JPH0678098B2 - Method for preventing opacity of wound polyester film for preventing bottle breakage - Google Patents

Description

The present invention relates to a method for preventing opacity of a wound polyester film for bottle breaking prevention, and more particularly to a variety of bottles using a heat-shrinkable stretched polyester film. The present invention relates to a method for preventing opacity of a rolled polyester film for bottle breaking prevention, which prevents the stretched polyester film from becoming opaque when heat-sterilized with steam, hot water, etc.

<Problems to be Solved by Conventional Techniques and Inventions> Conventionally, in order to protect various bottles such as beverage bottles and to improve the appearance, the stretched polyester film is heat-shrinked to wrap various bottles. What you have done is known. Further, the sterilization step of sterilizing the contents in the bottle, after filling the contents such as juice in a bottle wrapped and wrapped with the stretched polyester film, for rapid sterilization, high temperature, for example about 90 It is performed by a heating means such as steam or hot water having a temperature of ℃ or higher.

However, when sterilized by the heating means, a stretched polyester film, in particular, a portion of the stretched polyester film located at the upper and lower ends in the axial direction of the bottle is water vapor,
There is a problem that it becomes white and becomes opaque by hot water or the like. Further, when the film becomes opaque, not only the appearance of the bottle is deteriorated, but also when a film on which printing or the like is applied is used, the color tone is changed and the commercial value is lowered. was there.

<Object of the Invention> The present invention has been made in view of the above problems, and when heat sterilizing the contents of a bottle with steam, hot water, or the like, the stretched polyester film wrapped and wrapped becomes opaque. An object of the present invention is to provide a method for preventing opacity of a wound polyester film for preventing bottle breakage.

<Means and Actions for Solving Problems> The present invention relates to a method in which a stretched polyester film is heat-shrinked, wrapped in a bottle, and then the contents in the bottle are heat-sterilized. A film with a heat shrinkage of 40 to 90% in the width direction of the bottle and -10 to 20% in the axial direction of the bottle is used, and the residual heat shrinkage after heat shrinkage is the width of the bottle. The conventional problems described above are solved by heat-shrinking so as to be 35% or more in the direction and 15% or less in the axial direction of the bottle.

According to the present invention having the above-mentioned constitution, as the stretched polyester film, one having a specific heat shrinkage rate is used, and after the heat shrinkage, the heat shrinkage is performed so as to obtain the specific residual heat shrinkage rate. The stretched state of the film is maintained even after thermal contraction, and is not affected by water vapor or hot water that causes film opacity.

The present invention will be described in detail below.

In the method of the present invention, first, a stretched polyester film is heat-shrinked to be brought into close contact with various bottles such as a beverage bottle, and then wrapped.

The polyester constituting the stretched polyester film, ethylene glycol, 1,4-butanediol,
Polyesters having various film forming properties, which are condensation products of glycols such as polymethylene glycol and polyvalent carboxylic acids such as terephthalic acid, dimethyl terephthalate and dimethyl isophthalate, or alkyl esters thereof can be used. Among these polyesters, a polyester having heat resistance sufficient to withstand the temperature during heat sterilization and the like, particularly polyethylene terephthalate which is a condensate of ethylene glycol and dimethyl terephthalate having well-balanced properties, is preferable.

Further, in order to obtain a stretched polyester film using the polyester having the film forming property, the polyester is melt-extruded by a suitable method such as a plug method, an inflation method, a T-die method using a circular die or the like, and stretched. do it. This stretching process can be carried out by an appropriate method such as a conventional method, for example, a pin tenter method, a clip tenter method, a roll stretching method, a tube method, etc., at the same time as or after extrusion, at a predetermined temperature, for example, about 80. ~ 130
It is carried out by uniaxially or biaxially stretching while heating at a temperature of ℃, and quenching.

The heat shrinkage of the stretched polyester film is 135 ° C., 1
By heating for 5 seconds, it should be 40 to 90% in the width direction of the bottle and -10 to 20% in the axial direction of the bottle. When the heat shrinkage ratio in the width direction of the bottle is less than 40%, it is difficult to tightly cover the bottle during heat shrinkage, and when it exceeds 90%, it is possible to produce a product having a stable shrinkage ratio. Have difficulty. Further, if the heat shrinkage ratio in the axial direction of the bottle exceeds 20%, the appearance after contact packaging becomes poor, and if it is less than -10%, a product having a stable shrinkage ratio (expansion ratio) is produced. Is difficult.

