Insulating sheet and motor

Abstract

Provided is an insulating sheet provided with two outer layers disposed so as to face each other, two adhesive layers disposed so as to face each other between the two outer layers, and a base layer disposed between the two adhesive layers, the two outer layers being aromatic polyamide paper, the base material 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 mass%.

Description

[0001] Cross-references of related applications

[0002] This application claims the priority of Japanese Patent Application No. 2022-126162, which is hereby incorporated by reference into the description of the present application specification. Technical Field

[0003] The present invention relates to an insulating sheet which is a component of a motor, for example, and a motor including the insulating sheet. Background Art

[0004] Conventionally, there is known an insulating sheet including a base layer, two outer layers disposed to face one surface and the other surface of the base layer, and two adhesive layers disposed between one outer layer and the base layer and between the other outer layer and the base layer.

[0005] As such an insulating sheet, for example, an insulating sheet for a motor used in a state of being immersed in a cutting oil is known. As such an insulating sheet for a motor, for example, an insulating sheet having five layers stacked, in which a base layer and two outer layers are respectively formed of polyethylene naphthalate resin films, and adhesive layers are respectively arranged between the base layer and the two outer layers (for example, Patent Document 1) is known.

[0006] The insulating sheet described in Patent Document 1 has the above-mentioned structure and therefore has high tracking resistance.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2016-165806 Summary of the invention

[0010] Problem that the invention aims to solve

[0011] However, the insulating sheet described in Patent Document 1 does not necessarily have sufficient heat resistance. Therefore, an insulating sheet having high tracking resistance and sufficient heat resistance is desired.

[0012] In view of the above problems and desires, an object of the present invention is to provide an insulating sheet having high tracking resistance and sufficient heat resistance.

[0013] Solutions for solving problems

[0014] In order to solve the above problems, the insulating sheet of the present invention comprises:

[0015] two outer layers arranged so as to face each other, two adhesive layers arranged so as to face each other between the two outer layers, and a base material layer arranged between the two adhesive layers,

[0016] The two outer layers are both aromatic polyamide paper,

[0017] The substrate layer is a polyethylene terephthalate resin film,

[0018] The content of the oligomer component contained in the polyethylene terephthalate resin film is less than 0.8% by mass.

[0019] The electric motor according to the present invention includes the above-mentioned insulating sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] [ Figure 1 ] Figure 1 This is a schematic cross-sectional view of the insulating sheet of the present embodiment cut along the thickness direction.

[0021] [ Figure 2 ] Figure 2 It is a perspective view of the stator of the oil-cooled drive motor. DETAILED DESCRIPTION

[0022] Hereinafter, one embodiment of the insulating sheet of the present invention will be described with reference to the drawings.

[0023] like Figure 1 As shown, the insulating sheet 10 of the present embodiment includes two outer layers 13 arranged to face each other, two adhesive layers 12 arranged to face each other between the two outer layers 13 , and a base layer 11 arranged between the two adhesive layers 12 .

[0024] In other words, the insulating sheet 10 of the present embodiment includes one base layer 11 , two adhesive layers 12 arranged to sandwich the base layer 11 in the thickness direction, and two outer layers 13 arranged to sandwich the two adhesive layers 12 in the thickness direction.

[0025] In this embodiment, the base layer 11 is in direct contact with one adhesive layer 12, and the base layer 11 is in direct contact with the other adhesive layer 12. In addition, the adhesive layer 12 is in direct contact with the outer layer 13 on one surface of the base layer 11, and is in direct contact with the outer layer 13 on the other surface.

[0026] Each outer layer 13 may be the outermost layer of the insulating sheet 10 .

[0027] 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.

[0028] 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 order to further improve the tracking resistance.

[0029] The thickness of the base material layer 11 may be, for example, 25 μm or more and 200 μm or less. The thickness of the base material layer 11 is preferably 50 μm or more and 150 μm or less.

[0030] The thickness of the adhesive layer 12 (per layer) may be, for example, 1 μm to 80 μm. The thickness of the adhesive layer 12 is preferably 5 μm to 50 μm, more preferably 25 μm to 40 μm.

[0031] The difference between the thickness of one adhesive layer 12 and the thickness of the other adhesive layer 12 is preferably small. For example, the thickness of the other adhesive layer 12 may be 0.9 times or more and 1.1 times or less of the thickness of the one adhesive layer 12.

[0032] 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.

