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, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF INVENTION
Composition having improved thermal conductivity
INVENTORS
Keshawatkar Babu Rao and Ghosh Susmita, both of CG Global R&D Centre, High Voltage Insulation Lab, Crompton Greaves Limited, Kanjur (East), Mumbai 400042, Maharashtra, India and Bhatia Anilkumar Brijial of Technology Department, Transformer Division (Tl), Crompton Greaves Limited, Kanjur (East), Mumbai 400042, Maharashtra, India, all Indian Nationals
APPLICANTS
Name : CROMPTON GREAVES LIMITED
Nationality : Indian Company
Address : CG House, Dr Annie Besant Road, Worli,
Mumbai 400025, Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF INVENTION
This invention relates to a composition having improved thermal
conductivity.
This invention also relates to a composition having improved thermal conductivity and room temperature curing.
BACKGROUND OF INVENTION
Electrical apparatuses such as dry transformers or diverters are rendered compact by resin encapsulation thereof. Besides giving weather protection and mechanical strength, resin encapsulation also imparts electrical insulation properties and thermal conductivity (heat dissipation) to the apparatuses. Cycloaliphatic epoxy resin based compositions used for encapsulation of electrical apparatuses have good thermal insulation class properties of about 155°C and good thermal conductivity of about 0.9 - 1.0 watt per metre Kelvin (W/mk). Cycloaliphatic epoxy resin based compositions are, however, expensive and require high processing temperature (curing temperature) of the order of 80 - 140 °C. Unsaturated polyester resin based compositions are also used for encapsulation of electrical apparatuses. Unsaturated polyester resin based compositions are cheaper and are processable at room temperature. They have, however, lower thermal insulation class properties of about 130 °C and thermal conductivity of about 0.5 W/mk. Unsaturated polyesterimide resin based compositions are generally used for impregnation of electrical apparatuses. Unsaturated polyesterimide resin based compositions have higher thermal insulation class properties of about 155 to 180°C and are cheaper than cycloaliphatic resins based compositons. They are not, however, processable at room temperature and are usually curable at about 120 to 140 °C. Unsaturated
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polyesterimide resin based compositions comprise 20%o by weight of preaccelerated unsaturated polyesterimide resins including 0.2 to 0.5% by weight of methyl ethyl ketone peroxide and UV additive and 80% by weight of a filler system comprising 85%) by weight of silica and 15% by weight of aluminium trihydrate and colouring agent.
In order to improve the cooling efficiency and performance of electrical apparatuses it is important to encapsulate them with compositions having good thermal conductivity besides the other desirable properties. An object of the invention is to provide an unsaturated polyesterimide resin based composition having improved thermal conductivity besides the other desirable properties. The resin composition is ideal for use in the encapsulation of electrical apparatuses particularly outdoor distribution transformers because of its improved thermal conductivity. It has also the added advantages of being cheaper and processable (curable) at room temperature. Because of the resin composition being processable at room temperature thermal energy requirement for processing the resin composition is eliminated thereby realising considerable saving in cost.
DETAILED DESCRIPTION OF INVENTION
According to the invention there is provided a composition having improved thermal conductivity, the composition comprising 20% by weight of preaccelerated unsaturated polyesterimide resin including 0.2 to 0.5%o by weight of methyl ethyl ketone peroxide and UV additive and 80%) by weight of a filler system comprising 50 to 60 % by weight of silica, 25 to 35% by weight of calcined alumina and 15% by weight of aluminium trihydrate and colouring agent.
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According to the invention there is also provided a resin composition having improved thermal conductivity and room temperature curing with methyl ethyl ketone peroxide, the composition comprising 20% by weight of preaccelerated unsaturated polyesterimide resin including 0.2 - 0.5% by weight of methyl ethyl ketone peroxide and UV additive and 80% by weight of a filler system comprising 50 to 60 % by weight of silica, 25 to 35% by weight of calcined alumina and 15% by weight of aluminium trihydrate and colouring agent.
The UV additive is, for example, benztriazoles, substituted benztriazoles, benzophenones or phenylbenzotriazoles. The colouring agent is, for example, titanium dioxide, iron oxide or lead oxide.
A composition comprising 20% by weight of preaccelerated unsaturated polyesterimide resin including 0.3% by weight of methyl ethyl ketone peroxide and substituted benztriazole and 80% by weight of a filler system comprising 85% by weight of silica and 15% by weight of aluminium trihydrate and titanium dioxide was prepared (conventional composition). Another composition comprising 20% by weight of preaccelerated unsaturated polyesterimide resin including 0.3% by weight of methyl ethyl ketone peroxide and substituted benztriazole and 55% by weight of silica, 30% by weight of calcined alumina and 15% by weight of aluminium trihydrate and titanium dioxide was also prepared (composition of invention). The thermal insulation class properties and thermal conductivity of the resin compositions were compared and the results were as shown in the following Table 1 :
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Resin composition Properties
Maximum temperature withstandability in °C Thermal conductivity in W/mK
Conventional composition 155 0.51
Composition of invention 155 1.12
Because of the better thermal conductivity of the resin composition of the invention it is ideal for use in the encapsulation of electrical apparatuses especially outdoor distribution transformers so as to improve the cooling efficiency and performance of the apparatuses. It is to be, however, clearly understood that the scope of application of the resin composition of the invention is not confined to electrical apparatuses. It can be effectively used in any application where the properties of the resin composition, especially heat dissipation are desirable. The conventional resin composition was found to be curable at 140°C with tertiary butyl per benzoate as the hardner, whereas the resin composition of the invention was found to be curable at room temperature of 25 - 35°C with methyl ethyl ketone peroxide as the hardner. The thermal energy requirement in curing the resin composition is thus completely saved according to the invention.
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We claim :
1. A composition having improved thermal conductivity, the composition comprising 20% by weight of preaccelerated unsaturated polyesterimide resin including 0.2 - 0.5% by weight of methyl ethyl ketone peroxide and UV additive and 80% by weight of a filler system comprising 50 to 60 % by weight of silica, 25 to 35% by weight of calcined alumina and 15% by weight of aluminium trihydrate and colouring agent.
2. A composition as claimed in claim 1 comprising 55% by weight of silica, 30% by weight of calcined alumina and 15% by weight of aluminium trihydrate and colouring agent.
3. A composition having improved thermal conductivity and room temperature curing with methyl ethyl ketone peroxide, the composition comprising 20% by weight of preaccelerated unsaturated polyesterimide resin including 0.2 - 0.5% by weight of methyl ethyl ketone peroxide and UV additive and 80% by weight of a filler system comprising 50 to 60 % by weight of silica, 25 to 35% by weight of calcined alumina and 15% by weight of aluminium trihydrate and colouring agent.
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4. A composition as claimed in claim 3 comprising 55% by weight of silica, 30% by weight of calcined alumina and 15% by weight of aluminium trihydrate and colouring agent.
Dated this 27th day of March 2007

(Jose M A)
of Khaitan & Co
Agent for the Applicants
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ABSTRACT
A composition having improved thermal conductivity and room temperature curing with methyl ethyl ketone peroxide. The composition comprises 20% by weight of preaccelerated unsaturated polyesterimide resin including 0.2 - 0.5% by weight of methyl ethyl ketone peroxide and UV additive and 80% by weight of a filler system comprising 50 to 60 % by weight of silica, 25 to 35% by weight of calcined alumina and 15% by weight of aluminium trihydrate and colouring agent.