Corrugated mica product

A corrugated, highly flexible mica insulating structure is disclosed which comprises one or more layers of mica paper impregnated with about 5 percent to about 25 percent by weight of a flexible polysiloxane resin having about 1 percent to about 4 percent by weight of an organic titanate and about 0.5 percent to about 2 percent by weight of a naphthenate based on polymer solids, said resin binder being partially cured or B-staged wherein the resulting papers are then corrugated to impart greater flexibility without a substantial loss of its dielectric properties.

EXAMPLE I 
A typical mica laminate was prepared from two sheets of 5 mils muscovite 
mica paper which had been impregnated with 10 percent of the polyxiloxane 
binder GE SR-224 containing 2 percent of monoalkoxy, isopropyl 
tri(dioctylpyrophosphato) titanate and 1 percent zinc naphthenate 
containing 8 percent zinc (Nuodex Products Div.). The impregnated paper 
was then stacked, two plies of 5 mils one on top of the other, placed 
between release sheets in the press, and B-staged for fifteen minutes at 
350.degree. F. (177.degree. C.) and 100 psi. The laminate was then allowed 
to cool to below 100.degree. F. (37.8.degree. C.) while under pressure and 
then removed from the press. The release sheets were then removed from the 
laminate and the laminate was then passed through a corrugating machin 
affixed with rollers having 92 rows of ridges 0.086 inch apart and having 
indentations about 0.067 inch deep. 
TABLE II 
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10 mil alkoxy 
10 mil 10 mil 
titanate 
10 mil new 
tetra-n-butyl 
silicone 
silicone 
chemistry 
chemistry 
titanate 
uncorrugated 
corrugated 
uncorrugated 
corrugated 
corrugated 
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Dielectric 
519 519 538 555 500+ 
strength in VPM 
Dielectric 
469 469 519 500 500+ 
strength after 
24 hrs. @ 96% RH 
Dielectric 
-- -- 393 332 500+ 
strength after 
24 hrs, immersion 
in H.sub.2 O @ 23.degree. C. 
Tensile Strength 
51 37.2 53 39 - 
(PSI) 
Water absorption 
-- -- 18.1 25 13 
(%) by weight 
after 24 hrs. 
Gurley stiffness 
6116 999 5191 845 - 
Arc Resistance 
249 249 225 252 248 
seconds 
__________________________________________________________________________ 
-- indicates that the sample had deteriorated so much that the test could 
not be performed 
+ indicates greater than 500 vpm 
- indicates test not performed 
The results of the corrugated product compared with the same product 
noncorrugated, demonstrates the unique properties of these products in 
which they are extremely flexible yet substantially retain their 
dielectric strength and improved moisture resistance as shown in Table II. 
Also compared in this Table are mica laminates using only a flexible 
silicone resin system without the titanate and naphthenate demonstrating 
how this product totally loses its dielectric strength to the point where 
it is not possible to test such a property once it is immersed in water 
for a 24 hour period. 
No other known corrugated mica laminate possesses these qualities. Another 
surprising result is that this method allows for production of a thermally 
stable, moisture resistant, mica laminate up to about 1/4 inch in 
thickness. 
In conclusion, the mica laminates prepared using the present method have 
remarkable and surprisingly different properties than other corrugated 
mica laminates produced in the past. The present laminates are well bonded 
and have significantly greater mechanical and dielectric strength. Such 
novel laminates again, will allow for their use in many new and novel 
applications, as well as those conventional applications described earlier 
in the Background. 
It should be understood that the invention is not limited to the particular 
embodiments shown and described herein, but that various changes and 
modifications may be made without departing from the spirit and scope of 
this novel concept as defined by the following claims.