WO2009084420A1 - Heat-shrinkable polyester film - Google Patents

Abstract

A heat-shrinkable polyester film suitable for the use as labels for bottles which exhibits at least a high heat shrinkage factor and little causes whitening even when heat-shrunken, specifically, a heat-shrinkable polyester film which exhibits a heat shrinkage factor of 30 to 60% in the main shrinkage direction when immersed in hot water of 95±0.5°C for 10 seconds and which elongates in the direction perpendicular to the main shrinkage direction when immersed in hot water kept at a temperature of 59.5 to 90.5°C (with a tolerance of ±0.5°C) for 10 seconds. It is preferable that the film exhibit a heat shrinkage factor of less than 40% in the main shrinkage direction when immersed in hot water of 80±0.5°C for 10 seconds.

Description

Heat-shrinkable polyester film

The present invention relates to a heat-shrinkable polyester film that can be suitably used for label applications.

The heat-shrinkable plastic film having the property of shrinking by heating is widely used for applications such as packaging, labels, and cap seals. Stretched films such as polyvinyl chloride films, polystyrene films, and polyester films are known as heat-shrinkable plastic films. These films are used in various containers such as polyethylene terephthalate (PET) containers, polyethylene containers, and glass containers. Used for labels, cap seals, and integrated packaging applications.

Various plastic films are used as heat-shrinkable films as described above. Polyvinyl chloride films have low heat resistance, and cause generation of hydrogen chloride gas and dioxins when incinerated. I have a problem with environmental compatibility. In addition, when a container such as a PET container provided with a label of a polyvinyl chloride film is recycled, there is a problem that the label must be separated from the container.

Polystyrene film has good finish after shrinkage, but has poor solvent resistance. Therefore, when printing on the film surface, special composition ink must be used. In addition, when a polystyrene film is applied as a hot beverage PET bottle label, the label melts instantly when the label comes into contact with the hot wire of a heating equipment such as a hot warmer used in the bottle storage. There is a problem with. Other problems related to polystyrene films are low transparency that can be required as a good image of products (devitrification is likely to occur when polystyrene films are shrunk with hot air), and the incineration temperature for processing must be increased. There is a lot of black smoke and off-flavor generated during incineration.

Polyester films are used for container labels and the like as a film in which the above-mentioned problems such as heat resistance, environmental compatibility and solvent resistance of the polyvinyl chloride film and polystyrene film have been improved (for example, patents) Reference 1).

However, there is a demand for further improvement of the shrinkage property of the polyester film, and the first property that is desired to be improved is a label (film) when the label is attached to the container by heat shrinkage of the film. Of whitening. This whitening tends to occur particularly when the film is heated and shrunk by dry heat such as hot air, and tends to occur in a film having a high heat shrinkage rate. The resulting whitening tends to worsen over time. It may be possible to avoid the whitening of the label by selecting a film with a low heat shrinkage rate. However, since the amount of heat required for film shrinkage increases, in particular, damage is given to a container with low heat resistance, and the container is thermally expanded. When the film shrinks and returns to its original size, the problem is that the adhesion between the label and the container decreases. Due to the reduction in the amount of container raw materials used in recent years due to resource saving, the container is thinned and the heat resistance of the container tends to decrease. A decrease is likely to occur. Therefore, a film having a high heat shrinkage rate and capable of suppressing the occurrence of whitening is desired rather than selecting a film having a low heat shrinkage rate.

In addition, as a second characteristic desired for the polyester film, there is a suppression of occurrence of shrinkage unevenness, and further, as a third characteristic, the label jumps up (when the label is mounted on the container, the label can be moved from an arbitrary mounting position). (Random movement in the upper end direction of the container shaft). Together with the first characteristic, the second characteristic and the third characteristic are characteristics that are desired for mounting a good-appearance label on a container. Shrinkage unevenness is particularly likely to occur when the film is heated and shrunk by dry heat such as hot air, and is also likely to occur when the film has characteristics that cause rapid thermal shrinkage. The jumping of the label tends to occur when a film having a high thermal shrinkage rate in a direction orthogonal to the main shrinkage direction is heated and shrunk. Since both affect the appearance of the product at the store, a film that does not cause unevenness or jumping during shrinkage is desired.

In addition, since a conventionally known polyester film is an insulator, there is a problem that static electricity is easily generated and accumulated in the film. For example, static electricity that causes film wrapping around a roll in the film manufacturing process, film printing, adhesion between films, or electric shock to the human body becomes a factor that complicates the handling of the film. Moreover, since static electricity causes so-called printing mustaches, dirt on the film surface, and the like, it may induce a decline in commercial value. Therefore, a polyester film in which generation / accumulation of static electricity is suppressed is desired.

In addition, the peripheral surface of the container is covered with a heat-shrinkable film (heat-shrinkable label) that is processed into a cylindrical shape after being subjected to printing as necessary, and then the film is heat-shrinked to thereby surround the container. The method of covering the surface with a label is often used as a method for attaching a label to a container. In order to process a heat-shrinkable film into a cylindrical shape, a solvent is applied to one surface of the film, and this coated surface is applied. One means is to bond both surfaces of the film by contacting one surface of the film opposite to the other surface. However, depending on the composition of the polyester film, the adhesiveness at both ends of the film may be insufficient. If the adhesiveness is insufficient, that is, the adhesive strength is insufficient, the label attached to the container may be peeled off once during the heat shrinking process or the container handling. For this reason, a heat-shrinkable label having sufficient adhesiveness is desired.
JP 2002-46177 A

Moreover, when the contents of beverages or the like filled in the container are at a high temperature, blocking between the heat-shrinkable films (heat-shrinkable labels) attached to the containers may occur between adjacent containers. is there. In order to prevent troubles caused by static electricity during processing including printing, an antistatic agent is generally applied to the film, and the antistatic agent provides a heat-resistant blocking effect. However, after filling the container with high-temperature contents, the container is often cooled by taking a warm water shower or the like, and as a result, the antistatic agent applied to the film surface is washed away with warm water, substantially. The heat blocking effect may not be obtained.

In view of the above circumstances, an object of the present invention is to provide a heat-shrinkable polyester film having at least a high heat shrinkage rate and capable of suppressing the occurrence of whitening due to heat shrinkage. As a more preferred embodiment, a heat-shrinkable polyester film that can suppress the occurrence of trouble due to static electricity or a heat-shrinkable polyester film that suppresses the occurrence of blocking at high temperatures is provided, and heat suitable for labeling containers. An object is to provide a shrinkable polyester film.

That is, the heat-shrinkable polyester film according to the present invention has the following configuration.
1. The heat shrinkage rate in the main shrinkage direction when immersed in warm water of 95 ± 0.5 ° C. for 10 seconds is 30 to 60%,
The length in the direction perpendicular to the main contraction direction is extended when immersed for 10 seconds in warm water at any temperature corresponding to 59.5 to 90.5 ° C and [constant temperature ± 0.5 ° C]. A heat-shrinkable polyester film.
2. The heat-shrinkable polyester film according to the first aspect, wherein the anionic antistatic agent is present on at least one side.
3. The heat-shrinkable polyester film as described in the second item, wherein the anionic antistatic agent has an alkyl group and has 10 to 20 carbon atoms.
4). The heat-shrinkable polyester according to the first aspect, wherein a blocking resistance improving layer containing a polyester-based graft copolymer obtained by grafting at least one radical polymerizable monomer onto a hydrophobic copolymerized polyester is provided on at least one side of the film. Film.
5). The heat-shrinkable polyester film according to the fourth aspect, wherein the radical polymerizable monomer contains at least maleic anhydride and styrene.
6). A blocking resistance improving layer containing a polyester-based graft copolymer obtained by grafting at least one radical polymerizable monomer onto a hydrophobic copolymerized polyester is provided on at least one side of the film, and the anionic antistatic agent is provided with the anti-blocking property. The heat-shrinkable polyester film as described in the above item 1, which is present in the property improving layer.
7). The heat-shrinkable polyester film according to the sixth aspect, wherein the radical polymerizable monomer contains at least maleic anhydride and styrene.
8). The heat-shrinkable polyester film as described in the above item 6, wherein the anionic antistatic agent has an alkyl group and has 10 to 20 carbon atoms.
9. The thermal shrinkage rate in the main shrinkage direction when immersed in warm water of 80 ± 0.5 ° C. for 10 seconds is any one of the first, second, fourth, and sixth, which is less than 40%. Heat shrinkable polyester film.
10. 60 ± 0.5 ° C, 65 ± 0.5 ° C, 70 ± 0.5 ° C, 75 ± 0.5 ° C, 80 ± 0.5 ° C, 85 ± 0.5 ° C, 90 ± 0.5 ° C, and Thermal contraction in the main contraction direction begins with immersion in any warm water when immersed in warm water of 95 ± 0.5 ° C. for 10 seconds,
[(Thermal shrinkage rate in the main shrinkage direction + 10 ° C. in the main shrinkage direction + 10 ° C.)] to [(temperature shrinkage rate in the main shrinkage direction in excess of 0% −5 ° C.)] The heat-shrinkable polyester film according to any one of the first, second, fourth, and sixth aspects, wherein a value obtained by subtracting a heat shrinkage ratio in a main shrinkage direction is less than 20%.
11. The heat-shrinkable polyester film according to any one of the first, second, fourth, and sixth, wherein the haze after heat shrinkage is 10% or less.
12 The heat-shrinkable polyester film according to any one of the first, second, fourth, and sixth, which can be bonded with a non-chlorine organic solvent.
13. The heat-shrinkable label produced using the heat-shrinkable polyester film of any one of said 1st, 2nd, 4th, and 6th.

The heat-shrinkable polyester film according to the present invention has a heat shrinkage ratio of 30 to 60% in the main shrinkage direction when immersed in warm water of 95 ± 0.5 ° C. for 10 seconds, and 59.5 to 90.5. It is preferable that the length in the direction perpendicular to the main contraction direction is extended when immersed in warm water at 10 ° C. and any temperature corresponding to [constant temperature ± 0.5 ° C.] for 10 seconds. The thermal shrinkage rate in the main shrinkage direction is preferably less than 40% when immersed in warm water of 80 ± 0.5 ° C. for 10 seconds.

In the film according to the present invention, the “main shrinkage direction” means the most contracted direction of the sample film. When a square film is used as the sample, the vertical direction or the horizontal direction of the square is the shrink direction. “Thermal shrinkage” means that after immersing a sample film in warm water under no load condition, it is pulled up by immersing it in 25 ° C. water for 10 seconds before being immersed in warm water (before shrinkage) and in 25 ° C. water. This is a value calculated by applying the dimension of the sample film after immersion (after shrinkage) to the following formula (1). Further, “any temperature corresponding to 59.5 to 90.5 ° C. and [constant temperature ± 0.5 ° C.]” means, for example, 60 ± 0.5 ° C., 65 ± 0.5 ° C., 70 ± One or more temperatures selected from 0.5 ° C, 75 ± 0.5 ° C, 80 ± 0.5 ° C, 85 ± 0.5 ° C, and 90 ± 0.5 ° C.
Formula (1): Heat shrinkage rate (%) = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)

The film according to the present invention is 60 ± 0.5 ° C., 65 ± 0.5 ° C., 70 ± 0.5 ° C., 75 ± 0.5 ° C., 80 ± 0.5 ° C., 85 ± 0.5 ° C., Thermal contraction in the main contraction direction starts with immersion in warm water at 90 ± 0.5 ° C. and 95 ± 0.5 ° C. for 10 seconds. Thermal contraction rate in the main contraction direction at a temperature exceeding 10% + 10 ° C.] to [The thermal contraction rate in the main contraction direction at a temperature −5 ° C. where the thermal contraction rate in the main contraction direction exceeds 0%]] The value obtained by subtracting is preferably less than 20%.