[0033] It is preferable that the difference in thickness between one of the two outer layers 13 and the other outer layer 13 is small. For example, the thickness of the other outer layer 13 may be 0.9 times or more and 1.1 times or less relative to the thickness of the one outer layer 13.

[0034] The thickness of each layer is the average thickness. The thickness of each layer is obtained by randomly selecting the thickness of at least 5 locations and averaging them. The same applies to the following.

[0035] The thickness of each layer can be measured by observing the side surface or cross section of the insulating sheet 10 using a digital microscope, for example.

[0036] The ratio of the thickness of the base material layer 11 to the total thickness of the insulating sheet 10 may be 0.20 or more, preferably 0.30 or more. Alternatively, the ratio may be 0.50 or less.

[0037] The ratio of the total thickness of the adhesive layer 12 (the thickness of the 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 less. Alternatively, the ratio may be 0.40 or less, or 0.30 or less.

[0038] The ratio of the total thickness of the outer layer 13 (the thickness of the two layers) to the total thickness of the insulating sheet 10 is preferably greater than 0.20. In addition, the ratio may be 0.50 or less.

[0039] The ratio of the total 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. Alternatively, the ratio may be 0.35 or less.

[0040] The ratio of the total 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. Alternatively, the ratio may be less than 0.80, and preferably less than 0.79.

[0041] 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. Alternatively, the ratio may be 1.50 or less.

[0042] The ratio of each thickness of the adhesive layer 12 to each thickness of the outer layer 13 may be 0.20 or more, 0.35 or more, 0.40 or more, or 0.50 or more. Alternatively, the ratio may be 1.00 or less, or 0.80 or less.

[0043] The ratio of each thickness of the adhesive layer 12 to each thickness of the outer layer 13 is preferably 0.35 or more, and more preferably greater than 0.40. By setting this ratio to 0.35 or more, the tracking resistance of the insulating sheet 10 can be further improved.

[0044] It should be noted that it is preferred that at least one of the one side and the other side of the substrate layer 11 satisfies the above-mentioned numerical range for the ratio of each thickness of the adhesive layer 12 to each thickness of the outer layer 13. It is more preferred that on both sides, one side and the other side of the substrate layer 11, 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.

[0045] The base layer 11 is a polyethylene terephthalate resin film. The content of the oligomer component contained 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 the case where the polyethylene terephthalate resin film of the base layer 11 contains 0.8 mass % or more of the oligomer component.

[0046] The content of the above-mentioned oligomer component is determined as follows. Specifically, a roughly square film sample with a side 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, and the initial mass (M1[g]) is measured. Then, using a Soxhlet extractor, etc., the above-mentioned film sample is subjected to an extraction treatment using boiling xylene (about 400 mL) for 48 hours. Next, the mass of the film sample after the extraction treatment is measured (M2[g]). Then, the content of the oligomer component is determined by calculating the ratio of the mass reduction (M1-M2) to the initial mass (M1) [(M1-M2) / M1].

[0047] It should be noted that in order to accurately measure the mass reduction, the mass (M2[g]) of the film sample after the extraction treatment is measured after the xylene used in the extraction treatment is fully removed. Preferably, the film sample is washed with water after the extraction treatment, and then the xylene attached to the surface is gently wiped off, and then it is further dried in a hot air oven at 160°C for 8 hours, and the mass (M2[g]) of the film sample after the extraction treatment is measured after natural cooling in the dryer.

[0048] Examples of the polyethylene terephthalate resin film include films formed of polymers of dicarboxylic acids such as terephthalic acid and 2,6-naphthalene dicarboxylic acid and diols such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol.

[0049] In addition, the polyethylene terephthalate resin constituting the base material layer 11 may be a single type or two or more types.

[0050] In addition, the substrate layer 11 may be a single layer as in the present embodiment, or may be a laminated film in which a plurality of polyethylene terephthalate resin films are laminated. When the substrate layer 11 is a laminated film, at least one layer constituting the laminated film may be a polyethylene terephthalate resin film having an oligomer content of less than 0.8% by mass.

[0051] As the base material layer 11, for example, a commercially available product such as "Lumirror X10S" (manufactured by Toray Industries, Inc.) or "D Melinex 238" (manufactured by DuPont) can be used.

[0052] The adhesive layer 12 constituting the insulating sheet 10 of the present embodiment contains, for example, a polymer component. Examples of the polymer component include acrylic polymers, urethane polymers, and epoxy resins.

[0053] The acrylic polymer is preferably a polymer obtained by polymerizing at least an alkyl (meth)acrylate.

