KR102360899B1 - Flame retardant polyester film - Google Patents

Abstract

The present invention provides a masterbatch containing 0.05 to 1.0 parts by weight of a heat resistant agent in 100 parts by weight of a mixed resin comprising a) 40 to 85% by weight of polyester, b) 15 to 60% by weight of polyphosphate-based resin, and polyester-based A flame-retardant polyester film including a base resin, wherein the polyphosphate-based resin has a glass transition temperature of 90 to 120° C., and the phosphorus content in the polyester film relates to a flame-retardant polyester film of 1.5 to 4.5 wt%.

Description

Flame retardant polyester film

The present invention relates to a flame-retardant polyester film, and more particularly, to a flame-retardant polyester film having high flame retardancy while excellent in tensile strength, heat shrinkage, and film formability by using a halogen-free phosphorus-based flame retardant in a specific range.

Recently, the main cause of large-scale fatal accidents in various fires is the toxic gas generated when burning in fire, so the fire safety of polymer materials is increasingly emphasized, and interest in various flame retardants and flame retardant resins is increasing. In particular, non-halogen-based flame retardants to replace halogen-based flame retardants used as conventional flame retardants are being actively studied, and among them, phosphorus-based flame retardants are representative flame retardants. As a method of using the phosphorus-based flame retardant, a method of mixing a phosphoric acid ester compound with a general polymer resin, such as Korean Patent Application Laid-Open No. 2001-0057665, or copolymerizing a phosphorus compound with a polyester resin, such as Korean Patent Publication No. 2010-0127077, is used.

However, when a phosphoric acid ester compound is used, the polymer chain is decomposed by the transesterification reaction between the phosphoric acid ester and the polyester resin in the process of melt extrusion with the polyester resin, resulting in severe viscosity decrease. In this case, breakage of the film occurs frequently during the stretching process of the film, and the mechanical properties are severely deteriorated even after the film is formed.

In addition, the regular packing of the polymer is inhibited by the irregular polymer structure caused by the transesterification reaction, which prevents lowering of the melting point and crystallization, and causes a problem in the heat treatment process performed to impart dimensional stability of the film. That is, a case where the melting point is lower than the heat treatment temperature often occurs.

In addition, when a phosphorus compound is copolymerized with polyester, the possibility of causing mixing non-uniformity due to subsequent addition of other flame retardants is lowered, and the dispersibility of the flame retardant component is advantageous, and the flame retardancy of the film is excellently reproduced, but the crystalline polyester resin There is a problem that crystallization is not easily performed during the drying process of the resin before melt extrusion due to its own copolymerization effect, so there is a problem that fusion (lumping) between chips occurs very seriously. This can be directly connected to the problem of extremely poor workability in the drying process of the chip. Therefore, there is a problem in that it is difficult to exhibit sufficient flame retardancy because the content of the phosphorus compound to be copolymerized in the polyester is limited due to this problem.

Another method of imparting flame retardancy is when a metal hydroxide flame retardant such as phosphinic acid Al(OH) ₃ or Mg(OH) ₂ is applied. However, in this case, in order to obtain sufficient flame retardancy, a large amount of input is required, and the physical properties of the resin are greatly reduced. In addition, the aggregation of the particles frequently causes breakage during the stretching process of the film, resulting in poor workability, and increasing the roughness of the film to greatly decrease the gloss of the film, thereby causing loss of aesthetics of the product.

Republic of Korea Patent Publication 10-2001-0057665 (July 05, 2001) Republic of Korea Patent Publication 10-2010-0127077 (December 03, 2010)

The present invention was derived to solve the above problems, and while including a phosphoric acid ester-based flame retardant, there is no decrease in workability during film production, and excellent mechanical properties such as tensile strength and thermal shrinkage, and at the same time, UL 94 VTM Test An object of the measured flame retardancy is to provide a flame retardant polyester film having a high flame retardancy with a VTM-0 grade.

The present invention relates to a flame retardant polyester film.

One aspect of the present invention is a) 40 to 85% by weight of polyester, b) 100 parts by weight of a mixed resin comprising 15 to 60% by weight of a polyphosphate-based resin c) a masterbatch containing 0.05 to 1.0 parts by weight of a heat resistant agent and A flame-retardant polyester film comprising a polyester-based base resin, wherein the polyphosphate-based resin has a glass transition temperature of 90 to 120° C., and the phosphorus content in the polyester film is 1.5 to 4.5 wt% will be.

