FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
AND
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
“POLYMER COATING FORMULATION FOR HEATING ELEMENTS AND PROCESS FOR MAKING THE SAME”
We, Bajaj Electricals Ltd., 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 O595sent invention relates to the field of polymer-based coating compositions. In particular, the present invention relates to an anti-scaling polymer-based coating composition for heating elements.
BACKGROUND OF THE INVENTION
Heaters/ heating elements are essentially heat transfer means that permits current to flow into a conductor to generate and dissipate heat from the conductor to heat a substance, such as water. Such a heater is included in a variety of home electronic appliances. For example, water heaters, geysers, immersion rods, etc. are used to heat water. The heating element is typically based on Copper (Cu) metal due to its superior qualities. However, in heating elements exposed to water, it is desirous that the heating element has corrosion resistance qualities, wear resistance, uniform heat distribution, and importantly, anti-scaling properties.
Typically, as the temperature of the heating element increases in the presence of water, salts of calcium and magnesium present in hard water are deposited as scales on the heating element surface.
Over time, as scale deposition accumulates on the surface of the heating element, the heating efficiency of the heating element is compromised, risk of over-heating of certain portions of the heating element is magnified, which can lead to malfunction and bursting of the heating element.
Though “protective” coatings are known in the art, however, such coatings have multiple shortcomings, including affecting the heating efficiency of the heating element. Complexity and cost are another factor of such protective coatings. Yet

another shortcoming of coatings is the need for multiple additives to ensure that the coating adheres to the heating element (Copper) surface as lot of impurities like copper oxide present on the copper surface. Coatings known in the art are also typically applied at greater coating thicknesses to achieve the desired effect, which negatively affects the heating efficiency, makes the coating film prone to cracking, and increases the costs.
Therefore, there is a need in the art to device newer and more efficient compositions which overcome the limitations known in the art.
SUMMARY OF THE INVENTION
This summary is not intended to identify the essential features of the invention nor is it intended for use in determining or limiting the scope of the claimed subject matter.
In an aspect of the present invention, there is provided an anti-scaling polymer composition comprising: at least a polymeric resin; and at least an anti-corrosive material, wherein the anti-corrosive material weight concentration in the composition is in the range of 7-15wt%; and the polymer resin weight concentration in the composition is in the range of 30-35wt%.
In another aspect, the anti-corrosive material is selected from the group consisting of mica, zinc phosphate, and combinations thereof; mica weight concentration is in the range of 2-5wt%; and zinc phosphate weight concentration is in the range of 5-10wt%.
In yet another aspect, the polymer resin is selected from the group consisting of
Polytetrafluoroethylene (PTFE), Polyvinylidene fluoride (PVDF), Poly(1,1-

difluoroethene), Polyvinylidene difluoride, Polychlorotrifluororethene (PCTFE), and combinations thereof.
In yet another aspect, the composition comprising at least a heat conductive material.
In yet another aspect, the heat conductive material is carbon fibers having weight concentration in the range of 1-3wt%.
In yet another aspect, the composition comprising at least an anti-fungal additive.
In yet another aspect, the anti-fungal additive is selected from the group consisting of Copper (II) sulfate pentahydrate, Copper sulphate, and combinations thereof, having weight concentration in the range of 0.1-3wt%.
In yet another aspect, the composition comprising at least a filler.
In yet another aspect, the filler is silica having weight concentration in the range of 10-15wt%.
In still another aspect of the present invention, there is provided an anti-scaling coating on a heating element, said coating comprising an anti-scaling polymer composition comprising at least a polymer resin, and at least an anti-corrosive material, wherein the anti-corrosive material weight concentration in the composition is in the range of 7-15wt%; and polymer resin weight concentration in the composition is in the range of 30-35wt%; and the thickness of the coating is in the range of 50-60µm; contact angle is in the range of 90-100°; and surface energy value of the coating is ≤70mN/m.

