JP2005335368A - Heat shrinkable polyester-based film and heat shrinkable label - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat shrinkable polyester-based film improved in sliding properties on the outer surface when being used as a label for a drink. <P>SOLUTION: The heat shrinkable polyester-based film has a heat shrinkage in the maximum heat shrinkage direction of not less than 20%, a surface resistivity of not more than 1×10<SP>13</SP>(Ω/square) under the atmosphere of a temperature of 23°C and a relative humidity of 30% on at least one surface of the film a coefficient of dynamic friction at least between the film surfaces of not more than 0.24 under the atmosphere of a temperature of 23°C and a relative humidity of 50% when a square cut film specimen of 10 cm×10 cm is immersed in warm water of 85°C for 10 seconds and pulled up, and then is immersed in water of 25°C for 10 seconds and is pulled up, and has a coefficient of dynamic friction at least between the film surfaces of not more than 0.28 under the atmosphere of a temperature of 23°C and a relative humidity of 65% when the film is immersed in warm water of 80°C for 20 seconds while letting the film heat-shrink by 10% in the primary shrinkage direction and is pulled up and dried for 24 hours under the atmosphere of a temperature of 23°C and a relative humidity of 65%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat-shrinkable polyester film, and more particularly to a heat-shrinkable polyester film suitable for labeling and a heat-shrinkable label comprising the heat-shrinkable polyester film.

  In recent years, heat-shrinkable plastic films have been widely used for the purpose of packaging to improve the appearance of packaging, packaging to avoid direct impact of contents, label packaging that protects glass bottles or plastic bottles and displays products. Is used. Plastic materials used for these purposes include stretched films such as polyvinyl chloride films, polystyrene films, and polyester films. Labels are used in various containers such as polyethylene terephthalate (PET) containers, polyethylene containers, and glass containers. And used for the purpose of cap seals or integrated packaging.

  However, the polyvinyl chloride film has excellent shrinkage characteristics, but has low heat resistance, and also has problems such as generation of hydrogen chloride gas during incineration and causing dioxins. Further, when a heat-shrinkable vinyl chloride resin film is used as a shrinkable label for a PET container or the like, there is a problem that the label and the container must be separated when the container is recycled.

  On the other hand, a polystyrene film can be evaluated for its good finished appearance after shrinkage, but it is poor in solvent resistance, so an ink with a special composition must be used for printing. In addition, polystyrene resins need to be incinerated at a high temperature and have a problem that a large amount of black smoke and off-flavor are generated during incineration.

  Polyester films without these problems are highly expected as shrink labels to replace polyvinyl chloride films and polystyrene films, and the amount of use tends to increase as the amount of PET container used increases.

However, the conventional heat-shrinkable polyester film has been required to be further improved in its properties. Since the above-mentioned conventional film is an insulator, it has a drawback in that the generation of static electricity is liable to accumulate and causes various troubles due to static electricity failure. For example, in the printing process, the tubing process, or the label mounting process, the winding of the roll, the electric shock to the human body, the reduction of work efficiency such as the difficulty of handling, the occurrence of so-called printing whiskers, poor opening, the film surface There was a drawback that it caused a decrease in the commercial value such as dirt. In order to solve this problem, a method of setting the surface resistance value of the film to 1 × 10 ¹³ (Ω / □) or less has been proposed (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 7-1583

  However, although there is no problem with the workability at room temperature and normal humidity, troubles occur during processing due to a decrease in antistatic performance particularly in a low humidity atmosphere such as winter, and therefore further improvement has been demanded.

Furthermore, when beverages sold in vending machines are sold with vending machines using conventional polyester film as labels, label slipping is insufficient and clogging with vending machines, that is, products pass through the passageway. Therefore, there has been a problem that the product does not reach the outlet and the products are discharged in multiple layers.
In order to solve this problem, a method of laminating a layer having good slipperiness on the film surface has been made (for example, see Patent Document 2).
JP 2002-196677 A

  However, this method is due to post-processing on the film, and there are problems in terms of cost, and wear debris is generated due to rubbing between the roll and the like in the processing step and the laminated surface, resulting in lower productivity. It had been.

  The present invention has been made in view of the above circumstances, and is excellent in antistatic performance in a normal temperature and normal humidity atmosphere, as well as excellent in workability and transparency in a low humidity atmosphere in winter and the like. To provide a heat-shrinkable polyester film and a heat-shrinkable label, which are good and prevent clogging of products in a beverage vending machine by improving the lubricity of the outer surface when used as a beverage label. With the goal.

  The heat-shrinkable polyester film that has solved the above problems is the heat in the maximum heat-shrink direction when a sample obtained by cutting the film into a 10 cm × 10 cm square shape is dipped in hot water at 85 ° C. for 10 seconds and pulled up. The shrinkage rate is 20% or more. The heat-shrinkable polyester film has a heat shrinkage rate of less than 20% when the heat-shrinkable polyester film is in close contact with the container when the film shrinks due to insufficient heat shrinkage of the film. This is not preferable because an appearance defect occurs.

Furthermore, the heat-shrinkable polyester film of the present invention has a surface specific resistance value of at least one surface of the film of 1 × 10 ¹³ (Ω / □) or less in an atmosphere at a temperature of 23 ° C. and a relative humidity of 30%. By securing the surface specific resistance value under the low humidity, it is possible to impart excellent processing performance even in a low humidity atmosphere such as in winter.