The film according to the present invention preferably has a haze after heat shrinkage of 10% or less. The haze after the heat shrinkage is determined as follows. Using a heat-shrinkable polyester film stored for 4 weeks in an atmosphere at a temperature of 30 ° C. and a relative humidity of 85%, the following method using a tubular film having a diameter of 11 cm prepared so that the main shrinkage direction is the radial direction, The haze after the heat shrinkage is required. A cylindrical glass bottle (diameter 6.6 cm) having a temperature of 40 ° C. is placed in the tube-shaped film, hot air at 150 ° C. (wind speed 10 m / sec) is applied to the film for 13 seconds, and the film after shrinking with hot air (tube) 10) is cut out and used as a film sample after heat shrinkage. JIS for film haze after heat shrinkage
Measured according to K7136, the average value is the haze after heat shrinkage.

The heat-shrinkable polyester film according to the present invention may be used as a cylindrical heat-shrinkable label used for labels of containers such as beverages. In view of environmental problems and safety due to the solvent, it is preferable that the film according to the present invention can be bonded with a non-chlorine organic solvent.

In the heat-shrinkable polyester film of the present invention, an anionic antistatic agent is preferably present on at least one side of the film. The anionic antistatic agent preferably has an alkyl group and has 10 to 20 carbon atoms.

The heat-shrinkable polyester film of the present invention has a blocking resistance improving layer containing a polyester graft copolymer obtained by grafting at least one radical polymerizable monomer on a hydrophobic copolymer polyester on at least one side of the film. The provided aspect is also preferable.

In the present invention, it is preferable that the radical polymerizable monomer contains at least maleic anhydride and styrene.

The heat-shrinkable polyester film of the present invention can be suitably used for applications such as labels and packaging, and has excellent heat resistance not only when shrinking with water vapor but also when shrinking with hot air. It has shrinkage characteristics and can suppress the occurrence of whitening when the heat shrink treatment is performed. Furthermore, wrinkles due to heat shrinkage, folding of edges, and jumping up can be suppressed.

In addition, in an embodiment in which an anionic antistatic agent is present on the surface of the heat-shrinkable polyester film, the surface resistivity of the film is kept low because it is not kneaded inside the film, and troubles due to static electricity are suppressed. Is possible.

Further, in the embodiment in which the anti-blocking layer was provided on at least one side of the film, a heat-shrinkable polyester film in which occurrence of blocking at high temperature was suppressed could be obtained. An anionic antistatic agent can also be included in the anti-blocking layer, and both effects can be combined.

The heat-shrinkable polyester film according to the present invention preferably has a heat shrinkage ratio in the main shrinkage direction of 30 to 60% when immersed in warm water of 95 ± 0.5 ° C. for 10 seconds. The heat shrinkage rate is preferably 35 to 57%, more preferably 40 to 55%. The film having a heat shrinkage rate of less than 30% is insufficient in heat shrinkage rate. Therefore, when this film is used as a label, for example, the label is not tightly fixed to the container. Even if a film having a shrinkage rate of less than 30% is shrunk by applying a high amount of heat, the container may be thermally damaged, and label loosening due to thermal deformation of the container tends to occur. On the other hand, a film having a heat shrinkage ratio exceeding 60% tends to cause whitening due to heat shrinkage, shrinkage unevenness due to rapid shrinkage, distortion of a printed pattern when printed, and uneven finish on the label.

The thermal contraction rate in the main contraction direction when the film according to the present invention is immersed in warm water of 80 ± 0.5 ° C. is preferably less than 40%. If the thermal shrinkage rate exceeds 40%, rapid shrinkage tends to occur, and the transparency of the film may be lowered due to occurrence of shrinkage unevenness or whitening.

In the film according to the present invention, 60 ± 0.5 ° C., 65 ± 0.5 ° C., 70 ± 0.5 ° C., 75 ± 0.5 ° C., 80 ± 0.5 ° C., 85 ± 0.5 Thermal contraction in the main contraction direction starts with immersion in warm water at 10 ° C., 90 ± 0.5 ° C., and 95 ± 0.5 ° C. for 10 seconds. Heat shrinkage in the main shrinkage direction (temperature at which the heat shrinkage rate exceeds 0% + 10 ° C.)] to [(temperature at which the heat shrinkage rate in the main shrinkage direction exceeds 0% −5 ° C.)] The value obtained by subtracting the rate is preferably less than 20%. Even if this value exceeds 20%, rapid shrinkage tends to occur, and the transparency of the film may be lowered due to the occurrence of uneven shrinkage or whitening.

The heat-shrinkable polyester film according to the present invention comprises hot water having a temperature corresponding to 59.5 to 90.5 ° C. and [constant temperature ± 0.5 ° C.] together with the heat shrinkage rate in the main shrinkage direction. It is also characterized in that the length in the direction orthogonal to the main contraction direction is elongated when immersed in the interior for 10 seconds. Generation | occurrence | production of such an orthogonal direction means that the polyester-type film which concerns on this invention is suitable as a label member for containers. That is, the cylindrical heat-shrinkable label having the main shrinkage direction of the polyester film according to the present invention as the radial direction and the orthogonal direction of the main shrinkage direction of the film as the axial direction is the container due to the shrinkage in the radial direction. Before it is fixed to the sheet, the axial direction is extended or the axial contraction is small, so that it is easy to cause uneven finish of the upper end of the label and chevron of the upper and lower parts starting from the back-pasted part. The pulling in the axial direction can be suppressed.

The elongation in the orthogonal direction is performed by immersing the sample film in warm water in an unloaded state, then immersing it in 25 ° C. water for 10 seconds and pulling it up, before immersing in warm water (before shrinkage) and in 25 ° C. water. It is confirmed by applying the dimension of the sample film after immersion (after shrinkage) to the above formula (1) and calculating. If the value calculated at this time is a negative value, the expansion in the orthogonal direction has occurred.

As long as the above elongation occurs at any temperature corresponding to 59.5 to 90.5 ° C. and [constant temperature ± 0.5 ° C.], the heat shrinkage rate in the orthogonal direction is within 3% at any temperature. The film (preferably within 2%) also corresponds to the film according to the present invention.

As for the above elongation, the value obtained in the same manner as the thermal shrinkage rate is preferably 0% or less, and preferably -0.5% or less. Further, the elongation is preferably caused when immersed in warm water of 80 ± 0.5 ° C. and 85 ± 0.5 ° C. for 10 seconds.

The haze of the film according to the present invention after heat shrinkage is usually 10% or less, preferably 9.7% or less, and more preferably 9.5% or less.

The thickness of the film according to the present invention is preferably 20 to 100 μm, more preferably 30 to 60 μm.

A preferred film according to the present invention is a film that can be bonded to each other with a solvent. This “adhesive with a solvent” means that the solvent adhesive strength determined by the “solvent adhesiveness” evaluation method in the examples described later is 3 N / 15 mm or more. When the film according to the present invention is applied as a container label, the film needs to be formed into a cylindrical shape such as a cylindrical shape, and a solvent is used to form the cylindrical shape. That is, a solvent is used to produce a thermoplastic tubular film (thermoplastic label) by bonding the two ends of the film so that the main shrinkage direction is the radial direction. In addition, adhesion between films can be realized by applying a solvent to one surface of one film end, and pressing the applied surface to the surface of the other film end, and the produced thermoplastic label is: Usually cut to the required length.

Examples of the solvent for bonding the films include aromatic hydrocarbons such as benzene, toluene, xylene and trimethylbenzene; halogenated hydrocarbons such as methylene chloride and chloroform; phenols such as phenol; furans such as tetrahydrofuran. Organic solvents such as oxolanes such as 1,3-dioxolane are used. In view of the generation of toxic substances due to halogens such as chlorine atoms, non-chlorine organic solvents are preferable, and tetrahydrofuran and 1,3-dioxolane are preferable in view of safety.

Examples of the dicarboxylic acid component constituting the polyester include aromatic dicarboxylic acids, esters of aromatic dicarboxylic acids, and aliphatic dicarboxylic acids. More specific aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, and 5-sodium sulfoisophthalic acid. Examples of the esters include dialkyl esters and diaryl esters of the aromatic dicarboxylic acids specifically mentioned above, and examples of the aliphatic dicarboxylic acids include dimer acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, oxalic acid, Succinic acid is mentioned. An oxycarboxylic acid such as p-oxybenzoic acid; a trivalent or higher carboxylic acid such as trimellitic anhydride or pyromellitic anhydride may be a carboxylic acid component constituting the polyester, if necessary. .

Examples of the polyhydric alcohol component constituting the polyester include diol and triol. Examples of the diol include ethylene glycol, diethylene glycol, 1,3-propanediol, triethylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, 3- Alkylene glycols such as methyl-1,5-pentanediol, 2-methyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, 1,9-nonanediol, 1,10-decanediol An ether glycol such as an alkylene oxide adduct of polyoxytetramethylene glycol, polyethylene glycol, a bisphenol compound or a derivative thereof; a dimer diol; Examples of the triol include alkyl triols such as trimethylolpropane, glycerin, and pentaerythritol. Among the polyhydric alcohol components exemplified above, neopentyl glycol, 1,4-cyclohexanedimethanol, and the like are useful components for realizing film amorphization and high heat shrinkability, such as neopentyl glycol and The amount of 1,4-cyclohexanedimethanol or the like is preferably 5 to 40 mol%, preferably 10 to 35 mol%, based on 100 mol% of all diols. -40 mol% is more preferable, and 20-35 mol% is still more preferable. 1,4-butanediol, 1,3-propanediol, and the like are useful for lowering the glass transition temperature of the film and exhibiting heat shrinkability in a low temperature range. The amount of 1,4-butanediol and the like is appropriately set because rapid heat shrinkage may occur in the region and the finish and transparency after shrinkage may deteriorate.

When a unit having one unit derived from an acid component and one unit derived from a polyhydric alcohol component corresponding to a repeating structural unit of a polyester formed by condensation of a carboxylic acid and a polyhydric alcohol is used as a “unit”, the present invention Polyester film consists of units composed of ethylene glycol and terephthalic acid (ethylene terephthalate unit), neopentyl glycol and terephthalic acid, which can achieve excellent heat shrinkage properties, suppression of whitening, and good adhesion with solvents. Unit (neopentyl terephthalate unit), unit consisting of 1,4-cyclohexanedimethanol and terephthalic acid (1,4-cyclohexanedimethylene terephthalate unit), unit consisting of 1,4-butanediol and terephthalic acid (butylene terephthalate) Talay Units), units composed of propylene glycol and terephthalic acid (propylene terephthalate unit), units composed of ethylene glycol and terephthalic acid (ethylene naphthalate unit), units composed of ethylene glycol and isophthalic acid (ethylene isophthalate unit), etc. Having one or more selected units, the ethylene terephthalate unit is the main component in all polyesters in terms of film tear resistance, heat resistance, shrink finish, adhesion to containers due to increased yield point stress, cost, etc. It is a unit. The amount of the ethylene terephthalate unit in the whole polyester is preferably 60 mol% or more and less than 72 mol%, and preferably 70 mol% or less. If it is less than 72 mol%, it will be excellent in solvent adhesiveness, and if it is 70 mol% or less, it will become a more suitable heat shrinkage rate.

