JPS58119827A - Manufacture of film heat-shrinkable longitudinally - Google Patents

Abstract

PURPOSE:To obtain the titled film excellent in fusing sealability, heat shrinkage, and transparency, by producing a film of a linear low density polyethylene, preheating it to a specific temperature, and stretching it longitudinally by rolling. CONSTITUTION:After forming the film of a linear low density polyethylene, it is preheated to a temperature of from 90 deg.C up to the melting point (preferably between 100 and 110 deg.C). Then it is stretched longitudinally by three to five times the original at a rolling temperature preferably at around or below 60 deg.C to obtain the desired film. EFFECT:The rejected part can be reused. USE:The method is excellently suitable for sleeve packaging in particular, and is also suitable for automatic packaging machines.

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a method for producing a longitudinally heat-shrinkable film made of directly exposed low density polyethylene.

Conventionally, polyethylene heat-shrinkable films have mainly used polyethylene that has been irradiated with electron beams, etc.
When used in heat-sealable packaging due to its poor sealability, it is necessary to carry out regular sealing using an inverter or the like, and therefore it has been cut with a cutter or the like and used for packaging. Furthermore, even if attempts were made to reuse defective parts such as ears, their physical properties had changed due to exposure to electron beams, etc., and they could not be mixed with raw materials and reused, resulting in stagnation. Therefore, the present inventors focused on RI-directed low-density polyethylene,
By manufacturing linear low-temperature polyethylene using a patented method, which is the result of repeated efforts and efforts, it has excellent bath sealability, excellent physical properties, and is easy to replace defective parts. It was possible to create a usable longitudinally heat-shrinkable film using pJ technology.

That is, the present invention is characterized by forming a film made of straight-cut low-density polyethylene, preheating it from 90°C to a temperature below the melting point of the polyethylene, and then rolling it 3 to 5 times in the longitudinal direction. The present invention is based on the discovery of a method for producing a film that is stretched by /l/ and is heat-shrinkable in the longitudinal direction.

The single-sided low-density polyethylene according to the present invention refers to a low-density polyethylene in which a large number of irregular 1llds are present in an appropriate amount. Polyethylenes with short and low n% md are called medium and high strength polyethylenes, and the latter are manufactured by a high-pressure method, and the latter by a medium-low pressure method. However, the polyethylene of the present invention is produced by a medium-low pressure method, and by artificially introducing side chains, the polyethylene becomes heavier and less densely packed, resulting in the production of low-density polyethylene. This is the polyethylene according to the present invention, and in order to introduce side chains, Puden-1 or the like may be added to form a copolymer, or any other suitable method may be used.

A film made of such linear low density polyethylene 1-t-
Although the melt extrusion method is sufficient for the
It is also possible to use other film forming methods.

The stretching method may be low A/g stretching, for example, it may be passed through several uniform speed preheating rolls to preheat τ, and then stretched to a desired magnification using stretching rolls set at a predetermined stretching ratio. It is necessary to sufficiently preheat the film using the preheating roll, and the temperature is 90t.

It is sufficient that the temperature is below one point of the polyethylene according to the present invention, preferably in the range of 100 to 110°C. The temperature of the stretching roll may be either high or low, but if it is too high, problems such as shrinkage between the stretching roll and the winding roll may occur. Therefore, the temperature may preferably be 60°C or lower, and since the film is sufficiently preheated, there will be no particular problem even if the temperature of the stretching roll is low.The stretching ratio should be within the range of 3 to 5 times. If the value is other than n, a suitable longitudinally heat-shrinkable film cannot be obtained.

The present invention is as described above, and the method of the present invention allows the production of a lume to be easily made into a mJ function, which has a lot of utility value in general appropriate packaging, and is also excellent as a film for automatic packaging machines. It has a lot of utility value, especially for sleeve packaging, and is effective when applied to automatic machines for integrated packaging that use the packaging form.

Example 1 Molecule that is linear and has an excessive number of side chains approximately the length of the foot - 1
Low-density polyethylene with a density of 8,922 and Ml of 2.5 was extruded to form a raw film with a thickness of 160 μm. The raw film was sufficiently preheated to 108°C using a triple preheating roller, and then heated to 43°C at a speed ratio of 1:4.
A film which was heat-shrinkable in the longitudinal direction was obtained by passing it through a stretching roller T-.

<Example 2> A raw film with a thickness of 144) μ obtained using the same polyethylene as in Example 11) was stretched 4 times at a speed ratio of 1:4 using a preheating roller at 103°C and a stretching roller at 45°C. When the film was longitudinally stretched, a film having a thickness of 35 μm and heat-shrinkable in the longitudinal direction was obtained.

Comparative Example 1> Using the same polyethylene as in Example (1), the thickness was 160 mm.
An original film of μ was obtained. The raw film was heated using a preheating roller at 88°C and a stretching roller at 43°C at a speed ratio of 1:
4, a film with a thickness of 40 μm was obtained.

Example 2> Using polyethylene with a density of 0.921, a raw film with a thickness of 160 μm was formed by extrusion. After that, the film was irradiated with an electron beam, and stretched with a preheating roll at 110°C and a stretching roll/
This is a 40μ thick film that is heat-shrinked in the longitudinal direction by low/&/grind stretching at I/40°C and a speed ratio of 4:1.

Hata (1) Gear open 30sho heating (%) 02
) 20℃, JIS-, -6732 (We/15m
)11i(3) 20℃, JIS-Z-1702(
It can be seen that the film according to the present invention, which has a throughput of lv/15 m) or more, has not only bath-r sealing properties but also excellent heat shrinkage and transparency.

Using the film prepared in Example (1), 6 grams of juice was packaged using an automatic machine to obtain a packaged article having the shape of a sleeve package. Since this product can be used without bathing, a small and compact device can be used, which improves packaging efficiency. - However, since the conventional film of Comparative Example (2) cannot be fused and sealed, it requires a large device, making it inconvenient to handle, and its efficiency is not as high as that of the present invention.

Claims (1)

[Claims] A straight-curved film made of low-strength polyethylene is produced,
Thereafter, the bond is preheated at a temperature from 90° C. to a temperature below the melting point of the polyethylene, and is roll-stretched in the longitudinal direction from 3 to 5 degrees, thereby producing a heat-shrinkable film in the longitudinal direction.