Electrically insulating laminate for electromechanical applications

Abstract

To provide an electrically insulating laminate for electromechanical applications.SOLUTION: In a first aspect, an electrical insulating laminate includes a flexible polymer layer having a first thermoplastic polyimide having a glass transition temperature (Tg) in a range of 140 to 280 °C and a first flexible mat layer having a first organic material. The first organic material includes a woven fabric, a nonwoven fabric, or a fiber. The flexible polymer layer is thermally bonded and in direct contact with the first organic material. In a second aspect, an electrical machine comprises the electrical insulation laminate of the first aspect.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The field of this disclosure is electrical insulation laminates for electromechanical applications. [Background technology]

[0002] Slot liners are used in the stators and / or rotors of electric machines, such as generators and / or motors, to provide insulation between the stator core and / or rotor core and the stator windings and / or rotor windings. Similarly, slot liners separate the rotor windings from the rotor core.

[0003] Stator design constraints include stator laminations, magnet wires, slot insulation, and thermal management.

[0004] Common slot liner materials consist of multi-layer structures bonded together by glue or adhesive. Typically, a core layer is surrounded by two outer layers of different types of material and bonded to them with an additional layer of adhesive applied between the core and outer layers. Adhesives include polyurethane, acrylic, epoxy resins, and silicone chemicals.

[0005] In the case of electrical insulation laminate structures in which the outer layers are removed from the core layer solely by physical force, e.g., by a peel process, the typical mode of material failure observed is adhesive failure at the interface between the adhesive and the adherend. This is not the desired mode of failure. A more preferred mode of failure is cohesive failure, occurring either in the bulk layer of the adhesive or, in some cases, in the bulk of one of the adherends (i.e., the materials being bonded).

[0006] Good adhesive performance is especially important in high-temperature electric motor applications, where temperature exposure is coupled with exposure of laminate materials to chemicals (such as automatic transmission fluids) that may contain contaminants that can degrade typical adhesive formulations due to their low glass transition temperatures (Tg) or incompatibility with other chemicals. If delamination occurs in slot liner materials during the life of an electric machine, the fast-switching inverter can accumulate accumulated charge, reducing the effective partial discharge peak voltage of the electrical insulation system. Furthermore, there is a risk of unintentionally introducing voids into the adhesive layer when it is applied due to air entrapment during the coating process, which can initiate corona discharge or breakdown of the adhesive material when exposed to high electric fields. Therefore, it is in the OEM's best interest to use a chemically, electrically, and thermally stable insulation design to ensure machine reliability. One way to achieve this is to use slot liner materials that do not incorporate an adhesive layer between the adherends. An additional benefit of eliminating the adhesive layer is an overall thinner slot liner material construction that does not degrade any of the desired performance characteristics of the slot liner material, since the presence of the adhesive layer typically adds approximately 1 mil of thickness to the overall slot liner material laminate.

[0007] Previous efforts to eliminate the use of adhesives in slot liner laminate materials while using polyimide materials as the core are described in U.S. Patent Nos. 5,629,999, 5,629,999, 5,629,999, and 5,629,999, which describe plasma treating the surfaces of the materials to be bonded and then bonding them together by applying temperature and pressure. However, this approach requires additional material processing steps that add complexity and cost. In addition, U.S. Patent No. 5,629,999 describes laminating polyimide film and aramid paper together in the absence of adhesives by applying high temperature and pressure. However, the adhesive strength between the individual layers in the resulting laminate is only described qualitatively, thus leaving uncertainty as to whether the laminate will withstand subsequent processing steps such as bending. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Patent No. 10,173,403 B2 [Patent Document 2] U.S. Patent No. 10,836,112 B2 [Patent Document 3] US Patent Application Publication No. 2012 / 0128988A1 [Patent Document 4] U.S. Patent No. 10,836,112 B2 [Patent Document 5] Japanese Patent No. 4607826B2 [Patent Document 6] U.S. Patent No. 5,166,308A [Patent Document 7] U.S. Patent No. 5,298,331A [Patent Document 8] U.S. Patent No. 3,410,826A [Patent Document 9] U.S. Patent No. 3,063,966A [Patent Document 10] U.S. Patent No. 3,227,793A [Patent Document 11] U.S. Patent No. 3,287,324A [Patent Document 12] U.S. Patent No. 3,414,645A [Patent Document 13] U.S. Patent No. 5,667,743A [Patent Document 14] U.S. Patent No. 3,869,430A [Patent Document 15] U.S. Patent No. 3,869,429A [Patent Document 16] U.S. Patent No. 3,767,756A [Patent Document 17] U.S. Patent No. 3,756,908A [Patent Document 18] U.S. Patent No. 9,844,928B2 [Patent Document 19] U.S. Patent No. 10,173,403 B2 [Patent Document 20] U.S. Patent No. 10,836,112 B2 [Patent Document 21] Japanese Patent No. 4607826B2 [Patent Document 22] U.S. Patent No. 10,836,112 B2 Summary of the Invention [Means for solving the problem]

[0009] In a first embodiment, an electrical insulation laminate includes a flexible polymer layer having a first thermoplastic polyimide having a glass transition temperature (Tg) in the range of 140 to 280°C, and a first flexible mat layer having a first organic material. The first organic material includes a woven fabric, a nonwoven fabric, or a fiber. The flexible polymer layer is thermally bonded to and in direct contact with the first organic material.

[0010] In a second aspect, an electric machine includes the electrical insulation laminate of the first aspect.

[0011] Many aspects and embodiments have been described above, and are illustrative only, and not limiting. After reading this specification, those skilled in the art will appreciate that other aspects and embodiments are possible without departing from the scope of the invention. Other features and advantages of the invention will be apparent from the following detailed description and claims. DETAILED DESCRIPTION OF THE INVENTION

[0012] As used herein, "aromatic diamine" is intended to mean a diamine having at least one aromatic ring, either alone (i.e., a substituted or unsubstituted, functionalized or unfunctionalized benzene or similar type aromatic ring) or linked to another (aromatic or aliphatic) ring; such amines are to be considered aromatic regardless of any non-aromatic moieties that may also be components of the diamine. Thus, an aromatic diamine backbone segment is intended to mean at least one aromatic moiety between two adjacent imide bonds. As used herein, "aliphatic diamine" is intended to mean any organic diamine that does not meet the definition of an aromatic diamine.

[0013] Depending on the context, as used herein, "diamine" is intended to mean (i) the unreacted form (i.e., the diamine monomer), (ii) the partially reacted form (i.e., one or more moieties of an oligomer or other polyimide precursor derived from or otherwise resulting from the diamine monomer), or (iii) the fully reacted form (one or more moieties of a polyimide derived from or otherwise resulting from the diamine monomer). The diamine can be functionalized at one or more sites, depending on the particular embodiment selected in the practice of the present invention.

[0014] Indeed, the term "diamine" is not intended to be limiting (or to be interpreted literally) with respect to the number of amine moieties in the diamine component. For example, (ii) and (iii) above include polymeric materials that may have two, one, or zero amine moieties. Alternatively, the diamine may be functionalized with additional amine moieties (in addition to the amine moieties at the ends of the monomers that react with the dianhydride to grow the polymer chain). Such additional amine moieties could be used to crosslink the polymer or to provide other functional groups to the polymer.

[0015] Similarly, as used herein, the term "dianhydride" is intended to mean a component that reacts with (favors) a diamine and can react in combination to form an intermediate polyamic acid, which can then be cured to a polyimide. Depending on the context, as used herein, "anhydride" can refer not only to the anhydride moiety itself, but also to a precursor of the anhydride moiety, such as (i) a pair of carboxylic acid groups, which can be converted to an anhydride by dehydration or a similar type of reaction, or (ii) an acid halide (e.g., chloride) ester functional group (or any other functional group now known or developed in the future) that can be converted to an anhydride functional group.

[0016] Depending on the context, "dianhydride" can mean (i) the unreacted form (i.e., the dianhydride monomer, whether the anhydride functionality is in true anhydride form or in precursor anhydride form as discussed in the preceding paragraph above), (ii) the partially reacted form (i.e., one or more portions of an oligomer or other partially reacted or precursor polyimide composition reacted from or otherwise resulting from the dianhydride monomer), or (iii) the fully reacted form (one or more portions of a polyimide derived from or otherwise resulting from the dianhydride monomer).

[0017] The dianhydride can be functionalized with one or more sites, depending on the particular embodiment selected in the practice of this invention. Indeed, the term "dianhydride" is not intended to be limiting (or to be interpreted literally) with respect to the number of anhydride sites in the dianhydride component. For example, (i), (ii), and (iii) (in the paragraph above) include organic materials that can have two, one, or zero anhydride sites, depending on whether the anhydride is in a precursor state or a reacted state. Alternatively, the dianhydride component can be functionalized with additional anhydride-type sites (in addition to the anhydride sites that react with the diamine to provide the polyimide). Such additional anhydride sites could be used to crosslink the polymer or provide other functionality to the polymer.