  Furthermore, in the heat-shrinkable polyester film of the present invention, the dynamic friction coefficient between at least one side of the film is 0.24 or less in an atmosphere of 23 ° C. and 50% relative humidity according to JIS K-7125, and The film was thermally contracted by 10% in warm water at 80 ° C., dipped for 20 seconds, pulled up, and naturally dried in an atmosphere of 23 ° C. and relative humidity 65%, at least between one side of the film The dynamic friction coefficient is 0.28 or less. The heat-shrinkable polyester film having such properties has excellent slipperiness and good processability in the printing / tubing process, and is excellent even after being shrunk on a bottle container with a steam tunnel as a label, for example. It is possible to prevent clogging of products in a beverage vending machine.

  Further, the heat-shrinkable polyester film according to the present invention has a half-life of at least one side of the charge decay rate of 30 according to JIS-L-1094 method measured at a temperature of 23 ° C. and a relative humidity of 65%. It is preferable that it is below second. A film having such characteristics can impart further excellent processing performance particularly in preventing winding around a roll in a printing / tubing process.

  A preferred embodiment of the present invention is a heat-shrinkable polyester film in which a layer containing an antistatic agent component made of an amphoteric surfactant, a silicone component and a polyester resin component is provided on at least one surface of the film.

  Furthermore, as a preferable production method in the present invention, it is preferable to dry after applying a coating solution containing an antistatic agent comprising an amphoteric surfactant, a silicone component and a polyester resin component, and an unstretched polyester film or uniaxially stretched. A coating solution containing an antistatic agent composed of the above-mentioned amino acid-based amphoteric surfactant and / or an antistatic agent composed of a betaine-based surfactant is applied to at least one surface of the polyester film, followed by drying and stretching. It is more preferable in terms of ease and cost.

  The heat-shrinkable polyester film and heat-shrinkable label of the present invention are excellent in antistatic performance in a normal temperature and normal humidity atmosphere, as well as excellent in antistatic properties and slipperiness in a low humidity atmosphere. It is possible to reduce or prevent processing troubles even in winter. Furthermore, the film has a function of keeping the appearance of the film, particularly transparency, well and suppressing the friction between the films low. Furthermore, when it is used as a label for a beverage container by heat shrinkage treatment with steam or hot air, the friction between the containers can be kept low, so that clogging of goods in the vending machine can be prevented. Further, when used as a label, it is excellent in solvent adhesion and has a very high practical value.

  The heat-shrinkable polyester film of the present invention is a 10 cm × 10 cm square cut heat-shrinkable polyester film soaked in 85 ° C. warm water for 10 seconds and then immersed in 25 ° C. water for 10 seconds. When it is pulled up, the thermal shrinkage rate in the maximum shrinkage direction is 20% or more. If the film has a heat shrinkage rate of less than 20%, the film heat shrinkage rate is insufficient, and when the container is covered and shrunk, the film does not adhere to the container and an appearance defect occurs. A more preferable heat shrinkage rate is 25% or more, and further preferably 30% or more.

Here, the heat shrinkage rate in the maximum shrinkage direction means the heat shrinkage rate in the direction of the most shrinkage in the sample film plane, and the maximum shrinkage direction is a square vertical or horizontal direction (or oblique direction). It is decided by the length. The thermal shrinkage rate (%) was 10 cm × 10 cm of sample film immersed in warm water at 85 ° C. ± 0.5 ° C. for 10 seconds in a no-load state, and immediately heat shrunk. It is a value obtained by measuring the length of the film in the vertical direction and the horizontal direction (or diagonal direction) after being immersed in water at 0 ° C. for 10 seconds in an unloaded state, according to the following formula.
Thermal shrinkage rate (%) = (length before shrinkage−length after shrinkage) ÷ (length before shrinkage) × 100

Furthermore, the heat-shrinkable polyester film of the present invention has a surface specific resistance value of at least one surface of the film of 1 × 10 ¹³ (Ω / □) or less in an atmosphere at a temperature of 23 ° C. and a relative humidity of 30%. By securing the surface specific resistance value under the low humidity, it is possible to impart excellent processing performance even in a low humidity atmosphere such as in winter. When the surface specific resistance value is less than 1 × 10 ¹³ (Ω / □), various troubles due to electrostatic failure occur in a low humidity atmosphere. For example, generation of so-called printing whiskers in the printing process, winding around rolls in the printing / tubing process, adhesion of labels after label cutting, especially adhesion when picking up and mounting one by one after stacking the labels Difficulty in workability, troubles in opening of cut labels, and adhesion of dirt such as dust to the surface. The surface specific resistance value is 1 × 10 ¹³ (Ω / □) or less, preferably 5 × 10 ¹² (Ω / □) or less, more preferably 1 × 10 ¹² (Ω / □) or less.

Furthermore, the heat-shrinkable polyester film of the present invention preferably has a surface resistivity value of at least one side of the film of 1 × 10 ¹² (Ω / □) or less in an atmosphere at a temperature of 23 ° C. and a relative humidity of 65%. By ensuring the surface resistivity value under the humidity, it is possible to give excellent processing performance even under high humidity atmosphere such as normal humidity and summer, and prevent various troubles due to the above-mentioned electrostatic failure. can do. The surface specific resistance value under the humidity is preferably 1 × 10 ¹² (Ω / □) or less, more preferably 5 × 10 ¹¹ (Ω / □) or less, and further preferably 1 × 10 ¹⁰ (Ω / □). It is as follows.