In yet another aspect of the present invention, there is provided a method of preventing scale deposition on the surface of a heating element, said method comprising coating the surface of the heating element with a composition comprising at least a polymer resin, and at least an anti-corrosive material, wherein the anti-corrosive material weight concentration in the composition is in the range of 7-15wt%; and polymer resin weight concentration in the composition is in the range of 30-35wt% to obtain a coating, wherein said coating thickness is in the range of 50-60µm; contact angle is in the range of 90-100°; and surface energy value of the coating is ≤70mN/m, and wherein said method prevents scale deposition on the surface of the heating element.
In yet another aspect, the heating element is copper based, comprising at least 99wt% elemental copper.
In yet another aspect, the surface of the heating element is processed to enhance the surface roughness and surface energy prior to coating.
DETAILED DESCRIPTION OF THE INVENTION
Those skilled in the art will be aware that the invention described herein is subject to variations and modifications other than those specifically described. It is to be understood that the invention described herein includes all such variations and modifications. The invention also includes all such features referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more of said features.
For convenience, before further description of the present invention, certain terms/ definitions employed in the specification should be read in light of the remainder of the disclosure and understood as by a person of skill in the art. Unless defined

otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the art.
The present invention provides an anti-scaling polymer composition. The composition comprises at least a polymeric resin, and at least an anti-corrosive material, wherein the anti-corrosive material weight concentration in the composition is in the range of 7-15wt%; and polymer resin weight concentration in the composition is in the range of 30-35wt%. In a preferred embodiment, the weight concentration of the anti-corrosive material is in the range of 7-11wt%.
In an embodiment, the polymer resin is selected from the group consisting of
Polytetrafluoroethylene (PTFE), Polyvinylidene fluoride (PVDF), Poly(1,1-
difluoroethene), Polyvinylidene difluoride, Polychlorotrifluororethene (PCTFE), and combinations thereof. In a preferred embodiment, the polymer resin is PTFE.
In an embodiment, the anti-corrosive material is selected from the group consisting of mica, zinc phosphate, and combinations thereof. In a preferred embodiment, the anti-corrosive material is a combination of mica and zinc phosphate. Mica weight concentration in the composition is in the range of 2-5wt%; and zinc phosphate weight concentration in the composition is in the range of 5-10wt%. In a preferred embodiment, mica weigh concentration is in the range of 2-3wt%; and zinc phosphate weight concentration is in the range of 5-7wt%.
In an embodiment, the composition of the present invention further comprises at least a heat conductive material. In a preferred embodiment, the heat conductive material is carbon fibers. The weight concentration of carbon fibers in the said composition is in the range of 1-3wt%. In a preferred embodiment, the weight concentration of carbon fibers is in the range of 0.2-0.5wt%.

In an embodiment, the composition of the present invention further comprises at least an anti-fungal additive. In an embodiment, the anti-fungal additive is selected from the group consisting of Copper (II) sulfate pentahydrate, Copper sulphate, and combinations thereof. The weight concentration of the anti-fungal additive in the said composition in the range of 0.1-3wt%. In a preferred embodiment, the anti-fungal additive weight concentration in the said composition is in the range of 0.5-1wt%. In a more preferred embodiment, the weight concentration of the anti-fungal additive is in the range of 0.2-0.5wt%. In a preferred embodiment, the anti-fungal additive is Copper (II) sulfate pentahydrate.
In an embodiment, the composition of the present invention further comprises at least a filler. In a non-limiting example, the filler is included to increase the porosity of the applied composition. In a preferred embodiment, the filler is silica. Silica weight concentration in the said composition is in the range of 10-15wt%. In a preferred embodiment, the weight concentration of silica is in the range of 10-12wt%.
In a first preferred embodiment of the present invention, there is provided an anti-scaling composition comprising: (a) at least a polymer resin; (b) at least an anti-corrosive material; (c) at least a heat conductive material; and (d) at least a filler.
In the first preferred embodiment, the polymer resin is PTFE at a weight concentration in the range of 30-35wt%; the anti-corrosive material is a combination of mica at a weight concentration of 2-5wt% and zinc phosphate at a weight concentration of 5-10wt%; and the heat conducive material is carbon fibers at a weight concentration of 1-3wt%; and the filler is silica at a weight concentration of 10-15wt%. In a more preferred embodiment, PTFE weight concentration is in the range of 30-35wt%; mica weight concentration is in the range of 2-3wt%; zinc phosphate weight concentration is in the range of 5-7wt%; carbon fibers weight

