Heat-shrinkable films, packaging materials, molded articles, or containers

Abstract

To provide a heat-shrinkable film that has a balance of rigidity and excellent packaging suitability.SOLUTION: A heat-shrinkable film is a heat-shrinkable film having at least one layer made of a polyester-based resin composition, and the polyester-based resin composition contains 2-butyl-2-ethyl-1,3-propanediol as a diol residue, and the tensile strength in the direction perpendicular to the main shrinkage direction measured in accordance with JIS K7127 (1999) is 90 MPa or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a heat-shrinkable film that can be suitably used for packaging materials for foods, packaging materials for beverages, packaging materials for pharmaceuticals and medical products, packaging materials for chemicals, packaging materials for cosmetics, packaging materials for toiletries, industrial packaging materials, packaging materials for agricultural materials, and the like.

Background Art

[0002] In recent years, heat-shrinkable films that combine product protection and display, mainly for labeling PET bottles, have been widely used. For such heat-shrinkable films, polyester resins, polystyrene resins, and polyvinyl chloride resins are also used, but among them, the use of polyester resins with excellent solvent resistance during printing is increasing.

[0003] As such heat-shrinkable films, those that are greatly shrunk in a specific one direction are widely used. Generally, in order to exhibit shrinkage characteristics in the main shrinkage direction, high magnification stretching is performed. However, in the direction orthogonal to the main shrinkage direction (hereinafter, sometimes simply referred to as the "orthogonal direction"), sufficient stretching is not performed, so the rigidity in the orthogonal direction tends to be low. In such a situation, from the viewpoints of cost reduction and resource conservation in recent years in consideration of environmental issues, there has been an increasing demand for thinning in label packaging. However, with the thinning, the rigidity in the orthogonal direction further decreases, so the balance of rigidity throughout the film further deteriorates, causing problems such as creases during label packaging on bottles. Also, since the heat-shrinkable film has slightly shrinkage characteristics in the orthogonal direction, there has been a problem that the film after shrinkage does not remain on the top and bottom surfaces of the PET bottle, and the entire bottle container cannot be firmly packaged.

[0004] As an effort to improve rigidity, Patent Document 1 discloses a film consisting of 5 to 65 layers containing 50% by weight or more of polyester resin, stating that high rigidity can be maintained even when the thickness is thin by using a multilayer structure. However, the complex multilayer structure requires high costs in the manufacturing process and also contradicts the recent trend of promoting recycling through monomaterialization, so there is room for improvement.

[0005] Furthermore, Patent Document 2 discloses a polyester resin film containing 15 mol% or more of monomer components that can become amorphous components, and states that it has excellent mechanical strength in the longitudinal direction. A special stretching method for improving mechanical strength in the longitudinal direction is explicitly stated, but the improvement in mechanical strength due to molecular chain orientation during stretching is generally known, and there is little mention of the substrate composition, so there is room for improvement. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2015-179135 [Patent Document 2] Japanese Patent Publication No. 2008-291200 [Overview of the project] [Problems that the invention aims to solve]

[0007] This invention was made in view of the above problems, and aims to provide a heat-shrinkable film with excellent balance of rigidity, thereby offering superior packaging suitability. [Means for solving the problem]

[0008] The present invention provides the following [1] to

[10] . [1] A heat-shrinkable film having at least one layer made of a polyester resin composition. A heat-shrinkable film wherein the polyester resin composition contains 2-butyl-2-ethyl-1,3-propanediol as a diol residue, and the tensile strength in the direction perpendicular to the principal shrinkage direction, as measured in accordance with JIS K7127 (1999), is 90 MPa or less. [2] The heat-shrinkable film described in [1], wherein the tensile modulus in the direction perpendicular to the principal shrinkage direction, as measured in accordance with JIS K7161-1 (2014), is 2200 MPa or more. [3] The heat-shrinkable film described in [1] or [2], wherein, in accordance with JIS K7161-1 (2014), the difference between the tensile modulus in the principal shrinkage direction and the tensile modulus in the direction perpendicular to the principal shrinkage direction is 2100 MPa or less. [4] A heat-shrinkable film according to any one of [1] to [3], wherein the ratio of the tensile modulus in the principal shrink direction to the tensile modulus in the direction perpendicular to the principal shrink direction is 0.5 or more and less than 2.0. [5] A heat-shrinkable film according to any one of [1] to [4], comprising 3 mol% or more of diethylene glycol with respect to 100 mol% of all diol residues contained in the polyester resin composition. [6] A heat-shrinkable film as described in any of [1] to [4], wherein the haze measured in accordance with JIS K7136 (2000) is 10% or less. [7] A heat-shrinkable film according to any of [1] to [6], wherein the shrinkage rate when immersed for 10 seconds in 70°C hot water in a direction perpendicular to the principal shrinkage direction is -10 to 3%. [8] A heat-shrinkable film according to any one of [1] to [7], which is stretched in at least one axial direction. [9] Packaging material made using a heat-shrinkable film as described in any of [1] to [8].

[10] A molded article or container fitted with the packaging materials described in [9]. [Effects of the Invention]

[0009] The heat-shrinkable film of the present invention exhibits excellent packaging suitability due to its superior overall rigidity balance. [Modes for carrying out the invention]

[0010] The following describes a heat-shrinkable film, packaging material, molded article, and container of the present invention as an example of an embodiment of the present invention. However, the scope of the present invention is not limited to the embodiments described below.

[0011] In this specification, the term "film" encompasses a range of materials, from thick sheets to thin films.

[0012] In this specification, "at least one direction" means either the longitudinal direction or the transverse direction, or both, when the flow direction from the extruder in the manufacturing process of a heat-shrinkable film is defined as the longitudinal direction (MD) and the direction perpendicular to it as the transverse direction (TD). "Main shrinkage direction" means the direction of the longitudinal direction or the transverse direction in which the heat shrinkage rate is greater.

[0013] Furthermore, the upper and lower limits of the numerical ranges specified herein shall be included within the equivalent range of the present invention, even if they fall slightly outside the numerical range specified by the present invention, as long as they have the same effects and advantages as those within the numerical range specified by the present invention.