Suitably any combination of the following units is included in the film. The combination is an ethylene terephthalate unit, a neopentyl terephthalate unit or a 1,4-cyclohexanedimethylene terephthalate unit, and a butylene terephthalate unit or a propylene terephthalate unit. The molar ratio in this combination is preferably ethylene terephthalate unit: neopentyl terephthalate unit or 1,4-cyclohexanedimethylene terephthalate unit: butylene terephthalate unit or propylene terephthalate unit = 60 to 72: 5 to 40: 9 to 15. The analysis of the unit content can be performed using, for example, ¹ H-NMR.

In the polyester constituting the film, one or more selected from inorganic particles, organic salt particles, and crosslinked polymer particles may be added as a lubricant. Inorganic particles used as lubricants 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 In addition, when silica particles of aggregates formed by agglomerating primary particles are selected, such as riotium fluoride, etc., film handling properties are good and haze is low. Examples of the organic salt particles include terephthalates such as calcium oxalate, calcium, barium, zinc, manganese, and magnesium. Examples of the crosslinked polymer particles include one or more copolymers selected from vinyl monomers such as divinylbenzene, styrene, and (meth) acrylic acid; polytetrafluoroethylene; benzoguanamine resin; thermosetting Urea resin; thermosetting phenol resin.

Further, the polyester may contain an ultraviolet absorber, an antistatic agent, a coloring agent, an antibacterial agent, and the like as necessary.

As a preferred embodiment of the film according to the present invention, an anionic antistatic agent may be present on at least one side (preferably both sides) of this surface. Even if an anionic antistatic agent is included in the film raw material by kneading or the like, generation and accumulation of static electricity can be suppressed if the anionic antistatic agent oozes from the inside of the film to the surface. However, since the glass transition temperature of the polyester constituting the film is generally high, the anionic antistatic agent is often difficult to seep out to the film surface at room temperature and in the vicinity thereof, and sufficiently suppresses the generation and accumulation of static electricity. It tends to be impossible. In addition, since the film forming temperature for producing the film according to the present invention produced by stretching the resin is relatively high, and the reaction activity of the polar group of the polyester is high, the film raw material is antistatic. When an agent is blended, deterioration of the polyester is promoted at the time of film formation, so that the physical properties of the film may be lowered and coloring may occur.

The occurrence of trouble due to static electricity can be suppressed by adjusting the amount of the antistatic agent, and the degree of this suppression can be known from the surface specific resistance value of the film. In order to sufficiently suppress the occurrence of trouble due to static electricity, the surface specific resistance value of the film is preferably 13 logΩ or less, and preferably 12 logΩ or less. On the other hand, the lower limit value of the surface specific resistance value is not particularly limited, but may be 8 logΩ or more practically. The abundance of the anionic antistatic agent on the film surface for setting the above-mentioned surface resistivity is preferably 0.001 to 0.5 g / m ² . If the amount of the anionic antistatic agent is less than the above range, the antistatic effect may not be sufficiently secured. On the other hand, when the amount of the anionic antistatic agent exceeds the above range, the transparency and blocking resistance of the film may be lowered.

The anionic antistatic agent preferably has an alkyl group and has 10 to 20 carbon atoms. With such an antistatic agent, for example, even if there is scattering or disappearance due to heat in film production or secondary processing of the film, the amount of the scattering or the like can be kept low. Moreover, when carbon number exceeds 20, the antistatic effect of antistatic agent itself may be inadequate. More preferred anionic antistatic agents are those having 12 to 18 carbon atoms.

The anionic antistatic agent in the present invention can be selected from known antistatic agents, and sulfuric acid such as higher alcohol sulfates, sulfates of alkylphenol ethylene oxide adducts, alkylsulfonates, and alkylallylsulfonates. And sulfonic acid derivatives. More specifically, alkyl sulfonate, alkyl benzene sulfonate, alkyl sulfate ester salt, alkyl ethoxy sulfate ester salt, and alkyl phosphate ester salt are exemplified. Suitable anionic antistatic agents include, for example, dodecyl sulfonate and dodecyl benzene sulfonate.

The heat-shrinkable polyester film of the present invention comprises a polyester-based substrate film having a blocking resistance improving layer containing a polyester-based graft copolymer obtained by grafting at least one radical polymerizable monomer onto a hydrophobic copolymerized polyester. An embodiment provided on at least one side is also preferable. Hereinafter, the heat-shrinkable polyester film will be described.

(Radically polymerizable monomer)
The radical polymerizable monomer used in the present invention is preferably a radical polymerizable monomer that essentially contains a hydrophilic radical polymerizable monomer. This is because the blocking resistance improving layer of the present invention can be formed using a dispersion of an aqueous solvent of a polyester-based graft copolymer (details will be described later).

The hydrophilic radical polymerizable monomer means a radical polymerizable monomer having a hydrophilic group or a group that can be changed to a hydrophilic group later. Examples of the radical polymerizable monomer having a hydrophilic group include a radical polymerizable monomer containing a carboxyl group, hydroxyl group, phosphoric acid group, phosphorous acid group, sulfonic acid group, amide group, quaternary ammonium base and the like. . On the other hand, examples of the radical polymerizable monomer having a group that can be changed into a hydrophilic group include radical polymerizable monomers containing an acid anhydride group, a glycidyl group, a chloro group, and the like.

Specifically, fumaric acid and its anhydride, monoester or diester of fumaric acid such as monoethyl fumarate, diethyl fumarate, dibutyl fumarate; maleic acid and its anhydride, monoethyl maleate, diethyl maleate, maleic acid Monoester or diester of maleic acid such as dibutyl; itaconic acid and its anhydride, monoester or diester of itaconic acid; maleimide such as phenylmaleimide; styrene such as styrene, α-methylstyrene, t-butylstyrene, chloromethylstyrene Derivatives: vinyltoluene, divinylbenzene and the like.

In addition, alkyl acrylate, alkyl methacrylate (the alkyl group is methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, phenyl group, Benzyl group, phenylethyl group, etc.); hydroxy-containing acrylic monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate; acrylamide, methacrylamide, N-methyl methacryl Amide, N-methylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N, N-dimethylolacrylamide, N-methoxymethylacrylamide, N-methoxymethyl Amide group-containing acrylic monomers such as tacrylamide and N-phenylacrylamide; Amino group-containing acrylic monomers such as N, N-diethylaminoethyl acrylate and N, N-diethylaminoethyl methacrylate; Epoxy group-containing acrylic monomers such as glycidyl acrylate and glycidyl methacrylate; Examples thereof include acrylic monomers containing a carboxyl group such as acrylic acid, methacrylic acid and salts thereof (sodium salt, potassium salt, ammonium salt) or salts thereof.

The above hydrophilic radical polymerizable monomers may be used alone or in combination of two or more.

Among these, the hydrophilic group is preferably a carboxyl group from the viewpoint that the water-dispersibility of the polyester-based graft copolymer and the acid value are within a suitable range (described later). Therefore, the hydrophilic radical polymerizable monomer is a carboxyl group. A radical polymerizable monomer having a group or a group capable of generating a carboxyl group is preferred, and examples thereof include maleic anhydride and esters thereof.

In the present invention, the radically polymerizable monomer preferably contains at least maleic anhydride and styrene.

(Hydrophobic copolyester)
The hydrophobic copolyester used in the present invention is preferably an essentially water-insoluble polyester that does not inherently disperse or dissolve in water. This is because the water-dispersed or dissolved polyester is superior in water resistance as compared with the case where the polyester is used as a trunk polymer in graft polymerization.

The hydrophobic copolyester has an ester bond in the main chain or side chain, and is obtained by polycondensation of polyvalent carboxylic acid and glycol. Examples of the polyvalent carboxylic acid component constituting the hydrophobic copolyester include aromatic, aliphatic, and alicyclic dicarboxylic acids, dicarboxylic acids containing radical polymerizable double bonds, and trivalent or higher polyvalent carboxylic acids. Alternatively, these ester derivatives can be used.

Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, biphenyl dicarboxylic acid and the like. Examples of the aromatic dicarboxylic acid ester derivatives include the dialkyl esters and diaryl esters of the aromatic dicarboxylic acids specifically mentioned above. It is preferable not to use a hydrophilic group-containing dicarboxylic acid such as 5-sodium sulfoisophthalic acid because water resistance decreases.

Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, and dimer acid.

Examples of the alicyclic dicarboxylic acid include 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid and acid anhydrides thereof.

Examples of the dicarboxylic acid containing a radical polymerizable double bond include fumaric acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid and other α, β-unsaturated dicarboxylic acids; 2,5-norbornene dicarboxylic acid anhydride, Mention may be made of alicyclic dicarboxylic acids containing radically polymerizable double bonds such as tetrahydrophthalic anhydride. From the viewpoint of polymerizability, fumaric acid, maleic acid and 2,5-norbornene dicarboxylic acid are preferred.

The hydrophobic copolyester used in the present invention has an aromatic dicarboxylic acid of 60 to 99.5 mol%, an aliphatic dicarboxylic acid and / or an alicyclic dicarboxylic acid of 0 to 39.5 mol% in 100 mol% of the dicarboxylic acid component. The dicarboxylic acid containing a radical polymerizable double bond is preferably 0.5 to 10 mol%.

When the content of aromatic dicarboxylic acid is less than 60 mol%, or when the content of aliphatic dicarboxylic acid and / or alicyclic dicarboxylic acid exceeds 39.5 mol%, the heat resistance may decrease. . Moreover, when the content rate of the dicarboxylic acid containing a radically polymerizable double bond is less than 0.5 mol%, it becomes difficult to perform efficient grafting of the radically polymerizable monomer to the hydrophobic copolymerized polyester. Conversely, if the content of the dicarboxylic acid containing a radically polymerizable double bond exceeds 10 mol%, the viscosity will increase too late in the grafting reaction, which may hinder the uniform progress of the reaction. It is not preferable.

More preferably, the content of aromatic dicarboxylic acid is 63 to 98 mol%, the content of aliphatic dicarboxylic acid and / or alicyclic dicarboxylic acid is 0 to 30 mol%, and dicarboxylic acid containing a radical polymerizable double bond. The acid content is 2 to 7 mol%.

The glycol component constituting the hydrophobic copolyester is composed of an aliphatic glycol having 2 to 10 carbon atoms and / or an alicyclic glycol having 6 to 12 carbon atoms and / or an ether bond-containing glycol.

Examples of the aliphatic glycol having 2 to 10 carbon atoms include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6 -Hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol and the like.

Examples of the alicyclic glycol having 6 to 12 carbon atoms include 1,4-cyclohexanedimethanol.

Examples of the ether bond-containing glycol include diethylene glycol, triethylene glycol, dipropylene glycol, and glycols obtained by adding ethylene oxide or propylene oxide to two phenolic hydroxyl groups of bisphenols, such as 2,2-bis ( 4-hydroxyethoxyphenyl) propane and the like. Polyethylene glycol, polypropylene glycol, and polytetramethylene glycol may be used as necessary.