In the present invention, the flame-retardant polyester film has a flame retardancy of VTM-0 grade as measured by UL 94 VTM Test, a tensile strength of 14 kg/mm 2 or more in the longitudinal direction (MD), and is left in a hot air oven at 150° C. for 30 minutes. The longitudinal and transverse heat shrinkage of the film after it may be less than 2%.

In addition, in the present invention, the content of phosphorus in the polyester film may include 1.5 to 4.5% by weight.

In addition, the melting point of the polyester film in the present invention is 240 ℃ or more, the thickness of the film may be 10 to 500㎛.

The flame-retardant polyester film according to the present invention contains a phosphoric acid ester-based flame retardant, but there is no decrease in workability during film manufacturing, and has excellent mechanical properties such as tensile strength and heat shrinkage, and at the same time, the flame retardancy measured by the UL 94 VTM Test is VTM- It is possible to provide an environmentally friendly flame-retardant polyester film having high flame retardancy with a grade of 0.

The present invention will be described in more detail below with reference to specific examples. However, the following specific examples or examples are only a reference for describing the present invention in detail, and the present invention is not limited thereto and may be implemented in various forms.

Also, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is for the purpose of effectively describing particular embodiments only and is not intended to limit the invention.

Also, the singular forms used in the specification and appended claims may also be intended to include the plural forms unless the context specifically dictates otherwise.

In the present invention, the polyester film is a) 40 to 85% by weight of polyester, b) 100 parts by weight of a mixed resin containing 15 to 60% by weight of a polyphosphate-based resin c) 0.05 to 1.0 parts by weight of a heat resistant agent It can be prepared including batch and polyester-based base resin.

In the present invention, the polyester-based base resin, which is the main material of the masterbatch and the flame-retardant polyester film, is obtained by polymerizing an acid component containing carboxylic acid as a main component and a glycol component containing alkylene glycol as a main component. The dicarboxylic acid is not limited, but terephthalic acid or its alkyl ester or phenyl ester may be used, and some are bifunctional carboxylic acids such as isophthalic acid, oxyethoxybenzoic acid, adipic acid, sebacic acid, and 5-sodium sulfoisophthalic acid. It can be used by substituting with the main acid or its ester-forming derivative. In addition, the glycol component is not limited, but ethylene glycol is mainly used, and propylene glycol, neopentyl glycol, trimethylene glycol, 1,4-cyclohexanediol, 1.4-cyclohexanedimethanol, 1,4-bisoxyethoxy Benzene, bisphenol, polyoxyethylene glycol, etc. may be mixed and used, and a monofunctional compound or a trifunctional compound may be partially used in combination.

In the present invention, it is preferable to use polyethylene terephthalate, polybutylene terephthalate and polytrimethylene terephthalate as the polyester resin in the present invention. Excellent and preferred.

In the present invention, the polyester-based resin has an intrinsic viscosity (after melting with OCP (Ortho Chloro Phenol), measuring the sample viscosity in a viscosity tube using an automatic viscosity measuring instrument (Skyvis-4000) at 25° C.) is 0.5 to 0.8. When the intrinsic viscosity of the resin satisfies the above range, excellent processability can be realized, and mechanical properties of the film can be improved. In addition, if it exceeds the above range, processing is difficult and thermal decomposition occurs rapidly, making it difficult to manufacture a film.

In addition to the above components, the polyester-based resin is one or two or more components selected from additives commonly used in the film field, for example, a pinning agent, an antistatic agent, a UV stabilizer, a waterproofing agent, a slip agent, and a heat stabilizer. may include, but is not limited thereto.

The polyester-based resin may be prepared by a polymerization method conventional in the art. For example, it may be prepared by a terephthalic acid (TPA) polymerization method or a dimethyl terephthalate (DMT) polymerization method, but is not limited thereto.

In the present invention, the polyphosphate-based resin mainly generates polymetaphosphoric acid by thermal decomposition when burning, and when it forms a protective layer and when polymetaphosphoric acid is produced, the carbon film produced by dehydration blocks oxygen, It seems to exhibit a flame retardant effect in a way that prevents combustion. The polyphosphate-based resin according to the present invention may be mixed with the polyester resin to act as a film-forming material and exhibit a flame retardant effect by heat action.

