JP2008189781A - Thermally shrinkable polyester-based film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermally shrinkable polyester-based film which is used for labels and extremely little form wrinkles, shrinkage unevenness and strains due to shrinkage. <P>SOLUTION: This thermally shrinkable polyester-based film is obtained by charging and melting a polyester resin component A comprising butylene terephthalate units and other ester units and a polyester resin component B consisting mainly of ethylene terephthalate units and neopentyl terephthalate units and having a polyester composition different from that of the polyester resin component A 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 label applications. More specifically, the present invention relates to a heat-shrinkable polyester-based film that has very few wrinkles, shrinkage spots, and distortion due to heat shrinkage, has good perforation cutability, and has a sufficient label strength against impact.

  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, with polystyrene, there are problems such as difficulty in printing on polystyrene films. 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 recent years, cases in which heat-shrinkable polyester films are used for glass bottles for the purpose of preventing broken bottles and decorating the bottles are increasing. Among them, in particular, from the viewpoint of hygiene and safety, it may be used as a full bottle label that is used by attaching a label to the entire glass bottle, which may cause a problem in shrink finish. In particular, the type of the heat-shrinkable polyester-based heat-shrinkable film, which has a gentle shoulder inclination, may cause wrinkles, jumping, and uneven color after shrinkage at the shoulder of the bottle. Further, 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, label mounting and shrinking are fast, and the shrinking time is short. Therefore, the heat-shrinkable film requires a film that can withstand high-speed mounting and a shrinkage performance that provides a high shrinkage rate in a short time.

  Thus, in the case of full-bottle label use and further high-speed mounting, the performance of conventional polyester heat-shrinkable films has been insufficient.

  In addition, there are cases where the perforation for opening is provided on the label, but when the product is a glass bottle for beverages, it is usually refrigerated, and since the temperature is low when the label is opened, there is a problem that poor opening is likely to occur. is there. In order to improve it, there is one in which the temperature condition at the time of stretching is devised (for example, see Patent Document 1).

However, as a result, the degree of improvement in perforation opening is not sufficient, and the shrinkage rate that can be said to be a feature of the conventional polyester-based shrink film may be too fast or the maximum shrinkage may be too high. When a label is applied to the inclined portion of the PET bottle, particularly at an inclined part, shrinkage unevenness, wrinkles or color unevenness may occur when the label is attached at a high speed.

In addition, there is one that attempts to improve unevenness at the time of wearing by relatively reducing the contraction speed (see, for example, Patent Documents 2, 3, and 4). However, these have been problematic in that the perforation openability has not been improved.
JP 2003-268131 A JP-A-6-320621 JP-A-8-27285 JP-A-8-25477

  The present invention solves the above-mentioned problems, and the object of the present invention is that the occurrence of wrinkles, shrinkage unevenness and distortion due to shrinkage is extremely small, the perforation opening property is good, and the label adheres to the bottle. Relates to a sufficiently heat-shrinkable polyester film.

  The heat-shrinkable polyester film of the present invention capable of achieving the above object mainly comprises a polyester resin component A comprising a butylene terephthalate unit and other ester units, an ethylene terephthalate unit and neopentyl terephthalate, and a polyester resin component. A and a polyester resin component B having a different polyester composition from A are respectively charged in separate extruders A1 and B1 and melted. After the resin component A and the resin component B are charged into a static mixer in a molten state, T -It has a gist that it is obtained by stretching an unstretched sheet formed by extruding from a die and cooling at least 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 composed of a butylene terephthalate unit and other ester units, an ethylene terephthalate unit, and neopentyl terephthalate. And the Y layer containing the polyester resin component B having a polyester composition different from that of the polyester resin component A has a gist in that it has a structure in which 500 layers or more are alternately laminated.

  The heat-shrinkable polyester film is composed of 100% by mole of the total polyester constituent unit in the film, 10 to 45% by mole of butylene terephthalate unit, and 55 units of ethylene terephthalate unit and neopentyl terephthalate unit. It is preferable that -90 mol% and 0-12 mol% of other ester units are contained. In addition, when the other ester unit in the resin component A is neopentyl terephthalate, the other ester unit can be 0%.