The hydrophobic copolyester used in the present invention can be copolymerized with 0 to 5 mol% of a tri- or higher functional polycarboxylic acid and / or polyol. ) Trimellitic acid, (anhydrous) pyromellitic acid, (anhydrous) benzophenone tetracarboxylic acid, trimesic acid, ethylene glycol bis (anhydro trimellitate), glycerol tris (anhydro trimellitate) and the like. Examples of the tri- or higher functional polyol include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol.

The tri- or higher functional polycarboxylic acid and / or polyol is copolymerized in the range of 0 to 5 mol%, preferably 0 to 3 mol%, based on the total acid component or the total glycol component. If it exceeds 5 mol%, gelation tends to occur during polymerization.

The weight average molecular weight of the hydrophobic copolyester used in the present invention is preferably in the range of 5000 to 50000. When the weight average molecular weight is less than 5,000, the heat resistance is lowered. When the weight average molecular weight exceeds 50,000, problems such as gelation at the time of polymerization occur.

(Grafting of radically polymerizable monomer onto hydrophobic copolyester)
In the present invention, the grafting of the radically polymerizable monomer to the hydrophobic copolymerized polyester is performed by using at least one radically polymerizable monomer using a graft polymerization initiator in a state where the hydrophobic copolymerized polyester is dissolved in an organic solvent. By reacting.

The reaction product after completion of the grafting reaction is not limited to the graft copolymer of the desired hydrophobic copolymerized polyester and the radically polymerizable monomer, but the hydrophobic copolymerized polyester and the hydrophobic copolymer that have not undergone grafting. It also contains a (co) polymer obtained from a radically polymerizable monomer that has not been grafted to the polyester. The polyester-based graft copolymer in this specification is not only the above-mentioned polyester-based graft copolymer, but in addition to this, a hydrophobic copolymerized polyester that has not undergone grafting, and a radically polymerizable monomer that has not been grafted. Also included is a reaction mixture that also contains a (co) polymer and a monomer (residual monomer) obtained from

The mass ratio of the hydrophobic copolymerized polyester and the radical polymerizable monomer suitable for the purpose of the present invention is preferably in the range of polyester / radical polymerizable monomer = 40/60 to 95/5, and in the range of 55/45 to 93/7. Is more desirable, and the range of 60/40 to 90/10 is most desirable. When the mass ratio of the hydrophobic copolymerized polyester is less than 40% by mass, the excellent heat resistance of the polyester resin cannot be exhibited. On the other hand, when the mass ratio of the hydrophobic copolyester exceeds 95% by mass, blocking, which is a defect of the polyester resin, easily occurs.

Examples of the graft polymerization initiator that can be used in the present invention include organic peroxides and organic azo compounds known to those skilled in the art. Examples of the organic peroxide include benzoyl peroxide and t-butyl peroxypivalate. Examples of the organic azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylpareronitrile), azobisdimethylvaleronitrile, and the like. The amount of the polymerization initiator used for the graft polymerization is at least 0.2% by mass, preferably 0.5% by mass or more, based on the radical polymerizable monomer.

In the present invention, in addition to the graft polymerization initiator, a chain transfer agent for adjusting the chain length of the branched polymer, for example, octyl mercaptan, mercaptoethanol, 3-t-butyl-4-hydroxyanisole, etc. Can be used. In this case, the chain transfer agent is preferably added in the range of 0 to 5% by mass with respect to the radical polymerizable monomer.

The reaction solvent used for grafting the radically polymerizable monomer to the hydrophobic copolymerized polyester is preferably composed of an aqueous organic solvent having a boiling point of 50 to 250 ° C. Herein, the aqueous organic solvent means an organic solvent having a solubility in water at 20 ° C. of at least 10 g / L or more, desirably 20 g / L or more. An aqueous organic solvent having a boiling point exceeding 250 ° C. is inappropriate because the evaporation rate is too slow and the solvent cannot be sufficiently removed even by high-temperature baking of the coating film. In the case of an aqueous organic solvent having a boiling point of 50 ° C. or lower, when a grafting reaction is carried out in such a solvent, a graft polymerization initiator that cleaves into radicals at a temperature of 50 ° C. or lower must be used, which increases the handling risk. This is not preferable.

Of the aqueous organic solvent used in the present invention, a hydrophobic copolymerized polyester is well dissolved and a radical polymerizable monomer containing a carboxyl group-containing radical polymerizable monomer and a graft reaction product of the radical polymerizable monomer (polyester-based graft copolymer) are used. Examples of the first group of aqueous organic solvents that dissolve the polymer) relatively well include esters such as ethyl acetate; ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; tetrahydrofuran, dioxane, 1,3-dioxolane and the like. Cyclic ethers; glycol ethers such as ethylene glycol dimethyl ether, propylene glycol methyl ether, propylene glycol propyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether; methyl Carbitols such as rubitol, ethyl carbitol, butyl carbitol; glycols; lower esters of glycol ethers such as ethylene glycol diacetate and ethylene glycol ethyl ether acetate; ketone alcohols such as diacetone alcohol; dimethylformamide; And N-substituted amides such as dimethylacetamide and N-methylpyrrolidone.

In addition, the hydrophobic copolyester hardly dissolves, but a radically polymerizable monomer containing a carboxyl group-containing radically polymerizable monomer and a second group of aqueous organic solvents that dissolve a graft reaction product of the radically polymerizable monomer relatively well. Examples thereof include water, lower alcohols, lower carboxylic acids, and lower amines. A particularly preferred second group of aqueous organic solvents for the practice of the present invention are alcohols and glycols having 1 to 4 carbon atoms.

Examples of the mode in which the grafting reaction is performed with a single solvent include a mode in which only one kind is selected from the first group of aqueous organic solvents. As an embodiment performed with a mixed solvent, for example, an embodiment in which a plurality of types are selected only from the first group of aqueous organic solvents, or at least one type is selected from the first group of aqueous organic solvents, and at least one type is selected from the second group of aqueous organic solvents. A mode to add can be mentioned.

In both cases where the reaction solvent is a single solvent from the first group of aqueous organic solvents and when the reaction solvent is a mixed solvent composed of each of the first group and the second group of aqueous organic solvents, the graft polymerization reaction Can be performed. However, there are differences in the progress behavior of the grafting reaction, the appearance and properties of the grafting reaction product and the aqueous dispersion derived therefrom. In the graft reaction of the present invention, it is preferable to use a mixed solvent composed of each of the first group and the second group of aqueous organic solvents. This is because it is effective to prevent gelation during the grafting reaction by adjusting the dissolved state of the hydrophobic copolyester to make it difficult to cause intermolecular crosslinking. This can be achieved in the latter mixed solvent system. This is because the hydrophobic copolyester molecular chains are extended (largely spread) in the first group of solvents, while the hydrophobic copolyester molecular chains are in the first group / second group mixed solvent. Is based on the fact that it was confirmed by measuring the viscosity of the hydrophobic copolyester in these solutions that the thread is entangled (smallly spread).

In the present invention, the mass ratio of the mixed solvent of the first group / second group is more desirably 95/5 to 10/90, further desirably 90/10 to 20/80, and most desirably 85/15 to 30. The range is / 70. The optimum mass ratio is determined according to the solubility of the hydrophobic copolyester used.

(Polyester graft copolymer)
The polyester-based graft copolymer obtained by the grafting is in the form of an organic solvent solution or dispersion, or an aqueous solvent solution or dispersion. In particular, a dispersion of an aqueous solvent, that is, a form of an aqueous dispersion is preferable in terms of working environment and applicability. Such an aqueous dispersion is obtained by graft-polymerizing a radically polymerizable monomer containing a hydrophilic radically polymerizable monomer to a hydrophobic copolymerized polyester in the aqueous organic solvent, adding water, and then distilling off the aqueous organic solvent. Can be obtained.

In the present invention, the acid value of the polyester-based graft copolymer is preferably 600 eq / 10 ⁶ g or more. A more preferable acid value is 1200 eq / 10 ⁶ g or more. When the acid value of the polyester-based graft copolymer is less than 600 eq / 10 ⁶ g, it cannot be said that the adhesion with the layer coated with the primer treatment material is sufficient.

The glass transition temperature of the polyester-based graft copolymer is not particularly limited, but is preferably 30 ° C. or lower. By using a polyester-based graft copolymer having a glass transition temperature of 30 ° C. or less for the anti-blocking layer, a heat-shrinkable polyester film particularly excellent in heat-resistant blocking property can be obtained.

The aqueous dispersion in the present invention exhibits a translucent or milky white appearance with an average particle diameter measured by a laser light scattering method of 500 nm or less. By adjusting the polymerization method, water dispersions having various particle sizes can be obtained. The particle size is suitably 10 to 500 nm, preferably 400 nm or less, more preferably 300 nm or less from the viewpoint of dispersion stability. When the particle diameter exceeds 500 nm, the gloss of the coating film surface is lowered, and the transparency of the coating may be lowered. On the other hand, if the thickness is less than 10 nm, the heat blocking property which is the object of the present invention may be lowered.

The polyester-based graft copolymer preferably used in the present invention is preferably neutralized with a basic compound, and can be easily dispersed in water by neutralization. As the basic compound, a compound that volatilizes at the time of forming a coating film or baking and curing with a curing agent is desirable, and ammonia, organic amines, and the like are preferable. Examples of desirable compounds include triethylamine, N, N-diethylethanolamine, N, N-dimethylethanolamine, aminoethanolamine, N-methyl-N, N-diethanolamine, isopropylamine, iminobispropylamine, ethylamine, diethylamine , 3-ethoxypropylamine, 3-diethylaminopropylamine, sec-butylamine, propylamine, methylaminopropylamine, dimethylaminopropylamine, methyliminobispropylamine, 3-methoxypropylamine, monoethanolamine, diethanolamine, triethanol An amine etc. are mentioned.

In the basic compound, the pH value of the aqueous dispersion is in the range of 5.0 to 9.0 by at least partial neutralization or complete neutralization, depending on the carboxyl group content contained in the polyester-based graft copolymer. It is desirable to use it as is. If a basic compound having a boiling point of 100 ° C. or lower is used, the residual basic compound in the coating film after drying is easily reduced, and thus the coating film has excellent stability. Moreover, the transfer property of printing ink improves by using a basic compound 100 degreeC or more, or controlling drying conditions, and leaving 500 ppm or more of basic compounds in the coating film after drying.

In the polyester-based graft copolymer used in the present invention, the weight average molecular weight of the polymer of the radically polymerizable monomer (graft chain portion) is preferably 500 to 50,000. Generally, it is difficult to control the weight average molecular weight of the polymer of the radical polymerizable monomer to less than 500, the graft efficiency is lowered, and there is a tendency that hydrophilic groups are not sufficiently imparted to the hydrophobic copolymer polyester. is there. In addition, the graft polymer of the radical polymerizable monomer forms a hydrated layer of dispersed particles. To obtain a stable aqueous dispersion with a sufficient thickness of the hydrated layer, the graft polymer of the radical polymerizable monomer is used. The weight average molecular weight of is desirably 500 or more. Further, the upper limit of the weight average molecular weight of the graft polymer of the radical polymerizable monomer is preferably 50,000 from the viewpoint of polymerizability in solution polymerization. The weight average molecular weight within this range can be controlled by appropriately combining an initiator amount, a monomer dropping time, a polymerization time, a reaction solvent, a monomer composition or, if necessary, a chain transfer agent or a polymerization inhibitor.