In the present invention, as the polyphosphate-based resin, various phosphorus-based flame retardants such as phosphoric acid esters, phosphonates, phosphinates, phosphine oxides, and phosphazenes may be used.

In more detail, the polyphosphate-based resin may have a structure of Formula 1 below.

[Formula 1]

(In Formula 1, R is any one selected from (C1-C30)alkylene, (C3-C30)cycloalkylene, and (C6-C30)arylene, n is an integer from 1 to 100, m is from 50 to It is an integer of 5000.)

In the present invention, the polyphosphate-based resin preferably has a glass transition temperature (Tg) of 90 to 120°C. When the polyphosphate-based resin is mixed with the polyester, a phenomenon occurs in which the glass transition temperature of the mixed resin is lowered due to a transesterification reaction that occurs as a side reaction when mixed with the polyester.

When the glass transition temperature of the polyphosphate-based resin is less than 90°C, thermal stability such as a decrease in strength in the machine direction (MD) and thermal wrinkles occurring in the post-process of the final product may decrease, and if it exceeds 120°C, film forming Stretch workability, such as strength, may be deteriorated.

More specifically, it is preferable that the glass transition temperature of the masterbatch of the finally produced polyester and polyphosphate-based resin is 65°C to 100°C. When the glass transition temperature of the masterbatch is less than 65°C, during the crystallization and drying process of the chip, a lumping phenomenon occurs in which the surface of the chip is fused by heat to form a large mass before crystallization proceeds. It is difficult to transfer the completed masterbatch chip to the drying process, and the moisture inside the lumped chip is not completely dried, so the formability may be greatly reduced, such as breakage during film production. Conversely, when the glass transition temperature is more than 100° C., excessive stress is applied in the stretching process of the film, so that the stretching ratio cannot be sufficiently increased.

In the present invention, the molecular weight of the polyphosphate-based resin is preferably 30 to 350 kg/mol, more preferably 50 to 300 kg/mol. If the molecular weight of the polyphosphate-based resin is less than 30 kg / mol, the molecular weight is too low and miscibility with the polyester resin may be deteriorated. The crystallization progress of the masterbatch may be slow.

In the present invention, the greater the phosphorus content in the polyphosphate-based resin, the better the flame retardancy, but it is better to adjust the film in consideration of mechanical properties and moldability. More preferably, the content of phosphorus is 0.4 to 10% by weight, preferably 0.6 to 8% by weight, and most preferably 1 to 6% by weight based on the masterbatch. In the above range, sufficient flame retardancy is expressed, and orientation and crystallization occur sufficiently in the process of stretching and heat treatment of the film to satisfy mechanical properties and lower the thermal shrinkage rate of the film.

The masterbatch may include 40 to 85% by weight of a polyester-based resin and 15 to 60% by weight of a polyphosphate-based resin. Within the above range, it is preferable to secure the desired flame retardancy in the present invention and to satisfy mechanical properties and moldability.

In the present invention, the heat resistance agent is for simultaneously improving the thermal stability, oxidation stability, and storage stability of the produced film, and any heat resistance or oxidation stabilizer commonly used in the art may be used.

Examples of the heat-resistant agent usable in the present invention include 2,6-di-t-butyl-p-cresol (BHT), octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl) propion Nate, triethylene glycol-bis-3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate, 1,1,3-tris(5-t-butyl-4-hydroxy-5- Any one or two or more selected from methylphenyl)butane, dilauryl thiodipropionate, tris(nonylphenyl)phosphite, etc. may be used, and trade names include Irganox™ 1010, Irganox™ 1035, Irganox™ 1076, Irganox™ 1081, Irganox™ 1098, Irganox™ 1135, Irganox™ 1330, Irganox™ 1425 WL, Irganox™ 1520, Irganox™ 245, Irganox™ 3114, Irganox™ 565, Irganox™ E 201, or Irganox™ MD 1024, Chemtura (Middle CT, USA) berry), Lowinox™ 1790, Lowinox™ 22M46, Lowinox™ 44B25, Lowinox™ CA22, Lowinox™ CPL, Lowinox™ HD 98, Lowinox™ MD24, Lowinox™ TBM-6, or Lowinox™ WSP, by Cytec manufactured Cyanox™ 1741, Cyanox™ 2246, or Cyanox™ 425, and the like.

In the present invention, the heat resistance agent is preferably added in an amount of 0.05 to 1.0 parts by weight based on 100 parts by weight of the total masterbatch. Within the above range, the workability of the masterbatch is not impaired, and the mechanical strength and heat shrinkage of the film can be maintained at the same time.

