Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C61/00—Shaping by liberation of internal stresses; Making preforms having internal stresses; Apparatus therefor
  • B29C61/06—Making preforms having internal stresses, e.g. plastic memory
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets

Definitions

• the present invention relates to a polyester heat-shrinkable film (hereinafter, sometimes simply referred to as a heat-shrinkable film) and a method for producing a polyester resin film. More specifically, the present invention relates to a polyester heat-shrinkable film that exhibits excellent wrinkle resistance and other properties by controlling the neck-in ratio and other factors, even when applied to PET bottles of various different shapes, and a method for producing the same.
• heat-shrinkable films have been widely used as base films for labels on PET bottles, etc.
• polyester-based heat-shrinkable films are gaining a growing share of the market as base films for labels due to their excellent strength, transparency, etc.
• polyester heat-shrinkable films have these excellent properties, they have a rapid thermal response when heated, which causes them to shrink unevenly and prone to wrinkling. That is, the heat-shrinkable film is affected by storage conditions, particularly humidity, and the heat shrinkage rate at a given temperature varies, resulting in the problem of wrinkles easily forming when the shrink label is heat-shrunk.
• a heat-shrinkable polyester film is a polyester-based shrink film that has extremely excellent warm water resistance, shrinkage properties, strength, etc., and that can be used for narrow-necked cylindrical heat-resistant PET bottles, etc. (see, for example, Patent Document 1). More specifically, it was a preferred embodiment that the heat-shrinkable polyester film satisfied the following requirements (1) to (3) and also satisfied requirement (4).
• the thermal shrinkage rate of the film in the main shrinkage direction after 5 minutes in an air oven at 100°C is 20% or more in either the longitudinal or transverse direction.
• the breaking elongation of the film in the direction perpendicular to the shrinkage direction is within the range of 1 to 100%.
• the heat of fusion of the film is 8 cal/g or less.
• the neck-in ratio after immersion in 75°C warm water for 5 seconds is 10% or less.
• a heat-shrinkable polyester film has been proposed that is suppressed from wrinkling when used for wrapping labels on lunch boxes, noodle containers, etc. (see, for example, Patent Document 2). More specifically, it is a heat-shrinkable polyester film whose main shrinkage direction is the machine (longitudinal) direction and which satisfies the following requirements (1) to (6).
• the thermal shrinkage rate in the longitudinal direction after immersion in 80°C hot water for 10 seconds is 35% or more and 70% or less.
• the thermal shrinkage rate in the direction perpendicular to the longitudinal direction (width direction) after immersion in 80°C hot water for 10 seconds is -8% or more and 7% or less.
• the film has a widthwise change rate of 5 to 22% when the film is held in a constant length in the longitudinal direction, fixed only in the longitudinal direction, and held in a state of hot air at 90°C for 10 seconds.
• the film is fixed only in the longitudinal direction with a 10% slack in the longitudinal direction, and is held in hot air at 90°C for 10 seconds.
• the rate of change in the width direction of the film is within the range of 5 to 20%.
• the maximum heat shrinkage stress in the longitudinal direction measured under hot air at 90°C is within the range of 2 to 10 MPa%.
• the stress at 10% elongation (so-called F10) measured with hot air at a temperature of 90°C is a value within the range of 1 to 5 MPa% in the longitudinal direction and a value within the range of 0.5 to 3 MPa% in the width direction.
• a heat-shrinkable film has been proposed that, when used as a package for a battery cell or the like, has excellent durability and coating retention after coating (see, for example, Patent Document 3). More specifically, a preferred embodiment is a single-layer or multi-layer heat-shrinkable film having a resin layer containing a polyester resin as a main component on at least one side of the film, which satisfies the following requirements (a) to (d) and also satisfies requirement (e): (a) The polyester resin contains a copolymer polyester resin, and contains, in addition to a predetermined copolymerization component, at least one selected from the group consisting of 1,4-butanediol, neopentyl glycol, diethylene glycol, etc., and contains 15 mol % or more of a diol component other than ethylene glycol, relative to 100 mol % of the total amount of the diol components.
• the thermal shrinkage rate in the main shrinkage direction is within the range of 40 to 65%.
• the thermal shrinkage rate in the direction perpendicular to the main shrinkage direction is within the range of 4 to 15%.
• the difference in heat shrinkage between the heat shrinkage in the main shrinkage direction and the heat shrinkage in the direction perpendicular to the main shrinkage direction is within a range of 30 to 55%.
• the neck-in ratio after immersion in 70°C warm water for 10 seconds is 5% or less.
• the inventors of the present invention have made extensive efforts and have come to solve the conventional problems by limiting the absolute values of the heat shrinkage rates of a heat shrinkable film in the main shrinkage direction and in the direction perpendicular thereto, measured under specified conditions, and the ratio thereof, and by limiting the neck-in ratio measured under specified conditions.
• the present invention aims to provide a polyester-based heat-shrinkable film that not only requires fewer control items and is easy to produce stably, but also stably heat-shrinks and exhibits excellent wrinkle resistance even when applied to PET bottles or the like having complex shapes, and a method for stably producing such a polyester-based resin film.
• a polyester-based heat-shrinkable film derived from a polyester-based resin characterized in that the polyester-based heat-shrinkable film has the following configurations (a) to (d), which can solve the above-mentioned problems.
• A1 When the thermal shrinkage rate in the main shrinkage direction when shrunk in hot water at 80°C for 10 seconds is defined as A1, A1 is set to a value within the range of 21 to 65%.
• A2 is set to a value within the range of -5 to 10%.
• the absolute value of the ratio of the thermal shrinkage rates A1 and A2 (A1/A2) is set to 5.5 or more.
• the neck-in ratio measured in hot water at 70°C for 10 seconds is 6% or less. That is, by limiting the heat shrinkage rate (a) in the main shrinkage direction under predetermined conditions, the heat shrinkage rate (b) in the direction perpendicular thereto, the heat shrinkage rates of the heat shrinkable film in the main shrinkage direction and the direction perpendicular thereto measured under predetermined conditions, and the absolute value (c) of their ratio, and also by limiting the neck-in rate (d) measured under predetermined conditions, not only can stable production be facilitated, but also excellent wrinkle resistance can be exhibited when applied to various PET bottles, etc.
