Polyester heat-shrinkable film having improved shrinkage properties

Abstract

This polyester heat-shrinkable film in which dynamic viscoelasticity before and after shrinkage is adjusted to within a specific range may have an improved shrinkage rate and shrinkage uniformity at high temperatures. Therefore, the heat-shrinkable film can be applied to packaging and labeling of containers or bottles to improve quality.

Description

Polyester heat-shrinkable film with improved shrinkage properties

[0001] The present invention relates to a polyester heat-shrinkable film with improved shrinkage properties.

[0002] Among polymers, polyester resins are widely used in various fields due to their superior mechanical strength, heat resistance, transparency, and gas barrier properties. In particular, heat-shrinkable films manufactured using polyester resins exhibit high heat resistance and an appropriate heat shrinkage rate, making them suitable for packaging and / or labeling plastic containers such as PET bottles.

[0003] Labeling or packaging using heat-shrinkable film involves placing heat-shrinkable film, cut to an appropriate size and shape, onto a washed and dried container or bottle. The film is then subjected to a high-temperature heat treatment process, shrinking it to the shape of the container or bottle, thereby sealing it tightly. During this process, if the film shrinkage rate is low or uneven, it can break, resulting in poor printability in subsequent printing processes.

[0004] The shrinkage characteristics of heat-shrinkable films, such as shrinkage rate and shrinkage uniformity at high temperatures, are related to the crystallinity of the polymers they comprise. This crystallinity can vary depending on the polymer composition or the stretching and heat treatment processes during film manufacturing. Therefore, to achieve the desired shrinkage characteristics for heat-shrinkable films, the polymer resin composition is adjusted or the stretching and heat treatment conditions during the film manufacturing process are appropriately modified.

[0005] For example, Korean Patent No. 0785251 discloses a method of manufacturing a heat-shrinkable film using a resin containing 5 wt% or more of polyester elastomer, thereby suppressing the occurrence of wrinkles, shrinkage stains, distortion, etc. due to heat shrinkage when wrapping a plastic bottle on its entire surface.

[0006] [Prior Art Literature]

[0007] [Patent Document]

[0008] (Patent Document 1) Korean Patent No. 0785251 (December 5, 2007)

[0009] The shrinkage characteristics of heat-shrinkable films can vary depending on not only the raw resin but also the film manufacturing process, making it difficult to control.

[0010] The inventors of the present invention confirmed that the shrinkage characteristics were improved by controlling the tanδ ratio before and after shrinkage of a heat-shrinkable film within a specific range.

[0011] Therefore, the task of the present invention is to provide a polyester heat-shrinkable film controlled to have high shrinkage and uniform shrinkage.

[0012] The present invention provides a heat-shrinkable film comprising a copolymerized polyester resin containing a diol component and a dicarboxylic acid component, wherein the film is cut in the main shrinkage direction, mounted on a tensile clamp, and measured using a dynamic mechanical analyzer (DMA) under a temperature increase condition of 3°C / min from 30°C to 150°C at a frequency of 1 Hz, and the temperature (°C) at which tanδ is 1 or more is within the range of 65°C to 100°C, and the tanδ max ratio calculated by the following formula is 50% or more.

[0013] tanδ max ratio = (tanδ[1]max / tanδ[2]max) x 100

[0014] Here, tanδ[1]max is the maximum value of tanδ measured under the above temperature-elevated conditions for the heat-shrinkable film, and tanδ[2]max is the maximum value of tanδ measured under the above temperature-elevated conditions after shrinking the heat-shrinkable film at 95°C for 30 seconds, and is calculated as tanδ = G'' / G', where G'' is the loss modulus and G' is the storage modulus.

[0015] The polyester heat-shrinkable film according to the present invention can effectively control shrinkage rate and shrinkage uniformity at high temperatures by controlling dynamic viscoelasticity before and after shrinkage, specifically, the tanδ ratio, within a specific range.

[0016] Since this type of heat-shrinkable film has excellent shrinkage rate and shrinkage uniformity as well as stretchability and printability, it can be applied to packaging and labeling of containers or bottles to improve quality.

[0017] The terms used to refer to each component in this specification are used to distinguish it from other components and are not intended to limit the implementation examples. Furthermore, the singular expressions used in this specification include the plural expressions unless the context clearly dictates otherwise.

[0018] In this specification, the terms "first," "second," etc. are used to describe various components, and the components should not be limited by the terms. The terms are used for the purpose of distinguishing one component from another.

[0019] The word "comprising" or "including" in this specification is intended to specify particular features, regions, steps, processes, elements and / or components, and does not exclude the presence or addition of other features, regions, steps, processes, elements and / or components, unless specifically stated to the contrary.

[0020] In the numerical ranges that limit the size, physical properties, etc. of the components described in this specification, if a numerical range limited only to the upper limit and a numerical range limited only to the lower limit are separately exemplified, it should be understood that a numerical range in which these upper and lower limits are combined is also included in the exemplary range of the present invention.

[0021]

[0022] Characteristics of heat-shrinkable films

[0023] According to the present invention, by controlling the dynamic viscoelasticity of a polyester heat-shrinkable film, specifically the properties related to tanδ, within a specific range, a polyester heat-shrinkable film having high shrinkage, shrinkage uniformity, and stretchability can be provided.

[0024] Tanδ (tan delta) is defined as the loss modulus (G') divided by the storage modulus (G') (i.e. tanδ = G'' / G'), and can be an important indicator of the shrinkage characteristics of a film. Loss modulus represents viscous behavior and indicates the degree to which energy is lost, while storage modulus represents elastic behavior and indicates the degree to which energy is stored.

[0025] Tanδ represents the energy lost due to internal friction associated with molecular rearrangement when stress is applied to a polymer, and thus can be viewed as a quantifiable indicator of the damping properties of a polymer. Even if the composition of the polymer constituting the film remains the same, the elasticity and viscosity of the film can vary due to changes in molecular orientation during the stretching process, resulting in variations in tanδ.

[0026] Tanδ can be measured, for example, using a dynamic mechanical analyzer (DMA). First, a sample is cut to an appropriate size and mounted in a clamp or holder of the DMA. Then, the sample is subjected to cyclic stress or strain while heating or cooling. The phase difference between the cyclic stress and the response is measured in the DMA, from which the sample's loss modulus and storage modulus are derived, and tanδ is then calculated.

[0027] Specifically, the heat-shrinkable film is cut in the main shrinkage direction, mounted on a tensile clamp, and tanδ can be measured using a dynamic mechanical analysis device (DMA) under a temperature increase condition of 3°C / min from 30°C to 150°C at a frequency of 1 Hz.

[0028] In the temperature-dependent tanδ curve obtained from DMA, the maximum peak may appear near the glass transition temperature (Tg), the height of the peak may indicate the number of molecular chains moving with temperature, and the full width at half maximum (FWHM) of the peak may provide information about the movement of chain segments.

[0029] If the peak temperature is high or the peak height increases in the tanδ curve, it means that the film is flexible and has a structure that is easy to absorb shock, and this is reported to be caused by a decrease in the crystallinity of the resin or a reduction in the crystal size.

[0030] In particular, the temperature range where tanδ is 1 or greater is a range where viscosity is high compared to elasticity, so it can be interpreted as a temperature range where the heat-shrinkable film exhibits high shrinkage characteristics.

[0031] According to the present invention, the temperature (℃) at which the tanδ of the heat-shrinkable film is 1 or more is 65℃ or more. In addition, the temperature (℃) at which the tanδ of the heat-shrinkable film is 1 or more may be 100℃ or less.

