JPH0789019A - Liquid packaging laminated film and production thereof - Google Patents

Abstract

PURPOSE:To obtain a laminated film having excellent interlaminar strength between a polyester film being a base material and a heatsealing layer without using an anchor coating agent, excellent in content resistance and reduced in the contamination of packed content with an offensive smell such as a polyethylene smell. CONSTITUTION:A liquid packaging laminated film 3 is constituted by laminating an ethylene/methyl acrylate copolymer resin 1 to a polyester film 5 and produced by extruding the ethylene/methyl methacrylate copolymer resin 1 in a molten state at 300 deg.C or less to form a film and spraying air containing 1g/Nm<3> or more of ozone on at least the bonding surface of the molten extruded film under a condition of 0.5Nm<3>/hr or more before laminating the film 3 to the polyester film 5.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a laminated film for liquid packaging and a method for producing the same. For more details,
It has excellent interlayer adhesion without using an anchor coating agent or adhesive, and when used as a packaging bag, it has excellent resistance to various contents when filled with contents, especially liquids, and has less polyethylene odor. TECHNICAL FIELD The present invention relates to a laminated film and a manufacturing method thereof.

[0002]

2. Description of the Related Art Polyester films, especially biaxially stretched polyethylene terephthalate films, have various properties such as mechanical properties, dimensional stability, heat resistance, cold resistance, transparency, chemical resistance and oil resistance. It is used as a packaging material in many fields, including food packaging.

Further, when the polyester film alone cannot satisfy the required physical properties as a packaging material, various resin films,
Various laminated films satisfying the required physical properties by laminating paper, metal foil or the like are used as a substrate. For example, a typical example of such a laminated base material is an aluminum foil / polyester film.

Further, depending on the packaging application, it is often used as an inner layer material for a packaging container or a bag-shaped packaging material, and therefore it is necessary that the packaging material has a heat-sealing property. Therefore, as a heat seal layer, low density polyethylene, medium density polyethylene, linear low density polyethylene or ethylene-
A laminate film obtained by extrusion laminating a polyethylene resin film typified by a vinyl acetate copolymer on the inner surface of a substrate film such as the polyester film and a method for producing the same have been widely used.

Here, the extrusion laminating method is, for example, various resin films, paper, metal foil, or a laminated film of these is used as a base material, and molten resin such as polyethylene and polypropylene is extruded from an extruder to form a film. It is a method of forming a film and press-bonding and laminating to the various base materials. That is, the extrusion laminating method is a method in which one resin, in this case a polyethylene resin, is melted and heat-bonded to the base material.

However, when the polyethylene resin is melt-extruded and laminated on the polyester film, the polyester film has no affinity for both because of its crystallinity and the polyethylene resin film for its inertness, and both films are not compatible with each other. There is no mutual heat fusion property even if extrusion lamination is performed as it is.

Therefore, in extrusion lamination of polyethylene resin, polyethylene resin is usually used at 310 ° C.
A method of melt-extruding at the above high temperature, oxidatively activating the surface by contact with air, and further pressure-bonding and laminating to a base material subjected to anchor coat treatment is often used.

However, when the polyethylene resin is melt-extruded at a high temperature of 310 ° C. or higher, the polyethylene resin is decomposed and an offensive odor called polyethylene odor is generated due to the generation of low-molecular substances. There was a problem as a packaging material.

In order to solve this problem, a low-density polyethylene resin is extruded at a temperature of 260 ° C. or lower, and a gas containing ozone of 1 g / m ³ or more on at least one side of a molten film is added at a rate of 50 ml / m ² or more. A method for producing a laminated film by spraying with, and then superposing the anchor coat layer surface of another base material sheet for packaging material having an anchor coat layer and the ozone-treated surface of the low-density polyethylene resin film in close contact with each other, Is disclosed. (JP-A-57-102318)

However, also in the above-mentioned case, the base material subjected to the anchor coat treatment is used.
Examples of the anchor coating agent used in the anchor coating treatment described here include isocyanate-based, organic titanate-based, polyethyleneimine-based, polybutadiene-based resins, etc., but in terms of performance such as water resistance, moisture resistance, and boil resistance. The isocyanate-based anchor coating agent is most often used because it is excellent and has a wide range of applications.

However, the isocyanate-based anchor coating agent requires an aging period of at least about 24 to 48 hours, and since an organic solvent such as ethyl acetate, toluene, methyl ethyl ketone is used as a diluent, the solvent may evaporate. When the working environment is deteriorated, disaster prevention problems occur, and when the adhesive is not sufficiently dried, these organic solvents may remain in the laminate film and cause odors to the packaging contents, or the organic solvent. There are many problems such as the cost increase due to the use of, and improvements have been desired.