[0014] The heat-shrinkable film of the present invention (hereinafter sometimes referred to as "this film") has at least one layer made of a polyester resin composition containing 2-butyl-2-ethyl-1,3-propanediol as a diol residue.

[0015] (1) Thickness The thickness of this film is not particularly limited, but from the perspective of application to packaging materials, 5 to 200 μm is recommended. The thickness is preferably m, more preferably 10 to 150 μm, and even more preferably 15 to 70 μm. If the thickness is less than or equal to the above values, the transparency tends to be excellent. If the thickness is greater than or equal to the above values, the handling properties tend to be ensured.

[0016] (2) Haze The haze of this film measured in accordance with JIS K7136 (2000) is preferably 10% or less, more preferably 8% or less, and particularly preferably 6% or less. On the other hand, as the lower limit, 0.5% or more is preferable, and 1% or more is more preferable. If the haze is below the above numerical value, it tends to have excellent transparency. Also, if the haze is above the above numerical value, visibility can be ensured, and it tends to prevent accidental mixing into food during packaging.

[0017] (3) Tensile strength The tensile strength in the orthogonal direction of this film measured in accordance with JIS K7127 (1999) is 90 MPa or less from the viewpoint of the film's rigidity, preferably 80 MPa or less, more preferably 70 MPa or less, and particularly preferably 60 MPa or less. By the tensile strength in the orthogonal direction being below the above numerical value, when the orthogonal direction is the longitudinal direction (MD), the shrinkage rate in the longitudinal direction (MD) can be suppressed, and the rigidity balance of the entire film becomes excellent. Also, the tensile strength in the orthogonal direction is preferably 35 MPa or more, more preferably 40 MPa or more, and particularly preferably 45 MPa or more. By the tensile strength in the longitudinal direction (MD) being above the above numerical value, in secondary processing steps such as the printing step, problems such as the heat-shrinkable film breaking are less likely to occur.

[0018] The tensile strength in the main shrinkage direction of this film measured in accordance with JIS K7127 (1999) is not particularly limited, but from the viewpoint of the rigidity balance of the entire film, it is 400 MPa or less, preferably 300 MPa or less, and particularly preferably 200 MPa or less. The lower limit is preferably greater than the tensile strength in the orthogonal direction. For example, it is 60 MPa or more, preferably 80 MPa or more, more preferably 100 MPa or more, and particularly preferably 120 MPa or more. <​​The tensile elongation in the orthogonal direction of this film, measured in accordance with JIS K7127 (1999), is not particularly limited, but is preferably 100% or more, more preferably 150% or more, and even more preferably 200% or more. When the tensile elongation in the orthogonal direction is at or above the above values, there is a tendency for problems such as breakage of the heat-shrinkable film to occur less frequently in secondary processing steps such as the printing process.

[0020] The tensile elongation in the main shrinkage direction of this film, measured in accordance with JIS K7127 (1999), is not particularly limited, but is preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more. When the tensile elongation in the main shrinkage direction is at or above the above values, there is a tendency for problems such as breakage of the heat-shrinkable film to occur less frequently in secondary processing steps such as the printing process.

[0021] (4) Tensile modulus The tensile modulus in the orthogonal direction of this film, measured in accordance with JIS K***(2014) at an ambient temperature of 23°C, is preferably 2200 MPa or more, more preferably 2250 MPa or more, and particularly preferably 2300 MPa or more from the perspective of the film's rigidity. Also, the upper limit of the tensile modulus in the orthogonal direction is not particularly limited, but considering the upper limit values of the tensile modulus of commonly used heat-shrinkable films, it is preferably 5000 MPa or less. If the tensile modulus in the orthogonal direction is at or above the above values, the rigidity of the entire film is high, and especially when the film thickness is reduced, there is a tendency for processing problems such as the heat-shrinkable film folding to occur less frequently when the heat-shrinkable film is coated on a container using a labeling machine or the like. When the heat-shrinkable film is coated on a container using a labeling machine or the like, there is a tendency for processing problems such as the heat-shrinkable film folding to occur less frequently.

[0022] It should be noted that in the original text, the standard number in "JIS K***(未完整)" is incomplete. I translated it as "JIS K***(2014)" based on the context. If there is an error, please provide the correct content for more accurate translation.The tensile modulus of this film in the principal shrinkage direction at an ambient temperature of 23°C, as measured in accordance with JIS K7161-1 (2014), is preferably 6000 MPa or less, more preferably 5500 MPa or less, and even more preferably 5000 MPa or less. By keeping the tensile modulus in the principal shrinkage direction below the above values, the difference between the tensile modulus in the principal shrinkage direction and the direction perpendicular to it can be suppressed, resulting in an excellent rigidity balance for the film as a whole, and a tendency to cause problems during packaging.

[0023] Furthermore, the difference between the tensile modulus in the principal shrinkage direction and the tensile modulus in the orthogonal direction (tensile modulus in the principal shrinkage direction - tensile modulus in the orthogonal direction) of this film is preferably 2100 MPa or less, more preferably 2000 MPa or less, even more preferably 1900 MPa or less, and particularly preferably 1800 MPa or less. By keeping the difference between the tensile modulus in the principal shrinkage direction and the tensile modulus in the orthogonal direction below the above values, the difference between the tensile modulus in the principal shrinkage direction and the orthogonal direction can be suppressed, resulting in an excellent rigidity balance for the film as a whole, and a tendency to cause problems during packaging.

[0024] Furthermore, the ratio of the tensile modulus in the principal shrinkage direction to the tensile modulus in the orthogonal direction (tensile modulus in the principal shrinkage direction / tensile modulus in the orthogonal direction) of this film is preferably 0.5 or higher, more preferably 0.6 or higher, and even more preferably 0.7 or higher. The upper limit is preferably less than 2.0, more preferably less than 1.9, and even more preferably less than 1.8. By setting the ratio of the tensile modulus in the principal shrinkage direction to the tensile modulus in the orthogonal direction within the above numerical range, the film as a whole exhibits excellent rigidity balance, which tends to reduce the likelihood of problems during packaging.

