JP2013223985A - Film for electric insulation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise a peeling off preventing effect to water (moisture) after joining that can be joined without using an adhesive in laminating of a polyester film and a PPS film.SOLUTION: A film for electric insulation 1 that is structured by laminating a PPS film B at least on one surface of a polyester film A is formed by applying low temperature plasma processing to a faying surface of the polyester film A and PPS film B respectively, piling up the treated surfaces mutually and conducting thermal bonding without use of the adhesive, and the heat treatment is applied after the thermal bonding, and the thickness of the polyester film A is ≥25 μm, and ≤350 μm, and the thickness of the PPS film B is ≥9 μm and ≤50 μm, and the peel strength of 180-degree is ≥0.2 N/cm in a wet state and ≥1.0 N/cm in a dry state.

Description

  The present invention relates to an electrical insulating film formed by laminating a PPS film B on at least one surface of a polyester film A.

  For example, as a heat-resistant electrical insulation material used for electric motors and hybrid vehicle drive motors, compressor motors, etc. (for commercial, home, and automotive air conditioners), polyethylene terephthalate (excellent in mechanical strength) A laminated film in which a polyester film such as PET) and a biaxially oriented poly-p-phenylene sulfide (PPS) film excellent in heat resistance and hydrolysis resistance are laminated is known.

  For example, Patent Document 1 discloses a laminate in which a PPS film and a PET film are laminated via a polyurethane adhesive. Patent Document 2 discloses that a composite film having a polyester film as a center layer and a PPS film as a center layer is laminated using a coextrusion method.

JP 62-292431 A JP-A-62-255142

  However, as in Patent Document 1 described above, in the case where two films are bonded using an adhesive, the heat resistance and hydrolysis resistance are reduced due to the use of the adhesive, and the compressor motor Thus, when immersed in the refrigerant, the adhesive melts and peels off at the laminated interface, or the refrigerant characteristics are deteriorated. Moreover, in the thing using the coextrusion method like patent document 2, there existed a fault which two types of films did not fully join but peeled easily with moisture (humidity) etc.

  The present invention has been made in view of the above circumstances, and its purpose is to laminate a polyester film and a PPS film, which can be joined without using an adhesive, and prevents peeling after moisture (humidity) after joining. It is in providing the film for electrical insulation excellent in an effect.

  In order to achieve the above-described object, that is, the present inventor has made various tests and studies in order to be able to laminate a polyester film and a PPS film without using an adhesive. As a result, by applying low-temperature plasma treatment to the bonding surfaces of the polyester film and the PPS film to modify the surface, it was believed that heat bonding without an adhesive was impossible according to conventional knowledge It has been found that the film and the PPS film can be thermally bonded. Furthermore, the present invention was accomplished by confirming that the bonding strength (peeling strength) between the polyester film and the PPS film can be significantly increased by performing an appropriate heat treatment on the laminated film after heat bonding. It is.

  That is, the electrical insulating film of the present invention is an electrical insulating film obtained by laminating the PPS film B on at least one surface of the polyester film A, and the bonding surface between the polyester film A and the PPS film B has a low temperature. Applying plasma treatment, without using an adhesive, the treatment surfaces are overlapped and thermally bonded, and heat treatment is performed after the thermal bonding, and the thickness dimension of the polyester film A is 25 μm or more, 350 μm or less, the thickness of the PPS film B is 9 μm or more and 50 μm or less, and the 180 degree peel strength is 0.2 N / cm or more in the wet state and 1.0 N / cm in the dry state. It has the characteristics in the above (invention of Claim 1).

  In the present invention, the bonding surfaces of the polyester film A and the PPS film B are subjected to low-temperature plasma treatment, whereby oxygen atoms are taken into the surfaces of the films. Specifically, COOH groups and An OH group is added, and this is presumed to give direct bonding between the films A and B.

  The low temperature plasma treatment in the present invention means that the substrate to be treated is exposed to a discharge that starts and continues by applying a high voltage of direct current or alternating current between electrodes, for example, corona discharge under atmospheric pressure or glow discharge in vacuum. Refers to the processing performed by At this time, although not particularly limited, processing in a vacuum with a wide selection of processing gas is preferable. Although it does not specifically limit as process gas, He, Ne, Ar, nitrogen, oxygen, a carbon dioxide gas, air, water vapor | steam etc. are used in the state of individual or mixed. Of these, Ar and carbon dioxide are preferable from the viewpoint of discharge initiation efficiency. The treatment pressure is not particularly limited, but a glow discharge treatment in which discharge is sustained in a pressure range of 0.1 Pa to 1330 Pa, so-called low-temperature plasma treatment, is preferable from the viewpoint of treatment efficiency. More preferably, it is in the range of 1 Pa to 266 Pa.