[0032] If the temperature at which tanδ measured along the main shrinkage direction of the heat-shrinkable film is 1 or more is lower than 65°C, crack resistance at room temperature deteriorates and the film properties are more likely to change over time. In addition, if the temperature at which tanδ measured along the main shrinkage direction of the heat-shrinkable film is 1 or more exceeds 100°C, it becomes difficult to achieve the high shrinkage characteristics required by the present invention.

[0033] According to one embodiment, when the heat-shrinkable film is cut in the main shrinkage direction and mounted on a tensile clamp and measured using a dynamic mechanical analysis device (DMA) under a temperature increase condition of 3°C / min from 30°C to 150°C at a frequency of 1 Hz, the temperature (°C) at which tanδ is 1 or more is within the range of 65°C to 100°C.

[0034] For example, in the heat-shrinkable film, the temperature (℃) at which tanδ is 1 or more may be 65℃ or more, 68℃ or more, 70℃ or more, 73℃ or more, or 75℃ or more, and may also be 100℃ or less, 95℃ or less, 90℃ or less, or 85℃ or less. As a specific example, the temperature (℃) at which tanδ is 1 or more in the heat-shrinkable film may be 65℃ to 100℃, or 68℃ to 100℃.

[0035] In particular, the present invention is characterized by controlling the tanδ characteristics of the heat-shrinkable film before and after shrinkage.

[0036] A heat-shrinkable film according to one embodiment may be a film stretched in the main shrinkage direction, and thus, tanδ before shrinkage may refer to tanδ for the stretched film, and tanδ after shrinkage may refer to tanδ for the stretched and shrunk film. Meanwhile, since the film after shrinkage is almost similar to the film in an unstretched state, tanδ after shrinkage may also be regarded as tanδ for the unstretched film.

[0037] By considering tanδ before and after shrinkage of the film, the shrinkage characteristics of the film can be controlled more effectively.

[0038] According to one embodiment, the heat-shrinkable film may have a temperature (℃) in the range of 65℃ to 85℃ at which tanδ is 1 or more when measured under the above temperature-elevating conditions after shrinking at 95℃ for 30 seconds.

[0039] For example, the temperature (℃) at which tanδ is 1 or more after shrinkage of the heat-shrinkable film may be 65℃ or more, 68℃ or more, 70℃ or more, 73℃ or more, or 75℃ or more, and may also be 85℃ or less, 83℃ or less, 80℃ or less, or 77℃ or less. As a specific example, the temperature (℃) at which tanδ is 1 or more in the heat-shrinkable film may be 65℃ to 85℃, or 68℃ to 85℃.

[0040] In particular, by adjusting the ratio of the tanδ maximum value of the film before and after shrinkage within a specific range, the shrinkage rate and shrinkage uniformity can be effectively controlled. Specifically, the shrinkage rate and shrinkage stress due to the crystallinity of the resin itself or the crystallinity generated during the stretching process are reflected in the tanδ of the film, and this can be effectively controlled by adjusting the ratio of the tanδ maximum value before and after shrinkage within a specific range.

[0041] According to one embodiment, when the heat-shrinkable film is cut in the main shrinkage direction, mounted on a tensile clamp, and measured using a dynamic mechanical analysis device (DMA) under a temperature increase condition of 3°C / min from 30°C to 150°C at a frequency of 1 Hz, the tanδ max ratio calculated by the following formula is 50% or more.

[0042] tanδ max ratio = (tanδ[1]max / tanδ[2]max) x 100

[0043] Here, tanδ[1]max is the maximum value of tanδ measured under the above temperature-elevating conditions for the heat-shrinkable film, and tanδ[2]max is the maximum value of tanδ measured under the above temperature-elevating conditions after shrinking the heat-shrinkable film at 95°C for 30 seconds.

[0044] In contrast, when the tanδ max ratio is less than 50%, the crystallinity of the polyester constituting the heat-shrinkable film is too high, so that a whitening phenomenon may occur due to partial crystallization during heat shrinkage, and the adhesion between the films may deteriorate or adhesion may become impossible.

[0045] For example, the tanδ max ratio may be 50% or more, 55% or more, 60% or more, 65% or more, 70% or more, or 75% or more, and may also be 120% or less, 100% or less, 95% or less, 90% or less, 85% or less, or 80% or less. As specific examples, the tanδ max ratio may be 50% to 120%, 50% to 100%, 50% to 95%, 55% to 100%, or 55% to 95%.

[0046] Additionally, the temperature at which tanδ 1 or more is measured for the film before shrinkage may be higher than the temperature at which tanδ 1 or more is measured after shrinkage of the heat-shrinkable film according to one embodiment. This is because orientation of polymer chains occurs during the stretching process of the film, and the degree to which the oriented chains move with temperature is different from that of the film after shrinkage.

[0047] In one specific example, the heat-shrinkable film can satisfy the following equation (a).

[0048] Tmax[1] > Tmax[2] (a)

[0049] Here, Tmax[1] is the highest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more, measured under the above temperature-elevating conditions for the heat-shrinkable film, and Tmax[2] is the highest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more, measured under the above temperature-elevating conditions after shrinking the heat-shrinkable film at 95℃ for 30 seconds.

[0050] In another specific example, the heat-shrinkable film may satisfy the following equation (a').

[0051] Tmin[1] > Tmin[2] (a')

[0052] Here, Tmin[1] is the lowest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more measured under the above temperature-elevating conditions for the heat-shrinkable film,

[0053] Tmin[2] is the lowest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more, measured under the above temperature rising conditions after shrinking the above heat-shrinkable film at 95℃ for 30 seconds.

[0054] In addition, the heat-shrinkable film according to one embodiment can control the size of a temperature range of tanδ 1 or more within a specific range.

[0055] During the stretching process, the temperature range where tanδ 1 or more is greater than or equal to 1 varies depending on the degree of crystal orientation of the polymer chains, and as the crystal orientation increases, the temperature range where tanδ 1 or more is greater than or equal to 1 becomes larger. Accordingly, if the temperature range where tanδ 1 or more is too large, it may be difficult to satisfy a high shrinkage rate during the shrinkage process due to the increase in crystal orientation. Conversely, if the temperature range where tanδ 1 or more is too small, the polymer chains may not be sufficiently oriented due to the decrease in crystal orientation, making it difficult to satisfy shrinkage uniformity during the shrinkage process.

[0056] In one specific example, the heat-shrinkable film can satisfy the following equation (b).

[0057] 10℃ ≤ Tmax[1] - Tmin[1] ≤ 30℃ (b)

[0058] Here, Tmax[1] is the highest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more as measured for the heat-shrinkable film under the above temperature-elevating conditions, and Tmin[1] is the lowest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more as measured for the heat-shrinkable film under the above temperature-elevating conditions.

[0059] For example, in the above formula (b), the calculated value of Tmax[1] - Tmin[1] may be 10°C to 30°C, 15°C to 30°C, 10°C to 25°C, 15°C to 25°C, 15°C to 20°C, or 10°C to 20°C.

[0060] In another specific example, the heat-shrinkable film may satisfy the following equation (b').

[0061] 1℃ ≤ Tmax[2] - Tmin[2] ≤ 20℃ (b')

[0062] Here, Tmax[2] is the highest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more, measured under the above temperature-elevating conditions after shrinking the heat-shrinkable film at 95℃ for 30 seconds, and Tmin[2] is the lowest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more, measured under the above temperature-elevating conditions after shrinking the heat-shrinkable film at 95℃ for 30 seconds.

