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 THE INVENTION
Antistatic coating composition
APPLICANT (S)
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR (S)
Swain Sarojini, Bhattacharya Subhendu, Sharma Ram Avatar and Chaudhari Lokesh; all of Crompton Greaves Ltd., Advanced Material and Processing Technology Centre, Global R &b D Centre, Bhaskara Building, Kanjur Marg (East), Mumbai 400 042, Maharashtra, India; all 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:

FIELD OF INVENTION
The present invention relates to a coating composition.
Particularly, the present invention relates to a coating composition having antistatic properties.
BACKGROUND OF INVENTION
Coating is a covering that is applied to the surface of an object, usually referred to as the substrate. In many cases coatings are applied to improve surface properties of the substrate, such as appearance, adhesion, wetability, corrosion resistance, wear resistance, and scratch resistance. In other cases, in particular in printing processes and semiconductor device fabrication (where the substrate is a wafer), the coating forms an essential part of the finished product.
Static electricity refers to the build-up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Static electricity can be contrasted with current (or dynamic) electricity, which can be delivered through wires as a power source. Although charge exchange can happen whenever any two surfaces come into contact and separate, a static charge only remains when at least one of the surfaces has a high resistance to electrical flow (an electrical insulator).
Static electricity can cause a lot of problems. Sparks caused by static charges on non-conductive substrates during manufacturing and processing of photographic film can destroy images. Handling of non-conductive film materials can lead to dust attraction, jamming, and obstruction of film transports and dangerous de-charging shocks during contact with highly charged film rolls. Build up of static

electricity can be deadly near combustible or explosive products, such as gasoline. Critical, sensitive electronic components can be damaged or even destroyed by static charges >100 Volts.
The term "antistatic" refers to preventing or inhibiting the buildup of static electricity. It is also known as "antistat". An antistatic coating is a specialty coating that has the ability to dissipate a static charge, and will also prevent further static build-up generally caused by the triboelectric effect by increasing surface conductivity.
A custom antistatic coating composition applicable by any coating technology can be created for specific mechanical and optical behavior. For example, varying degrees of hardness can be designed, along with dry/wet adhesion properties for over-coatability. In general the coating dispersion offers permanent antistatic protection, high mechanical resistance, and does not need a protective overcoat.
Due to their excellent properties and special morphology (high aspect ratio, nano sized diameter), CNTs have the potential to be used as the perfect filler for polymer composites. This material has the potential to improve the mechanical properties unique tunable electrical properties of polymer composites, as well as add multi-functionality. Hence, many efforts have been made to disperse CNTs in polymer matrices and fabricate nano-composites. The high aspect ratio and excellent electrical property of CNTs promise their performance as conductive filler. As a result, research attentions have been drawn to electrical properties of the composites. Since the conductivity of CNT composites can be tuned by many parameters including CNT loading, their dispersion states, etc, it falls in the

requirement range for many applications, such as anti-static, EMI shielding , field emission and sensing etc.
CN 101407587 discloses a polyurethane / carbon nano-tube composite material which can be used as an antistatic material. US 2011147675 also disclose antistatic or electrically conductive, thermoset polyurethane containing carbon nanotube. However, the antistatic property measured by using the composition described in US 2011147675 is found to be in the range of 1017 Ohm/Sq to 1015 Ohm/Sq when the concentration of the non-functionalized CNT is in the range of 0.01% to 0.75%.
Also, CN 101165127 discloses a water soluble polyurethane paint containing carbon nanotube wherein the nanotube may be chemically modified for the surface to carry hydroxyl group. However, the system is a water based system which shows less water resistance. This makes the coating prone to peeling and also limits the end application of the coating.
Therefore there remains a need to develop an antistatic coating composition which is showing improved antistatic properties; at the same time showing better water resistance and keeps from peeling.
OBJECTS OF THE INVENTION:
An object of the invention is to provide a coating composition having antistatic properties
Another object of the invention is to provide a coating composition having antistatic properties wherein surface resistivity achieved is in the range of 10" to 106Ω/Sq.

Still another object of the invention is to provide a coating composition having antistatic properties with improvement in mechanicals and thermal properties.
Yet another object of the invention is to provide a coating composition having antistatic properties which further displays reduction in dust pick up properties.
Still yet another object of the invention is to provide a coating composition having antistatic properties which requires less cleaning and low maintenance.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates the graphical representation of the surface resistivity of surfaces with and without various types of coating.
Figure 2 illustrates the graphical representation of the surface resistivity of using different concentration of hydroxyl functionalized multiwalled carbon nano tube in the coating composition of the invention.
Figure 3 illustrates comparative graphical representation of the tensile strength of composition / films comprising different concentration of hydroxyl functionalized multiwalled carbon nano tube and non functionalized multiwall carbon nano tube.
DETAILED DESCRIPTION
The present invention as described below, it is to be understood that this invention is not limited to particular methodologies and materials described, as these may vary as per the person skilled in the art. It is also to be understood that the terminology used in the description is for the purpose of describing the particular embodiments only, and is not intended to limit the scope of the present invention.

