JPH03293129A - Manufacture of packaging material - Google Patents

Abstract

PURPOSE:To make it possible to realize enough laminate strength by one process by a method wherein easily tearable resin under molten state, the surface of which is oxidized by being jetted with ozone-containing gas, is laminated through anchor coating aged layer to base material sheet. CONSTITUTION:The base material sheet 2 of the packaging material 1 consists of paper layer 4, polyethylene resin layer 5, aluminum foil layer 6 and anchor coating agent layer 7. Easily tearable resin, which is melted and extruded from a T-die at 180-250 deg.C in the form of thin film and against one side of which ozone-containing gas is jetted, is laminated to the anchor coating agent layer 7 of the base material sheet 2 in such as manner that the surface jetted with the ozone-containing gas of the easily tearable resin under molten state abuts against the anchor coating agent layer 7 of the base material sheet 2. Thus, since the surface to be laminated of the tearable resin is oxidizingly treated by the jetting of the ozone-containing gas, the surface of the tearable resin is laminated to the anchor coating agent layer 7 with high laminate strength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a packaging material, and particularly to a method for manufacturing a packaging material having an easily openable resin layer.

[Conventional technology]

BACKGROUND ART Conventionally, packaging materials have been developed that are used as lids for sealing containers, such as expanded polystyrene, and that can be peeled off when the sealed container is opened. Generally, such packaging materials have an easily openable resin layer on the surface that is fused to the container or the like. FIG. 5 is a schematic cross-sectional view showing an example of a conventional packaging material. In FIG. 5, the packaging material 30 is the paper layer 3.
1, polyethylene resin layer 32, aluminum foil layer 33,
It has a multilayer structure in which an anchor coating agent layer 34, a polyethylene resin layer 35, and an easily openable resin layer 36 are laminated. Normally, such a multilayered packaging material 30 is produced by first laminating paper and aluminum foil with a polyethylene resin interposed therebetween to create a base sheet consisting of a paper layer 31, a polyethylene resin layer 32, and an aluminum foil layer 33. An anchor coating agent layer 34 is provided on the aluminum foil layer 33 of this base sheet. Then, after sand laminating a polyethylene resin on the base sheet, an easily openable resin is extruded and laminated.

[Problem to be solved by the invention]

However, considering the number of steps, production cost, etc., it is preferable that the packaging material with the above-mentioned structure be formed by directly extruding and laminating the easy-open resin onto the anchor coating agent layer 34 without using the polyethylene resin layer 35. However, there was a problem in that such a structure could not be achieved due to the characteristics of the easily openable resin. That is, the laminate strength by extrusion lamination tends to be improved by increasing the heating melting temperature of the extruded resin to promote oxidation of the resin. (330°C), thermal decomposition occurs, and it is usually necessary to extrude and laminate at about 180 to 250°C. For this reason, the surface oxidation degree of the easily openable resin layer extrusion laminated to the anchor coating agent layer is low, and the lamination strength is insufficient, making it impossible to put it into practical use. In addition, additives such as tackifiers contained in the easy-open resin layer bleed to the interface with the anchor coating agent layer, causing bleed to the isocyanate curing agent in the anchor coating agent before the crosslinking curing reaction. There was also the problem that sufficient adhesive strength between the aluminum foil layer and the easily openable resin layer could not be obtained due to the reaction between the aluminum foil layer and the easily opened resin layer. Therefore, although the lamination process involves multiple steps, it is necessary to extrude and laminate the easily openable resin through the polyethylene resin layer. As the lamination process becomes multi-step, the first lamination
Paper layer 31 and polyethylene resin layer 32 formed in the process
When the base sheet made of the aluminum foil layer 33 is rolled, the aluminum foil layer 33 may be contaminated due to contact between the ink on the printed surface of the paper layer 31 and the aluminum foil layer 33. be. For this reason, there was a problem in that lamination failure between the aluminum foil layer and the easily openable resin layer was likely to occur in the second lamination step.

The present invention has been made to solve the above-mentioned problems, and provides a packaging material in which an easy-to-open resin layer is directly formed on an anchor coating agent layer through a single lamination process. The purpose is to provide a manufacturing method for.

