Polyester heat shrink film

Abstract

Provided is a polyester heat-shrinkable film having improved recyclability and excellent assemblability and appearance. The polyester heat shrink film has the following characteristics: characteristic (A) in which the caking ratio of the polyester resin or the like is 1.2% or less; property (B) wherein the melting point is 190 DEG C to 230 DEG C; property (C) in which the heat of fusion is 25 mJ / mg to 45 mJ / mg; and characteristics (D1) to (D4) in which the thermal shrinkage rates in the main shrinkage direction measured under thermal shrinkage conditions for 10 seconds at 60 DEG C, 70 DEG C, and 80 DEG C are 0%-5%, 25%-50%, and 55%-85% respectively, and the standard deviation of the values of the thermal shrinkage rates measured under conditions for 10 seconds at 95 DEG C to 100 DEG C is 1.5% or less.

Description

Technical Field

[0001] The present invention relates to a polyester heat shrinkable film (sometimes referred to as a polyester-based shrinkable film, etc.).

[0002] More specifically, the present invention relates to a polyester heat-shrinkable film having a good balance between recyclability and heat shrinkability, which can be recycled together with a used PET bottle while still being assembled thereto, and which has excellent assemblability and appearance due to correction of the heat shrinkage ratio obtained even when the heat shrinkage temperature or the like is slightly changed. Background Art

[0003] Generally, bottles made of polyethylene resin (high-density polyethylene (HDPE)) or bottles made of polyester resin (polyethylene terephthalate (PET)) (hereinafter sometimes simply referred to as PET bottles) are 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 of their lightness, excellent durability, and extremely high convenience.

[0005] On the other hand, such PET bottles are discarded in rivers after use, and they flow into the ocean, etc., causing serious environmental problems.

[0006] Therefore, in order to solve such environmental problems, research on recovery or recycling technology of such PET bottles is being actively conducted.

[0007] In addition, in order to indicate various information related to the name and content and to improve decorativeness, etc., the PET bottle is wrapped with a predetermined display label.

[0008] That is, as a display label, it has become mainstream to use a display label using a polyester heat shrink film to wrap the entire periphery of a PET bottle.

[0009] More specifically, in order to obtain good heat shrinkability, a polyester heat shrinkable film derived from a non-crystalline polyester resin (polyethylene terephthalate-1,4-cyclohexanedimethanol (PETG)) is often used.

[0010] However, as a thermal characteristic of PETG, it has no melting point, and there is a problem that recycled pellets are easily adhered to each other in the recycling step of the PET bottle wrapped with a heat shrink film.

[0011] That is, when the PET bottle in a state of being wrapped by a heat shrink film is heat-melted in the recycling step, Fig.11A As shown, there occurs a problem that the heat shrink film and the recycled pellets including the heat shrink film adhere to each other to form lumps, causing blockage in the pipeline.

[0012] Therefore, there is inherently a problem that when the PET bottle including the heat shrink film is melted, the obtained recycled pellets do not adhere to each other, and it is difficult to efficiently and stably produce pellets having a predetermined shape using a pelletizer, such as Fig. 11B shown.

[0013] Therefore, in order to achieve various purposes, a polyester heat shrinkable film derived from a crystalline polyester resin having a predetermined melting point has been proposed in consideration of recyclability (Patent Documents 1 and 2).

[0014] That is, Patent Document 1 discloses a polyester heat shrinkable film for the purpose of reducing adverse effects of residual ink and achieving excellent recyclability and the like.

[0015] More specifically, for example, when a polyester heat shrinkable film is heat treated at 80°C for 10 seconds, the heat shrinkage rate in the main shrinkage direction is 30% or more, and the melting point measured by a differential scanning calorimeter (hereinafter sometimes referred to as DSC) is in the range of 170°C to 230°C.

[0016] Patent Document 2 also discloses a polyester heat shrinkable film for the purpose of obtaining excellent recyclability and the like.

[0017] More specifically, if Figure 12A to Figure 12B As shown, the present invention intends to control the blocking ratio measured under predetermined conditions to be 10% or less, and to control the melting point and crystallization temperature of the polyester heat shrinkable film as shown by the characteristic curve L6 and the characteristic curve L6'.

[0018] Moreover, for example, the heat shrinkage rate of the polyester heat shrinkable film in the main shrinkage direction at 70°C for 10 seconds is set to 0% to 50%, the heat shrinkage rate in the main shrinkage direction at 80°C for 10 seconds is set to 30% to 85%, the heat shrinkage rate in the main shrinkage direction at 100°C for 10 seconds is limited to the range of 40% to 90%, and the melting point is limited to the range of 170°C to 240°C.

[0019] On the other hand, Patent Document 3 discloses a polyester heat shrinkable film for the purpose of improving the printability of the polyester heat shrinkable film, limiting the change rate of the heat shrinkage rate within each predetermined temperature range, and exhibiting excellent finish when assembled in a PET bottle or the like.

[0020] More specifically, the rate of change (% / °C) of the heat shrinkage rate of the heat shrinkage of the heat shrinkable polyester film in the main shrinkage direction caused by temperature is 1.5 to 3.0 in the range of 60°C to 70°C, 2.5 to 3.5 in the range of 70°C to 80°C, 1.0 to 2.0 in the range of 80°C to 90°C, and 0.1 to 1.0 in the range of 90°C to 100°C.

[0021] Citation List

[0022] Patent Literature

[0023] Patent Document 1: JP2020-521823A (claims, etc.)

[0024] Patent Document 2: JP2022-510146A (claims, etc.)

[0025] Patent Document 3: JP2011-184690A (claims, etc.) Summary of the invention

[0026] Problems to be solved by the invention

[0027] However, the polyester heat shrinkable films disclosed in Patent Documents 1 and 2 have a problem that, although the values ​​of the agglomeration ratio and the blocking ratio measured under predetermined conditions are below predetermined values ​​and a certain degree of recyclability is achieved, the value of the heat shrinkage rate within a predetermined temperature range is prone to change.

[0028] That is, since a crystalline polyester resin having a wide melting point range is used, there is a problem that the value of the heat shrinkage rate tends to vary within a predetermined temperature range (60° C. to 100° C.), particularly within a temperature range of about 70° C.

[0029] Therefore, spots, wrinkles, etc. may occur during heat shrinkage, and the appearance and assembly properties are poor. Therefore, a good balance between the recyclability and heat shrinkability of the polyester heat shrinkable film has not yet been achieved.

[0030] On the other hand, when the polyester heat shrinkable film disclosed in Patent Document 3 is recycled in a state of being attached to a used PET bottle without any consideration of the blocking ratio measured under predetermined conditions, there is a problem that a sticking phenomenon (mutual adhesion phenomenon) may occur.

[0031] Moreover, all the examples (Examples 1 to 4) have the following problem: the value of the heat shrinkage rate under the condition of 70°C for 10 seconds is in the range of about 15% to less than 30%, which is quite low, and the usability as a polyester heat shrinkable film is poor, and stable heat shrinkage cannot be obtained.

[0032] Therefore, the inventors of the present invention conducted extensive studies to solve the above-mentioned problems, and as a result, found that, in a polyester heat shrinkable film derived from a polyester resin, when at least predetermined characteristics (A) to predetermined characteristics (B) of the raw material resin, such as the blocking ratio, and predetermined characteristics (C) and predetermined characteristics (D1) to predetermined characteristics (D4) of the polyester heat shrinkable film are controlled, the conventional problems can be solved.

[0033] That is, an object of the present invention is to provide a polyester heat-shrinkable film which can be efficiently and stably produced into pellets having a predetermined shape even when PET bottles coated with the polyester heat-shrinkable film are recycled together, and thus can be corrected even when the heat-shrinkage temperature and the like vary and the heat-shrinkage rate is not within a desired range, and the film has excellent assemblability and appearance.

[0034] Means of solving the problem

[0035] According to the present invention, the above-mentioned problems can be solved by providing a polyester heat-shrinkable film, which is derived from a polyester resin which is a reaction product of a polycarboxylic acid and a polyol, and has the following properties (A) to (C) and properties (D1) to (D4).

[0036] (A) The agglomeration ratio in a mixture of a polyester resin and other PET resins measured in accordance with the Association of Plastic Recyclers (APR) document identification code: PET-S-08 (hereinafter, sometimes simply referred to as the agglomeration ratio) is a value of 1.2% or less.

[0037] (B) The melting point of the polyester resin measured by DSC is a value within the range of 190°C to 230°C.

[0038] (C) The heat of fusion of the polyester heat shrinkable film corresponding to the melting peak area at the melting point measured by DSC is a value within the range of 25 mJ / mg to 45 mJ / mg.

[0039] (D1) The heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 60°C and 10 seconds is a value within a range of 0% to 5%.

[0040] (D2) The heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 70°C and 10 seconds is a value within a range of 25% to 50%.

[0041] (D3) The heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 80°C and 10 seconds is a value within a range of 55% to 85%.

[0042] (D4) The standard deviation of the values ​​of the heat shrinkage ratio in the main shrinkage direction measured under the heat shrinkage conditions of 95° C. to 100° C. and 10 seconds is 1.5% or less.

[0043] That is, when configurations (A) to (C) and (D1) to (D4) are satisfied in this manner, for a polyester resin as a raw material resin of a polyester heat shrinkable film in which other PET resins (recycled PET resins, etc.) are mixed, a good balance between recyclability and heat shrinkage can be achieved by controlling the agglomeration ratio measured under certain conditions, the melting point and the heat of fusion of the polyester resin as a raw material resin, and the heat shrinkage rate at a predetermined temperature within a predetermined range.

[0044] Therefore, the polyester heat shrinkable film can be recycled together in a state where it is still assembled to a predetermined PET bottle, and even if the heat shrinkage temperature, etc. changes from a relatively low temperature condition to a high temperature condition and the heat shrinkage rate is not within a desired range, correction is possible, thereby providing a polyester heat shrinkable film having excellent assemblability and appearance.

[0045] When the polyester heat shrinkable film of the present invention is formed, the heat shrinkage ratio in the main shrinkage direction (transverse direction (TD) direction) measured under heat shrinkage conditions of 95° C. to 100° C. for 10 seconds is preferably 70% or more as property (D4′).

[0046] When the heat shrinkage rate in the high temperature range is also controlled in this way, it is easy to control the heat shrinkage rate value in the relatively low temperature range of 60°C to 80°C within the desired range, thereby further improving the assembly property and appearance of the film during heat shrinkage.

