JP3825426B2 - Method for preventing folding of heat-shrinkable polyester film to the container side - Google Patents

Description

【００４３】

【００４４】

【００４５】

【００４６】

【００４７】

【００４８】
【発明の効果】
本発明は、以上説明したような形態で実施され、以下に記載するような効果を奏す。
印刷インキの溶剤が、フィルムへの膨潤率が３％以下であり、フィルムの延伸方向の寸法変化率が３％以下である、印刷インキを用いて印刷することにより、センターシール後長期間保管した熱収縮性ポリエステルフィルムであっても、容器に被せ熱収縮させる際、フィルムの上端部が容器側に折れ込まない。
【００４９】
印刷インキの溶剤の主成分を水及び／又はアルコールとすることにより、センターシール後長期間保管した熱収縮性ポリエステルフィルムであっても、容器に被せ熱収縮させる際、フィルムの上端部が容器側に折れ込まない。
【図面の簡単な説明】
【図１】フラット状熱収縮性ポリエステルフィルムをセンターシールして得られた筒状フィルムの簡略図である。
【図２】正常に容器に収縮装着されたフィルムの状態を示す簡略図である。
【図３】上端部が容器側に折れ込んだフィルムの状態を示す簡略図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method in which an upper end portion does not fold into a container side when a heat-shrinkable polyester film is heat-shrinked even if stored for a long time after the center seal.
[0002]
[Prior art]
In general, plastic bottles, glass bottles and other containers are equipped with heat-shrinkable films with printed surfaces on them to convey information such as product names and precautionary statements and to provide design. Yes.
Examples of the film include a polyvinyl chloride film, a polystyrene film, and a polyester film. However, since polyvinyl chloride films and polystyrene films have poor heat resistance, there is a problem that they cannot withstand high-temperature boil processing and retort processing.
On the other hand, since a polyester film has heat resistance, it is frequently used as an optimum film for such applications. However, if you try to heat-shrink the polyester film that has been stored for a long time after the center seal from the point of delivery date or amount of use, when you try to heat shrink it, the upper end of the film will fold into the container side and the appearance will deteriorate, There was a problem of having to sleep.
[0003]
[Problems to be solved by the invention]
The first problem to be solved by the present invention is that even if the heat-shrinkable polyester film is printed on the inner surface and stored for a long time after the center seal, it is folded into the container side when it is covered with the container and thermally contracted. It is to provide a method that does not occur.
[0004]
A second problem is to provide a container in which a heat-shrinkable polyester film having an inner surface printed is mounted without being folded.
[0005]
[Means for Solving the Problems]
As a means for solving the above-mentioned problems, the present invention provides an inner surface of a heat-shrinkable polyester film which is molded into a cylindrical shape by a center seal and attached to a container, and the upper end and the lower end are not That the heat-shrinkable polyester film prevents folding into the container side by printing in advance using a printing ink whose solvent is water and / or alcohol so that it becomes a printing part. Features.
[0006]
And it is the container which mounted | wore with the heat-shrinkable polyester film without folding by the said method, It is characterized by the above-mentioned.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail below.
[0008]
In the heat-shrinkable polyester film of the present invention, one direction is unstretched or low-magnification stretching of 2 times or less, and a direction perpendicular to the direction (hereinafter referred to as a main axis direction) is a film of high-magnification stretching of 4 times or more. .
The raw material resin for the film is mainly composed of what is generally called a copolyester. Preferably, it is a mixture in which a polyester resin produced from terephthalic acid and ethylene glycol is blended with a polyester resin produced from terephthalic acid, ethylene glycol and cyclohexanedimethanol.
The surface of the film may be subjected to a surface treatment such as a corona discharge treatment in order to increase the adhesion to the printing ink, or an antistatic agent may be applied to the opposite surface in order to provide an antistatic effect.
[0009]
The flat heat-shrinkable polyester film manufactured at the film manufacturing plant is printed on one side with a gravure printing machine (printed on the side that comes to the container side when mounted on a container) and, if necessary, the inner side of the printed surface is coated on paper. It is wound on a tube. The printed pattern is an intermittent pattern so that the upper end and the lower end are non-printed when mounted on the container, and the interval is 80 mm or less, usually 10 mm or less. (The reason for making an intermittent pattern is as follows. That is, if it is a continuous pattern, it is printed up to the upper end of the film when it is attached to the container, and this is heated and shrunk. The film at the upper end, i.e. the neck of the container, curls to the outside of the container just before the shrinkage is completed, and not only looks bad, but also the heating source is hot water or steam, or boil treatment or retort treatment in the later process In this case, hot water or steam enters between the film and the container, resulting in a defective product.The reason why the film curls outside is that the final ultimate shrinkage is larger on the outer surface than on the inner printed surface. )