The master batch according to the present invention can be prepared in the form of chips by mixing the polyester-based resin, the polyphosphate-based resin, and a heat-resistant agent. At this time, the extruder may use one commonly used in the art, for example, a twin screw extruder, and the temperature of the extruder is preferably set to 240 to 260°C.

In addition, the heat resistant agent may be mixed together during the production of the master batch, but may be added when the master batch and the polyester base resin are mixed just before the film production, or may be added during polymerization of the polyester base resin .

Next, the prepared masterbatch and the polyester-based base resin are put into an extruder and mixed. However, when the masterbatch and the base resin are mixed, the addition amount and phosphorus content of the polyphosphate-based resin are adjusted so that the phosphorus content in the film is 1.5 to 4.5% by weight while sufficiently increasing the flame retardancy of the produced film and mechanical properties and It is preferable without impairing the moldability. In addition, when mixing the master batch and the base resin, the temperature of the extruder is preferably 270 to 300 ℃. However, the extrusion conditions are not limited in the present invention, and can be freely adjusted according to the composition ratio of the base resin and the masterbatch.

After preparing an unstretched sheet through an extruder, a stretching process may be performed. At this time, the machine direction (MD) is preferably stretched 3 to 5 times at a temperature of 80 to 120 ℃. In addition, the transverse direction (TD) is preferably stretched at the same magnification as the machine direction at a temperature of 100 to 160 ℃, but the present invention is not necessarily limited thereto.

After stretching, the polyester film is preferably heat-treated to prevent shrinkage. At this time, the heat treatment temperature is not limited in the present invention, but it is preferable to proceed at 200 to 250 ℃.

The flame retardant polyester film produced through the present invention may have a thickness of 10 to 500㎛. However, the thickness can be freely adjusted according to the stretching process of the film, the amount of the composition added, the heat treatment temperature and the purpose of use, and the present invention is not limited thereto.

Hereinafter, examples are given for a more detailed description of the present invention, but the present invention is not limited to the following examples.

The physical properties of the specimens prepared in Examples below were measured as follows.

(Masterbatch Machinability)

The masterbatch was carried out at an extrusion temperature of 260° C. on a twin screw compounding machine with L/D = 40. Processability was classified according to the following conditions.

○: production yield of 90% or more

△: 80 to 85% production yield

×: 80% or less production yield

(Glass Transition Temperature)

TA Instrument's DSC (Q20) was used as a differential scanning calorimeter, and 10 mg of the sample was set on an aluminum pedestal, and nitrogen gas was introduced at a flow rate of 50 ml/min from 30°C to 300°C at a temperature increase rate of 20°C/min. The temperature was raised, and the glass transition temperature and melting point were calculated according to JIS K 7121-1987.

(film forming property)

The degree of fracture when the film was formed for 1 hour on a base having a tenter width of 6,200 mm in the transverse direction was measured.

○: break 0 times

△ : Break once

×: Break 2 times or more

(flame retardant (VTM grade))

Based on UL 94 VTM Test (Thin Material Vertical Burning Test), 20 specimens of 200 × 50 × 0.1 (mm) were prepared, rolled on a mandrel with a diameter of 13 mm, taped at the upper part, and fixed using a clamp. did Next, after the specimen was contacted twice for 3 seconds, the combustion aspect of the product and the degree of flame propagation to the surroundings were measured as shown in Table 1.

[Table 1]

(The tensile strength)

At the center of the full width of the film roll, the vertical direction is the MD direction of the film and the horizontal direction is the TD direction. First, for the collected sample, make a sample for measuring mechanical properties by setting the lengths in the MD and TD directions to 300 mm × 15 mm, then set the measurement sample width to 15 mm, the gauge length to be 50 mm, and the tensile speed ( Cross head-up speed) was 500 mm/min and the breaking strength in the machine direction (MD) of the film was measured 10 times using a universal tensile tester, and the average value was obtained excluding the maximum and minimum values.

Based on the values measured by the above method, the grades were determined as follows.

○ : Tensile strength 14 kg/㎟ or more

△: Tensile strength 12 to 14 kg/㎟

×: Tensile strength 12 kg/㎟ or less

(heat shrinkage)

Cut the film in the forward direction of 20 cm × 20 cm at the center of the full width of the film roll, heat it in a hot air oven at 150 ° C ± 0.5 ° C for 30 minutes, and then measure the values in the MD and TD directions of the film and use the formula below The thermal contraction rate was calculated accordingly.