The stretched polyester film may be untreated, or may be surface-treated by corona discharge or the like in order to improve printability, adhesiveness and the like.

Then, the above stretched polyester film is heat-shrinked to be closely attached to the bottle and wrapped and wrapped.

At that time, in order to prevent the stretched polyester film from becoming white and opaque in the heat sterilization step, the residual heat shrinkage rate after heat shrinking the stretched polyester film is 35% or more in the width direction of the bottle. , Heat-shrink to 15% or less in the axial direction of the bottle. When the residual heat shrinkage ratio is out of the above range, the film becomes opaque, particularly in the stretched polyester film at the portions corresponding to the upper and lower ends of the bottle in the axial direction.

More specifically, the film is prevented from becoming opaque by heat-shrinking so that the residual heat shrinkage in the axial direction increases as the residual heat shrinkage in the width direction after heat shrinking decreases. That is, when the residual heat shrinkage in the width direction is less than 35%, the film is likely to become opaque even if the residual heat shrinkage in the axial direction changes in a wide range. When the residual heat shrinkage after heat shrinkage is 35% or more and less than 55% in the width direction of the bottle, the residual heat shrinkage ratio in the width direction of the bottle is 1%. By heat shrinking as described above, it is possible to prevent the film from becoming opaque. In particular, when heat shrinking is performed so that the residual heat shrinkage in the width direction after heat shrinkage is 35% or more and less than 50%, the residual heat shrinkage in the axial direction is at least 1% or more, and preferably, Heat shrinking to about 2% or more can prevent the film from becoming opaque. Further, when heat shrinking is performed so that the residual heat shrinkage in the width direction is 50% or more and less than 55%, the heat shrinkage is performed so that the residual heat shrinkage in the axial direction is 1% or more. It is possible to prevent the polyester film from becoming opaque. On the other hand, the residual heat shrinkage in the width direction is 55%
When it exceeds, even if the residual heat shrinkage in the axial direction changes in a wide range, opacity of the film hardly occurs.

Incidentally, in order to make the residual heat shrinkage after heat shrinkage within the above range, the heat shrinkage of the stretched polyester film before heat shrinkage and the outer peripheral length of the bottle are measured in advance, and the The stretched polyester film before heat shrink may be wound around a bottle so as to have the above-mentioned residual heat shrinkage and heat shrunk.

When wrapped in various bottles under the above conditions, since the stretched state of the film is maintained even after wound packaging, the bottle can be tightly packed for a long period of time, and the influence of steam, hot water, etc. It is possible to prevent the film from becoming opaque without receiving it.

The heat shrinkage of the fill is usually performed at a temperature necessary for tightly packaging the bottle, for example, a temperature of 100 to 250 ° C. At this time, an appropriate means such as far infrared rays or hot air is used as the heating means for causing the heat shrinkage.

Then, the contents in the various wound bottles are heat-sterilized by a heating means such as steam or hot water. This heat sterilization condition varies depending on the contents of the bottle, but in order to sterilize quickly and increase productivity, it is preferable to carry out at a temperature of 50 to 60 ° C. in the case of carbonated drinks, and in the case of other contents. ,at least
It is carried out at a temperature of 80 ° C., preferably 90 ° C. or higher, for an appropriate time, for example, 1 to 30 minutes. When heat sterilization is performed under such conditions, the quality of the contents does not change.

In addition, the contents such as juice should be filled in any step before heat-shrinking the stretched polyester film and closely contacting with the bottle for wrapping, or after wrapping the bottle with the stretched polyester film. You can

As the stretched polyester film, those having various thicknesses such as 0.005 to 2 mm can be used. Furthermore, the stretched polyester film is various synthetic resin films or sheets within a range not hindering heat shrinkability, for example, polyethylene, polypropylene, polystyrene,
It may be laminated with a film or sheet of nylon, cellophane, polyvinyl chloride, polyvinylidene chloride or the like.
When such a laminated film is used, in addition to various properties such as heat resistance of polyester, properties such as thermal adhesiveness can be improved. The synthetic resin film or sheet may be stretched and heat-shrinkable, or may be a non-foamed or a foamed film or sheet extruded and foamed in combination with an ordinary foaming agent.