Further, when the laminated film thus obtained is filled and packaged with a liquid food containing components such as water, edible oil, alcohol, etc., as a content, from the heat-sealing resin layer in contact with the content, Since these components have the property of easily permeating, they are used to bond the adhesive interface by these permeable contents, that is, to bond the interlayer of the polyester film of the base material and the polyethylene resin of the heat seal resin layer. Since the above-mentioned anchor coating agent is corroded, it is pointed out that there are problems such as elution of components of the anchor coating agent and deterioration of adhesive strength between layers of the laminated film over time, and eventually delamination. Became.

In particular, for these volatile and highly permeable contents, a metal foil, mainly an aluminum foil, is often used in the packaging material composition in order to provide a barrier property. By blocking the permeation of the extremely active contents of the aluminum foil with the aluminum foil, a large amount of these contents are accumulated at the adhesive interface of the packaging material existing on the content side of the aluminum foil. Under the present circumstances, the presence of the anchor coat layer inevitably causes elution of the anchor coat agent component and deterioration of the adhesive strength.

Therefore, regarding such a problem,
With the advancement of high-grade packaged foods, reduction in odor packaging due to realization of genuine products, and diversification of packaged foods, development of a laminated film that solves these points has been strongly desired.

[0015]

As described above, in the production method of extruding and laminating the polyester resin surface of the conventionally used polyester film or the laminated film containing the film and the polyethylene resin, the use of the anchor coating agent is used. The taste and odor of package contents due to odor and polyethylene odor have been pointed out severely, and with the recent diversification of package contents, foods that easily penetrate through the polyethylene resin film of the inner layer In the present situation, it is difficult not only to deteriorate the taste but also to maintain a sufficient adhesive strength for a long time in some cases.

The present invention has been made in view of the above circumstances, and in order to solve such a problem, the polyester film as a base material and the polyethylene as a heat seal layer are used without using the anchor coating agent. It has excellent interlayer adhesion strength with the system resin, and has excellent content resistance to liquid contents containing components such as water, alcohol, oil, etc. that easily penetrate through the heat seal resin layer. An object of the present invention is to provide a laminated film in which the odor of the package contents due to the like is less and a method for producing the same.

[0017]

In order to solve the above-mentioned problems, the present invention provides a liquid packaging laminate in which an ethylene / methyl acrylate copolymer resin is laminated on a polyester film or a laminate film provided with a polyester film on the joint surface. It is a film. Further, the present invention is a packaging laminate film in which a polyethylene resin is melt-extruded and laminated on a base material made of either a polyester film or a laminate film provided with a polyester film on a joint surface, wherein the polyethyleneene resin is ethylene. -Methyl acrylate copolymer resin, which is melt-extruded at a temperature of 300 ° C or lower,
The film is formed into a film, and air containing 1 g / Nm ³ or more of ozone is blown onto at least the joint surface of the melt extruded film under the condition of 0.5 Nm ³ / hr or more, and then the polyester film surface of the substrate is treated with ozone. A method for producing a laminated film for liquid packaging, which comprises laminating the melt-extruded film having been subjected to pressure bonding.

The polyester in the present invention is a general term for a polymer containing an ester group obtained by a condensation method of a dicarboxylic acid and a diol component. Examples of the dicarboxylic acid component include terephthalic acid, adipic acid, sebacic acid, 2, Examples thereof include 6-naphthalenedicarboxylic acid and cyclohexanedicarboxylic acid. As the diol component, ethylene glycol, 1,4-butanediol, diethylene glycol, triethylene glycol,
Examples include neopentyl glycol, cyclohexanedimethanol, polyethylene glycol and the like. Also,
It may be a copolymer obtained from two or more kinds of dicarboxylic acids or diols, or a copolymer of other monomers or polymers. A typical example is polyethylene terephthalate composed of terephthalic acid and ethylene glycol.

The polyester film 5 as a base material of the laminated film of the present invention is a film formed from the above polyester, which is usually biaxially stretched and has a thickness of about 1 to 200 μm. Further, the surface to be laminated of the polyester film may be previously subjected to corona discharge treatment. Alternatively, when extrusion lamination is performed, the surface to be laminated of the polyester film 5 may be subjected to corona treatment in-line.

A laminated film having the above-mentioned polyester film 5 on the joint surface may be used as the base material. Such a laminated film 2 is obtained by laminating the polyester film 5 and a metal foil, a resin sheet, or a vapor deposition film of metal or inorganic oxide,
Alternatively, a film obtained by directly depositing a metal or an inorganic oxide on the polyester film 5 can be used.

