Polyester heat-shrinkable film

Abstract

Provided is a polyester heat-shrinkable film that effectively suppresses adhesion during recycling. The polyester heat-shrinkable film of the present invention is a polyester heat-shrinkable film from a first polyester resin and a second polyester resin that are different in crystallinity, and satisfies the following characteristics (A) to (E). (A) and (B) The first polyester resin contains terephthalic acid, and the reaction amount of ethylene glycol is in the range of 50 mol% or more and less than 90 mol%, and the second polyester resin contains terephthalic acid, and the reaction amount of ethylene glycol is 90 mol% or more. (C) and (D) In the case where a prescribed isothermal crystallization measurement is performed, an exothermic peak occurs within 12 minutes from the start, including the cooling process time, and the heat of the exothermic peak is 5 to 35 J / g. (E) The thermal shrinkage in the main shrinkage direction measured under prescribed conditions is 20% to 60%.

Description

Technical Field

[0001] This invention relates to a polyester heat shrink film (sometimes simply referred to as polyester heat shrink film or heat shrink film).

[0002] More specifically, it relates to a polyester heat-shrinkable film that effectively and quantitatively suppresses adhesion during recycling while maintaining excellent fit to PET bottles. Background Technology

[0003] In the past, bottles made of polyethylene resin (HDPE) and polyester resin (PET) were commonly used as containers for storing beverages and detergents (hereinafter sometimes simply referred to as PET bottles).

[0004] Especially as a beverage storage container, PET bottles have become widely used around the world due to their lightweight, excellent durability, and high convenience.

[0005] On the other hand, such PET bottles are discarded into rivers after use, and their flow into the ocean has become a serious environmental problem.

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

[0007] In addition, PET bottles are covered with prescribed display labels to indicate various information about their name and contents, as well as to enhance their decorative appeal.

[0008] In the past, paper-based labels were often used as display labels and attached with adhesive. However, in recent years, using heat-shrinkable film display labels to package the entire surface of PET bottles has become the mainstream approach.

[0009] However, in the case of full-coverage packaging using heat-shrink film, due to its airtight structure, it is difficult to easily separate the display label using heat-shrink film when recycling PET bottles.

[0010] Therefore, the preferred material for heat shrink film is one that is easy to separate from PET bottles and does not hinder the recycling process of PET bottles.

[0011] More specifically, in the past, vinyl chloride resin (PVC), polystyrene resin (PS), and modified polyester (PETG) were commonly used.

[0012] Here, the main material for beverage storage containers is basically PET. Since the raw materials are similar, it can be said that there is a high possibility that PETG film can be melted together with PET bottles as heat shrink film and recycled.

[0013] However, since PETG is essentially amorphous, it has virtually no melting point as a thermal property, or only a melting peak with low exothermic properties. Furthermore, in the recycling process of PET bottles packaged with heat-shrink film, there is a problem that the recycled particles tend to stick together.

[0014] That is, when PET bottles wrapped in heat-shrink film are heat-melted during the recycling process, the following problems are found: Figure 13 As shown in (a), the adhesion phenomenon is caused by the heat shrink film. Fragments from the recycled resin containing the heat shrink film stick together to each other and form clumps, causing blockage in the middle of the piping.

[0015] Therefore, under normal circumstances, when melting PET bottles, including heat-shrink film, the following problem is found: it is actually difficult to use a granulator such as... Figure 13 (b) shows the effective and stable production of recycled pellets of a specified shape.

[0016] Therefore, a polyester heat shrinkable film with a specified melting peak (melting point) in differential scanning calorimetry (DSC) measurement was proposed by adjusting the thermal properties of the PETG film (Patent Document 1 and Patent Document 2).

[0017] The polyester heat shrink film disclosed in the aforementioned patent document 1 is characterized in that, in order to improve the recyclability of PET bottles, the amount of amorphous polyester resin is reduced, for example, a crystalline copolyester resin containing diol and dicarboxylic acid components is used, and when heat-treated by immersion in warm water 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 DSC is 170°C or more.

[0018] In addition, the polyester heat shrink film disclosed in Patent Document 2 is composed of (1) 5 to 95% by weight of crystallizable polyester and (2) 5 to 95% by weight of an amorphous polyester composition in order to improve the recyclability of PET bottles.

[0019] More specifically, it is (1) a crystallizable polyester with terephthalic acid as the main component, and the polyol reacting with it includes a specified amount of ethylene glycol, and at least one of neopentyl glycol, 1,4-cyclohexanediol and diethylene glycol in a crystalline polyester heat shrink film.

[0020] In addition, (2) the amorphous polyester composition is as follows: the dicarboxylic acid component is about 70 to about 100 mol% of terephthalic acid residue, the diol component is about 40 mol% or less of neopentyl glycol residue, about 40 mol% or less of 1,4-cyclohexanediethanol residue, and the remainder is ethylene glycol and diethylene glycol residue.

[0021] Existing technical documents

[0022] Patent documents

[0023] Patent Document 1: Japanese Patent Publication No. 2020-521823 (Scope of Patent Claim, etc.)

[0024] Patent Document 2: WO2020 / 076749 (Scope of Patent Claim, etc.) Summary of the Invention

[0025] However, in the case of the polyester heat shrink film disclosed in Patent Document 1 and Patent Document 2, it is made of polyester heat shrink film from a variety of polyester resins with different crystallinity, and there is no intention to control their mixing ratio, etc.

[0026] Furthermore, there was no intention or control over the timing of the exothermic peak or the amount of heat equivalent to the area of ​​the exothermic peak during isothermal crystallization determination using DSC.

[0027] Therefore, the following problem was found: the amount of agglomerates generated during recycling deviated, and the adhesion phenomenon could not be effectively and quantitatively controlled.

[0028] On the other hand, both Patent Document 1 and Patent Document 2 have found the following problem: in order to further suppress adhesion and increase the crystallinity of polyester heat shrink film by increasing the melting point, it is difficult to adjust the heat shrinkage rate and heat shrinkage stress, and the installability is significantly reduced.

[0029] Therefore, the following method was previously used: tear lines were introduced to make the polyester heat shrink film easy to remove, and the installed polyester heat shrink film was removed manually in advance when recycling PET bottles.

[0030] Therefore, the inventors of the present invention conducted in-depth research in view of the above-mentioned issues and found that by simultaneously satisfying the characteristics of the exothermic peak time, exothermic peak area, and heat shrinkage rate in the main shrinkage direction generated by isothermal crystallization at a specified temperature in a polyester heat shrink film from a variety of polyester resins with different crystallinities (at least the first polyester resin and the second polyester resin), not only can good installation properties be obtained, but also adhesion phenomena during recycling can be effectively and quantitatively suppressed.

[0031] That is, the purpose of the present invention is to provide a polyester heat shrink film that, while maintaining excellent installability on PET bottles, can also achieve a good balance and quantitatively good installability and excellent anti-sticking properties even when the PET bottles covered with the polyester heat shrink film are recycled together.

[0032] According to the present invention, a polyester-based heat shrinkable film is provided, characterized in that it is a polyester-based heat shrinkable film derived from the reaction product of a polycarboxylic acid and a polyol, namely, a first polyester resin and a second polyester resin, which are various polyester resins with different crystallinities, and satisfies the following characteristics (A) to (E), thereby solving the above-mentioned problems.

[0033] (A) The first polyester resin is an amorphous polyester resin containing at least terephthalic acid in a polycarboxylic acid, wherein the total amount of polyol is set to 100 mol%, and the amount of ethylene glycol reacted is in the range of 50 mol% or more and less than 90 mol%.

[0034] (B) The second polyester resin is a crystalline polyester resin (hereinafter sometimes referred to as a low-crystallinity polyester resin) that contains at least terephthalic acid in a polycarboxylic acid, and when the total amount of the above polyol is set to 100 mol%, the amount of ethylene glycol reacted is 90 mol% or more.

[0035] (C) is a polyester heat shrinkable film that exhibits an exothermic peak within 12 minutes from the start of the process, including the cooling process time, under the condition of isothermal crystallization measurement at 150°C using DSC, including a cooling process at a certain temperature.

[0036] (D) is a polyester heat shrinkable film with a heat equivalent to the exothermic peak area in the range of 5 to 35 J / g, under the condition of isothermal crystallization measurement at 150°C using DSC, including a cooling process at a certain temperature.

[0037] (E) is a polyester heat shrink film with a heat shrinkage rate in the main shrinkage direction ranging from 20% to 60%, determined by immersion in warm water at 80°C for 10 seconds.

[0038] Thus, by simultaneously satisfying the characteristics of the exothermic peak time (Construction C), the exothermic peak area (Construction D), and the heat shrinkage rate in the main shrinkage direction (Construction E) generated by isothermal crystallization in polyester heat shrink films from specified first polyester resins (Construction A) and second polyester resins (Construction B) with different crystallinity, it is possible to effectively and quantitatively suppress adhesion during recycling while maintaining excellent installability.

[0039] More specifically, as long as the polyester heat shrink film meets the requirements of (A) to (E), it can be made into a polyester heat shrink film with good balance and quantitatively good installability and excellent anti-adhesion.

[0040] Furthermore, when constructing the polyester heat-shrinkable film of the present invention, it is preferable that the mixing ratio of the first polyester resin to the second polyester resin by weight is in the range of 20 / 80 to 80 / 20.

[0041] By limiting the mixing ratio of various polyester resins within a specified range, it is possible to produce polyester heat-shrinkable films that more effectively and quantitatively suppress adhesion during recycling while maintaining excellent fit to PET bottles.

[0042] Furthermore, when constituting the polyester-based heat-shrinkable film of the present invention, the first polyester resin is preferably an amorphous polyester resin that contains at least 1,4-cyclohexanediethanol, and when the total amount (reaction amount) of the polyol is set to 100 mol%, the reaction amount of the 1,4-cyclohexanediethanol is in the range of 1 mol% or more and less than 35 mol%.

[0043] By limiting the types and contents of polyols, which are one of the polymer components of the first polyester resin, to a specified range, crystallinity can be adjusted more effectively and quantitatively.

