Heat-shrinkable film, packaging material, molded article or container

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 as a packaging material for food, beverage, medicine and medical products, chemical products, cosmetics, toiletries, industrial packaging, agricultural supplies, etc. [Background technology]

[0002] In recent years, heat-shrinkable films have been widely used for both product protection and display, primarily for label packaging of PET bottles. Polyester-based resins, polystyrene-based resins, and polyvinyl chloride-based resins are also used for such heat-shrinkable films, but the use of polyester-based resins, which have excellent solvent resistance during printing, is increasing.

[0003] As such heat shrinkable films, those that shrink significantly in one specific direction are widely used. Generally, in order to exhibit shrinkage characteristics in the main shrinkage direction, high-magnification stretching is performed, but in the direction perpendicular to the main shrinkage direction (hereinafter sometimes simply referred to as the "perpendicular direction"), sufficient stretching is not performed, so the rigidity in the perpendicular direction tends to be low. Under such circumstances, there is an increasing demand for thinner label packaging from the viewpoint of cost reduction in recent years and resource saving in consideration of environmental issues. However, as the film is thinned, the rigidity in the perpendicular direction is further reduced, so the rigidity balance of the entire film is further reduced, and defects such as creases occur when labeling bottles. In addition, since the heat shrinkable film has a slight shrinkage characteristic in the perpendicular direction, there is a problem that the film does not remain on the top or bottom of the PET bottle after shrinkage, and the entire bottle container cannot be securely wrapped.

[0004] As an effort to improve rigidity, Patent Document 1 discloses a film having a laminated structure of 5 to 65 layers containing 50% by weight or more of polyester resin, and claims that the multi-layer structure makes it possible to maintain high rigidity even when the film is thin. However, the complex multi-layer structure requires high costs in the manufacturing process and goes against the recent trend toward mono-material recycling, so there is room for improvement.

[0005] Patent Document 2 discloses a polyester resin film containing 15 mol % or more of a monomer component that can become an amorphous component, and claims that the film has excellent mechanical strength in the longitudinal direction. Although a special stretching method is specified to improve the mechanical strength in the longitudinal direction, the improvement of mechanical strength due to molecular chain orientation during stretching is generally known, and there is little mention of the substrate configuration, so there is room for improvement. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-179135 A [Patent Document 2] JP 2008-291200 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a heat-shrinkable film that has an excellent balance of rigidity and therefore has excellent suitability for packaging. [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-based resin composition. The polyester resin composition contains 2-butyl-2-ethyl-1,3-propanediol as a diol residue, and the heat-shrinkable film has a tensile strength of 90 MPa or less in a direction perpendicular to the main shrinkage direction as measured in accordance with JIS K7127 (1999). [2] The heat-shrinkable film according to [1], having a tensile modulus of elasticity of 2200 MPa or more in a direction perpendicular to the main shrinkage direction as measured in accordance with JIS K7161-1 (2014). [3] A heat-shrinkable film according to [1] or [2], in which the difference between the tensile modulus in the main shrinkage direction and the tensile modulus in the direction perpendicular to the main shrinkage direction is 2100 MPa or less, as measured in accordance with JIS K7161-1(2014). [4] The heat shrinkable film according to any one of [1] to [3], wherein the ratio of the tensile modulus in the main shrinkage direction to the tensile modulus in a direction perpendicular to the main shrinkage direction is 0.5 or more and less than 2.0. [5] The heat-shrinkable film according to any one of [1] to [4], which contains 3 mol % or more of diethylene glycol relative to 100 mol % of all diol residues contained in the polyester resin composition. [6] The heat-shrinkable film according to any one of [1] to [4], which has a haze of 10% or less as measured in accordance with JIS K7136 (2000). [7] The heat shrinkable film according to any one of [1] to [6], which has a shrinkage percentage of -10 to 3% when immersed in 70°C warm water for 10 seconds in a direction perpendicular to the main shrinkage direction. [8] The heat-shrinkable film according to any one of [1] to [7], which is stretched at least uniaxially. [9] A packaging material comprising the heat-shrinkable film according to any one of [1] to [8].

[10] A molded article or container equipped with the packaging material described in [9]. Effect of the Invention

[0009] The heat-shrinkable film of the present invention has an excellent balance of rigidity as a whole film, and therefore exhibits excellent suitability for packaging. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the heat shrinkable film, packaging material, molded article, and container of the present invention will be described as an example of an embodiment of the present invention. However, the scope of the present invention is not limited to the embodiment described below.

[0011] In this specification, the term "film" is intended to encompass a wide 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 directions, when the flow direction from the extruder in the production process of the heat shrinkable film is defined as the longitudinal direction (MD) and the perpendicular direction is defined as the transverse direction (TD), and the "main shrinkage direction" means the direction of the longitudinal direction or the transverse direction which has the larger heat shrinkage rate.