  Furthermore, in the heat-shrinkable polyester film of the present invention, the coefficient of dynamic friction between at least one side of the film is 0.24 or less in an atmosphere of 23 ° C. and 50% relative humidity according to the JIS K-7125 method. By setting the dynamic friction coefficient to 0.24 or less, it is possible to provide excellent processing performance even in a low humidity atmosphere such as in winter. In particular, when performing high-speed printing or tubing, it is possible to prevent wrinkles and scratches due to poor lubricity. The dynamic friction coefficient is preferably 0.22 or less, more preferably 0.20 or less.

  Furthermore, in the heat-shrinkable polyester film of the present invention, the film was immersed in hot water at 80 ° C. for 10 seconds while being thermally shrunk in the main shrink direction for 20 seconds, then pulled up, and then heated in an atmosphere at 23 ° C. and 65% relative humidity. The coefficient of dynamic friction between at least one side of the film after being naturally dried for a period of time is 0.28 or less at a temperature of 23 ° C. and a relative humidity of 65%. By setting the dynamic friction coefficient to 0.28 or less, when the film is used as a label of a beverage container by coating shrinkage treatment with steam or hot air as a label, the friction between the containers can be kept low. The product can be prevented from clogging in the machine. The dynamic friction coefficient is preferably 0.26 or less, more preferably 0.24 or less.

Furthermore, in the present invention, at least half of the charge decay rate of one side of the film is JIS
According to the L-1094 method, it is preferably 30 seconds or less as measured in an atmosphere at a temperature of 23 ° C. and a relative humidity of 65%. The film having a half-life of the charge decay rate in the above range has an effect of preventing so-called printing whiskers in the printing process and winding around the roll in the printing / tubing process. The half-life of the charge decay rate is more preferably 25 seconds or less, and even more preferably 20 seconds or less.

  A preferred embodiment of the present invention is a heat-shrinkable polyester film obtained by coating an antistatic agent component comprising an amphoteric surfactant, a silicone component and a polyester resin component on at least one surface of the film. Surfactant is a general term for compounds having a hydrophilic group and a hydrophobic group. Antistatic agents made of surfactant can be classified into anionic, cationic, amphoteric and nonionic types according to the ionic type of the hydrophilic group. . Anion type refers to those having hydrophilic groups such as carboxylic acid, carboxylate, sulfate ester, sulfate ester salt, sulfonic acid, sulfonate salt, phosphate ester, phosphate ester salt and are widely used. However, it has a disadvantage that it is inferior in antistatic performance under low humidity, and the target performance of the present invention cannot be obtained. In addition, the cation type means primary amine, primary amine salt, secondary amine, secondary amine salt, tertiary amine, tertiary amine salt, quaternary ammonium, quaternary ammonium salt, etc. It has excellent antistatic performance under low humidity, but has the disadvantage of being inferior in heat resistance, so it is easily decomposed at high temperatures, and it is inferior in hygiene and is used for food packaging. Most of these films are unsuitable. In addition, the nonionic type has a hydrophilic group such as polyethylene glycol and polyhydric alcohol, but has a disadvantage in that it is inferior in antistatic performance under low humidity as in the case of an anionic type. On the other hand, the amphoteric type refers to those having any two types of hydrophilic groups among anionic, cationic and nonionic types. Since amphoteric types often have amine salts or quaternary ammonium salts as hydrophilic groups as cationic moieties, amphoteric types are generally classified by the type of anionic moiety. Amphoteric type, sulfate ester or sulfate salt type amphoteric type, sulfonic acid or sulfonate type amphoteric type, phosphate ester or phosphate ester type amphoteric type, antistatic performance and heat resistance under low humidity, hygiene All of these properties are preferable because they are excellent. Furthermore, when mixing and using together the silicone component and polyester resin component which are mentioned later, since compatibility of both and an amphoteric type surfactant is good, it is preferable when ensuring the transparency of a film. Among these, carboxylic acid or carboxylate-based amphoteric type is preferable because it is particularly excellent in hygiene. For example, an amino acid amphoteric surfactant represented by (Chemical Formula 1) and a betaine amphoteric surfactant represented by (Chemical Formula 2) can be mentioned.

  Specific examples of (Chemical Formula 1) include β-laurylaminopropionic acid, β-laurylaminopropionic acid sodium, and the like. Specific examples of (Chemical Formula 2) include lauryldimethylaminoacetic acid betaine, coconut oil fatty acid amidopropyldimethylamino. Examples include betaine acetate, myristic acid amidopropylaminobetaine, lauric acid amidopropyldimethylaminoacetic acid betaine, and the like.

Silicone components refer to organosiloxanes and have properties such as oil, rubber, and resin, which are called silicone oil, silicone rubber, and silicone resin, respectively. Since it has water repellent action, lubrication action, release action, etc., it is effective in reducing the friction coefficient of the surface when it is applied and laminated on the film surface layer. In addition, when used as a beverage container label, it is often shrunk and attached using steam or hot air, and if it is a slippery layer with low water resistance, the slipperiness using steam will significantly reduce slipperiness. However, due to the water-repellent effect of silicone, good slipperiness can be ensured even after treatment with steam.
In particular, silicone resin is recommended. Silicone resin refers to organopolysiloxane having a three-dimensional network structure. When it is rolled up as a slippery layer on the polyester film surface, it is transferred to the back of the film that comes into contact with it. hard. Moreover, when using as a drink label, although a printing process is given, the printability in that case is favorable. Furthermore, those having a methyl group as an organic group are particularly recommended because they have excellent heat resistance and are suitable for use as labels for hot beverage containers.

