Insulation sheet and motor

Abstract

To provide an insulating sheet that has relatively high tracking resistance and sufficient heat resistance.SOLUTION: Provided is an insulating sheet comprising two outer layers disposed so as to oppose each other, two adhesive layers disposed so as to oppose each other between the two outer layers, and a base material layer disposed between the two adhesive layers. The two outer layers are both aromatic polyamide sheets. The base material layer is a polyethylene terephthalate resin film. The content percentage of an oligomer component contained in the polyethylene terephthalate resin film is less than 0.8 mass%.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an insulating sheet that is, for example, a component of a motor, and a motor including the insulating sheet. [Background technology]

[0002] Conventionally, an insulating sheet has been known which includes a base layer, two outer layers arranged to face one side and the other side of the base layer, and two adhesive layers respectively arranged between one and the other outer layer and the base layer.

[0003] Known examples of this type of insulating sheet include an insulating sheet for motors that is used while immersed in cutting oil. For example, a known insulating sheet for motors of this type includes an insulating sheet in which two outer layers and a base layer are each made of a polyethylene naphthalate resin film, and five layers are laminated with adhesive layers disposed between the base layers and the outer layers (for example, Patent Document 1).

[0004] The insulating sheet described in Patent Document 1 has the above-mentioned configuration and therefore has relatively high tracking resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-165806 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the insulating sheet described in Patent Document 1 does not necessarily have sufficient heat resistance. Therefore, there is a demand for an insulating sheet that has relatively high tracking resistance and sufficient heat resistance.

[0007] In view of the above problems and demands, an object of the present invention is to provide an insulating sheet having relatively high tracking resistance and sufficient heat resistance. [Means for solving the problem]

[0008] In order to solve the above problems, the insulating sheet according to the present invention comprises: The present invention provides a method for manufacturing a heat-resistant sheet, comprising: two outer layers arranged to face each other; two adhesive layers arranged between the two outer layers to face each other; and a base material layer arranged between the two adhesive layers; The two outer layers are both aromatic polyamide papers; the base layer is a polyethylene terephthalate resin film, The content of oligomer components contained in the polyethylene terephthalate resin film is less than 0.8% by mass.

[0009] A motor according to the present invention includes the insulating sheet described above. Effect of the Invention

[0010] The insulating sheet according to the present invention has a relatively high tracking resistance and also has sufficient heat resistance. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view of an insulating sheet according to this embodiment cut in the thickness direction. [Diagram 2] FIG. 2 is a perspective view of the stator of the oil-cooled drive motor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of an insulating sheet according to the present invention will be described with reference to the drawings.

[0013] As shown in Figure 1, the insulating sheet 10 of this embodiment comprises two outer layers 13 arranged opposite each other, two adhesive layers 12 arranged opposite each other between the two outer layers 13, and a base material layer 11 arranged between the two adhesive layers 12. In other words, the insulating sheet 10 of this embodiment comprises one base material layer 11, two adhesive layers 12 arranged to sandwich the base material layer 11 in the thickness direction, and two outer layers 13 arranged to sandwich the two adhesive layers 12 in the thickness direction. In this embodiment, the base material layer 11 is in direct contact with one of the adhesive layers 12, and the base material layer 11 is in direct contact with the other adhesive layer 12. In addition, on one side of the base material layer 11, the adhesive layer 12 is in direct contact with the outer layer 13, and also on the other side, the adhesive layer 12 is in direct contact with the outer layer 13. Each outer layer 13 may be the outermost layer of the insulating sheet 10 .

[0014] The thickness of the insulating sheet 10 is, for example, 100 μm or more and 400 μm or less. The thickness of the insulating sheet 10 may be 120 μm or more, or 170 μm or more. The thickness of the insulating sheet 10 may be 350 μm or less, or 300 μm or less. The thickness of the insulating sheet 10 may be 190 μm or more and 270 μm or less. The thickness of the insulating sheet 10 is preferably 210 μm or more, and more preferably 220 μm or more, in that the tracking resistance can be further improved.

[0015] The thickness of the base layer 11 may be, for example, 25 μm or more and 200 μm or less, and is preferably 50 μm or more and 150 μm or less.

[0016] The thickness of the adhesive layer 12 (per layer) may be, for example, 1 μm or more and 80 μm or less. The thickness of the adhesive layer 12 is preferably 5 μm or more and 50 μm or less, and more preferably 25 μm or more and 40 μm or less. Of the two adhesive layers 12, it is preferable that there is a small difference in thickness between one adhesive layer 12 and the other adhesive layer 12. For example, the thickness of one adhesive layer 12 may be 0.9 to 1.1 times the thickness of the other adhesive layer 12.

