FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
TRACKING AND EROSION RESISTANT COMPOSITIONS OF ETHYLENE
PROPYLENE DIENE MONOMER (EPDM)
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Prabhadevi, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Keshawatkar Baburao of Crompton Greaves Ltd, Conition Monitoring & Diagnostic Centre, Global R&D Centre, Kanjur (E), Mumbai 400042, Maharashtra, India and Thekkeveetil Sethumadhavan of Crompton Greaves Ltd, Vacuum Interrupters and Instrument Transformers Division: Power Systems, Aurangabad -431136 , Maharashtra, India; both Indian Nationals.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

TECHNICAL FIELD OF THE INVENTION:
This invention relates to tracking and erosion resistant compositions of Ethylene Propylene diene monomer (EPDM) or rubber, especially the composition comprising silane treated calcined clay and zinc salt of fatty acid, which are suitable as high voltage electrical insulating characteristics and which are readily moldable into complex shapes.
BACKGROUND AND PRIOR ART:
Tracking resistance and erosion resistance of insulating material are important factors affecting the performance of a high voltage insulating material. Tracking means to the formation of conducting paths (tracks) of deteriorated material on the surface of the insulating material, caused by surface electric discharges. When a track bridges the gap between two or more conductors, leading to an electrical breakdown and a tracking fails. Erosion means to the progressive wearing away of the insulating material by the electrical discharges, with failure eventually occuring because too much insulating material has been worn away.
Organopolysiloxanes (also called silicones) are common high voltage insulating materials, because of their electrical properties, processability (including moldability), physical properties, chemical inertness and other desirable characteristics. Organopolysiloxanes used in high voltage equipment typically contain additives for enhancing their tracking and/or erosion resistance for e.g. US 3,511,698, Japanese Patent Laid Open No. 198604/1984, Japanese Patent Publication No. 35982/1978, US 3,965,065, US 3,511,698 and Japanese Patent Laid Open No. 198604/1984. Alumina hydrate is well-known anti-tracking additive (also referred to as aluminum hydroxide, alumina trihydrate, hydrated alumina or ALTH) and it is used either alone or in combination with other additives such as metal oxides for e.g. US 3,965,065; US 3,969,308; US 4,001,128; US 4,100,089; US 4,189,392; US 4,399,064; US 4,431,861; US 4,521,549; US 4,822,830; and US 5,369,161. The alumina hydrate is sometimes combined with other additives, such as other metal oxides or phosphorus compounds. Alumina hydrate makes the molded part difficult to demold in commercial embodiments.

Many other additives including metal oxides, silica, and metal salts, have been added to insulating material, for diverse purposes ranging from the aforementioned ones to thermal conductivity, reinforcement, and high temperature stability for e.g. US 3,884,950; US 4,604,424; US 4,897,027; US 5,008,317; US 5,023,295; WO 95/06552; EP 0,218,461 A2; and GB 1,538,432.
Silane treated clays are also used as fillers for polymers or elastomerics is known. Typically, treated clays employing sulfur functional silanes are utilized in sulfur cured elastomeric systems requiring properties such as high tensile strength, high modulus or the like. However, silane treated clays have had limited utility in elastomeric applications requiring high performance because of their relatively low reinforcing benefits. Their ability to replace or extend high performance fillers, such as carbon black or silica, has been modest at best.
Ethylene Propylene diene monomer (EPDM) / or and rubber is also used in the high voltage electrical insulator performance but material itself cannot be said fully satisfactory. Under severe contaminative or weather conditions, the EPDM rubber material undergoes a high electrical stress, thus causing such a deterioration phenomenon as tracking phenomenon or erosion phenomenon, resulting in that the high voltage electrical insulating performance thereof is deteriorated markedly.
Further, greater and greater performance demands are placed on high voltage insulating materials which are used in most polluted coastal area where tracking and erosion are particularly severe problems. Consequently, there is a need for more effective anti-tracking and erosion resistance which do not exhibit the limitations of prior art.
OBJECTS OF THE INVENTION :
An object of the invention is to provide tracking and erosion resistant compositions of Ethylene Propylene diene monomer (EPDM) or rubber capable which is superior in high voltage electrical

insulating characteristics such as resistance to weather, to erosion, to tracking and to arc under severe contaminative or weather conditions after heat-curing.
Another object of the invention is to provide tracking and erosion resistant compositions of Ethylene Propylene diene monomer (EPDM) or rubber capable which is superior in high voltage electrical insulating characteristics such as resistance to weather, to erosion, to tracking and to arc under severe contaminative or weather conditions after heat-curing.
DETAILED DESCRIPTION OF THE INVENTION:
According to the invention, there is provided tracking and erosion resistant compositions of Ethylene Propylene diene monomer (EPDM) or rubber, the composition comprises
a) 90 to 110 % of Ethylene Propylene Diene Monomer;
b) 225 to 275 % of Aluminum Trihydrate;
c) 90 to 110 % of Silane treated Calcined Clay;