  At this time, in the case where low temperature plasma processing is performed using an internal electrode type plasma processing machine, the processing strength (E value) of the low temperature plasma processing for the polyester film A and the PPS film B is both, A range of 50 W · min / m 2 to 5000 W · min / m 2 is preferable. Thereby, the favorable direct bondability is obtained.

  There is no particular limitation on the lamination method in which the polyester film A and the PPS film B are directly heat-bonded without using an adhesive. For example, a known method such as a method using a hot press, a method using a heating roll, a method using hot air, or a method using ultrasonic waves may be appropriately selected according to the purpose. In this case, it is desirable that the bonding temperature is as low as possible below the melting point of the polyester film A, for example, 180 ° C. to 250 ° C., which can prevent the deterioration of the polyester film and the like. Can be obtained. More preferably, it is in the range of 190 ° C to 230 ° C.

  And after heat joining (laminate), it was possible to increase the peel strength, particularly the peel strength (adhesive strength) in a wet state, by performing a heat treatment (aging treatment) on the laminated film. This heat treatment can be performed at, for example, 210 ° C. to 235 ° C. In the case of 210 ° C., for example, 150 minutes, and in the case of 235 ° C., for example, the treatment can be performed for about 15 minutes. It was. This heat treatment can be performed, for example, using a hot air oven or the like. As for the temperature and time of the heat treatment, the temperature may be increased if the temperature is low, and may be performed only for a short time if the temperature is high. If this heat treatment is insufficient, sufficient peel strength of the laminated film particularly in a wet state cannot be obtained. However, if the heat treatment is performed excessively, the polyester film A is altered (crystallized) and becomes brittle.

  By the way, by performing this heat treatment, the laminated film (particularly the PPS film B) which is colorless (natural color) and transparent is colored (discolored) into a light yellow (brown) while being transparent. It has been confirmed that this discoloration increases as the degree of heat treatment increases (temperature is high, time is long). In other words, by examining the color tone of the obtained film, it is possible to examine how much heat treatment has been performed, and thus how much peel strength (especially in a wet state) it has.

  The polyester film A in the present invention refers to a film obtained by biaxially stretching a linear thermoplastic polymer having an ester bond in the main chain, for example, and a low oligomer type film is particularly desirable. Typical examples include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutadiene terephthalate (PBT), and the like. These films may contain copolymer components, additives for improving properties (such as organic or inorganic fillers), plasticizers, or the like, or may be pure without them.

  As the PPS film B, a biaxially oriented poly-p-phenylene sulfide (PPS) film can be used. Inorganic and organic fillers may be added to the PPS resin as necessary. Copolymerizable sulfide bonds may be copolymerized randomly or in blocks. In the case of copolymerization, the content is preferably less than 30 mol% from the viewpoint of maintaining melting characteristics such as heat resistance, hydrolysis resistance, crystallinity, etc. possessed by the PPS resin.

  The electrical insulating film of the present invention is a laminate having both the excellent mechanical strength of the polyester film A and the excellent heat resistance and hydrolysis resistance of the PPS film B. The thickness of the polyester film A is preferably 25 μm or more and 350 μm or less from the viewpoint of obtaining sufficient mechanical strength as an electrical insulating film.

  The thickness dimension of the PPS film B is desirably 9 μm or more and 50 μm or less. In this case, since the PPS film B is relatively expensive, it is preferable that the PPS film B is thin from the viewpoint of cost. However, if the thickness dimension is less than 9 μm, the PPS film B is easily broken when the surface is damaged. There is a possibility that the film A is exposed. When the thickness dimension exceeds 50 μm, there is a problem that flexibility is impaired and cracking occurs during processing.

  In addition, as thickness dimension of the whole film for electrical insulation, it is desirable to set it as 75 micrometers-450 micrometers, More preferably, they are 100 micrometers-400 micrometers. Moreover, about the thickness dimension (thickness structure) of each film (layer), it can measure (evaluate) easily by observing the cut surface of a laminated film with a microscope.

  The film for electrical insulation of the present invention has a 180 degree peel strength of 0.2 N / cm or more in a wet state and 1.0 N / cm or more in a dry state. Thereby, the adhesiveness at the time of use can be ensured and peeling can be prevented.

