Polyester heat-shrinkable film

Abstract

The present invention relates to a heat-shrinkable polyester film showing a low shrink stress value like a vinyl chloride resin film. That is, a polyester-based heat-shrinkable film obtained from a plurality of non-crystalline polyester resins which are reaction products of a polybasic acid and both a first polyol having an alicyclic structure and a second polyol not having an alicyclic structure, has a heat-shrinkage stress of less than 6.8 MPa measured at 85°C.

Description

Technical Field

[0001] This invention relates to polyester-based heat-shrinkable films.

[0002] More specifically, it relates to polyester heat-shrinkable films that are mainly composed of amorphous polyester resins but exhibit low heat shrinkage stress comparable to that of vinyl chloride resin films. Background Technology

[0003] Previously, containers for beverages and detergents were made of high-density polyethylene (HDPE) and bottles of polyester (PET) (hereinafter sometimes simply referred to as PET bottles).

[0004] Especially as a beverage container, PET bottles have advantages such as being lightweight and highly durable, and are extremely convenient, making them widely used around the world.

[0005] On the other hand, the pollution caused by the empty PET bottles flowing into the ocean after the contents are consumed has become a profound and global problem.

[0006] Therefore, in order to solve the above-mentioned environmental problems, we are actively conducting research on PET bottle recycling and circularity technologies.

[0007] In addition, various labels are covered or affixed to the outer wall of PET bottles to indicate information about their name and contents.

[0008] In the past, paper labels were mostly pasted using adhesives, but in recent years, full-coverage packaging using heat-shrink film has become the mainstream.

[0009] Judging from the structure of the full-coverage packaging using heat-shrink film, which deforms when tightly sealed to the outer wall of the PET bottle, it is difficult to completely separate it from the PET bottle.

[0010] Therefore, materials that do not hinder the recycling process of PET bottles are preferred as heat shrink film materials.

[0011] Therefore, alternatives to vinyl chloride resin (PVC), polystyrene resin (PS), and modified polyester resin (PETG) have generally been tried as materials for heat shrink film.

[0012] However, as mentioned above, the main material of beverage containers is PET resin. Considering the similarity of raw material composition, PETG film is also considered suitable for the recyclability of PET bottles.

[0013] However, PETG films exhibit sharp shrinkage behavior as temperature rises, and show that their shrinkage stress is greater than that of other materials.

[0014] In other words, when PETG film is used in PET bottles, there are problems such as label damage due to rapid shrinkage, or container deformation due to high shrinkage stress, which may even lead to a decrease in the yield rate in manufacturing.

[0015] In recent years, in order to reduce the use of fossil resources, the wall thickness of PET bottles has been actively reduced. With this reduction in wall thickness, the overall rigidity of the bottle is also reduced, making the reduction of shrinkage stress in the heat-shrinkable film a top priority.

[0016] Therefore, in order to reduce shrinkage stress and improve impact resistance, it is proposed to add a specified polyester plasticizer to the raw materials of polyester heat shrink film (for example, see Patent Document 1).

[0017] More specifically, the aforementioned polyester-based heat-shrinkable film contains (a) a minimum half-crystallization time (t 1 / 2 (a) copolyester with a minimum of 8.6 minutes and (b) weight-average molecular weight (M w It is a polyester plasticizer with a concentration of 900–12000 g / mol.

[0018] In addition, copolyesters include:

[0019] (i) A dicarboxylic acid component containing 100 mol% terephthalic acid residues, and

[0020] (ii) A diol component containing residues of ethylene glycol, 1,4-cyclohexanediol, diethylene glycol, neopentyl glycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, or mixtures thereof.

[0021] In addition, the polyester plasticizer includes:

[0022] (i) a polyol component containing residues of 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, or mixtures thereof, and

[0023] (ii) A dicarboxylic acid component containing residues of phthalic acid, adipic acid, or mixtures thereof.

[0024] Furthermore, the glass transition temperature of polyester heat shrink film, measured under specified conditions, is 50–90°C.

[0025] Existing technical documents

[0026] Patent documents

[0027] Patent Document 1: Japanese Patent Application Publication No. 2018-168382 (claims, etc.) Summary of the Invention

[0028] However, in the polyester heat shrink film described in Patent Document 1, the specified polyester plasticizer may exhibit the following trend: it may seep out with changes in ambient temperature and over time, thereby reducing the heat shrinkage rate and mechanical properties. Furthermore, depending on the amount added, properties such as transparency and electrical properties may also decrease.

[0029] Therefore, the inventors of this invention have made great efforts to solve the above-mentioned problems and have found that by using a specified polyol (sometimes simply referred to as diol component) as one of the raw material components, it is possible to obtain a relatively low heat shrinkage stress that is comparable to that of polyvinyl chloride heat shrink film, which has a substantially amorphous portion.

[0030] That is, it was found that as long as the polyester heat shrink film with a relatively small heat absorption of the melting peak as measured by differential scanning calorimetry (DSC) and a specified glass transition temperature is a heat shrink film, a relatively low heat shrinkage stress is obtained.

[0031] Therefore, the object of the present invention is to provide a polyester heat shrink film that is mainly composed of a polyester resin having a substantially amorphous portion but exhibits low shrinkage stress comparable to that of polyvinyl chloride heat shrink film, thereby having excellent usability and applicability to various PET bottles, and generating few environmental problems.

[0032] In constituting the present invention (hereinafter sometimes referred to as the first invention), a polyester-based heat shrinkable film is provided, which is a polyester-based heat shrinkable film obtained from a mixture of various amorphous polyester resins, wherein the various amorphous polyester resins are reaction products of polycarboxylic acids and polyols, and the mixture of resins comprises a first polyester resin made using a first polyol having an alicyclic structure and a second polyester resin made using a second polyol not having an alicyclic structure, and the heat shrinkage stress of the polyester-based heat shrinkable film measured at 85°C is less than 6.8 MPa.

[0033] That is, by using specified polyols, it is possible to provide a polyester heat shrink film that is essentially amorphous, even when it is obtained from a resin mixture of a first amorphous polyester resin and a second amorphous polyester resin, exhibiting low shrinkage stress comparable to that of vinyl chloride resin films, excellent usability and suitability for various PET bottles, and with minimal environmental problems.

[0034] Furthermore, by using specific polyols in the first and second polyols with different polyol compositions, the glass transition temperature and compatibility of the first and second polyester resins can be adjusted, thereby making the value of thermal shrinkage stress less than the specified value.

[0035] In addition, when constituting the first invention, the first polyol preferably contains at least 1,4-cyclohexanediethanol, and the second polyol preferably contains at least 2-methyl-1,3-propanediol.

[0036] In this way, by using specific polyols in the first polyol and the second polyol respectively, it is easier to adjust the glass transition temperature, compatibility, etc., and further, it is also easier to adjust the heat shrinkage stress of the basically amorphous polyester heat shrink film.

[0037] Furthermore, when constituting the first invention, it is preferable to set the mixing ratio (by weight) of the first polyester resin and the second polyester resin to a value in the range of 20 / 80 to 80 / 20.

[0038] By controlling the mixing ratio (by weight) of the first polyester resin and the second polyester resin in this way, the properties of the essentially amorphous polyester resin can be maintained in the polyester heat shrink film, and the heat shrinkage stress at a specified temperature can be easily and stably adjusted.

[0039] Furthermore, in constituting the first invention, it is preferable to set the glass transition temperature (Tg1) of the first polyester resin to be higher than the glass transition temperature (Tg2) of the second polyester resin, and to set the glass transition temperature of the first polyester resin to a value in the range of 60 to 90°C, and to set the glass transition temperature of the second polyester resin to a value in the range of 50 to 80°C, and to have a baseline offset corresponding to a glass transition temperature in the range of 63 to 70°C during DSC measurement.

[0040] In this way, by controlling the glass transition temperatures (Tg1 and Tg2) of the first and second polyester resins within a specified range based on the relationship between their glass transition temperatures, it is possible to maintain the properties of the essentially amorphous polyester resin, and to more easily and stably adjust the values ​​of shrinkage stress and the like at the specified temperature to the desired range.

[0041] It should be noted that baseline shift refers to the deviation of the DSC curve obtained in DSC measurement from the previous baseline and its shift to a new baseline, as described in JIS K7121:2012, such as a step change.

[0042] Furthermore, when constituting the first invention, it is preferable to set the intrinsic viscosity of the first amorphous polyester resin to a value in the range of 0.65 to 0.85 dL / g, set the intrinsic viscosity of the second amorphous polyester resin to a value in the range of 0.65 to 0.85 dL / g, and set the difference between the intrinsic viscosity of the first amorphous polyester resin and the intrinsic viscosity of the second amorphous polyester resin to a value of ±0.2 dL / g or less.

[0043] By controlling the inherent viscosity of the first and second polyester resins in this way, not only can good mixing uniformity be obtained, but the characteristics of the essentially amorphous polyester resin can also be maintained, and the values ​​of shrinkage stress and other parameters at a specified temperature can be adjusted more easily and stably to the desired range.

[0044] Furthermore, when constituting the first invention, it is preferable to set the heat shrinkage rate in the main shrinkage direction measured at 70°C to a value in the range of 25 to 40%, and the heat shrinkage rate measured at 85°C to a value in the range of 55 to 75%.

[0045] In this way, by controlling the value of the heat shrinkage rate at a specified temperature, it is possible to maintain the properties of the essentially amorphous polyester resin, and it is easier and more stable to adjust the values ​​of shrinkage stress, etc., at the specified temperature to the desired range.

[0046] Furthermore, when constituting the first invention, when the thermal shrinkage rate in the main shrinkage direction of the object placed in an atmosphere of 23°C and 50%RH for 60 days and then immersed in hot water at 65°C is set as A1 (%) and A2 (%), the values ​​represented by A1-A2 are preferably in the range of 13 to 25%.

[0047] In this way, by controlling the change in the thermal shrinkage rate of the main shrinkage direction measured at 65°C before and after aging treatment within a specified range, it is easier and more stable to adjust the thermal shrinkage of the main shrinkage direction at the actual operating temperature of 70–85°C.

