JP2004339374A - Heat-shrinkable polyester-based film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare a heat-shrinkable film exhibiting good separability in an alkaline aqueous solution while exhibiting excellent adhesion to various kinds of ink, and having excellent characteristics such as blocking resistance, slipperiness and antistatic properties. <P>SOLUTION: This film is the heat-shrinkable polyester-based film having ≥20% shrinkage in the maximum shrinking direction measured by dipping a sample obtained by cutting the film into a square shape of 10 cm×10 cm in a hot water at 85°C for 10 sec, pulling up the dipped film, and dipping the pulled-up film in water at 25°C for 10 sec. The content of nitrogen atom in the most surface layer of the first surface of the film is 0.2-5.0 atomic %, and the dynamic friction coefficient μd of the second surface of the film to each other is ≤0.27. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００９２】
【表２】

【００９３】
実験Ｎｏ．８
実験Ｎｏ．１、２、３および５で得られた各フィルムを５００ｍｌ角型ＰＥＴボトル飲料に装着して熱収縮させたサンプルをそれぞれ３０個ずつ作製し、自動販売機内部にセットした。実験Ｎｏ．１（傾斜滑り出し角度１２．０°）、実験Ｎｏ．２（傾斜滑り出し角度１１．０゜）では３０個の内、詰りの発生はなかった。実験Ｎｏ．３（傾斜滑り出し角度１７．５゜）では、３０個の内１２個の詰りが発生し、実験Ｎｏ．５（傾斜滑り出し角度１４．５゜）では３０個の内４個の詰りが発生した。
【００９４】
【発明の効果】
本発明の熱収縮性フィルムは、様々なタイプのインクに対するインク密着性に優れ、かつアルカリ水溶液で脱離するタイプのインクに対して優れた脱離性を有している。また、耐ブロッキング性にも優れているので、フィルムをラベル状とする際のラベルカット後の開口不良等のトラブルの発生も抑制できる。また、滑り性、帯電防止性にも優れており、飲料用ラベルに使用した際、自動販売機内部で詰まったり、汚れを吸着したりすることもない。従って、ＰＥＴボトル等の容器被覆用ラベルとして非常に有用なものである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heat-shrinkable polyester film, and more particularly, has excellent ink adhesion at the time of printing, has excellent detachability with respect to an ink that can be detached with an alkaline aqueous solution, and makes the film a label. The present invention relates to a heat-shrinkable polyester film having excellent opening properties after label cutting. In addition, since it has good slipperiness on the outer surface when used as a label film for beverage bottles, it is also suitable as a label for vending machine beverages, has excellent workability in the printing process and tubing process, and has antistatic properties. It also relates to an excellent heat-shrinkable polyester film.
[0002]
[Prior art]
Conventionally, heat shrinkable films have been widely used in applications such as shrink wrapping and shrink labels, utilizing the property of shrinking by heating. Above all, stretched films made of vinyl chloride resin, polystyrene resin, polyester resin, etc. are used in various containers such as polyethylene terephthalate (PET) containers, polyethylene containers, glass containers, etc. for the purpose of labeling, cap sealing or integrated packaging. It is used.
[0003]
After production, these heat-shrinkable films undergo a printing process for various designs, and after printing, if necessary, are slit in accordance with the size of labels and the like used in the final product, and are further subjected to solvent bonding and the like. The left and right ends of the film are overlapped and sealed by means to form a tubular body, and the tubular body is cut and processed into a form such as a label or a bag. A label or bag is attached to the container while opening it, and the steam is blown to shrink the heat (steam tunnel) or hot air is blown to shrink the heat (hot air tunnel). ) Is passed through a belt conveyor or the like, and is heat-shrinked to adhere to the container.
[0004]
By the way, in recent years, for a PET bottle label and the like, an ink of a type which is desorbed in an alkaline aqueous solution for the purpose of recycling, an aqueous type ink which reduces or does not use an organic solvent which has an adverse effect on the environment, and the like have been developed. In some cases, these inks have lower performance such as adhesion of the ink to a film than conventional types in order to achieve a predetermined purpose. However, if the adhesion of the ink to the film is poor in the printing process, the ink may fall off, peel off, or the like, thereby impairing its value as a product. For this reason, a heat-shrinkable film which has excellent adhesion to these various inks and exhibits good detachability in an aqueous alkaline solution has been desired.
[0005]
In order to improve the adhesion with the ink, for example, there is a method of increasing the wetting tension of the film surface by performing a surface treatment such as a corona treatment on the film surface in a normal air atmosphere, but these surface treatments When the wetting tension on the film surface is increased, the solvent resistance of the film decreases when the solvent is bonded by tetrahydrofuran or 1,3-dioxolane to form a tube, and the solvent-bonded portion loses planarity, resulting in a so-called wakame-like shape. Or the solvent-adhered portion of the tube could block other film portions. Further, in the step of manufacturing a label by cutting a tube, the upper and lower films are fused and blocked at the cut portion, and an opening defect may occur when the label is mounted on a beverage bottle. Furthermore, when used as a label for beverages in PET bottles, when the product is transported inside the vending machine, the product is blocked in the aisle due to insufficient slipperiness of the label and does not reach the exit, or the product is blocked due to level blocking. In some cases, they adhere to each other on the outer surface of the film and are discharged multiple times.
[0006]
On the other hand, when a heat-shrinkable film is actually formed or processed at a high speed in a manufacturing site or when it is wound up in a long length, the film is required to have a winding property, a slip property, and an antistatic property against static electricity. You. If the slipperiness is insufficient, troubles such as poor handling at the time of long winding and occurrence of wrinkles and acne-like defects may occur. In addition, the running property is deteriorated, for example, the tension is increased by the frictional force when the film is in contact with the guide roll and the film surface is scratched. If the antistatic property due to static electricity is poor, there is a problem in that the process work efficiency is reduced due to the propagation of static electricity shock to the human body, and dust and dirt adhere to the surface of the film label when the final product is formed. In addition, when processing is performed under low-temperature or low-humidity atmosphere conditions in winter, inconveniences such as swimming of the printing ink may occur.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a heat-shrinkable film that can solve the various problems of the conventional heat-shrinkable film described above. An object of the present invention was to provide a heat-shrinkable film exhibiting good detachability and having excellent properties such as blocking resistance, slipperiness and antistatic property.
[0008]
[Means for Solving the Problems]
The heat-shrinkable polyester film of the present invention was prepared by immersing a sample cut into a square of 10 cm × 10 cm from the film in 85 ° C. warm water for 10 seconds and then immersing it in 25 ° C. water for 10 seconds and pulled up. A heat-shrinkable polyester film having a heat shrinkage rate of 20% or more in the maximum shrinkage direction when the nitrogen atom content of the outermost layer on the first surface of the film is 0.2 to 5.0 atom%. The point is that the dynamic friction coefficient μd between the second surfaces of the film is 0.27 or less.