[0047] When the polyester heat shrinkable film of the present invention is formed, the heat shrinkage ratio in the main shrinkage direction (TD direction) measured under heat shrinkage conditions of 60°C to 80°C and 10 seconds preferably satisfies the following relational expression (1) as a characteristic (D5).

[0048] In this way, within a predetermined temperature range, when the heat shrinkage temperature and the heat shrinkage rate satisfy a predetermined relational expression (1), these values ​​can be linearly controlled.

[0049] Therefore, even if the heat shrinkage temperature or the like changes while maintaining good recyclability, and the heat shrinkage rate is not within a desired range, correction can be accurately performed and good heat shrinkage can be obtained.

[0050] [Formula 1]

[0051] Thermal shrinkage rate (%) = a × (thermal shrinkage temperature (°C) - 60) + b (1)

[0052] a: corresponds to the slope of relational expression (1), which is a value greater than 3.25 and less than 4,

[0053] b: A constant corresponding to the relational expression (1), which is a value greater than or equal to 0 and less than or equal to 5.

[0054] When the polyester heat shrinkable film of the present invention is formed, the heat shrinkage rate in the main shrinkage direction (TD direction) measured under heat shrinkage conditions of 60° C. to 80° C. for 10 seconds preferably satisfies the following relational expression (2) as a property (D5′).

[0055] In this way, when the heat shrinkage temperature and the heat shrinkage rate satisfy the predetermined relationship (2) within a predetermined temperature range, these values ​​can be linearly controlled within a narrower range while maintaining good recyclability.

[0056] [Formula 2]

[0057] Thermal shrinkage rate (%) = a' × (thermal shrinkage temperature (°C) - 60) + b' (2)

[0058] a′: corresponds to the slope of relational expression (2), and is a value of 3.3 or more and 3.75 or less. b′: corresponds to the constant of relational expression (2), and is a value of 0 or more and 5 or less.

[0059] When the polyester heat shrinkable film of the present invention is formed, the heat shrinkage rate in the main shrinkage direction (TD direction) measured under heat shrinkage conditions of 60°C to 80°C and 10 seconds preferably satisfies the following relational expression (3) as a characteristic (D5”).

[0060] In this way, within a predetermined temperature range, when the heat shrinkage temperature and the heat shrinkage rate satisfy a predetermined relational expression (3), these values ​​can be linearly controlled within a narrower range.

[0061] [Formula 3]

[0062] Thermal shrinkage rate (%) = a" × (thermal shrinkage temperature (℃) - 60) + b" (3)

[0063] a": corresponds to the slope of relational expression (3), and is a value greater than or equal to 3.35 and less than or equal to 3.5; b": corresponds to the constant of relational expression (3), and is a value greater than or equal to 0 and less than or equal to 5.

[0064] When the polyester heat shrinkable film of the present invention is formed, as characteristic (D6), the heat shrinkage rate in the direction perpendicular to the main shrinkage direction (machine direction (MD) direction) measured under heat shrinkage conditions of 70°C and 10 seconds is preferably a value within the range of -3% to 5%.

[0065] When the heat shrinkage rate in the MD direction under a predetermined temperature condition is restricted in this way, even if the periphery of the PET bottle is covered and the PET bottle is heat-shrunk at a relatively low temperature, the assembly property and the appearance are improved, and as a result, the deformation of characters, graphics, etc. is reduced, and accurate information is easily obtained.

[0066] Furthermore, when the heat shrinkage rate in the MD direction is restricted in this way, the heat shrinkage of the polyester heat shrinkable film as a whole can be balanced, and even if the film is recycled together with PET bottles, pellets can be stably obtained by controlling the tackiness, fluidity, etc.

[0067] When the polyester heat shrinkable film of the present invention is formed, it is preferred that the average thickness of the film be within a range of 10 to 100 μm, and the standard deviation of the average thickness measured under predetermined conditions be 1.7 μm or less.

[0068] When the film thickness and the standard deviation as its variation are restricted in this way, the balance between recyclability and heat shrinkability is further improved, thereby obtaining a polyester heat shrinkable film having heat shrinkage controlled with high accuracy, transparency, and excellent mechanical properties.

[0069] In addition, when the polyester heat shrinkable film of the present invention is formed, the polyester resin is a mixture of a crystalline polyester resin and a non-crystalline polyester resin, and the weight mixing ratio is preferably a value within the range of 100:0 to 80:20.

[0070] When the weight mixing ratio is controlled in this way, the balance between recyclability and heat shrinkability is further improved, so that a polyester heat shrinkable film having highly accurately controlled heat shrinkability, assemblability, appearance, transparency, and excellent mechanical properties can be obtained.

[0071] [Brief description of the attached figure]

[0072] Figure 1A to Figure 1C Each of these is a diagram for explaining the form of a polyester heat shrinkable film.

[0073] Figure 2A This is a graph provided to explain the relationship between the maximum stretching speed when manufacturing a polyester heat shrinkable film and the standard deviation of the heat shrinkage rate in the main shrinkage direction at 100°C for 10 seconds. Figure 2B Also provided is a graph for illustrating the relationship between the maximum stretching speed and the standard deviation of the thickness.

[0074] Figure 3 This is a graph provided to explain the relationship between the standard deviation of the heat shrinkage rate in the main shrinkage direction under the condition of 100° C. for 10 seconds of a polyester heat shrinkable film produced at a predetermined maximum stretching speed and the evaluation (relative value) of the blocking ratio.

[0075] Figure 4 This is a graph provided to explain the relationship between the maximum stretching speed and the heat of crystallization when a polyester heat shrinkable film is produced.

[0076] Figure 5This is a graph provided to explain the relationship between the maximum stretching speed when a polyester heat shrinkable film is produced and the glass transition temperature of the polyester heat shrinkable film.

[0077] Figure 6 This is a graph provided to explain the relationship between the maximum stretching speed and the heat of fusion.

[0078] Figure 7 This is a diagram provided to explain the region (S1) defined by the relational expression (1) of the present invention.

[0079] Figure 8 This is a diagram provided to explain the region (S2) defined by the relational expression (2) of the present invention.

[0080] Fig. 9 This is a diagram provided to explain the region (S3) defined by the relational expression (3) of the present invention.

[0081] Fig. 10A is the DSC curve of the polyester heat shrinkable film of Example 1, Fig. 10B This is a DSC graph of the polyester resin (PET2) used when measuring the blocking ratio in Example 1 and the like.

[0082] Fig.11A is a schematic diagram showing the adhesion state of a PET bottle covered with a conventional polyester heat shrink film, Fig. 11B is a schematic diagram showing a recycled PET resin obtained in a recycling step derived from a PET bottle covered with the polyester heat-shrinkable film of the present invention.

[0083] Fig. 12A is a graph showing the relationship between the agglomeration ratio and the melting point in Patent Document 2 (Conventional Technology 2), Fig. 12B This is a graph showing the relationship between the agglomeration ratio and the heat of crystallization in Patent Document 2.

[0084] Mode for Carrying Out the Invention]

[0085] [First embodiment]

[0086] like Figure 1A to Figure 1C As illustrated, the first embodiment is a polyester heat shrinkable film derived from a polyester resin which is a reaction product of a polycarboxylic acid and a polyol.

[0087] Therefore, a polyester heat shrinkable film is provided which satisfies the following characteristics (A) to (C) and characteristics (D1) to (D4).

[0088] (A) The agglomeration ratio in a mixture of a polyester resin and other PET resins measured in accordance with APR document identification code: PET-S-08 is a value of 1.2% or less.

[0089] (B) The melting point of the polyester resin measured by DSC is a value within the range of 190°C to 230°C.

[0090] (C) The heat of fusion of the polyester heat shrinkable film corresponding to the melting peak area at the melting point measured by DSC is a value within the range of 25 mJ / mg to 45 mJ / mg.

[0091] (D1) The heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 60°C and 10 seconds is a value within a range of 0% to 5%.

[0092] (D2) The heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 70°C and 10 seconds is a value within a range of 25% to 50%.

[0093] (D3) The heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 80°C and 10 seconds is a value within a range of 55% to 85%.

[0094] (D4) The standard deviation of the values ​​of the heat shrinkage ratio in the main shrinkage direction measured under the heat shrinkage conditions of 95° C. to 100° C. and 10 seconds is 1.5% or less.

[0095] Hereinafter, the polyester heat shrinkable film of the first embodiment will be described in detail by dividing it into components with appropriate reference to the drawings.

[0096] 1. Polycarboxylic acid

[0097] There are no particular restrictions on the polycarboxylic acid as a constituent component (raw material component) of the polyester resin as long as it is a compound that can react with a polyol to form a polyester structure, and examples thereof include: aliphatic dicarboxylic acids such as adipic acid, sebacic acid and azelaic acid; aromatic dicarboxylic acids such as terephthalic acid, naphthalene dicarboxylic acid and isophthalic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexane dicarboxylic acid, and at least one of their ester-forming derivatives.

[0098] In particular, terephthalic acid is preferred because it has good reactivity with polyols, easily forms a crystalline polyester structure, is relatively inexpensive, and is economically advantageous.

[0099] Therefore, when the total amount of the polycarboxylic acid used is 100 mol %, the amount of terephthalic acid used is preferably 90 mol % or more, and more preferably within a range of 95 mol % to 100 mol %.

[0100] 2. Polyols

[0101] (1) Types

[0102] The polyol as a constituent component of the polyester resin is not particularly limited as long as it is a compound having a plurality of reactive hydroxyl groups, and for example, it is preferred to mix at least one of aliphatic diols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, neopentyl glycol and hexanediol, alicyclic diols other than 1,4-cyclohexanedimethanol, and aromatic diols.

[0103] This is because, when such a polyol is used, it reacts appropriately with a polycarboxylic acid, and a polyester resin having crystallinity and the like controlled within a predetermined range can be easily obtained.

[0104] Among these polyols, it is more preferable to use one or more diols selected from ethylene glycol, diethylene glycol, neopentyl glycol and the like.

[0105] That is, the reason for this is that when these specific polyols are used, the melting point, heat shrinkage ratio, heat shrinkage stress, etc. of the polyester resin obtained by reacting with the polycarboxylic acid can be more easily adjusted to values ​​within a predetermined range.

[0106] Therefore, when the total amount of the polyol used is 100 mol%, the amount of one or more diols selected from ethylene glycol, diethylene glycol, neopentyl glycol, etc. is preferably 90 mol% or more, more preferably 95 mol% to 100 mol%.