[0048] Furthermore, when constituting the first invention, when the heat shrinkage rate in the direction perpendicular to the main shrinkage direction after being immersed in hot water at 85°C for 60 days under an atmosphere of 23°C and 50%RH is set as B1 (%) and B2 (%), it is preferable that the values ​​represented by B1-B2 are in the range of 0 to 5%.

[0049] By controlling the heat shrinkage rate in the main shrinkage direction when immersed in hot water at 85°C before and after the specified aging treatment within a specified range, the heat shrinkage properties when actually used in various PET bottles can be adjusted more precisely.

[0050] Furthermore, when constructing the first invention, it is preferable that even when the polyester heat shrink film has a melting peak in the DSC measurement, the melting peak temperature is set to a value in the range of more than 164°C and less than 170°C, and the heat equivalent to the melting peak area is set to a value in the range of 6 to 18 mJ / mg.

[0051] In this way, even when a melting peak is present in the DSC measurement, by controlling the temperature (melting point) of the melting peak to a value within a specified range, and by controlling the heat equivalent to the melting peak area to a value within a specified range, it is possible to limit the proportion of the crystalline structure relative to the total amount and adjust it to include a wide melting region.

[0052] Therefore, by incorporating a relatively small crystalline structure into a polyester heat-shrinkable film that is essentially amorphous, it is possible to maintain mechanical strength, transparency, etc., and to more easily and stably adjust the values ​​of specified heat-shrinkage stress and heat shrinkage rate at specified temperatures.

[0053] In addition, another aspect of the present invention (hereinafter, sometimes referred to as the second invention) is a polyester heat-shrinkable film obtained from a single amorphous polyester resin, wherein the single amorphous polyester resin is a reaction product of a polycarboxylic acid and a polyol, wherein the polyol is a mixture of a first polyol having an alicyclic structure and a second polyol not having an alicyclic structure, and wherein the heat shrinkage stress of the polyester heat-shrinkable film measured at 85°C is less than 6.8 MPa.

[0054] That is, in the second invention, it is possible to maintain the properties of a polyester resin that has a substantially amorphous portion, and it is easier and more stable to adjust the values ​​of heat shrinkage stress, etc., at a specified temperature to the desired range.

[0055] Furthermore, it is a polyester heat shrink film that provides very low shrinkage stress, excellent usability and applicability to various PET bottles, and causes very few environmental problems, without actually using plasticizers or the like.

[0056] In addition, when constituting the second invention, the first polyol preferably contains at least 1,4-cyclohexanediethanol, and the second polyol preferably contains at least 2-methyl-1,3-propanediol.

[0057] In this way, by using specific polyols in the first and second polyols respectively, it becomes easier to adjust the glass transition temperature, the compatibility, etc., and consequently, it becomes easier to adjust the heat shrinkage stress of the obtained polyester heat shrink film.

[0058] Furthermore, when constituting the second invention, it is preferable that when the total amount of the polyol is set to 100% by weight, the total amount of the first polyol and the second polyol is in the range of 15% to 40% by weight.

[0059] In this way, by controlling the total amount of specified polyols, which are one of the raw materials, it becomes easier to adjust the heat shrinkage stress and other properties of polyester heat shrink films that have a substantial amorphous component.

[0060] Furthermore, when constructing the second invention, it is preferable to set the mixing ratio (by weight) of the first polyol to the second polyol to a value in the range of 10 / 90 to 90 / 10.

[0061] In this way, by controlling the mixing ratio of the specified polyols, which are one of the raw materials, it is possible to maintain the properties of polyester resins that have a substantially amorphous portion, and to easily and stably adjust the values ​​of heat shrinkage stress, etc., at a specified temperature.

[0062] Furthermore, in constituting the second invention, it is preferable that the DSC measurement has a baseline offset corresponding to a glass transition temperature in the range of 63 to 70°C.

[0063] In this way, by having a point of change in glass transition temperature within a specified temperature range in DSC measurements, it is possible to maintain the properties of polyester resins that have a substantially amorphous portion, and to more easily and stably adjust the values ​​of heat shrinkage stress, etc., at the specified temperature.

[0064] Furthermore, when constructing the second invention, it is preferable to set the heat shrinkage rate in the main shrinkage direction measured at 70°C to a value in the range of 25 to 40%, and the heat shrinkage rate measured at 85°C to a value in the range of 55 to 75%.

[0065] In this way, by controlling the value of the heat shrinkage rate at a specified temperature, it is possible to maintain the properties of polyester resin that has a substantially amorphous portion, and it is easier and more stable to adjust the values ​​of heat shrinkage stress, etc., at the specified temperature.

[0066] Furthermore, when constituting the second invention, when the thermal shrinkage rate in the main shrinkage direction after being immersed in hot water at 65°C for 60 days under an atmosphere of 23°C and 50%RH is set as A1 (%) and A2 (%), the values ​​represented by A1-A2 are preferably in the range of 13 to 25%.

[0067] In this way, by controlling the change in the thermal shrinkage rate of the main shrinkage direction measured at 65°C before and after aging treatment to a value within a specified range, it is easier and more stable to adjust the thermal shrinkage of the main shrinkage direction at the actual operating temperature of 70-85°C.

[0068] Furthermore, when constituting the second invention, when the heat shrinkage rate in the direction perpendicular to the main shrinkage direction after being immersed in hot water at 85°C for 60 days under an atmosphere of 23°C and 50%RH is set as B1 (%) and B2 (%), it is preferable that the values ​​represented by B1-B2 are in the range of 0 to 5%.

[0069] By controlling the heat shrinkage rate in the main shrinkage direction when immersed in hot water at 85°C before and after such aging treatment to a value within a specified range, the heat shrinkage properties when actually used in various PET bottles can be adjusted more precisely.

[0070] Furthermore, when constructing the second invention, it is preferable that even when the polyester heat shrink film has a melting peak in the DSC measurement, the melting peak temperature is set to a value in the range of more than 164°C and less than 170°C, and the heat equivalent to the melting peak area is set to a value in the range of 6 to 18 mJ / mg.

[0071] In this way, even when a melting peak is present in the DSC measurement, by controlling the temperature (melting point) of the melting peak to a value within a specified range, and by controlling the heat equivalent to the area of ​​the melting peak to a value within a specified range, it is possible to limit the proportion of the crystalline structure relative to the total amount, and adjust it to include a wide melting region. Attached Figure Description

[0072] Figures 1A-1C These are diagrams used to illustrate different forms of polyester heat shrink film.

[0073] Figures 2A-2B These are the DSC curves of the first polyester resin (PETG1) and the second polyester resin (PETG2) of the present invention (the first invention), respectively.

[0074] Figures 3A-3D The TG-DTA curves are those of the polyester heat-shrinkable film of Example 1, Example 2, and Comparative Example 1, and the second polyester resin (PETG2).

[0075] Figures 4A-4D The FT-IR curves are those of the polyester heat-shrinkable film of Example 1, Example 2, and Comparative Example 1, and the second polyester resin (PETG2).

[0076] Figures 5A-5B These are figures illustrating the effect of the mixing ratio of the first polyester resin (PETG1) and the second polyester resin (PETG2) of the present invention (the first invention) on the heat shrinkage stress and glass transition temperature.

[0077] Figure 6A The thermal shrinkage rates of Embodiment 1, Comparative Example 1, and Comparative Example 3 of the present invention (the first invention) are shown. Figure 6B This indicates the heat shrinkage rate (before and after aging treatment) of Examples 1 and 3 of the present invention (first invention). Furthermore, Figure 6C The thermal shrinkage rates (before and after aging treatment) of Comparative Examples 2 and 4 of the present invention (the first invention) are shown.

[0078] Figures 7A-7B The figures are the DSC curves of the polyester heat shrink film of Example 1 of the present invention (the first invention) and the DSC curves of the polyester heat shrink film of Comparative Example 1, respectively.

[0079] Figure 8 This is a graph used to illustrate the relationship between the melting point (°C) and heat shrinkage stress (MPa) of the polyester heat shrink film of the present invention (first invention). Detailed Implementation

[0080] [First Implementation]

[0081] like Figures 1A-1C As illustrated, the first embodiment is a polyester heat-shrinkable film 10 obtained from a mixture of various amorphous polyester resins that are reaction products of polycarboxylic acids and polyols.

[0082] Furthermore, it is a polyester heat-shrinkable film comprising a first polyester resin made using a first polyol having an alicyclic structure and a second polyester resin made using a second polyol not having an alicyclic structure, and having a heat shrinkage stress of less than 6.8 MPa measured at 85°C.

[0083] That is, the first embodiment is a polyester heat-shrinkable film that is substantially amorphous and is obtained from a mixture of a specified first polyester resin and a second polyester resin made using a different polyol.

[0084] Hereinafter, the first embodiment (hereinafter, sometimes referred to as the first invention) will be divided into various components, and will be specifically described with reference to the accompanying drawings as appropriate.

[0085] 1. Polycarboxylic acids

[0086] As one of the constituent components (raw material components) of polyester resin, polycarboxylic acids include fatty acid 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.

[0087] In particular, if the polycarboxylic acid is terephthalic acid, it reacts well with polyols and is relatively inexpensive, making it economically advantageous and therefore preferred.

[0088] 2. Polyols

[0089] (1) First polyol

[0090] In addition, the first polyester resin (hereinafter, sometimes referred to as a high Tg product), which is one of the raw material components of the polyester resin, is characterized by using a first polyol having at least an alicyclic structure.

[0091] That is, in the first polyester resin, by using a specific polyol as a raw material component, it is possible to achieve a relatively high glass transition temperature in the amorphous polyester resin obtained by reacting with polycarboxylic acids, and to easily adjust the heat shrinkage rate, heat shrinkage stress, etc., to values ​​within the desired range.

[0092] Therefore, the first polyol is preferably at least one adduct of an alcohol having an alicyclic structure, such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanediethanol, 1,4-cyclohexanediethanol, 5-norbornene-2,3-diethanol, hydrogenated bisphenol A, spirodiol, isosorbide, etc., and epoxides (ethylene oxide, propylene oxide, butane oxide, etc.) of alcohols having these alicyclic structures.