[0009]
The heat-shrinkable polyester film having the above properties has excellent shrinkage processability, excellent printability for various types of inks, excellent printability such as adhesion, and alkali desorption type inks. Is excellent in alkali desorption properties. Also, at the time of label cutting, fusion or blocking of the cut portion does not occur. Furthermore, by satisfying the above requirement for the coefficient of friction, clogging in the vending machine when used as a label for a PET bottled beverage could be prevented.
[0010]
The surface resistivity of the second surface of the film is 1 × 10^ThirteenIt is preferably Ω · cm or less, and the film forming property, workability, and handleability at high speed can be further improved.
[0011]
When the wetting tension of the film first surface is 40 mN / m or more, the adhesion to the ink is sufficient, and the peel strength after heat sealing the film first surfaces at 75 ° C. is 5 N / 15 mm width or less. All of these are preferred embodiments of the present invention because the blocking resistance is improved.
[0012]
Also, a hypothetical shape in which the maximum contraction direction of the film is applied along the short side to the bottom of a rectangular weight of 500 g having a rectangular bottom shape having a short side of 55 mm and a long side of 160 mm with the second surface of the film facing outward. The bottle sample is placed horizontally on the stainless steel plate, and the tilt angle of the stainless plate is increased by 1.0 °, and the tilt angle of the stainless plate when the virtual bottle sample slides down starts tilting with respect to stainless steel. In the case of an angle, it is preferable that the slanting start angle with respect to stainless steel is 13.0 ° or less. It is a guide to avoid troubles such as clogging in vending machines.
[0013]
The present invention also includes a heat-shrinkable label obtained from the heat-shrinkable polyester film.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Not only the heat-shrinkable polyester film, but also at the time of film formation or after the film formation, on one or both surfaces of the film surface, a corona treatment under an air atmosphere, a flame treatment, a plasma treatment, an ultraviolet ray treatment, etc. Improvement of adhesion to various inks has been performed. Among them, in actual industrial operation, corona treatment in an air atmosphere is most widely performed as a surface treatment.
[0015]
When the corona treatment is applied to the heat-shrinkable polyester film, the wettability of the surface is increased similarly to other films, and the adhesion to various types of ink is improved. However, when the corona treatment is performed, the alkali-releasing property of the ink that is desorbed with alkali is improved, but the problem that fusion and blocking are likely to occur when label-cutting the heat-shrinkable polyester film. There has occurred.
[0016]
The heat-shrinkable polyester film secures strength and the like by using an ethylene terephthalate unit as the most constituent unit. However, 1,4-cyclohexanedimethanol or neopentyl which has the effect of lowering the crystallinity of the polymer and causing it to become non-crystalline. A monomer component such as glycol (hereinafter, referred to as an amorphous component), and 1,4-butanediol and 1,3-propanediol for lowering the glass transition temperature (Tg) to exhibit a low-temperature heat shrinkage. By using a low Tg monomer component such as the above, a required heat shrinkage is obtained. In particular, due to the effect of the non-crystallizing component, even in a state where the film is not subjected to surface treatment (untreated state), the adhesion to the ink is superior to that of an untreated PET film.
[0017]
However, if the heat-shrinkable film is subjected to an energy level corona treatment that is performed for a general PET film in order to further increase the adhesion, the film surface is excessively oxidized due to the presence of the amorphous component. It was found that the wetting tension was increased more than necessary. As a result, fusion or blocking occurs when the film is cut with a label, the slipperiness of the film surface is reduced and the workability of the film is deteriorated, and the film is blocked when stored in a roll wound state. Troubles such as the occurrence of troubles.
[0018]
Therefore, it was considered to perform a corona treatment (low-level treatment) at an energy level lower than the corona treatment at the energy level carried out for a general PET film. It is difficult to perform low-level processing, and it is necessary to newly introduce a special power supply and electrode equipment for low-level processing. Although it is possible to improve the adhesion to ink with such a low-level corona treatment, if the corona treatment is performed to the level of ink adhesion necessary for practical use, again, when a film is cut with a label, There was a problem that fusion and blocking occurred, and it was difficult to achieve both properties.
[0019]
As a result of various studies by the present inventors, in order to ensure ink adhesion and releasability with respect to an alkali desorption type ink, and to prevent fusing or blocking when a film is cut with a label, the first It has been found that the presence of nitrogen atoms on one surface is effective. Then, they have found a heat-shrinkable polyester film that can solve the problems of the present invention. Hereinafter, the present invention will be described in detail.
[0020]
First, as for the heat-shrinkable polyester film of the present invention, a sample cut into a square of 10 cm × 10 cm was immersed in hot water at 85 ° C. for 10 seconds and then immersed in water at 25 ° C. for 10 seconds and pulled up. It is necessary that the heat shrinkage in the maximum shrinkage direction at that time is 20% or more. If the heat shrinkage of the film is less than 20%, the heat shrinkage of the film is insufficient, and when the film is shrunk to cover a container or the like, the film does not adhere to the container, resulting in poor appearance. The more preferable heat shrinkage is 30% or more, further preferably 40% or more.
[0021]
Here, the heat shrinkage in the maximum shrinkage direction means the heat shrinkage in the direction in which the sample shrinks most, and the maximum shrinkage direction is determined by the length of the square in the vertical or horizontal direction. The heat shrinkage (%) was determined by immersing a 10 cm × 10 cm sample in hot water at 85 ° C. ± 0.5 ° C. for 10 seconds under no load and shrinking it by heat. The film was immersed in water of 10 ° C. under no load for 10 seconds, and the length of the film in the vertical and horizontal directions was measured, and the value was obtained according to the following equation (hereinafter, the heat shrinkage in the maximum shrinkage direction measured under these conditions): The ratio is simply abbreviated as “heat shrinkage ratio”).
Heat shrinkage (%) = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)
[0022]
In the film of the present invention, the nitrogen atom content in the outermost layer on the first surface of the film must be 0.2 to 5.0 atomic%. By setting the content in this range, it is possible to improve the adhesion of the film to various inks, to impart the alkali desorption property of the alkali desorption type ink, and to increase the blocking resistance. This nitrogen atom content is the ratio of nitrogen atoms to the total amount of elements in the outermost layer of the film (several tens of degrees), which can be measured by XPS (X-ray photoelectron spectroscopy). When the content of nitrogen atoms on the film surface is less than 0.2 atomic%, the adhesion to various types of ink becomes insufficient. On the other hand, when the nitrogen atom content exceeds 5.0 atomic%, fusion and blocking occur after label cutting, and a change in the surface properties of the film causes a reduction in lubricity. A more preferred lower limit of the nitrogen atom content is 0.25 at%, and a still more preferred lower limit is 0.3 at%. Further, a more preferable upper limit of the nitrogen atom content is 4.9 atom%, and a still more preferable upper limit is 4.8 atom%.