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, the above heat-shrinkable polyester film contains 20 ppm (mass basis, the same shall apply hereinafter) of an alkaline earth metal compound based on the alkaline earth metal atom M ² to 400 ppm or less, and a phosphorus compound containing phosphorus. It is preferable to contain 5 ppm or more and 500 ppm or less based on the atom P.

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

  The heat-shrinkable polyester film of the present invention exhibits a beautiful shrink finish with very little wrinkling, shrinkage unevenness and distortion due to shrinkage, good perforation openability, and sufficient adhesion to the bottle of the label It has excellent practical characteristics.

  The present invention includes a polyester resin component A composed of a butylene terephthalate unit and other ester units, a polyester resin component B containing an ethylene terephthalate unit and neopentyl terephthalate, and having a polyester composition different from that of the polyester resin component A. 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 an unstretched sheet at least. It is a heat-shrinkable polyester film obtained by stretching uniaxially.

  In the present invention, butylene terephthalate refers to a unit represented by the following formula (1), for example, a unit obtained by reaction of 1,4-butanediol and terephthalic acid.

  The other ester units in the resin component A are ester units other than the butylene terephthalate unit. Specific examples include crystalline units such as ethylene terephthalate units, trimethylene terephthalate units, pentamethylene terephthalate units, hexamethylene terephthalate units, and ethylene-2,6-naphthalate units. Also, units other than the above, 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, 1, Any of alicyclic dicarboxylic acid such as 4-cyclohexanedicarboxylic acid, dicarboxylic acid such as dimer acid, and aliphatic diol such as ethylene glycol, propanediol, butanediol, neopentylglycol, hexanediol; 1,4-cyclohexanedi Examples thereof include units composed of any of alicyclic diols such as methanol and glycols such as aromatic diols. Other ester units may be not only one type but also two or more types. The other ester unit may be either a crystalline unit such as a trimethylene terephthalate unit or an amorphous unit such as a neopentyl terephthalate unit.

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

  The resin component A may be a mixture of polybutylene terephthalate and (co) polyester of other ester units, or may be a copolyester having a butylene terephthalate unit and other ester units. And a mixture of copolyester.

  For example, when the polyester having the other ester unit is included as a polyester different from the polyester including the butylene terephthalate unit, examples thereof include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), poly Examples thereof include crystalline polyesters such as pentamethylene terephthalate, polyhexamethylene terephthalate, and polyethylene-2,6-naphthalate (PEN). Further, based on these and polyethylene terephthalate, 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. It may be what you did. 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.

  Specific monomer components include, for example, dicarboxylic acid components such as terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, orthophthalic acid and other aromatic dicarboxylic acids, adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, and the like. 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.

  In the resin component A, it is preferable to contain 60 mol% or more of butylene terephthalate units. More preferably, it is 70 mol% or more, More preferably, it is 80 mol% or more. Therefore, other ester units are preferably 40 mol% or less.

  When the resin component A includes a copolymer polyester having a butylene terephthalate unit, the unit other than the butylene terephthalate unit in the copolymer polyester includes, for example, the resin component A as a component other than the butylene terephthalate unit exemplified above. Units (eg, ethylene terephthalate unit, trimethylene terephthalate unit, pentamethylene terephthalate unit, hexamethylene terephthalate unit, ethylene-2,6-naphthalate unit, etc.).

  Further, when the resin component A contains a copolymerized polyester having a butylene 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%. A dicarboxylic acid component other than the above and / or a glycol component other than butanediol may be copolymerized. 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, propanediol, 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 contained in the resin component B 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 neopentyl terephthalate unit refers to a unit represented by the following formula (3), for example, reaction of neopentyl glycol (2,2-dimethyl-1,3-propanediol) with terephthalic acid. It is a unit obtained by.

  That the resin component B contains an ethylene terephthalate unit and a neopentyl terephthalate unit means that the resin component B contains a copolyester having an ethylene terephthalate unit and a neopentyl terephthalate 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 a neopentyl terephthalate unit, or a copolymer polyester having a neopentyl terephthalate unit It means including. Of these, the resin component B preferably contains a copolymer polyester having an ethylene terephthalate unit and a neopentyl terephthalate unit.

