HEAT SHRINKABLE POLYESTER FILM

Abstract

Heat-shrinkable polyester film, derived from a first polyester resin and a second polyester resin as a plurality of polyester resins exhibiting different crystallinity, which are reaction products of a polyvalent carboxylic acid and a polyalcohol, wherein the heat-shrinkable polyester film fulfills the following features (A) to (E): (A) the first polyester resin is an amorphous polyester resin in which the polyvalent carboxylic acid contains at least terephthalic acid, and if a total amount of the polyalcohol is assumed to be 100 mol%, the reaction amount of ethylene glycol is in the range of 50 mol% or more and below 90 mol%; (B) the second polyester resin is a crystalline polyester resin in which the polyvalent carboxylic acid contains at least terephthalic acid, and if the total amount of the polyalcohol is assumed to be 100 mol%, a reaction amount of ethylene glycol is 90 mol% or more; (C) the heat-shrinkable polyester film is a heat-shrinkable polyester film which, when an isothermal crystallization measurement is performed by DSC at 150 °C, including a cooling process at a constant temperature, an exothermic peak occurs within 12 minutes of the start, including the cooling process time; (D) the heat-shrinkable polyester film is a heat-shrinkable polyester film in which, when an isothermal crystallization measurement is carried out by DSC at 150 °C, including a cooling process at a constant temperature, the amount of heat corresponding to the obtained exothermic peak area is in the range of 5 to 35 J / g; and (E) the heat-shrinkable polyester film is a heat-shrinkable polyester film in which a thermal shrinkage ratio in one principal shrinkage direction, measured under the thermal shrinkage conditions of immersion in hot water at 80 °C for 10 seconds, is in the range of 20% to 60%, wherein a weight-based mixing ratio of the first polyester resin / second polyester resin is in the range of 20 / 80 to 80 / 20, wherein the mass of the agglomerates as blockage resistance according to APR Document Code: PET-S-08 is less than 5%, and wherein the thickness of the heat-shrinkable polyester film is 25 to 70 µm.

Description

TECHNICAL AREA

[0001] The present invention relates to a heat-shrinkable polyester film (also simply referred to as heat-shrinkable polyester film or heat-shrinkable film).

[0002] In particular, the present invention relates to a heat-shrinkable polyester film which effectively and quantitatively suppresses a blocking phenomenon when recycled, while maintaining excellent conformability to PET bottles. BACKGROUND

[0003] Bottles made of polyethylene resin (HDPE) and polyester resin (PET) (hereinafter referred to simply as PET bottles) have been commonly used as beverage storage containers, detergent storage containers, and the like.

[0004] In particular, PET bottles are widely used worldwide as beverage storage containers because they have excellent lightweight properties and durability and are very practical.

[0005] On the other hand, such PET bottles are thrown into rivers after use, and the discarded bottles cause serious environmental problems such as ending up in the oceans.

[0006] To solve these environmental problems, studies have therefore been actively conducted to improve the technologies for collecting and recycling PET bottles.

[0007] In addition, PET bottles are covered all around with predetermined presentation labels to indicate the names and various information about the contents and to improve the decorative properties and the like.

[0008] In this context, a traditional method was often used to apply a label to paper-based material using an adhesive; however, in recent years the full-surface wrapping of a PET bottle with a presentation label using a heat-shrinkable film has become the standard.

[0009] However, in the case of full-surface wrapping using such a heat-shrinkable film, circumstances may arise where, when a PET bottle is recycled, it is difficult to easily separate a presentation label made using a heat-shrinkable film due to an adhesive structure of the heat-shrinkable film and the like.

[0010] Therefore, a material is preferred for a heat-shrinkable film that is easy to separate from a PET bottle and does not hinder a recycling process for PET bottles.

[0011] Traditionally, vinyl chloride resin (PVC), polystyrene resin (PS), modified polyester (PETG), and the like are often used.

[0012] Here, a main material used in beverage storage containers and the like is essentially PET, and since the component materials of the containers and the heat-shrinkable films are similar, it can be said that it is very possible to recycle a PETG film as a heat-shrinkable film by melting the film together with PET bottles.

[0013] However, since PETG is essentially amorphous, as a thermal property PETG has essentially no melting point or only a melting peak with a low calorific value, and there is a problem that PETG is likely to cause blockage in a recycling process of PET bottles wrapped with a heat-shrinkable film, where the recycled pellets stick together.

[0014] This means that if PET bottles are thermally melted in the recycling process while wrapped in a heat-shrinkable film, as in Fig. As shown in Figure 13A, a problem exists that, as a blockage phenomenon, flakes originating from a recycled resin containing the heat-shrinkable film stick together, forming clumps due to the heat-shrinkable film, and causing blockages in the middle of the pipes.

[0015] Therefore, a problem arises in that recycled pellets obtained when PET bottles containing the heat-shrinkable films are melted under normal circumstances do not adhere to each other, and it is practically difficult to produce recycled pellets with a predetermined shape, as in Fig. 13B shows how to produce pellets effectively and stably using a pelletizer.

[0016] Heat-shrinkable polyester films were proposed, which are obtained by adjusting the thermal properties of PETG films and have a predetermined melting peak (melting point) in differential scanning calorimetry (DSC) (Patent 1 and Patent 2).

[0017] Such a heat-shrinkable polyester film, disclosed in patent specification 1, is characterized in that the amount of mixture of an amorphous polyester resin is reduced to improve the recyclability of PET bottles, a crystalline copolymerized polyester resin derived from a diol component and a dicarboxylic acid component is included, and at the time of heat treatment by immersion of the heat-shrinkable polyester film in hot water at 80 °C for 10 seconds, the thermal shrinkage ratio in the main shrinkage direction is 30% or more, while the melting point measured by DSC is 170 °C or higher.

[0018] Furthermore, the heat-shrinkable polyester film disclosed in patent specification 2 is also configured to contain: (1) 5 to 95 wt.% of a crystallizable polyester, and (2) 5 to 95 wt.% of an amorphous polyester composition to improve the recyclability of PET bottles.

[0019] In particular, the heat-shrinkable polyester film is a heat-shrinkable crystalline polyester film in which the (1) crystallizable polyester contains terephthalic acid as a major component, and a polyalcohol which reacts with the crystallizable polyester contains a predetermined amount of ethylene glycol and at least one of neopentyl glycol, 1,4-cyclohexanedimethanol, and diethylene glycol.

[0020] Furthermore, in the (2) amorphous polyester composition, the dicarboxylic acid component contains about 70 to about 100 mol% terephthalic acid residue and the diol component contains about 40 mol% or less neopentyl glycol residue, about 40 mol% or less 1,4-cyclohexanedimethanol residue and as residue ethylene glycol and diethylene glycol residue.

[0021] JP 2010 248 496 A discloses a polyester-based heat-shrinkable tube suitable for coating electronic components. CITATION LIST PATENT PAPER Patent specification 1: JP 2020-521823 A (Claims and the like) Patent specification 2: WO 2020 / 076749 (Claims and the like) REVELATION OF THE INVENTIONAL TASK THAT IS TO BE SOLVED BY THE INVENTION

[0022] However, in the case of heat-shrinkable polyester films disclosed in patent specification 1 and patent specification 2, there was no intention to create a configuration of a heat-shrinkable polyester film derived from a variety of polyester resins with different crystallinities, and to control the mixing ratios of the polyester resins and the like.

[0023] Furthermore, when an isothermal crystallization measurement was performed by DSC for both heat-shrinkable polyester films, the time at which an exothermic peak occurs and the amount of heat corresponding to the area of ​​the exothermic peak were neither determined nor controlled.

[0024] Therefore, the problem is that the amount of agglomerates formed during recycling varies, and the blocking phenomenon cannot be effectively and quantitatively suppressed.

[0025] To further suppress the blocking phenomenon in the heat-shrinkable polyester films of patent specification 1 and patent specification 2, if the crystallinity of the heat-shrinkable polyester films is increased, on the other hand the problem arises that it is difficult to adjust the thermal shrink ratio and the thermal shrink stress in order to raise the melting point, and that the adaptability is noticeably worsened.

[0026] When PET bottles are recycled after break lines have been inserted to make the heat-shrinkable polyester films easy to remove, a conventional technique is used in which the surrounding heat-shrinkable polyester film is removed manually beforehand.

[0027] The inventors of the present invention have thus made intensive efforts with regard to the problems described above, and as a result, they found that, with regard to a heat-shrinkable polyester film derived from a plurality of polyester resins exhibiting different crystallinities (at least a first polyester resin and a second polyester resin), when various properties such as the exothermic peak time and the exothermic peak area, obtained by isothermal crystallization at a predetermined temperature, and the thermal shrinkage ratio in the main shrinkage direction are simultaneously satisfied, not only is satisfactory adaptability obtained, but the blocking phenomenon during recycling can also be effectively and quantitatively suppressed.

[0028] That is to say, it is an object of the present invention to provide a heat-shrinkable polyester film which, even when a PET bottle in a state where it is covered with the heat-shrinkable polyester film is recycled together with the heat-shrinkable polyester film, maintains a satisfactory conformability and excellent blockage resistance in a quantitatively balanced manner, while maintaining excellent conformability on a PET bottle. MEANS OF SOLVING THE TASK

[0029] According to the present invention, a heat-shrinkable polyester film is provided which is derived from a first polyester resin and a second polyester resin as a plurality of polyester resins having different crystallinity, which are reaction products of a polyvalent carboxylic acid and a polyalcohol, wherein the heat-shrinkable polyester film fulfills the following features (A) to (E) and the above-mentioned problems can be solved. (A) The first polyester resin is an amorphous polyester resin in which the polyvalent carboxylic acid contains at least terephthalic acid, and if a total amount of the polyalcohol is assumed to be 100 mol%, the reaction amount of ethylene glycol is in the range of 50 mol% or more and below 90 mol%. (B) The second polyester resin is a crystalline polyester resin (may hereinafter be referred to as a low-crystalline polyester resin) in which the polyvalent carboxylic acid contains at least terephthalic acid, and if the total amount of the polyalcohol is assumed to be 100 mol%, the reaction amount of ethylene glycol is 90 mol% or more. (C) The heat-shrinkable polyester film is a heat-shrinkable polyester film which, when an isothermal crystallization measurement is performed by DSC at 150 °C, including a cooling process at a constant temperature, an exothermic peak is observed within 12 minutes of the start, including the cooling process time. (D) The heat-shrinkable polyester film is a heat-shrinkable polyester film which, when an isothermal crystallization measurement is carried out by DSC at 150 °C, including a cooling process at a constant temperature, exhibits a quantity of heat corresponding to an exothermic peak area in the range of 5 to 35 J / g. (E) The heat-shrinkable polyester film is a heat-shrinkable polyester film in which a thermal shrinkage ratio in one principal shrinkage direction, measured under the thermal shrinkage conditions of immersion in hot water at 80 °C for 10 seconds, is in the range of 20% to 60%.

[0030] Furthermore, the weight-based mixing ratio of the first polyester resin / second polyester resin has a value in the range of 20 / 80 to 80 / 20, with the mass of the agglomerates having a blocking resistance value of less than 5% according to APR Document Code: PET-S-08, and with a thickness of the heat-shrinkable polyester film being 25 to 70 µm.

