WO2024185966A1

WO2024185966A1 - Polyester film and manufacturing method therefor

Info

Publication number: WO2024185966A1
Application number: PCT/KR2023/019890
Authority: WO
Inventors: 허영민; 임병재; 김철규; 송기윤
Original assignee: 에스케이마이크로웍스 주식회사
Priority date: 2023-03-03
Filing date: 2023-12-05
Publication date: 2024-09-12
Also published as: KR20240135144A

Abstract

An embodiment provides a polyester film and a manufacturing method therefor, the film comprising a polycyclohexylenedimethylene terephthalate resin, and having a tensile strength of MDTS25 in the machine direction measured at a temperature of 25°C, and a tensile strength of MDTS200 in the machine direction measured after being left in a container at a temperature of 200°C for 24 hours, wherein the reduction rate of the tensile strength in the machine direction, represented by {(MDTS25-MDTS200)/MDTS25}X100%, is 43.5% or less.

Description

Polyester film and method for producing the same

The invention relates to a polyester film and a method for producing the same.

In the case of vehicles using internal combustion engines, heating can be achieved by using the engine's waste heat in the form of a blower. However, electric vehicles and other electric vehicles have difficulty using engine waste heat for heating, so the heating energy efficiency may be somewhat reduced, and there is a concern that the driving distance may be slightly reduced depending on the season.

In order to supplement the heating efficiency of these electric vehicles, various heat radiation components and parts are built in, and films are attached to protect them. Low elongation polyethylene terephthalate (PET) and polyimide (PI) do not have good formability and adhesiveness for application to the curved surface of heat radiation components, making it difficult to maintain efficient heat transfer and heat generation performance.

Accordingly, there is a need to design an improved film that has excellent formability and can satisfy excellent reliability under harsh conditions for application to electric mobility.

The background technology described above is technical information that the inventor possessed for deriving the implementation example or acquired in the process of deriving the implementation example, and cannot necessarily be said to be publicly known technology disclosed to the general public prior to the application of the present invention.

Related prior art technologies include “Biaxially oriented polyester film and its manufacturing method” disclosed in Korean Patent Publication No. 10-2021-0088586 and “Biaxially oriented polyester film for molding” disclosed in Korean Patent Publication No. 10-2014-0113664.

The purpose of the embodiment is to provide a polyester film that has excellent formability and no significant difference in physical properties even after being exposed to harsh conditions of high temperature and high pressure for a long period of time, and is therefore suitable as a film for heat-resistant and heat-dissipating parts of electric vehicles.

Another object of the embodiment is to provide a method for manufacturing a polyester film in which the difference in physical properties under harsh conditions is not large through a low-temperature stretching process.

To achieve the above purpose, a polyester film according to an embodiment includes a polycyclohexylenedimethylene terephthalate resin.

The above polyester film may have a machine direction tensile strength of MDTS25 measured at a temperature of 25°C, a machine direction tensile strength of MDTS200 measured after leaving it in a container under temperature conditions of 200°C for 24 hours, and a machine direction tensile strength reduction rate expressed as {(MDTS25-MDTS200)/MDTS25}Х100% of 43.5% or less.

In one embodiment, the polyester film may have a width-direction tensile strength of TDTS25 measured at a temperature of 25°C, a width-direction tensile strength of TDTS200 measured at a temperature condition of 200°C, and a width-direction tensile strength reduction rate expressed as {(TDTS25-TDTS200)/TDTS25}Х100% of 29% or less.

In one embodiment, the polyester film may have a machine direction elongation of MDE25 measured at a temperature of 25° C., a machine direction elongation of MDE200 measured at a temperature condition of 200° C., and a change in machine direction elongation expressed as (|MDE25-MDE200|/MDE25)Х100% of 50% or less.

In one embodiment, the polyester film may have a transverse elongation of TDE25 measured at a temperature of 25° C., a transverse elongation of TDE200 measured at a temperature condition of 200° C., and a transverse elongation change rate expressed as (|TDE25-TDE200|/TDE25)Х100% of 15% or less.

In one embodiment, the polyester film may have a machine direction elongation of 35% or more measured under the temperature condition of 200° C., and a width direction elongation of 50% or more measured under the temperature condition of 200° C.

In one embodiment, the polyester film can be applied as a heat-resistant component film of an electric vehicle.

In one embodiment, the polycyclohexylenedimethylene terephthalate resin includes repeating units derived from a dicarboxylic acid compound and repeating units derived from a diol compound.

The repeating unit derived from the above dicarboxylic acid compound may include 80 mol% to 100 mol% of terephthalic acid residues and 0 mol% to 20 mol% of isophthalic acid residues.

