GB2052308A - Dual coated electrical conductor - Google Patents

Abstract

Electrical conductors such as mag- net wire and magnet strip are insulated with an undercoat of a polyester, a polyesterimide or a polyester amide imide and an overcoat of a polyetherimide, optionally including isocyanates, hydantoins, aliphatic amino compounds, phenolic resins, amino resins, epoxy resins or a mixture of any of the foregoing.

Description

SPECIFICATION Dual coated electrical conductor This application relates to the manufacture of insulated conductors generally referred to as magnet wire or magnet strip. More particularly it relates to electrical conductors insulated with polyester, polyesterimide or polyester amide imide undercoats and a tough and abrasion resistant overcoat of a polyetherimide, alone, or including organic additives.

Polyesters have long been used as magnet wire enamels see, for example, U.S. 2,936,296. More recently, there have been marketed polyester enamels wherein tris(2-hydroxyethyl)isocyanurate has constituted a portion of the polyols in the ester formulations, see, for example, U.S. 3,342,780. Even more recently, there have been introduced polyester imides and polyester amidimides which include within the polyester chain linkages formed from trimellitic anhydride and aromatic diamines such as diaminodiphenylmethane and diaminodiphenyl ether also known as methylenedianiline and oxydianiline, see U.K. Patent 973,377.

Obviously, such polyester-imides and polyester amide imides can also be modified with tris (2-hydroxyethyl)isocyanurate, see U.S. 3,426,098 and U.S. 3,688,175.

Still more recently, polyether imides comprising the reaction products of bisether an hydrides with organic diamines have been suggested for use as wire coatings, being deposited on the conductor either from high cost solvents, U.S. 3,847,867; or as powders from fluidized beds, U.S. 4,098,800; or from reactive ether solvents, U.S. 4,115,341; or as reaction products prepared in the presence of a phenolic solvent, U.S.

4,024,010.

While these enamels provide coatings with excellent thermal stability, there are problems with heat shock and solvent shock performance. In addition, toughness and abrasion resistance to withstand the high speeds by dereeling and winding, stopping and starting could stand improvement.

Such properties in the case of polyesters and polyesterimides have in the past been proposed to be improved by overcoating with a linear thermoplastic polyester, U.S. 3,022,200, or with a polyamideimide, U.S. 3,428,486 and 3,493,413. However, it is not possible to make an economical high solids solution of a linear polyester, and highly polar and expensive solvents, e.g. N-methylpyrrolidone and di methyl acetamide, are needed for the polyamide imide resins. All of the foregoing patents are incorporated herein by reference.

It has now been found that the heat shock and solvent shock of conductors coated with polyester, and polyesterimide and polyester amide imide wire enamels can be improved to a surprising degree by an overcoat of a polyetherimide, or a polyetherimide modified with an isocyanate, preferably a blocked isocyanate, a hydantoin, an aliphatic amino compound, a phenolic resin, an amino resin, an epoxy resin, or a mixture of any of the foregoing. Little extra cost is added because the polyetherimide is surprisingly amenable to solution in conventional wire enamel solvents, such as cresylic acid alone or combined with solvent naphthas.

According to the present invention there is provided an insulated electrical article comprising a conductor such as a copper wire, a wall of polyester, polyesterimide or polyester amide imide covering the conductor and a lesser wall of polyetherimide electrical insulation directly covering the polyester, polyesterimide or polyester amide imide insulation.

Preferably the polyester, polyesterimide or polyester amide imide comprises an isocyanurated polyester, isocyanurated polyesterimide or polyester amide imide. Espcially preferably the polyester comprises the reaction product of tris(2-hydroxyethyl)isocyanurate and a compound selected from terephthalic acid, dimethyl terephthalate, isophthalic acid, dimethyl isophthalate or a mixture of any of the foregoing; and the polyester-imide or polyester amide imide comprises the reaction product of tris(2-hydroxyethyl)ocyanurate; trimellitic anhydride; a compound selected from terephthalic acid, dimethyl terephthalate, sophthalic acid, dimethyl isophthalic acid or a mixture of any of the foregoing; and an aromatic diamine; preferably diaminodiphenyl methane.The polyetherimide will comprise the reaction product of an aromatic bis(ether anhydride) and an organic diamine, and especially preferably 2,2-bis-[4-(3,4- dicarboxyphenoxy)phenyl]propane dianhydride and metaphenylenediamine or diaminodiphenyl-methane.

In the drawing the figure shows a section of a magnet wire made according to this invention.