As the metal foil, aluminum foil, gold foil,
Examples are silver foil and copper foil. As the resin sheet, nylon resin, cellophane, polypropylene resin,
Examples thereof include polycarbonate resins, polyester resins, polystyrene resins, and films obtained by coating these resins with vinylidene chloride resin. The thickness of the metal foil and the resin sheet is preferably about 10 to 200 μm. As the vapor deposition film, aluminum, gold, silver,
Metals such as copper and tin, and alloys containing these metals, and inorganic oxides such as silicon oxide, magnesium oxide and aluminum oxide, which are vapor-deposited on the above resin sheet and polyester film, can be used. The thickness of this vapor deposition is suitably in the range of 100 to 2000Å. Typical examples of these laminated substrates include polyester / aluminum foil constructions used as liquid food packaging, barrier packaging and the like.

When the laminate film 2 is used as the base material and a material having a high barrier property such as a metal foil is used as in the above example, the polyester film 5 used as the base material is provided with a modified layer on the surface thereof. Care should be taken in using the coated type. Since such a modified layer is generally coated with a water-based substance, the modified layer itself has a weak content resistance, so that it is laminated with a film having a high barrier property, so that the permeated content is a barrier film. This is because when the barrier is covered by the particles and the amount of accumulation in the interior increases, contamination of the modified layer with the contents easily proceeds, and finally the adhesion strength between the layers deteriorates. Therefore, when using such a polyester film, it is necessary to confirm the content resistance of the modified layer before use.

The ethylene / methyl acrylate copolymer resin 1 according to the present invention is a resin obtained by copolymerizing ethylene and methyl acrylate. As this ethylene / methyl acrylate copolymer resin 1, it is necessary that extrusion laminating can be performed by the extruder 10.
Therefore, the density is 0.930 to 0.942 g / cm3,
MFR of 2 to 9 g / 10 minutes and methyl acrylate content of 6.5 to 20% can be used.

When the content of methyl acrylate is 20% or more, when it is extruded from the extruder 10, it becomes sticky and easily sticks to the cooling roll 30, resulting in poor workability. On the other hand, if it is 6.5% or less, the adhesion to the base material 2 cannot be expected.

The extruder 10 for extruding the ethylene / methyl acrylate copolymer resin 1 is not particularly limited, and a general resin sheet molding extruder can be used. Further, since the ethylene / methyl acrylate copolymer resin 1 has a weak adhesive property with a metal, an ethylene copolymer resin used for other extrusion lamination, for example, an ethylene / acrylic acid copolymer resin, an ionomer resin, ethylene.・ Compared to methacrylic acid copolymer resin, etc., the resin can be easily exchanged after use, and since it does not corrode the metal inside the extruder, it is a resin that is extremely excellent in terms of extrusion processability and economy. .

The extrusion temperature when melt-extruding the ethylene / methyl acrylate copolymer resin 1 from the extruder 10 is preferably 300 ° C. or less, more preferably 2
It is in the range of 00 to 300 ° C. When the extrusion temperature is 200 ° C. or lower, the viscosity is high to extrude the resin, and a large load is applied to the extruder 10, and it is difficult to stably form the molten resin 1 into a film. Furthermore, since the wettability of the molten resin 1 is low, it is not possible to obtain sufficient adhesive strength with the base material 2. On the other hand, when the temperature exceeds 300 ° C., the molten resin 1 is highly oxidized, and the polyethylene odor generated from the resin is accordingly increased, so that the taste and odor of the package contents are impaired. The extrusion thickness at this time is usually 10 to 2
It may be about 00 μm.

The ozone treatment of the ethylene / methyl acrylate copolymer resin 1 is performed by extruding the resin in a film shape from the extruder 10 and then forming a molten resin 1 in the gap between the resin 2 and the base material 2 to be laminated (called an air gap). Toward at least one surface to be laminated with the base material 2 of
This is done by blowing a gas containing ozone.
The ozone-containing gas is directed from a nozzle or slit-shaped outlet 40 installed in the air gap below the T-die of the extruder 10 toward the extruded molten resin surface or a laminated portion with the base material. To be sprayed.