The repeating unit derived from the above diol compound may contain 85 mol% to 100 mol% of cyclohexanedimethanol residues.

In order to achieve the above object, a method for manufacturing a polyester film according to an embodiment includes a sheet forming step of melting and extruding a film manufacturing composition including a polycyclohexylenedimethylene terephthalate resin to form a sheet; a stretching step of stretching the sheet formed in the sheet forming step in the machine direction and the width direction and heat-setting to manufacture a polyester film.

The above stretching step may sequentially include an MD stretching step for stretching in the machine direction and a TD stretching step for stretching in the width direction.

The above MD stretching step may include a preheating process for preheating the sheet formed in the sheet forming step; and an MD stretching process for stretching the sheet on which the preheating process has been performed in the machine direction.

The temperature of the above preheating process may be 80°C to 86.5°C, the temperature of the above MD stretching process may be 80°C to 89°C, and the widthwise stretching temperature of the above TD stretching step may be 100°C to 118°C.

The above polyester film may have a machine direction tensile strength of MDTS25 measured at 25°C, a machine direction tensile strength of MDTS200 measured after leaving it in a container under temperature conditions of 200°C for 24 hours, and a machine direction tensile strength reduction rate expressed as {(MDTS25-MDTS200)/MDTS25}Х100% of 43.5% or less.

In one embodiment, the TD stretching step includes a first preheating process of first preheating the sheet stretched in the MD stretching step; a second preheating process of second preheating the sheet that has undergone the first preheating process; and a TD stretching process of stretching the sheet that has undergone the second preheating process in the width direction.

The temperature of the first preheating process may be 90°C to 103°C, and the temperature of the second preheating process may be 90°C to 108°C.

The above TD stretching step may be a step of stretching the sheet 2.5 to 3.5 times.

The above MD stretching step may be a step of stretching the sheet 3.3 to 4.5 times.

A polyester film according to an embodiment is manufactured through a unique low-temperature stretching process, and thus can have properties suitable for heat-resistant and heat-dissipating components of an electric vehicle.

Figure 1 is a graph showing the results of the 25°C machine direction tensile strength (MDTS25) and the machine direction tensile strength after a high temperature test at 200°C (MDTS200) of samples of Examples 1 and 2 (E1, E2) and Comparative Examples 1 to 3 (CE1 to CE3).

Figure 2 is a graph showing the results of the transverse tensile strength (TDTS25) at 25°C and the transverse tensile strength (TDTS200) after a high-temperature test at 200°C of samples of Examples 1 and 2 (E1, E2) and Comparative Examples 1 to 3 (CE1 to CE3).

Figure 3 is a graph showing the results of the machine direction elongation at 25°C (MDE25) and the machine direction elongation after a high temperature test at 200°C (MDE200) of the samples of Examples 1 and 2 (E1, E2) and Comparative Examples 1 to 3 (CE1 to CE3).

Figure 4 is a graph showing the results of transverse elongation at 25°C (TDE25) and transverse elongation after a high-temperature test at 200°C (TDE200) of samples of Examples 1 and 2 (E1, E2) and Comparative Examples 1 to 3 (CE1 to CE3).

Figure 5 is a graph showing the results of the machine direction tensile strength reduction rate (MDTS_R) and the transverse direction tensile strength reduction rate (TDTS_R) of the samples of Examples 1 and 2 (E1, E2) and Comparative Examples 1 to 3 (CE1 to CE3).

Figure 6 is a graph showing the results of the machine direction elongation change rate (MDTS_R) and transverse direction elongation change rate (TDTS_R) of the samples of Examples 1 and 2 (E1, E2) and Comparative Examples 1 to 3 (CE1 to CE3).

Hereinafter, one or more implementation examples will be described in detail with reference to the attached drawings so that those skilled in the art can easily practice the invention. However, the implementation examples may be implemented in various different forms and are not limited to the embodiments described herein. Similar parts are designated by the same drawing reference numerals throughout the specification.

In this specification, when a configuration is said to "include" another configuration, this does not mean that it excludes other configurations, but rather that it may further include other configurations, unless otherwise specifically stated.

In this specification, when it is said that a configuration is "connected" to another configuration, this includes not only the case where it is "directly connected" but also the case where it is "connected with another configuration in between."

In this specification, the meaning of B being located on A means that B is located in direct contact with A or that B is located on A with another layer located in between, and is not limited to being interpreted as B being located in contact with the surface of A.

In this specification, the term "combination of these" included in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including one or more selected from the group consisting of said components.

In this specification, the description of "A and/or B" means "A, B, or A and B."

In this specification, terms such as “first”, “second” or “A”, “B” are used to distinguish the same terms from each other unless otherwise specified.

