CN1089777C - Polyester film for electrical insulation - Google Patents

Abstract

The present invention relates to a polyester film used for electric insulation. The present invention is characterized in that the apparent density of the film is from 1.37 to 0.85 g/cm<3>, and the modulus of elasticity in direct stress is from 2.0 to 4.5 GPa. The prepared film has the advantages of less oligomer content, low cost, high heat resistance, high impact resistance, excellent forming properties, high assembling stability, and good identity; in addition, when the present invention is used for the insulation of a motor, the present invention has effect of reducing leakage current.

Description

Polyester film for electrical insulation

field of invention

This invention relates to polyester films and laminated films for electrical insulation. More specifically, it relates to polyester films and laminated films used for insulation of motors on compressors used in refrigeration devices such as refrigerators and air conditioners, and various electrical insulation. The purpose is to reduce the content of oligomers and improve the quality of assembled devices Stability, visibility of dyed device parts, molding processability, etc., and reduction of leakage.

Background of the invention

In the past, the method of using polyester film with high intrinsic viscosity was adopted to reduce the content of oligomers. In addition, the method of using terminal blocking agent was adopted to improve the hydrolysis resistance of polyester film.

In addition, in order to satisfy the above two characteristics at the same time, although various methods of using heat-resistant films can also be adopted, there are various problems such as increased cost, difficulty in device assembly, and poor stability and molding processability of the assembled device. kind of problem.

Japanese Unexamined Patent Publication No. 9-100363 discloses a heat-resistant, low-dielectric plastic insulating film having holes and a dielectric constant below a specific value. The purpose of the development of this film is to reduce the leakage loss and lower the dielectric constant in the insulating part accompanying the high frequency of the instrument. When it is used as an electrical insulating material, it does not consider whether it is easy to assemble the device with less oligomers. and other issues, so there is no practicality. Also, JP-A-5-194773 discloses a polyester film having a specific apparent density and tensile modulus of elasticity, but does not discuss its use in electrical insulation.

These thin films for electrical insulation have the following problems.

(1) From the perspective of the global environment, it is necessary to use a refrigerant with less environmental pollution and to use an oil medium. In order to achieve these goals, it is desired to reduce the amount of oligomers used.

(2) In the above-mentioned refrigerant device, if the heat-resistant film is used alone, the cost will be high.

(3) When used for motor insulation, etc., molding processability (thermoforming, notch bending), stability after device assembly (sliding, unstable), visibility, etc. are not good.

(4) Leakage increases due to the replacement of refrigerants and oil products.

Solving these problems is an object of the present invention.

Contents of the invention

The invention provides a polyester film for electrical insulation, characterized in that the film has an apparent density of 1.37-0.85 g/cm ³ and a tensile elastic modulus of 2.0-4.5 GPa. In addition, there is provided a polyester film for electrical insulation having the above characteristics and having a dielectric constant of 2.2 to 3.0.

The present invention also provides a laminated film for electrical insulation, characterized in that a film having better heat resistance than the polyester film is laminated on at least one surface of the polyester film.

In addition, the present invention also provides an insulating device in which the electrical insulation is used in an atmosphere of a refrigerant mainly composed of a partially hydrogenated halogenated hydrocarbon and a polar oil. The polyester film and the laminated film for electrical insulation are used for electrical insulation. The present invention also provides a hermetic compressor equipped with a motor in which the above-mentioned insulating device is used to insulate the coil for excitation. Preferred Embodiments of the Invention

The polyester used in the polyester film of the present invention refers to a polymer crystalline thermoplastic resin composition obtained through esterification, and this polyester is obtained by polycondensation of a dicarboxylic acid component and a glycol component .

As the dicarboxylic acid component, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexanedicarboxylic acid, diphenylethanedicarboxylic acid, etc. can be used, and as the glycol component, ethylene glycol and propylene glycol can be used. , 1,4-butanediol, cyclohexanedimethanol, etc. Among them, terephthalic acid and naphthalene-2,6-dicarboxylic acid are preferable as the acid component, and ethylene glycol and propylene glycol are preferable as the glycol component.

The melting point of the polyester is preferably 250° C. or higher from the viewpoint of heat resistance, and preferably 300° C. or lower from the viewpoint of productivity. Examples of such ideal polyesters include polyethylene terephthalate, polyethylene naphthalene-2,6-dicarboxylate, polyethylene terephthalate-1,4-cyclohexanedimethylester, Polydipropyl terephthalate, etc. Considering the balance of their characteristics and cost, among them, polyethylene terephthalate and polyethylene naphthalene-2,6-dicarboxylate are the most ideal. It is also possible to copolymerize and mix other components in these polymers.

