JP2008189779A - Thermally shrinkable polyester-based film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermally shrinkable polyester-based film which is excellent in a shrink-finishing property, adhesiveness to bottles, and perforation-unsealing property and is suitable for labels. <P>SOLUTION: This thermally shrinkable polyester-based film is obtained by charging and melting a polyester resin component A consisting mainly of trimethylene terephthalate units, and a polyester resin component B consisting mainly of ethylene terephthalate units and ethylene isophthalate units in separate extruders A1 and B1, respectively, charging the resin component A and the resin component B in a static mixer in the melted state, extruding the mixture from a T-die, cooling the extruded sheet, and then stretching the formed un-stretched sheet at least monoaxially. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable polyester film, and more particularly to a heat-shrinkable polyester film suitable for labeling bottles such as PET bottles (polyethylene terephthalate (PET) bottles) and glass bottles.

  As a heat-shrinkable film, particularly a heat-shrinkable film for labeling the body of a bottle, a film made of polyvinyl chloride, polystyrene or the like is mainly used. However, with regard to polyvinyl chloride, in recent years, the generation of chlorine-based gas at the time of incineration of discarded vinyl chloride products has become a problem. On the other hand, polystyrene has problems such as difficulty in printing on a polystyrene film. Furthermore, when collecting and recycling PET bottles (PET bottles), it is necessary to separate labels of resins such as polyvinyl chloride and polystyrene at the time of disposal. For this reason, polyester-based heat-shrinkable films that do not have these problems are attracting attention.

  In the case of beverage bottles, in order to improve productivity, label mounting and shrinkage are increasingly performed in a beverage filling line. Since the filling line is high-speed, it is necessary to mount and shrink the label at high speed, and the shrinkage time tends to be short. Under such circumstances, when a polyester heat-shrinkable film is used for the label, wrinkles, jumping and color unevenness occur on the label at the shoulder of the bottle, and there is a problem with the shrink finish. Has occurred. In addition, there are problems such as poor adhesion to the bottle and the label slipping through the bottle.

  On the other hand, for the convenience of separation and disposal, it is common to provide a perforation on the label so that the label can be easily peeled off, or to provide an opening perforation on the label when labeling with a film up to the cap of the bottle. Is. Polyester film labels have the problem of poor perforation, especially when bottles are used for beverages, and are usually refrigerated at low temperatures. Is happening more frequently.

  It has been proposed that the problem of shrinkage finish and adhesion when a label is attached to a bottle is improved by controlling the shrinkage characteristics of the film (see, for example, Patent Documents 1, 2, and 3). However, although the film having specific shrinkage characteristics has somewhat improved the shrinkage finish and adhesion problems, the perforation openability is not sufficient.

On the other hand, as a film with improved perforation openability, there is a film obtained by devising a temperature condition at the time of stretching during production (see, for example, Patent Document 4). However, although the improvement degree of perforation opening has been seen, it is still not sufficient, and due to the shrinkage rate that is too fast and the maximum shrinkage rate that is too high, which is a feature of the conventional polyester shrink film, When a high-speed label was attached to a 500 mL PET bottle, uneven shrinkage, wrinkles or color unevenness occurred particularly in the shoulder portion of the bottle, and there was a problem in shrink finish.
JP-A-6-320621 JP-A-8-27285 JP-A-8-25477 Japanese Patent Laid-Open No. 11-207818

  As described above, the current situation is that a heat-shrinkable polyester film label excellent in shrink finish, adhesion to a bottle, and perforation opening is not obtained. Then, an object of this invention is to provide the heat-shrinkable polyester-type film suitable for the label which is excellent in all of shrink finishing property, adhesiveness with a bottle, and perforation openability.

  The heat-shrinkable polyester film of the present invention that can achieve the above object comprises a polyester resin component A mainly containing trimethylene terephthalate units, and a polyester resin component B mainly containing ethylene terephthalate units and ethylene isophthalate units. Each of the extruders A1 and B1 is charged and melted, and after the resin component A and the resin component B are charged into a static mixer in a molten state, they are extruded from a T-die and cooled to form at least an unstretched sheet. It has a gist where it can be obtained by stretching uniaxially.

  As another embodiment of the present invention, the heat-shrinkable polyester film of the present invention comprises an X layer containing a polyester resin component A mainly containing a trimethylene terephthalate unit, an ethylene terephthalate unit, and an ethylene isophthalate unit. The main point is that the Y layer containing the polyester resin component B mainly contained has a structure in which 500 layers or more are alternately laminated.

  In the heat-shrinkable polyester film, the constituent unit of all the polyester in the entire film is 100 mol%, the trimethylene terephthalate unit is 10 to 45 mol%, the ethylene terephthalate unit and the ethylene isophthalate unit are combined. It is preferable that 55-90 mol% and other polyester units are contained 0-12 mol% in total.

The heat-shrinkable polyester film has a heat shrinkage ratio in the main shrinkage direction of 35% to 80% after being immersed in warm water at 85 ° C. ± 0.5 ° C. for 10 seconds, and 70 ° C. ± It is preferable that the thermal shrinkage rate in the main shrinkage direction after being immersed in 0.5 ° C. warm water for 10 seconds is 10% or more and 50% or less. Further, in the heat-shrinkable polyester film, the resin component A has a glass transition temperature measured by DSC of −50 ° C. or higher and lower than 60 ° C., and a crystal melting heat amount of 5 (J / g) or more (100). J / g) the following crystalline polyester, and the resin component B has a glass transition temperature measured by DSC of 60 ° C. or higher and 150 ° C. or lower and a crystal melting heat of 0 (J / g) or higher and 3 (J / G) The following substantially amorphous polyester is preferred. Furthermore, in the heat-shrinkable polyester film, the alkaline earth metal compound may be 20 ppm (mass basis, the same shall apply hereinafter) or more and 400 ppm or less based on the alkaline earth metal atom M ² , and the phosphorus compound may be a phosphorus atom. It is preferable to contain 5 ppm or more and 500 ppm or less on the basis of P.

  A bottle label using the heat-shrinkable polyester film is also included in the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the heat-shrinkable polyester-type film suitable for the label which is excellent in all of shrink finishing, adhesiveness with a bottle, and perforation openability is provided. That is, the label using the heat-shrinkable polyester film of the present invention has a label shrinkage unevenness, wrinkle or wrinkle even when the label is attached to the bottle and contracted in the beverage filling line, that is, at a high speed. Occurrence of color unevenness is extremely suppressed, and the perforation formed on the label is excellent even at low temperatures. Therefore, it is useful for bottle applications such as PET bottles and glass bottles.

  In the present invention, polyester resin component A mainly containing trimethylene terephthalate unit and polyester resin component B mainly containing ethylene terephthalate unit and ethylene isophthalate unit are charged into separate extruders A1 and B1, respectively, and melted. Heat-shrinkable polyester film obtained by charging resin component A and resin component B in a molten state into a static mixer, and then extruding from a T-die and cooling to form at least a uniaxially stretched unstretched sheet It is.

  In the present invention, the trimethylene terephthalate unit refers to a unit represented by the following formula (1), for example, a unit obtained by reaction of trimethylene glycol and terephthalic acid.

  The resin component A containing a trimethylene terephthalate unit means that the resin component A contains polytrimethylene terephthalate, or that the resin component A contains a copolyester having a trimethylene terephthalate unit.

  The resin component A mainly contains trimethylene terephthalate units means that the resin component A contains 60 mol% or more of trimethylene terephthalate units when the total polyester constituent unit of the resin component A is 100 mol%. . The resin component A preferably contains 70 mol% or more of trimethylene terephthalate units, and more preferably contains 80 mol% or more.

  According to the resin component A containing 60% by mole or more of trimethylene terephthalate unit, the resulting film has excellent shrinkage characteristics in the temperature range of 60 to 70 ° C. (after being immersed in warm water at 70 ± 0.5 ° C. for 10 seconds. When the thermal shrinkage rate in the main shrinkage direction is 20% or more and 50% or less) and labeling and mounting on the bottle, shrinkage unevenness hardly occurs in the steam tunnel.

  In the present invention, the polyester constituent unit refers to a unit having one unit derived from an acid component and one unit derived from a glycol component, which corresponds to a repeating constituent unit of polyester formed by condensation of an acid component and a glycol component. Say.