[0023]
The form of the nitrogen atom on the first surface of the film includes a form of a nitrogen atom (N) and a form of a nitrogen ion (N⁺)). As a method for allowing the first surface of the film to contain nitrogen atoms, a method in which the first surface of the film is subjected to corona treatment or plasma treatment in a nitrogen atmosphere is preferable. By performing corona treatment or plasma treatment in a nitrogen atmosphere, nitrogen is converted into a nitrogen atom (N) form or a nitrogen ion (N).⁺) Can be present on the film surface.
[0024]
Further, in order to control the amount of nitrogen atoms in the surface layer of the first surface of the film, it is possible to change equipment and processing conditions in corona treatment or plasma treatment. On the equipment side, for example, the control of the frequency of the power supply of the corona processing equipment and the material and shape of the discharge electrode, the number, the material of the processing roll, the gap between the discharge electrode and the film processing surface, and the control of the nitrogen gas concentration under a nitrogen atmosphere are mentioned. In terms of conditions, control of film running speed, ambient temperature, roll surface temperature during processing, and the like can be mentioned.
[0025]
For example, as an example of preferred equipment for corona treatment, the frequency of the power supply is preferably in the range of 8 KHz to 60 KHz. The material of the discharge electrode is preferably aluminum or stainless steel, and the shape of the discharge electrode is preferably a knife-edge shape, a bar shape, or a wire shape. The number of discharge electrodes is preferably two or more in order to uniformly treat the film surface. The treatment roll serves as a counter electrode when performing corona discharge, but at least the surface material needs to be a dielectric. As the dielectric material, it is preferable to use silicone rubber, Hypalon rubber (Hypalon is a registered trademark of DuPont; chlorosulfonated polyethylene), EPT rubber, etc., and coat at least the surface of the processing roll with a thickness of 1 mm or more. Is preferred. The gap between the discharge electrode and the film-treated surface is preferably in the range of about 0.2 mm to 5 mm.
[0026]
In terms of conditions, the running speed (processing speed) of the film may be set at any speed within the range of the equipment capacity, but the film surface temperature during corona treatment under a nitrogen atmosphere is within the range of 20 to 50 ° C. When the oxygen concentration in the nitrogen atmosphere is controlled to 300 ppm or less, the nitrogen atom content on the film surface can be controlled within the above range. The temperature of the surface of the processing roll is preferably controlled by a temperature control facility, and is preferably adjusted from 30 ° C to 40 ° C. If necessary, a temperature control roll can be arranged before or after the treatment roll.
[0027]
Furthermore, if the nitrogen concentration in the atmosphere during the corona treatment or the plasma treatment changes, this causes a change in the nitrogen atom content on the film surface. Therefore, it is preferable to employ a method that does not change the nitrogen concentration in the atmosphere. Since the corona treatment is usually performed in an air atmosphere, the corona treatment equipment is not provided with a sealing means for keeping the atmosphere under a nitrogen atmosphere. Therefore, it is necessary to put the corona treatment equipment itself in the chamber in order to make it under a nitrogen atmosphere. At this time, if the inside of the chamber is replaced with nitrogen to form a nitrogen atmosphere and the film is run while performing corona treatment inside the chamber, air flows in as an accompanying flow of the running film, and the nitrogen concentration in the atmosphere is reduced. It fluctuates.
[0028]
In order to prevent the fluctuation of the nitrogen concentration, it is recommended that the gap between the film and the outer periphery of the film entrance in the chamber surrounding the corona treatment equipment be 0.4 mm or less, more preferably 0.3 mm or less. It is also a preferable means to cover the gap with a plastic film or cloth and cut the accompanying flow. It is also an effective means to form the chamber with two or more layers and separately supply nitrogen for cutting off the entrained flow on the outer layer side.
[0029]
In addition, oxygen is also present in the atmosphere of the corona treatment due to the inflow of air.However, since oxygen may increase the wetting tension on the film surface more than necessary, the oxygen in the nitrogen atmosphere where the corona treatment or the plasma treatment is performed is performed. It is preferable to control the oxygen concentration to 300 ppm or less. It is more preferably at most 250 ppm, further preferably at most 200 ppm. In the case of continuously producing a long film roll, it is preferable that the fluctuation range of the oxygen concentration in the nitrogen atmosphere from the start to the end of the roll is set to an average oxygen concentration of ± 80 ppm or less. More preferably, the average oxygen concentration is ± 60 ppm or less. In addition, regarding the second surface, which is the back surface of the first surface of the film, the nitrogen atom content does not have to be defined in the above range, but can of course be adjusted to the above range.
[0030]
By setting the nitrogen atom content of the outermost layer on the first surface of the film to a specific range as described above, a film satisfying both the adhesion to the ink and the blocking resistance could be obtained. A film that satisfies both the adhesion to the ink and the blocking resistance can also be used as a guide for the wetting tension. In the present invention, the wetting tension on the first surface of the film is preferably 45 mN / m or more. . When the wetting tension of the film surface is less than 45 mN / m, the adhesion to various types of ink becomes insufficient. A more preferred lower limit of the wetting tension is 47 mN / m, and a still more preferred lower limit is 48 mN / m. The upper limit of the wetting tension on the first surface of the film is not particularly limited. However, from the viewpoint that the occurrence of fusion and blocking after label cutting and blocking can be suppressed and the film lubricity can be ensured, the wetting tension is not limited. It is preferred to be 58 mN / m or less.
[0031]
On the other hand, the blocking resistance can also be evaluated by the peel strength of the heat-sealed portion. When the first surfaces of the films are heat-sealed at 75 ° C., if the peel strength of the heat-sealed portion is 5 N / 15 mm width or less, it is possible to prevent various troubles caused by the fusion and blocking of the film as described above. Further, it is preferable because label cutting can be performed at high speed. The more preferable upper limit of the peel strength (75 ° C.) is 4.5 N / 15 mm width, and the more preferable upper limit is 4 N / 15 mm width. In the case of peel strength after heat sealing at 85 ° C., the width is preferably 7 N / 15 mm or less. More preferably, the width is 6 N / 15 mm width or less, further preferably, 5 N / 15 mm width or less. It is preferable that these values are satisfied also on the second surface.