  The polyester resin component is not particularly limited as long as it is a copolyester, but in addition to terephthalic acid and an ethylene glycol component, isophthalic acid, sodium 5-sulfoisophthalate, fumaric acid, 1, Those containing 4-butanediol, neopentyl glycol, 1,3-propanediol, 1,4-cyclohexanedimethanol, diethylene glycol and the like are preferable, and a styrene component is preferably further included. A polyester resin component having a styrene component has an effect of increasing the hardness of the layer, so that it exhibits good lubricity when combined with a silicone component, and also has an adhesive property with an adhesive solvent such as 1,3-dioxolane in tubing. It is preferable because it is excellent. Furthermore, this resin component has an effect as a binder, improves the adhesion of the coat layer to the film, and also as a stretching aid for making a smooth surface even when the film is stretched after the coating layer is laminated. It also has an effect. Furthermore, as a polyester resin component having a styrene component, it is preferable to use an aqueous dispersion from the viewpoint of safety and environmental friendliness. In addition, when the film is stretched after laminating the coat layer, it is effective to make the surface layer tough, and it is possible to reduce the thickness.

A preferred range in the present invention is to apply an appropriate amount of a mixture of an antistatic agent component comprising the amphoteric surfactant of the above (Chemical Formula 1) or (Chemical Formula 2), a silicone component, and a polyester resin component to at least one surface of the film. It is possible to control the surface specific resistance value, the dynamic friction coefficient, and the half-life of the charge decay rate. The preferable blending ratio is 15 to 50% by weight of the antistatic agent component made of an amphoteric surfactant, 25 to 70% by weight of the silicone component, and 5 to 25% by weight of the polyester resin component. When the amount of the antistatic agent component is less than 5% by weight, the antistatic effect intended by the present invention cannot be obtained. On the other hand, if the amount of the silicone component is less than 25% by weight, the intended lubricity of the present invention cannot be imparted. On the other hand, when the polyester resin component is less than 5% by weight, the solvent adhesion deteriorates, the adhesion between the coat layer and the film decreases, and the stretchability also deteriorates. The preferable range of the coating amount is 0.003 (g / m ² ) to 0.060 (g / m ² ), more preferably 0.004 (g / m ² ) to 0.050 (g / m ² ), still more preferably ^{0.005 (g / m 2) ~0.040} (g / m 2). Below the lower limit coating amount, it becomes difficult to control the surface resistivity, dynamic friction coefficient, and half-life of charge decay rate within the preferred ranges in the present invention, and when the upper limit coating amount is exceeded, the solvent adhesion of the film is reduced. Since it inhibits, peeling may occur when producing a label by solvent adhesion, which is not preferable.

  In the present invention, if necessary, an antistatic agent other than the above (Chemical Formula 1) or (Chemical Formula 2), particles such as silica, a wax component, an ultraviolet absorber, a surfactant and the like are mixed in the coating solution. It is also possible to apply it.

As the dicarboxylic acid component constituting the polyester in the raw material composition used for the heat-shrinkable polyester film of the present invention, in addition to terephthalic acid constituting the ethylene terephthalate unit, any of aromatic dicarboxylic acid and alicyclic dicarboxylic acid Can be used.
Examples of aromatic dicarboxylic acids include benzenecarboxylic acids such as isophthalic acid, orthophthalic acid, 5-tert-butylisophthalic acid and 5-sodium sulfoisophthalic acid; naphthalenedicarboxylic acids such as 2,6-naphthalenedicarboxylic acid; 4,4′- Dicarboxybiphenyls such as dicarboxydiphenyl, 2,2,6,6-tetramethylbiphenyl-4,4′-dicarboxylic acid; 1,1,3-trimethyl-3-phenylindene-4,5-dicarboxylic acid and Examples thereof include 1,2-diphenoxyethane-4,4′-dicarboxylic acid and its substitutes.
Examples of fatty acid carboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, pimelic acid, suberic acid, undecanoic acid, dodecanedicarboxylic acid, brassylic acid, tetradecanedicarboxylic acid, tapsinic acid, Nonadecane dicarboxylic acid, docosane dicarboxylic acid, and substituted products thereof, 4,4′-dicarboxycyclohexane and substituted products thereof, and the like can be mentioned.

As the diol component of the polyester contained in the raw material composition, any of aliphatic diol, alicyclic diol, and aromatic diol can be used in addition to ethylene glycol constituting the polyethylene terephthalate unit.
Aliphatic diols include diethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, neopentyl glycol, 2-methyl-2-ethyl-1,3-propanediol 2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, and the like. Examples of the alicyclic diol include 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol. Aromatic diols include ethylene oxide adducts of bisgenol compounds such as 2,2-bis (4′-β-hydroxyethoxyphenyl) sulfone; xylylene glycol and the like. Polyalkylene glycols such as polyethylene glycol and polypropylene glycol can also be used as the diol component.