• the maximum shrinkage stress in the main shrinkage direction at a shrinkage temperature of 85° C. is defined as C
• C is a value within the range of 3 to 10 MPa. In this way, by limiting the maximum shrinkage stress (C) at a predetermined temperature to a predetermined range, it becomes easier to control the neck-in ratio, etc., and excellent wrinkle resistance can be more stably exhibited.
• the thickness of the polyester heat-shrinkable film of the present invention is preferably set to a value within the range of 10 to 100 ⁇ m.
• the main shrinkage direction of the polyester heat-shrinkable film is preferably the MD direction.
• the main shrinkage direction is preferably the MD direction.
• the polyester-based resin is a polyester-based resin derived from a dicarboxylic acid compound and a diol compound as reaction components, and that the diol compound contains at least ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol.
• the type of diol compound which is one of the reaction components, it becomes easier to adjust the heat shrinkage rate (A1 and A2), neck-in rate, absolute value (A1/A2), shrinkage stress, etc. under specified conditions, and ultimately, even better wrinkle resistance can be exhibited.
• Another aspect of the present invention is a method for producing a polyester-based resin film derived from a dicarboxylic acid compound and a diol compound as reaction components, the method comprising the following steps 1 and 2: Step 1: A step of preparing a dicarboxylic acid compound and a diol compound as reaction components and reacting them to produce a polyester resin. Step 2: A step of producing a polyester-based heat-shrinkable film having the following configurations (a) to (d) by stretching the polyester-based resin in the TD direction and/or MD direction. (a) When the thermal shrinkage rate in the main shrinkage direction when shrunk in hot water at 80°C for 10 seconds is defined as A1, A1 is set to a value within the range of 21 to 65%.
• the stretching treatment in step 1 is carried out along the MD direction.
• the stretching treatment in step 1 is carried out along the MD direction.
• FIG. 1(a) to 1(c) are diagrams illustrating the configuration of a polyester-based heat-shrinkable film.
• FIG. 2( a) is a diagram for explaining the relationship between the heat shrinkage rate (A1) in the main shrinkage direction of a polyester-based heat-shrinkable film under predetermined heating conditions (hot water at 80°C for 10 seconds) and the evaluation of shrinkage unevenness (relative value)
• FIG. 2( b) is a diagram for explaining the relationship between the heat shrinkage rate (A2) in the direction perpendicular to the main shrinkage direction of a polyester-based heat-shrinkable film under predetermined heating conditions (hot water at 80°C for 10 seconds) and the evaluation of shrinkage unevenness (relative value).
• FIG. 2( a) is a diagram for explaining the relationship between the heat shrinkage rate (A1) in the main shrinkage direction of a polyester-based heat-shrinkable film under predetermined heating conditions (hot water at 80°C for 10 seconds) and the evaluation of
• FIG. 3 is a diagram for explaining the relationship between the absolute value (A1/A2) of the ratio of the heat shrinkage rate (A2) in the perpendicular direction to the heat shrinkage rate (A1) in the main shrinkage direction of a polyester-based heat-shrinkable film, and the evaluation of shrinkage unevenness (relative value).
• FIG. 4 is a diagram for explaining the relationship between the neck-in ratio (%) and the evaluation of shrinkage unevenness (relative value) under predetermined heating conditions (hot water 70° C., 10 seconds) for a polyester heat-shrinkable film.
• FIG. 5 is a diagram illustrating the relationship between the shrinkage stress (MPa) in the main shrinkage direction and the evaluation of shrinkage unevenness (relative value) under predetermined heating conditions (hot water 85° C., 10 seconds) of a polyester-based heat-shrinkable film.
• Figure 6(a) corresponds to Example 1 and is a diagram (photograph) showing the appearance of a cylindrical label when no shrinkage unevenness occurs, and Figures 6(b) to (d) are enlarged views of areas P, Q, and R of the appearance shown in Figure 6(a), respectively.
• FIG. 7(a) corresponds to Comparative Example 1 and is a diagram (photograph) showing the appearance of a cylindrical label when uneven shrinkage occurs
• Figures 7(b) to (d) are enlarged views of the appearance areas S, T, and U shown in Figure 7(a).
• FIG. 8(a) is a diagram provided to explain a measurement sample for measuring the neck-in ratio
• FIG. 8(b) is a diagram provided to explain a fixing frame jig for measuring the neck-in ratio
• FIG. 8(c) is a diagram provided to explain a method for measuring the neck-in ratio.
• the first embodiment is a polyester-based heat-shrinkable film derived from a polyester-based resin, characterized in having the following configurations (a) to (d): (a) When the thermal shrinkage rate in the main shrinkage direction when shrunk in 80°C hot water for 10 seconds is defined as A1, A1 is set to a value within the range of 21 to 65%. (b) When the heat shrinkage rate when heat-shrunk in 80°C hot water for 10 seconds in a direction perpendicular to the main shrinkage direction (hereinafter, sometimes simply referred to as the perpendicular direction) is defined as A2, A2 is set to a value within the range of -5 to 10%.
• polyester resin that is the main component is basically of any type as long as it is a polyester resin that easily satisfies the above-mentioned structures (a) to (d).
• the polyester resin be a polyester resin made from a diol and a dicarboxylic acid, a polyester resin made from a diol and a hydroxycarboxylic acid, a polyester resin made from a diol, a dicarboxylic acid, and a hydroxycarboxylic acid, or a mixture of these polyester resins.
• examples of diols as raw material components of polyester resins include at least one of aliphatic diols such as ethylene glycol, diethylene glycol, propanediol, butanediol, neopentyl glycol, and hexanediol, alicyclic diols such as 1,4-hexanedimethanol, and aromatic diols.
• aliphatic diols such as ethylene glycol, diethylene glycol, propanediol, butanediol, neopentyl glycol, and hexanediol
• alicyclic diols such as 1,4-hexanedimethanol
• aromatic diols such as 1,4-hexanedimethanol
• ethylene glycol, diethylene glycol, and 1,4-hexanedimethanol are particularly preferred.