[0013] Furthermore, even if the upper and lower limits of the numerical ranges in this specification are slightly outside the numerical ranges specified by the present invention, they are included in the equivalent range of the present invention as long as they have the same action and effect as those within the numerical range.

[0014] The heat-shrinkable film of the present invention (hereinafter sometimes referred to as "the 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 the film is not particularly limited, but from the viewpoint of application to packaging materials, it is preferably 5 to 200 μm. The thickness is preferably 10 to 150 μm, more preferably 10 to 150 μm, and even more preferably 15 to 70 μm. If the thickness is less than the above-mentioned numerical value, the transparency tends to be excellent. Also, if the thickness is more than the above-mentioned numerical value, the handleability tends to be ensured.

[0016] (2) Haze The haze of the present film measured according to JIS K7136 (2000) is preferably 10% or less, more preferably 8% or less, and particularly preferably 6% or less. On the other hand, the lower limit is preferably 0.5% or more, and more preferably 1% or more. If the haze is less than the above value, the transparency tends to be excellent. Also, if the haze is more than the above value, visibility can be ensured, and it tends to be possible to prevent the film from being mixed into food during packaging.

[0017] (3) Tensile strength The tensile strength of the film in the orthogonal direction measured according to JIS K7127 (1999) is 90 MPa or less, preferably 80 MPa or less, more preferably 70 MPa or less, and particularly preferably 60 MPa or less, from the viewpoint of the rigidity of the film. By having the tensile strength in the orthogonal direction be equal to or less than the above-mentioned value, the shrinkage rate in the longitudinal direction (MD) when the orthogonal direction is the longitudinal direction (MD) can be suppressed, and the rigidity balance of the film as a whole becomes excellent. In addition, 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 having the tensile strength in the longitudinal direction (MD) be equal to or more than the above-mentioned value, the heat-shrinkable film is less likely to break during secondary processing such as printing.

[0018] The tensile strength of the present film in the main shrinkage direction 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, and the lower limit is preferably greater than the tensile strength in the perpendicular direction, for example, 60 MPa or more, preferably 80 MPa or more, more preferably 100 MPa or more, and particularly preferably 120 MPa or more.

[0019] The tensile elongation in the orthogonal direction of the present 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 equal to or greater than the above-mentioned numerical value, problems such as breakage of the heat-shrinkable film tend to be less likely to occur in secondary processing steps such as a printing step.

[0020] The tensile elongation of the present film in the main shrinkage direction 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 equal to or greater than the above value, problems such as breakage of the heat shrinkable film tend to be less likely to occur in secondary processing steps such as a printing step.

[0021] (4) Tensile modulus The tensile modulus of elasticity in the orthogonal direction of this film at an ambient temperature of 23°C, measured in accordance with JIS K7161-1 (2014), is preferably 2200 MPa or more, more preferably 2250 MPa or more, and particularly preferably 2300 MPa or more, from the viewpoint of the rigidity of the film. The upper limit of the tensile modulus of elasticity in the orthogonal direction is not particularly limited, but considering the upper limit of the tensile modulus of elasticity of heat-shrinkable films that are commonly used, it is preferably 5000 MPa or less. If the tensile modulus of elasticity in the orthogonal direction is equal to or more than the above value, the rigidity of the film as a whole is high, and the heat-shrinkability is high, particularly when the thickness of the film is reduced. When the film is applied to a container using a labeling machine or the like, processing problems such as the heat-shrinkable film breaking tend not to occur.

[0022] The tensile modulus of elasticity in the main shrinkage direction of this film at an ambient temperature of 23° C., 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 setting the tensile modulus of elasticity in the main shrinkage direction to the above-mentioned value or less, the difference between the tensile modulus of elasticity in the main shrinkage direction and the orthogonal direction can be suppressed, the film as a whole has an excellent rigidity balance, and tends to be less prone to defects during packaging.

[0023] Furthermore, the difference between the tensile modulus in the main shrinkage direction and the tensile modulus in the orthogonal direction (tensile modulus in the main shrinkage direction - tensile modulus in the orthogonal direction) of the present 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 making the difference between the tensile modulus in the main shrinkage direction and the tensile modulus in the orthogonal direction equal to or less than the above numerical value, the difference between the tensile modulus in the main shrinkage direction and the tensile modulus in the orthogonal direction can be suppressed, the film as a whole has an excellent rigidity balance, and tends to be less prone to defects during packaging.

[0024] Furthermore, the ratio of the tensile modulus in the main shrinkage direction to the tensile modulus in the orthogonal direction (tensile modulus in the main shrinkage direction / tensile modulus in the orthogonal direction) of the present film is preferably 0.5 or more, more preferably 0.6 or more, and even more preferably 0.7 or more. 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 main shrinkage direction to the tensile modulus in the orthogonal direction within the above numerical range, the film as a whole has an excellent rigidity balance, and therefore tends to be less prone to defects during packaging.