[0063] For example, in the above formula (b'), the calculated value of Tmax[2] - Tmin[2] may be 1°C to 20°C, 1°C to 15°C, 5°C to 20°C, 5°C to 15°C, 1°C to 10°C, or 5°C to 10°C.

[0064] In addition, the heat-shrinkable film according to one embodiment may have a temperature range where tanδ is 1 or greater than or equal to a certain level greater before shrinkage than after shrinkage. A difference of tanδ of a certain level or greater between the stretched / shrinkable film indicates the orientation of the polymer chains, and when chain orientation of a certain level or greater occurs, the heat-shrinkable film may exhibit high shrinkage and stretching uniformity, which are characteristics of the heat-shrinkable film.

[0065] In one specific example, the heat-shrinkable film can satisfy the following equation (c) with tanδ 1 or greater.

[0066] 3℃ ≤ (Tmax[1] - Tmin[1]) - (Tmax[2] - Tmin[2]) (c)

[0067] Here, Tmax[1] is the highest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more as measured under the above temperature-elevating conditions for the heat-shrinkable film, Tmin[1] is the lowest temperature (℃), Tmax[2] is the highest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more as measured under the above temperature-elevating conditions after shrinking the heat-shrinkable film at 95℃ for 30 seconds, and Tmin[2] is the lowest temperature (℃).

[0068] For example, in the above formula (c), the calculated value of Tmax[1] - Tmin[1]) - (Tmax[2] - Tmin[2]) may be 3°C or more, 5°C or more, 7°C or more, or 10°C or more, and may also be 30°C or less, 25°C or less, 20°C or less, or 15°C or less.

[0069] In addition, the heat-shrinkable film according to one embodiment can have excellent stretchability by controlling the stiffness ratio before and after shrinkage within a specific range.

[0070] Specifically, the heat-shrinkable film may have a stiffness ratio of 150% or more, as defined by the following equation.

[0071] Stiffness ratio = (Stiffness[2] / Stiffness[1]) x 100

[0072] Here, stiffness [1] is a stiffness measurement value (N / m) of the heat-shrinkable film, stiffness [2] is a stiffness measurement value (N / m) after shrinkage of the heat-shrinkable film at 95°C for 30 seconds, and the stiffness is measured at a temperature at which the tanδ measurement value of the heat-shrinkable film is 1.

[0073] Within the above preferred range, the orientation of the polymer constituting the film can be appropriately adjusted to improve stretchability.

[0074] For example, the stiffness ratio may be 150% or more, 200% or more, 250% or more, 300% or more, 350% or more, or 400% or more, and may also be 700% or less, 600% or less, or 500% or less. As specific examples, the stiffness ratio may be 150% to 700%, 150% to 600%, or 150% to 500%.

[0075] In addition, the heat-shrinkable film according to the above embodiment can have a shrinkage speed controlled within a certain range depending on the temperature in the heat-shrinkage process temperature range.

[0076] Specifically, the heat-shrinkable film is cut to have an initial dimension of 15.5 cm in the main shrinkage direction, mounted on a film tension clamp, and heated at a rate of 5°C / min from 65°C to 85°C, and held for 1 minute at 5°C intervals. The shrinkage that occurs during the heating may be -0.3 cm / °C to -0.7 cm / °C.

[0077]

[0078] In this way, the shrinkage rate according to temperature is high when the shrinkage is -0.3 cm / ℃ or higher, so sufficient shrinkage can be exhibited, and the change in shrinkage rate according to temperature is appropriate when the shrinkage rate is -0.7 cm / ℃ or lower, so uniformity of shrinkage according to temperature change can be secured.

[0079] Accordingly, the heat-shrinkable film has a low risk of the film breaking due to tension during the processing, which will result in a decrease in processing operability.

[0080] More specifically, the shrinkage may be -0.3 cm / °C to -0.7 cm / °C, -0.4 cm / °C to -0.7 cm / °C, -0.5 cm / °C to -0.7 cm / °C, -0.3 cm / °C to -0.6 cm / °C, -0.3 cm / °C to -0.5 cm / °C, or -0.4 cm / °C to -0.6 cm / °C.

[0081] The heat-shrinkable film may have a shrinkage ratio at a certain level or higher at high temperatures. For example, the heat-shrinkable film may have a shrinkage ratio in the main shrinkage direction of 60% or higher at 90°C for 15 seconds. Specifically, the heat-shrinkable film may have a shrinkage ratio in the main shrinkage direction of 60% to 80% at 90°C for 15 seconds.

[0082] A heat-shrinkable film according to one embodiment may be a film that is stretched in at least one direction. The heat-shrinkable film may be a film that is uniaxially stretched in the machine direction (MD) or the transverse direction (TD), or a film that is biaxially stretched in these two directions.

[0083] As an example, the heat-shrinkable film may be a film stretched 1 to 5 times in the machine direction (MD), or 1.1 to 4.5 times. As another example, the heat-shrinkable film may be a film stretched 1.5 to 6 times in the transverse direction (TD), or 2.5 to 5.5 times. As yet another example, the heat-shrinkable film may be a film stretched 1 to 5 times in the machine direction (MD) and 1.5 to 6 times in the transverse direction (TD).

[0084] The heat-shrinkable film may have a main shrinkage direction in the longitudinal direction (MD) or the transverse direction (TD). Specifically, the heat-shrinkable film may have a draw ratio in the main shrinkage direction of 1.5 to 6 times. More specifically, the heat-shrinkable film may be a film whose main shrinkage direction is the transverse direction (TD).

[0085]

[0086] Components of heat-shrinkable film

[0087] A heat-shrinkable film according to the present invention comprises a copolymerized polyester resin containing a diol component and a dicarboxylic acid component.

[0088] Additionally, at least one of the diol component and the dicarboxylic acid component may include a regenerated monomer.

[0089] According to the present invention, the diol component may be a diol component used in the production of a copolymerized polyester resin.

[0090] Specifically, the diol component is bis(2-hydroxyethyl)terephthalate (BHET), isosorbide, neopentyl glycol, ethylene glycol, cyclohexanedimethanol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-methylene-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, diethylene glycol, It may be at least one selected from the group consisting of 4-(hydroxymethyl)cyclohexylmethyl 4-(hydroxymethyl)cyclohexanecarboxylate, 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol.

[0091] Preferably, when considering the crystallinity, heat shrinkability, economic efficiency, etc. of the polyester heat-shrinkable film, the diol component may include two or more (specifically, three or more, four or more, or five or more) selected from the group consisting of bis(2-hydroxyethyl)terephthalate, isosorbide, ethylene glycol, cyclohexanedimethanol, neopentyl glycol, diethylene glycol, 4-(hydroxymethyl)cyclohexylmethyl 4-(hydroxymethyl)cyclohexanecarboxylate, and 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol.

[0092] For example, the diol component may include ethylene glycol and, as a comonomer, at least one (specifically, at least two, at least three, or at least four) selected from the group consisting of bis(2-hydroxyethyl)terephthalate, isosorbide, cyclohexanedimethanol, neopentylglycol, diethylene glycol, 4-(hydroxymethyl)cyclohexylmethyl 4-(hydroxymethyl)cyclohexanecarboxylate, and 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol.