[0017] The thickness of the outer layer 13 (per layer) may be, for example, 20 μm or more and 100 μm or less. The thickness of the outer layer 13 is preferably 30 μm or more and 70 μm or less, and more preferably 35 μm or more and 55 μm or less. Of the two outer layers 13, it is preferable that there is a small difference in thickness between one outer layer 13 and the other outer layer 13. For example, the thickness of one outer layer 13 may be 0.9 times or more and 1.1 times or less the thickness of the other outer layer 13.

[0018] The thickness of each layer mentioned above refers to the average thickness. The thickness of each layer is determined by averaging the thicknesses of at least five randomly selected locations. The same applies below. The thickness of each layer can be measured, for example, by observing the side or cross section of the insulating sheet 10 with a digital microscope.

[0019] The ratio of the thickness of the base layer 11 to the total thickness of the insulating sheet 10 may be 0.20 or more, and preferably 0.30 or more. The thickness ratio may be 0.50 or less.

[0020] The ratio of the total thickness of the adhesive layers 12 (thickness of two layers) to the total thickness of the insulating sheet 10 may be 0.10 or more, 0.15 or more, 0.19 or more, or 0.20 or more. Moreover, such a ratio may be 0.40 or less, or 0.30 or less.

[0021] The ratio of the total thickness of the outer layers 13 (the thickness of the two layers) to the total thickness of the insulating sheet 10 is preferably greater than 0.20, although this ratio may be 0.50 or less.

[0022] The ratio of the combined thickness of one adhesive layer 12 and one outer layer 13 to the total thickness of the insulating sheet 10 may be 0.30 or more, or may be 0.35 or less.

[0023] The ratio of the combined thickness of the base layer 11 and the two outer layers 13 to the total thickness of the insulating sheet 10 may be 0.70 or more, and may be less than 0.80, and is preferably less than 0.79.

[0024] The ratio of the total thickness of one adhesive layer 12 and one outer layer 13 (on one side of the base layer 11) to the thickness of the base layer 11 may be 0.50 or more, or may be 1.50 or less.

[0025] The ratio of the thickness of each of the adhesive layers 12 to the thickness of each of the outer layers 13 may be 0.20 or more, 0.35 or more, 0.40 or more, or 0.50 or more, or 1.00 or less, or 0.80 or less. The ratio of the thickness of the adhesive layer 12 to the thickness of the outer layer 13 is preferably 0.35 or more, and more preferably greater than 0.40. When such a ratio is 0.35 or more, the tracking resistance of the insulating sheet 10 can be improved.

[0026] It is preferable that the above-mentioned numerical range regarding the ratio of each thickness of the adhesive layer 12 to each thickness of the outer layer 13 is satisfied on at least one of the one surface side or the other surface side of the base layer 11. It is more preferable that the ratio of each thickness of the adhesive layer 12 to each thickness of the outer layer 13 is within the above-mentioned numerical range on both the one surface side and the other surface side of the base layer 11.

[0027] The base layer 11 is a polyethylene terephthalate resin film. The content of oligomer components in the polyethylene terephthalate resin film of the base layer 11 is less than 0.8 mass % (including 0 mass %). Therefore, the insulating sheet 10 of the present embodiment can have better heat resistance than when the polyethylene terephthalate resin film of the base layer 11 contains 0.8 mass % or more of oligomer components.

[0028] The content of the oligomer component is measured as follows. Specifically, a film sample having a roughly square shape with a side length of about 5 cm is washed with methanol, and then the film sample is dried in a hot air oven at 160°C for 1 hour to measure the initial mass (M1 [g]). Then, the film sample is subjected to extraction treatment with boiling xylene (about 400 mL) for 48 hours using a Soxhlet extractor or the like. Then, the mass (M2 [g]) of the film sample after the extraction treatment is measured. Then, the content of the oligomer component is calculated by calculating the ratio [(M1-M2) / M1] of the mass reduction (M1-M2) to the initial mass (M1). In order to accurately measure the mass loss, the xylene used in the extraction process is thoroughly removed, and then the mass (M2 [g]) of the film sample after the extraction process is measured. Preferably, the film sample after the extraction process is washed with water, and then the xylene adhering to the surface is lightly wiped off, and then the film sample is dried in a hot air oven at 160°C for 8 hours, and then cooled in a desiccator, and the mass (M2 [g]) of the film sample after the extraction process is measured.

[0029] Examples of the polyethylene terephthalate resin film include films formed from a polymer of a dicarboxylic acid such as terephthalic acid or 2,6-naphthalenedicarboxylic acid and a diol such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, or 1,4-cyclohexanedimethanol.