The solvent for gravure printing ink is mainly a mixed solvent of ethyl acetate, methyl ethyl ketone, and toluene, and isopropyl alcohol may be added thereto.
Next, a center seal (finished into a cylindrical shape) is used 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 approximately the center of the non-printing portion, and each film is placed on each container and thermally contracted to obtain a target container. There are cases where the container is pre-filled with a medium product, and there are cases where the container is filled with the medium product after the film is attached.
[0010]
In some cases, the entire amount of the center-sealed film is immediately attached to the container, but due to the delivery date, the amount used, etc., it generally takes 1-3 months after the center seal to use up all the film. During this time, it is stored in a skein-wound shape or a paper tube. When a film stored for a long period of time is cut and then covered with a container to try to heat shrink, the upper end of the film is folded to the container side, resulting in frequent defective products.
[0011]
In order to elucidate the cause, the present inventors conducted a verification experiment shown below.
[0012]
(Creation of verification object A)
An intermittent pattern having a non-printing part with a spacing of 4 mm was printed on one side of a flat heat-shrinkable polyester film with a gravure printing machine. The printing ink solvent used was a mixed solvent consisting of ethyl acetate, methyl ethyl ketone, toluene, and isopropyl alcohol. The next day, the film was sealed with a solvent so that the printing surface of the film would be the inner surface, and 5 rolls of a paper tube wound with a length of 100 m were obtained.
[0013]
(Creation of verification object B)
Except for the plain film which is not printed, the paper tube-wound film 5 was obtained in the same manner as the creation of the verification product A.
[0014]
(Verification experiment 1)
The next day after the center seal, 20 pieces of approximately one central part of each of the verification products A and B are cut, put on 20 PET bottles one by one, and heated in a 90 ° C. steam tunnel for 8 seconds. Thus, the heat shrinkage was applied. Then, the number of PET bottles in which the upper end portion was folded was examined. The results are shown in Table 1. As can be seen from Table 1, no folding of the film occurred.
[0015]
(Verification experiment 2)
Using the remaining 4 volumes, in the same way as in the verification experiment 1, 1 month, 2 months, 3 months, 4 months after the center seal (film is stored at 25 ° C during this time) Then, the number of PET bottles in which film folding occurred was examined. The results are shown in Table 1.
[0016]
From the difference between the verification object A and the verification object B in the verification experiments 1 and 2, the cause of the folding is in the gravure printing ink. And the present inventors came to have the presumption that residual solvent may be the cause among gravure printing inks. This is because the main components of gravure printing ink are vehicles, pigments, dispersants, and organic solvents, and only the residual solvent resulting from the organic solvent changes depending on the length of the storage period.
In order to prove this assumption, the following experiment was conducted.
[0017]
(Verification experiment 3)
A plain heat-shrinkable polyester film was center-sealed to produce a cylindrical film. Next, this cylindrical film was cut into 5 pieces of 1 m length, and each of them was mixed with five kinds of solvents, that is, ethyl acetate, methyl ethyl ketone, toluene, isopropyl alcohol, and a mixture of them by equal weight (of the verification product A). A few drops of each of the gravure printing ink solvents used in the preparation were dropped into a cylindrical shape, and both ends were immediately sealed with aluminum adhesive tape. And it stored at 40 degreeC for 30 hours for promotion.
Next, when these five were used in the same manner as in the verification experiment 1 and attached to a PET bottle and examined for folds, all folds except for those filled with isopropyl alcohol occurred. From this, it was found that the cause of folding was a residual solvent, and isopropyl alcohol was not related to folding.
Therefore, in order to see the effect of each solvent on the film, the following verification experiments 4, 5, and 6 were performed.
[0018]
(Verification experiment 4)
Permeation of each organic solvent in plain heat-shrinkable polyester film that has not been center-sealed, using the five types of solvents used in Verification Experiment 3 instead of calcium chloride in JIS Z0208, the standard for measuring moisture permeability of films. The amount was measured. The results are shown in Table 2.
