JPH07137748A - Heat-resistant packaging bag and production thereof - Google Patents

Abstract

PURPOSE:To provide a heat-resistant packaging bag having an aluminum foil as a barrier layer for the purpose of a reotort sterilization treatment, which does not bring about hygienic problems resulting from the residual organic solvents against the contents and which is excellent in the appearance and print, curl, etc., and further, which can be produced at a low cost. CONSTITUTION:An aluminum foil (e) is heat bonded on a polyethylene terephthalate film (c) through adhesive layers of a moclified oelfin polymer layer (f) positioning at the aluminum foil side (e) and having the concentration range of a carbonyl group as much as 1-600meq/100g (polymer) and a polyurethane thin layer (d) positioned at the polyethylene terephthalate film (c) side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retort sterilizable hermetically sealed packaging bag and a method for producing the same, more specifically, an aluminum foil, a seal layer provided on one surface of the aluminum foil, and The present invention relates to a heat-resistant packaging bag made of polyethylene terephthalate film provided on the other surface of an aluminum foil, and a method for producing the same.

[0002]

2. Description of the Related Art A material for a resealable sterilizable hermetically sealed bag is conventionally provided with a crystalline olefin resin layer such as polypropylene having heat sealability on one surface of an aluminum foil and a mechanical strength on the other surface. A film-like packaging material having a laminated structure provided with a large heat-resistant resin layer such as polyethylene terephthalate is widely used.

The film-like packaging materials are laminated on each other, and the peripheral edges thereof are heat-bonded to each other to form a bag shape.

The bag is filled with the contents, the bag is deaerated and sealed, and then the bag is sterilized by retort, that is, sterilized by heating in a retort kettle to produce a sealed package capable of storing the contents for a long period of time. .

[0005]

In the retort sterilization process, it is usually necessary to protect the sealed packaging bag filled with the contents, which is heated to a temperature of 120 ° C. or higher, from the external environment. .

Therefore, a resin having heat resistance, hot water resistance, and excellent mechanical strength has been conventionally used for the outermost layer of the packaging material.

For example, polyester such as polyethylene terephthalate, nylon, etc. are used.

In particular, polyethylene terephthalate is used as a packaging material for retort foods because it is excellent in heat resistance, dimensional stability and mechanical strength.

In order to undergo severe high-temperature sterilization, the polyethylene terephthalate film and the aluminum foil are joined with a heat- and water-resistant thermosetting adhesive such as a urethane-based adhesive and an epoxy-based adhesive. It is performed using a urethane adhesive.

This urethane-based adhesive gives generally good results for joining a polyethylene terephthalate film and an aluminum foil without impairing the adhesive strength, delamination resistance and impact resistance even at high temperature treatment.

However, since it takes 2 to 5 days at room temperature until the urethane adhesive layer is completely cured, it is necessary to age the laminate of the polyethylene terephthalate film and the aluminum foil for a certain period of time.

For this reason, the production efficiency is not good because it cannot be moved to the next step, for example, another resin film lamination and bag-making immediately after laminating polyethylene terephthalate and aluminum foil.

Further, the urethane-based adhesive generally contains an organic solvent such as toluene, ethyl acetate and acetone, unreacted polyisocyanate, etc., and these organic solvents and the like diffuse into the surroundings during drying or curing, From the viewpoint of worker health and environmental hygiene, it is desired to reduce the amount of urethane adhesive used.

Further, conventionally, in order to thermally adhere a polyolefin layer to an aluminum surface, a modified olefin polymer modified with an unsaturated carboxylic acid (eg, maleic anhydride) or the like is used as a hot-melt type thermoplastic resin adhesive. It is well known to be used.

The modified Frefin polymer has an advantage that it can be bonded at a high speed without problems such as organic solvents found in urethane-based adhesives, but in the conventional method, the aluminum foil of the outermost layer and the intermediate layer is used. And after laminating the modified olefin polymer and the seal layer, by further activating the modified olefin polymer, in order to firmly adhere to the aluminum foil, it is heated to a temperature not less than the Bicatt softening point of the polymer, A so-called heat-bonding process is required.

Since the method has large temperature and time factors,
Due to poor productivity and reheating, printing on the outermost film is likely to cause color tone changes and misalignment, and uneven wrinkles on the surface are likely to occur. It has a drawback that it tends to easily occur and tends to lower the commercial value.