[Equation 1]

Based on the values measured by the above method, the grades were determined as follows.

○: less than 2% heat shrinkage

△: 2% to 3% of heat shrinkage

×: Heat shrinkage rate exceeding 3%

(phosphorus content in film)

It was measured using an inductively coupled plasma spectrometer (Perkin Elmer's ICP-AES, Optima 5300DV).

(Example 1)

As a mixed resin, 85% by weight of polyethylene terephthalate (PET) having an intrinsic viscosity of 0.65 ㎗/g and 15% by weight of the polyphosphonate-based polymer resin of Formula 1 (PPH, phosphorus content: 15wt%, Tg: 105°C) was prepared A master batch was prepared by kneading and extruding 0.5 parts by weight of a heat resistant agent (BASF, trade name Irganox ^® 1010) at 260° C. with respect to 100 parts by weight of the mixed resin.

The masterbatch and polyethylene terephthalate having an intrinsic viscosity of 0.65 dl/g were mixed so that the phosphorus content in the film was 1.5 wt % as shown in Table 2 below, put into an extruder, and melt-extruded at 285 ° C. to prepare a sheet having a thickness of 1,100 μm did

The prepared unstretched sheet was stretched 3.3 times in the longitudinal preheating roll at 98° C. and 3.3 times in the yellow direction in a tenter at 130° C. and heat-treated at 230° C. to prepare a film having a thickness of 100 μm. The physical properties of the thus prepared film are shown in Table 3.

(Example 2)

70 wt% of polyethylene terephthalate having an intrinsic viscosity of 0.65 dl/g and 30 wt% of the polyphosphonate-based polymer resin of Formula 1 (phosphorus content: 15 wt%, Tg: 105°C) was used, and the phosphorus content in the film was 3.0 It was prepared in the same manner as in Example 1, except for mixing so as to be % by weight. The physical properties of the prepared film are shown in Table 3 below.

(Example 3)

50% by weight of polyethylene terephthalate having an intrinsic viscosity of 0.65 ㎗/g and 50% by weight of the polyphosphonate-based polymer resin of Formula 1 (phosphorus content: 11wt%, Tg: 108°C) was used, and the phosphorus content in the film was 3.5 It was prepared in the same manner as in Example 1, except for mixing so as to be % by weight. The physical properties of the prepared film are shown in Table 3 below.

(Example 4)

40 wt% of polyethylene terephthalate having an intrinsic viscosity of 0.65 dl/g and 60 wt% of the polyphosphonate-based polymer resin of Formula 1 (phosphorus content: 7.0%, Tg: 117°C) was used, and the phosphorus content in the film was 2.7 It was prepared in the same manner as in Example 1, except for mixing so as to be % by weight. The physical properties of the prepared film are shown in Table 3 below.

(Example 5)

The above example, except that 1.0 parts of the polyphosphonate-based polymer resin of Formula 1 (phosphorus content: 9.0%, Tg: 109°C) and a heat resistant agent were used and mixed so that the phosphorus content in the film was 3.9 wt% 4 was prepared in the same way. The physical properties of the prepared film are shown in Table 3 below.

(Example 6)

It was prepared in the same manner as in Example 1, except that 0.05 parts of the heat resistance agent was added. The physical properties of the prepared film are shown in Table 3 below.

(Example 7)

It was prepared in the same manner as in Example 1, except that the polyphosphonate-based polymer resin of Formula 1 having a Tg of 91° C. was used. The physical properties of the prepared film are shown in Table 3 below.

(Example 8)

It was prepared in the same manner as in Example 3, except that the polyphosphonate-based polymer resin of Formula 1 having a Tg of 120° C. was used and mixed so that the phosphorus content in the film was 4.5 wt%. The physical properties of the prepared film are shown in Table 3 below.

(Comparative Example 1)

85% by weight of polyethylene terephthalate having an intrinsic viscosity of 0.65 dl/g and 15% by weight of the polyphosphonate-based polymer resin of Formula 1 (phosphorus content: 15wt%, Tg: 105°C) was added, and the phosphorus content in the film was 1.35 It was prepared in the same manner as in Example 1, except for mixing so as to be % by weight. The physical properties of the prepared film are shown in Table 3 below.

