JP2016079279A - Polyester film used for application contacting r32 - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film excellent in heat resistance, pressure resistance and tolerance to R32 and used for an application containing R32.SOLUTION: There is provided a polyester film used for an application contacting R32 satisfying following (1) to (3). (1) Strength retention rate when retaining under 140°C 0% RH for 2000 hours is 30% or more. (2) Elongation retention rate when conducting pressure resistant test (repeating test with release pressure-application pressure of 10 MPa) is 50% or more. (3) Weight change rate when impregnated into a refrigerator oil under R32 atmosphere at 80°C for 200 hours is -0.3 to 1 mass%.SELECTED DRAWING: None

Description

The present invention relates to a polyester film suitable for a film for use in contact with R32.

  Polyester resins, especially polyethylene terephthalate (hereinafter sometimes abbreviated as PET) and polyethylene 2,6-naphthalene dicarboxylate (hereinafter sometimes abbreviated as PEN) are mechanical properties, thermal properties, chemical resistance, electrical properties, It has excellent moldability and is used for various purposes. The polyester film made from the polyester, especially the biaxially oriented polyester film, is a motor for car air conditioners used in solar battery back sheets, water heater motors, hybrid vehicles, etc. due to its excellent mechanical and electrical characteristics. It is used as various industrial materials such as electrical insulating materials for drive motors, magnetic recording materials, capacitor materials, packaging materials, building materials, photographic applications, graphic applications, thermal transfer applications, and the like.

  Among these applications, when used for electrical insulating materials (for example, compressor motors for air conditioners), it is used in an environment where the temperature becomes high as the refrigerant gas is compressed and expanded. And resistance to refrigerants are required. In addition, in recent years, hydrofluorocarbon (HFC) has been widely used as a refrigerant gas for air conditioners instead of hydrochlorofluorocarbon (HCFC) from the environmental aspect (Patent Document 1).

Special table 2011-525204 gazette JP 2009-67944 A JP 2011-12200 A Japanese Patent Laid-Open No. 11-60971 JP 2012-41520 A

R32 (chemical formula: CH ₂ F ₂ ), which is a refrigerant gas typified by HFC, has a higher operating environment temperature of the compressor than before and a higher operating environment pressure than conventional due to its thermal characteristics. Therefore, higher heat resistance and pressure resistance than those in the past are required for use in a film used for applications in contact with R32, particularly for an electrical insulating material of a device in which R32 is used as a refrigerant. In addition, the film used for the application in contact with R32, particularly for use as an electrical insulating material of a device in which R32 is used as a refrigerant, is resistant to R32 (the deterioration of film characteristics when contacting R32 is small, The component contained in is not released into R32. Hereinafter, it may be referred to as refrigerant resistance).

  As a means to improve the heat resistance of the film, pyrolysis caused by the catalyst used during polymerization by adding a phosphorus compound, phenolic antioxidant, and sulfurous antioxidant to the polyester resin composition constituting the film Methods for suppressing the reaction are disclosed (Patent Documents 2 to 5).

  However, when the film obtained by the method described in Patent Documents 2 to 5 is used in contact with R32, particularly as an electrical insulating material for a device in which R32 is used as a refrigerant, a phosphorus compound, a phenol-based antioxidant, a sulfur-based material Antioxidants elute in R32. In this case, since the property of R32 changes, the problem of deteriorating the characteristics of R32 as a refrigerant occurs. Moreover, there exists a subject that the heat resistance of a film deteriorates as a result of the phosphorus compound, a phenolic antioxidant, and a sulfur type antioxidant eluting from the polyester resin composition which comprises a film.

  The subject of this invention is providing the polyester film used for the use which contact | connects R32 excellent in heat resistance, pressure | voltage resistance, and the tolerance with respect to R32 in view of the background of this prior art.

In order to solve the above problems, the present invention has the following configuration. That is,
[I]
The polyester film used for the use which touches R32 which satisfies (1)-(3) below.
(1) The strength retention when held at 140 ° C. and 0% RH for 2000 hours is 30% or more.
(2) The elongation retention when the pressure resistance test (release pressure-pressurization 10 MPa repetition test) is 50% or more.
(3) The weight change rate when immersed in refrigeration oil at 80 ° C. for 200 hours in an R32 atmosphere is −0.3 to 1 mass%.
[II]
The polyester film used for the use which contacts R32 as described in [I] which satisfy | fills (4)-(5) below.
(4) When xylene is impregnated at 140 ° C. for 24 hours, the weight of the component eluted in xylene is 0 to 0.5% by mass with respect to the mass of the film.
(5) The strength retention when kept at 140 ° C. and 80% RH for 24 hours is 30% or more.
[III]
The polyester film used for the use which contacts R32 as described in [I] or [II] which satisfy | fills (6)-(8) below.
(6) A laminated polyester film comprising at least two layers.
(7) at least one surface, when measured by Fourier transform infrared spectroscopy (FT-IR), and the spectral intensity r1 observed in 1452Cm ^-1, the spectrum intensity r2 observed in 1332 cm ^-1 R1 and R2 obtained from the spectral intensity r observed at 1602 cm ⁻¹ satisfy the following relationship.
(I) 0.3 ≦ R1 ≦ 0.6
(Ii) 1.10 ≦ R2 ≦ 1.40
Here, R1 = r1 / r, R2 = r2 / r
Spectrum surface satisfying (8) (7), when measured at a Fourier transform infrared spectroscopy (FT-IR), and the spectral intensity r3 observed in 1018 cm ^-1, which is observed in 1602 cm ^-1 R3 obtained from the strength r satisfies the following relationship.
(Iii) 1.20 ≦ R3 ≦ 2.00
Where R3 = r3 / r
[IV]
A layered polyester film consisting of at least three layers having a layer having a surface satisfying the above (7) and (8) (this layer is A layer) on both sides of the film and having no surface layer (the layer) The intrinsic viscosity of the resin constituting the layer B) is 0.68 to 1.0 dl / g, and the terminal carboxyl group amount is 0 to 25 equivalent / t, according to any one of [I] to [III] Polyester film for use in contact with R32.
[V]
The content of the alkali metal element contained in the polyester resin composition constituting the A layer is M1 (mol / t), the content of the divalent metal element is M2 (mol / t), and the content of the phosphorus element is P (mol). / T), the metal content M (mol / t) in the polyester resin composition obtained by the following formula (iv) is used for contact with R32 described in [IV] that satisfies the following formula (v). Polyester film used.
(Iv) M = 0.5 × (M1) + M2
(V) 0.5 ≦ M / P ≦ 1.5
[VI]
The polyester film used for a use in contact with R32 according to [IV] or [V], wherein the thickness ratio of the A layer / B layer is 0.04 to 15.
[VII]
The polyester film used for the use which contact | connects R32 in any one of [I]-[VI] whose total thickness of a film is 20-350 micrometers.
[VIII]
The polyester film used for the use which contact | connects R32 in any one of [I]-[VII] used for the electrical insulation material of the device in which R32 is used as a refrigerant | coolant.