In this specification, singular expressions are interpreted to include the singular or plural as interpreted by the context, unless otherwise specified.

폴리에스테르 필름Polyester film

The machine direction tensile strength measured at a temperature of 25 ℃ is MDTS25.

MDTS200 is the machine direction tensile strength measured after leaving it in a container under temperature conditions of 200℃ for 24 hours.

The machine direction tensile strength reduction rate MDTS_R is expressed as {(MDTS25-MDTS200)/MDTS25}Х100%.

The above polyester film may have the MDTS_R of 43.5% or less.

The polycyclohexylenedimethylene terephthalate (PCT) resin of the above polyester film may be a copolymer of a dicarboxylic acid compound and a diol compound, and may include residues and repeating units derived therefrom.

The above polycyclohexylenedimethylene terephthalate resin may contain 80 mol% or more, 90 mol% or more, and 100 mol% or less of terephthalic acid residues, and 20 mol% or less, 10 mol% or less, 0 mol% or more, 1 mol% or more, and 2 mol% or more of isophthalic acid residues, based on 100 mol% of the total repeating units derived from dicarboxylic acid compounds.

The above polycyclohexylenedimethylene terephthalate resin may contain 70 mol% or more, 80 mol% or more, 90 mol% or more, and 100 mol% or less of cyclohexanedimethanol residues, based on 100 mol% of the total repeating units derived from diol compounds.

When the above dicarboxylic acid-derived repeating unit contains terephthalic acid residues and isophthalic acid residues in the above-mentioned contents, it can have relatively high melting point characteristics and low crystallization characteristics.

The above diol-derived repeating unit may include the following compound-derived repeating units other than the above cyclohexanedimethanol-derived repeating units. For example, it may include ethylene glycol, 1,3-propanediol, 1,2-octanediol, 1,3-octanediol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentylglycol), 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,1-dimethyl-1,5-pentanediol, and residues derived therefrom.

The above polycyclohexylenedimethylene terephthalate resin may have a weight average molecular weight (Mw) of 30,000 g/mol to 50,000 g/mol, or may be 30,000 g/mol to 40,000 g/mol.

The above polycyclohexylenedimethylene terephthalate resin can apply a catalyst to improve the efficiency of the polymerization reaction.

The above catalyst may be included in an amount of 0.1 ppm to 500 ppm, or may be included in an amount of 0.5 ppm to 100 ppm, based on 100 parts by weight of polycyclohexylenedimethylene terephthalate.

The catalyst may be a titanium compound, an antimony compound, a germanium compound, an aluminum compound, or a mixture thereof. For example, the catalyst may be a titanium compound. The titanium compound may include titanium tetraisopropoxide.

An antioxidant may be applied to the polymerization of the above polycyclohexylenedimethylene terephthalate resin. The antioxidant may be applied as needed for the purpose of suppressing thermal oxidation at the temperature at which the esterification reaction is carried out. However, it is common to apply an appropriate amount of the antioxidant applied at this time. If an excessive amount of antioxidant is added during polymerization, there is a concern that the reaction may be delayed and the inherent viscosity of the manufactured resin may decrease. An antioxidant that affects the polymerization of the resin is consumed during the polymerization process and can be distinguished from an antioxidant that is added during subsequent film production.

The above antioxidants may include phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants.

The above antioxidant may be included in an amount of 0.01 to 1 part by weight based on 100 parts by weight of the polycyclohexylenedimethylene terephthalate.

An electrostatic agent can be applied when manufacturing a film using the above polycyclohexylenedimethylene terephthalate resin. As the electrostatic agent, salts of alkali metals and salts of alkaline earth metals can be applied, and magnesium compounds and calcium compounds can be applied, and examples thereof include magnesium acetate and calcium acetate.

The metal or metal ion content of the electrostatic charging agent may be included to be 300 ppm to 1000 ppm based on 100 parts by weight of the polycyclohexylenedimethylene terephthalate resin.

In the above polyester film, the machine direction (MD) is a longitudinal direction parallel to the direction in which movement occurs during the film forming process, and the transverse direction (TD) is a direction perpendicular to the machine direction.

The above polyester film can have good physical property retention after the harsh conditions of the pressure vessel test and can have characteristics suitable for a heat-resistant and heat-dissipating film.

The machine direction tensile strength measured at a temperature of 25 ℃ is MDTS25, and the machine direction tensile strength measured at the temperature condition of 200 ℃ is MDTS200.

The above polyester film may have a machine direction tensile strength reduction rate MDTS_R expressed as {(MDTS25-MDTS200)/MDTS25}Х100% of 43.5% or less. The machine direction tensile strength reduction rate may be 42.6% or less, 41.6% or less, or 30% or less. In addition, the machine direction tensile strength reduction rate may be 10% or more.

