Polyester heat shrink film

Abstract

The present invention provides a polyester heat shrink film which does not interfere with the recyclability of PET bottles and has low heat shrinkage stress and the like so as to cope with the thinning of PET bottles. A polyester heat shrink film, characterized in that it is a polyester heat shrink film derived from a polyester resin, which is a reaction product of a polycarboxylic acid and a polyol, and has the following characteristics (A) to (D). (A) The melting point of the polyester resin measured by DSC is 190 to 255°C. (B) to (D) The heat shrinkage rate in the main shrinkage direction measured under specified conditions is 45 to 70%, the heat shrinkage rate in the non-main shrinkage direction is -1 to 6%, and the heat shrinkage stress in the main shrinkage direction is less than 16 MPa.

Description

Technical Field

[0001] The invention relates to a polyester heat shrinkable film.

[0002] More specifically, the present invention relates to a polyester heat shrinkable film that does not interfere with the recyclability of PET bottles and has low heat shrinkage stress generated during heat shrinkage so as to cope with the thinning of the wall of PET bottles. Background Art

[0003] Conventionally, polyethylene (HDPE) containers and polyester (PET) bottles (hereinafter, sometimes simply referred to as PET bottles) have been used in large numbers as beverage storage containers and detergent storage containers.

[0004] In particular, PET bottles are widely used as beverage storage containers throughout the world because of their lightness, excellent durability, and extremely high convenience.

[0005] On the other hand, such PET bottles are discarded in rivers, flow into the ocean, etc. after use, which has become a profound environmental problem.

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

[0007] In addition, PET bottles are covered with a predetermined identification label in order to indicate the name and information about the content and to enhance the decorativeness.

[0008] In this regard, the method of attaching a label to a paper base material using an adhesive has been widely used as a labeling label until now. However, in recent years, a method of completely packaging a PET bottle using a labeling label using a heat shrink film has become mainstream.

[0009] However, in the case of full packaging using the heat shrink film, it may be difficult to easily separate the identification label using the heat shrink film when the PET bottle is recycled due to reasons such as its close-fitting structure.

[0010] Therefore, as the raw material of the heat shrink film, it is preferred that the raw material can be easily separated from the PET bottle and does not interfere with the recycling process of the PET bottle. More specifically, vinyl chloride resin (PVC), polystyrene resin (PS), and modified polyester (PETG) are often used.

[0011] Here, since the main material of beverage storage containers and the like is basically PET and the materials are similar, it can be said that the PETG film is highly likely to be melted together with the PET bottle as a heat shrink film and recycled.

[0012] On the other hand, PETG is basically amorphous and therefore has no melting point as a thermal characteristic. In addition, there is a problem that recycled particles are easily adhered to each other in the recycling process of PET bottles packaged with heat shrink films.

[0013] That is, in the recycling process of PET bottles in a state of being packaged in a heat shrink film, when the pellets are dried, Fig.9A As shown in FIG. 1 , the recovered particles including the heat shrink film adhere to each other due to the heat shrink film, forming clumps. As a result, it can be seen that the clumps cause clogging in the middle of the pipe.

[0014] Therefore, when recycling PET bottles including heat shrink films, it is desirable to prevent the obtained recycled particles from adhering to each other and to use a pelletizer such as Fig. 9B It is very difficult to efficiently and stably produce pellets of a predetermined shape as shown (hereinafter referred to as the recycling problem).

[0015] Therefore, it has been proposed to adjust the thermal properties of the PETG film and use a polyester-based heat shrinkable film having a melting point (Patent Documents 1 and 2).

[0016] Patent document 1 discloses a polyester heat shrinkable film having a melting point, in which the amount of amorphous polyester resin incorporated is reduced. For example, the film is a crystalline polyester heat shrinkable film, which comprises a crystalline copolyester resin derived from a diol component and a dicarboxylic acid component, and has a heat shrinkage rate of 30% or more in the main shrinkage direction when subjected to a heat treatment at 80° C. for 10 seconds, and a melting point of 170° C. or more as measured by a differential scanning calorimeter (DSC).

[0017] The polyester heat shrinkable film with a melting point disclosed in Patent Document 2 is a crystalline polyester heat shrinkable film, which has terephthalic acid as a main component and the polyol reacted therewith is a predetermined amount of at least one of ethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol and diethylene glycol.

[0018] Prior art literature

[0019] Patent Literature

[0020] Patent Document 1: Japanese Patent Application No. 2020-521823 (scope of patent claims, etc.)

[0021] Patent Document 2: WO2020 / 076749 (scope of patent claims, etc.) Summary of the invention

[0022] However, in the case of the polyester heat shrinkable films having a melting point disclosed in Patent Documents 1 and 2, the value of the heat shrinkage stress generated during heat shrinkage is too large, and the problem that the PET bottle is easily deformed is found.

[0023] In addition, in order to reduce the use of fossil resources and reduce weight, the wall of the PET bottle is made thinner, so the overall rigidity of the PET bottle is further reduced. It can be seen that the deformation of the PET bottle is easily accelerated by the polyester heat shrinkable film having a melting point disclosed in Patent Documents 1 and 2.

[0024] Furthermore, in the case of the polyester heat shrinkable films having a melting point disclosed in Patent Documents 1 and 2, no consideration is given to the value of the heat shrinkage rate in the MD direction and the value of the heat shrinkage stress in the TD direction, and it can be seen that the problem of recyclability cannot be completely solved.

[0025] Therefore, the inventors of the present invention have conducted intensive research and efforts in view of the above circumstances, and as a result, solved the conventional problems by using a polyester-based heat shrinkable film made from a polyester resin, which is a reaction product of a polycarboxylic acid and a polyol, and having at least characteristics (A) to (D).

[0026] That is, an object of the present invention is to provide a polyester-based heat-shrinkable film that can effectively and stably produce pellets of a specified shape even when PET bottles covered with the polyester-based heat-shrinkable film are recycled together, and the heat shrinkage stress generated during heat shrinkage is low so as to cope with the thinning of the wall of the PET bottle.

[0027] According to the present invention, there is provided a polyester heat shrinkable film characterized in that the polyester heat shrinkable film is derived from a polyester resin which is a reaction product of a polycarboxylic acid and a polyol and has the following characteristics (A) to (D), thereby solving the above problems.

[0028] The melting point of the (A) polyester resin measured by DSC (hereinafter, sometimes simply referred to as the melting point) is a value within the range of 190 to 255°C.

[0029] (B) The heat shrinkage ratio in the main shrinkage direction (sometimes referred to as TD direction, hereinafter the same) measured under the heat shrinkage conditions of 85° C. for 10 seconds is a value within a range of 45 to 70%.