  Resin component A may contain components other than trimethylene terephthalate units, and when components other than trimethylene terephthalate units are included as resins separate from resins containing trimethylene terephthalate units, examples thereof Examples thereof include crystalline polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polypentamethylene terephthalate, polyhexamethylene terephthalate, and polyethylene-2,6-naphthalate (PEN). Further, based on these, an acid component and / or glycol component described later is copolymerized in an amount of 5 mol% or more, preferably 6 mol% or more and 40 mol% or less in 100 mol% of the acid component and / or glycol component. There may be. Furthermore, based on polyethylene terephthalate (PET), a copolymer of dimer acid (PET-D) or a copolymer of polyethylene-2,6-naphthalate (PEN) with isophthalic acid may be used. Further, based on a polyester composed of terephthalic acid as an acid component and ethylene glycol as a glycol component, the acid component and / or the glycol component are each 5 mol% or more, preferably 6 mol% or more and 40 mol% or less of different dicarboxylic acids in 100 mol%. An acid component and / or a glycol component may be copolymerized.

  Specific monomer components include, for example, dicarboxylic acid components such as aromatic dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid, and orthophthalic acid, and aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid. And alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid. Examples of the glycol component include aliphatic diols such as propanediol, butanediol, neopentylglycol, and hexanediol; alicyclic diols such as 1,4-cyclohexanedimethanol, and aromatic diols.

  When the resin component A contains a copolymerized polyester having a trimethylene terephthalate unit, as the unit other than the trimethylene terephthalate unit in the copolymerized polyester, for example, the resin component as a component other than the trimethylene terephthalate unit exemplified above Examples of the unit contained in the resin A include an ethylene terephthalate unit, a butylene terephthalate unit, a pentamethylene terephthalate unit, a hexamethylene terephthalate unit, an ethylene-2,6-naphthalate unit, and the like.

  When the resin component A contains a copolyester having a trimethylene terephthalate unit, the acid component and / or the glycol component are each 5 mol% or more, preferably 6 mol% or more and 40 mol% or less in 100 mol%. It may be a copolymer of a dicarboxylic acid component other than an acid and / or a glycol component other than propanediol. Examples of such other monomer components include dicarboxylic acid components such as aromatic dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid, and orthophthalic acid, and aliphatics such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid. Examples thereof include dicarboxylic acids and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid. Examples of the glycol component include aliphatic diols such as ethylene glycol, butanediol, neopentyl glycol, and hexanediol; alicyclic diols such as 1,4-cyclohexanedimethanol, and aromatic diols.

  The resin component A is a crystalline polyester component having a glass transition temperature measured by DSC of −50 ° C. or more and less than 60 ° C. and a crystal melting heat of 5 (J / g) or more and 100 (J / g) or less. Preferably there is.

  In the present invention, the ethylene terephthalate unit refers to a unit represented by the following formula (2), for example, a unit obtained by reaction of ethylene glycol and terephthalic acid.

  In the present invention, the ethylene isophthalate unit refers to a unit represented by the following formula (3), for example, a unit obtained by reaction of ethylene glycol and isophthalic acid.

  That the resin component B contains an ethylene terephthalate unit and an ethylene isophthalate unit means that the resin component B contains a copolyester having an ethylene terephthalate unit and an ethylene isophthalate unit. Alternatively, the resin component B contains polyethylene terephthalate or contains a copolymer polyester having an ethylene terephthalate unit, and contains a polyester whose repeating unit is only an ethylene isophthalate unit, or a copolymer polyester having an ethylene isophthalate unit. It means including. Among these, the resin component B preferably contains a copolymer polyester having an ethylene terephthalate unit and an ethylene isophthalate unit.

  The resin component B mainly includes an ethylene terephthalate unit and an ethylene isophthalate unit. When the total polyester constituent unit of the resin component B is 100 mol%, the ethylene terephthalate unit and the ethylene isophthalate unit are 60 mol%. This includes the above. The resin component B preferably contains 70 mol% or more of ethylene terephthalate units and ethylene isophthalate units, and more preferably contains 80 mol% or more.

  The resin component B may contain components other than the ethylene terephthalate unit and the ethylene isophthalate unit in 40 mol% or less in 100 mol% of all polyester constituent units. In the case where components other than the ethylene terephthalate unit and the ethylene isophthalate unit are included as a resin separate from the resin containing the ethylene terephthalate unit and / or the ethylene isophthalate unit, Crystalline polyesters such as butylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polypentamethylene terephthalate, polyhexamethylene terephthalate, polyethylene-2,6-naphthalate (PEN) may be used. Moreover, what copolymerized the following dicarboxylic acid component and / or glycol component based on these may be used. For example, polyethylene-2,6-naphthalate (PEN) copolymerized with isophthalic acid may be used. Examples of dicarboxylic acid components include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, orthophthalic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, and 1,4 -An alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid. Examples of the glycol component include aliphatic diols such as propanediol, butanediol, neopentylglycol, and hexanediol; alicyclic diols such as 1,4-cyclohexanedimethanol, and aromatic diols.

  When the resin component B contains a copolymer polyester having an ethylene terephthalate unit and an ethylene isophthalate unit, the copolymer polyester contains 40 mol% or less of units other than the ethylene terephthalate unit and the ethylene isophthalate unit (all polyester constituent units). Examples of the unit include butylene terephthalate unit, trimethylene terephthalate unit, pentamethylene terephthalate unit, hexamethylene terephthalate unit, ethylene-2,6-naphthalate unit, and the like. . In addition, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid and orthophthalic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid, and fats such as 1,4-cyclohexanedicarboxylic acid Any of dicarboxylic acids such as cyclic dicarboxylic acid and dimer acid, and aliphatic diols such as propanediol, butanediol, neopentylglycol and hexanediol; alicyclic diols such as 1,4-cyclohexanedimethanol, and aromatic diol The unit etc. which consist of either of glycols etc. may be sufficient.

  As a ratio of the ethylene terephthalate unit and the ethylene isophthalate unit contained in the resin component B, when the total of the ethylene terephthalate unit and the ethylene isophthalate unit is 100 mol%, the ethylene isophthalate unit is 31 to 49 mol%. It is preferable that it is 35 to 45 mol%.

  The resin component B is preferably based on a polyester composed of terephthalic acid as the acid component and ethylene glycol as the glycol component, based on 31 mol% to 49 mol% (more preferably 35 to 45 mol%) in 100 mol% of the acid component. This is a polyester copolymerized with isophthalic acid. Furthermore, you may have 0-12 mol% of polyester units other than an ethylene terephthalate unit and an ethylene isophthalate unit in 100 mol% of all the polyester structural units. According to the polyester, the heat shrinkage rate in the main shrinkage direction after immersion for 10 seconds in 85 ° C. ± 0.5 ° C. warm water tends to be 50% or more. Will improve.

  The resin component B is substantially amorphous having a glass transition temperature measured by DSC of 60 ° C. or more and 150 ° C. or less and a heat of crystal fusion of 0 (J / g) or more and 3 (J / g) or less. A polyester component is preferred.

  The resin component A and the resin component B need to have different compositions as polyester. This is because suitable properties as a laminated film are not expressed. The resin component A and the resin component B are made by various methods such as changing the types of other ester units of the respective components to different units, or not including a unit derived from dimer acid in the resin component B. The composition of component A and resin component B can be different.

  The resin component A and the resin component B have a difference in glass transition temperature between 3 ° C. and 100 ° C., and a difference in heat of crystal fusion between 5 (J / g) and 100 (J / g). preferable.

  The ratio of the resin component A and the resin component B is preferably 10/90 to 50/50, more preferably 12/88 to 40/60, and even more preferably 15 as the resin component A / resin component B (mass ratio). / 85 to 35/65. Outside this range, the effect of improving label mounting properties and shrink finish is small.

  In the film of the present invention, the resin component A and the resin component B were respectively charged into separate extruders A1 and B1 and melted, and the resin component A and the resin component B were charged into a static mixer in a molten state. It is characterized by having a composition and a structure of a film obtained by producing an unstretched sheet extruded from a T-die and cooled and then stretched at least uniaxially. Hereinafter, “resin component A and resin component B are charged into separate extruders A1 and B1, respectively, and melted. After resin component A and resin component B are charged into a static mixer in a molten state, T− The method for producing the film of the present invention will be described, including a specific explanation of “extending an unstretched sheet formed by extrusion from a die and cooling at least uniaxially”.