[0093] In addition, the diol component may include a regenerated monomer obtained by depolymerization of waste polyester. As a specific example, the diol component may include at least one regenerated monomer selected from the group consisting of regenerated diols and regenerated diol derivatives. As a more specific example, the diol component may include at least one regenerated monomer selected from the group consisting of, but not limited to, regenerated bis(2-hydroxyethyl)terephthalate, regenerated ethylene glycol, regenerated 1,4-cyclohexanedimethanol, regenerated diethylene glycol, and regenerated isosorbide.

[0094] When the above diol component includes ethylene glycol and a comonomer, the amounts of these components used are not particularly limited, but based on the total weight of the diol component, the amount of ethylene glycol used may be 10 wt% or more but less than 100 wt%, 15 to 90 wt%, 20 to 85 wt%, 30 to 85 wt%, 50 to 80 wt%, or 50 to 85 wt%, and the amount of the comonomer used may be more than 0 to 90 wt%, more than 0 to 85 wt%, 1 to 90 wt%, 1 to 50 wt%, 2 to 50 wt%, 10 to 85 wt%, 15 to 80 wt%, 15 to 70 wt%, or 15 to 50 wt%.

[0095] The amount of isosorbide as the comonomer may be 0 to 30 wt%, 0 to 10 wt%, 0 to 3 wt%, 0.1 to 20 wt%, 0.5 to 10 wt%, 0.5 to 5 wt%, 0.5 to 3 wt%, or 1 to 3 wt%, based on the total weight of the diol component. The amount of 1,4-cyclohexanediol as the comonomer may be 0 to 50 wt%, 0 to 40 wt%, 1 to 50 wt%, 2 to 50 wt%, 3 to 45 wt%, 4 to 40 wt%, or 5 to 35 wt%, based on the total weight of the diol component. The amount of neopentyl glycol used as the comonomer may be 0 to 50 wt%, 0 to 30 wt%, 1 to 50 wt%, 2 to 50 wt%, 3 to 45 wt%, 4 to 40 wt%, or 5 to 35 wt%, based on the total weight of the diol component. The amount of diethylene glycol used as the comonomer may be 0 to 50 wt%, 1 to 50 wt%, 1 to 30 wt%, 1 to 15 wt%, 2 to 50 wt%, 3 to 45 wt%, 4 to 40 wt%, 5 to 35 wt%, 5 to 25 wt%, or 5 to 15 wt%, based on the total weight of the diol component.

[0096] The polyester resin according to the present invention may contain 0 to 30 mol%, 0 to 10 mol%, 0 to 3 mol%, 0.1 to 20 mol%, 0.5 to 10 mol%, 0.5 to 5 mol%, 0.5 to 3 mol%, or 1 to 3 mol% of a structural unit derived from isosorbide as a copolymerization unit. The polyester resin according to the present invention may contain 0 to 50 mol%, 0 to 35 mol%, 1 to 50 mol%, 2 to 50 mol%, 3 to 45 mol%, 4 to 40 mol%, or 5 to 35 mol% of a structural unit derived from 1,4-cyclohexanediol as a copolymerization unit. The polyester resin according to the present invention may contain 0 to 50 mol%, 0 to 30 mol%, 1 to 50 mol%, 2 to 50 mol%, 3 to 45 mol%, 4 to 40 mol%, or 5 to 35 mol% of a structural unit derived from neopentyl glycol as a copolymerization unit. The polyester resin according to the present invention may contain 0 to 50 mol%, 1 to 50 mol%, 2 to 50 mol%, 3 to 45 mol%, 4 to 40 mol%, or 5 to 35 mol% of a structural unit derived from diethylene glycol as a copolymerization unit.

[0097] According to the present invention, the dicarboxylic acid component may be a commonly known dicarboxylic acid component.

[0098] Specifically, the dicarboxylic acid component may include at least one selected from the group consisting of isophthalic acid, terephthalic acid, dimethyl isophthalate, phthalic acid, dimethyl phthalate, phthalic anhydride, 2,6-naphthalene dicarboxylic acid, dimethyl 2,6-naphthalene dicarboxylate, diphenyl dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, 1,3-cyclohexane dicarboxylic acid, dimethyl 1,4-cyclohexane dicarboxylate, dimethyl 1,3-cyclohexane dicarboxylate, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, maleic anhydride, fumaric acid, adipic acid, glutaric acid, and azelaic acid.

[0099] Preferably, when considering the crystallinity and heat shrinkage properties of the polyester stretch film, the dicarboxylic acid component may include at least one selected from the group consisting of isophthalic acid, terephthalic acid, dimethyl phthalate, and dimethyl isophthalate.

[0100] In addition, the dicarboxylic acid component may include a regenerated monomer obtained by depolymerization of waste polyester. As a specific example, the dicarboxylic acid component may include one or more regenerated monomers selected from the group consisting of regenerated dicarboxylic acids and regenerated dicarboxylic acid derivatives. As a more specific example, the dicarboxylic acid component may include one or more regenerated monomers selected from the group consisting of regenerated isophthalic acid, regenerated terephthalic acid, regenerated dimethyl isophthalate, and regenerated dimethyl phthalate, but is not limited thereto.

[0101] The regenerated monomer obtained by depolymerizing waste polyester must be understood distinctly from virgin monomer or pure monomer compounds. Specifically, the regenerated monomer contains reagents or solvents used in the various chemical steps during depolymerization from waste polyester, or by-products generated by side reactions with these reagents or solvents. Therefore, the regenerated monomer obtained through typical depolymerization methods often contains organic and inorganic impurities in addition to the main monomer compound, resulting in a low purity. For this reason, the regenerated monomer can be viewed as a composition comprising two or more components.

[0102] According to the present invention, the polyester resin may have an intrinsic viscosity (IV) at 35°C of 0.5 dl / g or more or 0.6 dl / g or more, and may also have an IV of 1.2 dl / g or less, 1.1 dl / g or less, 1.0 dl / g or less, 0.9 dl / g or less or 0.8 dl / g or less.

[0103] According to one specific example, the copolymerized polyester resin may have an intrinsic viscosity of 0.5 dl / g to 0.9 dl / g at 35°C. This may be advantageous in ensuring the processability of the copolymerized polyester resin within the above preferred intrinsic viscosity range. Specifically, the intrinsic viscosity may be measured using a Ubbelrod viscometer in a constant temperature bath at 35°C after dissolving the polyester resin in orthochlorophenol (OCP) at a concentration of 0.12% at 100°C.

[0104]

[0105] Method for manufacturing heat-shrinkable film

[0106] A method for manufacturing a heat-shrinkable film according to the present invention may include a step (S-1) of manufacturing a polyester resin by polymerizing a diol component and a dicarboxylic acid component; a step (S-2) of manufacturing a stretched sheet from the polyester resin; and a step (S-3) of heat-setting the stretched sheet.

[0107] The above step (S-1) is a step for producing a polyester resin (copolymer) by polymerizing a diol component and a dicarboxylic acid component. Descriptions of each of the diol component and the dicarboxylic acid component for the polymerization are the same as those described above, and therefore are omitted.

[0108] The polymerization of the above diol component and the above dicarboxylic acid component can be carried out by a conventionally known method (e.g., liquid phase polymerization, solid phase polymerization, etc.), and a batch reactor or a continuous reactor can be used for the polymerization reaction. Specifically, the polymerization reaction can include an esterification reaction (esterification exchange reaction) in which the diol component and the dicarboxylic acid component are reacted to produce an oligomer, and a polycondensation reaction of the oligomer.