[0031] Therefore, with regard to a heat-shrinkable polyester film derived from a predetermined first polyester resin (configuration A) and a predetermined second polyester resin (configuration B) exhibiting different crystallinities, if various properties such as the exothermic peak time (configuration C) and the exothermic peak area (configuration D), obtained through isothermal crystallization, and the thermal shrinkage ratio (configuration E) in the main shrinkage direction are simultaneously satisfied, the blocking phenomenon can be effectively and quantitatively suppressed when the heat-shrinkable polyester film is subjected to recycling, while maintaining excellent adaptability.

[0032] In particular, a heat-shrinkable polyester film that meets configurations (A) to (E) can be used as a heat-shrinkable polyester film in which satisfactory conformability and excellent blocking resistance are each quantitatively balanced.

[0033] Furthermore, in the heat-shrinkable polyester film of the present invention, the weight-related mixing ratio of the first polyester resin / second polyester resin has a value in the range of 20 / 80 to 80 / 20.

[0034] By limiting the mixing ratio of a variety of polyester resins within a predetermined range in this way, a heat-shrinkable polyester film can be obtained in which the blocking phenomenon when subjected to recycling is suppressed more effectively and quantitatively, while maintaining excellent conformability to PET bottles.

[0035] Furthermore, in the configuration of the heat-shrinkable polyester film of the present invention, it is preferred that the first polyester resin is an amorphous polyester resin containing at least 1,4-cyclohexanedimethanol, and that the reaction amount of this 1,4-cyclohexanedimethanol is in the range of 1 mol% or more and below 35 mol% when the total amount (reaction amount) of the polyalcohol is assumed to be 100 mol%.

[0036] By limiting the type and content of the polyalcohol, which is one of the polymerization components of the first polyester resin, to predetermined ranges, the crystallinity can be adjusted more effectively and quantitatively.

[0037] Therefore, a predetermined ratio between the first polyester resin and the second polyester resin improves the balance between satisfactory adaptability and excellent blockage resistance, and these properties can be quantitatively adjusted.

[0038] Furthermore, in the configuration of the heat-shrinkable polyester film of the present invention, it is preferred that the second polyester resin is a crystalline polyester resin containing ethylene glycol alone or both ethylene glycol and diethylene glycol, wherein, when the second polyester resin contains both ethylene glycol and diethylene glycol, the reaction amount of ethylene glycol is 90 mol% or more, while the reaction amount of diethylene glycol is in the range of 1 mol% to 10 mol%, assuming the total amount of the polyalcohol is 100 mol%.

[0039] By limiting the type and amount of reaction of the polyalcohol, which is one of the polymerization components of the second polyester resin, to predetermined ranges, the percentage of a crystalline fraction can be effectively and quantitatively adjusted.

[0040] Therefore, a satisfactory adaptability and excellent blockage resistance can each be quantitatively balanced by a predetermined ratio between the first polyester resin and the second polyester resin.

[0041] Furthermore, in the configuration of the heat-shrinkable polyester film of the present invention, it is preferred that the second polyester resin is a homopolyester resin and a post-consumer recycled polyester resin (may be referred to as PCRP), or either one of these.

[0042] By limiting the type of second polyester resin in this way, waste is reduced, which contributes to the reuse of environmental resources, and at the same time the price is lowered, which is economically advantageous.

[0043] Therefore, by using a predetermined ratio between the first polyester resin and the second polyester resin, the balance between satisfactory adaptability and excellent blockage resistance is further improved, and these properties can be quantitatively maintained.

[0044] Furthermore, in the configuration of the heat-shrinkable polyester film of the present invention, it is preferred that, if the total amount of the first polyester resin and the second polyester resin is assumed to be 100 parts by weight (pbw), the amount of lubricant in the mixture has a value in the range of 0.01 to 5 parts by weight.

[0045] By mixing in a lubricant and limiting the amount of mixture in this way, even when the heat-shrinkable polyester film is formed into a long roll, the fusion between heat-shrinkable polyester films that come into contact can be prevented, while suppressing effects on the properties of the heat-shrinkable polyester film, and furthermore, the lubricant can help to further suppress the blocking phenomenon during recycling.

[0046] Furthermore, in the configuration of the heat-shrinkable polyester film of the present invention, it is preferred that the heat-shrinkable polyester film also fulfills the following feature (F).

[0047] (F) The thermal shrinkage ratio in a direction that intersects the principal shrinkage direction orthogonally, measured under the thermal shrinkage conditions of immersion in hot water at 80 °C for 10 seconds, is in the range of -3% to 10%.

[0048] Since feature (F) is fulfilled in this way, not only is adequate thermal shrinkage achieved and satisfactory adaptability to PET bottles and the like, but the blocking phenomenon during recycling can also be effectively and quantitatively suppressed.

[0049] Furthermore, in the configuration of the heat-shrinkable polyester film of the present invention, it is preferred that the heat-shrinkable polyester film also fulfills the following feature (G).

[0050] (G) The thermal shrinkage stress in the main shrinkage direction, measured under the thermal shrinkage conditions of immersion in hot water at 80 °C for 10 seconds, is 8 MPa or less.

[0051] Since feature (G) is fulfilled in this way, not only is adequate thermal shrinkage achieved and satisfactory adaptability obtained without damaging PET bottles and the like, but the blocking phenomenon during recycling can also be effectively and quantitatively suppressed. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A to 1C are diagrams illustrating different embodiments of a heat-shrinkable polyester film; Fig. 2A and Fig.2B are diagrams provided to explain the relationship between the weight-based mixing ratio of the first polyester resin / second polyester resin from which each of the heat-shrinkable polyester films is formed and the evaluation of conformability, or the relationship between the weight-based mixing ratio and the evaluation of blockage resistance; Fig. Figure 3 is a diagram provided to illustrate the relationship between the mixing ratio of the first polyester resin / second polyester resin and the thermal shrinkage stress; Fig. Figure 4 is a diagram provided to illustrate the relationship between the mixing ratio of the first polyester resin / second polyester resin and the glass transition temperature; Fig.Figure 5 is a diagram provided to illustrate the relationship between the mixing ratio of the first polyester resin / second polyester resin and the peak formation time by isothermal crystallization; Fig. Figure 6 is a diagram provided to illustrate the relationship between the mixing ratio of the first polyester resin / second polyester resin and the thermal shrinkage ratio when immersed in hot water at 80 °C for 10 seconds; Fig. Figure 7 is a diagram provided to illustrate the relationship between the peak formation time at the time of isothermal crystallization and the evaluation of blocking resistance; Fig. 8A and Fig.8B are diagrams provided to explain the DSC diagrams of heat-shrinkable polyester films (Example 1 or Comparative Example 1) obtained by isothermal crystallization including a cooling process at a constant temperature; Fig. 9A and Fig. 9B are diagrams provided to explain the relationship between the amount of heat corresponding to the exothermic peak area obtained by isothermal crystallization of heat-shrinkable polyester films and the evaluation of adaptability, respectively, and the relationship between the amount of heat and the evaluation of blockage resistance; Fig. Figure 10 is a diagram provided to illustrate the relationship between the thermal shrinkage temperature and the thermal shrinkage ratio of each heat-shrinkable polyester film; Fig. 11A and Fig.11B are diagrams provided to illustrate the relationship between the thermal shrinkage ratio under the shrinkage conditions of immersion in hot water at 80 °C for 10 seconds and the evaluation of the adaptability, or the relationship between the thermal shrinkage ratio and the evaluation of the blocking resistance for each of the heat-shrinkable polyester films; Fig. Figure 12 is a diagram provided to illustrate a recycling process for PET bottles covered with a heat-shrinkable polyester film; and Fig. Figure 13A is an outline diagram illustrating a condition in which the blocking phenomenon occurs in a recycling process for PET bottles covered with a conventional heat-shrinkable polyester film, and Fig.Figure 13B is an outline diagram of recycled pellets obtained in a PET bottle recycling process in which the blocking phenomenon does not occur. MEANS OF EXECUTING THE INVENTION [First embodiment]

[0052] In a first embodiment, as described in the Fig. Figures 1A to 1C show a heat-shrinkable polyester film derived from a first polyester resin and a second polyester resin as a variety of polyester resins exhibiting different crystallinity, which are reaction products of a polyvalent carboxylic acid and a polyalcohol, wherein the heat-shrinkable polyester film fulfills the following features (A) to (E) and the above-mentioned tasks can be solved. (A) The first polyester resin is an amorphous polyester resin in which the polyvalent carboxylic acid contains at least terephthalic acid, and when the total amount of the polyalcohol is assumed to be 100 mol%, the reaction amount of ethylene glycol is in the range of 50 mol% or more and below 90 mol%. (B) The second polyester resin is a crystalline polyester resin (may be referred to as a low-crystalline polyester resin) in which the polyvalent carboxylic acid contains at least terephthalic acid, and if the total amount of the polyalcohol is assumed to be 100 mol%, the reaction amount of ethylene glycol is 90 mol% or more. (C) A heat-shrinkable polyester film in which, when an isothermal crystallization measurement is performed by DSC at 150 °C, including a cooling process at a constant temperature, an exothermic peak occurs within 12 minutes of start, including the cooling process time. (D) A heat-shrinkable polyester film in which, when an isothermal crystallization measurement is performed by DSC at 150 °C, including a cooling process at a constant temperature, the amount of heat corresponding to the exothermic peak area is in the range of 5 to 35 J / g. (E) A heat-shrinkable polyester film in which the thermal shrinkage ratio in the main shrinkage direction, measured under the thermal shrinkage conditions of immersion in hot water at 80 °C for 10 seconds, is in the range of 20% to 60%.

[0053] The heat-shrinkable polyester film of the first embodiment is described in detail below by dividing the item into its individual components with reference to the drawings. 1. First polyester resin(1) Polyvalent carboxylic acid

[0054] The polyvalent carboxylic acid that is one of the polymerization components (raw material components) of the first polyester resin is not particularly limited, as long as it is a compound that can react with a polyalcohol and form a polyester structure, and, for example, the polyvalent carboxylic acid can be at least one of aliphatic dicarboxylic acids such as adipic acid, sebacic acid and azelaic acid; aromatic dicarboxylic acids such as terephthalic acid, naphthalenedicarboxylic acid and isophthalic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexaneedicarboxylic acid; and ester-forming derivatives of these acids.

[0055] In particular, when terephthalic acid is used, satisfactory reactivity with a polyalcohol is obtained, a crystalline polyester structure and the like are easily formed, and the material is relatively inexpensive, which is economically advantageous.

[0056] If the total amount of polyvalent carboxylic acid used is assumed to be 100 mol%, it is therefore preferred that the reaction amount of terephthalic acid has a value of 90 mol% or more, and preferably a value in the range of 95 mol% to 100 mol%. (2) Type of polyalcohol

[0057] The polyalcohol (which may also be called the diol component) should be a mixture containing at least ethylene glycol, which is one of the polymerization components of the first polyester resin.

[0058] By limiting the type of polyalcohol in this way, which is one of the polymerization components of the first polyester resin, the proportion of an amorphous component can be adjusted, and furthermore, not only can satisfactory adaptability be obtained, but the blocking phenomenon can also be suppressed more effectively by the relationship with the second polyester resin.

[0059] Furthermore, it is preferred, when using a mixture containing a predetermined amount of ethylene glycol, to use at least one other polyalcohol selected from diols having an alicyclic structure, such as 1,4-cyclohexanedimethanol; aliphatic diols, such as diethylene glycol, propanediol, butanediol, neopentyl glycol and hexanediol; and aromatic diols, in combination as a polyalcohol other than ethylene glycol.