  The polyester contained in the raw material composition is composed of the acid component and the diol component. In order to adjust the polyester, one or more acid components are used to improve the properties as a heat-shrinkable film. Alternatively, it is preferable to use a combination of diol components, and the type and content of the monomer components to be combined may be appropriately determined based on desired film characteristics, economy, and the like. The raw material composition contains one or more polyesters. When the contained polyester is one, it is a copolymerized polyester containing an ethylene terephthalate unit. When two or more kinds of polyesters are mixed, a mixture having a desired composition of a copolyester and a homopolyester is prepared. In general, copolymer polyester has a low melting point and low glass transition temperature, and therefore has problems such as difficulty in handling during drying. Therefore, homopolyester (polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polypropylene terephthalate, poly (1,4- It is preferable to use a mixture of cyclohexene diethylene terephthalate)) and a copolymer polyester. As the film composition, ethylene terephthalate is the main constituent as the film composition, and it is particularly preferable to contain any one or more of neopentyl glycol, 1,4 cyclohexanedimethanol and isophthalic acid as the other secondary constituent. preferable. By introducing these secondary components, the polymer can be made amorphous to exhibit heat shrinkability, and solvent adhesion can be imparted to the film. Ethylene terephthalate is preferably 60 mol% or more, more preferably 70 mol% or more, when the constituent components of all polyesters are 100 mol%. The content of any one or more of the neopentyl glycol, 1,4 cyclohexanedimethanol and isophthalic acid is the total amount when the total amount of acid components is 100 mol% and the total amount of diol components is 100 mol%. As for, the range of 8 mol%-30 mol% is preferable, and the range of 10-25 mol% is more preferable. Furthermore, it is also a preferred embodiment to contain any one or more of 1,4 butanediol and 1,3 propanediol, which lower the glass transition temperature of the film in order to impart low temperature shrinkage. The content of any one or more of 1,4 butanediol and 1,3 propanediol is the total amount when the total amount of acid components is 100 mol% and the total amount of diol components is 100 mol%. The range of 3 mol% to 30 mol% is preferable, and the range of 5 to 25 mol% is more preferable because it can exhibit low-temperature shrinkage and ensure the tear resistance of the film.

  Any of the polyesters in the raw material composition can be produced by a conventional method. For example, the polyester is prepared using a direct esterification method in which a dicarboxylic acid and a diol are directly reacted; a transesterification method in which a dicarboxylic acid dimethyl ester is reacted with a diol, and the like. The adjustment may be performed by either a batch method or a continuous method.

  In addition to the polyester, various known additives may be added to the raw material composition as necessary. Examples of additives include inorganic particles such as silica, titania, mica, talc and calcium carbonate as inert particle lubricants, polymethyl methacrylate (PMMA), styrene-divinylbenzene, formaldehyde resin, silicone resin, polyamideimide, benzoguanamine The slipperiness can be further improved by adding organic particles such as these or surface treated products, but the transparency of the film tends to decrease due to the formation of surface irregularities, etc. It is recommended to adjust the addition amount appropriately according to the conditions. Organic lubricants include paraffin wax, micro wax, polypropylene wax, polyethylene wax, ethylene acrylic wax, stearic acid, behenic acid, 12-hydroxystearic acid, stearic acid amide, oleic acid amide, erucic acid amide, and methylene. Bis-stearic acid amide, ethylene bis-stearic acid amide, ethylene bis-oleic acid amide, butyl stearate, monoglyceride stearate, pentaerythritol tetrastearate, hydrogenated castor oil, stearyl stearate, siloxane, higher alcohol polymer, stearyl alcohol, It is preferable to add calcium stearate, zinc stearate, magnesium stearate, lead stearate or the like. Among these, the addition of low molecular weight polyethylene wax can be expected to improve lubricity from the effect of preventing sticking by smoothing the layer surface. In addition to the above, an ultraviolet absorber; a colorant (dye etc.) may be added according to the purpose.

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, a flat shape or a tube shape, and is not particularly limited. As the stretching method, for example, a known method such as a roll stretching method, a long gap stretching method, a tenter stretching method, or a tubular stretching method can be employed. In any of these methods, stretching may be performed by sequential biaxial stretching, simultaneous biaxial stretching, uniaxial stretching, and combinations thereof.
In the biaxial stretching, stretching in the vertical and horizontal directions may be performed simultaneously, or either one may be performed first. The draw ratio is arbitrarily set in the range of 1.04 times to 7.00 times, and it is preferable to set the magnification in one predetermined direction to 3.5 times or more. More preferably, it is in the range of 3.5 times to 5.5 times in transverse uniaxial stretching.

  In the stretching step, preheating is preferably performed at a temperature not lower than the glass transition temperature (Tg) of the polymer constituting the film and not higher than Tg + 80 ° C., for example. The stretching temperature is preferably in the temperature range of Tg or more and 5 ° C. or less than the preheating temperature. As for the heat setting at the time of stretching, for example, it is recommended to pass the heating zone at 30 to 150 ° C. for about 1 to 30 seconds after stretching. Further, after stretching the film, it may be stretched at a predetermined degree before or after heat setting. Further, after the stretching, a step of cooling while keeping the stretched or tensioned state while applying stress to the film, or a step of cooling after releasing the tensioned state following the treatment may be added. The thickness of the obtained film is preferably in the range of 6 to 250 μm, and more preferably in the range of 20 to 60 μm.