  ADVANTAGE OF THE INVENTION According to this invention, the polyester film used for the use which contact | connects R32 excellent in heat resistance, pressure | voltage resistance, and the tolerance with respect to R32 can be provided.

  Hereinafter, the present invention will be described in detail with specific examples.

  The polyester used for the polyester film used in contact with R32 of the present invention has a dicarboxylic acid component and a diol component. In addition, in this specification, a structural component shows the minimum unit which can be obtained by hydrolyzing polyester.

  Examples of the dicarboxylic acid component constituting the polyester include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalon. Aliphatic dicarboxylic acids such as acid, ethylmalonic acid and the like, adamantane dicarboxylic acid, norbornene dicarboxylic acid, cyclohexane dicarboxylic acid, decalin dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalene Dicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 5-sodiumsulfoisophthalate Acid, fe Toluene boys carboxylic acid, anthracene dicarboxylic acid, phenanthrene carboxylic acid, 9,9'-bis (4-carboxyphenyl) dicarboxylic acids such as fluorene acids and aromatic dicarboxylic acids, or include an ester derivative thereof.

  Examples of the diol component constituting the polyester include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol. Aliphatic diols such as cyclohexanedimethanol, spiroglycol, bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9′-bis (4-hydroxy Phenyl) fluorene, diols such as aromatic diols, and those in which a plurality of the above diols are linked.

The polyester film used for the application in contact with R32 of the present invention must satisfy the following (1).
(1) The strength retention when held at 140 ° C. and 0% RH for 2000 hours is 30% or more.

  When R32 is used as a refrigerant, the use temperature is about 140 ° C., which is higher than the use temperature of a conventionally used refrigerant. Therefore, the polyester film used for the application in contact with R32 has a use temperature of 140 ° C. It is necessary that the strength retention at is high. Therefore, the polyester film used in the present invention needs to have a strength retention of 30% or more when held at 140 ° C. and 0% RH for 2000 hours. If it is less than 30%, it is brittle and the insulation cannot be maintained. More preferably, it is 40% or more, More preferably, it is 50% or more.

The polyester film used for the application in contact with R32 of the present invention must satisfy the following (2).
(2) The elongation retention when the pressure resistance test (release pressure-pressurization 10 MPa repetition test) is 50% or more.

  The motor using R32 as a refrigerant is repeatedly pressurized and released at a higher pressure than when a conventional refrigerant such as R22 or R410A is used. Therefore, high pressure resistance is required for polyester films used for applications in contact with R32, particularly polyester films used as electrical insulating materials for devices in which R32 is used as a refrigerant. Therefore, the polyester film of the present invention needs to have an elongation retention of 50% or more when subjected to a pressure resistance test (releasing pressure-pressurizing 10 MPa repetition test). More preferably, it is 55% or more, More preferably, it is 60% or more. Details of the pressure resistance test (releasing pressure-pressurizing 10 MPa repetition test) will be described later.

The polyester film used for the application in contact with R32 of the present invention must satisfy the following (3).
(3) The weight change rate when immersed in refrigeration oil at 80 ° C. for 200 hours in an R32 atmosphere is −0.3 to 1 mass%.

  The polyester film of the present invention needs to be resistant to R32. Therefore, the polyester film of the present invention needs to have a weight change rate of −0.3 to 1% by mass when immersed in refrigeration oil at 80 ° C. for 200 hours in an R32 atmosphere. If the weight change rate is less than −0.3%, it indicates that there is a large amount of extract from the polyester film, and the refrigerant contains impurities, which is not preferable. On the other hand, if it is larger than 1% by mass, the film is liable to swell and the insulation properties may be lowered. More preferably, it is -0.25-0.75%, More preferably, it is -0.2-0.5%. In addition, the weight change rate when immersed in the refrigerating machine oil in the present invention at 80 ° C. for 200 hours is a value obtained using Mobil EAL Arctic 68 manufactured by Mobil Co., Ltd. as the refrigerating machine oil in the measurement method described later. .

The polyester film used for the application in contact with R32 of the present invention preferably satisfies the following (4).
(4) When xylene is impregnated at 140 ° C. for 24 hours, the weight of the component eluted in xylene is 0 to 0.5% by mass with respect to the mass of the film.

  Compressor motors are sometimes used by enclosing lubricating oil such as refrigeration oil together with refrigerant inside the compressor motor. For this reason, it is preferable that the polyester film used for the electrical insulating material does not elute components with respect to the refrigerant and the lubricating oil (having high elution suppression properties with respect to the refrigerant and the lubricating oil). If the components are eluted in the refrigerant or the lubricating oil, it may not be preferable because it may cause clogging in the piping of the compressor or a problem of reducing the refrigerant capacity. The elution suppression for refrigerants and lubricating oils can be evaluated by the weight of components eluted in xylene when impregnated with xylene. The polyester film used in the present invention has a component weight of 0 to 0.5 relative to the mass of the film when impregnated with xylene for 24 hours at 140 ° C., which is the operating temperature of a compressor motor using R32 as a refrigerant. It is preferable that it is mass%. If it is larger than 0.5% by mass, the elution component becomes an impurity, which may cause clogging in the compressor pipe or reduce the refrigerant performance. More preferably, it is 0-0.4 mass%, More preferably, it is 0-0.3 mass%.

It is preferable that the polyester film used for the application in contact with R32 of the present invention satisfies the following (5).
(5) The strength retention when kept at 140 ° C. and 80% RH for 24 hours is 30% or more.

  Since refrigerant and refrigeration oil are hygroscopic, the refrigerant and refrigeration oil contain moisture in the compressor motor. Further, as described above, the use temperature when using R32 as a refrigerant is about 140 ° C., which is higher than the use temperature of a conventionally used refrigerant. Therefore, it is preferable that the polyester film of the present invention has moisture and heat resistance that suppresses the occurrence of hydrolysis at 140 ° C., which is a use temperature when R32 is used as a refrigerant. The polyester film of the present invention preferably has a strength retention of 30% or more after being held for 24 hours at a service temperature of 140 ° C. under a humidity of 80% RH. If it is less than 30%, deterioration due to moisture is likely to occur, and mechanical strength may decrease due to long-term use. More preferably 40% or more, still more preferably 50% or more.

It is preferable that the polyester film used for the application in contact with R32 of the present invention satisfies the following (6).
(6) A laminated polyester film comprising at least two layers.

  The polyester film of the present invention is preferably a laminated polyester film composed of at least two layers. More preferably, it is a laminated polyester film consisting of at least three layers in which both surface layers of the film are composed of A layers described later. It is preferable that the A layer having excellent heat resistance and heat-and-moisture resistance is disposed on both surface layers of the film, since the heat resistance and heat-and-moisture resistance of the entire laminated film are improved.

The polyester film used for the application in contact with R32 of the present invention preferably satisfies the following (7).
(7) at least one surface, when measured by Fourier transform infrared spectroscopy (FT-IR), and the spectral intensity r1 observed in 1452Cm ^-1, the spectrum intensity r2 observed in 1332 cm ^-1 R1 and R2 obtained from the spectral intensity r observed at 1602 cm ⁻¹ satisfy the following relationship.
(I) 0.3 ≦ R1 ≦ 0.6
(Ii) 1.10 ≦ R2 ≦ 1.40
Here, R1 = r1 / r, R2 = r2 / r.