[0044] Therefore, under the specified relationship between the first polyester resin and the second polyester resin, a good balance between good installability and excellent anti-blocking properties is achieved, and it can be quantitatively adjusted.

[0045] Furthermore, when constituting the polyester-based heat-shrinkable film of the present invention, the second polyester resin is preferably a crystalline polyester resin that contains only ethylene glycol or both ethylene glycol and diethylene glycol. When both ethylene glycol and diethylene glycol are contained, if the total amount of the polyol is set to 100 mol%, the amount of ethylene glycol reacting is 90 mol% or more, and the amount of diethylene glycol reacting is in the range of 1 to 10 mol%.

[0046] By limiting the types and amounts of polyols, which are one of the polymerizing components of the second polyester resin, to a specified range, the content of the crystalline portion can be effectively and quantitatively adjusted.

[0047] Therefore, under the specified relationship between the first polyester resin and the second polyester resin, good installability and excellent anti-blocking properties can be obtained in a balanced and quantitative manner.

[0048] Furthermore, when constituting the polyester-based heat-shrinkable film of the present invention, the second polyester resin is preferably a homopolymer polyester resin and a post-consumer recycled polyester resin (sometimes referred to as PCRP), or either one.

[0049] By limiting the types of second polyester resins in this way, waste is reduced, environmental resources are reused, and the process is inexpensive and economically advantageous.

[0050] Therefore, under the specified relationship between the first polyester resin and the second polyester resin, it is possible to achieve a better balance and quantitatively obtain good installability and excellent anti-blocking properties.

[0051] Furthermore, when constructing the polyester-based heat-shrinkable film of the present invention, if the total amount of the first polyester resin and the second polyester resin is set to 100 parts by weight, it is preferable that the amount of lubricant is in the range of 0.01 to 5 parts by weight.

[0052] By using lubricant in this way and limiting its amount, the influence on the properties of polyester heat shrink film can be suppressed, and even when it is made into long rolls, the welding between adjacent polyester heat shrink films can be prevented. In turn, it can sometimes help to further suppress adhesion during recycling.

[0053] In addition, when constituting the polyester heat shrink film of the present invention, it is preferable to further satisfy the following characteristic (F).

[0054] (F) The heat shrinkage rate in the direction orthogonal to the main shrinkage direction, determined under the heat shrinkage condition of immersion in warm water at 80°C for 10 seconds, is a value in the range of -3% to 10%.

[0055] By satisfying this property (F), not only can appropriate heat shrinkage and good installation properties for PET bottles be obtained, but also adhesion during recycling can be effectively and quantitatively suppressed.

[0056] In addition, when constituting the polyester heat shrink film of the present invention, it is preferable to further satisfy the following characteristic (G).

[0057] (G) The heat shrinkage stress in the main shrinkage direction, measured under the heat shrinkage condition of immersion in warm water at 80°C for 10 seconds, is less than 8 MPa.

[0058] By satisfying this characteristic (G), not only can appropriate heat shrinkage stress be obtained and good installation properties be achieved without damaging PET bottles, etc., but adhesion during recycling can also be effectively and quantitatively suppressed. Attached Figure Description

[0059] Figure 1 (a) to (c) are diagrams used to illustrate the different forms of polyester heat shrink film.

[0060] Figure 2 (a) to (b) are graphs illustrating the relationship between the mixing ratio of the first polyester resin / the second polyester resin constituting the polyester heat shrink film (based on weight) and the evaluation of installability and anti-adhesion.

[0061] Figure 3 This is a graph used to illustrate the relationship between the mixing ratio of the first polyester resin and the second polyester resin and the heat shrinkage stress.

[0062] Figure 4This is a graph used to illustrate the relationship between the mixing ratio of the first polyester resin and the second polyester resin and the glass transition temperature.

[0063] Figure 5 This is a graph used to illustrate the relationship between the mixing ratio of the first polyester resin and the second polyester resin and the peak generation time caused by isothermal crystallization.

[0064] Figure 6 This is a graph illustrating the relationship between the mixing ratio of the first polyester resin and the second polyester resin and the heat shrinkage rate when immersed in warm water at 80°C for 10 seconds.

[0065] Figure 7 This is a graph used to illustrate the relationship between peak generation time and anti-blocking properties during isothermal crystallization.

[0066] Figure 8 (a) to (b) are DSC diagrams illustrating polyester heat shrinkable films (Example 1 and Comparative Example 1) formed by isothermal crystallization, including a cooling process at a certain temperature.

[0067] Figure 9 (a) to (b) are figures illustrating the relationship between heat equivalent to the area of ​​the exothermic peak generated by isothermal crystallization of polyester heat shrink film and the evaluation of installability and anti-adhesion, respectively.

[0068] Figure 10 This is a graph used to illustrate the relationship between various heat shrinkage temperatures and heat shrinkage rates of polyester heat shrink films.

[0069] Figure 11 (a) to (b) are graphs illustrating the relationship between the heat shrinkage rate of polyester heat shrink film under shrinkage conditions of immersion in warm water at 80°C for 10 seconds and the evaluation of its installability and anti-adhesion properties.

[0070] Figure 12 This diagram illustrates the recycling process for PET bottles coated with polyester heat-shrink film.

[0071] Figure 13 (a) is a schematic diagram showing the adhesion phenomenon that occurs during the recycling process of PET bottles coated with conventional polyester heat-shrink film. Figure 13 (b) is a schematic diagram of the recycled particles obtained in the recycling process of PET bottles without sticking. Detailed Implementation

[0072] [First Implementation]

[0073] like Figure 1As illustrated in (a) to (c), the first embodiment provides a polyester-based heat shrink film, characterized in that it is a polyester-based heat shrink film derived from the reaction product of a polycarboxylic acid and a polyol, namely, a first polyester resin and a second polyester resin, which are various polyester resins with different crystallinities, and satisfies the following characteristics (A) to (E), thereby solving the above-mentioned problems.

[0074] (A) The first polyester resin is an amorphous polyester resin containing at least terephthalic acid in a polycarboxylic acid, wherein the total amount of polyol is set to 100 mol%, and the amount of ethylene glycol reacted is in the range of 50 mol% or more and less than 90 mol%.

[0075] (B) The second polyester resin is a crystalline polyester resin (sometimes called a low-crystallinity polyester resin) that contains at least terephthalic acid in a polycarboxylic acid, and when the total amount of the above polyol is set to 100 mol%, the amount of ethylene glycol reacted is 90 mol% or more.

[0076] (C) is a polyester heat shrinkable film that exhibits an exothermic peak within 12 minutes from the start of the process, including the cooling process time, under the condition of isothermal crystallization measurement at 150°C using DSC, including a cooling process at a certain temperature.

[0077] (D) is a polyester heat shrinkable film with a heat equivalent to the exothermic peak area in the range of 5 to 35 J / g, under the condition of isothermal crystallization measurement at 150°C using DSC, including a cooling process at a certain temperature.

[0078] (E) is a polyester heat shrink film with a heat shrinkage rate in the main shrinkage direction ranging from 20% to 60%, determined by immersion in warm water at 80°C for 10 seconds.

[0079] Hereinafter, the polyester heat shrink film of the first embodiment will be divided into its constituent components, and will be described in detail with reference to the accompanying drawings as appropriate.

[0080] 1. First polyester resin

[0081] (1) Polycarboxylic acids

[0082] As one of the polymerizing components (raw material components) of the first polyester resin, polycarboxylic acids are not particularly limited as long as they can react with polyols to form polyester structures. For example, aliphatic dicarboxylic acids such as adipic acid, sebacic acid, and azelaic acid, aromatic dicarboxylic acids such as terephthalic acid, naphthalic acid, and isophthalic acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, or at least one of their ester-forming derivatives can be mentioned.

[0083] In particular, if it is terephthalic acid, it reacts well with polyols and easily forms crystalline polyester structures, and is relatively inexpensive, which is also economical, so it is preferred.

[0084] Therefore, when the total amount of the polycarboxylic acid used is set to 100 mol%, it is preferable that the amount of terephthalic acid reacted is 90 mol% or more, and more preferably in the range of 95 to 100 mol%.

[0085] (2) Types of polyols

[0086] In addition, the polyol (sometimes called diol component), which is one of the polymer components belonging to the first polyester resin, is a mixture containing at least ethylene glycol.

[0087] By limiting the types of polyols that are one of the polymer components of the first polyester resin, the proportion of the amorphous portion can be adjusted, thereby not only achieving good installability, but also more effectively suppressing adhesion in relation to the second polyester resin.

[0088] In addition, when preparing a mixture containing a specified amount of ethylene glycol, other polyols other than ethylene glycol are preferably used, including at least one of alicyclic diols such as 1,4-cyclohexanediethanol, diethylene glycol, propylene glycol, butanediol, neopentyl glycol, hexanediol, etc., and aromatic diols.

[0089] This is because by using such a polyol, a moderate reaction with a polycarboxylic acid readily yields an amorphous polyester resin with at least controlled crystallinity / amorphity. Specifically, by using a specific polyol that is either unbranched or branched, linear or linear, the melting point, heat shrinkage rate, heat shrinkage stress, etc., of the polyester resin obtained by reacting with the polycarboxylic acid can be easily adjusted to values ​​within a specified range.

[0090] Therefore, 1,4-cyclohexanediol and diethylene glycol, or either of them, are more preferred as other polyols to be used in conjunction with ethylene glycol.

[0091] (3) The amount of polyol reacted

[0092] In addition, it is characterized in that, when using a mixture containing a specified amount of ethylene glycol, the amount of ethylene glycol reacted is at least 50 mol% and less than 90 mol%.

[0093] The reason is that if the amount of ethylene glycol reacted is less than 50 mol%, problems such as high melt viscosity, poor fluidity, and difficulty in molding may occur.

[0094] On the other hand, if the amount of ethylene glycol reacts is 90 mol% or more, sometimes too much crystallization is generated, and the properties of the resulting polyester heat shrink film, such as its installability, are significantly reduced.

