Copolymer polyester resin, heat-shrinkable film, heat-shrinkable label, and packaging material

Abstract

The present invention pertains to a copolymerized polyester resin that has superior recyclability, is such that film properties suitable for use in a heat-shrinkable label can be imparted, and has dicarboxylic acid and a diol as constituent components thereof. Terephthalic acid is used as the main component of the dicarboxylic acid component, and an ethylene glycol is used as the main component of the diol component. When all of the diol components are set to 100 mol%, the content of neopentyl glycol is 18-32 mol% and the diethylene glycol content is 7-15 mol%. The proportion of phosphorous compounds having a specified structure that are included in the copolymerized polyester resin satisfies a specific formula.

Description

[Technical Field]

[0001] The present invention relates to a copolymer polyester resin that is suitable for use in heat-shrinkable labels and has excellent recyclability, and to a heat-shrinkable film, a heat-shrinkable label, and a package that use the same. [Background technology]

[0002] In recent years, polyester heat-shrinkable films, which have high heat resistance, are easy to incinerate, and have excellent solvent resistance, have come to be widely used as shrink labels for applications such as label packaging, cap seals, and integrated packaging that combine the protection of glass or plastic bottles and product marking. The amount of these films used is also on the rise, along with the increase in PET (polyethylene terephthalate) bottle containers.

[0003] To date, heat-shrinkable polyester films that shrink significantly in the width direction have been widely used. It is also known that, in order to improve the shrinkage finish, the shrinkage rate in the non-shrinkable longitudinal direction is made negative (i.e., the film stretches upon heating) (see Patent Document 1).

[0004] Heat-shrinkable polyester films with increased shrinkage have been proposed to accommodate various containers (see Patent Documents 2 and 3). However, increasing the shrinkage rate leads to problems such as an increased natural shrinkage rate after storage at room temperature (after aging) and a decreased hot-water shrinkage rate when measured at 70°C. Patent Document 2 employs a biaxially stretched production method and improves the natural shrinkage rate by performing cooling strengthening after biaxial orientation and longitudinal stretching, but does not consider the hot-water shrinkage rate measured at 70°C before and after aging. For example, Patent Document 3 attempts to improve the natural shrinkage rate, but technical knowledge regarding improving the natural shrinkage rate is unclear. Furthermore, the shrinkage rate at 70°C before and after aging is not considered. A large decrease in the shrinkage rate at 70°C results in a difference in the initial shrinkage rate during shrinking, resulting in poor shrinkage finish. In particular, when using a shrinking device that uses hot air with a low heat transfer coefficient, a difference in the initial shrinkage rate due to the hot air can be undesirable, resulting in insufficient shrinkage and distortion of the label during finishing.

[0005] To solve these problems, a copolymer polyester raw material for film has been proposed, in which the main dicarboxylic acid component is terephthalic acid, the main diol component is ethylene glycol, and specific amounts of neopentyl glycol and diethylene glycol are contained, with the intrinsic viscosity and melt viscosity of the raw material being defined within specific ranges (see Patent Document 4). This copolymer polyester raw material can reduce the problems of natural shrinkage during film formation and hot water shrinkage when measured at 70°C, but compared to PET, diethylene glycol is copolymerized, which reduces the thermal stability of the resin, and the material is prone to thermal decomposition reactions and has poor heat resistance, leaving room for improvement in terms of recyclability.

[0006] Furthermore, the resin proposed in Patent Document 4 is polymerized using an antimony catalyst system, and has low thermal stability, which poses a problem in terms of recyclability of the scraps generated in the manufacturing process of the heat-shrinkable film. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 5-33895 [Patent Document 2] Patent No. 4411556 [Patent Document 3] Patent No. 5249997 [Patent Document 4] Patent No. 6607473 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made to solve the problems of the prior art, and its object is to provide a copolymer polyester resin that can impart film properties suitable for heat-shrinkable label applications (having a high heat shrinkage rate in the main shrinkage direction and small changes in the natural shrinkage rate and shrinkage rate even with aging) and that is also highly recyclable, as well as a heat-shrinkable film, heat-shrinkable label, and packaging material that use the same. [Means for solving the problem]

[0009] To achieve this objective, the present inventors have conducted extensive research into means for solving the problems of the invention of Patent Document 4 in particular. It was thought that the invention of Patent Document 4 has low thermal stability of the resin, and therefore heating the resin during film formation causes the resin to deteriorate, resulting in a significant decrease in the intrinsic viscosity of the film. Therefore, the present inventors conceived of changing the type of catalyst used in polymerizing the resin in order to improve the thermal stability of the resin. They then discovered that using a combination of an aluminum compound and a phosphorus compound instead of the antimony compound used as the polymerization catalyst in Patent Document 4 improves the thermal stability of the resin and also provides excellent activity as a polymerization catalyst. Therefore, even if the intrinsic viscosity of the resin is reduced to increase the film formation rate, the intrinsic viscosity of the resulting film does not decrease significantly. This allows for a reduction in film production costs without causing problems with film formability or film strength.

[0010] Furthermore, the present inventors have discovered that when a 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid compound is used as the phosphorus compound, an elimination reaction of the tert-butyl group occurs in the polymerization step of the copolymerized polyester resin, reducing the effect of improving the thermal stability of the resin; and that when a copolymerized polyester resin is produced by continuous polymerization, by setting the temperature of the final polymerization vessel within a preferred range, the elimination reaction of the tert-butyl group can be suppressed without significantly reducing the effect of improving the thermal stability of the resin, thereby completing the present invention.

[0011] The present invention was completed based on the above findings and has the following features [1] to [9]. [1] A copolymerized polyester resin having dicarboxylic acid and diol as constituent components, wherein the dicarboxylic acid component is mainly composed of terephthalic acid, the diol component is mainly composed of ethylene glycol, and when all the diol components are taken as 100 mol %, the content of neopentyl glycol is 18 to 32 mol % and the content of diethylene glycol is 7 to 15 mol %, and the molar ratios of phosphorus compounds having the following structures of residue A, residue B, and residue C contained in the copolymerized polyester resin satisfy the following (1): (1) Residue A (mol%) / [Residue B + Residue C] (mol%)>0.5

[0012] [ka] [ka] [ka]

[0013] [2] The copolymer polyester resin according to [1], characterized in that it contains aluminum atoms and phosphorus atoms, the content of aluminum atoms in the copolymer polyester resin is 15 to 40 ppm, and the molar ratio of phosphorus atoms to aluminum atoms in the copolymer polyester resin is 1.8 to 2.6.

[0014] [3] The method for producing a copolymer polyester resin according to [1] or [2], characterized in that an aluminum compound and a 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid compound are used as catalysts. [4] The method for producing a copolymer polyester resin according to [3], characterized in that the copolymer polyester resin is produced by a continuous polymerization method, and the temperature of the final polymerization tank in the production process is 270 to 280°C.

[0015] [5] A heat-shrinkable film comprising a copolymer polyester resin in which the dicarboxylic acid component is primarily terephthalic acid, the diol component is primarily ethylene glycol, and the total diol component is taken as 100 mol % and the neopentyl glycol content is 18 to 32 mol % and the diethylene glycol content is 7 to 15 mol %, an antiblocking agent, and an electrostatic adhesion imparting agent, wherein the molar ratios of phosphorus compounds having the following structures of residue A, residue B, and residue C contained in the heat-shrinkable film satisfy the following (1): (1) Residue A (mol%) / [Residue B + Residue C] (mol%)>0.5

[0016] [ka] [ka] [ka]

[0017] [6] A heat-shrinkable film comprising a polyester resin composition containing the copolymer polyester resin according to [1] or [2], an antiblocking agent, and an agent for imparting electrostatic adhesion. [7] A heat-shrinkable label characterized by using the heat-shrinkable film according to [5] or [6]. [8] A package characterized in that the heat-shrinkable label according to [7] is applied to at least a part of the outer periphery of an object to be packaged and is then heat-shrunk. [Effects of the Invention]

[0018] The copolymerized polyester resin of the present invention is composed of specific copolymerization components, uses an aluminum compound and a phosphorus compound as polymerization catalysts, and further has a high content of the phosphorus compound having a specific residue structure, resulting in high thermal stability. Furthermore, heat-shrinkable films obtained by forming the copolymerized polyester resin into films have excellent heat shrinkability and thermal stability. Furthermore, since the scraps generated during the heat-shrinkable film manufacturing process can be recycled, film manufacturing costs can be reduced.

[0019] Furthermore, packages wrapped with labels obtained from the heat-shrinkable film of the present invention can have an attractive appearance. DETAILED DESCRIPTION OF THE INVENTION

[0020] The heat-shrinkable film of the present invention and the copolymer polyester resin used therein will be described in detail below. The method for producing the heat-shrinkable film will be described in detail later, but the heat-shrinkable film is usually obtained by transporting and stretching the film using rolls or the like. Here, the transport direction of the film is referred to as the longitudinal direction, and the direction perpendicular to the longitudinal direction is referred to as the width direction of the film. Therefore, the width direction of the heat-shrinkable film described below refers to the direction perpendicular to the unwinding direction of the roll, and the longitudinal direction of the film refers to the direction parallel to the unwinding direction of the roll.

[0021] One method for obtaining a film with higher shrinkage is to increase the amount of monomer components (hereinafter simply referred to as amorphous components) that constitute units that can become amorphous components in the film. In films obtained by conventional transverse uniaxial stretching, increasing the amount of amorphous components has been shown to increase the shrinkage rate accordingly. However, while simply increasing the amount of amorphous components can achieve high shrinkage, it has been found that aging can cause problems such as an increase in the natural shrinkage rate and a decrease in the shrinkage rate measured at a low temperature of around 70°C. It has also been found that increasing the amount of amorphous components leads to poor thickness uniformity, impairing the appearance of the film product roll. Therefore, the present inventors focused on diethylene glycol.

[0022] Diethylene glycol has not been widely used in the past because an excessive amount of diethylene glycol deteriorates heat resistance and increases the discharge of foreign matter during melt extrusion. However, the present inventors have discovered that using diethylene glycol as a constituent unit of a copolymer polyester resin reduces the stretching stress during film stretching and also suppresses the decrease in shrinkage measured at a low temperature of about 70°C after aging.