[0109] The temperature at which the esterification reaction takes place is not particularly limited, but considering the properties of the polyester resin and the polyester stretched film, it may be 230°C to 270°C, 235°C to 268°C, 240°C to 265°C, or 240°C to 260°C. In addition, the time at which the esterification reaction takes place is not particularly limited, but may be 1 to 24 hours, 2 to 22 hours, 3 to 20 hours, or 4 to 18 hours. In addition, the pressure applied during the esterification reaction is not particularly limited, but may be 0 kgf / cm. 2 5.0 kgf / cm 2 , 0.1 kgf / cm 2 Up to 4.5 kgf / cm 2 , 0.1 kgf / cm 2 4.0 kgf / cm 2 , or 0.1 kgf / cm 2 3.0 kgf / cm 2 It could be.

[0110] The temperature at which the polycondensation reaction takes place is not particularly limited, but considering the properties of the polyester resin and the polyester stretched film, it may be 245°C to 290°C, 250°C to 285°C, 255°C to 280°C, or 255°C to 270°C. In addition, the time at which the polycondensation reaction takes place is not particularly limited, but may be 1 to 24 hours, 2 to 24 hours, 5 to 22 hours, or 7 to 20 hours.

[0111] Meanwhile, an additive including at least one selected from the group consisting of a catalyst, a stabilizer, a coloring agent, a crystallizer, an antioxidant, and a branching agent may be added to the polymerization reaction.

[0112] The catalyst is not particularly limited, but specifically, methylates of sodium and magnesium; acetates, borates, fatty acid salts, or carbonates of Zn, Cd, Mn, Co, Ca, Ba, etc.; oxides or hydrates of Mg, Pb, Mn, Ti, Zn, Sb, Ge, etc. can be used. For example, the catalyst can be tetraethyl titanate, acetyltripropyl titanate, tetrapropyl titanate, tetrabutyl titanate, 2-ethylhexyl titanate, octylene glycol titanate, triethanolamine titanate, acetylacetonate titanate, ethylacetoacetic ester titanate, isostearyl titanate, titanium dioxide, germanium dioxide, germanium tetrachloride, germanium ethyleneglycoxide, germanium acetate, or a combination thereof.

[0113] The above stabilizer is not particularly limited, but phosphorus compounds such as phosphoric acid, trimethyl phosphate, and triethyl phosphate can be used.

[0114] The above coloring agent is not particularly limited, but organic compounds such as cobalt compounds, anthraquinone compounds, perinone compounds, azo compounds, and methine compounds (e.g., cobalt acetate, cobalt propionate, Clarient's Polysynthren Blue RLS toner, Clarient's Solvaperm Red BB toner) can be used.

[0115] The above crystallizer is not particularly limited, but a crystal nucleating agent, an ultraviolet absorber, a polyolefin resin, a polyamide resin, etc. can be used.

[0116] The above antioxidant is not particularly limited, but hindered phenol compounds, phosphite compounds, thioether compounds, etc. can be used.

[0117] The above-mentioned branching agent is not particularly limited, but trimellitic anhydride, trimellitic propane, trimellitic acid, etc. can be used.

[0118] The above step (S-2) is a step for manufacturing a stretched sheet from the polyester resin obtained in the above step (S-1). The manufacturing of the stretched sheet can be carried out by a conventionally known method, and specifically, the stretched sheet can be manufactured through a melting and casting process of the polyester resin, a uniaxial or biaxial stretching process, etc.

[0119] The melting and casting process of the polyester resin may be performed through an extruder, and at this time, the melting temperature is not particularly limited, but may be 180°C to 310°C, 200°C to 310°C, 230°C to 310°C, 240°C to 300°C, 250°C to 290°C, 300°C, 250°C to 280°C, or 250°C to 275°C. By performing this process, an unstretched sheet may be obtained, and the obtained unstretched sheet may be passed to a stretching process. The unstretched sheet may be preheated to a predetermined temperature (e.g., 90°C to 120°C) before undergoing the stretching process.

[0120] The above-described single-axis or two-axis stretching process may include stretching the unstretched sheet obtained through the above-described melting and casting process in the machine direction (MD), the transverse direction (TD), or both. The stretching in the machine direction may be performed at a temperature of 55°C to 180°C, 60°C to 170°C, or 75°C to 90°C, and at a stretching ratio of 1 to 5 times, or 1.1 to 4.5 times. Additionally, the transverse stretching may be performed at a stretching ratio of 1.5 to 6 times, 2.5 to 5.5 times, 3.5 to 6 times, 4 to 6 times, 4.5 to 6 times, 4.5 to 5.5 times, or 3.5 to 5.5 times at a temperature of 55°C to 180°C, 60°C to 170°C, 60°C to 130°C, 60°C to 90°C, 60°C to 85°C, 75°C to 90°C, or 75°C to 85°C.

[0121] The above step (S-3) is a step of heat-setting the stretched sheet obtained in the above step (S-2). The temperature at which the stretched sheet is heat-set is not particularly limited, but may be similar to or higher than the stretching process temperature. Specifically, the heat-setting temperature may be 60°C to 200°C, 65°C to 190°C, 65°C to 180°C, or 65°C to 170°C. As the heat-setting temperature is within the above range, a polyester stretched film with increased crystallinity and mechanical strength can be manufactured.

[0122]

[0123] [Example]

[0124] Hereinafter, preferred examples are presented to aid in understanding the present invention. However, the following examples are provided solely to facilitate a better understanding of the present invention and are not intended to limit the scope of the present invention.

[0125]

[0126] <Manufacturing of heat-shrinkable film>

[0127]

[0128] Example 1

[0129] (1) Production of copolymerized polyester resin

[0130] Terephthalic acid (TPA, 3846.5 g), isosorbide (ISB, 48.3 g), ethylene glycol (EG, 1300.6 g), 1,4-cyclohexanedimethanol (CHDM, 778.6 g), diethylene glycol (DEG, 375.5 g), Ge catalyst (GeO2, 1.0 g), Ti catalyst (1.0 g), phosphoric acid (1.5 g), blue toner (0.005 g), and red toner (0.003 g) were added to a reactor connected to a column and a condenser that could be cooled by water. Then, the temperature of the reactor was increased to 2 kgf / cm2 above atmospheric pressure. 2 The esterification reaction was carried out at 265°C under high pressure to obtain a transparent reactant.

[0131] Next, the reactants were transferred to a polycondensation reactor, and the polycondensation reaction was performed at 270°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (IV) of the reactants inside the polycondensation reactor reached 0.77 dl / g, the reactants were discharged outside the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to an average weight of about 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0132] (2) Manufacturing of heat-shrinkable film

[0133] Each of the polyester resin chips obtained in the above manufacturing examples was fed into an extruder and melt-extruded at a temperature of 270°C and cast at a temperature of 40°C to produce an unstretched polyester sheet. Subsequently, the unstretched sheet was heated to 80°C and stretched only in the transverse direction (TD) at a stretch ratio of 5 times to produce a stretched polyester sheet. The stretched polyester sheet was heat-set to produce a stretched polyester film having a thickness of 50 μm.

[0134]

[0135] Example 2

[0136] (1) Production of copolymerized polyester resin

[0137] Terephthalic acid (TPA, 3831.6 g), ethylene glycol (EG, 1672.8 g), 1,4-cyclohexanedimethanol (CHDM, 627.8 g), neopentyl glycol (NPG, 53.3 g), diethylene glycol (DEG, 374.2 g), CHDM derivative (123.7 g), Ti catalyst (1.0 g), phosphoric acid (1.5 g), blue toner (0.005 g), and red toner (0.005 g) were added to a reactor connected to a column and a condenser that could be cooled by water. Then, the temperature of the reactor was increased to 1 kgf / cm2 above atmospheric pressure. 2 The esterification reaction was carried out at 255°C under high pressure to obtain a transparent reactant.