[0018] The polymer film can be made using any one of several polymer manufacturing processes. It would be impossible to discuss or describe all possible polymer manufacturing processes useful in the practice of the present invention. It should be understood that the monomer system of the present invention can provide the above-mentioned advantageous properties in various manufacturing processes. The composition of the present invention can be manufactured as described herein, and can be easily manufactured in any one of many (perhaps countless) ways by those skilled in the art using any conventional or unconventional polymer manufacturing technology.

[0019] Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

[0020] When an amount, concentration, or other value or parameter is described as a range, a preferred range, or a list of upper and lower preferred values, this should be understood to specifically disclose all ranges formed from any pairing of any upper range or preferred value with any lower range or preferred value, regardless of whether the ranges are individually disclosed. When a range of numerical values ​​is recited herein, unless otherwise specified, the range is intended to include the endpoints and all integers and fractions within the range. The scope of the present invention is not intended to be limited to the specific values ​​recited when defining a range.

[0021] It should be understood that when describing particular polymers, applicants may refer to polymers by the monomers used to make them or the amounts of monomers used to make them. Such descriptions may not include the specific nomenclature used to describe the final polymer, or may not include product-by-process terminology, but any such reference to monomers and amounts should be interpreted to mean that the polymer is made from those monomers or amounts of monomers and the corresponding polymers and their compositions.

[0022] The materials, methods, and examples herein are illustrative only and, except as specifically stated, are not intended to be limiting.

[0023] As used herein, the terms "comprise," "including," "includes," "including," "having," "having" or any other variation thereof are intended to cover a non-exclusive inclusion. For example, a method, process, article, or apparatus that includes a list of elements is not necessarily limited to only those elements and may include other elements not expressly listed or inherent to such method, process, article, or apparatus. Furthermore, unless expressly stated to the contrary, "or" means an inclusive or, not an exclusive or. For example, condition A or B is satisfied by any one of the following: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and A and B are both true (or exist).

[0024] Also, the use of "a" or "an" is used to describe elements and components of the invention. This is done merely for convenience and to give a general sense of the invention. This description should be read to include one or at least one, and the singular also includes the plural unless it is clear that otherwise is meant.

[0025] (organic solvent) Organic solvents useful in synthesizing the polymers of the present invention are preferably capable of dissolving the polymer precursor materials. Such solvents should also have a relatively low boiling point, such as less than 225°C, so that the polymer can be dried at moderate (i.e., more convenient and less costly) temperatures. Boiling points less than 210, 205, 200, 195, 190, or 180°C are preferred.

[0026] Useful organic solvents include N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetramethylurea (TMU), glycol ethyl ether, diethylene glycol diethyl ether, 1,2-dimethoxyethane (monoglyme), diethylene glycol dimethyl ether (diglyme), 1,2-bis-(2-methoxyethoxy)ethane (triglyme), γ-butyrolactone, and bis-(2-methoxyethyl)ether, tetrahydrofuran (THF), ethyl acetate, hydroxyethyl acetate glycol monoacetate, acetone, and mixtures thereof. In one embodiment, preferred solvents include N-methylpyrrolidone (NMP) and N,N-dimethylacetamide (DMAc).

[0027] (diamine) In one embodiment, diamines suitable for forming polyimide films include aliphatic diamines such as 1,2-diaminoethane, 1,6-diaminohexane (HMD), 1,4-diaminobutane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane (DMD), 1,11-diaminoundecane, 1,12-diaminododecane (DDD), 1,16-hexadecamethylenediamine, 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, isophoronediamine, bicyclo[2.2.2]octane-1,4-diamine, and combinations thereof. Other aliphatic diamines suitable for practicing the present invention include those having 6 to 12 carbon atoms or combinations of long-chain and short-chain diamines, as long as both flexibility and flexibility are maintained. Long-chain aliphatic diamines enhance flexibility.

[0028] In one embodiment, suitable diamines for forming the polymer backbone include 2,2′-bis(trifluoromethyl)benzidine (TFMB), trifluoromethyl-2,4-diaminobenzene, trifluoromethyl-3,5-diaminobenzene, 2,2′-bis-(4-aminophenyl)-hexafluoropropane, 4,4′-diamino-2,2′-trifluoromethyldiphenyloxide, 3,3′-diamino-5,5′-trifluoromethyldiphenyloxide, 9,9′-bis(4-aminophenyl)fluorene, 4,4′-trifluoromethyldiphenyloxide, 9,9′-bis(4-aminophenyl)fluorene, 9,9 ... Oromethyl-2,2'-diaminobiphenyl, 4,4'-oxy-bis-[2-trifluoromethyl)benzenamine] (1,2,4-OBABTF), 4,4'-oxy-bis-[3-trifluoromethyl)benzenamine], 4,4'-thio-bis-[(2-trifluoromethyl)benzenamine], 4,4'-thiobis[(3-trifluoromethyl)benzenamine], 4,4'-sulfoxyl-bis-[(2-trifluoromethyl)benzenamine], 4,4'-sulfoxyl-bis-[(3-trifluoromethyl)benzenamine] ], 4,4'-keto-bis-[(2-trifluoromethyl)benzenamine], 1,1-bis[4'-(4''-amino-2''-trifluoromethylphenoxy)phenyl]cyclopentane, 1,1-bis[4'-(4''-amino-2''-trifluoromethylphenoxy)phenyl]cyclohexane, 2-trifluoromethyl-4,4'-diaminodiphenyl ether, 1,4-(2'-trifluoromethyl-4',4''-diaminodiphenoxy)-benzene, 1,4-bis(4'-aminophenoxy)-2-[(3',5'-dito trifluoromethyl)phenyl]benzene, 1,4-bis[2'-cyano-3'(''4-aminophenoxy)phenoxy]-2-[(3',5'-ditrifluoro-methyl)phenyl]benzene (6FC-diamine), 3,5-diamino-4-methyl-2',3',5',6'-tetrafluoro-4'-trifluoromethyldiphenyloxide, 2,2-bis[4'(4''-aminophenoxy)phenyl]phthalein-3',5'-bis(trifluoromethyl)anilide (6FADAP) and 3,3',5,5'-tetrafluoro-4,Further examples of fluorinated aromatic diamines include 4'-diamino-diphenylmethane (TFDAM). In a specific embodiment, the fluorinated diamine is 2,2'-bis(trifluoromethyl)benzidine (TFMB). In one embodiment, the fluorinated aromatic diamine can be present in a range of 40 to 95 mole percent based on the total diamine components of the polyimide. In a more specific embodiment, the fluorinated aromatic diamine can be present in a range of 50 to 75 mole percent based on the total diamine components of the polyimide.

[0029] In one embodiment, p-phenylenediamine (PPD), m-phenylenediamine (MPD), 2,5-dimethyl-1,4-diaminobenzene, 2,5-dimethyl-1,4-phenylenediamine (DPX), 2,2-bis-(4-aminophenyl)propane, 1,4-naphthalenediamine, 1,5-naphthalenediamine, 4,4′-diaminobiphenyl, 4,4″-diaminoterphenyl, 4,4′-diaminobenzanilide, 4,4′-diaminophenylbenzoate, 4, 4'-Diaminobenzophenone, 4,4'-diaminodiphenylmethane (MDA), 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, bis-(4-(4-aminophenoxy)phenyl sulfone (BAPS), 4,4'-bis-(aminophenoxy)biphenyl (BAPB), 4,4'-diaminodiphenyl ether (ODA), 3,4'-diaminodiphenyl ether, 4,4'-diaminobenzof phenol, 4,4'-isopropylidenedianiline, 2,2'-bis-(3-aminophenyl)propane, N,N-bis-(4-aminophenyl)-n-butylamine, N,N-bis-(4-aminophenyl)methylamine, 1,5-diaminonaphthalene, 3,3'-dimethyl-4,4'-diaminobiphenyl, m-aminobenzoyl-p-aminoanilide, 4-aminophenyl-3-aminobenzoate, N,N-bis-(4-aminophenyl)aniline, 2,4-diaminoto Any number of additional diamines can be used in forming the polyimide film, such as toluene, 2,5-diaminotoluene, 2,6-diaminotoluene, 2,4-diamine-5-chlorotoluene, 2,4-diamine-6-chlorotoluene, 2,4-bis-(β-amino-t-butyl)toluene, bis-(p-β-amino-t-butylphenyl)ether, p-bis-2-(2-methyl-4-aminopentyl)benzene, m-xylylenediamine, and p-xylylenediamine.

[0030] Other useful diamines include 1,2-bis-(4-aminophenoxy)benzene, 1,3-bis-(4-aminophenoxy)benzene (RODA), 1,2-bis-(3-aminophenoxy)benzene, 1,3-bis-(3-aminophenoxy)benzene, 1-(4-aminophenoxy)-3-(3-aminophenoxy)benzene, 1,4-bis-(4-aminophenoxy)benzene, 1,4-bis-(3-aminophenoxy)benzene, 1-(4-aminophenoxy)-4-(3-aminophenoxy)benzene, 2,2-bis-(4-[4-aminophenoxy]phenyl)propane (BAPP), 2,2′-bis-(4-phenoxyaniline)isopropylidene, 2,4,6-trimethyl-1,3-diaminobenzene, and 2,4,6-trimethyl-1,3-diaminobenzene.