  As an application of the film for electrical insulation of the present invention, it can be used as an insulating material for a drive motor and a generator of a hybrid vehicle drive motor and an electric vehicle that require high heat resistance and hydrolysis resistance. Furthermore, it is preferably used for an insulation system used for electrical insulation under a mixed atmosphere of a refrigerant mainly composed of partially hydrogenated carbon halide and polar oil. Particularly preferably, in a hermetic compressor, under an atmosphere of a mixture of refrigerant (specific CFC such as R22, alternative CFC such as R410A, R407C, HFO1234yf, and R32) and polar oil (organic oil such as mineral oil, ester, ether). Used for insulation of excitation coil of motor used in

  Currently, in order to solve the problem of ozone layer destruction by CFCs, development of alternative CFCs based on the so-called Montreal Protocol, development of global warming prevention CFCs based on the Kyoto Protocol, and refrigeration / Air conditioner systems are being developed vigorously. In this case, a so-called alternative chlorofluorocarbon refrigerant in which a part of the halogen is replaced with hydrogen is used for the conventional fully halogenated carbon halide. Alternative fluorocarbons are bonded with hydrogen instead of halogen atoms, and since they have polarity, conventional non-polar mineral oils and alkylbenzene oils are difficult to dissolve and difficult to use. Polyol esters, polyalkylene glycols, carbonates, It is going to be used in combination with polar oils such as ethers and fluorine compounds. When conventional polyester films are used in these mixed atmospheres, there is a concern about an increase in leakage current due to an increase in the capacity of the insulation system, which is considered to be caused by the high dielectric constant of polar oil. When the electrical insulating film of the present invention is used, safety and reliability can be improved by reducing leakage current. This is particularly effective when used for insulation around the excitation coil of a motor used in a hermetic compressor.

  By the way, the electrical insulating film of the present invention can have a three-layer structure of PPS film B / polyester film A / PPS film B (invention of claim 2). Since the PPS film B with high hydrolysis resistance appears on the outer surface (both sides) of the electrical insulation film, it is impregnated with refrigerant and oil such as the above-mentioned compressor motor (for business use, home use, and automotive air conditioner). When used, it is excellent in hydrolysis resistance and can be highly effective in suppressing the generation of oligomers.

  According to the film for electrical insulation of the present invention, when the PPS film B is laminated on at least one side of the polyester film A, it can be joined without using an adhesive, and heat resistance and hydrolysis resistance can be improved, There is an excellent effect that it is excellent in the effect of preventing peeling against moisture (humidity) later.

The figure which shows schematically the cross-sectional structure of the film for electrical insulation of Example 1. A diagram schematically showing the peel strength test

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in Table 4 to be described later, Examples 1 to 5 are films for electrical insulation (laminated films) according to the present invention. The electrical insulating films of Examples 1 to 5 were obtained by directly heat-bonding the PPS film B on both sides or one side of the polyester film A without using an adhesive, for example, at a temperature of 180 ° C. to 250 ° C. It is configured. At this time, the joining surface of the polyester film A and the PPS film B is subjected to low temperature plasma treatment. Furthermore, the heat treatment is performed on the laminated film after heat bonding at a temperature of 210 ° C to 235 ° C, for example.

  And the thickness dimension of the polyester-type film A is 25 micrometers or more and 350 micrometers or less, and the thickness dimension of the PPS film B is 9 micrometers or more and 50 micrometers or less. In addition, the electrical insulating films of Examples 1 to 5 have a 180-degree peel strength of 0.2 N / cm or more in a wet state and 1.0 N / cm or more in a dry state.

  As schematically shown in FIG. 1, the electrical insulating film 1 of Examples 1 to 4 has a three-layer structure of PPS film B / polyester film A / PPS film B. Although not shown, the electrical insulating film of Example 5 has a two-layer structure of PPS film B / polyester film A.

  Specifically, a low oligomer type biaxially stretched PET film (for example, “Lumirror (registered trademark) X10S” manufactured by Toray Industries, Inc.) is employed as the polyester film A (hereinafter referred to as “PET film A”). ). At this time, the thickness dimension of the polyester film A is 75 μm in Example 1, 125 μm in Example 2, 188 μm in Example 3, 250 μm in Example 4, and 188 μm in Example 5.

  As the PPS film B, a biaxially oriented poly-p-polyphenylene sulfide resin film (for example, “Torelina (registered trademark) type 3030” manufactured by Toray Industries, Inc.) having a thickness (single layer) of 16 μm is employed. ing.

