CA1103841A - Water-soluble polyester imide resins - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Water soluble polyester-polyimide prepolymers are prepared (1) having 5 to 60%, preferably at least 35%, of polyimide, (2) an excess hydroxyl content in ex-cess of 60% and preferably more than 100%, and (3) a num-ber average molecular weight of 600-1300. To water solu-bilize the prepolymers formed, there are added amines, preferably tertiary amines. The products are useful as wire enamels. To enhance the thermoplastic flow of the enamel. there are added organic titanates.

Description

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_ACKG~OUND
Polyester-imlde wire coatings thinned in con-ventional cresylic acid/aromat:ic hydrocarbon solvent blends have been used comme~.rcially :Eor a numbe.r o:E years. Taking the base polymer one can solubilize it in water along with an amine. In attempting to use the same c~lratives as are employed in the non-aqueous or organic solvent system previously mentioned it was soon discovered that they were insoluble in water. This necessitated a search for cross-linkers that were soluble in water, and those were mainlyorganic titanates, such as Tyzor TE and LA which are titanium chelates of triethanolamine and the ammonium l.actate salt, respectively.
Following the teachings of Meyer et al in U.S.
Patent 3,426,098, if one were to take any of the polyester-imide base polymers and solubilize it with distilled water, an amine, a polar solvent and modi.fy it with Tyzor~ TE, the baked enamel on copper wire would be out-o~-round or ec-centric, grainy or rough because of poor flow in the wire tower during the baking or curing operation. Extensive wire tower runs with another standard polyester-imide base having a fixed diimidediacid molar content in relation to the terephthalic acid molar content present all ran with an ~ .

~,..,-appearance ra-ting of five (5) with or without a heavy grain and/or rough or blistery.
The present invention relates to novel polyester-polyimides and wire enamels prepared thereErom that are truly water-soluble, transparent, and truly clear ln appearance.
It is an object of the present invention to prepare novel polyes-ter-~polyimides.
Another object is to prepare novel wire enamels containing polyester-polyimides that are not only water-soluble, but soluble in the conventional cresylic acid/aromatic hydrocarbon blends and in each case perform equally as well.
An additional object is to prepare electrical conductors having improved high temperature resistant coatlngs .
A further object is to prepare wire enamels having unusually good flexibility aging and heat shocks as compared to presently available polyester wire enamels.
Another object of this invention is to prepare heat- -resistant wire enamels that have good heat shocks at 200C.without the use of a topcoat, such as polyethylene tereph-thalate, nylon, or an amide imide polymer.

SUMMARY OF THE INVENTION
It has now been found that these objects can be obtained by preparing a polyester-polyimide that is significantly different than its conventional organic solvent counterpart in three ways, namely:
1. A higher polyimide content, i.e., higher than 35%.

2. An excess hydroxyl content in excess of 60 and, preferably, more than 10~/o SO that the OH/COOH ratio is 1.8/1 to 2.50/1, and pref-erably 2.20-2.50/1.

3. The number average moledular weight of the base polyester-polyimide polymer is much lower than the solvent counterpart, namely 600-1300 for the newer polymers versus greater than 1300 for the conventional types.
The polyimide content can be five (5) to 60 per-cent of the total of polyimide and polyesterO Preferably, the polyimide content is 35-55% of the total.
Unless otherwise indicated, all parts are by weight As the polyimide forming components, there can be used (a) anhydridesO such as trimellitic anhydride, etc. and (b) polyamines, preferably aromatic amines, such as methylene dianiline, oxydianiline, phenylene diamines, etc. Additional aromatic tricarboxylic anhydrides in-.. . . . . . .. ...

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clude 3,4,3'-benzophenone tricarboxylic acid anhydride and hemimellitic anhydride. Other polyimide formin~ anhydrides are shown in Meyer U.S. patent 3,426,093. The preferred anhydride is trimellitic anhydride.
Other polyamines include 3,3'-diamino-diphenyl, benzidine, 1,4-diaminonaphthalene, p-phenylene diamine, ethylene diamine, nonamethylene diamine, hexamethylene diamine, diaminodiphenyl ketone, bis (4-aminophenyl)-~ p-xylene, m-phenylene diamine, m-xylylene diamine,

4,4'-dicyclohexylmethane diamine, diaminodiphenyl sulfone, octamethylene diamine, p-xylylene diamine, 3,3'-dichloro-benzidine, 3,3'-dimethyl benzidine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl propane, 3,3'-diaminodiphenyl sulfone.
The pre~erred diamines are methylene dianiline and oxydianiline.
Reactants (a) and (b) are usually employed in an amount of approximately two (2) moles of (a) per mole of (b) to ~orm the diimide-diacid. This reaction product may 2a be represented as follows: -2 moles ~IOOC ~ C \ + 1 mole Nd2 ~ -R ~ d2 3 ~ 3~

o o Il - 11 HOOC ~ C \ / ~ / ~ ~ C- ~ ~ -COOH
~ ~ ~N \ J ~ R-~ J ~ N~ C- ~ ~ + 2H2O
(~ . Il O O
where I~ is CH2 in the case of methylene dianiline or the oxygen atom (O) ln the case oE oxydianiline.
Then in the formulation oE the polymer, this diimidediacid is considered as a portion of the total di-carboxylic acid content which contains predominately aromatic diacids with or without a minor quantity of aliphatic diacids.
The preferred major diacid is terephthalic acid, although benzophenone-4,4'-dicarboxylic acid performs equally as well and isophthalic acid or mixtures thereof follow very closely.
Other aromatic dibasic acids include naphthalene-1,4-dicarbox-ylic acid, naphthalene-1,5-dicarboxylic acid, 4,4'-dicarboxy-diphenyl sulfide, 4,4'-dicarboxydiphenyl sulfone, 3,3'-di-carboxydiphenyl sulEone, 4,4'-dicarboxydiphenyl ether, 4,4'-dicarboxydiphenyl methane, 4,4'-dicarboxydiphenyl ketone, 4,4'-dicarboxydiphenyl propane. When aliphatic carboxylic -acids are included, e.g., in an amount up to 50 equivalent percent of the total acid, there can be used for example adipic acid, sebacic acid, maleic acid (or its anhydride), azelaic acid, glutaric acid.