[0031] Diamines that can be used in the polymer film include meta-phenylenediamine, para-phenylenediamine, 2,2-bis(4-aminophenyl)propane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 2,6-diaminopyridine, bis(3-aminophenyl)diethylsilane, benzidine, 3,3'-dichlorobenzidine, 3,3'-dimethoxybenzidine, 4,4'-diaminobenzophenone, N,N-bis(4-aminophenyl)-n-butyl ether ... m-xylylenediamine, p-xylylenediamine, positional isomers of the above, and mixtures thereof.

[0032] (dianhydride) In one embodiment, any number of suitable dianhydrides can be used to form the polymer film. The dianhydrides can be used in their tetraacid form (or as mono-, di-, tri-, or tetraesters of the tetraacid) or as their diester acid halides (chlorides). However, in some embodiments, the dianhydride forms can be preferred because they are generally more reactive than the acids or esters.

[0033] Examples of suitable dianhydrides include 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2-(3',4'-dicarboxyphenyl)5,6-dicarboxybenzimidazole dianhydride, 2-(3',4'-dicarboxyphenyl)5,6-dicarboxybenzoxazole dianhydride, 2-(3',4'-dicarboxyphenyl)5,6-dicarboxybenzothiazoline dianhydride, and 2-(3',4'-dicarboxyphenyl)5,6-dicarboxybenzothiazoline dianhydride. 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, bicyclo-[2,2,2]-octene-(7)-2,3,5,6-tetracarboxylic-2,3,5,6-dianhydride, 4,4'-thio-diphthalic anhydride, bis(3,4-dicarboxyphenyl)sulfonyl bis(3,4-dicarboxyphenyl) sulfoxide dianhydride (DSDA), bis(3,4-dicarboxyphenyloxadiazole-1,3,4)p-phenylene dianhydride, bis(3,4-dicarboxyphenyl)2,5-oxadiazole-1,3,4-dianhydride, bis-2,5-(3',4'-dicarboxydiphenyl ether)-1,3,4-oxadiazole dianhydride, 4,4'-oxydiphthalic anhydride (ODPA), bis(3,4-dicarboxyphenyl)thioether dianhydride, bisphenol A dianhydride (BPADA), bis Phenol S dianhydride, bis-1,3-isobenzofurandione, 1,4-bis(4,4'-oxyphthalic anhydride)benzene, bis(3,4-dicarboxyphenyl)methane dianhydride, cyclopentadienyl tetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride, ethylene tetracarboxylic dianhydride, perylene 3,4,9,10-tetracarboxylic dianhydride, pyromellitic dianhydride (PMDA), tetrahydrofuran tetracarboxylic dianhydride, 1,3-bis-(4,4'-oxydiphthalic anhydride)benzene, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, phenanthrene-1,8,9,10-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, and thiophene-2,3,4,5-tetracarboxylic dianhydride.

[0034] In one embodiment, suitable dianhydrides may include alicyclic dianhydrides such as cyclobutane dianhydride (CBDA), cyclohexane dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), hexahydro-4,8-ethano-1H,3H-benzo[1,2-c:4,5-c']difuran-1,3,5,7-tetrone (BODA), 3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic 1,4:2,3-dianhydride (TCA), and meso-butane-1,2,3,4-tetracarboxylic dianhydride.

[0035] In one embodiment, suitable dianhydrides for forming polymer films can include fluorinated dianhydrides such as 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 9,9-bis(trifluoromethyl)-2,3,6,7-xanthenetetracarboxylic dianhydride. In a particular embodiment, the fluorinated dianhydride is 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA).

[0036] Dianhydrides that can be used in the polymer film include pyromellitic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, naphthalene-2,3,6,7-tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 2,3,2',3'-benzophenonetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)sulfide dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propanhydride, Pan dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane, 3,4,4',4'-biphenyltetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, phenanthrene-1,8,9,10-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, and thiophene-2,3,4,5-tetracarboxylic dianhydride.

[0037] (polymer film) In one embodiment, the polymer film or layer can have a dielectric constant in the range of 3.0 to 4.5 when measured at 1 MHz according to the procedure set forth in IPC-TM 650 2.5.5.3. In one embodiment, the polymer film can have a coefficient of thermal expansion (CTE) in the X-Y axis in the range of 10 to 75 ppm / °C when measured over a temperature range of 50 to 250°C according to the procedure set forth in IPC-TM-650 2.4.41. In one embodiment, the polymer film can have a dielectric strength in the range of 3000 to 7000 V / mil when measured according to the procedure set forth in ASTM D149. In one embodiment, the polymer film has a thermal class H rating. In one embodiment, the polymer film has one or more of the aforementioned properties, but includes two, three, or more polymer layers.

[0038] Polymer films can be plasma-treated by passing them through an internal-electrode low-temperature plasma treatment device as described in Patent Document 5. The composition ratio of the number of oxygen atoms (O) to the number of carbon atoms (C) on the plasma-treated surface of the material exceeds 150% of the theoretical value of the ratio of the number of atoms before treatment. Methods for determining the composition ratio of the number of oxygen atoms (O) to the number of carbon atoms (C) on the surface of a material include X-ray photoelectron spectroscopy (XPS).

[0039] (flexible polymer layer) In one embodiment, the flexible polymer layer comprises a thermoplastic polymer having a glass transition temperature (Tg) in the range of 140 to 280° C. Suitable methods for determining Tg include, for example, using dynamic mechanical analysis (DMA) as described in ASTM E1640 or IPC-TM 650. In one embodiment, the thermoplastic polymer having a Tg in the range of 140 to 280° C. can include polyimide, polyamide, polycarbonate, polyester, polysulfone, poly(amide-imide), poly(ether-imide), poly(ether-sulfone), poly(ether-ether-sulfone), poly(phenyl-sulfone), bisphenol A polysulfone, poly(ether-ketone), poly(ether-ether-ketone), poly(1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylenecarbonyl), poly-para-phenylene copolymer, self-reinforced polyphenylene, perfluorosulfonic acid ionomer, or cyclic olefin copolymer.

[0040] In one embodiment, the flexible polymer layer comprises a polyimide film layer. In a more specific embodiment, the flexible polymer layer comprises a thermoplastic polyimide film layer. Polyimide film layers according to the present invention can be produced by combining a diamine and a dianhydride (monomer or other polyimide precursor form) together with a solvent to form a polyamic acid (also called polyamic acid) solution. The dianhydride and diamine can be combined in a molar ratio of about 0.90 to 1.10. The molecular weight of the polyamic acid formed therefrom can be adjusted by adjusting the molar ratio of the dianhydride to the diamine.

[0041] In one embodiment, the polyamic acid casting solution is derived from a polyamic acid solution. The polyamic acid casting solution preferably comprises a polyamic acid solution, optionally combined with conversion chemicals such as i) one or more dehydrating agents, such as fatty acid anhydrides (e.g., acetic anhydride) and / or aromatic acid anhydrides, and ii) one or more catalysts, such as aliphatic tertiary amines (e.g., triethylamine), aromatic tertiary amines (e.g., dimethylaniline), and heterocyclic tertiary amines (e.g., pyridine, picoline, isoquinoline). The anhydride dehydrating materials are often used in molar excess relative to the amount of amic acid groups in the polyamic acid. The amount of acetic anhydride used is typically about 2.0 to 4.0 moles per equivalent (repeating unit) of polyamic acid. Generally, a corresponding amount of tertiary amine catalyst is used.

[0042] In one embodiment, the polyamic acid solution, and / or polyamic acid casting solution, is dissolved in an organic solvent at a concentration of from about 5.0 or 10% by weight to about 15, 20, 25, 30, 35, or 40% by weight.

[0043] The polyamic acid (and casting solution) can further contain any one of several additives, such as processing aids (e.g., oligomers), antioxidants, light stabilizers, flame retardant additives, antistatic agents, heat stabilizers, UV absorbers, (organic or inorganic) fillers, or various reinforcing agents. Fillers can include inorganic fillers such as thermally conductive fillers, corona-resistant composite fillers, and conductive fillers such as metals, graphite carbon, and carbon fibers, as well as conductive polymers. Common inorganic fillers include alumina, silica, silicon carbide, diamond, clay, boron nitride, aluminum nitride, aluminum oxide, titanium dioxide, dicalcium phosphate, and fumed metal oxides. Common organic fillers include polyaniline, polythiophene, polypyrrole, polyphenylene vinylene, polydialkylfluorene, carbon black, graphite, multi-walled and single-walled carbon nanotubes and carbon nanofibers.