[0030] The polyethylene terephthalate resin constituting the base layer 11 may be of one type alone or of two or more types. The base layer 11 may be a single layer as in the present embodiment, or may be a laminate film in which a plurality of polyethylene terephthalate resin films are laminated. When the base layer 11 is a laminate film, at least one layer constituting the laminate film may be a polyethylene terephthalate resin film having an oligomer component content of less than 0.8% by mass.

[0031] As the base material layer 11, for example, a commercially available product such as "Lumirror X10S Type" (manufactured by Toray Industries, Inc.) or "D Melinex 238" (manufactured by DuPont) can be used.

[0032] The adhesive layer 12 constituting the insulating sheet 10 of this embodiment contains, for example, a polymer component. Examples of the polymer component include an acrylic polymer, a urethane polymer, and an epoxy resin.

[0033] The acrylic polymer is preferably a polymer formed by polymerization of at least an alkyl (meth)acrylate ester. The acrylic polymer may be, for example, a polymer of an alkyl (meth)acrylate ester, or a copolymer of an alkyl (meth)acrylate ester and another polymerizable monomer. In this specification, the term "(meth)acrylic" includes both "acrylic" and "methacrylic".

[0034] Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate [e.g., normal propyl (meth)acrylate, isopropyl (meth)acrylate, etc.], butyl (meth)acrylate [e.g., normal butyl (meth)acrylate, isobutyl (meth)acrylate, secondary butyl (meth)acrylate, tertiary butyl (meth)acrylate, etc.], 2-ethylhexyl (meth)acrylate, normal octyl (meth)acrylate, normal nonyl (meth)acrylate, and isononyl (meth)acrylate.

[0035] Examples of other polymerizable monomers include ethylene, styrene, vinyl chloride, acrylic acid, butadiene, and acrylonitrile.

[0036] Examples of the copolymer include ethylene-(meth)acrylic acid alkyl ester copolymer, ethylene-(meth)acrylic acid alkyl ester-acrylic acid copolymer, styrene-(meth)acrylic acid alkyl ester-acrylic acid copolymer, (meth)acrylic acid alkyl ester-vinyl chloride copolymer, (meth)acrylic acid alkyl ester-acrylic acid copolymer, (meth)acrylic acid alkyl ester-vinyl chloride copolymer, styrene-(meth)acrylic acid alkyl ester-butadiene copolymer, (meth)acrylic acid alkyl ester-acrylonitrile copolymer, and the like.

[0037] The adhesive layer 12 preferably contains a polymer compound in which polybutyl acrylate (PAB) is crosslinked with polyisocyanate. It is more preferable that the adhesive layer 12 contains a crosslinked reaction product of butyl acrylate (PAB), terpene phenol, and polyisocyanate. When the adhesive layer 12 contains such a crosslinked reaction product, the adhesive layer 12 has better adhesion to the outer layer 13 (aromatic polyamide paper) when the insulating sheet 10 is immersed in water-containing oil at a high temperature of 120 to 180° C. The amount of terpene phenol added is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of butyl acrylate (PAB). In addition, even when an alkylphenol is used instead of the terpene phenol, the adhesion can be improved as described above. The amount of the alkylphenol added is preferably 1 part by mass or more and 30 parts by mass or less relative to 100 parts by mass of butyl acrylate (PAB). Polybutyl acrylate (PAB) may have a carboxy group in part of the molecule.

[0038] The above acrylic polymers may be used alone or in combination of two or more.

[0039] The urethane polymer that may be contained in the adhesive layer 12 may be, for example, a urethane reaction product of a polyol component having multiple hydroxyl groups in the molecule and a polyisocyanate component having multiple isocyanate groups in the molecule. In this specification, the term "urethane polymer" does not include "polyurethane-urea resin" and is a polymer that does not substantially contain urea bonds.

[0040] The polyol component may be any of the conventionally known polyol components, such as polyester polyols, polyether polyols, and polycarbonate polyols.

[0041] Examples of the polyester polyols include polyethylene adipate diol, polybutylene adipate diol, polyhexamethylene adipate diol, polyneopentyl adipate diol, polyethylene / butylene adipate diol, polyneopentyl / hexyl adipate diol, poly-3-methylpentane adipate diol, polybutylene isophthalate diol, polycaprolactone diol, and poly-3-methylvalerolactone diol.

[0042] Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and random / block copolymers thereof.

[0043] Examples of the polycarbonate polyol include polytetramethylene carbonate diol, polypentamethylene carbonate diol, polyneopentyl carbonate diol, polyhexamethylene carbonate diol, poly(1,4-cyclohexanedimethylene carbonate) diol, and random / block copolymers thereof.

[0044] Other examples of the polyol component include dimer diol and its hydrogenated product, polybutadiene polyol and its hydrogenated product, polyisoprene polyol and its hydrogenated product, acrylic polyol, epoxy polyol, polyether ester polyol, siloxane-modified polyol, α,ω-polymethyl methacrylate diol, and α,ω-polybutyl methacrylate diol.