The transverse tensile strength measured at a temperature of 25°C is TDTS25, and the transverse tensile strength measured at the temperature condition of 200°C is TDTS200.

The polyester film may have a widthwise tensile strength reduction rate TDTS_R, expressed as {(TDTS25-TDTS200)/TDTS25}Х100%, of 29% or less. The widthwise tensile sensitivity reduction rate may be 27.7% or less, 21.4% or less, or 18% or less. The widthwise tensile strength reduction rate may be 5% or more.

The above polyester film has such a reduction rate in machine direction and width direction tensile strength, so it can maintain good durability under harsh conditions and can be effective in maintaining the protective function of heat-resistant and heat-dissipating parts.

The above polyester film may have a MDTS25 of 12 kgf/mm ² to 20 kgf/mm ² , 14 kgf/mm ² to 19 kgf/mm ² , or 15 kgf/mm ² to 18 kgf/mm ² .

The polyester film may have a MDTS200 of 5 kgf/mm ² to 15 kgf/mm ² , 6 kgf/mm ² to 14 kgf/mm ² , or 8.6 kgf/mm ² to 13 kgf/mm ² .

The polyester film may have a TDTS25 of 12 kgf/mm ² to 25 kgf/mm ² , 15 kgf/mm ² to 24 kgf/mm ² , or 16 kgf/mm ² to 23 kgf/mm ² .

The polyester film may have a density of 8 kgf/mm ² to 18 kgf/mm ² , 9 kgf/mm ² to 17 kgf/mm ² , or 11 kgf/mm ² to 16 kgf/mm ² of the TDTS200.

Since the above polyester film has these MDTS25, MDTS200, TDTS25, and/or TDTS200 ranges, there is no drastic difference in properties between general room temperature and harsh conditions, so that it can maintain good durability and can be effective in maintaining the protective function of heat-resistant and heat-dissipating parts.

The machine direction elongation measured at a temperature of 25 ℃ is MDE25, and the machine direction elongation measured at the temperature condition of 200 ℃ is MDE200.

The above polyester film may have a machine direction elongation change ratio MDE_D, expressed as (|MDE25-MDE200|/MDE25)Х100%, of 50 % or less. The machine direction elongation change ratio may be 40 % or less, 35.3 % or less, 20 % or less, or 2.4 % or less. The machine direction elongation change ratio may be 0.1 % or more. In the machine direction elongation change ratio formula and the formulas below, || represents an absolute value symbol.

The transverse elongation measured at a temperature of 25°C is TDE25, and the transverse elongation measured at the temperature condition of 200°C is TDE200.

The polyester film may have a transverse elongation change TDE_D, expressed as (|TDE25-TDE200|/TDE25)Х100%, of 15 % or less. The transverse elongation change may be 12 % or less, 9.4 % or less, or 7.2 % or less. The transverse elongation change may be 0.1 % or more.

The above polyester film has such a machine direction, width direction elongation change rate, so it can maintain good durability under harsh conditions and can be effective in maintaining the protective function of heat-resistant and heat-dissipating parts.

The above polyester film may have an MDE25 of 40% to 110%, 45% to 105%, or 55% to 100%.

The above polyester film may have a MDE200 content of 25% to 90%, 35% to 85%, or 40% to 80%.

The above polyester film may have a TDE25 of 45% to 90%, 47% to 80%, or 50% to 75%.

The above polyester film may have a TDE200 of 45% to 90%, 47% to 80%, or 55% to 80%.

Since the above polyester film has these MDES25, MDE200, TDES25, and/or TDES200 ranges, there is no drastic difference in properties between general room temperature and harsh conditions, so that it can maintain good durability and can be effective in maintaining the protective function of heat-resistant and heat-dissipating parts.

Here, elongation means the ratio of the length extended before rupture to the initial length of the film and can be calculated as follows.

Elongation = {(elongated length - initial length) / initial length} X 100%

The above tensile strength and elongation related properties can be measured according to ASTM D882 and can be measured using Instron's Model 4206-0010 device as described in the experimental example below.

The thickness of the above polyester film may be from 1 ㎛ to 1000 ㎛, or from 10 ㎛ to 500 ㎛.

The above polyester film is manufactured through a unique low-temperature stretching process in the manufacturing method below, and can have properties suitable for heat-resistant and heat-dissipating parts of electric vehicles.

To achieve the above purpose, the heat radiation member for an electric vehicle according to an embodiment may include the polyester film described above.

The above heat radiation member may include a carbon-based material, and examples thereof include graphite, carbon nanotubes, carbon fibers, graphene, diamond, fullerene, and the like.

