FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
AND
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
“CERAMIC COATING FORMULATION FOR HEATING ELEMENTS AND PROCESS FOR MAKING THE SAME”
We, Bajaj Electricals Limited, an Indian National, of 45/47, Veer Nariman Road, Fort, Mumbai 400001, Maharashtra, India
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF INVENTION
The present invention relates to the field of heating element coatings. In particular, the present invention provides a nano coating formulation for heating elements and process for making the same, which provides anti-scaling properties.
BACKGROUND OF THE INVENTION
Heating elements are essentially conductor elements that allow current to flow through them resulting in heat generation, which is dissipated from the heating element. The dissipated heat can be used/ harnessed to heat the ambient air around the heating element, or water which is in contact with the heating element surface, such as geysers, immersion rods, etc. used in households. Such heating elements are typically made of copper as copper has good heating characteristics. Such heating elements require corrosion resistance qualities, wear resistance, uniform heat distribution and most importantly anti-scaling properties.
Typically, as the temperature within such heating devices increases, insoluble salts of calcium and magnesium present in the hard water gets phased out and is deposited on the heating element surface. Over time, as sediment scales accumulates on the heating element surface, heat conductivity through the heating element is reduced and the heating efficiency of the devices degrades, which can lead to increased energy input and costs. Additionally, scale deposition can also cause localized over-heating beyond safety levels, causing a safety hazard, which can lead to bursting of the heating element.
Multiple attempts have been made to use “anti-scaling heat conductive” coatings over copper heating elements, in order to protect the parts from scale depositions as well as proper heat distribution. However, such coatings have

multiple shortcomings especially as they commonly affect the heating efficiency of the heater. Some anti-scaling coatings which focus on improving the heating efficiency often fall short as the coatings are complex and expensive. Yet another shortcoming of currently available coatings is the need for adhesives and added components to ensure the coating is well connected with the Copper surface of the heating element, this makes the coating thicker than desired, affecting the heating efficiency.
Such type of coatings sometime requires very high baking temperature which includes the extra process cost, sometimes it affects the heating element also. Therefore, there is a need to overcome at least one of the shortcomings listed above.
OBJECTS OF THE INVENTION
The following statements have been listed to clearly bring out the objectives to be achieved by the invention, they are not exhaustive in nature and by no means are intended to limit the scope of the present application.
An object of the present invention is to provide an anti-scaling heat conductive coating composition for copper-based heating elements.
Another object of the present invention is to provide an anti-scaling heat conductive coating composition for copper-based heating elements free of adhesives or additional components.
Yet another object of the present invention is to provide an anti-scaling heat conductive coating composition for copper-based heating elements which is cost effective and non-complex.

SUMMARY OF THE INVENTION
Before the present invention is described, it is to be understood that the scope of the invention is not limited to the particular disclosure and details described, as there can be multiple possible embodiments which are not expressly illustrated in the present disclosure. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only and is not intended to limit the scope of the invention. This summary is provided to introduce concepts related to the invention, which is further described below in the detailed description. This summary is not intended to identify all essential features of the subject matter nor is it intended for use in limiting the scope of the subject matter.
In an aspect of the present invention, there is provided an anti-scaling heat conductive coating composition for copper substrate comprising: (a) a colloidal suspension having weight concentration in the range of 60-70wt%; and (b) at least a rheological additive having weight concentration up to 2wt%, wherein the colloidal suspension comprises at least a pigment having weight concentration in the range of 5-15wt%.
In an aspect of the present invention, the pigment is an oxide selected from the group consisting of Al2O3, ZnO, WO3, and SiO2.
In an aspect of the present invention, the pigment is nano-pigment having size in the range of 0.2-0.8µm.
In another aspect of the present invention, the composition is a gel.
In yet another aspect of the present invention, the rheological additive is
selected from the group consisting of zeolite, and bentonite.
In still another aspect of the present invention, there is provided a copper