(Blocking resistance improvement layer)
The blocking resistance improving layer of the present invention can be formed only from the above-mentioned polyester-based graft copolymer, but for other purposes, general-purpose polyester-based resins, urethane-based resins, acrylic resins, copolymers thereof, Various water-soluble resins, or various functional resins such as conductive resins such as polyaniline and polypyrrole, antibacterial resins, ultraviolet-absorbing resins, and gas barrier resins may be mixed.

In the anti-blocking layer, various additives such as a surfactant, an antistatic agent, an inorganic lubricant, an organic lubricant, an antibacterial agent, a photooxidation catalyst, and an ultraviolet absorber are used within the range not impairing the effects of the present invention. An agent or the like may be blended.

In the present invention, a polyester-based graft copolymer obtained by grafting at least one radical polymerizable monomer onto a hydrophobic copolymerized polyester, and a blocking resistance improving layer containing an anionic antistatic agent are provided on at least one side of the film. It is also preferable that it is the aspect provided in. In this embodiment, an anionic antistatic agent is included in the solution or dispersion for forming the anti-blocking layer or the aqueous solvent solution or dispersion to give both components to the film surface. It can be shown.

Next, the manufacturing method of the film which concerns on this invention is demonstrated.
By producing an unstretched polyester film containing a mixture of one or two or more polyesters and then heat-treating the stretched polyester film, it is possible to produce the film according to the present invention having the above heat shrinkage characteristics and solvent adhesiveness. it can.

The polyester used to produce the unstretched polyester film is one or two selected from aromatic dicarboxylic acids, esters of aromatic dicarboxylic acids, aliphatic dicarboxylic acids, oxycarboxylic acids, and trivalent or higher carboxylic acids. By polymerizing one or more monomers and one or more monomers selected from polyhydric alcohols in the presence of a suitable ester exchange catalyst such as zinc acetate and / or a polymerization catalyst such as antimony trioxide. can get.

In order to obtain a polyester to which a lubricant or the like has been added, a method in which the lubricant or the like is dispersed in the polymerization system during the monomer polymerization process; the polyester obtained by polymerization is melted again, And a method of adding a lubricant and the like.

The polyester after polymerization is taken out from the polymerization apparatus in the form of a strand in a molten state, and then immediately cooled with water, and cut with a strand cutter into chips. The chip after this cut has a cylindrical shape with an elliptical bottom surface.

When manufacturing a film containing two or more kinds of polyesters having different components, two or more kinds of polyester chips having different components are mixed. At this time, the polyester chip having the highest use ratio and the elliptical shape of the chip are mixed. The same kind of polyester in the hopper by using polyester chips that are within ± 20% (preferably within ± 15%) of the average size of the major axis, minor axis, and cylindrical height of the bottom surface Since the uneven distribution phenomenon of the chip can be suppressed, uniform dispersion of the lubricant and the like in the film can be realized.

In addition, when mixing copolyester chips and homopolyester chips, copolyesters having a generally low melting point have problems such as difficulty in handling during drying, so homopolyester (polyethylene terephthalate, polyethylene It is preferable to mix naphthalate, poly (1,4-cyclohexene diethylene terephthalate, etc.) and a copolyester.

As a method for producing an unstretched film from a polyester chip, (1) the chip is previously dried using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer, and formed into a film at a temperature of 200 to 300 ° C. There are a method of extruding and cooling, and (2) a method of extruding an undried polyester chip into a film while removing moisture in a vent type extruder and cooling. For the extrusion, any known method such as a T-die method or a tubular method may be employed. The cooling after the extrusion is rapidly cooled with a chill roll having a surface temperature of 25 ° C., for example.

Since a heat-shrinkable label having a main shrinkage direction in the transverse direction is practical, the drawing process of an unstretched film suitable for manufacturing the label will be described below as an example. “Shrinkage direction” and “lateral direction” are synonymous, and “orthogonal direction” and “vertical direction” are synonymous. When manufacturing a heat-shrinkable label whose main shrinkage direction is the longitudinal direction, it is sufficient to change the stretching direction in the following unstretched film processing by 90 degrees.

When it is necessary to make the thickness distribution of the heat-shrinkable polyester film uniform, prior to stretching, the thermal conductivity coefficient to the film is 0.0013 calories / cm ² · sec · ° C. or less and Tg-20 ° C.- It is preferable to preheat the unstretched film until the film temperature reaches Tg + 60 ° C. The temperature at each position on the film surface in this preheating step should be within the average temperature ± 1 ° C. of the film surface within the range of the distance in the vertical direction corresponding to the roll film winding length of the film according to the present invention. The average temperature is preferably within ± 0.5 ° C.

Stretching may be performed using a tenter. The film is stretched at a temperature of Tg-30 ° C to Tg + 40 ° C, more preferably at a temperature of Tg-15 ° C to Tg + 30 ° C, and the transverse direction of the film is 2.3 to 7.3 times, preferably Set to 3.5 to 6.0 times. If hot air of 60 to 120 ° C. is blown onto the stretched film, the polyester orientation after stretching is fixed, so that the main shrinkage rate of the heat-shrinkable film is lowered. In addition, if hot air of 30-60 ° C. is blown onto the stretched film following the previous hot air blowing, the main shrinking direction of [(temperature at which the main shrinkage direction exceeds 0% + 10 ° C.)] The value obtained by subtracting [the heat shrinkage rate in the main shrinkage direction (temperature at which the heat shrinkage rate in the main shrinkage direction exceeds 0% −5 ° C.)] from the [heat shrinkage rate of

In addition, since the fluctuation | variation of the temperature conditions in extending | stretching tends to influence the shrinkage | contraction characteristic of a heat-shrinkable film, it is preferable to suppress the fluctuation | variation of the temperature at the time of extending | stretching, and the warm air temperature after extending | stretching. The temperature at each position on the film surface in the stretching step is preferably within an average temperature ± 1 ° C. within the range of the longitudinal distance corresponding to the roll film winding length of the film according to the present invention, and the average temperature ± 0. More preferably within 5 ° C. Moreover, if attention is paid to the fact that the internal heat generation of the film accompanying stretching is suppressed and the film temperature unevenness in the transverse direction is reduced, the heat transfer coefficient of the stretching process is preferably 0.0037 J / cm ² · sec · ° C. or more. .00544 to 0.00837
J / cm ² · sec · ° C. is more preferable.

Although it is not always necessary to perform longitudinal stretching that causes contraction in the longitudinal direction, from the viewpoint of improving the strength of the film, longitudinal stretching with a tenter may be performed as long as the characteristics of the film according to the present invention are not impaired. The stretching mode in the case of performing longitudinal and lateral biaxial stretching may be either sequential biaxial stretching or simultaneous biaxial stretching, and may be re-stretched as necessary. Further, in sequential biaxial stretching, any of stretching methods such as vertical and horizontal, horizontal and vertical, vertical and horizontal and horizontal and vertical and horizontal directions may be used. Even when these longitudinal stretching steps or biaxial stretching steps are adopted, the film surface temperature in the preheating step, the film surface temperature in the stretching step, and the heat transfer coefficient in the stretching step are the same as those in the transverse stretching.

Although a heat-shrinkable polyester film can be produced as described above, in order to produce a heat-shrinkable polyester film of a preferred embodiment in which an anionic antistatic agent is present on at least one side, an anionic charge is provided on at least one side of the film A liquid containing an inhibitor is applied. After application of the liquid, uniaxial stretching or biaxial stretching is performed. That is, (1) after applying an antistatic agent-containing liquid to an unstretched film, it is uniaxially or biaxially stretched, or (2) a polyester-based stretched film is produced by uniaxially or biaxially stretching an unstretched film. In the case of having a first stretching step and a second stretching step for further uniaxially stretching or biaxially stretching the polyester-based stretched film, an antistatic agent-containing liquid is added to the film between the first stretching step and the second stretching step. Apply. Rather than kneading the antistatic agent into the film, by adopting such a coating method, the antistatic agent can be directly present on the film surface, so that the glass transition temperature of the polyester constituting the film is high. Regardless of this, the antistatic effect is effectively exhibited, and film deterioration and coloring caused by the antistatic agent can be prevented. The stretching conditions themselves are not significantly different from the case where the anionic antistatic agent is not applied.

The solvent of the antistatic agent-containing liquid to be applied to the film surface is not particularly limited, but it is preferable to use a mixed solvent of a lower alcohol having 1 to 3 carbon atoms and water. A lower alcohol having 1 to 3 carbon atoms that can be mixed with water at an arbitrary ratio is preferable, and examples thereof include methanol, ethanol, n-propanol, and isopropanol. Alcohols with a large number of carbon atoms are not preferred because they are likely to cause coating spots due to phase separation with water. However, alcohols with a large number of carbon atoms may be used in combination with lower alcohols having 1 to 3 carbon atoms as long as they do not cause phase separation. It doesn't matter.

The amount of the lower alcohol in the antistatic agent-containing liquid is preferably 10% by mass or more. When the amount of the lower alcohol is less than 10% by mass, the surface tension of the antistatic agent-containing liquid is increased, the wettability to the film is lowered, and coating spots are likely to occur, and the reason is unknown. When drastic temperature / humidity changes occur during drying after coating, the transparency of the film may be lowered, impairing practicality. On the other hand, the upper limit of the lower alcohol in the antistatic agent-containing liquid is preferably 60% by mass. If it exceeds 60% by mass, it may be necessary to take explosion-proof measures to avoid the explosion risk of lower alcohols. In addition, when using alcohol with many carbon atoms simultaneously with lower alcohol, it is recommended that the total alcohol amount shall be 60 mass% or less.

Further, as a preferred embodiment, as a production method in the case of providing a blocking resistance improving layer on at least one surface of the film, a coating method of applying a coating solution containing a polyester-based graft copolymer on a polyester-based substrate film In addition, there is a laminating method in which a resin layer containing a polyester-based graft copolymer is laminated. In the present invention, it is preferable to use a coating method. This is because in the lamination method, there is a lower limit to the thickness of the anti-blocking layer, and adverse effects such as changes in the properties of the film serving as the substrate may occur. On the other hand, in the coating method, since the polyester-based graft copolymer can be present as a thin film on the film surface, blocking resistance can be imparted without changing the properties of the film serving as the substrate.

≪Application of coating liquid≫
As the coating solution containing the polyester-based graft copolymer, an organic solvent solution or an organic solvent dispersion of the polyester-based graft copolymer, or an aqueous solvent solution or an aqueous solvent dispersion can be used. In particular, an aqueous solvent solution or an aqueous solvent dispersion is preferable in that an organic solvent that is problematic for the environment is not used.

Specifically, it is preferable to use a mixed solvent of a lower alcohol having 1 to 3 carbon atoms and water as the solvent. As the lower alcohol having 1 to 3 carbon atoms, those that can be mixed with water at an arbitrary ratio, such as methanol, ethanol, n-propanol, and isopropanol, are preferable. Alcohols having a large number of carbon atoms are not preferable because they are phase-separated from water when a coating solution is prepared, and application of such coating solutions tends to cause coating spots. However, a lower alcohol having 1 to 3 carbon atoms may be used in combination as long as phase separation does not occur.

The amount of lower alcohol in the coating solution is preferably 10% by mass or more. When the amount of the lower alcohol is less than 10% by mass, the surface tension of the coating solution is increased, the wettability to the film is lowered, and coating spots are easily generated. The reason is unknown, but in a heat-shrinkable film obtained by applying and then drying a coating solution, when a sudden temperature / humidity change occurs, the transparency of the film is lowered and the practicality is impaired. Sometimes.