[0138] Next, the reactants were transferred to a polycondensation reactor, and the polycondensation reaction was performed at 285°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (IV) of the reactants inside the polycondensation reactor reached 0.65 dl / g, the reactants were discharged outside the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to an average weight of about 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0139] (2) Manufacturing of heat-shrinkable film

[0140] Each of the polyester resin chips obtained in the above manufacturing examples was fed into an extruder and melt-extruded at a temperature of 260°C and cast at a temperature of 25°C to produce an unstretched polyester sheet. Subsequently, the unstretched sheet was heated to 80°C and stretched only in the transverse direction (TD) at a stretch ratio of 4.5 times to produce a stretched polyester sheet. The stretched polyester sheet was heat-set to produce a stretched polyester film having a thickness of 50 μm.

[0141]

[0142] Example 3

[0143] (1) Production of copolymerized polyester resin

[0144] Into a reactor connected to a column and a water-cooled condenser, terephthalic acid (TPA, 2949.8 g), regenerated bis(2-hydroxyethyl) terephthalate (r-BHET, 1128.4 g), ethylene glycol (EG, 412.2 g), 1,4-cyclohexanedimethanol (CHDM, 1243.9 g), diethylene glycol (DEG, 277.0 g), Ge catalyst (1.0 g), phosphoric acid (1.5 g), blue toner (0.005 g), and red toner (0.005 g) were charged. Then, the temperature of the reactor was increased, and an esterification reaction was performed at 273°C under atmospheric pressure to obtain a transparent reactant.

[0145] Next, the reactants were transferred to a polycondensation reactor, and the polycondensation reaction was performed at 275°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (IV) of the reactants inside the polycondensation reactor reached 0.80 dl / g, the reactants were discharged outside the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to an average weight of about 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0146] (2) Manufacturing of heat-shrinkable film

[0147] Each of the polyester resin chips obtained in the above manufacturing examples was fed into an extruder and melt-extruded at a temperature of 260°C and cast at a temperature of 68°C to produce an unstretched polyester sheet. Subsequently, the unstretched sheet was heated to 78°C and stretched only in the transverse direction (TD) at a stretch ratio of 4.5 times to produce a stretched polyester sheet. The stretched polyester sheet was heat-set to produce a stretched polyester film having a thickness of 50 μm.

[0148]

[0149] Example 4

[0150] (1) Production of copolymerized polyester resin

[0151] Terephthalic acid (TPA, 3959.2 g), ethylene glycol (EG, 2040.3 g), 1,4-cyclohexanedimethanol (CHDM, 534.2 g), diethylene glycol (DEG, 416.4 g), Ge catalyst (1.0 g), phosphoric acid (1.5 g), blue toner (0.025 g), and red toner (0.010 g) were added to a reactor connected to a column and a condenser that could be cooled by water. Then, the temperature of the reactor was increased to 1 kgf / cm2 above atmospheric pressure. 2 The esterification reaction was carried out at 260°C under high pressure to obtain a transparent reactant.

[0152] Next, the reactants were transferred to a polycondensation reactor, and the polycondensation reaction was performed at 275°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (IV) of the reactants inside the polycondensation reactor reached 0.78 dl / g, the reactants were discharged outside the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to an average weight of about 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0153] (2) Manufacturing of heat-shrinkable film

[0154] Each of the polyester resin chips obtained in the above manufacturing examples was fed into an extruder and melt-extruded at a temperature of 275°C and cast at a temperature of 35°C to produce an unstretched polyester sheet. Subsequently, the unstretched sheet was heated to 78°C and stretched only in the transverse direction (TD) at a stretch ratio of 5 times to produce a stretched polyester sheet. The stretched polyester sheet was heat-set to produce a stretched polyester film having a thickness of 50 μm.

[0155]

[0156] Example 5

[0157] (1) Production of copolymerized polyester resin

[0158] Terephthalic acid (TPA, 4139.7 g), ethylene glycol (EG, 2216.1 g), neopentyl glycol (NPG, 432.3 g), diethylene glycol (DEG, 155.5 g), Ge catalyst (1.0 g), phosphoric acid (1.5 g), cobalt acetate (0.2 g), blue toner (0.015 g), and red toner (0.005 g) were added to a reactor connected to a column and a condenser that could be cooled by water. Then, the temperature of the reactor was increased to 1 kgf / cm2 above atmospheric pressure. 2 The esterification reaction was carried out at 250°C under high pressure to obtain a transparent reactant.

[0159] Next, the reactants were transferred to a polycondensation reactor, and the polycondensation reaction was performed at 285°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (IV) of the reactants inside the polycondensation reactor reached 0.70 dl / g, the reactants were discharged outside the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to an average weight of about 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0160] (2) Manufacturing of heat-shrinkable film

[0161] Each of the polyester resin chips obtained in the above manufacturing examples was fed into an extruder and melt-extruded at a temperature of 270°C and cast at a temperature of 36°C to produce an unstretched polyester sheet. Subsequently, the unstretched sheet was heated to 85°C and stretched only in the transverse direction (TD) at a stretch ratio of 4.5 times to produce a stretched polyester sheet. The stretched polyester sheet was heat-set to produce a stretched polyester film having a thickness of 50 μm.

[0162]

[0163] Example 6

[0164] (1) Production of copolymerized polyester resin

[0165] Terephthalic acid (TPA, 2291.3 g), regenerated bis(2-hydroxyethyl) terephthalate (r-BHET, 1144.2 g), ethylene glycol (EG, 369.7 g), 1,4-cyclohexanedimethanol (CHDM, 720.8 g), neopentyl glycol (NPG, 650.7 g), diethylene glycol (DEG, 196.6 g), Ge catalyst (1.0 g), phosphoric acid (1.5 g), cobalt acetate (0.2 g), blue toner (0.015 g), and red toner (0.005 g) were added to a reactor connected to a column and a condenser that could be cooled by water. Then, the temperature of the reactor was increased to 2 kgf / cm2 above atmospheric pressure. 2 The esterification reaction was carried out at 265°C under high pressure to obtain a transparent reactant.

[0166] Next, the reactants were transferred to a polycondensation reactor, and the polycondensation reaction was performed at 270°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (IV) of the reactants inside the polycondensation reactor reached 0.78 dl / g, the reactants were discharged outside the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to an average weight of about 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0167] (2) Manufacturing of heat-shrinkable film

[0168] Each of the polyester resin chips obtained in the above manufacturing examples was fed into an extruder and melt-extruded at a temperature of 260°C and cast at a temperature of 38°C to produce an unstretched polyester sheet. Subsequently, the unstretched sheet was heated to 85°C and stretched only in the transverse direction (TD) at a stretch ratio of 4.5 times to produce a stretched polyester sheet. The stretched polyester sheet was heat-set to produce a stretched polyester film having a thickness of 50 μm.