The polyester constituting the polyester film of the present invention preferably has an intrinsic viscosity [η] of 0.6 to 1.5 dl/g, more preferably 0.7 to 1.4 dl/g, particularly preferably 0.8 to 1.3 dl/g. If the intrinsic viscosity [η] is less than 0.6 dl/g, the amount of oligomers is too large, and it may not be suitable for use in electrical insulation. In addition, there may be problems in long-term heat resistance. If the intrinsic viscosity [η] exceeds 1.5 dl/g, the moldability may be deteriorated because the viscosity is too high.

In addition, the M/P of the polyester is preferably 1.8 or less, more preferably 1.4 or less, most preferably 1.2 or less, particularly preferably 1 or less, so that the insulation resistance of the polyester at room temperature and high temperature will increase, which is very ideal. . Here, M/P represents the molar ratio of all metal elements (M) and phosphorus elements (P) in the polymer after removing the polymerization catalyst.

The polyester film of the present invention is a biaxially stretched film, so it has good mechanical properties, thermal properties, electrical properties, moldability, and apparent density.

The apparent density of the polyester film for electrical insulation of the present invention needs to be in the range of 1.37-0.85 g/cm ³ , preferably 1.3-0.9 g/cm ³ , more preferably 1.2-0.9 g/cm ³ . When it exceeds 1.37 g/cm ³ , problems such as an increase in oligomer content, difficulty in molding, and increase in leakage current will arise. When the apparent density is reduced, although the reason for the reduction of the oligomer content is not clear, it can be speculated that this is due to the concentration and deflection of the oligomers around the pores formed inside or along the inner wall, which reduces the apparent density. oligomer content. Also, by reducing the apparent density, the amount of polyester used can be reduced when using a film of the same thickness, and the effect of reducing the absolute value of the oligomer content can also be seen. However, even when the apparent density is low, it is not necessarily limited to a reduction in the content of oligomers, and the relationship with Y/D described later is also important. In addition, if it is less than 0.85g/cm ³ , the mechanical strength and impact resistance will be insufficient. For example, when it is installed around the coil for motor excitation (wedge and spacer), it will break after installation. question. The apparent density can be made within this range by controlling the ratio of pores formed inside the membrane.

In addition, the tensile elastic modulus of the polyester film for electrical insulation of this invention must exist in the range of 2.0-4.5 GPa. It is more preferably in the range of 2.5-4.5 GPa, most preferably in the range of 3.0-4.5 GPa. If the tensile elastic modulus is less than 2.0 GPa, the film will not be stiff, and there will be a problem of breaking when it is installed around a coil for motor excitation, for example. If the tensile elastic modulus exceeds 4.5 GPa, the stiffness is too large, so that when it is bent or bent and mounted, its shape retention property deteriorates and handling becomes difficult. To make the tensile modulus of elasticity within this range can be achieved by controlling the ratio of membrane pores and stretching conditions.

In addition, the relationship between the apparent density D (g/cm ³ ) and the tensile elastic modulus Y (GPa) of the polyester film for electrical insulation of the present invention is preferably 2.5<Y/D<4. A large Y/D is related to sufficient orientation, and the heat resistance is improved by reducing the oligomer content due to orientation crystallization. That is, if Y/D is 2.5 or less, the content of oligomers or heat resistance will be problematic. However, if Y/D is 4 or more, the film is likely to be broken when stretched, so that there will be a problem in film-forming performance.

Next, an example of the production method of the present invention will be described.

First, an incompatible polymer or microparticles are added to the aforementioned polyester, which is supplied to an extruder and extruded through a T-die to form a sheet. The sheet is heated to a temperature above the glass transition temperature of the polyester and stretched in the longitudinal direction. Clamp both sides of the film with small clips and tighten it, heat it above the glass transition temperature, stretch it in the direction perpendicular to the longitudinal direction (width direction), and continue heat treatment (according to needs, it can also be used in the width direction and longitudinal direction). upper relaxation) to produce a biaxially stretched polyester film.