  The polyester raw material used in the present invention is dried using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer.

  When the resin component A and the resin component B include two or more kinds of polyester components, the blends may be blended by a chip blend method or a master batch method. It is known that even when two or more kinds of polyester components are blended, there is a strong tendency to transesterify and copolymerize due to the heat history during melt extrusion.

  Resin component A and resin component B are charged into different extruders A1 and B1, respectively, and melted. The melting temperature is not particularly limited as long as it does not cause deterioration or alteration for each resin component. As one index, in the case of a resin component exhibiting crystallinity, the melting point + (5 ° C. to 30 ° C.), and in the case of an amorphous resin component, the softening temperature + (20 ° C. to 150 ° C.).

  The molten resin component A and resin component B are guided to a static mixer in a molten state, and a laminate of an X layer containing the resin component A and a Y layer containing the resin component B is formed. In order to facilitate the charging of the molten resin component A and resin component B into the static mixer, a feed block is installed in front of the static mixer, and once the resin component A and the resin component B are merged with the feed block, You may lead to a static mixer.

The static mixer in the present invention is adjacent to an element having a shape obtained by twisting and bending a horizontally long rectangular plate so that an angle (torsion angle) between its short sides is 45 degrees to 270 degrees. It is the in-pipe mixing device arranged alternately so that the short sides of the elements intersect. When the molten resin passes through one element, the resin is divided into two layers, and each resin layer is twisted in the direction opposite to the turning direction of the element. Further, when passing through the next element, the resin is divided and twisted in the same manner, and divided into four layers. Therefore, when the resin component A and the resin component B are laminated one by one and introduced into the static mixer, theoretically, if the short side of the first element is horizontal to the lamination surface, it passes through n elements. Then the 2 ⁿ layer, but the short side of the first element is 2 ^{n + 1} layer as long perpendicular to the laminated surface, in fact, the flow channel diameters and lengths, twist angles of the element, the torsional gradient, the discharge of the resin The amount may vary due to the influence of melting characteristics such as the viscosity and surface tension of each resin.

  The L / D (pipe length / pipe inner diameter) ratio of the elements of the static mixer is preferably in the range of 1.0 to 3.0, more preferably in the range of 1.4 to 2.0. If the L / D ratio is smaller than 1.0, the resin dividing efficiency is deteriorated, and if it exceeds 3.0, the residence time of the resin passing through the mixer becomes longer, which is not practical.

  The torsion angle of the static mixer element is 45 degrees or more. This is because if the twist angle is less than 45 degrees, the twist of the resin layer becomes insufficient. The twist angle is more preferably 90 degrees or more, and further preferably 135 degrees or more. The upper limit of the twist angle is preferably 315 degrees. If it exceeds 315 degrees, a uniform laminated structure cannot be obtained due to excessive twisting. The twist angle is preferably 270 degrees or less, and more preferably 215 degrees or less. Note that the fact that a uniform laminated structure cannot be obtained means that the laminated structure is disturbed, for example, the laminated layers are wavy.

  Further, when the side surface of the static mixer pipe is cut and developed in the resin traveling direction, the angle formed by the straight line following the joint between the pipe inner wall and the element and the resin traveling direction, that is, the torsional gradient of the element is 27 More than the degree is preferable. If this twist gradient is less than 27 degrees, the twisting effect of the resin layer is small, and the L / D ratio must be increased in order to give a sufficient twist to the resin, which is not practical. The twist gradient is more preferably 38 degrees or more, and further preferably 42 degrees or more. On the other hand, when the torsional gradient exceeds 65 degrees, the turbulent flow of the resin becomes violent and the laminated structure is disturbed. The twist gradient is more preferably 54 degrees or less, and further preferably 50 degrees or less.

  The preferred shape of the elements of the static mixer can be appropriately selected according to the discharge amount and melting characteristics of the resin, and a plurality of elements having different shapes corresponding to changes in the melting characteristics of the resin passing through the static mixer. Can also be used in combination. The most preferred elements have L / D = 1.5, a twist angle of 180 degrees, and a twist gradient of 46 degrees.

  The arrangement of the elements of the static mixer is preferably changed alternately so that the twisting directions of the elements are right turn, left turn, and right turn. This is because a uniform laminated structure can be obtained. It is also preferable to arrange adjacent elements so as to intersect at right angles in order to obtain a uniform laminated structure.

  The number of elements of the static mixer is preferably 4 or more, more preferably 6 or more, and still more preferably 8 or more. The film of the present invention has a laminated structure, and the number of layers is particularly preferably 500 or more as described later. When the number of elements is 8 or more, a laminated structure of 500 or more layers is ensured. Easy to obtain. On the other hand, if the number of elements becomes too large, the laminated structure tends to be disturbed. Therefore, the number of elements is preferably 24 or less, more preferably 18 or less, and even more preferably 14 or less. .

  The structure of the static mixer described above is one typical example, the shape and arrangement are changed without departing from the object of the present invention, and another device is arranged before and after the static mixer and between the elements. Of course, it is possible. For example, two or more rows of static mixers smaller in diameter than the resin pipe may be arranged in parallel in the pipe. Another resin can be joined and laminated on the laminated resin obtained by laminating the resin component A and the resin component B through a static mixer.

  In addition, it is also possible to use a plurality of feed blocks and lead the laminated resin laminated in three or more layers to a static mixer to further increase the number of layers. In this case, the number of elements of the static mixer can be reduced by the number of layers in the feed block, but there is a unique effect of the film (improvement of perforation opening, etc.) caused by the lamination in the static mixer. In order to reduce the number, the number of stacked layers by the feed block is preferably within 100 layers.

  The temperature of the static mixer is set to the melting point + (5 ° C. to 30 ° C.) when the resin component exhibits crystallinity, and the softening temperature + (20 ° C. to 150 ° C.) when the resin component exhibits amorphousness. Most preferably, it is set to the same temperature as the temperature adopted as the melting temperature.

  The laminated body is extruded from a T-die and is brought into close contact with a cooling roll having a surface temperature of 10 to 40 ° C., thereby obtaining an unstretched sheet of the laminated body.

  Next, after preheating the obtained unstretched sheet as necessary at 50 to 120 ° C., preferably 60 to 100 ° C., it is 3.0 times or more by a tenter or the like in the lateral direction (direction perpendicular to the extrusion direction). The film is preferably stretched 3.5 times or more and 15 times or less. The stretching temperature is 60 ° C. or higher and 120 ° C. or lower, preferably 70 ° C. or higher and 100 ° C. or lower. It is not always necessary to perform longitudinal stretching before and after lateral stretching, but longitudinal stretching may be performed as necessary.

  Furthermore, it heat-processes at the temperature of 70-100 degreeC if needed, and obtains a heat-shrinkable polyester-type film. The said film is good also as a film roll by winding up in accordance with a conventional method.

  In addition, the stretching method is not limited to lateral uniaxial stretching with a tenter, but can be additionally stretched in the longitudinal direction and biaxially stretched. Such biaxial stretching may be performed by any of a sequential biaxial stretching method and a simultaneous biaxial stretching method, and may be re-stretched in the longitudinal direction or the transverse direction as necessary.

  In addition, when the film is stretched, if the fluctuation range of the surface temperature of the film is reduced (soaking), the film can be stretched and heat treated at the same temperature over the entire length of the film, and the thickness distribution value and heat shrinkage behavior are uniform. Can be

  The fluctuation range of the surface temperature is preferably such that the temperature at each point when the surface temperature of the film is measured at an arbitrary point is, for example, within the average temperature of the film ± 1 ° C. or less, and the average temperature ± 0.6 It is more preferable that the temperature is within a temperature.

  When stretching a film, since the film is stretched through various processes such as a preheating process before stretching, a stretching process, a heat treatment process after stretching, a relaxation process, and a re-stretching process, some of these processes are performed. Alternatively, it is preferable to use equipment that can reduce (homogenize) the fluctuation range of the surface temperature of the film in total. In particular, in order to make the thickness distribution value uniform over the entire length of the film, the fluctuation range of the surface temperature of the film can be reduced in the preheating step and the stretching step (and in the heat treatment step after stretching if necessary). It is preferable to use equipment. In order to make the thermal contraction rate behavior uniform, it is preferable to use equipment that can reduce the fluctuation range of the surface temperature of the film in the stretching step.