[0025] (5) Heat shrinkage rate The heat shrinkage rate of the present film in the main shrinkage direction when immersed in 100° C. warm water for 10 seconds is preferably 30% or more, more preferably 33 to 90%, and even more preferably 35 to 80%. The heat shrinkage rate in the present invention is specifically measured by the method described in the examples. Generally, a heat-shrinkable film is used to cover a container or other object to be covered, and then passed through an atmosphere heated by a heater, hot air, steam, or the like for a relatively short time (several seconds to a dozen seconds) to shrink and attach it to the object to be covered. Therefore, the heat shrinkage rate of a heat-shrinkable film is an index for judging the adhesion to the object to be covered and the shape-following ability. Therefore, if the heat shrinkage rate in the main shrinkage direction when immersed in 100°C warm water for 10 seconds is the above value or more, the heat-shrinkable film tends to be able to be sufficiently attached to the object to be covered within the shrink processing time.

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

[0027] The heat shrinkage rate of the present film in the orthogonal direction when immersed in 70°C warm 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 of the heat shrinkage rate indicates that the film expands in that direction. When used for applications requiring shrinkage characteristics in almost one direction, such as labels attached to food containers and beverage containers, if there is even a slight heat shrinkage rate in the orthogonal direction, the film after shrinkage does not remain on the top or bottom of the PET bottle, and the entire surface of the bottle container cannot be securely wrapped, which is likely to cause problems. If the heat shrinkage rate in the orthogonal direction is within the above range, there is a tendency that distortion of characters or patterns printed on the heat shrinkable film can be suppressed when the film is attached to the object to be covered. Furthermore, there is a tendency that deviation of the fixed position can be suppressed when the position is fixed by the above-mentioned pre-shrink.

[0028] The heat shrinkage rate of the present film in the orthogonal direction when immersed in warm water at 60° C. for 10 seconds is preferably −5 to 2%, and more preferably −2 to 1%. The heat shrinkage rate of the present film in the orthogonal direction when immersed in 80° C. warm water for 10 seconds is preferably −10 to 3%, more preferably −8 to 2.8%, and even more preferably −6 to 2.5%. The heat shrinkage rate of the present film in the orthogonal direction when immersed in 90° C. warm water for 10 seconds is preferably −10 to 10%, more preferably −8 to 8%, and further preferably −6 to 6%. The heat shrinkage rate of the present film in the orthogonal direction when immersed in 100° C. warm water for 10 seconds is preferably −10 to 10%, more preferably −8 to 8%, and further preferably −6 to 5%. When the thermal shrinkage rate in the orthogonal direction and at each temperature are within the above-mentioned preferred ranges, there is a tendency that distortion of characters or patterns printed on the heat-shrinkable film can be suppressed in the process of gradually shrinking the film onto the object to be covered from a lower temperature when the film is attached to the object to be covered.Furthermore, there is a tendency that deviation of the fixing position can be suppressed when the position is fixed by the above-mentioned pre-shrink.

[0029] <Polyester Resin Composition> As described above, the present film has at least one layer made of a polyester-based resin composition containing 2-butyl-2-ethyl-1,3-propanediol as a diol residue. The polyester-based resin composition contains a polyester-based resin as a main component. In this specification, the term "major component" refers to a component that occupies the largest percentage by mass when the total of the target substance is 100% by mass, and is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. Each component constituting the present film will be described below.

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

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

[0032] The polyester resin derived from the dicarboxylic acid residue and the diol residue is preferably a copolymer polyester resin, that is, at least one of the dicarboxylic acid residue and the diol residue, which are polymerization components of the polyester resin, is preferably a mixture of two or more types of residues. When the polyester resin is composed of two or more dicarboxylic acid residues, the dicarboxylic acid residue that occupies the largest mol% relative to 100 mol% of all dicarboxylic acid residues is referred to as the first dicarboxylic acid residue, and the second dicarboxylic acid residue, the third dicarboxylic acid residue, ..., in descending order of mol% (hereinafter, these are collectively referred to as the second or below dicarboxylic acid residue). Similarly, when the polyester resin is composed of two or more diol residues, the diol residue that occupies the largest mol% relative to 100 mol% of all diol residues is referred to as the first diol residue, and the second diol residue, the third diol residue, ..., in descending order of mol% (hereinafter, these are collectively referred to as the second or below diol residue). In the polyester-based resin, since at least one of the dicarboxylic acid residue and the diol residue is composed of two or more types of residues, the crystallinity of the polyester-based resin can be reduced, and therefore the progress of crystallization of the heat-shrinkable film tends to be inhibited, and sufficient heat-shrinkage properties can be imparted.