The ozone concentration in the sprayed gas is 1
g / Nm ³ or more, the blowing amount is desirably 0.5 Nm ³ or more per unit time. However, if the ozone concentration is made too high, it is effective in improving the adhesive strength, but there is a risk that the ozone treatment will be performed on the opposite surface of the resin surface to be subjected to ozone treatment. Due to this phenomenon, when the laminated film 3 is taken up by the take-up roll 60, the non-adhesive surfaces are also adhered to each other, which causes a defective phenomenon called blocking. Furthermore, when the ethylene / methyl acrylate copolymer resin 1 is heat-sealed to form a bag-like shape, oxidation of the sealing surface causes deterioration of the sealing property, and excessive ozone supply causes toxicity to the surrounding environment. Since there is a concern that some ozone will be scattered, it is desirable to perform extrusion laminating at an ozone concentration that matches the size of the extruder 10.

Further, if the amount of ozone sprayed is increased too much, the extrudability deteriorates due to the film sway of the extruded molten resin film due to the increased air flow, and the wettability decreases due to the cooling of the molten resin 1. Since the adhesiveness with the material 2 may be deteriorated, it is desirable to avoid excessive supply of ozone.

Further, ozone-containing gas is blown from both sides of the extruded ethylene / methyl acrylate copolymer resin 1, one of them is laminated with the substrate 2, and the other is heat-sealable resin film 80, for example, polyethylene resin film. It is also possible to laminate with sandwich. (Fig. 3) At this time, the ethylene / methyl acrylate copolymer resin 1 and the other polyethylene-based resin are the same kind of film, so that they easily adhere to each other without using an anchor coating agent, but at a temperature of 300 ° C or lower. Since the ethylene / methyl acrylate copolymer resin 1 is extruded, there is some concern about wettability and activation of the film surface necessary for adhesion. Therefore, it is effective to perform ozone treatment in order to obtain stronger adhesion. In this case, the extrusion thickness of the ethylene / methyl acrylate copolymer resin 1 is 5 to 50.
It is suitable that the thickness of the resin film that can be heat-sealed be approximately 10 μm to 200 μm.

Further, after the ethylene / methyl acrylate copolymer resin 1 and the base material 2 are extrusion-laminated, the heat-sealable resin 80 may be extrusion-laminated on the surface of the ethylene / methyl acrylate copolymer resin. The heat-sealable resin in this case can be extruded by an extruder, and can be bonded without using an ethylene / methyl acrylate resin and an anchoring agent, low density polyethylene, medium density polyethylene,
It is desirable to use a polyethylene resin such as linear low density polyethylene.

The laminated film 3 thus obtained is put into practical use by heat-sealing the heat-sealing layers of the polyethylene resins to form a bag and filling and packaging the contents. It

[0033]

EXAMPLES The present invention will now be described in more detail with reference to examples. <Example 1> Using a device as shown in FIG. 2, an aluminum foil having a thickness of 7 μm and a biaxially stretched polyethylene terephthalate film having a thickness of 12 μm (E5100 manufactured by Toyobo Co., Ltd., single-sided corona treatment) were used as a substrate. The laminated film 2 of No. 1 was unwound from the unwinding roll 60, and the surface of the polyethylene terephthalate film to be the joint surface was subjected to corona discharge treatment by the corona discharge treatment device 50 in-line. On the other hand, the density is 0.940 g / c
An ethylene / methyl acrylate copolymer resin having m ³ , MFR of 6 g / 10 min, and methyl acrylate content of 20% was extruded into a film form from a T-die of the extruder 10 under the conditions shown in (Table 1), and a melt extruded film. Toward one side of
The ozone treatment was performed by blowing air having an ozone concentration of 15 g / Nm ^{3 at} a flow rate of 1 Nm ³ / hr by an ozone treatment bar 40 installed at a position of about 20 mm below the die. Then, the ozone-treated surface of the molten resin film and the biaxially stretched polyethylene terephthalate film surface of the laminated base material are pressure-bonded laminated between a cooling roll 30 (having a matte surface) and a nip roll 20 (made of silicone rubber). Then, a laminated film 3 as shown in FIG. 1 was obtained.

Ethylene of the obtained laminated film
As a heat-sealing layer on the methyl acrylate copolymer resin surface, a density of 0.916 g / cm ³ , MFR of 12 g
A linear low density polyethylene (15100C manufactured by Mitsui Petrochemical Industry Co., Ltd.) for 10 minutes was extruded and laminated under the conditions shown in (Table 2) to obtain a laminated film for evaluation. By heat-sealing the linear low-density polyethylene resin layers of this laminated film, 10
A bag having a size of 0 × 100 mm was prepared. The heat sealing conditions are 160 ° C., 2 kgf / cm ² , and 1 second.

The contents were filled in the obtained bag under the conditions shown in (Table 3) and stored, and the biaxially stretched polyethylene terephthalate film of the base material and the ethylene / methyl acrylate copolymer resin laminate were aged over time. The interlayer adhesion strength with the film (g / 15 mm) and the heat seal strength between the laminated films (kg / 15 mm) were measured. The results are shown in (Table 4).

