FORM 2
THE PATENTS ACT. 1970
(39 OF 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
[SECTION 10; RULE 13]
"INORGANIC ANTIMICROBIAL NANOCOMPOSITE POWDER AND A METHOD OF MANUFACTURING THE SAME"
APPLICANT: PRISM CEMENT LIMITED
NATIONALITY: COMPANY INCORPORATED UNDER THE COMPANIES
ACT, 1956
ADDRESS: WINDSOR 7TH FLOOR, KALINA, C.S.T. ROAD,
SANTACRUZ (E) MUMBAI - 400 098, MAHARASHTRA,
INDIA
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

INTRODUCTION
The present invention relates to inorganic antimicrobial nanocomposite powder and the method of manufacturing the same. Particularly, it relates to an antimicrobial agent comprising silver metal particles of very fine size deposited on titanium dioxide and the method for preparing the same. The said powder is being evaluated for its antimicrobial activity. The said antimicrobial agent will find application in the diverse areas like Tiles, Sanitaryware, Plastics & Polymers, Textiles. Rubbers, Paints etc.
BACKGROUND OF THE INVENTION
Microbes (bacteria, fungi & algae) attacks on the various surfaces (like plastic, textile etc.) which leads to loss of aesthetic property and causes various diseases. To counter this problem, antimicrobial agents are incorporated inside the matrix which helps in arresting the bacterial growth. Large number of manufacturers used organic antimicrobials to counter the microbe problems, but organic compounds have disadvantage as the effect is not permanent & heat stability is poor. Its migratory, volatile and toxic nature, in more recent times, raised significant concerns about their long term impact on health, safety and the environment. Consequently, many have already been banned and new legislation will prevent the use of others. The commonly used organic antimicrobials are Triclosan, Quaternery ammonium salts etc.
There is need of permanent antimicrobial agent which is non-toxic, environment friendly and superior to organic counterpart. The present invention proposes inorganic antimicrobial agent with high antimicrobial activity and which does not have health

impact on humans. It can be used in diverse application areas like plastics, textile, tiles, sanitaryware etc.
Metal like silver, copper, mercury, and zinc are known for anti-bacterial properties. Among all these, silver has been widely used for the same. For thousands of years in various countries, especially India, silver has been used for its bactericidal properties -to keep water, and often foods, safer. According to literature some 275000 kg of edible metallic silver foil are consumed every year (in food) in India. No known adverse health effects have ever been recorded. This is evidence that silver as a metal is not toxic in any way.
The idea of the present invention is to choose a matrix or support on which the metals of small particles of silver can be deposited.
The matrix/support on which silver metal can be deposited should have high surface area, good heat resistance, with end application like plastics, textile, sanitaryware, tiles, paints etc. As titania is used in these areas, titania as matrix was obvious choice. Alternatively zinc oxide, silica, zeolites can be used as carrier.
The possible mechanism by which the silver particles arrest the growth of microbes is that in presence of moisture, metallic silver oxidizes, which results in the release of the silver ions. Silver ions are the species that are responsible for microbial inhibition. Because stiver oxidation is a slow reaction, the size of silver particles is critical to achieve microorganism growth inhibition. The smaller the particle size, the higher the surface area, and the greater the area available for oxidation. Accordingly, particles

with diameter less than 100 nm are required to have the necessary surface area to allow a continuous release of silver ions.
PRIOR ART
The use of antimicrobial agent to inhibit growth of microorganism on disposable products is reported in US 424404. However, the aforesaid document teaches binding of the silver halide particles to the fiber using a hydrophilic gelatin polymer composition to inhibit the growth of micro organism whereas the present invention teaches binding of nano silver particles on a carrier and the method of obtaining nano silver particles bonded on a carrier.
The US patent application US 6982289 discloses a method where an antibacterial agent is deposited on a surface of the polyamide that is a powder and is used for paint application. Polyamide is an organic material. The said document however does not teach the use of antibacterial agent at high temperature application (1200 degree Celsius). Further, the present invention relates to inorganic antimicrobial nano composite powder, unlike the above US patent which uses organic material
The European patent Application EP1878346 also reports the use of a silver-based inorganic antimicrobial agent by wet synthesis of silver ion-containing zirconium phosphate, Further, it describes the ion exchange process which takes place at 100 degree Celsius to obtain an antibacterial agent. However, it does not teach the use of antimicrobial agent comprising of nano silver particles bonded on a carrier having specific particle size and purity. In the present invention the purity and average particle size of titania (titanium dioxide) plays an important role in formation of silver