[Means to solve the problem]

In order to achieve this objective, the present invention injects ozone-containing gas onto one side of an easily openable resin that is melted from a T-die and extruded into a thin film at 180 to 250°C. The structure is such that the ozone-containing gas sprayed surface of the easily openable resin in a molten state is laminated so as to be in contact with the anchor coating agent layer of the base sheet provided with the coating agent layer.

[Effect]

The easy-open resin melted and extruded from the T-die in the form of a thin film is laminated with a base sheet, but before being extruded from the T-die and laminated with the base sheet having at least a barrier layer, the easy-open resin is The surface of the unsealable resin to be laminated with the base sheet is oxidized by spraying ozone-containing gas, and the easy-open resin with high lamination strength is applied to the anchor coating agent layer provided on the surface of the base sheet. Laminated.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of a tandem extrusion laminator for explaining the present invention, and FIGS. 2 to 4 are schematic sectional views of packaging materials manufactured according to the present invention. In FIG. 1, the tandem extrusion laminator 10 includes a T-die 11.15 for extruding molten resin into a thin film, and a molten thin-film resin extruded from the T-die 11.15 and a supplied sheet. Cooling rolls 12a, 16a and nip rolls 12b, 16 for laminating by pressing and cooling
b, and the sheet is passed through the cooling roll 12a and the nip roll 1.
Unwinder 17a, 17b for supplying between 2b
and a winder 18 for winding up the shaped packaging material.

There are no particular restrictions on the T-die 11.15, and a normal T-die for molding synthetic resin sheets can be used. And T
On the way that the molten thin film resin extruded from the die 15 reaches the cooling roll 16a1 and the nip roll 16b, an injection nozzle 19b for injecting ozone-containing gas to the molten thin film resin extruded from the T die 15 is disposed. Ori,
An ozone generator 19a is connected to this injection nozzle 19b.

Next, a method for manufacturing a packaging material according to the present invention will be explained using the packaging material shown in FIG. 2 as an example. Here, the packaging material 1 shown in FIG. 2 has a base sheet 2 and an easily openable resin layer 3, and the base sheet 2 includes a paper layer 4, a polyethylene resin layer 5, an aluminum foil layer 6, and an anchor. It consists of a coating agent layer 7, and has a five-layer structure as a whole.

Such a packaging material 1 is manufactured in the following manner according to the present invention. First, the polyethylene resin 21 is melted and extruded into a thin film from the T-die 11, and is extruded from the unwinder 17a.
A paper sheet 23 is supplied from the unwinder 17b, and an aluminum foil 25 is supplied from the unwinder 17b, and is pressed and cooled by the cooling roll 12a and the nip roll 12b to form a laminate sheet 26 constituting the base sheet 2. FIG. 3 is a schematic cross-sectional view of this laminate sheet 26, and the laminate sheet 26 is composed of a paper layer 4, a polyethylene resin layer 5, and an aluminum foil layer 6. Then, this laminate sheet 26 is attached to the coating unit 1.
In step 3, the aluminum foil layer 6 is coated with an anchor coating agent, and dried in the drying unit 14 to form a base sheet 27 (FIG. 4) on which the anchor coating agent layer 7 is formed. Next, the easy-open resin 28 is melted into a thin film and extruded from the T-die 15, and the ozone-containing gas supplied from the ozone generator 19a is injected onto the molten easy-open resin 28. It is injected from the nozzle 19b. The purpose of spraying the ozone-containing gas onto the molten easy-open resin 28 is to oxidize the surface of the easy-open resin 28. As a guideline for this surface oxidation, 2
The interfacial surface tension of the ozone-containing gas sprayed surface of the easily openable resin at 20°C is set to be 30 dyn/cm or more, preferably 35 dyn/cm or more. In order to perform such surface oxidation, the ozone-containing gas is a mixed gas that uses air as a base gas and has an ozone concentration of 1 g/m" or more, preferably about 2 to 20 g/m". Such ozone-containing gas may also contain an inert gas such as nitrogen gas. Moreover, it is preferable that the ozone-containing gas is injected at a flow rate of 50 to 500 ml/min. Furthermore, the ozone-containing gas may be injected in a preheated state in the range of room temperature to 80°C. On the other hand, the above-mentioned base sheet 27 on which the anchor coating agent layer 7 is formed
is supplied between the cooling roll 16a and the nip roll 16b, and the base sheet 27 and the molten easy-opening resin 28 are pressed and pressed by the cooling roll 16a and the nip roll 16b.
After cooling, the packaging material 1 having the laminated structure shown in FIG. 2 is formed and wound up in the winder 18.

