CA1167595A

CA1167595A - Polyetheramideimide resins and electrical conductors insulated therewith

Info

Publication number: CA1167595A
Application number: CA000379175A
Authority: CA
Inventors: Yue-Guey L. Lee; Otto S. Zamek
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1981-06-05
Filing date: 1981-06-05
Publication date: 1984-05-15

Abstract

ABSTRACT OF THE DISCLOSURE Novel high molecular weight resins, useful for electrically insulating conductors, are prepared by polycondensing a mixture of anhydrides, and a diisocyanate and/or a diamine in an inert organic solvent, preferably in the presence of a catalytic amount of 2 methyl-imidazole.

Description

3 ~75~5 POLYETHER~MIDEIMIDE RESINS AND ELECTRICAL
_ _CONDUCTORS INSULATED THEREWITH
The present invention relates to polyetheramideimide resins and to electrical conductors coated therewith.
More particularly it relates to polyetheramideimides deri~ed from a combination of a dianhydride of a diphenolic compound and a tribasic acid anhydride and a diisocyanate and/or a diamine.
Polyetherimidies comprisiny the reaction products of a dianhydride of a diphenolic compound and a diamine, e.g., methylenedianiline are known to form useful resinous coatings for electrical conductors. See, for example, Heath and Wirth, U.S. Pat 3,847,867 dated Nov 12, 1974.
Furthermore, polyamideimides comp~ising the reaction products of a carboxylic acid anhydride, a diamine and a diisocyanate are known to form useful coatings for electrical conductors. See, for e~ample Pauze and Holub, U.S. 3,817,926~dated June 18, 1974. In addition, polyamide-imide resins comprising the reaction products of a tri-basic acid anhydride and a diisocyanate are known to formuseful insulating coatings from Nakano and Koyama, U.S.
3,541,038 dated Nov. 17, 1970.
It has now been disco~red that uniquely use~ul reaction products comprising polyetheramideimide resins can be formed from the reaction of (A) a combination of a dianhydride of a diphenolic compound and a tribasic acid snhydride and (B) a diisocyanate and/or a diamine. Such products are preferred for use as insulating eoatin~s for electrical conductors, e.g.~ magnet wire and m~gnet strip, because ~hey are safer, better and more economi cal. The resins are preferably applied as compositions S diluted in an organic solvent.

DESCRIPTION OF THE INVENTION

According to the present invention ~here are provided high molecular weight polyetheramideimide resins.
prepared by subjecting ~A) a combination of anhydrides comprising: .
.. (i) rom 1 to ~ parts by weight of a clianhydride of the formula O . O

\CI ~L ~3 CU3 C and , (ii) from 99 to 1 parts by weight of a tribasic acid anhydride and t~) 0.99 to 1.01 moles, per mole of the anhydride, o a difunctional organic nitrcgen compound of ~he formula (i) O-C-N-R-N=C=O, (li3 H2N-R-~H2, or (iii~ a mixture of (i) and (ii), wherein ~ is ` -G~ CH~G--~-or a mixture tllereof, to polycondensation at a temper-35 ature of about 60 to 200C. in the presenee of the inert solv2nt .

1 1~7~95 o - It is also contemplated to provide electrical conductors having an insulating coating thereon com-prising a resin as above de~ined.

In addition, there are contemplated coating co~positions comprising a polyethera~ideimide resin dissolved in an organic solvent, the polyetheranideimide resin being as above defined.

10 In preferred features, the resin will be pre-pared in the presence of a catalytic amount, preferably, from a trace ~o about 10 mole percent (based on the anhy-drides) of 2-methylimidazole~ Preferably, the difunc-tional organic ni~rogen compound will be diphenylmethane-diisocyanate and/or diaminodiphenylmethane.

The dianhydride component (A)(i), 2,2-bis14~
(3,4-dicarb~xyphenoxy)phenyl]propane dianhydxide, also known as bisphenol-A diznhydride, is described in the above-mentioned Heath and Wirth, U.S. 3,847,867, and can be made by hydrolyzingt followed by dehydrating, ~he reaction product o a nitro-subs~ituted phenyl dinitrite with a metal sal~ of a dihydric aryl compound in the pres-ence of a dipolar aprotic solvent.
~5 The organic diisocyanate and th~ organic diamines, (B)(i) and (ii) can be prepared in ~ays known to those skilled in ~hïs art, and they are also commer-cially available.