[0044] Examples of suitable thermally conductive fillers that are also electrically insulating include BN, AlN, Al2O3, Si3N4, ZnO, MgCO3, MgO, BeO, diamond, SiC, and many other oxide, nitride, and carbide compounds and mixtures thereof. These thermally conductive fillers can be of any shape or size and have an average primary particle size (D) ranging from about 0.001 to about 8 μm. 50 In one embodiment, the flexible polymer layer comprising the thermally conductive filler has a thermal conductivity of 0.4 W / mK or greater, or 0.6 W / mK or greater, when the thermal conductivity is measured according to the method described in ASTM D5470.

[0045] In one embodiment, the corona-resistant composite filler can have an organic component and an inorganic ceramic oxide component, and the weight ratio of the organic component to the inorganic ceramic oxide component can be between 0.01:1 and 1:1. In some embodiments, the weight ratio of the organic component to the inorganic ceramic oxide component can range between (and optionally includes) any two of the following values: 0.01:1, 0.05:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, and 1:1. In one embodiment, at least a portion of the organic component can include organosiloxane or organometalloxane moieties (e.g., organozirconate, organotitanate, organoaluminate). In one embodiment, the inorganic ceramic oxide component can include silica, alumina, titania, zirconia, or mixtures thereof. In one embodiment, the inorganic ceramic oxide component comprises silica, alumina, or a mixture thereof. In one embodiment, the inorganic ceramic oxide component is fumed alumina. In one embodiment, the organic component of the corona-resistant composite filler material is selected primarily to provide or improve dispersibility of the corona-resistant composite filler material in a particular solvating polymer matrix or polymer matrix precursor. In some embodiments, the organic component of the corona-resistant composite filler material is selected to reduce moisture absorption in the inorganic ceramic oxide component. Routine skill and experimentation may be required in optimizing the organic component for any particular solvent system selected. In some embodiments, the organosiloxane moiety is n-octylsilane, or one of its structural isomers. In some embodiments, the corona-resistant composite filler is an inorganic ceramic oxide that is free of the organic component. In another embodiment, the organic component is a coating on the inorganic ceramic oxide component. The organic component may or may not cover the entire surface of the inorganic ceramic oxide component. In one embodiment, the electrically insulating, corona-resistant composite filler is present in an amount between and including any two of the following values: 5, 10, 15, 20, 25, and 30 weight percent, based on the total weight of the polymer film.In one embodiment, the corona-resistant composite filler is present in an amount ranging from 5 to 30, 5 to 25, or 5 to 20 weight percent, based on the total weight of the polymer film. In one embodiment, the corona-resistant composite filler can have a median particle size of 0.1 to 5 μm, where at least 80, 85, 90, 92, 94, 95, 96, 98, 99, or 100 percent of the dispersed corona-resistant composite filler is within the size range specified above. The median particle size can be measured using a Horiba LA-930 particle size analyzer (Horiba Instruments, Inc., Irvine, CA). DMAc can be used as the dispersing medium. In some embodiments, the corona-resistant composite filler is a nanofiller. The term "nanofiller" is intended to mean a filler having at least one dimension less than 1000 nm, i.e., less than 1 μm.

[0046] In one embodiment, the filler is dispersed or suspended in a polar aprotic solvent, such as DMAC or any other solvent or mixture of solvents compatible with polyamic acid. In one embodiment, the filler can be dispersed in an organic solvent at a concentration of about 5, 10, or 15 wt % to about 20, 30, 40, 50, or 75 wt %. In one embodiment, the solvent used for the filler dispersion or suspension can be the same or different from the solvent used for the polyamic acid solution. The filler dispersion or suspension can then be added to the polyamic acid casting solution to achieve the desired filler loading in the final film. The filler can be added using any commonly used technique, such as batch mixing using a solvent, dry mixing, or continuous mixing using a solvent. Parameters such as the order of ingredient addition, mixing speed, shear rate, type of mixing blade (e.g., shear blade), mixing time, temperature, and pressure are known to affect the final degree of mixing between the filler and the matrix material. In one embodiment, blending of the filler slurry and the polyamic acid solution to form the filled polyamic acid casting solution is performed using high shear mixing. In one embodiment, the first outer layer of a multilayer film may comprise a filler amount of greater than 0 to about 50% by weight of the dry film. In one embodiment, the core layer of a multilayer film may comprise a filler amount of greater than 0 to about 60% by weight of the dry film. In one embodiment, the second outer layer of a multilayer film may comprise a filler amount of greater than 0 to about 50% by weight of the dry film. In one embodiment, the first outer layer, core layer, and second outer layer can each have the same or different amount of filler, based on weight percent of the dry film, as the other layers of the multilayer film. In one embodiment, the weight percent of filler in the core layer may be higher than the weight percent of the first outer layer, the second outer layer, or both the first and second outer layers. In another embodiment, the weight percent of filler in the core layer can be lower than the weight percent of the first outer layer, the second outer layer, or both the first and second outer layers. In another embodiment, in a multilayer film, only the core layer contains filler, or conversely, only the outer layers contain filler.In one embodiment, the presence of a filler in a flexible polymer layer results in an improved failure time in a voltage endurance test compared to a flexible polymer layer of comparable thickness that does not contain significant amounts of filler when tested for voltage endurance according to the method described in ASTM D2275. The amount of filler present in a given layer can be determined using, for example, an ash test or thermogravimetric analysis (TGA). The chemical identity of the filler can be determined by mechanical preparation of cross sections in conjunction with microscopy-assisted optical evaluation using, for example, a scanning electron microscope using energy dispersive X-ray (EDX) analysis.

[0047] The solvated mixture (optionally further comprising a filler-containing polyamic acid casting solution) can then be cast or coated onto a support such as an endless belt or a rotating drum to provide a film. The solvent-containing film can then be converted into a free-standing film by heating (thermal curing) at an appropriate temperature in conjunction with a converting chemical reactant (chemical cure). The film can then be separated from the support and oriented, such as by tentering, while the thermal and chemical cure continues, to provide a polyimide film.

[0048] Useful methods for producing polyimide films according to the present invention can be found in U.S. Patent Nos. 5,629,999 and 5,629,999, which are incorporated herein by reference for all teachings therein. Many variations are also possible, such as: (a) A method in which the diamine and dianhydride components are premixed together and then added portionwise to the solvent while the mixture is being stirred. (b) A method in which the solvent is added to a stirred mixture of the diamine and dianhydride components (as opposed to (a) above). (c) A method in which the diamine is dissolved exclusively in a solvent and then the dianhydride is added thereto in a ratio that makes it possible to control the reaction rate. (d) A method in which the dianhydride component is dissolved exclusively in a solvent and then the amine component is added thereto in a ratio that makes it possible to control the reaction rate. (e) A method in which the diamine component and the dianhydride component are dissolved separately in a solvent and then these solutions are mixed in a reactor. (f) A process in which a polyamic acid containing an excess of an amine component and another polyamic acid containing an excess of a dianhydride component are preformed and then reacted with each other in a reactor in a manner that allows the formation of, inter alia, non-random or block copolymers. (g) A specific portion of the amine and dianhydride components are reacted first, followed by the remaining diamine component, or vice versa. (h) A method in which a conversion chemical is mixed with a polyamic acid to form a polyamic acid casting solution, which is then cast to form a gel film. (i) A method in which the ingredients are added, partially or as a whole, in any order, to either some or all of the solvent, and any ingredient may be added in part or all as a solution in some or all of the solvent. (j) One of the dianhydride components is first reacted with one of the diamine components to obtain a first polyamic acid, and then the other dianhydride component is reacted with the other amine component to obtain a second polyamic acid, which are then combined by any one of several methods before forming a film.

[0049] A polymer film layer can include two or more layers, with one or more polymer layers disposed on top of the first layer. The composition and thickness of each layer are selected independently and can be the same or different. As a result, the mechanical, thermal, and optical properties of each layer in a multilayer polymer film can be the same or different from those of the surrounding layers. In one embodiment, a multilayer film has at least two polymer layers. In another embodiment, a multilayer film has fewer than 10 layers. In one embodiment, a multilayer polymer film includes at least one core layer and two thermoplastic polymer layers. In a specific embodiment, the outermost layer of a multilayer polymer film having at least two layers is a thermoplastic polymer layer. In one embodiment, the polymer of each layer is a polyimide. In a more specific embodiment, the outermost layer of a multilayer polyimide film having at least three layers is a thermoplastic polyimide layer, in addition to the core polyimide layer as an inner layer. In the case of a multilayer polyimide film, the Tg of the core layer is higher than that of the thermoplastic polyimide layer.