• examples of dicarboxylic acids as a compound component of polyester resins include at least one of fatty acid dicarboxylic acids such as adipic acid, sebacic acid, and azelaic acid; aromatic dicarboxylic acids such as terephthalic acid, naphthalenedicarboxylic acid, and isophthalic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; and ester-forming derivatives thereof.
• terephthalic acid and isophthalic acid are particularly preferred.
• the hydroxycarboxylic acid as a compound component of the polyester resin may include at least one of lactic acid, hydroxybutyric acid, polycaprolactone, and the like.
• a suitable amorphous polyester resin is, for example, an amorphous polyester resin composed of a dicarboxylic acid containing at least 80 mol% of terephthalic acid and a diol consisting of 50 to 80 mol% of ethylene glycol and 20 to 50 mol% of one or more diols selected from 1,4-cyclohexanedimethanol, neopentyl glycol, and diethylene glycol.
• dicarboxylic acids and diols, or hydroxycarboxylic acids may be used to change and adjust the film properties. These may be used alone or in combination.
• examples of crystalline polyester resins include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, and polypropylene terephthalate, and it is also preferable to use these either alone or as a mixture.
• the polyester resin is a mixture of a crystalline polyester resin and a non-crystalline polyester resin
• the reason for this is that by setting the blending amount of crystalline polyester resin to a value within the specified range, it is possible to obtain a polyester-based heat-shrinkable film that exhibits good heat-shrinkage properties and exhibits little change in physical properties such as the heat-shrinkage rate at a specified temperature, even under high-humidity conditions.
• the content of the crystalline polyester resin is less than 10% by weight, it becomes difficult to suppress moisture absorption when the film is left in a specified high-humidity environment for a relatively short period of time, and it may become difficult to control the absolute value of the specified heat shrinkage ratio (A1/A2) within a specified range.
• the content of the crystalline polyester resin exceeds 50%, the shrinkage rate of the resulting polyester heat-shrinkable film may be excessively reduced. Therefore, it is more preferable to set the amount of crystalline polyester resin to a value within the range of 15 to 45% by weight, and even more preferable to set it to a value within the range of 20 to 40% by weight, relative to the total amount of resin (100% by weight).
• the constitution (a) is a necessary constitutional requirement that, in a polyester-based heat-shrinkable film, when the heat shrinkage percentage in the main shrinkage direction when shrunk in warm water at 80°C for 10 seconds is A1 (%), the heat shrinkage percentage A1 is a value within the range of 21 to 65%.
• the reason for this is that if the heat shrinkage rate A1 exceeds this range, the heat shrinkage rate under general heat shrinkage conditions (80°C, 10 seconds) becomes insufficient, and the film will not be able to follow the shape of the periphery of the PET bottle, making it difficult to prevent wrinkles from occurring.
• the thermal shrinkage rate A1 of such a film is less than 21%, it becomes difficult to limit the numerical value expressed by the absolute value (A1/A2) described later within a predetermined range, and the balance between the thermal shrinkage rates in the main shrinkage direction and the direction perpendicular thereto decreases, which may make it difficult to suppress the occurrence of wrinkles.
• the thermal shrinkage rate A1 of such a film becomes excessively large, it becomes difficult to limit the numerical value expressed by the absolute value (A1/A2) within a predetermined range, and the balance between the thermal shrinkage rates in the main shrinkage direction and the direction perpendicular thereto deteriorates, which may make it impossible to suppress the occurrence of wrinkles.
• the heat shrinkage factor A1 of such a film is set to a value within the range of 25 to 50%, and even more preferably within the range of 30 to 45%.
• FIG. 2(a) shows the relationship between the heat shrinkage rate A1 (%) measured under predetermined conditions and the wrinkle resistance property (relative value)
• the horizontal axis of FIG. 2( a) shows the heat shrinkage rate A1 (%) in the main shrinkage direction measured under the heat shrinkage condition of immersion in hot water at 80° C. for 10 seconds in the main shrinkage direction
• the vertical axis shows the evaluation (relative value) of the wrinkle resistance property.
• the wrinkle resistance evaluation (relative value) on the vertical axis is quantified as follows: ⁇ is 5 points, ⁇ is 3 points, ⁇ is 1 point, and ⁇ is 0 point.
• Example 2( a) is based on the evaluation results showing the relationship between the heat shrinkage rate in the main shrinkage direction and the wrinkle resistance property in the polyester heat-shrinkable films of Examples 1, 3 to 7 (however, in FIG. 2( a) , Example 2 is omitted from the viewpoint of the production conditions and is represented as Ex1, 3 to 7) and Comparative Examples 1 to 3 (represented as CE1 to 3 in FIG. 2( a) ) described below.
• the structure (a) by setting the heat shrinkage percentage A1 (%) in the main shrinkage direction when shrunk in hot water at 80°C for 10 seconds to a value within the range of 21 to 55%, it can be said that good wrinkle resistance can be obtained while maintaining excellent adhesion to an adherend such as a PET bottle.
• the constitution (b) is a necessary constitutional requirement that, when a polyester-based heat-shrinkable film is heat-shrunk in hot water at 80°C for 10 seconds, the heat shrinkage percentage A2 in a direction perpendicular to the main shrinkage direction is set to a value within the range of -5 to 10%.
• the reason for this is that if the heat shrinkage rate A2 exceeds the specified range, the heat shrinkage rate under general heat shrinkage conditions (80°C, 10 seconds) may be insufficient, or conversely, the heat shrinkage may be excessive, making it impossible to conform to the shape of the PET bottle periphery, and making it impossible to prevent wrinkles from occurring.
• thermal shrinkage rate A2 of such a film is less than ⁇ 5%, it becomes difficult to limit the numerical value expressed by the absolute value (A1/A2) described later within a predetermined range, and as a result, the balance between the thermal shrinkage rates in the main shrinkage direction and the direction perpendicular thereto decreases, which may make it difficult to suppress the occurrence of wrinkles.