Further, the amount of lower alcohol in the coating solution is preferably 60% by mass or less. If the amount of the lower alcohol exceeds 60% by mass, the amount of organic solvent in the coating solution will increase. It is necessary to take. In addition, when using alcohol with many carbon atoms simultaneously with lower alcohol, it is recommended that the total amount of alcohol in a coating liquid shall be 60 mass% or less.

The solid content of the polyester-based graft copolymer and the crosslinking agent (described later) in the organic solvent or aqueous solvent is preferably 0.5% by mass or more (more preferably 1% by mass or more), and 50% by weight or less. (More preferably 30% by weight or less) is preferable. In addition, it is also possible to mix | blend an inorganic lubricant with a coating liquid.

The method for applying the coating liquid containing the polyester-based graft copolymer to the polyester-based substrate film is not particularly limited, and known methods such as an air knife method, a gravure method, a reverse method, a die method, a bar method, and a dip method. The coating method can be used.

The coating amount of the coating solution is preferably 0.002 ~ 0.5g / m ² as polyester-based graft copolymer solids, and more preferably 0.004 ~ 0.05g / m ^2. If the coating amount is less than 0.002 g / m ² , the heat-resistant blocking effect may not be sufficiently ensured. On the other hand, if the coating amount exceeds 0.5 g / m ² , the transparency and gloss of the film may be lowered.

≪Dry≫
The polyester-based graft copolymer used in the present invention is self-crosslinkable and does not crosslink at room temperature, but crosslinks without a crosslinker by performing an intermolecular reaction such as a hydrogen abstraction reaction by a thermal radical with heat during drying. . This makes it possible for the first time to exhibit the blocking resistance that is the object of the present invention.

There are no particular restrictions on the drying conditions after coating, but in order to express the self-crosslinking property of the polyester-based graft copolymer, the polyester base film and the polyester-based graft copolymer are not subject to thermal degradation. And the conditions which increase calorie | heat amount are preferable. Specifically, it is 60 ° C to 250 ° C, more preferably 65 ° C to 220 ° C. However, by extending the drying time, sufficient self-crosslinking property is exhibited even at a relatively low temperature, and thus the present invention is not limited to the above conditions.

The crosslinkability of the coating film can be evaluated by various methods, for example, a method of measuring an insoluble fraction in a chloroform solvent that dissolves both the hydrophobic copolymerized polyester and the polyester-based graft copolymer. . The insoluble fraction of the coating film obtained by drying at 80 ° C. or less and heat-treating at 120 ° C. for 5 minutes is preferably 50% or more, more preferably 70% or more. When the insoluble fraction of the coating film is less than 50%, not only the water resistance is not sufficient, but also blocking occurs.

In the present invention, it is possible to impart high water resistance and solvent resistance by further adding a crosslinking agent to the coating solution. The cross-linking agent is not particularly limited as long as it is capable of cross-linking with a functional group or the like present in the polyester-based graft copolymer by heat or light and finally forming a three-dimensional network structure. .

Cross-linking agents include phenol formaldehyde resins that are condensates of alkylated phenols, cresols, and the like with formaldehyde; adducts of urea, melamine, benzoguanamine, and the like with formaldehyde, and these adducts having 1 to 6 carbon atoms. Examples include amino resins such as alkyl ether compounds composed of alcohols; polyfunctional epoxy compounds; polyfunctional isocyanate compounds; blocked isocyanate compounds; polyfunctional aziridine compounds; oxazoline compounds.

Examples of the phenol formaldehyde resin include alkylated (methyl, ethyl, propyl, isopropyl or butyl) phenol, p-tert-amylphenol, 4,4′-sec-butylidenephenol, p-tert-butylphenol, o-, m-, p-cresol, p-cyclohexylphenol, 4,4'-isopropylidenephenol, p-nonylphenol, p-octylphenol, 3-pentadecylphenol, phenol, phenyl-o-cresol, p-phenylphenol, xylenol, etc. And the condensates of phenols and formaldehyde.

Examples of amino resins include methoxylated methylol urea, methoxylated methylol N, N-ethylene urea, methoxylated methylol dicyandiamide, methoxylated methylol melamine, methoxylated methylol benzoguanamine, butoxylated methylol melamine, butoxylated methylol benzoguanamine, and the like. . Preferred are methoxylated methylol melamine, butoxylated methylol melamine, and methylolated benzoguanamine.

Examples of the polyfunctional epoxy compound include diglycidyl ether of bisphenol A and oligomer thereof, diglycidyl ether of hydrogenated bisphenol A and oligomer thereof, orthophthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, p-oxybenzoic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid diglycidyl ester, ethylene glycol diglycidyl ether, propylene Glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether And polyalkylene glycol diglycidyl ethers, trimellitic acid triglycidyl ester, triglycidyl isocyanurate, 1,4-diglycidyloxybenzene, diglycidyl propylene urea, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tris Examples thereof include glycidyl ether and triglycidyl ether of glycerol alkylene oxide adduct.

Examples of the polyfunctional isocyanate compound include low-molecular or high-molecular aromatic and aliphatic diisocyanates and trivalent or higher polyisocyanates. Examples of the polyisocyanate include tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and trimers of these isocyanate compounds. Furthermore, an excess amount of these isocyanate compounds and low molecular active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, or polyester polyols, poly The terminal isocyanate group containing compound obtained by making it react with polymer active hydrogen compounds, such as ether polyols and polyamides, can be mentioned.

The blocked isocyanate compound can be prepared by subjecting the isocyanate compound and the blocking agent to an addition reaction by a conventionally known appropriate method. Examples of the isocyanate blocking agent include phenols such as phenol, cresol, xylenol, resorcinol, nitrophenol, and chlorophenol; thiophenols such as thiophenol and methylthiophenol; oximes such as acetoxime, methyl etiketooxime, and cyclohexanone oxime. Alcohols such as methanol, ethanol, propanol and butanol; halogen-substituted alcohols such as ethylene chlorohydrin and 1,3-dichloro-2-propanol; tertiary alcohols such as t-butanol and t-pentanol ; Lactams such as ε-caprolactam, δ-valerolactam, ν-butyrolactam, β-propyllactam; aromatic amines; imides; acetylacetone, acetoacetate Active methylene compounds such as malonic acid ethyl ester; mercaptans; imines; ureas; diaryl compounds; and sodium bisulfite and the like.

The above crosslinking agents can be used alone or in combination of two or more. The amount of the crosslinking agent is preferably 1 to 40 parts by mass with respect to 100 parts by mass of the polyester-based graft copolymer. As a blending method of the crosslinking agent, (1) when the crosslinking agent is water-soluble, a method of directly dissolving or dispersing the graft copolymer in an aqueous solvent solution or an aqueous solvent dispersion, or (2) a crosslinking agent When oil-soluble, there is a method of adding to the reaction solution after the grafting reaction is completed. These methods can be appropriately selected depending on the type and properties of the crosslinking agent. Further, a curing agent or an accelerator can be used in combination with the crosslinking agent.

≪Stretching and heat setting≫
In the present invention, it is preferable to perform at least uniaxial stretching after the above drying and then heat-set. A thin film can be easily formed by stretching. Moreover, since the polyester orientation is fixed by heat setting, the main shrinkage rate of the heat-shrinkable film obtained using this is lowered. The stretching conditions are not significantly different from those in the case of not providing the anti-blocking layer.

If hot air of 60 to 120 ° C. is blown onto the stretched film, the orientation of the polyester after stretching is fixed, so that the main shrinkage rate of the heat-shrinkable film is lowered. Further, it is preferable to blow hot air of 30 to 60 ° C. on the stretched film following the previous hot air. As a result, [(heat shrinkage rate in the main shrinkage direction in the main shrinkage direction exceeds 0% + 10 ° C.)] [(Temperature at which the heat shrinkage rate in the main shrinkage direction exceeds 0% −5 The heat-shrinkable polyester film having a value obtained by subtracting the heat shrinkage ratio in the main shrinkage direction of [° C.] less than 20% can be obtained.

In order to obtain an embodiment in which the anionic antistatic agent is present in the anti-blocking layer, the anionic antistatic agent is added to the coating solution for forming the anti-blocking layer. Can be efficiently processed.

(Heat shrinkable label)
The heat-shrinkable label of the present invention is produced using the heat-shrinkable polyester film. At this time, printing may be performed as necessary.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. First, the evaluation method of the film produced in the Example and the comparative example is demonstrated. In the examples, “parts” means “parts by mass”, and “%” means “% by mass” unless otherwise specified.

(1) NMR analysis of polyester Each sample was dissolved in a solvent in which chloroform D (manufactured by Yurisop) and trifluoroacetic acid D1 (manufactured by Yurisopp) were mixed at 10: 1 (volume ratio) to prepare a sample solution. ¹ H-NMR of the sample solution was measured using NMR (“GEMINI-200”; manufactured by Varian) under the measurement conditions of a temperature of 23 ° C. and a total of 64 times. In NMR measurement, the peak intensity of a predetermined proton was calculated, and the chip composition and film composition were determined as mol%.

(2) Heat shrinkage rate The film was cut into a 10 cm × 10 cm square, and heat-shrinked by treatment in warm water at a predetermined temperature ± 0.5 ° C. (see Table 2 for the predetermined temperature) for 10 seconds under no load. Thereafter, the sample was immediately immersed in water at 25 ° C. ± 0.5 ° C. for 10 seconds, then the lengths of the sample in the vertical and horizontal directions were measured, and the thermal shrinkage rate was determined according to the following formula.
Thermal shrinkage rate (%) = (length before shrinkage−length after shrinkage) ÷ length before shrinkage × 100

(3) Haze Using a heat-shrinkable polyester film stored in an atmosphere at a temperature of 30 ° C. and a relative humidity of 85% for 4 weeks, the main shrinkage direction of the film becomes the radial direction by a solvent adhesion method or a heat seal method. In this tube-shaped film, a cylindrical glass bottle having a diameter of 6.6 cm and a diameter of 6.6 cm is arranged in the tube-shaped film, and 150 ° C. (wind speed 10 m / sec) toward the film. The hot air was applied for 13 seconds. A film after shrinkage with hot air (tubular film sample number 10) was cut out and used as a film sample after heat shrinkage. JIS for film haze after heat shrinkage
Measurement was performed according to K7136, and the average value was obtained. Moreover, the average value of haze was calculated | required also about the film before heat shrink.

(4) Solvent adhesion One side of the heat-shrinkable film is coated with 1,3-dioxolane with a cotton swab at a coating amount of 5 ± 0.3 g / m ² and a coating width of 5 ± 1 mm along the longitudinal direction of the film. A tube-shaped film was produced by pasting the coating portion and the uncoated longitudinal film surface. A tube-like film having a length of 15 mm including the bonded portion was cut out from the tube-like film after 24 hours under a temperature condition of 25 ° C., and this was cut into a universal tensile tester (“STM-50” manufactured by Baldwin Co., Ltd.). ”), And the bonded portion was peeled off at a tensile rate of 200 mm / min in a 90 ° peel test. The maximum strength in this peeling was defined as the solvent peeling strength.

