JP2669214B2 - Ultra low density polyethylene film with improved heat sealability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-low density polyethylene film having an improved heat-sealing property, which is used for a packaging material such as an inner bag of a bag-in-box.

[0002]

2. Description of the Related Art Recently, in a liquid paper container, a bag
In-box products with a plastic bag inside the inner bag are widely used for food products such as seasonings, alcoholic beverages, dairy products and other beverages, and non-food products such as developers, detergents and dyes. I've been This container has a large capacity of 2 liters to 30 liters for business use, and a small to medium capacity of 1 liter to 3 liters that can be used by general consumers, and this container has a wide range of applications.

The packing material used for the inner bag of the bag-in-box has a low density and a density of 0.915 due to characteristics such as pinhole resistance due to flexibility at low temperature and excellent heat sealability. The following ultra-low density polyethylene films were used:

[0004]

However, the ultra low density polyethylene film contains a large amount of low molecular weight components, and these low molecular weight components exude to the surface of the film depending on the aging time and temperature during storage of the film. There is a bleeding phenomenon that comes. When heat sealing is performed using a film in which low molecular weight components are bleeding on the surface of the film, the low molecular weight component film formed on the surface reduces the heat sealing strength of the heat seal surface, often resulting in poor heat sealing of the product. did. The present invention, even if the low molecular weight component is bleeding on the surface of the film,
An object of the present invention is to provide an ultra-low-density polyethylene film having improved heat sealability, in which the heat sealing strength of the heat seal portion is sufficiently obtained.

[0005]

As shown in FIG. 1, the present invention is designed to reduce the roughness of a roughened film surface (11, 21) when they are heat-sealed (FIG. 1b). It is an ultra-low density polyethylene film with improved heat-sealing property, characterized by roughening the film surface so that the molecular weight component film collapses (Fig. 1c).

The ultra low density polyethylene film (2) of the present invention
00) is an ultra-low density polyethylene having a density of 0.915 or less as shown in FIG. 3, which includes an extruder (210), a cooling device (230), a conveyor (240), a take-up machine (250) and a winder ( 260), and is extruded using a coat hanger die or a T-die on an extrusion die (220).

The roughening of the surface of the film of the present invention is carried out at the time of film production as shown in FIG. 3, in which one of the cooling rolls of the cooling device has a height of 0.5 to 1.0 μm and a diameter of 2.0 to 3 μm. 0.0μ
The surface of the film is roughened by using an embossing roll (231) having an embossment having an interval of 1.0 to 2.0 μm on the surface.

The low molecular weight component film on the film surface means that the low molecular weight component, which is contained in ultra-low density polyethylene in a large amount, causes a bleeding phenomenon depending on the elapsed time and the temperature during the storage of the film and exudes to the film surface. It is a thin film formed.

As shown in FIG. 1b, the method for heat-sealing the roughened film surfaces according to the present invention is performed by sandwiching between the heat upper plate (41) and the heat upper plate (42) with heat and pressure. In addition to the heat sealing method of the external heating method described above, an ultrasonic sealing method or a high frequency sealing method of the internal heating method may be used.

[0010]

When the surfaces of the roughened films are superposed and heat-sealed by the heat-sealing method, the surface of the heat-sealed surface is roughened as shown in FIG. The low-molecular weight component film that inhibits the heat-disintegration is largely collapsed by heat and pressure at the time of heat-sealing, and a new interface is formed on the heat-sealing surface, so that the fusing strength of the heat-sealing surface is improved. In the case of an ordinary film or a film whose surface is thinned, as shown in FIG. 2, the surface of the heat-sealing surface is a flat surface or a thin surface, and the low molecular weight component film on the surface does not largely collapse during heat sealing. A new interface cannot be formed, a low molecular weight component film remains on the heat-sealed surface, and the heat-sealing is inhibited, so that the welding strength is weak.
It is easy to peel off from the overlapping surface by external force.