[0030] (C) The heat shrinkage rate in a direction perpendicular to the main shrinkage direction (sometimes referred to as MD direction, hereinafter the same) measured under heat shrinkage conditions of 60 to 90°C for 10 seconds is a value within a range of -1 to 6%.

[0031] (D) The heat shrinkage stress in the main shrinkage direction (TD direction) measured under heat shrinkage conditions at 85° C. is a value of 16 MPa or less.

[0032] In this way, by using a polyester resin having a predetermined melting point measured by DSC in accordance with JIS K7121:2012 (characteristic A), and controlling the heat shrinkage rates in the TD direction and the MD direction (characteristics B and C) to values ​​within the predetermined ranges, even in the case where a PET bottle covered with a polyester-based heat shrinkable film is recycled, it is possible to effectively prevent the recyclability of the PET bottle from being disturbed.

[0033] Furthermore, according to the polyester-based heat shrinkable film, by controlling the heat shrinkage stress (characteristic D) in the TD direction, it is possible to appropriately cope with the thinning of the wall of a PET bottle and the like.

[0034] When the polyester heat shrinkable film of the present invention is formed, the heat shrinkage rate in the direction orthogonal to the main shrinkage direction (MD direction) measured under heat shrinkage conditions of 70°C for 10 seconds is preferably within a range of 0 to 3% as characteristic (C').

[0035] By limiting the heat shrinkage rate in the MD direction under the specified temperature conditions, the occurrence of wrinkles and shrinkage marks can be reduced even when heat shrinking is performed at a relatively low temperature around the coated PET bottle. As a result, a good appearance and accurate information can be easily obtained even with energy-saving heating.

[0036] Furthermore, by limiting the heat shrinkage rate in the MD direction in this way, the heat shrinkage of the entire polyester heat shrinkable film is balanced, and even if it is recycled together with PET bottles, the adhesion, fluidity, etc. can be controlled to obtain pellets stably.

[0037] In the polyester heat shrinkable film of the present invention, it is preferred that the heat shrinkage rate in the direction perpendicular to the main shrinkage direction (MD direction) measured under heat shrinkage conditions of 85°C for 10 seconds is within a range of 1 to 5% as property (C″).

[0038] By limiting the heat shrinkage rate in the MD direction at a relatively high temperature in this way, the occurrence of wrinkles and sink marks can be reduced, and as a result, a good appearance, accurate information, etc. can be easily obtained.

[0039] Furthermore, by limiting the heat shrinkage rate in the MD direction at a relatively high temperature, the heat shrinkage of the entire polyester heat shrinkable film can be balanced, the generated heat shrinkage stress can be reduced, and pellets can be obtained more stably even when recycled together with PET bottles.

[0040] In addition, when constituting the polyester heat-shrinkable film of the present invention, it is preferred that, as a characteristic (C′″), the heat shrinkage rate in a direction orthogonal to the main shrinkage direction (MD direction) measured under heat shrinkage conditions of 60 to 90° C. for 10 seconds has at least one minimum value, and the minimum value is a value of -1% or more.

[0041] By limiting the heat shrinkage curve in the MD direction under the specified temperature conditions to have a minimum value of a specified size, even when the temperature conditions are slightly different, it is still possible to more clearly determine whether a good appearance and accurate information can be obtained during heat shrinkage through simple measurement of the heat shrinkage curve, TMA measurement, etc.

[0042] Furthermore, by limiting the heat shrinkage rate in the MD direction 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 pellets can be obtained more stably even when recycled with PET bottles.

[0043] In addition, when constituting the polyester heat shrinkable film of the present invention, it is preferred that, as a characteristic (C″″), the heat shrinkage rate in the direction orthogonal to the main shrinkage direction (MD direction) measured under heat shrinkage conditions of 60 to 90° C. for 10 seconds has at least one maximum value, and the maximum value is a value of 0.8% or more.

[0044] By limiting the curve of the heat shrinkage rate in the MD direction under the specified temperature condition to have a local value of a specified size, it can be more clearly determined that a good appearance and accurate information are easily obtained during heat shrinkage and that the generated heat shrinkage stress is below a specified value.

[0045] In addition, when the heat shrinkage curve has a local maximum value of a predetermined size, it is preferable that the curve also has a local minimum value of the predetermined size.

[0046] When constituting the polyester heat shrinkable film of the present invention, the film thickness is preferably within a range of 10 to 100 μm.

[0047] By limiting the thickness to such a value, the heat shrinkage rate becomes more uniform, and as a result, the values ​​of the properties (B) and (C) of the polyester heat shrinkable film can be easily controlled within the prescribed ranges.

[0048] In the polyester heat shrinkable film of the present invention, the polycarboxylic acid preferably contains terephthalic acid (TPA) as a main component, and the polyol preferably contains at least one of ethylene glycol (EG), neopentyl glycol (NPG), 1,4-cyclohexanedimethanol (CHDM), and diethylene glycol (DEG).

[0049] By using such types of raw material components, the crystallinity contained in the polyester resin can be controlled. As a result, the crystallinity and thermal shrinkage calculated from the DSC curve measured in accordance with JIS K 7122:2012 can be easily adjusted to values ​​within a predetermined range.

[0050] Furthermore, when the polyester heat-shrinkable film of the present invention is constituted, it is preferred that the haze value of the film before shrinkage measured in accordance with ASTM D1003 is 7% or less.

[0051] By limiting the haze value to such a value, it becomes easy to align the position of PET bottles and the like and to inspect the contents, and it is possible to obtain a PET bottle including a polyester heat shrinkable film having excellent transparency, appearance, and further decorative properties not only before heat shrinking but also after heat shrinking.

[0052] In the polyester heat shrinkable film of the present invention, the heat amount corresponding to the melting peak area of ​​the polyester heat shrinkable film at the melting point measured by DSC is preferably within a range of 15 to 25 mJ / mg.

[0053] By controlling the heat (ΔH) corresponding to the melting peak area at the melting point of the polyester heat shrinkable film to a value within a predetermined range, the amount of the crystalline structure can be slightly limited, and the film can be adjusted to have a wide melting region.

[0054] Therefore, in the obtained polyester heat shrinkable film, the mechanical strength, transparency, etc. of the polyester resin as the main component can be maintained due to the predetermined crystal structure, and the shrinkage stress at a predetermined temperature and the heat shrinkage rate at each predetermined temperature can be easily and stably adjusted. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figures 1A to 1C These are diagrams for explaining different forms of polyester heat shrinkable films.

[0056] Figure 2 This is a diagram for explaining the relationship between the heat shrinkage temperature and the heat shrinkage rate in the MD direction of the polyester-based heat shrinkable film in Example 1 and the like and Comparative Example 1 and the like.

[0057] Figure 3 This is a diagram for explaining the relationship between the heat shrinkage temperature and the heat shrinkage rate in the MD direction of the polyester-based heat shrinkable films in Example 1 and Comparative Example 2, and the maximum and minimum values ​​of the heat shrinkage rate in the MD direction.