(Comparative Example 2)

87 wt% of polyethylene terephthalate having an intrinsic viscosity of 0.65 dl/g and 18 wt% of the polyphosphonate-based polymer resin of Formula 1 (phosphorus content: 15 wt%, Tg: 105°C) were added, and the phosphorus content in the film was 1.3 It was prepared in the same manner as in Example 1, except for mixing so as to be % by weight. The physical properties of the prepared film are shown in Table 3 below.

(Comparative Example 3)

35 wt% of polyethylene terephthalate having an intrinsic viscosity of 0.65 dl/g and 65 wt% of the polyphosphonate-based polymer resin of Formula 1 (phosphorus content: 7wt%, Tg: 117°C) were used, and the phosphorus content in the film was It was prepared in the same manner as in Example 1, except that the masterbatch alone was used so as to be 4.55% by weight. The physical properties of the prepared film are shown in Table 3 below.

(Comparative Example 4)

It was prepared in the same manner as in Example 2, except that 0.04 parts of the heat resistance agent was used. The physical properties of the prepared film are shown in Table 3 below.

(Comparative Example 5)

It was prepared in the same manner as in Example 3, except that 2.0 parts of the heat resistance agent were used. The physical properties of the prepared film are shown in Table 3 below.

(Comparative Example 6)

It was prepared in the same manner as in Example 3, except that 1.5 parts of the heat resistant agent were used. The physical properties of the prepared film are shown in Table 3 below.

(Comparative Example 7)

It was prepared in the same manner as in Example 1, except that the polyphosphonate-based polymer resin of Formula 1 having a Tg of 86° C. was used. The physical properties of the prepared film are shown in Table 3 below.

(Comparative Example 8)

It was prepared in the same manner as in Example 3, except that the polyphosphonate-based polymer resin of Formula 1 having a Tg of 127° C. was used. The physical properties of the prepared film are shown in Table 3 below.

[Table 2]

[Table 3]

As shown in Table 3, the flame-retardant polyester film according to the present invention shows excellent values in mechanical properties such as tensile strength and heat shrinkage and flame retardancy, as well as formability such as masterbatch processability and film forming property. On the other hand, Comparative Examples 1 and 2, in which the content of phosphorus in the entire film is less than 1.5% by weight, is inferior to that of Examples in terms of flame retardancy, and Comparative Example 3, in which the content of phosphorus in the film exceeds 4.5% by weight, has masterbatch moldability and mechanical properties It can be seen that it is lower than the example.

In addition, when the content of the heat resistant agent is less than 0.05 part or more than 2.0 part, the master batch processability is inferior, and it can be seen that the mechanical properties of the film are also decreased. In addition, in the case of Comparative Examples 7 (86 ℃) and Comparative Example 8 (127 ℃) in which the glass transition temperature of the polyphosphate-based polymer resin is outside the scope of the present invention, the masterbatch processability is satisfactory, but the film film forming property is poor, and Comparative Example 7 is It was found that even the mechanical properties of the film decreased.

As described above in detail a specific part of the present invention, for those of ordinary skill in the art, it is clear that this specific description is only a preferred embodiment, and the scope of the present invention is not limited thereby. something to do. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (5)

a) 40 to 85% by weight of polyester, b) 100 parts by weight of a mixed resin containing 15 to 60% by weight of a polyphosphate-based resin c) a masterbatch containing 0.05 to 1.0 parts by weight of a heat resistant agent and a polyester-based base resin A flame-retardant polyester film comprising:
The polyphosphate-based resin has a glass transition temperature of 90 to 120 ℃,
The molecular weight of the polyphosphate-based resin is 30 to 350 kg / mol,
The content of phosphorus in the polyester film is 1.5 to 4.5% by weight of the flame retardant polyester film. The method of claim 1,
The flame-retardant polyester film is a flame-retardant polyester film having a flame retardancy of VTM-0 grade as measured by UL 94 VTM Test. The method of claim 1,
The polyester film has a tensile strength of 14 kg/mm2 or more in the longitudinal direction (MD), and the longitudinal and transverse heat shrinkage of the film after being left for 30 minutes at 150° C. in a hot air oven is less than 2% flame retardant polyester film. The method of claim 1,
The melting point of the polyester film is a flame retardant polyester film of 240 ℃ or more. The method of claim 1,
The thickness of the polyester film is 10 to 500㎛ flame-retardant polyester film.