[0095] It should be noted that the reaction amount of each polyol containing ethylene glycol can actually be determined based on the residual amount of each alcohol component, and can be simply replaced by the amount of each alcohol component added.

[0096] In addition, when using a mixture containing a specified amount of ethylene glycol as a raw material component, it is preferable that the reaction amount of 1,4-cyclohexanediethanol and diethylene glycol, or either of them, is in the range of 1 to 35 mol%.

[0097] The reason is that if the amount of the above-mentioned 1,4-cyclohexanediethanol and other reactions is less than 1 mol%, the amount of amorphous part generated will be less, and on the contrary, the amount of crystalline part generated will be too much, and the installation properties of the obtained polyester heat shrink film will be significantly reduced.

[0098] On the other hand, if the total amount of the above-mentioned 1,4-cyclohexanediethanol and other reactants exceeds 35 mol%, problems such as high melt viscosity, poor flowability, and difficulty in molding may occur. In addition, it is sometimes difficult to effectively and quantitatively suppress crystallinity, glass transition temperature, and adhesion phenomena during recycling.

[0099] Therefore, it is more preferable that the total amount of the above-mentioned 1,4-cyclohexanediethanol and the like is in the range of 5 mol% or more and less than 30 mol%, and even more preferably in the range of 10 to 28 mol%.

[0100] Furthermore, it is more preferable that the molar ratio of 1,4-cyclohexanediethanol and diethylene glycol in the total reaction amount is in the range of 9:1 to 1:9.

[0101] In addition, in order to change the thermal and mechanical properties of polyester heat shrink film, other dicarboxylic acids or hydroxycarboxylic acids may be used alone or in combination without departing from the purpose of this invention.

[0102] (4) Amorphous

[0103] The first polyester resin is essentially amorphous. As a standard for this amorphousness, it can be determined, for example, by the absence of a specified melting peak in DSC measurements or by the near-detectability of exothermic heat.

[0104] Alternatively, the glass transition temperature can be determined by observing the change in specific heat, which indicates the glass transition temperature, within a specified temperature range during DSC measurement.

[0105] Furthermore, it can also be judged based on the low crystallinity measured according to JIS K 7112.

[0106] That is, the density (d) of a sample approximately 3 mm square can be determined using the density gradient tube method according to JIS K 7112 with an aqueous solution of calcium nitrate. The crystallinity of the polyester resin can be calculated by referring to the known density (dc) of fully crystalline polyethylene terephthalate and the density (da) of fully amorphous polyethylene terephthalate. The proportion of the amorphous portion can then be specifically calculated based on this crystallinity.

[0107] (5) Glass transition temperature

[0108] Furthermore, it is preferable to set the glass transition temperature of the first polyester resin to a value within the range of 50 to 90°C.

[0109] The reason is that if the glass transition temperature is less than 50°C, the display label using the polyester heat shrink film may become sticky during the drying process of recycling PET bottles, causing the fragments of the recycled sheet to stick together and resulting in adhesion.

[0110] On the other hand, if the glass transition temperature exceeds 90°C, the heat required for the extrusion and stretching of the polyester heat shrink film becomes too high, making the processing itself more difficult, or making it more difficult to control the heat shrinkage rate.

[0111] Therefore, it is preferable to select a glass transition temperature of the first polyester resin in the range of 60 to 85°C, and even more preferably in the range of 65 to 80°C.

[0112] It should be noted that the glass transition temperature of the first polyester resin can be determined, for example, in a DSC determination by the following steps (the same applies below).

[0113] 1) As the 1st run, the first polyester resin was used as the test sample and heated from room temperature to about 300°C at a heating rate of 10°C / min.

[0114] 2) Next, the temperature is rapidly reduced from 300°C to room temperature at a rate of about 30°C / minute.

[0115] 3) Next, as the 2nd run, the temperature is increased from room temperature to about 300°C at a heating rate of 10°C / minute.

[0116] Then, the point of change in specific heat that appears on the DSC chart obtained in the 2nd-Run can be taken as the glass transition temperature of the first polyester resin.

[0117] (6) Melting point

[0118] Furthermore, when the first polyester resin has a melting point, it is preferable that the melting point is within the range of 190 to 270°C.

[0119] The reason is that if the melting point is less than 190°C, the display label using polyester heat shrink film may sometimes become sticky during the drying process of recycling PET bottles, causing the fragments of the recycled sheet to stick together and easily cause adhesion.

[0120] On the other hand, if the melting point exceeds 270°C, the heat required for extrusion and stretching of the raw polyester heat shrink film becomes too high, making processing difficult or making it difficult to control the heat shrinkage rate, which significantly reduces its installability on PET bottles, etc.

[0121] Therefore, when the first polyester resin has a melting point, it is more preferable to have the melting point in the range of 200 to 270°C, and even more preferably in the range of 210 to 270°C.

[0122] It should be noted that, in the case where the first polyester resin has a melting point, for example, it can be determined as the peak temperature (Tm) of the heat of fusion shown as an endothermic reaction in the curve obtained using DSC.

[0123] (7) Intrinsic viscosity

[0124] Furthermore, it is preferable that the intrinsic viscosity (IV value) of the first polyester resin is in the range of 0.6 to 0.85 dL / g.

[0125] The reason is that if the intrinsic viscosity is less than 0.6 dL / g, the melt viscosity is sometimes too low, which can cause problems in extrusion molding or result in poor anti-blocking properties during recycling.

[0126] On the other hand, if the intrinsic viscosity exceeds 0.85 dL / g, the melt viscosity may be too high, which may cause problems with extrusion molding or result in poor installability.

[0127] Therefore, it is more preferable to have the intrinsic viscosity in the range of 0.65 to 0.83 dL / g, and even more preferably in the range of 0.7 to 0.8 dL / g.

[0128] It should be noted that the intrinsic viscosity of polyester resin can be determined according to JIS K 7390 (the same applies below).

[0129] That is, more specifically, the aforementioned intrinsic viscosity (IV value) was measured using an Ubbelohde viscometer at a temperature of 30°C in a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (weight ratio = 1 / 1).

[0130] (8) Additives

[0131] In addition, it is also preferable to incorporate various additives such as antioxidants, weather stabilizers, antistatic agents, antifogging agents, metallic soaps, waxes, mildew inhibitors, antibacterial agents, nucleating agents, flame retardants, and lubricants (slip agents) into the first polyester resin as needed in a specified amount (e.g., 0.01 to 10 parts by weight of the total amount).

[0132] Moreover, there are no particular restrictions on the method of adding additives; well-known methods can be used.

[0133] In addition, to improve the sliding properties of the film surface, inorganic lubricants containing calcium carbonate particles, silica particles, glass particles, etc. are preferred.

[0134] Furthermore, as for lubricants, which are one of the additives, there are no particular limitations on the types. They can be used alone or in combination with inorganic or organic lubricants commonly used in films.

[0135] More specifically, inorganic lubricants include, for example, particles composed of calcium carbonate particles, silica particles, glass particles, zeolite, talc, kaolin, etc.

[0136] In addition, examples of organic lubricants include microparticles composed of cross-linked polymethyl methacrylate, cross-linked polystyrene, silicone rubber, silicone copolymers, polyamides, and condensation resins having triazine rings, among which microparticles composed of silicone rubber and silicone copolymers are preferred.

[0137] 2. Second polyester resin

[0138] (1) Polycarboxylic acids

[0139] As one of the polymer components (raw material components) of the second polyester resin, namely polycarboxylic acid, it is characterized in that there are no particular restrictions as long as it is a compound that can react with polyols to form a polyester structure, but it must contain at least terephthalic acid.

[0140] If the substance is terephthalic acid, it reacts well with polyols, easily forming a crystalline polyester structure, and is relatively inexpensive, which is also economical.

[0141] Therefore, when the total amount of the polycarboxylic acid used is set to 100 mol%, it is preferable that the amount of terephthalic acid reacted is 90 mol% or more, and more preferably in the range of 95 to 100 mol%.

[0142] In addition, in order to change the thermal and mechanical properties of the polyester heat shrink film, it is preferable to include at least one of aliphatic dicarboxylic acids such as adipic acid, sebacic acid, and azelaic acid, aromatic dicarboxylic acids such as naphthalic acid and isophthalic acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, or their ester-forming derivatives, as a polycarboxylic acid other than terephthalic acid, within a specified amount without departing from the purpose of the present invention.

[0143] In particular, if the polycarboxylic acid other than terephthalic acid is isophthalic acid, it is easy to mix evenly with terephthalic acid, which increases the transparency and heat shrinkage rate of the polyester heat shrink film, thereby more effectively and quantitatively suppressing the adhesion phenomenon during recycling.

[0144] (2) Types of polyols

[0145] In addition, the polyol (sometimes called diol component) that is one of the polymer components belonging to the second polyester resin is at least ethylene glycol.

[0146] By limiting the types of polyols in this way, crystallinity can be adjusted to the desired range, thereby more effectively and quantitatively suppressing adhesion in relation to the first polyester resin.

[0147] In addition, other polyols besides ethylene glycol are preferably selected from at least one of aliphatic diols such as diethylene glycol, propylene glycol, butanediol, neopentyl glycol, and hexanediol, or alicyclic diols and aromatic diols that are different from 1,4-cyclohexanediol.

[0148] This is because by using such polyols, in moderate reaction with polycarboxylic acids, it is easy to obtain low-crystallinity polyester resins with at least controlled crystallinity / amorphity.

[0149] In particular, diethylene glycol or neopentyl glycol is more preferred as other polyols to form a combination of ethylene glycol and diethylene glycol, or a combination of ethylene glycol and neopentyl glycol.

[0150] That is, by using specific polyols that are either unbranched or branched straight-chain, the melting point, heat shrinkage rate, heat shrinkage stress, etc. of the polyester resin obtained by reacting with polycarboxylic acids can be easily adjusted to values ​​within a specified range.

[0151] (3) The amount of polyol reacted

[0152] When the total amount of the polyol used as one of the polymerization components of the second polyester resin is set to 100 mol%, it is preferable to make the amount of ethylene glycol reacted at 90 mol% or more.