nanoparticles at high temperature calcinations under reducing atmosphere. The lower and higher temperature at which the EP1878346 and present invention reactions take place play an important role in the respective reactions. Thus, the two reactions are different. Further, the raw (starting) materials in the aforesaid process as also the end products and the process steps followed to obtain the end product are substantially different.
The advantage of the present invention is that the Titania (Titanium dioxide) as also the silver particles are in nanometer range thus both form a truly nanocomposite compound of high surface area and high antibacterial activity. Also, the silver nanoparticles which are formed in the present invention have advantage over the silver ions since any species in ionic form is highly reactive and hence it can react easily with chlorine sulphate to form silver chloride or silver sulphate thereby reducing its antibacterial activity.
SUMMARY OF THE INVENTION
The present invention relates to an inorganic antimicrobial agent comprising of nano silver particles bonded on a carrier having average particle size of 20 nm to 400 nm wherein the carrier is selected from amongst titania (titanium dioxide), zinc oxide, silica or zeolite and wherein the surface area of the carrier is between 10 to 70 m2/g and wherein the average particle size of silver is 10 nm and wherein percentage of silver to carrier is 0.1 to 30: 99.9 to 70 w/w and wherein the ratio of silver to carrier is 5 : 95 w/vv. The said nanosilver particles are deposited preferably on titanium dioxide and which titanium dioxide is of nanometer size to micron size and has particle size

preferably of less than 0.4 micron, through high temperature processing. Further, the said antimicrobial agent comprises the silver particles preferably of 5-30% by weight and the content of the silver particles in the said antimicrobial agent is approximately 10% to 20% by weight. Still further, the silver particles are supplied from one or more kinds of silver containing compounds selected from a group consisting of silver nitrate, silver sulfate, silver carbonate and silver chloride. Still further, the said antimicrobial agent when tested according to time kill test (API-RP 38 method) shows reduction of microbes at different time intervals. The preferable method for preparing the antimicrobial agent according to the present invention comprises the steps of a. weighing the raw materials of titanium dioxide and silver compounds according to the following proportion: titanium dioxide (70 - 99.9%) by weight, silver (0.1 -30 %) by weight b. dissolving the silver compounds in distilled water followed by titanum dioxide c. stirring continuously for 15 min to 40 min d. drying the resulted mixture in a oven at 110— 150°C for 30 min to 60 min e. calcining the dried mixtures under reducing atmosphere (mixture of hydrogen& nitrogen) at 450 ~ 700°C for 60 min to 180 min to obtain the antimicrobial agent.
DESCRIPTION:
The object of the invention is to manufacture an inorganic antimicrobial agent having silver metal particles of small size loaded on the titania particles for diverse applications and evaluating its antimicrobial activity. The antimicrobial agent according to this invention comprises of silver nanoparticles deposited on titania through high temperature calcination using reducing atmosphere.

One aspect of the invention is that titanium dioxide used as precursor is in the range of 20 nm to 400 nm. Another aspect of the invention is that surface area of the titanium dioxide is 10- 70 m2/g. The silver compounds such as silver nitrate, silver sulfate, silver carbonate and silver chloride, can be used as one of the materials. Another aspects of invention is mixing titania and silver compounds and drying in oven at 110 to 150°C and then heating resulting mixture in reducing atmosphere (hydrogen& nitrogen) to 450-700°C for 60 min to 180 min to obtain the antimicrobial agent. During heating silver nitrate converts into silver dioxide and finally silver metal of very high surface area. An important aspect of the invention is that silver deposited on titania matrix is of very small size. The silver metal concentration in the antimicrobial agent is 0.1 to 30% and the rest is titanium dioxide. The XRD pattern of the antimicrobial products shows distinct peaks of titania and silver. Another important aspect of invention is that silver particles formed is less than 20 nm according to TEM Micrograph. The present invention confirms that the silver nanoparticles formed is of spherical shape and has wide size distribution. The average particle size calculated is 10 nm. The present invention also describes the test method by which antimicrobial nano composite powder is evaluated. The antibacterial activity/efficacy of the produced powder is done by International Protocol Time Kill Test (API-RP 38) method. One of the aspects of invention is that only titania does not show any antibacterial activity but titania with varying silver contents showed strong antibacterial properties against microbes like Staphylococcus aureus, Escherichia coll Psuedonomas Aureous, Bacillus Subtitis, Aspergillusniger and Algae. The silver nanoparticles loaded on titanium dioxide show antibacterial activity as silver nanoparticles are of very small.size and being small size