The present invention has been made in view of the above circumstances, and an object thereof is to efficiently manufacture a heat-resistant hermetically sealed packaging bag, reduce problems due to organic solvents and the like, and to obtain excellent adhesive strength. It is an object of the present invention to provide a heat-resistant packaging bag and a method for producing the same that can eliminate the drawbacks of the conventional products.

[0018]

DISCLOSURE OF THE INVENTION The inventors of the present invention have found that in bonding an aluminum foil and a polyethylene terephthalate film, two kinds of adhesive layers, a layer of a modified olefin polymer containing a carbonyl group and a thin layer of urethane, are used. It has been found that heat-bonding by means of is effective in achieving the above-mentioned object of the invention.

That is, according to the present invention, there is provided a laminated film comprising an aluminum foil, a seal layer provided on the first surface of the aluminum foil, and a polyethylene terephthalate film provided on the second surface of the aluminum foil. A layer of the modified olefin polymer which is on the aluminum foil side and has a carbonyl group content in the concentration range of 1 to 600 meq / 100 g (polymer), and a polyurethane thin layer on the side of the polyethylene terephthalate film are used to form an adhesive layer. The aluminum foil and the polyethylene terephthalate film are heat-bonded to each other.

Furthermore, according to the present invention, a hermetically sealed laminate film comprising an aluminum foil, a seal layer provided on the first side of the aluminum foil, and a polyethylene terephthalate film provided on the second side of the aluminum foil. A method of manufacturing a packaging bag, which includes the following (a)-
It is a method for manufacturing a heat-resistant packaging bag including the step (c).

(A) A step of forming a thin layer of a urethane adhesive containing a free isocyanate group on one surface of the polyethylene terephthalate film.

(B) The second side of the aluminum foil is adhered to the side of the polyethylene terephthalate film on which the urethane adhesive layer is formed, while the carbonyl content is 1 to 60.
A step of forming a laminated body by melt-forming a modified olefin polymer in a concentration range of 0 meq / 100 g (polymer) into a layer and then reheating them.

(C) A step of laminating the modified olefin polymer film while heating it to a temperature not lower than the Bicatt softening point of the film.

[0024]

The present invention configured as described above has the following operations.

First, a polyethylene terephthalate film and an aluminum foil are laminated with a urethane adhesive to obtain a laminated film having an aluminum foil inside.

On the other hand, a coextruded film of a modified polypropylene having a carbonyl content of 1 to 600 meq / 100 g (polymer) and a crystalline polypropylene having a modified polypropylene layer on the inner side is obtained. , The modified polypropylene layer.

In these films, when the aluminum foil and the polyethylene terephthalate film are heat-bonded through an adhesive layer of the modified olefin polymer layer and the polyurethane thin layer on the polyethylene terephthalate film side, a retort sterilizable seal is obtained. The packaging bag is manufactured.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the heat-resistant packaging bag and the manufacturing method thereof according to the present invention will be described below with reference to the drawings.

In a preferred embodiment of the present invention, when the seal layer is made of a crystalline olefin resin and the seal layer is a heat-resistant packaging material which is heat-bonded to an aluminum foil through a layer of modified olefin polymer, A structure of an example of the heat-resistant packaging bag of the embodiment is shown in a sectional view in FIG.

In FIG. 1, the heat-resistant packaging bag X is a laminated film composed of the following layers, a polyethylene terephthalate film c as the outermost layer, and a polyurethane thin layer d and an aluminum foil e sequentially inside. A bag is made from a laminated film composed of a modified olefin polymer layer f and a crystalline olefin resin g.

The polyethylene terephthalate film c used as the outermost layer of the heat-resistant packaging bag of the present invention may be either unstretched or biaxially stretched, and its thickness is determined according to the application of the heat-resistant packaging bag. You can

The thin layer d of polyurethane of the heat-resistant packaging bag according to the embodiment of the present invention is made of a polymer having a urethane bond.

Preferred is a polyurethane having a three-dimensional structure composed of a polyol prepolymer having hydroxyl groups at both ends and having a slightly high molecular weight, and a polyisocyanate having a polyfunctional isocyanate group.

In the examples of the present invention, the polyurethane d is
A thin layer is sufficient, and preferably has a polyurethane solid content of 0.05 to 1.0 g per 1 m ² (0.05 to 1.0 g).
(solid) / m ² ), more preferably 0.1-0.5 g (s
solid) / m ² ) formed on substantially the entire surface of the polyethylene terephthalate film.