The aforementioned incompatible polymers and fine particles are sufficient as long as the apparent density required by the present invention can be obtained. Specific examples of the incompatible polymer include polyethylene, polypropylene, polybutene, polymethylpentene and the like. In addition, these polymers are not limited to homopolymers, but copolymers thereof may be used. Among them, polyolefins with small critical surface tension and low dielectric constant are better, and polypropylene and polymethylpentene are ideal because they can reduce apparent density, have good heat resistance, and reduce leakage current.

These incompatible polymers are present in particulate form in the polyester. In order to control the particle size, a compatibilizer can be added, for example, polyalkylene glycol or its copolymer, more specifically polyethylene glycol and polypropylene glycol can be used. Although it can also be miniaturized by a surfactant, it must be within a range that does not cause deterioration of electrical properties.

As specific examples of microparticles, organic particles and inorganic particles can be used. As specific examples of organic particles, polysiloxane particles, polyimide particles, cross-linked styrene-divinylbenzene copolymer particles, cross-linked Polyester particles, "Teflon" (registered trade name) particles, etc. Examples of the inorganic particles include calcium carbonate, silicon dioxide, barium sulfate, and the like. In the case of fine particles, it is preferable not to use a surfactant or the like.

Next, as the method of adding to polyester, although there is no particular limitation, when using an immiscible polymer, it is better to make a compound with polyester resin in advance, and then supply it to a film-forming extruder. It can also be mixed with polyester resin and supplied to a film-forming extruder. However, in order to avoid the decrease in intrinsic viscosity [η] caused by thermal deterioration of polyester resin, the mixing method used, especially considering the problem of angle of repose, should be determined in the first supply system. For film extruders, it is best to force mixing by mechanical means immediately.

Also, when using fine particles, it is better to add them at the polymerization stage. Specifically, the method of adding to ethylene glycol is preferable. When calcium carbonate particles are added, a phosphorus compound is added, which is ideal for preventing yellowing and foaming.

Although the thickness of the polyester film of the present invention is not particularly limited, in order to take into account the two aspects of insulation performance and workability, the film thickness suitable for motor insulation is preferably within the range of 25-350 μm, preferably 50-250 μm. within range.

The polyester film of the present invention is not necessarily a single-layer film, but preferably has a multi-layer structure consisting of a base film and a surface layer provided on at least one side thereof. The surface layer is provided on both side surfaces of the base film, which is better for suppressing curling of the film. The apparent density of the surface layer is higher than that of the bottom film, which is ideal in terms of mechanical strength, impact resistance, and prevention of breakage during installation (wedges and pads). The film of the multilayer structure constitutes the base film, and the intrinsic viscosity of the polyester resin in the surface layer is preferably 0.6-1.5 dl/g. In addition, both layers are preferably mainly composed of polyethylene terephthalate or polyethylene naphthalate-2,6-dicarboxylate. Secondly, the relationship between the apparent density D (g/cm ³ ) of the film and the tensile elastic modulus Y (GPa) is preferably 2.5<Y/D<4. The reason for this is as described above. In the case of a multilayer film, the thickness of the surface layer is preferably 5 to 50% of the entire film thickness in terms of mechanical strength, impact resistance, and workability during installation. When the multilayer film of the present invention is prepared, it is by melting the polyester resins constituting the base film and the surface layer, converging and extruding before extruding from the mold, and carrying out biaxial stretching after cooling, which is beneficial to prevent the base film and the surface layer from forming at the interface. The stripping at the place is beneficial. The polyester resin constituting the base film is preferably one containing an incompatible polymer or fine particles in the above-mentioned polyester resin, and particularly one containing polyolefins such as polypropylene and polymethylpentene.

The present invention also provides a laminated film for electrical insulation, characterized in that, on at least one side of the above-mentioned polyester film of the present invention, a film having better heat resistance than the polyester film is laminated, in particular, The laminated film has an apparent density of 1.37-0.85 g/cm ³ and a tensile elastic modulus of 2.5-5.0 GPa. By laminating a heat-resistant film, the film can be used in areas requiring high heat resistance. Laminating films with good heat resistance on both sides of the polyester film will improve heat resistance and mechanical properties.

As a combination of a polyester film and a film having good heat resistance laminated on the polyester film, in the case of the same polyester, a polyester having a higher intrinsic viscosity [η] is used for the film having good heat resistance, In the case of different kinds of polyesters, polyesters based on polyethylene terephthalate are combined with polyesters based on polyethylene naphthalate or polyphenylene sulfide, and polyesters based on polyethylene terephthalate are used. A combination of polyester mainly composed of ethylene naphthalate and polyester mainly composed of polyphenylene sulfide or aromatic polyimide is more preferable.

