, the components of the adhesive layer 44 are shown in FIG.
This is different from the adhesive layer 14 of the laminate film 11 in (a), and is formed by solidifying a non-solvent type two-liquid mixed type adhesive.

For the adhesive, a coating viscosity of 50
It is an essential condition to have a property that can be suppressed to 0 cps or less.
PET coated with heated adhesive out of a single film
If the temperature of the film exceeds a certain temperature, the film may be deteriorated or shrink. Therefore, the coating viscosity is set to 500 cp at the upper limit of the temperature (90 ° C. for the PET film).
Adhesives that can secure s are preferable in that the heating range can be set wide.

In this case, the adhesives shown in Table 1 are also
An adhesive capable of satisfying these specifications is selected, and specifically, a mixture of "A-231" manufactured by Takeda Pharmaceutical Co., Ltd. as a main agent and "A-31" manufactured by Takeda Pharmaceutical Co., Ltd. as an auxiliary agent.

[0026]

As described above, according to the present invention,
When laminating a film with a solventless adhesive, the lamination is performed under the condition that the coating viscosity is 500 cps or less. The combination as a packaging base material has become possible.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a laminator that performs a conventional dry lamination method.

FIG. 2 is a configuration diagram of a laminated film manufactured by a conventional dry lamination method.

FIG. 3 is a schematic configuration diagram of a laminator used for carrying out the present invention.

FIG. 4 is a diagram showing a configuration around a coating part in the laminator of FIG. 3;

FIG. 5 is a configuration diagram of a laminated film manufactured by the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st base material 2 2nd base material 3 Laminate film 4 Adhesive 5 Coating part 6 Drying zone 7 Laminate part 8 Cooling roll 11,21 Laminate film 12,22 Inner film 13,23 Outer film 14,24 Adhesive layer 31 First base material 32 Second base material 33 Laminate film 34 Two-component mixed solventless adhesive 35 Coating part 35a Backup roll 35b Coating roll 35c Metering roll 35d Application roll 36 Laminating part 37 Adhesive supply part 41 Laminating film 42 Back side Film 43 Outer film 44 Adhesive layer

Claims (4)

[Claims] 1. A method for producing a laminate film in which a first base material is coated with a solvent-free adhesive and then bonded to the second base material by pressure bonding, wherein the solvent-free adhesive is applied under the condition that the coating viscosity is 500 cps or less. A method for producing a laminated film, comprising laminating using a mold adhesive. 2. A method for producing a laminate film, comprising applying a solventless adhesive to a first base material and then bonding the first base material to the second base material by pressure bonding. A method for producing a laminate film, comprising using an aluminum-evaporated polypropylene film as a substrate, and using a solvent-less adhesive having a viscosity of 500 cps or less at a liquid temperature of 90 ° C. or less. 3. A laminate film obtained by applying a solvent-free adhesive to a first base material and then bonding the first base material to the second base material by pressure bonding. A laminated film obtained by laminating using a solvent type adhesive. 4. A laminated film obtained by laminating a first base material and a second base material via a solventless adhesive,
A polyester film is used for the first base material and an aluminum-deposited polypropylene film is used for the second base material. The solventless adhesive has a viscosity of 500 cps at a liquid temperature of 90 ° C. or less.
A laminated film characterized by using the following.