From the verification experiment 4, it was found that ethyl acetate, methyl ethyl ketone, toluene and the mixed solution permeate the film, but the permeation amount, that is, the permeation speed is very small, while isopropyl alcohol does not permeate the film.
[0019]
(Verification experiment 5)
A plain heat-shrinkable polyester film that has not been center-sealed is cut into a size of length x width 100 mm x 100 mm and immersed in the five solvents used in verification experiment 3 at 25 ° C for 24 hours. Was measured. The results are shown in Table 3.
[0020]
(Verification Experiment 6)
A plain heat-shrinkable polyester film that has not been center-sealed is cut into a size of length x width 100 mm x 100 mm and immersed in the five solvents used in verification experiment 3 at 25 ° C for 24 hours. The dimensional change rate in the direction (lateral direction in this film) was measured. The results are shown in Table 4. In Table 4, “-” indicates that the film contracted.
From the verification experiments 5 and 6, it was found that ethyl acetate, methyl ethyl ketone, toluene and a mixed solution were absorbed into the film, and the film contracted due to its plasticizing effect, whereas isopropyl alcohol did not.
[0021]
From the verification experiments 4, 5, and 6, the present inventors have come to the conclusion that the phenomenon that the film is folded into the container side is due to the following action.
That is, the residual solvent of the printing ink confined in the cylindrical shape by the center seal has a low permeation speed, and is not absorbed by the film the day after the center seal as in the verification experiment 1. Therefore, since neither the cylinder inner side nor the cylinder outer side of the upper end film which is a non-printing part is affected by the residual solvent, folding does not occur.
[0022]
On the other hand, when 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 rate is slow, so the inner side of the upper end film cylinder absorbs the residual solvent from the outer side of the cylinder. This is a conclusion that folding is likely to occur due to an absorption gradient in which the amount increases.
[0023]
Preparation of isopropyl alcohol that does not affect the heat-shrinkable polyester film and ethyl acetate, methyl ethyl ketone, and toluene that affect the composition in various compositions and various composition ratios. As a result of repeating steps 5 and 6, the mixed solution has a swelling rate of 3% or less, preferably 1% or less, more preferably 0.5% or less, and a dimensional change rate of 3% in the stretching direction of the film. It has been found that a mixture that is not more than%, preferably not more than 1%, more preferably not more than 0.5% is 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 this range is advantageous for folding.
[0024]
In order to reduce the amount of residual solvent using conventional printing ink, I tried increasing the drying temperature of the printing machine, increasing the amount of hot air, or decreasing the printing speed within the range where the film does not shrink. However, it was not effective for folding.
[0025]
Specific examples of the solvent for the printing ink having a preferable swelling rate to the film and a preferable dimensional change rate in the stretching direction of the film include water and / or alcohol.
[0026]
Examples of the alcohol include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol and the like. However, the alcohol is not limited to these, and any alcohol having a hydroxyl group in the molecule such as cellsolve is included.
[0027]
Other liquid substances may be appropriately added to the printing ink according to the purpose within a range that does not impair the properties of the solvent. For example, a small amount of n-methylpyrrolidone may be added to increase the solubility of the vehicle.
[0028]
The vehicle used for the printing ink is not particularly limited as long as it is soluble in the above-described solvent. For example, water-soluble acrylic resins using methacrylic acid or acrylic acid as the main starting material can be exemplified. In addition, known pigments and dispersants may be used.
[0029]
A heat-shrinkable polyester film that has been internally printed in advance so that the upper end and the lower end are non-printed when molded into a cylinder with a center seal, and the solvent for printing ink is as described above And
And a container which is not folded in the upper end part of a film is obtained by covering this cylindrical body and carrying out heat contraction.
[0030]
The heat source for heat shrink is not particularly limited, and examples thereof include steam, hot water, hot air, and an electric heater.
[0031]