[0011]

EXAMPLE An ultra-low density polyethylene having a density of 0.906 (N
UC MG-015) using the film manufacturing apparatus shown in FIG. 3, a coat hanger die is used as the extrusion die, and one of the cooling rolls of the cooling device is an embossing roll (height 0.7 μm, diameter (2.5 μm, interval 1.5 μm) to produce a 75 μm-thick ultra-low-density polyethylene film having one surface roughened according to the present invention. At the same time, using the same film production apparatus for comparative evaluation, embossing rolls for thinning (height 0.3 μm, diameter 1.0 μm, interval 0.5
μm) to produce a 75 μm-thick ultra-low-density polyethylene film having one surface reduced.

[0012] The two types of films thus produced were subjected to 60 ° C.
Fig. 1
By the heat-sealing process shown in Fig. 1, the embossed surfaces are overlaid (1-a) and the same heat-sealing conditions (seal width 5 mm, seal pressure 1.0 kg / cm ² , seal time 1.0 sec, hot plate) Temperature 140 ° C and 150 °
C), heat-sealing was performed (1-b), and changes in the heat-sealing strength of the heat-sealed portion with time were examined. The heat-sealed ultra-low-density polyethylene film was allowed to stand at room temperature for 24 hours, cooled sufficiently, and the fusion strength of the heat-sealed portion was measured.
The measuring machine was a Tensilon tensile tester manufactured by Orientec, and the tensile speed was 300 mm / min and the number was 5. Table 1 shows the results.

[0013]

[Table 1]

Looking at the results of the evaluation, the storage at 60 ° C.
In both the rough surface and the fine surface, the fusion strength of the heat-sealed portion rapidly decreased in 5 days, and thereafter decreased gradually. However, a comparison between the case of the rough surface and the case of the thin surface revealed that the rough surface has a higher heat fusion strength and has the effect of roughening the film surface.

Next, as a practical test, 2
With respect to each type of film, the time-dependent change of the fused portion of the heat-sealed portion when stored at room temperature for about 3 months was examined. The temperature during normal temperature storage was 10 to 25 ° C. Table 2 shows the results.

[0016]

[Table 2]

In both the rough surface and the thin surface, the heat-sealing strength of the heat-sealed portion gradually decreases, but the thin surface has a large decrease rate and a small strength. This tendency was remarkable especially at 140 ° C. where the heat sealing temperature was low. By making the surface of the film rough, the heat sealing strength of the heat seal portion was improved.

[0018]

According to the present invention, an embossing roll (having a height of 0.5 to 1.0 .mu.m and a diameter of 2.times.
0-3.0 μm, 1.0-2.0 μm spacing) Heat-sealing the roughened surfaces when the packaging material is made by using the ultra-low density polyethylene fill with the roughened film surface on the side to be heat-sealed. By doing so, a packaging material having a good fusion strength at the heat seal portion can be obtained.

The ultra-low density polyethylene film having a roughened heat-sealing surface side according to the present invention has a small effect on the heat-sealing property of the low molecular weight component film formed on the film surface by bleeding, so that the film is stored for a long term in the warehouse However, sufficient heat seal strength can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a heat sealing step of a roughened film of the present invention.

FIG. 2 is an explanatory view showing a heat sealing step of a thinned film for comparison with the present invention.

FIG. 3 is an explanatory diagram of an apparatus for producing an ultra-low density polyethylene film of the present invention.

[Explanation of symbols]

10 ...... Roughened film surface 11 ...... Roughened film surface 20 ...... Roughened other film surface 21 ...... Roughened other film surface 30 ...... Roughening of the present invention Heat-sealed part of each film surface that has been heat-sealed 31 …… Collapsed low molecular weight component film 32 …… Completely heat-sealed and integrated part 41 …… Heat-sealing upper plate 42 …… Heat Hot bottom plate for sealing 110 …… Thinned film surface 111 …… Thinned film surface 120 …… Other thinned film surface 121 …… Other thinned film surface 130 …… Thinned film surface Heat-sealed part of each other by heat sealing 131 …… Low molecular weight component film remaining on the heat-sealed surface 200 ・ ・ ・ Ultra low density polyethylene film 210 …… Extruder 220 …… Extrusion die 230 …… Cooling device 231 …… … Emboss roll 240… Conveyor 250 …… Takeover Machine 260 ...... Winding machine

Claims (1)

(57) [Claims] 1. A heat-sealing property which is characterized in that a film surface is roughened so that a low molecular weight component film on the film surface is disintegrated when heat-sealed to each other. Ultra low density polyethylene film.