The term tribasic acid anhydride is used in the ar~-recognized sense set out in the above-mentioned U.S. 3,817,g26 and 3,541,038. In general, it includes aromatic, alicyclic and aliphatic tribasic anhydrides, such as, for exa~ple, tri~ellitic anhydride (which is 1 1~759~

preferred), hemimellitic anhydride, aconitic anhydride, - and the like~

The polymers are prepared from the reaction 5 of mixed bisphenol-A dianhydxide (BPA-D~) and, e. g., tri-mellitic anhydride and diphenylmethane diisocyanate (MDI), diphenyletherdiisocyanate, methylenedianiline (MDA), di-aminodiphenyl ether, or a mixture of any of the foregoing, in the prese~ce or absence of 2-methylimidazole (2-~IeIM) 10 catalyst, in an or"anic solvent, such as N-methylpyrroli-done (~), dimethylacetamide (I)MAC~, an aromatic hydro-carbon, e.g., of 6 to 40 carbon atoms, e.g., xylene, or a propriet:ary aro~atic hydrocarbon solvent , e . g O, Solvesso 100, or in mixtures thereof, such as ~-~MAC, NMP-xylene, ~ ~-DMAC-xylene or Solvesso 100, etc.

One typical reaction pathway is as follows:

~ ~7~95 ,~

o '_ C~
~ c~
o~ =o `--o S--Z ~ Z ~ ~3 o~ o o X ~ =" W_o o~~
o ~ Z) o=c~
t ~ Z :z / \ O=U/ ~=
o ~=~ o=~=o ~ ~

~cu~
2S~ T n 3u c~

o=c~ c~=o o~c~ c~=o ~ ~
x . ~ s e 1 16~59~

o.
Another typical reaction p~thway is as follows:

, ~, `J u +

~o \ ~\
O~ =o Z
~ O = I o=c.~ o O=C~ U=C~
X Z X Z
~' + ~ z ~
o=~ oo=~ c~=o 20 Z ¢~

25 +P' C ~ o ~
o=~ o o=c~ ~=o o~ =o ~
\0/

_ .

o The resulting resins can be random copolymers or random block copolymers.

The optimum mole ratio of MDI or MDA, BPA-DA
and TMA (trimellitic anhydride) is (1.98-2.02):1.00:1.00 and the catalyst is O.lO mole %, based on the mixed anhy-drides. To malce a coating composition the resin can be prepared in the organic solvent, e.g., NMP> NMP D~AC, NMP-xylene or Solvesso 100, etc., or the resin can be isolated, then redissolved in such solvents, or in nethy--lene chloride, dimethyl formamide, cresylic acid, phenol, and the like.

Conventional preparative methods are used.
See, for example, the above-mentione~ U.S. 3,541,038, which sets forth reaction times, temperatures, etc.

In one manner of proceeding, the BPA-DA and ~ are reac~ed with ~I (or MDA) in the presence of

2~ a mixture of N-methylpyrrolidone and the organic liquid ' ~ hydrocarbon Solvesso 100 at a temperature of 135Co for about 5 hours. ~uring the first period of reaction, the carbon dioxide (or water) is continuously evolved.
~ater, the s21u~ion gradually increases in ~7iscosity and 25 by-product (C2 or water, as the case may be) evolution substantially ceases. A suitable terminatian point is a Gardner viscosity of Z2. Suoh an enamel can be used as a sole coat o~ a wire con~uctor or i~ can be used as a top coat over a polyester or polyesterimide base coat.

In accord wi~h con~entional practices, other additi~s may be formulated into the compositions, such as, without limitation, minor proportions of aliphatic amino compounds, conventional phenolic resins, titanate -esters, blocked polyisocyanates, and ~he like.

.