  The resin component B mainly includes an ethylene terephthalate unit and a neopentyl terephthalate unit. When the total polyester constituent unit of the resin component B is 100 mol%, the ethylene terephthalate unit and the neopentyl terephthalate unit are 60 mol%. This includes the above. The resin component B preferably contains 70 mol% or more of ethylene terephthalate unit and neopentyl terephthalate unit, and more preferably contains 80 mol% or more. According to the resin component B containing 60 mol% or more of an ethylene terephthalate unit and a neopentyl terephthalate unit, the resulting film has a thermal shrinkage rate in the main shrinkage direction after being immersed in 85 ° C ± 0.5 ° C warm water for 10 seconds. It tends to be 50% or more, and when it is labeled, the adhesion to the bottle is improved.

  The resin component B may contain components other than the ethylene terephthalate unit and the neopentyl terephthalate unit in 40 mol% or less in 100 mol% of all the polyester constituent units. When components other than the ethylene terephthalate unit and the neopentyl terephthalate unit are included as a resin separate from the resin containing the ethylene terephthalate unit and / or the neopentyl terephthalate unit, examples thereof include polybutylene terephthalate (PBT), Crystalline polyesters such as 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 isophthalic acid, naphthalenedicarboxylic acid, orthophthalic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. And alicyclic dicarboxylic acids such as acids. Examples of the glycol component include aliphatic diols such as propanediol, butanediol, 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 a neopentyl terephthalate unit, the copolymer polyester contains 40 mol% or less of units other than the ethylene terephthalate unit and the neopentyl terephthalate unit (all polyester constituent units). The unit may be included in a range of 100 mol%, and 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. Is mentioned. Also, aromatic dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid and orthophthalic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid, and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid Any of dicarboxylic acids such as acid and dimer acid, aliphatic diols such as propanediol, butanediol, neopentyl glycol, hexanediol; alicyclic diols such as 1,4-cyclohexanedimethanol, glycols such as aromatic diol It may be a unit comprising any of the above.

  As a ratio of the ethylene terephthalate unit and neopentyl terephthalate unit contained in the resin component B, when the total of the ethylene terephthalate unit and neopentyl terephthalate unit is 100 mol%, the neopentyl terephthalate unit is 7 to 35 mol%. Preferably there is.

  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 B is preferably a polyester obtained by copolymerizing neopentyl glycol of 7 mol% or more and 35 mol% or less in 100 mol% of a glycol component based on a polyester composed of terephthalic acid as an acid component and ethylene glycol as a glycol component. Furthermore, 0-100 mol% of units other than the unit consisting of ethylene terephthalate unit, neopentyl glycol, and ethylene glycol may be included in 100 mol% of all polyester constituent units.

  As long as the polyesters A and B used as raw materials have different thermal characteristics, the polyesters can be selected in any combination so as to meet the object of the present invention. Polyesters A and B used as raw materials are homopolymers and copolymer polyesters, and can be used as raw material polyesters that have the glass transition temperature and the heat of crystal melting as a result of blending two or more arbitrary polyesters. It is also possible to do.

  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 different in the types of other ester units of the respective components, or the resin component B is not included in the resin component B by various methods such as not including a polybutylene terephthalate unit. And the resin component B can be made different in composition.

  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 amount of resin discharged and the melting characteristics, and a plurality of partitions having different shapes can be accommodated in response to changes in the melting characteristics of the resin passing through the static mixer. A combination of plates can also be used. 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 direction of the partition plate is 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 contains an X layer containing a polyester resin component A mainly containing a butylene terephthalate unit, and a polyester resin component B mainly containing an ethylene terephthalate unit and a neopentyl terephthalate unit. Y layers to be stacked have a structure in which they are alternately stacked.

  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 such that the constituent unit of all the polyester in the whole film is 100 mol%, butylene terephthalate unit is 10 to 45 mol%, ethylene terephthalate unit and neopentyl terephthalate unit. Are preferably contained in an amount of 55 to 90 mol% and other ester units in an amount of 0 to 12 mol%. More preferably, the butylene terephthalate unit is 11 to 42 mol%, the ethylene terephthalate unit and the neopentyl terephthalate unit are 58 to 89 mol% in total, and the other units are 0 to 11 mol%. More preferable is a film containing 12 to 40 mol% of butylene terephthalate unit, 60 to 88 mol% of ethylene terephthalate unit and neopentyl terephthalate unit, and 0 to 10 mol% of other units. . In addition, when the resin component A is a polyester having a neopentyl terephthalate unit as another ester unit, since the “other ester unit” other than the neopentyl terephthalate unit is not included in the film, “other ester unit” May be 0 mol%. 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) Number of layers inside 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). The signal recorded on the imaging plate is read out using digital luminography (Pixsys TEM manufactured by JEOL), recorded as digital image information on a Windows (registered trademark) personal computer, and confirmed from the difference in staining degree between the X and Y layers. Counted the number of layers to be played.