[0023] The copolymerized polyester resin of the present invention is a copolymerized polyester resin having dicarboxylic acid and diol as constituent components, and is composed mainly of ethylene terephthalate units. Specifically, terephthalic acid is used as the main dicarboxylic acid component and ethylene glycol is used as the main diol component in the entire resin components. Here, the term "main component" in the dicarboxylic acid component or diol component refers to a component that accounts for 50 mol% or more of each component. It is more preferably 60 mol% or more, and even more preferably 70 mol% or more.

[0024] Examples of dicarboxylic acid components other than terephthalic acid that constitute the copolymer polyester resin of the present invention include aromatic dicarboxylic acids such as isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid; and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid. In the present invention, terephthalic acid is preferably used in an amount of 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more, of 100 mol% of the dicarboxylic acid components. In a particularly preferred embodiment, no dicarboxylic acid components other than terephthalic acid are contained.

[0025] Here, the interpretation of the above-mentioned term "can become an amorphous component" will be explained in detail. "Amorphous polymer" specifically refers to a polymer that does not have an endothermic peak due to melting when measured with a DSC (differential scanning calorimeter). An amorphous polymer is one in which crystallization has not progressed substantially and is unable to assume a crystalline state, or if it does crystallize, the degree of crystallization is extremely low. Furthermore, "crystalline polymer" refers to a polymer that is not an "amorphous polymer" as described above, i.e., one that has an endothermic peak due to melting when measured with a DSC. A crystalline polymer is a polymer that can crystallize when heated, has the property of being crystallizable, or is already crystallized.

[0026] Generally, a polymer in which many monomer units are bonded will be an amorphous polymer if it meets various conditions, such as low stereoregularity, poor symmetry, large side chains, extensive branching, and weak intermolecular cohesive forces between polymers. However, depending on the state of existence, crystallization may progress sufficiently to become a crystalline polymer. For example, even if a polymer has a large side chain, if the polymer is composed of a single monomer unit, crystallization may progress sufficiently to become crystalline. Therefore, even if the same monomer unit is used, the polymer may be crystalline or amorphous, and therefore, the above uses the expression "monomer-derived units that can become amorphous components."

[0027] Here, in the present invention, the monomer unit refers to a repeating unit constituting a polymer derived from one polyhydric alcohol molecule and one polycarboxylic acid molecule.

[0028] When a monomer unit (ethylene terephthalate unit) composed of terephthalic acid and ethylene glycol is the main monomer unit constituting the polymer, examples of the monomer-derived unit that can become the amorphous component include a monomer unit composed of isophthalic acid and ethylene glycol, a monomer unit composed of terephthalic acid and neopentyl glycol, a monomer unit composed of terephthalic acid and 1,4-cyclohexanedimethanol, and a monomer unit composed of isophthalic acid and butanediol.

[0029] It is also preferable that the copolymer polyester resin does not contain monofunctional carboxylic acids (e.g., benzoic acid, lactic acid, glycolic acid, etc.) or trivalent or higher polycarboxylic acids (e.g., trimellitic acid, pyromellitic acid, and anhydrides thereof, etc.). A heat-shrinkable film obtained using a copolymer polyester resin containing these monofunctional carboxylic acids or polycarboxylic acids will have difficulty achieving the required high shrinkage ratio.

[0030] Examples of diol components other than ethylene glycol that constitute the copolymerized polyester resin of the present invention include aliphatic diols such as 1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, diisopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, and diethylene glycol; alicyclic diols such as 1,4-cyclohexanedimethanol; and aromatic diols such as bisphenol A.

[0031] The copolymer polyester resin of the present invention must contain neopentyl glycol as a diol component. The neopentyl glycol content, relative to 100 mol% of all diol components, is 18 mol% or more, preferably 19 mol% or more, and more preferably 20 mol% or more. Furthermore, the neopentyl glycol content, relative to 100 mol% of all diol components, is 32 mol% or less, preferably 30 mol% or less, more preferably 29 mol% or less, and even more preferably 28 mol% or less. Due to its branched structure, neopentyl glycol reduces the stereoregularity of the polymer and increases its amorphousness. In particular, increasing the amount of neopentyl glycol tends to increase the shrinkage rate. If the amount of neopentyl glycol is less than the above range, the amorphous component will be insufficient, and the target shrinkage rate will not be achieved. However, if the amount exceeds the above range, the target shrinkage rate can be achieved, but problems such as poor shrinkage rate after aging, poor shrinkage rate at low temperatures (70°C), and significant deterioration in heat resistance will occur.

[0032] The copolymerized polyester resin of the present invention must contain diethylene glycol as a diol component. The diethylene glycol content is 7 mol% or more, preferably 8 mol% or more, and more preferably 9 mol% or more, based on 100 mol% of all diol components. Furthermore, the diethylene glycol content is 15 mol% or less, preferably 14 mol% or less, and more preferably 13 mol% or less, based on 100 mol% of all diol components. Diethylene glycol has a longer chain structure than ethylene glycol and contributes to the polymer's flexibility. Combining diethylene glycol with neopentyl glycol reduces the stretching stress during film stretching, thereby suppressing deterioration in shrinkage at low temperatures (70°C) and after aging. If the amount of diethylene glycol is less than the above range, the improvement effect is weak, resulting in failure to achieve the target quality. If the amount of diethylene glycol exceeds the above range, the improvement effect plateaus, resulting in problems such as a significant deterioration in heat resistance and a strong yellowish tint of the film.

[0033] In the copolymerized polyester resin of the present invention, the molar ratio of phosphorus compounds having the following structures of Residue A, Residue B, and Residue C contained in the copolymerized polyester resin preferably satisfies the following (1). The molar ratio of the following (1) is more preferably 0.6 or more, and even more preferably 0.7 or more. There is no particular upper limit to the molar ratio, but in the present invention, it is preferably 1.0 or less. (1) Residue A (mol%) / [Residue B + Residue C] (mol%)>0.5

[0034] [ka] [ka] [ka]

[0035] The phosphorus compound residues contained in these copolymer polyester resins are derived from the phosphorus compounds used as polymerization catalysts during the polymerization of the copolymer polyester resins. Among these phosphorus compound residues, Residue A has a hindered phenol structure, which imparts excellent thermal stability to the copolymer polyester resin and has the effect of suppressing deterioration of the copolymer polyester resin due to heating during film formation. This allows for the recycling of scraps generated during the heat-shrinkable film manufacturing process, thereby reducing film manufacturing costs.

[0036] Furthermore, the copolymer polyester resin of the present invention contains aluminum atoms and phosphorus atoms in the copolymer polyester resin, and it is preferable that the content of aluminum atoms in the copolymer polyester resin is 15 to 40 ppm by mass, and the molar ratio of phosphorus atoms to aluminum atoms in the copolymer polyester resin (P / Al ratio) is 1.8 to 2.6.

[0037] In the present invention, the content of aluminum atoms in the copolymer polyester resin is preferably 15 to 40 ppm, more preferably 17 to 38 ppm, and even more preferably 20 to 35 ppm. If the content (residual amount) of aluminum atoms is less than the above range, the catalytic activity may not be fully exerted. On the other hand, if the content (residual amount) of aluminum atoms exceeds the above range, problems such as reduced thermal stability, generation of foreign matter due to aluminum, and increased coloration may occur.

[0038] In the present invention, the ratio of phosphorus atoms to aluminum atoms is also important. Specifically, in the present invention, the molar ratio of phosphorus atoms to aluminum atoms (P / Al ratio) in the copolymerized polyester resin is preferably 1.8 to 2.6, more preferably 2.0 to 2.4, and even more preferably 2.1 to 2.3. The aluminum atoms and phosphorus atoms in the copolymerized polyester resin are derived from the aluminum compound and phosphorus compound used as polymerization catalysts in the polymerization of the copolymerized polyester resin, respectively. However, even if an aluminum compound is used alone as a polymerization catalyst, it cannot fully exhibit catalytic activity. The catalytic activity can be sufficiently enhanced by using a phosphorus compound in combination with an aluminum compound as a polymerization catalyst in a specific ratio. If the molar ratio of phosphorus atoms to aluminum atoms in the copolymerized polyester resin is outside the above range, the copolymerized polyester resin may not fully function as a polymerization catalyst. In addition, if the molar ratio of phosphorus atoms to aluminum atoms in the copolymerized polyester resin is below the above range, problems such as reduced thermal stability, generation of foreign matter due to aluminum, and increased coloration may occur. On the other hand, if the molar ratio of phosphorus atoms to aluminum atoms in the copolymer polyester resin exceeds the above range, the catalytic activity may not be fully exerted.

[0039] In addition, even when placed under reduced pressure during polymerization of the polyester resin, aluminum atoms in the aluminum compound that functions as a polymerization catalyst remain in the copolymer polyester resin produced by polymerization at nearly 100% of the amount initially added to the system as a catalyst. Therefore, the amount of aluminum atoms used as a polymerization catalyst can be considered to be the content (residual amount) in the resin, and there is no problem in specifying the content (residual amount) instead of the amount used. Furthermore, when placed under reduced pressure during polymerization of the copolymer polyester resin, a portion of the amount initially added to the system as a catalyst is removed from the system, but this removal rate does not fluctuate significantly and is nearly constant. Therefore, considering that the removal rate of phosphorus atoms is also nearly stable, there is no problem in specifying the content (residual amount) instead of the amount used.

[0040] In the present invention, any known aluminum compound can be used as the aluminum compound for the polymerization catalyst without any limitation.

[0041] Specific examples of aluminum compounds include organic aluminum compounds such as aluminum acetate, basic aluminum acetate, aluminum lactate, aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride, aluminum acetylacetonate, and aluminum oxalate, as well as partial hydrolysates thereof. Of these, carboxylates, inorganic acid salts, and chelate compounds are preferred, and among these, aluminum acetate, basic aluminum acetate, aluminum lactate, aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride, and aluminum acetylacetonate are more preferred, aluminum acetate, basic aluminum acetate, aluminum chloride, aluminum hydroxide, and aluminum hydroxide chloride are even more preferred, and aluminum acetate and basic aluminum acetate are most preferred.