These diacids may then be subsequently esterified by polyols, such as tris(2-hydroxyethyl) isocyanurate (THEIC) alone, or in admixture with dihydrlc alcohols, such as ethylene g]ycol, neopentyl glycol, propylene glycol, dl-ethylene glycol, 1,3-hydroxyethyl, 5,5'-dimethyl hydantoin and others in various ratios.
Additional dihydric alcohols include butanediol-1,4, trimethylene glycol, pentanediol-1,5, butene-2-diol-1,4, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 1,4-cyclohexane dimethanol, hexanediol-1,6, decanediol-1,10, dipropylene glycol, 4,4'-di(hydroxymethyl) diphenyl, 4,4'-di(hydroxy-methyl) diphenyl methane, 4,4'-di(hydroxymethyl) diphenyl sulfone. The preEerred dihydric alcohols are used in the two working examples.
In place of THEIC, there can be used in whole or in part other alcohols containing at least three hydroxyl groups such as glycerine, trimethylol propane, 1,2,6-hexanetriol, pentaerythritol, trimethylol ethanel 3-methyl-1,3,5-hexane-triol. The preferred alcohol containing at least three hydroxyl groups is THEIC. The products using THEIC sur-prisingly are more soluble in water than those using glycer-ine. It is unexpected that the larger molecule gives a more water soluble product. Because the THEIC gives a more water soluble product less cosolvent need be employed in employing the products.

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Based on the total polyhydric alcohol usually 10 to 90~ of -the total equivalents is supplied by dihydric alcohol and the balance by the alcohol containing at least three hydroxyl groups.
The preparation of the polyester-polyimide is not restricted to any specific sequence of reactions. All the reactants may be charged to the reactor initially, heated to 400-460E'. and reacted in situ. In another instance a par-ticular sequence is followed whereby a polyamine, an aromatic anhydride and polyols are heated together to complete the imidization process, and then the aromatic dicarboxylic acid -:
or its alkyl ester is subsequently added to form the polyester component under suitable reaction conditions. The polyester-polyimide reaction is usually carried out in the absence of solvent, although it is not precluded to employ solvent. In attaining the best balance of properties with respect to heat shock, thermoplastic flow or cut-through temperature, and a smooth, concentric baked film (related to runnability) it was found that a high diimide-diacid content combined with a high excess of hydroxyl content favored a relatively low molecular weight polymer that accomplished these objectives. -:
With respect to the determination of diimide-diacid content, earlier mention was made of its formation by the reaction of approximately two moles of an aromatic anhydride : ~ .

with one mole of an aromatic diamine. The combination of the molar content oE this product and an aromatic diacid or aromatic-aliphatic diacicl mixture is used to calculate the percentacJe oE each. ~n example oE this would be:
Mols Mols Trimellitic Anhydride 1.00 l ~ or diimide diacid 0.50 Methylenedianiline 0.50 J
Terephthalic Acid 0.50 Terephthalic Acid 0.50 Thus, on a mol percent basis the diimide diacid content would be 50%. These calculations will appear later in the examples shown both as mol percent of diimide diacid and regular diacid and as mol percent of the total reactants employed ln the formation of the polyester-polyimide base polymer.
In the preparation of the polyester an excess of alcoholic groups (OH) over acid groups (COOH) is preferred in order to get better flow on wire due to the formation of a lower molecular weight polymer with a lower softening point range. This may be expressed as an OH/COOH ratio range of 1.80/1 to 2.50/l, and preferably 2.20/1 to 2.50/1. In other words, an excess of OH groups over COOH groups of B0 to 150 is required to get the flow and other properties needed.

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The polyester-polyimide wire enamel is modified by the incorporation of 1-10%, preferably 2-5%, of an organic titanate, such as a titana-te chelate or salt or an alkyl titanate based on -the total solids of the enamel. The addition of an adjuvant of this type enhances the thermo-plastic Elow properties of the enamel. Typical examples of suitable titanates include the triethanolamine chelate of titanium, known as Tyzor TE, and the ammonium lactate salt of titanium, known as Tyzor LA. These titanates and any others that are hydrolytically stable can be used as crosslinking agents. Thus, there can be used titanium acetylacetate.
Organic alkyl titanates, such as Tyzor TPT (tetra-isopropyl titanate), TBT (tetrabutyl titanate) tetrahexyl titanate and others that ordinarily undergo rapid hydrolysis in the presence of water may be pre-reacted with the pre-polymer previously thinned in a polar solvent. They may be subsequently solubilized in an amine and water without any deleterious effects. This technique is demonstrated in e~ample 9(b), 10(b), 12(b) and 13(b).
There is no need to employ solvents during the preparation o~ the polyester-imide prepolymer. Solvents o~ the polar type may be subsequently employed as co-solvents with distilled water in the preparation of aque- -~