Here, if the amount used is reduced below the minimum limit, the adhesive strength between the polyethylene terephthalate film and the modified olefin polymer layer will decrease, and if it exceeds the maximum limit, the adhesive strength will increase relative to the amount used. However, in terms of product cost, health and hygiene due to organic solvents, and further, it takes a long time to completely cure, which is an unfavorable problem.

The modified olefin polymer f according to the embodiment of the present invention has a carbonyl group content of 1 to 600 meq / 100 g.
It is in the range of (polymer).

It is known in the art that the modified olefin polymer f can adhere to a metal substrate such as aluminum, and also to an olefin resin.

That is, acrylic acid, maleic anhydride,
Methyl acrylate, acrylamide, and carbonyl group-containing ethylenically unsaturated monomers such as acrolein,
Graft copolymerization, block copolymerization, random copolymerization or endless treatment by a method such as ethylene, propylene and other polyolefins, and the main chain of olefin polymers such as copolymers of olefin and another monomer or It is introduced into the side chain.

In this way, the contained carbonyl group acts on the hydroxyl group on the surface of the adherend and also on the hydroxyl group of the moisture in the air or the adsorbed moisture to improve the adhesiveness.

Modified olefin polymer having a carbonyl content
If it is less than 1 meq per 100 g, the adhesive strength will be reduced and delamination will occur during retort sterilization, while if it exceeds 600 meq, the melt viscosity will be high and extrusion processing will be impossible. However, the adhesive strength does not increase, which causes an undesirable problem in terms of product cost.

The thickness of the modified olefin polymer f is at least 3 µ, preferably 5 µ to 20 µ.

If this thickness is smaller than the minimum limit, the adhesive strength that can withstand the retort sterilization cannot be obtained.

On the other hand, when the maximum limit is exceeded, the adhesive strength does not increase relative to the amount used, which is disadvantageous in terms of product cost.

The aluminum foil e provided with the seal layer on the first surface in the embodiment of the present invention is, for example, a laminated film in which an olefin resin film g is adhered to one surface of the aluminum foil e, an aluminum foil e. And the olefin resin film g are bonded with a modified olefin polymer, and the olefin resin film g is plated with aluminum.

The thickness of the aluminum foil e or the layer g can be appropriately changed depending on the use of the heat-resistant sealed bag X, and is, for example, 1 μ-100 μm.

The above-mentioned olefin resin film g functions as a sealing layer in the heat-resistant packaging bag X in the embodiment of the present invention.

Next, a heat-resistant packaging bag X according to an embodiment of the present invention
The manufacturing method of is explained.

In the step (a) of the production method according to the embodiment of the present invention, first, the polyethylene terephthalate film c
A thin layer of urethane adhesive d is formed on one surface of the.

For this urethane adhesive, heat-resistant packaging bag 1
There are various types depending on the application, the type and properties of the adherend.

Preferably, the adhesive is a reactive type having an isocyanate group, and is used, for example, diluted with an ethyl acetate solution.

This thin layer d is formed by immersing a liquid roll in an adhesive bath and bringing the film into contact with the adhesive pulled up by this roll to form a thin layer on a roll coater type or film surface. There are a spray type for spraying the adhesive, a dipping type for immersing the film in the adhesive bath, and the like.

After the step (a), the thin layer d of the adhesive is dried if necessary. This drying is preferably performed in a short time by heating or blowing air.

In the manufacturing method (b) according to the embodiment of the present invention, first, the adhesive layer d formed on the polyethylene terephthalate film c in the step (a) is laminated with the aluminum foil e.

On the other hand, the carbonyl content is 1 to 600 meq / 10
The modified olefin polymer f in the concentration range of 0 g (polymer) is melt-formed into a layer, which is (d)
As described above, the coextruded film is coextruded with the crystalline olefin resin film g which is the sealant layer of the embodiment of the present invention.

The coextrusion film is an inflation method,
It is performed by a method such as a lower die casting method.

Between the modified olefin polymer layer f and the crystalline olefin polymer layer g, a nylon resin or the like may be appropriately reinforced.