[0025] (5) Thermal shrinkage The thermal shrinkage rate of this film in the main shrinkage direction when immersed in 100°C hot water for 10 seconds is preferably 30% or more, more preferably 33-90%, and even more preferably 35-80%. Specifically, the thermal shrinkage rate in this invention is measured by the method described in the examples. Generally, heat-shrinkable films are attached to an object, such as a container, by covering it with the film and then passing it through a heated atmosphere (heated by a heater, hot air, or steam) for a relatively short time (a few seconds to about 10 seconds) to shrink it and attach it to the object. Therefore, the heat shrinkage rate of a heat-shrinkable film serves as an indicator for judging its adhesion and shape conformability to the object being covered. Accordingly, if the heat shrinkage rate in the main shrinkage direction when immersed in 100°C hot water for 10 seconds is greater than or equal to the aforementioned value, the heat-shrinkable film tends to be able to attach sufficiently to the object being covered within the shrinkage processing time.

[0026] The thermal shrinkage rate of this film in the main shrinkage direction when immersed in 90°C hot water for 10 seconds is preferably 20% or more, more preferably 25-80%, and even more preferably 30-75%. The thermal shrinkage rate of this film in the main shrinkage direction when immersed in 80°C hot water for 10 seconds is preferably 15% or more, more preferably 20-70%, and even more preferably 25-60%. The thermal shrinkage rate of this film in the main shrinkage direction when immersed in 70°C hot water for 10 seconds is preferably 5% or more, more preferably 6-60%, and even more preferably 8-55%. The thermal shrinkage rate of this film in the main shrinkage direction when immersed in 60°C hot water for 10 seconds is more preferably 0-5%, and even more preferably 0-3%. Generally, in the shrinking process in which a heat-shrinkable film is shrunk and attached to an object to be covered, Before completely covering the object to be covered with the heat-shrinkable film, the film is slightly shrunk (pre-shrinked) at a low temperature, and then the film is fixed in place on the object to be covered. In this case, if the heat shrinkage rate at each temperature is within the preferred range described above, there is a tendency to be able to gradually shrink the film onto the object to be covered starting from a lower temperature.

[0027] The thermal shrinkage rate of this film in the orthogonal direction when immersed in 70°C hot water for 10 seconds is preferably -10 to 3%, more preferably -8 to 2.8%, and even more preferably -6 to 2.5%. Here, a negative value for the thermal shrinkage rate indicates that the film expands in that direction. When used in applications requiring nearly unidirectional shrinkage characteristics, such as labels attached to food containers and beverage containers, even a slight thermal shrinkage rate in the orthogonal direction can cause problems because the film will not remain on the top and bottom of the PET bottle after shrinkage, preventing proper wrapping of the entire bottle container. When the thermal shrinkage rate in the orthogonal direction is within the above range, it tends to suppress distortion of characters and designs printed on the heat-shrinkable film when attached to the object to be covered. Furthermore, it tends to suppress misalignment of the fixed position when fixing the position with the pre-shrink method described above.

[0028] The thermal shrinkage rate of this film in the orthogonal direction when immersed in 60°C hot water for 10 seconds is preferably -5 to 2%, and more preferably -2 to 1%. The thermal shrinkage rate of this film in the orthogonal direction when immersed in 80°C hot water for 10 seconds is preferably -10 to 3%, more preferably -8 to 2.8%, and even more preferably -6 to 2.5%. The thermal shrinkage rate of this film in the orthogonal direction when immersed in 90°C hot water for 10 seconds is preferably -10 to 10%, more preferably -8 to 8%, and even more preferably -6 to 6%. The thermal shrinkage rate of this film in the orthogonal direction when immersed in 100°C hot water for 10 seconds is preferably -10 to 10%, more preferably -8 to 8%, and even more preferably -6 to 5%. When the thermal shrinkage rate in the orthogonal direction is within the preferred range described above for each temperature, it tends to suppress distortion of characters and designs printed on the heat-shrinkable film during the process of gradually shrinking the film onto the object to be covered, starting from a lower temperature. Furthermore, it tends to suppress misalignment of the fixed position during the pre-shrink fixing process described above.

[0029] <Polyester resin composition> As described above, this film has at least one layer made of a polyester resin composition containing 2-butyl-2-ethyl-1,3-propanediol as a diol residue. Furthermore, the polyester resin composition mainly contains a polyester resin. In this specification, "main component" refers to the component that accounts for the largest mass percentage when the total of the subject matter is 100% by mass, preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. The following describes each component that makes up this film.

[0030] [Polyester resin] The polyester resin contained as the main component in the aforementioned polyester resin composition is preferably a polyester resin derived from dicarboxylic acid residues and diol residues.

[0031] Examples of polyester resins derived from the dicarboxylic acid residue and diol residue include polyethylene terephthalate resins, polyethylene naphthalate resins, polybutylene terephthalate resins, polytrimethylene terephthalate resins, and poly-1,4- Examples include cyclohexylenedimethylene terephthalate resins, polyethylene succinate resins, and polybutylene succinate resins. These polyester resins may be used individually or in combination of two or more types. When two or more types of polyester resins are used, their total mass constitutes the total mass of the polyester resins, and the mass ratio of the polyester resins is calculated.

[0032] Furthermore, the polyester resin derived from the dicarboxylic acid residue and the diol residue is preferably a copolymerized polyester resin. That is, it is preferable that at least one of the dicarboxylic acid residue and the diol residue, which are polymerization components of the polyester resin, is a mixture of two or more residues. Furthermore, if the polyester resin is composed of two or more types of dicarboxylic acid residues, the dicarboxylic acid residue that accounts for the largest molar percentage of the total 100 mol% of dicarboxylic acid residues will be designated as the first dicarboxylic acid residue, and thereafter, in order of decreasing molar percentage, the second dicarboxylic acid residue, the third dicarboxylic acid residue, and so on (hereinafter, these will be collectively referred to as second and subsequent dicarboxylic acid residues). Similarly, if the polyester resin is composed of two or more types of diol residues, the diol residue that accounts for the largest molar percentage of the total 100 mol% of diol residues will be designated as the first diol residue, and thereafter, in order of decreasing molar percentage, the second diol residue, the third diol residue, and so on (hereinafter, these will be collectively referred to as second and subsequent diol residues). In the aforementioned polyester resin, if at least one of the dicarboxylic acid residues and diol residues consists of two or more types of residues, the crystallinity of the polyester resin can be reduced, which tends to suppress the progression of crystallization of the heat-shrinkable film and impart sufficient heat-shrinkability.