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ous solutions. Conventional cresylic acid-aromatic hy-drocarbon (e.g., xylene) blends may also be used to make solvent-type wire enamels that perform equally as well as the aqueous types. For a comparison of wire proper-ties of solvent versus water-based enamels u9ing the same polymer~ see Table ~ for details.
To solubilize these inherently water-insoluble resinous prepolymers in water, various amines may be em-ployed that react with the free carboxyl groups or amine acid groups available to form the salts that are soluble in water. These amines may be of the alkyl, alkanol-amine, or morpholine types. In general, the tertiary amines work best from the standpoint of fast cure, and least moisture sensitivity in the resultant baked film.
Thus, there can be used trialkyl amines, ~-alkyldiethan-olamine, N,N-dialkyl alkanolamines, N alkyl morpholine, N-hydroxyalkyl morpholine, etc. The alkyl group is us-ually lower alkyl, e.g., o~ l to 4 carbon atoms.
Typical examples of tertiary amines are:
triethyl amine, trimethyl amine, tributyl amine, triethanolamine ~,N-dimethyl ethanolamine (a preferred tertiary amine) ~,~-diethyl ethanolamine ~ .

~,N-diisopropyl ethanolamine N-~- dibutyl ethanolamina triisopropanolamine M,~-dibutyl isopropanolamine N-methyl diethanolamine ta preferred tertiary amine) N-ethyl diethanolamine, ~-propyl diethanol-amine ~-methyl morpholine ~-ethyl morp~oline N-(2-hydroxyethyl) morpholine 2-~mino-2-methyl l propanol 2-dimethylamino-2-methyl l-propanol A su~ficient quantity of amine is employed to lS raise the pH of the aqueous solution to a range of 7-9, and preferably 7.5-8.5.
The incorporation of a polar solvent~ as a minor component o~ a ~aterjco-solvent blend, enhances the flow : -. .~
during cure of the enamel, and, ultimately, the smoothnees ~ ~-and concen~ricit~ of the resultant baked film. The amount ~ :
of polar solvent, when presentj is pre~erably lO to 25%.
Typical polar solvents that may be used are principally water~miscihle, although cresylic acid may be incorporated in judicious amounts as well. They are:
N-methyl pyrrolidone , ~ 3~9~-~

butyrolackone dimethyl sulfoxide diacetone alcohol dioxane glycol ethers, e.g., methoxyethanol, ethoxy-ethanol, butoxyethanol, diethylene glycol monomethyl ether alcohols, e.g., ethyl alcohol, isopropyl alco-hol, methyl alcohol, glycols such as ethyl-ene glycol, diethylene glycol, triethylene glycol, trimekhylene glycol, propylene glycol, dipropylene glycol kekones, e.g., acetone, methyl ethyl ketone glycol ether acetates, e.g., methoxyethyl ace-tate, ethoxyethylacetate, butoxyethyl acetate glycol diethers, e.g., diethylene glycol di-methyl ether, diethylene glycol diethyl ether :
The amount of cosolvenk incorporated al g wi;th water may range from 0-4~/O of the total blend, and pre-erably 10-25%, e.~., 2~/o.
As a result of the use of low molecular weight prepolymers the solids of either water-~or solvent-based ;
enamels are much higher than the conventional solvent-based enamels, namely in the 50-55% solids range for both of the former versus 30-35% for the latter. The general sol.ids range may be 40-65%, and the preferred range is a, 5 - 6 (P~o .
rrhe products of the invention are applied to the wi.re, liks conventiona:l wlre enamels, by means of dies, felt wipe or free dip.
The follow.ing polyester-imide example~ illus-trate the invention:

a. Prepar~tion of Polymer Mol % Mol %
of of Total Weight Total React~
Reactants qrams Mo]s Diacids ants ~A) Ethylene Glycol273 4040 36.55 (B) Tris(hydroxyethyl) 935 3.58 29.73 :
isocyanurate (~HEIC) (C) Trimellitic Anhydride 603 3.14 2 0 (TMA) *
(D) Methylene Dianiline 310 1.56 (MD~) *
(E)Terephthalic Acid 415 2.50 61.58 20.76 : *or as Diimide Diacid 1.56 38~42 12.96 OH/COOH= 2.40/1 Materials A, B, C,~D and E were charged into a five liter, three-necked flask equipped with an agitator driven by an electronically-controlled motor, gas inlet ~ ~k~

tube, thermometers fox flask and dis~illing head, 3-bubblecap Snyder fractionating column and water-cooled condenser. A blanket of nitrogen was applied to the charge, and the temperature increased gradually to 450-460F~, and held there until the desired physicals wereaktained, ~t a viscosity of U 1/4 as measured at 30%
solids in cresylic acid the reaction was terminated, and the melt discharged into a pan to solidify.
b. Preparation of Aqueous Wire_Enamel The hard resin was then fractured into small chun]cs, and 400 grams of the polymer along with 50 grams of ~-methyl pyrrolidone (NMP) was charged to a 3-liter, 3-neck round-hottom flask, and heated to 250-270F until the polymer was fluid and dissolved. At a temperature of 240-250F, a mixture of 50 grams each of distilled water and dlmethylethanolamine (DMEA) were added to the flask carefully. Additional water, amine, and solvent were added to reduce the viscosity to Z (on the Gardner-Holdt scale), obtain a pH of 7.5-8.5, and a solids of 53.3%. Then on a solids-to-solids basis 4.5% Tyzor TE
was added to the solution to make the finlshed enamel ~ ;~
having a viscosity of X 1/4, a pEI of 8, and a solids of 54 ol% ~