[0032]
In terms of slipperiness, the film of the present invention must have a dynamic friction coefficient μd between the second surfaces of the films of 0.27 or less. When μd is 0.27 or less, it is possible to provide a film having good lubricity in a vending machine when used as a label for a PET bottle for beverages. For example, a contact area with the inside of the vending machine is large. Even if the rectangular bottle is easily clogged, the clogging can be prevented. However, when it exceeds 0.27, the lubrication becomes insufficient, and a trouble such as clogging of a container in a vending machine occurs. A more preferred upper limit of μd is 0.25. The coefficient of dynamic friction μd between the second surfaces of the film is a value measured under an environment of 23 ° C. and 65% RH in accordance with JIS K 7125. The variation R of μd is preferably 0.05 or less, and more preferably 0.03 or less.
[0033]
Further, as a method of examining the slipperiness of the film, a slanting start angle with respect to stainless steel may be evaluated. The slanting start angle with respect to stainless steel means that the maximum contraction direction of the film is on the short side while the second surface of the film is on the bottom at the bottom of a 500 g square weight whose bottom is a rectangular shape having a short side of 55 mm and a long side of 160 mm. The virtual bottle sample stuck along was placed horizontally on a stainless steel plate, and the inclination angle of the stainless steel plate was increased by 1 °, and the inclination angle of the stainless steel plate when the virtual bottle sample slipped was determined. is there. It is preferable that the slanting start angle with respect to stainless steel is 13.0 ° or less, because troubles due to insufficient slipperiness as described above can be prevented.
[0034]
The heat-shrinkable film of the present invention has a surface specific resistance of 1 × 10 2 on the second surface of the film.^ThirteenIt is preferably Ω · cm or less. Surface specific resistance value is 1 × 10^ThirteenIf it exceeds Ω · cm, the film is likely to be charged, generating and accumulating static electricity, and increasing the possibility of causing various troubles due to static electricity. Troubles due to static electricity damage include, for example, winding of a film around a roll in a tubing process or a label mounting process, troubles that reduce process operation efficiency due to an electric shock to a human body, etc., ink swimming in a printing process (film Ink does not get on well), poor opening of label due to static electricity, deterioration of commercial value such as adsorption of dirt on film or label surface, etc., and surface specific resistance value is 1 × 10^ThirteenBy setting the resistance to Ω · cm or less, occurrence of these troubles is suppressed. The surface resistivity of the film is 1 × 10¹²Ω · cm or less is more preferable. 1 × 10¹¹Ω · cm or less is more preferable.
[0035]
The composition and the production method of the heat-shrinkable polyester film of the present invention are not particularly limited as long as they satisfy the above-mentioned properties, but preferred embodiments will be described below.
[0036]
As the polyester resin constituting the heat-shrinkable film of the present invention, as a dicarboxylic acid component, one or more of aromatic dicarboxylic acids, their ester-forming derivatives, and aliphatic dicarboxylic acids are used, and polycondensation with a polyhydric alcohol component is performed. Known (copolymerized) polyesters described above can be used. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalene-1,4- or -2,6-dicarboxylic acid, and 5-sodium sulfoisophthalic acid. In addition, examples of these ester derivatives include derivatives such as dialkyl esters and diaryl esters. Examples of the aliphatic dicarboxylic acid include dimer acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, oxalic acid, and succinic acid. Further, an oxycarboxylic acid such as p-oxybenzoic acid or the like, or a polyvalent carboxylic acid such as trimellitic anhydride or pyromellitic anhydride may be used in combination as needed.
[0037]
Polyhydric alcohol components include ethylene glycol, diethylene glycol, dimer diol, propylene glycol, triethylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, Alkylene glycols such as methyl 1,5-pentanediol, 2-methyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, 1,9-nonanediol, and 1,10-decanediol; Examples include an alkylene oxide adduct of a bisphenol compound or a derivative thereof, trimethylolpropane, glycerin, pentaerythritol, polyoxytetramethylene glycol, and polyethylene glycol. Although not a polyhydric alcohol, ε-caprolactone can also be used.
[0038]
The polyester raw material constituting the polyester-based heat-shrinkable film may be used alone or in combination of two or more. When used alone, homopolyesters other than polyethylene terephthalate such as polybutylene terephthalate, polycyclohexylene dimethyl terephthalate, and polyethylene naphthalate are preferred. This is because polyethylene terephthalate alone does not exhibit heat shrinkability.
[0039]
However, in consideration of the tear resistance, strength, heat resistance, and the like of the film, it is preferable that a crystalline ethylene terephthalate unit is a main constituent component. It is recommended that the terephthalate unit be selected to be at least 50 mol%. Therefore, it is preferable that the terephthalic acid component is 50 mol% or more in the dicarboxylic acid component 100 mol%, and the ethylene glycol component is 50 mol% or more in 100 mol% of the polyhydric alcohol component. The ethylene terephthalate unit is more preferably at least 55 mol%, even more preferably at least 60 mol%. It is recommended that the units other than the ethylene terephthalate unit be 5 mol% or more, preferably 7 mol% or more, more preferably 9 mol% or more, in 100 mol% of the constituent units of the polyester raw material. This is because, by introducing the amorphousness improving component to the above extent, the solvent adhesiveness and heat shrinkability of the film can be ensured.
[0040]
From the viewpoint of heat shrinkage properties and productivity, it is preferable to use a blend of two or more polyesters having different Tg. It is preferable to use a mixture of polyethylene terephthalate and a copolyester (two or more copolyesters may be used), but a combination of copolyesters may be used. Further, polybutylene terephthalate, polycyclohexylene dimethyl terephthalate, and polyethylene naphthalate may be used in combination, or these may be used in combination with another copolymerized polyester. The three types of blends of polyethylene terephthalate, polybutylene terephthalate, a copolymerized diol component of ethylene glycol and neopentyl glycol, and a copolymerized polyester composed of terephthalic acid are most preferable in terms of heat shrinkage characteristics. When two or more polyesters are used in combination, it is preferable to blend the chips of each polymer in a hopper from the viewpoint of production efficiency.
[0041]
Polyester can be produced by melt polymerization according to a conventional method.However, a so-called direct polymerization method in which a dicarboxylic acid and a glycol are directly reacted to polycondensate an obtained oligomer, that is, a transesterification between a dimethyl ester of a dicarboxylic acid and a glycol. A so-called transesterification method in which polycondensation is performed after the reaction is performed, and an arbitrary production method can be applied. Further, a polyester obtained by another polymerization method may be used. The polymerization degree of the polyester is preferably 0.3 to 1.3 dl / g in terms of intrinsic viscosity.
[0042]
In order to avoid inconveniences such as coloring and gel formation, polyesters include, in addition to polymerization catalysts such as antimony oxide, germanium oxide, and titanium compounds, magnesium salts such as magnesium acetate and magnesium chloride, calcium acetate, calcium chloride, and the like. Ca salt, manganese acetate, Mn salt such as manganese chloride, zinc chloride, Zn salt such as zinc acetate, cobalt chloride, Co salt such as cobalt acetate, with respect to polyester, each 300 ppm or less as metal ions, phosphoric acid or Phosphate ester derivatives such as trimethyl phosphate and triethyl phosphate may be added in an amount of 200 ppm or less in terms of phosphorus (P).