[0093] In particular, if the first polyol is 1,4-cyclohexanediethanol, it reacts with the polycarboxylic acid in an accurate proportion, resulting in a small amount of unreacted components. Consequently, in the obtained first polyester resin, the glass transition temperature can be easily adjusted to the desired range, and the heat shrinkage rate, heat shrinkage stress, etc., can be easily adjusted to values ​​within the desired range. Therefore, it is a more preferred polyol component.

[0094] Furthermore, if the first polyol contains at least 1,4-cyclohexanediethanol and further contains a specified amount of ethylene glycol and diethylene glycol, the resulting first polyester resin also exhibits good compatibility with the second polyester resin obtained from the second polyol, as described later. This makes it easier to adjust the glass transition temperature, thermal shrinkage rate, thermal shrinkage stress, etc., to values ​​within the desired range, thus making it the most preferred option.

[0095] Therefore, when the total amount of the first polyol is set to 100 mol%, it is preferable to set the content of 1,4-cyclohexanediethanol to 20-35 mol%, the content of ethylene glycol to 50-65 mol%, and the content of diethylene glycol to a range of 5-20 mol%.

[0096] In addition, if the total amount exceeds 100% by weight, the diols of the first polyol can be allocated proportionally; conversely, if it is less than 100% by weight, it is preferable to include diols other than these diols.

[0097] (2) Second polyol

[0098] In addition, the second polyester resin (hereinafter, sometimes referred to as low Tg product) is characterized by the use of a second polyol, which is a polyol without an alicyclic structure, i.e., a straight-chain compound with branches or a straight-chain compound without branches.

[0099] Therefore, in the second polyester resin, by using a specific polyol as a raw material, the resulting polyester resin can have a relatively low glass transition temperature, at least lower than that of the first polyester resin, and the heat shrinkage rate, heat shrinkage stress, etc. can be easily adjusted to values ​​within the desired range.

[0100] Therefore, as the second polyol, at least one of ethylene glycol, diethylene glycol, propylene glycol, butanediol, hexanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, and 2,2-dimethyl-1,3-propanediol (neopentyl glycol) is preferably used.

[0101] In particular, if the second polyol is at least 2-methyl-1,3-propanediol, it reacts with the polycarboxylic acid in an accurate proportion, resulting in a small amount of unreacted components. Consequently, in the resulting second polyester resin, the glass transition temperature can be adjusted to the desired range, and the heat shrinkage rate and heat shrinkage stress can be easily adjusted to the desired values. Therefore, it is a more preferred polyol component.

[0102] Furthermore, if the second polyol contains at least 2-methyl-1,3-propanediol, and further contains a specified amount of ethylene glycol and diethylene glycol respectively, then a considerable amount of crystalline portion can be introduced into the obtained second polyester resin while keeping the amount of crystalline portion relatively small.

[0103] Furthermore, by including such a specified amount of ethylene glycol and diethylene glycol, the second polyester resin obtained has better compatibility with the first polyester resin, and it is easier to adjust the glass transition temperature, thermal shrinkage rate, thermal shrinkage stress, etc., to values ​​within the desired range, thus making it the optimal choice.

[0104] Therefore, as an example, when the total amount of the second polyol is set to 100 mol%, it is preferable to have a mixture in the range of 20 to 30 mol% of 2-methyl-1,3-propanediol, 50 to 65 mol% of ethylene glycol, and 5 to 20 mol% of diethylene glycol.

[0105] In addition, if the total amount of the mixture exceeds 100 mol%, the diols of the second polyol can be allocated proportionally; conversely, if it is less than 100 mol%, it is preferable to include other diol components besides these diols to fill it.

[0106] 3. Polyester resin

[0107] (1) First polyester resin

[0108] The first polyester resin is an amorphous polyester resin obtained by reacting a polyol having an alicyclic structure, such as at least 1,4-cyclohexanediethanol as a first polyol that is one of the raw material components, with a polycarboxylic acid.

[0109] Therefore, a polyester resin with a relatively large amorphous portion, formed by reacting 1,4-cyclohexanediethanol with a dicarboxylic acid composed of 60 to 80 mol% of terephthalic acid, is preferred, for example.

[0110] In addition, the first polyol may be a polyol having an alicyclic structure alone, and more preferably a mixture of polyols having alicyclic structures.

[0111] As a polyol that does not have an alicyclic structure, it is preferred to select one or more diol components from ethylene glycol, diethylene glycol, hexanediol, neopentyl glycol, etc.

[0112] More specifically, when the total amount of the first polyol is set to 100 mol%, it is also preferable to use polyols without alicyclic structures in combination in the range of, for example, 10 to 150 mol%.

[0113] Furthermore, depending on the need, in order to change the thermal and mechanical properties of polyester heat shrink film, other dicarboxylic acids and diols or hydroxycarboxylic acids can be used, either individually or as a mixture.

[0114] Furthermore, when constituting the first invention, provided that the glass transition temperature (Tg1) of the first polyester resin is higher than that of the second polyester resin, it is preferable to make the glass transition temperature (Tg1) of the first polyester resin in the range of 60 to 90°C.

[0115] The reason is that when Tg1 is less than 60℃, the heat resistance and durability of the first polyester resin are significantly reduced, which in turn increases the natural shrinkage of the polyester heat shrink film containing the first polyester resin and significantly reduces its shelf life.

[0116] On the other hand, this is because if Tg1 is a value exceeding 90°C, it is difficult to accurately adjust the heat shrinkage of the polyester heat shrink film, especially since the heat shrinkage rate measured below 85°C is prone to being outside the specified range.

[0117] Therefore, it is more preferable for Tg1 to be a value in the range of 55 to 75°C, and even more preferably a value in the range of 58 to 72°C.

[0118] here, Figure 2A An example of the DSC curve of the first polyester resin obtained by DSC according to JIS K7121:2012 is shown.

[0119] That is, as step 1, the sample to be measured is heated from 25°C to 280°C at a heating rate of 10°C / min using a DSC device.

[0120] Next, as step 2, the temperature is rapidly reduced from 280°C to 25°C at a rate of 30°C / min.

[0121] Furthermore, as step 3, the temperature is increased from 25°C to 280°C at a heating rate of 10°C / min, and the glass transition temperature (Tg1) of the first polyester resin is accurately determined based on the temperature of the specific heat change point of the DSC curve obtained therefrom.

[0122] It should be noted that the glass transition temperature (Tg1) is determined according to JIS K7121:2012 (hereinafter the same), and the Tg1 mentioned above is the temperature of the specific heat change point obtained in step 3.

[0123] Furthermore, when constituting the first invention, it is preferable that the intrinsic viscosity (IV value) of the first polyester resin is in the range of 0.65 to 0.85 dL / g.

[0124] Furthermore, in relation to the intrinsic viscosity (IV value) of the second polyester resin described later, it is preferable that the difference between the intrinsic viscosity and that of the first polyester resin is ±0.2 dL / g or less.

[0125] The reason is that if the intrinsic viscosity of the first polyester resin is less than 0.65 dL / g, the melt viscosity of the first polyester resin is too low, which sometimes causes problems with extrusion molding.

[0126] On the other hand, if the intrinsic viscosity of the first polyester resin is greater than 0.85 dL / g, the uniformity of mixing with the second polyester resin is sometimes significantly reduced.

[0127] Moreover, if the inherent viscosity of the first polyester resin is too high, the melt viscosity will also become too high, which can sometimes cause problems with extrusion molding.

[0128] Furthermore, because in relation to the intrinsic viscosity (IV value) of the second polyester resin, if the difference between the intrinsic viscosity and that of the first polyester resin exceeds ±0.2 dL / g, the compatibility and miscibility of the first and second polyester resins are sometimes significantly reduced.

[0129] Therefore, it is more preferable that the intrinsic viscosity of the first polyester resin is in the range of 0.68 to 0.83 dL / g, more preferably in the range of 0.7 to 0.8 dL / g, and even more preferably the difference between the intrinsic viscosity of the first polyester resin and the second polyester resin is in the range of ±0.1 dL / g.

[0130] It should be noted that the intrinsic viscosity of the first polyester resin and the second polyester resin can be determined according to JIS K7390 (hereinafter the same).

[0131] (2) Second polyester resin

[0132] The second polyester resin is, for example, an amorphous polyester resin obtained by reacting 2-methyl-1,3-propanediol as a second polyol with a polycarboxylic acid.

[0133] Therefore, for example, it is preferable to use an amorphous polyester resin prepared by reacting the above-mentioned second polyol, such as 2-methyl-1,3-propanediol, with a dicarboxylic acid composed of 100 mol% terephthalic acid in a ratio of 20 to 40 mol%.

[0134] Furthermore, depending on the need to change the properties of the membrane, other dicarboxylic acids and diols or hydroxycarboxylic acids are preferred to be used individually or as a mixture.

[0135] Furthermore, when constituting the first invention, it is preferable that the glass transition temperature (Tg2) of the second polyester resin is lower than the glass transition temperature (Tg1) of the first polyester resin, and that the glass transition temperature (Tg2) is a value in the range of 50 to 80°C.

[0136] The reason is that if Tg2 is less than 50℃, the heat resistance and durability of the second polyester resin will sometimes be significantly reduced. Consequently, the natural shrinkage of the polyester heat shrink film containing the second polyester resin will increase and its shelf life will be significantly reduced.

[0137] On the other hand, if Tg2 is a value exceeding 80°C, it is sometimes difficult to accurately adjust the heat shrinkage of the obtained polyester heat shrink film, especially since the heat shrinkage rate measured below 75°C is prone to be outside the specified range.

[0138] Therefore, it is more preferable for Tg2 to be a value in the range of 55 to 75°C, and even more preferably a value in the range of 58 to 70°C.

[0139] It should be explained that Figure 2B Zhongyu Figure 2A Similarly, an example of the DSC curve of the second polyester resin obtained by DSC determination according to JIS K7121:2012 is shown.

[0140] Furthermore, the glass transition temperature (Tg2) of the second polyester resin was also determined according to JIS K7121:2012, just like the Tg1 of the first polyester resin. The specific heat change point obtained in step 3 was used as the Tg2 mentioned above.