• the heat shrinkage rate A2 of such a film becomes excessively large and exceeds 10%, it becomes difficult to limit the numerical value expressed by the absolute value (A1/A2) within a predetermined range, and as a result, the balance between the heat shrinkage rates in the main shrinkage direction and the direction perpendicular thereto deteriorates, which may make it difficult to suppress the occurrence of wrinkles. Therefore, it is more preferable that the heat shrinkage rate A2 of the film in the orthogonal direction is set to a value within the range of -4 to 8%, and even more preferably within the range of -3 to 5%.
• the film under high humidity conditions of 20°C and 90% RH for 24 hours to stabilize it, not only before measuring heat shrinkage rate A1 but also before measuring heat shrinkage rate A2.
• FIG. 2(b) shows the relationship between the heat shrinkage rate A2 (%) measured under predetermined conditions and the wrinkle resistance property (relative value in the evaluation) in the horizontal axis of FIG. 2(b) in the direction perpendicular to the main shrinkage direction measured under heat shrinkage conditions in which the sample was immersed in warm water at 80°C for 10 seconds, and the vertical axis shows the evaluation (relative value) of the wrinkle resistance property.
• the wrinkle resistance evaluation (relative value) on the vertical axis is quantified with ⁇ being 5 points, ⁇ being 3 points, ⁇ being 1 point, and ⁇ being 0 point.
• Example 2(b) is based on the evaluation results showing the relationship between the heat shrinkage rate in the direction perpendicular to the main shrinkage direction and the wrinkle resistance of the polyester heat-shrinkable films of Examples 1, 3 to 7 (however, in FIG. 2(b) , Example 2 is omitted from the viewpoint of the production conditions and is represented as Ex1, 3 to 7) and Comparative Examples 1 to 3 (represented as CE1 to 3 in FIG. 2(b) ) described below. From the characteristic curve in FIG. 2(b), it can be seen that there is a predetermined relationship between the heat shrinkage rate A2 (%) in the direction perpendicular to the main shrinkage direction measured under predetermined conditions and the wrinkle resistance.
• Configuration (c) The configuration (c) is a necessary constituent requirement that the absolute value (A2/A1) of the ratio of the thermal shrinkage percentage A1 in the main shrinkage direction to the thermal shrinkage percentage A2 in the direction perpendicular thereto, measured under specified conditions, is 5.5 or more. The reason for this is that by controlling the numerical value expressed by the absolute value (A2/A1) in this manner, in combination with other configurations (a) to (b) and (d), etc., a good evaluation of wrinkle resistance properties can be obtained.
• the absolute value (A2/A1) is set to a value within the range of 10 to 150, and even more preferable that it is set to a value within the range of 15 to 100.
• the relationship between the absolute value (A1/A2) of the ratio of the heat shrinkage percentage (A2) in the direction perpendicular to the main shrinkage direction to the heat shrinkage percentage (A1) in the main shrinkage direction of a polyester-based heat-shrinkable film under predetermined heat shrinkage conditions (immersion in hot water at 80°C for 10 seconds) and shrinkage unevenness will be described. That is, the absolute value of the ratio of the thermal shrinkage rates (A1/A2) is plotted on the horizontal axis, and the evaluation value (relative value) of the shrinkage unevenness is plotted on the vertical axis. From the characteristic curve in FIG.
• the constitution (d) is an essential constitutional requirement that the neck-in ratio of the polyester heat-shrinkable film be 6% or less. That is, by taking into consideration the neck-in phenomenon that normally occurs during film production and limiting the neck-in ratio, which simulates this phenomenon, to a predetermined range, it is possible to achieve excellent wrinkle resistance even when applied to various PET bottles, etc. However, if the neck-in rate is too small, the manufacturing yield and the types of raw materials that can be used may be limited, which may be economically disadvantageous. Therefore, it is more preferable that the neck-in ratio is set to a value within the range of 0 to 5%, and even more preferable that it is set to a value within the range of 0.1 to 3%.
• the method for measuring the neck-in ratio will be described in detail in Example 1, etc., which will be described later.
• FIG. 4 shows the neck-in ratio (%) measured under the thermal shrinkage conditions of immersion in hot water at 70° C. for 10 seconds
• the vertical axis shows the evaluation (relative value) of the wrinkle resistance property.
• the wrinkle resistance evaluation (relative value) on the vertical axis is quantified with ⁇ being 5 points, ⁇ being 3 points, ⁇ being 1 point, and ⁇ being 0 point.
• the characteristic curves in FIG. 4 are based on the evaluation results of the wrinkle resistance of polyester heat-shrinkable films of Examples 1, 3 to 7 (however, in FIG.
• Example 2 is omitted from the viewpoint of manufacturing conditions and is represented as Ex1, 3 to 7) and Comparative Examples 1 to 3 (represented as CE1 to CE3 in FIG. 4), which will be described later.
• the characteristic curve in FIG. 4 it can be seen that there is a predetermined relationship between the neck-in ratio (%) and the wrinkle resistance characteristic (relative value). More specifically, from the characteristic curve in FIG. 4, for example, by limiting the neck-in ratio to a range of 6% or less, a good relative value of at least 3 or more is obtained in the evaluation of wrinkle resistance. Similarly, by limiting the neck-in ratio to a range of 5% or less, an even better result of a relative value of 5 was obtained in the evaluation of wrinkle resistance. In any case, regarding the configuration (d), it can be said that good wrinkle resistance can be obtained by setting the neck-in ratio when heat-shrunk under predetermined conditions to a value of 6% or less.
• Configuration (e) is a constitutional requirement relating to the thickness (average thickness) of the film before heat shrinkage in the polyester-based heat shrinkable film of the first embodiment, and is an optional constitutional requirement that the thickness is usually set to a value within the range of 10 to 100 ⁇ m. That is, by specifically limiting the thickness of the film before heat shrinkage to a value within a predetermined range in this manner, it becomes easy to control the heat shrinkage rate (A1 and A2), neck-in rate, absolute value (A1/A2), shrinkage stress, etc. under predetermined conditions.
• the influence of certain factors can be reduced, and uneven shrinkage due to a sudden thermal response can be suppressed in a polyester heat-shrinkable film during heat shrinkage, and as a result, the occurrence of fine wrinkles can also be suppressed.