.

o BRIEF D S CRIPTION OF THE DRA~JING

In the drawing, the figure shows a section ofmagnet wire made accordin~ to this invention~

DESCRIPTION OF X'HE PREFERRED_E~IBODIMENT

In the figure a magnet wire indicated generally by the numeral 10 has a conductor 11 covered with a layer 12 of a resinous polyethera~ideimide o bisphenol-A di-anhydride and trîmellitic anhydride and a diisocyanate and/or a dia~ine. Although the dra~ing illustrates a oonductor 11 that is circular in section, it will be understood that squar~ or rectangular conductors in the form of strips or foils may also be used without departing from the invention.

A sui~able polyetheramideimide for layer 12 can be made following Examples 1-3..

~ ~n mole (520 g.) of 2,2-bis[4-(3,4-dicarboxy-: phenoxy)phenyl]propane, 1 mole (192 g.) of trimelli~ic anhydride, 2 mole (500 g.~ o~ me~hylenediisocyana~e, 0.1 mole (8.2 g.) of 2-methyli~idazole, 1300.9 g. of N-. methylpyrrolidone and $65.6 g. of aromatic hydrocarbonsolvent (Sol~esso 100) are added to a five liter, three neck, round bottomed flask e~uipped with a stirrerJ

3~ ~hermometer, condenser, and a nitrogen inlet. The mix- -.
tur~ is heated from roo~ temperature to 135C. in approxi-mately two hours and held at 135C. for 3.25 hours until a Gardner viscosity ~f Z2 is obtained. In this reac~ion, the solution changes fro~ yellow, orange to clear red and clear dark red during the first two hours of heating, 759~

o and carbon dioxide is nearly completely removed after 1~ hour reaction at 135~C. Thereafter, the solution viscosity gradually increases with continued very l:ninor evolution o C02. The solids content is about 40% in the organic solvent, and the composltion can be used as an electrical conductor coating composition. If desired, the resin from this, and ~he other e~a~ples, can be isolated by pouring the cooled reaction mixture into ~ethanol to precipitate the poly~er.
AlthouOh diphenylmethanediisocyanate is shown, it can be parLially a completely replaced by diphenyl-ether diisocyana~e. Moreover, the catalyst can be omitted.

The c~mposition is further diluted with a mixture of 4 parts of ~ ~ to 1.74 parts of Solvesso 100 and co~ting compositions containing 36 and 32~ of solids . are al50 obtained.

The composition of Example 1 ~40% solids~ is applied to 0.0403" copper wire as a sole cost in a commer-cial wire ~ower. A build of 2.8-3.3 mils is obtained.
The following proper~ies are observed:

Speed ~ft. 1min. ) 40 45 50 Flexibility 25+ lX lX lX
` . lX* lX*
Heat Shock-20%-3~'-260C. 2X lX not lX* ~X* determined . .
30 Cut Through ~emperature, - .
C. at 2000 g. 378 376 not 415* 403* determined * Values after deposition fro~ 32% solids composition ~' ~ 35 applied as a topc~at over polyester (ISO~LT~678).
Excellent quality coated conductors are obtained.

7 ~ 9 5 - 10,-o The composition of Example 1 is applied to 0,0403 copper wire as an overcoat over an ethylene glycol-~ris(2-hydroxyethyl)isocyanrate-terephtnalate undercoa~ (Schenectady Chemical's ISONEL 6783. A final build of 2.9 to 3.1 is obtained. The follo~ing proper-ties are observed from 40% solids as a ~opcoat:

Speed (f~./min.) 40 45 Flexibility 25~ lX lX
Heat Shock-20%-30'-260C. 1~ lX
Cut Through Temperature~, C. at 2000 g. 407 412 Excellent coated conductors are obtained.
EXA~LE 2 m e general procedure of Example 1 is repeated with 416 g. (0.8 mole)of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]
propane, 307.,4 ~. (1. 6 1~1012$) O' trimelletic anhydride, 606 g. (2 . 42 moles) of diphenyll~ethanediisocyanate 9 . 84 g.
(0.12 mole) of 2-me~chylimidazole, 1098.8 g. of N methyl-pyrroli~one and 477.7 g..of xyLene. The viscosity after 1 hour i5 8g70 centistokes. The resin composition is cut with 293. 6 g. o N~' and 127 . 7 g. of xylene. The heating is continued for 0 . 5hour ~viscosity 3390 centistokes) .
At room tempexature, the viscosity is 3530 centistokes.
Heating at 135Co is resumed for 2 hours and 15 minutes.
Final viscosity in Gardner Z3~. Solids content is 35. 78%
3~ average. ..

The composition o~ Example 2 is applied to 0. 0403" copper wire as a sole coat in a com~ercial wire tower. A build of 2..8-3.3 mils~ is obtained. The follow-35 ing properties are observed:

~)7~5 60IN~605 Speed (ft./~in.) 35 Flexibility 25+ 2X
Heat Shock~2U%-30' 260C. 3X
Cut Through Temperature, C. at 2000 g. 474 The composition o Example 2 is applied to 00 0403 copper wire as an overcoat over an ethylene glycol-tris (2-hydroxyethyl) isoeyanurate terephthalate 10 undercoat ~Schenec~ady Chemioa~'s ISONEL 678). A final build of 2. 9-3. 2 mils. is obtained~, The following proper-ties are observed:

Speed (ft./min.~ 40 45 Flexibility 25+ lX lX
Heat Shock~20%-30'-260C. lX lX
Cut Through Temperature, C.
a~ 2000 g. 420 410 Excellent coated conductors are obtained.

Followirlg the genera-L procedure of Example 1, a polyetheramideimide is made using me~hylenedianiline (M~ instead of dlphenylmethanediisocyanate (MDI~.
There are used 520 g. ~1 mole) of 2,2-bis[4~(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 192 g.
(1 mole) of trimellitic anhydride/ 400.5 g. (2~02 mole) 3~ of MDA, 1277.9 g. of N-methyl pyrrolidone and 555.6 g.
of aromati.c hydrocarbon (Solvesso lOO)o No 2-methyl-imidazole i~ used. The ~emperature reaches 180C. durin~
heating. When 70.5 mls. of water has been collected., the very viscous reaction mixture is filtered. The very viscous liquid is 407D solids. Seven hundred grams of the ~ ~67~

- 12 ~
viscous composition is mixed with 97 g. of N-methyl pyrrolidone and 44.7 g. of solvesso 100 hydrocarbon solvent to produce a resin composition suitable for coating electrical conductors.

Suppl'ementa'ry D'lsclos'ure In addition to the foregoing it has also been found that divalent alkylene radicals may be employed as "R" group in the diisocyante or diamine reactants such that the polyetheramideimide resins of the present0 invention may be prepared by subjecting (A) a combination of anhydrides comprising:
(i) from 1 to 99 parts by weight of a dianhydride of the ~ormula O O

0/ ~ ~ CH3 ~ ~ \ 0 O O
or a mixture thereof with at least one other dianhydride of an organic tetracarboxylic acid, and (ii) from 99 to 1 parts by weight of a tribasic acid anhydride and (B) 0.99 to 1.01 moles, per mole of the anhydride, of a difunctional organic nitrogen compound of the formula (i) 0=C=N-R-N=C=0, (ii) H2N-R-NH2, or (iii) a mixture of (i) and (ii), wherein R is divalent alkylene of 2 to 20 carbon atoms, -~--C~2 ~
~ . ,,,~ .

1 ~75''35 60IN~605 0 ~, or a mixture thereof, to polycondensation at a temperature of about 60 to 200C. in the presence of the inert solvent.
Furthermore, the advantageous properties of the polymers of this invention can be varied by substituting for up to 50 mole per cent of the bisphenol-A dianhydride one or more dianhydrides of tetracarboxylic acids, which may be either aromatic dianhydrides or aliphatic dianhydrides, as follows:
Aromatic dianhydrides useful in the practice of this invention include those having the formula:
O O
ll ll 0 ~ R \/ / 0 ll ll O O
wherein R is a tetravalent radical containing at least one ring of 6 carbon atoms and hav:ing benzenoid unsatura-tion, each pair of carbo~yl groups being attached to a different adjacent carbon atoms. These dianhydrides include, for example, pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3l,4,4'-benzophenonetetracarboxylic dianhydride, benzene-1,2,3~4 tetracarboxylic dianhydride, bis (3,4 dicarboxyphenyl) sul~one dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, 2,6-dichloronapthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3~6,7-tetrachloronaphthalene-1,4,5,8-tetra-carboxylic dianhydride, .. ,~

J 1 ~, 7~

naphthalene-1l4,5,8 tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, naphthalene-1,2~4,5-tetracarboxylic dianhydride, 3,3' 4,4'-diphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2'2,2'-diphenyltetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-phenylenetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 2,2-bisl2,3-dicarboxyphenyl)propane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, l/l-bis(3,4-dicarboxyphenyl)ethane dianhydride, and the like.
Aliphatic dianhydrides useful in the practice of this invention include those having the formula:
O O

0 ~ \ R~ / \ 0 C \C/
O O
where R' is a straight-chain or alicyclic tetravalent radical having from 1 to lO carbon atoms. These dianhydrides include, for example:
methanetetracarboxylic dianhydride, ethanetetracarboxylic dianhydride, : propanetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, hexanetetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, - and the like.

Following the general procedure of Example l, a polyetheramideimide is prepared, substituting 20 mole percent of the 2,2 bis[4-(3,4-dicarboxyphenoxy)phenyl]
propane (BPA-DA) with benzophenonetetracarboxylic dianhydride (BTDA). There are used 416 g~ (.8 mole) of 9 ~

BPA-DA, 64.45 g. (.2 mole of BTDA, 192 g. (1 mole) of trimellitic anhy~ride, 505 ~. (2.02 moles) of ~DII 1278 y.
of NMP, 556 g of Solvesso 100, and ~.2 g~ (.1 mole) 2-methylimidazole. The ~emperature never exceeds 135C, and after 3 hours a viscosity of Gardner Z3 1/2 (about 1760 centistokes) is obtained. Part of this composition is cut with a solvent mixture t ~0 g. NMP and 35 g~ Solvesso 100, then mixed at room temperature for two hours. Final viscosity is ~ardner Z2. Solids content is 36 n 9% ~ This composition is labeled A.
The remaining portion is further reacted a-t 135C until a Gardner viscosity of Z5 is reached. This is cut with a solvent mixture, 200 g. NMP and 87 g.
Solvesso 100 to obtain a Gardner viscosity of Z 3/4 and a solids content of 33.25%. This composition is labeled B.
Both enamels are applied to 0.0403" copper wire as a sole coat in a commercia] wire tower. In both cases a build of 2.9-3.1 mils are obtained. The following properties were observed:
' En'ame'l'A
Speed (ft./min.) 40 45 50 Flexibility (25%+) 3X 2X lX
Dissipation Factor (260C)5.0 12.3 14.7 Heat Shock (20% - 30 min. at 240C) lX 2X 2X
Cut Thru (C at 2000g) 403 444 374 Dielectric Strength (KV)12O1 9.9 9.2 Enamel B
Speed (ft./min.) '40 ''45 ''50 Flexibility (25%+) lX lX lX
Dissipation Factor (260C)7.5 12.0 13.1 Heat Shock (20% - 30 min. at 240C) lX lX lX
Cut Thru (C at 2000g) 471 403 394 Dielectric Strength (KV) 9.3 9.7 11.9 'EXAMPLE 5 -The general procedure of Example 4 is repreated, except that 20 mole percent of the 2,2 bis[4-(3,4-dicarboxy-phen oxy)phenyl]propane (BPA-DA) is replaced with pyro-~ ~8~95 mellitic dianhydride (PMDA) instead of benzophenonete-tra-carboxylic dianhydride. 43.6 g. (.2 mole) of the PMDA are used; all other amounts are the same as in Example 4. The final enamels obtained, labeled A' and B', had respective Gardner viscosities of Z1 1/2 and Z1, and had respective solids contents of 38.5% and 32.2%.
These enamels were also applied to 0.0403l' copper wire as a sole coat in a commercial wire tower to builds of 2.9-3.1 mils. The following properties were observed:
Enamel A' Speed (ft./min.) 40 45 50 Flexibility (25%~) lX lX lX
Dissipation Factor (260C)9.S 10.9 1106 Heat Shock ~20% - 30 min. at 240C) lX lX lX
Cut Thru (C at 2000g) 461 422 395 Dielectric Strength (KV)12.4 12.9 10.4 Enamel B' Speed (ft./min.) 40 45 50 20 Flexibility (25%+) lX lX lX
Dissipation Factor (260C)7.5 9~0 13.3 Heat Shock (20% - 30 min. at 240C) lX lX lX
Cut Thru (C at 2000g) 463 436 384 Dielectric Strength (KV)9.7 9.9 12.2 .,.~,~,