폴리에스테르 필름의 제조방법Method for manufacturing polyester film

In order to achieve the above object, a polyester manufacturing method according to an embodiment includes a sheet forming step of melting and extruding a film manufacturing composition including a polycyclohexylenedimethylene terephthalate resin to form a sheet; a stretching step of stretching the sheet formed in the sheet forming step in the machine direction and the width direction and heat-setting to manufacture a polyester film.

The above stretching step may include an MD stretching step for stretching the sheet formed in the sheet forming step in the machine direction; a TD stretching step for stretching the sheet stretched in the MD stretching step in the width direction and heat-setting to produce a polyester film.

The above MD stretching step includes a preheating process for preheating the sheet formed in the sheet forming step; and an MD stretching process for stretching the sheet on which the preheating process has been performed in the machine direction.

The temperature of the above preheating process can be 80 ℃ to 86.5 ℃.

The temperature of the above MD stretching process can be 80 ℃ to 89 ℃.

The widthwise stretching temperature of the above TD stretching step can be 100°C to 118°C.

The machine direction tensile strength measured at 25 ℃ is MDTS25, and the machine direction tensile strength under pressure vessel test conditions is MDTS200.

The above pressure cooker test is conducted by leaving it in an oven under the conditions of 200℃ temperature, 1.4 atm pressure, and 100% relative humidity for 24 hours.

The above polyester film has the characteristics, composition, etc. of the polyester film mentioned above. For example, the polyester film may have a machine direction tensile strength reduction rate MDTS_R expressed as {(MDTS25-MDTS200)/MDTS25}Х100% of 43.5% or less.

The composition for manufacturing the above film may include polycyclohexylenedimethylene terephthalate resin, an antioxidant, an electrostatic agent, etc., and may be melt-extruded during film manufacturing. The antioxidant and electrostatic agent are the same as those described above, so redundant descriptions are omitted.

The composition for producing the above film can be dried before melting.

The drying may be performed at a temperature of 150° C. or lower. Alternatively, the drying may be performed at a temperature of 70 ° C. to 148° C.

The drying of the composition for manufacturing the above film may be carried out so that the moisture content relative to the total amount becomes 100 ppm or less, or 50 ppm or less. If the drying process is carried out at a temperature exceeding 150° C., there is a concern that an unintended color change may occur in the resin itself.

The composition for manufacturing the film may have a form such as a chip, pellet, plate, or plate, and may have a form that can be easily introduced into the film manufacturing process and effectively mixed.

The polycyclohexylenedimethylene terephthalate resin of the composition for manufacturing the above film can be manufactured by a conventional polymerization method, and for example, one polymerized under a metal-containing catalyst such as titanium or antimony can be applied.

The polycyclohexylenedimethylene terephthalate resin of the composition for manufacturing the above film may be a copolymer of a dicarboxylic acid compound and a diol compound as described above, and may include repeating units derived therefrom.

The extrusion in the above sheet forming step can be performed at a temperature of 230°C to 300°C, or at a temperature of 250°C to 290°C.

The preheating process of the above MD stretching step may heat treat the sheet at a temperature of 80° C. to 86.5° C. for 10 seconds to 1 minute. Alternatively, the preheating process of the above MD stretching step may heat treat the sheet at a temperature of 83° C. to 86° C. for the same period of time as above.

The MD stretching process of the above MD stretching step can stretch the sheet on which the above preheating process has been performed by 2.5 to 3.5 times in the machine direction at a temperature of 80 to 89° C. Alternatively, the MD stretching process can stretch the sheet on which the above preheating process has been performed by the same magnification in the machine direction at a temperature of 85 to 89° C., or at a temperature of 87 to 89° C.

The above MD stretching step may include a process of heating by providing an infrared heater at a position spaced 30 mm to 200 mm apart from the upper and/or lower portion of the preheated unstretched sheet. The surface temperature of the infrared heater may be 500° C. to 800° C.

The above MD stretching step can ensure that the film manufactured through the preheating process and MD stretching process satisfies the intended elongation and strength characteristics under harsh conditions.

The above TD stretching step may include a first preheating process of first preheating the sheet stretched in the MD stretching step; a second preheating process of second preheating the sheet that has undergone the first preheating process; and a TD stretching process of stretching the sheet that has undergone the second preheating process in the width direction.

The above first preheating process can be heat treated at a temperature of 90° C. to 103° C. for 10 to 60 seconds. Alternatively, the above first preheating process can be heat treated at a temperature of 95° C. to 103° C., or at a temperature of 98 ° C. to 102° C. for the same period of time as above.