it has high surface area. Bacteria coming in contact with it, is destroyed due to rupture of its cell wall.
The silver nitrate solution present in the titania (titanium dioxide) matrix when heated in reducing temperature forms silver nanoparticles. In the preferred embodiment, at high temperature between 200 and 600 degree Celcius, under reducing atmosphere comprising of mixture of hydrogen and nitrogen gases or coke or graphite, silver ions from silver nitrate get reduced to silver nanoparticles. The silver nanoparticles get bonded with titania (titanium dioxide) to form an antimicrobial agent.
The process of manufacture of said inorganic antimicrobial compound will now be explained with the help of drawings accompanying the provisional specification. However, the said drawings only illustrate the invention and in no way limits the same.
In the drawings accompanying the provisional specification:-
Figure 1 shows the flowchart for the process of manufacturing of said inorganic antimicrobial compound.
As shown in process flowchart, raw materials are mixed in the proportions and dried in the oven and heated above 450°C under reducing condition with heating rate of 5-10°C/min. During heating silver nitrate converts into silver dioxide and finally silver nanoparticle of very high surface area.

Figure 2 shows Particle Size Analysis of Antimicrobial Nanocomposite Powder CTD Enamb 05 The particle size of Antimicrobial Nanocomposite powder is 0.75 micron. The detailed report as measured by Horiba LA-920 is shown in Fig .2.
Figure 3 shows Xray Diffraction of Antimicrobial Nanocomposite Powder CTD Enamb 05. X- Ray diffraction confirms the presence of silver metal and titanium dioxide of Rutile crystal structure. Corresponding 29 values for silver are 38.1 & 44.2 while for titania rutile crystal structure is 27.4,36, 41.2, 54.3.
Figure 4 shows Transmission Electron Microscope of Antimicrobial nanocomposite Powder CTD Enamb 05.lt shows Silver particles deposited on titanium dioxide. The silver particle formed is of spherical shape. The size of silver particles measured is having wide range such as 6.99nm, 13.07, 10.08, 9.31nm, 13.32 nm. TEM microcgraph has been taken at different regions as to show the various size distribution of silver particles. Few of the silver particle measures were of size 6.99nm, 13.07nm, 10.08nm, 9.31nm, 13.32nm. The average particle size of silver calculated to be l0nm. The size of the titania matrix can is found out to be around 30-40 nm. TEM also confirms about the dispersion of silver nanoparticles on the titania matrix.
MICROBIOLOGICAL TESTING
0.3% solution of Antimicrobial Powder Samples were prepared and inoculated with Test Organisms. Test Inoculum used was Bacillus Subtilis (1.76X103 cfu/ml) which is one kind of bacteria. Culture controls were also put up along with the experiment as viability indicator. The samples were incubated at room temperature and Microbial

reduction percentage were determined after 10 minutes, 30minutes, 12 hours, 24 hours and 48 hours interval.
Test results are tabulated below and are done at Biotech Testing Services, Microbiological Laboratory in Mumbai.
Table 1

Sample Code Microbial Reduction Percentage

10 min 30 min 12 hrs 24 hrs 48 hrs

CTD ENAMB 0.1 28.4 30.68 51.7 86.93 100
CTD ENAMB 05 87.5 99.14 99.88 100 100
CTD ENAMB 10 59.09 75 99.43 100 100
CTD ENAMB 20 73.86 85.22 100 100 100
CTD ENAMB 30 65.9 79.54 99.88 100 100
From the Table 1 of microbial reduction percentage it is clear that CTD ENAMB 05 is the most effective & CTD ENAMB 0.1 is the least effective in short time interval of 10 minutes. As the concentration of silver is increased the microbe reduction percentage increases for first 2 compositions but does not follow the trend afterwards and can be treated almost equal. This can be explained by the fact that optimum quantity of silver concentration when dispersed in the inorganic matrix helps in getting very good

microbial reduction percentage. As we increase the silver concentration the nanoparticles which forms gets agglomerated and hence there is not increase in antimicrobial activity or microbial reduction percentage. However after 48 hours the microbial reduction percentage is 100 for all the compositions. Although after 48 hours microbial reductions percentage is 100 but if silver concentration is very less then the antimicrobial effectiveness cannot be permanent. So the composition should be selected such that its antimicrobial activity should be high and it should be permanent in nature.
The following Examples would further explain/describe the present invention. However, the examples in no way limit the scope of the invention.
Example 1:
99.9% Titanium dioxide and 0.15% silver nitrate is stirred in. distilled water for 30 minutes followed by drying at 130°C for 60 minutes. The dried mixture is milled properly and passed through 120# sieve. The sieved powder is calcined at 500°C for 2 hrs in reducing atmosphere to get nanosilver particle deposited on titania particles. The said antimicrobial agent is labeled as CTD Enamb 0.1. The antibacterial efficacy according to International Protocol time kill test (API-RP 38 method) is 28.40% in just 10 minutes.
Example 2:
95% Titanium dioxide and 7.87% silver nitrate is stirred in distilled water for 30 minutes followed by drying at 130°C for 60 minutes. The dried mixture is milled properly and passed through 120# sieve. The sieved powder is calcined at 500°C for 2