There is no particular limitation on the container as long as the effect of attaching the film to heat shrinkage is recognized. For example, a plastic bottle, a glass bottle, a metal can etc. can be illustrated.
[0032]
【Example】
Next, typical examples of the present invention will be described.
[0033]
The measurement method and evaluation method of the physical property values used in the present invention are as follows.
[0034]
The swelling ratio of the solvent into the film was measured as follows. A plain film with a size of length x width 100 mm x 100 mm is immersed in a solvent at 25 ° C for 24 hours, and the value obtained by dividing the weight of the increased film by the weight of the film before immersion is multiplied by 100. Rate.
[0035]
The dimensional change rate of the film was measured as follows. A plain film having a size of length × width 100 mm × 100 mm was immersed in a solvent at 25 ° C. for 24 hours, and the amount of change (mm) in the principal axis direction after immersion was defined as a dimensional change rate (%).
[0036]
Example 1
A mixture of 100 parts by weight of a polyester resin produced from terephthalic acid, ethylene glycol and cyclohexanedimethanol and 30 parts by weight of a polyester resin produced from terephthalic acid and ethylene glycol was extruded from a T die at 280 ° C., After cooling and solidification, the film was stretched 5.0 times in the transverse direction at 95 ° C. and subsequently annealed to obtain a heat-shrinkable polyester film having a thickness of 40 μm.
[0037]
(Example 2)
A gravure printing machine using two-color printing inks of white and indigo in which a 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 a vehicle is made of a water-soluble acrylic resin. Thus, two-color printing was performed on one side of the film obtained in Example 1. As the printed design, a design in which the non-printing portion was intermittently 4 mm wide in the film flow direction was used.
[0038]
Next, a center seal (finished into a cylindrical shape) was used as shown in FIG. 1 using a solvent so that the printed surface became the inner surface, and it was folded flat to obtain 5 rolls of a paper tube wound film having a length of 100 m.
[0039]
The next day after the center seal, 1 month, 2 months, 3 months, and 4 months (while the film is stored at 25 ° C.) Each was cut, covered with 20 PET bottles one by one, and heat-shrinked by heating in a 90 ° C. steam tunnel for 8 seconds. Then, the number of PET bottles in which the upper end portion of the film as the non-printing portion was folded was examined. The results are shown in Table 5. As can be seen from Table 5, there was no folding of the film.
[0040]
(Comparative Example 1)
A film was prepared in the same manner as in Example 2 except that the solvent was a mixed solvent in which equal weight of ethyl acetate, methyl ethyl ketone, toluene, isopropyl alcohol was mixed and the vehicle was made of two colors of white and indigo printing ink made of acrylic resin. 20 mounted PET bottles were obtained. Then, the number of PET bottles in which the folding of the upper end of the film occurred was examined. The results are shown in Table 5. As can be seen from Table 5, the longer the storage period, the higher the rate of folding.
[0041]
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. The results are shown in Table 6. From Table 6, it can be seen that neither the swelling rate nor the dimensional change rate was changed.
[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]
【The invention's effect】
The present invention is implemented in the form described above, and has the following effects.
The solvent of the printing ink was stored for a long time after the center seal by printing with the printing ink having a swelling rate to the film of 3% or less and a dimensional change rate of the film in the stretching direction of 3% or less. Even if it is a heat-shrinkable polyester film, when it is made to heat-shrink on a container, the upper end part of a film does not fold into the container side.
[0049]
By using water and / or alcohol as the main component of the solvent of the printing ink, even if it is a heat-shrinkable polyester film that has been stored for a long time after the center seal, the upper end of the film should be Do not fold into.
[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 shrink-mounted on a container.
FIG. 3 is a simplified diagram showing a state of a film having an upper end folded into the container.

Claims (2)

The solvent is water and / or alcohol so that the upper end and the lower end of the heat shrinkable polyester film formed into a cylindrical shape by a center seal and attached to the container are non-printing parts when attached to the container. A method for preventing folding of the heat-shrinkable polyester film into the container side, which is previously printed using a printing ink. A container equipped with a heat-shrinkable polyester film without folding by the method according to claim 1.

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