[0107] Furthermore, other dicarboxylic acids and diols, or hydroxycarboxylic acids may be used alone or in combination as a mixture to change the thermal and mechanical properties of the polyester heat shrinkable film as needed.

[0108] (2) Reaction volume

[0109] In addition, the reaction amount of the polyol is not particularly limited. It is generally preferred to react 100 mol of a polycarboxylic acid containing 80 mol % or more of terephthalic acid and the like with 130 mol to 220 mol of a polyol, more preferably with 150 mol to 210 mol of a polyol, and even more preferably with 180 mol to 200 mol of a polyol, and the polyester resin is preferably obtained by crystallizing these reactants.

[0110] In this case, the crystallinity index of the polyester resin, as the degree of crystallinity calculated from the DSC curve measured in accordance with Japanese Industrial Standard (JIS) K7122:2012, is preferably a value in the range of 1% to 15%, more preferably a value in the range of 2% to 10%, and even more preferably a value in the range of 3% to 8%.

[0111] That is, in the DSC curve, the heat of fusion (ΔHm) obtained from the melting peak area, the heat of crystallization (ΔHc) obtained from the crystallization peak area, and the heat of complete crystallization (ΔHm 0 ), and calculate the crystallinity of the polyester resin according to the following formula (4).

[0112] [Formula 4]

[0113]

[0114] ΔHm: Heat of fusion (J / g)

[0115] ΔHc: Heat of crystallization (J / g)

[0116] ΔHm 0 : 140.1 J / g (heat of complete crystallization of crystallized polyethylene terephthalate).

[0117] 3. Polyester resin

[0118] (1) Agglomeration ratio

[0119] The characteristic (A) of the polyester resin as a raw material resin constituting the polyester heat shrinkable film is that the blocking ratio of the polyester resin or the like as a mixture of the polyester resin and other PET resins measured according to APR document identification code: PET-S-08 is a value of 1.2% or less.

[0120] The reason is that when the agglomeration ratio exceeds 1.2%, the recyclability may be significantly reduced and the variation of the heat shrinkage rate may increase. As a result, when the heat shrinkage temperature varies slightly, it is difficult to suppress the occurrence of spots and wrinkles during heat shrinkage and to maintain good assembly properties.

[0121] However, when the blocking ratio is set to an excessively small value, the yield rate is significantly reduced, or the types of ingredients used in the polyester resin are excessively limited.

[0122] Therefore, the blocking ratio of the polyester resin or the like is more preferably a value within a range of 0.01% to 1%, and still more preferably a value within a range of 0.1% to 0.8%.

[0123] Furthermore, in the case of a conventional polyester resin, it is considered that the heat shrinkage rate of a polyester heat shrinkable film formed therefrom, for example, at 70° C. for 10 seconds is preferably in the range of 0% to 50%. Therefore, the melting point changes greatly, and the S-shaped characteristic curve is easily changed.

[0124] Therefore, in the case of a polyester heat shrinkable film made of a conventional polyester resin, even if the heat shrinkage temperature varies and a desired heat shrinkage ratio cannot be obtained, it is impossible to correct it promptly and accurately.

[0125] On the other hand, in the case of the present invention, since the thermal shrinkage temperature and the thermal shrinkage rate change linearly, even if the thermal shrinkage temperature changes and the desired thermal shrinkage rate cannot be obtained temporarily, the desired thermal shrinkage rate can be stably obtained by controlling the agglomeration ratio of the polyester resin, etc. and following the relationship equations (1) to (3) described later.

[0126] The blocking ratio of the polyester resin or the like according to the APR document identification code: PET-S-08 can be measured under the following measurement conditions.

[0127] 1) Preheat oven to 210°C.

[0128] 2) Then, the PET bottle or the like equipped with the polyester heat shrink film is washed, water-blasted, and crystallized to obtain an initial weight (1 kg) of PET sheets (corresponding to a mixture of polyester resin and other PET resins) and placed in a 22 cm×33 cm baking tray lined with aluminum foil.

[0129] 3) Then, the PET sheet contained in the baking tray was heated for 90 minutes in an oven maintained at a predetermined temperature.

[0130] 4) Then, take the baking tray out of the oven and cool directly to room temperature.

[0131] 5) The PET flakes were taken out from the baking tray and placed on a sieve having a stainless steel mesh with an opening of 12.5 mm.

[0132] 6) The sieve containing the PET flakes is vibrated by hand until all the PET flakes have passed through the sieve. Then, the PET flakes that have passed through the mesh are recovered below. Furthermore, the PET flakes (aggregates) that cannot pass through the mesh and remain on the mesh are appropriately removed.

[0133] 7) The weight of the aggregates that could not pass through the mesh was weighed. In addition, the PET flakes and residues attached to the aluminum foil were weighed separately.

[0134] 8) The agglomeration ratio was calculated from the weight of the PET flakes (aggregates) that could not pass through the mesh, the residues, etc., relative to the initial weight (1 kg).

[0135] (2) Melting point

[0136] In addition, as characteristic (B), the melting point of the polyester resin as the raw material resin of the polyester heat shrinkable film is defined as the temperature showing the maximum value of the melting peak in the DSC curve, and the melting point is a value within the range of 190°C to 230°C.

[0137] The reason is that when the melting point is a value lower than 190° C., the display label using the polyester heat shrinkable film may be easily melted in the drying step when the PET bottle is recycled. As a result, the PET bottle recycled pieces may adhere to each other and aggregate (agglomerate).

[0138] On the other hand, if the melting point is higher than 230° C., the heat required for extrusion and stretching of the original sheet of the polyester heat shrinkable film for labels becomes too high, and processing may become difficult.

[0139] Therefore, the melting point of the polyester resin is more preferably a value within the range of 195°C to 225°C, and still more preferably a value within the range of 200°C to 220°C.

[0140] That is, control of the melting point value of the polyester resin is also important, but when its range (the difference between the maximum and minimum values) is set to below 25°C, more preferably below 15°C, even when a crystalline polyester resin is used as the main component (for example, 80% by weight or more), the balance between recyclability and heat shrinkage will be further improved.

[0141] The melting point of the polyester resin can be measured, for example, as a melting peak temperature (Tpm) which is a peak temperature of heat of fusion shown as an endothermic reaction in a distribution chart obtained using DSC (the same applies hereinafter).

[0142] Furthermore, the crystallinity of the polyester resin can be estimated from the area of ​​the peak of the heat of fusion (peak area), the half width, and the like.

[0143] (3) Average molecular weight

[0144] The intrinsic viscosity (IV value) of the polyester resin as an average molecular weight is preferably a value within a range of 0.65 dL / g to 0.85 dL / g.

[0145] This is because, when the intrinsic viscosity is less than 0.65 dL / g, the melt viscosity is too low and there is a possibility that problems may arise in extrusion moldability.

[0146] On the other hand, when the intrinsic viscosity exceeds 0.85 dL / g, the melt viscosity is too high, which may cause problems in extrusion moldability.

[0147] Therefore, the intrinsic viscosity is more preferably a value within the range of 0.68 dL / g to 0.83 dL / g, and still more preferably a value within the range of 0.7 dL / g to 0.8 dL / g.

[0148] That is, control of the intrinsic viscosity value of the polyester resin is also important, but when its range (the difference between the maximum and minimum values) is set to below 0.15 dL / g, the balance between recyclability and thermal shrinkage will be further improved even when a crystalline polyester resin is used as the main component (for example, 80% by weight or more).

[0149] The intrinsic viscosity of the polyester resin can be measured in accordance with JIS K 7390 (the same shall apply hereinafter).

[0150] (4) Additives

[0151] In addition, it is preferred that additives such as antioxidants, weather stabilizers, antistatic agents, antifogging agents, metal soaps, waxes, mildew-proof agents, antibacterial agents, nucleating agents, flame retardants, and slip agents be mixed with the polyester resin as necessary.

[0152] In order to improve the slip properties of the film surface, it is preferred to mix an inorganic lubricant such as calcium carbonate particles, silica particles, glass particles, etc. in an amount ranging from 0.01% to 10% by weight of the total film amount (100% by weight).

[0153] The method of adding the additive is not particularly limited, and a known method can be used. However, addition based on a masterbatch is preferred in terms of simplicity and excellent uniform mixing properties.

[0154] For example, when the anti-blocking agent is mixed, a specific example (commercially available product) of the polyester resin masterbatch includes an anti-blocking agent (containing: 20% silica, manufactured by Sukano Corporation, trade name: Gdc S559-E).

[0155] Furthermore, it is also preferable to mix other resins without impairing the physical properties of the heat shrinkable film, particularly, without impairing the shrinkage rate and heat shrinkage stress.

[0156] (5) Mixture

[0157] The polyester resin as the raw material resin of the polyester heat shrinkable film is a mixture of a crystalline polyester resin and a non-crystalline polyester resin, and the weight mixing ratio is preferably within a range of 100:0 to 80:20.

[0158] The reason is that when the weight mixing ratio exceeds 80:20, the balance between recyclability and heat shrinkage becomes poor, recycled PET cannot be obtained stably, and the heat shrinkage rate in a desired temperature range may vary greatly.

[0159] That is, it is generally considered that when the mixing amount of the non-crystalline polyester resin is at least 60% by weight or more with respect to the total amount of the polyester resin (100% by weight), good shrinkage properties cannot be obtained.

[0160] However, in the case of the present invention, even when the mixing amount of the non-crystalline polyester resin is set to a value of 20 wt % or less relative to the total amount of the polyester resin (100 wt %), good heat shrinkage can be obtained taking into account the agglomeration ratio, melting point and its change, heat of fusion and its change, average molecular weight (intrinsic viscosity and its change) and stretching conditions during manufacturing (stretching temperature, stretching ratio, heat treatment temperature, etc.) of the polyester resin.

[0161] Therefore, the weight mixing ratio in the mixture of the crystalline polyester resin and the non-crystalline polyester resin is more preferably a value within the range of 99:1 to 85:15, and still more preferably a value within the range of 98:2 to 90:10.

[0162] 4. Heat of fusion (ΔHm)

[0163] As the characteristic (C) of the polyester heat shrinkable film, the heat of fusion (sometimes described as ΔHm) corresponding to the melting peak area at the melting point of the polyester heat shrinkable film measured by DSC is a value within a range of 25 mJ / mg to 45 mJ / mg.