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a. Prepar tion of PolYmer Mol % Mol %
of of Total Weight Total React-Reactants ~rams Mols Diacid~ ants (A) Ethylene Glycol j273 4.40 39.82 ~B) trH~Ic 935 3.58 32.40 (c ) ~rM~* 603 3.14 (D) MDA* 310 1.57 (E) ~exephkhalic Acid 249 1.50 48.86 13.57 * or as Diimide Diacid 1.57 51.14 14.21 OH/COOH = 3.19 The same equipment and pxocedure as outlined in example l(a) was employed in preparing this polymer.
It was controlled to a final viscosity of R 1/2 as meas-ured at 3~/0 solids in cresylic ac.id, and then discharged into a pan to solidify.
b. Preparation of Aqueous Wire Enamel Using the same equipment and procedure as da- -scribed in example l(b) an aqueous enamel was prepared by blending 500 grams of base polymer 2(a) with 62.5 grams NMP, 65 grams DMEA, 250 grams of distilled water, and 28.1 grams Tyzor TE to provide an enamel having the following liquid characteristics: Viscosity W 1/2, pH-8.35, % Solids-57~7, .

a, Preparation of Polymer Mol % Mol %
of of Total Weight Total React-e _ ants Gr~m~ MolS Diacids ants (A) Ethylene Glycol 440 7.10 54.83 (B) THEIC ~67 1.79 13.82 (C) TMA* 603 3.14 (D) MD~* 310 1.56 (E) Terephthali~ Acid ~lS 2.50 61.58 19.30 *or as Diimide Diacid 1.56 38.42 12.05 OH/COOH = 2.41 The same equipment and procedure as outlined in example l(a) was employed in preparing thls polymerO
It was reacted until the molten mass was clear and free of unreacted matter, and monitored to a viscosity of U 1/2 measured at 30% solids in cresylic acid and then allowed to solidify.
.20 b~ Preparat_ n of Aqueous Wire Enamel With the same equipment and procedure as out-lined in example l(b) an aqueous wire enamel was prepared thusly:
To 500 grams of base polymer 3(a) 65 grams of ~MP, 65 grams of DMEA, 252 grams of distilled water, and 28.1 grams of Tyzor TE were added to provide the follow-ing enamel properties ~iscosit~: X 3/4 % Solids: 57.54 ... . .
: : ~.: . .: . .

a. Pre~a ation of Poly~_ Mol % Mol %
of of Total Weight Total React-

5 Reac-tants Grams Mols Diacids ants (A) Ethylene Glycol 273 4~40 33.59 (B~ TEIEIC 935 3.58 27033 (C) ~M~* 385 2.00 (D) MDA* 1~8 1.00 10 (~) Terephthalic Acid 684 4.12 80.47 31~45 *or as Diimide Diacid 1.00 19.53 7.63 OH/COOH = 1.91/1 The same equipment and procedure as outlined in example l(a) was employed in preparing this polymerO
It was reacted until a sample was clear at 3~/0 solids in cxesylic acid, and then discharged into a pan to solidifyO
b. Preparation of Aqueous-Wire Enamel With the same equipment and procedure as out-lined in example l(b) an aqueous wire enamel was prepared thusly:
To 500 grams of base polymer 4(A) 130 gxams NMP, 50 grams-DMEA and 520 grams distilled water were added to provide an enamel with the following liquid properties ~iscosity: Y 1/2 +
% Solids: 41.7 ~18-~ 3~

EX~MPLE 5 a Preparation of Poly~mer .