[0042] In the present invention, the phosphorus compound used in the polymerization catalyst must be a 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid compound, and among these, dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate shown in the following (chemical formula 1) is preferred.

[0043] [ka]

[0044] (In (Chemical Formula 1), X 1 , X 2 represents hydrogen or an alkyl group having 1 to 4 carbon atoms. 1 , X 2 may be the same or different.)

[0045] Above X 1 , X 2 The alkyl group preferably has 1 to 4 carbon atoms. In particular, an ethyl ester having 2 carbon atoms is preferred because it is readily available as Irganox 1222 (manufactured by BASF). This compound is represented by (Chemical Formula 2).

[0046] [ka]

[0047] The amount of phosphorus compound used as a polymerization catalyst is preferably 31 to 119 ppm, more preferably 39 to 105 ppm, and even more preferably 48 to 92 ppm, of phosphorus atoms remaining in the resulting copolymerized polyester resin relative to the total mass. If phosphorus atoms remain in an amount exceeding the upper or lower limit, polymerization activity may be reduced. As mentioned above, when the copolymerized polyester resin is polymerized under a reduced pressure environment, a portion of the amount of phosphorus compound initially added to the system as a catalyst is removed from the system. However, since this removed amount is approximately constant, the phosphorus compound may be added taking the removed amount into consideration.

[0048] In the present invention, in addition to the aluminum compound and phosphorus compound described above, a metal-containing polycondensation catalyst such as an antimony compound, a titanium compound, a tin compound, or a germanium compound may be used in combination to further improve catalytic activity, provided that the effects of the present invention are not impaired. In this case, the metal-containing polycondensation catalyst preferably contains 5 ppm or less of metal atoms. However, antimony compounds, which are commonly used as polymerization catalysts, are inferior in improving the thermal stability of resins as described above, and therefore should not be used in the present invention.

[0049] In the present invention, in addition to the aluminum compound, a small amount of at least one selected from alkali metals, alkaline earth metals, and compounds thereof may be present as a second metal-containing component. The coexistence of such a second metal-containing component in the catalyst system not only suppresses the production of diethylene glycol but also enhances catalytic activity, thereby obtaining a catalyst component with a higher reaction rate, which is effective in improving productivity. When alkali metals, alkaline earth metals, or compounds thereof are added in combination, the amount used (mol%) is preferably 1×10 based on the number of moles of the dicarboxylic acid component constituting the copolymerized polyester resin. -5 Even when alkali metals, alkaline earth metals, or compounds thereof are placed in a reduced pressure environment during polyester polymerization, almost 100% of the amount used remains, so the amount used can be considered to be the residual amount.

[0050] A cobalt compound can be blended to improve the color tone of the copolymer polyester resin. Addition of this cobalt compound can particularly reduce the color b value. Examples of cobalt compounds include cobalt acetate, cobalt chloride, cobalt benzoate, and cobalt chromate. Among these, cobalt acetate is preferred. The cobalt compound is preferably contained in the copolymer polyester resin in an amount of 1 to 30 ppm, more preferably 3 to 20 ppm, and even more preferably 5 to 15 ppm. If the cobalt content of the copolymer polyester resin is less than the above range, the copolymer polyester resin will have a strong yellow tinge. If the cobalt content exceeds the above range, the copolymer polyester resin will darken or become more bluish due to reduction of the cobalt metal, resulting in a decrease in commercial value.

[0051] The metal compound can be added before the start of the esterification reaction or at any time between the end of the pressure esterification reaction and the start of the initial polycondensation reaction. However, when a titanium compound is used as a polycondensation catalyst, it is preferably added before the esterification reaction. Furthermore, other polycondensation catalysts, heat stabilizers, and additives are preferably added after the esterification reaction.

[0052] The intrinsic viscosity (IV) of the copolymerized polyester resin of the present invention is preferably 0.65 to 0.86 dL / g, more preferably 0.65 to 0.81 dL / g, and even more preferably 0.70 to 0.81 dL / g. If the intrinsic viscosity (IV) of the copolymerized polyester resin is below the above range, the intrinsic viscosity of the resulting film will be too low, resulting in significant drawdown during film formation and making film formation itself difficult. Furthermore, the strength of the resulting film will be weak, making it difficult to achieve the target quality. If the intrinsic viscosity (IV) exceeds the above range, a decomposition reaction will also proceed in parallel during melt polymerization, causing the viscosity increase to plateau. Furthermore, from the standpoint of the stirring capacity of the polymerization machine, the upper limit is approximately 0.86 dL / g. The copolymerized polyester resin of the present invention is an amorphous polymer that does not readily crystallize. Therefore, it cannot assume a crystalline state, or even if it does crystallize, the degree of crystallization is extremely low, resulting in an unclear melting point (the endothermic peak due to melting measured by DSC). Therefore, it is difficult to carry out solid-state polycondensation (solid-state polymerization) at a temperature below the melting point of the copolymer polyester resin, and for this reason, the upper limit of the intrinsic viscosity (IV) of the copolymer polyester resin of the present invention is approximately 0.86 dl / g.

[0053] Various additives, such as waxes, antioxidants, antistatic agents, crystal nucleating agents, viscosity reducers, heat stabilizers, coloring pigments, coloring inhibitors, and ultraviolet absorbers, may be added to the copolymer polyester resin of the present invention as needed.

[0054] Next, a method for producing the copolymer polyester resin of the present invention will be described. The copolymer polyester resin of the present invention can be produced by either a direct esterification reaction using terephthalic acid as a raw material or a transesterification reaction using dimethyl terephthalate as a raw material as a terephthalic acid component. In the present invention, the direct esterification reaction is preferred.

[0055] The method for producing the copolymerized polyester resin of the present invention is classified into a continuous method and a batch method depending on the raw material supply or polymer extrusion mode, but either method can be used. In the present invention, the continuous method is preferred because of its high productivity and high stability of product quality, in which raw materials are continuously supplied and the esterification reaction and subsequent polycondensation reaction are also continuously carried out. In either of these methods, the esterification reaction may be carried out in one stage or in multiple stages. The melt polycondensation reaction may also be carried out in one stage or in multiple stages.

[0056] When producing the copolymerized polyester resin of the present invention, a polymerization catalyst is used to increase the efficiency of the polycondensation reaction. In the present invention, it is preferable to use a polymerization catalyst containing at least one selected from aluminum compounds and at least one selected from phosphorus compounds. The polymerization catalyst can be added to the reaction system at any stage of the polymerization reaction. For example, it can be added to the reaction system before the start of the esterification reaction or transesterification reaction, at any stage during the reaction, immediately before the start of the polycondensation reaction, or at any stage during the polycondensation reaction. Among these, it is preferable to add the catalyst immediately before the start of the polycondensation reaction.

[0057] As described above, the phosphorus compound used in the polymerization catalyst must be a 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid compound. Among them, dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate shown in (Chemical Formula 1) is preferred, and the phosphorus compound shown in (Chemical Formula 2) is most preferred.

[0058] The phosphorus compound used in the polymerization catalyst is preferably added in the form of a slurry or a solution, more preferably solubilized in a solvent such as water or glycol, even more preferably solubilized in water and / or ethylene glycol, and most preferably solubilized in ethylene glycol.

[0059] The ethylene glycol solution of the phosphorus compound used in the present invention is preferably one that has been heat-treated in advance in ethylene glycol. The heat treatment in ethylene glycol is preferably carried out after the phosphorus compound has been dissolved, but it is not necessary for the phosphorus compound to be completely dissolved.

[0060] The heat treatment conditions are that the heat treatment temperature is preferably 175 to 196° C., more preferably 175 to 185° C., and even more preferably 175 to 180° C. The heat treatment time is preferably 30 to 240 minutes, more preferably 60 to 210 minutes.

[0061] The concentration of the phosphorus compound during the heat treatment is preferably 3 to 10% by mass.

[0062] The above heat treatment can make the acidity of the phosphorus compound contained in the ethylene glycol solution constant, and by using it in combination with an aluminum compound, it is possible to improve the polymerization activity and reduce the production of aluminum-based foreign matter.

[0063] In the heat treatment described above, when the phosphorus compound represented by (Chemical Formula 2) used in the present invention is used, a portion of the compound undergoes structural changes. For example, the compound undergoes elimination of the t-butyl group, hydrolysis of the ethyl ester group, and a change to a hydroxyethyl ester structure (a structure transesterified with ethylene glycol). (Note that elimination of the t-butyl group occurs significantly at high temperatures in the polymerization process.) Therefore, in the present invention, the phosphorus compound includes not only the phosphorus compound represented by (Chemical Formula 2), but also structurally modified phosphorus compounds such as those shown in Table 1. The component amounts of each phosphorus compound listed in Table 1 in an ethylene glycol solution can be quantified by P-NMR spectroscopy of the solution.

[0064] [Table 1]

[0065] Therefore, in the present invention, when the phosphorus compound represented by (Chemical Formula 2) is used as the phosphorus compound, the phosphorus compound includes not only diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate but also modified products of diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate shown in Table 1 above.

[0066] In copolymer polyester resins produced using diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate and its modified products as phosphorus compounds, 18 types of phosphorus compound structures as shown in Table 2 are present.

[0067] [Table 2]

[0068] As described above, among the phosphorus compound structures shown in Table 2, Residue A has a hindered phenol structure, and therefore imparts superior thermal stability to the copolymer polyester resin compared to Residues B and C, and has the effect of suppressing deterioration of the copolymer polyester resin due to heating during film formation. Residues B and C are formed by the elimination of the t-butyl group from Residue A. The elimination of the t-butyl group is affected by the temperature of the final polymerization vessel. Therefore, the temperature of the final polymerization vessel is important for increasing the content of Residue A.