[0050] The thickness of each polymer layer can be adjusted depending on the intended purpose or end-use specifications of the film. In one embodiment, the multilayer film has a total thickness of about 5 to about 150 μm. In one embodiment, the multilayer film has a total thickness of about 5 to about 75 μm. In one embodiment, the core layer thickness ranges from about 35 to about 73% of the total thickness of the multilayer film. For example, a multilayer film can have a total thickness of 30 μm with a 22 μm core layer and 4 μm first and second outer layers on either side of the core layer. In another example, for a thicker film, the multilayer film can have a total thickness of 50 μm with a 34 μm core layer and 7 μm first and second outer layers on either side of the core layer. In yet another example, for a very thin film, the multilayer film can have a total thickness of 5 μm with a 2 μm core layer and 1.5 μm first and second outer layers on either side of the core layer. In one embodiment, the thickness of the core layer is in the range of about 55 to about 73% of the total thickness of the multilayer film. Those skilled in the art will understand that a minimum thickness of the outer layer comprising the thermoplastic polyimide is necessary to provide sufficient adhesion when laminated to other layers. Additionally, a minimum thickness of the core layer is required to maintain the mechanical integrity of the multilayer film. Methods for determining the thickness of each layer include mechanical preparation of cross sections along with microscopy-assisted optical evaluation using, for example, a scanning electron microscope.

[0051] In one embodiment, the first thermoplastic polyimide and the second thermoplastic polyimide of the multilayer film both have a T in the range of about 140 to about 320°C. g In certain embodiments, the first thermoplastic polyimide and the second thermoplastic polyimide of the multilayer film both have a T in the range of about 160 to about 300°C. g In a more specific embodiment, both the first thermoplastic polyimide and the second thermoplastic polyimide of the multilayer film have a T in the range of about 180 to about 280°C. g Higher T gThe outer layer of a thermoplastic polyimide improves the thermal durability of the multilayer film. The laminate may undergo post-lamination processes such as hot bar treatment or spot welding, which can reach temperatures in excess of 300°C. Under these conditions, a low T g The thermoplastic polyimide layers are susceptible to adhesion loss and delamination, distortion, and blistering.

[0052] In one embodiment, the first and second thermoplastic polyimides of the multilayer film are each independently derived from an aromatic dianhydride selected from the group consisting of 4,4'-oxydiphthalic dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and mixtures thereof, and an aromatic diamine selected from the group consisting of 1,3-bis(4-aminophenoxy)benzene, hexamethylenediamine, 2,2-bis(4-[4-aminophenoxy]phenyl)propane, and mixtures thereof. In one embodiment, the first and second thermoplastic polyimides of the multilayer film are each independently derived from an aromatic dianhydride comprising 4,4'-oxydiphthalic dianhydride and pyromellitic dianhydride, and an aromatic diamine comprising 1,3-bis(4-aminophenoxy)benzene.

[0053] In one embodiment, the core layer has a Tg greater than 320° C. In a more particular embodiment, the core layer has a Tg greater than 340° C. In another particular embodiment, the core layer has no detectable Tg less than 375° C.

[0054] In one embodiment, the core and outer layers can be solution cast simultaneously by coextrusion. At the time of casting, the polyimide can be in the form of a polyamic acid solution. The cast solution forms an uncured polyamic acid film that subsequently cures to the polyimide. The adhesive strength of such a laminate can be improved by using various techniques to enhance adhesive strength.

[0055] In some embodiments, the resulting polyamic acid solution is filtered and pumped to a slot die, where the streams are split in a manner to form the first and second outer layers of a three-layer coextruded film. In some embodiments, the second stream of polyimide is filtered and then pumped to a casting die in a manner to form the central polyimide core layer of the three-layer coextruded film. The solution flow rate can be adjusted to achieve the desired layer thickness.

[0056] In some embodiments, multilayer films are prepared by co-extruding a first outer layer, a core layer, and a second outer layer. In some embodiments, the layers are extruded through a single-cavity or multiple-cavity extrusion die. In another embodiment, the multilayer film is produced using a single-cavity die. When a single-cavity die is used, the laminar flow should be of sufficiently high viscosity to prevent mixing of the streams and provide uniform layering. In some embodiments, the multilayer film is made by casting from a slot die onto a moving stainless steel belt. In one embodiment, the belt is then passed through a convection oven to evaporate the solvent and partially imidize the polymer, resulting in a "green" film. The green film can be stripped from the casting belt and wound up. The green film can then be passed through a tenter oven to produce a fully cured polyimide film. In some embodiments, shrinkage during tentering can be minimized by restraining the film along the edges (i.e., using clips or pins).

[0057] In one embodiment, the outer layer of the present invention can also be applied to the core layer during an intermediate manufacturing step that converts the polyimide film into a gel film or into a green film, or the like.

[0058] The term "gel film" refers to a polyamic acid sheet that can be formed in a chemical conversion process, saturated with volatile materials, primarily solvents, to such an extent that the polyamic acid is in a gel-swollen or rubbery state. The volatile material content typically ranges from 70 to 90% by weight of the gel film, and the polymer content typically ranges from 10 to 30% by weight. The final film becomes "free-standing" at the gel film stage; it can be peeled from the support onto which it was cast and heated to a final cure temperature. Gel films generally have an amic acid to imide ratio of 10:90 to 50:50, most often 30:70.

[0059] Gel film structures can be prepared by the method described in U.S. Patent No. 6,273,666. This patent discloses mixing a chemical converting agent and a catalyst, such as a lower fatty acid anhydride and a tertiary amine, into a polyamic acid solution at low temperature. This is followed by casting the polyamic acid solution in the form of a film onto a casting drum. The film is gently heated after casting, e.g., to 100°C, to activate the converting agent and catalyst, converting the cast film into a polyamic acid / polyimide gel film.

[0060] Another type of polyimide-based film is a "green film" that is partially polyamic acid and partially polyimide and can be formed in a thermal conversion process. Green films generally contain about 50-75% by weight of polymer and 25-50% by weight of solvent. Generally, it should be strong enough to be substantially self-supporting. Green films can be made by casting a polyamic acid solution into film form on a suitable support, such as a casting drum or belt, and removing the solvent by gentle heating at up to 150°C. A small percentage of the amic acid units in the polymer, e.g., up to 25%, can be converted to imide units.

[0061] The application of the polymeric films of the invention can be accomplished in a number of ways. These methods include the use of a slot die, dip coating, or kiss-roll coating of the film, followed by metering with a doctor knife, doctor roll, squeeze roll, or air knife. The coating can also be applied by brushing or spraying. Using such techniques, it is possible to prepare both one-sided and two-sided coated laminates. In preparing two-sided coated structures, the coatings can be applied to both sides of the polyimide either simultaneously or sequentially before proceeding to the polyimide curing and drying steps.

[0062] In one embodiment, the coefficient of thermal expansion (CTE) of the individual polymer layers or the entire polymer multilayer film is less than 70 ppm / °C (averaged over the machine and transverse directions), less than 40 ppm / °C, or less than 30 ppm / °C over a temperature range of 50 to 250°C. The thermoplastic polymer layers and the core layer in the multilayer film may have different CTE values ​​(when evaluated individually as a stand-alone film). In one embodiment, the CTE value of the core layer in the multilayer film is lower than the CTE value of the thermoplastic polymer layers (when evaluated individually as a stand-alone film). In one embodiment, the coefficient of thermal expansion of the core layer is less than 70 ppm / °C (averaged over the machine and transverse directions), less than 40 ppm / °C, or less than 30 ppm / °C over a temperature range of 50 to 250°C. Maintaining a low CTE over a wide temperature range allows the multilayer film to maintain good adhesion during higher temperature curing and can be used to stabilize materials subjected to higher temperature post-lamination processes. Laminates may be subjected to hot bar processing or spot welding, which can exceed 300°C. Under these conditions, multilayer films with high CTEs are prone to adhesion loss and delamination, distortion, and blistering. Suitable methods for determining CTE include measurements performed using a thermomechanical analyzer (TMA), as described in ASTM D3386, for example. In one embodiment, the multilayer film has a CTE close to that of the flexible matte layer (described below). Matching the CTE between the multilayer film and the flexible matte layer will minimize the risk of distortion, wrinkling, and curling when combining such layers into a laminate structure.

[0063] (flexible mat layer) In one embodiment, the first flexible mat layer comprises a first organic material thermally bonded to the flexible polymer layer, the first organic material comprising a woven fabric, a nonwoven fabric, or fibers. The first organic material may comprise 35-75 wt. % of the first binder and 25-65 wt. % of the first aramid flock, based on the total amount of the first binder and the first flock in the first flexible mat layer. In some embodiments, the first organic material comprises 40-60 wt. % of the first binder and 40-60 wt. % of the first aramid flock, based on the total amount of the first binder and the first flock in the first flexible mat layer. In some embodiments, the first flexible mat layer has more binder than flock.