The thickness of the easily openable resin layer 3 of such a packaging material 1 is 12 to 5
0 μm1 preferably about 15 to 35 μm. If the thickness of the easy-open resin layer 3 is less than 12 μm, sufficient heat-sealability will not be exhibited, and if it exceeds 50 μm, the easy-open resin will protrude during sealing and the cost will increase. Easy-open resins generally include polypropylene resins, linear low-density polyethylene resins, ethylene-vinyl acetate copolymers, ethylene-acrylic acid ester copolymers, ethylene-acrylic acid copolymers, and modified products thereof (
unsaturated cafubonic acid copolymers, graft copolymers, etc.) or mixtures of the above resins. Furthermore, tackifiers such as rosin-based, terpene-based, petroleum resin-based, alkylphenol-based, xylene-based tackifiers, lubricants, anti-blocking agents, etc. may be added to the easy-opening resin. Which easy-open resin to select from the above-mentioned easy-open resins can be determined depending on the material of the object to be heat-sealed. Examples of the object to be sealed include molded containers made of foams and sheets of polyvinyl chloride, polypropylene, polystyrene, polyethylene terephthalate, and the like.

In the base material sheet 2, the paper layer 4 forms the front side of the packaging material 1, and is used for printing and decorative processing, and is usually made of high quality paper, kraft paper, coated paper, art paper, etc. . The basis weight of each of these papers is 30 to 100 g/r
RF level is preferable. Further, the polyethylene resin layer 5 functions as an adhesive layer between the paper layer 4 and the aluminum foil layer 6, and general-purpose low-density polyethylene is generally used. The thickness of this polyethylene resin layer 5 is 10 to 30μ
It is about m. The aluminum foil layer 6 is used to provide the packaging material 1 with gas barrier properties. As the aluminum foil, a soft aluminum foil with a thickness of about 6 to 15 μm is usually used. Furthermore, the anchor coating agent layer 7 contains a urethane anchor coating agent at a concentration of 0.1 to 1.0 g/ff.
It is formed by applying a coating amount of 1. In addition, in the present invention, the base sheet 2 is not limited to the above-mentioned ones, and for example, various biaxially stretched films (about 6 to 75 μm thick) on which aluminum is vapor-deposited as a barrier layer instead of aluminum foil can be used. may also be used. Further, the paper layer 4 and the aluminum foil layer 6 may be laminated by dry lamination using a urethane adhesive without using the polyethylene resin layer 5.

Further, instead of the paper layer 4, biaxially stretched polyester, biaxially stretched polypropylene, biaxially stretched nylon, biaxially stretched cellophane, or a laminate thereof can be used.

In the present invention, as described above, the molten easy-opening resin 2
8 is injected with ozone-containing gas to perform surface oxidation, and in this state is laminated with the anchor coating agent layer 7 of the base sheet 27, so even if the heating melting temperature of the extruded easy-open resin is relatively low. A good lamination is made.

Further, the curing of the anchor coating agent layer 7 is accelerated, and additives such as tackifiers contained in the easily openable resin layer bleed and react with the isocyanate curing agent in the anchor coating agent before the crosslinking and curing reaction. This is effectively prevented.

Next, the present invention will be explained in more detail by showing experimental examples.

1 2 (Experimental example) In the tandem extrusion laminator shown in Fig. 1, extrusion lamination was performed using the following materials under the extrusion conditions described below, and in one step a packaging material with the laminated structure shown in Fig. 2 (in accordance with the present invention) was produced. sample) was manufactured.