[0043]
When the total amount of the metal ions other than the polymerization catalyst is 300 ppm with respect to the polyester, and when the P amount exceeds 200 ppm, not only the coloring of the polymer becomes remarkable, but also the heat resistance and hydrolysis resistance of the polymer are unpreferably reduced. .
[0044]
At this time, in terms of heat resistance, hydrolysis resistance, and the like, the molar atomic ratio (P / M) of the total P amount (P) to the total metal ion amount (M) is 0.4 to 1.0. Is preferred. When the molar atomic ratio (P / M) is less than 0.4 or more than 1.0, the film may be colored or coarse particles may be mixed in the film, which is not preferable.
[0045]
The timing of adding the metal ions and phosphoric acid and derivatives thereof is not particularly limited, but generally, the metal ions are added at the time of charging the raw materials, that is, before transesterification or esterification, and the phosphoric acids are added before the polycondensation reaction. Is preferred.
[0046]
In the heat-shrinkable polyester film of the present invention, inorganic particles, organic salt particles or crosslinked polymer particles can be added as a lubricant. Examples of the inorganic particles include calcium carbonate, kaolin, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, and riotium fluoride. Is mentioned. In particular, in order to obtain a film having a low haze while obtaining good handling properties, silica particles of an aggregate formed by aggregating primary particles are preferable as the inorganic particles. Examples of the organic salt particles include terephthalates such as calcium oxalate, calcium, barium, zinc, manganese, and magnesium.
[0047]
Examples of the crosslinked polymer particles include homopolymers or copolymers of vinyl monomers such as divinylbenzene, styrene, acrylic acid or methacrylic acid. In addition, organic particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting urea resin, and thermosetting phenol resin may be used.
[0048]
In order to impart lubricity to the film, there is a method of reducing the contact area by roughening the surface with the above-mentioned lubricant particles or the like. May be impaired. For this reason, it is preferable to use the above-mentioned lubricant particles at a level that suppresses the center plane average roughness of the second surface of the film to 0.03 or less. Within this range, lubricity can be imparted without impairing the transparency of the label film.
[0049]
Examples of the method of adding the lubricant include a method of dispersing the lubricant in the polymerization step of the polyester used as a film raw material, and a method of melting and adding the polyester after polymerization again. In order to uniformly disperse the lubricant over the entire length of the film roll, after dispersing the lubricant in the polyester by any of the methods described above, the raw material in the hopper is adjusted by adjusting the shape of the polymer chip in which the lubricant is dispersed. It is preferable to suppress the phenomenon of segregation. Polyester is taken out of the polymerization apparatus in the form of a strand in a molten state after polymerization, immediately cooled with water, and then cut by a strand cutter into chips. The chips have a cylindrical shape having an elliptical bottom surface. In order to suppress the segregation of the raw materials, different types of raw materials whose average size of the major axis, minor axis, and cylindrical height of the elliptical bottom surface are within ± 20% of the chip size of the type of raw material with the highest usage ratio It is preferable to use a chip, and it is more preferable that the size be within a range of ± 15%.
[0050]
In the raw material composition for producing the film, various known additives may be added as necessary in addition to the polyester and the lubricant. Examples of the additive include an antistatic agent; an antioxidant; an ultraviolet absorber; and a coloring agent (eg, a dye).
[0051]
The raw material composition is formed into a film by a known method (for example, an extrusion method or a calendar method). The shape of the film is, for example, planar or tubular, and is not particularly limited.
[0052]
In order to impart heat shrinkage to the unstretched film, a stretching step is performed. As the stretching method, for example, a known method such as a roll stretching method, a long gap stretching method, a tenter stretching method, and a tubular stretching method can be adopted. In any of these methods, the stretching may be performed by sequential biaxial stretching, simultaneous biaxial stretching, monoaxial stretching, or a combination thereof. In the biaxial stretching described above, stretching in the vertical and horizontal directions may be performed simultaneously, or either one may be performed first. The stretching ratio is preferably in the range of 1.0 to 7.0 times, and the ratio in one predetermined direction (the maximum contraction direction) is preferably 3.5 times or more.
[0053]
In the stretching step, preheating is preferably performed at a temperature equal to or higher than the glass transition temperature (Tg) of the polymer constituting the film and, for example, equal to or lower than Tg + 80 ° C. In the heat setting at the time of stretching, for example, it is recommended to pass through a heating zone at 30 to 150 ° C. for about 1 to 30 seconds after stretching. Further, after stretching the film, before or after performing the heat setting, the stretching may be performed at a predetermined degree. Further, after the stretching, a step of cooling while applying stress to the film while maintaining the stretched or tensioned state, or a cooling step after releasing the tensioned state may be added to this process.
[0054]
In the case of producing a label from a heat-shrinkable polyester film, it is preferable to perform tube forming with 1,3-dioxolan. This is because a sufficient adhesive force is provided. When forming into a tube, 1,3-dioxolane may be applied to one surface of the film, and the other surface of the film may be pressed against the applied surface. If the adhesiveness is insufficient, the label may be peeled off at the time of heat shrink mounting of the label or at the time of handling the beverage bottle.
[0055]
In order to obtain a film having the above-mentioned coefficient of kinetic friction μd, a configuration in which an easy-slip layer is formed on the second surface side of the film is preferable. In addition, by imparting antistatic properties to the slippery layer, the surface specific resistance value can be set in the above-mentioned preferable range. The method for forming the slippery layer is not particularly limited as long as it can be uniformly formed on the film surface, a method in which the slippery resin is melt-extruded and laminated on the surface layer, and a method for coating the slippery layer coating solution during the film forming process. Coating (in-line coating), coating of a coating solution for easy layer after film formation (off-line coating) and the like. The production by in-line coating is preferred from the viewpoint of cost and the effect of improving the adhesion between the coating layer and the film by heat treatment at the time of stretching after coating is expected. As a coating method, any of known methods such as a reverse roll method, an air knife method, and a fountain method can be adopted. As the above-mentioned coating liquid for an easy slipping layer, one containing a binder resin, a lubricant and an antistatic agent alone or in combination is preferable.
[0056]
Examples of the binder resin component include a polyester resin, a polyamide resin, a polyurethane resin, an epoxy resin, a phenol resin, an acrylic resin, a polyvinyl acetate resin, a polyolefin resin such as polyethylene or polypropylene, or a copolymer thereof. There are coalescing or modified resins, cellulosic resins, and others, especially polyester resins, polyurethane resins, or copolymers thereof show good lubricity in combination with a lubricant, and adhesiveness to a polyester film is also obtained. . Use of a water-dispersible material is preferable from the viewpoint of safety and environmental friendliness.