[0153] The reason is that if the reaction amount of the aforementioned ethylene glycol, etc., is less than 90 mol%, the amount of crystalline material formed is sometimes less, making it difficult to exhibit good crystallinity when mixed with the first polyester resin. That is, it is sometimes difficult to effectively and quantitatively suppress adhesion during recycling.

[0154] Therefore, it is more preferable to have the amount of the above-mentioned ethylene glycol and the like reactant be 95 mol% or more, and even more preferably a value in the range of 99 to 100 mol%.

[0155] Furthermore, in order to change the thermal and mechanical properties of polyester heat shrink film, diethylene glycol, alicyclic diols, hydroxycarboxylic acids, etc., may be used alone or in combination without departing from the purpose of this invention.

[0156] (4) Other types of polyester resins

[0157] In addition, the second polyester resin can be a polyester resin obtained by condensing a specified polycarboxylic acid and a specified polyol in a specified ratio as shown in (1) to (3) above. Specifically, homopolymer polyester resin, i.e., polyester resin composed only of terephthalic acid and ethylene glycol, is also preferred.

[0158] In addition, as a second polyester resin, it is also preferable to use a polyester resin obtained by recycling post-consumer recycled polyester resin, i.e., recycled PET bottles, etc., by washing, crushing, drying and granulating.

[0159] Furthermore, it is also preferable to use unused polyester resin in combination with at least one of homopolymer polyester resin and post-consumer recycled polyester resin.

[0160] Using this second polyester resin reduces waste, helps reuse environmental resources, and is inexpensive, making it economically advantageous.

[0161] Therefore, under the specified relationship between the first polyester resin and the second polyester resin, it is possible to achieve a better balance and quantitatively obtain good installability and excellent anti-blocking properties.

[0162] (5) Crystallinity and melting point

[0163] In addition, the crystallinity of the second polyester resin can be judged in the same way as that of the first polyester resin, based on the position of the melting peak (melting point) of the crystallized portion based on DSC, the heat of the melting peak, etc.

[0164] Alternatively, the crystallinity measured according to JIS K 7112 can be determined in the same way, and a judgment can be made based on the crystallinity.

[0165] In addition, the characteristic is that the melting point of the second polyester resin is in the range of 190 to 270°C.

[0166] The reason is that if the melting point is less than 190°C, the display label using the polyester heat shrink film may become sticky during the drying process of recycling PET bottles, causing the fragments used as recycling sheets to stick together and resulting in adhesion.

[0167] On the other hand, if the melting point is above 270°C, the heat required for extrusion and stretching of the raw polyester heat shrink film used in the label becomes too high, making processing difficult or significantly reducing its installability.

[0168] Therefore, it is more preferable to have the melting point of the polyester resin in the range of 200 to 270°C, and even more preferably in the range of 220 to 270°C.

[0169] Furthermore, the melting point of polyester resin can be determined, for example, as the peak temperature (Tm) of the heat of fusion shown as an endothermic reaction in the curve obtained using DSC (the same applies below).

[0170] It should be noted that the crystallinity of polyester resin can be inferred from the area and half-peak width of the peak of the above-mentioned heat of melting.

[0171] (6) Glass transition temperature

[0172] In addition, when the second polyester resin has a glass transition temperature, it is preferable that the temperature is within the range of 50 to 90°C.

[0173] The reason is that if the glass transition temperature is less than 50°C, the display labels using the polyester heat shrink film may become sticky during the drying process of recycling PET bottles with polyester heat shrink film, causing the recycled sheets to stick together and resulting in adhesion.

[0174] On the other hand, if the glass transition temperature exceeds 90°C, the heat required for the extrusion and stretching of the polyester heat shrink film becomes too high, making processing difficult or controlling the heat shrinkage rate difficult.

[0175] Therefore, when the second polyester resin has a glass transition temperature, it is more preferable that the temperature is in the range of 60 to 85°C, and even more preferably in the range of 65 to 80°C.

[0176] (7) Intrinsic viscosity

[0177] In addition, it is preferable that the intrinsic viscosity (IV value) of the second polyester resin is in the range of 0.6 to 0.85 dL / g.

[0178] The reason is that if the intrinsic viscosity is less than 0.6 dL / g, the melt viscosity is sometimes too low, which can cause problems with extrusion molding.

[0179] On the other hand, if the intrinsic viscosity exceeds 0.85 dL / g, the melt viscosity may be too high, which can also cause problems with extrusion molding properties.

[0180] Therefore, it is more preferable to have an intrinsic viscosity in the range of 0.63 to 0.83 dL / g, and even more preferably in the range of 0.65 to 0.8 dL / g.

[0181] (8) Additives

[0182] In addition, it is also preferable to add various additives such as antioxidants, weather stabilizers, antistatic agents, antifogging agents, metal soaps, waxes, mildew inhibitors, antibacterial agents, nucleating agents, flame retardants, and lubricants (slip agents) to the second polyester resin in the same way as the first polyester resin, within a specified range as needed.

[0183] Moreover, there are no particular restrictions on the method of adding additives; well-known methods can be used.

[0184] 3. Polyester-based heat shrink film

[0185] (1) Mixing ratio of the first polyester resin / the second polyester resin

[0186] Preferably, the mixing ratio of the first polyester resin to the second polyester resin (hereinafter, sometimes simply referred to as the mixing ratio) is in the range of 20 / 80 to 80 / 20.

[0187] The reason is that by limiting the mixing ratio of various polyester resins with different crystallinity to a specified range, it is possible to more effectively suppress adhesion during recycling while maintaining excellent fit to PET bottles.

[0188] Therefore, it is more preferable to make the mixing ratio of the first polyester resin to the second polyester resin in the range of 25 / 75 to 75 / 25, and even more preferably in the range of 30 / 70 to 70 / 30.

[0189] Here, it is mentioned Figure 2 Sections (a) to (b) explain the relationship between the mixing ratio of the first polyester resin to the second polyester resin in a specific combination of polyester resins constituting the polyester-based heat-shrinkable film of the present invention and the evaluation of installability and anti-adhesion.

[0190] Right now, Figure 2 (a) The horizontal axis is shown using the mixing ratio of the first polyester resin / the second polyester resin constituting the polyester heat shrink film, and the vertical axis is shown using an installation performance evaluation (relative value).

[0191] In addition, in the figures, Example 1 is referred to as Ex.1 and Comparative Example 1 is referred to as CE.1, and so on.

[0192] Then, according to the above Figure 2 The characteristic curve in (a) can achieve the highest installation score of 5, regardless of the mixing ratio, within the range of 100 / 0 to 70 / 30.

[0193] In addition, if the above mixing ratio exceeds 70 / 30 and becomes 50 / 50, a slight downward trend is observed in the installation performance evaluation, that is, the evaluation score decreases from 5 to around 3.

[0194] Furthermore, if the above mixing ratio exceeds 50 / 50 and falls below 20 / 80, although the installation performance evaluation is biased, a clear downward trend is observed, that is, the evaluation score tends to decrease to around 1 to 2.

[0195] Therefore, it can be understood that by using a mixing ratio of the first polyester resin to the second polyester resin in the polyester heat-shrinkable film of the present invention in a wide range of 20 / 80 to 80 / 20, and more preferably in the range of 30 / 70 to 70 / 30, a relatively good or sufficiently acceptable level of installability evaluation can be obtained.

[0196] in addition, Figure 2 (b) The mixing ratio of the first polyester resin / the second polyester resin constituting the polyester heat shrink film is used on the horizontal axis, and the evaluation of anti-adhesion (relative value) is used on the vertical axis.

[0197] Then, according to the above Figure 2 In the characteristic curve in (b), within the range of mixing ratios of 100 / 0 or more and less than 80 / 20, there is a trend that the lower the mixing ratio of the first polyester resin, the higher the evaluation of anti-blocking properties.

[0198] Furthermore, within the above-mentioned mixing ratio range of 80 / 20 to 20 / 80, regardless of the mixing ratio, a good evaluation of anti-blocking properties can be obtained.

[0199] Therefore, it can be understood that in the polyester heat shrink film of the present invention, even if the mixing ratio of the first polyester resin to the second polyester resin is at least in a wide range of 20 / 80 to 80 / 20, and more preferably in a range of 30 / 70 to 70 / 30, a good or acceptable level of anti-adhesion can be obtained respectively.

[0200] also, Figure 3The figure shows the relationship between the mixing ratio of the first polyester resin and the second polyester resin and the heat shrinkage stress (80°C) of the polyester heat shrink film.

[0201] However, since the heat shrinkage rate at 80℃ has a significant impact on the heat shrinkage stress at 80℃, therefore, Figure 3 Measurement data from examples, such as those with a heat shrinkage rate of 20-60% limited to 80°C, are recorded.

[0202] According to the above Figure 3 The characteristic curve in the figure can be understood as follows: even if the above mixing ratio is in a wide range of 20 / 80 to 80 / 20, and more preferably in the range of 30 / 70 to 70 / 30, the value of thermal shrinkage stress can be controlled to a low value of 8 MPa or less, so as to achieve the effect of preventing deformation of the installed object.

[0203] in addition, Figure 4 The figure shows the relationship between the mixing ratio of the first polyester resin and the second polyester resin and the glass transition temperature of the polyester heat shrink film.

[0204] According to the above Figure 4 The characteristic curve in the figure can be understood as follows: even if the above mixing ratio is in a wide range of 20 / 80 to 80 / 20, more preferably in the range of 30 / 70 to 70 / 30, by relatively reducing the proportion of the first polyester resin and relatively increasing the proportion of the second polyester resin, it is possible to control the glass transition temperature to a higher level with extremely good precision and quantitative control.

[0205] in addition, Figure 5 The figure shows the relationship between the mixing ratio of the first polyester resin and the second polyester resin and the peak generation time of isothermal crystallization (hereinafter sometimes simply referred to as peak generation time).

[0206] According to the above Figure 5 The characteristic curve in the figure can be understood as follows: even if the above mixing ratio is in a wide range of 20 / 80 to 80 / 20, more preferably in the range of 30 / 70 to 70 / 30, the peak generation time can be controlled with extremely good precision and quantitatively to a value of more than 5 minutes and less than 12 minutes, more preferably to a value of more than 5.5 minutes and less than 9 minutes.