Examples of the equipment that can reduce the fluctuation of the film surface temperature include, for example, equipment equipped with a wind speed control means (such as an inverter) for controlling the supply speed of hot air for heating the film, and stably heating the air. Examples include equipment equipped with heating means for preparing the hot air [heating means using low-pressure steam of 500 kPa or less (5 kgf / cm ² or less) as a heat source].

  In order to achieve the object of the present invention, since the transverse direction is practical as the main shrinkage direction, the above shows an example of a method for producing a film when the principal shrinkage direction is the transverse direction. Even when the main shrinkage direction is the longitudinal direction, a film can be produced according to the operation of the above method except that the stretching direction in the above method is changed by 90 degrees.

  The heat-shrinkable polyester film obtained as described above mainly contains an X layer containing a polyester resin component A mainly containing a trimethylene terephthalate unit, an ethylene terephthalate unit, and a 1,4-cyclohexanedimethylene terephthalate unit. The Y layer containing the polyester resin component B has a structure in which the layers are alternately laminated.

  When the film has such a laminated structure, the resin component A and the resin component B are present independently in the film. Therefore, the resin component that constitutes each layer has individual properties, which contributes to the improvement of shrinkage finish when the film is labeled and attached to the bottle, adhesion to the bottle, and perforation opening. It is thought that.

  In the laminated structure, the outermost layer may be either an X layer or a Y layer.

  The number of X layers and Y layers to be laminated is preferably 500 or more in total, more preferably 1000 to 100,000 layers, and most preferably 2000 to 20,000 layers. It is. When the total of the X layer and the Y layer is 500 layers or more, the perforation openability is particularly excellent.

  In order to measure the number of laminated films, the X-layer and the Y-layer are dyed separately, and then the film cross-section is observed by TEM. However, as the number of layers increases, it becomes difficult to visually count even if the magnification of the TEM image is increased. Therefore, in this case, as will be described in detail later, a method of obtaining the number of layers by clarifying the degree of shading of an image using image analysis software and then digitizing (binarizing) the image is adopted.

The composition of the heat-shrinkable polyester film of the present invention is as follows. The constituent unit of all the polyester in the whole film is 100 mol%, the trimethylene terephthalate unit is 10 to 45 mol%, the ethylene terephthalate unit and the ethylene isophthalate. It is preferable that the unit contains 55 to 90 mol% and 0 to 12 mol% of other units (units other than trimethylene terephthalate unit, ethylene terephthalate unit and ethylene isophthalate unit). The analysis of the content of these units can be performed using, for example, ¹ H-NMR.

  The heat-shrinkable polyester film of the present invention has a hot-water heat shrinkage rate of 30% or more and 90% or less in the main shrinkage direction when treated by immersing in hot water at 85 ° C. ± 0.5 ° C. for 10 seconds in a no-load state. It is preferable that it is 35% or more and 80% or less. If the heat shrinkage rate is less than 30%, there is a possibility that the label cannot be properly attached to the bottle due to insufficient heat shrinkage force. On the other hand, if the thermal shrinkage rate exceeds 90%, there is a possibility that a label jumping phenomenon may occur due to the excessively large shrinkage force of the label when the bottle is placed on a bottle and heated and shrunk.

  In addition, the heat-shrinkable polyester film of the present invention has a hot-water heat shrinkage rate of 10% or more and 50% in the main shrinkage direction when treated by immersing in hot water at 70 ° C. ± 0.5 ° C. for 10 seconds under no load. % Or less is preferable. When the heat shrinkage rate is less than 10%, the shrinkability is insufficient, and the shrinking process needs to be performed at a higher temperature. When the thermal shrinkage rate exceeds 50%, there is a possibility that a label jumping phenomenon occurs due to excessively large shrinkage force of the label when the bottle is placed on the bottle and heated and shrunk.

  Here, the hot water heat shrinkage ratio is obtained by measuring the length of the film before and after the dipping treatment, and the formula of [(length before shrinkage−length after shrinkage) / length before shrinkage] × 100 (%). Is a value obtained by Moreover, the main shrinkage direction means a direction having a high hot water thermal shrinkage rate in the longitudinal direction (longitudinal direction) and the transverse direction (width direction) of the film.

  In addition, when measuring the heat shrinkage rate, in order not to give the film an extra heat history, it is immersed in water at 25 ° C. ± 0.5 ° C. after being immersed in warm water at a predetermined temperature for a predetermined time. The film should be immersed so that it cools.

The heat-shrinkable polyester film used in the present invention preferably has a melting specific resistance value at a temperature of 275 ° C. of 0.70 × 10 ⁸ Ω · cm or less. When such a film is used, as will be described in detail below, the uniformity of the film thickness can be improved, and the printability on the film and the workability when processing the film into a form that can be mounted on a container. (Stable workability) can be improved.

  In the present invention, when the film melt-extruded from the extruder is cooled by a conductive cooling roll (such as a casting roll), an electrode is disposed between the extruder and the casting roll, and the film is interposed between the electrode and the casting roll. It is better to apply a voltage (that is, to apply electricity to the film from the electrode) and to electrostatically adhere the film to the roll. When the melting specific resistance value is reduced, the adhesion between the film and the roll (electrostatic adhesion) ) Can be increased. If the electrostatic adhesion to the roll is low, the thickness of the cast unstretched film becomes non-uniform, and in the stretched film obtained by stretching this unstretched film, the thickness non-uniformity is further expanded. If the electrostatic adhesion is sufficiently high, the stretched film can be made uniform in thickness.

  When the uniformity of the film thickness is increased, color misregistration can be prevented and printability can be improved when multicolor printing in which a plurality of colors are superimposed is applied to the film.

  In addition, when the uniformity of the film thickness is increased, it is easy to superimpose the bonded portions when processing the film into a tube or the like by solvent bonding. In addition, when multicolor printing is performed on the film, wrinkles can be prevented from easily entering the film, and the film can be prevented from meandering during traveling, thereby improving workability (stable workability).

  Further increasing the uniformity of the film thickness can prevent partial differences in winding hardness when the film is wound in a roll shape, causing looseness and wrinkles on the film, greatly impairing the appearance of the film. Can be prevented.

  If the melt specific resistance value is lowered to increase the electrostatic adhesion, not only the uniformity of the film thickness can be increased, but also the productivity of the film can be increased and the appearance of the film can be improved. That is, when the electrostatic adhesion is high, the stability of cooling and solidification of the film can be increased, and the casting speed (production speed) can be increased. Also, if electrostatic adhesion is high, cooling and solidification of the film will be incomplete, and air will enter locally between the roll and the film, preventing pinner bubbles (streaky defects) on the film surface. The film appearance can be enhanced.

The melting specific resistance value is preferably 0.65 × 10 ⁸ Ω · cm or less, more preferably 0.60 × 10 ⁸ Ω · cm or less.

  In order to control the melt specific resistance value within the above range, it is desirable to contain an alkaline earth metal compound and a phosphorus-containing compound in the film. The melting specific resistance value can be lowered only by the alkaline earth metal compound, but the melting specific resistance value can be remarkably lowered by the coexistence of the phosphorus-containing compound. It is not clear why the melting specific resistance value can be remarkably lowered by combining the alkaline earth metal compound and the phosphorus-containing compound. However, the inclusion of the phosphorus-containing compound can reduce the amount of foreign matter and charge carriers. It is estimated that the amount of can be increased.

The content of the alkaline earth metal compound in the film is, for example, 20 ppm (mass basis) or more, preferably 40 ppm (mass basis) or more, more preferably 50 ppm (mass basis), based on the alkaline earth metal atom M ^2. ) Or more, particularly 60 ppm (mass basis) or more. If the amount of the alkaline earth metal compound is too small, the melting specific resistance value cannot be lowered. Note that even if the content of the alkaline earth metal compound is excessively increased, the effect of reducing the melt specific resistance value is saturated, and adverse effects such as generation of foreign substances and coloring are increased. Therefore, the content of the alkaline earth metal compound is, for example, 400 ppm (mass basis) or less, preferably 350 ppm (mass basis) or less, more preferably 300 ppm (mass basis) or less, based on the alkaline earth metal atom M ^2. It is.