[0164] This is because, when the heat of fusion of the polyester heat shrinkable film is a value less than 25 mJ / mg, the heat resistance may be significantly reduced due to insufficient crystallization, and the polyester heat shrinkable film may be easily melted.

[0165] On the other hand, when the heat of fusion of the polyester heat shrinkable film exceeds 45 mJ / mg, although crystallization is sufficient, the heat required for extrusion and stretching of the original sheet of the polyester heat shrinkable film becomes too high, making it difficult to control the production conditions.

[0166] Therefore, the heat of fusion of the polyester heat shrinkable film is more preferably a value within the range of 28 mJ / mg to 40 mJ / mg, and still more preferably a value within the range of 30 mJ / mg to 35 mJ / mg.

[0167] 5. Thermal characteristics

[0168] (1) Thermal shrinkage D1 under predetermined measurement conditions (60°C, etc.)

[0169] As a characteristic (D1) of the polyester heat shrinkable film, the heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 60° C. and 10 seconds is a value within a range of 0% to 5%.

[0170] The reason for this is that when the heat shrinkage ratio measured at 60° C. and 10 seconds exceeds 5%, the storage period of the polyester heat shrinkable film becomes short, or the storage conditions must be strictly controlled in some cases.

[0171] On the other hand, when the heat shrinkage ratio is negative %, the function of the heat shrinkable film may not be fully exerted, or the mixing amount and mixing ratio of the raw material components that can be used may be severely limited.

[0172] Therefore, regarding the characteristic (D1), the heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 60°C and 10 seconds is preferably within a range of 0.1% to 4.5%, and more preferably within a range of 0.5% to 4%.

[0173] (2) Thermal shrinkage D2 under predetermined measurement conditions (70°C, etc.)

[0174] As a characteristic (D2) of the polyester heat shrinkable film, the heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 70° C. and 10 seconds is a value within a range of 25% to 50%.

[0175] This is because, when the heat shrinkage ratio is a value less than 25%, the function of the heat shrinkable film cannot be stably exerted, and the mixing amount and mixing ratio of the raw material components that can be used may be severely limited.

[0176] On the other hand, when the heat shrinkage rate exceeds 50%, the storage period of the polyester heat shrinkable film becomes short, or the storage conditions must be strictly controlled, and in the case of being assembled in a PET bottle, spots, wrinkles, etc. may be easily generated.

[0177] Therefore, regarding the characteristic (D2), the heat shrinkage ratio in the main shrinkage direction measured under the heat shrinkage conditions of 70°C and 10 seconds is preferably a value in the range of 30% to 45%, more preferably a value in the range of 35% to 40%.

[0178] (3) Thermal shrinkage D3 under predetermined measurement conditions (80°C, etc.)

[0179] As a characteristic (D3) of the polyester heat shrinkable film, the heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 80° C. and 10 seconds is a value within a range of 55% to 75%.

[0180] This is because, when the heat shrinkage ratio is less than 55%, the polyester heat shrinkable film may not be able to stably function, and the mixing amounts and mixing ratios of the raw material components that can be used may be severely limited.

[0181] On the other hand, when the heat shrinkage rate exceeds 75%, the storage period of the polyester heat shrinkable film becomes short, or the storage conditions must be strictly controlled, and in the case of being assembled in a PET bottle, spots, wrinkles, etc. may be easily generated.

[0182] Therefore, regarding the characteristic (D3), the heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 80°C and 10 seconds is preferably a value in the range of 58% to 72%, and more preferably a value in the range of 60% to 70%.

[0183] (4) Thermal shrinkage (D4') and its standard deviation (D4) under predetermined measurement conditions (100°C, etc.)

[0184] (4)-1 Thermal shrinkage

[0185] As a characteristic (D4') of the polyester heat shrinkable film, the heat shrinkage ratio in the main shrinkage direction (TD direction) measured under the heat shrinkage conditions of 95°C to 100°C and 10 seconds is preferably a value of 70% or more.

[0186] The reason for this is that when the heat shrinkage rate in the TD direction under high temperature conditions is restricted in this way, the occurrence of spots, wrinkles, etc. is reduced, so that good appearance and assemblability can be obtained.

[0187] That is, even if the periphery of the PET bottle is covered and the PET bottle is thermally shrunk not only under high temperature conditions but also under relatively low temperatures, not only the assembly properties are improved, but also the appearance is improved, and the characters, graphics, etc. laminated on the surface can be recognized with high accuracy.

[0188] However, when the heat shrinkage ratio (D4') is excessively increased, the yield rate is significantly reduced, which is economically disadvantageous, or the types of mixed components used in the polyester resin may be excessively limited.

[0189] Therefore, the thermal shrinkage ratio (D4′) is more preferably a value within a range of 71% to 90%, and even more preferably a value within a range of 72% to 85%.

[0190] (4)-2 Standard deviation of thermal shrinkage

[0191] Furthermore, as a characteristic (D4) of the polyester heat shrinkable film, the standard deviation of the heat shrinkage ratio in the main shrinkage direction (TD direction) measured under the heat shrinkage conditions of 95° C. to 100° C. and 10 seconds is a value of 1.5% or less.

[0192] This is because, when the standard deviation of the heat shrinkage ratio exceeds 1.5%, the polyester heat shrinkable film may not be able to stably function, and the mixing amounts and mixing ratios of the raw material components that can be used may be severely limited.

[0193] However, the reason is that when the standard deviation of the heat shrinkage rate is too small, the manufacturing yield is excessively reduced, the types of raw materials that can be used are excessively limited, and the storage conditions must be strictly controlled in some cases.

[0194] Therefore, regarding characteristic (D4), the standard deviation of the heat shrinkage rate in the main shrinkage direction (TD direction) measured under heat shrinkage conditions of 95°C to 100°C and 10 seconds is preferably a value in the range of 0.05% to 1.0%, and more preferably a value in the range of 0.1% to 0.8%.

[0195] Here, reference Figure 2A , to illustrate the relationship between the maximum stretching speed when manufacturing a polyester heat shrinkable film and the standard deviation of the heat shrinkage rate in the main shrinkage direction at 100°C and 10 seconds.

[0196] Right now, Figure 2A The horizontal axis represents the maximum stretching speed when producing the polyester heat shrinkable film, and the vertical axis represents the standard deviation of the heat shrinkage rate in the main shrinkage direction measured at 100° C. and 10 seconds.

[0197] According to the Figure 2A In the characteristic curve L1 in FIG. 1 , when the maximum stretching speed reaches 40% / s or more and reaches about 60% / s, the standard deviation of the heat shrinkage rate tends to gradually increase within the range of 0.3% to 0.5%. In addition, when the maximum stretching speed exceeds 60% / s and reaches 67% / s, the standard deviation of the heat shrinkage rate tends to increase at a considerable rate and reach a value of about 0.5% to 1.5%. Moreover, when the maximum stretching speed exceeds 67% / s, the standard deviation of the heat shrinkage rate further increases sharply and reaches a value exceeding 1.5%.

[0198] That is, it can be understood from the characteristic curve L1 that in the case of the polyester heat shrinkable film of the present invention, when the maximum stretching speed during production is controlled to a value within a predetermined range, the standard deviation of the heat shrinkage rate measured under predetermined conditions can be stably controlled to a low desired value.

[0199] For example, it is understood that when the maximum stretching speed is at least a value within a range of 40% / sec to 67% / sec, the standard deviation of the heat shrinkage ratio (%) can be controlled to a small value of 1.5% or less.

[0200] Here, the maximum stretching speed refers to the maximum stretching speed in the main shrinking direction (TD direction) of the film, and is a value defined as the maximum speed when an unstretched film is stretched at different predetermined speeds during the production of a polyester heat shrinkable film.

[0201] That is, the stretching speed reaches a maximum within several seconds, for example, within 0.1 to 12 seconds after the start of stretching of the unstretched film, and the maximum value of the stretching speed during this period can be regarded as the maximum stretching speed.

[0202] Here, the stretching speed in the TD direction can be defined by the following formula.

[0203] Stretching speed in TD direction (% / sec) = (W t2 -W t1 ) / W t1 ×100 / (t2-t1)

[0204] W t1 : Width of the film after 1 second of starting to stretch the unstretched film (m)

[0205] W t2 : Width of the film after t2 seconds after the start of stretching the unstretched film (m)

[0206] (where t1<t2, 0≤t1, 0.1≤t2≤12)

[0207] However, it has been found that Figure 2A In the case of Comparative Examples 2 and 3, the agglomeration ratio is quite large compared with the agglomeration ratio of the present invention (Example 5, etc.), and it should be noted that when the agglomeration ratio is at least 1.2 or lower as in the present invention, characteristic curve L1 can be obtained.

[0208] On the other hand, as described below, when the maximum stretching speed is controlled to a value within a predetermined range, Figure 2B As shown in the characteristic curve L1' in FIG. 1 , the standard deviation of the thickness of the polyester heat shrinkable film can also be stably controlled to a desired value.

[0209] That is, it can be understood that in the case of the characteristic curve L1', even in the cases of Comparative Examples 2 and 3 where the blocking ratio is high, a good correlation is shown with respect to the maximum stretching speed, and the standard deviation of the thickness of the polyester heat shrinkable film can be controlled to a predetermined value even when the blocking ratio is not strictly controlled.

[0210] Here, reference Figure 3 , the relationship between the standard deviation of the heat shrinkage ratio in the main shrinkage direction (TD direction) measured under predetermined heat shrinkage conditions (100° C. for 10 seconds) and the evaluation of the blocking ratio is described.

[0211] That is, the horizontal axis represents the standard deviation (%) of the heat shrinkage rate in the main shrinkage direction, and the vertical axis represents the evaluation result (relative value) of the blocking ratio.

[0212] According to the Figure 3From the characteristic curve L2 in FIG. 1 , it can be considered that, as the standard deviation of the heat shrinkage rate in the main shrinkage direction is smaller, the evaluation result (relative value) of the blocking ratio tends to become higher.

[0213] More specifically, it can be understood that the standard deviation of the heat shrinkage rate in the main shrinkage direction is 1.5%. If it is below 1.5%, a high evaluation of at least 3 can be obtained. If the standard deviation (%) of the heat shrinkage rate is below 1%, the highest evaluation, i.e. 5, can be obtained.

[0214] On the other hand, if the standard deviation of the heat shrinkage rate in the main shrinkage direction exceeds 1.5%, the evaluation result of the blocking ratio becomes sharply smaller. If the standard deviation is 1.9%, the evaluation result of the blocking ratio is 0. Furthermore, if the standard deviation is 2.6%, the evaluation result of the blocking ratio is definitely 0.