[0045] The polyisocyanate component may be any of the conventionally known polyisocyanate components.

[0046] Examples of the polyisocyanate component include aromatic diisocyanates such as toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-isopropyl-1,3-phenylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 4-butoxy-1,3-phenylene diisocyanate, 2,4-diisocyanate diphenyl ether, 4,4'-methylenebis(phenylene isocyanate) (MDI), crude or polymeric MDI, jurylene diisocyanate, xylylene diisocyanate (XDI), 1,5-naphthalene diisocyanate, benzidine diisocyanate, o-nitrobenzidine diisocyanate, and 4,4'-diisocyanate dibenzyl. Examples of the polyisocyanate component include aliphatic diisocyanates such as methylene diisocyanate and 1,4-tetramethylene diisocyanate. Examples of the polyisocyanate component include alicyclic isocyanates such as 1,4-cyclohexylene diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,5-tetrahydronaphthalene diisocyanate, isophorone diisocyanate, and hydrogenated XDI. Examples of the polyisocyanate component include polyurethane prepolymers obtained by reacting these diisocyanates with low molecular weight polyols so that the terminals are isocyanate groups.

[0047] The above urethane polymer can be produced by a conventionally known general production method. For example, the urethane polymer can be produced by subjecting the above-mentioned polyol component and the above-mentioned polyisocyanate component to a urethane reaction by a one-shot method or a multi-stage method. The one-shot method and the multi-stage method can be carried out at a temperature usually in the range of 20°C or higher and 150°C or lower, preferably 60°C or higher and 110°C or lower. To form the adhesive layer 12, a commercially available product containing a urethane polymer, such as "Tyforce SA-30-L" manufactured by DIC Corporation, can be used.

[0048] Examples of epoxy resins that may be contained in the adhesive layer 12 include phenol novolac type epoxy resins, triphenylmethane type epoxy resins, cresol novolac type epoxy resins, bisphenol A type epoxy resins, modified bisphenol A type epoxy resins, bisphenol F type epoxy resins, modified bisphenol F type epoxy resins, bisphenol AD ​​type epoxy resins, modified bisphenol AD ​​type epoxy resins, dicyclopentadiene type epoxy resins, and biphenyl type epoxy resins. The epoxy resin is preferably the above-mentioned phenol novolac type epoxy resin. The epoxy equivalent of the phenol novolac type epoxy resin is preferably 150 g / eq or more, more preferably 160 g / eq or more, and more preferably 170 g / eq or more. The epoxy equivalent of the phenol novolac type epoxy resin is preferably 200 g / eq or less, more preferably 190 g / eq or less, and more preferably 180 g / eq or less. The epoxy equivalent can be determined in accordance with JIS K 7236.

[0049] When the adhesive layer 12 contains an epoxy resin, it is preferable that the adhesive layer 12 further contains a curing agent for the epoxy resin. Examples of such curing agents include phenol-based curing agents, amine-based curing agents, and acid anhydride-based curing agents, with the phenol-based curing agents being preferred. The phenol-based curing agent, the amine-based curing agent, and the acid anhydride-based curing agent may be used alone or in combination of two or more kinds.

[0050] Examples of the phenol-based curing agent include phenol novolac resin, aralkyl-type phenol resin, dicyclopentadiene-modified phenol resin, naphthalene-type phenol resin, bisphenol-type phenol resin, and triphenylmethane-type phenol resin. Examples of the amine-based curing agent include diaminodiphenylsulfone, dicyandiamide, diaminophenylmethane, and triethylenetetramine. Examples of the acid anhydride curing agent include phthalic anhydride, trimellitic anhydride, and maleic anhydride.

[0051] When the adhesive layer 12 contains an epoxy resin, the adhesive layer 12 may contain the above-mentioned acrylic polymer in addition to the epoxy resin. Moreover, it is preferable that the adhesive layer 12 contains the above-mentioned phenol novolac type epoxy resin as the epoxy resin, and further contains the above-mentioned polybutyl acrylate (PAB) as the acrylic polymer. In this case, the adhesive layer 12 may contain 100 parts by mass or more, 150 parts by mass or more, or 200 parts by mass or more of the above acrylic polymer when the amount of the epoxy resin is 100 parts by mass. Furthermore, the adhesive layer 12 may contain 300 parts by mass or less, or 250 parts by mass or less of the acrylic polymer, when the amount of the epoxy resin is taken as 100 parts by mass.

