JPS6047107B2 - Laminated film for packaging - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laminated film for packaging, and more particularly to a laminated film for packaging that has good adhesion at the heat-sealed portion in high-speed filling packaging.

Recently, in bag making, filling and packaging, the speed of equipment has increased, and problems related to the hot-tack properties of packaging materials are frequently occurring.
Hot-tackiness refers to the sealing strength when a peeling force due to the weight of the filler is applied to the sealing portion of the packaging material before the sealant resin in the sealing portion of the packaging material is sufficiently cooled and solidified. In particular, strip packaging for tablets, multi-die-roll packaging for sugar, vertical pillow packaging for heavy items, etc. has caused problems such as peeling off of seals and the occurrence of pinholes. This problem arises because a peeling force due to the inertia of the filler acts on the rear seal portion.

Usually, the packaging material uses a heat-resistant plastic film such as stretched polyethylene terephthalate, stretched polyamide, or cellophane on the side that becomes the outer surface after bag making, and uses an olefin resin on the other side, that is, the heat-sealable side.

One or more layers of a third resin or a metal layer such as aluminum may be provided in the intermediate layer. The hot-tack properties of such packaging materials are determined not only by the overall layer structure and thickness, but also by the properties of the resin in the heat-sealing layer. Conventionally, ionomers which are metal ionized products of ethylene-methacrylic acid copolymers, ethylene-based copolymers such as ethylene-acrylic acid copolymers, or olefin-based J resins such as polypropylene have been used as heat-sealing resins with good hot-tack properties. I've been exposed to it. However, copolymers of ethylene and acrylic monomers are expensive, and have the problems of leaving behind an odor after processing, and polypropylene has a high heat-sealing temperature. The most preferred heat gate sealing resin from the viewpoints of low-temperature sealing properties, cost, and odor is low-density polyethylene, but this resin has poorer heat sealing properties than the above-mentioned ionomers, ethylene-acrylic acid copolymers, and polypropylene. Low density polyethylene has branches in the polymer chain produced by free radical catalysis at high temperature and pressure.

In contrast, by using α-olefin as a comonomer of ethylene under conventional high-density polyethylene production conditions, i.e., using a heterogeneous ionic catalyst, such as an organometallic or transition metal oxide catalyst, at low temperature and low pressure, It has become possible to obtain polyethylene copolymers with linear polymer chains and low density. Comparing the film produced from the linear low-density polyethylene copolymer obtained here with conventional high-pressure low-density polyethylene, it is found that the film has a high modulus, yield strength, tensile strength, elongation at break,
Both impact strength and tear strength show high values. In addition to these advantages, the copolymer film described above also has greatly improved hot-tack properties. However, linear low-density polyethylene copolymers have poor spreadability when melted and are not suitable for extrusion lamination. Furthermore, if the film is dry-laminated with the base material after production, the cost of the packaging material will be high, making it difficult to widely use it. Therefore, we investigated how to use inexpensive packaging materials to speed up manufacturing, filling, and packaging without causing heat-sealing accidents due to poor hot-tack properties.As a result, we decided to coextrude and laminate low-density linear polyethylene copolymer with high-pressure low-density polyethylene. It has been found that this object can be achieved by extrusion lamination by using a packaging material which is produced at a lower cost. The laminated film for packaging according to the present invention uses low-density polyethylene and low-density linear polyethylene copolymer as the base material, and the low-density polyethylene layer as the base material! Obtained by coextrusion lamination in contact with the surface. Coextrusion lamination is a process in which resins extruded from two or more extruders are combined in a special T-die (for example, a multi-manifold T-die) or a merging block (for example, a feed port block). This is a processing method in which resin is laminated onto a base material. Here, the base material is a film or sheet of cellophane, oriented polyethylene terephthalate, oriented polyamide, polycarbonate, oriented polypropylene, or paper, metal foil, or the like. If necessary, use one that has been subjected to surface treatment such as corona treatment or flame treatment. It is also possible to print on the base material in advance.
Further, as the base material, a film laminated in advance into two or more layers may also be used. Furthermore, to promote adhesion during lamination, organic titanates, polyethyleneimine,
It is desirable to apply an anchor coating agent such as isocyanate or polyurethane. Low-density polyethylene refers to 0.900 to 0.939yI produced by a high-pressure method.
This resin has a density of cc and has good suitability for extrusion lamination. Low-density linear polyethylene copolymer consists of ethylene as the main component, propylene, butene, pentenone,
It is a copolymer with an α-olefin having 3 to 10 carbon atoms such as hexene, octene, nonene, decene, 4-methylpentene-1, etc., and is preferably polymerized in the presence of a stereospecific catalyst (Ziegler type catalyst, etc.). 0.9 manufactured by
It is a resin having a density of 10 to 0.939y1cc. Although the low-density linear polyethylene copolymer cannot be extruded and laminated by itself, it can be extruded and laminated by coextruding it with low-density polyethylene as in the present invention. In addition, to perform coextrusion lamination, the temperature on the base material side should be 305 to 330°C and the temperature on the outside should be 270°C.
It is desirable to set the temperature to about 330°C. The thickness of the above copolymer layer is 10 μm based on heat sealability and processability.
The above is preferred, and depending on the thickness of the extruded laminate layer and the intended use, the thickness of the two layers on the base material is preferably adjusted to about 15 to 40p, centering on the thickness of the low density polyethylene layer. On the other hand, the hot-tack properties of low-density linear polyethylene copolymers are not impaired even under extrusion lamination processing conditions of 305° C. or higher. However, the resin tends to have better hot-tack properties when extruded at a lower temperature. Using the packaging material according to the present invention obtained by extruding and laminating the low-density linear polyethylene copolymer, which is obtained as described above and is inexpensive and does not have an odor like resins made of acrylic monomers, bag making, filling, and packaging are possible. This makes it possible to perform packaging at low cost, without reducing the commercial value of the contents due to the odor of the packaging material, and at high speed.

