FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
AND
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
“A WATER HEATER STORAGE TANK”
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 in general relates to the field of insulators, particularly insulation for water heater storage tanks.
BACKGROUND OF THE INVENTION
With domestic and international economic development and the gradual improvement in people’s living standards, the cost of energy and the demand for energy is increasing. This calls for research and development of high-quality and effective energy saving products that are cost effective and contribute to sustainable use of resources.
In the current scenario, thermal insulation materials employed in the construction industry and temperature regulation technologies use a uniform foam structure of polyurethane, polystyrene and other materials. Such foam structure materials by themselves cannot sufficiently provide the desired effect of heat retention and thermal insulation.
The current technical design of commercially available thermal insulation boards is limited to the low thermal conductivity of the foamed material structure to achieve thermal insulation effect, but no anti-heat radiation function. This contributes to heat transfer through the foamed material layers reducing energy efficiency.
Additionally, epoxy coatings are often used in industrial and automotive applications since they are more heat resistant than latex based and alkyl-based paints. Epoxy coatings tend to deteriorate, known as “chalking-out”, due to UV exposure. Epoxy coatings are also widely used in the packaging industry; cans and containers are often coated with epoxy to reduce susceptibility to rusting.

Epoxy coatings are also used as primers to improve the adhesion of automotive and marine paints especially on metal surfaces where corrosion (rusting) resistance is highly desired. Epoxy adhesives are a major part of the class of adhesives called “structural adhesives” or “engineering adhesives” (that include polyurethane, acrylic, cyanoacrylate, and other chemistries). These high-performance adhesives can be used on wood, metal, glass, stone, and some plastics. Epoxy adhesives are better in heat and chemical resistance than other common adhesives.
Polyurethane is an organic polymer formed by reacting a polyol (an alcohol with more than two reactive hydroxyl groups per molecule) with a diisocyanate or a polymeric isocyanate in the presence of suitable catalysts and additives. Polyurethane foam (PUF) can be used for heat and acoustic insulation purposes. Polyurethane is a generic term which covers a wide range of different formulations and applications derived from a reaction of diisocyanate with a polyol.
When we talk about polyurethane insulation, we are referring to a group of insulation materials based on PUR (polyurethane) or PIR (polyisocyanurate). The closed cell structure and high cross-linking density of PUR and PIR gives is the characteristics of good heat stability, high compressive strength and excellent insulation properties. Polyurethanes are flexible foams used in mattresses, chemical resistant coatings, adhesives and sealants, insulation for buildings and technical applications like heat exchangers, cooling pipes and much more.
PUF layers in water tanks act like heat insulators. These layers are poor conductors of heat, and act like a barrier for heat transmission from outside to the water stored inside the tank. This ensures that the water inside is less affected by the harsh climate outside, be it freezing temperatures or very high

heat.
In the current practice, insulation panels used upon tanks and storage structures are made using layered compositions of epoxy adhesives and PUF in various combinations to provide thermal insulation. However, it does not provide optimum insulation since heat is eventually lost by radiation into the surroundings thereby resulting in reduced energy efficiency.
Further, the efficiency of insulation is directly proportional to the thickness of insulation. However, increase in thickness may result in bulky structure and require more space for installation, also, increasing the thickness results in increase in cost as well.
The technologies being used currently fail to disclose a water storage tank than can optimize heat retention, prevent loss of heat by radiation and thereby increase insulation capacity while ensuring compact design. Moreover, there is a need to overcome at least one of the problems stated above.
SUMMARY OF THE INVENTION
In an aspect of the present invention, there is provided a multi-layer insulation for water heater, comprising: (a) at least a first insulating layer; and (b) an insulating layer comprising polyurethane foam, wherein the thickness of the insulating layer comprising polyurethane foam is in the range of 25-30µm.
In another aspect of the present invention, the first layer comprises at least an epoxy resin and hollow glass microspheres, said hollow glass microspheres density is in the range of 0.13-0.17g/cm3 and size is in the range of 30-125µm.

In another aspect of the present invention, the thickness of the first layer is in the range of 200-600µm.
In yet another aspect of the present invention, the multi-layer insulation further comprises at least a second layer of metallized film selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, nylon, and combinations thereof.
In still another aspect of the present invention, the thickness of the second layer is in the range of 0.03-0.07mm.
In an aspect of the present invention, the metallized film comprises fiberglass mesh support.
In an aspect of the present invention, the weight concentration of hollow glass microsphere in epoxy resin is in the range of 2-4wt%.
In an aspect of the present invention, the multi-layer insulation for water heater comprises: (a) a first insulating layer of at least an epoxy resin and hollow glass microspheres having thickness of 300µm; (b) a second insulating layer of metallized film having thickness of 0.05mm; and (c) an insulating layer comprising polyurethane foam having thickness of 25-30µm, wherein said insulating layer comprising polyurethane foam is outermost insulating layer, and said first insulating layer is innermost insulating layer.
In an aspect of the present invention, the multi-layer insulation for water heater comprises: (a) a first insulating layer of at least an epoxy resin and hollow glass microspheres having thickness of 500µm; and (b) an insulating layer comprising polyurethane foam having thickness of 25-30µm, wherein said first insulating layer is innermost insulating layer.