[0052] In the insulating sheet 10 according to the present embodiment, when the adhesive layer 12 is subjected to a thermogravimetric differential thermal analysis (TG-DTA), the temperature at which a mass loss of 5% by mass is observed is preferably 350° C. or lower, and more preferably 300° C. or lower. This makes it easier for organic substances such as resins contained in the adhesive layer 12 to be thermally decomposed when the insulating sheet 10 is exposed to a high-temperature atmosphere. Therefore, the thermal decomposition of the organic matter contained in the adhesive layer 12 is more likely to proceed before the thermal decomposition of the organic matter proceeds on the outer surface of the outer layer 13. When the insulating sheet 10 is used and the temperature becomes high, the heat at the high temperature is consumed for the thermal decomposition of the organic matter in the adhesive layer 12. The thermal decomposition of the organic matter contained in the outer layer 13 can be suppressed on the outer surface of the outer layer 13 to the extent that the heat is consumed for such thermal decomposition. The generation of a conductive path formed by free carbon on the outer surface of the outer layer 13 is suppressed to the extent that the thermal decomposition of the organic matter contained in the outer layer 13 is suppressed. In addition, since the organic matter contained in the adhesive layer 12 is more susceptible to thermal decomposition, the organic matter does not remain in the state of free carbon even after thermal decomposition, but can be fully thermally decomposed into gases such as carbon dioxide. Since the reaction that produces gas is often an endothermic reaction, the endothermic reaction also suppresses the thermal decomposition of the organic matter contained in the outer layer 13 on the outer surface of the outer layer 13. This suppresses the formation of a conductive path due to free carbon on the outer surface of the outer layer 13. As described above, the insulating sheet 10 of this embodiment can exhibit better tracking resistance even when the outer layer 13 is made of fully aromatic polyamide paper, because the temperature at which a 5% mass loss is observed in the adhesive layer 12 is 350°C or lower. The temperature at which a mass loss of 5% by mass is observed in the adhesive layer 12 can be determined by the method described in the Examples.

[0053] The adhesive layer 12 may contain additives such as a tackifier in addition to the above-mentioned polymer components. The content of components other than the above-mentioned resin components in the adhesive layer 12 is preferably less than 5% by mass, and more preferably less than 0.8% by mass.

[0054] The weight of the adhesive layer 12 is, for example, 10 g / m 2 More than 20g / m 2 It may be the following.

[0055] The adhesive layer 12 may be formed of, for example, a commercially available polymer. The adhesive layer 12 may be formed of, for example, a polymer composition in which a plurality of types of polymers are crosslinked.

[0056] The two outer layers 13 constituting the insulating sheet 10 of this embodiment are both made of aromatic polyamide paper. Because the outer layers 13 are made of aromatic polyamide paper, the insulating sheet 10 of this embodiment can have good heat resistance.

[0057] Examples of aromatic polyamide paper that can be used include fully aromatic polyamide paper made from at least one of short fibers made of fully aromatic polyamide and synthetic pulp made of fully aromatic polyamide, a sheet containing at least one of short fibers made of aromatic polyamide or synthetic pulp made of aromatic polyamide and mica powder (mica flakes), and sheets obtained by subjecting these papers or sheets to high-temperature and high-pressure calendar processing. As the aromatic polyamide paper, fully aromatic polyamide paper is preferred in that it has better heat resistance. Examples of the wholly aromatic polyamide constituting the above-mentioned short fibers or the above-mentioned synthetic pulp include a condensation polymer of m-phenylenediamine and isophthalic acid, and a condensation polymer of p-phenylenediamine and terephthalic acid.

[0058] The outer layer 13 may be laminated or surface-treated. The surface treatment may be performed using a coating agent containing a polyamide resin (e.g., a methoxymethylated polyamide resin in which an amide group is methoxymethylated). For example, a commercially available product (product name "Nomex" manufactured by DuPont, etc.) may be used as the outer layer 13.

[0059] The insulating sheet 10 of this embodiment is, for example, 1×10 13 The insulating sheet 10 has a volume resistivity of 1×10 14 It is preferable that the resistivity is Ω·cm or more.

[0060] The insulating sheet 10 of the present embodiment has relatively high tracking resistance and sufficient heat resistance. By including the acrylic polymer described above, the adhesive layer 12 can have better tracking resistance and good oil resistance. In addition, the temperature at which the adhesive layer 12 loses 5% by mass is preferably 350° C. or less, and more preferably 300° C. or less. This can improve tracking resistance. In addition, good oil resistance can be obtained.

[0061] Next, a method for producing the insulating sheet 10 of this embodiment will be described.

[0062] In the method for producing the insulating sheet 10 of this embodiment, for example, a mixture containing each component constituting the adhesive layer 12 and (if necessary) an organic solvent is prepared, the mixture is applied to both sides of the base layer 11, and the organic solvent contained in the applied mixture is volatilized (if necessary) to produce two adhesive layers 12. Furthermore, the insulating sheet 10 can be produced by bonding the outer layer 13 to each adhesive layer 12. As the coating device, for example, a roll coater can be used.