  The content of the phosphorus compound in the film is, for example, 5 ppm (mass basis) or more, preferably 20 ppm (mass basis) or more, more preferably 40 ppm (mass basis) or more, particularly 60 ppm (mass) based on the phosphorus atom P. Standard) or more. If the amount of the phosphorus compound is too small, the melting specific resistance cannot be lowered sufficiently, and the amount of foreign matter generated cannot be reduced. Even if the content of the phosphorus compound is increased too much, the effect of reducing the melt specific resistance value is saturated. Furthermore, since the production of diethylene glycol is promoted and it is difficult to control the production amount, the physical properties of the film may be different from those planned. Therefore, the content of the phosphorus compound is, for example, 500 ppm (mass basis) or less, preferably 450 ppm (mass basis) or less, more preferably 400 ppm (mass basis) or less, particularly 350 ppm (mass basis), based on the phosphorus atom P. It is as follows.

When lowering the melt resistivity value of the film with an alkaline earth metal compound and a phosphorus compound, the mass ratio (M ² / P) between the alkaline earth metal atom M ² and the phosphorus atom P in the film is 1.2 or more ( Preferably it is 1.3 or more, more preferably 1.4 or more. By setting the mass ratio (M ² / P) to 1.2 or more, the melt specific resistance value can be significantly reduced. When the mass ratio (M ² / P) exceeds 5.0, the amount of foreign matter generated increases or the film is colored. Therefore, the mass ratio (M ² / P) is 5.0 or less, preferably 4.5 or less, and more preferably 4.0 or less.

  In order to further reduce the melt specific resistance value of the film, it is desirable to contain an alkali metal compound in the film in addition to the alkaline earth metal compound and the phosphorus-containing compound. Alkali metal compounds cannot reduce the melt resistivity even if they are contained alone in the film, but by adding to the coexistence system of alkaline earth metal compounds and phosphorus-containing compounds, the melt resistivity can be significantly reduced. Can do. Although it is not clear about the reason, it is presumed that the melting specific resistance value is lowered by forming a complex of the alkali metal compound, the alkaline earth metal compound, and the phosphorus-containing compound.

The content of the alkali metal compound in the film is, for example, 0 ppm (mass basis) or more, preferably 5 ppm (mass basis) or more, more preferably 6 ppm (mass basis) or more, based on the alkali metal atom M ^1. 7 ppm (mass basis) or more. Even if the content of the alkali metal compound is excessively increased, the effect of reducing the melt specific resistance value is saturated, and further, the amount of foreign matter generated is increased. Therefore, the content of the alkali metal compound is, for example, 100 ppm (mass basis) or less, preferably 90 ppm (mass basis) or less, more preferably 80 ppm (mass basis) or less, based on the alkali metal atom M ¹ .

  Examples of the alkaline earth metal compound include an alkaline earth metal hydroxide, alkoxide, aliphatic carboxylate (acetate, butyrate, etc., preferably acetate), aromatic carboxylate (benzoate), And salts with a compound having a phenolic hydroxyl group (such as a salt with phenol). Examples of the alkaline earth metal include magnesium, calcium, strontium, barium and the like (preferably magnesium). Preferred alkaline earth metal compounds include magnesium hydroxide, magnesium methoxide, magnesium acetate, calcium acetate, strontium acetate, barium acetate and the like, especially magnesium acetate. The alkaline earth metal compounds can be used alone or in combination of two or more.

Examples of the phosphorus compound include phosphoric acids (phosphoric acid, phosphorous acid, hypophosphorous acid, etc.), and esters thereof (alkyl esters, aryl esters, etc.), as well as alkylphosphonic acids, arylphosphonic acids, and esters thereof (alkyl esters). And aryl esters). Preferable phosphorus compounds include phosphoric acid, aliphatic esters of phosphoric acid (phosphoric acid alkyl esters, etc .; for example, phosphoric acid monomethyl ester, phosphoric acid monoethyl ester, phosphoric acid monobutyl ester, phosphoric acid mono C _1-6 Phosphoric acid tri-C ₁ such as alkyl ester, phosphoric acid dimethyl ester, phosphoric acid diethyl ester, phosphoric acid dibutyl ester, phosphoric acid diC _1-6 alkyl ester, phosphoric acid trimethyl ester, phosphoric acid triethyl ester, phosphoric acid tributyl ester _-6 alkyl esters, etc.), aromatic esters of phosphoric acid (such as mono-, di- or tri-C _6-9 aryl esters of phosphoric acid such as triphenyl phosphate, tricresyl phosphate), aliphatic esters of phosphorous acid ( Alkyl esters of phosphorous acid; for example, trimethyl phosphite, tributyl phosphite Mono-, di-, or tri-C _1-6 alkyl esters of phosphorous acid such as, alkyl phosphonic acids (C _1-6 alkyl phosphonic acids such as methyl phosphonic acid, ethyl phosphonic acid), alkyl phosphonic acid alkyl esters (methyl phosphonic acid) dimethyl, a C _1-6 mono- or di-C _1-6 alkyl esters of alkyl phosphonic acid such as ethylphosphonic acid dimethyl), aryl phosphonic acid alkyl ester (phenylphosphonic acid dimethyl, C _6-9 aryl such as phenyl phosphonic acid diethyl Examples include phosphonic acid mono- or di-C _1-6 alkyl esters), arylphosphonic acid aryl esters (such as C _6-9 arylphosphonic acid mono- or di-C _6-9 aryl esters such as phenylphosphonic acid diphenyl), and the like. . Particularly preferred phosphorus compounds include phosphoric acid and trialkyl phosphate (such as trimethyl phosphate). These phosphorus compounds can be used alone or in combination of two or more.

  Examples of the alkali metal compound include alkali metal hydroxide, carbonate, aliphatic carboxylate (acetate, butyrate, etc., preferably acetate), aromatic carboxylate (benzoate), phenolic hydroxyl group And a salt with a compound having a salt (such as a salt with phenol). Examples of the alkali metal include lithium, sodium and potassium (preferably sodium). Preferred alkali metal compounds include lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, lithium acetate, sodium acetate, potassium acetate and the like, especially sodium acetate.

  For the X layer and Y layer, conventionally known additives, for example, organic particles (eg, crosslinked acrylic particles, crosslinked styrene particles, silicone particles), inorganic particles (eg, silica, kaolin, clay, carbonic acid) Calcium, aluminum oxide, barium sulfate, zinc oxide, zinc sulfide, etc.), lubricants, stabilizers, colorants, antioxidants, antifoaming agents, antistatic agents, ultraviolet absorbers, and the like.

  The thickness of the heat-shrinkable polyester film of the present invention is preferably 5 to 100 μm, and more preferably 20 to 50 μm.

  The heat-shrinkable polyester film of the present invention can be labeled by a conventionally known method. As an example, a heat-shrinkable polyester film cut to a desired width is appropriately printed, and the right and left ends of the film are overlapped and bonded together by solvent adhesion or the like to produce a tube film. The tube film is cut into an appropriate length to obtain a tube-shaped label. Alternatively, one opening of this tubular label is joined to form a bag-like label.

  These labels are perforated by a conventional method, and then covered with a plastic bottle. The plastic bottle is placed on a belt conveyor or the like, and steam is blown into a contracting tunnel (steam tunnel) or hot air is blown. Pass the inside of the type of shrinking tunnel (hot air tunnel). The label is attached to a bottle container such as a plastic bottle by the thermal contraction of the label when passing through these tunnels.

  Even when the label is attached and contracted to the bottle in the beverage filling line, that is, when the label is performed at high speed, the occurrence of label shrinkage unevenness, wrinkles or color unevenness is extremely suppressed. Even at low temperatures, the perforation formed on the label is good. For example, a tube label having a folding diameter of 109 mm, a label length of 90 mm, and two perforations provided with holes of 1 mm in length at intervals of 1 mm is provided at 80 ° C. for 2.5 seconds. Prepare a bottle that is heat-shrinked with water vapor and attached to the label, fill the bottle with about 500 mL of water, refrigerate at 5 ° C. for 12 hours, and tear the perforation immediately after removal from the refrigerator with a fingertip to evaluate its opening In this case, it is possible to achieve an unsuccessful opening rate of 20% or less, and it is also possible to achieve an unsuccessful opening rate of 7% or less, further 2% or less.

  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 created in the Example and the comparative example is demonstrated.