[0207] in addition, Figure 6 The figure shows the relationship between the mixing ratio of the first polyester resin and the second polyester resin and the heat shrinkage rate when immersed in warm water at 80°C for 10 seconds.

[0208] However, since the stretching ratio in the main shrinkage direction (TD direction) can have a significant impact on the heat shrinkage rate at 80℃, therefore, Figure 6The measurement data of the stretching ratio of 4 times in the main contraction direction (TD direction) were recorded.

[0209] According to the above Figure 6 The characteristic curve in the figure can be understood as follows: even if the above mixing ratio is in a wide range of 20 / 80 to 80 / 20, more preferably in the range of 30 / 70 to 70 / 30, the heat shrinkage rate at the specified temperature can be controlled with extremely good precision and quantitatively in the range of 20 to 60%, more preferably in the range of 25 to 50%.

[0210] (2) Peak generation time of isothermal crystallization

[0211] The characteristic is that it is a polyester-based heat-shrinkable film, such as... Figure 7 As shown, as characteristic (C), when isothermal crystallization is measured at 150°C using DSC, including a cooling process at a certain temperature (usually -10 to 10°C, 0°C as an example), an exothermic peak appears within 12 minutes from the start of the cooling process, including the cooling process time at a certain temperature (usually 1 to 5 minutes, 5 minutes being the norm).

[0212] For example, such as Figure 8 As shown in (a), isothermal crystallization at 150°C was measured, including the cooling process time (5 minutes) at a certain temperature (0°C). When an exothermic peak appeared 3.8 minutes after the start of heating at 150°C, the peak generation time was 5 + 3.8 = 8.8 minutes.

[0213] The reason is that by producing an exothermic peak corresponding to crystallization in a relatively short time, adhesion can be effectively and quantitatively suppressed during the drying process of recycling PET bottles with polyester heat-shrink film installed.

[0214] On the other hand, it is because of... Figure 8 As shown in (b), isothermal crystallization at 150°C was measured, including a cooling process time (5 minutes) at a certain temperature (0°C). If no exothermic peak appeared even after 12 minutes from the start of heating at 150°C, it was judged that the crystallization under the specified conditions was slow.

[0215] Therefore, during the drying process of recycling PET bottles, the slow crystallization of polyester heat shrink film easily leads to the adhesion of fragments that are to be recycled.

[0216] Therefore, as characteristic (C), it is more preferable that the peak generation time, including the cooling process time at a certain temperature, is within 10 minutes, and more preferably within 9 minutes.

[0217] Here, return to Figure 7 The relationship between the generation time of the exothermic peak generated by isothermal crystallization of each polyester heat shrink film (including the cooling process time at a certain temperature; hereinafter, it is sometimes simply referred to as peak generation time) and the evaluation of anti-blocking properties is explained.

[0218] Right now, Figure 7 The peak generation time is used on the horizontal axis, and the anti-adhesion evaluation (relative value) is used on the vertical axis.

[0219] Then, according to the above Figure 7 The characteristic curves showed that if the peak generation time was less than 12 minutes, a good anti-adhesion evaluation was obtained, but if the peak generation time exceeded 12 minutes, the anti-adhesion evaluation showed a significant downward trend.

[0220] Therefore, it can be understood that in the polyester heat shrink film of the present invention, by making the peak generation time during isothermal crystallization less than 12 minutes, more preferably more than 5 minutes and less than 10 minutes, adhesion can be effectively and quantitatively suppressed.

[0221] (3) The heat equivalent to the area of ​​the exothermic peak generated by isothermal crystallization

[0222] In addition, it is characterized by being a polyester-based heat-shrinkable film: such as Figure 8 As shown in (a), characteristic (D) is a value in the range of 5 to 35 J / g of heat equivalent to the exothermic peak area when isothermal crystallization is measured at 150°C using DSC, including a cooling process at a certain temperature.

[0223] The reason is that isothermal heating at a specified temperature, including a cooling process at a certain temperature, allows crystallization to occur in a relatively short time (e.g., 8.8 minutes from the start, including the 5 minutes of the cooling process time) corresponding to the crystallinity of the resin.

[0224] Moreover, by confirming the appearance of the corresponding exothermic peak, adhesion can be effectively and quantitatively suppressed during the drying process of recycling PET bottles with polyester heat-shrink film installed.

[0225] That is, if the heat equivalent to the exothermic peak area is less than 5 J / g, then during the drying process of recycling PET bottles, the fragments used as recycling sheets are prone to sticking together.

[0226] On the other hand, if the heat equivalent to the exothermic peak area exceeds 35 J / g, it means that the crystalline portion formed by isothermal crystallization is large, sometimes excessively limiting the applications of the recycled PET resin. Therefore, for example, it is sometimes impossible to apply it to the use of polyester heat-shrinkable films.

[0227] It should be explained that, for example Figure 8 As shown in (b), in Comparative Example 1, no exothermic peak was generated within a specified time (e.g., within 12 minutes from the start of the cooling process, including 5 minutes of cooling time), so adhesion occurred during the drying process when recycling PET bottles with polyester heat shrink film installed.

[0228] also, Figure 8 In (a), line T is the temperature curve and line H is the characteristic curve corresponding to the heat flow stream.

[0229] Here, it is mentioned Figure 9 (a) and (b) illustrate the relationship between the heat equivalent to the exothermic peak area generated by isothermal crystallization of polyester heat shrink film and the evaluation of installability and anti-adhesion.

[0230] Right now, Figure 9 (a) is a graph used to illustrate the relationship between the heat equivalent to the area of ​​the exothermic peak generated by isothermal crystallization and the evaluation of installability. The horizontal axis is the heat equivalent to the area of ​​the exothermic peak generated by isothermal crystallization (J / g), and the vertical axis is the evaluation of installability (relative value).

[0231] but, Figure 9 Although the data in (a) are based on the examples and comparative examples described later, the data on the measurement and installation evaluation of examples with a heat shrinkage rate of 20 to 60% at 80°C are limited to the range of 20 to 60% since the heat shrinkage rate under specified measurement conditions has a great influence on the installation performance evaluation.

[0232] Then, according to the above Figure 9 The characteristic curve in (a) shows that even if the heat equivalent to the exothermic peak area is less than 5 J / g, or even if it exceeds 5 J / g but is within 35 J / g, the installation performance evaluation can still obtain a value of more than 2 in relative terms.

[0233] However, if the heat equivalent to the exothermic peak area exceeds 35 J / g, the installation performance evaluation is less than 2 and tends to decrease.

[0234] Therefore, it can be understood that by using a combination of specific polyester resins constituting the polyester-based heat-shrinkable film of the present invention, the heat equivalent to the exothermic peak area can be in a wide range of 8 to 32 J / g, more preferably in the range of 11 to 29 J / g, to achieve good installability effectively and quantitatively.

[0235] in addition, Figure 9 (b) The heat (J / g) equivalent to the exothermic peak area generated by isothermal crystallization of the polyester heat shrink film is shown on the horizontal axis, and the evaluation of anti-adhesion (relative value) is shown on the vertical axis.

[0236] Then, according to the above Figure 9 In the characteristic curve in (b), a decreasing trend in the evaluation of anti-adhesion was observed in the range where the heat equivalent to the exothermic peak area was less than 5 J / g.

[0237] Furthermore, even if the heat equivalent to the exothermic peak area is 5 to 35 J / g or higher, there is a trend towards obtaining a good evaluation of anti-adhesion properties, regardless of the heat value mentioned above.

[0238] However, if the heat is too high, the evaluation of the installation performance may be reduced.

[0239] Therefore, it can be understood that by setting the heat equivalent to the exothermic peak area to a value in a wide range of 8 to 32 J / g, and more preferably in the range of 11 to 29 J / g, good installability can be achieved, and adhesion can also be effectively and quantitatively suppressed.

[0240] (4) Thermal shrinkage rate 1

[0241] Polyester heat shrink film is characterized by having the following property (E) regarding the heat shrinkage rate under specified temperature conditions.

[0242] That is, the characteristic is that the heat shrinkage rate (sometimes called heat shrinkage rate 1) in the main shrinkage direction (usually the TD direction at the time of manufacturing), measured under heat shrinkage conditions of immersion in warm water at 80°C for 10 seconds, is a value in the range of 20% to 60%.

[0243] The reason is that by controlling the thermal shrinkage rate in the TD direction during heat shrinkage at a specified temperature to a value within a specified range, wrinkles are less likely to occur, and shrinkage marks are reduced, resulting in a better appearance.

[0244] In addition, by limiting the thermal shrinkage rate in the TD direction at higher temperatures, a balance in the overall thermal shrinkage of the polyester heat shrink film is achieved, thereby reducing the generated thermal shrinkage stress. Furthermore, even when recycled together with PET bottles, granules can be obtained more stably.

[0245] Therefore, it is more preferable to have a heat shrinkage rate in the TD direction that is in the range of 25% to 55%, and even more preferably in the range of 30% to 50%.

[0246] here, Figure 10 The figure shows the relationship between the heat shrinkage temperature (70°C, 80°C, 90°C, 100°C) and the heat shrinkage rate obtained at that temperature for the polyester heat shrink films of Examples 1-6 and Comparative Examples 1-5.

[0247] According to the above Figure 10 For the polyester heat-shrinkable films of Examples 1-6, the higher the heat-shrinkage temperature, the greater the heat shrinkage rate. For example, in the range of heat-shrinkage temperature of 70-80°C, there is a tendency for the heat shrinkage rate to become quite large. However, in the range of heat-shrinkage temperature exceeding 80°C, especially 90-100°C, a tendency to saturate in the range of heat shrinkage rate of about 30-50% is found.

[0248] In contrast, at least for the polyester heat shrink films of Comparative Examples 1 to 3, the higher the heat shrinkage temperature, the greater the heat shrinkage rate. Even in the range of 90°C to 100°C, it was found that the heat shrinkage rate tended to increase further.