When measured by Fourier transform infrared spectroscopy (FT-IR), the spectrum observed at 1452 cm ⁻¹ and 1332 cm ⁻¹ is characterized by the molecular structure of polyethylene 2,6-naphthalenedicarboxylate. is there. That is, the polyester film of the present invention preferably contains polyethylene 2,6-naphthalenedicarboxylate in the resin constituting at least one surface. The content of polyethylene 2,6-naphthalenedicarboxylate in the resin constituting at least one surface is 70% by mass or more based on the total amount of the resin constituting at least one surface from the viewpoint of heat resistance and heat and moisture resistance. It is preferable that it is 85 mass% or more. In general, polyethylene 2,6-naphthalenedicarboxylate is known to have two types of conformation of the methylene group of polyethylene 2,6-naphthalate: a Gauche structure and a trans structure. . Of these two types, the trans structure is advantageous over the Gauche structure when the molecular chains are regularly arranged. From this, the Gauche type structure reflects the part where the molecular chain of polyethylene 2,6-naphthalene dicarboxylate is not regularly arranged (hereinafter referred to as amorphous part), and the trans type structure is polyethylene 2,6-naphthalene dicarboxylate. The molecular chains of the rate are oriented and regularly arranged to reflect a crystallized structure (hereinafter referred to as a crystal portion). When the surface of the laminated polyester film is measured by Fourier transform infrared spectroscopy (FT-IR), the conformation Gauche structure of the methylene group portion of polyethylene 2,6-naphthalate is observed at 1452 cm ⁻¹ . The trans-type structure is characterized by the spectrum observed at 1332 cm ⁻¹ . That is, r1 reflects a Gauche structure derived from the amorphous part, and r2 reflects a trans structure derived from the crystalline part. In addition, r reflects absorption due to C—H stretching vibration of naphthalene ring of polyethylene 2,6-naphthalene dicarboxylate and does not depend on the arrangement of molecular chains. Can be used. Therefore, the smaller R1 which is r1 / r and the larger R2 which is r2 / r, the more crystal parts having a regular structure. If R1 is smaller than 0.3, the crystallinity is too high, and there may be a problem in workability. When R1 is larger than 0.6, resistance to R32 may be inferior.

  In addition, it is preferable that the polyester film used for the electrical insulating material does not elute components with respect to the refrigerant or the lubricating oil (the elution suppression property with respect to the refrigerant or the lubricating oil is high). As a typical component eluted in the refrigerant or lubricating oil, there is an oligomer component of polyester, but since the oligomer is a low molecular weight substance, it has a certain size. Therefore, an oligomer cannot exist in a crystal part having a regular arrangement due to steric hindrance, and therefore inevitably exists in an amorphous part in a polyester film. A more amorphous part is advantageous for elution suppression.

  In general, the density of the crystal part of the polyester resin is higher than that of the amorphous part. Therefore, when the film is immersed in xylene, the xylene penetrates into the film. At that time, xylene is more likely to penetrate into the amorphous portion having a lower density than the crystalline portion having a higher density. For this reason, the direction with many crystal parts can suppress the elution to xylene as a result of suppressing the penetration | invasion to the inside of a film of xylene.

  In view of the above effects, R1 is preferably 0.3 or more and 0.6 or less in order to improve elution suppression.

  Moreover, when using a polyester film as an electrical insulation member used for an air-conditioner compressor, film cutting and bending processing according to the usage shape is required. A stress is applied to the film during the processing, and a large force is applied to a narrow range by the blade edge of the cutter particularly during cutting. At this time, the film cannot absorb the force concentrated in a narrow range, and the film may be broken by an excessive force. Here, when the molecular chain is regularly arranged, the crystal part is usually composed of a plurality of molecular chains, and thus has a role as a node connecting the molecular chains. When there are many crystal parts in the film, the force applied to the film is transmitted through the molecular chain and easily dispersed throughout the film. On the other hand, when the ratio of the crystal part is small, the force applied to the film is difficult to disperse, and cracks are likely to occur during cutting, which is not preferable. Therefore, in order to improve workability, R1 is preferably 0.3 or more.

  The preferable lower limit of R1 is 0.35, and the preferable upper limit is 0.55. If R2 is greater than 1.40, the crystallinity may be too high and there may be a problem in workability. If R2 is smaller than 1.10, resistance to R32 may be inferior. A preferred lower limit is 1.15 and a preferred upper limit is 1.35. By setting R1 and R2 in the above range, a film excellent in heat resistance, pressure resistance, and resistance to R32 satisfying (1) to (5) can be obtained while having good workability. preferable.

Moreover, it is preferable that the polyester film of this invention satisfy | fills following (8).
Spectrum surface satisfying the expression (8) (7), when measured at a Fourier transform infrared spectroscopy (FT-IR), and the spectral intensity r3 observed in 1018 cm ^-1, which is observed in 1602 cm ^-1 R3 obtained from the strength r satisfies the following relationship.
(Iii) 1.20 ≦ R3 ≦ 2.00
Here, R3 = r3 / r.

When measured by Fourier transform infrared spectroscopy (FT-IR), the spectrum observed at 1018 cm ⁻¹ is characterized by the molecular structure of polyethylene terephthalate (C—H stretching vibration of the benzene ring). . That is, the resin constituting either surface layer of the polyester film of the present invention contains polyethylene terephthalate. Compared to polyethylene 2,6-naphthalenedicarboxylate, polyethylene terephthalate has a low glass transition temperature, and therefore has high mobility of molecular chains with respect to heat. In addition, since the molecular structures of polyethylene 2,6-naphthalene dicarboxylate and polyethylene terephthalate are close to each other, the molecular chains are likely to cause a physical interaction. Therefore, when polyethylene terephthalate is contained in polyethylene 2,6-naphthalene dicarboxylate, the mobility of the molecular chain of polyethylene 2,6-naphthalene dicarboxylate is increased due to the high mobility of the molecular chain of polyethylene terephthalate. When the film is biaxially stretched, the laminated film of the present invention is easily biaxially oriented. If R3 is less than 1.20, there may be a problem in workability. If R3 is greater than 2.00, resistance to R32 may be inferior. A preferred lower limit is 1.25 and a preferred upper limit is 1.95. The value of R3 depends on the ratio of the content of polyethylene 2,6-naphthalenedicarboxylate and polyethylene terephthalate in the resin constituting either surface layer of the polyester film. In order to make the range of (iii) above, polyethylene terephthalate and polyethylene 2,6-naphthalenedicarboxylate are used as a raw material for the resin constituting one of the surface layers of the polyester film, and polyethylene terephthalate and polyethylene 2 , 6-naphthalenedicarboxylate is blended before melt film formation. In order to make the range (iii) above, it is important that the content of polyethylene terephthalate in the raw material is 2.5% by mass or more and 30% by mass or less with respect to polyethylene 2,6-naphthalenedicarboxylate. It is. By setting R3 within the above range, a film excellent in heat resistance, pressure resistance and resistance to R32 satisfying (1) to (5) can be obtained while having good workability.