[0033] Examples of the dicarboxylic acid residue include aromatic dicarboxylic acid residues such as terephthalic acid, isophthalic acid, furandicarboxylic acid, 2-chloroterephthalic acid, 2,5-dichloroterephthalic acid, 2-methylterephthalic acid, 4,4-stilbene dicarboxylic acid, 4,4-biphenyl dicarboxylic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, bisbenzoic acid, bis(p-carboxyphenyl)methane, anthracene dicarboxylic acid, 4,4-diphenyl ether dicarboxylic acid, 4,4-diphenoxyethane dicarboxylic acid, 5-Na sulfoisophthalic 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; and residues derived from ester derivatives thereof. These dicarboxylic acid residues may be contained alone or in combination of two or more.

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

[0035] When the polyester resin is composed of two or more kinds of dicarboxylic acid residues, the total content of the second or lower dicarboxylic acid residues is preferably 0.1 to 10 mol%, more preferably 0.5 to 5 mol%, based on 100 mol% of all dicarboxylic acid residues. If the total content of the second or lower dicarboxylic acid residues is equal to or higher than the lower limit of the numerical range, the crystallinity of the resulting polyester resin can be kept low, and the shrinkability of the heat-shrinkable film tends to be improved. In addition, if the total content of the second or lower dicarboxylic acid residues is equal to or lower than the upper limit of the numerical range, the heat resistance of the polyester resin tends not to be impaired.

[0036] Examples of the diol residue include ethylene glycol and 1,3-propanediol. , 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, isosorbide, etc. These diol residues may be used alone or in combination of two or more.

[0037] Among them, 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. It is important that the second or lower diol residue contains 2-butyl-2-ethyl-1,3-propanediol, and by containing 2-butyl-2-ethyl-1,3-propanediol as the second or lower diol residue, the orientation during stretching can be reduced, and the elastic modulus in the direction perpendicular to the stretching direction can be maintained high while suppressing excessive improvement in mechanical strength and elastic modulus in the stretching direction. Furthermore, in order to obtain a film having an excellent rigidity balance and packaging suitability, it is preferable that the second or lower diol residue contains neopentyl glycol or diethylene glycol in addition to the 2-butyl-2-ethyl-1,3-propanediol, and more preferably contains diethylene glycol.

[0038] When the polyester resin is composed of two or more kinds of diol residues, the total content of the second or lower diol residues is preferably 10 to 45 mol%, more preferably 15 to 40 mol%, based on 100 mol% of all diol residues. If the total content of the second or lower diol residues is equal to or greater than the lower limit of the numerical range, the crystallinity of the resulting polyester resin can be kept low, and the shrinkage properties and break resistance of the heat-shrinkable film tend to be improved. In addition, if the total content of the second or lower diol residues is equal to or less than the upper limit of the numerical range, the heat resistance and chemical resistance of the polyester resin tend not to be impaired.

[0039] In addition, when the total of the polyester resins is 100% by mass, the polyethylene terephthalate resin containing a terephthalic acid residue as the first dicarboxylic acid residue and an ethylene glycol residue as the first diol residue is preferably contained at 50% by mass or more, more preferably at 60% by mass or more, and even more preferably at 70% by mass or more. By containing the polyethylene terephthalate resin in the polyester resin at the above numerical value or more, it tends to be possible to impart suitable shrinkage characteristics as a heat shrinkable film. The polyethylene terephthalate resin may be used alone or may be used as two or more polyethylene terephthalate resins. When the polyethylene terephthalate resin is composed of two or more types, the total is the mass of the polyethylene terephthalate resin, and the mass ratio of the polyethylene terephthalate resin in the polyester resin is calculated.

[0040] Although the intrinsic viscosity (IV) of the polyethylene terephthalate (PET) resin is not particularly limited, the intrinsic viscosity (IV) of the PET resin 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 equal to or greater than the above-mentioned value, the mechanical strength of the film becomes sufficient, and if it is equal to or less than the above-mentioned value, the mechanical strength of the film and the fluidity when melted tend to be compatible.

[0041] Commercially available examples of the PET-based resin include "PETG coplyester" (manufactured by Eastman Chemical Company), "Embrace" (manufactured by Eastman Chemical Company), and "PETG KYGREEN" (manufactured by SK Chemical Company).

[0042] In the present invention, from the viewpoint of environmental compatibility, recycled PET bottle materials (hereinafter, sometimes simply referred to as "recycled materials") may be used as the polyethylene terephthalate-based resin. In general, recycled materials are mainly composed 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 made into a PET bottle.

[0043] Furthermore, the polyester resin used in the present invention may contain recycled resins such as trimming loss (end material) such as edges generated during the production process of the heat shrinkable film of the present invention, heat shrinkable film without printing, etc. When using the recycled resin, it is sufficient to use it in the form of fluff, repellets, etc.

[0044] The polyester resin used in the present invention may contain polyester resins other than the polyester resin derived from the dicarboxylic acid residue and the 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 one or more of the polyester resins contains 2-butyl-2-ethyl-1,3-propanediol as a diol group.