The intrinsic viscosity [η] of the polyester resin portion of these laminated films is preferably 0.6 to 1.5 dl/g.

In addition, the relationship between the apparent density D (g/cm ³ ) and the tensile modulus Y (GPa) of these laminated films is preferably 3.0<Y/D<4.5. The reason for this is also as described above.

The polyester film and laminated film of the present invention can be well used as an insulating device for electrical insulation in an atmosphere of a mixture of a refrigerant mainly composed of a partially hydrogenated halocarbon and a polar oil superior. Especially in the atmosphere of the mixture of refrigerant and polar oil mainly composed of partially hydrogenated halocarbon, it can be well used for the insulation of the excitation coil of the motor in the hermetic compressor.

For this purpose, the dielectric constant of the polyester film for electrical insulation of the present invention is preferably 2.2 to 3.0, more preferably 2.4 to 3.0, most preferably 2.5 to 3.0. In addition, the dielectric constant of the laminated film for electrical insulation of the present invention is preferably 2.4 to 3.0, more preferably 2.6 to 3.0. If the dielectric constant is too large, the leakage current will be large, and the instrument cannot be used safely. If the dielectric constant is too small, mechanical properties cannot be taken into account, so it is not practical.

At present, in order to solve the problem of ozone depletion caused by Flon gas, according to the so-called "Montreal Protocol", people are doing their best to develop Flon substitutes and refrigeration and air-conditioning devices using Flon substitutes. For halogenated halocarbons, refrigerants in which a part of the halogen is replaced by hydrogen, the so-called Flon substitutes. Flon substitute replaces the halogen atom and connects hydrogen. Because of its polarity, the original non-polar mineral oil and alkylbenzene oil are difficult to dissolve and difficult to use. Instead, polyester polyol, polyalkylene glycol, and carbonate should be used. , ether, fluoride and other polar oils can be used in conjunction with it. In these mixture atmospheres, when conventional polyester films are used, there is a particular concern that the capacitance of the insulating device increases due to the increase in the dielectric constant of the polar oil, which in turn increases the leakage current. When the polyester film and laminated film of the present invention are used for an insulating device, since leakage current is reduced, safety and reliability can be improved. Especially when it is used for insulation around the excitation coil of a motor used in a hermetic compressor, it is effective. [Evaluation method of physical properties and effects] (1) Apparent density

Measured with an electromagnetic scale (SD-120L manufactured by Kenseiko Co., Ltd.). (2) Intrinsic viscosity [η]

After drying the sample at 105°C for 20 minutes, weigh 6.8±0.005g in o-chlorophenol, stir at 160°C for 15 minutes to dissolve it. After cooling, the viscosity at 25° C. was measured with an automatic viscometer AVM-10S from Amatlabotec Co., Ltd. (3) Amount of oligomer

R407C (AC 9000, CH ₂ F ₂ : CF ₃ CHF ₂ : CF ₃ CH ₂ F = 23:25:52) was used as the refrigerant, and polyester polyol oil (VG 32) was used as the oil. In a pressure cooker at 150°C and 35kg/ ^cm2 , after 1000 hours of treatment, the amount of oligomers (cyclic trimers) in the oil/refrigerant is obtained by liquid chromatography, and the ratio relative to the sample amount is used as It is judged as follows.

More than 0.6% by weight: X

Below 0.35% by weight: ○

The intermediate quantity: △(4) Impact resistance

Cut a film sample with a thickness of 250 μm into a size of 10cm×20cm, make a circle on one side of 20cm, fix the side of 10cm on a self-adhesive tape to make a cylinder shape, and place the cylinder on a flat plate, Then put another flat plate on top of the cylinder, and when it is crushed under a load of 10kg, judge as follows.

○: The shape has not changed at all

△: Although partially deformed, it is still in shape

×: Leakage current of all squeezed rings (5)

Make the membrane sample as a lining and wedge, install it in the motor, fill it with AC 9000 and VG 32 refrigerant and oil, measure the leakage current, and make the following judgments.