[0033] Examples of the dicarboxylic acid residues include aromatic dicarboxylic acid residues such as terephthalic acid, isophthalic acid, franciocarboxylic acid, 2-chloroterephthalic acid, 2,5-dichloroterephthalic acid, 2-methylterephthalic acid, 4,4-stilbenidicarboxylic acid, 4,4-biphenyldicarboxylic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, bisbenzoic acid, bis(p-carboxyphenyl)methane, anthracenedicarboxylic acid, 4,4-diphenyletherdicarboxylic acid, 4,4-diphenoxyethanedicarboxylic acid, 5-Na sulfisoisophthalic acid, and ethylene-bis-p-benzoic acid; aliphatic dicarboxylic acid residues such as dimer acid, hydrogenated dimer acid, adipic acid, sebacic acid, succinic acid, azelaic acid, dodecanedioic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; or residues derived from their ester derivatives. These dicarboxylic acid residues may be present individually or in combination of two or more types.

[0034] In particular, the polyester resin used in the present invention preferably contains a terephthalic acid residue as the first dicarboxylic acid residue. Furthermore, it is preferable that the second and subsequent dicarboxylic acid residues contain at least one residue selected from the group consisting of isophthalic acid, franciocarboxylic acid, dimer acid, hydrogenated dimer acid, 1,4-cyclohexanedicarboxylic acid, and adipic acid, and it is more preferable that the second and subsequent dicarboxylic acid residues contain an isophthalic acid residue.

[0035] When the polyester resin is composed of two or more types of dicarboxylic acid residues, the total content of the second and subsequent dicarboxylic acid residues is preferably 0.1 to 10 mol%, and more preferably 0.5 to 5 mol%, based on 100 mol% of the total dicarboxylic acid residues. If the total content of the second and subsequent dicarboxylic acid residues is above the lower limit of the numerical range, the degree of crystallinity of the resulting polyester resin can be kept low, and the shrinkability of the heat-shrinkable film tends to be improved. Furthermore, if the total content of the second and subsequent dicarboxylic acid residues is below the upper limit of the numerical range, the heat resistance of the polyester resin tends to be less likely to be impaired.

[0036] Examples of the diol residues include ethylene glycol and 1,3-propanediol. Examples include 1,4-butanediol, 2-butyl-2-ethyl-1,3-propanediol, neopentyl glycol, diethylene glycol, polytetramethylene glycol, 1,4-cyclohexanedimethanol, spiroglycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and isosorbide. These diol residues may be used individually or in combination of two or more.

[0037] In particular, the polyester resin used in the heat-shrinkable film of the present invention preferably contains an ethylene glycol residue or a 1,4-butanediol residue as the first diol residue, and more preferably contains an ethylene glycol residue as the first diol residue. Furthermore, it is important that the second and subsequent diol residues include 2-butyl-2-ethyl-1,3-propanediol. By including 2-butyl-2-ethyl-1,3-propanediol as the second and subsequent diol residues, the orientation during stretching is reduced, suppressing excessive improvement in mechanical strength and elastic modulus in the stretching direction, while maintaining a high elastic modulus in the direction perpendicular to the stretching direction. Moreover, in order to obtain a film with an excellent balance of rigidity and packaging suitability, it is preferable that the second and subsequent diol residues include neopentyl glycol and diethylene glycol in addition to 2-butyl-2-ethyl-1,3-propanediol, and more preferably diethylene glycol.

[0038] When the polyester resin is composed of two or more types of diol residues, the total content of the second and subsequent diol residues is preferably 10 to 45 mol%, and more preferably 15 to 40 mol%, based on 100 mol% of the total diol residues. If the total content of the second and subsequent diol residues is above the lower limit of the numerical range, the degree of crystallinity of the resulting polyester resin can be kept low, and the shrinkage characteristics and break resistance of the heat-shrinkable film tend to be improved. Furthermore, if the total content of the second and subsequent diol residues is below the upper limit of the numerical range, the heat resistance and chemical resistance of the polyester resin tend to be less likely to be impaired.

[0039] Furthermore, when the total amount of the polyester resin is 100% by mass, it is preferable that the polyester resin contains 50% by mass or more of polyethylene terephthalate resin, more preferably 60% by mass or more, and even more preferably 70% by mass or more. When the polyethylene terephthalate resin is contained in the polyester resin in the above-mentioned values ​​or more, it tends to impart shrinkage characteristics suitable for a heat-shrinkable film. The polyethylene terephthalate resin may be used alone or two or more types of polyethylene terephthalate resin may be used. When two or more types of polyethylene terephthalate resin are used, their total mass becomes the mass of the polyethylene terephthalate resin, and the mass ratio of the polyethylene terephthalate resin in the polyester resin is calculated.

[0040] Furthermore, while the intrinsic viscosity (IV) of polyethylene terephthalate (PET) resin is not particularly limited, it is preferably 0.3 to 1.5 dl / g, more preferably 0.4 to 1.2 dl / g, and even more preferably 0.5 to 1.0 dl / g. If the intrinsic viscosity (IV) is above the above value, the mechanical strength of the film will be sufficient, and if it is below the above value, it tends to be possible to achieve both mechanical strength and fluidity during melting.

[0041] Examples of commercially available PET resins include "PETGcoplyester" (manufactured by Eastman Chemical Company), "Embrace" (manufactured by Eastman Chemical Company), and "PETGSKYGREEN" (manufactured by SK Chemical Company).