[0054] The acrylic polymer may be, for example, a polymer of an alkyl (meth)acrylate or a copolymer of an alkyl (meth)acrylate and other polymerizable monomers. It should be noted that in this specification, the term "(meth)acrylic acid" includes both "acrylic acid" and "methacrylic acid".

[0055] Examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate [e.g., n-propyl (meth)acrylate, isopropyl (meth)acrylate, etc.], butyl (meth)acrylate [e.g., n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, etc.], 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, and isononyl (meth)acrylate.

[0056] Examples of other polymerizable monomers include ethylene, styrene, vinyl chloride, acrylic acid, butadiene, and acrylonitrile.

[0057] Examples of the copolymer include ethylene-alkyl (meth)acrylate copolymers, ethylene-alkyl (meth)acrylate-acrylic acid copolymers, styrene-alkyl (meth)acrylate-acrylic acid copolymers, alkyl (meth)acrylate-vinyl chloride copolymers, alkyl (meth)acrylate-acrylic acid copolymers, alkyl (meth)acrylate-vinyl chloride copolymers, alkyl (meth)acrylate-acrylic acid copolymers, alkyl (meth)acrylate-vinyl chloride copolymers, styrene-alkyl (meth)acrylate-butadiene copolymers, and alkyl (meth)acrylate-acrylonitrile copolymers.

[0058] The adhesive layer 12 preferably includes a polymer compound obtained by cross-linking polybutyl acrylate (PAB) with polyisocyanate.

[0059] The adhesive layer 12 more preferably includes a crosslinked reaction product of butyl acrylate (PAB), terpene phenol and polyisocyanate. When the adhesive layer 12 includes the crosslinked reaction product, the adhesion with the outer layer 13 (aromatic polyamide paper) becomes better when the insulating sheet 10 is immersed in a high temperature water-containing oil of 120 to 180° C. The added amount of terpene phenol 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).

[0060] In addition, even when alkylphenol is used instead of terpenephenol, the above-mentioned adhesion can be further improved. The amount of alkylphenol added is preferably 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of butyl acrylate (PAB).

[0061] In addition, polybutyl acrylate (PAB) may have a carboxyl group in a part of the molecule.

[0062] The acrylic polymers may be used alone or in combination of two or more.

[0063] The urethane polymer that may be included in the adhesive layer 12 may be, for example, a urethanized reaction product of a polyol component having a plurality of hydroxyl groups in the molecule and a polyisocyanate component having a plurality of isocyanate groups in the molecule. It should be noted that in this specification, "urethane polymer" does not include "polyurethane-urea resin" and is a polymer that does not substantially contain a urea bond.

[0064] Examples of the polyol component include conventionally known polyol components, such as polyester polyol, polyether polyol, and polycarbonate polyol.

[0065] Examples of the polyester polyol include polyethylene adipate diol, polybutylene adipate diol, polyhexamethylene adipate diol, polyneopentyl adipate diol, polyethylene adipate / butylene adipate diol, polyneopentyl adipate / hexyl adipate diol, poly-3-methylpentane adipate diol, polybutylene isophthalate diol, polycaprolactone diol, and poly-3-methylvalerolactone diol.

[0066] Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and random / block copolymers thereof.

[0067] 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.

[0068] Examples of the polyol component include dimer diol or its hydride, polybutadiene polyol or its hydride, polyisoprene polyol or its hydride, acrylic polyol, epoxy polyol, polyether ester polyol, silicone-modified polyol, α,ω-polymethyl methacrylate diol, α,ω-polybutyl methacrylate diol, and the like.

[0069] Examples of the polyisocyanate component include conventionally known polyisocyanate components.

[0070] Examples of the polyisocyanate component include 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), and aromatic diisocyanates such as crude MDI or polymeric MDI, doxyl diisocyanate, xylylene diisocyanate (XDI), 1,5-naphthalene diisocyanate, benzidine diisocyanate, o-nitrobenzidine diisocyanate, and 4,4'-diisocyanate dibenzyl.

[0071] Moreover, as said polyisocyanate component, aliphatic diisocyanates, such as methylene diisocyanate and 1, 4-tetramethylene diisocyanate, are mentioned, for example.

[0072] 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.

[0073] Examples of the polyisocyanate component include polyurethane prepolymers obtained by reacting these diisocyanates with low-molecular-weight polyols so that the ends thereof become isocyanates.

[0074] In addition, the said urethane polymer can be produced by the conventionally well-known general production method.