• the thickness of the film before heat shrinkage is less than 10 ⁇ m or exceeds 100 ⁇ m, the polyester heat shrinkable film may not be able to suppress uneven shrinkage due to a sudden thermal response during heat shrinkage, and it may not be possible to suppress the occurrence of fine wrinkles. Therefore, as the configuration (e), it is more preferable that the thickness of the film before heat shrinkage is set to a value within the range of 30 to 80 ⁇ m, and even more preferably to a value within the range of 40 to 60 ⁇ m.
• the constitution (f) is an optional constitutional requirement that, in the polyester-based heat-shrinkable film of the first embodiment, when the maximum shrinkage stress in the TD direction at a shrinkage temperature of 85°C is C, C is set to a value within the range of 3 to 10 MPa. That is, as shown in FIG. 5, by controlling the maximum shrinkage stress to a value within a predetermined range, effective wrinkle resistance can be exhibited, and even wrinkles that occur due to excess or deficiency of the maximum shrinkage stress during thermal shrinkage can be effectively suppressed.
• the characteristic curves in FIG. 5 are based on the evaluation results of the wrinkle resistance of polyester heat-shrinkable films of Examples 1, 3 to 7 (however, in FIG.
• Example 2 is omitted from the viewpoint of manufacturing conditions and is represented as Ex1, 3 to 7) and Comparative Examples 1 to 3 (referred to as CE1 to CE3), which will be described later. More specifically, as shown in FIG. 5, if the maximum shrinkage stress C exceeds 10 MPa, the maximum shrinkage stress during thermal shrinkage will be excessive, and when the tape is attached to a PET bottle or the like, the shape of the PET bottle may be deformed, or wrinkles may occur due to the deformation, resulting in a decrease in wrinkle resistance.
• the maximum shrinkage stress C is more preferably set to a value within the range of 4.1 to 8 MPa, and even more preferably set to a value within the range of 5 to 7 MPa.
• polyester heat-shrinkable film of the first embodiment it is preferable to incorporate various additives into the polyester heat-shrinkable film of the first embodiment or to attach them to one or both surfaces thereof. More specifically, at least one of a hydrolysis inhibitor, an antistatic agent, an ultraviolet absorber, an infrared absorber, a colorant, an organic filler, an inorganic filler, an organic fiber, an inorganic fiber, and the like is preferably blended in an amount of 0.01 to 10% by weight, more preferably 0.1 to 1% by weight, based on the total amount of the polyester-based heat-shrinkable film.
• the polyester heat-shrinkable film 10 it is also preferable to laminate other resin layers 10 a and 10 b containing at least one of these various additives on one or both sides of the polyester heat-shrinkable film 10 .
• the single layer thickness or total thickness of the other resin layers to be additionally laminated is preferably set to a value within the range of 0.1 to 10%.
• the resin that constitutes the other resin layer as its main component may be a polyester resin similar to that used in polyester heat-shrinkable films, or it is preferably at least one of a different acrylic resin, olefin resin, urethane resin, rubber resin, etc.
• polyester-based heat-shrinkable film into a multilayer structure to further improve the hydrolysis prevention effect and mechanical protection, or to provide a shrinkage rate adjusting layer 10c on the surface of the polyester-based heat-shrinkable film 10 so that the shrinkage rate of the polyester-based heat-shrinkable film becomes uniform within the plane, as shown in Figure 1(c).
• a shrinkage adjusting layer can be laminated by using an adhesive, a coating method, or heat treatment depending on the shrinkage characteristics of the polyester heat shrinkable film.
• the thickness of the shrinkage rate adjusting layer is in the range of 0.1 to 3 ⁇ m, and if the shrinkage rate of the polyester heat-shrinkable film at a predetermined temperature is excessively large, it is preferable to laminate a shrinkage rate adjusting layer of a type that suppresses this. Furthermore, when the shrinkage rate of a polyester heat-shrinkable film at a predetermined temperature is excessively small, it is preferable to laminate a shrinkage rate adjusting layer of a type that expands the shrinkage rate. Therefore, the present invention aims to obtain a desired shrinkage rate by using a shrinkage rate adjusting layer as a polyester heat-shrinkable film, without producing various heat-shrinkable films with different shrinkage rates.
• FIGS. 6A and 6B are photographs of the appearance of a tubular label without wrinkles, corresponding to Example 1.
• Fig. 6A shows the entire body of a PET bottle covered with the tubular label.
• Figs. 6B to 6D are enlarged views of the upper (area P), middle (area Q), and lower (area R) parts of the body shown in Fig. 6A, respectively, and it can be seen that no wrinkles have occurred in any of the upper to lower parts.
• 7A and 7B are photographs of the appearance of a cylindrical label when wrinkles have occurred, corresponding to Comparative Example 1.
• FIG. 7A shows the entire body of a PET bottle covered with the cylindrical label.
• Figs. 7B to 7D are enlarged views of the upper (area S), middle (area T), and lower (area U) parts of the body shown in Fig. 7A, respectively, and it can be seen that wrinkles have occurred in all areas from the upper to the lower parts. Furthermore, it can be seen from FIG. 7(c) that the plastic bottle itself is also deformed in the central portion (region T) of the body of the plastic bottle.
• the second embodiment is a method for producing a polyester-based heat-shrinkable film derived from the dicarboxylic acid compound and diol compound of the first embodiment, and is characterized by having the following steps 1 and 2: Step 1: A step of preparing a dicarboxylic acid compound and a diol compound as reaction components and reacting them to produce a polyester resin. Step 2: A step of producing a polyester-based heat-shrinkable film having the following configurations (a) to (d) by stretching the polyester-based resin in a predetermined direction.
• the raw materials such as a base material and additives, including a crystalline polyester resin, a non-crystalline polyester resin, a rubber-based resin, an antistatic agent, and a hydrolysis inhibitor.
• the prepared crystalline polyester resin, amorphous polyester resin, etc. are preferably charged into the stirring vessel while being weighed, and mixed and stirred using a stirring device until homogeneous.
• extrusion molding is performed using an extruder (manufactured by Tanabe Plastic Machinery Co., Ltd.) with an L/D of 24 and an extrusion screw diameter of 50 mm under conditions of an extrusion temperature of 245°C, and a raw sheet of a predetermined thickness (usually 30 to 1000 ⁇ m) can be obtained.