[0064] The use of this first flexible mat layer provides electrical insulation laminate structures with higher mechanical strength, which is desirable when used in electromechanical applications. On an equal weight basis, multilayer structures including the first flexible mat layer have superior mechanical strength compared to structures having only a flexible polymer layer. Preferably, the first flexible mat layer is free of, or essentially free of, any inorganic fillers. As used herein, "essentially free" means that the first flexible mat layer functions thermally and mechanically as if no inorganic fillers were present in the layer, even if some trace amounts of inorganic filler contamination are present in the layer. In one embodiment, the binder can be any chemical, treatment, or additive known in the art for binding flock or fibrous materials to form paper, but in one embodiment, the binder is binder particles, e.g., particles having a filmy structure. In one embodiment, the binder particles can be fibrids, such as aramid fibrids.

[0065] As used herein, the term "floc" refers to fibers that have been cut into short lengths and are commonly used in the preparation of wet-laid sheets and / or paper. Typically, floc has a length of about 3 to about 20 mm. In one embodiment, floc has a length of about 3 to about 7 mm. Floc is usually made by cutting continuous fibers to the required length using methods well known in the art.

[0066] As used herein, the term "aramid" refers to an aromatic polyamide in which at least 85% of the amide (-CONH-) linkages are directly attached to two aromatic rings. Optionally, additives may be used with the aramid and dispersed throughout the polymer structure. It has been found that up to about 10 weight percent of other polymeric materials can be blended with the aramid. It has also been found that copolymers having up to about 10 mole percent of other diamines substituting for the diamines of the aramid, or up to about 10 mole percent of other diacid chlorides substituting for the diacid chlorides of the aramid, can be used.

[0067] In one embodiment, the aramid is a meta-aramid. An aramid polymer is considered to be a meta-aramid when two rings or radicals are oriented meta to each other along the molecular chain. In one embodiment, the meta-aramid is poly(meta-phenylene isophthalamide) (MPD-I). U.S. Patent Nos. 5,629,999, 5,729,969, 5,733,979, 5,749,983, 5,759,995, and 5,823,063 describe useful methods for producing aramid fibers that can be used to make aramid floc.

[0068] Alternatively, the aramid floc can be a para-aramid or an aramid copolymer. An aramid polymer is considered to be para-aramid when two rings or radicals are oriented para to each other along the molecular chain. Methods for making para-aramid fibers are generally disclosed, for example, in U.S. Patent Nos. 5,629, 5,729, 5,739, 5,749, 5,759, 5,769, 5,800, 5,929, 5,949, 5,959, 5,969, 5,979, 5,980, 5,990, 6,000. In one embodiment, the para-aramid is poly(paraphenylene terephthalamide). In one embodiment, the para-aramid copolymer is copoly(p-phenylene / 3,4' diphenyl ester terephthalamide).

[0069] In one embodiment, the aramid floc is meta-aramid floc, for example, floc made from meta-aramid poly(meta-phenylene isophthalamide) (MPD-I).

[0070] As used herein, the term "fibrid" refers to very small, non-granular, fibrous, or film-like particles having at least one of their three dimensions smaller than the largest dimension. These particles are produced by precipitating a solution of a polymeric material using a non-solvent under high shear. Aramid fibrids are non-granular, film-like particles of aromatic polyamides having a melting point or decomposition point above 320°C. Preferred aramid fibrids are meta-aramid fibrids, and particularly preferred are fibrids made from meta-aramid poly(meta-phenylene isophthalamide) (MPD-I). Aramid fibrids can be produced as generally described in U.S. Patent No. 5,629,999.

[0071] Fibrids generally have a maximum length dimension in the range of about 0.1 mm to about 1 mm with a length-to-width aspect ratio of about 5:1 to about 10:1. Thickness dimensions are on the order of a fraction of a micron, e.g., about 0.1 μm to about 1.0 μm. Although not required, the aramid fibrids can be incorporated into the layer while they are in a wet state.

[0072] As used herein, the term "flexible matte layer" refers to a thin, planar material of a particular composition that may be described as "paper." Paper can be produced as generally described in U.S. Patent Nos. 5,629,999; 5,629,999; and 5,629,999.

[0073] In one embodiment, the flexible mat layer has a thickness of 0.5 mm or less, 0.25 mm or less, 0.13 mm or less, or 0.1 mm or less. It is believed that an individual flexible mat layer needs to have a thickness of at least 0.025 mm to provide sufficient tensile strength for the electrical insulation laminate. An example of a flexible mat layer product is DuPont™ Nomex® paper (available from DuPont de Nemours Inc., Wilmington, DE).

[0074] In one embodiment, the flexible mat layer has a dielectric strength in the range of 400 to 800 V / mil, as measured according to the procedure set forth in ASTM D149. In one embodiment, the flexible mat layer has a dielectric constant in the range of 1.5 to 4.0, as measured at 60 Hz according to the procedure set forth in ASTM D150. In one embodiment, the flexible mat layer has desirable mechanical properties, such as a high tensile strength in the range of 40 to 200 N / cm in the machine direction (MD) and 5 to 20 N / cm in the transverse direction (TD), as measured according to the procedure set forth in ASTM D828, and an elongation at break in the range of 10 to 25% in the MD and 5 to 20% in the TD. In one embodiment, the flexible mat layer has a heat resistance class H rating.

[0075] In one embodiment, the flexible mat layer has a Tg greater than 320° C. In a more particular embodiment, the flexible mat layer has a Tg greater than 340° C. In another embodiment, the flexible mat layer has a Tg greater than 360° C.

[0076] In one embodiment, the flexible mat layer can be plasma treated by passing it through an inner-electrode low-temperature plasma treatment apparatus as described in Patent Document 21. The composition ratio of the number of oxygen atoms (O) to the number of carbon atoms (C) at the plasma-treated surface of the material exceeds 150% of the theoretical value of the ratio of the number of atoms before treatment.

[0077] (Preparation of Electrical Insulation Laminate) In one embodiment, a flexible mat layer is disposed on one or both sides of the electrical insulation laminate, and a polymer film is disposed as the core layer of the laminate. The flexible mat layer ensures satisfactory electrical insulation, chemical stability (chemical resistance), mechanical stability, and heat resistance, while the polymer film ensures not only satisfactory chemical stability and heat resistance, but also additional electrical insulation and gas / liquid impermeability. The individual layers can be laminated together by any method commonly used in the field that can apply temperature and pressure to the materials being laminated during the process. In one embodiment, methods for forming the electrical insulation laminate include heating, pressing, heating under pressure, etc. Examples of these methods include, but are not limited to, methods based on hot pressing, passing between a pair of heated rolls or belts, using hot air, ultrasonic bonding, etc. Here, it is desirable to raise the temperature for forming the laminate above the Tg of the polymer layer (or the individual thermoplastic polyimide layers in the case of a multilayer polyimide film), but not to raise the temperature for forming the laminate to a temperature close to, but lower than, the melting point or decomposition temperature of any layer. In one embodiment, the temperature used to form the laminate does not exceed the glass transition temperature of the polymer layers (or the individual thermoplastic polyimide layers in the case of a multilayer polyimide film) by more than 150°C.

[0078] The dimensions of the flexible mat layer and the polymer film are not limited to a specific size. The size to be used can be determined by taking into account various factors such as the application of the electrical insulation laminate, production costs, and existing equipment limitations. From the viewpoint of productivity, rolls of the flexible mat layer and rolls of the polymer film are prepared, and the laminate is manufactured using a continuous heating and pressure process. In the production of prototypes or custom products, the use of small-sized flexible mat layers and polymer films can make production more convenient.

[0079] The heating and pressure process refers to a process that applies both heat and pressure to a laminate. The device for performing the heating and pressure process is not limited to a specific device, but in one embodiment, a calendering device is used. Calendering devices are widely used in the industrial field and are formed by combining several calendering rolls. They apply a compressive force to a sheet target by passing the target between the rolls. By passing the target between the calendering rolls, the density of the target can be increased and the smoothness of the target can be improved. Rolls of appropriate size, such as steel rolls and elastic rolls, made of appropriate materials are selected depending on the pressure and temperature conditions to be applied to the target. The configuration of the calendering rolls is not limited to a specific configuration. A laminate in which different materials are laminated together can be produced by passing multiple sheet targets between the calendering rolls. An appropriate calendering device is selected depending on the dimensions of the sheets to be laminated. For example, if the flexible mat layer and the polymer film to be laminated have a long length and are in roll form, a calendering device with a paper feed function for two or more rolls can be used.

[0080] In one embodiment, the flexible mat layer and the polymer film are directly laminated to each other without an additional adhesive layer between them. This method can reduce manufacturing costs and improve productivity. The present invention can produce an electrical insulation laminate with sufficient bonding properties without the presence of an adhesive layer. Methods for determining the absence of an additional adhesive layer include mechanical preparation of cross sections, such as with a microscope-assisted optical evaluation using a scanning electron microscope, or with a mechanical evaluation using nanoindentation.

[0081] In one embodiment, the bonding surface between the flexible mat layer and the polymer film is not plasma treated before the heat and pressure process. Although the bonding properties can be improved by plasma treating the bonding surface, the present invention can produce an electrical insulation laminate with sufficient bonding properties without plasma treatment. Using a process for producing a laminate without plasma treatment can reduce manufacturing costs and improve productivity.