○: The leakage current is below 0.8mA

△: The leakage current is 0.8～1mA

×: Leakage current is above 1mA (6) heat resistance

Expose the sample in an oven at 180°C, take out the sample every 240 hours, and measure the tensile elongation, which is represented by the time required to reach 1/2 of the initial value. The determination of tensile elongation is carried out according to ASTM-D882-61T. (7) Tensile modulus of elasticity

According to the method stipulated in JIS-Z 1702, it is measured under the conditions of 25°C and 65%RH with a "Mostron" type strength testing machine.

Examples and Comparative Examples

Examples and comparative examples are listed below, and further detailed description will be given. Embodiment 1～8, comparative example 2～4

With the calcium acetate of 0.09 weight part as catalyst, with the dimethyl terephthalate of 85 weight parts and the ethylene glycol of 60 weight parts, carry out transesterification reaction by conventional method, add the trimethyl phosphate containing 0.20 weight % then Ethylene glycol solution, then add the ethylene glycol slurry containing calcium carbonate with an average particle size of 1.1 μm, relative to polyethylene terephthalate, the content of calcium carbonate is as shown in Table 1, then, with 0.03 parts by weight of antimony trioxide is used as a catalyst for polycondensation reaction to prepare polyethylene terephthalate with an intrinsic viscosity of 0.68dl/g.

After the polyethylene terephthalate was vacuum-dried at 170°C, it was supplied to an extruder heated to 280°C, extruded through a T-shaped die, and cooled and solidified with a cooling drum at 30°C to obtain an unstretched membrane. Then heat the film to 85-95°C, stretch it 3.3-4.1 times in the longitudinal direction, continue to stretch it 3.2-4.2 times in the transverse direction with a tenter heated to 110°C, heat it at 220°C, and cool it evenly to After winding at room temperature, a film with a thickness of 250 μm was obtained. Comparative example 1

Except not using calcium carbonate and trimethyl phosphonate, polymerization was carried out in the same manner as in Example 1 to obtain polyethylene terephthalate with an intrinsic viscosity of 0.68 dl/g.

The film forming conditions are exactly the same as in Example 1.

Example 9

With the same method as Example 1, only the polyethylene terephthalate with an intrinsic viscosity of 0.51dl/g was obtained, and samples were prepared with the same calcium carbonate addition and film-making conditions. In addition, when polyethylene terephthalate having an intrinsic viscosity of 1.6 dl/g was used, stretching could not be performed at all because the stretching stress was too high.

Example 10, 11

Add 5% by weight and 10% by weight of polymethylpentene in polyethylene terephthalate with an intrinsic viscosity of 0.68, then add 0.5% by weight of compatibilizer polyethylene glycol, then use the same method as in Example 1 Film formation was performed under the same film formation conditions. Example 12

The polymethylpentene in Example 10 was replaced with 5% by weight polypropylene homopolymer to form a film.

Example 13

Using polyethylene naphthalate with an intrinsic viscosity of 0.75 to which 10% by weight of calcium carbonate was added, a sample was produced in the same manner as in Example 1 except that the longitudinal stretching temperature was 100°C.

Example 14

Base resin is with the material identical with embodiment 1, surface layer resin is with the material that does not add calcium carbonate, with different extruders respectively, through T die head, extrude 3 layers of composite sheet, then, with embodiment 1 identical film forming conditions. The total thickness was made 250 μm, and the thicknesses of both surface layers were made 25 μm, respectively.

Example 15

As the polyester resin, polyethylene naphthalate with an intrinsic viscosity of 0.75 was used, and only 10% by weight of calcium carbonate was added to the base resin, and the rest was carried out in the same manner as in Example 14 to form a film.

Example 16

Film formation was performed under the same conditions as in Example 14, except that 3% by weight of calcium carbonate was added as the surface layer resin.

Example 17

As the surface layer resin, polyethylene terephthalate with an intrinsic viscosity of 0.85dl/g is used, and as the base resin, 10% by weight of carbonic acid is added to polyethylene terephthalate with an intrinsic viscosity of 0.68dl/g. As for the calcium material, film formation was carried out under the same conditions as in Example 14.