[0057]
Lubricants include paraffin wax, microcrystalline wax, polypropylene wax, polyethylene wax, ethylene acrylic wax, stearic acid, behenic acid, 12-hydroxystearic acid, stearic amide, oleic amide, erucamide, methylenebisstearic acid Amide, ethylenebisstearic acid amide, ethylenebisoleic acid amide, butyl stearate, monoglyceride stearate, pentaerythritol tetrastearate, hydrogenated castor oil, stearyl stearate, siloxane, higher alcohol polymer, stearyl alcohol, stearic acid Examples thereof include calcium, zinc stearate, magnesium stearate, and lead stearate, and it is preferable to add one or more of these. There. Above all, paraffin wax, microcrystalline wax, low molecular weight polyethylene wax and the like have a large effect of improving lubricity and are particularly preferable.
[0058]
As antistatic agents, surfactants such as quaternary ammonium salts, fatty acid polyhydric alcohol esters, polyoxyethylene adducts, betaine salts, alanine salts, phosphate salts, sulfonates, and polyacrylic acid derivatives are effective. . Sulfonates, especially sodium paraffin sulfonate, are recommended because of their excellent antistatic effect and little adverse effect on lubricity.
[0059]
As described above, a polyester resin as a resin component, a polyurethane resin, or a copolymer thereof, using a coating solution for an easy-smooth layer in which a low molecular weight polyethylene wax and a sulfonate compound are combined, by an inline coating method, It is particularly recommended to form a lubricious layer on the second surface side of the film before stretching. When used as a label, the container is covered so that the second surface side is on the outside.
[0060]
The amount of the coating solution is 0.002 to 0.5 g / m2 as the amount existing on the film after stretching.²Preferably, more preferably 0.005 to 0.4 g / m²It is. 0.002g / m²If less than 0.5 g / m, the lubricity and the antistatic effect are reduced.²It is not preferable that the ratio is more than 0, because the transparency of the film and the blocking property may be deteriorated, and the solvent adhesion may be deteriorated.
[0061]
Since the heat-shrinkable polyester film of the present invention has excellent adhesion to ink, an ink layer can be provided on the first surface side of the film. In particular, it exhibits excellent adhesion to ink having alkali desorption properties. Such a type of ink having alkali release properties is, for example, a sample in which 1 g of a sample having an ink layer laminated on a heat-shrinkable film is cut into 1 cm square and cut in a 100 cc NaOH 3% aqueous solution (90 ° C.) for 30 minutes. It means an ink having an ink removal rate of 90% by mass or more when washed with water and dried after stirring. The removal is due to the ink layer being mainly swollen or dissolved in alkaline hot water. Practically, washing with weak alkaline hot water is usually performed for about 20 to 30 minutes, during which the ink layer is preferably dropped.
[0062]
There is no particular limitation on the method of imparting alkali-releasing properties to the ink layer, but for example, a compound soluble or swellable in alkaline hot water, a commonly used ink, for example, a colored body comprising a pigment or a dye, a binder And a method in which a volatile organic solvent is added to an ink having a constituent component. Compounds soluble or swellable in alkaline hot water include inorganic salts such as sodium chloride, sodium nitrate, potassium nitrate, sodium acetate and ammonium sulfate; organic acids or salts thereof such as ascorbic acid, sebacic acid and azelaic acid; polyethylene oxide; Polymeric polyethers such as polytetramethylene oxide, poly (meth) acrylic acid or metal salts thereof, and copolymers thereof (for example, copolymers of styrene and acrylic compounds such as (meth) acrylic acid) can be used. No. Examples of the above compounds include those which are liquid at ordinary temperature, and specifically, alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, tert-butyl alcohol, cyclohexyl alcohol, and benzyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, and the like. Monoethyl, monopropyl, monobutyl ether or monomethyl, monoethyl, monopropyl, monobutyl ether or monomethyl, monoethyl ester, etc. of polyhydric alcohols such as ethylene glycol and pentaerythritol, and others, dioxane, acetone, methyl ethyl ketone, diacetone alcohol, dimethylformamide , Tetrahydrofuran and the like. Above all, it is preferable to have a high boiling point because it is necessary to remain in the ink layer, and specifically, it is preferable that the boiling point is 50 ° C. or higher. Further, monoalkyl ether of polyhydric alcohol is preferable because of its solubility in alkaline hot water. Is particularly preferred.
[0063]
The thickness of the heat-shrinkable film of the present invention is not particularly limited. For example, the heat-shrinkable film for a label preferably has a thickness of 10 to 200 μm, more preferably 20 to 100 μm.
[0064]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples do not limit the present invention, and include modifications that do not depart from the gist of the present invention. The methods for measuring the physical properties of the films obtained in the examples and comparative examples are as follows.
[0065]
(1) Heat shrinkage
The sample film was cut into a square of 10 cm × 10 cm along the maximum shrinkage direction and the direction orthogonal thereto, and was immersed in hot water of 85 ° C. ± 0.5 ° C. for 10 seconds in a no-load state and thermally shrunk. After immersion in water at 25 ° C. ± 0.5 ° C. for 10 seconds, the length of the sample in the vertical and horizontal directions was measured, and the value was obtained according to the following equation. The direction with the largest shrinkage was defined as the maximum shrinkage direction.
Heat shrinkage (%) = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)
[0066]
(2) Nitrogen atom content on the film surface (atomic%)
Using an X-ray photoelectron spectrometer (ESCA spectrometer “ES-200”; manufactured by Kokusai Electric Inc.), the ratio of the amount of nitrogen atoms to the total amount of elements on the first surface of the sample film was quantified and determined.
[0067]
(3) Surface resistivity
The surface specific resistance value on the second surface side of the film was measured with a specific resistance measuring device manufactured by Takeda Riken Co., Ltd. under the conditions of an applied voltage of 500 V, 23 ° C. and 50 RH%.
[0068]
(4) Film wetting tension
The wetting tension of the first surface of the film was measured according to the method of JIS K6768.
[0069]
(5) Ink adhesion
The ink "Dai-Eco SRF 915 Red" and "SRF diluent solvent No. 2" manufactured by Dainichi Seika Kogyo Co., Ltd. were mixed at a mass ratio of 100: 10, and applied to the first surface of the film using a Meyer bar # 5. And immediately dried for 15 seconds with the cool air of a dryer. After attaching a cellophane tape to the obtained sample, the tape was peeled off, and the occurrence of ink pinholes after peeling was evaluated according to the following.
：: No ink pinholes occurred
Δ: Ink pinholes are generated, but all are less than 1 mm in size
×: Some are 1 mm or more in size due to the occurrence of ink pinholes.