[0046] In general, the polyester resin contained in the polyester resin composition undergoes an ester exchange reaction in a molten state during molding, so when two or more polyester resins are used, it may be difficult to identify the content ratio of each resin or to distinguish whether it is a mixture or a copolymer. Therefore, the properties as a heat-shrinkable film can be examined by the type of residue contained in the polyester resin composition and the content of the residue.

[0047] In the present invention, the polyester resin composition contains 2-butyl-2-ethyl-1,3-propanediol residues as diol residues. The content of the 2-butyl-2-ethyl-1,3-propanediol residues 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 all 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. When the polyester resin composition contains 2-butyl-2-ethyl-1,3-propanediol residues as diol residues, By containing 3-propanediol in an amount equal to or greater than the lower limit of the numerical value, there is a tendency that the orientation during stretching is reduced, and excessive increases in mechanical strength and elastic modulus in the stretching direction are suppressed, while the elastic modulus in the direction perpendicular to the stretching direction is maintained high.

[0048] In the present invention, the polyester resin composition preferably contains 75 mol% or more of terephthalic acid residues, more preferably 80 mol% or more, and even more preferably 85 mol% or more of terephthalic acid residues, based on 100 mol% of all dicarboxylic acid residues contained in the polyester resin composition. The upper limit is usually 100 mol%. By containing terephthalic acid residues at or above the lower limit of the numerical value, the heat resistance and rigidity required for the heat shrinkable film tend to be maintained.

[0049] In the present invention, the polyester resin composition contains preferably 55 to 95 mol %, more preferably 60 to 90 mol %, and even more preferably 65 to 85 mol % of ethylene glycol residues relative to 100 mol % of all diol residues contained in the polyester resin composition. The film tends to be able to maintain the necessary heat and chemical resistance.

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

[0051] When the polyester resin composition contains a neopentyl glycol residue, the neopentyl glycol residue is preferably contained 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 all diol residues contained in the polyester resin composition. When the neopentyl glycol residue is within the above numerical range, a film having an excellent balance of rigidity and packaging suitability tends to be obtained.

[0052] When the polyester resin composition contains diethylene glycol residues, the diethylene glycol residues are preferably contained in an amount of 3 mol % or more, more preferably 3 to 20 mol %, and even more preferably 3.5 to 15 mol %, based on 100 mol % of all diol residues contained in the resin composition. By containing the diethylene glycol residues at or above the lower limit of the above numerical value, a film having an excellent balance of rigidity and packaging suitability tends to be obtained.

[0053] (Other Ingredients) The polyester-based resin composition may contain resins other than the polyester-based resins within a range that does not impair the effects of the present invention (for example, 10% by mass or less of the polyester-based resin composition).

[0054] Examples of 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, fluorine resins, polyvinyl alcohol resins, polyacrylonitrile resins, polyether resins, cellulose resins, polyimide resins, polyurethane resins, polyphenylene sulfide resins, polyphenylene ether resins, polyvinyl acetal resins, polyamideimide resins, polyamide bismaleimide resins, polyarylate resins, polyetherimide resins, polyetheretherketone resins, polyetherketone resins, polyethersulfone resins, polyketone resins, polyacetal resins, polysulfone resins, aramid resins, etc. These may be used alone or in combination of two or more.

[0055] The other polyester resins include thermoplastic elastomers. Examples of the 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 alone or in combination of two or more. However, since ester-based thermoplastic elastomers have ester bonds in the main chain, they are included in the polyester resins.

[0056] In addition, the polyester resin composition may be appropriately added with additives generally incorporated into resin compositions within a range that does not significantly impair the effects of the present invention. The additives are added for the purpose of improving and adjusting the molding processability, productivity, and various physical properties of the heat-shrinkable film. Examples of the additives include antiblocking agents, pigments such as titanium oxide and carbon black, flame retardants, weather resistance stabilizers, heat resistance stabilizers, antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, nucleating agents, plasticizers, antioxidants, antioxidants, light stabilizers, ultraviolet absorbers, neutralizers, antifogging agents, slip agents, and colorants. These may be used alone 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, and organic particles such as crosslinked acrylic resins, crosslinked polyester resins, crosslinked polystyrene resins, and silicone resins. As the organic particles, organic particles having a multilayer structure formed by polymerization in multiple stages can also be used. Among them, silica and organic particles are preferred.

[0058] The antiblocking agent roughens the film surface to exhibit slipperiness and blocking resistance, so unless an appropriate amount and type are selected, the transparency and gloss of the film tend to be impaired. Therefore, the amount of the antiblocking agent added is preferably 0.01 to 2 mass%, more preferably 0.015 to 1.5 mass%, and even more preferably 0.02 to 1 mass%, based on the mass of the entire resin composition (100 mass%). If the amount of the antiblocking agent added is too small, the antiblocking agent is difficult to precipitate on the film surface, and it is difficult to form unevenness on the film surface, so that sufficient slipperiness and blocking resistance tend to be difficult to exhibit. On the other hand, if the amount is too large, excessive unevenness on the film surface tends to occur, which tends to inhibit transparency due to surface roughness and to cause winding distortion of the film roll due to excessive slipperiness.