Mol % Mol %
of of Total Weight Total React-Reactants Grams Mols Diacids ants (A) Ethylene (;lycol 523 8.436 62.96 (B) THEIC 234 0.897 6.69 (C) TM~* 603 3.140 (D) MDA* 310 1.566 (E) Terephthalic Acid 415 2.500 61 49 18.66 *or as Diimide Diacid 1.566 38.51 11.69 o~/COo~ = 2.41/1 The same equipment and procedure as outlined in example l(a) was employed in preparing this polymer.
It was reacted until a sample was clear at 3~/O solids in cresylic acid, and then discharged into a pan to solidify.
b. ~ e _namel With the same equipment and procedure as out- :
lined in example l(b) an aqueous wire enamel was prepared thusly:
To 500 grams of base polymer 5(a) there were added 63 grams ~MP, 50 grams DMEA, 252 grams distilled water and 28 grams Tyzor TE to provide an enamel with the 5 following liquid properties:
~iscosity: X 3/4 ~% Solids: 58.5 a. Pre~aration of Polymer Mol % Mol %
of of total Weight Total React-Reactanta Grams _ols Diacids ants (A) Ethylene Glycol 78812.710 70.64 (B) TMA* 7844.083 (C) MDA* 4032.035 10 (D) Terephthalic Acid 539 3.247 61.47 18.05 *or a5 Diimide Diacid 2.035 38.53 11.31 OH/COOH = 2.41/1 The same equipment and procedure as outlined in example l(a) was employed in preparing this polymer. It was controllad to a final viscosity of I 3/4 measured at 30~ solids in cresylic acid, and then discharged into a pan to solidify.
b. Preparation of a Solvent-Based Wire Enamel To 400 yrams of base polymer 6~a) there were added 314 grams cresylic acid and 186 grams of petroleum naphtha ~aromatic hydrocarbon) and heated to 300F until the polymer was completely dissolvedO Then the flask contents were cooled to 160F and 65 grams cresylic acid, 35 grams petroleum naphtha, 50 grams of a cresol-p~enolic condensate at 4~/O solids, and 110 grams of a trimer of toluenediisocyanate at 4~/O solids, were added and mixed until the solution was homogeneous. Eighteen grams-TPT
(tetraisopropyl titanate) was added at 160F. The batch temperature was increased to 250F and held there for two hours. Its liquid properties were:
Viscosity: G 1/2 % Solids: ~0 Since this solvent-based enamel turned cloudy on standing after a week, no a~ueous version thereof was made.
E~AMPhE 7 a. Preparation of Pol~mer Mol % Mol %
of of Total Weight Mols Total React Reactants Grams Dlacids ants (A) Diethylene Glycol 425 4.009 32.24 .15 (B) THEIC 850 3.257 26.20 (C) TM~* 548 2.854 (D) MDA* 282 1~424 (E) Terephthalic ~cid 466 2.80754.3 22.58 (F) Azelai.c Acid 176 0.936 18.1 7.53 *or as Diimide Diacid 1.424 27.6 11045 OH/COOH = 1.72/1 ~ rocedure: The techni~ue employed in this ex-ample involves reacting the various chemical in a defin-ite sequenceO Reactants (A), (B) and (C) were charged into a five liter, three-necked flask equipped with a motor-driven agitator, gas lnlet tube, a Dean-Strap water trap fitted with a thermometer and water-cooled conden-ser. The flask was blanketed with nitrogen and the tem-perature raised to 228F. At 228F material ~D~ was added to the flask and the temperature gradually raised to 320F at which distillation commenced. The reaction was con-tinued until all of the T~ had reacted and the temperature peaked at 410F and 72 mls. of water as clistillate had been collected. The batch was cooled to 338E' and material (E) was added. The temperature was gradually raised to ~50F and held until another 98 mls. oE distillate was collec-ted and a sample of melt as a pill was clear cold. Batch was cooled -to 320F and material (F) was added. The temperature was raised to 330F and periodically sampled for progress of the reaction as measured by an increase in viscosity. When a viscosity of T 3/~ + of a resin sample thinned to 30% solids in cresylic acid was attained, the flask's contents were dis-charged shortly therea~ter into a metal gallon can and allowed to harden.
b. Preparation of Aqueous Wire Enamels Enamel -1 With the same equipment and procedure as outlined in example l(b) an aqueous wire enamel was prepared thusly:
To 220 grams o:E base polymer 7(a), there were added 110 grams butoxy ethanol, 11 grams of DMEA, 440 grams dis-tilled water, 12.4 grams hydroxymethylated derivative of diacetone acrylamide (~MDAA) and 4.8 grams Tyzor LA to provide an enamel with the following liquid properties:

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Viscosity: X 3/4 pH: 8.0 % Solids: 28~7 Enamel -2 The same equipment as outlined ln ecample l(b) was employed, but the procedure for preparing the aqueous wire enamel was different, namely:
To 240 grams of base polymer 7(a) there were added 60 grams of butoxy ethanol, and the two were heated to 290F
until the polymer was completely dissolved. Then 7.2 grams of Tyzor TPT (Tetraisopropyl titanate) were added at 2900F.
Then the temperature was raised to 320F and held there for one hour. The flask contents were cooled to 250F and 50 grams of butoxy ethanol were added and mixed until homogene-ous. Then 15 grams DMEA and 440 grams distilled water were added, and the mixkure stirred until solution was clear and uniform. Its liquid properties were:
Viscosity: M 1/4 - -~
pH: 8.06 % Solids: 29.56 ~i .

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a. Preparation of Polymer Mol % Mol %
Weight of Total of Total Reactants Grams Mols DiacidsReactants (A) Diethylene Glycol 425 4.009 32.25 (B) THEIC 850 3.257 26.20 (C) ~MA* 274 1.427 (D) p-Amino Benzoic 195 1.423 Acid*
(E) Terephthalic Acid 466 2.807 54.33 22.58 (F) Azelaic Acid 176 0.936 18.127.52 *Monoimide-Diacid 27.55 11.45 OH/COO~ = 1.72/1 The same equipment and procedure as outlined in example 7(a) was employed in preparing this polymer. It was controlled to a final viscosity of R 1/4 measured at 30%
solids in cresylic acid, and then discharged into a pan to solidify.
b. Preparation of Aqueous Wire Enamels Enamel -1 With the same equipment and procedure as outlined in example l(b) an aqueous wire enamel was prepared thusly: -To 640 grams of base polymer 8(a) there were added 270 grams butoxyethanol, 22 grams DMEA and 540 grams dis-tilled water to provide an enamel with no curative incorpo-rated therein, and havin~ the following liquid properties:

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Viscosity: Q l/4 pH: 7.8 ~ Solids: 43.5 Enamel ~-2 -To 850 grams oE enamel -l ahove, 20.8 grams of HMDAA and eight (8) grams of Tyzor L~ were added as curring agents. Its liquid properties were:
Viscosity: Q l/4 pH: 7.8 % Solids: 42.2 a. Preparation of Polymer Mol %Mol ~
Weight of Total of Total Reactants Grams Mols DiacidsReactants (A) Diethylene Glycol 493 4.651 39.10 (B) Glycerine (96%) 199 2.077 17.46 (C) TMA* 54~ 2.854 (D) MDA* 282 1.424 (E) Terephthalic Acid 466 2.807 54.30 23.60 (F) Azelaic Acid 176 0.936 18.107.87 *or as Diimide Diacid 1.424 27.60 11.97 OH/COOH = 1.50/1 The same procedure and technique as outlined in example 7(a) was employed in preparing this polymer. It was controlled to a final viscosity of V l/2~ at 30% solids in cresylic acid, and then discharged into a pan to solidify.

