JPH1142706A - Thermal contraction polyester film and vessel having the same mounted thereon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of folding into the vessel side even in an inner surface printed film being stored for a long period of time after the center sealing by carrying out printing with the use of printing ink having a predetermined value or lower in a swelling rate to the film and dimensional variation rate in the film orientation direction in a solvent of printing ink. SOLUTION: A thermal contraction polyester film is formed into a sleeve, which has non-orientation or two times or lower magnification orientation in one direction and four times or higher magnification orientation in the direction intersecting this, and inner surface printing is conducted such that the upper end part and lower end part thereof come to be non-printed parts as being mounted on the vessel. When printing is executed, a mixed solvent of ethyl acetate, methyl ethyl ketone, and toluene is used mainly for a solvent of gravure printing ink so as to implement printing by the use of printing ink having a 3% or lower swelling rate to the film and 3% or lower dimensional variation rate in the orientation direction of the film in the solvent. Thus, folding at its upper end never occurs even in the case where the printing film is put on the vessel to be thermally contracted after the long storage period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable polyester film whose upper end does not break into the container when heat-shrinkable even when stored for a long time after a center seal.

[0002]

2. Description of the Related Art Plastic bottles, glass bottles and other containers are provided with a heat-shrinkable film printed on the inner surface to convey information such as a product name and a precautionary statement and to impart design. Is commonly done. Examples of the film include a polyvinyl chloride film, a polystyrene film, and a polyester film. However, the polyvinyl chloride film and the polystyrene film have a problem that they cannot withstand high-temperature boil treatment or retort treatment because of their poor heat resistance. On the other hand, since polyester films have heat resistance, they are often used as optimal films for such applications. However, when the polyester film stored for a long time after the center seal is put on a container and heat shrinked from the point of delivery time and usage amount, the upper end of the film breaks into the container side and the appearance deteriorates, and as a defective product There was a problem of having to sleep.

[0003]

A first problem to be solved by the present invention is that a heat-shrinkable polyester film having an inner surface printed thereon and stored for a long time after sealing a center is placed on a container. An object of the present invention is to provide a film which does not bend on the container side when shrinking.

[0004] A second object is to provide a container in which a heat-shrinkable polyester film having an inner surface printed thereon is mounted without breaking.

[0005]

According to the present invention, there is provided a heat-shrinkable polyester film which has been internally printed in advance so that an upper end and a lower end are non-printed areas. The printing ink is characterized by being printed using a printing ink in which the solvent of the printing ink has a swelling ratio of 3% or less to the film and the dimensional change in the stretching direction of the film is 3% or less.

Further, the main component of the solvent is water and / or alcohol.

Then, a tubular heat-shrinkable polyester film which has been subjected to an inner surface printing using a printing ink containing the above-mentioned solvent so that the upper end and the lower end are non-printed portions is mounted without breaking. It is characterized by being a container made.

[0008]

Embodiments of the present invention will be described in detail below.

The first aspect of the present invention relates to a heat-shrinkable polyester film whose upper end does not break into the container when heat-shrinkable even when stored for a long time after the center seal. The heat-shrinkable polyester film is a non-stretched film in one direction or a low-magnification stretching of 2 times or less, and a high-magnification stretching film of 4 times or more in a direction perpendicular thereto (hereinafter referred to as a main axis direction). The raw material resin for the film is mainly composed of what is generally called a copolyester. In addition, the surface of the film may be subjected to a surface treatment such as corona discharge treatment to increase the adhesiveness with the printing ink,
Alternatively, an antistatic agent may be applied to the opposite surface to have an antistatic effect.

The flat heat-shrinkable polyester film manufactured at the film manufacturing factory is printed on one side by a gravure printing machine (when mounted on a container, printed on the surface that comes to the container side).
Then, if necessary, the printed surface is inner-coated and wound on a paper tube. The printed design is an intermittent design such that the upper end and the lower end become non-printed portions when mounted on the container, and the interval between them is 80 mm or less, usually 10 mm or less. (The reason for the intermittent design is as follows: if the design is continuous, it will be printed up to the upper end of the film when it is mounted on the container, and it is heated and shrunk. And, just before the completion of the shrinkage, the film at the upper end, i.e., the neck of the container, curls to the outside of the container, and not only looks bad, but also when the heating source is hot water or steam, or boil or retort in a later step. The reason for this is that hot water or steam penetrates between the film and the container, resulting in a defective product.The reason why the film curls outwardly is that the final ultimate shrinkage is higher on the outer surface than on the inner printing surface. The solvent for gravure printing ink is mainly ethyl acetate,
A mixed solvent of methyl ethyl ketone and toluene, to which isopropyl alcohol may be added. Next, the film is center-sealed (finished into a cylinder) as shown in FIG. 1 using a solvent that dissolves the film, folded flat, and wound around a skein or paper tube. Next, the film is cut at substantially the center of the non-printing portion, covered with each container, and thermally shrunk to obtain a target container. There are cases where the container is filled with the contents in advance, and cases where the container is filled with the contents after the film is attached.