A preferred method for producing the heat-shrinkable polyester film of the present invention is a method (offline coating) in which a coating liquid comprising the above-mentioned components is applied to at least one surface of a stretch-formed heat-shrinkable polyester film and dried. Any of the methods (in-line coating) in which the coating liquid composed of the above-described components is applied to one side of an unstretched polyester film or a uniaxially stretched polyester film and then dried and stretched is possible. In the off-line coating, if the temperature at the time of drying is high, the film undergoes heat shrinkage. Therefore, the drying temperature is preferably 60 ° C. or less. In the in-line coating, the coating amount of the coating solution before drying is 10 (g / m ²
) Is not preferable because drying is insufficient. Moreover, it is preferable to adjust PH within the range of 5.5-8.0 from the viewpoint of the rust prevention of process equipment, or safety | security for the coating liquid containing the above-mentioned component. Sodium chloride or the like can be used as the pH adjuster. As a method for applying the coating liquid, a reverse roll method, an air knife method, a fountain method, a gravure roll method, a bar coating method, or the like can be used.

  Hereinafter, a method for producing a label from a film will be described. When producing a label from the heat-shrinkable polyester film of the present invention, if necessary, tube forming is performed after printing on the film surface, but in this case, often using a solvent, from the viewpoint that, It is preferable that a solvent such as 1,3-dioxolane or tetrahydrofuran is applied on one side of the film, the other side of the film is pressure-bonded to the coated side, and peeled in the main shrinkage direction, and is in an adhesive state. More preferably, it is 4 N / 15 mm or more. A tube-like product is cut by the tube processing to obtain a label-like body. When the solvent adhesiveness is insufficient, there is a possibility that the label adhesion part may be peeled off when the label is heat-shrinked or when the beverage bottle is handled. In the present invention, the fact that the film can be solvent-bonded means that the solvent adhesive strength is 4 N / 15 mm or more in the measurement method of Examples described later.

    Furthermore, in the present invention, the haze value of the film is preferably 8% or less. If the haze value of the film exceeds 8%, the transparency when the film is made into a label is deteriorated, and an unclear appearance is obtained when a pattern or a product name is printed on the inner surface of the label. In order to control the haze value of the film, the coating layer of the film should be within the appropriate coating amount range using the above-mentioned preferred composition, and the above-mentioned preferred composition can be used for the base film. Can be achieved. The haze value of the film is more preferably 7% or less.

  Next, contents and effects of the present invention will be described with reference to examples, but the present invention is not limited to the following examples without departing from the gist thereof. In addition, the measuring method of the characteristic value in this specification is as follows.

(Heat shrinkage)
The film was cut into a 10 cm × 10 cm square so that one side thereof was parallel to the film flow direction, and immersed in a water bath heated to 85 ° C. for 10 seconds. Immediately after 10 seconds, the film was immersed in a separately prepared 25 ° C. water bath for 10 seconds and then pulled up, and the length of the film in the main shrinkage direction was measured to obtain the heat shrinkage rate. The most contracted direction was defined as the maximum contraction direction.
Shrinkage rate (%) = (size before heating−size after heating) / size before heating × 100

(Surface specific resistance)
The film is allowed to stand in a 23 ° C./65 RH% atmosphere for 24 hours, and then coated with a specific resistance measuring instrument manufactured by Takeda Riken Co., Ltd. under an applied voltage of 500 V in a 23 ° C./30 RH% atmosphere and a 23 ° C./65 RH% atmosphere. The surface resistivity of the surface was measured.

(Dynamic friction coefficient)
(1) Untreated The film was allowed to stand in an atmosphere of 23 ° C. and 50 RH% for 24 hours, and then the dynamic friction coefficient μd between the coated surfaces of the film was measured in an atmosphere of 23 ° C. and 50 RH% according to JIS K-7125.

(2) After hot water treatment The film was cut into a rectangle with a size of 34 cm in the maximum shrinkage direction and 20 cm in the orthogonal direction, and two marked lines parallel to the orthogonal direction were drawn so that the interval was 30 cm with respect to the maximum shrinkage direction. Next, each marked line is aligned with the inner side of the frame on the side of 24 cm on a rectangular metal frame with an inner side of 27 cm × 24 cm, and each marked line part is fixed with double-sided tape. It was fixed to a metal frame in a state of being relaxed 10% in the shrinking direction. Next, the film fixed to the metal frame is allowed to elapse for 20 seconds in a hot water tank heated to 80 ° C. together with the metal frame, and after shrinking the film, it is immediately immersed in a separately prepared 25 ° C. water tank for 10 seconds and then pulled up from the metal frame. After removing the film and leaving it for 24 hours in an atmosphere of 23 ° C. and 65 RH%, the coefficient of dynamic friction μd between the coated surfaces of the film is determined according to JIS.
Based on K-7125, it measured in 23 degreeC and 65RH% atmosphere.

(Half time of charge decay rate)
After leaving the film in an atmosphere at 23 ° C. and 65 RH% for 24 hours, the coated surface of the film is measured in an atmosphere of 23 ° C. and 65 RH% with a static horn meter at an applied voltage of 10 KV in accordance with JIS L-1094 method. The half time was determined.