(1) Heat shrinkage rate The film was cut into a 10 cm × 10 cm square, and heat-shrinked in 85 ° C. ± 0.5 ° C. or 70 ° C. ± 0.5 ° C. warm water for 10 seconds under no load condition. . The film was immediately immersed in water at 25 ° C. ± 0.5 ° C. for 10 seconds, then the vertical and horizontal dimensions of the film were measured, and the thermal shrinkage rate was determined according to the following formula (1). The direction in which the heat shrinkage rate is large was taken as the main shrinkage direction.
Thermal shrinkage rate = ((length before shrinkage−length after shrinkage) / length before shrinkage) × 100 (%) (1)

(2-1) Number of layers in the film (part 1)
The number of layers inside the film was determined by observation using a transmission electron microscope. First, the film was embedded in an epoxy resin. As the epoxy resin used, a mixture of Luabeck 812, Luavec NMA (manufactured by Nacalai Tesque) and DMP30 (manufactured by TAAB) in a ratio of 100: 89: 3 was used. Next, after embedding the sample film in the above-described mixed resin, the sample film was left in an oven adjusted to a temperature of 60 ° C. for 16 hours to cure the resin and obtain an embedded block.

  The obtained embedding block was attached to an ultra cut N manufactured by Nissan Sangyo Co., Ltd. and an ultrathin section was prepared. First, trimming was performed using a glass knife until a cross section of a portion desired to be observed for the film appeared on the resin surface. Next, an ultrathin section was cut out using a diamond knife (Sumitomo Electric Sumiknife SK2045). The cut sections were collected on a mesh and then stained by standing in a ruthenium tetroxide vapor for 30 minutes at room temperature, followed by thin carbon deposition.

  The electron microscope observation was performed using JEM-2010 manufactured by JEOL under the condition of an acceleration voltage of 200 kV. The obtained image was recorded on an imaging plate (“FDL UR-V” manufactured by Fuji Photo Film Co., Ltd.) The signal recorded on the imaging plate was read out using digital luminography (“Pixsys TEM” manufactured by JEOL Ltd.), and Windows Recorded as digital image information on a (registered trademark) personal computer, and the number of layers confirmed from the difference in dyeing degree between the X layer and the Y layer was counted.

(2-2) Number of layers inside the film (part 2)
The number of layers inside the film was determined by observation using a transmission electron microscope (TEM). First, the film was embedded in an epoxy resin. As the epoxy resin used, Luabeck 812, Luavec NMA (manufactured by Nacalai Tesque), and DMP30 (manufactured by TAAB) were mixed well at a ratio (mass) of 100: 89: 3, respectively. Next, after embedding the sample film in the above-described mixed resin, the sample film was left in an oven adjusted to a temperature of 60 ° C. for 16 hours to cure the resin and obtain an embedded block.

  The resin was cut with respect to the embedded block using a glass knife until the cross section of the film portion appeared on the block surface (surface exposure). The embedding block after the surface exposure was put in a vessel sealed with ruthenium chloride vapor for 3 days to carry out ruthenium staining. Ruthenium chloride vapor was replaced with fresh vapor every day.

  A number of ultrathin sections having a thickness of about 700 mm with a microtome were cut from the surface of the embedded block to about 1.5 μm from the surface of the embedded block. The ultra-thin slice with the clearest contrast was selected and subjected to carbon deposition to obtain a sample for TEM observation.

  The electron microscope observation was performed using JEM-2010 manufactured by JEOL Ltd. under the condition of an acceleration voltage of 200 kV. The obtained image was recorded on an imaging plate (“FDL UR-V” manufactured by Fuji Photo Film Co., Ltd.). The signal recorded on the imaging plate was read out using digital luminography (“Pixsys TEM” manufactured by JEOL Ltd.) and recorded as digital image information on a Windows (registered trademark) personal computer. The magnification was appropriately selected from 5000 to 20000 times.

  The image information was analyzed using image analysis software (Scion Image Alpha 4.0.3.2; manufactured by Scion Corporation). First, preliminary confirmation was performed before confirming the detailed number of layers. The preliminary confirmation was performed as follows.

1. The color density in the film thickness direction was quantified by a line profile. Specifically, the density of 100 pixels in width and 3000 pixels in length (the number of pixels can be changed arbitrarily) is read, and the curve is drawn with the horizontal axis as the pixel in the length direction and the vertical axis as the signal intensity (darkness). And graphed.

2. Since there are many peaks in the curve in the graph, for one peak, the number of pixels at the position where the maximum value exists and the number of pixels at the position where the minimum value exists are read, and the difference d (peak width) About half) was considered the thickness of the layer. About 30 peaks, d was calculated _| required and average value _dav was calculated.

3. The average value d _av was converted into nm units, and when the converted value was 100 nm or more, the number of layers was counted visually from the TEM image on the imaging plate. In the conversion, when the TEM image is 5000 times, one pixel is 5 nm, and when it is 20,000 times, one pixel is 1.25 nm.

4). When d _av (nm) after the above conversion was less than 100 nm, the following detailed layer number confirmation method was adopted to determine the number of layers.

  A detailed method for confirming the number of layers was performed as follows.

1. About the said TEM observation image, the correction process with the noise and the unevenness of the shade of an image was performed. First, the image was captured using image analysis software (L Process ver. 1.96; manufactured by FUJIFILM Science Lab99) (FIG. 1). With the setting of the image selector tool set to 2 ⁿ , Fourier transform (FFT) was performed in the maximum image range (2048 × 2048 pixels, but can be arbitrarily specified) (FIG. 2). In FIG. 1, the center of the figure is determined, and the layer direction (stripe direction) is taken as the X axis, and the direction perpendicular to the direction is taken as the Y axis. In FIG. 2, the center of FIG. 1 and the center of FIG. 2 (X = Y =), such that a collection of white bright spots is along the Y axis (in the figure, horizontal and vertical lines are visible, this is noise). (X, Y) = (100 pixels, +2.5 pixels), (X, Y) = (− 100 pixels, +2.5 pixels), (X, Y) = (100 pixels) , +1020 pixels), (X, Y) = (− 100 pixels, +1020 pixels), a rectangle having four vertices is drawn. In this image analysis software, when the first rectangle is drawn, a rectangle that is line-symmetric with respect to the X axis is automatically drawn. That is, (X, Y) = (100 pixels, −2.5 pixels), (X, Y) = (− 100 pixels, −2.5 pixels), (X, Y) = (100 pixels, −1020 pixels) ), (X, Y) = (− 100 pixels, −1020 pixels) is a rectangle having four vertices. White bright spots other than those enclosed by these two rectangles are treated as noise. Note that the position and size of the rectangle described above are numerical values derived empirically in order to remove noise. Only the part enclosed by the two rectangles was subjected to inverse Fourier transform (IFFT), and the obtained image was saved in TIFF format (16 bits) (FIG. 3).

  2. The image after the inverse Fourier transform was read into image analysis software (Scion Image Alpha 4.0.3.2; manufactured by Scion Corporation), and the density of the image was clarified by the Threshold function and changed to the BMP format (FIG. 4). (End of correction process)

  3. In this BMP format image, using the Profile Plot function, a line profile that is as long as possible (about 2000 to 2500 pixels) parallel to the Y axis is taken with a plot width of 1 pixel, so that the density of the film cross-sectional image is binarized. And saved in Plot Value format.

  4). This Plot Value format data was read into Microsoft Excel (registered trademark), and an average value (Av) of all data for each pixel of a line parallel to the Y axis was obtained. Next, when the data of a certain pixel is larger than the average value (Av), the judgment value +1 is given to the pixel, and otherwise, the judgment value -1 is given to the pixel. When the judgment value of each pixel is plotted with respect to the pixel (horizontal axis), the obtained graph is a horizontal straight line connecting +1 and +1 (or -1 and -1), +1 and -1 (or vice versa). It became a line consisting of diagonal straight lines connecting The number of diagonal lines was determined as the number of layers.

The number of layers obtained by the above method may be smaller than the 2 ⁿ layer or 2 ^{n + 1} layer theoretically obtained from the number n of elements of the static mixer. The polyester resin component A constituting the X layer and the polyester resin component B constituting the Y layer have different resin compositions, but the transesterification occurs at the interface between adjacent layers during the lamination process, and the X layer and the Y layer. A polyester having the same composition may be formed in the vicinity of the interface. For example, if the number of layers is increased and the thickness of one layer is reduced to a level of several nanometers, it is identified that a part of the X layer and the Y layer are layers of the same polyester composition. It is considered to be smaller than the theoretical value when the confirmation method is adopted.