[0069] The temperature of the final polymerization tank when producing the copolymerized polyester resin of the present invention is preferably 270 to 280°C, more preferably 272 to 278°C. If the temperature of the final polymerization tank is below the above range, the polymerization activity decreases, and the productivity of the copolymerized polyester resin decreases. On the other hand, if the temperature of the final polymerization tank exceeds the above range, the thermal stability of the copolymerized polyester resin and the heat-shrinkable film deteriorates.

[0070] The melt viscosity of the copolymer polyester resin of the present invention, measured at a shear rate of 6080 / s and 250°C, is preferably 200 Pa·S or less. High melt viscosity makes extrusion difficult unless the resin temperature is high. However, with raw materials containing a large amount of diethylene glycol, as in the present invention, high resin temperatures during extrusion are undesirable because they result in a large amount of foreign matter in the extruded film or sheet. Therefore, the resin temperature during extrusion is preferably 245°C or less, and more preferably 240°C or less. The lower limit of the resin temperature during extrusion is the melting point of the raw materials. However, the raw materials of the present invention do not have a clear melting point and are melted at 210°C, so 210°C is set as the lower limit. Furthermore, a melt viscosity of more than 200 Pa·S measured at 250°C is undesirable because it increases the load on the machine that melts and extrudes the raw materials and requires larger equipment. It is preferably 190 Pa·S or less, and more preferably 180 Pa·S or less. On the other hand, if the melt viscosity is too low, the shear stress at the discharge point of the molten resin is low, causing thickness unevenness, which is undesirable. The melt viscosity measured at 250°C is preferably 100 Pa·S or more, and more preferably 110 Pa·S or more.

[0071] The heat-shrinkable film of the present invention is a heat-shrinkable film containing a copolymerized polyester resin in which the main component of the dicarboxylic acid component is terephthalic acid, the main component of the diol component is ethylene glycol, and the content of neopentyl glycol is 18 to 32 mol % and the content of diethylene glycol is 7 to 15 mol % when all the diol components are taken as 100 mol %, and it is preferable that the molar ratios of phosphorus compounds having the following structures of residue A, residue B, and residue C contained in the heat-shrinkable film satisfy the following (1): (1) Residue A (mol%) / [Residue B + Residue C] (mol%)>0.5

[0072] [ka] [ka] [ka]

[0073] The copolymer polyester resin constituting the heat-shrinkable film of the present invention and (1) are achieved by using the copolymer polyester resin described above.

[0074] The heat-shrinkable film of the present invention preferably uses a polyester resin composition in which an antiblocking agent is blended with a copolymer polyester resin. When the copolymer polyester resin of the present invention is formed into a film, the antiblocking agent forms surface protrusions on the surface of the resulting heat-shrinkable film, thereby improving the handling properties of the film, such as slipperiness, running properties, abrasion resistance, and winding properties. The antiblocking agent is preferably blended as a masterbatch.

[0075] The base material constituting the masterbatch of the antiblocking agent is preferably a polyester resin, and more preferably a polyester resin having the same structure as the above-mentioned copolymer polyester resin.

[0076] The composition of the antiblocking agent is not limited as long as it is insoluble in polyester resin. It may be inorganic particles or organic particles. It may also be inorganic-organic composite particles. The antiblocking agent is preferably contained in the heat-shrinkable film in an amount of 150 to 500 ppm by mass. If the content of the antiblocking agent is less than the above range, the handling properties of the heat-shrinkable film will be reduced. On the other hand, if the content of the antiblocking agent exceeds the above range, the transparency of the heat-shrinkable film will be reduced, and the commercial value of heat-shrinkable labels using the heat-shrinkable film will be reduced.

[0077] The average particle size of the antiblocking agent is preferably 0.5 to 3.0 μm, more preferably 0.8 to 2.5 μm, and even more preferably 1.0 to 2.0 μm. An average particle size of less than 0.5 μm is undesirable because it reduces the effect of imparting handleability, such as smoothness and runnability. On the other hand, an average particle size of more than 3.0 μm is undesirable because it may impair the quality of the film due to the formation of coarse protrusions. The average particle size referred to in the present invention is determined from the particle size distribution measured by laser light scattering using water or ethylene glycol as a medium.

[0078] In the present invention, the blending amount of the antiblocking agent in the antiblocking agent masterbatch is preferably in the range of 0.5 to 20% by mass, more preferably in the range of 0.6 to 15% by mass. If the blending amount of the antiblocking agent is less than 0.5% by mass, it is necessary to blend a large amount of the antiblocking agent masterbatch (B), which is economically disadvantageous. On the other hand, if the blending amount of the antiblocking agent exceeds 20% by mass, aggregation of the antiblocking agent occurs, increasing the number of coarse particles, which can cause problems such as clogging of filters used to clarify the polymer in the film-forming process and increasing surface defects when the film is formed.

[0079] The inorganic particles used in the present invention can be particles made of oxides, carbonates, silicates, sulfates, or aluminates of metals such as titanium, aluminum, silicon, calcium, magnesium, and barium. Specific examples include, but are not limited to, titanium dioxide, alumina, aluminosilicate, silica, calcium oxide, calcium carbonate, and barium sulfate, as well as naturally occurring particles such as talc, mica, kaolinite, and zeolite. The organic particles used in the present invention can be silicone-based, crosslinked polyacrylic acid-based, and benzoguanamine resin-based. Among these, silica particles are preferred.

[0080] The method for producing the antiblocking agent masterbatch in the present invention is not limited, and may be, for example, a polymerization step addition method in which a slurry of the antiblocking agent is added in the polymerization step of the polyester resin, or a so-called melt kneading method in which the antiblocking agent is mixed with a molten polyester resin.

[0081] The timing of addition of the antiblocking agent slurry in the polymerization step addition method is not limited. It may be added at any time from the beginning of the transesterification reaction step or esterification reaction step to the start of initial polymerization. It may be added directly to the reaction vessel, or may be added to the transfer line between the reaction vessels using a mixer or the like. Alternatively, an addition vessel may be installed and the antiblocking agent added. In order to prevent aggregation of the antiblocking agent, it is more preferable to add the antiblocking agent after forming a slurry with glycols and then mechanically dispersing the slurry with a medium-agitation disperser such as a sand grinder, attritor, or ultrasonic wave, and then adding an alkali metal compound, an ammonium compound, or a phosphorus compound to improve dispersion efficiency.

[0082] The melt-kneading method is not limited, and may be carried out using a single-screw or multi-screw kneader, or may be carried out using a kneader.

[0083] The melt-kneading method may be carried out by melting the polyester resin, or by attaching a kneading device to the outlet of the polyester resin polymerization process.

[0084] The melt resistivity of the heat-shrinkable film of the present invention is 0.15×10 8 ~0.6×10 8 Ω·cm is preferable, and 0.15×10 8 ~0.4×10 8The melt resistivity is Ω·cm. If the melt resistivity is below the above range, when a heat-shrinkable film is produced by electrostatic adhesion casting, the resulting film may become permanently charged, resulting in poor handling. On the other hand, if the melt resistivity exceeds the above range, electrostatic adhesion will decrease, resulting in poor productivity of the heat-shrinkable film. The melt resistivity of the heat-shrinkable film is measured from the polyester resin composition that constitutes the heat-shrinkable film.

[0085] The heat-shrinkable film of the present invention preferably uses a polyester resin composition in which an electrostatic adhesion imparting agent is blended with a copolymer polyester resin. When the copolymer polyester resin of the present invention is formed into a film, the electrostatic adhesion imparting agent can improve the electrostatic adhesion of the sheet-like material to a cooling drum in an electrostatic adhesion casting method, thereby achieving effects such as improved film productivity and reduced thickness unevenness in the film. This can improve the productivity and quality of the heat-shrinkable film. The electrostatic adhesion imparting agent is preferably blended as a masterbatch.

[0086] The base material constituting the masterbatch of the electrostatic adhesion imparting agent is preferably a polyester resin, and more preferably a polyester resin having the same structure as the above-mentioned copolymer polyester resin.

[0087] The melt resistivity of the electrostatic adhesion agent masterbatch is 0.005 x 10 8 ~0.05×10 8 In order to improve the film formability of the heat-shrinkable film, it is preferable that the melt resistivity of the polyester resin composition containing the electrostatic adhesion imparting agent masterbatch is 0.15×10 8 ~0.6×10 8 It is preferable that the melt resistivity of the electrostatic adhesion imparting agent masterbatch is 0.05×10 8 If the melt resistivity is higher than Ω·cm, a large amount of electrostatic adhesion agent masterbatch must be added to improve the film-forming properties of the copolymer polyester resin, which can lead to problems such as increased manufacturing costs. 8It is technically difficult to achieve a melt resistivity of less than Ω·cm. A more preferable melt resistivity of the electrostatic adhesion imparting agent masterbatch is 0.005×10 8 ~0.025×10 8 Ω·cm.

[0088] The electrostatic adhesion-imparting masterbatch contains a magnesium compound and an alkali metal compound to reduce melt resistivity. Furthermore, a phosphorus compound is added to disperse these metal ion components in the polyester without converting them into foreign matter and to further improve thermal stability. The magnesium compound is preferably contained in the heat-shrinkable film in an amount of 15 to 150 ppm by mass in terms of the amount of magnesium atoms. If the magnesium compound content is less than the above range, the melt resistivity increases, electrostatic adhesion deteriorates, and film formability decreases. On the other hand, if the magnesium compound content exceeds the above range, the amount of insoluble foreign matter (magnesium salts) produced increases, and thermal stability decreases, resulting in severe film discoloration. The alkali metal compound is preferably contained in the heat-shrinkable film in an amount of 1.5 to 15 ppm by mass in terms of the amount of alkali metal atoms. If the alkali metal compound content is less than the above range, the melt resistivity increases, electrostatic adhesion deteriorates, and film formability decreases. On the other hand, if the alkali metal compound content exceeds the above range, thermal stability decreases, resulting in severe film discoloration. The phosphorus compound is preferably contained in the heat-shrinkable film in an amount of 7 to 80 ppm by mass in terms of the amount of phosphorus atoms. If the phosphorus compound is contained less than the above range, the amount of insoluble foreign matter produced increases, the melt resistivity increases, the electrostatic adhesion deteriorates, and the film-forming ability decreases. Furthermore, this leads to a decrease in thermal stability, resulting in severe coloration of the film. On the other hand, if the phosphorus compound is contained more than the above range, the melt resistivity increases, the electrostatic adhesion deteriorates, and the film-forming ability decreases.