(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 finish 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., passing steam of 1 kgf / cm ² (pressure gauge display: 98 kPa) with a transit time of 2.5 seconds and a zone temperature of 80 ° C. (display). The label was thermally shrunk by spraying to attach it to a 500 ml PET bottle (round shape, barrel 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) Label adhesion When the label mounted under the above condition (3) and the PET bottle were lightly twisted, the label did not move, and if the label slipped or the label and the bottle shifted, it was rated as x.

(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.

  Then, fill this bottle with about 500 ml of water, refrigerate at 5 ° C for 12 hours, tear the perforation of the bottle label immediately after taking it out of the refrigerator with your fingertips, tear it cleanly in the vertical direction, and remove the label from the bottle The percentage of bottles that could not tear the label cleanly with respect to 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, 57036 parts by mass of terephthalic acid (TPA), 33244 parts by mass of ethylene glycol (EG), 15733 parts by mass of neopentyl glycol (NPG), 23.2 parts by mass of antimony trioxide (polymerization catalyst) , 5.0 parts by weight of sodium acetate (alkali metal compound) and 46.1 parts by weight of trimethyl phosphate (phosphorus compound), adjusted to 0.25 MPa, and stirred at a temperature of 220 to 240 ° C. for 120 minutes to form an ester The reaction was carried out. The reaction vessel was returned to normal pressure, and 3.0 parts by mass of cobalt acetate tetrahydrate and 124.1 parts by mass of magnesium acetate tetrahydrate (alkaline earth metal compound) were added. After stirring for 5 minutes, the pressure was reduced to 1.33 hPa over 75 minutes and the temperature was raised to 280 ° C. Stirring was continued until the melt viscosity reached 4500 poise at a temperature of 280 ° C. (about 70 minutes), and then 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 0.75 dl / g.

Synthesis example 2
Polyester raw material chips A, C and D having the chip composition shown in Table 1 were obtained in the same manner as in Synthesis Example 1. In the table, CHDM is an abbreviation for 1,4-cyclohexanedimethanol, BD is butanediol, PD is 1,3-propanediol, and DEG is diethylene glycol. The intrinsic viscosity of the polyester chip A was 1.20 dl / g, the intrinsic viscosity of the polyester chip C was 0.72 dl / g, and the intrinsic viscosity of the polyester chip D 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.

Table 1 shows the characteristics of each resin.

Example 1
Polyester chips A and B obtained in the above synthesis examples were separately preliminarily dried. Polyester chip A and polyester chip B were introduced into an extruder A1 so that the ratio of the chips was A / B = 80/20 (mass ratio), and melted at 245 ° 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 of 270 ° C. ± 2 ° C. so that the ratio of the discharge amounts of the extruder A1 and the extruder B1 is A / B = 25/75 (mass ratio). 270 ° C ± 2 ° C static mixer (Noritake Co., 12 elements, inner diameter 38.4 mm, 1 element L / D = 1.5, 1 element plate twist angle 180 degrees, twist gradient 46 degrees) Laminated. Subsequently, it led to a T-die at 270 ° C. ± 2 ° C. 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 66 ° C.

  The unstretched sheet was preheated at 80 ° C. for 24 seconds in the tenter, and then stretched 4.8 times at 75 ° C. in the transverse direction, followed by heat treatment at 70 ° C. for 24 seconds, resulting in a heat shrinkability of 50 μm in thickness. A polyester film was obtained.

Example 2
The same method as in Example 1 except that the pre-dried polyester chip B and polyester chip C were introduced into the extruder B1 so that the chip ratio was B / C = 80/20 (mass ratio). Thus, a heat-shrinkable polyester film having a thickness of 50 μm was obtained.

Example 3
A heat of 50 μm in thickness was obtained in the same manner as in Example 1 except that the polyester chip B and the polyester chip C were introduced into the extruder B1 so that the chip ratio was B / C = 60/40 (mass ratio). A shrinkable polyester film was obtained.