[0215] Therefore, according to Figure 3 Judging from the characteristic curve in, it can be understood that the evaluation result of the agglomeration ratio can be adjusted by controlling the standard deviation of the heat shrinkage rate in the main shrinkage direction.

[0216] Here, if Figure 4 , Figure 5 and Figure 6 As shown, it is estimated that the maximum stretching speed when manufacturing the polyester heat shrinkable film has a predetermined correlation with the heat of crystallization, the glass transition temperature and the heat of fusion, which will be described in detail in the manufacturing method of the second embodiment.

[0217] (5) Thermal shrinkage D5 under the predetermined measurement conditions

[0218] As a characteristic (D5) of the polyester heat shrinkable film, the heat shrinkage ratio in the main shrinkage direction (TD direction) measured under heat shrinkage conditions of 60° C. to 80° C. and 10 seconds preferably satisfies the following relational expression (1).

[0219] The reason is that, within the predetermined temperature range, when the heat shrinkage temperature and the heat shrinkage rate satisfy the predetermined relationship (1), even when the mixing ratio of the crystalline polyester resin is high, good heat shrinkage can be obtained with high accuracy. Therefore, as a result, the control of the heat shrinkage force also becomes easy.

[0220] [Formula 5]

[0221] Thermal shrinkage rate (%) = a × (thermal shrinkage temperature (°C) - 60) + b (1)

[0222] a: corresponds to the slope of relational expression (1), which is a value greater than 3.25 and less than 4,

[0223] b: A constant corresponding to the relational expression (1), which is a value greater than or equal to 0 and less than or equal to 5.

[0224] More specifically, refer to Figure 7 The relationship between the heat shrinkage rate in the main shrinkage direction (TD direction) under the heat shrinkage conditions of 60°C to 80°C and 10 seconds is explained in terms of the relationship with relational expression (1).

[0225] Right now, Figure 7 The horizontal axis is represented by the heat shrinkage temperature (° C.), and the vertical axis is represented by the heat shrinkage rate (%) in the main shrinkage direction (TD direction) of the polyester heat shrinkable film.

[0226] In the Figure 7 It can be understood that as long as the shaded area (S1) sandwiched by the two straight lines located in the upper and lower directions is within the range defined by the relationship (1) of the present invention, that is, at least within the range of 60°C to 80°C, the thermal shrinkage rate increases linearly with the increase of the thermal shrinkage temperature.

[0227] Therefore, it is considered that even if the heat shrinkage temperature changes and the desired heat shrinkage cannot be obtained temporarily, the heat shrinkage (%) of the polyester heat shrinkable film can be controlled to a value within the desired range by controlling the agglomeration ratio according to the following relationship (1).

[0228] For example, when controlling the heat shrinkage ratios at 60° C., 70° C., and 80° C. of the present invention within a predetermined range, it is extremely effective to use the relational expression (1) or the like.

[0229] Furthermore, Figure 7 In the figure, the heat shrinkage ratio (%) of the polyester heat shrinkable film of the conventional art (Patent Document 2 and Patent Document 3) is represented by the curves assigned with Conventional Art 2 (Ex. 1) and Conventional Art 3 (Ex. 1).

[0230] In the case of these curves of D2 and D3, it is found that the heat shrinkage rate does not decrease linearly with the decrease of the heat shrinkage temperature, and a so-called S-shaped curve is formed as a whole. Moreover, it can be understood that: around 70°C, conventional technology 2 (Ex.1) and conventional technology 3 (Ex.1) greatly deviate from the range defined by the relationship (1) of the present invention.

[0231] Furthermore, more preferably, as the characteristic (D5′), the heat shrinkage temperature and the heat shrinkage rate satisfy a predetermined relational expression (2), and even more preferably, as the characteristic (D5″), a predetermined relational expression (3) is satisfied.

[0232] Right now, Figure 8 and Fig. 9, the shaded areas (S2 and S3) sandwiched by two straight lines located in the upper and lower directions are respectively within the ranges defined by the relational expressions (2) and (3) of the present invention. Therefore, it can be understood that when the range is at least 60°C to 80°C, the heat shrinkage rate increases linearly with increasing heat shrinkage temperature with higher accuracy.

[0233] Furthermore, with Figure 7 Likewise, Figure 8 and Fig. 9 In the figure, the heat shrinkage ratio (%) of the polyester heat shrinkable film of the conventional art (Patent Document 2 and Patent Document 3) is represented by the curves assigned with Conventional Art 2 (Ex. 1) and Conventional Art 3 (Ex. 1), respectively.

[0234] [Formula 6]

[0235] Thermal shrinkage rate (%) = a' × (thermal shrinkage temperature (°C) - 60) + b' (2)

[0236] a′: corresponds to the slope of relational expression (2), and is a value of 3.3 or more and 3.75 or less. b′: corresponds to the constant of relational expression (2), and is a value of 0 or more and 5 or less.

[0237] [Formula 7]

[0238] Thermal shrinkage rate (%) = a" × (thermal shrinkage temperature (℃) - 60) + b" (3)

[0239] a": corresponds to the slope of relational expression (3), and is a value greater than or equal to 3.35 and less than or equal to 3.5; b": corresponds to the constant of relational expression (3), and is a value greater than or equal to 0 and less than or equal to 5.

[0240] (6) Heat shrinkage D6 in the MD direction under the predetermined measurement conditions

[0241] As a characteristic (D6) of the polyester heat shrinkable film, the heat shrinkage rate in the direction orthogonal to the main shrinkage direction (MD direction) measured under heat shrinkage conditions of 70° C. and 10 seconds is preferably a value within a range of −3% to 5%.

[0242] The reason is that if the heat shrinkage rate in the MD direction under a predetermined temperature condition is restricted in this way, even if the periphery of the PET bottle is covered and the PET bottle heat shrinks at a relatively low temperature, the generation of spots, wrinkles, etc. is further reduced.

[0243] Therefore, even with energy-saving heating, it is easy to obtain good assembly properties, appearance, etc.

[0244] Furthermore, when the heat shrinkage rate in the MD direction is restricted in this way, the heat shrinkage of the entire polyester heat shrinkable film can be balanced, and even if the film is recycled together with PET bottles, pellets can be stably obtained by controlling the adhesion, fluidity, etc.

[0245] Therefore, as the characteristic (D6), the heat shrinkage rate in the MD direction is more preferably a value within a range of -2.5% to 4%, and even more preferably a value within a range of -2% to 3.5%.

[0246] (7) Heat shrinkage in the MD direction under the predetermined measurement conditions D7

[0247] As a characteristic (D7) of the polyester heat shrinkable film, the heat shrinkage rate in the direction orthogonal to the main shrinkage direction (MD direction) measured under heat shrinkage conditions of 60°C to 90°C and 10 seconds has at least one minimum value, and the minimum value is preferably a value of -3% or more.

[0248] The reason is that when the distribution diagram of the heat shrinkage rate in the MD direction under predetermined temperature conditions is limited to a minimum value having a predetermined size, even if the temperature conditions are slightly changed and the heat shrinkage rate changes, it is easy to obtain good appearance, accurate information, etc. when making corrections, and the heat shrinkage can be determined more clearly through simple measurement of the heat shrinkage curve, thermomechanical analysis (TMA) measurement, etc.

[0249] Furthermore, when the heat shrinkage rate in the MD direction is limited within a predetermined temperature range, the heat shrinkage of the entire polyester heat shrinkable film can be balanced, the generated heat shrinkage stress can be reduced, and even if the film is recycled together with PET bottles, pellets can be obtained more stably.

[0250] Therefore, as the characteristic (D7), the minimum value of the heat shrinkage in the MD direction is more preferably a value in the range of -1% to 2%, and even more preferably a value in the range of -0.5% to 1%.

[0251] (8) Heat shrinkage in the MD direction under the predetermined measurement conditions D8

[0252] As a characteristic (D8) of the polyester heat shrinkable film, the heat shrinkage rate in the direction orthogonal to the main shrinkage direction (MD direction) measured under heat shrinkage conditions of 60°C to 90°C and 10 seconds has at least one maximum value, and the maximum value is preferably a value of 3% or less.

[0253] The reason is that when the distribution diagram of the heat shrinkage rate in the MD direction under predetermined temperature conditions is limited in this way and has a maximum value of a predetermined size, it can be more clearly judged that a good appearance, accurate informativeness, etc. are easily obtained during heat shrinkage, and the generated heat shrinkage stress is below the predetermined value.

[0254] Furthermore, when the distribution diagram of the heat shrinkage rate has a local maximum value of a predetermined size, it is further preferred that it also has a local minimum value of the predetermined size.

[0255] Therefore, as the characteristic (D8), the maximum value of the heat shrinkage in the MD direction is more preferably a value in the range of -1% to 2%, and even more preferably a value in the range of -0.5% to 1.5%.

[0256] 6. Thickness

[0257] Here, the thickness (average thickness, the same below) of the polyester heat shrinkable film may vary depending on the shape of various PET bottles, but is usually preferably a value within the range of 10 μm to 100 μm.

[0258] The reason for this is that when the thickness of the polyester heat shrinkable film is a value less than 10 μm, handling becomes difficult and the breaking strength and the like may be significantly reduced.

[0259] On the other hand, when the thickness of the polyester heat-shrinkable film exceeds 100 μm, it may not be uniformly heat-shrunk when the film is heated at a predetermined temperature, or it may be difficult to manufacture a film having a uniform thickness.

[0260] Therefore, the thickness of the polyester heat shrinkable film is more preferably a value within the range of 20 μm to 70 μm, and still more preferably a value within the range of 40 μm to 60 μm.

[0261] Here, the thickness of the polyester heat shrinkable film can be measured and calculated using a micrometer (trade name "thickness gauge 547-401", commercially available from Mitutoyo Corporation) in accordance with the International Organization for Standardization (ISO) 4593.

[0262] Furthermore, as mentioned above based on Figure 2B As described above, the standard deviation, which is the deviation of the average thickness of the polyester heat shrinkable film measured under predetermined conditions, is preferably a value of 1.7 μm or less.

[0263] The reason is that when the standard deviation of the average thickness is set to a predetermined value or less, even in the case of a polyester heat-shrinkable film derived from a crystalline polyester resin as a main component (e.g., 80% by weight or more), the balance between recyclability and heat shrinkability is further improved.