• the obtained raw sheet is heated and pressed while being moved on or between rolls using a heat-shrinkable film manufacturing device to prepare a polyester-based heat-shrinkable film. That is, it is preferable to stretch the film in a predetermined direction while heating and pressing it at a predetermined preheating temperature, stretching temperature, heat setting temperature, and stretching ratio described below, while basically expanding the film width, thereby crystallizing the polyester molecules that make up the polyester-based heat-shrinkable film into a predetermined shape. Then, by solidifying it in this state, a heat-shrinkable polyester heat-shrinkable film that can be used for decoration, labels, etc. can be produced.
• the film can be stretched not only in the so-called transverse direction (stretching in the TD direction) but also in the longitudinal direction (stretching in the MD direction). That is, in the case of the present invention, regardless of the direction in which the stretching treatment is performed and the direction is set as the main shrinkage direction, the heat shrinkage rates A1, A2, absolute value (A1/A2), neck-in rate, heat shrinkage stress (C), etc. can be limited to values within predetermined ranges, and as a result, the occurrence of fine wrinkles can be suppressed.
• Stretching ratio in MD direction In the case of so-called transverse stretching, it is usually preferable that the stretching ratio in the MD direction of the polyester heat-shrinkable film before heat shrinking (sometimes referred to as the average MD stretching ratio or the MD stretching ratio) is set to a value within the range of 100 to 200%. The reason for this is that by specifically limiting the MD direction stretching ratio to a value within a predetermined range in this manner, the occurrence of fine wrinkles can be suppressed when the produced heat-shrinkable film is heat-shrunk.
• the MD stretching ratio is more preferably set to a value within the range of 110 to 180%, and even more preferably to a value within the range of 120 to 160%.
• the stretching ratio in the MD direction is preferably set to a value within the range of 300 to 600%, and more preferably to a value within the range of 400 to 500%.
• the stretching ratio in the TD direction of the polyester heat-shrinkable film before heat shrinking (sometimes referred to as the average TD direction stretching ratio or the TD direction stretching ratio) is set to a value within the range of 300 to 600%.
• the reason for this is that by specifically limiting not only the MD stretch ratio but also the TD stretch ratio to values within a predetermined range, and by specifically limiting the heat shrinkage rates A1, A2, B1, absolute value (A1/A2), neck-in rate, heat shrinkage stress (C), etc. to values within a predetermined range, it is possible to further suppress the occurrence of fine wrinkles.
• the TD stretch ratio is more preferably set to a value within the range of 350 to 550%, and even more preferably to a value within the range of 400 to 500%.
• the stretching ratio in the TD direction is preferably set to a value within the range of 100 to 200%, more preferably a value within the range of 110 to 180%.
• polyester-based heat-shrinkable film It is preferable to provide a predetermined inspection process in which the following characteristics are measured continuously or intermittently for the produced polyester-based heat-shrinkable film. That is, by measuring the following characteristics and the like through a predetermined inspection process and confirming that the values fall within the predetermined ranges, a polyester-based heat-shrinkable film having more uniform shrinkage characteristics can be obtained. 1) Visual inspection of the appearance of polyester heat-shrinkable film 2) Measurement of thickness variation 3) Measurement of tensile modulus 4) Measurement of tear strength 5) Measurement of viscoelastic properties using SS curve
• the polyester-based heat-shrinkable film of the second embodiment it is essential to measure at least the following components (a) to (d) and confirm that the values are within the predetermined ranges.
• A1 When the thermal shrinkage rate in the main shrinkage direction when shrunk in hot water at 80°C for 10 seconds is defined as A1, A1 is set to a value within the range of 21 to 65%.
• A2 When the thermal shrinkage rate in the direction perpendicular to the main shrinkage direction is A2 when the film is shrunk in hot water at 80°C for 10 seconds, A2 is set to a value within the range of -5 to 10%.
• the absolute value of the ratio of the thermal shrinkage rates A1 and A2 (A1/A2) is set to 5.5 or more.
• the neck-in ratio measured in hot water at 70°C for 10 seconds is 6% or less.
• the third embodiment relates to a method for using a polyester heat-shrinkable film. Therefore, any known method for using a heat shrinkable film can be suitably applied. For example, when using a polyester heat-shrinkable film, first, the polyester heat-shrinkable film is cut to an appropriate length and width and formed into a long cylindrical object. The long cylindrical object is then fed to an automatic label attachment device (shrink labeler) and further cut to the required length. Next, the container is fitted onto a PET bottle or the like filled with the contents.
• an automatic label attachment device shrink labeler
• the polyester heat-shrinkable film fitted onto the outside of the PET bottle or the like is subjected to a heat treatment by passing through a hot air tunnel or steam tunnel at a predetermined temperature.
• These tunnels provide radiant heat such as infrared rays or hot steam at about 90° C. is blown onto the polyester heat-shrinkable film from the surrounding area, thereby uniformly heating the film and causing it to shrink. Therefore, it is possible to quickly obtain a labeled container by adhering it to the outer surface of a PET bottle or the like.
• the polyester heat-shrinkable film of the present invention is characterized by satisfying at least the configurations (a) to (d) as described in detail in the first embodiment.
• polyester resins used in the examples are as follows:
• PET1 Dicarboxylic acid: 100 mol % of terephthalic acid, diol: polyester resin consisting of 69 mol % of ethylene glycol, 6 mol % of diethylene glycol, and 25 mol % of 1,4-cyclohexanedimethanol
• PET2 Dicarboxylic acid: 100 mol% terephthalic acid, diol: polyester resin consisting of 58 mol% ethylene glycol, 5 mol% diethylene glycol, 27 mol% 1,4-cyclohexanedimethanol, and 10 mol% 1,4-butanediol
• PET3 Dicarboxylic acid: 100 mol % of terephthalic acid, diol: 68 mol % of ethylene glycol, 12 mol % of diethylene glycol, 20 mol % of 1,4-cyclohexanedimethanol polyester resin
• PET4 Dicarboxylic acid: 100 mol % of terephthalic acid, diol: 74 mol % of ethylene glycol, 5 mol % of diethylene glycol, 21 mol % of 1,4-cyclohexanedimethanol polyester resin
• PET5 A polyester resin composed of dicarboxylic acid: 100 mol % of terephthalic acid and diol: 70 mol % of ethylene glycol, 2 mol % of diethylene glycol, and 28 mol % of 1,4-cyclohexanedimethanol.
