FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See Section 10)
B-STAGE HEAT BONDING, BOTH SIDES FORMULATED EPOXY COATED, CERAMIC PAPER BASED ELECTRICAL INSULATING MATERIAL AND THE PROCESS OF MANUFACTURING THE SAME.
PRS Solutions Private Limited, a Company incorporated under the Companies Act, 1956 and having its office at 63, Bombay Samachar Marg, Mumbai - 400 001 Maharashtra State, India.
The following specification particularly describes the nature of this invention and the manner in which it is to be performed

FIELD OF THE INVENTION :
This invention relates to manufacturing of B-stage heat bonding both sides formulated Epoxy coated ceramic paper based electrical insulating material and the process of manufacturing the same. The said material is used inter alia for Interterm insulation of salient poles of synchronous machine's rotor field coils.
DESCRIPTION OF THE PRIOR-ART :
It is common practice in the manufacture of insulated electrical windings, like those used in electrical motors , to insulate the respective turns of the windings from one another by placing insulating sheet material between the winding turns. Such insulation material is normally only required on high voltage windings having relatively large turns which inherently develop relatively high voltages between the adjacent turns of the winding. For a number of years sheets of polyaramide paper like material have been used to provide this dielectric function in making large windings for rotating dynamoelectric machines or for high voltage electric transformers. Polyaramide paper being hygroscopic in nature has a tendency to absorb moisture more particularly in high humid conditions. It is also desirable to have insulating material which are thermally conducting so that increase in temperature of winding is reduced thereby increasing the working efficiency of the electric motors and/or transformers. Ceramic papers have the unique property of less moisture absorption and high thermal conductivity as compared to Polyaramide papers.

INVENTION :
This invention relates to B-stage heat bonding, both sides formulated epoxy coated, ceramic paper based electrical insulating material for interturn insulation of salient poles of synchironous machine rotor field coils and the process of manufacturing the same.
More particularly, the invention relates to an insulating sheet material that can be thermally cured under pressure without causing the sheet material or any of its
component parts to either creep or be extruded from between members on which the material is bonded.
An electrical winding insulated with the material of the invention is characterised by incorporating sheets of the insulating material between flat sides of the turns of the winding. In the final manufactured form of the winding its turns are compressed and baked to thermally cure the resinous adhesive material and bond it to the sides of the winding and the ceramic paper. Due to the materials and structure of the invention, the pressure baking operation does not force either the resinous adhesive material or the ceramic paper to creep sufficiently to extrude them from between the facing sides of the winding; accordingly, the edges of the winding need not be scraped or otherwise cleaned in order to place the winding in condition for final assembly in dyanoelectric machine.

SUMMARY OF THE INVENTION :
In the present invention a sheet of ceramic paper is coated with thermosetting resinous adhesive material such as epoxy resin material on one side with a desirable deposition followed by drying with conventional methods. Thereafter, the opposite side of the said sheet is coated with the said material with a desirable deposition. In the alternative, the said sheet is coated with the said material on both the sides in one pass with desirable deposition followed by drying with conventional method. Thereafter, the coated ceramic paper is cut to desired sizes and shapes. Ceramic paper thickness used depends on the requirement of the application and preferably will be 2.0 mil to 10.0 mil thick. However, paper of other thickness can also be used. The epoxy resin used for the purpose is formulated to achieve the desirable properties such that it does not cure at below 100°C but cures to form bond with conducting component of the winding at a temperature of 160°C or higher. The product thus prepared can be cured at 160°C ± 10°C for 1 hour to obtain a good bond with copper and paper as well as between paper and paper.
The formulated epoxy varnish consists of Epoxy Resin such as Diglycidyi ether of Bisphenol A, Novolak Epoxy, etc., Curing agent such as various primary and secondary aliphatic amines, modified primary and secondary amines, aromatic amines, modified aromatic amines, latent curing catalyst such as Dicyandiamide and