[0082] The temperature in the heat and pressure process is set to at least the glass transition temperature of the polyimide material forming the laminate. If the heat and pressure process is carried out using a calender roll, the temperature of the calender roll is set to at least the glass transition temperature of the polyimide forming the laminate.

[0083] In one embodiment, a temperature in the range of 200 to 360°C can be used in the heating and pressure process. In certain embodiments, a temperature in the range of 240 to 340°C or 260 to 320°C can be used. The temperature in the heating and pressure process can generally be adjusted by using the control mechanism of the device used. For example, the temperature of a heat and pressure application device such as a calender roll can be controlled as the set temperature of the calender roll.

[0084] In one embodiment, in addition to the specific temperatures described above, a pressure in the range of 400 to 800 psi (2758 to 5516 kPa) can be used in the heating and pressure process. In certain embodiments, a pressure in the range of 450 to 750 psi (3103 to 5171 kPa), 500 to 700 psi (3447 to 4826 kPa), or 525 to 675 psi (3620 to 4654 kPa) can be used. The pressure in the heating and pressure process can generally be adjusted using the control mechanism of the device used. For example, the pressure of a heat and pressure application device such as a calender roll can generally be controlled using the control mechanism of the device.

[0085] In one embodiment of the electrical insulation laminate, the composition ratio of the number of oxygen atoms (O) to the number of carbon atoms (C) at the surface of the first thermoplastic polyimide layer differs by less than 1% compared to the same ratio found in the bulk of the first thermoplastic polyimide layer. In one embodiment, the composition ratio of the number of oxygen atoms (O) to the number of carbon atoms (C) at the surface of the first organic material differs by less than 1% compared to the same ratio found in the bulk of the first organic material.

[0086] In one embodiment of the electrical insulation laminate, the flexible polymer layer and the first flexible mat layer each have a heat class rating of at least H. In one embodiment of the electrical insulation laminate, the flexible polymer layer has a dielectric strength of at least 5000 V / mil and the first flexible mat layer has a dielectric strength of at least 400 V / mil. In one embodiment of the electrical insulation laminate, the peel strength between the flexible polymer layer and the first flexible matte layer is at least 0.100 N / mm.

[0087] The electrical insulation laminates of the present invention are useful in electric machines, for example, as slot liners for stators and rotors of generators and motors, providing electrical insulation between the stator core and / or rotor core and the stator windings and / or rotor windings. Similarly, the slot liners separate the rotor windings from the rotor core. In one embodiment, the electrical insulation laminate is used as a slot liner in folded sheet form. In another embodiment, the electrical insulation laminate is used as a slot liner in tubular form, more preferably as a multi-layer spiral tube made without overlapping layers, i.e., the thickness of the tube around its circumference is uniform throughout. [Example]

[0088] (Test Method) (peel strength) Peel strength results were obtained using an Instron 180° T peel test. Laminate specimens were 1 inch wide with an initial grip separation of 2 inches and were evaluated using a crosshead speed of 12 inches / minute. The maximum observed load was reported as achieved after 3 inches of extension. The numerical average of five independent specimens was reported.

[0089] (glass transition temperature) The glass transition temperature (T g ) was measured according to test method IPC-TM-650 using dynamic mechanical analysis (Q800 DMA, TA Instruments, New Castle, Del.). Specimens were conditioned at 23°C and 50% relative humidity for at least 24 hours before testing. Heat was applied at a rate of 5°C / min in dry air, and values ​​for the first tan δ peak were reported unless otherwise stated.

[0090] For selected samples, the glass transition temperature (Tg) of each material was measured using differential scanning calorimetry using the method described in US Pat. No. 5,999,499.

[0091] (thermal conductivity) Thermal conductivity was measured at 50°C and 150 psi without oil according to the method described in ASTM D5470. One, two, and four layers of material were used.

[0092] (Tensile test) Tensile tests allowing the determination of mechanical properties such as elongation at break, tensile strength and modulus were carried out according to ASTM D882.

[0093] (coefficient of thermal expansion) Testing was performed according to ASTM D3386. The reported results are the average of the CTE observed in both the cross direction (TD) and machine direction (MD).

[0094] Example 1 In Example 1 (E1), to prepare a polyamic acid solution with a monomer composition of BPDA 0.9 / BTDA 0.1 / RODA 0.25 / HMD 0.75, 0.05 moles of diamine were dissolved in DMAc and stirred under nitrogen using a mechanical stirrer. With continued stirring, 0.05 moles of dianhydride was added as a solid over a short period of time. The polyamic acid solution, approximately 20 wt.% solids, was decanted and then finished by incrementally adding a 6 wt.% solution of pyromellitic dianhydride (PMDA) in DMAc to obtain a maximum viscosity of 2500-3000 poise. Using a stainless steel casting rod, the polymer mixture was manually cast onto a glass plate and placed on a hot plate set at 80 °C. The film was heated until it could be peeled from the glass plate and transferred to a pin frame. The film was then imidized by heating in an oven to a temperature 100°C to approximately 20°C higher than the glass transition temperature of the final polyimide film. The film was then removed from the oven, allowed to cool to ambient temperature, and then removed from the pin frame. In this way, a polyimide film with a thickness of approximately 25 μm and a glass transition temperature of 199°C was obtained.

[0095] Example 2 In Example 2 (E2), a first polyamic acid solution "A" with a monomer composition of ODPA 0.8 / PMDA 0.2 / / RODA 0.7 / HMD 0.3 was prepared by following the procedure described above for E1. A second polyamic acid solution "B" with a monomer composition of BPDA 0.9 / PMDA 0.1 / / PPD 0.9 / ODA 0.1 was prepared by following the procedure described above for E1. Both polyamic acid solutions were co-cast onto a stainless steel belt and then imidized by heating in an oven. A polyimide three-layer ABA film with an overall thickness of approximately 25 μm was obtained. The glass transition temperatures of Layer A of the polyimide three-layer ABA film were determined to be 210°C and greater than 345°C for Layer B. The thickness of Layer A of this three-layer film was on the order of 3 μm. This three-layer film had a CTE of less than 30 ppm / °C.

[0096] Example 3 In Example 3 (E3), a first polyamic acid solution "A" with a monomer composition of 0.8% ODPA / 0.2% PMDA / 1.0% RODA was prepared by following the procedure described above for E1. A second polyamic acid solution "B" with a monomer composition of 0.35% BPDA / 0.65% PMDA / 0.13% PPD / 0.87% ODA was prepared by following the procedure described above for E1. Both polyamic acid solutions were co-cast onto a stainless steel belt and then imidized by heating in an oven. A polyimide three-layer ABA film with a total thickness of approximately 25 μm was obtained. The glass transition temperature of Layer A of the polyimide three-layer ABA film was determined to be 235°C and that of Layer B was greater than 345°C. The thickness of Layer A of this three-layer film was on the order of 3 μm. This three-layer film had a CTE of less than 30 ppm / °C.

[0097] Example 4 In Example 4 (E4), the procedure described above for E1 was followed to prepare a polyamic acid solution and fabricate a polyimide film of a monomer composition of ODPA 0.8 / PMDA 0.2 / / RODA 1.0. A polyimide film with a thickness of approximately 25 μm and a glass transition temperature of 233°C was thus obtained. The film had a CTE of less than 70 ppm / °C.

[0098] Example 5 In Example 5 (E5), the procedure described above for E1 was followed to prepare a polyamic acid solution and fabricate a polyimide film with a monomer composition of ODPA 0.8 / PMDA 0.2 / / RODA 1.0. A polyimide film with a thickness of approximately 75 μm and a glass transition temperature of 240°C was thus obtained. The film had a CTE of less than 70 ppm / °C.

[0099] Example 6 In Example 6 (E6), a first polyamic acid solution "A" with a monomer composition of ODPA 0.8 / PMDA 0.2 / RODA 1.0 was prepared by following the procedure described above for E1, and further incorporated 25 wt. % boron nitride as a filler (filler content relative to the polyimide content in the final film). A second polyamic acid solution "B" with a monomer composition of PMDA / ODA was prepared by following the procedure described above for E1, and further incorporated 50 wt. % boron nitride as a filler (filler content relative to the polyimide content in the final film). Both polyamic acid solutions were co-cast onto a stainless steel belt and then imidized by heating in an oven. A polyimide three-layer ABA film with a total thickness of approximately 38 μm was obtained. The glass transition temperatures of Layer A of the polyimide three-layer ABA film were determined to be 232°C and Layer B to be greater than 375°C. The thickness of Layer A of the three-layer film was on the order of 5 μm. The thermal conductivity of the final film was approximately 0.60 W / mK.