[0075] For example, the urethane polymer can be produced by subjecting the polyol component and the polyisocyanate component to a urethanization reaction by a one-step method or a multi-step method.

[0076] The one-step method and the multi-step method can be carried out usually at a temperature in the range of 20°C to 150°C, preferably 60°C to 110°C.

[0077] In order 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.

[0078] Examples of the epoxy resin that may be included in the adhesive layer 12 include phenol novolac epoxy resin, triphenylmethane epoxy resin, cresol novolac epoxy resin, bisphenol A epoxy resin, modified bisphenol A epoxy resin, bisphenol F epoxy resin, modified bisphenol F epoxy resin, bisphenol AD ​​epoxy resin, modified bisphenol AD ​​epoxy resin, dicyclopentadiene epoxy resin, or biphenyl epoxy resin.

[0079] As the epoxy resin, the above-mentioned phenol novolac epoxy resin is preferred. The epoxy equivalent of the phenol novolac epoxy resin is preferably 150 g / eq or more, more preferably 160 g / eq or more, and more preferably 170 g / eq or more. In addition, the epoxy equivalent of the phenol novolac epoxy resin is preferably 200 g / eq or less, more preferably 190 g / eq or less, and more preferably 180 g / eq or less.

[0080] The epoxy equivalent can be determined according to JIS K 7236.

[0081] When the adhesive layer 12 contains an epoxy resin, the adhesive layer 12 preferably further contains a curing agent for the epoxy resin.

[0082] Examples of the curing agent include phenolic curing agents, amine curing agents, and acid anhydride curing agents, and a phenolic curing agent is preferred.

[0083] Among the phenol-based curing agent, the amine-based curing agent, and the acid anhydride-based curing agent, one type may be used alone, or two or more types may be used in combination.

[0084] Examples of the phenolic curing agent include phenol novolac resins, aralkyl phenolic resins, dicyclopentadiene-modified phenolic resins, naphthalene phenolic resins, bisphenol phenolic resins, and triphenylmethane phenolic resins.

[0085] Examples of the amine-based curing agent include diaminodiphenyl sulfone, dicyandiamide, diaminophenylmethane, and triethylenetetramine.

[0086] Examples of the acid anhydride curing agent include phthalic anhydride, trimellitic anhydride, and maleic anhydride.

[0087] 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.

[0088] In addition, the adhesive layer 12 preferably 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.

[0089] 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 acrylic polymer relative to 100 parts by mass of the epoxy resin (assuming that the amount of the epoxy resin is 100 parts by mass).

[0090] The adhesive layer 12 may contain 300 parts by mass or less, or 250 parts by mass or less, of the acrylic polymer relative to 100 parts by mass of the epoxy resin (when the amount of the epoxy resin is 100 parts by mass).

[0091] In the insulating sheet 10 of the present embodiment, when the above-mentioned adhesive layer 12 is subjected to thermogravimetric differential thermal analysis (TG-DTA), the temperature at which 5% weight loss is confirmed is preferably 350° C. or less, and more preferably 300° C. or less. Therefore, when the insulating sheet 10 is exposed to a high-temperature atmosphere, organic substances such as resin contained in the adhesive layer 12 are more easily thermally decomposed.

[0092] Therefore, before the thermal decomposition of the organic matter on the outer surface of the outer layer 13 is performed, the thermal decomposition of the organic matter contained in the adhesive layer 12 is more likely to be performed. When the temperature becomes high during use of the insulating sheet 10, the thermal decomposition of the organic matter in the adhesive layer 12 consumes the heat at the high temperature. As the heat is consumed by the thermal decomposition, the thermal decomposition of the organic matter contained in the outer layer 13 on the outer surface of the outer layer 13 can be suppressed. As the thermal decomposition of the organic matter contained in the outer layer 13 is suppressed, the generation of a conductive path formed by free carbon on the outer surface of the outer layer 13 can be suppressed.

[0093] In addition, since the organic matter contained in the adhesive layer 12 is easily thermally decomposed, the organic matter will not remain in the state of free carbon even if it is thermally decomposed, but can be fully thermally decomposed into gas such as carbon dioxide. Most reactions that generate gas are endothermic reactions, so the thermal decomposition of the organic matter contained in the outer layer 13 is also suppressed in the outer surface of the outer layer 13 by this endothermic reaction. As a result, the formation of a conductive path formed by free carbon on the outer surface of the outer layer 13 can be suppressed.