[0249] Therefore, if the polyester heat-shrinkable film of Examples 1 to 6 of the present invention is used, a constant heat shrinkage rate can be obtained even if the value of the heat shrinkage temperature deviates slightly.

[0250] in addition, Figure 11 (a) to (b) are graphs showing the relationship between the heat shrinkage rate of polyester heat shrink film under specified shrinkage conditions and the evaluation of installability and anti-adhesion.

[0251] Right now, Figure 11 (a) The horizontal axis is shown using the heat shrinkage rate (%) of the polyester heat shrink film after immersion in warm water at 80°C for 10 seconds, and the vertical axis is shown using the evaluation of installability (relative value).

[0252] Then, according to the above Figure 11 In the characteristic curve in (a), when the heat shrinkage rate is less than 20%, a trend of significantly lower installability evaluation is found.

[0253] Furthermore, even if the heat shrinkage rate is in the range of 20% to 60%, or even exceeds 60%, good installability can be evaluated regardless of the heat shrinkage rate at 80°C.

[0254] Therefore, it can be understood that by using a heat shrinkage rate in the polyester heat shrink film of the present invention within the range of 20% to 60%, more preferably within the range of 25% to 50%, a stable evaluation of good installability can be obtained.

[0255] in addition, Figure 11 (b) The heat shrinkage rate (%) of the polyester heat shrink film after immersion in warm water at 80°C for 10 seconds is shown on the horizontal axis, and the evaluation of anti-adhesion (relative value) is shown on the vertical axis.

[0256] Then, according to the above Figure 11 The characteristic curve in (b) shows that even if the heat shrinkage rate is less than 20%, a good evaluation of anti-blocking property can be obtained. If it is in the range of more than 20% and less than 50%, a good evaluation of anti-blocking property can be obtained in a similar manner.

[0257] On the other hand, when the heat shrinkage rate exceeds 50% but is below about 60%, the evaluation of anti-adhesion is significantly reduced, but the evaluation of anti-adhesion to a degree that can be used in actual business is obtained.

[0258] Therefore, it can be understood that by using a heat shrinkage rate in the polyester heat shrink film of the present invention within the range of 20% to 60%, more preferably within the range of 25% to 50%, adhesion can be effectively and quantitatively suppressed.

[0259] (5) Thermal shrinkage rate 2

[0260] In addition, as a characteristic (F), it is preferable that the heat shrinkage rate (sometimes called heat shrinkage rate 2) in the direction orthogonal to the main shrinkage direction (usually the MD direction during manufacturing), measured under heat shrinkage conditions of immersion in warm water at 80°C for 10 seconds, is in the range of -3 to 10%.

[0261] The reason is that by controlling the heat shrinkage rate in the MD direction, which is measured under specified heat shrinkage conditions, within a specified range, wrinkles are less likely to occur, and shrinkage marks are reduced. As a result, a good appearance is easily obtained.

[0262] In addition, by limiting the heat shrinkage rate in the MD direction, a balance in the overall heat shrinkage of the polyester heat shrink film is achieved, which reduces the heat shrinkage stress generated. Even when recycled together with PET bottles, the adhesion phenomenon can be suppressed, and recycled particles can be obtained quantitatively and stably.

[0263] Therefore, as characteristic (F), it is more preferable to have the thermal shrinkage rate in the MD direction be in the range of -2 to 8%, and even more preferably in the range of 0 to 5%.

[0264] (6) Thermal shrinkage stress

[0265] In addition, as a characteristic (G), it is preferable that the heat shrinkage stress in the main shrinkage direction, measured under heat shrinkage conditions of immersion in warm water at 80°C for 10 seconds, is a value of 8 MPa or less.

[0266] The reason is that if the heat shrinkage stress exceeds 8 MPa, the same heat shrinkage stress as that of PVC heat shrink film cannot be obtained. As a result, it is sometimes impossible to obtain the versatility to cope with various PET bottles from thin-walled to thick-walled.

[0267] Therefore, it is more preferable to have the above-mentioned heat shrinkage stress in the range of 1 to 7 MPa, and even more preferably in the range of 2 to 6 MPa.

[0268] In addition, the heat shrinkage stress at 80°C can be calculated by dividing the heat shrinkage force (N / 15mm) of a strip-shaped test piece at 85°C, as measured by a film heat shrinkage tester according to ISO 14616-1997, by the thickness of the test piece.

[0269] (7) Thickness and haze

[0270] (7) -1 Thickness

[0271] In addition, the thickness of the polyester heat shrink film can be changed to correspond to the shape of various PET bottles, and is usually preferably in the range of 20 to 100 μm.

[0272] The reason is that if the thickness of the aforementioned polyester heat-shrinkable film is less than 20 μm, it is sometimes difficult to process, and the tensile strength and other properties are significantly reduced.

[0273] On the other hand, if the thickness of the aforementioned polyester heat-shrinkable film exceeds 100 μm, it may sometimes shrink unevenly when heated at a specified temperature, or it may be difficult to produce a uniform thickness.

[0274] Therefore, it is more preferable to have the thickness of the polyester heat-shrinkable film in the range of 25 to 70 μm, and even more preferably in the range of 30 to 50 μm.

[0275] It should be noted that the thickness of polyester heat shrink film can be measured using a micrometer (manufactured by Mitutoyo Corporation, product name "Thickness Gauge 547-401") according to ISO 4593.

[0276] (7) -2 Haze

[0277] In addition, for polyester heat-shrinkable films before shrinkage, it is preferable to have a haze value of 10% or less as measured according to ASTM D1003.

[0278] The reason is that by limiting the haze value to below a specified value, it is possible to produce PET bottles containing polyester heat-shrinkable films that make it easier to align PET bottles and inspect their contents. Furthermore, not only before heat shrinking, but also after heat shrinking, the transparency, appearance, and decorative properties are excellent.

[0279] Conversely, if the haze value exceeds 10%, the alignment and content recognition of PET bottles and other containers may be reduced, and even with a decorative layer, color rendering may be significantly reduced.

[0280] However, if the haze value is too low, the types and amounts of polymer components that can be used may be limited, making it difficult to control in manufacturing and resulting in excessively reduced production efficiency.

[0281] Therefore, it is more preferable to set the haze value to a value in the range of 1 to 8%, and even more preferably to set it to a value in the range of 2 to 5%.

[0282] (8) Functional layer, additives

[0283] (8) -1 Functional layer

[0284] Without prejudice to the purpose of the present invention, polyester heat shrinkable films are also preferably provided with functional layers on the surface and inner surface for imparting various functions as needed.

[0285] Examples of such functional layers include coatings, transfer layers, and printing layers used to impart surface smoothness, stain resistance, and durability.

[0286] Moreover, among these, especially if it is a coating layer using surfactants, it greatly helps to improve antistatic properties and surface smoothness, and is therefore a preferred way to use it as a functional layer.

[0287] For example, such as Figure 1 As shown in (b), it is also preferable to laminate other resin layers 10a, 10b containing at least one of these various additives onto one or both sides of the polyester heat shrink film 10.

[0288] In this case, when the thickness of the polyester heat shrink film is set to 100%, it is preferable that the single-layer thickness or total thickness of the additional resin layers is typically in the range of 0.1% to 10%.

[0289] Furthermore, the resin that forms the main component of the other resin layers can be the same polyester resin as the polyester heat shrink film, or preferably at least one of acrylic resin, olefin resin, polyurethane resin, rubber resin, etc., which are different from it.

[0290] Furthermore, it is also preferable to fabricate the polyester heat-shrinkable film into a multi-layer structure to further achieve hydrolysis resistance, mechanical protection, or other effects. Figure 1 As shown in (c), a shrinkage adjustment layer 10c is provided on the surface of the polyester heat shrink film 10 in such a way that the shrinkage rate of the polyester heat shrink film is uniform in the plane.

[0291] The aforementioned shrinkage adjustment layer can be laminated into a specified layer composed of polyester resin, etc., according to the shrinkage properties of the polyester heat shrink film, by means of adhesives, coating methods, or heat treatment.

[0292] (8) -2 Additives

[0293] Alternatively, it is preferable to incorporate various additives such as antioxidants, weather stabilizers, antistatic agents, antifogging agents, metallic soaps, waxes, mildew inhibitors, antibacterial agents, nucleating agents, flame retardants, and lubricants (slip agents) into the interior or surface of the polyester heat shrink film as needed (e.g., 0.01 to 10 parts by weight of the total amount), or to apply coatings (inks), wetting improvers, antistatic agents, etc.

[0294] In particular, it is preferable to contain inorganic lubricants and organic lubricants, or either, in a manner that improves the smoothness of the polyester heat shrink film and makes it easy to wind when made into long strips.

[0295] More specifically, as an inorganic lubricant, examples include at least one type of microparticle composed of calcium carbonate particles, silica particles, glass particles, zeolite, talc, kaolin, etc.

[0296] In addition, as an organic lubricant, examples include at least one particulate material composed of cross-linked polymethyl methacrylate, cross-linked polystyrene, silicone rubber, silicone copolymer, polyamide, condensation resin having a triazine ring, etc. Among them, the particulate material composed of silicone rubber and silicone copolymer can be moderately deformed and can exert good anti-blocking properties, and is therefore a more preferred organic lubricant.

[0297] [Second Implementation]

[0298] The second embodiment is a method for manufacturing a polyester heat-shrinkable film according to the first embodiment.

[0299] In addition, such as Figure 12 As shown, the recycling process for PET bottles coated with polyester heat-shrink film is also explained.

[0300] The following is a detailed explanation of each process.

[0301] 1. Raw material preparation and mixing process

[0302] As raw materials, prepare first polyester resin and second polyester resin, additives as needed, and other additive resins.

[0303] Next, it is preferable to weigh the above raw materials and put them into the mixing container at the same time, and use a stirring device to mix them until uniform.

[0304] 2. Production process of green sheet

[0305] Next, the obtained raw materials are preferably heated to a specified temperature (usually 10°C lower than the crystallization temperature) and dried in an absolutely dry state.