b. Preparation of Aqueous Wire Enamel To 480 grams of base polymer 9(a) there were added 120 grams butoxyethanol and the two heated to 290F until the polymer was completely d.issolved. Then 28.8 grams of a Tyzor TPT solution (50~ in butoxy ethanol) was addecl slowly to the flask at 280F d.ropwise over a period of 65 minutes and the flask stirred until the mixture was uniform. The temperature was raised to 320F and held there for one hour. The flask contents were cooled to 250F and 75 grams butoxy ethanol 10 were added, and stirring carried out until the solution was ~ :~
homogeneous. This was followed by the addition of 33 grams VMEA and 840 grams of distilled water and the mixture stirred until a homogeneous solution was obtained. Its liquid proper-ties were:
Viscosity: M
pH: 8.1 % Solids: 30.4 a. Preparation of Polymer Mol %Mol %
Weight of Total of Total Reactants Grams ~ols Diaci.ds Reactants (A) Diethylene Glycol 548 5.170 43.48 (B) Glycerine (96%) 149 1.555 13.08 (C) TMA* 548 2.857 (D) MDA* 282 1.424 (E) Terephthalic Acid 466 2.807 54.30 23.60 (F) Azelaic Acid 176 0.936 18.107.87 *or as Diimide Diacid 1.424 27.60 11.97 OH/COOH = 1.45/1 The same equipment and procedure as outlined in example 7(a) was employed in preparing this polymer. It was controlled to a :Einal viscosity of V l/4~ measured at 30%
solids in cresylic acid, and -then discharged into a pan to solidify. The hard resin had a ball and ring melt point of 79C.
b. Prepa _t on o Aq eous Wire Ena~el The same equipment as outlined in example l(b) was employed, but the procedure for preparing the aqueous wire enamel was different, namely:
To 480 grams of base polymer lO(a), 120 grams butoxy ethanol (previously dried over anhydrous CaSO4) were added, and the two heated to 290F until the polymer was completely dissolved~ The batch was cooled to 200F and 15 grams of Tyzor TPT added dropwise over a 20 minute period.
At 220F 50 grams of butoxy ethanol were added and the temperature raised to 253F in ten minutes, and held there for two hours. The flask contents were cooled to 170F and 30 grams of DMEA and 200 grams of distilled water were added 20. and mixed in until solution was homogeneous. An additional 30 grams butoxy ethanol and 655 grams distilled water were added to adjust the enamel to the following liquid properties:

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Viscosity: V 1/4 pH: 8.05 % Solids: 30.4 EXA~PLE 11 a. Preparation of Polymer Mol %Mol %
Weight of Total of Total Reactants Grams Mols DiacidsReactants ~A) Diethylene Glycol 578 5.453 46.17 (B) Glycerine (96%) 114 1.190 10.07 (C) TMA* 548 2.854 (D) MDA* 282 1.424 (E) Terephthalic Acid 466 2.807 54.30 23.77 (F) Azelaic Acid 176 0.936 18.107.93 *or as Diimide Diacid 1.424 27.60 12.06 OH/COOH = 1.40/1 The same equipment and procedure as outlined in example 7(a) was employed in preparing this polymer.
It was reacted until the molten polymer was free of unreacted solid matter, i.e., clear and speck-free. A total of 218 mls. distillate was collected.
b. Preparation of Aqueous Wire Enamels Unmodified Enamel The same equipment as outlined in example l(b) was employed in preparing this aqueous enamel without curatives or in an unmodified form, namely:

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To 600 grams of base polymer ll(a) there were added 67 grams butoxy ethanol and the two heated to 290F until the polymer was completely dissolved. The temperature was lowered to 250F and 30 grams oE DMEA were added, and mixed in until the solution was clear. Then 268 grams of distilled water we.re added, and the mixture stirred until homogeneous. An additional 480 grams of distilled water, 120 grams butoxy ethanol and 30 grams DMEA were added to adjust to the follow-ing liquid properties:
Viscosity: W 1/4 pH: 7.8 % Solids: 37.8 % Butoxy-ethanol: 20 (of total solvent blend) Enamel -1 To 700 grams of unmodified enamel ll(b) there were added 14.82 grams HMDAA and 48.8 grams Tyzor LA, and the composition stirred until homogeneous. Its liquid properties were:
Viscosity: Y 1/2 .

pH: 7.85 % Solids: 38.8 Enamel ~2 To 800 grams of unmodified enamel ll(b) there were added 16.93 grams HMDAA and 34.87 grams Tyzor TE, and the composition was stirred until homogeneous. Its liquid properties were:
visc05ity: Q 3/4 pH; 8.4 % Solids 39,7 EXA~PLE 12 a. _eparation of Polymer Mol %Mol %
ofof Total Weight ~otal React-Reactants Grams Mols Diacids ants (A) Diethylene Glycol 425 4.009 31.62 (B) Dantocol~DHE~ 202 1.074 8.47 (C) THEIC 634 2.429 19.16 (D) TMA* 548 2.854 (E) MDA 282 1.424 (F) Terephthalic Acid 466 2.807 54.30 22.14 (G) Azelaic Acid 176 0.936 18.107.38 *or as Diimide Diacid 1.424 27.6011.23 OH/C~OH = 1.66/1 Manufactured by Glyco Chemicals, Inc. The chemical name is 1,3-bis(hydroxyethyl), 5,5'-dimethyl hydantoin.
The same e~uipment and procedure as outlined in example 7(a) was employed in preparing this polymer.