their blends dissolved in solvents such as ketones, esters etc. Other additives like fillers, pigments etc may also be used.
The epoxy resin is evenly deposited on ceramic paper by conventional coating technique such as dip-squeeze. The most optimum deposition of epoxy resin of about 20 to 40 g/m2 is maintained to achieve perfect bond. Optionally the ceramic paper can be coated by other coating techniques such as reverse roll coating or clearance coating or knife over roll coating. The coated ceramic paper is dried at a temperature below 100°C and at a suitable speed to ensure that the epoxy resin remains in B-stage condition. Polyethylene film is used as interlayer separator to prevent B-stage coated ceramic paper sticking with each other. The insulating product thus obtained is further slit and/or cut to desired size and shapes by conventional cutting techniques.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
////////////////////////////////////// ► Epoxy Coating
///////////////////////////////////// ► Ceramic paper
/////////////////////////////////// ► Epoxy Coating

WE CLAIM :
1. B-stage heat bonding both sides formulated, epoxy coated, ceramic paper based
electrical insulating material and the process of manufacturing the same which
comprises of the following steps :
(a) (i) coating one side of a ceramic paper with thermosetting resinous adhesive material such as formulated epoxy resin with a desirable deposition of 10 to 20 g/m2 by use of conventional coating methods followed by drying with conventional methods;
(ii) coating other side of the formulated epoxy resin coated ceramic paper with a desirable deposition of 10 to 20 g/m2 by use of conventional coating methods followed by drying with conventional methods;
(b) alternatively coating both sides of a ceramic paper in one pass with formulated
epoxy resin with a desirable deposition of 20 to 40 g/m2 by use of conventional
coating methods followed by drying with conventional methods;
(c) the coated ceramic paper so obtained is cut to desired sizes and shapes
2. B-stage heat bonding both sides formulated, epoxy coated, ceramic paper based electrical insulating material as claimed in Claim 1 wherein ceramic paper used is of 2.0 mil to 10.0 mil thickness.
3. B-stage heat bonding both sides formulated, epoxy coated, ceramic paper based electrical insulating material as claimed in Claim 1 wherein formulated epoxy resin is

prepared using: Epoxy Resin such as Diglycidyl ether of Bisphenol A, Novolak Epoxy, etc., Curing agent such as various primary and secondary aliphatic amines, modified primary and secondary amines, aromatic amines, moidified aromatic amines, latent curing catalyst such as Dicyandiamide and their blends dissolved in solvents such as ketones, esters etc. other additives like fillers, pigments etc.
4. B-stage heat bonding both sides formulated, epoxy coated, ceramic paper based electrical insulating material as claimed in Claims 1, 2 and 3 where epoxy resin is formulated to achieve retention of B-stage properties up to 100°C and forms bond with conducting component of the winding at 160 ± 10°C.
5. B-stage heat bonding both sides formulated, epoxy coated, ceramic paper based electrical insulating material as claimed in the above Claims and substantially as hereinbefore described.
6. B-stage heat bonding both sides formulated, epoxy coated, ceramic paper based electrical insulating material as claimed in claims 1 to 5 whereby heat bonding, epoxy coated, ceramic paper based electrical insulating material is obtained.
Dated this 21st day of December, 2006
(B. S. SHAH) Constituted Attorney

ABSTRACT
B-stage heat bonding both sides formulated, epoxy coated, ceramic paper based electrical insulating material and the process of manufacturing the same which comprises of (a) (i) coating one side of a ceramic paper with thermosetting resinous adhesive material such as formulated epoxy resin with a desirable deposition of 10 to 20 g/m2 by use of conventional coating methods followed by drying with conventional methods; (ii) coating other side of the formulated epoxy resin coated ceramic paper with a desirable deposition of 10 to 20 g/m2 by use of conventional coating methods followed by drying with conventional methods; (b) alternatively coating both sides of a ceramic paper in one pass with formulated epoxy resin with a desirable deposition of 20 to 40 g/m2 by use of conventional coating methods followed by drying with conventional methods; (c) the coated ceramic paper so obtained is cut to desired sizes and shapes.
(Bharat S. Shah)
Duly Constituted Attorney