d) 1.8 to 3.3 % of silane as Coupling agent;
e) 15 to 33 %of Paraffmic Oil;
f) 4.5 to 5.5 % of Zinc Oxide;
g) 0.9 to 1.65 % of Triallylisocyanuarate as co-agent;
h) 3.6 to 9.9 % of peroxide selected from TDQ, Bis (tert-butylperoxy isopropyl)
benzene Peroxide, dicumyl peroxide, etc; i) 1.8 to 2.2 % of Zinc stearate; j) 0.8 to 2.2 % of antioxidant selected from polymerised 2,2, 4- methyl-1, 2 Dihydro
Quinoline, styrenated-Phenol, etc; k) 2.7 to 3.3 % of Paraffin wax; 1) 0.45 to 1.1 % of pigment including carbon; m) 4.5 to 5.5 % of Titanium Dioxide; and n) 1.8 to 5.5 % of Salts of Zinc Fatty acids

Preferably, the tracking and erosion resistant compositions of Ethylene Propylene diene monomer (EPDM) or rubber comprises 90 to 110 % of Ethylene Propylene Diene Monomer; 135 to 165 % of Aluminum Trihydrate; 90 to 110 % of Silane treated Calcined Clay; 1.8 to 2.2% of silane as Coupling agent; 15 to 16.5 % of Paraffinic Oil; 4.5 to 5.5 % of Zinc Oxide; 1.35 to 1.65 % of Triallylisocyanuarate as co-agent; 8.1 to 9.9 % of peroxide selected from TDQ, Bis (tert-butylperoxy isopropyl) benzene Peroxide, dicumyl peroxide, etc; 1.8 to 2.2 % of Zinc stearate; 0.8 to 2.2 % of antioxidant selected polymerised 2,2, 4- methyl-1, 2 Dihydro Quinoline, styrenated-Phenol, etc; 2.7 to 3.3 % of Paraffin wax; 0.45 to 1.1 % of pigment including carbon; 4.5 to 5.5 % of Titanium Dioxide; and t.8 to 2.2 % of Salts of Zinc Fatty acids.
Accordign to the inevntion, there is also provided a method for the production of the tracking and erosion resistant compositions of Ethylene Propylene diene monomer (EPDM) or rubber; the method comprises
1. Masticating Ethylene Propylene diene monomer (EPDM) rubber at temperature of 70 to 80° C;
2. Masticating the rubber with other fillers and additives like Aluminum Trihydrate; Silane treated Calcined Clay; silane as Coupling agent; Paraffinic Oil; Zinc Oxide; Zinc stearate; Antioxidant selected from polymerised 2,2, 4- methyl-1, 2 Dihydro Quinoline, styrenated-Phenol, etc; Paraffin wax; Pigment including carbon; Titanium Dioxide; and Salts of Zinc Fatty acids till integrated power rises more than 50 amps and the temeprature rises more than 110° C followed by mixing at 120° C with monitoring color uniformity to obtain masterbatch; and sheet out the master batch on a cleaned hot mill;
3. Adding Triallylisocyanuarate as co-agent; and peroxide selected from TDQ, Bis (tert-butylperoxy isopropyl) benzene Peroxide, dicumyl peroxide, etc into the master batch and mixing at 70 to 90° C to obtain the said composition.
The master batch of the said composition of the invention is stored by wrapping in a clean polythene sheet and kept it in a cool dry place at ambient temperature or below. Master batch has shelf life of two weeks from the date of mixing.

The said composition is used for housing of high voltage insulator including lightening arrester which is used in outdoor applications where it required good erosion and tracking resistance. The composition is tested for erosion resistance and tracking resistance and compared with the silicone rubber and found to be superior.
The tracking resistance of the said composition of the invention is 7kV for 1 hr and passed the erosion resistance test as compared to silicone rubber which has tracking and erosion resistance of3.5kV.
According to the invention there is provided tracking and erosion resistant compositions of Ethylene Propylene diene monomer (EPDM) or rubber wherein the tracking resistance is 7kV for 1 hr and passed the erosion resistance test as compared to silicone rubber which has tracking and erosion resistance of 3.5kV.
Thus, the compositions of Ethylene Propylene Diene monomer (EPDM) or rubber of the invention has very good tracking resistance and erosion resistance as compared to that of silicone rubber. Therefore it may be used for housing of high voltage insulator including lightening arrester which is used in outdoor applications with good erosion and tracking resistance.
The following experimental examples are illustrative of the invention but not limitative of the scope thereof:
Example 1:
Comparative example of composition without Silane trated calcined clay and Zinc salt of
fatty acid
100 parts of Ethylene Propylene diene monomer (EPDM) rubber was masticated at temperature of 70 to 80° C. The said rubber was masticated with other fillers and additives like 250 parts of Aluminum Trihydrate (Martinal OL 104); 2 parts of silane as Coupling agent; 15 parts of