concentration is in the range of 0.2-0.5wt%; and silica weight concentration is in the range of 10-12wt%.
In a second preferred embodiment of the present invention, there is provided an anti-scaling composition comprising: (a) at least a polymer resin; (b) at least an anti-corrosive material; (c) at least a heat conductive material; (d) at least a filler; and (e) at least an anti-fungal additive.
In the second preferred embodiment, the polymer resin is PTFE at a weight concentration in the range of 30-35wt%; the anti-corrosive material is a combination of mica at a weight concentration of 2-5wt% and zinc phosphate at a weight concentration of 5-10wt%; and the heat conducive material is carbon fibers at a weight concentration of 1-3wt%; the filler is silica at a weight concentration of 10-15wt%; and the anti-fungal additive is Copper(II) sulfate pentahydrate at a weight concentration of 0.1-3wt%. In a more preferred embodiment, PTFE at a weight concentration in the range of 30-35wt%; mica weight concentration is in the range of 2-3wt%; zinc phosphate weight concentration is in the range of 5-7wt%; carbon fibers weight concentration is in the range of 0.2-0.5wt%; silica weight concentration is in the range of 10-12wt%; and Copper (II) sulfate pentahydrate weight concentration is 0.2-0.5wt%.
The present invention also provides an anti-scale coating on a heating element. The anti-scale coating essentially comprises the composition as substantially described herein. In a preferred embodiment, the heating element is Copper based.
In an embodiment, the thickness of the anti-scaling coating is in the range of 50-60µm. In an embodiment, the anti-scaling coating has a contact angle with water in the range of 90-100°. In a preferred embodiment, the contact angle is 93.5°.

In an embodiment, the surface energy value of the anti-scaling coating is ≤70 mN/m. In a preferred embodiment, the surface energy value of the anti-scaling coating is ≤40 mN/m.
The present invention also provides a method of preventing scale deposition on the surface of a heating element, the method comprising: (a) coating the surface of the heating element with a composition as substantially described in the present specification to obtain a coating as substantially described in the present specification, wherein said method prevent scale deposition on the surface of the heating element.
In a preferred embodiment, the method as described herein further comprises the step of processing the surface of the heating element prior to application of the composition to obtain a coating of the said composition on the heating element surface.
In an embodiment, the composition of the present invention is coated onto the substrate (heating element) surface by Direct to Metal (DTM) technology. It is noted that DTM technology facilitates a single layer coating without using adhesion-promoting primer(s), which ensures good adhesion over copper at a low thickness, therefore optimizing thermal conductivity of the heating element.
In another embodiment, the composition of the present invention is applied onto the substrate (heating element) surface by spray method. In yet another embodiment, the composition of the present invention is applied onto the substrate (heating element) surface using Dip Spin technique. It is to be noted that the composition of the present invention can be applied onto the substrate (heating element) surface by any other technique, or modification thereof, known in the art.

In an embodiment, sandblasting is performed to prepare the surface of the copper-based substrate. In general, sandblasting refers to a process of propelling very fine particles of an abrasive material at high velocity & pressure onto the surface to clean it. In an embodiment, sandblasting increases the surface roughness of the substrate surface. In a preferred embodiment, the surface roughness of the substrate surface is 2.5 Ra. However, value of the surface roughness of the copper substrate surface may vary without limiting the scope of the invention.
The processing of the surface advantageously, aids in removal of copper oxide from the surface; and increase surface energy of the copper substrate surface. In addition, increased surface roughness allows for improved adhesion of the coating of the composition on the substrate surface.
EXAMPLES
In a first exemplification of the present invention, tests were performed to establish the advantage(s) and efficacy of performing surface preparation of the heating element surface prior to application of the composition of the present invention. In a first test, the surface of the heating element is prepared without sandblasting. More particularly, the surface of the heating element is prepared with emery paper rub. In general, emery paper is a type of abrasive paper used for rubbing and polishing metal. In a second test, the surface of the heating element is prepared with sandblasting and the surface roughness of the heating element is set at 2.5 Ra.
In the first test, blister formation was observed during standing loss test (measurement of energy consumption of filler water heater calculated when connected to electrical supply and when no water is drawn for 24 hours after reaching steady state condition) as well as endurance test (ability of heating element/product to withstand thermal cycles without failure) in heating elements