[0058] Figure 4 This is a diagram for explaining the relationship between the heat shrinkage temperature of the polyester heat shrinkable film in Example 3 and the heat shrinkage ratios in the TD direction and the MD direction.

[0059] Figure 5 This is a diagram for explaining the relationship between the heat shrinkage temperature of the polyester heat shrinkable film in Example 7 and the heat shrinkage ratios in the TD direction and the MD direction.

[0060] Figure 6 This is a diagram for explaining the relationship between the heat shrinkage temperature of the polyester heat shrinkable film in Comparative Example 1 and the heat shrinkage ratios in the TD direction and the MD direction.

[0061] Figure 7This is a diagram for explaining the relationship between the heat shrinkage temperature of the polyester heat shrinkable film in Comparative Example 2 and the heat shrinkage ratios in the TD direction and the MD direction.

[0062] Figure 8 This is a diagram for explaining the relationship between the heat shrinkage temperature of the polyvinyl chloride-based heat shrinkable film in Comparative Example 5 and the heat shrinkage ratios in the TD direction and the MD direction.

[0063] Fig.9A This is a diagram showing the state of a conventional PET bottle covered with a polyester heat shrinkable film after a recycling process. Fig. 9B This is a diagram showing the recovered PET resin after the recovery step of the PET bottle coated with the polyester heat-shrinkable film of the present invention.

[0064] Fig.10 This is the DSC curve of the polyester heat shrinkable film of Example 1.

[0065] Explanation of symbols

[0066] 10: Polyester heat shrink film

[0067] 10a: Other resin layer 1

[0068] 10b: Other resin layer 2

[0069] 10c: Shrinkage Adjustment Layer DETAILED DESCRIPTION

[0070] [First embodiment]

[0071] like Figure 1A As exemplified in the above, the first embodiment is a polyester-based heat shrinkable film derived from a polyester resin which is a reaction product of a polycarboxylic acid and a polyol.

[0072] Furthermore, it is possible to provide a polyester heat shrinkable film having the following characteristics (A) to (D), which can exhibit low heat shrinkage stress even though it contains a crystalline portion, and can solve the above-mentioned problems.

[0073] (A) The melting point of the polyester resin measured by DSC is a value within the range of 190 to 255°C.

[0074] (B) The heat shrinkage ratio in the main shrinkage direction (TD direction) measured under the heat shrinkage conditions of 85° C. for 10 seconds is a value within a range of 45 to 70%.

[0075] (C) The heat shrinkage ratio in the direction perpendicular to the main shrinkage direction (MD direction) measured under heat shrinkage conditions of 60 to 90° C. for 10 seconds is a value within a range of −1 to 6%.

[0076] (D) The heat shrinkage stress in the main shrinkage direction (TD direction) measured under heat shrinkage conditions at 85°C is a value of 16 MPa or less.

[0077] Hereinafter, the polyester heat shrinkable film of the first embodiment will be specifically described by dividing the components into respective components and referring to drawings as appropriate.

[0078] 1. Polycarboxylic acid

[0079] The polycarboxylic acid as one of the constituent components (raw material component) of the polyester resin is not particularly limited as long as it is a compound that can react with a polyol to form a polyester structure, and examples thereof include at least one of 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 ester-forming derivatives thereof.

[0080] 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.

[0081] Therefore, when the total amount of the polyvalent carboxylic acid used is 100 mol %, the amount of terephthalic acid used is preferably 90 mol % or more, more preferably 95 to 100 mol %.

[0082] 2. Polyols

[0083] (1) Types

[0084] The polyol as one of the constituent components of the polyester resin is not particularly limited as long as it is a compound having a plurality of reactive hydroxyl groups. For example, it is preferably aliphatic diols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, and hexanediol, or at least one of alicyclic diols different from 1,4-cyclohexanedimethanol, and aromatic diols.

[0085] This is because by using such a polyol, a polyester resin having crystallinity and the like controlled within a predetermined range can be easily obtained by reacting the polyol with the polycarboxylic acid appropriately.

[0086] Among these polyols, it is more preferable to use one or more polyols selected from ethylene glycol, diethylene glycol, neopentyl glycol and the like.

[0087] That is, by using these specific polyols, it is possible to more easily adjust the melting point, heat shrinkage ratio, heat shrinkage stress, etc. of the polyester resin obtained by reacting with the polyvalent carboxylic acid to values ​​within a predetermined range.

[0088] Therefore, when the total amount of the polyol used is 100 mol %, the amount of one or more polyols selected from ethylene glycol, diethylene glycol, neopentyl glycol, etc. is preferably 90 mol % or more, more preferably 95 to 100 mol %.

[0089] Furthermore, other dicarboxylic acids and polyols, or hydroxycarboxylic acids may be used to change the thermal and mechanical properties of the polyester heat shrinkable film as needed, and they may be used alone or in combination as a mixture.

[0090] (2) Reaction volume

[0091] In addition, the reaction amount of the polyol is not particularly limited. It is usually preferred to react in a ratio of 100 mol of a polycarboxylic acid containing 80 mol % or more of terephthalic acid and 130 to 220 mol of a polyol, more preferably 150 to 210 mol of a polyol, and further preferably 180 to 200 mol of a polyol, and it is preferred to crystallize these reactants to obtain a polyester resin.

[0092] In this case, as a standard of crystallinity in the polyester resin, the crystallinity calculated from the DSC curve measured in accordance with JIS K7122:2012 is preferably set to a value in the range of 1 to 15%, more preferably set to a value in the range of 2 to 10%, and further preferably set to a value in the range of 3 to 8%.

[0093] That is, in this DSC curve, the heat of melting (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 ), the crystallinity of the polyester resin can be calculated according to the following formula (1).

[0094]

[0095] ΔHm: Melting heat (J / g)

[0096] ΔHc: Heat of crystallization (J / g)

[0097] ΔHm 0 :140.2J / g (Complete crystallization heat of crystallized polyethylene terephthalate)

[0098] 3. Polyester resin

[0099] (1) Melting point

[0100] In addition, as characteristic (A), it is characterized in that the melting point of the polyester resin is a value within the range of 190 to 255°C.

[0101] The reason is that if the melting point is less than 190° C., the identification label using the polyester heat shrinkable film may melt during the drying process when the PET bottle is recycled, causing the PET bottle recycled pieces to adhere to each other.

[0102] On the other hand, if the melting point is higher than 255° C., the heat required for extrusion and stretching of a raw sheet of a polyester heat shrinkable film used for a label becomes too high, and processing may become difficult.

[0103] Therefore, the melting point of the polyester resin is more preferably within a range of 200 to 250°C, and further preferably within a range of 210 to 240°C.