In the figure a magnet wire indicated generally by the numeral 10 has a conductor 11 covered with a layer 12 of a polyester, polyesterimide or polyester amide imide enamel and immediately over it a layer 13 of polyether imide enamel. Although the drawing illustrates a conductor 11 that is circular in section, it will be understood that square or rectangular conductors in the form of flat strips or foils may also be used without departing from the invention.

The layer 12 comprises a polymeric resin formed by (i) reacting glycerine ortris(2-hydroxyethyl)- isocyanurate with dimethyl terephthalate or terephthalic acid (a polyester) or (ii) by further adding trimellitic anhydride and 4,4'-diaminodiphenylmethane (a polyester imide) or (iii) by reacting (1) a monoanhydride of an aromatic tricarboxylic acid, e.g., trimellitic anhydride, (2) an aromatic primary diamine compound, and (3) a polyester of a polyfunctional acid and a polyhydroxy compound (a polyester amide imide). The quantity of diacid-diimide precursor used is such that 7-25 molar percent of the total carbonyl content of the polyester imide resin after being totally cured is due to imide groups.

Tris(2-hydroxyethyl)-isocyanurate imparts maximum heat aging properties to enamel 12 but other polyols may be substituted for it or glycerine up to 50 equivalent percent, including ethylene glycol, pentaerythritol, 1,1 ,l-trimethylolpropane, sorbitol, mannitol, dipentaerythritol, butanediol-1,4, pentanediol-1,5; 1 ,4-cyclohexanedimethanol, and the like.

A suitable isocyanurated polyester for layer 12 can be made by any one of the examples of above-mentioned U.S. 3,342,780. One procedure (Example 5) is as follows: Ingredient Amount Tris(2-hydroxyethyl)isocyanurate, g. 992 Ethylene glycol, g. 88 Dimethyl terephthalate, g. 920 Litharge, g. 0.3 Xylol, ml. 100 Solvesso 100 naphtha, ml. 200 The above mixture is heated slowly in a suitable vessel to 440"F. Cresylic acid then is added to yield a solids content of 67.2%. One thousand grams of the above material is then mixed with 680 g. of cresylic acid, 1008 g. of Solvesso 100 and 26.9 g. of tetraisopropyl titanate.

For convenience, a commercial wire enamel of this type which also include conventional additives, is available from Schenectady Chemicals, Inc., Schenectady, N.Y., U.S.A., under the tradename ISONEL 200E.

A suitable isocyanurated polyester imide for layer 12 can be made by Example 1 of above-mentioned U.S.

3,493,413, as follows: Ingredient Amount Tris(2-hydroxyethyl)isocyanurate 810 Dimethyl terephthalate 486 Cresol 100 Cerium naphthenate 5 Calcium naphthenate 1.5 The listed components are heated slowly until 3 mols. of methanol distill off at about 200"C.; diluted with 850 g. of cresol and cooled to 90"C. Thereafter 745 g. oftrimellitic anhydride and 382 g. of 4,4'-diaminodiphenylmethane are added. The water is distilled off and, after the precipitate has become clear, it is diluted with cresol to a concentration of about 60%. Thereafter, 1.7% of the solid resin weight of tetrabutyl titanate and 0.28% ofp-toluenesulfonic acid are added along with cresol, solvent-naphtha and xylene to a solids content of about 30%.

Although 4,4'-diaminodiphenylmethane has been shown, other divalent aromatic amines can be used, such as metaphenylene-diamine, diaminobiphenyl, diaminodiphenylsulfone, diaminodiphenyl ether, diaminoditolyl ether, diaminodiphenyl propane, 4,4'-diaminotriphenylamine, and the like. It is specifically contemplated also to include, if desired, isocyanates such as the trimer of trisu bstituted phenol or cresol blocked cyanuric acid, from 1 to 25%; preferably 5 to 10%, on a solids basis (MODUR SH).

For convenience, a commercial isocyanurated polyester imide wire enamel of the foregoing type is available from Schenectady Chemicals, Inc. underthetradename Isomid and an example from General Electric Co is known as IMIDEX-E.

A suitable isocyanurated polyester amide imide for layer 12 can be made by any of the Examples of the above-mentioned U.S. 3,668,175. One procedure (Example 3) is as follows: Ingredients Parts by Weight PartA: tris(2-hydroxyethyl)isocyanurate 234 trimellitic anhydride 69 isopropyl titanate 1.6 Part B: methylene dianiline (MDA) 268 trimellitic anhydride (TMA) 415 Part A, with 53.9 g. of m. p-cresol is heated to 200"C at a rate of 10"C per hour and held at 200"C until a thread forming stage is reached. Then 1010 parts of m,p-cresol is added. The MDA of Part B is added. The TMA is added slowly over one hour. Temperature is increased to 19 C and held until clear and thread-forming stage is reached. Dilute with 803 parts of cresylic acid and 648 parts of Solvesso 100 and then to viscosity of 9 poises at 25 C with 1:1 cresylic acid-Solvesso 100.