[0141] Additionally, for reference, Figures 3A-3D The TG-DTA curves of the polyester heat shrink film of Example 1, Example 2, Comparative Example 1 and the second polyester resin (PETG2) are shown in the figure.

[0142] Based on the above TG-DTA curves, it can be seen that as the content of PETG2 in the polyester heat shrink film decreases, the glass transition temperature increases.

[0143] Furthermore, for the decomposition behavior near the decomposition initiation temperature, there is a trend that the slope of the TG curve decreases as the content of PETG2 decreases.

[0144] Additionally, for reference only, Figures 4A-4D The FT-IR curves of the polyester heat shrink film of Example 1, Example 2, and Comparative Example 1 and the second polyester resin (PETG2) are shown in the figure.

[0145] Based on the above FT-IR plot, it can be seen that as the content of PETG2 in the polyester heat-shrinkable film decreases, the wavenumber at 2950 cm⁻¹ decreases. －1 Nearby peaks (attributed to CH stretching of alkanes, see reference) Figures 4A-4D The area of ​​P4 in the graph has increased slightly, and the peak height has also increased.

[0146] On the other hand, for wavenumber 2850cm －1 The nearby peaks (also attributed to CH stretching of alkanes, see reference) Figures 4A-4D In P5, the peak areas are almost the same, only the peak height shows a trend of increasing.

[0147] Based on the above explanation, it can be said that... Figures 3A-3D The trend of the TG-DTA curve Figures 4A-4D The FT-IR images are used as a reference in the identification of the first polyester resin, the second polyester resin, and the polyester-based heat shrink film of this application.

[0148] Furthermore, when constituting the first invention, it is preferable that the intrinsic viscosity (IV value) of the second polyester resin is in the range of 0.65 to 0.85 dL / g.

[0149] The reason is that if the intrinsic viscosity of the second polyester resin is less than 0.65 dL / g, the melt viscosity is too low, which sometimes causes problems with extrusion molding.

[0150] On the other hand, if the intrinsic viscosity of the second polyester resin exceeds 0.85 dL / g, the uniformity of mixing with the first polyester resin may be significantly reduced, or it may become difficult to adjust for heat shrinkage stress. Moreover, because the melt viscosity of the second polyester resin is too high, extrusion molding properties may sometimes be problematic.

[0151] Therefore, it is more preferable that the intrinsic viscosity of the second polyester resin is in the range of 0.68 to 0.83 dL / g, and even more preferably in the range of 0.7 to 0.8 dL / g.

[0152] When determining the intrinsic viscosity of the second polyester resin, it is more preferable to consider the intrinsic viscosity of the first polyester resin.

[0153] That is, preferably the difference between the intrinsic viscosity of the second polyester resin and the intrinsic viscosity of the first polyester resin is within the range of ±0.2 dL / g, more preferably within the range of ±0.01 to 0.1 dL / g, and even more preferably within the range of ±0.05 to 0.1 dL / g.

[0154] (3) Mixing ratio

[0155] When constituting the first invention, the mixing ratio (by weight) of the first polyester resin and the second polyester resin is preferably in the range of 20 / 80 to 80 / 20.

[0156] The reason is that if the mixing ratio of the first polyester resin to the second polyester resin is less than 20 / 80, the heat shrinkage stress of the resulting polyester heat shrinkage film becomes difficult to adjust, and sometimes it can easily cause deformation or damage to the label during installation due to rapid shrinkage behavior.

[0157] On the other hand, if the mixing ratio of the first polyester resin to the second polyester resin exceeds 80 / 20, the heat shrinkage stress of the resulting polyester heat shrinkage film becomes difficult to adjust, and sometimes it can easily cause deformation of the container due to high shrinkage stress.

[0158] Therefore, a more preferred value is the mixing ratio (by weight) of the first polyester resin and the second polyester resin in the range of 30 / 70 to 70 / 30, and a more preferred value is the range of 40 / 60 to 60 / 40.

[0159] Here, refer to Figure 5A This illustrates the effect of the mixing ratio of the first polyester resin and the second polyester resin of the first invention on the heat shrinkage stress.

[0160] That is, the horizontal axis represents the mixing ratio of the first polyester resin and the second polyester resin (-), and the vertical axis represents the heat shrinkage stress (MPa) at 85℃.

[0161] Depend on Figure 5A As can be seen from the characteristic curves, by making the mixing ratio (by weight) of the first polyester resin and the second polyester resin in the range of 20 / 80 to 80 / 20, a low heat shrinkage stress of less than 6.8 MPa, comparable to that of polyvinyl chloride resin, can be obtained at 85°C.

[0162] That is, by reducing the amount of the first polyester resin and conversely increasing the amount of the second polyester resin, so that the mixing ratio is 80 / 20 or less, a value of less than 6.8 MPa, which is equivalent to that of polyvinyl chloride heat shrink film, can be obtained.

[0163] Furthermore, by using the mixing ratio in the range of 40 / 60 to 60 / 40, a low thermal shrinkage stress in the range of 4.5 to 6 MPa can be stably obtained at 85°C.

[0164] (4) Additives

[0165] The heat shrink film of the first invention may also be formulated with antioxidants, weather stabilizers, antistatic agents, antifogging agents, metallic soaps, waxes, mildew inhibitors, antibacterial agents, nucleating agents, flame retardants, slip agents and other additives as needed.

[0166] In particular, to improve the lubricity of the film surface, inorganic lubricants containing calcium carbonate particles, silica particles, glass particles, etc. are preferred.

[0167] In addition, as an additive, it is preferable to combine it with crystalline polyester resin, even in small amounts, to further adjust the good heat resistance and heat shrinkage rate.

[0168] That is, when the total amount of the resin constituting the polyester heat shrink film is set to 100% by weight, the amount of crystalline polyester resin is preferably in the range of 1 to 40% by weight, more preferably in the range of 2 to 40% by weight, and even more preferably in the range of 3 to 30% by weight.

[0169] Furthermore, there are no particular limitations on the method of adding the additive; any known method can be used. Among these methods, the use of masterbatch is preferred due to its simplicity and excellent uniform mixing properties.

[0170] For example, a specific example (commercially available product) of a polyester resin masterbatch used in conjunction with an anti-blocking agent is Anti-Blocking Agent (Contains: 20% silica, manufactured by Sukano Corporation, trade name: G dc S559-E).

[0171] Furthermore, other resins, including the aforementioned crystalline polyester resin, are preferably used without compromising the physical properties of the heat-shrinkable film of the first invention, particularly its shrinkage rate and shrinkage stress.

[0172] (5) Thermal shrinkage stress

[0173] Furthermore, the heat-shrinkable film of the first invention is characterized in that the heat-shrinkage stress in the main shrinkage direction, measured at 85°C, is less than 6.8 MPa.

[0174] The reason is that if the heat shrinkage stress measured at 85°C is above 6.8 MPa, the same heat shrinkage stress as that of polyvinyl chloride heat shrink film cannot be obtained. As a result, it is sometimes not possible to obtain the versatility to cope with various PET bottles from thin-walled to thick-walled.

[0175] Therefore, a value within the range of 4 to 5.8 MPa is more preferred, and a value within the range of 4.5 to 5.5 MPa is even more preferred.

[0176] It should be noted that the heat shrinkage stress at 85℃ is calculated according to the following steps.

[0177] That is, it is calculated by dividing the heat shrinkage stress (N / 15mm) of a strip-shaped test piece at 85°C by the thickness of the test piece, measured using a film heat shrinkage testing machine according to ISO 14616-1997.

[0178] (6) Thermal shrinkage rate

[0179] In addition, for polyester heat shrink films, the preferred heat shrinkage rate in the main shrinkage direction (usually the TD direction, the same below) is in the range of 25% to 40% when measured in hot water at 70°C, and the preferred heat shrinkage rate in the main shrinkage direction is in the range of 55% to 75% when measured in hot water at 85°C.

[0180] The reason is that if the heat shrinkage rate of the main shrinkage direction measured at 70°C and 85°C deviates from the above-mentioned specified range, polyester heat shrink film sometimes cannot achieve the same versatility as polyvinyl chloride heat shrink film in dealing with various PET bottles from thin-walled to thick-walled and complex shapes.

[0181] Therefore, a more preferred value is a thermal shrinkage rate in the main shrinkage direction measured in hot water at 70°C that is in the range of 26% to 38%, and even more preferred is a value in the range of 27% to 36%.

[0182] Furthermore, a value of 56% to 73% for the thermal shrinkage rate in the main shrinkage direction, measured in hot water at 85°C, is more preferably found, and even more preferably, a value in the range of 58% to 70%.

[0183] In addition, in order to make the polyester heat shrink film of the first invention closer to the thermal properties of the polyvinyl chloride heat shrink film and to effectively prevent natural shrinkage during storage, it is more preferable that the heat shrinkage rate in the main shrinkage direction (TD direction) measured in hot water at 60°C is 8% or less, and even more preferably that the heat shrinkage rate in the main shrinkage direction measured in hot water at 75°C is in the range of 42% to 48%.

[0184] It should be noted that the heat shrinkage rate is determined according to ASTM D2732-08. Furthermore, as a pretreatment specified for heat shrinkage rate determination, the material is placed at 23°C and 50% RH for at least 40 hours.

[0185] in addition, Figure 6A For the polyester heat-shrinkable films of Example 1, Comparative Example 1 and Comparative Example 3 described later, the heat shrinkage rate (main shrinkage direction, i.e. TD direction) at each measurement temperature is shown as characteristic curves (L1, L2, L3).

[0186] Similarly, for the polyester heat-shrinkable films of Example 1, Comparative Example 1 and Comparative Example 3 described later, the heat shrinkage rate at each measurement temperature (in the MD direction orthogonal to the TD direction) is shown as characteristic curves (L4, L5, L6).

[0187] Moreover, it can be said that Figure 6A The characteristic curve (L1) corresponding to Example 1 is approximately the same as the characteristic curve (L2) corresponding to Comparative Example 1, which uses the first polyester resin alone as a polyester heat shrink film, at least in the temperature range of 70°C to 85°C, as the characteristic curve (L3) corresponding to Comparative Example 3, which uses the polyvinyl chloride heat shrink film.