Comparative Example 1
Polyester chip A and polyester chip B are charged into a single extruder C1 so that the resin ratio is A / B = 50/50 (mass ratio) and melted (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 an unstretched sheet was obtained without using a static mixer and setting the temperature of the T-die to 280 ° C. ± 2 ° C.

  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 layer number confirmation method of (2-2) above (the same applies to the following examples).

(In Table 3, TPA is a unit derived from terephthalic acid, EG is a unit derived from ethylene glycol, NPG is a unit derived from neopentyl glycol, CHDM is a unit derived from 1,4-cyclohexanedimethanol, and BD is 1,4-butane. A unit derived from diol, DEG represents a unit derived from diethylene glycol, BT represents a butylene terephthalate unit, CHD-T represents a 1,4-cyclohexanedimethylene terephthalate unit, ET represents an ethylene terephthalate unit, and NPG-T represents a neopentyl terephthalate unit. NPG-T & ET indicates the total amount of these.)

Example 4
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 245 ° C. ± 2 ° C. On the other hand, only the polyester chip B was put into the extruder B1 and melted at 280 ± 2 ° C. The resin melted in both extruders is led to a feed block of 270 ° C. ± 2 ° C. so that the ratio of the discharge amount of the extruder A1 and the extruder B1 is A1 / B1 = 25/75 (mass ratio), Furthermore, it is laminated with a static mixer (manufactured by Noritake Co., 12 elements, inside diameter 38.4 mm, 1 element L / D = 1.5, 1 element twist angle 180 degrees, twist gradient 46 degrees) at 270 ° C. ± 2 ° C. Turned into. Subsequently, it led to a T-die at 270 ° C. ± 2 ° C. 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 67 ° C.

  The unstretched sheet was preheated at 80 ° C. for 24 seconds in the tenter, and then stretched 4.8 times at 75 ° C. in the transverse direction, followed by heat treatment at 70 ° C. for 24 seconds, resulting in a heat shrinkability of 50 μm in thickness. A polyester film was obtained.

Example 5
A heat-shrinkable polyester film having a thickness of 50 μm was obtained in the same manner as in Example 4 except that the resin ratio of the extruder A1 was changed to A / D = 70/30 (mass ratio).

Example 6
A heat-shrinkable polyester film having a thickness of 50 μm was obtained in the same manner as in Example 4 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 4 to 6 are shown in Tables 4 and 5.

(In Table 5, TPA, BD, EG, NPG, DEG, BT, ET, and NPG-T have the same meaning as in Table 3, PD is a unit derived from propanediol, TT is a trimethylene terephthalate unit, and NPG-T & ET Indicates total amount.)

  The heat-shrinkable polyester film of the present invention exhibits a beautiful shrink finish with very little wrinkling, shrinkage unevenness and distortion due to shrinkage, good perforation openability, and sufficient adhesion to the bottle of the label It has a very high industrial utility value.

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 composed of a butylene terephthalate unit and other ester units, a polyester resin component B mainly containing an ethylene terephthalate unit and neopentyl terephthalate, and having a polyester composition different from that of the polyester resin component A. Injected into extruders A1 and B1, melted, and after resin component A and resin component B were charged into a static mixer in a molten state, extruded from a T-die and cooled to stretch an unstretched sheet formed at least uniaxially A heat-shrinkable polyester film obtained by   A polyester resin component B containing a polyester resin component A composed of a butylene terephthalate unit and other ester units, a polyester resin component B mainly containing an ethylene terephthalate unit and neopentyl terephthalate, and having a polyester composition different from that of the polyester resin component A A heat-shrinkable polyester-based film having a structure in which 500 layers or more in total are laminated alternately.   In the film, the composition unit of all polyester of the whole film is 100 mol%, butylene terephthalate unit is 10 to 45 mol%, ethylene terephthalate unit and neopentyl terephthalate unit are 55 to 90 mol%, and other ester units are The heat-shrinkable polyester film according to claim 1 or 2, wherein 0 to 12 mol% is contained.   The thermal shrinkage rate in the main shrinkage direction is 35% or more and 80% or less after being immersed in hot water of 85 ° C ± 0.5 ° C for 10 seconds, and after being immersed in hot 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 a heat shrinkage rate in the main shrinkage direction is from 10% to 50%.   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 or less 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.