Although the center-sealed film may be immediately mounted on a container, it usually takes 1 to 3 months to completely use up all the films from the viewpoint of delivery time and amount of use. During this time, it is stored in the form of a skein or a paper tube. If the film stored for a long time is cut and put on a container for thermal shrinkage, the upper end of the film breaks into the container side, and defective products with poor appearance frequently appear.

The present inventors conducted the following verification experiments to elucidate the cause.

(Preparation of Verification Material A) An intermittent pattern having a non-printing portion with a spacing of 4 mm was printed on one side of a flat heat-shrinkable polyester film by a gravure printing machine. The solvent of the printing ink used was a mixed solvent consisting of ethyl acetate, methyl ethyl ketone, toluene, and isopropyl alcohol. The next day, the center of the film was sealed with a solvent so that the printed surface of the film became the inner surface.
5 rolls of a paper tube wound film were obtained.

(Preparation of Verification Material B) Five rolls of a paper tube-wound film were obtained in the same manner as in the preparation of the verification material A except that the film was not printed.

(Verification Experiment 1) The day after the center seal,
Heat-shrinkage was performed by cutting approximately 20 central bottles of one volume of each of the verification materials A and B, placing them on 20 PET bottles one by one, and heating them in a steam tunnel at 90 ° C. for 8 seconds. And attached. Then, the number of PET bottles in which the upper end had been folded was examined. Table 1 shows the results. As can be seen from Table 1, no folding of the film occurred.

(Verification Experiment 2) One month, two months, three months, and four months after center sealing, using the remaining four volumes in the same manner as in verification experiment 1, (Stored at 200 ° C.), and the number of PET bottles in which the film was broken by heat shrink mounting was examined. Table 1 shows the results.

From the difference between the verification object A and the verification object B in the verification experiments 1 and 2, the cause of the fold is the gravure printing ink. The present inventors have speculated that the residual solvent may be the cause of the gravure printing ink.
This is because the main components of the gravure printing ink are a vehicle, a pigment, a dispersant, and an organic solvent, and only the residual solvent due to the organic solvent changes with the length of the storage period. To verify this assumption, the following experiment was performed.

(Verification Experiment 3) A plain heat-shrinkable polyester film was center-sealed to form a cylindrical film. Next, this cylindrical film was cut into five pieces each having a length of 1 m, and five kinds of solvents, namely, ethyl acetate,
Methyl ethyl ketone, toluene, isopropyl alcohol, and a liquid mixture obtained by mixing equal weights thereof (verification product A
Of the gravure printing ink used in the preparation of the gravure printing ink) was dropped into the cylinder, and both ends were immediately sealed with aluminum adhesive tape. Then, it was stored at 40 ° C. for 30 hours for promotion. Next, these five pieces were mounted on a PET bottle in the same manner as in the verification experiment 1 and checked for folds. As a result, folds occurred except for those containing isopropyl alcohol. From this, it was found that the cause of the fold was the residual solvent, and that isopropyl alcohol had nothing to do with the fold. Therefore, the following verification experiments 4, 5, and 6 were performed to see the effect of each solvent on the film.

(Verification Experiment 4) The five types of solvents used in Verification Experiment 3 were used in place of calcium chloride in JIS Z0208, which is a standard for measuring the moisture permeability of a film, and a plain heat-shrinkability without a center seal was used. The permeation amount of each organic solvent of the polyester film was measured. Table 2 shows the results. From the verification experiment 4, it was found that ethyl acetate, methyl ethyl ketone, toluene and the mixed solution permeated the film, but the permeation amount, that is, the permeation speed was very small, while isopropyl alcohol did not permeate the film.

(Verification experiment 5) A plain heat-shrinkable polyester film without a center seal was vertically and horizontally 1 ×
Cut out to a size of 00 mm x 100 mm, verification experiment 3
Was immersed in the five kinds of solvents used at 25 ° C. for 24 hours, and the swelling ratio of each solvent was measured. Table 3 shows the results.