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It was controlled to a final ViSCoBity of U 3/4+ measur-ed at 3~O solids in cresylic acid, and then discharged into a pan to solidify.
b. Preparation of AqLeous Wire ~namel To 480 grams of base polymer 12~a) there were added l20 gram~ butoxyethanol and the two were heated to 290F until the polymer was completaly dissolved. Then 28.8 grams of a T~zor TPT solution (5~% in butoxy-ethanol) was added dropwise to the flask at 300F over a period of 85 minutes. This was followed immediately wit~ the addi-tion o~ lO grams of butoxyethanol, and the temperature held at 300F for 90 minutes. At a temperature of 180F, 25 gram~ of ~MEA and 200 gram~ of distilled water were added, and the composition stirred until the solution was homogeneous. The enamel was very viscous and so an addi-tional 42 grams of butoxyethanol and 504 grams of dis-tilled water were added to adjust it to the following liquid characteristics Viscosity: X~
pH: 8.l % Solids 34.3 EXA~æLE 13 a~ r~ti ~ ~

Mol % Mol %
of of Total Wt. Total React-~eactant~ Grams Mols :tPiacids ants (P~) Diethylene Glycol 425 4.009 32.28 (El) TH~IC 850 3,257 26.23 ~C) TMA* 548 2.854 ~D) oxydianiline* 282 1.410 ~E) Terephthalic Acid 466 2.80754.47 22.60 10 (F) Azelaic Acid 176 0.936 18.177.54 *or as Diimide Diacid 27.36 11.35 OH/COOH- 1.72/1 The same equipment and procedure as outlined in example 7(a) was employed in preparing this polymer.
15 It was controlled to a ~inal viscosity of U 3/4+ at 30/0 solids ln cresylic acid, and then dumped into a metal can to harden~
b. Preparation of Aqueous Wire Enamel To 480 grams~of base polymer 13(a) there were 20 added 120 grams butoxyethanol and t~e two heated to 290 F until the pol~ner was completely di~solved. Then 28.8 grams of a Tyzor TPT solution (50% in butoxyethanol) was added to the flask a~ 290F dropwise over a period of 50 minutes and the compvsitivn sti~red until ur~ifs:~rm., Im-25 mediately thereafter 4û gramæ of buto~yethanol were added,and the .contents held at 300F for ~ne hour. me hatch was cooled to 135F and 30 grams o~ DMEA and 660 grams of distilled water were added, and the composition stirred , . .
; . . .
, ' ' until the solution was homogen~ous. Its liquid proper-ties were:
Viscosity: U 3/4 pH: 7.8 % Solid~: 35.3 a. Praparation of Polymer ~ol ~ Mol %
of of Total Wt. Total React-~eactants Grams Mols Diacids ants (A) Ethylene Glycol 244 3.9355 30.50 H~IC B64 3.3103 25.70 (C) TMA* S48 2.8542 (~) MD~* 282 1.4242 (~) Terephthalic Acid 271 1.632528.89 12.65 (F) Terephthalic Acid 270 1.62652~.79 12.60 (G) Benzoic Acid 118 0.9672 17.127.50 *or as Diimide Diacid 25.20 11.05 The same equipment and procedure as outlined:
in example 7(a) was employed in prepari~g this polymer.
It was controlled to a final viscosity of~V 1/4+ at 3~/O
solids in cresylic acid, and then discharged into a pan to solidify, b. Preparation of Agueous Wire Enamel To 200 grams of base polymer 14~a~ there were added 50 grams of ~-methyl pyrrolidone and ~he two were heated ko 270F~ The batch was cooled to 200DF and 10 grams of DMæA and 150 grams of di~tilled watar were added.

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After mixing for one hour the enamel was very viscous and 325 grams of di3tilled water, 50 gram3 of N-methyl p~rrolidone, 7 grams of DMEA and 10 grams of Tyzor TE
were added to adjust the enamel to the following liquid properties Vl8cosity: H 1/2 pH: 7.9 % Solids: 25.93 To illustrate the excellent electrical proper-ties of these aqueous wire anamels, several of the exam-ples were selected and their solvent-based counterparts using the same base polymer were c~mpared propertywise.
In practically all properties the aqueous based enamels compared very avorably.
The solvent employed in the solvent based enam-els in-Table I was a mixture of cresylia acid and aro-matic naphtha at a ratio of 55% to 35%, respectively.
After applying the enamels to the wire at room temperature, they were baked on in conventional manner at 900F. Conventional baking temperatures can be em~
ployed, e.g~, 700 to 900P.
~ he effect of titanate content was studied with wire enamels prepared with the polymer of ~xample 1. As indicated in Table II, the principal effect of increased 25 titanate content was the large ri~e in the dissipation ;

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S The other wire properties were all quite comparable with those of solvent based enamels.
The compositions can comprise, consist essen-tially of, or consist of the materials set ~orth and the process can comprise, consist essentially of, or consi~t o~ the steps recited.

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Claims (50)

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

1. A water soluble thermosetting second polyester-imide prepolymer composition prepared by reacting reactants consisting essentially of a tertiary amine and a first polyester- imide prepolymer having a number average molecular weight 600-1300, an OH:COOH ratio of from 1.8:1 to 2.5:1 and an imide content of 5 to 60% based on the total imide and ester moieties, the alcohol of the ester moiety consisting essentially of 10 to 90% of the total equivalents of dihydric alcohol and the balance of the alcohol containing at least three hydroxyl groups, the acid component of the ester moiety consisting essentially of di-carboxylic acid, the imide moiety consisting of essentially of the reaction product of approximately two moles of an aromatic monocarboxylic acid monoanhydride with one mole of an aromatic diamine.