[0094] As described above, the insulating sheet 10 of the present embodiment can exhibit better tracking resistance even if the outer layer 13 is made of wholly aromatic polyamide paper by setting the temperature at which 5% weight loss is observed in the adhesive layer 12 to 350° C. or less.

[0095] In addition, the temperature at which 5 mass % weight loss is observed in the adhesive layer 12 can be obtained by the following method.

[0096] <Measurement of Thermal Decomposition by Thermogravimetric Differential Thermal Analysis (TG-DTA)>

[0097] For the adhesive layer 12, the temperature at which 5% weight loss was observed was determined according to the following procedure.

[0098] (1) A mixture for an adhesive layer (described later) was applied to the entire surface of one surface of the outer layer, and then dried at 100° C. for 1 minute. The coating was performed so that the thickness of the adhesive layer after drying would be 12 μm.

[0099] (2) The adhesive layer was placed in an oven at 130° C. for 24 hours to allow a curing reaction to occur in the adhesive layer. After the curing reaction occurred, the outer layer was peeled off from the adhesive layer.

[0100] (3) A TG-DTA curve of the adhesive layer after the curing reaction was obtained using a thermogravimetric differential thermal analyzer (manufactured by SII Nano Technology, model "EXSTAR6000"). It should be noted that the temperature was raised from room temperature (23±2°C) at a rate of 10°C / min in an atmosphere of 100 mL / min of air. Then, the temperature at which 5% weight loss was confirmed was read.

[0101] The adhesive layer 12 may contain additives such as a tackifier in addition to the above-mentioned polymer component. The content of components other than the above-mentioned resin component in the adhesive layer 12 is preferably less than 5% by mass, more preferably less than 0.8% by mass.

[0102] The weight per unit area of ​​the adhesive layer 12 may be, for example, 10 g / m 2 Above and 20g / m 2 the following.

[0103] 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 obtained by cross-linking a plurality of polymers.

[0104] The two outer layers 13 constituting the insulating sheet 10 of the present embodiment are both made of aromatic polyamide paper. Since the outer layers 13 are made of aromatic polyamide paper, the insulating sheet 10 of the present embodiment can have good heat resistance.

[0105] As the aromatic polyamide paper, for example, there can be used: a wholly aromatic polyamide paper made by making at least one of short fibers containing wholly aromatic polyamide and synthetic pulp containing wholly aromatic polyamide, a sheet containing at least one of short fibers containing wholly aromatic polyamide or synthetic pulp containing wholly aromatic polyamide and containing mica powder (mica flakes), or a sheet obtained by subjecting these papers or sheets to a high-temperature and high-pressure calendering process.

[0106] As the aromatic polyamide paper, fully aromatic polyamide paper is preferred from the viewpoint of having better heat resistance.

[0107] Examples of the wholly aromatic polyamide constituting the short fibers or the synthetic pulp include a polycondensate of metaphenylenediamine and isophthalic acid and a polycondensate of paraphenylenediamine and terephthalic acid.

[0108] The outer layer 13 may be subjected to lamination or surface treatment. The surface treatment may be carried out using a coating agent containing a polyamide resin (e.g., a methoxymethylated polyamide resin in which the amide group is methoxymethylated). It should be noted that, as the outer layer 13, for example, a commercially available product (product name "Nomex" manufactured by DuPont, etc.) may be used.

[0109] The insulating sheet 10 of the present embodiment has, for example, 1×10 13 The volume resistivity of the insulating sheet 10 is preferably 1×10 14 Ω·cm or more.

[0110] The insulating sheet 10 of the present embodiment has high tracking resistance and sufficient heat resistance.

[0111] When the adhesive layer 12 contains the acrylic polymer, the tracking resistance can be further improved and the oil resistance can be improved.

[0112] The temperature at which the weight loss of 5% by mass of the adhesive layer 12 is confirmed is preferably 350° C. or lower, and more preferably 300° C. or lower. This can further improve the tracking resistance and oil resistance.

[0113] Next, a method for manufacturing the insulating sheet 10 according to the present embodiment will be described.

[0114] In the manufacturing method of the insulating sheet 10 of the present embodiment, for example, a mixture containing the components constituting the above-mentioned adhesive layer 12 and an organic solvent (if necessary) 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 prepare two adhesive layers 12. Furthermore, by bonding the outer layer 13 to each adhesive layer 12, the insulating sheet 10 can be manufactured.

[0115] In addition, as a coating device, a roll coater etc. can be used, for example.

[0116] As the organic solvent, for example, ethyl acetate, methyl ethyl ketone (MEK), toluene, or the like can be used.