[0104] The melting point of the polyester resin can be measured, for example, as the peak temperature of the heat of fusion represented by an endothermic reaction, that is, the melting peak temperature (Tpm) in a curve obtained by using DSC (the same applies hereinafter).

[0105] In addition, the crystallinity of the polyester resin can be estimated from the area of ​​the peak of the heat of fusion (peak area), the half peak width, and the like.

[0106] (2) Average molecular weight

[0107] In addition, the intrinsic viscosity (IV value) of the polyester resin is preferably a value within the range of 0.65 to 0.85 dL / g.

[0108] The reason for this is that if the intrinsic viscosity is a value less than 0.65 dL / g, the melt viscosity is too low, and a problem may arise in extrusion moldability.

[0109] On the other hand, if the intrinsic viscosity is greater than 0.85 dL / g, the melt viscosity becomes too high, which causes a problem in extrusion moldability.

[0110] Therefore, the intrinsic viscosity is more preferably a value within the range of 0.68 to 0.83 dL / g, and even more preferably a value within the range of 0.7 to 0.8 dL / g.

[0111] In addition, the intrinsic viscosity of a polyester resin can be measured according to JIS K 7390 (the same applies hereinafter).

[0112] (3) Additives

[0113] The polyester heat shrinkable film is preferably blended with additives such as antioxidants, weather stabilizers, antistatic agents, antifogging agents, metal soaps, waxes, mildewproofing agents, antibacterial agents, nucleating agents, flame retardants, and slip agents as necessary.

[0114] In order to improve the lubricity of the film surface, it is preferred to contain an inorganic lubricant such as calcium carbonate particles, silica particles, or glass particles.

[0115] The method for adding the additives is not particularly limited, and a known method can be used. Among them, adding the additives using a masterbatch is preferred because it is simple and has excellent uniform mixing properties.

[0116] For example, as a specific example (commercially available product) of a polyester resin masterbatch when a release agent is added, there can be mentioned a silica masterbatch (containing 20% ​​silica, manufactured by Sukano Corporation, trade name: Gdc S559-E).

[0117] Furthermore, other resins may be preferably added within a range that does not impair the physical properties of the heat shrinkable film, particularly the shrinkage ratio and shrinkage stress.

[0118] 4. Thermal characteristics

[0119] (1) Heat shrinkage rate 1

[0120] The polyester heat shrinkable film is characterized by having at least the following properties (B) to (C) as properties related to heat shrinkage.

[0121] and, Figure 2 The relationship between the heat shrinkage temperature and the heat shrinkage rate in the MD direction of the polyester heat shrinkable film in Example 1 and Comparative Example 1 described later is shown in FIG.

[0122] The heat shrinkage rate can be measured in accordance with ASTM D2732-08. In addition, when measuring the heat shrinkage rate, as a predetermined pretreatment, a treatment of leaving the sample in an atmosphere of 23° C. and 50% RH for 40 hours or more can be performed (the same applies hereinafter).

[0123] 1) Characteristics (B)

[0124] The characteristic (B) is characterized in that the heat shrinkage in the main shrinkage direction (TD direction) measured under heat shrinkage conditions of 85°C for 10 seconds (for example, in hot water, the same applies hereinafter) is a value within the range of 45 to 70%.

[0125] The reason for this is that by controlling the heat shrinkage rate in the TD direction to a value within a predetermined range when heat shrinking is performed at such a predetermined temperature, wrinkles are less likely to occur and the occurrence of sink marks is reduced, and as a result, a good appearance is easily obtained.

[0126] Furthermore, by limiting the heat shrinkage rate in the TD direction at a relatively high temperature, the heat shrinkage of the polyester heat shrinkable film as a whole can be balanced, the generated heat shrinkage stress can be reduced, and pellets can be obtained more stably even when recycled together with PET bottles.

[0127] Therefore, the heat shrinkage rate in the TD direction is more preferably a value within the range of 50 to 65%, and further preferably a value within the range of 55 to 63%.

[0128] 2) Characteristics (C)

[0129] The characteristic (C) is characterized in that the heat shrinkage rate in the direction orthogonal to the main shrinkage direction (MD direction) measured under heat shrinkage conditions at 60 to 90° C. for 10 seconds is within a range of −1 to 6%.

[0130] The reason for this is that by controlling the heat shrinkage rate in the MD direction within a predetermined range when heat shrinking is performed within a predetermined temperature range, wrinkles are less likely to occur and the occurrence of sink marks is reduced, and as a result, a good appearance is easily obtained.

[0131] Furthermore, by limiting the heat shrinkage rate in the MD direction at a predetermined temperature, the heat shrinkage of the entire polyester heat shrinkable film can be balanced, the generated heat shrinkage stress can be reduced, and pellets can be obtained more stably even when recycled together with PET bottles.

[0132] Therefore, as the characteristic (C), the heat shrinkage in the MD direction is more preferably a value within the range of 0 to 5%, and further preferably a value within the range of 0.5 to 3%.

[0133] (2) Heat shrinkage 2

[0134] 1) Characteristics (C′)

[0135] Moreover, as characteristic (C'), it is preferable that the heat shrinkage rate in the direction (MD direction) perpendicular to the main shrinkage direction measured under the heat shrinkage conditions of 70°C for 10 seconds is a value within the range of 0 to 3%.

[0136] The reason for this is that by controlling the heat shrinkage rate in the MD direction within a predetermined range when heat shrinking is performed within a predetermined temperature range, the occurrence of wrinkles and sink marks can be further reduced, and as a result, a good and smooth appearance can be easily obtained.

[0137] Furthermore, by limiting the heat shrinkage rate in the MD direction at a relatively high temperature, the heat shrinkage of the entire polyester heat shrinkable film can be balanced, the generated heat shrinkage stress can be reduced, and pellets can be obtained more stably even when recycled together with PET bottles.

[0138] Therefore, as the characteristic (C′), the heat shrinkage in the MD direction is more preferably a value within the range of 0 to 2.5%, and even more preferably a value within the range of 0 to 2%.

[0139] 2) Characteristics (C″)

[0140] The characteristic (C") is preferably a value within a range of 1 to 5% of the heat shrinkage rate in a direction (MD direction) perpendicular to the main shrinkage direction measured under heat shrinkage conditions at 85°C for 10 seconds.

[0141] The reason for this is that by controlling the heat shrinkage rate in the MD direction within a predetermined range when heat shrinking is performed within a predetermined temperature range, the occurrence of wrinkles and sink marks can be further reduced, and as a result, a good and smooth appearance can be easily obtained.

[0142] Furthermore, by limiting the heat shrinkage rate in the MD direction at a relatively high temperature, the heat shrinkage of the entire polyester heat shrinkable film can be balanced, the generated heat shrinkage stress can be reduced, and pellets can be obtained more stably even when recycled together with PET bottles.