The present invention can prevent opaqueness due to whitening of the film, and is therefore particularly suitable when a stretched polyester film having various patterns and the like applied by printing or the like is used.

<Example> Hereinafter, the present invention will be described in detail based on examples.

G-PET (manufactured by Eastman Kodak Company, USA) was used as the polyester, melt-extruded by a T-die method using a circular die, and uniaxially stretched at various stretching ratios by a pin tenter method in the same manner as extrusion, followed by rapid cooling. . The obtained stretched polyester film had a heat shrinkage ratio shown in Table 1.

Then, the polyester films having various heat shrinkage ratios shown in Table 1 were wrapped around a glass bottle filled with juice, and heated at a temperature of 200 ° C. for 8 seconds so that the residual heat shrinkage ratio shown in Table 1 was achieved. It was wrapped in. At this point, no whitening phenomenon was observed in any of the films and they were transparent.

Then, in order to heat and sterilize the juice in the glass bottle, it was treated with hot water at 90 ° C. for 20 minutes, and the results shown in Table 1 were obtained.

In the table, the heat shrinkage rate of the film before heat shrinkage was determined by the following equation from the dimensions of the film before and after heat shrinkage by heat shrinking the film in an oven at 130 ° C for 15 seconds.

Further, the residual heat shrinkage rate of the film after heat shrinkage, the film is heat shrunk and wrapped in a bottle, and then the film having heat shrinkability is cut off, and the cut film is heat-treated in the same manner as above. The shrinkage was determined from the dimensions of the excised film before and after thermal shrinkage.

Further, the opacity of the film was visually evaluated according to the following criteria.

○: transparent, △: slightly opaque to a practically acceptable degree, ×: opaque Also, in the table, 55/18 etc. means that the heat shrinkage ratio in the width direction of the bottle is 55%, The heat shrinkage ratio in the axial direction of the bottle
It shows that it is 18%.

As is clear from Table 1, all of the above stretched polyester films having a residual heat shrinkage ratio of less than 35% after heat shrinkage became opaque. The residual heat shrinkage in the width direction after heat shrinkage is 50%, and the residual heat shrinkage in the axial direction is 0%.
One of them was slightly opaque to the extent that there was no practical problem, but all others were transparent.

In the same manner as in the above example, the heat shrinkage ratio before heat shrinkage 55
When a 10% stretched polyester film was used and heat-shrinked so that the residual heat-shrinkage rate after heat-shrinkage was 51/7, the film was transparent.

<Effects of the Invention> As described above, according to the method for preventing opacity of the bottle-breaking wound polyester film of the present invention, a stretched polyester film having a specific heat shrinkage rate is used, and Since the film is heat-shrinked so that the residual heat-shrinkage rate becomes a specific value, and closely adhered to various bottles and wrapped and wrapped, the film does not whiten and become opaque during heat sterilization.
Further, since the stretched state of the stretched polyester film is maintained even after the heat shrinkage, there is an effect peculiar to the present invention in that the stretched polyester film can be kept in a tightly tightly packed state for a long period of time.

Claims (2)

[Claims] 1. A method in which a stretched polyester film is heat-shrinked and wrapped in a bottle, and then the contents in the bottle are heat-sterilized, wherein the stretched polyester film has a heat shrinkage ratio of the width of the bottle. 40 to 90% in the direction of the bottle and -10 to 20% in the direction of the axis of the bottle, the residual heat shrinkage after heat shrinkage is 35% or more in the width direction of the bottle, the axis of the bottle A method for preventing opacity of a wound polyester film for bottle breaking prevention, which comprises heat-shrinking so as to be 15% or less with respect to the direction. 2. The residual heat shrinkage ratio of the stretched polyester film after heat shrinkage is 35% or more in the width direction of the bottle and 55
When it is less than%, the shrinkage prevention method of the wound polyester film for bottle breaking prevention according to claim 1, wherein the shrinkage rate of the residual heat in the axial direction of the bottle is 1% or more. .