(Solvent adhesive strength)
Each test film is used and sealed with 1,3-dioxolane to form a tube. For sealing, a solvent is applied to the coated surface side of the film at a speed of 10 m / min, a coating amount of 2 g / m ^{2 and a} coating width of 3 mm, and then the other side of the film is immediately overlaid and a nip roll It was performed by pressure bonding with. Then, the seal part is cut to a width of 15 mm in the main stretching direction of the film, and is set in a universal tension tester STM-50 manufactured by Baldwin Co., Ltd., and measured at a pulling speed of 200 mm / min in a 180 ° peel test. The following criteria were used for evaluation.
○: ≧ 4N / 15mm
×: <4 N / 15 mm

(Haze)
According to JIS K6714, it measured using the haze meter (made by Nippon Seimitsu Co., Ltd.).

(Example 1)
(1) Polyester resin and unstretched film Ultimate limit consisting of 36% by weight of polyethylene terephthalate having an intrinsic viscosity of 0.72 (dl / g), 100% by mole of terephthalic acid, 30% by mole of neopentyl glycol and 70% by mole of ethylene glycol A polyester composition in which 54% by weight of a polyester having a viscosity of 0.75 (dl / g) and 10% by weight of a polybutylene terephthalate having an intrinsic viscosity of 1.20 (dl / g) is preliminarily dried and melted at 280 ° C. Then, it was extruded from a T-die and quenched on a chill roll having a surface temperature of 20 ° C. to obtain an unstretched film.

(2) Preparation of coating solution The solid content of an amino acid amphoteric surfactant (sodium β-laurylaminopropionate) solution (trade name “Bister SLA” manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) 45% by weight of the water, 47% by weight of the aqueous dispersion of the silicone resin (S4005: manufactured by Nisshin Chemical), and 8% of the solid content of the aqueous dispersion of the styrene copolymer polyester resin (AGN709: manufactured by Toyobo) % (Isopropyl alcohol-water) solution was used as a coating solution. The isopropyl alcohol concentration in the solution was 25% by weight.

(3) Production of coat film Apply the coating solution prepared in (2) on one side of the unstretched film obtained in (1) by the bar coater method, heat it until the film temperature reaches 80 ° C, and then use the tenter After stretching 3.8 times in the direction, the film was heat-set at 80 ° C. to obtain a heat-shrinkable polyester film having a coating amount of 0.025 g / m ² and a thickness of 40 μm.
Table 1 shows the results of testing the stretched film by the above method.

(Example 2)
(1) Production of heat-shrinkable polyester film Limit consisting of 36% by weight of polyethylene terephthalate having an intrinsic viscosity of 0.72 (dl / g), 100% by mole of terephthalic acid, 30% by mole of neopentyl glycol and 70% by mole of ethylene glycol A polyester composition in which 54% by weight of a polyester having a viscosity of 0.75 (dl / g) and 10% by weight of a polybutylene terephthalate having an intrinsic viscosity of 1.20 (dl / g) is preliminarily dried and melted at 280 ° C. Then, it was extruded from a T-die and quenched on a chill roll having a surface temperature of 20 ° C. to obtain an unstretched film. The film was heated until the temperature reached 80 ° C., stretched 3.8 times in the transverse direction with a tenter, and heat-set at 80 ° C. to obtain a heat-shrinkable polyester film having a thickness of 50 μm.

(2) Preparation of coating solution The solid content of an amino acid amphoteric surfactant (sodium β-laurylaminopropionate) solution (trade name “Bister SLA” manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) 20% by weight of the water, 65% by weight of the solid dispersion of the silicone resin (S4005: manufactured by Nisshin Chemical), and 15% of the solid content of the aqueous dispersion of the styrene copolymer polyester resin (AGN709: manufactured by Toyobo) % (Isopropyl alcohol-water) was used as the coating solution. The isopropyl alcohol concentration in the solution was 25% by weight.

(3) Production of Coat Film After applying the coating solution on one side of the heat-shrinkable polyester film of (1) with a gravure coater, it was dried in a dryer at a temperature of 40 ° C. to obtain a heat-shrinkable polyester film. The coating amount was 0.025 g / m ² . Table 1 shows the results of testing the film by the above method.

(Example 3)
Solid content of betaine amphoteric surfactant (lauryldimethylaminoacetic acid betaine) aqueous solution (trade name “Vistor ML” manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) is 35% by weight of the total solid content in the coating solution, A solution containing 45% by weight of solid content of an aqueous dispersion (S4005: manufactured by Nisshin Chemical) and 20% by weight of solid content of an aqueous dispersion of styrene copolymer polyester resin (AGN709: manufactured by Toyobo) (isopropyl alcohol-water) Was used as a coating solution. The isopropyl alcohol concentration in the solution was 25% by weight. A heat-shrinkable polyester film was obtained in the same manner as in Example 1 except that the coating amount was 0.010 g / m ² .
Table 1 shows the results of testing the film by the above method.

(Comparative Example 1)
An aqueous solution of an anionic surfactant (sodium paraffin sulfonate) (trade name “TB214” manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), 30% by weight of the total solid content in the coating solution, an aqueous dispersion of a silicone resin (S4005: manufactured by Nissin Chemical Co., Ltd.) Coating solution containing 55% by weight of a solid content of styrene copolymer polyester resin (AGN709: manufactured by Toyobo Co., Ltd.) and 15% by weight of a solid content of isopropyl alcohol-water It was. The isopropyl alcohol concentration in the solution was 25% by weight. A heat-shrinkable polyester film was obtained in the same manner as in Example 1 except that the coating amount was 0.020 g / m ² .
Table 1 shows the results of testing the film by the above method.