[0143] Therefore, as the characteristic (C"), the heat shrinkage in the MD direction is more preferably a value within the range of 1.5 to 4.5%, and further preferably a value within the range of 2 to 4%.

[0144] 3) Characteristics (C″′)

[0145] In addition, as characteristic (C''"), it is preferred that the heat shrinkage rate in a direction orthogonal to the main shrinkage direction (MD direction) measured under heat shrinkage conditions of 60 to 90°C for 10 seconds has at least one minimum value, and the minimum value is -1% or more.

[0146] The reason is that by controlling the material to have a minimum value of a predetermined size, it is possible to clearly determine through actual measurement of heat shrinkage, TMA, etc. that the occurrence of wrinkles and sink marks during heat shrinkage is further reduced, and a good and smooth appearance is easily obtained.

[0147] Furthermore, by controlling the heat shrinkage rate in the MD direction at a predetermined temperature together with the curve shape (minimum value), it is possible to balance the heat shrinkage of the entire polyester heat shrinkable film, reliably reduce the generated heat shrinkage stress, and further stably obtain pellets even when recycled together with PET bottles.

[0148] Therefore, as the characteristic (C''"), the minimum value of the heat shrinkage in the MD direction is more preferably a value within the range of 0 to 5%, and further preferably a value within the range of 0.5 to 3%.

[0149] Here, Figure 2 , Figure 3 In the characteristic curves, the minimum value of the thermal shrinkage rate is the smallest thermal shrinkage rate in the range before and after the thermal shrinkage temperature corresponding to the minimum value. When the value of the thermal shrinkage rate is differentiated, it can be defined as the place where the slope of the change point is 0 (extreme value).

[0150] More specifically, in Figure 3 In the case of Example 1, the minimum value is at a change point of the heat shrinkage temperature of 80°C, and the value is 1.4%.

[0151] In contrast, Figure 3 In the case of Comparative Example 2, the minimum value is at a change point of the heat shrinkage temperature of 75°C, and the value is -8.0%.

[0152] In order to ensure that wrinkles are not easily generated during heat shrinkage and to easily obtain a good appearance, it is more preferable that the heat shrinkage rate in the MD direction is not a negative value but a positive value in the prescribed temperature range of 60 to 90°C regarding the characteristic (C′″).

[0153] 4) Characteristics (C″″)

[0154] Furthermore, as characteristic (C″″), it is preferred that the heat shrinkage rate in a direction orthogonal to the main shrinkage direction (MD direction) measured under heat shrinkage conditions of 60 to 90° C. for 10 seconds has at least one local maximum value, and the local maximum value is 0.8% or more.

[0155] The reason is that by controlling the curve of the heat shrinkage rate in the MD direction under the specified temperature condition to have a maximum value of a specified size, it is possible to clearly determine through actual measurement of heat shrinkage, TMA, etc. that wrinkles are less likely to occur during heat shrinkage and a good appearance is easily obtained.

[0156] Furthermore, by controlling the heat shrinkage rate in the MD direction at a predetermined temperature together with the curve shape (maximum), it is possible to balance the heat shrinkage of the entire polyester heat shrinkable film, reliably reduce the generated heat shrinkage stress, and further stably obtain pellets even when recycled together with PET bottles.

[0157] Therefore, as the characteristic (C″″), the maximum value of the heat shrinkage in the MD direction is more preferably a value in the range of 1 to 8%, and further preferably a value in the range of 1.2 to 5%.

[0158] Here, Figure 2 , Figure 3 In the characteristic curves of the above, the maximum value of the thermal shrinkage rate is the maximum thermal shrinkage rate in the range before and after the thermal shrinkage temperature corresponding to the maximum value, and when the value of the thermal shrinkage rate is differentiated, it can be defined as the place where the slope of the change point is 0.

[0159] More specifically, in Figure 3 In the case of Example 1, the maximum value is a change point of the heat shrinkage temperature of 75°C, and the value is 2.1%.

[0160] In contrast, Figure 3In the case of Comparative Example 2, the maximum value is a change point of the heat shrinkage temperature of 65°C, and the value is 2.0%.

[0161] (3) Heat shrinkage rate 3

[0162] In addition, in the polyester heat shrinkable film, the heat shrinkage conditions are generally preferably a value in the range of 0 to 1% in the main shrinkage direction (TD direction) measured at 60°C for 10 seconds, a value in the range of 0.5 to 10% in the main direction measured at 70°C for 10 seconds, a value in the range of 40 to 65% in the main direction measured at 80°C for 10 seconds, and a value in the range of 50 to 75% in the main direction measured at 90°C for 10 seconds.

[0163] The reason is that, in a polyester-based heat shrinkable film, if the heat shrinkage ratio in the main shrinkage direction measured at 60°C, 70°C, 80°C, and 90°C for 10 seconds is outside the above-specified range, the same versatility as a polyvinyl chloride-based heat shrinkable film in that it can cope with various PET bottles from thin-walled to thick-walled or with complex shapes may not be obtained.

[0164] Therefore, in the polyester heat shrinkable film, it is more preferred that the heat shrinkage rate in the main shrinkage direction (TD direction) measured at 60°C for 10 seconds is within a range of 0 to 0.5%, the heat shrinkage rate in the main direction measured at 70°C for 10 seconds is within a range of 1 to 9%, the heat shrinkage rate in the main direction measured at 80°C for 10 seconds is within a range of 45 to 60%, and the heat shrinkage rate in the main direction measured at 90°C for 10 seconds is within a range of 55 to 70%.

[0165] (4) Thermal shrinkage stress

[0166] Moreover, as characteristic (D), the heat shrinkage stress in the main shrinkage direction measured under the heat shrinkage condition of 85° C. is a value of 16 MPa or less.

[0167] The reason is that if the heat shrinkage stress measured at 85°C is a value greater than 16 MPa, the same heat shrinkage stress as that of a polyvinyl chloride-based heat shrinkable film cannot be obtained, and as a result, versatility to cope with various PET bottles from thin-walled to thick-walled may not be obtained.

[0168] Therefore, the thermal shrinkage stress is more preferably a value within the range of 3 to 15 MPa, and further preferably a value within the range of 6 to 14 MPa.

[0169] The heat shrinkage stress at 85° C. can be calculated by measuring the heat shrinkage force (N / 15 mm) of a long test piece at 85° C. using a film heat shrinkage tester in accordance with ISO 14616-1997 and dividing the result by the thickness of the test piece.

[0170] (5) Thickness

[0171] The thickness of the polyester heat shrinkable film can be changed according to the form of various PET bottles, but is usually preferably set to a value within the range of 20 to 100 μm.