[0063] As the organic solvent, for example, ethyl acetate, methyl ethyl ketone (MEK), toluene, etc. can be used.

[0064] A general coating method such as die coating or reverse coating can be used when applying the mixture containing an organic solvent to the outer layer 13. The temperature during application is, for example, room temperature (15 to 25° C.).

[0065] The insulating sheet 10 manufactured as described above is used, for example, as a component of a motor. The insulating sheet 10 may be used, for example, as an insulating sheet for a drive motor of an automobile.

[0066] Examples of automobiles include hybrid electric vehicles (HEVs) and electric vehicles (EVs). Examples of drive motors include HV motors, motor generators, alternators, 4WD motors, oil pump motors, EPS motors, compressor motors, and in-wheel motors.

[0067] An example of a drive motor for an automobile is an oil-cooled drive motor, which is a drive motor that is cooled by cooling oil such as ATF.

[0068] For example, the insulating sheet 10 may be used in a heated state. If the insulating sheet 10 is used in a heated state for a long period of time, oxidation degradation may occur. For example, the insulating sheet 10 may be used while immersed in oil. Examples of the oil include automatic transmission oil (ATF). When the insulating sheet 10 is used while immersed in oil, the moisture contained in the oil such as ATF may cause a hydrolysis reaction. In contrast, the insulating sheet of the present embodiment has good tracking resistance and good heat resistance, and therefore can suppress the above-mentioned oxidative deterioration. In some cases, the insulating sheet of the present embodiment also has good oil resistance and can suppress the above-mentioned hydrolysis reaction.

[0069] Next, an embodiment of a motor according to the present invention will be described with reference to the drawings.

[0070] The motor of this embodiment includes the above-mentioned insulating sheet 10. The insulating sheet 10 is, for example, an insulating sheet for a motor.

[0071] For example, the motor is a drive motor mounted on a hybrid vehicle or an electric vehicle, etc. Such a drive motor is, for example, an oil-cooled drive motor.

[0072] An oil-cooled drive motor for an automobile includes a rotor with a permanent magnet and a stator 20 that generates a force to rotate the rotor. As shown in Fig. 2, the stator 20 has a coil 21 and a stator core 22. The stator 20 rotates the rotor by causing the coil 21 to generate a magnetic field.

[0073] In the oil-cooled drive motor as described above, the coil 21 is formed, for example, by a plurality of segment conductors connected to each other. In the oil-cooled drive motor as described above, a core such as the stator core 22 or the rotor core has a plurality of slot grooves, and each of the coils 21 is housed in each of the plurality of slot grooves. In addition, in the oil-cooled drive motor as described above, a motor insulating sheet is used to ensure insulation between the coil 21 and the inner wall surface of the slot groove. The motor insulating sheet and the coil 21 are housed in the slot groove. More specifically, the motor insulating sheet is housed in the slot groove while being wrapped around the coil 21. The coil 21 wound around the motor insulating sheet is fixed in the slot groove via insulating resin (for example, epoxy varnish) impregnated in the slot groove.

[0074] The insulating sheet and motor of this embodiment are as exemplified above, but the present invention is not limited to the insulating sheet or motor exemplified above. In other words, various configurations used in general insulating sheets or motors can be adopted as long as they do not impair the effects of the present invention.

[0075] The matters disclosed in this specification include the following. (1) The present invention provides a method for manufacturing a heat-resistant sheet, comprising: two outer layers arranged to face each other; two adhesive layers arranged between the two outer layers to face each other; and a base material layer arranged between the two adhesive layers; The two outer layers are both aromatic polyamide papers; the base layer is a polyethylene terephthalate resin film, The insulating sheet, wherein the content of an oligomer component contained in the polyethylene terephthalate resin film is less than 0.8% by mass. (2) The insulating sheet according to (1) above, wherein when the adhesive layer is subjected to thermogravimetric differential thermal analysis (TG-DTA), the temperature at which a mass loss of 5% by mass is observed is 350° C. or lower. (3) The insulating sheet according to (1) or (2) above, wherein a ratio of a total thickness of the adhesive layers to a total thickness of the insulating sheet is 0.10 or more and 0.40 or less. (4) An insulating sheet according to any one of (1) to (3) above, wherein on one surface side of the base material layer, the ratio of the thickness of the adhesive layer to the thickness of the outer layer is 0.20 or more and 1.00 or less. (5) The insulating sheet according to any one of (1) to (4) above, wherein each of the two adhesive layers contains an acrylic polymer. (6) The insulating sheet according to (5) above, wherein the acrylic polymer is an acrylic polymer formed by polymerization of at least an alkyl (meth)acrylate ester. (7) The insulating sheet according to (6) above, wherein the acrylic polymer is a crosslinked reaction product of (meth)acrylic acid butyl ester, a terpene phenol, and a polyisocyanate. (8) A motor comprising the insulating sheet according to any one of (1) to (7) above. EXAMPLES

[0076] The present invention will now be described in more detail with reference to experimental examples, but the present invention is not limited to these.