hrs in reducing atmosphere to get nanosilver particle deposited on titania particles. The said antimicrobial agent is labeled as CTD Enamb 05. The antibacterial efficacy according to International Protocol time kill test (API-RP38 method) is 87.50% in just 10 minutes.
Example 3:
90% Titanium dioxide and 15.7% silver nitrate is stirred in. distilled water for 30 minutes followed by drying at 130°C for 60 minutes. The dried mixture is milled properly and passed through 120# sieve. The sieved powder is calcined at 500°C for 2 hrs in reducing atmosphere to get nanosilver particle deposited on titania particles. The said antimicrobial agent is labeled as CTD Enamb 10. The antibacterial efficacy according to International Protocol time kill test (API-RP 38 method) is 59.09% in just 10 minutes.
Example 4:
80% Titanium dioxide and 31.4% silver nitrate is stirred in distilled water for 30 minutes followed by drying at 130°C for 60 minutes. The dried mixture is milled properly and passed through 120# sieve. The sieved powder is calcined at 500°C for 2 hrs in reducing atmosphere to get nanosilver particle deposited on titania particles. The said antimicrobial agent is labeled as CTD Enamb 20. The antibacterial efficacy according to International Protocol time kill test (API-RP 38 method) is 73.86% in just 10 minutes.

Example 5:
70% titanium dioxide and 47.1% silver nitrate is stirred in distilled water for 30 minutes, followed by drying at 130°C for 60 minutes. The dried mixture is milled properly and passed through 120# sieve. The sieved powder is calcined at 500°C for 2 hrs in reducing atmosphere (hydrogen and nitrogen mixture) to get nanosilver particle deposited on titania particles. The said antimicrobial agent is labeled as CTD Enamb 30. The antibacterial efficacy according to International Protocol time kill test (API-RP 38 method) is 65.90% in just 10 minutes.

WE CLAIM:
1. An inorganic antimicrobial agent comprising of nano silver particles bonded on a carrier having average particle size of 20 nm to 400 nm.
2. An inorganic antimicrobial agent as claimed in claim 1. wherein carrier is selected from amongst titania (titanium dioxide), zinc oxide, silica or zeolite.
3. An inorganic antimicrobial agent claimed in claim 1 wherein the surface area of the carrier is between 10 to 70 m /g.
4. An inorganic antimicrobial agent as claimed in claim 1, wherein the average particle size of silver is 10 nm.
5. An inorganic antimicrobial agent as claimed in claim 1, wherein percentage of silver to carrier is 0.1 to 30: 99.9 to 70 w/w.
6. An inorganic antimicrobial agent as claimed in claim 5, wherein the ratio of silver to carrier is 5: 95 w/w.
7. A method of manufacturing an inorganic antimicrobial agent comprising of nano silver particles bonded on a carrier having average particle size of 20 to 400 nm comprising of the following steps :

(a) Dissolving silver containing compound in distilled or demineralised or ionised water followed by addition of the carrier;
(b) Stirring the above mixture continuously for 15 to 40 minutes;
(c) Drying the above mixture; and
(d) calcining the dried mixture under reducing atmosphere between 450°C
and 700°C and for a period of 60 to 180 minutes.
8. A method of manufacturing an inorganic antimicrobial agent as claimed in claim 7 above, wherein the reducing atmosphere is either mixture of hydrogen and nitrogen or coke or graphite.
9. A method of manufacturing an inorganic antimicrobial agent as claimed in claim 7 above, wherein the mixture in step (c) is dried in an oven at 110°Cto 150°C for 30 to 60 minutes.
10. A method of manufacturing an inorganic antimicrobial agent as claimed in claim 7 above, wherein the carrier is selected from amongst the titania (titanium dioxide), zinc oxide, silica and zeolite.

11. A method of manufacturing an inorganic antimicrobial agent as claimed in claim 7 above wherein the carrier does not have impurities of more than 1% preferably not more than 0.1%.
12. A method of manufacturing an inorganic antimicrobial agent as claimed in claim 7 above, wherein silver containing compound is selected from amongst silver nitrate, silver sulphate, silver carbonate and silver chloride.
13. A method of manufacturing an inorganic antimicrobial agent as claimed in claim 7 above wherein the proportion of silver containing compound and carrier is 0.1 to 30 : 99.9 to 70 w/w.
14. An inorganic antimicrobial agent claimed in claim 13 above wherein the proportion of silver containing compound to carrier is 5 : 95 w/w.
15. An inorganic antimicrobial agent and the method of manufacturing the same more particularly described in the Complete Specification with reference to the figures and examples accompanying the Specification.