[0264] However, when the standard deviation of the average thickness is too small, the yield rate may be significantly reduced, which is economically disadvantageous, or the types of mixed components used in the polyester resin may be excessively limited.

[0265] Therefore, the standard deviation of the average thickness of the polyester heat shrinkable film is more preferably a value within a range of 0.05 μm to 1.4 μm, and still more preferably a value within a range of 0.1 μm to 1.2 μm.

[0266] The method for measuring the standard deviation of the average thickness will be described in detail in Example 1.

[0267] 7. Functional layer

[0268] The polyester heat shrinkable film preferably has a functional layer for imparting various functions as necessary, unless the object of the present invention is impaired.

[0269] Examples of the functional layer include a coating layer for imparting surface smoothness, stain resistance, weather resistance, etc., a transfer layer, and a printing layer for imparting design properties.

[0270] Among these functional layers, a coating layer using a surfactant is particularly preferred as the functional layer because it greatly contributes to the improvement of antistatic properties and surface smoothness.

[0271] For example, Figure 1B As shown, it is also preferred that other resin layers 10 a and 10 b containing at least one of the various additives are laminated on one or both sides of the polyester heat shrinkable film 10 .

[0272] In such a case, when the thickness of the polyester heat shrinkable film is set to 100%, the single layer thickness or the total thickness of the other resin layers to be laminated is usually preferably a value within a range of 0.1% to 10%.

[0273] Furthermore, the resin as a main component constituting the other resin layer may be a polyester resin similar to the polyester heat shrinkable film, or preferably at least one different acrylic resin, olefin resin, urethane resin, rubber material, or the like.

[0274] In addition, the polyester heat shrinkable film has a multi-layer structure to further improve the anti-hydrolysis effect and mechanical protection, or, as Figure 1C As shown, it is also preferable to provide a shrinkage ratio adjusting layer 10 c on the surface of the polyester heat shrinkable film 10 so that the shrinkage ratio of the polyester heat shrinkable film becomes uniform within the surface.

[0275] The shrinkage ratio adjusting layer may be laminated as a predetermined layer made of a polyester resin or the like using an adhesive, a coating method, a heating treatment, or the like according to the shrinkage characteristics of the polyester heat shrinkable film.

[0276] 8. Haze value and haze value / thickness

[0277] (1) Haze value

[0278] Here, the haze value of the polyester heat shrinkable film measured in accordance with American Society for Testing and Materials (ASTM) D1003 is preferably a value within a range of 2% to 8%.

[0279] This is because when the haze value exceeds 8%, there is a risk that the transparency may be deteriorated and the appearance may be deteriorated when producing a label, which is not preferable.

[0280] Therefore, the haze value is more preferably 7% or less, and still more preferably 6% or less.

[0281] The haze value can be measured using a haze meter or the like. Generally, the smaller the value, the higher the transparency. However, considering that a predetermined amount of lubricant must be added to the film in order to impart practically required slip properties, the lower limit of the value is about 2%.

[0282] (2) Haze value / thickness

[0283] The haze value / thickness of the polyester heat shrinkable film is preferably a value of 0.15% / μm or less.

[0284] The reason for this is that when the haze value / thickness exceeds 0.15% / μm, the balance between recyclability and heat shrinkage may be reduced.

[0285] Therefore, the haze value / thickness is more preferably a value of 0.14% / μm or less, and still more preferably a value of 0.13% / μm or less.

[0286] However, when the haze value / thickness becomes too small, the manufacturing management of the polyester heat shrinkable film, the restriction of mixed materials, etc. become too strict.

[0287] Therefore, the haze value / thickness is preferably a value of 0.03% / μm or more, more preferably a value of 0.04% / μm or more, and still more preferably a value of 0.05% / μm or more.

[0288] [Second embodiment]

[0289] The second embodiment is a method for producing a polyester heat shrinkable film according to the first embodiment. Hereinafter, each step will be specifically described.

[0290] 1. Raw materials preparation and mixing steps

[0291] As raw materials, prepare Fig. 11B Main agents and additives such as recycled crystalline polyester resin pellets, rubber resin, antistatic agent and anti-hydrolysis agent are shown.

[0292] When preparing the raw materials, it is preferred that recycled crystalline polyester resin pellets as a main component are heated at a predetermined temperature (for example, at a temperature 10° C. lower than the crystallization temperature) for a predetermined time (for example, 3 to 10 hours) to be in an absolutely dry state.

[0293] Then, the recycled crystalline polyester resin pellets and the like are preferably added into the stirring container while being weighed, and the recycled crystalline polyester resin pellets and the like are mixed and stirred using a stirring device until the mixture becomes uniform.

[0294] Here, as the crystalline polyester resin, in addition to recycled crystalline polyester resin pellets, non-recycled crystalline polyester resin pellets may also be used.

[0295] That is, economically, as the crystalline polyester resin, it is preferred to use a relatively large amount of recycled crystalline polyester resin pellets, for example, 50% by weight or more of recycled crystalline polyester resin pellets with respect to the total amount.

[0296] On the other hand, in order to easily adjust the agglomeration ratio, melting point, heat of fusion, haze value, etc. to the desired range, it is preferred to use a larger amount of non-recycled crystalline polyester resin pellets, for example, 50% by weight or more of the total amount.

[0297] 2. Production steps of the original film

[0298] Then, typically, extrusion molding (T-die method), blow molding method or cast molding method is preferably performed to produce a green sheet having a predetermined thickness.

[0299] More specifically, for example, by performing extrusion molding using an extruder under the condition of an extrusion temperature of 245° C., a raw sheet having a predetermined thickness (usually 200 μm to 300 μm) can be obtained.

[0300] 3. Manufacturing of polyester heat shrinkable film

[0301] Then, the obtained original sheet is heated and pressed while being moved on or between rolls using a heat shrink film manufacturing apparatus (tenter), thereby manufacturing a polyester heat shrink film.

[0302] However, as a stretching treatment method for expressing the shrinkage property, a blow molding method, a roll stretching method, a tenter stretching method, and a combination thereof are known.

[0303] Here, in terms of better productivity, it is more preferable to combine sheet forming by a casting method, roll stretching, and tenter stretching.

[0304] That is, while preheating at a predetermined preheating temperature, for example, a temperature in the range of 110°C to 150°C, the width of the film is basically expanded at a predetermined stretching temperature, maximum stretching speed and stretching ratio, and the film is stretched in a predetermined direction while heating and pressing, so it is preferred that the molecules of the polyester resin constituting the polyester heat shrinkable film are crystallized into a predetermined state.

[0305] Here, the film is cured at a predetermined heat setting temperature, for example, at a temperature in the range of 60° C. to 80° C., so that a heat-shrinkable polyester heat-shrinkable film used as a decoration, a label, or the like can be obtained.

[0306] That is, after the original film is usually manufactured by a T-die method, a blow molding method, etc., the original film is heated to a temperature above the glass transition temperature of the resin, and is preferably stretched at a maximum stretching speed in the range of 40% / second to 67% / second, preferably in the range of 45% / second to 62% / second, at least along the main stretching direction (the width direction of the original film, i.e., the TD direction) at a value in the range of 3 to 8 times, preferably in the range of 4 to 6 times.

[0307] 4. Influence of Maximum Stretching Speed

[0308] (1) Relationship with the standard deviation of the expected thermal shrinkage

[0309] As mentioned above Figure 2A As shown in the characteristic curve L1 in , it is found that there is a predetermined correlation between the maximum stretching speed and the standard deviation of the heat shrinkage rate in the main shrinkage direction at 100° C. and 10 seconds, assuming a predetermined agglomeration ratio.

[0310] Here, if Figure 2B As shown in the characteristic curve L1' in FIG. 1 , it is found that regardless of whether there is a predetermined agglomeration ratio, there is a predetermined correlation between the maximum stretching speed and the standard deviation of the thickness. Here, according to the characteristic curve L1', it can be understood that when the maximum stretching speed is less than 40% / sec, the standard deviation of the thickness is a value exceeding at least 1.7 μm.

[0311] (2) Relationship with heat of crystallization

[0312] Here, if Figure 4 As shown in the characteristic curve L3 in FIG. , it is found that there is a predetermined correlation between the maximum stretching speed and the heat of crystallization of the obtained polyester heat shrinkable film.

[0313] That is, under certain necessary conditions, when the value of the maximum stretching speed is set within a predetermined range, the value of the heat of crystallization of the obtained polyester heat shrinkable film can be stably controlled to a value within a desired range.

[0314] For example, when the maximum stretching speed is controlled within a range of 40% / sec to 65% / sec, the value of the heat of crystallization of the obtained polyester heat shrinkable film can be controlled within a range of 12 mJ / mg to 15 mJ / mg.

[0315] (3) Relationship with glass transition temperature

[0316] Here, if Figure 5 As shown in the characteristic curve L4 in FIG. , it is found that there is a predetermined correlation between the maximum stretching speed and the glass transition temperature of the obtained polyester heat shrinkable film.

[0317] That is, under certain necessary conditions, when the value of the maximum stretching speed is set within a predetermined range, the value of the glass transition temperature of the obtained polyester heat shrinkable film can be stably controlled to a value within a desired range.

[0318] For example, when the maximum stretching speed is controlled within a range of 40% / sec to 58% / sec or less, the glass transition temperature of the obtained polyester heat shrinkable film can be controlled to be around 74.5°C.

[0319] Here, for example, when the maximum stretching speed exceeds 58% / sec and reaches a range of about 65% / sec, the glass transition temperature of the obtained polyester heat shrinkable film tends to decrease from about 74.5°C to about 74.3°C.

[0320] Furthermore, for example, it can be understood that when the maximum stretching speed is in a range exceeding 65% / sec, the value of the glass transition temperature of the obtained polyester heat shrinkable film is definitely lowered to 74.3° C. or less and the tendency of this situation persists.

[0321] (4) Relationship with heat of fusion (ΔHm)

[0322] Here, if Figure 6 As shown by the characteristic curve L5 in FIG. 1 , it was found that there was a predetermined correlation (linear relationship) between the maximum stretching speed and the heat of fusion (ΔHm) of the obtained polyester heat shrinkable film.

[0323] That is, under certain necessary conditions, for example, when the maximum stretching speed is set within the range of 40% / sec to 65% / sec, the crystallization temperature and the fusion heat of the obtained polyester heat shrinkable film can be stably controlled to desired values ​​using a linear relationship.