[0188] Moreover, 70℃~85℃ is the commonly used actual operating temperature for heat shrinking polyester heat shrink film.

[0189] Therefore, by Figure 6A A comparison of the characteristic curves L1, L2, and L3 shows that if a polyester-based heat shrink film (e.g., Example 1) is obtained from a mixture of a first polyester resin (PETG1) and a second polyester resin (PETG2) in a specified ratio, it is easy to obtain the same versatility as polyvinyl chloride-based heat shrink films in dealing with various PET bottles of various shapes, from thin-walled to thick-walled.

[0190] (7) Changes in thermal shrinkage rate before and after aging treatment

[0191] In addition, as an aging treatment, when the thermal shrinkage rate in the main shrinkage direction is set as A1 (%) and A2 (%) after being placed in a 23°C, 50%RH atmosphere for 60 days and then immersed in hot water at 65°C, the values ​​represented by A1-A2 are preferably in the range of 13 to 25%.

[0192] In addition, when the heat shrinkage rate in the main shrinkage direction of the product after being placed in a 23°C, 50%RH atmosphere for 60 days and then immersed in hot water at 70-85°C, especially at 85°C, is set as B1 (%) and B2 (%), the values ​​represented by B1-B2 are preferably in the range of 0-5%.

[0193] The reason is that if the values ​​represented by A1-A2 in the polyester heat shrink film deviate from the above-mentioned specified range, it may sometimes affect the change in the heat shrinkage rate in the main shrinkage direction measured at 70-85°C.

[0194] As a result, it is sometimes difficult to easily adjust the shrinkage stress at a specified temperature and the applicability to various PET bottles in the obtained polyester heat shrink film.

[0195] Furthermore, if the values ​​represented by B1-B2 in the polyester heat shrink film deviate from the specified range mentioned above, the shrinkage rate will change. Therefore, when actually used in various PET bottles, the settings of the equipment used need to be significantly changed.

[0196] here, Figure 6B The heat shrinkage rates of the polyester heat shrinkage film of Example 1 (L1) described below and Example 3 (L1′) of the polyester heat shrinkage film aged under specified environmental conditions (23°C, 50% RH atmosphere, 60 days) are shown at various test temperatures for reference.

[0197] according to Figure 6B The comparison of characteristic curves L1 and L1′ shows that if the polyester heat shrink film is obtained from a mixture of the first polyester resin (PETG1) and the second polyester resin (PETG2) in a specified ratio (e.g., Example 1), then even if aging treatment is performed under specified conditions, there is almost no significant difference in the heat shrinkage rate, at least in the temperature range of 70°C to 85°C.

[0198] That is, when aging is performed under specified conditions, the thermal shrinkage rate in the low-temperature region such as 65°C is reduced by only about 15%.

[0199] Therefore, according to the present invention, it can be understood that if a polyester heat-shrinkable film is obtained by mixing a specific first polyester resin and a second polyester resin in a prescribed ratio, then even during aging treatment, there will not be as many practical problems.

[0200] In contrast, Figure 6C The heat shrinkage rates (before and after aging treatment) of Comparative Examples 2 and 4 of the present invention (first invention) are shown in the figure.

[0201] According to such Figure 6C The comparison of characteristic curves L7 and L7′ shows that, if the polyester heat shrink film is obtained by mixing the first polyester resin (PETG1) and the second polyester resin (PETG2) in a specified ratio (for example, the comparison between Comparative Example 2 and Comparative Example 4), when aged under specified conditions, at least in the low temperature region of 65°C to 75°C, there is a trend of a relatively large decrease in the value of heat shrinkage rate.

[0202] That is, it was confirmed that when aging treatment was performed under specified conditions, the thermal shrinkage rate in the low-temperature region decreased by more than 15%.

[0203] (8) Melting peak temperature and heat equivalent to the melting peak area

[0204] Furthermore, when the polyester heat-shrinkable film of the first invention has a melting point, it is preferable that the melting peak temperature measured by DSC is set to a value in the range of more than 164°C and less than 170°C, and it is also preferable that the heat equivalent to the melting peak area is in the range of 6 to 18 mJ / mg.

[0205] The reason is that even if the above-mentioned polyester heat shrink film has a melting point determined by DSC, by controlling the melting point within a specified range and controlling the heat equivalent to the peak area of ​​the film's melting point within a specified range, it is possible to slightly limit the amount of crystalline structure present, thereby adjusting it to have a wide melting region.

[0206] Therefore, the resulting polyester heat-shrinkable film can maintain a wide range of mechanical strength and transparency due to fewer crystalline structures, and it is easier and more stable to adjust the heat shrinkage stress and heat shrinkage rate at a specified temperature.

[0207] Conversely, if the melting point measured by DSC deviates from the specified range, the thermal shrinkage stress in the main shrinkage direction measured at 85°C may sometimes exceed the specified value, thus reducing usability and failing to achieve versatility for various PET bottles ranging from thin-walled to thick-walled.

[0208] Furthermore, in the aforementioned polyester-based heat shrink film, if the heat equivalent to the melting peak area deviates from the specified range, it contains an excessive amount of crystalline structure, making it difficult to further approach the thermal and mechanical properties of polyvinyl chloride-based heat shrink films, etc.

[0209] Therefore, for the above-mentioned polyester heat shrinkable film, a melting peak temperature measured by DSC is more preferably in the range of 164.5 to 169.5°C, and even more preferably in the range of 165 to 169°C.

[0210] Furthermore, the heat equivalent to the melt peak area measured using DSC for the aforementioned polyester heat shrink film is more preferably a value in the range of 7 to 16 mJ / mg, and even more preferably a value in the range of 8 to 14 mJ / mg.

[0211] Here, refer to Figures 7A-7B The DSC curves of polyester heat shrink film are explained.

[0212] Right now, Figures 7A-7BThe DSC curves of the polyester heat-shrinkable films of Example 1 and Comparative Example 1 of the first invention, obtained by DSC measurement (only steps 1 and 3 are shown, and the curves of step 2 are omitted), are shown respectively.

[0213] When the above DSC curve is obtained, it can be measured using a DSC apparatus or the like, as described in the sections on first and second polyester resins, according to JIS K7121:2012.

[0214] Moreover, at least the DSC curve in step 1 can accurately determine the melting start temperature (extrapolated melting start temperature), melting peak temperature, melting end temperature (extrapolated melting end temperature), and the heat equivalent to the melting peak area.

[0215] Furthermore, in the case of the polyester heat-shrinkable film of the present invention, such as Figure 7A As shown, in step 1, the specified crystallization melting peak appears at 160-170°C, but it can be understood that the height of the melting peak and the heat equivalent to the melting peak area are significantly wider and smaller than those of typical polyester resins.

[0216] More specifically, the preferred range of heat equivalent to the melting peak area is approximately 140°C to 185°C, and the heat equivalent to the melting peak area is approximately 11 mJ / mg or less.

[0217] Next, refer to Figure 8 The relationship between the melting point (°C) and heat shrinkage stress (MPa) of the polyester heat shrink film in this invention (the first invention) will be explained.

[0218] Right now, Figure 8 The horizontal axis represents the melting point (°C) of the polyester heat shrink film, and the vertical axis represents the heat shrinkage stress (MPa) of the polyester heat shrink film measured in the main shrinkage direction at 85°C.

[0219] By this Figure 8 As shown in the characteristic curves, there is a high correlation between the melting point of the polyester heat shrink film and the heat shrinkage stress (MPa) in the main shrinkage direction measured at 85°C (in the linear approximation, the correlation coefficient (R) is, for example, 0.96).

[0220] Therefore, it can be understood that by controlling the melting point of the polyester heat shrink film, the heat shrinkage stress (MPa) in the main shrinkage direction of the polyester heat shrink film, as measured at 85°C, can be controlled.

[0221] (9) The difference between the melting end temperature and the melting start temperature

[0222] In addition, when the melting start temperature of the polyester heat shrink film measured by DSC is set as Tm1 (°C) and the melting end temperature is set as Tm2 (°C), the value represented by Tm2-Tm1 is quite wide, preferably a value in the range of 35 to 55°C.

[0223] The reason is that in polyester heat shrink film, if the value represented by Tm2-Tm1 deviates from the above-mentioned specified range, it is sometimes difficult to control the heat equivalent to the above-mentioned melting peak area within the specified range.

[0224] Therefore, it is more preferable that the value of the polyester heat shrink film, represented by Tm2-Tm1, is in the range of 38 to 53°C, and even more preferably in the range of 41 to 51°C.

[0225] It should be noted that since the Tm2-Tm1 of conventional polyester heat shrink films is around 8 to 20°C, it is understandable that melting occurs over a fairly wide temperature range in the case of this invention.

[0226] (10) Thickness

[0227] In addition, the thickness of the polyester heat shrink film can be varied to accommodate the shape of various PET bottles (hereinafter, sometimes referred to as PET bottle containers), but it is generally preferred to be a value in the range of 20 to 70 μm.

[0228] The reason is that if the thickness of the aforementioned polyester heat-shrinkable film is less than 20 μm, processing becomes difficult, and sometimes the tensile strength and other properties are significantly reduced.

[0229] On the other hand, if the thickness of the aforementioned polyester heat-shrinkable film exceeds 70 μm, it may sometimes shrink unevenly when heated at a specified temperature, or it may be difficult to manufacture a uniform thickness.

[0230] Therefore, a thickness of 30 to 60 μm is more preferred for the polyester heat shrink film, and a thickness of 40 to 55 μm is even more preferred.

[0231] 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.

[0232] (11) Functional layer

[0233] Polyester heat shrink film may be provided with functional layers to impart various functions as needed, without compromising the purpose of the present invention.

[0234] Examples of such functional layers include coatings, transfer layers, and printing layers used to impart surface smoothness, stain resistance, and durability.

[0235] Moreover, in particular, if a coating or metal vapor deposition layer is used that contains at least one of surfactants, silica, titanium dioxide, zinc oxide, zirconium oxide, aluminum oxide, or metal salts, it greatly contributes to the improvement of antistatic properties and surface smoothness, and is therefore a preferred form of functional layer.