The compositions and evaluation results of the films of Examples 1 to 17 and Comparative Examples 1 to 4 are summarized in Tables 1 to 3. Since the polyester film of the present invention has little extraction amount of oligomers, there is almost no problem in impact resistance, and it is also excellent in heat resistance, so it is very suitable as an electrical insulating material. In addition, most of them can be safely used in new Flon devices due to their low dielectric constant and low leakage current. In Example 4, there was no problem in terms of performance at all, but since the Y/D was high, it was often broken during stretching, so stable film formation could not be performed. In addition, in Example 6, the tensile strength was close to the lower limit, and the impact property was also slightly problematic. In addition, in Example 9, since the intrinsic viscosity was 0.51, the extraction amount of oligomers was slightly large, and the heat resistance was also slightly inferior. Comparative example 1 has a high apparent density and a large amount of oligomer extraction. Comparative examples 2 and 3 have high apparent density due to insufficient extension. There are problems in performance and heat resistance. In Comparative Example 4, the apparent density was too low, and at the same time, since the tensile elastic modulus was also low, there was also a problem in impact resistance, so it could not be used for motor insulation and the like.

In the following tables, PET refers to polyethylene terephthalate, PEN refers to polyethylene naphthalene-2,6-dicarboxylate, PPS refers to polyphenylene sulfide, and PMP refers to polymethylpentene.

Table 1 membrane composition Intrinsic viscosity of polyester (dl/g) Example 1 PET+CaCO ₃ (10%) 0.68 Example 2 PET+CaCO ₃ (10%) 0.68 Example 3 PET+CaCO ₃ (10%) 0.68 Example 4 PET+CaCO ₃ (10%) 0.68 Example 5 PET+CaCO ₃ (10%) 0.68 Example 6 PET+CaCO ₃ (20%) 0.68 Example 7 PET+CaCO ₃ (5%) 0.68 Example 8 PET+CaCO ₃ (1%) 0.68 Example 9 PET+CaCO ₃ (10%) 0.51 Example 10 PET+PMP (5%) 0.68 Example 11 PET+PMP (10%) 0.68 Example 12 PET+PP(5%) 0.68 Example 13 PEN+CaCO ₃ (10%) 0.75 Example 14 PET/PET+CaCO ₃ (10%)/PET 0.68 Example 15 PEN/PEN+CaCO ₃ (10%)/PEN 0.75 Example 16 PET+CaCO ₃ (3%)/PET+CaCO ₃ (10%)/PET+CaCO ₃ (3%) 0.68 Example 17 PET1/PET2+CaCO ₃ (10%)/PET1 PET1: 0.68, PET2: 0.85 Comparative example 1 PET 0.68 Comparative example 2 PET+CaCO ₃ (10%) 0.68 Comparative example 3 PET+CaCO ₃ (20%) 0.68 Comparative example 4 PET+CaCO ₃ (20%) 0.68

Table 2 Longitudinal stretching temperature (°C) Stretch ratio (vertical × horizontal) Apparent density (g/cm ³ ) Tensile modulus of elasticity (GPa) Y/D Dielectric constant Example 1 90 3.8×3.8 1.03 3.5 3.4 2.6 Example 2 90 3.3×3.2 1.3 2.7 2.1 3.1 Example 3 85 3.7×3.6 0.89 3.4 3.8 2.5 Example 4 85 4.1×4.2 0.88 3.9 4.4 2.3 Example 5 95 3.8×3.8 1.23 3.3 2.7 3 Example 6 90 3.8×3.8 0.86 2.6 2.9 2.3 Example 7 90 3.8×3.8 1.2 3.7 3.1 2.9 Example 8 90 3.8×3.8 1.36 4.4 3.2 3.2 Example 9 90 3.8×3.8 1.05 3.3 3.1 2.6 Example 10 90 3.8×3.8 1.15 3.4 3 2.8 Example 11 90 3.8×3.8 0.98 3.4 3.5 2.6 Example 12 90 3.8×3.8 1.1 3.3 3 2.7 Example 13 100 3.8×3.8 1.1 4.2 3.8 2.6 Example 14 90 3.8×3.8 1.18 3.8 3.2 2.9 Example 15 100 3.8×3.8 1.2 4.4 3.7 2.8 Example 16 90 3.8×3.8 1.15 3.7 3.2 2.8 Example 17 90 3.8×3.8 1.15 3.9 3.4 2.9 Comparative example 1 90 3.8×3.8 1.39 4.5 3.2 3.3 Comparative example 2 100 3.1×3.0 1.38 2.2 1.6 3.3 Comparative example 3 100 3.1×3.1 1.32 1.8 1.4 3.1 Comparative example 4 90 4.1×4.2 0.67 1.9 2.8 2.1