Then, in the step (c), the modified olefin polymer film f surface of the coextrusion film is heated to a temperature not lower than the Vicat softening point of the film f and laminated with the aluminum foil e surface. A suitable method such as infrared irradiation, contact with a heating roll, or irradiation with hot air is selected. When the olefin is polypropylene, the heating temperature is preferably 150 to 230 ° C.

One of the features of the manufacturing process of the embodiment of the present invention is that the heat-bonding laminating apparatus which is the step (f) is incorporated in the automatic bag-making machine, and the laminating and bag-making are performed in-line. That is, the heat-resistant packaging bag X is rationally manufactured.

The manufacturing method of the embodiment of the present invention will be described with reference to the manufacturing example and the configuration example of FIG.

As shown in FIG. 2, the heating and laminating line A and the bag making line B are in-line.

In FIG. 1, W1 represents the winding of the polyethylene terephthalate film c laminated on the aluminum foil e with the urethane adhesive, and the inside of the winding is the aluminum foil e.

In 2, W2 has a carbonyl content of 1 to
It is a coextrusion film of 600 meq / 100 g (polymer) of modified polypropylene and crystalline polypropylene, and the inside of the roll is the modified polypropylene layer.

The W2 film was heated by the preheating roll H1 at 3 at an appropriate temperature in the range of 150 to 230 ° C., and then the aluminum foil e side of the W1 film and the temperature of 150 to 230 ° C. At an appropriate temperature within the range,
Laminated by the Nipro roll 4.

Thereafter, the laminated film is cooled by the cooling roll 5.

Then, the laminate is accumulated from the take-up roll 7 by the accumulator 8 in accordance with the intermittent operation of the next bag making line.

Next, in the bag-making line of B, the mechanism 9, the half-cut 11, the vertical seal 12, the cooling 13, and the cooling 13,
The horizontal seal 14, the cooling 15, and the cut are sequentially operated by the drive device 10 to perform bag making, and the heat-resistant packaging bag X is obtained.

(Examples and Comparative Examples) Examples and comparative examples of the present invention will be specifically described below with reference to examples.

(Example) As a thermal adhesive layer with an aluminum foil, maleic anhydride was grafted to random polypropylene having a melting point of 145 ° C., a density of 0.90 g / cm ³ , and an MFR (melt flow rate) of 12 g / 10 min. A modified polypropylene polymer having was prepared.

Average carbonyl group concentration 200 meq / 100 g (polymer), MFR 16 g / 10 min, melting point 150 ° C., density 0.91 g / cm
³ , the innermost layer sealant of the bag, melting point 165 ℃,
Using a block copolymer type polypropylene having a density of 0.91 g / cm ³ and an MFR of 2 g / 10 min, the modified polypropylene: block copolymer type polypropylene = 1: 2 at an extrusion temperature of 250 ° C. by a two-layer coextrusion T die casting apparatus. 7
A coextrusion film having a total thickness of 80 μm was prepared.

On the other hand, a 12 μ-thick biaxially stretched polyethylene terephthalate film printed with a printing ink for retort and a 9 μ-thick aluminum foil were applied to the pasting surface by a general dry lamination method using an ester type urethane adhesive. The laminate was obtained by pasting together.

The winding of each of these laminates was set in an automatic bag-making machine incorporating a heat-adhesive laminating apparatus.

The subsequent steps are, as described above with reference to FIG. 2, 15 cm × 20 cm (seal width 1 cm) of the constitution of the embodiment of the present invention.
The heat-resistant packaging bag of the size was manufactured at a bag-making speed of 30 bags per minute.

The peel strength between the aluminum foil surface and the modified polypropylene surface of the produced product was 800 g / 1.5 cm.

The bag was filled and sealed with a commercially available dry type cooked curry, and then subjected to retort treatment at 121 ° C. for 40 minutes.

No abnormalities were found in the appearance of this product, and the peel strength between the aluminum foil surface and the modified polypropylene surface was 900 g / 1.5 cm, which was higher than that before the retort treatment.

(Comparative Example) As a completely identical structure to the above-mentioned (Example), laminated on the aluminum foil surface of the laminate of the biaxially oriented polyester and aluminum foil by the modified polypropylene and block copolymerized polypropylene coextrusion laminating method. The wound roll was placed in an automatic bag-making machine incorporating the heat-adhesive laminating apparatus, and the bag-making operation was performed after heating with a preheating roll, nipping with a heat-adhesive roll, and cooling, as in (Example).