[0089] The magnesium compound used in the present invention can be any known magnesium compound. For example, lower fatty acid salts such as magnesium acetate and alkoxides such as magnesium methoxide can be used alone or in combination of two or more. Magnesium acetate is particularly preferred.

[0090] The amount of magnesium atoms in the electrostatic adhesion-imparting masterbatch is preferably 400 to 2700 ppm by mass relative to the electrostatic adhesion-imparting masterbatch. If the amount of magnesium atoms is less than 400 ppm, the melt resistivity will be high, and a large amount of the electrostatic adhesion-imparting masterbatch will need to be added to improve the film-forming properties of the polyester resin composition, resulting in problems such as reduced efficacy as a masterbatch and increased production costs. If the amount of magnesium atoms exceeds 2700 ppm, the amount of insoluble foreign matter (magnesium salts) produced will increase, and heat resistance will decrease, resulting in severe film coloration. The amount of magnesium atoms is more preferably 450 to 2500 ppm, and even more preferably 450 to 2000 ppm.

[0091] Examples of the alkali metal in the alkali metal compound used in the present invention include lithium, sodium, and potassium. Examples of the alkali metal compound include lower fatty acid salts such as lithium acetate and potassium acetate, and alkoxides such as potassium methoxide. These may be used alone or in combination of two or more. Potassium is preferred as the alkali metal, as it has a significant effect of lowering the melt resistivity. Preferred alkali metal compounds are acetates, with potassium acetate being particularly preferred.

[0092] The amount of alkali metal atoms in the electrostatic adhesion-imparting masterbatch is preferably 40 to 270 ppm by mass relative to the electrostatic adhesion-imparting masterbatch. If the amount of alkali metal atoms is less than 40 ppm, the melt resistivity increases, and a large amount of the electrostatic adhesion-imparting masterbatch must be added to improve the film-forming properties of the polyester resin composition, resulting in problems such as reduced effectiveness as a masterbatch and increased production costs. If the amount of alkali metal atoms exceeds 270 ppm, the improvement in melt resistivity saturates, and heat resistance decreases, resulting in severe film coloration. The amount of alkali metal atoms is more preferably 45 to 250 ppm, and even more preferably 45 to 200 ppm.

[0093] Examples of phosphorus compounds that can be used in the electrostatic adhesion-imparting masterbatch of the present invention include phosphoric acid, phosphorous acid, hypophosphorous acid, phosphonic acid, phosphinic acid, and ester compounds thereof. Examples include phosphoric acid, trimethyl phosphate, tributyl phosphate, triphenyl phosphate, monomethyl phosphate, dimethyl phosphate, monobutyl phosphate, dibutyl phosphate, phosphorous acid, trimethyl phosphite, tributyl phosphite, methylphosphonic acid, dimethyl methylphosphonate, dimethyl ethylphosphonate, dimethyl phenylphosphonate, diethyl phenylphosphonate, diphenyl phenylphosphonate, ethyl diethyl phosphonoacetate, phosphinic acid, methylphosphinic acid, dimethylphosphinic acid, phenylphosphinic acid, diphenylphosphinic acid, methyl dimethylphosphinate, and methyl diphenylphosphinate. Among these, in order to fully exhibit the effects of the present invention, the phosphorus compound is preferably at least one selected from the group consisting of a phosphoric acid trialkyl ester in which the alkyl group of the alkyl ester has 2 to 4 carbon atoms, and ethyl diethyl phosphonoacetate. Among these, it is preferable to use a phosphate triester having an alkyl group having 2 to 4 carbon atoms. Specific examples include triethyl phosphate, tripropyl phosphate, and tributyl phosphate. These may be used alone or in combination of two or more. Triethyl phosphate is particularly preferable because it is believed to form a complex with magnesium ions that has a moderately strong interaction, and it can provide an electrostatic adhesion-imparting masterbatch with low melt resistivity, little foreign matter, and excellent color tone.

[0094] The amount of phosphorus atoms in the electrostatic adhesion-imparting masterbatch is preferably 200 to 1700 ppm by mass relative to the electrostatic adhesion-imparting masterbatch. If the amount of phosphorus atoms is less than 200 ppm, the effect of stabilizing magnesium ions and alkali metal ions and dispersing them in polyester is reduced, resulting in a large amount of insoluble foreign matter being generated. Furthermore, the foreign magnesium loses its effect of reducing melt resistivity, resulting in a high melt resistivity relative to the amount of magnesium added. This also leads to a decrease in heat resistance and severe discoloration of the film. If the amount of phosphorus atoms exceeds 1700 ppm, excess phosphorus compounds interact with magnesium ions, preventing the charge of the magnesium ions from contributing to the effect of reducing melt resistivity, resulting in a high melt resistivity relative to the amount of magnesium added. A more preferred amount of phosphorus atoms is 220 to 1000 ppm.

[0095] The contents of magnesium atoms, alkali metal atoms, and phosphorus atoms in the electrostatic adhesion-imparting agent masterbatch can be quantified by the method described in the Examples section below. The timing of adding the magnesium compound, alkali metal compound, and phosphorus compound to the polyester resin is not particularly limited, but adding them during polyester polymerization, particularly during the esterification (or transesterification) step, or between the end of the esterification (or transesterification) step and the start of the polycondensation step, is preferred because it can prevent the acid component of the polyester and the magnesium ions or alkali metal ions from forming salts and becoming foreign substances, and also allows them to be dispersed uniformly in the oligomer. When these compounds are added during polymerization of a polyester resin, the magnesium atoms and alkali metal atoms remain in the polyester resin composition in almost the same amounts as added, but phosphorus atoms may be distilled out of the polymerization system under reduced pressure. Therefore, it is necessary to determine the amount of phosphorus compound to be added by understanding in advance the relationship between the added amount and the remaining amount.

[0096] When the polyester is a polyester having a dicarboxylic acid component and a glycol component as constituent components, the effects of the present invention can be achieved by the molar ratio of magnesium atoms, alkali metal atoms, and phosphorus atoms satisfying the following formula (2), where m (mol %) is the amount of magnesium atoms, k (mol %) is the amount of alkali metal atoms, and p (mol %) is the amount of phosphorus atoms relative to the dicarboxylic acid component. (2) 2≦(m+k / 2) / p≦3.5

[0097] It is thought that the phosphorus atoms stabilize the magnesium ions and alkali metal ions without turning them into foreign substances. Because magnesium ions are divalent and alkali metal ions are monovalent, the sum of the amounts of magnesium ions and alkali metal ions is expressed as (m+k / 2), and the ratio obtained by dividing this by p, "(m+k / 2) / p," is the relative amount of magnesium ions and alkali metal ions to the phosphorus atoms. If the value of "(m+k / 2) / p" exceeds 3.5, the amount of phosphorus atoms is relatively small compared to the magnesium atoms and alkali metal atoms, which reduces the effect of stabilizing the magnesium ions and alkali metal ions and dispersing them in the polyester, resulting in a large amount of insoluble foreign matter (magnesium salts, alkali metal salts) being produced. Furthermore, the foreign magnesium loses its effect of lowering the melt resistivity, resulting in a high melt resistivity relative to the amount of magnesium added. This also leads to a decrease in heat resistance, which deteriorates the color tone of the electrostatic adhesion agent masterbatch and film. If the value of "(m+k / 2) / p" is less than 2, the amount of phosphorus atoms will be in excess relative to the magnesium atoms and alkali metal atoms, and the excess phosphorus compounds will interact with the magnesium ions, improving the color tone deterioration. However, the electric charge of the magnesium ions will not contribute to the effect of reducing the melting resistivity, and the melting resistivity will increase relative to the amount of magnesium added. "(m+k / 2) / p" is more preferably 2.3 or more and 3 or less, and even more preferably 2.5 or more and 3 or less.

[0098] When the heat-shrinkable film of the present invention is formed into a film having a thickness of 40 μm, it is preferable that the number of defects of 1 mm or more in the longitudinal or transverse direction of the film per 10 square meters is 1.5 or less. A large number of defects is undesirable because the ink will be lost at the defect (foreign matter) during printing, which will impair the appearance of the printed label. The number of defects in the longitudinal or transverse direction of the film per 10 square meters is preferably 1 or less, and more preferably 0.5 or less.

[0099] The heat-shrinkable film of the present invention is immersed in 98°C hot water for 10 seconds without load, and then immediately immersed in 25°C±0.5°C water for 10 seconds. The heat shrinkage rate in the width direction (main shrinkage direction) of the film (i.e., the hot water heat shrinkage rate at 98°C) is preferably 60% or more and 85% or less, calculated from the lengths before and after shrinkage using the following formula (3). The hot water heat shrinkage rate at 98°C is more preferably 63% or more, and even more preferably 66% or more. Note that there is little demand for a film whose hot water heat shrinkage rate for the main shrinkage at 98°C exceeds 85%, so the upper limit of the hot water heat shrinkage rate is set to 85%. (3) Heat shrinkage rate (%) = {(length before shrinkage - length after shrinkage) / length before shrinkage} x 100

[0100] If the hot water heat shrinkage rate in the main shrinkage direction at 98°C is less than the above range, the film will not be able to meet the demand for a highly shrinkable film that covers the entire container (so-called full label), and since the shrinkage amount is small, when the film is used as a label, there is a risk that the label will be distorted, insufficient in shrinkage, wrinkled, loose, etc. after heat shrinkage.