[0077] The materials or raw materials for the outer layer, adhesive layer, and base layer used to manufacture the insulating sheet are shown below.

[0078] <Outer layer material> · Fully aromatic polyamide paper (PA paper) Product name: "Nomex Series" (manufactured by DuPont Teijin Advanced Papers) Use the part number with the desired thickness each time <Raw materials for adhesive layer> Acrylic polymer (Ac) A mixed solution was prepared by mixing polybutyl acrylate (PAB), terpene phenol, polyisocyanate, and an organic solvent (methyl ethyl ketone (MEK)). When forming an adhesive layer from such a mixed solution, the organic solvent was evaporated, and then a heat curing treatment was performed at a temperature of 130°C for 24 hours. Polyurethane (Pu) The urethane reaction product of the polyol component and the isocyanate component was mixed with an organic solvent (toluene and methyl ethyl ketone) so that the solid content concentration was 25% by mass to obtain a mixed solution. When forming an adhesive layer from such a mixed solution, after the organic solvent was evaporated, a curing treatment was further performed at 130°C for 24 hours. Epoxy resin-containing polymer compound (Ep) A mixed solution was used in which a phenol novolac epoxy resin and a phenol-based hardener were added to an organic solvent (MEK) containing polybutyl acrylate (PAB). The mixed solution contained 140 parts by mass of polybutyl acrylate per 100 parts by mass of the organic solvent, and 60 parts by mass of the phenol novolac epoxy resin per 100 parts by mass of the organic solvent. The mixed solution also contained 45 parts by mass of the phenol-based hardener and 3 parts by mass of a hardening accelerator per 100 parts by mass of the phenol novolac epoxy resin. When forming the adhesive layer from the above mixed solution, a curing treatment was further carried out at 130° C. for 24 hours after the organic solvent had evaporated.

[0079] <Material for base layer> · Low oligomer content polyethylene terephthalate resin film (L-PET) Oligomer content: less than 0.8% by mass Product name: Melinex 238 (manufactured by DuPont) ·Polyethylene naphthalate resin film (PEN) Product name: Teonex Q5100 (manufactured by Toyobo Co., Ltd.) · Ordinary polyethylene terephthalate resin film (N-PET) Oligomer content: 0.8% by mass or more Product name: "Lumirror Series" (manufactured by Toray Industries, Inc.)

[0080] Example 1 and 2. Comparative Example 1, Reference Example 3~8 and A~C ) The configurations (such as the thickness and material of each layer) of the insulating sheets of each of the Examples and Comparative Examples are shown in Tables 1 and 2. Unless otherwise specified, each of the insulating sheets of the Examples and Comparative Examples has a five-layer laminate structure as shown in FIG. Each of Reference Examples 1 to 3 has a structure of one layer of resin film.

[0081] <Insulating sheet manufacturing> A mixture containing each component constituting the adhesive layer and an organic solvent was prepared. The mixture was applied to both sides of the base layer using a roll coater so that the adhesive layer would have a predetermined thickness after drying. The organic solvent contained in the applied mixture was volatilized (dried) to prepare an adhesive layer on each side of the base layer. Furthermore, an outer layer was attached to each adhesive layer to produce each insulating sheet.

[0082] <Measurement of thermal decomposition by thermogravimetric differential thermal analysis (TG-DTA)> The adhesive layer of each example was evaluated for thermal decomposition by thermogravimetric differential thermal analysis (TG-DTA). Specifically, the evaluation was performed according to the following procedure. (1) The adhesive layer of each example was applied to the entire surface of one side of the outer layer, and then dried for 1 minute at 100° C. The coating was performed so that the adhesive layer had a thickness of 12 μm after drying. (2) The adhesive layer was left in an oven at 130° C. for 24 hours to allow the curing reaction to proceed. After the curing reaction had proceeded, the outer layer was peeled off from the adhesive layer. (3) A TG-DTA curve was obtained for the adhesive layer after the curing reaction using a thermogravimetric differential thermal analyzer (manufactured by SII NanoTechnology, model "EXSTAR6000"). The temperature was raised from room temperature (23±2°C) at a rate of 10°C / min in an air atmosphere of 100mL / min. The temperature at which a mass loss of 5% by mass was observed was then read. The results are shown in Tables 1 and 2 below, respectively.