  The polyester film for use in contact with R32 of the present invention is a laminated polyester composed of at least three layers having a layer having a surface satisfying the above (7) and (8) (this layer is A layer) on both sides of the film. The intrinsic viscosity of the resin constituting the layer having no surface layer (this layer is referred to as B layer) is 0.68 to 1.0 dl / g, and the terminal carboxyl group amount is 0 to 25 equivalent / t. It is preferable. A more preferable lower limit of the intrinsic viscosity is 0.70 dl / g, and a more preferable upper limit is 0.9 dl / g. If it is less than 0,68 dl / g, the heat resistance, pressure resistance, and resistance to R32 may be inferior. If it is greater than 1.0 dl / g, there may be a problem in workability. When the amount of terminal carboxyl groups is larger than 25 equivalent / t, heat resistance and resistance to R32 may be inferior.

The polyester film used for the application in contact with R32 of the present invention includes the content of the alkali metal element contained in the polyester resin composition constituting the A layer, the content of M1, the content of the bivalent metal element of M2, the content of the trivalent metal element When the amount is M3 and the phosphorus element content is P (mol / t), the metal content M (mol / t) in the polyester resin composition determined by the following formula (iv) is the following formula (v): It is preferable that it is a polyester film used for the use which contact | connects R32 as described in [IV] which satisfy | fills.
(Iv) M = 0.5 × (M1) + M2 + 1.5 × (M3)
(V) 0.5 ≦ M / P ≦ 1.5
If M / P is less than 0.5, the amount of phosphorus element is excessive, the polymerization catalyst is easily deactivated, a large amount of low molecular weight substances are present, and elution suppression and resistance to R32 may deteriorate. If the ratio is larger than 1.5, the amount of metal is excessive, which may accelerate thermal degradation and deteriorate heat resistance.

  M in this formula represents the cation content of the metal element that interacts with the anion derived from phosphoric acid in the polyester resin composition constituting the film. It is necessary to consider not only a divalent metal element but also an alkali metal element cation having a high electronegativity as a cation of a metal element that interacts with an anion derived from phosphoric acid.

  In general, anions derived from phosphoric acid have a trivalent negative charge, so that the cation of the monovalent metal element is 1: 3, and the cation of the divalent metal element is 2: 3, 3. It is thought that it interacts 1: 1 with the cation of the valent metal element. However, as a result of intensive studies by the present inventors, the anion derived from phosphoric acid is assumed to interact with the cation of the metal element as a divalent anion (iv), (v) (ie, The anion derived from phosphoric acid has a cation of a monovalent metal element of 1: 2, a cation of a divalent metal element of 1: 1, and a cation of a trivalent metal element of 3: 2 It was found that elution suppression, resistance to R32, and heat resistance are improved by making M / P within the above range under the equation of Although this is not clarified at this time, it is presumed to be due to the degree of ionization of phosphoric acid. Phosphoric acid has a trivalent negative charge, but in general, phosphoric acid has a low degree of ionization at the third stage, and thus has an apparently divalent anion in the polyester composition (divalent anion). Interact with metal cations 1: 1).

  By setting M / P within the above numerical range, it is possible to obtain a polyester resin composition excellent in elution suppression, resistance to R32, and heat resistance.

  The thickness ratio of the A layer / B layer of the polyester film used for the application in contact with R32 of the present invention is preferably 0.04 to 15. If it is less than 0.04, the B layer may be too thick and heat resistance may deteriorate. If it is greater than 15, the A layer may be too thick and workability may deteriorate.

  The polyester film used for the application in contact with R32 of the present invention preferably has a total thickness of 20 μm to 350 μm. If it is thinner than 20 μm, the handleability is poor and the workability may be deteriorated. If it is thicker than 350 μm, it may be easily broken by bending or the like, and the workability may deteriorate.

In order to obtain a polyester film satisfying (1) to (3),
(A) A method for producing a film under the conditions described later, using a polyester resin constituting the surface layer of the film as a specific polyester resin (b) A polyester resin constituting the surface layer and the inner layer as a laminated polyester film comprising at least three layers As a specific polyester resin, a method for producing a film under the conditions described below (c) can be obtained by combining the above methods.

  First, the method according to (a) will be described.

  The surface layer of the polyester film of the present invention preferably contains a polyester resin having a high melting point. Preferably it is 245 degreeC or more, More preferably, it is 260 degreeC or more.

More preferably, when measuring the surface of the polyester film at a Fourier transform infrared spectroscopy (FT-IR), and the spectral intensity r3 observed in 1018 cm ^-1, from the spectral intensities r observed in 1602 cm ^-1 It is preferable that R3 required satisfies the following relationship.
(Ii) 1.2 ≦ R3 ≦ 2.0
Where R3 = r3 / r
Here, the equation (ii) represents the following. That is, when measured by Fourier transform infrared spectroscopy (FT-IR), the spectrum observed at 1018 cm ⁻¹ is characterized by the molecular structure of polyethylene terephthalate (C—H bending vibration of the benzene ring). Is. That is, the resin constituting one of the surface layers of the laminated polyester film of the present invention preferably contains polyethylene terephthalate. When measured by Fourier transform infrared spectroscopy (FT-IR), the spectrum observed at 1602 cm ⁻¹ is characterized by absorption due to CC stretching vibration of the naphthalene ring of polyethylene 2,6-naphthalenedicarboxylate. It is attached. Since this spectral intensity does not depend on the orientation of the molecular chain, it can be used as a normalized absorption peak in the intensity comparison. Since the spectrum observed at 1018 cm ⁻¹ does not depend on the orientation of the molecular chain, R3 reflects the amount of polyethylene terephthalate contained in the resin constituting the surface layer of the film.

  Compared to polyethylene 2,6-naphthalenedicarboxylate, polyethylene terephthalate has a low glass transition temperature, and therefore has high mobility of molecular chains with respect to heat. In addition, since the molecular structures of polyethylene 2,6-naphthalene dicarboxylate and polyethylene terephthalate are close to each other, the molecular chains are likely to cause a physical interaction. Therefore, when polyethylene terephthalate is contained in polyethylene 2,6-naphthalene dicarboxylate, the mobility of the molecular chain of polyethylene 2,6-naphthalene dicarboxylate is increased due to the high mobility of the molecular chain of polyethylene terephthalate. When it manufactures by the method to do, it becomes easy to control the ratio of the crystalline part of the film of this invention, and an amorphous part. Furthermore, when a resin having high molecular chain mobility is present, it is preferable because the moldability of the film is improved. Resins having high molecular chain mobility are easily deformed by stress, and therefore can absorb stress during film processing.

  The value of R3 depends on the ratio of the content of polyethylene 2,6-naphthalenedicarboxylate and polyethylene terephthalate in the resin constituting either surface layer of the polyester film. In order to set the range of (ii) above, polyethylene terephthalate and polyethylene 2,6-naphthalenedicarboxylate are used as a raw material for the resin constituting one of the surface layers of the polyester film, and polyethylene terephthalate and polyethylene 2 are used. , 6-naphthalenedicarboxylate is blended before melt film formation. In order to make the range (ii) above, it is important that the content of polyethylene terephthalate in the raw material is 5% by mass or more and 25% by mass or less with respect to polyethylene 2,6-naphthalene dicarboxylate. . On the other hand, when the above (ii) is satisfied by copolymerizing polyethylene 2,6-naphthalene dicarboxylate and polyethylene terephthalate, the crystallinity and melting point of the polyester resin satisfying (ii) are lowered. When the crystallinity is lowered, crystallization due to stretching does not occur and (i) may not be satisfied. If (i) is not satisfied, the workability, heat resistance, pressure resistance, and resistance to R32 may be reduced. It becomes an inferior film. Further, when the melting point of the polyester resin constituting the surface layer of the film is lowered, the film may be inferior in workability, heat resistance, pressure resistance, and resistance to R32.

  As a result of forming a film from a polyester resin satisfying the above (ii), the mobility of the molecular chain is increased, the molecular chain of the polyester resin is regularly arranged by biaxial stretching, and the crystal starting point can be easily formed. Therefore, it is preferable from the viewpoint of workability as well as heat resistance, pressure resistance, and resistance to R32.

  Next, the method according to (b) will be described. Even if a polyester resin that does not satisfy the above (ii) is used as the resin constituting the surface layer, for example, a resin consisting only of PEN, the resin constituting the layer not having the surface layer has high molecular chain mobility. By using a resin to form a laminated polyester film composed of at least three layers, the surface layer of the film can be a surface layer satisfying R1. When the resin constituting the surface layer is polyethylene 2,6-naphthalene dicarboxylate, the polyester resin constituting the layer other than the surface layer is preferably polyethylene terephthalate because the mobility of the molecular chain is high.

  When the molecular chain of the resin constituting the layer other than the surface layer is close to the structure of the molecular chain of the resin constituting the surface layer, the resin constituting the surface layer is the molecular chain of the resin constituting the layer other than the surface layer during stretching. Follow the movement of the regular arrangement, so that it becomes easy to arrange the molecular chains of the resin constituting the surface layer. Moreover, when the mobility of the molecular chain of the resin constituting the layer other than the surface layer is high and the resin is easily ordered by stretching, the molecular chain of the resin constituting the surface layer is more easily arranged regularly. As a result, even if a polyester resin that does not satisfy the above (ii) is used as the resin constituting the surface layer, for example, a resin composed only of PEN, the molecular chain of PEN is oriented to the extent that the formula (i) is satisfied. Is possible. As a result, a film having excellent heat resistance, pressure resistance, and resistance to R32 can be obtained. Moreover, when the film structure is the above three-layer structure, the ratio of the resin having high molecular chain mobility in the film is increased, so that the processability of the film is improved.

  Next, the method according to (c) will be described. In the case of a laminated polyester film, when a layer made of a resin satisfying (ii) is laminated so as to be a surface layer and the other layers are made of a resin having a high molecular chain mobility, the layers constituting the film Since the mobility of the molecular chain of each of the resins forming the resin is high, it is easy to stretch biaxially, which is preferable from the viewpoints of film forming properties and elution suppression properties (oil resistance). When a layer made of a resin satisfying the following (ii) is laminated so as to become the outermost layer and the other layers are made of a resin having a high molecular chain mobility, each molecule of the resin constituting the layer constituting the film Since the chain mobility is high, it is easy to biaxially stretch, which is preferable from the viewpoints of film-forming properties and elution suppression properties (oil resistance).

  The polyester film used for the application in contact with R32 of the present invention is produced, for example, as follows. In order to produce a polyester film, for example, polyester pellets are melted using an extruder, discharged from a die, and then cooled and solidified to form a sheet. At this time, in order to remove the unmelted material in the polymer, the polymer may be filtered with a fiber sintered stainless metal filter.

  Furthermore, various additives such as compatibilizers, plasticizers, weathering agents, antioxidants, thermal stabilizers, lubricants, antistatic agents, whitening agents, coloring, as long as the effects of the present invention are not impaired. Agents, conductive agents, ultraviolet absorbers, flame retardants, flame retardant aids, pigments and dyes may be added.

  Subsequently, the sheet-like material obtained as described above is heat-treated after being stretched biaxially in the longitudinal direction and the width direction. As the stretching method, a sequential biaxial stretching method such as stretching in the width direction after stretching in the longitudinal direction, a simultaneous biaxial stretching method in which the longitudinal direction and the width direction are simultaneously stretched using a simultaneous biaxial tenter, etc. A method combining a sequential biaxial stretching method and a simultaneous biaxial stretching method is included.

  After each layer constituting the polyester film used for the application in contact with R32 is dried under reduced pressure at 180 ° C. for 3 hours or more at a temperature of 180 ° C., the raw material pellets of each layer (and, if necessary, a master batch) are then used. Is supplied to an extruder heated to a temperature of 265 to 280 ° C. under a nitrogen stream or reduced pressure so as not to decrease, and is extruded from a slit-shaped T die and cooled on a casting roll to obtain an unstretched film. The film is laminated by melt lamination using two or more extruders and a manifold or merging block. At this time, the temperature unevenness in the extruder is preferably 2 ° C. or less. If there is temperature unevenness in the extruder, the structure of the unstretched film is likely to be uneven, and the structure control during stretching becomes difficult.

  Next, the unstretched film thus obtained is biaxially stretched. Biaxial stretching method using a longitudinal stretching machine in which several rolls are arranged, stretching in the longitudinal direction using the difference in peripheral speed of the rolls (MD stretching), followed by transverse stretching with a stenter (TD stretching) Will be described.

  First, the unstretched film is MD stretched. The longitudinal stretching machine comprises a preheating roll, a stretching roll, and a cooling roll, and further comprises a nip roll that cuts the tension and suppresses slipping of the film. In MD stretching, the film running on the stretching roll is pressed by a stretching nip roll with a constant pressure (nip pressure) to sandwich the film and cut the tension. Stretched. At this time, the surface roughness of the stretching roll is preferably 0.35 to 0.45S. In a stretching roll that does not satisfy 0.35 to 0.45 S, the film slips on the roll, and uneven orientation may occur in the stretching, which may make it difficult to control the structure. The MD stretching temperature is (glass transition temperature (hereinafter referred to as Tg) +10) to (Tg + 50) ° C., and the stretching ratio of MD stretching is 1.2 to 5.0 times. It cools with the cooling roll group of the temperature of 20-50 degreeC after extending | stretching. At this time, the surface roughness of the cooling roll is preferably 0.35 to 0.45S. In a cooling roll that does not satisfy 0.35 to 0.45 S, the slippage of the film changes on the roll, and unevenness may occur in the cooling rate of the film, making structural control difficult.