(3) Shrinkage Finishing Evaluation Three-color printing was performed on a heat-shrinkable film in advance with grass, gold, and white ink from Toyo Ink Manufacturing Co., Ltd. A tube-shaped label was prepared by adhering both ends of the printed film with 1,3-dioxolane. The label size was a folding diameter of 109 mm and a label length of 90 mm.

Using a steam tunnel (model: SH-1500-L) manufactured by Fuji Astec Inc., spraying water vapor with a passage time of 2.5 seconds and a zone temperature of 80 ° C. (indication) with a vapor pressure of 1 kgf / cm ² (pressure gauge indication: 98 kPa). The label was heat-shrinked and attached to a 500 mL PET bottle (round shape, trunk diameter 62 mm, minimum neck diameter 25 mm). At this time, a portion (shoulder portion) having a diameter of about 40 mm was set to one end of the label. Evaluation was made visually and the criteria were as follows.

Neither wrinkles, jumping up nor under-shrinkage occurs and no color unevenness is seen: ◎
Although wrinkles, jumping up, or insufficient shrinkage cannot be confirmed, color unevenness is slightly observed: ○
Neither jumping up nor insufficient shrinkage has occurred, but unevenness in the neck is seen:
Wrinkles, jumping up, insufficient shrinkage occurred: ×

(4) Evaluation of label adhesion When the label mounted on the condition (3) and the PET bottle were lightly twisted, the label was evaluated as “O” if it did not move, and “X” if it slipped through and the label and the bottle shifted.

(5) Perforation openability test Three colors were printed on a heat-shrinkable film in advance with grass, gold, and white ink from Toyo Ink Mfg. Co., Ltd. A tube-shaped label was prepared by adhering both ends of the printed film with 1,3-dioxolane. The label size was a folding diameter of 109 mm and a label length of 90 mm.

The label was perforated in a direction perpendicular to the main shrinkage direction of the label. Two sheets of cardboard with a thickness of 1 mm are placed under the folded label, and a sewing machine blade (a blade with a total length of 100 mm with 1 mm pitch blades spaced at 1 mm intervals) is placed on a test sealer (made by Seibu Kikai Co., Ltd.). Attach and press the sewing machine blade to the label with a gauge pressure of 2 kgf / cm ² , and put a perforation parallel to the label edge at a position 5 mm from the edge of the folded label. The label was provided with two perforations provided with holes of 1 mm in length at intervals of 1 mm over the entire length of the label, and the interval between the two perforations was 10 mm.

Using a steam tunnel (model: SH-1500-L) manufactured by Fuji Astec Inc., spraying water vapor with a passage time of 2.5 seconds and a zone temperature of 80 ° C. (indication) with a vapor pressure of 1 kgf / cm ² (pressure gauge indication: 98 kPa). The label was heat-shrinked and attached to a 500 mL PET bottle (round shape, trunk diameter 62 mm, minimum neck diameter 25 mm). At this time, a portion (shoulder portion) having a diameter of about 40 mm was set to one end of the label.

  After that, this bottle is filled with about 500 mL of water, refrigerated at 5 ° C. for 12 hours, tearing the perforation of the label on the bottle immediately after taking it out of the refrigerator with a fingertip, and tearing it off vertically to remove the label from the bottle I counted the number of completed. The ratio of the bottles that could not tear the label cleanly for all 50 samples was shown as the perforation failure rate (%).

(6) Thermal analysis of polyester component Thermal analysis of the polyester component was performed using a DSC apparatus (model: DSC220) manufactured by Seiko Denshi Kogyo Co., Ltd. 10 ± 1 mg each of the chip synthesized in the synthesis example described later or the obtained film was used as a sample, this sample was heated at 300 ° C. for 2 minutes, immediately put in liquid nitrogen and rapidly cooled, and then the temperature was −40 ° C. to 300 ° C. The temperature was raised at a rate of 20 ° C./min until the heat flow rate curve (DSC curve) was measured. The intersection of tangent lines drawn before and after the endothermic start curve in the DSC curve was defined as the glass transition temperature (Tg). The temperature showing the maximum value of the endothermic peak in the DSC curve was defined as the melting temperature (Tm). The integrated value of the endothermic peak of the DSC curve was defined as the heat of fusion (Hm). The results are shown in Table 1.

(7) NMR analysis of polyester film Each sample was dissolved in 10: 1 (volume ratio) of chloroform D (manufactured by Yurisop) and trifluoroacetic acid D1 (manufactured by Yurisopp) to prepare a sample solution. Then, 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 number of times of 64 times. In NMR measurement, the peak intensity of a predetermined proton was calculated, and the chip composition and film composition were determined in mol%.

Synthesis Example 1 (Synthesis of polyester)
In an esterification reactor, 34222 parts by mass of terephthalic acid (TPA), 22814 parts by mass of isophthalic acid (IPA), 46868 parts by mass of ethylene glycol (EG), 20.7 parts of antimony trioxide (polymerization catalyst), 5 0.0 parts by mass of sodium acetate (alkali metal compound) and 26.6 parts by mass of trimethyl phosphate (phosphorus compound) were charged, and the inside of the container was pressurized to 0.25 MPa (2.5 kg / cm ² ) with nitrogen. The mixture was heated with stirring, and the esterification reaction was performed at an internal temperature of 220 to 240 ° C. for 120 minutes. The pressure inside the reaction vessel was restored to normal pressure, 60.0 parts by mass of magnesium acetate tetrahydrate (alkaline earth metal compound) was added, and the mixture was stirred at 240 ° C. for 10 minutes, and then pressure 1.33 hPa over 75 minutes. The pressure was reduced to 280 ° C. and the polycondensation was performed. Stirring was continued until the melt viscosity reached 4500 poise at 280 ° C. (about 70 minutes), the polycondensation reaction was terminated, and the polymer obtained under nitrogen pressure was discharged into water in the form of a strand. Polyester chip B was obtained by cutting the discharged material with a strand cutter. The intrinsic viscosity of the polyester chip B was 0.69 dl / g.

Synthesis example 2
A polyester raw material chip A having the chip composition shown in Table 1 was obtained in the same manner as in Synthesis Example 1. In the table, PD is an abbreviation for 1,3-propanediol and DEG is diethylene glycol. The intrinsic viscosity of the polyester chip A was 0.92 dl / g.

  The intrinsic viscosity was precisely weighed with 0.1 g of a chip, dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane = 3/2 (mass ratio), and then measured with an Ostwald viscometer at 30 ± 0.1 ° C. . The intrinsic viscosity [η] is obtained by the following formula (Huggins formula).

Here, η _sp : specific viscosity, t ₀ : solvent dropping time using Ostwald viscometer, t: chip solution dropping time using Ostwald viscometer, and C: concentration of chip solution. In the actual measurement, the intrinsic viscosity was calculated by the following approximate equation where k = 0.375 in the Huggins equation.

Here, η _{r is the} relative viscosity.

Example 1
Polyester chips A and B obtained in the above synthesis examples were separately preliminarily dried. The polyester chip A was put into the extruder A1 and melted at 255 ° C. ± 2 ° C. On the other hand, the polyester chip B was put into the extruder B1 and melted at 280 ° C. ± 2 ° C. The resin melted by both extruders is led to a feed block of 265 ° C. ± 2 ° C. so that the resin ratio is A / B = 15/85 (mass ratio), and further, a static mixer (265 ° C. ± 2 ° C.) Noritake Co., Ltd., 12 elements, inner diameter 38.4 mm, 1 element L / D = 1.5, 1 element plate twist angle 180 degrees, twist gradient 46 degrees). Subsequently, it led to the T-die of 265 degreeC +/- 2 degreeC, and melt-extruded. The extruded resin was electrostatically adhered onto a cooling roll having a surface temperature of 20 ° C. ± 2 ° C. to obtain an unstretched sheet. The unstretched sheet had a Tg of 65 ° C.

  The unstretched sheet was preheated at 82 ° C. for 24 seconds in the tenter, and then stretched 4.8 times at 77 ° C. in the transverse direction, followed by heat treatment at 70 ° C. for 24 seconds. A polyester film was obtained.

Example 2
A heat-shrinkable polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the resin ratio was changed to A / B = 20/80 (mass ratio).