[0101] Furthermore, the heat-shrinkable film of the present invention preferably has a hot water shrinkage rate at 98°C in the direction perpendicular to the main shrinkage direction of the film (longitudinal direction), measured in the same manner as above, of -5% to 10%. The hot water shrinkage rate at 98°C in the direction perpendicular to the main shrinkage direction is more preferably 8% or less, and even more preferably 6% or less. If the hot water shrinkage rate at 98°C in the direction perpendicular to the main shrinkage direction is less than the above range, the film will elongate too much upon heating, which is undesirable because it will not provide a good shrink appearance when used as a label for a container. Conversely, if the hot water shrinkage rate at 98°C in the direction perpendicular to the main shrinkage direction exceeds the above range, the label will become shorter after heat shrinkage (the label height will decrease) and the label area will become smaller, which is undesirable as a full label and is also undesirable because the label will be more likely to become distorted after heat shrinkage.

[0102] If the hot water heat shrinkage rate in the direction perpendicular to the main shrinkage direction at 98°C is lower than -5%, the height of the label will increase after shrinkage, resulting in excess labeling and wrinkles. Therefore, the lower limit was set at -5%.

[0103] The heat-shrinkable film of the present invention preferably has a maximum shrinkage stress in the main shrinkage direction of the film measured under hot air at 90°C of 2 MPa to 7 MPa, and the shrinkage stress 30 seconds after the start of shrinkage stress measurement is 60% to 100% of the maximum shrinkage stress. The maximum shrinkage stress at 90°C is more preferably 6 MPa or less, and even more preferably 5 MPa or less. The maximum shrinkage stress at 90°C is more preferably 2.5 MPa or more, and even more preferably 3 MPa or more. The shrinkage stress is measured by the method described in the examples.

[0104] If the maximum shrinkage stress at 90°C in the main shrinkage direction of the film exceeds the above range, it is not a problem for PET bottles and other containers, but is not preferable for thin-walled containers, as the shrinkage stress can cause collapse during shrinkage. Also, if the maximum shrinkage stress in the main shrinkage direction of the film at 90°C falls below the above range, the label may become loose and not adhere tightly to the container when used as a label for the container, which is also not preferable.

[0105] The heat-shrinkable film of the present invention is immersed in 70°C hot water for 10 seconds without load, and then immediately immersed in water at 25°C±0.5°C for 10 seconds. The heat shrinkage rate in the width direction (main shrinkage direction) of the film (i.e., the hot water heat shrinkage rate at 70°C) calculated from the lengths before and after shrinkage using the above formula (3) is preferably 25% to 50%. The hot water heat shrinkage rate at 70°C is more preferably 30% or more, and even more preferably 35% or more. If the hot water heat shrinkage rate in the main shrinkage direction at 70°C is less than the above range, the shrinkage amount is small when shrunk using a device that uses hot air as a heat source. Therefore, when used as a label, distortion, insufficient shrinkage, wrinkles, slack, etc., may occur in the label after heat shrinkage. Since there is little demand for a film whose hot water heat shrinkage rate in the main shrinkage at 70°C exceeds 50%, the upper limit of the hot water heat shrinkage rate is set to 50%.

[0106] The heat-shrinkable film of the present invention preferably has a difference of 0% to 5% between the hot water shrinkage rate at 70°C before aging and the hot water shrinkage rate when the film is immersed in 70°C hot water for 10 seconds after aging for 672 hours at a temperature of 40°C and a humidity of 65% (see formula (4) below). The difference in shrinkage rate is more preferably 4% or less, and even more preferably 3% or less. A large difference in the hot water shrinkage rate at 70°C before and after aging is undesirable because it results in different temperature conditions in the process of shrinking the film to form labels before and after aging. In particular, when pre- and post-aging films are mixed due to inventory, continuous industrial heat shrinkage is undesirable because the appearance of the shrunk film will differ. Note that it is most desirable for the hot water shrinkage rate to remain unchanged before and after aging, so the lower limit is set to 0%. (4) Difference in thermal shrinkage rate (%) = (hot water shrinkage rate before aging - hot water shrinkage rate after aging)

[0107] The heat-shrinkable film of the present invention preferably has a natural shrinkage percentage in the main shrinkage direction of 0.1% or more and 0.6% or less, as calculated by the following formula (5), after aging for 672 hours at a temperature of 40°C and a humidity of 65%. A value of 0.5% or less is more preferable, and 0.4% or less is even more preferable. If the natural shrinkage percentage in the main shrinkage direction (film width direction) is higher than the above range, the width of the film product roll will decrease, which may result in an inability to match the width during processing such as printing. Although a natural shrinkage percentage of 0% is most preferable, in the present invention, only a value up to 0.1% was confirmed, so the lower limit was set at 0.1%. (5) Natural shrinkage rate (%) = (length after aging - length before aging) ÷ length before aging × 100

[0108] The heat-shrinkable film of the present invention preferably has a tensile breaking elongation of 30% or more in the direction perpendicular to the main shrinkage direction (longitudinal direction) of the film after aging for 672 hours at a temperature of 40°C and a humidity of 65%. The tensile breaking elongation is more preferably 40% or more, and even more preferably 50% or more. If the tensile breaking elongation is below the above range, the film may tear due to the tension in the longitudinal direction applied when the product roll is printed or processed.

[0109] The thickness of the heat-shrinkable film of the present invention is not particularly limited, but is preferably 10 μm or more and 50 μm or less, and the more preferable lower limit of the thickness is 15 μm.

[0110] The heat-shrinkable film of the present invention can be obtained by melt-extruding the copolymerized polyester resin of the present invention using an extruder to form an unstretched film, and then stretching the unstretched film in the width direction. The copolymerized polyester resin can be obtained by polycondensing the above-mentioned suitable dicarboxylic acid component and diol component using a known method. In addition, chip-like copolymerized polyester resin is usually used as a raw material for the film.

[0111] When melt-extruding the copolymer polyester resin, it is preferable to dry the copolymer polyester resin in advance using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer. After drying the copolymer polyester resin in this way, it is melted at a temperature of 230 to 270°C using an extruder and extruded into a film. For extrusion, any existing method such as a T-die method or a tubular method can be used.

[0112] The extruded sheet-like molten resin can then be rapidly cooled to obtain an unstretched film. A suitable method for rapidly cooling the molten resin is to cast the molten resin from a die onto a rotating drum and rapidly cool and solidify it to obtain a substantially unoriented resin sheet.

[0113] The heat-shrinkable film of the present invention can exhibit its properties more favorably by producing it by employing the following methods (1) and (2). (1) Control of transverse stretching conditions For transverse stretching, the film is preheated to a temperature of Tg + 10°C to Tg + 25°C in a tenter while being held at both widthwise edges with clips. It is then preferably stretched 3.5 to 6 times in the widthwise direction while cooling to a temperature of Tg - 5°C to Tg + 9°C. Stretching in the widthwise direction while cooling increases the stress ratio (tensile stress at final stretching ÷ upper yield point stress) in the stress-strain curve, enabling reduction of thickness unevenness in the widthwise direction. After transverse stretching, the film is preferably heat-treated at a temperature between + 1°C and + 10°C above the stretching temperature. Heat treatment at a temperature lower than the stretching temperature is undesirable because the relaxation of molecular orientation is insufficient and the natural shrinkage rate increases. Heat treatment at a temperature higher than the stretching temperature + 10°C is undesirable because the shrinkage rate in the widthwise direction decreases.

[0114] (2) Relaxation in the width direction after transverse stretching In the heat treatment step, the film is preferably relaxed by 0% to 5% in the width direction while being held by clips at both ends in the width direction inside the tenter (0% means no relaxation). Relaxation slightly reduces the shrinkage rate in the width direction, but it also relaxes the molecular orientation in the width direction, allowing for a reduction in shrinkage stress and natural shrinkage. Furthermore, in the final heat treatment step, heat treatment at a temperature higher than the stretching temperature relaxes the molecular orientation, allowing for a reduction in shrinkage stress and natural shrinkage.

[0115] The heat-shrinkable label of the present invention is formed using the heat-shrinkable film of the present invention. The package of the present invention is formed by covering at least a portion of the outer periphery of an object to be packaged with a heat-shrinkable label having perforations or notches obtained from the heat-shrinkable film of the present invention and then heat-shrinking the label. Examples of objects to be packaged include PET beverage bottles, various bottles, cans, plastic containers for confectionery and lunch boxes, and paper boxes. Typically, when a label obtained from a heat-shrinkable film is heat-shrunk to cover such objects, the label is heat-shrunk by approximately 5 to 70% to be tightly attached to the package. The label to be covered on the object to be packaged may or may not be printed.

[0116] To prepare a heat-shrinkable label from the heat-shrinkable film of the present invention, an organic solvent is applied to one side of a rectangular film, slightly inward from the edge, and the film is then immediately rolled up and the edges are overlapped and glued together to form a label. Alternatively, an organic solvent is applied to one side of a rolled film, slightly inward from the edge, and the film is then immediately rolled up and the edges are overlapped and glued together to form a tubular body, which is then cut into labels. Preferred organic solvents for adhesive use are cyclic ethers such as 1,3-dioxolane and tetrahydrofuran. Other suitable organic solvents include aromatic hydrocarbons such as benzene, toluene, xylene, and trimethylbenzene; halogenated hydrocarbons such as methylene chloride and chloroform; and phenols such as phenol, as well as mixtures of these. [Example]

[0117] Next, the present invention will be specifically explained using examples and comparative examples, but the present invention is not limited to the embodiments of these examples and can be appropriately modified within the scope of the present invention. Note that the property values ​​in the examples were evaluated according to the following methods.

[0118] Method for analyzing the composition of copolymer polyester resin 5 mg of sample was dissolved in 0.6 mL of a mixed solution of deuterated chloroform and trifluoroacetic acid (volume ratio 9 / 1). 1 The copolymerization rates of terephthalic acid, ethylene glycol, neopentyl glycol, and diethylene glycol were determined using H-NMR (Varian, UNITY50).

[0119] Aluminum atom content of copolymer polyester resin 0.1 g of the sample was dissolved in 6 M hydrochloric acid solution, left to stand for one day, and then diluted with pure water to make a 1.2 M hydrochloric acid measurement solution. The prepared solution sample was analyzed by high-frequency plasma emission spectroscopy.