The above second preheating process can be heat treated at a temperature of 90° C. to 108° C. for 10 to 60 seconds. Alternatively, the above second preheating process can be heat treated at a temperature of 97° C. to 105° C., or at a temperature of 100° C. to 105° C. for the same period of time as above.

The above TD stretching process can stretch the sheet that has undergone the second preheating process by 3.3 to 4.5 times in the width direction at a temperature of 100 to 118° C. Alternatively, the TD stretching process can stretch the sheet that has undergone the second preheating process by the same magnification in the width direction at a temperature of 105 to 115° C., or at a temperature of 107 to 113° C.

The heat setting of the above TD elongation step may be performed at a temperature of 200° C. to 250° C. for 5 to 600 seconds. Alternatively, the heat setting of the above TD elongation step may be performed for 10 to 200 seconds.

The above TD stretching step can ensure that the film manufactured through the preheating process and TD stretching process satisfies the intended elongation and strength characteristics under harsh conditions.

The film that has undergone the above TD stretching step may be subjected to a predetermined relaxation treatment in the longitudinal direction and/or the width direction. The temperature during the relaxation may be 150° C. to 250° C. The relaxation rate during the relaxation may be 1% to 10%, or 3% to 7%.

Hereinafter, the present invention will be described more specifically through specific examples. The following examples are merely examples to help understand the present invention, and the scope of the present invention is not limited thereto.

실시예 1 - 저온연신 PCT 필름의 제조 1Example 1 - Preparation of low temperature stretched PCT film 1

A monomer mixture of 100 mol% cyclohexanedimethanol (CHDM) as a diol compound and 96 mol% terephthalic acid (TPA) and 4 mol% isophthalic acid (IPA) as dicarboxylic acid compounds was introduced into a stirrer, and 1 ppm of a titanium catalyst was introduced based on 100 parts by weight of the mixture, and then an ester interchange reaction was performed at 275°C.

The ester exchange-reacted material was transferred to a separate reactor equipped with a vacuum facility and polymerized at 285°C for 160 minutes to obtain polycyclohexylenedimethylene terephthalate (PCT) resin.

The above PCT resin was processed into a master batch chip together with an antioxidant, an electrostatic agent, etc., and dried at a temperature of 140°C. Thereafter, the raw material was fed into an extruder, extruded into a sheet shape at a temperature of approximately 295°C, and cast onto a casting roll.

The above extruded sheet was preheated at 83°C for 30 seconds and then stretched 3 times in the machine direction (MD) at 85°C. During stretching in the machine direction, a heating process was additionally performed at the top and bottom, 80 mm apart from the top and bottom of the film, using infrared heaters; the surface temperature of the top heater was 600°C, and the surface temperature of the bottom heater was 500°C. Next, a first preheating treatment was performed at 95°C for 10 seconds, a second preheating treatment was performed at 100°C for 30 seconds, and then stretched 3.5 times in the transverse direction (TD) at 110°C. Thereafter, the stretched sheet was heat-set at 240°C for about 30 seconds and allowed to relax to produce a PCT film having a thickness of 50 μm.

실시예 2 - 저온연신 PCT 필름의 제조 2Example 2 - Preparation of low temperature stretched PCT film 2

In the above Example 1, the extruded sheet was preheated to a temperature of 85° C. and stretched 3.2 times in the machine direction to produce a PCT film.

비교예 1 - PCT 필름의 제조 1Comparative Example 1 - Manufacturing of PCT Film 1

In the above Example 1, the preheating temperature before machine direction (MD) stretching was changed to 87°C, the temperature during machine direction stretching was changed to 90°C, the first preheating temperature before transverse direction (TD) stretching was changed to 105°C, the second preheating temperature was changed to 110°C, the temperature during transverse direction stretching was changed to 120°C, and the heat setting temperature was changed to 230°C, thereby manufacturing a PCT film.

비교예 2 - PCT 필름의 제조 2Comparative Example 2 - Manufacturing of PCT Film 2

In the above Example 1, the preheating temperature before machine direction (MD) stretching was changed to 92°C, the temperature during machine direction stretching was changed to 95°C, the first preheating temperature before transverse direction (TD) stretching was changed to 115°C, the second preheating temperature was changed to 115°C, and the temperature during transverse direction stretching was changed to 120°C, and the surface temperature of the upper heater was applied to 600°C and the surface temperature of the lower heater was applied to 500°C, thereby manufacturing a PCT film.

비교예 3 - PCT 필름의 제조 3Comparative Example 3 - Manufacturing of PCT Film 3

In the above Comparative Example 2, a PCT film was manufactured by omitting the heating process using the infrared heater.

The above examples and comparative examples are summarized in Table 1 below (temperature unit: ℃).