[0060] Therefore, an amorphous polyester resin in which at least one aspect of the crystallinity or amorphism is controlled can be readily obtained by using such a polyalcohol that reacts appropriately with the polyvalent carboxylic acid. This means that by using a specific polyalcohol in a straight-chain form without branches or in a straight-chain form with branches, the melting point, thermal shrinkage ratio, thermal shrinkage stress, and similar properties of the polyester resin obtained by the reaction of the polyalcohol with the polyvalent carboxylic acid can be more easily adjusted to values ​​within predetermined ranges.

[0061] Therefore, the other polyalcohol used in combination with ethylene glycol is preferably 1,4-cyclohexanedimethanol and diethylene glycol, or either one of these. (3) Reaction amount of polyalcohol

[0062] Furthermore, when using a mixture containing a predetermined amount of ethylene glycol, at least the reaction amount of ethylene glycol has a value of 50 mol% or more and less than 90 mol%.

[0063] The reason for this is that with a reaction amount of less than 50 mol% ethylene glycol, problems such as high melt viscosity, poor flowability and difficulties in shaping can occur.

[0064] On the other hand, if the reaction amount of ethylene glycol is 90 mol% or more, an excessively large crystalline fraction is formed, and the properties, such as the adaptability, of the resulting heat-shrinkable polyester film may be noticeably impaired.

[0065] Moreover, the reaction amount of each polyalcohol, including ethylene glycol, can indeed be determined from the residual amount of each alcohol component and the like; however, the reaction amount can simply be replaced by the amount supplied by each alcohol component.

[0066] Furthermore, when using a mixture containing a predetermined amount of ethylene glycol as a raw material component, it is preferred that the reaction amount of 1,4-cyclohexanedimethanol and diethylene glycol, or either of them, has a value in the range of 1 mol% to 35 mol%.

[0067] The reason for this is that if the reaction amount of 1,4-cyclohexanedimethanol and the like is below 1 mol%, a smaller amorphous fraction is formed, and conversely, an excessively large crystalline fraction is formed, and the properties, such as the adaptability, of the resulting heat-shrinkable polyester film may be noticeably worsened.

[0068] On the other hand, if the total reaction amount of 1,4-cyclohexanedimethanol and similar compounds exceeds 35 mol%, problems such as high melt viscosity, poor flowability, and difficulties in shaping can occur. Furthermore, it can be difficult to effectively and quantitatively suppress crystallinity, glass transition temperature, and blockage during recycling.

[0069] Therefore, it is preferred that the total reaction amount of 1,4-cyclohexanedimethanol and the like be in the range of 5 mol% or more and below 30 mol%, and even more preferably in the range of 10 mol% to 28 mol%.

[0070] It is preferred that the molar ratio of 1,4-cyclohexanedimethanol and diethylene glycol, based on the total reaction amount of 1,4-cyclohexanedimethanol and diethylene glycol, has a value in the range of 9:1 to 1:9.

[0071] Furthermore, to modify the thermal and mechanical properties of the heat-shrinkable polyester film, another dicarboxylic acid or hydroxycarboxylic acid alone, or a mixture of two or more types thereof, can be used, provided that this does not deviate from the purpose of the present invention. (4) Amorphy

[0072] The first polyester resin is essentially amorphous, and with regard to the criteria for amorphism, the amorphism can be determined, for example, by the fact that no predetermined melting peak occurs during DSC measurement or that a calorific value is hardly detectable.

[0073] Furthermore, the amorphity can also be determined by displaying the change point of the specific heat, which indicates the glass transition temperature, within a predetermined temperature range during DSC measurement.

[0074] Furthermore, amorphism can also be determined by the fact that the degree of crystallinity, which is measured according to JIS K 7112, is low.

[0075] That is, the degree of crystallinity of a polyester resin can be calculated by measuring the density (d) of a sample, which is about 3 mm in size on each of the four sides, using the density gradient column method according to JIS K 7112, using an aqueous calcium nitrate solution and with reference to the known density (dc) of perfectly crystalline polyethylene terephthalate and the density (da) of perfectly amorphous polyethylene terephthalate, and the proportion of the amorphous fraction can be specifically calculated from this. (5) Glass transition temperature

[0076] Furthermore, it is preferred that the glass transition temperature of the first polyester resin has a value in the range of 50 °C to 90 °C.

[0077] The reason for this is that if the glass transition temperature is below 50 °C, in a drying process carried out when recycling PET bottles wrapped with heat-shrinkable polyester film, it is likely that the presentation labels using the heat-shrinkable polyester film will become sticky, recycled pieces may stick together in the form of flakes, and the blocking phenomenon may easily occur.

[0078] On the other hand, if the glass transition temperature is above 90 °C, the amount of heat required for extrusion processing and stretching of a raw film of heat-shrinkable polyester film becomes too high, and the processing itself can become difficult, or it can be difficult to control the thermal shrinkage ratio.

[0079] Therefore, it is preferred that the glass transition temperature of the first polyester resin has a value in the range of 60 °C to 85 °C, and even more preferably a value in the range of 65 °C to 80 °C.

[0080] The glass transition temperature of the first polyester resin can be measured, for example, using the following method in DSC measurement (the same applies below). 1) In the first run, the temperature of the first polyester resin is increased from room temperature to approximately 300 °C as a test sample at a heating rate of 10 °C / min. 2) The temperature is then rapidly reduced from 300 °C to room temperature at a rate of approximately 30 °C / min. 3) In the second cycle, the temperature is increased from room temperature to approximately 300 °C at a heating rate of 10 °C / min.

[0081] Then the change point of the specific heat shown on the DSC diagram, obtained in the second pass, can be called the glass transition temperature of the first polyester resin. (6) Melting point

[0082] If the first polyester resin has a melting point, it is preferred that the melting point has a value in the range of 190 °C to 270 °C.

[0083] The reason for this is that if the melting point is below 190 °C, in a drying process carried out during the recycling of PET bottles and the like, it is likely that the presentation labels using heat-shrinkable polyester film will become sticky, recycled parts may clump together, and the blocking phenomenon may easily occur.

[0084] On the other hand, if the melting point is more than 270 °C, the amount of heat required for extrusion processing and stretching of a raw film of heat-shrinkable polyester film becomes too high, processing can become difficult, or it can be difficult to control the thermal shrinkage ratio, and the adaptability to PET bottles and the like can be noticeably impaired.

[0085] If the first polyester resin has a melting point, it is therefore preferred that the melting point has a value in the range of 200 °C to 270 °C, and even more preferably a value in the range of 210 °C to 270 °C.

[0086] Furthermore, if the first polyester resin has a melting point, the melting point can, for example, be specified as a peak temperature (Tm) of the heat of fusion, which is represented as an endothermic reaction in a profile obtained by DSC. (7) Intrinsic viscosity

[0087] It is also preferred that the intrinsic viscosity (IV value) of the first polyester resin has a value in the range of 0.6 to 0.85 dL / g.

[0088] The reason for this is that if the intrinsic viscosity has a value below 0.6 dL / g, the melt viscosity is too low, which can lead to problems with extrusion formability or unsatisfactory blocking resistance during recycling.

[0089] On the other hand, if the marginal viscosity is above 0.85 dL / g, the melt viscosity is too high, and conversely, there may be problems with extrusion formability, or satisfactory conformability may not be achieved.

[0090] Therefore, it is preferred that the intrinsic viscosity has a value in the range of 0.65 to 0.83 dL / g, and even more preferably a value in the range of 0.7 to 0.8 dL / g.

[0091] The intrinsic viscosity of a polyester resin can be measured according to JIS K 7390 (the same applies below).

[0092] That is to say, in particular, the intrinsic viscosity (IV value) in a mixed solvent of phenol and 1,1,2,2-tetrachloroethane (weight ratio = 1 / 1) at a temperature of 30 °C was measured using an Ubbelohde viscometer. (8) Additive

[0093] Furthermore, it is preferred that the first polyester resin is mixed as required with various additives such as an oxidation inhibitor, a weather-resistant stabilizer, an antistatic agent, an anti-fogging agent, a metal soap, a wax, an antifungal agent, an antibacterial agent, a nucleating agent, a flame retardant and a lubricant in a specific quantity (e.g. in a proportion of 0.01 to 10 parts by weight of the total quantity).

[0094] Furthermore, the method of adding the additives is not particularly limited, and a known method can be used.

[0095] Furthermore, it is preferred that the first polyester resin contains an inorganic lubricant such as calcium carbonate particles, silicon dioxide particles or glass particles to improve the lubricity on the film surface.

[0096] Furthermore, as regards the lubricant as one of the additives, the type is not particularly restricted, and inorganic lubricants and organic lubricants commonly used for films can be used individually or as mixtures.

[0097] In particular, examples of anoarganic lubricants include calcium carbonate particles, silicon dioxide particles, glass particles and microparticles formed from zeolite, talc and kaolin.

[0098] Furthermore, examples of organic lubricants include microparticles formed from cross-linked polymethyl methacrylate, cross-linked polystyrene, silicone rubber, a silicone copolymer, polyamide and a condensed resin containing a triazine ring, with microparticles made of silicone rubber and a silicone copolymer being particularly preferred. 2. Second polyester resin(1) Polyvalent carboxylic acid

[0099] The polyvalent carboxylic acid, which is one of the polymerization components (raw material components) of the second polyester resin, is not particularly limited as long as it is a compound that can react with a polyalcohol and form a polyester structure; however, the polyvalent carboxylic acid contains at least terephthalic acid.

[0100] When terephthalic acid is used in this way, satisfactory reactivity with a polyalcohol is obtained, a crystalline polyester structure is likely to form, and the material is relatively inexpensive, which is economically advantageous.

[0101] If the total amount of polyvalent carboxylic acid used is assumed to be 100 mol%, it is therefore preferred that the reaction amount of terephthalic acid has a value of 90 mol% or more, and preferably a value in the range of 95 mol% to 100 mol%.

[0102] To modify the thermal and mechanical properties of the heat-shrinkable polyester film, it is also preferred that the second polyester resin contains a predetermined amount of at least one of the following: aliphatic dicarboxylic acids such as adipic acid, sebacic acid and azelaic acid; aromatic dicarboxylic acids such as naphthalenedicarboxylic acid and isophthalic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexaneedicarboxylic acid; and ester-forming derivatives thereof, as a polyvalent carboxylic acid other than terephthalic acid, insofar as this does not deviate from the purpose of the present invention.

[0103] In particular, when the polyvalent carboxylic acid is isophthalic acid, unlike terephthalic acid, isophthalic acid mixes easily and uniformly with terephthalic acid, increases the transparency and thermal shrinkage ratio of the heat-shrinkable polyester film, and can suppress the blocking phenomenon during recycling more effectively and quantitatively. (2) Type of polyalcohol

[0104] At least ethylene glycol should be used as the polyalcohol (which can also be called the diol component), which is one of the polymerization components of the second polyester resin.

[0105] By limiting the type of polyalcohol in this way, the crystallinity can be adjusted to a desired range, and by relating it to the first polyester resin, the blocking phenomenon can be suppressed more effectively and quantitatively.

[0106] Furthermore, at least one aliphatic diol, such as diethylene glycol, propanediol, butanediol, neopentyl glycol and hexanediol; alicyclic diol other than 1,4-cyclohexanedimethanol; aromatic diol and the like, is preferably mixed as a polyalcohol other than ethylene glycol.

[0107] Therefore, a low-crystalline polyester resin, in which at least the crystallinity or amorphism is controlled, can easily be obtained by using such a polyalcohol that reacts appropriately with the polyvalent carboxylic acid.