[0120] Phosphorus atom content of copolymer polyester resin One gram of sample was converted to orthophosphoric acid by dry ashing in the presence of sodium carbonate, or by wet decomposition in a mixture of sulfuric acid, nitric acid, and perchloric acid, or a mixture of sulfuric acid and hydrogen peroxide. Molybdate was then reacted in a 1 mol / L sulfuric acid solution to form phosphomolybdic acid, which was then reduced with hydrazine sulfate to form heteropoly blue. The absorbance at a wavelength of 830 nm was measured using a Shimadzu UV-150-02 spectrophotometer. The amount of phosphorus atoms in the sample was quantified using a previously prepared calibration curve.

[0121] Antimony atom content of copolymer polyester resin 1 g of sample was wet decomposed in a mixture of sulfuric acid and hydrogen peroxide. Then, sodium nitrite was added to convert antimony atoms to Sb 5+Brilliant Green was added to form a blue complex with antimony. After extracting this complex with toluene, the absorbance at a wavelength of 625 nm was measured using an absorptiometer (Shimadzu Corporation, UV-150-02). The amount of antimony atoms in the sample was colorimetrically determined using a calibration curve prepared in advance.

[0122] Cobalt atom content of copolymer polyester resin 1 g of sample was incinerated in a platinum crucible, and 6 mol / L hydrochloric acid was added and evaporated to dryness. This was then dissolved in 1.2 mol / L hydrochloric acid, and the emission intensity was measured using an ICP emission spectrometer (Shimadzu Corporation, ICPS-2000). The amount of cobalt atoms in the sample was quantified using a previously prepared calibration curve.

[0123] Measurement method for intrinsic viscosity (IV) of copolymer polyester resin 0.1 g of a sample dried at 60°C for 24 hours was precisely weighed and dissolved in 25 mL of a mixed solvent of phenol / tetrachloroethane (3 / 2 (mass ratio)), and the intrinsic viscosity was measured at 30°C using an Ostwald viscometer.

[0124] Measurement method for carboxyl end group concentration (AV) of copolymer polyester resin Accurately weigh out 0.2 g of sample that has been dried at 60°C for 24 hours, and let the weight be W (g). Add 10 ml of benzyl alcohol and the weighed sample to a test tube, immerse the test tube in an oil bath heated to 205°C, and dissolve the sample while stirring with a glass rod. The samples obtained after dissolution times of 3, 5, and 7 minutes are designated A, B, and C, respectively. Next, prepare a new test tube, add only benzyl alcohol, and repeat the same procedure. The samples obtained after dissolution times of 3, 5, and 7 minutes are designated a, b, and c, respectively. Titrate with a 0.04 mol / l potassium hydroxide solution (ethanol solution) whose factor is known. Use phenol red as the indicator, and determine the titer (ml) of potassium hydroxide solution when the color changes from yellow-green to pale pink as the endpoint. Let the titer of samples A, B, and C be XA, XB, and XC (ml). Let the titer of samples a, b, and c be Xa, Xb, and Xc (ml). Using the titer values ​​XA, XB, and XC for each dissolution time, the titer value V (ml) at dissolution time 0 minutes is calculated by the least squares method. Similarly, using Xa, Xb, and Xc, the titer value V0 (ml) is calculated. Next, AV is calculated according to the following formula. AV(eq / t)=[(V-V0)×NF×1000] / W NF: Factor of 0.04 mol / l potassium hydroxide solution W: Sample weight (g)

[0125] Measurement method for color b value of copolymer polyester resin Using a colorimeter (ZE-6000, manufactured by Nippon Denshoku), the color b value was measured using the tristimulus values ​​XYZ, which express the basic stimulus amount of a color. The higher the value, the stronger the yellowness.

[0126] P-NMR spectrum measurement 270 mg of copolymer polyester resin was dissolved in 1.2 mL of a hexafluoroisopropanol + deuterated benzene (1 + 1) mixed solvent, and 7 μL of a 25% phosphoric acid solution in deuterated acetone was added and centrifuged. 95-100 mg of trifluoroacetic acid was then added to the supernatant, and P-NMR measurement was immediately performed. Note that the measurement method is not limited to the above method, and any method that can confirm the peaks corresponding to Table 2 above may be used. Equipment: Fourier transform nuclear magnetic resonance spectrometer (BRUKER, AVANCE500) 31 P resonance frequency: 202.456MHz Lock solvent: deuterated benzene Detection pulse flip angle: 65° Data acquisition time: 1.5 seconds Delay time: 0.5 seconds Proton decoupling: Full decoupling Measurement temperature: 25~35℃ Accumulation count: 20,000 to 30,000 times

[0127] Evaluation method for phosphorus compound structure in copolymer polyester resin and heat-shrinkable film From the spectrum obtained by the P-NMR measurement, the ratio of the total peak integral values ​​of the phosphorus compounds having the structures of residue A, residue B, and residue C to the total peak integral values ​​corresponding to all phosphorus compounds was calculated and expressed as mole %. The molar ratio of the phosphorus compound having the residue A structure was calculated from the mole percentages of residue A, residue B, and residue C according to the following formula. Molar ratio of phosphorus compounds having residue A structure = residue A (mol%) / [residue B + residue C] (mol%)

[0128] Average particle size of silica particles Using a laser light scattering particle size distribution analyzer (Leeds & Northrup, Microtrac HRA model 9320-X100), the ethylene glycol slurry of silica particles was diluted with water and measured in a substantially aqueous system. The diameter at 50% of the cumulative volume of the measurement result was taken as the average particle size.

[0129] Melting resistivity (ρi) Two electrodes (stainless steel wires with a diameter of 0.6 mm) were placed on both ends of a polyester resin composition melted at 275°C, and the composition was sandwiched between two quartz plates with a width of 2 cm, forming a uniform layer of molten polyester resin composition with a width of 2 cm and a thickness of 0.6 mm. A DC voltage of 120 V was applied at a temperature of 280°C, and the current (io) was measured. This was then applied to the following equation to calculate the melt resistivity ρi (Ω·cm). ρi(Ω·cm)=(A / L)×(V / io) [A: electrode area (cm2), L: electrode distance (cm), V: voltage (V)] A(cm 2 ) = [width of molten polyester composition layer] × [thickness] = 2 (cm) × 0.06 (cm), and V = 120 (V). L is a value measured excluding the diameter of the electrode, and is 1.3 cm.

[0130] Evaluation of recyclability of copolymer polyester resin Copolymer polyester resin dried at 60°C for 24 hours was placed in a tabletop kneader (Toyo Seiki, Labo Plastomill 20C200) preheated to 280°C and kneaded at 60 rpm for 2 minutes. After removal, the cut pieces were measured for IV, AV, and color b value using the same method as above. Those satisfying all the following criteria were judged to have good recyclability (denoted by ○); those not satisfying all the criteria were judged to have poor recyclability (denoted by ×). The thermal history in this evaluation corresponds to the thermal history during film formation. If the recyclability was judged to be good, the polyester resin film scraps could be reused.

[0131] Thermal stability (ΔIV) of copolymer polyester resin 1 g of copolymer polyester resin was placed in a glass ampoule and dried at 60°C for 24 hours. The glass ampoule was then sealed under a reduced pressure of 13.3 kPa (in a nitrogen atmosphere) and heat-treated at 300°C for 2 hours. The intrinsic viscosity (IV) was measured before and after heat treatment, and the decrease in intrinsic viscosity due to heating (ΔIV = [IV after heat treatment] - [IV before heat treatment]) was calculated. A ΔIV greater than -0.20 dL / g was judged to have good thermal stability (indicated by ◯), and a value of -0.20 dL / g or less was judged to have poor thermal stability (indicated by ×).

[0132] Static friction coefficient of heat shrinkable film (μs) In accordance with JIS K-7125, a tensile testing machine (Tensilon RTG-1210, manufactured by A&D Co., Ltd.) was used to determine the static friction coefficient (μs) when the front and back surfaces of the film were joined together in an environment of 23°C and 65% RH.

[0133] Heat shrinkage rate before aging (hot water heat shrinkage rate) The film was cut into a 10 cm x 10 cm square and immersed in warm water of a specified temperature ±0.5°C for 10 seconds without load to allow it to heat shrink. After that, it was immersed in water at 25°C ±0.5°C for 10 seconds and then pulled out of the water. The longitudinal and transverse dimensions of the film were measured and the thermal shrinkage rate was calculated according to the following formula. Heat shrinkage rate (%) = {(length before shrinkage - length after shrinkage) / length before shrinkage} x 100

[0134] Heat shrinkage rate after aging The film was aged for 672 hours in an environmental test room at a temperature of 40°C and a humidity of 65%, and then the longitudinal and transverse dimensions of the film were measured in the same manner as in the measurement of the thermal shrinkage rate above, and the thermal shrinkage rate after aging was calculated according to the above formula.

[0135] Shrinkage stress before aging A rectangular film sample measuring 200 mm in length in the main shrinkage direction (transverse direction) and 20 mm in width was cut from the film, and shrinkage stress was measured using a Tensilon universal testing machine PTM-250 (a registered trademark of Orientec) with a heating furnace and a tenacity / elongation tester manufactured by Toyo Baldwin Co., Ltd. (now Orientec). The heating furnace of the tenacity / elongation tester was preheated to 90°C, and the distance between the chucks for holding the film sample was 100 mm. To attach the sample to the chucks of the tenacity / elongation tester, the air flow to the heating furnace was stopped, the furnace door was opened, and 25 mm of each end of the 150 mm long sample was clamped between the chucks. The distance between the chucks was 100 mm, and the sample was secured tightly so that the distance between the chucks was aligned with the length of the sample and the sample was horizontal. After attaching the sample to the chucks, the heating furnace door was quickly closed and the air flow was resumed. The door of the heating furnace was closed and air flow was resumed, and the shrinkage stress (MPa) was measured for 30 seconds starting from the time when the measurement of shrinkage stress was started.