구분division	MD연신 전 예열 온도, ℃Preheating temperature before MD extension, ℃	MD연신 온도, ℃MD extension temperature, ℃	적외선히터 온도, ℃Infrared heater temperature, ℃	TD연신 전 1차예열 온도, ℃1st preheating temperature before TD extension, ℃	TD연신 전 2차예열 온도, ℃Secondary preheating temperature before TD extension, ℃	TD연신 온도, ℃TD extension temperature, ℃	열고정 온도, ℃Heat fixation temperature, ℃	연신비율Extension ratio
실시예 1Example 1	8383	8585	상단 600하단 500Top 600 Bottom 500	9595	100100	110110	240240	MD 3.0배TD 3.5배MD 3.0x TD 3.5x
실시예 2Example 2	8585	8787	상단 600하단 500Top 600 Bottom 500	9595	100100	110110	240240	MD 3.2배TD 3.5배MD 3.2x TD 3.5x
비교예 1Comparative Example 1	8787	9090	상단 600하단 500Top 600 Bottom 500	105105	110110	120120	230230	MD 3.2배TD 3.5배MD 3.2x TD 3.5x
비교예 2Comparative Example 2	9292	9595	상단 600하단 500Top 600 Bottom 500	115115	115115	120120	240240	MD 3.2배TD 3.5배MD 3.2x TD 3.5x
비교예 3Comparative Example 3	9292	9595	--	115115	115115	120120	240240	MD 3.2배TD 3.5배MD 3.2x TD 3.5x

실험예 - 200 ℃ 고온 테스트 전 후의 인장강도 및 신율 측정Experimental Example - Tensile strength and elongation measurements before and after 200℃ high temperature test

The tensile strength and elongation of the PCT films manufactured in Examples 1 and 2 and Comparative Examples 1 to 3 were measured as follows.

Each film of the above examples and comparative examples was cut to 100 mm x 15 mm and processed into samples, and tensile tests were performed 5 times in the machine direction (MD) and the transverse direction (TD) according to ASTM D882 at a speed of 50 mm/min at a room temperature of 25 ℃ using an Instron 4206-001 device, and the average values of the measured machine direction tensile strength (MDTS25), transverse direction tensile strength (TDTS25), machine direction elongation (MDE25), and transverse direction elongation (TDE25) were derived.

Then, each film of the above examples and comparative examples was processed into a sample again in the same manner, and then left in an oven at a temperature of 200°C for 24 hours, and the tensile test was performed in the same manner to derive the machine direction tensile strength (MDTS200), transverse direction tensile strength (TDTS200), machine direction elongation (MDE200), and transverse direction elongation (TDE200) after the high temperature test.

The tensile strength, elongation, reduction rate, and change rate results of the samples before and after the high temperature test are shown in Tables 2 and 3 and FIGS. 1 to 5. In FIGS. 1 to 5, E indicates an example, CE indicates a comparative example, MDTS_R indicates a machine direction tensile strength reduction rate, TDTS_R indicates a width direction tensile strength reduction rate, MDE_D indicates a machine direction elongation change rate, and TDE_D indicates a width direction elongation change rate.

구분division	MDTS25MDTS25	MDTS200MDTS200	TDTS25TDTS25	TDTS200TDTS200	MDE25MDE25	MDE200MDE200	TDE25TDE25	TDE200TDE200
실시예 1Example 1	1616	11.911.9	16.816.8	13.913.9	6161	6262	6464	7070
실시예 2Example 2	16.116.1	9.49.4	17.117.1	13.413.4	7474	4848	6161	6565
비교예 1Comparative Example 1	1717	8.48.4	19.619.6	13.513.5	8888	1212	6060	4141
비교예 2Comparative Example 2	16.316.3	9.09.0	19.819.8	13.113.1	9393	2424	5151	3434
비교예 3Comparative Example 3	15.115.1	7.57.5	20.120.1	13.913.9	7878	44	5151	3838

Tensile strength unit: kgf/mm ² , elongation unit: %

구분division	MDTS_R(%)MDTS_R(%)	TDTS_R(%)TDTS_R(%)	MDE_D(%)MDE_D(%)	TDE_D(%)TDE_D(%)
실시예 1Example 1	25.925.9	17.517.5	2.42.4	9.49.4
실시예 2Example 2	41.641.6	21.421.4	35.335.3	7.27.2
비교예 1Comparative Example 1	50.350.3	31.031.0	86.786.7	32.232.2
비교예 2Comparative Example 2	45.045.0	33.933.9	74.374.3	34.034.0
비교예 3Comparative Example 3	50.650.6	30.830.8	94.894.8	26.326.3