[0070]
(6) Alkali desorption of ink
After applying the ink on the first surface of the film by the method (5), a sample of 2 cm × 20 cm is cut out and placed in a 1.5% NaOH aqueous solution whose temperature is controlled within a range of 85 ° C. ± 2 ° C. for 20 minutes. Dipped. The sample was taken out and immediately immersed in water at 25 ° C. ± 2 ° C. for 20 seconds, and the detached state of the ink layer after taking out was visually judged according to the following criteria.
：: All ink layers detached
Δ: The ink layer is partially detached, or easily peeled off when the ink layer is rubbed with a cotton swab after removal.
×: The ink layer did not come off, and the ink layer was not peeled off even after rubbing it with a cotton swab after taking it out.
[0071]
(7) Openness after label cutting
The heat-shrinkable film was slit, and then, using a center seal machine, a tube was formed by solvent bonding with 1,3-dioxolane so that the first surface was on the inside, and the tube was wound in a folded state. Next, the tube was left for 24 hours in a room controlled at 12 ± 1 ° C. and RH 30 ± 2%. Thereafter, the tube was continuously cut by a cutting machine under the same indoor atmosphere conditions (cut label number: 200) to prepare a heat-shrinkable film label. The label was fully opened by hand, and the openability of the cut portion was determined according to the following criteria (a maximum of 6 points).
6: Labels do not cling to each other due to static electricity and can be opened without resistance
5: Labels cling to each other due to static electricity during cutting, but can be opened without resistance
4: Labels do not cling to each other due to static electricity during cutting, and may have light resistance but can be opened
3: Labels cling to each other due to static electricity during cutting, which may have light resistance but can be opened
2: Labels do not cling to each other due to static electricity at the time of cutting, and there is a part where the cutting part cannot be opened.
1: At the time of cutting, labels are clinged together due to static electricity, and there is a portion where the cut portion cannot be opened.
[0072]
(8) Peel strength of heat seal part
Using a heat sealer, set the surface temperature of the seal bar to the range of the evaluation temperature ± 0.5 ° C. and set the pressure to 40 N / cm.²The first surfaces of the films were heat-sealed with each other for 300 seconds. A sample having a width of 15 mm was cut out from the heat-sealed portion, and the peel strength was measured with a tensile tester at a peel speed of 200 mm / min. The ambient temperature was 23 ° C.
[0073]
(9) Energy conversion value per film area during surface treatment
Energy conversion value per surface area of film (kW / m²/ Min)
= High frequency power supply current value (A) x voltage (kV) ÷ electrode width (m) ÷ film running speed (m / min)
Asked.
[0074]
(10) Dynamic friction coefficient
The dynamic friction coefficient μd and variation R between the second surfaces of the films were measured at 23 ° C. and 65% RH in accordance with JIS K 7125.
[0075]
(11) Antistatic properties
The antistatic property of the second surface of the film was measured using a surface resistor (a specific resistance measurement device manufactured by KAWAGUCHI ERECTIC WORKS) under an environment of an applied voltage of 500 V, 23 ° C. and 65% RH.
[0076]
(12) Center plane average roughness
The surface roughness of the second surface of the film was measured using a surface roughness measuring device (Surfcoder ET-30HK; manufactured by Kosaka Laboratories). The center plane is a plane in which the sum of squares of the deviation between the plane and the cross-sectional curved surface is equal to the top and bottom and equal to a minimum and the center plane average roughness: SRa is the center plane of the roughness curve. When the orthogonal coordinate axes X and Y are placed on the top, the axis orthogonal to the center plane is the Z axis, the roughness surface is f (x, y), and the size of the reference plane is Lx, Ly, given by the following equation. Value.
SRa = 1 / (L_x× L_y) ∫₀ ^Lx∫₀ ^Ly| F (x, y) | dx · dy
[0077]
(13) Slope start angle to stainless steel
A virtual bottle sample is attached to the bottom of a rectangular weight of 500 g having a rectangular shape with a short side of 55 mm and a long side of 160 mm, with the second side of the film facing outward with the maximum shrinkage direction of the film along the short side. Is prepared. Prepare a smooth stainless steel plate whose inclination is changed by 1 °, place the virtual bottle sample horizontally on this stainless steel plate, and tilt the stainless steel plate when the virtual bottle sample slides down (average value). Was defined as the angle of sliding out of stainless steel.
[0078]
(14) Haze
It was measured using a haze meter (manufactured by Nippon Seimitsu Kikai) according to JIS K 7136. The case where the haze was 8.0% or less was evaluated as ○, and the case where the haze exceeded 8.0% was evaluated as ×.
[0079]
Synthesis Example 1 (Synthesis of polyester)
In a stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux condenser, 100 mol% of dimethyl terephthalate (DMT) as a dicarboxylic acid component and 70 mol% of ethylene glycol (EG) and neopentyl glycol as a glycol component (NPG) 30 mol% was charged so that the glycol was 2.2 times the molar ratio of methyl ester, and 0.05 mol% of zinc acetate (based on the acid component) as a transesterification catalyst was added to the polycondensation catalyst. Then, 0.025 mol% of antimony trioxide (based on the acid component) was added, and the transesterification reaction was performed while distilling off the generated methanol out of the system. Thereafter, a polycondensation reaction was performed at 280 ° C. under a reduced pressure of 26.7 Pa to obtain a polyester A having an intrinsic viscosity of 0.73 dl / g, which was formed into chips.
[0080]
Synthesis Examples 2 and 3
In the same manner as in Synthesis Example 1, polyester raw material chips B and C shown in Table 1 were obtained. In the table, BD is 1,4-butanediol. The intrinsic viscosity of each polyester was 0.72 dl / g for chip B and 1.20 dl / g for chip C. In addition, when adding an inorganic lubricant in an experimental example described later, a master batch in which 0.7% by mass of the inorganic lubricant used in the polyester B was added was prepared and used in a necessary amount. The method of adding the lubricant was such that the lubricant was dispersed in ethylene glycol in advance and polymerized by the above method.
[0081]
Experiment No. 1
(1) Polyester resin and unstretched film
Each chip obtained in the above synthesis example was separately pre-dried, and as shown in Table 1, 55% by weight of chip A, 35% by weight of chip B, 10% by weight of chip C, and a hopper just above the extruder. While continuously and separately supplied by a fixed screw feeder, mixed in this hopper, melt-extruded with a single screw extruder at 280 ° C., and then quenched to obtain an unstretched film having a thickness of 180 μm. .
[0082]
(2) Formulation of coating liquid for easy slip layer
An aqueous dispersion of polyester resin (PEs) (trade name "TIE51"; manufactured by Takemoto Yushi) is solid at 25% by mass, and an aqueous emulsion of polyethylene wax (trade name "HYTEC E-4BS"; manufactured by Toho Chemical Industry) is solid. 1% by mass, 35% by mass of water, and 31% by mass of isopropanol were mixed with an antistatic agent (trade name: "TB702", manufactured by Takemoto Oil & Fats Co., Ltd.) to give a coating solution.