• PET6 A polyester resin composed of dicarboxylic acids: 79 mol% terephthalic acid and 21 mol% isophthalic acid, and diols: 85 mol% ethylene glycol, 2 mol% diethylene glycol, and 13 mol% neopentyl glycol.
• a silica masterbatch (manufactured by Sumika Color Co., Ltd., product name "EPM-7E325") containing 5% by weight of silica relative to 100% by weight of matrix resin (PET resin) and having an average silica particle size of 2.7 ⁇ m.
• Example 1 Preparation of polyester-based heat-shrinkable film 100 parts by weight of amorphous polyester (PET1) and 1 part by weight of an additive (silica particles) as an antiblocking agent were placed in a stirring vessel and uniformly mixed and stirred to prepare raw materials. Next, after drying the raw material, it was extruded at an extrusion temperature of 260°C using an extruder (manufactured by Tanabe Plastic Machinery Co., Ltd.) with an L/D of 24 and an extrusion screw diameter of 50 mm to obtain a raw sheet having a thickness of 150 ⁇ m.
• PET1 amorphous polyester
• an additive silicon particles
• the raw sheet was longitudinally stretched to produce a polyester heat shrinkable film having a thickness of 30 ⁇ m at a preheating temperature of 95°C, a stretching temperature of 85°C, a heat setting temperature of 84°C, and a stretch ratio (MD direction: 100%, TD direction: 530%).
• Evaluation 1 Heat shrinkage rate A1 The obtained polyester heat-shrinkable film was shrunk in hot water at 80°C for 10 seconds, and the heat shrinkage rate (A1) in the main shrinkage direction was measured and evaluated according to the following criteria.
• ⁇ The heat shrinkage rate (A1) is within the range of 30 to 50%.
• Good The heat shrinkage rate (A1) is in the range of 21 to less than 30%, or more than 50 to 65%.
• Fair The heat shrinkage rate (A1) is in the range of 16 to less than 21%, or more than 65 to 70%.
• ⁇ The heat shrinkage rate (A1) is less than 16% or more than 70%.
• both ends of the measurement sample in the main shrinkage direction were fixed to a fixing frame jig having an inner length of 140 mm and a width of 140 mm, with the main shrinkage direction and the inner length direction aligned.
• both ends of the measurement sample in the main shrinkage direction were fixed to the fixing frame jig.
• the long measurement sample was arranged and fixed so that a predetermined space was left between both sides of the long measurement sample in the orthogonal direction and the fixing frame jig.
• the measurement sample attached to the fixing frame jig was immersed in warm water at 70° C. for 10 seconds, and then in water at 30° C.
• Neck-in rate (%) (L 0 - L ) / 2L 0 ⁇ 100 (1)
• L 0 Length of the gauge line on the measurement sample before heat treatment
• L Length of the gauge line on the measurement sample after heat treatment
• the neck-in ratio is within the range of 0 to 4%. Good: The neck-in ratio is in the range of more than 4 to 6%. ⁇ : The neck-in ratio is in the range of more than 6 to 8%. ⁇ : The neck-in ratio is more than 8%.
• the absolute value (A1/A2) of the obtained polyester heat-shrinkable film was calculated and evaluated according to the following criteria.
• ⁇ The absolute value (A1/A2) is within the range of 10 to 100.
• Good The absolute value (A1/A2) is 5.5 to less than 10, or is in the range of more than 100 to 110.
• ⁇ The absolute value (A1/A2) is 4.5 or more but less than 5.5, or is a value in the range of more than 110 to 120.
• the absolute value (A1/A2) is less than 4.5 or more than 120.
• the maximum shrinkage stress (C) is within the range of 4 to 8 MPa.
• Good The maximum shrinkage stress (C) is 3 to less than 4 MPa, or more than 8 to 10 MPa.
• the maximum shrinkage stress (C) is 2 to less than 3 MPa, or is in the range of more than 10 to 12 MPa.
• the maximum shrinkage stress (C) is less than 2 MPa or more than 12 MPa.
• the cylindrical label was placed over the body of the prepared cylindrical PET bottle, and the bottle was placed on a belt conveyor and moved through a steam tunnel maintained at 85°C at a speed of 6 m/min, causing the cylindrical label to be thermally shrunk so that it adhered tightly to the body of the cylindrical PET bottle from the top to the bottom.
• the tubular label after heat shrinkage was visually inspected, and its wrinkle resistance was evaluated based on whether wrinkles of a specified length (1 cm or more) or width (1 mm or more) had occurred, according to the following criteria.
• ⁇ No wrinkles were observed on any of the five cylindrical labels.
• Good No wrinkles of the specified size were observed in three or more of the five cylindrical labels.
• ⁇ No wrinkles of the specified size were observed in one or more of the five cylindrical labels.
• x The occurrence of predetermined wrinkles was observed in all five of the five cylindrical labels.
• Example 2 In Example 2, as shown in Table 1, PET1 was used as the polyester resin, and the values of the components (a) to (d) were changed to limit the production conditions for longitudinal stretching. That is, in Example 2, a polyester-based heat-shrinkable film having a thickness of 40 ⁇ m was produced from the raw sheet at a preheating temperature of 105°C, a stretch ratio (MD direction: 100%, TD direction: 500%), a stretching temperature of 88°C, and a heat setting temperature of 75°C. The resulting polyester heat-shrinkable film was evaluated for wrinkle resistance and other properties in the same manner as in Example 1. The results are shown in Table 2.