not sandblasted prior to application of the anti-scaling coating. In contrast, no blister formation was observed when the surface was sandblasted prior to application of the anti-scaling coating. In addition, no blister formation or film failure was observed even after 500 cycles of operation in the case where the surface was sandblasted prior to application of the anti-scaling coating.
In a second exemplification of the present invention, tests were performed to determine the breathability of the anti-scaling coating of the present invention applied on the heating element. In a first test, a conventional coating (PTFE coating without mica and reduced amount of filler material) was applied on the heating element. Blistering was observed after 72 hours of standing loss test. In a second test, the anti-scaling coating of the present invention was applied on the heating element surface. No blistering was observed on the coating film even after 72 hours of standing loss test.
In a third exemplification of the present invention, tests were performed to identify the desired dry film thickness (DFT) of the coating. In a first test, the coating was applied on the surface of the heating element with a DFT in a range of 80 to 120µm. At this range of DFT it was observed that the coating was unable to absorb thermal shock. In a second test, the coating was applied on the surface of the heating element with a DFT in a range of 50 to 60µm. In the second test, it was observed that due to the low DFT of the coating, the coating was able to absorb the thermal shock.
In a fourth exemplification of the present invention, tests were performed to determine the effectiveness of the anti-scaling coating. In a first test, the copper substrate of the heating element was not coated with the anti-scaling coating. The heating element was subjected to varying number of heating cycles when exposed to 1000 ppm hardness of water. In the case of the heating element not coated with the composition of the present invention, after 200 cycles, about 78 grams of scale

deposition was observed. In contrast, in heating element coated with the composition of the present invention, after 200 cycles, only about 8-10 grams of scale deposition was observed.
In another test with higher cycle number, it was observed that in the case of heating element not coated as per the present invention, after 1000 cycles, 600 grams of scale was deposited on the surface of the heating element. In contrast, the copper substrate of the heating element when coated with the anti-scaling composition of the present invention, only 20-80 grams of scale was deposited even after approximately 6000-12500 cycles. In particular, in a first test, heating element coated with the composition of the present invention when cycled 6307 times, only 20-40 grams of scale deposition was reported. In a second test, heating element coated with the composition of the present invention when cycled 12743 times, only 50-80 grams of scale deposition was reported.
ADVANTAGES OF THE PRESENT INVENTION
The anti-scaling polymer-based composition of the present invention is free of adhesives or any additional components, which in one aspect, makes the composition more cost effective compared to what is known in the art. Further, the anti-scaling coating ensures uniform heat distribution for optimized heating efficiency of the heating element. Further, the thickness of the coating is significantly less, resulting in reduced usage of materials and being cost effective. Furthermore, the coating prevents corrosion of the heating element; and significantly reduces deposition of salts and/or scale on the copper-based surface of the heating element.
The anti-scaling coating also ensures long-term performance of the heating element as the coating does not easily crack due to thermal expansion and contraction of the

heating element. The anti-scaling coating reduces formation of pin holes on the surface of copper-based heating element.

I/We Claim:
1. An anti-scaling polymer composition comprising:
a. at least a polymeric resin; and
b. at least an anti-corrosive material,
wherein the anti-corrosive material weight concentration in the composition is in the range of 7-15wt%; and polymer resin weight concentration in the composition is in the range of 30-35wt%.
2. The composition as claimed in claim 1, wherein the anti-corrosive material is selected from the group consisting of mica, zinc phosphate, and combinations thereof; mica weight concentration is in the range of 2-5wt%; and zinc phosphate weight concentration is in the range of 5-10wt%.
3. The composition as claimed in claim 1, wherein the polymer resin is selected from the group consisting of Polytetrafluoroethylene (PTFE), Polyvinylidene fluoride (PVDF), Poly(1,1-difluoroethene), Polyvinylidene difluoride, Polychlorotrifluororethene (PCTFE), and combinations thereof.
4. The composition as claimed in claim 1, comprising at least a heat conductive material.
5. The composition as claimed in claim 4, wherein the heat conductive material is carbon fibers having weight concentration in the range of 1-3wt%.
6. The composition as claimed in claim 1, comprising at least an anti-fungal additive.
7. The composition as claimed in claim 6, wherein the anti-fungal additive is selected from the group consisting of Copper (II) sulfate pentahydrate, and combinations thereof, having weight concentration in the range of 0.1-3wt%.

8. The composition as claimed in claim 1, comprising at least a filler.
9. The composition as claimed in claim 8, wherein the filler is silica having weight concentration in the range of 10-15wt%.
10. An anti-scaling coating on a heating element, said coating comprising: a composition claimed in claim 1, wherein the thickness of the coating is in the range of 50-60µm; contact angle is in the range of 90-100°; and surface energy value of the coating is ≤70 mN/m.
11. A method of preventing scale deposition on the surface of a heating element, said method comprising: coating the surface of the heating element with a composition as claimed in claim 1 to obtain a coating as claimed in claim 10, wherein said method prevents scale deposition on the surface of the heating element.
12. The method as claimed in claim 11, wherein the heating element is a copper based.
13. The method as claimed in claim 11, wherein the surface of the heating element is processed to enhance the surface roughness and surface energy prior to coating.