Paraffmic Oil; 5 parts of Zinc Oxide; 2 parts of Zinc stearate; 2 parts of TDQ (Polymerised 2,2, 4- methyl-1, 2 Dihydro Quinoline) as antioxidant; 3 parts of Paraffin wax; 0.05 parts of Carbon SRF; and 5 parts of Titanium Dioxide till integrated power raised to more than 50 amps and the temeprature raised to more than 110° C. The mixture is further mixed at 120° C with monitoring color uniformity to obatin masterbatch. To the masterbatch, 1.5 parts of Triallylisocyanuarate as co-agent and 4 parts of Bis (tert-butylperoxy isopropyl) benzene Peroxide was added and mixed at 80 to 90° C to obtain the composition. The composition was tested for its mechanical and electrical properties. The results are tabulated in table 1.
Example 2:
Comparative example of composition without Zinc salt of fatty acid
100 parts of Ethylene Propylene diene monomer (EPDM) (Nordel IP 3722) was masticated at temperature of 70 to 80° C. The said rubber was masticated with other fillers and additives like 150 parts of Aluminum Trihydrate (Martinal OL 104); 100 parts of Silane treated Calcined Clay(Polarite 103 A); 2 parts of silane (Silane A 172) as Coupling agent; 15 parts of Paraffmic Oil (Ipol 2300); 5 parts of Zinc Oxide; 2 parts of Zinc stearate; 2 parts of TDQ (Polymerised 2,2, 4- methyl-1, 2 Dihydro Quinoline) as antioxidant; 3 parts of Paraffin wax; 0.05 parts of Carbon SRF; and 5 parts of Titanium Dioxide till integrated power raised to more than 50 amps and the temeprature raised to more than 110° C. The mixture is further mixed at 120° C with monotroing color uniformity to obatin masterbatch. To the masterbatch, 1.5 parts of Triallylisocyanuarate as co-agent and 4 parts of Bis (tert-butylperoxy isopropyl) benzene Peroxide was added and mixed at 80 to 90° C to obtain the composition. The composition was tested for its mechanical and electrical properties. The results are tabulated in table 1.
Example 3:
Comparative example of composition without Silane trated calcined clay
100 parts of Ethylene Propylene diene monomer (EPDM) (Nordel IP 3722) was masticated at temperature of 70 to 80° C. The said rubber was masticated with other fillers and additives like 250 parts of Aluminum Trihydrate (Martinal OL 104); 2 parts of silane (Silane A 172) as Coupling agent; 15 parts of Paraffmic Oil (Ipol 2300); 5 parts of Zinc Oxide; 2 parts of Zinc

stearate; 2 parts of TDQ (Polymerised 2,2, 4- methyl-1, 2 Dihydro Quinoline) as antioxidant; 3 parts of Paraffin wax; 0.05 parts of Carbon SRF; 5 parts of Titanium Dioxide; and 2 parts of Zinc metal salt of fatty acid till integrated power raised to more than 50 amps and the temeprature raised to more than 110° C. The mixture is further mixed at 120° C with monitoring color uniformity to obatin masterbatch. To the masterbatch, 1.5 parts of Triallylisocyanuarate as co-agent and 9 parts of Di-Cumil Peroxide was added and mixed at 80 to 90° C to obtain the composition. The composition was tested for its mechanical and electrical properties. The results are tabulated in table 1.
Example 4:
Composition with Silane trated calcined clay and Zinc salt of fatty acid
100 parts of Ethylene Propylene diene monomer (EPDM) (Nordel IP 3722) was masticated at temperature of 70 to 80° C. The said rubber was masticated with other fillers and additives like 150 parts of Aluminum Trihydrate (Martinal OL 104); 100 parts of Silane treated Calcined Clay(Polarite 103 A); 2 parts of silane (Silane A 172) as Coupling agent; 15 parts of Paraffinic Oil (Ipol 2300); 5 parts of Zinc Oxide; 2 parts of Zinc stearate; 2 parts of TDQ (Polymerised 2,2, 4- methyl-1, 2 Dihydro Quinoline) as antioxidant; 3 parts of Paraffin wax; 0.05 parts of Carbon SRF; 5 parts of Titanium Dioxide; and 2 parts of Zinc metal salt of fatty acid till integrated power raised to more than 50 amps and the temeprature raised to more than 110° C. The mixture is further mixed at 120° C with monotroing color uniformity to obatin masterbatch. To the masterbatch, 1.5 parts of Triallylisocyanuarate as co-agent and 9 parts of Bis (tert-butylperoxy isopropyl) benzene Peroxide was added and mixed at 80 to 90° C to obtain the composition. The composition was tested for its mechanical and electrical properties. The results are tabulated in table 1.
Example 5:
HTV silicone rubber POWERSIL® 310 is ready to use, peroxide curing compound that cures to an electrical insulating, highly erosion resistive silicone elastomer. This material is also tested for

its physical, mechanical and electrical properties. The comparative results of the same with respect to the above examples are given in table 1.