[0059] The shape of the antiblocking agent is not particularly limited, but from the viewpoints of suppressing aggregation, uniform dispersion, suppressing diffuse reflection of transmitted light, and unevenness formed on the film surface, spherical ones are preferably used. 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 deposit on the surface, and even the antiblocking agent deposited on the surface tends to be difficult to impart sufficient unevenness to exhibit slip properties and blocking resistance. On the other hand, if the particle size of the antiblocking agent is too large, when the heat shrinkable film of the present invention is printed to enhance the design, ink loss and the like tend to occur, which tends to impair the appearance of the printed pattern. The particle size distribution of the antiblocking agent is not particularly limited, but a narrow particle size distribution is preferable in view of the adverse effects due to the size of the particle size. If the particle size distribution is too wide, it is possible that particles deviating from the above-mentioned range of particle sizes that are preferably used will be included.

[0060] <Method of manufacturing heat shrinkable film> The heat-shrinkable film of the present invention can be produced by a conventionally known production method. The shape of the heat-shrinkable film of the present invention is not particularly limited, and may be either planar or tubular, but is preferably planar from the viewpoints of productivity (several pieces can be produced in the width direction of the raw film) and ease of printing.

[0061] As a method for producing the flat film, for example, a method for producing a flat heat-shrinkable film includes melting a polyester resin composition using an extruder, extruding the molten resin in a flat shape from a die such as a T-die, cooling and solidifying the resin with a cooling roll to obtain an unstretched film, stretching the unstretched film in at least one axial direction, and then annealing, cooling, and optionally subjecting the film to a corona discharge treatment or the like. A pressure reducer may be connected to the vent port to remove moisture and low molecular weight substances.

[0062] Alternatively, a polyester-based resin composition is melted using an extruder, the molten resin is extruded into a tubular shape from a die or other nozzle, and the extruded molten resin is cooled and solidified using an air or water cooling device to obtain an unstretched film. Then, the tube is stretched in at least one direction by applying internal pressure to the tube in a heated tunnel furnace by the tubular method, inflating it like a balloon, and the tubular stretched film is then annealed and cooled, and cut open to produce a flat film.

[0063] Examples of the stretching method include a method of stretching at least uniaxially by a roll stretching method, a tenter stretching method, a tubular stretching method, etc. Also, a combination of these stretching methods may be used, and the film may be stretched only in the longitudinal direction, or only in the transverse direction, or may be stretched in the longitudinal direction and then in the transverse direction, or may be stretched in the transverse direction and then in the longitudinal direction. Also, the film may be stretched two or more times in the same direction. Furthermore, the film may be stretched in the longitudinal direction, then in the transverse direction, and then in the longitudinal direction. Also, the film may be stretched simultaneously in the longitudinal and transverse directions by a simultaneous biaxial stretching machine. Also, a tubular unstretched film may be radially stretched by internal pressure by tubular molding.

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

[0065] In addition, the stretching ratio needs to be changed depending on the components of the heat-shrinkable film, the stretching method, the stretching temperature, the desired heat shrinkage rate, etc., but the stretching ratio in the main shrinkage direction is preferably 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 preferably stretched in the longitudinal and transverse directions. In this case, the main shrinkage direction may be either the longitudinal or transverse direction. When the film is used for applications requiring shrinkage properties in approximately one direction, such as labels attached to food containers and beverage containers, it is preferably stretched uniaxially in the main shrinkage direction, but it may be stretched at a stretch ratio of 1.03 to 1.5 times in the direction perpendicular to the main shrinkage direction as long as it is within the above-mentioned shrinkage ratio range. In the heat shrinkable film of the present invention, it is preferable that the main shrinkage direction is the transverse direction (TD) and the direction perpendicular to the main shrinkage direction is the longitudinal direction (MD).

[0067] After stretching, if necessary, heat treatment or relaxation treatment can be performed at a temperature of 50 to 120°C for the purpose of adjusting the thermal shrinkage rate and various physical properties of the heat shrinkable film. In addition, after stretching, heat treatment or relaxation treatment, the heat shrinkable film can be quickly cooled within a time period in which the molecular orientation does not relax, thereby imparting shrinkage properties to the heat shrinkable film. Furthermore, the cooled heat shrinkable film can be trimmed of edges and the like, and the heat shrinkable film can be wound around a core using a winder or the like 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-based resin composition, and it may further have other layers as long as they are within the range of the physical property specifications of 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 make it into a packaging material such as a heat-shrinkable label to be attached to glass containers or plastic containers such as PET bottles.