[0083] [Table 1]

[0084] [Table 2]

[0085] The insulating sheets produced in the respective Examples and Comparative Examples were evaluated for tracking resistance, heat resistance, and oil resistance as described below.

[0086] <Tracking resistance evaluation test> Testing was carried out in accordance with International Electrotechnical Commission standards, specifically IEC60112. Specifically, 20 flat test samples with a size of 100 mm x 100 mm and a thickness of 3 mm or more are prepared. Platinum electrodes are placed on the surface of the test samples, a voltage is applied between the electrodes, and while the voltage is applied, electrolyte (0.1% by mass ammonium chloride aqueous solution) is dropped between the electrodes at regular intervals. The test is continued until tracking occurs or the number of drops reaches 100. The number of drops of electrolyte required until tracking occurs is then counted. Five tests are performed for each voltage, and if all counted drops are 50 or more, the applied voltage is deemed to have passed. This procedure is repeated at various voltages in 25V increments to determine the CTI (comparative tracking index).

[0087] <Heat resistance evaluation test> A test sample of the insulating sheet cut into a square of 150 mm x 150 mm was heated in a dryer at 240°C for 1000 hours. After that, the specimens were cooled to room temperature, and the dielectric breakdown voltage (BDV) of each specimen was measured at room temperature while increasing the voltage (1000 V / sec). The measurements were continued for up to 1000 hours. When the BDV at 500 hours was less than 50% of the initial BDV, it was evaluated as poor (◯), and when it was 50% or more, it was evaluated as good (◯). The results are shown in Tables 1 and 2, respectively.

[0088] <Evaluation test of oil resistance (hydrolysis resistance)> A test specimen was prepared by cutting an insulating sheet into a square of 150 mm x 150 mm and forming it into a loop shape. A pressure cooker test (PCT) was carried out on the test specimen under conditions of 120°C, 100% relative humidity, and 0.2 MPa atmospheric pressure. After that, the specimens were cooled to room temperature, and the dielectric breakdown voltage (BDV) of each specimen was measured at room temperature while increasing the voltage (1000 V / sec). The measurements were carried out for up to 150 hours. When the BDV at 100 hours was less than 80% of the initial BDV, it was evaluated as poor (◯), and when it was 80% or more, it was evaluated as good (◯). The results are shown in Tables 1 and 2, respectively.

[0089] The results of the above evaluation tests are shown in Tables 1 and 2, respectively. As can be seen from Tables 1 and 2, the insulating sheets of the examples had higher tracking resistance and higher heat resistance than the insulating sheets of the comparative examples. Among the examples, a particular insulating sheet (in which the adhesive layer contained an acrylic polymer) also had good oil resistance. Furthermore, when the adhesive layer of the examples was subjected to thermogravimetric differential thermal analysis (TG-DTA), the temperature at which a mass loss of 5% by mass was observed was 350°C or lower, and even 300°C or lower, thereby improving tracking resistance. [Industrial Applicability]

[0090] The insulating sheet of the present invention is preferably used, for example, as a component of a motor. The insulating sheet of the present invention is preferably used, for example, when it is provided in a motor and immersed in automatic transmission oil (ATF). [Explanation of symbols]

[0091] 11: Base material layer, 12: Adhesive layer, 13: Outer layer, 10: Insulating sheet.

Claims

1. An insulating sheet comprising: two outer layers arranged to face each other; two adhesive layers arranged between the two outer layers to face each other; and a base material layer arranged between the two adhesive layers, The two outer layers are both aromatic polyamide papers; the base layer is a polyethylene terephthalate resin film, and the content of an oligomer component contained in the polyethylene terephthalate resin film is less than 0.8% by mass; Both of the two adhesive layers each contain an acrylic polymer, and each of the two adhesive layers has a thickness of 25 μm or more and 40 μm or less; The thickness of the insulating sheet is 190 μm or more and 270 μm or less, An insulating sheet, wherein a ratio of the thicknesses of the two adhesive layers to the thicknesses of the two outer layers is greater than or equal to 0.50 and less than or equal to 1.

00.

2. The insulating sheet according to claim 1 , wherein a ratio of a total thickness of the two adhesive layers to a thickness of the insulating sheet is not less than 0.19 and not more than 0.

40.

3. a ratio of a total thickness of the two outer layers to a thickness of the insulating sheet is greater than 0.20 and is equal to or less than 0.50; a ratio of a total thickness of the base layer and the two outer layers to a thickness of the insulating sheet is 0.70 or more and less than 0.80; 3. The insulating sheet according to claim 1, wherein, when the adhesive layer is subjected to differential thermal analysis, a temperature at which a mass loss of 5% by mass is observed is 350°C or lower.

4. A motor comprising the insulating sheet according to claim 1 or 2.

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