JP2009160775A - Heat-shrinkable polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable polyester film which has a high heat shrinkage and is capable of controlling the occurrence of whitening due to heat shrinkage and is suitable for labelling of containers. <P>SOLUTION: When immersed in warm water at 95±0.5°C for 10 secs, the heat-shrinkable polyester film has a heat shrinkage in the principal shrinkage direction of 30-60%. When immersed in warm water at a constant temperature of 59.5-90.5°C with a tolerance of ±0.5°C for 10 secs, the film elongates in the direction perpendicular to the principal shrinkage direction. Preferably, when immersed in warm water at 80±0.5°C for 10 secs, the heat shrinkage in the principal shrinkage direction is 40% or lower. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  A heat-shrinkable plastic film having a 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.

  For polystyrene films, the finish after shrinkage is good, but due to poor solvent resistance, ink with a special composition must be used when printing on the film surface. 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.

By the way, the peripheral surface of the container is covered with a heat-shrinkable film (heat-shrinkable label) that has been subjected to printing as necessary and then processed into a cylindrical shape. 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

  In view of the above circumstances, an object of the present invention is to provide a heat-shrinkable polyester film that has a high heat shrinkage rate and can suppress the occurrence of whitening due to heat shrinkage, and is suitable for labeling containers.

  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 characterized in that the length in the direction perpendicular to the main contraction direction is extended when immersed in warm water at a temperature corresponding to 0 ° 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.]” is, 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): Thermal 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. The haze of the film after heat shrinkage is measured according to JIS K7136, and 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.

  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.

  The heat shrinkable polyester film according to the present invention is characterized in that the heat shrinkage rate in the main shrinkage direction is 30 to 60% when immersed in warm water of 95 ± 0.5 ° C. for 10 seconds. The thermal shrinkage rate is preferably 35 to 57%, and 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.

  It is preferable that the thermal shrinkage rate in the main shrinkage direction when the film according to the present invention is immersed in warm water of 80 ± 0.5 ° C. is 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 exceeded 0% + 10 ° C.)] to [heat shrinkage in the main shrinkage direction (temperature at which the heat shrinkage rate in the main shrinkage direction exceeded 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 has hot water at 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), 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 thermal 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.

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

  20-100 micrometers is preferable and, as for the thickness of the film concerning this invention, 30-60 micrometers is more preferable.

  A suitable 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 consideration of generation of toxic substances due to halogen such as chlorine atom, 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. Note that 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 and the like is preferably 5 to 40 mol%, preferably 10 to 35 mol% when the total diol is 100 mol%, and further considering the solvent adhesiveness of the film, 18 -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) Knit), 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 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 content of the unit can be performed using, for example, ¹ H-NMR.

  One or more selected from inorganic particles, organic salt particles, and crosslinked polymer particles may be added as a lubricant to the polyester constituting the film. 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.

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 dried in advance 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, the thermal conductivity coefficient to the film is 0.0013 calories / cm ² · sec · ° C. or less at a low wind speed of 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, and the temperature is Tg-30 ° C to Tg + 40 ° C, more preferably Tg-15 ° C to Tg + 30 ° C, and the transverse direction of the film is 2.3 to 7.3 times, preferably 3.5-6.0 times. If hot air of 60 to 120 ° C. is blown onto the stretched film, the stretched polyester orientation is fixed, so that the main shrinkage rate of the heat-shrinkable film is lowered. If the hot air of 30 to 60 ° C. is blown on the stretched film following the previous hot air blowing, the main shrinkage 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 in the main shrinkage direction is less than 20%.

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 longitudinal stretching that causes shrinkage in the longitudinal direction is not necessarily performed, 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.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not restrict | limited to these Examples at all. First, the evaluation method of the film produced in the Example and the comparative example is demonstrated.

(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. , NMR (“GEMINI-200”; manufactured by Varian) was used to measure ¹ H-NMR of the sample solution under the measurement conditions of a temperature of 23 ° C. and an integration count 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.
Heat 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. The haze of the film after heat shrinkage was measured according to JIS 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 adhesiveness On the one side of the heat shrinkable film, 1,3-dioxolane was applied with a cotton swab in the longitudinal direction of the film at an application amount of 5 ± 0.3 g / m ² and an application width of 5 ± 1 mm. A tube-shaped film was produced by pasting the coating portion and the uncoated longitudinal film surface. A tube-like film having a longitudinal 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)

(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 (however, an inorganic lubricant was not used), polyester B to D chips having the compositions shown in Table 1 were obtained.

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 and fed to the extruder, and then melt extruded at 275 ° C., with a surface temperature of 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.

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

(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 Example 1 except that A was 15 wt%, C was 10 wt%, and D was 75 wt%. A heat-shrinkable polyester film of this example was obtained.

Example 4
According to the same method as in Example 1, except that the ratio of the polyester A to C chips was 15 wt% for A, 75 wt% for B, 10 wt% for C, and the film after stretching was subjected to primary heat treatment at 92 ° C. for 14 seconds. The heat-shrinkable polyester film of this example was obtained.

(Example 5)
According to the same method as in Example 1, except that the ratio of the polyester A to C chips was 15 wt% for A, 75 wt% for B, 10 wt% for C, and the film after stretching was subjected to primary heat treatment at 104 ° C. for 14 seconds. The heat-shrinkable polyester film of this example was obtained.

(Comparative Example 1)
A heat-shrinkable polyester film of this comparative example was obtained in the same manner as in Example 1 except that the primary heat treatment temperature after stretching in the transverse direction was 85 ° C.

(Comparative Example 2)
A heat-shrinkable polyester film of this comparative example was obtained in the same manner as in 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%. .

(Comparative Example 3)
A method similar to that of Example 1 except that the ratio of the polyester A to C chips is 40 wt% A, 50 wt% B, 10 wt% C, and the primary heat treatment temperature after stretching in the transverse direction is 85 ° C. Thus, a heat-shrinkable polyester film of this comparative example was obtained.

(Comparative Example 4)
The heat-shrinkable polyester of this comparative example was prepared in the same manner as in 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 extending in the transverse direction was 85 ° C. A system film was obtained.

  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.

Claims (6)

The thermal shrinkage rate in the main shrinkage direction when immersed in warm water of 95 ± 0.5 ° C. for 10 seconds is 30 to 60%,
59.5 to 90.5 ° C. and the length in the direction perpendicular to the main contraction direction is extended when immersed in warm water at any temperature corresponding to [constant temperature ± 0.5 ° C.] for 10 seconds. A heat-shrinkable polyester film.   The heat-shrinkable polyester film according to claim 1, 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%. 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 in the main shrinkage direction exceeds 0% + 10 ° C.)] from ((temperature shrinkage rate in the main shrinkage direction exceeds 0% −5 ° C.) The heat-shrinkable polyester film according to claim 1 or 2, wherein a value obtained by subtracting the heat shrinkage ratio in the main shrinkage direction is less than 20%.   The heat-shrinkable polyester film according to any one of claims 1 to 3, wherein the haze after heat shrinkage is 10% or less.   The heat-shrinkable polyester film according to any one of claims 1 to 4, which can be bonded with a non-chlorine organic solvent.   The heat-shrinkable label produced using the heat-shrinkable polyester film of any one of Claims 1-5.