[0324] On the other hand, it can be understood that, for example, when the value of the maximum stretching speed exceeds 65% / sec, since the correlation (linear relationship) decreases, it is difficult to control the heat of fusion to a desired value.

[0325] 5. Inspection steps of polyester heat shrink film

[0326] It is preferred that the following characteristics and the like be measured continuously or intermittently for the produced polyester heat shrinkable film, and a predetermined inspection step be provided.

[0327] That is, by measuring the following characteristics and the like according to a predetermined inspection procedure and confirming that the values ​​fall within a predetermined range, a polyester heat shrinkable film having more uniform shrinkage characteristics and the like can be obtained.

[0328] 1) Visual inspection of the appearance of polyester heat shrinkable film

[0329] 2) Thickness change measurement

[0330] 3) Tensile strength test (ASTM D882)

[0331] 4) Tensile elongation determination (ASTM D882)

[0332] 5) Surface smoothness inspection (ASTM D1894)

[0333] 6) Specific gravity measurement (ASTM D792)

[0334] 7) Ring break test (Technical Association of Pulp and Paper (TAPPI) T882)

[0335] 8) Tear strength test (ASTM D1922) [Example]

[0336] Hereinafter, the present invention will be described in detail based on examples. However, unless otherwise specified, the scope of rights of the present invention is not limited by the description of the examples.

[0337] Here, the crystalline polyester resin, the non-crystalline polyester resin, and the like used in Example 1 and the like are as follows.

[0338] Here, the intrinsic viscosity (IV value) described in the column of the non-crystalline polyester resin in the mixed solvent of phenol / 1,1,2,2-tetrachloroethane (weight ratio = 1 / 1) is measured at a temperature of 30° C. using an Ubbelohde viscometer.

[0339] (PET1)

[0340] As a crystalline polyester resin, PET1 (commercially available from Eastman Chemical Company, trade name "Embrace Encore", glass transition temperature (Tg): 74° C., melting point: 217° C., density: 1.3 g / cm 3 ).

[0341] (PET2)

[0342] As a crystalline polyester resin, PET2 (a crystalline polyester resin containing dicarboxylic acid: 98.6 mol % of terephthalic acid, 1.4 mol % of isophthalic acid, diol: 97.3 mol % of ethylene glycol, 2.7 mol % of diethylene glycol (glass transition temperature (Tg): 78° C., melting point: 251° C., intrinsic viscosity (IV value): 0.72, density: 1.3 g / cm) was prepared as a crystalline polyester resin different from PET1. 3 That is, after recycling commercially available PET bottles, Fig. 11B As shown, the crystalline polyester resin is obtained by pelletizing.

[0343] Here, PET2 was used only in Evaluation 1 (blocking ratio) of Examples described below.

[0344] Here, Fig. 10B An example of a DSC graph of PET2 obtained by DSC measurement in accordance with JIS K7121:2012 is shown in FIG.

[0345] That is, in step 1, the temperature of the measurement sample is increased from 30° C. to 300° C. at a temperature increase rate of 10° C. / min using a DSC apparatus.

[0346] Then, in step 2, the temperature is rapidly lowered from 300°C to 0°C at a temperature-lowering rate of 100°C / min. Fig. 10B (not shown in the figure).

[0347] Furthermore, in step 3, the temperature was raised from 0° C. to 300° C. at a heating rate of 10° C. / min.

[0348] Here, based on the temperature of the specific heat change point, the temperature of the peak point, etc. of the DSC curve obtained in steps 1 and 3, the glass transition temperature, melting peak, etc. that define the characteristics of PET2 can be determined with high accuracy.

[0349] (PETG)

[0350] As a non-crystalline polyester resin, PETG (a non-crystalline polyester containing dicarboxylic acid: 100 mol% of terephthalic acid, diol: ethylene glycol, 1,4-cyclohexanedimethanol and diethylene glycol (commercially available from Eastman Chemical Company, trade name "Embrace LV", glass transition temperature (Tg): 68.2° C., no melting point, intrinsic viscosity (IV value): 0.7, density: 1.3 g / cm 3 )).

[0351] (additive)

[0352] As an additive (anti-caking agent), a silica masterbatch (commercially available from Sukano Corporation, trade name "GdcS559-E", a product containing 20 wt% of silica) was prepared by mixing 20 parts by mass of silica with 80 parts by mass of polyethylene terephthalate resin.

[0353] [Example 1]

[0354] 1. Manufacturing of polyester heat shrinkable film

[0355] As the crystalline polyester resin, the above-mentioned PET1 was prepared.

[0356] Then, 1000 g of the prepared PET1 was put into the stirring container.

[0357] Here, the above-mentioned anti-blocking agent dried under predetermined conditions was mixed as an anti-blocking agent for a heat shrinkable film at a ratio of 1 part by weight based on 100 parts by weight of PET1, thereby obtaining a raw material for forming a heat shrinkable film.

[0358] Then, the heat shrinkable film-forming raw material was extruded by an extruder at an extrusion temperature of 245° C. using a vented twin-screw extruder to obtain a raw sheet having a thickness of 250 μm.

[0359] Finally, a heat shrink film manufacturing device was used to make a polyester heat shrink film with a set thickness of 50 μm from the original sheet with a preheating temperature of 125°C, a maximum stretching speed of 56% / s, a stretching temperature of 86°C, a heat fixing temperature of 72°C, and a stretching ratio (MD direction: 1.07 times, TD direction: 4.8 times).

[0360] 2. Evaluation of polyester heat shrinkable film

[0361] (1) Evaluation 1 (caking ratio)

[0362] As shown in Table 1, PET1, PET2 and PETG were appropriately mixed to obtain a polyester resin.

[0363] Then, according to the APR document identification code: PET-S-08, the blocking ratio of the polyester resin (crystalline polyester resin, non-crystalline polyester resin, or a mixture thereof) was measured and evaluated according to the following criteria.

[0364] ◎ (very good): The agglomeration ratio is 1% or less.

[0365] ○ (good): The agglomeration ratio is 1.2% or less.

[0366] △ (average): The agglomeration ratio is 1.4% or less.

[0367] × (poor): The agglomeration ratio exceeded 1.4%.

[0368] (2) Evaluation 2 (DSC measurement of polyester heat shrinkable film)

[0369] The obtained polyester heat shrinkable film was measured for melting point (melting peak temperature) and the like under predetermined conditions using a DSC apparatus (commercially available from Hitachi-High-Tech Science, Ltd., trade name "DSC7000X").

[0370] More specifically, a sample of the polyester heat shrinkable film was dried in a drying oven at 60° C. for 6 hours or more.

[0371] Then, the sample was placed in a differential scanning calorimeter and the temperature was temporarily raised to a high temperature region in step 1 (from 25° C. to 250° C. at a heating rate of 10° C. / min).

[0372] Then, in step 2, the temperature is temporarily lowered to a low temperature region (from 250°C to 25°C at a temperature lowering rate of 10°C / min). Finally, in step 3, the temperature is again raised to a high temperature region (from 25°C to 250°C at a temperature raising rate of 10°C / min).

[0373] Here, if Fig. 10A As shown, based on the obtained DSC curve, the glass transition temperature, crystallization temperature, heat of crystallization, melting point (melting peak temperature) and heat of fusion (ΔHm) corresponding to the melting peak area were measured respectively.

[0374] (3) Evaluation 3 (heat shrinkage)

[0375] The heat shrinkage rate of the obtained polyester heat shrinkable film was measured according to ASTM D2732-08.

[0376] That is, the film was cut into a square shape having a length of 100 mm in the main shrinking direction (TD direction) and a length of 100 mm in the non-shrinking direction (MD direction), and this was used as a measurement sample.

[0377] Then, the obtained polyester heat shrinkable film was immersed for 10 seconds in a thermostatic bath filled with warm water whose temperature was controlled at 60° C., 70° C., 80° C., 90° C., and 100° C. in increments of 10° C. to heat shrink.

[0378] Then, at each temperature, the heat shrinkage ratio (%) in the main shrinkage direction (TD direction) and the non-shrinkage direction (MD direction) was calculated according to the following formula (5) based on the dimensional change before and after the heat treatment.

[0379] [Formula 8]

[0380]

[0381] (4) Evaluation 4 (Standard Deviation of Heat Shrinkage)

[0382] The heat shrinkage rate of the obtained polyester heat shrinkable film was measured according to the following procedure in accordance with ASTM D2732-08, and the standard deviation was calculated.

[0383] First, eight measurement samples were obtained evenly in the width direction of the obtained polyester heat shrinkable film.

[0384] That is, the film was cut into a square shape having a length of 100 mm in the main shrinking direction (TD direction) and a length of 100 mm in the non-shrinking direction (MD direction), and eight pieces were prepared as measurement samples.

[0385] Then, as a pretreatment, the prepared eight measurement samples were left to stand in an environment of 23° C. and 50% RH for 40 hours or more.

[0386] Then, the eight pre-treated measurement samples were immersed in a thermostatic bath containing warm water controlled at 100° C. for 10 seconds to thermally shrink them.

[0387] Then, the heat shrinkage ratio (%) in the main shrinkage direction (TD direction) was calculated according to the above formula (5) based on the dimensional changes before and after the heat treatment.

[0388] Then, the standard deviation was calculated from the calculated heat shrinkage rates of the eight measurement samples, and evaluation was performed according to the following criteria.

[0389] ◎ (very good): The standard deviation of the heat shrinkage ratio is 1.0% or less.

[0390] ○ (good): The standard deviation of the heat shrinkage ratio is 1.5% or less.

[0391] Δ (average): The standard deviation of the heat shrinkage ratio is 2.5% or less.

[0392] × (poor): The standard deviation of the heat shrinkage ratio exceeds 2.5%.

[0393] (5) Evaluation 5 and Evaluation 6 (Thickness and Standard Deviation)

[0394] The thickness of the obtained polyester heat shrinkable film was measured at 20 points at equal intervals in the width direction of the film using a micrometer (trade name "thickness gauge 547-401", commercially available from Mitutoyo Corporation) in accordance with ISO4593, and the average value was calculated and used as the thickness (average thickness).

[0395] Here, the standard deviation was calculated from the measured values ​​at 20 points used for calculating the thickness (average thickness) of the obtained polyester heat shrinkable film, and the evaluation was performed according to the following criteria.

[0396] ◎ (very good): The standard deviation of thickness is 1.4 μm or less.