[0136] Label shrinkage evaluation after aging A three-color print was applied to the heat-shrinkable film using Toyo Ink Mfg. Co., Ltd.'s grass, gold, and white inks. Both ends of the printed film were then glued together with dioxolane to create cylindrical labels (labels with the main shrinkage direction of the heat-shrinkable film aligned circumferentially). These were then cut. The diameter of the label in the shrinking direction was 70 mm. The labels were then attached to 500 ml PET bottles (body diameter 62 mm, minimum neck diameter 25 mm) by heat shrinking them in a Fuji Astec Inc. steam tunnel (model: SH-1500-L) at a zone temperature of 90°C for 4 seconds. The neck was adjusted so that the 30 mm diameter was at one end of the label. The finished appearance after shrinkage was evaluated visually, and the label shrinkage was evaluated according to the following criteria. ○: There is no slack between the attached label and the container and it has shrunk. ×: There is slack between the label and the container due to insufficient shrinkage.

[0137] Wrinkle evaluation of label after aging The state of wrinkles on the label attached to the container was evaluated according to the following criteria. ○: The number of wrinkles 2 mm or larger is 2 or less. ×: Three or more wrinkles of 2 mm or larger.

[0138] Preparation of phosphorus compounds Irganox 1222 (manufactured by BASF) as a phosphorus compound was charged into a blending tank together with ethylene glycol, and heated at a liquid temperature of 175°C for 2.5 hours while stirring under nitrogen substitution to prepare an ethylene glycol solution containing 50 g / L of the phosphorus compound.

[0139] Method for producing copolymer polyester resin According to the reaction conditions and quality shown in Table 3, copolymerized polyester resins of raw material resins 1 to 7 were obtained by a known method of carrying out polycondensation via the following esterification reaction.

[0140] Production example 1: Raw resin 1~5 A slurry prepared by mixing terephthalic acid and glycols (ethylene glycol, neopentyl glycol, diethylene glycol) at a certain ratio (G / T: molar ratio of glycol / terephthalic acid) was continuously supplied to a continuous polyester production apparatus comprising three continuous esterification reactors and three polycondensation reactors, with an in-line mixer having a high-speed agitator installed on the transfer line from the third esterification reactor to the first polycondensation reactor, and reacted at a reaction temperature of 256°C and 155 kPa in the first esterification reactor, a reaction temperature of 257°C in the second esterification reactor, and a reaction temperature of 257°C in the third esterification reactor, to obtain a low-order condensate. The low-order condensation product was continuously transferred to a continuous polycondensation apparatus consisting of three reactors, and polycondensation was carried out at a reaction temperature of 261°C in the initial polymerization reactor, a reaction temperature of 272°C and 0.58 kPa in the middle polymerization reactor, and a reaction temperature of 275°C and 0.20 kPa in the final polymerization reactor to obtain a copolymerized polyester resin. The copolymerized polyester resin was extruded into a strand shape, cooled in water, cut, and pelletized. An ethylene glycol solution of an aluminum compound (basic aluminum acetate) and an ethylene glycol solution of a phosphorus compound (Irganox 1222) prepared by the above method were added from the in-line mixer so that the remaining amounts after the completion of polymerization would be the amounts shown in Table 3 relative to the mass of the resulting copolymerized polyester resin.

[0141] Production example 2: Raw resin 6 A copolymer polyester resin was obtained in the same manner as in Production Example 1, except that the reaction temperature in the post-polymerization reactor was 285°C.

[0142] Production example 3: Raw resin 7 A copolymer polyester resin was obtained in the same manner as in Production Example 1, except that in the polymerization method of Production Example 1, instead of the ethylene glycol solution of an aluminum compound and the ethylene glycol solution of a phosphorus compound, an antimony compound (antimony trioxide), a cobalt compound (cobalt acetate), and trimethyl phosphate were added so that the remaining amounts after completion of polymerization would be the amounts shown in Table 3 relative to the mass of the obtained copolymer polyester resin.

[0143] [Table 3]

[0144] Manufacturing Example 4: Antiblocking Agent Masterbatch Raw material resin 1 obtained in Production Example 1 was blended with 99 parts by mass and 1 part by mass of silica particles (manufactured by Fuji Silysia Chemical, Sylysia 266, average particle size 1.5 μm) as an antiblocking agent, and the blend was then melt-kneaded at a cylinder temperature of 300°C using a twin-screw extruder (manufactured by The Japan Steel Works, Ltd., TEX30α) to obtain an antiblocking agent masterbatch.

[0145] Manufacturing Example 5: Electrostatic Adhesion Agent Masterbatch Terephthalic acid, ethylene glycol, and triethylamine were charged into a polymerization system equipped with a stirrer, distillation column, and pressure regulator, and an esterification reaction was carried out according to standard methods. Subsequently, basic aluminum acetate, magnesium acetate dihydrate, potassium acetate, and triethyl phosphate were added so that the aluminum, magnesium, potassium, and phosphorus atoms were 60 ppm, 1000 ppm, and 100 ppm, respectively, of the theoretical amounts of the copolymerized polyester resin. The system temperature was raised to 280°C over one hour, during which the system pressure was gradually reduced to 150 Pa. Under these conditions, a polycondensation reaction was carried out for 80 minutes to obtain an electrostatic adhesion-imparting masterbatch. The resulting electrostatic adhesion-imparting masterbatch had an IV of 0.5 dl / g and a ρi of 0.011 x 10. 8 The resistance was Ω·cm.

[0146] Examples 1 to 3, Comparative Examples 1 to 6 Comparative Examples 5 and 6 are positioned as working examples as copolymer polyester resins, but as heat-shrinkable films, are positioned as comparative examples. The resulting copolymer polyester resins and masterbatches were blended in the amounts listed in Table 4, vacuum-dried at 60°C for 48 hours, and then loaded into an extruder. The resins were melted at 250°C, extruded through a T-die, and rapidly cooled by being wound around a rotating metal roll cooled to a surface temperature of 30°C, yielding an unstretched film with a thickness of 190 μm. The take-up speed of the unstretched film (the rotational speed of the metal roll) was approximately 20 m / min. The resulting unstretched film was introduced into a tenter, preheated to a surface temperature of 90°C, and then stretched 5 times in the width direction while cooling to a surface temperature of 73°C. Next, the film was heated to a surface temperature of 74°C and relaxed 5% in the width direction. The film was then cooled, both edges were trimmed, and wound into a roll with a width of 500 mm, continuously producing a uniaxially stretched film with a thickness of 40 μm over a predetermined length. The properties of the resulting film were evaluated using the methods described above.

[0147] Table 4 shows the evaluation results of Examples 1 to 3 and Comparative Examples 1 to 6.

[0148] [Table 4]

[0149] All of the heat-shrinkable films obtained in the Examples were of high quality. On the other hand, the Comparative Examples were of low quality due to their respective inferior properties. Furthermore, in terms of the recyclability of the copolymer polyester resin, Comparative Examples 1, 3, and 4 did not satisfy ΔIV. However, Comparative Examples 5 and 6, like the Examples, were excellent in recyclability and thermal stability as copolymer polyester resins. [Industrial Applicability]

[0150] The copolymer polyester resin of the present invention can ensure film formability and film strength while reducing the film production cost of the heat-shrinkable film. Furthermore, heat-shrinkable films using the copolymer polyester resin of the present invention have a high heat shrinkage rate, but show little decrease in heat shrinkage rate after aging, making them suitable for label applications. Packages such as containers obtained by using the heat-shrinkable polyester film of the present invention as a label have an attractive appearance. Furthermore, the copolymer polyester resin of the present invention can suppress deterioration of the physical properties of the heat-shrinkable film during film formation, and further allows for a high rate of recycling and reuse of waste film.

Claims

1. A copolymerized polyester resin having dicarboxylic acid and diol as constituent components, wherein 50 mol % or more of the dicarboxylic acid component is terephthalic acid, 50 mol % or more of the diol component is ethylene glycol, and when all of the diol components are taken as 100 mol %, the content of neopentyl glycol is 18 to 32 mol % and the content of diethylene glycol is 7 to 15 mol %, and the molar ratios of phosphorus compounds having the following structures of Residue A, Residue B, and Residue C contained in the copolymerized polyester resin satisfy the following (1): (1) Residue A (mol %) / [Residue B + Residue C] (mol %)>0.5 【Chemical 1】 【Chemistry 2】 【Chemistry 3】

2. The copolymer polyester resin according to claim 1, wherein the copolymer polyester resin contains aluminum atoms and phosphorus atoms, the content of aluminum atoms in the copolymer polyester resin is 15 to 40 ppm, and the molar ratio of phosphorus atoms to aluminum atoms in the copolymer polyester resin is 1.8 to 2.

6.

3. 3. The method for producing a copolymer polyester resin according to claim 1, wherein an aluminum compound and a 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid compound are used as catalysts.

4. 4. The method for producing a copolymer polyester resin according to claim 3, wherein the copolymer polyester resin is produced by a continuous polymerization method, and the temperature of the final polymerization vessel in the production process is 270 to 280°C.

5. A heat-shrinkable film comprising a copolymer polyester resin in which 50 mol % or more of the dicarboxylic acid components are terephthalic acid, 50 mol % or more of the diol components are ethylene glycol, and when all of the diol components are taken as 100 mol %, the content of neopentyl glycol is 18 to 32 mol % and the content of diethylene glycol is 7 to 15 mol %, an antiblocking agent, and an electrostatic adhesion imparting agent, wherein the molar ratios of phosphorus compounds having the following structures of Residue A, Residue B, and Residue C contained in the heat-shrinkable film satisfy the following (1): (1) Residue A (mol %) / [Residue B + Residue C] (mol %)>0.5 【Chemistry 4】 【Chemistry 5】 【Chemistry 6】

6. A heat-shrinkable film comprising a polyester resin composition containing the copolymer polyester resin according to claim 1 or 2, an antiblocking agent, and an agent for imparting electrostatic adhesion.

7. A heat-shrinkable label using the heat-shrinkable film according to claim 5 or 6.

8. A package characterized in that the heat-shrinkable label according to claim 7 is applied to at least a part of the outer periphery of an object to be packaged and then heat-shrunk.

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