[0117] When applying the mixture containing an organic solvent to the outer layer 13, a common coating method such as a die coating method or a reverse coating method can be used. The temperature during coating is, for example, room temperature (15°C to 25°C).

[0118] The insulating sheet 10 manufactured as described above is used, for example, as a member constituting an electric motor. The insulating sheet 10 can also be used, for example, as an insulating sheet for a driving motor of an automobile.

[0119] Examples of the automobile include a hybrid electric vehicle (HEV) and an electric vehicle (EV).

[0120] Examples of the drive motor include an HV motor, a motor generator, an AC generator, a 4WD motor, an oil pump motor, an EPS motor, a compressor motor, and a hub motor.

[0121] As a driving motor for an automobile, an oil-cooled driving motor can be mentioned. The oil-cooled driving motor is a driving motor cooled by cooling oil such as ATF.

[0122] For example, the insulating sheet 10 can be used in a heated state. If the insulating sheet 10 is used for a long time in a heated state, oxidation degradation may occur.

[0123] For example, the insulating sheet 10 can be used in a state of being immersed in oil. Examples of the oil include automatic oil (ATF) and the like. If the insulating sheet 10 is used in a state of being immersed in oil, water contained in the oil such as ATF causes a hydrolysis reaction.

[0124] In contrast, the insulating sheet of the present embodiment has good tracking resistance and can also have good heat resistance. Therefore, the above-mentioned oxidative degradation can be suppressed. Depending on the situation, the insulating sheet of the present embodiment also has good oil resistance and can also suppress the above-mentioned hydrolysis reaction.

[0125] Next, one embodiment of the electric motor of the present invention will be described with reference to the drawings.

[0126] The motor of the present embodiment includes the above-mentioned insulating sheet 10. The insulating sheet 10 is, for example, an insulating sheet for a motor.

[0127] For example, the electric motor is a drive motor mounted on a hybrid vehicle, an electric vehicle, etc. The drive motor is, for example, an oil-cooled drive motor.

[0128] The oil-cooled drive motor of a vehicle has a rotor having permanent magnets and a stator 20 that generates a force to rotate the rotor. Figure 2 As shown, 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.

[0129] In the oil-cooled drive motor described above, the coil 21 is composed of, for example, a plurality of segment conductors connected to each other. In the oil-cooled drive motor described above, the stator core 22, the rotor core, or the like has a plurality of slots, and the coils 21 are housed in the plurality of slots.

[0130] In addition, in the oil-cooled drive motor as described above, in order to ensure the insulation between the coil 21 and the inner wall surface of the slot, an insulating sheet for the motor is used. The insulating sheet for the motor and the coil 21 are respectively accommodated in the slot. In detail, the insulating sheet for the motor is accommodated in the slot in a state of being wound around the coil 21.

[0131] Then, the coil 21 wound by the motor insulating sheet is fixed in the slot via the insulating resin (for example, epoxy varnish) impregnated in the slot.

[0132] The insulating sheet and the motor of the present embodiment are as exemplified above, but the present invention is not limited to the insulating sheet or the motor exemplified above.

[0133] That is, various forms used in common insulating sheets or motors can be adopted within a range that does not impair the effects of the present invention.

[0134] Matters disclosed in this specification include the following matters. (1)

[0136] An insulating sheet comprises: two outer layers arranged to face each other, two adhesive layers arranged to face each other between the two outer layers, and a base material layer arranged between the two adhesive layers.

[0137] The two outer layers are both aromatic polyamide paper,

[0138] The substrate layer is a polyethylene terephthalate resin film,

[0139] The content of the oligomer component contained in the polyethylene terephthalate resin film is less than 0.8% by mass.

[0140] The insulating sheet having the above-mentioned structure has high tracking resistance and sufficient heat resistance. (2)

[0142] The insulating sheet according to the above (1), wherein, when the adhesive layer is subjected to thermogravimetric differential thermal analysis (TG-DTA), a temperature at which a weight loss of 5% by mass is confirmed is 350° C. or less. (3)

[0144] 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 to 0.40. (4)

[0146] The insulating sheet according to any one of (1) to (3) above, wherein, on one surface side of the base layer, a 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)

[0148] The insulating sheet according to any one of (1) to (4) above, wherein both of the two adhesive layers contain an acrylic polymer. (6)

[0150] The insulating sheet according to the above (5), wherein the acrylic polymer is an acrylic polymer obtained by polymerizing at least an alkyl (meth)acrylate. (7)

[0152] The insulating sheet according to the above (6), wherein the acrylic polymer is a cross-linked reaction product of butyl (meth)acrylate, terpene phenol, and polyisocyanate. (8)

[0154] An electric motor includes the insulating sheet according to any one of (1) to (7) above.