table 3 Oligomer Impact heat resistance leakage current Example 1 ○ ○ ○ ○ Example 2 △ ○ △ x Example 3 ○ ○ ○ ○ Example 4 ○ ○ ○ ○ Example 5 ○ ○ ○ ○ Example 6 ○ △ ○ ○ Example 7 ○ ○ ○ ○ Example 8 ○ ○ ○ x Example 9 △ ○ △ ○ Example 10 ○ ○ ○ ○ Example 11 ○ ○ ○ ○ Example 12 ○ ○ ○ ○ Example 13 ○ ○ ○ ○ Example 14 ○ ○ ○ ○ Example 15 ○ ○ ○ ○ Example 16 ○ ○ ○ ○ Example 17 ○ ○ ○ ○ Comparative example 1 x ○ ○ x Comparative example 2 x △ x x Comparative example 3 x x x x Comparative example 4 ○ x ○ ○ Example 18, 19

Using the same conditions as in Example 11, a polyester film having a thickness of 188 µm was produced. 100 parts (weight) of heat-resistant polyurethane adhesive "Adocoat" 76 P1 manufactured by Toyo Motor Co., Ltd., 8 parts (weight) of curing agent, and 32 parts (weight) of ethyl acetate. The solution is coated on a 25 μm thick polyethylene naphthalate film by gravure coating method to form a 6 μm thick coating film after curing. 1. The condition of line pressure 3kg/cm makes it bonded, as embodiment 18. In addition, a sample obtained by replacing the polyethylene naphthalate film with a polyphenylene sulfide film ("Trelina" manufactured by To V Co., Ltd.) was used as Example 19.

Example 20, 21

A polyethylene naphthalate film having a thickness of 188 μm was prepared under the same conditions as in Example 13. In the same manner as in Examples 18 and 19, a 25 μm thick polyphenylene sulfide film and a 25 μm thick polyimide film ("Capton" manufactured by East Vdupon Co., Ltd.) were bonded together, as Examples 20 and 21. .

Table 4 and Table 5 show the compositions, evaluation results, and the like of the films in Examples 18 to 21.

The laminated film of the present invention is suitable for electrical insulation due to its good oligomer extraction, impact resistance and heat resistance, low dielectric constant and low leakage current.

Table 4 membrane composition Intrinsic viscosity of polyester (dl/g) Example 18 PEN/PET+PMP(10%)PEN PET: 0.68, PEN: 0.85 Example 19 PPS/PET+PMP(10%)PPS 0.68 Example 20 PPS/PEN+CaCO ₃ (10%)PPS 0.75 Example 21 PI/PEN+CaCO ₃ (10%)/PI 0.68

table 5 Apparent density (g/cm ³ ) Tensile elasticity (GPa) Y/D Dielectric constant Oligomer Impact heat resistance leakage current Example 18 1.08 3.7 3.4 2.8 ○ ○ ○ ○ Example 19 1.06 3.6 3.4 2.7 ○ ○ ○ ○ Example 20 1.15 4.3 3.7 2.8 ○ ○ ○ ○ Example 21 1.17 3.8 3.2 2.9 ○ ○ ○ ○

Possibility of industrial use

A polyester film with an apparent density and a tensile elastic modulus in a specific range or a laminated film laminated with a heat-resistant film can be used as a material for electrical insulation, and can be produced with low polymer properties and It is a film that is low in cost, excellent in heat resistance, impact resistance, and moldability, and also has good assembly stability and good visibility.

In addition, the apparent dielectric constant can be made small, and when used in a refrigerant system with a high dielectric constant, the leakage current value that is worried about can be made small.

Claims (26)

1. polyester film that electrical isolation is used, the apparent density that it is characterized in that this film is 1.37～0.85g/cm ³, the modulus of elasticity in direct stress is 2.0～4.5GPa.

2. the polyester film used of the electrical isolation of claim 1, the limiting viscosity that it is characterized in that forming the polyester resin of polyester film is 0.6～1.5dl/g.

3. the polyester film used of the electrical isolation of claim 1 is characterized in that the apparent density D (g/cm of film ³) and the pass of modulus of elasticity in direct stress Y (GPa) be 2.5＜Y/D＜4.

4. the polyester film in the electrical isolation week of claim 1 is characterized in that this polyester film is to comprise basic unit and be provided with the film top layer, that have multilayered structure at least one face of this basic unit.

5. the polyester film used of the electrical isolation of claim 4, the limiting viscosity that it is characterized in that forming the polyester resin of polyester film is 0.6～1.5dl/g.