[0397] ○ (good): The standard deviation of thickness is 1.7 μm or less.

[0398] △ (average): The standard deviation of thickness is 2 μm or less.

[0399] × (poor): The standard deviation of the thickness exceeds 2 μm.

[0400] (6) Evaluation 7 (Haze value)

[0401] The haze value of the obtained polyester heat shrinkable film was measured using a haze meter (commercially available from BYK, trade name “haze-gard dual”) in accordance with ASTM D1003, and evaluated according to the following criteria.

[0402] ◎ (very good): The haze value is 7% or less.

[0403] ○ (good): The haze value is 8% or less.

[0404] △ (average): The haze value is 10% or less.

[0405] × (bad): The haze value exceeds 10%.

[0406] (7) Evaluation 8 (Assembly / Appearance)

[0407] An eggplant-shaped PET bottle filled with commercially available drinking water (trade name "Limmi Lemon Juice", volume: 200 ml) was prepared.

[0408] Then, 1,3-dioxolane was applied to the end portions in the width direction of a long strip sample obtained by cutting the polyester heat shrinkable film into a width of 20.5 cm.

[0409] Then, the ends in the width direction were overlapped and attached so as to overlap by about 1 cm, thereby obtaining a cylindrical label with a diameter of about 6.2 cm. Furthermore, the cylindrical label was cut at intervals of 11 cm in the length direction to obtain a plurality of cylindrical labels.

[0410] Then, the tubular label is placed on the prepared roughly cylindrical PET bottle body, placed on a belt conveyor in a steam tunnel maintained at 80°C, and moved while being heated for 8 seconds to heat shrink the tubular label so that the tubular label is in close contact with the roughly cylindrical PET bottle body from top to bottom.

[0411] Next, visual observation was made to see whether there was any assembly failure in which the tubular label after heat shrinking did not come into close contact with the PET bottle under the conditions of a predetermined length (5 mm or more) and a predetermined width (1 mm or more), or whether there were any spots or wrinkles, and the assembly property was evaluated according to the following criteria.

[0412] ◎ (very good): Among the 5 cylindrical labels, no assembly failure, spots, and wrinkles were observed.

[0413] ○ (good): No assembly failure, spots, or wrinkles were observed in 3 or more of the 5 cylindrical labels.

[0414] △ (fair): Among 5 cylindrical labels, at least one was not observed to have poor assembly, spots, or wrinkles.

[0415] × (poor): In all 5 cylindrical labels, assembly failure, spots, and wrinkles were observed.

[0416] [Example 2]

[0417] In Example 2, a polyester heat shrinkable film was prepared and evaluated in the same manner as in Example 1 except that the preheating temperature (° C.) and the maximum stretching speed (% / sec) were changed as shown in Table 1. The obtained results are shown in Table 2.

[0418] [Example 3]

[0419] In Example 3, a polyester heat shrinkable film was prepared and evaluated in the same manner as in Example 1 except that the set thickness of the polyester heat shrinkable film was set to 45 μm and the maximum stretching speed (% / sec) was changed as shown in Table 1. The results obtained are shown in Table 2.

[0420] [Example 4 and Example 5]

[0421] In Examples 4 and 5, polyester heat shrinkable films were prepared and evaluated in the same manner as in Example 1 except that the stretching temperature (° C.), heat setting temperature (° C.), and maximum stretching speed (% / sec) were changed as shown in Table 1. The results obtained are shown in Table 2.

[0422] [Example 6]

[0423] In Example 6, as shown in Table 1, a polyester heat shrinkable film was prepared and evaluated in the same manner as in Example 1 except that the above-mentioned PET1 and PETG (mixing ratio = 80 / 20) were used as PET resins. The obtained results are shown in Table 2.

[0424] [Comparative Example 1]

[0425] In Comparative Example 1, a polyester heat shrinkable film was prepared and evaluated in the same manner as in Example 1 except that the preheating temperature (° C.), stretching temperature (° C.), and maximum stretching speed (% / sec) were changed as shown in Table 1. The results obtained are shown in Table 2.

[0426] [Comparative Example 2]

[0427] In Comparative Example 2, as shown in Table 1, a polyester heat shrinkable film was prepared and evaluated in the same manner as in Example 1 except that the above-mentioned PET1 and PETG (mixing ratio = 80 / 20) were used as PET resins, and the preheating temperature (° C.), stretching temperature (° C.), heat fixing temperature (° C.), and maximum stretching speed (% / sec) were changed. The obtained results are shown in Table 2.

[0428] [Comparative Example 3]

[0429] In Comparative Example 3, as shown in Table 1, a polyester heat shrinkable film was prepared and evaluated in the same manner as in Example 1 except that the above-mentioned PET1 and PETG (mixing ratio = 60 / 40) were used as PET resins, and the preheating temperature (°C), stretching temperature (°C), heat fixing temperature (°C), and maximum stretching speed (% / sec) were changed. The results obtained are shown in Table 2.

[0430] [Table 1]

[0431]

[0432] [Table 2]

[0433]

[0434] [Industrial Applicability]

[0435] According to the present invention, when at least predetermined characteristics (A) to (C) such as the blocking ratio and (D1) to (D4) related to the thermal shrinkage rate are controlled, a good balance between recyclability and thermal shrinkage is achieved.

[0436] That is, when a predetermined agglomeration ratio or the like is strictly controlled as in the case of recycled PET mainly using a crystalline polyester resin, even when a PET bottle in a state of being equipped with a polyester heat shrinkable film is recycled, the interlocking phenomenon can be effectively prevented, and desired recycled pellets can be efficiently and stably produced.

[0437] Here, the heat shrinkage rate variation and thickness variation of the polyester heat shrinkable film are reduced, the heat shrinkage stress generated during heat shrinkage, etc. are controlled, and a polyester heat shrinkable film showing excellent assembly properties and appearance in a wide temperature range can be provided.

[0438] Furthermore, according to the polyester heat shrinkable film of the present invention, even if the desired heat shrinkage ratio cannot be obtained due to a slight change in the heat shrinkage temperature, etc., regardless of the thickness, the heat shrinkage ratio can be accurately corrected to be controlled within a desired range.

[0439] Therefore, it can be considered that excellent assembly properties and appearance can be exhibited for various PET bottles, etc., and not only that, the film can be recycled together with various PET bottles, etc. in a state of being assembled thereon, so that the versatility can be significantly expanded while maintaining environmental and economic efficiency, and its industrial applicability is extremely high.

[0440]

Explanation of symbols

[0441] 10:Polyester heat shrink film

[0442] 10a: Other resin layer 1

[0443] 10b: Other resin layer 2

[0444] 10c: Shrinkage adjustment layer

Claims

1. A polyester heat shrinkable film, which is derived from a polyester resin which is a reaction product of a polycarboxylic acid and a polyol, wherein the polyester heat shrinkable film has the following properties (A) to (C) and properties (D1) to (D4): (A) a lump ratio in a mixture of the polyester resin and other PET resins of 1.2% or less as measured in accordance with the Plastics Recyclers Association document identification code: PET-S-08; (B) the melting point of the polyester resin measured by a differential scanning calorimeter is a value within a range of 190° C. to 230° C.; (C) the heat of fusion of the polyester heat shrinkable film corresponding to the melting peak area at the melting point measured by a differential scanning calorimeter is a value within a range of 25 mJ / mg to 45 mJ / mg; (D1) a value in the range of 0% to 5% in the main shrinkage direction measured under heat shrinkage conditions of 60°C and 10 seconds; (D2) a heat shrinkage rate in the main shrinkage direction measured under heat shrinkage conditions of 70° C. and 10 seconds is a value in the range of 25% to 50%; (D3) a value in the range of 55% to 85% in the main shrinkage direction measured under heat shrinkage conditions of 80°C and 10 seconds; (D4) The standard deviation of the values ​​of the heat shrinkage ratio in the main shrinkage direction measured under the heat shrinkage conditions of 95° C. to 100° C. and 10 seconds is 1.5% or less.

2. The polyester heat shrinkable film according to claim 1, which has a property (D4') wherein a heat shrinkage rate in a main shrinkage direction measured under heat shrinkage conditions of 95°C to 100°C and 10 seconds is a value of 70% or more.

3. The polyester heat shrinkable film according to claim 1, which has a characteristic (D5), wherein the heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 60°C to 80°C and 10 seconds satisfies the following relationship (1), [Formula 1] Thermal shrinkage rate (%) = a × (thermal shrinkage temperature (°C) - 60) + b (1) a: corresponds to the slope of relational expression (1), which is a value greater than 3.25 and less than 4, b: A constant corresponding to the relational expression (1), which is a value greater than or equal to 0 and less than or equal to 5.

4. The polyester heat shrinkable film according to claim 1, which has a characteristic (D5'), wherein the heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 60°C to 80°C and 10 seconds satisfies the following relationship (2): [Formula 2] Thermal shrinkage rate (%) = a' × (thermal shrinkage temperature (°C) - 60) + b' (2) a': corresponds to the slope of relational expression (2), which is a value greater than or equal to 3.3 and less than or equal to 3.75, b': A constant corresponding to relational expression (2), which is a value greater than or equal to 0 and less than or equal to 5.

5. The polyester heat shrinkable film according to claim 1, which has a characteristic (D5"), wherein the heat shrinkage rate in the main shrinkage direction measured under the heat shrinkage conditions of 60°C to 80°C and 10 seconds satisfies the following relationship (3): [Formula 3] Thermal shrinkage rate (%) = a" × (thermal shrinkage temperature (℃) - 60) + b" (3) a”: corresponds to the slope of relation (3), which is a value greater than 3.35 and less than 3.5, b": a constant corresponding to relational expression (3), and a value greater than or equal to 0 and less than or equal to 5.

6. The polyester heat shrinkable film according to claim 1, which has a characteristic (D6) in which a heat shrinkage rate in a direction perpendicular to a main shrinkage direction measured under heat shrinkage conditions of 70°C and 10 seconds is a value in the range of -3% to 5%. 7 . The polyester heat-shrinkable film according to claim 1 , wherein the thickness of the film is set to a value within a range of 10 μm to 100 μm, and a standard deviation of the thickness measured under predetermined conditions is 1.7 μm or less. 8 . The polyester heat-shrinkable film according to claim 1 , wherein the polyester resin is a mixture of a crystalline polyester resin and a non-crystalline polyester resin, and a weight mixing ratio thereof is a value within a range of 100:0 to 80:20.

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