In another aspect of the present invention, the multi-layer insulation thickness is in the range of 0.4-0.8mm.
In still another aspect of the present invention, there is provide a water heater storage tank comprising a multi-layer insulation, said insulation comprising: (a) at least a first insulating layer; and (b) an insulating layer comprising polyurethane foam, wherein the thickness of the insulating layer comprising polyurethane foam is in the range of 25-30µm.
In an aspect of the present invention, the first layer is the innermost layer.
In another aspect of the present invention, the first layer is coated on the
external surface of the tank.
In yet another aspect of the present invention, the tank has a plastic or metal
outside body.
BRIEF DESCRIPTION OF THE DRAWINGS
The detailed description is described with reference to the accompanying figures. In the figures, the left most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like figures and components.
Referring to Figure 1, illustrates the water storage tank comprising the adhesive multi-layered insulation coating in accordance with an exemplary embodiment of the present invention.
Referring to Figure 2, illustrates the water storage tank comprising the adhesive multi-layered insulation coating in accordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
Some embodiments of the present disclosure, illustrating all its features, will now be discussed in detail. 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.
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 for an improved water heater storage tank 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 a multi-layer insulation for water heater, comprising: (a) at least a first insulating layer; and (b) an insulating layer comprising polyurethane foam, wherein the thickness of the insulating layer comprising polyurethane foam is in the range of 25-30µm.
In an embodiment, the multi-layer insulation further comprises at least a second layer of metallized film selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, nylon, and combinations thereof. In a preferred embodiment, the metal is aluminum. In an embodiment, the metallized film comprises fiberglass mesh support. In an embodiment, the thickness of the second layer of metallized film is in the range of 0.03-0.07mm. In a preferred embodiment, the thickness of the second layer of metallized film is 0.05mm.

The first insulating layer of the multi-layer insulation comprises at least an epoxy resin and hollow glass microspheres, said hollow glass microspheres density is in the range of 0.13-0.17g/cm3 and size is in the range of 30-125µm. In an embodiment, the weight concentration of hollow glass microsphere in epoxy resin is in the range of 2-4wt%. In an embodiment, the thickness of the said first insulating layer is in the range of 200-600µm. In a preferred embodiment, the thickness of the first insulating layer is 300µm. In another preferred embodiment, the thickness of the first insulating layer is 500µm.
In an embodiment of the present invention, the thickness of the multi-layer insulation in the range of 0.4-0.8mm. In a preferred embodiment, the thickness of the multi-layer insulation is in the range of 0.375-0.38mm. In another preferred embodiment, the thickness of the multi-layer insulation is in the range of 0.525-0.53mm.
In an implementation of the present invention, there is provided a multi-layer insulation for water heater comprising: (a) a first insulating layer of at least an epoxy resin and hollow glass microspheres having thickness of 300µm; (b) a second insulating layer of metallized film having thickness of 0.05mm; and (c) an insulating layer comprising polyurethane foam having thickness of 25-30µm, wherein said insulating layer comprising polyurethane foam is outermost insulating layer, and said first insulating layer is innermost insulating layer.
In another implementation of the present invention, there is provided a multi¬layer insulation for water heater comprising: (a) a first insulating layer of at least an epoxy resin and hollow glass microspheres having thickness of 500µm; and (b) an insulating layer comprising polyurethane foam having thickness of 25-30µm, wherein said first insulating layer is innermost insulating layer.

The present invention also provides a water heater storage tank comprising a multi-layer insulation as described herein. In an embodiment, the tank has a plastic outer body. In another embodiment, the tank has a metal outside body. In a preferred embodiment, there is provided a water heater storage tank coated with a first insulating layer of at least an epoxy resin and hollow glass microspheres having thickness of 300µm; a middle second insulating layer of metallized film having thickness of 0.05mm; and an outermost insulating layer comprising polyurethane foam having thickness of 25-30µm. In another preferred embodiment, there is provided a water heater storage tank coated with a first insulating layer of at least an epoxy resin and hollow glass microspheres having thickness of 500µm; and an outermost insulating layer comprising polyurethane foam having thickness of 25-30µm.
In order to ascertain and establish the power savings by using the multi-layer insulation of the present invention, the 24-hour power consumption (Wh) requirement as per BEE standard was measured using two different insulations.
Briefly, the epoxy glass-microsphere based coating was coated on the outer part of the tank to a desired thickness (300 or 500µm) and cured at room temperature. Next, the epoxy coated tank was wrapped with metallized film (optional) and the tank was placed in a plastic body cavity (outer casing of water storage heater). Polyurethane foam was injected into the cavity and allowed to set.
In a first exemplary working of the present invention, a water heater storage tank coated with a multi-layer insulation comprising a first insulating layer of at least an epoxy resin and hollow glass microspheres having thickness of 500µm; and an outermost insulating layer comprising polyurethane foam having thickness of 25-30µm results in a 17.53Wh saving as measured over a 24hour