[0108] In particular, it is preferable to select diethylene glycol or neopentyl glycol as the other polyalcohol and to use a combination of ethylene glycol and diethylene glycol or a combination of ethylene glycol and neopentyl glycol.

[0109] This means that by using a specific polyalcohol in straight-chain form without branches or in straight-chain form with branches, the melting point, thermal shrinkage ratio, thermal shrinkage stress, and the like of the polyester resin obtained by reacting the polyalcohol with the polyvalent carboxylic acid can be more easily adjusted to values ​​within a predetermined range. (3) Reaction amount of the polyalcohol

[0110] If the total amount of the polyalcohol used as one of the polymerization components of the second polyester resin is assumed to be 100 mol%, it is preferred that the reaction amount of ethylene glycol has a value of 90 mol% or more.

[0111] The reason for this is that if the reaction amount of ethylene glycol and similar components is below 90 mol%, a smaller crystalline fraction is formed, and when this is mixed with the initial polyester resin, it can be difficult to achieve satisfactory crystallinity. This means that it can be difficult to effectively and quantitatively suppress the blocking phenomenon during recycling.

[0112] Therefore, it is preferred that the reaction amount of ethylene glycol and the like has a value of 95 mol% or more, and even more preferably a value in the range of 99 mol% to 100 mol%.

[0113] In order to modify the thermal and mechanical properties of the heat-shrinkable polyester film to an extent that does not deviate from the purpose of the present invention, the above-mentioned diethylene glycol and the like, diols having an alicyclic structure, hydroxycarboxylic acids and the like can be used individually, or two or more types thereof can be used as mixtures. (4) Type of other polyester resin

[0114] As shown in (1) to (3) above, the second polyester resin can be a polyester resin obtained by carrying out a condensation reaction of a predetermined polyvalent carboxylic acid and a predetermined polyol in predetermined proportions; however, it is also particularly preferred to use a homopolyester resin, that is, a polyester resin consisting only of terephthalic acid and ethylene glycol.

[0115] Furthermore, it is also preferred to use a post-consumer recycled polyester resin as a second polyester resin, that is, a polyester resin obtained by collecting used PET bottles and the like and by carrying out washing, shredding, drying and pelletizing the PET bottles and the like.

[0116] Furthermore, it is also preferred to use unused polyester resin and at least one made from a homopolyester resin and a post-consumer recycled polyester resin in combination.

[0117] A second polyester resin like this one reduces waste, contributes to the reuse of environmental resources, and is also cost-effective, which is economically advantageous.

[0118] Therefore, a predetermined ratio between the first polyester resin and the second polyester resin improves the balance between satisfactory adaptability and excellent blockage resistance, and these properties can be quantitatively maintained. (5) Crystallinity and melting point

[0119] Furthermore, as regards the criteria for the crystallinity of the second polyester resin, the crystallinity can be determined, just as with the first polyester resin, from the position of the melting peak (melting point) of the crystalline fraction, the heat quantity of the melting peak, and the like, which are obtained by DSC.

[0120] Furthermore, the degree of crystallinity can also be measured according to JIS K 7112, and the crystallinity can be determined from this.

[0121] Furthermore, the melting point of the second polyester resin should have a value in the range of 190 °C to 270 °C.

[0122] The reason for this is that if such a melting point has a value of less than 190 °C, in a drying process carried out when recycling PET bottles wrapped with heat-shrinkable polyester film, it is likely that the presentation labels using the heat-shrinkable polyester film will become sticky, recycled pieces may stick together in the form of flakes, and the blocking phenomenon may easily occur.

[0123] On the other hand, if the melting point has a value of more than 270 °C, the amount of heat required for the extrusion processing and stretching of a raw film of heat-shrinkable polyester film becomes too high, and processing can become difficult, or the adaptability during use can be noticeably impaired.

[0124] Therefore, it is preferred that the melting point of the polyester resin has a value in the range of 200°C to 270°C, and even more preferably a value in the range of 220°C to 270°C.

[0125] The melting point of the polyester resin can be measured, for example, as the peak temperature (Tm) of the heat of fusion, which is represented as an endothermic reaction in a diagram obtained using DSC (the same applies below).

[0126] Furthermore, the crystallinity of the polyester resin can be estimated based on the area, the half-width, and the like of the peak of the heat of fusion. (6) Glass transition temperature

[0127] If the second polyester resin has a glass transition temperature, it is preferred that this temperature is in the range of 50°C to 90°C.

[0128] The reason for this is that if this glass transition temperature is less than 50°C, in a drying process carried out when recycling PET bottles wrapped with heat-shrinkable polyester film, it is likely that the presentation labels using the heat-shrinkable polyester film will become sticky, recycled pieces may stick together in the form of flakes, and the blocking phenomenon may easily occur.

[0129] On the other hand, if the glass transition temperature is above 90°C, the amount of heat required for extrusion processing and stretching of a raw film of heat-shrinkable polyester film becomes too high, and processing can become difficult, or it can be difficult to control the thermal shrinkage ratio.

[0130] If the second polyester resin has a glass transition temperature, it is therefore preferred that the temperature be in the range of 60 °C to 85 °C, and even more preferably in the range of 65 °C to 80 °C. (7) Intrinsic viscosity

[0131] It is also preferred that the intrinsic viscosity (IV value) of the second polyester resin has a value in the range of 0.6 to 0.85 dL / g.

[0132] The reason for this is that if the intrinsic viscosity is below 0.6 dL / g, the melt viscosity may be too low, and there may be a problem with extrusion formability.

[0133] On the other hand, if the intrinsic viscosity has a value above 0.85 dL / g, the melt viscosity is too high, and there may be a problem with extrusion formability.

[0134] Therefore, it is preferred that the intrinsic viscosity has a value in the range of 0.63 to 0.83 dL / g, and even more preferably a value in the range of 0.65 to 0.8 dL / g. (8) Additive

[0135] Furthermore, as with the first polyester resin, it is preferred that the second polyester resin be mixed as required with various additives such as an oxidation inhibitor, a weather-resistant stabilizer, an antistatic agent, an anti-fogging agent, a metal soap, a wax, an antifungal agent, an antibacterial agent, a nucleating agent, a flame retardant and a lubricant in a predetermined quantity.

[0136] Furthermore, the method of adding the additives is not particularly restricted, and a known method can be used. 3. Heat-shrinkable polyester film(1) Mixing ratio of first polyester resin / second polyester resin

[0137] According to the invention, the weight-related mixing ratio (hereinafter simply referred to as the mixing ratio) of the first polyester resin / second polyester resin has a value in the range of 20 / 80 to 80 / 20.

[0138] The reason for this is that by limiting the mixing ratio of a variety of polyester resins exhibiting different crystallinity to predetermined ranges, the blocking phenomenon when PET bottles are recycled can be suppressed more effectively, while maintaining excellent adaptability to PET bottles.

[0139] Therefore, it is preferred that the mixing ratio of the first polyester resin / second polyester resin has a value in the range of 25 / 75 to 75 / 25, and even more preferably a value in the range of 30 / 70 to 70 / 30.

[0140] With regard to the combination of the specific polyester resins that form the heat-shrinkable polyester film of the present invention, reference is made here to the Fig. The relationship between the mixing ratio of the first polyester resin / second polyester resin and the evaluation of adaptability and the relationship between the mixing ratio and the evaluation of blockage resistance are described.

[0141] That means, in Fig. 2A, the abscissa axis represents the mixing ratio of the first polyester resin / second polyester resin that form the heat-shrinkable polyester film, and the ordinate axis represents the evaluation (relative value) of the adaptability.

[0142] Furthermore, in the diagram, Example 1 is referred to as Ex. 1, while the comparison example 1 is referred to as VB 1, and the same applies in the following.

[0143] From the characteristic curve in Fig.2A shows that if the mixing ratio is in the range of 100 / 0 to 70 / 30, the highest evaluation point of adaptability is obtained, so that the evaluation point is 5, regardless of the mixing ratio.

[0144] Furthermore, when the mixing ratio is in the range of over 70 / 30 and 50 / 50 or less, the evaluation of adaptability tends to decrease slightly, and there is a tendency for the evaluation point to decrease from 5 to about 3.

[0145] When the mixing ratio is in the range of over 50 / 50 and 20 / 80 or less, although the evaluation of adaptability varies, there is a clear tendency towards decrease, and a tendency is observed for the evaluation point to decrease to about 1 to 2.

[0146] With regard to the heat-shrinkable polyester film of the present invention, it is therefore assumed that by adjusting the mixing ratio of the first polyester resin / second polyester resin to a value in a relatively wide range of 20 / 80 to 80 / 20, and preferably to a value in the range of 30 / 70 to 70 / 30, a relatively satisfactory or sufficiently acceptable evaluation of the adaptability will be obtained.

[0147] In Fig. 2B, the abscissa represents the mixing ratio of the first polyester resin / second polyester resin that form the heat-shrinkable polyester film, and the ordinate represents the evaluation (relative value) of the blocking resistance.

[0148] From the characteristic curve in Fig.2B shows that the evaluation of blockage resistance tends to be improved when the mixing ratio is in the range of 100 / 0 or more and below 80 / 20, since the mixing ratio of the first polyester resin is smaller.

[0149] Furthermore, if the mixing ratio is in the range of 80 / 20 to 20 / 80, a satisfactory evaluation of the blocking resistance is obtained, regardless of the mixing ratio. Therefore, with regard to the heat-shrinkable polyester film of the present invention, it is assumed that even if the mixing ratio of the first polyester resin / second polyester resin has a value in a relatively wide range of at least 20 / 80 to 80 / 20, and preferably a value in the range of 30 / 70 to 70 / 30, a satisfactory or sufficiently acceptable blocking resistance is obtained.

[0150] Furthermore, it shows Fig.3. The relationship between the mixing ratio of the first polyester resin / second polyester resin and the thermal shrinkage stress (80 °C) of the heat-shrinkable polyester film. However, since the thermal shrinkage stress at 80 °C is strongly influenced by the thermal shrinkage ratio at 80 °C, the description is limited to… Fig. 3 on the measurement data of the examples and the like, where the thermal shrinkage ratio at 80 °C is in the range of 20% to 60%.

[0151] From the characteristic curve in Fig. Paragraph 3 shows that even if the mixing ratio has a value in a relatively wide range from 20 / 80 to 80 / 20, and preferably a value in the range of 30 / 70 to 70 / 30, the value of the thermal shrinkage stress can be controlled to a low value of 8 MPa or less, and effects such as preventing deformation of the object to be encased or the like can be demonstrated.

[0152] Furthermore, it shows Fig. 4 the relationship between the mixing ratio of the first polyester resin / second polyester resin and the glass transition temperature of the heat-shrinkable polyester film.

[0153] From the characteristic curve in Fig. 4 shows that even if the mixing ratio has a value in a relatively wide range from 20 / 80 to 80 / 20, and preferably a value in the range from 30 / 70 to 70 / 30, the glass transition temperature can be quantitatively controlled with very high accuracy to a higher glass transition temperature by relatively decreasing the mixing ratio of the first polyester resin, or conversely, by relatively increasing the mixing ratio of the second polyester resin.

[0154] Furthermore, it shows Fig.5 the relationship between the mixing ratio of the first polyester resin / second polyester resin and the peak formation time for the isothermal crystallization, which is described below (hereinafter referred to simply as peak formation time).