(Comparative Example 2)
Amino acid-based amphoteric surfactant (sodium β-lauryldimethylaminopropionate) solution (trade name “Bister SLA” manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) is diluted with an (isopropyl alcohol / water) solution to obtain a coating solution. . A heat-shrinkable polyester film was obtained in the same manner as in Example 1 except that the coating amount was 0.004 g / m ² .
Table 1 shows the results of testing the film by the above method.

(Comparative Example 3)
Amino acid-based amphoteric surfactant (sodium β-laurylaminopropionate) aqueous solution (trade name “Bister SLA” manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) is used as the solid content of 40% by weight of the total solid content in the coating solution, silicone Resin aqueous dispersion (S4005: manufactured by Nissin Chemical Co., Ltd.) contains 48% by weight of solid content and styrene copolymer polyester resin aqueous dispersion (AGN709: manufactured by Toyobo Co., Ltd.) contains 12% by weight (isopropyl alcohol-water) ) The solution was used as a coating solution. The isopropyl alcohol concentration in the solution was 25% by weight. A heat-shrinkable polyester film was obtained in the same manner as in Example 1 except that the coating amount was 0.001 g / m ² . Table 1 shows the results of testing the film by the above method.

(Comparative Example 4)
Amino acid-based amphoteric surfactant (sodium β-laurylaminopropionate) aqueous solution (trade name “Bister SLA” manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) is used as a solid, 10% by weight of the total solid content in the coating solution, silicone Resin aqueous dispersion (S4005: manufactured by Nissin Chemical Co., Ltd.) contains 75% by weight of solid content and styrene copolymer polyester resin aqueous dispersion (AGN709: manufactured by Toyobo Co., Ltd.) contains 15% by weight (isopropyl alcohol-water ) The solution was used as a coating solution. The isopropyl alcohol concentration in the solution was 25% by weight. A heat-shrinkable polyester film was obtained in the same manner as in Example 1 except that the coating amount was 0.020 g / m ² . Table 1 shows the results of testing the film by the above method.

On the non-coated surface side of the films of Examples 1 to 3 and Comparative Examples 1 to 4, the temperature was 10 ° C. and the relative humidity was 35%.
Using a printing machine in a room of the atmosphere, grass color, gold color, and white color printing was performed on the non-coated surface side. The films of Comparative Example 1, Comparative Example 3, and Comparative Example 4 had beard-like printing defects, and misalignment occurred due to color superposition, but the other films could be printed without problems.

After creating a label from the films of Examples 1 to 3 and Comparative Examples 1 to 4 so that the coated surface becomes the outer surface of the label, the label is attached to a 500 ml PET bottle containing beverage, and heat-shrinked in a steam tunnel, and then sold automatically. Filled the machine. In Comparative Example 1, 7 of 500 PET bottles were clogged. In Comparative Example 2 and Comparative Example 3, 4 of the 500 PET bottles were clogged. No clogging occurred in the 500 bottles.

  The heat-shrinkable polyester film of the present invention and the production method thereof, the heat-shrinkable label has excellent antistatic performance in a warm and humid atmosphere, and is excellent in processability even in a low humidity atmosphere such as in winter. Moreover, transparency is good, and when used as a beverage label, it is possible to prevent clogging of products in a beverage vending machine by improving the lubricity on the outer surface side. Moreover, since it is excellent also in the solvent adhesiveness at the time of using as a label, it can be used suitably for uses, such as a drink container label.

Claims (5)

The maximum heat shrinkage rate in the direction of maximum heat shrinkage when a sample obtained by cutting a film into a 10 cm × 10 cm square shape is dipped in hot water at 85 ° C. for 10 seconds and then dipped in water at 25 ° C. for 10 seconds. 20% or more, the surface resistivity of at least one side of the film is 1 × 10 ¹³ (Ω / □) or less in an atmosphere with a temperature of 23 ° C. and a relative humidity of 30%, and the dynamic friction coefficient between at least one side of the film is the temperature It is 0.24 or less in an atmosphere of 23 ° C. and a relative humidity of 50%, and the film is immersed in hot water at 80 ° C. for 10% in the main shrinkage direction and immersed for 20 seconds and then pulled up. The heat yield is characterized in that the dynamic friction coefficient between at least one side of the film after being naturally dried in a 65% atmosphere for 24 hours is 0.28 or less at a temperature of 23 ° C. and a relative humidity of 65%. Shrinkable polyester film.   2. The heat-shrinkable polyester according to claim 1, wherein the half-life of at least one side of the charge decay rate is 30 seconds or less as measured in an atmosphere at a temperature of 23 ° C. and a relative humidity of 65% according to JIS L-1094 method. Film.   The heat-shrinkable polyester film according to claim 1 or 2, wherein a coating layer containing an antistatic agent component comprising an amphoteric surfactant, a silicone component and a polyester resin component is provided on at least one surface of the film.   The heat-shrinkable polyester film according to any one of claims 1 to 3, wherein the film can be bonded to a solvent.   A heat-shrinkable polyester-based label, wherein the heat-shrinkable polyester-based film according to claim 4 is used to adhere one surface of the film and a part of the other surface with an organic solvent.