[0236] In addition, in the case of a printed layer (coating), the shrinkage rate and shrinkage direction of the polyester heat shrink film are assumed in advance, and text, graphics, symbols, etc. are preferably formed by, for example, gravure printing.

[0237] Furthermore, the polyester heat shrink film of the present invention has a relatively large surface energy, excellent coatability when coated with various coatings, and excellent adhesion between the formed printed layer and the polyester heat shrink film as the substrate.

[0238] More specifically, when the checkerboard test according to JIS K5400 is performed on Example 1, it is found that the number of residuals is usually 90 / 100 or more, more preferably 95 / 100 or more, and even more preferably 99 / 100 or more.

[0239] In addition, such as Figure 1B As shown, it is also preferable to laminate other resin layers 10a, 10b containing at least one of these various additives on one or both sides of the polyester heat shrink film 10.

[0240] When the thickness of the polyester heat-shrinkable film is set to 100%, the single-layer thickness or total thickness of the additional resin layers is usually preferably in the range of 0.1% to 10%.

[0241] 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.

[0242] Furthermore, it is preferable to make the polyester heat-shrinkable film a multi-layer structure to further achieve waterproofing and mechanical protection, or as... Figure 1C As shown, a shrinkage adjustment layer 10c is provided on the surface of the polyester heat shrink film 10 to make the shrinkage rate of the polyester heat shrink film uniform in the plane.

[0243] Based on the shrinkage characteristics of polyester heat shrink film, the shrinkage rate adjustment layer can be laminated by means of adhesive, coating method or heat treatment as a specified layer composed of polyester resin, etc.

[0244] [Second Implementation]

[0245] The second embodiment is a polyester-based heat shrinkable film, characterized in that it is a polyester-based heat shrinkable film obtained from a polyester resin having an amorphous portion as a reaction product of a polycarboxylic acid and a polyol, wherein the polyol is a mixture of a first polyol having an alicyclic structure and a branched linear compound or an unbranched linear compound, namely a second polyol, and the heat shrinkage stress measured at 85°C is less than 6.8 MPa.

[0246] That is, the second embodiment is a polyester heat-shrinkable film obtained from a polyester resin having essentially a single, relatively amorphous portion.

[0247] Hereinafter, the second embodiment (hereinafter, sometimes referred to as the second invention) will be divided into its constituent parts, and will be specifically described with reference to the accompanying drawings regarding the differences from the first embodiment (hereinafter, sometimes referred to as the first invention).

[0248] 1. Polycarboxylic acids

[0249] The polycarboxylic acid of the second invention can be the same as that described in the first invention, so the description is omitted here.

[0250] 2. Polyols

[0251] (1) Types

[0252] When constituting the second invention, the characteristic is that, as a polyol, a combination of a first polyol having an alicyclic structure and a branched linear compound or an unbranched linear compound, namely a second polyol, is used.

[0253] Furthermore, as described in the first embodiment, 1,4-cyclohexanediol or the like is preferably used as the first polyol, and 2-methyl-1,3-propanediol or the like is preferably used as the second polyol.

[0254] The reason is that by combining these specific polyols, it is possible to precisely adjust the heat shrinkage stress, glass transition temperature, and other properties of polyester heat shrink films, which are essentially composed of a considerable amorphous portion.

[0255] (2) Mixture amount

[0256] Furthermore, when constituting the second invention, if the amount of polyol is set to 100% by weight, the total amount of the first polyol, such as 1,4-cyclohexanediol, and the second polyol, such as 2-methyl-1,3-propanediol, is preferably in the range of 15 to 40% by weight.

[0257] The reason is that if the total amount of the mixture is less than 15% by weight, it is sometimes difficult to accurately adjust the heat shrinkage and glass transition temperature of the obtained polyester heat shrink film, and the value of the heat shrinkage rate measured at 85°C is easy to become smaller.

[0258] On the other hand, if the total amount of the compound exceeds 40% by weight, it is sometimes difficult to accurately adjust the heat shrinkage, glass transition temperature, etc. of the obtained polyester heat shrink film. The heat shrinkage rate and natural shrinkage measured at 60°C tend to increase.

[0259] Therefore, when the amount of polyol is set to 100% by weight, it is more preferable that the total amount of the first polyol, such as 1,4-cyclohexanediol, and the second polyol, such as 2-methyl-1,3-propanediol, is in the range of 20 to 35% by weight, and even more preferably in the range of 25 to 33% by weight.

[0260] (3) Mixing ratio

[0261] Furthermore, when constituting the second invention, the preferred mixing ratio (by weight) of the first polyol such as 1,4-cyclohexanediol and the second polyol such as 2-methyl-1,3-propanediol is a value in the range of 10 / 90 to 90 / 10.

[0262] The reason is that if the above mixing ratio is less than 10 / 90, it is sometimes difficult to accurately adjust the heat shrinkage and glass transition temperature of the obtained polyester heat shrink film, and the change in heat shrinkage rate before and after aging treatment increases.

[0263] On the other hand, if the above mixing ratio exceeds 90 / 10, it is sometimes difficult to accurately adjust the heat shrinkage and glass transition temperature of the obtained polyester heat shrink film, and the value of heat shrinkage stress measured at 85°C is prone to increase.

[0264] Therefore, a more preferred ratio of the first polyol, such as 1,4-cyclohexanediol, to the second polyol, such as 2-methyl-1,3-propanediol, is in the range of 20 / 80 to 80 / 20, and a more preferred ratio is in the range of 30 / 70 to 70 / 30.

[0265] 3. Polyester resin

[0266] (1) Glass transition temperature

[0267] When constituting the second invention, it is preferable that the glass transition temperature (Tg) of the polyester resin having a substantially amorphous portion (the same applies in the case of polyester heat-shrinkable films; the same applies hereinafter) is in the range of 50 to 90°C.

[0268] The reason is that if the above-mentioned Tg is less than 50°C, the heat resistance and durability of the polyester resin will sometimes be significantly reduced, and the natural shrinkage of the polyester heat shrink film obtained from the polyester resin will increase, resulting in a significant reduction in its shelf life.

[0269] On the other hand, if the Tg value exceeds 90°C, it is difficult to accurately adjust the heat shrinkage stress of the obtained polyester heat shrink film, especially since the heat shrinkage stress measured below 85°C is prone to be outside the specified range.

[0270] Therefore, it is more preferable for the above-mentioned Tg to be a value in the range of 55 to 85°C, and even more preferably a value in the range of 60 to 80°C.

[0271] (2) Thermal shrinkage stress

[0272] The thermal shrinkage stress of the second invention can be the same as that described in the first invention.

[0273] That is, the characteristic of polyester heat shrink film is that the heat shrinkage stress in the main shrinkage direction measured at 85°C is less than 6.8 MPa.

[0274] (3) Thermal shrinkage rate

[0275] The heat shrinkage rate of the second invention can be the same as that described in the first invention.

[0276] That is, it is generally preferred to set the heat shrinkage rate in the main shrinkage direction (usually the TD direction, the same below) measured in hot water at 70°C to a value in the range of 25 to 40%, and to set the heat shrinkage rate in the main shrinkage direction measured in hot water at 85°C to a value in the range of 55 to 75%.

[0277] (4) Changes in thermal shrinkage rate before and after aging treatment

[0278] The thermal shrinkage rate before and after the aging treatment in the second invention can be the same as that described in the first invention.

[0279] That is, as an aging treatment, it is preferable to set the thermal shrinkage rate in the main shrinkage direction when the product is placed in a 23°C, 50%RH atmosphere for 60 days and then immersed in hot water at 65°C as A1 (%) and A2 (%), with the value represented by A1-A2 being in the range of 13 to 25%.

[0280] Furthermore, it is even more preferable that when the heat shrinkage rate in the main shrinkage direction of the product is set as B1 (%) and B2 (%) after being placed in a 23°C, 50%RH atmosphere for 60 days and then immersed in hot water at 70-85°C, especially at 85°C, the values ​​represented by B1-B2 are in the range of 0-5%.

[0281] (5) Melting peak temperature and heat equivalent to the melting peak area

[0282] The melting peak temperature and the heat equivalent to the melting peak area in the second invention can also be the same as those described in the first invention.

[0283] That is, when the polyester heat shrink film has a melting peak in DSC (step 1), the melting peak temperature is preferably a value in the range of more than 164°C and less than 170°C.

[0284] Furthermore, the heat equivalent to the melting peak area in the second invention can also be the same as that described in the first invention, that is, the heat equivalent to the melting peak area of ​​the polyester heat shrink film measured by DSC is generally preferably a value in the range of 6 to 18 mJ / mg.

[0285] (6) The difference between the melting end temperature and the melting start temperature

[0286] The difference between the melting end temperature (Tm2) and the melting start temperature (Tm1) in the second invention, namely Tm2-Tm1, is preferably a fairly wide temperature range, just as described in the first invention.

[0287] That is, preferably, the values ​​represented by Tm2-Tm1 are in the range of 35 to 55°C, more preferably in the range of 38 to 53°C, and even more preferably in the range of 41 to 51°C.

[0288] (7) Thickness

[0289] In the second invention, the thickness of the polyester heat-shrinkable film is preferably within the same numerical range as that in the first invention.

[0290] Therefore, the thickness of the above-mentioned polyester heat shrink film is generally preferably in the range of 20 to 70 μm, more preferably in the range of 25 to 65 μm, and even more preferably in the range of 30 to 60 μm.

[0291] 4. Additives

[0292] Similar to the first invention, the second invention can also incorporate additives such as antioxidants, weather stabilizers, antistatic agents, antifogging agents, metal soaps, waxes, mildew inhibitors, antibacterial agents, nucleating agents, flame retardants, and inorganic slip agents into the polyester heat shrink film as needed. It can also incorporate a specified amount of crystalline polyester within the scope of the invention's purpose.

[0293] 5. Polyester-based heat shrink film

[0294] The polyester heat shrinkable film of the second invention, without prejudice to the purpose of the invention, may preferably be provided with functional layers as needed to impart various functions, such as coatings, transfer layers, and printing layers for imparting surface smoothness, stain resistance, durability, etc., as well as for imparting design features, in the same manner as the first invention.