[0070] In general, a heat-shrinkable film used for label applications has a printed layer or an overcoat layer formed on the entire surface or part of at least one of the front and back surfaces by a known method such as gravure printing, flexographic printing, offset printing, bar coating, etc. The printing ink is not particularly limited and can be appropriately selected depending on the printing method, and examples thereof include solvent-based (non-aqueous) or aqueous acrylic resin-based or urethane resin-based inks, foaming inks, heat-foaming inks, etc.

[0071] Packaging materials for label applications are processed from a flat shape to a cylindrical shape or the like depending on the packaged item and then used for packaging. For example, for cylindrical containers such as PET bottles that require printing, first, the required image is printed on one side of a wide flat film wound on a roll, and while cutting it to the required width, it is folded so that the printed side is on the inside and center-sealed (the shape of the sealed part is so-called envelope pasting) to form a cylindrical shape. Center-sealing methods include a sealing method using an organic solvent, a heat sealing method, a method using an adhesive, and a method using an impulse sealer, but in consideration of the appearance, it is preferable to use an organic solvent sealing method.

[0072] <Article or container> The heat-shrinkable film of the present invention is excellent in film stiffness (rigidity at room temperature), shrink finish, transparency, mechanical strength, etc., and therefore, when attached to a molded product or container, it can adhere closely to the shape of even a molded product or container having a complex shape (for example, a cylinder with a narrowed center, a rectangular prism with corners, a pentagonal prism, a hexagonal prism, etc.) and can be used as a packaging material that can be attached beautifully without wrinkles, pockmarks, etc. Therefore, examples of 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, containers for deli food, and containers for dairy products. In particular, when the heat-shrinkable film of the present invention is used as a heat-shrinkable label for a blown bottle, it is particularly advantageous in that it can adhere closely to even complex shapes, as described above, and can produce containers with beautiful labels that are free of wrinkles, pitting, etc.

[0073] Examples of materials constituting the plastic container to which the packaging material of the present invention is attached include polyethylene terephthalate, polystyrene, rubber modified impact resistant 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, phenol resin, urea resin, melamine resin, epoxy resin, unsaturated polyester resin, silicone resin, etc., with polyethylene terephthalate being preferred. These plastic containers may be mixtures or laminates of two or more resins. EXAMPLES

[0074] The heat shrinkable film of the present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited in any way. Prior to the following examples, the following components were prepared.

[0075] <Polyester resin> (PET-1) A polyester resin (intrinsic viscosity (IV): 0.75 dl / g) consisting of 100 mol% terephthalic acid residue as dicarboxylic acid residue, 77 mol% ethylene glycol residue, 15 mol% 2-butyl-2-ethyl-1,3-propanediol residue, and 8 mol% diethylene glycol residue as diol residue. (PET-2) A polyester resin (intrinsic viscosity (IV): 0.01%) consisting of 100 mol% terephthalic acid residue as a dicarboxylic acid residue, 68 mol% ethylene glycol residue, 30 mol% neopentyl glycol residue, and 2 mol% diethylene glycol residue as a diol residue. .83dl / g) (PET-3) A polyester resin (intrinsic viscosity (IV): 0.84 dl / g) consisting of 100 mol% terephthalic acid residue as dicarboxylic acid residue, 65 mol% ethylene glycol residue, 32 mol% 1,4-cyclohexanedimethanol residue, and 3 mol% diethylene glycol residue as diol residue. (PET-4) A polyester resin consisting of 100 mol % of terephthalic acid residue as dicarboxylic acid residue, and 65 mol % of ethylene glycol residue, 23 mol % of 1,4-cyclohexanedimethanol residue, and 12 mol % of diethylene glycol residue as diol residue. (Intrinsic viscosity (IV): 0.82dl / g) (PET-5) PET bottle recycled material: polyester resin consisting of 98.6 mol% terephthalic acid residue, 1.4 mol% isophthalic acid residue as dicarboxylic acid residue, 97 mol% ethylene glycol residue, and 3 mol% diethylene glycol residue as diol residue (intrinsic viscosity (IV): 0.75 dl / g)

[0076] <Anti-blocking agent> (Silica-1) Silica 320 (average particle size 3.2 μm, manufactured by Fuji Silysia Chemical)

[0077] Example 1 According to the composition 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. Then, the mixed raw materials were respectively fed to a twin-screw extruder with a set temperature of 250°C, and melt-kneaded in the extruder to extrude a single-layered unstretched film, which was taken up by a cast roll at 70°C and cooled and solidified to obtain an unstretched film. Next, in a film tenter facility set to a preheating temperature of 95 to 105°C, a stretching temperature of 90°C, and a heat treatment temperature of 70°C, the obtained unstretched film was uniaxially stretched in the TD at a stretch ratio of 4.0 times to obtain a heat-shrinkable film. The main shrinkage direction of the obtained heat-shrinkable film is the TD.