(5) Shrinkage finishing property Three colors of Toyo Ink Mfg. Co., Ltd. grass, blue gold, and white ink were printed in advance on a heat shrinkable film using a printing machine. Next, using this film, a heat-shrinkable label was prepared by a solvent adhesion method or a heat seal method so that the transverse direction (radial direction) was the main shrinkage direction. This label was placed on a glass bottle having a temperature of 60 ° C., and was subjected to heat shrinkage by applying hot air of 175 ° C. (wind speed 12 m / sec) for 10 seconds. The shrinkage and finish of the entire label after heat shrinkage were visually confirmed and evaluated according to the following four criteria. In the following evaluation criteria, “◯” is a pass level and “Δ”, “×”, and “XX” are bad. Further, “defects” in the following evaluation criteria correspond to jumping, wrinkling, insufficient shrinkage, label edge folding, and shrinkage whitening.
○: Good finish △: Some defects (within 2 locations)
×: Defects (3-5 locations)
XX: Many defects (over 6 locations)

(6) Glass transition temperature (Tg)
A solution or dispersion of the polyester-based graft copolymer was applied to a glass plate and then dried at 170 ° C. to obtain a graft polymer solid. 10 mg of this solid content is taken in a sample pan, and using a differential scanning calorimeter (manufactured by Shimadzu Corporation, atmosphere control device: FC-60A, workstation: TA-60WS), the temperature rising rate is 10 ° C./min under a nitrogen atmosphere. The glass transition temperature (Tg) was determined from the data obtained by the measurement.

(7) Blocking property Heat seal the surface temperature of the seal bar within a range of 95 ± 0.5 ° C, heat seal the film surfaces at a pressure of 40 N / cm2 and time of 300 seconds, and then remove a 15 mm wide sample. The peel strength was measured using a tensile tester and evaluated according to the following criteria.
○: Peel strength less than 0.1 N / 15 mm ×: Peel strength of 0.1 N / 15 mm or more

(8) Surface resistivity Using a surface resistivity measuring instrument (main body: R8340, sample box: R12704) manufactured by Advantest Co., Ltd., measured in an atmosphere with an applied voltage of 100 V, 23 ° C. and 65% RH, the reading of the measuring instrument Was the surface resistivity.

(Synthesis Example A: Synthesis of polyester)
In a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux cooler, a dicarboxylic acid component, dimethyl terephthalate (DMT), and a polyhydric alcohol component, ethylene glycol (EG), have a molar ratio EG / It was charged so that DMT = 2.2. When the EG was charged, an inorganic lubricant was dispersed in ethylene glycol. In addition, 0.05 mol% (based on the dicarboxylic acid component) of zinc acetate as the transesterification catalyst and 0.025 mol% of antimony trioxide (based on the dicarboxylic acid component) as the polycondensation catalyst The transesterification reaction was allowed to proceed while adding methanol and distilling the produced methanol out of the reaction system. Thereafter, the polycondensation reaction is allowed to proceed under the conditions of 280 ° C. and 26.7 Pa, the polycondensation reaction is terminated under reduced pressure, and the polymer obtained under nitrogen pressurization is discharged into water in the form of a strand. By cutting with a strand cutter, a polyester A chip having an ethylene terephthalate unit and containing 0.7% by mass of an inorganic lubricant was obtained. The composition is shown in Table 1.

(Synthesis Examples B to D: Synthesis of polyester)
Same as Synthesis Example A using DMT as the dicarboxylic acid component and EG, EG and neopentyl glycol, 1,4-butanediol, or ethylene glycol and 1,4-cyclohexanedimethanol as the polyhydric alcohol component By using the above method (but without using an inorganic lubricant), polyester B to D chips having the compositions shown in Table 1 were obtained.

(Preferable Experimental Examples 1 to 5)
(Experimental example 1)
Separately pre-dried polyester A to C chips were mixed at a ratio of 15 wt% A, 75 wt% B, and 10 wt% C, fed to the extruder, melt extruded at 275 ° C., and surface temperature 25 ° C. The film was rapidly cooled on a chill roll to obtain an unstretched film having a thickness of 180 μm. Subsequently, the unstretched film was introduced into the tenter, and as a preheating, the unstretched film temperature was set to 70 ° C., and the unstretched film having a temperature of 72 ° C. was stretched 4.0 times in the transverse direction. Next, the film after stretching was subjected to a primary heat treatment at 95 ° C. for 14 seconds, followed by a secondary heat treatment at 50 ° C. for 10 seconds to obtain a heat-shrinkable polyester film having a thickness of 45 μm. Table 2 shows the evaluation results of the characteristics of the film.

(Experimental example 2)
A heat-shrinkable polyester film of this experimental example was obtained in the same manner as in Experimental Example 1 except that the ratio of the polyester A to C chips was changed to 5 wt% for A, 80 wt% for B, and 15 wt% for C. .

(Experimental example 3)
Polyester A, C, and D chips were used as the polyester chips, and the ratio of these chips was the same as in Experimental Example 1 except that A was 15 wt%, C was 10 wt%, and D was 75 wt%. The heat-shrinkable polyester film of this experimental example was obtained.

(Experimental example 4)
The ratio of the polyester A to C chips was 15 wt%, B was 75 wt%, C was 10 wt%, and the stretched film was subjected to primary heat treatment at 92 ° C. for 14 seconds. The heat-shrinkable polyester film of this experimental example was obtained.

(Experimental example 5)
The ratio of the polyester A to C chips was 15 wt%, B was 75 wt%, C was 10 wt%, and the stretched film was subjected to a primary heat treatment at 104 ° C. for 14 seconds. The heat-shrinkable polyester film of this experimental example was obtained.

(Experimental Examples 6 to 9 which are not preferable to Experimental Examples 1 to 5)
(Experimental example 6)
A heat-shrinkable polyester film of this experimental example was obtained in the same manner as in Experimental Example 1 except that the primary heat treatment temperature after stretching in the transverse direction was 85 ° C.

(Experimental example 7)
A heat-shrinkable polyester film of this experimental example was obtained in the same manner as in Experimental Example 1, except that the ratio of the polyester A to C chips was 40 wt%, B was 50 wt%, and C was 10 wt%. .

(Experimental example 8)
The same method as in Experimental Example 1 except that the ratio of the polyester A to C chips was 40 wt% A, 50 wt% B, 10 wt% C, and the primary heat treatment temperature after stretching in the transverse direction was 85 ° C. Thus, a heat-shrinkable polyester film of this experimental example was obtained.

(Experimental example 9)
The heat-shrinkable polyester of this experimental example was prepared in the same manner as in Experimental Example 1 except that 75 wt% of the polyester B chip and 25 wt% of the C chip were used, and the primary heat treatment temperature after stretching in the transverse direction was 85 ° C. A system film was obtained.

(Particularly preferred experimental examples 10 to 11)
(Anionic antistatic agent-containing liquid 1)
Water is added to the dodecyl sulfonate to dilute it, and isopropanol is further added to add an anionic antistatic agent-containing liquid 1 having a solid content concentration of 2 mass% (dodecyl sulfonate: 2 mass%, water: 63 mass%, isopropanol: 35 mass%). )

(Anionic antistatic agent-containing liquid 2)
Diluted by adding water to dodecylbenzenesulfonate, and further added isopropanol, an anionic antistatic agent-containing liquid 2 having a solid content concentration of 2 mass% (dodecylbenzenesulfonate: 2 mass%, water: 63 mass%, isopropanol: 35 Mass%).

(Experimental example 10)
Separately pre-dried polyester A to C chips were mixed at a ratio of 15 wt% A, 75 wt% B, and 10 wt% C, fed to the extruder, melt extruded at 275 ° C., and surface temperature 25 ° C. The film was rapidly cooled on a chill roll to obtain an unstretched film having a thickness of 180 μm. An anionic antistatic agent-containing liquid 1 is applied to one side of this unstretched film by an air knife method, and the unstretched film is subsequently introduced into a tenter. The prestretched film temperature is set to 70 ° C. The stretched film was stretched 4.0 times in the transverse direction. Next, the film after stretching was subjected to a primary heat treatment at 95 ° C. for 14 seconds, followed by a secondary heat treatment at 50 ° C. for 10 seconds to obtain a heat-shrinkable polyester film having a thickness of 45 μm. Table 3 shows the evaluation results of the characteristics of the film.

(Experimental example 11)
A heat-shrinkable polyester film was obtained in the same manner as in Experimental Example 10, except that the anionic antistatic agent-containing liquid 1 was changed to the anionic antistatic agent-containing liquid 2.

(Experimental Examples 12 to 20 which are not preferable to Experimental Examples 10 to 11)
(Experimental example 12)
A heat-shrinkable polyester film was obtained in the same manner as in Experimental Example 10 except that the anionic antistatic agent-containing liquid 1 was not applied.

(Experimental example 13)
A heat-shrinkable polyester film of this experimental example was obtained in the same manner as in Experimental Example 12, except that the ratio of the polyester A to C chips was 5 wt%, B was 80 wt%, and C was 15 wt%. .

(Experimental example 14)
Polyester A, C, and D chips were used as the polyester chips, and the ratio of these chips was the same as in Experimental Example 12, except that A was 15 wt%, C was 10 wt%, and D was 75 wt%. The heat-shrinkable polyester film of this experimental example was obtained.

(Experimental example 15)
The ratio of the polyester A to C chips was 15 wt%, B was 75 wt%, C was 10 wt%, and the stretched film was subjected to a primary heat treatment at 92 ° C. for 14 seconds. The heat-shrinkable polyester film of this experimental example was obtained.

(Experimental example 16)
The ratio of the polyester A to C chips was 15 wt%, B was 75 wt%, C was 10 wt%, and the stretched film was subjected to a primary heat treatment at 104 ° C. for 14 seconds. The heat-shrinkable polyester film of this experimental example was obtained.

(Experimental example 17)
A heat-shrinkable polyester film of this experimental example was obtained in the same manner as in Experimental Example 12 except that the primary heat treatment temperature after stretching in the transverse direction was 85 ° C.

(Experiment 18)
A heat-shrinkable polyester film of this experimental example was obtained in the same manner as in Experimental Example 12 except that the ratio of the polyester A to C chips was 40 wt%, B was 50 wt%, and C was 10 wt%. .

(Experimental example 19)
The same method as in Experimental Example 12 except that the ratio of the polyester A to C chips was 40 wt% for A, 50 wt% for B, 10 wt% for C, and the primary heat treatment temperature after lateral stretching was 85 ° C. Thus, a heat-shrinkable polyester film of this experimental example was obtained.

(Experiment 20)
The heat-shrinkable polyester of this experimental example was prepared in the same manner as in Experimental Example 12 except that 75 wt% of the polyester B chip and 25 wt% of the C chip were used and the primary heat treatment temperature after extending in the transverse direction was 85 ° C. A system film was obtained.

(Particularly preferred experimental examples 21 to 22)
(Preparation of polyester base film)
Separately pre-dried polyester A to C chips were mixed at a ratio of 15 wt% A, 75 wt% B, and 10 wt% C, fed to the extruder, melt extruded at 275 ° C., and surface temperature 25 ° C. It was rapidly cooled on a chill roll to obtain an unstretched polyester base film having a thickness of 180 μm. The obtained film was subjected to NMR analysis to examine its composition. The results are shown in Table 4.