[0083]
(3) Production of coated film
The coating solution prepared in (2) was applied to the unstretched film obtained in (1) by an air knife method. Next, after preheating at 100 ° C. for 10 seconds, the film was stretched 4.0 times in the transverse direction with a tenter and heat-set at 80 ° C. The coating amount of the slippery layer of this heat-shrinkable polyester film is 0.01 g / m2.²And the thickness was 45 μm.
[0084]
Subsequently, a corona treatment under a nitrogen atmosphere was performed on the opposite side of the film from the surface on which the smooth layer was formed, under the following conditions. The processing electrode and the processing portion of the corona processing apparatus were surrounded by a double chamber, and nitrogen was continuously supplied to replace the atmosphere with a nitrogen atmosphere. The processing electrode of the corona processing apparatus used was a bar electrode made of aluminum, and the processing roll used was one whose surface material was made of silicone rubber. The gap between the processing electrode and the film was 0.5 mm, the gap between the film and the chamber was 0.3 mm, and the gap was covered with a cotton cloth (another). The high-frequency power supply used was a device manufactured by Kasuga Electric Co., Ltd., and the corona treatment was performed under the conditions shown in Table 2 with the transmission frequency being 45 ± 3 KHz, the processing atmosphere temperature and the processing roll surface temperature being both 40 ° C. The film surface temperature during the treatment was 40 ° C., and the oxygen concentration in the nitrogen atmosphere was 250 ppm. Table 2 shows the physical property values of the obtained film.
[0085]
Experiment No. 2
Experiment No. Experiment No. 1 except that an aqueous dispersion of polyurethane resin (PU) (trade name “Hydran HW345”; manufactured by Dainippon Ink and Chemicals) was added in place of the aqueous dispersion of the polyester resin in the coating liquid for easy-smoothing layer of Example 1. Production and evaluation of the film were performed in the same manner as in Example 1. Table 2 shows the physical property values of the obtained film.
[0086]
Experiment No. 3
Experiment No. A heat-shrinkable polyester film having a thickness of 45 μm was obtained in the same manner as in Example 1 except that the slippery layer was not formed. Table 2 shows the physical property values of the obtained film.
[0087]
Experiment No. 4
Experiment No. 1 using an aqueous dispersion of a polyurethane resin (trade name “Hydran HW345”; manufactured by Dainippon Ink Industries, Ltd.). Further, 0.2% by mass of PMMA particles (“Eposter MA1001”, manufactured by Nippon Shokubai) was added to the coating solution for easy lubrication of No. 2, and the coating amount after stretching was 0.04 g / m 2.²The experiment Nos. In the same manner as in Example 1, a heat-shrinkable polyester film was obtained. Table 2 shows the physical property values of the obtained film.
[0088]
Experiment No. 5
Experiment No. A heat-shrinkable polyester film was obtained in the same manner as in 1, except that the polyethylene wax was not added to the coating solution. Table 2 shows the physical property values of the obtained film.
[0089]
Experiment No. 6
Experiment No. In Example 1, a heat-shrinkable polyester film having a thickness of 45 μm was obtained in the same manner as in Example 1 except that the corona treatment was not performed. Table 2 shows the physical properties of the obtained film.
[0090]
Experiment No. 7
Experiment No. An unstretched film was obtained in the same manner as in Example 1. After preheating this unstretched film at 100 ° C. for 10 seconds, it is stretched 4.0 times with a tenter in the transverse direction at 80 ° C., and then heat-treated at 80 ° C. for 10 seconds to form a heat-shrinkable polyester system having a thickness of 45 μm. A film was formed. Subsequently, the film was guided to a corona treatment device in an air atmosphere, and subjected to corona treatment under the conditions shown in Table 2. The processing equipment at this time was the same as in Experiment No. The same as 1 was used. Table 2 shows the physical property values of the obtained film.
[0091]
[Table 1]

[0092]
[Table 2]

[0093]
Experiment No. 8
Experiment No. Each of the films obtained in 1, 2, 3 and 5 was attached to a 500 ml square PET bottle beverage, and heat-shrinked 30 samples each were prepared, and set in a vending machine. Experiment No. Experiment No. 1 (inclined sliding angle 12.0 °) In the case of 2 (inclination start angle of 11.0 °), no clogging occurred among 30 pieces. Experiment No. In the case of Experiment No. 3 (inclination start angle of 17.5 °), 12 out of 30 clogging occurred. At 5 (inclination angle of 14.5 °), 4 out of 30 clogs occurred.
[0094]
【The invention's effect】
The heat-shrinkable film of the present invention has excellent ink adhesion to various types of inks, and has excellent releasability to inks that can be released with an alkaline aqueous solution. In addition, since the film has excellent blocking resistance, it is possible to suppress occurrence of troubles such as defective opening after label cutting when the film is formed into a label. It also has excellent slipperiness and antistatic properties, and when used for beverage labels, does not clog or adsorb dirt inside the vending machine. Therefore, it is very useful as a label for coating containers such as PET bottles.

Claims (6)

A sample cut into a square of 10 cm × 10 cm from the film was immersed in hot water at 85 ° C. for 10 seconds and pulled up, and then immersed in water at 25 ° C. for 10 seconds and pulled up to have a heat shrinkage in the maximum shrinkage direction of 20%. % Or more, wherein the nitrogen atom content in the outermost layer of the first surface of the film is 0.2 to 5.0 atomic%, and the coefficient of kinetic friction μd between the second surfaces of the film is Is 0.27 or less. 2. The heat-shrinkable polyester film according to claim 1, wherein the surface specific resistance value of the second surface of the film is 1 × 10 ¹³ Ω · cm or less. The heat-shrinkable polyester film according to claim 1 or 2, wherein the first surface of the film has a wetting tension of 40 mN / m or more. The heat-shrinkable polyester film according to any one of claims 1 to 3, wherein a peel strength after heat sealing the first surfaces of the films at 75 ° C is 5 N / 15 mm width or less. A virtual bottle sample attached to the bottom of a rectangular weight of 500 g having a rectangular shape with a short side of 55 mm and a long side of 160 mm, with the second side of the film facing outward with the maximum contraction direction of the film along the short side. Was placed horizontally on a stainless steel plate to increase the tilt angle of the stainless steel plate by 1.0 °, and the tilt angle of the stainless steel plate when the virtual bottle sample slipped was defined as The heat-shrinkable polyester film according to any one of claims 1 to 4, wherein the slanting start angle with respect to stainless steel is 13.0 ° or less. A heat-shrinkable label obtained from the heat-shrinkable polyester film according to claim 1.