[0042] Furthermore, in the present invention, from the viewpoint of environmental compatibility, recycled PET bottle material (hereinafter sometimes simply referred to as "recycled material") may be used as the polyethylene terephthalate resin. Generally, recycled material mainly consists of polyethylene terephthalate, which contains terephthalic acid as the first carboxylic acid residue, ethylene glycol as the first diol residue, and isophthalic acid as the second carboxylic acid residue to improve moldability when making PET bottles.

[0043] Furthermore, the polyester resin used in the present invention may include recycled resins such as trimming loss (scrap material) like selvages, or unprinted heat-shrinkable film, which are generated during the manufacturing process of the heat-shrinkable film of the present invention. When using such recycled resins, they may be used in the form of fluff or repelletized resins.

[0044] Furthermore, the polyester resin used in the present invention may include polyester resins other than those derived from the dicarboxylic acid residue and diol residue. Examples of such polyester resins include polyester resins obtained by polymerizing monomers having a carboxylic acid residue and an alcohol residue in one molecule, such as polylactic acid and poly-ε-caprolactam, and copolymers thereof.

[0045] As described above, in the present invention, it is important that the polyester resin composition containing the polyester resin alone or two or more contains 2-butyl-2-ethyl-1,3-propanediol as a diol group.

[0046] Generally, when two or more types of polyester resins are used in a polyester resin composition, transesterification reactions occur in the molten state during molding. Therefore, it can be difficult to determine the content ratio of each resin or whether it is a mixture or a copolymer. For this reason, the properties of the heat-shrinkable film can be carefully examined based on the types and content of residues contained in the polyester resin composition.

[0047] In the present invention, the polyester resin composition contains a 2-butyl-2-ethyl-1,3-propanediol residue as a diol residue. The content of the 2-butyl-2-ethyl-1,3-propanediol residue is preferably 3 mol% or more, more preferably 4 mol% or more, and even more preferably 5 mol% or more, based on 100 mol% of the total diol residues contained in the polyester resin composition. The upper limit is usually 30 mol% or less, preferably 25 mol% or less, and more preferably 20 mol% or less. By including 3-propanediol in amounts above the lower limit of the aforementioned numerical value, the orientation during stretching is reduced, and while suppressing excessive increases in mechanical strength and elastic modulus in the stretching direction, it tends to be possible to maintain a high elastic modulus in the direction perpendicular to the stretching direction.

[0048] In the present invention, it is preferable that the polyester resin composition contains 75 mol% or more of terephthalic acid residues, more preferably 80 mol% or more, and even more preferably 85 mol% or more, based on 100 mol% of the total dicarboxylic acid residues contained in the composition. The upper limit is usually 100 mol%. By including terephthalic acid residues at or above the lower limit of the above values, it tends to be possible to maintain the heat resistance and rigidity required for a heat-shrinkable film.

[0049] In the present invention, it is preferable that the polyester resin composition contains 55 to 95 mol% of ethylene glycol residues, more preferably 60 to 90 mol%, and even more preferably 65 to 85 mol% of ethylene glycol residues, based on 100 mol% of the total diol residues contained in the polyester resin composition. The presence of ethylene glycol residues within the above numerical range ensures that the heat shrinkability is maintained. It tends to maintain the heat resistance and chemical resistance required for film.

[0050] Furthermore, in the present invention, it is preferable that at least one of neopentyl glycol residues and diethylene glycol residues is present in an amount of 3 to 35 mol%, more preferably 4 to 30 mol%, and even more preferably 5 to 25 mol%, relative to 100 mol% of all diol residues contained in the polyester resin composition. When at least one of the neopentyl glycol residues and diethylene glycol residues is within the above numerical range, it tends to be possible to obtain a film with an excellent balance of rigidity and packaging suitability.

[0051] When the polyester resin composition contains neopentyl glycol residues, it is preferable that the neopentyl glycol residues are present in an amount of 1 to 40 mol%, more preferably 2 to 30 mol%, and even more preferably 3 to 20 mol%, relative to 100 mol% of the total diol residues contained in the polyester resin composition. When the neopentyl glycol residues are within the above numerical range, it tends to be possible to obtain a film with an excellent balance of rigidity and packaging suitability.

[0052] When the polyester resin composition contains diethylene glycol residues, it is preferable that the diethylene glycol residues are present in an amount of 3 mol% or more, more preferably 3 to 20 mol%, and even more preferably 3.5 to 15 mol%, relative to 100 mol% of the total diol residues contained in the resin composition. Including diethylene glycol residues above the lower limit of the above values ​​tends to result in a film with excellent rigidity balance and packaging suitability.

[0053] (Other ingredients) The polyester resin composition may also contain other resins besides the polyester resin in an amount that does not hinder the effects of the present invention (for example, 10% by mass or less of the polyester resin composition).

[0054] Other resins include polystyrene resins, polyester resins other than those described above (hereinafter referred to as "other polyester resins"), polyvinyl chloride resins, polyolefin resins, polycarbonate resins, polyamide resins, fluororesins, polyvinyl alcohol resins, polyacrylonitrile resins, polyether resins, cellulose resins, polyimide resins, polyurethane resins, polyphenylene sulfide resins, polyphenylene ether resins, polyvinyl acetal resins, polyamide-imide resins, polyamide-bismaleimide resins, polyarylate resins, polyetherimide resins, polyetheretherketone resins, polyetherketone resins, polyethersulfone resins, polyketone resins, polyacetal resins, polysulfone resins, polysulfone resins, aramid resins, etc. These may be used individually or in combination of two or more types.

[0055] Other polyester resins include thermoplastic elastomers. Examples of thermoplastic elastomers include styrene-based thermoplastic elastomers, amide-based thermoplastic elastomers, olefin-based thermoplastic elastomers, urethane-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, acrylic-based thermoplastic elastomers, fluorine-based thermoplastic elastomers, silicone-based thermoplastic elastomers, ionomers, and blends, alloys, modified products, dynamically crosslinked products, block copolymers, graft copolymers, random copolymers, core-shell type multilayer rubbers, etc. These may be used individually or in combination of two or more. However, ester-based thermoplastic elastomers are included in the polyester resins because they have ester bonds in their main chain.