[0172] The reason is that if the thickness of the polyester heat shrinkable film is less than 20 μm, it may become difficult to use, or the breaking strength and the like may be significantly reduced.

[0173] On the other hand, if the thickness of the polyester heat shrinkable film is greater than 100 μm, it may not be heat-shrunk uniformly when heated at a predetermined temperature, or it may be difficult to produce a film with a uniform thickness.

[0174] Therefore, the thickness of the polyester heat shrinkable film is more preferably within a range of 25 to 70 μm, and further preferably within a range of 30 to 50 μm.

[0175] The thickness of the polyester heat shrinkable film can be measured in accordance with ISO 4593 using a micrometer (manufactured by Mitutoyo Corporation, product name: "Thickness gauge 547-401").

[0176] (6) Functional layer

[0177] The polyester heat shrinkable film preferably has a functional layer imparting various functions as necessary within a range not impairing the purpose of the present invention.

[0178] Examples of the functional layer include a coating layer for imparting surface smoothness, stain resistance, weather resistance, and the like, a transfer layer, and a print layer for imparting design properties.

[0179] Among them, a coating layer using a surfactant can significantly contribute to the improvement of antistatic properties and surface smoothness, and is therefore a preferred embodiment as a functional layer.

[0180] For example, Figure 1B As shown in FIG. 1 , it is preferred that other resin layers 10 a and 10 b containing at least one of these various additives be laminated on one or both surfaces of the polyester heat shrinkable film 10 .

[0181] In this 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 set to a value within a range of 0.1 to 10%.

[0182] The resin constituting the other resin layer as a main component is preferably the same polyester resin as the polyester heat shrinkable film, or may be at least one of acrylic resin, olefin resin, polyurethane resin, rubber resin, etc. different therefrom.

[0183] It is further preferred that the polyester heat shrinkable film has a multilayer structure so as to improve the hydrolysis resistance and scratch resistance, or Figure 1C As shown in the figure, a shrinkage ratio adjusting layer 10 c is provided on the surface of the polyester heat shrinkable film 10 so that the shrinkage ratio of the polyester heat shrinkable film is uniform in the surface.

[0184] The shrinkage ratio adjusting layer can be laminated as a predetermined layer made of a polyester resin or the like by using an adhesive, a coating method, or a heat treatment, etc., depending on the shrinkage characteristics of the polyester-based heat shrinkable film.

[0185] (7) Heat equivalent to the melting peak area

[0186] Moreover, it is preferable that the heat amount corresponding to the melting peak area at the melting point of the polyester-based heat shrinkable film is a value within the range of 15 to 25 mJ / mg.

[0187] The reason is that by controlling the heat of the melting peak area corresponding to the melting point in the polyester heat shrinkable film to a value within a predetermined range, the amount of the crystalline structure can be slightly limited, and the film can be adjusted to have a wide melting region.

[0188] Therefore, in the obtained polyester-based heat shrinkable film, the mechanical strength and transparency derived from the polyester resin as the main component can be maintained by a relatively wide and slightly crystalline structure, and the shrinkage stress at a predetermined temperature and the heat shrinkage rate at each predetermined temperature can be easily and stably adjusted.

[0189] On the other hand, in the polyester heat shrinkable film, if the heat amount corresponding to the melting peak area is outside the above range, the film may contain excessive crystal structures and may not be closer to the thermal and mechanical properties of polyvinyl chloride heat shrinkable films.

[0190] Therefore, the heat amount corresponding to the melting peak area measured by DSC of the polyester heat shrinkable film is more preferably a value within the range of 16 to 24 mJ / mg, and further preferably a value within the range of 17 to 23 mJ / mg.

[0191] Here, refer to Fig.10 , the DSC curve of the polyester heat shrinkable film is explained.

[0192] Right now, Fig.10 The DSC curve of the polyester heat shrinkable film of Example 1 obtained by DSC measurement is shown.

[0193] When obtaining this DSC curve, the temperature is usually raised to a high temperature region once in Step 1 (heating from 25°C to 280°C at a heating rate of 10°C / min). Next, although not shown in the figure, the temperature is once lowered to a low temperature region in Step 2 (lowering from 280°C to 25°C at a cooling rate of 30°C / min), and the temperature is further raised to a high temperature region again in Step 3 (highering from 25°C to 280°C at a heating rate of 10°C / min), so that a thermal curve indicating the glass transition temperature can be obtained.

[0194] Moreover, based on at least the DSC curve in Step 1, the extrapolated melting start temperature (hereinafter sometimes referred to as the melting start temperature), the melting point (melting peak temperature), the extrapolated melting end temperature (hereinafter sometimes referred to as the melting end temperature), and the heat equivalent to the melting peak area can be measured with good accuracy.

[0195] [Second embodiment]

[0196] The second embodiment is a method for producing the polyester heat shrinkable film of the first embodiment.

[0197] Hereinafter, each step will be specifically described.

[0198] 1. Raw material preparation and mixing process

[0199] As raw materials, main ingredients and additives such as crystalline polyester resin particles, rubber resin, antistatic agent, anti-hydrolysis agent, and inorganic slip agent are prepared.

[0200] In this preparation, the crystalline polyester resin particles to be the main component are preferably heated at a predetermined temperature (usually a temperature -10°C lower than the crystallization temperature) for a predetermined time (generally 3 to 10 hours) and dried to an absolutely dry state.

[0201] Next, preferably, crystalline polyester resin pellets and the like are weighed and added into a stirring container, and mixed and stirred using a stirring device until the mixture becomes uniform.

[0202] 2. Production process of blank sheet

[0203] Next, typically, extrusion molding (T-die method), inflation method, or casting molding method is preferably used to produce a green sheet having a predetermined thickness.

[0204] More specifically, for example, by extrusion molding using an extruder at an extrusion temperature of 245° C., a green sheet having a predetermined thickness (usually 200 to 300 μm) can be obtained.

[0205] 3. Production of polyester heat shrinkable film

[0206] Next, the obtained raw sheet was heated and pressed while being moved on and between rolls using a heat shrink film production apparatus (tenter), thereby producing a polyester heat shrink film.

[0207] Among them, as a stretching treatment method for expressing the shrinkage property, an inflation method, a roll stretching method, a tenter stretching method, and a combination thereof are known.

[0208] Furthermore, since productivity is better, sheet molding by a casting method and a combination of roll stretching and tenter stretching are more preferred.

[0209] That is, it is preferred that the polyester molecules constituting the polyester heat shrinkable film be crystallized into a predetermined shape by substantially expanding the film width at a predetermined stretching temperature and stretching ratio, and stretching the film in a predetermined direction while heating and pressing.

[0210] Then, by curing the film in this state, a heat-shrinkable polyester-based heat-shrinkable film for use as a decoration, a label, etc. can be produced.