[0155] From the characteristic curve in Fig. Paragraph 5 shows that even if the mixing ratio has a value in a relatively wide range from 20 / 80 to 80 / 20, and preferably a value in the range of 30 / 70 to 70 / 30, the peak formation time can be quantitatively controlled with very high accuracy to a value of more than 5 minutes and 12 minutes or less, and preferably to a value of 5.5 minutes or more and 9 minutes or less.

[0156] Fig. Figure 6 shows the relationship between the mixing ratio of the first polyester resin / second polyester resin and the thermal shrinkage ratio when immersed in hot water at 80 °C for 10 seconds.

[0157] However, since the thermal shrinkage ratio at 80 °C is potentially strongly influenced by the stretch ratio in the main shrinkage direction (TD direction), the description is limited to Fig. 6 on the measurement data where the stretch ratio in the main shrinkage direction (TD direction) is four times greater.

[0158] From the characteristic curve in Fig. Figure 6 shows that even if the mixing ratio has a value in a relatively wide range from 20 / 80 to 80 / 20, and preferably a value in the range of 30 / 70 to 70 / 30, the thermal shrinkage ratio at a predetermined temperature can be quantitatively controlled with very high accuracy to a value in the range of 20% to 60%, and preferably to a value in the range of 25% to 50%. (2) Peak formation time during isothermal crystallization

[0159] As in Fig.Figure 7 shows heat-shrinkable polyester films which feature (C) that when an isothermal crystallization measurement is performed by DSC at 150 °C, including a cooling process at a constant temperature (normally -10 °C to 10 °C, and for example 0 °C), an exothermic peak occurs within 12 minutes of the start of the measurement, including a cooling process time at a constant temperature (normally 1 to 5 minutes and generally 5 minutes).

[0160] For example, as in Fig. Figure 8A shows that if an isothermal crystallization measurement is performed at 150 °C, including a cooling process time (5 minutes) at a constant temperature (0 °C), and an exothermic peak occurs after 3.8 minutes after the start of heating to 150 °C, the peak formation time is 5 + 3.8 = 8.8 minutes.

[0161] Because an exothermic peak corresponding to crystallization occurs in a relatively short time, the blocking phenomenon can be effectively and quantitatively suppressed in a drying process carried out during the recycling of PET bottles wrapped with heat-shrinkable polyester film.

[0162] On the other hand, as in Fig. Figure 8B shows that if an isothermal crystallization measurement is performed at 150 °C, including a cooling process time (5 minutes) at a constant temperature (0 °C), and an exothermic peak does not occur even after 12 minutes after starting the heating to 150 °C, it is determined that the crystallization proceeds slowly under the predetermined conditions.

[0163] This is because, during a drying process carried out in the recycling of PET bottles and the like, the recycled parts stick together in the form of flakes, and the blocking phenomenon occurs due to the slow crystallization of the heat-shrinkable polyester film.

[0164] As feature (C), it is therefore preferred that the peak formation time is 10 minutes or less, more preferably 9 minutes or less, including a cooling process time at constant temperature.

[0165] Here, back to Fig. 7, the relationship between the formation time for an exothermic peak caused by isothermal crystallization (including a cooling process time at constant temperature; hereinafter referred to simply as peak formation time) and the evaluation of the blocking resistance in each of the heat-shrinkable polyester films is described.

[0166] That means, in Fig. Figure 7 represents the abscissa axis as the peak formation time and the ordinate axis as the evaluation of the blocking resistance (relative value).

[0167] From the characteristic curve in Fig. 7 shows that if the peak formation time is 12 minutes or less, a satisfactory evaluation of the blocking resistance is obtained; however, if the peak formation time is more than 12 minutes, the evaluation of the blocking resistance tends to decrease noticeably.

[0168] With regard to the heat-shrinkable polyester film of the present invention, it is therefore assumed that the blocking phenomenon can be effectively and quantitatively suppressed if the peak formation time at the time of isothermal crystallization is 12 minutes or less, and preferably more than 5 minutes and 10 minutes or less. (3) Quantity of heat corresponding to the exothermic peak area obtained by isothermal crystallization

[0169] Furthermore, as in Fig. Figure 8A shows a heat-shrinkable polyester film provided where, as feature (D), when an isothermal crystallization measurement is performed by DSC at 150 °C, including a cooling process at a constant temperature, the amount of heat corresponding to the exothermic peak area has a value in the range of 5 to 35 J / g.

[0170] The reason for this is that if isothermal heating to a predetermined temperature, including a cooling process at constant temperature, is carried out, crystallization occurs in a relatively short time according to the crystallinity of the resin (for example, 8.8 minutes from start, including the cooling process time of 5 minutes).

[0171] By confirming the occurrence of a corresponding exothermic peak, the blocking phenomenon in a drying process carried out during the recycling of PET bottles wrapped with heat-shrinkable polyester film can be effectively and quantitatively suppressed.

[0172] This means that if the amount of heat corresponding to the exothermic peak area is below 5 J / g, the recycled parts in the form of flakes will stick together in a drying process carried out in the recycling of PET bottles, and the blocking phenomenon is likely to occur.

[0173] On the other hand, if the amount of heat corresponding to the exothermic peak area exceeds 35 J / g, this means that the crystalline fraction formed by isothermal crystallization is large, and the potential uses of the PET resin obtained through recycling may be excessively limited. Therefore, the PET resin may not be suitable for applications such as a heat-shrinkable polyester film.

[0174] Incidentally, as in Fig. As shown in 8B, in comparative example 1 and the like, since an exothermic peak does not occur within a predetermined time (e.g. within 12 minutes after the start, including the cooling process time of 5 minutes), the blocking phenomenon occurs in the drying process carried out in the recycling of PET bottles wrapped with heat-shrinkable polyester film.

[0175] Furthermore, the T line in Fig.8A represents the temperature profile, and line H represents a characteristic curve corresponding to the heat flow.

[0176] Here, in relation to Fig. 9A and Fig. 9B describes the relationship between the amount of heat corresponding to the exothermic peak area obtained by isothermal crystallization and the evaluation of the adaptability and the relationship between the amount of heat and the evaluation of the blockage resistance of heat-shrinkable polyester films.

[0177] That means, Fig.Figure 9A is a diagram illustrating the relationship between the amount of heat corresponding to the exothermic peak area obtained by isothermal crystallization and the evaluation of the adaptability, where the abscissa represents the amount of heat (J / g) corresponding to the exothermic peak area obtained by isothermal crystallization, while the ordinate represents the evaluation (relative value) of the adaptability. Although the data in Fig. 9A, based on the examples and comparative examples described below, the description is limited to the data for the measurement and evaluation of adaptability in examples and the like where the thermal shrinkage ratio at 80 °C is in the range of 20% to 60%, since it is assumed that the evaluation of adaptability is strongly influenced by the thermal shrinkage ratio under predetermined measurement conditions.

[0178] From the characteristic curve in Fig. 9A further indicates that even if the amount of heat corresponding to the exothermic peak area is below 5 J / g or above 5 J / g and 35 J / g or less, a value greater than 2 is obtained as a relative value for the evaluation of adaptability. However, if the amount of heat corresponding to the exothermic peak area is above 35 J / g, the evaluation of adaptability has a value below 2 and tends to decrease.

[0179] With regard to the combination of specific polyester resins that form the heat-shrinkable polyester film of the present invention, it is therefore assumed that a satisfactory adaptability is effectively and quantitatively obtained when the amount of heat corresponding to the exothermic peak area has a value in a relatively wide range of 8 to 32 J / g, and preferably a value within the range of 11 to 29 J / g.

[0180] Furthermore, in Fig. 9B the abscissa axis represents the amount of heat (J / g) corresponding to the exothermic peak area obtained by isothermal crystallization of heat-shrinkable polyester films, and the ordinate axis represents the evaluation (relative value) of the blocking resistance.

[0181] From the characteristic curve in Fig.As can be seen in 9B, the evaluation of blockage resistance tends to decrease when the amount of heat corresponding to the exothermic peak area is in the range of less than 5 J / g.

[0182] Furthermore, even if the amount of heat corresponding to the exothermic peak area has a value of 5 to 35 J / g or a higher value than this, a satisfactory evaluation of the blocking resistance tends to be obtained, regardless of the amount of heat.

[0183] However, if the amount of heat is excessively large, the evaluation of adaptability may tend to decrease.

[0184] Therefore, it is assumed that if the amount of heat corresponding to the exothermic peak area has a value in a relatively wide range of 8 to 32 J / g, and preferably a value in the range of 11 to 29 J / g, each of the heat-shrinkable polyester films will have a satisfactory adaptability, and the blocking phenomenon can also be effectively and quantitatively suppressed. (4) Thermal shrinkage ratio 1

[0185] The heat-shrinkable polyester film exhibits the following property (E) with respect to the thermal shrinkage ratio under predetermined temperature conditions.

[0186] This means that the thermal shrinkage ratio (which may be referred to as thermal shrinkage ratio 1) in the main shrinkage direction (usually TD direction during manufacturing), measured under the thermal shrinkage conditions of immersion in hot water at 80 °C for 10 seconds, has a value in the range of 20% to 60%.

[0187] The reason for this is that if the thermal shrinkage ratio in the TD direction, obtained by heat shrinking at a predetermined temperature in this way, is controlled to a value within a predetermined range, wrinkles are less likely to occur, the formation of a shrinkage cavity is reduced, and as a result, a satisfactory appearance is likely to be obtained.

[0188] Furthermore, by limiting the thermal shrinkage ratio in the TD direction at relatively high temperatures, the total thermal shrinkage of the heat-shrinkable polyester film can be compensated, the resulting thermal shrinkage stress can be reduced, and more stable pellets can be obtained, even when the heat-shrinkable polyester film is recycled together with PET bottles.

[0189] Therefore, it is preferred that the thermal shrinkage ratio in the TD direction has a value in the range of 25% to 55%, and even more preferably a value in the range of 30% to 50%.

[0190] Fig. Figure 10 shows the relationship between each thermal shrinkage temperature (70 °C, 80 °C, 90 °C and 100 °C) and the thermal shrinkage ratio obtained at that temperature in the heat-shrinkable polyester films of Examples 1 to 6 and Comparative Examples 1 to 5.

[0191] Out of Fig. Paragraph 10 shows that for the heat-shrinkable polyester films of Examples 1 to 6, the obtained value of the thermal shrink ratio increases with increasing thermal shrinkage temperature, and that, for example, the value of the thermal shrink ratio tends to increase significantly at a thermal shrinkage temperature in the range of 70 °C to 80 °C. However, if the thermal shrinkage temperature is above 80 °C, and particularly in the range of 90 °C to 100 °C, the value of the thermal shrinkage ratio tends to be saturated in the range of approximately 30% to 50%.

[0192] In contrast, at least with the heat-shrinkable polyester films of comparison examples 1 to 3, the obtained value of the thermal shrink ratio also increases with increasing thermal shrinkage temperature, and it is evident that even in the range of 90 °C to 100 °C the obtained value of the thermal shrink ratio tends to increase further.

[0193] Therefore, with the heat-shrinkable polyester films of Examples 1 to 6 of the present invention, even if the value of the thermal shrinkage temperature fluctuates to some extent, a constant thermal shrinkage ratio can be obtained.

[0194] Fig. 11A and Fig.11B are diagrams showing the relationship between the thermal shrinkage ratio under predetermined shrinkage conditions of the heat-shrinkable polyester films and the evaluation of conformability, and the relationship between the thermal shrinkage ratio and the evaluation of blockage resistance.