For convenience, a commercial isocyanurated polyester amide imide wire enamel of the foregoin type is available from Westinghouse Electric Company under the tradename OMEGA.

A suitable polyether imide for layer 13 can be made by any of the Examples of above-mentioned U.S.

3,847,867. One procedure (Example 2) is as follows: Ingredients Parts by weight 2,2-Bis-[4-(2,3-dicarboxyphenoxy)- 100.0 phenyl]propane dianhydride 4,4'-diaminodiphenylmethane 37.3 Ortho-dichlorobenzene 1300 Toluene 50 The mixture of ingredients is stirred and heated to reflux for five hours under a nitrogen atmosphere. In the course of reaction, water forms and is removed by azeotropic distillation. Upon cooling, the reaction mixture is poured into methanol to isolate the polymer.

The procedure can be repeated with the following: Ingredients Parts by weight 4,4'-Bis[2,3-carboxyphenoxy)- 100.0 phenyl]propane dianhydride Meta-phenylenediamine 20.4 Ortho-dichlorobenzene 1300 Toluene 50 An enamel solution is prepared by adding to asuitablefiask the following: Ingredients Parts by weight Polyether-imide (isolated) 800 Cresylic acid 2240 Solvesso 100 naphtha 960 The above is heated to 90"C with agitation for two hours to provide a clear wire enamel.

Although 2,2-bis-[4-(2,3-dicarboxyphenoxy)phenyl]propane dianhydride and methylene dianiline and metaphenylene-diamine have been shown, other divalent aromatic bis(ether anhydrides) and organic diamines can be used, such as 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride; 4,4'-bis(3,4dicarboxy phenoxy)diphenyl sulfide dianhydride, and the like, as well as 4,4'-diaminodiphenylether, hexamethylene-diamine, and the like. U.S. 3,847,867 is incorporated to avoid unnecessarily repetitious disclosure.

Example 1 A solution of commercially available isocyanurated polyester enamel, tradename Isonel E (see above), is applied as a base coat to copper magnet wire using a 6' electric two zone oven in four passes to give a 2.3 mail. coating. To this coating is then applied a coating of the polyether imide comprising the reaction product of equimolar amounts of 2,2-bis-[3-(3,4-dicarboxyphenoxy)-phenyl]-propane dianhydride and methylenedianiline as described above. The total build is 3.0 mil and therefore the outer, thinner layer of polyetherimide is 0.7 mils. thick. Wire speeds and 10', 9' and 8' per minute through the tower having a "C temp. profile of 180 Rad.; 230 Bottom; 365 Top; 415 Aux.The properties of the coated wires are set forth in Table 1: TABLE 1 Properties of dual coated magnet wire Wire Speed 10' 9' 8' Surface Appearance B B-B B-B+ Flex 25% 1X 1X 1X NMP Resis 5"-70"C fail borderline pass Dissipation Factor210 C 52 17 4 Cut Thru 2000g., "C. 300 305 340 Dielectric Strength, KV 8.1 8.7 10.3 Burnout overload figure of merit (OFM) 7.5 8.8 7.8 The optimum overcoating speed 8' gives an eminently satisfactory coated conductor.

Example 2 A base enamel solution is prepared from: Ingredients Parts by weight Polyether-imide from 4,4-bis[(2,3 carboxyphenoxy)-phenyl]propane di anhydride and metaphenylenediamine 800 Cresylic acid 2240 Solvesso 100 naphtha 960 The mixture is heated in a flask, at 900C., for two hours to provide a clear enamel. 18 AWG copper wire coated with a commercially available polyesterimide wire enamel, IMIDEX-E, to a thickness of 2.4 mils., is overcoated with two passes of the above-described base enamel. Total build is 3.0 mils., of which the thinner overcoat comprises 0.6 mils. The cutthru temperature is 355"C., heat-shock-1X, and burnout overload figure of merit (OFM) is 6.16.

Example 3 A modified base enamel solution is prepared from: Ingredients Parts by weight Polyether imide enamel of Example 2 1000 Hydantoin (Mobay 2324), 30% solution 30 The isocyanurated polyesterimide wire is again coated in two passes to provide a thinner outer overcoat of hydantoin-modified polyether imide. When tested, the coated wire has a cut-thru temperature of 352"C.; heat shock-1X; and burnout (OFM) is 7.18.