・Paper: Special Cormorant (79,1
g/G, manufactured by Fuji Kakoshi Co., Ltd.) / Aluminum foil: Soft aluminum foil (thickness 7 μm 1 Showa Aluminum (
・Polyethylene resin: Low density polyethylene M-LIP (manufactured by Mitsui Petrochemical Co., Ltd.) ・Anchor coating agent: Urethane anchor coating agent AD506X/CATIO
(manufactured by Toyo Morton Co., Ltd.) - Easy-to-open resin: Ethylene-vinyl acetate copolymer resin (Peel Resin V606, manufactured by Mitsui Petrochemical Co., Ltd.) - Extrusion conditions for polyethylene resin: Screw L/D = 28, cylinder temperature = 140°C, 220℃, 300℃, 32
0°C Adapter temperature = 320°C T-die temperature = 320°C Laminate thickness = 15 μm Cooling roll temperature = 4°C ・Extrusion conditions for easy-open resin Screw L/D = 28 Cylinder temperature = 100°C, 160°C, 200°C °C, 22
0°C Adapter temperature = 220°C T-die temperature = 220°C Laminate thickness = 25 μm Cooling roll temperature = 4°C ・Ozone-containing gas injection conditions: Base gas = Air 3 4 Flow rate = 80 mA/m/Easy-to-open resin Interfacial surface tension -36 dyn/cm As a comparison, a packaging material (comparative sample) as shown in FIG. 5 was manufactured according to a conventional method. The lamination conditions in the process of creating a base sheet consisting of a paper layer, a polyethylene resin layer, and an aluminum foil layer, the conditions for providing an anchor coating agent layer on the aluminum foil layer of this base sheet, and the materials used are as described in the above book. It was the same as the invention sample. Also,
The extrusion conditions for the polyethylene resin layer interposed between the anchor coating agent layer and the easy-open resin layer and the extrusion conditions for the easy-open resin (no injection of ozone-containing gas) were used. The materials were the same as those of the present invention sample.

・Polyethylene resin extrusion conditions Screw L/D = 28 Cylinder temperature = 140°C, 220°C, 300°C, 32
0°C Adapter temperature = 320°C T-die temperature = 320°C Laminate thickness = 15 μm Cooling roll temperature = 4°C ・Extrusion conditions for easy-open resin Screw L/D = 28 Cylinder temperature = 100°C, 160°C, 200℃, 22
0°C Adapter temperature -220°C T-die temperature = 220°C Laminate thickness = 25 μm Cooling roll temperature -4°C The above-mentioned inventive samples and comparative samples were heated in a polystyrene foam container through an easy-to-open resin layer. After sealing, each sample was peeled off, and both samples showed good peelability without causing delamination between the aluminum foil layer of the packaging material and the easy-open resin layer. In other words, although the sample of the present invention formed the easy-open resin layer directly on the anchor coating agent layer in one lamination process, it was demonstrated that the lamination strength of the easy-open resin layer was sufficiently high. Ta.

5 6 The method for manufacturing a packaging material of the present invention is not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit thereof. For example, an injection nozzle that injects ozone-containing gas may have a shape with a large number of injection holes in the width direction of the easy-to-open resin that is extruded in a molten state, or a shape with a single injection port extending in the width direction. It may be any shape.

〔Effect of the invention〕

As is clear from the detailed description above, according to the present invention, the molten easy-open resin is oxidized by spraying ozone-containing gas onto the base sheet through the anchor coating agent layer. Because it is laminated, sufficient lamination strength can be obtained despite the relatively low heating and melting temperature of the extruded easy-open resin, and the curing of the anchor coating agent layer is accelerated, allowing the easy-open resin contained in the easy-open resin layer to It is possible to effectively prevent additives such as tackifiers from bleeding out and reacting with the anchor coating agent, and it is possible to significantly shorten the manufacturing process of the packaging material.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a tandem extrusion laminator for explaining the present invention, Fig. 2 is a schematic sectional view of a packaging material manufactured by the present invention, and Figs. 3 and 4 are packaging materials in the process of being manufactured. FIG. 5 is a schematic sectional view showing an example of a conventional packaging material.

Claims (1)

[Claims] An ozone-containing gas is injected onto one side of the easy-open resin that is melted from a T-die and extruded into a thin film at 180 to 250°C,
Laminating so that the ozone-containing gas sprayed surface of the easily openable resin in a molten state is in contact with the anchor coating agent layer of a base sheet having at least a barrier layer and an anchor coating agent layer on the surface. A method for producing a packaging material characterized by: