JPWO2015019885A1 - Laminated polyester film - Google Patents

Abstract

To provide a polyester film for motor electrical insulation that has excellent heat and humidity resistance, heat resistance, withstands use at high temperature and humidity for a long period of time, and has excellent processability. (1) On at least one surface, a spectral intensity r1 of 1452 cm−1, a spectral intensity r2 of 1332 cm−1 and a spectral intensity r of 1602 cm−1 observed by Fourier transform infrared spectroscopy (FT-IR) measurement R1 (= r1 / r) and R2 (= r2 / r) obtained from the above are values that satisfy a specific numerical range, and are observed by the FT-IR measurement on the surface that satisfies (2) (1). R3 (= r3 / r) obtained from the spectral intensity r3 of 1018 cm-1 and the spectral intensity r of 1602 cm-1 is a value satisfying a specific numerical range, and the surface satisfying (3) (1) (2) is satisfied. The laminated polyester film which consists of at least 2 layer from which melting | fusing point of resin which comprises the layer which has becomes temperature which satisfy | fills a specific numerical range.

Description

The present invention relates to a laminated polyester film having good heat resistance and wet heat resistance and excellent workability.

  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. Polyester films made from polyester, especially biaxially oriented polyester films, are used in solar cell backsheets, water heater motor electrical insulation materials, and hybrid vehicles because of their excellent mechanical and electrical properties. It is used as various industrial materials such as electric insulation materials, magnetic recording materials, capacitor materials, packaging materials, building materials, photographic applications, graphic applications, thermal transfer applications, etc.

  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 is compressed and expanded. PEN was often used (Patent Documents 1 and 2). However, PEN has poor processability due to its molecular structure, and causes a problem that the film breaks during processing. Therefore, a special processing step is required to solve such a problem (Patent Document 3). In addition, when used for electrical insulating materials, so-called wet heat resistance that does not cause degradation due to hydrolysis even under high-temperature and high-humidity conditions is required to withstand long-term use.

  In addition, in recent years, hydrofluorocarbon (HFC) has been widely used as a refrigerant for air conditioners instead of hydrochlorofluorocarbon (HCFC) from the environmental aspect (Patent Document 4). The refrigerant R32 represented by HFC has been pointed out that the operating environment temperature of the compressor is higher than before due to its thermal characteristics, and heat resistance requirements for films used for compressor motor applications for air conditioners. Is growing.

Japanese Patent Laid-Open No. 9-300452 JP 2007-99971 A JP-A-6-335960 Special table 2011-525204 gazette

  The subject of this invention is providing the film excellent in heat resistance, moist heat resistance, and workability 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] A laminated polyester film comprising at least two layers that satisfies the following requirements (1) to (3).
(1) 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) 0.2 ≦ R1 ≦ 0.4
(Ii) 1.25 ≦ R2 ≦ 1.50
Here, R1 = r1 / r, R2 = r2 / r
(2) a surface that satisfies (1), when measured at a Fourier transform infrared spectroscopy (FT-IR), and the spectral intensity r3 observed in 1018 cm ^-1, the spectrum intensity observed in 1602 cm ^-1 R3 calculated from r satisfies the following relationship.
(Iii) 1.20 ≦ R3 ≦ 2.00
Where R3 = r3 / r
(3) The melting point of the resin constituting the layer having a surface satisfying (1) and (2) (this layer is referred to as layer A) is 260 ° C. or higher and 280 ° C. or lower.
[II] The laminated polyester film according to [I], which satisfies the following (4).
(4) The total thickness T of the film is 120 μm or more and 500 μm or less.
[III] Glass transition temperature (Tg1) ° C. of the resin constituting the A layer and glass transition temperature (Tg2) of the resin constituting the layer adjacent to the layer having the A plane (this layer is referred to as B layer) The laminated polyester film according to [I] or [II], in which a difference from ° C. satisfies the following relationship.
(Iv) 30 ° C. ≦ Tg1-Tg2 ≦ 40 ° C.
[IV] the layer B, when measured by Fourier transform infrared spectroscopy (FT-IR), obtained from the spectral intensity r5 observed in spectral intensity r4 and 1372cm ^-1 which is observed 1388Cm ^-1 The laminated polyester film according to any one of [I] to [III], wherein R4 satisfies the following relationship.
(V) 0.95 ≦ R4 ≦ 1.05
Here, R4 = r4 / r5
[V] The laminated polyester film according to any one of [I] to [IV], in which both surface layers of the film are composed of A layers and are composed of at least three layers.
[VI] The laminated polyester film according to any one of [I] to [V], wherein the resin constituting the B layer has a melting point of 253 ° C. or higher and 258 ° C. or lower.
[VII] The amount of terminal carboxyl groups of the polyester resin constituting the laminated polyester film is 15 eq. The laminated polyester film according to any one of [I] to [VI], which is / t or less.
[VIII] The laminated polyester film according to any one of [I] to [VII], which is used as an electric insulating member of a motor.
[IX] A laminated film including the laminated polyester film according to any one of [I] to [VIII] and having a surface satisfying (1) and (2) of the laminated polyester film on at least one outermost layer.

  According to the present invention, it is possible to provide a polyester film that is excellent in heat resistance, heat and humidity resistance, and processability, and that satisfies long-term use. Since the film obtained by the present invention suppresses deterioration of physical properties even under high temperature and high humidity conditions, a laminated polyester film that can withstand long-term use even when used as an electric insulating member of a motor using a refrigerant composed of HFC Can be provided.

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

  The polyester film of the present invention needs to be a laminated polyester film composed of at least two layers.

  The polyester here is a polymer having an ester bond synthesized from a dicarboxylic acid component and a diol component as the main bond chain of the main chain. 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 Examples include, but are not limited to, dicarboxylic acids such as ruendandicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, aromatic dicarboxylic acids such as 9,9′-bis (4-carboxyphenyl) fluorenic acid, or ester derivatives 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 Examples include, but are not limited to, diols such as aromatic diols such as phenyl) fluorene, and a series of a plurality of the aforementioned diols.

The laminated polyester film of the present invention must satisfy the following (1).
(1) 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) 0.2 ≦ R1 ≦ 0.4
(Ii) 1.25 ≦ R2 ≦ 1.50
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, polyethylene 2,6-naphthalenedicarboxylate is contained in the resin constituting the layer having a surface satisfying (1). The content of polyethylene 2,6-naphthalenedicarboxylate in the resin constituting the layer having a surface satisfying (1) constitutes a layer having a surface satisfying (1) from the viewpoint of heat resistance and heat-and-moisture resistance. It is preferable that it exceeds 70 mass% with respect to the total amount of resin, More preferably, 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. The spectral intensity r observed at 1602 cm ⁻¹ reflects absorption due to C—H stretching vibration of the naphthalene ring of polyethylene 2,6-naphthalene dicarboxylate, and does not depend on the arrangement of molecular chains. It can be used as a standardized absorption peak in intensity comparison. Therefore, the smaller R1 which is r1 / r and the larger R2 which is r2 / r, the more crystal parts having a regular structure.

  When polyethylene 2,6-naphthalenedicarboxylate is placed under a high temperature or a moist heat atmosphere, molecular chain scission due to oxidative degradation or molecular chain scission due to hydrolysis occurs. When polyethylene 2,6-naphthalene dicarboxylate is in the form of a film, the film becomes more brittle. As the embrittlement progresses, the mechanical elongation decreases. When the mechanical elongation is lowered, the film is broken even with a slight impact, so that it cannot be used as an electrical insulating member. It is considered that molecular chain breakage due to oxidative degradation or molecular chain breakage due to hydrolysis preferentially occurs from an amorphous part having high molecular chain mobility. Therefore, in polyethylene 2,6-naphthalenedicarboxylate, it is considered that the heat resistance and the moist heat resistance increase as the crystal part increases. On the other hand, the mechanical strength of the film is derived from a crystal part in which molecular chains are regularly arranged. However, since the mechanical elongation is derived from an amorphous part, not only heat resistance and moist heat resistance but also workability is improved. Therefore, it is important that the crystal part and the amorphous part are in a certain range, that is, R1 and R2 are in a range satisfying the expressions (i) and (ii). In order to set R1 and R2 in the above range, the polyester resin constituting the surface satisfying (1) is a polyester resin that satisfies the following condition (iii), and the film is biaxially oriented under the conditions described later. Can be obtained. In general, the orientation of the film is related to the mobility of the polyester molecular chain. As will be described in detail later, by using a polyester resin that satisfies (iii), the mobility of the molecular chain can be increased and the molecular chain of the polyester resin can be easily oriented. When the following (iii) is not satisfied, for example, a layer composed only of polyethylene 2,6-naphthalenedicarboxylate cannot sufficiently orient the molecular chain of the resin, resulting in (i) (ii) The film cannot be satisfied and is inferior in heat resistance and moist heat resistance.

Moreover, the laminated polyester film of the present invention must satisfy the following (2).
(2) a surface that satisfies (1), when measured at a Fourier transform infrared spectroscopy (FT-IR), and the spectral intensity r3 observed in 1018 cm ^-1, the spectrum intensity observed in 1602 cm ^-1 R3 calculated from 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 bending vibration of the benzene ring). is there. That is, the resin constituting the layer having a surface satisfying (1) of the laminated 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-naphthalenedicarboxylate and polyethylene terephthalate are similar, molecular chains are likely to cause 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 biaxial stretching is performed by this method, the laminated polyester film of the present invention can be easily biaxially oriented. That is, by satisfying the above condition (iii), the above conditions (i) and (ii) are satisfied. In addition, the present inventors have found that, by satisfying the condition of (iii), the mobility of the molecular chain of the entire resin constituting the surface layer is increased and the processability of the film is improved.

  The value of R3 depends on the ratio of the contents of polyethylene 2,6-naphthalenedicarboxylate and polyethylene terephthalate in the resin constituting the layer having a surface satisfying (1) of the laminated polyester film of the present invention. In order to make the range (iii) above, polyethylene terephthalate and polyethylene 2,6-naphthalenedicarboxylate are used as raw materials for the resin constituting the layer having a surface satisfying (1) of the polyester film. And a method of blending polyethylene 2,6-naphthalenedicarboxylate 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 5% by mass or more and 35% by mass or less with respect to polyethylene 2,6-naphthalenedicarboxylate. . On the other hand, when (iii) is satisfied by copolymerizing polyethylene 2,6-naphthalenedicarboxylate and polyethylene terephthalate, the crystallinity and melting point of the polyester resin satisfying (iii) are lowered. If the crystallinity is lowered, orientation may not be imparted by stretching, and (i) (ii) may not be satisfied. If (i) (ii) is not satisfied, the heat and moisture resistance is poor. Film. Moreover, although mentioned later in detail, when melting | fusing point falls, it becomes a film inferior to heat resistance.

Moreover, the laminated polyester film of the present invention must satisfy the following (3).
(3) The melting point of the resin constituting the layer having a surface satisfying (1) and (2) (this layer is referred to as layer A) is 260 ° C. or higher and 280 ° C. or lower. In the present invention, the melting point is obtained from 1st RUN of differential scanning calorimetry (DSC) by the measurement method described later. When two or more crystal melting peaks are observed, the peak top with the highest temperature is obtained. Is the melting point.

  When the melting point of the resin constituting the A layer is less than 260 ° C., when the film is exposed to a high temperature, the heat resistance of the film surface affected by the highest temperature is not sufficient, and the film surface is likely to deteriorate due to heat. As a result, the heat resistance of the entire film is poor. When the melting point exceeds 280 ° C., it cannot be melt-extruded well. The upper limit of the melting point of the resin constituting the A layer is preferably 275 ° C. or lower, and more preferably 270 ° C. or lower. By setting it as this range, it can be set as the film excellent in heat resistance. For example, polyethylene terephthalate and polyethylene 2,6-naphthalenedicarboxylate are used as a raw material for the resin constituting the A layer, and the method of setting the melting point of the resin constituting the A layer in the above range is as follows. The content of is made from 5% by mass to 25% by mass with respect to polyethylene 2,6-naphthalene dicarboxylate, and blended before melt film formation to obtain a film.

Moreover, it is preferable that the laminated polyester film of this invention satisfy | fills following (4).
(4) The total thickness of the laminated polyester film is 120 μm or more and 500 μm or less.

When the polyester is decomposed at a high temperature or in a moist heat atmosphere, the polyester proceeds from the film surface. Therefore, when the thickness of the whole film is 120 μm or more, the amount of polyester decomposed at high temperature or in a moist heat atmosphere is small with respect to the total amount of polyester constituting the film, and deterioration of the whole film can be suppressed. In addition, the conventional film having excellent heat resistance and heat and humidity resistance deteriorates the handleability of the film by increasing the film thickness. Therefore, when the total film thickness is 120 μm or more, the workability of the film, in particular, the bendability is inferior. Therefore, the film thickness could not be increased. Moreover, when the thickness of the film is less than 120 μm, there is a problem that punchability is deteriorated in the workability of the film. However, the laminated polyester film of the present invention is not only excellent in heat resistance and moist heat resistance, but also has a good film processability (bendability and punchability) even when the total film thickness is 120 μm or more. Suitable for electrical insulation applications. If the thickness of the film exceeds 500 μm, it may be difficult to make the film biaxially oriented. The bendability can be evaluated by the bending strength (FE) based on JIS P-8115 (1994). The folding strength (FE) is obtained from the following formula (a) using the number of times N of folding until the film breaks due to deformation caused by folding in a test based on JIS P-8115 (1994). .
Formula (a) FE = logN
When FE is small, it is not preferable because it breaks during bending. If the FE is large, it is difficult to shape by bending. A preferable range is 4.1 ≦ FE ≦ 4.5. Moreover, satisfying the condition of (iii) is also a preferred embodiment for improving the bendability of the film.

  In the laminated polyester film of the present invention, the difference between the glass transition temperature (Tg1) ° C. of the resin constituting the A layer and the glass transition temperature (Tg2) ° C. of the resin constituting the B layer satisfies the following relationship: Is preferred. In addition, in this invention, a glass transition temperature is calculated | required from 2ndRUN of differential scanning calorimetry (DSC) by the measuring method mentioned later.

(Iv) 30 ° C. ≦ Tg1-Tg2 ≦ 40 ° C.
When the above conditions are satisfied, when the laminated polyester film is biaxially stretched by the method described later, the glass transition temperature of the resin constituting the A layer is below the A layer, and the B layer is the B layer. It becomes possible to stretch at a temperature equal to or higher than the glass transition temperature of the resin constituting the. Under these conditions, the resin constituting the B layer can be usually stretched, but the resin constituting the A layer cannot be stretched. However, by forming the film of the present invention into a laminated polyester film in which the A layer and the B layer are adjacent, the resin constituting the A layer is stretched following the stretching of the resin constituting the B layer. Thus, stretching can be performed at a temperature lower than the glass transition temperature of the resin constituting the A layer. By stretching below the glass transition temperature of the resin constituting the A layer, the orientation of the resin constituting the A layer can be easily imparted to the orientation. As a result, the above conditions (i) and (ii) are satisfied, and the heat resistance and heat and humidity resistance are improved. It can be set as the laminated polyester film excellent in.

  In the laminated polyester film of the present invention, the resin constituting the B layer is preferably a polyester mainly composed of polyethylene terephthalate from the viewpoint of processability, mechanical properties, and heat resistance of the laminated polyester film. Polyester having polyethylene terephthalate as a main constituent is a ratio of terephthalic acid constituents in all dicarboxylic acid constituents of 95 mol% to 100 mol%, and a ratio of ethylene glycol constituents in all diol constituents is 95 mol% or more. The polyester is 100 mol% or less. More preferably, the proportion of the terephthalic acid component in the total dicarboxylic acid component is 98 mol% or more and 100 mol% or less, and the proportion of the ethylene glycol component in the total diol component is 98 mol% or more and 100 mol% or less. Moreover, it is preferable that melting | fusing point of resin which comprises the said B layer is 253 degreeC or more and 258 degrees C or less. If it is lower than 253 ° C., the heat resistance may be inferior. If it exceeds 258 ° C., it becomes necessary to increase the stretching temperature, so that it becomes difficult to strengthen the orientation of the A layer, and the heat and moisture resistance and heat resistance may be inferior.

The B layer is, when measured by Fourier transform infrared spectroscopy (FT-IR), R4 is less obtained from the spectral intensity r5 observed in spectral intensity r4 and 1372cm ^-1 which is observed 1388Cm ^-1 It is preferable to satisfy the relationship.
(V) 0.95 ≦ R4 ≦ 1.05
Here, R4 = r4 / r5.

When measured by Fourier transform infrared spectroscopy (FT-IR), the spectra observed at 1388 cm ⁻¹ and 1372 cm ⁻¹ are characterized by the molecular structure of polyethylene terephthalate. That is, the laminated polyester film of the present invention preferably contains polyethylene terephthalate in the resin constituting the B layer. Generally, in polyethylene terephthalate, it is known that the conformation of the methylene group portion of polyethylene terephthalate takes two types, a Gauche type structure and a trans type structure, as in polyethylene 2,6-naphthalate. The mold structure reflects the amorphous part of polyethylene terephthalate, and the trans structure reflects the crystal part due to the orientation of polyethylene terephthalate. That is, r4 reflects the Gauche structure derived from the amorphous part, and r5 reflects the trans structure derived from the crystalline part. It represents that there are many crystal parts with a regular structure, so that R4 is small.

  When R4 is in the above range, it is preferable that the crystalline portion and the amorphous portion are present in a well-balanced manner, and the mechanical properties of the film are improved in addition to heat resistance and moist heat resistance. Moreover, in order to make R4 into said range, making a film biaxially align on the conditions mentioned later is mentioned.

  The laminated polyester film of the present invention is preferably a film composed of at least three layers in which both surface layers of the film are composed of A layers. Since the A layer excellent in heat resistance and heat and moisture resistance is disposed on both surfaces of the film, the heat resistance and heat and moisture resistance of the entire laminated polyester film are improved, which is preferable.

  Next, although an example is given and demonstrated about the manufacturing method of the laminated polyester film of this invention, this invention is limited to only the thing obtained by this example, and is not interpreted.

  As a method for obtaining the polyester used in the present invention, a conventional polymerization method can be employed. For example, it can be obtained by subjecting a dicarboxylic acid component such as terephthalic acid or a derivative thereof and a diol component such as ethylene glycol to a transesterification reaction or an esterification reaction by a known method, and then performing a melt polymerization reaction. If necessary, the polyester obtained by the melt polymerization reaction may be subjected to a solid phase polymerization reaction at a temperature lower than the melting point of the polyester. Moreover, you may add the mixture of phosphoric acid and an alkali metal phosphate from a viewpoint of improving the heat-and-moisture resistance of polyester. The addition amount of the mixture of phosphoric acid and alkali metal phosphate is 1.0 mol / t or more and 5.0 mol / t or less as the amount of phosphorus with respect to the polyester resin in order to reduce the influence of the polymerization delay due to the phosphorus compound. It is preferable.

  The laminated polyester film of the present invention can be obtained by a conventionally known production method, but the surface of the laminated polyester film is subjected to Fourier transform infrared spectroscopy (FT) by producing the stretching and heat treatment steps under the following conditions. -IR) is preferable because a laminated polyester film having a spectral intensity measured in the above range can be stably obtained.

  The laminated polyester film of the present invention can use a method (melt cast method) in which a dried raw material is heated and melted in an extruder as necessary, and is extruded onto a cast drum cooled from a die and processed into a sheet shape. . As another method, the raw material is dissolved in a solvent, and the solution is extruded from a die onto a support such as a cast drum or an endless belt to form a film, and then the solvent is dried and removed from the film layer to form a sheet. A method (solution casting method) or the like can also be used.

  When the film is produced by the melt casting method, an extruder is used for each layer constituting the laminated polyester film, the raw materials of each layer are melted, and these are melted in a joining device provided between the extrusion device and the die. A method is preferably used in which the layers are laminated, guided to a die, and extruded from the die onto a cast drum and processed into a sheet shape. The laminated sheet is closely cooled and solidified by static electricity on a drum cooled to a surface temperature of 10 ° C. or higher and 40 ° C. or lower to produce an unstretched sheet. The polyethylene terephthalate film of the present invention can be obtained by biaxially stretching this unstretched sheet.

  When performing melt extrusion in an extruder, it is better that the time from melting in a nitrogen atmosphere to supplying chips to the extruder and extruding with a die is as short as possible. As a guideline, it is 30 minutes or less, more preferably 15 minutes. Hereinafter, more preferably 5 minutes or less, from the viewpoint of suppressing the increase in the amount of terminal carboxyl groups, and when using a plurality of types of polyester raw material, the polyester is copolymerized by a transesterification reaction in the extruder. It is preferable from the viewpoint of suppression. The amount of terminal carboxyl groups of the resin constituting the laminated polyester film of the present invention is 15 eq. From the viewpoint of improving the heat and moisture resistance. / T (equivalent / t) or less is preferable. The temperature of the extruder at the time of melt extrusion with an extruder is from the viewpoint of suppressing an increase in the amount of terminal carboxyl groups, and when multiple types of polyester raw materials are used, the polyester is copolymerized by a transesterification reaction in the extruder. From the viewpoint of suppressing this, it is preferably less than 300 ° C, more preferably less than 290 ° C.

The obtained unstretched sheet is biaxially stretched under the condition (5).
(5) At a temperature T1n satisfying the following formula (vi), the film is biaxially stretched in an area magnification of 12 times or more in the longitudinal direction (MD) of the film and the width direction (TD) of the film.
(Vi) Tg2 ≦ T1n ≦ Tg2 + 30 ° C.
Tg2: Glass transition temperature (° C.) of the resin constituting the B layer of the laminated polyester film
As a method of biaxial stretching, in addition to a sequential biaxial stretching method in which stretching in the longitudinal direction (MD) of the film and stretching in the width direction of the film (direction perpendicular to the longitudinal direction of the film, TD) is performed, the longitudinal direction Examples thereof include a simultaneous biaxial stretching method in which stretching in the direction and the width direction is simultaneously performed.

  When the stretching temperature (T1n) is Tg2 or less, stretching cannot be performed. Moreover, when T1n is in the above range, it becomes possible to impart orientation to the resin constituting the B layer of the laminated polyester film.

  The preferable aspect of the laminated polyester film of this invention is (iv) 30 degreeC <= Tg1-Tg2 <= 40 degreeC as above-mentioned. Therefore, when the film satisfying (iv) is stretched under the condition satisfying (vi), T1n is the same temperature as the glass transition temperature (Tg1) of the resin constituting the A layer of the laminated polyester film, or The temperature is lower than Tg1. In the case of a polyester film composed of a single layer, it is usually impossible to provide orientation by stretching at or below the glass transition temperature of the polyester constituting the film. However, in the laminated polyester film of the present invention, even if the stretching temperature is equal to or lower than the glass transition temperature of the resin constituting the A layer, the layer A can be sufficiently stretched under the condition that the layer B in contact with the layer A can be sufficiently stretched. It can be stretched following this. Furthermore, since the resin constituting the A layer is stretched below the glass transition temperature of the resin constituting the A layer, it becomes easier to impart orientation. Moreover, in order to set it as the extending | stretching temperature which B layer can fully extend | stretch, it is preferable that T1n is the range which satisfy | fills (vi), More preferably, it is Tg2 <= T1n <= Tg2 + 20 degreeC. In order to stretch the film under the condition (5), from the viewpoint of stretchability, the thickness of the A layer (the total thickness of the A layer when the A layer is present on both surfaces of the film) T1 and the thickness of the B layer The ratio T1 / T2 of T2 is preferably 1/8 or more and 1/5 or less.

  In the present invention, either one of the surface layers of the laminated polyester film is configured to satisfy the condition (iii), and is stretched at a temperature satisfying the above (vi), whereby R1, R2 are (i), (ii) Can be met. When the surface layer of either one of the laminated polyester films is configured to satisfy the condition (iii), the mobility of the polyester molecular chain constituting the layer is improved, and the orientation by stretching can be further increased.

  When R3 is less than 1.20 (when the content of polyethylene terephthalate with respect to polyethylene 2,6-naphthalenedicarboxylate is low in the polyester resin constituting layer A), the mobility of the polyester molecular chain is insufficient, and the area magnification Even when the film is stretched by 12 times or more, the orientation by stretching cannot be imparted, so that the value of R1 exceeds 0.4 or the value of R2 becomes less than 1.25. Moreover, since the mobility of the polyester molecular chain is insufficient, when the draw ratio is increased to 13 times or more, the film forming property is deteriorated and the film cannot be formed. The value of R3 increases by increasing the weight ratio of polyethylene terephthalate to polyethylene 2,6-naphthalenedicarboxylate in the resin constituting the A layer. And in connection with it, since the molecular mobility of resin which comprises A layer becomes high, it becomes easy to attach orientation. That is, R1 decreases and the value of R2 increases. On the other hand, as the weight ratio of polyethylene terephthalate to polyethylene 2,6-naphthalenedicarboxylate in the resin constituting the A layer is increased, the mobility of the molecular chains of the resin constituting the A layer increases, and the order is regular. It becomes difficult to have an array. That is, as a result of the decrease in crystallinity, it becomes difficult to achieve orientation.

  When R3 exceeds 2.00 (when the content of polyethylene terephthalate with respect to polyethylene 2,6-naphthalenedicarboxylate is high in the polyester resin constituting the A layer), the mobility of the polyester molecular chains constituting the A layer is Even when stretched at an area magnification of 12 times or more, sufficient orientation cannot be imparted to the polyester of the layer, and the value of R1 exceeds 0.4 or the value of R2 satisfies 1.25. Disappear.

  On the other hand, even when the condition (iii) is satisfied, if the draw ratio is less than 12, the orientation cannot be sufficiently imparted, the value of R1 exceeds 0.4, and the value of R2 is 1. .25 may not be met. Moreover, when satisfy | filling the conditions of said (iii), although the one where an area magnification is large can provide an orientation, Preferably it is 17 times or less. When it exceeds 17 times, not only the value of R1 is less than 0.2 and the value of R2 exceeds 1.50, but also the film forming property may be deteriorated.

  Moreover, when extending | stretching at the temperature which satisfy | fills said (vi), if area magnification is less than 12 times, orientation cannot fully be provided to the polyester resin which comprises B layer, and R4 exceeds 1.05. , May be inferior in heat and humidity resistance and heat resistance. A larger area magnification can provide orientation, but it is preferably 17 times or less. When it exceeds 17 times, R4 becomes less than 0.94, and not only the heat and moisture resistance and heat resistance are inferior, but also the film forming property may be deteriorated.

  Next, in order to complete the crystal orientation of the obtained biaxially stretched film and impart flatness and dimensional stability, heat treatment is performed at a temperature of Tg2 or more and less than the melting point of the laminated polyester film for 1 second or more and 30 seconds or less. The laminated polyester film of the present invention can be obtained by uniformly cooling slowly and then cooling to room temperature.

  As described above, the laminated polyester film of the present invention has the characteristics of being excellent in heat resistance and moist heat resistance and excellent in workability. Therefore, the laminated film including the laminated polyester film of the present invention and having a surface satisfying (1) and (2) of the laminated polyester film on at least one outermost layer is an electrically insulating material, a magnetic recording material, a capacitor material, and a packaging material. It can be suitably used for building materials, photographic applications, graphic applications, thermal transfer applications, and the like. As a method for obtaining the above laminated film, the surface satisfying (1) and (2) of the laminated polyester film of the present invention is provided for the purpose of imparting slipperiness, concealment and the like within a range not impairing the effects of the present invention. On the opposite side, a layer by coating is provided on the surface of the laminated polyester film. Moreover, the laminated polyester film of this invention can be obtained by the method of bonding with another layer so that the surface which satisfy | fills (1) (2) may become an outermost layer.

  In addition, organic particles, inorganic particles, dyes, and the like can be added to each layer constituting the film for the purpose of imparting easy slipperiness, concealing property and the like within a range not impairing the effects of the present invention.

Since the film obtained by the present invention suppresses deterioration of physical properties even under high-temperature and high-humidity conditions, it uses HFC or the like as a refrigerant, as an electric insulating member for a motor in which the operating environment temperature of the compressor is higher than before. It can be used suitably.
[Characteristic evaluation method]
A. Terminal carboxyl group content It is measured under the following conditions according to the method of Malice (references 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. / Polyester 1t (shown as eq./t in the table). 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.

B. Melting point (° C) of resin constituting each layer
Using a method based on JIS K-7121 (1999), a differential scanning calorimeter “Robot DSC-RDC220” manufactured by Seiko Denshi Kogyo Co., Ltd. and a disk session “SSC / 5200” are used for data analysis. The measurement was carried out in the following manner.
The sample was weighed in a sample pan by 5 mg, and the sample was heated from 25 ° C. to 300 ° C. at a heating rate of 20 ° C./min (1st RUN). A 1st RUN differential scanning calorimetry chart (the vertical axis is thermal energy and the horizontal axis is temperature) is obtained. In the differential scanning calorimetry chart of 1stRun, the peak top temperature at the crystal melting peak, which is the endothermic peak, is determined, and this is defined as the melting point (° C.). When two or more crystal melting peaks are observed, the temperature at the peak top with the highest temperature is taken as the melting point.

  For the sample, only the resin constituting each layer is cut out from the laminated polyester film using a microtome and used for measurement.

C. Glass transition temperature Tg1 of the resin constituting the surface layer, glass transition temperature Tg2 (° C.) of the resin constituting the layer in contact with the surface layer
In accordance with JIS K7121 (1999), a differential scanning calorimeter “Robot DSC-RDC220” manufactured by Seiko Denshi Kogyo Co., Ltd. was used, and a disk session “SSC / 5200” was used for data analysis. Perform the measurement.

  5 mg of a sample is weighed in a sample pan, and the sample is heated from 25 ° C. to 300 ° C. at a heating rate of 20 ° C./min (1stRUN), held in that state for 5 minutes, and then rapidly cooled to 25 ° C. or lower. Immediately thereafter, the temperature was increased again from 25 ° C. to 300 ° C. at a rate of temperature increase of 20 ° C./minute, and a 2ndRUN differential scanning calorimetry chart (the vertical axis represents thermal energy and the horizontal axis represents temperature) Get. In the 2ndRUN differential scanning calorimetry chart, in the step change portion of the glass transition, a straight line that is equidistant from the extended straight line of each base line in the vertical axis direction and a curve of the step change portion of the glass transition are Find from the point of intersection. When two or more glass transition steps are observed, the glass transition temperature is obtained for each, and the average of these temperatures is taken as the glass transition temperature (Tg1) (° C.) of the sample.

  In the Tg1 measurement, only the resin constituting the surface layer is scraped from the laminated polyester film using a microtome and used for the measurement. In the Tg2 measurement, only the resin constituting the layer in contact with the surface layer is further cut out from the film after the thickness of the resin constituting the surface layer is cut from the laminated polyester film using a microtome, and used for measurement.

D. Fourier Transform Infrared Spectroscopy (FT-IR) Spectral Intensity Using a Frontier FT-IR (Spectrum One 400) manufactured by PerkinElmer Co., Ltd. and using a UATR IR unit, the medium crystal is attenuated as diamond / ZnSe. The spectral intensity is measured by the total reflection method (ATR method). 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 polyester 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.

  A spectrum is measured in advance without a sample. The spectrum is subtracted from the spectrum obtained by measuring the sample. In addition, the baseline is corrected by an automatic baseline correction program installed in the operation software “SPECTRUM” of this apparatus.

  When measuring the spectrum of the layer in contact with the surface layer of the laminated polyester film, the surface of the film after the thickness of the resin constituting the surface layer has been trimmed from the laminated polyester film using a microtome, is closely attached to the medium crystal. carry out.

  When the layer by coating is provided in the surface layer of either one or both of the laminated polyester films, the layer provided by the coating is scraped off and used for measurement.

E. Heat-and-moisture resistance of the laminated polyester film The laminated polyester film is cut into a size of 1 cm × 20 cm so that the long side is parallel to the longitudinal direction and the width direction of the film, respectively, and 5 cm between chucks based on ASTM-D882 (1997). The elongation at break when measured at a pulling speed of 300 mm / min is measured. The number of samples is n = 5, and after measuring in the longitudinal direction and the width direction of the film, the average value thereof is obtained, and this is defined as the elongation at break E0 of the film.

Next, the film cut out in the same manner is treated with a pressure cooker manufactured by Tabai Espec Co., Ltd. under high-humidity heat conditions of a temperature of 125 ° C. and a relative humidity of 100% RH, and then the elongation at break is measured. In addition, it is set as n = 5 and it measures about each of the longitudinal direction of a film, and the width direction, and let the average value be the breaking elongation E1. Using the obtained breaking elongations E0 and E1, the elongation retention is calculated by the following equation (a). The treatment time is changed by one hour, and the treatment time at which the elongation retention is 50% or less is defined as the elongation half-life.
(A) Elongation retention (%) = E1 / E0 × 100
From the obtained elongation half-life, the heat-and-moisture resistance of the film was determined as follows.
When elongation half-life is 70 hours or more: A
When the elongation half-life is 60 hours or more and less than 70 hours: B
When the elongation half-life is 51 hours or more and less than 60 hours: C
When elongation half-life is less than 51 hours: D
A, B, and C are good, and A is the best among them.

F. Heat resistance of the laminated polyester film The laminated polyester film is cut into a size of 1 cm × 20 cm so that the long side is parallel to the longitudinal direction and the width direction of the film, and 5 cm between chucks based on ASTM-D882 (1997). The breaking strength when pulled at a pulling speed of 300 mm / min is measured. The number of samples is n = 5, and after measuring in the longitudinal direction and the width direction of the film, the average value thereof is obtained, and this is defined as the breaking strength S0 of the film.

Next, the film cut in the same manner is subjected to a dry heat treatment under a high temperature condition of 200 ° C. in a gear oven manufactured by Tabai Espec Co., Ltd., and then the breaking strength is measured. In addition, it is set as n = 5 and it measures about each of the longitudinal direction of a film, and the width direction, and let the average value be breaking strength S1. Using the obtained breaking strengths S0 and S1, the elongation retention is calculated by the following equation (b). The treatment time is changed by one hour, and the treatment time at which the strength retention is 50% or less is defined as the strength half-life.
(B) Strength retention (%) = S1 / S0 × 100
From the obtained elongation half-life, the heat resistance of the film was determined as follows.
When the strength half-life is 60 hours or more: A
When the strength half-life is 48 hours or more and less than 60 hours: B
When the strength half-life is 36 hours or more and less than 48 hours: C
When the strength half-life is less than 36 hours: D
A, B, and C are good, and A is the best among them.

G. Laminated polyester film thickness (μm)
The film thickness was measured at any five locations using a dial gauge in accordance with JIS K7130 (1992) A-2 method with 10 films stacked. The average value was divided by 10 to obtain the film thickness.

H. Thickness (μm) of each layer of laminated polyester film
A film cross section is cut out with a microtome in a direction parallel to the film width direction and in a direction perpendicular to the film thickness 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.

I. Bendability A test is performed based on JIS P-8115 (1994). Cut out the laminated polyester film to 5 mm x 100 mm so that the direction to be measured is the long side, and using a folding tester manufactured by Toyo Seiki Co., Ltd., tension 9.8 N / mm ² , clamp R0.38 mm, folding resistance The test is performed at an angle of 135 ° and a rotation speed of 175 cpm. The test is performed with n = 5 in each of the width direction and the longitudinal direction of the laminated polyester film, and the number of times until the film breaks is measured. The folding strength FE is calculated from the average value N by the following formula (c), and the bendability is evaluated.
(C) FE = logN
FE <4.1: Poor bendability (described as “poor” in the table)
4.1 ≦ FE ≦ 4.5: Good bendability (described as fine in the table)
4.5 <FE: Poor bending property (described as “poor” in the table)
J. et al. Punching property A laminated polyester film is punched into a No. 5 type dumbbell shape described in JIS K-6251 using a test piece punching machine manufactured by Kobunshi Keiki Co., Ltd. The number of sheets M in which the end face is cracked or peeled when punching 10 sheets one by one is counted, and the punchability is evaluated.
0 ≦ M ≦ 2: Punchability A
3 ≦ M ≦ 5: Punchability B
6 ≦ N ≦ 10: Punchability C
A is the best and C is the worst.

K. Intrinsic viscosity IV
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)).

  In the above measurement, when the longitudinal direction and the width direction of the film to be measured are not known, the direction having the maximum refractive index in the film is regarded as the longitudinal direction, and the direction perpendicular to the longitudinal direction is regarded as the width direction. The direction of the maximum refractive index in the film may be obtained by measuring the refractive index in all directions of the film with a refractometer, and the slow axis direction may be determined by a phase difference measuring device (birefringence measuring device) or the like. It may be obtained by deciding.

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

  [Production of PET-A and PET-B] Polymerization was carried out by a conventional method using terephthalic acid and ethylene glycol as raw materials and antimony trioxide as a catalyst to obtain PET-B. The obtained PET-B had a glass transition temperature of 81 ° C., a melting point of 255 ° C., an intrinsic viscosity of 0.68, and a terminal carboxyl group content of 20 eq. / T. Next, PET-B was solid-phase polymerized by a conventional method to obtain PET-A. The obtained PET-A had a glass transition temperature of 82 ° C., a melting point of 255 ° C., an intrinsic viscosity of 0.85, and a terminal carboxyl group content of 11 eq. / T.

  [Production of PEN-A] Transesterification was carried out using dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol as raw materials and manganese acetate as a catalyst. After the transesterification reaction, PEN-A 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 concentration of 25 eq. / T.

  [Production of PET / NA] Using 100 parts by mass of dimethyl 2,6-naphthalenedicarboxylate, 10 parts by mass of dimethyl terephthalate and ethylene glycol as raw materials, a transesterification reaction was carried out using manganese acetate as a catalyst. After completion of the transesterification reaction, copolymer polyester PET / NA was obtained by a conventional method using antimony trioxide as a catalyst. The obtained PET / NA has a glass transition temperature of 120 ° C., a melting point of 255 ° C., an intrinsic viscosity of 0.62, and a terminal carboxyl group concentration of 20 eq. / T.

  [Production of PET / NB] Transesterification was performed using 100 parts by mass of dimethyl 2,6-naphthalenedicarboxylate, 20 parts by mass of dimethyl terephthalate and ethylene glycol as raw materials and using manganese acetate as a catalyst. After completion of the transesterification reaction, a copolyester PET / NB was obtained by a conventional method using antimony trioxide as a catalyst. The obtained PET / NB has a glass transition temperature of 115 ° C., a melting point of 250 ° C., an intrinsic viscosity of 0.62, and a terminal carboxyl group concentration of 20 eq. / T.

  [Production of PET / IA] The transesterification reaction was carried out using 97 parts by mass of dimethyl terephthalate, 3 parts by mass of dimethyl isophthalate and ethylene glycol as raw materials and using manganese acetate as a catalyst. After completion of the transesterification reaction, a copolyester β was obtained by a conventional method using antimony trioxide as a catalyst. The obtained polyester β was solid-phase polymerized by a conventional method to obtain PET / IA. PET / IA has a glass transition temperature of 80 ° C., a melting point of 249 ° C., an intrinsic viscosity of 0.82, and a terminal carboxyl group concentration of 13 eq. / T.

  [Production of PET-C and PET-D] Polymerization was carried out using terephthalic acid and ethylene glycol as raw materials and antimony trioxide as a catalyst. Simultaneously with antimony trioxide, a solution of phosphoric acid and sodium dihydrogen phosphate dihydrate dissolved in ethylene glycol was added. Phosphoric acid was added in an amount corresponding to 2.0 mol / t with respect to PET, and sodium dihydrogen phosphate dihydrate was added in an amount corresponding to 1.7 mol / t with respect to PET. Further, in order to suppress the deactivation of the polymerization catalyst by the phosphorus compound, manganese acetate was added in an amount equivalent to 2.4 mol / t with respect to PET simultaneously with the addition of the phosphorus compound, and the polymerization reaction was advanced to obtain PET-D. . The obtained PET-D had a glass transition temperature of 81 ° C., a melting point of 255 ° C., an intrinsic viscosity of 0.68, and a terminal carboxyl group content of 20 eq. / T. Next, PET-D was solid-phase polymerized by a conventional method to obtain PET-C. The obtained PET-C had a glass transition temperature of 82 ° C., a melting point of 255 ° C., an intrinsic viscosity of 0.85, and a terminal carboxyl group amount of 11 eq. / T.

  [Production of PEN-B] Transesterification was carried out using dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol as raw materials and manganese acetate as a catalyst. After the transesterification reaction, polymerization was carried out using antimony trioxide as a catalyst. Simultaneously with antimony trioxide, a solution of phosphoric acid and sodium dihydrogen phosphate dihydrate dissolved in ethylene glycol was added. Phosphoric acid was added so as to be equivalent to 2.0 mol / t with respect to PET, and sodium dihydrogen phosphate dihydrate was added so as to be equivalent to 1.7 mol / t with respect to PET, and the polymerization reaction was allowed to proceed, so that PEN-B Got. The obtained PEN-B 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 concentration of 25 eq. / T.

Example 1
As a resin constituting the surface layer, 95 parts by mass of PEN-A and 5 parts by mass of PET-A were blended, vacuum dried at 160 ° C. for 2 hours, and then charged into the extruder 1. Further, 100 parts by mass of PET-A as a resin constituting a layer in contact with the surface layer was vacuum-dried at 160 ° C. for 2 hours, and then charged into the extruder 2. Each raw material was melted in an extruder, and the resin charged into the extruder 1 was merged by a merger so as to be both surface layers of the film, and extruded into a casting drum shape to produce a laminated sheet having a three-layer structure. Subsequently, the sheet is preheated with a heated roll group, then stretched 3.3 times in the longitudinal direction (MD direction) at a temperature of 95 ° C., and then cooled with a roll group at a temperature of 25 ° C. to be a uniaxially stretched film. Got. The obtained uniaxially stretched film was stretched 3.7 times in the width direction (TD direction) perpendicular to the longitudinal direction in a heating zone at a temperature of 110 ° C. in the tenter while holding both ends with clips. 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 125 μm. Each characteristic of the obtained film is shown in the table. It was found that the film was excellent in heat resistance, moist heat resistance and processability.

(Examples 2-4, 9-16, 25, 26)
A laminated polyester film in the same manner as in Example 1 except that the mixing ratio of PEN-A and PET-A used for the resin constituting the surface layer, the thickness of the laminated polyester film, and the thickness of each layer were changed as described in the table. Got. Each characteristic of the obtained film is shown in the table. It was found that the film was excellent in heat resistance, moist heat resistance and processability.

(Examples 5 to 8)
A laminated polyester film was obtained in the same manner as in Example 1 except that the mixing ratio of PEN-A and PET-A used for the resin constituting the surface layer and the stretching process of the laminated polyester film were changed as described in the table. . Each characteristic of the obtained film is shown in the table. By increasing the draw ratio, R1 and R2 became more preferable ranges, and a film excellent in heat resistance and moist heat resistance was obtained.

(Examples 17 to 20)
In Example 17, a laminated polyester film was obtained in the same manner as in Example 1, except that the laminated structure of the film was two layers and the thickness of each layer of the laminated polyester film was changed as described in the table. In Examples 18 to 20, a laminated polyester film was obtained in the same manner as in Example 17 except that the resin constituting the A layer was changed as described in the table. Each characteristic of the obtained film is shown in the table. It was found that the film was excellent in heat resistance, moist heat resistance and processability.

(Examples 21 to 24)
A laminated polyester film was obtained in the same manner as in Example 1 except that the thickness of the surface layer and the thickness of the laminated polyester film were changed. Each characteristic of the obtained film is shown in the table. It was found that the film was excellent in heat resistance, moist heat resistance and processability.

(Examples 27 and 28)
A laminated polyester film was obtained in the same manner as in Example 4 except that the raw material used for the B layer was PET / IA and the stretching conditions were changed as described in the table. Each characteristic of the obtained film is shown in the table. It was found that the film was excellent in heat resistance, moist heat resistance and processability.

(Example 29)
A laminated polyester film was obtained in the same manner as in Example 4 except that the raw material used for the B layer was PET-B. Each characteristic of the obtained film is shown in the table. It was found that the film was excellent in heat resistance, moist heat resistance and processability.

(Comparative Examples 1-4, 7-12)
Example except that the mixing ratio of PEN-A and PET-A used for the resin constituting the surface layer, the thickness of the laminated polyester film, the thickness of each layer, and the stretching process of the laminated polyester film were changed as described in the table. 1 to obtain a laminated polyester film. Each characteristic of the obtained laminated polyester film is shown in the table. In Comparative Example 1, since the resin constituting the surface layer is only PEN, orientation is not easily achieved by stretching, and the values of R1 and R2 do not satisfy (i) and (ii), and the heat resistance, moist heat resistance, and workability are poor. In Comparative Example 2, the resin constituting the surface layer was only PEN, so that the stretchability was poor. When high-strength stretching was used, tearing occurred frequently during film formation, and a film could not be obtained.

  In Comparative Examples 3, 4, 7, and 8, since the amount of PET with respect to the entire resin constituting the surface layer is large, the orientation is difficult to be achieved, and the values of R1 and R2 do not satisfy (i) and (ii), and the heat resistance and moist heat resistance are improved. Inferior. In Comparative Example 9, since the area ratio of stretching is low, the values of R1 and R2 do not satisfy (i) and (ii), so that the heat resistance and the moist heat resistance are poor. Moreover, in Comparative Examples 10-13, not only is the film thick and inferior in workability but also inferior in heat resistance and moist heat resistance because orientation cannot be imparted by stretching.

(Comparative Examples 5 and 6)
A laminated polyester film was obtained in the same manner as in Example 1 except that the raw materials used for the resin constituting the surface layer were PET / NA and PET / NB. Each characteristic of the laminated polyester film is shown in the table. Since a copolymer is used, it is difficult to impart orientation by stretching, the values of R1 and R2 do not satisfy (i) and (ii), and the melting point of the resin constituting the surface layer is less than 260 ° C. Therefore, it turned out that it is inferior to heat resistance and heat-and-moisture resistance.

(Comparative Examples 13 and 14)
The extrusion temperature of the resin constituting the surface layer is 300 ° C., the mixing ratio of PEN-A and PET-A used for the resin constituting the surface layer, the thickness of the laminated polyester film, the thickness of each layer, and the stretching process of the laminated polyester film A laminated polyester film was obtained in the same manner as in Example 1 except that it was as described in the table. The extrusion temperature of the resin constituting the surface layer is high, the copolymerization proceeds by transesterification of the resins constituting the surface layer, it is difficult to impart orientation by stretching, and the values of R1 and R2 are (i) (ii) It did not satisfy | fill, and since melting | fusing point of resin which comprises a surface layer was less than 260 degreeC, it turned out that it is inferior to heat resistance and heat-and-moisture resistance.

(Examples 30 to 36)
Example except that the mixing ratio of PEN-A and PET-A used for the resin constituting the surface layer, the thickness of the laminated polyester film, the thickness of each layer, and the stretching process of the laminated polyester film were changed as described in the table. 1 to obtain a laminated polyester film. Each characteristic of the obtained laminated polyester film is shown in the table. Although the thickness of the film was 120 μm or less, it was found that by reducing the ratio of the thickness of the A layer to the B layer, the resin constituting the A layer was easily oriented, and the heat and heat resistance and heat resistance were excellent. On the other hand, although the film thickness was thin, the workability (punchability) was slightly inferior to that of Example 1, but the level was satisfactory.

(Examples 37 and 38)
Using the laminated polyester film of Example 35, paste Torayna (registered trademark) 3000 manufactured by Toray Industries, Inc. on the B layer side with an adhesive layer so that the A layer of Example 35 is the outermost layer. Combined. The configuration was the film / adhesive layer / tolerina of Example 35. The adhesive layer was adjusted with a gravure coater so that the thickness after drying epoxy adhesive chemit TE2301 manufactured by Toray Fine Chemical was 3 μm. The thickness of Toray Industries, Inc.'s Torelina was 100 μm in Example 37 and 15 μm in Example 38. The properties of the obtained film are shown in the table. It was found to be excellent in heat resistance, moist heat resistance and processability.

(Example 39)
Using the film of Example 35, both layers of Torayna (registered trademark) 3000 (thickness 100 μm) manufactured by Toray Industries, Inc. are bonded via an adhesive layer so that layer A of Example 35 is the outermost layer. It was. The configuration was the film of Example 35 / adhesive layer / tolerina / adhesive layer / film of Example 35. The properties of the obtained film are shown in the table. It was found to be excellent in heat resistance, moist heat resistance and processability.

(Example 40)
After uniaxially stretching in the longitudinal direction of the film, the same coating as in Example 1 was applied except that the following coating agent was applied to one surface of the film with a coating thickness of about 8 μm using a bar coat for the purpose of imparting easy slipperiness. Thus, a laminated polyester film was obtained. As a coating agent, water is used as a coating solution, and 100 parts by weight of DIC Corporation Barnock (registered trademark) 310E is used, and Nissan Chemical Industry Co., Ltd. colloidal silica snowtex (registered trademark) ST-50 is used. The concentration was adjusted to 5 parts by weight, and the solid content weight was 5% by weight. The properties of the obtained film are shown in the table. As in Example 1, it was found that heat resistance, heat and humidity resistance, and workability were excellent.

(Example 41)
A laminated polyester film was obtained in the same manner as in Example 1 except that PEN-B and PET-C were used as the resin constituting the surface layer, and PET-C was used as the resin constituting the layer in contact with the surface layer. Each characteristic of the obtained film is shown in the table. It was found that the film was excellent in heat resistance, moist heat resistance and processability. Since PEN-B was used instead of PEN-A and PET-C was used instead of PET-A, it was found that the heat and moisture resistance was excellent.

(Example 42)
A laminated polyester film was obtained in the same manner as in Example 1 except that PEN-A and PET-D were used as the resin constituting the surface layer, and PET-A was used as the resin constituting the layer in contact with the surface layer. Each characteristic of the obtained film is shown in the table. It was found that the film was excellent in heat resistance, moist heat resistance and processability.

(Comparative Example 15)
Example except that the mixing ratio of PEN-A and PET-A used for the resin constituting the surface layer, the thickness of the laminated polyester film, the thickness of each layer, and the stretching process of the laminated polyester film were changed as described in the table. 1 to obtain a laminated polyester film. Each characteristic of the obtained laminated polyester film is shown in the table. Since the area ratio at the time of stretching exceeds 17 times, the molecular chains of the resin constituting the surface layer are regularly arranged, and the number of crystal parts increases, so the values of R1 and R2 do not satisfy (i) (ii) and workability is improved. Inferior.

  According to the present invention, it is possible to provide a polyester film that is excellent in heat resistance, heat and humidity resistance, and processability, and that satisfies long-term use. Since the film obtained by the present invention suppresses deterioration of physical properties even under high temperature and high humidity conditions, a laminated polyester film that can withstand long-term use even when used as an electric insulating member of a motor using a refrigerant composed of HFC Can be provided.

Claims (9)

A laminated polyester film composed of at least two layers that satisfies the following (1) to (3).
(1) 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) 0.2 ≦ R1 ≦ 0.4
(Ii) 1.25 ≦ R2 ≦ 1.50
Here, R1 = r1 / r, R2 = r2 / r
(2) a surface that satisfies (1), when measured at a Fourier transform infrared spectroscopy (FT-IR), and the spectral intensity r3 observed in 1018 cm ^-1, the spectrum intensity observed in 1602 cm ^-1 R3 calculated from r satisfies the following relationship.
(Iii) 1.20 ≦ R3 ≦ 2.00
Where R3 = r3 / r
(3) The melting point of the resin constituting the layer having a surface satisfying (1) and (2) (this layer is referred to as layer A) is 260 ° C. or higher and 280 ° C. or lower. The laminated polyester film according to claim 1 or 2, which satisfies the following (4).
(4) The total thickness T of the film is 120 μm or more and 500 μm or less. The difference between the glass transition temperature (Tg1) ° C. of the resin constituting the A layer and the glass transition temperature (Tg2) ° C. of the resin constituting the layer adjacent to the A layer (this layer is referred to as B layer) is as follows: The laminated polyester film according to claim 1 or 2, satisfying the relationship:
30 ° C ≦ Tg1-Tg2 ≦ 40 ° C The B layer is, when measured by Fourier transform infrared spectroscopy (FT-IR), R4 is less obtained from the spectral intensity r5 observed in spectral intensity r4 and 1372cm ^-1 which is observed 1388Cm ^-1 The laminated polyester film according to any one of claims 1 to 3, which satisfies the above relationship.
(Iv) 0.95 ≦ R4 ≦ 1.05
Here, R4 = r4 / r5 The laminated polyester film according to any one of claims 1 to 4, wherein the surface layers on both sides of the film are composed of A layers and are composed of at least three layers. The laminated polyester film according to any one of claims 1 to 5, wherein the resin constituting the B layer has a melting point of 253 ° C or higher and 258 ° C or lower. The amount of terminal carboxyl groups of the polyester resin constituting the laminated polyester film is 15 eq. The laminated polyester film according to any one of claims 1 to 6, which is / t or less. The laminated polyester film according to any one of claims 1 to 7, which is used as an electric insulating member of a motor. A laminated film comprising the laminated polyester film according to claim 1 and having a surface satisfying (1) and (2) of the laminated polyester film on at least one outermost layer.