  Next, stretching in the width direction (TD stretching) is performed using a stenter. The stenter is a device that stretches the film between the clips at both ends while holding the both ends of the film with clips, and is stretched into a preheating zone, a stretching zone, a heat treatment zone, and a cooling zone. At this time, the fluctuation of the width to be gripped by the clip is preferably 5 mm or less. When the gripping width varies, the stretched distance changes, so that the structure due to stretching may be uneven. The stretching ratio of TD stretching is 2.0 to 6.0 times, and the stretching temperature is in the range of (Tg) to (Tg + 50) ° C. After TD stretching, heat setting is performed. In the heat setting treatment, the film is heat-treated in a temperature range of 150 to 240 ° C. while being relaxed under tension or in the width direction. The heat treatment time is in the range of 0.5 to 10 seconds. Thereafter, it is cooled to 25 ° C. in the cooling zone. Then, a film edge is removed and the polyester film of this invention can be obtained.

[Characteristic evaluation method]
(1) Measurement of breaking strength / breaking elongation Based on ASTM-D882 (1997), a sample was cut into a size of 1 cm × 20 cm, and when it was pulled at a chuck distance of 5 cm and a pulling speed of 300 mm / min, the breaking strength and breaking The elongation was measured. In addition, about each of the vertical direction of a film, and the horizontal direction, after measuring the number of samples by n = 5, those average values were made into breaking strength and breaking elongation.

(2) Heat resistance evaluation (Elongation retention when held at 140 ° C. and 0% RH for 2000 hours)
After the sample was cut into the shape of the measurement piece (1 cm × 20 cm), it was treated for 2000 hours under the condition of a temperature of 140 ° C. (humidity 0% RH) in a heat treatment device GPHH-102 manufactured by ESPEC Corporation The breaking strength was measured according to the above item (1). In addition, the measurement was made into n = 5, and after measuring about 5 samples of the vertical direction and the horizontal direction of a film, the average value was made into breaking strength S1. Moreover, also about the film before processing, the breaking strength S0 was measured according to the said (1) term, and strength retention was computed by following Formula (iv) using the obtained breaking strength S0 and S1.
Strength retention (%) = (S1 / S0) × 100 (iv)
(3) Pressure resistance evaluation (elongation retention rate when pressure resistance test (relief pressure-pressurization 10 MPa repeated test))
A film sample cut into the shape of a measurement piece (1 cm × 20 cm) is prepared and placed in an autoclave device (TVS-N2 type manufactured by Pressure Glass Industrial Co., Ltd.). The internal pressure of the autoclave device is set to a vacuum state (100 Pa or less) with a pump. The whole autoclave apparatus is warmed to 140 ° C., and R32 is introduced to 10 MPa. The pressure is maintained at 10 MPa for 6 hours, and then the pressure is released and the vacuum is maintained at 100 Pa or less for 6 hours. The cycle of holding at 10 MPa for 6 hours and then holding at 100 Pa or less for 6 hours was repeated 10 times, and then the breaking elongation was measured according to the above item (1). In addition, the measurement was made into n = 5, and after measuring about 5 samples of the vertical direction of a film, and a horizontal direction, the average value was made into breaking elongation E1. Moreover, also about the film before processing, break elongation E0 is measured according to the said (1) term, and elongation retention is calculated by following Formula (v) using the obtained break elongation E0 and E1. did.
Elongation retention (%) = (E1 / E0) × 100 (v)
(4) Resistance evaluation for R32 (weight change rate when immersed in refrigeration oil at 80 ° C. for 200 hours in R32 atmosphere)
A film sample cut into 10 cm on a side is prepared and the weight W0 is measured. Mobil EAL Arctic 68 manufactured by Mobil Corporation is used as the refrigerator oil. 100 g of the oil is weighed, the film sample is completely immersed, and placed in an autoclave apparatus (TVS-N2 type manufactured by Pressure Glass Industrial Co., Ltd.). The internal pressure of the autoclave device is set to a vacuum state (100 Pa or less) with a pump. R32 is introduced therein so as to be 5 MPa, and the whole autoclave apparatus is warmed and maintained at 80 ° C. for 200 hours. Thereafter, the pressure is released, the film sample is taken out, the oil is wiped off, and the weight W1 is measured. Using the obtained weights W0 and W1, the weight change rate was calculated by the following equation (vi).
Weight change rate (%) = ((W1-W0) / W0) × 100 (vi)
(5) Evaluation of dissolution inhibition (weight percentage of components eluted in xylene when impregnated in xylene at 140 ° C. for 24 hours)
Twenty pieces of film samples cut out to 10 cm on a side are prepared, and the weight W2 is measured. Then, the film sample is put in an autoclave apparatus (TVS-N2 type manufactured by Pressure Glass Industrial Co., Ltd.). A weight W3 of 100 ml of xylene (Wako Pure Chemical Industries, Ltd. reagent first grade; xylene isomer mixture) is measured, and 200 ml is introduced into the autoclave. The internal pressure of the autoclave device is set to a vacuum state (100 Pa or less) with a pump. Then, the entire autoclave apparatus is warmed and maintained at 140 ° C. for 24 hours. Thereafter, the film sample was taken out, 100 ml of xylene was weighed, the weight W4 was measured, and the obtained weights W2, W3, and W4 were used to calculate the amount of the eluted component by the following formula (vii).
Weight ratio of components eluted in xylene (%) = ((W4−W3) / W2) × 100 (vii)
(6) Evaluation of hydrolysis resistance (strength retention when held at 140 ° C. and 80% RH for 24 hours)
After the sample was cut into the shape of the measurement piece (1 cm × 20 cm), it was processed for 24 hours under the conditions of 140 ° C. and relative humidity of 80% RH in the advanced accelerated life test device EHS-411 manufactured by ESPEC CORP. After that, the breaking strength was measured according to the above item (1). In addition, the measurement was made into n = 5, and after measuring about 5 samples of the vertical direction and the horizontal direction of a film, the average value was made into breaking strength S2. Moreover, also about the film before processing, the breaking strength S0 was measured according to the above item (1), and the elongation retention was calculated by the following equation (viii) using the obtained breaking elongations S0 and S2. .
Strength retention (%) = (S2 / S0) × 100 (viii)
(7) D.E. Fourier Transform Infrared Spectroscopy (FT-IR) Spectral Intensity Using Frontier FT-IR manufactured by PerkinElmer Co., Ltd., using UATR IR unit, medium crystal as diamond / ZnSe, attenuated total reflection method (ATR) ) To measure the spectral intensity. The resolution of the spectroscope is 1 cm ⁻¹ and the number of spectrum integrations is 16 times. The spectral intensity is the absorbance (arb. Unit) at each wavelength.

  When measuring the spectrum of the surface layer of the laminated film, the surface layer of the film is closely attached to the medium crystal, and the measurement is performed. The contact between the medium crystal and the sample is performed by applying pressure using a jig attached to the apparatus. The pressure is increased while observing the spectrum of the sample, and measurement is performed when the spectrum shape does not change due to the pressure.

  When measuring the spectrum of the layer in contact with the surface layer of the laminated film, the surface of the film after the thickness of the resin constituting the surface layer is trimmed from the laminated polyester film using a microtome, and measurement is carried out. To do. For peak detection, IR spectrum analysis software Spectrum (manufactured by Perkin Elmer Co., Ltd.) (ver. 10.2) is used, and the wave number of the peak is read from the IR spectrum measured by the peak detection function.

(8) Intrinsic viscosity The polyester composition is dissolved in 100 ml of orthochlorophenol (solution concentration C = 1.2 g / dl), and the viscosity of the solution at 25 ° C. is measured using an Ostwald viscometer. Similarly, the viscosity of the solvent is measured. Using the obtained solution viscosity and solvent viscosity, [η] (dl / g) is calculated by the following equation (c), and the obtained value is used as the intrinsic viscosity (IV).
(C) ηsp / C = [η] + K [η] ² · C
(Where ηsp = (solution viscosity (dl / g) / solvent viscosity (dl / g)) − 1, K is a Huggins constant (assuming 0.343)).

(9) Amount of terminal carboxyl group Measured according to the following conditions according to the method of Malice (reference MJ Malice, F. Huizinga, Anal. Chim. Acta, 22 363 (1960)). 2 g of the polyester composition was dissolved in 50 mL of o-cresol / chloroform (weight ratio 7/3) at a temperature of 150 ° C., titrated with a 0.05N KOH / methanol solution, the amount of terminal carboxyl groups was measured, eq. / Indicated by the value of polyester 1t. In addition, the indicator at the time of titration uses phenol red, and the place where it changed from yellowish green to light red is set as the end point of titration.

(10) M / P
(10-1) Content of phosphorus element and divalent metal element (excluding alkali metal element) of polyester resin composition constituting film Film X-ray fluorescence analyzer (model number: 3270) manufactured by Rigaku Corporation Use to measure.

(10-2) Content of alkali metal element of polyester resin composition constituting film Quantified by atomic absorption spectrometry (manufactured by Sasatsu Seisakusho: Polarized Zeeman atomic absorption photometer 180-80, frame: acetylene-air). It was.

(10-3) M / P
The content of alkali metal element is M1 (mol / t), the content of bivalent metal element is M2 (mol / t), the content of trivalent metal element is M3, and the content of phosphorus element is P (mol / t). As
The metal content M (mol / t) in the polyester resin composition was determined as 0.5 × (M1) + M2 + 1.5 × (M3), and M / P was calculated.

(11) Lamination ratio A film cross section is cut out with a microtome in a direction parallel to the film width direction. The cross section is observed with a scanning electron microscope at a magnification of 5000 times to determine the thickness ratio of each layer. The thickness of each layer is calculated from the obtained lamination ratio and the above-described film thickness.

(12) Insulation evaluation evaluation 100 hermetic motors mounted with the film sample as an insulation film were prepared, and the refrigerant (R32) and vacuum-dried insulating oil (polyol ester oil) were added at a weight ratio of 3: Incorporated into a compressor for room air conditioner filled to 1 and tested at 2160 hours, 3240 hours and 4320 hours under high speed and high load conditions. Since the motor stops when the insulation deteriorates, the insulation was evaluated from the number of normal operation.
A: All 100 motors operated normally at 4320 hours B: One or more motors stopped during evaluation at 4320 hours, but 100 motors operated normally at 3240 hours C: One or more motors evaluated at 3240 hours Stopped during 2160 hours, but all 100 operated normally D: Stopped 1-5 motors during evaluation in 2160 hours E: Stopped 6 motors during evaluation in 2160 hours
A to D were accepted.

(13) Evaluation of cooling performance The compressor for room air conditioner tested in the above (12) was connected to a simple cycle, and a cooling performance test was conducted after 2160 hours. If the R32 refrigerant resistance is low, the extract to the insulating oil increases and the cooling efficiency of the refrigerant decreases. The cooling performance test was evaluated by the time (minutes) for cooling the space (15 m ³ ) adjusted to 35 ° C. to 20 ° C.
A: The set temperature is reached within 6 minutes B: The set temperature is reached within 10 minutes longer than 6 minutes C: The set temperature is reached within 15 minutes longer than 10 minutes D: The set temperature within 20 minutes longer than 15 minutes E: The set temperature is not reached even after 20 minutes.
A to D were accepted.

(14) Workability
Using a motor processing machine manufactured by Odawara Engineering Co., Ltd., the film is punched into a size of 12 x 80 mm (the longitudinal direction of the film is set to 80 mm), and further creased at a total processing speed of 2 pieces / second. 1000 samples were prepared and the number of cracks and cracks generated was counted (number of cracks generated). In addition, among 1000 samples, the number of samples in which the inner angle of the fold was 90 ° or more was counted (number of deformation defects) for those in which no cracks or cracks occurred. In any of the values, the smaller the count number, the better the workability, and the value obtained by adding the number of crack occurrences and the number of deformation defects and dividing by 10 was obtained as the defect rate (%).
A: The defect rate is less than 0.5% B: The defect rate is 0.5% or more and less than 1% C: The defect rate is 1% or more and less than 5% D: The defect rate is 5% or more and less than 10% E: The defect rate was 10% or more and A to D were accepted.
As a comprehensive evaluation of the polyester film, a film having no failure in insulation, cooling performance, and workability was regarded as acceptable.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not necessarily limited to these.

  [Production of PET] 100 parts by mass of dimethyl terephthalate, 57.5 parts by mass of ethylene glycol, 0.03 parts by mass of magnesium acetate dihydrate, 0. 03 parts by mass were melted at 150 ° C. in a nitrogen atmosphere. While stirring this melt, the temperature was raised to 230 ° C. over 3 hours to distill methanol, and the transesterification reaction was completed. After completion of the transesterification reaction, an ethylene glycol solution (pH 5.0) in which 0.005 parts by mass of phosphoric acid was dissolved in 0.5 parts by mass of ethylene glycol was added. The intrinsic viscosity of the polyester composition at this time was less than 0.2. Thereafter, the polymerization reaction was performed at a final temperature of 285 ° C. and a degree of vacuum of 0.1 Torr to obtain polyethylene terephthalate having an intrinsic viscosity of 0.52 and a terminal carboxyl group amount of 15 equivalents / ton. The obtained polyethylene terephthalate was dried and crystallized at 160 ° C. for 6 hours. Thereafter, solid phase polymerization was performed at 220 ° C. and a vacuum degree of 0.3 Torr for 8 hours to obtain polyethylene terephthalate (PET) having an intrinsic viscosity of 0.80, a terminal carboxyl group amount of 10 equivalents / ton, and M / P = 1.0. Obtained. The obtained polyethylene terephthalate composition had a glass transition temperature of 82 ° C. and a melting point of 255 ° C.

  [Production of PEN] A transesterification reaction was carried out from dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol using manganese acetate as a catalyst. After the transesterification reaction, PEN was obtained by a conventional method using antimony trioxide as a catalyst. The obtained PEN-A had a glass transition temperature of 124 ° C., a melting point of 265 ° C., an intrinsic viscosity of 0.62, and a terminal carboxyl group content of 25 eq. / T.