Example 3
A heat-shrinkable polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the resin ratio was changed to A / B = 30/70 (mass ratio).

Comparative Example 1
Polyester chip A and polyester chip B are put into a single extruder C1 and melted so that the resin ratio becomes A / B = 20/80 (mass ratio) (melting temperature 280 ° C. ± 2 ° C.) A heat-shrinkable polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that a static mixer was not used and the temperature of the T-die was 280 ° C. ± 2 ° C. to obtain an unstretched sheet. It was.

  Tables 2 and 3 show the evaluation results of the films obtained in Examples 1 to 3 and Comparative Example 1. The number of layers in each example was determined by adopting the detailed method for confirming the number of layers in (2-2) above (the same applies to Examples 4 and later).

(In Table 3, TPA represents a unit derived from terephthalic acid, IPA represents a unit derived from isophthalic acid, EG represents a unit derived from ethylene glycol, PD represents a unit derived from 1,3-propanediol, and DEG represents a unit derived from diethylene glycol. TT represents a trimethylene terephthalate unit, ET represents an ethylene terephthalate unit, EI represents an ethylene isophthalate unit, and ET + EI represents the total amount of both.)

Synthesis example 3
Polyester raw material chips C and D having the chip composition shown in Table 4 were obtained in the same manner as in Synthesis Example 1. In the table, NPG is neopentyl glycol. The intrinsic viscosity of chip C was 0.75 dl / g, and the intrinsic viscosity of chip D was 1.20 dl / g.

Example 4
Polyester chips A and B obtained in the above synthesis examples were separately preliminarily dried. Polyester chip A and polyester chip B were charged into extruder A1 so that the resin ratio was A / B = 80/20 (mass ratio), and melted at 255 ° C. ± 2 ° C. On the other hand, only the polyester chip B was put into the extruder B1 and melted at 280 ° C. ± 2 ° C. The resin melted by both extruders is guided to a feed block at 265 ° C ± 2 ° C so that the discharge ratio is A1 / B1 = 20/80 (mass ratio), and further, a static mixer at 265 ° C ± 2 ° C (Noritake Company, 12 elements, inner diameter 38.4 mm, 1 element L / D = 1.5, 1 element plate twist angle 180 degrees, twist gradient 46 degrees). Subsequently, it led to the T-die of 265 degreeC +/- 2 degreeC, and melt-extruded. The extruded resin was electrostatically adhered onto a cooling roll having a surface temperature of 20 ° C. ± 2 ° C., and an unstretched sheet was obtained. The unstretched sheet had a Tg of 65 ° C.

  The unstretched sheet was preheated at 82 ° C. for 24 seconds in the tenter, and then stretched 4.8 times at 77 ° C. in the transverse direction, followed by heat treatment at 70 ° C. for 24 seconds. A polyester film was obtained.

Example 5
The same method as in Example 4 except that polyester chip B and polyester chip C, which had been pre-dried, were added to extruder B1 so that the resin ratio was B / C = 80/20 (mass ratio). Thus, a heat-shrinkable polyester film having a thickness of 50 μm was obtained.

Example 6
The same method as in Example 4 except that polyester chip B and polyester chip C, which had been pre-dried, were added to extruder B1 so that the resin ratio was B / C = 60/40 (mass ratio). Thus, a heat-shrinkable polyester film having a thickness of 50 μm was obtained.

  The evaluation results of the films obtained in Examples 4 to 6 are shown in Tables 5 and 6.

(In Table 6, TPA, IPA, EG, PD, DEG, TT, ET + EI have the same meaning as in Table 3, NPG is a unit derived from neopentyl glycol, NPG-T is a unit derived from neopentyl glycol and a unit derived from ethylene glycol. Indicates a unit consisting of

Example 7
Polyester chips A, B and D obtained in the above synthesis examples were separately pre-dried. Polyester chip A and polyester chip D were introduced into extruder A1 so that the resin ratio was A / B = 80/20 (mass ratio) and melted at 255 ° C. ± 2 ° C. On the other hand, only the polyester chip B was put into the extruder B1 and melted at 280 ° C. ± 2 ° C. The resin melted by both extruders is guided to a feed block at 265 ° C ± 2 ° C so that the discharge ratio is A1 / B1 = 20/80 (mass ratio), and further, a static mixer at 265 ° C ± 2 ° C (Noritake Company, 12 elements, inner diameter 38.4 mm, 1 element L / D = 1.5, 1 element plate twist angle 180 degrees, twist gradient 46 degrees). Subsequently, it led to the T-die of 265 degreeC +/- 2 degreeC, and melt-extruded. The extruded resin was electrostatically adhered onto a cooling roll having a surface temperature of 20 ° C. ± 2 ° C., and an unstretched sheet was obtained. The Tg of this unstretched sheet was 60 ° C.

  The unstretched sheet was preheated at 82 ° C. for 24 seconds in the tenter, and then stretched 4.8 times at 77 ° C. in the transverse direction, followed by heat treatment at 70 ° C. for 24 seconds. A polyester film was obtained.

Example 8
A heat-shrinkable polyester film having a thickness of 50 μm was obtained in the same manner as in Example 7 except that the resin ratio of the extruder A1 was changed to A / D = 70/30 (mass ratio).

Example 9
A heat-shrinkable polyester film having a thickness of 50 μm was obtained in the same manner as in Example 7 except that the resin ratio of the extruder A1 was changed to A / D = 60/40 (mass ratio).

  The evaluation results of the films obtained in Examples 7 to 9 are shown in Tables 7 and 8.

(In Table 8, TPA, IPA, EG, PD, DEG, TT, ET + EI have the same meaning as in Table 3, BD represents a unit derived from 1,4-butanediol, and BT represents a butylene terephthalate unit unit.)

  The heat-shrinkable polyester film of the present invention is suitable for labels for bottles such as PET bottles and glass bottles.

It is the TEM photograph of the film taken in into image analysis software. It is an image after the Fourier transform of FIG. 3 is an image after the inverse Fourier transform of FIG. It is an image after clarifying the shading of FIG.

Claims (7)

  A polyester resin component A mainly containing trimethylene terephthalate units and a polyester resin component B mainly containing ethylene terephthalate units and ethylene isophthalate units are charged into separate extruders A1 and B1, respectively, and melted. A heat-shrinkable polyester film obtained by putting resin component A and resin component B into a static mixer as they are, and then extruding from a T-die and cooling to stretch at least uniaxially.   Layers of X containing polyester resin component A mainly containing trimethylene terephthalate units and Y layers containing polyester resin component B mainly containing ethylene terephthalate units and ethylene isophthalate units are alternately laminated in total of 500 layers or more. Heat-shrinkable polyester film having a structured structure.   In the film, the composition unit of all the polyester of the whole film is 100 mol%, trimethylene terephthalate unit is 10 to 45 mol%, ethylene terephthalate unit and ethylene isophthalate unit are 55 to 90 mol%, other polyester units The heat-shrinkable polyester film according to claim 1, wherein 0 to 12 mol% is contained in total.   The thermal shrinkage rate in the main shrinkage direction after immersion for 10 seconds in warm water of 85 ° C. ± 0.5 ° C. is 35% or more and 80% or less, and after immersion in warm water of 70 ° C. ± 0.5 ° C. for 10 seconds. The heat-shrinkable polyester film according to any one of claims 1 to 3, wherein the heat shrinkage rate in the main shrinkage direction is 10% or more and 50% or less.   The resin component A is a crystalline polyester having a glass transition temperature measured by DSC of −50 ° C. or more and less than 60 ° C. and a crystal melting heat of 5 (J / g) or more and 100 (J / g) or less, The resin component B is substantially amorphous having a glass transition temperature measured by DSC of 60 ° C. or more and 150 ° C. or less and a heat of crystal fusion of 0 (J / g) or more and 3 (J / g) or less. It is polyester, The heat-shrinkable polyester film in any one of Claims 1-4. In the film, the alkaline earth metal compound is contained in an amount of 20 ppm (mass basis, the same shall apply hereinafter) to 400 ppm based on the alkaline earth metal atom M ² , and the phosphorus compound is contained in an amount of 5 ppm to 500 ppm based on the phosphorus atom P. The heat-shrinkable polyester film according to any one of claims 1 to 5.   The label for bottles using the heat-shrinkable polyester-type film in any one of Claims 1-6.