From Table 4, according to Example 1, high adhesive strength and heat seal strength are maintained without using an anchor coating agent for various liquid contents, and the content resistance is extremely high. It can be said that it is an excellent packaging material. In addition, sensory tests for odors were performed during the extrusion laminating process and after the extrusion laminating process, and the results were good.

Example 2 The same as Example 1 except that the substrate was changed to a single layer of biaxially stretched polyethylene terephthalate film having a thickness of 12 μm instead of the laminated film of aluminum foil and biaxially stretched polyethylene terephthalate film. A laminated film was produced under the conditions and the same evaluation was performed. The results are shown in (Table 4). Example 1
Similarly, it can be seen that the high content resistance is maintained without using the anchor coating agent.

Comparative Example 1 A laminated film was prepared under the same conditions except that the ozone treatment was not carried out in Example 1, and the same evaluation was carried out. The results are shown in (Table 4).
In Comparative Example 1, although the initial strength is sufficiently high without using the anchor coating agent, the adhesive strength between layers and the heat seal strength are deteriorated due to the influence of the permeation of the contents with the passage of time, and the packaging is shown. As a material, unsatisfactory results were obtained regarding the content resistance.

<Comparative Example 2> Instead of the ethylene-methyl acrylate copolymer resin shown in Example 1, a density of 0.
Laminated films were prepared under the same conditions except that a linear low-density polyethylene resin having 916 g / cm ³ and MFR of 12 g / 10 min was used, and evaluated. The results are shown in (Table 4). In Comparative Example 2 as well, the adhesive strength between layers and the heat seal strength were decreased in various contents with the passage of time, and sufficient content resistance as a packaging material was not obtained.

Comparative Example 3 Ethylene shown in Example 1
Density instead of methyl acrylate copolymer resin;
A laminate film was prepared under the same conditions except that an ethylene / methacrylic acid copolymer resin having 940 g / cm ³ , MFR; 8 g / 10 min, and methacrylic acid content; 9 wt% was used, and the evaluation was performed. The results are shown in (Table 4).
In Comparative Example 3, it can be seen that the content resistance is not sufficient.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

[Table 4]

[0045]

As described above, when the laminated film of the present invention is used, good adhesive strength is exhibited without using an anchor coating agent, and when the contents are packed and packaged in the form of a bag, the strength is improved with time. The packaging material has little deterioration in content, and has extremely excellent content resistance, especially resistance to liquid foods containing components such as water, alcohol and oil that easily penetrate through the heat seal resin layer. Can be obtained. This makes it possible not only to maintain the required physical properties as a packaging material, but also to eliminate the risk of elution of the anchor coating agent component or residual solvent component into the packaging contents, and to improve the taste and odor of the contents. It is possible to obtain an excellent laminate film for packaging which is capable of preventing deterioration in terms of surface quality, and makes a great contribution to the field of packaging materials.

[0046]

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing an embodiment of a packaging laminate film of the present invention.

FIG. 2 is a schematic explanatory view showing an example showing a production line for a laminated film of the present invention.

FIG. 3 is a schematic explanatory view showing another embodiment showing the production line for a laminated film of the present invention.

[Explanation of sign]

 1 ... Ethylene / methyl acrylate copolymer resin 2 ... Base material 3 ... Laminate film 4 ... Metal foil, various resin sheets, vapor deposition film, etc. 5 ... Biaxially oriented polyethylene terephthalate film 10 ... Extruder 20 ... Nip roll 30 ... Cooling roll 40 ... Ozone treatment bar 50 ... Corona discharge treatment device 60 ... Unwinding roll 70 ... Winding roll 80 ... Heat sealable resin

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Claims (2)

[Claims] 1. A laminated film for liquid packaging in which an ethylene / methyl acrylate copolymer resin is laminated on a polyester film or a laminated film provided with a polyester film on the joint surface. 2. A method for producing a laminate film for packaging, which comprises melt-extrusion laminating a polyethylene resin on a base material made of a polyester film or a laminate film having a polyester film provided on a joint surface, wherein the polyethylene resin comprises: It is an ethylene / methyl acrylate copolymer resin, and the resin is melt-extruded at a temperature of 300 ° C. or lower to form a film, and the air containing ozone of 1 g / Nm ³ or more is 0 at least on the joint surface of the melt-extruded film. A method for producing a laminated film for liquid packaging, which comprises spraying under a condition of 0.5 Nm ³ / hr or more, and then pressure-bonding the melt-extruded film subjected to ozone treatment on the polyester film surface of the substrate.