(Verification experiment 6) A plain heat-shrinkable polyester film without a center seal was used.
Cut out to a size of 00 mm x 100 mm, verification experiment 3
Was immersed in the five kinds of solvents used in the above at 25 ° C. for 24 hours, and the dimensional change in the main axis direction (transverse direction in this film) before immersion was measured. Table 4 shows the results. In Table 4, "-" indicates that the film shrank. From verification experiments 5 and 6, it was found that ethyl acetate, methyl ethyl ketone, toluene and the mixed solution were absorbed into the film and the film shrank due to its plasticizing effect, whereas isopropyl alcohol did not.

From the verification experiments 4, 5, and 6, the present inventors concluded that the phenomenon that the film was folded toward the container was due to the following effect. That is, the residual solvent of the printing ink trapped in the cylinder by the center seal has a low permeation rate, and is not absorbed by the film the day after the center seal as in the verification experiment 1. Therefore,
Both the inner side and the outer side of the film at the upper end, which is the non-printing portion, are not affected by the residual solvent, so that no folding occurs.

On the other hand, if the film is stored for a long time after the center seal, the residual solvent other than isopropyl alcohol is gradually absorbed by the film, but the permeation speed is low, so that the inner side of the film at the upper end remains more than the outer side of the tube. It is concluded that folds are likely to occur due to the absorption gradient in which the absorption amount of the solvent increases.

The invention of claim 1 has been derived from the above conclusion. Mixtures were prepared with isopropyl alcohol that does not affect the heat-shrinkable polyester film, and ethyl acetate, methyl ethyl ketone, and toluene, which have an effect, on various compositions and in various composition ratios. As a result of repeating steps 5 and 6, the swelling ratio of the mixed solution to the film is 3% or less, preferably 1% or less, more preferably 0.5% or less, and the dimensional change in the film stretching direction is 3% or less. % Or less, preferably 1% or less, more preferably 0.5% or less has been found to be advantageous for folding. That is, printing on a heat-shrinkable polyester film using a printing ink in which the solvent of the printing ink is within the range of this condition is advantageous for folding.

In order to reduce the amount of residual solvent using conventional printing ink, the drying temperature of the printing press was increased, the amount of hot air was increased, or the printing speed was reduced within a range where the film did not shrink. However, none of them had any effect on the folding.

The invention of claim 2 relates to a preferred specific solvent for printing ink. In a heat-shrinkable polyester film which has been formed into a tubular shape with a center seal and which has been subjected to internal printing in advance so that the upper end and the lower end become non-printing portions when mounted on a container, the solvent of the printing ink is changed to water and / or water. Alternatively, by using alcohol, a film without folding can be obtained even when stored for a long time after the center seal.

The alcohol is, for example, methyl alcohol,
Examples thereof include ethyl alcohol, isopropyl alcohol, and n-butyl alcohol. However, the present invention is not limited to these, and all compounds having a hydroxyl group in the molecule such as cellosolve are included.

Other liquid substances may be appropriately added to the printing ink according to the purpose within a range that does not impair the characteristics of the solvent. For example, a small amount of n-methylpyrrolidone may be added to enhance the solubility of the vehicle.

The vehicle used for the printing ink is not particularly limited as long as it can be dissolved in the above-mentioned solvent. For example, a water-soluble acrylic resin using methacrylic acid or acrylic acid as a main starting material can be exemplified. Known pigments and dispersants may be used.

The invention of claim 3 relates to a container to which a polyester film is heat-shrink-mounted. A heat-shrinkable polyester film formed in a tubular shape with a center seal and subjected to internal printing in advance so that an upper end and a lower end are non-printed portions when mounted on a container, wherein the solvent for the printing ink is as described above. And Then, the tubular body is covered and thermally shrunk, whereby a container having no fold at the upper end of the film is obtained.

The heat source to be thermally shrunk is not particularly limited, and examples thereof include steam, hot water, hot air, and an electric heater.

The container is not particularly limited as long as the effect of mounting the film by heat shrinkage can be recognized. For example, plastic bottles, glass bottles,
A metal can is exemplified.

[0033]

EXAMPLES Next, typical examples of the present invention will be described.

The methods for measuring and evaluating the physical properties used in the present invention are as follows.

The swelling ratio of the solvent to the film was measured as follows. A plain film having a size of 100 mm × 100 mm in length × width is immersed in a solvent at 25 ° C for 24 hours, and the value obtained by dividing the weight of the film increased after immersion by the weight of the film before immersion and multiplying by 100 is swelled. Rate.