As a result, under the condition that a sufficient heat-adhesive strength is obtained, a change in color tone occurs in the printed part due to the excessive heat applied to the printed part, and the urethane adhesive layer is softened to cause printing deviation. occured.

Uneven wrinkles and the like were formed on the entire surface, and large curl was generated in the bag after bag making, resulting in a great loss of commercial value.

[0079]

The heat resistant packaging bag and the manufacturing method of the present invention have the following effects.

A. Compared to the conventional method of laminating each layer with a solvent-based urethane adhesive and laminating it, the aluminum foil and the sealant layer are heat-bonded by the modified polyolefin, so hygiene due to the residual organic solvent on the side in contact with the contents There is no problem and it is safe, and food, medical products, etc. are especially useful.

B. Compared with the conventional methods, the surface condition is excellent and there is little curl, so the commercial value is high.

C. Since the lamination by thermal bonding is performed in-line in the pre-process of bag making, the process is streamlined,
Products can be made at low cost.

[Brief description of drawings]

FIG. 1 is a partial enlarged sectional view showing an embodiment of a heat resistant packaging bag according to the present invention.

FIG. 2 is an explanatory view schematically showing a production line of the heat resistant packaging bag in FIG.

[Explanation of symbols]

 x heat-resistant packaging bag c polyethylene terephthalate film d thin layer of polyurethane e aluminum foil f modified olefin polymer layer g crystalline olefin resin

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[Procedure amendment]

[Submission date] November 17, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

Claims (6)

[Claims] 1. A laminated film comprising an aluminum foil, a seal layer provided on the first surface of the aluminum foil, and a polyethylene terephthalate film provided on the second surface of the aluminum foil, wherein the aluminum foil is provided on the aluminum foil side. Yes, and has a carbonyl group content of 1-60
The aluminum foil and the polyethylene terephthalate film are heat-bonded through the adhesive layer of the modified olefin polymer layer in the concentration range of 0 meq / 100 g (polymer) and the polyurethane thin layer on the polyethylene terephthalate film side. A heat-resistant packaging bag characterized by being used. 2. The heat-resistant packaging bag according to claim 1, wherein the sealing layer is made of a crystalline olefin resin, and the sealing layer is heat-bonded to the aluminum foil via the layer of the modified olefin polymer. 3. A thin layer of polyurethane is 0.1 to 0.5 g (soli).
The heat-resistant packaging bag according to claim 1, which is a polyurethane layer of d) / m ² . 4. A method for producing a heat-resistant packaging bag, which is a laminated film comprising an aluminum foil, a sealing layer provided on the first side of the aluminum foil, and a polyethylene terephthalate film provided on the second side of the aluminum foil. Then, the manufacturing method of the heat-resistant packaging bag is characterized by including the following steps (a) to (c). (A) A step of forming a thin layer of a urethane adhesive containing a free isocyanate group on one surface of the polyethylene terephthalate film. (B) The second side of the aluminum foil is adhered to the urethane adhesive layer forming side of the polyethylene terephthalate film, while the carbonyl content is 1 to 600 meq / 100 g.
A step of forming a laminated body by melt-forming a modified olefin polymer in a concentration range of (polymer) into a layer and then reheating them. (C) A step of laminating the modified olefin polymer film while heating it to a temperature not lower than the Vicat softening point of the film. 5. A method for producing a heat-resistant packaging bag, wherein the sealing layer is made of a crystalline olefin resin, and the sealing layer is heat-bonded to the first surface of the aluminum foil through the layer of the modified olefin polymer. 5. The method for producing a heat-resistant packaging bag according to claim 4, including the following step (d), (e) or (f). (D) The modified olefin polymer film and the crystalline olefin resin film are coextruded into a coextruded film. (E) The coextruded film is heat-bonded and laminated on the aluminum foil surface of the polyester film / aluminum foil laminate in a state of being heated above the Vicat softening point of the modified olefin polymer layer. (F) Lamination and bag making are performed in-line by a device in which the heat-bonding laminating device of the step (e) is incorporated in an automatic bag making machine. 6. The urethane adhesive is added in an amount of 0.1 to 0.5 g (soli).
The method for producing a heat-resistant packaging bag according to claim 4, wherein the polyethylene terephthalate film is applied on one side at a ratio of d) / m ² .