Composition for bonding windings or core laminates in an electrical machine, and associated method

Patent metadata

Field	Value
Publication number	US-10370569-B2
Application number	US-201815864073-A
Country	US
Kind code	B2
Filing date	Jan 8, 2018
Priority date	Jun 6, 2014
Publication date	Aug 6, 2019
Grant date	Aug 6, 2019

Abstract

A curable composition for bonding windings or core laminates in an electrical machine is presented. The curable composition includes: (A) about 10 weight percent to about 25 weight percent of a polyfunctional cyanate ester; (B) about 35 weight percent to about 65 weight percent of a first difunctional cyanate ester, or a prepolymer thereof; (C) about 15 weight percent to about 40 weight percent of a second difunctional cyanate ester, or a prepolymer thereof. An associated method is also presented.

First claim

The invention claimed is:

1. A method for bonding a winding or a core laminate of an electrical machine, comprising:
impregnating the winding or the core laminate with a curable composition, comprising:
(A) about 10 weight percent to about 25 weight percent of a polyfunctional cyanate ester having a structure (I)
NCO—Ar 1 R 1 Y—R 1 n Ar 1 —OCN,  (I)

wherein “n” is an integer equal to or greater than 1, Y has a structure (i) or (ii)
*R 2 —Ar 2 —OCN, or  (i)

*Ar 2 —OCN,  (ii)

Ar 1 and Ar 2 are independently at each occurrence a C 5 -C 30 aromatic radical, R 1 and R 2 are independently at each occurrence a C 1 -C 3 aliphatic radical or a C 3 -C 20 cycloaliphatic radical, and * represents the bonding site;
(B) about 35 weight percent to about 65 weight percent of a first difunctional cyanate ester having a structure (II), or a prepolymer thereof
NCO—Ar 3 —R 3 —Ar 3 —OCN,  (II)

wherein Ar 3 is a C 5 -C 30 aromatic radical, R 3 is a bond or a C 1 -C 2 aliphatic radical; and
(C) about 15 weight percent to about 40 weight percent of a second difunctional cyanate ester having a structure (III), or a prepolymer thereof
NCO—Ar 4 —R 5 —Ar 4 —OCN,  (III)

wherein Ar 4 is a C 5 -C 30 aromatic radical, and R 5 is a C 3 -C 10 aliphatic radical;

applying a vacuum to the winding or the core laminate; and
heating the winding or the core laminate of the electrical machine to cure the curable composition and form a bonding material comprising the cured composition, wherein the electrical machine is selected from the group consisting of a motor, a generator, a transformer, a toxoid; an inductor, and combinations thereof.

2. The method of claim 1 , wherein the curable composition is substantially free of a solvent.

3. The method of claim 1 , wherein the curable composition further comprises a solvent.

4. The method of claim 1 , wherein a cured composition of the curable composition shows thermal dimensional stability such that the cured composition has less than 60 percent mean density change after heating at 280° C. for a time period greater than about 500 hours.

5. The method of claim 1 , wherein the polyfunctional cyanate ester comprises phenolic novolac cyanate ester, dicyclopentadiene novolac cyanate ester, 1,2,3-tris(4-cyanatophenyl)-propane, or combinations thereof.

6. The method of claim 1 , wherein the first difunctional cyanate ester comprises a structure having a formula (IV):

wherein Ar 3 is a C 5 -C 30 aromatic radical.

7. The method of claim 1 , wherein the second difunctional cyanate ester comprises a prepolymer of a difunctional cyanate ester having a formula (V):
NCO—Ar 4 —R 4 —Ar 4 —OCN,  (V)

wherein Ar 4 is a C 5 -C 30 aromatic radical, and R 4 is C 3 -C 20 aliphatic radical.

8. The method of claim 1 , wherein the second difunctional cyanate ester comprises a prepolymer of a difunctional cyanate ester having a formula (VI):

wherein Ar 4 is a C 5 -C 30 aromatic radical.

9. The method of claim 1 , wherein the curable varnish composition has a viscosity less than about 1000 centiPoise at 70° C.

10. The method of claim 1 , wherein a cured varnish composition of the curable composition has a crack resistance such that the average number of cracks having a dimension greater than 2 mm in length is equal to or less than one.

Assignees

• Gen Electric

Inventors

• Yin Weijun
• Yeager Gary William
• Flanagan Kevin Warner
• Simon David Andrew
• Boden Eugene Pauling
• Misner Kathryn Amanda

Classifications

• C08G2261/12

  Copolymers · CPC title

• B05D3/0493

  using vacuum · CPC title

• C08G73/10

  Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors · CPC title

• C08G73/0655 Primary

  from polycyanurates · CPC title

• C08G2190/00

  Compositions for sealing or packing joints · CPC title