[0306] Next, extrusion molding (T-die method), blow molding, or casting molding is preferred to produce green sheets of the specified thickness.

[0307] More specifically, it is preferable to use a specified extruder, for example, to extrude the raw material at an extrusion temperature of 245°C to obtain a green sheet of a specified thickness (typically 200–300 μm).

[0308] 3. Fabrication of Polyester-Based Heat Shrink Film

[0309] Next, preferably, the obtained green sheet is heated and extruded using a heat shrink film manufacturing device (stenter) while it is moved on and between rollers to produce a polyester heat shrink film.

[0310] Furthermore, as a stretching treatment method for exhibiting the aforementioned shrinkage, the blow-blowing method, the roller stretching method, the tenter frame stretching method, and combinations thereof are preferred.

[0311] From the perspective of better productivity, the combination of sheet forming based on the casting method and roll stretching and tenter stretching is further optimized.

[0312] In addition, it is preferable that when making polyester heat shrink film, the film width is substantially expanded by using a specified stretching temperature and stretching ratio, and the film is stretched in a specified direction while being heated and extruded, so that the polyester molecules constituting the polyester heat shrink film crystallize into a specified structure.

[0313] Then, by curing it in this state, it is possible to produce heat-shrinkable polyester heat-shrinkable films for use as decorations, labels, etc.

[0314] It should be noted that, generally, after manufacturing the green sheet of the film using the T-die method, blow molding method, etc., the green sheet of the film is heated to a temperature above the glass transition temperature of the resin, and stretched in the main stretching direction (the width direction of the green sheet of the film, i.e., the TD direction) by about 3 to 8 times, preferably 4 to 6 times.

[0315] 4. Inspection procedures for polyester heat shrink film

[0316] In order to continuously or intermittently measure the following characteristics of the produced polyester heat shrink film, it is preferable to set up a prescribed inspection process.

[0317] That is, by measuring the following characteristics through a prescribed inspection process and confirming that the values ​​fall within a prescribed range, it is possible to provide polyester heat shrink film with more uniform shrinkage.

[0318] 1) Visual inspection of the appearance of polyester heat shrink film

[0319] 2) Determination of thickness deviation

[0320] 3) Tensile strength test (ASTM D882)

[0321] 4) Tensile elongation determination (ASTM D882)

[0322] 5) Surface smoothness inspection (ASTM D1894)

[0323] 6) Specific gravity determination (ASTM D792)

[0324] 7) Ring crush test (TAPPI T882)

[0325] 8) Tear strength test (ASTM D1922)

[0326] 5. Installation procedure for polyester heat shrink film

[0327] Preferably, the obtained polyester heat shrink film is used to install the PET bottle according to the following steps.

[0328] 1) Prepare commercially available PET bottles filled with drinking water.

[0329] 2) Next, the width end of the polyester heat shrink film is welded using a pulse sealing machine (manufactured by FUJI IMPULSE) to obtain a tubular label.

[0330] 3) Next, wrap the tubular label around the prepared cylindrical PET bottle.

[0331] 4) As an example, in a steam tunnel maintained at 80°C, the tube is placed on a conveyor belt and moved at a throughput speed of 6 m / min to perform heat shrinkage so that the tubular label is sealed to the cylindrical PET bottle.

[0332] It should be noted that infrared lamps, warm baths, etc., can also be used as other heating tools to replace the steam tunnel or in combination with the steam tunnel.

[0333] 6. PET bottle recycling process

[0334] Mention Figure 12 The flowchart provides a more detailed illustration of an example of the recycling process for PET bottles with used polyester heat-shrink film attached.

[0335] Figure 12In this context, S1 represents the process of compressing and bundling used PET bottles. This process ensures the good preservation and transportability of used PET bottles.

[0336] Next, step S2 involves using a debundling device to break down temporarily bundled used PET bottles into pieces a few centimeters in length, and then sorting and removing vinyl chloride bottles, colored bottles, etc. This process allows for the efficient recycling of only the used PET bottles in question.

[0337] Next, S3 represents the process of cleaning the used PET bottles to remove contaminants and residues.

[0338] Next, step S4 involves using a specified shredding device to break the cleaned PET bottles into fragments several millimeters in length. This shredding process, which produces fragments with an average particle size of several millimeters but a thickness of micrometers, ensures good operability for the next step.

[0339] Next, step S5 represents the process of removing the ink layer from the heat-shrink film. For example, this involves immersing the fragments obtained in step S4 in an ink-removing solution such as an alkaline hot water solution (e.g., sodium hydroxide solution) to remove the ink layer. This further reduces adhesion caused by the ink layer during the subsequent drying step.

[0340] Next, step S6 represents the process of separating the ink, the ink removal liquid, and cleaning the separated fragments.

[0341] Next, step S7 represents the process of drying the cleaned fragments obtained in step S6. This drying process further improves the operability of the next step.

[0342] Finally, step S8 involves heating and melting the fragments obtained in step S7 and using a granulator or similar device to produce recyclable pellets with an average particle size of, for example, 1 to 8 mm. By producing recyclable pellets with a uniform average particle size in this way, reuse in various applications becomes easier.

[0343] In this way, compared with the past, the process of manually removing the polyester heat shrink film installed on the PET bottle beforehand or removing it after crushing can be omitted. Therefore, the number of processes is reduced, the manufacturing cost is lowered, and it is also extremely advantageous in terms of economy and shortening the recycling time.

[0344] Therefore, if it is the polyester heat shrink film of the present invention, it can suppress adhesion even when installed in a PET bottle, and effectively and economically produce recyclable granules.

[0345] Example

[0346] The polyester heat shrink film of the present invention will be described in more detail below based on embodiments.

[0347] Unless otherwise specified, the scope of the present invention is not narrowed by the description of the embodiments.

[0348] In addition, the amorphous polyester resin and crystalline polyester resin (low-crystallinity polyester resin) used in the embodiments are as follows.

[0349] (First polyester resin: PET1)

[0350] An amorphous polyester resin composed of dicarboxylic acid: 100 mol% terephthalic acid, glycol: 63 mol% ethylene glycol, 24 mol% 1,4-cyclohexanediethanol, and 13 mol% diethylene glycol.

[0351] Glass transition temperature (Tg): 69℃

[0352] Melting point: None

[0353] (Second polyester resin: PET2)

[0354] A crystalline polyester resin, consisting of 100 mol% dicarboxylic acid: terephthalic acid and 100 mol% glycol: ethylene glycol, as homopolymer PET.

[0355] Glass transition temperature (Tg): 78℃

[0356] Melting point: 253℃

[0357] (Other second polyester resin: PET3)

[0358] A crystalline polyester resin, composed of dicarboxylic acid (98 mol% terephthalic acid), isophthalic acid (2 mol% terephthalic acid), glycol (97 mol% ethylene glycol), and diethylene glycol (3 mol% terephthalic acid), is used as a post-consumer recycled polyester resin (PCRP).

[0359] Glass transition temperature (Tg): 78℃

[0360] Melting point: 251℃

[0361] [Example 1]

[0362] 1. Fabrication of polyester heat shrink film

[0363] PET1, which is the first polyester resin, and PET2, which is the second polyester resin, are prepared respectively.

[0364] Next, add 700g of PET1, 300g of PET2 and 10g of lubricant to the mixing container, mix them evenly, and make the raw material for molding.

[0365] Next, the raw material for molding is extruded using a vented twin-shaft extruder at an extrusion temperature of 245°C to obtain a green sheet with a thickness of 250 μm.

[0366] Finally, using a heat shrink film manufacturing apparatus, a polyester-based heat shrink film with a thickness deviation of less than 5% is obtained from a green sheet at a preheating temperature of 120°C, a stretching temperature of 84°C, a heat setting temperature of 86.5°C, and a stretching ratio (MD direction: 1.06 times, TD direction: 4 times) with a thickness of 40μm.

[0367] 2. Evaluation of polyester heat shrink film

[0368] (1) Peak generation time of isothermal crystallization

[0369] The polyester heat-shrinkable film was subjected to isothermal crystallization measurement after undergoing the following pre-treatment process using a DSC (PerkinElmer, input-compensated dual-furnace differential scanning calorimeter, product name "DSC8500", hereinafter the same). Specifically, the time from the start of the cooling process (5 minutes) at a certain temperature (0°C) until the exothermic peak generated by isothermal crystallization was measured based on the DSC chart obtained from the isothermal crystallization measurement.

[0370] (Previous process)

[0371] 1) Keep the test sample isothermal at 30°C for 1 minute.

[0372] 2) Next, the temperature is increased from 30°C to 300°C at a rate of 750°C / minute.

[0373] 3) Next, maintain an isothermal temperature of 300℃ for 5 minutes.

[0374] 4) Next, cool it rapidly to 0°C.

[0375] (Isothermal crystallization determination)

[0376] 1) Maintain isothermal temperature at 0℃ for 5 minutes.

[0377] 2) Next, the temperature is increased from 0°C to 150°C at a rate of 750°C / minute.

[0378] 3) Next, crystallize by maintaining an isothermal temperature of 150°C for at least 10 minutes (15 minutes including the previous process).

[0379] (2) The heat equivalent to the area of ​​the exothermic peak generated by isothermal crystallization

[0380] Based on the DSC diagram obtained from the determination of the peak generation time of isothermal crystallization in (1) above, the heat release equivalent to the area of ​​the peak of isothermal crystallization is determined.

[0381] (3) Thermal shrinkage rate

[0382] The heat shrinkage rate of the obtained polyester heat shrink film was determined according to ASTM D2732-08.

[0383] That is, it is cut into a square shape with a length of 100 mm along the main contraction direction (TD direction) and a length of 100 mm along the direction orthogonal to the main contraction direction (MD direction), and used as the test sample.

[0384] Next, the test samples of the polyester heat-shrinkable film were immersed in a constant temperature bath containing 80°C warm water for 10 seconds to allow them to heat-shrink.

[0385] Next, at each temperature, based on the dimensional changes before and after heat treatment, the thermal shrinkage rate (%) in the main shrinkage direction and the direction orthogonal to the main shrinkage direction is calculated according to the following formula (1).