[0155] Example

[0156] Next, the present invention will be described in more detail using experimental examples, but the present invention is not limited thereto.

[0157] The materials or raw materials for each of the outer layer, the adhesive layer, and the base layer used to produce the insulating sheet are shown below.

[0158] <Outer Material>

[0159] Fully aromatic polyamide paper (PA paper)

[0160] Product name: "Nomex series" (manufactured by DuPont Teijin Advanced Papers)

[0161] Use the product number with the required thickness each time

[0162] <Raw materials for adhesive layer>

[0163] Acrylic polymer (Ac)

[0164] 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 the mixed solution, the organic solvent was volatilized and then heat-cured at 130° C. for 24 hours.

[0165] Polyurethane (Pu)

[0166] The urethanization 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. It should be noted that when the adhesive layer was formed from the mixed solution, after the organic solvent was volatilized, a curing treatment was further performed at 130° C. for 24 hours.

[0167] ·High molecular weight compound containing epoxy resin (Ep)

[0168] A mixed solution was used in which a phenol novolac epoxy resin and a phenolic curing agent were added to a solution containing polybutyl acrylate (PAB) and an organic solvent (MEK). The mixed solution contained 140 parts by mass of polybutyl acrylate relative to 100 parts by mass of the organic solvent, and 60 parts by mass of the phenol novolac epoxy resin relative to 100 parts by mass of the organic solvent. In addition, the mixed solution contained 45 parts by mass of the phenolic curing agent and 3 parts by mass of the curing accelerator relative to 100 parts by mass of the phenol novolac epoxy resin.

[0169] In addition, when the adhesive layer is formed from the mixed solution, after the organic solvent is volatilized, a curing treatment is further performed at 130° C. for 24 hours.

[0170] <Material of base material layer>

[0171] ·Low oligomer content polyethylene terephthalate resin film (L-PET)

[0172] Oligomer content: less than 0.8% by mass

[0173] Product name: "Melinex 238" (manufactured by Du Pont)

[0174] Polyethylene naphthalate resin film (PEN)

[0175] Product name: "Teonex Q5100" (manufactured by Toyobo Co., Ltd.)

[0176] ·Normal polyethylene terephthalate resin film (N-PET)

[0177] Oligomer content: 0.8% by mass or more

[0178] Product name: "Lumirror Series" (made by Toray Industries, Inc.)

[0179] (Example 1 to Example 8, Comparative Example 1, Reference Examples 1 to 3)

[0180] The structures (thickness of each layer, material, etc.) of the insulating sheets of the embodiments and comparative examples are shown in Tables 1 and 2. It should be noted that, unless otherwise specified, any insulating sheet of the embodiments and comparative examples has the following structure: Figure 1 The 5-layer stacked structure shown.

[0181] It should be noted that all of Reference Examples 1 to 3 have a structure of one layer of resin film.

[0182] <Manufacturing of Insulating Sheet>

[0183] A mixture containing the components constituting the above-mentioned adhesive layer and an organic solvent is prepared. The mixture is applied to both sides of the substrate layer using a roll coater in such a manner that the thickness of the adhesive layer after drying becomes a predetermined thickness. The organic solvent contained in the applied mixture is volatilized (dried) to form adhesive layers on both sides of the substrate layer. Furthermore, each insulating sheet is manufactured by laminating an outer layer on each adhesive layer.

[0184] <Measurement of Thermal Decomposition by Thermogravimetric Differential Thermal Analysis (TG-DTA)>

[0185] The adhesive layer of each example was evaluated for thermal decomposition properties by thermogravimetric differential thermal analysis (TG-DTA).

[0186] Specifically, the evaluation was performed according to the following steps.

[0187] (1) The mixture for the adhesive layer of each example was applied to the entire surface of one side of the outer layer, and then dried at 100° C. for 1 minute. The application was performed so that the thickness of the adhesive layer after drying would be 12 μm.

[0188] (2) The adhesive layer was placed in an oven at 130° C. for 24 hours to allow a curing reaction to occur in the adhesive layer. After the curing reaction occurred, the outer layer was peeled off from the adhesive layer.