[0195] That means, in Fig. 11A the abscissa represents the thermal shrinkage ratio (%) of the heat-shrinkable polyester film when immersed in hot water at 80 °C for 10 seconds, and the ordinate represents the evaluation (relative value) of the conformability.

[0196] From the characteristic curve in Fig. 11A indicates that if the thermal shrinkage ratio is less than 20%, the evaluation of adaptability tends to be significantly lower.

[0197] Furthermore, even if the thermal shrinkage ratio is in the range of 20% to 60%, or above 60%, a satisfactory evaluation of adaptability will be obtained, regardless of the thermal shrinkage ratio at 80°C.

[0198] Therefore, with regard to the heat-shrinkable polyester films of the present invention, it is assumed that a satisfactory evaluation of the adaptability is stably maintained when the thermal shrinkage ratio has a value in the range of 20% to 60%, and preferably a value in the range of 25% to 50%.

[0199] Furthermore, in Fig. 11B the abscissa axis represents the thermal shrinkage ratio (%) of the heat-shrinkable polyester film when immersed in hot water at 80°C for 10 seconds, and the ordinate axis represents the evaluation (relative value) of the blocking resistance.

[0200] From the characteristic curve in Fig. Paragraph 11B shows that even if the thermal shrinkage ratio is below 20%, a satisfactory evaluation of the blocking resistance is obtained, and if the thermal shrinkage ratio is in the range of 20% or more and below 50%, a satisfactory evaluation of the blocking resistance is likewise obtained.

[0201] On the other hand, if the thermal shrinkage ratio is above 50% or up to about 60%, the evaluation of blockage resistance decreases noticeably; however, a practically usable evaluation of blockage resistance will still be obtained.

[0202] With regard to each of the heat-shrinkable polyester films of the present invention, it is therefore assumed that if the thermal shrinkage ratio has a value in the range of 20% to 60%, and preferably a value in the range of 25% to 50%, the blocking phenomenon can be effectively and quantitatively suppressed. (5) Thermal shrinkage ratio 2

[0203] As feature (F) it is preferred that the thermal shrinkage ratio (may be referred to as thermal shrinkage ratio 2) in a direction (normally MD direction during manufacturing) that intersects the main shrinkage direction orthogonally, measured under the thermal shrinkage conditions of immersion in hot water at 80 °C for 10 seconds, has a value in the range of -3% to 10%.

[0204] The reason for this is that if the thermal shrinkage ratio in the MD direction, measured under predetermined thermal shrinkage conditions, is controlled to a predetermined range, wrinkles are less likely to occur, the formation of shrinkage cavities is reduced, and as a result, a satisfactory appearance is likely to be obtained.

[0205] Furthermore, by limiting the thermal shrinkage ratio in the MD direction, the total thermal shrinkage of the heat-shrinkable polyester film can be balanced, the resulting thermal shrinkage stress can be reduced, and even if the heat-shrinkable polyester film is recycled together with PET bottles, the occurrence of the blocking phenomenon can be suppressed, while recycled pellets can be obtained in more quantitative and stable quantities.

[0206] Therefore, it is preferred that the thermal shrinkage ratio in the MD direction as feature (F) has a value in the range of -2% to 8%, and even more preferably a value in the range of 0% to 5%. (6) Thermal shrinkage stress

[0207] Furthermore, it is preferred as feature (G) that the thermal shrinkage stress in the main shrinkage direction, measured under the thermal shrinkage conditions of immersion in hot water at 80 °C for 10 seconds, has a value of 8 MPa or less.

[0208] The reason for this is that if the thermal shrinkage stress exceeds 8 MPa, a similar thermal shrinkage stress to that of heat-shrinkable polyvinyl chloride films cannot be obtained, and as a result, general usability for various PET bottles, ranging from thin-walled to thick-walled bottles, cannot be achieved.

[0209] Therefore, it is preferred that the thermal shrinkage stress has a value in the range of 1 to 7 MPa, and even more preferably a value in the range of 2 to 6 MPa.

[0210] Furthermore, the thermal shrinkage stress at 80 °C can be calculated by dividing the thermal shrinkage force (N / 15 mm) at 85 °C for a long test specimen, measured using a thermal shrinkage tester according to ISO 14616-1997, by the thickness of the test specimen. (7) Thickness and haze value (7)-1 Thickness

[0211] It is preferred that the thickness of the heat-shrinkable polyester film can be varied according to the different shapes of PET bottles; however, according to the invention, the thickness has a value in the range of 25 to 70 µm.

[0212] The reason for this is that if the thickness of the heat-shrinkable polyester film is less than 20 µm, handling can be difficult, and tear resistance and the like can be noticeably impaired.

[0213] On the other hand, if the thickness of the heat-shrinkable polyester film exceeds 100 µm, it may not be possible to subject the heat-shrinkable polyester film to uniform thermal shrinkage when heated to a predetermined temperature, or it may be difficult to produce the film with a uniform thickness.

[0214] Therefore, it is preferable that the thickness of the heat-shrinkable polyester film has a value in the range of 30 to 50 µm.

[0215] Furthermore, the thickness of the heat-shrinkable polyester film can be measured according to ISO 4593 using a micrometer (manufacturer: Mitutoyo Corporation, product name “Thickness Gauge 547-401”). (7)-2 Turbidity value

[0216] With regard to the heat-shrinkable polyester film prior to shrinking, it is also preferred that the turbidity value, measured according to ASTM D1003, is 10% or less.

[0217] The reason for this is that by limiting the turbidity value to a value equal to or less than a predetermined value, alignment with respect to the PET bottle or the like and the testability of the contents are facilitated, while on the other hand a PET bottle containing a heat-shrinkable polyester film can be obtained which is excellent not only before thermal shrinking but also after thermal shrinking in terms of transparency, appearance, decorativeness and the like.

[0218] Conversely, if the turbidity value exceeds 10%, the alignment with respect to the PET bottle or the like and the recognizability of the contents may be impaired, and even if a decorative layer is provided, the color development properties and the like may be noticeably deteriorated.

[0219] However, if the turbidity value is excessively low, the types, mixing quantities, and the like of usable polymerization components are limited, it can be difficult to control the manufacturing process, and production efficiency can decrease excessively.

[0220] Therefore, it is preferred that the turbidity value be in the range of 1% to 8%, and even more preferably in the range of 2% to 5%. (8) Functional layer and additives (8)-1 Functional layer

[0221] It is also preferred that the heat-shrinkable polyester film has a functional layer to give different functions to the surface or an inner area as required, provided that this does not impair the purpose and suitability of the present invention.

[0222] Examples of such functional layers include coating layers to provide surface lubricity, dirt resistance, weather resistance, and the like; a transfer layer; and a printing layer to impart design properties.

[0223] Among these, a coating layer that uses a surfactant is particularly preferred as a functional layer, since the coating layer contributes significantly to improving the antistatic properties and surface lubricity.

[0224] As in Fig.As shown in Figure 1B, it is also preferred, for example, to laminate other resin layers 10a and 10b, containing at least one of these different additives, onto one or both surfaces of the heat-shrinkable polyester film 10.

[0225] In this case, it is preferred that, if the thickness of the heat-shrinkable polyester film is assumed to be 100%, the individual layer thickness or the total thickness of the other resin layers that are additionally laminated normally has a value in the range of 0.1% to 10%.

[0226] The resin, as a main component forming the other resin layers, can be a polyester resin similar to that of the heat-shrinkable polyester film, or preferably the resin is at least one of an acrylic resin, an olefin resin, a urethane resin, a rubber resin and the like, which differ from a polyester resin.

[0227] Furthermore, it is preferred that the heat-shrinkable polyester film has a multi-layered structure, and that a shrink-ratio-adjusting layer 10c is provided on the surface of the heat-shrinkable polyester film 10 to further promote a hydrolysis-preventing effect and mechanical protection, or to adjust the shrink ratio of the heat-shrinkable polyester film within the range specified in the Fig. To make the plane shown in 1C uniform.

[0228] Such a shrinkage-adjusting layer can be laminated as a predetermined layer formed from a polyester resin or the like, by using an adhesive, a coating process, a heat treatment or the like, depending on the shrinkage and the like of the heat-shrinkable polyester film. (8) -2 Additive

[0229] Furthermore, it is preferred to mix a certain amount (for example, in a proportion of 0.01 to 10 parts by weight of the total amount) of various additives, such as an oxidation inhibitor, a weather-resistant stabilizer, an antistatic agent, an anti-fogging agent, a metal soap, a wax, an antifungal agent, an antibacterial agent, a nucleating agent, a flame retardant, and a lubricant, or to apply a varnish, a wettability improver, an antistatic agent, or the like to the inner part or to the surface of the heat-shrinkable polyester film.

[0230] In particular, it is preferred to incorporate an inorganic lubricant and an organic lubricant, or one of them, to improve the sliding properties of the heat-shrinkable polyester film and to facilitate easy winding or the like when it is formed into a long roll.

[0231] Examples of inorganic lubricants include, in particular, calcium carbonate particles, silicon dioxide particles, glass particles and microparticles formed from at least one of zeolite, talc, kaolin and the like.

[0232] Furthermore, examples of organic lubricants include microparticles formed from at least one of cross-linked polymethyl methacrylate, cross-linked polystyrene, silicone rubber, silicone copolymer, polyamide, a condensed resin having a triazine ring, and the like, and in particular, microparticles formed from silicone rubber or silicone copolymer are preferred as organic lubricants from the point of view of being adequately deformable and having satisfactory resistance to blocking. [Second embodiment]

[0233] A second embodiment is a method for producing the heat-shrinkable polyester film of the first embodiment.

[0234] Furthermore, as in Fig. Figure 12 shows a recycling process for PET bottles covered with heat-shrinkable polyester film.

[0235] The process is divided into individual steps and described in detail below. 1. Production of the component materials and mixing step

[0236] The component materials used are a first polyester resin and a second polyester resin, and optionally additives and other additive resins.

[0237] Next, the component materials described above are preferably placed in a mixing container while the component materials are weighed, and the component materials are mixed and stirred using a stirring device until they are uniform. 2. Raw film production step

[0238] Next, the resulting component material is preferably dried by heating it to a predetermined temperature (usually a temperature that is 10 °C lower than the crystallization temperature) until it is absolutely dry.

[0239] Next, an extrusion process (T-die method), a blow molding process (inflation method) or an injection molding process is preferably carried out to produce a raw film with a certain thickness.

[0240] In particular, it is preferred to carry out extrusion of the component material by using a predetermined extruder, for example under conditions with an extrusion temperature of 245 °C, and to obtain a raw film with a predetermined thickness (usually 200 to 300 µm). 3. Production of a heat-shrinkable polyester film

[0241] It is then preferred to heat and press the raw film obtained while moving it over or between rollers, using a device for producing heat-shrinkable films (tenter) to produce a heat-shrinkable polyester film.

[0242] Preferably used as stretching treatment methods to achieve such shrinkage are a blowing process, a roller stretching process, a tensioning process and combinations thereof.

[0243] However, from the point of view of satisfactory productivity, film formation according to the injection molding process and a combination of rolling sections and clamping sections are more suitable.

[0244] Furthermore, in the production of the heat-shrinkable polyester film, it is preferred that the polyester molecules forming the heat-shrinkable polyester film are crystallized to a predetermined structure by substantially expanding the film width at a predetermined stretching temperature and stretching ratio, and by stretching the film in a predetermined direction during heating and pressing.