[0386]

[0387] (4) Thermal shrinkage force and thermal shrinkage stress

[0388] The heat shrinkage force of the obtained polyester heat shrink film was determined according to ISO 14616-1997.

[0389] That is, the obtained polyester heat shrink film is cut into strips with a length of 90 mm along the main shrinkage direction and a length of 15 mm along the direction orthogonal to the main shrinkage direction, and these are used as test pieces.

[0390] Next, a film heat shrinkage tester was used to determine the heat shrinkage force (N / 15mm) of the test piece after immersion in warm water at 80°C for 10 seconds.

[0391] Next, the obtained thermal shrinkage force is divided by the thickness (40 μm) to obtain the thermal shrinkage stress (MPa) at 80°C.

[0392] (5) Anti-adhesion

[0393] According to APR Document Code: PET-S-08, the anti-blocking properties of the obtained polyester heat shrink film were evaluated following the steps below.

[0394] 1) Install polyester heat-shrink film around the cylindrical bottle, empty the container and clean it. Next, while the polyester heat-shrink film is installed, crush the bottle into fragments with a diameter of less than 12.5 mm.

[0395] 2) Next, 1 kg of the pulverized fragments are placed in a heat-resistant container and heated in an oven at 210°C.

[0396] 3) Next, after 90 minutes, remove the heat-resistant container containing the fragments from the oven and allow it to cool naturally to room temperature.

[0397] 4) Next, use a 12.5mm mesh sieve for grading.

[0398] 5) Then, measure the mass of the aggregate that cannot pass through the sieve and calculate the agglomeration rate (%) using the following formula (2).

[0399]

[0400] 6) Based on the calculated cohesion rate, evaluate the anti-adhesion property according to the following criteria.

[0401] ○: A value with a cohesion rate of less than 5%.

[0402] △: A value with a cohesion rate of 5% or more but less than 10%.

[0403] ×: Values ​​with a cohesion rate of 10% or higher.

[0404] (6) Installation

[0405] The suitability of the obtained polyester heat shrink film for PET bottles was evaluated according to the following criteria.

[0406] That is, prepare 10 commercially available cylindrical PET bottles filled with drinking water (product name: Evian, volume: 500ml).

[0407] Next, corresponding to the cylindrical PET bottles, the width-direction ends of the polyester heat-shrink film are welded together using a pulse sealing machine (manufactured by FUJI IMPULSE) to produce 10 cylindrical labels.

[0408] Next, the 10 cylindrical labels were wrapped around 10 cylindrical PET bottles to serve as test samples.

[0409] Next, in a steam tunnel maintained at 85°C, the tube is moved at a throughput speed of 6 m / min while being placed on a conveyor belt, and heat shrinkage is performed to make the tubular label seal tightly to the cylindrical PET bottle.

[0410] Finally, visually inspect the finish of the heat-shrinked cylindrical label, i.e., whether there are defects such as wrinkles, insufficient shrinkage, label folding, and shrinkage whitening. Evaluate the installability of the polyester heat-shrink film according to the following criteria.

[0411] ◎: No defects were found in any of the 10 test samples.

[0412] 0: Among the 10 tested samples, the average number of defects was 1 to 3.

[0413] △: Among the 10 tested samples, there were an average of 4 to 5 defects.

[0414] ×: Among the 10 test samples, there were an average of more than 6 defects.

[0415] [Example 2]

[0416] In Example 2, as shown in Table 1, PET3 was used instead of PET2 as the second polyester resin. Otherwise, polyester heat-shrinkable films were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0417] [Example 3]

[0418] In Example 3, as shown in Table 1, the mixing ratio of the first polyester resin and the second polyester resin was 50 / 50. Otherwise, a polyester heat-shrinkable film was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0419] [Example 4]

[0420] In Example 4, as shown in Table 1, PET3 was used instead of PET2 as the second polyester resin, and the mixing ratio of the first polyester resin to the second polyester resin was 50 / 50. Otherwise, a polyester heat-shrinkable film was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0421] [Example 5]

[0422] In Example 5, as shown in Table 1, the mixing ratio of the first polyester resin to the second polyester resin was 30 / 70, and the stretch ratio in the TD direction was 2.5. Otherwise, a polyester heat-shrinkable film was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0423] [Example 6]

[0424] In Example 6, as shown in Table 1, PET3 was used instead of PET2 as the second polyester resin, and the mixing ratio of the first polyester resin to the second polyester resin was 30 / 70 with a stretch ratio of 2.5 in the TD direction. Otherwise, a polyester heat-shrinkable film was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0425] [Comparative Example 1]

[0426] In Comparative Example 1, as shown in Table 1, only PET1 was used as the first polyester resin, and the mixing ratio of the first polyester resin to the second polyester resin was 100 / 0. Otherwise, a polyester heat-shrinkable film was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0427] [Comparative Example 2]

[0428] In Comparative Example 2, as shown in Table 1, the mixing ratio of the first polyester resin to the second polyester resin was 90 / 10. Otherwise, a polyester heat-shrinkable film was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0429] [Comparative Example 3]

[0430] In Comparative Example 3, as shown in Table 1, PET3 was used instead of PET2 as the second polyester resin, and the mixing ratio of the first polyester resin to the second polyester resin was 90 / 10. Otherwise, a polyester heat-shrinkable film was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0431] [Comparative Example 4]

[0432] In Comparative Example 4, as shown in Table 1, only PET3 was used instead of PET2 as the second polyester resin, and the mixing ratio of the first polyester resin to the second polyester resin was 0 / 100. Otherwise, the polyester heat-shrinkable film was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0433] [Comparative Example 5]

[0434] In Comparative Example 5, as shown in Table 1, the mixing ratio of the first polyester resin to the second polyester resin was 30 / 70, and the value of the heat shrinkage rate corresponding to characteristic (E) was less than 20%. Otherwise, a polyester heat shrink film was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0435] [Table 1]

[0436]

[0437] [Table 2]

[0438]

[0439] Industrial availability

[0440] According to the present invention, by satisfying at least characteristics (A) to (E), adhesion can be suppressed even when PET bottles covered with polyester heat-shrink film are recycled while maintaining excellent installability.

[0441] That is, in particular, by controlling the exothermic peak time of characteristic (C) generated by isothermal crystallization and the heat equivalent to the exothermic peak area of ​​characteristic (D) within a specified range, it is possible to effectively and stably produce recycling particles of a specified shape.

[0442] Therefore, the polyester heat shrink film of the present invention can be recycled not only for coatings of various PET bottles, regardless of whether they are thin-walled or thick-walled, or even complex in shape, but also together with various PET bottles.

[0443] Therefore, by omitting the previously manual removal process of the installed polyester heat shrink film, manufacturing costs are reduced, which is extremely advantageous in terms of economics and the reduction of recycling time. It can be said that the industrial applicability is extremely high.

Claims

1. A polyester-based heat-shrinkable film, characterized in that, It is a polyester-based heat-shrinkable film derived from the reaction products of polycarboxylic acids and polyols, namely, a first polyester resin and a second polyester resin, which are various polyester resins with different crystallinity. The weight ratio of the first polyester resin to the second polyester resin is in the range of 20 / 80 to 80 / 20. The polyester heat shrink film satisfies the following characteristics (A) to (E). (A) The first polyester resin is an amorphous polyester resin in which the polycarboxylic acid contains more than 90 mol% terephthalic acid, the polyol contains at least ethylene glycol, 1,4-cyclohexanediethanol and diethylene glycol, and when the total amount of the polyol is set to 100 mol%, the amount of ethylene glycol reacting is in the range of more than 50 mol% and less than 90 mol%, and the amounts of 1,4-cyclohexanediethanol and diethylene glycol reacting are in the range of 1 to 35 mol%. (B) The second polyester resin is a crystalline polyester resin in which the polycarboxylic acid contains more than 90 mol% terephthalic acid, and when the total amount of the polyol is set to 100 mol%, the amount of ethylene glycol reacted is more than 90 mol%. (C) refers to polyester heat-shrinkable films that exhibit an exothermic peak within 12 minutes from the start of isothermal crystallization at 150°C, including the cooling process, under DSC conditions. (D) refers to polyester heat-shrinkable films with a heat equivalent to the obtained exothermic peak area in the range of 5–35 J / g, under the condition of isothermal crystallization measurement at 150°C including a cooling process at 0°C using DSC. (E) is a polyester heat shrink film with a heat shrinkage rate in the main shrinkage direction ranging from 20% to 60%, determined by immersion in warm water at 80°C for 10 seconds.

2. The polyester-based heat-shrinkable film according to claim 1, characterized in that, The weight-based mixing ratio of the first polyester resin and the second polyester resin is a value in the range of more than 50 / 50 and less than 80 / 20.

3. The polyester-based heat-shrinkable film according to claim 1 or 2, characterized in that, The second polyester resin is a crystalline polyester resin that contains ethylene glycol alone or both ethylene glycol and diethylene glycol. When the total amount of the polyol is 100 mol%, the amount of ethylene glycol reacting is 90 mol% or more, and the amount of diethylene glycol reacting is in the range of 1 to 10 mol%.

4. The polyester-based heat-shrinkable film according to claim 1 or 2, characterized in that, The second polyester resin is a post-consumer recycled polyester resin.

5. The polyester-based heat-shrinkable film according to claim 1 or 2, characterized in that, When the total amount of the first polyester resin and the second polyester resin is set to 100 parts by weight, it contains a lubricant in the range of 0.01 to 5 parts by weight.

6. The polyester-based heat-shrinkable film according to claim 1 or 2, characterized in that, Further satisfy the following property (F) (F) The heat shrinkage rate in the direction orthogonal to the main shrinkage direction, determined under the heat shrinkage condition of immersion in warm water at 80°C for 10 seconds, is a value in the range of -3% to 10%.

7. The polyester-based heat-shrinkable film according to claim 1 or 2, characterized in that, Further satisfy the following characteristic (G). (G) The thermal shrinkage stress in the main shrinkage direction, measured under thermal shrinkage conditions of 80°C and 10 seconds, is less than 8 MPa.

Images