The dimensional change of the film was measured as follows. A plain film having a size of 100 mm × 100 mm in length × width was immersed in a solvent at 25 ° C. for 24 hours, and the amount (mm) of dimensional change in the main axis direction after immersion was defined as a dimensional change rate (%).

Example 1 Polyester resin 100 in which the dicarboxylic acid component is terephthalic acid and the diol components are ethylene glycol and cyclohexanedimethanol
A mixture of 30 parts by weight of a polyester resin in which the dicarboxylic acid component is terephthalic acid and the diol component is ethylene glycol is extruded from a T-die at 280 ° C., cooled and solidified, and cooled at 95 ° C. The film was stretched by a tenter and subsequently annealed to obtain a heat-shrinkable polyester film having a thickness of 40 μm.

Example 2 Printing in two colors, white and indigo, in which the solvent is a mixed solvent of 100 parts by weight of water, 200 parts by weight of ethyl alcohol, and 2 parts by weight of n-methylpyrrolidone, and the vehicle is a water-soluble acrylic resin Using ink, two-color printing was performed on one side of the film obtained in Example 1 with a gravure printing machine. As the printed pattern, a pattern having a non-printed portion intermittently with a width of 4 mm in the film flow direction was used.

Next, as shown in FIG. 1, the center is sealed (finished into a cylindrical shape) using a solvent so that the printing surface becomes the inner surface, and the sheet is folded flat to obtain five 100-m long paper-tube-wrapped films. Was.

The day after the center seal, 1 month, 2 months, 3 months, and 4 months (the film was kept at 25 ° C. during this period)
), Cut about 20 sheets in the center of each volume at the center of the non-printing section, and cut 20 sheets of PET one by one.
The bottle was covered, heated in a steam tunnel at 90 ° C. for 8 seconds, and heat shrunk to be mounted. Then, the number of PET bottles in which the upper end portion of the film, which is the non-printing portion, was broken was examined. Table 5 shows the results. As can be seen from Table 5, there was no fold in the film.

(Comparative Example 1) The procedure was carried out except that the solvent was a mixed solvent in which ethyl acetate, methyl ethyl ketone, toluene and isopropyl alcohol were mixed in equal weights, and the vehicle was a two-color printing ink consisting of acrylic resin and white and indigo. PET bottle 20 equipped with a film in the same manner as in Example 2.
Got a book. Then, the number of PET bottles in which the upper end of the film was folded was examined. Table 5 shows the results. As can be seen from Table 5, the longer the storage period, the higher the rate of occurrence of breakage.

Example 3 Using the film obtained in Example 1, the swelling ratio and dimensional change ratio of the mixed solvent of the printing ink used in Example 2 were measured. Table 6 shows the results. Table 6 shows that there was no change in both the swelling rate and the dimensional change rate.

[0043]

The present invention is embodied in the form described above, and has the following effects. The solvent of the printing ink has a swelling ratio of 3% or less to the film and a dimensional change rate of 3% or less in the stretching direction of the film. Even in the case of a heat-shrinkable polyester film, the upper end of the film does not break into the container when the heat-shrinkable polyester film is placed on the container.

When the main component of the solvent of the printing ink is water and / or alcohol, even if the heat-shrinkable polyester film is stored for a long time after the center seal, it is placed on the container and heat-shrinked. Does not break into the container.

[Brief description of the drawings]

FIG. 1 is a simplified diagram of a tubular film obtained by center-sealing a flat heat-shrinkable polyester film.

FIG. 2 is a simplified diagram showing a state of a film normally contracted and mounted on a container.

FIG. 3 is a simplified diagram showing a state of a film whose upper end is folded toward a container.

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroe Tanimura 163 Morikawaramachi, Moriyama-shi, Shiga Prefecture Gunze Co., Ltd. Moriyama Plant

Claims (3)

[Claims] 1. A heat-shrinkable polyester film which has been formed into a cylindrical shape by a center seal and has been subjected to internal printing in advance so that the upper end and the lower end become non-printing portions when mounted on a container. A heat-shrinkable polyester film printed with a printing ink, wherein the solvent has a swelling ratio of 3% or less to the film and a dimensional change in a stretching direction of the film is 3% or less. 2. The heat-shrinkable polyester film according to claim 1, wherein the main component of the solvent is water and / or alcohol. 3. A container provided with the heat-shrinkable polyester film according to claim 1 without being folded.