[0295] [Third Implementation]

[0296] The third embodiment is a method for manufacturing polyester heat-shrinkable film according to the first and second embodiments.

[0297] 1. Raw material preparation and mixing process

[0298] As raw materials, prepare amorphous polyester resin, crystalline polyester resin, rubber-based resin, antistatic agent, hydrolytic agent and other main agents and additives.

[0299] During the above preparation, it is preferable to pre-dry the amorphous polyester resin, which is the main component, at a specified temperature (generally Tg-10℃) for a specified time (generally 3 to 10 hours) to achieve an absolutely dry state.

[0300] Next, the prepared amorphous polyester resin, crystalline polyester resin, etc. are weighed and added into the mixing container, and mixed and stirred until uniform.

[0301] 2. Fabrication process of blank sheets

[0302] Next, typically, extrusion molding (T-die method), blow molding, or casting molding is preferred to produce blank sheets of a specified thickness.

[0303] More specifically, for example, extrusion molding using an extruder at an extrusion temperature of 245°C can produce preform sheets of a specified thickness (typically 200–300 μm).

[0304] 3. Fabrication of Polyester-Based Heat Shrink Film

[0305] Next, the obtained blank sheet is heated and extruded while moving on and between rollers using a heat shrink film manufacturing device (stenter). Polyester heat shrink film is then produced.

[0306] Among the stretching treatment methods used to embody the aforementioned shrinkage, blow-up method, roller stretching method, tenter frame stretching method, and combinations thereof are known.

[0307] Furthermore, due to better productivity, a combination of sheet forming obtained by casting and roll stretching and tenter stretching is preferred.

[0308] That is, preferably, the polyester molecules constituting the polyester heat shrink film are crystallized into a specified shape by heating and extruding the film while it is substantially expanded at a specified stretching temperature and stretching ratio, and stretching it in a specified direction.

[0309] Furthermore, curing it in this state allows for the production of heat-shrinkable polyester heat-shrinkable films for use as decorations, labels, etc.

[0310] It should be noted that, generally, it is preferred to manufacture the preform sheet using methods such as T-die method or blow molding method, and then heat the preform sheet to a temperature above the glass transition temperature of the resin, and stretch it 3 to 8 times in the main stretching direction (the width direction of the film preform, i.e., the TD direction), preferably about 4 to 6 times.

[0311] 4. Inspection procedures for polyester heat shrink film

[0312] Preferably, the following characteristics are continuously or intermittently measured on the manufactured polyester heat shrink film, and a prescribed inspection procedure is set up.

[0313] That is, by measuring the following characteristics through a prescribed inspection process and confirming that the values ​​fall within the prescribed range, a polyester heat shrink film with more uniform shrinkage characteristics can be produced.

[0314] 1) Visual inspection of the appearance of polyester heat shrink film

[0315] 2) Thickness fluctuation measurement

[0316] 3) Tensile strength test (ASTM D882)

[0317] 4) Tensile elongation determination (ASTM D882)

[0318] 5) Surface smoothness inspection (ASTM D1894)

[0319] 6) Specific gravity determination (ASTM D792)

[0320] 7) Ring Collision Test (TAPPI T882)

[0321] 8) Tear strength test (ASTM D1922)

[0322] 9) Determination of glass transition temperature, melting point, and heat equivalent to the melting peak area obtained from DSC.

[0323] [Fourth Implementation]

[0324] The fourth embodiment is an embodiment of the method of using the polyester heat shrink film of the first and second embodiments.

[0325] Therefore, any method of using polyester heat shrink film that is at least known can be used.

[0326] For example, when implementing the method of using polyester heat shrink film, the polyester heat shrink film is first cut into appropriate lengths and widths to form long cylindrical strips.

[0327] In the formation of the above-mentioned elongated cylindrical material, solvents such as tetrahydrofuran, 1,3-dioxolane, xylene, and their mixtures are preferably used to dissolve / bond the membrane.

[0328] Next, the long cylindrical material is fed to an automatic label mounting device (SHRINK LABELE RS, shrink film labeling machine) and further cut to the required length.

[0329] Next, it is embedded in PET bottles, etc.

[0330] Next, the polyester heat-shrink film, which is embedded in PET bottles, is subjected to heat treatment so that it passes through the interior of shrink tunnels such as hot air tunnels and steam tunnels.

[0331] Furthermore, the polyester heat-shrinkable film is uniformly heated and heat-shrinkable by the radiant heat such as infrared rays present in the aforementioned shrinkage tunnel and by the heating steam blown from the surroundings.

[0332] Therefore, it can be tightly fitted to the outer surface of PET bottles, etc., to quickly obtain labeled containers.

[0333] Example

[0334] The present invention will now be described in detail based on embodiments. Unless otherwise specified, the scope of the invention will not be narrowed by the description of these embodiments.

[0335] In addition, the amorphous polyester resin, crystalline polyester resin, and additives used in the embodiments are as follows.

[0336] It should be noted that the intrinsic viscosity (IV value) listed in the amorphous polyester resin section 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).

[0337] (PETG1)

[0338] The first polyester resin (manufactured by Eastman Chemical Company, trade name "Embrace LV"), obtained from 100 mol% dicarboxylic acid (i.e., terephthalic acid), 1,4-cyclohexanediol, ethylene glycol, and diethylene glycol, has a glass transition temperature (Tg) of 68.2 °C, an intrinsic viscosity (IV value) of 0.7, and a density of 1.30 g / cm³. 3 )

[0339] More specifically, the proportions of the compounding components of PETG1, or Embrace LV, are: terephthalic acid: 100 mol%, ethylene glycol: 63 mol%, diethylene glycol: 13 mol%, and 1,4-cyclohexanediethanol: 24 mol%.

[0340] It should be noted that when the total amount of the first polyol used in the production of PETG1 is set to 100 mol%, it can be changed as long as the content of 1,4-cyclohexanediethanol is within the specified range of 20-35 mol%, ethylene glycol is within the specified range of 50-65 mol%, and diethylene glycol is within the specified range of 5-20 mol%.

[0341] (PETG2)

[0342] A second polyester resin (manufactured by Tainan Spinning Co., Ltd., trade name "MKD3", glass transition temperature (Tg): 61.6℃, intrinsic viscosity (IV value): 0.7) was obtained from approximately 100 mol% of dicarboxylic acid (terephthalic acid), glycol components (64.4 mol% ethylene glycol, 25.6 mol% 2-methyl-1,3-propanediol and 10 mol% diethylene glycol).

[0343] It should be noted that when the total amount of the second polyol used in the production of PETG2 is set to 100 mol%, it can be varied within the range of 20-35 mol% for 2-methyl-1,3-propanediol, 50-65 mol% for ethylene glycol, and 5-20 mol% for diethylene glycol.

[0344] (PETG3)

[0345] A third amorphous polyester resin composed of 1,4-cyclohexanediethanol-modified polyethylene terephthalate (manufactured by Eastman Corporation, trade name: EASTAR PETG6763, dicarboxylic acid: 100 mol% dicarboxylic acid, 1,4-cyclohexanediethanol relative to the total amount of polyol component: 20-50 mol%, total amount of ethylene glycol and diethylene glycol: 50-80 mol%, glass transition temperature (Tg): 83℃, intrinsic viscosity (IV value): 0.75).

[0346] It should be noted that when the total amount of the second polyol used in the production of PETG3 is set to 100 mol%, the 1,4-cyclohexanediethanol, ethylene glycol, and diethylene glycol can be changed within the above-mentioned range.

[0347] (PVC film)

[0348] Vinyl chloride resin (manufactured by Shintech, trade name "SE800", K value: 60.6~62.0)

[0349] (Additive (Anti-Blocking Agent))

[0350] The silica masterbatch (manufactured by Sukano Corporation, trade name "G dc S559-E"), which is made by combining 80 parts by weight of polyethylene terephthalate resin with 20 parts by weight of silica, contains 20% by weight of silica.

[0351] [Example 1]

[0352] 1. Preparation of polyester heat shrink film

[0353] As amorphous polyester resins, PETG1 was prepared to be dried at 60°C (i.e., in the range of Tg-10°C) for 6 hours and PETG2 was prepared to be dried at 50°C (i.e., in the range of Tg-10°C) for 6 hours.

[0354] Next, add 1000g of PETG1 and PETG2 into the mixing container according to the prepared mixing ratio (by weight) of 60 / 40.

[0355] In addition, when the total amount of amorphous polyester resins PETG1 and PETG2 is set to 100 parts by weight, the above-mentioned Anti-Blocking Agent, dried under specified conditions, is mixed in a ratio of 1 part by weight as an anti-blocking agent for heat shrink film to prepare a raw material for heat shrink film formation.

[0356] Next, the heat shrink film forming material is extruded using an extruder at an extrusion temperature of 245°C to obtain a preform sheet with a thickness of 250 μm.

[0357] Finally, using a heat shrink film manufacturing device, a polyester heat shrink film with a thickness of 50μm and a thickness fluctuation of less than 5% is produced from the blank sheet at a preheating temperature of 110℃, a stretching temperature of 77℃, an annealing temperature of 83.5℃, and a stretching ratio (MD direction: 1.08 times, TD direction: 5 times).

[0358] 2. Evaluation of polyester heat shrink film

[0359] (1) Thermal shrinkage rate

[0360] The heat shrinkage rate of the obtained polyester heat shrink film was determined according to ASTM D2732-08.

[0361] That is, it is cut into a quadrilateral shape with a length of 100 mm along the main contraction direction (TD direction) and a length of 100 mm along the non-main contraction direction (MD direction), and used as the test sample.

[0362] Next, they were immersed for 10 seconds each in a constant temperature bath containing hot water with a temperature controlled at 60-100°C using a 5°C scale, to induce thermal shrinkage.

[0363] Next, at each temperature, the thermal shrinkage rate (%) in the main shrinkage direction (TD direction) and the non-main shrinkage direction (MD direction) is calculated according to the following formula (1) based on the dimensional changes before and after the heat treatment.

[0364] Heat shrinkage rate = (100mm - length of the film after heat shrinkage) / 100mm × 100 (1)

[0365] (2) Thermal shrinkage stress

[0366] The heat shrinkage stress of the obtained polyester heat shrink film was determined according to ISO 14616-1997.