[0189] (3) A TG-DTA curve of the adhesive layer after the curing reaction was obtained using a thermogravimetric differential thermal analyzer (manufactured by SII Nano Technology, model "EXSTAR6000"). It should be noted that the temperature was raised from room temperature (23±2°C) at 10°C / min in an atmosphere of 100 mL / min of air. Then, the temperature at which 5% weight loss was confirmed was read. The results are shown in Tables 1 and 2 below, respectively.

[0190] [Table 1]

[0191]

[0192] [Table 2]

[0193]

[0194] As described below, the insulating sheets produced in the examples and comparative examples were evaluated for tracking resistance, heat resistance, and oil resistance.

[0195] <Evaluation test of tracking resistance>

[0196] The test was carried out in accordance with the standards of the International Electrotechnical Commission, specifically, in accordance with IEC60112.

[0197] In detail, prepare 20 flat test samples with a size of 100mm×100mm and a thickness of 3mm or more. Place platinum electrodes on the surface of the test sample, apply voltage between the electrodes, and drip electrolyte (0.1 mass% ammonium chloride aqueous solution) between the electrodes at a certain interval while the voltage is applied. Continue the test until leakage tracking occurs, or until the number of drops reaches 100 drops. Then, count the number of drops of electrolyte required until leakage tracking occurs. Perform 5 tests for each voltage. If the counted number of drops is all more than 50 drops, it is judged to be qualified under the applied voltage. Repeat this operation at various voltages with increments of 25V to calculate the CTI (relative leakage tracking index).

[0198] <Heat resistance evaluation test>

[0199] A test sample of the insulating sheet cut into a square of 150 mm×150 mm was heated in a dryer at 240° C. for 1000 hours.

[0200] Then, the samples were cooled to room temperature, and the dielectric breakdown voltage (BDV) of each test sample was measured at room temperature while the voltage was increased (1000 V / sec). The measurement was performed for up to 1000 hours.

[0201] The case where the BDV at 500 hours was less than 50% of the initial BDV was evaluated as poor (×), and the case where it was 50% or more was evaluated as good (○).

[0202] The results are shown in Tables 1 and 2, respectively.

[0203] <Evaluation Test of Oil Resistance (Hydrolysis Resistance)>

[0204] A test specimen prepared by cutting a test sample of an insulating sheet into a square of 150 mm x 150 mm and forming it into a ring shape was prepared and a pressure cooker test (PCT) was performed on the test specimen under the conditions of 120°C, 100% relative humidity and 0.2 MPa air pressure.

[0205] Then, the samples were cooled to room temperature, and the dielectric breakdown voltage (BDV) of each test sample was measured at room temperature while the voltage was increased (1000 V / sec). The measurement was carried out for up to 150 hours.

[0206] The case where the BDV at 100 hours was less than 80% of the initial BDV was evaluated as poor (×), and the case where it was 80% or more was evaluated as good (○).

[0207] The results are shown in Tables 1 and 2, respectively.

[0208] The results of the above evaluation tests are shown in Tables 1 and 2, respectively.

[0209] As can be seen from Tables 1 and 2, the insulating sheet of the example has higher tracking resistance and higher heat resistance than the insulating sheet of the comparative example.

[0210] The insulating sheet specified in the examples (when the adhesive layer contains an acrylic polymer) also has good oil resistance.

[0211] In addition, when the adhesive layer of the example was subjected to thermogravimetric differential thermal analysis (TG-DTA), it was confirmed that the temperature at which the weight loss of 5 mass% was achieved was 350° C. or lower, and further 300° C. or lower, whereby the tracking resistance was further improved.

[0212] Industrial Applicability

[0213] The insulating sheet of the present invention can be suitably used, for example, in a member constituting a motor. The insulating sheet of the present invention can also be suitably used, for example, in a state where it is provided in a motor and immersed in automatic transmission fluid (ATF).

[0214] Description of Reference Numerals

[0215] 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 to face each other between the two outer layers, and a base layer arranged between the two adhesive layers, The two outer layers are both aromatic polyamide paper, The substrate layer is a polyethylene terephthalate resin film, The content of the oligomer component contained in the polyethylene terephthalate resin film is less than 0.8% by mass.

2. The insulating sheet according to claim 1, wherein: When the adhesive layer was subjected to thermogravimetric differential thermal analysis, it was confirmed that the temperature at which 5% by mass of weight loss occurred was 350° C. or less.

3. The insulating sheet according to claim 1 or 2, wherein: The two adhesive layers each contain an acrylic polymer. 4 . An electric motor comprising the insulating sheet according to claim 1 .

Images