[0169]

[0170] Comparative Example 1

[0171] (1) Production of copolymerized polyester resin

[0172] Into a reactor connected to a column and a condenser that can be cooled by water, terephthalic acid (TPA, 3280.6 g), regenerated bis(2-hydroxyethyl) terephthalate (r-BHET, 1254.9 g), ethylene glycol (EG, 1487.6 g), 1,4-cyclohexanedimethanol (CHDM, 395.3 g), diethylene glycol (DEG, 154.0 g), Ti catalyst (1.0 g), phosphoric acid (1.5 g), blue toner (0.005 g), and red toner (0.005 g) were added. Then, the temperature of the reactor was increased to 1 kgf / cm2 above atmospheric pressure. 2 The esterification reaction was carried out at 263°C under high pressure to obtain a transparent reactant.

[0173] Next, the reactants were transferred to a polycondensation reactor, and the polycondensation reaction was performed at 285°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (IV) of the reactants inside the polycondensation reactor reached 0.70 dl / g, the reactants were discharged outside the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to an average weight of about 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0174] (2) Manufacturing of heat-shrinkable film

[0175] Each of the polyester resin chips obtained in the above manufacturing examples was fed into an extruder and melt-extruded at a temperature of 280°C and cast at a temperature of 25°C to produce an unstretched polyester sheet. Subsequently, the unstretched sheet was heated to 90°C and stretched only in the transverse direction (TD) at a stretch ratio of 4.5 times to produce a stretched polyester sheet. The stretched polyester sheet was heat-set to produce a stretched polyester film having a thickness of 50 μm.

[0176]

[0177] Comparative Example 2

[0178] (1) Production of copolymerized polyester resin

[0179] Into a reactor connected to a column and a water-cooled condenser, terephthalic acid (TPA, 3259.2 g), regenerated bis(2-hydroxyethyl) terephthalate (r-BHET, 554.1 g), ethylene glycol (EG, 971.5 g), 1,4-cyclohexanedimethanol (CHDM, 349.0 g), diethylene glycol (DEG, 272.0 g), a Ti catalyst (1.0 g), phosphoric acid (1.5 g), blue toner (0.010 g), and red toner (0.005 g) were charged. Subsequently, the temperature of the reactor was increased, and an esterification reaction was performed at 263°C under atmospheric pressure to obtain a transparent reactant.

[0180] Next, the reactants were transferred to a polycondensation reactor, and the polycondensation reaction was performed at 275°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (IV) of the reactants inside the polycondensation reactor reached 0.78 dl / g, the reactants were discharged outside the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to an average weight of about 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0181] (2) Manufacturing of heat-shrinkable film

[0182] Each of the polyester resin chips obtained in the above manufacturing examples was fed into an extruder and melt-extruded at a temperature of 270°C and cast at a temperature of 25°C to produce an unstretched polyester sheet. Subsequently, the unstretched sheet was heated to 85°C and stretched only in the transverse direction (TD) at a stretch ratio of 4 times to produce a stretched polyester sheet. The stretched polyester sheet was heat-set to produce a stretched polyester film having a thickness of 50 μm.

[0183]

[0184] Comparative Example 3

[0185] (1) Production of copolymerized polyester resin

[0186] Terephthalic acid (TPA, 3316.3 g), ethylene glycol (EG, 122.2 g), 1,4-cyclohexanedimethanol (CHDM, 2237.5 g), diethylene glycol (DEG, 49.8 g), Ti catalyst (1.0 g), phosphoric acid (1.5 g), blue toner (0.005 g), and red toner (0.005 g) were added to a reactor connected to a column and a condenser that could be cooled by water. Then, the temperature of the reactor was increased to 1 kgf / cm2 above atmospheric pressure. 2 The esterification reaction was carried out at 263°C under high pressure to obtain a transparent reactant.

[0187] Next, the reactants were transferred to a polycondensation reactor, and the polycondensation reaction was performed at 275°C while maintaining the pressure of the polycondensation reactor lower than atmospheric pressure. When the intrinsic viscosity (IV) of the reactants inside the polycondensation reactor reached 0.70 dl / g, the reactants were discharged outside the polycondensation reactor to form strands, which were then solidified with a cooling liquid and granulated to an average weight of about 12 to 14 mg, thereby manufacturing polyester resin (copolymer) chips.

[0188] (2) Manufacturing of heat-shrinkable film

[0189] Each of the polyester resin chips obtained in the above manufacturing examples was fed into an extruder and melt-extruded at a temperature of 290°C and cast at a temperature of 40°C to produce an unstretched polyester sheet. Subsequently, the unstretched sheet was heated to 95°C and stretched only in the transverse direction (TD) at a stretch ratio of 4 times to produce a stretched polyester sheet. The stretched polyester sheet was heat-set to produce a stretched polyester film having a thickness of 50 μm.

[0190]

[0191] <Evaluation of heat-shrinkable films>

[0192]

[0193] Test Example 1: tanδ (DMA)

[0194] The tanδ of the heat-shrinkable films manufactured in the above examples and comparative examples was measured.

[0195]

[0196] (1) tanδ - stretched film

[0197] - Sample: A film with a thickness of approximately 50 ㎛ stretched in the TD direction was cut in the width direction (TD).

[0198] - The stretched film sample was mounted on a tension clamp and a dynamic mechanical analysis device (DMA, TA Q800) was used to obtain the tanδ curve under the temperature increasing condition of 3℃ / min from 30℃ to 150℃ at a frequency of 1 Hz (tanδ = E' / E", where E' is the storage modulus and E'' is the loss modulus).

[0199] - Among the temperatures where tanδ ≥ 1, the lowest temperature (min) and the highest temperature (max) were obtained, and their difference value (max-min) was obtained.

[0200]

[0201] (2) tanδ - after shrinkage

[0202] - Sample: A film with a thickness of approximately 50 ㎛ stretched in the TD direction was cut in the width direction (TD) and then shrunk at 95°C for 30 seconds.

[0203] - After shrinkage, the tanδ curve of the film sample was obtained in the same manner as in (1) above.

[0204] - Among the temperatures where tanδ ≥ 1, the lowest temperature (min) and the highest temperature (max) were obtained, and their difference value (max-min) was obtained.

[0205]

[0206] (3) tanδ gap

[0207] The difference value (i.e., the value of (1)-(2)) between the temperature gap (max-min) of the stretched film measured in (1) above with tanδ ≥ 1 and the temperature gap (max-min) of the film after shrinkage measured in (2) above with tanδ ≥ 1 was obtained.

[0208]

[0209] (4) tanδ maximum value ratio

[0210] The ratio of the maximum value of tanδ of the stretched film measured in (1) above and the maximum value of tanδ of the film after shrinkage measured in (2) above (i.e., the value of (1) / (2)) was obtained.

[0211]

[0212] Test Example 2: Stiffness

[0213] The stiffness of the films manufactured in the above examples and comparative examples was measured.

[0214]

[0215] (1) Stiffness - Stretched film

[0216] - Sample: A film with a thickness of approximately 50 ㎛ stretched in the TD direction was cut in the width direction (TD).

[0217] - The stretched film sample was mounted on a tension clamp and the stiffness was measured using a dynamic mechanical analysis device (DMA, TA Q800) at a frequency of 1 Hz under a temperature increase condition of 3°C / min from 30°C to 150°C.

[0218]

[0219] (2) Stiffness - After shrinkage

[0220] - Sample: A film with a thickness of approximately 50 ㎛ stretched in the TD direction was cut in the width direction (TD) and then shrunk at 95°C for 30 seconds.

[0221] - After shrinkage, stiffness was measured in the same manner as in (1) above.

[0222]

[0223] (3) Stiffness ratio

[0224] The ratio of the stiffness of the film after shrinkage measured in (2) to the stiffness of the stretched film measured in (1) above (i.e., the value of (2) / (1)) was obtained. The stiffness was obtained using the value measured at the temperature at which the tanδ of the film was 1.