[0056] Furthermore, the polyester resin composition may contain additives that are commonly used in resin compositions, provided that they do not significantly impair the effects of the present invention. These additives are added to improve and adjust the various physical properties of the moldability, productivity, and heat shrinkability of the film. Examples of these additives include antiblocking agents, pigments such as titanium dioxide and carbon black, flame retardants, weather stabilizers, heat stabilizers, antistatic agents, melt viscosity modifiers, crosslinking agents, lubricants, nucleating agents, plasticizers, anti-aging agents, antioxidants, light stabilizers, ultraviolet absorbers, neutralizing agents, anti-fogging agents, slip agents, and colorants. These may be used individually or in combination of two or more.

[0057] Examples of the antiblocking agent include inorganic particles such as silica, talc, and calcium carbonate, inorganic oxides, carbonates, or organic particles such as crosslinked acrylic resins, crosslinked polyester resins, crosslinked polystyrene resins, and silicone resins. Furthermore, organic particles forming a multilayer structure through multi-stage polymerization can also be used. Among these, silica and organic particles are preferred.

[0058] The antiblocking agent exerts slipperiness and antiblocking properties by roughening the film surface. Therefore, if the appropriate amount and type of antiblocking agent are not selected, it tends to impede transparency and gloss of the film. For this reason, the amount of antiblocking agent added is preferably 0.01 to 2% by mass, more preferably 0.015 to 1.5% by mass, and even more preferably 0.02 to 1% by mass, based on the total mass of the resin composition (100% by mass). If the amount of antiblocking agent added is too small, it is difficult for the antiblocking agent to precipitate on the film surface, making it difficult to form irregularities on the film surface, and thus it tends to be difficult to exert sufficient slipperiness and antiblocking properties. Conversely, if the amount is too large, excessive irregularities are likely to occur on the film surface, which tends to impede transparency due to surface roughness and cause misalignment of the film roll due to excessive slipperiness.

[0059] The shape of the antiblocking agent is not particularly limited, but a spherical shape is preferably used from the viewpoint of suppressing aggregation, uniform dispersion, suppressing diffuse reflection of transmitted light, and creating irregularities on the film surface. The particle size of the antiblocking agent is preferably 0.5 to 10 μm, more preferably 1 to 8 μm, and even more preferably 1 to 6 μm. If the particle size of the antiblocking agent is too small, it is difficult to precipitate on the surface, and even if the antiblocking agent precipitates on the surface, it tends to be difficult to impart sufficient irregularities to exhibit slipperiness and antiblocking properties. On the other hand, if the particle size of the antiblocking agent is too large, when printing is applied to the heat-shrinkable film of the present invention to enhance its design, ink bleeding and other issues are likely to occur, and the appearance of the printed design tends to be impaired. The particle size distribution of the antiblocking agent is not particularly limited, but due to the relationship between the disadvantages of different particle sizes, a narrow particle size distribution is preferable. If the particle size distribution is too wide, it may include particles that deviate from the range of particle sizes that are preferably used as described above.

[0060] <Method for manufacturing heat-shrinkable film> The heat-shrinkable film of the present invention can be manufactured by conventionally known manufacturing methods. Furthermore, the form of the heat-shrinkable film of the present invention is not particularly limited and may be planar or tubular, but a planar form is preferred from the viewpoint of productivity (several pieces can be produced as products in the width direction of the original film roll) and ease of printing.

[0061] As a method for manufacturing the planar film, for example, a method is used in which a polyester resin composition is melted using an extruder, the molten resin is extruded in a planar shape from a die such as a T-die, and the molten resin is cooled and solidified with a cooling roll to obtain an unstretched film. The obtained unstretched film is then stretched in at least one axial direction, and subsequently, a process of annealing, cooling, and corona discharge treatment as needed is performed to produce a planar heat-shrinkable film. Furthermore, depending on the equipment structure and requirements, Alternatively, a vacuum pump may be connected to the vent to remove moisture and low molecular weight substances.

[0062] Alternatively, a polyester resin composition can be melted using an extruder, the molten resin can be extruded in a tubular shape from a die such as a round die, and then cooled and solidified in an air-cooling or water-cooling device to obtain an unstretched film. Subsequently, the tube can be stretched at least in one axial direction by applying internal pressure to the tube in a heated tunnel furnace using the tubular method, causing it to inflate into a balloon shape, and then the annealed and cooled tubular stretched film can be cut open to produce a flat film.

[0063] Examples of the stretching methods include stretching in at least one axial direction by methods such as roll stretching, tenter stretching, and tubular stretching. Combinations of these stretching methods are also possible; stretching may be performed only in the longitudinal direction, only in the transverse direction, stretching may be performed longitudinally followed by transverse stretching, or stretching may be performed transversely followed by longitudinal stretching. Furthermore, stretching may be performed two or more times in the same direction. Moreover, stretching may be performed longitudinally, then transversely, and then longitudinally again. Additionally, stretching may be performed simultaneously in the longitudinal and transverse directions using a biaxial stretching machine. Furthermore, a tubular unstretched film may be stretched radially by internal pressure using tubular molding.

[0064] The stretching temperature needs to be adjusted depending on the softening temperature of the resin constituting the heat-shrinkable film and the shrinkage characteristics required for the heat-shrinkable film, but it is preferably 60 to 130°C, more preferably 70 to 120°C, and even more preferably 80 to 110°C.

[0065] Furthermore, the stretching ratio needs to be varied depending on the components of the heat-shrinkable film, the stretching method, the stretching temperature, and the required heat shrinkage rate, but it is preferable that the stretching ratio in the main shrinkage direction be 2 to 8 times, more preferably 3 to 7 times, and even more preferably 4 to 6 times.

[0066] When the heat-shrinkable film of the present invention is used for applications such as overlapping containers and trays, it is preferable to stretch it in the longitudinal and transverse directions. In this case, the primary shrinkage direction may be either the longitudinal or transverse direction. Furthermore, when used for applications requiring substantially unidirectional shrinkage characteristics, such as labels attached to food containers and beverage containers, it is preferable to stretch it uniaxially in the primary shrinkage direction. However, within the aforementioned shrinkage rate range, it may also be stretched at a stretching ratio of 1.03 to 1.5 times in the direction perpendicular to the primary shrinkage direction. In addition, in the heat-shrinkable film of the present invention, it is preferable that the primary shrinkage direction is the transverse direction (TD) and the direction perpendicular to the primary shrinkage direction is the longitudinal direction (MD).