heating substrate coated with an anti-scaling heat conduction coating composition, said composition comprising (a) a colloidal suspension having weight concentration in the range of 60-70wt%; and (b) at least a rheological additive having weight concentration up to 2wt%, wherein the colloidal suspension comprises at least a pigment having weight concentration in the range of 5-15wt%.
In an aspect of the present invention, the coating thickness is in the range of 6-10µm.
In yet another aspect of the present invention, there is provided a method of coating a copper heating substate with an anti-scaling heat conduction coating composition, said composition comprising (a) a colloidal suspension having weight concentration in the range of 60-70wt%; and (b) at least a rheological additive having weight concentration up to 2wt%, wherein the colloidal suspension comprises at least a pigment having weight concentration in the range of 5-15wt%; said method comprising: (a) dissolving a pigment selected from the group consisting of Al2O3, ZnO, WO3, and SiO2 having particle size in the range of 0.2-0.8µm in alcohol and water to obtain a colloidal structure of metal alkoxide; (b) condensing the colloidal structure to obtain a gel; (c) applying the gel on surface of copper substrate by a method selected from the group consisting of spin drying, and drip coating; and (d) drying the gel on the surface to obtain nano sol gel coating, wherein the thickness of the coating is in the range of 6-10µm.
In an aspect of the present invention, the method comprises formic acid as catalyst having concentration in the range of 0.02-0.04wt%.

DETAILED DESCRIPTION OF THE INVENTION
Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any systems and methods similar or equivalent to those described herein can be used in the practice, the exemplary, systems and methods are now described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.
Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments illustrated but is to be accorded the widest scope consistent with the principles and features described herein.
The present invention provides an anti-scaling heat conductive coating composition for copper substrate comprising: (a) a colloidal suspension having weight concentration in the range of 60-70wt%; and (b) at least a rheological additive having weight concentration up to 2wt%, wherein the colloidal suspension comprises at least a pigment having weight concentration in the range of 5-15wt%.
In an embodiment of the present invention, the pigment is an oxide selected

from the group consisting of Al2O3, ZnO, WO3, and SiO2. In another embodiment, the pigment is ZnO. In yet another embodiment, the pigment is WO3. In still another embodiment, the pigment is SiO2. In a preferred embodiment, the pigment is Al2O3. In a preferred embodiment, the pigment concentration is in the range of 2-10wt%.
In an embodiment of the present invention, the pigment is nano-pigment having size in the range of 0.2-0.8µm. In a preferred embodiment, the pigment is nano Al2O3 having particle size in the range of 0.2-0.8µm.
In a preferred embodiment of the present invention, the composition is a gel. In a preferred embodiment, the compositions is a nano-ceramic nano sol gel. In a preferred embodiment, the composition is prepared by sol-gel method.
In an embodiment of the present invention, the rheological additive is selected from the group consisting of zeolite, and bentonite. In a preferred embodiment, the rheological additive is zeolite. In a preferred embodiment, the weight concentration of the rheological additive is in the range of 0.2-1%gm.
The present invention also provides a copper heating substrate coated with an anti-scaling heat conduction coating composition, said composition as substantively described herein. In an embodiment, the thickness of the coating is in the range of 5-15µm. In a preferred embodiment, the thickness of the coating is in the range of 6-10µm. In a more preferred embodiment, the thickness of the coating is in the range of 5-8µm.
The present invention further provides a method of coating a copper heating substate with an anti-scaling heat conduction coating composition as claimed in claim 1, said method comprising: (a) dissolving a pigment selected from the