[0245] By solidifying the film in this state, a heat-shrinkable polyester film with thermal shrinkability can be produced, which can be used as decoration, label or the like.

[0246] Furthermore, it is generally preferred that a raw film is produced by a T-matrices process, a blowing process or the like, the raw film is subsequently heated to a temperature equal to or higher than the glass transition temperature of the resin, and the raw film is stretched 3 to 8 times, and preferably about 4 to 6 times, in the main stretching direction (latitudinal direction of the raw film, i.e. TD direction). 4th test step of a heat-shrinkable polyester film

[0247] For the manufactured heat-shrinkable polyester film, it is preferred to provide a predetermined test step so that the following characteristics and the like can be measured continuously or intermittently.

[0248] This means that by measuring the following characteristics and the like through a predetermined test step and checking whether the values ​​of the characteristics are within predetermined ranges, a heat-shrinkable polyester film that exhibits more uniform shrinkage and the like can be provided. 1) Visual inspection of the appearance of the heat-shrinkable polyester film 2) Measurement of thickness differences 3) Measurement of tensile strength (ASTM D882) 4) Measurement of tensile strain (ASTM D882) 5) Surface smoothness testing (ASTM D1894) 6) Measurement of specific gravity (ASTM D792) 7) Ring diving test (TAPPI T882) 8) Measurement of tensile strength (ASTM D1922) 5. Wrapping step with a heat-shrinkable polyester film

[0249] For the obtained heat-shrinkable polyester film, it is preferable to carry out a step of wrapping PET bottles with the film according to the following procedure. 1) PET bottles are manufactured and filled with commercially available drinking water. 2) Subsequently, the edges of the heat-shrinkable polyester film are welded in the width direction using an impulse welding machine (manufactured by FUJI IMPULSE CO., LTD.) to obtain a tubular label. 3) The manufactured cylindrical PET bottle is then labelled with this tubular label. 4) The wrapped PET bottle is placed, for example, on a conveyor belt and moved in a steam tunnel at a temperature of 80 °C and a throughput speed of 6 m / min, whereby the tubular label is thermally shrunk so that it adheres tightly to the cylindrical PET bottle.

[0250] Furthermore, instead of or in combination with the steam tunnel, an infrared lamp, a hot bath, or similar devices can also be used as additional heating devices. 6. PET bottle recycling process

[0251] Referring to the flowchart in Fig. Section 12 describes in more detail an example of a recycling process for PET bottles after use in a state in which they are wrapped with a heat-shrinkable polyester film.

[0252] In Fig.Step 12, represented by S1, is a step in which used PET bottles undergo a pressing process, a so-called baling process. This step ensures satisfactory storage, transportability, and the like for used PET bottles.

[0253] The next step, represented by S2, involves loosening the baled used PET bottles into clumps several centimeters long using a baling machine. At the same time, vinyl chloride bottles, colored bottles, and similar items are sorted out and removed. This step ensures that only the used PET bottles can be efficiently recycled.

[0254] The next step, represented by S3, is one in which the used PET bottles are washed and any contaminants or residues are removed.

[0255] The subsequent step, represented by S4, involves cutting the washed PET bottles into flakes several millimeters long using a predetermined shredding device. This shredding step allows PET bottles to be cut into flakes with an average particle size of several millimeters and a thickness of micrometers, ensuring satisfactory handling in the subsequent step.

[0256] The subsequent step, represented by S5, involves removing any color layer present on the heat-shrinkable film. For example, this step involves immersing the flakes obtained in S4 in a color-removing liquid, such as alkaline hot water or an aqueous sodium hydroxide solution, and removing the color layer. This means that the occurrence of the blocking phenomenon caused by the color layer can be further reduced in the subsequent drying step.

[0257] The next step, represented by S6, is one in which the dye and the dye removal liquid are separated and the separated flakes are washed.

[0258] The next step, represented by S7, involves drying the washed flakes obtained in S6. Drying them in this way further improves their handling in the subsequent step.

[0259] Finally, the step represented by S8 involves heating and melting the flakes obtained in S7 to produce, for example, recycled pellets with an average particle size of 1 to 8 mm using a pelletizer or similar equipment. Producing recycled pellets with a uniform average particle size in this way facilitates reuse in various applications.

[0260] Since the step of manually removing the heat-shrinkable polyester film with which the PET bottles are wrapped can be eliminated in advance or by removing the film after shredding, the number of steps is reduced, production costs are lowered, and it is economical as well as very advantageous in terms of reducing recycling time compared to a conventional method.

[0261] Therefore, with the heat-shrinkable polyester film of the present invention, even when the film is wrapped around PET bottles, the blocking phenomenon can be suppressed, and recycled pellets can be produced efficiently and economically. EXAMPLES

[0262] The heat-shrinkable polyester film of the present invention will now be described in more detail using examples.

[0263] However, the scope of the rights to the present invention may not be limited by the description of the examples without a specific reason.

[0264] Furthermore, the examples use amorphous polyester resin and crystalline polyester resin (low-crystalline polyester resin) as follows. (First polyester resin: PET1) Amorphous polyester resin consisting of dicarboxylic acid: 100 mol% terephthalic acid, and diol: 63 mol% ethylene glycol, 24 mol% 1,4-cyclohexanedimethanol, and 13 mol% diethylene glycol Glass transition temperature (Tg): 69°C Melting point: None (Second polyester resin: PET2) Low-crystalline polyester resin, which is homo-PET, consisting of dicarboxylic acid: 100 mol% terephthalic acid, and diol: 100 mol% ethylene glycol Glass transition temperature (Tg): 78°C Melting point: 253°C (another second polyester resin: PET3) Crystalline polyester resin, which is a post-consumer recycled polyester resin (PCRP) consisting of dicarboxylic acid: 98 mol% terephthalic acid and 2 mol% isophthalic acid, and diol: 97 mol% ethylene glycol and 3 mol% diethylene glycol Glass transition temperature (Tg): 78°C Melting point: 251°C [Example 1] 1. Production of a heat-shrinkable polyester film

[0265] PET1, a first polyester resin, and PET2, a second polyester resin, were each produced.

[0266] Subsequently, 700 g of PET1, 300 g of PET2 and 10 g of a lubricant were weighed out and placed in a mixing container, and the mixture was mixed evenly to obtain a raw material for production.

[0267] This raw material was then extruded using a deaerated twin-screw extruder at an extrusion temperature of 245 °C, resulting in a raw film with a thickness of 250 µm.

[0268] Finally, a heat-shrinkable polyester film, having a thickness of 40 µm and a thickness deviation of less than 5%, was produced from the raw film using a device for producing heat-shrinkable films at a preheating temperature of 120 °C, a stretching temperature of 84 °C, a thermal fixing temperature of 86.5 °C and stretch ratios (MD direction: 1.06x, TD direction: 4x). 2. Evaluation of a heat-shrinkable polyester film (1) Peak formation time during isothermal crystallization

[0269] The resulting heat-shrinkable polyester films underwent heat treatment using the following pre-processing procedure with a DSC (manufactured by PerkinElmer, Inc., input compensation-type dual-furnace differential scanning calorimeter, product name "DSC8500"; hereinafter referred to as the same) and were then subjected to an isothermal crystallization measurement. This means that, based on a DSC diagram obtained during the isothermal crystallization measurement, the time from the start of the process until the generation of an exothermic peak caused by isothermal crystallization, including a cooling process (5 minutes) at a constant temperature (0 °C), was measured. (Preliminary proceedings) 1) A measurement sample was kept isothermal at 30 °C for 1 minute. 2) Subsequently, the temperature was increased from 30 °C to 300 °C at a temperature increase rate of 750 °C / min. 3) The sample was then kept isothermal at 300 °C for 5 minutes. 4) The sample was then rapidly cooled to 0 °C. (Isothermal crystallization measurement) 1) The sample was kept isothermal at 0°C for 5 minutes. 2) Subsequently, the temperature was increased from 0°C to 150°C at a temperature increase rate of 750°C / min. 3) The sample was then kept isothermal at 150°C for at least 10 minutes (15 minutes or more including the pre-processing) and crystallized. (2) Quantity of heat corresponding to the exothermic peak area of ​​the isothermal crystallization

[0270] Based on a DSC diagram obtained by measuring a peak formation time during the isothermal crystallization of the above described (1), the amount of heat generated was measured, which corresponds to the peak area of ​​the isothermal crystallization. (3) Thermal shrinkage ratio

[0271] The thermal shrink ratio of the obtained heat-shrinkable polyester films was measured according to ASTM D2732-08.

[0272] That is, a heat-shrinkable polyester film was cut into a square shape with a length of 100 mm along the main shrinkage direction (TD direction) and a length of 100 mm along the direction that intersects the main shrinkage direction orthogonally (MD direction), and this was used as a measurement sample.

[0273] Subsequently, samples of the heat-shrinkable polyester films were immersed for 10 seconds each in a bath with a constant temperature of 80 °C and hot water and thermally shrunk.

[0274] Subsequently, the thermal shrinkage ratios (%) in the principal shrinkage direction and in the direction intersecting the principal shrinkage direction orthogonally were calculated from the dimensional changes before and after heat treatment at each temperature according to the following formula (1). Thermal shrinkage ratio (%) = 10 mm - Length of film after thermal shrinkage 100 mm × 100 (4) Thermal shrinkage force and thermal shrinkage stress

[0275] The thermal shrinkage force of the obtained heat-shrinkable polyester films was measured according to ISO 14616-1997.

[0276] That is, a obtained heat-shrinkable polyester film was cut into a short strip having a length of 90 mm along the main shrinkage direction and a length of 15 mm along the direction that intersects the main shrinkage direction orthogonally and was used as a test sample.

[0277] Subsequently, the thermal shrinkage force (N / 15 mm) of the test specimen was measured when immersed in hot water at 80 °C for 10 seconds using a thermal shrinkage tester.

[0278] The thermal shrinkage force obtained was then divided by the thickness (40 µm) to obtain the thermal shrinkage stress (MPa) at 80 °C. (5) Blocking resistance

[0279] The blocking resistance of the obtained heat-shrinkable polyester films was evaluated according to the following procedure as per APR document code: PET-S-08.

[0280] 1) A tubular bottle was wrapped with a heat-shrinkable polyester film, and the container was emptied and washed.

[0281] The bottle, which was wrapped in heat-shrinkable polyester film, was then crushed into flaky objects with a diameter of 12.5 mm or less.

[0282] 2) Subsequently, 1 kg of the crushed flaky objects was placed in a heat-resistant container, and the flaky objects were heated in an oven at 210°C.

[0283] 3) Subsequently, after 90 minutes, the heat-resistant container containing the flaky objects was removed from the oven and cooled naturally to reach room temperature.

[0284] 4) The flaky objects were then classified using a sieve with a 12.5 mm mesh size.

[0285] 5) Then the mass of the agglomerates that could not pass through the sieve was measured, and the agglomeration ratio (%) was calculated using the following formula (2). Agglomeration ratio (%) = mass of agglomerates (kg) / 1 (kg) × 100

[0286] 6) Based on the calculated agglomerates, the evaluation of blockage resistance was carried out according to the following criteria. ◯ (good) The mass of the agglomerates has a value of less than 5%. △ (medium) The mass of the agglomerates has a value of 5% or more and less than 10%. × (bad) The mass of the agglomerates has a value of 10% or more. (6) Adaptability

[0287] The adaptability of the heat-shrinkable polyester films obtained for PET bottles was evaluated according to the following criteria.