[0067] After stretching, the heat-shrinkable film can be heat-treated or relaxed at temperatures of 50-120°C as needed to adjust its heat shrinkage rate and other physical properties. Furthermore, by rapidly cooling the film within the time it takes for molecular orientation to relax after stretching, heat treatment, or relaxation, shrinkage properties can be imparted to the heat-shrinkable film. In addition, the cooled heat-shrinkable film can be trimmed at the edges, etc., and wound onto a core using a winding machine or similar device to form a film roll.

[0068] The layer structure of the heat-shrinkable film of the present invention is not particularly limited as long as it has at least one layer made of a polyester resin composition, and may further include other layers as long as they are within the range of the physical properties specified in the present invention.

[0069] <Packaging materials> The heat-shrinkable film of the present invention can be used for various purposes, but preferably, a printed layer is formed on one or both sides of the heat-shrinkable film to create packaging materials such as heat-shrinkable labels that can be attached to glass containers or plastic containers such as PET bottles.

[0070] Generally, heat-shrinkable films used for label applications have a printed layer or overcoat layer formed on at least one of their front and back surfaces, either entirely or partially, by known methods such as gravure printing, flexographic printing, offset printing, or bar coating. The printing ink is not particularly limited and can be appropriately selected according to the printing method. Examples include solvent-based (non-aqueous) or aqueous acrylic resin-based or urethane resin-based inks, foaming inks, and heat-foaming inks.

[0071] Packaging materials for labeling are processed into various shapes, from flat to cylindrical, depending on the object being packaged. For example, for cylindrical containers such as PET bottles that require printing, the necessary image is first printed on one side of a wide flat film wound onto a roll. This is then cut to the required width, folded so that the printed side faces inward, and center-sealed (the shape of the seal is similar to an envelope seal) to form a cylindrical shape. There are several center-sealing methods, including sealing with organic solvents, heat sealing, adhesives, and impulse sealing. However, considering the appearance, it is preferable to use the sealing method with organic solvents.

[0072] <Molded product or container> The heat-shrinkable film of the present invention is excellent in terms of stiffness (rigidity at room temperature), shrinkage finish, transparency, and mechanical strength. Therefore, when attached to molded products or containers, it can adhere closely to the shape of molded products or containers with complex shapes (for example, cylinders with a constricted center, square prisms with corners, pentagonal prisms, hexagonal prisms, etc.), and can be used as a packaging material that is attached beautifully without wrinkles or blemishes. Accordingly, objects to which the heat-shrinkable film of the present invention can be attached include molded products or containers of various shapes, such as PET bottles, plastic containers, metal, porcelain, glass, paper, bottles, trays, lunch boxes, prepared food containers, dairy product containers, etc. In particular, when the heat-shrinkable film of the present invention is used as a heat-shrinkable label for blow-molded bottles, it can adhere closely to even complex shapes as described above, and is especially excellent in that it can produce containers with beautiful labels that are free from wrinkles and blemishes.

[0073] Examples of materials that make up the plastic containers to which the packaging material of the present invention is attached include polyethylene terephthalate, polystyrene, rubber-modified high-impact polystyrene (HIPS), styrene-butyl acrylate copolymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, acrylonitrile-butadiene-styrene copolymer (ABS), methacrylate-butadiene-styrene copolymer (MBS), polyvinyl chloride resin, phenolic resin, urea resin, melamine resin, epoxy resin, unsaturated polyester resin, silicone resin, etc., with polyethylene terephthalate being preferred. These plastic containers may be mixtures of two or more resins or laminates. [Examples]

[0074] Examples and comparative examples are shown below to further explain the heat-shrinkable film of the present invention, but the present invention is not limited in any way. Prior to the following examples, the following components were prepared.

[0075] <Polyester resin> • A polyester resin consisting of (PET-1) dicarboxylic acid residues (100 mol%), ethylene glycol residues (77 mol%), 2-butyl-2-ethyl-1,3-propanediol residues (15 mol%), and diethylene glycol residues (8 mol%) (intrinsic viscosity (IV): 0.75 dl / g) • A polyester resin consisting of (PET-2) dicarboxylic acid residues: 100 mol% terephthalic acid residue, and diol residues: 68 mol% ethylene glycol residue, 30 mol% neopentyl glycol residue, and 2 mol% diethylene glycol residue (intrinsic viscosity (IV): 0 0.83 dl / g) (PET-3) A polyester resin consisting of 100 mol% terephthalic acid residue as dicarboxylic acid residues, and 65 mol% ethylene glycol residue, 32 mol% 1,4-cyclohexanedimethanol residue, and 3 mol% diethylene glycol residue as diol residues (intrinsic viscosity (IV): 0.84 dl / g) A polyester resin consisting of (PET-4) dicarboxylic acid residues (100 mol%), ethylene glycol residues (65 mol%), 1,4-cyclohexanedimethanol residues (23 mol%), and diethylene glycol residues (12 mol%). (Intrinsic viscosity (IV): 0.82dl / g) • (PET-5) Recycled PET bottle material: A polyester resin consisting of 98.6 mol% terephthalic acid residues and 1.4 mol% isophthalic acid residues as dicarboxylic acid residues, and 97 mol% ethylene glycol residues and 3 mol% diethylene glycol residues as diol residues (intrinsic viscosity (IV): 0.75 dl / g)

[0076] <Antiblocking agent> • (Silica-1) Silicia 320 (average particle size 3.2 μm, manufactured by Fuji Silicia Chemical Co., Ltd.)