[0211] It should be noted that it is usually preferred to manufacture the blank sheet using the T-die method, inflation method, etc., then heat the blank sheet to a temperature above the glass transition temperature of the resin, and stretch it 3 to 8 times, preferably about 4 to 6 times, in the main stretching direction (the width direction of the film blank, i.e., the TD direction).

[0212] 4. Inspection process of polyester heat shrinkable film

[0213] It is preferred to continuously or intermittently measure the following characteristics and the like of the produced polyester heat shrinkable film and provide a predetermined inspection step.

[0214] That is, by measuring the following characteristics and the like in a predetermined inspection process and confirming that the values ​​fall within a predetermined range, a polyester-based heat shrinkable film having more uniform shrinkage characteristics and the like can be obtained.

[0215] 1) Visual inspection of the appearance of polyester heat shrinkable film

[0216] 2) Thickness fluctuation measurement

[0217] 3) Tensile strength test (ASTM D882)

[0218] 4) Tensile elongation determination (ASTM D882)

[0219] 5) Surface smoothness inspection (ASTM D1894)

[0220] 6) Specific gravity measurement (ASTM D792)

[0221] 7) Ring impact test (TAPPI T882)

[0222] 8) Tear strength test (ASTM D1922)

[0223] 9) Determination of melting point (melting peak temperature) and heat equivalent to melting peak area obtained by DSC

[0224] Example

[0225] Hereinafter, the present invention will be described in detail based on examples. However, unless there are special reasons, the scope of protection claimed in the present invention will not be narrowed by the description of the examples.

[0226] In addition, the crystalline polyester resin, the non-crystalline polyester resin, the vinyl chloride resin and the additives used in the examples are as follows.

[0227] The intrinsic viscosity (IV value) described in the column of the amorphous polyester resin was measured in a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (weight ratio = 1 / 1) at a temperature of 30° C. using an Ubbelohde viscometer.

[0228] (PET1)

[0229] Polyester resin (manufactured by Eastman Chemical Co., trade name "Embrace Encore", glass transition temperature (Tg): 74°C, melting point: 217°C, density: 1.3 g / cm 3 )

[0230] (PETG1)

[0231] Amorphous polyester resin, composed of dicarboxylic acid and diol, dicarboxylic acid: 100 mol% of terephthalic acid, diol: ethylene glycol, 1,4-cyclohexanedimethanol and diethylene glycol (manufactured by Eastman Chemical Co., trade name "Embrace LV", glass transition temperature (Tg): 68.2°C, intrinsic viscosity (IV value): 0.7, density: 1.30 g / cm 3 )

[0232] (PETG2)

[0233] Amorphous polyester resin, composed of dicarboxylic acid and diol, dicarboxylic acid: 100 mol% of terephthalic acid, diol: ethylene glycol, 1,4-cyclohexanedimethanol and diethylene glycol (manufactured by Eastman Chemical Company, trade name "Easter Copolyester GN001", glass transition temperature (Tg): 80°C, no melting point, density: 1.27 g / cm 3 )

[0234] (PVC)

[0235] Vinyl chloride resin (manufactured by Shintech Co., Ltd., trade name "SE800", K value: 60.6 to 62.0)

[0236] (Additives (anti-adhesive agents))

[0237] A silica masterbatch prepared by mixing 20 parts by mass of silica with 80 parts by mass of polyethylene terephthalate resin (manufactured by Sukano Co., Ltd., trade name "Gdc S559-E", containing 20% ​​by weight of silica)

[0238] [Example 1]

[0239] 1. Production of polyester heat shrinkable film

[0240] As a crystalline polyester resin, PET1 was prepared.

[0241] Next, 1000 g of the prepared PET1 was placed in the stirring container.

[0242] Furthermore, the above-mentioned anti-blocking agent dried under predetermined conditions was blended at a ratio of 1 part by weight as an anti-blocking agent for a heat shrinkable film, based on 100 parts by weight of PET1, to prepare a raw material for forming a heat shrinkable film.

[0243] Next, the heat shrinkable film-forming raw material was extruded by using a vented twin-screw extruder at an extrusion temperature of 245° C. to obtain a green sheet having a thickness of 250 μm.

[0244] Finally, a heat shrink film manufacturing device is used to produce a polyester heat shrink film with a thickness of 40 μm and a thickness fluctuation of less than 5% from the blank sheet at a preheating temperature of 120°C, a stretching temperature of 84°C, an annealing temperature of 86.5°C, and a stretching ratio (MD direction: 1.06 times, TD direction: 5 times).

[0245] 2. Evaluation of polyester heat shrinkable film

[0246] (1) Thermal shrinkage

[0247] The heat shrinkage rate of the obtained polyester heat shrinkable film was measured in accordance with ASTM D2732-08.

[0248] That is, the sample 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-main shrinking direction (MD direction), and the square shape was used as a measurement sample.

[0249] Next, each of the sheets was immersed in a thermostatic bath containing hot water controlled at 60 to 100° C. in 5° C. increments for 10 seconds to allow heat shrinkage.

[0250] Next, the heat shrinkage ratio (%) in the main shrinkage direction and the non-main shrinkage direction was calculated from the dimensional changes before and after the heat treatment at each temperature according to the following formula (2).

[0251]

[0252] (2) Thermal shrinkage stress

[0253] The obtained polyester heat shrinkable film was measured for heat shrinkage stress in accordance with ISO14616-1997.

[0254] That is, the obtained polyester heat shrinkable film was cut into a strip having a length of 90 mm in the main shrinking direction and a length of 15 mm in the non-main shrinking direction, and the strip was used as a test piece.

[0255] Next, the shrinkage force (N / 15 mm) of the test piece at 85° C. was measured using a film heat shrinkage tester (manufactured by Labthink, product name “FST-02”).

[0256] Next, the obtained shrinkage force was divided by the thickness (40 μm) to obtain the heat shrinkage stress (MPa) at 85° C.

[0257] (3) Haze

[0258] The haze value of the obtained polyester heat shrinkable film was measured using a haze meter (manufactured by BYK, product name: "haze-gard dual") in accordance with ASTM D1003, and evaluated based on the following criteria.

[0259] ◎: The haze value is 7% or less.

[0260] ○: The haze value is 10% or less.

[0261] △: The haze value is 13% or less.

[0262] ×: The haze value is larger than 13%.

[0263] (4)DSC measurement

[0264] The obtained polyester heat shrinkable film was measured for melting start temperature, melting point (melting peak temperature), melting end temperature and heat quantity corresponding to the melting peak area under predetermined conditions using a DSC apparatus (manufactured by Hitachi High-Tech Sciences, Ltd., product name "DSC7000X").

[0265] More specifically, a sample of the polyester-based heat shrinkable film is dried in a drying oven at 60° C. for 6 hours or more.