time period (401.48Wh power requirement as compared to 419Wh as per BEE standard). Referring to Figure 1, there is provided a water heater storage tank comprising an MS tank (1), an epoxy resin and hollow glass microspheres coating (2), a metallized film (3), PUF coating (4) and plastic/ metal outer body (5).
In a second exemplary working of the present invention, a water heater storage tank coated with a multi-layer insulation comprising a first insulating layer of at least an epoxy resin and hollow glass microspheres having thickness of 300µm; a middle second insulating layer of metallized film having thickness of 0.05mm; and an outermost insulating layer comprising polyurethane foam having thickness of 25-30µm results in a 9.23Wh saving as measured over a 24 hour time period (409.77Wh power requirement as compared to 419Wh as per BEE standard). Referring to Figure 2, there is provided a water heater storage tank comprising an MS tank (1), an epoxy resin and hollow glass microspheres coating (2), PUF coating (3) and plastic/ metal outer body (4).
These data clearly show that by using the multi-layer insulation of the present invention, there is a clear and significant power saving as compared to the standards, which is of economic significance and benefit.
ADVANTAGES OF THE PRESENT INVENTION
A few advantages of the water heater storage tank of the present invention are disclosed below. It is stated that the below mentioned advantages are non-limiting and is provided to give a broad understanding of the invention without limiting the scope of understanding of the same.
1. The multi-layer insulation of the present invention is able to save on the amount of polyurethane foam required for insulation effect, which is

otherwise an expensive but essential material for insulation purposes. Therefore, any reduction in amount of polyurethane foam used represents a significant cost benefit without sacrificing on insulating benefits and efficiency. In fact, the data clearly shows that higher insulating efficiency is achieved (power savings) by using the multi-layer insulation of the present invention, while using reduced amounts of polyurethane foam.
2. Reduction in standing heat loss of hot water stored in the tank.
3. Reduction in conductive heat loss of hot water stored in the tank.
4. Reduction of radiative heat loss of hot water stored in the tank.
5. Lower cost production of water heater storage tank.
6. Low running cost of water heater storage tank.
7. Improved efficiency/ star rating, leading to cost effectiveness and sustainable use of energy.

I/We claim:
1. A multi-layer insulation for water heater, comprising:
a. at least a first insulating layer; and
b. an insulating layer comprising polyurethane foam,
wherein the thickness of the insulating layer comprising polyurethane foam is in the range of 25-30µm.
2. The insulation as claimed in claim 1, wherein the first layer comprises at least an epoxy resin and hollow glass microspheres, said hollow glass microspheres density is in the range of 0.13-0.17g/cm3 and size is in the range of 30-125µm.
3. The insulation layer as claimed in claim 2, wherein the thickness of the first layer is in the range of 200-600µm.
4. The insulation as claimed in claim 1, further comprising at least a second layer of metallized film selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, nylon, and combinations thereof.
5. The insulation layer as claimed in claim 4, wherein the thickness of the second layer is in the range of 0.03-0.07mm.
6. The insulation as claimed in claim 4, said metallized film comprises fiberglass mesh support.
7. The insulation as claimed in claim 1, wherein the weight concentration of hollow glass microsphere in epoxy resin is in the range of 2-4wt%.

8. The insulation as claimed in claim 1, comprising:
a. a first insulating layer of at least an epoxy resin and hollow glass
microspheres having thickness of 300µm;
b. a second insulating layer of metallized film having thickness of
0.05mm; and
c. an insulating layer comprising polyurethane foam having thickness
of 25-30µm;
wherein said insulating layer comprising polyurethane foam is outermost insulating layer, and said first insulating layer is innermost insulating layer.
9. The insulation as claimed in claim 1, comprising:
a. a first insulating layer of at least an epoxy resin and hollow glass
microspheres having thickness of 500µm; and
b. an insulating layer comprising polyurethane foam having thickness
of 25-30µm,
wherein said first insulating layer is innermost insulating layer.
10. The insulation as claimed in claim 1, having thickness in the range of 0.4-0.8mm.
11. A water heater storage tank comprising a multi-layer insulation as claimed in claim 1, wherein the first layer is the innermost layer.
12. The tank as claimed in claim 11, wherein the first layer is coated on the external surface of the tank.

13. The tank as claimed in claim 11, wherein the tank has a plastic or metal outside body.