[0100] Example 7 In Example 7 (E7), a first polyamic acid solution "A" with a monomer composition of ODPA 0.8 / PMDA 0.2 / / RODA 1.0 was prepared by following the procedure described above for E1. A second polyamic acid solution "B" with a monomer composition of PMDA / / ODA was prepared by following the procedure described above for E1. Both polyamic acid solutions were co-cast onto a stainless steel belt and then imidized by heating in an oven. A polyimide three-layer ABA film with a total thickness of approximately 25 μm was obtained. The glass transition temperatures of Layer A of the polyimide three-layer ABA film were determined to be 228°C and greater than 345°C for Layer B. The thickness of Layer A of this three-layer film was on the order of 3 μm. This three-layer film had a CTE of less than 70 ppm / °C.

[0101] Example 8 In Example 8 (E8), a first polyamic acid solution "A" with a monomer composition of ODPA 0.8 / PMDA 0.2 / RODA 1.0 was prepared by following the procedure described above for E1. A second polyamic acid solution "B" with a monomer composition of PMDA / ODA was prepared by following the procedure described above for E1. Both polyamic acid solutions were co-cast onto a hot rotating drum under chemical curing conditions, and the resulting free-standing film was removed from the drum, then further dried and imidized by heating in an oven. A polyimide three-layer ABA film with a total thickness of approximately 25 μm was obtained. The glass transition temperatures of Layer A of the polyimide three-layer ABA film were determined to be 228°C and greater than 345°C for Layer B. The thickness of Layer A of this three-layer film was on the order of 3 μm. This three-layer film had a CTE of less than 40 ppm / °C.

[0102] (Comparative Examples 1 and 2) Comparative Examples 1 and 2 (CE1 and CE2) used a polyimide film Kapton® HA (DuPont) with the composition PMDA / / ODA, a thickness of 25 μm, and a glass transition temperature above 375°C.

[0103] (Comparative Examples 3 and 4) Comparative Examples 3 and 4 (CE3 and CE4) used a polyimide film Kapton® HN (DuPont) with the composition PMDA / / ODA, a thickness of 25 μm, and a glass transition temperature above 375°C.

[0104] (Comparative Examples 5 and 6) Comparative Examples 5 and 6 (CE5 and CE6) used a polyimide film Kapton® HN with the composition PMDA / / ODA, a thickness of 12.5 μm, and a glass transition temperature above 375°C.

[0105] (Comparative Examples 7 and 8) In Comparative Examples 7 and 8 (CE7 and CE8), the procedure described above for E1 was followed to prepare a polyamic acid solution and fabricate a polyimide film with a monomer composition of BPDA0.88 / PMDA0.12 / / ODA0.5 / PPD0.95. A polyimide film with a thickness of approximately 25 μm and a glass transition temperature of greater than 345° C. but less than 375° C. was thus obtained.

[0106] Comparative Example 9 Comparative Example 9 (CE9) used a polyimide film, Kapton® HN, with the composition PMDA / / ODA, a thickness of 25 μm, and a glass transition temperature of greater than 375° C. The film was plasma treated on both sides (treatment time 30 seconds, power setting 100 W, gas type argon, chamber pressure 100 mTorr) and used within 24 hours after the treatment was applied. Similarly, a sheet of Nomex® Type 464 LAM was also plasma treated and used within 24 hours after the treatment was applied.

[0107] (Comparative Example 10 (CE10)) Comparative Example 10 (CE10) used the polyimide film obtained in CE7 and CE8. The film was plasma treated on both sides (treatment time 30 seconds, power setting 100 W, gas type argon, chamber pressure 100 mTorr) and used within 24 hours after treatment application. Similarly, a sheet of Nomex® Type 464 LAM was also plasma treated and used within 24 hours after treatment application.

[0108] (Comparative Example 11) Comparative Example 11 (CE11) used a polyimide film Kapton® H (DuPont-Toray Co., Japan) with the composition PMDA / / ODA, a thickness of 50 μm, and a glass transition temperature above 375° C. Using DSC, no endothermic change could be observed in the film below 375° C., which would traditionally be associated with the glass transition temperature.

[0109] (Comparative Example 12) Comparative Example 12 (CE12) used a polyimide film Kapton® HA with the composition PMDA / / ODA, a thickness of 25 μm, and a glass transition temperature above 375°C.

[0110] (Comparative Example 13) Comparative Example 13 used a polyimide film Kapton® HN with the composition PMDA / / ODA, a thickness of 25 μm, and a glass transition temperature above 375°C.

[0111] (Comparative Example 14) Comparative Example 14 (CE14) used a polyimide film Kapton® HN with the composition PMDA / / ODA, a thickness of 12.5 μm, and a glass transition temperature above 375°C.

[0112] (electrical insulating laminate) Using the polyimide films prepared in Examples E1-E6 and Comparative Examples CE1-CE14, three-layer electrical insulation laminate structures were prepared in which a core layer of polyimide was bonded to two outer layers of flexible matting. Thermoplastic polyimides having glass transition temperatures ranging from approximately 199°C to 240°C were laminated to 50 μm aramid paper. For Examples E1-E5 and Comparative Examples CE1-CE11, Nomex® Type 464 LAM (DuPont) was used. Nomex® 464 LAM exhibited a glass transition temperature of approximately 275°C by DSC. For Example E6 and Comparative Examples CE12-CE14, Nomex® Type 410 (DuPont) was used. For Examples E7 and E8, Nomex® Type 410 (DuPont) was used.

[0113] The individual films of the three-layer laminate structure were dried to reduce the moisture content to less than 3% before lamination. The three-layer structure was then laminated together using mirror-finished steel platens with two buffer layers of 1.0 mil Kapton® HN (DuPont) at temperatures of 280°C, 300°C, and 320°C, respectively, and 625 psi using a hydraulic hot press to form an electrical insulation laminate. The Nomex® sheet was prepared with a 2-inch elongation in the machine direction relative to the polyimide layer to allow for peel initiation in subsequent peel strength tests. Peel strength and T g The values ​​are shown in Table 1. An "*" means that the interlayer bond strength exceeded the tear strength of the material being pulled and was assigned a peel strength value of greater than 0.400 N / mm based on experimental observations.

[0114] [Table 1]

Claims

1. Glass transition temperature (T) in the range of 140 to 280°C ｇ a flexible polymer layer comprising a first thermoplastic polyimide having a a first flexible matte layer comprising a first organic material; An electrical insulation laminate comprising: the first organic material comprises a woven fabric, a nonwoven fabric, or a fiber; the flexible polymer layer is thermally bonded to and in direct contact with the first organic material; 1. An electrical insulating laminate comprising:

2. 10. The electrical insulation laminate of claim 1, wherein said first organic material is selected from the group consisting of aramid paper, aramid fiber, and mixtures thereof.

3. 10. The electrical insulation laminate of claim 1, further comprising a second flexible mat layer adhered to the flexible polymer layer opposite the first flexible mat layer, the second flexible mat layer comprising a second organic material, the second organic material comprising a woven fabric, a nonwoven fabric, or a fiber.

4. 4. The electrical insulation laminate of claim 3, wherein said second organic material is selected from the group consisting of aramid paper, aramid fiber, and mixtures thereof.

5. The first thermoplastic polyimide is an aromatic dianhydride selected from the group consisting of 4,4'-oxydiphthalic dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and mixtures thereof; an aromatic diamine selected from the group consisting of 1,3-bis(4-aminophenoxy)benzene, hexamethylenediamine, 2,2-bis(4-[4-aminophenoxy]phenyl)propane, and mixtures thereof; 10. The electrical insulation laminate of claim 1, comprising:

6. The flexible polymer layer comprises: a core layer comprising a polyimide adhered to the first thermoplastic polyimide; a second thermoplastic polyimide adhered to the core layer opposite the first thermoplastic polyimide; 10. The electrical insulation laminate of claim 1 further comprising:

7. The second thermoplastic polyimide is an aromatic dianhydride selected from the group consisting of 4,4'-oxydiphthalic dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and mixtures thereof; an aromatic diamine selected from the group consisting of 1,3-bis(4-aminophenoxy)benzene, hexamethylenediamine, and mixtures thereof; 7. The electrical insulation laminate of claim 6, comprising:

8. 7. The electrical insulation laminate of claim 6, wherein the first thermoplastic polyimide and the second thermoplastic polyimide are the same or different.

9. 7. The electrical insulation laminate of claim 6, wherein the core layer comprises an aromatic dianhydride selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, bisphenol A dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, and 2,3,6,7-naphthalenetetracarboxylic dianhydride, and mixtures thereof.

10. 7. The electrical insulation laminate of claim 6, wherein the core layer comprises an aromatic diamine selected from the group consisting of p-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 2,2'-bis(trifluoromethyl)benzidine, m-phenylenediamine, and 4,4'-diaminodiphenylmethane.

11. 10. The electrical insulation laminate of claim 1, wherein the flexible polymer layer comprises an inorganic filler, an organic filler, or a mixture thereof.

12. 7. The electrical insulation laminate of claim 6, wherein the core layer and both thermoplastic polyimide layers contain inorganic fillers, organic fillers, or mixtures thereof.

13. An electrical machine comprising the electrical insulation laminate of claim 1.

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