Table 1 : Comparative results of mechanical and electrical properties of the composition of examples 1,2, 3, 4 and HTV silicone rubber POWERSIL® 310.

Sr. No. Properties Housing Materials
Composition of Example 1 Composition of Example 2 Composition of Example 3 Composition of Example 4 HTV silicone rubber
POWERSIL® 310
/ Physical Properties
1. Specific gravity 1.53 1.58 1.55 1.59 1.52
2. Hardness, Shore A 78 Shore A 89 Shore A 83 Shore A 91 Shore A 70 Shore A
// Mechanical Properties
1. Tensile Strength (N/mm2) 4.3 6.5 4.5 8.5 5.0
2. Elongation at Break 700 300 600 200 300
3. Tear Strength (N/mm), Notch Tear 2 28 2 45 15
Ill Electrical Properties
1. Tracking and erosion resistance (kV) 3.3 kV 3.7kV 3.5kV 7kV for 1 hr passed 3.5 kv
2. Dielectric constant 3.8 3.9 4.1 3.40 4.0
3. Dissipation factor (tan 8) 1 0.031 0.014 0.023 0.012 0.01
4. Volume resistivity 0.79 x 1015 (Ohm - cm) | 1.1 x 10,s 0.88 x 1015 1.5 xlO15 lxl015

The above results indicated that the present composition has superior tracking and erosion resistance properties as well as other electrical and mechanical properties including tensile strength, tear strength, dielectric constant, dissipation factor and volume resistivity as compared to that HTV silicone rubber POWERSIL® 310.

We claim :
1. Tracking and erosion resistant compositions of Ethylene Propylene diene monomer (EPDM) or rubber, the composition comprises
a) 90 to 1 ] 0 % of Ethylene Propylene Diene Monomer;
b) 225 to 275 % of Aluminum Trihydrate;
c) 90 to 110 %ofSilane treated Calcined Clay;

d) 1.8 to 3.3 % of silane as Coupling agent;
e) 15 to 33 %of Paraffinic Oil;
f) 4.5 to 5.5 % of Zinc Oxide;
g) 0.9 to 1.65 % of Triallylisocyanuarate as co-agent;
h) 3.6 to 9.9 % of peroxide selected from TDQ, Bis (tert-butylperoxy isopropyl)
benzene Peroxide, dicumyl peroxide, etc; i) 1.8 to 2.2% of Zinc stearate,' j) 0.8 to 2.2 % of antioxidant selected from polymerised 2,2, 4- methyl-1, 2 Dihydro
Quinoline, styrenated-Phenol, etc; k) 2.7 to 3.3 % of Paraffin wax; 1) 0.45 to 1.1 % of pigment including carbon; m) 4.5 to 5.5 % of Titanium Dioxide; and n) 1.8 to 5.5 % of Salts of Zinc Fatty acids
2. The composition as claimed in claim 1, wherein preferably, the tracking and erosion resistant compositions of Ethylene Propylene diene monomer (EPDM) / or and rubber comprises 90 to 110 % of Ethylene Propylene Diene Monomer; 135 to 165 % of Aluminum Trihydrate; 90 to 110 % of Silane treated Calcined Clay; 1.8 to 2.2 % of silane as Coupling agent; 15 to 16.5 % of Paraffinic Oil; 4.5 to 5.5 % of Zinc Oxide; 1.35 to 1.65 % of Triallylisocyanuarate as co-agent; 8.1 to 9.9 % of peroxide selected from TDQ, Bis (tert-butylperoxy isopropyl) benzene Peroxide, dicumyl peroxide, etc; 1.8 to 2.2 % of Zinc stearate; 0.8 to 2.2 % of antioxidant selected polymerised 2,2, 4-

methyl-1, 2 Dihydro Quinoline, styrenated-Phenol, etc; 2.7 to 3.3 % of Paraffin wax; 0.45 to 1.1 % of pigment including carbon; 4.5 to 5.5 % of Titanium Dioxide; and 1.8 to 2.2 % of Salts of Zinc Fatty acids.
3. The composition as cliamed in any of the preceding cliams, wherein the tracking and erosion resistance is 7kV for 1 hr.
4. The composition as cliamed in any of the preceding cliams, wherein the compostion is used for housing of high voltage insulator including lightening arrester which is used in outdoor applications where it required good erosion and tracking resistance.