  For the bonding surface of PET film A (both surfaces in Examples 1 to 4 and one surface in Example 5), using an internal electrode type plasma processing machine, in a CO2 atmosphere, at a pressure of 0.275 torr, for example, a processing strength of 500 W -Low temperature plasma treatment is performed at min / m2. The bonding surface (one side) of the PPS film B is also subjected to low-temperature plasma processing in advance in a CO 2 atmosphere, for example, at a processing strength of 500 W · min / m 2 using an internal electrode type plasma processing machine.

  The joint surface of the PPS film B that has been subjected to the same low-temperature plasma treatment on the joint surface (one side) is overlapped with the joint surface of the PET film A that has been subjected to the low-temperature plasma treatment in advance. Bonding was performed under the conditions of a speed of 0.5 m / min and a laminate linear pressure of 4 kg / cm. Thereafter, the laminated film obtained by thermal bonding was heat-treated in a circulating hot air oven while changing the heating conditions. By electrically cooling to room temperature, electrical insulating films (laminated films) of Examples 1 to 5 were obtained.

  On the other hand, as shown in Table 3, Comparative Examples 1 and 2 were manufactured using the same manufacturing method as in Examples 1 to 4 above, without using an adhesive on both sides of PET film A having a thickness of 125 μm. It is a laminated film constituted by directly thermally bonding the film B. However, in these, the thickness dimension of the PPS film B is out of the scope of claims, and is 6 μm in the comparative example 1 and 60 μm in the comparative example 2. Further, Comparative Examples 3 and 4 are obtained by bonding a PPS film B having a thickness dimension of 16 μm to both surfaces of a PET film A having a thickness dimension of 75 μm and 250 μm using a heat-resistant polyurethane adhesive. The thickness of each adhesive layer is 7 μm after curing.

Now, in order to verify the suitability of the present invention, various tests described below were performed on the electrical insulating films (laminated films) of Examples 1 to 5 and Comparative Examples 1 to 4 described above.
(1) Relationship between Laminating Temperature and Adhesive Strength Regarding a laminated film having the same thickness configuration (B / A / B = 16/250/16 (μm)) as in Example 4, the laminating (thermal bonding) temperature is 150 ° C. to Various changes were made at 250 ° C., and the adhesiveness, cracking, and warping after thermal bonding were examined. The results are shown in Table 1 below. In the table, the evaluation item is a double circle “◎” for a very good one, a circle “◯” for a good one, a triangle “△” for a normal one, and a “not good” (or an unevaluable one). ".

  From this result, the heat bonding temperature when the PET film A and the PPS film B are directly heat bonded can be as low as possible below the melting point of the PET film A, that is, 180 ° C. to 250 ° C. Thereby, alteration of a polyester-type film etc. can be prevented and a high quality laminated body can be obtained. A range of 190 ° C to 230 ° C is more preferable.

(2) Relationship between heat treatment temperature and time and adhesive force Regarding the laminated film similar to Example 4 (those subjected to thermal bonding), as shown in the following Table 2, at various temperatures and times after thermal bonding Heat treatment was performed. Using a Tensilon tester, the end of the lower PET film A and the upper PPS were used for a sample obtained by cutting a laminated film that had been heat-treated in accordance with JIS C-6481 into a width of 10 mm and a length of 120 mm. The ends of the film B were clamped, and a 180 degree peel strength test (peel strength test) was performed at a tensile speed of 50 mm / min. FIG. 2 schematically shows the state during the test. This peel test was conducted in both a dry state and a wet state. Among them, the wet state test is performed by dropping pure water, for example, with a spoid 2 or the like, onto the tensile interface as shown in the figure.

  The results of the peel strength test are shown in Table 2. However, those with excellent peel strength in the wet state (ordinary or higher) can obtain the same excellent results (all 1.0 N / cm or higher) even in the dry state. Omitted.

  At this time, as evaluation, 2.0 N / cm or more (very good) is a double circle “◎”, 1.0 N / cm or more and less than 2.0 N / cm (good) is a circle “◯”, 0.2 N / cm cm or more and less than 1.0 N / cm (ordinary) is indicated by a triangle “Δ” and less than 0.2 N / cm (impossible) by “×”.

  As is clear from this result, it was possible to increase the peel strength, particularly the peel strength (adhesive strength) in a wet state, by performing heat treatment on the laminated film after the thermal bonding. This heat treatment can be performed at 210 ° C. to 235 ° C., and in the case of 210 ° C., for example, 150 minutes, and in the case of 235 ° C., the desired peel strength can be obtained by, for example, about 15 minutes. .