2. A composition according to Claim 1, including a titamate curing agent.

3. A composition according to Claim 2, wherein the titanate is water soluble titanate.

4. A composition according to Claim 1, dissolved in water said composition being suitable for use as a wire enamel.

5. A composition according to Claim 4, including a minor amount of a water soluble polar organic solvent.

6. A composition according to Claim 5, including a water soluble titanate curing agent.

7. A composition according to Claim 4 wherein the polyimide comprises the reaction product of an aro-matic diamine and an aromatic monocarboxylic acid mono-anhydride.

8. A composition according to Claim 7, wherein the aromatic monocarboxylic acid monoanhydride is trimellitic anhydride.

9. A composition according to Claim 8, wherein the alcohol of the polyester comprises tris(hydroxyethyl)-isocyanurate.

10. A composition according to Claim 8, wherein the acid of the polyester comprises terephthalic acid or iso-phthalic acid.

11. A composition according to Claim 10, wherein the acid of the polyester comprises terephthalic acid.

12. A composition according to Claim 11, wherein the acid of the polyester comprises a diimide-dicarboxylic acid wherein the imide groups are contained in five-membered imide rings.

13. A composition according to Claim 12, wherein the polyimide is the imide of 2 moles of trimellitic anhydride and 1 mole of oxydianiline or methylene dianiline.

14. A composition according to Claim 13, wherein the polyimide is 35 to 55% of the total of polyimide and polyester.

15. A composition according to Claim 14, wherein the ratio of OH:COOH is from 2.20 to 2.50:1.

16. A composition according to Claim 15 including a titanate curing agent for polyesters.

17. A composition according to Claim 16, wherein the titanate is water-soluble.

18. A process for the production of an insulating coating on an electrical conductor comprising coating the conductor by passing it through the aqueous composition of Claim 17.

19. A coated electrical conductor prepared by the process of Claim 18.

20. A process for the production of an insulating coating on an electrical conductor comprising coating the conductor by passing it through the aqueous composition of Claim 16.

21. A coated electrical conductor prepared by the process of Claim 20.

22. A process for the production of an insulating coating on an electrical conductor comprising coating the conductor by passing it through the aqueous composition of Claim 15.

23. A coated electrical conductor prepared by the process of Claim 22.

24. A process for the production of an insulating coating on an electrical conductor comprising coating the conductor by passing it through the aqueous composition of Claim 14.

25. A coated electrical conductor prepared by the process of Claim 24.

26. A process for the production of an insulating coating on an electrical conductor comprising coating the conductor by passing it through the aqueous composition of Claim 13.

27. A coated electrical conductor prepared by the process of Claim 26.

28. A process for the production of an insulating coating on an electrical conductor comprising coating the conductor by passing it through the aqueous composition of Claim 12.

29. A coated electrical conductor prepared by the process of Claim 28.

30. A process for the production of an insulat-ing coating on an electrical conductor comprising coating the conductor by passing it through the aqueous composi-tion of Claim 11.

31. A coated electrical conductor prepared by the process of Claim 30.

32. A process for the production of an insul-ating coating on an electrical conductor comprising coat-ing the conductor by passing it through the aqueous com-position of Claim 10.

33. A coated electrical conductor prepared by the process of Claim 32.

34. A process for the production of an insul-ating coating on an electrical conductor comprising coat-ing the conductor by passing it through the aqueous com-position of Claim 9.

35. A coated electrical conductor prepared by the process of Claim 34.

36. A process for the production of an insul-ating coating on an electrical conductor comprising coat-ing the conductor by passing it through the aqueous com-position of Claim 8.

37. A coated electrical conductor prepared by the process of Claim 36.

38. A process for the production of an insul-ating coating on an electrical conductor comprising coat-ing the conductor by passing it through the aqueous com-position of Claim 7.

39. A coated electrical conductor prepared by the process of Claim 38.

40. A process for the production of an insul-ating coating on an electrical conductor comprising coat-ing the conductor by passing it through the aqueous com-position of Claim 6.

41. A coated electrical conductor prepared by the process of Claim 40.

42. A process for the production of an insul-ating coating on an electrical conductor comprising coat-ing the conductor by passing it through the aqueous com-position of Claim 5.

43. A coated electrical conductor prepared by the process of Claim 42.

44. A process for the production of an insul-ating coating on an electrical conductor comprising coat-ing the conductor by passing it through the aqueous com-position of Claim 4.

45. A coated electrical conductor prepared by the process of Claim 44.

46. A process of preparing the composition of Claim 5 comprising dissolving the initial prepolymer in a water soluble polar organic solvent and then adding water.

47. A composition according to Claim 5, wherein the solvent is N-methyl pyrrolidone, butyrolactone, di-methyl sulfoxide, diacetone alcohol, dioxane, a mono al-koxy ether of a glycol, a glycol, a ketone, a mono alkoxy ether of a glycol acetate, an alkanol or a dialkoxy ether of a glycol and is present in an amount of 10 to 40% of the total solvent.

48. A composition according to Claim 5, wherein the tertiary amine is an alkyl alkanolamine, an alkyl mor-pholine or a hydroxyalkyl morpholine.

49. A composition according to Claim 5, wherein the tertiary amine is dimethyl ethanolamine.

50. A composition according to Claim 16, where-in the tertiary amine is dimethyl ethanolamine.