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A high molecular weight polyetheramideimide resin prepared by subjecting (A) a combination of anhydrides comprising:
(i) from l to 99 parts by weight of a dianhydride of the formula (ii) from 99 to 1 parts by weight of a tribasic acid anhydride and (B) 0.99 to 1.01 moles, per mole of the anhydride, of a difunctional organic nitrogen compound of the formula (i) O=C=N-R-N=C=O, (ii) H2N-R-NH2, or (iii) a mixture of (i) and (ii), wherein R is or a mixture thereof, to polycondensation at a temperature of about 60 to 200°C. in the presence of an inert solvent.

2. A polyetheramideimide resin as defined in claim 1 wherein polycondensation is carried out in the presence of a catalytic amount of 2-methylimidazole.

3. A polyetherimide resin as defined in claim 2 wherein the amount of 2-methylimidazole comprises from trace amounts up to about 10 mole percent, based on anhydri.de component (A).

4. A polyetheramideimide as defined in claim 1 wherein, in component (A), (i) comprises from 40 to 60 parts by weight, and (ii) comprises from 60 to 40 parts by weight.

5. A polyetheramideimide resin as defined in claim 1 wherein, in difunctional component (B) (i), R is

6. A polyetheramideimide resin as defined in claim 1 wherein, in difunctional component (B) (ii), R is

7. A polyetheramideimide resin as defined in claim 1 wherein the inert solvent comprises N methylpyrro-lidone, dimethylacetamide, an aromatic hydrocarbon, or a mixture of any of the foregoing.

8. An electrical conductor haviny an insulating resin coating thereon, said resin being as defined in claim 1.

9. An electrical conductor having an insulating resin coating thereon, said resin being as defined in claim 5.

10. An electrical conductor having an insulat-ing resin coating thereon, said resin being as defined in claim 6.

11. A coating composition comprising a polyetheramideimide resin dissolved in an organic solvent, said polyetheramideimide resin being as defined in claim 1.

12. A coating composition as defined in claim 11, said organic solvent being selected from N-methyl-pyrrolidone, dimethylacetamide, an aromatic hydrocarbon, or a mixture of any of the foregoing.

13. An electrical conductor having an insulat-ing resin coating thereon, said coatiny solely consistlng of a resin as defined in claim 1.

14. An electrical conductor having an insulat-ing resin coating thereon, said coating consisting of a base coat of a polyester of polyesterimide and an overcoat of a resin as defined in claim 1.
Claims Supported by Supplementary Disclosure

15. A high molecular weight polyetheramide-imide resin prepared by subjecting (A) a combination of anhydrides comprising:
(i) from 1 to 99 parts by weigh-t of a dianhydride of the formula or a mixture thereof with at least one other dianhydride of an organic tetracarboxylic acid, and (ii) from 99 to 1 parts by weight of a tribasic acid anhydride, and (B) 0.99 to 1.01 moles, per mole of the anhydride, of a difunctional oryanic nitrogen compound of the formula (i) O=C=N-R-N=C=O, (ii) H2N-R-NH2, or (iii) a mixture of (i) and (ii), wherein R is divalent alkylene of 2 to 20 carbon atoms, or a mixture thereof, to polycondensation at a temperature of about 60 to 200°C. in the presence of an inert solvent.

16. A polyetheramideimide resin as defined in claim 15 wherein in component (A) (i), the other dianhydride is benzophenonetetracarboxylic dianhydride.

17. A polyetheramideimide as defined in claim 15 wherein in component (A) (i), the other dianhydride is pyromellitic dianhydride.