[0288] That is, ten cylindrical PET bottles were produced, filled with commercially available drinking water (trade name: EVIAN, volume: 500 ml).

[0289] Subsequently, the edges in the width direction of a heat-shrinkable polyester film were welded using an impulse welding machine (manufactured by FUJI IMPULSE CO., LTD.) and ten tubular labels were produced that correspond to the cylindrical PET bottles.

[0290] Subsequently, each of the ten cylindrical PET bottles was covered with each of the ten tubular labels obtained in this way, in order to use them as measurement samples.

[0291] The samples were then placed on a conveyor belt and moved through a steam tunnel at a temperature of 85 °C and a speed of 6 m / min. The tubular labels were thermally shrunk to ensure a tight fit on the cylindrical PET bottles.

[0292] Finally, the final quality in a state where the tubular labels had thermally shrunk, i.e., the presence or absence of defects such as creases, insufficient shrinkage, label folding, and lightening due to shrinkage, was observed by visual inspection, and the conformability of the heat-shrinkable polyester film was evaluated based on the following criteria. ⊙ (Very good) No defects were found in the ten test samples. O (Good) On average, defects are found in one or more places and in three or fewer places in the ten measurement samples. △ (Mean) On average, defects are found in four or more places and in five or fewer places in the ten measurement samples. × (Bad) On average, defects are found in six or more places among the ten measurement samples. [Example 2]

[0293] In Example 2, a heat-shrinkable polyester film was prepared and evaluated in the same way as in Example 1, except that PET3 was used instead of PET2 as the second polyester resin, as shown in Table 1. The results obtained are shown in Table 2. [Example 3]

[0294] In Example 3, a heat-shrinkable polyester film was prepared and evaluated in the same way as in Example 1, except that the mixing ratio of the first polyester resin to the second polyester resin was 50 / 50, as shown in Table 1. The results obtained are shown in Table 2. [Example 4]

[0295] In Example 4, a heat-shrinkable polyester film was prepared and evaluated in the same way as in Example 1, except that PET3 was used instead of PET2 as the second polyester resin, and the mixing ratio of the first polyester resin to the second polyester resin was 50 / 50, as shown in Table 1. The results obtained are shown in Table 2. [Example 5]

[0296] In Example 5, a heat-shrinkable polyester film was prepared and evaluated in the same manner as in Example 1, except that the mixing ratio of the first polyester resin to the second polyester resin was 30 / 70 and the stretch ratio in the TD direction was 2.5, as shown in Table 1. The results obtained are presented in Table 2. [Example 6]

[0297] In Example 6, a heat-shrinkable polyester film was prepared and evaluated in the same manner as in Example 1, except that PET3 was used instead of PET2 as the second polyester resin, the mixing ratio of the first polyester resin to the second polyester resin was 30 / 70, and the stretch ratio in the TD direction was 2.5, as shown in Table 1. The results obtained are presented in Table 2. [Comparison example 1]

[0298] In comparative example 1, a heat-shrinkable polyester film was produced and evaluated in the same manner as in Example 1, except that only PET1 was used as the first polyester resin and the mixing ratio of the first polyester resin to the second polyester resin was 100 / 0, as shown in Table 1. The results obtained are presented in Table 2. [Comparative example 2]

[0299] In comparative example 2, a heat-shrinkable polyester film was produced and evaluated in the same way as in example 1, except that the mixing ratio of the first polyester resin to the second polyester resin was 90 / 10, as shown in Table 1. The results obtained are presented in Table 2. [Comparative example 3]

[0300] In comparative example 3, a heat-shrinkable polyester film was produced and evaluated in the same way as in example 1, except that PET3 was used instead of PET2 as the second polyester resin, and the mixing ratio of the first polyester resin to the second polyester resin was 90 / 10, as shown in Table 1. The results obtained are presented in Table 2. [Comparative example 4]

[0301] In comparative example 4, a heat-shrinkable polyester film was produced and evaluated in the same manner as in example 1, except that only PET3 was used instead of PET2 as the second polyester resin, and the mixing ratio of the first polyester resin to the second polyester resin was 0 / 100, as shown in Table 1. The results obtained are presented in Table 2. [Comparative example 5]

[0302] In comparative example 5, a heat-shrinkable polyester film was produced and evaluated in the same way as in example 1, except that only PET3 was used instead of PET2 as the second polyester resin, the mixing ratio of the first polyester resin to the second polyester resin was 30 / 70, and the value of the thermal shrinkage ratio corresponding to feature (E) was less than 20%, as shown in Table 1. The results obtained are presented in Table 2. [Table 1] Mix Stretch ratio in TD direction First polyester resin Second polyester resin Additive(pbw) PET1 (pbw) PET2 (pbw) PET3 (pbw) Example 1 70 30 1 4 Example 2 70 30 1 4 Example 3 50 50 1 4 Example 4 50 50 1 4 Example 5 30 70 1 2,5 Example 6 30 70 1 2,5 Comparison example 1 100 1 4 Comparison example 2 90 10 1 4 Comparison example 3 90 10 1 4 Comparison example 4 100 1 4 Comparison example 5 30 70 1 4 [Table 2] Thermal shrinkage ratio at 80 °C in TD direction (%) Thermal shrinkage ratio at 80 °C in MD direction (%) Thermal shrinkage stress (MPa) Turbidity value (%) Isothermalization at 150°C Glass transition temperature (°C) Blocking resistance adaptability Peak area (J / g) Peak formation time (min) Example 1 40 (%)-2 6,7 4,6 12,9 8,8 71 ⊙ Example 2 37 -1 7,3 4,1 16,9 8,86,7 7170,9 ◯◯ ⊙⊙ Example 3 22 3 7,8 5,3 26 6,1 72,6 ◯ ⊙◯ Example 4 29 2 5,9 4,5 24,9 5,7 72,7 Example 5 45 4 3, 0 4, 0 23,4 23,45,6 23,475,1 ◯◯ ◯⊙ Example 6 49 5 3, 5 3, 7 21,3 5,6 74 ◯ ⊙ Comparative example 1 59 -4 6, 4 3,3 - >15 68, 8 × ⊙⊙ Comparative example 2 48 6 5, 6 4, 1 - >15 69,7 Δ ⊙ Comparative example 3 49 5 6, 9 4, 9 <1 12,9 69,8 Δ ⊙ Comparative example 4 8 5 8,2 4,3 15,3 5,3 78 ◯ × Comparative example 5 17 8 8, 2 4,5 14,3 5,7 75,1 ◯ Δ INDUSTRIAL APPLICABILITY

[0303] Since the heat-shrinkable polyester film fulfills at least the features (A) to (E), according to the present invention, even PET bottles covered with the heat-shrinkable polyester film can be recycled, the blocking phenomenon is suppressed, and excellent adaptability is maintained.

[0304] This means that, in particular by controlling the exothermic peak time, obtained as feature (C) through isothermal crystallization, and the amount of heat corresponding to the exothermic peak area, obtained as feature (D) through isothermal crystallization, to values ​​in predetermined ranges, recycled pellets having a predetermined shape can be produced effectively and stably.

[0305] Therefore, the heat-shrinkable polyester film of the present invention can not only be used to cover various PET bottles and the like, regardless of whether they are thin-walled or thick-walled or even have a complicated shape, but also to enable recycling together with various PET bottles and the like.

[0306] Therefore, a process for removing the surrounding heat-shrinkable polyester film, which previously relied on manual labor, can be eliminated, production costs can be reduced, it is both economical and very advantageous in terms of shortening the recycling time, and the industrial applicability can be described as very high.

Claims

[1] Heat-shrinkable polyester film derived from a first polyester resin and a second polyester resin as a plurality of polyester resins having different crystallinity, which are reaction products of a polyvalent carboxylic acid and a polyalcohol, wherein the heat-shrinkable polyester film fulfills the following features (A) to (E): (A) the first polyester resin is an amorphous polyester resin in which the polyvalent carboxylic acid contains at least terephthalic acid, and if a total amount of the polyalcohol is assumed to be 100 mol%, the reaction amount of ethylene glycol is in the range of 50 mol% or more and below 90 mol%; (B) the second polyester resin is a crystalline polyester resin in which the polyvalent carboxylic acid contains at least terephthalic acid, and if the total amount of the polyalcohol is assumed to be 100 mol%, a reaction amount of ethylene glycol is 90 mol% or more; (C) the heat-shrinkable polyester film is a heat-shrinkable polyester film which, when an isothermal crystallization measurement is performed by DSC at 150 °C, including a cooling process at a constant temperature, an exothermic peak occurs within 12 minutes of the start, including the cooling process time; (D) the heat-shrinkable polyester film is a heat-shrinkable polyester film in which, when an isothermal crystallization measurement is carried out by DSC at 150 °C, including a cooling process at a constant temperature, the amount of heat corresponding to the obtained exothermic peak area is in the range of 5 to 35 J / g; and (E) the heat-shrinkable polyester film is a heat-shrinkable polyester film in which a thermal shrinkage ratio in one principal shrinkage direction, measured under the thermal shrinkage conditions of immersion in hot water at 80 °C for 10 seconds, is in the range of 20% to 60%, wherein a weight-based mixing ratio of the first polyester resin / second polyester resin is in the range of 20 / 80 to 80 / 20, wherein the mass of the agglomerates as blockage resistance according to APR Document Code: PET-S-08 is less than 5%, and wherein the thickness of the heat-shrinkable polyester film is 25 to 70 µm. [2] Heat-shrinkable polyester film according to claim 1, wherein the glass transition temperature of the first polyester resin is in the range of 50 °C to 69 °C. [3] Heat shrinkable polyester film according to claim 1 or 2, wherein the first polyester resin is an amorphous polyester resin containing at least 1,4-cyclohexanedimethanol, and wherein, assuming the total amount of the polyalcohol to be 100 mol%, the reaction amount of the 1,4-cyclohexanedimethanol is in the range of 1 mol% or more and below 35 mol%. [4] Heat-shrinkable polyester film according to any one of claims 1 to 3, wherein the second polyester resin is a crystalline polyester resin containing ethylene glycol alone or both ethylene glycol and diethylene glycol, and in a case where both ethylene glycol and diethylene glycol are present, when the total amount of the polyalcohol is assumed to be 100 mol%, the reaction amount of ethylene glycol is 90 mol% or more, while the reaction amount of diethylene glycol is in the range of 1 mol% to 10 mol%. [5] Heat-shrinkable polyester film according to any one of claims 1 to 4, wherein the second polyester resin is a homopolyester resin and a post-consumer recycled polyester resin, or either one of these. [6] Heat-shrinkable polyester film according to any one of claims 1 to 5, wherein, if a total amount of the first polyester resin and the second polyester resin is assumed to be 100 parts by weight, the heat-shrinkable polyester film contains a lubricant in an amount in the range of 0.01 to 5 parts by weight. [7] Heat-shrinkable polyester film according to any one of claims 1 to 6, wherein the following feature (F) is further satisfied: (F) a thermal shrinkage ratio in a direction that intersects the principal shrinkage direction orthogonally, measured under the thermal shrinkage conditions of immersion in hot water at 80 °C for 10 seconds, is in the range of -3% to 10%. [8] Heat-shrinkable polyester film according to any one of claims 1 to 7, further comprising the following feature (G): (G) a thermal shrinkage stress in the main shrinkage direction, measured under thermal shrinkage conditions at 80 °C for 10 seconds, is 8 MPa or less.

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