[0078] (Examples 2 to 5, Comparative Examples 1 to 6) A mixture was prepared according to the raw material blending ratio shown 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 heat-shrinkable films obtained in the Examples and Comparative Examples were measured for thickness, haze, tensile strength and elongation, tensile modulus, and heat shrinkage rate by 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 recorded as the thickness.

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

[0082] (3) Tensile strength and elongation The obtained heat-shrinkable film was cut into a size of 200 mm in MD and 15 mm in TD. The tensile strength and tensile elongation in the MD of the film were measured in accordance with JIS K7127 at an atmospheric temperature of 23°C with a chuck distance of 150 mm and a tensile speed of 200 mm / min. The average values ​​of five measured values ​​were calculated. The obtained heat-shrinkable film was cut into a size of MD 15 mm and TD 200 mm, and tensile strength was measured according to JIS K7127 at a chuck distance of 150 mm and a pulling speed of 200 mm / min. The TD tensile strength and tensile elongation of the film were measured at an atmospheric temperature of 23° C., and the average values ​​of five measured values ​​were calculated.

[0083] (4) Tensile modulus The obtained heat-shrinkable film was cut into a size of 200 mm in MD and 15 mm in TD, and the tensile modulus of the film in MD was measured at an ambient temperature of 23°C in accordance with JIS K7161-1 (2014) with a chuck distance of 150 mm and a tensile speed of 200 mm / min. The average of five measured values ​​was calculated. The obtained heat-shrinkable film was cut into a size of 15 mm in MD and 200 mm in TD, and the tensile modulus of the film in TD was measured at an ambient temperature of 23°C in accordance with JIS K7161-1 (2014) with a chuck distance of 150 mm and a tensile speed of 200 mm / min. The average of five measured values ​​was calculated.

[0084] (5) Heat shrinkage rate The obtained heat shrinkable film was cut into strips with a size of 200 mm in MD and 10 mm in TD, and marked lines were placed at intervals of 100 mm so that the center of the MD was the center of the MD. The strips were then immersed in hot water baths set at temperatures of 60°C, 70°C, 80°C, 90°C, and 100°C for 10 seconds, and the distance between the marks after shrinkage was measured, and the amount of shrinkage in the MD (= distance between marks before shrinkage - distance between marks after shrinkage) was measured. The heat shrinkage rate in the MD was calculated as the ratio of the amount of shrinkage to the distance between marks before shrinkage (= (amount of shrinkage / distance between marks before shrinkage) x 100%). The obtained heat shrinkable film was cut into a size of 10 mm in MD and 200 mm in TD, and marked with lines 100 mm apart so that the center of the TD was the center. Then, the same measurement as for the heat shrinkage rate measurement in MD was performed to measure the heat shrinkage rate in TD.

[0085] The evaluation results for the examples and comparative examples are shown in Table 1 below.

[0086] [Table 1]

[0087] The heat-shrinkable films of Examples 1 to 5 each contain a polyester resin composition having a diol residue. Since the heat-shrinkable films of Comparative Examples 1 to 6 contain 2-butyl-2-ethyl-1,3-propanediol and satisfy the values ​​specified in the present invention, the films have excellent rigidity balance as a whole and exhibit excellent 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, so the films have poor rigidity balance as a whole and may cause problems during packaging. [Industrial Applicability]

[0088] The heat-shrinkable film of the present invention can be suitably used as a packaging material for food, beverage, pharmaceutical and medical products, chemical products, cosmetics, toiletries, industrial products, agricultural supplies, and the like.

Claims

1. A heat-shrinkable film having at least one layer made of a polyester-based resin composition, the polyester-based resin composition containing 2-butyl-2-ethyl-1,3-propanediol as a diol residue, and having a tensile strength of 90 MPa or less in a direction perpendicular to a main shrinkage direction as measured in accordance with JIS K7127 (1999).

2. The heat shrinkable film according to claim 1, having a tensile modulus of elasticity of 2200 MPa or more in a direction perpendicular to the main shrinkage direction as measured in accordance with JIS K7161-1 (2014).

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

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

0.

5. The heat shrinkable film according to any one of claims 1 to 4, comprising 3 mol% or more of diethylene glycol relative to 100 mol% of all diol residues contained in the polyester resin composition.

6. The heat shrinkable film according to any one of claims 1 to 4, having a haze of 10% or less as measured in accordance with JIS K7136 (2000).

7. The heat shrinkable film according to any one of claims 1 to 6, wherein the shrinkage percentage when immersed in 70°C warm water for 10 seconds in a direction perpendicular to the main shrinkage direction is -10 to 3%.

8. The heat shrinkable film according to any one of claims 1 to 7, which is stretched at least uniaxially.

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

10. A molded article or container to which the packaging material according to claim 9 is attached.

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