• Example 3 In Example 3, as shown in Table 1, PET2 was used as the polyester resin, and the values of the components (a) to (d) were changed to limit the production conditions for longitudinal stretching. That is, a polyester heat-shrinkable film having a thickness of 25 ⁇ m was produced from the raw sheet at a preheating temperature of 90°C, a stretching ratio (MD direction: 100%, TD direction: 515%), a stretching temperature of 90°C, and a heat setting temperature of 80°C. The resulting polyester heat-shrinkable film was evaluated for wrinkle resistance and other properties in the same manner as in Example 1. The results are shown in Table 2.
• Example 4 In Example 4, as shown in Table 1, PET3 was used as the polyester resin, and the values of the components (a) to (d) were changed to limit the production conditions for longitudinal stretching. That is, a polyester heat-shrinkable film having a thickness of 40 ⁇ m was produced from the raw sheet at a preheating temperature of 90°C, a stretching ratio (MD direction: 400%, TD direction: 100%), a stretching temperature of 82°C, and a heat setting temperature of 80°C. The resulting polyester heat-shrinkable film was evaluated for wrinkle resistance and other properties in the same manner as in Example 1. The results are shown in Table 2.
• Example 5 In Example 5, as shown in Table 1, PET4 was used as the polyester resin, and the values of the components (a) to (d) were changed to limit the production conditions for longitudinal stretching. That is, a polyester heat-shrinkable film having a thickness of 45 ⁇ m was produced from the raw sheet at a preheating temperature of 84°C, a stretch ratio (MD direction: 400%, TD direction: 100%), a stretching temperature of 84°C, and a heat setting temperature of 75°C. The resulting polyester heat-shrinkable film was evaluated for wrinkle resistance and other properties in the same manner as in Example 1. The results are shown in Table 2.
• Example 6 In Example 6, as shown in Table 1, PET4 was used as the polyester resin, and the values of the components (a) to (d) were changed to limit the production conditions for longitudinal stretching. That is, a polyester heat-shrinkable film having a thickness of 50 ⁇ m was produced from the raw sheet at a preheating temperature of 97°C, a stretching ratio (MD direction: 400%, TD direction: 100%), a stretching temperature of 93°C, and a heat setting temperature of 88°C. The resulting polyester heat-shrinkable film was evaluated for wrinkle resistance and other properties in the same manner as in Example 1. The results are shown in Table 2.
• Example 7 In Example 7, as shown in Table 1, PET1 was used as the polyester resin, and the values of the components (a) to (d) were changed to limit the production conditions for longitudinal stretching. That is, a polyester heat-shrinkable film having a thickness of 45 ⁇ m was produced from the raw sheet at a preheating temperature of 70°C, a stretch ratio (MD direction: 420%, TD direction: 100%), a stretching temperature of 85°C, and a heat setting temperature of 83°C. The resulting polyester heat-shrinkable film was evaluated for wrinkle resistance and other properties in the same manner as in Example 1. The results are shown in Table 2.
• Comparative Example 1 In Comparative Example 1, as shown in Table 1, PET5 was used as the polyester resin, and the values of the components (a) to (d) were changed to limit the production conditions for longitudinal stretching. That is, a polyester heat-shrinkable film having a thickness of 45 ⁇ m was prepared from the raw sheet at a preheating temperature of 75°C, a stretching ratio (MD direction: 100%, TD direction: 500%), a stretching temperature of 75°C, and a heat setting temperature of 50°C. The resulting polyester heat-shrinkable film was evaluated for wrinkle resistance and other properties in the same manner as in Example 1. The results are shown in Table 2.
• Comparative Example 2 In Comparative Example 2, as shown in Table 1, PET6 was used as the polyester resin, and the values of the components (a) to (d) were changed and the manufacturing conditions were modified to limit the values. That is, a polyester heat-shrinkable film having a thickness of 47 ⁇ m was produced from the raw sheet at a preheating temperature of 75°C, a stretching ratio (MD direction: 100%, TD direction: 500%), a stretching temperature of 75°C, and a heat setting temperature of 50°C. The resulting polyester heat-shrinkable film was evaluated for wrinkle resistance and other properties in the same manner as in Example 1. The results are shown in Table 2.
• Comparative Example 3 In Comparative Example 3, as shown in Table 1, PET6 was used as the polyester resin, and the values of the components (a) to (d) were changed and the manufacturing conditions were modified to limit the values. That is, a polyester heat-shrinkable film having a thickness of 42 ⁇ m was produced from the raw sheet at a preheating temperature of 90°C, a stretching ratio (MD direction: 100%, TD direction: 500%), a stretching temperature of 90°C, and a heat setting temperature of 60°C. The resulting polyester heat-shrinkable film was evaluated for wrinkle resistance and other properties in the same manner as in Example 1. The results are shown in Table 2.
• the polyester heat-shrinkable film of the present invention has at least the following configurations (a) to (c), and therefore can stably heat-shrink and exhibit excellent wrinkle resistance even when applied to various PET bottles, etc.
• (a) The heat shrinkage percentage A1 in the main shrinkage direction when shrunk in hot water at 80°C for 10 seconds is set to a value within the range of 21 to 55%.
• (b) The heat shrinkage percentage A2 in the direction perpendicular to the main shrinkage direction when shrunk in hot water at 80°C for 10 seconds is set to a value within the range of -5 to 10%.
• the neck-in ratio measured in hot water at 70°C for 10 seconds is 6% or less.
• the method for producing a polyester-based heat-shrinkable film of the present invention by producing a polyester-based heat-shrinkable film having at least the following components (a) to (c) in a predetermined process, it is possible to efficiently obtain a polyester-based heat-shrinkable film that stably heat-shrinks and exhibits excellent wrinkle resistance, even when applied to various PET bottles, etc.
• polyester-based heat-shrinkable film of the present invention by controlling not only the heat shrinkage rate (A1 and A2) under predetermined conditions but also the neck-in rate under at least predetermined conditions, it has become possible to achieve stable heat shrinkage and excellent wrinkle resistance even when applied to PET bottles or the like having complex shapes. Therefore, it can be suitably applied to various PET bottles, outer covering materials for lunch boxes, etc., and its versatility can be significantly expanded, so it can be said that its industrial applicability is extremely high.
• Polyester-based heat-shrinkable film 10a Other resin layer 1
• 10b Other resin layer 2
• 10c Shrinkage rate adjusting layer

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