Example 4 A modified base enamel solution is prepared from: Ingredients Parts by weight Polyetherimideenamel of Example 2 1000 Bisphenol-A-diglicidyl ether epoxy resin prepolymer (Shell, Epon 828) 10 The isocyanurated polyesterimide wire is again coated in two passes to provide a thinner outer overcoat of epoxy resin-modified polyether imide. When tested, the coated wire has a cut-thru temperature of 334"C.; heat shock-1X; and burnout (OFM) - 6.13.

Example 5 A modified base enamel solution is prepared from: Ingredients Parts by weight Polyetherimideenamel of Example 2 1000 Melamine-formaldehyde resin (Type 881) (American Cyanamide Co.) 10 The isocyanurated polyesterimide wire is again coated in two passes to provide a thinner outer overcoat of melamine-modified polyether imide. When tested, the coated wire has a cut thru temperature of 337"C.; heat shock-1X; and burnout (OFM) is 6.37.

Example 6 A modified base enamel solution is prepared from: Ingredients Parts by weight Polyether-imide from 4,4'-Bis[(2,3 carboxyphenoxy)phenyljpropane dian hydride and metaphenylenediamine 800 Solvesso 100 naphtha 960 Ingredients Parts by weight Cresylic acid 2240 Dibutyl tin dilaurate 6.8 Blocked isocyanate (Mondur SH, 40% solution) 81 The mixture is heated at 90"C for two hours to provide a clear enamel.

18 AGW copper wire coated with a commercially available isocyanurated polyester amide imide, OMEGA, is overcoated with a thinner layer of the above-described blocked isocyanate-modified base enamel. The cut thru temperature is 321 C.; heat shock-3X; and burnout (OFM) is 7.31.

Many variations will suggest themselves to those skilled in this art in light of the above-detailed description. For example, minor amounts of reactive compounds can be included in the base enamel for their conventional purposes. In this connection, the base enamel can include 3 and 6 parts by weight of 40% phenolic resin per hundred of polyether imide; or 5 parts of dimethylethanol amine per 100 parts of polyether imide; or a combination of phenolic and amino compound, or a combination of phenolic and blocked isocyanate (Mondur SH) can be used, and so forth. In general, the use of blocked isocyanate increases the cut thru temperature substantially. All such modifications are with in the full intended scope of the appended claims.

Claims (10)

1. An insulated electrical article comprising (a) a metallic conductor: (b) an undercoat of a polyester, a polyesterimide or a polyester amide imide electrical insulation covering said conductor; and (c) an overcoat of polyetherimide electrical insulation directly covering said undercoat.

2. An article as claimed in Claim 1 wherein undercoat further includes an isocyanate, a hydantoin, an aliphatic amino compound, a phenolic resin, an amino resin, an epoxy resin or a mixture of any of the foregoing.

3. An article as claimed in Claim 1 or 2 wherein undercoat (b) comprises an isocyanurated polyester, an isocyanurated polyesterimide or an isocyanurated polyester amide imide.

4. An article as claimed in any preceding Claim wherein said undercoat is a polyester comprising the reaction product of tris(2-hydroxyethyl)isocyanurate and terephthalic acid, dimethyl terephthalate, isophthalic acid, dimethyl isophthalate or a mixture of any of the foregoing.

5. An article as claimed in any of Claims 1 to 3 wherein the undercoat is a polyesterimide or polyester amide imide comprising the reaction product of an aromatic diamine; tris(2-hydroxyethyl)isocyanurate; trimellitic anhydride; and a compound selected from terephthalic acid, dimethyl terephthalate, isophthalic acid, dimethyl isophthalic acid or a mixture of any of the foregoing.

6. An article as claimed in Claim 5 wherein the diamine is diaminodiphenylmethane.

7. An article as claimed in any preceding Claim wherein the undercoat (c) comprises the reaction product of an aromatic bis(ether anhydride) and an organic diamine.

8. An article as claimed in Claim 7 wherein said aromatic bis(ether anhydride) is 2,2-bis-[4-(3,4dicarboxyphenoxy)phenyl]propane dianhydride and said organic diamine is metaphenylenediamine or diaminodiphenylmethane.

9. An article as claimed in any preceding Claim wherein the conductor is a copper wire.

10. An article as claimed in Claim 1 and substantially as herein before described with reference to any of the Examples.