(Preparation of polyester graft copolymer)
<Preparation of hydrophobic copolyester>
In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 345 parts of dimethyl terephthalate (DMT) as a dicarboxylic acid component, 211 parts of 1,4 butanediol (BD) as a glycol component, ethylene glycol ( EG) 270 parts and 0.5 part of tetra-n-butyl titanate as a polymerization catalyst were charged, and a transesterification reaction was performed from 160 ° C. to 220 ° C. over 4 hours. Next, 14 parts of fumaric acid and 160 parts of adipic acid were added as dicarboxylic acid components, and the temperature was raised from 200 ° C. to 220 ° C. over 1 hour to carry out an esterification reaction. Next, the temperature was raised to 255 ° C., and the pressure of the reaction system was gradually reduced, followed by reaction for 1 hour 30 minutes under a reduced pressure of 0.22 mmHg to obtain a hydrophobic copolyester. The obtained hydrophobic copolyester had a weight average molecular weight of 20,000 and was pale yellow and transparent.

<Grafting of radically polymerizable monomer>
In a reactor equipped with a stirrer, a thermometer, a reflux device and a quantitative dropping device, 75 parts of the hydrophobic copolymer polyester, 56 parts of methyl ethyl ketone and 19 parts of isopropyl alcohol are heated and stirred at 65 ° C. The polymerized polyester was dissolved. After the hydrophobic copolyester was completely dissolved, 15 parts of maleic anhydride (MA) as a radical polymerizable monomer was added to the polyester solution. Next, a solution prepared by dissolving 10 parts of styrene (ST) as a radical polymerizable monomer and 1.5 parts of azobisdimethylvaleronitrile as a graft polymerization initiator in 12 parts of methyl ethyl ketone was dropped into the polyester solution at 0.1 ml / min. The stirring was continued for another 2 hours. After sampling for analysis from the reaction solution, 5 parts of methanol was added. Next, 300 parts of water and 15 parts of triethylamine were added to the reaction solution and stirred for 1 hour. Thereafter, the reactor internal temperature was raised to 100 ° C., and methyl ethyl ketone, isopropyl alcohol, and excess triethylamine were distilled off to obtain a water-dispersed polyester graft copolymer. The polyester graft copolymer was light yellow and transparent and had a glass transition temperature of −10 ° C.

(Preparation of coating solution 3)
The water-dispersed polyester-based graft copolymer is diluted by adding water, and colloidal silica and isopropanol are further added to form a coating solution having a solid concentration of 1% by mass (polyester-based graft copolymer: 1% by mass, colloidal silica: 1% by mass, water: 63% by mass, isopropanol: 35% by mass).

(Experimental example 21)
On one side of the unstretched polyester base film, coating solution 3 is applied as a polyester graft copolymer solid content by an air knife method so that it becomes 0.006 g / m ² after drying, and is continuously led to a tenter. After preheating until the film temperature reached 70 ° C., the film was stretched 4.0 times in the transverse direction at a temperature of 72 ° C. Next, heat treatment was carried out at 95 ° C. for 14 seconds, followed by treatment at 50 ° C. for 10 seconds to obtain a heat-shrinkable polyester film having a thickness of 45 μm. At this time, the heat transfer coefficient in the preheating process was 0.0009, and the heat transfer coefficient in the stretching process was 0.0056. Table 4 shows the physical property values of the film of the obtained film roll.

(Experimental example 22)
In Experimental Example 21, a heat-shrinkable polyester film was obtained in the same manner as in Experimental Example 21, except that the coating amount of the coating liquid 3 was set to 0.003 g / m ² after drying as a polyester-based graft copolymer solid content. . Table 4 shows the physical property values of the film of the obtained film roll.

(Experimental Example 23 which is not preferable to Experimental Examples 21 to 22)
(Experimental example 23)
A heat-shrinkable polyester film having a thickness of 45 μm was obtained in the same manner as in Example 21 except that the coating liquid 3 was not applied. Table 4 shows the physical property values of the film of the obtained film roll.

(Particularly preferred experimental examples 24 to 25)
(Preparation of polyester base film)
Separately pre-dried polyester A to C chips were mixed at a ratio of 15 wt% A, 75 wt% B, and 10 wt% C, fed to the extruder, melt extruded at 275 ° C., and surface temperature 25 ° C. It was rapidly cooled on a chill roll to obtain an unstretched polyester base film having a thickness of 180 μm. The obtained film was subjected to NMR analysis to examine its composition. The results are shown in Table 5.

(Preparation of polyester graft copolymer)
<Preparation of hydrophobic copolyester>
In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 345 parts of dimethyl terephthalate (DMT) as a dicarboxylic acid component, 211 parts of 1,4 butanediol (BD) as a glycol component, ethylene glycol ( EG) 270 parts and 0.5 part of tetra-n-butyl titanate as a polymerization catalyst were charged, and a transesterification reaction was performed from 160 ° C. to 220 ° C. over 4 hours. Next, 14 parts of fumaric acid and 160 parts of adipic acid were added as dicarboxylic acid components, and the temperature was raised from 200 ° C. to 220 ° C. over 1 hour to carry out an esterification reaction. Next, the temperature was raised to 255 ° C., and the pressure of the reaction system was gradually reduced, followed by reaction for 1 hour 30 minutes under a reduced pressure of 0.22 mmHg to obtain a hydrophobic copolyester. The obtained hydrophobic copolyester had a weight average molecular weight of 20,000 and was pale yellow and transparent.

<Grafting of radically polymerizable monomer>
In a reactor equipped with a stirrer, a thermometer, a reflux device and a quantitative dropping device, 75 parts of the hydrophobic copolymer polyester, 56 parts of methyl ethyl ketone and 19 parts of isopropyl alcohol are heated and stirred at 65 ° C. The polymerized polyester was dissolved. After the hydrophobic copolyester was completely dissolved, 15 parts of maleic anhydride (MA) as a radical polymerizable monomer was added to the polyester solution. Next, a solution prepared by dissolving 10 parts of styrene (ST) as a radical polymerizable monomer and 1.5 parts of azobisdimethylvaleronitrile as a graft polymerization initiator in 12 parts of methyl ethyl ketone was dropped into the polyester solution at 0.1 ml / min. The stirring was continued for another 2 hours. After sampling for analysis from the reaction solution, 5 parts of methanol was added. Next, 300 parts of water and 15 parts of triethylamine were added to the reaction solution and stirred for 1 hour. Thereafter, the reactor internal temperature was raised to 100 ° C., and methyl ethyl ketone, isopropyl alcohol, and excess triethylamine were distilled off to obtain a water-dispersed polyester graft copolymer. The polyester graft copolymer was light yellow and transparent and had a glass transition temperature of −10 ° C.

(Preparation of coating solution 4)
The water-dispersed polyester-based graft copolymer is diluted by adding water, dodecyl sulfonate is added, isopropanol is added, and a solid content concentration is 3% by mass (polyester-based graft copolymer: 2.6% by mass, Antistatic agent: 0.4% by mass, water: 62% by mass, isopropanol: 35% by mass).

(Experimental example 24)
On one side of the unstretched polyester base film, the coating liquid 4 is applied as a polyester graft copolymer solid content by an air knife method so as to be 0.03 g / m ² after drying, and continuously led to a tenter. After preheating until the film temperature reached 70 ° C., the film was stretched 4.0 times in the transverse direction at a temperature of 72 ° C. Next, heat treatment was carried out at 95 ° C. for 14 seconds, followed by treatment at 50 ° C. for 10 seconds to obtain a heat-shrinkable polyester film having a thickness of 45 μm. At this time, the heat transfer coefficient in the preheating process was 0.0009, and the heat transfer coefficient in the stretching process was 0.0056. Table 5 shows the physical property values of the film of the obtained film roll.

(Experimental example 25)
In Example 24, a heat-shrinkable polyester film was obtained in the same manner as in Example 1 except that the coating amount of the coating liquid 4 was set to 0.004 g / m ² after drying as a polyester graft copolymer solid content. . Table 5 shows the physical property values of the film of the obtained film roll.

(Experimental example 26 which is not preferable to Experimental examples 24 to 25)
(Comparative Example 26)
A heat-shrinkable polyester film having a thickness of 45 μm was obtained in the same manner as in Experimental Example 24 except that the coating solution 4 was not applied. Table 5 shows the physical property values of the film of the obtained film roll.

The heat-shrinkable polyester film of the present invention can maintain a good appearance, is suitable for label use, and has high industrial utility value. In addition to suppressing the occurrence of troubles due to static electricity, it can also be resistant to blocking at high temperatures, and is suitable for labeling containers that are filled with high-temperature contents.

Claims (13)

1. The heat shrinkage rate in the main shrinkage direction when immersed in warm water of 95 ± 0.5 ° C. for 10 seconds is 30 to 60%,
   The length in the direction perpendicular to the main contraction direction is extended when immersed for 10 seconds in warm water at any temperature corresponding to 59.5 to 90.5 ° C and [constant temperature ± 0.5 ° C]. A heat-shrinkable polyester film.
2. The heat-shrinkable polyester film according to claim 1, wherein the anionic antistatic agent is present on at least one side.
3. The heat-shrinkable polyester film according to claim 2, wherein the anionic antistatic agent has an alkyl group and has 10 to 20 carbon atoms.
4. The heat-shrinkable polyester according to claim 1, wherein a blocking resistance improving layer containing a polyester-based graft copolymer obtained by grafting at least one radical polymerizable monomer onto a hydrophobic copolymerized polyester is provided on at least one side of the film. Film.
5. The heat-shrinkable polyester film according to claim 4, wherein the radical polymerizable monomer contains at least maleic anhydride and styrene.
6. A blocking resistance improving layer containing a polyester-based graft copolymer obtained by grafting at least one radical polymerizable monomer onto a hydrophobic copolymerized polyester is provided on at least one side of the film, and the anionic antistatic agent is provided with the anti-blocking property. The heat-shrinkable polyester film according to claim 1, which is present in the property improving layer.
7. The heat-shrinkable polyester film according to claim 6, wherein the radical polymerizable monomer contains at least maleic anhydride and styrene.
8. The heat-shrinkable polyester film according to claim 6, wherein the anionic antistatic agent has an alkyl group and has 10 to 20 carbon atoms.
9. The heat shrinkage according to any one of claims 1, 2, 4, and 6, wherein the heat shrinkage rate in the main shrinkage direction when immersed in warm water of 80 ± 0.5 ° C for 10 seconds is less than 40%. Polyester film.
10. 60 ± 0.5 ° C, 65 ± 0.5 ° C, 70 ± 0.5 ° C, 75 ± 0.5 ° C, 80 ± 0.5 ° C, 85 ± 0.5 ° C, 90 ± 0.5 ° C, and Thermal contraction in the main contraction direction begins with immersion in any warm water when immersed in warm water of 95 ± 0.5 ° C. for 10 seconds,
    [(Thermal shrinkage rate in the main shrinkage direction + 10 ° C. in the main shrinkage direction + 10 ° C.)] to [(temperature shrinkage rate in the main shrinkage direction in excess of 0% −5 ° C.)] The heat-shrinkable polyester film according to any one of claims 1, 2, 4, and 6, wherein a value obtained by subtracting the heat shrinkage ratio in the main shrinkage direction is less than 20%.
11. The heat-shrinkable polyester film according to any one of claims 1, 2, 4, and 6, wherein the haze after heat shrinkage is 10% or less.
12. The heat-shrinkable polyester film according to any one of claims 1, 2, 4, and 6, which can be bonded with a non-chlorine organic solvent.
13. A heat-shrinkable label produced using the heat-shrinkable polyester film according to any one of claims 1, 2, 4, and 6.