The bag making and filling packaging referred to here means any method such as three-sided sealed vertical pillow packaging, three-sided sealed vertical bifold packaging, three-sided sealed horizontal pillow packaging, three-sided sealed horizontal bi-fold packaging, four-sided sealed vertical type bag-made packaging, etc. I don't mind. The contents to be filled include powdered sugar, instant soup, baby food, ramen soup, chili oil, etc.
These include liquid foods such as dressings, solid foods such as candy and beans, and medicines such as powders, granules, and tablets. Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 After applying a polyurethane anchor coating agent to biaxially oriented polyethylene terephthalate (12μ thick) printed in advance as a base material, low density polyethylene (
Mitsui Polychemical Co., Ltd.: Mirason-16) and a low-density linear polyethylene copolymer which is a copolymer of ethylene and 4-methylpentene-1 (Mitsui Petrochemical Co., Ltd.: Urtozex 20201., density 0.922, melt index 25) ) were coextruded and laminated to a thickness of 15 μm each with low density polyethylene adhered to the base material surface.

For coextrusion lamination, a coextrusion lamination apparatus equipped with a multi-manifold type T-die was used.
The extrusion temperature was 310°C for both the base material side and the outside. Using the thus obtained laminated film according to the present invention, the following bag making and filling packaging was performed.

Using a vertical pillow type automatic bag making and filling machine (manufactured by Kawashima Kikai Co., Ltd.), each bag after bag making had a size of 14 CITL x 20 cm, a bag making speed of 9 images/min, and was filled with 200 g of rock sugar. However, no peeling was observed in the heat-sealed parts of any of the products. Example 2 The laminated film obtained in Example 1 was transferred to a multi-layer vertical bag making machine (
When granulated sugar was packaged at 1V each using a 10-row type (manufactured by Toyo Kikai Seisakusho, 500 bags/min), no peeling was observed at the heat-sealed portion.

Comparative Example In the same manner as in Example 1, a laminated film made by extruding and laminating 30 μm of low-density polyethylene (Milason-16, manufactured by Mitsui Polychemicals Co., Ltd.) on biaxially oriented polyethylene terephthalate was used to form and fill bags in the same manner as in Example 1. I did the packaging.

The seal part was 13 when averaged over 100 bags. Of the width, 5
The garlic peeled off.

Claims (1)

[Claims] 1. Two layers, a low density polyethylene layer and a low density linear polyethylene polymer layer of ethylene and an α-olefin having 3 to 10 carbon atoms, are formed on a base material, and the low density polyethylene layer is a base material. It is coextruded and laminated on the side. Laminated film for packaging with good hot-tack properties. 2 The low density linear polyethylene copolymer has ethylene as a main component, and propylene, butene, pentene, hexene, octene, nonene, decene, 4-methylpentene-1
The laminated film for packaging according to item 1 above, which is a copolymer of at least one comonomer selected from the following. 3. The low density linear polyethylene copolymer produced by polymerization in the presence of a stereospecific catalyst has a density of 0.9.
The laminated film for packaging according to item 1 or 2 above, which has a weight of 10 to 0.939 g/cc.