[0225]

[0226] Test Example 3: Shrinkage Uniformity

[0227] The shrinkage uniformity of the films manufactured in the above examples and comparative examples was measured.

[0228] - Sample: A film with a thickness of approximately 50 ㎛ stretched in the TD direction was cut to have an initial dimension of 15.5 cm in the width direction (TD).

[0229] - The stretched film sample was mounted on a tension clamp and heated at a rate of 5°C / min from 65°C to 85°C, held for 1 minute at 5°C intervals, and the shrinkage (cm) occurring during the heating was measured. Based on the measured values, the shrinkage (cm / °C) according to temperature was calculated to evaluate the shrinkage uniformity.

[0230]

[0231] Test Example 4: Intrinsic Viscosity

[0232] The polyester resins obtained in the examples were dissolved in orthochlorophenol (OCP) at 100°C at a concentration of 0.12%, and then the intrinsic viscosity (IV, dl / g) was measured using a Ubbelrod viscometer in a constant temperature bath at 35°C. As a result, it was confirmed that all polyester resins obtained in the examples had intrinsic viscosities within the range of 0.5 dl / g to 9 dl / g at 35°C.

[0233]

[0234] The results of the above test are shown in the table below.

[0235]

[0236]

[0237]

[0238]

[0239]

[0240]

[0241]

[0242]

[0243]

[0244]

[0245] As can be seen from the test results above, the heat-shrinkable films of Examples 1 to 6 had the tanδ characteristics and stiffness characteristics before and after shrinkage controlled within a desirable range, and as a result, the shrinkage uniformity was excellent, within the range of -0.3 cm / ℃ to -0.7 cm / ℃ at 65 to 85°C.

[0246] On the other hand, the heat-shrinkable films of Comparative Examples 1 to 3 had tanδ characteristics and stiffness characteristics that were outside the desired range, and in particular, the films of Comparative Examples 1 and 3 did not have a temperature range in which tanδ was 1 or higher, and as a result, the films of Comparative Examples 1 to 3 were evaluated to have poor shrinkage uniformity.

Claims

1. A film comprising a copolymerized polyester resin containing a diol component and a dicarboxylic acid component, A heat-shrinkable film, wherein the temperature (℃) at which tanδ is 1 or more falls within the range of 65℃ to 100℃ when the above film is cut in the main shrinkage direction, mounted on a tensile clamp, and measured under a temperature increase condition of 3℃ / min from 30℃ to 150℃ at a frequency of 1 Hz using a dynamic mechanical analysis device (DMA), and the tanδ max ratio calculated by the following formula is 50% or more: tanδ max ratio = (tanδ[1]max / tanδ[2]max) x 100 Here, tanδ[1]max is the maximum value of tanδ measured under the above temperature-elevated conditions for the heat-shrinkable film, and tanδ[2]max is the maximum value of tanδ measured under the above temperature-elevated conditions after shrinking the heat-shrinkable film at 95°C for 30 seconds, and is calculated as tanδ = G'' / G', where G'' is the loss modulus and G' is the storage modulus.

2. In paragraph 1, The above heat-shrinkable film A heat-shrinkable film, which, after shrinking at 95°C for 30 seconds, has a temperature (°C) within the range of 65°C to 85°C at which tanδ is 1 or more when measured under the above temperature-elevating conditions.

3. In paragraph 1, The above heat-shrinkable film is a heat-shrinkable film that satisfies the following formula (a): Tmax[1] > Tmax[2] (a) Here, Tmax[1] is the highest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more measured under the above temperature-elevating conditions for the heat-shrinkable film, Tmax[2] is the highest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more, measured under the above temperature rising conditions after shrinking the heat-shrinkable film at 95℃ for 30 seconds.

4. In paragraph 1, The above heat-shrinkable film is a heat-shrinkable film that satisfies the following formula (b): 10℃ ≤ Tmax[1] - Tmin[1] ≤ 30℃ (b) Here, Tmax[1] is the highest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more measured under the above temperature-elevating conditions for the heat-shrinkable film, Tmin[1] is the lowest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more when measured under the above temperature-elevating conditions for the above heat-shrinkable film.

5. In paragraph 1, The above heat-shrinkable film is a heat-shrinkable film that satisfies the following formula (c): 3℃ ≤ (Tmax[1] - Tmin[1]) - (Tmax[2] - Tmin[2]) (c) Here Tmax[1] is the highest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more measured under the above temperature-elevating conditions for the above heat-shrinkable film, and Tmin[1] is the lowest temperature (℃). Tmax[2] is the highest temperature (℃) among the temperatures (℃) at which tanδ is 1 or more as measured under the above temperature rising conditions after shrinking the above heat-shrinkable film at 95℃ for 30 seconds, and Tmin[2] is the lowest temperature (℃).

6. In paragraph 1, The above heat-shrinkable film A heat-shrinkable film having a stiffness ratio of 150% or more, as defined by the following equation: Stiffness ratio = (Stiffness[2] / Stiffness[1]) x 100 Here Stiffness [1] is the stiffness measurement value (N / m) of the heat-shrinkable film, Stiffness [2] is the stiffness measurement value (N / m) after shrinkage of the heat-shrinkable film at 95°C for 30 seconds. The above stiffness is measured at a temperature at which the tanδ measurement value of the heat-shrinkable film is 1.

7. In paragraph 1, The above heat-shrinkable film is a heat-shrinkable film having a stretching ratio in the main shrinkage direction of 1.5 to 6 times.

8. In paragraph 1, The above heat-shrinkable film A heat-shrinkable film, which is cut to an initial dimension of 15.5 cm in the main shrinkage direction, mounted on a film tension clamp, and heated at a rate of 5°C / min from 65°C to 85°C while holding for 1 minute at 5°C intervals, and then has a shrinkage of -0.3 cm / °C to -0.7 cm / °C during heating.

9. In paragraph 1, The above diol components are bis(2-hydroxyethyl)terephthalate (BHET), isosorbide, neopentyl glycol, ethylene glycol, cyclohexanedimethanol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-methylene-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-isopropyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, diethylene glycol, At least one selected from the group consisting of 4-(hydroxymethyl)cyclohexylmethyl 4-(hydroxymethyl)cyclohexanecarboxylate and 4-(4-(hydroxymethyl)cyclohexylmethoxymethyl)cyclohexylmethanol, A heat-shrinkable film, wherein the above dicarboxylic acid component is at least one selected from the group consisting of isophthalic acid, terephthalic acid, dimethyl isophthalate, phthalic acid, dimethyl phthalate, phthalic anhydride, 2,6-naphthalene dicarboxylic acid, dimethyl 2,6-naphthalene dicarboxylate, diphenyl dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, 1,3-cyclohexane dicarboxylic acid, dimethyl 1,4-cyclohexane dicarboxylate, dimethyl 1,3-cyclohexane dicarboxylate, sebacic acid, succinic acid, isodecylsuccinic acid, maleic acid, maleic anhydride, fumaric acid, adipic acid, glutaric acid, and azelaic acid.

10. In paragraph 1, A heat-shrinkable film, wherein at least one of the diol component and the dicarboxylic acid component comprises a regenerated monomer.

11. In paragraph 1, The above copolymerized polyester resin A heat-shrinkable film having an intrinsic viscosity of 0.5 dl / g to 0.9 dl / g at 35°C.

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