[0266] Next, the sample is placed in a differential scanning calorimeter and the temperature is raised to the high temperature region in Step 1 (heating from 25°C to 280°C at a heating rate of 10°C / min). Next, the temperature is lowered to the low temperature region in Step 2 (cooling from 280°C to 25°C at a cooling rate of 30°C / min). Finally, the temperature is raised to the high temperature region again in Step 3 (heating from 25°C to 280°C at a heating rate of 10°C / min). Next, the melting start temperature, melting point (melting peak temperature), melting end temperature, and the amount of heat equivalent to the melting peak area are determined from the DSC curve obtained in Step 1.

[0267] [Examples 2 to 7]

[0268] In Examples 2 to 7, polyester heat shrinkable films were prepared and evaluated in the same manner as in Example 1 except that the thickness (μm), preheating temperature (°C), stretching temperature (°C), annealing temperature (°C), and stretching ratio (%) of the polyester heat shrinkable film were changed as shown in Table 1. The obtained results are shown in Table 2.

[0269] In addition, for Examples 3 and 7, Figure 4 and Figure 5 2 and 3 show characteristic curves for explaining the relationship between the heat shrinkage temperature and the heat shrinkage rate in the TD direction and the heat shrinkage rate in the MD direction, respectively.

[0270] [Comparative Example 1]

[0271] In Comparative Example 1, a polyester heat shrinkable film was prepared and evaluated in the same manner as in Example 1 except that the thickness (μm), preheating temperature (°C), stretching temperature (°C), annealing temperature (°C), and stretching ratio (%) of the polyester heat shrinkable film were changed as shown in Table 1. The obtained results are shown in Table 2.

[0272] in addition, Figure 6 Graphs for explaining the relationship between the heat shrinkage temperature of the polyester heat shrinkable film in Comparative Example 1 and the heat shrinkage ratios in the TD direction and the MD direction are shown in FIG.

[0273] [Comparative Example 2]

[0274] In Comparative Example 2, a polyester heat shrinkable film was produced and evaluated in the same manner as in Example 1 except that the above-mentioned PETG1 was used as the PET resin as shown in Table 1. The obtained results are shown in Table 2.

[0275] in addition, Figure 7 Graphs for explaining the relationship between the heat shrinkage temperature of the polyester heat shrinkable film in Comparative Example 2 and the heat shrinkage rates in the TD direction and the MD direction are shown in FIG.

[0276] [Comparative Example 3]

[0277] In Comparative Example 3, a polyester heat shrinkable film was produced and evaluated in the same manner as in Example 1 except that PETG1 was used as the PET resin as shown in Table 1. The obtained results are shown in Table 2.

[0278] [Comparative Example 4]

[0279] In Comparative Example 4, a polyester heat shrinkable film was produced and evaluated in the same manner as in Example 1 except that PETG1 and PETG2 (compounding ratio = 70 / 30) were used as PET resins as shown in Table 1. The obtained results are shown in Table 2.

[0280] [Comparative Example 5]

[0281] In Comparative Example 5, as shown in Table 1, the heat shrinkage ratio at each temperature was evaluated in the same manner as in Example 1 except that the polyvinyl chloride resin (PVC) was used to produce a polyvinyl chloride-based heat shrinkable film.

[0282] in addition, Figure 8 Graphs for explaining the relationship between the heat shrinkage temperature of the polyvinyl chloride-based heat shrinkable film in Comparative Example 5 and the heat shrinkage rates in the TD direction and the MD direction are shown in FIG.

[0283] [Table 1]

[0284]

[0285] [Table 2]

[0286]

[0287] Industrial Applicability

[0288] According to the present invention, by having at least characteristics (A) to (D), it is possible to provide a polyester-based heat-shrinkable film that can effectively and stably produce pellets of a predetermined shape even when PET bottles covered with the polyester-based heat-shrinkable film are collected together, and the heat shrinkage stress generated during heat shrinkage is low so as to cope with the thinning of the wall of the PET bottle.

[0289] Therefore, the polyester heat shrinkable film according to the present invention can be recycled regardless of whether it is thin-walled, thick-walled, or has a complex shape, and can be recycled not only for covering various PET bottles, but also together with various PET bottles, etc. As a result, its versatility can be significantly broadened, and it can be said that its industrial utilization possibility is extremely high.

Claims

1. A polyester heat shrinkable film, characterized in that: The polyester heat shrinkable film is a polyester resin derived from the reaction product of a polycarboxylic acid and a polyol, and has the following characteristics (A) to (D): (A) the melting point of the polyester resin measured by DSC is a value within the range of 190 to 255° C.; (B) a heat shrinkage ratio in the main shrinkage direction measured under heat shrinkage conditions of 85° C. for 10 seconds is a value within a range of 45 to 70%; (C) a heat shrinkage ratio in a direction perpendicular to the main shrinkage direction measured under heat shrinkage conditions of 60 to 90° C. for 10 seconds, which is a value within a range of −1 to 6%; (D) the heat shrinkage stress in the main shrinkage direction measured under heat shrinkage conditions of 85°C is a value of 16 MPa or less; Furthermore, the heat amount corresponding to the melting peak area of ​​the melting point of the polyester heat shrinkable film measured by DSC is a value within the range of 15 to 25 mJ / mg.

2. The polyester heat shrinkable film according to claim 1, characterized in that: (C′) The heat shrinkage rate in the direction perpendicular to the main shrinkage direction measured under heat shrinkage conditions of 70° C. for 10 seconds is a value within a range of 0 to 3%.

3. The polyester heat shrinkable film according to claim 1, characterized in that: (C″) The heat shrinkage ratio in the direction perpendicular to the main shrinkage direction measured under heat shrinkage conditions of 85° C. for 10 seconds is a value within a range of 1 to 5%.

4. The polyester heat shrinkable film according to claim 1, characterized in that: (C'") The heat shrinkage ratio in a direction perpendicular to the main shrinkage direction measured under heat shrinkage conditions of 60 to 90°C for 10 seconds has at least one minimum value, and the minimum value is a value of -1% or more.

5. The polyester heat shrinkable film according to claim 1, characterized in that: (C″″) The heat shrinkage ratio in a direction perpendicular to the main shrinkage direction measured under heat shrinkage conditions of 60 to 90° C. for 10 seconds has at least one local maximum value, and the local maximum value is a value of 0.8% or more.

6. The polyester heat shrinkable film according to claim 1, characterized in that: The film thickness is a value within the range of 10 to 100 μm.

7. The polyester heat shrinkable film according to claim 1, characterized in that: The polycarboxylic acid contains terephthalic acid as a main component, and the polyol is at least one of ethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, and diethylene glycol.

8. The polyester heat shrinkable film according to claim 1, characterized in that: The haze value of the film before shrinkage measured in accordance with ASTM D1003 is 7% or less.

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