Before the present invention is described, it is to be understood that unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it is to be understood that the present invention is not limited to the methodologies and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described, as these may vary within the specifications indicated. Unless stated to the contrary, any use of the words such as "including," "containing," "comprising," "having" and the like, means "including without limitation" and shall not be construed to limit any general statement that it follows to the specific or similar items or matters immediately following it. Embodiments of the invention are not mutually exclusive, but may be implemented in various combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limitation of the invention as set forth the appended claims. Further the terms disclosed embodiments are merely exemplary methods of the invention, which may be embodied in various forms.
The term "hydroxyl functionalized multiwalled carbon nano tube" intends to cover multiwalled carbon nano tube fiinctionalized with hydroxyl group having at least 1.0% of OH groups irrespective of the method by which it is prepared.
According to the current invention, there is provided a coating composition having antistatic properties,
the said composition comprising hydroxyl fiinctionalized multiwalled carbon nano tube dispersed in polyurethane in a solvent-based system.

The hydroxyl functionalized multiwalled carbon nano tube is dispersed in polyurethane using any of the method known in the art like mechanical mixing, high-speed dispersion at 45°C, ultrasonication and the like
Preferably, the hydroxyl functionalized multiwalled carbon nano tube is dispersed in polyurethane using ultrasonication.
The hydroxyl functionalized multiwalled carbon nano tube dispersed in the coating composition is in the range of 0.01% to 2% of the total weight of polyurethane resin.
Preferably, the hydroxyl functionalized multiwalled carbon nano tube dispersed in the coating composition is in the range of 0.01% to 0.75%) of the total weight of polyurethane resin.
In accordance with another embodiment of the invention, there is provided a coating composition having antistatic properties;
the said composition comprising hydroxyl functionalized multiwalled carbon nano tube dispersed in polyurethane in a solvent-based system, optionally comprising additives, hardeners and the like.
The additives comprised in the coating composition include but not limited to flow and rheology modifiers, impact modifiers, dispersants, wetting agents, anti-settling agents and the like.
The additives comprised in the coating composition are in the range of 5% to 10%> of the total weight of the resin.

The hardener comprised in the coating composition is selected from but not limited to aliphatic polyisocyanate, 2-methoxy-l-methylethyl acetate, Hexamethylene-di-isocyanate, and the like.
The hardeners comprised in the coating composition are in the range of 20% to 25% of the total weight of resin.
In a preferred embodiment of the invention, the hydroxyl functionalized multiwalled carbon nano tube has the following characteristics:
1. Outer Diameter: 10-50 nm
2. Inside Diameter: 3-10 nm
3. Ash: 1.5 wt%
4. Purity: >80 wt%
5. Length: 10-30um
6. Specific Surface Area: 60 m /g
7. Electrical Conductivity: 100 S/cm
8. Bulk density: 0.28 g/cm3
9. True density: 2.1 g/cm3
10. OH-MWNTs contain 2.48 % OH groups
In a more preferred embodiment of the invention, the hydroxyl functionalized multiwalled carbon nano tube has the following characteristics:
1. Outer Diameter: 10-30nm
2. Inside Diameter: 5-10nm
3. Ash:<1.5wt%
4. Purity: >85 wt%

5. Length: 10-20um
6. Specific Surface Area: 60 m /g
7. Electrical Conductivity: >100 S/cm
8. Bulk density: 0.28 g/cm3
9. True density: -2.1 g/cm3
10. OH-MWNTs contain 1.0% OH groups
In a preferred embodiment of the invention, the polyurethane has the molecular weight (Mn) in the range of 2000-4000 and OH number in the range of 140- 145 g KOH/g and has an average OH functionality of 3.7 to 4.7 per polymer chain.
The coating composition has the surface resistivity in the range of 1012 to 106 Ω/Sq. Thus, the coating composition of the invention has antistatic properties with improvement in mechanicals properties like peel resistance, tear resistance, tensile strength, elongation at break, etc and thermal properties like thermal stability, etc. Tensile strength details Shown in Fig 3. The composition also shows reduction in dust pick up thus requiring easy maintenance.
The following experimental examples are illustrative of the invention but not limitative of the scope thereof.
Example 1:
0.01 parts by weight of non-functionalised multiwalled carbon nanotube having a purity of 90%, outer diameter of 10-30 nm and a length of 10-20 microns (obtained from Cheaptubes.com) is dispersed in 100 parts by weight of polyurethane resin having solid content of 36.36% (obtained from M/s SHREE SURYA COATINGS,

Nasik) using an ultrasonic tip (30 W, total energy up to 8 kJ). Further dispersion is achieved by mechanical continuous stirring and ultrasonication for 4 hours at 60°C. Films of-lmm thickness are formed by casting over mercury @ 65 °C for 2 hours after adding the amide hardner (obtained from M/s SHREE SURYA COATINGS, Nasik) in 3:1 volume ratio in the polyurethane resin. The films are post cured for 2 hours at 80°C.
Example 2:
Films are prepared in accordance with Example 1 by varying the concentration of non-functionalized multiwalled carbon nanotubes like 0, 0.025, 0.05, 0.075, 0.1, 0.2 0.3, 0.4, 0.5 and 0.75 in the composition (i.e. Films A to J). The surface resistivities of the films are tested and the results are given in table 1.
Example 3
0.01 parts by weight of hydroxyl-functionalized multiwalled carbon nanotube having outer Diameter of 30-50nm, Inside Diameter of 5-10nm, length of 10-20um, purity more than 95%, Specific Surface Area of 60 m /g, Electrical Conductivity more than 100 S/cm, Bulk density of 0.28 g/cm3, True density of around 2.1 g/cm3, ash content less than 1.5% and having at least 1% of hydroxyl group (obtained from Cheaptubes.com) is dispersed in 100 parts by weight of polyurethane resin having solid content of 36.36% (obtained from M/s SHREE SURYA COATINGS ,Nasik) using an ultrasonic tip (30 W, total energy up to 8 kJ). Further dispersion is achieved by mechanical continuous stirring and ultrasonication for 4 hours at 60°C. Films of -1mm thickness are formed by casting over mercury @ 65°C for 2 hours after adding the amide hardner (obtained

from M/s SHREE SURYA COATINGS, Nasik) in 3:1 volume ratio in the polyurethane resin. The films are post cured for 2 hours at 80°C.
Example 4:
Films are prepared in accordance with Example 2 by varying the concentration of hydroxyl functionalized multiwalled carbon nanotubes like 0, 0.025, 0.05, 0.075, 0.1, 0.2 0.3, 0.4, 0.5 and 0.75 in the composition (ie. Films K to T). The surface resistivities of the films are tested and the results are given in table 1.
Table 1: Comparison of Surface resistivity of the films of Example 1 and 2

Sr.
No. Concentration
ofnon-
functionalised
multiwalled
carbon
nanotubes in
Films of
Example 1 Resistivity
in films of
Example 1
(in Ohm/Sq) Concentration of
hydroxyl
functionalized
multiwalled
carbon nanotubes in
Films of Example 2 Resistivity
in films of
Example 2
(in Ohm/Sq)
1 0 1.87E+17 0 1.87E+17
2 0.01 1.02E+15 0.01 1.87E+14
3 0.025 1.29E+15 0.025 1.70E+14
4 0.05 1.06E+15 0.05 6.37E+13
5 0.075 1.89E+15 0.075 1.54E+13
6 0.1 1.11E+15 0.1 1.59E+10
7 0.2 1.86E+15 0.2 2.00E+10
8 0.3 3.94E+15 0.3 2.44E+10
9 0.4 1.61E+15 0.4 1.82E+09

10 0.5 1.65E+15 0.5 7.12E+07
11 0.75 1.41E+15 0.75 1.42E+13
The surface resistivity achieved is in the range of 1012 to 106 Ω/Sq.
Figure 1 illustrates the comparative graphical representation of the surface resistivity of examples 1 and 2
Figure 2 illustrates the graphical representation of the surface resistivity using different concentration of hydroxyl functionalized multiwalled carbon nano tube in the coating composition of the invention.
According to results obtained of surface resistivity for the films of example 2 shows that the addition of hydroxyl functionalized multiwalled carbon nanotubes increases the surface resistivity as compared to that of non-functionalized multiwalled carbon nanotubes, thus, improving the antistatic properties of the coating composition of the invention.
The films according to examples 1 and 2 having varying concentration of non-functionalized multiwalled carbon nanotubes (films A to J) and hydroxyl functionalized multiwalled carbon nanotubes (films K to T) respectively are tested for mechanical properties like peel resistance, tear resistance, tensile strength and elongation at break. It was found that the films according to example 1 have better peel resistance, tear resistance, tensile strength and elongation at break than that of films according to example 2.
Figure 3 illustrates evaluation of mechanical properties of films based on compositions based CNTs i.e. Compositions A to J and ACNTs i.e. Compositions

K to T with respect to standard unsaturated polyester resin. The addition of CNTs resulted in an increase in the tensile strength of the composites A to J; however, ACNTs based composites K to T showed a higher increase in tensile strength as compared to CNTs. In both cases it was observed that agglomeration of the particles occurred at 0.075%, after which the strength of the composites were seen to decrease. The optimum concentration of ACNTs was seen to be 0.075%. This increased performance of ACNT based composites films K to T was due to the increase interaction between the polymer matrix and the ACNTs.
The films according to examples 1 and 2 having varying concentration of non-functionalized multiwalled carbon nanotubes and hydroxyl functionalized multiwalled carbon nanotubes respectively are tested for thermal properties like thermal degradation temperature. It was found that the films according to example 2 have higher thermal stability than that of films according to example 1. The results of thermal stability is given in table -2
Table 2: Comparison of Thermal stability of the films of Example 1 and 2

Concentration of non- Concentration of hydroxyl
Sr.
No. functionalized
multiwalled
carbon Degradation temperature
(°C) functionalized
multiwalled
carbon Degradation temperature
(°C)
nanotubes in
nanotubes in

Films of Example 1 Films of Example 2
1 0 318.20 0 318.20
2 0.01 318.20 0.01 325.88
3 0.025 329.98 0.025 329.18

4 0.05 325.04 0.05 333.65
5 0.075 312.36 0.075 318.02
6 0.1 312.04 0.1 320.43
Thus, the coating composition of the invention shows improved mechanical and thermal properties along with antistatic properties.
Example 5:
The films of polyurethane without carbon nanotubes having varying thickness like 10-15, 15-20, 20-25 and 25-30 microns were prepared according to Example 1. The films of polyurethane with 0.75 % non-functionalized multiwalled carbon nanotubes having varying thickness like 10-15, 15-20, 20-25 and 25-30 microns were prepared according to Example 1.
The films of polyurethane with 0.75 % hydroxyl functionalized multiwalled carbon nanotubes having varying thickness like 10-15, 15-20, 20-25 and 25-30 microns were prepared according to Example 2.
The dust pick up properties of all the films were tested for 7 days and 15 days and the results for the same were tabulated in table 3.
Table 3 illustrates the comparison of dust pick up of films of polyurethane prepared according to example 5 after 7 days and 15 days.

Sr.
No. Dry Film Thickness
(micron) Polyurethane (PU) without CNT PU with 0.75 % non-functionalized CNT PU with 0.75 % OH-functionalized CNT

Dust pick
up in 7
days
(mg) Dust
pick up
in 15
days
(mg) Dust pick
up in 7
days
(mg) Dust pick
up in 15
days
(mg) Dust pick
up in 7
days
(mg) Dust pick up in 15
days
(mg)
1 10-15 0.625 1.5 0.36 0.78 0.22 0.36
2 15-20 0.72 1.62 0.38 0.62 0.23 0.32
3 20-25 0.75 1.67 0.37 0.68 0.24 0.38
4 25-30 0.69 1.7 0.38 0.76 0.27 0.33
From the table it can be seen that the dust pick up of the films having hydroxyl-functionalized multiwalled carbon nanotube is less than the films having non-functionalized multiwalled carbon nanotubes. Thus, the dust pick up of the coating composition is also found to be reduced. As a result of this, the said coating is easy to clean and maintain..
The antistatic coating composition of the invention is a transparent coating which is applied on the surface of equipments.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim;
1) A coating composition having antistatic properties, the said composition comprising hydroxyl functionalized multiwalled carbon nano tube dispersed in polyurethane in a solvent-based system.
2) The antistatic coating composition as claimed in claim 1, wherein the hydroxyl functionalized multiwalled carbon nano tube is dispersed in the range of 0.015% to 2%.
3) The antistatic coating composition as claimed in claim 1, wherein the said composition comprises hydroxyl functionalized multiwalled carbon nano tube dispersed in polyurethane in a solvent-based system, optionally comprising additives, fillers, hardeners, and the like.
4) The antistatic coating composition as claimed in claim 3, wherein the additives include but not limited to flow and rheology modifiers, impact modifiers, dispersants, wetting agents, anti-settling agents and the like.
5) The antistatic coating composition as claimed in claim 3, wherein the said, wherein the additives are in the range of 5% to 10% of the total weight of the resin.
6) The antistatic coating composition as claimed in claim 3, wherein the hardner include from but not limited to aliphatic polyisocyanate, 2-methoxy-1-methylethyl acetate, Hexamethylene-di-isocyanate, and the like.

7) The antistatic coating composition as claimed in claim 3, wherein the hardener is in the range of 20% to 25% of the total weight of polyurethane resin.
8) The antistatic coating as claimed in any of the preceding claims having the surface resistivity in the range of 10 to 10 Ω/Sq.