Referring to Tables 2 and 3 and FIGS. 1 to 4, etc., in the examples in which the low-temperature stretching process was performed in the machine direction and the width direction, it was confirmed that the machine direction tensile strength reduction rate (MDTS_R), the width direction tensile strength reduction rate (TDTS_R), the machine direction elongation change rate (MDE_D), and the width direction elongation change rate (TDE_D) were better than in the comparative examples in which the low-temperature stretching process was performed. Since the amount of change in physical properties in a situation where the film was exposed to high temperature and high pressure for a long period of time was not large compared to the comparative examples, it is thought that the film is suitable as a heat-resistant and heat-dissipating film for electric vehicles, etc.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

Containing polycyclohexylenedimethylene terephthalate resin,

The machine direction tensile strength measured at a temperature of 25 ℃ is MDTS25,

The machine direction tensile strength measured after leaving it in a container under temperature conditions of 200 ℃ for 24 hours is MDTS200.

A polyester film having a machine direction tensile strength reduction rate of 43.5% or less, expressed as {(MDTS25-MDTS200)/MDTS25}Х100%.
In the first paragraph,

The width direction is perpendicular to the machine direction,

The transverse tensile strength measured at a temperature of 25 ℃ is TDTS25.

The transverse tensile strength measured under the above temperature conditions of 200 ℃ is TDTS200,

A polyester film having a reduction in transverse tensile strength of 29% or less, expressed as {(TDTS25-TDTS200)/TDTS25}Х100%.
In the first paragraph,

The machine direction elongation measured at a temperature of 25 ℃ is MDE25,

The machine direction elongation measured under the above temperature conditions of 200 ℃ is MDE200,

(|MDE25-MDE200|/MDE25)Х100%, a polyester film having a change in machine direction elongation of 50% or less.
In the first paragraph,

The width direction is perpendicular to the machine direction,

The transverse elongation measured at a temperature of 25 ℃ is TDE25,

The transverse elongation measured under the above temperature conditions of 200 ℃ is TDE200,

A polyester film having a transverse elongation change of 15% or less, expressed as (|TDE25-TDE200|/TDE25)Х100%.
In the first paragraph,

The machine direction elongation measured under the above temperature conditions of 200 ℃ is 35% or more,

A polyester film having a transverse elongation of 50% or more as measured under the above temperature conditions of 200°C.
In the first paragraph,

Polyester film applied as a heat-resistant component film for electric vehicles.
In the first paragraph,

The above polycyclohexylenedimethylene terephthalate resin contains a repeating unit derived from a dicarboxylic acid compound and a repeating unit derived from a diol compound,

The repeating unit derived from the above dicarboxylic acid compound comprises 80 mol% to 100 mol% of terephthalic acid residues and 0 mol% to 20 mol% of isophthalic acid residues,

A polyester film, wherein the repeating unit derived from the above diol compound comprises 85 mol% to 100 mol% of cyclohexanedimethanol residues.
A sheet forming step of melting a composition for producing a film including a polycyclohexylenedimethylene terephthalate resin and extruding it to form a sheet;

An MD stretching step for stretching the sheet formed in the above sheet forming step in the machine direction;

Including a TD stretching step for stretching the sheet stretched in the MD stretching step in the width direction and heat-fixing it to manufacture a polyester film;

The above MD stretching step includes a preheating process for preheating the sheet formed in the sheet forming step; and an MD stretching process for stretching the sheet on which the preheating process has been performed in the machine direction.

The temperature of the above preheating process is 80 ℃ to 86.5 ℃,

The temperature of the above MD stretching process is 80 ℃ to 89 ℃,

The width direction stretching temperature of the above TD stretching step is 100 ℃ to 118 ℃,

The above polyester film,

The machine direction tensile strength measured at 25 ℃ is MDTS25,

The machine direction tensile strength measured after leaving it in a container under temperature conditions of 200 ℃ for 24 hours is MDTS200.

A method for manufacturing a polyester film having a machine direction tensile strength reduction rate of 43.5% or less, expressed as {(MDTS25-MDTS200)/MDTS25}Х100%.
In Article 8,

The above TD extension step is,

A first preheating process for first preheating the sheet stretched in the above MD stretching step;

A second preheating process for preheating the sheet that has undergone the first preheating process; and

Including a TD stretching process for stretching the sheet in the width direction after the above second preheating process;

The temperature of the above first preheating process is 90 ℃ to 103 ℃,

A method for manufacturing a polyester film, wherein the temperature of the above secondary preheating process is 90 ℃ to 108 ℃.
In Article 8,

The above TD elongation step elongates the sheet by 2.5 to 3.5 times,

The above MD stretching step is a method for manufacturing a polyester film, wherein the sheet is stretched 3.3 to 4.5 times.