Example 1
As polymer α constituting the surface layer (A layer), 90 parts by mass of PEN and 10 parts by mass of PET as polymer β were blended, vacuum-dried at 180 ° C. for 3 hours, and then charged into the extruder 1. Further, 100 parts by mass of PET as polymer γ constituting the layer in contact with the surface layer (B layer) was vacuum-dried at 180 ° C. for 2 hours, and then charged into the extruder 2. Each raw material is melted when the temperature unevenness in the extruder is 2 ° C. or less, and the resin introduced into the extruder 1 is merged by a merging device so as to be both surface layers of the film, and extruded into a casting drum shape. / B / A, lamination ratio A / B = 0.25) was produced. Subsequently, the sheet was preheated with a heated group of rolls having a surface roughness of 0.40, then stretched 2.6 times in the longitudinal direction (MD direction) at a temperature of 95 ° C., and then the surface roughness at a temperature of 25 ° C. It cooled with the roll group of the degree 0.40, and obtained the uniaxially stretched film. The width of the uniaxially stretched film obtained by gripping both ends with a clip is 3.0 mm or less in the width direction (TD direction) perpendicular to the longitudinal direction in the heating zone at a temperature of 110 ° C. in the tenter while gripping at 5 mm or less. Stretched. Subsequently, a heat treatment was performed for 10 seconds at a temperature of 220 ° C. in a heat treatment zone in the tenter, and a relaxation treatment was further performed in the 4% width direction at a temperature of 220 ° C. Next, the film was gradually cooled in a cooling zone and wound up to obtain a laminated polyester film having a thickness of 250 μm. Each characteristic of the obtained film is shown in the table. It was found that the film was excellent in heat resistance, pressure resistance, and resistance to R32.

(Examples 2 to 20)
A laminated film was obtained in the same manner as in Example 1 except that the mixing ratio of the polymer α and the polymer β and the laminated structure, laminated ratio, and film forming conditions of the laminated film were changed as described in the table. The heat resistance, pressure resistance, and resistance to R32 of the obtained film are as shown in the table. In addition, the IR spectrum of Example 10 evaluated the A layer side.

(Example 21)
A laminated film was obtained in the same manner as in Example 1 except that the polymer α was changed from PEN to polyester 13319 (Eastman), which is a PCHT resin. The heat resistance, pressure resistance, and resistance to R32 of the obtained film are as shown in the table.

(Example 22)
A laminated film was obtained in the same manner as in Example 1 except that the polymer α was changed from PEN to ULTEM 1010 (manufactured by SABIC), which is a PEI resin, and the mixing ratio was changed. The heat resistance, pressure resistance, and resistance to R32 of the obtained film are as shown in the table.

(Example 23)
A laminated film was obtained in the same manner as in Example 1 except that the amount of terminal carboxyl groups of polyethylene terephthalate constituting the B layer was changed as described in the table. The heat resistance, pressure resistance, and resistance to R32 of the obtained film are as shown in the table.

(Comparative Examples 1-4)
A laminated film was obtained in the same manner as in Example 1 except that the mixing ratio of the polymer α and the polymer β and the laminated structure, laminated ratio, and film forming conditions of the laminated film were changed as described in the table. The heat resistance, pressure resistance and resistance to R32 of the obtained film were inferior as shown in the table.
The COOH amount in the table means the amount of terminal carboxyl groups.

  According to the polyester film of the present invention, since it is excellent in heat resistance, pressure resistance and resistance to R32, a polyester film suitable for use in contact with R32, particularly an electrical insulating material of a device in which R32 is used as a refrigerant, A polyester film suitable for use in a compressor member of an air conditioner in which R32 is used as a refrigerant can be provided.

Claims (8)

The polyester film used for the use which contacts R32 which satisfy | fills (1)-(3) below.
(1) The strength retention when held at 140 ° C. and 0% RH for 2000 hours is 30% or more.
(2) The elongation retention when the pressure resistance test (release pressure-pressurization 10 MPa repetition test) is 50% or more.
(3) The weight change rate when immersed in refrigeration oil at 80 ° C. for 200 hours in an R32 atmosphere is −0.3 to 1 mass%. The polyester film used for the use which contacts R32 of Claim 1 which satisfy | fills (4)-(5) below.
(4) When xylene is impregnated at 140 ° C. for 24 hours, the weight of the component eluted in xylene is 0 to 0.5% by mass with respect to the mass of the film.
(5) The strength retention when kept at 140 ° C. and 80% RH for 24 hours is 30% or more. The polyester film used for the use which contacts R32 of Claim 1 or Claim 2 which satisfy | fills (6)-(8) below.
(6) A laminated polyester film comprising at least two layers.
(7) at least one surface, when measured by Fourier transform infrared spectroscopy (FT-IR), and the spectral intensity r1 observed in 1452Cm ^-1, the spectrum intensity r2 observed in 1332 cm ^-1 R1 and R2 obtained from the spectral intensity r observed at 1602 cm ⁻¹ satisfy the following relationship.
(I) 0.3 ≦ R1 ≦ 0.6
(Ii) 1.10 ≦ R2 ≦ 1.40
Here, R1 = r1 / r, R2 = r2 / r
Spectrum surface satisfying (8) (7), when measured at a Fourier transform infrared spectroscopy (FT-IR), and the spectral intensity r3 observed in 1018 cm ^-1, which is observed in 1602 cm ^-1 R3 obtained from the strength r satisfies the following relationship.
(Iii) 1.20 ≦ R3 ≦ 2.00
Where R3 = r3 / r A layered polyester film consisting of at least three layers having a layer having a surface satisfying the above (7) and (8) (this layer is A layer) on both sides of the film and having no surface layer (the layer) R32 according to any one of claims 1 to 3, wherein the intrinsic viscosity of the resin that constitutes the B layer is 0.68 to 1.0 dl / g, and the amount of terminal carboxyl groups is 0 to 25 equivalent / t. Polyester film used for contact applications. The content of the alkali metal element contained in the polyester resin composition constituting the A layer is M1 (mol / t), the content of the bivalent metal element is M2 (mol / t), and the content of the trivalent metal element is M3. When the phosphorus element content is P (mol / t), the metal content M (mol / t) in the polyester resin composition determined by the following formula (iv) satisfies the following formula (v): The polyester film used for the use which contact | connects R32 of claim | item 4.
(Iv) M = 0.5 × (M1) + M2 + 1.5 × (M3)
(V) 0.5 ≦ M / P ≦ 1.5 The thickness ratio of A layer / B layer is 0.04-15, The polyester film used for the use which contacts R32 of Claim 4 or 5 characterized by the above-mentioned. The polyester film used for the use which contacts R32 in any one of Claims 1-6 whose total thickness of a film is 20-350 micrometers. The polyester film used for the use which contacts R32 in any one of Claims 1-7 used for the electrical-insulation material of the device in which R32 is used as a refrigerant | coolant.