group consisting of Al2O3, ZnO, WO3, and SiO2 having particle size in the range of 0.2-0.8µm in alcohol and water to obtain a colloidal structure of metal alkoxide; (b) condensing the colloidal structure to obtain a gel; (c) applying the gel on surface of copper substrate by a method selected from the group consisting of spin drying, and drip coating; and (d) drying the gel on the surface to obtain nano sol gel coating, wherein the thickness of the coating is in the range of 6-10µm. in a preferred embodiment, the gel is applied on the surface of the copper substrate by dip coating. In an embodiment, the gel is dried on the surface by exposing to a temperature in the range of 60-80C.
The composition forms a high-performance binder layer and dense network of strong chemical bond with the copper substrate and develops high hydrophobic and oleophobic contact surface.
In a preferred embodiment of the present invention, the method further comprises formic acid as catalyst having concentration in the range of 0.02-0.04wt%. In another preferred embodiment, the pigment is Al2O3.
Advantageously, the composition of the present invention is capable of adhering to the copper heating element substrate surface with low surface energy and has frictionless property.
EXAMPLES
In a particular exemplary application of the present invention, copper heating element was prepared by sand blasting the substrate surface prior to application of the coating composition. Subsequent to surface preparation, the substrate surface was coated with the composition of the present invention to obtain a coating having thickness of 5-8µm. Standing loss test was carried out to ascertain the effect of surface preparation. In copper heating element where the surface

was not prepared as described herein, the coating developed cracks. In contrast, copper heating element where the surface was prepared as described herein, the coating did not develop cracks even after 200 cycles upon endurance testing. The effect of the coating composition was also tested with regard to scale deposition on the copper heating substrate surface. Conducting standing loss test on copper heating element not coated with the composition of the present invention, scale deposition (15-20gm) was observed when the heating element was exposed to hard water (150-200ppm) for 72 hours. In contrast, copper heating element coated with the composition of the present invention had only about 5gm of accumulated scales upon exposure to hard water (150-200ppm) for 72 hours.
Endurance test was also carried out to ascertain scale deposition. When the copper heating element not coated with the composition of the present invention was exposed to hard water (150-200ppm) for 200 cycles, 40-50gm scale deposition was seen. In contrast, when copper heating element coated with the composition of the present invention was exposed to similar conditions, only 15-20gm of scale deposition was seen.
These data clearly establish that the composition of the present invention is able to significantly reduce scale accumulation, which translates to better heat conductivity and energy saving. The coating is also able to withstand cyclical expansion and contraction of the copper metal substrate, which results due to heating and cooling of the copper heating element, as evidenced from no cracks in the coating even after 200 cycles upon endurance testing. This translates to extended utility and longevity of the copper heating element coated with the said composition. The coating of the present invention is also flexible, which prevents cracking and also prevents “rattling” sounds which is created in water heating elements. Further, fungal growth is also retarded on copper heating

element substrate surface coated with the composition of the present invention. The coating of the present invention is also resistant to a wide range of pH changes.

I/We claim:
1. Anti-scaling heat conductive coating composition for copper substate
comprising:
a. a colloidal suspension having weight concentration in the range of
60-70wt%; and
b. at least a rheological additive having weight concentration up to
2wt%,
wherein the colloidal suspension comprises at least a pigment having weight concentration in the range of 5-15wt%
2. The composition as claimed in claim 1, wherein the pigment is an oxide selected from the group consisting of Al2O3, ZnO, WO3, and SiO2.
3. The composition as claimed in claim 1, wherein the pigment is nano-pigment having size in the range of 0.2-0.8µm.
4. The composition as claimed in claim 1, wherein said composition is a gel.
5. The composition as claimed in claim 1, wherein the rheological additive is selected from the group consisting of zeolite, and bentonite.
6. A copper heating substrate coated with an anti-scaling heat conduction coating composition as claimed in claim 1.
7. The substrate as claimed in claim 6, wherein the coating thickness is in the range of 6-10µm.
8. A method of coating a copper heating substate with an anti-scaling heat conduction coating composition as claimed in claim 1, said method

comprising:
a. dissolving a pigment selected from the group consisting of Al2O3,
ZnO, WO3, and SiO2 having particle size in the range of 0.2-0.8µm
in alcohol and water to obtain a colloidal structure of metal
alkoxide;
b. condensing the colloidal structure to obtain a gel;
c. applying the gel on surface of copper substrate by a method
selected from the group consisting of spin drying, and drip
coating; and
d. drying the gel on the surface to obtain nano sol gel coating,
wherein the thickness of the coating is in the range of 6-10µm.
9. The method as claimed in claim 8, comprising formic acid as catalyst having concentration in the range of 0.02-0.04wt%.