6. the polyester film used of the electrical isolation of claim 4 is characterized in that the apparent density D (g/cm of film ³) and the pass of modulus of elasticity in direct stress Y (GPa) be 2.5＜Y/D＜4.

7. the polyester film used of the electrical isolation of claim 4 is characterized in that the apparent density on top layer is bigger than the apparent density of basic unit.

8. the polyester film used of the electrical isolation of claim 4, the thickness that it is characterized in that the top layer is 5～50% of film total thickness.

9. the polyester film used of the electrical isolation of claim 4 is characterized in that it is to form the vibrin fusion on basic unit and top layer, before extruding, it is converged and extrudes by mould, cooling after two-way stretch make.

10. the polyester film used of the electrical isolation of claim 4 is characterized in that the vibrin that forms basic unit and top layer is made up of the polymethylpentene or the polyacrylic mixture of polyethylene terephthalate or polyethylene terephthalate and no more than 10% weight.

11. the polyester film that the electrical isolation of claim 4 is used, the vibrin that it is characterized in that forming basic unit and top layer are by poly-naphthalene-2,6-dioctyl phthalate second diester is formed.

12. the polyester film that the electrical isolation of claim 4 is used, the vibrin that it is characterized in that forming basic unit is to contain non-polymkeric substance that mixes or atomic vibrin in this vibrin, described incompatible polymers is the polyolefine that is selected from polypropylene and polymethylpentene, and the described non-micropartical that mixes is a lime carbonate.

13. the polyester film that any one electrical isolation in the claim 1～12 is used is characterized in that specific inductivity is 2.2～3.0.

14. the laminate film that electrical isolation is used is characterized in that, this electrical isolation laminate film is the laminated thermotolerance film better than this polyester film at least one face of any one polyester film in claim 1～12.

15. the laminate film that the electrical isolation of claim 14 is used is characterized in that, this electrical isolation laminate film is the laminated thermotolerance film better than this polyester film on the two sides of polyester film.

16. the laminate film that the electrical isolation of claim 14 is used, it is characterized in that, polyester film is made up of the polymethylpentene or the polyacrylic mixture of polyethylene terephthalate and no more than 10%, and the film of good heat resistance is made up of polyphenylene sulfide or Polyethylene Naphthalate.

17. the laminate film that the electrical isolation of claim 15 is used is characterized in that polyester film is by poly-naphthalene-2,6-dioctyl phthalate second diester is formed, and the film of good heat resistance is made up of polyphenylene sulfide or aromatic polyimide.

18. the laminate film that the electrical isolation of claim 14 is used is characterized in that, the apparent density of laminate film is 1.37～0.85g/cm ³, the modulus of elasticity in direct stress is 2.5～5.0GPa.

19. the laminate film that the electrical isolation of claim 15 is used is characterized in that, the apparent density of laminate film is 1.37～0.85g/cm ³, the modulus of elasticity in direct stress is 2.5～5.0GPa.

20. the laminate film that the electrical isolation of claim 14 is used, the limiting viscosity that it is characterized in that forming the polyester resin of polyester film is 0.6～1.5dl/g.

21. the laminate film that the electrical isolation of claim 14 is used is characterized in that the film apparent density D (g/cm of laminate film ³) and the pass of modulus of elasticity in direct stress Y (GPa) be 3.0＜Y/D＜4.5.

22. the laminate film that the electrical isolation of claim 14 is used is characterized in that specific inductivity is 2.4～3.0.

23. a seal is characterized in that, is the cooling agent of principal constituent and has in the atmosphere of polar oil product that at the halocarbon of partial hydrogenation the polyester film that any one electrical isolation in the claim 1～12 is used is used in the electrical isolation purposes.

24. a seal is characterized in that, is the cooling agent of principal constituent and has in the atmosphere of polar oil product that at the halocarbon of partial hydrogenation the polyester film that the electrical isolation of claim 13 is used is used in the electrical isolation purposes.

25. a seal is characterized in that, is the cooling agent of principal constituent and has in the atmosphere of polar oil product that at the halocarbon of partial hydrogenation the polyester film that the electrical isolation of claim 14 is used is used in the electrical isolation purposes.

26. a seal is characterized in that, is the cooling agent of principal constituent and has in the atmosphere of polar oil product that at the halocarbon of partial hydrogenation the polyester film that any one electrical isolation in the claim 15～22 is used is used in the electrical isolation purposes.