[0077] (Example 1) According to the formulation and composition shown in Table 1 below, 100 parts by mass of "PET-1" and 0.15 parts by mass of "Silica-1" were mixed. The mixed raw materials were then supplied to twin-screw extruders set to a temperature of 250°C, and melt-kneaded in the extruders to extrude a single-layer unstretched film. The film was taken up by a cast roll at 70°C and cooled and solidified to obtain an unstretched film. Next, the obtained unstretched film was uniaxially stretched in the TD direction at a stretch ratio of 4.0 times in a film tenter facility set to a preheating temperature of 95-105°C, a stretching temperature of 90°C, and a heat treatment temperature of 70°C to obtain a heat-shrinkable film. The main shrinkage direction of the obtained heat-shrinkable film is TD.

[0078] (Examples 2-5, Comparative Examples 1-6) A mixture was prepared using the raw material ratios listed in Table 1 below, and a single-layer unstretched film was obtained in the same manner as in Example 1. The obtained unstretched film was stretched in the same manner as in Example 1 to obtain a heat-shrinkable film.

[0079] The thickness, haze, tensile strength, tensile modulus, and thermal shrinkage coefficient of the heat-shrinkable films obtained in the examples and comparative examples were measured using the following methods.

[0080] (1) Thickness The thickness of the obtained heat-shrinkable film was measured at 10 random points using a 1 / 1000 mm dial gauge, and the average value (μm) was taken as the thickness.

[0081] (2) Haze The obtained heat-shrinkable film was measured for haze in accordance with JIS K7136 (2000).

[0082] (3) Tensile strength, tensile elongation The obtained heat-shrinkable film was cut to a size of MD200mm and TD15mm. In accordance with JIS K7127, the tensile strength and elongation of the MD of the film were measured at an ambient temperature of 23°C with a chuck distance of 150mm and a tensile speed of 200mm / min, and the average of five measured values ​​was calculated. Furthermore, the obtained heat-shrinkable film was cut to a size of MD15mm and TD200mm, and stretched in accordance with JIS K7127, with a chuck spacing of 150mm and a tensile speed of 200mm / min. The tensile strength and tensile elongation of the film's TD were measured at an ambient temperature of 23°C, and the average of five measurements was calculated.

[0083] (4) Tensile modulus The obtained heat-shrinkable film was cut to a size of MD200mm and TD15mm. In accordance with JIS K7161-1 (2014), the tensile modulus of the MD of the film was measured at an ambient temperature of 23°C with a chuck distance of 150mm and a tensile speed of 200mm / min, and the average of five measured values ​​was calculated. Furthermore, the obtained heat-shrinkable film was cut to a size of MD15mm and TD200mm, and the tensile modulus of the TD of the film was measured in accordance with JIS K7161-1 (2014) with a chuck distance of 150mm and a tensile speed of 200mm / min at an ambient temperature of 23°C. The average of five measured values ​​was calculated.

[0084] (5) Thermal shrinkage The obtained heat-shrinkable film was cut into strips measuring 200 mm on the medium diameter (MD) and 10 mm on the medium diameter (TD). Marks were made at 100 mm intervals, with the center of the MD aligned to the center of the MD. The strips were then immersed for 10 seconds in hot water baths set to 60°C, 70°C, 80°C, 90°C, and 100°C, respectively. The distance between the markings after shrinkage was measured, and the amount of shrinkage of the MD (= markings before shrinkage - markings after shrinkage) was determined. The heat shrinkage rate of the MD was calculated as the ratio of the amount of shrinkage to the markings before shrinkage (= (amount of shrinkage / markings before shrinkage) × 100%). Furthermore, the obtained heat-shrinkable film was cut to sizes of MD 10 mm and TD 200 mm, and markings were made at 100 mm intervals so that the center of the TD was in the middle. Then, the heat shrinkage rate of the TD was measured using the same procedure as for measuring the heat shrinkage rate of the MD.

[0085] Table 1 below shows the evaluation results for the examples and comparative examples.

[0086] [Table 1]

[0087] The heat-shrinkable films of Examples 1-5 were composed of a polyester resin composition with diol residues as part of the composition. The film containing 2-butyl-2-ethyl-1,3-propanediol satisfies the numerical values ​​specified in this invention, resulting in excellent overall rigidity balance and superior packaging suitability. On the other hand, the heat-shrinkable films of Comparative Examples 1 to 6 do not contain 2-butyl-2-ethyl-1,3-propanediol as a diol residue, resulting in poor overall rigidity balance and the potential for problems during packaging. [Industrial applicability]

[0088] The heat-shrinkable film of the present invention can be suitably used as packaging material for food, beverages, pharmaceuticals and medical products, chemicals, cosmetics, toiletries, industrial products, agricultural materials, and the like.

Claims

1. A heat-shrinkable film having at least one layer made of a polyester resin composition, wherein the polyester resin composition contains 3 to 8 mol% of diethylene glycol as a diol residue, and also contains 2-butyl-2-ethyl-1,3-propanediol as a diol residue, and the heat-shrinkable film having a tensile strength in the main shrinkage direction of 200 MPa or less, as measured in accordance with JIS K7127 (1999).

2. The heat-shrinkable film according to claim 1, wherein the tensile strength in the direction perpendicular to the principal shrinkage direction, as measured in accordance with JIS K7127 (1999), is 90 MPa or less.

3. The heat-shrinkable film according to claim 1 or 2, wherein, in accordance with JIS K7161-1 (2014), the difference between the tensile modulus in the principal shrinkage direction and the tensile modulus in a direction perpendicular to the principal shrinkage direction is 2100 MPa or less.

4. A heat-shrinkable film according to any one of claims 1 to 3, wherein the ratio of the tensile modulus in the principal shrinkage direction to the tensile modulus in the direction perpendicular to the principal shrinkage direction is 0.5 or more and less than 2.

0.

5. A heat-shrinkable film according to any one of claims 1 to 4, wherein the haze measured in accordance with JIS K7136 (2000) is 10% or less.

6. A heat-shrinkable film according to any one of claims 1 to 5, wherein the shrinkage rate when immersed for 10 seconds in 70°C hot water in a direction perpendicular to the principal shrinkage direction is -10 to 3%.

7. A heat-shrinkable film according to any one of claims 1 to 6, which is stretched in at least one axial direction.

8. A packaging material comprising a heat-shrinkable film according to any one of claims 1 to 7.

9. A molded article or container fitted with the packaging material described in claim 8.

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