[0367] That is, the obtained polyester heat shrink film is cut into strips with a length of 90 mm along the main shrinkage direction (TD direction) and a length of 15 mm along the non-main shrinkage direction (MD direction), and these are used as test pieces.

[0368] Next, the shrinkage force (N / 15mm) of the test piece at 85°C was measured using a film heat shrinkage tester (Labthink Corporation, product name "FST-02").

[0369] Next, the obtained shrinkage force is divided by the thickness (50 μm) to obtain the thermal shrinkage stress (MPa) at 85°C.

[0370] (3) DSC measurement

[0371] The obtained polyester heat shrink film was measured using a DSC device (manufactured by Hitachi Advanced Technology & Science Co., Ltd., product name "DSC7000X") under specified conditions, including glass transition temperature, extrapolated melt start temperature, melting point (melting peak temperature), extrapolated melt end temperature, and heat equivalent to the melting peak area.

[0372] More specifically, the sample of polyester heat shrink film was dried in a drying oven at 60°C for 6 hours.

[0373] Next, the sample was placed in a differential scanning calorimeter (DSC). In step 1 (heating from 25°C to 280°C at a rate of 10°C / min), the temperature was increased to the high-temperature region. Then, in step 2 (cooling from 280°C to 25°C at a rate of 30°C / min), the temperature was decreased to the low-temperature region. Finally, in step 3 (heating from 25°C to 280°C at a rate of 10°C / min), the temperature was increased back to the high-temperature region. The extrapolated melting start temperature, melting point (melting peak temperature), extrapolated melting end temperature, and the heat equivalent to the melting peak area were determined from the DSC curve obtained in step 1. The glass transition temperature was determined from the DSC curve obtained in step 3.

[0374] [Examples 2-3]

[0375] In Examples 2 and 3, as shown in Table 1, the effect of the mixing ratio (by weight) of PETG1 and PETG2 was studied respectively.

[0376] Specifically, in Example 2, the ratio of PETG1 / PETG2 was changed to 40 / 60, and in Example 3, the ratio of PETG1 / PETG2 was changed to 50 / 50. Polyester heat-shrinkable films were prepared accordingly. Otherwise, the heat shrinkage rate at each temperature, the heat shrinkage stress at 85°C, the melting point, and the heat equivalent to the melting peak area were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0377] [Examples 4-5]

[0378] In Examples 4 and 5, as shown in Table 1, a mixture of PETG1 and PETG3 (weight mixing ratio: 80 / 20) was used instead of PETG1 in Examples 2 and 3. Otherwise, polyester heat-shrinkable films were prepared in the same manner as in Example 1, and the heat shrinkage rate at each temperature, the heat shrinkage stress at 85°C, the melting point, and the heat equivalent to the melting peak area were evaluated. The results are shown in Table 2.

[0379] [Examples 6-7]

[0380] In Examples 6 and 7, as shown in Table 1, the effects of a specified aging treatment after the fabrication of a polyester heat-shrinkable film were investigated.

[0381] That is, in Example 6, a polyester heat shrink film with the same compatibility as in Example 1 is produced, and in Example 7, a polyester heat shrink film with the same compatibility as in Example 2 is produced.

[0382] Next, these heat-shrink films were cut into 800mm × 800mm sizes and further aged under environmental conditions of 23°C, 50% RH, and 60 days. In addition, the heat shrinkage rate at each temperature and the heat shrinkage stress at 85°C were evaluated in the same manner as in Examples 1 and 2. The results are shown in Table 2.

[0383] [Comparative Examples 1-2]

[0384] In Comparative Examples 1 and 2, as shown in Table 1, the mixing ratio (by weight) of PETG1 and PETG2 was changed to 100 / 0 (Comparative Example 1) and 81 / 19 (Comparative Example 2), respectively. Otherwise, various polyester-based heat-shrinkable films were prepared in the same manner as in Example 1, and the heat shrinkage rate at each temperature, the heat shrinkage stress at 85°C, the melting point, and the heat equivalent to the melting peak area were evaluated. The results are shown in Table 2.

[0385] [Comparative Example 3]

[0386] In Comparative Example 3, as shown in Table 1, a polyvinyl chloride (PVC) heat-shrinkable film was prepared using PVC resin. Otherwise, the heat shrinkage rate at each temperature and the heat shrinkage stress at 85°C were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0387] [Comparative Example 4]

[0388] In Comparative Example 4, as shown in Table 1, the effect of the specified aging treatment after the production of polyester heat shrink film was studied.

[0389] That is, in Comparative Example 4, after producing a film identical to the polyester heat-shrinkable film of Comparative Example 2, the film was cut into 800mm × 800mm sizes and further aged under environmental conditions of 23°C, 50% RH atmosphere, and 60 days. The heat shrinkage rate at each temperature and the heat shrinkage stress at 85°C were evaluated in the same manner as in Comparative Example 2. The results are shown in Table 2.

[0390] [Table 1]

[0391]

[0392] [Table 2]

[0393]

[0394] Industrial availability

[0395] According to the present invention (the first invention), it is possible to provide a polyester heat-shrinkable film with a heat shrinkage stress of less than a specified value, obtained from a mixed resin of various amorphous polyester resins that are reaction products of polycarboxylic acids and polyols.

[0396] More specifically, the mixed resin comprises a first polyester resin made using a second polyol having an alicyclic structure and a second polyester resin made using a second polyol not having an alicyclic structure.

[0397] Moreover, through this configuration, even if the resulting polyester heat-shrinkable film is mainly composed of polyester resin, it can exhibit the same low shrinkage stress as the vinyl chloride resin film.

[0398] Furthermore, according to the present invention (the second invention), it is possible to provide a polyester heat-shrinkable film composed of a single amorphous polyester resin, which is a reaction product of a polycarboxylic acid and a polyol, and having a heat shrinkage stress of less than a specified value, wherein the polyol is a mixture of a first polyol having an alicyclic structure and a second polyol not having an alicyclic structure.

[0399] Moreover, through this configuration, even though the polyester heat-shrinkable film is mainly composed of polyester resin, it can exhibit the same low shrinkage stress as the vinyl chloride resin film.

[0400] Therefore, the heat-shrinkable polyester film of the present invention (the first invention and the second invention) can cope with the reduction in thickness of PET bottles, etc.

[0401] That is, even if the overall rigidity of the PET bottle is low due to the reduction in the thickness of the PET bottle, it can effectively prevent the PET bottle from breaking due to the shrinkage of the low rigidity and heat-shrinkable film.

[0402] Moreover, the polyester heat-shrinkable film of the present invention has excellent aging resistance, and even when stored for a long time under specified conditions, it can reduce changes in physical properties such as heat shrinkage rate and heat shrinkage stress.

[0403] Furthermore, compared to heat-shrinkable polyvinyl chloride films, this invention does not produce dioxins during incineration, effectively eliminating the need for plasticizers, thus reducing the risk of environmental problems. It also has the advantage of easy recycling.

[0404] Furthermore, the polyester heat shrink film according to the present invention is easy to use regardless of whether it is thin-walled, thick-walled, or even complex in shape, and can be applied to various PET bottles, etc. As a result, its versatility is significantly improved, and its industrial applicability is extremely high.

[0405] Symbol Explanation

[0406] 10: Polyester heat shrink film

[0407] 10a: Other resin layers 1

[0408] 10b: Other resin layers 2

[0409] 10c: Shrinkage adjustment layer

Claims

1. A polyester-based heat-shrinkable film, characterized in that, It is a polyester-based heat-shrinkable film obtained by mixing various amorphous polyester resins, wherein the various amorphous polyester resins are reaction products of polycarboxylic acids and polyols. The mixed resin comprises a first polyester resin made using a first polyol having an alicyclic structure and a second polyester resin made using a second polyol not having an alicyclic structure. 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. Furthermore, the heat shrinkage stress of the polyester heat shrink film measured at 85°C is less than 6.8 MPa. The first polyol contains at least 1,4-cyclohexanediol, and the second polyol contains at least 2-methyl-1,3-propanediol.

2. The polyester-based heat-shrinkable film according to claim 1, characterized in that, The glass transition temperature of the first polyester resin is higher than that of the second polyester resin, and the glass transition temperature of the first polyester resin is in the range of 60–90°C, while the glass transition temperature of the second polyester resin is in the range of 50–80°C. Furthermore, in DSC measurements, there is a baseline shift corresponding to a glass transition temperature in the range of 63–70°C.

3. The polyester-based heat-shrinkable film according to claim 1, characterized in that, The intrinsic viscosity of the first polyester resin is in the range of 0.65 to 0.85 dL / g, the intrinsic viscosity of the second polyester resin is in the range of 0.65 to 0.85 dL / g, and the difference between the intrinsic viscosity of the first polyester resin and the intrinsic viscosity of the second polyester resin is less than ±0.2 dL / g.

4. The polyester-based heat-shrinkable film according to claim 1, characterized in that, The heat shrinkage rate measured at 70℃ is in the range of 25% to 40% in the main shrinkage direction, and the heat shrinkage rate measured at 85℃ is in the range of 55% to 75%.

5. The polyester-based heat-shrinkable film according to claim 1, characterized in that, When the thermal shrinkage rate in the main shrinkage direction is defined as A1 and A2 when the product is immersed in hot water at 65°C before and after being placed in an atmosphere of 23°C and 50%RH for 60 days, the value represented by A1-A2 is a value in the range of 13% to 25%, and the units of A1 and A2 are ( ).

6. The polyester-based heat-shrinkable film according to claim 1, characterized in that, When the thermal shrinkage rate in the main shrinkage direction after being immersed in hot water at 85°C for 60 days at 23°C and 50% RH is defined as B1 and B2, the values ​​represented by B1-B2 are in the range of 0-5%, and the units of B1 and B2 are ( ).

7. The polyester-based heat-shrinkable film according to claim 1, characterized in that, The polyester heat-shrinkable film exhibits a melting peak when measured by DSC. The melting peak temperature is in the range of 164°C to 170°C, and the heat equivalent to the melting peak area is in the range of 6 to 18 mJ / mg.

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