  As for the temperature and time of the heat treatment, the temperature may be increased if the temperature is low, and may be performed only for a short time if the temperature is high. If the heat treatment is insufficient, sufficient peel strength of the laminated film particularly in a wet state could not be obtained. However, when the temperature of the heat treatment is relatively high, the appearance is deteriorated. Moreover, when heat processing is performed excessively, the quality change (crystallization) of the polyester-type film A will be caused and it will become weak. Therefore, in order to satisfy both peel strength and appearance, it is desirable to perform heat treatment at a relatively low temperature of 210 ° C. to 220 ° C. for a relatively long time.

(3) Color tone Regarding the laminated film similar to that in Example 4 (those subjected to thermal bonding), as shown in the following Table 3, heat treatment was performed at various temperatures and times after thermal bonding to obtain sample films. . The relationship between the color tone of each sample film and the peel strength in the wet state was examined. The peel strength was examined by the same test method as in (2) above. The color tone of the sample film was measured according to JIS K-7105 using an integrating sphere color meter. Here, the tristimulus values X, Y, and Z were measured when the sample film was allowed to transmit the standard light C, which is a light source, and L, a, and b were calculated therefrom. Table 3 shows the results of examining the relationship between the Δb value, which is the difference between the b value after the heat treatment and the b value before the heat treatment, and the peel strength (Wet peel). As for evaluation, double circle “◎” for very good ones, circle “◯” for good ones, triangle “△” for normal ones, “×” for those that cannot (or cannot be evaluated), Is shown.

  In the laminated film not subjected to the heat treatment (Δb value column is “-”), it was colorless (natural color) and relatively high in transparency. It is colored (discolored) to brown. This discoloration increases as the degree of heat treatment increases (temperature is high, time is long), and the b value increases according to the degree of heat treatment (and thus the peel strength in the wet state). In other words, by examining the color tone (Δb value) of the obtained film, it becomes possible to examine how much heat treatment has been performed, and thus how much peel strength (wet state) it has. . According to the knowledge of the present inventors, if the Δb value is 0.5 or more and less than 4.5, good peel strength can be obtained.

(4) Impact resistance and heat resistance For Examples 1 to 5 and Comparative Examples 1 to 4, impact resistance and heat resistance tests were performed.
The impact resistance test (so-called fir test) was measured in accordance with JIS K-6404-6 using a Scott Hazard Wear Tester (manufactured by Toyo Baldwin). The size of the sample is 10 mm wide and 200 mm long, the distance between chucks is 30 mm, the stroke distance is 50 mm, the load is 2.5 kg, the speed is 120 times / min. Asked.

  In the heat resistance (hydrolysis resistance) test, the sample was placed in an oven at 180 ° C., the sample was taken every 240 hours, and the tensile elongation was measured repeatedly. The time required to reach a value of 2 or less was determined. The tensile elongation was measured according to ASTM D882-61T.

  The impact resistance and heat resistance test results for Examples 1 to 5 and Comparative Examples 1 to 4 are shown in Table 3 below. For convenience, the test results are shown as approximate numbers for both the number of times and the time. Further, the column of the thickness component ratio is indicated by a value of (total thickness of PPS film B) / (thickness of PET film A).

  All the films for electrical insulation of Examples 1 to 5 were able to obtain excellent impact resistance and heat resistance. In contrast, Comparative Example 1 in which the thickness of the PPS film B was small was inferior in heat resistance. Moreover, in Comparative Example 2 in which the thickness dimension of the PPS film B was too large, the impact resistance was poor. Comparative Examples 3 and 4 use an adhesive, and the heat resistance of the entire laminate is lowered due to the deterioration of the adhesive. Furthermore, when immersed in a refrigerant, such as a compressor motor, the adhesive may melt and the laminate interface may peel off, or the refrigerant may be altered.

  In the drawings, 1 is an electrical insulating film, A is a polyester film, and B is a PPS film.

Claims (2)

In the film for electrical insulation formed by laminating the PPS film B on at least one side of the polyester film A,
The bonded surfaces of the polyester film A and the PPS film B are subjected to low-temperature plasma treatment, and are heat-bonded by overlapping the treated surfaces without using an adhesive, and heat-treated after the heat-bonding. And
The thickness dimension of the polyester film A is 25 μm or more and 350 μm or less, the thickness dimension of the PPS film B is 9 μm or more and 50 μm or less, and
180 degree peel strength is 0.2 N / cm or more in a wet state, and 1.0 N / cm or more in a dry state.   The film for electrical insulation according to claim 1, wherein the film has a three-layer structure of PPS film B / polyester film A / PPS film B.

Images